Molecularly imprinted silver-halide reflection holograms for label-free opto-chemical sensing

Hierarchical structuring of materials offers exciting opportunities to construct functional devices that exploit the ordering at different length scales to impart key functional properties. Herein, multiple processes are combined to create complex materials organized at the molecular, nano, and microscales for selective detection of testosterone by label-free opto-chemical sensing. Molecular imprinting is used to construct molecular scale analyte-selective cavities. Microphase separation produces a porous polymer film within which sensitized silver halide nanocolloids are dispersed by a process of infusion and controled precipitation, then converted to periodic layers of silver nanoparticles by holographic patterning followed by chemical development. Testosterone binding is followed via wavelength changes of the holographic reflection peak as a function of testosterone concentration and incubation time. Polymer cross-linking and film porosity are optimized with respect to the needs of both molecular recognition and hologram quality. The silver halide infusion step does not destroy the molecular selectivity of the molecularly imprinted polymers (MIP). Selective, label-free sensing of testosterone is possible at concentrations down to 1 μm. The approach is generic and should be applicable to many types of molecules and conventional MIP formulations, individually or in multiplexed arrays.