Functionalised nanoparticle films for the targeted detection of particular analytes at low concentrations using surface-enhanced resonance Raman spec

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Functionalised nanoparticle films are being employed for the targeted detection of particular analytes at low concentrations using surface-enhanced resonance Raman spectroscopy (SERRS). The films are formed through the controlled migration of the nanoparticles to the interface between two immiscible liquids. This is achieved through the addition of a species that alters the surface charge present on citrate-stabilised nanoparticles through either modification or promotion. Modifying requires a species that binds to the surface of the nanoparticle and changing the hydrophobicity. Promotion works by using a species that disrupts the electrostatic forces between the nanoparticles. In addition to nanoparticle liquid-liquid interfaces, solid substrates will also be employed for the same purpose. In this instance, the Re complexes are designed to act as a modifying species. The work involves the synthesis of a collection of Re centred complexes with ligand species that aid with both the binding of the complex to the nanoparticle and the sensing capabilities. The complexes modify the nanoparticle sufficiently so film formation is successful. The ligands themselves are bipyridyl derivatives that involve a relatively easy synthesis and then complexation with Re to form the complexes. Modification of the nanoparticles is also easily achieved through simple addition of a Re complex solution to a volume of nanoparticles. The modified nanoparticles can then be shaken in the presence of a solvent that is immiscible with water. Film formation is observed when a metallic film forms at the interface. Once the functionalised films have been produced, they are tested for their SERRS activity before being washed with solutions containing the analyte. Sensing is reliant on changes to the Raman response of the complex upon the addition of the targeted species. Once the desired interaction has been observed, the selectivity and limits of detection of the platform can be assessed.