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Tuning HOMO and LUMO of three region (UV, Vis and IR) photoluminescent nitrogen doped graphene quantum dots for photodegradation of methylene blue
摘要： Low cost, gram scale and highly N doped graphene quantum dots (NGQDs) with a broad absorption spectrum was synthesized using hydrothermal method by citric acid and urea. The obtained NGQDs possess wide absorption spectrum from ultraviolet to visible and IR range of wavelength. Optical characterization revealed that NGQDs are highly photoluminescent in three region of light (i.e. UV, Vis and IR). The average thickness is lower than 1 nm, meaning that the NGQDs are single, two or three layers of graphene. Lowest unoccupied molecular orbital (LUMO) and highest occupied molecular orbital (HOMO) of the NGQDs determined using a cyclic voltammetry (CV) method, and energy band gap was obtained ～ 1.91 eV. A mechanism of charge carrier generation, separation, transport and photodegradation of methylene blue under illumination was proposed using the energy states. Finally the effect of N concentration on the band gap of NGQDs was simulated and discussed.
关键词： HOMO,NGQD,photodegradation,Quantum ESPRESSO,LUMO,cyclic voltammetry
更新于2025-09-23 15:19:57
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Enhanced UV-Vis Photodegradation of Nanocomposite Reduced Graphene Oxide/Ferrite Nanofiber Films Prepared by Laser-Assisted Evaporation
摘要： Nanocomposite films of rGO/MFeO3 (M = Bi, La) nanofibers were grown by matrix-assisted pulsed laser evaporation of frozen target dispersions containing GO platelets and MFeO3 nanofibers. Electron microscopy investigations confirmed the successful fabrication of MFeO3 nanofibers by electrospinning Part of nanofibers were broken into shorter units, and spherical nanoparticles were formed during laser processing. Numerical simulations were performed in order to estimate the maximum temperature values reached by the nanofibers during laser irradiation. X-ray diffraction analyses revealed the formation of perovskite MFeO3 phase, whereas secondary phases of BiFeO3 could not be completely avoided, due to the high volatility of bismuth. XPS measurements disclosed the presence of metallic bismuth and Fe2+ for BiFeO3, whereas La2(CO3)3 and Fe2+ were observed in case of LaFeO3 nanofibers. High photocatalytic efficiencies for the degradation of methyl orange were achieved for nanocomposite films, both under UV and visible light irradiation conditions. Degradation values of up to 70% after 400 min irradiation were obtained for rGO/LaFeO3 nanocomposite thin layers, with weights below 10 μg, rGO platelets acting as reservoirs for photoelectrons generated at the surface of MFeO3.
关键词： MAPLE,graphene oxide,photodegradation,nanofibers,electrospinning
更新于2025-09-23 15:19:57
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Thioglycolic Acid FTIR Spectra on Ag2S Quantum Dots Interfaces
摘要： The mechanism features of colloidal quantum dots (QDs) passivation with thioglycolic acid molecules (TGA) for cases of different luminescent properties is considered using FTIR. This problem is considered based on FTIR spectra analysis for various ionic forms of TGA. Experimental TGA molecules FTIR spectra is interpreted, basing on the data on modeling of TGA vibrational modes, realized in the framework of density functional method (DFT /B3LYP/6-31+G(d)) taking into account the vibrations anharmonicity of every functional group. This approach provides a significant improvement in the agreement between the experimental and calculated data. FTIR spectra of Ag2S/TGA QDs with exciton and recombination luminescence are differ from each other and B “freeB” TGA molecules. The ν(S ? H) TGA peak (2559 cm?1) disappears in FTIR spectra of Ag2S/TGA QD samples. This fact indicates the interactions between TGA thiol group and dangling bonds of Ag2S nanocrystals. Ag2S QDs passivation with TGA molecules leads to emergence νas(COO?) (1584 cm?1) and νs(COO?) (1387 cm?1) peaks. It indicates TGA adsorption in ionic form. For Ag2S/TGA QDs with exciton luminescence we observed (a) significant low-frequency shift of νs(COO?) peak from 1388 cm?1 to 1359 cm?1 and high-frequency shift of νas(COO?) peak from 1567 cm?1 to 1581 cm?1; (b) change in the ratio of intensities of νas(COO?) and νs(COO?) vibrations. This feature is caused by the change in the symmetry of TGA molecules due to passivation of Ag2S quantum dots.For Ag2S/TGA QDs with recombination luminescence, the insignificant high-frequency shift of 7–10 cm?1 for νas (COO?) at 1567 cm?1 and low-frequency shift of 3–5 cm?1 for νs (COO?) at 1388 cm?1, probably caused by the interaction of thiol with Ag2S surface is observed. Using FTIR spectra, it was found that IR luminescence photodegradation is also accompanied by changes in the thioglycolic acid molecules, which capped Ag2S QDs. In the case of Ag2S QDs with exciton luminescence, the degradation process is non-reversible. It is accompanied by TGA photodegradation with the formation of α-thiol-substituted acyl radical (S-CH2-CO?) TGA.
