Organic-based plasmonic emitters for sensing applications

Plasmonic emissions generated by excitation of an organic layer on a metal grating structure are demonstrated. The emissions correspond to the resonant condition of surface plasmon (SP) modes on the Alq3/Au interface, and the grating structure is coupled to the Au/air interface to provide light emissions. Experimental variations in pitch to control plasmonic bandgap obtained highly directional plasmonic emissions with enhanced intensity. This method is readily applicable for detecting refractive index changes by using SP-coupled fluorophores to obtain emissions of varying wavelengths and viewing angles. The calculations showed that the wavelength of the plasmonic emitter changed from 480 to 680 nm at certain viewing angles, while the concentration of contacting glucose increased from 10% to 40%. Accordingly, a device with a pitch size of 500 nm had a sensitivity of δθe/δn = 37.76° and δn = 1.681 × 10^-4 RIU (refractive index unit). Therefore, the proposed approach has potential applications in low-cost, disposable, point-of-care biosensors.