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排序方式: 共有878条查询结果,搜索用时 15 毫秒
71.
A simple and highly sensitive sensor based on edge-plane pyrolytic graphite electrode (EPPGE) coated with single-wall carbon nanotubes is proposed for diclofenac determination in nanomolar concentrations. The oxidation of diclofenac occurred in two well-defined peaks having peak potentials ∼439 and ∼854 mV at pH 7.2. The modified electrode showed excellent catalytic activity presenting much higher peak currents than those measured on a bare EPPGE. Under the optimum conditions, the calibration curve was linear in the concentration range 1 × 10−9-500 × 10−9 M and 25 × 10−9-1500 × 10−9 M for peaks I and II, respectively. The limit of detection for peaks I and II was found as 0.82 × 10−9 and 22.5 × 10−9 M, respectively. The developed sensor was applied for the determination of diclofenac in biological and pharmaceutical samples using square-wave voltammetry and the validation of results using high performance liquid chromatography showed excellent agreement. 相似文献
72.
Abdollah Karami Reem Shomal Rana Sabouni Sana Z. M. Murtaza Mehdi Ghommem 《加拿大化工杂志》2023,101(5):2660-2676
In this work, TiO2 and ZnO were incorporated successfully into a MIL-53(Al) metal–organic framework (MOF) to form nanocomposites via a facile post-modification technique. The hybrid MIL-53(Al)@TiO2 and MIL-53(Al)@ZnO were characterized by several characterization tests. The X-ray diffraction (XRD), Fourier-transform infrared (FTIR), and field-emission scanning electron microscopy (FE-SEM) analyses showed evidence of the successful incorporation of TiO2 and ZnO within the MIL-53(Al) framework. The thermal gravimetric analysis (TGA) analysis demonstrated the excellent thermal stability of MIL-53(Al)@TiO2 and MIL-53(Al)@ZnO, while diffuse reflectance spectroscopy (DRS) determined the direct optical band gaps of MIL-53(Al)@ZnO and MIL-53(Al)@TiO2 to be 3.24 and 3.34 eV, respectively. The composites were also tested for the photocatalytic degradation of diclofenac (DCF) as a micropollutant. The DCF degradation efficiency of the photocatalysts was ranked in the following order: MIL-53(Al)@TiO2 > MIL-53(Al) > TiO2 > ZnO > MIL-53(Al)@ZnO. The incorporation of TiO2 enhanced the optical properties of MIL-53 (Al), which was confirmed with the superior photodegradation efficiency of MIL-53(Al)@TiO2 (>85% in 2 h) as compared to the pristine MIL-53(Al) (around 80% in 2 h). The improvement in the photodegradation of the hybrid-MOF is mostly associated with the possible dual function of the adsorption and photodegradation mechanisms. The reusability of MIL-53(Al) and its composites was inspected over 3 cycles of photodegradation experiments with DCF. The photocatalytic activity of MIL-53(Al)@TiO2 remained unchanged (>90%), while for MIL-53(Al) and MIL-53(Al)@ZnO a slight drop was observed over three cyclic degradation experiments. Fluorescence measurements revealed that the hydroxyl radical is an important reactive oxygen species produced by all the photocatalysts that aid in the photodegradation of DCF. Furthermore, the kinetic modelling of the photoreaction identified a second-order kinetics for all catalysts. Experiments with scavengers showed that hydroxyl radicals played a major role in the photocatalytic process, and it was found that only 2 h of treatment was sufficient to obtain a considerable chemical oxygen demand (COD) reduction of 58%. 相似文献
73.
