We have studied the scanning tunneling microscope-induced light emission from Au surfaces in air. The effect of adsorbates on the light emission was investigated. Atmospheric contaminants appear as nonemissive clusters in the luminescence images. Preliminary results suggest that UV/ozone exposure partially reverses the effect of atmospheric contamination. Self-assembled monolayer chemisorption was also studied. The presence of an octadecylthiol (ODT) monolayer on the Au surface decreases the light emission intensity by one order of magnitude. Selective inhibition of luminescence is demonstrated using a microcontact printed pattern of ODT.