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What is Mxene?

Mxene is a class of two-dimensional (2D) transition metal carbides, nitrides, and carbonitrides that exhibit unique properties such as high electrical conductivity, excellent mechanical strength, and high surface areas. Mxenes were first discovered in 2011 by researchers at Drexel University and have since gained significant attention in the scientific community due to their potential applications in various fields such as energy storage, catalysis, and sensing.

There are several different types of mxenes that have been synthesized, with the most common being titanium carbide (Ti3C2), which is typically prepared by selectively etching aluminum atoms from layered ternary carbides known as MAX phases. Other types of mxenes include vanadium carbide (V2C), niobium carbide (Nb2C), and tantalum carbide (Ta4C3), among others.

The preparation of mxenes typically involves the following steps:

1. Synthesis of MAX phase: The first step in preparing mxenes is to synthesize the parent MAX phase material, which is a layered ternary compound consisting of a transition metal (M), a group A element (A), and carbon or nitrogen (X). Common MAX phases include Ti3AlC2, V2AlC, and Nb4AlC3.

2. Selective etching: The next step involves selectively etching the A element (usually aluminum) from the MAX phase using strong acids or other etchants. This process leaves behind a layered structure of transition metal carbides, nitrides, or carbonitrides, which are the mxene precursors.

3. Intercalation: In some cases, additional intercalation steps may be performed to introduce other elements or molecules between the layers of mxene to modify its properties.

4. Delamination: The final step in preparing mxenes involves delaminating the layered structure to obtain single or few-layered sheets of mxene. This can be achieved through mechanical exfoliation, sonication, or other methods.

Once prepared, mxenes can be further functionalized or integrated into various devices and applications. Their unique combination of properties makes them promising candidates for use in energy storage devices such as batteries and supercapacitors, as well as in catalysis, electromagnetic shielding, and water purification.

Therefore, mxenes represent a new class of 2D materials with exciting potential for a wide range of applications. Continued research into their synthesis, properties, and applications will likely uncover even more possibilities for these versatile materials in the future.

Raman spectroscopy for characterization of Mxene

Raman spectroscopy is a powerful technique used to characterize the structural and chemical properties of materials, including Mxenes. Mxenes, a class of two-dimensional transition metal carbides, nitrides, and carbonitrides, have gained significant attention in the scientific community due to their unique properties and potential applications in various fields. In this article, we will explore how Raman spectroscopy can be utilized to study and analyze Mxene materials.

Raman spectroscopy is a non-destructive analytical technique that provides information about the vibrational modes of a material. When a material is irradiated with monochromatic light, some of the incident photons are scattered at different energies due to interactions with the material’s molecular vibrations. These energy shifts, known as Raman shifts, provide valuable insights into the material’s chemical composition, crystal structure, and bonding characteristics.

For Mxenes, Raman spectroscopy offers several advantages in characterizing their properties. One key advantage is the ability to identify the presence of different functional groups and chemical bonds within the Mxene structure. The Raman spectrum of Mxenes typically exhibits characteristic peaks corresponding to the stretching and bending vibrations of metal-carbon or metal-nitrogen bonds, as well as other functional groups present in the material.

Additionally, Raman spectroscopy can be used to determine the crystallinity and layer thickness of Mxene samples. The intensity and position of Raman peaks can provide information about the stacking order and interlayer interactions within the Mxene structure. By analyzing the Raman spectra of Mxenes obtained from different synthesis methods or processing conditions, researchers can gain valuable insights into the structural properties of these materials.

Furthermore, Raman spectroscopy can be employed to study the electronic properties of Mxenes. By analyzing the Raman spectra at different excitation wavelengths or under different environmental conditions, researchers can probe the charge carrier dynamics, doping effects, and electronic band structure of Mxene materials. This information is crucial for understanding the electrical conductivity and optoelectronic properties of Mxenes, which are important for their applications in energy storage and electronic devices.

In conclusion, Raman spectroscopy is a versatile tool for characterizing Mxene materials and gaining insights into their structural, chemical, and electronic properties. By utilizing Raman spectroscopy in conjunction with other analytical techniques, researchers can further elucidate the fundamental properties of Mxenes and optimize their performance for various applications. Continued research in this area will undoubtedly contribute to unlocking the full potential of Mxene materials in the field of materials science and beyond.

XRD technique for characterization of Mxene

X-ray diffraction (XRD) is a powerful analytical technique widely used for the characterization of materials, including Mxenes. Mxenes, a class of two-dimensional transition metal carbides, nitrides, and carbonitrides, have garnered significant interest in the scientific community due to their unique properties and potential applications in various fields. In this article, we will explore how XRD can be utilized to study and analyze the structural properties of Mxene materials.

X-ray diffraction is based on the principle of Bragg’s law, which states that when X-rays are incident on a crystalline material, they will be diffracted at specific angles depending on the crystal structure and interatomic spacing of the material. By measuring the intensity and angle of the diffracted X-rays, researchers can obtain valuable information about the crystal structure, phase composition, crystallite size, and lattice parameters of a material.

For Mxenes, X-ray diffraction is a valuable tool for determining their crystal structure and phase composition. The XRD pattern of Mxene materials typically exhibits sharp diffraction peaks corresponding to the ordered atomic arrangement within the crystal lattice. By analyzing the positions and intensities of these peaks, researchers can identify the crystallographic phases present in the Mxene sample and determine the crystal symmetry and unit cell parameters.

Moreover, XRD can be used to study the layer stacking and interlayer spacing of Mxene materials. The interlayer distance between adjacent Mxene layers can be calculated from the position of the diffraction peaks in the XRD pattern. By analyzing the changes in interlayer spacing under different synthesis conditions or processing methods, researchers can gain insights into the structural properties and stability of Mxenes.

Additionally, X-ray diffraction can provide information about the crystallite size and degree of crystallinity of Mxene samples. The broadening of XRD peaks is often used to estimate the average crystallite size of the material, with smaller peak widths indicating smaller crystallite sizes. By quantifying the crystallite size distribution in Mxene samples, researchers can assess the degree of structural ordering and defects present in the material.

Furthermore, X-ray diffraction can be employed to investigate the thermal stability and phase transformations of Mxene materials. By performing in situ XRD measurements at different temperatures or under controlled atmospheres, researchers can monitor changes in the crystal structure and phase composition of Mxenes as a function of temperature or environmental conditions. This information is crucial for understanding the thermal behavior and performance of Mxene materials in high-temperature applications.

In conclusion, X-ray diffraction is a versatile technique for characterizing the structural properties of Mxene materials and gaining insights into their crystallographic features, interlayer spacing, crystallite size, and phase composition. By combining XRD with other analytical techniques, researchers can further elucidate the fundamental properties of Mxenes and optimize their performance for various applications. Continued research in this area will undoubtedly contribute to advancing our understanding of Mxene materials and harnessing their full potential in materials science and technology.

FT-IR spectroscopy for characterization of Mxene

Fourier-transform infrared spectroscopy (FT-IR) is a powerful analytical technique that is widely used for the characterization of materials, including Mxenes. Mxenes, a class of two-dimensional transition metal carbides, nitrides, and carbonitrides, have garnered significant interest in the scientific community due to their unique properties and potential applications in various fields. In this article, we will explore how FT-IR can be utilized to study and analyze the structural and chemical properties of Mxene materials.

FT-IR spectroscopy is based on the principle that molecules absorb infrared radiation at specific frequencies that are characteristic of their chemical bonds and functional groups. When infrared light is passed through a sample, certain wavelengths are absorbed by the sample, resulting in the excitation of molecular vibrations. By measuring the intensity of the absorbed infrared radiation as a function of wavelength, researchers can obtain valuable information about the chemical composition, bonding environment, and structural properties of a material.

For Mxenes, FT-IR spectroscopy is a valuable tool for identifying the functional groups present in the material and probing the bonding interactions between the transition metal atoms, carbon or nitrogen atoms, and other constituents. The FT-IR spectrum of Mxene materials typically exhibits characteristic absorption bands corresponding to the vibrational modes of different chemical groups, such as C-C, C-H, C=O, and M-X bonds (where M represents the transition metal and X represents carbon or nitrogen).

By analyzing the positions and intensities of these absorption bands in the FT-IR spectrum, researchers can identify the functional groups present in the Mxene sample and gain insights into the chemical structure and composition of the material. For example, the presence of specific absorption bands can indicate the presence of carbide or nitride groups in the Mxene structure, while shifts in peak positions can provide information about the coordination environment of the transition metal atoms.

Moreover, FT-IR spectroscopy can be used to study the surface chemistry and functionalization of Mxene materials. By analyzing changes in the FT-IR spectrum before and after surface modification or functionalization reactions, researchers can monitor the introduction of new chemical groups or functional moieties onto the Mxene surface. This information is crucial for tailoring the surface properties and reactivity of Mxenes for specific applications, such as catalysis, sensing, or energy storage.

Additionally, FT-IR spectroscopy can provide insights into the thermal stability and decomposition behavior of Mxene materials. By performing in situ FT-IR measurements at different temperatures or under controlled atmospheres, researchers can monitor changes in the infrared absorption bands associated with thermal degradation processes. This information is essential for understanding the thermal behavior and stability of Mxene materials under different environmental conditions.

