Structural,thermal, optical and conductivity studies of Co/ZnO nanoparticles doped CMC polymer for solid state battery applications

In this study, a simple chemical precipitation method was used to synthesize ZnO: Co²⁺ as nanoparticles. The solution casting technique was used for the preparation of polymer films of Carboxymethyl cellulose (CMC) doped with different contents (0.5, 1.5, 3, and 5 wt%) of ZnO/Co NPs. As shown by the X-ray diffraction, the average size of ZnO/Co crystallite of the NPs is 25.6 nm. Meanwhile, the addition of ZnO/Co reduced the semi-crystallinity of CMC. The Fourier transform infrared (FTIR) confirmed the interaction between the ZnO/Co NPs and the polymer CMC. The direct and indirect band gap (Eg) was reduced from (5.32–5.01 eV and 5.20 to 4.99 eV respectively) with the increase in ZnO/Co NPs content up to 3 wt% after this content the Eg is increased as shown by the UV–Vis spectra. In addition, the results of TGA displayed the decomposition of the nanocomposite to be little compared to that of the pure CMC indicating the success of fabrication of products. The improvement of the ionic conductivity was noticed upon the addition of ZnO/Co NPs into the polymer CMC system which can be explained in terms of an increase in amorphicity as shown by the impedance spectroscopic study. It was found that the optimum ionic conductivity (3.209 × 10⁻⁶ Scm⁻¹) at ambient temperature was higher for the sample containing 1.5 wt% ZnO/Co NPs with highest of amorphicity and the lowest total loss of weight. Therefore, the improvements in optical properties, thermal stability, and AC conductivity which were observed represent a strong support for the use of the nanocomposite films in the solid state battery applications.     

Improvement in the light conversion efficiency of silicon solar cell by spin coating of CuO,ZnO nanoparticles and CuO/ZnO mixed metal nanocomposite material

Synthesis of pure Zinc oxide (ZnO), Copper oxide (CuO) nanoparticles (NPs) and their (ZnO/CuO) nanocomposites (NCs) in 1:1 M ratio were successfully prepared by co-precipitation method. The structural properties of the as synthesized nanoparticles and nanocomposite materials were investigated using scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDX) and X-ray diffraction (XRD) techniques. Optical band-gap studies were done using UV–Visible absorption spectroscopy. Photovoltaic properties of pure ZnO NPs, CuO NPs and ZnO/CuO NCs coated over a single-crystalline silicon solar cell were carried out to compare improvement of light-conversion efficiency in coated solar cell. The maximum light conversion efficiencies were found to be of 8.02% for CuO (3 mg/ml concentration) and 7.28% for ZnO NPs (3 mg/ml concentration), whereas that of mixed metal nanocomposite CuO/ZnO NCs was found to be 7.62%. at very low concentration of 1 mg/ml. This indicates with low concentration of mixed metal NCs an improvement in light efficiency can be obtained. The enhancement in efficiency could be due to formation of p - n heterojunction by CuO/ZnO NCs composites which enhances the number of electrons and holes participating in conduction on the surface.     

The surface modification of spherical ZnO with Ag nanoparticles: A novel agent,biogenic synthesis,catalytic and antibacterial activities

Nowadays, the industrial wastewater pollutants including toxic dyes and pathogenic microbes have caused serious environmental contaminations and human health problems. In the present study, eco-friendly and facile green synthesis of Ag modified ZnO nanoparticles (ZnO-Ag NPs) using Crataegus monogyna (C. monogyna) extract (ZnO-Ag@CME NPs) is reported. The morphology and structure of the as-biosynthesized product were characterized by field emission scanning electron microscopy (FESEM), X-Ray diffraction (XRD), differential reflectance spectroscopy (DRS), dynamic light scattering (DLS), transmission electron microscopy (TEM), Fourier-transform infrared spectroscopy (FT-IR), and energy-dispersive X-ray spectroscopy (EDS) techniques. TEM and FESEM images confirmed the oval and spherical-like structure of the products with a size of 55–70 nm. The EDS analysis confirmed the presence of Zn, Ag, and O elements in the biosynthesized product. The photocatalytic results showed ZnO-Ag@CME NPs were degraded (89.8% and 75.3%) and (94.2% and 84.7%) of methyl orange (MO) and basic violet 10 (BV10), under UV and sunlight irradiations, respectively. The Ag modified ZnO nanoparticles exhibited enhanced catalytic activity towards organic pollutants, and showed better performance than the pure ZnO nanoparticles under UV and sunlight irradiations. This performance was probably due to the presence of silver nanoparticles as a plasmonic material. Antibacterial activity was performed against different bacteria. ZnO-Ag@CME NPs showed high antibacterial activity against K. pneumoniae, S. typhimurium, P. vulgaris, S. mitis, and S. faecalis with MIC values of 50, 12.5, 12.5, 12.5, and 12.45 µg/mL, respectively. All in all, the present investigation suggests a promising method to achieve high-efficiency antibacterial and catalytic performance.     

