Showing papers in "Chemical Physics Letters in 2009"
TL;DR: In this paper, the thermal stability of graphite oxides to heat treatment under ambient argon gas was investigated using X-ray diffraction, and it was found that the interlayer distances dropped off in a stepwise manner by approximately 0.1nm in relation to the annealing time.
Abstract: We investigated the thermal stability of graphite oxides to heat treatment under ambient argon gas. Using X-ray diffraction, we observed the development of three phases in the annealed graphite oxides, instead of a mono-dispersed expanded interlayer distance as in the pristine graphite oxide. We found that the interlayer distances dropped off in a stepwise manner by approximately 0.1 nm in relation to the annealing time. The three phases are related to the stepwise decrease in the interlayer distances which is attributed to the removal of water molecules, hydrogen atoms from hydroxyl groups, and hydroxyl groups in the annealed graphite oxide. These changes were confirmed using Fourier-transformed infrared spectroscopy, thermogravimetric analysis, and elemental analysis.
416 citations
TL;DR: The gas sensing properties of graphene-like nano-sheets deposited on 36° YX lithium tantalate (LiTaO3) surface acoustic wave (SAW) transducers are reported in this paper.
Abstract: The gas sensing properties of graphene-like nano-sheets deposited on 36° YX lithium tantalate (LiTaO3) surface acoustic wave (SAW) transducers are reported. The thin graphene-like nano-sheets were produced via the reduction of graphite oxide which was deposited on SAW interdigitated transducers (IDTs). Their sensing performance was assessed towards hydrogen (H2) and carbon monoxide (CO) in a synthetic air carrier gas at room temperature (25 °C) and 40 °C. Raman and X-ray photoelectron spectroscopy (XPS) revealed that the deposited graphite oxide (GO) was not completely reduced creating small, graphitic nanocrystals ∼2.7 nm in size. © 2008 Elsevier B.V.
350 citations
TL;DR: RI-JK turns out to be more robust than RIJCOSX due to an overall positive error in the total energies, however, RIJcOSX outperforms RI- JK regarding speed-ups for the largest (gly) 8 chain and maintains comparable accuracy.
Abstract: The efficiency of two approximate Hartree–Fock approaches was benchmarked. Weigend’s RI-JK algorithm is compared to the recently developed RIJCOSX technique in terms of accuracy and total wall clock times. Both methods reproduce the canonical results within the chemical accuracy of ∼kcal mol −1 . RI-JK turns out to be more robust than RIJCOSX due to an overall positive error in the total energies. However, RIJCOSX outperforms RI-JK regarding speed-ups for the largest (gly) 8 chain and maintains comparable accuracy.
293 citations
TL;DR: In this paper, the heat transfer enhancement of two water-based nanofluids was investigated under different pH values and different sodium dodecylbenzene sulfonate (SDBS) dispersant concentrations.
Abstract: The heat transfer enhancement of two water-based nanofluids was investigated under different pH values and different sodium dodecylbenzene sulfonate (SDBS) dispersant concentrations. We found that the stability of nanofluids has a good corresponding relation with thermal conductivity, the better dispersion stability behavior and the higher thermal conductivity of the nanofluids, an optimal pH value and optimal SDBS concentration can result in the highest thermal conductivity of the nanofluids. Therefore, the combined treatment with both the pH and chemical surfactant concentration was recommended to improve the heat transfer enhancement for practical applications of nanofluid.
245 citations
TL;DR: In this article, a review summarizes the knowledge gathered from various ultrafast time-resolved techniques addressing the two most discussed dark excited states (1B(u)(-) and S*).
Abstract: Excited-state dynamics of carotenoids has attracted considerable recent interest, but it has also engendered a number of controversial hypotheses. This review summarizes the knowledge gathered from various ultrafast time-resolved techniques addressing the two most discussed dark excited states (1B(u)(-) and S*). These two states have been subjects of numerous earlier studies, because while the 1B(u)(-) state was predicted by theory a long time ago but never clearly observed in experiment, the S* state is readily observed in transient absorption data, but no theoretical explanation of its origin has been available until recently. The major focus of this review is (1) the possible role of the 1B(u)(-) state in excited-state processes and (2) the origin and mechanism of formation of the S* state in carotenoids. (c) 2009 Elsevier B. V. All rights reserved. (Less)
238 citations
TL;DR: In this article, the authors demonstrate two independent non-photochemical quenching sites in vivo which depend differently on the actions of PsbS and Zx, and the first site is formed in the functionally detached major light-harvesting complex of PS II and depends strictly on PSbS.
