Abstract

A nanophotonic structure with electric control based photocatalytic nanocomposite is proposed to realize label-free optical detection of foodborne pathogens. The photocatalytic response of Cu-ZnO/TiO₂ (CZT) nanocomposite, in terms of the photocurrent, is utilized to detect E. coli in the surrounding media of Luria Bertani broth (LB) solution. An engineered nanophotonic structure based on an optical slot waveguide is presented to provide a two-fold benefit - enhanced light-matter interaction and flexibility to accommodate bio-sample. CZT nanocomposite is synthesised and prepared by a cost-effective sol-gel process, acting as an active layer in the structure, is responsible for the generation of photo-excited carriers which provide photocurrent on the application of a voltage. The fabricated structure with a synthesised nanocomposite slot waveguide exhibits a measured photocurrent of 22 μA with LB media, decreasing to a value of 13 μA in the presence of E. coli. The fabricated biosensor is capable of detecting E. coli bacteria concentrations of 5000 CFU/ml. Altogether a change in photocurrent of 9 μA is obtained with E. coli on applying a low voltage of 3.5 volts. The combination of photocatalytic nanocomposite with engineered optical waveguide carries great potential for applications in biochemical detection and in realizing other integrated photonic devices with slotted nanocomposites.

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