Hydrothermal Synthesis and Photocatalytic Performance of Barium Carbonate/tin Dioxide Nanoparticles

Background: Crystal violet dye is stable and difficult to be biodegraded owing to the existence of the multiple aromatic rings of the crystal violet molecules. Removing crystal violet dye from the wastewater is a major challenge. Objective: The aim of the research is to synthesize barium carbonate/tin dioxide nanoparticles and investigate the photocatalytic performance for the degradation of crystal violet. Methods: Barium carbonate/tin dioxide nanoparticles were synthesized via a facile hydrothermal route without any surfactants. The crystal structure, micro-morphology, size and optical performance of the barium carbonate/tin dioxide nanoparticles were investigated by powder X-ray diffraction, scanning electron microscopy, transmission electron microscopy and solid ultraviolet-visible diffuse reflectance spectrum. Results : The size of the barium carbonate/tin dioxide nanoparticles is 20 nm to 200 nm with the band gap of 3.71 eV. The photocatalytic activity of the barium carbonate/tin dioxide nanoparticles was measured by the photocatalytic degradation of crystal violet. The crystal violet degradation efficiency reaches 92.1% with the ultraviolet-visible irradiation time of 8 h using 10 mg barium carbonate/tin dioxide nanoparticles. The crystal violet degradation ratio increases to 96.1% when the dosage of the barium carbonate/tin dioxide nanoparticles increases to 20 mg/10 mL crystal violet dye solution. Active species capture photocatalytic experiments showed that the holes, hydroxyl radicals and superoxide ion radicals are the main active species. Reusability experiments displayed that the barium carbonate/tin dioxide nanoparticles are stable for the crystal violet dye degradation. Conclusion: The barium carbonate/tin dioxide nanoparticles show good photocatalytic performance toward crystal violet under ultraviolet light irradiation.

Fe-Doped Graphitic Carbon Nitride for Methylene Blue Degradation with Visible-Light

In the present work, degradation of methylene blue (MB) dye in aqueous solution through H2O 2and iron doped g-C3N4 (Fe-g-C3N4) was studied. The hybrid was fabricated by thermal polymerization with iron (III) nitrate nonahydrate and melamine, and it was characterized by X-ray diffraction, Fourier transform infrared, UV-Vis diffuse reflectance spectrum, X-ray photoelectron spectroscopy, transmission electron microscope and Brunner-Emmet-Teller. The various experimental conditions such as doping amount, a dose of the sample, solution pH, the addition of H2O2, and concentration of MB on the degradation of MB dye were optimized. The maximum extent of degradation of methylene blue was obtained at pH 5, doping amount of 2.7 wt% and dose of 0.07 g. The molar ratio of Fe:H2O2 is 1:1000 showed 99% of MB (30 mg/L) decolorization over 60 min. The hybrid showed good stability and recyclability after three cycles of use. Photo-Fenton reaction exhibited a higher synergetic effect than the combination of Fenton and photocatalytic process.

High Photocatalytic Performance of Modified Bismuth Oxychloride Semiconductor under Sunlight

In recent years, the bismuth compounds have gained much interest due to their potential applications in the field of Photocatalysis. In our present work, Bismuth oxychloride Photocatalyst and Aluminium fluoride doped Bismuth oxychloride photocatalyst were synthesized by simple chemical methods using Bismuth nitrate pentahydrate as the precursor. The synthesized photocatalysts were characterized by different analytical techniques such as X-ray diffraction analyses, Ultra Violet –Diffuse reflectance spectrum, Field Emission – Scanning Electron Microscopy, Energy dispersive X-ray analyses,Fourier transform infrared spectroscopy studies and BET surface area analysis. The photocatalytic performances of the as-synthesized doped and undoped Bismuth oxychloride photocatalyst were tested towards the degradation of Acid green 1 dye. The parameters such as the effect of pH, catalyst concentration and initial dye concentration are optimized, and the kinetic studies are carried out for the photocatalytic dye degradation process. The experimental results showed that about 80% of the Acid green 1 dye got decolourized within 90 minutes by effective air purging under natural sunlight radiation in the presence of the AlF-BiOCl photocatalyst under optimized conditions.

