Recent developments of advanced Ti3+-self-doped TiO2 for efficient visible-light-driven photocatalysis

© 2020 by the authors. Licensee MDPI, Basel, Switzerland.Research into the development of efficient semiconductor photocatalytic materials is a promising approach to solving environmental and energy problems worldwide. Among these materials, TiO2 photocatalysts are one of the most commonly used due to their efficient photoactivity, high stability, low cost and environmental friendliness. However, since the UV content of sunlight is less than 5%, the development of visible light-activated TiO2-based photocatalysts is essential to increase the solar energy efficiency. Here, we review recent works on advanced visible light-activated Ti3+-self-doped TiO2 (Ti3+–TiO2) photocatalysts with improved electronic band structures for efficient charge separation. We analyze the different methods used to produce Ti3+–TiO2 photocatalysts, where Ti3+ with a high oxygen defect density can be used for energy production from visible light. We categorize advanced modifications in electronic states of Ti3+–TiO2 by improving their photocatalytic activity. Ti3+–TiO2 photocatalysts with large charge separation and low recombination of photogenerated electrons and holes can be practically applied for energy conversion and advanced oxidation processes in natural environments and deserve significant attention11sci

Experimental and computational investigations of the abnormal slow dissociation behavior of CH4 hydrate in the presence of Poly (N-vinylcaprolactam)

In this study, the dissociation behavior of CH4 hydrate in the absence and presence of poly(N-vinylcaprolactam) (PVCap) was closely investigated using a combination of experimental techniques, including in-situ Raman spectroscopy and high-pressure micro-differential scanning calorimetry (HP & mu;-DSC), and molecular dynamics (MD) simulations. The experimental results clearly demonstrated that CH4 hydrate dissociated more slowly and in two steps in the presence of PVCap. The MD simulations revealed that this slow and two-step dissociation was mainly due to the adsorption of PVCap onto the hydrate surface, which hindered the mass transfer of CH4 from the hydrate into the solution. The high viscosity and steric hindrance of PVCap also impeded the formation and growth of CH4 bubbles during the hydrate dissociation, contributing to the slower dissociation of CH4 hydrate in the PVCap solution. The broad and asymmetric shape of the last endothermic peak observed via HP & mu;-DSC was caused by the adsorption of PVCap during CH4 hydrate dissociation. The findings of this study provide valuable insights into the precise mechanism of hydrate dissociation in the presence of kinetic hydrate inhibitors

Electrochemical Nanoscale Templating: Laterally Self-Aligned Growth of Organic–Metal Nanostructures

The electrodeposition of Ag into organized surfactant templates adsorbed onto (22 × √3) reconstructed Au(111) is investigated by in situ electrochemical scanning tunneling microscopy. Ag⁺ concentrations of as low as 2.5 × 10^–6 M allow the visualization of the electrochemical molecular templating effect of a sodium dodecyl sulfate (SDS) adlayer. The SDS hemicylindrical stripes determine the adsorption sites of the Ag⁺ ions and the directionality of Ag nanodeposition. The SDS-Ag nanostructures grow along the long axis of SDS hemicylindrical stripes, and an interaction of Ag with the Au(111) substrate leads to a structural change in the SDS stripe pattern. The SDS-Ag nanostructures undergo dynamic rearrangement in response to changes in the applied electrode potential. At negative potentials, the orientations of SDS-Ag nanostructures are pinned by the (22 × √3) reconstructed pattern. Furthermore, observed differences in Ag nanostructuring on Au(111) without molecular templates (i.e., on a bare Au(111) surface) confirm the role of self-assembled organic templates in producing metal–organic nanostructures under control of the surface potential, which can determine the feature size, shape, and period of the metal nanostructure arrays

A molecular approach to an electrocatalytic hydrogen evolution reaction on single-layer graphene

A major challenge in the development of electrocatalysts is to determine a detailed catalysis mechanism on a molecular level for enhancing catalytic activity. Here, we present bottom-up studies for an electrocatalytic hydrogen evolution reaction (HER) process through molecular activation to systematically control surface catalytic activity corresponding to an interfacial charge transfer in a porphyrin monolayer on inactive graphene. The two-dimensional (2D) assembly of porphyrins that create homogeneous active sites (e.g., electronegative tetrapyrroles (N4)) on graphene showed structural stability against electrocatalytic reactions and enhanced charge transfer at the graphene-liquid interface. Performance operations of the graphene field effect transistor (FET) were an effective method to analyse the interfacial charge transfer process associated with information about the chemical nature of the catalytic components. Electronegative pristine porphyrin or Pt-porphyrin networks, where intermolecular hydrogen bonding functioned, showed larger interfacial charge transfers and higher HER performance than Ni-, or Zn-porphyrin. A process to create surface electronegativity by either central N-4 or metal (M)-N-4 played an important role in the electrocatalytic reaction. These findings will contribute to an in-depth understanding at the molecular level for the synergetic effects of molecular structures on the active sites of electrocatalysts toward HER1441sciescopu

