Hydrothermal temperature effect on crystal structures, optical properties and electrical conductivity of ZnO nanostructures

NASA Astrophysics Data System (ADS)

Dhafina, Wan Almaz; Salleh, Hasiah; Daud, Mohd Zalani; Ghazali, Mohd Sabri Mohd; Ghazali, Salmah Mohd

2017-09-01

ZnO is an wide direct band gap semiconductor and possess rich family of nanostructures which turned to be a key role in the nanotechnology field of applications. Hydrothermal method was proven to be simple, robust and low cost among the reported methods to synthesize ZnO nanostructures. In this work, the properties of ZnO nanostructures were altered by varying temperatures of hydrothermal process. The changes in term of morphological, crystal structures, optical properties and electrical conductivity were investigated. A drastic change of ZnO nanostructures morphology and decreases of 002 diffraction peak were observed as the hydrothermal temperature increased. The band gap of samples decreased as the size of ZnO nanostructure increased, whereas the electrical conductivity had no influence on the band gap value but more on the morphology of ZnO nanostructures instead.

Highly sensitive H2 gas sensor of Co doped ZnO nanostructures

NASA Astrophysics Data System (ADS)

Bhati, Vijendra Singh; Ranwa, Sapana; Kumar, Mahesh

2018-04-01

In this report, the hydrogen gas sensing properties based on Co doped ZnO nanostructures are explored. The undoped and Co doped nanostructures were grown by RF magnetron sputtering system, and its structural, morphological, and hydrogen sensing behavior are investigated. The maximum relative response was occurred by the 2.5% Co doped ZnO nanostructures among undoped and other doped sensors. The enhancement of relative response might be due to large chemisorbed sites formation on the ZnO surface for the reaction to hydrogen gas.

Colloidal ZnO and Zn(1-x)Co(x)O tetrapod nanocrystals with tunable arm lengths.

PubMed

Hodges, James M; Fenton, Julie L; Gray, Jennifer L; Schaak, Raymond E

2015-10-28

Tetrapod-shaped ZnO nanocrystals exhibit exceptional optoelectronic properties, including intense ultraviolet photoluminescence emission, that make them attractive for applications that include lasers, sensors, and photocatalysts. However, synthetic methods that produce ZnO tetrapods typically include high-temperature vapor-deposition approaches that do not readily achieve characteristic dimensions of less than 100 nm or colloidal methods that require added metal dopants, which modify the inherent properties of ZnO. Here, we report a robust, modified solution-phase synthetic protocol for generating colloidal ZnO tetrapods that does not require the use of metal dopants. The ZnO tetrapod arm lengths can be tuned from 10 to 25 nm by adjusting the amount of Zn reagent used in the reaction. Subsequent seeded-growth produced even larger colloidal ZnO tetrapods with 62 nm arms. Photoluminescence (PL) measurements confirm that the tetrapods are of high crystalline quality, and the ultraviolet PL emission wavelengths that are observed fall between those of previously reported metal-doped colloidal ZnO tetrapods, which exhibit dopant-induced red- or blue-shifts. Furthermore, the reaction strategy can be modified to produce cobalt-substituted ZnO, offering a chemical pathway to tetrapod-shaped Zn1-xCoxO nanocrystals.

Nanostructured ZnO Films for Room Temperature Ammonia Sensing

NASA Astrophysics Data System (ADS)

Dhivya Ponnusamy; Sridharan Madanagurusamy

2014-09-01

Zinc oxide (ZnO) thin films have been deposited by a reactive dc magnetron sputtering technique onto a thoroughly cleaned glass substrate at room temperature. X-ray diffraction revealed that the deposited film was polycrystalline in nature. The field emission scanning electron micrograph (FE-SEM) showed the uniform formation of a rugby ball-shaped ZnO nanostructure. Energy dispersive x-ray analysis (EDX) confirmed that the film was stoichiometric and the direct band gap of the film, determined using UV-Vis spectroscopy, was 3.29 eV. The ZnO nanostructured film exhibited better sensing towards ammonia (NH3) at room temperature (˜30°C). The fabricated ZnO film based sensor was capable of detecting NH3 at as low as 5 ppm, and its parameters, such as response, selectivity, stability, and response/recovery time, were also investigated.

Growth of hybrid carbon nanostructures on iron-decorated ZnO nanorods

NASA Astrophysics Data System (ADS)

Mbuyisa, Puleng N.; Rigoni, Federica; Sangaletti, Luigi; Ponzoni, Stefano; Pagliara, Stefania; Goldoni, Andrea; Ndwandwe, Muzi; Cepek, Cinzia

2016-04-01

A novel carbon-based nanostructured material, which includes carbon nanotubes (CNTs), porous carbon, nanostructured ZnO and Fe nanoparticles, has been synthetized using catalytic chemical vapour deposition (CVD) of acetylene on vertically aligned ZnO nanorods (NRs). The deposition of Fe before the CVD process induces the presence of dense CNTs in addition to the variety of nanostructures already observed on the process done on the bare NRs, which range from amorphous graphitic carbon up to nanostructured dendritic carbon films, where the NRs are partially or completely etched. The combination of scanning electron microscopy and in situ photoemission spectroscopy indicate that Fe enhances the ZnO etching, and that the CNT synthesis is favoured by the reduced Fe mobility due to the strong interaction between Fe and the NRs, and to the presence of many defects, formed during the CVD process. Our results demonstrate that the resulting new hybrid shows a higher sensitivity to ammonia gas at ambient conditions (∼60 ppb) than the carbon nanostructures obtained without the aid of Fe, the bare ZnO NRs, or other one-dimensional carbon nanostructures, making this system of potential interest for environmental ammonia monitoring. Finally, in view of the possible application in nanoscale optoelectronics, the photoexcited carrier behaviour in these hybrid systems has been characterized by time-resolved reflectivity measurements.

Luminescence studies of laser MBE grown GaN on ZnO nanostructures

NASA Astrophysics Data System (ADS)

Dewan, Sheetal; Tomar, Monika; Kapoor, Ashok K.; Tandon, R. P.; Gupta, Vinay

2017-08-01

GaN films have been successfully fabricated using Laser Molecular Beam Epitaxy (LMBE) technique on bare c-plane sapphire substrate and ZnO nanostructures (NS) decorated Si (100) substrates. The ZnO nanostructures were grown on Si (100) substrate using high pressure assisted Pulsed laser deposition technique in inert gas ambience. Discrete nanostructured morphology of ZnO was obtained using the PLD growth on Si substrates. Photoluminescence studies performed on the prepared GaN/Sapphire and GaN/ZnO-NS/Si systems, revealed a significant PL enhancement in case of GaN/ZnO-NS/Si system compared to the former. The hexagonal nucleation sites provided by the ZnO nanostructures strategically enhanced the emission of GaN film grown by Laser MBE Technique at relatively lower temperature of 700°C. The obtained results are attractive for the realization of highly luminescent GaN films on Si substrate for photonic devices.

EFFECTS OF Au ON THE GROWTH OF ZnO NANOSTRUCTURES ON Si BY MOCVD

NASA Astrophysics Data System (ADS)

Cong, Chen; Fan, Lu Yang; Ping, He Hai; Wei, Wu Ke; Zhen, Ye Zhi

2013-06-01

The effects of Au on the growth of ZnO nanostructures on Si by metal organic chemical vapor deposition (MOCVD) at a relatively low temperature (450°C) were investigated. The experimental results showed that Au nanoparticles played a critical role during the growth of the ZnO nanostructures and affected their morphology and optical properties. It was found that Au nanoparticles particularly affected the nucleation of ZnO nanostructures during the growth process and the Au-assisted growth mechanism of ZnO nanostructures should be ascribed to the vapor-solid (VS) mechanism. The formation of a nanoneedle may be attributed to a more reactive interface between Au and ZnO, which leads to more zinc gaseous species absorbed near the interface. Different nucleation sites on ZnO nuclei resulted in the disorder of ZnO nanoneedles. Moreover, the crystalline quality of nano-ZnO was improved due to the presence of Au, according to the smaller full width at half maximum (FWHM) of the low-temperature exciton emission. We confirmed that ZnO nanoneedles showed better crystalline quality than ZnO nanorods through the HRTEM images and the SAED patterns. The reason for the improvement of the crystalline quality of nano-ZnO may be due to the less lattice mismatch.

Anti-iridescent colloidal photonic nanostructure from thermal gradients and polymeric brush effects

NASA Astrophysics Data System (ADS)

Lee, Seung Yeol; Kim, Hyoungsoo; Kim, Shin-Hyun; Stone, Howard

2017-11-01

Colloidal nanostructures induced by self-assembly are important in reflective displays, plasmonic or photonic sensors, and color pigments. During the evaporation of droplets of colloidal suspension, due to the non-uniform evaporation rate along the droplet interface, a radially outward flow is created and it carries colloidal particles to the pinned contact line of the droplet. We document that the packing at the contact line is a face-center-cubic (fcc) colloidal nanostructure in a ring shape. The fcc structure of the colloidal nanoparticles exhibits angle-dependent color. In particular, we introduce a novel method to suppress the familiar coffee-ring effect and modify colloidal nanostructures to exhibit angle-independent optical properties. A suspension of polyethylene oxide (PEO)-coated silica nanoparticles dispersed in ethanol-water mixture is prepared. The droplet containing the nanoparticles dries on a heated substrate, which creates a thermal gradient along the interface of the droplet. This thermal gradient induces thermal-Marangoni stresses that suppress the coffee-ring effects. PEO adsorbed on the surface of silica nanoparticles produces an additional interaction between colloidal nanoparticles, which makes the final structure disordered. The disordered photonic nanostructures in our experiments exhibit angle-independent structural color. This technique can be applied to printing or optical filtering systems.

Luminescence of colloidal ZnO nanoparticles synthesized in alcohols and biological application of ZnO passivated by MgO

NASA Astrophysics Data System (ADS)

Sikora, Bożena; Fronc, Krzysztof; Kamińska, Izabela; Koper, Kamil; Stępień, Piotr; Elbaum, Danek

2013-05-01

This report presents the results of spectroscopic measurements of colloidal ZnO nanoparticles synthesized in various alcohols. Luminescence of colloidal ZnO was monitored under different reaction conditions to elucidate the mechanism of the visible emission. We performed the process in different alcohols, temperatures and reaction times for two different reactants: water and NaOH. Based on the presented and previously published results it is apparent that the luminescence of the nanoparticles is influenced by several competing phenomena: the formation of new nucleation centers, the growth of the nanoparticles and surface passivation. Superimposed on the above effects is a size dependent luminescence alteration resulting from the quantum confinement. The study contributes to our understanding of the origin of ZnO nanoparticles’ green emission which is important in a rational design of fluorescent probes for nontoxic biological applications. The ZnO nanoparticles were coated with a magnesium oxide layer and introduced into a HeLa cancer cell.

Luminescence of colloidal ZnO nanoparticles synthesized in alcohols and biological application of ZnO passivated by MgO.

PubMed

Sikora, Bożena; Fronc, Krzysztof; Kamińska, Izabela; Koper, Kamil; Stępień, Piotr; Elbaum, Danek

2013-05-15

This report presents the results of spectroscopic measurements of colloidal ZnO nanoparticles synthesized in various alcohols. Luminescence of colloidal ZnO was monitored under different reaction conditions to elucidate the mechanism of the visible emission. We performed the process in different alcohols, temperatures and reaction times for two different reactants: water and NaOH. Based on the presented and previously published results it is apparent that the luminescence of the nanoparticles is influenced by several competing phenomena: the formation of new nucleation centers, the growth of the nanoparticles and surface passivation. Superimposed on the above effects is a size dependent luminescence alteration resulting from the quantum confinement. The study contributes to our understanding of the origin of ZnO nanoparticles' green emission which is important in a rational design of fluorescent probes for nontoxic biological applications. The ZnO nanoparticles were coated with a magnesium oxide layer and introduced into a HeLa cancer cell.

Development of nanostructured ZnO thin film via electrohydrodynamic atomization technique and its photoconductivity characteristics.

PubMed

Duraisamy, Navaneethan; Kwon, Ki Rin; Jo, Jeongdai; Choi, Kyung-Hyun

2014-08-01

This article presents the non-vacuum technique for the preparation of nanostructured zinc oxide (ZnO) thin film on glass substrate through electrohydrodynamic atomization (EHDA) technique. The detailed process parameters for achieving homogeneous ZnO thin films are clearly discussed. The crystallinity and surface morphology of ZnO thin film are investigated by X-ray diffraction and field emission scanning electron microscopy. The result shows that the deposited ZnO thin film is oriented in the wurtzite phase with void free surface morphology. The surface roughness of deposited ZnO thin film is found to be ~17.8 nm. The optical properties of nanostructured ZnO thin films show the average transmittance is about 90% in the visible region and the energy band gap is found to be 3.17 eV. The surface chemistry and purity of deposited ZnO thin films are analyzed by fourier transform infrared and X-ray photoelectron spectroscopy, conforming the presence of Zn-O in the deposited thin films without any organic moiety. The photocurrent measurement of nanostructured ZnO thin film is examined in the presence of UV light illumination with wavelength of 365 nm. These results suggest that the deposited nanostructured ZnO thin film through EHDA technique possess promising applications in the near future.

Influence of the morphology of ZnO nanostructures on luminescent and photovoltaic properties

NASA Astrophysics Data System (ADS)

Ibrayev, N. Kh.; Ilyassov, B. R.; Afanasyev, D. A.

2017-03-01

Arrays of ZnO nanorods and nanoplates are synthesized by the hydrothermal and electrochemical methods, respectively. The photoluminescence spectra indicate that the nanoplates have a more defective structure than the nanorods. The obtained ZnO nanostructures are used as the basis to construct dye-sensitized solar cells. The influence of morphology and defectiveness of ZnO nanostructures on the luminescent and photovoltaic properties of the cells is studied.

Soluble Supercapacitors: Large and Reversible Charge Storage in Colloidal Iron-Doped ZnO Nanocrystals.

PubMed

Brozek, Carl K; Zhou, Dongming; Liu, Hongbin; Li, Xiaosong; Kittilstved, Kevin R; Gamelin, Daniel R

2018-05-09

Colloidal ZnO semiconductor nanocrystals have previously been shown to accumulate multiple delocalized conduction-band electrons under chemical, electrochemical, or photochemical reducing conditions, leading to emergent semimetallic characteristics such as quantum plasmon resonances and raising prospects for application in multielectron redox transformations. Here, we demonstrate a dramatic enhancement in the capacitance of colloidal ZnO nanocrystals through aliovalent Fe 3+ -doping. Very high areal and volumetric capacitances (33 μF cm -2 , 233 F cm -3 ) are achieved in Zn 0.99 Fe 0.01 O nanocrystals that rival those of the best supercapacitors used in commercial energy-storage devices. The redox properties of these nanocrystals are probed by potentiometric titration and optical spectroscopy. These data indicate an equilibrium between electron localization by Fe 3+ dopants and electron delocalization within the ZnO conduction band, allowing facile reversible charge storage and removal. As "soluble supercapacitors", colloidal iron-doped ZnO nanocrystals constitute a promising class of solution-processable electronic materials with large charge-storage capacity attractive for future energy-storage applications.

The growth of ZnO nanostructures using Arginine

NASA Astrophysics Data System (ADS)

Singh, Baljinder; Moudgil, Lovika; Singh, Gurinder; Kaura, Aman

2018-05-01

The growth mechanism of Zinc oxide (ZnO) nanomaterial with amino acid (Arginine) is explained at different shapes. The present study of ZnO nanostructures (NSs) in the presence of Arginine has enabled us to not only determine the growth mechanism of ZnO NSs but also to determine the effect of Arginine at different temperature of reactants. The synthesized samples are characterized using transmission electron microscopy (TEM) and X-ray diffraction (XRD). Results reveal that Arginine is responsible for formation of NSs. Based on these results, a plausible mechanism is explained.

Fabrication of nanostructured ZnO film as a hole-conducting layer of organic photovoltaic cell

NASA Astrophysics Data System (ADS)

Kim, Hyomin; Kwon, Yiseul; Choe, Youngson

2013-05-01

We have investigated the effect of fibrous nanostructured ZnO film as a hole-conducting layer on the performance of polymer photovoltaic cells. By increasing the concentration of zinc acetate dihydrate, the changes of performance characteristics were evaluated. Fibrous nanostructured ZnO film was prepared by sol-gel process and annealed on a hot plate. As the concentration of zinc acetate dihydrate increased, ZnO fibrous nanostructure grew from 300 to 600 nm. The obtained ZnO nanostructured fibrous films have taken the shape of a maze-like structure and were characterized by UV-visible absorption, scanning electron microscopy, and X-ray diffraction techniques. The intensity of absorption bands in the ultraviolet region was increased with increasing precursor concentration. The X-ray diffraction studies show that the ZnO fibrous nanostructures became strongly (002)-oriented with increasing concentration of precursor. The bulk heterojunction photovoltaic cells were fabricated using poly(3-hexylthiophene-2,5-diyl) and indene-C60 bisadduct as active layer, and their electrical properties were investigated. The external quantum efficiency of the fabricated device increased with increasing precursor concentration.

Fabrication of nanostructured ZnO film as a hole-conducting layer of organic photovoltaic cell

PubMed Central

2013-01-01

We have investigated the effect of fibrous nanostructured ZnO film as a hole-conducting layer on the performance of polymer photovoltaic cells. By increasing the concentration of zinc acetate dihydrate, the changes of performance characteristics were evaluated. Fibrous nanostructured ZnO film was prepared by sol-gel process and annealed on a hot plate. As the concentration of zinc acetate dihydrate increased, ZnO fibrous nanostructure grew from 300 to 600 nm. The obtained ZnO nanostructured fibrous films have taken the shape of a maze-like structure and were characterized by UV-visible absorption, scanning electron microscopy, and X-ray diffraction techniques. The intensity of absorption bands in the ultraviolet region was increased with increasing precursor concentration. The X-ray diffraction studies show that the ZnO fibrous nanostructures became strongly (002)-oriented with increasing concentration of precursor. The bulk heterojunction photovoltaic cells were fabricated using poly(3-hexylthiophene-2,5-diyl) and indene-C60 bisadduct as active layer, and their electrical properties were investigated. The external quantum efficiency of the fabricated device increased with increasing precursor concentration. PMID:23680100

Formation of quasi-single crystalline porous ZnO nanostructures with a single large cavity

NASA Astrophysics Data System (ADS)

Cho, Seungho; Kim, Semi; Jung, Dae-Won; Lee, Kun-Hong

2011-09-01

We report a method for synthesizing quasi-single crystalline porous ZnO nanostructures containing a single large cavity. The microwave-assisted route consists of a short (about 2 min) temperature ramping stage (from room temperature to 120 °C) and a stage in which the temperature is maintained at 120 °C for 2 h. The structures produced by this route were 200-480 nm in diameter. The morphological yields of this method were very high. The temperature- and time-dependent evolution of the synthesized powders and the effects of an additive, vitamin C, were studied. Spherical amorphous/polycrystalline structures (70-170 nm in diameter), which appeared transitorily, may play a key role in the formation of the single crystalline porous hollow ZnO nanostructures. Studies and characterization of the nanostructures suggested a possible mechanism for formation of the quasi-single crystalline porous ZnO nanostructures with an interior space.We report a method for synthesizing quasi-single crystalline porous ZnO nanostructures containing a single large cavity. The microwave-assisted route consists of a short (about 2 min) temperature ramping stage (from room temperature to 120 °C) and a stage in which the temperature is maintained at 120 °C for 2 h. The structures produced by this route were 200-480 nm in diameter. The morphological yields of this method were very high. The temperature- and time-dependent evolution of the synthesized powders and the effects of an additive, vitamin C, were studied. Spherical amorphous/polycrystalline structures (70-170 nm in diameter), which appeared transitorily, may play a key role in the formation of the single crystalline porous hollow ZnO nanostructures. Studies and characterization of the nanostructures suggested a possible mechanism for formation of the quasi-single crystalline porous ZnO nanostructures with an interior space. Electronic supplementary information (ESI) available: TEM images and the corresponding SAED image of a ZnO

Effect of Eu3+ doping on the structural, morphological and luminescence properties ZnO nanostructures

NASA Astrophysics Data System (ADS)

Vinoditha, U.; Balakrishna, K. M.; Sarojini, B. K.; Narayana, B.; Kumara, K.

2018-05-01

Pure and Eu3+ ions (1, 3, 5 atomic wt%) doped ZnO nanostructures are synthesized by a surfactant assisted hydrothermal method. The effect of doping concentrations on structural, morphological and optical properties of ZnO nanostructures is studied. The XRD analysis shows good crystallinity and the phase purity of the ZnO nanostructures. A shift in the standard Zn-O stretching mode after Eu3+ doping is observed in the FTIR spectra. The images of FESEM demonstrate the morphological variations from hexagonal nanorods to nanoflowers on varying the dopant concentrations. Substitution of Eu3+ ions into Zn2+ sites is confirmed by EDX analysis. The dominance of particle shape over the UV-Visible absorption properties of the prepared samples is noticed. The photoluminescence (PL) emission of undoped and doped ZnO nanostructures show dominant near band edge emission (NBE) in the UV region and minor defect induced deep level emissions in the visible region.

On-chip surface modified nanostructured ZnO as functional pH sensors

NASA Astrophysics Data System (ADS)

Zhang, Qing; Liu, Wenpeng; Sun, Chongling; Zhang, Hao; Pang, Wei; Zhang, Daihua; Duan, Xuexin

2015-09-01

Zinc oxide (ZnO) nanostructures are promising candidates as electronic components for biological and chemical applications. In this study, ZnO ultra-fine nanowire (NW) and nanoflake (NF) hybrid structures have been prepared by Au-assisted chemical vapor deposition (CVD) under ambient pressure. Their surface morphology, lattice structures, and crystal orientation were investigated by scanning electron microscopy (SEM), x-ray diffraction (XRD), and transmission electron microscopy (TEM). Two types of ZnO nanostructures were successfully integrated as gate electrodes in extended-gate field-effect transistors (EGFETs). Due to the amphoteric properties of ZnO, such devices function as pH sensors. We found that the ultra-fine NWs, which were more than 50 μm in length and less than 100 nm in diameter, performed better in the pH sensing process than NW-NF hybrid structures because of their higher surface-to-volume ratio, considering the Nernst equation and the Gouy-Chapman-Stern model. Furthermore, the surface coating of (3-Aminopropyl)triethoxysilane (APTES) protects ZnO nanostructures in both acidic and alkaline environments, thus enhancing the device stability and extending its pH sensing dynamic range.

Forging Colloidal Nanostructures via Cation Exchange Reactions

PubMed Central

2016-01-01

Among the various postsynthesis treatments of colloidal nanocrystals that have been developed to date, transformations by cation exchange have recently emerged as an extremely versatile tool that has given access to a wide variety of materials and nanostructures. One notable example in this direction is represented by partial cation exchange, by which preformed nanocrystals can be either transformed to alloy nanocrystals or to various types of nanoheterostructures possessing core/shell, segmented, or striped architectures. In this review, we provide an up to date overview of the complex colloidal nanostructures that could be prepared so far by cation exchange. At the same time, the review gives an account of the fundamental thermodynamic and kinetic parameters governing these types of reactions, as they are currently understood, and outlines the main open issues and possible future developments in the field. PMID:26891471

Forging Colloidal Nanostructures via Cation Exchange Reactions.

PubMed

De Trizio, Luca; Manna, Liberato

2016-09-28

Among the various postsynthesis treatments of colloidal nanocrystals that have been developed to date, transformations by cation exchange have recently emerged as an extremely versatile tool that has given access to a wide variety of materials and nanostructures. One notable example in this direction is represented by partial cation exchange, by which preformed nanocrystals can be either transformed to alloy nanocrystals or to various types of nanoheterostructures possessing core/shell, segmented, or striped architectures. In this review, we provide an up to date overview of the complex colloidal nanostructures that could be prepared so far by cation exchange. At the same time, the review gives an account of the fundamental thermodynamic and kinetic parameters governing these types of reactions, as they are currently understood, and outlines the main open issues and possible future developments in the field.

Hydrothermal Synthesis of Various Hierarchical ZnO Nanostructures and Their Methane Sensing Properties

PubMed Central

Zhou, Qu; Chen, Weigen; Xu, Lingna; Peng, Shudi

2013-01-01

Hierarchical flower-like ZnO nanorods, net-like ZnO nanofibers and ZnO nanobulks have been successfully synthesized via a surfactant assisted hydrothemal method. The synthesized products were characterized by X-ray powder diffraction and field emission scanning electron microscopy, respectively. A possible growth mechanism of the various hierarchical ZnO nanostructures is discussed in detail. Gas sensors based on the as-prepared ZnO nanostructures were fabricated by screen-printing on a flat ceramic substrate. Furthermore, their gas sensing characteristics towards methane were systematically investigated. Methane is an important characteristic hydrocarbon contaminant found dissolved in power transformer oil as a result of faults. We find that the hierarchical flower-like ZnO nanorods and net-like ZnO nanofibers samples show higher gas response and lower operating temperature with rapid response-recovery time compared to those of sensors based on ZnO nanobulks. These results present a feasible way of exploring high performance sensing materials for on-site detection of characteristic fault gases dissolved in transformer oil. PMID:23666136

Fabrication of nanostructured Al-doped ZnO thin film for methane sensing applications

DOE Office of Scientific and Technical Information (OSTI.GOV)

Shafura, A. K., E-mail: shafura@ymail.com; Azhar, N. E. I.; Uzer, M.

2016-07-06

CH{sub 4} gas sensor was fabricated using spin-coating method of the nanostructured ZnO thin film. Effect of annealing temperature on the electrical and structural properties of the film was investigated. Dense nanostructured ZnO film are obtained at higher annealing temperature. The optimal condition of annealing temperature is 500°C which has conductivity and sensitivity value of 3.3 × 10{sup −3} S/cm and 11.5%, respectively.

Facile synthesis of one dimensional ZnO nanostructures for DSSC applications

NASA Astrophysics Data System (ADS)

Marimuthu, T.; Anandhan, N.

2016-05-01

Development of zinc oxide (ZnO) nanostructure based third generation dye sensitized solar cell is interesting compared to conventional silicon solar cells. ZnO nanostructured thin films were electrochemically deposited onto fluorine doped tin oxide (FTO) glass substrate. The effect of ethylene-diamine-tetra-acetic acid (EDTA) on structural, morphological and optical properties is investigated using X-ray diffraction (XRD) meter, field emission scanning electron microscope (FE-SEM) and micro Raman spectroscopy. XRD patterns reveal that the prepared nanostructures are hexagonal wutrzite structures with (101) plane orientation, the nanostructure prepared using EDTA exhibits better crystallinity. FE-SEM images illustrate that the morphological changes are observed from nanorod structure to cauliflower like structure as EDTA is added. Micro Raman spectra predict that cauliflower like structure possesses a higher crystalline nature with less atomic defects compared to nanorod structures. Dye sensitized solar cell (DSSC) is constructed for the optimized cauliflower structure, and open circuit voltage, short circuit density, fill factor and efficiency are estimated from the J-V curve.

CoFe2O4-TiO2 and CoFe2O4-ZnO thin film nanostructures elaborated from colloidal chemistry and atomic layer deposition.

PubMed

Clavel, Guylhaine; Marichy, Catherine; Willinger, Marc-Georg; Ravaine, Serge; Zitoun, David; Pinna, Nicola

2010-12-07

CoFe(2)O(4)-TiO(2) and CoFe(2)O(4)-ZnO nanoparticles/film composites were prepared from directed assembly of colloidal CoFe(2)O(4) in a Langmuir-Blodgett monolayer and atomic layer deposition (ALD) of an oxide (TiO(2) or ZnO). The combination of these two methods permits the use of well-defined nanoparticles from colloidal chemistry, their assembly on a large scale, and the control over the interface between a ferrimagnetic material (CoFe(2)O(4)) and a semiconductor (TiO(2) or ZnO). Using this approach, architectures can be assembled with a precise control from the Angstrom scale (ALD) to the micrometer scale (Langmuir-Blodgett film). The resulting heterostructures present well-calibrated thicknesses. Electron microscopy and magnetic measurement studies give evidence that the size of the nanoparticles and their intrinsic magnetic properties are not altered by the various steps involved in the synthesis process. Therefore, the approach is suitable to obtain a layered composite with a quasi-monodisperse layer of ferrimagnetic nanoparticles embedded in an ultrathin film of semiconducting material.

Controlled Growth of Parallel Oriented ZnO Nanostructural Arrays on Ga2O3 Nanowires

DTIC Science & Technology

2008-11-01

Controlled Growth of Parallel Oriented ZnO Nanostructural Arrays on Ga2O3 Nanowires Lena Mazeina,* Yoosuf N. Picard, and Sharka M. Prokes Electronics...Manuscript ReceiVed NoVember 6, 2008 ABSTRACT: Novel hierarchical ZnO- Ga2O3 nanostructures were fabricated via a two stage growth process. Nanowires of Ga2O3 ...nanobrushes (NBs) with Ga2O3 as the core and ZnO as the branches self-assembling symmetrically in six equiangular directions around the core

A flexible UV nanosensor based on reduced graphene oxide decorated ZnO nanostructures

NASA Astrophysics Data System (ADS)

Wang, Zhenxing; Zhan, Xueying; Wang, Yajun; Muhammad, Safdar; Huang, Ying; He, Jun

2012-03-01

A low-cost, compatible with flexible electronics, high performance UV sensor has been achieved from a reduced graphene oxide (RGO) decorated hydrangea-like ZnO film on a PDMS substrate. The hydrangea-like ZnO UV sensor has the best UV sensing performance among devices made of three kinds of ZnO nanostructures synthesized by a hydrothermal method, and demonstrated a dramatic enhancement in on/off ratio and photoresponse current by introducing an appropriate weight ratio of RGO. The on/off ratio of the 0.05% RGO/ZnO sensor increases almost one order of magnitude compared to that of a pristine hydrangea-like ZnO UV sensor. While for the 5% RGO decorated ZnO sensor, the photoresponse current reaches as high as ~1 μA and exceeds 700 times that of a ZnO UV sensor. These results indicate that RGO is an appropriate material to enhance the performance of ZnO nanostructure UV sensors based on its unique features, especially the high optical transparency and excellent electronic conductivity. Our findings will make RGO/ZnO nanohybrids extraordinarily promising in optoelectronics, flexible electronics and sensor applications.

A flexible UV nanosensor based on reduced graphene oxide decorated ZnO nanostructures.

PubMed

Wang, Zhenxing; Zhan, Xueying; Wang, Yajun; Muhammad, Safdar; Huang, Ying; He, Jun

2012-04-21

A low-cost, compatible with flexible electronics, high performance UV sensor has been achieved from a reduced graphene oxide (RGO) decorated hydrangea-like ZnO film on a PDMS substrate. The hydrangea-like ZnO UV sensor has the best UV sensing performance among devices made of three kinds of ZnO nanostructures synthesized by a hydrothermal method, and demonstrated a dramatic enhancement in on/off ratio and photoresponse current by introducing an appropriate weight ratio of RGO. The on/off ratio of the 0.05% RGO/ZnO sensor increases almost one order of magnitude compared to that of a pristine hydrangea-like ZnO UV sensor. While for the 5% RGO decorated ZnO sensor, the photoresponse current reaches as high as ∼1 μA and exceeds 700 times that of a ZnO UV sensor. These results indicate that RGO is an appropriate material to enhance the performance of ZnO nanostructure UV sensors based on its unique features, especially the high optical transparency and excellent electronic conductivity. Our findings will make RGO/ZnO nanohybrids extraordinarily promising in optoelectronics, flexible electronics and sensor applications.

Effect of morphology on the non-ohmic conduction in ZnO nanostructures

NASA Astrophysics Data System (ADS)

Praveen, E.; Jayakumar, K.

2016-05-01

Nanostructures of ZnO is synthesized with nanoflower like morphology by simple wet chemical method. The structural, morphological and electrical characterization have been carried out. The temperature dependent electrical characterization of ZnO pellets of thickness 1150 µm is made by the application of 925MPa pressure. The morphological dependence of non-ohmic conduction beyond some arbitrary tunneling potential and grain boundary barrier thickness is compared with the commercially available bulk ZnO. Our results show the suitability of nano-flower like ZnO for the devices like sensors, rectifiers etc.

Dimensional-Hybrid Structures of 2D Materials with ZnO Nanostructures via pH-Mediated Hydrothermal Growth for Flexible UV Photodetectors.

PubMed

Lee, Young Bum; Kim, Seong Ku; Lim, Yi Rang; Jeon, In Su; Song, Wooseok; Myung, Sung; Lee, Sun Sook; Lim, Jongsun; An, Ki-Seok

2017-05-03

Complementary combination of heterostructures is a crucial factor for the development of 2D materials-based optoelectronic devices. Herein, an appropriate solution for fabricating complementary dimensional-hybrid nanostructures comprising structurally tailored ZnO nanostructures and 2D materials such as graphene and MoS 2 is suggested. Structural features of ZnO nanostructures hydrothermally grown on graphene and MoS 2 are deliberately manipulated by adjusting the pH value of the growing solution, which will result in the formation of ZnO nanowires, nanostars, and nanoflowers. The detailed growth mechanism is further explored for the structurally tailored ZnO nanostructures on the 2D materials. Furthermore, a UV photodetector based on the dimensional-hybrid nanostructures is fabricated, which demonstrates their excellent photocurrent and mechanical durability. This can be understood by the existence of oxygen vacancies and oxygen-vacancies-induced band narrowing in the ZnO nanostructures, which is a decisive factor for determining their photoelectrical properties in the hybrid system.

Fabrication of Flower-like ZnO Micro/Nanostructures for Photodegradation of Pre-treated Palm Oil Mill Effluent

NASA Astrophysics Data System (ADS)

Lam, Sze-Mun; Wong, Kok-Ann; Sin, Jin-Chung

2018-01-01

Flower-like ZnO micro/nanostructures were fabricated by a simple and surfactant-free reflux method. X-ray diffraction findings showed that the prepared ZnO product was highly crystallite with hexagonal wurtzite structure. The band gap energy of ZnO sample was measured to be 3.18 eV via an optical reflectance spectrum. The flower-like morphological features of ZnO micro/nanostructures were witnessed through field-emission scanning electron microscopy. Such micro/nanoparticles could be used in the photodegradation of pre-treated palm oil mil effluent (POME) under UV irradiation.

Enhanced photocatalytic performance of ZnO nanostructures by electrochemical hybridization with graphene oxide

NASA Astrophysics Data System (ADS)

Pruna, A.; Wu, Z.; Zapien, J. A.; Li, Y. Y.; Ruotolo, A.

2018-05-01

Synthesis of zinc oxide (ZnO) nanostructures is reported by electrochemical deposition from an aqueous electrolyte in presence of graphene oxide (GO) with varying oxidation degree. The properties of hybrids were investigated by scanning electron microscopy, X-ray diffraction, Raman, Fourier-Transform Infrared and X-ray photoelectron spectroscopy techniques and photocatalytic measurements. The results indicated the electrodeposition of ZnO in presence of GO with increased oxygen content led to marked differences in the morphology while Raman measurements indicated an increased defect level both in the ZnO and the electrochemically reduced GO (ErGO) within the hybrids. The decrease in C/O atomic ratio of GO (from 0.79 to 0.71) employed for the electrodeposition of ZnO resulted in an increase in photocatalytic efficiency for methylene blue degradation under UV irradiation from 4-folds to 10-folds with respect to non-hybridized ZnO. The observed synergetic effect of cathodic deposition potential and oxygen content in GO towards improving the photocatalytic activity of immobilized ZnO is expected to contribute to further development of more effective deposition approaches for the preparation of high performance hybrid nanostructures.

Toxicity evaluation of ZnO nanostructures on L929 fibroblast cell line using MTS assay

NASA Astrophysics Data System (ADS)

Bakhori, Siti Khadijah Mohd; Mahmud, Shahrom; Ann, Ling Chuo; Mohamed, Azman Seeni; Saifuddin, Siti Nazmin; Masudi, Sam'an Malik; Mohamad, Dasmawati

2015-04-01

ZnO has wide applications in medical and dentistry apart from being used as optoelectronic devices such as solar cells, photodetectors, sensors and light emitting diodes (LEDs). Therefore, the toxicity evaluation is important to know the toxicity level on normal cell line. The toxicity of two grades ZnO nanostructures, ZnO-4 and ZnO-8 have been carried out using cytotoxicity test of MTS assay on L929 rat fibroblast cell line. Prior to that, ZnO-4 and ZnO-8 were characterized for its morphology, structure and optical properties using FESEM, X-ray diffraction, and Photoluminescence respectively. The two groups revealed difference in morphology and exhibit slightly shifted of near band edge emission of Photoluminescence other than having a similar calculated crystallite size of nanostructures. The viability of cells after 72h were obtained and the statistical significance value was calculated using SPSS v20. The p value is more than 0.05 between untreated and treated cell with ZnO. This insignificant value of p>0.05 can be summarized as a non-toxic level of ZnO-4 and ZnO-8 on the L929 cell line.

Toxicity evaluation of ZnO nanostructures on L929 fibroblast cell line using MTS assay

DOE Office of Scientific and Technical Information (OSTI.GOV)

Bakhori, Siti Khadijah Mohd; Mahmud, Shahrom; Ann, Ling Chuo

2015-04-24

ZnO has wide applications in medical and dentistry apart from being used as optoelectronic devices such as solar cells, photodetectors, sensors and light emitting diodes (LEDs). Therefore, the toxicity evaluation is important to know the toxicity level on normal cell line. The toxicity of two grades ZnO nanostructures, ZnO-4 and ZnO-8 have been carried out using cytotoxicity test of MTS assay on L929 rat fibroblast cell line. Prior to that, ZnO-4 and ZnO-8 were characterized for its morphology, structure and optical properties using FESEM, X-ray diffraction, and Photoluminescence respectively. The two groups revealed difference in morphology and exhibit slightly shiftedmore » of near band edge emission of Photoluminescence other than having a similar calculated crystallite size of nanostructures. The viability of cells after 72h were obtained and the statistical significance value was calculated using SPSS v20. The p value is more than 0.05 between untreated and treated cell with ZnO. This insignificant value of p>0.05 can be summarized as a non-toxic level of ZnO-4 and ZnO-8 on the L929 cell line.« less

Effect of annealing on the sub-bandgap, defects and trapping states of ZnO nanostructures

NASA Astrophysics Data System (ADS)

Wahyuono, Ruri Agung; Hermann-Westendorf, Felix; Dellith, Andrea; Schmidt, Christa; Dellith, Jan; Plentz, Jonathan; Schulz, Martin; Presselt, Martin; Seyring, Martin; Rettenmeyer, Markus; Dietzek, Benjamin

2017-02-01

Annealing treatment was applied to different mesoporous ZnO nanostructures prepared by wet chemical synthesis, i.e. nanoflowers (NFs), spherical aggregates (SPs), and nanorods (NRs). The sub-bandgap, defect properties as well as the trapping state characteristics after annealing were characterized spectroscopically, including ultrasensitive photothermal deflection spectroscopy (PDS), photoluminescence and photo-electrochemical methods. The comprehensive experimental analysis reveals that annealing alters both the bandgap and the sub-bandgap. The defect concentration and the density of surface traps in the ZnO nanostructures are suppressed upon annealing as deduced from photoluminescence and open-circuit voltage decay analysis. The photo-electrochemical investigations reveal that the surface traps dominate the near conduction band edge of ZnO and, hence, lead to high recombination rates when used in DSSCs. The density of bulk traps in ZnO SPs is higher than that in ZnO NFs and ZnO NRs and promote lower recombination loss between photoinjected electrons with the electrolyte-oxidized species on the surface. The highest power conversion efficiency of ZnO NFs-, ZnO SPs-, and ZnO NRs-based DSSC obtained in our system is 2.0, 4.5, and 1.8%, respectively.

Growth and properties of electrodeposited transparent Al-doped ZnO nanostructures

NASA Astrophysics Data System (ADS)

Baka, O.; Mentar, L.; Khelladi, M. R.; Azizi, A.

2015-12-01

Al-doped zinc oxide (AZO) nanostructures were fabricated on fluorine-doped tin-oxide (FTO)- coated glass substrates by using electrodeposition. The effects of the doping concentration of Al on the morphological, microstructural, electrical and optical properties of the nanostructures were investigated. From the field emission scanning electron microscopy (FE-SEM) observation, when the amount of Al was increased in the solution, the grains size was observed to decreases. The observed changes in the morphology indicate that Al acts as nucleation centers in the vacancy sites of ZnO and destroys the crystalline structure at high doping level. Effectively, the X-ray diffraction (XRD) analysis indicated that the undoped and the doped ZnO nanostructures has a polycrystalline nature and a hexagonal wurtzite structure with a (002) preferential orientation. The photoluminescence (PL) room-temperature measurements showed that the incorporation of Al in the Zn lattice can improve the intensity of ultraviolet (UV) emission, thus suggesting its greater prospects for use in UV optoelectronic devices.

ZnO thin films and nanostructures for emerging optoelectronic applications

NASA Astrophysics Data System (ADS)

Rogers, D. J.; Teherani, F. H.; Sandana, V. E.; Razeghi, M.

2010-02-01

ZnO-based thin films and nanostructures grown by PLD for various emerging optoelectronic applications. AZO thin films are currently displacing ITO for many TCO applications due to recent improvements in attainable AZO conductivity combined with processing, cost and toxicity advantages. Advances in the channel mobilities and Id on/off ratios in ZnO-based TTFTs have opened up the potential for use as a replacement for a-Si in AM-OLED and AM-LCD screens. Angular-dependent specular reflection measurements of self-forming, moth-eye-like, nanostructure arrays grown by PLD were seen to have <0.5% reflectivity over the whole visible spectrum for angles of incidence between 10 and 60 degrees. Such nanostructures may be useful for applications such as AR coatings on solar cells. Compliant ZnO layers on mismatched/amorphous substrates were shown to have potential for MOVPE regrowth of GaN. This approach could be used as a means to facilitate lift-off of GaN-based LEDs from insulating sapphire substrates and could allow the growth of InGaN-based solar cells on cheap substrates. The green gap in InGaN-based LEDs was combated by substituting low Ts PLD n-ZnO for MOCVD n-GaN in inverted hybrid heterojunctions. This approach maintained the integrity of the InGaN MQWs and gave LEDs with green emission at just over 510 nm. Hybrid n-ZnO/p-GaN heterojunctions were also seen to have the potential for UV (375 nm) EL, characteristic of ZnO NBE emission. This suggests that there was significant hole injection into the ZnO and that such LEDs could profit from the relatively high exciton binding energy of ZnO.

On the possibility of room temperature ferromagnetism on chunk-shape BaSnO3/ZnO core/shell nanostructures

NASA Astrophysics Data System (ADS)

Rajamanickam, N.; Jayakumar, K.; Ramachandran, K.

2018-04-01

Core/shell BaSnO3/ZnO (BS-ZO) nanostructures were prepared by oxalate precipitation method and wet-chemical method. BaSnO3 (BSO) cubic perovskite structure and ZnO hexagonal wurtzite structure were confirmed by X-ray diffraction (XRD). The crystallite sizes is 23 nm, 29 nm and 27 nm for BSO, ZnO and BS-ZO, respectively. Chunk-shape and cuboids morphology observed from scanning electron microscopy (SEM) analysis. The magnetic properties were studied by VSM for bare and core-shell nano systems and the room temperature ferromagnetism observed for core-shell nanostructures. The BSO/ZnO shows enhanced coercivity and saturated magnetization as compared with BSO and ZnO nanostructures.

Fabrication and Characterization of Vertically Aligned ZnO Nanorod Arrays via Inverted Monolayer Colloidal Crystals Mask

NASA Astrophysics Data System (ADS)

Chen, Cheng; Ding, Taotao; Qi, Zhiqiang; Zhang, Wei; Zhang, Jun; Xu, Juan; Chen, Jingwen; Dai, Jiangnan; Chen, Changqing

2018-04-01

The periodically ordered ZnO nanorod (NR) arrays have been successfully synthesized via a hydrothermal approach on the silicon substrates by templating of the TiO2 ring deriving from the polystyrene (PS) nanosphere monolayer colloidal crystals (MCC). With the inverted MCC mask, sol-gel-derived ZnO seeds could serve as the periodic nucleation positions for the site-specific growth of ZnO NRs. The large-scale patterned arrays of single ZnO NR with good side-orientation can be readily produced. According to the experimental results, the as-integrated ZnO NR arrays showed an excellent crystal quality and optical property, very suitable for optoelectronic applications such as stimulated emitters and ZnO photonic crystal devices.

Mechanisms of electron transport and recombination in ZnO nanostructures for dye-sensitized solar cells.

PubMed

Vega-Poot, Alberto G; Macías-Montero, Manuel; Idígoras, Jesus; Borrás, Ana; Barranco, Angel; Gonzalez-Elipe, Agustín R; Lizama-Tzec, Francisco I; Oskam, Gerko; Anta, Juan A

2014-04-14

ZnO is an attractive material for applications in dye-sensitized solar cells and related devices. This material has excellent electron-transport properties in the bulk but its electron diffusion coefficient is much smaller in mesoporous films. In this work the electron-transport properties of two different kinds of dye-sensitized ZnO nanostructures are investigated by small-perturbation electrochemical techniques. For nanoparticulate ZnO photoanodes prepared via a wet-chemistry technique, the diffusion coefficient is found to reproduce the typical behavior predicted by the multiple-trapping and the hopping models, with an exponential increase with respect to the applied bias. In contrast, in ZnO nanostructured thin films of controlled texture and crystallinity prepared via a plasma chemical vapor deposition method, the diffusion coefficient is found to be independent of the electrochemical bias. This observation suggests a different transport mechanism not controlled by trapping and electron accumulation. In spite of the quite different transport features, the recombination kinetics, the electron-collection efficiency and the photoconversion efficiency are very similar for both kinds of photoanodes, an observation that indicates that surface properties rather than electron transport is the main efficiency-determining factor in solar cells based on ZnO nanostructured photoanodes. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Impact of nanostructured thin ZnO film in ultraviolet protection.

PubMed

Sasani Ghamsari, Morteza; Alamdari, Sanaz; Han, Wooje; Park, Hyung-Ho

2017-01-01

Nanoscale ZnO is one of the best choices for ultraviolet (UV) protection, not only because of its antimicrobial properties but also due to its potential application for UV preservation. However, the behavior of nanostructured thin ZnO films and long-term effects of UV-radiation exposure have not been studied yet. In this study, we investigated the UV-protection ability of sol gel-derived thin ZnO films after different exposure times. Scanning electron microscopy, atomic force microscopy, and UV-visible optical spectroscopy were carried out to study the structure and optical properties of the ZnO films as a function of the UV-irradiation time. The results obtained showed that the prepared thin ZnO films were somewhat transparent under the visible wavelength region and protective against UV radiation. The UV-protection factor was 50+ for the prepared samples, indicating that they were excellent UV protectors. The deposited thin ZnO films demonstrated promising antibacterial potential and significant light absorbance in the UV range. The experimental results suggest that the synthesized samples have potential for applications in the health care field.

Nucleation effect and growth mechanism of ZnO nanostructures by electrodeposition from aqueous zinc nitrate baths

NASA Astrophysics Data System (ADS)

Sun, Sujuan; Jiao, Shujie; Zhang, Kejun; Wang, Dongbo; Gao, Shiyong; Li, Hongtao; Wang, Jinzhong; Yu, Qingjiang; Guo, Fengyun; Zhao, Liancheng

2012-11-01

We presented a systematic study of the nucleation effect and growth mechanism of ZnO nanostructures from electrolyte mixed with different concentration of Zn(NO3)2·6H2O and KCl by cathodic electrochemical deposition. Scanning electron microscopy images reveal that the concentration of Zn(NO3)2·6H2O is important to control the dimension and nucleation rate, which 1D ZnO nanostructures with smaller diameters and rougher facets are formed at lower Zn(NO3)2 precursor concentration(1 mM) and dense and well-defined nanorods are achieved above 5 mM. We also found other major effects of KCl besides as a supporting electrolyte. A high [Cl-] not only makes the transition of morphology from 1D to 2D, but also has important influence on the nucleation in the initial stage in electrodeposition. Very sparse ZnO nanoclusters composed of two dimensional nanosheets evolve from dense ZnO nanotowers when the KCl supporting electrolyte concentration is added to 2 M. Thus, altering the content of Zn(NO3)2 precursor and KCl is a effective method to obtain ZnO nanostructures with different morphology for more applications.

Detectors based on Pd-doped and PdO-functionalized ZnO nanostructures

NASA Astrophysics Data System (ADS)

Postica, V.; Lupan, O.; Ababii, N.; Hoppe, M.; Adelung, R.; Chow, L.; Sontea, V.; Aschehoug, P.; Viana, V.; Pauporté, Th.

2018-02-01

In this work, zinc oxide (ZnO) nanostructured films were grown using a simple synthesis from chemical solutions (SCS) approach from aqueous baths at relatively low temperatures (< 95 °C). The samples were doped with Pd (0.17 at% Pd) and functionalized with PdO nanoparticles (NPs) using the PdCl2 aqueous solution and subsequent thermal annealing at 650 °C for 30 min. The morphological, micro-Raman and optical properties of Pd modified samples were investigated in detail and were demonstrated to have high crystallinity. Gas sensing studies unveiled that compared to pure ZnO films, the Pd-doped ZnO (ZnO:Pd) nanostructured films showed a decrease in ethanol vapor response and slight increase in H2 response with low selectivity. However, the PdO-functionalized samples showed excellent H2 gas sensing properties with possibility to detect H2 gas even at room temperature (gas response of 2). Up to 200 °C operating temperature the samples are highly selective to H2 gas, with highest response of 12 at 150 °C. This study demonstrates that surface functionalization of n-ZnO nanostructured films with p-type oxides is very important for improvement of gas sensing properties.

Simultaneous tuning of electric field intensity and structural properties of ZnO: Graphene nanostructures for FOSPR based nicotine sensor.

PubMed

Tabassum, Rana; Gupta, Banshi D

2017-05-15

We report theoretical and experimental realization of a SPR based fiber optic nicotine sensor having coatings of silver and graphene doped ZnO nanostructure onto the unclad core of the optical fiber. The volume fraction (f) of graphene in ZnO was optimized using simulation of electric field intensity. Four types of graphene doped ZnO nanostructures viz. nanocomposites, nanoflowers, nanotubes and nanofibers were prepared using optimized value of f. The morphology, photoluminescence (PL) spectra and UV-vis spectra of these nanostructures were studied. The peak PL intensity was found to be highest for ZnO: graphene nanofibers. The optimized value of f in ZnO: graphene nanofiber was reconfirmed using UV-vis spectroscopy. The experiments were performed on the fiber optic probe fabricated with Ag/ZnO: graphene layer and optimized parameters for in-situ detection of nicotine. The interaction of nicotine with ZnO: graphene nanostructures alters the dielectric function of ZnO: graphene nanostructure which is manifested in terms of shift in resonance wavelength. From the sensing signal, the performance parameters were measured including sensitivity, limit of detection (LOD), limit of quantification (LOQ), stability, repeatability and selectivity. The real sample prepared using cigarette tobacco leaves and analyzed using the fabricated sensor makes it suitable for practical applications. The achieved values of LOD and LOQ are found to be unrivalled in comparison to the reported ones. The sensor possesses additional advantages such as, immunity to electromagnetic interference, low cost, capability of online monitoring, remote sensing. Copyright © 2017 Elsevier B.V. All rights reserved.

Flower-like ZnO nanostructure based electrochemical DNA biosensor for bacterial meningitis detection.

PubMed

Tak, Manvi; Gupta, Vinay; Tomar, Monika

2014-09-15

Zinc oxide (ZnO) nanostructures possessing flower-like morphology have been synthesised onto platinized silicon substrate by simple and economical hydrothermal method. The interaction of physically immobilized single stranded thiolated DNA (ss th-DNA) probe of N. meningitides onto the nanostructured ZnO (ZNF) matrix surface have been investigated using cyclic voltammetry (CV) and electrochemical impeadance spectroscopy (EIS). The electrochemical sensing response behaviour of the DNA bioelectrode (ss th-DNA/ZNF/Pt/Si) has been studied by both differential pulse voltammetric (DPV) as well as impedimetric techniques. The fabricated DNA biosensor can quantify wide range of the complementary target ss th-DNA in the range 5-240 ng μl(-1) with good linearity (R=0.98), high sensitivity (168.64 μA ng(-1) μl cm(-2)) and low detection limit of about 5 ng μl(-1). Results emphasise that the fabricated flower-like ZnO nanostructures offer a useful platform for the immobilization of DNA molecules and could be exploited for efficient detection of complementary target single stranded DNA corresponding to N. meningitides. Copyright © 2014 Elsevier B.V. All rights reserved.

Polarization induced conductive AFM on cobalt doped ZnO nanostructures

NASA Astrophysics Data System (ADS)

Sahoo, Pradosh Kumar; Mangamma, G.; Rajesh, A.; Kamruddin, M.; Dash, S.

2017-05-01

In the present work cobalt doped ZnO (CZO) nanostructures (NS) have been synthesized by of sol-gel and spin coating process. After the crystal phase confirmation by GIXRD and Raman spectroscopy, Conductive Atomic Force Microscopy (C-AFM) measurement was performed on CZO NS which shows the random distribution of electrically conducting zones on the surface of the material exhibiting current in the range 4-170 pA. We provide the possible mechanisms for variation in current distribution essential for quantitative understanding of transport properties of ZnO NS in doped and undoped forms.

Ligand induced ferromagnetism in ZnO nanostructures.

PubMed

Wang, Qian; Sun, Qiang; Jena, P

2008-10-28

Complementary to the experimental finding that ZnO nanoparticles become ferromagnetic when coated with N and S containing ligands such as dodecylamine and dodecanethiol [Garcia et al., Nano Lett. 7, 1489 (2007)], we provide the first theoretical understanding of the origin of magnetism in ligated ZnO nanoparticles as well as the structural properties of the ligated systems by using density functional theory and generalized gradient approximation for exchange and correlation, and a cluster model for the nanoparticles. We show that N or S atoms of the ligand bind to the Zn sites. The accompanying changes in the Zn-O bond length, hybridization between Zn 4s orbitals with N 2p or S 3p orbitals, and consequently the redistribution of charges between Zn and O atoms result in a magnetic system where the 2p electrons in O and N, and 3p electrons in S sites are spin polarized. Furthermore, the sites nearest to the Zn atom attached to the ligand carry bulk of the magnetic moment. Studies, as a function of cluster size, also illustrate that magnetism resides only on the surface. Our results confirm that the use of ligands can pave a new way for introducing magnetism in ZnO nanostructures, which can be used to develop magnetic sensors to detect N and S containing molecules.

Growth mechanism, surface and optical properties of ZnO nanostructures deposited on various Au-seeded thickness obtained by mist-atomization

DOE Office of Scientific and Technical Information (OSTI.GOV)

Afaah, A. N., E-mail: afaahabdullah@yahoo.com; Aadila, A., E-mail: aadilaazizali@gmail.com; Asib, N. A. M., E-mail: amierahasib@yahoo.com

2016-07-06

In this paper, growth mechanisms of ZnO nanostructures on non-seeded glass, 6 nm and 12 nm Au seed layer obtained by mist-atomization was proposed. ZnO films were successfully deposited on glass substrate with different thickness of Au seed layer i.e. 6 nm and 12 nm. The surface and optical properties of the prepared samples were investigated using Field emission scanning electron microscopy (FESEM) and photoluminescence (PL). FESEM micrograph show that ZnO nanostructure deposited on 6 nm Au seed layer has uniform formation and well distributed. From PL spectroscopy, the UV emission shows that ZnO deposited on 6 nm Au seedmore » layer has the more intense UV intensity which proved that high crystal quality of nanostructured ZnO deposited on 6 nm Au seed layer.« less

Impact of nanostructured thin ZnO film in ultraviolet protection

PubMed Central

Sasani Ghamsari, Morteza; Alamdari, Sanaz; Han, Wooje; Park, Hyung-Ho

2017-01-01

Nanoscale ZnO is one of the best choices for ultraviolet (UV) protection, not only because of its antimicrobial properties but also due to its potential application for UV preservation. However, the behavior of nanostructured thin ZnO films and long-term effects of UV-radiation exposure have not been studied yet. In this study, we investigated the UV-protection ability of sol gel-derived thin ZnO films after different exposure times. Scanning electron microscopy, atomic force microscopy, and UV-visible optical spectroscopy were carried out to study the structure and optical properties of the ZnO films as a function of the UV-irradiation time. The results obtained showed that the prepared thin ZnO films were somewhat transparent under the visible wavelength region and protective against UV radiation. The UV-protection factor was 50+ for the prepared samples, indicating that they were excellent UV protectors. The deposited thin ZnO films demonstrated promising antibacterial potential and significant light absorbance in the UV range. The experimental results suggest that the synthesized samples have potential for applications in the health care field. PMID:28096668

Nanostructured ZnO films for potential use in LPG gas sensors

NASA Astrophysics Data System (ADS)

Latyshev, V. M.; Berestok, T. O.; Opanasyuk, A. S.; Kornyushchenko, A. S.; Perekrestov, V. I.

2017-05-01

The aim of the work was to obtain ZnO nanostructures with heightened surface area and to study relationship between formation method and gas sensor properties towards propane-butane mixture (LPG). In order to synthesize ZnO nanostructures chemical and physical formation methods have been utilized. The first one was chemical bath deposition technology and the second one magnetron sputtering of Zn followed by oxidation. Optimal method and technological parameters corresponding to formation of material with the highest sensor response have been determined experimentally. Dynamical gas sensor response at different temperature values and dependencies of the sensor sensitivity on the temperature at different LPG concentrations in air have been investigated. It has been found, that sensor response depends on the sample morphology and has the highest value for the structure consisting of thin nanowires. The factors that lead to the decrease in the gas sensor operating temperature have been determined.

Studies of surface morphology and optical properties of ZnO nanostructures grown on different molarities of TiO{sub 2} seed layer

DOE Office of Scientific and Technical Information (OSTI.GOV)

Asib, N. A. M., E-mail: amierahasib@yahoo.com; Afaah, A. N.; Aadila, A.

Titanium dioxide (TiO{sub 2}) seed layer was prepared by using sol-gel spin-coating technique, followed by growth of 0.01 M of Zinc oxide (ZnO) nanostructures by solution-immersion. The molarities of TiO{sub 2} seed layer were varied from 1.1 M to 0.100 M on glass substrates. The nanostructures thin films were characterized by Field Emission Scanning Electrons Microscope (FESEM), Photoluminescence (PL) spectroscopy and Ultraviolet-Visible (UV-Vis) spectroscopy. FESEM images demonstrate that needle-like ZnO nanostructures are formed on all TiO{sub 2} seed layer. The smallest diameter of needle-like ZnO nanostructures (90.3 nm) were deposited on TiO{sub 2} seed layer of 0.100 M. PL spectramore » of the TiO{sub 2}: ZnO nanostructures thin films show the blue shifted emissions in the UV regions compared to the ZnO thin film. Meanwhile, UV-vis spectra of films display high absorption in the UV region and high trasparency in the visible region. The highest absorbance at UV region was recorded for sample which has 0.100 M of TiO{sub 2} seed layer.« less

Blue emitting ZnO nanostructures grown through cellulose bio-templates.

PubMed

Oudhia, Anjali; Sharma, Savita; Kulkarni, Pragya; Kumar, Rajesh

2016-06-01

This paper presents a green and cost-effective recipe for the synthesis of blue-emitting ZnO nanoparticles (NPs) using cellulose bio-templates. Azadirachta indica (neem) leaf extract prepared in different solvents were used as biological templates to produce nanostructures of wurtzite ZnO with a particle size ~12-36 nm. A cellulose-driven capping mechanism is used to describe the morphology of ZnO NPs. The scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD), Fourier transform infra-red (FTIR) and photoluminescence (PL) studies showed that solvents affect the growth process and the capping mechanism of bio-template severely. Structural changes in ZnO NPs were evident with variation in pH, dielectric constants (DC) and boiling points (BP) of solvents. Furthermore, an energy band model is proposed to explain the origin of the blue emission in the as-obtained ZnO NPs. PL excitation studies and the theoretical enthalpy values of individual defects were used to establish the association between the interstitial-zinc-related defect levels and the blue emission. Copyright © 2015 John Wiley & Sons, Ltd. Copyright © 2015 John Wiley & Sons, Ltd.

Microwave-assisted Facile and Ultrafast Growth of ZnO Nanostructures and Proposition of Alternative Microwave-assisted Methods to Address Growth Stoppage

NASA Astrophysics Data System (ADS)

Rana, Abu Ul Hassan Sarwar; Kang, Mingi; Kim, Hyun-Seok

2016-04-01

The time constraint in the growth of ZnO nanostructures when using a hydrothermal method is of paramount importance in contemporary research, where a long fabrication time rots the very essence of the research on ZnO nanostructures. In this study, we present the facile and ultrafast growth of ZnO nanostructures in a domestic microwave oven within a pressurized environment in just a few minutes. This method is preferred for the conventional solution-based method because of the ultrafast supersaturation of zinc salts and the fabrication of high-quality nanostructures. The study of the effect of seed layer density, growth time, and the solution’s molar concentration on the morphology, alignment, density, and aspect ratio of ZnO nanorods (ZNRs) is explored. It is found in a microwave-assisted direct growth method that ~5 mins is the optimum time beyond which homogeneous nucleation supersedes heterogeneous nucleation, which results in the growth stoppage of ZNRs. To deal with this issue, we propound different methods such as microwave-assisted solution-replacement, preheating, and PEI-based growth methods, where growth stoppage is addressed and ZNRs with a high aspect ratio can be grown. Furthermore, high-quality ZnO nanoflowers and ZnO nanowalls are fabricated via ammonium hydroxide treatment in a very short time.

Controlling of ZnO nanostructures by solute concentration and its effect on growth, structural and optical properties

NASA Astrophysics Data System (ADS)

Kumar, Yogendra; Rana, Amit Kumar; Bhojane, Prateek; Pusty, Manojit; Bagwe, Vivas; Sen, Somaditya; Shirage, Parasharam M.

2015-10-01

ZnO nanostructured films were prepared by a chemical bath deposition method on glass substrates without any assistance of either microwave or high pressure autoclaves. The effect of solute concentration on the pure wurtzite ZnO nanostructure morphologies is studied. The control of the solute concentration helps to control the nanostructure to form nano-needles, and -rods. X-ray diffraction (XRD) studies revealed highly c-axis oriented thin films. Scanning electron microscopy (SEM) confirms the modification of the nanostructure dependent on the concentration. Transmission electron microscopy (TEM) results show the single crystalline electron diffraction pattern, indicating high quality nano-material. UV-vis results show the variation in the band gap from 3.20 eV to 3.14 eV with increasing concentration as the nanostructures change from needle- to rod-like. Photoluminescence (PL) data indicate the existence of defects in the nanomaterials emitting light in the yellow-green region, with broad UV and visible spectra. A sharp and strong peak is observed at ˜438 cm-1 by Raman spectroscopy, assigned to the {{{{E}}}2}{{high}} optical mode of ZnO, the characteristic peak for the highly-crystalline wurtzite hexagonal phase. The solute concentration significantly affects the formation of defect states in the nanostructured films, and as a result, it alters the structural and optical properties. Current-voltage characteristics alter with the measurement environment, indicating potential sensor applications.

Layer-by-layer deposition of nanostructured CsPbBr3 perovskite thin films

NASA Astrophysics Data System (ADS)

Reshetnikova, A. A.; Matyushkin, L. B.; Andronov, A. A.; Sokolov, V. S.; Aleksandrova, O. A.; Moshnikov, V. A.

2017-11-01

Layer-by-layer deposition of nanostructured perovskites cesium lead halide thin films is described. The method of deposition is based on alternate immersion of the substrate in the precursor solutions or colloidal solution of nanocrystals and methyl acetate/lead nitrate solution using the device for deposition of films by SILAR and dip-coating techniques. An example of obtaining a photosensitive structure based on nanostructures of ZnO nanowires and layers of CsBbBr3 nanocrystals is also shown.

