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1.
Novel visible-light-driven Ag3PO4@C3N4PO4 loaded with metal Ag were synthesised via an anion-exchange precipitation method and regenerated by H2O2 and NaNH3HPO4. The obtained Ag/Ag3PO4@C3N4 and regenerated Ag/Ag3PO4@C3N4 were characterised by XRD, XPS, SEM and UV–vis. The XRD and UV–vis results revealed that the crystal structure and light adsorption property of Ag/Ag3PO4@C3N4 were similar to that of regenerated Ag/Ag3PO4@C3N4. The XPS result showed that the metallic Ag0 deposited on the surface of Ag/Ag3PO4@C3N4 and regenerated Ag/Ag3PO4@C3N4. The Ag/Ag3PO4@C3N4 hybrids displayed remarkable photocatalytic activity and stability after regeneration. Compared with pure Ag3PO4 or C3N4, the Ag/Ag3PO4@C3N4 and regenerated Ag/Ag3PO4@C3N4 enhancement in the photodegradation rate towards methyl orange is observed over under visible light irradiation. The enhanced photocatalytic performance was attributed to the synergistic effect between Ag3PO4 and C3N4 and a small amount of Ag0 which suppresses the charge recombination during photocatalytic process. This work could provide new insights into the fabrication of high stability visible photocatalysts and facilitate their practical application in environment issues.  相似文献   

2.
Temperature sensing in biological media (cells, tissues, and living organisms) has become essential in the development of the last generation of diagnostics and therapeutic strategies. Thermometry can be used for early detection of different diseases, such as cancer, stroke, or inflammation processes, one of whose incipient symptoms is the appearance of localized temperature singularities. Luminescence nanothermometry, as a tool to accurately provide temperature sensing in biological media, requires the rational design and development of nanothermometers operating in the second biological window. In this work, this is achieved using Ag/Ag2S nanocrystals as multiparametric thermal sensing probes. Temperature sensing with remarkably high sensitivity (4% °C?1) is possible through intensity‐based measurements, as their infrared emission is strongly quenched by small temperature variations within the biological range (15–50 °C). Heating also results in a remarkable redshift of the emission band, which allows for concentration‐independent temperature sensing based on infrared ratiometric measurements, with thermal sensitivity close to 2% °C?1. These results make Ag/Ag2S nanocrystals the most sensitive among all noncomposite nanothermometers operating in the second biological window reported so far, allowing for deep‐tissue temperature measurements with low uncertainty (0.2 °C).  相似文献   

3.
Mesostructured silica nanofibers synthesized in high yields with cetyltrimethylammonium bromide as the structure‐directing agent in HBr solutions are used as templates for the assembly of Au and Ag nanoparticles and the formation of thin Au shells along the fiber axis. Presynthesized spherical Au and Ag nanoparticles are adsorbed in varying amounts onto the silica nanofibers through bifunctional linking molecules. Nonspherical Au nanoparticles with sharp tips are synthesized on the nanofibers through a seed‐mediated growth approach. The number density of nonspherical Au nanoparticles is controlled by varying the amount of seeded nanofibers relative to the amount of supplied Au precursor. This seed‐mediated growth is further used to form continuous Au shells around the silica nanofibers. Both the Au‐ and Ag‐nanoparticle/silica‐nanofiber hybrid nanostructures and silica/Au core/shell fibers exhibit extinction spectra that are distinct from the spectra of Au and Ag nanoparticles in solution, indicating the presence of new surface plasmon resonance modes in the silica/Au core/shell fibers and surface plasmon coupling between closely spaced metal nanoparticles assembled on silica nanofibers. Spherical Au‐ and Ag‐nanoparticle/silica‐nanofiber hybrid nanostructures are further used as substrates for surface‐enhanced Raman spectroscopy, and the enhancement factors of the Raman signals obtained on the Ag‐nanoparticle/silica‐nanofiber hybrid nanostructures are 2 × 105 for 4‐mercaptobenzoic acid and 4‐mercaptophenol and 7 × 107 for rhodamine B isothiocyanate. These hybrid nanostructures are therefore potentially useful for ultrasensitive chemical and biological sensing by using molecular vibrational signatures.  相似文献   