Extraction of the Structural Properties of Skin Tissue via Diffuse Reflectance Spectroscopy: An Inverse Methodology

For the laser treatment of vascular dermatosis, the blood vessel morphology and depth in skin tissue is essential to achieve personalized intelligent therapy. The morphology can be obtained from the laser speckle imaging, and vessel depth was extracted by an inverse methodology based on diffuse reflectance spectrum. With optimized spot size of 0.5 mm and known optical properties, the proposed method was experimentally validated via the spectral measurement of microcapillary with known size and depth embedded in an epoxy resin-based skin phantom. Results prove that vessel depth can be extracted with an average relative error of 5%, thereby providing the foundation for a personalized, precise, and intelligent laser treatment of vascular dermatosis.

Fabrication and characterization of InN-based metal-semiconductor-metal infrared photodetectors prepared using sol–gel spin coated technique

We report on the growth and characterization of undoped indium nitride (InN) thin films grown on a silicon substrate. The InN thin films were grown on aluminium nitride (AlN) template with gallium nitride (GaN) nucleation layer using a relatively simple and low-cost sol–gel spin coating method. The crystalline structure and optical properties of the deposited films were investigated. X-ray diffraction and Raman results revealed that InN thin films with wurtzite structure were successfully grown. For InN thin film grown on a substrate with the GaN nucleation layer, its strain and dislocation density are lower than that of the substrate with the AlN nucleation layer. From the ultra-violet-visible diffuse reflectance spectrum analysis, the energy bandgap of the InN thin films with the GaN layer was 1.70 eV. The potential application of the sol–gel spin-coated InN thin films was also explored. Metal–semiconductor–metal (MSM) infrared (IR) photodetectors were fabricated by depositing the platinum contacts using two interdigitated electrodes metal mask on the samples. The finding shows that the device demonstrates good sensitivity and repeatability towards IR excitation at a wavelength of 808 nm. The photodetector characteristics at dark and photocurrent conditions such as Schottky barrier height (SBH) and ideality factor are determined. Upon exposure to the IR source at 3V applied bias, InN/AlN/Si device configuration displays rapid rise time of 0.85 s and decay time of 0.78 s, while InN/GaN/AlNSi demonstrates slow rise time of 7.45 s and decay time of 13.75 s.

Preparation of TiO2/Ag[BMIM]Cl Composites and Their Visible Light Photocatalytic Properties for the Degradation of Rhodamine B

In order to degrade toxic pollutants such as dyes during the process of sewage treatment, considerable attention has been paid to photocatalytic technologies. In this paper, TiO2/Ag[BMIM]Cl (1-butyl-3-methyl imidazolium chloride ([BMIM]Cl)) nanocomposites were prepared with TiO2 as the carrier, silver ions as dopants and ionic liquids (IL) as modifiers. The morphologies, microstructures, crystalline structure and optical properties of the TiO2/Ag[BMIM]Cl nanospheres are investigated by transmission electron microscopy (TEM), X-ray diffraction (XRD), total organic carbon (TOC), and UV-vis diffuse reflectance spectrum (UV-vis DRS) techniques. The TiO2/Ag[BMIM]Cl nanocomposites can selectively degrade rhodamine B (Rh B) under visible light because of the unstable quaternary ammonium salt. The as-obtained nanocomposites exhibit better photocatalytic activity performance than pure TiO2, TiO2/IL, and TiO2/Ag+. The experimental results show that the Rh B degradation rate can reach 98.87% under optimized producing conditions by using the TiO2/Ag[BMIM]Cl composites as the catalyzer. It shows that simultaneous doping with silver ions and ionic liquids can significantly improve the photocatalytic activity of TiO2 in Rh B degradation, indicating the formation of photosensitive AgCl in the process of TiO2/Ag[BMIM]Cl preparation. Ag+ and IL addition exchange the band gap of TiO2 and lengthen the visible wavelength range of the composite. The material has the advantages of low cost, facile preparation and reusability with the excellent degradation effect of Rh B.

