Diameter Of ZnO Nanorods Research Articles

ZnO nanorod array grown on Ag layer: a highly efficient fluorescence enhancement platform.

ZnO nanorods (NRs) are known for ultra-sensitive biomolecule detection through fluorescence enhancement. In this work, we demonstrate that ZnO NR arrays grown on Ag layers can significantly improve the enhancement up to 86 times compared to that grown on bare Si, and the enhancement can be modified in a controlled manner by varying Ag thickness. The much improved waveguide properties are attributed to the high reflectance of the Ag layers and their tuning effect on the diameters of ZnO NRs. Our results provide a deep insight into the mechanism of NRs-based fluorescence enhancement platform.

Enhanced photovoltaic performance of quantum dot-sensitized solar cell fabricated using Al-doped ZnO nanorod electrode

ZnO and Al doped ZnO nanorods have been successfully synthesized on ITO substrate via solgel dip coating method without using any catalyst. The X-ray diffraction studies showed that the Al doped ZnO samples are of hexagonal wurtzite structure. The Al ions were successfully incorporated into the ZnO lattice. Scanning electron microscopy images reveal that the average diameter of ZnO nanorods and Al doped ZnO nanorods are ∼300nm and ∼200nm respectively. The energy dispersive X-ray (EDS) analysis confirmed the presence Al in the ZnO thin films. The CdS quantum dot sensitized Al doped ZnO solar cell exhibited a power conversion efficiency of 1.5%.

Optimization of headspace solid phase microextraction based on nano-structured ZnO combined with gas chromatography–mass spectrometry for preconcentration and determination of ultra-traces of chlorobenzenes in environmental samples

In this study, a simple, novel and efficient preconcentration method for the determination of some chlorobenzenes (monochlorobenzene (MCB), three isomeric forms of dichlorobenzene (diCB), 1,3,5-trichlorobenzene (triCB) and hexachlorobenze (hexaCB)) has been developed using a headspace solid phase microextraction (HS-SPME) based on nano-structured ZnO combined with capillary gas chromatography–mass spectrometry (GC–MS). ZnO nanorods have been grown on fused silica fibers using a hydrothermal process. The diameter of ZnO nanorods was in the range of 50–80nm. The effect of different variables on the extraction efficiency was studied simultaneously using an experimental design. The variables of interest in the HS-SPME were stirring rate, desorption time and temperature, ionic strength, extraction time and temperature. For this purpose, a multivariate strategy was applied based on an experimental design using a Plackett–Burman design for screening and a Box–Behnken design for optimizing of the significant factors. The detection limit and relative standard deviation (RSD) (n=5) for the target analytes were in the range of 0.01–0.1ngL−1 and 4.3–7.6%, respectively. The developed technique was found to be successfully applicable to preconcentration and determination of the target analytes in environmental water and soil samples.

Growth of Aligned ZnO Nanorods Grown on Polyethylene Naphthalate Substrates: Effect of the Growth Duration

Aligned ZnO nanorods were synthesized on a polyethylene naphthalate (PEN) substrates using a chemical bath deposition method. The growth temperature and precursor concentration were 95 °C and 0.025 M, respectively. The effects of growth duration (2 h to 8 h) on the optical and structural properties of the obtained ZnO nanorods on seed layer ZnO/PEN substrate were then investigated using X-ray diffraction, field-emission scanning electron microscopy (FESEM), and photoluminescence (PL) spectroscopy at room temperature. The high intensity of (002) peak compared with (100) and (101) in the X-ray diffraction (XRD) pattern demonstrated that the ZnO nanorods grown for 6.5 h had more vertical higher crystal quality than the samples grown for other durations. The average diameter of ZnO nanorods grown on PEN substrates increased from 19 nm to 45 nm with increased growth duration from 2 h to 8 h, respectively.

Effect of annealing treatment on morphologies and gas sensing properties of ZnO nanorods

The high-temperature stabilization of ZnO nanorods synthesized by hydrothermal treatment was investigated. The structure and morphologies of ZnO nanorods were characterized by XRD and SEM, respectively. The thermal stability of ZnO nanorods was also detected by thermal gravity analyzing. Thermal annealing treatment results indicate that ZnO nanorods are fundamentally stable when annealing temperature is lower than 600 °C. When annealing temperature is beyond 600 °C, the diameters of ZnO nanorods obviously decrease and the aggravating tendency of nanorods between each other also increase. Annealing treatment can greatly influence the gas sensing properties of ZnO nanorods. Comparing with ZnO nanorods without annealing treatment, the gas sensing property of ZnO nanorods to H2 with concentration of 2.5×10−6 can increase from 2.22 to 3.56. ZnO nanorods annealed at 400 °C exhibit optimum gas sesing property to H2 gas.

