Spectroscopic Study on CdS/Ni/KNbO3: Confirming Ni Effect to Photocatalytic Activity.

Herein, we report the structural and photophysical properties of CdS/Ni/KNbO3 composites with a quantum yield for photocatalytic H2 generation that is CdS and Ni amount dependent. The nonstoichiometric KNbO3 (1:1.1) structure indicates the defect at the K site, which is Ni-occupied during its deposit process. It exhibits a tendency like a Ni-doped characteristic up to 0.1 wt % Ni and then forms a Ni cluster in case the Ni amount exceeds 0.1 wt %. The related structural and photophysical properties of CdS/Ni/KNbO3 are examined with Fourier transform infrared, X-ray diffraction, ultraviolet-visible absorption, and luminescence spectral analysis. It demonstrates the CdS/Ni/KNbO3 composites to be an efficient light conversion caused by efficient charge/electron transfer between KNbO3 and CdS via doped Ni. The photocatalytic activity of CdS/Ni/KNbO3 exhibits a CdS and Ni amount dependency. The best photocatalytic activity for H2 generation is obtained with 0.1 wt % Ni and 2.9 wt % CdS as it gradually declines with the excess Ni amount than 0.1 wt % caused by a formed Ni cluster.

α-NiO/Ni(OH)2/AgNP/F-Graphene Composite for Energy Storage Application.

The α-NiO/Ni(OH)2/AgNP/F-graphene composite, which is silver nanoparticles preanchored on the surface of fluorinated graphene (AgNP/FG) and then added to α-NiO/Ni(OH)2, is investigated as a potential battery material. The addition of AgNP/FG endows the electrochemical redox reaction of α-NiO/Ni(OH)2 with a synergistic effect, resulting in enhanced Faradaic efficiency with the redox reactions of silver accompanied by the OER and the ORR. It resulted in enhanced specific capacitance (F g-1) and capacity (mA h g-1). The specific capacitance of α-NiO/Ni(OH)2 increased from 148 to 356 F g-1 with the addition of AgNP(20)/FG, while it increased to 226 F g-1 with the addition of AgNPs alone without F-graphene. The specific capacitance of α-NiO/Ni(OH)2/AgNP(20)/FG further increased up to 1153 F g-1 with a change in the voltage scan rate from 20 to 5 mV/s and the Nafion-free α-NiO/Ni(OH)2/AgNP(20)/FG composite. In a similar trend, the specific capacity of α-NiO/Ni(OH)2 increased from 266 to 545 mA h g-1 by the addition of AgNP(20)/FG. The performance of hybrid Zn-Ni/Ag/air electrochemical reactions by α-NiO/Ni(OH)2/AgNP(200)/FG and Zn-coupled electrodes indicates a potential for a secondary battery. It results in a specific capacity of 1200 mA h g-1 and a specific energy of 660 W h kg-1, which is divided into Zn-Ni reactions of ∼95 W h kg-1 and Zn-Ag/air reactions of ∼420 W h kg-1, while undergoing a Zn-air reaction of ∼145 W h kg-1.

A Polymer-Based Extended Release System for Stable, Long-term Intracochlear Drug Delivery.

OBJECTIVE: Investigate a new polymer-based drug coating suitability for safe intracochlear delivery and ability to maintain long-term physiologically active levels of the corticosteroid fluticasone propionate. STUDY DESIGN: In vitro dissolution study to evaluate release profiles of polymer-coated drug particles and in vivo studies using a guinea pig model to measure perilymph drug concentrations at specific time points after implantation with polymer-coated drug particles and evaluate their effect on hearing function. METHODS: Polymer-coated fluticasone propionate (FP) particles were surgically implanted in guinea pigs through the round window membrane into the cochlear scala tympani. In the pilot study, pre- and post-op hearing thresholds were conducted on days 7, 14, and 42. In a second study, post-op hearing thresholds were conducted on days 90, 120, and 180. Perilymph drug concentrations were measured on the same time points. RESULTS: In 15 of 16 animals from day 7 through day 90, drug levels were within the targeted range, with no initial burst release detected. Drug was present in all animals on day 90 and was detected in some animals at 120 and 180 days. Hearing was tested and compared with non-implanted ears. Very good hearing preservation was observed in ears implanted with intracochlear particles when compared with contralateral ears. CONCLUSIONS: The polymer-based extended release system is effective in providing long-term, stable drug delivery for at least 90 days with good hearing outcomes. The results of this study support the potential for achieving long-term drug delivery with a single intracochlear administration.

Fluorescence spectroscopic and time-dependent DFT studies for intramolecular excimer formation of Di-9H-fluoren-9-yldimethylsilane: dynamics and energetics for conformational change.

Intramolecular excimer formation of di-9H-fluoren-9-yldimethylsilane in various solvents was studied by means of steady-state and time-resolved fluorescence spectroscopies. Solvent viscosity effect on the kinetics for the monomer-excimer transition was found to be very slight, indicating that the transformation is accompanied by a slight conformational change presumably involving a transition from a near face-to-face conformer to a true sandwich conformer. The excitation energies and the corresponding oscillator strengths were derived with the time-dependent B3LYP/cc-pVTZ method. The simulated absorption spectrum involving the variation of the oscillator strengths in terms of the wavelengths accords with the experimental absorption pattern. The TD DFT calculations also reveal that excitation energy is significantly decreased with decreasing the interchromophore separation and the dihedral angle in a fluorene dimer, as an indication that the excimer state emitting the significantly red-shifted fluorescence corresponds to a sandwich conformer.

Protic solvent effects on the photophysical properties of O=Ti(IV)TSPP: photoinduced electron transfer.

The photophysical properties of oxotitanium(IV)meso-tetra(4-sulfonatophenyl) porphyrin (O=Ti(IV)TSPP) have been investigated in water and methanol by laser spectroscopic techniques. The fluorescence emission spectrum of O=Ti(IV)TSPP in methanol exhibits two strong emission bands at 610 and 670 nm at room temperature with the decay time of ca. 310 +/- 10 ps and the rise time shorter than 30 ps, in contrast to the extremely weak emission with the decay time of ca. 27 +/- 4 ps in water, indicating that the fluorescence emissive states are different in the two solvents as supported by the solvent dependences of the excitation spectrum. The transient Raman spectra of O=Ti(IV)TSPP in water has been observed to exhibit a remarkable enhancement of phenyl-related mode at 1599 cm(-1), while in methanol, the Raman frequencies of the porphyrin skeletal modes (upsilon2 and upsilon4) are down-shifted without any apparent enhancement of the phenyl-related mode, indicating different interactions of the two solvents with the excited O=Ti(IV)TSPP. These Raman studies reveal that methanol molecule interacts with the photoexcited O=Ti(IV)TSPP more strongly than water, forming the exciplex, O=Ti(IV)TSPP(MeOH)*, suggesting that the two different emissive states are the singlet Franck-Condon state and the exciplex state in methanol and water, respectively. A broad triplet transient absorption of O=Ti(IV)TSPP has been also observed at 480 nm in water as well as in methanol, which is decreased upon addition of methyl viologen (MV2+) with appearance of a new absorption band at 620 nm. This indicates that the photoinduced electron transfer (PET) takes place from the porphyrin to MV2+ in both solvents. The kinetic analysis of the transient absorption band exhibits the PET rate constants of 4.76 x 10(5) s(-1) and 3,03 x 10(4) s(-1) in methanol and water, respectively. All these results infer that the PET takes place from the (d,pi) CT state and the triplet state of the excited porphyrin in methanol and water, respectively.