Influence of External Gaseous Environments on the Electrical Properties of ZnO Nanostructures Obtained by a Hydrothermal Method

PubMed Central

Procek, Marcin; Pustelny, Tadeusz; Stolarczyk, Agnieszka

2016-01-01

This paper deals with experimental investigations of ZnO nanostructures, consisting of a mixture of nanoparticles and nanowires, obtained by the chemical (hydrothermal) method. The influences of both oxidizing (NO2) and reducing gases (H2, NH3), as well as relative humidity (RH) on the physical and chemical properties of ZnO nanostructures were tested. Carrier gas effect on the structure interaction with gases was also tested; experiments were conducted in air and nitrogen (N2) atmospheres. The effect of investigated gases on the resistance of the ZnO nanostructures was tested over a wide range of concentrations at room temperature (RT) and at 200 °C. The impact of near- ultraviolet (UV) excitation (λ = 390 nm) at RT was also studied. These investigations indicated a high response of ZnO nanostructures to small concentrations of NO2. The structure responses to 1 ppm of NO2 amounted to about: 600% in N2/230% in air at 200 °C (in dark conditions) and 430% in N2/340% in air at RT (with UV excitation). The response of the structure to the effect of NO2 at 200 °C is more than 105 times greater than the response to NH3, and more than 106 times greater than that to H2 in the relation of 1 ppm. Thus the selectivity of the structure for NO2 is very good. What is more, the selectivity to NO2 at RT with UV excitation increases in comparison at elevated temperature. This paper presents a great potential for practical applications of ZnO nanostructures (including nanoparticles) in resistive NO2 sensors. PMID:28335355

Electrical properties of Mg doped ZnO nanostructure annealed at different temperature

DOE Office of Scientific and Technical Information (OSTI.GOV)

Mohamed, R., E-mail: ruziana12@gmail.com; Mamat, M. H., E-mail: hafiz-030@yahoo.com; Rusop, M., E-mail: nanouitm@gmail.com

In this work, ZincOxide (ZnO) nanostructures doped with Mg were successfully grown on the glass substrate. Magnesium (Mg) metal element was added in the ZnO host which acts as a doping agent. Different temperature in range of 250°C to 500°C was used in order to investigate the effect of annealing temperature of ZnO thin films. Field Emission Scanning Electron Microscopy (FESEM) was used to investigate the physical characteristic of ZnO thin films. FESEM results have revealed that ZnO nanorods were grown vertically aligned. The structural properties were determined by using X-Ray Diffraction (XRD) analysis. XRD results showed Mg doped ZnOmore » thin have highest crystalinnity at 500°C annealing temperature. The electrical properties were investigating by using Current-Voltage (I-V) measurement. I-V measurement showed the electrical properties were varied at different annealing temperature. The annealing temperature at 500°C has the highest electrical conductance properties.« less

Acoustoelectric Effect on the Responses of SAW Sensors Coated with Electrospun ZnO Nanostructured Thin Film

PubMed Central

Tasaltin, Cihat; Ebeoglu, Mehmet Ali; Ozturk, Zafer Ziya

2012-01-01

In this study, zinc oxide (ZnO) was a very good candidate for improving the sensitivity of gas sensor technology. The preparation of an electrospun ZnO nanostructured thin film on a 433 MHz Rayleigh wave based Surface Acoustic Wave (SAW) sensor and the investigation of the acoustoelectric effect on the responses of the SAW sensor are reported. We prepared an electrospun ZnO nanostructured thin film on the SAW devices by using an electrospray technique. To investigate the dependency of the sensor response on the structure and the number of the ZnO nanoparticles, SAW sensors were prepared with different coating loads. The coating frequency shifts were adjusted to fall between 100 kHz and 2.4 MHz. The sensor measurements were performed against VOCs such as acetone, trichloroethylene, chloroform, ethanol, n-propanol and methanol vapor. The sensor responses of n-propanol have opposite characteristics to the other VOCs, and we attributed these characteristics to the elastic effect/acoustoelectric effect.

Enhanced room temperature ferromagnetism in electrodeposited Co-doped ZnO nanostructured thin films by controlling the oxygen vacancy defects

DOE Office of Scientific and Technical Information (OSTI.GOV)

Simimol, A.; Department of Physics, National Institute of Technology Calicut, Calicut 673601; Anappara, Aji A.

We report the growth of un-doped and cobalt doped ZnO nanostructures fabricated on FTO coated glass substrates using electrodeposition method. A detailed study on the effects of dopant concentration on morphology, structural, optical, and magnetic properties of the ZnO nanostructures has been carried out systematically by varying the Co concentration (c.{sub Co}) from 0.01 to 1 mM. For c.{sub Co }≤ 0.2 mM, h-wurtzite phase with no secondary phases of Co were present in the ZnO nanostructures. For c.{sub Co} ≤ 0.2 mM, the photoluminescence spectra exhibited a decrease in the intensity of ultraviolet emission as well as band-gap narrowing with an increase in dopantmore » concentration. All the doped samples displayed a broad emission in the visible range and its intensity increased with an increase in Co concentration. It was found that the defect centers such as oxygen vacancies and zinc interstitials were the source of the visible emission. The X-ray photoelectron spectroscopy studies revealed, Co was primarily in the divalent state, replacing the Zn ion inside the tetrahedral crystal site of ZnO without forming any cluster or secondary phases of Co. The un-doped ZnO nanorods exhibited diamagnetic behavior and it remained up to a c.{sub Co} of 0.05 mM, while for c.{sub Co }> 0.05 mM, the ZnO nanostructures exhibited ferromagnetic behavior at room temperature. The coercivity increased to 695 G for 0.2 mM Co-doped sample and then it decreased for c.{sub Co }> 0.2 mM. Our results illustrate that up to a threshold concentration of 0.2 mM, the strong ferromagnetism is due to the oxygen vacancy defects centers, which exist in the Co-doped ZnO nanostructures. The origin of strong ferromagnetism at room temperature in Co-doped ZnO nanostructures is attributed to the s-d exchange interaction between the localized spin moments resulting from the oxygen vacancies and d electrons of Co{sup 2+} ions. Our findings provide a new insight for

Colloidal graphite/graphene nanostructures using collagen showing enhanced thermal conductivity.

PubMed

Bhattacharya, Soumya; Dhar, Purbarun; Das, Sarit K; Ganguly, Ranjan; Webster, Thomas J; Nayar, Suprabha

2014-01-01

In the present study, the exfoliation of natural graphite (GR) directly to colloidal GR/graphene (G) nanostructures using collagen (CL) was studied as a safe and scalable process, akin to numerous natural processes and hence can be termed "biomimetic". Although the exfoliation and functionalization takes place in just 1 day, it takes about 7 days for the nano GR/G flakes to stabilize. The predominantly aromatic residues of the triple helical CL forms its own special micro and nanoarchitecture in acetic acid dispersions. This, with the help of hydrophobic and electrostatic forces, interacts with GR and breaks it down to nanostructures, forming a stable colloidal dispersion. Surface enhanced Raman spectroscopy, X-ray diffraction, photoluminescence, fluorescence, and X-ray photoelectron spectroscopy of the colloid show the interaction between GR and CL on day 1 and 7. Differential interference contrast images in the liquid state clearly reveal how the GR flakes are entrapped in the CL fibrils, with a corresponding fluorescence image showing the intercalation of CL within GR. Atomic force microscopy of graphene-collagen coated on glass substrates shows an average flake size of 350 nm, and the hexagonal diffraction pattern and thickness contours of the G flakes from transmission electron microscopy confirm ≤ five layers of G. Thermal conductivity of the colloid shows an approximate 17% enhancement for a volume fraction of less than approximately 0.00005 of G. Thus, through the use of CL, this new material and process may improve the use of G in terms of biocompatibility for numerous medical applications that currently employ G, such as internally controlled drug-delivery assisted thermal ablation of carcinoma cells.

Colloidal graphite/graphene nanostructures using collagen showing enhanced thermal conductivity

PubMed Central

Bhattacharya, Soumya; Dhar, Purbarun; Das, Sarit K; Ganguly, Ranjan; Webster, Thomas J; Nayar, Suprabha

2014-01-01

In the present study, the exfoliation of natural graphite (GR) directly to colloidal GR/graphene (G) nanostructures using collagen (CL) was studied as a safe and scalable process, akin to numerous natural processes and hence can be termed “biomimetic”. Although the exfoliation and functionalization takes place in just 1 day, it takes about 7 days for the nano GR/G flakes to stabilize. The predominantly aromatic residues of the triple helical CL forms its own special micro and nanoarchitecture in acetic acid dispersions. This, with the help of hydrophobic and electrostatic forces, interacts with GR and breaks it down to nanostructures, forming a stable colloidal dispersion. Surface enhanced Raman spectroscopy, X-ray diffraction, photoluminescence, fluorescence, and X-ray photoelectron spectroscopy of the colloid show the interaction between GR and CL on day 1 and 7. Differential interference contrast images in the liquid state clearly reveal how the GR flakes are entrapped in the CL fibrils, with a corresponding fluorescence image showing the intercalation of CL within GR. Atomic force microscopy of graphene-collagen coated on glass substrates shows an average flake size of 350 nm, and the hexagonal diffraction pattern and thickness contours of the G flakes from transmission electron microscopy confirm ≤ five layers of G. Thermal conductivity of the colloid shows an approximate 17% enhancement for a volume fraction of less than approximately 0.00005 of G. Thus, through the use of CL, this new material and process may improve the use of G in terms of biocompatibility for numerous medical applications that currently employ G, such as internally controlled drug-delivery assisted thermal ablation of carcinoma cells. PMID:24648728

Potentiometric Titrations for Measuring the Capacitance of Colloidal Photodoped ZnO Nanocrystals.

PubMed

Brozek, Carl K; Hartstein, Kimberly H; Gamelin, Daniel R

2016-08-24

Colloidal semiconductor nanocrystals offer a unique opportunity to bridge molecular and bulk semiconductor redox phenomena. Here, potentiometric titration is demonstrated as a method for quantifying the Fermi levels and charging potentials of free-standing colloidal n-type ZnO nanocrystals possessing between 0 and 20 conduction-band electrons per nanocrystal, corresponding to carrier densities between 0 and 1.2 × 10(20) cm(-3). Potentiometric titration of colloidal semiconductor nanocrystals has not been described previously, and little precedent exists for analogous potentiometric titration of any soluble reductants involving so many electrons. Linear changes in Fermi level vs charge-carrier density are observed for each ensemble of nanocrystals, with slopes that depend on the nanocrystal size. Analysis indicates that the ensemble nanocrystal capacitance is governed by classical surface electrical double layers, showing no evidence of quantum contributions. Systematic shifts in the Fermi level are also observed with specific changes in the identity of the charge-compensating countercation. As a simple and contactless alternative to more common thin-film-based voltammetric techniques, potentiometric titration offers a powerful new approach for quantifying the redox properties of colloidal semiconductor nanocrystals.

Tuning the nanostructures and optical properties of undoped and N-doped ZnO by supercritical fluid treatment

NASA Astrophysics Data System (ADS)

Li, Yaping; Wang, Hui-Qiong; Chu, Tian-Jian; Li, Yu-Chiuan; Li, Xiaojun; Liao, Xiaxia; Wang, Xiaodan; Zhou, Hua; Kang, Junyong; Chang, Kuan-Chang; Chang, Ting-Chang; Tsai, Tsung-Ming; Zheng, Jin-Cheng

2018-05-01

Treatment of ZnO films in a supercritical fluid (SCF) has been reported to improve the performance of devices in which the treated ZnO films are incorporated; however, the mechanism of this improvement remains unclear. In this paper, we study the transformation of the surface morphologies and emission properties of ZnO films before and after SCF treatment, establishing the relationship between the treated and untreated structures and thereby enabling tuning of the catalytic or opto-electronic performance of ZnO films or ZnO-film-based devices. Both undoped and N-doped ZnO nanostructures generated by SCF treatment of films are investigated using techniques to characterize their surface morphology (scanning electron microscopy (SEM) and atomic force microscopy (AFM)) as well as room-temperature photoluminescence (RT-PL) spectroscopy. The water-mixed supercritical CO2 (W-SCCO2) technology was found to form nanostructures in ZnO films through a self-catalyzed process enabled by the Zn-rich conditions in the ZnO films. The W-SCCO2 was also found to promote the inhibition of defect luminescence by introducing -OH groups onto the films. Two models are proposed to explain the effects of the treatment with W-SCCO2. This work demonstrates that the W-SCCO2 technology can be used as an effective tool for the nanodesign and property enhancement of functional metal oxides.

Effects of surface morphology on the optical and electrical properties of Schottky diodes of CBD deposited ZnO nanostructures

NASA Astrophysics Data System (ADS)

Mwankemwa, Benard S.; Akinkuade, Shadrach; Maabong, Kelebogile; Nel, Jackie M.; Diale, Mmantsae

2018-04-01

We report on effect of surface morphology on the optical and electrical properties of chemical bath deposited Zinc oxide (ZnO) nanostructures. ZnO nanostructures were deposited on the seeded conducting indium doped tin oxide substrate positioned in three different directions in the growth solution. Field emission scanning electron microscopy was used to evaluate the morphological properties of the synthesized nanostructures and revealed that the positioning of the substrate in the growth solution affects the surface morphology of the nanostructures. The optical absorbance, photoluminescence and Raman spectroscopy of the resulting nanostructures are discussed. The electrical characterization of the Schottky diode such as barrier height, ideality factor, rectification ratios, reverse saturation current and series resistance were found to depend on the nanostructures morphology. In addition, current transport mechanism in the higher forward bias of the Schottky diode was studied and space charge limited current was found to be the dominant transport mechanism in all samples.

Annealing Temperature Dependence of ZnO Nanostructures Grown by Facile Chemical Bath Deposition for EGFET pH Sensors

NASA Astrophysics Data System (ADS)

Bazilah Rosli, Aimi; Awang, Zaiki; Sobihana Shariffudin, Shafinaz; Herman, Sukreen Hana

2018-03-01

Zinc Oxide (ZnO) nanostructures were deposited using chemical bath deposition (CBD) technique in water bath at 95 °C for 4 h. Post-deposition heat treatment in air ambient at various temperature ranging from 200-600 °C for 30 min was applied in order to enhance the electrical properties of ZnO nanostructures as the sensing membrane of extended-gate field effect transistor (EGFET) pH sensor. The as-deposited sample was prepared for comparison. The samples were characterized in terms of physical and sensing properties. FESEM images showed that scattered ZnO nanorods were formed for the as-deposited sample, and the morphology of the ZnO nanorods changed to ZnO nanoflowers when the heat treatment was applied from 200-600 °C. For sensing properties, the samples heated at 300 °C showed the higher sensitivity which was 39.9 mV/pH with the linearity of 0.9792. The sensing properties was increased with the increasing annealing treatment temperature up to 300 °C before decreased drastically.

Anomalous luminescence phenomena of indium-doped ZnO nanostructures grown on Si substrates by the hydrothermal method

PubMed Central

2012-01-01

In recent years, zinc oxide (ZnO) has become one of the most popular research materials due to its unique properties and various applications. ZnO is an intrinsic semiconductor, with a wide bandgap (3.37 eV) and large exciton binding energy (60 meV) making it suitable for many optical applications. In this experiment, the simple hydrothermal method is used to grow indium-doped ZnO nanostructures on a silicon wafer, which are then annealed at different temperatures (400°C to 1,000°C) in an abundant oxygen atmosphere. This study discusses the surface structure and optical characteristic of ZnO nanomaterials. The structure of the ZnO nanostructures is analyzed by X-ray diffraction, the superficial state by scanning electron microscopy, and the optical measurements which are carried out using the temperature-dependent photoluminescence (PL) spectra. In this study, we discuss the broad peak energy of the yellow-orange emission which shows tendency towards a blueshift with the temperature increase in the PL spectra. This differs from other common semiconductors which have an increase in their peak energy of deep-level emission along with measurement temperature. PMID:22647253

Redox Potentials of Colloidal n-Type ZnO Nanocrystals: Effects of Confinement, Electron Density, and Fermi-Level Pinning by Aldehyde Hydrogenation.

PubMed

Carroll, Gerard M; Schimpf, Alina M; Tsui, Emily Y; Gamelin, Daniel R

2015-09-02

Electronically doped colloidal semiconductor nanocrystals offer valuable opportunities to probe the new physical and chemical properties imparted by their excess charge carriers. Photodoping is a powerful approach to introducing and controlling free carrier densities within free-standing colloidal semiconductor nanocrystals. Photoreduced (n-type) colloidal ZnO nanocrystals possessing delocalized conduction-band (CB) electrons can be formed by photochemical oxidation of EtOH. Previous studies of this chemistry have demonstrated photochemical electron accumulation, in some cases reaching as many as >100 electrons per ZnO nanocrystal, but in every case examined to date this chemistry maximizes at a well-defined average electron density of ⟨Nmax⟩ ≈ (1.4 ± 0.4) × 10(20) cm(-3). The origins of this maximum have never been identified. Here, we use a solvated redox indicator for in situ determination of reduced ZnO nanocrystal redox potentials. The Fermi levels of various photodoped ZnO nanocrystals possessing on average just one excess CB electron show quantum-confinement effects, as expected, but are >600 meV lower than those of the same ZnO nanocrystals reduced chemically using Cp*2Co, reflecting important differences between their charge-compensating cations. Upon photochemical electron accumulation, the Fermi levels become independent of nanocrystal volume at ⟨N⟩ above ∼2 × 10(19) cm(-3), and maximize at ⟨Nmax⟩ ≈ (1.6 ± 0.3) × 10(20) cm(-3). This maximum is proposed to arise from Fermi-level pinning by the two-electron/two-proton hydrogenation of acetaldehyde, which reverses the EtOH photooxidation reaction.

Ionic pH and glucose sensors fabricated using hydrothermal ZnO nanostructures

NASA Astrophysics Data System (ADS)

Wang, Jyh-Liang; Yang, Po-Yu; Hsieh, Tsang-Yen; Juan, Pi-Chun

2016-01-01

Hydrothermally synthesized aluminum-doped ZnO (AZO) nanostructures have been adopted in extended-gate field-effect transistor (EGFET) sensors to demonstrate the sensitive and stable pH and glucose sensing characteristics of AZO-nanostructured EGFET sensors. The AZO-nanostructured EGFET sensors exhibited the following superior pH sensing characteristics: a high current sensitivity of 0.96 µA1/2/pH, a high linearity of 0.9999, less distortion of output waveforms, a small hysteresis width of 4.83 mV, good long-term repeatability, and a wide sensing range from pHs 1 to 13. The glucose sensing characteristics of AZO-nanostructured biosensors exhibited the desired sensitivity of 60.5 µA·cm-2·mM-1 and a linearity of 0.9996 up to 13.9 mM. The attractive characteristics of high sensitivity, high linearity, and repeatability of using ionic AZO-nanostructured EGFET sensors indicate their potential use as electrochemical and disposable biosensors.

Composite multifunctional nanostructures based on ZnO tetrapods and superparamagnetic Fe3O4 nanoparticles.

PubMed

Villani, M; Rimoldi, T; Calestani, D; Lazzarini, L; Chiesi, V; Casoli, F; Albertini, F; Zappettini, A

2013-04-05

A nanocomposite material is obtained by coupling superparamagnetic magnetite nanoparticles (Fe3O4 NP) and vapor phase grown zinc oxide nanostructures with 'tetrapod' morphology (ZnO TP). The aim is the creation of a multifunctional material which retains the attractive features of ZnO (e.g. surface reactivity, strong UV emission, piezoelectricity) together with added magnetism. Structural, morphological, optical, magnetic and functional characterization are performed. In particular, the high saturation magnetization of Fe3O4 NP (above 50 A m(2) kg(-1)), the strong UV luminescence and the enhanced photocatalytic activity of coupled nanostructures are discussed. Thus the nanocomposite turns out to be suitable for applications in energy harvesting and conversion, gas- and bio-sensing, bio-medicine and filter-free photocatalysis.

Study of quantum confinement effects in ZnO nanostructures

NASA Astrophysics Data System (ADS)

Movlarooy, Tayebeh

2018-03-01

Motivation to fact that zinc oxide nanowires and nanotubes with successful synthesis and the mechanism of formation, stability and electronic properties have been investigated; in this study the structural, electronic properties and quantum confinement effects of zinc oxide nanotubes and nanowires with different diameters are discussed. The calculations within density functional theory and the pseudo potential approximation are done. The electronic structure and energy gap for Armchair and zigzag ZnO nanotubes with a diameter of about 4 to 55 Angstrom and ZnO nanowires with a diameter range of 4 to 23 Å is calculated. The results revealed that due to the quantum confinement effects, by reducing the diameter of nanowires and nanotubes, the energy gap increases. Zinc oxide semiconductor nanostructures since having direct band gap with size-dependent and quantum confinement effect are recommended as an appropriate candidate for making nanoscale optoelectronic devices.

Effect of growth parameters on the optical properties of ZnO nanostructures grown by simple solution methods

NASA Astrophysics Data System (ADS)

Kothari, Anjana

2017-05-01

ZnO, a wide band gap semiconductor is of significant interest for a range of practical applications. One of the highly attractive features of ZnO is to grow variety of nanostructures by using low-cost techniques. In this paper, we report deposition of ZnO nanostructure rod-arrays (NRA) via low-temperature, solution-based deposition techniques such as chemical bath deposition (CBD) and microwave-assisted chemical bath deposition (MACBD). A detailed study of film deposition parameters such as variation in concentration of precursors and deposition temperature has been carried out. Compositional and structural study of the films has been done by X-ray Diffractometer to know the phase and purity of the final product. Morphological study of these structures has been carried out by Scanning Electron Microscopy. Optical study such as transmittance and diffuse reflectance of the films has been carried out as a function of growth parameters.

Application of electrochemically deposited nanostructured ZnO layers on quartz crystal microbalance for NO2 detection

NASA Astrophysics Data System (ADS)

Georgieva, B.; Petrov, M.; Lovchinov, K.; Ganchev, M.; Georgieva, V.; Dimova-Malinovska, D.

2014-11-01

The research was fixed on sensing behavior of ZnO nanostructured (NS) films to NO2 concentrations in the environment. The ZnO NS layers are deposited by electrochemical method on quartz resonators with Au electrodes. The sorption properties of ZnO layers were defined by measuring the resonant frequency shift (Δf) of the QCM-ZnO structure for different NO2 concentrations. The measurements were based on the correlation between the frequency shift of the QCM and additional mass loading (Δm) on the resonator calculated using Sauerbrey equation for the AT-cut quartz plate. Frequency - Time Characteristics (FTCs) of the samples were measured as a function of different NO2 concentrations in order to define the sorption abilities of ZnO layers. The experiments were carried out on a special set up in a dynamical regime. From FTCs the response and the recovery times of the QCM-ZnO structure were measured with varying NO2. Frequency shift changed from 23 Hz to 58Hz when NO2 was varied in the range of 250ppm - 5000ppm. The process of sorption was estimated as reversible and the sorption as physical. The obtained results demonstrated that QCM covered with the electrochemically deposited nanostructured ZnO films can be used as application in NO2 sensors.

Synthesis and characterization of ZnO nanostructures using palm olein as biotemplate

PubMed Central

2013-01-01

Background A green approach to synthesize nanomaterials using biotemplates has been subjected to intense research due to several advantages. Palm olein as a biotemplate offers the benefits of eco-friendliness, low-cost and scale-up for large scale production. Therefore, the effect of palm olein on morphology and surface properties of ZnO nanostructures were investigated. Results The results indicate that palm olein as a biotemplate can be used to modify the shape and size of ZnO particles synthesized by hydrothermal method. Different morphology including flake-, flower- and three dimensional star-like structures were obtained. FTIR study indicated the reaction between carboxyl group of palm olein and zinc species had taken place. Specific surface area enhanced while no considerable change were observed in optical properties. Conclusion Phase-pure ZnO particles were successfully synthesized using palm olein as soft biotemplating agent by hydrothermal method. The physico-chemical properties of the resulting ZnO particles can be tuned using the ratio of palm olein to Zn cation. PMID:23601826

Visible and UV photo-detection in ZnO nanostructured thin films via simple tuning of solution method.

PubMed

Khokhra, Richa; Bharti, Bandna; Lee, Heung-No; Kumar, Rajesh

2017-11-08

This study demonstrates significant visible light photo-detection capability of pristine ZnO nanostructure thin films possessing substantially high percentage of oxygen vacancies [Formula: see text] and zinc interstitials [Formula: see text], introduced by simple tuning of economical solution method. The demonstrated visible light photo-detection capability, in addition to the inherent UV light detection ability of ZnO, shows great dependency of [Formula: see text] and [Formula: see text] with the nanostructure morphology. The dependency was evaluated by analyzing the presence/percentage of [Formula: see text] and [Formula: see text] using photoluminescence (PL) and X-ray photoelectron spectroscopy (XPS) measurements. Morphologies of ZnO viz. nanoparticles (NPs), nanosheets (NSs) and nanoflowers (NFs), as a result of tuning of synthesis method contended different concentrations of defects, demonstrated different photo-detection capabilities in the form of a thin film photodetector. The photo-detection capability was investigated under different light excitations (UV; 380~420 nm, white ; λ > 420 nm and green; 490~570 nm). The as fabricated NSs photodetector possessing comparatively intermediate percentage of [Formula: see text] ~ 47.7% and [Formula: see text] ~ 13.8% exhibited superior performance than that of NPs and NFs photodetectors, and ever reported photodetectors fabricated by using pristine ZnO nanostructures in thin film architecture. The adopted low cost and simplest approach makes the pristine ZnO-NSs applicable for wide-wavelength applications in optoelectronic devices.

Synthesis of porous and nonporous ZnO nanobelt, multipod, and hierarchical nanostructure from Zn-HDS

NASA Astrophysics Data System (ADS)

Jang, Eue-Soon; Won, Jung-Hee; Kim, Young-Woon; Cheng, Zhen; Choy, Jin-Ho

2010-08-01

Zn based hydroxide double salts (Zn-HDS) with an interlayer spacing of 20 Å was produced by dissolving dumbbell-like ZnO crystal. The resulting Zn-HDS with a ribbon-like shape has a suitable morphology to explore the remarkably mild procedure for synthesis of ZnO nanobelts. We found that the intercalated water molecules into the Zn-HDS could play a key role in the ZnO nanobelts porosity. The nonporous ZnO nanobelts were successfully synthesized from the Zn-HDS by soft-solution process at 95 °C through mild dehydration agent as Na 2CO 3. As-synthesized ZnO nanobelts were grown along not only the [0 1 -1 0], but also the [2 -1 -1 0]. On the other hand, the porous ZnO nanobelts were obtained from the Zn-HDS by calcinations at 200 and 400 °C. In addition, flower-like ZnO multipod and hierarchical nanostructures were produced from the Zn-HDS by using of strong dehydration agent (NaOH) through hydrothermal reaction at 150 and 230 °C.

Simple chemical synthesis of novel ZnO nanostructures: Role of counter ions

NASA Astrophysics Data System (ADS)

Pudukudy, Manoj; Yaakob, Zahira

2014-04-01

This article reports the synthesis, characterisation and photocatalytic activity of novel ZnO nanostructures prepared via the thermal decomposition of hydrozincite. Hydrozincites were obtained by the conventional precipitation route using different zinc salts such as acetate, nitrate, chloride and sulphate. The effect of counter ions (CH3COO-, Cl-, NO3-, and SO42-) on the structural, textural, morphological and optical properties was investigated. Various characterisations depicted the active role of counter ions in the properties of ZnO. Hexagonal wurtzite structure of ZnO with fine crystalline size was obvious from the XRD results, irrespective of the counter ions. Electron microscopic images indicated the role of counter ions in the surface and internal morphology of ZnO nanomaterials. Special coral like agglomerated morphology of elongated particles with high porosity was observed for the ZnO prepared from acetate precursor. Spherical, elongated and irregular shaped bigger lumps of ZnO nanoparticles with various novel morphologies were resulted for the sulphate, nitrate and chloride precursors respectively. Highly ordered porous micro disc like morphology was noted for the ZnO samples prepared from the sulphate and nitrate salts. Photoluminescence spectra showed the characteristic blue and green emission bands, depicting the presence of large crystal defects and high oxygen vacancies in the samples. Photocatalytic activity of the as-prepared ZnO catalysts was examined by the degradation of methylene blue under UV light irradiation. Degradation results indicated their substantial activity with respect to the counter ions. ZnO prepared from the acetate precursor showed highest photoactivity due to its high surface area, special morphology and high oxygen vacancies.

The SL-assisted synthesis of hierarchical ZnO nanostructures and their enhanced photocatalytic activity

NASA Astrophysics Data System (ADS)

Miao, Ting-Ting; Guo, Yuan-Ru; Pan, Qing-Jiang

2013-06-01

Hierarchical ZnO nanoparticle-bar, nanomesh-lamina, and quasi-nanosphere structures have been successfully synthesized by the precipitation method with assistance of sodium lignosulphonate (SL). It is shown that the obtained ZnO nanomaterials are well crystallized and possess hexagonal wurtzite structure after calcination. Morphologies of ZnO with particle sizes ranging from 50 to 200 nm can be fabricated by tuning the SL amount in our synthetic route. Plenty of pores have been observed both in nanoparticle-bar and nanomesh-lamina ZnO. This may provide scaffold microenvironments to enhance their photocatalytic activity. It is evident that the synthesized ZnO exhibits good photocatalytic activity of degrading methylene blue, even under a very low-power UV illumination, which allows for the treatment of wastewater containing organic pollutants in an effective way. Among our synthesized nanomaterials, the nanomesh-lamina ZnO has the highest photodegradation efficiency, achieving nearly 100 % degradation only within 1.5 h (UV irradiation power of 12 W). As these ZnO nanomaterials are simply synthesized using SL which is a pulp industry by-product and their intrinsic hierarchical nanostructures show outstanding photocatalytic behavior, we expect the present controllable, environment-friendly, and cost-effective approach to be applied in the synthesis of small-sized ZnO materials.

Band-gap engineering by molecular mechanical strain-induced giant tuning of the luminescence in colloidal amorphous porous silicon nanostructures.

PubMed

Mughal, A; El Demellawi, J K; Chaieb, Sahraoui

2014-12-14

Nano-silicon is a nanostructured material in which quantum or spatial confinement is the origin of the material's luminescence. When nano-silicon is broken into colloidal crystalline nanoparticles, its luminescence can be tuned across the visible spectrum only when the sizes of the nanoparticles, which are obtained via painstaking filtration methods that are difficult to scale up because of low yield, vary. Bright and tunable colloidal amorphous porous silicon nanostructures have not yet been reported. In this letter, we report on a 100 nm modulation in the emission of freestanding colloidal amorphous porous silicon nanostructures via band-gap engineering. The mechanism responsible for this tunable modulation, which is independent of the size of the individual particles and their distribution, is the distortion of the molecular orbitals by a strained silicon-silicon bond angle. This mechanism is also responsible for the amorphous-to-crystalline transformation of silicon.

CuO-Decorated ZnO Hierarchical Nanostructures as Efficient and Established Sensing Materials for H2S Gas Sensors

PubMed Central

Vuong, Nguyen Minh; Chinh, Nguyen Duc; Huy, Bui The; Lee, Yong-Ill

2016-01-01

Highly sensitive hydrogen sulfide (H2S) gas sensors were developed from CuO-decorated ZnO semiconducting hierarchical nanostructures. The ZnO hierarchical nanostructure was fabricated by an electrospinning method following hydrothermal and heat treatment. CuO decoration of ZnO hierarchical structures was carried out by a wet method. The H2S gas-sensing properties were examined at different working temperatures using various quantities of CuO as the variable. CuO decoration of the ZnO hierarchical structure was observed to promote sensitivity for H2S gas higher than 30 times at low working temperature (200 °C) compared with that in the nondecorated hierarchical structure. The sensing mechanism of the hybrid sensor structure is also discussed. The morphology and characteristics of the samples were examined by scanning electron microscopy (SEM), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), UV-vis absorption, photoluminescence (PL), and electrical measurements. PMID:27231026

Facile Hydrothermal Preparation of ZNO/CO3O4 Heterogeneous Nanostructures and its Photovoltaic Effect

NASA Astrophysics Data System (ADS)

Wei, Fanan; Jiang, Minlin; Liu, Lianqing

2015-07-01

Photovoltaic technology offers great potential in the replacement of fossil fuel resources, but still suffers from high device fabrication cost. Herein, we attempted to provide a solution to these issues with heterogeneous nanostructures. Firstly, Zinc oxide (ZnO)/cobalt oxide (Co3O4) heterojunction nanowires are prepared through facile fabrication methods. By assembling Co(OH)2 nanoplates on ZnO nanowire arrays, the ZnO/Co3O4 heterogeneous nanostructures are uniformly synthesized on ITO coated glass and wafer. Current (I)-voltage (V) measurement through conductive atomic force microscope shows excellent photovoltaic effect. And, the heterojunction nanostructures shows unprecedented high open circuit voltage. Therefore, the potential application of the heterogeneous nanostructures in solar cells is demonstrated.

Nanostructured ZnO films on stainless steel are highly safe and effective for antimicrobial applications.

PubMed

Shim, Kyudae; Abdellatif, Mohamed; Choi, Eunsoo; Kim, Dongkyun

2017-04-01

The safety and effectiveness of antimicrobial ZnO films must be established for general applications. In this study, the antimicrobial activity, skin irritation, elution behavior, and mechanical properties of nanostructured ZnO films on stainless steel were evaluated. ZnO nanoparticle (NP) and ZnO nanowall (NW) structures were prepared with different surface roughnesses, wettability, and concentrations using an RF magnetron sputtering system. The thicknesses of ZnO NP and ZnO NW were approximately 300 and 620 nm, respectively, and ZnO NW had two diffraction directions of [0002] and [01-10] based on high-resolution transmission electron microscopy. The ZnO NW structure demonstrated 99.9% antimicrobial inhibition against Escherichia coli, Staphylococcus aureus, and Penicillium funiculosum, and no skin irritation was detected using experimental rabbits. Approximately 27.2 ± 3.0 μg L -1 Zn ions were eluted from the ZnO NW film at 100 °C for 24 h, which satisfies the WHO guidelines for drinking water quality. Furthermore, the Vickers hardness and fracture toughness of ZnO NW films on stainless steel were enhanced by 11 and 14% compared to those of the parent stainless steel. Based on these results, ZnO NW films on STS316L sheets are useful for household supplies, such as water pipes, faucets, and stainless steel containers.

Influences of Co doping on the structural and optical properties of ZnO nanostructured

NASA Astrophysics Data System (ADS)

Majeed Khan, M. A.; Wasi Khan, M.; Alhoshan, Mansour; Alsalhi, M. S.; Aldwayyan, A. S.

2010-07-01

Pure and Co-doped ZnO nanostructured samples have been synthesized by a chemical route. We have studied the structural and optical properties of the samples by using X-ray diffraction (XRD), field-emission scanning electron microscopy (FESEM), field-emission transmission electron microscope (FETEM), energy-dispersive X-ray (EDX) analysis and UV-VIS spectroscopy. The XRD patterns show that all the samples are hexagonal wurtzite structures. Changes in crystallite size due to mechanical activation were also determined from X-ray measurements. These results were correlated with changes in particle size followed by SEM and TEM. The average crystallite sizes obtained from XRD were between 20 to 25 nm. The TEM images showed the average particle size of undoped ZnO nanostructure was about 20 nm whereas the smallest average grain size at 3% Co was about 15 nm. Optical parameters such as absorption coefficient ( α), energy band gap ( E g ), the refractive index ( n), and dielectric constants ( σ) have been determined using different methods.

Electrochemical synthesis of one-dimensional ZnO nanostructures on ZnO seed layer for DSSC applications

NASA Astrophysics Data System (ADS)

Marimuthu, T.; Anandhan, N.; Thangamuthu, R.

2018-01-01

Electrochemical deposition of vertically aligned zinc oxide (ZnO) nanorods were prepared on ZnO seeded fluorine doped tin oxide (FTO) substrate in the solutions consisting of different concentrations of hexamethylenetetramine (HMTA). The electrochemical, structural, morphological, vibrational and optical properties were characterized by cyclic voltammetry (CV), X-ray diffraction (XRD), scanning electron microscope (SEM), Raman spectroscopy and photoluminescence (PL) spectroscopy, respectively. CV curves confirm that metallic zinc phase is not deposited as the HMTA concentration is about 9 mM in a deposition solution. XRD patterns of the as-prepared films show that the increasing HMTA concentrations from 0 mM to 9 mM not only increase the formation of zinc hydrate chloride (Zn5(OH)8Cl2·H2O) but also decrease and finally disappear the metallic Zn deposition. After the as-prepared films annealed at 450 ° C, the crystalline phases of Zn and Zn5(OH)8Cl2·H2O are completely converted to ZnO hexagonal wurtzite phase with high intense growth (002) plane orientation. SEM images support that the vertical growth of ZnO nanostructures (nanorods and petals) with a few flowers is found to be in the cordillera structure as the films are deposited in the solutions consisting of 3 mM, 6 mM and 9 mM HMTA respectively. Raman and PL spectra confirm that the ZnO film deposited in the solution consisting of 9 mM HMTA has a higher crystalline nature with lesser atomic defects and is also higher c-axis growth than that of other films deposited in the solutions consisting of 0 mM, 3 mM and 6 mM, respectively. UV-vis absorbance spectra corroborate that the ZnO film deposited in the solution consisting of 9 mM HMTA shows a high dye absorbance as compared with other films. The efficiency of DSSCs based on ZnO photoanodes deposited in the solutions consisting of 0 mM and 9 mM HMTA was 1.79 and 3.75%, respectively. Electrochemical impedance spectra revealed that DSSC based on ZnO photoanode

Precursor-controlled synthesis of hierarchical ZnO nanostructures, using oligoaniline-coated Au nanoparticle seeds

NASA Astrophysics Data System (ADS)

Krishnan, Deepti; Pradeep, T.

2009-07-01

Shape-selected synthesis of a large number of zinc oxide (ZnO) nano- and microstructures was achieved by the seed-mediated growth of oligoaniline-coated gold nanoparticle precursors. Distinctive ZnO structures such as nanoplates, nanospheres, microstars, microflowers, microthorns and micromultipods were synthesized by this method. Slightly different shapes were obtained in the absence of the seed solution. This is a fast, low temperature (60 °C) and biomimetic route to make a wide variety of structures. The structure and morphology of the nanostructures were studied by transmission electron microscopy (TEM) and scanning electron microscopy (SEM), respectively. Raman spectroscopy, Fourier-transform infrared (FTIR) spectroscopy and X-ray diffraction (XRD) were utilized for the characterization of the nanostructures. A growth mechanism for these nanostructures was proposed based on these results. The concentrations of the reacting species were the main parameter causing the changes in the morphologies. The variation in morphologies of these structures is believed to be due to the ability of the seed solution as well as polyvinylpyrrolidone (PVP) to selectively suppress/depress the growth of certain planes, allowing growth to occur only in certain specific directions. Changes in the amount of growth nuclei with varying sodium hydroxide (NaOH) concentration is also seen to affect the morphology of these structures.

Round-patterned ZnO nanostructure coated with siloxane-based polymer for nerve agent detection

NASA Astrophysics Data System (ADS)

Choi, Hyun Ji; Lee, Ji Won; Jeong, Dong-Cheol; Ha, Seonggyun; Song, Changsik; Boo, Jin-Hyo

2018-01-01

The alignment of zinc oxide (ZnO) nanostructures is expected to improve device sensitivities due to large surface areas which can be utilized to capture significant quantities of gas particles. In this study, we investigated patterned ZnO nanorods modified with polystyrene monolayers synthesized directly onto a quartz crystal microbalance (QCM) cell to increase the coating surface area of the sensing material. Also, we designed and synthesized a siloxane-based polymer (S1 polymer) as a sensing material. The patterned ZnO nanorods coated with S1 polymers were fabricated and used for the detection of dimethyl methylphosphonate (DMMP). The resonance frequency of QCM was shifted due to the adsorption and desorption of a compound at the surface of the modified electrodes. We have synthesized an S1 polymer that exhibited high sensitivity to DMMP. The patterned ZnO nanorods coated with the polymer also exhibited improved sensitivity due to an enhanced surface area capable of adsorbing more DMMP vapor.

Aqueous Black Colloids of Reticular Nanostructured Gold

NASA Astrophysics Data System (ADS)

Stanca, S. E.; Fritzsche, W.; Dellith, J.; Froehlich, F.; Undisz, A.; Deckert, V.; Krafft, C.; Popp, J.

2015-01-01

Since ancient times, noble gold has continuously contributed to several aspects of life from medicine to electronics. It perpetually reveals its new features. We report the finding of a unique form of gold, reticular nanostructured gold (RNG), as an aqueous black colloid, for which we present a one-step synthesis. The reticules consist of gold crystals that interconnect to form compact strands. RNG exhibits high conductivity and low reflection, and these features, coupled with the high specific surface area of the material, could prove valuable for applications in electronics and catalysis. Due to high absorption throughout the visible and infrared domain, RNG has the potential to be applied in the construction of sensitive solar cells or as a substrate for Raman spectroscopy.

Effect of co-doping process on topography, optical and electrical properties of ZnO nanostructured

NASA Astrophysics Data System (ADS)

Mohamed, R.; Mamat, M. H.; Malek, M. F.; Ismail, A. S.; Yusoff, M. M.; Syamsir, S. A.; Khusaimi, Z.; Rusop, M.

2018-05-01

We investigated of Undoped ZnO and Magnesium (Mg)-Aluminium (Al) co-doped Zinc Oxide (MAZO) nanostructured films were prepared by sol gel spin coating technique. The surface topography was analyzed using Atomic Force Microscopy (AFM). Based on the AFM results, Root Mean Square (RMS) of MAZO films have rougher surface compared to pure ZnO films. The optical and electrical properties of thin film samples were characterized using Uv-Vis spectroscopy and two point probes, current-voltage (I-V) measurements. The transmittance spectra for both thin samples was above 80% in the visible wavelength. The MAZO film shows the highest conductivity compared to pure ZnO films. This result indicates that the improvement of carrier mobility throughout doping process and possibly contribute by extra ion charge.

Highly Sensitive and Selective Ethanol Sensor Fabricated with In-Doped 3DOM ZnO.

PubMed

Wang, Zhihua; Tian, Ziwei; Han, Dongmei; Gu, Fubo

2016-03-02

ZnO is an important n-type semiconductor sensing material. Currently, much attention has been attracted to finding an effective method to prepare ZnO nanomaterials with high sensing sensitivity and excellent selectivity. A three-dimensionally ordered macroporous (3DOM) ZnO nanostructure with a large surface area is beneficial to gas and electron transfer, which can enhance the gas sensitivity of ZnO. Indium (In) doping is an effective way to improve the sensing properties of ZnO. In this paper, In-doped 3DOM ZnO with enhanced sensitivity and selectivity has been synthesized by using a colloidal crystal templating method. The 3DOM ZnO with 5 at. % of In-doping exhibits the highest sensitivity (∼88) to 100 ppm ethanol at 250 °C, which is approximately 3 times higher than that of pure 3DOM ZnO. The huge improvement to the sensitivity to ethanol was attributed to the increase in the surface area and the electron carrier concentration. The doping by In introduces more electrons into the matrix, which is helpful for increasing the amount of adsorbed oxygen, leading to high sensitivity. The In-doped 3DOM ZnO is a promising material for a new type of ethanol sensor.

Porous inorganic nanostructures with colloidal dimensions: synthesis and applications in electrochemical energy devices.

PubMed

Tartaj, Pedro; Amarilla, Jose M

2014-02-28

Porous inorganic nanostructures with colloidal dimensions can be considered as ideal components of electrochemical devices that operate on renewable energy sources. They combine nanoscale properties with good accessibility, a high number of active sites, short diffusion distances and good processability. Herein, we review some of the liquid-phase routes that lead to the controlled synthesis of these nanostructures in the form of non-hollow, hollow or yolk-shell configurations. From solar and fuel cells to batteries and supercapacitors, we put special emphasis on showing how these sophisticated structures can enhance the efficiency of electrochemical energy devices.

Accelerated Thermal-Aging-Induced Degradation of Organometal Triiodide Perovskite on ZnO Nanostructures and Its Effect on Hybrid Photovoltaic Devices.

PubMed

Kumar, S; Dhar, A

2016-07-20

Organometal halide perovskite materials are presently some of the pacesetters for light harvesting in hybrid photovoltaic devices because of their excellent inherent electrical and optical properties. However, long-term durability of such perovskite materials remains a major bottleneck for their commercialization especially in countries with hot and humid climatic conditions, thus violating the international standards for photovoltaic technology. Albeit, TiO2 as an electron-transport layer has been well investigated for perovskite solar cells; the high-temperature processing makes it unsuitable for low-cost and large-scale roll-to-roll production of flexible photovoltaic devices. Herein, we have chosen low-temperature (<150 °C)-processable nanostructured ZnO as the electron-selective layer and used a two-step method for sensitizing ZnO nanorods with methylammonium lead iodide (MAPbI3) perovskite, which is viable for flexible photovoltaic devices. We have also elaborately addressed the effect of the annealing duration on the conversion of a precursor solution into the required perovskite phase on ZnO nanostructures. The investigations show that the presence of ZnO nanostructures accelerates the rate of degradation of MAPbI3 films under ambient annealing and thus requires proper optimization. The role of ZnO in enhancing the degradation kinetics of the perovskite layer has been investigated by X-ray photoelectron spectroscopy and a buffer layer passivation technique. The effect of the annealing duration of the MAPbI3 perovskite on the optical, morphological, and compositional behavior has been closely studied and correlated with the photovoltaic efficiency. The study captures the degradation behavior of the commercially interesting MAPbI3 perovskite on a ZnO electron-transport layer and thus can provide insight for developing alternative families of perovskite material with better thermal and environmental stability for application in low-cost flexible photovoltaic

Two-color beam improvement of the colloidal particle lens array assisted surface nanostructuring

NASA Astrophysics Data System (ADS)

Afanasiev, Andrei; Bredikhin, Vladimir; Pikulin, Alexander; Ilyakov, Igor; Shishkin, Boris; Akhmedzhanov, Rinat; Bityurin, Nikita

2015-05-01

We consider laser nanostructuring of the material surface by means of a colloidal particle lens array. Here, the monolayer of dielectric micro- or nanospheres placed on the surface acts as an array of near-field lenses that focus the laser radiation into the multitude of distinct spots, allowing the formation of many structures in a single stage. We show that conversion of a small part of the energy of the femtosecond beam into the second harmonic (SH) is an efficient way to increase the surface density of obtained nanostructures. By combining the fundamental frequency and the SH, one benefits both from the power of the former and from the focusing ability of the latter. This combination provides an efficient nanostructuring with sphere diameter close to the wavelength of the second harmonic. The possibility to create arrays of nanostructures with surface density above 5 × 10 8 cm - 2 with femtosecond Ti:sapphire laser operating at 800 nm was demonstrated by employing 0.45 μm spheres.

Oxygen vacancy mediated enhanced photo-absorption from ZnO(0001) nanostructures fabricated by atom beam sputtering

DOE Office of Scientific and Technical Information (OSTI.GOV)

Solanki, Vanaraj; Joshi, Shalik R.; Mishra, Indrani

2016-08-07

The nanoscale patterns created on the ZnO(0001) surfaces during atom beam irradiation have been investigated here for their photo absorption response. Preferential sputtering, during irradiation, promotes Zn-rich zones that serve as the nucleation centers for the spontaneous creation of nanostructures. Nanostructured surfaces with bigger (78 nm) nanodots, displaying hexagonal ordering and long ranged periodic behavior, show higher photo absorption and a ∼0.09 eV reduced bandgap. These nanostructures also demonstrate higher concentration of oxygen vacancies which are crucial for these results. The enhanced photo-response, as observed here, has been achieved in the absence of any dopant elements.

In2O3-ZnO heterostructure development in electrical and photoluminescence properties of In2O3 1-D nanostructures

NASA Astrophysics Data System (ADS)

Shariati, M.; Ghafouri, V.

2014-05-01

Indium Oxide quasi one-dimensional (1D) nanostructures known as nanowires and nanorods synthesis using the thermal evaporation method, has been articulated. To nucleate growth sites, substrate seeding promoted 1D nanostructures growth. The catalyst-mediated growth mechanism showed more favorable morphologies and physical properties in under vacuum conditions associated with bottom-up technique. Scanning electron microscopy (SEM) results showed that the Zn-doped 1D nanostructures had spherical caps. The X-ray diffraction (XRD) pattern and energy-dispersive X-ray (EDX) spectrum indicated that these caps intensively associated with ZnO. Therefore, it was reasonable that the vapor-liquid-solid mechanism (VLS) was responsible for the growth of the In2O3-ZnO heterostructure nanowires. This technique enhances optical and electrical properties in nanostructures. The photoluminescence (PL) analysis in Zn-doped In2O3 nanowires and nanorods shows that the intensity of the visible and UV-region emissions overwhelmingly increases and resistance measurement professes the improvement of linear conductance in VLS growth mechanism.

Effects of optical band gap energy, band tail energy and particle shape on photocatalytic activities of different ZnO nanostructures prepared by a hydrothermal method

NASA Astrophysics Data System (ADS)

Klubnuan, Sarunya; Suwanboon, Sumetha; Amornpitoksuk, Pongsaton

2016-03-01

The dependence of the crystallite size and the band tail energy on the optical properties, particle shape and oxygen vacancy of different ZnO nanostructures to catalyse photocatalytic degradation was investigated. The ZnO nanoplatelets and mesh-like ZnO lamellae were synthesized from the PEO19-b-PPO3 modified zinc acetate dihydrate using aqueous KOH and CO(NH2)2 solutions, respectively via a hydrothermal method. The band tail energy of the ZnO nanostructures had more influence on the band gap energy than the crystallite size. The photocatalytic degradation of methylene blue increased as a function of the irradiation time, the amount of oxygen vacancy and the intensity of the (0 0 0 2) plane. The ZnO nanoplatelets exhibited a better photocatalytic degradation of methylene blue than the mesh-like ZnO lamellae due to the migration of the photoelectrons and holes to the (0 0 0 1) and (0 0 0 -1) planes, respectively under the internal electric field, that resulted in the enhancement of the photocatalytic activities.

Room-temperature sensitivity to NO2 exposure of electrochemically-deposited nanostructured ZnO layers

NASA Astrophysics Data System (ADS)

Lovchinov, K.; Petrov, M.; Ganchev, M.; Georgieva, V.; Nichev, H.; Georgieva, B.; Dimova-Malinovska, D.

2014-05-01

This paper reports studies on the sensitivity of ZnO layers to NO2 exposure. ZnO layers were fabricated by electrochemical deposition on the surface of a quartz crystal microbalance (QCM) with Au electrodes. The sensitivity was estimated using the frequency-time characteristics of the QCM. For this purpose, the resonance frequency shift was measured. The sorption process was investigated in a NO2 gas flow. The change in the resonance frequency, f of the QCM as a function of the loaded mass of NO2 was followed for a NO2 concentration of 500 ppm. Under gas exposure, the frequency decreased and reached saturation in five min. A frequency shift of 38 Hz was measured and a mass loading of 8.39 ng was calculated. The resonance frequency showed a very good recovery within two minutes after the NO2 flow was switched off. The results demonstrate that the electrodeposited nanostructured ZnO layers have a potential for application as NO2 gas sensors.

Growth Method-Dependent and Defect Density-Oriented Structural, Optical, Conductive, and Physical Properties of Solution-Grown ZnO Nanostructures.

PubMed

Rana, Abu Ul Hassan Sarwar; Lee, Ji Young; Shahid, Areej; Kim, Hyun-Seok

2017-09-10

It is time for industry to pay a serious heed to the application and quality-dependent research on the most important solution growth methods for ZnO, namely, aqueous chemical growth (ACG) and microwave-assisted growth (MAG) methods. This study proffers a critical analysis on how the defect density and formation behavior of ZnO nanostructures (ZNSs) are growth method-dependent. Both antithetical and facile methods are exploited to control the ZnO defect density and the growth mechanism. In this context, the growth of ZnO nanorods (ZNRs), nanoflowers, and nanotubes (ZNTs) are considered. The aforementioned growth methods directly stimulate the nanostructure crystal growth and, depending upon the defect density, ZNSs show different trends in structural, optical, etching, and conductive properties. The defect density of MAG ZNRs is the least because of an ample amount of thermal energy catered by high-power microwaves to the atoms to grow on appropriate crystallographic planes, which is not the case in faulty convective ACG ZNSs. Defect-centric etching of ZNRs into ZNTs is also probed and methodological constraints are proposed. ZNS optical properties are different in the visible region, which are quite peculiar, but outstanding for ZNRs. Hall effect measurements illustrate incongruent conductive trends in both samples.

Impedance analysis of PbS colloidal quantum dot solar cells with different ZnO nanowire lengths

NASA Astrophysics Data System (ADS)

Fukuda, Takeshi; Takahashi, Akihiro; Wang, Haibin; Takahira, Kazuya; Kubo, Takaya; Segawa, Hiroshi

2018-03-01

The photoconversion efficiency of colloidal quantum dot (QD) solar cells has been markedly improved by optimizing the surface passivation and device structure, and details of device physics are now under investigation. In this study, we investigated the resistance and capacitance components at the ZnO/PbS-QD interface and inside a PbS-QD layer by measuring the impedance spectrum while the interface area was controlled by changing the ZnO nanowire length. By evaluating the dependence of optical intensity and DC bias voltage on the ZnO nanowire length, only the capacitance was observed to be influenced by the interface area, and this indicates that photoinduced carriers are generated at the surface of PbS-QD. In addition, since the capacitance is proportional to the surface area of the QD, the interface area can be evaluated from the capacitance. Finally, photovoltaic performance was observed to increase with increasing ZnO nanowire length owing to the large interface area, and this result is in good agreement with the capacitance measurement.

Electrical and photocatalytic properties of boron-doped ZnO nanostructure grown on PET-ITO flexible substrates by hydrothermal method

NASA Astrophysics Data System (ADS)

Wang, Wei; Ai, Taotao; Yu, Qi

2017-02-01

Boron-doped zinc oxide sheet-spheres were synthesized on PET-ITO flexible substrates using a hydrothermal method at 90 °C for 5 h. The results of X-ray diffraction and X-ray photoelectron spectroscopy indicated that the B atoms were successfully doped into the ZnO lattice, the incorporation of B led to an increase in the lattice constant of ZnO and a change in its internal stress. The growth mechanism of pure ZnO nanorods and B-doped ZnO sheet-spheres was specifically investigated. The as-prepared BZO/PET-ITO heterojunction possessed obvious rectification properties and its positive turn-on voltage was 0.4 V. The carrier transport mechanisms involved three models such as hot carrier tunneling theory, tunneling recombination, and series-resistance effect were explored. The BZO/PET-ITO nanostructures were more effective than pure ZnO to degrade the RY 15, and the degradation rate reached 41.45%. The decomposition process with BZO nanostructure followed first-order reaction kinetics. The photocurrent and electrochemical impedance spectroscopy revealed that the B-doping could promote the separation of photo-generated electron-hole pairs, which was beneficial to enhance the photocatalytic activity. The photocurrent density of B-doped and pure ZnO/PET-ITO were 0.055 mA/cm2 and 0.016 mA/cm2, respectively. The photocatalytic mechanism of the sample was analyzed by the energy band theory.

Growth stimulation of Bacillus cereus and Pseudomonas putida using nanostructured ZnO thin film as transducer element

NASA Astrophysics Data System (ADS)

Loukanov, Alexandre; Filipov, Chavdar; Valcheva, Violeta; Lecheva, Marta; Emin, Saim

2015-04-01

The semiconductor zinc oxide nanomaterial (ZnO or ZnO:H) is widely used in advanced biosensor technology for the design of highly-sensitive detector elements for various applications. In the attempt to evaluate its effect on common microorganisms, two types of nanostructured transducer films have been used (average diameter 600-1000 nm). They have been prepared by using both wet sol-gel method and magnetron sputtering. Their polycrystalline structure and specific surface features have been analyzed by X-ray diffraction (XRD), scanning electron microscope, and atomic force microscope. The assessment of growth stimulation of bacteria was determined using epifluorescent microscope by cell staining with Live/Dead BacLight kit. In our experiments, the growth stimulation of Gram-positive and Gram-negative bacteria on nanostructured ZnO film is demonstrated by Bacillus cereus and Pseudomonas putida. These two bacterial species have been selected, because they are well known and studied in biosensor technologies, with structural difference of their cell walls. These pathogens are easy for with common source in the liquid food or some commercial products. Our data has revealed that the method of transducer film preparation influences strongly bacterial inhibition and division. These results present the transforming signal precisely, when ZnO is used in biosensor applications.

Low-temperature synthesis of rose-like ZnO nanostructures using surfactin and their photocatalytic activity.

PubMed

Reddy, A Satyanarayana; Kuo, Yi-Hao; Atla, Shashi B; Chen, Chien-Yen; Chen, Chien-Cheng; Shih, Ruey-Chyuan; Chang, Young-Fo; Maity, Jyoti Prakash; Chen, How-Ji

2011-06-01

Rose-like ZnO nanostructures were synthesized by the precipitation method using a biosurfactant (surfactin) as a templating-agent stabilizer. The concentration of surfactin in the precursor solution significantly influenced the thickness and density of the petals in the rose-like structures, and all samples were of a wurtzite phase. The thickness of the petal was found to decrease with increasing surfactin concentration. The average thickness of the petals was found to be between 10 and 13 nm. Photocatalytic degradation of methylene blue using rose-like ZnO nanostuctures was investigated, and the morphology, density and thickness of the ZnO petals were found to influence the photodegradation activity. The samples with loosely-spread petals, or plate-like ZnO structures, brought about the strongest photodegradation in comparison with the dense rose-like structures. The greater activity of the loose-petal structures was correlated with their higher absorption in the UV region in comparison with the other samples. The ZnO samples prepared using low surfactin concentrations had higher rate constant values, i.e., 9.1 x 10(-3) min(-1), which revealed that the photodegradation of methylene blue under UV irradiation progressed by a pseudo first-order kinetic reaction.

Effect of starting powders on the sintering of nanostructured ZrO2 ceramics by colloidal processing

NASA Astrophysics Data System (ADS)

Suárez, Gustavo; Sakka, Yoshio; Suzuki, Tohru S.; Uchikoshi, Tetsuo; Zhu, Xinwen; Aglietti, Esteban F.

2009-04-01

The effect of starting powders on the sintering of nanostructured tetragonal zirconia was evaluated. Suspensions were prepared with a concentration of 10 vol.% by mixing a bicomponent mixture of commercial powders (97 mol.% monoclinic zirconia with 3 mol.% yttria) and by dispersing commercially available tetragonal zirconia (3YTZ, Tosoh). The preparation of the slurry by bead-milling was optimized. Colloidal processing using 50 μm zirconia beads at 4000 rpm generated a fully deagglomerated suspension leading to the formation of high-density consolidated compacts (62% of the theoretical density (TD) for the bicomponent suspension). Optimum colloidal processing of the bicomponent suspension followed by the sintering of yttria and zirconia allowed us to obtain nanostructured tetragonal zirconia. Three different sintering techniques were investigated: normal sintering, two-step sintering and spark plasma sintering. The inhibition of grain growth in the bicomponent mixed powders in comparison with 3YTZ was demonstrated. The inhibition of the grain growth may have been caused by inter-diffusion of cations during the sintering.

Immobilization and direct electrochemistry of glucose oxidase on a tetragonal pyramid-shaped porous ZnO nanostructure for a glucose biosensor.

PubMed

Dai, Zhihui; Shao, Guojian; Hong, Jianmin; Bao, Jianchun; Shen, Jian

2009-01-01

A tetragonal pyramid-shaped porous ZnO (TPSP-ZnO) nanostructure is used for the immobilization, direct electrochemistry and biosensing of proteins. The prepared ZnO has a large surface area and good biocompatibility. Using glucose oxidase (GOD) as a model, this shaped ZnO is tested for immobilization of proteins and the construction of electrochemical biosensors with good electrochemical performances. The interaction between GOD and TPSP-ZnO is examined by using AFM, N(2) adsorption isotherms and electrochemical methods. The immobilized GOD at a TPSP-ZnO-modified glassy carbon electrode shows a good direct electrochemical behavior, which depends on the properties of the TPSP-ZnO. Based on a decrease of the electrocatalytic response of the reduced form of GOD to dissolved oxygen, the proposed biosensor exhibits a linear response to glucose concentrations ranging from 0.05 to 8.2mM with a detection limit of 0.01mM at an applied potential of -0.50V which has better biosensing properties than those from other morphological ZnO nanoparticles. The biosensor shows good stability, reproducibility, low interferences and can diagnose diabetes very fast and sensitively. Such the TPSP-ZnO nanostructure provides a good matrix for protein immobilization and biosensor preparation.

Multiscale modeling of nanostructured ZnO based devices for optoelectronic applications: Dynamically-coupled structural fields, charge, and thermal transport processes

NASA Astrophysics Data System (ADS)

Abdullah, Abdulmuin; Alqahtani, Saad; Nishat, Md Rezaul Karim; Ahmed, Shaikh; SIU Nanoelectronics Research Group Team

Recently, hybrid ZnO nanostructures (such as ZnO deposited on ZnO-alloys, Si, GaN, polymer, conducting oxides, and organic compounds) have attracted much attention for their possible applications in optoelectronic devices (such as solar cells, light emitting and laser diodes), as well as in spintronics (such as spin-based memory, and logic). However, efficiency and performance of these hybrid ZnO devices strongly depend on an intricate interplay of complex, nonlinear, highly stochastic and dynamically-coupled structural fields, charge, and thermal transport processes at different length and time scales, which have not yet been fully assessed experimentally. In this work, we study the effects of these coupled processes on the electronic and optical emission properties in nanostructured ZnO devices. The multiscale computational framework employs the atomistic valence force-field molecular mechanics, models for linear and non-linear polarization, the 8-band sp3s* tight-binding models, and coupling to a TCAD toolkit to determine the terminal properties of the device. A series of numerical experiments are performed (by varying different nanoscale parameters such as size, geometry, crystal cut, composition, and electrostatics) that mainly aim to improve the efficiency of these devices. Supported by the U.S. National Science Foundation Grant No. 1102192.

Spontaneous formation of nanostructures inside inkjet-printed colloidal drops

NASA Astrophysics Data System (ADS)

Yang, Xin; Thorne, Nathaniel; Sun, Ying

2013-11-01

Nanostructures formed in inkjet-printed colloidal drops are systematically examined with different substrates and ink formulations. Various deposition patterns from multi-ring, radial spoke, firework to spider web, foam and island structures are observed. With a high particle loading, deposition transitions from multi-ring near the drop edge to spider web and finally to foam and islands in the center of the drop with 20 nm sulfate-modified polystyrene particles. At the same particle loading, 200 nm particles self-assemble into radial spokes at the drop edge and islands in the center, due to reduced contact line pinning resulted from less particles. In drops with a low particle concentration, due to fingering instability of the contact line, 20 nm particles form radial spokes enclosed by a ring, while 200 nm particles assemble into firework-like structures without a ring. Moreover, at a high particle loading, ruptures are observed on the multi-ring structure formed by 20 nm carboxylic-modified particles, due to stronger capillary forces from the contact line. Furthermore, for a drop printed on a less hydrophilic substrate, the interparticle interactions enable a more uniform deposition rather than complex nanostructures.

Superhydrophobic Ag decorated ZnO nanostructured thin film as effective surface enhanced Raman scattering substrates

NASA Astrophysics Data System (ADS)

Jayram, Naidu Dhanpal; Sonia, S.; Poongodi, S.; Kumar, P. Suresh; Masuda, Yoshitake; Mangalaraj, D.; Ponpandian, N.; Viswanathan, C.

2015-11-01

The present work is an attempt to overcome the challenges in the fabrication of super hydrophobic silver decorated zinc oxide (ZnO) nanostructure thin films via thermal evaporation process. The ZnO nanowire thin films are prepared without any surface modification and show super hydrophobic nature with a contact angle of 163°. Silver is further deposited onto the ZnO nanowire to obtain nanoworm morphology. Silver decorated ZnO (Ag@ZnO) thin films are used as substrates for surface enhanced Raman spectroscopy (SERS) studies. The formation of randomly arranged nanowire and silver decorated nanoworm structure is confirmed using FESEM, HR-TEM and AFM analysis. Crystallinity and existence of Ag on ZnO are confirmed using XRD and XPS studies. A detailed growth mechanism is discussed for the formation of the nanowires from nanobeads based on various deposition times. The prepared SERS substrate reveals a reproducible enhancement of 3.082 × 107 M for Rhodamine 6G dye (R6G) for 10-10 molar concentration per liter. A higher order of SERS spectra is obtained for a contact angle of 155°. Thus the obtained thin films show the superhydrophobic nature with a highly enhanced Raman spectrum and act as SERS substrates. The present nanoworm morphology shows a new pathway for the construction of semiconductor thin films for plasmonic studies and challenges the orderly arranged ZnO nanorods, wires and other nano structure substrates used in SERS studies.

