Physical properties of fish gelatin-based bio-nanocomposite films incorporated with ZnO nanorods

Well-dispersed fish gelatin-based nanocomposites were prepared by adding ZnO nanorods (NRs) as fillers to aqueous gelatin. The effects of ZnO NR fillers on the mechanical, optical, and electrical properties of fish gelatin bio-nanocomposite films were investigated. Results showed an increase in Young''s modulus and tensile strength of 42% and 25% for nanocomposites incorporated with 5% ZnO NRs, respectively, compared with unfilled gelatin-based films. UV transmission decreased to zero with the addition of a small amount of ZnO NRs in the biopolymer matrix. X-ray diffraction showed an increase in the intensity of the crystal facets of (10^ī1) and (0002) with the addition of ZnO NRs in the biocomposite matrix. The surface topography of the fish gelatin films indicated an increase in surface roughness with increasing ZnO NR concentrations. The conductivity of the films also significantly increased with the addition of ZnO NRs. These results indicated that bio-nanocomposites based on ZnO NRs had great potentials for applications in packaging technology, food preservation, and UV-shielding systems.     

Optical dispersion analysis of template assisted 1D-ZnO nanorods for optoelectronic applications

Morphology and size play crucial influential roles in semiconductor nanotechnology. Capping agents have been adopted in this study for controlled fabrication of symmetrical zinc oxide (ZnO) nanostructures, with a preferred orientation and agglomeration inhibition. Elongated one-dimensional (1D) ZnO nanorods were successfully synthesised in a simple two-step process. X-ray diffraction (XRD) revealed high crystalline films with a preferred (002) plane orientation. Ethylene glycol (EG) surfactant was found to produce substantial effect on both the morphology and crystallinity as relatively small uniform nanorods with crocked ends were observed from morphological analysis. All the synthesised ZnO films depicted optical transmittance of over 50% in the visible range and a strong absorption peak in the UV proximity, at 380 nm. An evaluation of the optical parameters calculated from the measured transmittance indicated that surfactants can be used to modify the refractive index, real and imaginary dielectric constants of ZnO nanorods, to optimize the performance of optoelectronic devices.     

Selective growth of ZnO nanorods on microgap electrodes and their applications in UV sensors

Selective area growth of ZnO nanorods is accomplished on microgap electrodes (spacing of 6 μm) by using a facile wet chemical etching process. The growth of ZnO nanorods on a selected area of microgap electrode is carried out by hydrothermal synthesis forming nanorod bridge between two electrodes. This is an attractive, genuine, direct, and highly reproducible technique to grow nanowire/nanorod onto the electrodes on selected area. The ZnO nanorods were grown at 90°C on the pre-patterned electrode system without destroying the electrode surface structure interface and geometry. The ZnO nanorods were tested for their application in ultraviolet (UV) sensors. The photocurrent-to-dark (Iph/Id) ratio was 3.11. At an applied voltage of 5 V, the response and recovery time was 72 and 110 s, respectively, and the response reached 2 A/W. The deposited ZnO nanorods exhibited a UV photoresponse that is promising for future cost-effective and low-power electronic UV-sensing applications.     

Highly sensitive C2H2 gas sensor based on Ag modified ZnO nanorods

The sliver (Ag) modified zinc oxide (ZnO) nanorods were successfully obtained with a simplified and environmentally friendly solvothermal method. Materials characterization indicated that the metallic Ag was located on the outside of ZnO nanorods after annealing. In comparison with ZnO nanorods, Ag modified ZnO (Ag–ZnO) nanorods exhibited a considerably enhanced response to C₂H₂. The response of the 3 at% Ag–ZnO based sensor operating at 175 °C is 539 (R_a/R_g), which is the highest value among all the sensors in detecting 100 ppm C₂H₂. The Ag–ZnO based sensors exhibited fast response speed, lower operation temperature and higher selectivity.     

