Chitosan-Stabilized Noble Metal Nanoparticles: Study of their Shape Evolution and Post-Functionalization Properties.

Massimo Ottonelli,Anna Demartini,Stefania Zappia,Marina Alloisio

doi:10.3390/nano10020224

Massimo Ottonelli, Anna Demartini + Show 2 more

Open Access

https://doi.org/10.3390/nano10020224

Copy DOI

Abstract

Noble metal anisotropic nanostructures have achieved a growing interest in both academic and industrial domains mostly because of their shape-dependent plasmonic properties in the near-infrared region. In this paper, gold and gold-silver anisotropic nanostructures were synthesized in very high shape-yields through a wet, seed-mediated approach based on the use of nearly spherical silver nanoparticles as seeds and chitosan as stabilizing agent. Two chitosans of different origin and molecular properties were selected for the synthetic pathway, leading to the formation of variously sized and shaped end products. In detail, quite homogeneous nanoplatelets of about 25-nm size and 7-nm thickness or nearly spherical, highly porous nanocages of about 50-nm size were obtained, depending on the type of polysaccharide employed. The shape transition towards anisotropic morphologies occurred through a slow, spontaneous process, in which the chitosan nature seemed to play a key role. As expected, both nanoplatelets and nanocages exhibit shape-dependent plasmonic features and surface properties tunable for a variety of application fields. To prove this point, the nanostructures were successfully post-functionalized with poly(10,12-pentacosadiynoic acid) (PCDA), a carboxylic-endowed diacetylene able to anchor on noble metal substrates, to obtain versatile, chromic platforms suitable for sensing and spectroscopic purposes.

Highlights

Anisotropic noble metal nanostructures (NSs) represent a fascinating class of nanomaterials because of their size- and shape-dependent physical and chemical properties, which make them ideal candidates for the development of new technologies [1]
Gold and gold-silver anisotropic nanostructures were synthesized in very high shape-yields through a wet, seed-mediated approach based on the use of nearly spherical silver nanoparticles as seeds and chitosan as stabilizing agent
Starting on these bases and with the aim of combining the intrinsic properties of CS with those of noble metal NSs to produce novel platforms with implemented biocompatibility and plasmonic features, we investigated the capability of chitosan to act as shape-directing agent in the fabrication of gold-based nanostructures through a standard galvanic replacement route involving nearly spherical silver nanoparticles as seeds

Summary

Introduction

Anisotropic noble metal nanostructures (NSs) represent a fascinating class of nanomaterials because of their size- and shape-dependent physical and chemical properties, which make them ideal candidates for the development of new technologies [1]. The anisotropy of NSs was proved to help their self-assembly into ordered 2D and 3D lattices with spatially dependent properties at the macroscale level, which still constitutes a challenging issue in nanomaterials research [7,8] In view of their promising use in such various fields, a strict control of the size and shape of anisotropic noble metal nanoparticles is required. Its antibacterial, antifungal, mucoadhesive, wound healing, and even anticancer activities are well recognized and deeply exploited in the pharmaceutical and biomedical areas [25] For these reasons, the European Commission-DG RTD, operating in the framework for mapping innovative products deriving from biomass components, recently inserted third-generation chitosan in the top 20s emerging bio-based products (BBS) to be used in industrial applications for the development of highly demanding systems [26]

Methods

Results

Conclusion