Fabrication of hybrid solar cells using poly(2,5-dimethoxyaniline) hexagonal structures and zinc oxide nanorods

Flower-shaped zinc oxide (ZnO) structures have been synthesized in a microwave at 180 °C for 20 min using zinc nitrate and KOH. Detailed structural and morphology observation showed that the micron-sized ZnO nano-pencils grow out of the base of the flower-shaped ZnO structures. Photoluminescence spectrum measured at room temperature showed a sharp UV emission band around 390 nm which is attributed to the radiative annihilation of excitons. The synthesized PDMA and ZnO nanopencils are highly crystalline materials with one-dimensional morphology which improves the electron charge transport in the device. A distinctive photoluminescence quenching effect was observed indicating a photo-induced electron transfer. The solar cell devices fabricated from these materials demonstrated a short circuit current density of about 0.93 μA/cm², open-circuit voltage 0.58 V, and efficiency of 0.16 %.     

Photo-initiated growth of zinc oxide (ZnO) nanorods

A photo-initiated process via femtosecond pulse-induced heterogeneous nucleation in zinc ammine complex (Zn(NH₃)₄²⁺)-based aqueous solution without catalyst and surfactant, followed by hydrothermal treatments for crystal growth into zinc oxide (ZnO) nanorods, was investigated. Flat-top hexagonal ZnO nanorods with smooth planes of diameter ≥ 100 nm and length ≤ 1 μm were grown with laser irradiation, compared to porous rod-like structures without irradiation. The flat-top planes indicate slow growth rate, due to the intermediate step of Zn(NH₃)₄²⁺ decomposition to Zn(OH)₄²⁻, before dehydration to ZnO. Prolonged hydrothermal treatment produced nanotubes and lateral splits due to OH⁻ erosion of the crystal faces. XRD analysis showed a hexagonal crystal structure while photoluminescence study indicated a peak at about 380 nm.     

Oversized hexagonal nanosheets of layered zinc hydroxysulfates via the hexamethylenetetramine-mediated solution route

Well-defined hexagonal nanosheets of layered zinc hydroxysulfate (Zn(OH)₂)₃(ZnSO₄)(H₂O)₅ with the side length of 1–20 μm and thickness of ∼50 nm has been synthesized by the thermal treatment of ZnSO₄–hexamethylenetetramine precursor in water–ethanol mixed solvent at 75 °C. The sheet-like morphology was found to closely depend upon the experimental conditions, such as the solvent and the precursor composition. In particular, the products can be easily converted to ZnO nanosheets upon exposing to the irradiation of electron beam.     

Growth of zinc oxide nanorod structures: pressure controlled hydrothermal process and growth mechanism

Zinc oxide (ZnO) nanorods of various morphologies are grown on zinc substrate by pressure-assisted hydrothermal process and the growth mechanism is investigated with the help of molecular dynamics (MD) simulation results. Hydrothermally reacted ZnO₂ nanostructure bottom-up formation from Zn substrate is a useful process employed here. A systematic study on the role of process control parameters such as pressure and temperature on nanorod growth has been carried out. Correlation among the process parameters to form ordered nanostructures is established. The effect of pressure on the diameter and length of the grown ZnO nanorod structures is studied, which is precisely tunable. With a decrease in pressure from 500 to 400 kPa, the nanorod diameter is reduced by 22.2 %, while its length is increased by 24.8 %. At lower vapor pressure, the nanorod tips are sharper, whereas at higher vapor pressure they are flat. These variations along with a detailed analysis of MD simulations helps us hypothesize that pressure plays an important role in governing the diffusion of oxygen atom onto zinc surface and generating wurtzite phase. Simulation results clearly show that ZnO nanorods lift off due to their interaction with the Zn atoms on the substrate and the resulting forces.     

