Aqueous Solutions Of ZnCl2 Research Articles

Preparation, characterization, and desulfurization ability of bulk porous silica-supported ZnO

The facile preparation of bulk porous silica and a desulfurization ability of this silica-supported ZnO as application are reported. Bulk porous silica was prepared by the sol–gel method using tetraethoxysilane (TEOS) and surfactant as a template. The swollen gel was filled in a plastic vial followed by curing for 1 day. Bulk porous silica was prepared by the calcination of the cured gel. The bulk porous silica was characterized by nitrogen adsorption–desorption measurements and transmission electron microscopy (TEM). The bulk porous silica has micropore and mesopore: the micropore distribution was calculated to be 1.7 nm by the MP method and the mesopore-size distribution was calculated as 6.3 nm by the Barrett–Joyner–Halenda method. The volume of micropore was larger than that of mesopore; hence, bulk porous silica would be formed as a pillared-clay-like structure. Bulk porous silica-supported ZnO was prepared by the impregnation of ZnCl2 followed by calcination in air. The content of ZnO in bulk porous silica (1.9, 15.3, 33.8, and 46.2 wt%) was determined by inductively coupled plasma atomic emission spectrometry, and the ZnO content was depended on the concentration of ZnCl2 aqueous solution. Characterization was achieved by nitrogen adsorption–desorption measurements and TEM. The specific surface area decreased with increasing concentration of ZnO because ZnO deposited onto wall within pores. The sulfurization capacity of the bulk porous silica-supported ZnO was evaluated, and the sulfurization capacity per gram of the bulk porous silica-supported 46.2 wt% ZnO showed 12.56 mg/g.

Fabrication of ZnO@Cotton fabric with anti-bacterial and radiation barrier properties using an economical and environmentally friendly method

Recent years have witnessed the explosive progress of functional materials, which are made by loading various metal oxides onto fabrics. A cost-effective, facile, and simple approach of loading hexagonal zinc oxide (ZnO) sheets onto fabrics is highly desired. Here, the fabrication of the multifunctional ZnO@cotton fabrics is demonstrated using a surface micro-dissolution method by sodium hydroxide/urea (NaOH/urea) and zinc chloride (ZnCl2) aqueous solution. The hexagonal sheet ZnO forms the reflective layer to ultraviolet and near-infrared rays. The UV reflectivity of ZnO@cotton fabric is higher than the raw fabric in the range of 10.9–18.8% and UPF value of treated fabric was 100 + . Infrared barrier results were obtained through the phenomenon of heat radiation transfer obstruction, when fabrics being placed on the hot plate of 120 °C, the temperature difference between raw and treated fabrics is 6.6 °C. Also, the high antibacterial activity against Escherichia coli and Staphylococcus aureus cultures of ZnO@cotton fabric was testified.

Ultrasound assisted surface micro-dissolution to embed nano TiO2 on cotton fabrics in ZnCl2 aqueous solution

In this paper, a simple and environment friendly approach was used to prepare the multifunctional composite fabrics via coating commercial TiO2 nanoparticles (NPs) on the surface of cotton fibers by surface micro-dissolution process in 55%wt ZnCl2 aqueous solution under the aid of ultrasound without any adhesive. The TiO2/cotton composite fabrics were characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD), energy dispersive X-ray spectroscopy (EDS), Fourier transform infrared spectroscopy (FTIR) and thermal gravity (TG) methods. The treated fabric had photocatalytic property in Rhodamine B (RhB) degradation, and had good antibacterial activity against Escherichia coli (E. coli) and Staphylococcus aureus (S. aureus) cultures. The results of contamination degradation and antibacterial experiments confirmed that ultrasonic vibration had a significant effect on the tightly coating of nanoparticles on cotton fiber surface in the process of micro-dissolution. Even after intense ultrasonic washing, the contamination degradation rate and antibacterial efficiency of S3 (with ultrasonic) still reach 95% and 99% respectively, while S4 (without ultrasonic) only remained 72% and 59% of S2, which was attributed that ultrasonic facilitated the entry and load of nanoparticles onto the fabrics. The mechanical property of treated cotton fabrics kept well.

