Synthesis of colloidal PbS nanosheets with nearly 100% success rate
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Synthesis of colloidal PbS nanosheets with nearly 100% success rate Shashini M Premathilaka,1, 2 Zhoufeng Jiang,1,2 Antara Antu,1 Joey Leffler,1 Jianjun Hu,3 Ajit Roy,3 Liangfeng Sun1,2 1
Department of Physics and Astronomy, Bowling Green State University, Bowling Green, OH 43403,USA 2 Center for Photochemical Sciences, Bowling Green State University, Bowling Green, OH 43403,USA 3 Materials and Manufacturing Directorate, Air Force Research Laboratory, Wright-Patterson Air Force Base, Ohio 45433, USA
ABSTRACT We report a robust method by which colloidal PbS nanosheets can be synthesized with nearly 100% success rate. It is achieved by replacing the lead acetate by lead oxide for preparation of the lead precursor. Acetic acid either injected externally or produced during the reaction can significantly affect the growth of the nanosheets. The existence of water in the reaction solution makes the nanosheets smaller in lateral size while the purity of trioctylphosphine has no significant effect on the nanosheet growth. INTRODUCTION Since the first invention of the colloidal synthesis of PbS nanosheets by Schliehe and coworkers,1 many research work follow up.2-8 Aerts and coworkers reported highly efficient carrier multiplication in PbS nanosheets.3 Bhandari and coworkers demonstrated thicknessdependent energy gaps of the PbS nanosheets.5 Dogan and coworkers report large carrier mobility in single PbS nanosheets,2, 7 making it promising for photovoltaic applications. However, synthesis of colloidal PbS nanosheets is still in its infancy. Although it has been demonstrated that chloroalkane (e.g. chloroform) ligands can drive two-dimensional attachment of PbS quantum dots to form nanosheets,1, 5 the synthesis itself has a low success rate. Bielewicz and coworkers believed that the purity of trioctylphosphine might have negative effect on the synthesis of nanosheets.6 Hence they developed a new synthesis of PbS nanosheets without using trioctylphosphine.6 Zhang and coworkers developed another method that lead oxide (PbO) and bis(trimethylsilyl)sulfide (TMS) are used as the lead and the sulfur precursors, respectively. Nanosheets were synthesized successfully but mixed with quantum dots.9 Along this line, we conducted a systematic study of the effect of acetic acid on the formation of the PbS nanosheets and found there was a threshold of the amount of acetic acid, above which the nanosheets will not form. Water in the reaction solution tends to decrease the lateral size of the nanosheets and created quantum dots. In the new synthesis, the purity of trioctylphosphine has no significant effect on the nanosheet growth. With the knowledge obtained, we developed a new robust synthesis method that can produce quantum-dot-free nanosheets with virtually a 100% success rate.
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EXPERIMENT In the original syn
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