Abstract: The regulation of light-harvesting (called non-photochemical quenching, NPQ) is an essential photoprotective mechanism active in plants. Total NPQ is dependent on PsbS, a pH-sensing protein, and on the action of the xanthophyll carotenoid zeaxanthin (Zx). Using ultrafast fluorescence on intact leaves we demonstrate two independent NPQ quenching sites in vivo which depend differently on the actions of PsbS and Zx. The first site is formed in the functionally detached major light-harvesting complex of PS II and depends strictly on PsbS. The second site is in the minor antennae of photosystem (PS) II and quenching depends on the presence of Zx.
233 citations
TL;DR: A mixture of graphene oxide and TiO2 nanocomposites was reduced photocatalytically by UV-irradiation and applied as interfacial layer between a fluorine doped tin oxide (FTO) layer and a nanocrystalline TiO 2 film.
Abstract: A mixture of graphene oxide (GO) and TiO2 nanocomposites was reduced photocatalytically by UV-irradiation and applied as interfacial layer between a fluorine doped tin oxide (FTO) layer and a nanocrystalline TiO2 film. Impedance spectra implied a decreased back-transport reaction of electrons. The graphene–TiO2 interfacial layer effectively reduced the contact between I � 3 ions in the electrolyte and FTO layer, which inhibited back-transport reaction. The introduction of graphene–TiO2 increased Voc by 54 mV and the photoconversion efficiency was improved from 4.89% to 5.26%. 2009 Published by Elsevier B.V.
231 citations
TL;DR: In this article, the latest developments, challenges and applications of TERS are discussed, focusing on tip plasmonics, single molecule detection and nanoscale chemical analysis of biological samples.
Abstract: Tip-enhanced Raman Spectroscopy (TERS) has shown promise as a tool for in situ nanoscale chemical analysis, and is also leading to a better understanding of the fundamentals of surface-enhanced Raman Spectroscopy. In this work, the latest developments, challenges and applications of TERS are discussed. The focus is on tip plasmonics, single molecule detection and nanoscale chemical analysis of biological samples.
229 citations
TL;DR: In this article, different interaction mechanisms of impurities with graphene are introduced in terms of simple models and the requirements for impurity states in the vicinity of the Fermi level and compare graphene to normal metals and semiconductors.
Abstract: In this review, we discuss adsorbate effects on the electronic properties of graphene. Firstly, different interaction mechanisms of impurities with graphene are introduced in terms of simple models. We discuss the requirements for impurity states in the vicinity of the Fermi level and compare graphene to normal metals and semiconductors. With this background, we consider realistic adsorbates based on density functional theory. Open-shell and inert impurities exhibit very different interaction mechanisms with graphene. The former interact directly with graphene, strongly hybridize or become charged, whereas inert impurities usually physisorb and substrate mediated doping effects become very important.
214 citations
TL;DR: In this paper, a generalized Poisson-Boltzmann approach that includes ionic potentials of mean force from simulation almost quantitatively matches experimental interfacial tension increments for 1 molar sodium halides and alkali chlorides and was shown to be transferable to interfacial environments and hold the potential for unravelling ion-specific effects even in biological situations involving peptidic surfaces.
Abstract: Classical force fields for molecular simulations of aqueous electrolytes are still controversial. We study alkali and halide ions at the air/water interface using novel non-polarizable force fields that were optimized based on bulk thermodynamics. In qualitative agreement with polarizable force-field simulations, ion repulsion from the interface decreases with increasing ion size. Iodide is even enhanced at the interface, which is rationalized by hydrophobic solvation at the interface, but exhibits a smaller surface propensity than in previous polarizable simulations. Surprisingly, lithium is less repelled than other cations because of its tightly bound hydration shell. A generalized Poisson–Boltzmann approach that includes ionic potentials of mean force from simulation almost quantitatively matches experimental interfacial tension increments for 1 molar sodium halides and alkali chlorides. We conclude that properly optimized non-polarizable force fields are transferable to interfacial environments and hold the potential for unravelling ion-specific effects even in biological situations involving peptidic surfaces.
208 citations
TL;DR: In this paper, a compact auxiliary basis set matched to the standard augcc-pVnZ and aug-cc- pV(n + d)Z orbital basis sets has been developed for use as resolution-of-the-identity (RI) sets in explicitly correlated F12 calculations.
