Plasmonic tuning of aluminum doped zinc oxide nanostructures by atomic layer deposition

Currently there is a strong interest in plasmonic materials operating in the near‐infrared (NIR), however, conventional metals such as gold and silver possess high optical losses in this region. In this work we demonstrate localized surface plasmon resonances (LSPRs) with low loss in the NIR region by utilizing atomic layer deposition to deposit thin films of aluminium doped zinc oxide onto silicon nanopillars created via nanopshere lithography. The deposited films have excellent conformality and the LSPRs can be tuned from the mid‐infrared to the NIR by controlling the doping concentration, deposition temperature and nanostructure morphology. (© 2014 WILEY‐VCH Verlag GmbH &Co. KGaA, Weinheim)     

Excited state dynamics and activation parameters of remarkably slow photoinduced CO loss from (η⁶-benzene)Cr(CO)₃ in n-heptane solution: a DFT and picosecond-time-resolved infrared study

The electronic structure of (η?-benzene)Cr(CO)? has been calculated using density functional theory and a molecular orbital interaction diagram constructed based on the Cr(CO)? and benzene fragments. The highest occupied molecular orbitals are mainly metal based. The nature of the lowest energy excited states were determined by time-dependent density functional theory, and the lowest energy excited state was found to have significant metal to carbonyl charge transfer character. The photochemistry of (η?-benzene)Cr(CO)? was investigated by time-resolved infrared spectroscopy with picosecond time resolution. The low energy excited state was detected following irradiation at 400 nm, and this exhibited ν(CO) bands at lower energy than the equivalent ν(CO) bands of (η?-benzene)Cr(CO)?, consistent with metal to carbonyl charge transfer character, and is formed with excess vibrational energy, relaxing to the v = 0 vibrational state within 3 ps. The resulting "cold" excited state decays to form the CO-loss species (η?-benzene)Cr(CO)? in approximately 70% yield and to reform (η?-benzene)Cr(CO)? within 150 ps. The rates of relaxation from the vibrationally hot state to the cold excited state and its subsequent reaction to yield (η?-benzene)Cr(CO)? were measured over a range of temperatures from 274 to 320 K, and the activation parameters for both processes were obtained from Eyring plots. The vibrational relaxation exhibits a negative activation enthalpy ΔH(?) (-10 (±4) kJ mol?1) and a negative activation entropy ΔS(?) (-50 (±16) J mol?1 K?1). A significant barrier (ΔH(?) = +12 (±4) kJ mol?1) was obtained for the formation of (η?-benzene)Cr(CO)? with a ΔS(?) value close to zero. These data are used to propose a model for the CO-loss process to yield (η?-benzene)Cr(CO)? and to explain why low temperature irradiation of (η?-benzene)Cr(CO)? with light of wavelengths greater than 400 nm produced relatively minor amounts of (η?-benzene)Cr(CO)?.     

Total internal reflection ellipsometry as a label-free assessment method for optimization of the reactive surface of bioassay devices based on a functionalized cycloolefin polymer

We report a label-free optical detection technique, called total internal reflection ellipsometry (TIRE), which can be applied to study the interactions between biomolecules and a functionalized polymer surface. Zeonor (ZR), a cycloolefin polymer with low autofluorescence, high optical transmittance and excellent chemical resistance, is a highly suitable material for optical biosensor platforms owing to the ease of fabrication. It can also be modified with a range of reactive chemical groups for surface functionalization. We demonstrate the applications of TIRE in monitoring DNA hybridization assays and human chorionic gonadotrophin sandwich immunoassays on the ZR surface functionalized with carboxyl groups. The Ψ and Δ spectra obtained after the binding of each layer of analyte have been fitted to a four-layer ellipsometric model to quantitatively determine the amount of analytes bound specifically to the functionalized ZR surface. Our proposed TIRE technique with its very low analyte consumption and its microfluidic array format could be a useful tool for evaluating several crucial parameters in immunoassays, DNA interactions, adsorption of biomolecules to solid surfaces, or assessment of the reactivity of a functionalized polymer surface towards a specific analyte.     

A 1D Schiff base zinc polymer as a versatile metallo-ligand for the synthesis of polynuclear zinc cages

The 1D polymeric Schiff base zinc complex, [LZn(2)Et(2)](n), where LH(2) = (NN'-ethylene-bis(4-iminopentan-2-one)) has been demonstrated as a useful synthetic metallo building block for the synthesis of homo and heteronuclear zinc cages. The reaction of [LZn(2)Et(2)](n) with CdI(2) afforded the hetero-nuclear cage, 1, [L(2)Zn(4)(Et)(2)CdI(4)], while reaction with HgI(2) afforded a hexanuclear zinc cage, [L(2)Zn(6)(Et)(4)(μ(4)O)(μ(3)OEt)I], 2. The versatility of [LZn(2)Et(2)](n) as a metallo building block is demonstrated through the reaction with ferrocenyl carboxylic acid, affording the ferrocenyl supported zinc cage, [L(2)Zn(8)(FcCO(2))(4)(Et)(2)(OEt)(2)(μ(4)O)(2)], 3, while the reaction with Er(III) acetate afforded the decanuclear zinc cage, [L(3)Zn(10)(μ(4)O)(4)(Et)(6)], 4.     