In conclusion, Fourier-transform infrared spectroscopy is a versatile technique for characterizing the structural and chemical properties of Mxene materials and gaining insights into their functional groups, bonding interactions, surface chemistry, and thermal behavior. By combining FT-IR with other analytical techniques, researchers can further elucidate the fundamental properties of Mxenes and optimize their performance for various applications. Continued research in this area will undoubtedly contribute to advancing our understanding of Mxene materials and unlocking their full potential in materials science and technology.

XPS for characterization of Mxene

X-ray photoelectron spectroscopy (XPS) is a powerful analytical technique that is widely used for the characterization of materials, including Mxenes. Mxenes, a class of two-dimensional transition metal carbides, nitrides, and carbonitrides, have garnered significant interest in the scientific community due to their unique properties and potential applications in various fields. In this article, we will explore how XPS can be utilized to study and analyze the surface chemistry, elemental composition, and electronic structure of Mxene materials.

X-ray photoelectron spectroscopy is based on the principle that when a material is irradiated with X-rays, electrons from the inner shells of atoms are ejected, resulting in the emission of photoelectrons. By measuring the kinetic energy and intensity of these emitted electrons, researchers can obtain valuable information about the elemental composition, chemical bonding, oxidation states, and surface properties of a material.

For Mxenes, XPS spectroscopy is a valuable tool for probing the surface chemistry and elemental composition of the material. The XPS spectrum of Mxene materials typically exhibits characteristic peaks corresponding to the core levels of different elements present in the sample, such as transition metals (M), carbon (C), nitrogen (N), and oxygen (O). By analyzing the positions and intensities of these peaks, researchers can identify the elemental composition of the Mxene sample and gain insights into the bonding environment and oxidation states of the constituent elements.

Moreover, XPS can provide information about the electronic structure and valence band properties of Mxene materials. By analyzing the valence band spectrum obtained from XPS measurements, researchers can study the energy distribution of valence electrons in the material and investigate the electronic interactions between different atomic species. This information is crucial for understanding the electronic properties and charge transfer mechanisms in Mxene materials, which are important for their performance in various applications, such as energy storage, catalysis, and sensing.

Additionally, XPS spectroscopy can be used to study the surface functionalization and chemical modifications of Mxene materials. By performing XPS measurements before and after surface treatments or functionalization reactions, researchers can monitor changes in the elemental composition, chemical states, and surface functionalities of the Mxene sample. This information is essential for tailoring the surface properties and reactivity of Mxenes for specific applications and optimizing their performance in various technological applications.

Furthermore, XPS can provide insights into the stability and degradation behavior of Mxene materials under different environmental conditions. By performing in situ XPS measurements at elevated temperatures or under controlled atmospheres, researchers can monitor changes in the chemical states and oxidation states of the Mxene sample during thermal treatments or exposure to reactive gases. This information is crucial for understanding the thermal stability and reactivity of Mxene materials and optimizing their performance for high-temperature applications.

In conclusion, X-ray photoelectron spectroscopy is a versatile technique for characterizing the surface chemistry, elemental composition, electronic structure, and stability of Mxene materials. By combining XPS with other analytical techniques, researchers can gain comprehensive insights into the fundamental properties of Mxenes and tailor their surface properties for specific applications. Continued research in this area will undoubtedly contribute to advancing our understanding of Mxene materials and unlocking their full potential in materials science and technology.

UV-Vis spectroscopy for characterization of Mxene

Ultraviolet-visible (UV-Vis) spectroscopy is a powerful analytical technique that is commonly used for the characterization of materials, including Mxenes. Mxenes, a class of two-dimensional transition metal carbides, nitrides, and carbonitrides, have garnered significant interest in the scientific community due to their unique properties and potential applications in various fields. In this article, we will explore how UV-Vis spectroscopy can be utilized to study and analyze the optical properties, electronic transitions, and bandgap of Mxene materials.

UV-Vis spectroscopy is based on the principle that when a material is irradiated with ultraviolet or visible light, electrons in the material can be excited from the ground state to higher energy states. By measuring the absorption or transmission of light at different wavelengths, researchers can obtain valuable information about the electronic transitions, band structure, and optical properties of the material.

For Mxenes, UV-Vis spectroscopy is a valuable tool for probing the electronic structure and optical properties of the material. The UV-Vis spectrum of Mxene materials typically exhibits characteristic absorption peaks corresponding to electronic transitions between different energy levels in the material. These absorption peaks can provide insights into the bandgap energy, electronic band structure, and optical transitions in Mxene materials.

The bandgap energy of a material is a critical parameter that determines its electronic and optical properties. By analyzing the absorption spectrum obtained from UV-Vis measurements, researchers can estimate the bandgap energy of Mxene materials and gain insights into their electronic band structure. The bandgap energy of Mxenes can be influenced by various factors, such as the composition, structure, and surface functionalization of the material, making UV-Vis spectroscopy an essential tool for studying and optimizing the optical properties of Mxenes for specific applications.

Moreover, UV-Vis spectroscopy can provide information about the electronic transitions and excitonic effects in Mxene materials. Excitonic effects arise from the interaction between photo-excited electrons and holes in a material, leading to the formation of excitons with distinct optical properties. By analyzing the absorption spectrum and peak shapes in UV-Vis measurements, researchers can study the excitonic effects in Mxene materials and investigate their impact on the optical properties and charge carrier dynamics of the material.

Additionally, UV-Vis spectroscopy can be used to study the surface plasmon resonance (SPR) properties of Mxene materials. SPR is a phenomenon that occurs when free electrons in a material collectively oscillate in response to incident light, leading to enhanced light absorption and scattering at specific wavelengths. By performing UV-Vis measurements at different angles or polarizations, researchers can investigate the SPR properties of Mxene materials and tailor their optical properties for applications such as sensors, photodetectors, and plasmonic devices.

Furthermore, UV-Vis spectroscopy can be employed to study the stability and degradation behaviour of Mxene materials under different environmental conditions. By performing in situ UV-Vis measurements under controlled temperatures or atmospheres, researchers can monitor changes in the optical properties and electronic transitions of the material during thermal treatments or exposure to reactive gases. This information is crucial for understanding the stability and reactivity of Mxene materials and optimizing their performance for applications requiring high temperatures or harsh environments.

In conclusion, UV-Vis spectroscopy is a versatile technique for characterizing the optical properties, electronic transitions, and bandgap of Mxene materials. By combining UV-Vis spectroscopy with other analytical techniques, researchers can gain comprehensive insights into the fundamental properties of Mxenes and tailor their optical properties for specific applications. Continued research in this area will undoubtedly contribute to advancing our understanding of Mxene materials and unlocking their full potential in materials science and technology.

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In the realm of chemistry, the concept of allotropy unveils the mesmerizing ability of an element to exist in multiple forms, known as allotropes, each exhibiting distinct physical and chemical properties. Among the myriad elements that showcase this intriguing phenomenon, carbon stands out as a versatile and captivating element with a plethora of allotropes. Understanding the diverse carbon allotropes, their mechanical and chemical properties, as well as the characterization methods used to unveil their secrets, is essential for unlocking their potential in various scientific and technological applications.

Carbon Allotropes: A Kaleidoscope of Structures and Properties

Carbon, with its ability to form strong covalent bonds and diverse molecular structures, manifests in several allotropes, each with unique properties and applications. Here are some of the prominent carbon allotropes:

1. Diamond: The epitome of elegance and durability, diamond features a three-dimensional network of carbon atoms arranged in a tetrahedral structure. Renowned for its exceptional hardness, thermal conductivity, and optical properties, diamond finds applications in jewellery, cutting tools, and industrial abrasives.

2. Graphite: In contrast to diamond’s rigid structure, graphite embodies layers of carbon atoms arranged in hexagonal rings, imparting lubricating properties. Graphite is commonly used in pencil leads, lubricants, and electrodes due to its soft and slippery nature.

3. Graphene: A single layer of graphite arranged in a two-dimensional hexagonal lattice structure, graphene boasts remarkable mechanical strength, electrical conductivity, and thermal properties. This wonder material holds promise for applications in electronics, energy storage, and sensors.

4. Carbon Nanotubes: These cylindrical structures composed of rolled-up graphene sheets exhibit exceptional mechanical strength, electrical conductivity, and thermal properties. Carbon nanotubes find applications in nanotechnology, composites, and electronics due to their unique structural characteristics.

5. Fullerenes: Hollow carbon molecules with cage-like structures, fullerenes like Buckminsterfullerene (C60) possess intriguing properties such as high electron affinity and reactivity. Fullerenes are utilized in diverse fields ranging from drug delivery to superconductors.

Mechanical and Chemical Properties of Carbon Allotropes

Each carbon allotrope showcases a distinctive set of mechanical and chemical properties based on its unique structure and bonding arrangement:

– Diamond: Exceptional hardness, transparency, high thermal conductivity.
– Graphite: Softness, lubricating properties, opaque nature.
– Graphene: High electrical conductivity, mechanical strength, thermal conductivity.
– Carbon Nanotubes: Exceptional mechanical strength, electrical conductivity, and thermal properties.
– Fullerenes: High electron affinity, reactivity, unique cage-like structures.

