Compositional modulation and surface stability in InGaP films: Understanding and controlling surface properties

We investigate the formation of compositional modulation and atomic ordering in InGaP films. Such bulk properties - as well as surface morphologies - present a strong dependence on growth parameters, mainly the V/III ratio. Our results indicate the importance of surface diffusion and, particularly, surface reconstruction for these processes. Most importantly from the application point of view, we show that the compositional modulation is not necessarily coupled to the surface instabilities, so that smooth InGaP films with periodic compositional variation could be obtained. This opens a new route for the generation of templates for quantum dot positioning and three-dimensional arrays of nanostructures. © 2007 American Institute of Physics.

Strain relaxation and stress-driven interdiffusion in InAsInGaAsInP nanowires

The authors have investigated strain relaxation in InAsInGaAsInP nanowires (NW's). Transmission electron microscopy images show an additional stress field attributed to compositional modulation in the ternary layer, which disrupts NW formation and drives Ga interdiffusion into InAs, according to grazing incidence x-Ray diffraction under anomalous scattering conditions. The strain profile along the NW, however, is not significantly affected when interdiffusion is considered. Results show that the InAs NW energetic stability is preserved with the introduction of ternary buffer layer in the structure. © 2007 American Institute of Physics.

Treatment of experimental periodontitis in rats using repeated adjunctive antimicrobial photodynamic therapy

The aim of this study was to histologically and histometrically evaluate the influence of repeated adjunctive antimicrobial photodynamic therapy (aPDT) on bone loss (BL) in furcation areas in rats. Periodontitis was induced by placing a ligature around the mandibular molar in 75 rats. The animals were divided into five groups: the SS group was treated with saline solution (SS); the SRP group received scaling and root planing (SRP); the aPDT1 group received SRP as well as toluidine blue (TBO) and low-level laser therapy (LLLT; InGaAlP, 660 nm; 4.94 J/cm2/point) postoperatively at 0 h; the aPDT2 group received SRP as well as TBO and LLLT postoperatively at 0, 24, 28, and 72 h; and the aPDT3 group received SRP, TBO, and LLLT postoperatively at 0, 48, 96, and 144 h. The area of BL in the furcation region of the molar was histometrically analyzed. Data were analyzed statistically (P < 0.05). Animals treated with a single episode of aPDT showed less BL at days 7 and 30 than those who received only SRP treatment. No significant differences were found among the aPDT groups (P > 0.05). Repeated aPDT did not improve BL reduction when compared to a single episode of aPDT. © 2012 Springer-Verlag London Ltd.

Quantification of water in ethanol using a photothermal transparent transducer

Ethanol with added water may be found during the process of assessing its physical and chemical properties. This addition can damage automotive vehicle engines and also may contribute to tax evasion. The present contribution describes a method based on a photothermal transparent transducer to determine the water content in ethanol. A chamber with a window of lithium tantalate coated with a thin layer of indium tin oxide was used, and a 1450-nm laser diode was employed as the excitation source. The results indicated a nearly linear response of the apparatus, as a function of the water content in water/ethanol solutions ranging from 0 to 100 (vol.%). The results for the dependency of the photothermal signal on the laser power and chopping frequency suggested that reliable results can be obtained using laser power and chopping rates above 100 mW and 10 Hz, respectively. The results reported here may be useful in the development of an alternative method that can provide real-time data on the water concentration in ethanol in a rapid, portable and unambiguous way, and that can be easily used in laboratory analyses or in gas stations. © 2013 Elsevier B.V.

Preparation and photoluminescence characteristics of In(OH) 3:xTb3+ obtained by Microwave-Assisted Hydrothermal method

Crystalline terbium-doped indium hydroxide structures were prepared by a rapid and efficient Microwave-Assisted Hydrothermal (MAH) method. Nanostructures were obtained at a low temperature. FE-SEM images confirm that these samples are composed of 3D nanostructures. XRD, optical diffuse reflectance and photoluminescence (PL) measurements were used to characterize the products. Emission spectra of terbium-doped indium hydroxide (In(OH)3:xTb 3+) samples under excitation (350.7 nm) presented broad band emission referent to the indium hydroxide matrix and 5D4 → 7F6, 5D4 → 7F 5, 5D4 → 7F4, and 5D4 → 7F3 terbium transitions at 495, 550, 590 and 627 nm, respectively. Relative intensities of the Tb 3+ emissions increased as the concentration of this ion increased from 0, 1, 2, 4 and 8 mol%, of Tb3+, but the luminescence is drastically quenched for the In(OH)3 matrix. © 2012 Elsevier B.V. All rights reserved.

Switchable biosensor controlled by biocatalytic process

The poly(dimethylamino methacrylate) (PDMAEMA) brush-modified indium tin oxide (ITO) electrode was used to test the switch properties of interfacial activity caused by bioelectrochemical signals. The swelling of the polymer brushes increased when the medium's pH changed from alkaline to acid after glucose was added to the system. A pH change generated in situ by means of biocatalytic reactions enabled bioelectrocatalytic interface's reversible activation. © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Desenvolvimento e caracterização de dispositivos luminescentes híbridos

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Estudo do crescimento e caracterização de nanofitas do sistema ITO

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Modelo estatístico de rede de resistores para o estudo de processos de condução em nanocompósitos poliméricos

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Estudo das propriedades elétricas e ópticas de nanocompósitos transparentes e condutores

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Ressonância paramagnética eletrônica (RPE) aplicada em semicondutores orgânicos

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Filmes finos de ZnO como óxidos condutores transparentes aplicados à células solares

Pós-graduação em Ciência e Tecnologia de Materiais - FC

Preparação e estudo termoanalítico dos 2-clorobenzalpiruvatos de alumínio, de gálio, de índio e de escândio no estado sólido

Pós-graduação em Química - IQ

Desenvolvimento de uma câmara fototérmica com transdutor transparente para monitoramento de água em etanol combustível

Pós-graduação em Engenharia Elétrica - FEIS

Síntese de nanofios de óxidos semicondutores para aplicações em dispositivos ópticos e eletrônicos

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)