Bloch Surface Wave‐Coupled Enhanced Fluorescence on a Nano‐Assembly–Photonic Crystal Hybrid Interface for Ultrasensitive Detection

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Abstract
There is an ever‐increasing demand for miniaturization and portability of reliable sensor platforms for individualized health monitoring in diagnostics. Photonic crystals (PC)‐based frameworks in conjugation with fluorescence techniques efficiently address these requirements on account of their high sensitivity, compactness, and robust integrated features. Here we demonstrate fluorophore emission engineering via Bloch surface waves (BSWs) supported by one‐dimensional PCs. Since brighter emission directly translates to improved detection performance, achieving highly sensitive PC platforms necessitates careful interfacial nano‐engineering. In this context, cryosorets, which are hybrid nano‐assemblies composed of gold nanoparticles (AuNPs) and TiO 2 nanorods (TiO 2 NRs), are used to generate three‐dimensional multi‐fold hotspots. When interfaced with a PC, the resulting metallo‐dielectric hybrid yields photonic crystal‐coupled emission (PCCE), mitigating the challenge of fluorescence quenching. The nanoscale gaps between the plasmonic AuNPs, high refractive index (HRI) TiO 2 NRs, and graphene oxide (GO) hybrid interface generate strong hotspots, augmenting the fluorescence coupling via the underlying BSW. Integrating such sensors onto smartphones and other personalized devices to enable rapid, on‐site sensing of target analytes is need of the hour. The high 1300‐fold PCCE enhancement enables attomolar sensing of rhodamine reporter molecule and is demonstrated here using a smartphone camera as a detector amenable for resource limited settings.
Funding Information
  • Department of Science and Technology, Government of Kerala (DST/TTI/TDP‐21/2024)

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