We describe the design and fabrication of composite agarose gels, highly loaded with silver nanoparticles. Because the gel can collapse upon drying and recover when rehydrated, it can be foreseen as an excellent mechanical molecular trap that additionally gives rise to dynamic hot spots as the network volume decreases and the silver particles get close to each other, thereby generating the high electromagnetic fields that are needed for ultradetection. Additionally, as silver nanoparticles are physically trapped inside the polymer network, analytes can be washed out by dialysis when immersed in a washing solution, so that recycling can be achieved. Finally, the use of SERS for ultradetection of dichlorodiphenyl-trichloroethane (DDT) is reported for the first time, demonstrating the ability of this novel nanocomposite material to reversibly sequester nonconventional SERS analytes.

Gold nanoparticles are obtained by reduction of a Au(iii) precursor within an agarose hydrogel where they form percolating networks upon partial dehydration and shrinkage of the gel.

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