4.
Single‐crystalline Ag2Se nanowires have been successfully synthesized through a template‐engaged topotactic reaction in which nanowires of trigonal selenium were transformed into Ag2Se by reacting with aqueous AgNO3 solutions at room temperature (RT). An interesting size‐dependent transition between two crystal structures has also been observed for this newly synthesized one‐dimensional system: The Ag2Se nanowires adopted a tetragonal structure when their diameters were less than ∼40 nm; an orthorhombic structure was found to be more favorable as the diameter of these nanowires was increased beyond 40 nm. Since this reaction can be carried out at ambient pressure and temperature, it should be straightforward to scale up the entire process for the high‐volume production of Ag2Se nanowires with well‐controlled sizes and crystal structures. These highly uniform nanowires of single‐crystalline Ag2Se are potentially useful as photosensitizers, superionic conductors, magnetoresistive compounds, or thermoelectric materials. This work also represents the first demonstration of a template‐engaged process capable of generating single‐crystalline nanowires from the solution‐phase and at RT.  相似文献   

5.
An ultrathin V2O5 layer was electrodeposited by cyclic voltammetry on a self‐standing carbon‐nanofiber paper, which was obtained by stabilization and heat‐treatment of an electrospun polyacrylonitrile (PAN)‐based nanofiber paper. A very‐high capacitance of 1308 F g?1 was obtained in a 2 M KCl electrolyte when the contribution from the 3 nm thick vanadium oxide was considered alone, contributing to over 90% of the total capacitance (214 F g?1) despite the low weight percentage of the V2O5 (15 wt%). The high capacitance of the V2O5 is attributed to the large external surface area of the carbon nanofibers and the maximum number of active sites for the redox reaction of the ultrathin V2O5 layer. This ultrathin layer is almost completely accessible to the electrolyte and thus results in maximum utilization of the oxide (i.e., minimization of dead volume). This hypothesis was experimentally evaluated by testing V2O5 layers of different thicknesses.  相似文献   

6.
Ultrathin β‐MnOOH nanofibers can be produced on a large scale via a green‐chemical method using an aqueous solution of very dilute Mn(NO3)2 and aminoethanol at room temperature. High‐magnification electron microscopy demonstrates that the β‐MnOOH nanofibers are 3–5 nm thin and up to 1 micrometer long and the nanofibers are parallel assembled into bundles with an average diameter of 25 nm. By a filtration process, ultrathin mesoporous membranes with strong mechanical, thermal, and chemical stabilities are prepared from the β‐MnOOH nanofiber bundles. The membranes can separate 10‐nm nanoparticles from water at a flux of 15120 L m?2·h?1·bar?1, which was 2–3 times higher than that of commercial membranes with similar rejection properties. Based on the Young‐Laplace equation, β‐MnOOH nanofiber/polydimethylsiloxane composite membranes are developed through a novel downstream‐side evaporation process. From nanoporous to dense separation membranes can be achieved by optimizing the experimental conditions. The membranes show desirable separation performance for proteins, ethanol/water mixtures, and gases. The synthesis method of β‐MnOOH nanofibers is simple and environmentally friendly, and it is easily scalable for industry and applicable to other metal oxide systems. These composite membranes constitute a significant contribution to advanced separation technology.  相似文献   