关键词： photodegradation,FTIR spectra,thioglycolic acid (TGA),dimer,luminescence,Ag2S quantum dots,ionic form
更新于2025-09-23 15:19:57
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Nitrogen-doped graphene-cerium oxide (NG-CeO <sub/>2</sub> ) photocatalyst for the photodegradation of methylene blue in waste water
摘要： This study shows a facile approach for the preparation of CeO2 nanoparticles decorated with porous nitrogen-doped graphene (NG) nanosheets for effective photocatalytic degradation of methylene blue (MB). NG nanosheets were first synthesized using a hydrothermal method and then nitrogen-doped graphene-cerium oxide (NG-CeO2) was prepared through mixing of cerium nitrate with different concentrations of NG under ultrasonication followed by hydrothermal treatment. The synthesized nanocomposites were characterized using X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), transmission electron microscopy (TEM), and field emission scanning electron microscopy (FE-SEM). The photocatalytic activity of the synthesized nanocomposites was analyzed against MB dye. Results showed that the nanocomposites of NG-CeO2 have an average particle size of 20 nm. The as-prepared NG-CeO2 nanocomposites exhibited outstanding photocatalytic activity for dye degradation under visible light irradiation, which could be attributed to synergistic effects between the NG nanosheets and CeO2. The quantum of photodegradation increases with the increase of the NG content in the nanocomposites.
关键词： nitrogen-doped graphene,CeO2,methylene blue,photodegradation
更新于2025-09-23 15:19:57
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N-Doped K3Ti5NbO14@TiO2 Core-Shell Structure for Enhanced Visible-Light-Driven Photocatalytic Activity in Environmental Remediation
摘要： A novel N-doped K3Ti5NbO14@TiO2 (NTNT) core-shell heterojunction photocatalyst was synthesized by firstly mixing titanium isopropoxide and K3Ti5NbO14 nanobelt, and then calcinating at 500 °C in air using urea as the nitrogen source. The samples were analyzed by X-ray diffraction pattern (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), UV-Vis absorption spectroscopy and X-ray photoelectron spectroscopic (XPS) spectra. Anatase TiO2 nanoparticles were closely deposited on the surface of K3Ti5NbO14 nanobelt to form a nanoscale heterojunction structure favorable for the separation of photogenerated charge carriers. Meanwhile, the nitrogen atoms were mainly doped in the crystal lattices of TiO2, resulting in the increased light harvesting ability to visible light region. The photocatalytic performance was evaluated by the degradation of methylene blue (MB) under visible light irradiation. The enhanced photocatalytic activity of NTNT was ascribed to the combined effects of morphology engineering, N doping and the formation of heterojunction. A possible photocatalytic mechanism was proposed based on the experimental results.
关键词： visible-light photodegradation,core-shell structure,TiO2,K3Ti5NbO14 nanobelt
更新于2025-09-19 17:15:36
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Glucose Induced Formation of Oxygen Vacancy and Bi-Metal Co-modified Bi5O7Br Nanotubes for efficient Performance Photocatalysis
摘要： Here, we prepared Bi metal modified defective-Bi5O7Br nanotubes (Bi/Bi5O7Br-OV) by hydrothermal synthesis to be an efficient photocatalyst. The density function theory (DFT) revealed that oxygen vacancies in Bi5O7Br could form an intermediate level, which could allow electron transfer to new intermediate level, and finally move to the conduction band. The Bi/Bi5O7Br-OV nanotubes demonstrate superior photocatalytic degradation of phenol, showing 3 times higher than that of pristine Bi5O7Br. The defects and Bi endow Bi5O7Br nanotubes with abundant active sites and improve the solar absorption. The increased and more dispersed charge density allow enhanced electronic conductivity and the separation of photogenerated carriers. Furthermore, more ·OH radicals are generated during photochemical reaction, which is beneficial in improving the photocatalytic performance. This work will play significant roles and create opportunities in modifying Bi-based materials for promoting photocatalysis.
关键词： photodegradation,bismuth oxybromide,water treatment,visible light irradiation
更新于2025-09-19 17:15:36
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Preparation and characterization of bismuth oxychloride/reduced graphene oxide for photocatalytic degradation of rhodamine B under white-light light-emitting-diode and sunlight irradiation
摘要： Facile and template-free two-step synthesis of bismuth oxychloride/graphene oxide (BiOCl/GO) and bismuth oxychloride/reduced graphene oxide (BiOCl/rGO) photocatalysts for degradation of rhodamine B (RhB) under low-power white light–emitting diode (wLED) irradiation (1.6 W/cm2) and sunlight is demonstrated. These photocatalysts were characterized by transmission electron microscopy, scanning electron microscopy, energy-dispersive X-ray spectrometry, X-ray di?raction, and micro-Raman, Fourier-transform infrared, X-ray photoelectron, and UV–Vis di?use re?ectance spectroscopy. Under wLED irradiation, the prepared BiOCl/rGO photocatalysts exhibited excellent photodegradation activity toward RhB through chromophore cleavage mechanism and toward phenol in the presence of RhB with notable dye-sensitized e?ect. Through scavenging experiments, superoxide radicals were notably involved in RhB degradation. With the highest charge separation e?ciency and lowest recombination rate, the photocatalytic activity of BiOCl/rGO reached a maximum rate constant of 0.1899 min?1, 2.0 and 3.0 times higher than those of BiOCl/GO and BiOCl, respectively. In the stability study, only a slight loss (4.5%) in photodegradation was observed after BiOCl/rGO was used in ?ve cycles of photodegradation runs. Compared with commonly used photocatalyst such as TiO2 (P25), BiOCl/rGO demonstrated superior photocatalytic activity and stability under wLED irradiation for various dyestu?s (rhodamine 6 G, methylene blue, and fast green FCF) in di?erent environmental water samples (lake, pond, and sea water).
