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Defect-assisted symmetric cleavage of naphthalene sulphonic acid group in azo dyes using β-In2S3 quantum dots as visible light photocatalyst
摘要： Naphthalene sulfonic acid, which is used in the synthesis of azo dye pigments, rubber processing chemicals and pharmaceuticals, is a carcinogenic substance that pollutes water bodies. In this work, we report on the visible light-driven symmetric cleavage of naphthalene sulfonic acid group, present in methyl orange dye and its conversion into the intermediate compounds. These compounds further degrade to inorganic ions such as carbon-di-oxide, nitrates, sulfates, water, and chlorine. Complete degradation of the dye, under visible light irradiation, is attained using β-In2S3 quantum dots as photocatalyst. During homogenous precipitation process, the β-In2S3 quantum dots (~ 9 nm) self-assemble to form microflowers (~ 50 nm) with high surface-to-volume ratio. These quantum dots exhibit size-dependent, active F2g, Eg and Ag1 Raman modes with peaks at ~ 150 cm?1 (In–In stretching mode), 219 cm?1 (In–S bending mode) and 300 cm?1, corresponding to the vibrational modes of cubic phase β-In2S3. The cubic phase β-In2S3 quantum dots are photoactive under visible light exposure and releases highly oxidizing OH· radicals. They have strong band-to-band emission in ultraviolet region (~ 380 nm) and exhibit broad band defect emission with maxima at blue (~ 484 nm), green (~ 580 nm) and red (~ 600 nm) region of electromagnetic spectrum. The emission intensity from these defect energy bands, which are due to sulfur vacancy, indium interstitials and oxygen incorporation, are tuned by varying the In-to-S ratio in the sample. These defects enhance their visible light absorption coefficient and assist in improving the photocatalytic efficiency of the cubic phase β-In2S3 quantum dots. Thus, defect-assisted complete (100%) photodegradation of the azo dye is achieved using cubic β-In2S3 quantum dots with low In-to-S ratio (1:1), low mass of 20 mg and minimum irradiation time (30 min). These photocatalysts can be reused 4 times under 30-min visible light irradiation. Cubic β-In2S3 quantum dots-microflowers is a highly efficient, ecofriendly photocatalyst, which even in very low concentration can remove toxicity from the dye-contaminated water, by exposure to direct sunlight for 30 min.
关键词： Indium sulphide,Defect emission,photocatalysis,Water treatment
更新于2025-11-19 16:56:42
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Monitoring plasmonic hot-carrier chemical reactions at the single particle level
摘要： Plasmon excitation in metal nanoparticles triggers the generation of highly energetic charge carriers that - properly manipulated and exploited - can mediate chemical reactions. Single-particle techniques are key to unearth the underlying mechanisms of hot-carrier generation, transport and injection as well as to disentangle the role of the temperature increase and the enhanced near-field at the nanoparticle-molecule interface. Gaining a nanoscopic insight of these processes and their interplay could aid in the rational design of plasmonic photocatalysts. Here, we present three different approaches to monitor hot-carrier reactivity at the single-particle level. We use a combination of dark-field microscopy and photo-electrochemistry to track a hot-hole driven reaction on a single Au nanoparticle. We image hot-electron reactivity with sub-particle spatial resolution using nanoscopy techniques. Finally, we push the limits looking for a hot-electron induced chemical reaction that generates a fluorescent product, which should enable imaging of active plasmonic photocatalysis at the single-particle and single-molecule levels.
关键词： dark-field microscopy,fluorescent product,single-particle techniques,Plasmonic hot-carriers,plasmonic photocatalysis,photo-electrochemistry,nanoscopy techniques
更新于2025-11-19 16:56:42
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Visible-Light Plasmonic Enhancement of Catalytic Activity of Anisotropic Silver Nanoparticles
摘要： Synthesis of silver nanoparticles (AgNPs) in presence of copper salt (as the etchant) led to the formation of nanoparticle samples with different fractions of anisotropic particles. The proportion of anisotropic nanoparticles decreased with increase in ratio of precursor Cu salt in the preparation protocol. These AgNPs samples were found to catalyse p-nitrophenol reduction by glycerol and Fenton oxidation of methyl orange. The catalytic activity of these AgNPs samples for these reactions increased with the fraction of anisotropic nanoparticles in the catalyst samples. On conducting these reactions under cool white LED visible light, the catalytic activity of AgNPs catalyst samples increased by 2 to 3 times compared to that observed in dark. The photo-Fenton MO degradation catalytic activity obtained is among the best reported in literature. However, the order of the reaction did not change whether the reaction was conducted under visible light or in dark. Direct plasmonic catalytic mechanisms are proposed to explain the enhancement in reactivity under visible light.
