Silver-enhanced fluorescence of bimetallic Au/Ag nanoclusters as ultrasensitive sensing probe for the detection of folic acid.

Folic acid (FA) is the natural form of water-soluble vitamins widely found in most plants and animal products and its deficiency leads to several human body abnormalities. The advancements of metal nanoclusters are highly increasing due to their molecule-like optical properties and attractive applications. Because of increasingly demand of noble metal nanoclusters as sensing templates, different synthesis methods have been developed for facile synthesis of noble metal nanoclusters. Herein, red-emitting fluorescent bovine serum albumin (BSA)-capped Au-Ag bimetallic NCs are facilely synthesized through green one-pot synthetic approach. The effect of silver on the fluorescence properties of Au NCs was investigated and it was found that introduction of silver can enhance the fluorescence intensity. The fluorescence intensity of the as-prepared Au-Ag nanoclusters gets quenched in the presence of folic acid in an aqueous medium and it was used as ultrasensitive sensing probe for FA detection. The developed Au-Ag NCs-based sensing probe shows linear response in the wide range of 0-100 µM and the detection limit is as low as 0.47 nM. Its applicability has also been confirmed successfully in real human serum, urine and FA tablet samples. Due to the high stability, sensitivity and selectivity, the developed bimetallic cluster sensing system is highly promising to be applied in the pharmaceutical and clinical laboratories.

Energetic-Materials-Driven Synthesis of Graphene-Encapsulated Tin Oxide Nanoparticles for Sodium-Ion Batteries.

By evenly mixing polytetrafluoroethylene-silicon energetic materials (PTFE-Si EMs) with tin oxide (SnO2) particles, we demonstrate a direct synthesis of graphene-encapsulated SnO2 (Gr-SnO2) nanoparticles through the self-propagated exothermic reaction of the EMs. The highly exothermic reaction of the PTFE-Si EMs released a huge amount of heat that induced an instantaneous temperature rise at the reaction zone, and the rapid expansion of the gaseous SiF4 product provided a high-speed gas flow for dispersing the molten particles into finer nanoscale particles. Furthermore, the reaction of the PTFE-NPs with Si resulted in a simultaneous synthesis of graphene that encapsulated the SnO2 nanoparticles in order to form the core-shell nanostructure. As sodium storage material, the graphene-encapsulated SnO2 nanoparticles exhibit a good cycling performance, superior rate capability, and a high initial Coulombic efficiency of 85.3%. This proves the effectiveness of our approach for the scalable synthesis of core-shell-structured graphene-encapsulated nanomaterials.

Pd-Doping-Induced Oxygen Vacancies in One-Dimensional Tungsten Oxide Nanowires for Enhanced Acetone Gas Sensing.

Metal oxide semiconductors (MOS) with different nanostructures have been widely used as gas sensing materials due to the tunable interface structures and properties. However, further improvement of the sensing sensitivity and selectivity is still challenging in this area. Constructing appropriate heterogeneous interface structures and oxygen vacancies is one of the important strategies to tune the sensing properties of MOS. In the present study, interfacial heterostructures in PdxW18O49 nanowires (PdxW18O49 NWs) were fabricated and manipulated by doping different Pd contents through a simple hydrothermal process. Relevant characterization proved that the structure and composition of the one-dimensional (1D) nanomaterial can be effectively changed by Pd doping. It was found that the oxygen vacancy concentration increases first with the increase of Pd content, and when the Pd content increases to 7.18% (Pd7.18%W18O49 NWs), the oxygen vacancy content reaches the maximum (52.5%). If the Pd content continues to increase, the oxygen vacancy ratio decreases. The gas sensing investigations illustrated that the PdxW18O49 NWs exhibited enhanced sensing properties than pure W18O49 NWs toward acetone. Among the as-prepared catalysts, the Pd7.18%W18O49 NWs showed the best sensing response and the fastest response-recovery speeds (5 and 10 s, respectively) at a working temperature of 175 °C. In addition, this 1D nanostructure with fabricated heterostructures also delivers a good sensing selectivity and a wide detection range from 100 ppb to 300 ppm, with maintaining excellent performance in the presence of high concentrations of ethanol and carbon dioxide. The excellent gas sensing behavior could be attributed to the generated oxygen vacancies and the heterostructures upon Pd doping. This study offers a novel strategy for the design of high-performance gas sensors for ppb-level acetone sensing.

Interfacial heterojunction construction by introducing Pd into W18O49 nanowires to promote the visible light-driven photocatalytic degradation of environmental organic pollutants.

