Colloidal Semiconductor Nanocrystals- Crystal Phase control to form - PowerPoint PPT Presentation

Colloidal Cu 2 ZnSn(SSe) 4 (CZTSSe) Nanocrystals- Shape and Colloidal Semiconductor Nanocrystals- Crystal Phase control to form Dots, Arrows, Ellipsoids and Structure as Resolved by TEM Rods Shalini Singh, Pai Liu, Claudia Coughlan, Matteo Lusi, Kevin M. Ryan Materials and Surface Science Institute, University of Limerick, Limerick, Ireland. nanoresearchul.org

Semiconductor Metal Chalcogenide Nanocrystals Element Groups I II III IV VI Zn S Cu In S Cu Zn S Se Sn  Low Toxicity  Earth Abundance  Band Gap Tunability Singh A., Singh S., Levcenko S., Unold T., Laffir F. and Ryan K. M. Angew. Chem. Int. Ed. 2013, 52, 9120 nanoresearchul.org

Colloidal Approach Nanocrystal Growth (002) nanoresearchul.org

Challenges in the Synthesis of CZTSSe Nanocrystals  Five elements  Multiple precursors  Reactivity differences of metal precursors  Narrow temperature window  Wide choice of ligands  Size distribution  Phase selection Singh S. and Ryan K. M. J. Phy. Chem. Lett. 2015, 6, 3141 nanoresearchul.org

Phase and Shape Controlled Synthesis of CZTSSe Nanocrystals Zinc -Blende Singh S., Liu P., Singh A., Coughlan C., Wang J., Lussi M. and Ryan K. M . Chem Mater. 2015, 27, 4742. nanoresearchul.org

Ellipsoidal Shaped Polytypic CZTSSe Nanocrystals Ligands: Oleylamine and phosphonic ligands Precursors: Copper chloride, zinc and tin acetates, thiol, diphenyldiselenide Temperature: 150-160 ° C injection /250-270 ° C growth . nanoresearchul.org

Time Dependent Aliquot Study of Ellipsoidal Nanocrystals (1 min) (3 min) 5 nm 50 nm 50 nm (5 min) (10 min) 5 nm 5 nm 5 nm 5 nm 50 nm 0.1 µm 50 nm 0.1 µm nanoresearchul.org

Arrow Shaped Polytypic CZTSSe Nanocrystals Ligands: Oleylamine and phosphonic ligands Precursors: Metal acetates, thiol, diphenyldiselenide Temperature: 150-160 ° C injection /250-270 ° C growth . nanoresearchul.org

Time Dependent Aliquot Study of Arrow Shaped Nanocrystals (1 min) (3 min) (001) WZ 2 nm 2 nm (e) (5 min) (10 min) 2 nm 2 nm 2 nm nanoresearchul.org

Bullet Shaped Polytypic CZTSSe Nanocrystals Two step process: 1. Wurtzite Nanocrystals synthesis- Copper acetylacetonate, zinc and tin acetates, thiol, DPDSe in OLA. 2. Post-treatment with TOPO-ODPA-Se.S in OLA at 270 ° C. nanoresearchul.org

Formation Pathway for Bullet Shaped Nanocrystals nanoresearchul.org

Synthesis of Wurtzite CZTSSe Nanorods Cu-1.5 mmol Cu-1.2 mmol Cu-2 mmol Cu-2 mmol Cu-1.5 mmol Cu-1.2 mmol Ligands: ODE, TOPO Precursors: Copper acetylacetonate, zinc and tin acetate, DDT, DPDSe. Temperature: 150-160 ° C injection /250-270 ° C growth . Cu-1.0 mmol Cu-0.8 mmol Cu-0.8 mmol Cu-1.0 mmol nanoresearchul.org

Conclusion  A range of synthetic approaches were developed to obtain control over shape and phase of anisotropic CZTSSe nanocrystals.  The combination of coordinating solvent (OLA), TOPO and PAs entails the evolution of atypical polytypic heterostructure whose shape could be controlled by the nature of metal precursors.  The concomitant polytypism could be ruled out by replacing OLA and PAs by non-coordinating solvent (ODE).  Wurtzite nanorods are formed whose aspect ratio could be increased by gradual reduction of Cu concentrations in the initial reaction flask.  This study confirms the ability to controllably engineer the anisotropic shape and phase of complex quinary nanostructures and gives better understanding of shape evolution in compound copper based semiconductor nanocrystals. nanoresearchul.org

Acknowledgment Supervisor: Dr Kevin M. Ryan Dr Ajay Singh Dr Jianjun Wang Dr Yina Guo Nanoresearch Group nanoresearchul.org