ZnO nanorods Research Papers - Academia.edu (original) (raw)

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- Solid State Physics, Nanotechnology, ZnO nanorods, Nanoscience

Narrow band gap zinc oxide (ZnO) nanoparticles (NPs) were synthesized using unboiled and boiled leaf extracts of Costus woodsonii. The as-synthesized NPs were characterized using a range of techniques. The as-synthesized ZnO NPs were crystalline with a hexagonal wurtzite structure similar to the commercial ZnO (ZnO-C). The maximum absorbance was observed at ~390 nm for ZnO-C and the as-synthesized ZnO NPs (ZnO-UL and ZnOBL) showed a red shift, i.e. ~448 nm to ~462 nm, hence, a lower band gap of ~2.68–2.77 eV. The band gap energy of the as-synthesized ZnO NPs was lower than that of commercial ZnO. The surface of ZnO was coated/modified with the components of the leaf extract. The as-synthesized ZnO NPs showed similar particle sizes and were spherical in shape. These studies confirmed the green synthesis of ZnO NPs using Costus woodsonii and the significantly reduced band gap (Eg =~2.68 eV to ~2.77 eV) of the as-synthesized ZnO NPs compared to the ZnO-C (Eg =3.18 eV).

A B S T R A C T Hydrothermal zinc oxide (ZnO) nanorod (NR)-based p-Si/n-ZnO and p-Si/i-SiO 2 /n-ZnO heterojunctions were fabricated, and the effects of interfacial native SiO 2 (~4 nm) on the I-V characteristics of heterojunctions under dark and ultraviolet illumination conditions were investigated. First, the structural and optical properties of ZnO seed crystals grown by sol-gel method and hydrothermal ZnO NRs on two different substrates of p-Si and p-Si/i-SiO 2 were examined, and more improved optical and crystalline quality was obtained as revealed by photoluminescence and X-ray diffraction. The p-in heterojunctions showed ~3 times greater forward-bias currents and enhanced rectifying property than those of p-n junctions, which is attributed to the role of native SiO 2 in carrier confinement by promoting the electron-hole recombination current through the deep level states of ZnO crystal. The measured ratios of photocurrent to dark current of the p-in structure were also greater under reverse bias (92–260) and forward bias (2.3–7.1) conditions than those (28–225 for reverse bias, 1.6–6.8 for forward bias) of p-n structure, and the improved photosensitivity of the p-in structure under reverse bias is due to lower density of recombination centers in the ZnO NR crystals. Fabricated ZnO NR heterojunction showed repeatable and fast photo-response transients under forward bias condition of which response and recovery times were 7.2 and 3.5 s for p-in and 4.3 and 1.7 s for p-n structures, respectively.

- by Waqar Khan
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- ZnO nanorods, ZnO (Zinc Oxide), UV photodetector

In this report, the polyaniline (PANI)/ZnO nanocomposite system exhibits superior degradation of methyl orange and methylene blue under visible light condition, due to the intermolecular interaction between conducting PANI sponsoring more number of electrons to the conduction band of ZnO nanoparticles. The pure ZnO and the different mole ratios of PANI into ZnO catalysts were prepared by precipitation followed by sonication process. The bandgap of the nanocomposite system revealed in the red region was estimated by Tauc plot. The X-ray diffrac-tion results indicate that the high quantity of PANI into ZnO system reduces the crystallite size and also the crystallinity of the materials. On comparing with the other prepared materials, PZ1.5 illustrated higher degradation of methyl orange and methylene blue. The reason for high catalytic activity and their mechanism of visible light activities were discussed in this paper.

This paper focuses on the solar-assisted photodegradation of Methyl Orange (MO) dye as model molecule using Cu-doped ZnO nanorods synthesized through a chemical method using a solution of zinc chloride (ZnCl2) as precursor, and with the addition of different concentrations of Cu(NO3)2 and NaOH at 65 °C. The samples were characterized by TEM, XRD, XPS, BET and UV–Vis spectroscopy. The amount of Cu and catalyst dosage on the rate of photodegradation were investigated. The measurements of the band gap made by visible UV-Vis spectroscopy showed that it decreased as the dopant material increased. The Cu doped ZnO nanorods showed excellent photodegradation efficiency and good recycling performance. The decomposition reaction was found to be pseudo–first order. Optimal experimental conditions were determined for Cu-doped ZnO nanorods with a catalyst dose of 0.3 g/L and 99% of MO degradation was obtained after 120 min of solar exposure.

