Laser synthesis of Si nanopillars-based SERS for efficient chlorpyrifos detection

A uniform and high-density Si nanopillars-based SERS layer was synthesized; as an efficient means, for detecting ultra-low concentration of chlorpyrifos. A low (20 %) laser pulse duty cycle of 405 nm wavelength and 600mW/cm² intensity from a laser diode was used to achieve laser–induced etching. A simple, low-cost, and stable current wave driver circuit was utilized to drive the laser diode. Structural and spectroscopic features of the based SERS layer and AuNPs/Si nano-pillars sensor were studied by scanning probe microscopy, (FESEM) images, x-ray diffraction patterns and Raman spectroscopy. The results revealed that the Si nano-pillars layer provided superior features for creating high density hot spot gaps. A uniform, high population and unique size distributions of (AuNPs) layers on the AuNPs/Si nano-pillars layer were achieved by ion reduction process. The sensor performance displays an excellent detection of chlorpyrifos with an exponential relationship with Raman signal. The highest chlorpyrifos enhancement factor (EF= 1.1*10⁶) with minimum limit of detection (LOD= 22*10⁻⁸ M); equivalent to 0.07 mg/Kg, was obtained with Si nano pillars of high value altitude populated with partially three dimensions AuNPs layer. This limit of detection is much lower than the recognized (0.1 mg/kg) value by the European Union. (paper)