Precision Chemistry最新文献

One-dimensional (1D) functional nanowires are widely used as nanoscale building blocks for assembling advanced nanodevices due to their unique functionalities. However, previous research has mainly focused on nanowire functionality, while neglecting the structural stability and damage resistance of nanowire assemblies, which are critical for the long-term operation of nanodevices. Biomaterials achieve excellent mechanical stability and damage resistance through sophisticated structural design. Here, we successfully prepared a mechanically stabilized monolamella silver nanowire (Ag NW) film, based on a facile bubble-mediated assembly and nondestructive transfer strategy with the assistance of a porous mixed cellulose ester substrate, inspired by the hierarchical structure of biomaterial. Owing to the closely packed arrangement of Ag NWs combined with their weak interfaces, the monolamellar Ag NW film can be transferred to arbitrary substrates without damage. Furthermore, freestanding multilamellar Ag NW films with impressive damage resistance can be obtained from the monolamellar Ag NW film, through the introduction of bioinspired closely packed crossed-lamellar (CPCL) structure. This CPCL structure maximizes intra- and interlamellar interactions among Ag NWs ensuring efficient stress transfer and uniform electron transport, resulting in excellent mechanical durability and stable electrical properties of the multilamellar Ag NW films.

One-dimensional (1D) functional nanowires are widely used as nanoscale building blocks for assembling advanced nanodevices due to their unique functionalities. However, previous research has mainly focused on nanowire functionality, while neglecting the structural stability and damage resistance of nanowire assemblies, which are critical for the long-term operation of nanodevices. Biomaterials achieve excellent mechanical stability and damage resistance through sophisticated structural design. Here, we successfully prepared a mechanically stabilized monolamella silver nanowire (Ag NW) film, based on a facile bubble-mediated assembly and nondestructive transfer strategy with the assistance of a porous mixed cellulose ester substrate, inspired by the hierarchical structure of biomaterial. Owing to the closely packed arrangement of Ag NWs combined with their weak interfaces, the monolamellar Ag NW film can be transferred to arbitrary substrates without damage. Furthermore, freestanding multilamellar Ag NW films with impressive damage resistance can be obtained from the monolamellar Ag NW film, through the introduction of bioinspired closely packed crossed-lamellar (CPCL) structure. This CPCL structure maximizes intra- and interlamellar interactions among Ag NWs ensuring efficient stress transfer and uniform electron transport, resulting in excellent mechanical durability and stable electrical properties of the multilamellar Ag NW films.

Using density functional theory, we carefully calculated the relative stability of monolayer, few-layer, and cluster structures with Penta PdSe₂, T-phase PdSe₂, and Pd₂Se₃-phase. We found that the stability of Penta PdSe₂ increases with the number of layers. The Penta PdSe₂, T-phase PdSe₂, and Pd₂Se₃ monolayers are all semiconducting, with band gaps of 1.77, 0.81, and 0.65 eV, respectively. The formation energy of palladium selenide clusters with different phase structures is calculated, considering the cluster size, stoichiometry, and chemical environment. Under typical experimental conditions, Pd₂Se₃ phase clusters are found to be dominant, having the lowest formation energy among all of the phases considered, with this dominance increasing as cluster size grows. Adjusting the Pd-Se ratio in the environment allows for controlled synthesis of specific palladium selenide phases, providing theoretical insights into the nucleation mechanisms of PdSe₂ and other transition metal chalcogenides.

Using density functional theory, we carefully calculated the relative stability of monolayer, few-layer, and cluster structures with Penta PdSe₂, T-phase PdSe₂, and Pd₂Se₃-phase. We found that the stability of Penta PdSe₂ increases with the number of layers. The Penta PdSe₂, T-phase PdSe₂, and Pd₂Se₃ monolayers are all semiconducting, with band gaps of 1.77, 0.81, and 0.65 eV, respectively. The formation energy of palladium selenide clusters with different phase structures is calculated, considering the cluster size, stoichiometry, and chemical environment. Under typical experimental conditions, Pd₂Se₃ phase clusters are found to be dominant, having the lowest formation energy among all of the phases considered, with this dominance increasing as cluster size grows. Adjusting the Pd–Se ratio in the environment allows for controlled synthesis of specific palladium selenide phases, providing theoretical insights into the nucleation mechanisms of PdSe₂ and other transition metal chalcogenides.

Synthesis of functional polyethylene from ethylene alone is tricky and heavily dependent on both the type and structure of the precatalyst and the choice of cocatalyst used in the polymerization. In the present study, a series of cobalt precatalysts was prepared and investigated for ethylene polymerization under various conditions. By incorporation of strong electron-withdrawing groups (F and NO₂) and a steric component (benzhydryl) into the parent bis(imino)pyridine ligand, the catalytic performance of these precatalysts was optimized. On activation with MAO or MMAO, these precatalysts with relatively open structure achieved unprecedented ethylene polymerization rates at 60 °C (up to 27.6 × 10⁶ g mol^–1 h^–1) and remained effective at temperatures up to 100 °C. Chain growth reactions were moderate, resulting in polyethylene with molecular weights up to 61.0 kg/mol and broad bimodal dispersity index. High crystallinity and melt temperature indicated a strictly linear microstructure, as further confirmed by high-temperature ¹H/¹³C NMR measurements. Of significant note that chain termination predominantly occurred through β-elimination (up to 84.5%), yielding vinyl-terminated long-chain olefins. These functional α-macro-olefins are valuable as precursors for postfunctionalization, expanding the potential applications of polyethylene across various sectors.