7.
A new kind of SnO2 nanotubes loaded with Ag2O nanoparticles can be synthesized by using Ag@C coaxial nanocables as sacrificial templates. The composition of silver in SnO2 nanotubes can be controlled by tuning the compositions of metallic Ag in Ag@C sacrificial templates, and the morphology of tubular structures can be changed by use of nanocables with different thicknesses of carbonaceous layer. This simple strategy is expected to be extended for the fabrication of similar metal‐oxide doped nanotubes using different nanocable templates. In contrast to SnO2@Ag@C nanocables as well as to other types of SnO2 reported previously, the Ag2O‐doped SnO2 nanotubes exhibit excellent gas sensing behaviors. The dynamic transients of the sensors demonstrated both their ultra‐fast response (1–2 s) and ultra‐fast recovery (2–4 s) towards ethanol, and response (1–4 s) and recovery (4–5 s) towards butanone. The combination of SnO2 tubular structure and catalytic activity of Ag2O dopants gives a very attractive sensing behavior for applications as real‐time monitoring gas sensors with ultra‐fast responding and recovering speed.  相似文献   

8.
Thin film of silver tin sulfides (Ag–Sn–S) has been deposited on indium tin oxide coated glass (ITO) substrates using potentiostatic cathodic electrodeposition technique. New procedure for the growth of Ag–Sn–S film is presented. An electrolyte solution containing Silver Nitrate (AgNO3), Tin(II) Chloride (SnCl2) and Sodium Thiosulfate (Na2S2O3)in acidic solution (pH ~2) and at temperature of the bath 55 °C were used for the growth of Ag–Sn–S thin film. Prior to the deposition, a cyclic voltammetry technique was performed in binary (Ag–S, Sn–S) and ternary (Ag–Sn–S) systems. This study was carried out to examine the behavior of electroactive species at the electrode surface. Based on these results, the cathodic applied potential was fixed at −1000 mV versus Ag/AgCl to obtain a uniform and good adhesion of ternary thin film. After that, structural, morphological and optical performances of films have been investigated. The X-ray diffraction patterns of the samples demonstrate the presence of the orthorhombic phase of Ag8SnS6 at applied potential of −1000 mV versus Ag/AgCl. Based on the scanning electron microscopy (SEM), it was found that the surface morphology and grain size were strongly influenced by the presence of Sn and/or Ag in the electrolyte bath. The band gaps of binaries and ternary compound are evaluated from optical absorption measurements. Band gap of Ag8SnS6 determined from transmittance spectra is in the range 1.56 eV. Flat-band potential and free carrier concentration have been determined from Mott–Schottky plot and are estimated to be around 0.18 V and 2.21×1014 cm−3 respectively. The photoelectrochemical test of Ag8SnS6 was studied and the experimental observations are discussed in detail.  相似文献   

9.
The interfacial reaction between liquid In-49Sn solders and Ag substrates results in the formation of a thicker Ag2In intermetallic compound accompanied with the development of a thin AgIn2 layer. Through further aging of the In-49Sn/Ag soldered specimens at various temperatures ranging from room to 100°C, solid/solid trnasitions between Ag2In and AgIn2 intermetallic compounds can be observed. When the temperature drops below 75°C, Ag2In will react with the In-49Sn solder to form the dominant AgIn2 phase. Conversely, AgIn2 is consumed at a higher temperature (e.g., 100°C) when reacting with the Ag substrate to create a now dominant Ag2In phase. Lastly, the different mechanical, electrical, magnetic, and corrosion behaviors of both intermetallic compounds are respectively made known through direct measurements of the material properties of the individual Ag2In and AgIn2 bulk samples.  相似文献   

10.
The interfacial reactions between In49Sn solders and Ag thick films at temperatures ranging from 200°C to 350°C have been studied. The intermetallic compound formed at the Ag/In49Sn interface is Ag2In enveloped in a thin layer of AgIn2. Through the measurement of the thickness decrease of Ag thick films, it has been determined that the reaction kinetics of Ag2In has a linear relation to reaction time. Morphology observations indicated that the linear reaction of Ag2In was caused by the floating of Ag2In into the In49Sn solder as a result of the In49Sn solder penetrating into the porous Ag thick film. A sound joint can be obtained when a sufficient thickness of the Ag thick film (over 19.5 μm) reacts with the In49Sn solder. In this case, the tensile tested specimens fracture in the In49Sn matrix.  相似文献   

