MOF nanosheet array-derived NiS with Co,N-doped carbon layer: A highly efficient oxygen evolution electrocatalyst

The development of the hydrogen industry from electrolytic water is confined in great measure to the slow kinetics of oxygen evolution reaction (OER), which means the rational design of a stabilized and efficient OER electrode is the key. The construction of easily accessible hydroxide ion (OH^?) adsorption sites can effectively accelerate the kinetics of the OER. Herein, the NiS/CoNC electrocatalysts, which can effectively adsorb OH^? and exhibited excellent OER performance in an alkaline environment, were obtained by pyrolysis and sulfidation of NiCo-MOF nanosheets on nickel foam (NF). In particular, the optimized NiS/CoNC electrocatalyst achieved an overpotential of 46/106 mV at 10/100 mA cm^?2 and Tafel slope of 57.41 mV dec^?1, which is superior to most reported materials. The outstanding function of OER results from the NiOOH/CoOOH active component generated by surface reconstruction after activation of the NiS/CoNC catalyst and the excellent charge transfer capability of the NiS component. This work offers a scheme to construct the electrocatalysts derived from MOF with excellent OER performance.     

Silicon nanowire arrays-induced graphene oxide reduction under UV irradiation

This paper reports on efficient UV irradiation-induced reduction of exfoliated graphene oxide. Direct illumination of an aqueous solution of graphene oxide at λ = 312 nm for 6 h resulted in the formation of graphene nanosheets dispersible in water. X-Ray photoelectron spectroscopy (XPS), UV-vis spectroscopy, atomic force microscopy (AFM) and electrochemical measurements (cyclic voltammetry and electrochemical impedance spectroscopy) suggest a restoration of the sp(2) carbon network. The results were compared with graphene nanosheets prepared by photochemical irradiation of a GO aqueous solution in the presence of hydrogenated silicon nanowire (SiNW) arrays or silicon nanowire arrays decorated with silver (SiNW/Ag NPs) or copper nanoparticles (SiNW/Cu NPs). Graphene nanosheets obtained by illumination of the GO aqueous solution at 312 nm for 6 h in the presence of SiNW/Cu NPs exhibited superior electrochemical charge transfer characteristics. This is mainly due to the higher amount of sp(2)-hybridized carbon in these graphene sheets found by XPS analysis. The high level of extended conjugated carbon network was also evident by the water insoluble nature of the resulting graphene nanosheets, which precipitated upon photochemical reduction.     

Highly stable and sub-3 nm Ni nanoparticles coated with carbon nanosheets as a highly active heterogeneous hydrogenation catalyst

An efficient catalyst of Ni/C hybrid nanosheets was prepared via a facile and simple procedure. The highly dispersed and sub-3 nm Ni nanoparticles (NPs) were coated with the carbon nanosheets which can prevent the aggregation and growth of the Ni NPs. The Ni/C hybrid nanosheets exhibited high activity for the catalytic reduction of 4-nitrophenol (4-NP), which was much higher than many noble metal NPs. Additionally, the magnetic Ni/C hybrid nanosheets showed good separation ability and reusability.     

Synthesis of highly dispersed phosphotungstic acid encapsulated in MIL-100(Fe) catalyst and its performance in heterogeneous oxidative desulfurization

Highly efficient HPW(x)/MIL-100(Fe) catalysts with different phosphotungstic acid (HPW) loading (x, wt%) were successfully synthesized by a one-step hydrothermal method and characterized by XRD, SEM, FTIR, and BET. The influences of HPW loading, catalyst dosage, temperature, and O/S molar ratio on oxidative desulfurization (ODS) were investigated. The results indicated that the HPW(x)/MIL-100(Fe) retained the structure of its parent MIL-100(Fe). The MIL-100(Fe) presented a high surface area, which is beneficial to dispersion of HPW. The HPW(x)/MIL-100(Fe) with HPW loading of 40% exhibited excellent ODS activity. At a temperature of 50?°C, a catalyst dosage of 0.06?g, and an O/S molar ratio of 4, 100% desulfurization was achieved within 90?min for benzothiophene, dibenzothiophene, and 4,6-dimethyl-dibenzothiophene. The high catalytic activity of HPW(x)/MIL-100(Fe) can be attributed to highly dispersed HPW active sites with a high specific surface area.     