Photocatalytic paper using zinc oxide nanorods

Abstract

Zinc oxide (ZnO) nanorods were grown on a paper support prepared from soft wood pulp. The photocatalytic activity of a sheet of paper with ZnO nanorods embedded in its porous matrix has been studied. ZnO nanorods were firmly attached to cellulose fibers and the photocatalytic paper samples were reused several times with nominal decrease in efficiency. Photodegradation of up to 93% was observed for methylene blue in the presence of paper filled with ZnO nanorods upon irradiation with visible light at 963 Wm^–2 for 120 min. Under similar conditions, photodegradation of approximately 35% was observed for methyl orange. Antibacterial tests revealed that the photocatalytic paper inhibits the growth of Escherichia coli under room lighting conditions.     

Photocatalytic paper using zinc oxide nanorods

Zinc oxide (ZnO) nanorods were grown on a paper support prepared from soft wood pulp. The photocatalytic activity of a sheet of paper with ZnO nanorods embedded in its porous matrix has been studied. ZnO nanorods were firmly attached to cellulose fibers and the photocatalytic paper samples were reused several times with nominal decrease in efficiency. Photodegradation of up to 93% was observed for methylene blue in the presence of paper filled with ZnO nanorods upon irradiation with visible light at 963 Wm^–2 for 120 min. Under similar conditions, photodegradation of approximately 35% was observed for methyl orange. Antibacterial tests revealed that the photocatalytic paper inhibits the growth of Escherichia coli under room lighting conditions.     

纳米T-ZnOW的制备及其生长机理研究

以锌粒为原料，分子筛为催化剂，利用真空控氧高温气相氧化法，制备了纳米四针状氧化锌晶须（T—ZnOw）。利用XRD和SEM、TEM对产物进行物相分析和形貌观察。结果表明：产物为纯六方晶系纤锌矿结构氧化锌；体系压力和反应温度是影响晶须形貌的两个重要因素。当温度恒定为1038℃，而压力低于11083Pa时，均可获得根部直径为20—80nm、针长500nm-2μm、形貌规整的纳米T—ZnOw。TEM研究表明，纳米T—ZnOw的针部为单晶，而核心为多重孪晶结构，其生长遵循气固生长机理。     

Fabrication of hollow mesoporous NiO hexagonal microspheres via hydrothermal process in ionic liquid

The novel NiO hexagonal hollow microspheres have been successfully prepared by annealing Ni(OH)₂, which was synthesized via an ionic liquid-assisted hydrothermal method. The samples were characterized by X-ray diffraction (XRD), field emission scanning electron microscope (FE-SEM), transmission electron microscopy (TEM), N₂ adsorption-desorption and Fourier transform infrared spectrometer (FTIR). The results show that the hollow NiO microstructures are self-organized by mesoporous cubic and hexagonal nanocrystals. The mesoporous structure possessed good thermal stability and high specific surface area (ca. 83 m²/g). The ionic liquid 1-butyl-3methylimidazolium tetrafluoroborate ([Bmim][BF₄]) was found to play a key role in controlling the morphology of NiO microstructures during the hydrothermal process. The special hollow mesoporous architectures will have potential applications in many fields, such as catalysts, absorbents, sensors, drug-delivery carriers, acoustic insulators and supercapacitors.     

Directed spatial organization of zinc oxide nanorods

The ability to precisely place nanomaterials at predetermined locations is necessary for realizing applications using these new materials. Using an organic template, we demonstrate directed growth of zinc oxide (ZnO) nanorods on silver films from aqueous solution. Spatial organization of ZnO nanorods in prescribed arbitrary patterns was achieved, with unprecedented control in selectivity, crystal orientation, and nucleation density. Surprisingly, we found that caboxylate endgroups of omega-alkanethiol molecules strongly inhibit ZnO nucleation. The mechanism for this observed selectivity is discussed.     

Glancing angle deposition of crystalline zinc oxide nanorods

Zinc oxide nanorod films produced by glancing angle deposition were fabricated within the parameter space defined by the process variables pitch (nanorod growth per substrate rotation), deposition rate, and throw distance to investigate the effect these parameters have on morphology and crystallinity. Statistical analysis was used to identify important relationships. Final film morphology depends on both pitch and deposition rate, where two growth regimes distinguished by deposition rate are observed and interpreted as arising from competition between geometric shadowing and crystalline growth kinetics. Optimal growth conditions for nanostructured films of isolated zinc oxide nanorods occurred for pitch values of approximately 1 nm to 10 nm. Pole-figure measurements confirm that the films consist of oriented single-crystal nanorods. Films deposited at all pitch values between 0.001 nm to 6.5 μm are crystalline and textured, and greater texturing is achieved for conditions of decreased surface diffusion.     

