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Blue Bell, AR, United States

Lisunova M.,202 Bell Engineering Center | Dunklin J.R.,United Microelectronics | Jenkins S.V.,University of Arkansas | Chen J.,University of Arkansas | And 2 more authors.
RSC Advances

An optical phenomena based on the incident light absorption and transduction to the detectable thermal signal by plasmonic bimetallic Ag and Au nanocages (Ag@AuNCs) has been researched on free standing layer-by-layer (LbL) films of poly(vinyl alcohol) (PVA) and poly(vinyl pyrrolidone) (PVPON), (PVA/PVPON-Ag@AuNCs). Unlike well-studied monometallic Au nanocages (NCs), which possess a photothermal response in the near-infrared region, the bimetallic nanocages show a pronounced photothermal response in the visible range (532 nm) and near-infrared range (780 nm) due to the presence of two characteristic peaks at both wavelength ranges. The photothermal response in the visible range (532 nm) is distinguishable. Specifically increasing the laser power to 100 mW led to visual burning of the free standing film (temperature increased greater than >150 °C). The photothermal response by (PVA/PVPON-Ag@AuNCs)n films increases in proportion to the number (n) of bilayers (bl). It also increases as the molar concentration of the Ag@AuNCs introduced to the PVPON layer is increased. Therefore the molar concentration of the plasmonic Ag@AuNCs in (PVA/PVPON-Ag@AuNCs)n films is a primary factor that affects the photothermal dynamic response along with Ag@AuNCs distribution. This is supposed to result from the Ag@AuNCs assembled in a layer that leads to electromagnetic field enhancement. The unusual observation in multilayered (PVA/PVPON-Ag@AuNCs)n films is that the UV-visible spectra (extinction efficiency) and photothermal response (Tmax) do not rely on the content of the adjacent layer of PVA and show a comparable (by value in magnitude) photothermal response at a different PVA composition of 2 mg ml-1 and 20 mg ml-1 at the same Ag@AuNCs concentration in the PVPON layer. © 2015 The Royal Society of Chemistry. Source

Russell A.G.,202 Bell Engineering Center | McKnight M.D.,202 Bell Engineering Center | Hestekin J.A.,202 Bell Engineering Center | Roper D.K.,202 Bell Engineering Center | And 2 more authors.

Dynamic and equilibrium thermal behavior of plasmon-heated gold/silica capillary nanocomposite during evaporative cooling by water or butanol is accurately described at centimeter length scales by continuum optoplasmonic thermodynamics for continuous-wave laser irradiation of 15-50 mW. Gold nanoparticles randomly distributed on the capillary via electroless plating exhibited a composite extinction cross section of 66.74 ± 0.72% of the area of the laser spot, more than 2-fold larger than the physical cross-section of the AuNPs. The extinction cross-section of the AuNPs capillary was invariant for incident laser powers of 15-150 mW and was reduced slightly in the presence of butanol and water due to absorption peak-shifting to lower energies. Introducing composite thermal parameters into the optoplasmonic thermodynamic relation extended its ability to predict heat transfer to laser powers of 100 and 150 mW for water and butanol, respectively. Nonlinear behaviors such as exponential thermal profiles caused by limited thermal conductivity and film boiling are identified at higher laser powers and prevent further extension of the relation. Mathematical reduction of temperature and time variables of the mathematical description shows it accounts for all measured thermodynamic effects when the aforementioned nonlinear behaviors are not present. This confirms that extraordinary thermal transport observed in some nanocomposites are absent for AuNP/silica systems in the given ranges, which allows a macroscale, continuum approach to describe thermal transport. © 2011 American Chemical Society. Source

Lisunova M.,202 Bell Engineering Center | Norman J.,202 Bell Engineering Center | Blake P.,202 Bell Engineering Center | Forcherio G.T.,University of Arkansas | And 3 more authors.
Journal of Physics D: Applied Physics

The modulation of Fano resonance by nanoparticle shape in ordered arrays is studied. The variation of the particle plasmon resonance mode changes the interference with the photonic modes of the particle in array that consequently shifts the Fano resonance mode. The elongation of the nanodiscs in arrays allowed modulation of Fano resonance via the changing of electromagnetic field propagation by particles' orientation and light polarization. © 2013 IOP Publishing Ltd. Source

Lisunova M.,202 Bell Engineering Center | Wei X.,202 Bell Engineering Center | Dejarnette D.,University of Arkansas | Forcherio G.T.,University of Arkansas | And 4 more authors.
RSC Advances

Photothermal transduction of light to heat by evaporated and electroless plated gold (Au) films has been compared. Bare film was compared to film decorated by an ordered lattice of Au nanocylinders. The effects of plasmonic absorption of incident light, heat dissipation in the substrate, and interfacial effects between Au nanoparticles and the substrate were evaluated. Differences in the photothermal response of the films emerged due to interactions between these effects. Significant photothermal transduction was achieved by 30-40 nm Au grains as well as by conglomerate nanocylinders assembled from Au grains. An electroless Au film decorated with conglomerate Au nanocylinders ordered into a hexagonal array enhanced attenuation by 22% and increased light-to-heat conversion by 26%. This was attributed to photon-plasmon coupling. An evaporated Au film of 57 nm thickness attenuated 30% of incident light, compared to 45% attenuation for the electroless film of 35 nm thickness. The evaporated film had a photothermal response of 280 °C per watt of incident light in contrast to 1400 °C per watt for the electroless film. This journal is © the Partner Organisations 2014. Source

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