Toward an efficient antibacterial agent: Zn- and Mg-doped hydroxyapatite nanopowders

The use of synthetic hydroxyapatites (HAps) in biomedical and environmental applications is well warranted given that they have been shown to behave as an excellent bio-compatible material in human teeth and bones. In this paper, a series of HAps doped and co-doped with two metal cations (zinc and magnesium) has been successfully synthesized by means of the precipitation method using CaCl2, Na2HPO4, ZnCl2 and MgCl2 aqueous solutions as reagents. The synthesized samples have been characterized using Fourier transform infrared (FTIR), X-ray diffraction (XRD), scanning electron microscopy (SEM) and X-ray fluorescence spectroscopy (XRF). All samples prepared using over 10 mol% of Zn and Mg ions were identified as HAp. However, the presence of metal cations caused a significant increase in their crystallite sizes (30–50 nm) along with the appearance of a second phase (scholzite, whitlockite). The XRF spectra indicated the presence of Ca, P, Zn and Mg in the powders prepared with a high Metal/P ratio (1.7–2). The antimicrobial activity of these nanopowders has been tested in vitro against five bacteria (Escherichia coli, Klebsiella pneumoniae, and Pseudomonas aeruginosa as Gram-negative; Staphylococcus aureus and Bacillus subtilis as Gram-positive) and two fungal strains (Candida albicans and Aspergillus niger). The outcomes revealed that these nanopowders exhibited strong antimicrobial activity, starting at 15 mol% of Zn and/or Mg.

Electrodeposition of Zn-Terephthalate Metal-Organic Framework Thin Films

Electrochemical self-assembly (ESA) of metal-organic framework (MOF) thin films of Zn2+ ions and terephthalic acids (TPA) in a layered structure and with a composition of Zn3(OH)4(TPA)•6H2O was made possible by addition of TPA into the bath for electrodeposition of ZnO, namely, O2-saturated aqueous solution of ZnCl2. The deposition of Zn-TPA MOF, however, resulted in a strong passivation of the electrode towards O2 reduction to limit the electrochemical growth. Interestingly, chemical precipitation of Zn-TPA MOF was found to take over the film growth to achieve a thickness of about 2 µm in the extended electrolysis, in spite of the negligibly small current. Due to decrease of TPA concentration in the solution bulk, the electrode finally recovered the activity for the O2 reduction, which, however, resulted in the electrodeposition of ZnO to be overlaid on the Zn-TPA MOF. The electrodeposited Zn-TPA MOF was well adherent to the substrate.

Al-doped ZnS thin films: Physical and electrochemical characterizations

This study evaluated the effect of Al incorporation on the structural, optical, electrical and electrochemical properties of ZnS thin films. An electrochemical route was used to synthesize the studied un- and Al-doped ZnS thin films on indium tin oxide (ITO) glass substrates using an aqueous solution of ZnCl2 and Na2S2O3. The Al-doped ZnS samples were prepared by adding different amounts of AlCl3 to the main electrolyte. Cyclic voltammetry determined −0.9 to −1.1 V as the appropriate potential range for deposition of the ZnS thin films. In addition, appearance of a new reduction peak in the cyclic voltammograms of the Al-doped ZnS samples approved the presence of the Al dopant in the structure of the electrodeposited films. The recorded X-ray diffraction (XRD) patterns exhibited that all deposited samples contain cubic ZnS crystals and indicated that Al-doping decreases the crystallite size of the ZnS samples. Field emission scanning electron microscopy (FESEM) demonstrated that all samples are composed of big grains with 150–600 nm dimension distributed in a background phase including 15–60 nm grains. The photoluminescence (PL) spectra showed that all samples emit five PL peaks due to their different crystal defects. UV–Vis spectroscopy clarified that Al-doping decreases the band gap energy of the ZnS samples from 3.93 to 3.50 eV. Furthermore, it showed that the Al-doped ZnS samples present a lower capacitance and a shorter response time, which are suitable properties for application of these materials in fast photodetectors. The Mott-Schottky plots demonstrated n-type conductivity for all samples and revealed that the existence of the Al dopant increases the carrier concentration of the ZnS thin films. The electrochemical impedance spectroscopy (EIS) results confirmed that Al incorporation reduces the time constant and capacitance of the ZnS samples. Consequently, all results declared that Al incorporation has significant effects on the physical, optical and electrical properties of ZnS thin films.

