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The influence of poly(o-toluidine) (POT) interlayer as a hole transporting layer (HTL) and iodine doping on electrical properties of hybrid solar cells based on a mixture of didecyl-sexithiophène (2D6T) and nanostructured zinc oxide as blend donor/acceptor-active layer have been investigated. The sexithiophene 2D6T was synthesized by a chemical route through the oxidative coupling of the corresponding terthiophene derivatives, and the nanostructured ZnO powders were prepared by a one-pot solution route at ambient conditions. A series of ITO/(2D6T: nanostructured ZnO)/Al solar cells with and without POT interlayer were fabricated by successive deposition using the spin coating technic, and they are completed by thermal evaporation of aluminium circular contacts on the active layer. The non-linear dark current–voltage I(V) characteristics of these devices indicate a rectifying behaviour. The diode parameters were calculated from I(V) characteristics using the modified Shockley equation and discussed. On the other hand, I(V) characteristics measured under illumination are also presented, studied and compared. The short-circuit current (Isc) and open-circuit voltage (Voc) of solar cells are improved by the incorporation of the HCl-doped POT thin films and by iodine doping, provided that the iodine concentrations do not exceed 10%. [ABSTRACT FROM AUTHOR]

Advanced antimicrobial biomaterials for wound healing applications are an active field of research for their potential in addressing severe and infected wounds and overcoming the threat of antimicrobial resistance. Beta-glucans have been used in the preparation of these materials for their bioactive properties, but very little progress has been made so far in producing biomedical devices entirely made of beta-glucans and in their integration with effective antimicrobial agents. In this work, a simple and eco-friendly method is used to produce flexible beta-glucan/nanostructured zinc oxide films, using glucans derived from the yeast Saccharomyces cerevisiae. The properties of the films are characterized through scanning electron microscopy, energy-dispersive X-ray spectroscopy, X-ray photoelectron spectroscopy, X-ray diffraction, infrared and UV–visible spectroscopy, thermogravimetric analysis, differential scanning calorimetry, and water absorption tests. Finally, the antibacterial properties of the nanostructured zinc oxide and of the composite films are assessed against Staphylococcus epidermidis and Escherichia coli, showing a marked effectiveness against the former. Overall, this study demonstrates how a novel bionanocomposite can be obtained towards the development of advanced wound healing devices. [ABSTRACT FROM AUTHOR]

In this work, the surface of nanostructured fluorine-doped ZnO (nZnO·F) is functionalized with protein A (PrA), and used as a model biomolecule. The chemical procedure is characterized by several analytical techniques such as Fourier Transform Infrared Spectroscopy, water contact angle analysis, and fluorescence microscopy. The surface modification of nZnO·F by binding increasing concentrations of PrA is also investigated by two label-free optical techniques, i.e., the spectroscopic reflectometry and the steady-state photoluminescence. The results are compared with those obtained using undoped nZnO substrates in order to highlight the better performances of nZnO·F due to the fluorine doping. The results of this study pave the way for the design and realization of a ZnO-based nanostructured platform for label-free optical sensing. [ABSTRACT FROM AUTHOR]

Abstract Electronic devices such as solar cells and thin-film transistors can be fabricated using thin-film deposition. Low-cost, low-temperature and high-speed deposition methods are required to ensure that the production of devices using thin-film deposition is affordable. Herein, we report the development of a low-cost and simple thin-film deposition method using microwave-excited atmospheric pressure plasma jet (MWAPPJ). MWAPPJ produces a low-temperature (several hundred degrees) plasma under atmospheric conditions, does not require expensive vacuum equipment, and it enables high-speed deposition of thin-films. Zinc acetylacetonate sol-gel precursors that were adhered to stainless steel mesh targets were irradiated by MWAPPJ with oxygen, which resulted in zinc oxide (ZnO) nanosheet thin-films with diameters of 100–200 nm on silicon substrates. We used 50-nm-thick ZnO thin-films that were processed using MWAPPJ as the electron collection layer in organic photovoltaic (OPV) cells. This work represents an important contribution to the design and production of low-cost OPV solar cells. Highlights • Microwave-excited atmospheric pressure plasma jet fabrication of ZnO nanosheets. • Low temperature growth of ZnO nanosheets. • ZnO nanosheets used as an electron collection layer in organic photovoltaic cells. • Enabled simple thin-film fabrication for low-cost mass production. [ABSTRACT FROM AUTHOR]

