Photocatalytic Reduction of Aqueous Cr(VI) with CdS under Visible Light Irradiation: Effect of Particle Size

Stringent environmental standards have made the removal of Cr(VI) from water an important problem for environmental scientist and engineering. Heterogeneous photocatalysis using suspended photocatalyst is an interesting technique to consider for this application. In this work, the influence of particle size of suspended CdS on the photocatalytic reduction of aqueous Cr(VI) ion was investigated. The efficiency of Cr(VI) reduction was monitored through UV-visible analysis. The experimental results showed that the nanoparticle size has a dramatic effect on the adsorption and reduction of Cr(VI). As surface area increased from 44.2±0.6 to 98.7±0.5 m2/g due to particle size reduction, the rate of Cr(VI) reduction nearly doubled in the first 20 min of visible light irradiation. The results evidenced the inverse relationship between the apparent reduction rate constant and the CdS particle size. Conversely, the half-life (t1/2) period of the photocatalytic reduction has a direct relationship with CdS particle sizes.

Determination of Trace Elements in Sediments Samples by Using Neutron Activation Analysis

The Juru River is a highly industrialized, urbanized, and agricultural catchment. This study aimed to investigate trace elements in Juru mangrove sediments, including geochemical baselines and enrichment. Sediment was collected from the mangrove in Juru, Penang, Malaysia. A total of eight target elements was examined.  Instrumentation activation analysis (INAA) was used to determine the concentration of Fe, V, Cr, Zn and Co. Atomic absorption spectrometry (AAS) was used to determine the concentration of elements that not detectable by INAA (Cd, Pb, and As). In both methods, validated reference material studies were used for validation of the methodology. Metal pollution was estimated using the Enrichment Factor (EF), Geoaccumulation Index (Igeo), Contamination Factor (CF), and Pollutant Load Index (PLI). The EF, Igeo, and CF ranges from 0.45–7.96, -2.18 – 1.95, and 0.33–5.83 respectively. The order of accumulation of the elemental concentration found was Fe > Zn> Cr > V > Pb > As > Co >Cd. The computed mean value of PLI exceeds the unit (PLI > 1)

Influence of parameters and radical scavengers on the visible-light-induced degradation of ciprofloxacin in ZnO/SnS 2 nanocomposite suspension: Identification of transformation products

Removal of ciprofloxacin (CIP) pollutant from wastewater using conventional process is particularly challenging due to poor removal efficiency. In this work, CIP was photocatalytically degraded using a porous ZnO/SnS2 photocatalyst prepared via microwaves. The influence of process parameters (e.g., pH, catalyst mass and initial CIP concentration) and radical scavengers on visible-light induced degradation of CIP on the catalyst was investigated. From the study, it was found that visible-light induced degradation of CIP on ZnO/SnS2 is a surface-mediated process and the reaction kinetics followed the Langmuir-Hinshelwood first-order kinetics. It was found that the optimum condition for CIP degradation was at pH of 6.1 and catalyst dosage of 500 mg L−1. Higher catalyst dosage however led to a decline in reaction rate due to light scattering effect and reduction in light penetration

A Novel Research on Behavior of Zinc Ferrite Nanoparticles in Different Concentration of Poly(vinyl pyrrolidone) (PVP)

Zinc ferrite nanocrystals were prepared from an aqueous solution containing metal nitrates and various of concentrations of poly(vinyl pyrrolidone) (PVP), i.e., 0, 15, 40, and 55 g/L, as a capping agent. To stabilize the particles, they were thermally treated at 873 K, as an optimum calcination temperature. The behaviors of the polymeric precursor were analyzed by use of simultaneous thermo-gravimetry (TG) and derivative thermo-gravimetry analyses (DTG). The presence of the crystalline phase in each sample was confirmed by X-ray diffraction (XRD) analysis. The average particle size and the morphology of the nanoparticles were determined by transmission electron microscopy (TEM), and these parameters were found to differ at various concentrations of PVP. Fourier transform infrared spectroscopy (FT-IR) confirmed the presence of metal oxide bands for all the PVP concentrations and confirmed the absence of organic bands for PVP concentrations less than 55 g/L. Measurements of the magnetization value of the zinc ferrite nanoparticles were obtained at room temperature by using a vibrating sample magnetometer (VSM), which showed that, in the absence of PVP, the sample exhibited a paramagnetic behavior while, in the presence of PVP, samples have a super-paramagnetic behavior

Fabrication and characterization of semiconductor nickel oxide (NiO) nanoparticles manufactured using a facile thermal treatment

