Core-Shell structure of gold nanoparticles with inositol hexaphosphate nanohybrids for label-free and rapid detection by SERS nanotechnology

Gold nanoparticles bound with inositol hexaphosphate (IP6) (AuNPs/IP6) were prepared by in situ reduction of various concentrations of IP6 (0-320 µM) through modified Frens method for surface-enhanced Raman scattering (SERS) detection. The resultant AuNPs/IP6 were subject to characterization including UV/Vis spectroscopy, transmission electron microscopy (TEM), dynamic light scattering (DLS), zeta potential, and X-ray photoelectron spectroscopy (XPS). The results showed that AuNPs with 65 µM of IP6 would result in a core AuNPs-shell (IP6 layer) structure, which exhibited the strongest SERS signal, due to the "hot spot effect" generated from the 1-2 nm interparticle gaps of AuNPs/IP6 nanohybrids (ionic interaction of IP6 and Au+). Furthermore, the reaction kinetics of Au and IP6 were also investigated in this work. Higher concentration of IP6 (190 and 260 µM) will make AuNPs become irregularly shaped, because IP6 is a basic salt and served as a pH mediator. The morphology and distribution of AuNPs were greatly improved by addition of 65 µM of IP6. This novel AuNPs/IP6 nanohybrid showed great stability and Raman enhancement. It is promising in the application of rapid and label-free biological detection of bacteria or tumor cells.