Diameter Of ZnO Nanorods Research Articles

Facile synthesis of 2D acid-etched g-C3N4 nanosheets with 1D ZnO nanorods as a promising electrode material for supercapacitor

A low-cost, non-toxic nanocomposite of two-dimensional (2D) nanosheets of acid-etched graphitic carbon nitride (TGCN) and one-dimensional (1D) nanorods of zinc oxide (ZnO NRs) is prepared using one-step calcination method. The average size and diameter of ZnO nanorods in TGCN/ZnO (T-ZnO) nanocomposite is reduced to 0.5 and 0.73 times than pristine ZnO NRs, respectively. After the acid-etching process, the size of the T-ZnO nanocomposite is further reduced which enhanced its specific surface area to 16.82 m2/g as compared to pristine ZnO NRs (3.56 m2/g). T-ZnO NRs shows a specific capacitance of 398.47 F/g using 0.5 M H2SO4 which is higher as compared to T-ZnO NRs using 0.5 M Na2SO4 (278.16 F/g) and 6 M KOH (106.10 F/g). Using Electrochemical impedance spectroscopy, diffusion coefficient (D) value 1.85 × 10−11 is obtained for T-ZnO NRs (0.5 M H2SO4). T-ZnO NRs also exhibits a higher specific capacitance of 311.80 F/g at 1 A/g using 0.5 M H2SO4. The nanocomposite shows superior energy density of 97.43 Wh/kg at 750 W/kg of power density. The superior capacitance retention (>95 %) and stable coulombic efficiency (>80 %) of T-ZnO NRs enables the nanocomposite for practical applications in energy storage devices. The electric double layer (EDL) and pseudocapacitive (PC) contribution of 6.04 % and 93.96 % to the total specific capacitance of T-ZnO NRs is evaluated using Trasatti method. The capacitive and diffusion-controlled contribution is also investigated for T-ZnO NRs using Dunn's method. The practical aspect of a supercapacitor using leakage current and self-discharge is also tested for the T-ZnO NRs. T-ZnO NRs is a promising energy storage material to fill the gap in the ongoing energy crisis.

WS2 coating and Au nanoparticle decoration of ZnO nanorods for improving light-activated NO2 sensing

ZnO-based heterogenous nanostructures are considered as excellent active materials for fabricating highly sensitive and selective gas sensors. In this work, nanocomposite WS2/Au/ZnO nanorods were synthesized by covering WS2 thin coatings on the surface of ZnO nanorods and embedding Au nanoparticles between the WS2 coatings and the ZnO nanorods, and the light activated sensing performance of the sensor using the WS2/Au/ZnO nanorods as the sensing material was evaluated. With an average ZnO nanorod diameter of 60 nm, WS2 coating thickness of 10 nm, and Au nanoparticle diameter of 5 nm, the WS2/Au/ZnO nanorods present high photoactivity because of widened photoresponse region, increased light absorption, and quenched photoluminescence. The performance for sensing NO2 gas of the WS2/Au/ZnO nanorod-based sensor under 365, 455 or 655 nm light activation was compared with that of a bare ZnO nanorod-based sensor. The WS2/Au/ZnO nanorod-based sensor exhibits better sensing performance than the bare ZnO nanorod-based sensor under 365 or 455 light activation, with the response to 20 ppm NO2 of the former 40% higher than that of the latter. The improved sensing performance is attributed to the co-sensitization of semiconductors and metals.

