Rapid and Easy Fabrication of Tryptophan Amino Acid Plasmonic Detection Kit

In this experimental study, silver colloidal solution was synthesized using Tollens method. Plasmonic kit was fabricated by drop-coating of silver colloidal solution on glass substrate and finally, detection of tryptophan amino acid was performed using plasmonic kit and surface enhanced Raman spectroscopy. The field emission scanning electron microscopy (FESEM) image shows the most of silver nanoparticles on plasmonic kit have the sizes between from 1400 to 1500 nm. Plasmon peak at around 410 and observation of FCC structure in XRD characterization confirmed the formation of silver nanoparticles. Surface plasmon resonance of silver nanoparticles as well as light scattering from larger agglomerated silver particles enhance the molecular vibrations of tryptophan amino acid. By calibrating the intensity of molecular vibrations in terms of tryptophan amino acid concentration, a quadratic relationship was obtained from which the concentration of the tryptophan amino acid could be determined by measuring SERS spectra. Raman spectroscopy improves the Raman signals of tryptophan amino acid due to the resonance of surface plasmons of silver nanoparticles and the light scattering from larger silver particles. As the tryptophan amino acid concentration decreases, the SERS signals are attenuated by the decrease in the number of molecular vibrations in which rapid and convenient detection of tryptophan amino acid could be performed up to a concentration of 10-7 M using the silver plasmonic substrates. In addition, by calibration, the concentration of the amino acid could be determined using silver plasmonic substrates and Raman spectroscopy, which could lead to the development of nano-sensors.