Effect of Time Conditions on the Growth of ZnO Nanorods via Hydrothermal Method

In this study, ZnO nanorod arrays were fabricated using a hydrothermal method on ITO glass substrate. We can find that the dimension of ZnO nanorod will changes with different growth temperature. X-ray diffraction (XRD) patterns show that the nanorods are high-quality crystals growing along [00 direction with a high consistent orientation perpendicular to the substrate and it is also revealed that nanorods have wurtzite crystal structure. The diameter of ZnO nanorods were 100300 nm depending on the time of growth process. The surface morphology of ZnO nanorods were analyse using Scanning Electron Microscope (SEM).

Controllable growth of oriented ZnO nanorods using Ga-doped seed layers and surface acoustic wave humidity sensor

ZnO nanorods were grown on a Si/AlN structure using hydrothermal method. The fabricated ZnO nanorod film was used as a sensitive material layer for surface acoustic wave (SAW) humidity sensor. The concentration of gallium, which was doped into ZnO seed layers prior to ZnO nanorod chemical growth, varied from 0wt% to 3wt% to control ZnO nanorod growth. The result shows that gallium dopant was crucial for controllable dimension of ZnO nanorods. ZnO nanorod length increased and ZnO nanorod diameter decreased when Ga concentration increased from 0wt% to 3wt%. The ZnO nanorods had a hexagonal wurtzite structure, and were aligned vertically on the substrate. SAW properties (e.g., resonance frequency) over relative humidity (RH) ranging from 10% to 90% at room temperature were investigated. The results show that the frequency shift of the SAW humidity sensors increased with increasing Ga dopant concentration. The largest shift in the frequency response was approximately 970kHz at 90% RH for sensors with ZnO nanorods grown on 3wt% Ga-doped ZnO seed layer. This result was caused by the highest surface-to-volume ratio of the ZnO nanorod sensing layer.

Diameter regulated ZnO nanorod synthesis and its application in gas sensor optimization

ZnO nanorods with a range of diameter were synthesized by a one-step solvothermal method via adjusting ethanol content in solvents. Material characterization has included XRD, SEM, PL and XPS. It was found that diameter of the ZnO nanorods can be regulated by adjusting ethanol content in solvent. When the ethanol content was increased from 10% to 50%, average diameter of the resultant ZnO nanorods decreased from 360 to 220 nm monotonically. It is also found that ZnO nanorods (a20) prepared with 20% ethanol in solvent has the best crystallinity as revealed in XRD analysis. PL and XPS analyses suggest that the ZnO nanorods are Zn-rich – a beneficial factor to gas sensing response. Gas sensor fabricated using a20 gave the best alcohol vapor response.

Facile hydrothermal synthesis of large scale ZnO nanorod arrays and their growth mechanism

Large scale ZnO nanorod arrays (ZNAs) were grown on the indium-doped tin oxide (ITO) glass substrate by a novel and facile hydrothermal method at low temperature. The obtained nanorods were characterized by SEM, XRD, TEM and PL. It is shown that the average diameter of ZnO nanorods (~500nm) grown on the bare substrate is much bigger than that of nanorods grown on the ZnO-seed-coated substrate (~100nm). ZNAs grown on ZnO-seed-coated substrate are highly aligned. All the as-grown ZnO nanorods have a very good crystallinity with hexagonal wurtzite structure and grow along the c-axis. Zinc metal spiral plays important roles for the growth of ZnO nanorods, which conduces to generate the additional growth unit of [Zn(OH)4]2−.

Enhancement of Light Extraction Efficiency of GaN-Based Light-Emitting Diodes by ZnO Nanorods with Different Sizes

The improvement of the optical output power of GaN-based light emitting diodes (LEDs) was achieved by employing nano-sized flat-top hexagonal ZnO rods. ZnO nanorods (NRs) with the average diameters of 250, 350, and 580 nm were grown on p-GaN top surfaces by a simple wet-chemical method at relatively low temperature (90 degrees C) to investigate the effect of the diameter of ZnO NRs on the light extraction efficiency. Consequently, the enhancement by the factor of as high as 2.63 in the light output intensity at 20 mA for the LED with 350 nm ZnO NRs was demonstrated without the increase in the operation voltage compared to the reference LED.

