Synthesis and properties of metallized cellulose nanomaterials

Abstract

Considerable interest in cellulose nanomaterials is driven by their sustainable worldwide availability, biodegradability, and versatility. Their extraordinary physical (optical, rheological, thermal, etc.) and mechanical properties (tensile strength, stiffness) make them promising engineering materials of the future. Additionally, cellulose nanomaterials possess a high aspect ratio, rod/fiber-like morphology with easily modifiable surfaces, which make them attractive for template assisted synthesis of functional 1-D nanoparticles. Anisotropic nanomaterials are of great scientific interest because, using directed self-assembly, their individual nanoscale direction dependent properties can be translated to macroscopic materials; such materials have the potential to stimulate breakthroughs in many modern technologies. Unfortunately, numerous state-of-the-art synthesis methods for direct fabrication of 1-D nanomaterials involve the use of complex chemistries and expensive reagents that complicate large scale implementation, and many of these methods are not applicable across material chemistries. Therefore, this research is focused on generating functional nanomaterials through application of conformal coatings of tailorable composition onto high aspect ratio cellulose nanomaterial templates as well as exploring the physical properties of these organic/inorganic hybrid nanomaterials. This work is divided into four specific research thrusts. First, a wet chemical surface modification process is developed to generate stable suspensions of individually dispersed cationic cellulose nanocrystals. Second, a wet chemical electroless deposition method for applying thin, conformal, and continuous gold coatings onto the surface-modified cellulose nanocrystals is used to produce gold nanoshell-bearing CNCs with tailorable plasmonic properties. Third, correlated single-particle spectroscopy is used to gain further understanding of how size, surface roughness, and surrounding environment affect the plasmonic properties of gold nanoshell-bearing bacterial cellulose nanocrystals (AuNS-BCNCs); this data is then used to establish structure-property relationships. Finally, the versatility of the methods developed in the first two thrusts is demonstrated by extending these techniques to two new material systems, nickel and silver, which produced magnetic and electrically conductive 1-D nanoparticles, respectively.