Functional molybdenum sulfide catalyst obtained with an in situ approach demonstrated quite high efficiency for catalyzing H2 evolution in a noble-metal-free dye-sensitized system under visible ...light.
•MoSx nanoparticles were obtained with a simple in situ photoreduction approach.•MoSx catalyzed H2 evolution efficiently in the presence of organic sensitizer.•A noble-metal-free system for photocatalytic hydrogen production was established.•A two-step reaction mechanism was proposed.
The establishment of cost-effective photocatalytic system based on earth-abundant materials is crucial for the practical utilizations of solar energy. To achieve this goal, it is highly desirable to employ photosensitizers and catalysts that are both derived from earth-abundant materials. Herein, we report an efficient noble-metal-free system by integrating the above two components. We found that functional MoSx nanoparticles can be obtained with an in situ photoreduction manner during photocatalytic reactions in the presence of inexpensive organic sensitizers. The thus-obtained MoSx catalysts demonstrated quite high efficiency for catalyzing H2 evolution under visible light. The factors influencing the performance of the photocatalytic system was investigated and a two-step reaction mechanism was proposed. The concept of in situ formation of hydrogen evolution catalyst paves the way for investigating biomimetic molybdenum sulfide catalysts for photocatalytic H2 production in systems without the presence of noble metals.
Surfactant-free CuAgSe nanoparticles were successfully synthesized on a large scale within a short reaction time via a simple environmentally friendly aqueous approach under room temperature. The ...nanopowders obtained were consolidated into pellets for investigation of their thermoelectric properties between 3 and 623 K. The pellets show strong metallic characteristics below 60 K and turn into an n-type semiconductor with increasing temperature, accompanied by changes in the crystal structure (i.e., from the pure tetragonal phase into a mixture of tetragonal and orthorhombic phases), the electrical conductivity, the Seebeck coefficient, and the thermal conductivity, which leads to a figure of merit (ZT) of 0.42 at 323 K. The pellets show further interesting temperature-dependent transition from n-type into p-type in electrical conductivity arising from phase transition (i.e., from the mixture phases into cubic phase), evidenced by the change of the Seebeck coefficient from −28 μV/K into 226 μV/K at 467 K. The ZT value increased with increasing temperature after the phase transition and reached 0.9 at 623 K. The sintered CuAgSe pellets also display excellent stability, and there is no obvious change observed after 5 cycles of consecutive measurements. Our results demonstrate the potential of CuAgSe to simultaneously serve (at different temperatures) as both an n-type and a p-type thermoelectric material.
Based on theoretical prediction, a g-C3N4@carbon metal-free oxygen reduction reaction (ORR) electrocatalyst was designed and synthesized by uniform incorporation of g-C3N4 into a mesoporous carbon to ...enhance the electron transfer efficiency of g-C3N4. The resulting g-C3N4@carbon composite exhibited competitive catalytic activity (11.3 mA cm–2 kinetic-limiting current density at −0.6 V) and superior methanol tolerance compared to a commercial Pt/C catalyst. Furthermore, it demonstrated significantly higher catalytic efficiency (nearly 100% of four-electron ORR process selectivity) than a Pt/C catalyst. The proposed synthesis route is facile and low-cost, providing a feasible method for the development of highly efficient electrocatalysts.
This contribution describes the preparation of multifunctional yolk–shell nanoparticles (YSNs) consisting of a core of silica spheres and an outer shell based on periodic mesoporous organosilica ...(PMO) with perpendicularly aligned mesoporous channels. The new yolk–shell hybrid materials were synthesised through a dual mesophase and vesicle soft templating method. The mesostructure of the shell, the dimension of the hollow space (4∼52 nm), and the shell thickness (16∼34 nm) could be adjusted by precise tuning of the synthesis parameters, as evidenced by X‐ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM) and nitrogen sorption investigations. Various metal nanoparticles (e.g., Au, Pt, and Pd) were encapsulated and confined in the void space between the core and the shell using impregnation and reduction of adequate metal precursors. The selective oxidation of various alcohol substrates was then carried out to illustrate the benefits of such an architecture in catalysis. High conversion (∼100%) and excellent selectivity (∼99%) were obtained over Pd nanoparticles encapsulated in the hybrid PMO yolk–shell structures.
