Non-perpendicular incidence angle of cold atmospheric-pressure plasma treatment for fabrication of silver-based surface plasmon resonance biosensor for detection of Escherichia coli in water

Abstract

In this study, for the first time, to our knowledge, a biosensor was produced using cold atmospheric plasma (CAP) treatment of silver thin film surface with non-perpendicular incidence angle for identification of Escherichia coli in the distilled water. Field emission scanning electron microscopy (FESEM) exhibits that before deposition, non-perpendicular CAP treatment of glass surface substrate leads to the production of pinhole-free silver thin film. The results of atomic force microscopy (AFM), and curve fitting show that non-perpendicular CAP treatment of this pinhole-free silver thin film indicates to the appearance of Ag NPs with smaller size and larger surface area compared to untreated silver film deposited on the untreated glass substrate. The silver-based pinhole-free SPR biosensor produced with non-perpendicular CAP treatment of both glass substrate and silver film shows E. coli detection in the distilled water in the range of 104 Colony forming unit (CFU/ml) to 108 CFU/ml with better sensitivity compared to the untreated silver-based SPR biosensor.