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Surfactant-free stable SnS2 nanoparticles dispersion for deposition of device-quality films
摘要： Tin sulfide (SnS2) has recently attracted considerable attention due to its layered structure that may form two dimensional morphologies. It is an n-type semiconductor with band gap and electron affinity similar to CdS and In2S3; therefore can be regarded as an alternative for these materials in thin film solar cells. Here, we synthesis of SnS2 nanoparticles with different morphology in different ratio of water-ethanol mixed solution by solvothermal method, and observe that more ethanol leads to large sheet like morphologies, while water based synthesis results in very small nanosheets. A challenge in wet deposition of device-quality thin films of SnS2 is the requirement for highly dispersed particles/sheets. We found highly polar dimethylformamide (DMF) as the right dispersing medium, yielding highly stable dispersions. Very uniform nanocrystalline thin films with [001] preferred orientation and good adhesion to substrate are simply deposited by drop casting and spin coating a 0.5 wt% DMF sol of SnS2 at 2000 rpm for 1 min. Electron affinity and band gap of the films are 4.33 eV and 2.27 eV, which is well aligned for copper indium gallium sulfo-selenide (CIGS) solar cells.
关键词： Two dimensional structures,Surfactant-free dispersion,copper indium gallium sulfo-selenide solar cells,SnS2 thin film,Dimethylformamide,Buffer layer
更新于2025-09-23 15:21:21
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Photocatalytic degradation and adsorption of phenol by solvent-controlled TiO2 nanosheets assisted with H2O2 and FeCl3: Kinetic, isotherm and thermodynamic analysis
摘要： Hydrofluoric acid (HF) has been widely employed to regulate the surface characteristics of TiO2 containing sheet-like morphology with (001) facets for various environmental applications. However, carcinogenic effects associated with HF are the main stumbling blocks on its way towards global commercialization. In the same line of action, an eco-friendly approach for the synthesis of anatase TiO2 nanosheets (TNSs) via employing hydrothermal process and N, N dimethylformamide (DMF) as a novel morphology-controlling agent has been reported. The as-produced TNSs were characterized by XRD, HRTEM, Raman, FTIR, XPS and DRS characterizations. The photoactivity of as-produced TNSs was studied for photocatalytic degradation of phenol under visible light irradiation in the presence of green oxidants such as hydrogen peroxide (H2O2) and ferric chloride (FeCl3) to produce free hydroxyl radicals for speedily reduction of recombination of photogenerated electrons hole-pairs. The results revealed that as-produced TNSs could activate by green oxidants with yielding upto 94.19 and 97.12 % phenol degradation in the presence of H2O2 and FeCl3, respectively. Moreover, phenol adsorption data was well explained via pseudo first order and pseudo second order kinetics while Langmuir and Freundlich isotherms were more suitable to explain the adsorption of phenol onto TNSs, providing maximum adsorption capacity up to 23.596 mg/g. Various thermodynamic parameters were evaluated, suggesting the favourable, spontaneous and endothermic adsorption process. The values of activation energy (18.505 kJ/mol) confirmed the physical adsorption of phenol onto TNSs. The excellent aptitude of anatase TNSs to produce hydroxyl radicals and super-oxides radicals with promptly lessening of recombination of photogenerated electron hole-pairs makes them motivated applicant for wastewater treatment.
关键词： N, N dimethylformamide,green oxidants,adsorption mechanism,Hydrothermal process,TiO2 nanosheets,phenol
更新于2025-09-23 15:21:01
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Development of Synthetic Methods to Grow Long-Wavelength Infrared-Emitting HgTe Quantum Dots in Dimethylformamide
摘要： Most successful syntheses of long wavelength infrared (IR) absorbing/emitting Hg-chalcogenide quantum dots (QDs) use either aqueous or organic solvent-based methods. Accounts of IR QD growth in aprotic solvents such as dimethyl sulfoxide (DMSO) or dimethyl formamide (DMF) are much less common, and yet producing QDs in such solvents can be useful from the perspective of further reactions to conjugate or incorporate the QDs with other materials since such solvents can be a useful meeting ground for both organic and ionic solutes. Here we start by demonstrating long wavelength infrared emission (across the wide spectral range up to 4500 nm) in HgTe QDs grown in DMF under basic conditions. Whilst many existing synthetic approaches use soluble chalcogen precursors in adduct, salt or organo-chalcogenide forms, we have opted to take the approach of using slow addition of gaseous H2Te generated under programmed control, which allowed us to investigate the growth kinetics in order to manipulate the different competing processes, and to obtain larger HgTe QDs with the best size distributions on a repeatable and controlled basis. We demonstrate how the nucleation process of HgTe QDs can be carried out analogously to how it occurs in classic hot injection syntheses, but in our case at a far lower (sub-ambient) temperature owing to the use of a much more labile Te precursor. We also demonstrate the use of a two stage, seeded QD growth process which allows the synthesis conditions for the initial nucleation step and the subsequent enlargement stage to be decoupled, in other words the QD concentration during the enlargement phase need not be forced to be excessively large by the choice of nucleation conditions. This approach should eventually be extendable to making >5000 nm emitting HgTe QD based materials, and the use of aprotic solvents will offer compatibility with other nanomaterial chemistries, e.g. oxide glass formers etc., for the synthesis of composites. By comparing the emission spectra of HgTe QDs grown in DMF with those grown in DMSO, we show that polaron mediated coupling to ligand and solvents, previously seen when using DMSO, can be substantially suppressed using our new synthetic method.
关键词： nucleation,dimethylformamide,synthetic methods,growth kinetics,HgTe quantum dots,infrared emission
更新于2025-09-23 15:19:57