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Síntese e caracterização de nanopartículas de ZnO e TiO2 dopadas com Ag para aplicação em materiais dentários; Synthesis and characterization of Ag doped ZnO and TiO2 nanoparticles for use in dental materials

Dias, Hércules Bezerra
Fonte: Biblioteca Digitais de Teses e Dissertações da USP Publicador: Biblioteca Digitais de Teses e Dissertações da USP
Tipo: Dissertação de Mestrado Formato: application/pdf
Publicado em 09/05/2014 PT
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Resinas compostas comumente utilizadas em restaurações, anteriores e posteriores, resultam em maior acúmulo de biofilme bacteriano do que outros materiais restauradores, o que contribui para a formação de cáries secundárias e levam à falha das restaurações. Métodos para inibir a formação do biofilme sobre materiais restauradores dentais vêm sendo estudados há décadas e a inserção de nanopartículas (NPs) representa o que há de mais avançado nos estudos de formulação de materiais dentários antibacterianos. A literatura recente relata que resinas compostas contendo NPs de óxidos metálicos, tais como óxido de zinco (ZnO) e dióxido de titânio (TiO2), têm demonstrado capacidade antibacteriana, contribuindo para o controle do biofilme oral cariogênico. Por outro lado, a inserção dessas NPs pode alterar a cor e as propriedades mecânicas para níveis clínicos inaceitáveis e até mesmo dificultar o processo de fotopolimerização, se inseridas em grandes quantidades. Uma vez que o efeito antibacteriano e as propriedades de resinas compostas modificadas com NPs de óxidos de metais não foram amplamente estudados, esse estudo visou a compreensão destes aspectos, a partir da síntese e caracterização de nanopartículas de ZnO e TiO2 dopados ou não com Ag...

The effect of cooling rate during hydrothermal synthesis of ZnO nanorods

Savu, Raluca; Parra, Rodrigo; Joanni, Ednan; Jancar, Bostjan; Eliziario, Sayonara A.; de Camargo, Rorivaldo; Bueno, Paulo R.; Varela, José Arana; Longo, Elson; Zaghete, Maria A.
Fonte: Elsevier B.V. Publicador: Elsevier B.V.
Tipo: Artigo de Revista Científica Formato: 4102-4108
ENG
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Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP); Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq); The hydrothermal method was employed in order to obtain zinc oxide nanorods directly on Si/Si02/Ti/ Zn substrates forming brush-like layers. In the final stages of synthesis, the reaction vessel was naturally cooled or submitted to a quenching process. X-ray diffraction results showed that all the nanostructures grew [0 0 0 1] oriented perpendicular to the substrate. The influence of the cooling process over the morphology and dimensions of the nanorods was studied by scanning electron microscopy. High-resolution transmission electron microscopy images of the quenched samples showed that the zinc oxide (ZnO) crystal surfaces exhibit a thin-layered coating surrounding the crystal with a high degree of defects, as confirmed by Raman spectroscopy results. Photodetectors made from these samples exhibited enhanced UV photoresponses when compared to the ones based on naturally cooled nanorods. (C) 2009 Elsevier B.V. All rights reserved.

Influence of Hydrothermal Synthesis Conditions and Device Configuration on the Photoresponse of UV Sensors Based on ZnO Nanorods

Savu, Raluca; Parra, Rodrigo; Jancar, Bostjan; Zaghete, Maria Aparecida; Joanni, Ednan
Fonte: Institute of Electrical and Electronics Engineers (IEEE) Publicador: Institute of Electrical and Electronics Engineers (IEEE)
Tipo: Artigo de Revista Científica Formato: 1820-1825
ENG
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Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP); Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq); Processo FAPESP: 05/59270-0; Zinc oxide nanorods in the form of powder or nanostructured films were synthesized by the hydrothermal method using aqueous solutions. Once the synthesis time was completed, the reaction vessel was naturally cooled or submitted to a quenching process. X-ray diffraction, Scanning Electron Microscopy and Transmission Electron Microscopy techniques were employed to characterize the crystallinity, morphology, and dimensions of the nanorods, as well as their growth direction. Suspensions of powder material were spin-coated over oxidized silicon substrates in order to obtain nanostructured layers. Photodetectors based on in-situ grown and spin-coated films were prepared in order to evaluate the influences of cooling rate and device configuration on the UV sensing characteristics. Spin-coated layers showed an excellent performance (current change by more than four orders of magnitude), better than nanorods grown directly on the substrate during the hydrothermal process. For both configurations, the sensitive layers built from quenched samples exhibited enhanced UV photoresponses when compared to the naturally cooled ones.

