Papers by Keyword: Visible Light

Abstract: In₂S₃/In₂O₃ composites were fabricated by annealing using metal-organic framework (In-MOF) as precursor, following by sulfurization of In₂O₃. Structural characterization showed that two kinds of In₂S₃/In₂O₃ with different morphologies were obtained by controlling the pH condition during the sulfurization process. Optical characterization results revealed that In₂S₃/In₂O₃ heterojunctions display an evidently decreased visible light emission and enhanced visible light absorption compared with that of pure In₂O₃. The In₂S₃/In₂O₃ heterojunction exhibited improved visible-light photocatalytic activities, the optimal composite (pH=2) showed the highest efficiency of 91.14%. The improvement of photocatalytic performance was attributed to the construction of heterojunction.

Abstract: In this research, visible-light responsive g-C₃N₄, photocatalyst was achieved through the simple calcination of urea at 600 °C by using the muffle furnace. The effects of calcination soaking time on preparation of high performance g-C₃N₄ were studied at 1, 2, 3, and 4 h. The g-C₃N₄ prepared at various soaking times were characterized by the X-ray diffraction (XRD) for crystallographic information and the Fourier-transform infrared spectroscopy (FTIR) for chemical composition analysis. Further, in the case of morphology and surface area of prepared photocatalysts, the Transmission Electron Microscope (TEM) and Brunauer, Emmett and Teller (BET) were applied. The results demonstrated that g-C₃N₄ with tri-s-triazine based units could be synthesized by calcination of urea at 600 °C and soaking for 1-4 h, as evidently confirmed by XRD and FTIR. For photocatalytic performance in rhodamine B dye degradation under visible light irradiation of achieved g-C₃N₄ tended to increase as soaking time increased. Moreover, the dye adsorption ability of prepared photocatalysts was obviously developed upon increase of soaking times. Herein, the highest photocatalytic performance was obtained from sample which was soaked at 4 h.

Abstract: Other portion of solar spectrum apart from UV, particularly blue light, is currently reported to induce the damaging effects to human skin. This study was aimed to investigate the effect of the combination of tris-biphenyl triazine (TBPT) and inorganic metal oxides as well as the effect of the matrix formulations on UV and blue light protection efficiencies. The protection efficiency of various combinations against UVB, UVA and blue light was determined through sun protection factor (SPF), UVA protection factor (UVA-PF) and porphyrin protection factor (PPF), respectively. The results demonstrated that TBPT combined with nanosize titanium dioxide and blended iron oxides (TT60-IR) achieved the highest SPF and UVA-PF. On the other hand, TBPT combined with submicron-size titanium dioxide and blended iron oxides (TT300-IR) yielded the highest PPF value. The matrix formulation affected the scattering property of the filters (i.e. combined TBPT and inorganic metal oxides). Containing the same amount and types of the filters, the matrix formulation that possessed a high transparency property showed high scattering efficiency against the blue light.

Abstract: A visible active antibacterial agent, namely TiO₂-Ag-Nanoparticle has been prepared, characterized, and examined to combat E.coli bacteria in the present of the visible light. The preparation was carried out by reduction of AgNO₃ solution over TiO₂ photocatalyst under UV light exposure. TiO₂-Ag nanoparticle was characterized using XRD, SEM and DRS instruments. The activity as an antibacterial agent has been tested for disinfection of E. coli bacteria in the contaminated well water. The antibacterial assay was carried out by visible light irradiation of the contaminated well water in the present of TiO₂-Ag, as well as TiO₂for comparison, for the various period. The antibacterial performance was represented as the number of the bacteria determined by colony counting method. Their XRD patterns probe that the Ag doping leads to the crystalline of TiO₂partially destroyed and the average particle size of TiO₂ in TiO₂-Ag is larger thanTiO₂bare, and no peaks of Ag metal appeared, implying that the Ag silver is very small(nanoparticle) that may be inserted into the TiO₂crystal lattice. Based on the DRS spectra it is observed that TiO₂-Ag has visible light absorption meanwhile TiO₂only can absorb the UV light. The antibacterial assessment demonstrates that the TiO₂-Ag has high performance in the bacterial inactivation under visible light. Meanwhile, very low activity is shown by TiO₂. Moreover, the increase of Ag loaded gives rise in the bacterial inactivation, but further increase leads to the inactivation slightly reduced. The extension time of the visible light exposure is found to promote more effective antibacterial process up to maximum level, and no effect was observed with the much longer time. It is also confirmed that a small amount of Ag is dissolved from TiO₂-Ag NP during the antibacterial testing.