Characterization Methods for Carbon Allotropes

To unravel the mysteries of carbon allotropes and understand their properties at a molecular level, various sophisticated characterization techniques are employed:

1. Fourier Transform Infrared Spectroscopy (FTIR)

Fourier-transform infrared (FTIR) spectroscopy is another powerful analytical technique that can aid in the characterization of different allotropies of carbon by providing information about their chemical bonding, functional groups, and structural properties. Here’s how FTIR analysis can be utilized to study various carbon allotropes:

a. Functional Group Identification: FTIR spectroscopy can be used to identify specific functional groups present in different carbon allotropes based on the characteristic absorption bands observed in their infrared spectra. For example, the presence of sp2 and sp3 hybridized carbon bonds in graphene, carbon nanotubes, and diamond can be distinguished by analyzing the peaks corresponding to C=C and C-H stretching vibrations, respectively. Additionally, functional groups such as hydroxyl (-OH), carbonyl (C=O), carboxyl (-COOH), and epoxy (-O-) groups can be detected in carbon materials through their distinctive IR absorption bands, allowing researchers to assess the surface chemistry and reactivity of the allotropes.

b. Structural Analysis: FTIR spectroscopy can provide insights into the structural characteristics of carbon allotropes by probing the vibrational modes of carbon-carbon bonds and other chemical interactions within the materials. The presence of sp2 and sp3 hybridized carbon atoms, aromatic rings, double bonds, and functional groups can be inferred from the intensity, position, and shape of the absorption bands in the FTIR spectrum. By correlating the vibrational frequencies of carbon allotropes with their structural features, researchers can elucidate the bonding configurations, lattice arrangements, and crystallographic orientations of the materials.

c. Surface Modification and Functionalization: FTIR spectroscopy is a valuable tool for studying surface modifications, functionalization reactions, and chemical interactions on the surface of carbon allotropes. By comparing the FTIR spectra of pristine and modified carbon samples, researchers can identify changes in the absorption bands associated with functional groups introduced during surface treatments, chemical derivatization, or doping processes. This enables the characterization of surface functionalization strategies, quantification of surface coverage, and evaluation of chemical stability in functionalized carbon materials.

d. Quantitative Analysis: FTIR spectroscopy can be utilized for quantitative analysis of functional groups, impurities, and contaminants in carbon allotropes by measuring the absorbance intensities at specific wavenumbers corresponding to characteristic vibrational modes. By establishing calibration curves or using peak area integration methods, researchers can quantify the relative concentrations of different functional groups or impurities in a carbon sample, providing valuable information about its chemical composition, purity, and quality.

e. Stability and Degradation Studies: FTIR spectroscopy can be employed to investigate the stability, degradation mechanisms, and chemical reactivity of carbon allotropes under various environmental conditions. By monitoring changes in the FTIR spectra over time or upon exposure to external factors (e.g., temperature, humidity, oxidation), researchers can assess the material’s resistance to degradation, identify degradation products or by-products, and elucidate the underlying chemical processes that influence its performance and longevity.

2. Raman Spectroscopy

By studying the vibrational modes of carbon materials, Raman spectroscopy offers valuable information about their structural properties and defects. Raman spectroscopy is a powerful analytical technique that can provide valuable insights into the structural and vibrational properties of different carbon allotropes. Here’s how Raman spectroscopy can help characterize various carbon allotropes:

a. Structural Analysis: Raman spectroscopy can distinguish between different carbon allotropes based on their unique structural characteristics. Each allotrope exhibits specific Raman-active vibrational modes, allowing researchers to identify and differentiate between diamond, graphite, graphene, carbon nanotubes, and fullerenes.

b. Defect Detection: Carbon allotropes may contain defects or impurities that can influence their properties. Raman spectroscopy can detect and characterize these defects by analyzing changes in the Raman spectra, such as shifts in peak positions or intensity variations. This information is crucial for understanding the quality and purity of carbon materials.

c. Quantitative Analysis: Raman spectroscopy can be used for quantitative analysis of carbon allotropes, providing information about the relative abundance of different phases or structures within a sample. By correlating Raman spectral features with specific carbon allotropes, researchers can quantitatively assess the composition and distribution of various forms of carbon in a sample.

d. Chemical Functionalization: Raman spectroscopy is sensitive to chemical modifications and functional groups present on the surface of carbon allotropes. By analyzing changes in Raman spectra upon functionalization or chemical treatment, researchers can characterize the interaction between carbon materials and other substances, enabling the design of tailored functionalized carbon materials for specific applications.

3. X-ray Photoelectron Spectroscopy (XPS)

XPS is another valuable technique that can aid in the characterization of different allotropies of carbon. Here’s how XPS analysis can provide insights into the structural and chemical properties of various carbon allotropes:

a. Elemental Composition: XPS analysis can determine the elemental composition of carbon allotropes by measuring the binding energies of core-level electrons, such as the carbon 1s peak. Different carbon allotropes exhibit distinct binding energy values for their core-level electrons due to variations in the local chemical environment and bonding configurations. By comparing the XPS spectra of carbon allotropes with reference data, researchers can identify the presence of specific elements and quantify their relative concentrations.

b. Chemical State Analysis: XPS analysis can reveal information about the chemical state and bonding characteristics of carbon allotropes. The peak shapes, positions, and intensities in the XPS spectra provide insights into the oxidation state, functional groups, and bonding configurations present in a carbon sample. For example, XPS can differentiate between sp2 and sp3 hybridized carbon atoms in graphene and diamond, respectively, based on their distinct chemical environments and electronic structures.

c. Surface Sensitivity: XPS analysis is a surface-sensitive technique that probes the top few nanometers of a material, making it well-suited for characterizing the surface chemistry of carbon allotropes. By analyzing the elemental composition and chemical states at the surface of a carbon sample, researchers can gain valuable information about surface contaminants, functionalization, and modifications that may influence the material’s properties and reactivity.

d. Dopant Identification: XPS analysis can help identify dopants or impurities incorporated into carbon allotropes to modify their electronic, optical, or catalytic properties. By analyzing the XPS spectra of doped carbon materials, researchers can detect changes in the core-level binding energies and chemical states of the dopant atoms, providing insights into their distribution, concentration, and interaction with the host carbon lattice.

e. Depth Profiling: XPS analysis can also be combined with depth profiling techniques to investigate the chemical composition and structure of carbon allotropes as a function of depth below the surface. Depth profiling methods, such as angle-resolved XPS or sputter depth profiling, allow researchers to study the layer-by-layer composition, doping profiles, and interface properties of carbon materials, enabling a comprehensive understanding of their structure-property relationships.

4. Ultraviolet-Visible Spectroscopy (UV-Vis)

UV-Vis spectroscopy aids in studying the optical properties of carbon allotropes, including absorption and emission spectra.

UV-Vis spectroscopy is another valuable technique that can aid in the characterization of different allotropies of carbon by providing insights into their electronic and optical properties. Here’s how UV-Vis analysis can be utilized to study various carbon allotropes:

a. Bandgap Determination: UV-Vis spectroscopy can be used to determine the bandgap energy of carbon allotropes, which is a crucial parameter that influences their electronic and optical properties. By measuring the absorption spectrum of a carbon sample in the UV and visible regions, researchers can identify the onset of absorption (i.e., the bandgap energy) and characterize the material’s semiconducting or insulating behavior. Different carbon allotropes, such as graphene, carbon nanotubes, and diamond, exhibit distinct bandgap energies due to variations in their electronic structure and bonding configurations.

b. Optical Absorption Features: UV-Vis spectroscopy can reveal information about the optical absorption features of carbon allotropes, such as excitonic transitions, interband transitions, and localized electronic states. The absorption spectrum of a carbon sample can exhibit characteristic peaks, shoulders, or broad absorption bands corresponding to specific electronic transitions within the material. By analyzing the shape, intensity, and position of these absorption features, researchers can gain insights into the electronic structure, energy levels, and optical properties of different carbon allotropes.

c. Defects and Functional Groups: UV-Vis spectroscopy can be used to detect defects, functional groups, and chemical modifications in carbon allotropes that affect their electronic and optical properties. Defect-induced states, surface functionalization, and doping can introduce additional absorption features or modify the intensity of existing peaks in the UV-Vis spectrum of a carbon sample. By comparing the UV-Vis spectra of pristine and modified carbon materials, researchers can identify changes in the electronic structure, bandgap energy, and optical response resulting from defects or functionalization.

d. Quantitative Analysis: UV-Vis spectroscopy can also be employed for quantitative analysis of carbon allotropes by correlating the absorption intensity with the concentration of specific components or impurities in a sample. By measuring the absorbance at characteristic wavelengths and establishing calibration curves for different carbon species or dopants, researchers can quantify the relative abundance of components in a complex mixture or determine the doping level in doped carbon materials.

e. Stability and Degradation Studies: UV-Vis spectroscopy can provide valuable information about the stability, degradation, and photochemical behavior of carbon allotropes under various environmental conditions. By monitoring changes in the UV-Vis absorption spectrum over time or under different exposure conditions (e.g., light irradiation, temperature variations), researchers can assess the material’s photochemical stability, degradation mechanisms, and resistance to environmental factors that may impact its performance and longevity.

