查看更多>>摘要：Four new Bi(III) phosphates, K_6Bi_(13)(PO_4)_(15), K_5Bi(P_2O_7)_2, and A_5Bi_5(PO_4)_4(P_2O_7)_2 (A= K, Rb) with the different condensed P-0 groups have been successfully synthesized via the solid-state reactions. The single crystals X-ray diffractions show that they crystallize in the different space groups (K_6Bi_(13)(PO_4)_(15): C2; K_5Bi(P_2O_7)_2: P1; K_5Bi_5(PO_4)_4(P_2O_7)_2 and Rb_5Bi_5(PO_4)_4(P_2O_7)_2: P2_1/c). The structure of K_6Bi_(13)(PO_4)_(15) can be described as a three-dimensional (3D) network composed of the Bi-0 polyhedra and PO_4 tetrahedra with K atoms filling in the space to balance the residual charges. K_5Bi(P_2O_7)_2 features 2D [BiP_4O_(14)]_∞, layers built by the BiO_6 oc-tahedra and P_2O_7 dimers and the adjacent [BiP_4O_(14)]_∞ layers are bridged by the K atoms. A_5Bi_5(PO_4)_4(P_2O_7)_2 (A = K, Rb) contain two different condensed P-0 groups, PO_4 tetrahedra and P_2O_7 dimers, which are connected by Bi-0 polyhedra to construct the complicated 3D framework with K/Rb atoms located in the tunnels. Note that, the compounds that simultaneously contain two different types of P-0 groups are still rare in phosphates. Detailed structural comparisons of Bi~(3+)-containing phosphates indicate that the Bi/P ratios have a significant effect on the condensed degrees of PO_4 groups. Furthermore, TG-DSC, IR, UV-Vis-NIR diffuse reflectance spectra and SHG test for title compounds have also been reported.
查看更多>>摘要：Enthalpic interaction between the elements determines the stability of the local structures in the alloy system. Multicomponent synergistic effect is expected to improve the thermal stability and the relevant properties, by regulating the enthalpic interaction. In this work, the composition of Cu-Ni-Sn alloys is explained by introducing the cluster-plus-glue-atom mode, and the strong and weak enthalpic interaction elements Si and Zn, respectively, are chosen for multi-componentization of Cu-Ni-Sn alloys. The results demonstrate that the synergistic effect of Zn and Si improves the stability of both the Cu matrix and D0_(22) or L1_2-γ' phase, inhibits the discontinuous precipitation effectively and gains a notable higher strength-over-resistivity ratio (H_(R/ρR)) than the Cu-15Ni-8Sn (wt. %) (C72900) alloy. After adding Si and Zn, the reinforcing enthalpic interaction between the elements is the crucial factor for the stability enhancement of the alloys, and it is embodied by two aspects: (a) the reducing elastic strain energy in the solution treated alloys; (b) the more homogeneous surface potential and the higher work function in the age treated alloys. Additionally, Compared with the Cu_(80)Ni_(15)Sn_5 alloy that based on the ideal cluster formula, the Cu_(79.68)Ni_(15.63)Sn_(4.69) alloy, based on the modified cluster formula: {[Cu-Cu_xNi_(12-x)]Cu_3}_a{[Sn-Ni_yCu_(12-y)]Sn_3}_(16-a), possesses a preferable thermal stability whatever solution treated or age treated state, and exhibits a decreasing amount of discontinuous precipitation although has a slightly lower H_(R/ρR), which is beneficial to the improvement of the workability of the alloys. The modified cluster formula is more suitable for the compositional design of Cu-Ni-Sn alloys. The work provides an effective theoretical and experimental basis for the composition design of high stability Cu-Ni-Sn alloys.
查看更多>>摘要：Lead selenide (PbSe) is one of the most promising materials for the uncooled mid-IR detectors. Sensitization of PbSe consists of thermal treatment in the oxygen/iodine atmosphere, and was experimentally examined before. However, there were no computational studies supporting the experiments. Density functional theory (DFT) calculations have been applied for better understanding of the influence of iodine and oxygen dopants have on PbSe crystal lattice, band structure, conductance. Calculations proved that oxygen induces a more robust effect on band structure, while iodine reduces work function, increasing surface reactivity. Structural characterizations confirmed the crystallization of the lead selenite phase, during sensitization in oxygen, while the new Pb_3Se_2(IO_3)_2 phase crystallized during sensitization in iodine/oxygen rich atmosphere. U/I characterization confirmed IR sensitivity of the samples treated at 400 °C in oxygen rich atmosphere for 3 h, and for the samples treated in the iodine/oxygen rich atmosphere at 375 °C for just twenty minutes.
