Thermal rectification is a phenomenon in which thermal transport along a specific axis is dependent upon the sign of the temperature gradient or heat current. This phenomenon offers improved thermal management of electronics as size scales continue to decrease and new technologies emerge by having directions of preferred thermal transport. For most applications where thermally rectifying materials could be of use they would need to exhibit one direction with high thermal conductivity to allow for efficient transport of heat from heat generating components to a sink and one direction with low conductivity to insulate the temperature and heat flux sensitive components. In the process of understanding and developing these materials multiple mechanisms have been found which produce thermally rectifying behavior and much work has been and is being done to improve our understanding of the mechanisms and how these mechanisms can be used with our improved ability to fabricate at the nanoscale to produce efficient materials which have high levels of thermal rectification.

In the emerging field of thermoplasmonics, Joule heating associated with optically resonant plasmonic structures is exploited to generate nanoscale thermal hotspots.In the present study, new methods for designing and thermally probing thermoplasmonic structures are reported. A general design rationale, based on Babinet's principle, is developed for understanding how the complementary version of ideal electromagnetic antennae can yield efficient nanoscale heat sources with maximized current density. Using this methodology, we show that the diabolo antenna is more suitable for heat generation compared with its more well-known complementary structure, the bow-tie antenna. We also demonstrate that highly localized and enhanced thermal hot spots can be realized by incorporating the diabolo antenna into a plasmonic lens. Using a newly developed thermal microscopy method based on the temperature-dependent photoluminescence lifetime of thin-film thermographic phosphors, we experimentally characterize the thermal response of various antenna and superstructure designs. Data from FDTD simulations and the experimental temperature measurements confirm the validity of the design rationale. The thermal microscopy technique, with its robust sensing method, could overcome some of the drawbacks of current micro/nanoscale temperature measurement schemes.

No abstract

We are investigating the properties of corrole-sensitized TiO 2 solar cells. The TiO 2-adsorbed free base and Ga III corroles display cell efficiencies under AM 1.5 illumination that are about half that of a standard N 3-sensitized cell ( N 3 = cis-bis(4,4'-dicarboxy-2,2'-bipyridine)dithiocyanato ruthenium(II)), while that of the Sn IV-based cell is much lower. The properties of the corrole- TiO 2 solar cells, along with results obtained with electrodes of lower conduction band energies clearly reveal that the reducing power of the singlet excited states of the free base and Ga III corrole, but not of the Sn IV derivative, is sufficiently high for efficient injection into the TiO 2 conduction band.

The interplay between mechanical strains and battery electrochemistry, or the tunable mechanochemistry of batteries, remains an emerging research area with limited experimental progress. In this report, we demonstrate how elastic strains applied to vanadium pentoxide (VO), a widely studied cathode material for Li-ion batteries, can modulate the kinetics and energetics of lithium-ion intercalation. We utilize atomic layer deposition to coat VO materials onto the surface of a shapememory superelastic NiTi alloy, which allows electrochemical assessment at a fixed and measurable level of elastic strain imposed on the VO, with strain state assessed through Raman spectroscopy and X-ray diffraction. Our results indicate modulation of electrochemical intercalation potentials by ∼40 mV and an increase of the diffusion coefficient of lithium ions by up to 2.5-times with elastic prestrains of <2% imposed on the VO. These results are supported by density functional theory calculations and demonstrate how mechanics of nanomaterials can be used as a precise tool to strain engineer the electrochemical energy storage performance of battery materials.