A highly sensitive technique is reported to detect NO using X-ray photoelectron spectroscopy (XPS) of a silicon-bound iron hemelike complex. A self-assembled monolayer of an hydroxyalkylphosphonic acid was grown on the native oxide surface of silicon and was used for covalent attachment of hematin. XPS analysis for the hematin nitrogens gives a single peak in the N(1s) region. After reaction with NO, a new, distinct peak is observed in the N1s spectrum, at approximately 5.5 eV higher binding energy, which is attributed to the heme-bound NO. On the basis of measurements of surface loading of hematin species using quartz crystal microgravimmetry and XPS, detection of <= 50 picomoles of NO in the sampled region can be accomplished.