Influence of ZnO nanostructures in liquid crystal interfaces for bistable switching applications

NASA Astrophysics Data System (ADS)

Pal, Kaushik; Zhan, Bihong; Madhu Mohan, M. L. N.; Schirhagl, Romana; Wang, Guoping

2015-12-01

The controlled fabrication of nanometer-scale objects is without doubt one of the central issues in current science and technology. In this article, we exhibit a simple, one-step bench top synthesis of zinc oxide nano-tetrapods and nano-spheres which were tailored by the facial growth of nano-wires (diameter ≈ 24 nm; length ≈ 118 nm) and nano-cubes (≈395 nm edge) to nano-sphere (diameter ≈ 585 nm) appeaded. The possibilities of inexpensive, simple solvo-chemical synthesis of nanostructures were considered. In this article, a successful attempt has been made that ZnO nano-structures dispersed on well aligned hydrogen bonded liquid crystals (HBLC) comprising azelaic acid (AC) with p-n-alkyloxy benzoic acid (nBAO) by varying the respective alkyloxy carbon number (n = 5). The dispersion of nanomaterials with HBLC is an effective route to enhance the existing functionalities. A series of these composite materials were analyzed by polarizing optical microscope's electro-optical switching. An interesting feature of AC + nBAO is the inducement of tilted smectic G phase with increasing carbon chain length. Phase diagrams of the above hybrid ZnO nanomaterial influenced LC complex and pure LC were constructed and compared. The switching times, the contrast ratio and spontaneous polarization of the nanostructures-HBLC composite film were carried out by systematic investigation. The sample preparation parameters, such as the curing time and curing intensity were optimized. The critical applied voltage to achieve the switching bi-stability of our device is only 4.5 V, which is approximately twice its threshold voltage for Freedericksz transition. This performance puts the hybrid structure at the top level in the state of the art in application oriented research in optics of liquid crystalline composite materials.

Enhanced super-hydrophobic and switching behavior of ZnO nanostructured surfaces prepared by simple solution--immersion successive ionic layer adsorption and reaction process.

PubMed

Suresh Kumar, P; Sundaramurthy, J; Mangalaraj, D; Nataraj, D; Rajarathnam, D; Srinivasan, M P

2011-11-01

A simple and cost-effective successive ionic layer adsorption and reaction (SILAR) method was adopted to fabricate hydrophobic ZnO nanostructured surfaces on transparent indium-tin oxide (ITO), glass and polyethylene terephthalate (PET) substrates. ZnO films deposited on different substrates show hierarchical structures like spindle, flower and spherical shape with diameters ranging from 30 to 300 nm. The photo-induced switching behaviors of ZnO film surfaces between hydrophobic and hydrophilic states were examined by water contact angle and X-ray photoelectron spectroscopy (XPS) analysis. ZnO nanostructured films had contact angles of ~140° and 160°±2 on glass and PET substrates, respectively, exhibiting hydrophobic behavior without any surface modification or treatment. Upon exposure to ultraviolet (UV) illumination, the films showed hydrophilic behavior (contact angle: 15°±2), which upon low thermal stimuli revert back to its original hydrophobic nature. Such reversible and repeatable switching behaviors were observed upon cyclical exposure to ultraviolet radiation. These biomimetic ZnO surfaces exhibit good anti-reflective properties with lower reflectance of 9% for PET substrates. Thus, the present work is significant in terms of its potential application in switching devices, solar coatings and self-cleaning smart windows. Copyright © 2011 Elsevier Inc. All rights reserved.

A Colloidal Route to Detection of Organic Molecules Based on Surface-Enhanced Raman Spectroscopy Using Nanostructured Substrate Derived from Aerosols

NASA Astrophysics Data System (ADS)

Gen, Masao; Kakuta, Hideo; Kamimoto, Yoshihito; Wuled Lenggoro, I.

2011-06-01

A detection method based on the surface-enhanced Raman spectroscopy (SERS)-active substrate derived from aerosol nanoparticles and a colloidal suspension for detecting organic molecules of a model analyte (a pesticide) is proposed. This approach can detect the molecules of the derived from its solution with the concentration levels of ppb. For substrate fabrication, a gas-phase method is used to directly deposit Ag nanoparticles on to a silicon substrate having pyramidal structures. By mixing the target analyte with a suspension of Ag colloids purchased in advance, clotianidin analyte on Ag colloid can exist in junctions of co-aggregated Ag colloids. Using (i) a nanostructured substrate made from aerosol nanoparticles and (ii) colloidal suspension can increase the number of activity spots.

Efficiency enhancement of ZnO nanostructure assisted Si solar cell based on fill factor enlargement and UV-blue spectral down-shifting

NASA Astrophysics Data System (ADS)

Gholizadeh, A.; Reyhani, A.; Parvin, P.; Mortazavi, S. Z.

2017-05-01

ZnO nanostructures (including nano-plates and nano-rods (NRs)) are grown in various temperatures and Ar/O2 flow rates using thermal chemical vapor deposition, which affect the structure, nano-plate/NR population, and the quality of ZnO nanostructures. X-ray diffraction (XRD) attests that the peak intensity of the crystallographic plane (1 0 0) is correlated to nano-plate abundance. Moreover, optical properties elucidate that the population of nano-plates in samples strongly affect the band gap, binding energy of the exciton, and UV-visible (UV-vis) absorption and spectral luminescence emissions. In fact, the exciton binding energy reduces from ~100 to 80 meV when the population of nano-plates increases in samples. Photovoltaic characteristics based on the drop-casting on Si solar cells reveals three dominant factors, namely, the equivalent series resistance, decreasing reflectance, and down-shifting, in order to scale up the absolute efficiency by 3%. As a consequence, the oxygen vacancies in ZnO nanostructures give rise to the down-shifting and increase of free-carriers, leading to a reduction in the equivalent series resistance and an enlargement of fill factor. To obtain a larger I sc, reduction of spectral reflectance is essential; however, the down-shifting process is shown to be dominant by lessening the surface electron-hole recombination rate over the UV-blue spectral range.

Hydrodynamic fabrication of structurally gradient ZnO nanorods.

PubMed

Kim, Hyung Min; Youn, Jae Ryoun; Song, Young Seok

2016-02-26

We studied a new approach where structurally gradient nanostructures were fabricated by means of hydrodynamics. Zinc oxide (ZnO) nanorods were synthesized in a drag-driven rotational flow in a controlled manner. The structural characteristics of nanorods such as orientation and diameter were determined by momentum and mass transfer at the substrate surface. The nucleation of ZnO was induced by shear stress which plays a key role in determining the orientation of ZnO nanorods. The nucleation and growth of such nanostructures were modeled theoretically and analyzed numerically to understand the underlying physics of the fabrication of nanostructures controlled by hydrodynamics. The findings demonstrated that the precise control of momentum and mass transfer enabled the formation of ZnO nanorods with a structural gradient in diameter and orientation.

Screen-Printing of ZnO Nanostructures from Sol-Gel Solutions for Their Application in Dye-Sensitized Solar Cells.

PubMed

Sarkar, Kuhu; Braden, Erik V; Bonke, Shannon A; Bach, Udo; Müller-Buschbaum, Peter

2015-08-24

Diblock copolymers have been used in sol-gel synthesis to successfully tailor the nanoscale morphology of thin ZnO films. As the fabrication of several-micron-thick mesoporous films such as those required in dye-sensitized solar cells (DSSCs) was difficult with this approach, we exploited the benefits of diblock-copolymer-directed synthesis that made it compatible with screen printing. The simple conversion of the diblock copolymer ZnO precursor sol to a screen-printing paste was not possible as it resulted in poor film properties. To overcome this problem, an alternative route is proposed in which the diblock copolymer ZnO precursor sol is first blade coated and calcined, then converted to a screen-printing paste. This allows the benefits of diblock-copolymer-directed particle formation to be compatible with printing methods. The morphologies of the ZnO nanostructures were studied by SEM and correlated with the current density-voltage characteristics. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Growth parameter dependent structural and optical properties of ZnO nanostructures on Si substrate by a two-zone thermal CVD.

PubMed

Lee, Hee Kwan; Yu, Jae Su

2012-04-01

We investigated the effect of growth parameters on the structural and optical properties of the ZnO nanostructures (NSs) grown on Au-coated Si substrate by a two-zone thermal chemical vapor deposition. The morphologies of ZnO NSs were controlled by various growth parameters, such as growth temperature, O2 flow rate, and working pressure, for different thicknesses of Au layer. The nanorod-like ZnO NSs were formed at 915 degrees C and the growth of two-dimensional structures, i.e., nanosheets, was enhanced with the increase of growth temperature up to 965 degrees C. It was found that the low working pressure contributed to improvement in vertical alignment and uniformity of ZnO NSs. The Zn/O atomic % ratio, which plays a key role in the growth mechanism of ZnO NSs, was changed by the growth parameters. The Zn/O atomic % ratio was increased with increasing the growth temperature, while it was decreased with increasing the working pressure. Under proper O2 flow rate, the ZnO nanorods with good crystallinity were fabricated with a Zn/O atomic % ratio of -0.9. For various growth parameters, the photoluminescence emission was slightly shifted with the ultraviolet emission related to the near band edge transition.

Colloidal CdSe Quantum Rings.

PubMed

Fedin, Igor; Talapin, Dmitri V

2016-08-10

Semiconductor quantum rings are of great fundamental interest because their non-trivial topology creates novel physical properties. At the same time, toroidal topology is difficult to achieve for colloidal nanocrystals and epitaxially grown semiconductor nanostructures. In this work, we introduce the synthesis of luminescent colloidal CdSe nanorings and nanostructures with double and triple toroidal topology. The nanorings form during controlled etching and rearrangement of two-dimensional nanoplatelets. We discuss a possible mechanism of the transformation of nanoplatelets into nanorings and potential utility of colloidal nanorings for magneto-optical (e.g., Aharonov-Bohm effect) and other applications.

Bactericidal impact of Ag, ZnO and mixed AgZnO colloidal nanoparticles on H37Rv Mycobacterium tuberculosis phagocytized by THP-1 cell lines.

PubMed

Jafari, Alireza; Mosavari, Nader; Movahedzadeh, Farahnaz; Nodooshan, Saeedeh Jafari; Safarkar, Roya; Moro, Rossella; Kamalzadeh, Morteza; Majidpour, Ali; Boustanshenas, Mina; Mosavi, Tahereh

2017-09-01

The purpose of this research project was to infection of human macrophages (THP-1) cell lines by H 37 Rv strain of Mycobacterium tuberculosis (H 37 RvMTB) and find out the ratio/dilution of mixture silver (Ag NPs) and zinc oxide nanoparticles (ZnO NPs) whose ability to eliminate phagocytized bacteria compared to rifampicin. The colloidal Ag NPs and ZnO NPs were synthesized and their characteristics were evaluated. The THP-1 cell lines were infected with different concentration of H 37 RvMTB. Next, the infected cells were treated with different ratios/dilutions of Ag NPs, ZnO NPs and rifampicin. The THP-1 were lysed and were cultured in Lowenstein-Jensen agar medium, for eight weeks. The TEM and AFM images of NPs and H 37 RvMTB were supplied. It is observed that Ag NPs, 2 Ag :8 ZnO and 8 Ag :2 ZnO did not have any anti-tubercular effects on phagocytized H 37 RvMTB. Conversely, ZnO NPs somehow eliminated 18.7 × 10 4  CFU ml -1 of H 37 RvMTB in concentration of ∼ 0.468 ppm. To compare with 40 ppm of rifampicin, ∼ 0.663 ppm of 5 Ag :5 ZnO had the ability to kill of H 37 RvMTB, too. Based on previous research, ZnO NPs had strong anti-tubercular impact against H 37 RvMTB to in-vitro condition, but it was toxic in concentration of ∼ 0.468 ppm to both of THP-1 and normal lung (MRC-5) cell lines. It also seems that 5 Ag :5 ZnO is justified because in concentration of ∼ 0.663 ppm of 5 Ag :5 ZnO , phagocytized H 37 RvMTB into the THP-1 had died without any toxicity effects against THP-1 and also MRC-5 cell lines. It is obvious that the mixture of colloidal silver and zinc oxide NPs with ratio of 5 Ag :5 ZnO would be trustworthy options as anti-tubercular nano-drugs in future researches. Copyright © 2017. Published by Elsevier Ltd.

Improvement of antimony sulfide photo absorber performance by interface modification in Sb2S3-ZnO hybrid nanostructures

NASA Astrophysics Data System (ADS)

Ali, Asad; Hasanain, Syed Khurshid; Ali, Tahir; Sultan, Muhammad

2017-03-01

Metal-oxide chalcogenide nanostructures as part of hybrid systems are very important for photovoltaic and optoelectronic applications. It is however known that the various interfaces within the hybrid structures play a crucial role in limiting the efficiency of these devices. Here we report on the improvement of Sb2S3 structure through modification of interface between Zn-oxide nanostructures and chalcogenides. ZnO nanorods were grown on fluorine doped tin oxide (FTO) substrate by chemical bath deposition (CBD) method. X-ray diffraction (XRD) and SEM analysis confirmed the single phase wurtzite structure and c-axis orientation of the ZnO nanorod arrays. Antimony tri-sulfide (Sb2S3) was deposited on ZnO nanords by CBD and subsequently annealed at 300 °C in argon environment for 30 min. XRD and the XPS analysis of ZnO-Sb2S3 system showed the dominant presence of Sb2O3 rather than Sb2S3. Since oxidation of Sb2S3 is understood to proceed mainly from the ZnO-Sb2S3 interface, a ZnS interlayer was introduced between ZnO nanorods and Sb2S3 by chemical route. The subsequent structural and optical properties of the ZnO-ZnS-Sb2S3 system are analyzed in detail. The introduction of sulfide interlayer prevents the oxidation of Sb2S3 which is evident from reduced oxide phase in Sb2S3. Significant improvement in the structural and optical properties of Sb2S3 are reported as compared to the parent ZnO-Sb2S3 system. This gain in the optical properties of hybrid ZnO-ZnS-Sb2S3 nanostructures is explained as being related to successful prevention of Sb2O3 formation at the Sb-ZnO interface and stabilization of the desired Sb2S3.

Room-temperature synthesis of carnation-like ZnO@AgI hierarchical nanostructures assembled by AgI nanoparticles-decorated ZnO nanosheets with enhanced visible light photocatalytic activity.

PubMed

Huang, He; Huang, Ni; Wang, Zhonghua; Xia, Guangqiang; Chen, Ming; He, Lingling; Tong, Zhifang; Ren, Chunguang

2017-09-15

The preparation of highly efficient visible-light-driven photocatalyst for the photodegradation of organic pollutants has received much attention due to the increasing global energy crises and environmental pollution. In this study, carnation-like ZnO@AgI hierarchical nanostructures assembled by AgI nanoparticles-decorated ZnO nanosheets were successfully prepared via a room-temperature route. The as-prepared ZnO@AgI nanostructures exhibited highly efficient photocatalytic activity under visible light irradiation (λ>400nm). Under optimized AgI content, the ZnO@AgI-5% sample showed high photocatalytic activity, which was 25.7 and 1.5 times the activity of pure ZnO and pure AgI, respectively. Mechanism studies indicated that superoxide anion radicals (O 2 - ) was the main reactive species in the photocatalytic process. The high photocatalytic activity of the ZnO@AgI nanostructures is attributed to the highly active AgI nanoparticles and the heterojunction between AgI nanoparticles and ZnO nanosheets. The heterojunction structure reduced the recombination of the photogenerated electron-hole pairs in the conduction band (CB) and valence band (VB) of AgI nanoparticles by transferring the electrons from the CB of AgI nanoparticles to the CB of ZnO nanosheets. The composite of ZnO and AgI not only improves photocatalytic efficiency but also reduces photocatalyst cost, which is beneficial for practical application. Copyright © 2017 Elsevier Inc. All rights reserved.

Hybrid nanostructure heterojunction solar cells fabricated using vertically aligned ZnO nanotubes grown on reduced graphene oxide.

PubMed

Yang, Kaikun; Xu, Congkang; Huang, Liwei; Zou, Lianfeng; Wang, Howard

2011-10-07

Using reduced graphene oxide (rGO) films as the transparent conductive coating, inorganic/organic hybrid nanostructure heterojunction photovoltaic devices have been fabricated through hydrothermal synthesis of vertically aligned ZnO nanorods (ZnO-NRs) and nanotubes (ZnO-NTs) on rGO films followed by the spin casting of a poly(3-hexylthiophene) (P3HT) film. The data show that larger interfacial area in ZnO-NT/P3HT composites improves the exciton dissociation and the higher electrode conductance of rGO films helps the power output. This study offers an alternative to manufacturing nanostructure heterojunction solar cells at low temperatures using potentially low cost materials.

Effective tuning of electron charge and spin distribution in a dot-ring nanostructure at the ZnO interface

NASA Astrophysics Data System (ADS)

Chakraborty, Tapash; Manaselyan, Aram; Barseghyan, Manuk

2018-05-01

Electronic states and the Aharonov-Bohm effect in ZnO quantum dot-ring nanostructures containing few interacting electrons reveal several unique features. We have shown here that in contrast to the dot-rings made of conventional semiconductors, such as InAs or GaAs, the dot-rings in ZnO heterojunctions demonstrate several unique characteristics due to the unusual properties of quantum dots and rings in ZnO. In particular the energy spectra of the ZnO dot-ring and the Aharnov-Bohm oscillations are strongly dependant on the electron number in the dot or in the ring. Therefore even small changes of the confinement potential, sizes of the dot-ring or the magnetic field can drastically change the energy spectra and the behavior of Aharonov-Bohm oscillations in the system. Due to this interesting phenomena it is possible to effectively control with high accuracy the electron charge and spin distribution inside the dot-ring structure. This controlling can be achieved either by changing the magnetic field or the confinement potentials.

Eosin-Y sensitized core-shell TiO2-ZnO nano-structured photoanodes for dye-sensitized solar cell applications.

PubMed

Manikandan, V S; Palai, Akshaya K; Mohanty, Smita; Nayak, Sanjay K

2018-06-01

In the current investigation, TiO 2 and TiO 2 -ZnO (core-shell) spherical nanoparticles were synthesized by simple combined hydrolysis and refluxing method. A TiO 2 core nanomaterial on the shell material of ZnO was synthesized by utilizing variable ratios of ZnO. The structural characterization of TiO 2 -ZnO core/shell nanoparticles were done by XRD analysis. The spherical structured morphology of the TiO 2 -ZnO has been confirmed through field emission scanning electron microscopy (FE-SEM) and transmission electron microscopy (TEM) studies. The UV-visible spectra of TiO 2 -ZnO nanostructures were also compared with the pristine TiO 2 to investigate the shift of wavelength. The TiO 2 -ZnO core/shell nanoparticles at the interface efficiently collect the photogenarated electrons from ZnO and also ZnO act a barrier for reduced charge recombination of electrolyte and dye-nanoparticles interface. This combination improved the light absorption which induced the charge transfer ability and dye loading capacity of core-shell nanoparticles. An enhancement in the short circuit current (J sc ) from 1.67 mA/cm 2 to 2.1 mA/cm 2 has been observed for TiO 2 -ZnObased photoanode (with platinum free counter electrode), promises an improvement in the energy conversion efficiency by 57% in comparison with that of the DSSCs based on the pristine TiO 2 . Henceforth, TiO 2 -ZnO photoelectrode in ZnO will effectively act as barrier at the interface of TiO 2 -ZnO and TiO 2 , ensuring the potential for DSSC application. Copyright © 2018 Elsevier B.V. All rights reserved.

Luminescence dynamics of bound exciton of hydrogen doped ZnO nanowires

DOE PAGES

Yoo, Jinkyoung; Yi, Gyu -Chul; Chon, Bonghwan; ...

2016-04-11

In this study, all-optical camera, converting X-rays into visible photons, is a promising strategy for high-performance X-ray imaging detector requiring high detection efficiency and ultrafast detector response time. Zinc oxide is a suitable material for all-optical camera due to its fast radiative recombination lifetime in sub-nanosecond regime and its radiation hardness. ZnO nanostructures have been considered as proper building blocks for ultrafast detectors with spatial resolution in sub-micrometer scale. To achieve remarkable enhancement of luminescence efficiency n-type doping in ZnO has been employed. However, luminescence dynamics of doped ZnO nanostructures have not been thoroughly investigated whereas undoped ZnO nanostructures havemore » been employed to study their luminescence dynamics. Here we report a study of luminescence dynamics of hydrogen doped ZnO nanowires obtained by hydrogen plasma treatment. Hydrogen doping in ZnO nanowires gives rise to significant increase in the near-band-edge emission of ZnO and decrease in averaged photoluminescence lifetime from 300 to 140 ps at 10 K. The effects of hydrogen doping on the luminescent characteristics of ZnO nanowires were changed by hydrogen doping process variables.« less

The effect of induced strains on photoluminescence properties of ZnO nanostructures grown by thermal evaporation method

NASA Astrophysics Data System (ADS)

Arjmand, Yaser; Eshghi, Hosein

2016-03-01

In this paper, ZnO nanostructures have been synthesized by thermal evaporation process using metallic zinc powder in the presence of oxygen on p-Si (100) at different distances from the boat. The structural and optical characterizations have been carried out. The morphological study shows various shape nanostructures. XRD data indicate that all samples have a polycrystalline wurtzite hexagonal structure in such a way that the closer sample has a preferred orientation along (101) while the ones farther are grown along (002) direction. From the structural and optical data analysis, we found that the induced strains are the main parameter controlling the UV/green peaks ratios in the PL spectra of the studied samples.

Removal of micrometer size morphological defects and enhancement of ultraviolet emission by thermal treatment of Ga-doped ZnO nanostructures.

PubMed

Manzoor, Umair; Kim, Do K; Islam, Mohammad; Bhatti, Arshad S

2014-01-01

Mixed morphologies of Ga-doped Zinc Oxide (ZnO) nanostructures are synthesized by vapor transport method. Systematic scanning electron microscope (SEM) studies of different morphologies, after periodic heat treatments, gives direct evidence of sublimation. SEM micrographs give direct evidence that morphological defects of nanostructures can be removed by annealing. Ultra Violet (UV) and visible emission depends strongly on the annealing temperatures and luminescent efficiency of UV emission is enhanced significantly with each subsequent heat treatment. X-Ray diffraction (XRD) results suggest that crystal quality improved by annealing and phase separation may occur at high temperatures.

Voltammetric Sensor Based on Fe-doped ZnO and TiO2 Nanostructures-modified Carbon-paste Electrode for Determination of Levodopa

NASA Astrophysics Data System (ADS)

Anaraki Firooz, Azam; Hosseini Nia, Bahram; Beheshtian, Javad; Ghalkhani, Masoumeh

2017-10-01

In this study, undoped and 1 wt.% Fe-doped with ZnO, and TiO2 nanostructures were synthesized by a simple hydrothermal method without using templates. The influence of the Fe dopant on structural, optical and electrochemical response was studied by x-ray diffraction, scanning electron microscopy, UV-Vis spectra, photoluminescence spectra and electrochemical characterization system. The electrochemical response of the carbon paste electrode modified with synthesized nanostructures (undoped ZnO and TiO2 as well as doped with Fe ions) toward levodopa (L-Dopa) was studied. Cyclic voltammetry using provided modified electrodes showed electro-catalytic properties for electro-oxidation of L-Dopa and a significant reduction was observed in the anodic overvoltage compared to the bare electrode. The results indicated the presence of the sufficient dopants. The best response was obtained in terms of the current enhancement, overvoltage reduction, and reversibility improvement of the L-Dopa oxidation reaction under experimental conditions by the modified electrode with TiO2 nanoparticles doped with Fe ions.

Ultrasound-assisted synthesis of nano-structured Zinc(II)-based metal-organic frameworks as precursors for the synthesis of ZnO nano-structures.

PubMed

Bigdeli, Fahime; Ghasempour, Hosein; Azhdari Tehrani, Alireza; Morsali, Ali; Hosseini-Monfared, Hassan

2017-07-01

A 3D, porous Zn(II)-based metal-organic framework {[Zn 2 (oba) 2 (4-bpmn)]·(DMF) 1.5 } n (TMU-21), (4-bpmn=N,N'-Bis-pyridin-4-ylmethylene-naphtalene-1,5-diamine, H 2 oba=4,4'-oxybis(benzoic acid)) with nano-rods morphology under ultrasonic irradiation at ambient temperature and atmospheric pressure was prepared and characterized by scanning electron microscopy. Sonication time and concentration of initial reagents effects on the size and morphology of nano-structured MOFs were studied. Also {[Zn 2 (oba) 2 (4-bpmn)] (TMU-21) and {[Zn 2 (oba) 2 (4-bpmb)] (TMU-6), 4-bpmb=N,N'-(1,4-phenylene)bis(1-(pyridin-4-yl)methanimine) were easily prepared by mechanochemical synthesis. Nanostructures of Zinc(II) oxide were obtained by calcination of these compounds and their de-solvated analogue as activated MOFs, at 550°C under air atmosphere. As a result of that, different Nanostructures of Zinc(II) oxide were obtained. The ZnO nanoparticles were characterized by powder X-ray diffraction (XRD), scanning electron microscopy (SEM) and FT-IR spectroscopy. Copyright © 2016 Elsevier B.V. All rights reserved.

The use of novel biodegradable, optically active and nanostructured poly(amide-ester-imide) as a polymer matrix for preparation of modified ZnO based bionanocomposites

DOE Office of Scientific and Technical Information (OSTI.GOV)

Abdolmaleki, Amir, E-mail: abdolmaleki@cc.iut.ac.ir; Nanotechnology and Advanced Materials Institute, Isfahan University of Technology, Isfahan 84156-83111, Islamic Republic of Iran; Mallakpour, Shadpour, E-mail: mallak@cc.iut.ac.ir

Highlights: Black-Right-Pointing-Pointer A novel biodegradable and nanostructured PAEI based on two amino acids, was synthesized. Black-Right-Pointing-Pointer ZnO nanoparticles were modified via two different silane coupling agents. Black-Right-Pointing-Pointer PAEI/modified ZnO BNCs were synthesized through ultrasound irradiation. Black-Right-Pointing-Pointer ZnO particles were dispersed homogeneously in PAEI matrix on nanoscale. Black-Right-Pointing-Pointer The effect of ZnO nanoparticles on the properties of synthesized polymer was examined. -- Abstract: A novel biodegradable and nanostructured poly(amide-ester-imide) (PAEI) based on two different amino acids, was synthesized via direct polycondensation of biodegradable N,N Prime -bis[2-(methyl-3-(4-hydroxyphenyl)propanoate)]isophthaldiamide and N,N Prime -(pyromellitoyl)-bis-L-phenylalanine diacid. The resulting polymer was characterized by FT-IR, {sup 1}H NMR,more » specific rotation, elemental analysis, thermogravimetric analysis (TGA), differential scanning calorimetry (DSC), X-ray diffraction (XRD) and field emission scanning electron microscopy (FE-SEM) analysis. The synthesized polymer showed good thermal stability with nano and sphere structure. Then PAEI/ZnO bionanocomposites (BNCs) were fabricated via interaction of pure PAEI and ZnO nanoparticles. The surface of ZnO was modified with two different silane coupling agents. PAEI/ZnO BNCs were studied and characterized by FT-IR, XRD, UV/vis, FE-SEM and TEM. The TEM and FE-SEM results indicated that the nanoparticles were dispersed homogeneously in PAEI matrix on nanoscale. Furthermore the effect of ZnO nanoparticle on the thermal stability of the polymer was investigated with TGA and DSC technique.« less

Nanostructured ZnO films with various morphologies prepared by ultrasonic spray pyrolysis and its growing process

NASA Astrophysics Data System (ADS)

Ma, H. L.; Liu, Z. W.; Zeng, D. C.; Zhong, M. L.; Yu, H. Y.; Mikmekova, E.

2013-10-01

Nanostructured ZnO films were prepared by the ultrasonic spray pyrolysis method using Zn(CH3COO)2·2H2O as a precursor. The effects of substrate temperature (Ts) on the morphology and properties were systematically studied. As the Ts increased from 430 °C to 610 °C, the morphology of the film transforms from closed packed nanosheets to dense nanocrystalline film and then to hexagonal nanorod array. The dense film formed at a temperature of 550 °C has the lowest electric resistivity and highest carrier concentration. The optical transmittance for all prepared samples was higher than 90%. The photoluminescence (PL) properties varied with the Ts due to the internal defect difference. The growth mechanism of ZnO film involves island growth and diffusion, which was evident by observing the samples prepared at various times.

Sonochemical Synthesis of Zinc Oxide Nanostructures for Sensing and Energy Harvesting

NASA Astrophysics Data System (ADS)

Vabbina, Phani Kiran

Semiconductor nanostructures have attracted considerable research interest due to their unique physical and chemical properties at nanoscale which open new frontiers for applications in electronics and sensing. Zinc oxide nanostructures with a wide range of applications, especially in optoelectronic devices and bio sensing, have been the focus of research over the past few decades. However ZnO nanostructures have failed to penetrate the market as they were expected to, a few years ago. The two main reasons widely recognized as bottleneck for ZnO nanostructures are (1) Synthesis technique which is fast, economical, and environmentally benign which would allow the growth on arbitrary substrates and (2) Difficulty in producing stable p-type doping. The main objective of this research work is to address these two bottlenecks and find a solution that is inexpensive, environmentally benign and CMOS compatible. To achieve this, we developed a Sonochemical method to synthesize 1D ZnO Nanorods, core-shell nanorods, 2D nanowalls and nanoflakes on arbitrary substrates which is a rapid, inexpensive, CMOS compatible and environmentally benign method and allows us to grow ZnO nanostructures on any arbitrary substrate at ambient conditions while most other popular methods used are either very slow or involve extreme conditions such as high temperatures and low pressure. A stable, reproducible p-type doping in ZnO is one of the most sought out application in the field of optoelectronics. Here in this project, we doped ZnO nanostructures using sonochemical method to achieve a stable and reproducible doping in ZnO. We have fabricated a homogeneous ZnO radial p-n junction by growing a p-type shell around an n-type core in a controlled way using the sonochemical synthesis method to realize ZnO homogeneous core-shell radial p-n junction for UV detection. ZnO has a wide range of applications from sensing to energy harvesting. In this work, we demonstrate the successful fabrication of an

Scalable Manufacturing of Plasmonic Nanodisk Dimers and Cusp Nanostructures using Salting-out Quenching Method and Colloidal Lithography

PubMed Central

Juluri, Bala Krishna; Chaturvedi, Neetu; Hao, Qingzhen; Lu, Mengqian; Velegol, Darrell; Jensen, Lasse; Huang, Tony Jun

2014-01-01

Localization of large electric fields in plasmonic nanostructures enables various processes such as single molecule detection, higher harmonic light generation, and control of molecular fluorescence and absorption. High-throughput, simple nanofabrication techniques are essential for implementing plasmonic nanostructures with large electric fields for practical applications. In this article we demonstrate a scalable, rapid, and inexpensive fabrication method based on the salting-out quenching technique and colloidal lithography for the fabrication of two types of nanostructures with large electric field: nanodisk dimers and cusp nanostructures. Our technique relies on fabricating polystyrene doublets from single beads by controlled aggregation and later using them as soft masks to fabricate metal nanodisk dimers and nanocusp structures. Both of these structures have a well-defined geometry for the localization of large electric fields comparable to structures fabricated by conventional nanofabrication techniques. We also show that various parameters in the fabrication process can be adjusted to tune the geometry of the final structures and control their plasmonic properties. With advantages in throughput, cost, and geometric tunability, our fabrication method can be valuable in many applications that require plasmonic nanostructures with large electric fields. PMID:21692473

Low-cost and facile synthesis of Ni(OH)2/ZnO nanostructures for high-sensitivity glucose detection

NASA Astrophysics Data System (ADS)

Strano, V.; Mirabella, S.

2018-01-01

An efficient electrode for non-enzymatic glucose detection is produced with low-cost techniques on a Cu wire. ZnO nanorods (NRs) were grown on a Cu wire by chemical bath deposition and were used as the substrate for pulsed electrodeposition of nanostructured Ni(OH)2 flakes. The effect of the electrodeposition potential on the final morphology and electrochemical behavior of the Ni(OH)2/ZnO/Cu structures is reported. ZnO NRs resulted to be well dressed by Ni(OH)2 flakes and were tested as glucose sensing electrodes in 0.1 M NaOH solution, showing high sensitivities (up to 3 mA mM-1 cm-2) and long-term stability. The presence of ZnO NRs was shown to improve the performance of the glucose sensor in terms of electrochemical stability over the time and sensitivity compared to Ni(OH)2/Cu sample. The reported data demonstrate a simple, versatile and low-cost fabrication approach for effective glucose sensing system within a urban mines framework.

Probing defects in ZnO nanostructures by Photoluminescence and Positron Annihilation Spectroscopy

NASA Astrophysics Data System (ADS)

Ghosh, Manoranjan; Raychaudhuri, A. K.; Chaudhuri, S. K.; Das, Dipankar

2008-03-01

We have investigated defect related emission in the blue green region (2.2 eV -- 2.5 eV) of ZnO nanostructures having spherical (5 nm-15 nm) as well as those with hexagonal platelet and rod like morphologies (20nm-100 nm), synthesized by solvo-thermal route. This emission show anomalous size dependence. Emission energy near 2.2 eV, shifts to higher energy (2.5 eV) for increase in size beyond 20nm when shape of the nanostructures changes. This change in photoluminescence has a close correlation with the size (and shape) induced change in the positron trapping rate which is directly proportional to the defect concentration. The trapping rates show non-monotonous dependence on size. It increases initially as the size increases (5nm-15nm) and then decreases as the size increases beyond 20nm. While increase of the trapping rate on size reduction is expected due to accumulation of more defects at the surface, the initial dependence of the trapping rate on the size (below 20nm) is anomalous. The data are explained by the presence of defects like Zn vacancy and confinement due to size reduction.

Lattice diffusion and vapor solid growths forming nanoarchitectures on ZnO nanowires

NASA Astrophysics Data System (ADS)

Sombrio, Guilherme; Rivaldo-Gómez, C. M.; Pomar, Cesar A. D.; Souza, Jose A.

2017-12-01

We report hierarchical nanoarchitectures formed on the tips and sidewalls of ZnO nanowires which is formed on the top of microtubes. The whole growth process of these micro/nanostructures during thermal oxidation combines lattice/grain/surface ionic diffusion along with vapor solid mechanism. All the process takes place along with the presence of an electric current, which plays an important role forming the ZnO molecules due to Zn metal evaporation and attracting them to condense into nanostructures of several morphologies. The observation of a very long needle-like nanowire reveals the stack nature of the growth. These nanoarchitectures are rarely observed experimentally. Raman scattering confirms phonon confinement in the nanostructures. Photoluminescence measurements indicate a route for engineering defects on the surface of ZnO microtubes after the complete coalescence of the nanostructures through heat treatment. This experiment would be useful for improving nanostructure organization which could provide an impact in the manufacturability of nanostructure-based systems.

Uniform Fe3O4 coating on flower-like ZnO nanostructures by atomic layer deposition for electromagnetic wave absorption.

PubMed

Wan, Gengping; Wang, Guizhen; Huang, Xianqin; Zhao, Haonan; Li, Xinyue; Wang, Kan; Yu, Lei; Peng, Xiange; Qin, Yong

2015-11-21

An elegant atomic layer deposition (ALD) method has been employed for controllable preparation of a uniform Fe3O4-coated ZnO (ZnO@Fe3O4) core-shell flower-like nanostructure. The Fe3O4 coating thickness of the ZnO@Fe3O4 nanostructure can be tuned by varying the cycle number of ALD Fe2O3. When serving as additives for microwave absorption, the ZnO@Fe3O4-paraffin composites exhibit a higher absorption capacity than the ZnO-paraffin composites. For ZnO@500-Fe3O4, the effective absorption bandwidth below -10 dB can reach 5.2 GHz and the RL values below -20 dB also cover a wide frequency range of 11.6-14.2 GHz when the coating thickness is 2.3 mm, suggesting its potential application in the treatment of the electromagnetic pollution problem. On the basis of experimental observations, a mechanism has been proposed to understand the enhanced microwave absorption properties of the ZnO@Fe3O4 composites.

Removal of Micrometer Size Morphological Defects and Enhancement of Ultraviolet Emission by Thermal Treatment of Ga-Doped ZnO Nanostructures

PubMed Central

Manzoor, Umair; Kim, Do K.; Islam, Mohammad; Bhatti, Arshad S.

2014-01-01

Mixed morphologies of Ga-doped Zinc Oxide (ZnO) nanostructures are synthesized by vapor transport method. Systematic scanning electron microscope (SEM) studies of different morphologies, after periodic heat treatments, gives direct evidence of sublimation. SEM micrographs give direct evidence that morphological defects of nanostructures can be removed by annealing. Ultra Violet (UV) and visible emission depends strongly on the annealing temperatures and luminescent efficiency of UV emission is enhanced significantly with each subsequent heat treatment. X-Ray diffraction (XRD) results suggest that crystal quality improved by annealing and phase separation may occur at high temperatures. PMID:24489725

Ultrafast Formation of ZnO Nanorods via Seed-Mediated Microwave Assisted Hydrolysis Process

NASA Astrophysics Data System (ADS)

Tan, S. T.; Umar, A. A.; Yahaya, M.; Yap, C. C.; Salleh, M. M.

2013-04-01

One dimensional (1D) zinc oxide, ZnO nanostructures have shown promising results for usage in photodiode and optoelectronic device due to their high surface area. Faster and conventional method for synthesis ZnO nanorods has become an attention for researcher today. In this paper, ZnO nanorods have been successfully synthesized via two-step process, namely alcothermal seeding and seed-mediated microwave hydrolysis process. In typical process, the ZnO nanoseeds were grown in the growth solution that contained equimolar (0.04 M) of zinc nitrate hexahydrate, Zn (NO3).6H2O and hexamethylenetetramine, HMT. The growth process was carried inside the inverted microwave within 5- 20 s. The effect of growth parameters (i.e. concentration, microwave power, time reaction) upon the modification of ZnO morphology was studied. ZnO nanostructures were characterized by Field emission scanning electron microscope (FESEM) and X-ray diffraction (XRD). The densities of nanorods were evaluated by the Image J analysis. It was found that the morphology (e.g. shape and size) of nanostructures has changed drastically with the increment of growth solution concentration. The density of ZnO nanorods was proven to increase with the increasing of reaction time and microwave power. We hypothesize that the microwave power might enhance the rate of nucleation and promote the faster nanostructure growth as compared with the normal heating condition due to the superheating phenomenon. This method might promote a new and faster alternative way in nanostructure growth which can be applied in currently existing application.

Enhanced photoluminescence and Raman properties of Al-Doped ZnO nanostructures prepared using thermal chemical vapor deposition of methanol assisted with heated brass.

PubMed

Thandavan, Tamil Many K; Gani, Siti Meriam Abdul; San Wong, Chiow; Md Nor, Roslan

2015-01-01

Vapor phase transport (VPT) assisted by mixture of methanol and acetone via thermal evaporation of brass (CuZn) was used to prepare un-doped and Al-doped zinc oxide (ZnO) nanostructures (NSs). The structure and morphology were characterized by field emission scanning electron microscopy (FESEM) and x-ray diffraction (XRD). Photoluminescence (PL) properties of un-doped and Al-doped ZnO showed significant changes in the optical properties providing evidence for several types of defects such as zinc interstitials (Zni), oxygen interstitials (Oi), zinc vacancy (Vzn), singly charged zinc vacancy (VZn-), oxygen vacancy (Vo), singly charged oxygen vacancy (Vo+) and oxygen anti-site defects (OZn) in the grown NSs. The Al-doped ZnO NSs have exhibited shifted PL peaks at near band edge (NBE) and red luminescence compared to the un-doped ZnO. The Raman scattering results provided evidence of Al doping into the ZnO NSs due to peak shift from 145 cm-1 to an anomalous peak at 138 cm-1. Presence of enhanced Raman signal at around 274 and 743 cm-1 further confirmed Al in ZnO NSs. The enhanced D and G band in all Al-doped ZnO NSs shows possible functionalization and doping process in ZnO NSs.

Morphology evolution of hierarchical ZnO nanostructures modulated by supersaturation and growth temperature

NASA Astrophysics Data System (ADS)

Yan, Youguo; Zhou, Lixia; Yu, Lianqing; Zhang, Ye

2008-07-01

Three kinds of ZnO hierarchical structures, nanocombs with tube- and needle-shaped teeth and hierarchical nanorod arrays, were successfully synthesized through the chemical vapor deposition method. Combining the experimental parameters, the microcosmic growing conditions (growth temperature and supersaturation) along the flux was discussed at length, and, based on the conclusions, three reasonable growth processes were proposed. The results and discussions were beneficial to further realize the relation between the growing behavior of the nanomaterial and microcosmic conditions, and the hierarchical nanostructures obtained were also expected to have potential applications as functional blocks in future nanodevices. Furthermore, the study of photoluminescence further indicated that the physical properties were strongly dependent on the crystal structure.

Nucleant layer effect on nanocolumnar ZnO films grown by electrodeposition

NASA Astrophysics Data System (ADS)

Tolosa, Maria D. Reyes; Damonte, Laura C.; Brine, Hicham; Bolink, Henk J.; Hernández-Fenollosa, María A.

2013-03-01

Different ZnO nanostructured films were electrochemically grown, using an aqueous solution based on ZnCl2, on three types of transparent conductive oxides grow on commercial ITO (In2O3:Sn)-covered glass substrates: (1) ZnO prepared by spin coating, (2) ZnO prepared by direct current magnetron sputtering, and (3) commercial ITO-covered glass substrates. Although thin, these primary oxide layers play an important role on the properties of the nanostructured films grown on top of them. Additionally, these primary oxide layers prevent direct hole combination when used in optoelectronic devices. Structural and optical characterizations were carried out by scanning electron microscopy, atomic force microscopy, and optical transmission spectroscopy. We show that the properties of the ZnO nanostructured films depend strongly on the type of primary oxide-covered substrate used. Previous studies on different electrodeposition methods for nucleation and growth are considered in the final discussion.

Nucleant layer effect on nanocolumnar ZnO films grown by electrodeposition.

PubMed

Tolosa, Maria D Reyes; Damonte, Laura C; Brine, Hicham; Bolink, Henk J; Hernández-Fenollosa, María A

2013-03-23

Different ZnO nanostructured films were electrochemically grown, using an aqueous solution based on ZnCl2, on three types of transparent conductive oxides grow on commercial ITO (In2O3:Sn)-covered glass substrates: (1) ZnO prepared by spin coating, (2) ZnO prepared by direct current magnetron sputtering, and (3) commercial ITO-covered glass substrates. Although thin, these primary oxide layers play an important role on the properties of the nanostructured films grown on top of them. Additionally, these primary oxide layers prevent direct hole combination when used in optoelectronic devices. Structural and optical characterizations were carried out by scanning electron microscopy, atomic force microscopy, and optical transmission spectroscopy. We show that the properties of the ZnO nanostructured films depend strongly on the type of primary oxide-covered substrate used. Previous studies on different electrodeposition methods for nucleation and growth are considered in the final discussion.

Functional zinc oxide nanostructures for electronic and energy applications

NASA Astrophysics Data System (ADS)

Prasad, Abhishek

ZnO has proven to be a multifunctional material with important nanotechnological applications. ZnO nanostructures can be grown in various forms such as nanowires, nanorods, nanobelts, nanocombs etc. In this work, ZnO nanostructures are grown in a double quartz tube configuration thermal Chemical Vapor Deposition (CVD) system. We focus on functionalized ZnO Nanostructures by controlling their structures and tuning their properties for various applications. The following topics have been investigated: (1) We have fabricated various ZnO nanostructures using a thermal CVD technique. The growth parameters were optimized and studied for different nanostructures. (2) We have studied the application of ZnO nanowires (ZnONWs) for field effect transistors (FETs). Unintentional n-type conductivity was observed in our FETs based on as-grown ZnO NWs. We have then shown for the first time that controlled incorporation of hydrogen into ZnO NWs can introduce p-type characters to the nanowires. We further found that the n-type behaviors remained, leading to the ambipolar behaviors of hydrogen incorporated ZnO NWs. Importantly, the detected p- and n- type behaviors are stable for longer than two years when devices were kept in ambient conditions. All these can be explained by an ab initio model of Zn vacancy-Hydrogen complexes, which can serve as the donor, acceptors, or green photoluminescence quencher, depend on the number of hydrogen atoms involved. (3) Next ZnONWs were tested for electron field emission. We focus on reducing the threshold field (Eth) of field emission from non-aligned ZnO NWs. As encouraged by our results on enhancing the conductivity of ZnO NWs by hydrogen annealing described in Chapter 3, we have studied the effect of hydrogen annealing for improving field emission behavior of our ZnO NWs. We found that optimally annealed ZnO NWs offered much lower threshold electric field and improved emission stability. We also studied field emission from ZnO NWs at moderate

Patterned Well-Aligned ZnO Nanorods Assisted with Polystyrene Monolayer by Oxygen Plasma Treatment.

PubMed

Choi, Hyun Ji; Lee, Yong-Min; Yu, Jung-Hoon; Hwang, Ki-Hwan; Boo, Jin-Hyo

2016-08-05

Zinc oxide is known as a promising material for sensing devices due to its piezoelectric properties. In particular, the alignment of ZnO nanostructures into ordered nanoarrays is expected to improve the device sensitivity due to the large surface area which can be utilized to capture significant quantities of gas particles. However, ZnO nanorods are difficult to grow on the quartz substrate with well-ordered shape. So, we investigated nanostructures by adjusting the interval distance of the arranged ZnO nanorods using polystyrene (PS) spheres of various sizes (800 nm, 1300 nm and 1600 nm). In addition, oxygen plasma treatment was used to specify the nucleation site of round, patterned ZnO nanorod growth. Therefore, ZnO nanorods were grown on a quartz substrate with a patterned polystyrene monolayer by the hydrothermal method after oxygen plasma treatment. The obtained ZnO nanostructures were characterized by X-ray diffraction (XRD) and field-emission scanning electron microscope (FE-SEM).

Incorporation of ZnO and their composite nanostructured material into a cotton fabric platform for wearable device applications.

PubMed

Veluswamy, Pandiyarasan; Sathiyamoorthy, Suhasini; Khan, Faizan; Ghosh, Aranya; Abhijit, Majumdar; Hayakawa, Yasuhiro; Ikeda, Hiroya

2017-02-10

The central idea of this paper is to innovate a new approach for the development of wearable device materials through the coating of cotton fabric with ZnO and Sb-/Ag-/ZnO composites. The study was designed in order to have a clear understanding of the role of ZnO as well as the modified composite thereof under investigation. Cotton fabric with uniform ZnO/ZnO-composite layers on the surface was successfully synthesized via a solvothermal method. The growth behaviors were investigated by comparing ZnO and ZnO-composites. The structural, morphological, chemical states, optical, electrical and thermopower properties of these fabrics were studied. Nanostructured ZnO-composite fabric had enhanced UV shielding with a value of 83.96. It is found that the ZnO-composite fabrics have increased electrical conductivity. The thermopower value of the ZnO-composite fabric could reach 471.9μVK -1 . Such materials are anticipated to be worthwhile as wearable electronic devices and as protective textiles. Copyright © 2016 Elsevier Ltd. All rights reserved.

Impact of Temperature and UV Irradiation on Dynamics of NO2 Sensors Based on ZnO Nanostructures

PubMed Central

Pustelny, Tadeusz

2017-01-01

The main object of this study is the improvement of the dynamics of NO2 sensors based on ZnO nanostructures. Investigations presented in this paper showed that the combination of temperature and ultraviolet (UV) activation of the sensors can significantly decrease the sensor response and regeneration times. In comparison with the single activation method (elevated temperature or UV), these times for 1 ppm of NO2 decreased from about 10 min (or more) to less than 40 s. In addition, at the optimal conditions (200 °C and UV), sensors were very stable, were fully scalable (in the range on NO2 concentration of 1–20 ppm) and baseline drift was significantly reduced. Furthermore, in this paper, extensive studies of the influence of temperature and carrier gas (nitrogen and air) on NO2 sensing properties of the ZnO nanostructures were conducted. The NO2 sensing mechanisms of the sensors operating at elevated temperatures and under UV irradiation were also discussed. Our study showed that sensor responses to NO2 and response/regeneration times are comparable from sensor to sensor in air and nitrogen conditions, which suggests that the proposed simple technology connected with well-chosen operation conditions is repeatable. The estimated limit of detection of the sensors is within the level of ≈800 ppb in nitrogen and ≈700 ppb in air. PMID:29019924

Enabling antibacterial coating via bioinspired mineralization of nanostructured ZnO on fabrics under mild conditions.

PubMed

Manna, Joydeb; Begum, Gousia; Kumar, K Pranay; Misra, Sunil; Rana, Rohit K

2013-05-22

Herein, we present an environmentally benign method capable of mineralization and deposition of nanomaterials to introduce antibacterial functionalities into cotton fabrics under mild conditions. Similar to the way in which many naturally occurring biominerals evolve around the living organism under ambient conditions, this technique enables flexible substrates like the cotton fabric to be coated with inorganic-based functional materials. Specifically, our strategy involves the use of long-chain polyamines known to be responsible in certain biomineralization processes, to nucleate, organize, and deposit nanostructured ZnO on cotton bandage in an aqueous solution under mild conditions of room temperature and neutral pH. The ZnO-coated cotton bandages as characterized by SEM, confocal micro-Raman spectroscopy, XRD, UV-DRS, and fluorescence microscopy demonstrate the importance of polyamine in generating a stable and uniform coating of spindle-shaped ZnO particles on individual threads of the fabric. As the coating process requires only mild conditions, it avoids any adverse effect on the thermal and mechanical properties of the substrate. Furthermore, the ZnO particles on cotton fabric show efficient antibacterial activity against both gram-positive and gram-negetive bacteria. Therefore, the developed polyamine mediated bioinspired coating method provides not only a facile and "green" synthesis for coating on flexible substrate but also the fabrication of antibacterial enabled materials for healthcare applications.

In-vitro antibacterial study of zinc oxide nanostructures on Streptococcus sobrinus

NASA Astrophysics Data System (ADS)

Bakhori, Siti Khadijah Mohd; Mahmud, Shahrom; Ann, Ling Chuo; Sirelkhatim, Amna; Hasan, Habsah; Mohamad, Dasmawati; Masudi, Sam'an Malik; Seeni, Azman; Rahman, Rosliza Abd

2014-10-01

Zinc oxide nanostructures were prepared using a pilot plant of zinc oxide boiling furnace. Generally, it produced two types of nanostructures different in morphology; one is rod-like shaped (ZnO-1) and a plate-like shape (ZnO-2). The properties of ZnO were studied by structural, optical and morphological using XRD, PL and FESEM respectively. The XRD patterns confirmed the wurtzite structures of ZnO with the calculated crystallite size of 41 nm (ZnO-1) and 42 nm (ZnO-2) using Scherrer formula. The NBE peaks were determined by photoluminescence spectra which reveal peak at 3.25 eV and 3.23 eV for ZnO-1 and ZnO-2 respectively. Prior to that, the morphologies for both ZnO-1 and ZnO-2 were demonstrated from FESEM micrographs. Subsequently the antibacterial study was conducted using in-vitro broth dilution technique towards a gram positive bacterium Streptococcus sobrinus (ATCC 33478) to investigate the level of antibacterial effect of zinc oxide nanostructures as antibacterial agent. Gradual increment of ZnO concentrations from 10-20 mM affected the inhibition level after twenty four hours of incubation. In conjunction with concentration increment of ZnO, the percentage inhibition towards Streptococcus sobrinus was also increased accordingly. The highest inhibition occurred at 20 mM of ZnO-1 and ZnO-2 for 98% and 77% respectively. It showed that ZnO has good properties as antibacterial agent and relevancy with data presented by XRD, PL and FESEM were determined.

Nucleant layer effect on nanocolumnar ZnO films grown by electrodeposition

PubMed Central

2013-01-01

Different ZnO nanostructured films were electrochemically grown, using an aqueous solution based on ZnCl2, on three types of transparent conductive oxides grow on commercial ITO (In2O3:Sn)-covered glass substrates: (1) ZnO prepared by spin coating, (2) ZnO prepared by direct current magnetron sputtering, and (3) commercial ITO-covered glass substrates. Although thin, these primary oxide layers play an important role on the properties of the nanostructured films grown on top of them. Additionally, these primary oxide layers prevent direct hole combination when used in optoelectronic devices. Structural and optical characterizations were carried out by scanning electron microscopy, atomic force microscopy, and optical transmission spectroscopy. We show that the properties of the ZnO nanostructured films depend strongly on the type of primary oxide-covered substrate used. Previous studies on different electrodeposition methods for nucleation and growth are considered in the final discussion. PMID:23522332

Studies on visible light photocatalytic and antibacterial activities of nanostructured cobalt doped ZnO thin films prepared by sol-gel spin coating method.

PubMed

Poongodi, G; Anandan, P; Kumar, R Mohan; Jayavel, R

2015-09-05

Nanostructured cobalt doped ZnO thin films were deposited on glass substrate by sol-gel spin coating technique and characterized by X-ray diffraction, X-ray photoelectron spectroscopy, field-emission scanning electron microscopy, energy-dispersive X-ray spectroscopy and UV-Vis spectroscopy. The XRD results showed that the thin films were well crystalline with hexagonal wurtzite structure. The results of EDAX and XPS revealed that Co was doped into ZnO structure. FESEM images revealed that the films possess granular morphology without any crack and confirm that Co doping decreases the grain size. UV-Vis transmission spectra show that the substitution of Co in ZnO leads to band gap narrowing. The Co doped ZnO films were found to exhibit improved photocatalytic activity for the degradation of methylene blue dye under visible light in comparison with the undoped ZnO film. The decrease in grain size and extending light absorption towards the visible region by Co doping in ZnO film contribute equally to the improved photocatalytic activity. The bactericidal efficiency of Co doped ZnO films were investigated against a Gram negative (Escherichia coli) and a Gram positive (Staphylococcus aureus) bacteria. The optical density (OD) measurement showed better bactericidal activity at higher level of Co doping in ZnO. Copyright © 2015 Elsevier B.V. All rights reserved.

Seed/catalyst-free vertical growth of high-density electrodeposited zinc oxide nanostructures on a single-layer graphene

NASA Astrophysics Data System (ADS)

Aziz, Nur Suhaili Abd; Mahmood, Mohamad Rusop; Yasui, Kanji; Hashim, Abdul Manaf

2014-02-01

We report the seed/catalyst-free vertical growth of high-density electrodeposited ZnO nanostructures on a single-layer graphene. The absence of hexamethylenetetramine (HMTA) and heat has resulted in the formation of nanoflake-like ZnO structure. The results show that HMTA and heat are needed to promote the formation of hexagonal ZnO nanostructures. The applied current density plays important role in inducing the growth of ZnO on graphene as well as in controlling the shape, size, and density of ZnO nanostructures. High density of vertically aligned ZnO nanorods comparable to other methods was obtained. The quality of the ZnO nanostructures also depended strongly on the applied current density. The growth mechanism was proposed. According to the growth timing chart, the growth seems to involve two stages which are the formation of ZnO nucleation and the enhancement of the vertical growth of nanorods. ZnO/graphene hybrid structure provides several potential applications in electronics and optoelectronics such as photovoltaic devices, sensing devices, optical devices, and photodetectors.

High-quality ZnO inverse opals and related heterostructures as photocatalysts produced by atomic layer deposition

NASA Astrophysics Data System (ADS)

Long, Jie; Fu, Ming; Li, Caixia; Sun, Cuifeng; He, Dawei; Wang, Yongsheng

2018-10-01

ZnO with various nanostructures is widely investigated for high photoelectrochemical (PEC) catalysis performances due to its abundant and inert semiconducting properties with elevated electronic mobility and variable morphologies. Because the solar energy conversion efficiencies could possibly be further enhanced by the introduction of nanophotonic structures with larger surface ratios, high-quality ZnO inverse opals (IOs) were achieved by ALD method using O3 as the oxidant. The intrinsic UV emission peaks and PEC currents of ZnO IOs produced by O3 atomic layer deposition (ALD) method were much improved when compared to those made by H2O ALD and electrodeposition. ALD at higher temperatures (240 °C) can further enhance the crystalline quality and PEC performances. The optimal ALD thickness and filling fraction obtained by controlling ALD cycles, as well as the optimal photonic stop band position obtained by colloidal crystals with different sphere diameters were also discussed. It was found that conformally coated samples with TiO2 protection layers by ALD method using titanium tetrachloride as a precursor enhanced the photochemical stability of ZnO IOs. The photocorrosion was further reduced by inserting ALD Al2O3 inside the TiO2 protection layers. Heterostructured photonic crystals with double-layer IO structures with different pore periodicities were also developed for enhancing the PEC performances.

Structural studies of ZnO nanostructures by varying the deposition parameters

NASA Astrophysics Data System (ADS)

Yunus, S. H. A.; Sahdan, M. Z.; Ichimura, M.; Supee, A.; Rahim, S.

2017-01-01

The effect of Zinc Oxide (ZnO) thin film on the growth of ZnO nanorods (NRs) was investigated. The structures of ZnO NRs were synthesized by chemical bath deposition (CBD) method in aqueous solution of N2O6Zn.6H2O and C6H12N4 at 90°C of deposition temperature. One of the ZnO NRs samples was deposited on a ZnO seed layer coated on a glass substrate to investigate the properties of ZnO NRs without receiving effect of other materials. Next, for diode application, the ZnO NRs was deposited on tin monosulfide (SnS) coated on indium-tin-oxide (ITO) coated glass substrate (SnS/ITO). The next, the ZnO structural properties were studied from surface morphology, X-ray diffractometer (XRD) spectra, and chemical composition by using field emission scanning electron microscope (FESEM), XRD and energy dispersive X-ray Spectroscopy (EDX). The growth of ZnO NRs on ZnO seed layer was investigated by ZnO seed layer condition while the growth of ZnO NRs on SnS/ITO was investigated by deposition time and deposition temperature parameters. From FESEM images, aligned ZnO NRs were obtained, and the diameters of ZnO NRs were 0.024-3.94 µm. The SnS thin film was affected by the diameter of ZnO NRs which are the ZnO NRs grow on SnS thin films has a larger diameter compared to ZnO NRs grow on ZnO seed layer. Besides that, all of ZnO peaks observed from XRD corresponding to the wurzite structure and preferentially oriented along the c-axis. In addition, EDX shows a high composition of zinc (Zn) and oxygen (O) signals, which indicated that the NRs are indeed made up of Zn and O.

Photoluminescence of Sequential Infiltration Synthesized ZnO nanostructures

NASA Astrophysics Data System (ADS)

Ocola, Leonidas; Gosztola, David; Yanguas-Gil, Angel; Connolly, Aine

We have investigated a variation of atomic layer deposition (ALD), called sequential infiltration synthesis (SiS), as an alternate method to incorporate ZnO and other oxides inside polymethylmethacrylate (PMMA) and other polymers. Energy dispersive spectroscopy (EDS) results show that we synthesize ZnO up to 300 nm inside a PMMA film. Photoluminescence data on a PMMA film shows that we achieve a factor of 400X increase in photoluminescence (PL) intensity when comparing a blank Si sample and a 270 nm thick PMMA film, where both were treated with the same 12 alternating cycles of H2O and diethyl zinc (DEZ). PMMA is a well-known ebeam resist. We can expose and develop patterns useful for photonics or sensing applications first, and then convert them afterwards into a hybrid polymer-oxide material. We show that patterning does indeed affect the photoluminescence signature of native ZnO. We demonstrate we can track the growth of the ZnO inside the PMMA polymer using both photoluminescence and Raman spectroscopy and determine the point in the process where ZnO is first photoluminescent and also at which point ZnO first exhibits long range order in the polymer. This work was supported by the Department of Energy under Contract No. DE-AC02-06CH11357. Use of the Center for Nanoscale Materials was supported by the U. S. Department of Energy, Office of Basic Energy Sciences, under Contract No. DE-AC02-06CH11357.

Nanostructured TiO2 and ZnO prepared by using pressurized hot water and their eco-toxicological evaluation

NASA Astrophysics Data System (ADS)

Troppová, Ivana; Matějová, Lenka; Sezimová, Hana; Matěj, Zdeněk; Peikertová, Pavlína; Lang, Jaroslav

2017-06-01

The eco-toxicological effects of unconventionally prepared nanostructured TiO2 and ZnO were evaluated in this study, since both oxides are keenly investigated semiconductor photocatalysts in the last three decades. Unconventional processing by pressurized hot water was applied in order to crystallize oxide materials as an alternative to standard calcination. Acute biological toxicity of the synthesized oxides was evaluated using germination of Sinapis alba seed (ISO 11269-1) and growth of Lemna minor fronds (ISO 20079) and was compared to commercially available TiO2 Degussa P25. Toxicity results revealed that synthesized ZnO as well as TiO2 is toxic contrary to commercial TiO2 Degussa P25 which showled stimulation effect to L. minor and no toxicity to S. alba. ZnO was significantly more toxic than TiO2. The effect of crystallite size was considered, and it was revealed that small crystallite size and large surface area are not the toxicity-determining factors. Factors such as the rate of nanosized crystallites aggregation and concentration, shape and surface properties of TiO2 nanoparticles affect TiO2 toxicity to both plant species. Seriously, the dissolution of Ti4+ ions from TiO2 was also observed which may contribute to its toxicity. In case of ZnO, the dissolution of Zn2+ ions stays the main cause of its toxicity.

Ultra-Fast Microwave Synthesis of ZnO Nanorods on Cellulose Substrates for UV Sensor Applications

PubMed Central

Pimentel, Ana; Samouco, Ana; Araújo, Andreia; Martins, Rodrigo; Fortunato, Elvira

2017-01-01

In the present work, tracing and Whatman papers were used as substrates to grow zinc oxide (ZnO) nanostructures. Cellulose-based substrates are cost-efficient, highly sensitive and environmentally friendly. ZnO nanostructures with hexagonal structure were synthesized by hydrothermal under microwave irradiation using an ultrafast approach, that is, a fixed synthesis time of 10 min. The effect of synthesis temperature on ZnO nanostructures was investigated from 70 to 130 °C. An Ultra Violet (UV)/Ozone treatment directly to the ZnO seed layer prior to microwave assisted synthesis revealed expressive differences regarding formation of the ZnO nanostructures. Structural characterization of the microwave synthesized materials was carried out by scanning electron microscopy (SEM) and X-ray diffraction (XRD). The optical characterization has also been performed. The time resolved photocurrent of the devices in response to the UV turn on/off was investigated and it has been observed that the ZnO nanorod arrays grown on Whatman paper substrate present a responsivity 3 times superior than the ones grown on tracing paper. By using ZnO nanorods, the surface area-to-volume ratio will increase and will improve the sensor sensibility, making these types of materials good candidates for low cost and disposable UV sensors. The sensors were exposed to bending tests, proving their high stability, flexibility and adaptability to different surfaces. PMID:29140304

Colloidal synthesis of Cu-ZnO and Cu@CuNi-ZnO hybrid nanocrystals with controlled morphologies and multifunctional properties

NASA Astrophysics Data System (ADS)

Zeng, Deqian; Gong, Pingyun; Chen, Yuanzhi; Zhang, Qinfu; Xie, Qingshui; Peng, Dong-Liang

2016-06-01

Metal-semiconductor hybrid nanocrystals have received extensive attention owing to their multiple functionalities which can find wide technological applications. The utilization of low-cost non-noble metals to construct novel metal-semiconductor hybrid nanocrystals is important and meaningful for their large-scale applications. In this study, a facile solution approach is developed for the synthesis of Cu-ZnO hybrid nanocrystals with well-controlled morphologies, including nanomultipods, core-shell nanoparticles, nanopyramids and core-shell nanowires. In the synthetic strategy, Cu nanocrystals formed in situ serve as seeds for the heterogeneous nucleation and growth of ZnO, and it eventually forms various Cu-ZnO hetero-nanostructures under different reaction conditions. These hybrid nanocrystals possess well-defined and stable heterostructure junctions. The ultraviolet-visible-near infrared spectra reveal morphology-dependent surface plasmon resonance absorption of Cu and the band gap absorption of ZnO. Furthermore, we construct a novel Cu@CuNi-ZnO ternary hetero-nanostructure by incorporating the magnetic metal Ni into the pre-synthesized colloidal Cu nanocrystals. Such hybrid nanocrystals possess a magnetic Cu-Ni intermediate layer between the ZnO shell and the Cu core, and exhibit ferromagnetic/superparamagnetic properties which expand their functionalities. Finally, enhanced photocatalytic activities are observed in the as-prepared non-noble metal-ZnO hybrid nanocrystals. This study not only provides an economical way to prepare high-quality morphology-controlled Cu-ZnO hybrid nanocrystals for potential applications in the fields of photocatalysis and photovoltaic devices, but also opens up new opportunities in designing ternary non-noble metal-semiconductor hybrid nanocrystals with multifunctionalities.Metal-semiconductor hybrid nanocrystals have received extensive attention owing to their multiple functionalities which can find wide technological applications

Enhanced photoluminescence and heterojunction characteristics of pulsed laser deposited ZnO nanostructures

NASA Astrophysics Data System (ADS)

Mannam, Ramanjaneyulu; Kumar, E. Senthil; Priyadarshini, D. M.; Bellarmine, F.; DasGupta, Nandita; Ramachandra Rao, M. S.

