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1.
A simple method for synthesis of gold nanoparticles (AuNPs) using Aspergillum sp. WL-Au was presented in this study. According to UV–vis spectra and transmission electron microscopy images, the shape and size of AuNPs were affected by different parameters, including buffer solution, pH, biomass and HAuCl4 concentrations. Phosphate sodium buffer was more suitable for extracellular synthesis of AuNPs, and the optimal conditions for AuNPs synthesis were pH 7.0, biomass 100 mg/mL and HAuCl4 3 mM, leading to the production of spherical and pseudo-spherical nanoparticles. The biosynthesized AuNPs possessed excellent catalytic activities for the reduction of 2-nitrophenol, 3-nitrophenol, 4-nitrophenol, o-nitroaniline and m-nitroaniline in the presence of NaBH4, and the catalytic rate constants were calculated to be 6.3×10−3 s−1, 5.5×10−3 s−1, 10.6×10−3 s−1, 8.4×10−3 s−1 and 13.8×10−3 s−1, respectively. The AuNPs were also able to catalyze the decolorization of various azo dyes (e.g. Cationic Red X-GRL, Acid Orange II and Acid scarlet GR) using NaBH4 as the reductant, and the decolorization rates reached 91.0–96.4% within 7 min. The present study should provide a potential candidate for green synthesis of AuNPs, which could serve as efficient catalysts for aromatic pollutants degradation.  相似文献   

2.
《Current Applied Physics》2009,9(5):1129-1133
Measurements of In2S3 and ZnIn2S4 sprayed thin films thermal characteristics have been carried out using the photodetection technique. The thermal conductivity k and diffusivity D were obtained using a new protocol based on photothermal signal parameters analysis. Measured values of k and D were respectively, (15.2 ± 0.85) W m−1K−1 and (69.8 ± 7.1) × 10−6 m2s−1 for In2S3, (7.2 ± 0.7) W m−1K−1 and (32.7 ± 4.3) × 10−6 m2s−1 for ZnIn2S4. These values are extremely important since similar compounds are more and more proposed as Cd-free alternative materials for solar cells buffer layers.  相似文献   

3.
This paper reports on the thermo (TL), iono (IL) and photoluminescence (PL) properties of nanocrystalline CaSiO3:Eu3+ (1–5 mol %) bombarded with 100 MeV Si7+ ions for the first time. The effect of different dopant concentrations and influence of ion fluence has been discussed. The characteristic emission peaks 5D07FJ (J=0, 1, 2, 3, 4) of Eu3+ ions was recorded in both PL (1×1011–1×1013 ions cm?2) and IL (4.16×1012–6.77×1012 ions cm?2) spectra. It is observed that PL intensity increases with ion fluence, whereas in IL the peaks intensity increases up to fluence 5.20×1012 ions cm?2, then it decreases. A well resolved TL glow peak at ~304 °C was recorded in all the ion bombarded samples at a warming rate of 5 °C s?1. The TL intensity is found to be maximum at 5 mol% Eu3+ concentration. Further, TL intensity increases sub linearly with shifting of glow peak towards lower temperature with ion fluence.  相似文献   

4.
《Solid State Ionics》2006,177(1-2):73-76
Ionic conduction in fluorite-type structure oxide ceramics Ce0.8M0.2O2−δ (M = La, Y, Gd, Sm) at temperature 400–800 °C was systematically studied under wet hydrogen/dry nitrogen atmosphere. On the sintered complex oxides as solid electrolyte, ammonia was synthesized from nitrogen and hydrogen at atmospheric pressure in the solid states proton conducting cell reactor by electrochemical methods, which directly evidenced the protonic conduction in those oxides at intermediate temperature. The rate of evolution of ammonia in Ce0.8M0.2O2−δ (M = La, Y, Gd, Sm) is up to 7.2 × 10 9, 7.5 × 10 9, 7.7 × 10 9, 8.2 × 10 9 mol s 1 cm 2, respectively.  相似文献   

