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Presidente Prudente, Brazil

Cabrera F.C.,Quimica e Biologia | Dognani G.,Quimica e Biologia | Faita F.L.,University of Minho | dos Santos R.J.,Sao Paulo State University | And 4 more authors.
Journal of Materials Science | Year: 2016

Natural rubber microfluidic devices are based on the replication of microchannels and chambers through the casting of latex and combine the flexibility and transparency of the polymeric platform. Natural rubber is a proposed alternative material to prepare microfluidic devices, owing to the advantages of flexibility, eco-friendliness, and lower cost compared to other commonly used polymeric microfluidic materials. However, the challenges for the use of natural rubber are the leaching of compounds when it is in contact with fluids, the low stretching resistance, and the decreases of transparency rate in terms of the water absorption rate. To overcome these issues, we report the evaluation of the essential mechanical, optical, and structural properties of natural rubber for centrifuged and pre-vulcanized rubber membranes, as well as the polymeric coating over the membrane surfaces. We propose the centrifugation process for decreasing the leach composition of the natural rubber platform and vulcanization to improve the mechanical resistance of the polymeric membrane devices. The polymeric coating prevents the leaching of compounds from natural rubber membranes and water absorption without significant reduction in transparency or increase in the hydrophobicity of the surface. Once the centrifuging, vulcanization, and coating processes improve the rubber properties, this polymer will become an alternative flexible and low-cost material for microfluidic technology. © 2015, Springer Science+Business Media New York.

Alessio P.,Quimica e Biologia | Alessio P.,University of Valladolid | Rodriguez-Mendez M.L.,University of Valladolid | De Saja Saez J.A.,University of Valladolid | Constantino C.J.L.,Quimica e Biologia
Physical Chemistry Chemical Physics | Year: 2010

The application of organic thin films as transducer elements in electronic devices has been widely exploited, with the electrostatic layer-by-layer (LbL) technique being one of the most powerful tools to produce such films. The conventional LbL method, however, is restricted in many cases to water soluble compounds. Here, an alternative way to produce LbL films containing iron phthalocyanine (FePc) in non-aqueous media (chloroform) is presented. This film fabrication was made possible by exploiting the specific interactions between Fe and NH2 groups from PAH, poly(allylamine hydrochloride) used as the supporting layer, leading to the formation of bilayers structured as (PAH/FePc)n. We have also incorporated silver nanoparticles (AgNPs) in LbL films with (PAH/FePc/AgNP)n trilayers, making it possible to achieve the surface-enhanced Raman scattering (SERS) phenomenon. The molecular architecture of the LbL films was determined through different techniques. The growth was monitored with UV-Vis absorption spectroscopy, their morphology characterized by optical and scanning electron (SEM) microscopes, and their molecular organization determined using FTIR. The electrochemical properties of the LbL films were successfully applied in detecting dopamine in KCl aqueous solutions at different concentrations using cyclic voltammetry. The results confirmed that the LbL films from FePc in non-aqueous media keep their electroactivity, while showing an interesting electrocatalytic effect. The SERS phenomenon suggested that FePc aggregates might be directly involved in the maintenance of the electroactivity of the LbL films. © 2010 the Owner Societies.

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