Low-temperature Precipitation Research Articles

Scaled-up development of magnetically recyclable Fe3O4/La(OH)3 composite for river water phosphate removal: From bench-scale to pilot-scale study

The use of magnetic lanthanum-based materials for phosphate removal from river water has gained increasing attention. However, challenges to produce and use lanthanum-based materials in large-scale or pilot-scale studies remain. In this work, a kilogram-scale Fe3O4/La(OH)3 magnetically recyclable composite for removing phosphate from river water was developed through a low-temperature precipitation route. The composite was used to remove phosphate from river water at both bench- and pilot-scales. Based on the bench-scale tests, the developed Fe3O4/La(OH)3 composite was found to have excellent magnetic particle separation efficiency (>98%) and a sorption capacity of 11.77 mg/g for phosphate. A 1.0 g/L dosage of the composite in the river water sample was able to selectively reduce the phosphate level from 0.089 to 0.005 mg/L in 60 min over five consecutive adsorption cycles. At the pilot-scale, the Fe3O4/La(OH)3 composite only achieved 36.0% phosphate removal efficiency, which is considerably different from the bench-scale results over an operational time of five months and a total treatment volume of 300 m3. This significantly reduced removal efficiency is mainly attributable to turbidity, suspended solids, and organic matter in the river water and the deteriorated magnetic separation efficiency. This study revealed potential challenges and shed new insights on moving magnetic nanocomposite-based technology from the bench-scale to the pilot-scale, which can inspire new designs for the application of similar technology.

Facile synthesis of Gd2O2SO4:Tb and Gd2O2S:Tb green phosphor nanopowders of unimodal size distribution and photoluminescence

Suppressing the crystallization and plate-like crystallite growth of RE2(OH)4SO4·2H2O compound by low-temperature (~4 °C) precipitation produced an amorphous RE2(OH)3.3(CO3)0.35SO4·2H2O precursor (RE = Gd1-xTbx) that can be decomposed to Gd2O2SO4:Tb and Gd2O2S:Tb green phosphor nanopowders of unimodal size distributions upon calcination in air at 1000 °C (average particle size ~156.9 nm) and in hydrogen at 800 °C (average particle size ~130.2 nm), respectively. The optimal RE3+ concentration for precursor synthesis was determined to be ~0.10 mol/L. Through detailed characterization by XRD, FTIR, DTA/TG, FE-SEM, TEM and particle sizing, the courses of phase/morphology evolution were clarified. Photoluminescence study found that the (Gd0.99Tb0.01)2O2SO4 and (Gd0.98Tb0.02)2O2S representative phosphors have quantum efficiencies of ~16.8% (λex = 275 nm) and 38.5% (λex = 286 nm), fluorescence lifetimes of ~3.70 and 1.75 ms and activation energies for thermal quenching of ~0.552 and 0.385 eV, respectively. The values are remarkably larger than those reported for Gd2O2S:Tb, which are considered to be due to higher purity, better crystallization and fewer luminescence-quenching defects of the product. Particularly, the (Gd0.99Tb0.01)2O2SO4 phosphor has negative thermal quenching up to ~150 °C and can retain over 85% of its room temperature emission intensity at 250 °C, which may enlighten its application in high-power LEDs.

Effectiveness of zinc oxide nanoparticles against helminthiasis: a preliminary investigation conducted on Pheretima posthuma

Based on paralyzed and death time, zinc oxide (ZnO) nanoparticles (NPs) were preliminarily investigated for possible biological effectiveness of anthelmintic activity on Pheretima Posthuma. After synthesizing ZnO NPs by low-temperature precipitation method with slight modification, size, morphology, and shape evaluation of these nanoparticles were characterized by scanning electron microscopy and annealing temperature in the range 400-700C. In this anthelmintic assay, the paralyzed time (PT) was gradually shorter with the increase of the sample concentration, for instance, when high concentration (40mg/ml) sample was applied on adult worms the paralyzed time was 35.6 minutes only. The death time (DT) was 450 and 80 minutes when the sample concentration was 20 and 40 mg/ml respectively. These results were compared with albendazole as a reference showed PT and DT 378.6 and 402.3 minutes respectively, and showed maximum dose-dependent anthelmintic activity. Finally, at higher concentration paralytic effect (PE) was showed much earlier and subsequently, it is important to note that the time taken for death observation was shorter.

