Abstract: The present disclosure pertains to the use of intense, narrow-linewidth surface, chemically-switchable ultraviolet photoluminescence from radiative recombination of the two-dimensional electron liquid with photo-excited holes in complex oxide heterostructures, such as LaAlO3/SrTiO3 (LAO/STO). Such photoluminescence from the interface between the upper and lower layers can be suppressed and restored reversibly under oxidizing and reducing conditions, respectively, as induced by chemisorption and reversal of chemisorption on the exposed surface of the heterostructure's upper member. Making use of this chemically-switchable ultraviolet photoluminescence, the present disclosure provides, inter alia, systems for detection of a chemical species, methods for determining the absence or presence of a chemical species in a sample, optoelectronic devices, and methods for producing optoelectronic devices.