Covalently Linking Reduced Graphene Oxide Facilitated Electrodeposition of MoS2 on Silicon Pyramidal Photocathode To Enhance Hydrogen Evolution.

In recent years, increasing attention has been paid to photoelectrochemical (PEC) hydrogen production owing to the utilization of sustainable solar energy and its promising performance. Silicon-based composites are generally considered ideal materials for PEC hydrogen production. However, slow reaction kinetics and poor stability are still key factors hindering the development of silicon-based photoelectrocatalysts. Herein, we present an n+-p Si pyramidal photocathode assembly method to load reduced graphene oxide (rGO) onto the surface of the n+-p Si pyramid by covalently linking (Si/rGO). rGO is utilized as a conductive layer to reduce the interfacial charge-transfer resistance. Then, MoS2 can be successfully electrodeposited on the surface of Si/rGO to form the Si/rGO/MoS2 composite, which possesses excellent PEC hydrogen evolution performance with a high and stable photocurrent of -41.6 mA cm-2 and a hydrogen evolution rate of about 18.1 µmol min-1 cm-2 under 0 V (vs RHE). The covalently linking rGO layer effectively enhances the transfer of photogenerated carriers between the Si substrate and MoS2. MoS2 provides abundant hydrogen evolution active sites, which accelerate the surface reaction kinetics, as well as a protective layer for the Si pyramidal array structure. This work provides a low-cost, convenient, and efficient way of preparing silicon-based photocathodes.

Two-way rushing travel: Cathodic-anodic coupling of Bi2O3-SnO@CuO nanowires, a bifunctional catalyst with excellent CO2RR and MOR performance for the efficient production of formate.

Electrocatalytic carbon dioxide reduction reaction (CO2RR) generates high value-added products and simultaneously reduces excess atmospheric CO2 concentrations, is regarded as a potential approach to achieve carbon neutrality. However, the kinetic process of the anode oxygen evolution reaction (OER) is slow, resulting in a poor electrochemical efficiency of CO2RR. It is a breakthrough to replace OER with methanol oxidation reaction (MOR), which has more advantageous reaction kinetics. Herein, this work proposed a bifunctional catalyst Bi2O3-SnO modified CuO nanowires (Bi2O3-SnO@CuO NWs) with excellent CO2RR and MOR performance. For CO2RR, Bi2O3-SnO@CuO NWs achieved more than 90% formate selectivity at wide potential windows from -0.88 to -1.08 V (vs. reversible hydrogen electrode (RHE)), peaking at 96.6%. Meanwhile, anodic Bi2O3-SnO@CuO NWs achieved 100 mA cm-2 at a low potential of 1.53 V (vs. RHE), possessing nearly 100% formate selectivity ranging from 1.6 to 1.8 V (vs. RHE). Impressively, by coupling cathodic CO2RR and anodic MOR, the integrated electrolytic cell realized co-production of formate (cathode: 94.7% and anode: 97.5%), minimizing the energy input by approximately 69%, compared with CO2RR. This work provided a meaningful perspective for the design of bifunctional catalysts and coupling reaction systems in CO2RR.

Gold-Promoted Electrodeposition of Metal Sulfides on Silicon Nanowire Photocathodes To Enhance Solar-Driven Hydrogen Evolution.

Constructing composite structures is the key to breaking the dilemma of slow reaction kinetics and easy oxidation on the surface of lightly doped p-type silicon nanowire (SiNW) array photocathodes. Electrodeposition is a convenient and fast technique to prepare composite photocathodes. However, the low conductivity of SiNWs limits the application of the electrodeposition technique in constructing composite structures. Herein, SiNWs were loaded with Au nanoparticles by chemical deposition to decrease the interfacial charge transfer resistance and increase active sites for the electrodeposition. Subsequently, co-catalysts CoS, MoS2, and Ni3S2 with excellent hydrogen evolution activity were successfully composited by electrodeposition on the surface of SiNWs/Au. The obtained core-shell structures exhibited excellent photoelectrochemical hydrogen evolution activity, which was contributed by the plasma property of Au and the abundant hydrogen evolution active sites of the co-catalysts. This work provided a simple and efficient solution for the preparation of lightly doped SiNW-based composite structures by electrodeposition.

A multifunctional Fe2O3@MoS2@SDS Z-scheme nanocomposite: NIR enhanced bacterial inactivation, degradation antibiotics and inhibiting ARGs dissemination.

