바이오 고분자를 이용한 비등방성 금속 나노 구조체의 친환경 합성과 응용 연구

Abstract

Noble metal nanocrystals (Ag, Au, Pt, Pd) have been applied in many fields such as catalysts, antibacterial activity, Surface-enhanced Raman scattering, and drug delivery because of their great chemical, physical, optical properties. A lot of synthetic methods have been developed to synthesize metal nanocrystals, but most of them use toxic solvents or reducing agents. In this study, we report an eco-friendly synthetic method using a biopolymer as reducing agent and colloidal stabilizer. And, water was only used as a reaction medium and the reaction was carried out at ambient conditions. Alginate which is one of biocompatible hydrogel polymers was used in this work because it has multifunctional ability to reduce, cap and stabilize metal nanocrystals. However, since noble metal nanocrystals are easily aggregate to minimize their surface areas to be thermodynamically stable in solution phase, we developed the method that alginate was used a support material for immobilization of Ag nanostructures. Ag+ ion crosslinked alginate polymer chains and was reduced and embedded in surface of crosslinked 3D alginate beads. Various methods using hydrogel polymers for support materials were developed for immobilization of Ag nanocrystals. There are a lot of ways to synthesize and immobilize Ag nanoparticles, however, most of them still use a two-step method in which hydrogel polymer is crosslinked first before the Ag precursor is reduced. In this study, an easy one-step method, which crosslinking of alginate hydrogel and synthesizing of Ag nanoparticles occurred at the same time (in situ), is introduced. Also we investigated that alginate polymer could make a unique shape of gold nanocrystals. It was one-step and green synthesis as well. Two kind of noble metal nanocrystals we made were used as catalyst for 4-Nitrophenol (4-NP) reduction reaction. When the metal nanocrystals were used as a heterogeneous catalyst for 4-NP reduction reaction by sodium borohydride, they showed excellent catalytic activity and reusability