Transition metal oxides (TMOs) generally suffer severe capacity degradation as the potential anode materials for lithium-ion batteries, since the large volume changes of TMO anodes during conversion reactions result in the collapse of electrode structures. Fabricating specific nanostructures of TMOs has been demonstrated as a successful approach to partially solve this issue. Besides the concern of capacity retention, our previous work has demonstrated that the specific capacities of TMOs can be improved by enhancing their degrees of crystallinity. Therefore, the TMO nanostructures with high degrees of crystallinity are highly desired to achieve both high specific capacity and good capacity retention. However, the high crystallinity and desired nanostructure are usually contradictory in nanofabrication since the thermal treatment will lead to the collapse of a nanostructure. To overcome the obstacle, herein, the polydopamine coating followed by a thermal treatment in nitrogen is first introduced as a confined crystallization strategy to enhance the degree of crystallinity and simultaneously maintain the nanostructure of ZnO microspheres. Electrochemical performance tests demonstrate that the appropriate coating thickness and heat treatment can enhance the specific capacity from 288.0 mAh g −1 of pristine ZnO to 527.0 mAh g −1 of carbon coated ZnO after 100 cycles. The present work provides a good opportunity to develop TMO anodes with high capacities and superior cycling performances by the polydopamine-derived carbon coating and confined crystallization. [ABSTRACT FROM AUTHOR]

Environmental friendly natural dye curcumin extracted from low-cost Curcumina longa stem is used as a photo-sensitizer for the fabrication of ZnO-based dye-sensitized solar cells (DSSC). Nanostructured ZnO is fabricated on a transparent conducting glass (TCO), using a cost-effective chemical bath deposition technique. Scanning electron microscopic images show hexagonal patterned ZnO nano-towers decorated with several nanosteps. The average length of ZnO nano-tower is 5 μm and diameter is 1.2 μm. The UV–Vis spectroscopic study of the curcumin dye is used to understand the light absorption behavior as well as band gap energy of the extracted natural dye. The dye shows wider absorption band-groups over 350–470 nm and 500–600 nm with two peaks positioned at 425 nm and 525 nm. The optical band gap energy and energy band position of the dye is derived which supports its stability and high electron affinity that makes it suitable for light harvesting and effortless electron transfer from dye to the semiconductor or interface between them. FTIR spectrum of curcumin dye-sensitized ZnO-based DSSC shows the presence of anchoring groups and colouring constitutes. The I-V and P-V curves of the fabricated DSSC are measured under simulated light (100 mW/cm 2 ). The highest visible light to electric conversion efficiency of 0.266% (using ITO) and 0.33% (using FTO) is achieved from the curcumin dye-sensitized cell. [ABSTRACT FROM AUTHOR]

In this work, the surface of nanostructured fluorine-doped ZnO (nZnO·F) is functionalized with protein A (PrA), and used as a model biomolecule. The chemical procedure is characterized by several analytical techniques such as Fourier Transform Infrared Spectroscopy, water contact angle analysis, and fluorescence microscopy. The surface modification of nZnO·F by binding increasing concentrations of PrA is also investigated by two label-free optical techniques, i.e., the spectroscopic reflectometry and the steady-state photoluminescence. The results are compared with those obtained using undoped nZnO substrates in order to highlight the better performances of nZnO·F due to the fluorine doping. The results of this study pave the way for the design and realization of a ZnO-based nanostructured platform for label-free optical sensing.

The report explores the effect of surface properties of nanostructured ZnO thin films, especially the effective surface area, on the conversion of UV light to hydrogen energy via photoelectrochemical (PEC) splitting of water. It deals with the sol-gel synthesis of films from zinc acetate dihydrate [(CH·COO)Zn·2HO], followed by a controlled surface etching using five different acids. The XRD, SEM, and AFM analysis of pristine and etched films revealed the dominant growth of hexagonal wurtzite ZnO with uniquely evolved nano-ridges at the surface. Average crystallite size ranged from 40 to 51 nm with marginal drop in etched samples. Etching did not influence optical bandgap energy, which lied in the expected range. Nonetheless, effective surface area increased significantly and it directly correlated with the enhancement in PEC photocurrent. The hallmark of the study is that it highlights the fact that compared to exotic combinations, viz., mixing, doping or layering, the low-cost simple method of surface etching can also lead to a matching gain in the performance of ZnO towards the hydrogen energy generation from UV light by photosplitting of water. [ABSTRACT FROM AUTHOR]

