Search query: applications of persistence photoconductivity of zno

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abstract: Whereas size effects have been investigated extensively and are largely understood, it is significantly more challenging to elucidate how functional properties of semiconductors can be altered and ultimately be improved by a hierarchical nanoarchitecture. For semiconductor applications, such as in photovoltaics or photocatalysis, it is of great importance to learn how to avoid the recombination of photogenerated charge carriers and how to enhance their lifetime. A gas phase synthesis method is explored, which enables the generation of spherical zinc oxide nanostructures with compact, mesoporous, a special type of core shell, so called yolk shell, or hollow character. The particles with hollow character exhibit an extraordinarily long persistence of photogenerated charge carriers. It is demonstrated that the presence of the ZnO shell and its special orientation with respect to the polar character of the wurtzite lattice represent deciding factors. After photoexcitation, electrons and holes migrate to oppos.
author_names: Stefan Dilger

Martin Wessig

M R Wagner

Juan Sebastian Reparaz

Clivia M Sotomayor Torres

Liang Qijun

Thomas Dekorsy

Sebastian Polarz
title: Nanoarchitecture Effects on Persistent Room Temperature Photoconductivity and Thermal Conductivity in Ceramic Semiconductors: Mesoporous, Yolk Shell, and Hollow ZnO Spheres
year: 2014

abstract: In this work, we investigate the optoelectronic properties of zinc oxide (ZnO) nanowires, which are good candidates for applications based on integrated optics. Single ZnO nanowire photodetectors were fabricated with ohmic contacts. By taking current transient measurements in different atmospheres (oxygen, air, vacuum and argon) and at various temperatures, we point out the importance of surface effects on the electrical behaviour. Results confirm that oxygen chemisorption is responsible for the existence of a high photoconductive gain in these devices, and for the first time a two step process in the photocurrent rise transient is reported. A maximum gain of G 7.8 x 107 is achieved. However, under certain conditions, the persistence of the photocurrent can last up to several hours and as such may prevent the device from operating at useful rates. From a knowledge of the photocurrent response mechanisms, we establish a method to restore the photodetector to its initial state, with very low dark current, by applying an appropriate gate voltage sequence. This advances the state of the art for these detectors towards commercial applications.
author_names: J Ph Girard

Louis Giraudet

Sergei Kostcheev

Bogdan Bercu

Tim J Puchtler

R A Taylor

Christophe Couteau
title: Mitigating the photocurrent persistence of single ZnO nanowires for low noise photodetection applications.
venue: Nanotechnology
year: 2018

abstract: Persistent organic pollutants (POPs) are carbon based chemical substances that are resistant to environmental degradation and may not be completely removed through treatment processes. Their persistence can contribute to adverse health impacts on wild life and human beings. Thus, the solar photocatalysis process has received increasing attention due to its great potential as a green and eco friendly process for the elimination of POPs to increase the security of clean water. In this context, ZnO nanostructures have been shown to be prominent photocatalyst candidates to be used in photodegradation owing to the facts that they are low cost, non toxic and more efficient in the absorption across a large fraction of the solar spectrum compared to TiO2. There are several aspects, however, need to be taken into consideration for further development. The purpose of this paper is to review the photo degradation mechanisms of POPs and the recent progress in ZnO nanostructured fabrication methods including doping, heterojunction and modification techniques as well as improvements of ZnO as a photocatalyst. The second objective of this review is to evaluate the immobilization of photocatalyst and suspension systems while looking into their future challenges and prospects.
author_names: Chin Boon Ong

Law Yong Ng

Abdul Wahab Mohammad
title: A review of ZnO nanoparticles as solar photocatalysts: Synthesis, mechanisms and applications
year: 2018

abstract: Polymer composites have established an excellent position among the technologically essential materials because of their wide range of applications. An enormous research interest has been devoted to zinc oxide (ZnO) based polymer nanocomposites, due to their exceptional electrical, optical, thermal, mechanical, catalytic, and biomedical properties. This article provides a review of various polymer composites consisting of ZnO nanoparticles (NPs) as reinforcements, exhibiting excellent properties for applications such as the dielectric, sensing, piezoelectric, electromagnetic shielding, thermal conductivity and energy storage. The preparation methods of such composites including solution blending, in situ polymerization, and melt intercalation are also explained. The current challenges and potential applications of these composites are provided in order to guide future progress on the development of more promising materials. Finally, a detailed summary of the current trends in the field is presented to progressively show the future prospects for the development of ZnO containing polymer nanocomposite materials.
author_names: Deepalekshmi Ponnamma

