Latest ArticlesQuantum interference (QI) effects, which offer unique opportunities to widely manipulate the charge transport properties in the molecular junctions, will have the potential for achieving high thermopower. Here we developed a scanning tunneling microscope break junction technique to investigate the thermopower through single-molecule thiophene junctions. We observed that the thermopower of 2, 4-TP-SAc with destructive quantum interference (DQI) was nearly twice of 2, 5-TP-SAc without DQI, while the conductance of the 2, 4-TP-SAc was two orders of magnitude lower than that of 2, 5-TP-SAc. Furthermore, we found the thermopower was almost the same by altering the anchoring group or thiophene core in the control experiments, suggesting that the QI effect is responsible for the increase of thermopower. The density functional theory (DFT) calculations are in quantitative agreement with the experimental data. Our results reveal that QI effects can provide a promising platform to enhance the thermopower of molecular junctions.
Near UV highly luminescent colloidal Cs2NaBiCl6 nanocrystals (NCs) were synthesized by a simple low-cost ligand-assisted reprecipitation method. In our strategy, metal chloride precursors were added to the mixture of anti-solvent and ligand at room-temperature. The obtained Cs2NaBiCl6 NCs exhibited a bright blue emission with significantly improved photoluminescence quantum yield (PLQY) of 39.05%. The optical properties and stability were greatly enhanced by doping Sb where Cs2NaBi0.75Sb0.25Cl6 showed a high PLQY of 46.57%, and both the powder and the colloidal solution exhibited superior stability.
A novel ZnII-based metal-organic framework with the formula of {[Zn2(BBIP)2(NDC)2]·H2O}n (JXUST-5) derived from 3, 5-bis(benzimidazol-1-yl)pyridine (BBIP) and 1, 4-naphthalenedicarboxylic acid (H2NDC) has been synthesized. The adjacent ZnII ions are linked through two BBIP ligands to form a [Zn2(BBIP)2] secondary building unit (SBU). The neighbouring SBUs are further connected by NDC2− with μ2-η1: η1 and μ2-η1: η1: η1 bridging modes to form a two-dimensional (2D) framework. Topological analysis shows that JXUST-5 could be simplified as an uninodal fes topology with a point symbol of {4.82}. Furthermore, the 2D framework net could be extended through C-H···π interaction to form the three-dimensional supramolecular structure. Luminescent experiments suggest that JXUST-5 could selectively and sensitively recognize Al3+ and Ga3+ through fluorescence enhancement effect along with a relatively large red shift. The detection limits for Al3+ and Ga3+ are 0.17 and 0.69 ppm, respectively. Interestingly, the sensing process for both Al3+ and Ga3+ could be directly observed with naked eyes under 365 nm UV lamp. Notably, JXUST-5 could be recycled at least five times as a fluorescent sensor toward Al3+ and Ga3+, which is the second example of turn-on MOF based fluorescent sensor toward Ga3+.
One-dimensional ultrathin nanowires (NWs) offer a great deal of promising properties for electrochemical energy storage and conversion due to their nanoscale confinement effect and high surface-to-volume ratios. It is highly desirable to precisely design and synthesize ultrathin Ti3C2 NWs in the aspect of size, crystalline structure and composition. Here, we report a simple alkalization strategy to design the ultrathin Ti3C2 NWs for hydrogen evolution reaction (HER) by modulating the surface-active sites. The design principle can well improve the amount of the defect sites and ion accessibility to increase the interactions between Ti3C2 NWs and H*. The optimized Ti3C2 NWs achieve an overpotential of 476 mV at the current density of 10 mA/cm2 and a Tafel slope of 129 mV/dec for HER catalysis, which are superior to that of Ti3C2 nanosheets and m-Ti3C2. It paves an avenue for the rational transformation of MXene bulks to one-dimensional NWs catalysts for HER.
Sulfur-containing organic compounds display wide applications in the field of materials science, synthetic chemistry, and pharmaceutical industry. Thus, numerous synthetic strategies have been developed for the synthesis of sulfur-containing compounds in synthetic chemistry. In recent years, the utilization of sulfinic acids as versatile synthons has emerged as attractive and powerful approach to access various organosulfur compounds through sulfonylation, sulfinylation or sulfenylation reactions. In this review, we summarized the recent progress in the construction of various sulfur-containing compounds from sulfininc acids. Selected examples of substrates and the related reaction mechanisms are described here. This review intends to provide readers a comprehensive understanding on the synthesis of sulfur-containing molecules from sulfinic acids and provide help for future synthetic research.