5. X-ray Diffraction (XRD)

X-ray diffraction (XRD) analysis is another powerful technique that can provide valuable insights into the structural properties of different carbon allotropes. Here’s how XRD analysis can help characterize various allotropies of carbon:

a. Crystal Structure Determination: XRD analysis can be used to determine the crystal structure of carbon allotropes by analyzing the diffraction patterns generated when X-rays interact with the periodic arrangement of atoms in a material. Different carbon allotropes have distinct crystal structures, such as the hexagonal lattice of graphite, the cubic structure of diamond, and the helical structure of carbon nanotubes. By comparing experimental XRD patterns with reference data, researchers can identify and confirm the crystal structure of a carbon allotrope.

b. Phase Identification: XRD analysis can help identify and distinguish between different phases or polymorphs of carbon allotropes present in a sample. By analyzing the positions and intensities of diffraction peaks in the XRD pattern, researchers can determine the presence of specific allotropes, such as graphite, diamond, graphene, carbon nanotubes, and fullerenes. This information is essential for characterizing the composition and phase distribution within a carbon sample.

c. Crystallite Size and Orientation: XRD analysis can provide information about the crystallite size and orientation of carbon allotropes. By analyzing the broadening of XRD peaks, researchers can estimate the average crystallite size of a material, which is crucial for understanding its structural properties. Additionally, XRD can reveal information about the preferred orientation or texture of crystallites within a sample, offering insights into the growth and alignment of carbon allotropes.

d. Strain Analysis: XRD analysis can also be used to investigate the presence of strain or defects in carbon allotropes. Changes in the peak positions and peak shapes in the XRD pattern can indicate the presence of lattice strain, dislocations, or defects in the crystal structure of a material. By quantifying these structural imperfections, researchers can assess the mechanical stability and performance of carbon allotropes.

e. Thermal Stability and Phase Transitions: XRD analysis can be employed to study the thermal stability and phase transitions of carbon allotropes under varying temperature and pressure conditions. By monitoring changes in the XRD patterns as a function of temperature or pressure, researchers can identify phase transformations, melting points, and structural changes in carbon materials, providing crucial information for understanding their behaviour under different environmental conditions.

Conclusion

In conclusion, the captivating world of carbon allotropes unveils a treasure trove of possibilities for scientific exploration and technological innovation. By delving into the diverse structures and properties of carbon allotropes and employing advanced characterization methods, researchers can unlock the full potential of these fascinating materials across a wide range of applications. The allure of carbon allotropes continues to inspire groundbreaking discoveries and advancements in materials science and beyond.

Two common methods for corrosion monitoring are electrochemical impedance spectroscopy (EIS) and polarization methods. While both methods are used to measure the corrosion rate, they differ in their approach and the information they provide.

EIS measures the impedance of a material as a function of frequency. By analyzing the impedance spectrum, it is possible to determine the electrical properties of the material, such as its resistance, capacitance, and conductivity. EIS can be used to monitor corrosion by measuring changes in the impedance spectrum over time. Corrosion can cause changes in the electrical properties of a material, which can be detected by EIS.

Polarization methods, on the other hand, measure the potential and current of a material under an applied voltage or current. There are two main types of polarization methods: potentiodynamic and potentiostatic. Potentiodynamic polarization measures the current as the potential is swept over a range of values, while potentiostatic polarization measures the potential as the current is held constant.

One of the main differences between EIS and polarization methods is their sensitivity to different types of corrosion. EIS is more sensitive to localized corrosion, such as pitting and crevice corrosion, while polarization methods are more sensitive to uniform corrosion. This is because localized corrosion can cause changes in the electrical properties of a material, which can be detected by EIS, while uniform corrosion does not typically cause such changes.

Another difference between EIS and polarization methods is their ability to provide information about the corrosion mechanism. EIS can provide information about the electrochemical reactions that occur during corrosion, such as the formation of passive films and the dissolution of metal ions. Polarization methods, on the other hand, provide information about the kinetics of the corrosion reaction, such as the activation energy and the rate constant.

EIS and polarization methods also differ in their ease of use and cost. EIS requires specialized equipment and expertise to perform, while polarization methods can be performed with simpler equipment and require less expertise. However, EIS provides more detailed information about the corrosion mechanism and is more sensitive to localized corrosion, which can be important in certain applications.

In summary, both EIS and polarization methods are useful for corrosion monitoring, but they differ in their sensitivity to different types of corrosion, their ability to provide information about the corrosion mechanism, and their ease of use and cost. Choosing the appropriate method for a particular application depends on the specific corrosion concerns and the desired level of detail in the corrosion monitoring.

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Adsorption is a process where a solid or liquid substance is attracted and held onto the surface of another material. It is an essential process in many industries, including water treatment, food processing, and pharmaceuticals. The effectiveness of adsorption depends on the properties of the adsorbent material, such as its surface area, pore size distribution, and chemical composition. Therefore, finding an optimum adsorbent material is crucial to achieving efficient and cost-effective adsorption processes.

One of the most powerful tools for determining the properties of an adsorbent material is the BET analysis. The BET (Brunauer-Emmett-Teller) analysis is a technique used to measure the specific surface area of a material by measuring the amount of gas adsorbed onto its surface at different pressures. The data obtained from BET analysis can be used to calculate the pore size distribution and other critical parameters that determine the adsorption capacity and efficiency of the material.

BET analysis can be used to evaluate various types of materials, including activated carbon, zeolites, silica gels, and metal-organic frameworks. By using BET analysis, researchers can determine the optimum conditions for preparing and using these materials as adsorbents. Here are some ways BET analysis can help in finding an optimum material for using as an adsorbate:

1. Determining the Specific Surface Area

The specific surface area of an adsorbent material is one of the most critical parameters that affect its adsorption capacity. BET analysis can accurately measure the specific surface area of a material by analyzing the amount of gas adsorbed onto its surface at different pressures. The higher the specific surface area, the more adsorption sites are available for attracting and holding onto target molecules.

2. Calculating Pore Size Distribution

The pore size distribution of an adsorbent material is another crucial factor that affects its adsorption capacity. BET analysis can provide information about the pore size distribution of a material by analyzing the adsorption isotherm data. The pore size distribution can be used to determine the optimum pore size range for the target molecules to be adsorbed.

3. Evaluating Adsorption Capacity

BET analysis can also be used to evaluate the adsorption capacity of an adsorbent material. By measuring the amount of gas adsorbed onto the material at different pressures, researchers can determine the maximum amount of target molecules that can be adsorbed onto the material. This information can be used to optimize the adsorption process and determine the most effective operating conditions.

4. Comparing Different Materials

BET analysis can also be used to compare the properties of different adsorbent materials. By analyzing the specific surface area, pore size distribution, and other parameters, researchers can determine which material is most suitable for a specific application. This information can help in selecting the best material for a particular adsorption process and improve its efficiency and cost-effectiveness.

In conclusion, BET analysis is a powerful tool for evaluating the properties of adsorbent materials and finding an optimum material for using as an adsorbate. By analyzing the specific surface area, pore size distribution, and other parameters, researchers can determine the most effective operating conditions and select the best material for a specific application. BET analysis can help in improving the efficiency and cost-effectiveness of adsorption processes in various industries, making it an essential technique for researchers and engineers working in this field.

Raman and Fourier Transform Infrared (FTIR) spectroscopy are two of the most widely used analytical techniques in the field of chemistry. Both techniques are used to identify the chemical composition of a sample, but they differ in their mechanisms of analysis and the types of information they provide. In this article, we will explore the differences between Raman and FTIR spectroscopy and their applications.

Raman spectroscopy is a non-destructive technique that uses laser light to excite the molecules in a sample. The scattered light is analyzed to determine the vibrational modes of the molecules, which can be used to identify the chemical composition of the sample. The Raman effect was first discovered by C.V. Raman in 1928 and has since become an important analytical tool in chemistry, materials science, and biology.

FTIR spectroscopy, on the other hand, uses infrared radiation to excite the molecules in a sample. The sample is irradiated with a broad range of infrared wavelengths, and the absorption spectrum is measured. The absorption spectrum provides information about the functional groups present in the sample, which can be used to identify the chemical composition of the sample. FTIR spectroscopy was first developed in the 1940s and has since become an essential analytical technique in many fields, including chemistry, materials science, and biology.

One of the main differences between Raman and FTIR spectroscopy is their sensitivity to different types of molecular vibrations. Raman spectroscopy is more sensitive to vibrations involving changes in polarizability, such as stretching and bending vibrations of C-H, N-H, and O-H bonds. FTIR spectroscopy, on the other hand, is more sensitive to vibrations involving changes in dipole moment, such as stretching and bending vibrations of C=O, C-N, and C=C bonds.

Another difference between Raman and FTIR spectroscopy is their ability to identify different types of chemical compounds. Raman spectroscopy is particularly useful for identifying inorganic compounds, such as minerals and ceramics, which have strong Raman scattering signals. FTIR spectroscopy, on the other hand, is more useful for identifying organic compounds, such as polymers and biomolecules, which have strong infrared absorption signals.

