Highly sensitive nickel sensor based on repeatable fluorescence quenching-emerging mechanism was developed. Highly luminescent thioglycolic acid capped CdTe nanocrystals in aqueous solution were applied as the fluorescence probe. These nanocrystals represented a considerable photoluminescence quantum yield as high as 61%. The florescence was quenched by addition of Ni ions to the CdTe nanocrystals soltition. Then it was recovered by injection of the proper amount of dimethylglyoxime as the releasing reagent. The relative fluorescence intensity (F-o/F) was linearly proportional to the concentration of nickel ions in the range of 0.01-10 mu M, with detection limit as low as 7 nM. Described method is able to selectively determine without any tangible influence of some potentially interfering ions such as Ag+, Cu2+, Zn2+, Co2+ and Hg2+. The developed technique was employed for determination of Ni2+ in different environmental water samples, and the results were verified by inductively coupled plasma-optical emission spectrometry. (C) 2017 Elsevier Ltd. All rights reserved.