Abstract: Compact auxiliary basis sets matched to the standard aug-cc-pVnZ and aug-cc-pV(n + d)Z orbital basis sets have been developed for use as resolution-of-the-identity (RI) sets in explicitly correlated F12 calculations. The resulting RI errors from using these sets have been benchmarked in calculations of atomization energies and electron affinities for a number of representative small molecules. These errors were always more than an order of magnitude smaller than the residual basis set error for a given choice of orbital basis set.
TL;DR: In this paper, it was shown that a slow quantum bath helps to sustain quantum entanglement of two pairs of Forster coupled excitons, in contrast to a Markovian environment.
Abstract: We show that quantum coherence of biomolecular excitons is maintained over exceedingly long times due to the constructive role of their non-Markovian protein-solvent environment. Using a numerically exact approach, we demonstrate that a slow quantum bath helps to sustain quantum entanglement of two pairs of Forster coupled excitons, in contrast to a Markovian environment. We consider the cross-over from a fast to a slow bath and from weak to strong dissipation and show that a slow bath can generate robust entanglement. This persists to surprisingly high temperatures, even higher than the excitonic gap and is absent for a Markovian bath.
TL;DR: In contrast with the previously accepted paradigm, it is now well established that molecular hydrogen may be contained within the nano-sized cavities of clathrates as discussed by the authors, with interesting features such as multiple cavity occupation.
Abstract: In contrast with the previously accepted paradigm, it is now well established that molecular hydrogen may be contained within the nano-sized cavities of clathrates. Specifically, water-based clathrate hydrates can host a significant amount of H 2 within hydrogen-bonded water cages, with interesting features such as multiple cavity occupation. Additionally, clathrate hydrate analogues have been demonstrated to hold hydrogen and novel hydrogen clathrate materials are continuing to be developed. This work discusses the structures, stabilities, occupancies, and dynamics of hydrogen clathrates and highlights recent developments towards hydrogen storage.
TL;DR: In this paper, a single-crystalline ZnO nanodisk and nanowires with well-developed facets have been synthesized hydrothermally and the results indicate that photocatalytic activity strongly depend on specific crystal planes.
Abstract: Uniform single-crystalline ZnO nanodisks and nanowires (thick and thin nanowires) with well-developed facets have been synthesized hydrothermally. It is demonstrated that the unique ZnO nanodisks with a high (0 0 0 1) facet population and small surface area show the best photocatalytic activity among the samples. All the samples are in the same comparable dimension and surface area regime and the design of nanodisk and nanowire reduce the effect of unwanted facet effect to a degree as minimum as possible when catalytic activity of (0 0 0 1) and { 1 0 1 ¯ 0 } facets are compared. The results indicate that photocatalytic activity strongly depend on specific crystal planes.
TL;DR: In this paper, a high temperature heat treatment study of CVD-grown graphene nanoribbons up to 2800 °C is presented, demonstrating a progressive annihilation of lattice defects as the heat treatment temperature is raised.
Abstract: We present a high temperature heat treatment study of CVD-grown graphene nanoribbons annealed up to 2800 °C, demonstrating a progressive annihilation of lattice defects as the heat treatment temperature is raised. Starting at 1500 °C, single and multiple loop formation were observed on the ribbons edges as the temperature was increased. The structural changes of the samples are documented by X-ray diffraction, Raman spectroscopy, TGA, SEM, and HRTEM. This work indicates that nanoribbon annealing eventually leads to defect-free samples, through graphitization and edge loop formation. The annealed material exhibits structural differences that could be tailored for a variety of specific applications.
TL;DR: In this article, the electronic parameters of plain 1,2,4-triazole and three isomeric forms of amino-1, 2, 4, 5 triazole have been studied at the B3LYP/6-31G(d,p) level of theory.
Abstract: The electronic parameters of plain 1,2,4-triazole and three isomeric forms of amino-1,2,4-triazole have been studied at the B3LYP/6-31G(d,p) level of theory. Their inhibitory effectiveness was investigated by means of chemical reactivity parameters and reactive centers were analyzed on the basis of Fukui indices. The solvent effect on the studied parameters was found to be insignificant. 3-amino-1,2,4-triazole (3-ATA) with preferred corrosion inhibition performance possesses two electrophilic and two nucleophilic attack centers, implying multicenter adsorption of the molecule on a metal surface. Its interaction with the Cu atom is dominated by the electron donation from the Cu atom to the carbon atom C3 and the back-donation from the amino atom N6.
