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1.
On the enzymatic formation of platinum nanoparticles   总被引:1,自引:0,他引:1  
A dimeric hydrogenase enzyme (44.5 and 39.4 kDa sub units) was isolated in a 39.5% yield from the fungus Fusarium oxysporum and purified 4.64-fold by ion exchange chromatography on Sephacryl S-200. Characterisation of the enzyme afforded pH and temperature optima of 7.5 and 38 °C, respectively, a half-life stability of 36 min and a V max and K m of 3.57 nmol min−1 mL−1 and 2.25 mM, respectively. This enzyme was inhibited (non-competitively) by hydrogen hexachloroplatinic acid (H2PtCl6) at 1 or 2 mM with a K i value of 118 μM. Incubation of the platinum salt with the pure enzyme under an atmosphere of hydrogen and optimum enzyme conditions (pH 7.5, 38 °C) afforded <10% bioreduction after 8 h while at conditions suitable for platinum nanoparticle formation (pH 9, 65 °C) over 90% reduction took place after the same length of time. Cell-free extract from the fungal isolates produced nearly 90% bioreduction of the platinum salt under both pH and temperature conditions. The bioreduction of the platinum salt by a hydrogenase enzyme takes place by a passive process and not an active one as previously understood.  相似文献   

2.
The thin-film solid polymer electrolyte based on polyethylene oxide (PEO) with sodium chlorite (NaClO3) has been prepared by a solution-cast technique. The electrolyte was characterized by X-ray diffraction (XRD), infrared (IR), cyclic voltammetry, alternating current conductivity, and Wagner’s polarization studies. The complexation of NaClO3 with PEO was confirmed through the XRD and IR studies. The transference number measurement has shown that the ion transport is predominant over electrons in the polymer electrolytes (t ions ≈ 0.94). The conductivity enhancement was observed in the case of the PEO/NaClO3 system with the addition of plasticizers (low-molecular-weight polyethylene glycol, organic solvents propylene carbonate and dimethyl formamide. Cyclic voltammetry analysis showed the stability and redox character of the electrolyte and electrode. Finally, polymer electrolyte systems were examined by electrochemical cell studies using V2O5 and composite V2O5 cathode at temperature of 35 °C. Overall, the plasticized electrolyte shows a better electrochemical performance, and a higher discharge capacity was observed in composite V2O5-based cells over V2O5-based cells.  相似文献   

3.
Li1 .2V3O8 and Cu-doped Li1.2V3O8 were prepared at a temperature as low as 300 °C by a sol-gel method. The structure, morphology, and electrochemical performance of the as-prepared samples were characterized by means of X-ray diffraction, scanning electron microscopy, electrochemical impedance spectroscopy, and the galvanostatic discharge–charge techniques. It is found that the Cu-doped Li1.2V3O8 sample exhibits less capacity loss during repeated cycling than the undoped one. The Cu-doped Li1.2V3O8 sample demonstrates the first discharge capacity of 275.9 mAh/g in the range of 3.8–1.7 V at a current rate of 30 mA/g and remains at a stable discharge capacity of 264 mAh/g within 30 cycles. Furthermore, the possible role that copper plays in enhancing the cycleability of Li1.2V3O8 has also been elucidated.  相似文献   

4.
We report for the first time the use of lithiated crystalline V2O5 thin films as positive electrode in all-solid-state microbatteries. Crystalline LixV2O5 films (x ≈ 0.8 and 1.5) are obtained by vacuum evaporation of metallic lithium deposited on sputtered c-V2O5. An all-solid-state lithium microbattery of Li1.5V2O5/LiPON/Li exhibited a typical reversible capacity of 50 μAh/cm2 in the potential range 3.8/2.15 V which exceeds by far the results known on all-solid-state lithium batteries using amorphous V2O5 films and lithiated amorphous LixV2O5 thin films as positive electrode. Hence, the present work opens the possibility of using high performance crystalline lithiated V2O5 thin films in rocking-chair solid-state microbatteries.  相似文献   

5.
The effects of SO2 and CO2 additives in electrolytes on the cycle properties of liquid-state Al-plastic film lithium-ion batteries were first investigated. The experimental electrolytes were added with different amounts of SO2 and CO2. The baseline electrolyte was 1 mol L−1 LiPF6 in ethylene carbonate/dimethylcarbonate/ethyl-methyl carbonate (1:1:1, by volume), and graphite was used as anode. The main analysis tools were cycling test, rate capability, internal resistance test, low-temperature performance, and thermal stability. The results showed that both of the additives could promote to form an excellent solid electrolyte interface film on the surface of graphite anode, leading to excellent cycle performances, the capacity retentions of CO2 and S5 were 94% and 97% after 400 cycles, respectively. Besides, the results also exhibited that the electrochemical performances of internal resistance, rate capability, low-temperature performance, and thermal stability were not changed significantly by the use of SO2 and CO2 as electrolyte additives.  相似文献   