Low-temperature synthesis of micro- and nano-crystalline CuFeS2 polymorphs

Micro- and nano-crystalline polymorphs of CuFeS2 have been synthesized by using simple, low temperature solvothermal and precipitation methods. A solvothermal process at 170 °C, using ethylenediamine produced micro- and nano-crystalline CuFeS2 with various shapes and morphologies, which include polygons, pyramids, hexagonal rods and plates etc. In addition to the expected tetragonal, chalcopyrite phase, a new, relatively low symmetry, hexagonal, wurtzite phase of CuFeS2 was also obtained. The wurtzite phase fraction was found to be ~21 wt% by Rietveld analysis using X-ray powder diffraction data. Further, the effects of solvent concentration, reaction temperature and annealing on the crystallites have been studied. By the solvothermal process carried out at 140 °C, hexagonal, wurtzite phase CuFeS2 was obtained with a phase fraction as high as ~92 wt%. A relatively, simple and low-temperature precipitation process using (NH4)2S and distilled water produced micro- and nano-crystalline CuFeS2 with various shapes including rods, hexagonal plates, and spheres etc. The synthesis methods reported here are believed to be beneficial for the further development of CuFeS2 in the field of nanotechnology.

Low-Temperature Synthesis of LiFePO4 Nanoplates/C Composite for Lithium Ion Batteries

The LiFePO4 nanoplates/C composite was synthesized by a low-temperature precipitation approach around 106 °C. X-ray powder diffraction refinement revealed a smaller crystallographic cell volume of this composite compared to stoichiometric LiFePO4, implying the presence of Li vacancies. Moreover, Mössbauer analysis evidenced Fe3+ with content as large as 26 at. %, which was related to amorphous ferric phase (LiFePO4(OH)) in the composite. A short low-temperature annealing under reducing condition can convert this amorphous phase to crystalline LiFePO4. This achieves significant improvement in the electrochemical performance of the LiFePO4/C composite with reversible discharge capacity of 142 mAh g–1 at C/20 and 82 mAh g–1 at 2 C, which are much higher than 105 and 49 mAh g–1 of the bare LiFePO4 at the same current rates, respectively.

Optimization of a Simplified and Effective Analytical Method of Pesticide Residues in Mealworms (Tenebrio molitor Larvae) Combined with GC-MS/MS and LC-MS/MS.

An effective analytical method was optimized for residues including chlorpyrifos–methyl, deltamethrin, fenoxanil, thiobencarb and fludioxonil in mealworms, the larval form of Tenebrio molitor. They are listed for pest control during wheat cultivation and can be found in wheat-bran feed for growing mealworms in South Korea. Analytes were extracted using acetonitrile and salt packet. Four clean-up methods ((1) MgSO4 + 25 mg PSA + 25 mg C18; (2) MgSO4 + 50 mg PSA + 50 mg C18; (3) EMR-lipidTM tube; and (4) 10 mL n-hexane) were investigated and the method (1) was selected due to its robustness. Low-temperature precipitation of fat and proteins improved the recoveries. Recoveries from the Method (1) were satisfying with 70–120% with <20% relative SD at a spiking level of 0.01 mg/kg. With the simultaneous sample preparation, fenoxanil, thiobencarb and fludioxonil were analyzed by liquid chromatography tandem mass spectrometry (LC–MS/MS) and chlorpyrifos–methyl and deltamethrin by gas chromatography tandem mass spectrometry (GC–MS/MS). Quantification limits for LC–MS/MS and GC–MS/MS were 0.5 and 2.5 μg/L, respectively. No pesticides of interest were detected in 30 real samples collected across the nation. However, the data can be provided for establishing maximum residue limits for the pesticides in mealworms in response to the positive list system.