TL;DR: In this paper, the binding energy between a single platinum atom and several nitrogen-doped carbon graphene structures was calculated and it was shown that the addition of nitrogen to the support can double the binding energies.
Abstract: Platinum on carbon black is a common catalyst/support combination where modifying the support can increase the durability of the catalyst. Density functional theory is used to evaluate the binding energy between a single platinum atom and several nitrogen-doped carbon graphene structures. It was calculated that the addition of nitrogen to the support can double the binding energy. This increase in binding energy is proportional to the number and proximity of nitrogen atoms to the carbon–platinum bond and is a result of the nitrogen atoms locally destabilizing the delocalized double bond present in the pure carbon structure.
TL;DR: In symmetry-adapted perturbation theory, the charge transfer energy is normally absorbed into the induction energy, but it can be treated separately as discussed by the authors, and the net contribution to hydrogen bond energies is a few kJ −1 at equilibrium, and is approximately proportional to the exchange-repulsion energy at other geometries and no more than 10% of it in magnitude.
Abstract: In Symmetry-Adapted Perturbation Theory the charge-transfer energy is normally absorbed into the induction energy, but it can be treated separately. There are two contributions: the long-range or polarization term, which ignores effects due to exchange of electrons between the interacting molecules, and an exchange term. The sum of the two is much smaller than the polarization term, by up to an order of magnitude. The net contribution to hydrogen bond energies is a few kJ mol −1 at equilibrium, and is approximately proportional to the exchange-repulsion energy at other geometries and no more than 10% of it in magnitude.
TL;DR: In this article, a red shift in V-O charge transfer (CT) with an increase in heat treatment due to increase in covalent bond interaction was found in Ln3+ ion.
Abstract: YVO4:Ln3+ (Ln3+ = Dy3+, Eu3+) nanoparticles show red shift in V–O charge transfer (CT) with increase in heat treatment due to increase in covalent bond interaction. Luminescence intensity of electric dipole transition is dominating over magnetic dipole transition indicating the asymmetric environment of Ln3+ ion. Lifetimes for 4F9/2 (Dy3+) and 5D0 (Eu3+) levels increase with heat treatment from 500 to 900 °C due to extent of reduction in non-radiative process arising from surface of particles, and similar trend is found in quantum yield study. Monoexponential and biexponential decay processes have been discussed on basis of cross-relaxation process as well as surface effect.
TL;DR: The inhibition of prostate cancer cells (PC3 and DU145) viability from tubes encapsulating cisplatin proved the efficiency of the produced delivery system, and the development of CNTs as drug containers would pave the way to their employment as nanovectors into the cells.
Abstract: Conventional administration of chemotherapeutic agents is compromised by their lack of selectivity which is the cause of a lethal effect accomplishment on healthy tissues. Since therapeutic and diagnostic agents could functionalize the structure of carbon nanotubes (CNTs), the development of CNTs as drug containers would pave the way to their employment as nanovectors into the cells. Here a study on cisplatin (Cis-Diamminedichloroplatinum (CDDP) – a platinum-based chemotherapy drug) embedding to single-wall CNTs (SWCNTs) is shown.Being sure that the anticancer drug discharge occurred, in vitro analysis have been performed. The inhibition of prostate cancer cells (PC3 and DU145) viability from tubes encapsulating cisplatin proved the efficiency of the produced delivery system.
TL;DR: In this paper, the role of different types of oxygen centers in catalytic oxidation reactions was investigated using gas-phase cluster reactivity experiments, combined with theoretical calculations, provided insight into how factors such as size, stoichiometry and charging effects influence reactions promoted by metal and metal oxide catalysts.
Abstract: Gas-phase cluster reactivity experiments, combined with theoretical calculations, provide insight into how factors such as size, stoichiometry and charging effects influence reactions promoted by metal and metal oxide catalysts. In this Letter, we describe the use of clusters to investigate the role of different types of oxygen centers in catalytic oxidation reactions. First, we focus on recent results from our laboratory concerning the oxidation of carbon monoxide by gold clusters and how the charge state of the cluster determines the mechanism of oxidation. We then discuss how radical oxygen centers in zirconium oxide clusters promote the oxidation of carbon monoxide, ethylene and acetylene and how charge state may be used to tune the selectivity of these reactions. An overview of future directions for the research is given in conclusion.
