Strategy for Tuning the Photophysical Properties of Photosensitizers for Use in Photodynamic Therapy

A novel approach for tuning spectral properties, as well as minimizing aggregation, in zinc porphyrin and zinc phthalocyanine‐based compounds is presented. Particular emphasis is placed on use of these compounds as photosensitizers in photodynamic therapy (PDT). To accomplish this aim, a bulky hydrophobic cation, trihexyltetradecylphosphonium, is paired with anionic porphyrin and phthalocyanine dyes to produce a group of uniform materials based on organic salts (GUMBOS) that absorb at longer wavelengths with high molar absorptivity and high photostability. Nanoparticles derived from these GUMBOS possess positively charged surfaces with high zeta potential values, which are highly desirable for PDT. Upon irradiation at longer wavelengths, these GUMBOS produced singlet oxygen with greater efficiency as compared to the respective parent dyes.     

Chemical sensing in two dimensional porous covalent organic nanosheets

Two new imide-based crystalline, porous, and chemically stable covalent organic frameworks (COFs) (TpBDH and TfpBDH) have been successfully synthesized employing solvothermal crystallization route. Furthermore, thin layered covalent organic nanosheets (CONs) were derived from these bulk COFs by the simple liquid phase exfoliation method. These 2D CONs showcase increased luminescence intensity compared to their bulk counterparts (COFs). Notably, TfpBDH-CONs showcase good selectivity and prominent, direct visual detection towards different nitroaromatic analytes over TpBDH-CONs. Quite interestingly, TfpBDH-CONs exhibit a superior “turn-on” detection capability for 2,4,6-trinitrophenol (TNP) in the solid state, but conversely, they also show a “turn-off” detection in the dispersion state. These findings describe a new approach towards developing an efficient, promising fluorescence chemosensor material for both visual and spectroscopic detection of nitroaromatic compounds with very low [10^–5 (M)] analyte concentrations.     

Biorthogonal bases with local support and approximation properties

We construct locally supported basis functions which are biorthogonal to conforming nodal finite element basis functions of degree in one dimension. In contrast to earlier approaches, these basis functions have the same support as the nodal finite element basis functions and reproduce the conforming finite element space of degree . Working with Gauß-Lobatto nodes, we find an interesting connection between biorthogonality and quadrature formulas. One important application of these newly constructed biorthogonal basis functions are two-dimensional mortar finite elements. The weak continuity condition of the constrained mortar space is realized in terms of our new dual bases. As a result, local static condensation can be applied which is very attractive from the numerical point of view. Numerical results are presented for cubic mortar finite elements.

     

Phosphorescent Trinuclear Pt–Ir–Pt Complexes: Insights into the Photophysical and Electrochemical Properties and Interaction with Guanine Nucleobase

In this study we have analysed the comparative photophysical and electrochemical properties of two isomeric heterotrinuclear Pt^II–Ir^III–Pt^II complexes 3 and 6 and the four corresponding intermediate isomeric homonuclear cyclometalated iridium(III) complexes 1 , 2 , 4 and 5 . The isomerisation originates from positional differences in the formyl, di-2-picolylamine and Pt–di-2-picolylamine moieties appended to cyclometalated or ancillary ligands. The interaction of 5′-GMP with the trinuclear complexes 3 and 6 shows that platinum centres appended to the cyclometalated ligand in 3 facilitate the binding of two 5′-GMP units per Pt^II centre in preference to a single 5′-GMP unit per Pt^II centre as observed in 6 . The 1:2 and 1:1 Pt^II–5′-GMP binding patterns probably arise from the convenient arrangements of the Pt–di-2-picolylamine units in different planes in complex 3 , which is absent in complex 6 .     

A Bragg-like chirped clad all-solid microstructured optical fiber with ultra-wide bandwidth for short pulse delivery and pulse reshaping

Chirped cladding is proposed as a novel tailoring tool to simultaneously attain wider transmission window and reduced temporal dispersion in an all-solid Bragg-like microstructured optical fiber as compared to its perfectly periodic cladding counterpart. This design route for photonic bandgap microstructured fibers could be exploited as an additional degree of freedom for bandgap engineering. A suitably chirped clad fiber could be gainfully exploited to deliver femto-second pulse with ultra wide bandwidth. Further, generation of self-similar parabolic profile pulse is demonstrated by simulating propagation of an input Gaussian pulse through a 2 m long sample of such a linearly tapered Bragg like fiber.     