The choice between Raman and FTIR spectroscopy depends on the specific application and the type of sample being analyzed. Raman spectroscopy is often used for the analysis of inorganic materials, such as minerals, ceramics, and semiconductors. It is also useful for the analysis of biological samples, such as cells and tissues, where the Raman scattering signal can provide information about the chemical composition of the sample.

FTIR spectroscopy is often used for the analysis of organic materials, such as polymers, biomolecules, and pharmaceuticals. It is also useful for the analysis of environmental samples, such as air and water, where the infrared absorption spectrum can provide information about the presence of pollutants and other contaminants.

In addition to their traditional applications, both Raman and FTIR spectroscopy are finding new uses in emerging fields such as nanotechnology and biomedical imaging. Raman spectroscopy has been used to study the properties of individual nanoparticles and to image biological tissues at the cellular level. FTIR spectroscopy has been used to study the structure of proteins and to develop new diagnostic tools for diseases such as cancer.

In conclusion, Raman and FTIR spectroscopy are two powerful analytical techniques that are widely used in chemistry, materials science, and biology. While they differ in their mechanisms of analysis and sensitivity to different types of molecular vibrations, they both provide valuable information about the chemical composition of a sample. The choice between Raman and FTIR spectroscopy depends on the specific application and the type of sample being analyzed, but both techniques have a wide range of applications in many fields.

Falsification of data in a paper refers to the deliberate manipulation or fabrication of research data to support a particular hypothesis or conclusion. This can include altering or omitting data, selectively reporting results, or creating false data altogether.

There are various reasons why some researchers may falsify data for their papers, although it is important to note that this behavior is unethical and goes against the principles of scientific integrity. Some of the reasons may include:

1. Pressure to publish: In academia, there is often a strong emphasis on publishing research papers in order to advance one’s career. This pressure to publish can lead some researchers to cut corners and falsify data in order to get their papers accepted for publication.

2. Desire for recognition: Researchers may also falsify data in order to gain recognition and prestige in their field. This can be especially tempting for early-career researchers who are trying to establish themselves in the field.

3. Financial gain: In some cases, researchers may falsify data in order to secure funding or financial support for their research.

4. Personal bias: Researchers may also falsify data if they have a personal bias or preconceived notion about the outcome of their research. This can lead them to manipulate the data in order to support their hypothesis.

We cannot promote or encourage any unethical practices. However, we can provide some examples of how XRD, FTIR, UV-Vis, Raman, BET, PL, NMR, SEM, TEM, TGA, EIS, or XPS results can be falsified:

1. Fabricating data: A person may create fictitious data and present it as genuine experimental results.

2. Selective reporting: A person may selectively report only those results that support their hypothesis or conclusion, while omitting contradictory data.

3. Altering data: A person may manipulate the experimental conditions or alter the raw data to produce desired results.

4. Misrepresenting data: A person may misinterpret or misrepresent the data to support their hypothesis or conclusion, even if the data does not actually support it.

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It is well known that determination of concentrations of materials in different solutions is an important step for investigation of the under-studied solution. Usually, photometric techniques are used due to this fact that they are accessible and cost-effective options.

Generally, absorption of irradiated light to a solution by the presence molecules is the base of (spectro)-photometric techniques. In UV/Vis spectroscopy visible and ultraviolet light uses for detection of concentration of a solution.

Spectroscopy is a science that studies the interaction of electromagnetic radiation with matter. In such interactions, electromagnetic radiation can be thought of as a set of separate energy packets called photons. The dual property of electromagnetic radiation as a particle and a wave is not only non-existent but also complementary. According to the theory, electromagnetic radiation is made up of two components, electric fields and magnetic field. These fields are propagating the wave in the environment, on the environment and also perpendicular to the wave propagation (Figure 1).

The electric field of electromagnetic radiation causes phenomena such as transmission, reflection, refraction, and absorption when it interacts with matter. The magnetic field of electromagnetic radiation is also effective in the process of absorbing waves related to radio frequencies in nuclear magnetic resonance. Therefore, here only the electric field of electromagnetic radiation is examined due to its effectiveness in the above phenomena.

As was mentioned previously, determination of concentrations of materials in different solutions is an important step for investigation of the under-studied solution. Usually, photometric techniques are used due to this fact that they are accessible and cost-effective options.

For the calculation of an analytic concentration, the Lambert-Beer law form the basis can be used as follow:

1. Transmission or transmittance (T) = I/I₀
   
2. Absorbance (A) = log (I₀/I)
   
3. Absorbance (A) = C x L x Ɛ => Concentration (C) = A/(L x Ɛ)
   

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Fourier transform infrared spectroscopy (FTIR) is an experimental test to identify organic/inorganic materials. But for understanding and interpretation of FTIR results, the principles of the analysis should be studied.

Principles of FTIR

To better interpretation of FTIR results, it’s useful to know about the principles of the test.

Generally, by introducing infrared radiation (IR) to a material, FTIR’s detectors detect a sample’s absorbance of infrared light at various wavenumbers to determine the material’s chemical structure. FTIR spectrometer converts the experimental data from the broadband source to the absorbance level at each wavenumber.

This method can be employed for solids, liquids, and gaseous samples. Some times, the weight of samples required for a viable analysis is very low and most analyses can be conducted with little sampling process.

How to interpret FTIR spectra

The X-Axis

The horizontal axis shows the IR spectrum, which represents the intensity of the IR spectra. The absorbance peaks, can be attributed to the various vibrations of the sample’s bonds exposed to the IR energy of the electromagnetic spectrum. Usually, the wavenumber on the IR spectrum is drew between 4000 to 400 cm-1.

The Y-Axis

The vertical axis shows the amount of IR absorbance/transmittance by the under-studied material.

The Absorbance Bands

Generally, absorbance bands can be derived into two groups: Group frequencies and fingerprint frequencies.

Group frequencies are assigned to small groups of bonds such as C-H, O-H, and C=O. These types of bonds are usually observable at 1500-400 cm-1 in the IR spectrum and they are typically unique to a specific bond or functional group in a structure.

For fingerprint frequencies, these are assigned to the chemical structure as a whole. These types of absorbances are usually observable at 400-1500cm-1 in the IR spectrum. Therefore, this region is less reliable for identification, however the absence of a peak is often more indicative than the presence of a peak in this region.

How to analyze FT-IR Spectra

Generally, interpretation of FT-IR spectra starts at the high frequencies end to identify the presence functional groups. The fingerprint regions are then investigated to identify the chemical bonds.

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FTIR is a useful technique for manufacturers and researchers of various industries. If you have more questions about the analysis or are wondering if it may be a fit for your testing needs, contact us for a quote.

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We present here results on a Raman spectroscopic study of the deposited defected graphene on Si substrates by chemical vapor deposition (thermal decomposition of acetone). The graphene films are not deposited on the (001) Si substrate directly but on two types of interlayers of mixed phases unintentionally deposited on the substrates: а diamond-like carbon (designated here as DLC) and amorphous carbon (designated here as αC) are dominated ones.

The performed thorough Raman spectroscopic study of as-deposited as well as exfoliated specimens by two different techniques using different excitation wavelengths (488, 514, and 613 nm) as well as polarized Raman spectroscopy establishes that the composition of the designated DLC layers varies with depth: the initial layers on the Si substrate consist of DLC, nanodiamond species, and C₇₀fullerenes while the upper ones are dominated by DLC with an occasional presence of C₇₀ fullerenes. The αC interlayer is dominated by turbostratic graphite and contains a larger quantity of C₇₀ than the DLC-designated interlayers. The results of polarized and unpolarized Raman spectroscopic studies of as-grown and exfoliated graphene films tend to assume that single- to three-layered defected graphene is deposited on the interlayers. It can be concluded that the observed slight upshift of the 2D band as well as the broadening of 2D band should be related to the strain and doping.

1. Introduction

Graphene is a one-atom-thick layered material that consists of completely sp²-bonded carbon atoms tightly packed into a honeycomb lattice. It has a lot of unique properties promising a huge number of possible applications (see, e.g., [1]). A lot of different ways of synthesizing graphene were experimentally tested during the last decade; however, only thermally and plasma-assisted chemical vapor deposition (CVD/PECVD) on metal substrates (copper, nickel, etc.) [2, 3] as well as epitaxial growth on SiC substrates and so on [4, 5] were developed for industrial application. The latter method is based on C (or Si) termination of the (0001)_C (or (0001)_Si) SiC surface and requires high temperature and expensive SiC substrates. The CVD method is based on the plasma-enhanced thermal decomposition of a carbon-containing precursor on a catalytic metal surface. This method provides high reliability and relatively high quality of graphene films, and now, there are a lot of suppliers of reactors for PECVD of graphene. The most preferred precursor is methane (CH₄) as the chemical bond in CH₄ is relatively strong and prevents fast decomposition of the reagent at temperatures below 1000°C (see, e.g., [6]). However, production for microelectronic applications requires transfer of the graphene layers on an insulating surface and, consequently, a large number of additional defects affecting the properties of graphene can be introduced. Therefore, the problem with the deposition of graphene on silicon (or surfaces compatible with silicon technology such as SiO₂) still remains unsolved. We demonstrated the possible application of acetone as a precursor in a thermally assisted CVD and showed that few-layered defected graphene/folded graphene can be deposited on commercially available metal foils—Ni, (Cu_0.5Ni_0.5), μ-metal, and stainless steel SS 304 in a recently published work [7]. Further, we established (see [8]) by Raman spectroscopy, scanning electron microscopy (SEM), X-ray diffraction (XRD), and grazing incidence X-ray diffraction (GIXRD) as well as by X-ray photoelectron spectroscopy (XPS) the presence of single- to few-layered defected graphene on two different types of interlayers deposited on (100) Si surface: (i) a diamond-like carbon (DLC) layer with some SiC contents (in the range below 5w%) and some residual quantities of SiO₂, and (ii) a complex amorphous carbon layer consisting of a mixture of sp²– and sp³-hybridized carbon as well as very small amount of fullerenes, SiO, and so on.