- by Mariel Atia
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- Decomposition, ZnO nanorods, Photocatalysis, ZnO (Zinc Oxide)

In this research the effect of ZnO nanorods is simulated and investigated on the performance of poly (2-methoxy-5-(2-ethylhexyloxy)-1, 4-phenylene vinylene (MEH-PPV) based organic light-emitting diode (OLED) located between two electrodes (ITO as an anode and Calcium as a cathode) for emitting in near ultraviolet (UV) region. To study the irradiation in these regions, three structures (ITO/MEH-PPV/Ca, ITO/ZnO/MEH-PPV/Ca and ITO/ZnO/ZnO NR/MEH-PPV/Ca) were considered. Results showed that the OLED simulated with ZnO nanorods had a better performance in comparison with two other structures with higher irradiation intensity at the wave length of 380 nm.

- by Farhad A Boroumand and +1
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- Organic Electronics, Optoelectronics, ZnO nanorods, OLED

An electrochemical glucose sensor based on zinc oxide (ZnO) nanorods is fabricated, characterized and tested. The ZnO nanorods are synthesized on indium titanium oxide (ITO) coated glass substrate, using the hydrothermal sol-gel technique. The working principle of the sensor under investigation is based on the electrochemical reaction taking place between cathode and anode, in the presence of an electrolyte. A platinum plate, used as the cathode and Nafion/Glucose Oxidase/ZnO nanorods/ITO-coated glass substrate used as anode, is immersed in pH 7.0 phosphate buffer solution electrolyte to test for the presence of glucose. Several amperometric tests are performed on the fabricated sensor to determine the esponse time, sensitivity and limit of detection of the sensor. A fast response time less than 3 s with a high sensitivity of 1.151 mA cm-2mM-1 and low limit of detection of 0.089 mM is reported. The glucose sensor is characterized using the cyclic voltammetry method in the range from -0.8 – 0.8 V with a voltage scan rate of 100 mV/s.

- by Sanghamitra Mandal
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- Nanotechnology, Electrochemical Sensors, ZnO nanorods
- by Majid Khan
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- ZnO, ZnO nanorods, Hybrid nanomaterials, ZnO (Zinc Oxide)

A cost-effective phytogenic fabrication of zinc oxide (ZnO) and copper-doped zinc oxide (Cu-doped ZnO) using aqueous leaf extract of Ziziphus mauritiana Lam. was successfully demonstrated. The structural, morphological and optical studies have been carried out using various techniques. XPS, XRD analysis and FT-IR spectroscopic studies confirmed the successful synthesis, crystalline nature and purity of synthesized ZnO and Cu-doped ZnO. UV–visible diffuse reflectance spectra showed reduction of band gap energies from 3.11 to 2.54 eV as Cu doping increases from 0% to 5%. SEM images revealed the synthesized ZnO and Cu-doped ZnO are irregular and spherical shaped, respectively. Antibacterial property of the synthesized materials were evaluated against Gram positive Staphylococcus aureus and Gram negative Escherichia coli using different concentrations. This investigation revealed that the synthesized materials were able to inhibit the activity of Staphylococcus aureus better than Escherichia coli under both dark and visible light conditions with the highest inhibition of 9.33 ± 0.58 mm under light irradiation. The synthesized materials were also found to effectively scavenge 2,2-diphenyl-1-picrylhydrazyl radicals in the dark and an enhancement of the scavenging activity was observed under visible light irradiation.

A novel and simple wet chemical hydrothermal synthesis method was employed in the preparation of zinc oxide (ZnO) nanoparticles using neem (N), pepper (P) and turmeric (T) extracts as solvent media. The structural and optical properties as well as the antibacterial and anticancer properties of all the samples (ZnO, N/ZnO, P/ZnO, T/ZnO and NPT/ZnO) were characterized and analyzed. Solvent media was found to have an effect on both the size and the morphology of the nanoparticles, which in turn effected their optical and cytotoxic properties. The colony forming unit (CFU) assays were done for E. coli, S. aureus and S. typhi in which T/ZnO (~2) and P/ZnO (~3) showed a remarkable effect on S. aureus for 100 µg/ml and nearly zero for 150 µg/ml. The zone of inhibition (ZoI) was measured for S. agalactiae, S. dysgalactiae and S. pyogenes.The results showed that S. dysgalactiae is more sensitive to N/ZnO.Finally, the anticancer properties of these compounds towardsprostate cancer cells was investigated. Among the active compounds T ZnO showed the highest activity with low IC50 value (37.751 µg/ml) followed by P ZnO (45.68 µg/ml).