关键词： Plasmonic Photocatalysis,Visible Light,Anisotropic Silver Nanoparticles
更新于2025-11-19 16:56:42
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Sensitized photochemical CO2 reduction by hetero-Pacman compounds linking a Re(I) tricarbonyl with a porphyrin unit
摘要： The hetero-Pacman architecture places two different metal coordination sites in close proximity, which can support efficient energy and/or electron transfer and allow for cooperative activation of small molecules. Herein, we present the synthesis of dyads consisting of a porphyrin unit as photosensitizer and a rhenium unit as catalytically active site, which are held together by the rigid xanthene backbone. Mononuclear [(NN)Re(CO)3(Cl)] complexes for CO2 reduction where NN represents a bidentate diimine ligand (e.g. bipyridine or phenanthroline) lack light absorption in the visible region, resulting in poor photocatalysis upon illumination with visible light. In order to improve their visible light absorption, we have focused on the incorporation of a strongly absorbing free base or zinc porphyrin unit. Resulting photocatalytic experiments showed a strong dependence of catalytic performance on both the type of photosensitizer and also the excitation wavelengths. Most notably, the intramolecular hetero-Pacman system containing a zinc porphyrin unit showed much better catalytic activity in the visible region (excitation wavelengths >450 nm) than the free base version, the corresponding mononuclear rhenium compound or an intermolecular system comprised of a 1:1 mixture of the mononuclear analogues.
关键词： photocatalysis,CO2 reduction,electron transfer,porphyrin,rhenium
更新于2025-11-19 16:56:35
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Visible light-driven photoelectrocatalytic degradation of Acid Yellow 17 using Sn3O4 flower-like thin films supported on Ti substrate (Sn3O4/TiO2/Ti)
摘要： This article reports a new method for preparing mixed valence tin oxide (Sn3O4) flower-like nanostructures using a microwave-assisted route. Thin-film Sn3O4/TiO2/Ti electrodes demonstrated highly efficient visible light driven photocatalytic degradation of monoazo acid yellow 17 (AY17) dye, reaching 95% color removal after 60 min at pH 2. Moreover, under low bias potential (0.5 V), the photoelectrocatalytic efficiency increased to 97% color removal and 83% removal of total organic carbon at a kinetic rate almost 3 times higher than in photocatalysis. Liquid chromatography mass spectrometry was used to identify intermediate formation, and oxidation performance was proposed for photocatalytic and photoelectrocatalytic degradation with no organics identified after 120 min of treatment. The results indicate that Sn3O4/TiO2/Ti photoelectrodes offer a simple, green method for wastewater treatment employing visible light source.
关键词： Dye degradation,Photoelectrocatalysis,Microwave-assisted hydrothermal synthesis,Sn3O4,Visible-light photocatalysis
更新于2025-11-19 16:56:35
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Tuning the wettability and photocatalytic efficiency of heterostructure ZnO-SnO2 composite films with annealing temperature
摘要： ZnO-SnO2 composite films were spin-coated and annealed at different temperatures. The characteristics of the films were studied by using XRD, FESEM, AFM, FT-IR and UV–Vis spectroscopy. The wetting nature of the films was assessed by observing the water contact angle by sessile drop method. It was seen that the annealing temperature had a significant role in increasing the surface roughness. This leads to a change in water contact angles which are consistent with the Wenzel state of wetting. Photodegradation of model pollutants in liquid phase (cationic methylene blue, anionic methyl orange) and solid phase (octadecanoic acid) was performed to measure the photocatalytic efficiency of the films. The enhanced photocatalytic efficiency of films annealed at higher temperatures is due to better crystallinity and formation of heterostructure that inhibits the re-combination of charge entities (electron-hole).
关键词： Roughness,Contact angles,Heterostructures,Photocatalysis
更新于2025-11-19 16:56:35
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Photocatalytic and Antimicrobial Properties of Ga Doped and Ag Doped ZnO Nanorods for Water Treatment
摘要： Water contamination is a worldwide concerning problem. Emerging contaminants have made conventional water treatment processes ineffective. This makes the search for new materials with improved physical-chemical properties for water treatment an urgent necessity. Doping metal oxides nanostructures can improve the photocatalytic degradation of contaminants and the antimicrobial activity of the material. During this process, water treatment not only involves the degradation of toxic pollutants, but also the elimination of virus and bacteria. Then, it is important to study not only the effect of a dopant in a material as photocatalyst but also the effect in its antimicrobial properties. In this work ZnO nanorods, Ga doped ZnO nanorods and Ag doped ZnO nanorods are synthesized and supported in polyethylene by a fast-hydrothermal microwave heating synthesis. Their photocatalytic performance and antimicrobial properties for water treatment were evaluated. Experiments show that Ag and Ga can improve the photocatalytic and antimicrobial properties of ZnO nanorods; the relationship between doping concentrations, with both the toxicity effect of the nanorods toward bacteria and the nanorods photocatalytic performance, is shown.
