Molecularly designed layer-by-layer (LbL) films to detect catechol using information visualization methods

The control of molecular architectures has been exploited in layer-by-layer (LbL) films deposited on Au interdigitated electrodes, thus forming an electronic tongue (e-tongue) system that reached an unprecedented high sensitivity (down to 10-12 M) in detecting catechol. Such high sensitivity was made possible upon using units containing the enzyme tyrosinase, which interacted specifically with catechol, and by processing impedance spectroscopy data with information visualization methods. These latter methods, including the parallel coordinates technique, were also useful for identifying the major contributors to the high distinguishing ability toward catechol. Among several film architectures tested, the most efficient had a tyrosinase layer deposited atop LbL films of alternating layers of dioctadecyldimethylammonium bromide (DODAB) and 1,2-dipalmitoyl-sn-3-glycero-fosfo-rac-(1-glycerol) (DPPG), viz., (DODAB/DPPG)5/DODAB/Tyr. The latter represents a more suitable medium for immobilizing tyrosinase when compared to conventional polyelectrolytes. Furthermore, the distinction was more effective at low frequencies where double-layer effects on the film/liquid sample dominate the electrical response. Because the optimization of film architectures based on information visualization is completely generic, the approach presented here may be extended to designing architectures for other types of applications in addition to sensing and biosensing. © 2013 American Chemical Society.

Lodos de esgoto, escória de aciaria e lama cal na cultura da soja sob sistema plantio direto em latossolo vermelho

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Estudo por simulação computacional da interação entre polieletrólitos fracos e macroíons esféricos

Pós-graduação em Biofísica Molecular - IBILCE

Emprego do extrato de moringa (Moringa oleífera Lamarck) na clarificação do caldo de cana para produção de açúcar

Pós-graduação em Microbiologia Agropecuária - FCAV

Escoria de aciaria , lama cal e lodos de esgoto no cultivo da soja sob sistema de plantio direto

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Interação de ácido algínico com surfactantes catiônicos em solução aquosa

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Extratos de moringa no tratamento do caldo de cana e reflexos sobre a fermentação alcoólica

Pós-graduação em Agronomia (Produção Vegetal) - FCAV

Disponibilidade de fósforo em solo tratado com resíduos urbanos e industriais sob sistema de plantio direto cultivado com soja

Pós-graduação em Agronomia (Agricultura) - FCA

Adsorção de polieletrólitos em superfícies opostamente carregadas

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Characterization and application of nanostructured films containing Au and TiO2 nanoparticles supported in bacterial cellulose

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Emprego do extrato de Moringa (Moringa oleífera Lamarck) na clarificação do caldo de cana para produção de açúcar e etanol

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Analysis of the environmental impact on a stream: is only tannery to blame?

The contribution of wastewater from a tannery industry to the pollution of a stream was investigated. The main parameters studied were biochemical oxygen demand, chemical oxygen demand, chromium, dissolved oxygen, fecal and total conforms, nitrogen, oils and greases, pH, phosphorous, sulfides, suspended solids, turbidity, and volatile solids. Three sampling points were located: (I) at the discharge point of tannery wastewater, (2) 50 m upstream, and (3) 80 m downstream of discharge point. Also was investigated the pollution at the stream source.

Long-Term Stability at High Temperatures for Birefringence in PAZO/PAH Layer-by-Layer Films

Optical memories with long-term stability at high temperatures have long been pursued in azopolymers with photoinduced birefringence. In this study, we show that the residual birefringence in layer-by-layer (LbL) films made with poly[1-[4-(3-carboxy-4 hydroxyphenylazo)benzene sulfonamido]-1,2-ethanediyl, sodium salt] (PAZO) alternated with poly(allylamine hydrochloride) (PAH) can be tuned by varying the extent of electrostatic interactions with film fabrication at different pHs for PAH. The dynamics of both writing and relaxation processes could be explained with a two-stage mechanism involving the orientation of the chromophores per se and the chain movement. Upon calculating the activation energies for these processes, we demonstrate semiquantitatively that reduced electrostatic interactions in films prepared at higher pH, for which PAH is less charged, are responsible for the longer stability at high temperatures. This is attributed to orientation of PAZO chromophores via cooperative aggregation, where the presence of counterions hindered relaxation.

Influence of the type of phospholipid head and of the conformation of the polyelectrolyte on the growth of calcium carbonate thin films on LB/LbL matrices

Calcium carbonate is one of the most important biominerals, and it is the main constituent of pearls, seashells, and teeth. The in vitro crystallization of calcium carbonate using different organic matrices as templates has been reported. In this work, the growth of calcium carbonate thin films on special organic matrices consisting of layer-by-layer (LbL) polyelectrolyte films deposited on a pre-formed phospholipid Langmuir-Blodgett (LB) film has been studied. Two types of randomly coiled polyelectrolytes have been used: lambda-carrageenan and poly(acrylic acid). A precoating comprised of LB films has been prepared by employing a negatively charged phospholipid, the sodium salt of dimyristoilphosphatidyl acid (DMPA), or a zwitterionic phospholipid, namely dimyristoilphosphatidylethanolamine (DMPE). This approach resulted in the formation of particulate calcium carbonate continuous films with different morphologies, particle sizes, and roughness, as revealed by scanning electron microscopy (SEM) and atomic force microscopy (AFM). The crystalline structure of the calcium carbonate particles was analyzed by Raman spectroscopy. The randomly coiled conformation of the polyelectrolytes seems to be the main reason for the formation of continuous films rather than CaCO3 isolated crystals. (C) 2012 Elsevier B.V. All rights reserved.

Tailoring Molecular Architectures with Cobalt Tetrasulfonated Phthalocyanine: Immobilization in Layer-by-Layer Films and Sensing Applications

In the field of organic thin films, manipulation at the nanoscale can be obtained by immobilization of different materials on platforms designed to enhance a specific property via the layer-by-layer technique. In this paper we describe the fabrication of nanostructured films containing cobalt tetrasulfonated phthalocyanine (CoTsPc) obtained through the layer-by-layer architecture and assembled with linear poly(allylamine hydrochloride) (PAH) and poly(amidoamine) dendrimer (PAMAM) polyelectrolytes. Film growth was monitored by UV-vis spectroscopy following the Q band of CoTsPc and revealed a linear growth for both systems. Fourier transform infrared (FTIR) spectroscopy showed that the driving force keeping the structure of the films was achieved upon interactions of CoTsPc sulfonic groups with protonated amine groups present in the positive polyelectrolyte. A comprehensive SPR investigation on film growth reproduced the deposition process dynamically and provided an estimation of the thicknesses of the layers. Both FTIR and SPR techniques suggested a preferential orientation of the Pc ring parallel to the substrate. The electrical conductivity of the PAH films deposited on interdigitated electrodes was found to be very sensitive to water vapor. These results point to the development of a phthalocyanine-based humidity sensor obtained from a simple thin film deposition technique, whose ability to tailor molecular organization was crucial to achieve high sensitivity.