- by Joshua Pearce and +1
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- Synthesis of nanoparticles, Nanomaterials Characterization, Cancer, Nanobiotechnology

The photocatalytic degradation of p-aminobenzoic acid was studied using C-doped ZnO nanorods as the catalyst synthesized through a low cost and simple precipitation method. The as-synthesized nanorods were fully characterized by SEM, TEM, XRD, BET and XPS. The photocatalytic degradation of p-aminobenzoic acid was carried out under sunlight irradiation. Optimal experimental conditions were determined for C-doped ZnO nanorods with a catalyst dosage of 0.5 g/L in a p-aminobenzoic acid solution, and 97% degradation was obtained. The results showed that the C-doped ZnO nanorods can be reusable and retain good photodegradation efficiency. A pseudo first order reaction was found to provide the best correlations, with a constant rate of 0.028 min −1 .

- by Mariel Atia
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- ZnO nanorods, Photodegradation, p-aminobenzoic acid
- by kottai samy
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- Materials Science, Solid State Physics, Nanotechnology, Advanced Materials

In this study, dual-doping of zinc oxide (ZnO) with magnesium (Mg) and copper (Cu) were successfully performed using aqueous leaf extract of Ziziphus mauritiana Lam. The surface morphological, structural and optical properties of ZnO and Mg/Cu-dual doped ZnO were examined using various techniques. The particle size and optical band gap energy of the synthesized ZnO were reduced when Mg/Cu dopants were introduced. The presence of phytochemicals which played an important role in stabilizing and capping of the phytogenic synthesized ZnO were also confirmed. Furthermore, the effect of light on antibacterial and radical scavenging activities of ZnO and Mg/Cu-dual doped ZnO were examined. It was observed that the synthesized materials exhibited good antibacterial activities towards Staphylococcus aureus compared to Escherichia coli in the absence and presence of light. The phytogenic synthesized ZnO and Mg/Cu-dual doped ZnO were also found to exhibit good 2,2-diphenyl-1-picrylhydrazyl free radicals scavenging activity under visible light irradiation.

Zinc oxide (ZnO) is considered as a potential antimicrobial agent. This work aims to investigate the properties of ZnO and Mn-doped ZnO (1% and 5%) fabricated using aqueous leaf extract of Melastoma malabathricum via green synthesis and its antibacterial activities. The synthesized ZnO and Mn-doped ZnO were characterized using different techniques such as powder X-ray diffraction, scanning electron microscopy, X-ray photoelectron spectroscopy and UV-Vis diffuse reflectance spectroscopy. The synthesized ZnO and Mn-doped ZnO were tested for its antibacterial properties on two Gram-negative bacteria: Escherichia coli and Pseudomonas aeruginosa, and two Gram-positive bacteria: Bacillus subtilis and Staphylococcus aureus. The results showed positive antibacterial effects for B. subtilis and S. aureus only. Among the three materials tested, 1% Mn-doped ZnO exhibited the highest antibacterial activity for B. subtilis with the minimum inhibitory concentration being 50 mg/mL.

- by Prof. Dr. Mohammad Mansoob Khan
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- ZnO nanorods, ZnO (Zinc Oxide), Zno Nanoparticles

In this study, pure ZnO, CeO2 and ZnO/CeO2 nanocomposites were synthesized using a thermal decomposition method and subsequently characterized using different standard techniques. High-resolution X-ray photoelectron spectroscopy measurements confirmed the oxidation states and presence of Zn2+ , Ce4+ , Ce3+ and different bonded oxygen species in the nanocomposites. The prepared pure ZnO and CeO2 as well as the ZnO/CeO2 nanocomposites with various proportions of ZnO and CeO2 were tested for photocatalytic degradation of methyl orange, methylene blue and phenol under visible-light irradiation. The optimized and highly efficient ZnO/CeO2 (90:10) nanocomposite exhibited enhanced photocatalytic degradation performance for the degradation of methyl orange, methylene blue, and phenol as well as industrial textile effluent compared to ZnO, CeO2 and the other investigated nanocomposites. Moreover, the recycling results demonstrate that the ZnO/CeO2 (90:10) nanocomposite exhibited good stability and long-term durability. Furthermore, the prepared ZnO/CeO2 nanocomposites were used for the electrochemical detection of uric acid and ascorbic acid. The ZnO/CeO2 (90:10) nanocomposite also demonstrated the best detection, sensitivity and performance among the investigated materials in this application. These findings suggest that the synthesized ZnO/CeO2 (90:10) nanocomposite could be effectively used in various applications.

