Fluorescence resonant energy transfer (FRET) has been clearly demonstrated between CdSe/ZnS type I quantum dots and CdSe/ZnTe type II quantum dots by photoluminescence, time-resolved photoluminescence (TRPL), and photoluminescence excitation (PLE) measurements. The result of PLE experiment provides us concrete evidence that the emission of CdSe/ZnTe quantum dots is indeed influenced by CdSe/ZnS quantum dots. It is found that by changing the size of CdSe/ZnS quantum dots, the emission spectra of CdSe/ZnTe quantum dots can be selectively enhanced in a particular wavelength range and the emission intensity of type II quantum dots can be greatly enlarged by up to four times. Together with the large tunability of the emission energy in the infrared region, our finding provides an opportunity for creating highly efficient optoelectronic devices and bioimaging labels derived from type II quantum dots. We stress here that the large difference in emission energies between donors and acceptors in our studied system...