6.
40 alternate a-Si/SiN x multilayer are incorporated as an absorber layer in a p–i–n solar cell. The device is fabricated using hot-wire chemical vapor deposition (HWCVD) technique. The structure of the multilayer film is examined by high resolution transmission electron microscopy (HR-TEM) which shows distinct formation of alternate a-Si and SiN x layers. The a-Si and SiN x layers have thickness of ~3.5 and 4 nm, respectively. The photoluminescence (PL) of multilayer film shows bandgap energy of ~2.52 eV, is larger than that of the c-Si and a-Si. Dark and illuminated current–voltage (IV) characterization of the ML films shows that these ML are photosensitive. In the present work, it is seen that the p–i–n structure with i-layer as ML quantum well (QW) structures show photovoltaic effect with relatively high open-circuit voltage (V OC). The increment of bandgap energy in PL and high V OC of the device is attributed to the quantum confinement effect (QCE).  相似文献   

7.
The monoclinic (space group C2/m) superstructure of V14O6, which is formed in the atom-vacancy ordering of the tetragonal solid solution of oxygen in vanadium, is studied by the methods of x-ray diffraction and symmetry analysis. It has been found that the channel of the order-disorder phase transition attributed to the formation of the monoclinic suboxide V14O6 includes six superstructure vectors belonging to three non-Lifshitz stars {k 1−1}, {k 1−2}, and {k 1–3} of one type {k 1}. The distribution function of the O atoms in the V14O6 monoclinic superstructure has been calculated. It has been shown that the displacements of V atoms distort the body-centered tetragonal metal sublattice, thus preparing the formation of the fcc sublattice and the transition from the suboxide V14O6 to the cubic vanadium monoxide with the B1 structure.  相似文献   

8.
The three thermo-optic coefficients of the biaxial laser host KLu(WO4)2 are measured at 633 nm by a deflection method. Their values at 300 K amount to n g / T=−7.4×10−6 K−1; n m / T=−1.6×10−6 K−1 and n p / T=−10.8×10−6 K−1. Nearly athermal propagation directions are found for polarizations along the N m and N p dielectric axes.  相似文献   

9.
Optical properties (photoluminescence and absorption) of Eu(bta)3(B) n (B = H2O or 1,10-phenanthroline) polycrystalline powders and fluoroacrylate polymers (FAPs) impregnated with these compounds using supercritical CO2 (SC CO2) were investigated. It was established that impregnation of Eu(bta)3phen into the FAPs using an SC CO2 solution was difficult to achieve. The type of B (ancillary ligand) and the polymer matrix were shown to influence the temperature quenching of photoluminescence of Eu3+ ions in the range 25–100°C. A comparative analysis of quantum yields (λex = 300 and 380 nm) and photoluminescence decay times (λex = 337.1 nm) for Eu(bta)3B n and for Eu(bta)3B n -doped FAPs was performed.  相似文献   

10.
The magnetic and thermal properties of the anion-deficient La0.70Sr0.30MnO2.85 manganite are investigated in wide temperature (4–350 K) range, including under hydrostatic pressure (0–1.1 GPa). Throughout the pressure range investigated, the sample is spin glass with diffused phase transition into paramagnetic state. It is established, that spin glass state is a consequence of exchange interaction frustration of the ferromagnetic clusters embeded into antiferromagnetic clusters. The magnetic moment freezing temperature T f of ferromagnetic clusters increases under pressure, freezing temperature dependence on pressure is characterized by derivative value ∼4.5 K/GPa, while the magnetic ordering T MO temperature dependence is characterized by derivative value ∼13 K/GPa. The volume fraction of sample having ferromagnetic state is V fer ∼ 13% and it increases under a pressure of 1.1 GPa by ΔV fer ≈ 6%. Intensification of ferromagnetic properties of the anion-deficient La0.70Sr0.30MnO2.85 manganite under hydrostatic pressure is a consequence of oxygen vacancies redistribution and unit cell parameters decrease. The most likely mechanism of frustrated exchange interactions formation is discussed.  相似文献   

