Investigation of ultrafast carrier dynamics in curcumin dye for environment friendly dye-sensitized solar cell.

Natural dyes have been widely employed in the fabrication of dye-sensitized solar cells (DSSCs). DSSCs are favored for their cost-effective, and simple fabrication process relies on metal-based and organic dyes. The choice of dyes greatly affects the performance of DSSCs. DSSCs have found a lot of applications in indoor, solar power gadgets with reasonable efficiency up to 13%. Nonetheless, despite advances in DSSC technology, the complex photophysics and excited state dynamics associated with natural dyes employed in DSSCs remain elusive and have not been adequately investigated. This information gap emphasizes the need for more study and analysis into the behavior of these dyes, since understanding their underlying principles might lead to major improvements in DSSC performance and efficiency. In this work, we have investigated the fundamental characteristics and excited-state carrier dynamics of natural dye curcumin using ultrafast transient absorption (TA) spectroscopy technique. The curcumin dye shows delay time-dependent positive and negative signals in the TA spectra, which are related to excited state absorption and stimulated emission. We also found that hydrogen bonding and polarity effect of solvent significantly influence the carrier dynamics of curcumin. Ultrafast lifetime component indicates that hydrogen-bond rearrangements are involved in the kinetics of the relaxation process of the S1 state of curcumin photo-sensitizer.

Catalytic effect on hydrogen de/absorption properties of MgH2 - x wt% MM (x = 0, 10, 20, 30) nanomaterials.

Reversible hydrogen storage in MgH2 under specified conditions is a possible way for the positive reception of hydrogen economy, in which the developments of cheap and highly efficient catalysts are the major challenge, still now. Herein, MgH2 - x wt% MM (x = 0, 10, 20, 30) nanomaterials are prepared via ball milling method and has been evaluated for the hydrogen storage performance, which are characterized by XRD, SEM and DTA/DSC. The hydrogen absorption properties of nanomaterials are measured by pressure composition isotherm, and analysis show that the MgH2 - 30 wt% MM nanomaterials have the maximum hydrogen absorption capacity (~ 3.27 wt% at 300 °C) than MgH2. The activation energy of nanomaterials is remarkably changed by the introduction of MM as additives in MgH2.

Hydrogenation properties and kinetic study of MgH2 - x wt% AC nanocomposites prepared by ball milling.

The high de-/hydrogenation temperature of magnesium hydride is still a challenge in solid-state hydrogen storage system for automobiles applications. To improve the hydrogenation properties of MgH2, we select activated carbon/charcoal (AC) as a catalyst. A systematic investigation was performed on the hydrogen storage behaviors of MgH2 and MgH2 - 5 wt% AC nanocomposites, which were prepared by a high-energy planetary ball mill. These synthesized nanocomposites were characterized by X-ray diffraction (XRD), high-resolution transmission electron microscope (HRTEM) for phase identification, surface morphology and microstructural analysis. The pressure-composition-temperature (PCT) isotherm investigation shows the maximum hydrogen storage capacity ~ 6.312 wt% for MgH2-AC nanocomposites, while 3.417 wt% for MgH2 at 300 °C. The onset temperature for MgH2-AC nanocomposites is shifted towards lower side than the 50 h milled MgH2. The HRTEM study show the activated carbon helps to reduce oxygen from MgO phase in MgH2, so that significantly improvement achieved in the absorption capacity and kinetics also for the MgH2-AC nanocomposites. The presence of ß- and γ-phases of MgH2 in MgH2-AC nanocomposites also supports the high hydrogenation properties and with the support of XRD data.

Engineering high-performance Pd core-MgO porous shell nanocatalysts via heterogeneous gas-phase synthesis.

We report on the design and synthesis of high performance catalytic nanoparticles with a robust geometry via magnetron-sputter inert-gas condensation. Sputtering of Pd and Mg from two independent neighbouring targets enabled heterogeneous condensation and growth of nanoparticles with controlled Pd core-MgO porous shell structure. The thickness of the shell and the number of cores within each nanoparticle could be tailored by adjusting the respective sputtering powers. The nanoparticles were directly deposited on glassy carbon electrodes, and their catalytic activity towards methanol oxidation was examined by cyclic voltammetry. The measurements indicated that the catalytic activity was superior to conventional bare Pd nanoparticles. As confirmed by electron microscopy imaging and supported by density-functional theory (DFT) calculations, we attribute the improved catalytic performance primarily to inhibition of Pd core sintering during the catalytic process by the metal-oxide shell.