In this study, CdTeS nanocrystals, which are known as quantum dots, were colloidally synthesized in water-dispersible form. Analysis and characterization of the obtained nanocrystals were carried out by UV–Vis and fluorescence spectrophotometry, TEM, XRD, SEM–EDX, XRF, Raman spectroscopy and FTIR techniques. These particles have had facility of application in electronic and biological areas where they are used to detect some pollutants with sensor applications. Their fluorescence properties can be changed by interaction with some materials. The obtained CdTeS nanocrystals were used in the detection of heavy metal ions such as Cr(III), Mn(II), Ni(II), Zn(II), Pb(II), Hg(II), Cu(II), Ag(I), V(II), Cd(II), Co(II), Fe(II), Al(III), Sn(II) for designing optic sensors. According to the obtained findings, the highest quenching effect was observed in the presence of Cr(III) ions.