查看更多>>摘要：Nano-structured metallic oxides and carbon composites (NiO@C, Fe_3O_4@C and NiFe_3O_4@C) are successfully fabricated by the low-temperature calcinations of Ni/Fe precursors in an inert atmosphere. Density functional theory calculations show that atom rearrangements of NiFe_3O_4@C in unit cells are observed with respect to NiO@C and Fe_3O_4@C, leading to the altered exposed crystal planes and oxygen atoms redistributions on these exposed planes. Likewise, the metallic electron distributions are also changed within NiFe_2O_4@C due to bimetallic synergistic effects. In such fabricated scheme with the terephthalic acid template, the unique morphologies and structural characteristics of NiFe_2O_4@C are obtained with oxygen-rich exposed crystal planes, which are conductive to improving the conductivity, accommodating volume changes, providing rapid electron and Li ion transportations. Compared with NiO@C and Fe_3O_4@C, the fabricated NiFe_2O_4@C as lithium ion anodes can achieve the extremely high discharge capacity of 1808.8 mAh g~(-1) at 100 mA g~(-1) impressive reversible capacity of 1153.6 mAh g~(-1) after 200 cycles at 500 mA g~(-1) and average capacity of 647.1 mAh g~(-1) at 5000 mA g~(-1). The full battery is also assembled by NiFe_2O_4@C and LiNi_(0.8)Co_(0.1)Mn_(0.1)O_2 as anode and cathode, and shows a superior high specific energy of 432.0 Wh kg~(-1), which is far higher (1.5 times) than commercial full batteries.
查看更多>>摘要：Semiconductor catalyst with high photocatalytic activity can be exploited via heterojunction. In this study, a new S-scheme SrTiO_3/porous ZnO composite was rationally devised, successfully prepared by utilizing a two-step pyrolysis of SrTiO_3/ZIF-8, and analyzed by various characterization technologies including XRD, SEM, TEM, BET, XPS, PL, UV-vis DRS, and photoelectrochemical and DFT theoretical calculations. A porous structure, tight contact, and a heterojunction formed between SrTiO_3 and porous ZnO (ZnOT) can be observed by SEM and TEM images. BET testing indicates that the SrTiO_3/porous ZnO composite (S3ZT) shows the highest specific surface area (30.37 m~2/g). The band gap values (E_g) of SrTiO_3 and ZnOT are around 3.17 and 2.95 eV, which agree with those obtained from DFT calculations. Compared to other samples, the SrTiO_3/porous ZnO composite (S3ZT) shows higher light absorption and lower transfer resistance as demonstrated by UV-vis DRS and EIS results. S3ZT presents a superior photocatalytic efficiency of 48.8% in degrading 5 mg/L methyl orange (MO) irradiated by 1 h UV-vis light, which are 7- and 1.5-fold higher than pristine SrTiO_3 and ZnOT, respectively. Moreover, based on Mott-Schottky theory, active species trapping experiments, XPS determination, and DFT calculations (energy band gap and work function), it was shown to be reasonable to utilize the S-scheme charge migration process for an explanation regarding the better photocatalytic activity of SrTiO_3/porous ZnO composite. Overall, this work will provide an effective protocol for devising and preparing semiconductor photocatalysts with S-scheme heterojunction by utilizing the superior characteristics of MOFs.
查看更多>>摘要：We fabricate the Ag/TaO_x/TiN device and confirm the structure of the element with transmission electron microscopy (TEM) and energy dispersive spectroscopy line scan (EDS). The device shows non-volatile bipolar resistive switching as well as volatile threshold switching. In order to identify the threshold switching, the first reset voltage is needed to activate the device and check how much the current level decreases by the reset voltage. The current gradually increases and drops at a relatively high compliance current (CC) with positive and negative values, respectively. To demonstrate the temporal learning in the volatile switching with short-term memory effect, the states of [1111], [1001], and [1000] 4-bits are controlled by applying different pulse streams, which outputs the letter "P" in the reservoir computing system. At the lowest CC, the abrupt threshold switching is obtained, and the relaxation time in transient measurement is investigated depending on the voltage amplitude.