5.
《Solid State Ionics》2006,177(19-25):1747-1752
Oxygen tracer diffusion coefficient (D) and surface exchange coefficient (k) have been measured for (La0.75Sr0.25)0.95Cr0.5Mn0.5O3−δ using isotopic exchange and depth profiling by secondary ion mass spectrometry technique as a function of temperature (700–1000 °C) in dry oxygen and in a water vapour-forming gas mixture. The typical values of D under oxidising and reducing conditions at ∼ 1000 °C are 4 × 10 10 cm2 s 1 and 3 × 10 8 cm2 s 1 respectively, whereas the values of k under oxidising and reducing conditions at ∼ 1000 °C are 5 × 10 8 cm s 1 and 4 × 10 8 cm s 1 respectively. The apparent activation energies for D in oxidising and reducing conditions are 0.8 eV and 1.9 eV respectively.  相似文献   

6.
The decomposition of dimethyl ether (CH3OCH3) has been investigated behind incident shock waves in a diaphragmless shock tube using laser schlieren densitometry, LS (T = 1500–2450 K, P = 57 ± 4, 125 ± 5 and 253 ± 12 Torr). The LS density gradient profiles were simulated and excellent agreement was found between the simulations and experimental profiles. Rate coefficients for CH3OCH3  CH3O + CH3 were obtained. They showed strong fall-off, and at the lower end of the experimental temperature range are close to the low pressure limit. First order rate coefficient expressions were determined over 1500 < T < 2450 K. k57Torr = (3.10 ± 1.0) × 1079T?19.03 exp(?54417/T) s?1, k125Torr = (1.12 ± 0.3) × 1083T?19.94 exp(?55554/T) s?1and k253Torr = (1.02 ± 0.3) × 1073T?17.09 exp(?51500/T) s?1. The effect of a roaming channel for decomposition of dimethyl ether was assessed and the best agreement was obtained with 1% dissociation of DME via the roaming path.  相似文献   

7.
To elucidate the thermoelectric properties at high temperatures, the electrical conductivity and Seebeck coefficient were measured at temperatures between 423 K and 973 K for perovskite-type ceramics of BaBi1?xSbxO3 solid solutions with x=0.0–0.5. All the ceramics exhibit p-type semiconducting behaviors and electrical conduction is attributed to hopping of small polaronic holes localized on the pentavalent cations. Substitution of Bi with Sb causes the electrical conductivity σ and cell volume to decrease, but the Seebeck coefficient S to increase, suggesting that the Sb atoms are doped as Sb5+ and replace Bi5+, reducing 6s holes conduction from Bi5+(6s0) to Bi3+ (6s2). The thermoelectric power factor S 2σ has values of 6×10?8–3×10?5 W m?1 K?2 in the measured temperature range, and is maximized for an Sb-undoped BaBiO3?δ, but decreases upon Sb doping due to the decreased σ values.  相似文献   