Metal-free doping process to enhance the conductivity of zinc oxide nanorods retaining the transparency

The well-ordered metal oxide nanostructures can be synthesized successfully, but the conductance of these structures is limited, which is a disadvantage for applying these in photovoltaic and display devices. Conductivity of a semiconductor can be improved by using metal doping, but the issue becomes a major challenge in nanostructures since their high surface energy usually hinders any metal doping process. Here we show an entirely new metal-free doping strategy to enhance the current conduction of ZnO nanorods' (NRs) arrays through a sulphidation technique. The process is based on the electronegativity difference between S and O because of which one can expect a rigorous bond rearrangement at the interface and a ZnOS-ZnS composite is formed as O is being partially replaced by S. The current conduction by the metal oxide NRs arrays is significantly enhanced by nearly 4 orders of magnitude without sacrificing the transparency of the NRs arrays. The increased current conduction is assigned due to an increase in the Zn(i) concentration as evidenced from the electron paramagnetic resonance measurements. The composite layer grown on p-Si forms a photodiode which is highly sensitive to visible light with a very fast response time.     

Epitaxial growth of the zinc oxide nanorods, their characterization and in vitro biocompatibility studies

Here, we have synthesized Zinc Oxide (ZnO) nanorods at room temperature using zinc acetate and hexamethylenetetramine as precursors followed by characterization using X-ray diffraction (XRD), fourier transform infra red spectroscopy, scanning electron microscopy (SEM) and transmission electron microscopy. The growth of the synthesized ZnO was found to be very close to its hexagonal nature, which is confirmed by XRD. The nanorods were grown perpendicular to the long-axis and grew along the [001] direction, which is the nature of ZnO growth. The morphology of the synthesized ZnO nanorods was also confirmed by SEM. The size of the nanorod was estimated to be around 20-25?nm in diameter and approximately 50-60?nm in length. Our biocompatibility studies using synthesized ZnO showed no significant dose- or time-dependent increase in the formation of free radicals, accumulation of peroxidative products, antioxidant depletion or loss of cell viability on lung epithelial cells.     

Synthesis and characterization of crystalline hexagonal bipods of zinc oxide

The preparation of nano- and submicrometre-sized one-dimensional (1D) zinc oxides (ZnOs) from zinc nitrate was performed by precipitation with urea in two types of solvents (water and water/polyol mixtures). The influence of different polyols (ethylene glycol, diethylene glycol and tetraethylene glycol) on the size of the final particles (length and diameter) is presented for the first time. As well as the influence of the solvents used, the ratio of water/polyol, temperature, pH and time of synthesis was correlated with the size and morphology of the final particles. In all cases crystalline ZnO was synthesized in the form of hexagonal bipods. The morphological and crystalline properties of the samples obtained were characterized by SEM, IR, and XRD.     

Synthesis and growth mechanism of zinc oxide nanostructures in arc discharge

Nanodimensional tubes, needles, and tetrapods of zinc oxide (ZnO) with lengths up to ～1 μm and diameters up to several hundred nanometers have been synthesized for the first time using an arc discharge method. A distinctive feature of the proposed method is the broad variety of evaporated and deposited products. The possible mechanism of evaporation, nucleation, and growth is suggested. Initially, the primary sheets are growing; these sheets turn into rolls and tubes, which eventually transform into needles. Tetrapods crystallize and grow in the gas phase and form a white snowlike deposit.     

Fabrication and characterization of novel nanostructured copper oxide films via a facile solution route

Nanostructured CuO film was prepared using glass or stainless steel slices as substrate via a simple ammonia-assisted solution route at 60 °C. The obtained CuO film was made up of well-crystallized nanosheets of 50-360 nm in thickness and 0.7-4.5 μm in width. The reaction time and the substrate have significant effects not only on the thickness, width, arrangement of the nanosheets but also on the morphology and the thickness of the films. The CuO film was characterized by SEM, TEM, XRD, IR, and Raman spectroscopy techniques.     

