2 research outputs found

    Order–Disorder Transition in Doped Microgel Colloidal Crystals and Its Application for Optical Sensing

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    Hydrogel photonic crystal-based optical sensors usually can only be used as free-standing films. Here, a doped microgel colloidal crystal film was developed as glucose sensor, which exploits structural order–disorder transition, instead of change in lattice constant, to report an analyte. Changing glucose concentration induces a change in structural order degree in the crystal and hence a change in the intensity of the stop band, and thus reports glucose concentration in the media. The response is fast and reversible. As the overall swelling degree of the gel does not change, it can be used as substrate-attached film

    Glucose-Induced Transition among Three States of a Doped Microgel Colloidal Crystal

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    For the first time here, we report a colloid crystal capable of undergoing transition among three states in response to external stimuli. The colloidal crystal was assembled from poly­(<i>N</i>-isopropylacrylamide) (PNIPAM) microgel and doped with poly­(<i>N</i>-isopropylacrylamide-<i>co</i>-2-acrylamido-phenylboronic acid) (P­(NIPAM-2-AAPBA)) microgel. The ordered structure was locked by in situ photopolymerization. Taking advantage of the different responses of the two microgels to external stimuli, defect state can be induced and erased reversibly. Particularly, because the dopant, that is, P­(NIPAM-2-AAPBA) microgel sphere, shrinks with increasing glucose concentration, its size changes from larger than the host, that is, PNIPAM microgel sphere, to equal to the host, and finally smaller than the host. Therefore, upon addition of glucose, the crystal undergoes transition from a state with acceptor-type defect, to no defect state, and then to a state with donor-type defect. The transition among the three states is fully reversible. In addition, the response of the doped crystal to glucose is relatively fast