Urea sensing materials via solidified crystalline colloidal arrays

An intelligent urea sensing material via solidified crystalline colloidal array (SCCA) was prepared. The urease—the recognition element was incorporated into the SCCA, which is a mesoscopically periodic crystalline colloidal array (CCA) of spherical polystyrene colloids polymerized within a thin polymer hydrogel film. CCA can efficiently diffract visible light meeting the Bragg condition. When urease in the SCCA interacts with urea, the hydrogel swells in response to the urea concentration. The swelling of the hydrogel changes the periodicity of the CCA, which results in a shift in the diffracted wavelength; hence, the urea concentration can be measured. In addition, the effects of the thickness of SCCA on the response rate of the urea sensing SCCA are studied experimentally as well.