Cadmium selenide (CdSe) aqueous quantum dots (AQDs) with broadband trap-state emissions were synthesized using an environmentally friendly, aqueous method under room temperature. By treating CdSe AQDs with Pb precursor in solution, the photoluminescence (PL) intensity and quantum yield of the CdSe AQDs doubled. Furthermore, the absorption edge and PL peak wavelength of CdSe blue-shifted. It was found that the presence of excess Cd in the CdSe is essential to the observed behavior. A possible cation exchange between Pb and the excess Cd is proposed to explain the observation. Our study provides a unique way to increase the photoluminescence intensity of trap-state emission quantum dots.