No evidence for carbon enrichment in the mantle source of carbonatites in eastern Africa

Abstract Carbonatites are unusual, carbon-rich magmas thought to form either by the melting of a carbon-rich mantle source or by low-degree partial melting of a carbon-poor (&amp;lt;80 ppm C) mantle followed by protracted differentiation and/or immiscibility. Carbonate-bearing mantle xenoliths from Oldoinyo Lengai (East African Rift), the only active volcano erupting carbonatites, have provided key support for a C-rich mantle source. Here, we report unique microscale O and C isotopic analyses of those carbonates, which are present as interstitial grains in the silicate host lava, veins in the xenoliths, and pseudo-inclusions in olivine xenoliths. The δ18O values vary little, from 19‰ to 29‰, whereas δ13C values are more variable, ranging from –23‰ to +0.5‰. We show that such carbonate δ18O values result from the low-temperature precipitation of carbonate in equilibrium with meteoric water, rather than under mantle conditions. In this framework, the observed δ13C values can be reproduced by Rayleigh distillation driven by carbonate precipitation and associated degassing. Together with petrological evidence of a physical connection between the three types of carbonates, our isotopic data support the pedogenic formation of carbonates in the studied xenoliths by soil-water percolation and protracted crystallization along xenolith cracks. Our results refute a mechanism of C enrichment in the form of mantle carbonates in the mantle beneath the Natron Lake magmatic province and instead support carbonatite formation by low-degree partial melting of a C-poor mantle and subsequent protracted differentiation of alkaline magmas.

Effects of Chromium Doping on the Electrical Properties of ZnO Nanoparticles

Nanostructured ZnO has gained a considerable amount of attention due to its unique physical and chemical properties and due to its remarkable performance in the fields of optics, photonics and electronics. The scope of this work is to study the Structural, Optical and Electronic properties of Pure Zinc Oxide (ZnO) and Chromium doped Zinc Oxide nanoparticles. These nanoparticles were synthesized by low-temperature precipitation method at various concentrations in the range (Zn1-xCrxO; (x = 0, 0.1&amp; 0.3)). The precursors used were analytical grade Zinc Nitrate Hexahydrate and Chromium Nitrate Nona hydrate. The synthesized nanoparticles were annealed at 400°C. The Structural property of the synthesized nanoparticles was analysed by XRD (X-Ray diffraction) and was confirmed to exhibit a crystalline hexagonal wurtzite structure with an average crystallite size of 55nm. The functional groups were analysed using FTIR (Fourier Transformed Infra-red spectroscopy). The Morphology was analysed by FESEM (Field Emission Scanning Electron Microscope) and a change in morphology from spherical to spindle like structure was observed. The Optical properties were analysed using UV-Vis spectroscopy, the absorption spectrum for electromagnetic spectrum was observed and the changes in the optical band gap of ZnO nanoparticles with Chromium dopant addition were calculated to be in the range of 3.6 eV. The Electrical property of the synthesised nanoparticles was analysed using Electrochemical Impedance Spectroscopy (EIS) and the conductivity was calculated to be in the range of 1.1e-07S/m.