关键词： wLED-induced photodegradation,Rhodamine B,Reduced graphene oxide,Phenol,Sunlight irradiation,Bismuth oxychloride
更新于2025-09-19 17:15:36
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A facile single-pot synthesis of WO3/AgCl composite with enhanced photocatalytic and photoelectrochemical performance under visible-light irradiation
摘要： In this work, a visible-light-driven WO3/AgCl composite photocatalyst was synthesized by a facile single-pot hydrothermal method using α-Ag2WO4 and HCl as precursors. A series of WO3/AgCl composite photocatalysts were synthesized with the addition of different amount (0.5, 1.0, 1.5 and 2.0 mL) of 2 M HCl solution to α-Ag2WO4. Afterwards, the photocatalytic abilities of the WO3/AgCl composite photocatalysts were investigated towards the photodegradation of Rhodamine B (RhB) under visible-light illumination. Results show that the WO3/AgCl composite exhibits an outstanding photocatalytic activity as compared with those pure WO3 and AgCl. This enhancement may be due to the fast charge separation efficiency of the photoexcited electron-holes pairs. However, among various composites, the WO3/AgCl composite obtained with the addition of 1 mL of HCl is found to display the highest photocatalytic activity. This optimized composite shows a complete degradation of RhB within 30 min. Furthermore, the WO3/AgCl composite has an excellent photostability. Finally, a possible photocatalytic degradation mechanism of RhB degradation using WO3/AgCl composite is also proposed. Therefore, these high photocatalytic activity and stability results reveal that the WO3/AgCl composite is a promising material for wastewater treatment and other environmental remediation applications.
关键词： Photodegradation,Visible-light,WO3/AgCl composite,Photocatalysis,Rhodamine B
更新于2025-09-19 17:15:36
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The crystal structure and photocatalytic properties of a one-dimensional Zinc(II) coordination complex
摘要： [Zn(CPDC)(NO3)2] coordination complex (CP1) was synthesized using 1,2-cyclopentanedicarboxylic acid (CPDC) with Zn(NO3)2·6H2O by solution solvothermal method. The crystal structure of CP1 was characterized by power X-ray diffractograms, thermogravimetric analysis, Fourier transform infrared Spectroscopy, UV spectrophotometer and fluorescence photometer. On the basis of UV-visible and fluorescence spectroscopy, the strong absorption and photoluminescence properties were found in visible wavelength region. Furthermore, photocatalytic experiments indicated that the coordination complex might possess relatively well-done photocatalytic property and recycling stability towards the degradation of rhodamine B in aqueous solution under visible light irradiation. These results indicated that the prepared CP1 might work as a potential photocatalyst for treating the organic pollutants efficiently.
关键词： 2-cyclopentanedicarboxylic acid,Crystal,Photodegradation,1,Zinc,Rhodamine B,Coordination complex
更新于2025-09-19 17:15:36
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Hydrothermal synthesis of manganese oxide and nitrogen doped graphene (NG-MnO <sub/>2</sub> ) nanohybrid for visible light degradation of methyl orange dye
摘要： MnO2 nanoparticles and its nanocomposite with nitrogen-doped graphene (NG) have been fabricated via simple hydrothermal synthesis procedure using water as a solvent. X-ray diffraction (XRD) analysis of the as-prepared samples was used to ascertain the phase purity and crystallite size. Field emission scanning electron microscopy (FE-SEM) and transmission electron microscopy (TEM) were employed to study the surface features and particle size of the synthesised samples. The photocatalytic ability of the methyl orange (MO) dye with bare MnO2 and its hybrid with nitrogen-doped graphene (NG-MnO2) wer compared with visible light prompted degradation of the dye in absence of these catalysts. The prepared nanohybrid (NG-MnO2) showed improved photocatalytic efficacy as compared to the pure MnO2 nanoparticles. The strong ferromagnetic character of nanohybrid helps in easy separation of catalyst even with a bar magnet.
关键词： photodegradation,MnO2 nanoparticles,nitrogen-doped graphene,Methyl orange,visible light
更新于2025-09-19 17:15:36