Analysis of the effect of pH on the stability and optical spectra of Au nanoparticles linked by conductive BPE molecule

The preparation of detergent-free gold NPs by the citrate method is shown. The procedure of functionalization of monomeric Au NPs with 1,2-bis(2-pyridyl)ethylene (termed BPE) molecule to obtain Au-BPE dimers is described. According to the results of TEM analysis, the shape of the obtained NPs is close to spherical with a diameter of 21.94 $\pm$ 0.28 nm. In dimers, the distance between NPs is controlled by the linker and is 0.75 $\pm$ 0.12 nm, which is in agreement with the dimensions of the BPE molecule. According to the results of Experimental absorption UV-Vis spectra, measured over time, in 0.15 M nitric acid solution, Au-BPE dimers are more stable than in an alkali solution of the same molarity. Long-term exposure leads to a decrease in the intensity of the LSP peak of the dimers.