沉淀法制备花状ZnO粉体及性能研究

以二水合乙酸锌提供锌源,氨水调节pH值,聚乙二醇-2000为改性剂,采用沉淀法在一定的工艺条件下得到了花状ZnO粉体。并以SEM、TEM及XRD等测试手段对产物的形貌及结构方面进行了表征。利用X射线衍射仪进行结晶结构分析,表明花状ZnO为六方纤锌矿结构;利用场发射电子扫描电镜进行样品形貌分析,表明花状结构ZnO是由纺锤状棒状结构组成,棒的长径比为2.10;利用场发射透射电镜进行结晶结构分析,表明花状ZnO是单晶与多晶的混合体,室温光致发光谱表明花状ZnO在380nm左右存在紫外发射峰。     

Synergistic effect of Fe and Ag co-doping on the persistent photoconductivity of vertical ZnO nanorods

Undoped, doped and co-doped vertically aligned ZnO nanorods (NRs) are synthesized using sonicated sol-gel immersion method. A significant variation in structural, morphological, optical and photoconductivity properties of ZnO NRs after incorporation of transition metal ions (Fe or/and Ag) is obtained. XRD analysis revealed that incorporation of Fe ameliorates while that of Ag deteriorates the c-axis growth of NRs. The diameter of the NRs is tuned from 236 nm to 103 nm. The Fe-doped ZnO NRs exhibit significantly thinner diameter, longer length, and highest aspect ratio. The doping and co-doping reduces the optical band gap of ZnO by 20 meV and 10 meV respectively. A reduction in near band edge emission whereas enhancement in defect-related-green-emission is obtained. Noticeable enhancement in the light harvesting efficiency and significant quenching of the persistent photoconductivity is obtained by co-doping.     

Preparation,characterization of 1D ZnO nanorods and their gas sensing properties

The 1D ZnO nanorods (NR's) were grown with Zinc (Zn) ion precursor concentration variation on seed layer glass substrate by the low temperature hydrothermal method and utilized for nitrogen dioxide (NO₂) gas sensing application. Zn ion precursor concentration varied as 0.02, 0.03, 0.04, 0.05 and 0.06 M and thin films were characterized for structural, morphological, optical, electrical, surface defect study and gas sensing properties. All the film showed dominant orientation along the (002) direction, the intensity of the peak vary with the length of the nanorods. SEM cross images confirmed that nanorods had vertical alignment perpendicular to the plane of the substrate surface. The PL intensity of oxygen vacancy related defects for prepared samples was found to be linearly proportional to gas sensing phenomena. This result in good agreement with the theoretical postulation that, oxygen vacancies plays the important role for adsorption sites to NO₂ molecule. The gas sensing performance was studied as a function of operating temperature, Zn ion precursor concentration variation, and gas concentration. The maximum gas response is 113.32–100 ppm NO₂ gas at 150 °C for 0.05 M sample out of all prepared samples. Additionally, ZnO thin film sensor has potential to detect NO₂ as low as 5 ppm.     

Growth of vertically aligned ZnO nanorods using textured ZnO films

A hydrothermal method to grow vertical-aligned ZnO nanorod arrays on ZnO films obtained by atomic layer deposition (ALD) is presented. The growth of ZnO nanorods is studied as function of the crystallographic orientation of the ZnO films deposited on silicon (100) substrates. Different thicknesses of ZnO films around 40 to 180 nm were obtained and characterized before carrying out the growth process by hydrothermal methods. A textured ZnO layer with preferential direction in the normal c-axes is formed on substrates by the decomposition of diethylzinc to provide nucleation sites for vertical nanorod growth. Crystallographic orientation of the ZnO nanorods and ZnO-ALD films was determined by X-ray diffraction analysis. Composition, morphologies, length, size, and diameter of the nanorods were studied using a scanning electron microscope and energy dispersed x-ray spectroscopy analyses. In this work, it is demonstrated that crystallinity of the ZnO-ALD films plays an important role in the vertical-aligned ZnO nanorod growth. The nanorod arrays synthesized in solution had a diameter, length, density, and orientation desirable for a potential application as photosensitive materials in the manufacture of semiconductor-polymer solar cells.

PACS

61.46.Hk, Nanocrystals; 61.46.Km, Structure of nanowires and nanorods; 81.07.Gf, Nanowires; 81.15.Gh, Chemical vapor deposition (including plasma-enhanced CVD, MOCVD, ALD, etc.)     

Rapid synthesis and dye-sensitized solar cell applications of hexagonal-shaped ZnO nanorods

This paper reports, for the first time, a very rapid and large-scale synthesis and dye-sensitized solar cells (DSSCs) application of well-crystallized hexagonal-shaped ZnO nanorods at very low temperature of about 70 °C in 20 min. The thin films of as-grown nanorods were used as photo-anode materials to fabricate the DSSCs which exhibited an overall light to electricity conversion efficiency (ECE) of 1.86% with a fill factor of 74.4%, short-circuit current of 3.41 mA/cm² and open-circuit voltage of 0.73 V.     

