Synergistic Modulation of π-π* and n-π* Transitions by In Situ Phenol-Like Structure Integration for Efficiently Wide-Spectrum Hydrogen Production of Ultrathin Carbon Nitride.

2D carbon nitride nanosheets, exemplified by g-C3N4, offers significant structural benefits and enhanced photocatalytic activity. Nonetheless, the quantum confinement effect prevalent in nanoscale photocatalysts would result in an enlarged bandgap, potentially restricting the spectral absorption range and impeding improvements in photocatalytic efficiency. Here, a high-performance 2D photocatalyst with an extended spectral response is achieved by incorporating a novel phenol-like structure into the conjugated framework of ultrathin g-C3N4 nanosheet. This novel strategy features targeted pyrimidine doping to create a conjugated carbon zone in heptazine structure, offering a thermodynamically favorable pathway for hydroxyl functionalization during the annealing exfoliation process. Consequently, the π-π* transition energy in the material is significantly decreased, and the active lone pair electrons in phenol-like structure induces a new n-π* transition with notably enhanced absorption from 500 to 650 nm. The optimized material shows a dramatic enhancement in photocatalytic activity, achieving ≈72 times than the activity of bulk g-C3N4, and demonstrating a measurable H2 production rate of 6.57 µmol g-1 h-1 under 650 nm light. This study represents a significant step forward in the strategic design of 2D photocatalysts, with tailored electronic structures that significantly boost light absorption and photocatalytic efficiency.

A Heterogeneous Viscosity Flow Model for Liquid Transport through Nanopores Considering Pore Size and Wettability.

The confinement effect in micro- and nanopores gives rise to distinct flow characteristics in fluids. Clarifying the fluid migration pattern in confined space is crucial for understanding and explaining the abnormal flow phenomena in unconventional reservoirs. In this study, flow characteristics of water and oil in alumina nanochannels were investigated with diameters ranging from 21 nm to 120 nm, and a heterogeneous viscosity flow model considering boundary fluid was proposed. Compared with the prediction of the HP equation, both types of fluids exhibit significant flow suppression in nanochannels. As the channel size decreases, the deviation degree increases. The fluid viscosity of the boundary region displays an upward trend as the channel size decreases and the influence of the interaction between the liquid and solid walls intensifies. The thickness of the boundary region gradually decreases with increasing pressure and eventually reaches a stable value, which is primarily determined by the strength of the interaction between the liquid and solid surfaces. Both the pore size and wettability are essential factors that affect the fluid flow. When the space scale is extremely small, the impact of wettability becomes more pronounced. Finally, the application of the heterogeneous flow model for permeability evaluation has yielded favorable fitting results. The model is of great significance for studying the fluid flow behavior in unconventional reservoirs.

Comparative Thermal Research on Energetic Molecular Perovskite Structures.

Molecular perovskites are promising practicable energetic materials with easy access and outstanding performances. Herein, we reported the first comparative thermal research on energetic molecular perovskite structures of (C6H14N2)[NH4(ClO4)3], (C6H14N2)[Na(ClO4)3], and (C6H14ON2)[NH4(ClO4)3] through both calculation and experimental methods with different heating rates such as 2, 5, 10, and 20 °C/min. The peak temperature of thermal decompositions of (C6H14ON2)[NH4(ClO4)3] and (C6H14N2) [Na(ClO4)3] were 384 and 354 °C at the heating rate of 10 °C/min, which are lower than that of (C6H14N2)[NH4(ClO4)3] (401 °C). The choice of organic component with larger molecular volume, as well as the replacement of ammonium cation by alkali cation weakened the cubic cage skeletons; meanwhile, corresponding kinetic parameters were calculated with thermokinetics software. The synergistic catalysis thermal decomposition mechanisms of the molecular perovskites were also investigated based on condensed-phase thermolysis/Fourier-transform infrared spectroscopy method and DSC-TG-FTIR-MS quadruple technology at different temperatures.

Confined Magnetic-Dielectric Balance Boosted Electromagnetic Wave Absorption.

