SUNUM Seminer -Ganpati Ramanath
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  • SUNUM Seminer -Ganpati Ramanath

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New classes of molecularly-tailored inorganic nanomaterials and heterointerfaces

 

Ganpati Ramanath

John Tod Horton Professor of Materials Science and Engineering

Rensselaer Polytechnic Institute, Troy, NY 12180, USA

 

Realizing novel nanomaterials and heterointerfaces with control over electrical, thermal and mechanical properties is crucial for many applications such as electronics and energy harvesting. The first part of my talk will discuss the synthesis and properties of a new class of bulk semiconductor and oxide thermoelectric materials obtained by surfactant-directed sculpting and doping for solid-state cooling and electricity harvesting from waste heat. The second part of my talk will describe the use of single nanolayers of organic coupling agents to tailor multiple properties of soft-hard or organic-inorganic heterointerfaces germane to emergent nanodevices. I will demonstrate a scalable microwave-solvothermal approach to sculpt nanocrystals with controllable shape, size, trace doping and surface chemistry. Bulk pellets made from these nanocrystals exhibit multifold superior figures of merit than their non-nanostructured and non-alloyed counterparts. While nanostructuring leads to ultralow thermal conductivities, doping-induced alterations in defect chemistry and electronic band structure of the materials lead to high electrical conductivities and high Seebeck coefficients. Atomistic and electronic structure level property enhancement mechanisms will be discussed based upon a variety of microscopies, spectroscopies, and density functional theory calculations. I will then describe how interfacial nanolayers of coupling agents with suitably chosen termini are attractive for tailoring the chemical, electrical, mechanical and thermal properties of metal-oxide heterointerfaces. I will demonstrate multifold enhancement in electrical stability, mechanical toughness and thermal conductance by understanding and manipulating the interfacial bond chemistry using molecular nanolayers. I will conclude by discussing the property interrelationships, the enhancement mechanisms, and the utility of using nanomolecular layers to access atomistic details of nanoscopic interfacial phenomena via macro-experiments.

 

Selected references

 

Nature Materials 12, 118 (2013); Nature Materials 11, 233 (2012); Nano Lett. 12, 4523 (2012); Nano Lett. 11(10), 4337 (2011); ACS Nano 4, 5055 (2010); Nano Lett. 10, 4417-22 (2010); Nature 447, 299 (2007); Phys. Rev. B. 83, 035412 (2011); Appl. Phys. Lett. 99, 133103 (2011); Appl. Phys. Lett. 99, 133101 (2011); ACS Appl. Mater. Interf. 2(5), 1275 (2010).