关键词： doping,water,antimicrobial,nanorods,contamination,metal oxide,photocatalysis,zinc oxide
更新于2025-11-19 16:56:35
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The coherence between TiO2 nanoparticles and microfibrillated cellulose in thin film for enhanced dispersal and photodegradation of dye
摘要： Microfibrillated cellulose (MFC) was used to enhance the dispersal and photocatalytic properties of TiO2 nanoparticles. With the small amount of MFC (0.1 wt.% or 0.3 wt.%), TEM images showed that particle agglomeration was greatly minimized due to the coherence between TiO2 nanoparticles and MFC. The surface area and pore volume of TiO2 nanoparticles was enhanced as proven in N2 adsorption-desorption analysis. Thermogravimetric and Fourier transform infrared spectra further confirmed the presence of MFC in TiO2/MFC coating solution. Using commercial adhesive, TiO2 and TiO2/MFC were spray coated on polyvinyl chloride sheet. The photocatalytic thin films were examined using scanning electron microscope with Energy dispersive X-ray analysis. The presence of MFC was not only helpful to enhance particle dispersal but also supportive to increase the hydrophilicity of the thin film. In comparison to TiO2 coating, the films were capable to adsorb 50% more methylene blue in 90 min. TiO2/MFC coatings removed 90% of methylene blue dye in 90 min under UV irradiation.
关键词： Spray coating,Photocatalysis,Dye,TiO2 nanoparticles,Microfibrillated cellulose,Adsorption
更新于2025-11-19 16:56:35
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Probing the Role of Nickle Dopant in Aqueous Colloidal ZnS Nanocrystals for Efficient Solar-Driven CO2 Reduction
摘要： Photocatalytic CO2 reduction reaction (CO2RR) on a heterogeneous catalyst offers the possibility for CO2 abatement and emerges as a promising avenue for renewable carbonaceous fuels production at ambient temperature and pressure using solar light as the sole energy input. Here, we report a newly aqueous colloidal comprised of monodispersed Ni-doped ZnS (ZnS:Ni) nanocrystals as excellent visible-light-responsive photocatalysts for CO2RR into formate. The wavelength-dependent quantum yield shows a significant contribution of Ni doping for visible light absorption. A high selectivity (>95%) of HCOOH production and a remarkable quantum efficiency of 59.1% at 340 nm and 5.6 % at 420 nm are obtained over ZnS:Ni (0.1 %) colloidal nanocrystals modified by Cd2+. The abundant sulfur vacancies and extended visible light absorption of the constructed colloidal ZnS:Ni nanocrystals contribute to the prominent performance for CO2RR. However, excessive doping of Ni does not guarantee an increase of photocatalytic CO2RR due to a diminish of sulfur vacancy. The regulation of sulfur vacancies by Ni doping and their interplay on photocatalytic CO2RR activity are presented and discussed. This work provides an in-depth insight of the role of dopant on vacancy modulation in photocatalyst beyond light absorption and a guidance for design of the potential photocatalyst for CO2RR.
关键词： CO2 reduction,vacancy,photocatalysis,doping,ZnS
更新于2025-11-19 16:51:07
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Efficient visible light-driven hydrogen generation on g-C3N4 coupled with iron phosphide
摘要： Transition metal phosphides as promising noble-metal-free cocatalysts are gaining increasing interest for hydrogen generation and other energy conversion reactions. Herein, the present study reports a new Fe2P/g-C3N4 hybrid for efficient photocatalytic hydrogen generation by water splitting under visible light irradiation, whose H2 production rate is ~15 times higher than that of pure g-C3N4, and is comparable with that of Pt/g-C3N4 at the same condition. According to the detailed analyses of UV-vis diffuse reflectance, photoluminescence spectra, and photoelectrochemical measurements, the reason for the high efficiency of Fe2P/g-C3N4 hybrid is due to highly effective separation and low recombination rate of photo-generated electrons and holes rather than absorption light. The present study shows a promising photocatalyst with non-toxicity, low cost, and natural abundance for improving photocatalytic H2 generation.
关键词： photocatalysis,g-C3N4,hydrogen generation,noble metal-free,Fe2P
更新于2025-11-19 16:51:07