A new and facile route to prepare gold nanoparticle clusters on anodic aluminium oxide as a SERS substrate

In the present study, a new SERS-active gold nanoparticle clusters having a flower-shape have been prepared easily on nano porous anodic aluminium oxide (AAO) by immersing it in auric chloride solution without any need for complex production steps. In this process, presented for the first time, the metallic aluminum which were released under the influence of chloride ions due to pitting corrosion act as a reducing agent, while gold ions were reduced onto the AAO layer based on the difference in standard reduction potentials between aluminum and gold. Gold nanoparticle clusters on AAO layer formed "hot spots" providing enhanced Raman signal. Optical microscope, SEM, EDX, AFM, and UV-vis spectrophotometer have been used to characterize the substrate. In order to demonstrate applicability of the method, label free SERS measurements of nitrate ion was performed on the proposed sensing platform. A high sensitivity with 1.03 ppm of limit of detection level and the enhancement factor of 2.9 × 10⁵ were obtained for nitrate ion. In addition, remarkable recoveries ranging from 98.4% to 106.8% were obtained for nitrate spiked into drinking water samples. The inter-day and intra-day precisions of the method as relative standard deviation (RSD) were determined as 3.3% and 5.2%, respectively. The sensor platform, developed using a facile method and a low-cost base material (aluminum), can be a good alternative for SERS based sensing applications.