John-John Cabibihan

Mariappan Rajan

Sethu Sundar Pethaiah

Kalim Deshmukh

Jyoti Prasad Gogoi

S K Khadheer Pasha

M Basheer Ahamed

Jagadish Krishnegowda

Bananakere Nanjegowda Chandrashekar

Anji Reddy Polu

Chun Cheng
title: Synthesis, optimization and applications of ZnO/polymer nanocomposites.
venue: Materials science engineering. C, Materials for biological applications
year: 2019

abstract: We studied experimentally the granular structures prepared on the base of ZnO thin films. The influence of acceptor or donor complex, caused by oxygen vacancy and interstitial zinc atom, and impurities (Li or Ga) on the crystallite structure conductivity has been investigated. The effect of granule size and crystallite structure on conductivity and photoconductivity was studied. The new method for determination of electric current dependence on spatial coordinates in thin conducting film was developed, which allowed to diagnose a one dimensional conductivity in ZnO:Ga films. The experimental results are interpreted on the basis of the scaling hypothesis and the percolation theory.
author_names: Armen Poghosyan

N R Aghamalyan

E Y Elbakyan

Ruyan Guo

Ruben K Hovsepyan

S I Petrosyan
title: Photoconductivity of ZnO based granular structures
venue: Optics Photonics Optical Engineering Applications
year: 2014

abstract: The advance of reliable and eco friendly strategies for the development of nanoparticles is a fundamental key to the discipline of nanotechnology. Nanoparticles have been continuously evaluated and have been used in many industrial applications for a decade. In particular, the role of zinc oxide nanoparticles (ZnO NPs) has received a great interest because of various properties such as UV filter properties and photochemical, antifungal, high catalyst, and antimicrobial activities. Because of the high rate of poisonous chemicals and the extreme surroundings used within the chemical and physical methods, the green techniques have been adopted using plants, fungi, bacteria, and algae for the synthesis of nanoparticles. Therefore, this paper considers various green synthesis methods to provide the evidence of ZnO NP role to several applications, and in addition, biomedical applications and toxic effect were reviewed. Therefore, the paper used various secondary sources to collect the relevant review articles. From the findings, the green route of synthesis is rather safe and eco friendly when compared to physical and chemical means of synthesis. On the other hand, its biomedical applications in this sector are increased day by day in various processes including bioimaging, drug delivery, biosensors, and gene delivery. With respect to its toxicity properties, ZnO NPs can act as smart weapons against multiple drug resistant microorganisms and as a talented substitute for antibiotics.
author_names: V N Kalpana

V Devi Rajeswari
title: A Review on Green Synthesis, Biomedical Applications, and Toxicity Studies of ZnO NPs
venue: Bioinorganic chemistry and applications
year: 2018

abstract: Herein, we synthesized ZnO nanorods using a solvothermal reaction technique at 200 degC for 24 h, and the prepared ZnO nanorods were decorated with silver (Ag) nanoparticles to enhance their photocatalytic activity. The Ag nanoparticles were photochemically deposited on the ZnO rods with varying molar concentrations (from 0.5 to 10 mol% and their various physicochemical properties were studied. The prepared material was characterised using different spectroscopic techniques. XRD revealed the formation of a highly crystalline hexagonal phase of ZnO. For a higher silver loading >5 mol% separate peaks corresponding to cubic silver were observed in the XRD pattern. The photoluminescence spectra of the Ag/ZnO nanostructures show two distinct peaks at 390 and 500 nm; interestingly, the PL intensity of the ZnO emission peak at 500 nm decreases with an increase in the silver concentration. The diffuse reflectance spectra of Ag/ZnO indicate absorbance at 380 nm due to ZnO and a slight hump at 440 nm that corresponds to silver nanoparticles. The FE SEM and TEM analysis indicates the formation of a hexagonal rod like morphology, with the lengths of the rods ranging from around 50 to 200 nm and a diameter of around 30 nm. TEM also confirms the presence of Ag nanoparticles with sizes in the range of 20 to 30 nm on the surface of the ZnO nanorods. The photocatalytic activity of the Ag/ZnO nanostructures was evaluated by following the degradation of methylene blue (MB) dye under a 400 W mercury vapour lamp. ZnO with 10 mol% Ag loading shows the highest photocatalytic activity as compared to the 0.5, 1 5 mol% Ag ZnO catalysts. The observed apparent rate constant for the photocatalytic MB degradation using 10 mol% Ag ZnO (Kapp 6.01 x 10 2 min 1) was six times that of pure ZnO (Kapp 1.09 x 10 2 min 1) A gradual increase in the photocatalytic activity of Ag/ZnO was observed with an increase in the silver concentration. The photocurrent response of the prepared Ag ZnO nanostructures was examined by a photoconductivity study. Moreover, the photocatalytic performance of the sample was correlated with the photoconductivity of the samples. The photoconductivity of the samples was stable, and the photoconductivity of 10 mol% Ag ZnO was almost 20 times that of pure ZnO, resulting in a higher photocatalytic activity.
author_names: Prashant Pimpliskar