Investigação de métodos de síntese de nanobastões de ZnO para aplicação em dispositivos piezoelétricos; Investigation of method of synthesis of ZnO nanorods for use in piezoelectric devices

Natiara Vaughn Madalossi
Fonte: Biblioteca Digital da Unicamp Publicador: Biblioteca Digital da Unicamp
Tipo: Dissertação de Mestrado Formato: application/pdf
Publicado em 27/07/2012 PT
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Este trabalho reporta a síntese e caracterização de nanoestruturas de ZnO com morfologia de nanobastões hexagonais, crescidas verticalmente ao substrato de silício. Para o crescimento vertical dos nanobastões foi depositado um filme constituído por grãos de ZnO para atuar como camada de nucleação. Neste trabalho, as sínteses dos nanobastões e das camadas de nucleação foram preparadas por métodos químicos. As camadas de nucleação foram obtidas com a calcinação do filme de precursor polimérico e de 2-etilhexanoato de zinco, os quais foram depositados sobre o substrato de silício com o uso da técnica de spin coating e tratados termicamente em diferentes temperaturas para a formação dos grãos cristalinos de ZnO. Os nanobastões crescidos sobre as camadas de nucleação foram obtidos via síntese hidrotermal e síntese de deposição por banho químico (CBD). As camadas de nucleação e os nanobastões apresentaram estrutura cristalina tipo wurtzita com crescimento preferencial na direção [002] na qual a propriedade piezoelétrica se manifesta. As análises de espectroscopia Raman corroboraram com as análises de difração de raios X, sendo que não houve os deslocamentos das bandas do ZnO, indicando que os nanobastões não estavam no modo de confinamento quântico. Os nanobastões apresentam vários tipos de defeitos cristalinos...

Enhanced visible light photocatalysis through fast crystallization of zinc oxide nanorods

Baruah, Sunandan; Mahmood, Mohammad Abbas; Myint, Myo Tay Zar; Bora, Tanujjal; Dutta, Joydeep
Fonte: Beilstein-Institut Publicador: Beilstein-Institut
Tipo: Artigo de Revista Científica
Publicado em 22/11/2010 EN
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Hydrothermally grown ZnO nanorods have inherent crystalline defects primarily due to oxygen vacancies that enhance optical absorption in the visible spectrum, opening up possibilities for visible light photocatalysis. Comparison of photocatalytic activity of ZnO nanorods and nanoparticle films on a test contaminant methylene blue with visible light irradiation at 72 kilolux (klx) showed that ZnO nanorods are 12–24% more active than ZnO nanoparticulate films. This can be directly attributed to the increased effective surface area for adsorption of target contaminant molecules. Defects, in the form of interstitials and vacancies, were intentionally created by faster growth of the nanorods by microwave activation. Visible light photocatalytic activity was observed to improve by ≈8% attributed to the availability of more electron deficient sites on the nanorod surfaces. Engineered defect creation in nanostructured photocatalysts could be an attractive solution for visible light photocatalysis.

