Nanoplasmonic paper for surface-enhanced raman scattering and metal-enhanced fluorescence

Abstract

Small molecules in human body play important roles in biological processes, and they also act as biomarkers. Paper consists of three-dimensional cellulose micro-/nanofiber matrices with abundant micro-/nanopores, which allow capillary-driven flow without external forces. Moreover, the micro-/nanostructures in paper provides three-dimensional backbone to assign plasmonic properties to metal nanoislands on the cellulose matrices. The controlled thermal evaporation provides modulation of metal nanostructures including Au nanostructures and plasmonic alloy of AuAg nanocomposites. Numerical analysis and extinction measurement evaluate the nanoplasmonic properties with tailoring plasmon resonance wavelength. Plasmonic Schirmer strip provides effective collection of human tears by capillary-driven flow and highly sensitive detection of biomarkers. The Au nanoislands enclosing the cellulose micro-/nanofibers generate three-dimensional volumetric electromagnetic hotspots for superior sensitivity. In addition, matching plasmon resonance wavelength to excitation wavelength allows highly sensitive identification of tear constituents. This approach allows SERS detection of biomarkers in artificial tear solution, and it further provides the SERS-based tear screening for diagnosis of diseases. This functional paper strip opens up a new platform for simple tear assay in healthcare sensing and diagnosis applications. Paper-based plasmonic alloy substrate provides extraordinary enhancement in MEF and SERS signals by matching plasmon resonance wavelength to excitation wavelength. The composition control in AuAg nanocomposites enables broad-range tuning of plasmon resonance wavelength, which further enhances. MEF signals by matching to the fluorescence excitation wavelength, MEF signals of each dye in mixture phase were individually measured after chromatographic separation. Also, this nanoplasmonic paper substrate enables picomolar SERS detection of folic acid. In summary, this study presents nanoplasmonic paper for non-invasive SERS diagnosis of gouty arthritis using human tears and highly sensitive plasmonic biosensing using plasmonic alloy. This unique approach enables diagnosis of diseases using human tears, selective MEF detection of each component in mixture phase after chromatographic separation, and picomolar SERS detection of biomolecules.