Impact of Radio Frequency Plasma Power on the Structure, Crystallinity, Dislocation Density, and the Energy Band Gap of ZnO Nanostructure

The aim of this study is to investigate the effect of radio frequency (RF) plasma power on the morphology, crystal structure, elemental chemical composition, and optical properties of ZnO nanostructure using a direct current magnetron sputtering technique. This study emphasized that the growth rate and surface morphology of the polycrystalline ZnO were enhanced as the radio frequency (RF) plasma power increased. This can be observed by fixing other parameters such as the growth time, substrate temperature, and chamber partial pressure. The RF plasma power alteration from 150 to 300 W can produce uniform nanograin, spheroid, and nanorods. Additionally, the RF plasma power alteration leads to the alteration in the ZnO nanorod diameter from 14 to 202 nm. It was observed that the XRD intensities are increased at higher plasma powers. This, perhaps, can be inferred from the transformation of the granular microcrystals to the needlelike or platelike large crystals, as already examined using SEM images. This also has an impact on the average crystalline size, which increased from 10 to 40 nm on increasing the RF plasma power. Moreover, the increase of the RF plasma power has an obvious impact upon the optical band-gap energy, which was accordingly decreased from 3.26 to 3.22 eV. Finally, the absorption band edge was shifted to a lower-energy region due to the quantum size effect at the nanorange.

Free-standing ZnO nanorod arrays modified with single-walled carbon nanotubes for betavoltaics and photovoltaics

A full-duplex radiant energy converter based on both betavoltaic and photovoltaic effects in an easy-to-implement way is an attractive alternative for the autonomous wireless sensor microsystem. Here, we report a novel beta/photovoltaic cell based on free-standing ZnO nanorod arrays (ZNRAs) modified with metallic single-walled carbon nanotubes (m-SWCNTs), using radioisotope 63Ni as beta-emitting source. The ZNRAs were grown on Al-doped ZnO (AZO) conductive glass using hydrothermal method. The optimum length and diameter of ZnO nanorods were determined by Monte Carlo simulation for beta energy deposition in ZNRAs. The m-SWCNTs were anchored into the ZNRAs to form a three-dimensional (3-D) Schottky junction structure for effectively separating the beta/photo-excited electron-hole pairs. Experimentally, the betavoltaic and photovoltaic effects were confirmed through the I–V measurements of beta/photovoltaic cells under beta/UV/Vis irradiations, respectively. It is suggested that the m-SWCNTs play key role for the enhancement of beta/photovoltaic performance through the formation of extensive 3-D Schottky junction, the conductive network for hole transport, and the surface plasmon resonance exciton absorption for visible light.

The effects of substrate on enhancement of UV emission of ZnO nanorods

We have synthesized ZnO nanorods by hydrothermal at 95 °C for two hours on different substrates i.e. glass, ZnO, and ITO. Morphologically, the average diameter of ZnO nanorods on glass, ZnO, ITO are 117.6 µm, 133 µm, 98.4 µm, respectively. According to the international center for diffraction data (ICDD) number #01-079-0207, the ZnO nanorods on all substrates possess a polycrystalline wurtzite structure. By full width at half maximum (FWHM) of ZnO NRs in (002) plane, we have determined crystallite size and micro-strain using Scherer’s equation and Stokes-Wilson equation, respectively. The crystallite size and micro-strain of ZnO NRs vary with different kind of substrates. Optically, ZnO nanorods on a glass substrate have the strongest excitonic-related ultraviolet (UV) emission. Further observation, we have determined the UV/GB ratio to confirm the crystalline quality of ZnO NRs on glass, ZnO, and ITO substrates. These UV/GB ratios are 101.35, 68.14, and 22.74. It is indicating the ZnO NRs on glass has a better crystalline quality which indicates fewer native defects concentration compared to the others.

New Design of ZnO Nanorod- and Nanowire-Based NO2 Room-Temperature Sensors Prepared by Hydrothermal Method

Room-temperature gas sensors are attracting attention because of their low power consumption, safe operation, and long-term stability. Herein, ZnO nanorods (NRs) and nanowires (NWs) were on-chip grown via a facile hydrothermal method and used for room-temperature NO2 gas sensor applications. The ZnO NRs were obtained by a one-step hydrothermal process, whereas the NWs were obtained by a two-step hydrothermal process. To obtain ZnO NW sensor, the length of NRs was controlled short enough so that none of the nanorod-nanorod junction was made. Thereafter, the NWs were grown from the tips of no-contact NRs to form nanowire-nanowire junctions. The gas-sensing characteristics of ZnO NRs and NWs were tested against NO2 gas at room temperature for comparison. The gas-sensing characteristics of the sensors were also tested at different applied voltages to evaluate the effect of the self-activated gas-sensing performance. Results show that the diameter of ZnO NRs and NWs is the dominant parameter of their NO2 gas-sensing performance at room temperature. In addition, self-activation by local heating occurred for both sensors, but because the NWs were smaller and sparser than the NRs, local heating thus required a lower applied voltage with maximal response compared with the NRs.

