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Tin (IV) oxide (SnO2) sols have been synthesized from SnCl2.2H2O precursor solution by applying two different processing conditions. The prepared sols were then deposited on UV-Ozone treated quartz and soda lime glass (SLG) substrates by spin coating. The as-synthesized film was soft-baked at about 100 deg. C. for 10 min. This process was repeated five times to get a compact film, followed by air-annealing at 250 deg. C. for 2 hours. The pristine and annealed films were characterized by UV-Vis-NIR spectroscopy, Grazing Incident X-Ray Diffraction (GIXRD), and Field Emission Scanning Electron Microscope (FESEM). The effect of the substrate surface was investigated by measuring the contact angles with De-Ionized (DI) water. UV-Ozone treatment of substrate provides a cleaner surface to grow a homogeneous film. The electrical resistivity of annealed thin films was carried out by a four-point-collinear probe employing the current reversal technique and found in the range of approx. 2x10^3 to 3x10^3 Ohm-cm. Film thickness was found in the range of approx. 137-285 nm, measured by a stylus profilometer. UV-VIs-NIR Transmission data revealed that all the thin film samples showed maximum (82-89) % transmission in the visible range. The optical bandgap of the thin films was estimated to be approx. 3.75-4.00 eV and approx. 3.78-4.35 eV for the films grown on SLG and quartz substrates, respectively., Comment: 7 pages, 4 figures

Herein, paper mill waste sludge (PMS) from two different sources has been investigated to extract calcium hydroxide, Ca(OH)2 by a facile and inexpensive extraction process. This green process exploits typical chemical precipitation (CP) in an aqueous medium at room temperature to develop an economically and industrially viable technique for the effective utilization of calcium-containing waste sludge. PMS samples, collected from local paper mill plants of Bangladesh, were the main precursors wherein HCl and NaOH were utilized for chemical treatment. The as-synthesized products were analyzed by a variety of characterization tools including X-ray diffraction (XRD), Fourier transform infrared (FTIR) spectroscopy, Raman spectroscopy, Scanning electron microscopy (SEM), and Energy Dispersive X-ray (EDX) elemental analyses. Our studies confirm that the extracted product contains Ca(OH)2 as a major content, albeit it also includes CaCO3 phase formed owing to the inescapable carbonation process from the surrounding environment. The particle size of the synthesized products is in the range of 450 - 500 nm estimated from SEM micrographs. The crystallite domain size of the same estimated from XRD analyses and was found to be ~47 nm and ~31 nm respectively for product-A and product-B considering major (101) Bragg peak of Ca(OH)2. The yield percentage of the isolated products is about 65% for samples collected from both sources.

Raman Spectroscopy offers an in-situ, rapid, and non-destructive characterization tool for chemical analysis of diverse samples with no or minimal preparation. However, due to the inherent weak signal of conventional Raman spectroscopy, surface plasmon resonance features of noble metal nanoparticles have been utilized to conduct Surface Enhanced Raman Spectroscopy (SERS) in detecting trace label contaminants in foods and foodstuffs. In this effort, we synthesized gold nanoparticles (AuNPs) by reduction of chloroauric acid (HAuCl4) with sodium citrate dehydrate. We prepared different sizes of AuNPs at a fixed temperature (100 oC) but with varying pHs of 4 and 8. The as-synthesized AuNPs were characterized by UV-Vis spectroscopy, dynamic light scattering (DLS), and Field Emission Scanning Electron Microscopy (FE-SEM). FE-SEM micrographs revealed spherical AuNPs with an average diameter of approx. 55 nm and rod-shaped AuNPs with an average length of approx. 170 nm for sample synthesis at pH 8 and 4, respectively. The effectiveness of the as-prepared AuNPs for SERS is tested by detecting Rhodamine 6G diluted at a trace level. This study suggests that plasmonic nanoparticles coupled with SERS have great potential for broad applications in detecting other trace amounts of hazardous chemicals in foods and foodstuffs., Comment: 4 pages, 5 figures

Cuprous oxide (Cu

In this work, cuprous oxide (Cu2O) thin films have been grown on both soda lime glass (SLG) microscopy slides and Fluorine doped Tin Oxide (FTO) substrates by a modified SILAR method. The pH level of the cationic precursor, adjusted by adding acetic acid and sulfuric acid separately, as well as the concentration of anionic precursor (NaOH) were varied to elucidate their effect on the physical properties of the deposited films. The XRD measurement shows that all films were polycrystalline in nature but single phase Cu2O with (111) preferred orientation. The surface morphology examined by scanning electron microscopy (SEM) revealed that the deposited films are micro-crack and pin hole free and coherently carpet the underlying substrate. The estimated optical band gap and resistivity of the deposited products were found to be in the range of 2.05–2.16 eV and 180–380 Ω.cm respectively where the latter is at least one order of magnitude less than the reported results for Cu2O thin films grown by similar methods. Both the optical band gap and electrical resistivity were found to be decreasing with decreasing the pH level of the cationic precursor solutions and attributed to the improve crystallization of the deposit. The LED ON/OFF modulated transient surface photovoltage of modified SILAR grown Cu2O electrode shows p-type conductivity consistent with hot point probe results and these photocathodes were found to be stable over more than 1 h in a Photoelectrochemical cell filled with aqueous electrolyte.