查看更多>>摘要：A sensing platform based on porous ZnO/Co_3O_4 is introduced for determination of hydrazine in alkaline media. The bimetallic oxides were prepared by calcination of bimetallic zeolitic imidazolate framework (Zn/ CoZIF) as a sacrificial template. Zn/CoZIF and ZnO/Co_3O_4 were characterized via several techniques. The porous ZnO/Co_3O_4 was utilized to modify glassy carbon electrode (ZnO/Co_3O_4/GCE), followed by immobilization of Au nanoparticles (NPs) on its surface to prepare Au/ZnO/Co_3O_4/GCE. The electrode exhibited two linear ranges of 2-1900 μM and 1900-8500 μM with sensitivity of 0.058 and 0.048 μA μM~(-1) for determination of hydrazine in aqueous solution. The sensor showed remarkable lower oxidation potential and limit of detection rather than ZnO/Co_3O_4/GCE. Furthermore, the sensor displayed acceptable selectivity toward oxidation of hydrazine in the presence of some interfering species. The results confirm that Au/ZnO/ Co_3O_4/GCE can be considered as sensitive and reliable sensor toward the oxidation of hydrazine due to the porous structure of ZnO/Co_3O_4, high conductivity of Au NPs, and the synergic effect among the constituents.
查看更多>>摘要：In this work, a novel CoMn_2O_4@CoMn_2S_4 core-shell nanocluster@nanosheet was successfully grown onto Ni foam via a hydrothermal reaction, which omitted the addition of a binder and conductive additive and the need for a complicated electrode preparation process. CoMn_2S_4 nanosheets as "shells" were found to be uniformly distributed on the surface of CoMn_2O_4 nanoclusters as "cores" to form a typical core-shell structure. These structures possess a high specific surface area and abundant active sites, which not only shorten the transmission path for electrons and ions, but also prevent collapse of the structure, thus improving its cycling stability. The specific capacity of CoMn_2O_4@CoMn_2S_4 is 1542.0 C g~(-1) at a current density of 1 A g~(-1) which is 3.1 times higher than that obtained for CoMn_2O_4. Moreover, CoMn_2O_4@CoMn_2S_4 shows excellent electrochemical cycling performance, and the specific capacity retention rate for CoMn_2O_4@CoMn_2S_4reaches 95.81% after 5000 cycles at a current density of 20 A g~(-1). The specific energy of the CoMn_2O_4@CoMn_2S_4 reaches 44.30 Wh kg~(-1) at a specific power of 774.98 W kg~(-1). Therefore, the CoMn_2O_4@CoMn_2S_4//AC device shows excellent practical application capability.
查看更多>>摘要：Prussian White (PW) layers were deposited on Au/Cr/Si substrates by electrodeposition and characterized by different techniques. Scanning electron microscopy (SEM) images and Raman mapping reveal a uniform and homogeneous deposit while scanning transmission electron microscopy (STEM) images disclose the grain boundary pattern and the thickness of 300 nm of the PW layer. Resistive switching (RS) effect with an ON/OFF ratio of about 10~2 was observed. The RS mechanism was investigated from the log-log current-voltage plots. Ionic conduction was observed with an activation energy of 0.4 eV that could be associated with potassium ions as possible charge carriers at the grain boundaries. The endurance characteristics were investigated and a stable abnormal RS was observed for consecutive 500 cycles. Moreover, the retention was also evaluated and the high resistive state (HRS) and low resistive state (LRS) were stable up to 1000 s.
查看更多>>摘要：Due to rampant misuse of antibiotics, certain bacterial organisms have developed resistance against them as a result of genetic modifications, rendering a lot of the traditionally used antibiotics ineffective. Thus, introduction of a new class of antibacterial materials is paramount. This article reports exploring the comparative performances of monometallic Au, bimetallic AuPt and trimetallic AUPtCu as potential antibacterial agents for the future. The materials were obtained as nanofluids via a one-pot microwave synthesis procedure and subsequently were subjected to characterization by high-resolution electron microscopy, dynamic light scattering, X-ray diffraction, absorption spectroscopy and X-ray photoelectron spectroscopy, etc. It was found that the multimetallic particles were composed of several bimetallic alloy nano-islands and with increasing number of components the particle size became smaller and the mi-crostructure became littered with defects. This had a profound effect on the antibacterial activity as the trimetallic AuPtCu was found to be the most effective against both the gram-negative and gram-positive bacterial strains. A detailed rationalization for the same has been provided based on the analysis of the structure-property-activity correlation. We anticipate the findings to be really important going forward; in the research and fabrication of new age medicines against drug-resistant micro-organisms.
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Elsevier