The effect of ultrafine WO3 nanoparticles on the organization of thylakoids enriched in photosystem II and energy transfer in photosystem II complexes

In this work, a new approach to construct self-assembled hybrid systems based on natural PSII-enriched thylakoid membranes (PSII BBY) is demonstrated. Superfine m-WO3 NPs (≈1-2 nm) are introduced into PSII BBY. Transmission electron microscopy (TEM) measurements showed that even the highest concentrations of NPs used did not degrade the PSII BBY membranes. Using atomic force microscopy (AFM), it is shown that the organization of PSII BBY depends strongly on the concentration of NPs applied. This proved that the superfine NPs can easily penetrate the thylakoid membrane and interact with its components. These changes are also related to the modified energy transfer between the external light-harvesting antennas and the PSII reaction center, shown by absorption and fluorescence experiments. The biohybrid system shows stability at pH 6.5, the native operating environment of PSII, so a high rate of O2 evolution is expected. In addition, the light-induced water-splitting process can be further stimulated by the direct interaction of superfine WO3 NPs with the donor and acceptor sides of PSII. The water-splitting activity and stability of this colloidal system are under investigation. RESEARCH HIGHLIGHTS: The phenomenon of the self-organization of a biohybrid system composed of thylakoid membranes enriched in photosystem II and superfine WO3 nanoparticles is studied using AFM and TEM. A strong dependence of the organization of PSII complexes within PSII BBY membranes on the concentration of NPs applied is observed. This observation turns out to be crucial to understand the complexity of the mechanism of the action of WO3 NPs on modifications of energy transfer from external antenna complexes to the PSII reaction center.

Photocatalytic reduction of Cr(VI) using Mg-doped WO3 nanoparticles

The hydrothermal synthesis method was employed for the fabrication of pristine tungsten trioxide (WO₃) and that of varying dopant percentages (1, 3 and 5% m/m) of magnesium (Mg-WO₃). The optical and structural properties of the synthesized materials were characterized using DRS, XRD, FTIR, TEM, BET, FESEM, XPS, PL, and Raman. Rectangular shaped nanostructures were observed through FESEM, wherein confirmed as monoclinic with the aid of XRD, FTIR and Raman analysis. Visualization of the doping was carried out using HRTEM imagery, which was also confirmed by a slight increase (0.0069 nm) of d spacing. As a consequence, band gaps were diminished and band edge positions were shifted. Band edge position shifts were confirmed via XPS analysis (0.08 eV). The point of zero charge was observed to shift towards positive upon doping at working pH 1 and 3.75 pH was the highest recorded. The rate of recombination was greatly reduced upon doping was observed through PL analysis. This was supported by DFT calculations, in which case the reduction of the rate of recombination was attributed to the introduction of Mg orbital. An improved efficiency was observed via the photo reduction of Cr(VI) metal ion in waste water, in which case, 97% reduction was attained.

An efficient triple-junction polymer solar cell having a power conversion efficiency exceeding 11%

Tandem solar cells have the potential to improve photon conversion efficiencies (PCEs) beyond the limits of single-junction devices. In this study, a triple-junction tandem design is demonstrated by employing three distinct organic donor materials having bandgap energies ranging from 1.4 to 1.9 eV. Through optical modeling, balanced photon absorption rates are achieved and, thereby, the photo-currents are matched among the three subcells. Accordingly, an efficient triple-junction tandem organic solar cell can exhibit a record-high PCE of 11.5%.