2017-10-01

We report on the growth of ZnO nanostructures in different gas ambient (Ar and N2) using pulsed laser deposition technique. Despite the similar growth temperature, use of N2 ambient gas resulted in well-aligned nanorods with flat surface at the tip, whereas, nanorods grown with Ar ambient exhibited tapered tips. The Nanorods grown under N2 ambient exhibited additional Raman modes corresponding to N induced zinc interstitials. The nanorods are c-axis oriented and highly epitaxial in nature. Photoluminescence spectroscopy reveals that the UV emission can be significantly enhanced by 10 times for the nanorods grown under Ar ambient. The enhanced UV emission is attributed to the reduction in polarization electric field along the c-axis. n-ZnO nanorods/p-Si heterojunction showed rectifying I-V characteristics with a turn of voltage of 3.4 V.

Ag-ZnO nanostructure for ANTA explosive molecule detection

DOE Office of Scientific and Technical Information (OSTI.GOV)

Shaik, Ummar Pasha; Sangani, L. D. Varma; Gaur, Anshu

2016-05-23

Ag/ZnO nanostructure for surface enhanced Raman scattering application in the detection of ANTA explosive molecule is demonstrated. A highly rough ZnO microstructure was achieved by rapid thermal annealing of metallic Zn film. Different thickness Ag nanostructures are decorated over these ZnO microstructures by ion beam sputtering technique. Surface enhanced Raman spectroscopic studies carried out over Ag/ZnO substrates have shown three orders higher enhancement compared to bare Ag nanostructure deposited on the same substrate. The reasons behind such huge enhancement are discussed based on the morphology of the sample.

Influence of Protamine Functionalization on the Colloidal Stability of 1D and 2D Titanium Oxide Nanostructures.

PubMed

Rouster, Paul; Pavlovic, Marko; Horváth, Endre; Forró, László; Dey, Sandwip K; Szilagyi, Istvan

2017-09-26

The colloidal stability of titanium oxide nanosheets (TNS) and nanowires (TiONW) was studied in the presence of protamine (natural polyelectrolyte) in aqueous dispersions, where the nanostructures possessed negative net charge, and the protamine was positively charged. Regardless of their shape, similar charging and aggregation behaviors were observed for both TNS and TiONW. Electrophoretic experiments performed at different protamine loadings revealed that the adsorption of protamine led to charge neutralization and charge inversion depending on the polyelectrolyte dose applied. Light scattering measurements indicated unstable dispersions once the surface charge was close to zero or slow aggregation below and above the charge neutralization point with negatively or positively charged nanostructures, respectively. These stability regimes were confirmed by the electron microscopy images taken at different polyelectrolyte loadings. The protamine dose and salt-dependent colloidal stability confirmed the presence of DLVO-type interparticle forces, and no experimental evidence was found for additional interactions (e.g., patch-charge, hydrophobic, or steric forces), which are usually present in similar polyelectrolyte-particle systems. These findings indicate that the polyelectrolyte adsorbs on the TNS and TiONW surfaces in a flat and extended conformation giving rise to the absence of surface heterogeneities. Therefore, protamine is an excellent biocompatible candidate to form smooth surfaces, for instance in multilayers composed of polyelectrolytes and particles to be used in biomedical applications.

Fabrication of bioinspired nanostructured materials via colloidal self-assembly

NASA Astrophysics Data System (ADS)

Huang, Wei-Han

ultimate strains than nacre and pure GO paper (also synthesized by filtration). Specifically, it exhibits ˜30 times higher fracture energy than filtrated graphene paper and nacre, ˜100 times tougher than filtrated GO paper. Besides reinforced nanocomposites, we further explored the self-assembly of spherical colloids and the templating nanofabrication of moth-eye-inspired broadband antireflection coatings. Binary crystalline structures can be easily accomplished by spin-coating double-layer nonclose-packed colloidal crystals as templates, followed by colloidal templating. The polymer matrix between self-assembled colloidal crystal has been used as a sacrificial template to define the resulting periodic binary nanostructures, including intercalated arrays of silica spheres and polymer posts, gold nanohole arrays with binary sizes, and dimple-nipple antireflection coatings. The binary-structured antireflection coatings exhibit better antireflective properties than unitary coatings. Natural optical structures and nanocomposites teach us a great deal on how to create high performance artificial materials. The bottom-up technologies developed in this thesis are scalable and compatible with standard industrial processes, promising for manufacturing high-performance materials for the benefits of human beings.

ZnO nanomaterials based surface acoustic wave ethanol gas sensor.

PubMed

Wu, Y; Li, X; Liu, J H; He, Y N; Yu, L M; Liu, W H

2012-08-01

ZnO nanomaterials based surface acoustic wave (SAW) gas sensor has been investigated in ethanol environment at room temperature. The ZnO nanomaterials have been prepared through thermal evaporation of high-purity zinc powder. The as-prepared ZnO nanomaterials have been characterized with scanning electron microscopy (SEM), transmission electron microscopy (TEM) and X-ray Diffraction (XRD) techniques. The results indicate that the obtained ZnO nanomaterials, including many types of nanostructures such as nanobelts, nanorods, nanowires as well as nanosheets, are wurtzite with hexagonal structure and well-crystallized. The SAW sensor coated with the nanostructured ZnO materials has been tested in ethanol gas of various concentrations at room temperature. A network analyzer is used to monitor the change of the insertion loss of the SAW sensor when exposed to ethanol gas. The insertion loss of the SAW sensor varies significantly with the change of ethanol concentration. The experimental results manifest that the ZnO nanomaterials based SAW ethanol gas sensor exhibits excellent sensitivity and good short-term reproducibility at room temperature.

Characteristics of ZnO nanostructures synthesized by sonochemical reaction: Effects of continuous and pulse waves

DOE Office of Scientific and Technical Information (OSTI.GOV)

Widiyastuti, W., E-mail: widi@chem-eng.its.ac.id; Machmudah, Siti; Kusdianto,

Nanostructured ZnO was synthesized by a sonochemical reaction. Ultrasonic irradiation were set up in continuous, pulse in 3 seconds on and a second off (on:off=3:1), and pulse in 2 seconds on and a second off (on:off=2:1) wave modes for 1.5 hours. The characteristics of particles generated by these modes such as morphology, crystallinity, FTIR, photoluminescence, and photocatalytic activity to degrade methylene blue were compared. Zinc nitrate and ammonia water-based solutions were selected as chemicals without the addition of other surfactants. The morphology of the generated ZnO particles could be tuned from flower-like, needle- or hairy-like, and spherical structures by changingmore » the mode of ultrasonic irradiation from continuous, on:off=3:1, and on:off=2:1 modes, respectively. The generated particles indicated that a wurtzite structure of ZnO in a hexagonal phase was formed. The crystalline sizes of particles generated in continuous, on:off=3:1, and on:off=2:1 modes were 28, 27, 24 nm. A similar position of reduction peak of FTIR in all samples indicated that no differences in particles chemical bonding characteristics. Photoluminescence intensity was also decreased with changes the wave mode from continuous to pulse. Photocatalytic activity was also evaluated resulting in particles synthesized by continuous mode had the highest methylene blue degradation degree following by on:off=3:1, and on:off=2:1 modes.« less

Characteristics of ZnO nanostructures synthesized by sonochemical reaction: Effects of continuous and pulse waves

NASA Astrophysics Data System (ADS)

Widiyastuti, W.; Machmudah, Siti; Kusdianto, Nurtono, Tantular; Winardi, Sugeng

2015-12-01

Nanostructured ZnO was synthesized by a sonochemical reaction. Ultrasonic irradiation were set up in continuous, pulse in 3 seconds on and a second off (on:off=3:1), and pulse in 2 seconds on and a second off (on:off=2:1) wave modes for 1.5 hours. The characteristics of particles generated by these modes such as morphology, crystallinity, FTIR, photoluminescence, and photocatalytic activity to degrade methylene blue were compared. Zinc nitrate and ammonia water-based solutions were selected as chemicals without the addition of other surfactants. The morphology of the generated ZnO particles could be tuned from flower-like, needle- or hairy-like, and spherical structures by changing the mode of ultrasonic irradiation from continuous, on:off=3:1, and on:off=2:1 modes, respectively. The generated particles indicated that a wurtzite structure of ZnO in a hexagonal phase was formed. The crystalline sizes of particles generated in continuous, on:off=3:1, and on:off=2:1 modes were 28, 27, 24 nm. A similar position of reduction peak of FTIR in all samples indicated that no differences in particles chemical bonding characteristics. Photoluminescence intensity was also decreased with changes the wave mode from continuous to pulse. Photocatalytic activity was also evaluated resulting in particles synthesized by continuous mode had the highest methylene blue degradation degree following by on:off=3:1, and on:off=2:1 modes.

ZnO based potentiometric and amperometric nanosensors.

PubMed

Willander, Magnus; Khun, Kimleang; Ibupoto, Zafar Hussain

2014-09-01

The existence of nanomaterials provides the solid platform for sensing applications due to owing of high sensitivity and a low concentration limit of detection. More likely used nanomaterials for sensing applications includes gold nanoparticles, carbon nanotubes, magnetic nanoparticles such as Fe3O4, quantum dots and metal oxides etc. Recently nanomaterial and biological detection becomes an interdisciplinary field and is very much focussed by the researchers. Among metal oxides ZnO is largely considered due to its less toxic nature, biocompatible, cheap and easy to synthesis. ZnO nanomaterial is highly used for the chemical sensing, especially electrochemical sensing due to its fascinating properties such as high surface to volume ratio, atoxic, biosafe and biocompatible. Moreover, ZnO nanostructures exhibit unique features which could expose a suitable nanoenviroment for the immobilization of proteineous material such as enzymes, DNA, antibodies, etc. and in doing so it retains the biological efficiency of the immobilized bio sensitive material. The following review describes the two different coatings (i.e., ionophore and enzyme) on the surface of ZnO nanorods for the chemical sensing of zinc ion detection, thallium (I) ion detection, and L-lactic acid and the measurement of galactose molecules. ZnO nanorods provide the excellent transducing properties in the generation of strong electrical signals. Moreover, this review is very much focused on the applications of ZnO nanostructures in the sensing field.

Colloidal synthesis of Cu-ZnO and Cu@CuNi-ZnO hybrid nanocrystals with controlled morphologies and multifunctional properties.

PubMed

Zeng, Deqian; Gong, Pingyun; Chen, Yuanzhi; Zhang, Qinfu; Xie, Qingshui; Peng, Dong-Liang

2016-06-02

Metal-semiconductor hybrid nanocrystals have received extensive attention owing to their multiple functionalities which can find wide technological applications. The utilization of low-cost non-noble metals to construct novel metal-semiconductor hybrid nanocrystals is important and meaningful for their large-scale applications. In this study, a facile solution approach is developed for the synthesis of Cu-ZnO hybrid nanocrystals with well-controlled morphologies, including nanomultipods, core-shell nanoparticles, nanopyramids and core-shell nanowires. In the synthetic strategy, Cu nanocrystals formed in situ serve as seeds for the heterogeneous nucleation and growth of ZnO, and it eventually forms various Cu-ZnO hetero-nanostructures under different reaction conditions. These hybrid nanocrystals possess well-defined and stable heterostructure junctions. The ultraviolet-visible-near infrared spectra reveal morphology-dependent surface plasmon resonance absorption of Cu and the band gap absorption of ZnO. Furthermore, we construct a novel Cu@CuNi-ZnO ternary hetero-nanostructure by incorporating the magnetic metal Ni into the pre-synthesized colloidal Cu nanocrystals. Such hybrid nanocrystals possess a magnetic Cu-Ni intermediate layer between the ZnO shell and the Cu core, and exhibit ferromagnetic/superparamagnetic properties which expand their functionalities. Finally, enhanced photocatalytic activities are observed in the as-prepared non-noble metal-ZnO hybrid nanocrystals. This study not only provides an economical way to prepare high-quality morphology-controlled Cu-ZnO hybrid nanocrystals for potential applications in the fields of photocatalysis and photovoltaic devices, but also opens up new opportunities in designing ternary non-noble metal-semiconductor hybrid nanocrystals with multifunctionalities.

Nanostructured zinc oxide films synthesized by successive chemical solution deposition for gas sensor applications

DOE Office of Scientific and Technical Information (OSTI.GOV)

Lupan, O.; Department of Physics, University of Central Florida, 4000 Central Florida Blvd., Orlando, FL 32816-2385; Chow, L.

2009-01-08

Nanostructured ZnO thin films have been deposited using a successive chemical solution deposition method. The structural, morphological, electrical and sensing properties of the films were studied for different concentrations of Al-dopant and were analyzed as a function of rapid photothermal processing temperatures. The films were investigated by X-ray diffraction, scanning electron microscopy, energy dispersive X-ray spectroscopy, X-ray photoelectron and micro-Raman spectroscopy. Electrical and gas sensitivity measurements were conducted as well. The average grain size is 240 and 224 A for undoped ZnO and Al-doped ZnO films, respectively. We demonstrate that rapid photothermal processing is an efficient method for improving themore » quality of nanostructured ZnO films. Nanostructured ZnO films doped with Al showed a higher sensitivity to carbon dioxide than undoped ZnO films. The correlations between material compositions, microstructures of the films and the properties of the gas sensors are discussed.« less

Second-harmonic generation of ZnO nanoparticles synthesized by laser ablation of solids in liquids

NASA Astrophysics Data System (ADS)

Rocha-Mendoza, Israel; Camacho-López, Santiago; Luna-Palacios, Yryx Y.; Esqueda-Barrón, Yasmín; Camacho-López, Miguel A.; Camacho-López, Marco; Aguilar, Guillermo

2018-02-01

We report the synthesis of small zinc oxide nanoparticles (ZnO NPs) based colloidal suspensions and the study of second-harmonic generation from aggregated ZnO NPs deposited on glass substrates. The colloidal suspensions were obtained using the laser ablation of solids in liquids technique, ablating a Zn solid target immersed in acetone as the liquid medium, with ns-laser pulses (1064 nm) of a Nd-YAG laser. The per pulse laser fluence, the laser repetition rate frequency and the ablation time were kept constant. The absorption evolution of the obtained suspensions was optically characterized through absorption spectroscopy until stabilization. Raman spectroscopy, SEM and HRTEM were used to provide evidence of the ZnO NPs structure. HRTEM results showed that 5-8 nm spheroids ZnO NPs were obtained. Strong second-harmonic signal is obtained from random ZnO monocrystalline NPs and from aggregated ZnO NPs, suggesting that the high efficiency of the nonlinear process may not depend on the NPs size or aggregation state.

Aqueous chemical growth of free standing vertical ZnO nanoprisms, nanorods and nanodiskettes with improved texture co-efficient and tunable size uniformity

NASA Astrophysics Data System (ADS)

Ram, S. D. Gopal; Ravi, G.; Athimoolam, A.; Mahalingam, T.; Kulandainathan, M. Anbu

2011-12-01

Tuning the morphology, size and aspect ratio of free standing ZnO nanostructured arrays by a simple hydrothermal method is reported. Pre-coated ZnO seed layers of two different thicknesses (≈350 nm or 550 nm) were used as substrates to grow ZnO nanostructures for the study. Various parameters such as chemical ambience, pH of the solution, strength of the Zn2+ atoms and thickness of seed bed are varied to analyze their effects on the resultant ZnO nanostructures. Vertically oriented hexagonal nanorods, multi-angular nanorods, hexagonal diskette and popcorn-like nanostructures are obtained by altering the experimental parameters. All the produced nanostructures were analysed by X-ray powder diffraction analysis and found to be grown in the (002) orientation of wurtzite ZnO. The texture co-efficient of ZnO layer was improved by combining a thick seed layer with higher cationic strength. Surface morphological studies reveal various nanostructures such as nanorods, diskettes and popcorn-like structures based on various preparation conditions. The optical property of the closest packed nanorods array was recorded by UV-VIS spectrometry, and the band gap value simulated from the results reflect the near characteristic band gap of ZnO. The surface roughness profile taken from the Atomic Force Microscopy reveals a roughness of less than 320 nm.

Photoluminescence quenching processes by NO2 adsorption in ZnO nanostructured films

NASA Astrophysics Data System (ADS)

Cretı, A.; Valerini, D.; Taurino, A.; Quaranta, F.; Lomascolo, M.; Rella, R.

2012-04-01

The optical response by NO2 gas adsorption at different concentrations has been investigated, at room temperature, in ZnO nanostructured films grown by controlled vapor phase deposition. The variation (quenching) in the photoluminescence signal from excitonic and defects bands, due to the interactions between the oxidizing gas molecules and the sample surface, has been detected and dynamic responses and calibration curves as a function of gas concentration have been obtained and analyzed for each band. We showed that the sensing response results larger in excitonic band than in defect one and that the emission signal rises from two different quenchable and unquenchable states. A simple model was proposed in order to explain the quenching processes on the emission intensity and to correlate them to the morphological features of the samples. Finally, the reversibility of the quenching effects has also been tested at high gas concentration.

Pulsed laser deposited hexagonal wurzite ZnO thin-film nanostructures/nanotextures for nanophotonics applications

NASA Astrophysics Data System (ADS)

John Chelliah, Cyril Robinson Azariah; Swaminathan, Rajesh

2018-01-01

The high-quality and transparent thin-film zinc oxide (ZnO) nanostructures/nanotextures deposited on glass and silicon substrates using pulsed laser deposition (PLD) technique are reported. A solid-state, Nd-YAG laser was used for the PLD process. The films were deposited (i) at room temperature of 25°C (as deposited), (ii) at 150°C, (iii) at 300°C, (iv) at 450°C, and (v) at 600°C and annealed in the vacuum chamber. The depositions were also carried out at different laser repetition rates such as 10 and 5 Hz. UV spectroscopy and photoluminescence (PL) spectroscopy were carried out for optical studies. X-ray diffraction studies were carried out for all samples and analyzed the effects of the laser repetition rate, deposition, and annealing temperatures on the structural properties. Field-emission scanning electron microscope images are recorded for the best-structured samples. The electrical parameters were calibrated using the Hall effect measurement system and the IV characterization was performed using a CHI Electrochemical workstation. The deposition temperature has a significant effect on the microstrain and dislocation density of the ZnO thin film and optical phenomena with various electrical parameters, including the electron mobility, conductivity, and magnetoresistance. These promising results are suitable conditions for nanophotonics applications.

Hydrothermal-electrochemical growth of heterogeneous ZnO: Co films

NASA Astrophysics Data System (ADS)

Yilmaz, Ceren; Unal, Ugur

2017-10-01

This study demonstrates the preparation of heterogeneous ZnO: Co nanostructures via hydrothermal-electrochemical deposition at 130 °C and -1.1 V (vs Ag/AgCl (satd)) in dimethyl sulfoxide (DMSO)-H2O mixture. Under the stated conditions, ZnO: Co nanostructures grow preferentially along (002) direction. Strength of directional growth progressively increases with the increasing concentration of Co(II) in the deposition bath. Films are composed of hexagonal Wurtzite ZnO, metallic cobalt, and mixed cobalt oxide on the surface and cobalt(II) oxide in deeper levels. Increasing the Co(II) concentration in the deposition bath results in different morphological features as well as phase separation. Platelets, sponge-like structures, cobalt-rich spheres, microislands of cobalt-rich spheres which are interconnected by ZnO network can be synthesized by adjusting [Co(II)]: [Zn(II)] ratio. Growth mechanisms giving rise to these particular structures, surface morphology, crystal structure, phase purity, chemical binding characteristics, and optical properties of the deposits are discussed in detail.

Realizing a facile and environmental-friendly fabrication of high-performance multi-crystalline silicon solar cells by employing ZnO nanostructures and an Al2O3 passivation layer

PubMed Central

Chen, Hong-Yan; Lu, Hong-Liang; Sun, Long; Ren, Qing-Hua; Zhang, Hao; Ji, Xin-Ming; Liu, Wen-Jun; Ding, Shi-Jin; Yang, Xiao-Feng; Zhang, David Wei

2016-01-01

Nowadays, the multi-crystalline silicon (mc-Si) solar cells dominate the photovoltaic industry. However, the current acid etching method on mc-Si surface used by firms can hardly suppress the average reflectance value below 25% in the visible light spectrum. Meanwhile, the nitric acid and the hydrofluoric contained in the etching solution is both environmental unfriendly and highly toxic to human. Here, a mc-Si solar cell based on ZnO nanostructures and an Al2O3 spacer layer is demonstrated. The eco-friendly fabrication is realized by low temperature atomic layer deposition of Al2O3 layer as well as ZnO seed layer. Moreover, the ZnO nanostructures are prepared by nontoxic and low cost hydro-thermal growth process. Results show that the best passivation quality of the n+ -type mc-Si surface can be achieved by balancing the Si dangling bond saturation level and the negative charge concentration in the Al2O3 film. Moreover, the average reflectance on cell surface can be suppressed to 8.2% in 400–900 nm range by controlling the thickness of ZnO seed layer. With these two combined refinements, a maximum solar cell efficiency of 15.8% is obtained eventually. This work offer a facile way to realize the environmental friendly fabrication of high performance mc-Si solar cells. PMID:27924911

Realizing a facile and environmental-friendly fabrication of high-performance multi-crystalline silicon solar cells by employing ZnO nanostructures and an Al2O3 passivation layer

NASA Astrophysics Data System (ADS)

Chen, Hong-Yan; Lu, Hong-Liang; Sun, Long; Ren, Qing-Hua; Zhang, Hao; Ji, Xin-Ming; Liu, Wen-Jun; Ding, Shi-Jin; Yang, Xiao-Feng; Zhang, David Wei

2016-12-01

Nowadays, the multi-crystalline silicon (mc-Si) solar cells dominate the photovoltaic industry. However, the current acid etching method on mc-Si surface used by firms can hardly suppress the average reflectance value below 25% in the visible light spectrum. Meanwhile, the nitric acid and the hydrofluoric contained in the etching solution is both environmental unfriendly and highly toxic to human. Here, a mc-Si solar cell based on ZnO nanostructures and an Al2O3 spacer layer is demonstrated. The eco-friendly fabrication is realized by low temperature atomic layer deposition of Al2O3 layer as well as ZnO seed layer. Moreover, the ZnO nanostructures are prepared by nontoxic and low cost hydro-thermal growth process. Results show that the best passivation quality of the n+ -type mc-Si surface can be achieved by balancing the Si dangling bond saturation level and the negative charge concentration in the Al2O3 film. Moreover, the average reflectance on cell surface can be suppressed to 8.2% in 400-900 nm range by controlling the thickness of ZnO seed layer. With these two combined refinements, a maximum solar cell efficiency of 15.8% is obtained eventually. This work offer a facile way to realize the environmental friendly fabrication of high performance mc-Si solar cells.

Au functionalized ZnO rose-like hierarchical structures and their enhanced NO2 sensing performance

NASA Astrophysics Data System (ADS)

Shingange, K.; Swart, H. C.; Mhlongo, G. H.

2018-04-01

Herein, we present ZnO rose-like hierarchical nanostructures employed as support to Au nanoparticles to produce Au functionalized three dimensional (3D) ZnO hierarchical nanostructures (Au/ZnO) for NO2 detection using a microwave-assisted method. Comparative analysis of NO2 sensing performance between the pristine ZnO and Au/ZnO rose-like structures at 300 °C revealed improved NO2 response and rapid response-recovery times with Au incorporation owing to a combination of high surface accessibility induced by hierarchical nanostructure design and catalytic activity of the small Au nanoparticles. Structural and optical analyses acquired from X-ray diffraction, scanning electron microscopy, transmission electron microscope and photoluminescence spectroscopy were also performed.

Nanoparticle Self-Assembled Grain Like Curcumin Conjugated ZnO: Curcumin Conjugation Enhances Removal of Perylene, Fluoranthene, and Chrysene by ZnO

PubMed Central

Moussawi, Rasha N.; Patra, Digambara

2016-01-01

Curcumin conjugated ZnO, referred as Zn(cur)O, nanostructures have been successfully synthesized, these sub-micro grain-like structures are actually self-assemblies of individual needle-shaped nanoparticles. The nanostructures as synthesized possess the wurtzite hexagonal crystal structure of ZnO and exhibit very good crystalline quality. FT-Raman and TGA analysis establish that Zn(cur)O is different from curcumin anchored ZnO (ZnO@cur), which is prepared by physically adsorbing curcumin on ZnO surfaces. Chemically Zn(cur)O is more stable than ZnO@cur. Diffuse reflectance spectroscopy indicates Zn(cur)O have more impurities compared to ZnO@cur. The solid-state photoluminescence of Zn(cur)O has been investigated, which demonstrates that increase of curcumin concentration in Zn(cur)O suppresses visible emission of ZnO prepared through the same method, this implies filling ZnO defects by curcumin. However, at excitation wavelength 425 nm the emission is dominated by fluorescence from curcumin. The study reveals that Zn(cur)O can remove to a far extent high concentrations of perylene, fluoranthene, and chrysene faster than ZnO. The removal depends on the extent of curcumin conjugation and is found to be faster for PAHs having smaller number of aromatic rings, particularly, it is exceptional for fluoranthene with 93% removal after 10 minutes in the present conditions. The high rate of removal is related to photo-degradation and a mechanism has been proposed. PMID:27080002

Designing deoxidation inhibiting encapsulation of metal oxide nanostructures for fluidic and biological applications

NASA Astrophysics Data System (ADS)

Ghosh, Moumita; Ghosh, Siddharth; Seibt, Michael; Schaap, Iwan A. T.; Schmidt, Christoph F.; Mohan Rao, G.

2016-12-01

Due to their photoluminescence, metal oxide nanostructures such as ZnO nanostructures are promising candidates in biomedical imaging, drug delivery and bio-sensing. To apply them as label for bio-imaging, it is important to study their structural stability in a bio-fluidic environment. We have explored the effect of water, the main constituent of biological solutions, on ZnO nanostructures with scanning electron microscopy (SEM) and photoluminescence (PL) studies which show ZnO nanorod degeneration in water. In addition, we propose and investigate a robust and inexpensive method to encapsulate these nanostructures (without structural degradation) using bio-compatible non-ionic surfactant in non-aqueous medium, which was not reported earlier. This new finding is an immediate interest to the broad audience of researchers working in biophysics, sensing and actuation, drug delivery, food and cosmetics technology, etc.

ZnO nanostructures with different morphology for enhanced photocatalytic activity

NASA Astrophysics Data System (ADS)

Peter, I. John; Praveen, E.; Vignesh, G.; Nithiananthi, P.

2017-12-01

ZnO nanomaterials of different morphologies have been synthesized and the effect of morphology on Photocatalytic activity on natural dye has been investigated. Crystalline size and lattice strain of the synthesized particles are determined by XRD analysis and Williamson-Hall (W-H) method respectively. All other important physical parameters such as strain, stress and energy density values are also calculated using W-H analysis using different models such as uniform deformation model, uniform deformation stress model and uniform deformation energy density model. A shift in the peak of FTIR spectrum of ZnO is observed due to morphology effects. The SEM analysis reveals that the synthesized ZnO nanoparticles appear as flake, rod and dot. ZnO quantum dot exhibits higher photocatalytic activity comparing to the other morphologies. Larger surface area, high adsorption rate, large charge separation and the slow recombination of electrons/holes in ZnO dots establish dots as favorable morphology for good photocatalysis. Among the three, ZnO quantum dot shows three-times enhancement in the kinetic rate constants of photocatalysis. The results confirm that availability of specific (active) surface area, photocatalytic potential and quantum confinement of photo-induced carriers differ with morphology.

Direct in situ observation of ZnO nucleation and growth via transmission X-ray microscopy

NASA Astrophysics Data System (ADS)

Tay, S. E. R.; Goode, A. E.; Nelson Weker, J.; Cruickshank, A. A.; Heutz, S.; Porter, A. E.; Ryan, M. P.; Toney, M. F.

2016-01-01

The nucleation and growth of a nanostructure controls its size and morphology, and ultimately its functional properties. Hence it is crucial to investigate growth mechanisms under relevant growth conditions at the nanometer length scale. Here we image the nucleation and growth of electrodeposited ZnO nanostructures in situ, using a transmission X-ray microscope and specially designed electrochemical cell. We show that this imaging technique leads to new insights into the nucleation and growth mechanisms in electrodeposited ZnO including direct, in situ observations of instantaneous versus delayed nucleation.The nucleation and growth of a nanostructure controls its size and morphology, and ultimately its functional properties. Hence it is crucial to investigate growth mechanisms under relevant growth conditions at the nanometer length scale. Here we image the nucleation and growth of electrodeposited ZnO nanostructures in situ, using a transmission X-ray microscope and specially designed electrochemical cell. We show that this imaging technique leads to new insights into the nucleation and growth mechanisms in electrodeposited ZnO including direct, in situ observations of instantaneous versus delayed nucleation. Electronic supplementary information (ESI) available: Methods and videos of nanoparticle growth. See DOI: 10.1039/c5nr07019h

Oxidized guar gum-ZnO hybrid nanostructures: synthesis, characterization and antibacterial activity

NASA Astrophysics Data System (ADS)

Singh, Vandana; Dwivedi, Lalit Mohan; Baranwal, Kirti; Asthana, Sugandha; Sundaram, Shanthy

2018-04-01

In the present study, guar gum (GG) and oxidized guar gum (OGG) have been used for modulating the antibacterial activity of ZnO. Oxidized guar gum-zinc oxide (OGG-ZnO) or guar gum-zinc oxide (GG-ZnO) nanostructures were synthesized by adding aqueous ammonia to zinc acetate solution in the presence of OGG or GG, respectively. OGG could significantly enhance the antibacterial activity of ZnO for a range of Gram-negative and Gram-positive bacterial strains and this enhancement was most pronounced for Bacillus subtilis and Salmonella typhi. At the same time, GG-ZnO nanostructures were found to be less bioactive than the pure ZnO for the same strains. TEM analysis revealed that optimum OGG-ZnO nanostructure (Z4) is of 200 nm size, oblong in shape, and has slightly clustered texture, while XRD confirmed its crystalline structure with hexagonal phase. The extra surface oxygen species (thus oxygen deficiency) has been assigned for better antibacterial behavior of OGG-ZnO. The study may be extended for other polysaccharide/derivatives to obtain ZnO nanostructures with enhanced antibacterial properties.

Single-crystalline twinned ZnO nanoleaf structure via a facile hydrothermal process.

PubMed

Qiu, Jijun; Lil, Xiaomin; Gao, Xiangdong; Gan, Xiaoyan; He, Weizhen; Kim, Hyung-Kook; Hwang, Yoon-Hwae

2011-03-01

A single-crystalline twinned ZnO nanostructure with a 2-dimensional leaf-like morphology (nanoleaves) was synthesized using a facile hydrothermal strategy. The ZnO nanoleaves had 2-fold symmetric branches, which were identified by the existence of an inversion domain boundary (IDB) along the [2110] growth direction of the ribbon-like stems with both side surfaces of the stems terminated with a chemically active Zn-(0001) plane. A proposed growth mechanism suggested that the formation of IDB and the leaf-like shape are related to the dissolution of seed particles on the substrate surfaces and an OH- shielding effect in solution, respectively. Optical measurements revealed visible emission, suggesting the possession of defects in the as-grown and annealed ZnO nanoleaves. In addition, various ZnO nanostructures were synthesized by simply controlling the fabrication conditions.

Fe-tannic acid complex dye as photo sensitizer for different morphological ZnO based DSSCs

NASA Astrophysics Data System (ADS)

Çakar, Soner; Özacar, Mahmut

2016-06-01

In this paper we have synthesized different morphological ZnO nanostructures via microwave hydrothermal methods at low temperature within a short time. We described different morphologies of ZnO at different Zn(NO3)2/KOH mole ratio. The ZnO nanostructures were characterized via X-ray diffraction (XRD), field emission scanning electron microscopy (FE-SEM) and UV-vis spectrophotometry. All ZnO structures have hexagonal wurtzite type structures. The FESEM images showed various morphologies of ZnO such as plate, rod and nanoparticles. Dye sensitized solar cells have been assembled by these different morphological structures photo electrode and tannic acid or Fe-tannic acid complex dye as sensitizer. We have achieved at maximum efficiencies of photovoltaic cells prepared with ZnO plate in all dye systems. The conversion efficiencies of dye sensitized solar cells are 0.37% and 1.00% with tannic acid and Fe-tannic acid complex dye, respectively.

Coherent spectroscopic methods for monitoring pathogens, genetically modified products and nanostructured materials in colloidal solution

NASA Astrophysics Data System (ADS)

Moguilnaya, T.; Suminov, Y.; Botikov, A.; Ignatov, S.; Kononenko, A.; Agibalov, A.

2017-01-01

We developed the new automatic method that combines the method of forced luminescence and stimulated Brillouin scattering. This method is used for monitoring pathogens, genetically modified products and nanostructured materials in colloidal solution. We carried out the statistical spectral analysis of pathogens, genetically modified soy and nano-particles of silver in water from different regions in order to determine the statistical errors of the method. We studied spectral characteristics of these objects in water to perform the initial identification with 95% probability. These results were used for creation of the model of the device for monitor of pathogenic organisms and working model of the device to determine the genetically modified soy in meat.

Electromagnetic and Microwave Absorption Properties of Carbonyl Tetrapod-Shaped Zno Nanostructures Composite Coatings

NASA Astrophysics Data System (ADS)

Yu, Haibo; Qin, Hui; Huang, Yunhua

2012-08-01

CIP/T-ZnO/EP composite coatings with carbonyl iron powders (CIP) and tetrapodshaped ZnO (T-ZnO) nanostructures as absorbers, and epoxy resin (EP) as matrix were prepared. The complex permittivity, permeability and microwave absorption properties of the coatings were investigated in the frequency range of 2-18 GHz. The effects of the weight ratio (CIP/T-ZnO/EP), the thickness and the solidification temperature on microwave absorption properties were discussed. When the weight ratio (CIP/TZnO/ EP), the thickness and the solidification temperature is 28:2:22, 1.8 mm, and 10°C, respectively, the optimal wave absorption with the minimum reflection loss (RL) value of -22.38 dB at 15.67 GHz and the bandwidth (RL<-10 dB) of 5.74 GHz was obtained, indicating that the composite coatings may have a promising application in Ku-band (12-18 GHz).

Influence Al doped ZnO nanostructure on structural and optical properties

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ramelan, Ari Handono, E-mail: aramelan@mipa.uns.ac.id; Wahyuningsih, Sayekti; Chasanah, Uswatul

2016-04-19

The preparation of Al-doped ZnO (AZO) thin films prepared by the spin-coating method was reported. Preparation of AZO was conducted by annealing treatment at a temperature of 700°C. While the spin-coating process of AZO thin films were done at 2000 and 3000 rpm respectively. The structural properties of ZnO were determined by X- ray diffraction (XRD) analysis. ZnOnanostructure was formed after annealed at atemperature of 400°C.The morphology of ZnO was determined by Scanning Electron Microscopy (SEM) showed the irregular morphology about 30-50µm in size. Al doped on ZnO influenced the optical properties of those material. Increasing Al contain on ZnO causemore » of shifting to the lower wavelength. The optical properties of the ZnO as well as AZO films showed that higher reflectance on the ultraviolet region so those materials were used as anti-reflecting agent.Al addition significantly enhance the optical transparency and induce the blue-shift in optical bandgap of ZnO films.« less

Structural, optical, and improved field-emission properties of tetrapod-shaped Sn-doped ZnO nanostructures synthesized via thermal evaporation.

PubMed

Zhou, Xiongtu; Lin, Tihang; Liu, Yuhui; Wu, Chaoxing; Zeng, Xiangyao; Jiang, Dong; Zhang, Yong-ai; Guo, Tailiang

2013-10-23

High-quality tetrapod-shaped Sn-doped ZnO (T-SZO) nanostructures have been successfully synthesized via the thermal evaporation of mixed Zn and Sn powder. The effects of the Sn dopant on the morphology, microstructure, optical, and field-emission (FE) properties of T-SZO were investigated. It was found that the growth direction of the legs of T-SZO is parallel to the [0001] crystal c-axis direction and that the incorporation of Sn in the ZnO matrix increases the aspect ratio of the tetrapods, leads to blue shift in the UV region, and considerably improves the FE performance. The results also show that tetrapod cathodes with around a 0.84 atom % Sn dosage have the best FE properties, with a turn-on field of 1.95 V/μm, a current density of 950 μA/cm2 at a field of 4.5 V/μm, and a field-enhancement factor as high as 9556.

Accelerated stability assay (ASA) for colloidal systems.

PubMed

Chong, Josephine Y T; Mulet, Xavier; Boyd, Ben J; Drummond, Calum J

2014-05-12

Assessment of the stability of colloidal systems, in particular lyotropic liquid crystalline dispersions, such as cubosomes and hexosomes, is typically performed qualitatively or with limited throughput on specialized instruments. Here, an accelerated stability assay for colloidal particles has been developed in 384-well plates with standard laboratory equipment. These protocols enable quantitative assessments of colloidal stability. To demonstrate the applicability of the assay, several steric stabilizers for cubic phase nanostructured particles (cubosomes) have been compared to the current "gold standard" Pluronic F127.

A mixture toxicity approach to predict the toxicity of Ag decorated ZnO nanomaterials.

PubMed

Azevedo, S L; Holz, T; Rodrigues, J; Monteiro, T; Costa, F M; Soares, A M V M; Loureiro, S

2017-02-01

Nanotechnology is a rising field and nanomaterials can now be found in a vast variety of products with different chemical compositions, sizes and shapes. New nanostructures combining different nanomaterials are being developed due to their enhancing characteristics when compared to nanomaterials alone. In the present study, the toxicity of a nanostructure composed by a ZnO nanomaterial with Ag nanomaterials on its surface (designated as ZnO/Ag nanostructure) was assessed using the model-organism Daphnia magna and its toxicity predicted based on the toxicity of the single components (Zn and Ag). For that ZnO and Ag nanomaterials as single components, along with its mixture prepared in the laboratory, were compared in terms of toxicity to ZnO/Ag nanostructures. Toxicity was assessed by immobilization and reproduction tests. A mixture toxicity approach was carried out using as starting point the conceptual model of Concentration Addition. The laboratory mixture of both nanomaterials showed that toxicity was dependent on the doses of ZnO and Ag used (immobilization) or presented a synergistic pattern (reproduction). The ZnO/Ag nanostructure toxicity prediction, based on the percentage of individual components, showed an increase in toxicity when compared to the expected (immobilization) and dependent on the concentration used (reproduction). This study demonstrates that the toxicity of the prepared mixture of ZnO and Ag and of the ZnO/Ag nanostructure cannot be predicted based on the toxicity of their components, highlighting the importance of taking into account the interaction between nanomaterials when assessing hazard and risk. Copyright © 2016 Elsevier B.V. All rights reserved.

Morphologically manipulated Ag/ZnO nanostructures as surface enhanced Raman scattering probes for explosives detection

NASA Astrophysics Data System (ADS)

Shaik, Ummar Pasha; Hamad, Syed; Ahamad Mohiddon, Md.; Soma, Venugopal Rao; Ghanashyam Krishna, M.

2016-03-01

The detection of secondary explosive molecules (e.g., ANTA, FOX-7, and CL-20) using Ag decorated ZnO nanostructures as surface enhanced Raman scattering (SERS) probes is demonstrated. ZnO nanostructures were grown on borosilicate glass substrates by rapid thermal oxidation of metallic Zn films at 500 °C. The oxide nanostructures, including nanosheets and nanowires, emerged over the surface of the Zn film leaving behind the metal residue. We demonstrate that SERS measurements with concentrations as low as 10 μM, of the three explosive molecules ANTA, FOX-7, and CL-20 over ZnO/Ag nanostructures, resulted in enhancement factors of ˜107, ˜107, and ˜104, respectively. These measurements validate the high sensitivity of detection of explosive molecules using Ag decorated ZnO nanostructures as SERS substrates. The Zn metal residue and conditions of annealing play an important role in determining the detection sensitivity.

Zinc oxide nanostructured layers for gas sensing applications

NASA Astrophysics Data System (ADS)

Caricato, A. P.; Cretí, A.; Luches, A.; Lomascolo, M.; Martino, M.; Rella, R.; Valerini, D.

2011-03-01

Various kinds of zinc oxide (ZnO) nanostructures, such as columns, pencils, hexagonal pyramids, hexagonal hierarchical structures, as well as smooth and rough films, were grown by pulsed laser deposition using KrF and ArF excimer lasers, without use of any catalyst. ZnO films were deposited at substrate temperatures from 500 to 700°C and oxygen background pressures of 1, 5, 50, and 100 Pa. Quite different morphologies of the deposited films were observed using scanning electron microscopy when different laser wavelengths (248 or 193 nm) were used to ablate the bulk ZnO target. Photoluminescence studies were performed at different temperatures (down to 7 K). The gas sensing properties of the different nanostructures were tested against low concentrations of NO2. The variation in the photoluminescence emission of the films when exposed to NO2 was used as transduction mechanism to reveal the presence of the gas. The nanostructured films with higher surface-to-volume ratio and higher total surface available for gas adsorption presented higher responses, detecting NO2 concentrations down to 3 ppm at room temperature.

Sulfur-Doped Zinc Oxide (ZnO) Nanostars: Synthesis and Simulation of Growth Mechanism

DTIC Science & Technology

2011-10-01

Zinc Oxide ( ZnO ) Nanostars: Synthesis and Simulation of Growth Mechanism Jinhyun Cho1, Qiubao Lin2,3, Sungwoo...characterization, and ab initio simulations of star-shaped hexagonal zinc oxide ( ZnO ) nanowires. The ZnO nanostructures were synthesized by a low...Introduction Zinc oxide ( ZnO ) is a wide bandgap (3.37 eV), Ⅱ–Ⅵ semiconductor of great interest for optoelectronic applications [1–3]. Its

Microwave-assisted synthesis of C-doped TiO2 and ZnO hybrid nanostructured materials as quantum-dots sensitized solar cells

NASA Astrophysics Data System (ADS)

Rangel-Mendez, Jose R.; Matos, Juan; Cházaro-Ruiz, Luis F.; González-Castillo, Ana C.; Barrios-Yáñez, Guillermo

2018-03-01

The microwave-assisted solvothermal synthesis of C-doped TiO2 and ZnO hybrid materials was performed. Saccharose, titanium isopropoxide and zinc acetate were used as organic and inorganic sources for the synthesis. The influence of temperature and reaction time on the textural and optoelectronic properties of the hybrid materials was verified. Carbon quantum-dots of TiO2 and ZnO nanostructured spheres were obtained in a second pot by controlled calcination steps of the precursor hybrid materials. A carefully characterization by adsorption-desorption N2 isotherms, XRD, XPS, SEM, UV-vis/DR and electro- and photo-electrochemistry properties of the carbon quantum-dots TiO2 and ZnO spheres was performed. The photoelectrochemical activity of TiO2-C and ZnO-C films proved to be dependent on the conditions of synthesis. It was found a red-shift in the energy band gap of the semiconductors with values of 3.02 eV and 3.13 eV for the TiO2-C and ZnO-C, respectively, clearly lower than those on bare semiconductors, which is associated with the C-doping effect. From the photo-electrochemistry characterization of C-doped TiO2 and ZnO films can be concluded that the present materials have potential applications as photoelectrodes for quantum-dots sensitized solar cells.

Hydrothermal Synthesis and Acetylene Sensing Properties of Variety Low Dimensional Zinc Oxide Nanostructures

PubMed Central

Chen, Weigen; Peng, Shudi; Zeng, Wen

2014-01-01

Various morphologies of low dimensional ZnO nanostructures, including spheres, rods, sheets, and wires, were successfully synthesized using a simple and facile hydrothermal method assisted with different surfactants. Zinc acetate dihydrate was chosen as the precursors of ZnO nanostructures. We found that polyethylene glycol (PEG), polyvinylpyrrolidone (PVP), glycine, and ethylene glycol (EG) play critical roles in the morphologies and microstructures of the synthesized nanostructures, and a series of possible growth processes were discussed in detail. Gas sensors were fabricated using screen-printing technology, and their sensing properties towards acetylene gas (C2H2), one of the most important arc discharge characteristic gases dissolved in oil-filled power equipments, were systematically measured. The ZnO nanowires based sensor exhibits excellent C2H2 sensing behaviors than those of ZnO nanosheets, nanorods, and nanospheres, indicating a feasible way to develop high-performance C2H2 gas sensor for practical application. PMID:24672324

Low-cost synthesis of pure ZnO nanowalls showing three-fold symmetry

NASA Astrophysics Data System (ADS)

Scuderi, Mario; Strano, Vincenzina; Spinella, Corrado; Nicotra, Giuseppe; Mirabella, Salvo

2018-04-01

ZnO nanowalls (NWLs) represent a non-toxic, Earth abundant, high surface-to-volume ratio, semiconducting nanostructure which has already showed potential applications in biosensing, environmental monitoring and energy. Low-cost synthesis of these nanostructures is extremely appealing for large scale upgrading of laboratory results, and its implementation has to be tested at the nanoscale, at least in terms of chemical purity and crystallographic orientation. Here, we have produced pure and texturized ZnO NWLs by using chemical bath deposition (CBD) synthesis followed by a thermal treatment at 300 °C. We examined the NWL formation process and the new obtained structure at the nanoscale, by means of scanning and transmission electron microscopy in combination with x-ray diffraction and Rutherford backscattering spectrometry. We have shown that only after annealing at 300 °C in nitrogen does the as-grown material, composed of a mixture of Zn compounds NWLs, show its peculiar crystal arrangement. The resulting ZnO sheets are in fact made by ZnO wurtzite domains (4-5 nm) that show a particular kind of texturization; indeed, they are aligned with their own c-axis always perpendicular to the sheets forming the wall and rotated (around the c-axis) by multiples of 20° from each other. The presented data show that low-cost CBD, followed by an annealing process, gives pure ZnO with a peculiarly ordered nanostructure that shows three-fold symmetry. Such evidence at the nanoscale will have significant implications for realizing sensing or catalyst devices based on ZnO NWLs.

The immunomodulatory effects of Zn-incorporated micro/nanostructured coating in inducing osteogenesis.

PubMed

Zhang, Ranran; Liu, Xujie; Xiong, Zhiyuan; Huang, Qianli; Yang, Xing; Yan, Hao; Ma, Jing; Feng, Qingling; Shen, Zhijian

2018-03-08

Micro/nanostructured TiO 2 /ZnO coating has been shown to possess multiple functions, including antibacterial activity and bioactivity. Osteoblast-like SaOS-2 cells were employed for evaluating the in vitro osteogenic capacity of this coating and positive results were obtained. However, traditional principles of osseointegration focus only on the osteogenic differentiation alone. The effects of immunomodulation on the osteogenic activity have been largely ignored. In this study, the inflammatory responses of macrophages on the micro/nanostructured TiO 2 /ZnO coating were investigated. The extract media of macrophage cell line RAW264.7 cultured on the TiO 2 /ZnO coating were collected as indirect co-culture conditioned media. The osteogenic activity of SaOS-2 cells in the conditioned media was investigated. Adhesion, ALP activity and extracellular mineralization of cells grown in the conditioned media extracted from the micro/nanostructured TiO 2 /ZnO coating were found to be enhanced, compared to those grown in the conditioned media extracted from the macroporous TiO 2 coating. The immune microenvironment produced by the micro/nanostructured TiO 2 /ZnO coating showed excellent capacity to promote osteogenesis, indicating that this coating could be a promising candidate for implant surface modification in orthopaedic and dental applications. Furthermore, this work could help us understand the interplay between the host immune system and the osteoimmunomodulatory properties of the biomaterials, and optimize the design for coating biomaterials.

Plasmonic enhanced optical characteristics of Ag nanostructured ZnO thin films

NASA Astrophysics Data System (ADS)

Sarkar, Arijit; Gogurla, Narendar; Shivakiran Bhaktha, B. N.; Ray, Samit K.

2016-04-01

We have demonstrated the enhanced photoluminescence and photoconducting characteristics of plasmonic Ag-ZnO films due to the light scattering effect from Ag nanoislands. Ag nanoislands have been prepared on ITO-coated glass substrates by thermal evaporation followed by annealing. Plasmonic Ag-ZnO films have been fabricated by depositing ZnO over Ag nanoislands by sol-gel process. The band-edge emission of ZnO is enhanced for 170 nm sized Ag nanoislands in ZnO as compared to pure ZnO. The defect emission is also found to be quenched simultaneously for plasmonic Ag-ZnO films. The enhancement and quenching of photoluminescence at different wavelengths for Ag-ZnO films can be well understood from the localized surface plasmon resonance of Ag nanoislands. The Ag-ZnO M-S-M photoconductor device showed a tenfold increment in photocurrent and faster photoresponse as compared to the control ZnO device. The enhancement in photoresponse of the device is due to the increased photon absorption in ZnO films via scattering of the incident illumination.

Enhanced photoelectrochemical performance and photocatalytic activity of ZnO/TiO2 nanostructures fabricated by an electrostatically modified electrospinning

NASA Astrophysics Data System (ADS)

Ramos, Pierre G.; Flores, Edson; Sánchez, Luis A.; Candal, Roberto J.; Hojamberdiev, Mirabbos; Estrada, Walter; Rodriguez, Juan

2017-12-01

In this work, ZnO/TiO2 nanostructures were fabricated by an electrostatically modified electrospinning technique using zinc acetate and commercially available TiO2-P25, polyvinyl alcohol, and a solvent. The ZnO/TiO2 nanostructures were fabricated on fluorine-doped tin oxide (FTO) glass substrate by electrospinning of aqueous solution containing different amounts of zinc acetate. The TiO2-P25 nanoparticles were immobilized within zinc acetate/PVA nanofibers. The precursor nanofibers obtained were converted into polycrystalline ZnO and ZnO/TiO2 by calcination at 600 °C. The structure and morphology of the obtained nanostructures were characterized by X-ray diffraction and field emission scanning electron microscopy, respectively. It was found that the TiO2-P25 nanoparticles were attached to the ZnO nanostructures, and the mean diameter of the nanoparticles forming the nanostructures ranged from 31 to 52 nm with increasing the amount of zinc acetate. The incident photon-to-current efficiency (IPCE) spectra of the fabricated nanostructures were measured in a three-electrode cell. The photocatalytic activities of ZnO and ZnO/TiO2 nanostructures were evaluated toward the decomposition of methyl orange. The obtained results evidenced that the coupling of TiO2 with ZnO enhanced the IPCE and improved the photocatalytic activity of ZnO. Particularly, the ZnO/TiO2 nanostructures fabricated with a zinc acetate-to-PVA ratio of 2:3 exhibited the highest IPCE and photocatalytic activity.

Theory and Device Modeling for Nano-Structured Transistor Channels

DTIC Science & Technology

2011-06-01

zinc oxide ( ZnO ) thin film transistors ( TFTs ) that contain nanocrystalline grains on the order of ~20nm. The authors of ref. 1 present results...problem in order to determine the threshold voltage. 15. SUBJECT TERMS nano-structured transistor , mesoscopic, zinc oxide , ZnO , field-effect...and R. Neidhard, “Microwave ZnO Thin - Film Transistors ”, IEEE Electron Dev. Lett. 29, 1024 (2008); doi: 10.1109/LED.2008.2001635.

Performance and stability analysis of curcumin dye as a photo sensitizer used in nanostructured ZnO based DSSC

NASA Astrophysics Data System (ADS)

Sinha, D.; De, D.; Ayaz, A.

2018-03-01

Environmental friendly natural dye curcumin extracted from low-cost Curcumina longa stem is used as a photo-sensitizer for the fabrication of ZnO-based dye-sensitized solar cells (DSSC). Nanostructured ZnO is fabricated on a transparent conducting glass (TCO), using a cost-effective chemical bath deposition technique. Scanning electron microscopic images show hexagonal patterned ZnO nano-towers decorated with several nanosteps. The average length of ZnO nano-tower is 5 μm and diameter is 1.2 μm. The UV-Vis spectroscopic study of the curcumin dye is used to understand the light absorption behavior as well as band gap energy of the extracted natural dye. The dye shows wider absorption band-groups over 350-470 nm and 500-600 nm with two peaks positioned at 425 nm and 525 nm. The optical band gap energy and energy band position of the dye is derived which supports its stability and high electron affinity that makes it suitable for light harvesting and effortless electron transfer from dye to the semiconductor or interface between them. FTIR spectrum of curcumin dye-sensitized ZnO-based DSSC shows the presence of anchoring groups and colouring constitutes. The I-V and P-V curves of the fabricated DSSC are measured under simulated light (100 mW/cm2). The highest visible light to electric conversion efficiency of 0.266% (using ITO) and 0.33% (using FTO) is achieved from the curcumin dye-sensitized cell.

The structural, magnetic and optical properties of TMn@(ZnO)42 (TM = Fe, Co and Ni) hetero-nanostructure.

PubMed

Hu, Yaowen; Ji, Chuting; Wang, Xiaoxu; Huo, Jinrong; Liu, Qing; Song, Yipu

2017-11-28

The magnetic transition-metal (TM) @ oxide nanoparticles have been of great interest due to their wide range of applications, from medical sensors in magnetic resonance imaging to photo-catalysis. Although several studies on small clusters of TM@oxide have been reported, the understanding of the physical electronic properties of TM n @(ZnO) 42 is far from sufficient. In this work, the electronic, magnetic and optical properties of TM n @(ZnO) 42 (TM = Fe, Co and Ni) hetero-nanostructure are investigated using the density functional theory (DFT). It has been found that the core-shell nanostructure Fe 13 @(ZnO) 42 , Co 15 @(ZnO) 42 and Ni 15 @(ZnO) 42 are the most stable structures. Moreover, it is also predicted that the variation of the magnetic moment and magnetism of Fe, Co and Ni in TM n @ZnO 42 hetero-nanostructure mainly stems from effective hybridization between core TM-3d orbitals and shell O-2p orbitals, and a magnetic moment inversion for Fe 15 @(ZnO) 42 is investigated. Finally, optical properties studied by calculations show a red shift phenomenon in the absorption spectrum compared with the case of (ZnO) 48 .

Characterization of spatial manipulation on ZnO nanocomposites consisting of Au nanoparticles, a graphene layer, and ZnO nanorods

NASA Astrophysics Data System (ADS)

Huang, Shen-Che; Lu, Chien-Cheng; Su, Wei-Ming; Weng, Chen-Yuan; Chen, Yi-Cian; Wang, Shing-Chung; Lu, Tien-Chang; Chen, Ching-Pang; Chen, Hsiang

2018-01-01

Three types of ZnO-based nanocomposites were fabricated consisting of 80-nm Au nanoparticles (NPs), a graphene layer, and ZnO nanorods (NRs). To investigate interactions between the ZnO NRs and Au nanoparticle, multiple material analysis techniques including field-emission scanning electron microscopy (FESEM), surface contact angle measurements, secondary ion mass spectrometry (SIMS), X-ray photoelectron spectroscopy (XPS), and Raman spectroscopic characterizations were performed. Results indicate that incorporating a graphene layer could block the interaction between the ZnO NRs and the Au NPs. Furthermore, the Raman signal of the Au NPs could be enhanced by inserting a graphene layer on top of the ZnO NRs. Investigation of these graphene-incorporated nanocomposites would be helpful to future studies of the physical properties and Raman analysis of the ZnO-based nanostructure design.

Morphological driven photocatalytic activity of ZnO nanostructures

NASA Astrophysics Data System (ADS)

Abbas, Khaldoon N.; Bidin, Noriah

2017-02-01

Using a simple combination of pulse laser ablation in liquid and hydrothermal (PLAL-H) approaches, we control the morphology of ZnO nanostructures (ZNSs) to determine the feasibility of their photocatalytic efficacy. These ZNSs are deposited on Si (100) substrates and two different morphologies are achieved. In this synergistic approach, PLAL synthesized NSs are used as a nutrient solution with different pH for further hydrothermal treatment at 110 °C under varying growth time (5, 30 and 60 min). Surface morphology, structure, composition, and optical characteristics of the prepared ZNSs are determined using FESEM, XRD, FTIR and Photoluminescence (PL) and UV-vis absorption measurements. The morphology revealed remarkable transformation from nanorods (NRs)/nanoflowers (NFs) (at pH 7.6) to nanoparticles (NPs)-like (at pH 10.5) structure. XRD patterns showed better polycrystallinity for NPs with enlarged band gap than NR/NF-like structures. Both PL and UV-vis spectral analysis of ZNPs exhibited higher surface area and deep level defects density dependent morphology, where the nutrient pH and growth time variation are found to play a significant role towards structural evolution. Furthermore, the photocatalytic activities of, such ZNSs are evaluated via sunlight driven photo-degradation of methylene blue (MB) dye. The photocatalytic efficiency of ZNPs is demonstrated to be much superior (97.4%) than ZNRs/ZNFs-like morphology (86%). Such enhanced photocatalytic activities of as-synthesized ZNPs is attributed to the synergism of the improved surface area and defects density, which is useful for promoting the adsorption of the MB dye and suppressed surface recombination of photo-generated charge carriers.

pH effect on structural and optical properties of nanostructured zinc oxide thin films

DOE Office of Scientific and Technical Information (OSTI.GOV)

Munef, R. A.

2015-03-30

ZnO nanostructures were Deposited on Objekttrager glasses for various pH values by chemical bath deposition method using Zn (NO3)2·6H2O (zinc nitrate hexahydrate) solution at 75°C reaction temperature without any posterior treatments. The ZnO nanostructures obtained were characterized by X-ray Diffraction (XRD, UV). The structure was hexagonal and it was found that some peaks disappear with various pH values. The grain sizes of ZnO films increases from 22-to-29nm with increasing pH. The transmission of the films was (85-95%)

ZnO synthesized in air by fs laser irradiation on metallic Zn thin films

NASA Astrophysics Data System (ADS)

Esqueda-Barrón, Y.; Herrera, M.; Camacho-López, S.

2018-05-01

We present results on rapid femtosecond laser synthesis of nanostructured ZnO. We used metallic Zn thin films to laser scan along straight tracks, until forming nanostructured ZnO. The synthesis dependence on laser irradiation parameters such as the per pulse fluence, integrated fluence, laser scan speed, and number of scans were explored carefully. SEM characterization showed that the morphology of the obtained ZnO is dictated by the integrated fluence and the laser scan speed; micro Raman and XRD results allowed to identify optimal laser processing conditions for getting good quality ZnO; and cathodoluminescence measurements demonstrated that a single laser scan at high per pulse laser fluence, but a medium integrated laser fluence and a medium laser scan speed favors a low density of point-defects in the lattice. Electrical measurements showed a correlation between resistivity of the laser produced ZnO and point-defects created during the synthesis. Transmittance measurements showed that, the synthesized ZnO can reach down to the supporting fused silica substrate under the right laser irradiation conditions. The physical mechanism for the formation of ZnO, under ultrashort pulse laser irradiation, is discussed in view of the distinct times scales given by the laser pulse duration and the laser pulse repetition rate.

Growth of ZnO nanorods on glass substrate deposited using dip coating method

NASA Astrophysics Data System (ADS)

Rani, Rozina Abdul; Ghafar, Safiah Ab; Zoolfakar, Ahmad Sabirin; Rusop, M.

2018-05-01

ZnO unique properties make it attractive for electronics and optoelectronics application. There are varieties synthesis of ZnO nanostructure but one of the best ways is by using dip coating method due to its simplicity, low cost and reliability. This research investigated the effect of precursor concentration on the morphology of ZnO nanorods using dip coating technique. ZnO nanorods is synthesized by using zinc nitrate as precursor and glass slide as substrate. The morphology of ZnO is characterized using Field Emission Scanning Electron Microscope (FESEM). By using different concentration of precursor, each outcome demonstrated diverse morphologies.

Hierarchical structures of ZnO spherical particles synthesized solvothermally

NASA Astrophysics Data System (ADS)

Saito, Noriko; Haneda, Hajime

2011-12-01

We review the solvothermal synthesis, using a mixture of ethylene glycol (EG) and water as the solvent, of zinc oxide (ZnO) particles having spherical and flower-like shapes and hierarchical nanostructures. The preparation conditions of the ZnO particles and the microscopic characterization of the morphology are summarized. We found the following three effects of the ratio of EG to water on the formation of hierarchical structures: (i) EG restricts the growth of ZnO microcrystals, (ii) EG promotes the self-assembly of small crystallites into spheroidal particles and (iii) the high water content of EG results in hollow spheres.

Effect of Surfactant on the Morphology of ZnO/Al:ZnO Nanostructures and Their Ethanol Sensing Applications at Room Temperature

NASA Astrophysics Data System (ADS)

Chitra, M.; Uthayarani, K.; Rajasekaran, N.; Neelakandeswari, N.; Girija, E. K.; Padiyan, D. Pathinettam

2016-11-01

Zinc oxide (ZnO) and aluminum (Al) doped ZnO nanostructures with and without surfactant have been successfully prepared via sol-gel route. The effect of the surfactant glyoxalic acid and various concentration of Al on the structural property of ZnO was analyzed by X-ray powder diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR). The morphology of the samples was recorded using field emission scanning electron microscopy. The uniform distribution of ZnO nanostructures with hexagonal facets is facilitated by the surfactant and the grain growth is further inhibited by the increase in concentration of Al. The ethanol (0-300ppm) sensing characteristics of the as-prepared samples were systematically investigated at room temperature. Surfactant-assisted ZnO/Al:ZnO nanostructures show higher sensitivity of 94% at room temperature than ZnO/Al:ZnO nanostructures without surfactant. Faster response at 68s and recovery at 50s is also achieved by the samples. The surfactant-assisted ZnO nanostructures exhibit sharp selective detection towards ethanol when compared to the samples without surfactant. The enhanced ethanol sensing property may be ascribed to the larger surface area which is due to uniform and smaller crystallite size of the surfactant-assisted sample.

Formation, transformation and superhydrophobicity of compound surfactant-assisted aligned ZnO nanoplatelets

NASA Astrophysics Data System (ADS)

Xue, Mingshan; Xu, Tao; Xie, Xiaolin; Ou, Junfei; Wang, Fajun; Li, Wen

2015-11-01

Synthesis and understanding of hierarchically nanostructured materials are significant for exploring peculiar functional properties and underlying applications. In this study, the self-assembly formation and detailed transformation process of ZnO nanoplatelets grown by hydrothermal methods with the addition of compound surfactants (CTAB and Tween-20) have been investigated. The initial growth of ZnO nanoplatelets as well as the subsequent formation of bilayer nanorod arrays and divergent nanocone arrays on the surface and side face of these nanoplatelets were found. Compared with the formation of bulk/block crystals without the case of surfactants, the addition of compound surfactants into zinc nitrate solution is responsible for the self-assembly processes of ZnO because of the effective role of CTAB in decreasing the degree of crystallinity and the positive effect of Tween-20 on decreasing the particle size owing to the space hindered effect. As-formed hierarchically micro-nanostructured ZnO exhibits superhydrophobicity without any chemical modification, which can make water droplets suspend on the air film trapped between the nanoplatelet and nanoplatelet as well as between nanocone and nanocone.

Increased osteoblast and decreased Staphylococcus epidermidis functions on nanophase ZnO and TiO2.