The effects of structural patterns and degree of crystallinity on the electrochemical performance of ZnO were systematically studied using a controllable synthesis. The microspheres assembled with distorted nanosheets, hexagonal nanorods and radial assembly of nanorods of ZnO were successfully prepared by the hydrothermal reaction of zinc nitrate, hexamethylenetetramine and different amount of trisodium citrate. ZnO microspheres were calcinated at different temperatures (300, 600 and 900 °C) to increase their degree of crystallization. Constant current charge and discharge measurements show that the capacity retention of the microspheres and radial assembled nanorods are higher than that of hexagonal nanorods. This may be due to their inner spacing of specific structure patterns that can accommodate and restrain the volume changes during cycling. Additionally, the capacity of ZnO microspheres can be improved by short-time calcinations at 600 or 900 °C for their crystallization. The studies of differential capacity versus potential plots indicate that the enhanced degree of crystallization facilitates the alloying and dealloying of the reduction products of ZnO. Therefore, both large specific capacity and good capacity retention can be expected with highly crystallized specific nanostructures of ZnO with the sufficient inner spacing. The ZnO microspheres calcinated at 600 °C show the best performance with a specific capacity of 1328.2 mA h g −1 for the first cycle and 662.8 mA h g −1 for the 50th cycle at 0.1 C with an operating potential of 0.05–3.00 V. [ABSTRACT FROM AUTHOR]

Nanostructured zinc oxide thin films, prepared by sol-gel, were subjected to surface loading of silver/gold nano-isles by controlled electrodeposition, using aqueous solutions (10 M) of silver nitrate and chloroauric acid as precursor. The deposition potentials were, respectively, −400 and −200 mV for silver and gold depositions, as the deposition time varied from 5 to 60 s. Pristine samples (i.e., samples with no deposition of metal nano-isles) were also obtained for comparison. X-ray diffractometry indicated dominant evolution of wurtzite zinc oxide phase, with a possible diffusion of silver/gold into zinc oxide lattice. However, changes in the band gap energy were insignificant. Atomic force microscopic and scanning electron microscopic analyses revealed the surface topography and morphology. Energy-dispersive X-ray analysis confirmed the elemental stoichiometry and existence of silver and gold nanoparticles in films. Samples exhibited significant gain in photoelectrochemical water splitting current, which is largely attributable to the facilitative role played by silver/gold nano-isles in the separation and transport of photogenerated charge-carriers. [ABSTRACT FROM AUTHOR]

Abstract: We report on the electrosynthesis of nanostructured zinc oxide (ZnO) thin films using organic molecule templates self-assembled on indium-doped tin oxide substrates in an aqueous medium. The organic molecule templates alter the morphology and microscopic defect configuration of the ZnO film having a hexagonal wurtzite structure. Low-temperature photoluminescence (PL) study reveals that the ZnO films exhibit ultraviolet (3.36eV and 3.22eV), violet (3.06eV), blue (2.88eV), and green (2.50eV) emissions that originate from transitions related to deep-level (zinc interstitials and vacancies) and acceptor-like (ionized zinc vacancies) defect states. A defect energy level diagram based on the PL measurement is proposed. [Copyright &y& Elsevier]

Zinc oxide (ZnO) nanoparticles are synthesized by polymeric sol-gel method and characterized by X-ray diffraction, field-emission scanning electron microscopy. The cure characteristics, mechanical properties and thermal behaviour of natural rubber (NR) systems containing nano ZnO are investigated and compared to those of NR with micro-sized (conventional) ZnO. The NR vulcanizate with 0.5 phr (parts per hundred parts of rubber) sol-gel derived nano ZnO shows improvement in the curing and mechanical properties in comparison to the NR vulcanizate with 5 phr conventional ZnO. Thermogravimetric analysis reveals that nano ZnO impose better thermal stability than conventional ZnO in the NR vulcanizates. Thus, nano ZnO not only acts as a curing activator but also nano filler to improve the resulting properties of the NR vulcanizates. More essentially nano ZnO leads to the reduction of ZnO level in the NR compounds. Therefore, sol-gel derived nano ZnO diminishes the pollution of aquatic environment due to higher amount of conventional ZnO in rubber compounds. [ABSTRACT FROM AUTHOR]

