Multi-responsive cellulose nanocrystal-rhodamine conjugates: an advanced structure study by solid-state dynamic...

Area of Science:

• Materials Science
• Nanotechnology
• Polymer Chemistry

Background:

• Cellulose nanocrystals (CNCs) offer a sustainable platform for advanced materials.
• Developing multi-stimuli responsive materials, particularly those activated by light, remains a key challenge.
• Precisely characterizing functional groups on CNC surfaces is difficult due to their low abundance.

Purpose of the Study:

• To create novel CNC-based hybrid materials responsive to multiple stimuli (pH, heat, UV light).
• To investigate the structural mechanisms behind the stimuli-induced optical changes.
• To utilize advanced solid-state NMR techniques for detailed structural analysis.

Main Methods:

• Immobilization of rhodamine spiroamide groups onto CNC surfaces.
• Exposure of the hybrid material to external stimuli (pH, heat, UV light).
• Solid-state Nuclear Magnetic Resonance (NMR) spectroscopy with Dynamic Nuclear Polarization (DNP) for (13)C and (15)N analysis.

Main Results:

• The hybrid CNC-rhodamine spiroamide material demonstrated reversible optical and fluorescent changes upon exposure to pH, heat, and UV light.
• The switching mechanism involves a ring-opening and closing process of the rhodamine spiroamide groups, facilitated by amine and amide functionalities.
• Solid-state NMR-DNP revealed the formation of temporary electrostatic bonds during heat treatment and the crucial role of CNC carboxyl groups in stabilizing the open state.

Conclusions:

• The study successfully engineered multi-stimuli responsive CNC-based materials with tunable optical properties.
• The findings provide fundamental insights into the structure-property relationships of functionalized CNCs.
• This work opens avenues for advanced applications in sensing and smart materials.