저온수열합성방법에 의해 성장한 ZnO 나노로드의 전구체 몰농도 변화에 따른 특성 연구

In this research, we investigated the effect of mole concentration of precursor on morphological, structural and optical properties of ZnO nanorods. ZnO nanorods were hydrothermally grown on c-plane sapphire substrates in aqueous solution which contains zinc nitrate hexahydrate and hexamethylenetetramine at 90 o C in the precursor range of 0.01 M to 0.025 M. With the increase of mole concentration, length and diameter of ZnO nanorods increased. In all the conditions, the growth direction of rods was longitudinally c-axis direction. From the strong emission peak at 380 nm of PL spectra at room temperature, we could confirm that the crystal quality of ZnO nanorods is good to emit radiative recombination spectra.

Correlation between ZnO nanorod growth and the dislocations in AlN-based substrates

ZnO nanorods were selectively grown on AlN-based substrates by hydrothermal synthesis without employing seed layers. The correlation between ZnO nanorod growth and the dislocation density in the substrates was revealed. Furthermore, the alignment and average diameter of ZnO nanorods were found to be affected by dislocation etch pits exposed on the surface of AlN. A red-shift in photoluminescence emission spectra of ZnO nanorods on etched-AlN was also observed, which can be attributed to the surface effect.

One-Dimensional ZnO Nanostructures by Wet-Chemistry Technique for Dye Sensitized Solar Cell Application

In the current work, ZnO nanoflowers have been synthesized via sol-gel technique using a mixture of zinc-nitratetetrahydrate, ammonia and polyethylene glycol (PEG). Variation in PEG concentration and ammonia evaporation delay time was performed and the resulting nanoflowers have been investigated using x-ray diffraction (XRD) and scanning electronmicroscope (SEM). To explore the potential of the resulting ZnO nanorods, a prototype of dye sensitized solar cell (DSSC) has been fabricated. For this purpose, the nanorods were grown directly on conducting ITO substrates by nanoseeding technique. With a variation in nano seeding time for 2, 4 and 6 days, followed by hydrothermal process at 80oC for 20 hours, ZnO nanorods with average diameter of 82, 332 and 1385 nm have been synthesized. The performance test showed the resulting open circuit voltage (Voc) was increased from 398 to 486 mV when the diameter of ZnO nanorods increased from 82 to 332 nm. However, the Voc decreased slightly to 456 mV when the nanorods further increased to 1385nm. The phenomenon is related to the interaction between the semiconductor oxide and the Ruthenium complex organic dye.

Influence of ZnO Nanorods Morphology on the Photovoltaic Properties of ZnO/Cu<SUB>2</SUB>O Heterostructural Solar Cells

ZnO nanorods were prepared by electrochemical deposition (ECD). The influence of ECD parameters on the morphologies of ZnO nanorods was studied and optical properties of the ZnO nanorods were measured with optical absorption and specular reflection spectra. It is found that deposition time has significant influence on the length and diameter of ZnO nanorods which is also proved by the optical measurements. ZnO/Cu2O heterostructural solar cells were constructed by ECD with n-type ZnO nanowires and p-type Cu2O films and their photovoltaic characteristics such as open-circuit voltage, short-circuit current density and efficiency were measured. With the increase of nanorods ' length, the photovoltaic properties of ZnO/Cu2O solar cells are enhanced. Finally, the relation between the solar cell performance and the morphologies of ZnO nanorods are discussed. It is indicates that, by increasing the length of nanorods, the light scattering is enhanced, which improves the electronic collection efficiency and photon utilization rate, and accordingly, the performance of solar cells.

Patterned Zn-seeds and selective growth of ZnO nanowire arrays on transparent conductive substrate and their field emission characteristics

A method for the patterned growth of ZnO nanorods with better field emission properties is presented that combines nanoimprinting, electroplated Zn seeds and aqueous solution growth of ZnO. A patterned Zn layer over large area was prepared using the poly(dimethylsiloxane) (PDMS) template to pattern PMMA masking layer without residual layer. ZnO nanorods were selectively deposited on the Zn seeds instead of growing on the bare ITO regions due to the preferred growth on Zn seeds/ITO substrate. The diameter of ZnO nanorods was decided by the concentration of reactants of zinc nitrate and hexamethyltetramine (C6H12N4) (0.025–0.1M) at low temperature. This approach provides the capability of creating patterned 1D ZnO micro/nanopatterns at low temperature, ambient condition, and low cost with large area on flexible devices.