Here, we focus our experimental study on the Raman spectroscopic characterization of defected as-deposited graphene layers (including polarized spectroscopy) as well as graphene flakes exfoliated from similar specimens by two different ways using 488, 514, and 633 nm excitation laser wavelengths aiming at unambiguous confirmation of the graphene deposition of as well as the identification of the exact composition of the interlayers between the Si substrate and graphene layer/s.

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2. Experimental

2.1. CVD Process

We use 2 inches in diameter (001) Si substrates and a horizontal tube quartz CVD reactor with an internal diameter of approximately 70 mm. The experimental setup also consists of a gas-supply system (inlet and outlet parts), a thermostat with acetone evaporation alert/indication system, a quartz substrate holder, and a resistive heating furnace. The CVD process is based on thermal decomposition of acetone in Ar main gas flow. The deposition temperature was in the range 1150–1160°C. The temperature of the thermostat was kept at 12°C. In order to prevent the supersaturation in the high-temperature zone of the reactor, we used a “pulsed” regime in experiments by alternating the flow of the gas mixture of Ar + C₃H₆O) for 3 min on top of the main flow of pure Ar of about 150–180 cm³/min for 1.5 min for each pulse. The optimal results (predominantly single-layered graphene) were obtained after two deposition pulses.

2.2. Exfoliation

We exfoliated the carbon films deposited on (001) Si substrates by the following two different techniques:(i)The Scotch tape method (see, e.g., [9]): we put tightly the adhesive Scotch tape on the multilayered graphene side of the specimens. After peeling the tape off the specimen, a single- to few-layered graphene remains on the tape’s surface and the interlayer between the upper few layers of graphene and the substrate becomes accessible for spectroscopic examination. Then, we put tightly the Scotch tape with graphene flakes either on 320 nm SiO₂/Si or on glass substrate. About 30–50% of the graphene flakes remain adhered to the SiO₂ or glass substrate after removing the tape due to the Van der Waals force.(ii)We also adhered the multilayered graphene side of the specimens to epoxy resin. After careful cleavage, the most part of the graphene layer/s remains on the surface of the resin. Then, the adhered to the resin graphene film becomes accessible for spectroscopic examination. The Raman spectrum of the epoxy resin does not contain strong peaks around the 2D band of graphene (the area around 2630–2670 cm⁻¹). We established that the 2D band of graphene is clearly distinguishable for graphene regions lying on gas bubbles close to the surface of the resin; otherwise, the 2D band of graphene is weak.

2.3. Characterization

The Raman measurements were carried out in backscattering geometry at a micro-Raman HORIBA Jobin Yvon Labram HR 800 visible spectrometer equipped with a Peltier-cooled CCD detector with a He-Ne (633 nm wavelength and 0.5 mW) laser excitation. The 514 nm (about 23 mW) as well as 488 nm (about 24 mW) lines of an external Ar laser were also used. The laser beam was focused on a spot of about 1 μm in diameter, the spectral resolution being 0.5, 0.7, and 1 cm⁻¹, respectively, or better.

The Raman spectrum of graphene is a clearly established fingerprint of this 2D material (see [10]). The main first-order features in the Raman spectra of graphene and defect-infested graphene excited at 633 nm wavelength are the following:(i)G band (~1582 cm⁻¹) is the only band in graphene allowed by selection rules for first-order Raman effect; it is ascribed to optical (iTO and LO) doubly degenerate phonons of E_2g symmetry at the Γ point (initially described by Tuinstra and Koenig [11]).(ii)D band (~1330 cm⁻¹) is due to breathing-like bands of C hexagonal rings (corresponding to transverse optical phonons near the K point) and requires a defect for its activation via an intervalley double-resonance Raman process (see [12]).(iii)D’ band (at about 1615 cm⁻¹; defect induced similarly to the D band) occurs via an intravalley double-resonance process (see, e.g., [13]).(iv)D” band (at about 1145 cm⁻¹) is resulting from double-resonance intervalley scattering of LA phonons on defects (see [14]). The intensity of this band should be about 100 times lower than that of the D band.

Overtones and combination bands:(i)2D band (historically known from graphite and carbon nanotube-related literature as G’- peak) appears at about 2648–2665 cm⁻¹. It is clearly shown [15–20] that the shape and width of the 2D band can be used for the identification of the mono-, bi-, and three-layered graphene.(ii)The overtone of the D’- peak (2D’) and combination G (phonons), as well as (D+D’) bands, occur around 3230, 2450, and 2930 cm⁻¹, respectively (see [21]).

3. Results and Discussion

Two areas with different surface morphologies are observed by optical microscopy (Figure 1(a)): a clear relief (ridge-like formations) lying along <001> directions covers the first area denoted as DLC while the second area (denoted as αC) is covered by an inhomogeneous film with a constant depth. It should be also mentioned that optical inhomogeneities are observed on the DLC as well as αC-marked areas.
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(e)Figure 1Optical microscopy image of the surface morphology of (a) as-deposited graphene and graphene-related phases on diamond-like carbon (DLC) and amorphous carbon (αC) interlayers. The arrows remarked [100] and [010] directions of the Si substrate. The marker represents 20 μm. (b) The exfoliated and transferred graphene flakes on 320 nm SiO₂. The Raman spectra are taken from “+”-marked positions. The marker represents 30 μm. (c) The layers remaining on the surface of the substrate after exfoliation by Scotch tape. The Raman spectra are taken from the “+”-marked positions near points 1, 2, and 3. The marker represents 30 μm. (d) The exfoliated and transferred graphene flakes on glass substrate. The Raman spectra are taken from the “+”-marked positions near points 1 and 2. The marker represents 20 μm. (e) A graphene flake on air bubble near the epoxy resin surface. The Raman spectra are taken from the square-marked position. The marker represents 20 μm.

It should be recalled that the Raman spectrum (excited at 633 nm laser wavelength) taken from αC- and DLC-denoted areas (see [8]) contains all features typical for graphene: symmetric and clearly pronounced 2D band with full width at a half maximum (FWHM) of 40–56 cm⁻¹, I_2D/I_G ratio between 2 and 3.5, and I_2D/I_D ratio between 2 and 4. However, the 2D band appears at about 2660–2668 cm⁻¹ (for single- and bilayered graphene, respectively), that is, it is blueshifted by about 20 cm⁻¹ relative to the results presented in [15, 22, 23].

Due to the double-resonance origin of most of the monitored spectral features, we perform a Raman spectroscopy examination of as-deposited defected graphene at 488, 514, and 633 nm excitation wavelengths and the results are presented in Figure 2. The 2D bands are blueshifted by about 20 cm⁻¹ and can be typically deconvoluted into (a) a single Lorentzian with FWHM of about 40-41 cm⁻¹ (see Figure 3(a)); (b) four Lorentzians (FWHM of 22 (±1) cm⁻¹) for 2D band with total width of 45–56 cm⁻¹ (see Figure 3(b)); and (c) six Lorentzians (Figure 3(c)) for 2D band with total width larger than 56 cm⁻¹. The results of the deconvolution indicate the presence of single-, bi-, and three-layered defected graphene, respectively (see [15–20]). We did not establish a clear difference between the graphene layers deposited on αC and DLC interlayers; however, bi- and three-layered areas were more frequently observed on DLC interlayers. The results for predominantly single-layered (SL) and bilayered (BL) defected graphene (according to the deconvolution of 2D bands) are summarized in Table 1.

Figure 2Raman spectra taken from as-grown films excited at 633 nm (red trace), 514 nm (blue trace), and 488 nm (green trace) laser wavelengths.
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(c)Figure 3Deconvolution of 2D band identified as coming from single-layered (a), bilayered (b), and three-layered defected graphene deposited on αC. The spectrum is excited at 633 nm laser wavelength.Table 1Summarized results of Raman spectroscopy examination of as-deposited defected graphene films.

In order to access the interlayers as well as graphene flakes for Raman examination, the so-called Scotch tape method was initially used for exfoliation. The Raman spectra of the graphene flakes exfoliated in this way with some occasional amorphous (αC) interlayers transferred to Si/SiO₂ (300 nm) or glass substrate are shown in Figures 4 and 5, respectively.

Figure 4The Raman spectrum of defected 1-2-layered graphene transferred on 320 nm SiO₂. The 2D band is symmetric and appears at 2658-2659 cm⁻¹ with FWHM of 38–40 cm⁻¹ (measured in point 2) and 40–42 cm⁻¹ (measured in point 1).