Cellulose-Derived Highly Porous Three-Dimensional Activated Carbons for Supercapacitors.

A novel “selective surface dissolution” (SSD) method was successfully utilized in previous research to prepare “all-polymer composites” aiming to structural applications. In the current study, this simple, cost-effective, and environmentally friendly method was employed for the first time to synthesize cellulose-derived highly porous three-dimensional (3D) activated carbon materials to assemble superior electrodes for supercapacitors. ZnCl2 aqueous solution was used to partially dissolve the surface of cellulose fibers. The partially dissolved cellulose I crystalline phase at the fiber surface can be consolidated into fibrillar cellulose polymorphs (e.g., cellulose II) which connects remaining fibers together. By a carefully controlled SSD method, a highly porous 3D cellulosic skeleton with interconnected bridge-like fibrillar linkages and hierarchical pore structures can be created. After carbonization, the 3D fiber construct with interconnected fibrillar linkages and hierarchical pore structures remains and highly porous activated carbons were obtained. The effects of various processing parameters (e.g., solvent concentration, immersion time, etc.) on the morphology of the as-formed activated porous carbons and their electrochemical performance as electrodes in supercapacitors were systematically investigated and discussed. It was concluded that the SSD method is a promising chemical approach to produce large-scale cellulose-derived activated porous carbons in an environmentally friendly manner.

Influence of solution composition on sprayed ZnO nanorods properties and formation process: Thermoanalytical study of the precursors

ZnO is an important inorganic material for numerous applications. Different physical and chemical methods have been applied to deposit ZnO. Spray pyrolysis method being simple, rapid and low-cost is amongst the many options and has been chosen for this study. Fabrication of ZnO nanorods crystals by chemical spray pyrolysis was performed using an acidic solution of ZnCl21 or a basic ammonia-containing solution of ZnCl22. All layers were studied using X-ray diffractometry and Scanning Electron Microscopy. The formation of ZnO nanorods from 2 appeared at 450 °C, whereas spraying acidic solution 1 yielded ZnO nanorods like morphology at 550 °C.Thermal decomposition of precursors for ZnO layers prepared by de-watering of acidic aqueous solution of ZnCl2 with pH = 3 (1) and basic solution of ZnCl2 and NH4OH with pH = 10 (2) was monitored by simultaneous thermogravimetric and differential thermal analysis (TG/DTA) in air coupled online with evolved gas analyses by Fourier transformed infrared spectroscopy (FTIR).The precursor (1) is ZnCl2 *nH2O; the precursor (2) is a mixture of (NH4)3(ZnCl4)Cl, Zn(NH3)2Cl2, NH4Cl(NH3)3 and Zn(OH)2 phases. The thermal decomposition of (1) and (2) in the temperature range of 30–700 °C consists of two steps with total mass losses of 86.2% and 93.8%, respectively. The main evolved gases from (1) are H2O and HCl, whereas the main evolved gases from (2) are H2O, NOx and NH3. Degradation of (1) and (2) is completed by 670 and 620 °C, respectively. The final decomposition product of (1) and (2) at 700 °C is ZnO.This study shows that the use of basic solutions enables to decrease the temperature of ZnO formation and the deposition temperature of ZnO nanorods layers.