- by Prof. Dr. Mohammad Mansoob Khan and +2
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- Nanomaterials Characterization, Nanomateriala Characterization, Nanocomposites, Nanomaterials

ZnO based varistors are widely used for overvoltage protection in many electrical and electronic circuits, at
voltages ranging from a few to over a million volts. By careful control of the microstructure, through nanostructuring
by chemical routes, it should be possible to produce varistors with high breakdown voltage (Vc),
as this is proportional to the number of active grain boundaries in the sintered body. This property is
particularly important for the production of the small-sized varistors needed for modern electronic
instruments such as tablet computers and mobile phones. The current review will outline the recent
advances in the chemical processing (e.g. sol–gel, combustion synthesis plasma pyrolysis, micro-emulsion
synthesis and precipitation routes) of varistors from ZnO nanomaterials and the properties of these
materials. Uncontrolled grain growth at higher temperature is highlighted as a major challenge for
obtaining desirable electrical properties for nano-varistors. Various novel sintering techniques such as
step-sintering, spark plasma and microwave sintering methods are expected to deliver a varistor with
controlled grain growth and optimum electrical characteristics.

- by J. Kelly and +2
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- Materials Engineering, Materials Science, Synthesis of nanoparticles, Composite Materials and Structures

Strong electrophilic natured acetaldehyde present in various food and beverages damages genetic material and induces diseases like atherosclerosis. Detection and quanti ﬁ cation of such a carcinogen poses a major challenge. In this context, a novel room temperature acetaldehyde sensor made up of hierarchical ZnO nanostructures and prepared by a simple and template-free method has been reported. ZnO nanostructures were grown on glass substrates by a chemical spray pyrolysis technique at the substrate temperature of 523 K. Di ﬀ erent nanostructures, namely tiny nanoplatelets, branched nanorods and thicker nanoplatelets, were formed by an annealing process. The crystal structures, morphologies and optical absorbances of the hierarchical ZnO nanostructures were investigated by X-ray di ﬀ raction (XRD), ﬁeld emission scanning electron microscopy (FE-SEM) and UV-vis spectrophotometry, respectively. The branched nanorods showed an excellent sensing response towards 20 to 500 ppm of acetaldehyde
vapour. The role of high density junctions of the branched ZnO architecture in enhancing the vapour sensing performance has been highlighted. The observed selectivity, range of detection and stability of the branched ZnO nanorods have proven their potential as a sensing element for the detection of acetaldehyde.

Rapid transmission of infectious microorganisms such as viruses and bacteria through person-to-person contact has contributed significantly to global health issues. The high survivability of these microorganisms on the material surface enumerates their transmissibility to the susceptible patient. The antimicrobial coating has emerged as one of the most interesting technologies to prevent growth and subsequently kill disease-causing microorganisms. It offers an effective solution a non-invasive, low-cost, easy-in-use, side-effect-free, and environmentally friendly method to prevent nosocomial infection. Among antimicrobial coating, zinc oxide (ZnO) stands as one of the excellent materials owing to zero toxicity, high biocompatibility to human organs, good stability, high abundancy, affordability, and high photocatalytic performance to kill various infectious pathogens. Therefore, this review provides the latest research progress on advanced applications of ZnO nanostructure-based antibacterial coatings for medical devices, biomedical applications, and health care facilities. Finally, future challenges and clinical practices of ZnO-based antibacterial coating are addressed.

ZnO nanomaterials with controlled size, shape and surface chemistry are required for applications in diverse areas, such as optoelectronics, photocatalysis, biomedicine and so on. Here, we report on ZnO nanostructures with rod-like and spherical shapes prepared via laser ablation in liquid using a laser with millisecond-long pulses. By changing laser parameters (such as pulse width and peak power), the size or aspect ratio of such nanostructures could be tuned. The surface chemistry and defects of the products were also strongly affected by applied laser conditions. The preparation of different structures is explained by the intense heating of liquid media caused by millisecond-long pulses and secondary irradiation of already-formed nanostructures.

- by Sergei Kulinich
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- ZnO nanorods, Zno Nanoparticles, Laser Ablation in Liquids

We report electrical and optoelectrical properties of a cross-junction of two semiconducting nanowires. Semiconducting nanowires and their junction play an important role in nanonetwork device. By mechanically manipulating the nanowires, cross-junction nanodevices are fabricated on SiO2/Si substrate using VO2 and ZnO nanowires. These junctions are formed across prepatterned two-probe Au electrodes and contacted through Pt metal deposition. The cross-junction devices were studied using global and focused laser beam irradiation with a wavelength of 532 nm at sweeping bias and fixed external bias. Furthermore multi-junction in nanonetwork between VO2 and ZnO nanowires device is demonstrated as a viable photodetector for potential application.