PubMed

Colon, Gabriel; Ward, Brian C; Webster, Thomas J

2006-09-01

Many engineers and surgeons trace implant failure to poor osseointegration (or the bonding of an orthopedic implant to juxtaposed bone) and/or bacteria infection. By using novel nanotopographies, researchers have shown that nanostructured ceramics, carbon fibers, polymers, metals, and composites enhance osteoblast adhesion and calcium/phosphate mineral deposition. However, the function of bacteria on materials with nanostructured surfaces remains largely uninvestigated. This is despite the fact that during normal surgical insertion of an orthopedic implant, bacteria from the patient's own skin and/or mucosa enters the wound site. These bacteria (namely, Staphylococcus epidermidis) irreversibly adhere to an implant surface while various physiological stresses induce alterations in the bacterial growth rate leading to biofilm formation. Because of their integral role in determining the success of orthopedic implants, the objective of this in vitro study was to examine the functions of (i) S. epidermidis and (ii) osteoblasts (or bone-forming cells) on ZnO and titania (TiO(2)), which possess nanostructured compared to microstructured surface features. ZnO is a well-known antimicrobial agent and TiO(2) readily forms on titanium once implanted. Results of this study provided the first evidence of decreased S. epidermidis adhesion on ZnO and TiO(2) with nanostructured when compared with microstructured surface features. Moreover, compared with microphase formulations, results of this study showed increased osteoblast adhesion, alkaline phosphatase activity, and calcium mineral deposition on nanophase ZnO and TiO(2). In this manner, this study suggests that nanophase ZnO and TiO(2) may reduce S. epidermidis adhesion and increase osteoblast functions necessary to promote the efficacy of orthopedic implants.

Trioctylphosphine-assisted morphology control of ZnO nanoparticles

NASA Astrophysics Data System (ADS)

Hong, Yun-Kun; Cho, GeonHee; Park, YoonSu; Oh, Soong Ju; Ha, Don-Hyung

2018-06-01

This study investigates the morphological change in colloidal ZnO nanoparticles (NPs) synthesized with trioctylphosphine (TOP). The addition of TOP to the synthesis causes an evolution in the shape of ZnO NPs to tadpole-like particles from quasi-spherical particles at 300 °C. The total length of the tadpole-like ZnO NPs can be modified by controlling the molar ratio of TOP to oleylamine (OLAM). The tadpole-like particles are elongated as the concentration of TOP increased but decreased when the addition of TOP is excessive. These tadpole-like ZnO NPs transform to quasi-spherical NPs regardless of the amount of TOP at a reaction time of 3 h at 300 °C. At 200 °C, the effect of TOP on the ZnO NP synthesis differs from that at 300 °C. The ZnO NPs synthesized by controlling the molar ratios of surfactant ligands (TOP:OLAM = 2:100 and 70:100) at 200 °C share similar amorphous structures, while a crystalline ZnO phase is formed when the reaction time is 3 h. X-ray photoelectron spectroscopy analysis shows that TOP influences the oxidation of ZnO and suggests that a combination of OLAM and TOP plays a role in controlling the shape of ZnO NPs. These results provide critical insights to the utilization of TOP for a shape controlling ligand in ZnO NPs and suggest a new route to design oxide NPs.

Trioctylphosphine-assisted morphology control of ZnO nanoparticles.

PubMed

Hong, Yun-Kun; Cho, GeonHee; Park, YoonSu; Oh, Soong Ju; Ha, Don-Hyung

2018-06-01

This study investigates the morphological change in colloidal ZnO nanoparticles (NPs) synthesized with trioctylphosphine (TOP). The addition of TOP to the synthesis causes an evolution in the shape of ZnO NPs to tadpole-like particles from quasi-spherical particles at 300 °C. The total length of the tadpole-like ZnO NPs can be modified by controlling the molar ratio of TOP to oleylamine (OLAM). The tadpole-like particles are elongated as the concentration of TOP increased but decreased when the addition of TOP is excessive. These tadpole-like ZnO NPs transform to quasi-spherical NPs regardless of the amount of TOP at a reaction time of 3 h at 300 °C. At 200 °C, the effect of TOP on the ZnO NP synthesis differs from that at 300 °C. The ZnO NPs synthesized by controlling the molar ratios of surfactant ligands (TOP:OLAM = 2:100 and 70:100) at 200 °C share similar amorphous structures, while a crystalline ZnO phase is formed when the reaction time is 3 h. X-ray photoelectron spectroscopy analysis shows that TOP influences the oxidation of ZnO and suggests that a combination of OLAM and TOP plays a role in controlling the shape of ZnO NPs. These results provide critical insights to the utilization of TOP for a shape controlling ligand in ZnO NPs and suggest a new route to design oxide NPs.

Glucose biosensor based on functionalized ZnO nanowire/graphite films dispersed on a Pt electrode

NASA Astrophysics Data System (ADS)

Gallay, P.; Tosi, E.; Madrid, R.; Tirado, M.; Comedi, D.

2016-10-01

We present a glucose biosensor based on ZnO nanowire self-sustained films grown on compacted graphite flakes by the vapor transport method. Nanowire/graphite films were fragmented in water, filtered to form a colloidal suspension, subsequently functionalized with glucose oxidase and finally transferred to a metal electrode (Pt). The obtained devices were evaluated using scanning electron microscopy, energy-dispersive x-ray spectroscopy, cyclic voltammetry and chronoamperometry. The electrochemical responses of the devices were determined in buffer solutions with successive glucose aggregates using a tripolar electrode system. The nanostructured biosensors showed excellent analytical performance, with linear response to glucose concentrations, high sensitivity of up to ≈17 μA cm-2 mM-1 in the 0.03-1.52 mM glucose concentration range, relatively low Michaelis-Menten constant, excellent reproducibility and a fast response. The detection limits are more than an order of magnitude lower than those achievable in commercial biosensors for glucose control, which is promising for the development of glucose monitoring methods that do not require blood extraction from potentially diabetic patients. The strong detection enhancements provided by the functionalized nanostructures are much larger than the electrode surface-area increase and are discussed in terms of the physical and chemical mechanisms involved in the detection and transduction processes.

Synthesis of ZnO Photocatalysts Using Various Surfactants

NASA Astrophysics Data System (ADS)

Yao, Chengli; Zhu, Jinmiao; Li, Hongying; Zheng, Bin; Wei, Yanxin

2017-12-01

Zinc oxide (ZnO) nanostructured materials have received significant attention because of their unique physicochemical and electronic properties. In particular, the functional properties of ZnO are owed to its morphology and defect structure. ZnO particles were successfully synthesized by chemical precipitation. CTAB (cetyltrimethylammonium bromide), BS-12 (dodecyl dimethyl betaine) and graphene oxide (GO) were selected as templates to induce the formation of ZnO, respectively. By varying the amount of surfactant added during the synthesis process, the structural properties and the crystalline phase of the synthesized nanospheres were characterized by X-ray powder diffraction (XRD), scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FT-IR), ultraviolet and visible spectrophotometry (UV‒Vis). Simultaneously, photo catalytic degradation of Rhodamine B (RhB) was carried out under natural sunlight irradiation while ZnO or ZnO/GO particles were used as catalyst. GO is prone to induce formation of wurtzite hexagonal phase of ZnO. Compared with CTAB and BS-12, ZnO/GO composites had a remarkably photocatalytic degradation.

Piezoelectric nanogenerators based on ZnO and M13 Bacteriophage nanostructures (Conference Presentation)

NASA Astrophysics Data System (ADS)

Shin, Dong-Myeong; Kim, Kyujungg; Hong, Suck Won; Oh, Jin-Woo; Kim, Hyung Kook; Hwang, Yoon-Hwae

2016-09-01

Recently, the portable and wearable electronic devices, operated in the power range of microwatt to miliwatt, become available thank to the nanotechnology development and become an essential element for a comfortable life. Our recent research interest mainly focuses on the fabrication of piezoelectric nanogenerators based on smart nanomaterials such as zinc oxide novel nanostructure, M13 bacteriophage. In this talk, we present a simple strategy for fabricating the freestanding ZnO nanorods/graphene/ZnO nanorods double sided heterostructures. The characterization of the double sided heterostructures by using SEM, and Raman scattering spectroscopy reveals the key process and working mechanism of a formation of the heterostructure. The mechanism is discussed in detail in term of the decomposed seed layer and the vacancy defect of graphene. The approach consists of a facile one-step fabrication process and could achieve ZnO coverage with a higher number density than that of the epitaxial single heterostructure. The resulting improvement in the number density of nanorods has a direct beneficial effect on the double side heterostructured nanogenerator performance. The total output voltage and current density are improved up to 2 times compared to those of a single heterostructure due to the coupling of the piezoelectric effects from both upward and downward grown nanorods. The facile one-step fabrication process suggests that double sided heterostructures would improve the performance of electrical and optoelectrical device, such as touch pad, pressure sensor, biosensor and dye-sensitized solar cells. Further, ioinspired nanogenerators based on vertically aligned phage nanopillars are inceptively demonstrated. Vertically aligned phage nanopillars enable not only a high piezoelectric response but also a tuneable piezoelectricity. Piezoelectricity is also modulated by tuning of the protein's dipoles in each phage. The sufficient electrical power from phage nanopillars thus

ZnO nanosheet arrays constructed on weaved titanium wire for CdS-sensitized solar cells

PubMed Central

2014-01-01

Ordered ZnO nanosheet arrays were grown on weaved titanium wires by a low-temperature hydrothermal method. CdS nanoparticles were deposited onto the ZnO nanosheet arrays using the successive ionic layer adsorption and reaction method to make a photoanode. Nanoparticle-sensitized solar cells were assembled using these CdS/ZnO nanostructured photoanodes, and their photovoltaic performance was studied systematically. The best light-to-electricity conversion efficiency was obtained to be 2.17% under 100 mW/cm2 illumination, and a remarkable short-circuit photocurrent density of approximately 20.1 mA/cm2 was recorded, which could attribute to the relatively direct pathways for transportation of electrons provided by ZnO nanosheet arrays as well as the direct contact between ZnO and weaved titanium wires. These results indicate that CdS/ZnO nanostructures on weaved titanium wires would open a novel possibility for applications of low-cost solar cells. PMID:24618047

Investigations of rapid thermal annealing induced structural evolution of ZnO: Ge nanocomposite thin films via GISAXS

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ceylan, Abdullah, E-mail: aceylanabd@yahoo.com; Ozcan, Yusuf; Orujalipoor, Ilghar

2016-06-07

In this work, we present in depth structural investigations of nanocomposite ZnO: Ge thin films by utilizing a state of the art grazing incidence small angle x-ray spectroscopy (GISAXS) technique. The samples have been deposited by sequential r.f. and d.c. sputtering of ZnO and Ge thin film layers, respectively, on single crystal Si(100) substrates. Transformation of Ge layers into Ge nanoparticles (Ge-np) has been initiated by ex-situ rapid thermal annealing of asprepared thin film samples at 600 °C for 30, 60, and 90 s under forming gas atmosphere. A special attention has been paid on the effects of reactive and nonreactivemore » growth of ZnO layers on the structural evolution of Ge-np. GISAXS analyses have been performed via cylindrical and spherical form factor calculations for different nanostructure types. Variations of the size, shape, and distributions of both ZnO and Ge nanostructures have been determined. It has been realized that GISAXS results are not only remarkably consistent with the electron microscopy observations but also provide additional information on the large scale size and shape distribution of the nanostructured components.« less

Zinc oxide nanostructures as low-cost templates for neuronal circuit

NASA Astrophysics Data System (ADS)

Kritharidou, A.; Georgoussi, Z.; Tsamis, C.; Makarona, E.

2013-05-01

ZnO nanostructures were explored as templates for the development of topography-mediated neuronal cultures. Nanostructures of varying features were produced on 4" Si substrates via a rapid, facile and low-cost technique that allows the systematic investigation of nanotopographically-mediated formation of neuronal cultures. The developed ZnO-nanowire based templates were seeded with Neuro-2A mouse neuroblastoma cells and their viability over the course of 1 to 4 days was assessed. Our studies demonstrate that the ZnO-templates can support neuronal cell growth and proliferation suggesting that ZnO substrate can be used for the development of neuronal cell-based platform technologies.

Tunable Electromagnetic Coupling in Plasmonic Nanostructures Mediated by Thermoresponsive Polymer Brushes.

PubMed

Nguyen, Mai; Kanaev, Andrei; Sun, Xiaonan; Lacaze, Emmanuelle; Lau-Truong, Stéphanie; Lamouri, Aazdine; Aubard, Jean; Felidj, Nordin; Mangeney, Claire

2015-11-24

A smart and highly SERS-active plasmonic platform was designed by coupling regular arrays of nanotriangles to colloidal gold nanorods via a thermoresponsive polymer spacer (poly(N-isopropylacrylamide), PNIPAM). The substrates were prepared by combining a top-down and a bottom-up approach based on nanosphere lithography, surface-initiated controlled radical polymerization, and colloidal assembly. This multistep strategy provided regular hexagonal arrays of nanotriangles functionalized by polymer brushes and colloidal gold nanorods, confined exclusively on the nanotriangle surface. Interestingly, one could finely tune the gold nanorod impregnation on the polymer-coated nanostructures by adjusting the polymer layer thickness, leading to highly coupled plasmonic systems for intense SERS signal. Moreover, the thermoresponsive properties of the PNIPAM brushes could be wisely handled in order to monitor the SERS activity of the nanostructures coupled via this polymer spacer. The coupled hybrid plasmonic nanostructures designed in this work are therefore very promising smart platforms for the sensitive detection of analytes by SERS.

Significant enhancement of yellow-green light emission of ZnO nanorod arrays using Ag island films

NASA Astrophysics Data System (ADS)

Lin, Chin-An; Tsai, Dung-Sheng; Chen, Cheng-Ying; He-Hau, Jr.

2011-03-01

Surface plasmon (SP) mediated emission from ZnO nanorod arrays (NRAs)/Ag/Si structures has been investigated. The ratio of visible emission to UV emission can be increased by over 30 times via coupling with SP without deterioration of the crystal quality. The fact that the effect of SP crucially depends on the size of Ag island films provides the feasibility to significantly enhance the yellow-green emission of the ZnO nanostructures without sacrificing the crystallinity of ZnO.Surface plasmon (SP) mediated emission from ZnO nanorod arrays (NRAs)/Ag/Si structures has been investigated. The ratio of visible emission to UV emission can be increased by over 30 times via coupling with SP without deterioration of the crystal quality. The fact that the effect of SP crucially depends on the size of Ag island films provides the feasibility to significantly enhance the yellow-green emission of the ZnO nanostructures without sacrificing the crystallinity of ZnO. Electronic supplementary information (ESI) available. See DOI: 10.1039/c0nr00732c

ZnO Nanostructures for Drug Delivery and Theranostic Applications.

PubMed

Martínez-Carmona, Marina; Gun'ko, Yurii; Vallet-Regí, María

2018-04-23

In the last two decades, zinc oxide (ZnO) semiconductor Quantum dots (QDs) have been shown to have fantastic luminescent properties, which together with their low-cost, low-toxicity and biocompatibility have turned these nanomaterials into one of the main candidates for bio-imaging. The discovery of other desirable traits such as their ability to produce destructive reactive oxygen species (ROS), high catalytic efficiency, strong adsorption capability and high isoelectric point, also make them promising nanomaterials for therapeutic and diagnostic functions. Herein, we review the recent progress on the use of ZnO based nanoplatforms in drug delivery and theranostic in several diseases such as bacterial infection and cancer.

ZnO Nanostructures for Drug Delivery and Theranostic Applications

PubMed Central

Martínez-Carmona, Marina

2018-01-01

In the last two decades, zinc oxide (ZnO) semiconductor Quantum dots (QDs) have been shown to have fantastic luminescent properties, which together with their low-cost, low-toxicity and biocompatibility have turned these nanomaterials into one of the main candidates for bio-imaging. The discovery of other desirable traits such as their ability to produce destructive reactive oxygen species (ROS), high catalytic efficiency, strong adsorption capability and high isoelectric point, also make them promising nanomaterials for therapeutic and diagnostic functions. Herein, we review the recent progress on the use of ZnO based nanoplatforms in drug delivery and theranostic in several diseases such as bacterial infection and cancer. PMID:29690644

Defect-induced ferromagnetism in ZnO nanoparticles prepared by mechanical milling

NASA Astrophysics Data System (ADS)

Phan, The-Long; Zhang, Y. D.; Yang, D. S.; Nghia, N. X.; Thanh, T. D.; Yu, S. C.

2013-02-01

Though ZnO is known as a diamagnetic material, recent studies have revealed that its nanostructures can be ferromagnetic (FM). The FM origin has been ascribed to intrinsic defects. This work shines light on an alternate method based on mechanical milling to induce defect-related ferromagnetism in ZnO nanoparticles (NPs) from initial diamagnetic ZnO powders. Our idea is motivated by the fact that mechanical milling introduces more defects to a ground material. We point out that the FM order increases with increasing the density of defects in ZnO NPs. The experimental results obtained from analyzing X-ray absorption, electron spin resonance, and Raman scattering spectra demonstrate that the ferromagnetism in ZnO NPs is due to intrinsic defects mainly related to oxygen and zinc vacancies. Among these, zinc vacancies play a decisive role in introducing a high FM order in ZnO NPs.

One-pot ultrasonic-assisted method for preparation of Ag/AgCl sensitized ZnO nanostructures as visible-light-driven photocatalysts

NASA Astrophysics Data System (ADS)

Naghizadeh-Alamdari, Sara; Habibi-Yangjeh, Aziz; Pirhashemi, Mahsa

2015-02-01

Ultrasonic-assisted method was applied for preparation of Ag/AgCl sensitized ZnO nanostructures by one-pot procedure in water without using any post preparation treatments. The resultant nanocomposites were characterized by XRD, EDX, SEM, DRS, XPS, BET, and PL techniques. In the nanocomposites, ZnO and AgCl have wurtzite hexagonal and cubic crystalline phases, respectively and their surface morphologies remarkably change with increasing mole fraction of silver chloride. The EDX and XPS techniques show that the prepared samples are extremely pure. Ability of the nanocomposites for absorption of visible-light irradiation enhanced with increasing AgCl content. Photocatalytic examination of the nanocomposites was carried out using aqueous solution of methylene blue under visible-light irradiation. The degradation rate constant on the nancomposite rapidly increases with mole fraction of silver chloride up to 0.237. Enhancing activity of the nanocomposite was attributed to its ability for absorbing visible light and separation of electron-hole pairs. Furthermore, influence of ultrasonic irradiation time, calcination temperature, catalyst weight, pH of solution, and scavengers of reactive species on the degradation activity was investigated and the results were discussed. Finally, the photocatalyst has good activity after five successive cycles.

Effect of doping on structural, optical and electrical properties of nanostructure ZnO films deposited onto a-Si:H/Si heterojunction

NASA Astrophysics Data System (ADS)

Sali, S.; Boumaour, M.; Kermadi, S.; Keffous, A.; Kechouane, M.

2012-09-01

We investigated the structural; optical and electrical properties of ZnO thin films as the n-type semiconductor for silicon a-Si:H/Si heterojunction photodiodes. The ZnO film forms the front contact of the super-strata solar cell and has to exhibit good electrical (high conductivity) and optical (high transmittance) properties. In this paper we focused our attention on the influence of doping on device performance. The results show that the X-ray diffraction (XRD) spectra revealed a preferred orientation of the crystallites along c-axis. SEM images show that all films display a granular, polycrystalline morphology and the ZnO:Al exhibits a better grain uniformity. The transmittance of the doped films was found to be higher when compared to undoped ZnO. A low resistivity of the order of 2.8 × 10-4 Ω cm is obtained for ZnO:Al using 0.4 M concentration of zinc acetate. The photoluminescence (PL) spectra exhibit a blue band with two peaks centered at 442 nm (2.80 eV) and 490 nm (2.53 eV). It is noted that after doping the ZnO films a shift of the band by 22 nm (0.15 eV) is recorded and a high luminescence occurs when using Al as a dopant. Dark I-V curves of ZnO/a-Si:H/Si structure showed large difference, which means there is a kind of barrier to current flow between ZnO and a-Si:H layer. Doping films was applied and the turn-on voltages are around 0.6 V. Under reverse bias, the current of the ZnO/a-Si:H/Si heterojunction is larger than that of ZnO:Al/a-Si:H/Si. The improvement with ZnO:Al is attributed to a higher number of generated carriers in the nanostructure (due to the higher transmittance and a higher luminescence) that increases the probability of collisions.

One-Step Synthesis of Monodisperse In-Doped ZnO Nanocrystals

NASA Astrophysics Data System (ADS)

Wang, Qing Ling; Yang, Ye Feng; He, Hai Ping; Chen, Dong Dong; Ye, Zhi Zhen; Jin, Yi Zheng

2010-05-01

A method for the synthesis of high quality indium-doped zinc oxide (In-doped ZnO) nanocrystals was developed using a one-step ester elimination reaction based on alcoholysis of metal carboxylate salts. The resulting nearly monodisperse nanocrystals are well-crystallized with typically crystal structure identical to that of wurtzite type of ZnO. Structural, optical, and elemental analyses on the products indicate the incorporation of indium into the host ZnO lattices. The individual nanocrystals with cubic structures were observed in the 5% In-ZnO reaction, due to the relatively high reactivity of indium precursors. Our study would provide further insights for the growth of doped oxide nanocrystals, and deepen the understanding of doping process in colloidal nanocrystal syntheses.

Simple mass production of zinc oxide nanostructures via low-temperature hydrothermal synthesis

NASA Astrophysics Data System (ADS)

Ghasaban, Samaneh; Atai, Mohammad; Imani, Mohammad

2017-03-01

The specific properties of zinc oxide (ZnO) nanoparticles have attracted much attention within the scientific community as a useful material for biomedical applications. Hydrothermal synthesis is known as a useful method to produce nanostructures with certain particle size and morphology however, scaling up the reaction is still a challenging task. In this research, large scale hydrothermal synthesis of ZnO nanostructures (60 g) was performed in a 5 l stainless steel autoclave by reaction between anionic (ammonia or sodium hydroxide) and cationic (zinc acetate dehydrate) precursors in low temperature. Hydrothermal reaction temperature and time were decreased to 115 °C and 2 or 6 h. In batch repetitions, the same morphologies (plate- and needle-like) with reproducible particle size were obtained. The nanostructures formed were analyzed by powder x-ray diffraction, Fourier-transform infrared spectroscopy, energy dispersive x-ray analysis, scanning electron microscopy and BET analysis. The nanostructures formed were antibacterially active against Staphylococcus aureus.

Nanostructured hybrid ZnO thin films for energy conversion

PubMed Central

2011-01-01

We report on hybrid films based on ZnO/organic dye prepared by electrodeposition using tetrasulfonated copper phthalocyanines (TS-CuPc) and Eosin-Y (EoY). Both the morphology and porosity of hybrid ZnO films are highly dependent on the type of dyes used in the synthesis. High photosensitivity was observed for ZnO/EoY films, while a very weak photoresponse was obtained for ZnO/TS-CuPc films. Despite a higher absorption coefficient of TS-CuPc than EoY, in ZnO/EoY hybrid films, the excited photoelectrons between the EoY levels can be extracted through ZnO, and the porosity of ZnO/EoY can also be controlled. PMID:21711909

The Influence of Shape on the Output Potential of ZnO Nanostructures: Sensitivity to Parallel versus Perpendicular Forces.

PubMed

Cardoso, José; Oliveira, Filipe F; Proenca, Mariana P; Ventura, João

2018-05-22

With the consistent shrinking of devices, micro-systems are, nowadays, widely used in areas such as biomedics, electronics, automobiles, and measurement devices. As devices shrunk, so too did their energy consumptions, opening the way for the use of nanogenerators (NGs) as power sources. In particular, to harvest energy from an object's motion (mechanical vibrations, torsional forces, or pressure), present NGs are mainly composed of piezoelectric materials in which, upon an applied compressive or strain force, an electrical field is produced that can be used to power a device. The focus of this work is to simulate the piezoelectric effect in different ZnO nanostructures to optimize the output potential generated by a nanodevice. In these simulations, cylindrical nanowires, nanomushrooms, and nanotrees were created, and the influence of the nanostructures' shape on the output potential was studied as a function of applied parallel and perpendicular forces. The obtained results demonstrated that the output potential is linearly proportional to the applied force and that perpendicular forces are more efficient in all structures. However, nanotrees were found to have an increased sensitivity to parallel applied forces, which resulted in a large enhancement of the output efficiency. These results could then open a new path to increase the efficiency of piezoelectric nanogenerators.

Tailoring surface and photocatalytic properties of ZnO and nitrogen-doped ZnO nanostructures using microwave-assisted facile hydrothermal synthesis

NASA Astrophysics Data System (ADS)

Rangel, R.; Cedeño, V.; Ramos-Corona, A.; Gutiérrez, R.; Alvarado-Gil, J. J.; Ares, O.; Bartolo-Pérez, P.; Quintana, P.

2017-08-01

Microwave hydrothermal synthesis, using an experimental 23 factorial design, was used to produce tunable ZnO nano- and microstructures, and their potential as photocatalysts was explored. Photocatalytic reactions were conducted in a microreactor batch system under UV and visible light irradiation, while monitoring methylene blue degradation, as a model system. The variables considered in the microwave reactor to produce ZnO nano- or microstructures, were time, NaOH concentration and synthesis temperature. It was found that, specific surface area and volume/surface area ratio were affected as a consequence of the synthesis conditions. In the second stage, the samples were plasma treated in a nitrogen atmosphere, with the purpose of introducing nitrogen into the ZnO crystalline structure. The central idea is to induce changes in the material structure as well as in its optical absorption, to make the plasma-treated material useful as photocatalyst in the visible region of the electromagnetic spectrum. Pristine ZnO and nitrogen-doped ZnO compounds were characterized by means of X-ray diffraction (XRD), scanning electron microscopy (SEM), specific surface area (BET), XPS, and UV-Vis diffuse reflectance spectroscopy. The results show that the methodology presented in this work is effective in tailoring the specific surface area of the ZnO compounds and incorporation of nitrogen into their structure, factors which in turn, affect its photocatalytic behavior.

Biofunctionalization of carbon nanostructures through enzyme immobilization in colloidal silica

NASA Astrophysics Data System (ADS)

Goulet, Evan M.

Multi-walled carbon nanotubes (MWNT) and carbon nanopipettes (CNP) provide interesting high aspect ratio scaffolds on which to base functionally gradient materials. In this dissertation, we present a general method for the production of an enzymatically active composite material based on MWNTs. Polyethyleneimine (PEI) was applied to purified MWNTs, generating a positive electrostatic potential on the MWNTs. This positive potential was used to apply negatively charged colloidal silica particle in the presence of a high concentration of enzyme. The silica coating continued to grow via localized condensation of silica particles driven by the buffered saline conditions, immobilizing the enzyme within the coating. The mesoporous nanostructure was characterized via transmission electron microscopy. Optical spectroscopy experiments on the material employed as an active suspension showed that the immobilized enzymes horseradish peroxidase (HRP) and tyrosinase (TV) retained their activity upon incorporation into the material. Using HRP as a model enzyme, it was determined that the MWNT-HRP-Silica material showed similar pH and temperature dependencies in activity to those of free HRP in solution. An examination of the Michaelis-Menten kinetics showed that the material had a slightly higher value of KM than did free HRP. The MWNT-HRP-Silica material was also employed as an active filter membrane, which allowed us to explore the reusable nature of the material. We were able to show the denaturation of the filter due to the loss of Ca2+ cations at low pH and then restore the activity by soaking the filter membrane in 1 mM CaCl2. The MWNT-HRP-Silica material was used to modify a carbon microelectrode and produce a functioning electrochemical sensor for H2O2 . Utilizing cyclic voltammetry, the sensor was shown to have a linear response in limiting current versus concentration of H2O2 of 4.26 pA/microM. We also determined a lower detection limit of 0.67 microM H2O2. CNPs were

ZnO Nanostructure Templates as a Cost-Efficient Mass-Producible Route for the Development of Cellular Networks

PubMed Central

Makarona, Eleni; Peter, Beatrix; Szekacs, Inna; Tsamis, Christos; Horvath, Robert

2016-01-01

The development of artificial surfaces which can regulate or trigger specific functions of living cells, and which are capable of inducing in vivo-like cell behaviors under in vitro conditions has been a long-sought goal over the past twenty years. In this work, an alternative, facile and cost-efficient method for mass-producible cellular templates is presented. The proposed methodology consists of a cost-efficient, two-step, all-wet technique capable of producing ZnO-based nanostructures on predefined patterns on a variety of substrates. ZnO—apart from the fact that it is a biocompatible material—was chosen because of its multifunctional nature which has rendered it a versatile material employed in a wide range of applications. Si, Si3N4, emulated microelectrode arrays and conventional glass cover slips were patterned at the micrometer scale and the patterns were filled with ZnO nanostructures. Using HeLa cells, we demonstrated that the fabricated nanotopographical features could promote guided cellular adhesion on the pre-defined micron-scale patterns only through nanomechanical cues without the need for further surface activation or modification. The basic steps of the micro/nanofabrication are presented and the results from the cell adhesion experiments are discussed, showing the potential of the suggested methodology for creating low-cost templates for engineered cellular networks. PMID:28773382

Building Materials from Colloidal Nanocrystal Assemblies: Molecular Control of Solid/Solid Interfaces in Nanostructured Tetragonal ZrO 2

DOE Office of Scientific and Technical Information (OSTI.GOV)

Shaw, Santosh; Silva, Tiago F.; Bobbitt, Jonathan M.

We describe in this paper a bottom-up approach to control the composition of solid/solid interfaces in nanostructured materials, and we test its effectiveness on tetragonal ZrO 2, an inorganic phase of great technological significance. Colloidal nanocrystals capped with trioctylphosphine oxide (TOPO) or oleic acid (OA) are deposited, and the organic fraction of the ligands is selectively etched with O 2 plasma. The interfaces in the resulting all-inorganic colloidal nanocrystal assemblies are either nearly bare (for OA-capped nanocrystals) or terminated with phosphate groups (for TOPO-capped nanocrystals) resulting from the reaction of phosphine oxide groups with plasma species. The chemical modification ofmore » the interfaces has extensive effects on the thermodynamics and kinetics of the material. Different growth kinetics indicate different rate limiting processes of growth (surface diffusion for the phosphate-terminated surfaces and dissolution for the “bare” surfaces). Phosphate termination led to a higher activation energy of growth, and a 3-fold reduction in interfacial energy, and facilitated significantly the conversion of the tetragonal phase into the monoclinic phase. Finally, films devoid of residual ligands persisted in the tetragonal phase at temperatures as high as 900 °C for 24 h.« less

Building Materials from Colloidal Nanocrystal Assemblies: Molecular Control of Solid/Solid Interfaces in Nanostructured Tetragonal ZrO 2

DOE PAGES

Shaw, Santosh; Silva, Tiago F.; Bobbitt, Jonathan M.; ...

2017-08-28

We describe in this paper a bottom-up approach to control the composition of solid/solid interfaces in nanostructured materials, and we test its effectiveness on tetragonal ZrO 2, an inorganic phase of great technological significance. Colloidal nanocrystals capped with trioctylphosphine oxide (TOPO) or oleic acid (OA) are deposited, and the organic fraction of the ligands is selectively etched with O 2 plasma. The interfaces in the resulting all-inorganic colloidal nanocrystal assemblies are either nearly bare (for OA-capped nanocrystals) or terminated with phosphate groups (for TOPO-capped nanocrystals) resulting from the reaction of phosphine oxide groups with plasma species. The chemical modification ofmore » the interfaces has extensive effects on the thermodynamics and kinetics of the material. Different growth kinetics indicate different rate limiting processes of growth (surface diffusion for the phosphate-terminated surfaces and dissolution for the “bare” surfaces). Phosphate termination led to a higher activation energy of growth, and a 3-fold reduction in interfacial energy, and facilitated significantly the conversion of the tetragonal phase into the monoclinic phase. Finally, films devoid of residual ligands persisted in the tetragonal phase at temperatures as high as 900 °C for 24 h.« less

Magnetic assembly route to colloidal responsive photonic nanostructures.

PubMed

He, Le; Wang, Mingsheng; Ge, Jianping; Yin, Yadong

2012-09-18

Responsive photonic structures can respond to external stimuli by transmitting optical signals. Because of their important technological applications such as color signage and displays, biological and chemical sensors, security devices, ink and paints, military camouflage, and various optoelectronic devices, researchers have focused on developing these functional materials. Conventionally, self-assembled colloidal crystals containing periodically arranged dielectric materials have served as the predominant starting frameworks. Stimulus-responsive materials are incorporated into the periodic structures either as the initial building blocks or as the surrounding matrix so that the photonic properties can be tuned. Although researchers have proposed various versions of responsive photonic structures, the low efficiency of fabrication through self-assembly, narrow tunability, slow responses to the external stimuli, incomplete reversibility, and the challenge of integrating them into existing photonic devices have limited their practical application. In this Account, we describe how magnetic fields can guide the assembly of superparamagnetic colloidal building blocks into periodically arranged particle arrays and how the photonic properties of the resulting structures can be reversibly tuned by manipulating the external magnetic fields. The application of the external magnetic field instantly induces a strong magnetic dipole-dipole interparticle attraction within the dispersion of superparamagnetic particles, which creates one-dimensional chains that each contains a string of particles. The balance between the magnetic attraction and the interparticle repulsions, such as the electrostatic force, defines the interparticle separation. By employing uniform superparamagnetic particles of appropriate sizes and surface charges, we can create one-dimensional periodicity, which leads to strong optical diffraction. Acting remotely over a large distance, magnetic forces drove the

Colloidal lithography nanostructured Pd/PdO x core-shell sensor for ppb level H2S detection.

PubMed

Benedict, Samatha; Lumdee, Chatdanai; Dmitriev, Alexandre; Anand, Srinivasan; Bhat, Navakanta

2018-06-22

In this work we report on plasma oxidation of palladium (Pd) to form reliable palladium/palladium oxide (Pd/PdO x ) core-shell sensor for ppb level H 2 S detection and its performance improvement through nanostructuring using hole-mask colloidal lithography (HCL). The plasma oxidation parameters and the sensor operating conditions are optimized to arrive at a sensor device with high sensitivity and repeatable response for H 2 S. The plasma oxidized palladium/palladium oxide sensor shows a response of 43.1% at 3 ppm H 2 S at the optimum operating temperature of 200 °C with response and recovery times of 24 s and 155 s, respectively. The limit of detection (LoD) of the plasma oxidised beam is 10 ppb. We further integrate HCL, a bottom-up and cost-effective process, to create nanodiscs of fixed diameter of 100 nm and varying heights (10, 15 and 20 nm) on 10 nm thin Pd beam which is subsequently plasma oxidized to improve the H 2 S sensing characteristics. The nanostructured Pd/PdO x sensor with nanodiscs of 100 nm diameter and 10 nm height shows an enhancement in sensing performance by 11.8% at same operating temperature and gas concentration. This nanostructured sensor also shows faster response and recovery times (15 s and 100 s, respectively) compared to the unstructured Pd/PdO x counterpart together with an experimental LoD of 10 ppb and the estimated limit going all the way down to 2 ppb. Material characterization of the fabricated Pd/PdO x sensors is done using UV-vis spectroscopy and x-ray photoemission spectroscopy.

Colloidal lithography nanostructured Pd/PdO x core–shell sensor for ppb level H2S detection

NASA Astrophysics Data System (ADS)

Benedict, Samatha; Lumdee, Chatdanai; Dmitriev, Alexandre; Anand, Srinivasan; Bhat, Navakanta

2018-06-01

In this work we report on plasma oxidation of palladium (Pd) to form reliable palladium/palladium oxide (Pd/PdO x ) core–shell sensor for ppb level H2S detection and its performance improvement through nanostructuring using hole-mask colloidal lithography (HCL). The plasma oxidation parameters and the sensor operating conditions are optimized to arrive at a sensor device with high sensitivity and repeatable response for H2S. The plasma oxidized palladium/palladium oxide sensor shows a response of 43.1% at 3 ppm H2S at the optimum operating temperature of 200 °C with response and recovery times of 24 s and 155 s, respectively. The limit of detection (LoD) of the plasma oxidised beam is 10 ppb. We further integrate HCL, a bottom-up and cost-effective process, to create nanodiscs of fixed diameter of 100 nm and varying heights (10, 15 and 20 nm) on 10 nm thin Pd beam which is subsequently plasma oxidized to improve the H2S sensing characteristics. The nanostructured Pd/PdO x sensor with nanodiscs of 100 nm diameter and 10 nm height shows an enhancement in sensing performance by 11.8% at same operating temperature and gas concentration. This nanostructured sensor also shows faster response and recovery times (15 s and 100 s, respectively) compared to the unstructured Pd/PdO x counterpart together with an experimental LoD of 10 ppb and the estimated limit going all the way down to 2 ppb. Material characterization of the fabricated Pd/PdO x sensors is done using UV–vis spectroscopy and x-ray photoemission spectroscopy.

Growth of catalyst-free high-quality ZnO nanowires by thermal evaporation under air ambient

PubMed Central

2012-01-01

ZnO nanowires have been successfully fabricated on Si substrate by simple thermal evaporation of Zn powder under air ambient without any catalyst. Morphology and structure analyses indicated that ZnO nanowires had high purity and perfect crystallinity. The diameter of ZnO nanowires was 40 to 100 nm, and the length was about several tens of micrometers. The prepared ZnO nanowires exhibited a hexagonal wurtzite crystal structure. The growth of the ZnO nanostructure was explained by the vapor-solid mechanism. The simplicity, low cost and fewer necessary apparatuses of the process would suit the high-throughput fabrication of ZnO nanowires. The ZnO nanowires fabricated on Si substrate are compatible with state-of-the-art semiconductor industry. They are expected to have potential applications in functional nanodevices. PMID:22502639

Enhanced light absorption of silicon solar cells with dielectric nanostructured back reflector

NASA Astrophysics Data System (ADS)

Ren, Rui; Zhong, Zheng

2018-06-01

This paper investigates the light absorption property of nanostructured dielectric reflectors in silicon thin film solar cells using numerical simulation. Flat thin film solar cell with ZnO nanostructured back reflector can produce comparable photocurrent to the control model with Ag nanostructured back reflector. Furthermore, when it is integrated with nano-pillar surface decoration, a photocurrent density of 29.5 mA/cm2 can be achieved, demonstrating a photocurrent enhancement of 5% as compared to the model with Ag nanostructured back reflector.

Fabrication and characterization of hexagonally patterned quasi-1D ZnO nanowire arrays

PubMed Central

2014-01-01

Quasi-one-dimensional (quasi-1D) ZnO nanowire arrays with hexagonal pattern have been successfully synthesized via the vapor transport process without any metal catalyst. By utilizing polystyrene microsphere self-assembled monolayer, sol–gel-derived ZnO thin films were used as the periodic nucleation sites for the growth of ZnO nanowires. High-quality quasi-1D ZnO nanowires were grown from nucleation sites, and the original hexagonal periodicity is well-preserved. According to the experimental results, the vapor transport solid condensation mechanism was proposed, in which the sol–gel-derived ZnO film acting as a seed layer for nucleation. This simple method provides a favorable way to form quasi-1D ZnO nanostructures applicable to diverse fields such as two-dimensional photonic crystal, nanolaser, sensor arrays, and other optoelectronic devices. PMID:24521308

Atomic layer deposition in nanostructured photovoltaics: tuning optical, electronic and surface properties

NASA Astrophysics Data System (ADS)

Palmstrom, Axel F.; Santra, Pralay K.; Bent, Stacey F.

2015-07-01

Nanostructured materials offer key advantages for third-generation photovoltaics, such as the ability to achieve high optical absorption together with enhanced charge carrier collection using low cost components. However, the extensive interfacial areas in nanostructured photovoltaic devices can cause high recombination rates and a high density of surface electronic states. In this feature article, we provide a brief review of some nanostructured photovoltaic technologies including dye-sensitized, quantum dot sensitized and colloidal quantum dot solar cells. We then introduce the technique of atomic layer deposition (ALD), which is a vapor phase deposition method using a sequence of self-limiting surface reaction steps to grow thin, uniform and conformal films. We discuss how ALD has established itself as a promising tool for addressing different aspects of nanostructured photovoltaics. Examples include the use of ALD to synthesize absorber materials for both quantum dot and plasmonic solar cells, to grow barrier layers for dye and quantum dot sensitized solar cells, and to infiltrate coatings into colloidal quantum dot solar cell to improve charge carrier mobilities as well as stability. We also provide an example of monolayer surface modification in which adsorbed ligand molecules on quantum dots are used to tune the band structure of colloidal quantum dot solar cells for improved charge collection. Finally, we comment on the present challenges and future outlook of the use of ALD for nanostructured photovoltaics.

Tartaric acid assisted hydrothermal synthesis of different flower-like ZnO hierarchical architectures with tunable optical and oxygen vacancy-induced photocatalytic properties

NASA Astrophysics Data System (ADS)

Liu, Tingzhi; Li, Yangyang; Zhang, Hao; Wang, Min; Fei, Xiaoyan; Duo, Shuwang; Chen, Ying; Pan, Jian; Wang, Wei

2015-12-01

Different flower-like ZnO hierarchical architectures were prepared by tartaric acid assisted hydrothermal synthesis, especially four flower-like ZnO nanostructures were obtained simultaneously under the same reaction condition. The cauliflower-like ZnO is assembled by spherical shaped nanoparticles, and the chrysanthemum-like and other flower-like ZnO nanostructures are assembled by hexagonal rods/prisms with from planar to semi-pyramid, and to pyramid tips. TA acts as a capping agent and structure-directing agent during the synthesis. All ZnO possess the hexagonal wurtzite structure. The PL spectra can be tuned by changing TA concentration. XRD, PL and Raman spectra confirmed that oxygen vacancies mainly come from the ZnO surface. The flower-like samples of 1:4.5 and 1:3 with the largest aspect ratios have highest photocatalytic performance. They decompose 85% MB within 60 min. Combining PL Gaussian fitting with K, the higher content of oxygen vacancy is, the higher photocatalytic activity is. The enhanced photocatalytic performance is mainly induced by oxygen vacancy of ZnO. The possible formation mechanism, growth and change process of flower-like ZnO were proposed.

Wettability control of micropore-array films by altering the surface nanostructures.

PubMed

Chang, Chi-Jung; Hung, Shao-Tsu

2010-07-01

By controlling the surface nanostructure, the wettability of films with similar pore-array microstructure can be tuned from hydrophilic to nearly superhydrophobic without variation of the chemical composition. PA1 pore-array film consisting of the horizontal ZnO nanosheets was nearly superhydrophobic. PA2 pore-array film consisting of growth-hindered vertically-aligned ZnO nanorods was hydrophilic. The influences of the nanostructure shape, orientation and the micropore size on the contact angle of the PA1 films were studied. This study provides a new approach to control the wettability of films with similar pore-array structure at the micro-scale by changing their surface nanostructure. PA1 films exhibited irradiation induced reversible wettability transition. The feasibility of creating a wetted radial pattern by selective UV irradiation of PA1 film through a mask with radial pattern and water vapor condensation was also evaluated.

Application of Nanostructures in Electrochromic Materials and Devices: Recent Progress.

PubMed

Wang, Jin Min; Sun, Xiao Wei; Jiao, Zhihui

2010-11-26

The recent progress in application of nanostructures in electrochromic materials and devices is reviewed. ZnO nanowire array modified by viologen and WO₃, crystalline WO₃ nanoparticles and nanorods, mesoporous WO₃ and TiO₂, poly(3,4-ethylenedioxythiophene) nanotubes, Prussian blue nanoinks and nanostructures in switchable mirrors are reviewed. The electrochromic properties were significantly enhanced by applying nanostructures, resulting in faster switching responses, higher stability and higher optical contrast. A perspective on the development trends in electrochromic materials and devices is also proposed.

Carrier Multiplication Mechanisms and Competing Processes in Colloidal Semiconductor Nanostructures

PubMed Central

Kershaw, Stephen V.; Rogach, Andrey L.

2017-01-01

Quantum confined semiconductor nanoparticles, such as colloidal quantum dots, nanorods and nanoplatelets have broad extended absorption spectra at energies above their bandgaps. This means that they can absorb light at high photon energies leading to the formation of hot excitons with finite excited state lifetimes. During their existence, the hot electron and hole that comprise the exciton may start to cool as they relax to the band edge by phonon mediated or Auger cooling processes or a combination of these. Alongside these cooling processes, there is the possibility that the hot exciton may split into two or more lower energy excitons in what is termed carrier multiplication (CM). The fission of the hot exciton to form lower energy multiexcitons is in direct competition with the cooling processes, with the timescales for multiplication and cooling often overlapping strongly in many materials. Once CM has been achieved, the next challenge is to preserve the multiexcitons long enough to make use of the bonus carriers in the face of another competing process, non-radiative Auger recombination. However, it has been found that Auger recombination and the several possible cooling processes can be manipulated and usefully suppressed or retarded by engineering the nanoparticle shape, size or composition and by the use of heterostructures, along with different choices of surface treatments. This review surveys some of the work that has led to an understanding of the rich carrier dynamics in semiconductor nanoparticles, and that has started to guide materials researchers to nanostructures that can tilt the balance in favour of efficient CM with sustained multiexciton lifetimes. PMID:28927007

Hierarchical Si/ZnO trunk-branch nanostructure for photocurrent enhancement

PubMed Central

2014-01-01

Hierarchical Si/ZnO trunk-branch nanostructures (NSs) have been synthesized by hot wire assisted chemical vapor deposition method for trunk Si nanowires (NWs) on indium tin oxide (ITO) substrate and followed by the vapor transport condensation (VTC) method for zinc oxide (ZnO) nanorods (NRs) which was laterally grown from each Si nanowires (NWs). A spin coating method has been used for zinc oxide (ZnO) seeding. This method is better compared with other group where they used sputtering method for the same process. The sputtering method only results in the growth of ZnO NRs on top of the Si trunk. Our method shows improvement by having the growth evenly distributed on the lateral sides and caps of the Si trunks, resulting in pine-leave-like NSs. Field emission scanning electron microscope image shows the hierarchical nanostructures resembling the shape of the leaves of pine trees. Single crystalline structure for the ZnO branch grown laterally from the crystalline Si trunk has been identified by using a lattice-resolved transmission electron microscope. A preliminary photoelectrochemical (PEC) cell testing has been setup to characterize the photocurrent of sole array of ZnO NR growth by both hydrothermal-grown (HTG) method and VTC method on ITO substrates. VTC-grown ZnO NRs showed greater photocurrent effect due to its better structural properties. The measured photocurrent was also compared with the array of hierarchical Si/ZnO trunk-branch NSs. The cell with the array of Si/ZnO trunk-branch NSs revealed four-fold magnitude enhancement in photocurrent density compared with the sole array of ZnO NRs obtain from VTC processes. PMID:25246872

Metal oxide nanostructures: preparation, characterization and functional applications as chemical sensors.

PubMed

Zappa, Dario; Bertuna, Angela; Comini, Elisabetta; Kaur, Navpreet; Poli, Nicola; Sberveglieri, Veronica; Sberveglieri, Giorgio

2017-01-01

Preparation and characterization of different metal oxide (NiO, WO 3 , ZnO, SnO 2 and Nb 2 O 5 ) nanostructures for chemical sensing are presented. p-Type (NiO) and n-type (WO 3 , SnO 2 , ZnO and Nb 2 O 5 ) metal oxide nanostructures were grown on alumina substrates using evaporation-condensation, thermal oxidation and hydrothermal techniques. Surface morphologies and crystal structures were investigated through scanning electron microscopy and Raman spectroscopy. Furthermore, different batches of sensors have been prepared, and their sensing performances towards carbon monoxide and nitrogen dioxide have been explored. Moreover, metal oxide nanowires have been integrated into an electronic nose and successfully applied to discriminate between drinking and contaminated water.

Nanostructure CdS/ZnO heterojunction configuration for photocatalytic degradation of Methylene blue

NASA Astrophysics Data System (ADS)

Velanganni, S.; Pravinraj, S.; Immanuel, P.; Thiruneelakandan, R.

2018-04-01

In the present manuscript, thin films of Zinc Oxide (ZnO) have been deposited on a FTO substrate using a simple successive ionic layer adsorption and reaction (SILAR) and chemical bath deposition (CBD) method. Cadmium Sulphide (CdS) nanoparticles are sensitized over ZnO thin films using SILAR method. The synthesized nanostructured CdS/ZnO heterojunction thin films was characterized by X-ray diffraction (XRD), Scanning electron microscopy (SEM), High resolution transmission electron microscopy (HR-TEM), X-ray photoelectron spectroscopy (XPS), UV-Vis spectroscopy and Raman spectroscopy techniques. The band gap of CdS nanoparticles over ZnO nanostructure was found to be about 3.20 eV. The photocatalytic activities of the deposited CdS/ZnO thin films were evaluated by the degradation of methylene blue (MB) in an aqueous solution under sun light irradiation.

Control of the ZnO nanowires nucleation site using microfluidic channels.

PubMed

Lee, Sang Hyun; Lee, Hyun Jung; Oh, Dongcheol; Lee, Seog Woo; Goto, Hiroki; Buckmaster, Ryan; Yasukawa, Tomoyuki; Matsue, Tomokazu; Hong, Soon-Ku; Ko, HyunChul; Cho, Meoung-Whan; Yao, Takafumi

2006-03-09

We report on the growth of uniquely shaped ZnO nanowires with high surface area and patterned over large areas by using a poly(dimethylsiloxane) (PDMS) microfluidic channel technique. The synthesis uses first a patterned seed template fabricated by zinc acetate solution flowing though a microfluidic channel and then growth of ZnO nanowire at the seed using thermal chemical vapor deposition on a silicon substrate. Variations the ZnO nanowire by seed pattern formed within the microfluidic channel were also observed for different substrates and concentrations of the zinc acetate solution. The photocurrent properties of the patterned ZnO nanowires with high surface area, due to their unique shape, were also investigated. These specialized shapes and patterning technique increase the possibility of realizing one-dimensional nanostructure devices such as sensors and optoelectric devices.

Highly sensitive hydrogen detection of catalyst-free ZnO nanorod networks suspended by lithography-assisted growth.

PubMed

Huh, Junghwan; Park, Jonghyurk; Kim, Gyu Tae; Park, Jeong Young

2011-02-25

We have successfully demonstrated a ZnO nanorod-based 3D nanostructure to show a high sensitivity and very fast response/recovery to hydrogen gas. ZnO nanorods have been synthesized selectively over the pre-defined area at relatively low temperature using a simple self-catalytic solution process assisted by a lithographic method. The conductance of the ZnO nanorod device varies significantly as the concentration of the hydrogen is changed without any additive metal catalyst, revealing a high sensitivity to hydrogen gas. Its superior performance can be explained by the porous structure of its three-dimensional network and the enhanced surface reaction of the hydrogen molecules with the oxygen defects resulting from a high surface-to-volume ratio. It was found that the change of conductance follows a power law depending on the hydrogen concentration. A Langmuir isotherm following an ideal power law and a cross-over behavior of the activation energy with respect to hydrogen concentration were observed. This is a very novel and intriguing phenomenon on nanostructured materials, which suggests competitive surface reactions in ZnO nanorod gas sensors.

Seedless-grown of ZnO thin films for photoelectrochemical water splitting application

NASA Astrophysics Data System (ADS)

Abdullah, Aidahani; Hamid, Muhammad Azmi Abdul; Chiu, W. S.

2018-04-01

We developed a seedless hydrothermal method to grow a flower like ZnO nanorods. Prior to the growth, a layer of Au thin film is sputtered onto the surface of indium tin oxide (ITO) coated glass substrate. The morphological, structural and optical properties of the ZnO nanostructures were characterized by means of scanning electron microscopy (SEM), X-ray diffraction (XRD), and diffuse reflection measurement to understand the growth process of the working thin film. The photoelectrochemical (PEC) results suggest that the deposition of ZnO nanorods on Au nanoparticles plays an important role in enhancing the photoelectrode activity. H2 evolution from photo-splitting of water over Au-incorporated ZnO in the 0.1M NaOH liquid system was enhanced, compared to that over bare ZnO; particularly, the production of 15.5 µL of H2 gas after twenty five minutes exposure of ZnO grown on Au-coated thin film.

Structural, optical and field emission properties of urchin-shaped ZnO nanostructures.

PubMed

Al-Heniti, Saleh; Umar, Ahmad

2013-01-01

In this work, well-crystallized urchin-shaped ZnO structures were synthesized on silicon substrate by simple non-catalytic thermal evaporation process by using metallic zinc powder in the presence of oxygen as source materials for zinc and oxygen, respectively. The synthesized ZnO structures were characterized in detail in terms of their morphological, structural, optical and field emission properties. The detailed morphological investigations revealed that the synthesized structures possess urchin-shape and grown in high-density over the substrate surface. The detailed structural and optical characterizations revealed that the synthesized urchin-shaped ZnO structures are well-crystallized and exhibiting good optical properties. The field emission analysis for urchin-shaped ZnO structures exhibits a turn-on field of 4.6 V/microm. The emission current density reached to 0.056 mA/cm2 at an applied electrical field of 6.4 V/microm and shows no saturation. The calculated field enhancement factor 'beta', from the F-N plot, was found to be approximately 2.2 x 10(3).

Efficient acetone sensor based on Ni-doped ZnO nanostructures prepared by spray pyrolysis technique

NASA Astrophysics Data System (ADS)

Darunkar, Swapnil S.; Acharya, Smita A.

2018-05-01

Ni-doped ZnO thin film was prepared by home-built spray pyrolysis unit for the detection of acetone at 300°C. Scanning electron microscopic (SEM) images of as-developed thin film of undoped ZnO exhibits large quantity of spherical, non-agglomerated particles with uniform size while in Ni-doped ZnO, particles are quite non-uniform in nature. The particle size estimated by using image J are obtained to be around 20-200 nm. Ni-doping effect on band gaps are determined by UV-vis optical spectroscopy and band gap of Ni-doped ZnO is found to be 3.046 eV. Nickel doping exceptionally enhances the sensing response of ZnO as compared to undoped ZnO system. The major role of the Ni-doping is to create more active sites for chemisorbed oxygen on the surface of sensor and correspondingly, to improve the sensing response. The 6 at.% of Ni-doped ZnO exhibits the highest response (92%) for 100 ppm acetone at 300 °C.

A colloidal quantum dot photonic crystal phosphor: nanostructural engineering of the phosphor for enhanced color conversion.

PubMed

Min, Kyungtaek; Jung, Hyunho; Park, Yeonsang; Cho, Kyung-Sang; Roh, Young-Geun; Hwang, Sung Woo; Jeon, Heonsu

2017-06-29

Phosphors, long-known color-converting photonic agents, are gaining increasing attention owing to the interest in white LEDs and related applications. Conventional material-based approaches to phosphors focus on obtaining the desired absorption/emission wavelengths and/or improving quantum efficiency. Here, we report a novel approach for enhancing the performance of phosphors: structural modification of phosphors. We incorporated inorganic colloidal quantum dots (CQDs) into a lateral one-dimensional (1D) photonic crystal (PhC) thin-film structure, with its photonic band-edge (PBE) modes matching the energy of 'excitation photons' (rather than 'emitted photons', as in most other PBE application devices). At resonance, we observed an approximately 4-fold enhancement of fluorescence over the reference bulk phosphor, which reflects an improved absorption of the excitation photons. This nano-structural engineering approach is a paradigm shift in the phosphor research area and may help to develop next-generation higher efficiency phosphors with novel characteristics.

A dual-colored bio-marker made of doped ZnO nanocrystals

NASA Astrophysics Data System (ADS)

Wu, Y. L.; Fu, S.; Tok, A. I. Y.; Zeng, X. T.; Lim, C. S.; Kwek, L. C.; Boey, F. C. Y.

2008-08-01

Bio-compatible ZnO nanocrystals doped with Co, Cu and Ni cations, surface capped with two types of aminosilanes and titania are synthesized by a soft chemical process. Due to the small particle size (2-5 nm), surface functional groups and the high photoluminescence emissions at the UV and blue-violet wavelength ranges, bio-imaging on human osteosarcoma (Mg-63) cells and histiocytic lymphoma U-937 monocyte cells showed blue emission at the nucleus and bright turquoise emission at the cytoplasm simultaneously. This is the first report on dual-color bio-images labeled by one semiconductor nanocrystal colloidal solution. Bright green emission was detected on mung bean seedlings labeled by all the synthesized ZnO nanocrystals. Cytotoxicity tests showed that the aminosilanes capped nanoparticles are non-toxic. Quantum yields of the nanocrystals varied from 79% to 95%. The results showed the potential of the pure ZnO and Co-doped ZnO nanocrystals for live imaging of both human cells and plant systems.

Study of morphology effects on magnetic interactions and band gap variations for 3d late transition metal bi-doped ZnO nanostructures by hybrid DFT calculations

NASA Astrophysics Data System (ADS)

Datta, Soumendu; Kaphle, Gopi Chandra; Baral, Sayan; Mookerjee, Abhijit

2015-08-01

Using density functional theory (DFT) based electronic structure calculations, the effects of morphology of semiconducting nanostructures on the magnetic interaction between two magnetic dopant atoms as well as a possibility of tuning band gaps have been studied in the case of the bi-doped (ZnO)24 nanostructures with the impurity dopant atoms of the 3d late transition metals—Mn, Fe, Co, Ni, and Cu. To explore the morphology effect, three different structures of the host (ZnO)24 nano-system, having different degrees of spatial confinement, have been considered: a two dimensional nanosheet, a one dimensional nanotube, and a finite cage-shaped nanocluster. The present study employs hybrid density functional theory to accurately describe the electronic structure of all the systems. It is shown here that the magnetic coupling between the two dopant atoms remains mostly anti-ferromagnetic in the course of changing the morphology from the sheet geometry to the cage-shaped geometry of the host systems, except for the case of energetically most stable bi-Mn doping, which shows a transition from ferromagnetic to anti-ferromagnetic coupling with decreasing aspect ratio of the host system. The effect of the shape change, however, has a significant effect on the overall band gap variations of both the pristine as well as all the bi-doped systems, irrespective of the nature of the dopant atoms and provides a means for easy tunability of their optoelectronic properties.

Application of Nanostructures in Electrochromic Materials and Devices: Recent Progress

PubMed Central

Wang, Jinmin; Sun, Xiao Wei; Jiao, Zhihui

2010-01-01

The recent progress in application of nanostructures in electrochromic materials and devices is reviewed. ZnO nanowire array modified by viologen and WO3, crystalline WO3 nanoparticles and nanorods, mesoporous WO3 and TiO2, poly(3,4-ethylenedioxythiophene) nanotubes, Prussian blue nanoinks and nanostructures in switchable mirrors are reviewed. The electrochromic properties were significantly enhanced by applying nanostructures, resulting in faster switching responses, higher stability and higher optical contrast. A perspective on the development trends in electrochromic materials and devices is also proposed. PMID:28883368

Low Temperature Annealed Zinc Oxide Nanostructured Thin Film-Based Transducers: Characterization for Sensing Applications

PubMed Central

Haarindraprasad, R.; Hashim, U.; Gopinath, Subash C. B.; Kashif, Mohd; Veeradasan, P.; Balakrishnan, S. R.; Foo, K. L.; Poopalan, P.

2015-01-01

The performance of sensing surfaces highly relies on nanostructures to enhance their sensitivity and specificity. Herein, nanostructured zinc oxide (ZnO) thin films of various thicknesses were coated on glass and p-type silicon substrates using a sol-gel spin-coating technique. The deposited films were characterized for morphological, structural, and optoelectronic properties by high-resolution measurements. X-ray diffraction analyses revealed that the deposited films have a c-axis orientation and display peaks that refer to ZnO, which exhibits a hexagonal structure with a preferable plane orientation (002). The thicknesses of ZnO thin films prepared using 1, 3, 5, and 7 cycles were measured to be 40, 60, 100, and 200 nm, respectively. The increment in grain size of the thin film from 21 to 52 nm was noticed, when its thickness was increased from 40 to 200 nm, whereas the band gap value decreased from 3.282 to 3.268 eV. Band gap value of ZnO thin film with thickness of 200 nm at pH ranging from 2 to 10 reduces from 3.263eV to 3.200 eV. Furthermore, to evaluate the transducing capacity of the ZnO nanostructure, the refractive index, optoelectric constant, and bulk modulus were analyzed and correlated. The highest thickness (200 nm) of ZnO film, embedded with an interdigitated electrode that behaves as a pH-sensing electrode, could sense pH variations in the range of 2-10. It showed a highly sensitive response of 444 μAmM-1cm-2 with a linear regression of R2 =0.9304. The measured sensitivity of the developed device for pH per unit is 3.72μA/pH. PMID:26167853

SrZnO nanostructures grown on templated <0001> Al2O3 substrates by pulsed laser deposition

NASA Astrophysics Data System (ADS)

Labis, Joselito P.; Alanazi, Anwar Q.; Albrithen, Hamad A.; El-Toni, Ahmed Mohamed; Hezam, Mahmoud; Elafifi, Hussein Elsayed; Abaza, Osama M.

2017-09-01

The parameters of pulsed laser deposition (PLD) have been optimized to design different nanostructures of Strontium-alloyed zinc oxide (SrZnO). In this work, SrZnO nanostructures are grown on <0001>Al2O3 substrates via two-step templating/seeding approach. In the temperature range between 300 - 750 oC and O2 background pressures between 0.01 and 10 Torr, the growth conditions have been tailored to grow unique pointed leaf-like- and pitted olive-like nanostructures. Prior to the growth of the nanostructures, a thin SrZnO layer that serves as seed layer/template is first deposited on the Al2O3 substrates at ˜300oC and background oxygen pressure of 10 mTorr. The optical properties of the nanostructures were examined by UV/Vis spectroscopy and photoluminescence (PL), while the structures/morphologies were examined by SEM, TEM, and XRD. The alloyed SrZnO nanostructures, grown by ablating ZnO targets with 5, 10, 25% SrO contents, have in common a single-crystal hexagonal nanostructure with (0002) preferential orientation and have shown remarkable changes in the morphological and optical properties of the materials. To date, this is the only reported work on optimization of laser ablation parameters to design novel SrZnO nanostructures in the 5-25% alloying range, as most related Sr-doped ZnO studies were done below 7% doping. Although the physical properties of ZnO are modified via Sr doping, the mechanism remains unclear. The PLD-grown SrZnO nanostructures were directly grown onto the Al2O3 substrates; thus making these nanomaterials very promising for potential applications in biosensors, love-wave filters, solar cells, and ultrasonic oscillators.

Parameters optimization for synthesis of Al-doped ZnO nanoparticles by laser ablation in water

NASA Astrophysics Data System (ADS)

Krstulović, Nikša; Salamon, Krešimir; Budimlija, Ognjen; Kovač, Janez; Dasović, Jasna; Umek, Polona; Capan, Ivana

2018-05-01

Al-doped ZnO crystalline colloidal nanoparticles were synthesized by a laser ablation of ZnO:Al2O3 in MilliQ water. Experiments were performed systematically by changing the number of applied laser pulses and laser output energy with the aim to affect the nanoparticle size, composition (Al/Zn ratio) and characteristics (band-gap, crystallinity). Distinctly, set of nanoparticle syntheses was performed in deionized water for comparison. SEM investigation of colloidal nanoparticles revealed that the formed nanoparticles are 30 nm thick discs with average diameters ranging from 450 to 510 nm. It was found that craters in the target formed during the laser ablation influence the size of synthesized colloidal nanoparticles. This is explained by efficient nanoparticle growth through diffusion process which take place in spatially restricted volume of the target crater. When laser ablation takes place in deionized water the synthesized nanoparticles have a mesh-like structure with sparse concentration of disc-like nanoparticles. Al/Zn ratio and band-gap energy of nanoparticles are highly influenced by the number and output energy of applied laser pulses. In addition, the procedure how to calculate the concentration of colloidal nanoparticles synthesized by laser ablation in liquids is proposed. The Al-doped ZnO colloidal nanoparticles properties were obtained using different techniques like scanning electron microscopy, optical microscopy, energy-dispersive X-ray spectroscopy, grazing-incidence X-ray diffraction, photoabsorption, photoluminescence and X-ray photoelectron spectroscopy.