Near IR emitting BODIPY fluorophores with mega-Stokes shifts

A novel Near Infra-Red emitting BODIPY derivative is presented which exhibits the largest Stokes shift thus far reported for a BODIPY compound.     

Attributed Grammatical Evolution with Lookahead for the Multiple Knapsack Problem

This paper presents an Attribute Grammar with Lookahead (AG+LA) approach, a technique to solve heavily constrained Multiple Knapsack Problem. This approach incorporates a form of lookahead into the mapping process of Grammatical Evolution (GE) using Attribute Grammar (AG) to focus only on feasible solutions, thereby avoiding issues such as repeated remapping and introns, both of which are limitations of previous approaches based on AG. We also present AG+LAE (AG+LA with an efficiency measure to bias the search towards the most efficient, i.e., best value, objects), the successor of AG+LA where a biasing process is incorporated using problem specific knowledge to significantly improve the performance of its predecessor, both in terms of the number of evaluations required and the quality of solutions obtained. Degenerate code, as used in DNA, is code that uses redundancy, so that different codons can represent the same thing. Many developmental systems, such as GE, use a degenerate encoding to help promote neutral mutations, that is, minor genetic changes that do not result in a phenotypic change. While early work in GE suggested that some level of degeneracy was important, it does come at the cost of increasing the size of the search space. Duplicate Elimination techniques, as opposed to degenerate encoding, are employed in decoder-based Evolutionary Algorithms to ensure that the newly generated solutions are not already contained in the current population. The results and analysis show that it is crucial to incorporate duplicate elimination to improve the performance of both approaches, while the reduced level of degeneracy is crucial only for AG+LA.     

Hydrogel‐Forming and Dissolving Microneedles for Enhanced Delivery of Photosensitizers and Precursors

We present “one‐step application” dissolving and hydrogel‐forming microneedle arrays (MN) for enhanced delivery of photosensitizers/precursors. MN (280 μm) prepared from 20% w/w poly(methylvinylether/maelic acid) and cross‐linked with glycerol by esterification to form hydrogels upon skin insertion, or allowed to dissolve rapidly in skin, were combined with patches containing 19 mg cm^?2 of 5‐aminolevulinic acid (ALA) or meso‐tetra (N‐methyl‐4‐pyridyl) porphine tetra tosylate (TMP) for drug delivery. Both MN types were mechanically robust, with compression forces of 20.0 N only causing height reductions of 14%. Application forces as low as 8.0 N per array allowed >95% of the MN in each array type to penetrate excised porcine skin, with the MN penetrating to approximately 220 μm. MN significantly enhanced transdermal delivery of ALA and TMP in vitro, with the hydrogel‐forming system comparable with the dissolving system for ALA delivery (approximately 3000 nmol cm^?2 over 6 h), but superior for delivery of the much larger TMP molecule (approximately 14 nmol cm^?2 over 24 h, compared to 0.15 nmol cm^?2). As this technology clearly has potential in enhanced photodynamic therapy of neoplastic skin lesions, we are currently planning animal studies, to be followed by preliminary human evaluations. GMP manufacturing scale‐up is ongoing.     

Photochemistry of (η(6)-arene)Cr(CO)3 (arene = methylbenzoate, naphthalene, or phenanthrene) in n-heptane solution: population of two excited states following 400 nm excitation as detected by picosecond time-resolved infrared spectroscopy

The photochemistry of (η(6)-methylbenzoate)Cr(CO)(3), (η(6)-naphthalene)Cr(CO)(3), and (η(6)-phenanthrene)Cr(CO)(3) in n-heptane solution was investigated by picosecond time-resolved infrared spectroscopy (TRIR). The observation of two transient IR features in the organic carbonyl region at 1681 and 1724 cm(-1) following 400 nm excitation of (η(6)-methylbenzoate)Cr(CO)(3) confirms formation of two excited states which are classified as metal-to-arene charge transfer (MACT) and metal-to-CO charge transfer (MCCT), respectively. Time-dependent density functional theory calculations have been used to support these assignments. Population of the MCCT excited state results in a slow (150 ps) expulsion of one CO ligand. Excitation of (η(6)-naphthalene)Cr(CO)(3) or (η(6)-phenanthrene)Cr(CO)(3) at either 400 or 345 nm produced two excited states: the MCCT state results in CO loss, while the MACT excited state results in a change to the coordination mode of the polyaromatic ligands before relaxing to the parent complex. A comparison of the infrared absorptions observed following the population of the MACT excited state with those calculated for nonplanar polyaromatic intermediates provides a model for the reduced hapticity species.     

Backscatter tolerant squeezed light source for advanced gravitational-wave detectors

We report on the performance of a dual-wavelength resonant, traveling-wave optical parametric oscillator to generate squeezed light for application in advanced gravitational-wave interferometers. Shot noise suppression of 8.6±0.8 dB was measured across the detection band of interest to Advanced LIGO, and controlled squeezing measured over 5900 s. Our results also demonstrate that the traveling-wave design has excellent intracavity backscattered light suppression of 47 dB and incident backscattered light suppression of 41 dB, which is a crucial design issue for application in advanced interferometers.