TL;DR: In this paper, the authors present a review of recent work in their laboratory examining CO oxidation kinetics on Pt-group single crystals using PM-IRAS, XPS, and mass spectrometry from low (10 −8 −10 −3 ) to high (1 −10 2 ǫ ) pressures.
Abstract: Producing a definitive picture of the CO oxidation reaction (CO + O 2 → CO 2 ) on Pt-group metals (Rh, Pd, Pt, and Ru) across the ‘pressure gap’ has proved to be a challenging task. Surface-sensitive techniques amenable to high pressure environments (e.g. PM-IRAS) have sparked a renewed interest in this reaction under realistic pressures. Here, we review recent work in our laboratory examining CO oxidation kinetics on Pt-group single crystals using PM-IRAS, XPS, and mass spectrometry from low (10 −8 –10 −3 Torr) to high (1–10 2 Torr) pressures. These studies have shown that at both low and high pressures (a) Langmuir–Hinshelwood kinetics adequately describe CO oxidation kinetics on Pt-group metals (Pt, Pd, Rh) (i.e. there is no pressure gap) and (b) the most active surface is one with minimal CO coverage. Additionally, recent investigations of high pressure CO oxidation kinetics on SiO 2 film supported Rh particles prepared in situ are discussed.
TL;DR: In this paper, phase-sensitive sum-frequency vibrational spectroscopy was used to obtain the OH and OD stretch spectra of the imaginary part of the nonlinear susceptibility, ImχS(2)(ωIR), for H2O/vapor, D2O-vapor interfaces that explicitly characterize their resonances.
Abstract: Phase-sensitive sum-frequency vibrational spectroscopy was used to obtain the OH and OD stretch spectra of the imaginary part of the nonlinear susceptibility, ImχS(2)(ωIR), for H2O/vapor, D2O/vapor, and 2:1 H2O–D2O/vapor interfaces that explicitly characterize their resonances. They all exhibit a positive and a negative resonance band in the bonded-OH region, clearly different from those deduced from fitting of the |χS(2)(ωIR)|2 spectra, and from MD simulations. The broad continuum is characteristic of inhomogeneously broadened resonances associated with interfacial water species of various hydrogen-bonding geometries and strengths. Spectral changes due to excess ions at the interfaces support the picture.
TL;DR: An improved version of the method for computing QTAIM with vectorization and parallelization of the previous algorithm, together with molecular symmetry, make the present algorithm as much as two orders of magnitude faster than the original method.
Abstract: An improved version of our method for computing QTAIM [J.I. Rodriguez, A.M. Koster, P.W. Ayers, A. Santos-Valle, A. Vela, G. Merino, J. Comput. Chem. (2009), in press, doi:10.1002/jcc.21134] is presented. Vectorization and parallelization of the previous algorithm, together with molecular symmetry, make the present algorithm as much as two orders of magnitude faster than our original method. The present method scales linearly with both system size and the number of processors. The performance of the method is demonstrated by computing the QTAIM atomic properties of a series of carbon nanotubes. Our results show that the CPU time for a QTAIM property calculation is comparable to that of a SCF-single point calculation. The accuracy of the original method is also improved.
TL;DR: This study forms an Au nanoshell-based complex designed to release single-stranded DNA from its surface when illuminated with plasmon-resonant light, and examines DNA dehybridization induced by excitation of localized surface plasmons on the nanoparticle, relative to the thermal DNA de Hybridization (melting).
Abstract: Surface-plasmon driven DNA dehybridization is a topic of intense current interest due to its highly promising potential for enabling light-controlled gene therapy: it is also of inherent interest as a light-driven nanoscale actuation process. In this study we formulate an Au nanoshell-based complex designed to release single-stranded DNA (ssDNA) from its surface when illuminated with plasmon-resonant light. This system allows us to examine DNA dehybridization induced by excitation of localized surface plasmons on the nanoparticle, relative to the thermal DNA dehybridization (melting). The dehybridization temperatures, and the percentage of DNA released per nanoparticle, differ markedly between the two processes.
TL;DR: In this paper, high quality graphene sheets were synthesized on stainless steel substrates at ∼500°C by microwave plasma chemical vapor deposition (CVD) in an atmosphere of methane/hydrogen mixture.
Abstract: High-quality graphene sheets (GS) were synthesized on stainless steel substrates at ∼500 °C by microwave plasma chemical vapor deposition (CVD) in an atmosphere of methane/hydrogen mixture. The GS product was characterized to contain mostly 1- or 2–3-layers using scanning electron microscopy, transmission electron microscopy/selective area electron diffraction, atomic force microscopy, and Raman spectroscopy. The present CVD approach is capable of producing graphenes with high yield and high purity with no carbon impurities such as carbon nanotubes.