Biologically inspired silk fibroin grafted polyacrylonitrile filtration membrane prepared in ZnCl2 aqueous solution

In this study, biologically inspired silk fibroin grafted polyacrylonitrile (SF-g-PAN) filtration membrane was prepared using ZnCl2 aqueous solution as solvent, avoiding the use of organic solvents. Phase inversion occurred when Zn2+ and Cl− ions gradually diffused into water, creating a well-connected ion channel network and the SF-g-PAN filtration membrane was obtained. The membranes were observed by SEM and 3D ultra-depth microscope. The hydrophilic property, pore size distribution and dye rejection of the membrane were investigated. Results showed that the membrane has no finger hole formation because ZnCl2 aqueous solution has a lower curing rate parameter compared with organic solvents. SF-g-PAN membrane possessed good anti-fouling properties and pH sensitivity. The pore size distribution of the SF-g-PAN membrane was 0.25–1.04 nm. The rejection of direct yellow 27 (Mw = 662.6) and amaranth (Mw = 604.5) was 96.51% and 30.63%, with the flux of 72.32 L m−2 h−1 and 73.83 L m−2 h−1 respectively at 0.1 MPa. The SF-g-PAN membrane has a wide range of applications prospect in fine separation, dye desalination, waste water treatment and biomedical fields.

Preparation of smart and reversible wettability cellulose fabrics for oil/water separation using a facile and economical method

Successful fabrication of smart membrane based on cellulose fabric for controllable oil/water separation was reported. Sheet hexagonal ZnO was in situ synthesized on surface of cellulose fibers using NaOH/urea and ZnCl2 aqueous solution which were also exploited to fix ZnO steadily due to their swelling and dissolving effects on cellulose. Reversible wettability transition between superhydrophobicity/superoleophilicity and superhydrophilicity/superoleophobicity underwater was manipulated easily by dipping into a lauric acid ethanol solution and NaOH/ethanol water solution in turn for 2min. In detail, the as-prepared functionalized membranes can separate weight or light oil/water mixtures with separation efficiency higher than 98% of water removing and 96.5% of oil removing and high oil flux of 2900–3200 L h−2 m-2 and water flux of 3100–3400 L h−2 m−2. Simultaneously, the modified fabrics exhibited good stability and excellent recyclability via 20 times cycle operations of wettability transition and separation.

Electrodeposited ZnO-Based, Organic-Dye Sensitized Solar Cells: Advantages and Limitations

The dye-sensitized solar cell (DSSC) is one of the most promising third generation photovoltaic technologies, which nowadays shows conversion efficiencies as high as 14 %. The attractive qualities of DSSCs include promising efficiencies, but also the low cost projected for their large-scale production for niche applications, in particular, for semi-transparent windows and indoor lighting conditions. This implies the optimization of all processing steps and components used, and a better understanding of the mechanisms of generation and loss of electrons involved in the solar cell functioning. Based on these observations, we have selected ZnO as the electron transporting material, not only for its much better electrical properties (when comparing with the commonly used TiO2), but also for the simple synthesis methods by which it can be obtained, such as electrodeposition (a low temperature an scalable technique), which offers to move toward the fabrication of more economically profitable devices. Hence, part of this work presents a detailed study on the effect of the bath composition, additives and deposition conditions used on the morphological and structural features of materials electrodeposited from ZnCl2 and Zn(NO3)2 solutions. The combination of this material with organic dyes with high absorption coefficient in the solar spectrum regime, promise an increase in cell current and voltage. For that reason, we have prepared solar cells with nanostructured, mesoporous ZnO films electrodeposited from an optimized aqueous ZnCl2 solution, an organic fluorenyl-thiophene dye (OD-8) as sensitizer, and an electrolyte solution with either the I-/I3 - or the [Co(2,2'-bipyridyl)3]2+/3+ redox couple. An improvement in efficiency may be expected, related to the more positive redox potential of the [Co(2,2'-bipyridyl)3]2+/3+ couple and faster dye regeneration kinetics, but this can only be achieved if the recombination rate at the semiconductor/electrolyte interface is sufficiently slow. Hence, we have evaluated the effect of CDCA (chenodeoxycholic acid) as coabsorbent in the dye solution, with the purpose to diminish the amount of uncovered area of the electrode surface, in order to minimize recombination. We use I-V curves in combination with intensity-modulated photovoltage spectroscopy, charge extraction measurements, and surface photovoltage spectroscopy to gain insight in the factors involved into the photochemical charge separation in ZnO-based organic-DSSCs.

