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Ag-Ag2S quantum-dots modified TiO2 nanorod arrays with enhanced photoelectrochemical and photocatalytic properties
摘要： In this paper, highly ordered titanium dioxide nanorod (TNR) arrays decorated with Ag-Ag2S quantum-dots (QDs) were synthesized on FTO substrate through hydrothermal treatment and in-situ vulcanization. The content of Ag2S QDs on Ag/TNR was controlled by changing the immersion time of Ag/TNR in the N-N-dimethyl formamide (DMF) solution containing dissolved sulfur element. The morphology, structure, composition and optical, photoelectric and photocatalytic properties of QDs/TNR arrays were studied in detail. In the visible range, the QDs/TNR array with a soaking time of 12 h exhibits the maximal photocurrent density (0.082 mA/cm2) and photodegradation rate (62.2%), which is 5.5 and 1.85 times higher than that of pure TNR. The improvement of these properties could be attributed to synergy effect between Ag and Ag2S materials. That is, Ag QDs can stably capture and transmit photo-generated electrons from the TNR surface, whereas the Ag2S promoter is regarded as the interface active sites to enhance photocatalytic reactions. Therefore, the synergistic effect of Ag-Ag2S can significantly enhance the photoelectrochemical and photocatalytic propertise of the TNR arrays.
关键词： Ag-Ag2S quantum-dots,photoelectrochemical and photocatalytic properties,synergistic effect,TiO2 nanorod arrays
更新于2025-09-10 09:29:36
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Central Composite Design (CCD) Optimized Synthesis of Fe3O4@SiO2@AgCl/Ag/Ag2S as a Novel Magnetic Nano-Photocatalyst for Catalytic Degradation of Organic Pollutants
摘要： In this study, we formulated and synthesized an efficient visible light-active magnetic nano-photocatalyst, Fe3O4@SiO2@AgCl/Ag/Ag2S, to decompose methyl orange (MO) as a model organic pollutant. XRD, SEM, TEM, EDS, DRS, and VSM analyses were used to characterize the developed magnetic nano-photocatalyst. Moreover, central composite design (CCD) modeling, which is based on response surface methodology (RSM) modeling, is utilized to optimize the synthetic and operating conditions to maximize the photocataytic performance. The CCD-optimized values for molar ratio of AgCl to Fe3O4, molar ratio of Ag2S to Fe3O4, and the photocatalyst dosage are found to be 0.8, 0.27, and 1.27 g/L, respectively. The developed Fe3O4@SiO2@AgCl/Ag/Ag2S nano-photocatalyst shows a superior photocatalytic activity in decomposition of MO, degrading around 90% and 99% of MO in 30 min and one hour, respectively, under visible light illumination, at which the predicted values are in a good agreement with the experimental values (R2=0.971 and Adj-R2=0.945). Meanwhile, the morphological, physicochemical, and magnetic properties of the developed nano-photocatalyst are largely retained over ten successive cycles of photocatalytic reactions, and no significant decline in the photocatalytic activity is observed.
关键词： Magnetic Nano-Photocatalyst,Central Composite Design (CCD),Organic Pollutant,AgCl/Ag/Ag2S,Water Treatment
更新于2025-09-10 09:29:36
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Synthesis and physical properties of un- and Zn-doped Ag2S nanoparticles
摘要： This study is devoted to the sonochemical synthesis of un- and Zn-doped silver sulfide (Ag2S) nanostructures and evaluation of the parameters that affect its structural, morphological and optical properties. To unravel any changes in the characteristics of the particles, the XRD and FESEM techniques, in addition to photoluminescence (PL), Raman and UV–Vis spectroscopies, were applied. According to the analyses, 15 min sonication using 200 W power can provide the highest quality of the Ag2S crystals. Moreover, it was found out that Zn doping shifts the XRD peaks of Ag2S to higher angles and declines crystallinity of the samples while it does not change the spherical shape of the Ag2S particles. The other impact of Zn presence in the crystal lattice of Ag2S was declared to be increasing the size of the Ag2S nanostructures. Importantly, based on the PL results, the un- and Zn-doped Ag2S particles present several emission bands lying in the visible spectrum of light due to their specific optical near band emission (NBE) and crystal defects. As the PL spectra demonstrated, increasing the Zn concentration decreases the optical band gap energy of the Ag2S nanostructures. Also, the Raman results unraveled the impact of synthesis conditions on the optical and crystalline properties of the grown structures.