8.
A novel 4-(2-dimethylaminoethyloxy)-N-octadecyl-1,8-naphthalimide (DON) has been synthesized as a spectrofluorimetric probe for the determination of proteins. Photophysics of DON in different solvents has been delineated in this paper. Progressive redshift with polarity of solvents in emission and absorption spectra hints at intramolecular charge transfer. The interactions of DON with serum albumins (i.e., human serum albumin (HSA) and bovine serum albumin (BSA)) were studied by fluorescence and absorption spectroscopy. Fluorescence data revealed that the quenching of HSA/BSA by DON were static quenching and the DON–HSA/BSA complexes were formed. The binding constant (Kb) for HSA and was found to be 8.44×10?4 and 60.26×10?4 M?1 and the number of binding sites (n) were 1.00 and 1.40, respectively. The thermodynamic parameters, ΔH and ΔS, for the DON–HSA system was calculated to be ?14.83 kJ mol?1 and 23.61 J mol?1 K?1, indicating the hydrogen bonds and hydrophobic interactions were the dominant intermolecular force. ΔH and ΔS for the binding of DON with BSA was ?60.08 kJ mol?1 and ?90.7441 mol?1 K?1, suggesting the hydrogen bonds and van der Waals force played the main role in the interaction. The results of displacement experiments showed that DON bound HSA/BSA occurred at the Trp-214 proximity, located in subdomain IIA of the serum albumin structure (the warfarin binding pocket). The effect of DON on the conformation of HSA was also analyzed by synchronous and three-dimensional fluorescence spectra. The fluorescence of DON could be quenched by HSA, based on which, a fluorometric method for the determination of microamount protein using DON in the medium of HCl?Tris buffer solution (pH=7.4) was developed. The linear range of the calibration curves was 0.1–10.0 μM for HSA, 0.1–11.2 μM for BSA and 0.2–9.7 μM for egg albumin (EA). The detection limit (3σ) for HSA was 1.12×10?10 M, for BSA it was 0.92×10?10 M and for EA it was 4.33×10?10 M. The effect of metal cations on the fluorescence spectra of DON in ethanol was also investigated. The method has been applied to detect the total proteins in human serum samples and the results were in good agreement with those reported by the hospital.  相似文献   

9.
Using high-intensity ultrasound, in situ generated α-amylase nanoparticles (NPs) were immobilized on polyethylene (PE) films. The α-amylase NP-coated PE films have been characterized by E-SEM, FTIR, DLS, XPS and RBS. The PE was reacted with HNO3 and NPs of the α-amylase were also deposited on the activated PE. The PE impregnated with α-amylase (4 μg per 1 mg PE) was used for hydrolyzing soluble potato starch to maltose. The immobilization improved the catalytic activity of α-amylase at all the reaction conditions studied. The kinetic parameters, Km (5 and 4 g L?1 for the regular and activated PE, respectively) and Vmax (5 × 10?7 mol ml?1 min?1, almost the same numbers were obtained for the regular and activated PEs) for the immobilized amylase were found to slightly favor the respective values obtained for the free enzyme (Km = 6.6 g L?1, Vmax = 3.7 × 10?7 mol ml?1 min?1). The enzyme remained bound to PE even after soaking the PE in a starch solution for 72 h and was still found to be weakly active.  相似文献   

10.
β-Carboline alkaloids are present in medicinal plants such as Peganum harmala L. that have been used as folk medicine in anticancer therapy. BSA1 is the major soluble protein constituent of the circulatory system, and has many physiological functions including the transport of a variety of compounds. This study is the first attempt to investigate the binding of β-carboline alkaloids to BSA by using a constant protein concentration and varying drug concentrations at pH 7.2. FTIR2 and UV–Vis3 spectroscopic methods were used to analyze the binding modes of β-carboline alkaloids, the binding constants and the effects of drug complexation on BSA stability and conformation. Spectroscopic evidence showed that β-carboline alkaloids bind BSA via hydrophobic interaction and van der Waals contacts along with H-bonding with the –NH groups, with overall binding constants of Kharmine–BSA=2.04×104 M?1, Ktryptoline–BSA=1.2×104 M?1, Kharmaline–BSA=5.04×103 M?1, Kharmane–BSA=1.41×103 M?1 and Kharmalol–BSA=1.01×103 M?1, assuming that there is one drug molecule per protein. The BSA secondary structure was altered with a major decrease of α-helix from 64% (free protein) to 59% (BSA–harmane), 56% (BSA–harmaline and BSA–harmine), 55% (BSA–tryptoline), 54% (BSA–harmalol) and β-sheet from 15% (free protein) to 6–8% upon β-carboline alkaloids complexation, inducing a partial protein destabilization.  相似文献   