超薄MOF纳米片前驱体高效电催化OER反应

金属-有机骨架材料作为前驱体制备特定形貌的纳米材料用于水氧化反应(OER)，成为新的研究热点。使用溶剂热法在泡沫镍基底上合成超薄的NiCoFe-MOF纳米片，在保留其纳米片形貌的基础上原位电化学转化为金属氢（羟基）氧化物。在1 M KOH电解液中，10 mA?cm-2电流密度时的过电位仅为189 mV，Tafel斜率为35 mV/dec，且长时间电解实验表明其具有较高稳定性。原位拉曼结果表明，反应的高活性来源于反应过程中的“活性氧物种”中间体。     

Heterostructure interface effect on the ORR/OER kinetics of Ag–PrBa0.5Sr0.5Co2O5+δ for high-efficiency Li–O2 battery

Developing high-efficiency and cost-effective bifunctional electrocatalysts toward the oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) is an urgent issue for the oxygen-based electrochemical devices. Herein, an interface engineering concept has been proposed to achieve high-performance Ag–PBSC (Ag–PrBa_0.5Sr_0.5Co₂O_5+δ) heterostructure nanofibers catalyst. Benefiting from the significant ligand action and interparticle cooperation of exsolved Ag NPs and PBSC double perovskite, ORR/OER catalytic kinetics have been successfully boosted. In details, the PBSC double perovskite possessing abundant oxygen vacancies can provide oxygen channels and facilitate the transfer of electrons and oxygen. The embedded Ag NPs can deliver superior catalytic durability for the heterostructure interface. As expected, the as-synthesized Ag-PBSC heterostructure catalyst performs a favorable electrochemical performance in the oxygen-based applications. In alkaline media, the catalyst exhibits an excellent activity for ORR (E_onset: 0.88 V vs. RHE and E_1/2: 0.72 V vs. RHE) and OER (1.67 V at 10 mA cm^–2). When adopting the Ag–PBSC heterostructure catalyst in LOBs, the corresponding battery provides an outperforming capacity performance (13 000 mAh g^–1), low discharge–charge polarization (1.37 V), and considerable cycling performance (128 cycles at the restricted capacity of 3 000 mAh g^–1 and 400 mA g^–1). Apparently, the work described here confirms that the interface engineering of perovskites can open up opportunities to develop highly active and durable heterostructure electrocatalysts for multitudinous oxygen-based electrochemical applications.     

The nonlinear optical properties of silver nanoparticles decorated glass obtained from sintering mesoporous powders

Silver nanoparticles (Ag NPs) have excellent third-order nonlinear optical properties but it is still difficult to obtain silica glass containing Ag NPs with homogenous dispersion and small particle size. Herein, silica glass with homogenously distributed Ag NPs in its matrix was derived from sintering a famous type of mesoporous silica (FDU-12) encapsulated with Ag NPs (Ag NPs/FDU-12) through Spark Plasma Sintering (SPS) technique. Benefited from the low-temperature sintering property of the Ag NPs/FDU-12 powders (~930°C within 5 min), the Ag NPs can be directly trapped in the derived silica glass with small particle size (<3.0 nm) and without mass loss. The as-prepared Ag NPs/glass showed a typical reverse saturable absorption curve, which is measured via the Z-scan method by using a 532 nm nanosecond laser. The nonlinear coefficient and imaginary third-order susceptibility were calculated as 11.46 cm/GW and 2.22 × 10⁻¹² esu, respectively, indicating the excellent third-order nonlinear optical properties of the Ag NPs/glass. This study demonstrates a great potential for preparing silica glasses functionalized with well dispersed ultrafine functional particles, which is appealing in photonic field.     

Enhanced through-plane thermal conductive properties of Ag/rGO nanocomposite

High thermal conductivity of nanocomposite-based polymer matrix is one of the most important keys in developing many heat exchanger instruments. Here, we report a novel nanocomposite system based on silver-coated reduced graphene oxide (Ag/rGO) in silane cross-linked low-density polyethylene (XLPE) matrix with unprecedented through-plane thermal conductivity. Compared to the virgin rGO, Ag/rGO nanocomposite showed 67% higher thermal conductivity due to the Ag nanoparticles (NPs) decoration. The Ag NPs within the nanocomposites are believed to act as a thermal conductor among rGO nanosheets and eventually enhance the heat conduction in 3D manner.     