Synthesis of functional polyethylene from ethylene alone is tricky and heavily dependent on both the type and structure of the precatalyst and the choice of cocatalyst used in the polymerization. In the present study, a series of cobalt precatalysts was prepared and investigated for ethylene polymerization under various conditions. By incorporation of strong electron-withdrawing groups (F and NO₂) and a steric component (benzhydryl) into the parent bis(imino)pyridine ligand, the catalytic performance of these precatalysts was optimized. On activation with MAO or MMAO, these precatalysts with relatively open structure achieved unprecedented ethylene polymerization rates at 60 °C (up to 27.6 × 10⁶ g mol^-1 h^-1) and remained effective at temperatures up to 100 °C. Chain growth reactions were moderate, resulting in polyethylene with molecular weights up to 61.0 kg/mol and broad bimodal dispersity index. High crystallinity and melt temperature indicated a strictly linear microstructure, as further confirmed by high-temperature ¹H/¹³C NMR measurements. Of significant note that chain termination predominantly occurred through β-elimination (up to 84.5%), yielding vinyl-terminated long-chain olefins. These functional α-macro-olefins are valuable as precursors for postfunctionalization, expanding the potential applications of polyethylene across various sectors.

The integration of multiple chromophore units into a single molecule is expected to improve the performance of photon upconversion based on triplet-triplet annihilation (TTA-UC) that can convert low energy photons to higher energy photons at low excitation intensity. In this study, a macrocyclic parallel dimer of 9,10-diphenylanthracene (DPA) with a precisely parallel orientation, named MPD-2, is synthesized, and its TTA-UC properties are investigated. MPD-2 shows a green-to-blue TTA-UC emission in the presence of a triplet sensitizer, platinum octaethylporphyrin (PtOEP). Compared to monomeric DPA, MPD-2 results in an enhancement of the spin statistical factor of TTA and a decrease in the excitation light intensity due to the intramolecular TTA process. The obtained structure-property relationship provides important information for the further improvement of TTA-UC properties.

The integration of multiple chromophore units into a single molecule is expected to improve the performance of photon upconversion based on triplet–triplet annihilation (TTA-UC) that can convert low energy photons to higher energy photons at low excitation intensity. In this study, a macrocyclic parallel dimer of 9,10-diphenylanthracene (DPA) with a precisely parallel orientation, named MPD-2, is synthesized, and its TTA-UC properties are investigated. MPD-2 shows a green-to-blue TTA-UC emission in the presence of a triplet sensitizer, platinum octaethylporphyrin (PtOEP). Compared to monomeric DPA, MPD-2 results in an enhancement of the spin statistical factor of TTA and a decrease in the excitation light intensity due to the intramolecular TTA process. The obtained structure–property relationship provides important information for the further improvement of TTA-UC properties.

The interfacial proton transfer (PT) reaction on the metal oxide surface is an important step in many chemical processes including photoelectrocatalytic water splitting, dehydrogenation, and hydrogen storage. The investigation of the PT process, in terms of thermodynamics and kinetics, has received considerable attention, but the individual free energy barriers and solvent effects for different PT pathways on rutile oxide are still lacking. Here, by applying a combination of ab initio and deep potential molecular dynamics methods, we have studied interfacial PT mechanisms by selecting the rutile SnO₂(110)/H₂O interface as an example of an oxide with the characteristic of frequently interfacial PT processes. Three types of PT pathways among the interfacial groups are found, i.e., proton transfer from terminal adsorbed water to bridge oxygen directly (surface-PT) or via a solvent water (mediated-PT), and proton hopping between two terminal groups (adlayer PT). Our simulations reveal that the terminal water in mediated-PT prefers to point toward the solution and forms a shorter H-bond with the assisted solvent water, leading to the lowest energy barrier and the fastest relative PT rate. In particular, it is found that the full solvation environment plays a crucial role in water-mediated proton conduction, while having little effect on direct PT reactions. The PT mechanisms on aqueous rutile oxide interfaces are also discussed by comparing an oxide series composed of SnO₂, TiO₂, and IrO₂. Consequently, this work provides valuable insights into the ability of a deep neural network to reproduce the ab initio potential energy surface, as well as the PT mechanisms at such oxide/liquid interfaces, which can help understand the important chemical processes in electrochemistry, photoelectrocatalysis, colloid science, and geochemistry.

The interfacial proton transfer (PT) reaction on the metal oxide surface is an important step in many chemical processes including photoelectrocatalytic water splitting, dehydrogenation, and hydrogen storage. The investigation of the PT process, in terms of thermodynamics and kinetics, has received considerable attention, but the individual free energy barriers and solvent effects for different PT pathways on rutile oxide are still lacking. Here, by applying a combination of ab initio and deep potential molecular dynamics methods, we have studied interfacial PT mechanisms by selecting the rutile SnO₂(110)/H₂O interface as an example of an oxide with the characteristic of frequently interfacial PT processes. Three types of PT pathways among the interfacial groups are found, i.e., proton transfer from terminal adsorbed water to bridge oxygen directly (surface-PT) or via a solvent water (mediated-PT), and proton hopping between two terminal groups (adlayer PT). Our simulations reveal that the terminal water in mediated-PT prefers to point toward the solution and forms a shorter H-bond with the assisted solvent water, leading to the lowest energy barrier and the fastest relative PT rate. In particular, it is found that the full solvation environment plays a crucial role in water-mediated proton conduction, while having little effect on direct PT reactions. The PT mechanisms on aqueous rutile oxide interfaces are also discussed by comparing an oxide series composed of SnO₂, TiO₂, and IrO₂. Consequently, this work provides valuable insights into the ability of a deep neural network to reproduce the ab initio potential energy surface, as well as the PT mechanisms at such oxide/liquid interfaces, which can help understand the important chemical processes in electrochemistry, photoelectrocatalysis, colloid science, and geochemistry.