Resonance Rayleigh scattering study on the interaction of gold nanoparticles with berberine hydrochloride and its analytical application.

The interaction of gold nanoparticles with berberine hydrochloride has been studied by using resonance Rayleigh scattering (RRS) spectra. In pH 3.8-5.5 aqueous solution, citrate acid ([H2L2-]) self-assembled on the surface of positively charged gold nanoparticles (average diameter is about 12.0 nm) to form a supermolecular complex with negative charges. By virtue of electrostatic attraction, hydrophobic force and charge transfer, the complex bound with berberine to form complex, which had bigger diameter (35 nm) than gold nanoparticles. The formation of the binding production not only resulted in the red shift of absorption of gold nanoparticles from 518 to 672 nm, but also led to the greatly enhancement of RRS intensity. At the same time, the intensities of second-order scattering (SOS) and frequency-doubling scattering (FDS) were also increased. Under definite condition, the increment of the RRS (DeltaI) were proportional to the concentration of berberine. A sensitive and simple method for the determination of berberine based on the RRS technique has been developed. The detection limit (3sigma) for berberine was 0.40 ng mL(-1) and the quantitative determination range was 1.33-240 ng mL(-1). In this work, the optimum conditions of reaction, the effect of foreign substances and the analytical application had been investigated.