A free-standing graphene oxide film (GOF) obtained by self-assembly at a liquid/air interface was annealed in a confined space between two stacked substrates to form a free-standing highly conductive ...graphene film. Characterization indicates that the oxygen-containing functional groups (e.g. epoxy, carboxyl, and carbonyl) were removed as small molecules (e.g. H
2O, CO
2, and CO) during the annealing, meanwhile the size of sp
2 domains in the film was decreased. When annealed between two stacked wafers, random interlayer expansion and fractional movement in the GOF were suppressed by the pressure-induced friction, which helps preserve the morphology of the film. The conjugation in the basal plane of graphene and π–π interactions between well stacked graphene sheets favor the transportation of charge carriers in the film, to produce a good electrical conductivity of the resulting free-standing reduced GOF (increased from 1.26
×
10
−5 to 272.3
S/cm).
Clay minerals are efficient adsorbents for metal ions and have been widely used to control heavy metals, while a number of critical issues remain elusive. In this study, the fully flexible models for ...smectites (montmorillonite and beidellite) nanoparticles are developed and then subject to molecular dynamics simulations. Edge rather than basal and interlayer surfaces show much higher adsorption efficacy, and therein univalent metal ions always cause excessive adsorption. For montmorillonite, inner-sphere Pb2+ ions emerge and predominate only at edge surfaces, and have higher stability than inner-sphere Na+ ions, manifesting the central role of edge surfaces to remove heavy metals. The peculiar distribution of edge-O atoms causes similar coordination environments for inner- and outer-sphere metal ions, and inner-sphere metal ions are preferred significantly due to bonding with edge-hydroxyls. Metal ions with smaller radii are more favorable to adsorb at edge surfaces, and those with considerable hydration effects (e.g., heavy metals) can be preferred. Edge surfaces of montmorillonite rather than beidellite are more efficient for adsorption, mainly as a result of distinct adsorption behaviors at basal surfaces that show reversed trends. (010) rather than (110) edges are superior for adsorption, which is caused mainly by structural differences. (010) edges are more exposed to adsorbates, and cleavage of smectites nanoparticles along (010) edges enhances removal of heavy metals. Diffusion, mobility and stability of adsorbed metal ions are also discussed, which further understanding of adsorption at edge surfaces. The findings are consistent with experimental observations available and provide new insights to the complicated processes at clay minerals/water interfaces including control of heavy metals.
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•Fully flexible models for smectites nanoparticles with edges have been developed.•Edges prefer inner-sphere adsorption and play a central role to control heavy metals.•Ionic radius (decisive) and hydration effect affect adsorption of metal ions at edges.•Edges of montmorillonite rather than beidellite are more efficient for adsorption.•(010) rather than (110) edges are obviously superior for adsorption.
The electrocatalytic nitrogen reduction reaction (NRR) is one of the most promising ways to achieve NH3 production at room temperature and pressure. However, there exists significant disagreement ...between the theoretically predicted potentials required for the NRR by the conventional quantum–theoretical calculations and those observed experimentally. Here, an explicit computational model incorporating the solvation effect and electrode potential has been proposed for NRR on single iron atoms supported on nitrogen-doped graphene. We find that the aqueous environment plays an essential role in NRR by promoting N2 adsorption, whereas the electrode potential impacts considerably on the electrode–electrolyte interface where NRR occurs. The constrained molecular dynamics (cMD) simulations and a thermodynamic integration method are used to explore the free energy profiles of N2 adsorption and the proton transfer process. The results are consistent with experimental observations, i.e., the NRR can take place at a relatively low electrode potential, thus revealing the critical role of the explicit inclusion of the solvation effect and electrode potential in computationally studying electrochemical reactions. With this approach, we have provided atomic-level mechanistic insights into the electrode–electrolyte interface for NRR through electrochemical catalysis.