Magnetic-dielectric property plays a critical significance for the functional expression toward advanced materials. Within nanoscale, the simultaneous regulation of the electrical and magnetic properties of electromagnetic (EM) wave absorption materials faces huge challenges. Herein, using the metal-organic frameworks (MOF) as templates, highly-dispersed ZnO and Co nanoparticles are uniformly confined inside graphited N-doped carbon skeleton, constructing the balanced EM property in the Co@NC-ZnO absorbers. Meanwhile, a dynamics and symmetrical morphology optimization of MOF-derived Co@NC-ZnO are dependent on the Co/Zn mass ratio and adjusting MOF frameworks, which evolves from the cube, truncated cube, dodecahedron, and to the final microsphere. Simultaneously, both the electronic conduction network and magnetic coupling network are compatible together in the in situ transformed Co@NC-ZnO system. Boosted magnetic responding ability and unique magnetic coupling are verified by the off-axis electronic holography. Plentiful heterojunction interfaces and special electronic conduction paths can be built in this Co-Zn-MOF derivatives, facilitating the dielectric loss behaviors. As expected, MOF-derived Co@NC-ZnO absorber displays outstanding EM wave absorption ability with strongest reflection loss value of -69.6 dB at only 1.9 mm thickness and wideband absorption covering 6.8 GHz at 2.4 mm. Confined EM balance provides new design strategy toward MOF-derived excellent MA materials and functional devices.

Highly Crystalized MAPbX3 Perovskite Triangular Nanowire Arrays for Optoelectronic Applications.

Here, a facile fabrication approach for the high-quality 1D perovskite triangular nanowire (TNW) array synthesis through space-confined effect is reported. A soft stamp containing 1D triangular linear array pattern is used to confine the MAPbX3 solution and to guide the growth of the nanowires along the prescribed direction with good crystallinity. The further constructed photodetectors based on the obtained MAPbI3 TNWs exhibit superior photoresponse properties with a responsivity of (125.2 ± 2.5) A W-1 and detectivity of (2.8 ± 0.8) × 1013 Jones at the wavelength of 650 nm. This excellent performance is attributed to the highly crystalline TNW with optical anisotropy and a small asymptotic height, which reduces the probability of the photon reflection and promotes the carrier transport. More interestingly, the increased surface area of the triangular device can present superior flexibility after a couple of thousands of bending cycles. Furthermore, by fabricating 7 × 7 photodetector arrays, the potential image sensor application is demonstrated. The perovskite nanowire fabrication approach is scalable and compatible with current semiconductor manufacturing, which indicates their great potential in broad applications.

Spaced-Confined Janus Engineering Enables Controlled Ion Transport Channels and Accelerated Kinetics for Secondary Ion Batteries.

The large grain boundary resistance between different components of the anode electrode easily leads to the low ion transport efficiency and poor electrochemical performance of lithium-/sodium-ion batteries (LIBs/SIBs). To address the issue, a Janus heterointerface with a Mott-Schottky structure is proposed to optimize the interface atomic structure, weaken interatomic resistance, and improve ion transport kinetics. Herein, Janus Co/Co2P@carbon-nanotubes@core-shell (Janus Co/Co2P@CNT-CS) refined urchin-like architecture derived from metal-organic frameworks is reported via a coating-phosphating process, where the Janus Co/Co2P heterointerface nanoparticles are confined in carbon nanotubes and a core-shell polyhedron. Such a Janus Co/Co2P heterointerface shows the strong built-in electric field, facilitating the controllable ion transport channels and the high ion transport efficiency. The Janus Co/Co2P@CNT-CS refined urchin-like architecture composed of a core-shell structure and the grafting carbon nanotubes enhances the structure stability and electronic conductivity. Benefiting from the spaced-confined Janus heterointerface engineering and synergistic effects between the core-shell structure and the grafting carbon nanotubes, the Janus Co/Co2P@CNT-CS refined urchin-like architecture demonstrates the fast ion transport rate and excellent pseudocapacitance performance for LIBs/SIBs. In this case, the Janus Co/Co2P@CNT-CS refined urchin-like architecture shows high specific capacities of 709 mA h g-1 (200 cycles) and 203 mA h g-1 (300 cycles) at a current density of 500 mA g-1 for LIBs/SIBs, respectively.