The present paper reports on the facile formation of ZnO nanorod photocatalyst electrodeposited on Zn foil in the production of hydrogen gas via water photoelectrolysis. Based on the results, ZnO nanorod films were successfully grown via electrochemical deposition in an optimum electrolyte set of 0.5 mM zinc chloride and 0.1 M potassium chloride at pH level of 5-6 and electrochemical deposition temperature of around 70 ∘ C. The study was also conducted at a very low stirring rate with different applied potentials. Applied potential was one of the crucial aspects in the formation of self-organized ZnO nanorod film via control of the field-assisted dissolution and field-assisted deposition rates during the electrochemical deposition process. Interestingly, low applied potentials of 1 V during electrochemical deposition produced a high aspect ratio and density of self-organized ZnO nanorod distribution on the Zn substrate with an average diameter and length of ∼37.9 nm and ∼249.5 nm, respectively. Therefore, it exhibited a high photocurrent density that reached 17.8 mA/cm 2 under ultraviolet illumination and 12.94 mA/cm 2 under visible illumination. This behaviour was attributed to the faster transport of photogenerated electron/hole pairs in the nanorod's one-dimensional wall surface, which prevented backward reactions and further reduced the number of recombination centres.

- by NUR AZIMAH ABD SAMAD
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- ZnO nanorods, ZnO (Zinc Oxide)

Controlled light coupling from surrounding to the cladding mode of zinc oxide (ZnO) nanorod coated multimode optical fiber induced by the light scattering properties of the nanorod coating and their applications of sensing are reported here. A dense and highly ordered array of ZnO nanorods is grown on the cladding of silica fibers by using low temperature hydrothermal process and the effect of the hydrothermal growth conditions of the nanorods on the light scattering and coupling to the optical fibers is experimentally investigated. The nanorod length and its number per unit area are found to be most crucial parameters for the optimum side coupling of light into the fibers. Maximum excitation of the cladding mode by side coupling of light is obtained with ZnO nanorods of length ∼2.2 μm, demonstrating average coupling efficiency of ∼2.65%. Upon exposure to different concentrations of various chemical vapors, the nanorod coated fibers demonstrated significant enhancement in the side coupled light intensity, indicating the potential use of these ZnO nanorod coated fibers as simple, low cost and efficient optical sensors. The sensor responses to methanol, ethanol, toluene and benzene vapor were investigated and compared, while the effect of humidity in the sensing environment on the sensor performance was explored as well.

- by Tanujjal Bora
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- Light Scattering, Optical fiber sensors, Gas Sensors, ZnO nanorods

An investigation into the catalyst-free growth of highly crystalline zinc oxide nanowires from metallic zinc powder on Si (100) substrate was investigated through the vapor solid (VS) process at 900◦C in a tube furnace. The effect of substrate position on the morphology, structure and photoluminescence (PL) properties of the fabricated ZnO nanowires was evaluated. The diameter of the resulted nanowires varies from 50 nm to 300 nm upon increasing the separation distance, between the substrate and the Zn powder source, from 12 cm to 16 cm. The EDX and XRD results showed that the zinc to oxygen ratio and the crystallinity of the fabricated nanowires are dependent on the substrate position. Also, the ratio of the UV to visible emission peaks of the fabricated ZnO nanowires was found to be strongly dependent on the substrate position. The PL spectra showed the enhancement in UV emissions for the samples fabricated on the substrate farther away from the Zn source with enhanced near band-edge emission for thicker nanowires. A possible mechanism for the growth of ZnO nanowires is discussed.

- by Nageh K. Allam
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- ZnO nanorods
- by Yaoguo Fang
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- Engineering, Physics, Applied Physics, Nanotechnology

This paper reports the study of the sensitizing effect and the structure of the water soluble polymeric dye of polythiopene sodium poly [2-(3-thienyl)-ethoxy-4-buthylsulfonate] (PTEBS) ink-jet thin film on the performance of the dye sensitized solar cells (DSSC) based-ZnO nanorods (ZNRs). DSSC device with sandwich structure of FTO/ZNRs/PTEBS/electrolyte/ Pt was prepared in this study with the electrolyte used was I-/I-3 redox couple. The PTEBS thin film was deposited onto the ZNRs-coated FTO substrate via an inkjet printing technique from the aqueous solution. To obtain a variation in the thin film structure, the PTEBS was grown via a multiple-step printing approach, namely from three to up to seven times. It was found that the PTEBS ink-jet printed film exhibit effective sensitizing effect on the DSSC by giving enhanced photovoltaic performance of multiple higher order (approximately 3 times) compared to a controlled device, the device without PTEBS and its structure was found to influence the charge transfer process in the device. A high performance DSSC device can be obtained from the PTEBS film with highly compact and even structure that prepared by three time printing process, which gives performance of J sc , V oc and FF as high as 0.96 mA/cm 2 , 0.42 V and 34%, respectively, which is corresponding to power conversion efficiency (PCE) as high as 0.14%.