Decolorization of commercial zein via protein precipitation involving organic solvents at low temperatures

The low-temperature organic solvent precipitation of proteins is a reversible denaturation process. In this study, the effect of the low-temperature precipitation decolorization of zein was investigated on the basis of this reversible process by using the pigment clearance rate and zein recovery rate as evaluation indicators. Low-temperature anhydrous ethanol was used as a precipitant. Furthermore, with the volume ratio of precipitator to zein solution (the volume ratio), precipitator temperature and zein solution pH as three factors. A low-temperature precipitation method was compared with an activated carbon adsorption method to determine the decolorization effect of zein via response surface methodology to optimize decolorization. Results showed that the decolorization effect of low-temperature precipitation was significantly affected by precipitator temperature, volume ratio, and zein solution pH. The primary order of their effects was as follows: precipitator temperature > volume ratio > zein solution pH. The decolorization effect of zein was optimal under the following parameters: precipitator temperature of −30 °C, zein solution pH of 6.8, and volume ratio of 2.5:1. Under these conditions, the zein recovery rate and the pigment clearance rate were 86.93 % and 98.72 %, respectively. By contrast, the zein recovery rate and the pigment clearance rate were 68.50 % and 79.22 % under the optimized activated carbon decolorization process, respectively. In conclusion, the effect of low-temperature precipitation decolorization and the recovery rate of zein were obviously better than those of activated carbon decolorization.

Study on the safe disposal and resource utilization of cyanobacterial bloom biomass in Dianchi Lake, China

To solve the problem of utilizing massive harmful algal blooms (HABs) biomass, we developed a technique involving physical purification methods, namely, microfiltration (2 μm, 0.45 μm), ultrafiltration (100 kDa cutoff), and low-temperature precipitation (4 °C, 48 h), as the core methodology and used the toxic Microcystis biomass in Dianchi Lake for batch preparations of microcystins (MCs) and phycocyanin (PC). The results were as follows: (1) From 1.0 kg of Dianchi Lake cyanobacteria, 57 g of PC powder with a purity (A620/A280) of 1.78 was prepared. An acute oral toxicity test in mice showed that the LD50 of the prepared PC was >5.25 g kg−1, practically non-toxic. The LD50 of PC administered by intraperitoneal injection was >4.71 g kg−1. The Ames test showed that the mutagenic effect was negative independent of the addition of S9. The overall results of the toxicity tests suggested that the prepared PC was not potentially toxic. (2) From 666.7 g of cyanobacteria, 2.262 g of MC extract powder (containing 192.7 mg of MC-RR and 54.3 mg of MC-LR) was prepared. MC-RR and MC-LR accounted for 8.52% and 2.40%, respectively, and the extraction ratios for MC-RR and MC-LR were 40.1% and 83.1%, respectively. A further purification by preparative HPLC was carried out, obtaining 2.338 mg of pure MC-RR (chromatographic purity >85%) from 70 mg of MC extract powder, which was used as an HPLC chromatographic standard and in routine toxicology experiments. The efficiency of the ultrafiltration treatment of cyanobacterial powder reached 49.3 kg d−1, and the cost of producing food-grade PC powder in this study was 17.6 US$ g−1, which is only 13.6% of the current price of food-grade PC on the international market. Thus, the cost advantage was significant. Therefore, this study provides an approach for the safe disposal of HABs and the large-scale commercial utilization of HAB biomass.

Delineation of point defect state in Czochralski Si by modified background haze

A novel haze technique for analyzing point-defect distribution in Czochralski Si (CZ-Si) wafers without intentional contamination by transition metals was proposed. Based on the background haze in high-temperature oxidation, a three-step oxidation process including two-step low-temperature precipitation and a single-step high-temperature wet oxidation process was designed. After the newly designed heat processing and preferential etching, surface haze was formed selectively on the interstitial-dominant region of the wafer. Through electron microscopy analysis, surface defects decorated with Ni were observed, which suggested that the surface accumulation of non-gettered Ni adsorbed from the furnace causes surface haze on the interstitial-dominated region. The widths of the hazes could be optimized by adjusting the processing times of the first two steps, which affected the Ni gettering ability in the vacancy-dominated regions of the wafers. Additionally, the second stage at 1000 °C was associated with precipitate growth, as well as with haze formation.