11.
Pressure effects on magnetic properties of two La0.7Ca0.3MnO3 nanoparticle samples with different mean particle sizes were investigated. Both the samples were prepared by the glycine-nitrate method: sample S—as-prepared (10 nm), and sample S900—subsequently annealed at 900 °C for 2 h (50 nm). Magnetization measurements revealed remarkable differences in magnetic properties with the applied pressure up to 0.75 GPa: (i) for S sample, both transition temperatures, para-to-ferromagnetic T C = 120 K and spin-glass-like transition T f = 102 K, decrease with the pressure with the respective pressure coefficients dT C/dP = −2.9 K/GPa and dT f/dP = −4.4 K/GPa; (ii) for S900 sample, para-to-ferromagnetic transition temperature T C = 261 K increases with pressure with the pressure coefficient dT C/dP = 14.8 K/GPa. At the same time, saturation magnetization M S recorded at 10 K decreases/increases with pressure for S/S900 sample, respectively. Explanation of these unusual pressure effects on the magnetism of sample S is proposed within the scenario of the combined contributions of two types of disorders present in the system: surface disorder introduced by the particle shell, and structural disorder of the particle core caused by the prominent Jahn–Teller distortion. Both disorders tend to vanish with the annealing of the system (i.e., with the nanoparticle growth), and so the behavior of the sample S900 is similar to that previously observed for the bulk counterpart.  相似文献   

12.
In view of increasing commercial applications of metal oxide nanoparticles their toxicity assessment becomes important. Alumina (Al2O3) nanoparticles have wide range of applications in industrial as well as personal care products. In the absence of prior report on toxicological impact of alumina nanoparticles to microalgae, the principal objective of this study was to demonstrate the effect of the nanoparticles on microalgae isolated from aquatic environment (Scenedesmus sp. and Chlorella sp.). The growth inhibitory effect of alumina nanoparticles was observed for both the species (72 h EC50 value, 45.4 mg/L for Chlorella sp.; 39.35 mg/L for Scenedesmus sp.). Bulk alumina also showed toxicity though to a lesser extent (72 h EC50 value, 110.2 mg/L for Chlorella sp.; 100.4 mg/L for Scenedesmus sp.). A clear decrease in chlorophyll content was observed in the treated cells compared to the untreated ones, more effect being notable in the case of nanoparticles. Preliminary results based on FT-IR studies, optical and scanning electron microscopic images suggest interaction of the nanoparticles with the cell surface.  相似文献   

13.
Novel multifunctional ceria based materials may show an improved performance in catalytic processes involving CO2 activation and reforming of hydrocarbons. Towards a more detailed understanding of the underlying surface chemistry, we have investigated CO2 activation on single crystal based ceria and magnesia/ceria model catalysts. All model systems are prepared starting from well-ordered and fully stoichiometric CeO2(111) films on a Cu(111) substrate. Samples with different structure, oxidation state and compositions are generated, including CeO2-x/Cu(111) (reduced), MgO/CeO2-x/Cu(111) (reduced), mixed MgO-CeO2/Cu(111) (stoichiometric), and mixed MgO-CeO2-x/Cu(111) (reduced). The morphology of the model surfaces is characterized by means of scanning tunneling microscopy (STM), whereas the electronic structure and reactivity is probed by X-ray photoelectron spectroscopy (XPS). The experimental approach allows us to compare the reactivity of samples containing different types of Ce3+, Ce4+, and Mg2+ ions towards CO2 at a sample temperature of 300 K. Briefly, we detect the formation of two CO2-derived species, namely carbonate (CO3 2-) and carboxylate (CO2 -) groups, on the surfaces of all investigated samples after exposure to CO2 at 300 K. In parallel to formation of the carbonate species, slow partial reoxidation of reduced CeO2-x/Cu(111) occurs at large doses of CO2. The reoxidation of the reduced ceria is largely suppressed on MgO-containing samples. The tendency for reoxidation of Ce3+ to Ce4+ by CO2 decreases with increasing degree of intermixing between MgO and CeO2-x. Additionally, we have studied the stability of the formed carbonate species as a function of annealing temperature.  相似文献   

14.
The FTIR spectrum of pentafluoroethane (R125) was measured in the mid infrared region from 900 to 4000 cm−1. Vibrational assignments for R125 are revised by comparison of previous and current experimental data with ab initio calculations at both the MP2/6-311+(d,p) and B3LYP/TZV+(3df,3p) levels of theory. High resolution FTIR spectra were recorded at room temperature and in an enclosive flow cell at a rotational temperature of 140 K. The cold spectrum was sufficiently resolved to enable rovibrational analyses of the overlapping ν4 (1200.7341 cm−1) and ν13 (1223.3 cm−1) bands, which have a/c hybrid and b-type character, respectively. Ground state combination differences were used to confirm assignment of 2375 lines to ν4 (Jmax = 86, Ka max = 50) and 2921 lines to ν13 (Jmax = 60, Ka max = 54). Effective rotational and centrifugal distortion constants were determined for ν4, and the polarization ratio was found to be . Severe Coriolis perturbations prevent any satisfactory fit to the ν13 band.  相似文献   

