Nanocomposites and nanomaterials 

Acidic Polysaccharides as Single Reducing and Capping Agent for Introducing pH depended Anisotropic Growth of Gold Nanoparticles
Boltovets P.M. 1, Kravchenko S.O. 1, Kovalenko O.G. 2, Snopok B.A. 1
 1Institute of Seniconductor Physics of the NAS of Ukraine. 
Prospect Nauki, 41, Kyiv-03039, Ukraine. 
E-mail: paraskeva2013@gmail.com
2 Institute of Microbiology and Virology of the NAS of Ukraine.
Zabolotnyny Str, 154, Kyiv-03680 

A rapid, environmentally friendly wet-chemical synthesis of shaped, either stable or coagulated, water-soluble, gold nanoparticles (GNPs) using the acid polysaccharide as reducing and capping agent to introduce pH depended anisotropic growth is described. As acidic polysaccharide glucuronoxylomannan (GXM) from the yellow brain mushroom Tremella mesenterica has been used. GXM consists of a linear backbone of (1→3)-linked -D-mannose with mainly xylose and glucuronic acid in the side chains. Carboxylic group in sugar backbone presents additional possibility for forming three-dimensional arrays determined by polysaccharide structure in different pH solutions with following formation of variable shaped GNPs. Thus, GXM was suggested to form bundle conformation at acidic pH due to protonization of carboxilic groups with H-bond forming. Correspondingly, GXM mesh conformation at neutral pH and GXM fibril conformation at basic pH were formed due to partial and complete ionization of geteroglycan carboxilic groups. 
Gold (III) ion reduction to elemental state in basic GXM solution caused the production of crystalline and mostly geometrical-shaped GNPs whereas the formation of supracrystals based on aggregated small GNPs were found to occur in neutral GXM solution. No GNPs formation proved to be observed in GSM acidic solution.
This research was partly funded by the NATO Science for Peace and Security Programme under the Grant G5140 and Projects of the National Academy of Sciences of Ukraine.