Improving the formaldehyde gas sensing performance of the ZnO/SnO2 nanoparticles by PdO decoration

In this work, a series of PdO catalytic ZnO/SnO2 (PdO–ZSO) nanoparticles have been synthesized by a two-step approach including a low-temperature (− 10 °C) precipitation followed by a PdO dipping process. The composition, surface morphology, and crystal structure of the as-obtained samples were characterized by multi-techniques. And the gas-sensing properties toward formaldehyde (HCHO) were evaluated. The results indicate that the PdO–ZSO nanoparticles exhibit high sensitivity (5.4) and rapid response (37 s)/recovery (87 s) to 10 ppm HCHO at 140 °C through optimizing the ratio of PdO, ZnO, and SnO2 in nanoparticles. Comparing with the traditional SnO2 sensor without ZnO and PdO, the sensors’ working temperature is much lower and the response–recovery speed is also improved. In addition, the specific sensing mechanism was discussed preliminarily.

Modifications in the Structural and Optical Properties of ZnO Nanophosphor on Doping with Tb

Background:The characteristic visible emission from ZnO being attributed to the defect energy states can be tailored by doping as well as by synthesis techniques. Rare-earth elements, among various dopants, are interesting because of their unique emission properties in the visible region. Terbium (Tb), in particular, is reported to contribute significantly to the creation of the defect energy states when doped in ZnO. This study investigated the Tb concentration dependent modifications in the structural and optical properties of ZnO nanophosphor.Methods:Tb (0.1, 0.5, 01.0 mol%) doped nanophosphor powder samples prepared by low temperature precipitation method, were sintered in air at 700oC using a home-built temperature controlled (±1oC) muffle furnace. Powder XRD and EDX spectra at room temperature were recorded using Philips X perts x-ray spectrometer while Jeol JSM-7600F was used to record SEM images. Photoluminescence spectra excited by the 280, 300, 380 and 460nm radiation from a Xe lamp were recorded using Carry 8000 spectrophotometer. Raman spectra excited by 514.5nm radiation from an Ar-ion laser, was investigated using Morrison microscope Olympus Bx 41 while UV-VIS absorption spectra were recorded on UV- 1800 UV-VIS Spectrophotometer.Results:FTIR and XRD spectra showed that the basic ZnO wurtzite crystal structure remained unchanged on doping. However, XRD data analysis indicated that the 0.1 mol% Tb might be incorporated in ZnO unit cell at an interstitial and / or substitutional site(s) while at 0.5 and 1.0 mol% doping levels migration of Tb to the surface could be the dominant process. This was further confirmed by Raman and photoluminescence studies. Broad emission (122nm FWHM) peaking around 510nm was observed when the doped samples were excited with 280 and 300nm radiation while characteristic ZnO emission was observed with 380 and 460nm radiation. The calculated chromaticity color coordinates (x,y) of the emission excited by 280nm in 0.5 mol% doped ZnO were: x=0.29 and y=0.31, which are very close to those of the daylight at noon.Conclusion:Concentration dependent lattice distortions were observed; it was concluded that at 0.1mol% concentration level Tb was incorporated in ZnO lattice resulting in interstitial or substitutional defects. On the other hand, at 0.5 and 1.0 mol% doping levels diffusion of Tb to the surface producing strain due to "hydrostatic like pressure" seemed to be the dominating process; maximum strain was observed at 0.5mol% doping. The calculated chromaticity color coordinates of the 280nm excited emission from ZnO:Tb (0.5mol%) were found to be very close to those of the "day light at noon” indicating the suitability of the material for the realization of white light sources.

