Studies of surface plasmon resonance effect on different metallic layers of silver (Ag) and copper (Cu) with molybdenum trioxide (MoO3) for formaldehyde sensor

This paper reports the implementation of surface plasmon resonance in optical fiber sensor for formaldehyde detection. The studies involve comparison effects of different metallic layer of silver (Ag) and copper (Cu) to enhance evanescence wave in optical fiber sensor (OFS). We integrate the MoO3 materials due to its natural advantage where it can be used as high-activity metal oxide catalyst. The sensor will be focusing on sensing formaldehyde which is an environmental pollutant and is considered hazardous if more than 0.1 ppm is inhaled. MoO3 contributes to the sensitivity enhancement and improvement of the oxidation resistance on the metal films. The independent variables are the different metal films namely Ag and Cu at 40 nm thickness obtained from previous work. Formaldehyde sensing using bare Cu film, bare Ag film and the combination of Cu/Ag-MoO3 is compared via transmission-wavelength graphs to check if there is sensitivity enhancement in the Cu/Ag-MoO3 combination. Ag-MoO3 displays a better red shift with formaldehyde, by 10 nm at a resonant wavelength of 350 nm where Cu shows highest responsive metallic layer in formaldehyde detection.