Investigation of biocatalytic enlargement of gold nanoparticles using dynamic light scattering and atomic force microscopy

Abstract

The aim of this study was the investigation of the biocatalytic enlargement of colloidal gold nanoparticles (AuNPs) using enzyme glucose oxidase (GOx), glucose and tetrachloroauric acid by UV–vis spectroscopy, dynamic light scattering (DLS) and atomic force microscopy (AFM). The appropriate ratio of 13nm AuNPs seeds and growing solutions equal to 1:2 was determined from absorbance spectra of AuNPs. At this ratio the most AuNP seeds were biocatalytically enlarged and it resulted in the higher difference of plasmon absorbance after 60 and 90min of AuNPs incubation in growing solution. In order to determine the size of AuNPs after biocatalytic enlargement, DLS measurements in the solution and AFM measurements after the immobilization of AuNPs seeds on sensor disc coated with a planar Au layer, which was functionalized with 1,6-hexanedithiol self-assembled monolayer, were performed. The DLS and AFM measurements showed that hydrodynamic diameter of biocatalytically enlarged AuNPs in the solution and the height of nanoparticles immobilized on the surface depends on the glucose concentration in the solution and on the duration of synthesis. Therefore, the biocatalytic enlargement of AuNPs could be applied in the development of glucose biosensors using UV–vis spectroscopy, DLS and AFM methods.