Fabrication of SERS substrates by laser restructuring of interconnected Au nanostructures for urea detection

Abstract

We discuss a facile, fast, simple, and reproducible fabrication method to modulate the structural morphology of the SERS substrate to improve its performance. The interconnected Au network structure named as nanoporous Au (NP–Au) is prepared by the dealloying method and further exposed with varied laser power in order to check the effect of power variation on the morphology as well as on the SERS performance. The effectiveness of the substrate has been tested by detecting Rhodamine 6G as a probe molecule. The Raman results show a good linear relationship with the laser power increment up to 3.2 mW and after that, the signal becomes saturated for a further increment in the power. The substrate is able to enhance the signal up to 102-fold as well able to show all the characteristic peaks without any damage to the probe molecule. Morphological identification reveals that different sizes and shapes of the pores (open, diffused, and interlinked) are responsible for the SERS signal enhancement. Subsequently, the sensitivity of SERS substrate has been examined and the result suggested that the optimal concentration of Rhodamine is 10−9 M. Furthermore, the substrate possesses good uniformity by representing a relative standard deviation value of less than 15 %. The substrate potential for real-world application has been examined by identifying urea (pesticide) molecules. The prepared nanoporous substrate is able to show a well-intensified signal with ∼16-fold enhancement compared to planar Silicon substrate.