Nanoceria surface: the most sensitive redox-triggered one step nano-amplifier for fluorescence signal of ochratoxin A

Sensitive detection of redox active analytes utilising its fluorescent nature requires a direct non-complicated approach to amplify its emission intensity. In this regard, we investigated nanoscale cerium oxide for its unique nanosized structure, surface reactivity and redox activity coupled with surface complexation. Variations in either oxidation state or the surface-terminated oxygen of the cerium oxide nanoparticales provide gaps for the adsorption of redox functionalities. It enables ceria particles to concentrate the analyte molecules on their surface promoting fluorescence signal amplification. As a proof of concept, we integrated surface complexation feature of nanoceria towards improved fluorescent response and successively implemented them for ultra-sensitive identification of a redox active Ochratoxin A (OTA) at specific wavelength range. Results obtained indicate that higher amplification efficacy of nanoparticles is due to its higher electron mobility along with good absorbability. Different identification techniques including XRD SEM, UV–Vis, EDX, FTIR, photoluminescence, RAMAN spectroscopy and finally fluorescence assays were performed to examine morphology and nano-surface chemistry along with signal amplified strategy of the developed nano-probe. Various experimental factors including incubation time, pH and concentrations of OTA and ceria particles were also optimised. Under optimised environment, the limit of detection was as smaller as 0.1 ng mL −1 with 0.5–100 ng mL −1 of linear range. Thus, we proposed a highly sensitive and selective fluorescent nanoprobe for analytical applications based on surface complexation affinity and fluorescence signal amplification ability of nanoceria.