Structural, magnetic and optical properties of ZnO nanostructures converted from ZnS nanoparticles

DOE Office of Scientific and Technical Information (OSTI.GOV)

Patel, Prayas Chandra; Ghosh, Surajit; Srivastava, P.C., E-mail: pcsrivastava50@gmail.com

Graphical abstract: The phase conversion of ZnS to highly crystalline hexagonal ZnO was done by heat treatment. - Highlights: • Phase change of cubic ZnS to hexagonal ZnO via heat treatment. • Band gap was found to decrease with increasing calcinations temperature. • ZnO samples have higher magnetic moment than ZnS. • Blocking Temperature of the samples is well above room temperature. • Maximum negative%MR with saturation value ∼38% was found for sample calcined at 600° C. - Abstract: The present work concentrates on the synthesis of cubic ZnS and hexagonal ZnO semiconducting nanoparticle from same precursor via co-precipitation method.more » The phase conversion of ZnS to highly crystalline hexagonal ZnO was done by heat treatment. From the analysis of influence of calcination temperature on the structural, optical and vibrational properties of the samples, an optimum temperature was found for the total conversion of ZnS nanoparticles to ZnO. Role of quantum confinement due to finite size is evident from the blue shift of the fundamental absorption in UV–vis spectra only in the ZnS nanoparticles. The semiconducting nature of the prepared samples is confirmed from the UV–vis, PL study and transport study. From the magnetic and transport studies, pure ZnO phase was found to be more prone to magnetic field.« less

Production of zinc oxide nanowires power with precisely defined morphology

NASA Astrophysics Data System (ADS)

Mičová, Júlia; Remeš, Zdeněk; Chan, Yu-Ying

2017-12-01

The interest about zinc oxide is increasing thanks to its unique chemical and physical properties. Our attention has focused on preparation powder of 1D nanostructures of ZnO nanowires with precisely defined morphology include characterization size (length and diameter) and shape controlled in the scanning electron microscopy (SEM). We have compared results of SEM with dynamic light scattering (DLS) technique. We have found out that SEM method gives more accurate results. We have proposed transformation process from ZnO nanowires on substrates to ZnO nanowires powder by ultrasound peeling to colloid followed by lyophilization. This method of the mass production of the ZnO nanowires powder has some advantages: simplicity, cost effective, large-scale and environment friendly.

Nanostructured silver sulfide: synthesis of various forms and their application

NASA Astrophysics Data System (ADS)

Sadovnikov, S. I.; Rempel, A. A.; Gusev, A. I.

2018-04-01

The results of experimental studies on nanostructured silver sulfide are analyzed and generalized. The influence of small particle size on nonstoichiometry of silver sulfide is discussed. Methods for the synthesis of various forms of nanostructured Ag2S including nanopowders, stable colloidal solutions, quantum dots, core–shell nanoparticles and heteronanostructures are described. The advantages and drawbacks of different synthetic procedures are analyzed. Main fields of application of nanostructured silver sulfide are considered. The bibliography includes 184 references.

A study on different morphological structures of zinc oxide nanostructures for humidity sensing application

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ismail, A. S., E-mail: kyrin-samaxi@yahoo.com; Mamat, M. H., E-mail: mhmamat@salam.uitm.edu.my; Rusop, M., E-mail: rusop@salam.uitm.my

2016-07-06

Effects of different morphological structures of ZnO to the performance of the device in the humidity sensing have been studied. Two different kinds of nanostructures were obtained which are nanords and nanoflakes. From the surface morphology image, the ZnO nanoflakes has lower diameter size of 100 nm compared to ZnO nanorods of 250 nm. The ZnO nanoflakes are not aligned and has low porous structure compared to ZnO nanorods. The humidity sensor performance of ZnO nanorods has superior performance compared to ZnO nanoflakes. The sensitivity of the ZnO nanorods sensor is 3.20 which are almost two times higher than themore » ZnO nanoflakes of 1.65. The structural properties of the samples have been characterized using field emission scanning electron microscopy (FESEM) electrical properties has been characterized using current voltage (I-V) measurement.« less

Enhanced Ethanol Gas Sensing Properties of SnO2-Core/ZnO-Shell Nanostructures

PubMed Central

Tharsika, T.; Haseeb, A. S. M. A.; Akbar, Sheikh A.; Sabri, Mohd Faizul Mohd; Hoong, Wong Yew

2014-01-01

An inexpensive single-step carbon-assisted thermal evaporation method for the growth of SnO2-core/ZnO-shell nanostructures is described, and the ethanol sensing properties are presented. The structure and phases of the grown nanostructures are investigated by field-emission scanning electron microscopy (FESEM), transmission electron microscopy (TEM) and X-ray diffraction (XRD) techniques. XRD analysis indicates that the core-shell nanostructures have good crystallinity. At a lower growth duration of 15 min, only SnO2 nanowires with a rectangular cross-section are observed, while the ZnO shell is observed when the growth time is increased to 30 min. Core-shell hierarchical nanostructures are present for a growth time exceeding 60 min. The growth mechanism for SnO2-core/ZnO-shell nanowires and hierarchical nanostructures are also discussed. The sensitivity of the synthesized SnO2-core/ZnO-shell nanostructures towards ethanol sensing is investigated. Results show that the SnO2-core/ZnO-shell nanostructures deposited at 90 min exhibit enhanced sensitivity to ethanol. The sensitivity of SnO2-core/ZnO-shell nanostructures towards 20 ppm ethanol gas at 400 °C is about ∼5-times that of SnO2 nanowires. This improvement in ethanol gas response is attributed to high active sensing sites and the synergistic effect of the encapsulation of SnO2 by ZnO nanostructures. PMID:25116903

Fabrication and characterization of ZnS/ZnO core shell nanostructures on silver wires

NASA Astrophysics Data System (ADS)

Kao, Chyuan Haur; Su, Wei Ming; Li, Cheng Yuan; Weng, Wei Chih; Weng, Chen Yuan; Cheng, Chin-Chi; Lin, Yung-Sen; Lin, Chia Feng; Chen, Hsiang

2018-06-01

In this research, ZnS nanoparticles were synthesized on ZnO/silver wires to form ZnS/ZnO core shell structures. Various outward appearance and colors could be observed by different ZnO growth and sulfurization conditions. To evaluate the properties of these nanostructures, optical properties and chemical bindings were analyzed by photoluminescence, Raman analysis, and X-ray photoelectron spectroscopy. Furthermore, material characterizations including transmission electron microscopy and X-ray diffraction confirmed that cubic ZnS (311)/ZnO nanostructures were grown on silver wires for the first time. ZnS/ZnO core shell structures on silver wires are promising for future optoelectronic and biomedical applications.

Chemical growth of ZnO nanorod arrays on textured nanoparticle nanoribbons and its second-harmonic generation performance

NASA Astrophysics Data System (ADS)

Gui, Zhou; Wang, Xian; Liu, Jian; Yan, Shanshan; Ding, Yanyan; Wang, Zhengzhou; Hu, Yuan

2006-07-01

On the basis of the highly oriented ZnO nanoparticle nanoribbons as the growth seed layer (GSL) and solution growth technique, we have synthesized vertical ZnO nanorod arrays with high density over a large area and multi-teeth brush nanostructure, respectively, according to the density degree of the arrangement of nanoparticle nanoribbons GSL on the glass substrate. This controllable and convenient technique opens the possibility of creating nanostructured film for industrial fabrication and may represent a facile way to get similar structures of other compounds by using highly oriented GSL to promote the vertical arrays growth. The growth mechanism of the formation of the ordered nanorod arrays is also discussed. The second-order nonlinear optical coefficient d31 of the vertical ZnO nanorod arrays measured by the Maker fringes technique is 11.3 times as large as that of d36 KH 2PO 4 (KDP).

Facile and Chemically Pure Preparation of YVO4:Eu3+ Colloid with Novel Nanostructure via Laser Ablation in Water

PubMed Central

Wang, Haohao; Odawara, Osamu; Wada, Hiroyuki

2016-01-01

A YVO4:Eu3+ colloid with an interesting nanostructure was formed by pulsed laser ablation in deionized water without any additives or surfactants. Analyses of particle morphology, composition and optical properties were accomplished by SEM, TEM, EDS PL and UV-vis. Ovoid-like particles formed by the agglomeration of numerous nanocrystals were observed by SEM and TEM, while EDS with area-mode analysis revealed that the content of dopant ion was well retained within the nanoparticles. In addition, the formation mechanism is deduced and discussed for the first time in this research. The findings of this study could provide new insights into the understanding of laser-induced oxide materials and offer an opportunity for other research groups to pursue red emitting nanophosphors with outstandingly purity. PMID:26842419

Synthesis and gas sensing properties of α-Fe(2)O(3)@ZnO core-shell nanospindles.

PubMed

Zhang, Jun; Liu, Xianghong; Wang, Liwei; Yang, Taili; Guo, Xianzhi; Wu, Shihua; Wang, Shurong; Zhang, Shoumin

2011-05-06

α-Fe(2)O(3)@ZnO core-shell nanospindles were synthesized via a two-step hydrothermal approach, and characterized by means of SEM/TEM/XRD/XPS. The ZnO shell coated on the nanospindles has a thickness of 10-15 nm. Considering that both α-Fe(2)O(3) and ZnO are good sensing materials, we have investigated the gas sensing performances of the core-shell nanocomposite using ethanol as the main probe gas. It is interesting to find that the gas sensor properties of the core-shell nanospindles are significantly enhanced compared with pristine α-Fe(2)O(3). The enhanced sensor properties are attributed to the unique core-shell nanostructure. The detailed sensing mechanism is discussed with respect to the energy band structure and the electron depletion theory. The core-shell nanostructure reported in this work provides a new path to fabricate highly sensitive materials for gas sensing applications.

Optical and Photothermal Behaviors of Colloidal and Self-Assembled Magnetic-Plasmonic Nanostructures

NASA Astrophysics Data System (ADS)

Liu, Kai

This dissertation is based on numerous efforts in exploring the capabilties of numerical simulation for investigating novel optical phenomena in different colloidal plasmonic systems. The dissertation includes five chapters. Chapter 1 contains a general introduction to the fundamentals of plasmonic behaviors in colloidal clusters and bottom-up self-assembly methods for manufacturing colloidal clusters which include magnetic based and DNA-assisted pathways. Chapter 2 presents a systematic comparison of optical and thermodynamic properties of near-infrared colloidal nanoparticles, including SiO2 Au core-shell, Au nanocage and Au nanorod, and an example of the nanobubble-based photothermal therapy application. In Chapter 3, a optical phenomenon named Fano resonance is demonstrated in a colloidal heptamer design which consists of seven Fe 3O4 Au core-shell nanoparticles. The incorporation of the magnetic core enables a magnetic-assisted self-assembly process which will be discussed after the photonic analysis. In Chapter 4, the optical behaviors in a 1D magnetic-plasmonic chain are explored. A demonstration of the magnetic-based self-assembly of this 1D chain is given. Chapter 5 is focused on the study of the chiral optical responses in a helical nanoscale system which follows a 3D helical arrangement of Fe3O4 Au core-shell nanoparticles.

Fabrication of ZnO nanoparticles based sensitive methanol sensor and efficient photocatalyst

NASA Astrophysics Data System (ADS)

Faisal, M.; Khan, Sher Bahadar; Rahman, Mohammed M.; Jamal, Aslam; Abdullah, M. M.

2012-07-01

ZnO nanoparticles (NPs) were prepared by hydrothermal treatment with starting materials (zinc chloride and urea) in the presence of ammonium hydroxide and characterized by powder X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), Fourier transform infrared spectroscopy (FTIR), Raman spectroscopy and UV-vis spectroscopy. The synthesized nanoparticles are crystalline with wurtzite hexagonal phase having average particle size in the range of 80-130 nm. Photocatalytic activity of the prepared ZnO NPs was evaluated by the degradation of methylene blue and almost complete degradation (91.0%) takes place within 85 min of irradiation time. Prepared ZnO nanostructures possessed high photocatalytic activity when compared with TiO2-UV100. Additionally, the sensing properties of the ZnO films were investigated for various concentrations of methanol in liquid phase by simple I-V technique at room conditions. It was observed that ZnO thin film exhibits good sensitivity (0.9554 μA cm-2 mM-1) towards detection of methanol at room conditions.

Bismuth oxide aqueous colloidal nanoparticles inhibit Candida albicans growth and biofilm formation

PubMed Central

Hernandez-Delgadillo, Rene; Velasco-Arias, Donaji; Martinez-Sanmiguel, Juan Jose; Diaz, David; Zumeta-Dube, Inti; Arevalo-Niño, Katiushka; Cabral-Romero, Claudio

2013-01-01

Multiresistance among microorganisms to common antimicrobials has become one of the most significant concerns in modern medicine. Nanomaterials are a new alternative to successfully treat the multiresistant microorganisms. Nanostructured materials are used in many fields, including biological sciences and medicine. Recently, it was demonstrated that the bactericidal activity of zero-valent bismuth colloidal nanoparticles inhibited the growth of Streptococcus mutans; however the antimycotic potential of bismuth nanostructured derivatives has not yet been studied. The main objective of this investigation was to analyze the fungicidal activity of bismuth oxide nanoparticles against Candida albicans, and their antibiofilm capabilities. Our results showed that aqueous colloidal bismuth oxide nanoparticles displayed antimicrobial activity against C. albicans growth (reducing colony size by 85%) and a complete inhibition of biofilm formation. These results are better than those obtained with chlorhexidine, nystatin, and terbinafine, the most effective oral antiseptic and commercial antifungal agents. In this work, we also compared the antimycotic activities of bulk bismuth oxide and bismuth nitrate, the precursor metallic salt. These results suggest that bismuth oxide colloidal nanoparticles could be a very interesting candidate as a fungicidal agent to be incorporated into an oral antiseptic. Additionally, we determined the minimum inhibitory concentration for the synthesized aqueous colloidal Bi2O3 nanoparticles. PMID:23637533

Efficiency improvement of silicon solar cells enabled by ZnO nanowhisker array coating

PubMed Central

2012-01-01

An efficient antireflection coating is critical for the improvement of silicon solar cell performance via increased light coupling. Here, we have grown well-aligned ZnO nanowhisker (NW) arrays on Czochralski silicon solar cells by a seeding-growth two-step process. It is found that the ZnO NWs have a great effect on the macroscopic antireflection effect and, therefore, improves the solar cell performance. The ZnO NW array-coated solar cells display a broadband reflection suppression from 500 to 1,100 nm, and the minimum reflectance smaller than 3% can easily be achieved. By optimizing the time of ZnO NW growth, it has been confirmed that an increase of 3% relatively in the solar cell efficiency can be obtained. These results are quite interesting for the application of ZnO nanostructure in the fabrication of high-efficiency silicon solar cells. PMID:22704578

Two-dimensional vanadium-doped ZnO nanosheet-based flexible direct current nanogenerator.

PubMed

Gupta, Manoj Kumar; Lee, Ju-Hyuck; Lee, Keun Young; Kim, Sang-Woo

2013-10-22

Here, we report the synthesis of lead-free single-crystalline two-dimensional (2D) vanadium(V)-doped ZnO nanosheets (NSs) and their application for high-performance flexible direct current (DC) power piezoelectric nanogenerators (NGs). The vertically aligned ZnO nanorods (NRs) converted to NS networks by V doping. Piezoresponse force microscopy studies reveal that vertical V-doped ZnO NS exhibit typical ferroelectricity with clear phase loops, butterfly, and well-defined hysteresis loops with a piezoelectric charge coefficient of up to 4 pm/V, even in 2D nanostructures. From pristine ZnO NR-based NGs, alternating current (AC)-type output current was observed, while from V-doped ZnO NS-based NGs, a DC-type output current density of up to 1.0 μAcm(-2) was surprisingly obtained under the same vertical compressive force. The growth mechanism, ferroelectric behavior, charge inverted phenomena, and high piezoelectric output performance observed from the V-doped ZnO NS are discussed in terms of the formation of an ionic layer of [V(OH)4(-)], permanent electric dipole, and the doping-induced resistive behavior of ZnO NS.

Matrix-assisted energy conversion in nanostructured piezoelectric arrays

DOEpatents

Sirbuly, Donald J.; Wang, Xianying; Wang, Yinmin

2013-01-01

A nanoconverter is capable of directly generating electricity through a nanostructure embedded in a polymer layer experiencing differential thermal expansion in a stress transfer zone. High surface-to-volume ratio semiconductor nanowires or nanotubes (such as ZnO, silicon, carbon, etc.) are grown either aligned or substantially vertically aligned on a substrate. The resulting nanoforest is then embedded with the polymer layer, which transfers stress to the nanostructures in the stress transfer zone, thereby creating a nanostructure voltage output due to the piezoelectric effect acting on the nanostructure. Electrodes attached at both ends of the nanostructures generate output power at densities of .about.20 nW/cm.sup.2 with heating temperatures of .about.65.degree. C. Nanoconverters arrayed in a series parallel arrangement may be constructed in planar, stacked, or rolled arrays to supply power to nano- and micro-devices without use of external batteries.

ZnO Hierarchical Nanostructure Photoanode in a CdS Quantum Dot-Sensitized Solar Cell

PubMed Central

Liu, Huan; Zhang, Gengmin; Sun, Wentao; Shen, Ziyong; Shi, Mingji

2015-01-01

A hierarchical array of ZnO nanocones covered with ZnO nanospikes was hydrothermally fabricated and employed as the photoanode in a CdS quantum dot-sensitized solar cell (QDSSC). This QDSSC outperformed the QDSSC based on a simple ZnO nanocone photoanode in all the four principal photovoltaic parameters. Using the hierarchical photoanode dramatically increased the short circuit current density and also slightly raised the open circuit voltage and the fill factor. As a result, the conversion efficiency of the QDSSC based on the hierarchical photoanode was more than twice that of the QDSSC based on the simple ZnO nanocone photoanode. This improvement is attributable to both the enlarged specific area of the photoanode and the reduction in the recombination of the photoexcited electrons. PMID:26379268

Plasmonic nanostructures for bioanalytical applications of SERS

NASA Astrophysics Data System (ADS)

Kahraman, Mehmet; Wachsmann-Hogiu, Sebastian

2016-03-01

Surface-enhanced Raman scattering (SERS) is a potential analytical technique for the detection and identification of chemicals and biological molecules and structures in the close vicinity of metallic nanostructures. We present a novel method to fabricate tunable plasmonic nanostructures and perform a comprehensive structural and optical characterization of the structures. Spherical latex particles are uniformly deposited on glass slides and used as templates to obtain nanovoid structures on polydimethylsiloxane surfaces. The diameter and depth of the nanovoids are controlled by the size of the latex particles. The nanovoids are coated with a thin Ag layer for fabrication of uniform plasmonic nanostructures. Structural characterization of the surfaces is performed by scanning electron microscopy (SEM) and atomic force microscopy (AFM). Optical properties of these plasmonic nanostructures are evaluated via UV/Vis spectroscopy, and SERS. The sample preparation step is the key point to obtain strong and reproducible SERS spectra from the biological structures. When the colloidal suspension is used as a SERS substrate for the protein detection, the electrostatic interaction of the proteins with the nanoparticles is described by the nature of their charge status, which influences the aggregation properties such as the size and shape of the aggregates, which is critical for the SERS experiment. However, when the solid SERS substrates are fabricated, SERS signal of the proteins that are background free and independent of the protein charge. Pros and cons of using plasmonic nano colloids and nanostructures as SERS substrate will be discussed for label-free detection of proteins using SERS.

Functionalized ZnO nanowires for microcantilever biosensors with enhanced binding capability.

PubMed

Stassi, Stefano; Chiadò, Alessandro; Cauda, Valentina; Palmara, Gianluca; Canavese, Giancarlo; Laurenti, Marco; Ricciardi, Carlo

2017-04-01

An efficient way to increase the binding capability of microcantilever biosensors is here demonstrated by growing zinc oxide nanowires (ZnO NWs) on their active surface. A comprehensive evaluation of the chemical compatibility of ZnO NWs brought to the definition of an innovative functionalization method able to guarantee the proper immobilization of biomolecules on the nanostructured surface. A noteworthy higher amount of grafted molecules was evidenced with colorimetric assays on ZnO NWs-coated devices, in comparison with functionalized and activated silicon flat samples. ZnO NWs grown on silicon microcantilever arrays and activated with the proposed immobilization strategy enhanced the sensor binding capability (and thus the dynamic range) of nearly 1 order of magnitude, with respect to the commonly employed flat functionalized silicon devices. Graphical Abstract An efficient way to increase the binding capability of microcantilever biosensors is represented by growing zinc oxide nanowires (ZnO NWs) on their active surface. ZnO NWs grown on silicon microcantilever arrays and activated with an innovative immobilization strategy enhanced the sensor binding capability of nearly 1 order of magnitude, with respect to the commonly employed flat functionalized silicon devices.

Enhanced photoelectrochemical property of ZnO nanorods array synthesized on reduced graphene oxide for self-powered biosensing application.

PubMed

Kang, Zhuo; Gu, Yousong; Yan, Xiaoqin; Bai, Zhiming; Liu, Yichong; Liu, Shuo; Zhang, Xiaohui; Zhang, Zheng; Zhang, Xueji; Zhang, Yue

2015-02-15

We have realized the direct synthesis of ZnO nanorods (ZnO NRs) array on reduced graphene layer (rGO), and demonstrated the enhanced photoelectrochemical (PEC) property of the rGO/ZnO based photoanode under UV irradiation compared with the pristine ZnO NRs array. The introduction of the rGO layer resulted in a favorable energy band structure for electron migration, which finally led to the efficient photoinduced charge separation. Such nanostructure was subsequently employed for self-powered PEC biosensing of glutathione in the condition of 0 V bias, with a linear range from 10 to 200 µM, a detection limit of 2.17 µM, as well as excellent selectivity, reproducibility and stability. The results indicated the rGO/ZnO nanostructure is a competitive candidate in the PEC biosensing field. Copyright © 2014 Elsevier B.V. All rights reserved.

Structural, Optical, and Photocatalytic Properties of Quasi-One-Dimensional Nanocrystalline ZnO, ZnOC:nC Composites, and C-doped ZnO

NASA Astrophysics Data System (ADS)

Shalaeva, E. V.; Gyrdasova, O. I.; Krasilnikov, V. N.; Melkozerova, M. A.; Baklanova, I. V.; Buldakova, L. Yu.

Various thermolysis rotes of zinc glicolate complexes are considered for the synthesis of quasi-one-dimensional nanostructured aggregates ZnO and Zn-O-C used as photocatalysts. Structural features of quasi-one-dimensional aggregates Zn-O-C and ZnO are investigated in detail. Transmission electron microscopy, Raman spectroscopy, and electron paramagnetic resonance spectroscopy methods demonstrate that the aggregates Zn-O-C have either composite structure (ZnO crystallites in amorphous carbon matrix) or a C-doped ZnO single-phase structure depending on heat treatment conditions, and that all the aggregates exhibit as a rule a tubular morphology, a nanocrystalline structure with a high specific surface area, and a high concentration of singly charged oxygen vacancies. The mechanism of the nanocrystalline structure formation is discussed and the effect of thermolysis condition on the formation of the textured structure of aggregates is investigated. The results of examination of the photocatalytic and optical absorption properties of the synthesized aggregates are presented. The photocatalytic activity for the hydroquinone oxidation reaction under ultraviolet and visible light increases in the series: the reference ZnO powder, quasi-one-dimensional ZnO, quasi-one-dimensional aggregates C-doped ZnO, and this tendency correlates with the reduction of the optical gap width. As a result of our studies, we have arrived at an important conclusion that thermal treatment of ZnO:nC composites allows a C-doped ZnO with high catalytic activity. This increasing photoactivity of C-doped ZnO aggregates is attributed to the optimal specific surface area and electron-energy spectrum restructuring to be produced owing to the presence of singly charged oxygen vacancies and carbon dissolved in the ZnO lattice.

Bright and multicolor luminescent colloidal Si nanocrystals prepared by pulsed laser irradiation in liquid

DOE Office of Scientific and Technical Information (OSTI.GOV)

Nakamura, Toshihiro, E-mail: nakamura@el.gunma-u.ac.jp; Watanabe, Kanta; Adachi, Sadao

2016-01-11

We reported the preparation of bright and multicolor luminescent colloidal Si nanocrystal (Si-nc) by pulsed UV laser irradiation to porous Si (PSi) in an organic solvent. The different-luminescence-color (different-sized) colloidal Si-nc was produced by the pulsed laser-induced fragmentation of different-sized porous nanostructures. The colloidal Si-nc samples were found to have higher photoluminescence quantum efficiencies (20%–23%) than the PSi samples (1%–3%). The brighter emission of the colloidal Si-nc was attributed to an enhanced radiative band-to-band transition rate due to the presence of a surface organic layer formed by UV laser-induced hydrosilylation.

Field emission and photoluminescence of ZnO nanocombs

NASA Astrophysics Data System (ADS)

Wang, B.; Wu, H. Y.; Zheng, Z. Q.; Yang, Y. H.

2013-11-01

Three kinds of new comb-shape nanostructures of ZnO have been grown on single silicon substrates without catalyst-assisted thermal evaporation of Zn and active carbon powders. The morphology and structure of the prepared nanorods are determined on the basis of field-emission scanning electron microscopy (FESEM), transmission electron microscopy (TEM) and x-ray diffraction (XRD). The growth mechanism of the ZnO nanocombs can be explained on the basis of the vapor-solid (VS) processes. In nanocombs 1 and nanocombs 2, the comb teeth grow along [0001] and the comb stem grows along [], while in nanocombs 3, nanoteeth grow along [] and stem grows along [0001]. The photoluminescence and field-emission properties of ZnO nanocombs 1-3 have been investigated. The turn-on electric field of ZnO nanocombs 1-3, which is defined as the field required to producing a current density of 10 μA/cm2, is 9, 7.7 and 7.1 V/μm, respectively. The field-emission performance relies not only on the tip’s radius of curvature and field enhancement factor, but also on the factor evaluating the degree of the screening effect.

Influence of amines as surfactant on the optical, thermal, and structural properties of nanostructured ZnO

NASA Astrophysics Data System (ADS)

Sehgal, Preeti; Narula, A. K.

2015-06-01

Zinc oxide nanoparticles were synthesized by precipitation method using triethanolamine (TEA) and hexamine (HA) as capping agents, and their effects on the optical, thermal, and morphological properties were analyzed. We have also analyzed the role of solvents on the aforementioned properties of ZnO nanoparticles. The optical properties of capped zinc oxide nanoparticles were investigated by UV-visible and fluorescent techniques. The HA@ZnO and TEA@ZnO that showed blueshift in comparison with ZnO without surfactant revealed the role of surfactant in reducing the trap sites by forming defect-free nanoparticles. TG-DTA curves indicated that optimum annealing temperature for ZnO nanoparticles was in the range of 360-469 °C depending upon the surfactant and solvent; no weight loss was observed above 469 °C. Synthesized ZnO nanoparticles had pure wurtzite structure as elucidated by X-ray diffraction studies (XRD). Scanning electron microscope revealed that the ZnO synthesized in isopropyl alcohol had spherical morphology, whereas ZnO nanoparticles synthesized in methanol had agglomerate sheet-like structure. The average size of the nanocrystal was estimated around 85-169 nm for ZnO.

Nanostructured ZnO in a Metglas/ZnO/Hemoglobin Modified Electrode to Detect the Oxidation of the Hemoglobin Simultaneously by Cyclic Voltammetry and Magnetoelastic Resonance.

PubMed

Sagasti, Ariane; Bouropoulos, Nikolaos; Kouzoudis, Dimitris; Panagiotopoulos, Apostolos; Topoglidis, Emmanuel; Gutiérrez, Jon

2017-07-25

In the present work, a nanostructured ZnO layer was synthesized onto a Metglas magnetoelastic ribbon to immobilize hemoglobin (Hb) on it and study the Hb's electrochemical behavior towards hydrogen peroxide. Hb oxidation by H₂O₂ was monitored simultaneously by two different techniques: Cyclic Voltammetry (CV) and Magnetoelastic Resonance (MR). The Metglas/ZnO/Hb system was simultaneously used as a working electrode for the CV scans and as a magnetoelastic sensor excited by external coils, which drive it to resonance and interrogate it. The ZnO nanoparticles for the ZnO layer were grown hydrothermally and fully characterized by X-Ray Diffraction (XRD), Scanning Electron Microscopy (SEM) and photoluminescence (PL). Additionally, the ZnO layer's elastic modulus was measured using a new method, which makes use of the Metglas substrate. For the detection experiments, the electrochemical cell was performed with a glass vial, where the three electrodes (working, counter and reference) were immersed into PBS (Phosphate Buffer Solution) solution and small H₂O₂ drops were added, one at a time. CV scans were taken every 30 s and 5 min after the addition of each drop and meanwhile a magnetoelastic measurement was taken by the external coils. The CV plots reveal direct electrochemical behavior of Hb and display good electrocatalytic response to the reduction of H₂O₂. The measured catalysis currents increase linearly with the H₂O₂ concentration in a wide range of 25-350 μM with a correlation coefficient 0.99. The detection limit is 25-50 μM. Moreover, the Metglas/ZnO/Hb electrode displays rapid response (30 s) to H₂O₂, and exhibits good stability and reproducibility of the measurements. On the other hand, the magnetoelastic measurements show a small linear mass increase versus the H₂O₂ concentration with a slope of 152 ng/μM, which is probably due to H₂O₂ adsorption in ZnO during the electrochemical reaction. No such effects were detected during

Surface nanostructuring of thin film composite membranes via grafting polymerization and incorporation of ZnO nanoparticles

NASA Astrophysics Data System (ADS)

Isawi, Heba; El-Sayed, Magdi H.; Feng, Xianshe; Shawky, Hosam; Abdel Mottaleb, Mohamed S.

2016-11-01

A new approach for modification of polyamid thin film composite membrane PA(TFC) using synthesized ZnO nanoparticles (ZnO NPs) was shown to enhance the membrane performances for reverse osmosis water desalination. First, active layer of synthesis PA(TFC) membrane was activated with an aqueous solution of free radical graft polymerization of hydrophilic methacrylic acid (MAA) monomer onto the surface of the PA(TFC) membrane resulting PMAA-g-PA(TFC). Second, the PA(TFC) membrane has been developed by incorporation of ZnO NPs into the MAA grafting solution resulting the ZnO NPs modified PMAA-g-PA(TFC) membrane. The surface properties of the synthesized nanoparticles and prepared membranes were investigated using the FTIR, XRD and SEM. Morphology studies demonstrated that ZnO NPs have been successfully incorporated into the active grafting layer over PA(TFC) composite membranes. The zinc leaching from the ZnO NPs modified PMAA-g-PA(TFC) was minimal, as shown by batch tests that indicated stabilization of the ZnO NPs on the membrane surfaces. Compared with the a pure PA(TFC) and PMAA-g-PA(TFC) membranes, the ZnO NPs modified PMAA-g-PA(TFC) was more hydrophilic, with an improved water contact angle (∼50 ± 3°) over the PMAA-g-PA(TFC) (63 ± 2.5°). The ZnO NPs modified PMAA-g-PA(TFC) membrane showed salt rejection of 97% (of the total groundwater salinity), 99% of dissolved bivalent ions (Ca2+, SO42-and Mg2+), and 98% of mono valent ions constituents (Cl- and Na+). In addition, antifouling performance of the membranes was determined using E. coli as a potential foulant. This demonstrates that the ZnO NPs modified PMAA-g-PA(TFC) membrane can significantly improve the membrane performances and was favorable to enhance the selectivity, permeability, water flux, mechanical properties and the bio-antifouling properties of the membranes for water desalination.

Comparative study of ZnO nanorods and thin films for chemical and biosensing applications and the development of ZnO nanorods based potentiometric strontium ion sensor

NASA Astrophysics Data System (ADS)

Khun, K.; Ibupoto, Z. H.; Chey, C. O.; Lu, Jun.; Nur, O.; Willander, M.

2013-03-01

In this study, the comparative study of ZnO nanorods and ZnO thin films were performed regarding the chemical and biosensing properties and also ZnO nanorods based strontium ion sensor is proposed. ZnO nanorods were grown on gold coated glass substrates by the hydrothermal growth method and the ZnO thin films were deposited by electro deposition technique. ZnO nanorods and thin films were characterised by field emission electron microscopy [FESEM] and X-ray diffraction [XRD] techniques and this study has shown that the grown nanostructures are highly dense, uniform and exhibited good crystal quality. Moreover, transmission electron microscopy [TEM] was used to investigate the quality of ZnO thin film and we observed that ZnO thin film was comprised of nano clusters. ZnO nanorods and thin films were functionalised with selective strontium ionophore salicylaldehyde thiosemicarbazone [ST] membrane, galactose oxidase, and lactate oxidase for the detection of strontium ion, galactose and L-lactic acid, respectively. The electrochemical response of both ZnO nanorods and thin films sensor devices was measured by using the potentiometric method. The strontium ion sensor has exhibited good characteristics with a sensitivity of 28.65 ± 0.52 mV/decade, for a wide range of concentrations from 1.00 × 10-6 to 5.00 × 10-2 M, selectivity, reproducibility, stability and fast response time of 10.00 s. The proposed strontium ion sensor was used as indicator electrode in the potentiometric titration of strontium ion versus ethylenediamine tetra acetic acid [EDTA]. This comparative study has shown that ZnO nanorods possessed better performance with high sensitivity and low limit of detection due to high surface area to volume ratio as compared to the flat surface of ZnO thin films.

Significantly enhanced UV luminescence by plasmonic metal on ZnO nanorods patterned by screen-printing.

PubMed

Zhao, Jun; Cui, Shuyuan; Zhang, Xingang; Li, Wenqing

2018-08-31

A smart synthetic method is conceived to construct large batches of ZnO nanostructures to meet market demand for light-emitting diodes. Utilizing the localized surface plasmon resonance of metal nanoparticles (NPs) facilitates the recombination of electron-hole pairs and the release of photons. Compared to raw ZnO nanorods (NRs), ZnO NRs@HfO 2 @Al NPs show a ∼120× enhancement in ultraviolet (UV) photoluminescence (PL), while ZnO NRs@HfO 2 @Ag NPs show a six-fold enhancement. Because the surface plasmon energy of Al is nearer the ZnO band gap, the PL enhancement of ZnO NRs covered with Al is stronger than that of those covered with Ag. Based on this analysis, three-dimensional graphical ZnO NR arrays were manufactured by screen-printing, a mass production technique. After covering the arrays with layers of HfO 2 and Al NPs, the UV PL intensities of the corresponding substrates were increased by approximately 16×. This indicates the potential to mass-produce highly efficient optoelectronic devices.

The Redox Potentials of n-type Colloidal Semiconductor Nanocrystals

NASA Astrophysics Data System (ADS)

Carroll, Gerard Michael

This thesis presents investigations for two related fields of semiconductor electrochemistry: redox potential determination of colloidal semiconductor nanocrystals, and mechanistic analysis of photoelectrochemical water oxidation with electrocatalyst modified mesostructured hematite photoanodes. Adapting electrochemical techniques to colloidal semiconductor nanocrystals (SC NC) is a long-standing challenge for this class of materials. Subject to a variety of complications, standard voltammetric techniques are not as straight forward for SC NCs as they are for small molecules. As a result, researchers have developed creative ways to side step these complications by coupling electrochemistry with NC spectroscopy. Chapter 1 discusses the fundamental electronic and spectroscopic properties of SC NCs at different redox states. We present a brief review of some of the notable studies employing SC NC spectroelectrochemistry that provide the theoretical and experimental context for the following chapters. Chapter 2 presents an investigation on NC redox potentials of photochemically reduced colloidal ZnO NCs using a solvated redox-indicator method. In the one electron limit, conduction band electrons show evidence of quantum confinement, but at higher electron concentrations, the NC Fermi-level becomes dependent on the electron density across all NC sizes. Chapter 3 outlines a poteniometric method for monitoring the NC redox potentials in situ. NC redox potentials for ZnO and CdSe are measured, and as predicted from these measurements, spontaneous electron transfer from CdSe to ZnO is demonstrated. Chapter 4 details the impact of the surface of CdSe NCs on the NC redox potentials. We find that the ratio of Cd2+:Se2- on the surface of CdSe NCs changes both the NC band edge potentials, as well as the maximum electron density achievable by photochemical reduction. These changes are proposed to arise from interfacial dipoles when CdSe has a Se2-rich surface. Chapters 5 and 6

Protein functionalization of ZnO nanostructure exhibits selective and enhanced toxicity to breast cancer cells through oxidative stress-based cell death mechanism.

PubMed

Mahanta, Sailendra; Prathap, S; Ban, Deependra Kumar; Paul, Subhankar

2017-08-01

Zinc oxide nanostructure (ZnONS) was chemically synthesized and functionalized (FZnONS BLA ) with a small protein bovine α-lactalbumin (BLA) by chemical cross-linking methods. Both nano-structures were characterized using various techniques such as electron microscopy, dynamic light scattering (DLS), UV-Vis spectroscopy, FT-IR, photo-luminescence and X-ray diffraction. Electron microscopy and DLS analysis revealed their (ZnONS and FZnONS BLA ) average size of 200nm and 450nm, respectively. When cytotoxicity of both the nanostructures were assessed in breast cancer cells MCF-7 and MDAMB231 by MTT assay and PI/Annexin V staining (FACS), FZnONS BLA demonstrated higher cell death than ZnONS primarily due to generation of intracellular reactive oxygen species (ROS). Our experimental results also suggested that such enhanced toxicity was due to the lethal structural variant of BLA in FZnONS BLA as well as higher cellular uptake than ZnONS by cancer cells. The death kinetics study with time in cancer cells further proved that FZnONS BLA caused toxicity much faster than ZnONS, thus suggested a strong role of lethal variant of BLA in FZnONS BLA as a cytotoxic agent in cancer cells. Furthermore, FZnONS BLA demonstrated excellent cytocompatibility (normal cells) and hemocompatibility compared to ZnONS. Hence, considering the biodegradable nature of ZnO nonmaterial, our results demonstrated that BLA functionalized ZnONS could be used to develop a suitable therapeutic strategy in cancer. Copyright © 2017. Published by Elsevier B.V.

ZnO deposition on metal substrates: Relating fabrication, morphology, and wettability

NASA Astrophysics Data System (ADS)

Beaini, Sara S.; Kronawitter, Coleman X.; Carey, Van P.; Mao, Samuel S.

2013-05-01

It is not common practice to deposit thin films on metal substrates, especially copper, which is a common heat exchanger metal and practical engineering material known for its heat transfer properties. While single crystal substrates offer ideal surfaces with uniform structure for compatibility with oxide deposition, metallic surfaces needed for industrial applications exhibit non-idealities that complicate the fabrication of oxide nanostructure arrays. The following study explored different ZnO fabrication techniques to deposit a (super)hydrophobic thin film of ZnO on a metal substrate, specifically copper, in order to explore its feasibility as an enhanced condensing surface. ZnO was selected for its non-toxicity, ability to be made (super)hydrophobic with hierarchical roughness, and its photoinduced hydrophilicity characteristic, which could be utilized to pattern it to have both hydrophobic-hydrophilic regions. We investigated the variation of ZnO's morphology and wetting state, using SEMs and sessile drop contact angle measurements, as a function of different fabrication techniques: sputtering, pulsed laser deposition (PLD), electrodeposition and annealing Zn. We successfully fabricated (super)hydrophobic ZnO on a mirror finish, commercially available copper substrate using the scalable electrodeposition technique. PLD for ZnO deposition did not prove viable, as the ZnO samples on metal substrates were hydrophilic and the process does not lend itself to scalability. The annealed Zn sheets did not exhibit consistent wetting state results.

The Critical Role of Thioacetamide Concentration in the Formation of ZnO/ZnS Heterostructures by Sol-Gel Process

PubMed Central

Kiatkoski Kaminski, Renata Cristina; Caetano, Bruno Leonardo; Magnani, Marina; Meneau, Florian; Rochet, Amélie; Santilli, Celso Valentim; Briois, Valérie; Bourgaux, Claudie

2018-01-01

ZnO/ZnS heterostructures have emerged as an attractive approach for tailoring the properties of particles comprising these semiconductors. They can be synthesized using low temperature sol-gel routes. The present work yields insight into the mechanisms involved in the formation of ZnO/ZnS nanostructures. ZnO colloidal suspensions, prepared by hydrolysis and condensation of a Zn acetate precursor solution, were allowed to react with an ethanolic thioacetamide solution (TAA) as sulfur source. The reactions were monitored in situ by Small Angle X-ray Scattering (SAXS) and UV-vis spectroscopy, and the final colloidal suspensions were characterized by High Resolution Transmission Electron Microscopy (HRTEM). The powders extracted at the end of the reactions were analyzed by X-ray Absorption spectroscopy (XAS) and X-ray diffraction (XRD). Depending on TAA concentration, different nanostructures were revealed. ZnO and ZnS phases were mainly obtained at low and high TAA concentrations, respectively. At intermediate TAA concentrations, we evidenced the formation of ZnO/ZnS heterostructures. ZnS formation could take place via direct crystal growth involving Zn ions remaining in solution and S ions provided by TAA and/or chemical conversion of ZnO to ZnS. The combination of all the characterization techniques was crucial to elucidate the reaction steps and the nature of the final products. PMID:29360735

Nanostructure based EO/IR sensor development for homeland security applications

NASA Astrophysics Data System (ADS)

Sood, Ashok K.; Welser, Roger E.; Sood, Adam W.; Puri, Yash R.; Manzur, Tariq; Dhar, Nibir K.; Polla, Dennis L.; Wang, Zhong L.; Wijewarnasuriya, Priyalal S.; Anwar, A. F. M.

2011-06-01

Next Generation EO/IR focal plane arrays using nanostructure materials are being developed for a variety of Defense and Homeland Security Sensor Applications. Several different nanomaterials are being evaluated for these applications. These include ZnO nanowires, GaN Nanowires and II-VI nanowires, which have demonstrated large signal to noise ratio as a wide band gap nanostructure material in the UV band. Similarly, the work is under way using Carbon Nanotubes (CNT) for a high speed detector and focal plane array as two-dimensional array as bolometer for IR bands of interest, which can be implemented for the sensors for homeland security applications. In this paper, we will discuss the sensor design and model predicting performance of an EO/IR focal plane array and Sensor that can cover the UV to IR bands of interest. The model can provide a robust means for comparing performance of the EO/IR FPA's and Sensors that can operate in the UV, Visible-NIR (0.4- 1.8μ), SWIR (2.0-2.5μ), MWIR (3-5μ), and LWIR bands (8-14μ). This model can be used as a tool for predicting performance of nanostructure arrays under development. We will also discuss our results on growth and characterization of ZnO nanowires and CNT's for the next generation sensor applications. We also present several approaches for integrated energy harvesting using nanostructure based solar cells and Nanogenerators that can be used to supplement the energy required for nanostructure based sensors.

Tuning plasmons layer-by-layer for quantitative colloidal sensing with surface-enhanced Raman spectroscopy.

PubMed

Anderson, William J; Nowinska, Kamila; Hutter, Tanya; Mahajan, Sumeet; Fischlechner, Martin

2018-04-19

Surface-enhanced Raman spectroscopy (SERS) is well known for its high sensitivity that emerges due to the plasmonic enhancement of electric fields typically on gold and silver nanostructures. However, difficulties associated with the preparation of nanostructured substrates with uniform and reproducible features limit reliability and quantitation using SERS measurements. In this work we use layer-by-layer (LbL) self-assembly to incorporate multiple functional building blocks of collaborative assemblies of nanoparticles on colloidal spheres to fabricate SERS sensors. Gold nanoparticles (AuNPs) are packaged in discrete layers, effectively 'freezing nano-gaps', on spherical colloidal cores to achieve multifunctionality and reproducible sensing. Coupling between layers tunes the plasmon resonance for optimum SERS signal generation to achieve a 10 nM limit of detection. Significantly, using the layer-by-layer construction, SERS-active AuNP layers are spaced out and thus optically isolated. This uniquely allows the creation of an internal standard within each colloidal sensor to enable highly reproducible self-calibrated sensing. By using 4-mercaptobenzoic acid (4-MBA) as the internal standard adenine concentrations are quantified to an accuracy of 92.6-99.5%. Our versatile approach paves the way for rationally designed yet quantitative colloidal SERS sensors and their use in a variety of sensing applications.

Fabrication of ZnO and doped ZnO waveguides deposited by Spin Coating

NASA Astrophysics Data System (ADS)

Mohan, Rosmin Elsa; R, Neha P.; T, Shalu; C, Darshana K.; Sreelatha, K. S.

2015-02-01

In this paper, the synthesis of ZnO and doped Zn1-xAgxO (where x=0.03) nanoparticles by co- precipitation is reported. The precursors used were Zinc Nitrate and Potassium hydroxide pellets. For doping, 3% AgNO3 in ZnNO3 was considered as a separate buffer solution. The prepared nanoparticles were subsequently spin coated onto silica glass substrates at a constant chuck rate of 3000 rpm. The substrate acts as the lower cladding of a waveguide structure. The upper cladding is assumed to be air in the present investigation. The nanostructures of the ZnO powders in the doped and undoped cases were studied using X-ray Diffraction patterns. There was a decrease in the grain size with doping which increase the tunability of the powders to be used as photoluminescent devices. The optical characteristics of the sample were also investigated using UV-Visible spectrophotometer at 200-900 nm wavelengths. The photoluminescence peaks also report a dramatic increase in intensity at the same wavelength for the doped case compared to the undoped one.

On Controlling the Hydrophobicity of Nanostructured Zinc-Oxide Layers Grown by Pulsed Electrodeposition

DOE Office of Scientific and Technical Information (OSTI.GOV)

Klochko, N. P., E-mail: klochko-np@mail.ru; Klepikova, K. S.; Kopach, V. R.

The possibility of fabricating highly hydrophobic nanostructured zinc-oxide layers by the inexpensive method of pulsed electrodeposition from aqueous solutions without water-repellent coatings, adapted for large-scale production, is shown. The conditions of the deposition of highly hydrophobic nanostructured zinc-oxide layers exhibiting the “rose-petal” effect with specific morphology, optical properties, crystal structure and texture are determined. The grown ZnO nanostructures are promising for micro- and nanoelectronics as an adaptive material able to reversibly transform to the hydrophilic state upon exposure to ultraviolet radiation.

Supported versus colloidal zinc oxide for advanced oxidation processes

NASA Astrophysics Data System (ADS)

Laxman, Karthik; Al Rashdi, Manal; Al Sabahi, Jamal; Al Abri, Mohammed; Dutta, Joydeep

2017-07-01

Photocatalysis is a green technology which typically utilizes either supported or colloidal catalysts for the mineralization of aqueous organic contaminants. Catalyst surface area and surface energy are the primary factors determining its efficiency, but correlation between the two is still unclear. This work explores their relation and hierarchy in a photocatalytic process involving both supported and colloidal catalysts. In order to do this the active surface areas of supported zinc oxide nanorods (ZnO NR's) and colloidal zinc oxide nanoparticles (having different surface energies) were equalized and their phenol oxidation mechanism and capacity was analyzed. It was observed that while surface energy had subtle effects on the oxidation rate of the catalysts, the degradation efficiency was primarily a function of the surface area; which makes it a better parameter for comparison when studying different catalyst forms of the same material. Thus we build a case for the use of supported catalysts, wherein their catalytic efficiency was tested to be unaltered over several days under both natural and artificial light, suggesting their viability for practical applications.

Performance of Dye-Sensitized Solar Cells (DSSCs) Fabricated with Zinc Oxide (ZnO) Nanpowders and Nanorods

NASA Astrophysics Data System (ADS)

Chatterjee, Suman

2018-03-01

Due to their high efficiencies, along with lower production costs, many researchers are working on dye-sensitized solar cells (DSSCs) over last few decades as a substitute technology for nonconventional energy. Nanostructured ZnO has got many interesting properties such as wide band gap, large exciton binding energy, good exciton stability, and high breakdown strength, which are applicable as DSSC electrodes. This present work compares the device properties of DSSC fabricated using ZnO nanorods on a ZnO film and ZnO nanopowders. Different types of ZnO photoanode and dye combinations are used to study the stability and photovoltaic properties of the DSSC cell. The photovoltaic properties of the ZnO-based DSSC samples were systematically investigated. The photovoltaic properties of fabricated cell obtained are discussed in the light of band structure and density of states of different types of ZnO nanolayers. The ZnO nanorods fabricated through the sol-gel route have more uniform thickness resulting in enhanced photovoltaic properties of the fabricated device.

A Comprehensive Review of Glucose Biosensors Based on Nanostructured Metal-Oxides

PubMed Central

Rahman, Md. Mahbubur; Saleh Ahammad, A. J.; Jin, Joon-Hyung; Ahn, Sang Jung; Lee, Jae-Joon

2010-01-01

Nanotechnology has opened new and exhilarating opportunities for exploring glucose biosensing applications of the newly prepared nanostructured materials. Nanostructured metal-oxides have been extensively explored to develop biosensors with high sensitivity, fast response times, and stability for the determination of glucose by electrochemical oxidation. This article concentrates mainly on the development of different nanostructured metal-oxide [such as ZnO, Cu(I)/(II) oxides, MnO2, TiO2, CeO2, SiO2, ZrO2, and other metal-oxides] based glucose biosensors. Additionally, we devote our attention to the operating principles (i.e., potentiometric, amperometric, impedimetric and conductometric) of these nanostructured metal-oxide based glucose sensors. Finally, this review concludes with a personal prospective and some challenges of these nanoscaled sensors. PMID:22399911

Nanostructured zinc oxide photoelectrodes by green routes M-SILAR and electrodeposition for dye sensitized solar cell

NASA Astrophysics Data System (ADS)

Gaikwad, M. A.; Suryawanshi, M. P.; Maldar, P. S.; Dongale, T. D.; Moholkar, A. V.

2018-04-01

Surfactant-free, ultrasound assisted modified successive ionic layer adsorption and reaction (M-SILAR) method and home-made microcontroller based low-cost potentiostat system are employed to prepare zinc oxide (ZnO) nanostructure based thin films. The comparison between physicochemical as well as photoelectrochemical (PEC) properties of the nanostructures prepared via two different template free, simplistic and cost-effective green routes have been discussed in detail. X-ray diffraction and Raman analysis confirm the formation of phase pure ZnO with the hexagonal crystal structure. Surface morphology significantly affects the physicochemical as well as PEC properties of ZnO thin films. Nanorods (NRs) and nanosheets (NSs) based ZnO thin films sensitized with N3 dye have been directly used as photoelectrodes in the dye-sensitized solar cell (DSSC). The power conversion efficiency (PCE) of 0.59% is achieved with Jsc of 4.04 mA/cm2 and Voc of 0.44 V for the DSSC in which the M-SILAR deposited 1-D ZnO NRs based thin film is used as the photoanode. While relatively less PCE of 0.29% with Jsc of 2.53 mA/cm2 and Voc of 0.36 V is obtained for DSSC prepared using electrodeposited 2-D ZnO NSs. In the NSs like 2-D surface morphology, the presence of multiple grain boundaries are acted as traps for the diffusing electrons, which reduces the electron mobility through it.

Study of Growth Kinetics in One Dimensional and Two Dimensional ZnO Nanostructures

NASA Astrophysics Data System (ADS)

Yin, Xin

Because of the merits arising from the unique geometry, nanostructure materials have been an essential class of materials, which have shown great potentials in the fields of electronics, photonics, and biology. With various nanostructures being intensively investigated and successfully complemented into device applications, there has been one increasing demand to the investigation of the growth mechanism devoted to the controlled nanostructure synthesis. Motivated by this situation, this thesis is focused on the fundamental understanding of the nanostructure growth. Specifically, by taking zinc oxide as an example material, through controlling the basic driving force, that is, the supersaturation, I have rationally designed and synthesized various of nanostructures, and further applied the classical layer-by-layer growth mechanism to the understanding on the formation of these nanostructures, they are, the convex-plate-capped nanowires, the concave-plate-capped nanowires, the facet evolution at the tip of the nanowires, and the ultrathin 2D nanosheets.

An optimal thermal evaporation synthesis of c-axis oriented ZnO nanowires with excellent UV sensing and emission characteristics

DOE Office of Scientific and Technical Information (OSTI.GOV)

Saha, Tridib, E-mail: tridib.saha@monash.edu; Achath Mohanan, Ajay, E-mail: ajay.mohanan@monash.edu; Swamy, Varghese, E-mail: varghese.swamy@monash.edu

Highlights: • c-Axis alignment of ZnO nanowires was optimized using self-seeding thermal evaporation method. • Influence of purified air on the morphology and optoelectronic properties were studied. • Nanowires grown under optimal conditions exhibit strong UV emission peak in PL spectrum. • Optimized growth condition establish nanowires of excellent UV sensing characteristics - Abstract: Well-aligned (c-axis oriented) ZnO nanowire arrays were successfully synthesized on Si (1 0 0) substrates through an optimized self-seeding thermal evaporation method. An open-ended chemical vapor deposition (CVD) setup was used in the experiment, with argon and purified air as reaction gases. Epitaxial growth of c-axismore » oriented ZnO nanowires was observed for 5 sccm flow rate of purified air, whereas Zn/Zn suboxide layers and multiple polycrystalline layers of ZnO were obtained for absence and excess of purified air, respectively. Ultraviolet (UV) sensing and emission properties of the as-grown ZnO nanostructures were investigated through the current–voltage (I–V) characteristics of the nanowires under UV (λ = 365 nm) illumination of 8 mW/cm{sup 2} and using photoluminescence spectra. Nanowires grown under optimum flow of air emitted four times higher intensity of 380 nm UV light as well as exhibited 34 times higher UV radiation sensitivity compared to that of other nanostructures synthesized in this study.« less

Fabrication of high responsivity deep UV photo-detector based on Na doped ZnO nanocolumns

NASA Astrophysics Data System (ADS)

Agrawal, Jitesh; Dixit, Tejendra; Palani, I. A.; Ramachandra Rao, M. S.; Singh, Vipul

2018-05-01

We report a variety of the hydrothermally synthesized ZnO nanostructures with a significant suppression in defect-related emission and huge enhancement in the photo-current to the dark current ratio (approximately six orders of magnitude) upon UV light illumination. Interestingly, the photo-detector shows lower dark current of 1.6 nA with high responsivity of 507 A W‑1 at 254 nm. Here, a systematic analysis of the growth process as well as the physical, chemical and electrical properties of as-grown ZnO nanostructures has been performed. We have utilized the duo effect of both the inorganic (KMnO4) and organic (Na3C6H5O7) additives, which has facilitated the precise tuning of the morphology and intrinsic defects in nanostructures that have made an impact on the photo-responsivity, photoluminescence (PL) and adhesivity of the film on to the underlying substrate. PL analysis of as-grown ZnO nanostructures has suggested 11 times improvement in the near band emission (NBE) to defect level emission (DLE) ratio. Interestingly, thermal annealing of the samples has shown a dramatic change in the morphology with significant improvement in the crystallinity. Notably, the band gap was observed to be modulated from 3.3 eV to 3.1 eV after annealing. In addition to UV photo-detector based applications, the work presented here has provided a subtle solution towards the rectification of various problems pertaining to hydrothermal processes like poor adhesivity, feeble UV emission and problem in precise tuning of the morphology along with the bandgap in one go. Therefore, these investigations assume critical significance towards the development of next-generation optoelectronic devices.

Effect of protons on the redox chemistry of colloidal zinc oxide nanocrystals.

PubMed

Valdez, Carolyn N; Braten, Miles; Soria, Ashley; Gamelin, Daniel R; Mayer, James M

2013-06-12

Electron transfer (ET) reactions of colloidal 3-5 nm diameter ZnO nanocrystals (NCs) with molecular reagents are explored in aprotic solvents. Addition of an excess of the one-electron reductant Cp*2Co (Cp* = pentamethylcyclopentadienyl) gives NCs that are reduced by up to 1-3 electrons per NC. Protons can be added stoichiometrically to the NCs by either a photoreduction/oxidation sequence or by addition of acid. The added protons facilitate the reduction of the ZnO NCs. In the presence of acid, NC reduction by Cp*2Co can be increased to over 15 electrons per NC. The weaker reductant Cp*2Cr transfers electrons only to ZnO NCs in the presence of protons. Cp*2M(+) counterions are much less effective than protons at stabilizing reduced NCs. With excess Cp*2Co or Cp*2Cr, the extent of reduction increases roughly linearly with the number of protons added. Some of the challenges in understanding these results are discussed.

Effect of Ce doping on structural, optical and photocatalytic properties of ZnO nano-structures.

PubMed

Selvam, N Clament Sagaya; Vijaya, J Judith; Kennedy, L John

2014-03-01

A novel self-assembled pure and Ce doped ZnO nano-particles (NPs) were successfully synthesized by a simple low temperature co-precipitation method. The prepared photocatalysts were characterized by X-ray diffraction (XRD), High resolution scanning electron microscopy (HR-SEM), High resolution transmission electron microscopy (HR-TEM), diffuse reflectance spectroscopy (DRS) and Photoluminescence (PL) spectroscopy. The results indicated that the prepared photocatalysts shows a novel morphology, high crystallinity, uniform size distribution, and more defects. Photocatalytic degradation (PCD) of nonylphenol, a potent endocrine disrupting chemical in aqueous medium was investigated. Higher amount of oxygen defects exhibits enhanced PCD of nonylphenol. In addition, the influence of the Ce contents on the structure, morphology, absorption, emission and photocatalytic activity of ZnO nanoparticles (NPs) were investigated systematically. The relative PCD efficiency of pure ZnO, Ce-doped ZnO NPs and commercial TiO2 (Degussa P-25) have also been discussed.

Structure and Properties of Al and Ga- Doped ZnO

NASA Astrophysics Data System (ADS)

Temizer, Namik Kemal

. Micro-structural, transport, optical and magnetic properties in ZnGa0.002Al 0.02O films grown by pulsed laser deposition under different growth conditions was studied. In ZnO films grown at substrate temperatures of 600°C most interesting features are the concomitant occurrence of high temperature resistivity minima and room temperature ferromagnetism with a high saturation magnetic moment and considerable coercivity. The temperature dependent resistivity data has been interpreted in the light of quantum corrections to conductivity in disordered systems, suggesting that the e-e interactions is the dominant mechanism in the weak-localization (WL) limit in the case of films showing resistivity minima. We propose that formation of oxygen vacancy-Zinc interstitial defect complex (VO-IZn) is responsible for the enhancement in n-type conductivity, and zinc vacancies (VZn) for the observed room temperature ferromagnetism. ZnO nanostructures are gaining importance in various applications, from gas sensing to thin film transistors (TFTs). We have studied the micro-structural, transport, optical and magnetic properties in ZnO nanostructured films grown by pulsed laser deposition under different ambient conditions. We have investigated the nanostructures in detail through x-ray diffraction, SEM and TEM techniques. We have achieved relatively low room temperature resistivity and the occurrence of room temperature ferromagnetism with significant saturation magnetic moment of 1000 A/m with coercivity in the range of 100-150 Oe. Photoluminescence measurements were conducted to get an insight about the types of defects that occur under different growth conditions. Correlations between transport, optical and magnetic properties has been established in terms of these defects and their complexes. These nanostructured oxides with magnetic and optical properties are promising candidates in multifunctional spintronic and photonic devices.

Gas Sensing Properties of ZnO-SnO2 Nanostructures.

PubMed

Chen, Weigen; Li, Qianzhu; Xu, Lingna; Zeng, Wen

2015-02-01

One-dimensional (1D) semiconductor metal oxide nanostructures have attracted increasing attention in electrochemistry, optics, magnetic, and gas sensing fields for the good properties. N-type low dimensional semiconducting oxides such as SnO2 and ZnO have been known for the detection of inflammable or toxic gases. In this paper, we fabricated the ZnO-SnO2 and SnO2 nanoparticles by hydrothermal synthesis. Microstructure characterization was performed using X-ray diffraction (XRD) and surface morphologies for both the pristine and doped samples were observed using field emission scanning electron microscope (FESEM), transmission electron microscopy (TEM) and high resolution transmission electron microscopy (HRTEM). Then we made thin film gas sensor to study the gas sensing properties of ZnO-SnO2 and SnO2 gas sensor to H2 and CO. A systematic comparison study reveals an enhanced gas sensing performance for the sensor made of SnO2 and ZnO toward H2 and CO over that of the commonly applied undecorated SnO2 nanoparticles. The improved gas sensing properties are attributed to the size of grains and pronounced electron transfer between the compound nanostructures and the absorbed oxygen species as well as to the heterojunctions of the ZnO nanoparticles to the SnO2 nanoparticles, which provide additional reaction rooms. The results represent an advance of compound nanostructures in further enhancing the functionality of gas sensors, and this facile method could be applicable to many sensing materials, offering a new avenue and direction to detect gases of interest based on composite tin oxide nanoparticles.

Design and development of plasmonic nanostructured electrodes for ITO-free organic photovoltaic cells on rigid and highly flexible substrates

NASA Astrophysics Data System (ADS)

Richardson, Beau J.; Zhu, Leize; Yu, Qiuming

2017-04-01

Indium tin oxide (ITO) is the most common transparent electrode used in organic photovoltaics (OPVs), yet limited indium reserves and poor mechanical properties make it non-ideal for large-scale OPV production. To replace ITO, we designed, fabricated, and deployed plasmonic nanostructured electrodes in inverted OPV devices. We found that active layer absorption is significantly impacted by ZnO thickness which affects the optical field distribution inside the resonant cavity formed between the plasmonic nanostructured electrode and top electrode. High quality Cr/Au nanostructured electrodes were fabricated by nanoimprint lithography and deployed in ITO-free inverted devices on glass. Devices with thinner ZnO showed a PCE as high as 5.70% and higher J SC’s than devices on thicker ZnO, in agreement with finite-difference time-domain simulations. In addition, as the active layer was made optically thin, ITO-based devices showed diminished J SC while the resonant cavity effect from plasmonic nanostructured electrodes retained J SC. Preliminary ITO-free, flexible devices on PET showed a PCE of 1.82% and those fabricated on ultrathin and conformable Parylene substrates yielded an initial PCE over 1%. The plasmonic electrodes and device designs in this work show promise for developing highly functioning conformable devices that can be applied to numerous needs for lightweight, ubiquitous power generation.

Portraits of colloidal hybrid nanostructures: controlled synthesis and potential applications.

PubMed

Nguyen, Thanh-Dinh

2013-03-01

Inorganic hybrid nanostructures containing two or more nanocomponents have been emerging in many areas of materials science in recent years. The particle-particle interactions in a hybrid particle system could significantly improve existing local electronic structure and induce tunable physiochemical responses. The current work reviews the diverse inorganic hybrid nanostructures formed by adhesion of the different single components via seed-mediated method. The hybrid nanomaterials have great potentials for real applications in many other fields. The nanohybrids have been used as efficient heterocatalysts for carbon monoxide conversion and photodegradation of organic contaminants. The enhanced catalytic activity of these hybrid nanocatalysts could be attributed the formation of oxygen vacancies and electron transfer across the structural junction in a hybrid system as a result of the interfacial particle-particle interactions. The synergistic combination of up-converting and semiconducting properties in an up-converting semiconducting hybrid particle results in appearance of sub-band-gap photoconductivity. This behavior has a great significance for the design of photovoltaic devices for effective solar energy conversion. The functionalization and subsequent bioconjugation of the hybrid nanostructures to afford the multifunctional nanomedical platforms for simultaneous diagnosis and therapy are reviewed. The conjugated multifunctional hybrid nanostructures exhibit high biocompatibility and highly selective binding with functional groups-fabricated alive organs through delivering them to the tumor sites. The clever combinations of multifunctional features and antibody conjugation within these vehicles make them to generally offer new opportunities for clinical diagnostics and therapeutics. Crown Copyright © 2012. Published by Elsevier B.V. All rights reserved.

Synthesis of hollow ZnO microspheres by an integrated autoclave and pyrolysis process.

PubMed

Duan, Jinxia; Huang, Xintang; Wang, Enke; Ai, Hanhua

2006-03-28

Hollow zinc oxide microspheres have been synthesized from a micro ZnBr2·2H2O precursor obtained by an autoclave process in bromoform steam at 220 °C /2.5 MPa. Field-emission scanning electron microscropy (FE-SEM) and transmission electron microscopy (TEM) show that the products are about 1.0 µm single crystal spherical particles with hollow interiors, partly open surfaces and walls self-assembled by ZnO nanoparticles. X-ray diffraction (XRD) analysis shows that the as-prepared ZnO hollow spheres are of a hexagonal phase structure. A possible formation mechanism is suggested on the basis of the shape evolution of ZnO nanostructures observed by SEM and TEM. The room-temperature photoluminescence (PL) spectrum shows UV emission around 386 nm and weak green emission peaks indicating that there are few defects in the single crystal grains of the ZnO microspheres.

