Sensors and Actuators Reports (Nov 2022)
Enhanced Electrochemiluminescence from 3D Nanocavity Electrode Arrays
Abstract
3D arrays comprising interconnected voids have been created using nanosphere lithography (2000≤diameter≤240 nm) followed by electrodeposition of gold. The top surface was blocked with 11-mercaptoundecanoic acid and then the templating polystyrenes were dissolved using THF. The interior surfaces were then functionalized with DNA capture strands that are complementary for part of a target sequence associated with methicillin-resistant Staphylococcus aureus, MRSA, genomic DNA. Once the target is hybridised, a probe sequence that is functionalised with [Ru(bpy)2 PIC]2+, is hybridised to the overhang of the target, bpy is 2,2’-bipyridyl and PIC is (2,2′-bipyridyl)-2(4-carboxy phenyl) imidazo [4,5][1,10] phenanthroline. The electrochemiluminescence, ECL, intensity generated from the hybridised ruthenium dye in the presence of tri-propyl amine and normalised for the charge passed depends on the size of the nanocavity. Significantly, the normalised ECL intensity is approximately 7-fold higher for the 820 nm array than either the 2000 nm array or a planar electrode. The array that is functionalised with the capture-target-Ru probe can be used as a 3D bipolar electrode to wirelessly generate ECL. The peak shape and intensity of the wireless ECL spectra depend on the cavity size with the brightest ECL being observed for the 820 nm cavity array. The results are consistent with a fraction of the ECL light activating the broad cavity plasmon of the array and enhancing the overall ECL intensity. The 820 nm array has been used to develop an assay for the detection of MRSA DNA giving a linear dynamic range from 10 nM to 30 µM with an LOD of 1 µM and an LOQ of 3.2 µM. Significantly, the analytical sensitivity of the wireless ECL assay is approximately 7 times higher for the 820 nm array than that observed for a planar electrode.