Synthesis and characterization of Mn-doped ZnO nanorods grown in an ordered periodic honeycomb pattern using nanosphere lithography

We report a study of the structural, optical and magnetic properties of undoped and Mn-doped ZnO nanorods grown by chemical bath deposition in a periodic honeycomb lattice formation. Mn-doping is accomplished by a diffusion process at a constant time of 8 h for different temperatures of 500 °C, 600 °C and 700 °C. Undoped and Mn-doped ZnO nanorods had a hexagonal wurtzite structure with a (0 0 2) preferred orientation. From SEM results, it was seen that Mn-doped ZnO nanorods grew vertically in the honeycomb lattice with lengths of 0.8 μm. XPS results showed that Mn³⁺ ions was successfully incorporated in the ZnO matrix by substituting for Zn²⁺ ions and that Mn-doping increased the number of oxygen vacancies in ZnO compared to undoped ZnO. This result was also supported by photoluminescence data at 10 K. Magnetic data showed that all the samples exhibited ferromagnetic character. Although the origin of undoped ZnO is related to oxygen vacancy-induced d⁰ ferromagnetism, bound magnetic polarons are responsible from the ferromagnetism of Mn-doped ZnO samples which have T_c values above the room temperature.     

Orthorhombic tantalum pentoxide nanorods for electrochemical applications

Water splitting is an important method for hydrogen production. Notably, tantalum oxide has the potential to employ extensive variety appliances because of its outstanding electrical and optical properties. Tantalum pentoxide (Ta₂O₅) nanopowders were produced using the sol–gel process. The effect of calcination time plays a main role on Ta₂O₅ crystal structure configuration. Transmission electron microscope images explored obtained Ta₂O₅ nanorod formation and investigated by electrochemical studies for its use in electrochemical water-splitting applications. The calculated specific capacitance values of Ta₂O₅ electrodes at different temperature conditions were 146.4, 191.7, and 221.7 F/g. Fabricated Ta₂O₅ electrodes showed overpotential of 304, 278, and 267 mV. Current densities of Ta₂O₅ electrodes at different calcinations times were 353, 419, and 461 mA/g. Ta₂O₅ powder calcined for 6 h revealed high specific capacitance and low overpotential, indicating better electrochemical reactivity suitable for water oxidation applications.     

Enhanced mechanical properties of yttrium doped ZnO nanoparticles as determined by instrumented indentation technique

Yttrium doped (1, 3 and 5?wt%) zinc oxide nanoparticles were synthesized via sol-gel process. The phase, structural and mechanical properties were investigated using X-ray diffraction, scanning electron microscopy, energy dispersive X-ray spectroscopy and micro hardness based on indentation technique. The lattice parameters and grain sizes of the samples were calculated from the XRD data. As the lattice parameters increased, the grain sizes decreased dramatically, resulting in more grain boundaries and strong grain connectivity in the ZnO microstructure. Load-depth curves were obtained by applying indentation loads in the range from 400 to 2000?mN at room temperature. As the Y concentration increased, a significant increase was observed in the hardness values computed from loading-unloading curves using the Oliver and Pharr method. The indentation modulus of the samples reached a saturation value for 3% Y and then decreased as the doping rate increased. Moreover, the crack formation around the indent on the sample surface was examined by electron microscopy and was identified as radial/median type. The fracture toughness of the samples was calculated using the Vickers indentation fracture method. Increased fracture toughness values confirm that ZnO nanoparticles are mechanically strengthened by Y doping.     

Studying the optoelectronic properties and emission quenching dynamics of poly-TPD by incorporating ZnO nanoparticles and multiwalled carbon nanotubes