Protein Biosensors Based on Polymer Nanowires, Carbon Nanotubes and Zinc Oxide Nanorods

M., Anish Kumar; Jung, Soyoun; Ji, Taeksoo
Fonte: Molecular Diversity Preservation International (MDPI) Publicador: Molecular Diversity Preservation International (MDPI)
Tipo: Artigo de Revista Científica
Publicado em 09/05/2011 EN
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The development of biosensors using electrochemical methods is a promising application in the field of biotechnology. High sensitivity sensors for the bio-detection of proteins have been developed using several kinds of nanomaterials. The performance of the sensors depends on the type of nanostructures with which the biomaterials interact. One dimensional (1-D) structures such as nanowires, nanotubes and nanorods are proven to have high potential for bio-applications. In this paper we review these three different kinds of nanostructures that have attracted much attention at recent times with their great performance as biosensors. Materials such as polymers, carbon and zinc oxide have been widely used for the fabrication of nanostructures because of their enhanced performance in terms of sensitivity, biocompatibility, and ease of preparation. Thus we consider polymer nanowires, carbon nanotubes and zinc oxide nanorods for discussion in this paper. We consider three stages in the development of biosensors: (a) fabrication of biomaterials into nanostructures, (b) alignment of the nanostructures and (c) immobilization of proteins. Two different methods by which the biosensors can be developed at each stage for all the three nanostructures are examined. Finally...

Structural and photoluminescence studies on catalytic growth of silicon/zinc oxide heterostructure nanowires

Chong, Su Kong; Dee, Chang Fu; Abdul Rahman, Saadah
Fonte: Springer Publicador: Springer
Tipo: Artigo de Revista Científica
Publicado em 17/04/2013 EN
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Silicon/zinc oxide (Si/ZnO) core-shell nanowires (NWs) were prepared on a p-type Si(111) substrate using a two-step growth process. First, indium seed-coated Si NWs (In/Si NWs) were synthesized using a plasma-assisted hot-wire chemical vapor deposition technique. This was then followed by the growth of a ZnO nanostructure shell layer using a vapor transport and condensation method. By varying the ZnO growth time from 0.5 to 2 h, different morphologies of ZnO nanostructures, such as ZnO nanoparticles, ZnO shell layer, and ZnO nanorods were grown on the In/Si NWs. The In seeds were believed to act as centers to attract the ZnO molecule vapors, further inducing the lateral growth of ZnO nanorods from the Si/ZnO core-shell NWs via a vapor-liquid-solid mechanism. The ZnO nanorods had a tendency to grow in the direction of [0001] as indicated by X-ray diffraction and high resolution transmission electron microscopy analyses. We showed that the Si/ZnO core-shell NWs exhibit a broad visible emission ranging from 400 to 750 nm due to the combination of emissions from oxygen vacancies in ZnO and In2O3 structures and nanocrystallite Si on the Si NWs. The hierarchical growth of straight ZnO nanorods on the core-shell NWs eventually reduced the defect (green) emission and enhanced the near band edge (ultraviolet) emission of the ZnO.

Solvothermal Preparation of ZnO Nanorods as Anode Material for Improved Cycle Life Zn/AgO Batteries

Ullah, Shafiq; Ahmed, Fiaz; Badshah, Amin; Ali Altaf, Ataf; Raza, Ramsha; Lal, Bhajan; Hussain, Rizwan
Fonte: Public Library of Science Publicador: Public Library of Science
Tipo: Artigo de Revista Científica
Publicado em 17/10/2013 EN
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Nano materials with high surface area increase the kinetics and extent of the redox reactions, thus resulting in high power and energy densities. In this study high surface area zinc oxide nanorods have been synthesized by surfactant free ethylene glycol assisted solvothermal method. The nanorods thus prepared have diameters in the submicron range (300∼500 nm) with high aspect ratio. They have uniform geometry and well aligned direction. These nanorods are characterized by XRD, SEM, Specific Surface Area Analysis, solubility in alkaline medium, EDX analysis and galvanostatic charge/discharge studies in Zn/AgO batteries. The prepared zinc oxide nanorods have low solubility in alkaline medium with higher structural stability, which imparts the improved cycle life stability to Zn/AgO cells.