Two mechanisms of oral malodor inhibition by zinc ions.

ObjectivesThe aim of this study was to reveal the mechanisms by which zinc ions inhibit oral malodor.Material and MethodsThe direct binding of zinc ions to gaseous hydrogen sulfide (H2S) was assessed in comparison with other metal ions. Nine metal chlorides and six metal acetates were examined. To understand the strength of H2S volatilization inhibition, the minimum concentration needed to inhibit H2S volatilization was determined using serial dilution methods. Subsequently, the inhibitory activities of zinc ions on the growth of six oral bacterial strains related to volatile sulfur compound (VSC) production and three strains not related to VSC production were evaluated.ResultsAqueous solutions of ZnCl2, CdCl2, CuCl2, (CH3COO)2Zn, (CH3COO)2Cd, (CH3COO)2Cu, and CH3COOAg inhibited H2S volatilization almost entirely. The strengths of H2S volatilization inhibition were in the order Ag+ > Cd2+ > Cu2+ > Zn2+. The effect of zinc ions on the growth of oral bacteria was strain-dependent. Fusobacterium nucleatum ATCC 25586 was the most sensitive, as it was suppressed by medium containing 0.001% zinc ions.ConclusionsZinc ions have an inhibitory effect on oral malodor involving the two mechanisms of direct binding with gaseous H2S and suppressing the growth of VSC-producing oral bacteria.

Fabrication of magnetic cotton fabrics using surface micro-dissolving technology in ZnCl2 aqueous solution

A facile and environmentally friendly surface micro-dissolving technology was applied to embed commercial ferroferric oxide (Fe3O4) nanoparticles into superficial zones of cotton fabrics and obtain magnetic cotton fabrics. 55 wt% zinc chloride (ZnCl2) aqueous solution, as the cellulose dissolving agent, was used to implement micro-dissolving process of cotton fabrics and facilitate to embed Fe3O4 nanoparticles into the surfaces of cotton fabrics at elevated temperature. The magnetic cotton fabrics were characterized through employing scanning electron microscopy, X-ray photoelectron spectroscopy, Fourier transform infrared spectroscopy, X-ray diffraction, thermogravimetric analysis. The magnetic property of the modified cotton fabrics was measured by vibrating sample magnetometer. Tensile strength and laundering durability tests of the magnetic cotton fabrics were also carried out. The results indicated that Fe3O4 nanoparticles were successfully embedded into the surfaces of cotton fabrics tightly and modified cotton fabrics showed durable magnetism without using any adhesive agents. The tensile strength in both the warp and weft directions of the modified cotton fabrics was improved.

Controllable degradation of polyurethane elastomer via selective cleavage of C[sbnd]O and C[sbnd]N bonds

The degradation and recovery of waste polyurethane materials have confronted enormous challenge. Controllable degradation of polyurethane elastomer is developed via selective cleavage of CO of urethane linkages and CN bonds. It was founded that the selective cleavage of carbon-heteroatom bonds could be efficiently performed in 70% ZnCl2 aqueous solution. The transition metal Zn2+ coordinated with N and O atoms due to their unshared electron pairs. The CO of urethane linkages and CN bonds were readily cleaved using ZnCl2 as catalysts at 140 °C for 2 h. However, the CC bonds and COC of ether linkages as framework structure remain intact in the degradation process. Eventually, the high-value-added chemicals including 2,4-diaminotoluene, polytetramethylene ether glycol (PTMEG) and 3,3′-dichloro-4,4′-diaminodiphenylmethane (MOCA) were retrieved via selective cleavage of CO of urethane bonds and CN bonds.