Synthesis of small diameter ZnO nanorods via refluxing route in alcohol-water mixing solution containing zinc salt and urea

A single-step refluxing route was proposed to prepare small diameter ZnO nanorods, using zinc salt and urea as reactants, alcohol and water mixing solvents as reaction media, without any surfactants and/or seeds added. The resulting materials were characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), electron diffraction (ED) and high resolution transmission electron microscopy (HRTEM).     

Direct synthesis of highly crystalline single-phase hexagonal tungsten oxide nanorods by spray pyrolysis

The metastable state hexagonal-tungsten oxide (h-WO₃) has been attracting attention over the past decade because of its high reactivity that arises from the hexagonal channels in its crystal structure. Simplification of the process used to synthesize h-WO₃ is an important step to facilitate the industrial applications of this material. In this study, we addressed this challenge by developing a spray pyrolysis process to synthesize highly crystalline h-WO₃. The ratio of the monoclinic to the hexagonal phase was controlled by adjusting the segregation time. Single-phase h-WO₃ nanorods were synthesized using a carrier gas flow rate of 1?L/min, which was equivalent to a segregation time of 18.4?s. The ability of the h-WO₃ nanorods to adsorb nitrogen and carbon dioxide was evaluated to confirm the presence of hexagonal channels in the crystal structure.     

Temperature dependant characteristics of zinc oxide nanorods based heterojunction diode

Temperature-dependant characteristics of heterojunction diode made by n-ZnO nanorods grown on p-silicon substrates has been characterized and demonstrated in this paper. ZnO nanorods were grown onto the silicon substrate via simple thermal evaporation process by using metallic zinc powder in the presence of oxygen at approximately 550 degrees C without the use of any metal catalysts or additives. The as-grown ZnO nanorods were characterized in terms of their structural and optical properties. The detailed structural studies by XRD, TEM, HRTEM and SAED revealed that the grown nanorods are well-crystalline with the wurtzite hexagonal phase and preferentially grown along the [0001] direction. The as-grown n-ZnO nanorods grown on p-Si substrate were used to fabricate p-n heterojunction diode. The fabricated p-n junction diode attained almost similar turn-on voltage of approximately 0.6 V. The values of turn-on voltage and least current are same with the variations of temperature (i.e., 27 degrees C, 70 degrees C and 130 degrees C).     

Ultraviolet sensing properties of polyvinyl alcohol-coated aluminium-doped zinc oxide nanorods

Undoped and aluminium (Al)-doped zinc oxide (ZnO) nanorods have been synthesized by electrochemical route. The synthesized materials have been characterized by X-ray diffraction, UV–visible spectrometer and scanning electron microscope. The Al-doped ZnO nanorods have been coated with polyvinyl alcohol. Current–voltage characteristics have been investigated in dark and under UV-light illumination. Aluminium doping in ZnO increase its electrical conductivity and further polyvinyl alcohol coating on Al-doped ZnO increase UV sensitivity of the material. Response and recovery time of Al-doped ZnO and PVA-coated Al-doped ZnO nanorods have been recorded. PVA-coated Al-doped ZnO nanorods shows very fast response and recovery time of 10 s in comparison to uncoated ZnO (20 min) nanorods.     

Charge influence and growth mechanism of ZnO nanorods

We demonstrate the influence of charges near the substrate surface on vertically aligned ZnO nanorod growth. ZnO nanorods were fabricated on n-type GaN with and without H+ treatments by catalyst-free metal-organic chemical vapor deposition. The ZnO nanorods grown on n-GaN films were vertically well-aligned and had a well-ordered wurtzite structure. However, the ZnO did not form into nanorods and the crystal quality was very degraded as they were deposited on the H+ treated n-GaN films. The charge influence was also observed in the ZnO nanorod growth on sapphire substrates. These results implied that the charges near the substrate surface dominantly affected on the crystalization and formation of ZnO nanorods.