This study is devoted to the thermal decomposition of ZnCO·2HO, which was synthesized by solid-state reaction using CHO·2HO and Zn(CHCOO)·2HO as raw materials. The initial samples and the final solid thermal decomposition products were characterized by Fourier transform infrared and X-ray diffraction. The particle size of the products was observed by transmission electron microscopy. The thermal decomposition behavior was investigated by thermogravimetry, derivative thermogravimetric and differential thermal analysis. Experimental results show that the thermal decomposition reaction includes two stages: dehydration and decomposition, with nanostructured ZnO as the final solid product. The Ozawa integral method along with Coats-Redfern integral method was used to determine the kinetic model and kinetic parameters of the second thermal decomposition stage of ZnCO·2HO. After calculation and comparison, the decomposition conforms to the nucleation and growth model and the physical interpretation is summarized. The activation energy and the kinetic mechanism function are determined to be 119.7 kJ mol and G( α) = −ln(1 - α), respectively. [ABSTRACT FROM AUTHOR]

Abstract: This paper reports additive-free, reproducible, low-temperature solution-based process for the preparation of crystalline ZnO nanorods by homogeneous precipitation from zinc acetate. Also, ZnO nanorod structured dye sensitized solar cells using ruthenium dye (Z907) have been fabricated and characterized. The formation and growth of zinc oxide nanorods are successfully achieved. We analyzed three different synthesis method using solution phase, autoclave and microwave. The calcination effects on the morphology of ZnO nanorods are also investigated. Analysis of ZnO nanorods shows that calcination at lower temperature is resulted in a nanorod growth. Additive-free, well-aligned ZnO nanorods are obtained with the length of 330–558nm and diameters of 14–36nm. The XRD, SEM, and PL spectra have been provided for the characterization of ZnO nanorods. Microwave-assisted ZnO nanostructured dye sensitized solar cell devices yielded a short-circuit photocurrent density of 6.60mA/cm2, an open-circuit voltage of 600mV, and a fill factor of 0.59, corresponding to an overall conversion efficiency of 2.35% under standard AM 1.5 sun light. [Copyright &y& Elsevier]

Abstract: Zinc oxide (ZnO) thin-films were grown on glass substrates by using simple wet chemical approach and then the films were annealed at 450°C in air atmosphere for 2h. The scanning electron microscopy images could confirm the uniform deposition and formation of cabbage leaf-like ZnO nanostructures. The optical band gap was found to be 3.14eV for annealed films. The sensor showed higher sensitivity towards liquid petroleum gas (LPG) at optimized temperature of 200°C. The response and recovery times with 200ppm of LPG were found to be ∼6 and ∼ 8s, respectively. [Copyright &y& Elsevier]

• A green chemistry route in combination with ultrasonic power had been adopted to prepare ZnO nanoparticles without and with Hibiscus extract. • After characterization, the impact of the extract addition revealed size and bandgap reduction along with surface area increase. • The improved photocatalytic performance of the nanoparticles has been tested and proved using the Methylene Blue organic dye. • The radical scavenger study indicated a significant role of superoxide radicals in the photodegradation of MB. In the present work, a green chemistry route for synthesizing zinc oxide (ZnO) nanostructures using Hibiscus extract as a stabilizing and a reducing agent under ultrasonic energy. The ZnO nanostructures obtained without (ZnO) and with Hibiscus extract (ZnO-H) were characterized to explore the effect of the plant extract on ZnO structure, morphology, and photocatalytic activity. The X-ray diffraction (XRD) data showed a reduction in ZnO crystallite size from 40 to 31 upon treatment with the Hibiscus extract. In addition, thinner ZnO nanorods were formed due to the use of the extract, as perceived from the scanning electron microscopic (SEM) analysis. The N 2 physisorption data revealed that surface area and porosity increased with Hibiscus extract treatment, where the S BET increased from 4.0–10.0 m2. g−1, while the pore size and pore volume increased from 0.021 to 0.06 cm3. g−1 and 12.5–18.2 nm, respectively. The X-ray photoelectron spectroscopy (XPS) confirmed the formation of ZnO with minor shift in the binding energies as an effect of using the extract. As a consequence of band gap narrowing, surface area and porosity increase, the ZnO-H nanostructures exhibited better photocatalytic degradation performance for the methylene blue (MB) dye. The high efficiency for MB degradation was reflected by the higher photodegradation percentage and greater pseudo-first-order kinetics rate constant. The radical scavenger study revealed that superoxide radicals played a major role in the photodegradation of MB, especially over ZnO-H. The inexpensive, simple, eco-friendly approach of the previously described protocol for "one-pot" synthesis and alteration of ZnO characteristics could be expanded to fabricate other kinds of nanoparticles and to extend their utility in different areas of nanotechnology. [ABSTRACT FROM AUTHOR]