Plasmon‐enhanced Raman scattering of coaxial hybrid nanowires made with light‐emitting polymer and gold

We report on the plasmon‐enhanced Raman scattering of coaxial hybrid nanowires (NWs) made with light emitting poly(3‐methylthiophene) (P3MT) and gold (Au) core or coating. Absorption spectra of coaxial hybrid NWs showed the absorption peaks because of localized surface plasmon (SP) excitation at ~ 567 and ~ 610 nm, in addition to the π–π* transition peaks of P3MT. Raman spectra of a single strand of coaxial hybrid NW and plain P3MT NW was obtained by using three different wavelengths of laser excitation of 514, 633, and 785 nm. We found that Raman intensities of hybrid coaxial NWs were enhanced by 4 to 15 times over those of plain P3MT NWs with the Raman excitation wavelengths close to the observed SP energies of coaxial NWs. We attributed the observed enhancement of the Raman signal to the resonance of the incident laser with the matching SP energies, rather than the possible doping level change, in hybrid coaxial NWs. Copyright © 2012 John Wiley & Sons, Ltd.     

Role of optical nonlinearity on transverse localization of light in a disordered one-dimensional optical waveguide lattice

We report a detailed numerical investigation on transverse localization of light in a 1D disordered lattice consisting of a large array of coupled waveguides in the presence of nonlinearity in the medium. Our study reveals that the presence of a focusing type of nonlinearity favors faster localization of light while a defocusing type of nonlinearity degrades the quality of localization. It is shown that presence of either of these could over-shadow localization of light unless the strength of disorder is sufficiently strong. Influence of the input beam width on propagation of light in such a disordered nonlinear medium has also been discussed. The present study should be useful in potential applications, in which one could exploit dominance of focusing nonlinearity on transverse localization of light in a disordered medium.     

A symmetric mixed finite element method for nearly incompressible elasticity based on biorthogonal systems

We present a symmetric version of the nonsymmetric mixed finite element method presented in (Lamichhane, ANZIAM J 50 (2008), C324–C338) for nearly incompressible elasticity. The displacement–pressure formulation of linear elasticity is discretized using a Petrov–Galerkin discretization for the pressure equation in (Lamichhane, ANZIAM J 50 (2008), C324–C338) leading to a non‐symmetric saddle point problem. A new three‐field formulation is introduced to obtain a symmetric saddle point problem which allows us to use a biorthogonal system. Working with a biorthogonal system, we can statically condense out all auxiliary variables from the saddle point problem arriving at a symmetric and positive‐definite system based only on the displacement. We also derive a residual based error estimator for the mixed formulation of the problem. © 2011 Wiley Periodicals, Inc. Numer Methods Partial Differential Eq, 2012     

Value-Added Production of Nisin from Soy Whey

The objective of this study was to evaluate the potential of low/negative value soy whey (SW) as an alternative, inexpensive fermentation substrate to culture Lactococcus lactis subsp. lactis for nisin production. Initially, a microtiter plate assay using a Bioscreen C Microbiology Plate Reader was used for rapid optimization of culture conditions. Various treatments were examined in efforts to optimize nisin production from SW, including different methods for SW sterilization, ultrasonication of soy flake slurries for possible nutrient release, comparison of diluted and undiluted SW, and supplementation of SW with nutrients. In subsequent flask-based experiments, dry bacterial mass and nisin yields obtained from SW were 2.18 g/L and 619 mg/L, respectively, as compared to 2.17 g/L and 672 mg/L from a complex medium, de Man–Rogosa–Sharpe broth. Ultrasonication of soybean flake slurries (10% solid content) in water prior to production of SW resulted in ∼2% increase in biomass yields and ∼1% decrease in nisin yields. Nutrient supplementation to SW resulted in ∼3% and ∼7% increase in cell and nisin yields, respectively. This proof-of-concept study demonstrates the potential for use of a low/negative value liquid waste stream from soybean processing for production of a high-value fermentation end product.