One-vessel synthesis of 5-hydroxymethylfurfural in concentrated zinc chloride solution from lignocellulosic materials

The synthesis of bio-based chemicals, such as 5-hydroxymethylfurfural (HMF) and its derivatives, from cellulosic biomass resources has been attempted for years. However, the harsh reaction condition, toxicity of the catalysts applied, and low efficiency of the conversion process have deterred its industrial implementation. Herein, the authors investigated the degradation and conversion of cellulose into HMF in a concentrated zinc chloride solution. The effects of reaction conditions and co-catalysts on the conversion were evaluated. A 69.5% HMF yield from cellulose was obtained in the condition of 1 h and 150 °C using 0.2 mol·L-1 of HCl without co-catalyst during the conversion. Moreover, the ZnCl2 aqueous solution displayed good reusability. Finally, a simplified kinetic model of the conversion of cellulose to HMF in a concentrated zinc chloride solution was developed, and the reaction kinetics were investigated.

Homojunction Cu2O Solar Cells Fabricated with Various Impurity-Doped Epitaxially Grown n-Type Cu2O Thin Film By Electrochemical Deposition

This paper describes the photovoltaic properties of a homojunction Cu2O solar cells fabricated with a various impurity-doped epitaxially grown n-type Cu2O thin-film by electrochemical deposited (ECD) method. The various impurity-doped n-type Cu2O thin film layer was prepared on thermally oxidized polycrystalline p-type sodium-doped Cu2O (p-Cu2O:Na) sheet substrates under various deposition conditions using the following ECD process. Initially, an acetic acid and Copper (II) acetate aqueous solution was prepared with 0.08 M acetic acid, 0.02 M Copper (II) acetate and de-ionized water; then a 0.1-1.0×10-5 M CuCl2, InCl3, CdCl2, ZnCl2 or MnCl2 aqueous solution was added to the solution as a doping impurity; and after that, a 3 M LiOH, NaOH or KOH aqueous solution was added to adjust the pH. Next, a p-Cu2O:Na sheet substrate was immersed in the above solution at a temperature of 60-90 oC; a Pt plate and the p-Cu2O:Na sheet substrate were used as the anode and cathode electrodes, respectively, of the ECD. Finally, the deposition was carried out under various current densities of 0.1-2.0 mA/cm2 for durations of 1-30 min. In addition, various n-type oxide semiconductor, such as GaXAl1-X-O or Zn1-XGeX-O multicomponent oxide thin films and an Al-doped ZnO (AZO) thin film were deposited at room temperature using a pulsed laser deposition or magnetron sputtering methods as the n-type semiconductor layer and the transparent electrode, respectively. The solar cells were fabricated by forming an AZO/n-oxide semiconductor/various impurity-doped n-type Cu2O/p-Cu2O:Na structure on the front surface of the Cu2O:Na sheets and an Au ohmic electrode on the back surface (the sheets function as the active layer as well as the substrate). The photovoltaic properties of the resulting solar cells were measured under AM1.5G solar illumination. For example, the Cu2O homojunction solar cells was fabricated by epitaxialiy growing a Cl-doped Cu2O (Cu2O:Cl) thin film on p-Cu2O:Na (with a hole concentration of 1015-1019 cm-3) sheets by ECD. Significantly enhanced open circuit voltage (VOC) and conversion efficiency (η) were achieved in AZO/n-Cu2O:Cl/p-Cu2O:Na heterojunction solar cells fabricated by Cu2O:Cl thin-film as the n-type layer by using ECD; these values were higher than those obtained in AZO/p-Cu2O and AZO/n-ZnO/p-Cu2O solar cells. The obtained enhanced Voc and η suggest that the Cu2O:Cl thin-film n-type layer acts as an appropriate active layer. In addition, significant improvement of photovoltaic properties was achieved in heterojunction solar cells fabricated with a Ga1-XAlX-O or Zn1-XGeX-O multicomponent oxide thin film n-type semiconductor window layer prepared by optimizing the chemical composition (the Ga or Ge content). Note that the photovoltaic properties obtained in AZO/Ga0.975Al0.025-O or Zn0.38Ge0.62-O/n-Cu2O:Cl/p-Cu2O:Na (with a hole concentration on the order of 1015 cm-3) heterojunction solar cells could be controlled by changing the Cl content doped into the Cu2O:Cl thin film.

