Stop band shift based chemical sensing with three-dimensional opal and inverse opal structures

Chemical sensing ability of polystyrene opal and gold and titania inverse opal structures was demonstrated with sensitive response of stop band position with respect to refractive index variations of flowing media or bound analytes. Ethanol solutions of 80, 40, and 20% (v/v) were demonstrated to be consistently differentiated with a 1.5–2 nm shift in stop band position with the polystyrene opal structure. The sensitivity was enhanced, by using gold and titania inverse opal structures as the sensing host, to 4.5–6 nm in shifts of the stop band position. Detection of the presence of analytes was also demonstrated by shifts of 3.5 and 4.5 nm in stop band position effected by binding of C8H18S and C18H38S, respectively, onto the surface of the gold inverse opal.