Efficient photodegradation of methyl orange and bactericidal activity of Ag doped ZnO nanoparticles

In the present work, silver-doped ZnO (Ag–ZnO NPs) with different concentrations of silver ions (0.3, 0.5, 1.0 and 1.5 mol %) were synthesized by using a simple co-precipitation method. The Ag–ZnO NPs were primarily characterized by XRD, FT-IR, SEM, EDS, TEM, UV–Vis. DRS, PL and BET surface area. The XRD analysis of Ag–ZnO NPs shows a wurtzite structure and optimized Ag–ZnO NPs (1.0 mol %) exhibit a lower crystallite size of 15.96 nm than that of bare ZnO (19.07 nm). Optical study shows a decrease in band gap from 3.13 to 2.97 eV as the concentration of Ag ions increases from 0.3 to 1.5 mol%. TEM images reveal the spherical shape particle with sizes ranging between 10 and 15 nm. From the multipoint BET plot, the surface area of Ag–ZnO NPs found 38.06 m²/gwhich is higher than the ZnO NPs (34.48 m²/g). The photocatalytic study demonstrated that the Ag–ZnO NPs (1.0 mol %) has an excellent photodegradation efficiency of Methyl Orange (96.74%)with a 26% increment as compared to bare ZnO (70.47%). Furthermore, the bactericidal activity of Ag–ZnO NPs (1.0 mol %) was investigated against four different bacterial strains. The results explored that the Gram-negative bacteria (E. coli and P. vulgaris) are more sensitive than Gram-positive (S. aureus and B. cereus) to Ag–ZnO NPs. Overall, the anticipated material is economical and reusable for photodegradation and antibacterial activity.     

On the synthesis and characterization of ZnO/MgO nanocomposite by thermal evaporation technique

ZnO/MgO nanocomposites have been synthesized by an easy and cost effective thermal evaporation technique. Various growth temperatures ranging from 800 to 900 °C were tried. It is observed that the process temperature plays a key role in the formation of ZnO/MgO nanocomposite and the proper formation of ZnO/MgO nanocomposite occurs at 875 °C temperature as confirmed by X-ray diffraction studies. Scanning electron microscopic images indicate that the ZnO/MgO nanocomposite is formed as agglomerated nanoparticles distributed over a large area. Energy dispersive X-ray analyses also reveal that the Mg composition in the synthesized nanocomposite strongly depends on the process temperature. Photoluminescence (PL) spectrum exhibits a blue shift for the ZnO/MgO nanocomposite synthesized at 875 °C indicating the incorporation of Mg into the ZnO crystal lattice. A higher PL intensity ratio of band-edge to deep band emission has been observed for this sample indicating the presence of low crystalline defects.     

Transparent polymeric hybrid film of ZnO nanoparticle quantum dots and PMMA with high luminescence and tunable emission color

ZnO nanoparticle quantum dots (QDs)/poly(methyl methacrylate) (PMMA) composites are synthesized by conventional radical polymerization in the presence of 3-(trimethoxysilyl)propylmethacrylate (TPM)-modified ZnO nanoparticle QDs. Although unmodified ZnO nanoparticle QDs were precipitated in tetrahydrofuran (THF) and show only weak emissions under UV irradiation, ZnO nanoparticle QDs/PMMA composite is well dispersed in THF and shows high emissions. TPM acts as the stabilizer and promotes the compatibility between the ZnO nanoparticle QDs and the PMMA matrix. After evaporation of THF from the ZnO nanoparticle QDs/PMMA composite solution, transparent polymeric hybrid films of ZnO nanoparticle QDs and PMMA are obtained. These polymeric hybrid films are characterized by photoluminescence (PL) spectroscopy, Fourier transform infrared (FT-IR) spectroscopy, transmission electron microscopy (TEM), and thermogravimetric analysis. The hybrid film exhibited a high quantum yield and PL emission under ultraviolet excitation. PL emission has been successfully tuned from blue to yellow.     