Structure and Electrochemical Properties of Li4Ti5O12 Prepared via Low-Temperature Precipitation

This work aimed to prepare the spinel phase Li4Ti5O12 by a combination of the low-temperature precipitation technique and assisted calcination step. X-ray diffraction (XRD) revealed that the intermediated phase was Li2TiO3, and the spinel phase could be evidently formed at 700°C for 12 to 20 hours. The morphology of spinel powder, determined by SEM and TEM, exhibited a good distribution at the submicrometric scale that promoted a fast kinetic of Li migration and an excellent performance at the high-rate cycling test. The stable performances were achieved in the charge-discharge test at different current densities: 80 mA/g (165 mAh/g), 320 mA (160 mAh/g), and 1600 mA (145 mAh/g) upon 100 cycles. Moreover, we observe a capacity retention of 48% (corresponding 80 mA/g) at a high rate of 5000 mAh/g. The cyclic voltammetry measurement displayed a reversible system and revealed the lithium diffusion coefficient of 1.15 × 10−11 cm2/s.

Evaluation of Fe-Doped CGO Electrolyte for Application in IT-SOFCs

A challenge encountered with intermediate temperature solid oxide fuel cells (IT-SOFCs) is lowering the densification temperature of the doped ceria electrolyte and improving its ionic conductivity. Ceria doped with 10 mol% gadolinium oxide and 0, 1, 5 mol% iron oxide were synthesized by a low temperature precipitation route based on hexamethylenetetramine as the precipitating agent. The as-synthesized precursors are nanocrystalline powders with a homogeneous morphology. Co-doping with Fe3+ changes the sintering behaviour of the doped cerium oxide and favours densification at lower temperatures. Through a comprehensive elementary, structural, microstructural and electrochemical analysis of the co-doped cerium oxide, it was established the doping mechanism of Fe3+ and its effect on the bulk and grain boundary conductivities. The overall aim is to evaluate its suitability for application as an electrolyte in IT-SOFC applications.

Investigation of photodegradation of rhodamine B over a BiOX (X = Cl, Br and I) photocatalyst under white LED irradiation

In this study, a low temperature precipitation method was applied to prepare BiOX (X = Cl, Br and I) nanostructures using HCl, HBr and HI as halogen sources. The as-prepared samples were characterized by various techniques such as X-ray diffraction, field emission scanning electron microscopy, energy dispersive spectroscopy, Fourier-transform infrared spectroscopy, diffuse reflectance spectroscopy and nitrogen adsorption–desorption analysis. The photoactivity of BiOX samples to degrade rhodamine B (RhB) molecules in aqueous solution was investigated under white LED irradiation. The results indicated that BiOCl exhibits a higher photodegradation performance in comparison with BiOBr and BiOI. Ninety six percent of the RhB molecules was degraded over BiOCl after 25 min light irradiation, whereas under the same conditions, the degradation efficiencies of BiOBr and BiOI samples are 62 and 24%, respectively. The enhanced photodegradation activity of BiOCl is ascribed to the higher specific surface area which increases the physical adsorption of RhB molecules on the photocatalyst surface. Moreover, the photodegradation mechanism and the main radical species in the degradation reactions over BiOCl were investigated.

ZnS nanoparticles as new additive for polyethersulfone membrane in humic acid filtration

In this report, well-dispersed ZnS nanoparticles were applied as inorganic additives for polyethersulfone (PES) membrane to improve anti-fouling performance. ZnS nanoparticles were synthesized by low temperature precipitation and phase inversion method was used to embed them into PES membrane for humic acid (HA) filtration. Intrinsic properties of the PES-ZnS composite membrane developed were investigated at different ZnS loadings. Compared to the control PES membrane, the PES-ZnS membrane improved hydrophilicity, porosity and thermal stability. Effect of ZnS on the flux recovery of the PES membrane fouled with HA was more pronounced than that as TiO2 was used as embedding materials.

