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Microwave-assisted synthesis of graphene quantum dots and nitrogen-doped graphene quantum dots: Raman characterization and their optical properties
摘要： In this report we will present completely new results on the improvement of the graphene quantum dots (GQDs) and nitrogen-doped graphene quantum dots (N-GQD) production method, using the microwave with different power levels and durations, from citric acid and urea. This is a new and unprecedented method of fabrication. The use of microwave has allowed ultra-fast fabrication of GQDs and nitrogen doped GQDs. These GQDs had their characteristics identi?ed by Raman scattering spectra for the characteristic C–C graphene vibration mode (G-peak) and defects of GQDs (D-peak). The absorption spectra of GQDs samples were fabricated under different conditions, with the expectation of different sizes, to be compared and analyzed. These absorption spectra were also compared with those of the N-GQD produced under the same conditions. The absorption mechanism of GQDs and N-GQD will be presented in detail. Measurements of the photoluminescence (PL) spectra in GQDs and N-GQD have also been recorded and analyzed. The ?uorescence mechanism will be presented, explained, and compared with other international publications of other authors. Some of the TEM and HR-TEM images of these two samples were also presented to con?rm the shape, size and in-plane spacing lattice of the GQD structure.
关键词： graphene quantum dots (GQDs),PL spectra,nitrogen-doped graphene quantum dots (N-GQD),microwave,Raman spectra,absorption spectra
更新于2025-11-19 16:56:42
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Polycrystal Synthesis, Crystal Growth, Structure, and Optical Properties of AgGaGe <sub/><i> <i>n</i> </i> </sub> S <sub/> 2( <i> <i>n</i> </i> +1) </sub> ( <i>n</i> = 2, 3, 4, and 5) Single Crystals for Mid-IR Laser Applications
摘要： AgGaGenS2(n+1) crystal is a series of quaternary for mid-IR laser applications of nonlinear optical materials converting a 1.064 μm pump signal (Nd:YAG laser) to 4?11 μm laser output, but only AgGaGeS4 has attracted the most attention, remaining the other promising AgGaGenS2(n+1) crystal whose physicochemical properties can be modulated by n value. In this work, AgGaGenS2(n+1) (n = 2, 3, 4, and 5) polycrystals are synthesized by vapor transport and mechanical oscillation method with di?erent cooling processes. High-resolution X-ray di?raction analysis and re?nement have revealed that all the four compounds are crystallized in the noncentrosymmetric orthorhombic space group Fdd2, resulting in the excellent nonlinear optical property, and the distortion of tetrahedron with the variation of n value causes the discrepancy of physicochemical property. Besides, using the modi?ed Bridgman method, AgGaGenS2(n+1) single crystals with 15 mm diameter and 20?40 mm length have been grown. We have discussed the structure and composition of AgGaGenS2(n+1) by XPS spectra and analyzed the three kinds of vibration modes of tetrahedral clusters by the Raman spectra. The Hall measurement indicates that the AgGaGenS2(n+1) single crystals are p-type semiconductor, and the carrier concentration decreases with the increasing n value. All the transmittances of as-grown AgGaGenS2(n+1) samples exceeds 60% in the transparent range, especially the transmittance of AgGaGe2S6, is up to 70% at 1064 nm, and the band gap of as-grown crystal increases from 2.85 eV for AgGaGe2S6 to 2.92 eV for AgGaGe5S12. After a thermal annealing treatment, the absorptions at 2.9, 4, and 10 μm have been eliminated, and the band gap changed into the range of 2.89?2.96 eV.
关键词： Hall measurement,nonlinear optical materials,thermal annealing treatment,vapor transport,AgGaGenS2(n+1),Bridgman method,Raman spectra,mid-IR laser applications,XPS spectra,mechanical oscillation method
更新于2025-11-14 15:27:09
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Solvation structures formed in the MgCl2:AlCl3-dimethoxyethane system: A look through Raman and IR spectroscopies
摘要： A concentration-dependent vibrational spectroscopic study is carried out for the 1:1 MgCl2:AlCl3-DME system and detailed information on the precursor and the electrochemically active species formed in this rechargeable Mg battery electrolyte are presented for the first time in solution. An equilibrium between trans-[MgCl2(DME)2] and cis-[MgCl2(DME)2] isomers is proposed as well as the formation of [Mg2(μ-Cl)2]2+ and [AlCl4]- by using Raman and IR spectroscopies. The combination of the quantitative analysis made at the CO stretching region of DME with the spectral trend exhibited in low wavenumber suggests the existence of the [Mg2(μ-Cl)2(DME)4]2+ complex, similar to structure previously resolved by X-ray diffraction, in which two [AlCl4]- anions maintain the neutrality of the system.
