A sensor has a sensor substance, an electromagnetic energy source, and a detector. The sensor substance may be able to emit electromagnetic energy different than that provided by the energy source when an analyte of interest is in contact with the sensor substance and electromagnetic energy is received by the sensor substance. The energy source and the detector may be provided on the same side of the sensor substance.In a method according to the invention, a determination may be made as to whether an analyte is present in a sample. Such a method may provide a sensor, such as that described above. Electromagnetic energy may be provided to the sensor substance using the energy source, and the sensor substance may be contacted with a sample. Electromagnetic energy may be emitted from the sensor substance and received at the detector. The detector may provide a signal indicating the type of electromagnetic energy emitted from the sensor substance. The signal from the detector may be analyzed to determine whether the analyte was detected.