Improvement of m‐plane ZnO films formed on buffer layers on sapphire substrates by mist chemical vapor deposition

The crystal quality of ZnO films grown by mist chemical vapor deposition (mist‐CVD) was improved by introducing ZnO buffer layers on sapphire substrates. The ZnO films were grown by high‐speed rotation‐type mist‐CVD with a ZnCl2 aqueous solution, which provided uniform epitaxial layers over 2‐inch wafers. To grow the ZnO buffer layers, it is necessary to form small grains of polycrystal. Therefore, we attempted to grow the ZnO buffer layers using a Zn(CH3COO)2 aqueous solution, which provides a small grain size of about 100 nm. By using the buffer layers, the full width at half‐maximum of an X‐ray ω‐rocking curve for the ZnO film was reduced from 0.69° to 0.38°, showing improvement of the crystal quality.

In situassessment of degradable carbon effusion for industrial waste water treatment

AbstractThe need for safe and economical methods for wastewater purification has necessitated this research. Blends of different peels: Potato-, apple- and pineapples-peels (PAP-peels) were impregnated with aqueous solutions of ZnCl2 following the variant of the incipient wetness method for activation of activated carbon (AC). Scanning Electron Microscope with attached energy dispersive spectrometer, Atomic Adsorption Spectrometry and Fourier Transform Infrared spectrometer equipment were used for the characterization of the AC produced. The result shows that PAP-peels derived ACs had micro porous characteristics. The study revealed that these new combined adsorbents materials are inexpensive, easily available and they have applications for the removal of Cu, Pb and Cr contained in industrial effluents.

Preparation of ZnO–cellulose nanocomposites by different cellulose solution systems with a colloid mill

In this work, a novel means of producing zinc oxide (ZnO)–cellulose nanocomposites was developed. ZnO–cellulose nanocomposites were prepared by mixing a cellulose zinc chloride (ZnCl2) aqueous solution with a cellulose NaOH/urea aqueous solution in a colloid mill at room temperature. Solutions as high as 65 wt% ZnCl2 were considered for use as a concentrated zinc source. Nano-ZnO particles were obtained when the generated ZnO–cellulose nanocomposite was calcined at 575 °C. The properties of the ZnO–cellulose nanocomposite were characterized by X-ray diffraction, scanning electron microscopy, transmission electron microscopy, Raman spectra, UV–Vis spectroscopy, and photoluminescence (PL). The results indicated that the sizes of ZnO–cellulose nanocomposite were 30–50 nm. The concentration of cellulose in the dissolution system had an obvious effect on the sizes and shapes of the ZnO particles. The size of the ZnO–cellulose nanocomposites and nano-ZnO particles decreased and the shapes of the nano-ZnO changed from rods with a diameter of approximately 40 nm and length of 110 nm to spheroids with a diameter of approximately 40–45 nm as the cellulose concentration increased. In addition, UV absorption and photoluminescence were observed from the ZnO–cellulose nanocomposite.