Unique Temporal and Spatial Biomolecular Emission Profile on Individual Zinc Oxide Nanorods

Singh, Manpreet; Song, Sheng; Hahm, Jong-in
Fonte: PubMed Publicador: PubMed
Tipo: Artigo de Revista Científica
EN
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Zinc oxide nanorods (ZnO NRs) have emerged in recent years as extremely useful, optical signal-enhancing platforms in DNA and protein detection. Although the use of ZnO NRs in biodetection has been demonstrated so far in systems involving many ZnO NRs per detection element, their future applications will likely take place in a miniaturized setting while exploiting single ZnO NRs in a low-volume, high-throughput bioanalysis. In this paper, we investigate temporal and spatial characteristics of biomolecular fluorescence on individual ZnO NR systems. Quantitative and qualitative examinations of biomolecular intensity and photostability are carried out as a function of two important criteria, time and position along the long axis (length) of NRs. Photostability profiles are also measured with respect to the position on NRs and compared to those characteristics of biomolecules on polymeric control platforms. Unlike uniformly distributed signal observed on the control platforms, both fluorescence intensity and photostability are position-dependent on individual ZnO NRs. We have identified a unique phenomenon of highly localized, fluorescence intensification on the nanorod ends (FINE) of well-characterized, individual ZnO nanostructures. When compared to the polymeric controls...

Photovoltaic properties of ZnO nanorods/p-type Si heterojunction structures

Pietruszka, Rafal; Witkowski, Bartlomiej Slawomir; Luka, Grzegorz; Wachnicki, Lukasz; Gieraltowska, Sylwia; Kopalko, Krzysztof; Zielony, Eunika; Bieganski, Piotr; Placzek-Popko, Ewa; Godlewski, Marek
Fonte: Beilstein-Institut Publicador: Beilstein-Institut
Tipo: Artigo de Revista Científica
Publicado em 14/02/2014 EN
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Selected properties of photovoltaic (PV) structures based on n-type zinc oxide nanorods grown by a low temperature hydrothermal method on p-type silicon substrates (100) are investigated. PV structures were covered with thin films of Al doped ZnO grown by atomic layer deposition acting as transparent electrodes. The investigated PV structures differ in terms of the shapes and densities of their nanorods. The best response is observed for the structure containing closely-spaced nanorods, which show light conversion efficiency of 3.6%.

Zinc Oxide Nanomaterials for Biomedical Fluorescence Detection

Hahm, Jong-in
Fonte: PubMed Publicador: PubMed
Tipo: Artigo de Revista Científica
Publicado em /01/2014 EN
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One-dimensional zinc oxide nanomaterials have been recently developed into novel, extremely effective, optical signal-enhancing bioplatforms. Their usefulness has been demonstrated in various biomedical fluorescence assays. Fluorescence is extensively used in biology and medicine as a sensitive and noninvasive detection method for tracking and analyzing biological molecules. Achieving high sensitivity via improving signal-to-noise ratio is of paramount importance in fluorescence-based, trace-level detection. Recent advances in the development of optically superior one-dimensional materials have contributed to this important biomedical area of detection. This review article will discuss major research developments that have so far been made in this emerging and exciting topical field. The discussion will cover a broad range of subjects including synthesis of zinc oxide nanorods (ZnO NRs), various properties differentiating them as suitable optical biodetection platforms, their demonstrated applicability in DNA and protein detection, and the nanomaterial characteristics relevant for biomolecular fluorescence enhancement. This review will then summarize the current status of ZnO NR-based biodetection and further elaborate future utility of ZnO NR platforms for advanced biomedical assays...