Morphology dependent UV photoresponse of Sn-doped ZnO microstructures

In this work, the UV sensing properties of Sn-doped and/or alloyed zinc oxide (ZnO) microstructures with different morphologies were investigated in order to elaborate the high performance UV photodetectors. We have compared two types of morphologies, i.e. Sn-doped ZnO films (ZnO:Sn) and ZnO microtetrapod (T) networks alloyed- and doped-with Sn (ZnO-T:Sn). The UV response (I_UV/I_dark) of ZnO:Sn is about 10³ and 10² for 0.1 and 0.4 at% Sn, respectively. The three-dimensional highly porous ZnO-T:Sn networks demonstrated higher UV response (by two orders of magnitude) and much faster recovery for detection of UV light, which were attributed to the domination of fast processes such as modulation of potential barriers formed at the interface of the tetrapod arms, which are less dependent on adsorbed species. Thus, the UV response for devices with a distance between the pads (interelectrode distance) of about 60, 400, 800 and 1500 μm is 1.7 × 10⁵, 2.4 × 10⁴, 6.7 × 10³ and 925, respectively. All samples demonstrated a sharp increase in photocurrent under illumination with UV light, as well as a fast recovery to the initial electrical baseline. Also, the influence of relative humidity on the rapidity of photodetectors based on ZnO:Sn films and ZnO-T:Sn networks was investigated, confirming a low impact on the rapidity of ZnO-T:Sn networks, with good repeatability and stable electrical baseline, which is very important for effective applications.     

Visible light-emitting and temperature-sensitive copolymer gel/ZnO nanocomposites loaded with surface-modified ZnO nanoparticles having polyethylene glycol chains

New visible light-emitting and temperature-sensitive poly(VCL-co-SA)/ZnO gel nanocompsites (GNs) 4 loaded with surface-modified ZnO nanoparticles NPs 3 with polyethylene glycol (PEG) chains were successfully prepared by the cross-linking of N-vinylcaprolactam (VCL), sodium acrylate (SA) and tetraethylene glycol dimethacrylate (TEGDM) in the presence of NPs 3. The NPs 3 having nanostructured size were prepared from ZnO NPs 2 with 2-bromo-2-methylpropionyl linkages on the surface, and sodium alcoholate of polyethylene glycol monomethyl ether (PEGME). The NPs 3 and the GNs 4 were characterized by FTIR, UV–vis absorption and photoluminescent (PL) spectroscopies, X-ray analysis measurements, TEM and SEM observations and dynamic light scattering (DLS) measurements. The measurements indicated that the GNs 4 with wurtzite crystal structures based on the ZnO NPs show absorptions and yellow light-emitting properties arising from the NPs 3, except for the GNs 4 containing a high weight % of NPs 3. The size of the GNs 4 drastically decreased with increasing temperature in the range of 20–35 °C, probably because of the induction of steric hindrance and enhancement of hydrophilic PEG chain concentrations inside the GN networks 4.     

Improvement of glass ionomer restoration by adding ZnO nanoparticles prepared by laser in (Vitro study)

The technique of pulsed laser ablation in liquid media was successfully used to prepare zinc oxide ZnO nanoparticles NPs to enhance glass ionomer GI restorative. The synthesized ZnO NPs were confirmed using UV–Visible spectroscopy, XRD, and TEM. The absorption spectra revealed that the absorbance intensity of the prepared ZnO NPs increased as the number of laser pulses increased, with an absorbance peak at 230 nm due to quantum confinement. The crystalline nature of NPs with hexagonal structure is revealed by XRD analysis. The TEM images demonstrated the nanorod shape with a length of about 3.33 nm and there were spherical nanoparticles ranging from 5 nm to 30 nm. ZnO NPs with and without GI were tested for antibacterial activity against Streptococcus mutans bacteria, which shows slight improvement after adding ZnO NPs to glass ionomer as a result of containing effective ingredients in its composition. The agar well diffusion method results revealed that ZnO with GI had a higher antibacterial activity compared with pure ZnO NPs. Finally, the compressive strength test illustrated significant enhancement of up to 50% associated with the ZnO NP's concentration increase.     

