Molecularly-tailored nanomaterials and interfaces with novel properties

Realizing novel nanomaterials and tailored heterointerfaces with control over electrical, thermal and mechanical properties is key for many applications such aselectronics devices and energy harvesting. The first part of my talk willdiscuss the synthesis and properties of a new class of bulk doped bulk nanothermoelectric materials obtained by surfactant-directed sculpting and dopingfor solid-state cooling and electricity harvesting from waste heat. The second part of my talk will describe the use of nanomolecular layers of organic coupling agents to tailor multiple properties of soft-hard or organic-inorganic heterointerfacesgermane toemergent electronics devices. I will demonstrate a scalable microwave-solvothermal approach to sculpt nanocrystals with controlled shape, size, trace doping and surface chemistry. Bulk pellets made from these nanocrystalsexhibit multifold higher figures of merit than their non-nanostructured and/or non-alloyed counterparts. While nanostructuring leads to ultralow thermal conductivities, doping-induced alterations in defect chemistry and electronic band structure of the materials leads to high electrical conductivities and high Seebeck coefficients. Atomistic and electronic property enhancement mechanisms will be discussed based upon electron microscopy, spectroscopy and density functional theory calculations for sulfur-doped V-VI compounds and Al-doped ZnO. 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 heterointerfaces. In particular, I will demonstrate multifold enhancement in electrical stability, mechanical toughness and thermal conductance by understanding and manipulating the interfacial bond chemistry using organosilane or organophosphonatenanolayers. The interrelationships between these properties, the enhancement mechanisms, and the utility of using nanomolecular layers to access atomistic details of interfacial phenomena will be discussed in light of spectroscopic probing of the interfaces and their fracture surfaces,and theoretical calculations. 

Selected references
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