In this paper, thermal treatment procedures were utilised to prepare crystalline nickel oxide semiconductor nanoparticles, derived from an aqueous solution. The solution consists of three compounds, primarily nickel nitrate, polyvinyl pyrrolidine and deionised H2O acting as metal precursor, capping agent and solvent, respectively. The solution was made prior to the drying, grinding and calcination at varying temperature settings up to 800 °C. The scanning Electron Microscopy (SEM) images allowed a detailed study on the morphological of the monocrystalline grains which were obviously observed in the specimen, showing them to be almost identical in shape and size. The Infrared Fourier Transform (FTIR) and X-ray diffraction (XRD) results demonstrated a transformation of the amorphous structure at room temperature to the crystalline structure at higher temperatures during calcination process. The mean particle diameter and particle distribution were found to be directly proportional to temperature increased. The transmission electron microscopic (TEM) analysis revealed that the particle diameters vary between 15 and 35 nm when temperature increased between 500 and 800 °C. The composition of the specimens was delineated by energy dispersed X-ray spectroscopy (EDX), which identified nickel and oxygen atomic percentages in the final products. Optical characteristics were deducted from a UV–Vis reflectance spectrophotometer, which demonstrated the energy band gap decrement as the calcination temperatures increased. Magnetic properties were determined through electron spin resonance spectroscopy (ESR), which revealed the presence of unpaired electrons. The magnetic field resonance decreases along with an increase of the g-factor value as the calcination temperature increased from 500 to 800 °C. Keywords: Nanoparticles, Nickel oxide, Thermal treatment, Calcination, Optical propertie

A facile thermal-treatment route to synthesize ZnO nanosheets and effect of calcination temperature.

A facile thermal-treatment route was successfully used to synthesize ZnO nanosheets. Morphological, structural, and optical properties of obtained nanoparticles at different calcination temperatures were studied using various techniques. The FTIR, XRD, EDX, SEM and TEM images confirmed the formation of ZnO nanosheets through calcination in the temperature between 500 to 650 °C. The SEM images showed a morphological structure of ZnO nanosheets, which inclined to crumble at higher calcination temperatures. The XRD and FTIR spectra revealed that the samples were amorphous at 30 °C but transformed into a crystalline structure during calcination process. The average particle size and degree of crystallinity increased with increasing calcination temperature. The estimated average particle sizes from TEM images were about 23 and 38 nm for the lowest and highest calcination temperature i.e. 500 and 650 °C, respectively. The optical properties were determined by UV-Vis reflection spectrophotometer and showed a decrease in the band gap with increasing calcination temperature

Fabrication of p-type Double gate and Single gate Junctionless silicon nanowire transistor by Atomic Force Microscopy Nanolithography

Keywords: Local anodic oxidation (LAO); Silicon-on-insulator (SOI); Atomic force microscope (AFM), Double gate (DG) and Single gate (SG) Junction-less silicon nanowire transistor (JLSNWT). Abstract. In this work, we have investigated the fabrication of Double gate and Single gate Junctionless silicon nanowire transistor using silicon nanowire patterned on lightly doped (10 5 cm -3 ) p-type Silicon on insulator wafer fabricated by Atomic force microscopy nanolithography technique. Local anodic oxidation followed by two wet etching steps, Potassium hydroxide etching for Silicon removal and Hydrofluoric acid etching for oxide removal, were implemented to reach the structures. Writing speed and applied tip voltage were held in 0.6 µm/s and 8 volt respectively for Cr/Pt tip. Scan speed was held in 1.0 µm/s. The etching processes were elaborately performed and optimized Online: 2013-01-25 ISSN: 2234-9871, Vol. 3, pp 93-113 doi:10.4028/www.scientific.net/NH.3.93 © 2013 This is an open access article under the CC-BY 4.0 license (https://creativecommons.org/licenses/by/4.0/) by 30%wt. Potassium hydroxide + 10%vol. Isopropyl alcohol in appropriate time, temperature and humidity. The structure is a gated resistor turned off based on a pinch-off effect principle, when essential positive gate voltage is applied. Negative gate voltage was unable to make significant effect on drain current to drive the device into accumulation mode. Nano Hybrid

SEM images of ZnO nanosheets at calcination temperatures of (a) 500 and (b) 550, (c) 600 and (d) 650°C.

<p>SEM images of ZnO nanosheets at calcination temperatures of (a) 500 and (b) 550, (c) 600 and (d) 650°C.</p

A proposed mechanism of the interaction between metallic ions and PVP.

<p>A proposed mechanism of the interaction between metallic ions and PVP.</p