Investigation on Sodium Benzoate Release from Poly(Butylene Adipate‐Co‐Terephthalate)/Organoclay/Sodium Benzoate Based Nanocomposite Film and Their Antimicrobial Activity
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Dibyendu Mondal Biplab Bhowmick Dipanwita Maity Md. Masud R. Mollick Dipak Rana Vivek Rangarajan Ramkrishna Sen Dipankar Chattopadhyay 《Journal of food science》2015,80(3):E602-E609
Polymeric nanocomposites embedded with nontoxic antimicrobial agents have recently gained potential industrial significance, mainly for their applicability to preserve food quality and ensure safety. In this study, a poly(butylene adipate‐co‐terephthalate) (PBAT)/organoclay (CMMT) based nanocomposite film doped with sodium benzoate (SB) as antimicrobial agent was prepared by a solution mixing process. A homogenous dispersion of organoclay (cetyltrimethylammonium‐modified montmorillonite [CMMT]) in PBAT matrix was observed by X‐ray diffraction and transmission electron microscopy. PBAT/CMMT nanocomposite film showed higher barrier properties against water and methanol vapor compared to the PBAT film. The release of SB from PBAT and its nanocomposite film was measured and the relevant data were fitted to the Weibull model. The higher values of Weibull's shape factor and scale parameter as corroborated by experimental findings indicated faster rate of SB release from PBAT/CMMT/SB nanocomposite film, when compared to the pristine PBAT film. Bacterial inhibition studies were accomplished against 2 food pathogenic bacteria, Bacillus subtilis and Staphylococcus aureus, by determining the zone of inhibition and corresponding growth profiles. Both bacterial inhibition studies and growth profiles established that PBAT/CMMT/SB demonstrated better antimicrobial activity than PBAT/SB film. Therefore, PBAT/CMMT/SB nanocomposite film can be used for food packaging application as it showed good barrier properties and antimicrobial activity against food pathogenic bacteria. 相似文献
74.
75.
Rayisa Voytovych Rana Israel Noelia Calderon Fiqiri Hodaj Nicolas Eustathopoulos 《Journal of the European Ceramic Society》2012,32(14):3825-3835
The fundamental issues of the reaction at liquid Si/graphite interfaces between Si melting point (1412 °C) and 1600 °C are studied on the basis of results obtained with polycrystalline graphite concerning the growth kinetics of the interfacial reaction layer and the microstructure and morphology of this layer. Experiments were also performed using vitreous carbon substrates. Results are also reported for Si–Al alloys at 1000 °C. The elementary process controlling the growth kinetics is determined and a model is proposed to describe the different stages of the interfacial reaction. 相似文献
76.
Swati Ghosh Vishav Preet Singh Rana Vivekanand Kain Vivek Mittal S.K. Baveja 《Materials & Design》2011,32(7):3823-3831
Effect of residual stress generated during tube fabrication, roll expansion and machining of stainless steel on the stress corrosion cracking (SCC) susceptibility was studied by testing fabricated tubes, tube–tube sheet joint and heavily machined plate of austenitic stainless steel (SS) in boiling MgCl2. U bend samples of machined plate were exposed to acidified SO4 + Cl? environment at room temperature to study its ambient temperature SCC behavior. The results correlate the SCC behavior of the SS tubes and roll expanded joints to the nature and magnitude of residual stresses present. The study also highlights the distinct difference in ambient temperature SCC behavior of machined vs. nonmachined surfaces. 相似文献
77.
In present communication, we propose a modified resource allocation strategy, namely, hybrid connection algorithm, for achieving efficient restoration in WDM optical networks. The main theme of the algorithm is that, while attempting connection establishment, a wavelength is reserved in advance for providing resources for backup lightpaths. The analysis and the comparison of the proposed strategy with other existing strategies has been undertaken using metrics such as, restoration efficiency, number of wavelength links used by primary and backup lightpaths, and the percent link utilization. The proposed strategy provides 100% restoration efficiency and much better performance than the existing techniques. 相似文献
78.
79.
80.
Crop Reference Evapotranspiration: A Discussion of the Concept,Analysis of the Process and Validation 总被引:2,自引:0,他引:2
The study at first recalls the concept of “potential evapotranspiration” (PET), originally considered equal to the evaporation
climatic demand; then, it reminds the steps of its progressive evolution toward the concept of “reference crop evapotranspiration”
(ET0) determined on irrigated grass. A physical analysis conducted on the evaporation process is subsequently reported to help
clarifying the links between ET0 and evaporation climatic demand. This analysis clearly demonstrates that the equivalence of ET0 to evaporation climatic demand is not correct, although still common assumption in recent scientific literature, particularly
in hydrology. The study also identifies two processes acting in opposite directions in the dynamics of ET0: (1) the climatic variables determining the evaporation demand, and (2) the canopy resistance which slows down the response
of irrigated grass to such demand. The analysis of the respective impact of these two processes on ET0 dynamics shows that the available energy is the dominant process. This variable takes into account the 60–70% of the variation
of ET0, both at hourly and daily scales, while canopy resistance only explains 10–20% of ET0 variation of irrigated grass. The study regards different climatic situations. Possible effects on practical applications
were also discussed in the conclusions, together with comments on the correct canopy resistance modelling. 相似文献