Figure 5The Raman spectrum of the interlayer (point 1, Figure 1(c)) of αC after exfoliation by Scotch tape. The features observed at about 1450 and 1530 cm⁻¹ are typical for C₇₀ fullerenes.

A lot of flakes (of the order of 10²) were transferred on Si/SiO₂ and examined by Raman spectroscopy. The Raman spectra are enhanced due to interference effects caused by the SiO₂ 300 nm layer over the Si substrate, and I_2D/I_G varies in the range 3.5-6.0. However, it was impossible to isolate single-layered graphene flake (or to obtain clear Raman response of single-layered graphene) in this way. The exfoliated flakes were never transparent (see point 1 in Figure 1(b)). The best spectra were recorded from the points in a darker contrast (point 2 in Figure 1(b)), but the FWHM of 2D Raman band remains >35 cm⁻¹. Moreover, the D” band slightly overlaps with the second order of Si substrate when the spectrum is excited at 514 as well as 488 nm laser wavelengths.

After peeling the tape off the specimen, the interlayer between the upper flake and the substrate is accessed. The remaining interlayers have different optical contrasts (see Figure 1(c)) and Raman spectra: the spectrum of typically retained interlayer (point 1 in Figure 1(c)) in Figure 5 is very similar to that of turbostratic graphite (see [24]), but weak peaks of C₇₀ fullerenes (the features observed at about 1450 and 1530 cm⁻¹ (see [25, 26])) are also clearly distinguished (Figure 5). The strong modes of fullerenes C₇₀ at about 1180 and 1568 cm⁻¹ are merged with D” and G bands.

The Raman spectra (Figure 6) taken from points 2 and 3 (Figure 1(c)) are similar as they contain the most prominent modes of C₇₀ peaks at 1160, 1220, 1454, 1526, and 1565 cm⁻¹ [25, 26], nanodiamond (Nd) peaks at 1330 and 1620 cm⁻¹ (see [27]), and turbostratic graphite. The D, G, and D’ bands are found at 1335, 1590, and 1612 cm⁻¹, respectively, but in a different proportion: the spectrum from point 3 is dominated by the peaks of C₇₀ and Nd while the spectrum from point 2 is dominated by turbostratic graphite (see Figure 6). It should be also remarked that features of C₆₀ fullerenes (see, e.g., [25, 26]) were not observed.

Figure 6Raman spectra of the interlayer that remains on the substrate after exfoliation by the Scotch tape method taken from points 2 and 3 (Figure 1(c)).

As it was mentioned above, the D” band overlaps with the second-order band of Si substrate especially when the spectrum is excited at 488 and 514 nm laser wavelengths. In order to distinguish the dispersion of the D” band of several Scotch tape methods, exfoliated flakes were transferred on glass substrates. The flakes have very similar surface morphology to those transferred on SiO₂/Si substrates (Figure 1(d)). The Raman spectrum of such flakes is not significantly different from that of the as-deposited layers (Figure 7); however, the D” band appears at 1096 (for 488 nm excitation) and at 1135 cm⁻¹ (for 633 nm excitation), respectively, that is, they coincide with the data of Herziger et al. [14].

Figure 7The Raman spectra of as-grown graphene on αC excited at 488 nm (green trace) and 633 nm (black trace) wavelengths. The similar spectra of exfoliated graphene transferred on a glass substrate excited at 488 nm (blue trace) and 633 nm (red trace). The inset: magnified part of the region 900–1200 cm⁻¹.

According to the above results, we conclude that the exfoliation by the Scotch tape method does not enable splitting up between the defected graphene and the interlayers (especially the αC-designated one). Another way for exfoliation was probed (by exfoliation on epoxy resin), and the optical micrograph image of the area of the edge of a resin bubble and the Raman spectrum taken from this area (excited at 633 nm) are shown in Figures 1(e) and 8, respectively. The Raman spectrum of epoxy resin does not contain any features in the 2D region of graphene (upper trace in Figure 8); hence, 2D bands of a single- and bilayered graphene were identified at the edge of a lot of bubbles on the surface of the resin (Figure 1(e)). It should be clearly remarked that the measured FWHM of the 2D band of such single-layered graphene is about 27–29 cm⁻¹, but it is situated at 2654–2656 cm⁻¹, that is, it remains upshifted with about 10–15 cm⁻¹.

Figure 8Raman spectra of graphene films situated on air bubbles/cavities. The 2D band is situated at 2655 cm⁻¹ and has FWHM ~28 cm⁻¹ (i.e., it corresponds to single-layered graphene—blue trace).

Recently, Li et al. [28] established that the intensity of 2D band varies as a cosine to the fourth power when the laser propagation direction is parallel to the graphene layer and the polarization is rotated around it. They also derived the orientation distribution function of monolayered graphene as well as that of graphene paper and highly oriented pyrolytic graphite. We perform similar measurements in X(Y_φY_φ)X geometry, φ being the angle between the incident laser beam polarization and the graphene layer plane; Z is the axis perpendicular to the graphene plane, and the laser beam propagates transversely to the graphene layer along the X direction (see Figure 9(a)). The excitation laser beam was focused in a manner to comprise no more than 30% of the edge of the Si substrate and graphene film (Figure 9(a)). The parallel scattering geometry was used. The measurements were performed starting from φ = 0° (corresponding to X(YY)X in Porto notations) and finished at φ = 180°. The preliminary results of these rotational angle-dependent Raman measurements of as-deposited specimen are presented in Figure 9. The signal significantly drops upon changing the angle from 0° to 90° and increases again in the interval between 90 and 180° which resembles indeed the cos⁴ law. At 90° (corresponding to X(ZZ)X in Porto notations), the Raman signal is very weak but still observable (Figure 9), and the rotational angle-independent features of C₇₀ fullerenes and nanodiamond (Nd) dominate the spectrum. The residual features in the Raman spectra taken at φ = 90° point out that the measured polarized Raman spectra are taken from graphene deposited on DLC interlayer. The measurements in this scattering geometry (X(YY)X in Porto notations) access measurements of the interlayer/s without exfoliation. On the other hand, the polarized Raman study confirms the deposition of graphene because the intensities of the most prominent Raman features of graphite (D, G, and 2D bands) show similar behavior in similar conditions as those of graphene. However, the intensity of the Raman features of graphene decreases significantly slower than those of graphene as it is shown in [28].
(a)
(b)
(a)
(b)Figure 9(a) Optical photography of the specimen in X(YY)X geometry (in Porto notations). The inset: optical photography of the specimen in Z(YY)Z geometry (in Porto notations). The arrow-remarked laser spots are eye guide showing the real area of the laser spot during measurements. The marker represents 10 μm. (b) Spatially resolved Raman spectra of as-deposited defected graphene at 633 nm excitation.

It is worth noting that the 2D band from the single-layered graphene regions is symmetric and strong, but it is somewhat broadened with FWHM of about 40–42 cm⁻¹and is blueshifted by 15–20 cm⁻¹ in as-grown specimens. It is well known that such behavior is usually related to strain (see [29–32]) and doping [33]. Moreover, Lee et al. [34] and Bouhafs et al. [35] experimentally studied the influence of these parameters on the position and FWHM of G and 2D bands in single- and bi-/multilayered graphene, respectively. The deduced simple plot of the 2D versus G band positions enables distinguishing the influence of doping and strain on the positions of G and 2D bands. In our single-layered specimens, the G band is slightly uphifted by 1-2 cm⁻¹ while the 2D band is more significantly blueshifted and broadened by 10–20 cm⁻¹. Therefore it can be assumed that the 2D band blueshift and broadening are due to the lattice strain predominantly as well as to the doping. It can be suggested that the lattice strain is due to the bonding between graphene and the interlayers while the doping should be related to charge transfer from the interlayers/interfaces to graphene as well as to different intrinsic (grain boundaries, etc.) and extrinsic (trapped nitrogen, oxygen, and impurities during the deposition) defects, that is, it can be related to the influence of the interlayers/substrates as well as of the deposition process.

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4. Conclusions

We extended the analysis of defected graphene deposited by CVD as well as the two types of interlayers between the defected graphene layer/s and Si substrates by both unpolarized and polarized Raman spectroscopy. The performed Raman spectroscopy examination of as-deposited defected graphene at 488, 514, and 633 nm excitation wavelengths enables the most of the monitored spectral features of double-resonance origin (D, D”, and 2D bands). The Raman studies of exfoliation by the so-called Scotch tape method revealed that (a) the composition of the designated DLC interlayers varies with depth: the initial layers on the Si substrate consist of a mixed phase of turbostratic graphite, nanodiamond/diamond-like carbon, and C₇₀ fullerenes while the upper ones are dominated by diamond-like carbon and some C₇₀ fullerenes and (b) the amorphous carbon interlayer is dominated by turbostratic graphite and contains a larger quantity of C₇₀ than the DLC-designated interlayers. Single- and bilayered defected graphene flakes were exfoliated on epoxy resin. The preliminary results of polarized Raman experiments show that the intensity of the 2D band varies as a cosine to the fourth power when the laser propagation direction is parallel to the graphene layer and the polarization is rotated around it which is an additional indication of the deposition of single-layered graphene. The results of Raman spectroscopic studies of as-grown and exfoliated graphene films tend to assume that the observed slight upshift of the 2D band as well as the broadening of 2D band is due to the strain and can be related to the bonding between the graphene and the interlayers, that is, it could be regarded as an influence of the interlayers between the defected graphene and the Si substrates.

