Optical properties of CdSe nanoparticles synthesized by hot injection in air

The hot injection technique is used to produce CdSe nanoparticles with quantum dot properties. There are many reports about the synthesis of quantum dots by the hot injection method; this successful synthesis approach included a semiconductor precursor, organic species such as coordinating agent trioctylphosphine (TOP) and/or trioctylphosphine oxide (TOPO). In all cases, they have considered that inert atmosphere (nitrogen or argon) is necessary for a successful synthesis, which requires specific laboratory facilities, making it cost sensitive and, consequently, complicating the experimental setup. The novelty of this work is the synthesis of CdSe under air condition instead of inert atmosphere by hot injection method, although several works report some precursors and products are highly susceptible to degradation by moisture and oxygen. The synthesis of QDs in air has the advantage that simplifies the experimental setup. To avoid undesirable interactions with oxygen, well-defined concentrations of the organic species were used during the synthesis. The influence of air over growth rate of particles was observed. To establish a comparison, the same experimental methodology was applied in both nitrogen and in air atmospheres. Results show that nanoparticles synthesized in air presented a higher growth rate than those synthesized in nitrogen at the same reaction times. Additionally, similar optical behaviors and band gaps were observed in both cases, showing the important fact that an inert atmosphere is not necessary for the synthesis of quantum dots made of CdSe nanoparticles.