Single‐atom catalysts (SACs) have attracted extensive attention owing to their high catalytic activity. The development of efficient SACs is crucial for applications in heterogeneous catalysis. In ...this article, the geometric configuration, electronic structure, stabilitiy and catalytic performance of phosphorene (Pn) supported single metal atoms (M=Ru, Rh, Pd, Ir, Pt, and Au) have been systematically investigated using density functional theory calculations and ab initio molecular dynamics simulations. The single atoms are found to occupy the hollow site of phosphorene. Among the catalysts studied, Ru‐decorated phosphorene is determined to be a potential catalyst by evaluating adsorption energies of gaseous molecules. Various mechanisms including the Eley‐Rideal (ER), Langmuir‐Hinshelwood (LH) and trimolecular Eley‐Rideal (TER) mechanisms are considered to validate the most favourable reaction pathway. Our results reveal that Ru−Pn exhibits outstanding catalytic activity toward CO oxidation reaction via TER mechanism with the corresponding rate‐determining energy barrier of 0.44 eV, making it a very promising SAC for CO oxidation under mild conditions. Overall, this work may provide a new avenue for the design and fabrication of two‐dimensional materials supported SACs for low‐temperature CO oxidation.
Monolayer phosphorene (Pn) supported single‐atom catalysts (SACs) with strong metal‐support interactions were designed, in which Ru−Pn SAC exhibits outstanding thermal stability and superior CO oxidation catalytic performance. This kind of material of phosphorene supported SACs may become promising for CO oxidation with high activity.
Single-atom site catalysts (SACs) have been used in multitudinous reactions delivering ultrahigh atom utilization and enhanced performance, but it is challenging for one single atom site to catalyze ...an intricate tandem reaction needing different reactive sites. Herein, we report a robust SAC with dual reactive sites of isolated Pt single atoms and the Ni3Fe intermetallic support (Pt1/Ni3Fe IMC) for tandem catalyzing the hydrodeoxygenation of 5-hydroxymethylfurfural (5-HMF). It delivers a high catalytic performance with 99.0% 5-HMF conversion in 30 min and a 2, 5-dimethylfuran (DMF) yield of 98.1% in 90 min at a low reaction temperature of 160 °C, as well as good recyclability. These results place Pt1/Ni3Fe IMC among the most active catalysts for the 5-HMF hydrodeoxygenation reaction reported to date. Rational control experiments and first-principles calculations confirm that Pt1/Ni3Fe IMC can readily facilitate the hydrodeoxygenation reaction by a tandem mechanism, where the single Pt site accounts for C=O group hydrogenation and the Ni3Fe interface promotes the C–OH bond cleavage. This interfacial tandem catalysis over the Pt single-atom site and Ni3Fe IMC support may develop new opportunities for the rational structural design of SACs applied in other heterogeneous tandem reactions.
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•The furfural hydrogenation mechanisms are systematically investigated in vapor phase and aqueous phase.•A proton-shuttling mechanism in aqueous phase is proposed.•The presence of ...water enhances the stability and activity of reaction intermediates.•The dynamic charge separation between the catalyst and the intermediates results in low hydrogenation barriers.
The catalytic hydrogenation of biomass-derived compounds in the aqueous phase is crucial to upgrading renewable biochemicals and biofuels. Herein, by combining density functional theory (DFT) and ab initio molecular dynamics (AIMD) simulations, we have explored the selective hydrogenation mechanism of furfural on the copper surface with a fully explicit solvation model. The presence of water solvent could significantly affect the reaction mechanism, in adjunct with the charge interactions between the reaction intermediates and the Cu surface. It demonstrates a proton-shuttling mechanism for furfural hydrogenation where the initial hydrogen source for reducing the carbonyl group is from the dissociation of the adjacent water. Furthermore, the water solvation effect results in the dynamic charge separation between the copper surface and the reaction intermediates, significantly reducing the energy barrier. These results deepen our mechanistic understanding of selective hydrogenation of furfural over Cu-catalysts, paving the way for upgrading renewable biomass derivatives in applications.
