Green synthesis of bio-compatible carboxylate-functionalized carbon layers of 4 to 26 nm thickness on gold plasmonic nanoparticles

Abstract

Polycrystalline spherical plasmonic gold nanoparticles (GNPs) were coated with carboxylate-functionalized carbon layers with unprecedented thinness down to 4 nm, tunable between 4 and 26 nm, via a hydrothermal approach using glucose, fructose or sucrose as carbon sources. This synthetic approach allows for the formation of conformally coated GNPs with well-controlled carbon-layer thicknesses as a function of initial carbon source concentration. These carbon coated GNPs exhibit plasmon resonance at ∼545 nm and have an increased absorbance at 400 nm, which is found to correlate linearly with the thickness of the carbon layer with a squared Pearson correlation coefficient of 0.94. The coated GNPs are shown to be bio-compatible through incubation with SH-SY5Y cells with varying carbon coating thicknesses, without changes in cellular morphology and exhibiting increased proliferation with no notable differences when compared with the control or citrate capped GNPs, over 48 hours.