11.
Cationic Au4Ag2 heterohexanuclear aromatic acetylides cluster complexes supported by bis(2‐diphenylphosphinoethyl)phenylphosphine (dpep) are prepared. The Au4Ag2 cluster structure originating from the combination of one anionic [Au(C≡CR)2]? with one cationic [Au3Ag2(dpep)2(C≡CR)2]3+ through the formation of Ag?acetylide η2‐bonds is highly stabilized by Au–Ag and Au–Au contacts. The Au4Ag2 alkynyl cluster complexes are moderately phosphorescent in the fluid CH2Cl2 solution, but exhibit highly intense phosphorescent emission in solid state and film. As revealed by theoretical computational studies, the phosphorescence is ascribable to significant 3[π (aromatic acetylide) → s/p (Au)] 3LMCT parentage with a noticeable Au4Ag2 cluster centered 3[d → s/p] triplet state. Taking advantage of mCP and OXD‐7 as a mixed host with 20 wt% dopant of phosphorescent Au4Ag2 cluster complex in the emitting layer, solution‐processed organic light‐emitting diodes (OLEDs) exhibit highly efficient electrophosphorescence with the maximum current, power, and external quantum efficiencies of 24.1 cd A?1, 11.6 lm W?1, and 7.0%, respectively. Introducing copper(I) thiocyanate (CuSCN) as a hole‐transporting layer onto the PEDOT:PSS hole‐injecting layer through the orthogonal solution process induces an obvious improvement of the device performance with lower turn‐on voltage and higher electroluminescent efficiency.  相似文献   

12.
Several novel micro-nano Ag3PO4/ZnFe2O4 with excellent magnetic separation property and photocatalytic performance were successfully synthesized using different organic additives for the first time. In the composite, Ag3PO4 with flower-like, quadrangular prism and flake structures were obtained when the organic additive is hexadecyl trimethyl ammonium bromide (CTAB), sodium diethyldithiocarbamate (DDTC), or DL-malic acid (DLMA), respectively, while the ZnFe2O4 showed uniform spherical structure. From the results of the photocatalytic activity analysis, the Ag3PO4/ZnFe2O4 gained with the organic additive of DDTC showed the highest photocatalytic capability for 2, 4-dichlorophenol (2, 4-DCP) degradation under visible light irradiation compared with those of CTAB and DLMA as the additives. Moreover, the composition of the composite seriously influences the photocatalytic activity, and when the mass ratio of Ag3PO4 and ZnFe2O4 in the Ag3PO4/ZnFe2O4 (DITCH) is 9:1, the apparent photo degradation rate constant of 2, 4-DC is 0.0155 min−1, which is 5.74 times of ZnFe2O4 (0.0027 min−1) and 1.89 times of Ag3PO4 (0.0082 min−1). Finally, the photocatalytic mechanism of Ag3PO4/ZnFe2O4 was discussed based on the heterojunction energy-band theory and Z-Scheme theory in detail.  相似文献   

13.
Thermoelectric delafossite (CuAlO2)1−x(Ag2O)x with 0<x<0.06 is prepared at three different sintering temperatures, 1323 K, 1373 K, and 1473 K. The samples are obtained from a mixture of CuO, Al2O3, and additive Ag2O powders. The mixture is ground and then pressed with uniaxial pressure into pellets. Differential scanning calorimetry and X-ray diffraction spectroscopy show that the sintering temperature to synthesize delafossite CuAlO2 with Ag2O addition is below 1473 K. X-ray diffraction patterns show the major phase of delafossite 3R-CuAlO2 along with a trace amount of 2H-CuAlO2. A small amount of the Ag phase is present in the samples depending on the amount of Ag2O addition and sintering temperature. Energy dispersive spectroscopy and backscattered electron image analyses show that the Ag phase is segregated around the grain boundary. Liquid-phase sintering is used to explain the growth mechanism. The CuAlO2 samples with Ag2O addition obviously exhibit enhanced bulk density, grain size, and electrical conductivity. The highest power factor (PF), obtained by CuAlO2 with 2 at% of Ag2O sintered at 1373 K, is 8.23×10−5 W/(m K2) at 873 K. Hence, our findings show an improvement for delafossite CuAlO2 by Ag2O addition.  相似文献   