关键词： Mg battery electrolytes,IR spectra,Raman spectra,Solution chemistry
更新于2025-09-23 15:23:52
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Characterization, optical and luminescence features of cobalt ions in multi-component PbO Al2O3TeO2GeO2SiO2 glass ceramics
摘要： Glass ceramics of the composition PbOeAl2O3eTeO2eGeO2eSiO2 doped with CoO (ranging between 0 and 1.0 mol %) were prepared by melt quenching technique followed by heat treatment. The techniques such as XRD, SEM, EDS and DTA were employed for the characterization of the prepared samples. Conventional spectroscopic studies viz., optical absorption, photoluminescence, FTIR and Raman were also performed on these samples. The optical absorption spectra of the titled glass ceramics exhibited two principal absorption bands, one at about 594 nm and the second one consisting of multiplets with the meta centre at about 1455 nm ascribed to the 4A2 (4F) → 4T1 (4P) and 4A2 (4F) → 4T1 (4F) transitions of tetrahedrally coordinated Co2+ ions, respectively. Besides these, the spectra also exhibited two feeble bands at about 532 and 643 nm which are the characteristics of octahedrally coordinated Co2+ and Co3+ ions, respectively. Using Tanabe Sugano diagram the crystal field splitting parameter Dq, Racah parameters B, C and nephelauxetic ratio, β were evaluated for Co2+ ions. The photoluminescence spectra of the titled glass ceramics have exhibited two broad emission bands at 628 and 870 nm ascribed to 4T1 (4P) → 4A2 (4F) and 4T1 (4P) → 4T2 (4F) tetrahedral transitions of Co2+ ions, respectively. FTIR and Raman spectra of the titled samples exhibited various asymmetrical and symmetrical vibrational bands due to viz., silicate, germanate, PbO4, PbO6, AlO6, TeO4, TeO3 and CoIIIeO vibrations in the glass ceramic matrix. The spectroscopic investigations on the titled glass ceramics have revealed that if CoO is present in small quantities the cobalt ions predominantly occupy the octahedral sites in the glass network, whereas the tetrahedrally coordinated Co2+ ions are found to increase if the concentration of nucleating agent CoO is gradually increased up to 1.0 mol%. As a result the degree of depolymerization of the glass network decreases which in turn enhances its rigidity with increasing the concentration of nucleating agent CoO. From these investigations we report that the glass ceramics doped with 1.0 mol% of CoO are suitable for insulating devices as well as for photonic devices.
关键词： Photoluminescence,Raman spectra,XRD,Multi-component glass ceramics,SEM,Optical absorption,Cobalt ions
更新于2025-09-23 15:23:52
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Influence of Sm2O3 Ion Concentration on Structural and Thermal Modification of TeO2-Na2O Glasses
摘要： The effect of Sm+3 ions concentration doped TeO2-Na2O glasses on structural and thermal parameters have been discussed. Glass samples with molar composition (80-x) TeO2-20Na2O-xSm2O3 glasses (x=0, 0.3, 0.6, 1, 1.2, 1.5) are prepared by melt quenching technique. Crystallization temperature (Tc), melting temperature (Tm) and glass transition temperature (Tg) are measured by using differential thermal analysis (DTA), it is found that the stability factor (ΔT) increases from (58.5-97.8) oC with the increasing of Sm2O3. The amorphous phase nature of the glass samples are observed by using X-ray diffraction (XRD), scanning electron microscopy (SEM) and energy dispersive x-ray (EDX) spectrometer are applied to study the structural properties of the glass samples. Values of density (ρ), molar volume (VM), and ionic packing density (Vt) were calculated for each of the glass compositions. The effect of the Sm2O3 on the glass structure have been investigated by using FTIR and Raman spectroscopies, the FTIR spectra are characterized by a band of 637 cm-1 for the telluride glass, high frequency peak at 668 cm-1 presented by Raman spectra which indicates that these glasses network are basically consists of TeO4 and TeO3/TeO3+1 structural units. The spectra of Raman shows the presence of Sm-O bond, Na-O bond, Te-O-Te bridging configurations, vibrations of Te-O-Te bonds and stretching modes of non-bonding oxygen found on the TeO3/TeO3+1 structural unit.
关键词： Telluride glass,FTIR,Raman spectra,Rare Earth,Glass transition
更新于2025-09-23 15:22:29
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Diamond nanofeathers
摘要： This paper reports a special diamond nanostructure which we call diamond nanofeathers (DNFs). The nanostructure was discovered after electrochemically etching doped nanocrystalline diamond (NCD) films. With high resolution SEM, we have repeatedly observed highly porous, fractal-like geometry with “shafts”, “barbs” and “barbules” of the DNFs. A DNF has very high aspect ratio, with a height comparable to the thickness of the etched diamond film and a lateral size as small as several nanometers. This diamond nanostructure seems not to belong to either conventionally defined NCD or ultrananocrystalline diamond (UNCD). The Raman spectra tell that after the electrochemical etch, the DNFs have lower signals from the grain boundaries, compared with the Raman spectra before the etch, which suggests the pores of the DNFs was related with mass loss from the grain boundaries. Preliminary electrochemical characterization has observed more than 300× capacitance increase after the DNFs are fabricated out of a NCD film. With the specific pore size and the ease of fabrication, the DNFs could be a great material choice for supercapacitors, batteries, sensors, and solar cells etc.