- by Marjoni Imamora
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- Dye Sensitized Solar Cells, ZnO nanorods
- by Paromita Kundu
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- ZnO nanorods, Photocatalysis, Photosensitivity, Nanohybrids Materials

A simple energy harvesting strategy has been developed to selectively catalyze glucose in the presence of
oxygen in a glucose/O2 fuel cell. The anode consists of an abiotic catalyst Al/Au/ZnO, in which ZnO seed
layer was deposited on the surface of Al/Au substrate using hydrothermal method. The cathode is
constructed from a single rod of platinum with an outer diameter of 500 mm. The abiotic glucose fuel cell
was studied in phosphate buffer solution (pH 7.4) containing 5 mM glucose at a temperature of 22 C. The
cell is characterized according to its open-circuit voltage, polarization profile, and power density plot.
Under these conditions, the abiotic glucose fuel cell possesses an open-circuit voltage of 840 mV and
delivered a maximum power density of 16.2 mW cm2 at a cell voltage of 495 mV. These characteristics
are comparable to biofuel cell utilizing a much more complex system design. Such low-cost lightweight
abiotic catalyzed glucose fuel cells have a great promise to be optimized, miniaturized to power bioimplantable
devices.

- by Joshua Sunday and +1
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- ZnO nanorods, ZnO (Zinc Oxide), Abiotic Biofuel cells
- by Riski Titian Ginting
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- Organic Photovoltaics, Impedance Spectroscopy, Doping, Photoluminescence

An aqueous solution-based doping strategy was developed for controlled doping impurity atoms into a ZnO nanowire (NW) lattice. Through this approach, antimony-doped ZnO NWs were successfully synthesized in an aqueous solution containing zinc nitrate and hexamethylenetetramine with antimony acetate as the dopant source. By introducing glycolate ions into the solution, a soluble antimony precursor (antimony glycolate) was formed and a good NW morphology with a controlled antimony doping concentration was successfully achieved. A doping concentration study suggested an antimony glycolate absorption doping mechanism. By fabricating and characterizing NW-based field effect transistors (FETs), stable p-type conductivity was observed. A field effect mobility of 1.2?cm2?V ? 1?s ? 1 and a carrier concentration of 6 × 1017?cm ? 3 were achieved. Electrostatic force microscopy (EFM) characterization on doped and undoped ZnO NWs further illustrated the shift of the metal?semiconductor barrier due to Sb doping. This work provided an effective large-scale synthesis strategy for doping ZnO NWs in aqueous solution.

- by Fei Wang
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- ZnO,TiO2 nanowires, Field effect transistors, ZnO nanorods, Nanogenerators
- by kottai samy
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- Materials Science, Solid State Physics, Nanotechnology, Advanced Materials
- by Declan McCormack
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- Materials Science, Metallurgy, Nanomaterials, Nanotechnology

ZnO microstructures were synthesized by the hydrothermal method. Scanning electron microscopy (SEM) revealed the formation of ZnO microrods in absence of trisodium citrate and hexagon-shaped ZnO microdisks in presence of trisodium citrate. The length and width of ZnO microrods were 3–5 μm and 500 nm–1 μm, respectively and they were tapered at both ends, whereas ZnO microdisks were 1–2 μm in diameter. Crystal growth mechanism suggested that citrate suppressed the growth of ZnO along c-axis which resulted into the formation of microdisks like structure. Photoluminescence (PL) spectroscopy showed a weak ultraviolet (UV) and strong green emission in ZnO microrods but a strong UV and very weak green emission in ZnO microdisks. It was suggested that the green emission in ZnO microrods was due to structural defects present at polar planes which was reduced in microdisks with reduction in polar planes.

- by Dr. Sudarsan Raj
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- ZnO nanorods

We discuss a recently proposed novel photonic approach for enhancing the fluorescence of extremely thin chemosensing polymer layers. We present theoretical and experimental results demonstrating the concept of gain-assisted waveguided energy transfer (G-WET) on a very thin polymer nanolayer spincoated on an active ZnO thin film. The G-WET approach is shown to result in an 8-fold increase in polymer fluorescence. We then extend the G-WET concept to nanostructured media. The benefits of using active nanostructured substrates on the sensitivity and fluorescence of chemosensing polymers are discussed. Preliminary theoretical results on enlarged sensing surface and photonic band-gap are presented.