Photocatalytic degradation of organic dyes by sunlight can greatly simplify the catalytic devices and save the cost. The development of photocatalysts for organic pollutants degradation driven by sunlight at room temperature still faces serious challenges. In this work, we developed a novel Pd-W18O49 nanowire photocatalyst for high efficiency, high stability, and sunlight-induced degradation of methylene blue and neutral red. It was found that after Pd introducing, the band gap energy of W18O49 nanowires lowers from 2.77 to 2.44 eV, which can accelerate the electron jump from the valence band to the conduction band, resulting in the efficient separation of electrons and holes. Meanwhile, with Pd introducing to the W18O49 nanowires, interfacial heterojunction with the Schottky barrier is formed, which can reduce the rate of electron-hole recombination. The catalytic results show that the obtained Pd-W18O49 nanowires demonstrate enhanced photodegradation capacity in comparison with W18O49 nanowires. Especially, with Pd-W18O49 nanowires (10 mg) as photocatalyst, 98.4% of methylene blue and 96.1% of neutral red can be decomposed within 40 min under sunlight irradiation. Besides, the photocatalytic degradation pathways of methylene blue and neutral red on the Pd-W18O49 nanowires are also proposed. This study provides a good strategy for the design and preparation of highly efficient 1D heterojunction-based photocatalysts for the degradation of environmental organic pollutants.

Insights into the Mo-Doping Effect on the Electrocatalytic Performance of Hierarchical CoxMoyS Nanosheet Arrays for Hydrogen Generation and Urea Oxidation.

Energy-efficient, low-cost, and highly durable catalysts for the electrochemical hydrogen evolution reaction (HER) and urea oxidation reaction (UOR) are extremely important for related sustainable energy systems. In the present work, hierarchical coassembled cobalt molybdenum sulfide nanosheets deposited on carbon cloth (CC) were synthesized as catalysts for hydrogen evolution and urea oxidation. By adjusting the doping amount of Mo, 2D nanosheets with different morphologies and compositions (CoxMoyS-CC) can be obtained. The as-prepared nanosheet materials with abundant active sites exhibit superior properties on the electrochemical HER and UOR in alkaline medium. Significantly, the Mo-doping concentration and composition of the formed nanosheets have large effects on the electrocatalytic activity. The fabricated nanosheets with optimal Mo doping (Co3Mo1S-CC) illustrate the best catalytic properties for the HER in N2-saturated 1.0 M KOH. A small overpotential (85 mV) is needed to meet the current density of 10 mA/cm2. This study indicates that the doping of an appropriate amount of molybdenum into CoS2 nanosheets can efficiently improve the catalytic performance. Also, the nanosheet catalyst exhibits an extremely high electrocatalytic activity for the UOR, and the electrochemical results indicate that a relatively low cell voltage of 1.50 V is needed to obtain the current density of 10 mA/cm2. The present work demonstrates the potential application of CoMoS nanosheets in the energy electrocatalysis area and the insights into performance-boosting through heteroatom doping and optimization of the composition and structure.

Insights into the morphology and composition effects of one-dimensional CuPt nanostructures on the electrocatalytic activities and methanol oxidation mechanism by in situ FTIR.

Morphology modulation and surface structure-controlled synthesis are two effective ways to tune the electrocatalytic activities of metal nanomaterials. Pt-based binary or ternary metal nanostructures have become a class of promising catalysts toward the oxygen reduction reaction (ORR) and the methanol oxidation reaction (MOR) for direct methanol fuel cells. Herein to reveal the morphology and surface structure effects of one-dimensional (1D) Pt-based nanostructures on their electrocatalytic properties, two types of 1D CuPt nanowires (CuPt NWs) and CuPt nanotubes (CuPt NTs) with tunable surface structures and compositions were fabricated using a convenient and easy strategy. It was found that among all the studied samples, CuPt2.22 NWs exhibited the highest efficiency catalytic performances for both the ORR and MOR in an acidic electrolyte. For the ORR, CuPt2.22 NWs exhibited an onset potential (Eonset) of 0.749 V and a half-wave potential (E1/2) of 0.577 V, which are more positive than those of the commercial Pt/C (0.668 V and 0.558 V). On the other hand, CuPt2.22 NWs show a specific activity of 20.76 mA cm-2 and a mass activity of 0.171 mA µgPt-1 for the MOR, which are 7.75 and 1.82 times, respectively, larger than those of Pt/C (2.679 mA cm-2 and 0.094 mA µgPt-1). Meanwhile, the reaction mechanism of the MOR on CuPt2.22 NWs was examined by in situ FTIR. From the enhanced IR absorption, the linear- and bridge-adsorbed CO intermediates can be determined during the methanol oxidation on CuPt2.22 NWs, from which the MOR proceeds through a dual reaction pathway. This work reveals that rationally tuning the electronic structures of 1D metal nanomaterials by well-controlling the composition and surface morphology on the nanoscale could greatly enhance the catalytic properties, which are very important for their application in fuel cells.

