A water-soluble, functionalized nanocrystal comprising:(a) a quantum dot having a core wherein the core comprises CdX, and wherein X is Se, Te or S; (b) a shell, wherein the shell comprises YZ, and wherein Y is Cd or Zn, and Z is S, or Se; (c) a capping compound operably linked to the quantum dot, wherein the capping compound comprises a compound having the formula HS(CH2)n X, and wherein X is a c