| 1. |
- Hornyak, G. L., et al.
(författare)
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Effective medium theory characterization of Au/Ag nanoalloy-porous alumina composites
- 1997
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Ingår i: Nanostructured materials. - : Elsevier BV. - 0965-9773 .- 1872-9150. ; 9:1-8, s. 571-574
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Tidskriftsartikel (refereegranskat)abstract
- The optical constants nAl and kAl of a 50/50 volume fraction Au/Ag alloy were derived synthetically by application of a Bruggeman (BG) effective medium expression. The alloy data base was then input into a Maxwell-Garnett (MG) effective medium expression to determine the absorption maximum of the nano- alloy/insulator composite (the volume fraction of the nano-alloy was equal to 5%). The absorption maximum (λmax) of the hypothetical composite was found to be 499 nm for spherical particles and was blue-shifted relative to that of a composite containing pure gold nanospheres (499 vs. 528 nm respectively). The transmission color at this wavelength was a red-orange. λmax in the range 512 to 519 nm (Au/Ag alloy between 60/40 - 70/30 volume fraction respectively) is needed to obtain the scarlet-red exhibited by the famous Lycurgus cup of 4th century Rome (1). © 1997 Acta Metallurgica Inc.
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| 5. |
- Bin Abdul Rahim, H. R., et al.
(författare)
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Applied light-side coupling with optimized spiral-patterned zinc oxide nanorod coatings for multiple optical channel alcohol vapor sensing
- 2016
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Ingår i: Journal of Nanophotonics. - : SPIE - International Society for Optical Engineering. - 1934-2608. ; 10:3
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Tidskriftsartikel (refereegranskat)abstract
- The width of spiral-patterned zinc oxide (ZnO) nanorod coatings on plastic optical fiber (POF) was optimized theoretically for light-side coupling and found to be 5 mm. Structured ZnO nanorods were grown on large core POFs for the purpose of alcohol vapor sensing. The aim of the spiral patterns was to enhance signal transmission by reduction of the effective ZnO growth area, thereby minimizing light leakage due to backscattering. The sensing mechanism utilized changes in the output signal due to adsorption of methanol, ethanol, and isopropanol vapors. Three spectral bands consisting of red (620 to 750 nm), green (495 to 570 nm), and blue (450 to 495 nm) were applied in measurements. The range of relative intensity modulation (RIM) was determined to be for concentrations between 25 to 300 ppm. Methanol presented the strongest response compared to ethanol and isopropanol in all three spectral channels. With regard to alcohol detection RIM by spectral band, the green channel demonstrated the highest RIM values followed by the blue and red channels, respectively.
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| 6. |
- Chaudhari, M. B., et al.
(författare)
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Chromatic tuning of plasmon resonance of tri-layered composites : Silver, gold and copper nanoparticles for optical thin film colour filter
- 2012
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Ingår i: Micro & Nano Letters. - : Institution of Engineering and Technology. - 1750-0443. ; 7:2, s. 146-148
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Tidskriftsartikel (refereegranskat)abstract
- The authors describe an approach to control colour shades by varying the volume fractions of three metal nanoparticles (NPs), Cu, Au and Ag, of fixed size and shape. The NPs were designed to match the absorption peaks of the three primary colours. Using the dynamic Maxwell Garnett equation, an analytical model is extracted that calculates the volume fraction value of each metal for the desired transmission red, green and blue values. The model considers the cross-talk between colours because of the broadening of the plasmon peaks. Maximum error of 10% was observed when producing secondary colour and grey shades.
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| 7. |
- Hornyak, G. L., et al.