Sol–gel synthesized zinc oxide nanorods and their structural and optical investigation for optoelectronic application

Foo, Kai Loong; Hashim, Uda; Muhammad, Kashif; Voon, Chun Hong
Fonte: Springer Publicador: Springer
Tipo: Artigo de Revista Científica
Publicado em 25/08/2014 EN
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Nanostructured zinc oxide (ZnO) nanorods (NRs) with hexagonal wurtzite structures were synthesized using an easy and low-cost bottom-up hydrothermal growth technique. ZnO thin films were prepared with the use of four different solvents, namely, methanol, ethanol, isopropanol, and 2-methoxyethanol, and then used as seed layer templates for the subsequent growth of the ZnO NRs. The influences of the different solvents on the structural and optical properties were investigated through scanning electron microscopy, X-ray diffraction, Fourier transform infrared spectroscopy, ultraviolet–visible spectroscopy, and photoluminescence. The obtained X-ray diffraction patterns showed that the synthesized ZnO NRs were single crystals and exhibited a preferred orientation along the (002) plane. In addition, the calculated results from the specific models of the refractive index are consistent with the experimental data. The ZnO NRs that grew from the 2-methoxyethanol seeded layer exhibited the smallest grain size (39.18 nm), largest diffracted intensities on the (002) plane, and highest bandgap (3.21 eV).

Synthesis of zinc oxide nanostructures on graphene/glass substrate by electrochemical deposition: effects of current density and temperature

Hambali, Nur Ashikyn; Yahaya, Hafizal; Mahmood, Mohamad Rusop; Terasako, Tomoaki; Hashim, Abdul Manaf
Fonte: Springer Publicador: Springer
Tipo: Artigo de Revista Científica
Publicado em 11/11/2014 EN
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The electrochemical growth of zinc oxide (ZnO) nanostructures on graphene on glass using zinc nitrate hexahydrate was studied. The effects of current densities and temperatures on the morphological, structural, and optical properties of the ZnO structures were studied. Vertically aligned nanorods were obtained at a low temperature of 75°C, and the diameters increased with current density. Growth temperature seems to have a strong effect in generating well-defined hexagonal-shape nanorods with a smooth top edge surface. A film-like structure was observed for high current densities above -1.0 mA/cm2 and temperatures above 80°C due to the coalescence between the neighboring nanorods with large diameter. The nanorods grown at a temperature of 75°C with a low current density of -0.1 mA/cm2 exhibited the highest density of 1.45 × 109 cm-2. X-ray diffraction measurements revealed that the grown ZnO crystallites were highly oriented along the c-axis. The intensity ratio of the ultraviolet (UV) region emission to the visible region emission, IUV/IVIS, showed a decrement with the current densities for all grown samples. The samples grown at the current density below -0.5 mA/cm2 showed high IUV/IVIS values closer to or higher than 1.0...

Surface Modification of ZnO Nanorods with Hamilton Receptors

Zeininger, Lukas; Klaumünzer, Martin; Peukert, Wolfgang; Hirsch, Andreas
Fonte: MDPI Publicador: MDPI
Tipo: Artigo de Revista Científica
Publicado em 13/04/2015 EN
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A new prototype of a Hamilton receptor suitable for the functionalization of inorganic nanoparticles was synthesized and characterized. The hydrogen bonding receptor was coupled to a catechol moiety, which served as anchor group for the functionalization of metal oxides, in particular zinc oxide. Synthesized zinc oxide nanorods [ZnO] were used for surface functionalization. The wet-chemical functionalization procedure towards monolayer-grafted particles [ZnO-HR] is described and a detailed characterization study is presented. In addition, the detection of specific cyanurate molecules is demonstrated. The hybrid structures [ZnO-HR-CA] were stable towards agglomeration and exhibited enhanced dispersability in apolar solvents. This observation, in combination with several spectroscopic experiments gave evidence of the highly directional supramolecular recognition at the surface of nanoparticles.