Preparation of ZnO:CeO2-x thin films by AP-MOCVD: Structural and optical properties

The growth of columnar CeO₂, ZnO and ZnO:CeO_2−x films on quartz and AA6066 aluminum alloy substrates by economic atmospheric pressure metal-organic chemical vapor deposition (AP-MOCVD) is reported. A novel and efficient combination of metal acetylacetonate precursors as well as mild operating conditions were used in the deposition process. The correlation among crystallinity, surface morphology and optical properties of the as-prepared films was analyzed by X-ray diffraction (XRD), scanning electron microscopy (SEM), atomic force microscopy (AFM), transmission electron microscopy (TEM) and UV-vis spectroscopy. The synthesized films showed different crystallographic orientations depending on the ZnO and CeO₂ lattice mismatch, cerium content and growth rate. The CeO₂ films synthesized in this work showed plate-like compact structures as a result of the growth process typical of CVD. Both pure and ZnO:CeO_2−x films were obtained with a hexagonal structure and highly preferred orientation with the c-axis perpendicular to both substrates under the optimal deposition conditions. The microstructure was modified from dense, short round columns to round structures with cavities (“rose-flower-like” structures) and the typical ZnO morphology by controlling the cerium doping the film and substrate nature. High optical transmittance (>87%) was observed in the pure ZnO films. As for the ZnO:CeO_2−x films, the optical transmission was decreased and the UV absorption increased, which subsequently was affected by an increase in cerium content. This paper assesses the feasibility of using ZnO:CeO_2−x thin films as UV-absorbers in industrial applications.     

Combustion synthesis of calcium doped ZnO nanoparticles for the photocatalytic degradation of methylene blue dye

ZnO nanoparticles are one of the prominent photocatalysts for environmental applications due to its high redox ability, nontoxic and higher stability. This report explains the synthesis of ZnO nanoparticles by a simple solution combustion method using zinc nitrate hexahydrate as an oxidizing agent and incense stick powder as fuel at 400 °C. Several techniques were adopted for the characterization of the obtained product. X-ray diffraction (XRD) pattern shows that a lower concentration of fuel gives pure ZnO and a higher concentration of fuel results in calcium doped ZnO with a cubic phase having a crystallite size of 32–28 nm. UV–vis spectrum shows that as the fuel concentration increases, band gap decreases and reaches to 3.33 eV for 3 g of fuel. Spongy networks with many pores wereobserved in the scanning electron microscope (SEM) and transmission electron microscope (TEM) images showed the average particle size of Ca doped ZnO NPs is about 20 nm. Pure and Ca doped ZnO nanoparticles were examined for photocatalytic degradation of methylene blue (MB) dye under UV light irradiation. The results prove that Ca doped ZnO nanoparticles show good photocatalytic activity.     

Adding Value in Production of Multifunctional Polylactide (PLA)–ZnO Nanocomposite Films through Alternative Manufacturing Methods

Due to the added value conferred by zinc oxide (ZnO) nanofiller, e.g., UV protection, antibacterial action, gas-barrier properties, poly(lactic acid) (PLA)–ZnO nanocomposites show increased interest for utilization as films, textile fibers, and injection molding items. The study highlights the beneficial effects of premixing ZnO in PLA under given conditions and its use as masterbatch (MB), a very promising alternative manufacturing technique. This approach allows reducing the residence time at high processing temperature of the thermo-sensitive PLA matrix in contact of ZnO nanoparticles known for their aptitude to promote degradation effects onto the polyester chains. Various PLA–ZnO MBs containing high contents of silane-treated ZnO nanoparticles (up to 40 wt.% nanofiller specifically treated with triethoxycaprylylsilane) were produced by melt-compounding using twin-screw extruders. Subsequently, the selected MBs were melt blended with pristine PLA to produce nanocomposite films containing 1–3 wt.% ZnO. By comparison to the more traditional multi-step process, the MB approach allowed the production of nanocomposites (films) having improved processing and enhanced properties: PLA chains displaying higher molecular weights, improved thermal stability, fine nanofiller distribution, and thermo-mechanical characteristic features, while the UV protection was confirmed by UV-vis spectroscopy measurements. The MB alternative is viewed as a promising flexible technique able to open new perspectives to produce more competitive multifunctional PLA–ZnO nanocomposites.     