Veronico beccabungae-Mimuletum guttati, a new plant community in Slovakia

Vegetation with high coverage by the alien species &lt;em&gt;Mimulus guttatus&lt;/em&gt; was studied in the hilly regions of central Slovakia in 2015 and 2016. The floristic composition of these stands was recorded in ten phytosociological relevés corresponding to the &lt;em&gt;Veronico beccabungae-Mimuletum guttati&lt;/em&gt; (alliance &lt;em&gt;Glycerio-Sparganion&lt;/em&gt;) association. This association was reported for the first time in Slovakia in this study. This association was found to be closed or almost closed (mean coverage value of herb layer = 92%) and formed relatively species-rich stands (15 species per relevé), usually in narrow and small patches along the upper parts of streams and their spring areas in uplands at altitudes from 561 to 1,048 m. Localities with the &lt;em&gt;Veronico beccabungae-Mimuletum guttati&lt;/em&gt; association were characterized by typical mountain climates, with both relatively low mean annual air temperature (5.5°C) and high mean annual precipitation (885 mm). While water temperature (~13°C) of these habitats varied considerably among streams (7.4–19.9°C), their herbaceous vegetation preferred neutral to slightly alkaline water (pH = 6.1–7.5) with low amounts of soluble mineral matter (~72.6 μS cm&lt;sup&gt;−1&lt;/sup&gt;). This kind of vegetation was most often developed on sites with coarser sediments (stone, gravel, and sand) formed from crystalline bedrock. A comparison of vegetation data of the &lt;em&gt;Veronico beccabungae-Mimuletum guttati&lt;/em&gt; association across Central Europe demonstrated considerable floristic variability among regions.

Low-Temperature Synthesis of Cuboid Silver Tetrathiotungstate (Ag2WS4) as Electrocatalyst for Hydrogen Evolution Reaction.

Ternary bimetallic sulfide silver tetrathiotungstate (Ag2WS4) was prepared by a simple low-temperature precipitation method. The structure of Ag2WS4 was determined using the data from powder X-ray diffraction, which is in space group I4̅2 m (I-phase) with a tetragonal unit cell of a = b = 5.950 71 Å and c = 9.562 65 Å, containing layers of edge-sharing AgS4 and WS4 tetrahedra. The Ag2WS4 was also used as an electrocatalyst for the hydrogen evolution reaction (HER) in acid electrolyte. The results demonstrated that, attributed to its unique composition, large electrochemical active surface area, and high electric conductivity, the Ag2WS4 exhibited superior electrocatalytic activity for HER, in comparison with the ternary counterparts of WS2 and Ag2S with a low onset potential and small Tafel slope. The Ag2WS4 also presented superior stability and maintained the electrocatalytic activity of HER for at least 24 h in 0.5 M H2SO4.

Enhancement in power conversion efficiency of silicon solar cells with cobalt doped ZnO nanoparticle thin film layers

In this study, we report results on coating silicon solar cells with undoped and cobalt-doped zinc oxide (5%, 10%, 15%, and 20%) nanoparticles ranging in diameter from 46 nm to 87 nm, synthesized by a simple low-temperature precipitation method. The morphology and structure of nanoparticles have been characterized by transmission electron microscopy and X-ray diffraction spectroscopy. The average size of nanoparticles was found to increases with the increase in cobalt concentration. Doped and undoped zinc oxide thin films were deposited by a simple spin coating technique on silicon solar cells. Optical properties of the cobalt-doped zinc oxide layer have been investigated. We estimated the thin film stress by adding nanoparticles layers and found that the stress is lowest for the 139 nm cobalt-doped zinc oxide layer. Bandgap was found to increase with an increase in zinc oxide nanoparticle thin film thickness. Photoluminescence spectra show a blue shift in the near band edge emission peak with increase in thickness. Current-Voltage measurement confirms that there is an enhancement in power conversion efficiency as the thickness of zinc oxide nanoparticles varied from 58 nm to 139 nm. In general, the conversion efficiency shows an increasing trend up to 139 nm of thickness in silicon solar cells coated with doped and undoped zinc oxide nanoparticles. In addition, there is an enhancement of external quantum efficiency with an increase in thickness of zinc oxide layer. The optimal thickness of nanostructured zinc oxide film layer to enhance the efficiency of the silicon photovoltaic cell was experimentally determined to be 139 nm.