Conflicts of Interest

The authors declare that there is no conflict of interest regarding the publication of this paper.

References

1. А. Ferrari, F. Bonaccorso, V. Fal’ko et al., “Science and technology roadmap for graphene, related two-dimensional crystals, and hybrid systems,” Nanoscale, vol. 7, pp. 4598–4810, 2015.View at: Publisher Site | Google Scholar
2. K. S. Kim, Y. Zhao, H. Jang et al., “Large-scale pattern growth of graphene films for stretchable transparent electrodes,” Nature, vol. 457, pp. 706–710, 2009.View at: Publisher Site | Google Scholar
3. A. Reina, X. Jia, J. Ho et al., “Large area, few-layer graphene films on arbitrary substrates by chemical vapor deposition,” Nano Letters, vol. 9, pp. 30–35, 2009.View at: Publisher Site | Google Scholar
4. C. Berger, Z. Song, T. Li et al., “Ultrathin epitaxial graphite: 2D electron gas properties and a route toward graphene-based nanoelectronics,” The Journal of Physical Chemistry, vol. 108, pp. 19912–19916, 2004.View at: Publisher Site | Google Scholar
5. C. Berger, Z. Song, T. Li et al., “Electronic confinement and coherence in patterned epitaxial graphene,” Science, vol. 312, pp. 1191–1196, 2006.View at: Publisher Site | Google Scholar
6. R. Muñoz and C. Gómez-Aleixandre, “Review of CVD synthesis of graphene,” Chemical Vapor Deposition, vol. 19, pp. 297–322, 2013.View at: Publisher Site | Google Scholar
7. T. I. Milenov, I. Avramova, E. Valcheva, and S. S. Tinchev, “Deposition of graphene/graphene-related phases on different substrates by thermal decomposition of acetone,” Optical & Quantum Electronics, vol. 48, p. 135-1-12, 2016.View at: Google Scholar
8. T. I. Milenov, I. Avramova, E. Valcheva et al., “Deposition of defected graphene on (001) Si substrates by thermal decomposition of acetone,” Superlattices and Microstructures, In press.View at: Publisher Site | Google Scholar
9. K. S. Novoselov, D. Jiang, F. Schedin et al., “Two-dimensional atomic crystals,” PNAS, vol. 102, pp. 10451–10453, 2005.View at: Google Scholar
10. A. C. Ferrari and D. M. Basko, “Raman spectroscopy as a versatile tool for studying the properties of graphene,” Nature Nanotechnology, vol. 8, pp. 235–246, 2013.View at: Publisher Site | Google Scholar
11. F. Tuinstra and J. L. Koenig, “Raman spectrum of graphite,” The Journal of Chemical Physics, vol. 53, pp. 1126–1130, 1970.View at: Publisher Site | Google Scholar
12. C. Thomsen and S. Reich, “Double resonant Raman scattering in graphite,” Physical Review Letters, vol. 85, pp. 5214–5217, 2000.View at: Publisher Site | Google Scholar
13. A. C. Ferrari, “Raman spectroscopy of graphene and graphite: disorder, electron–phonon coupling, doping and nonadiabatic effects,” Solid State Communications, vol. 143, pp. 47–57, 2007.View at: Publisher Site | Google Scholar
14. F. Herziger, C. Tyborski, O. Ochedowski, M. Schleberger, and J. Maultzsch, “Double-resonant LA phonon scattering in defective graphene and carbon nanotubes,” Physical Review B, vol. 90, p. 245431-1-6, 2014.View at: Google Scholar
15. A. C. Ferrari, J. C. Meyer, V. Scardaci et al., “Raman spectrum of graphene and graphene layers,” Physical Review Letters, vol. 97, pp. 187401–187404, 2007.View at: Google Scholar
16. L. M. Malard, M. A. Pimenta, G. F. Dresselhaus, and M. S. Dresselhaus, “Raman spectroscopy in graphene,” Physics Reports, vol. 473, pp. 51–87, 2009.View at: Publisher Site | Google Scholar
17. A. K. Gupta, T. J. Russin, H. R. Gutiérrez, and P. C. Eklund, “Probing graphene edges via Raman scattering,” ACS Nano, vol. 3, pp. 45–52, 2009.View at: Publisher Site | Google Scholar
18. Y. Hao, Y. Wang, L. Wang et al., “Probing layer number and stacking order of few‐layer graphene by Raman spectroscopy,” Small, vol. 6, pp. 195–200, 2010.View at: Publisher Site | Google Scholar
19. S. Chen, W. Cai, R. D. Piner et al., “Synthesis and characterization of large-area graphene and graphite films on commercial Cu–Ni alloy foils,” Nano Letters, vol. 11, pp. 3519–3525, 2011.View at: Publisher Site | Google Scholar
20. J. U. Lee, N. M. Seck, D. Yoon, S. M. Choi, Y. W. Son, and H. Cheong, “Polarization dependence of double resonant Raman scattering band in bilayer graphene,” Carbon, vol. 72, pp. 257–263, 2014.View at: Publisher Site | Google Scholar
21. V. N. Popov and P. Lambin, “Theoretical polarization dependence of the two-phonon double-resonant Raman spectra of graphene,” European Physical Journal B, vol. 85, p. 418, 2012.View at: Google Scholar
22. P. Klar, E. Lidorikis, A. Eckmann, I. A. Verzhbitskiy, A. C. Ferrari, and C. Casiraghi, “Raman scattering efficiency of graphene,” Physical Review B, vol. 87, p. 205435-1-12, 2013.View at: Google Scholar
23. P. Poncharal, A. Ayari, T. Michel, and J.-L. Sauvajol, “Raman spectra of misoriented bilayer graphene,” Physical Review B, vol. 78, p. 113407-1-4, 2008.View at: Google Scholar
24. P. H. Tan, C. Y. Hu, J. Dong, W. C. Shen, and B. F. Zhang, “Polarization properties, high-order Raman spectra, and frequency asymmetry between Stokes and anti-Stokes scattering of Raman modes in a graphite whisker,” Physical Review B, vol. 64, p. 214301-1-12, 2001.View at: Google Scholar
25. K. A. Wang, P. Zhou, A. M. Rao, P. C. Eklund, R. A. Jishi, and M. S. Dresselhaus, “Intramolecular-vibrational-mode softening in alkali-metal-saturated C70 films,” Physical Review B: Condensed Matter, vol. 48, pp. 3501–3506, 1993.View at: Publisher Site | Google Scholar
26. P. M. Rafailov, V. G. Hadjiev, H. Jantoljak, and C. Thomsen, “Raman depolarization ratio of vibrational modes in solid C 60,” Solid State Communications, vol. 112, pp. 517–520, 1999.View at: Publisher Site | Google Scholar
27. S. Prawer, K. W. Nugent, D. N. Jamieson, J. O. Orwa, L. A. Bursill, and J. L. Peng, “The Raman spectrum of nanocrystalline diamond,” Chemical Physics Letters, vol. 332, pp. 93–97, 2000.View at: Publisher Site | Google Scholar
28. Z. Li, R. J. Young, I. A. Kinloch et al., “Quantitative determination of the spatial orientation of graphene by polarized Raman spectroscopy,” Carbon, vol. 88, pp. 215–224, 2015.View at: Publisher Site | Google Scholar
29. M. Mohr, J. Maultzsch, and C. Thomsen, “Splitting of the Raman 2 D band of graphene subjected to strain,” Physical Review B, vol. 82, p. 201409-1-4 R, 2010.View at: Google Scholar
30. O. Frank, M. Mohr, J. Maultzsch et al., “Raman 2D-band splitting in graphene: theory and experiment,” ACS Nano, vol. 5, pp. 2231–2239, 2011.View at: Publisher Site | Google Scholar
31. V. N. Popov and P. Lambin, “Theoretical 2 D Raman band of strained graphene,” Physical Review B, vol. 87, p. 155425-1-7, 2013.View at: Google Scholar
32. V. N. Popov and P. Lambin, “Theoretical Raman intensity of the G and 2D bands of strained graphene,” Carbon, vol. 54, pp. 86–93, 2013.View at: Publisher Site | Google Scholar
33. A. Das, S. Pisana, B. Chakraborty et al., “Monitoring dopants by Raman scattering in an electrochemically top-gated graphene transistor,” Nature Nanotechnology, vol. 3, pp. 210–215, 2008.View at: Publisher Site | Google Scholar
34. J. E. Lee, G. Ahn, J. Shim, Y. S. Lee, and S. Ryu, “Optical separation of mechanical strain from charge doping in graphene,” Nature Communications, vol. 3, p. 1024-1-8, 2012.View at: Google Scholar
35. C. Bouhafs, A. A. Zakharov, I. G. Ivanov et al., “Multi-scale investigation of interface properties, stacking order and decoupling of few layer graphene on C-face 4H-SiC,” Carbon, vol. 116, pp. 722–732, 2017.View at: Publisher Site | Google Scholar

Authors: T. I. Milenov,¹ E. Valcheva,² and V. N. Popov²