A novel approach for fabrication ZnO/CuO nanocomposite via laser ablation in liquid and its antibacterial activity

Pulsed laser ablation in liquid (PLAL) has verified its surpassing advantages in the fabrication of several high purity nanostructured metals and metal oxides. In this work, ZnO/CuO heterostructure nanocomposites have been fabricated by laser ablation a Q switched Nd: YAG laser beam (1064 nm, 10 Hz, pulse energy and pulse with 30 mJ and 10 ns) is focused on the surface of the ZnO thin film for 10 min. The fabricated ZnO/CuO nanocomposite was then characterized using transmission electron microscopy (TEM), UV–vis spectrophotometer, X-ray diffraction (XRD), and Raman spectroscopy to investigate the structural, compositional, and optical properties of the fabricated nanocomposite. The synthesized nanocomposites were evaluated as antibacterial agents against both the gram-positive bacterium S. aureus subsp. aureus ATCCBAA-977, and the gram-negative bacteria E. coli ATCC8739, K. pneumoniae subsp. pneumoniae ATCC700603, and P. aeruginosa ATCC27853. The as-fabricated ZnO/CuO nanocomposite demonstrated outstanding antibacterial activity except in the case of K. pneumoniae subsp. pneumoniae ATCC700603 while the maximum activity was observed against E. coli ATCC8739.     

Preparation and Characterization of Transparent and UV‐Shielding Epoxy/SR‐494/APTMS/ZnO Nanocomposites with High Heat Resistance and Anti‐Static Properties

This research is to develop transparent and UV‐shielding Epoxy/SR‐494/APTMS/ZnO nanocomposite materials with high heat resistant and anti‐static properties. Firstly, the APTMS (3‐(acryloxypropyl)trimethoxysilane) performs the silanol intermediates by hydrolysis in pH 4～5 acid solution. The inorganic anti‐static fillers of powder ZnO can be successfully coupled and crosslinked to Epoxy/SR‐494 organic matrixes with these silanols of APTMS coupling agents. The remained active ‐OH functional groups of the APTMS/ZnO complexes can network bonding with epoxy prepolymers. Therefore, the Epoxy/APTMS/ZnO complexes with good anti‐static composites will be successfully prepared. Finally, in order to improve the thermal resistant and mechanical properties, the polyfunctionalized SR‐494 (pentaery‐thritol tetracrylate) acrylate monomers and the Epoxy/APTMS/ZnO composites are chain polymerized to form an excellent cross‐linking structure of organic/inorganic nanocomposites. The chemical bonding formation and the best weight contents of reaction components are identified by FT‐IR spectra. The thermal resistance, transparence, surface electric resistance, and hardness of these nanocomposites are measured by TGA, DSC, UV‐Visible, surface resistant meter, and pencil hardness tester respectively. Experimental results show that these nanocomposites have 90% transmittance and the best Td value is 389.3 °C which is 109.0 °C and 78.6 °C higher than those of pure epoxy resin and pure SR‐494 acrylate resin respectively. The glass transition temperature is not detected below 200 °C. The surface electric resistances of Epoxy/SR‐494/APTMS/ZnO hybrid thin films are decreased from 3.14 × 10¹³ to 5.13 × 10⁷ Ω/cm². The hardness of these nanocomposites is as high as 8H, and those hybrid films have high UV‐shielding properties. The morphology structures of the hybrid thin films are estimated by SEM. The results show that the optical thin films are evenly distributed with inorganic colloidal particles and the average particle size of these nanocomposites is 45～80 nm, while the powder ZnO (particle size: 2～5 μm) was used as inorganic filler.     