Electrical characteristics of amyloid beta peptides in vertical junctions

© 2021 Springer Nature Limited. Assembled amyloid beta (A beta) peptides have been considered pathological assemblies involved in human brain diseases, and the electron transfer or electron transport characteristics of A beta are important for the formation of structured assemblies. Here, we report the electrical characteristics of surface-assembled A beta peptides similar to those observed in Alzheimer's patients. These characteristics correlate to their electron transfer characteristics. Electrical current-voltage plots of A beta vertical junction devices show the A beta sequence dependence of the current densities at both A beta monomers (mono-A beta s) and A beta oligomers (oli-A beta s), while A beta sequence dependence is not clearly observed in the electrical characteristics of A beta planar field effect transistors (FETs). In particular, surface oligomerization of A beta peptides drastically decreases the activity of electron transfer, which presents a change in the electron transport pathway in the A beta vertical junctions. Electron transport at oli-A beta junctions is symmetric (tunneling/tunneling) due to the weak and voltage-independent coupling of the less redox-reactive oli-A beta to the contacts, while that at mono-A beta junctions is asymmetric (hopping/tunneling) due to redox levels of mono-A beta voltage-dependently coupled with contact electrodes. Consequently, through vertical junctions, the sequence- and conformation-dependent electrical characteristics of A beta s can reveal their electron transfer activities.11Nsciescopu

Newly isolated Lactobacillus paracasei strain modulates lung immunity and improves the capacity to cope with influenza virus infection

Abstract Background The modulation of immune responses by probiotics is crucial for local and systemic immunity. Recent studies have suggested a correlation between gut microbiota and lung immunity, known as the gut–lung axis. However, the evidence and mechanisms underlying this axis remain elusive. Results In this study, we screened various Lactobacillus (L.) strains for their ability to augment type I interferon (IFN-I) signaling using an IFN-α/β reporter cell line. We identified L. paracasei (MI29) from the feces of healthy volunteers, which showed enhanced IFN-I signaling in vitro. Oral administration of the MI29 strain to wild-type B6 mice for 2 weeks resulted in increased expression of IFN-stimulated genes and pro-inflammatory cytokines in the lungs. We found that MI29-treated mice had significantly increased numbers of CD11c+PDCA-1+ plasmacytoid dendritic cells and Ly6Chi monocytes in the lungs compared with control groups. Pre-treatment with MI29 for 2 weeks resulted in less weight loss and lower viral loads in the lung after a sub-lethal dose of influenza virus infection. Interestingly, IFNAR1−/− mice did not show enhanced viral resistance in response to oral MI29 administration. Furthermore, metabolic profiles of MI29-treated mice revealed changes in fatty acid metabolism, with MI29-derived fatty acids contributing to host defense in a Gpr40/120-dependent manner. Conclusions These findings suggest that the newly isolated MI29 strain can activate host defense immunity and prevent infections caused by the influenza virus through the gut–lung axis. Video Abstrac

Nitrogen-Doped Partially Reduced Graphene Oxide Rewritable Nonvolatile Memory

As memory materials, two-dimensional (2D) carbon materials such as graphene oxide (GO)-based materials have attracted attention due to a variety of advantageous attributes, including their solution-processability and their potential for highly scalable device fabrication for transistor-based memory and cross-bar memory arrays. In spite of this, the use of GO-based materials has been limited, primarily due to uncontrollable oxygen functional groups. To induce the stable memory effect by ionic charges of a negatively charged carboxylic acid group of partially reduced graphene oxide (PrGO), a positively charged pyridinium N that served as a counterion to the negatively charged carboxylic acid was carefully introduced on the PrGO framework. Partially reduced N-doped graphene oxide (PrGO_DMF) in dimethylformamide (DMF) behaved as a semiconducting nonvolatile memory material. Its optical energy band gap was 1.7–2.1 eV and contained a sp² CC framework with 45–50% oxygen-functionalized carbon density and 3% doped nitrogen atoms. In particular, rewritable nonvolatile memory characteristics were dependent on the proportion of pyridinum N, and as the proportion of pyridinium N atom decreased, the PrGO_DMF film lost memory behavior. Polarization of charged PrGO_DMF containing pyridinium N and carboxylic acid under an electric field produced N-doped PrGO_DMF memory effects that followed voltage-driven rewrite-read-erase-read processes