To fight the flourishment of drug-resistant bacteria caused by antibiotics and the dissemination of antibiotic resistance genes (ARGs), it is of great urgency to develop multifunctional non-antibiotic agents with residual antibiotics elimination, and ARGs dissemination inhibition properties. Herein, sodium dodecyl sulfate (SDS) was modified onto the surface of Fe2O3 @MoS2 by ultrasonic method to obtain the Z-scheme, multifunctional Fe2O3 @MoS2 @SDS nanocomposites. The Fe2O3 @MoS2 @SDS (weight ratio of Fe2O3 @MoS2 and SDS was 1:1) was selected as the optimal agent. Under NIR irradiation, the Fe2O3 @MoS2 @SDS had a photothermal conversion efficiency of 45.96%, and could generate plenty of reactive oxygen species (ROS) at the same time. Under the synergy of photothermal and photodynamic, the antibacterial efficiency of Fe2O3 @MoS2 @SDS to E. coli, MRSA and P. aeruginosa could reach 99.95%, 99.97% and 99.58%, respectively, indicating excellent photothermal-photodynamic therapy (PPT) effect. The Fe2O3 @MoS2 @SDS also displayed photocatalytic activity in degradation of tetracycline (TC). The degradation rate of TC could reach 92.3% after 2 h of visible light irradiation. The obtained results indicated that a promising Fe2O3 @MoS2 @SDS composite based multifunctional nanoplatform could be constructed for NIR induced bacterial inactivation, antibiotics degradation and ARGs dissemination inhibition.

SDS coated Fe3O4@MoS2 with NIR-enhanced photothermal-photodynamic therapy and antibiotic resistance gene dissemination inhibition functions.

Infection caused by antibiotic-resistant bacteria is serious threat for public health, and calls for novel antibacterial agents with versatile functions. In particular, nanomaterial is one of promising candidates to fight the increasing antibiotic resistance crisis. Here, we synthesized distinct Fe3O4@MoS2@SDS nanocomposites by ultrasonication assisted SDS coating on the Fe3O4@MoS2. Photothermal investigation indicated that the Fe3O4@MoS2@SDS showed excellent and stable photothermal performance and could be a NIR-induced photothermal reagent. It also displayed superior disinfection ability of Escherichia coli (E. coli), Methicillin-resistant Staphylococcus aureus (MRSA), and Pseudomonas aeruginosa (P. aeruginosa) and in vivo wound healing ability with the help of NIR irradiation. According to the results of electron paramagnetic resonance (EPR) and radical capture tests, plenty of superoxide, hydroxyl radicals, singlet oxygen and living cell reactive oxygen species can be observed under NIR irradiation. Besides, the synergistic effect Fe3O4@MoS2@SDS and NIR irradiation eradicated almost all the biofilms of MRSA, so this kind of function enhanced the disinfection ability of Fe3O4@MoS2@SDS under NIR irradiation. Furthermore, its inhibition effect on antibiotic resistance gene dissemination was also investigated. As expected, the Fe3O4@MoS2@SDS could efficiently and broadly block the horizontal transfer of antibiotic resistance genes which mediated by conjugative plasmids, and its blocking effect was better than that we have reported Fe3O4@MoS2. Overall, our findings revealed that the Fe3O4@MoS2@SDS could be a potential candidate for photothermal-photodynamic therapy and antibiotic resistance gene dissemination inhibition.

Indirect reduction of Ralstonia solanacearum via pathogen helper inhibition.

The rhizosphere microbiome forms a first line of defense against soilborne pathogens. To date, most microbiome enhancement strategies have relied on bioaugmentation with antagonistic microorganisms that directly inhibit pathogens. Previous studies have shown that some root-associated bacteria are able to facilitate pathogen growth. We therefore hypothesized that inhibiting such pathogen helpers may help reduce pathogen densities. We examined tripartite interactions between a model pathogen, Ralstonia solanacearum, two model helper strains and a collection of 46 bacterial isolates recovered from the tomato rhizosphere. This system allowed us to examine the importance of direct (effects of rhizobacteria on pathogen growth) and indirect (effects of rhizobacteria on helper growth) pathways affecting pathogen growth. We found that the interaction between rhizosphere isolates and the helper strains was the major determinant of pathogen suppression both in vitro and in vivo. We therefore propose that controlling microbiome composition to prevent the growth of pathogen helpers may become part of sustainable strategies for pathogen control.

Fe3O4 composited with MoS2 blocks horizontal gene transfer.

In this study, we found that Fe3O4 promoted horizontal gene transfer (HGT), but when Fe3O4 was composited with MoS2, the Fe3O4@MoS2 nanocomposite interacting with bacteria significantly blocked the HGT in the conjugation system. qPCR was used to analyze the expression of genes belonging to the chromosome and plasmid in the conjugation system. Results demonstrated that Fe3O4@MoS2 inhibited conjugation by promoting the expression of the global regulatory gene (trbA) and inhibiting the expression of conjugative transfer genes involved in mating pair formation (traF, trbB), DNA replication (trfA), and porins (outer membrane protein (omp) A and ompC). All of these genes are related to the permeability of the cell membrane, except for trfA. The results showed that Fe3O4@MoS2 interacted with bacteria to decrease their permeability against exogenous DNA. MoS2 may play an essential role in the HGT-inhibiting activity of Fe3O4@MoS2. This study highlights the diverse biological properties of nano-materials and provides clues for nano-scientists to develop environmentally friendly materials.

