Fluorescent silver nanoclusters with a size of about 2 nm were synthesized within 90 s by irradiating a mixture of silver precursor and polymethacrylic acid sodium salt solution under Xe lamp. The proposed method was well optimized by a systematical investigation of experimental parameters, such as irradiation time, initial concentration, pH of the solution. The obtained nanoclusters were well dispersed in water and exhibited bright emission upon visible light excitation. This approach can be further extended to use solar light for the large scale synthesis. Strikingly, the emission intensity of as-prepared silver nanoclusters could be enhanced up to similar to 60% by the addition of 1-(2'-hydroxylethyl)-3-methylimidazolium tetrafluoroborate ([HOEtMIm][BF4]) ionic liquid. Meanwhile, these nanoclusters, in between molecules and normal nanoparticles, intensely absorb light around 510 nm covering the most intense part of solar light, should be a promising visible light sensitizer in solar cell and water splitting applications. Copyright (C) 2013, Hydrogen Energy Publications, LLC. Published by Elsevier Ltd. All rights reserved.