Rational Design of S-Scheme Heterojunction toward Efficient Photocatalytic Cellulose Reforming for H2 and Formic Acid in Pure Water.

Photocatalytic cellulose reforming usually requires harsh conditions due to its sluggish kinetics. Here, a hollow structural S-scheme heterojunction of ZnSe and oxygen vacancy enriched TiO2 , namely, h-ZnSe/Pt@TiO2 , is designed and fabricated, with which the photocatalytic reforming of cellulose for H2 and formic acid is realized in pure water. H2 and formic acid productivity of 1858 and 372 µmol g-1 h-1 and a steady H2 evolution for 300 h are achieved with α-cellulose. Comparable photocatalytic activity can also be achieved using various cellulose sources. It is experimentally proven that the photogenerated charge transfer follows an S-scheme mechanism, which not only promotes the charge separation but also preserves the higher reductive and oxidative abilities of the ZnSe and TiO2 , respectively. Furthermore, the polyhydroxy species produced during cellulose degradation are favored to adsorb on the oxygen vacancy enriched TiO2 surface, which promotes the photocatalytic reforming process and is accounted to the preservation of formic acid as the major solution-phase product. In addition, sequential reactions of oxidation of aldehydes and elimination of formic acid of the cellulose degradation process are revealed. This work provides a photocatalytic strategy to sustainably produce hydrogen and value-added chemicals from biomass under the most environmentally benign condition, i.e., pure water.

Lighting the way to sustainable development: Physiological response and light control strategy in microalgae-based wastewater treatment under illumination.

The Sustainable Development Goals link pollutant control with carbon dioxide reduction. Toward the goal of pollutant and carbon reduction, microalgae-based wastewater treatment (MBWT), which can simultaneously remove pollutants and convert carbon dioxide into biomass with value-added metabolites, has attracted considerable attention. The photosynthetic organism microalgae and the photobioreactor are the functional body and the operational carrier of the MBWT system, respectively; thus, light conditions profoundly influence its performance. Therefore, this review takes the general rules of how light influences the performance of MBWT systems as a starting point to elaborate the light-influenced mechanisms in microalgae and the light control strategies for photobioreactors from the inside out. Wavelength, light intensity and photoperiod solely or interactively affect biomass accumulation, pollutant removal, and value-added metabolite production in MBWT. Physiological processes, including photosynthesis, photooxidative damage, light-regulated gene expression, and nutrient uptake, essentially explain the performance influence of MBWT and are instructive for specific microalgal strain improvement strategies. In addition, light causes unique reactions in MBWT systems as it interacts with components such as photooxidative damage enhancers present in types of wastewater. In order to provide guidance for photobioreactor design and light control in a large-scale MBWT system, wavelength transformation, light transmission, light source distribution, and light-dark cycle should be considered in addition to adjusting the light source characteristics. Finally, based on current research vacancies and challenges, future research orientation should focus on the improvement of microalgae and photobioreactor, as well as the integration of both.

Hollow mesoporous cubic silica self-assembling into photonic crystals with rhombohedral lattices and vivid structural colors for anti-counterfeiting.

Colloidal photonic crystals (PCs) feature face-centered cubic (FCC) lattices since spherical particles are usually used as building blocks; however, constructing structural colors originating from PCs with non-FCC lattices is still a big challenge due to the difficulty in preparing non-spherical particles with tunable morphologies, sizes, uniformity, and surface properties and assembling them into ordered structures. Here, uniform, positively charged, and hollow mesoporous cubic silica particles (hmc-SiO2) with tunable sizes and shell thicknesses prepared by a template approach are used to self-assemble into PCs with rhombohedral lattice. The reflection wavelengths and structural colors of the PCs can be controlled by altering the sizes or the shell thicknesses of the hmc-SiO2. Additionally, photoluminescent PCs have been fabricated by taking the advantage of the click chemistry between amino silane and isothiocyanate of a commercial dye. The PC pattern achieved by a hand-writing way with the solution of the photoluminescent hmc-SiO2 instantly and reversibly shows the structural color under visible light but a different photoluminescent color under UV illumination, which is useful for anticounterfeiting and information encryption. The non-FCC structured and photoluminescent PCs will upgrade the basic understanding of the structural colors and facilitate their applications in optical devices, anti-counterfeiting, and so forth.

Tuning the current rectification behavior of Rh2-based molecular junctions by varying their supramolecular structures.

Molecular junctions with similar backbones, tunable chemical structures and controllable length are critical for the systematic study of the structure-functionality relationships of their charge transport behavior. Taking advantage of the feasibility and tunability of stepwise fabrication, we built series of asymmetric supramolecular SAMs on gold using Rh2(O2CCR3)4 (Rh2, R = CH3, H, and F) as the building blocks and conjugated N,N'-bidentate ligands (pyrazine (LS), 4,4'-bipyridine (LM) and 1,2-bis(4-pyridyl)ethene (LL)) as the bridges. By varying the Rh2 units and bridging ligands, series of supramolecules with similar backbone and tunable chemical structures were assembled on gold. Their charge transport behavior was examined using conductive-probe atomic force microscopy. Notably, current rectification diminishes gradually as the degree of conjugation of the bridging ligands gets larger from LS to LL due to the decrease in the energy gap between the donor and the acceptor in π(Rh2)-π(L) conjugated MO arrays. Additionally, current rectification can be enhanced when the charge transport mechanistic transits from tunneling in dimers to hopping in tetramers. Unlike charges hopping along the MO arrays in tetramers, charges tunnel through the frontier MOs in dimers. The occupied frontier MOs of dimers localize near the center of the supramolecules or delocalize on the donor and acceptor, which contributes to the weakening of the asymmetric charge tunneling. This work reveals that the frontier MO configurations of these supramolecules could be adjusted by varying their chemical structures, and consequently realize tuning of their charge transport behavior, which deepens the understanding of the charge transport behavior and benefits the establishment of the structure-functionality relationship of Rh2-based molecular junctions.

Biomimetic fabrication of superhydrophobic loofah sponge: robust for highly efficient oil-water separation in harsh environments.

Oil/water separation has become an increasingly important field due to frequent industrial oily wastewater emission and crude oil spill accidents. Herein, we fabricate a robust superhydrophobic loofah sponge via a versatile, environmentally friendly, and low-cost dip coating strategy, which involves the modification of commercial loofah sponge with waterborne polyurea and fused SiO2 nanoparticles without the modification of any toxic low-surface-energy compound. The as-prepared loofah sponge showed excellent superhydrophobic/superoleophilic properties and exhibited robustness for effective oil-water separation in extremely harsh environments (such as 1 M HCl, 1 M NaOH, saturated NaCl solution and hot water higher than 95 °C) due to the remarkably high chemical stability. In addition, the as-prepared loofah sponge was capable of excellent anti-fouling, has self-cleaning ability and could act as the absorber for effective separation of surfactant-free oil-in-water emulsions. More importantly, the as-prepared loofah sponge demonstrated remarkable robustness against strong sandpaper abrasion and finger wipes, while retaining its superhydrophobicity and efficient oil/water separation efficiency even after more than 50 abrasion cycles. This facile and green synthesis approach presented here has the advantage of large-scale fabrication of a multifunctional biomass-based adsorbent material as a promising candidate in anti-fouling, self-cleaning, and versatile water-oil separation.