Investigation on Temperature Sensing of Nanostructured Zinc Oxide Synthesized via Oxalate Route

A detailed study is reported of the synthesis and characterization of n- type ZnO nanomaterial and its application as temperature sensor. The ZnO nanomaterial has been synthesized through pyrolysis of the oxalate produced by a conventional precipitation method. It is synthesized by flash heating the oxalate at 450°C for 15 min. Pellet of this material was prepared and used as a sensing element. The variations in resistance of sensing pellet at different temperatures were recorded. The relative resistance was decreased linearly with increasing temperatures over the range, 120°C - 260°C. The activation energy of ZnO calculated from Arrhenius plot was found 1.12 eV. Temperature response in terms of the relative variation, ΔR, of sensor resistance to a given temperature was measured. Scanning electron micrograph of the sensing element has been studied. Pellet of the ZnO is comprised of nanorods of varying diameters and different lengths. Diameter of ZnO nanorods varies from 75 to 300 nm. X-ray diffraction pattern of the sensing element reveal their nano-crystalline nature. Optical characterization of the sensing material was carried out by UV-visible spectrophotometer. By UV-Vis spectra, the estimated value of band gap of ZnO was found 4.7 eV.

Controlled synthesis of oriented ZnO nanorod arrays by seed-layer-free electrochemical deposition

Oriented ZnO nanorod arrays were successfully prepared on transparent conductive substrates by seed-layer-free electrochemical deposition in solution of Zn(NO3)2 at a low temperature of 70°C without using any catalysts, additives, and additional seed crystals. The effects of the Zn(NO3)2 concentration, deposition time and applied current on the localized nanorod arrays are investigated. X-ray powder diffraction (XRD) and field emission scanning electron microscopy (FE-SEM) were used to characterize the structures and the morphologies of ZnO nanorod arrays. The heights and diameters of ZnO nanorods can be tuned by controlling the electrodeposition parameters.

GROWTH, PROPERTIES AND SENSOR APPLICATIONS OF LOW TEMPERATURE GROWN ZnO NANORODS

ZnO nanorods with the average diameter of about 60–300 nm have been grown by the low temperature aqueous chemical growth technique. The impact of growth time and reactant concentration on the morphology on ZnO structures was tested by scanning electron microscopy and photoluminescence spectroscopy. High optical quality of obtained ZnO nanorod films was evidenced by dominating free exciton transitions. The reduction of surface to volume ratio by increasing the diameter of ZnO nanorods resulted in a linear increase of excitonic luminescence intensity with respect to the defect related emission. Excellent photoluminescence properties and high surface area of ZnO nanorods can be used for the detection of organic contaminants dissolved in water. The quenching of both excitonic and defect luminescence was observed upon exposure of ZnO nanorod films to various organic contaminants.

Effect of Zn<SUP>2+</SUP> Source Concentration on Hydrothermally Grown ZnO Nanorods

We studied the effect of Zn2+ source concentration on the structural and optical properties of hydrothermally grown ZnO nanorods. The nanorods were grown on ZnO/p-Si(111) substrate using by a hydrothermal process in various concentrations of reagent at a low temperature (approximately 95 degrees C) and the structural and optical characteristics of ZnO nanorods were subsequently investigated by X-ray diffraction, field-emission scanning electron microscopy, and room temperature photoluminescence. The results demonstrate that the morphology and crystallinity of ZnO nanorods are influenced by the overall concentration of the precursor. The density and diameter of ZnO nanorods with a hexagonal structure are especially sensitivite to concentration of reactants. Furthermore, the structural transition is shown by increasing concentration. At the lowest concentration of Zn2+, the ZnO nanorods grow as single crystals with a low density and variable orientations. On the contrary, at the highest concentration, the nanorods grow as polycrystas due to the supersaturated Zn2+ source.

Gallium ion-assisted room temperature synthesis of small-diameter ZnO nanorods

We report a method for synthesizing small-diameter ZnO nanorods at room temperature (20°C), under normal atmospheric pressure (1atm), and using a relatively short reaction time (1h) by adding gallium salts to the reaction solution. The ZnO nanorods were, on average, 92nm in length and 9nm in diameter and were single crystalline in nature. Quantitative analyses revealed that gallium atoms were not incorporated into the synthesized nanocrystals. On the basis of the experimental results, we propose a mechanism for the formation of small-diameter ZnO nanorods in the presence of gallium ions. The optical properties were probed by UV–Vis diffuse reflectance spectroscopy. The absorption band of the small-diameter ZnO nanorods was blue-shifted relative to the absorption band of the ∼230nm diameter ZnO nanorods (control samples). Control experiments demonstrated that the absence of metal ion-containing precipitants (except ZnO) at room temperature is essential, and that the ZnO nanorod diameter distributions were narrow for the stirred reaction solution and broad when prepared without stirring.