Available online Integrating transition metal centered MOFs with conductive materials is a feasible route to enhance electron transfer efficiency of materials. Herein, a composite porous structure CQDs10@NiFe-MOF-A was fabricated via introducing carbon quantum dots (CQDs) into porous NiFe-MOF. The CQDs would make partial loss of lattice in MOF during its growth, leading to the composite building block with the coexistance of crystalline region and amorphous region. The calcining treatment would produce an ultrathin protective layer as well as some lattice collapse. The synergy effect between NiFe ions effectively regulated electronic structure of metal active sites, and successful grafting of CQDs to NiFe-MOF significantly improved electrical conductivity. As expected, the catalyst exhibited outstanding OER performances with high mass activity of 91.6 A/g at overpotential of 300 mV and robust durability of 10, 000 cycles in 1 mol/L KOH, which outperformed that of noble catalyst IrO2 of 25.2 A/g. The strategy paves a feasible and effective avenue for the non-noble metal catalysts.
Owing to their high surface area, stable structure and easy fabrication, composite nanomaterials with encapsulation structures have attracted considerable research interest as sensing materials to detect volatile organic compounds. Herein, a hydrothermal route is designed to prepare foam shaped α-MoO3@SnS2 nanosheets that exhibit excellent sensing performance for triethylamine (TEA). The developed sensor, based on α-MoO3@SnS2 nanosheets, displays a high response of 114.9 for 100 ppm TEA at a low working temperature of 175 ℃ with sensitivity higher than many other reported sensors. In addition, the device shows a wide concentration detection range (from 500 ppb to 500 ppm), good stability after exposure to air for 80 days, and excellent selectivity. The superior sensing characteristics of the developed sensor are attributed to the high crystallinity of α-MoO3/SnS2, excessive and accessible active sites provided by the good permeability of porous SnS2 shells, and the excellent conductivity of the encapsulation heterojunction structure. Thus, the foam shaped α-MoO3@SnS2 nanosheets presented herein have promising practical applications in TEA gas sensing devices.
There is a great demand for high-performance hydrogen sulfide (H2S) sensors with low operating temperatures. Ag/In2O3 hexagonal tubes with different proportions were prepared by the calcination of Ag+-impregnated indium-organic frameworks (CPP-3(In)), and the developed sensors exhibit enhanced gas-sensing performance toward H2S. Gas sensing measurements indicate that the response of Ag/In2O3 (2.5 wt%) sensor to 5 ppm H2S has the highest response (119), operated at 70 ℃. The Ag/In2O3 (2.5 wt%) based sensor exhibits short response time (20 s), low detection limit (300 ppb), and good selectivity toward H2S gas, which imply that the CPP-3(In)-derived Ag/In2O3 hexagonal tube is a promising candidate to be constructed a low power-consumption H2S sensor.
We develop the effective modification strategy based on molecular engineering of s-triazine and its derivatives to improve the photoelectric performance of all-inorganic perovskites (AIP) for the first time. The surface modification strategy with cyanuric acid successfully increases the PLQY of AIP from 40.55% to 88.15%, and significantly enhances the current of the AIP film under 3 V by almost 20-fold (from 4.44 mA to 81.20 mA). This work has proven the effectiveness of improving the photoelectric performances of AIP via s-triazine and its derivatives and also suggested the potential risks of reducing the photoelectric performance of AIP due to inappropriate substituents in conjugated organic ligands.
In-situ monitoring of pesticide residues during crop growth or/and in related products is of great significance in avoiding the abuse of pesticides but remains challenging thus far. In this report, we proposed a background-free surface-enhanced Raman spectroscopy (bf-SERS) platform to non-destructively track the nitrile-bearing pesticide residues in soybean leaves with high sensitivity and selectivity. The outstanding feature of the assay stems from the dramatic Raman enhancement effect of the 50 nm-sized gold nanoparticles (AuNPs) towards the pesticides and simultaneously the background-free Raman signal of the nitrile group in the so-called Raman-silent region (1800–2800 cm‒1). This bf-SERS assay was applied to evaluate the penetration effects of nitrile-bearing pesticides and monitor their residues in soybean leaves after rinsing with various solutions, providing a reliable tool for guiding the safe use of nitrile-bearing pesticides in agriculture.
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