Preparation and Characterization of New Modified System: Polyaniline/1.5-Naphtalene Disulfonic Acid as Novel Photocatalyst in the H2 Production

The semiconducting properties of the system Polyaniline / 1.5-naphtalene disulfonic acid are investigated for the first time to assess its photocatalytic performance for the hydrogen evolution under visible light irradiation. PANI is thermally stable up to ~ 300 °C, above which a weight loss of ~ 1.2% occurs. The X-ray diffraction pattern shows broad peaks with a particle size of ~ 7 nm, leading to an active surface area of ∼ 400 m2 g−1. A direct optical transition at 1.96 eV, is determined from the diffuse reflectance spectrum. The electrical conductivity of PANI-NDSA follows an exponential law with activation energy of 0.24 eV. The p-type conduction of PANI-NDSA is evidenced from the (capacitance-2 – potential) characteristic plot; a flat band potential (Efb) of 0.82 VSCE and a holes density (NA) of 8.43× 1024 m-3 are determined in neutral solution (Na2SO4 0.1 M). The electrochemical impedance spectroscopy, measured over an extended frequency domain (1 mHz - 1010 Hz), indicates the contribution of both the bulk and grain boundaries with a constant phase element (CPE). As application, PANI-NDSA is successfully tested for the hydrogen production upon visible light owing to the potential of its conduction band (-0.75 VSCE), less cathodic than that of H2O/H2 (~ -0.30 VSCE). H2 liberation rate of 3840 h-1 (g catalyst)-1 and a quantum efficiency of 0.34% under full light (29 mW cm-2) are obtained using Fe(CN)64- as reducing agent. The photoactivity is completely restored during the second cycle.

Sodium Ligninsulfonate-assisted Synthesis of Lithium Bismuthate/bismuth Oxide Microspheres and Solar Light Photocatalytic Performance

Background: Great attention has been paid to the environmental pollution by organic dyes which are difficult to be degraded in natural environment and have been an unavoidable and urgent global problem. It is essential to develop green waste water treatment technology with high removal efficiency and low cost to protect surroundings and human health. Objective: The aim of the research is to synthesize lithium bismuthate/bismuth oxide microspheres with good photocatalytic performance for the removal of gentian violet (GV). Methods: Lithium bismuthate/bismuth oxide microspheres were successfully prepared by a sodium ligninsulfonate-assisted hydrothermal synthesis route. The lithium bismuthate/bismuth oxide microspheres were investigated by X-ray diffraction (XRD), scanning electron microscopy (SEM), Fourier Transform infrared spectroscopy (FTIR) and solid UV-vis diffuse reflectance spectrum. Results: XRD pattern and SEM observation show that the lithium bismuthate/bismuth oxide microspheres are composed of cubic LiBi12O18.50 and monoclinic Bi2O3 with the diameter of 250 nm-1 μm. Irregular microscale and nanoscale particles are formed under low hydrothermal temperature, low sodium ligninsulfonate concentration and short duration time. With increasing the sodium ligninsulfonate concentration, hydrothermal temperature and duration time, irregular particles are transferred into microspheres. Lithium bismuthate/bismuth oxide microspheres possess a band gap energy of 1.85 eV suggesting good visible light absorption ability. The photocatalytic removal ability for GV is enhanced by prolonging light irradiation time and microspheres dosage. GV solution with the concentration of 10 mg•L-1 is able to be totally degraded by 10 mg lithium bismuthate/bismuth oxide microspheres in 10 mL GV solution under solar light irradiation for 6 h. Conclusion: The lithium bismuthate/bismuth oxide microspheres show good photocatalytic removal ability toward GV in waste water under solar light irradiation.

Effect of Li+ doping on the luminescence performance of a novel KAlSiO4:Tb3+ green-emitting phosphor

A new green-emitting phosphor, KAlSiO4:1.5 mol% Tb3+, x mol% Li+, was prepared via a high-temperature solid-phase method, and its crystal structure, diffuse reflectance spectrum, and luminescence were studied. The results show that the Li+ doping shifts the strongest diffraction peak to a high angle direction, reducing grain size by 11.4%. The entry of Li2CO3 improves the luminescence performance of KAlSiO4:1.5 mol% Tb3+. At a Li+ concentration of 1.5 mol%, the sample has strong absorption in the ultraviolet light range from 250 to 400 nm. The luminous intensity of the sample at 550 nm approximately quadruples after Li+ doping. Additionally, the colour purity of the sample and the internal quantum yield increase to 83.3% and 42%, respectively. The sample changes colour with time when exposed to air without an obvious fading phenomenon. The emission intensity at 200 °C is 95.1% of its value at room temperature, indicating that the phosphor has excellent thermal stability when x = 1.5. These results show the feasibility of using the silicate phosphor for generating the green light component of white light-emitting diodes for solid-state lighting.