11.
A novel flow injection method for detection of l-proline was proposed in the presence of CdTe quantum dots (QDs). This method is based on the enhanced anodic electrochemiluminescence (ECL) emission of CdTe QDs l-proline in aqueous system. CdTe QDs were modified with thioglycolic acid to obtain stable water-soluble QDs and intensive anodic ECL emission in Na2CO3–NaHCO3 buffer solution at an indium tin oxide (ITO) electrode, which was used for the sensitive detection of ECL enhancement using our homemade flow cell. Under the optimal conditions, the ECL intensity was correlated linearly with the concentration of l-proline over the range of 1.0×10?8?1.0×10?4 g mL?1 (r=0.9996) and the detection limit was 5.0×10?9 g mL?1. The relative standard deviation was 1.12% for 6.0×10?5 g mL?1 l-proline (n=11). The possible mechanism was discussed. This method put forward a new efficient ECL methodology for enhancement-related determination of l-proline successfully.  相似文献   

12.
Highly luminescent complexes of Eu and Tb ions with norfloxacin (NFLX) and gatifloxacin (GFLX) were prepared in sol–gel matrix. The red and green emissions of Eu and Tb ions were obtained by the energy transfer from the triplet state of (NFLX) and (GFLX) to the excited emitting states (5D0 and 5D4) of Eu and Tb, respectively. The intensity of the electric field emission bands (5D07F2, 617 nm and 5D47F5, 545 nm) of Eu and Tb ions were proportional to the concentration of (NFLX at pH 6.0) and (GFLX at pH 3.5) in acetonitrile with excitation wavelengths (λex) (340 and 395) and (370 and 350 nm) for Eu and Tb ions, respectively. The monitored luminescence intensity of the system showed a good linear relationship with the concentration of NFLX within a range of 5×10?9–5.8×10?6 and 5×10?8–1.0×10?6 mol L?1 with a correlation coefficient of 0.990, and for GFLX within a range of 2.4×10?9–3.2×10?5 and 5×10?8–8.0×10?6 mol L?1 with a correlation coefficient of 0.995. The detection limit (LOD) was determined as 3.0×10?9 and 1.0×10?8 mol L?1 for NFLX and 1.6×10?10 and 2.0×10?8mol L?1 for GFLX. The limit of quantification (LOQ) is 9×10?9 and 3.0×10?8 and 4.8×10?10 and 6.0×10?8 in case of Eu and Tb, respectively.  相似文献   

13.
New solid electrolytes containing acetamide and lithium bioxalato borate (LiBOB) with different molar ratios have been investigated. Their melting points (Tm) are around 42 °C. The ionic conductivities and activation energies vary drastically below and above Tm, indicating a typical feature of phase transition electrolyte. The ionic conductivity of the LiBOB/acetamide electrolyte with a molar ratio of 1:8 is 5 × 10? 8 S cm? 1 at 25 °C but increases to 4 × 10? 3 S cm? 1 at 60 °C. It was found that anode materials, such as graphite and Li4Ti5O12, could not discharge and charge properly in this electrolyte at 60 °C due to the difficulty in forming a stable passivating layer on the anodes. However, a Li/LiFePO4 cell with this electrolyte can be charged properly after heating to 60 °C, but cannot be charged at room temperature. Although the LiBOB/acetamide electrolytes are not suitable for Li-ion batteries due to poor electrode compatibility, the current results indicate that a solid electrolyte with a slightly higher phase transition temperature than room temperature may find potential application in stationary battery for energy storage where the electrolyte is at high conductive liquid state at elevated temperature and low conductive solid state at low temperature. The interaction between acetamide and LiBOB in the electrolyte is also studied by Raman and FTIR spectroscopy.  相似文献   

