Individually Dispersed Gold Nanoshell-Bearing Cellulose Nanocrystals with Tailorable Plasmon Resonance

Cellulose nanocrystals (CNCs) can be attractive templates for the generation of functional inorganic/organic nanoparticles, given their fine sizes, aspect ratios, and sustainable worldwide availability in abundant quantities. Here, we present for the first time a scalable, surfactant-free, tailorable wet chemical process for converting commercially available CNCs into individual aspected gold nanoshell-bearing particles with tunable surface plasmon resonance bands. Using a rational cellulose functionalization approach, stable suspensions of positively charged CNCs have been generated. Continuous, conductive, nanocrystalline gold coatings were then applied to the individual, electrostatically stabilized CNCs via decoration with 1-3 nm diameter gold particles followed by electroless gold deposition. Optical analyses indicated that these core-shell nanoparticles exhibited two surface plasmon absorbance bands, with one located in the visible range (near 550 nm) and the other at near infrared (NIR) wavelengths. The NIR band possessed a peak maximum wavelength that could be tuned over a wide range (1000-1300 nm) by adjusting the gold coating thickness. The bandwidth and wavelength of the peak maximum of the NIR band were also sensitive to the particle size distribution and could be further refined by fractionation using viscosity gradient centrifugation.