The growth and transformation of α-SeNPs into metal selenides was observed by UV/Vis spectroscopy. The metal selenide NPs (e.g., ZnSe and CdSe) precipitate from solution upon formation. Therefore we can monitor the growth and decay of the characteristic α-SeNP absorbance at 375 nm over time (Figure ). From this data, it appears that 30 seconds after borohydride addition to selenite, α-SeNP formation is apparent. The reaction proceeds for 5 minutes prior to addition of either Zn(OAc)2 or Cd(OAc)2 in a 100:1 molar ratio of Zn/Cd:Se. In the case of ZnSe, a change in the absorbance profile begins to occur after approximately 3 minutes, and in the case of CdSe this occurs after approximately 4 minutes (Figure ). During this time there is a gradual decay of the absorbance of α-SeNPs, indicating that the particles are precipitating from solution as the reaction proceeds.