Optoplasmonic Hybrid Materials for Trace Detection of Methamphetamine in Biological Fluids through SERS

Abstract

Optoplasmonic materials comprising both photonic and plasmonic elements are of particular interest for the development of substrates for surface-enhanced Raman spectroscopy (SERS). In this work, a layer of analyte-carrying dielectric nano/microspheres is placed on top of a monolayer of gold nanoparticles to enhance the intensity of the electric (E-) field localization and to enrich the analyte close to the electromagnetic hot spots. Numerical simulations of the hybrid structure confirm an increased and spatially expanded E-field enhancement at the interface. Due to a decreasing filling fraction with increasing size of the dielectric spheres, simulations predict a saturated SERS enhancement for dielectric microspheres with a diameter larger than 4 μm, which is confirmed by experimental SERS measurements. The dielectric microsphere can be functionalized with surface ligands that facilitate the binding of target molecules in solution. The deposition of the analyte-loaded microspheres on the self-assembled gold nanoparticle ensures a high local concentration of analytes in the electromagnetic “hot” surface. The performance of the optoplasmonic SERS approach for detecting methamphetamine in saliva and urine is tested, and the detection of analytes at nanomolar (nM) concentrations is demonstrated.

Methods in Raman spectroscopy for saliva studies – a review

“…[193,194] Other investigations also have a primary SERS substrate optimization characteristic. [195,196]…”

“…Nanosystems combining photonic and plasmonic components have recently found sensing applications, [350] notably whispering gallery mode sensors. [351] In a Raman-saliva context, Hong et al [195] have presented an optical-plasmonic hybrid FDTD model consisting of an AuNP underlayer and a larger silica microsphere (Figure 7C). The authors measure methamphetamine-doped urine and saliva with the optoplasmonic arrangement, presenting spectra down to concentrations of 1 Â 10 À8 M and 1 Â 10 À9 M, respectively.…”

Photonics of human saliva: potential optical methods for the screening of abnormal health conditions and infections

“…Deposition of the analyte loaded microspheres on the self-assembled gold nanoparticle ensures a high local concentration of analytes in the electromagnetic “hot” surface. Optoplasmonic SERS substrates have been found effective in the detection of methamphetamine in saliva and urine at nanomolar concentrations (Hong et al 2020 ). Li et al have developed an immunochromatographic assay (ICA) based on SERS technique for detecting morphine, which is the main metabolic end product of opium and heroin.…”

Recent advances in developing optical and electrochemical sensors for analysis of methamphetamine: A review

“…Accordingly, a MAMP-carrying dielectric layer was attached to AuNPs monolayer to enhance the electric field localization intensity and provide more MAMP in the electromagnetic "hot" surface. The resulted sensor was detected MAMP in saliva and urine at nanomolar concentrations (Hong et al, 2020).…”