螺线型碳纳米纤维基整体式催化剂活性载体

本工作采用一种简便的一步化学气相沉积(chemical vapor deposition, CVD)法，在泡沫镍基底上直接生长螺线形碳纳米纤维（CNFs/NF）作为对析氧反应有活性的整体式催化剂载体。在1 mol/L KOH为电解质溶液的三电极电解池中，与 CNFs/NF电极材料电化学表面积(ECSA)成正比的的双层电容Cdl值达到13.69 mF/cm2。通过循环伏安法，电化学阻抗谱和线性扫描伏安曲线等电化学手段，验证了CNFs/NF适于做具有析氧反应活性的催化剂载体。CNFs/NF需要260 mV，385 mV的析氧反应过电势以实现10 mA/cm2和100 mA/cm2的电流密度。     

螺线型碳纳米纤维基整体式催化剂活性载体

本工作采用一种简便的一步化学气相沉积(chemical vapor deposition, CVD)法，在泡沫镍基底上直接生长螺线形碳纳米纤维（CNFs/NF）作为对析氧反应有活性的整体式催化剂载体。在1 mol/L KOH为电解质溶液的三电极电解池中，与 CNFs/NF电极材料电化学表面积(ECSA)成正比的的双层电容Cdl值达到13.69 mF/cm2。通过循环伏安法，电化学阻抗谱和线性扫描伏安曲线等电化学手段，验证了CNFs/NF适于做具有析氧反应活性的催化剂载体。CNFs/NF需要260 mV，385 mV的析氧反应过电势以实现10 mA/cm2和100 mA/cm2的电流密度。     

MIL-100(Fe) Sub-Micrometric Capsules as a Dual Drug Delivery System

Nanoparticles of metal–organic frameworks (MOF NPs) are crystalline hybrid micro- or mesoporous nanomaterials that show great promise in biomedicine due to their significant drug loading ability and controlled release. Herein, we develop porous capsules from aggregate of nanoparticles of the iron carboxylate MIL-100(Fe) through a low-temperature spray-drying route. This enables the concomitant one-pot encapsulation of high loading of an antitumor drug, methotrexate, within the pores of the MOF NPs, and the collagenase enzyme (COL), inside the inter-particular mesoporous cavities, upon the formation of the capsule, enhancing tumor treatment. This association provides better control of the release of the active moieties, MTX and collagenase, in simulated body fluid conditions in comparison with the bare MOF NPs. In addition, the loaded MIL-100 capsules present, against the A-375 cancer cell line, selective toxicity nine times higher than for the normal HaCaT cells, suggesting that MTX@COL@MIL-100 capsules may have potential application in the selective treatment of cancer cells. We highlight that an appropriate level of collagenase activity remained after encapsulation using the spray dryer equipment. Therefore, this work describes a novel application of MOF-based capsules as a dual drug delivery system for cancer treatment.     

Hydrothermal synthesis of α-MnO2/MIL-101(Cr) composite and its bifunctional electrocatalytic activity for oxygen reduction/evolution reactions

An α-MnO₂/MIL-101(Cr) composite catalyst was synthesised using a hydrothermal process. In this composite, α-MnO₂ nanoparticles are embedded in an MIL-101(Cr) matrix with abundant micropores and a high specific surface area, which improves the reactant's accessibility to catalytically active sites, resulting in a significant improvement in oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) in an alkaline electrolyte. The strong interactions between α-MnO₂ nanoparticles and MIL-101(Cr) matrix result in a high structural stability and therefore excellent activity stability.     