Size-dependent water splitting activity of ZnO nanorods

In this study, we investigated the size-dependent photoelectrochemical (PEC) water splitting activity of ZnO nanorods. Large area one-dimensional (1D) ZnO nanorod arrays were grown on ZnO seed layers by a hydrothermal method. Morphology analysis revealed that different-sized ZnO nanorods can be successfully prepared by controlling the reaction time. PEC activities of different-sized ZnO nanorods were tested using a three-electrode configuration under simulated solar illumination. Different photocurrent values were obtained for different-sized ZnO nanorods. Thus, our results indicate that PEC activity of prepared photocathodes can be optimized by adjusting the length and diameter of ZnO nanorods

Investigation of Optical Properties of ZnO Nanorods Grown on Different Substrates

ZnO nanorods arrays are synthesized over the different substrates namely; Indium Tin Oxide (ITO), Kapton Tape (KT), Polyethylene terephthalate (PET), Porous Silicon (PS) and Silicon (Si) using modified chemical bath deposition (MCBD) method at 95 ºC for 4 h. The MCBD is the air bubbles inside growth solution during CBD process. The ZnO nano-seed layers are coated on different substrates using RF magnetron sputtering technique. The optical properties (transmittance, reflectance and energy band gap) and surface morphology of ZnO nanorods grown on different substrates have been investigated in details by using UV-Visible Spectrometer and Field emission scanning electron microscopy (FESEM), respectively. The results found that the morphology and diameter of ZnO nanorods is closely concerned to the nature of substrates. Also it is indicated that the substrate has strong and important impact on the growth, optical properties, Egand quality of synthesized ZnO nanorods (NRs). The higher transmittance has been observed for ZnO NRs grown over KT substrates and is about (~ 33 %). The average transmittance decreases sharply near UV region at wavelength around 393 nm for ZnO nanorods grown on ITO substrate. However, for PET and KT substrates, the transmittance decreases sharply near visible region around 401nm and 498 nm, respectively. Besides, the ZnO NRs grown on PS substrate have the strong reflectance characteristics after approximately 395 nm, and then decreases in the wavelength range of 410 nm to 700 nm. On the other hand, the strong reflectance property of ZnO NRs grown on Si substrate is observed at 400 nm. Also the minimum and maximum Egare obtained for ZnO nanorods that fabricated on the KT substrate and porous silicon substrate, respectively.

Tuning the rod diameter of ZnO nanorods on porous silicon by incorporating graphene

Abstract In this research, graphene was incorporated into the ZnO nanorods (NRs) growth in two different ways to enlarge the rod diameter of ZnO NRs on porous silicon (PS) substrates. We etched the P-type Si (1 0 0) wafer to form the PS layer in solution with HF and C2H5OH and H2O2 for appropriate time. Then, ZnO NRs with and without incorporating graphene were grown with solgel/hydrothermal methods on top of the PS substrates, respectively. To characterize the graphene incorporated ZnO NRs on PS substrates, multiple material analyses including field-emission scanning electron microscopy, energy dispersive X-ray spectroscopy, X-ray diffraction, photoluminescence, IV curves were used to study the graphene-incorporated ZnO NRs. Results indicate that ZnO NRs with larger diameters could be viewed with graphene included into the ZnO NR growth in two different ways. Furthermore, higher defect concentrations could be observed for the graphene-contained NRs. In addition, the ZnO/PS contact exhibited rectifying electrical behaviors without graphene addition but non-rectifying electrical behaviors with graphene incorporation. Tuning ZnO NRs growth on PS substrates with graphene is promising for future ZnO NRs/Si-based device applications.

