Studies on the interaction between humic substances and conducting polymers for sensor application

The interaction between humic substances and poly(o-ethoxyaniline) (POEA), a conducting polymer, was investigated for both solution and self-assembled films. The results have shown that the humic substances induce a doping of POEA by protonation, as indicated by UV-Vis and Raman spectroscopies. The atomic force microscopy (AFM) studies on the self-assembled films have shown that the average roughness of the polymer film has increased after exposing it to humic substances (fulvic and humic acids), consistent with the interaction between POEA and humic substances. However, this change in morphology is reversible by washing the films with water in agreement with the electrical data allowing using this system in sensor applications. Here, the sensor formed by an array of different sensing units was able to detect and distinguish humic substances in aqueous solution, as shown by multivariate analysis (principal component analysis). The motivation to detect humic substance comes due to its importance in terms of quality control of water or soil. ©2005 Sociedade Brasileira de Química.

Effect of controlled conductivity on thermal sensing property of 0-3 pyroelectric composite

Composite films made of lead zirconate titanate ceramic particles coated with polyaniline and poly(vinylidene fluoride) - PZT-PAni/PVDF were produced by hot pressing the powder mixtures in the desired ceramic volume fraction. The ceramic particles were coated during the polyaniline synthesis and the conductivity of the conductor polymer was controlled by different degrees of protonation. Composites were characterized by Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), ac and dc electrical measurements, the longitudinal d33 piezo coefficient and the photopyroelectric response. Results showed that the presence of PAni increased the dielectric permittivity of the composite and allowed better efficiency in the poling process, which increased the piezo- and pyroelectric activities of the composite film and reduced both the poling time and the poling electric field. The thermal sensing of the material was also analyzed, showing that this composite can be used as pyroelectric sensor. © 2013 IOP Publishing Ltd.

Fast assembly of non-thiolated DNA on gold surface at lower pH

In a typical protocol for attaching DNA to a gold electrode, thiolated DNA is incubated with the electrode at neutral pH overnight. Here we report fast adsorption of non-thiolated DNA oligomers on gold electrodes at acidic pH (i.e., pH ~3.0). The peak-to-peak potential difference and the redox peak currents in typical cyclic voltammetry of [Fe(CN)6]3- are investigated to monitor the attachment. Compared with incubation at neutral pH, the lower pH can significantly promote the adsorption processes, enabling efficient adsorption even in 30min. The adsorption rate is DNA concentration-dependent, while the ionic strength shows no influence. Moreover, the adsorption is base-discriminative, with a preferred order of A>C≫G, T, which is attributed to the protonation of A and C at low pH and their higher binding affinity to gold surface. The immobilized DNA is functional and can hybridize with its complementary DNA but not a random DNA. This work is promising to provide a useful time-saving strategy for DNA assembly on gold electrodes, allowing fast fabrication of DNA-based biosensors and devices. © 2013 Elsevier Inc.

Otimização do processamento para obtenção de compósitos polímero/cerâmica com propriedades piezo e piroelétricas

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Caracterização e estudo do comportamento térmico dos adutos flunixina-meglumina e diclofenaco-meglumina

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Theoretical insight into the mechanism for the inhibition of the cysteine protease cathepsin B by 1,2,4-thiadiazole derivatives

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Estudo de estirilpironas de Cryptocarya mandioccana por espectrometria de massas e análise configuracional por ressonância magnética nuclear e dicroísmo circular

Pós-graduação em Química - IQ

Combining Experimental Evidence and Molecular Dynamic Simulations To Understand the Mechanism of Action of the Antimicrobial Octapeptide Jelleine-I

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

Oligomeric state and structural stability of two hyperthermophilic beta-glucosidases from Thermotoga petrophila

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

Complexation of some trivalent lanthanides, scandium(III) and thorium(IV) by benzylidenepyruvates and cinnamylidenepyruvate in aqueous solution

The protonation constants of benzylidenepyruvate, 2-chloro-, 4-chlorobenzylidinepyruvate and cinnamylidenepyruvate as well as the stability constants of their binary 1:1 complexes with Cu(II), La(III), Pr(III), Sm(III), Lu(III), Sc(III) and Th(IV) have been determined spectrophotometrically in an aqueous medium at 25 °C and ionic strength 0.500 M, held with sodium perchlorate. Coordination centres in the aforementioned ligands are suggested. © 1995.

Estudos computacionais de esfingomielinases D: docking, dinâmica molecular e métodos híbridos QM/MM

Pós-graduação em Biofísica Molecular - IBILCE