SERS sensors decorated with AuAg bimetallic nanoparticles produced by laser patterning for ultrasensitive detection of biomolecules

Jithin Kundalam Kadavath, Rene Fabian Cienfuegos Pelaes, Selene Sepulveda ́ Guzman, Nora Aleyda Garcia Gomez, David Avellaneda Avellaneda, Bindu Krishnan, Sadasivan Shaji

Facultad de Ingeniería Mecánica y Eléctrica (FIME),
Universidad Autónoma de Nuevo León (UANL)

Abstract:
Surface Enhanced Raman Spectroscopy (SERS) is a versatile and ultrasensitive technique capable of identification of pollutants, contaminants, food additive, pesticides and other molecules that impacting health and ecosystem. It utilizes plasmonic nanomaterials mainly gold (Au) and silver (Ag) to increase the intensity of electric field around nanoparticles thereby paving the way for intense Raman scattering. Here we demonstrate ultrasensitive, reusable, and stable SERS sensors operational in visible and near IR excitation wavelengths. Ultrapure bimetallic AuAg (50:50) nanoparticles are synthesized by laser ablation in liquid technique. The nanoparticles are incorporated on Si/Ag substrate surface to fabricate SERS sensors. The effect of laser patterning on surface morphology of sensor was deeply explored by changing the scribing parameters.

because of laser pattering parameters. The tunability in surface morphology created all generations of SERS hotspots resulted femtomolar dye detection of dyes. The analyte molecules are removed from sensor surface by a rapid thermal treatment and the sensor is reused for next SERS measurement verifying its reusability. The SERS signal uniformity and homogeneity of the sensors are tested by random points measurements and the calculated relative standard deviation. The sensors exhibited excellent linear response (χ2 = 0.99) to SERS intensity with analyte concentrations revealed quantitative detection capability. These SERS sensors stand out from conventional SERS sensor
synthesis routes due to absence of surfactants, capping agents or any other chemicals, which are nonfavourable SERS performance in biological environments.