(författare)
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Dynamical Maxwell-Garnett optical modeling of nanogold-porous alumina composites : Mie and kappa influence on absorption maxima
- 1997
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Ingår i: Nanostructured materials. - : Elsevier BV. - 0965-9773 .- 1872-9150. ; 9:1-8, s. 575-578
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Tidskriftsartikel (refereegranskat)abstract
- Composites consisting of nanogold in porous alumina host membranes have been fabricated and characterized. Nanocluster size (11 nm to 60 nm radius) and shape (prolate to oblate) were varied experimentally. Two phenomena were responsible for the position of maximum absorption (λmax) of the composites. First, light scattering due to extrinsic electrodynamic effects became important as particle size was increased. This resulted in red shifts in λmax and is known as the Mie effect. Secondly, blue shifts were induced as particle aspect ratio was increased. We have designated shifts due to particle shape and orientation as the "kappa" effect. The two appeared to exert their influence independently. Simulations by means of the dynamical Maxwell-Garnett (DMG) expression resulted in good correlation with experimental λmax. We demonstrate again the versatility of the template method of synthesizing nanostructured materials. © 1997 Acta Metallurgica Inc.
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| 8. |
- Khan, Zaheer Abbas, et al.
(författare)
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Optical thin film filters of colloidal gold and silica nanoparticles prepared by a layer-by-layer self-assembly method
- 2011
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Ingår i: Journal of Materials Science. - : Springer. - 0022-2461 .- 1573-4803. ; 46:21, s. 6877-6882
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Tidskriftsartikel (refereegranskat)abstract
- A novel fabrication method for optical thin film filters based on the self-organization of alternating layers of colloidal gold and silica nanoparticles (NP) is reported. The filter is designed to work in the deep-UV to visible spectral range. The spectral absorption peaks are tuned by three parameters: the organic capping ligand of the gold NPs (citrate, chitosan, poly (diallyl-dimethylammonium)- chloride or PDDA); the capping environment (bare, chitosan, or PDDA) of the silica NPs and the thickness of the film. Precise control of the transmission color (less than 1% color distance per layer), is achieved by changing the film thickness. Exploitation of the self-assembly process should lead to the facile production of highly reliable large area thin film optical filters at considerably lower costs.
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| 9. |
- Kitsomboonloha, R., et al.
(författare)
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Plasmon resonance tuning of gold and silver nanoparticle-insulator multilayered composite structures for optical filters
- 2011
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Ingår i: Micro & Nano Letters. - : IEEE. - 1750-0443. ; 6:6, s. 342-344
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Tidskriftsartikel (refereegranskat)abstract
- A novel approach for optical filter implementation by tuning the plasmon resonance absorption of gold and silver nanoparticles in layer-by-layer (LBL) composite structures is presented. The LBL composite structures consisted of alternating layers of polyacrylic acid (PAA)-capped Au and PAA-capped Ag bi-layers. The results show clear spectrum tuning of green and blue peaks. Spectrum tuning can be extended when more metals or oxide nanoparticles are incorporated.
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| 10. |
- Myint, M. T. Z., et al.
(författare)
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Hydrophobic/hydrophilic switching on zinc oxide micro-textured surface
- 2013
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Ingår i: Applied Surface Science. - : Elsevier. - 0169-4332 .- 1873-5584. ; 264, s. 344-348
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Tidskriftsartikel (refereegranskat)abstract
- Switchable wettability of zinc oxide (ZnO) microrod coated surfaces was controlled in two different ways: (1) by physical geometry (surface coverage area SA: the area covered by solid) and (2) by irradiation with ultraviolet (UV) light followed by infrared (IR) or furnace heating. In the first approach, the threshold coverage area for achieving hydrophobic surfaces was found to be <40%, which is in good agreement with predicted values in the literature leading to a metastable Cassie-Baxter regime. The transformation of hydrophobic to hydrophilic surfaces was studied by alternating cycles of 3 h exposure to ultraviolet (λpeak ∼ 253 nm) light followed by 1 h of annealing or IR irradiation alone. Three different annealing temperatures (120 °C, 200 °C and 250 °C) were utilized. Results of this work can be applied for designing surfaces with controlled wettability.
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