A photoisomerizable thiolated nitrospiropyran SP, (1a), monolayer is assembled on a Au electrode by the primary deposition of thiolated nitromerocyanine isomer 1b as a monolayer on the electrode, followed by the irradiation of the surface with visible light, lambda > 475 nm. The surface coverage of nitrospiropyran units (1a) on the electrode is 2 x 10(-10) mole cm(-2). Irradiation of the electrode with UV light, 320 nm < lambda < 360 nm, results in the nitromerocyanine, MR, monolayer on the electrode that binds Ag+ ions to the phenolate units. The Ag+ ions associated with the MR monolayer undergo cyclic reduction to surface-confined Ag-0 nanoclusters, and reoxidation and dissolution of the Ag0 nanoclusters to Ag+ ions associated with the monolayer are demonstrated. The electron-transfer rate constants for the reduction of Ag+ to A(0) and for the dissolution of Ag-0 were determined by chronoamperometry and correspond to k(et)(red)) 12.7 s(-1) and k(et)(ox)) 10.5 s(-1), respectively. The nanoclustering rate was characteri degrees zed by surface plasmon resonance measurements, and it proceeds on a time scale of 10 min. The size of the Ag-0 nanoclusters is in the range of 2 to 20 nm. The electrochemically induced reduction of the MR-Ag+ monolayer to the MR-Ag-0 surface and the reoxidation of the MR-Ag-0 surface control the hydrophilic-hydrophobic properties of the surface. The advancing contact angle of the MR-Ag-0-functionalized surface is 59, and the contact angle of the MR-Ag+-monolayer-functionalized surface is 74. Photoisomerization of the Ag-0-MR surface to the Ag-0-SP state, followed by the oxidation of the Ag-0 nanoclusters, results in the dissolution of the Ag+ ions into the electrolyte solution.