Activity

This study provides molecular insights into the structural and energetic characteristics that determine the formation of pre-nucleation clusters between SO2 and a volatile organic compound like cyclohexanol.To maximize the potential of transition-metal dichalcogenides (TMDCs) in device applications, the development of a sophisticated technique for stable and highly efficient carrier doping is critical. Here, we report the efficient n-type doping of monolayer MoS2 using KOH/benzo-18-crown-6, resulting in a doped TMDC that is air-stable. MoS2 field-effect transistors show an increase in on-current of three orders of magnitude and degenerate the n-type behaviour with high air-stability for ∼1 month as the dopant concentration increases. Transport measurements indicate a high electron density of 3.4 × 1013 cm-2 and metallic-type temperature dependence for highly doped MoS2. First-principles calculations support electron doping via surface charge transfer from the K/benzo-18-crown-6 complex to monolayer MoS2. Patterned doping is demonstrated to improve the contact resistance in MoS2-based devices.Nickel transition-metal catalysts are important materials which are widely used in (de)hydrogenation reactions. Typical NiII catalysts adopt a square planar geometry and a low-spin state owing to their d8 electronic configuration. Here, we describe a mechanistic investigation of a novel octahedral NiII catalyst with a paramagnetic nature catalysing the α-alkylation of amides. Both non-bifunctional and bifunctional pathways were considered. In addition, we clarified the superiority of the high-spin state by comparing the geometries, valence electronic configurations, and rate-limiting energy barriers of the high- and low-spin states. Our results indicate that the novel octahedral nickel catalyst favours the bifunctional pathway and tends to maintain a high-spin state throughout the reaction due to the N-arm ligand. This computational study suggests that the spin state has the potential to influence the catalyst structure and reaction mechanism. Furthermore, these findings present novel insights for the design of NiII catalysts with high-spin states.The peroxymonosulfate (PMS) activation reaction using transition-metal-based catalysts has been proven to be a promising approach for the degradation of refractory organic contaminants; however, the ambiguous structure-property relationship between the intrinsic free-radical and non-radical mechanistic pathway selectivity and structural characteristics greatly hinders the development of active catalysts. KRIBB11 Taking Ni(OH)2 as a model catalyst, this work reveals that the pathway selectivity during PMS activation can be controlled via the construction of crystalline and amorphous structures. Electron paramagnetic resonance and radical quenching experiments verified that amorphous Ni(OH)2 with disordered -OH, synthesized via a formamide-assisted precipitation method, dramatically promotes the generation of ˙OH and SO4˙- (the radical pathway), which highly improved the degradation efficiencies toward organic contaminants. However, crystalline Ni(OH)2 was found to activate PMS through via a non-radical pathway. Density functional theory calculations reveal that amorphous Ni(OH)2 possesses an electron-rich active surface, which favors the breaking of O-O bonds instead of O-H bonds in PMS molecules and triggers radical production. As confirmed via electrochemical measurements, the essence of PMS activation was uncovered; it was found that pathway selectivity was determined based on the electron-donating capabilities, which were highly dependent on the -OH group environments. Impressively, the catalytic mechanism of the same material can be successfully and precisely regulated from a non-radical to a radical pathway for PMS activation via a structural engineering method, which can simultaneously improve the catalytic performance for the effective elimination of emerging contaminants in aquatic environments.The surface activation of titanium plays a key role in the biological properties of titanium implants as bone repair materials. Improving the ability to induce apatite precipitation on the surface was a well-accepted titanium bioactivation route. In this study, advanced femtosecond laser microfabrication was applied to modify titanium surfaces, and the effect of femtosecond laser etching on apatite precipitation was investigated and compared with popular titanium modification methods. Meanwhile, the mechanism of apatite formation after femtosecond laser modification was interpreted from the point of materials science. The surface physical-chemical characterization results showed that femtosecond laser etching can improve the surface hydrophilicity and increase the surface energy. Compared with traditional abrasive paper and acid-alkali treatment, this method increased the contents of active sites including titanium oxide and titanium-hydroxyl on titanium surfaces. TiO2 on the surface was transformed to TiO after femtosecond laser treatment. The samples etched with 0.3 W and 0.5 W femtosecond lasers had a better ability to induce apatite deposition than those treated with traditional mechanical treatment and popular acid-alkali modification, which would lead to better bioactivity and osteointegration. Considering the technical advantages of femtosecond lasers in microfabrication, it provides a more efficient and controllable scheme for the bioactivation of titanium. This research would improve the application potential of femtosecond laser treatment, such as micropattern preparation and surface activation, in the field of biomaterials.A lithium-sulfur (Li-S) battery is considered a promising next-generation secondary battery owing to its high theoretical capacity and energy density. However, the volume change and poor conductivity of sulfur, and the shuttle effect, restrict its practical applications. Herein, we develop a yolk-shell Fe3O4@S@C nanochain as the Li-S battery cathode in which sulfur is encapsulated between the Fe3O4 core and the carbon shell. After cycling 500 times at 0.2C, the Fe3O4@S@C nanochains exhibit a stable capacity of 625 mA h g-1 and a coulombic efficiency exceeding 99.8%. When measuring at temperatures of -5 and 45 °C, the capacities remain stable, and a well-reversible rate performance under repeated testing for three rounds is also achieved. Furthermore, density functional theory (DFT) calculations show large adsorption energies of Fe3O4 towards polysulfides, indicating the capability of suppressing the shuttle effect during long-term charge and discharge.