Title : Bottom-up plasmonic microstructures for Surface Enhanced Raman Spectroscopy (SERS)
Abstract:
Raman spectroscopy is a non-invasive, label-free, and extremely sensitive technique for detecting a wide variety of molecules. Although Raman is a highly effective experimental technique, its narrow scattering cross-section reduces signal strength, resulting in a low signal-to-noise ratio. SERS is a method of boosting the Raman signal that takes advantage of the local enhanced field in a plasmonic material. SERS prerequisites the fabrication of the plasmonic substrate, which is commonly created using top-down methods. Top-down approaches can produce precise plasmonic structures, but they also require clean room facilities and harsh chemicals, making them expensive and unsuitable for biological applications. The bottom- up approach addresses these challenges, however it is based on the natural self-assembly mechanism, which is exceedingly sluggish and unable to produce defined geometries. Our protocol overcomes the challenge of employing a bottom-up self-assembly technique to create a plasmonic system capable of boosting the Raman signal. We address the issue of slow pace and undefined geometry by employing a laser-assisted and directed bottom-up technique known as Microbubble Lithography to manufacture defined micro geometries of metal nanoparticles in real time. Thus, we create different dimensions of SERS substrates by varying experimental parameters such as nanoparticle concentration, laser intensity, and translation speed of the microscope's translation stage. We also observed that the relative distance between self-assembled nanoparticles serves as a hot spot with increased field intensity. Finally, we use these self-assembled SERS substrates to measure the nanomolar concentration of a physiologically active chemical in real time. Thus, our technique addresses the issue of low Raman signal by boosting it with our engineered plasmonic structure, which may be used to identify a relevant biomarker with enhanced Raman signal, resulting in a higher signal-to-noise ratio.
