Surface-enhanced Raman scattering and micro-Raman imaging of Langmuir-Blodgett films of rhodium phthalocyanine

Rhodium phthalocyanine (RhPc) was synthesized and ultra thin Langmuir-Blodgett (LB) films of RhPc were successfully fabricated. The LB film characterization was carried out using both UV-vis absorption spectra and Raman scattering. The Raman spectroscopy was carried out using 633 and 780 nm laser lines. LB films were deposited onto Ag nanoparticles to achieve the surface-enhanced pre-resonance Raman scattering (pre-SERRS) and surface-enhanced Raman scattering (SERS) for both laser lines, respectively, which allowed the characterization of the RhPc ultra thin films. The morphology of the LB RhPc neat film is extracted from micro-Raman imaging. (C) 2003 Elsevier B.V. All rights reserved.

Taking Advantage of Electrostatic Interactions To Grow Langmuir-Blodgett Films Containing Multilayers of the Phospholipid Dipalmitoylphosphatidylglycerol

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

Iron phthalocyanine in non-aqueous medium forming layer-by-layer films: growth mechanism, molecular architecture and applications

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

Layer-by-Layer Technique as a New Approach to Produce Nanostructured Films Containing Phospholipids as Transducers in Sensing Applications

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

Molecular architecture and electrical properties in evaporated films of cobalt phthalocyanine

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

Natural Polysaccharides as Active Biomaterials in Nanostructured Films for Sensing

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

Toward the Optimization of an e-Tongue System Using Information Visualization: A Case Study with Perylene Tetracarboxylic Derivative Films in the Sensing Units

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

Numerical simulation of the liquid phase in SnO2 thin film deposition by sol-gel-dip-coating

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Immobilization of streptavidin in sol-gel films: Application on the diagnosis of hepatitis C virus

Recent advances have accelerated the development of biosensors for the analysis of specific gene sequences. In this kind of biosensor, a DNA probe is immobilized on a transducer and the hybridization with the target DNA is monitored by suitable methodology. In the present work, the streptavidin (STA) was encapsulated in thin films siloxane-poly(propylene oxide) hybrids prepared by sol-gel method and deposited on the graphite electrode surface by dip-coating process. Biotinylated 18-mer probes were immobilized through STA and a novel amperometric DNA biosensor for the detection and genotyping of the hepatitis C virus (genotypes 1, 2A/C, 2B and 3) is described. The HCV RNA from serum was submitted to reverse transcriptase-linked polymerase chain reaction (RT-PCR) and biotin-labeled cDNA was obtained. Thus, the cDNA was hybridized to the target-specific oligonucleotide probe immobilized on the graphite electrode surface and following the avidin-peroxidase conjugate was added. The enzymatic response was investigated by constant potential amperometry at -0.45 V versus Ag/AgCl using H2O2 and KI solutions. HCV RNA negative and positive controls and positive samples of sera patients were analyzed and the results were compared to commercial kit. The proposed methodology appeared to be suitable and convenient tool for streptavidin immobilization and diagnose of HCV disease. (c) 2006 Elsevier B.V. All rights reserved.

Growth of Al2O3 thin film by oxidation of resistively evaporated Al on top of SnO2, and electrical properties of the heterojunction SnO2/Al2O3

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Enhancement of optical absorption by modulation of the oxygen flow of TiO2 films deposited by reactive sputtering

Oxygen-deficient TiO2 films with enhanced visible and near-infrared optical absorption have been deposited by reactive sputtering using a planar diode radio frequency magnetron configuration. It is observed that the increase in the absorption coefficient is more effective when the O-2 gas supply is periodically interrupted rather than by a decrease of the partial O-2 gas pressure in the deposition plasma. The optical absorption coefficient at 1.5 eV increases from about 1 x 10(2) cm(-1) to more than 4 x 10(3) cm(-1) as a result of the gas flow discontinuity. A red-shift of similar to 0.24 eV in the optical absorption edge is also observed. High resolution transmission electron microscopy with composition analysis shows that the films present a dense columnar morphology, with estimated mean column width of 40nm. Moreover, the interruptions of the O-2 gas flow do not produce detectable variations in the film composition along its growing direction. X-ray diffraction and micro-Raman experiments indicate the presence of the TiO2 anatase, rutile, and brookite phases. The anatase phase is dominant, with a slight increment of the rutile and brookite phases in films deposited under discontinued O-2 gas flow. The increase of optical absorption in the visible and near-infrared regions has been attributed to a high density of defects in the TiO2 films, which is consistent with density functional theory calculations that place oxygen-related vacancy states in the upper third of the optical bandgap. The electronic structure calculation results, along with the adopted deposition method and experimental data, have been used to propose a mechanism to explain the formation of the observed oxygen-related defects in TiO2 thin films. The observed increase in sub-bandgap absorption and the modeling of the corresponding changes in the electronic structure are potentially useful concerning the optimization of efficiency of the photocatalytic activity and the magnetic doping of TiO2 films. (C) 2012 American Institute of Physics. [http://dx.doi.org/10.1063/1.4724334]

Electrochemical impedance spectroscopy as a tool to estimate thickness in PB films

The analysis of the faradaic impedance of electroactive films provides a characteristic point from which it is possible to estimate the thickness of thin films. Thus, electrochemical impedance spectroscopy was used in this paper as a fast and easy technique to estimate this thickness. The proposed method was checked on PB films. (c) 2006 Elsevier B.V. All rights reserved.

Influence of particle size on the photoactivity of Ti/TiO2 thin film electrodes, and enhanced photoelectrocatalytic degradation of indigo carmine dye

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

Asymmetrical penetration of microwave in a conducting media and determination of microwave conductivity for very thin samples using electron spin resonance

Dyson's theory of conduction electron spin resonance (CESR) has been used in the limit d less than or equal to delta (d being the thickness of the sample and delta the skin depth of the microwave field) to obtain the microwave conductivity from the (A/B) ratio of the CESR absorbed power derivative. In this work we calculate the CESR absorbed power derivative using Kaplan's approach and show that the (A/B) ratio can be enhanced if asymmetrical penetration of microwave is used, which means that the microwave field enters into the sample from one of the faces. Therefore, the determination of the microwave conductivity from the (A/B) ratio of the CESR line can be performed for thinner samples. Experimentally, asymmetrical penetration can be obtained if one of the sample's faces is covered with a thin gold layer. The determination of microwave conductivity in conducting polymers films is among the possible applications of this method. (C) 2001 Elsevier B.V. Ltd. All rights reserved.

Study of the growth process of in situ polyaniline deposited films

Polyaniline (PAni) thin films were deposited onto BK7 glass substrates using the in situ deposition technique. The control of the time and the aniline concentration in the PAni polymerization reaction on the film deposition allowed us to prepare films with different thickness, down to similar to 25 nm. The film growth process was monitored by measuring the UV-vis spectra and the AFM height profiles of the film surface. The curves of adsorption kinetics were analyzed with the Avrami's model, yielding an exponent it n = 3, thus indicating nucleation of spheroids at the initial stages of polymerization that grow through a diffusion process. AFM images of the surface height profiles corroborate this hypothesis, with spheroids growing with no preferred orientation during the in situ deposition. (C) 2007 Elsevier B.V. All rights reserved.