TL;DR: In this article, a frequency-stepped WURST-QCPMG pulse sequence was used to obtain ultra-wideline NMR spectra of quadrupolar nuclei.
Abstract: Ultra-wideline NMR spectra of quadrupolar nuclei have been obtained using a frequency stepped WURST–QCPMG pulse sequence. This method offers a significant advantage over other frequency stepped techniques due to the much wider excitation bandwidth of the WURST pulses. The incorporation of proton decoupling leads to further signal enhancement in certain cases. The experiment is shown to be applicable to central and satellite transitions of half-integer quadrupoles and also to integer spin nuclei. Frequency stepped WURST–QCPMG is the most efficient way of obtaining ultra-wideline NMR spectra yet reported, and increases the opportunity to study nuclei that were previously considered inaccessible.
TL;DR: In this paper, a phase-alternated recoupling irradiation scheme (PARIS) was proposed to enhance the efficiency of magnetization transfer between different spins S such as chemically inequivalent carbon-13 nuclei.
Abstract: The efficiency of magnetization transfer between different spins S such as chemically inequivalent carbon-13 nuclei in solid samples that are spinning at high frequencies about the magic angle can be enhanced by a phase-alternated recoupling irradiation scheme (PARIS). Dipolar recoupling is assisted by a radio-frequency (rf) field applied to the abundant I ( proton) spins. In contrast to rotary resonance-based recoupling schemes, the new method does not depend critically on the rf amplitude, which need not be matched with the spinning frequency. Modest rf amplitudes suffice to bring about efficient magnetization transfer even at high spinning speeds, thus avoiding excessive sample heating. The new method compensates efficiently for rf field inhomogeneity, so that the full sample volume is used more effectively. (C) 2008 Elsevier B. V. All rights reserved.
TL;DR: In this paper, the average hydrogen bond strength and its distribution are inferred from surface sum-frequency generation (SFG) spectra through the center frequency and width, respectively, of the O-D stretch vibration of isotopically diluted HDO in H 2 O. The use of partially deuterated water prevents complications due to intramolecular vibrational coupling, which gives rise to features in the SFG spectra that are unrelated to hydrogen bonding interactions.
Abstract: We demonstrate that marked variations exist in hydrogen bonding interactions of interfacial water at different aqueous interfaces. The average hydrogen bond strength and its distribution are inferred from surface sum-frequency generation (SFG) spectra through the center frequency and width, respectively, of the O–D stretch vibration of isotopically diluted HDO in H 2 O. The use of partially deuterated water prevents complications due to intramolecular vibrational coupling, which we show gives rise to features in the SFG spectra that are unrelated to hydrogen bonding interactions. At the water–air interface, the SFG spectrum in the hydrogen-bonded region strongly resembles the bulk Raman spectrum, indicating that, at this interface, the interfacial hydrogen bonding properties are very similar to those in bulk water. In contrast, for silica–water and lipid–water interfaces, interfacial hydrogen bonding is substantially stronger, with a larger degree of heterogeneity.
TL;DR: In this paper, the authors reported measurements of the Raman spectra of graphitic g -C 3 N 4 phase using deep ultraviolet (UV, 244 nm) and near-infrared (NIR, 785 nm) light for excitation of Raman scattering.
Abstract: Here, we report measurements of the Raman spectra of graphitic g -C 3 N 4 phase, using deep ultraviolet (UV, 244 nm) and near-infrared (NIR, 785 nm) light for excitation of Raman scattering. It is demonstrated that the UV and NIR Raman spectra of g -C 3 N 4 phases are substantially different from those measured with visible Raman spectroscopy. A typical Raman spectrum of the g -C 3 N 4 phase obtained with visible Raman spectroscopy shows two main overlapping bands at 1357 and 1560 cm −1 . In contrast, UV and NIR Raman spectra of g -C 3 N 4 phase exhibit two strong peaks around 691 and 988 cm −1 . These peaks are tentatively assigned to different types of the s -triazine ring breathing modes. Strong and distinguished features of the UV and NIR Raman spectra of g -C 3 N 4 phases should provide a valuable ‘fingerprint’ for Raman spectroscopy studies of phase transition of these phases under high pressure and high temperatures.