Template Synthesis of Nanostructured Metals Using Cellulose Nanocrystal - The Nanoscience and Technology of Renewable Biomaterials - page 315

12

Template Synthesis
of Nanostructured Metals Using
Cellulose Nanocrystal

Yongsoon Shin and Gregory J. Exarhos

12.1 Overview

In this chapter, cellulose nanocrystal (CNXL) has been used as a template and reducing
agent for synthesizing nanoscale inorganic solids such as metal oxide, metal carbide,
and nanocrystalline metals. CNXL selectively nucleates metal or metal oxide phases in
ordered arrangements commensurate with the attendant structure and chemistry of the
fiber. The reaction has an analogy to the well-known Tollen's reagent where addition
of an aldehyde or glucose analyte to a glass vessel containing a soluble ammoniacal
silver complex causes reduction of the silver to form a mirror on the vessel surface. For
the synthesis of TiO 2 , CNXL produced mesoporous anatase with 5-10 nm particle sizes
and 170-200 m 2 /g surface area after air-calcination. Silica-infiltrated CNXL produced
very homogeneous SiC nanowires with 70 nm in diameter at 1400 ◦ CinAr. Forthe
syntheses of metal nanoparticles, upon addition of aqueous metal ion containing solutions
(Cu(II), Ni(II), Ag(I), Au(III), Pd(II), Pt(IV), or even selenite, Se(IV)) into the CNXL
suspension, reduction to the metal occurs under hydrothermal conditions to form ordered
metal nanostructures. Ni(II) and Cu(II) ions required high temperature (300-400 ◦ C) to
be reduced due to their low reduction potentials. However, metal ions including Ag(I),
Au(III), Pt(IV), Pd(II), Se(IV) needed lower temperatures (160-200 ◦ C) to be reduced.
Enhanced catalytic activity on these templated surfaces has been demonstrated for a
methylene-blue dye photo-induced decomposition (Se nanocrystals resident on crystalline
cellulose).