Novel theoretical studies based on CIELab and deconvolution methods to characterize AuNPs aggregation processes

Abstract

The study of the interaction of spherical gold nanoparticles when they undergo aggregation phenomena due to the presence of a ligand in solution is presented, based on both colorimetric parameters (using CIELab space) and traditional deconvolution analysis. The feasibility of using CIELab space for this purpose can be an important method to simplify the required instrumentation (colorimeter versus UV spectrophotometer) as well as being less time consuming compared with the traditional computational analysis. For these reasons, in this work we present the first experimental approach of the proposed methodology for its application in this field of research. The synthetized AuNPs employed in this work have been previously characterized by means of the maxima of their LSPR bands, zeta potential and electron microscopy images. The aggregation of spherical AuNPs (with a diameter of 12 nm) by an inert electrolyte (NaCl) is investigated in a first step with successfully results, allowing to obtain the characteristic CIELab parameters (a*, b* and L*). At a later stage, the color changes induced in the optical properties of the solution due to the interaction of AuNPs (with increasing diameters of 12, 25 and 33 nm) with an amino acid such as lysine at neutral pH, have been also described using the CIELab spatial framework. The obtained a*, b* and L* parameters of the CIELab space allow to characterize satisfactorily the color change from red to blue which describes the aggregation phenomena, relying on deconvolution analysis of the LSPR bands. The results obtained support the validity of the CIELab space as a valid tool for the investigation of the aggregation process of colloidal solutions. It will allow simplifying the whole process using simpler and cheaper instrumentation as well as a decrease in the required analysis time.