15.
The dielectric properties of zirconium dioxide (ZrO2) ceramic thin films were characterized up to 50 GHz using coplanar waveguides (CPWs) and metal–insulator–metal (MIM) capacitors with top circular electrodes. The ZrO2 films were deposited using a chemical solution onto high-resistivity Si wafers and metal layers. The real part of the dielectric constant of approximately 22 and 26 was extracted at 50 GHz for CPW and MIM structures, respectively, and the loss tangent was approximately 0.09 at 50 GHz. CV and IV measurements were carried out to determine low-frequency and DC dielectric properties. The measurement results indicate that ZrO2 is a promising material to be used as a dielectric layer for radio-frequency (RF) microelectromechanical systems (MEMS) capacitive switches.  相似文献   

16.
The 2ν3 overtone (A1E) and the ν1 + ν3 (E) combination bands of the oblate symmetric top 14NF3 were studied by FTIR spectroscopy with a resolution of 2.5 × 10−3 cm−1. Nearly 500 lines up to Kmax/Jmax = 30/43 were observed for the weak A1 component reaching the v3 = 20 substate (1803.1302 cm−1), the majority of which corresponded to reinforced K = 3p-type transitions. For the strong E component reaching the v3 = 2±2 substate (1810.4239 cm−1), about 3550 transitions were assigned up to Kmax/Jmax = 65/69, favoring a clear observation of the ℓ(4, −2) and ℓ(4, 4) splittings within the kℓ = −2 and +4 sublevels, respectively. The two v3 = 2 substates are linked by the ℓ(2, 2)- and ℓ(2, −1)-type interactions, providing severe crossings, respectively, at K′ = 6 and near K′ = 24 on the v3 = 2+2 side. A model working in the D-reduction and including all these ℓ-type interactions could reproduce together 3695 nonzero weighted experimental data (NZW) through 33 free parameters with a standard deviation of σ = 0.357 × 10−3  cm−1. As for the ν1 + ν3 (E) combination band, about 3690 lines were assigned up to Kmax/Jmax = 45/55. Its v1 = v3 = 1 upper state (1931.577 5 cm−1) was treated using the same model recently applied to the v3 = 1 (E, 907.5413 cm−1) state. It yielded 21 free parameters through 3282 NZW experimental data, adjusted with σ = 0.344 × 10−3  cm−1 in the D-reduction. For the two excited states, the small and unobserved ℓ(0, 6) interaction was tested as useless. To confirm the adequacy of the vibrationally isolated models used, some other reductions of the Hamiltonian were tried. For the v3 = 2 state, the D-, L-, and LD-reductions led to similar σ’s, while the Q one was not successful. For the v1 = v3 = 1 state, the D- and Q-reductions gave comparable σ’s, while the QD-reduction was not as good. The corresponding unitary equivalence relations are generally more nicely fulfilled for the v3 = 2 state than for the v1 = v3 = 1 state. The three derivable anharmonicity constants in cm−1 are x33 = −4.1528, g33 = +1.8235 and x13 = −7.9652.  相似文献   

17.
Tris(2,2′‐bipyridine)ruthenium(II) complex‐based carbonic anhydrase (CA) inhibitors, [Ru(bpy)2(bpydbs)]2+ {bpy = 2,2′‐bipyridine and bpydbs = 2,2′‐bipyridinyl‐4,4′‐dicarboxilic acid bis[(2‐{2‐[2‐(4‐sulfamoylbenzoylamino)ethoxy]ethoxy}ethyl)amide]} and [Ru(bpydbs)3]2+, tethering plural benzenesulfonamide groups have been prepared. The CA catalytic activity was effectively suppressed by these synthetic [Ru(bpy)2(bpydbs)]2+ and [Ru(bpydbs)3]2+ inhibitors, and their dissociation constants at pH = 7.2 and at 25°C were determined to be KI = 0.93 ± 0.02 μM and KI = 0.24 ± 0.03 μM, respectively. Next, 2 photoinduced electron‐transfer (ET) systems comprising a Ru2+‐CA complex and an electron acceptor, such as chloropentaamminecobalt(III) ([CoCl(NH3)5]2+) or methylviologen (MV2+) were studied. In the presence of CA and a sacrificial electron acceptor, such as pentaamminechlorocobalt(III) complex, the photoexcited triplet state of 3([Ru(II)]2+)* was quenched through an intermolecular photoinduced ET mechanism. In case of the [Ru(bpydbs)3]2+‐CA‐MV2+ system, the photoexcited triplet state of 3([Ru(bpydbs)3]2+)* was quenched by sacrificial quencher through an intermolecular photoinduced ET mechanism, giving the oxidized [Ru(bpydbs)3]3+. Then the following intramolecular ET from the amino acid residue, Tyr6, near the active site of CA proceeded. We observed a transient absorption around at 410 nm, arising from the formation of a Tyr?+ in the [Ru(bpydbs)3]2+‐CA‐MV2+ system. These artificial Ru(II)‐CA systems may clearly demonstrate both intermolecular and intramolecular photoinduced ET reactions of protein and could be one of the interesting models of the ET proteins. Their photophysical properties and the detailed ET mechanisms are discussed in order to clarify the multistep ET reactions.  相似文献   