14.
Searching for gas exhalation around major tectonic contacts raises important methodological issues such as the role of the superficial soil and the possible long distance transport. These effects have been studied on the Xidatan segment of the Kunlun Fault, Qinghai Province, China, using measurement of the radon-222 and carbon dioxide exhalation flux. A significant radon flux, reaching up to 538 ± 33 mBq m?2 s?1 was observed in a 2–3 m deep trench excavated across the fault. On the soil surface, the radon flux varied from 7 to 38 mBq m?2 s?1, including on the fault trace, with an average value of 14.1 ± 1.0 mBq m?2 s?1, similar to the world average. The carbon dioxide flux on the soil surface, with an average value of 12.9 ± 3.3 g m?2 day?1, also remained similar to regular background values. It showed no systematic spatial variation up to a distance of 1 km from the fault, and no clear enhancement in the trench. However, a high carbon dioxide flux of 421 ± 130 g m?2 day?1 was observed near subvertical fractured phyllite outcrops on a hill located about 3 km north of the fault, at the boundary of the large-scale pull-apart basin associated with the fault. This high carbon dioxide flux was associated with a high radon flux of 607 ± 35 mBq m?2 s?1. These preliminary results indicate that, at the fault trace, it can be important to measure gas flux at the bottom of a trench to remove superficial soil layers. In addition, gas discharges need to be investigated also at some distance from the main fault, in zones where morphotectonics features support associated secondary fractures.  相似文献   

15.
T.B. Wang  H.Y. Xie  W.J. Xu 《Optik》2012,123(2):181-184
We proposed a spectrum method to determine birefraction of the sample. When the infrared incident light transmits in the birefraction direction of the cube crystal, because of the birefraction of the sample, the transmit spectrum appears interference fringes. The equation Δn = 1/[D(/dm)] shows the relationship between the birefraction and the wave-number, with the interference-number of crystals in the infrared band at room temperature. Via the infrared transmitting along the x-axis of cube lithium niobate crystal, the interference fringes were found. By the fitted polynomial method, the relationship of the birefraction and the wave-number or wavelength of the lithium niobate crystal be educed, which is, Δn = 0.4149 ? 9.00174 × 10?5υ + 5.64347 × 10?9υ2,or n = 0.05366 ? 5.20334 × 10?5λ + 3.99694 × 10?8λ2.  相似文献   

16.
We have studied the electrical and optical properties of Cu–Al–O films deposited on silicon and quartz substrates by using radio frequency (RF) magnetron sputtering method under varied oxygen partial pressure PO. The results indicate that PO plays a critical role in the final phase constitution and microstructure of the films, and thus affects the electrical resistivity and optical transmittance significantly. The electrical resistivity increases with the increase of PO from 2.4 × 10?4 mbar to 7.5 × 10?4 mbar and afterwards it decreases with further increasing PO up to 1.7 × 10?3 mbar. The optical transmittance in visible region increases with the increase of PO and obtains the maximum of 65% when PO is 1.7 × 10?3 mbar. The corresponding direct band gap is 3.45 eV.  相似文献   

17.
The series of Gd4 ? xMxAl2O9 ? x/2 (M = Ca, Sr) with x = 0, 0.01, 0.05, 0.10 and 0.25 was prepared by the citrate complexation method. Both Gd4 ? xCaxAl2O9 ? x/2 and Gd4 ? xSrxAl2O9 ? x/2 show the monoclinic cuspidine structure with space group of P21/c up to 0.05–0.1 and 0.01–0.05 mol for Ca and Sr, respectively. Beyond the substitution limit of Gd4Al2O9, GdAlO3 and SrGd2Al2O7 appear as additional phases. The highest electrical conductivity obtained at 900 °C yielded σ = 1.49 × 10? 4 S/cm for Gd3.95Ca0.05Al2O8.98. In comparison, the conductivity of pure Gd4Al2O9 was σ = 1.73 × 10? 5 S/cm. The conductivities determined are in a similar range as those of other cuspidine materials investigated previously. The thermal expansion coefficient of Gd4Al2O9 at 1000 °C was 7.4 × 10? 6 K? 1. The phase transition between 1100 and 1200 °C reported earlier changes with increasing substitution of Ca and Sr.  相似文献   

