Papers by Keyword: ZnO Nanorod

Abstract: Photo-supercapacitor (PSC) is integrated harvesting energy, that a combination of DSSC with a symmetric supercapacitor. A crucial part of the conversion of photon energy by DSSC is a photoanode. The DSSC photoanode used ZnO NR, because it is known as one of the optical semiconductor materials, which has bandgap of 3.37 eV. Due to good cycle stability and high conductivity, the supercapacitor electrode uses activated carbon-carbon black (AC-CB) materials. This study observed the enhance of temperature growth on the structure, morphology, and optical properties of ZnO NR photoanode to improve the photo-supercapacitor's performance. The hydrothermal method has been chosen to grow ZnO NR photoanode at growth temperature of 100, 150, and 200 °C for 4 hours. The structure, morphology, and optical properties of ZnO NR were analyzed by XRD, SEM-EDX, and UV Vis, respectively. The electrical performance of photo-supercapacitor were analyzed by IV data. XRD pattern has identified an increase peak in the hkl (002) of c-axis orientation and SEM data has identified that ZnO NR grows perpendicular to the substrate according to the preferred orientation. The optical properties has identified a shift to a small bandgap (redshift). For the electrical performance, photo-supercapacitor has increased in maximum current (I_max) as the growth temperature increases, and the maximum current is obtained by a growth temperature of 200 °C, which is 14.45 μA.

Abstract: To date, dye-sensitized solar cells (DSSCs) based on TiO₂ nanoparticles have been widely investigated due to their high conversion efficiency. However, constructing TiO₂ into a structure of nanorods with a high aspect ratio is difficult to be achieved. On the other hand, nanorod/nanowire arrays may provide some advantages, such as an efficient pathway for electron transport and a larger surface area for dye absorption. ZnO is one kind of metal oxides that can be formed into nanorods easily with various methods. Here, we reported our works on the preparation of ZnO nanorods and investigate its DSSC performance. We found that the cell performance was very affected by the diameter of the nanorods, which may then indicate that charge transfer and charge extraction processes are more effective in the cell with a smaller nanorod diameter.

Abstract: Arsenic contaminants in drinking water pose a threat to human health. In this study, we report the use of nanotechnology to enhance the efficiency of arsenic removal. In here, zinc oxide (ZnO) has been selected for this application due to its environmentally friendly to human being. One-dimensional ZnO nanorods were grown on porous ceramic substrate by hydrothermal technique. The monolith nano-adsorbents were investigated using field emission scanning electron microscope (FESEM, Hitachi, SE-8030), while phase compositions and specific surface area were examined by x-ray diffractometer (XRD, PAnalitical, X’Pert PRO). Experiments of arsenic adsorption were conducted by using 200 ppb arsenic concentration solution with a continuously stirring system. After the adsorption, each water sample was then measured the arsenic content by inductively coupled plasma-optical emission spectroscope (ICP-OES) as compare to the original water sample to calculate the percentage of arsenic removal. We found that morphology of nano-adsorbent on using the growth solution concentration of 20mM of growth solution concentration and 20 hours of growth time showed the highest density of ZnO hexagonal nanorods with about 100 nm in diameter. The optimization studies obtained 30 minute of adsorption time, pH as 7. This nano-adsorbent exhibited about 98% of arsenic removal. For the comparison with commercial adsorbent (As600), ZnO nano-adsorbent has a better efficiency. The strong competitive ion on the arsenic removal was PO₄^3-. Moreover, the real groundwater after treatment doesn’t have any toxic residue. Therefore, ZnO nanorods coated on porous ceramic can be the candidate material for arsenic removal from groundwater.

Abstract: The ZnO nanorod was synthesized by the hydrothermal method, and Cu/ZnO nanorod was synthesized by modifying the prepared ZnO nanorod. The TEM was used to characterize the morphology and microstructure for ZnO and Cu/ZnO nanorod. The length of nanorod ZnO was about 700-800 nm, and the diameter about 40-50 nm. There was no change of ZnO in length and diameter when doped with Cu. The degradation of methylene blue (MB) in an aqueous solution under sunlight irradiation was carried out to evaluate the photocatalytic activity. The Cu/ZnO nanorod shows significantly higher photocatalytic activity (99.91%) than ZnO nanorod (89.66%) under sunlight irradiation. The degradation of MB accords with pseudo-first order kinetics, and the appear rate constants kapp of 7% Cu/ZnO nanorod was about 3 times higher than ZnO nanorod. The synergetic effect between ZnO nanorod and Cu on the photocatalytic degradation of MB exists clearly for all the nanorods, and the optimum synergetic effect was found at a weight ratio of 7 wt % (Cu/ZnO). It hoped our works could provide valuable information on the synthesis and application of ZnO-based heterogeneous photocatalysis.