Nanoparticle Linker-Controlled Molecular Wire Devices Based on Double Molecular Monolayers

© 2019 WILEY-VCH Verlag GmbH & Co. KGaA, WeinheimHighly conductive molecular wires are an important component for realizing molecular electronic devices and have to be explored in terms of interactions between molecules and electrodes in their molecular junctions. Here, new molecular wire junctions are reported to enhance charge transport through gold nanoparticle (AuNP)-linked double self-assembled monolayers (SAMs) of cobalt (II) bis-terpyridine molecules (e.g., Co(II)(tpyphS)2). Electrical characteristics of the double-SAM devices are explored in terms of the existence of AuNP. The AuNP linker in the Co(II)(tpyphS)2–AuNP–Co(II)(tpyphS)2 junction acts as an electronic contact that is transparent to electrons. The weak temperature dependency of the AuNP-linked molecular junctions strongly indicates sequential tunneling conduction through the highest occupied molecular orbitals (HOMOs) of Co(II)(tpyphS)2 molecules. The electrochemical characteristics of the AuNP–Co(II)(tpyphS)2 SAMs reveal fast electron transfer through molecules linked by AuNP. Density functional theory calculations reveal that the molecular HOMO levels are dominantly affected by the formation of junctions. The intermolecular charge transport, controlled by the AuNP linker, can provide a rational design for molecular connection that achieves a reliable electrical connectivity of molecular electronic components for construction of molecular electronic circuit

Catalyst-free bottom-up growth of graphene nanofeatures along with molecular templates on dielectric substrates

Synthesis of graphene nanostructures has been investigated to provide outstanding properties for various applications. Herein, we report molecular thin film-assisted growth of graphene into nanofeatures such as nanoribbons and nanoporous sheets along with a predetermined molecular orientation on dielectric substrates without metal catalysts. A Langmuir-Blodgett (LB) method was used for the formation of the molecularly patterned SiO2 substrates with ferric stearate layers, which acted as a template for the directional growth of the polypyrrole graphene precursor. The nanofeatures of the graphene were determined by the number of ferric stearate layers (e.g., nanoribbons from multiple layers and nanoporous sheets from a single layer). The graphene nanoribbons (GNRs) containing pyrrolic N enriched edges exhibited a p-type semiconducting behavior, whereas the nanoporous graphene sheets containing inhomogeneous pores and graphitic N enriched basal planes exhibited the typical electronic transport of nitrogen-doped graphene. Our approaches provide two central methods for graphene synthesis such as bottom-up and direct processes for the future development of graphene nanoelectronics. © 2016 The Royal Society of Chemistry1331sciescopu

Efficient and Stable Solar Hydrogen Generation of Hydrophilic Rhenium-Disulfide-Based Photocatalysts via Chemically Controlled Charge Transfer Paths

© 2020 American Chemical Society.Effective charge separation and rapid transport of photogenerated charge carriers without self-oxidation in transition metal dichalcogenide photocatalysts are required for highly efficient and stable hydrogen generation. Here, we report that a molecular junction as an electron transfer path toward two-dimensional rhenium disulfide (2D ReS2) nanosheets from zero-dimensional titanium dioxide (0D TiO2) nanoparticles induces high efficiency and stability of solar hydrogen generation by balanced charge transport of photogenerated charge carriers. The molecular junctions are created through the chemical bonds between the functionalized ReS2 nanosheets (e.g., -COOH groups) and -OH groups of two-phase TiO2 (i.e., ReS2-C6H5C(≠O)-O-TiO2 denoted by ReS2-BzO-TiO2). This enhances the chemical energy at the conduction band minimum of ReS2 in ReS2-BzO-TiO2, leading to efficiently improved hydrogen reduction. Through the molecular junction (a Z-scheme charge transfer path) in ReS2-BzO-TiO2, recombination of photogenerated charges and self-oxidation of the photocatalyst are restrained, resulting in a high photocatalytic activity (9.5 mmol h-1 per gram of ReS2 nanosheets, a 4750-fold enhancement compared to bulk ReS2) toward solar hydrogen generation with high cycling stability of more than 20 h. Our results provide an effective charge transfer path of photocatalytic TMDs by preventing self-oxidation, leading to increases in photocatalytic durability and a transport rate of the photogenerated charge carrier