Fabrication Methods and Luminescent Properties of ZnO Materials for Light-Emitting Diodes

PubMed Central

Lee, Ching-Ting

2010-01-01

Zinc oxide (ZnO) is a potential candidate material for optoelectronic applications, especially for blue to ultraviolet light emitting devices, due to its fundamental advantages, such as direct wide band gap of 3.37 eV, large exciton binding energy of 60 meV, and high optical gain of 320 cm−1 at room temperature. Its luminescent properties have been intensively investigated for samples, in the form of bulk, thin film, or nanostructure, prepared by various methods and doped with different impurities. In this paper, we first review briefly the recent progress in this field. Then a comprehensive summary of the research carried out in our laboratory on ZnO preparation and its luminescent properties, will be presented, in which the involved samples include ZnO films and nanorods prepared with different methods and doped with n-type or p-type impurities. The results of ZnO based LEDs will also be discussed.

Nanostructured ZnO in a Metglas/ZnO/Hemoglobin Modified Electrode to Detect the Oxidation of the Hemoglobin Simultaneously by Cyclic Voltammetry and Magnetoelastic Resonance

PubMed Central

Sagasti, Ariane; Bouropoulos, Nikolaos; Kouzoudis, Dimitris; Panagiotopoulos, Apostolos; Topoglidis, Emmanuel; Gutiérrez, Jon

2017-01-01

In the present work, a nanostructured ZnO layer was synthesized onto a Metglas magnetoelastic ribbon to immobilize hemoglobin (Hb) on it and study the Hb’s electrochemical behavior towards hydrogen peroxide. Hb oxidation by H2O2 was monitored simultaneously by two different techniques: Cyclic Voltammetry (CV) and Magnetoelastic Resonance (MR). The Metglas/ZnO/Hb system was simultaneously used as a working electrode for the CV scans and as a magnetoelastic sensor excited by external coils, which drive it to resonance and interrogate it. The ZnO nanoparticles for the ZnO layer were grown hydrothermally and fully characterized by X-Ray Diffraction (XRD), Scanning Electron Microscopy (SEM) and photoluminescence (PL). Additionally, the ZnO layer’s elastic modulus was measured using a new method, which makes use of the Metglas substrate. For the detection experiments, the electrochemical cell was performed with a glass vial, where the three electrodes (working, counter and reference) were immersed into PBS (Phosphate Buffer Solution) solution and small H2O2 drops were added, one at a time. CV scans were taken every 30 s and 5 min after the addition of each drop and meanwhile a magnetoelastic measurement was taken by the external coils. The CV plots reveal direct electrochemical behavior of Hb and display good electrocatalytic response to the reduction of H2O2. The measured catalysis currents increase linearly with the H2O2 concentration in a wide range of 25–350 μM with a correlation coefficient 0.99. The detection limit is 25–50 μM. Moreover, the Metglas/ZnO/Hb electrode displays rapid response (30 s) to H2O2, and exhibits good stability and reproducibility of the measurements. On the other hand, the magnetoelastic measurements show a small linear mass increase versus the H2O2 concentration with a slope of 152 ng/μM, which is probably due to H2O2 adsorption in ZnO during the electrochemical reaction. No such effects were detected during the control experiment

A study on photoelectrochemical properties of ZnO@ZnS nanostructures synthesized via facile ion-exchange approach

NASA Astrophysics Data System (ADS)

Sharma, Akash; Sahoo, Pooja; Thangavel, R.

2018-05-01

In this work, ZnO nanorods (NRs) were fabricated, on cleaned ITO substrates by using sol-gel spin coating followed by hydrothermal technique. In order to coat zinc sulphide (ZnS) layers on the earlier prepared NRs a facile ion-exchange approach was adopted. The ZnO@ZnS nanostructures so prepared were characterised by using X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), UV-visible spectroscopy and photoelectrochemical study. XRD spectra confirmed the hexagonal wurtzite structure of all the samples along with preferential c-axis orientation. Further it was also observed from the FESEM images that sulfidation process doesn't affect the structure of ZnO NRs arrays. From the absorption spectra it can be clearly observed that the light absorbing property has increased in within the visible range due to the formation of ZnS layer on the ZnO nanostructures, which is not possible for either of the material individually. The cyclic voltammetry results indicates the enhancement in photocurrent density after illumination for the synthesized nanostructures. The electrocatalytic behaviour of ZnO@ZnS electrodes have been studied using a 3-electrode system in presence of 0.1M NaOH electrolyte solution with respect to an Ag/AgCl reference electrode.

Analysis of ultraviolet photo-response of ZnO nanostructures prepared by electrodeposition and atomic layer deposition

NASA Astrophysics Data System (ADS)

Makhlouf, Houssin; Karam, Chantal; Lamouchi, Amina; Tingry, Sophie; Miele, Philippe; Habchi, Roland; Chtourou, Radhouane; Bechelany, Mikhael

2018-06-01

In this work, ZnO nanowires (ZnO NWs) and urchin-like ZnO nanowires (U-ZnO NWs) based on self-assembled ordered polystyrene sphere (PS) were successfully prepared by combining atomic layer deposition (ALD) and electrochemical deposition (ECD) processes to build UV photosensors. The photo-response of the prepared samples was investigated and compared. The growth of the nanowires on self-assembled, ordered PS introduces a significant modification on the morphology, crystal orientation and grain size of U-ZnO NWs compared to randomly, vertically aligned ZnO NWs, and therefore improves the photo-response of U-ZnO NWs. The photocurrent may be produced by either a surface or bulk-related process. For ZnO NW-based photosensors, the photocurrent was monitored by a surface related process, whereas, it was mainly governed by a bulk related process for U-ZnO NWs, resulting in a higher and faster photo-response. The study of the rise and decay time constants for both materials showed that these parameters were strikingly sensitive to the optical properties.

Size-Dependent Melting Behavior of Colloidal In, Sn, and Bi Nanocrystals

PubMed Central

Liu, Minglu; Wang, Robert Y.

2015-01-01

Colloidal nanocrystals are a technologically important class of nanostructures whose phase change properties have been largely unexplored. Here we report on the melting behavior of In, Sn, and Bi nanocrystals dispersed in a polymer matrix. This polymer matrix prevents the nanocrystals from coalescing with one another and enables previously unaccessed observations on the melting behavior of colloidal nanocrystals. We measure the melting temperature, melting enthalpy, and melting entropy of colloidal nanocrystals with diameters of approximately 10 to 20 nm. All of these properties decrease as nanocrystal size decreases, although the depression rate for melting temperature is comparatively slower than that of melting enthalpy and melting entropy. We also observe an elevated melting temperature during the initial melt-freeze cycle that we attribute to surface stabilization from the organic ligands on the nanocrystal surface. Broad endothermic melting valleys and very large supercoolings in our calorimetry data suggest that colloidal nanocrystals exhibit a significant amount of surface pre-melting and low heterogeneous nucleation probabilities during freezing. PMID:26573146

Systematic study of inorganic functionalization of ZnO nanorods by Sol-Gel method

NASA Astrophysics Data System (ADS)

Gamarra, J. K.; Solano, C.; Piñeres, I.; Gómez, H.; Mass, J.; Montenegro, D. N.

2017-01-01

A systematic study of the inorganic surface functionalization of ZnO nanostructures by sol-gel method is shown. We have emphasized on the evolution of morphology properties of samples as a function of functionalization parameters. In addition, the effects on thermal stability and some optical properties of samples are discussed.

Growth of ZnO films in sol-gel electrophoretic deposition by different solvents

NASA Astrophysics Data System (ADS)

Hallajzadeh, Amir Mohammad; Abdizadeh, Hossein; Taheri, Mahtab; Golobostanfard, Mohammad Reza

2018-01-01

This article introduces a process to fabricate zinc oxide (ZnO) films through combining sol preparation and electrophoretic deposition (EPD). The experimental results have proved that the EPD process is a powerful route to fabricate ZnO films with desire thickness from stable colloidal suspension under a direct current (DC) electric field. In this method, ZnO sol is prepared by dissolving zinc acetate dehydrate (ZAD) as the main precursor and diethanolamine (DEA) as the additive in various solvents such as methanol (MeOH), ethanol (EtOH), and 2-proponal (2-PrOH). The deposition was performed under a constant voltage of 30 V for 2 min. Scanning electron microscopy (SEM), X-ray diffraction (XRD), and diffuse reflectance spectroscopy (DRS) were used to characterize ZnO films. XRD pattern of the ZnO film prepared by MeOH shows the highest degree of preferential orientation and this is mainly attributed to the higher dielectric constant of the MeOH which results in higher current density in electrophoretic deposit ion. The SEM cross section images also show that the thickness of the ZnO film enhances by decreasing the solvent chain length. According to SEM results, as the viscosity of the medium increased, more compact layers are formed, which can be attributed to the lower deposition rates in heavier alcohols.

Electrosynthesis of ZnO nanorods and nanotowers: Morphology and X-ray Absorption Near Edge Spectroscopy studies

NASA Astrophysics Data System (ADS)

Sigircik, Gokmen; Erken, Ozge; Tuken, Tunc; Gumus, Cebrail; Ozkendir, Osman M.; Ufuktepe, Yuksel

2015-06-01

Deposition mechanism of nano-structured ZnO films has been investigated in the absence and presence of chloride ions from aqueous solution. The resulting opto-electronic properties were interpreted extensively, using X-ray diffraction (XRD), X-ray Absorption Near Edge Spectroscopy (XANES), field emission scanning electron microscopy (FE-SEM), UV-Visible spectroscopy and four probe techniques. The ZnO deposition is mass transport controlled process and the interaction of chloride ions with the surface has great influence on diffusion kinetics, considering the substantial species (Zn2+ and OH-) involved in the construction of ZnO film. This effect does not change major lattice parameters, as shown with detailed analysis of XRD data. However, the texture coefficient (Tc) (0 0 2) value is higher in presence of chloride ions containing synthesis solution which gave vertically aligned, well defined and uniformly dispersed nanorods structure. The calculated Eg values are in the range 3.28-3.41 eV and 3.22-3.31 eV for ZnO nanorods and nanotowers synthesized at different deposition periods, respectively. Furthermore, the charge mobility values regarding the deposition periods were measured to be in the ranges from 130.4 to 449.2 cm2 V-1 s-1 and 126.2 to 204.7 cm2 V-1 s-1 for nanorods and nanotowers, respectively. From XANES results, it was shown that the Zn K-edge spectrum is dominated by the transition of Zn 1s core electrons into the unoccupied Zn 4p states of the conduction band. Comparing the rod and tower nano-structured ZnO thin films, the excitation behavior of valence band electrons is different. Moreover, the density states of Zn 4p are higher for ZnO nanorods.

Preferential cytotoxicity of ZnO nanoparticle towards cervical cancer cells induced by ROS-mediated apoptosis and cell cycle arrest for cancer therapy

NASA Astrophysics Data System (ADS)

Sirelkhatim, Amna; Mahmud, Shahrom; Seeni, Azman; Kaus, Noor Haida Mohd

2016-08-01

The present study aimed to synthesize multifunctional ZnO-NP samples, namely ZnO-20, ZnO-40, and ZnO-80 nm, using different approaches, to be used as efficient anticancer agents. Systematic characterizations revealed their particle sizes and demonstrated nanostructures of nanorods (ZnO-80 nm) and nanogranules (ZnO-20 and ZnO-40 nm). They exhibited significant ( p < 0.05) toxicity to HeLa cancer cells. HeLa cell viabilities at 1 mM dose reduced to 37, 32, 15 %, by ZnO-80, ZnO-40, and ZnO-20 nm, respectively, at 48 h. However, the same dose exerted different effects of 79.6, 76, and 75 % on L929 normal cells at 48 h. Measurement of reactive oxygen species (ROS) showed a considerable ROS yields on HeLa cells by all samples with a pronounced percentage (50 %) displayed by ZnO-20 nm. Moreover, ROS-mediated apoptosis induction and blocked cell cycle progression in the S, G2/M, and G0/G1 phases significantly ( p < 0.05). Apoptosis induction was further confirmed by DNA fragmentation and Hoechst-PI costained images viewed under fluorescence microscope. Additionally, morphological changes of HeLa cells visualized under light microscope showed assortment of cell death involved shrinkage, vacuolization and apoptotic bodies' formation. Most importantly, results exposed the impact of size and morphology of ZnO samples on their toxicity to Hela cells mediated mainly by ROS production. ZnO-20 nm in disk form with its nanogranule shape and smallest particle size was the most toxic sample, followed by ZnO-40 nm and then ZnO-80 nm. An additional proposed mechanism contributed in the cell death herein was ZnO decomposition producing zinc ions (Zn2+) into the acidic cancer microenvironment due to the smaller sizes of ZnO-NPs. This mechanism has been adopted in the literatures as a size-dependent phenomenon. The emerged findings were suggested to provide new platforms in the development of therapeutics as selective agents to the fatal cervical cancer, and to benefit from the

Efficient room temperature hydrogen sensor based on UV-activated ZnO nano-network

NASA Astrophysics Data System (ADS)

Kumar, Mohit; Kumar, Rahul; Rajamani, Saravanan; Ranwa, Sapana; Fanetti, Mattia; Valant, Matjaz; Kumar, Mahesh

2017-09-01

Room temperature hydrogen sensors were fabricated from Au embedded ZnO nano-networks using a 30 mW GaN ultraviolet LED. The Au-decorated ZnO nano-networks were deposited on a SiO2/Si substrate by a chemical vapour deposition process. X-ray diffraction (XRD) spectrum analysis revealed a hexagonal wurtzite structure of ZnO and presence of Au. The ZnO nanoparticles were interconnected, forming nano-network structures. Au nanoparticles were uniformly distributed on ZnO surfaces, as confirmed by FESEM imaging. Interdigitated electrodes (IDEs) were fabricated on the ZnO nano-networks using optical lithography. Sensor performances were measured with and without UV illumination, at room temperate, with concentrations of hydrogen varying from 5 ppm to 1%. The sensor response was found to be ˜21.5% under UV illumination and 0% without UV at room temperature for low hydrogen concentration of 5 ppm. The UV-photoactivated mode enhanced the adsorption of photo-induced O- and O2- ions, and the d-band electron transition from the Au nanoparticles to ZnO—which increased the chemisorbed reaction between hydrogen and oxygen. The sensor response was also measured at 150 °C (without UV illumination) and found to be ˜18% at 5 ppm. Energy efficient low cost hydrogen sensors can be designed and fabricated with the combination of GaN UV LEDs and ZnO nanostructures.

Tuning the field distribution and fabrication of an Al@ZnO core-shell nanostructure for a SPR-based fiber optic phenyl hydrazine sensor.

PubMed

Tabassum, Rana; Kaur, Parvinder; Gupta, Banshi D

2016-05-27

We report the fabrication and characterization of a surface plasmon resonance (SPR)-based fiber optic sensor that uses coatings of silver and aluminum (Al)-zinc oxide (ZnO) core-shell nanostructure (Al@ZnO) for the detection of phenyl hydrazine (Ph-Hyd). To optimize the volume fraction (f) of Al in ZnO and the thickness of the core-shell nanostructure layer (d), the electric field intensity along the normal to the multilayer system is simulated using the two-dimensional multilayer matrix method. The Al@ZnO core-shell nanostructure is prepared using the laser ablation technique. Various probes are fabricated with different values of f and an optimized thickness of core-shell nanostructure for the characterization of the Ph-Hyd sensor. The performance of the Ph-Hyd sensor is evaluated in terms of sensitivity. It is found that the Ag/Al@ZnO nanostructure core-shell-coated SPR probe with f = 0.25 and d = 0.040 μm possesses the maximum sensitivity towards Ph-Hyd. These results are in agreement with the simulated ones obtained using electric field intensity. In addition, the performance of the proposed probe is compared with that of probes coated with (i) Al@ZnO nanocomposite, (ii) Al nanoparticles and (iii) ZnO nanoparticles. It is found that the probe coated with an Al@ZnO core-shell nanostructure shows the largest resonance wavelength shift. The detailed mechanism of the sensing (involving chemical reactions) is presented. The sensor also manifests optimum performance at pH 7.

Two-dimensional ZnO nanosheets grown on flexible ITO-PET substrate for self-powered energy-harvesting nanodevices

NASA Astrophysics Data System (ADS)

Wang, Qingyi; Yang, Dechao; Qiu, Yu; Zhang, Xiaotong; Song, Wenbin; Hu, Lizhong

2018-02-01

Here, we report the two-step growth method of two-dimensional (2-D) ZnO nanosheets (NSs) and explore their formation mechanism. Additionally, we illustrate their application for high-performance piezoelectric nanogenerators (NGs) by using grown products from various reaction times. The result shows that NGs based on 2-D NSs demonstrated better output performance than those based on 1-D NWs, which surprisingly increased from ˜40 nA to ˜0.15 μA under the same compressive force of ˜1 kgf. It can also be observed that the output current is slightly elevated as the 2-D nanostructures become thinner. Our results offer a unique way to improve the output performance of NGs by means of controlling the synthesis period of ZnO nanostructures, which have important applications in flexible electronics and wearable devices.

Analytical theory of polymer-network-mediated interaction between colloidal particles

PubMed Central

Di Michele, Lorenzo; Zaccone, Alessio; Eiser, Erika

2012-01-01

Nanostructured materials based on colloidal particles embedded in a polymer network are used in a variety of applications ranging from nanocomposite rubbers to organic-inorganic hybrid solar cells. Further, polymer-network-mediated colloidal interactions are highly relevant to biological studies whereby polymer hydrogels are commonly employed to probe the mechanical response of living cells, which can determine their biological function in physiological environments. The performance of nanomaterials crucially relies upon the spatial organization of the colloidal particles within the polymer network that depends, in turn, on the effective interactions between the particles in the medium. Existing models based on nonlocal equilibrium thermodynamics fail to clarify the nature of these interactions, precluding the way toward the rational design of polymer-composite materials. In this article, we present a predictive analytical theory of these interactions based on a coarse-grained model for polymer networks. We apply the theory to the case of colloids partially embedded in cross-linked polymer substrates and clarify the origin of attractive interactions recently observed experimentally. Monte Carlo simulation results that quantitatively confirm the theoretical predictions are also presented. PMID:22679289

Effect of Er3+ doping on structural, morphological and photocatalytical properties of ZnO thin films

NASA Astrophysics Data System (ADS)

Bouhouche, S.; Bensouici, F.; Toubane, M.; Azizi, A.; Otmani, A.; Chebout, K.; Kezzoula, F.; Tala-Ighil, R.; Bououdina, M.

2018-05-01

In this research work, structure, microstructure, optical and photocatalytic properties of undoped and Erbium doped nanostructured ZnO thin films prepared by sol-gel dip-coating are investigated. X-ray diffraction (XRD) analysis indicates that the deposited films crystallize within the hexagonal wurtzite-type structure with a preferential growth orientation along (002) plane. Morphological observations using scanning electron microscopy (SEM) reveal important influence of Er concentration; displaying homogeneous and dense aspect for undoped to 0.3% then grid-like morphology for 0.4 and 0.5%. UV/vis/NIR transmittance spectroscopy spectra display a transmittance over 70%, and small variation in the energy gap energy 3.263–3.278 eV. Wettability test of ZnO thin films surface ranges from hydrophilic aspect for pure ZnO to hydrophobic one for Er doped ZnO, and the contact angle is found to increase from 58.7° for pure ZnO up to 98.4° for 0.4% Er doped ZnO. The photocatalytic activity measurements evaluated using the degradation of methylene blue (MB) under UV light irradiation demonstrate that undoped ZnO film shows higher photocatalytic activity compared to Er doped ZnO films, which may be attributed to the deterioration of films’crystallinity resulting in lower transmittance.

Experimental and theoretical studies of the colloidal stability of nanoparticles-a general interpretation based on stability maps.

PubMed

Segets, Doris; Marczak, Renata; Schäfer, Stefan; Paula, Carolin; Gnichwitz, Jan-Frederik; Hirsch, Andreas; Peukert, Wolfgang

2011-06-28

The current work addresses the understanding of the stabilization of nanoparticles in suspension. Specifically, we study ZnO in ethanol for which the influence of particle size and reactant ratio as well as surface coverage on colloidal stability in dependence of the purification progress was investigated. The results revealed that the well-known ζ-potential determines not only the colloidal stability but also the surface coverage of acetate groups bound to the particle surface. The acetate groups act as molecular spacers between the nanoparticles and prevent agglomeration. Next to DLVO calculations based on the theory of Derjaguin, Landau, Verwey and Overbeek using a core-shell model we find that the stability is better understood in terms of dimensionless numbers which represent attractive forces as well as electrostatic repulsion, steric effects, transport properties, and particle concentration. Evaluating the colloidal stability in dependence of time by means of UV-vis absorption measurements a stability map for ZnO is derived. From this map it becomes clear that the dimensionless steric contribution to colloidal stability scales with a stability parameter including dimensionless repulsion and attraction as well as particle concentration and diffusivity of the particles according to a power law with an exponent of -0.5. Finally, we show that our approach is valid for other stabilizing molecules like cationic dendrons and is generally applicable for a wide range of other material systems within the limitations of vanishing van der Waals forces in refractive index matched situations, vanishing ζ-potential and systems without a stabilizing shell around the particle surface.

Renewable Lignosulfonate-Assisted Synthesis of Hierarchical Nanoflake-Array-Flower ZnO Nanomaterials in Mixed Solvents and Their Photocatalytic Performance

NASA Astrophysics Data System (ADS)

Li, Yue; Zuo, Hong-Fen; Guo, Yuan-Ru; Miao, Ting-Ting; Pan, Qing-Jiang

2016-05-01

With the assistance of sodium lignosulfonate, hierarchical nanoflake-array-flower nanostructure of ZnO has been fabricated by a facile precipitation method in mixed solvents. The sodium lignosulfonate amount used in our synthetic route is able to fine-tune ZnO morphology and an abundance of pores have been observed in the nanoflake-array-flower ZnO, which result in specific surface area reaching as high as 82.9 m2 · g-1. The synthesized ZnO exhibits superior photocatalytic activity even under low-power UV illumination (6 W). It is conjectured that both nanoflake-array structure and plenty of pores embedded in ZnO flakes may provide scaffold microenvironments to enhance photocatalytic activity. Additionally, this catalyst can be used repeatedly without a significant loss in photocatalytic activity. The low-cost, simple synthetic approach as well as high photocatalytic and recycling efficiency of our ZnO nanomaterials allows for application to treat wastewater containing organic pollutants in an effective way.

Polarity in GaN and ZnO: Theory, measurement, growth, and devices

NASA Astrophysics Data System (ADS)

Zúñiga-Pérez, Jesús; Consonni, Vincent; Lymperakis, Liverios; Kong, Xiang; Trampert, Achim; Fernández-Garrido, Sergio; Brandt, Oliver; Renevier, Hubert; Keller, Stacia; Hestroffer, Karine; Wagner, Markus R.; Reparaz, Juan Sebastián; Akyol, Fatih; Rajan, Siddharth; Rennesson, Stéphanie; Palacios, Tomás; Feuillet, Guy

2016-12-01

The polar nature of the wurtzite crystalline structure of GaN and ZnO results in the existence of a spontaneous electric polarization within these materials and their associated alloys (Ga,Al,In)N and (Zn,Mg,Cd)O. The polarity has also important consequences on the stability of the different crystallographic surfaces, and this becomes especially important when considering epitaxial growth. Furthermore, the internal polarization fields may adversely affect the properties of optoelectronic devices but is also used as a potential advantage for advanced electronic devices. In this article, polarity-related issues in GaN and ZnO are reviewed, going from theoretical considerations to electronic and optoelectronic devices, through thin film, and nanostructure growth. The necessary theoretical background is first introduced and the stability of the cation and anion polarity surfaces is discussed. For assessing the polarity, one has to make use of specific characterization methods, which are described in detail. Subsequently, the nucleation and growth mechanisms of thin films and nanostructures, including nanowires, are presented, reviewing the specific growth conditions that allow controlling the polarity of such objects. Eventually, the demonstrated and/or expected effects of polarity on the properties and performances of optoelectronic and electronic devices are reported. The present review is intended to yield an in-depth view of some of the hot topics related to polarity in GaN and ZnO, a fast growing subject over the last decade.

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.

PubMed

Ghasemi, Ensieh; Sillanpää, Mika

2014-12-01

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 50-80 nm. 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 0.01-0.1 ng L(-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. Copyright © 2014 Elsevier B.V. All rights reserved.

Enhanced Dibutyl Phthalate Sensing Performance of a Quartz Crystal Microbalance Coated with Au-Decorated ZnO Porous Microspheres

PubMed Central

Zhang, Kaihuan; Fan, Guokang; Hu, Ruifen; Li, Guang

2015-01-01

Noble metals addition on nanostructured metal oxides is an attractive way to enhance gas sensing properties. Herein, hierarchical zinc oxide (ZnO) porous microspheres decorated with cubic gold particles (Au particles) were synthesized using a facile hydrothermal method. The as-prepared Au-decorated ZnO was then utilized as the sensing film of a gas sensor based on a quartz crystal microbalance (QCM). This fabricated sensor was applied to detect dibutyl phthalate (DBP), which is a widely used plasticizer, and its coating load was optimized. When tested at room temperature, the sensor exhibited a high sensitivity of 38.10 Hz/ppb to DBP in a low concentration range from 2 ppb to 30 ppb and the calculated theoretical detection limit is below 1 ppb. It maintains good repeatability as well as long-term stability. Compared with the undecorated ZnO based QCM, the Au-decorated one achieved a 1.62-time enhancement in sensitivity to DBP, and the selectivity was also improved. According to the experimental results, Au-functionalized ZnO porous microspheres displayed superior sensing performance towards DBP, indicating its potential use in monitoring plasticizers in the gaseous state. Moreover, Au decoration of porous metal oxide nanostructures is proved to be an effective approach for enhancing the gas sensing properties and the corresponding mechanism was investigated. PMID:26343661

Engineering safer-by-design, transparent, silica-coated ZnO nanorods with reduced DNA damage potential

PubMed Central

Sotiriou, Georgios A.; Watson, Christa; Murdaugh, Kimberly M.; Darrah, Thomas H.; Pyrgiotakis, Georgios; Elder, Alison; Brain, Joseph D.; Demokritou, Philip

2014-01-01

Zinc oxide (ZnO) nanoparticles absorb UV light efficiently while remaining transparent in the visible light spectrum rendering them attractive in cosmetics and polymer films. Their broad use, however, raises concerns regarding potential environmental health risks and it has been shown that ZnO nanoparticles can induce significant DNA damage and cytotoxicity. Even though research on ZnO nanoparticle synthesis has made great progress, efforts on developing safer ZnO nanoparticles that maintain their inherent optoelectronic properties while exhibiting minimal toxicity are limited. Here, a safer-by-design concept was pursued by hermetically encapsulating ZnO nanorods in a biologically inert, nanothin amorphous SiO2 coating during their gas-phase synthesis. It is demonstrated that the SiO2 nanothin layer hermetically encapsulates the core ZnO nanorods without altering their optoelectronic properties. Furthermore, the effect of SiO2 on the toxicological profile of the core ZnO nanorods was assessed using the Nano-Cometchip assay by monitoring DNA damage at a cellular level using human lymphoblastoid cells (TK6). Results indicate significantly lower DNA damage (>3 times) for the SiO2-coated ZnO nanorods compared to uncoated ones. Such an industry-relevant, scalable, safer-by-design formulation of nanostructured materials can liberate their employment in nano-enabled products and minimize risks to the environment and human health. PMID:24955241

Tunable UV- and Visible-Light Photoresponse Based on p-ZnO Nanostructures/n-ZnO/Glass Peppered with Au Nanoparticles.

PubMed

Hsu, Cheng-Liang; Lin, Yu-Hong; Wang, Liang-Kai; Hsueh, Ting-Jen; Chang, Sheng-Po; Chang, Shoou-Jinn

2017-05-03

UV- and visible-light photoresponse was achieved via p-type K-doped ZnO nanowires and nanosheets that were hydrothermally synthesized on an n-ZnO/glass substrate and peppered with Au nanoparticles. The K content of the p-ZnO nanostructures was 0.36 atom %. The UV- and visible-light photoresponse of the p-ZnO nanostructures/n-ZnO sample was roughly 2 times higher than that of the ZnO nanowires. The Au nanoparticles of various densities and diameter sizes were deposited on the p-ZnO nanostructures/n-ZnO samples by a simple UV photochemical reaction method yielding a tunable and enhanced UV- and visible-light photoresponse. The maximum UV and visible photoresponse of the Au nanoparticle sample was obtained when the diameter size of the Au nanoparticle was approximately 5-35 nm. On the basis of the localized surface plasmon resonance effect, the UV, blue, and green photocurrent/dark current ratios of Au nanoparticle/p-ZnO nanostructures/n-ZnO are ∼1165, ∼94.6, and ∼9.7, respectively.

Interfacial engineering of CuO nanorod/ZnO nanowire hybrid nanostructure photoanode in dye-sensitized solar cell

NASA Astrophysics Data System (ADS)

Kilic, Bayram; Turkdogan, Sunay; Astam, Aykut; Baran, Sümeyra Seniha; Asgin, Mansur; Gur, Emre; Kocak, Yusuf

2018-01-01

Developing efficient and cost-effective photoanode plays a vital role determining the photocurrent and photovoltage in dye-sensitized solar cells (DSSCs). Here, we demonstrate DSSCs that achieve relatively high power conversion efficiencies (PCEs) by using one-dimensional (1D) zinc oxide (ZnO) nanowires and copper (II) oxide (CuO) nanorods hybrid nanostructures. CuO nanorod-based thin films were prepared by hydrothermal method and used as a blocking layer on top of the ZnO nanowires' layer. The use of 1D ZnO nanowire/CuO nanorod hybrid nanostructures led to an exceptionally high photovoltaic performance of DSSCs with a remarkably high open-circuit voltage (0.764 V), short current density (14.76 mA/cm2 under AM1.5G conditions), and relatively high solar to power conversion efficiency (6.18%) . The enhancement of the solar to power conversion efficiency can be explained in terms of the lag effect of the interfacial recombination dynamics of CuO nanorod-blocking layer on ZnO nanowires. This work shows more economically feasible method to bring down the cost of the nano-hybrid cells and promises for the growth of other important materials to further enhance the solar to power conversion efficiency.

Electromechanical phenomena in semiconductor nanostructures

NASA Astrophysics Data System (ADS)

Lew Yan Voon, L. C.; Willatzen, M.

2011-02-01

Electromechanical phenomena in semiconductors are still poorly studied from a fundamental and an applied science perspective, even though significant strides have been made in the last decade or so. Indeed, most current electromechanical devices are based on ferroelectric oxides. Yet, the importance of the effect in certain semiconductors is being increasingly recognized. For instance, the magnitude of the electric field in an AlN/GaN nanostructure can reach 1-10 MV/cm. In fact, the basic functioning of an (0001) AlGaN/GaN high electron mobility transistor is due to the two-dimensional electron gas formed at the material interface by the polarization fields. The goal of this review is to inform the reader of some of the recent developments in the field for nanostructures and to point out still open questions. Examples of recent work that involves the piezoelectric and pyroelectric effects in semiconductors include: the study of the optoelectronic properties of III-nitrides quantum wells and dots, the current controversy regarding the importance of the nonlinear piezoelectric effect, energy harvesting using ZnO nanowires as a piezoelectric nanogenerator, the use of piezoelectric materials in surface acoustic wave devices, and the appropriateness of various models for analyzing electromechanical effects. Piezoelectric materials such as GaN and ZnO are gaining more and more importance for energy-related applications; examples include high-brightness light-emitting diodes for white lighting, high-electron mobility transistors, and nanogenerators. Indeed, it remains to be demonstrated whether these materials could be the ideal multifunctional materials. The solutions to these and other related problems will not only lead to a better understanding of the basic physics of these materials, but will validate new characterization tools, and advance the development of new and better devices. We will restrict ourselves to nanostructures in the current article even though the

Photoelectrochemical water splitting strongly enhanced in fast-grown ZnO nanotree and nanocluster structures† †Electronic supplementary information (ESI) available. See DOI: 10.1039/c6ta02788a Click here for additional data file.

PubMed Central

Sangle, Abhijeet; Zhang, Siyuan; Yuan, Shuai; Zhao, Yin; Shi, Liyi; Hoye, Robert L. Z.; Cho, Seungho; Li, Dongdong

2016-01-01

We demonstrate selective growth of ZnO branched nanostructures: from nanorod clusters (with branches parallel to parent rods) to nanotrees (with branches perpendicular to parent rods). The growth of these structures was realized using a three-step approach: electrodeposition of nanorods (NRs), followed by the sputtering of ZnO seed layers, followed by the growth of branched arms using hydrothermal growth. The density, size and direction of the branches were tailored by tuning the deposition parameters. To our knowledge, this is the first report of control of branch direction. The photoelectrochemical (PEC) performance of the ZnO nanostructures follows the order: nanotrees (NTs) > nanorod clusters (NCs) > parent NRs. The NT structure with the best PEC performance also possesses the shortest fabrication period which had never been reported before. The photocurrent of the NT and NC photoelectrodes is 0.67 and 0.56 mA cm–2 at 1 V vs. Ag/AgCl, respectively, an enhancement of 139% and 100% when compared to the ZnO NR structures. The key reason for the improved performance is shown to be the very large surface-to-volume ratios in the branched nanostructures, which gives rise to enhanced light absorption, improved charge transfer across the nanostructure/electrolyte interfaces to the electrolyte and efficient charge transport within the material. PMID:27774147

Physico-chemical changes of ZnO nanoparticles with different size and surface chemistry under physiological pH conditions.

PubMed

Gwak, Gyeong-Hyeon; Lee, Won-Jae; Paek, Seung-Min; Oh, Jae-Min

2015-03-01

We studied the physico-chemical properties of ZnO nanoparticles under physiological pH conditions (gastric, intestinal and plasma) as functions of their size (20 and 70 nm) and surface chemistry (pristine, L-serine, or citrate coating). ZnO nanoparticles were dispersed in phosphate buffered saline under physiological pH conditions and aliquots were collected at specific time points (0.5, 1, 4, 10 and 24 h) for further characterization. The pH values of the aqueous ZnO colloids at each condition were in the neutral to slightly basic range and showed different patterns depending on the original size and surface chemistry of the ZnO nanoparticles. The gastric pH condition was found to significantly dissolve ZnO nanoparticles up to 18-30 wt%, while the intestinal or plasma pH conditions resulted in much lower dissolution amounts than expected. Based on the X-ray diffraction patterns and X-ray absorption spectra, we identified partial phase transition of the ZnO nanoparticles from wurtzite to Zn(OH)2 under the intestinal and plasma pH conditions. Using scanning electron microscopy, we verified that the overall particle size and morphology of all ZnO nanoparticles were maintained regardless of the pH. Copyright © 2015 Elsevier B.V. All rights reserved.

Abnormal temperature dependence of conductance of single Cd-doped ZnO nanowires

NASA Astrophysics Data System (ADS)

Li, Q. H.; Wan, Q.; Wang, Y. G.; Wang, T. H.

2005-06-01

Positive temperature coefficient of resistance is observed on single Cd-doped ZnO nanowires. The current along the nanowire increases linearly with the bias and saturates at large biases. The conductance is greatly enhanced either by ultraviolet illumination or infrared illumination. However, the conductance decreases with increasing temperature, in contrast to the reported temperature behavior either for ZnO nanostructures or for CdO nanoneedles. The increase of the conductance under illumination is related to surface effect and the decrease with increasing temperature to bulk effect. These results show that Cd doping does not change surface effect but affects bulk effect. Such a bulk effect could be used to realize on-chip temperature-independent varistors.

Integration of ZnO and CuO nanowires into a thermoelectric module

PubMed Central

Dalola, Simone; Faglia, Guido; Comini, Elisabetta; Ferroni, Matteo; Soldano, Caterina; Ferrari, Vittorio; Sberveglieri, Giorgio

2014-01-01

Summary Zinc oxide (ZnO, n-type) and copper oxide (CuO, p-type) nanowires have been synthesized and preliminarily investigated as innovative materials for the fabrication of a proof-of-concept thermoelectric device. The Seebeck coefficients, electrical conductivity and thermoelectric power factors (TPF) of both semiconductor materials have been determined independently using a custom experimental set-up, leading to results in agreement with available literature with potential improvement. Combining bundles of ZnO and CuO nanowires in a series of five thermocouples on alumina leads to a macroscopic prototype of a planar thermoelectric generator (TEG) unit. This demonstrates the possibility of further integration of metal oxide nanostructures into efficient thermoelectric devices. PMID:24991531

Integration of ZnO and CuO nanowires into a thermoelectric module.

PubMed

Zappa, Dario; Dalola, Simone; Faglia, Guido; Comini, Elisabetta; Ferroni, Matteo; Soldano, Caterina; Ferrari, Vittorio; Sberveglieri, Giorgio

2014-01-01

Zinc oxide (ZnO, n-type) and copper oxide (CuO, p-type) nanowires have been synthesized and preliminarily investigated as innovative materials for the fabrication of a proof-of-concept thermoelectric device. The Seebeck coefficients, electrical conductivity and thermoelectric power factors (TPF) of both semiconductor materials have been determined independently using a custom experimental set-up, leading to results in agreement with available literature with potential improvement. Combining bundles of ZnO and CuO nanowires in a series of five thermocouples on alumina leads to a macroscopic prototype of a planar thermoelectric generator (TEG) unit. This demonstrates the possibility of further integration of metal oxide nanostructures into efficient thermoelectric devices.

Fabrication of nanostructured electrodes and interfaces using combustion CVD

NASA Astrophysics Data System (ADS)

Liu, Ying

-aligned ZnO nanorods, and two-dimensional ZnO flakes. Solid-state gas sensors based on single piece of these nanostructures demonstrated superior gas sensing performances. These size-tunable nanostructures could be the building blocks of or a template for fabrication of functional devices. In summary, this research has developed new ways for fabrication of high-performance solid-state ionic devices and has helped generating fundamental understanding of the correlation between processing conditions, microstructure, and properties of the synthesized structures.

Self-Styled ZnO Nanostructures Promotes the Cancer Cell Damage and Supresses the Epithelial Phenotype of Glioblastoma

NASA Astrophysics Data System (ADS)

Wahab, Rizwan; Kaushik, Neha; Khan, Farheen; Kaushik, Nagendra Kumar; Choi, Eun Ha; Musarrat, Javed; Al-Khedhairy, Abdulaziz A.

2016-01-01

Extensive researches have been done on the applications of zinc oxide nanoparticles (ZnO-NPs) for the biological purposes. However, the role and toxicity mechanisms of ZnO nanostructures (ZnO-NSts) such as nanoplates (NPls), nanorods (NRs), nanosheets (NSs), nanoflowers (NFs) on cancer cells are not largely known. Present study was focused to investigate the possible mechanisms of apoptosis induced by self-designed ZnO-NSts, prepared at fix pH via solution process and exposed against human T98G gliomas including various cancers and non-malignant embryonic kidney HEK293, MRC5 fibroblast cells. NSts were used for the induction of cell death in malignant human T98G gliomas including various cancers and compared with the non-malignant cells. Notably, NRs were found to induce higher cytotoxicity, inhibitory effects on cancer and normal cells in a dose dependent manner. We also showed that NRs induced cancer cell death through oxidative stress and caspase-dependent pathways. Furthermore, quantitative and qualitative analysis of ZnO-NSts have also been confirmed by statistical analytical parameters such as precision, accuracy, linearity, limits of detection and limit of quantitation. These self-styled NSts could provide new perception in the research of targeted cancer nanotechnology and have potentiality to improve new therapeutic outcomes with poor diagnosis.

Unravelling the origin of the giant Zn deficiency in wurtzite type ZnO nanoparticles

PubMed Central

Renaud, Adèle; Cario, Laurent; Rocquelfelte, Xavier; Deniard, Philippe; Gautron, Eric; Faulques, Eric; Das, Tilak; Cheviré, François; Tessier, Franck; Jobic, Stéphane

2015-01-01

Owing to its high technological importance for optoelectronics, zinc oxide received much attention. In particular, the role of defects on its physical properties has been extensively studied as well as their thermodynamical stability. In particular, a large concentration of Zn vacancies in ZnO bulk materials is so far considered highly unstable. Here we report that the thermal decomposition of zinc peroxide produces wurtzite-type ZnO nanoparticles with an extraordinary large amount of zinc vacancies (>15%). These Zn vacancies segregate at the surface of the nanoparticles, as confirmed by ab initio calculations, to form a pseudo core-shell structure made of a dense ZnO sphere coated by a Zn free oxo-hydroxide mono layer. In others terms, oxygen terminated surfaces are privileged over zinc-terminated surfaces for passivation reasons what accounts for the Zn off-stoichiometry observed in ultra-fine powdered samples. Such Zn-deficient Zn1-xO nanoparticles exhibit an unprecedented photoluminescence signature suggesting that the core-shell-like edifice drastically influences the electronic structure of ZnO. This nanostructuration could be at the origin of the recent stabilisation of p-type charge carriers in nitrogen-doped ZnO nanoparticles. PMID:26333510

Mace-like gold hollow hierarchical micro/nanostructures fabricated by co-effect of catalytic etching and electrodeposition and their SERS performance

NASA Astrophysics Data System (ADS)

Zhang, Haibao; Wang, Jingjing; Wang, Hua; Tian, Xingyou

2017-09-01

In this paper, we presented the fabrication of mace-like gold hollow hierarchical micro/nanostructures (HMNs) grafted on ZnO nanorods array by using an electrochemical deposition in chloroauric acid solution on gold layer pre-coated ZnO nanorods array. Different from general electrochemical deposition process, the catalytic etching to ZnO and electrodeposition of gold are co-existed in our case, which lead to an inner hollow structure and an outer gold shell. Due to the appropriate electrodeposition conditions, the outer gold shell was built of many wimble-like nanoparticles, and the hierarchical micro/nanostructures were thus formed. In addition, because of the deposition rate is decreased gradually away from the top of ZnO nanorods, the final structures show mace-like appearance. The surface-enhanced Raman scattering (SERS) effect of the as-prepared gold hollow HMNs was further studied by using rhodamine 6G as probe molecule. It is demonstrated that these structures show ultrahigh SERS activity, and the detecting low limit of R6G solution can be to 10-10 M on single mace-like gold HMNs, which is quite important for their potential application in SERS-based surface analysis and sensors.

Tri-functional Fe2O3-encased Ag-doped ZnO nanoframework: magnetically retrievable antimicrobial photocatalyst

NASA Astrophysics Data System (ADS)

Karunakaran, Chockalingam; Vinayagamoorthy, Pazhamalai

2016-11-01

Fe2O3-encased ZnO nanoframework was obtained by hydrothermal method and was doped with Ag through photoreduction process. Energy dispersive x-ray spectroscopy, transmission electron microscopy (TEM), high resolution TEM, selected area electron diffractometry, x-ray diffractometry and Raman spectroscopy were employed for the structural characterization of the synthesized material. While the charge transfer resistance of the prepared nanomaterial is larger than those of Fe2O3 and ZnO the coercivity of the nanocomposite is less than that of hydrothermally obtained Fe2O3 nanostructures. Although Fe2O3/Ag-ZnO exhibits weak visible light absorption its band gap energy does not differ from that of ZnO. The photoluminescence of the fabricated nanoframework is similar to that of ZnO. The radiative recombination of charge carriers is slightly slower in Fe2O3/Ag-ZnO than in ZnO. The synthesized Fe2O3-encased Ag-doped ZnO, under UV A light, exhibits sustainable photocatalytic activity to degrade dye and is magnetically recoverable. Also, the Fe2O3/Ag-ZnO nanocomposite disinfects bacteria effectively in absence of direct illumination.

REVIEW ARTICLE: Structure, microstructure and physical properties of ZnO based materials in various forms: bulk, thin film and nano

NASA Astrophysics Data System (ADS)

Singh, Shubra; Thiyagarajan, P.; Mohan Kant, K.; Anita, D.; Thirupathiah, S.; Rama, N.; Tiwari, Brajesh; Kottaisamy, M.; Ramachandra Rao, M. S.

2007-10-01

ZnO is a unique material that offers about a dozen different application possibilities. In spite of the fact that the ZnO lattice is amenable to metal ion doping (3d and 4f), the physics of doping in ZnO is not completely understood. This paper presents a review of previous research works on ZnO and also highlights results of our research activities on ZnO. The review pertains to the work on Al and Mg doping for conductivity and band gap tuning in ZnO followed by a report on transition metal (TM) ion doped ZnO. This review also highlights the work on the transport and optical studies of TM ion doped ZnO, nanostructured growth (ZnO polycrystalline and thin films) by different methods and the formation of unique nano- and microstructures obtained by pulsed laser deposition and chemical methods. This is followed by results on ZnO encapsulated Fe3O4 nanoparticles that show promising trends suitable for various applications. We have also reviewed the non-linear characteristic studies of ZnO based heterostructures followed by an analysis on the work carried out on ZnO based phosphors, which include mainly the nanocrystalline ZnO encapsulated SiO2, a new class of phosphor that is suitable for white light emission.

Enhancement of Si solar cell efficiency using ZnO nanowires with various diameters

NASA Astrophysics Data System (ADS)

Gholizadeh, A.; Reyhani, A.; Parvin, P.; Mortazavi, S. Z.; Mehrabi, M.

2018-01-01

Here, Zinc Oxide nanowires are synthesized using thermal chemical vapor deposition of a Zn granulate source and used to enhance a significant Si-solar cell efficiency with simple and low cost method. The nanowires are grown in various O2 flow rates. Those affect the shape, yield, structure and the quality of ZnO nanowires according to scanning electron microscopy and x-ray diffraction analyses. This delineates that the ZnO nanostructure is dependent on the synthesis conditions. The photoluminescence spectroscopy of ZnO indicates optical emission at the Ultra-Violet and blue-green regions whose intensity varies as a function of diameter of ZnO nano-wires. The optical property of ZnO layer is measured by UV-visible and diffuse reflection spectroscopy that demonstrate high absorbance at 280-550 nm. Furthermore, the photovoltaic characterization of ZnO nanowires is investigated based on the drop casting on Si-solar cell. The ZnO nanowires with various diameters demonstrate different effects on the efficiency of Si-solar cells. We have shown that the reduction of the spectral reflectance and down-shifting process as well as the reduction of photon trapping are essential parameters on the efficiency of Si-solar cells. However, the latter is dominated here. In fact, the trapped photons during the electron-hole generation are dominant due to lessening the absorption rate in ZnO nano-wires. The results indicate that the mean diameters reduction of ZnO nanowires is also essential to improve the fill factor. The external and internal quantum efficiency analyses attest the efficiency improvement over the blue region which is related to the key parameters above.

Development of nanostructured and surface modified semiconductors for hybrid organic-inorganic solar cells.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hsu, Julia, W. P.

2008-09-01

Solar energy conversion is increasingly being recognized as one of the principal ways to meet future energy needs without causing detrimental environmental impact. Hybrid organic-inorganic solar cells (SCs) are attracting particular interest due to the potential for low cost manufacturing and for use in new applications, such as consumer electronics, architectural integration and light-weight sensors. Key materials advantages of these next generation SCs over conventional semiconductor SCs are in design opportunities--since the different functions of the SCs are carried out by different materials, there are greater materials choices for producing optimized structures. In this project, we explore the hybrid organic-inorganicmore » solar cell system that consists of oxide, primarily ZnO, nanostructures as the electron transporter and poly-(3-hexylthiophene) (P3HT) as the light-absorber and hole transporter. It builds on our capabilities in the solution synthesis of nanostructured semiconducting oxide arrays to this photovoltaic (PV) technology. The three challenges in this hybrid material system for solar applications are (1) achieving inorganic nanostructures with critical spacing that matches the exciton diffusion in the polymer, {approx} 10 nm, (2) infiltrating the polymer completely into the dense nanostructure arrays, and (3) optimizing the interfacial properties to facilitate efficient charge transfer. We have gained an understanding and control over growing oriented ZnO nanorods with sub-50 nm diameters and the required rod-to-rod spacing on various substrates. We have developed novel approaches to infiltrate commercially available P3HT in the narrow spacing between ZnO nanorods. Also, we have begun to explore ways to modify the interfacial properties. In addition, we have established device fabrication and testing capabilities at Sandia for prototype devices. Moreover, the control synthesis of ZnO nanorod arrays lead to the development of an efficient anti

Insights into the sonochemical synthesis and properties of salt-free intrinsic plutonium colloids

NASA Astrophysics Data System (ADS)

Dalodière, Elodie; Virot, Matthieu; Morosini, Vincent; Chave, Tony; Dumas, Thomas; Hennig, Christoph; Wiss, Thierry; Dieste Blanco, Oliver; Shuh, David K.; Tyliszcak, Tolek; Venault, Laurent; Moisy, Philippe; Nikitenko, Sergey I.

2017-03-01

Fundamental knowledge on intrinsic plutonium colloids is important for the prediction of plutonium behaviour in the geosphere and in engineered systems. The first synthetic route to obtain salt-free intrinsic plutonium colloids by ultrasonic treatment of PuO2 suspensions in pure water is reported. Kinetics showed that both chemical and mechanical effects of ultrasound contribute to the mechanism of Pu colloid formation. In the first stage, fragmentation of initial PuO2 particles provides larger surface contact between cavitation bubbles and solids. Furthermore, hydrogen formed during sonochemical water splitting enables reduction of Pu(IV) to more soluble Pu(III), which then re-oxidizes yielding Pu(IV) colloid. A comparative study of nanostructured PuO2 and Pu colloids produced by sonochemical and hydrolytic methods, has been conducted using HRTEM, Pu LIII-edge XAS, and O K-edge NEXAFS/STXM. Characterization of Pu colloids revealed a correlation between the number of Pu-O and Pu-Pu contacts and the atomic surface-to-volume ratio of the PuO2 nanoparticles. NEXAFS indicated that oxygen state in hydrolytic Pu colloid is influenced by hydrolysed Pu(IV) species to a greater extent than in sonochemical PuO2 nanoparticles. In general, hydrolytic and sonochemical Pu colloids can be described as core-shell nanoparticles composed of quasi-stoichiometric PuO2 cores and hydrolyzed Pu(IV) moieties at the surface shell.

Insights into the sonochemical synthesis and properties of salt-free intrinsic plutonium colloids

PubMed Central

Dalodière, Elodie; Virot, Matthieu; Morosini, Vincent; Chave, Tony; Dumas, Thomas; Hennig, Christoph; Wiss, Thierry; Dieste Blanco, Oliver; Shuh, David K.; Tyliszcak, Tolek; Venault, Laurent; Moisy, Philippe; Nikitenko, Sergey I.

2017-01-01

Fundamental knowledge on intrinsic plutonium colloids is important for the prediction of plutonium behaviour in the geosphere and in engineered systems. The first synthetic route to obtain salt-free intrinsic plutonium colloids by ultrasonic treatment of PuO2 suspensions in pure water is reported. Kinetics showed that both chemical and mechanical effects of ultrasound contribute to the mechanism of Pu colloid formation. In the first stage, fragmentation of initial PuO2 particles provides larger surface contact between cavitation bubbles and solids. Furthermore, hydrogen formed during sonochemical water splitting enables reduction of Pu(IV) to more soluble Pu(III), which then re-oxidizes yielding Pu(IV) colloid. A comparative study of nanostructured PuO2 and Pu colloids produced by sonochemical and hydrolytic methods, has been conducted using HRTEM, Pu LIII-edge XAS, and O K-edge NEXAFS/STXM. Characterization of Pu colloids revealed a correlation between the number of Pu-O and Pu-Pu contacts and the atomic surface-to-volume ratio of the PuO2 nanoparticles. NEXAFS indicated that oxygen state in hydrolytic Pu colloid is influenced by hydrolysed Pu(IV) species to a greater extent than in sonochemical PuO2 nanoparticles. In general, hydrolytic and sonochemical Pu colloids can be described as core-shell nanoparticles composed of quasi-stoichiometric PuO2 cores and hydrolyzed Pu(IV) moieties at the surface shell. PMID:28256635

Influence of Co doping on combined photocatalytic and antibacterial activity of ZnO nanoparticles

NASA Astrophysics Data System (ADS)

Anandan, M.; Dinesh, S.; Krishnakumar, N.; Balamurugan, K.

2016-11-01

The present work aims to investigate the structural, optical, photocatalyst and antibacterial properties of bare and cobalt doped ZnO nanoparticles (NPs) with different concentrations Zn1-x Co x O (x = 0, 0.03, 0.06 and 0.09) synthesized by co-precipitation method. The XRD patterns confirmed that all samples of cobalt doped ZnO nanostructures revealed the formation of single phase having hexagonal wurtzite structure with crystallite size in the range of 31-41 nm. Further, the decreasing trend in lattice parameters and grain sizes were also seen with increasing doping concentrations which confirms the incorporation of Co ions into the ZnO lattice. This result was further supported by the FT-IR data. HR-TEM images demonstrated the distinct hexagonal like morphology with small agglomeration. The UV-visible absorption spectra exhibits red shift with increase in Co doping concentration in ZnO while corresponding bandgap energy of cobalt doped ZnO NPs decreased with increased Co doping concentration. PL spectra showed a weak UV and visible emission band which may be ascribed to the reduction in oxygen vacancy and defects by cobalt doping. XPS and EDX spectral results confirm the composition and the purity of Co doped ZnO NPs. Furthermore, the Co doped ZnO NPs were found to exhibit lesser photocatalytic activity for the degradation of methyl green dye under UV light illumination in comparison with the bare ZnO NPs. Moreover, anti-bacterial studies reveals that the Co doped ZnO NPs possess more antibacterial effect against gram positive Basillus subtills and gram negative Klebsiella pneumoniae bacterial strains than the bare ZnO NPs.

A simple route to vertical array of quasi-1D ZnO nanofilms on FTO surfaces: 1D-crystal growth of nanoseeds under ammonia-assisted hydrolysis process

PubMed Central

2011-01-01

A simple method for the synthesis of ZnO nanofilms composed of vertical array of quasi-1D ZnO nanostructures (quasi-NRs) on the surface was demonstrated via a 1D crystal growth of the attached nanoseeds under a rapid hydrolysis process of zinc salts in the presence of ammonia at room temperature. In a typical procedure, by simply controlling the concentration of zinc acetate and ammonia in the reaction, a high density of vertically oriented nanorod-like morphology could be successfully obtained in a relatively short growth period (approximately 4 to 5 min) and at a room-temperature process. The average diameter and the length of the nanostructures are approximately 30 and 110 nm, respectively. The as-prepared quasi-NRs products were pure ZnO phase in nature without the presence of any zinc complexes as confirmed by the XRD characterisation. Room-temperature optical absorption spectroscopy exhibits the presence of two separate excitonic characters inferring that the as-prepared ZnO quasi-NRs are high-crystallinity properties in nature. The mechanism of growth for the ZnO quasi-NRs will be proposed. Due to their simplicity, the method should become a potential alternative for a rapid and cost-effective preparation of high-quality ZnO quasi-NRs nanofilms for use in photovoltaic or photocatalytics applications. PACS: 81.07.Bc; 81.16.-c; 81.07.Gf. PMID:22027275

Taheri-Saramad x-ray detector (TSXD): a novel high spatial resolution x-ray imager based on ZnO nano scintillator wires in polycarbonate membrane.

PubMed

Taheri, A; Saramad, S; Ghalenoei, S; Setayeshi, S

2014-01-01

A novel x-ray imager based on ZnO nanowires is designed and fabricated. The proposed architecture is based on scintillation properties of ZnO nanostructures in a polycarbonate track-etched membrane. Because of higher refractive index of ZnO nanowire compared to the membrane, the nanowire acts as an optical fiber that prevents the generated optical photons to spread inside the detector. This effect improves the spatial resolution of the imager. The detection quantum efficiency and spatial resolution of the fabricated imager are 11% and <6.8 μm, respectively.

Nanoscale patterning of colloidal quantum dots on transparent and metallic planar surfaces.

PubMed

Park, Yeonsang; Roh, Young-Geun; Kim, Un Jeong; Chung, Dae-Young; Suh, Hwansoo; Kim, Jineun; Cheon, Sangmo; Lee, Jaesoong; Kim, Tae-Ho; Cho, Kyung-Sang; Lee, Chang-Won

2012-09-07

The patterning of colloidal quantum dots with nanometer resolution is essential for their application in photonics and plasmonics. Several patterning approaches, such as the use of polymer composites, molecular lock-and-key methods, inkjet printing and microcontact printing of quantum dots have been recently developed. Herein, we present a simple method of patterning colloidal quantum dots for photonic nanostructures such as straight lines, rings and dot patterns either on transparent or metallic substrates. Sub-10 nm width of the patterned line could be achieved with a well-defined sidewall profile. Using this method, we demonstrate a surface plasmon launcher from a quantum dot cluster in the visible spectrum.

Percentage of different aluminum doping influence the morphological and optical properties of ZnO nanostructured growth for sensor application

DOE Office of Scientific and Technical Information (OSTI.GOV)

Mohamed, R., E-mail: ruziana12@gmail.com; NANO-SciTech Centre, Institue of Science, Universiti Teknologi MARA, 40450 Shah Alam, Selangor; Faculty of Applied Sciences, Universiti Teknologi MARA Pahang, 26400 Bandar Tun Razak Jengka, Pahang

In this work, Zinc Oxide (ZnO) with different aluminum (Al) doping percentage was synthesis by sol gel immersion method. Al doped ZnO at various doping percentage from 1, 2, 3, 4 and 5. It was found that with different Al percentage influence the morphological and optical properties of ZnO growth. Field Emission Scanning Electron Microscope (FESEM) image showed the use of different Al doping causes the difference in geometry and size of ZnO nanorods growth. Based on UV-Vis spectroscopy, the transmittance at 1% Al doping has the highest spectrum.

Super low threshold plasmonic WGM lasing from an individual ZnO hexagonal microrod on an Au substrate for plasmon lasers.

PubMed

Dong, H M; Yang, Y H; Yang, G W

2015-03-05

We demonstrate an individual ZnO hexagonal microrod on the surface of an Au substrate which can become new sources for manufacturing miniature ZnO plasmon lasers by surface plasmon polariton coupling to whispering-gallery modes (WGMs). We also demonstrate that the rough surface of Au substrates can acquire a more satisfied enhancement of ZnO emission if the surface geometry of Au substrates is appropriate. Furthermore, we achieve high Q factor and super low threshold plasmonic WGM lasing from an individual ZnO hexagonal microrod on the surface of the Au substrate, in which Q factor can reach 5790 and threshold is 0.45 KW/cm(2) which is the lowest value reported to date for ZnO nanostructures lasing, at least 10 times smaller than that of ZnO at the nanometer. Electron transfer mechanisms are proposed to understand the physical origin of quenching and enhancement of ZnO emission on the surface of Au substrates. These investigations show that this novel coupling mode holds a great potential of ZnO hexagonal micro- and nanorods for data storage, bio-sensing, optical communications as well as all-optic integrated circuits.

Rapid and selective detection of acetone using hierarchical ZnO gas sensor for hazardous odor markers application.

PubMed

Jia, Qianqian; Ji, Huiming; Zhang, Ying; Chen, Yalu; Sun, Xiaohong; Jin, Zhengguo

2014-07-15

Hierarchical nanostructured ZnO dandelion-like spheres were synthesized via solvothermal reaction at 200°C for 4h. The products were pure hexagonal ZnO with large exposure of (002) polar facet. Side-heating gas sensor based on hierarchical ZnO spheres was prepared to evaluate the acetone gas sensing properties. The detection limit to acetone for the ZnO sensor is 0.25ppm. The response (Ra/Rg) toward 100ppm acetone was 33 operated at 230°C and the response time was as short as 3s. The sensor exhibited remarkable acetone selectivity with negligible response toward other hazardous gases and water vapor. The high proportion of electron depletion region and oxygen vacancies contributed to high gas response sensitivity. The hollow and porous structure of dandelion-like ZnO spheres facilitated the diffusion of gas molecules, leading to a rapid response speed. The largely exposed (002) polar facets could adsorb acetone gas molecules easily and efficiently, resulting in a rapid response speed and good selectivity of hierarchical ZnO spheres gas sensor at low operating temperature. Copyright © 2014 Elsevier B.V. All rights reserved.

New Insights into Mechanism of Surface Reactions of ZnO Nanorods During Electrons Beam Irradiation.

PubMed

Cho, Youngseung; Ji, Hyunjin; Kim, Hyoungsub; Yoon, Jinsuop; Choi, Byoungdeog

2018-09-01

This study provides new insight into mechanisms of ionic reactions on the surface of ZnO nanorod networks, which could result in enhanced performance in optical or molecular sensors. The current- voltage characteristics of ZnO nanorod network devices exhibit typical nonlinear behavior in air, which implies the formation of a Schottky barrier when metals are used as contacts. The conductance of the device increased significantly in vacuum, which can be explained by the desorption of hydroxyl groups at very low pressure. While physisorbed water or oxygen-related ions can detach from the ZnO surface during evacuation, exposure to high energy in the electron beam is believed to detach the chemisorbed anions of O- and O-2 from the surface of ZnO nanorods, which releases more electrons into the channel. The increase in available electrons enhances the conductance of the ZnO nanorods. Slow initialization of the conductance under ambient conditions indicates that the ionic re-adsorption is inactive under these conditions. Thus, the electron irradiation process can be used to reset the surface ionic molecules on metal oxide nano-structures by tuning the surface potential prior to the passivation process.

Optical and magneto-optical properties of zinc-oxide nanostructures grown by the low-temperature chemical route

NASA Astrophysics Data System (ADS)

Willander, M.; Alnoor, H.; Savoyant, A.; Adam, Rania E.; Nur, O.

2018-02-01

We demonstrate that the low temperature synthesis chemical route can be utilized to control the functionality of zinc oxide (ZnO) nanoparticles (NPs) and nanorods (NRs) for optical and magneto-optical performance. Different structural, optical, electro- and magneto-optical results will be displayed and analyzed. In the first part, we show how high quality ZnO NPs can be efficient for photodegradation using ultra-violet radiation. In the second part we will present our recent results on the control of the core defects in cobalt doped ZnO NR. Here and by using electron paramagnetic resonance (EPR) measurements, the substitution of Co2+ ions in the ZnO NRs crystal is shown. The relation between the incorporation and core defects concentration will be discussed. The findings give access to the magnetic anisotropy of ZnO NRs grown by the low temperature chemical route and can lead to demonstrate room temperature ferromagnetism in nanostructures with potential for different device applications.

Development and surface characterization of a glucose biosensor based on a nanocolumnar ZnO film

NASA Astrophysics Data System (ADS)

Rodrigues, A.; Castegnaro, M. V.; Arguello, J.; Alves, M. C. M.; Morais, J.

2017-04-01

Highly oriented nanostructured ZnO films were grown on the surface of stainless steel plates (ZnO/SS) by chemical bath deposition (CBD). The films consisted of vertically aligned ZnO nanocolumns, ∼1 μm long and ∼80 nm wide, as observed by SEM (scanning electron microscopy) and FIB (focused ion beam). XRD (X-ray diffraction) confirmed the c-axis preferred orientation of the ZnO columns, which were functionalized with the glucose oxidase (GOx) enzyme into a biosensor of glucose. The electrochemical response studied by CV (cyclic voltammetry) proved that the biosensor was capable of detecting glucose from 1.5 up to 16 mM concentration range. XPS (X-ray photoelectron spectroscopy) analysis, excited with synchrotron radiation, probed the atom specific chemical environment at the electrode's surface and shed some light on the nature of the ZnO-GOx interaction.

Synthesis of stable ZnO nanocolloids with enhanced optical limiting properties via simple solution method

NASA Astrophysics Data System (ADS)

Ramya, M.; Nideep, T. K.; Vijesh, K. R.; Nampoori, V. P. N.; Kailasnath, M.

