Simple synthesis of gold-decorated silica nanoparticles by in situ precipitation method with new plasmonic properties

Lizbet León Félix,Fermín Fidel Herrera Aragón,Joaquin Martinez Porcel,Marcelo Henrique Sousa,David Gregorio Pacheco-Salazar

doi:10.1007/s42452-021-04456-0

Abstract

We describe a simple method for the preparation of gold-decorated silica (SiO2) nanoparticles (NPs) by the in situ precipitation method using simple BH4− ions reduction as a procedure, where BH4− ions are adsorbed onto PEI-functionalized SiO2 NPs for stabilizing and reducing gold ions onto PEI-SiO2 surface in water under ambient conditions. The result was 3-nm gold nanoshell NPs attached to SiO2 core (~ 75 nm) with a surface plasmon resonance (SPR) at ~ 680 nm. SPR band is associated with Au NP aggregates that arise from strong interparticle interaction. This is an alternative to the gold-seeding methods and the use of anionic gold species for the obtention of gold-decorated SiO2 NPs with an important red-shift in UV–Vis absorption and with potential applications in biosensors and photothermal therapy.

Highlights

Core–shell engineered nanostructures are good candidates for the building of new materials with controlled properties of importance in several technological applications [1]
Gold cations (e.g. Au3+) are expected to be poorly adsorbed on positively charged PEI-coated SiO2 NPs to form an Au shell by in situ reductions. For overcoming this constraint and to obtain gold-shelled SiO2 NPs from PEI-coated cores and using gold (III) acetate as A u3+ source, we propose a simple route of synthesis where a reductant anion (BH4−) is prior adsorbed on SiO2 NPs charged positively, decreasing substantially the superficial charge of silica and allowing the adsorption of A u3+ for a further reduction of these ions form a gold shell by the in situ-precipitation method
The morphology and size distribution of NPs were characterized by Transmission electron microscopy (TEM) images that were collected with a JEOL JEM 1010 microscope operating at 120 kV

Summary

Introduction

Core–shell engineered nanostructures are good candidates for the building of new materials with controlled properties of importance in several technological applications [1]. Gold nanoparticles (AuNPs) in hollow gold-shell configuration exhibit unique physical–chemical characteristics, low toxicity, and optical properties due to AuNPs. the synthesis of gold nanoshells NPs with various dimensions and shapes presents us the possibility of obtaining metallic nanoshells with SPR band in the near-infrared ranges. The synthesis of gold nanoshells NPs with various dimensions and shapes presents us the possibility of obtaining metallic nanoshells with SPR band in the near-infrared ranges These are of considerable interest by a wide range of possible applications in fluorescent sensors [2], biosensors [3], photothermal therapy [4, 5], biomedical imaging [6], or drug carriers for cancer treatment [7]. The position, intensity, and shape of the SPR band depend on the size and size distribution of AuNPs, morphology, shape or geometry, the inter-particle distances, the polarization of the incident light [11], the dielectric constant of the surrounding medium around the NPs, and interparticle interaction [10,11,12,13] which are important parameters to define their plasmonic properties

Methods

Results

Conclusion