Seed-mediated synthesis of branched gold nanoparticles with the assistance of citrate and their surface-enhanced Raman scattering properties

Abstract

We report an easy synthesis of highly branched gold particles through a seed-mediated growth approach in the presence of citrate. The addition of citrate in the growth solution is found to be crucial for the formation of these branched gold particles. Their size can be varied from 47 to 185 nm. The length of the thumb-like branch is estimated to be between about 5 and 20 nm, and changes slightly as the particle size increases. Owing to these obtuse and short branches, their surface plasmon resonance displays a marked red-shift with respect to the normal spherical particles. These branched gold particles exhibit stronger SERS activity than the non-branched ones, which is most likely related to these unique branching features.

Functionalised gold nanoparticles for selective induction ofin vitroapoptosis among human cancer cell lines

“…The existence of strong plasmon response (SPR) was also evident because of the substantial absorbance of gold nanoparticles recorded at around 520 nm. This phenomenon is reported earlier [11] and considered as responsible for imparting the ruby red colour to the conventional gold colloids. From this experiment, it was evident that surface conjugation of GNP with citrate is not creating any differences in the fundamental affluence of GNP, but only modifying its surface texture.…”

A freeze substitution fixation-based gold enlarging technique for EM studies of endocytosed Nanogold-labeled molecules

“…Although the small size of 1.4 nm Nanogold makes it ideal for preserving the proper binding and function of a labeled ligand, these clusters were not large enough to be located directly in EM projection images and in most tomograms derived from stained cell sections. We therefore adapted autometallography and nanoparticle seeding techniques that are used to enlarge 1.4 nm Nanogold clusters by selectively depositing silver and/or gold atoms onto their surfaces (Busbee et al, 2003;Daniel and Astruc, 2004;Gole and Murphy, 2004;Hainfeld and Furuya, 1995;Hainfeld et al, 1999;Jana et al, 2001;Meltzer et al, 2001;Okitsu et al, 2005;Zou et al, 2006).…”

“…The FSF procedure described above was modified to include a preembedding gold-enlarging technique for HPF cells by adapting approaches that involve silver or gold enhancement at room temperature (Danscher, 1981;Hacker et al, 1988;Hainfeld and Furuya, 1995;Scopsi, 1989), gold-toning (Sawada and Esaki, 2000), seed-mediated gold-enlarging (Busbee et al, 2003;Daniel and Astruc, 2004;Gole and Murphy, 2004;Handley, 1989;Jana et al, 2001;Meltzer et al, 2001;Okitsu et al, 2005;Zou et al, 2006) and a FSF-based silver-enhancement procedure (Morphew et al, 2007). To avoid the background that results from spontaneous autonucleation, we designed a three-step enlarging protocol in which silver enhancement was used to slightly enlarge the Nanogold, the silver shell was coated by gold toning to make it insoluble in osmium, and the particles were further enlarged to 10 -16 nm using gold enhancement.…”

Spatially resolved measurements of plasmonic eigenstates in complex-shaped, asymmetric nanoparticles: gold nanostars

“…Their particular shape, plus the fact that they are made of gold (very stable and biocompatible), makes them suitable for several applications, including biosensing on live cells [9] or Surface Enhanced Raman Spectroscopy (SERS) detection of very low concentrations of molecules [10]. Nanostars with different symmetry levels, aspect ratios and number of tips have been synthesized by several research groups [9,[11][12][13][14]. Their optical properties have been explored by means of many different experimental and numerical techniques such as UV-visible scattering [11,14], Rayleigh scattering in a dark-field microscope [9,15], SERS [10,13], Finite Difference Time Domain (FDTD) simulations [16], Boundary Elements Method (BEM) [10,14] and Discrete Dipole Approximation (DDA) calculations [9,11].…”