Ultrasonic treatment as recent and environmentally friendly route for the synthesis and characterization of polymer nanocomposite having PVA and biosafe BSA‐modified ZnO nanoparticles

The present study deals with the immobilization of ZnO nanoparticles (NPs) as nanofiller inside poly(vinyl alcohol) (PVA) by solution casting method which is a low‐cost, environmental‐friendly, and rapid method of sonochemistry. Firstly, the surface of ZnO NPs was treated by bovine serum albumin (BSA) in the phosphate‐buffered solution under ultrasonic cavitation. Three diverse polymeric nanocomposites (NCs) are formed by changing the percentage of ZnO@BSA NPs (3, 6, and 9 wt%) with same amount of PVA. The structure properties, morphology, and thermal stability of prepared NCs were determined through Fourier transform‐infrared spectroscopy, X‐ray diffraction, energy‐dispersive X‐ray spectroscopy (EDX) and optical UV‐Visible spectrum, transmission electron microscopy (TEM), and field emission scanning electron microscopy. The presence and the dispersal of the ZnO@BSA NPs in the PVA matrix were recognized by TEM. In the X‐ray diffraction analysis, the values of mean particle size using Debye‐Scherrer equation were estimated in the range 4 to 6 nm that is almost in agreement with TEM analysis. Increase of 14% in thermal stability and also increase of more than 2‐fold of the tensile strength of PVA/ZnO@BSA NC 9 wt% in respect to the pure PVA showed that the modified NPs well dispersed within PVA and attached to it.     

Organic–inorganic nanocomposites of (2‐hydroxypropyl)cellulose as a precursor of nanocrystalline zinc oxide layers

The sol–gel method of synthesis of the hybrid nanocomposite films of ZnO/(2‐hydroxypropyl) cellulose (HPC) on silica glass is presented. The sol phases were prepared for different weight ratios of zinc acetate dihydrate to HPC in the presence of triethylamine (TEA). Raman spectrum of the mixture of ZnAc and HPC indicates coordinating interaction between zinc ion and HPC. The generation of ZnO nanoparticles in the HPC matrix proceeds in situ through the annealing of the gel phase at a temperature of 160°C. Identification of ZnO nanoparticles in the HPC matrix is done by using photoluminescence (PL), UV–Vis, and Raman spectroscopy. The films of ZnO/HPC nanocomposite are transparent in the visible light and show a higher energy value of absorption edge compared with ZnO in the bulk. Nanocrystalline films of ZnO were obtained by the calcination of ZnO/HPC nanocomposite at 500°C. ZnO films possess a good transparency for the visible light and high absorbance for UV light. Nanocrystallite sizes of ZnO particles were estimated from the X‐ ray lines broadening. The properties of ZnO layers were studied by the evaluation of PL, X‐ray investigation and atom force microscope (AFM) scanning, and the optical absorption edge. Copyright © 2008 John Wiley & Sons, Ltd.     

Magnesium doped ZnO nanoparticles embedded ZnO nanorod hybrid electrodes for dye sensitized solar cells

We report a novel type of Mg doped ZnO nanoparticles (ZMP) embedded on hydrothermally grown ZnO nanorod (ZR) based photoanode dye sensitized solar cells. The crystallinity, composition and morphology of the photoanodes were characterized by using X-ray diffraction analysis, X-ray photoelectron spectroscopy and scanning electron microscopy. The amount of dye absorbed in the photoanode was observed using UV visible spectral analysis. The improved internal resistance and charge-transfer kinetics of the fabricated cells were analyzed using electrochemical impedance spectroscopy. The ZMP embedded electrode of low thickness (~2.5 μm) gained an enhanced short-circuit current density of 8.56 mA/cm², open-circuit photo voltage of 0.71 V, fill factor of 0.51, and overall conversion efficiency of 2.91 % under 1 sun illumination. This shows high conversion efficiency and performance than that of ZnO nanorod (η ~ 0.22 %) and bare ZnO nanoparticles (ZP) embedded ZnO nanorod (η ~ 1.04 %) based cells. The presence of Mg ions in the ZnO nanoparticle hinders the interfacial recombination of the photo-excited electrons with the electrolyte and also shows better dye absorption than that of ZR. These factors can significantly enhance solar-cell performance and increase the efficiency of the ZMP based dye sensitized solar cells.     