An Electrochemical Glucose Sensor Based on Zinc Oxide Nanorods

Marie, Mohammed; Mandal, Sanghamitra; Manasreh, Omar
Fonte: MDPI Publicador: MDPI
Tipo: Artigo de Revista Científica
Publicado em 30/07/2015 EN
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A glucose electrochemical sensor based on zinc oxide (ZnO) nanorods was investigated. The hydrothermal sol–gel growth method was utilized to grow ZnO nanorods on indium tin oxide-coated glass substrates. The total active area of the working electrode was 0.3 × 0.3 cm2 where titanium metal was deposited to enhance the contact. Well aligned hexagonal structured ZnO nanorods with a diameter from 68 to 116 nm were obtained. The excitonic peak obtained from the absorbance spectroscopy was observed at ~370 nm. The dominant peak of Raman spectroscopy measurement was at 440 cm−1, matching with the lattice vibration of ZnO. The uniform distribution of the GOx and Nafion membrane that has been done using spin coating technique at 4000 rotations per minute helps in enhancing the ion exchange and increasing the sensitivity of the fabricated electrochemical sensor. The amperometric response of the fabricated electrochemical sensor was 3 s. The obtained sensitivity of the fabricated ZnO electrochemical sensor was 10.911 mA/mM·cm2 and the lower limit of detection was 0.22 µM.

Characterization of ZnO Nanorods Grown on GaN Using Aqueous Solution Method

Quang, Hong Le; Chua, Soo-Jin; Loh, Kian Ping; Chen, Zhen; Thompson, Carl V.; Fitzgerald, Eugene A.
Fonte: MIT - Massachusetts Institute of Technology Publicador: MIT - Massachusetts Institute of Technology
Tipo: Artigo de Revista Científica Formato: 69588 bytes; application/pdf
EN
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Uniformly distributed ZnO nanorods with diameter 70-100 nm and 1-2μm long have been successfully grown at low temperatures on GaN by using the inexpensive aqueous solution method. The formation of the ZnO nanorods and the growth parameters are controlled by reactant concentration, temperature and pH. No catalyst is required. The XRD studies show that the ZnO nanorods are single crystals and that they grow along the c axis of the crystal plane. The room temperature photoluminescence measurements have shown ultraviolet peaks at 388nm with high intensity, which are comparable to those found in high quality ZnO films. The mechanism of the nanorod growth in the aqueous solution is proposed. The dependence of the ZnO nanorods on the growth parameters was also investigated. While changing the growth temperature from 60°C to 150°C, the morphology of the ZnO nanorods changed from sharp tip (needle shape) to flat tip (rod shape). These kinds of structure are useful in laser and field emission application.; Singapore-MIT Alliance (SMA)

Growth of ZnO Nanorods on GaN Using Aqueous Solution Method

Quang, Hong Le; Chua, Soo-Jin; Loh, Kian Ping; Chen, Zhen; Thompson, Carl V.; Fitzgerald, Eugene A.
Fonte: MIT - Massachusetts Institute of Technology Publicador: MIT - Massachusetts Institute of Technology
Tipo: Artigo de Revista Científica Formato: 553272 bytes; application/pdf
EN
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Uniformly distributed ZnO nanorods with diameter 80-120 nm and 1-2µm long have been successfully grown at low temperatures on GaN by using the inexpensive aqueous solution method. The formation of the ZnO nanorods and the growth parameters are controlled by reactant concentration, temperature and pH. No catalyst is required. The XRD studies show that the ZnO nanorods are single crystals and that they grow along the c axis of the crystal plane. The room temperature photoluminescence measurements have shown ultraviolet peaks at 388nm with high intensity, which are comparable to those found in high quality ZnO films. The mechanism of the nanorod growth in the aqueous solution is proposed. The dependence of the ZnO nanorods on the growth parameters was also investigated. While changing the growth temperature from 60°C to 150°C, the morphology of the ZnO nanorods changed from sharp tip with high aspect ratio to flat tip with smaller aspect ratio. These kinds of structure are useful in laser and field emission application.; Singapore-MIT Alliance (SMA)

