February 17, 2015 at 8:00 pm

INPP Seminar: Heat Transport across a Gold Nanowire/water Interface Enhanced by Ionic Strength of Aqueous Ssolution, Feb .17

Susil Baral

Susil Baral

The Institute of Nuclear and Particle Physics (INPP) presents Susil Baral, of  Ohio University, presenting Heat transport across a gold nanowire/water interface enhanced by the ionic strength of aqueous solution.” on Tuesday, Feb. 17, at at 4:00 p.m. in Edwards Accelerator Lab, Roger W. Finlay Conference Room.

Abstract: Thermal transport at interfaces impact various aspects of new technologies where nanoscale heaters are used to drive processes for solar steam generation, thermal energy harvesting, photothermal therapy, drug delivery, water sterilization, biological imaging, biological actuation, catalysis, data storage and in optoelectronic devices. The efficiency and performance of a nanosystem is limited by various structural and physical properties of an interface.  These properties affect thermal processes and play a key role on heat dissipation and transport across an interface. Conventional acoustic or diffuse mismatch models can only give a limited understanding concerning thermal boundary resistance across a solid-fluid interface. The acoustic mismatch model assumes that the boundary resistance is a consequence of impedance on the flow of thermal phonons across the interface. Only a fraction of the incident phonons (determined by the acoustic mismatch between the solid and liquid) will pass through the interface.  This model assumes specular transmission of phonons with no scattering at the interface and usually represents an upper bound on thermal boundary resistance. The diffuse mismatch model, on the other hand, represents a lower bound of thermal boundary resistance. This model assumes that phonons are diffusively scattered at the interface and the probability of the phonon transmission is related to the mismatch between the densities of states across the interface. Both models consider only the bulk properties of the two interfacial materials with no accounting for the interaction between the solid and liquid. Numerous works on solid/liquid interface suggest the heat transport across an interface increases with increase in interfacial adhesion energy. These studies use relatively strong interaction between the ligand molecules covalently functionalized onto the solid and the aqueous environment.  In this talk I will present how the addition of charges affect thermal transport across a weakly interacting bare gold nanowire/water interface. The local temperature change from optically excited single gold nanowires, lithographically prepared on Al0.94Ga0.06N embedded with Er3+ ions, is measured in air, pure water and various concentration aqueous solutions of ionic solutes NaCl, Na2SO4 and MgSO4. The interface thermal resistivity for heat transfer from the heated nanowires into the surrounding water is calculated from the slopes of the temperature change versus laser intensity plots obtained for the nanowire excitation under different concentration solutions. Addition of ionic solute molecules into the solution increases the heat dissipation into the surrounding water thereby decreasing the interface thermal resistivity. Saturation in interface thermal resistivity around zero is observed for solution ionic strength 0.3 moles per liter and higher.

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