A carboxymethyl-dithiocarbamate immobilized polyacrylonitrile fiber colorimetric sensor has been synthesized. This fiber sensor exhibits excellent selectivity and sensitivity for Ag+ in aqueous solution with a remarkable color change from light pink to red-brown over a wide pH range of 2-12. The sensor responds selectively to Ag* in the presence of other ions, including Mg2+, Al3+, Ca2+, Cr3+, Mn2+, Co2+, Ni2+, Cu2+, Zn2+, Cd2+, Hg2+ and Pb2+. The colorimetric sensor has an extremely fast response time (10s) and a low visual limit of detection (5.53 x 10(-12) mol/L). The fiber sensor also undergoes an obvious color change in the presence of Ag+ solutions containing EDTA, NaCI or NaBr. Density functional theory optimization reveals that the sensor and Ag+ interact via a seven-membered ring complexation mechanism. (C) 2015 Elsevier B.V. All rights reserved.