In this study, the optoelectronic properties and emission dynamic quenching of poly-TPD were investigated upon incorporating ZnO nanoparticles and multiwalled carbon nanotubes (MWCNTs). A solution blending method was utilized to successfully prepare poly-TPD incorporated with various contents of ZnO/MWCNT nanocomposites. The optoelectronic properties of the nanocomposites were analyzed using UV–Vis and photoluminescence spectrophotometry. The incorporation of the nanocomposites resulted in a decrease in transmittance, reflectance, and absorption edge, indicating a reduction in the poly-TPD's bandgap. Parameters such as extinction coefficient, Urbach energy, and charge carrier density also decreased with addition of the nanocomposites, suggesting increased scattering, disorder, and the presence of defect states. The decrease in bandgap from 2.970 to 2.852 eV with increasing the nanocomposite content confirmed the emergence of new electronic states. Furthermore, the nature of the transitions changed from direct allowed for pure poly-TPD to direct forbidden upon incorporation of the nanocomposites. The inclusion of the nanocomposites also led to a decrease in refractive index and fluorescence intensity. The observed fluorescence quenching primarily exhibited dynamic characteristics, with a Stern–Volmer constant of 5.14 L/g and quenching rate constants surpassing the minimum threshold for efficient quenching. The increase in charge transfer rate constants with the nanocomposite content indicated enhanced quenching efficiency and charge transfer, likely due to the increased surface area and presence of defects. These findings suggest that poly-TPD incorporated with ZnO/MWCNT nanocomposites displays promising properties for applications in optoelectronic devices.     

Comparison of ZnO and Ti-doped ZnO sensing membrane applied in electrolyte-insulator-semiconductor structure

In this paper, we demonstrate electrolyte-insulator-semiconductor devices for biochemical sensing applications prepared from ZnO and Ti-doped ZnO sensing membranes deposited on Si substrates by radio frequency sputtering. The structural, morphological, and compositional features of these deposited films with multitemperature annealing were studied using X-ray diffraction, atomic force microscopy, and X-ray photoelectron spectroscopy, respectively. Sensitivity, linearity, hysteresis, and drift rate were measured to determine the sensing and reliability performance of all fabricated devices. Compared to the ZnO electrolyte-insulator-semiconductor (EIS), the Ti-doped ZnO EIS sensor annealed at 700 °C exhibits a higher sensitivity of 57.56 mV/pH, lower hysteresis of 2.79 mV, and lower drift rate of 0.29 mV/h. For Ti-doped ZnO, sensitivities of 3.62 mV/mM and 6.42 mV/mM were obtained for urea and glucose sensing, respectively. The improvements are owing to Ti-doping, which produces a rougher sensing surface, a well-crystallized grain structure, and thinner silicate and SiO₂ at the silicon-oxide interface.     

Facile Synthesis of ZnO Nanorods by Microwave Irradiation of Zinc–Hydrazine Hydrate Complex

ZnO nanorods have been successfully synthesized by a simple microwave-assisted solution phase approach. Hydrazine hydrate has been used as a mineralizer instead of sodium hydroxide. XRD and FESEM have been used to characterize the product. The FESEM images show that the diameter of the nanorods fall in the range of about 25–75 nm and length in the range of 500–1,500 nm with an aspect ratio of about 20–50. UV–VIS and photoluminescence spectra of the nanorods in solution have been taken to study their optical properties. A mechanism for microwave synthesis of the ZnO nanorods using hydrazine hydrate precursor has also been proposed.     

Effect of post-deposition annealing on the properties of ZnO films obtained by high temperature,micro-controller based SILAR deposition

The ZnO thin films were prepared by successive ionic layer adsorption and reaction (SILAR) method at elevated precursor temperature. The films were later subjected to post-deposition annealing at different temperatures. This annealing process was found to be beneficial as it improved the structural and optical properties of the films. The ZnO films obtained by SILAR were found to be polycrystalline with hexagonal crystal structure. The crystallite size of the films increased considerably after annealing. The annealed films also showed very high absorption in UV region with marginal change in band gap. Both the crystallite size and optical absorbance were found to increase proportionately with the annealing temperature.     

Dielectric and electrical properties of La@NiO SNPs for high-performance optoelectronic applications