关键词： Diamond nanofeathers,Supercapacitors,Nanocrystalline diamond,Raman spectra,Electrochemical etching
更新于2025-09-23 15:21:21
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Luminescence of Phosphate Glasses: P2O5-ZnO-BaF2-K2TeO3-Al2O3-Nb2O5 Doped with Sm3+ Ions for Display and Laser Material
摘要： Luminescent phosphate glasses having the composition 40P2O5-30ZnO-20BaF2-3.8K2TeO3-1.2Al2O3-5Nb2O5 in mol.% doped with 3 9 103 ppm and 4 9 103 ppm Sm2O3 were successfully prepared by a melt-quenching technique. The investigated glasses were characterized by x-ray diffraction, UV–visible–NIR, absorption, emission, and ?uorescence lifetime analysis. The radiative properties were calculated using Judd–Ofelt (J–O) spectral intensity parameters for each of the glasses, which revealed the following trend: X2 > X4 > X6. The J–O intensity parameters were used to evaluate the spontaneous emission properties including branching ratios, transition probabilities, and radiative lifetime. The value of the optical energy band gap was found to decrease with an increase in Sm3+ content, which is explained on the basis of structural changes. The calculated stimulated emission cross-section studied was high, and increased from rSE; at 1.62 lm of glasses 3.81 9 10(cid:2)21 cm2 to 4.38 9 10(cid:2)21 cm2 with increasing Sm3+ ion concentration. The structure of the glasses was investigated by computing Internuclear (cid:3) and ?eld strength F( ) and measurement of Raman spectra.
关键词： refractive index,UV–Vis–NIR,Judd–Ofelt analysis,emission cross-section,Raman spectra,Oxide glasses,density,optical energy gap
更新于2025-09-23 15:21:01
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Nonresonant Polarized Raman Spectra Calculations of Nitrogen-Doped Single-Walled Carbon Nanotubes: Diameter, Chirality, and Doping Concentration Effects
摘要： Raman spectra of nitrogen-doped single-walled carbon nanotubes are calculated using the spectral moment’s method combined with the bond polarizability model. The influence of the nanotube diameter and chirality is investigated. We also address the important question of the effect of the N-doping concentration, and we propose an equation to estimate the doping concentration from the knowledge of the tube diameter and the frequency of the radial breathing mode.
关键词： spectral moment’s method,Raman spectra,N-doping concentration,nanotube diameter,nitrogen-doped single-walled carbon nanotubes,bond polarizability model,chirality
更新于2025-09-23 15:21:01
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Microstructure property study of ZnO single crystal irradiated with 200 MeV 86Kr17+ ions
摘要： ZnO single crystal materials irradiated with 200 MeV energy 86Kr17+ ions have been analyzed by a series of theoretical calculations, Raman spectroscopy and TEM tests, etc. After irradiation by 200 MeV 86Kr17+ ions, two broad vibrational absorption peaks appeared and there is no obvious change in other characteristic peaks. By measuring the Raman spectra of the incident light perpendicular to and parallel to the z axis of the crystal, it was proved that the vibration absorption peak of 526 cm-1 ~ 600 cm-1 is caused by defects related to oxygen vacancy (VO). The experimental data fully proved that ZnO single crystal has good radiation resistance. These data are of great significance for the application of ZnO materials in various new devices in the future.
关键词： ZnO,Transmission electron microscopy,Raman spectra,86Kr17+ ions irradiation
更新于2025-09-23 15:21:01
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Phase transitions and critical phenomena of tiny grains carbon films synthesized in microwave-based vapor deposition system
摘要： Different peak trends of tiny grains carbon film have been observed under the investigations of the Raman spectroscopy and energy loss spectroscopy. Carbon films known in nanocrystalline and ultrananocrystalline diamond films are synthesized by employing microwave‐based vapor deposition system. Carbon atoms exhibit several state behaviors depending on the incurred positions of their electrons. Different morphology of tiny grains under different chamber pressure is related to different rate of arriving typical energies at/near substrate surface. Those tiny grains of carbon film, which evolved in graphitic state atoms are converted to structure of smooth elements where elongation of atoms of one‐dimensional arrays is as per exerting surface format forces along opposite poles from their centers. Such tiny grains in the film are the cause of v1 peak under the investigation of the Raman spectrum because of the enhanced propagation of input laser signals through channelized inter‐state electron gaps of elongated graphitic state atoms. Those tiny grains of carbon film, which evolved in fullerene state are the cause of v2 peak. The tiny grains related to v1 peak possess a low intensity as compared with the ones which comprised atoms having state behaviors known in their exceptional hardness. Tiny grains representing v1 peak in the Raman spectrum are also the cause of field emission characteristic of a carbon film. Different peak recordings were made for the Raman at defined positions indicating a different state of carbon atoms for a different phase of deposited tiny grains, which is in line to their energy loss spectroscopy.
关键词： field emission,tiny grains carbon films,Raman spectra,phase transition,heat energy,energy loss spectroscopy
更新于2025-09-23 15:21:01