Binary Au/MWCNT and Ternary Au/ZnO/MWCNT Nanocomposites: Synthesis,Characterisation and Catalytic Performance

Gold nanoparticles of 10–24 and 5–8 nm in size were obtained by chemical citrate reduction and UV photoreduction, respectively, on acid‐treated multiwalled carbon nanotubes (MWCNTs) and on ZnO/MWCNT composites. The shape and size of the deposited Au nanoparticles were found to be dependent upon the synthetic method used. Single‐crystalline, hexagonal gold particles were produced in the case of UV photoreduction on ZnO/MWCNT, whereas spherical Au particles were deposited on MWCNT when the chemical citrate reduction method was used. In the UV photoreduction route, n‐doped ZnO serves as the e^? donor, whereas the solvent is the hole trap. All materials were fully characterised by UV/Vis spectroscopy, scanning electron microscopy, transmission electron microscopy, X‐ray photoelectron spectroscopy, Raman spectroscopy and BET surface analysis. The catalytic activity of the composites was studied for the selective hydrogenation of α,β‐unsaturated carbonyl compound 3,7‐dimethyl‐2,6‐octadienal (citral). The Au/ZnO/MWCNT composite favours the formation of unsaturated alcohols (selectivity=50 % at a citral conversion of 20 %) due to the presence of single‐crystalline, hexagonal gold particles, whereas saturated aldehyde formation is favoured in the case of the Au/MWCNT nanocomposite that contains spherical gold particles.     

Preparation and characterization of nanocomposite ZnO–Ag thin film containing nano-sized Ag particles: influence of preheating,annealing temperature and silver content on characteristics

Nanocomposite ZnO–Ag thin film containing nano-sized Ag particles have been grown on glass substrate by spin-coating technique using zinc acetate dihydrate as starting precursor in 2-propanol as solvent and monoethanolamine as stabilizer. Silver nanoparticles were added in the ZnO sol using silver nitrate dissolved in ethanol-acetonitrile. Their structural, electrical, crystalline size and optical properties were investigated as a function of preheating, annealing temperature and silver content. The results indicated that the crystalline phase was increased with increase of annealing temperature up to 550 °C at optimum preheating temperature of 275 °C. Thermal gravimetric differential thermal analysis results indicated that the decomposition of pure ZnO and nanocomposite ZnO–Ag precursors occurred at 225 and 234 °C, respectively with formation of ZnO wurtzite crystals. The scanning electron microscopy and atomic force microscopy revealed that the surface structure (the porosity and grain size) of the ZnO–Ag thin film (the film thickness is about 379 nm) was changed compared to pure ZnO thin film. The result of transmission electron microscopy showed that Ag particles were about 5 nm and ZnO particles 58 nm with uniform silver nanoclusters. Optical absorption results indicated that optical absorption of ZnO–Ag thin films decreased with increase of annealing temperature. Nanocomposite ZnO–Ag thin films with [Ag] = 0.068 M and [Ag] = 0.110 M showed an intense absorption band, whose maximum signals appear at 430 nm which is not present in pure ZnO thin films. The result of X-ray photoelectron spectroscopy revealed that the binding energy of Ag 3d_5/2 for ZnO–Ag shifts remarkably to the lower binding energy compared to the pure metallic Ag due to the interaction between Ag and ZnO.     

Fabrication of zinc oxide/poly(styrene) grafted nanocomposite latex and its dispersion

Zinc oxide nanoparticles, with an average size of about 40 nm, were encapsulated by polystyrene using in situ emulsion polymerization in the presence of 3-methacryloxypropyltrimethoxysilane (MPTMS) as a coupling agent and polyoxyethylene nonylphenyl ether (OP-10) as a surfactant. Polymerization mechanism of nanocomposite latex was discussed. Transmission electron microscopy (TEM) proved the presence of ZnO nanoparticle appeared to be monodisperse in nanosize in polymer composite particles. ZnO/PS nanocomposites were characterized by Fourier transform infrared spectra (FT-IR), X-ray photoelectron spectroscopy (XPS), thermo-gravimetric analysis (TGA) and differential scanning calorimetry (DSC). The results of FT-IR and XPS revealed that the surface of ZnO particle was successfully grafted by PS through the link of the coupling agent between ZnO and polymer. TGA and DSC results indicated an enhancement of thermal stability of composite materials compared with the pure polymer. SEM (scanning electron microscope) images showed a perfect dispersion of the ZnO particles in latex film. In addition, UV-visible absorption measurements demonstrated that the ZnO/PS composite coatings display a perfect performance of absorbing UV light.