- by Roy Aad
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- Fluorescence Spectroscopy, Photonic Crystals, Spectroscopy, Photonics

ZnO nanowire arrays were synthesised for dye-sensitised solar cell applications using the chemical bath deposition technique. To study the effect of the particle size in the seed layer on the growth and resultant photoconversion efficiency, we prepared various seeded FTO substrates by repeating the seed layer sol-gel coating process. It was found that changing the number of coating process merely increases the particle size of the ZnO seeds, and the increase in the seed particle size induces low growth rates. In addition, to enhance the nanowire growth rates, ammonia was added with polyethylenimine. Based on various characterisations such as XRD, SEM, and J-V curves, we discuss the effect of ammonia on the growth rates of ZnO nanowire, and suggest the optimum ammonia concentration for solar cell applications.

- by Alagappan Annamalai
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- Solar Cell, Dye Sensitized Solar Cells, ZnO nanorods, Solar Energy

A novel concept is introduced that utilizes the scattering properties of zinc oxide nanorods to control light guidance
and leakage inside optical fibers coated with nanorods. The effect of the hydrothermal growth conditions of the
nanorods on light scattering and coupling to optical fiber are experimentally investigated. At optimum conditions,
5% of the incident light is side coupled to the cladding modes. This coupling scheme could be used in different
applications such as distributed sensors and light combing. Implementation of the nanorods on fiber provides low
cost and controllable nonlithography-based solutions for free space to fiber coupling. Higher coupling efficiencies
can be achieved with further optimization.

- by Tanujjal Bora
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- Light Scattering, ZnO nanorods, Fabry Perot Interferometery, Fiber-optics sensing

Doping semiconductor nanowires (NWs) for altering their electrical and optical properties is a critical strategy for tailoring the performance of nanodevices. ZnO NWs grown by hydrothermal method are pervasively used in optoelectronic, photovoltaic, and piezoelectric energy-harvesting devices. We synthesized in situ Cl-doped ZnO NWs with metallic conductivity that would fit seamlessly with these devices and improve their performance. Possible Cl doping mechanisms were discussed. UV–visible absorption spectroscopy confirmed the visible light transparency of Cl-doped ZnO NWs. Cl-doped ZnO NW/TiO2 core/shell-structured photoelectrochemical (PEC) anode was fabricated to demonstrate the application potential of highly conductive ZnO NWs. Higher photocurrent density and overall PEC efficiency compared with the undoped ZnO NW-based device were achieved. The successful doping and low resistivity of ZnO could unlock the potential of ZnO NWs for applications in low-cost flexible transparent electrodes.

- by Fei Wang
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- Solid State Physics, ZnO,TiO2 nanowires, Nanotechnology, Sol-Gel Technology

We demonstrate a novel, one-step, catalyst-free method for the production of size-controlled vertical highly conductive ZnO nanorod (NR) arrays with highly desirable characteristics by pulsed laser deposition using a Gd-doped ZnO target. Our study shows that an in situ transparent and conductive Gd nanolayer (with a uniform thickness of $1 nm) at the interface between a lattice-matched (11À20) a-sapphire substrate and ZnO is formed during the deposition. This nanolayer significantly induces a relaxation mechanism that controls the dislocation distribution along the growth direction; which consequently improves the formation of homogeneous vertically aligned ZnO NRs. We demonstrate that both the lattice orientation of the substrate and the Gd characteristics are important in enhancing the NR synthesis, and we report precise control of the NR density by changing the oxygen partial pressure. We show that these NRs possess high optical and electrical quality, with a mobility of 177 cm 2 (V s) À1 , which is comparable to the best-reported mobility of ZnO NRs. Therefore, this new and simple method has significant potential for improving the performance of materials used in a wide range of electronic and optoelectronic applications.

- by Assa Aravindh and +1
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- Density-functional theory, ZnO nanorods, Band Structure, ZnO (Zinc Oxide)
- by Majda Žigon
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- ZnO nanorods, PMMA nanocomposites

Low-temperature wet chemical bath deposition (CBD) method is one of the most efficient and least hazardous solution-based techniques which is widely employed to grow ZnO NRs. In CBD method, a seed layer is usually deposited on the substrate. In this paper, high quality ZnO and aluminum doped ZnO (AZO) seed layers are sputtered on the indium tin oxide (ITO) coated glass. In continue, aligned ZnO NRs are grown on the AZO and ZnO seed layers via CBD technique. The effect of the growth time and seed layer on the physical properties of as-grown ZnO NRs are investigated. According to the results, the seed layer plays an essential role on the growth orientation and growth rate of the ZnO NRs. The ZnO NRs grown on AZO seed layer are more aligned rather than ZnO seed layer due to their higher texture coefficients. The relative photoluminescence (PL) intensity ratio of near band emission (NBE) to deep level emission (DLE) (INBE/IDLE) for the ZnO NRs grown on AZO and ZnO seed layers are calculated as 7.45 and 2.62, respectively. To investigate the performance of the as-grown ZnO NRs, near ultraviolet organic light-emitting diodes (UV-OLEDs) using ZnO NRs array as n-type material and poly [2-methoxy-5-(2-ethyl-hexyloxy)-1,4-phenylene-vinylene] (MEH-PPV) conjugated polymer as p-type material have been fabricated. The total concentration of traps (), the characteristic energies () and the turn-on voltages for the devices with the structures of ITO/AZO/ZnO NRs/MEH-PPV/Al (device A) and ITO/ZnO/ZnO NRs/MEH-PPV/Al (device B) are attained 7.65 × 1016 and 7.75 × 1016 cm−3, 0.232 and 0.206 eV, 23 and 21 V, respectively. Moreover, based on the electroluminescence (EL) spectra, the NBE peaks for device A and B are obtained nearly in the wavelengths of 382 and 388 nm, respectively. Finally, various charge carrier transportation processes of prepared UV-OLEDs have been studied, systematically.

