Abstract: Sensors for detecting microorganisms in gases, liquids, and aerosols are provided which include molecular receptors to interact with the microorganisms, polymeric membranes containing luminescent reagents, optional non-drying membrane additives, an optical substrate as a sensor support, an optional conformable optical substrate or rotating film to refresh the sensor chemistry, and means for detecting the signal from the sensor. Optical sign can be enhanced by immobilizing biocidal compounds in the sensing membrane, immobilizing metal colloids in the sensing membrane, or immobilizing sol-gel coated colloidal particles in the sensing membrane.