The development of efficient enzyme immobilization to promote their recyclability and activity is highly desirable. Zeolitic imidazolate framework‐8 (ZIF‐8) has been proved to be an effective ...platform for enzyme immobilization due to its easy preparation and biocompatibility. However, the intrinsic hydrophobic characteristic hinders its further development in this filed. Herein, a facile synthesis approach was developed to immobilize pepsin (PEP) on the ZIF‐8 carrier by using Ni2+ ions as anchor (ZIF‐8@PEP‐Ni). By contrast, the direct coating of PEP on the surface of ZIF‐8 (ZIF‐8@PEP) generated significant conformational changes. Electrochemical oxygen evolution reaction (OER) was employed to study the catalytic activity of immobilized PEP. The ZIF‐8@PEP‐Ni composite attains remarkable OER performance with an ultralow overpotential of only 127 mV at 10 mA cm−2, which is much lower than the 690 and 919 mV overpotential values of ZIF‐8@PEP and PEP, respectively.
A facile synthesis approach was developed to immobilize enzyme on the ZIF‐8 carrier by using Ni2+ ions as anchor, which can significantly promote the recyclability and activity of the enzyme.
The non-contact three-dimensional measurement and reconstruction techniques have played a significant role in the packaging and transportation of precious cultural relics. This paper develops a ...structured light based three-dimensional measurement system, with a low-cost for cultural relics packaging. The structured light based system performs rapid measurements and generates 3D point cloud data, which is then denoised, registered and merged to achieve accurate 3D reconstruction for cultural relics. The multi-frequency heterodyne method and the method in this paper are compared. It is shown that the relative accuracy of the proposed low-cost system can reach a level of 1/1000. The high efficiency of the system is demonstrated through experimental results.
Cuproptosis is a novel copper-dependent form of programmed cell death, displaying important regulatory functions in many human diseases, including cancer. However, the relationship between the ...changes in mitochondrial viscosity, a key factor associated with cellular malfunction, and cuproptosis is still unclear. Herein, we prepared a phosphorescent iridium (Ir) complex probe for precisely monitoring the changes of mitochondrial viscosity during cuprotosis via phosphorescence lifetime imaging. The Ir complex probe possessed microsecond lifetimes (up to 1 μs), which could be easily distinguished from cellular autofluorescence to improve the imaging contrast and sensitivity. Benefiting from the long phosphorescence lifetime, excellent viscosity selectivity, and mitochondrial targeting abilities, the Ir complex probe could monitor the increase in the mitochondrial viscosity during cuproptosis (from 46.8 to 68.9 cP) in a quantitative manner. Moreover, through in situ fluorescence imaging, the Ir complex probe successfully monitored the increase in viscosity in zebrafish treated with lipopolysaccharides or elescolomol-Cu2+, which were well-known cuproptosis inducers. We anticipate that this new Ir complex probe will be a useful tool for in-depth understanding of the biological effects of mitochondrial viscosity during cuproptosis.
Fluorescent dithienylethene-based photochromic materials have been attracting considerable attention owing to their wide applications in biological and materials sciences. However, the limitations of ...detrimental UV irradiation for photocyclization, short emission lifetime, and inefficient photoresponsive speed still need to be addressed. Herein, a novel dithienylethene photochromic molecule,
BFBDTE
, has been prepared by the incorporation of a difluoroboron β-diketonate (BF
2
bdk) unit. The strong electron acceptor BF
2
bdk not only reduces the energy gap of the open isomer, ensuring visible light-controlled fluorescence switching, but also promotes intersystem crossing for the generation of thermally activated delayed fluorescence (TADF). Upon alternating irradiation with green and NIR light,
BFBDTE
presents a rare example of photochromism, fluorescence and TADF switching in various polar solvents and a poly(methyl methacrylate) (PMMA) film. Meanwhile, it shows rapid and well repeatable cyclization (12 s) and cycloreversion reactions (20 s) in PMMA, accompanied by fast TADF switching within 11 s. Furthermore, photo-electrochemical measurements reveal a remarkable on-off photoelectronic response (photocurrent density ratio:
I
light
/
I
dark
= 684) between the open- and closed-form of
BFBDTE
. These remarkable merits make
BFBDTE
promising for photoswitchable molecular devices, optical memory storage systems, NIR detectors, and photoelectric switching.
Controlled by the alternating irradiation of green and NIR light, difluoroboron modifed dithienylethene shows rapid photochromism and photoelectronic switching.
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