2018-07-01

In present work, we report the synthesis of stable ZnO nanocolloids through a simple solution method which exhibit enhanced optical limiting threshold. The influences of reaction temperature on the crystal structure as well as linear and nonlinear optical properties of prepared ZnO nanoparticles were carried out. The XRD and Raman analysis reveal that the prepared ZnO nanoparticles retain the hexagonal wurtzite crystal structure. HRTEM analysis confirms the effect of reaction temperature, solvent effect on crystallinity as well as nanostructure of ZnO nanoparticles. It has been found that crystallinity and average diameter increase with reaction temperature where ethylene glycol act as both solvent and growth inhibiter. EDS spectra shows formation of pure ZnO nanoparticles. The direct energy band gap of the nanoparticles increases with decrease in particle size due to quantum confinement effect. The third order nonlinear optical properties of ZnO nanoparticles were investigated by z scan technique using a frequency doubled Nd-YAG nanosecond laser at 532 nm wavelength. The z-scan result reveals that the prepared ZnO nanoparticles exhibit self - defocusing nonlinearity. The two photon absorption coefficient and third - order nonlinear optical susceptibility increases with increasing particle size. The third-order susceptibility of the ZnO nanoparticles is found to be in the order of 10-10 esu, which is at least three order magnitude greater than the bulk ZnO. The optical limiting threshold of the nanoparticles varies in the range of 54 to 17 MW/cm2. The results suggest that ZnO nanoparticles considered as a promising candidates for the future photonic devices.

Effect of gamma radiation on the optical and structural properties of ZnO nanowires with various diameters

NASA Astrophysics Data System (ADS)

Reyhani, A.; Gholizadeh, A.; vahedi, V.; Khanlary, M. R.

2018-01-01

The effects of gamma-irradiation are studied on the morphology and structural properties of ZnO nanowire with various diameters. The ZnO nanowires are grown using Zn thin films at various initial thicknesses including 125, 250 and 500 nm in air ambient. The results illustrate dramatic effects of Gamma-irradiation on the deformation of ZnO nanowires. Thus, radiation induce ripple ZnO surfaces instead ZnO nanowires. Gamma-irradiation has also been effective on the optical and crystalline properties of the nanowires. X-ray diffraction attests that size of the ZnO nano-structures has changed and (l00) crystalline direction related to Zn metal has been created after irradiation. UV-Visible spectra display two areas for transmittance of irradiated ZnO nanowires, one in the Visible-light and the other in IR sub-region. In the Visible-light area, the layer gets thicker from 125 to 500 nm; the difference between the layer transmittance spectra is reduced before and after gamma irradiation. In the IR-light region, with increasing of ZnO initial thickness, the difference between the layer transmittance spectra is increased before and after gamma irradiation. The photoluminescence spectroscopy displays that intensity of green-yellow band improves in compared to near-band-edge emission due to formation of Zn metal and oxygen vacancies after gamma irradiation.

Enhanced glucose biosensor properties of gold nanoparticle-decorated ZnO nanorods

NASA Astrophysics Data System (ADS)

Wang, Zi-Hao; Yang, Chih-Chiang; Su, Yan-Kuin; Ruand, Jian-Long

2017-04-01

As new materials have been reported and more knowledge on detailed mechanism of glucose oxidation has been unveiled, the non-enzymatic glucose sensor keeps coming closer to practical applications. Nanostructures with higher surface specific area has great potential applications in sensing devices ZnO nanoords were synthesized in a hydrothermal method using simply available laboratory chemicals. Results showed that as-synthesized Gold Nanoparticle-decorated ZnO Nanorods possessing higher specific surface area, significantly increased the non-enzyme efficiency which in turn improved the sensing performances. The electrode also demonstrated excellent performance in sensing glucose concentration with remarkable sensitivity (46.6 μA/mM-cm2) and good repeatability. This work is expected to open a new avenue to fabricate non-enzymatic electrochemical sensors of glucose involving co-mediating.

Nanoscale calibration of n-type ZnO staircase structures by scanning capacitance microscopy

DOE Office of Scientific and Technical Information (OSTI.GOV)

Wang, L., E-mail: lin.wang@insa-lyon.fr; Laurent, J.; Brémond, G.

2015-11-09

Cross-sectional scanning capacitance microscopy (SCM) was performed on n-type ZnO multi-layer structures homoepitaxially grown by molecular beam epitaxy method. Highly contrasted SCM signals were obtained between the ZnO layers with different Ga densities. Through comparison with dopant depth profiles from secondary ion mass spectroscopy measurement, it is demonstrated that SCM is able to distinguish carrier concentrations at all levels of the samples (from 2 × 10{sup 17 }cm{sup −3} to 3 × 10{sup 20 }cm{sup −3}). The good agreement of the results from the two techniques indicates that SCM can be a useful tool for two dimensional carrier profiling at nanoscale for ZnO nanostructure development. Asmore » an example, residual carrier concentration inside the non-intentionally doped buffer layer was estimated to be around 2 × 10{sup 16 }cm{sup −3} through calibration analysis.« less

Insights into the sonochemical synthesis and properties of salt-free intrinsic plutonium colloids

DOE PAGES

Dalodière, Elodie; Virot, Matthieu; Morosini, Vincent; ...

2017-03-03

Fundamental knowledge on intrinsic plutonium colloids is important for the prediction of plutonium behaviour in the geosphere and in engineered systems. The first synthetic route to obtain salt-free intrinsic plutonium colloids by ultrasonic treatment of PuO 2 suspensions in pure water is reported. Kinetics showed that both chemical and mechanical effects of ultrasound contribute to the mechanism of Pu colloid formation. In the first stage, fragmentation of initial PuO 2 particles provides larger surface contact between cavitation bubbles and solids. Furthermore, hydrogen formed during sonochemical water splitting enables reduction of Pu(IV) to more soluble Pu(III), which then re-oxidizes yielding Pu(IV)more » colloid. A comparative study of nanostructured PuO 2 and Pu colloids produced by sonochemical and hydrolytic methods, has been conducted using HRTEM, Pu LIII-edge XAS, and O K-edge NEXAFS/STXM. Characterization of Pu colloids revealed a correlation between the number of Pu-O and Pu-Pu contacts and the atomic surface-to-volume ratio of the PuO 2 nanoparticles. NEXAFS indicated that oxygen state in hydrolytic Pu colloid is influenced by hydrolysed Pu(IV) species to a greater extent than in sonochemical PuO 2 nanoparticles. In general, hydrolytic and sonochemical Pu colloids can be described as core-shell nanoparticles composed of quasi-stoichiometric PuO 2 cores and hydrolyzed Pu(IV) moieties at the surface shell.« less

Heterogeneous nucleation for synthesis of sub-20nm ZnO nanopods and their application to optical humidity sensing.

PubMed

Majithia, R; Ritter, S; Meissner, K E

2014-02-17

We present a novel method for colloidal synthesis of one-dimensional ZnO nanopods by heterogeneous nucleation on zero-dimensional ZnO nanoparticle 'seeds'. Ultra-small ZnO nanopods, multi-legged structures with sub-20 nm individual leg diameters, can be synthesized by hydrolysis of a Zn2+ precursor growth solution in presence of ∼4 nm ZnO seeds under hydrothermal conditions via microwave-assisted heating in as little as 20 min of reaction time. One-dimensional ZnO nanorods are initially generated in the reaction mixture by heterogeneous nucleation and growth along the [0001] direction of the ZnO crystal. Growth of one-dimensional nanorods subsequently yields to an 'attachment' and size-focusing phase where individual nanorods fuse together to form multi-legged nanopods having diameters ∼15 nm. ZnO nanopods exhibit broad orange-red defect-related photoluminescence in addition to a near-band edge emission at 373 nm when excited above the band-gap at 350 nm. The defect-related photoluminescence of the ZnO nanopods has been applied towards reversible optical humidity sensing at room temperature. The sensors demonstrated a linear response between 22% and 70% relative humidity with a 0.4% increase in optical intensity per % change in relative humidity. Due to their ultra-small dimensions, ZnO nanopods exhibit a large dynamic range and enhanced sensitivity to changes in ambient humidity, thus showcasing their ability as a platform for optical environmental sensing. Copyright © 2014 Elsevier B.V. All rights reserved.

Synthesis, characterization and photocatalytic activity of magnetically separable hexagonal Ni/ZnO nanostructure

NASA Astrophysics Data System (ADS)

Senapati, Samarpita; Srivastava, Suneel K.; Singh, Shiv B.

2012-09-01

The hexagonal zinc oxide coated nickel (Ni/ZnO) nanostructure photocatalyst has successfully been prepared by the reduction of nickel chloride hexahydrate using hydrazine hydrate through the solvothermal process at 140 °C followed by surface modification of the product by the reflux method at 110 °C for 1 h. The X-ray diffraction (XRD) pattern showed that the `as prepared' sample consists of face centered cubic Ni and hexagonal wurtzite ZnO without any traces of impurity. Field emission scanning electron microscopy (FESEM) and transmission electron microscopy (TEM) images confirmed the formation of nickel nanoparticles under solvothermal conditions. These nickel nanoparticles, when subjected to reflux, formed the hexagonal zinc oxide coated nickel nanostructure. Fourier transform infrared (FTIR) spectra, photoluminescence (PL) and Raman studies also confirmed the presence of zinc oxide in the hybrid nanostructure. The growth mechanism for the development of the hexagonal zinc oxide coated nickel (Ni/ZnO) nanostructure has also been proposed. The appearance of the hysteresis loop, in the as-prepared Ni/ZnO hybrid nanostructure, demonstrated its ferromagnetic character at room temperature. The hexagonal Ni/ZnO nanostructure also acts as an efficient photocatalyst in the degradation of methylene blue under ultraviolet light irradiation. It is observed that the catalytic efficiency of the hybrid nanocatalyst is better compared to pure zinc oxide. Most importantly, the Ni/ZnO catalyst could also be easily separated, simply by applying an external magnetic field, and reused.The hexagonal zinc oxide coated nickel (Ni/ZnO) nanostructure photocatalyst has successfully been prepared by the reduction of nickel chloride hexahydrate using hydrazine hydrate through the solvothermal process at 140 °C followed by surface modification of the product by the reflux method at 110 °C for 1 h. The X-ray diffraction (XRD) pattern showed that the `as prepared' sample consists of face

Enhanced photochemical catalysis of TiO2 inverse opals by modification with ZnO or Fe2O3 using ALD and the hydrothermal method

NASA Astrophysics Data System (ADS)

Liu, Jiatong; Sun, Cuifeng; Fu, Ming; Long, Jie; He, Dawei; Wang, Yongsheng

2018-02-01

The development of porous materials exhibiting photon regulation abilities for improved photoelectrochemical catalysis performance is always one of the important goals of solar energy harvesting. In this study, methods to improve the photocatalytic activity of TiO2 inverse opals were discussed. TiO2 inverse opals were prepared by atomic layer deposition (ALD) using colloidal crystal templates. In addition, TiO2 inverse opal heterostructures were fabricated using colloidal heterocrystals by repeated vertical deposition using different colloidal spheres. The hydrothermal method and ALD were used to prepare ZnO- or Fe2O3-modified TiO2 inverse opals on the internal surfaces of the TiO2 porous structures. Although the photonic reflection band was not significantly varied by oxide modification, the presence of Fe2O3 in the TiO2 inverse opals enhanced their visible absorption. The conformally modified oxides on the TiO2 inverse opals could also form energy barriers and avoid the recombination of electrons and holes. The fabrication of the TiO2 photonic crystal heterostructures and modification with ZnO or Fe2O3 can enhance the photocatalytic activity of TiO2 inverse opals.

Cu0-loaded SBA-15@ZnO with improved electrical properties and affinity towards hydrogen

NASA Astrophysics Data System (ADS)

Bouazizi, N.; Louhichi, S.; Ouargli, R.; Bargougui, R.; Vieillard, J.; Derf, F. Le; Azzouz, A.

2017-05-01

A core-shell material was prepared using SBA-15 crystallites as cores for the growth of a ZnO shell, followed by Cu0 dispersion. The resulting Cu/SBA-15@ZnO nanostructure displayed higher specific surface area (SSA) and higher number of smaller pores as compared to the starting materials. Dispersion of fine Cu0NPs induced a compaction of the host matrice and a marked decay of the hydrophilic character, explained in terms of the involvement of terminal hydroxyl groups in competitive sbnd HO:Cu interaction at the expense of H-bridges with water. Heating at 400-450 °C seems to trigger ZnO dehydroxylation with possible self-polycondensation and/or the formation of Si-O-Zn bridges. This is an additional explanation of the significant SSA increase and decrease in the average pore diameter. Both ZnO and Cu0NP incorporation induced shifts in the UV-vis absorption band towards higher wavelengths, indicating a decrease in the optical band gap energy and an improvement of the conductance properties. As compared to ZnO, Cu0NPs produced stronger improvement of the conductance, which was found to increase with higher frequencies. Cu/SBA-15@ZnO also displayed higher affinity towards hydrogen as compared to SBA-15@ZnO and SBA-15 at ambient conditions. These outstanding properties combined to an appreciable thermal stability are worth to be prone to deeper investigations, because they can open promising prospects for Cu/SBA-15@ZnO as sensor, electrode material, electrocatalyst and/or hydrogen capture matrice.

A Comprehensive Review of One-Dimensional Metal-Oxide Nanostructure Photodetectors

PubMed Central

Zhai, Tianyou; Fang, Xiaosheng; Liao, Meiyong; Xu, Xijin; Zeng, Haibo; Yoshio, Bando; Golberg, Dmitri

2009-01-01

One-dimensional (1D) metal-oxide nanostructures are ideal systems for exploring a large number of novel phenomena at the nanoscale and investigating size and dimensionality dependence of nanostructure properties for potential applications. The construction and integration of photodetectors or optical switches based on such nanostructures with tailored geometries have rapidly advanced in recent years. Active 1D nanostructure photodetector elements can be configured either as resistors whose conductions are altered by a charge-transfer process or as field-effect transistors (FET) whose properties can be controlled by applying appropriate potentials onto the gates. Functionalizing the structure surfaces offers another avenue for expanding the sensor capabilities. This article provides a comprehensive review on the state-of-the-art research activities in the photodetector field. It mainly focuses on the metal oxide 1D nanostructures such as ZnO, SnO2, Cu2O, Ga2O3, Fe2O3, In2O3, CdO, CeO2, and their photoresponses. The review begins with a survey of quasi 1D metal-oxide semiconductor nanostructures and the photodetector principle, then shows the recent progresses on several kinds of important metal-oxide nanostructures and their photoresponses and briefly presents some additional prospective metal-oxide 1D nanomaterials. Finally, the review is concluded with some perspectives and outlook on the future developments in this area. PMID:22454597

Visualizing the optical field strengths in Au/dielectric nanostructures and its correlation to SERS enhancements

NASA Astrophysics Data System (ADS)

Rajesh, Y.; Sangani, L. D. Varma; Shaik, Ummar Pasha; Gaur, Anshu; Mohiddon, Md Ahamad; Krishna, M. Ghanashyam

2017-05-01

The role of dielectric surrounding over the Au nanostructure for surface plasmon resonance (SPR) behavior is investigated by scanning near field optical microscopy (SNOM). The observed optical field strengths are correlated with the surface enhanced Raman scattering (SERS) enhancement recorded for R6G molecule. Discontinuous nanostructured Au thin films are deposited by RF magnatron sputtering at very low rate on to three different dielectric substrates, ZnO, TiO2 and SiO2. These three Au/dielectric nanostructures are investigated using SNOM by illuminating it in near field and collecting in transmission far field configuration. The observed optical near field images of the three different nanostructures are discussed by taking their dielectric constant into the account. The SERS enhancements are correlated with the optical field strengths derived from the near field optical imaging.

Electrically conductive nanostructured silver doped zinc oxide (Ag:ZnO) prepared by solution-immersion technique

DOE Office of Scientific and Technical Information (OSTI.GOV)

Afaah, A. N., E-mail: afaahabdullah@yahoo.com; Asib, N. A. M., E-mail: amierahasib@yahoo.com; Aadila, A., E-mail: aadilaazizali@gmail.com

2016-07-06

p-type ZnO films have been fabricated on ZnO-seeded glass substrate, using AgNO{sub 3} as a source of silver dopant by facile solution-immersion. Cleaned glass substrate were seeded with ZnO by mist-atomisation, and next the seeded substrates were immersed in Ag:ZnO solution. The effects of Ag doping concentration on the Ag-doped ZnO have been investigated. The substrates were immersed in different concentrations of Ag dopant with variation of 0, 1, 3, 5 and 7 at. %. The surface morphology of the films was characterized by field emission scanning electron microscope (FESEM). In order to investigate the electrical properties, the films weremore » characterized by Current-Voltage (I-V) measurement. FESEM micrographs showed uniform distribution of nanostructured ZnO and Ag:ZnO. Besides, the electrical properties of Ag-doped ZnO were also dependent on the doping concentration. The I-V measurement result indicated the electrical properties of 1 at. % Ag:ZnO thin film owned highest electrical conductivity.« less

Enhanced biostability and cellular uptake of zinc oxide nanocrystals shielded with a phospholipid bilayer.

PubMed

Dumontel, B; Canta, M; Engelke, H; Chiodoni, A; Racca, L; Ancona, A; Limongi, T; Canavese, G; Cauda, V

2017-11-28

The widespread use of ZnO nanomaterials for biomedical applications, including therapeutic drug delivery or stimuli-responsive activation, as well as imaging, imposes a careful control over the colloidal stability and long-term behaviour of ZnO in biological media. Moreover, the effect of ZnO nanostructures on living cells, in particular cancer cells, is still under debate. This paper discusses the role of surface chemistry and charge of zinc oxide nanocrystals, of around 15 nm in size, which influence their behaviour in biological fluids and effect on cancer cells. In particular, we address this problem by modifying the surface of pristine ZnO nanocrystals (NCs), rich of hydroxyl groups, with positively charged amino-propyl chains or, more innovatively, by self-assembling a double-lipidic membrane, shielding the ZnO NCs. Our findings show that the prolonged immersion in simulated human plasma and in the cell culture medium leads to highly colloidally dispersed ZnO NCs only when coated by the lipidic bilayer. In contrast, the pristine and amine-functionalized NCs form huge aggregates after already one hour of immersion. Partial dissolution of these two samples into potentially cytotoxic Zn 2+ cations takes place, together with the precipitation of phosphate and carbonate salts on the NCs' surface. When exposed to living HeLa cancer cells, higher amounts of lipid-shielded ZnO NCs are internalized with respect to the other samples, thus showing a reduced cytotoxicity, based on the same amount of internalized NCs. These results pave the way for the development of novel theranostic platforms based on ZnO NCs. The new formulation of ZnO shielded with a lipid-bilayer will prevent strong aggregation and premature degradation into toxic by-products, and promote a highly efficient cell uptake for further therapeutic or diagnostic functions.

Inactivation of bacterial biofilms using visible-light-activated unmodified ZnO nanorods

NASA Astrophysics Data System (ADS)

Aponiene, Kristina; Serevičius, Tomas; Luksiene, Zivile; Juršėnas, Saulius

2017-09-01

Various zinc oxide (ZnO) nanostructures are widely used for photocatalytic antibacterial applications. Since ZnO possesses a wide bandgap, it is believed that only UV light may efficiently assist bacterial inactivation, and diverse crystal lattice modifications should be applied in order to narrow the bandgap for efficient visible-light absorption. In this work we show that even unmodified ZnO nanorods grown by an aqueous chemical growth technique are found to possess intrinsic defects that can be activated by visible light (λ = 405 nm) and successfully applied for total inactivation of various highly resistant bacterial biofilms rather than more sensitive planktonic bacteria. Time-resolved fluorescence analysis has revealed that visible-light excitation creates long-lived charge carriers (τ > 1 μs), which might be crucial for destructive biochemical reactions achieving significant bacterial biofilm inactivation. ZnO nanorods covered with bacterial biofilms of Enterococcus faecalis MSCL 302 after illumination by visible light (λ = 405 nm) were inactivated by 2 log, and Listeria monocytogenes ATCL3C 7644 and Escherichia coli O157:H7 biofilms by 4 log. Heterogenic waste-water microbial biofilms, consisting of a mixed population of mesophilic bacteria after illumination with visible light were also completely destroyed.

A hetero-homogeneous investigation of chemical bath deposited Ga-doped ZnO nanorods

NASA Astrophysics Data System (ADS)

Rakhsha, Amir Hosein; Abdizadeh, Hossein; Pourshaban, Erfan; Golobostanfard, Mohammad Reza

2018-01-01

One-dimensional nanostructures of zinc oxide (ZnO) have been in the center of attention, mostly for electronic applications due to their distinctive properties such as high electron mobility (100 cm2V-1s-1) and crystallinity. Thanks to its high density of vacancies and interstitial sites, wurtzite lattice of ZnO is a suitable host for gallium (Ga) as a dopant element. Herein, ZnO nanorod arrays (NRAs) are synthesized by a low-temperature chemical bath deposition (CBD) method with various concentrations of gallium nitrate hydrate as a dopant precursor. Structural and morphological analyses confirm that optimum properties of gallium-doped ZnO (GZO) are obtained at 1% (Ga to Zn molar ratio). Owing to the replacement of smaller Ga3+ ions with Zn2+ ions in the GZO structure, a slight shift of (002) peak to higher angles could be observed in XRD pattern of GZO NRAs. The scanning electron microscope images demonstrate a proliferation in the ZnO NRAs length from 650 nm for undoped ZnO (UZO) to 1200 nm for GZO-1%. However, increasing the dopant concentration above 2.5% results in formation of homogeneous zinc gallium oxide in the bulk solution, which is a sign of inefficient process of doping in GZO NRAs. Furthermore, photoluminescence spectroscopy is used to characterize the band-gap variation of the samples, which demonstrates a small red-shift in the UV emission peak and a decrease in visible emission peak intensity with introducing Ga in ZnO lattice. Lower resistivity for GZO-1% (1.1 MΩ) sample compared to UZO (1.4 MΩ) is recorded, which is compelling evidence for the presence of Ga3+ in ZnO lattice. The results suggest that incorporating Ga into ZnO lattice using CBD method is an easy and effective technique to improve the electrical properties of ZnO NRAs that is an essential factor for a broad range of devices.

Self-assembled ultra small ZnO nanocrystals for dye-sensitized solar cell application

DOE Office of Scientific and Technical Information (OSTI.GOV)

Patra, Astam K.; Dutta, Arghya; Bhaumik, Asim, E-mail: msab@iacs.res.in

2014-07-01

We demonstrate a facile chemical approach to produce self-assembled ultra-small mesoporous zinc oxide nanocrystals using sodium salicylate (SS) as a template under hydrothermal conditions. These ZnO nanomaterials have been successfully fabricated as a photoanode for the dye-sensitized solar cell (DSSC) in the presence of N719 dye and iodine–triiodide electrolyte. The structural features, crystallinity, purity, mesophase and morphology of the nanostructure ZnO are investigated by several characterization tools. N{sub 2} sorption analysis revealed high surface areas (203 m{sup 2} g{sup −1}) and narrow pore size distributions (5.1–5.4 nm) for different samples. The mesoporous structure and strong photoluminescence facilitates the high dyemore » loading at the mesoscopic void spaces and light harvesting in DSSC. By utilizing this ultra-small ZnO photoelectrode with film thickness of about 7 μm in the DSSC with an open-circuit voltage (V{sub OC}) of 0.74 V, short-circuit current density (J{sub SC}) of 3.83 mA cm{sup −2} and an overall power conversion efficiency of 1.12% has been achieved. - Graphical abstract: Ultra-small ZnO nanocrystals have been synthesized with sodium salicylate as a template and using it as a photoanode in a dye-sensitized solar cell 1.12% power conversion efficiency has been observed. - Highlights: • Synthesis of self-assembled ultra-small mesoporous ZnO nanocrystals by using sodium salicylate as a template. • Mesoporous ZnO materials have high BET surface areas and void space. • ZnO nanoparticles serve as a photoanode for the dye-sensitized solar cell (DSSC). • Using ZnO nanocrystals as photoelectrode power conversion efficiency of 1.12% has been achieved.« less

Does doping with aluminum alter the effects of ZnO nanoparticles on the metabolism of soil pseudomonads?

PubMed

Fang, Tommy; Watson, Jean-Luc; Goodman, Jordan; Dimkpa, Christian O; Martineau, Nicole; Das, Siddhartha; McLean, Joan E; Britt, David W; Anderson, Anne J

2013-02-22

Doping of ZnO nanoparticles (NPs) is being used to increase their commercialization in the optical and semiconductor fields. This paper addresses whether doping with Al alters how ZnO NPs at nonlethal levels modifies the metabolism of soil-borne pseudomonads which are beneficial in performing bioremediation or promoting plant growth. The differences in X-ray diffraction (XRD) patterns, observed between commercial ZnO and Al-doped ZnO NPs indicated the aluminum was present as Al NPs. Both particles aggregated in the bacterial growth medium and formed colloids of different surface charges. They had similar effects on bacterial metabolism: rapid, dose-dependent loss in light output indicative of temporary toxicity in a biosensor constructed in Pseudomonas putida KT2440; increased production of a fluorescent pyoverdine-type siderophore, and decreased levels of indole acetic acid and phenazines in Pseudomonas chlororaphis O6. Solubilization of Zn and Al from the NPs contributed to these responses to different extents. These findings indicate that Al-doping of the ZnO NPs did not reduce the ability of the NPs to alter bacterial metabolism in ways that could influence performance of the pseudomonads in their soil environment. Copyright © 2012. Published by Elsevier GmbH.

Ag nanodots decorated SiO2 coated ZnO core-shell nanostructure with enhanced luminescence property as potential imaging agent

NASA Astrophysics Data System (ADS)

Gupta, Jagriti; Barick, K. C.; Hassan, P. A.; Bahadur, Dhirendra

2018-04-01

Ag decorated silica coated ZnO nanocomposite (Ag@SiO2@ZnO NCs) has been synthesized by soft chemical approach. The physico-chemical properties of Ag@SiO2@ZnO NCs are investigated by various sophisticated characterization techniques such as X-ray diffraction, Transmission electron microscopy, X-ray photoelectron spectroscopy, UV-visible absorption and photoluminescent spectroscopy. X-ray diffraction confirms the phase formation of ZnO and Ag in nanocomposite. TEM micrograph clearly shows that Ag nanodots are well decorated over silica coated ZnO NCs. The photoluminescent study reveals the enhancement in the photoluminance property when the Ag nanodots are decorated over silica coated ZnO nanocomposite due to an electromagnetic coupling between excitons and plasmons. Furthermore, the photoluminescent property is an important tool for bio-imaging application, reveal that NCs give green and red emission after excitation with 488 and 535 nm. Therefore, low cytotoxicity and excellent fluorescence stability in vitro makes it a more suitable material for both cellular imaging and therapy for biomedical applications.

Synthesis and integration of one-dimensional nanostructures for chemical gas sensing applications

NASA Astrophysics Data System (ADS)

Parthangal, Prahalad Madhavan

The need for improved measurement technology for the detection and monitoring of gases has increased tremendously for maintenance of domestic and industrial health and safety, environmental surveys, national security, food-processing, medical diagnostics and various other industrial applications. Among the several varieties of gas sensors available in the market, solid-state sensors are the most popular owing to their excellent sensitivity, ruggedness, versatility and low cost. Semiconducting metal oxides such as tin oxide (SnO2), zinc oxide (ZnO), and tungsten oxide (WO3) are routinely employed as active materials in these sensors. Since their performance is directly linked to the exposed surface area of the sensing material, one-dimensional nanostructures possessing very high surface to volume ratios are attractive candidates for designing the next generation of sensors. Such nano-sensors also enable miniaturization thereby reducing power consumption. The key to achieve success in one-dimensional nanotechnologies lies in assembly. While synthesis techniques and capabilities continue to expand rapidly, progress in controlled assembly has been sluggish due to numerous technical challenges. In this doctoral thesis work, synthesis and characterization of various one-dimensional nanostructures including nanotubes of SnO2, and nanowires of WO3 and ZnO, as well as their direct integration into miniature sensor platforms called microhotplates have been demonstrated. The key highlights of this research include devising elegant strategies for growing metal oxide nanotubes using carbon nanotubes as templates, substantially reducing process temperatures to enable growth of WO3 nanowires on microhotplates, and successfully fabricating a ZnO nanowire array based sensor using a hybrid nanowire-nanoparticle assembly approach. In every process, the gas-sensing properties of one-dimensional nanostructures were observed to be far superior in comparison with thin films of the same

Power generation from base excitation of a Kevlar composite beam with ZnO nanowires

NASA Astrophysics Data System (ADS)

Malakooti, Mohammad H.; Hwang, Hyun-Sik; Sodano, Henry A.

2015-04-01

One-dimensional nanostructures such as nanowires, nanorods, and nanotubes with piezoelectric properties have gained interest in the fabrication of small scale power harvesting systems. However, the practical applications of the nanoscale materials in structures with true mechanical strengths have not yet been demonstrated. In this paper, piezoelectric ZnO nanowires are integrated into the fiber reinforced polymer composites serving as an active phase to convert the induced strain energy from ambient vibration into electrical energy. Arrays of ZnO nanowires are grown vertically aligned on aramid fibers through a low-cost hydrothermal process. The modified fabrics with ZnO nanowires whiskers are then placed between two carbon fabrics as the top and the bottom electrodes. Finally, vacuum resin transfer molding technique is utilized to fabricate these multiscale composites. The fabricated composites are subjected to a base excitation using a shaker to generate charge due to the direct piezoelectric effect of ZnO nanowires. Measuring the generated potential difference between the two electrodes showed the energy harvesting application of these multiscale composites in addition to their superior mechanical properties. These results propose a new generation of power harvesting systems with enhanced mechanical properties.

Metal-free organic dyes for TiO2 and ZnO dye-sensitized solar cells

PubMed Central

Selopal, Gurpreet Singh; Wu, Hui-Ping; Lu, Jianfeng; Chang, Yu-Cheng; Wang, Mingkui; Vomiero, Alberto; Concina, Isabella; Diau, Eric Wei-Guang

2016-01-01

We report the synthesis and characterization of new metal-free organic dyes (namely B18, BTD-R, and CPTD-R) which designed with D-π-A concept to extending the light absorption region by strong conjugation group of π-linker part and applied as light harvester in dye sensitized solar cells (DSSCs). We compared the photovoltaic performance of these dyes in two different photoanodes: a standard TiO2 mesoporous photoanode and a ZnO photoanode composed of hierarchically assembled nanostructures. The results demonstrated that B18 dye has better photovoltaic properties compared to other two dyes (BTD-R and CPTD-R) and each dye has higher current density (Jsc) when applied to hierarchical ZnO nanocrystallites than the standard TiO2 mesoporous film. Transient photocurrent and photovoltage decay measurements (TCD/TVD) were applied to systematically study the charge transport and recombination kinetics in these devices, showing the electron life time (τR) of B18 dye in ZnO and TiO2 based DSSCs is higher than CPTD-R and BTD-R based DSSCs, which is consistent with the photovoltaic performances. The conversion efficiency in ZnO based DSSCs can be further boosted by 35%, when a compact ZnO blocking layer (BL) is applied to inhibit electron back reaction. PMID:26738698

Low-temperature processed Ga-doped ZnO coatings from colloidal inks.

PubMed

Della Gaspera, Enrico; Bersani, Marco; Cittadini, Michela; Guglielmi, Massimo; Pagani, Diego; Noriega, Rodrigo; Mehra, Saahil; Salleo, Alberto; Martucci, Alessandro

2013-03-06

We present a new colloidal synthesis of gallium-doped zinc oxide nanocrystals that are transparent in the visible and absorb in the near-infrared. Thermal decomposition of zinc stearate and gallium nitrate after hot injection of the precursors in a mixture of organic amines leads to nanocrystals with tunable properties according to gallium amount. Substitutional Ga(3+) ions trigger a plasmonic resonance in the infrared region resulting from an increase in the free electrons concentration. These nanocrystals can be deposited by spin coating, drop casting, and spray coating resulting in homogeneous and high-quality thin films. The optical transmission of the Ga-ZnO nanoparticle assemblies in the visible is greater than 90%, and at the same time, the near-infrared absorption of the nanocrystals is maintained in the films as well. Several strategies to improve the films electrical and optical properties have been presented, such as UV treatments to remove the organic compounds responsible for the observed interparticle resistance and reducing atmosphere treatments on both colloidal solutions and thin films to increase the free carriers concentration, enhancing electrical conductivity and infrared absorption. The electrical resistance of the nanoparticle assemblies is about 30 kΩ/sq for the as-deposited, UV-exposed films, and it drops down to 300 Ω/sq after annealing in forming gas at 450 °C, comparable with state of the art tin-doped indium oxide coatings deposited from nanocrystal inks.

Morphology Transition Engineering of ZnO Nanorods to Nanoplatelets Grafted Mo8O23-MoO2 by Polyoxometalates: Mechanism and Possible Applicability to other Oxides.

PubMed

Abdelmohsen, Ahmed H; Rouby, Waleed M A El; Ismail, Nahla; Farghali, Ahmed A

2017-07-19

A new fundamental mechanism for reliable engineering of zinc oxide (ZnO) nanorods to nanoplatelets grafted Mo 8 O 23 -MoO 2 mixed oxide with controlled morphology, composition and precise understanding of the nanoscale reaction mechanism was developed. These hybrid nanomaterials are gaining interest due to their potential use for energy, catalysis, biomedical and other applications. As an introductory section, we demonstrate a new expansion for the concept 'materials engineering' by discussing the fabrication of metal oxides nanostructures by bottom-up approach and carbon nanoparticles by top-down approach. Moreover, we propose a detailed mechanism for the novel phenomenon that was experienced by ZnO nanorods when treated with phosphomolybdic acid (PMA) under ultra-sonication stimulus. This approach is expected to be the basis of a competitive fabrication approach to 2D hybrid nanostructures. We will also discuss a proposed mechanism for the catalytic deposition of Mo 8 O 23 -MoO 2 mixed oxide over ZnO nanoplatelets. A series of selection rules (SRs) which applied to ZnO to experience morphology transition and constitute Abdelmohsen theory for morphology transition engineering (ATMTE) will be demonstrated through the article, besides a brief discussion about possibility of other oxides to obey this theory.

Nanostructures and functional materials fabricated by interferometric lithography.

PubMed

Xia, Deying; Ku, Zahyun; Lee, S C; Brueck, S R J

2011-01-11

Interferometric lithography (IL) is a powerful technique for the definition of large-area, nanometer-scale, periodically patterned structures. Patterns are recorded in a light-sensitive medium, such as a photoresist, that responds nonlinearly to the intensity distribution associated with the interference of two or more coherent beams of light. The photoresist patterns produced with IL are a platform for further fabrication of nanostructures and growth of functional materials and are building blocks for devices. This article provides a brief review of IL technologies and focuses on various applications for nanostructures and functional materials based on IL including directed self-assembly of colloidal nanoparticles, nanophotonics, semiconductor materials growth, and nanofluidic devices. Perspectives on future directions for IL and emerging applications in other fields are presented.

Magnetic domains and defects in ferromagnetic liquid crystal colloids realized with optical patterning

NASA Astrophysics Data System (ADS)

Hess, Andrew; Liu, Qingkun; Smalyukh, Ivan

A promising approach in designing composite materials with unusual physical behavior combines solid nanostructures and orientationally ordered soft matter at the mesoscale. Such composites not only inherit properties of their constituents but also can exhibit emergent behavior, such as ferromagnetic ordering of colloidal metal nanoparticles forming mesoscopic magnetization domains when dispersed in a nematic liquid crystal. Here we demonstrate the optical patterning of domain structures and topological defects in such ferromagnetic liquid crystal colloids which allows for altering their response to magnetic fields. Our findings reveal the nature of the defects in this soft matter system which is different as compared to non-polar nematic and ferromagnetic systems alike. This research was supported by the NSF Grant DMR-1420736.

Low-temperature hydrothermal synthesis of ZnO nanorods: Effects of zinc salt concentration, various solvents and alkaline mineralizers

DOE Office of Scientific and Technical Information (OSTI.GOV)

Edalati, Khatereh, E-mail: kh_ed834@stu.um.ac.ir; Shakiba, Atefeh; Vahdati-Khaki, Jalil

2016-02-15

Highlights: • We synthesized ZnO nanorods by a simple hydrothermal process at 60 °C. • Effects of zinc salt concentration, solvent and alkaline mineralizer was studied. • Increasing concentration of zinc salt changed ZnO nucleation system. • NaOH yielded better results in the production of nanorods in both solvents. • Methanol performed better in the formation of nanorods using the two mineralizers. - Abstract: ZnO has been produced using various methods in the solid, gaseous, and liquid states, and the hydrothermal synthesis at low temperatures has been shown to be an environmentally-friendly one. The current work utilizes a low reactionmore » temperature (60 °C) for the simple hydrothermal synthesis of ZnO nanorod morphologies. Furthermore, the effects of zinc salt concentration, solvent type and alkaline mineralizer type on ZnO nanorods synthesis at a low reaction temperature by hydrothermal processing was studied. Obtained samples were analyzed using X-ray powder diffraction (XRD) and scanning electron microscopy (SEM). Increasing the concentration of the starting zinc salt from 0.02 to 0.2 M changed ZnO nucleation system from the homogeneous to the heterogeneous state. The XRD results confirmed the production hexagonal ZnO nanostructures of with a crystallite size of 40.4 nm. Varying the experimental parameters (mineralizer and solvent) yielded ZnO nanorods with diameters ranging from 90–250 nm and lengths of 1–2 μm.« less

Nanoscale Seebeck effect at hot metal nanostructures

NASA Astrophysics Data System (ADS)

Ly, Aboubakry; Majee, Arghya; Würger, Alois

2018-02-01

We theoretically study the electrolyte Seebeck effect in the vicinity of a heated metal nanostructure, such as the cap of an active Janus colloid in an electrolyte, or gold-coated interfaces in optofluidic devices. The thermocharge accumulated at the surface varies with the local temperature, thus modulating the diffuse part of the electric double layer. On a conducting surface with non-uniform temperature, the isopotential condition imposes a significant polarization charge within the metal. Surprisingly, this does not affect the slip velocity, which takes the same value on insulating and conducting surfaces. Our results for specific-ion effects agree qualitatively with recent observations for Janus colloids in different electrolyte solutions. Comparing the thermal, hydrodynamic, and ion diffusion time scales, we expect a rich transient behavior at the onset of thermally powered swimming, extending to microseconds after switching on the heating.

Conductive Photo-Activated Porphyrin-ZnO Nanostructured Gas Sensor Array.

PubMed

Magna, Gabriele; Catini, Alexandro; Kumar, Raj; Palmacci, Massimo; Martinelli, Eugenio; Paolesse, Roberto; di Natale, Corrado

2017-04-01

Chemoresistors working at room temperature are attractive for low-consumption integrated sensors. Previous studies show that this feature can be obtained with photoconductive porphyrins-coated ZnO nanostructures. Furthermore, variations of the porphyrin molecular structure alter both the chemical sensitivity and the photoconductivity, and can be used to define the sensor characteristics. Based on these assumptions, we investigated the properties of an array of four sensors made of a layer of ZnO nanoparticles coated with porphyrins with the same molecular framework but different metal atoms. The array was tested with five volatile organic compounds (VOCs), each measured at different concentrations. Results confirm that the features of individual porphyrins influence the sensor behavior, and the differences among sensors are enough to enable the discrimination of volatile compounds disregarding their concentration.

Enhanced photoelectrochemical and optical performance of ZnO films tuned by Cr doping

NASA Astrophysics Data System (ADS)

Salem, M.; Akir, S.; Massoudi, I.; Litaiem, Y.; Gaidi, M.; Khirouni, K.

2017-04-01

In this paper, pure and Cr-doped nanostructured Zinc oxide thin films were synthesized by simple and low cost co-precipitation and spin-coating method with Cr concentration varying between 0.5 and 5 at.%. Crystalline structure of the prepared films was investigated by X-ray diffraction (XRD) and Raman spectroscopy techniques. XRD analysis indicated that the films were indexed as the hexagonal phase of wurtzite-type structure and demonstrated a decrease in the crystallite size with increasing Cr doping content. Cr doping revealed a significant effect on the optical measurements such as transmission and photoluminescence properties. The optical measurements indicated that Cr doping decreases the optical band gap and it has been shifted from 3.41 eV for pure ZnO film to 3.31 eV for 5 at.% Cr-doped one. The photoelectrochemical (PEC) sensing characteristics of Cr-doped ZnO layers were investigated. Amongst all photo-anodes with different Cr dopant concentration, the 2 at.% Cr incorporated ZnO films exhibited fast response and higher photoconduction sensitivity.

Synthesis of nano-sized ZnO particles by co-precipitation method with variation of heating time

DOE Office of Scientific and Technical Information (OSTI.GOV)

Purwaningsih, S. Y., E-mail: sriyanisaputri@gmail.com; Pratapa, S.; Triwikantoro

Zinc oxide powders have been synthesized by a co-precipitation method at low temperature (85 °C), using zinc acetate dihydrate, ammonia, hydrochloric acid solutions as the reactants. A number of process parameters such as reaction temperature, solution basicity or pH and heating time are the main factors affecting the morphology and physical properties of the ZnO nanostructures. In this work the effect of heating time on the morphology and particles size were studied. The as-synthesized ZnO powders were characterized using transmission electron microscopy (TEM) and X-ray diffraction (XRD) techniques. The samples were also analyzed using Fourier transform infrared (FTIR). Rietveld refinementmore » of XRD data confirms that ZnO crystallizes in the hexagonal wurtzite structure with high degree of purity and the (101) plane predominant. The XRD results show that the average crystallite sizes were about 66, 27 and 12 nm for 3, 4 and 5 h of heating times, respectively. The XRD analysis indicated that a fraction of nano-sized ZnO powders were in the form of aggregates, which was also verified by TEM image. The TEM photograph demonstrated that the nano-sized ZnO particles were a pseudo-spherical shape.« less

Arbitrary Multicolor Photodetection by Hetero-integrated Semiconductor Nanostructures

PubMed Central

Sang, Liwen; Hu, Junqing; Zou, Rujia; Koide, Yasuo; Liao, Meiyong

2013-01-01

The typical photodetectors can only detect one specific optical spectral band, such as InGaAs and graphene-PbS quantum dots for near-infrared (NIR) light detection, CdS and Si for visible light detection, and ZnO and III-nitrides for UV light detection. So far, none of the developed photodetector can achieve the multicolor detection with arbitrary spectral selectivity, high sensitivity, high speed, high signal-to-noise ratio, high stability, and simplicity (called 6S requirements). Here, we propose a universal strategy to develop multicolor photodetectors with arbitrary spectral selectivity by integrating various semiconductor nanostructures on a wide-bandgap semiconductor or an insulator substrate. Because the photoresponse of each spectral band is determined by each semiconductor nanostructure or the semiconductor substrate, multicolor detection satisfying 6S requirements can be readily satisfied by selecting the right semiconductors. PMID:23917790

Influence of rare earth ions on microstructural and optical properties of ZnO nanostructures

DOE Office of Scientific and Technical Information (OSTI.GOV)

Riyajuddin, Sk., E-mail: riyaj5303@gmail.com; Ahmad, Shabbir; Faizan, M.

2016-05-23

Pure and 3% rare earth ions (Nd{sup 3+} & Gd{sup 3+}) doped ZnO samples were synthesized by sol-gel method, followed by annealing at temperature 450°C for 2hr. The samples were characterized by XRD, FTIR and UV-visible spectroscopy. XRD result confirmed single phase nature of all samples with crystalline structure. The average crystallite size of the doped samples found to be decreases as caculated using Debye-Scherrer’s formula. FTIR spectra indicate absorption band centered at 464 cm{sup −1} which is attributed to Zn-O lattice vibration. It confirms the formaton of compounds. UV-visible spectroscopy was used to study the optical properties and band gapmore » of the synthesised materials using Tauc’s relation.« less

ZnO nanostructures as electron extraction layers for hybrid perovskite thin films

NASA Astrophysics Data System (ADS)

Nikolaidou, Katerina; Sarang, Som; Tung, Vincent; Lu, Jennifer; Ghosh, Sayantani

Optimum interaction between light harvesting media and electron transport layers is critical for the efficient operation of photovoltaic devices. In this work, ZnO layers of different morphologies are implemented as electron extraction and transport layers for hybrid perovskite CH3NH3PbI3 thin films. These include nanowires, nanoparticles, and single crystalline film. Charge transfer at the ZnO/perovskite interface is investigated and compared through ultra-fast characterization techniques, including temperature and power dependent spectroscopy, and time-resolved photoluminescence. The nanowires cause an enhancement in perovskite emission, which may be attributed to increased scattering and grain boundary formation. However, the ZnO layers with decreasing surface roughness exhibit better electron extraction, as inferred from photoluminescence quenching, reduction in the number of bound excitons, and reduced exciton lifetime in CH3NH3PbI3 samples. This systematic study is expected to provide an understanding of the fundamental processes occurring at the ZnO-CH3NH3PbI3 interface and ultimately, provide guidelines for the ideal configuration of ZnO-based hybrid Perovskite devices. This research was supported by National Aeronautics and Space administration (NASA) Grant No: NNX15AQ01A.

Negative differential resistance and resistive switching in SnO2/ZnO interface

NASA Astrophysics Data System (ADS)

Pant, Rohit; Patel, Nagabhushan; Nanda, K. K.; Krupanidhi, S. B.

2017-09-01

We report a very stable negative differential resistance (NDR) and resistive switching (RS) behavior of highly transparent thin films of the SnO2/ZnO bilayer, deposited by magnetron sputtering. When this bilayer of SnO2/ZnO was annealed at temperatures above 400 °C, ZnO diffuses into SnO2 at the threading dislocations and gaps between the grain boundaries, leading to the formation of a ZnO nanostructure surrounded by SnO2. Such a configuration forms a resonant tunneling type structure with SnO2/ZnO/SnO2…….ZnO/SnO2 interface formation. Interestingly, the heterostructure exhibits a Gunn diode-like behavior and shows NDR and RS irrespective of the voltage sweep direction, which is the characteristic of unipolar devices. A threshold voltage of ˜1.68 V and a peak-to-valley ratio of current ˜2.5 are observed for an electrode separation of 2 mm, when the bias is swept from -5 V to +5 V. It was also observed that the threshold voltage can be tuned with changing distance between the electrodes. The device shows a very stable RS with a uniform ratio of about 3.4 between the high resistive state and the low resistive state. Overall, the results demonstrate the application of SnO2/ZnO bilayer thin films in transparent electronics.

Tuning the morphology, stability and photocatalytic activity of TiO{sub 2} nanocrystal colloids by tungsten doping

DOE Office of Scientific and Technical Information (OSTI.GOV)

Xu, Haiping; Liao, Jianhua; School of Pharmaceutical Sciences, Gannan Medical University, Ganzhou, Jiangxi 341000

2014-03-01

Graphical abstract: - Highlights: • W{sup 6+}-doped TiO{sub 2} nanocrystal colloids were prepared by hydrothermal methods. • The properties of TiO{sub 2} nanocrystal colloids can be tuned by tungsten doping. • W{sup 6+}-doped TiO{sub 2} nanocrystal colloids show higher stability and dispersity. • W{sup 6+}-doped TiO{sub 2} nanocrystal colloids show higher photocatalytic activity. - Abstract: The effects of tungsten doping on the morphology, stability and photocatalytic activity of TiO{sub 2} nanocrystal colloids were investigated. The nanostructure, chemical state of Ti, W, O, and the properties of tungsten doped TiO{sub 2} samples were investigated carefully by TEM, XRD, XPS, UV–vis, PLmore » and photocatalytic degradation experiments. And the structure–activity relationship was discussed according to the analysis and measurement results. The analysis results reveal that the morphology, zeta potential and photocatalytic activity of TiO{sub 2} nanocrystals can be easily tuned by changing the tungsten doping concentration. The tungsten doped TiO{sub 2} colloid combines the characters of high dispersity and high photocatalytic activity.« less

Hierarchically structured nanowires on and nanosticks in ZnO microtubes

PubMed Central

Rivaldo-Gómez, C. M.; Cabrera-Pasca, G. A.; Zúñiga, A.; Carbonari, A. W.; Souza, J. A.

2015-01-01

We report both coaxial core-shell structured microwires and ZnO microtubes with growth of nanosticks in the inner and nanowires on the outer surface as a novel hierarchical micro/nanoarchitecture. First, a core-shell structure is obtained—the core is formed by metallic Zn and the semiconducting shell is comprised by a thin oxide layer covered with a high density of nanowires. Such Zn/ZnO core-shell array showed magnetoresistance effect. It is suggested that magnetic moments in the nanostructured shell superimposes to the external magnetic field enhancing the MR effect. Second, microtubes decorated with nanowires on the external surface are obtained. In an intermediate stage, a hierarchical morphology comprised of discrete nanosticks in the inner surface of the microtube has been found. Hyperfine interaction measurements disclosed the presence of confined metallic Zn regions at the interface between linked ZnO grains forming a chain and a ZnO thicker layer. Surprisingly, the metallic clusters form highly textured thin flat regions oriented parallel to the surface of the microtube as revealed by the electrical field gradient direction. The driving force to grow the internal nanosticks has been ascribed to stress-induced migration of Zn ions due to compressive stress caused by the presence of these confined regions. PMID:26456527

Growth and characterization of ZnO multipods on functional surfaces with different sizes and shapes of Ag particles

NASA Astrophysics Data System (ADS)

A, Kamalianfar; S, A. Halim; Mahmoud Godarz, Naseri; M, Navasery; Fasih, Ud Din; J, A. M. Zahedi; Kasra, Behzad; K, P. Lim; A Lavari, Monghadam; S, K. Chen

2013-08-01

Three-dimensional ZnO multipods are successfully synthesized on functional substrates using the vapor transport method in a quartz tube. The functional surfaces, which include two different distributions of Ag nanoparticles and a layer of commercial Ag nanowires, are coated onto silicon substrates before the growth of ZnO nanostructures. The structures and morphologies of the ZnO/Ag heterostructures are investigated using X-ray diffraction and field emission scanning electron microscopy. The sizes and shapes of the Ag particles affect the growth rates and initial nucleations of the ZnO structures, resulting in different numbers and shapes of multipods. They also influence the orientation and growth quality of the rods. The optical properties are studied by photoluminescence, UV-vis, and Raman spectroscopy. The results indicate that the surface plasmon resonance strongly depends on the sizes and shapes of the Ag particles.

In Situ X-ray Absorption Near-Edge Structure Spectroscopy of ZnO Nanowire Growth During Chemical Bath Deposition

DOE Office of Scientific and Technical Information (OSTI.GOV)

McPeak, Kevin M.; Becker, Matthew A.; Britton, Nathan G.

2010-12-03

Chemical bath deposition (CBD) offers a simple and inexpensive route to deposit semiconductor nanostructures, but lack of fundamental understanding and control of the underlying chemistry has limited its versatility. Here we report the first use of in situ X-ray absorption spectroscopy during CBD, enabling detailed investigation of both reaction mechanisms and kinetics of ZnO nanowire growth from zinc nitrate and hexamethylenetetramine (HMTA) precursors. Time-resolved X-ray absorption near-edge structure (XANES) spectra were used to quantify Zn(II) speciation in both solution and solid phases. ZnO crystallizes directly from [Zn(H{sub 2}O){sub 6}]{sup 2+} without long-lived intermediates. Using ZnO nanowire deposition as an example,more » this study establishes in situ XANES spectroscopy as an excellent quantitative tool to understand CBD of nanomaterials.« less

Observation of the origin of d0 magnetism in ZnO nanostructures using X-ray-based microscopic and spectroscopic techniques

NASA Astrophysics Data System (ADS)

Singh, Shashi B.; Wang, Yu-Fu; Shao, Yu-Cheng; Lai, Hsuan-Yu; Hsieh, Shang-Hsien; Limaye, Mukta V.; Chuang, Chen-Hao; Hsueh, Hung-Chung; Wang, Hsaiotsu; Chiou, Jau-Wern; Tsai, Hung-Ming; Pao, Chih-Wen; Chen, Chia-Hao; Lin, Hong-Ji; Lee, Jyh-Fu; Wu, Chun-Te; Wu, Jih-Jen; Pong, Way-Faung; Ohigashi, Takuji; Kosugi, Nobuhiro; Wang, Jian; Zhou, Jigang; Regier, Tom; Sham, Tsun-Kong

2014-07-01

Efforts have been made to elucidate the origin of d0 magnetism in ZnO nanocactuses (NCs) and nanowires (NWs) using X-ray-based microscopic and spectroscopic techniques. The photoluminescence and O K-edge and Zn L3,2-edge X-ray-excited optical luminescence spectra showed that ZnO NCs contain more defects than NWs do and that in ZnO NCs, more defects are present at the O sites than at the Zn sites. Specifically, the results of O K-edge scanning transmission X-ray microscopy (STXM) and the corresponding X-ray-absorption near-edge structure (XANES) spectroscopy demonstrated that the impurity (non-stoichiometric) region in ZnO NCs contains a greater defect population than the thick region. The intensity of O K-edge STXM-XANES in the impurity region is more predominant in ZnO NCs than in NWs. The increase in the unoccupied (occupied) density of states at/above (at/below) the conduction-band minimum (valence-band maximum) or the Fermi level is related to the population of defects at the O sites, as revealed by comparing the ZnO NCs to the NWs. The results of O K-edge and Zn L3,2-edge X-ray magnetic circular dichroism demonstrated that the origin of magnetization is attributable to the O 2p orbitals rather than the Zn d orbitals. Further, the local density approximation (LDA) + U verified that vacancies in the form of dangling or unpaired 2p states (due to Zn vacancies) induced a significant local spin moment in the nearest-neighboring O atoms to the defect center, which was determined from the uneven local spin density by analyzing the partial density of states of O 2p in ZnO.Efforts have been made to elucidate the origin of d0 magnetism in ZnO nanocactuses (NCs) and nanowires (NWs) using X-ray-based microscopic and spectroscopic techniques. The photoluminescence and O K-edge and Zn L3,2-edge X-ray-excited optical luminescence spectra showed that ZnO NCs contain more defects than NWs do and that in ZnO NCs, more defects are present at the O sites than at the Zn sites

Semiconductor nanostructures for plasma energetic systems

NASA Astrophysics Data System (ADS)

Mustafaev, Alexander; Smerdov, Rostislav; Klimenkov, Boris

2017-10-01

In this talk we discuss the research results of the three types of ultrasmall electrodes namely the nanoelectrode arrays based on composite nanostructured porous silicon (PS) layers, porous GaP and nanocrystals of ZnO. These semiconductor materials are of great interest to nano- and optoelectronic applications by virtue of their high specific surface area and extensive capability for surface functionalization. The use of semiconductor (GaN) cathodes in photon-enhanced thermionic emission systems has also proved to be effective although only a few (less than 1%) of the incident photons exceed the 3.3 eV GaN band gap. This significant drawback provided us with a solid foundation for our research in the field of nanostructured PS, and composite materials based on it exhibiting nearly optimal parameters in terms of the band gap (1.1 eV). The band gap modification for PS nanostructured layers is possible in the range of less than 1 eV and 3 eV due to the existence of quantum confinement effect and the remarkable possibilities of PS surface alteration thus providing us with a suitable material for both cathode and anode fabrication. The obtained results are applicable for solar concentration and thermionic energy conversion systems. Dr. Sci., Ph.D, Principal Scientist, Professor.

Colloid particle formulations for antimicrobial applications.

PubMed

Halbus, Ahmed F; Horozov, Tommy S; Paunov, Vesselin N

2017-11-01

Colloidal particles are being extensively studied in various antimicrobial applications due to their small size to volume ratio and ability to exhibit a wide spectrum of antibacterial, antifungal, antialgal and antiviral action. The present review focuses on various nanoparticles (NPs) of inorganic, organic and hybrid materials, and discusses some of the methods for their preparation as well as mechanisms of their antimicrobial action. We consider the antimicrobial applications of metal oxide nanoparticles (ZnO, MgO, CuO, Cu 2 O, Al 2 O 3 , TiO 2 , CeO 2 and Y 2 O 3 ), metal nanoparticles (NPs), such as copper, silver and gold, metal hydroxide NPs such as Mg(OH) 2 as well as hybrid NPs made from biodegradable materials, such as chitosan, lignin and dextran, loaded with other antimicrobial agents. Recent developments for targeted delivery of antimicrobials by using colloid antibodies for microbial cell shape and surface recognition are also discussed. We also consider recent advances in the functionalization of nanoparticles and their potential antimicrobial applications as a viable alternative of conventional antibiotics and antiseptic agents which can help to tackle antimicrobial resistance. The review also covers the recently developed environmentally benign NPs (EbNPs) as a "safer-by-design" green chemistry solution of the post use fate of antimicrobial nanomaterials. Copyright © 2017 Elsevier B.V. All rights reserved.

Large-Scale Noniridescent Structural Color Printing Enabled by Infiltration-Driven Nonequilibrium Colloidal Assembly.

PubMed

Bai, Ling; Mai, Van Cuong; Lim, Yun; Hou, Shuai; Möhwald, Helmuth; Duan, Hongwei

2018-03-01

Structural colors originating from interaction of light with intricately arranged micro-/nanostructures have stimulated considerable interest because of their inherent photostability and energy efficiency. In particular, noniridescent structural color with wide viewing angle has been receiving increasing attention recently. However, no method is yet available for rapid and large-scale fabrication of full-spectrum structural color patterns with wide viewing angles. Here, infiltration-driven nonequilibrium assembly of colloidal particles on liquid-permeable and particle-excluding substrates is demonstrated to direct the particles to form amorphous colloidal arrays (ACAs) within milliseconds. The infiltration-assisted (IFAST) colloidal assembly opens new possibilities for rapid manufacture of noniridescent structural colors of ACAs and straightforward structural color mixing. Full-spectrum noniridescent structural colors are successfully produced by mixing primary structural colors of red, blue, and yellow using a commercial office inkjet printer. Rapid fabrication of large-scale structural color patterns with sophisticated color combination/layout by IFAST printing is realized. The IFAST technology is versatile for developing structural color patterns with wide viewing angles, as colloidal particles, inks, and substrates are flexibly designable for diverse applications. © 2018 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Strong visible and near infrared photoluminescence from ZnO nanorods/nanowires grown on single layer graphene studied using sub-band gap excitation

NASA Astrophysics Data System (ADS)

Biroju, Ravi K.; Giri, P. K.

2017-07-01

Fabrication and optoelectronic applications of graphene based hybrid 2D-1D semiconductor nanostructures have gained tremendous research interest in recent times. Herein, we present a systematic study on the origin and evolution of strong broad band visible and near infrared (NIR) photoluminescence (PL) from vertical ZnO nanorods (NRs) and nanowires (NWs) grown on single layer graphene using both above band gap and sub-band gap optical excitations. High resolution field emission scanning electron microscopy and X-ray diffraction studies are carried out to reveal the morphology and crystalline quality of as-grown and annealed ZnO NRs/NWs on graphene. Room temperature PL studies reveal that besides the UV and visible PL bands, a new near-infrared (NIR) PL emission band appears in the range between 815 nm and 886 nm (1.40-1.52 eV). X-ray photoelectron spectroscopy studies revealed excess oxygen content and unreacted metallic Zn in the as-grown ZnO nanostructures, owing to the low temperature growth by a physical vapor deposition method. Post-growth annealing at 700 °C in the Ar gas ambient results in the enhanced intensity of both visible and NIR PL bands. On the other hand, subsequent high vacuum annealing at 700 °C results in a drastic reduction in the visible PL band and complete suppression of the NIR PL band. PL decay dynamics of green emission in Ar annealed samples show tri-exponential decay on the nanosecond timescale including a very slow decay component (time constant ˜604.5 ns). Based on these results, the NIR PL band comprising two peaks centered at ˜820 nm and ˜860 nm is tentatively assigned to neutral and negatively charged oxygen interstitial (Oi) defects in ZnO, detected experimentally for the first time. The evidence for oxygen induced trap states on the ZnO NW surface is further substantiated by the slow photocurrent response of graphene-ZnO NRs/NWs. These results are important for tunable light emission, photodetection, and other cutting edge

Photochemical Synthesis of Shape-Controlled Nanostructured Gold on Zinc Oxide Nanorods as Photocatalytically Renewable Sensors.

PubMed

Xu, Jia-Quan; Duo, Huan-Huan; Zhang, Yu-Ge; Zhang, Xin-Wei; Fang, Wei; Liu, Yan-Ling; Shen, Ai-Guo; Hu, Ji-Ming; Huang, Wei-Hua

2016-04-05

Biosensors always suffer from passivation that prevents their reutilization. To address this issue, photocatalytically renewable sensors composed of semiconductor photocatalysts and sensing materials have emerged recently. In this work, we developed a robust and versatile method to construct different kinds of renewable biosensors consisting of ZnO nanorods and nanostructured Au. Via a facile and efficient photochemical reduction, various nanostructured Au was obtained successfully on ZnO nanorods. As-prepared sensors concurrently possess excellent sensing capability and desirable photocatalytic cleaning performance. Experimental results demonstrate that dendritic Au/ZnO composite has the strongest surface-enhanced Raman scattering (SERS) enhancement, and dense Au nanoparticles (NPs)/ZnO composite has the highest electrochemical activity, which was successfully used for electrochemical detection of NO release from cells. Furthermore, both of the SERS and electrochemical sensors can be regenerated efficiently for renewable applications via photodegrading adsorbed probe molecules and biomolecules. Our strategy provides an efficient and versatile method to construct various kinds of highly sensitive renewable sensors and might expand the application of the photocatalytically renewable sensor in the biosensing area.

Sampling colloids and colloid-associated contaminants in ground water

USGS Publications Warehouse

Backhus, Debera A.; Ryan, Joseph N.; Groher, Daniel M.; MacFarlane, John K.; Gschwend, Philip M.

1993-01-01

It has recently been recognized that mobile colloids may affect the transport of contaminants in ground water. To determine the significance of this process, knowledge of both the total mobile load (dissolved + colloid-associated) and the dissolved concentration of a ground-water contaminant must be obtained. Additional information regarding mobile colloid characteristics and concentrations are required to predict accurately the fate and effects of contaminants at sites where significant quantities of colloids are found. To obtain this information, a sampling scheme has been designed and refined to collect mobile colloids while avoiding the inclusion of normally immobile subsurface and well-derived solids. The effectiveness of this sampling protocol was evaluated at a number of contaminated and pristine sites.The sampling results indicated that slow, prolonged pumping of ground water is much more effective at obtaining ground-water samples that represent in situ colloid populations than bailing. Bailed samples from a coal tar-contaminated site contained 10–100 times greater colloid concentrations and up to 750 times greater polycyclic aromatic hydrocarbon concentrations as were detected in slowly pumped samples. The sampling results also indicated that ground-water colloid concentrations should be monitored in the field to determine the adequacy of purging if colloid and colloid-associated contaminants are of interest. To avoid changes in the natural ground-water colloid population through precipitation or coagulation, in situ ground-water chemistry conditions must be preserved during sampling and storage. Samples collected for determination of the total mobile load of colloids and low-solubility contaminants must not be filtered because some mobile colloids are removed by this process. Finally, suggestions that mobile colloids are present in ground water at any particular site should be corroborated with auxiliary data, such as colloid levels in �

Bio-industrial waste silk fibroin protein and carbon nanotube induced carbonized growth of one dimensional ZnO based bio-nanosheets and their enhanced optoelectronic properties.

PubMed

Saravanan, Adhimoorthy; Huang, Bohr-Ran; Kathiravan, Deepa

2018-06-01

High performance UV/visible photodetectors are successfully fabricated from ZnO/fibroin protein-carbon nanotube (ZFPCNT) composites using a simple hydrothermal method. The as-fabricated ZnO nanorods (ZnO NRs) and ZFPCNT nanostructures were measured under different light illuminations. The measurements showed the UV-light photoresponse of the as-fabricated ZFPCNT nanostructures (55,555) to be approximately 26454% higher than that of the as-prepared ZnO NRs (210). This photodetector can sense photons with energies considerably smaller (2.75 eV) than the band gap of ZnO (3.22 eV). It was observed that the finest distribution of fibroin and CNT into 1D ZnO resulted in rapid electron transportation and hole recombination via carbon/nitrogen dopants from the ZFPCNT. Carbon dopants create new energy levels on the conduction band of the ZFPCNT, which reduces the barrier height to allow for charge carrier transportation under light illumination. Moreover, the nitrogen dopants increase the adsorptivity and amount of oxygen vacancies in the ZFPCNT so that it exhibits fast response/recovery times both in the dark and under light illumination. The selectivity of UV light among the other types of illumination can be ascribed to the deep-level energy traps (ET) of the ZFPCNT. These significant features of ZFPCNT lead to the excellent optical properties and creation of new pathways for the production of low-cost semiconductors and bio-waste protein based UV/visible photodetectors. © 2018 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.