Enhancing photoresponsivity of ultraviolet photodetectors based on ZnO/ZnO:Eu (x = 0, 0.2, 1, 5 and 20 at.%) core/shell nanorods

In this work, the effect of europium concentration (0, 0.2, 1, 5 and 20 at.%) as a dopant in the shell of ZnO/ZnO:Eu core/shell nanorods structure was studied and their optical properties were compared with the pure ZnO/ZnO core/shell nanorods structure. The core ZnO nanorods are synthesized by hydrothermal and then encapsulated with ZnO nanorods doped by Eu in different concentration by dip coating method. The encapsulated ZnO nanorods are characterized by scanning electron microscopy (SEM), ultraviolet (UV)–vis spectrophotometry, X-ray diffraction (XRD) and photoluminescence (PL) spectroscopy. The XRD results showed that the Eu doping decreases the crystallinity of ZnO nanorods. SEM images revealed a well nanorods arrays growth perpendicular to the surface and confirmed the morphological structure of nanorods didn’t change by encapsulating. With encapsulating, the diameter of ZnO nanorods increased about 20–40 nm. The UV detecting properties of the nanorods are investigated and the results showed that 1 at.% Eu doping significantly enhances the photo detecting properties.

Hydrothermal synthesis of photo-induced hydrophilic ZnO nanorods

Zinc oxide nanorods have been synthesized on ZnO seed layer/glass substrate by hydrothermal at a low temperature of 90 °C using zinc acetate and hexamethylenetramine. The effect of precursor concentration/growth time on structural, physical morphologie characteristics were investigated by X-ray diffraction (XRD), field emission scanning electron microscopy (FE-SEM) and transmission electron microscope (TEM). The contact angle measurement was used to determine the hydrophilicity of the films after exposing to UV light. The XRD results show that the structure of ZnO nanorods is wurtzite structure. The growth rate of ZnO nanorods was depended on the growth time. From the contact angle measurement, the hydrophilicity of the ZnO nanorods tended to improve as the length and diameter of ZnO nanorods increased.

Modulating the size of ZnO nanorods on SiO2 substrates by incorporating reduced graphene oxide into the seed layer solution

In this research, reduced graphene oxide was incorporated into the ZnO seed layer to modulate the rod diameter of ZnO nanorods (NRs) during solgel/hydrothermal growth. To characterize the reduced graphene oxide incorporated ZnO NRs, multiple material analysis techniques including field-emission scanning electron microscopy, surface contact angle measurements, X-ray diffraction, and photoluminescence were used to explore distinct properties of these size modulatable NRs. Results indicate ZnO NRs with smaller diameters could be observed with more reduced graphene oxide added into the ZnO seed layer. Furthermore, better crystallinity, higher hydrophobicity and lower defect concentration could be obtained with more amount of reduced graphene oxide added into the ZnO seed layer. The modulatable reduced graphene oxide-incorporated ZnO NRs growth is promising for future ZnO NRs based nanodevice applications.

Diameter-controlled synthesis of ZnO nanorods on Fe-doped ZnO seed layer and enhanced photodetection performance

In this study, we fabricated ZnO nanorods grown on Fe-doped ZnO seed layer by a hydrothermal method. The effects of seed layer on growth of ZnO nanorods and their electrical and photodetection properties were systematically investigated. Results indicate that the average diameter of ZnO nanorods decreases with increasing Fe concentration while the nanorods number density has an increasing trend. The X-ray analysis showed that there is a preferred growth orientation rods in all samples. The electrical resistance of ZnO NRs reduces with increasing of Fe dopant up to 1.5at.% and then increases with 4.5% Fe in seed layer. Also, the photodetection performance of ZnO nanorod-based photodetectors grown on the Fe-doped seed layer improved as sensitivity increased ∼377 for the sample grown on ZnO seed layer with 4.5at.% Fe dopant under ultraviolet illumination and the responsivity increased ∼18.6A/W for sensor including seed layer with 1.5at.% Fe.