Yolk–shell‐structured metal (Au, Pt, Pd) catalysts with periodic mesoporous organosilica (PMO) shells and tunable void space and shell thickness are synthesized by a simple soft templating method. The Pd‐loaded hybrid yolk–shell PMO catalysts exhibit high catalytic activities (≈100% conversions) and selectivity (≈99%) in various selective oxidation reaction of alcohol in aqueous conditions.
A well-organized flexible interleaved composite of graphene nanosheets (GNSs) decorated with Fe3O4 particles was synthesized through in situ reduction of iron hydroxide between GNSs. The GNS/Fe3O4 ...composite shows a reversible specific capacity approaching 1026 mA h g−1 after 30 cycles at 35 mA g−1 and 580 mAh g−1 after 100 cycles at 700 mA g−1as well as improved cyclic stability and excellent rate capability. The multifunctional features of the GNS/Fe3O4 composite are considered as follows: (i) GNSs play a “flexible confinement” function to enwrap Fe3O4 particles, which can compensate for the volume change of Fe3O4 and prevent the detachment and agglomeration of pulverized Fe3O4, thus extending the cycling life of the electrode; (ii) GNSs provide a large contact surface for individual dispersion of well-adhered Fe3O4 particles and act as an excellent conductive agent to provide a highway for electron transport, improving the accessible capacity; (iii) Fe3O4 particles separate GNSs and prevent their restacking thus improving the adsorption and immersion of electrolyte on the surface of electroactive material; and (iv) the porosity formed by lateral GNSs and Fe3O4 particles facilitates ion transportation. As a result, this unique laterally confined GNS/Fe3O4 composite can dramatically improve the cycling stability and the rate capability of Fe3O4 as an anode material for lithium ion batteries.
In this paper, we report the successful synthesis of amine-functionalized FDU-12-type mesoporous silica with a very large pore (30.2 nm) and a highly ordered mesostructure by using ...3-aminopropyltriethoxysilane (APTES) as an organosilane source. Small angle X-ray scattering (SAXS) and transmission electron microscopy (TEM) measurements confirmed that the materials possessed a face-centered cubic (space group Fm3̅m) mesostructure. Different techniques were used to obtain a significant pore and entrance size enlargement: low synthesis temperature and high hydrothermal treatment temperature. The amount of amine organosilane influenced the mesostructure of the mesoporous silica. It was found that the addition of inorganic salt (KCl) could help to maintain an ordered structure of the large pore mesoporous material. X-ray photoelectron spectroscopy (XPS), solid-state magic-angle spinning (MAS) 13C nuclear magnetic resonance (NMR) and thermogravimetric analysis (TGA) verified the incorporation of amine functional groups on the surface of the materials. The addition of amine organosilane extended the synthesis temperature domain of ordered FDU-12 materials. The amine functional group significantly enhanced the adsorption capacity of the mesoporous materials, e.g., the amine functionalized mesoporous silica had 8-fold higher bovine serum albumin (BSA) adsorption capacity than that of the unfunctionalized one. It also had 2 times higher adsorption capacity for large cellulase enzymes. The amine functional group introduced positively charged groups on the surface of the mesoporous silica, which created strong electrostatic interactions between the protein and the silica.