S C Motekar

G G Umarji

Wonyoung Lee

Sudhir S Arbuj
title: Synthesis of silver loaded ZnO nanorods and their enhanced photocatalytic activity and photoconductivity study.
venue: Photochemical photobiological sciences Official journal of the European Photochemistry Association and the European Society for Photobiology
year: 2019

abstract: The deposition of oxygen defective ZnO films exhibiting varied nanostructures via Solution Precursor Plasma Spray (SPPS) route, a one step, minute scaled duration and large scale method, is reported. The in situ formation of oxygen vacancies in ZnO films was confirmed by UV Visible, Raman and photoluminescence (PL) spectroscopy and the as prepared samples exhibit a bandgap as low as 3.02 eV. Density functional theory (DFT) simulation demonstrates that the polarization of ZnO is enhanced by the created oxygen vacancies, leading to substantially improved photocatalytic activity. The comparative experiments also revealed that forming and preserving appropriate ZnO precursor clusters inside the plasma plume is requisite for obtaining propitious ZnO nanostructures, which was followed by the in situ transfer and growth of the clusters on the preheated substrate. The ZnO NRs films fully degrade the aqueous Orange II dye solutions within 120 min and maintain a quasi intact activity (95.8% retention) after five test runs, which highlight their good stability. The oxygen vacancies and the narrowing of the bandgap also enable a visible light driven photodegradation activity with conversions as high as 54.1% In summary, this work not only reveals that the photocatalytic activity of SPPS deposited ZnO films benefit from oxygen vacancies and well nanostructures, but also suggests that the SPPS route is of high potential for preparing metal oxides films destined to functional applications.
author_names: Zexin Yu

Hatem Moussa

Yangzhou Ma

Meimei Liu

Bilel Chouchene

Raphael Schneider

Michel Moliere

Hanlin Liao
title: Oxygen defective ZnO films with various nanostructures prepared via a rapid one step process and corresponding photocatalytic degradation applications.
venue: Journal of colloid and interface science
year: 2019

abstract: We successfully synthesized of ZnO/Mn TiO2 (Mn Ti) nano composite for different ZnO:Mn (Zn M) concentrations. These composites with high photo catalytic activity derived from TiO2 and Zn M nanoparticles elaborated by the sol gel method. The SEM and TEM images indicated that samples reveals well ordered and good size distribution of particles. In addition, the composite sample showed no aggregation in similitude with the anatase TiO2 sample. The study of optical properties of nano composites shows that Zn M nanoparticles caused to increase the optical activity of Mn Ti composites samples and it established by UV Vis, photo luminescence, and photo catalytic tests. The XRD study exhibited that in ours composites samples with increasing the Zn M concentration, the particle size increased from 10 to 27 nm. PL measurements suggest that co emission of a strong luminescence, high yellow emission at 563 nm, at 640 nm and at 774 nm is observed from the Mn Ti composites samples. The photo catalytic activity of the prepared nano composite was examined for the degradation of methyl orange (MO) by the irradiation of UV light.
author_names: K Omri

Norah Alonizan
title: Effects of ZnO/Mn Concentration on the Micro structure and Optical Properties of ZnO/Mn TiO2 Nano composite for Applications in Photo Catalysis
venue: Journal of Inorganic and Organometallic Polymers and Materials
year: 2018

abstract: Zinc oxide films are typically found to be n type, and conductive under most growth conditions and growth methods. Co doping with multiple elements is one strategy for improving the electrical and optical properties of zinc oxide materials for optoelectronic device applications. Using pulsed laser deposition, thin ZnO films were grown on c axis oriented sapphire. The films were co doped with nitrogen and tellurium. Depending on the relative concentrations of the dopants, the resistivity of the films was observed to increase by several orders of magnitude, significantly improving the photoconductive response. The enhancement of the photosensitivity reached a maximum at a tellurium concentration of around 1020cm 3.
author_names: H L Porter

A L Cai

John F Muth

Jagdish Narayan
title: Enhanced photoconductivity of ZnO films Co doped with nitrogen and tellurium
year: 2005