The role of Mg dopant on the morphological, structural and optical properties of Mg doped zinc oxide grown through hydrothermal method

ZnO nanorods is a low cost II-VI semiconductor compound with huge potential to be applied in optoelectronic devices i.e. light emitting diodes, solar cells, gas sensor, spintronic devices and lasers. In order to improve the electrical and optical properties, group II, III and IV elements were widely investigated as dopand elements on ZnO. In this work, magnesium (Mg) was doped into ZnO nanorods. Samples were prepared firstly by deposition of undoped ZnO seed layer on indium thin oxide coated glass substrates by ultrasonic spray pyrolysis method and then followed by the growth of ZnO nanorods doped by three different Mg concentrations by hydrothermal method. Based on the morphological, microstructural and optical characterizations results, it is concluded that the increase of magnesium concentration tends to reduce the diameter of ZnO nanorods, increases the bandgap energy and decreases the UV absorption the luminescence in UV and visible range.

Facile bottom-up growth of pyramidally textured ZnO:Al films by combined chemical bathing and DC sputtering deposition

We developed a facile bottom-up approach to achieve the well-faceted pyramidally textured ZnO:Al (AZO) thin films on non-conductive glass substrates by combining chemical bathing and DC magnetron sputtering deposition. The chemical bathing deposition (CBD) was adopted to generate the ZnO nanorods (NRs) with a terminated plane of (001), followed by the further growth of (101)-faceted AZO pyramidal tips using DC sputtering. The structural, optical, and electrical properties of pyramidally textured AZO films were mainly governed by the size and distribution of ZnO NRs. When the length and the diameter of ZnO NRs were around 450 and 150 nm, respectively, controlled through the CBD process, the AZO film grown on the NRs showed a low resistivity of 9.7 × 10−4 Ω cm and a high average transmittance of 85.7 % at wavelengths of 400–1100 nm. The well-faceted pyramidal textures brought about a maximum haze value of 66.0 % at 355 nm and an average haze of 14.5 % at wavelengths of 355–1100 nm. This proposed simple strategy may benefit the studies on growth of pyramidally textured transparent conducting oxides on non-conductive substrates for high-efficient light harvesting through a low-cost and scalable process.

Role of ZnO thin film in the vertically aligned growth of ZnO nanorods by chemical bath deposition

The effect of ZnO thin film on the growth of ZnO nanorods was investigated. ZnO thin films were sputter-deposited on Si substrate with varying the thickness. ZnO nanorods were grown on the thin film using a chemical bath deposition (CBD) method at 90°C. The ZnO thin films showed granular structure and vertical roughness on the surface, which facilitated the vertical growth of ZnO nanorods. The average grain size and the surface roughness of ZnO film increased with an increase in film thickness, and this led to the increase in both the average diameter and the average length of vertically grown ZnO nanorods. In particular, it was found that the average diameter of ZnO nanorods was very close to the average grain size of ZnO thin film, confirming the role of ZnO film as a seed layer for the vertical growth of ZnO nanorods. The CBD growth on ZnO seed layers may provide a facile route to engineering vertically aligned ZnO nanorod arrays.

Effect of molar ratio of zinc nitrate: hexamethylenetetramine on the properties of ZnO thin film nanotubes and nanorods and the performance of dye-sensitized solar cell (DSSC)