Improvements on electrical conductivity of the electrospun microfibers using the silver nanoparticles

Conductive electrospun polymer fibers have attracted a great deal of interest in recent years. This study describes the preparation of electrically conductive microfibers composed of polyethersulfone/polydopamine/silver nanoparticles (PES/PDA/Ag NPs). Ag NPs acted as conductive centers, while hydroxyl- and amino-rich functional groups and excellent adhesion properties of PDA served to connect the Ag NPs and PES microfibers. Fourier transform infrared spectroscopy and scanning electron microscopy (SEM) showed that PDA was firmly adhered to PES microfibers. PES/PDA microfibers absorbed considerable amounts of silver ion from AgNO₃ solution, resulting in Ag NPs. X-ray diffraction, X-ray photoelectron spectroscopy, and SEM data represented the successful formation of PES/PDA/Ag NPs microfibers. Microfibers with optimal conductivity were obtained using a solution of 2% AgNO₃ at pH 9 at 50 °C for 45 min. The electrical resistivity of our PES/PDA/Ag NPs microfibers was only 202 Ω/cm, much lower than that of regular PES microfibers (2.1 × 10⁹ Ω/cm). These results show that the PES/PDA/Ag NPs microfibers are suitable for use as conductive polymer fibers in electromagnetic shielding, and conductivity-sensing applications, and in flexible electronic devices and biosensors. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2020 , 137, 48788.     

Preparation and Characterization of Gelatin Nanofibers Containing Silver Nanoparticles

Ag nanoparticles (NPs) were synthesized in formic acid aqueous solutions through chemical reduction. Formic acid was used for a reducing agent of Ag precursor and solvent of gelatin. Silver acetate, silver tetrafluoroborate, silver nitrate, and silver phosphate were used as Ag precursors. Ag⁺ ions were reduced into Ag NPs by formic acid. The formation of Ag NPs was characterized by a UV-Vis spectrophotometer. Ag NPs were quickly generated within a few minutes in silver nitrate (AgNO₃)/formic acid solution. As the water content of formic acid aqueous solution increased, more Ag NPs were generated, at a higher rate and with greater size. When gelatin was added to the AgNO₃/formic acid solution, the Ag NPs were stabilized, resulting in smaller particles. Moreover, gelatin limits further aggregation of Ag NPs, which were effectively dispersed in solution. The amount of Ag NPs formed increased with increasing concentration of AgNO₃ and aging time. Gelatin nanofibers containing Ag NPs were fabricated by electrospinning. The average diameters of gelatin nanofibers were 166.52 ± 32.72 nm, but these decreased with the addition of AgNO₃. The average diameters of the Ag NPs in gelatin nanofibers ranged between 13 and 25 nm, which was confirmed by transmission electron microscopy (TEM).     

Noble-metal-free cobalt hydroxide nanosheets for efficient electrocatalytic oxidation

Cobalt hydroxide has been emerging as a promising catalyst for the electrocatalytic oxidation reactions, including the oxygen evolution reaction (OER) and glucose oxidation reaction (GOR). Herein, we prepared cobalt hydroxide nanoparticles (CoHP) and cobalt hydroxide nanosheets (CoHS) on nickel foam. In the electrocatalytic OER, CoHS shows an overpotential of 306 mV at a current density of 10 mA·cm^–2. This is enhanced as compared with that of CoHP (367 mV at 10 mA·cm^–2). In addition, CoHS also exhibits an improved performance in the electrocatalytic GOR. The improved electrocatalytic performance of CoHS could be due to the higher ability of the two-dimensional nanosheets on CoHS in electron transfer. These results are useful for fabricating efficient catalysts for electrocatalytic oxidation reactions.     

Ultrathin graphitic carbon nitride nanosheets and graphene composite material as high-performance PtRu catalyst support for methanol electro-oxidation

Graphitic carbon nitride (g-C₃N₄) has been demonstrated as an advanced support material for Pt nanoparticles (NPs) due to its excellent stability and abundant Lewis acid for anchoring metal NPs. However, its non-conductive nature and low surface areas still impede its application in electrochemical fields. Herein, a π–π stacking method is presented to prepare graphene/ultrathin g-C₃N₄ nanosheets composite support for PtRu catalyst. The weaknesses of g-C₃N₄ are greatly overcome by establishing a 2D layered structure. The significantly enhanced performance for this novel PtRu catalyst is ascribed to reasons as follows: the homogeneous dispersion of PtRu NPs on g-C₃N₄ nanosheets due to its abundant Lewis acid sites for anchoring PtRu NPs; the excellent mechanical resistance and stability of g-C₃N₄ nanosheets in acidic and oxidative environments; the increased electron conductivity of support by forming a layered structure and the strong metal-support interaction (SMSI) between metal NPs and g-C₃N₄ NS.     