Monodispersed water‐soluble and biocompatible ultrasmall magnetic iron oxide nanoparticles (UMIONs, D = 3.3 ± 0.5 nm) generated from a high‐temperature coprecipitation route are successfully used as ...efficient positive and negative dual contrast agents of magnetic resonance imaging (MRI). Their longitudinal relaxivity at 4.7 T (r1 = 8.3 mM−1 s−1) is larger than that of clinically used T1‐positive agent Gd‐DTPA (r1 = 4.8 mM−1 s−1), and three times that of commercial contrast agent SHU‐555C (r1 = 2.9 mM−1 s−1). The transversal relaxivity (r2 = 35.1 mM−1 s−1) is six times that of Gd‐DTPA (r2 = 5.3 mM−1 s−1), half of SHU‐555C (r2 = 69 mM−1 s−1). The in vivo results show that the liver signal from T1‐weighted MRI is positively enhanced 26%, and then negatively decreased 20% after injection of the iron oxide nanoparticles, which is stronger than those obtained from Gd‐DTPA (<10%) using the same dosage. The kidney signal is positively enhanced up to 35%, similar to that obtained from Gd‐DTPA. Under T2‐weighted conditions, the liver signal is negatively enhanced ≅70%, which is significantly higher than that from Gd‐DTPA (≅6%). These results demonstrate the great potential of the UMIONs in dual contrast agents, especially as an alternative to Gd‐based positive contrast agents, which have risks of inducing side effects in patients.
Ultrasmall monodispersed magnetic iron oxide nanoparticles produced by a high‐temperature coprecipitation are successfully used as efficient dual contrast agents for magnetic resonance imaging (MRI). Both in vitro and in vivo results show their excellence as dual contrast agents, in particular as an alternative to Gd‐based positive agents, which have the risk of inducing side effects in patients.
Current investigations show that layered double hydroxide (LDH) nanoparticles have high potential as effective non-viral agents for cellular drug delivery due to their low cytotoxicity, good ...biocompatibility, high drug loading, control of particle size and shape, targeted delivery and drug release control. Two types of Mg
2Al–LDH nanoparticles with fluorescein isothiocyanate (FITC) were controllably prepared. One is morphologically featured as typical hexagonal sheets (50–150 nm laterally wide and 10–20 nm thick), while the other as typical rods (30–60 nm wide and 100–200 nm long). These LDH
FTIC nanoparticles are observed to immediately transfect into different mammalian cell lines. We found that internalized LDH
FITC nanorods are quickly translocated into the nucleus while internalized LDH
FITC nanosheets are retained in the cytoplasm. Inhibition experiments show that the cellular uptake is a clathrin-mediated time- and concentration-dependent endocytosis. Endosomal escape of LDH
FITC nanoparticles is suggested to occur through the deacidification of LDH nanoparticles. Since quick nuclear targeting of LDH
FITC nanorods requires an active process, and although the exact mechanism is yet to be fully understood, it probably involves an active transport via microtubule-mediated trafficking processes. Targeted addressing of two major subcellular compartments by simply controlling the particle morphology/size could find a number of applications in cellular biomedicine.
Constructing photocatalytically favorable surface structure in synthesizing photocatalysts plays an important role in enhancing the photocatalytic activity of semiconductor photocatalysts. In this ...report, oxygen-deficient anatase TiO2 sheets with dominant {001} facets were synthesized via a facile one-pot hydrothermal route with solid metallic titanium diboride as precursor. In contrast to anatase TiO2 sheets with dominant {001} facets free of oxygen deficiency and surface fluorine, anatase TiO2 sheets with oxygen deficiency and surface fluorine are subject to obvious surface reconstruction as evidenced by two new Raman-active modes at 155 and 171 cm−1 and the weakened B1g mode at 397 cm−1. Further analysis based on X-ray photoelectron spectroscopy (XPS) spectra of Pt 4f and F 1s provided a clear evidence for the greatly strengthened interaction between Pt-loaded and TiO2 matrix as a result of a special electron-transfer process on the reconstructed surface structure of TiO2 with both oxygen deficiency and fluorine. Importantly, the reconstructed surface structure as well as the strengthened interaction between Pt-loaded and TiO2 matrix can substantially enhance the hydrogen evolution rate from photocatalytic water splitting reactions.
Wiry frame: Manganese‐doped cadmium selenide (Mn‐CdSe) colloidal nanowires (see picture) exhibit ferromagnetism and good conductivity without any changed to their optical properties. The nanowires ...are synthesized by a novel solution–liquid–solid approach that offers a low‐cost route towards magnetically active quantum wires with excellent potential applications in electronics, photonics, and spintronics.
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