Heterojunction Solar Cells Fabricated with a Cu2o:Mn Thin Film Grown Epitaxially on p-Type Cu2o:Na Sheets By Electrochemical Deposition

This paper describes the effect of inserting a impurity-doped Cu2O thin-film buffer layer on the obtainable photovoltaic properties in heterojunction solar cells. The heterojunction solar cells were fabricated by preparing an n-type oxide semiconductor thin-film window layer on a Cu2O homojunction that was formed by epitaxially growing the doped Cu2O thin film buffer layer on p-type Cu2O sheets by electrochemical deposition (ECD). The doped Cu2O thin film buffer layer, incorporating various impurities, was prepared on thermally oxidized polycrystalline p-type sodium-doped Cu2O (p-Cu2O:Na) sheet substrates under various deposition conditions using the following ECD process. Initially, an acetic acid and Copper (II) acetate aqueous solution was prepared with 0.08 M acetic acid, 0.02 M Copper (II) acetate and de-ionized water; then a 0.1-1.0×10-5 M InCl3, CdCl2, ZnCl2 or MnCl2 aqueous solution was added to the solution as a doping impurity; and after that, a 3 M LiOH, NaOH or KOH aqueous solution was added to adjust the pH. Next, a p-Cu2O:Na sheet substrate was immersed in the above solution at a temperature of 60-90 oC; a Pt plate and the p-Cu2O:Na sheet substrate were used as the anode and cathode electrodes, respectively, of the ECD. Finally, the deposition was carried out under various current densities of 0.1-2.0 mA/cm2 for durations of 1-30 min. Various n-type GaXAl1-X-O or Zn1-XGeX-O multicomponent oxide thin films and an Al-doped ZnO (AZO) thin film were deposited at room temperature using a pulsed laser deposition as the n-type semiconductor layer and the transparent electrode, respectively. The solar cells were fabricated by forming an AZO/n-oxide semiconductor/doped Cu2O/p-Cu2O:Na structure on the front surface of the Cu2O:Na sheets and an Au ohmic electrode on the back surface (the sheets function as the active layer as well as the substrate). The photovoltaic properties of the resulting solar cells were measured under AM1.5G solar illumination. The Cu2O homojunction was formed by epitaxially growing a doped Cu2O thin film on p-Cu2O:Na (with a hole concentration of 1015-1019 cm-3) sheets by ECD. Significantly enhanced open circuit voltage (VOC) and conversion efficiency (η) were achieved in AZO/Ga0.98Al0.02-O/Cu2O:Mn/p-Cu2O:Na heterojunction solar cells fabricated by inserting a Mn-doped Cu2O (Cu2O:Mn) thin-film as the buffer layer with an appropriate thickness using ECD; these values were higher than those obtained in AZO/Cu2O:Mn/p-Cu2O and AZO/Ga0.98Al0.02-O/p-Cu2O solar cells. The obtained enhanced Voc and η suggest that the Cu2O:Mn thin-film buffer layer has excellent crystallinity as well as acts as an appropriate active layer. In addition, significant improvement of photovoltaic properties was achieved in heterojunction solar cells fabricated with a GaXAl1-X-O or Zn1-XGeX-O multicomponent oxide thin film n-type semiconductor window layer prepared by optimizing the chemical composition (the Ga or Ge content). Note that the photovoltaic properties obtained in AZO/Ga0.98Al0.02-O or Zn0.28Ge0.62-O/Cu2O:Mn/p-Cu2O:Na (with a hole concentration on the order of 1015 cm-3) heterojunction solar cells could be controlled by changing the Mn content doped into the Cu2O:Mn thin film. An efficiency over 8% was obtained in an AZO/ Zn0.28Ge0.62-O/Cu2O:Mn/p-Cu2O:Na heterojunction solar cell fabricated with a Cu2O:Mn thin film that was identified as an i-type semiconductor.