14.
Dense bulk samples of (Ag,In)‐co‐doped Cu2SnSe3 have been prepared by a fast and one‐step method of combustion synthesis, and their thermoelectric properties have been investigated from 323 to 823 K. The experimental results show that Ag‐doping at Cu site remarkably enhances the Seebeck coefficient, reduces both electrical and thermal conductivities, and finally increases the figure of merit (ZT) value. The ZT of the Cu1.85Ag0.15SnSe3 sample reaches 0.80 at 773 K, which is improved by about 70% compared with the unadulterated sample (ZT = 0.46 at 773 K). First principle calculation indicates that Ag‐doping changes the electronic structure of Cu2SnSe3 and results in larger effective mass of carriers, thus enhancing the Seebeck coefficient and reducing the electrical conductivity. The low electrical conductivity caused by Ag‐doping can be repaired by accompanying In‐doping at Sn site, and by (Ag,In)‐co‐doping the thermoelectric properties are further promoted. The (Ag,In)‐co‐doped sample of Cu1.85Ag0.15Sn0.9In0.1Se3 shows the maximum ZT of 1.42 at 823 K, which is likely the best result for Cu2SnSe3‐based materials up to now. This work indicates that co‐doping may provide an effective solution to optimize the conflicting material properties for increasing ZT.  相似文献   

15.
Nanocrystalline acanthite-structured silver sulfide of the monoclinic structure and a Ag2S/Ag nanoheterostructure are produced. The high-temperature X-ray diffraction technique is applied to the in situ study of the (acanthite α-Ag2S)–(argentite β-Ag2S) phase transformation in nanocrystalline silver sulfide. The crystal structure of argentite is refined, and it is found that the content of vacant sites in the metal sublattice of argentite exceeds 92%. A model of a resistive switch, whose operation is based on the reversible acanthite–argentite transformation in a Ag2S/Ag heterostructure, is considered.  相似文献   

16.
1D hierarchical porous nanocomposites with tailored chemical composition are gaining popularity in lithium‐ion batteries. Here, with core@shell Te@ZIF‐8 (Zn, Co) nanofibers as a starting point, rational designed porous Te@ZnCo2O4 nanocomposite has been fabricated by a simple morphology‐maintained and calcination‐induced oxidative decomposition process, with the purpose of simultaneously settling the pulverization and conductivity issues of transition metal oxides. This is the first time to integrate Te and ZnCo2O4 into one architecture at nanometer level. The Te@ZnCo2O4 nanofibers combine both advantages of Te such as excellent electrical conductivity and ZnCo2O4 with high capacity as well as take full use of their synergistic effect. With the favorable 1D porous structure and the unique composition, this novel Te@ZnCo2O4 nanofiber manifests strong ability to improve the lithium storage performances with a high specific capacity of 1364 mA h g?1 in the initial discharge and a reversible capacity of 956 mA h g?1 after 100 cycles. When increased the current density to 2000 mA g?1, the capacity still remains as 307 mA h g?1, demonstrating superior rate capability. Furthermore, this general strategy can be extended to construct other core@shell Te@MOFs composites.  相似文献   

17.
Temperature dependences of electrical conductivity σ, thermoelectric power α, results of differential thermal analysis ΔT y , thermal conductivity χ, temperature conductivity κ, and heat capacity C p were studied in Ag2Te and Ag2Se semiconductors in the region of the phase transition. Two extrema are observed in the temperature dependence χ(T): a maximum in the region of the α′ → β′ transition and a minimum in the region of the β′ → β transition; these extrema are caused by the similar dependence C p (T). It is shown that the α → α′ and β′ → β transitions are displacement transitions, while the α′ → β′ transition is of reconstruction type. It is established that the disorder parameter η in silver chalcogenides is highly smeared in the region of the phase transition; therefore, disordering of phases at the point of the phase transition is incomplete: 73, 62, and 48% in Ag2Te, Ag2Se, and Ag2S, respectively. The minimum volumes V ph for new phases are calculated; it is shown that the value of V ph in displacement transitions is larger than in the reconstruction-type transitions.  相似文献   