MoS2 decorated nanocomposite: Fe2O3@MoS2 inhibits the conjugative transfer of antibiotic resistance genes.

Nanomaterials of Al2O3 and TiO2 have been proved to promote the spread of antibiotic resistance genes (ARGs) by horizontal gene transfer. In this work, we found that Fe2O3@MoS2 nanocomposite inhibited the horizontal gene transfer (HGT) by inhibiting the conjugative transfer mediated by RP4-7 plasmid. To discover the mechanism of Fe2O3@MoS2 inhibiting HGT, the bacterial cells were collected under the optimal mating conditions. The collected bacterial cells were used for analyzing the expression levels of genes unique to the plasmid and the bacterial chromosome in the conjugation system by qPCR. The results of genes expression demonstrated that the mechanism of Fe2O3@MoS2 inhibited conjugation by promoting the expression of global regulatory gene (trbA) and inhibiting the expression of conjugative transfer genes involved in mating pair formation (traF, trbB) and DNA replication (trfA). The risk assessment of Fe2O3@MoS2 showed that it had very low toxicity to organisms. The findings of this paper showed that Fe2O3@MoS2, as an inhibitor of horizontal gene transfer, is an environment-friendly material.

Electrocatalytic determination of nitrite based on straw cellulose/molybdenum sulfide nanocomposite.

Cellulose is the most abundant, renewable, biodegradable natural polymer resource on earth, which can be a good substrate for catalysis. In this work, straw cellulose has been oxidized through 2,2,6,6-tetramethylpiperidine-1-oxyl radical (TEMPO)-mediated oxidation, and then a TEMPO oxidized straw cellulose/molybdenum sulfide (TOSC-MoS2) composite has been synthesized via a hydrothermal method. Fourier transform infrared spectroscopy (FT-IR) and X-ray diffraction (XRD) analysis confirm that TOSC and MoS2 have successfully composited. Scanning electron microscopy (SEM) and transmission electron microscopy (TEM) images show the TOSC as a carbon nanotube-like structure and edged MoS2 grows on the TOSC substrate. The TOSC-MoS2 modified glassy carbon electrode (GCE) is used as a simple and non-enzymatic electrochemical sensor. Cyclic Voltammetry (CV) result shows TOSC-MoS2 has excellent electrocatalytic activity for the oxidation of nitrite. The amperometric response result indicates the TOSC-MoS2 modified GCE can be used to determine nitrite concentration in wide linear ranges of 6.0-3140 and 3140-4200µM with a detection limit of 2.0µM. The proposed sensor has good anti-interference property. Real sample analysis and the electrocatalytic mechanism have also been presented.

CONSTANS-LIKE 7 regulates branching and shade avoidance response in Arabidopsis.

Branching is an important trait of plant development regulated by environmental signals. Phytochromes in Arabidopsis mediate branching in response to the changes in the red light:far-red light ratio (R:FR), the mechanisms of which are still elusive. Here it is shown that overexpression of CONSTANS-LIKE 7 (COL7) results in an abundant branching phenotype which could be efficiently suppressed by shade or a simulated shade environment (low R:FR). Moreover, col7 mutants develop shorter hypocotyls and COL7 overexpression lines develop longer hypocotyls in comparison with the wild type in low R:FR, indicating that COL7 acts as an enhancer of the shade avoidance response. In shade or transient low R:FR, transcriptional and post-transcriptional expression levels of COL7 are up-regulated and positively associated with rapid mRNA accumulation of PHYTOCHROME INTERACTING FACTOR 3-LIKE 1 (PIL1), a marker gene of shade avoidance syndrome (SAS). Taken together, the results suggest a dual role for COL7 which promotes branching in high R:FR conditions but enhances SAS in low R:FR conditions.

Analysis of clock gene homologs using unifoliolates as target organs in soybean (Glycine max).

Soybean is a typical short-day crop, and its photoperiodic response of flowering is critical to its yield. This phenomenon was well studied during the last century, but the molecular mechanism governing it is unknown. The clock-gene homologs, GmLCL1 and GmLCL2 (Glycine max LHY/CCA1 Like 1 and 2) and GmTOC1 (Glycine max TOC1) were cloned from Glycine max L. KN18, and their expression patterns were analyzed using a system developed in this study. We employed 8h light/16h dark and 18h light/6h dark as short- and long-day conditions, respectively, because in these conditions soybean plants had significant indexes of flowering time. We also used unifoliolates, not the whole plant as Arabidopsis, as target organs for gene expression analysis. GmLCL1 and GmLCL2 had similar circadian expression patterns and both were morning genes, while GmTOC1 was an evening gene and peaked in the evening. The expressions of GmLCL1 and GmLCL2 were obviously antiphase to that of GmTOC1.Our study provided a system that simplified the experiments without compromising the quality of data obtained and was suitable for analyzing the molecular mechanism of flowering in soybean. GmLCL1, GmLCL2 and GmTOC1 may be the components of central clock in soybean.