18.
Zerovalent iron (ZVI) has been demonstrated to be suitable for the dehalogenation of environmental pollutants such as chloroethenes. The construction of ZVI reactive barriers by conventional engineering measures is expensive and limited to shallow aquifers. The use of nanosized ZVI particles opens new opportunities to construct ZVI barriers with less invasive techniques. However, nanosized particles of pure ZVI are pyrophoric and react spontaneously with atmospheric oxygen.In this study, nanosized air-stable ZVI particles were produced by applying ultrasound to a solution of Fe(CO)5 in edible oil. The resulting iron nanoparticles were dispersed in a carbon matrix, and coated with a non-crystalline carbon layer of approx. 2.5 nm. Although, these nanoparticles are non-pyrophoric and stable in air, dechlorination of tetrachloroethene was demonstrated in synthetic aqueous medium and in polluted groundwater. Additionally, hydrogen was formed. Due to the larger surface area, significantly higher mass-normalized reaction rates of the novel carbon-coated nanoparticles were obtained as compared to conventional bulk ZVI material. Surface normalized pseudo-first-order-reaction rates of kSA = 3.49 × 10?3 L h?1 m?2 and 2.33 × 10?2 L h?1 m?2 were calculated for the nano-ZVI and the bulk ZVI, respectively. Dechlorination reaction products of the novel nano-ZVI were trichloroethene, cis-dichloroethene, vinyl chloride, ethene, and ethane.  相似文献   

19.
Reaction rate coefficients for the major high-temperature methyl formate (MF, CH3OCHO) decomposition pathways, MF  CH3OH + CO (1), MF  CH2O + CH2O (2), and MF  CH4 + CO2 (3), were directly measured in a shock tube using laser absorption of CO (4.6 μm), CH2O (306 nm) and CH4 (3.4 μm). Experimental conditions ranged from 1202 to 1607 K and 1.36 to 1.72 atm, with mixtures varying in initial fuel concentration from 0.1% to 3% MF diluted in argon. The decomposition rate coefficients were determined by monitoring the formation rate of each target species immediately behind the reflected shock waves and modeling the species time-histories with a detailed kinetic mechanism [12]. The three measured rate coefficients can be well-described using two-parameter Arrhenius expressions over the temperature range in the present study: k1 = 1.1 × 1013 exp(?29556/T, K) s?1, k2 = 2.6 × 1012 exp(?32052/T, K) s?1, and k3 = 4.4 × 1011 exp(?29 078/T, K) s?1, all thought to be near their high-pressure limits. Uncertainties in the k1, k2 and k3 measurements were estimated to be ±25%, ±35%, and ±40%, respectively. We believe that these are the first direct high-temperature rate measurements for MF decomposition and all are in excellent agreement with the Dooley et al. [12] mechanism. In addition, by also monitoring methanol (CH3OH) and MF concentration histories using a tunable CO2 gas laser operating at 9.67 and 9.23 μm, respectively, all the major oxygen-carrying molecules were quantitatively detected in the reaction system. An oxygen balance analysis during MF decomposition shows that the multi-wavelength laser absorption strategy used in this study was able to track more than 97% of the initial oxygen atoms in the fuel.  相似文献   

20.
A new spectroflurometric method for the determination of adenosine disodium triphosphate (ATP) is developed. Fluorometric interaction between ATP and enoxacin (ENX)–Eu3+ complex was studied using UV–vis and fluorescence spectroscopy. Weak luminescence spectra of Eu3+ were enhanced after complexation with ENX at 589 nm and 614 nm upon excitation at 395 nm due to energy transfer from the ligand to the lanthanide ion. It was observed that luminescence spectrum of Eu3+ was strongly enhanced further at 614 nm after incorporation of ATP into the ENX–Eu3+ complex. Under optimal conditions, the enhancement of luminescence at 614 nm was responded linearly with the concentration of ATP. The linearity was maintained in the range of 1.5×10?10–1.15×10?8 M (R=0.9973) with the limit of detection (3σ) of 4.71×10?11 M. The relative standard deviation (RSD) for 9 repeated measurements of 1×10?9  M ATP was 1.25%. Successful determinations of ATP in soil, milk, and a pharmaceutical formulation with the proposed method were demonstrated.  相似文献   

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