- by Mahdiyar Nouri Rezaie
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- ZnO nanorods, ZnO (Zinc Oxide), UV/Vis spectroscopy, Seed Layer Effect
- by Suresh C . Pillai and +1
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- Engineering, Materials Chemistry, Materials, Nanomaterials
- by joydeep dutta
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- ZnO nanorods, Environmental Sciences, Photocatalysis, ZnO (Zinc Oxide)

We demonstrate how light force, irrespective of the polarization of the light, can be used to run a simple nanorotor. While the gradient force of a single beam optical trap is used to hold an asymmetric nanorod, we utilize the scattering force to generate a torque on the nanorod, making it rotate about the optic axis. The inherent textural irregularities or morphological asymmetries of the nanorods give rise to the torque under the radiation pressure. Even a small surface irregularity with non-zero chirality is sufficient to produce enough torque for moderate rotational speed. Different sized rotors can be used to set the speed of rotation over a wide range with fine tuning possible through the variation of the laser power. We present a simple dimensional analysis to qualitatively explain the observed trend of the rotational motion of the nanorods.

- by Manas Khan
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- Optical Tweezers, ZnO nanorods, Nanorotors
- by Declan Mccormack
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- Engineering, Materials Chemistry, Materials, Nanomaterials

As a low temperature and low cost synthesis method, the hydrothermal deposition is widely used to grow ZnO nanowire arrays. Their optical properties are closely related to concentration of the structural defects in the ZnO nanowires. In this work we report on investigation on the evolution of the structural defects of ZnO nanowire arrays for different growth time, before and after post-annealing. The photo-emission properties of the ZnO nanowire arrays have been investigated in detail by using photoluminescence (PL) spectroscopy both on the as-grown nanowires and on the annealed ones. The PL analysis results showed an increasing intensity in the visible emission band with the growth time which is closely related to the change of the concentration of the structural defects in the ZnO nanowires regarding to the UV near-edge emission. The visible PL emission band can be deconvoluted into three Gaussians components, which correspond to the green, yellow-orange and red emissions, respectively. It is further revealed that the intensity of the orange and red emission bands increase with the increase of the growth time, which are ascribed to the interstitial oxygen and/or hydroxide groups and adsorbed oxygen, respectively. The correlation between energy-dispersive X-ray spectroscopy (EDS) analysis and PL measurements revealed that the excess zinc can be formed in the nanowires during the hydrothermal process.

- by Clotaire CHEVALIER-CESAR and +1
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- ZnO nanorods, Optical Properties

The well-aligned Zinc Oxide Nanorods (ZnONRs) arrays was obtained through a hydrothermal process at various precursor concentrations (PC) under a growth temperature of 90 °C for an hour. The effect of PC (0.02, 0.03, 0.04, 0.05, and 0.06 M which is denoted as K0.01–K0.06) to the structural, optical, and morfology (diameter, height, slope, and density) of ZnONRs were studied by using X-ray diffraction, UV–Vis spectroscopy, and field emission scanning electron microscopy (FESEM). As-synthesized ZnONRs exhibit an uniform growth direction along the [002] orientations with average diameters in the range of 40–90 nm. These nanorods showed a strong optical absorption peak centering at 367 nm,which is equivalent to optical energy band gap of ZnO 3.37 eV, confirming the formation of ZnONRs. The morfology of ZnONRs in term of diameter, height, slope, and density increases with the PC. The highest density of approximately 182 number/µm −2 with average slope of 6 degree (aligning percentage of 83 ± 12%) was obtained at the PC of K0.04. It is interesting to find that the dye sensitized solar cell utilizing the sample K0.04 showed five times increasing in the power conversion efficiency as compared to that of device utilizing K0.02 sample.

- by Marjoni Imamora
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- ZnO nanorods