PDMS-gold nanocomposite platforms with enhanced sensing properties.

Gold-poly(dimethyl siloxoxane) (Au-PDMS) nanocomposite films with a high elasticity were fabricated for sensing experiments. The nanocomposite was prepared by a novel in-situ method by using the ethanol solution of the chloroauric acid. The high rate of permeation of ethanol in the polymer film, compared to an aqueous solution, allows the introduction of the gold precursor into the polymer network with a higher rate and, thus the reduction reaction is accelerated. The strong hydrophobicity of the as-prepared films precludes the diffusion of aqueous solutions of biomolecules in the polymer network, essential for sensing purposes. In order to modify the morphology and the surface properties of the samples, they have been heat-treated and the polymer network has been expanded mechanically by repeated swellings and shrinkages. As a result, the free volume of the polymer is increased substantially and thus, the biosensing capability of the material is improved. The effect of gold nanoparticles on the porosity and the mechanical properties of the material has been studied. The highest value of the sensitivity (around 70 nm/RIU) has been obtained for the samples that were annealed and, subsequently swollen in toluene. Biosensing experiments involving antigen-antibody interactions showed a high sensitivity. The results of this work are relevant for sensing in a microfluidic environment.