18.
Natural polymer nanofibers are attractive sustainable raw materials to fabricate separators for high‐performance lithium ion batteries (LIBs). Unfortunately, complicated pore‐forming processes, low ionic conductivity, and relatively low mechanical strength of previously reported natural polymer nanofiber‐based separators severely limit their performances and applications. Here, a chemical modification strategy to endow high performance to natural polymer nanofiber‐based separators is demonstrated by grafting cyanoethyl groups on the surface of chitin nanofibers. The fabricated cyanoethyl‐chitin nanofiber (CCN) separators not only exhibit much higher ionic conductivity but also retain excellent mechanical strength in comparison to unmodified chitin nanofiber separators. Through density function theory calculations, the mechanism of high Li+ ion transport in the CCN separator is unraveled as weakening of the binding of Li+ ions over that of PF6? ions with chitin, via the cyanoethyl modification. The LiFePO4/Li4Ti5O12 full cells using CCN separators show much better rate capability and enhanced capacity retention compared to the cell using commercial polypropylene (PP) separators. Beyond this, the CCN separator can work very well even at an elevated temperature of 120 °C in the LiFePO4/Li cell. The proposed strategy chemical modification of natural polymer nanofibers will open a new avenue to fabricate sustainable separators for LIBs with superior performance.  相似文献   

19.
Anisotropic Ag2S‐edged Au‐triangular nanoprisms (TNPs) are constructed by controlling preferential overgrowth of Ag2S as plasmonic photocatalysts for hydrogen generation. Under visible and near‐infrared light irradiation, Ag2S‐edged Au‐TNPs exhibit almost fourfold higher efficiency (796 µmol h−1 g−1) than those of Ag2S‐covered Au‐TNPs (216 µmol h−1 g−1) and pure Au‐TNPs in hydrogen generation. A single‐particle photoluminescence study demonstrates that the plasmon‐induced hot electrons transfer from Au‐TNPs to Ag2S for hydrogen generation. Finite‐difference‐time‐domain simulations verify that the corners/edges of Au‐TNPs are high‐curvature sites with maximum electric field distributions facilitating hot electron generation and transfer. Therefore, Ag2S‐edged Au‐TNPs are efficient plasmonic photocatalyst with the desired configurations for charge separation boosting hydrogen generation.  相似文献   

20.
Highly efficient visible-light-driven AgBr/Ag3PO4 hybrid photocatalysts with different mole ratios of AgBr were prepared via an in-situ anion-exchange method and characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), UV–vis diffuse reflectance spectroscopy (DRS) and photoluminescence (PL) technique. Under visible light irradiation (>420 nm), the AgBr/Ag3PO4 photocatalysts displayed the higher photocatalytic activity than pure Ag3PO4 and AgBr for the decolorization of acid orange 7 (AO 7). Among the hybrid photocatalysts, AgBr/Ag3PO4 with 60% of AgBr exhibited the highest photocatalytic activity for the decolorization of AO 7. X-ray photoelectron spectroscopy (XPS) results revealed that AgBr/Ag3PO4 readily transformed to be Ag@AgBr/Ag3PO4 system while the photocatalytic activity of AgBr/Ag3PO4 remained after 5 recycling runs. In addition, the quenching effects of different scavengers displayed that the reactive h+ and O2∙− play the major role in the AO 7 decolorization. The photocatalytic activity enhancement of AgBr/Ag3PO4 hybrids can be ascribed to the efficient separation of electron–hole pairs through a Z-scheme system composed of Ag3PO4, Ag and AgBr, in which Ag nanoparticles act as the charge separation center.  相似文献   

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