This study presents a time‐ and solvent‐saving method, pressurized liquid extraction (PLE), to extract polybrominated diphenyl ethers (PBDEs) in sediment samples. The effects of various operating parameters (i.e., extraction solution, temperature, pressure, static/dynamic extraction times) for the quantitative extraction of PBDEs by home‐made PLE were systematically investigated and optimized. The analytes were then identified and quantitated by gas chromatography‐mass spectrometry (GC‐MS) in selected ion monitoring (SIM) mode. The 16 PBDE congeners (from tri‐ to deca‐BDE) can be completely extracted by dichloromethane: n‐hexane (3/2, v/v) at 100 °C and 100 atm combined with 15 min static and then 15 min dynamic extraction steps. Recovery of PBDEs in spiked sediment samples ranged from 52 to 104% with 2‐16% RSD, except for BDE‐206. Limits of quantitation (LOQ) were established between 4 and 400 pg/g (dry weight) in 10 g of sediment sample. The extraction efficiency of the PLE was also compared with the traditional Soxhlet extraction method. The total contents of PBDEs ranged from 8.0 to 37.9 ng/g (dry weight) in various river and coastal sediment samples in Taiwan. Deca‐BDE (BDE‐209) was the major PBDE detected in these sediment samples. 相似文献
Three-dimensional (3D) heterostructured molybdenum disulfide (MoS2) is used as base materials for aniline monomer in situ polymerization on its surface. It is found that the aniline addition has a remarkable effect on the energy storage of the final compounds due to the improvement of the conductivity and structure stability combined with the synergistic effect between the two types of species. The optimal compound of PANI@MoS2-150 not only shows a high capacitance value of 801.4 F ⋅ g−1 at a current density of 0.5 A ⋅ g−1 but also provides a high retention rate of 77.4 % after 10,000 cycles. The capacitance fading may be due to the increase of the internal resistance analyzed by EIS. Furthermore, a flexible symmetric supercapacitor based on PANI@MoS2-150 has also been fabricated and the specific capacitance reaches 105 F ⋅ g−1 at a current density of 1 A ⋅ g−1. Impressively, the capacitance retention is larger than 100 % undergoing 10,000 cycles. Besides, the highest energy density of 21 Wh ⋅ kg−1 was obtained. Additionally, the fabricated symmetric supercapacitor demonstrates excellent flexibility. 相似文献
This paper presents different experimental results of the influence of an immersion angle (θ, the angle between the surface of a quartz crystal resonator and the horizon) on the resonant frequency of a quartz crystal microbalance (QCM) sensor exposed one side of its sensing surfaces to liquid. The experimental results show that the immersion angle is an added factor that may influence the frequency of the QCM sensor. This type of influence is caused by variation of the reflection conditions of the longitudinal wave between the QCM sensor and the walls of the detection cell. The frequency shifts, measured by varying θ, are related to the QCM sensor used. When a QCM sensor with a weak longitudinal wave is used, its resonant frequency is nearly independent of θ. But, if a QCM sensor with a strong longitudinal wave is employed, the immersion angle is a potential error source for the measurements performed on the QCM sensor. When the reflection conditions of the longitudinal wave are reduced, the influence of θ on the resonant frequency of the QCM sensor is negligible. The slope of the plot of frequency shifts (ΔF) versus (ρη)1/2, the square root of the product of solution density (ρ) and viscosity (η), may be influenced by θ in a single experiment for the QCM sensor with a strong longitudinal wave in low viscous liquids, which can however, be effectively weakened by using the averaged values of reduplicated experiments. In solutions with a large (ρη)1/2 region (0-55 wt% sucrose solution as an example, with ρ value from 1.00 to 1.26 g cm−3 and η value from 0.01 to 0.22 g cm−1 s−1, respectively), the slope of the plot of ΔF versus (ρη)1/2 is independent of θ even for the QCM sensor with a strong longitudinal wave in a single experiment. The influence of θ on the resonant frequency of the QCM sensor should be taken into consideration in its applications in liquid phase. 相似文献
The quaternary compound Rb2BaNb2Se11 has been synthesized by reacting Nb metal with an in situ formed flux of Rb2Se3, BaSe and Se at 773 K. Rb2BaNb2Se11 crystallizes in the monoclinic space group P21/c with four formula units and lattice parameters a=7.8438(5) Å, b=13.6959(6) Å, c=17.0677(13) Å, β=97.917(9)°. The structure consists of one-dimensional anionic chains formed by interconnection of dimeric [Nb2Se11] units. The chains are directed along the crystallographic c-axis with Rb+ and Ba2+ ions being located between the chains. The [Nb2Se11] units are formed by face sharing of two NbSe7 bipyramids and are joined by Se22− dianions to form infinite 1∞[Nb2Se114−] chains. The compound was characterized with infrared spectroscopy in the FIR region, Raman and UV/Vis diffuse reflectance spectroscopy. 相似文献
The highly efficient CuO-based oxygen carrier is prospectively applied in chemical-looping combustion process. The metal precursors and synthetic methods greatly affect the performance of the synthetic CuO-based oxygen carriers. The inorganic precursors are commonly used to synthesize CuO-based oxygen carriers, while the organometallic precursors are scarcely adopted. In this work, the organometallic copper precursor [copper (II) acetate] and three other different organometallic support precursors (magnesium l-lactate hydrate, silicon tetraacetate and magnesium acetate) were adopted to produce CuO-based oxygen carriers via the methods of wet-mixing and spray-drying, respectively. It is found that the synthetic oxygen carriers incorporated with inert supports (MgO and SiO2) exhibit remarkably stable redox reactivity, compared to the pure CuO. Moreover, the redox reactivity of the MgO-incorporated CuO-based oxygen carriers is superior to that of the SiO2-incorporated CuO-based oxygen carriers. It is mainly attributed to the higher Tammann temperature of MgO (1549 K) compared to that of SiO2 (937 K), which more effectively contribute CuO to inhibit particle growth and agglomeration due to sintering. Additionally, the MgO-incorporated CuO-based oxygen carriers prepared via scalable spray-drying method also exhibit the relatively high redox reactivity. It indicates that the spray-dried, synthetic CuO-based oxygen carriers from organometallic precursors possess the potential to be industrialized amplification.