Here we report the effect of substrate, sonication process, and post-annealing on the structural, morphological, and optical properties of ZnO thin films grown in the presence of isopropyl alcohol (IPA) at temperature 30 – 65 ℃ by successive ionic layer adsorption and reaction (SILAR) method on both soda lime glass (SLG) and Cu foil. The X-ray diffraction (XRD) patterns confirmed the preferential growth thin films along (002) and (101) plane of wurtzite ZnO structure while grown on SLG and Cu foil substrate respectively. Both XRD and Raman spectra confirmed the ZnO and Cu-oxide phases of the deposited films. Scanning electron microscope (SEM) image of the deposited films shows compact and uniformly distributed grains for samples grown without sonication while using IPA at temperature 50 and 65 ℃. The post-annealing treatment improves the crystallinity of the films, further evident by XRD and transmission and reflection results. The estimated optical bandgaps are in the range of 3.37-3.48 eV for as-grown samples. Results revealed that high-quality ZnO thin films could be grown without sonication using IPA dispersant at 50 ℃, which is much lower than the reported results using the SILAR method. This study suggests that in the presence of IPA, the SLG substrate results in better c-axis oriented ZnO thin films than that of DI water, ethylene glycol, propylene glycol at the optimum temperature of 50 ℃. Air-annealing of the samples grown on Cu foils induced the formation of CuxO/ZnO junctions which is evident from the characteristic I-V curve including the structural and optical data.

Oriented ZnO seed layers were deposited by three different techniques, namely, simple drop casting (DC), sol-gel derived dip coating (DPC) and spin coating of ball-milled ZnO powder solution(BMD) for the subsequent growth of vertically aligned ZnO nanorods along the substrate normal. X-ray diffraction (XRD) analyses revealed that ZnO(DC) seed layer exhibit the highest preferential c-axis texturing among the ZnO seed layers synthesized by different techniques. The Scanning Electron Microscopy (SEM) analysis evident that the morphology of ZnO seed layer surface is compact and coherently carpets the underlying substrate. ZnO nanorods(NRs) were then grown by hydrothermal method atop the ZnO seeded and non-seeded substrates grown by different techniques to elucidate the best ZnO seed layer promoting well-aligned ZnO Nanorods. The presence of c-axis oriented ZnO(DC) seeding layers was found to significantly affect the surface morphology and crystallographic orientation of the resultant ZnO NRs films. The optical band gap of ZnO(DC) seed and ZnO NRs were estimated to be 3.30 eV and in the range of 3.18 – 3.25 eV respectively by using UV-VIS-NIR diffuse reflection spectroscopy. The room temperature photoluminescence analyses revealed that nanostructured ZnO films exhibit a sharp near-band-edge luminescence peak at ~380 nm consistent with the estimated optical band gap and the ZnO nanorod arrays are notably free from defect-related green-yellow emission peaks.

Oriented zine oxide (ZnO) seed layers were deposited by simple drop casting of zinc acetate dihydrate (ZAD) solution on glass substrates at room temperature followed by a post-heat treatment at 250 oC. X-ray diffraction (XRD) analyses revealed that ZAD solutions with concentration 0.0025 – 0.0100 M produced amorphous type thin films, whereas 0.0200 M ZAD solutions produced ZnO seed layers with a preferential c-axis texturing.The Scanning Electron Microscopy (SEM) analyses evident that the morphology of ZnO seed layer surface is compact and coherently carpets the underlying glass substrate. ZnO nanorods were then grown by hydrothermal method atop the ZnO seeded and non-seeded substrates. The presence of ZnO seeding layers was found to be beneficial for growing ZnO NRs films vertically. The optical bandgap of ZnO seed and ZnO NR were estimated to be in the range of 3.40 – 3.95 eV and 3.20 – 3.25 eV respectively by using UV-VIS-NIR diffuse reflection spectroscopy. The room temperature photoluminescence analyses revealed that nanostructured ZnO films exhibit a sharp near-band-edge luminescence peak at ~380 nm consistent with the estimated optical band gap and the ZnO nanorod arrays are notably free from defect-related green-yellow emission peaks.Bangladesh J. Sci. Ind. Res.53(4), 233-244, 2018

Herein, we have investigated the reinforcing potential of starch and cellulose pulp in a matrix of polyvinyl alcohol (PVA). Polyvinyl alcohol, starch, and pulp fibers having different compositions were constructed in order to achieve better reinforced composite films. Various techniques were utilized for extract the physical, mechanical as well as thermal properties. The magnitudes of tensile strength were reduced with rising of starch content in PVA. Tensile strength values of (PVA + starch) mixtures were enhanced with the enhancement of pulp fibers content. The properties of bulk density and water absorption revealed the significant impact of starch and pulp fibers. The obtained result of thermal stability of PVA was superior which was reduced by addition of starch content; therefore, regained with the insertion of pulp fibers content in PVA–starch matrix.