One-step rapid synthesis of Ni6(C12H25S)12 nanoclusters for electrochemical sensing of ascorbic acid.

Metal nanoclusters (NCs) are highly desirable as active catalysts due to their highly active surface atoms. Among the reported metal clusters, nickel nanoclusters (Ni NCs) have been less well developed than others, such as gold, silver and copper. Herein a simple method is developed to synthesize atomically precise Ni clusters with the molecular formular of Ni6(C12H25S)12. Moreover, the single crystal of the Ni6(C12H25S)12 cluster is also obtained. The composition, morphology and optical properties of the prepared Ni6 clusters are characterized by X-ray crystallography, XPS, XRD, SEM, HRTEM, FTIR and UV-Vis spectroscopy. The Ni cluster is composed of six nickel atoms that form a hexagonal ring with an exterior 1-dodecanethiol shell, resembling a double crown. Meanwhile, the Ni6 NCs can be self-assembled into nanosheets due to their uniform size. It was found that the Ni6(C12H25S)12 clusters loaded on carbon black exhibit higher electrocatalytic activity than Ni nanoparticles towards ascorbic acid (AA) oxidation. The Ni6 clusters show high sensing performance for AA with a wide linear range (1-3212 µM) and a low detection limit of 0.1 µM (S/N = 3). The significantly enhanced catalytic activity can be ascribed to the high fraction of surface Ni atoms with low coordination in the sub-nanometer clusters. The present work not only provides a straightforward method for synthesizing atomically precise metal clusters but also indicates that ultrasmall Ni clusters can be used as highly efficient catalysts for the electrochemical detection of AA.

Fe/Ni bimetal organic framework as efficient oxygen evolution catalyst with low overpotential.

Electrochemical water-splitting is an ideal strategy to produce the promising substitutable energy source, hydrogen (H2). However, the sluggish kinetics of electrochemical oxygen evolution reaction (OER) and the prohibitive cost, low reserves and easy oxidation of noble metal-based electrocatalysts force researchers to explore efficient and low-cost electrocatalysts. Bimetal nanostructred materials are proved to have enhanced OER catalytic performances. In this study, a series of bimetallic metal-organic frameworks (Fe/Ni-MOFs) are prepared by a solvothermal method. The prepared MOFs present abundant unsaturated metal active sites for OER. The optimized Fe/Ni bimetal-MOF has low overpotentials of 236 mV at 10 mA cm-2 and 284 mV at 100 mA cm-2 for OER. In addition, in comparison with most of the previously reported OER electrocatalysts, the present MOF shows a lower Tafel slope of 49 mV dec-1. Besides, the MOF catalyst exhibits high electrochemical stability and the OER activity shows a negligible change after stability test for 15 h and 10,000 voltammetric cycles. Meanwhile, the Fe-doped Ni-MOFs show faster catalytic kinetics and higher conductivity than the monometallic Ni-MOF. This work paves a way to exploit bi- or multi-metallic MOFs with high conductivities and electrocatalytic performances for electrochemical energy conversion.

Balancing the Micro-Mesoporosity for Activity Maximization of N-Doped Carbonaceous Electrocatalysts for the Oxygen Reduction Reaction.

Carbonaceous porous structures have instigated global research interest as promising low-cost electrocatalysts for numerous energy technologies. However, the rational design principle of pore structures for activity maximization is still unclear. In this work, a series of N-doped carbon (N-C) catalysts with exclusively different micro-mesoporosity are investigated for the oxygen reduction reaction (ORR). By combining the experiment results and a pioneering mathematical model, it was observed that the best catalytic activity can only be attained by balancing the micro-mesoporosity. These findings offer a definite criterion for pore structure optimization in carbon-based ORR catalysts, which is of great importance for various energy technologies.

Ultra-low loading of Pd5 nanoclusters on carbon nanotubes as bifunctional electrocatalysts for the oxygen reduction reaction and the ethanol oxidation reaction.

