ABSTRACT
A nanocomposite of Polypyrrole (PPy) and zinc oxide (ZnO), termed as PPy-ZnO, was synthesized by two step route. In the first step, synthesis of PPy was carried out by chemical oxidative route. In the second step, the PPy-ZnO nanocomposite was synthesized under hydrothermal conditions. The as-synthesized PPy-ZnO nanocomposites were characterized using X-ray Diffraction (XRD), scanning electron microscopy (SEM), Fourier Transform Infra-red (FTIR) and Ultra violetvisible (UV-vis) spectroscopy to reveal the phase, morphology, chemical and optical properties. The physical and chemical characterizations confirmed presence of both PPy and ZnO phases in the nanocomposite. In the present work, antimicrobial activity of the PPy-ZnO nanocomposite against human pathogen Y. lipolytica has been investigated. Attempts have been made to reveal the influence of PPy percentage on the antimicrobial activity. Interestingly, all PPy-ZnO nanocomposites, irrespective of PPy percentage, showed 90 to 95% inhibited growth of Yarrowia lipolytica. The results obtained herein imply the potential of PPy-ZnO biofilm in inhibiting the growth of Y. lipolytica and thus preventing infections caused due to Y. lipolytica in humans.
ABSTRACT
Single-photon Coulomb explosion of methanol is instigated using the broad bandwidth pulse achieved through high-order harmonics generation. Using 3D coincidence fragment imaging of one molecule at a time, the kinetic energy release (KER) and angular distributions of the products are measured in different Coulomb explosion (CE) channels. Two-body CE channels breaking either the C-O or the C-H bonds are described as well as a proton migration channel forming H2O+, which is shown to exhibit higher KER. The results are compared to intense-field Coulomb explosion measurements in the literature. The interpretation of broad bandwidth single-photon CE data is discussed and supported by ab initio calculations of the predominant C-O bond breaking CE channel. We discuss the importance of these findings for achieving time resolved imaging of ultrafast dynamics.
ABSTRACT
The efficient intense field double detachment of molecular anions observed in SF6() is studied by 3D coincidence imaging of the dissociation products. The dissociation anisotropy and kinetic energy release distributions are determined for the energetically lowest double detachment channel by virtue of disentangling the SF5(+) + F fragmentation products. The observed nearly isotropic dissociation with respect to the linear laser polarization and surprisingly high kinetic energy release events suggest that the dissociation occurs on a highly excited state. Rydberg (SF6(+))* states composed of a highly repulsive dication core and a Rydberg electron are proposed to explain the observed kinetic energy release, accounting also for the efficient production of all possible cationic fragments at equivalent laser intensities.
ABSTRACT
Bodipy laser dyes are highly efficient but degrade rapidly in solution by reacting with in situ generated singlet oxygen ((1)O(2)). To increase the lasing lifetimes of these dyes, we have designed and synthesised two different congeners of the widely studied Pyrromethene 567 (PM567) by substitution at the boron centre and/or at both the boron centre and the meso position. The two new dyes showed high lasing efficiencies with increased photostability. The results of theoretical and pulse radiolysis studies revealed that the substitution at the boron centre reduced the (1)O(2) generation capacity of these dyes as well as their rate of reaction with (1)O(2), thereby enhancing their lifetimes even under lasing conditions.
ABSTRACT
The binding of the laser dyes rhodamine B (RhB) and sulforhodamine B (kiton red S or KRS) to a cucurbit[7]uril (CB[7]) host has been investigated using density functional theory. Both guests (RhB and KRS) contain two N,N-diethylamino groups on a xanthene core. The lowest-energy structure of these host-guest complexes has one of the N,N-diethylamino groups encapsulated within the host cavity, that engenders C-H···O interactions with portals, while the remaining noninteracting diethylamino group resides outside the cavity. The (1)H NMR chemical shifts derived using the gauge-independent atomic orbital method are consistent with those observed in experiments.
Subject(s)
Bridged-Ring Compounds/chemistry , Fluorescent Dyes/chemistry , Imidazoles/chemistry , Rhodamines/chemistry , Computer Simulation , Hydrogen Bonding , Models, Molecular , Molecular Conformation , Quantum Theory , ThermodynamicsABSTRACT
A water-based narrow-band high-efficiency dye laser was designed by means of a supramolecular host-guest chemical approach. The lasing characteristics of rhodamine B and sulforhodamine B (Kiton Red S) dyes in aqueous solution with the macrocyclic host cucurbit[7]uril (CB7) as additive were investigated in a narrow-band dye laser setup. Significant improvements in both photostability and thermo-optical properties of the aqueous CB7-complexed dye systems were observed as compared to the uncomplexed dyes in ethanol solution. The tuning curves for the new dye-CB7-water systems were constructed by measuring the laser output at different wavelengths, which showed similar peak efficiencies and red-shifted gains compared to the ethanolic solutions of the dyes, while dye laser operation revealed comparable pump threshold energies and slope efficiencies. The combined results render the dye-CB7-water system an attractive active medium for high-repetition rate dye laser operation.