A successful flash combustion synthesis of NiO spherical nanoparticles with various contents of lanthanum (La) doping (La@NiO SNPs) with remarkably enhanced dielectric and electrical properties are reported. Single phase has been confirmed through X-ray diffraction and FT-Raman spectroscopic analysis. Increasing La content in NiO reduced the crystallite size by 341% to 6.65 nm from 22.70 nm. The composition of elements in the final product was assessed via EDX analysis. Moreover, monophasic La@NiO SNPs synthesis with size reduction was observed using field emission scanning electron microscopy (FESEM). A red shift in optical energy gaps (3.52–3.26 eV) was observed with increasing La contents from pure to 10 wt%. Capacitance (109–964 PF), impedance (9.41 × 10⁴–1.67 × 10⁴ kΩ), dielectric constant (100–967), dielectric loss (335–10666), and electrical conductivity (4–5 S/m) values were remarkably improved with La doping. The current (I)–voltage (V) characteristics of pure and La@NiO NPs were performed under the biased voltage of ±20 V. Current was noticed in the range of (3.81 × 10^?4–9.91 × 10^?3 amp) at pure, 1.0, 3.0, 5.0, and 10 wt% of La@NiO NPs. Enhancements in the dielectric and electrical properties of as-synthesized NPs make them suitable for optoelectronics uses.     

Enhanced wettability and photocatalytic activity of seed layer assisted one dimensional ZnO nanorods synthesized by hydrothermal method

The wettability and photocatalytic activity of ZnO nanostructures synthesized by hydrothermal method are reported. XRD, FESEM, XPS, TEM, AFM, Contact angle, UV/Vis and photoluminescence spectroscopy are used to characterize the samples. It is observed that ZnO seeded layer results in the formation of nanorods whereas the absence of seed gives rise to flake like morphology. The XRD indicates that ZnO nanorods have preferred orientation along (002) direction. The formation of ZnO nanorods along (002) direction is due to the existence of nucleation sites resulting from the lattice matching of ZnO seed. Wettability studies show that the ZnO nanorods grown on seeded substrate approaches superhydrophobic state with water contact angle (WCA) of 137.0°. The high contact angle is due to the large surface roughness and low surface energy. The enhanced catalytic performance of ZnO nanorods is attributed to the 1D structure, enhanced roughness, crystallinity and a large number of reactive oxidizing species.     

Improved optical and structural properties of cadmium sulfide nanostructures for optoelectronic applications

In this study, the effect of ZnO seed layer on the growth of uniform CdS nanostructures was investigated using chemical bath deposition technique. Besides, the influence of molar concentration of reagents on the surface morphology, structural and optoelectrical properties of the deposited CdS thin films were examined. The CdS nanostructures were grown on bare glass and ZnO/glass substrates with different reagent molar concentrations. The results indicated an improvement in the homogeneity and uniformity of the grown CdS nanostructures on ZnO seed layer which can be due to the low lattice mismatch between ZnO and CdS structures. The CdS/ZnO samples were optimized by changing the molar concentration of reagents. A three–dimensional intersecting vertical nanosheet morphology with hexagonal structure was obtained when modified chemical concentration of 0.5 M was applied. The XRD pattern of CdS nanosheets indicated the hexagonal phase of CdS which were strongly orientated along (002) plane. The elevated intensity of dominant peak related to this sample confirmed the improved crystal quality of this CdS nanostructure comparing to the other samples. The UV–Vis spectrum demonstrated a high absorption coefficient for CdS intersecting nanosheets which might be due to the high specific surface area and light trapping behavior of this sample. The photoluminescence study also showed an improvement in optical properties of optimized CdS nanostructures. In order to study the optoelectrical properties of CdS nanostructures, metal–semiconductor–metal photodetectors were fabricated with different CdS samples and their current–voltage characteristics were analyzed. The results indicated an enhancement in photosensitivity, responsivity, and speed of photodetectors based on optimized CdS nanostructures.     

Optimization of mechanical and tribological properties of carbon fabric/resin composites via controlling ZnO nanorods morphology

The multi-scale reinforcements of ZnO nanorods/carbon fabric with different morphologies were obtained using a simple water bath method via controlling the concentration of growth solution for a new application in wet friction materials. The ZnO nanorods/carbon fabric were characterized via X-ray diffraction, Scanning electron microscopy, Fourier transform infrared spectroscopy and Raman spectra. As a result, the ZnO nanorods/carbon fabric/resin composite (sample CP3) possesses the maximum bending and tensile strength of 62.7?MPa and 170.0?MPa, which increases by 40.2% and 59.1% compared with that of bare carbon fabric/resin composite due to the best mechanical interlocking and chemical adhesion at the interfacial region of the composite. Meanwhile, the wear rate of the sample CP3 decreases obviously by 81.5% together with stable friction coefficient under various friction condition. From view point of material design, it is necessary to control the morphologies of ZnO nanorods to optimize mechanical and tribological properties of ZnO nanorods/carbon fabric/resin composites.