Facile solid-state synthesis of Ag/graphene oxide nanocomposites as highly active and stable catalyst for the reduction of 4-nitrophenol

A facile solid-state synthetic route was used to fabricate graphene oxide (GO) decorated with Ag nanoparticles. Ag/GO nanocomposites were prepared by reducing silver acetate with ascorbic acid in the presence of GO at ambient conditions. The characterization results showed that Ag nanoparticles with an average diameter of ~ 50 nm were well dispersed on the surface of GO nanosheets. Moreover, an application of the obtained Ag/GO nanocomposites as a catalyst in the reduction of 4-nitrophenol (4-NP) to 4-aminophenol by NaBH₄ was demonstrated. The Ag/GO nanocomposites exhibited high activity and stability for the catalytic reduction of 4-NP.     

In vitro anticancer activity and comparative green synthesis of ZnO/Ag nanoparticles by moringa oleifera,mentha piperita,and citrus lemon

This study proposes a simple, effective, and environmentally friendly approach for the synthesis of zinc oxide/silver nanoparticles (ZnO/Ag NPs) using three different plant extracts. The plants used in this study were moringa oleifera (MO), mentha piperita (MP), and citrus lemon (CL). Characterizations of ZnO/Ag NPs were done using ultraviolet–visible spectroscopy (UV vis), X-ray diffraction (XRD), field emission scanning electron microscope (FESEM) along with energy dispersive spectroscopy (EDX), and fourier transform infrared spectroscopy (FTIR). In accordance with size distribution findings, ZnO/Ag NPs synthesized with MO have a narrow size distribution, with the average particle size being 119 ± 36 nm. Among these three reducing agent MO act as the best reducing agent. Moreover, the anticancer activity of silver nanoparticles (Ag NPs), zinc oxide nanoparticles (ZnO NPs) and ZnO/Ag NPs synthesized with MO were demonstrated in human cervical cancer cells (HeLA). The results revealed that ZnO/Ag NPs demonstrate in vitro cell viability of 72%, 81%, and 84% using 2.5, 5, and 10 μgml^?1of ZnO/Ag NPs for 24 h. While Ag NPs and ZnO NPs prepared with MO showed 50% and 60% cell viability using 2.5 μgml^?1concentration for 24 h. This showed that the ZnO/Ag NPs act as a strong anticancer agent compared to Ag NPs and ZnO NPs. Overall, this research proposes a green synthesis approach for ZnO/Ag NPs with a wide range of potential uses, particularly in biomedicine.     

The effect of Ag nanoparticles content on dielectric and microwave absorption properties of β-SiC

In the present work, high purity cubic silicon carbide (β-SiC) was synthesized by using resorcinol-formaldehyde aerogel coated silica as precursor at high temperature. Subsequently, β-SiC was coated with various concentrations of silver nanoparticles (Ag NPs) by tin sensitization electroless plating. Thereafter, the effect of various Ag NPs contents on the dielectric and microwave absorption properties of β-SiC was investigated in detailed. It is found that the Ag NPs can significantly increase the overall complex permittivity, reduce the thickness of the absorber and increase the absorption bandwidth to some extent. Despite, the improvement of the attenuation ability of electromagnetic wave with increasing contents of Ag NPs also has an adverse effect on impedance matching. The improvement in the microwave absorption of β-SiC coated with Ag NPs mainly comes from the enhancement of dipole polarization, interface polarization and conductivity loss. In the 2–18 GHz band, Ag@SiC (1.0 g/L) can achieve an effective bandwidth of 4.99 GHz at a thickness of 1.6 mm, and it is a kind of lightweight, high-temperature microwave absorbent with excellent performance.     

Ionic-liquid-assisted facile synthesis of silver nanoparticle-reduced graphene oxide hybrids by gamma irradiation

A simple and environmentally friendly approach for the preparation of graphene nanosheets decorated with silver nanoparticles (Ag NPs) has been developed by gamma irradiation at room temperature. Graphene oxide (GO) and silver ions are simultaneously reduced by the electrons generated from the radiolysis of solvent. The addition of ionic liquid plays an important role in GO reduction by scavenging oxidative radicals generated during irradiation. Besides, the ionic liquid also benefits the dispersion and size distribution of Ag NPs. Raman signals of the obtained Ag-reduced graphene oxide are significantly enhanced, exhibiting obvious surface-enhanced Raman scattering activity.