How to reduce the usage of precious metals in electrocatalysts is a big challenge for the development of fuel cells. Metal nanoclusters (NCs) are highly desirable as active catalysts, but palladium nanoclusters (Pd NCs) have been less well developed than other metal clusters, such as gold, silver and copper, owing partly to the difficulties in size-controlled synthesis. Here, based on N, N-dimethylformamide (DMF)-mediation and ligand-exchange reaction, atomically precise Pd5(C12H25S)13 nanoclusters are successfully synthesized. By loading the as-prepared Pd5 nanoclusters on multiwalled carbon nanotubes (MWCNTs) and the following pyrolysis to remove the thiolate ligands, the surface-cleaned Pd5 clusters (Pd5 NCs/MWCNTs) can serve as efficient electrocatalysts for the oxygen reduction reaction (ORR) and the ethanol oxidation reaction (EOR). With ultra-low mass loading of Pd (2%), the Pd5 NCs showed higher mass and specific activities and better durability than the commercial Pd/C catalyst (5 wt%) for the ORR. At 0.8 V, the mass and specific activities of Pd5 NCs/MWCNTs are 5.70 and 4.53 times higher than the commercial Pd/C catalyst, respectively. As for the EOR, the Pd5 NCs/MWCNTs exhibited lower onset potential (0.39 V) and peak potential (0.81 V) than the commercial Pd/C catalyst (0.44 and 0.89 V). Electrochemical impedance spectroscopy (EIS) measurements indicated that for the EOR, the Pd5 nanoclusters have a much smaller charge transfer resistance (Rct) than the commercial Pd/C. The high-performance electrocatalytic properties of Pd5 NCs for the ORR and EOR could be ascribed to the relatively high surface area-to-volume ratio and high density of exposed surface atoms of the Pd5 nanoclusters.

3D Network and 2D Paper of Reduced Graphene Oxide/Cu2O Composite for Electrochemical Sensing of Hydrogen Peroxide.

In this study, two-dimensional (2D) and three-dimensional (3D) freestanding reduced graphene oxide-supported Cu2O composites (Cu2O-rGO) were synthesized via simple and cost-efficient hydrothermal and filtration strategies. The structural characterizations clearly showed that highly porous 3D graphene aerogel-supported Cu2O microcrystals (3D Cu2O-GA) have been successfully synthesized, and the Cu2O microcrystals are uniformly assembled in the 3D GA. Meanwhile, paper-like 2D reduced graphene oxide-supported Cu2O nanocrystals (2D Cu2O-rGO-P) have also been prepared by a filtration process. It was found that the products prepared from different precursors and methods exhibited different sensing performances for H2O2 detection. The electrochemical measurements demonstrated that the 3D Cu2O-GA has high electrocatalytic activity for the H2O2 reduction and excellent sensing performance for the electrochemical detection of H2O2 with a detection limit of 0.37 µM and a linear detection range from 1.0 µM to 1.47 mM. Meanwhile, the 2D Cu2O-rGO-P structure also showed good electrochemical sensing performance toward H2O2 detection with a much wider linear response over the concentration range from 5.0 µM to 10.56 mM. Compared to the previously reported sensing materials, the as-obtained 2D and 3D Cu2O-rGO materials exhibited higher electrochemical sensing properties toward the detection of H2O2 with high sensitivity and selectivity. The 2D and 3D Cu2O-rGO composites also exhibited high sensing performance for the real-time detection of H2O2 in human serum. The present study indicates that 2D and 3D graphene-Cu2O composites have promising applications in the fabrication of nonenzymatic electrochemical sensing devices.

Nasal administration of a novel recombinant human parathyroid hormone (1-34) analog for the treatment of osteoporosis of ovariectomized rats.

Synthetic human parathyroid (1-34) (hPTH (1-34)) is known to have the full biological activity of the holohormone for osteoporosis. This study is about designing a novel analog of hPTH (1-34) which is more suitable for intranasal administration. We likewise evaluate effectiveness of the nasal drops against osteoroporosis. Through fusion expression of combining gene, cell disruption, inclusion body washing, ethanol fraction precipitation, acid hydrolysis, and CM-52 ion exchange column chromatography Pro-Pro-[Arg¹¹] hPTH (1-34)-Pro-Pro was designed and produced. Nasal drops of Pro-Pro-[Arg¹¹] hPTH (1-34)-Pro-Pro were prepared and administrated to ovariectomized rats. After 12 weeks of raising, Bone Material Densities (BMD) of vertebrae were examined by Dual Energy X-Ray Absorptiometry (DEXA). The average BMD of these groups treated with nasal drops of the peptide were 28.0%-47.2% (P<0.01) higher than that of the group treated with normal saline (NS). The subchondral bone plates of the femoral heads were examined by scanning electron microscopy and a defined planar section was photographed. Percentage of the area of the cancellous bone was calculated. Percentages of the groups treated with nasal drops of the peptide increased; values were significantly different to that of the group treated with NS (P<0.001) and were even equivalent to that of normal groups. These results show that nasal drops of Pro-Pro-[Arg¹¹] hPTH (1-34)-Pro-Pro are effective against osteoporosis.