Ultrastable water-dispersible one-dimensional gold nanoparticles@cellulose nanocrystal

Cellulose nanocrystals (CNCs) with high aspect ratio, ultrafine template structure and surface modifiability were used as the multifunctional support to fabricate one dimensional (1D) nanoprobe based on surface-enhanced Raman scattering spectroscopy (SERS) technology. Quaternary ammonium groups were first introduced at the hydroxyl sites on the surface of CNCs to improve the dispersion stability in aqueous solution, and then sulfhydryl groups were conjugated to the carboxyl sites through amidation. Gold nanospheres (AuNSs) were self-assembled on CNCs via strong Au-S bonds to form dense hot spots, which can easily distinguish the rhodamine (R6G) signal of six orders of magnitude when used as a SERS probe. Because the hot spots are fixed along a single CNC, the SERS signal stability and reproducibility are greatly improved compared to those of changeable hot spots formed via the irreversible aggregation of gold colloids. In addition, owing to the cationic charge repulsion effect, the nanoprobe exhibits excellent dispersion stability even in high concentration salt solutions. Considering the good sensitivity, reproducibility and dispersibility, the 1D SERS nanoprobe based on CNCs possess potential application in the field of sensing and detection in aqueous solutions.