A Simple Way To Prepare PbS Nanocrystals with Morphology Tuning at Room Temperature

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Abstract
A simple way to synthesize PbS nanocrystals with the ability to tune their morphology at room temperature is reported. The preparation utilizes an amine-catalyzed decomposition of a precursor and the amine was found to play dual roles as both the catalyst and the capping agent. Spherical PbS nanocrystals of diameters 5 to 10 nm were obtained when long chain alkylamines were used in the pot. When difunctional ethylenediamine was used instead, exclusively PbS dendrites can be isolated from the same precursor at room temperature. Uniform six- and four-armed dendrites are observed, with regular branches of ∼20 nm in diameter growing in a parallel order. In a further step, morphology tuning of the dendrites to induce 1D growth into nanorods is achievable through the addition of a trace amount of stronger capping dodecanethiol molecules. Thus, PbS nanorods with aspect ratios of ∼20 to 30 could be successfully obtained and illustrated. A possible formation mechanism is discussed and the initial step of the reaction mechanism was modeled with DFT calculations as a nucleophilic attack.