Temperature dependence of gold nanostar particles morphology and its SERS application

Gold nano-star particles (GNS) have broad application prospects in Raman enhancement, photovoltaic, and catalysis fields because of the hot spot effect of their tip structure. However, metal nanoparticles will accumulate heat during applications of high-power laser-focused irradiation, which may lead to the morphological degradation of the nanoparticles. In this paper, we have studied the effect of annealing temperature on the surface tip structure of GNS. Firstly, GNS with the multi-tip structure were synthesised by the two-step method, and GNS thin films were prepared by self-assembly technique without auxiliaries. By means of SEM characterisation, the film is found to be compact and uniform. Secondly, we systematically studied the morphology degradation of GNS at 100 degrees C, 150 degrees C, 200 degrees C and 250 degrees C. The results show that the tip of GNS does not change obviously until the temperature reaches 200 degrees C. Then the four kinds of GNS films were used as surface-enhanced Raman scattering (SERS) substrates, and their Raman enhancement properties have been studied with adenine as the analyte, and stronger Raman enhancement effect can be found for the tip of nanoparticles. For a SERS substrate corresponding to an annealing temperature of 100 degrees C, we have obtained the limit sensitivity of adenine molecule of 10-9 M. Finally, the surface electric field distribution and local resonance spectrum curves of four kinds of gold nanoparticles with different tip sizes were simulated theoretically by using the finite element method, and the results are consistent with the experimental data.