18.
Bi2S3 nanotubes and de-doped poly(3,4-ethylenedioxythiophene) (PEDOT) composite nanopowders were synchronously synthesized by a one-pot self-assembly method. The powders were characterized by X-ray powder diffraction, infrared spectroscopy, and transmission electron microscopy, respectively. Thermoelectric properties of the Bi2S3–PEDOT composite nanopowders with different Bi2S3 contents after being cold pressed into pellets were measured at room temperature. The sample with 36.1 wt% Bi2S3 has a highest power factor of 2.3 μWm−1K−2, which is higher than that of both pure PEDOT (0.445 μWm−1K−2) and Bi2S3 (1.94 μWm−1K−2).  相似文献   

19.
The layered LiNi0.5Mn0.47Al0.03O2 was synthesized by wet chemical method and characterized by X-ray diffraction and analysis of magnetic measurements. The powders adopted the α-NaFeO2 structure. This substitution of Al for Mn promotes the formation of Li(Ni0.472+Ni0.033+Mn0.474+Al0.033+)O2 structures and induces an increase in the average oxidation state of Ni, thereby leading to the shrinkage of the lattice unit cell. The concentration of antisite defects in which Ni2+ occupies the (3a) Li lattice sites in the Wyckoff notation has been estimated from the ferromagnetic Ni2+(3a)–Mn4+(3b) pairing observed below 140 K. The substitution of 3% Al for Mn reduces the amount of antisite defects from 7% to 6.4–6.5%. The analysis of the magnetic properties in the paramagnetic phase in the framework of the Curie–Weiss law agrees well with the combination of Ni2+ (S = 1), Ni3+ (S = 1/2) and Mn4+ (S = 3/2) spin-only values. Delithiation has been made by the use of K2S2O8. According to this process, known to be softer than the electrochemical one, the nickel ions in the (3b) sites are converted into Ni4+ in the high spin configuration, while Ni2+(3a)–Mn4+(3b) ferromagnetic pairs remain, as the Li+(3b) ions linked to the Ni2+(3a) ions in the antisite defects are not removed. The results show that the antisite defect is surrounded by Mn4+ ions, implying the nonuniform distribution of the cations in agreement with previous NMR and neutron experiments.  相似文献   

20.
The metastable liquid phase separation and rapid solidification of Cu60Fe30Co10 ternary peritectic alloy were investigated by using the drop tube technique and the differential scanning calorimetry method. It was found that the critical temperature of metastable liquid phase separation in this alloy is 1623.5 K, and the two separated liquid phases solidify as Cu(Fe,Co) and Fe(Cu,Co) solid solutions, respectively. The undercooling and cooling rate of droplets processed in the drop tube increase with the decrease of their diameters. During the drop tube processing, the structural morphologies of undercooled droplets are strongly dependent on the cooling rate. With the increase of the cooling rate, Fe(Cu,Co) spheres are refined greatly and become uniformly dispersed in the Cu-rich matrix. The calculations of Marangoni migration velocity (V M) and Stokes motion velocity (V S) of Fe(Cu,Co) droplets indicated that Marangoni migration contributes more to the coarsening and congregation of the minor phase during free fall. At the same undercooling, the V M/V S ratio increases drastically as Fe(Cu,Co) droplet size decreases. On the other hand, a larger undercooling tends to increase the V M/V S value for Fe(Cu,Co) droplets with the same size. Supported by the National Natural Science Foundation of China (Grant Nos. 50121101 and 50395105) and the Scientific and Technological Creative Foundation of Youth in Northwestern Polytechnical University of China (Grant No. W016223)  相似文献   

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