The effect of hexamethylenetetramine (HMT) concentration while keeping zinc nitrate [Zn(NO3)2] at constant concentration and vice versa on the morphology, optical absorption, structure of ZnO nanostructure and the performance of the DSSC utilizing the ZnO samples has been investigated. The ZnO photoanode samples were deposited on FTO substrate via hydrothermal growth at 90 °C for 8 h followed by cooling at 50 °C for 16 h. It was found that the structure and morphology of ZnO nanostructure are significantly influenced by the molar ratio of precursor concentration. The high density and smaller diameter of ZnO nanorods were formed when molar ratio of OH− ion concentration was increased. The modification on the shape and porosity of ZnO nanostructure are seemingly influenced by the amount of free ion Zn+2 in the growth solution. The samples have been utilized as photoanode in DSSC. The DSSC utilizing ZnO nanosheets performs the J SC, V OC, FF and η of 3.6 mA cm−2, 0.50 V, 0.31 and 0.56 %, respectively. The highest performance of that cell is due to the high density and unique morphology of ZnO nanosheets that offered high specific surface area for higher dye loading and light harvesting.

Preparation of Cu(OH)2 and ZnO nanoarrays on surface of metal substrates by a simple method and application as ammonia sensors

One dimensional (1D) nano-structured arrays have attracted great interests in recent years. In this paper, Cu(OH)2 and ZnO nanoarrays on corresponding metal substrates have been successfully prepared by a gas-solution-solid method. The nanoribbons arrays of Cu(OH)2 were about 10μm in length on average and the widths vary from 0.6 to 3.2μm depending on different treatment conditions. Similarly, the diameters of ZnO nanorods could be controlled from 20 to 200nm by adjusting ammonia concentrations. The growth mechanisms for Cu(OH)2 and ZnO nanoarrays were studied and proposed. Briefly, Cu(OH)2 and ZnO nanoarrays were grown from the tips with the help of ammonium in the solution as transporters of copper and zinc ions. Moreover, the NH3 sensing properties were measured and the results showed that both nanoarray sensors have high sensitivity and reversibility for NH3 probing at room temperature.

The effects of precursor concentration and thermal annealing on the growth of zinc oxide nanostructures grown on silicon substrate

This study focuses on the growth of Zinc Oxide (ZnO) nanostructures on SiO2/Si(100) substrate via chemical bath deposition (CBD) with varying NH4OH concentration and annealing temperature. The grown ZnOnanostructures were characterized via SEM-EDS for the surface morphology and elemental composition and UV-Vis spectroscopy for the reflectance measurement. Increasing the concentration of NH4OH produced denser ZnOnanostructures composed of rods having smaller diameter. It is believed that at higher concentration of NH4OH, more Zn(OH)2 seed will act as nucleation site for ZnOformation which suggests higher probability of ZnOgrowth. Thermal annealing increased the average diameter of ZnOnanorods. Annealing provided enough energy for unstable atoms to rearrange into a more suitable position. This would result to larger rods that have been formed in expense of the smaller rods. Furthermore, it is confirmed in the UV-Vis spectroscopy results that ZnOnanostructures were successfully grown on SiO2/Si(100) substrate. This successful growth of ZnOnanostructures is a promising material for solar cell technology.

Enhanced photocatalytic activity of ZnO nanorods grown on Ga doped seed layer

ZnO nanorods have been successfully grown on Ga doped (0–5wt%) ZnO seed layer by using simple hydrothermal method. Changing Ga content in the seed layers lead to formation of ZnO nanorods with high aspect ratio and increased density. The effects of Ga doped seed layer on optical and structural morphology of ZnO nanorods are investigated in detail by using Field-emission scanning electron microscope (FESEM), X-ray diffraction (XRD) and Photo luminescence spectroscopy (PL). It has been observed that the Ga doped seed layer strongly affected the structural morphology of ZnO nanorods. XRD results show that all the samples have hexagonal wurtzite shape and (002) is preferred direction of growth. The intensity of (002) peak increases with increasing Ga concentration in seed layer indicating that the Ga doped seed layer has promoted growth of nanorods along (002). SEM images show a decrease in diameter of ZnO nanorods with increasing Ga concentration in seed layer. The PL spectra of all the samples have two emission bands, UV and defect emission. UV emission shows a small blue shift with increasing Ga concentration in seed layer. The photocatalytic activity of as grown ZnO nanorods increases with aspect ratio (length) and density.