Zinc Oxide Nanostructures by Solvothermal Synthesis

Sotomayor, C.; González, G.; Benavente Espinosa, Eglantina; Segovia, M.
Fonte: Taylor & Francis Publicador: Taylor & Francis
Tipo: Artículo de revista
EN
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Artículo de publicación ISI; The synthesis, characterization, and properties of three types of one-dimensional zinc oxide nanostructures are described. They were obtained by solvothermal treatment of nanometric zinc oxide as zinc ion source (i.e., starting from pure oxide), from a mixture of the oxide with stearic acid, and from intercalated oxide in the layered nanocomposite ZnO(stearic acid)0.38. The reactions were performed at 180◦C in a (1:1) ethanol/water mixture. Depending on the precursor and reaction times, morphologically homogenous phases corresponding to ZnO nanoneedles, nanorods or nanowires were obtained. Photoluminescence emissions were observed and are attributed to exciton transitions and to the presence of intrinsic defects such as oxygen and zinc interstitials. The band gap energies (Eg) were comparable to the values of bulk ZnO. The prepared nanostructures showed photocatalytic activities with respect to the degradation of methylene blue which were comparable to that of bulk zinc oxide.; Research partially financed by FONDECYT (Contracts 1090282, 1111029) Basal Financing Program CONICYT, FB0807 (CEDENNA), Millennium Science Nucleus P10-061-F.

Evolution of Zinc Oxide Nanostructures Grown on Graphene by Ultrasonic Spray Pyrolysis and Its Statistical Growth Modelling

Ali, Amgad Ahmed; Hashim, Abdul Manaf
Fonte: Springer US Publicador: Springer US
Tipo: Artigo de Revista Científica
Publicado em 25/11/2015 EN
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The evolution of zinc oxide nanostructures grown on graphene by alcohol-assisted ultrasonic spray pyrolysis was investigated. The evolution of structures is strongly depended on pyrolysis parameters, i.e., precursor molarity, precursor flow rate, precursor injection/deposition time, and substrate temperature. Field-effect scanning electron microscope analysis, energy dispersive X-ray spectroscopy, X-ray diffraction, and transmission electron microscopy were used to investigate the properties of the synthesized nanostructures and to provide evidence for the structural changes according to the changes in the pyrolysis parameters. The optimum parameters to achieve maximum density and well-defined hexagonally shaped nanorods were a precursor molarity of 0.2 M, an injection flow rate of 6 ml/min, an injection time of 10 min, and a substrate temperature of 250–355 °C. Based on the experimental results, the response surface methodology (RSM) was used to model and optimize the independent pyrolysis parameters using the Box-Behnken design. Here, the responses, i.e., the nanostructure density, size, and shape factor, are evaluated. All of the computations were performed using the Design-Expert software package. Analysis of variance (ANOVA) was used to evaluate the results of the model and to determine the significant values for the independent pyrolysis parameters. The evolution of zinc oxide (ZnO) structures are well explained by the developed modelling which confirms that RSM is a reliable tool for the modelling and optimization of the pyrolysis parameters and prediction of nanostructure sizes and shapes.

In-situ hydrothermal synthesis of zinc oxide nanostructures using microheaters

Lin, Wei-Chih; Lin, Yu-Ching; Esashi, Masayoshi; Seshia, Ashwin A.
Fonte: IEEE Publicador: IEEE
Tipo: Article; accepted version
EN
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This is the author accepted manuscript. The final version is available from IEEE via http://dx.doi.org/10.1109/TNANO.2015.2468076; A technique for in-situ hydrothermal synthesis of transversely suspended zinc oxide nanowires (ZnO NWs) using microfabricated heaters is presented. A number of issues relating to seed layer preparation, directed alignment, local heating control and the concentration of the synthesis solution are investigated for this method. It is shown that ZnO NWs can be synthesized and aligned from the ZnO seed surface to bridge two adjacent microheater elements. Moreover, hybrid ZnO nanotubes and nanorods are also synthesized by controlling the concentration of the synthesis solution employed. The crystalline structure of synthesized ZnO nanostructures are characterized by the transmission electron microscope (TEM) and selective area electron diffraction (SAED). Finally, ZnO NW devices based on proposed microheater synthesis approach are characterised for UV photoresponsivity demonstrating the potential of this approach to address practical device applications.; Funding support by the WPI-AIMR, Tohoku University and by the Royal Society is gratefully acknowledged.