关键词： Zn-doped,Optical properties,Sonochemical,Ag2S nanostructures,Synthesis parameters
更新于2025-09-10 09:29:36
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Photocatalytic performance of Ag2S/ZnO/ZnS nanocomposites with high visible light response prepared via microwave-assisted hydrothermal two-step method
摘要： A series of different ratios of Ag2S/ZnO/ZnS nanocomposites with visible light response were prepared by a microwave-assisted hydrothermal two-step method, whose composition, crystalline structure, morphology and surface physicochemical properties were well-characterized via X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), UV–vis diffuse reflectance spectroscopy (UV–vis/DRS), photoluminescence spectrum (PL), scanning electron microscopy (SEM), high-resolution transmission electron microscopy (HR-TEM) and N2 adsorption–desorption measurements. Results showed that as-composites mainly consisted of ZnS crystal phase, whose grain size increased obviously compared with non Ag2S samples. At the same time, due to the introduction of narrow band gap Ag2S, the synthesized composite can effectively increase the visible optical absorption of ZnO/ZnS composites. Among them, 1% Ag2S/ZnO/ZnS showed a mixed structure of nano-line and nano-particle, of which BET value increased significantly, and the morphology was more excellent. Photocatalytic activities of a series of Ag2S/ZnO/ZnS composites under different light sources were studied using methyl orange as a model molecule, and 1% Ag2S/ZnO/ZnS was taken as the best one. Meanwhile, 1% Ag2S/ZnO/ZnS also showed a good degradation effect on other dyes with different structures, and its degradation efficiency did not change significantly after three cycles, showing certain stability. In addition, composites with Ag2S loading of 1% possessed the highest hydrogen production ability of photolysis water, indicating that the introduction of Ag2S had significantly enhanced the catalytic performance.
关键词： microwave-assisted,Ag2S,photocatalysis,visible light,photolysis of water to hydrogen,ZnO/ZnS
更新于2025-09-09 09:28:46
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Al-doped Ag2S nanostructures: ultrasonic synthesis and physical properties
摘要： Un- and aluminum (Al)-doped silver sulfide (Ag2S) nanostructures were grown by the sonochemical method. The samples were studied by employing various identification methods including X-ray diffraction (XRD), field emission electron microscopy (FESEM), photoluminescence (PL), Raman and UV-Visible. The results showed that adding Al dopant shifts the diffraction peaks to higher angles and reduces their intensity. Furthermore, the size of the nanocrystal was reduced compared to the undoped sample. It was found that the strain in the doped samples is greater than the un-doped sample by the use of Hall-Williamson (W-H) method. FESEM images demonstrate the composition of spherical forms of nanostructures, which is converted to a quadrilateral shape by adding dopant. PL analysis illustrated the presence of emission bands in the visible region that was resulted by the emission of the near band edge (NBE), as well as the percentage of the density and type of defects. Moreover, Al reduced the optical energy band gap of the nanostructures. Finally, the influence of the parameters affecting the crystalline and the optical properties of the material over the growth process was investigated using Raman analysis.
关键词： Al-doped Ag2S nanostructures,Structural features,Sonochemical,Optical properties
更新于2025-09-04 15:30:14
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Direct Observation of Curved Surface Enhanced Disordering in Ag <sub/>2</sub> S Nanoparticles
摘要： Surface induced order-disorder phase transition has been widely studied on flat bulk surfaces, while such a transition is poorly understood on curved surfaces in nanoscale. Here, we report a direct observation of the dynamic behaviors of surface-initiated disordering in Ag2S nanoparticles using atomic resolution in-situ transmission electron microscopy. It was found that the disordering behavior is different from the traditional model that the disordered layer follows a logarithmical thickness dependence with temperature. In particular, the disordering is largely enhanced at higher temperature when the radius of the residual order phase is getting smaller. Moreover, the correlation length of disordered phase was found to be several times larger than the typical value for bulk surfaces. This significantly enhanced disordering in nanoparticles could be attributed to the extra driving force provided by the decreasing of order-disorder interface area.
关键词： nanoscale,Ag2S nanoparticles,in-situ TEM,phase transition,surface-initiated disordering
更新于2025-09-04 15:30:14