Abstract: Titanium dioxide (TiO₂) nanotubes with a highly ordered structure were grown by a self-organized anodization process. The photodeposition process was used to improve the visible light response of titanium dioxide (TiO₂) nanotubes. The irradiation was carried out with 500 W halogen lamp for 1, 5, 15, 30 and 60 min in the mixed ethanol solution of antimony trisulfide (Sb₂S₃). The obtained samples were annealed at 250 °C for 30 min. The morphology of the fabricated sample was characterized by a field emission scanning electron microscope (FE-SEM). The phase of samples was determined by X- ray diffractometer (XRD). The weight percentages of a component in the sample were measured by X-ray fluorescence spectrometry (XRF). UV-Vis diffuse reflectance spectra (DRS) of the samples were recorded. All titanium dioxide (TiO₂) nanotube samples prepared by anodization process were anatase phase. All composite titanium dioxide (TiO₂) nanotube /Sb₂S₃ samples were a crystalline phase. The percentage of Sb and S increase with increasing of photodeposition’s time. The increasing photodeposition of antimony trisulfide (Sb₂S₃) on titanium (TiO₂) nanotubes from 1 to 60 min lead to increasing of photoabsorption property of the material in the visible region.

Abstract: The Cu_1.8Se/CuAgSe nanostructure was synthesized by a simple two-step process. Starting with the template of cubic Cu_1.8Se nanoplate by precipitation method, Cu_1.8Se/CuAgSe nanostructure and ternary CuAgSe were prepared through a rapid ion exchange reaction using various amount of AgNO₃ at room temperature. The as-prepared samples were analyzed by XRD, SEM and DRS. It was found that Cu_1.8Se/CuAgSe heterostructure and the pure CuAgSe phase were formed without changing the morphology, and these samples had efficient light absorption from UV light to near-infrared light region. Photocatalytic properties of these samples were evaluated by the degradation of Congo red under visible and near-infrared light. The Cu_1.8Se/CuAgSe nanostructure showed enhanced photocatalytic activity due to the lower recombination of charge-carrier in the photodegradation process.

Abstract: In order to enhance hole/electron separation and charge transfer in photocatalysts, the heterostructured g-C₃N₄/CoAPO-5 hybrids materials were synthesized via a simple grinding method and were investigated using X-ray diffraction (XRD), fourier transform infrared spectroscopy (FT-IR) and scanning electron microscopy (SEM). The optical properties of g-C₃N₄/CoAPO-5 hybrids materials were measured by ultraviolet-visible diffuse-reflectance spectroscopy (DRS), photoluminescence (PL) spectra and ultraviolet-visible absorption (UV-Vis) spectra. Under visible-light illumination, this work shows the heterogeneous g-C₃N₄/CoAPO-5 hybrids present a superior photocatalytic activity.

Abstract: Chitosan, β-glycerophosphate, and glycerol are all biocompatible materials for biomedical application. This work successfully developed a thermosensitive hydrogel composed of CS, β-GP and glycerol. The CS/β-GP/glycerol hydrogel can be made as a transparent solution at room temperature and becomes an opaque and turbid hydrogel after heating. The transmission of visible light at different temperature can be measured by a visible micro spectrophotometer combined with a precise temperature control of the demountable liquid cell. A tunable transmission of visible light hydrogel was developed. Moreover, the composition of such hydrogel is safely used and it is potential for biomedical applications.

Abstract: Photocatalyst coatings had been successfully fabricated by molten salt treatment at 673 K for 3 h for titanium (Ti) coatings, which coated on alumina (Al₂O₃) balls by mechanical coating technique with Ti powder. The influence of molten salt treatment on the formed compounds, surface morphology and photocatalytic activity under visible light irradiation on degradation of MB solution and suppression of Microcystis aeruginosa of photocatalyst coatings was investigated. XRD results show that potassium titanate (K₂Ti₆O₁₃) forms on the surface of Ti coatings during molten salt treatment. The visible light photocatalytic activity of photocatalyst coatings has been effectively enhanced by molten salt treatment.

Abstract: In the present study, visible light active CuS/CdS nanocomposites of various compositions (1%, 2% and 3%) were synthesized via wet impregnation method and these photocatalysts were characterized by scanning electron microscopy (SEM), powder X-ray diffraction (XRD), Fourier transform infrared (FT-IR) spectroscopy and UV-visible diffuse reflectance spectroscopy (DRS). The photocatalytic degradation efficiency of the synthesized photocatalysts was evaluated from the degradation of methylene blue (MB) under the visible light irradiation. Among all compositions, a 1% CuS/CdS nanocomposite showed about 89.5% degradation in 90 min than the pure CuS, CdS and other composites. Photoluminescence and photoelectrochemical measurements indicated that the 1% CuS/CdS nanocomposite greatly enhanced the charge generation and restrained the recombination of photogenerated electron-hole pairs. A possible mechanism of photocatalytic degradation has been proposed.