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Issue 47, 2014
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Multi-responsive cellulose nanocrystal–rhodamine conjugates: an advanced structure study by solid-state dynamic nuclear polarization (DNP) NMR

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Abstract

Multi-stimuli responsive materials based on cellulose nanocrystals (CNCs), especially using non-conventional stimuli including light, still need more explorations, to fulfill the requirements of complicated application environments. The structure determination of functional groups on the CNC surface constitutes a significant challenge, partially due to their low amounts. In this study, rhodamine spiroamide groups are immobilized onto the surface of CNCs leading to a hybrid compound being responsive to pH-values, heat and UV light. After the treatment with external stimuli, the fluorescent and correlated optical color change can be induced, which refers to a ring opening and closing process. Amine and amide groups in rhodamine spiroamide play the critical role in this switching process. Solid-state NMR spectroscopy coupled with sensitivity-enhanced dynamic nuclear polarization (DNP) was used to measure 13C and 15N in natural abundance, allowing the determination of structural changes during the switching process. It is shown that a temporary bond through an electrostatic interaction could be formed within the confined environment on the CNC surface during the heat treatment. The carboxyl groups on the CNC surface play a pivotal role in stabilizing the open status of rhodamine spiroamide groups.

Graphical abstract: Multi-responsive cellulose nanocrystal–rhodamine conjugates: an advanced structure study by solid-state dynamic nuclear polarization (DNP) NMR

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Supplementary files

Article information


Submitted
11 Sep 2014
Accepted
23 Oct 2014
First published
24 Oct 2014

Phys. Chem. Chem. Phys., 2014,16, 26322-26329
Article type
Paper
Author version available

Multi-responsive cellulose nanocrystal–rhodamine conjugates: an advanced structure study by solid-state dynamic nuclear polarization (DNP) NMR

L. Zhao, W. Li, A. Plog, Y. Xu, G. Buntkowsky, T. Gutmann and K. Zhang, Phys. Chem. Chem. Phys., 2014, 16, 26322
DOI: 10.1039/C4CP04096A

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