A thin film of Al(0.94)Ga(0.06)N embedded with Er(3+) ions is used as an optical temperature sensor to image the temperature profile around optically excited gold nanostructures of 40 nm gold nanoparticles and lithographically prepared gold nanodots. The sensor is calibrated to give the local temperature of a hot nanostructure by comparing the measured temperature change of a spherical 40 nm gold NP to the theoretical temperature change calculated from the absorption cross section. The calibration allows us to measure the temperature where a lithographically prepared gold nanodot melts, in agreement with the bulk melting point of gold, and the size of the nanodot, in agreement with SEM and AFM results. Also, we measure an enhancement in the Er(3+) photoluminescence due to an interaction of the NP and Er(3+). We use this enhancement to determine the laser intensity that melts the NP and find that there is a positive discontinuous temperature of 833 K. We use this discontinuous temperature to obtain an interface conductance of ∼10 MW/m(2)-K for the gold NP on our thermal sensor surface.

No abstract

The combined influences of Hall current and thermophoresis on a magnetohydrodynamic mixed convective heat and mass transfer flow of a thin film second-grade fluid with viscous dissipation and thermal radiation past a stretching sheet are analyzed. An external strong and uniform magnetic field is applied transversely to the stretching sheet. The surface of the stretching sheet is taken to move with a linear velocity and subject to the constant reference temperature and concentration. Entropy generation is introduced to investigate the irreversibility associated with flow, heat and mass transfer. The basic governing equations for the velocities, temperature and concentration of the fluid motion have been modeled by employing appropriate similarity transformations which result in high nonlinear coupled differential equations with physical conditions. The solution of the transformed systems of equations has been achieved by employing Homotopy Analysis Method (HAM) which lead to detailed expressions for the velocities, temperature and concentration components. The obtained results are compared with the published results in the tables 3-5 demonstrating an excellent agreement and correlation. Graphs are discussed to elucidate the effects of various parameters.

No abstract

No abstract