Evanston, IL, United States
Evanston, IL, United States

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Scheerder J.,Royal DSM | Breur R.,Materials Innovation Center | Slaghek T.,TNO | Holtman W.,Fytagoras B.V. | And 2 more authors.
Progress in Organic Coatings | Year: 2012

Exopolysaccharides (EPS) are a class of renewable polymers that show interesting anti-corrosive properties and could potentially be used as an alternative for zinc phosphates. When combined with a waterborne styrene-acrylic polymer dispersion (SA-1), exopolysaccharides were shown to give an improvement in the anti-corrosive performance. Electrochemical studies show higher charge transfer resistance (R ct) values for the SA-1/EPS combinations as compared to the SA-1 itself suggesting that in the presence of EPS less corrosion took place. Outdoor exposure test shows that the presence of EPS188 gave good corrosion protection for up to a year when exposed under marine conditions. The distribution of EPS modification throughout the coating was made visible using Confocal Laser Scanning Microscopy and indicated that EPS was distributed rather homogeneously. A working mechanism was proposed in which the carboxylic acid groups on the oxidised EPS form a complex with iron ions formed by the anodic reaction and this insoluble complex forms a protective layer between the coating and metal. The results in this paper show that by using renewable polysaccharide additives the anti-corrosive coating performance can be improved. © 2012 Elsevier B.V.


Li S.-Q.,Northwestern University | Sakoda K.,Japan National Institute of Materials Science | Sakoda K.,Materials Innovation Center | Ketterson J.B.,Materials Innovation Center | And 3 more authors.
Applied Physics Letters | Year: 2015

There is currently much discussion within the nanophotonics community regarding the origin of wavelength selective absorption/scattering of light by the resonances in nanorod arrays. Here, we report a study of resonances in ordered indium-tin-oxide nanorod arrays resulting from waveguide-like modes. We find that with only a 2.4% geometrical coverage, micron-length nanorod arrays interact strongly with light across a surprisingly wide band from the visible to the mid-infrared, resulting in less than 10% transmission. Simulations show excellent agreement with our experimental observations. The field profile in the vicinity of the rods obtained from simulations shows that the electric field is mainly localized on the surfaces of the nanorods for all resonances. Based on our analysis, the resonances in the visible are different in character from those in the infrared. When light is incident on the array, part of it propagates in the space between the rods and part of it is guided within the rods. The phase difference (interference) at the ends of the rods forms the basis for the resonances in the visible region. The resonances in the infrared are Fabry-Perot-like resonances involving standing surface waves between the opposing ends of the rods. Simple analytical formulae predict the spectral positions of these resonances. It is suggested that these phenomena can be utilized for wavelength-selective photodetectors, modulators, and nanorod-based solar cells. © 2015 AIP Publishing LLC.


Li S.-Q.,Northwestern University | Zhou W.,Northwestern University | Guo P.,Northwestern University | Buchholz D.B.,Northwestern University | And 8 more authors.
Proceedings of SPIE - The International Society for Optical Engineering | Year: 2014

We report our recent development in pursuing high Quality-Factor (high-Q factor) plasmonic resonances, with vertically aligned two dimensional (2-D) periodic nanorod arrays. The 2-D vertically aligned nano-antenna array can have high-Q resonances varying arbitrarily from near infrared to terahertz regime, as the antenna resonances of the nanorod are highly tunable through material properties, the length of the nanorod, and the orthogonal polarization direction with respect to the lattice surface,. The high-Q in combination with the small optical mode volume gives a very high Purcell factor, which could potentially be applied to various enhanced nonlinear photonics or optoelectronic devices. The 'hot spots' around the nanorods can be easily harvested as no index-matching is necessary. The resonances maintain their high-Q factor with the change of the environmental refractive index, which is of great interest for molecular sensing. © 2014 SPIE.


Li S.-Q.,Northwestern University | Guo P.,Northwestern University | Buchholz D.B.,Northwestern University | Zhou W.,Northwestern University | And 10 more authors.
ACS Photonics | Year: 2014

We present a systematic study of light scattering from indium-tin-oxide (ITO) nanorods in the near-infrared with a special focus on the resonant coupling of plasmonic transverse mode and photonic modes in 2-D periodic arrays. Using theoretical analysis combined with simulations, a set of experiments has been designed to study such interactions. Near-field mapping from the simulations shows a strong interaction of localized surface plasmon resonances (LSPR) with a photonic resonance; together they explain the scattering phenomenon observed in our experiments carried out in the far field. We observed the shift of LSPR as the plasma frequency was varied, resulting in a modification of the spectral shape. Utilizing the high aspect ratios of the ITO nanorods, the LSPR strength can be turned on and off by the polarization of the incident light. (Graph Presented). © 2014 American Chemical Society.


Li S.-Q.,Northwestern University | Zhou W.,Harvard University | Bruce Buchholz D.,Northwestern University | Ketterson J.B.,Northwestern University | And 5 more authors.
Applied Physics Letters | Year: 2014

Diffractively coupled plasmonic resonances possess both ultra-sharp linewidths and giant electric field enhancement around plasmonic nanostructures. They can be applied to create a new generation of sensors, detectors, and nano-optical devices. However, all current designs require stringent index-matching at the resonance condition that limits their applicability. Here, we propose and demonstrate that it is possible to relieve the index-matching requirement and to induce ultra-sharp plasmon resonances in an ordered vertically aligned optical nano-antenna phased array by transforming a dipole resonance to a monopole resonance with a mirror plane. Due to the mirror image effect, the monopole resonance not only retained the dipole features but also enhanced them. The engineered resonances strongly suppressed the radiative decay channel, resulting in a four-order of magnitude enhancement in local electric field and a Q-factor greater than 200. © 2014 AIP Publishing LLC.

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