Abstract: In this work, we report the characteristics of ZnO nanorod (NR) arrays grown on bare Si (100) substrates by a one-step hydrothermal method, using equimolar aqueous solutions of zinc nitrate hexahydrate (Zn[NO₃]₂·6H₂O) and hexamethy lenetetramine (C₆H₁₂N₄) with concentrations of 0.01, 0.03, 0.05, and 0.10 M. For the top two precursor concentrations, 0.05 and 0.10 M, the fabricated ZnO NRs can densely distribute on the substrates; they have average diameters of 192 and 416 nm, and average lengths of 3.20 and 4.48 µm. Metal-semiconductor-metal (MSM) ultraviolet (UV) photodetectors (PDs) with interdigitated Au electrodes plated on top of the ZnO NR arrays were also evaluated. Under UV illumination of 370 nm and bias voltage of 3 V, the MSM UV PD based on ZnO NR arrays fabricated with the precursor concentration of 0.05 M has the largest photo-to-dark current contrast ratio of 47.28 among our samples, and its responsivity reaches 1.06´10^-1 A/W, where the corresponding UV-to-Vis rejection ratio is 8.69.

Abstract: Aluminium (Al)-doped zinc oxide (ZnO) nanorod arrays have been synthesized on a glass substrate, where the seed layer is Al-doped ZnO thin film as well, using the sonicated sol–gel immersion method. The nanorods structure was synthesized by preparing a solution 0.0026 M of zinc nitrate hexahydrate (Zn (NO₃)₂·6H₂O, 98%, Systerm) as a precursor, 0.1 M hexamethylenetetramine (HMT, C₆H₁₂N₄, 99%, Aldrich) as a stabilizer and 0.001M aluminum nitrate nonahydrate (Al (NO₃)₃∙9H₂O, 98%, Analar) as a dopant, dissolved in deionized (DI) water. The resistivity is 7626.72 Ωcm and the conductivity is 1.31 x 10^-4 Scm^-1. The peak of UV emission of the sample is at 380 nm.

Abstract: ZnO nanostructures were synthesized by two wet-chemical methods (hydrothermal and electrochemical) featuring low temperature (95°C) and atmospheric pressure onto nonwoven substrates. We investigated a hydrothermal method using reagents Zn (NO₃)₂.6H₂O and hexamethylenetetramine (HMTA) as well as an electrochemical method using ZnCl₂, and KCl containing electrolyte with H₂O₂ and/or O₂ bubbling. The surface condition of substrate material and the experimental conditions played a key role in the nanowire formation. The morphologies observed by scanning electron microscopy (SEM) include wurtzit or cabbage-like. These morphologies were found to vary with the method applied.

Abstract: One dimensional ZnO nanorod has been extensively studied in sensor application due to its unique properties in direct energy band gap and high binding energy. In this report, ZnO nanorod arrays were synthesized via hydrothermal approach. Highly oriented (002) nanorods array with diameter of (22.42 ± 1.40) nm was successfully grown on the quartz surface. A low cost and room temperature optical based NO sensor was introduced. ZnO nanorods array show a high sensitivity upon the NO gas which is 20.1 % within 3 minutes. This newly established method can be potentially used in detection of other toxicity gas.

Abstract: Zinc oxide layer have been prepared by spray pyrolysis technique. The effect of substrate temperature on structural and optical properties of the prepared layer has been investigated. XRD patterns show that ZnO layers are polycrystalline with (002) plane as preferential orientation. FESM images show that ZnO layeres consist of nanorods. Semi-conducting MEH-PPV polymer, which prepared in our lab, was dissolved in THF and sprayed on glass and KBr substrates at 150 oC with two different carrier gases. Organic-inorganic solar cell from MEH-PPV with ZnO nanorods layers was constructed, characterized and its efficiency was calculated.

Abstract: Natural dye sensitized solar cells (nDSSC) mostly suffer from low solar cell performance, that vertically aligned nanotube TiO₂ as the photoanode is expected to increase the performance by providing higher surface area and direct electron transport. Nanostructured TiO₂ films have been fabricated on glass substrates employing ZnO nanorod films as the template. First, vertically oriented ZnO nanorod on a glass substrate was prepared hydrothermally. Then, sol-gel dip-coating technique was used to deposit TiO₂. The template films were dip-coated into sols of titanium tetraisopropoxide-ethanol-diethanol ammine with withdrawing rate of 2 cm/min for three- (Ti3) and seven-times (Ti7). After drying at 100 °C for 10 min, the films were calcined at 550 °C for 1h and washed with HCl 3% (v/v). The films were characterized by X-ray diffraction (XRD), Scanning Electron Microscopy (SEM) and Transmission Electron Microscopy (TEM). It is observed that different coating cycles resulted in different film morphologies. Nanotube TiO₂ with diameter of ~50 nm was identified for Ti3, while Ti7 displayed sheet-like structure. The diffraction patterns confirmed the presence of only anatase crystalline phase with crystallite size of 10.3 nm (Ti3) and 21.7 nm (Ti7). The dye absorption was red-shifted indicating dye monomeric adsorption on TiO₂ via chelation. Enhanced absorption of anthocyanin dye extracted from pericarps of mangosteen (Garcinia mangostana l.) fruit on TiO₂ nanotube compared to TiO₂ nanoparticle (P25) was observed leading to improved photovoltaic performance of the constructed nDSSC.