Stable and reusable SERS sensors with femtomolar sensitivity using metal/bimetallic nanoparticles synthesized by laser ablation in liquid

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

Facultad de Ingeniería Mecánica y Eléctrica, Universidad Autónoma de Nuevo León, Nuevo León, Mexico.
Centro de Innovación, Investigación y Desarrollo en Ingeniería y Tecnología (CIIDIT)- Universidad Autónoma de Nuevo León, Parque de Investigación e Innovación Tecnológica (PIIT),
Apodaca, Nuevo León, 66600, México.
Facultad de Ciencias Quimicas, Universidad Autónoma de Nuevo León, Nuevo León, Mexico.



Surface Enhanced Raman Spectroscopy (SERS) is a powerful technology for fast, label free detection of broadband class of molecules. Here we present novel, ultrasensitive, reusable, and chemically stable SERS sensors using plasmonic nanoparticles (Ag, Au and Ag:Au) generated by pulsed laser ablation in liquid. The nanoparticles and SERS substrates are characterized for their structure, morphology, composition and SERS activities. Single step incorporation and surface modification of metal/bimetallic nanoparticles on silver deposited Si wafer substrates formed first, second and third generation hotspots for SERS and the synergistic effect between Au and Ag contributed to the ultra-sensitivity (pico and femto molar concentrations). The SERS sensors showed excellent signal homogeneity and uniformity with relative standard deviation of 11.75 for picomolar dye concentration. The sensors are found to be chemically stable for more than a month and maintaining the vibrational profile of the analyte. They showed femtomolar sensitivity and Raman signal enhancement (analytical enhancement factor ~108 to 1010) for 532 and 780 nm excitation wavelengths for different organic dyes. The SERS samples can be easily reused after a quick microwave treatment to remove the analyte molecules. It is also found that the SERS enhancement improved after microwave treatment and the substrates are reusable. The sensors showed excellent linear intensity response to analyte concentration revealed its qualitative detection capabilities. SERS spectra for other compounds are also evaluated at different concentrations suggesting broadband detection different classes of analytes. These SERS sensors can be created in a relatively short time, and the experimental methodologies can be scaled up to large-scale manufacturing.

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