Spectrophotometric evidence to the formation of AuCl4-CTA complex and synthesis of gold nano-flowers with tailored surface textures.

In this paper we report the UV-visible and transmission electron microscopy (TEM) evidence to the formation of stable yellow-orange colored complex, which is attributed to the formation of ion-pair between sub-aggregates of cetyltrimethylammonium bromide (CTAB) and gold at room temperature. The position of wavelength maxima (λmax) and shape of the spectra strongly depends on the reaction conditions, i.e., [HAuCl4] and [CTAB]. As the reaction proceeds, typical two bands (one peak and one shoulder) at ca. 409 nm and 470 nm appears and the intensities increase with the time. TEM photographs indicate that the gold-CTA complex consist of aggregated nano-flower like gold with particle size range ca. 40-60 nm. N-(4-hydroxyphenyl)ethanamide (paracetamol) was used to the reduction of resulting gold-CTA complex which leads to the formation of beautiful nano-flower, branched-leaves, and bird-plume like AuNPs. Paracetamol concentrations have marked influence on the morphology (shape, size and the size distribution) and nature of the surface resonance plasmon band of AuNPs whereas [CTAB] have no impact on their spectra. Suitable mechanism have been proposed and discussed to the AuNPs formation.