Coupling effect of critical properties shift and capillary pressure on confined fluids: A simulation study in tight reservoirs.

Critical properties shift and large capillary pressure are important contributors for the phase behavior altering of nanopore fluid. However, the effects of critical properties shift and large capillary pressure on the phase behavior are ignored in traditional compositional simulators, leading to inaccurate evaluation results of tight reservoirs. In this study, phase behavior and production of confined fluid in nanopores are studied. First, we developed a method for coupling the effect of critical properties shift and capillary pressure into the vapor-liquid equilibrium calculation base on Peng-Robinson equation of state. Second, a novel fully compositional numerical simulation algorithm considering effect of critical properties shift and capillary pressure on phase behavior is accomplished. Third, we have discussed the alterations of critical properties shift effect, capillary pressure effect and coupling effect on the composition of oil and gas production in detail. The critical properties shift and capillary pressure effects on oil and gas production in tight reservoirs are analyzed quantitatively through four cases, and the influences of the two effects in oil/gas production are compared. Based on the fully compositional numerical simulation, the simulator can rigorously simulate the impacts of component changes during production. The simulation results show that both the critical properties shift effect and the capillary pressure effect reduce the bubble point pressure of Changqing shale oil, and the influence are more prevalent in pores of smaller radius. In pores is larger than 50 nm, the phase behavior altering of the fluid can be ignored. In addition, we devised four cases to comprehensively investigate the effects of critical properties shift and large capillary pressure on production performance of tight reservoirs. The comparisons between the four cases show that the capillary pressure effect impacts the reservoir production performances greater than the critical properties shift effect, such as higher oil production, higher GOR, and lower content of lighter component and higher content of heavier component in the residual oil/gas. The results of coupling effects indicate that the critical properties shift effect would suppress the effect of the capillary pressure effect. In particular, the difference between the simulation results of the coupling effects and the base case is smaller than that between the simulation results of the capillary pressure effect and the base case.

Space Confinement to Regulate Ultrafine CoPt Nanoalloy for Reliable Oxygen Reduction Reaction Catalyst in PEMFC.

A Co-based zeolitic imidazolate framework (ZIF-67) derived catalyst with ultrafine CoPt nanoalloy particles is designed via a two-step space confinement method, to achieve a robust oxygen reduction reaction (ORR) performance for proton exchange membrane fuel cell (PEMFC). The core-shell structure of ZIF-67 (core) and SiO2 (shell) is carefully adjusted to inhibit the agglomeration of Co nanoparticles. In the subsequent adsorption-annealing process, the in situ formed graphene shell on the surface of Co nanoparticles further protects metal particles from coalescence, leading to the ultrafine CoPt nanoalloy (average diameter is 2.61 nm). Benefitting from the high utilization of Pt metal, the mass activity of CoPt nanoalloy catalyst reaches 681.8 mA mgPt -1 at 0.9 V versus RHE according to the rotating disk electrode test in 0.1 m HClO4 solution. The CoPt nanoalloy-based PEMFC provides a high maximum power density of 2.22 W cm-2 (H2 /O2 ) and 0.923 W cm-2 (H2 /air). Simultaneously, it shows good stability in the long-time dynamic test at low humidity, due to the robust CoPt@graphene core-shell nanostructure. This work provides a viable strategy for designing Pt-based nanoalloy catalysts with ultrafine metal particles and high stability.

Pivotal roles of N-doped carbon shell and hollow structure in nanoreactor with spatial confined Co species in peroxymonosulfate activation: Obstructing metal leaching and enhancing catalytic stability.

Metal leaching and catalytic stability are the key issues in Fenton-like reaction. Herein, a hollow yolk-shell nanoreactor (HYSCN) with shell confined Co species was fabricated for peroxymonosulfate (PMS) activation to degrade carbamazepine (CBZ). The uniform Co nanoparticles were completely anchored in a hollow void, further confined by a porous N-doped carbon shell. The unique construction significantly reduces Co species leaching in PMS activation and enhances catalytic stability. Co leaching came from HYSCN dropped by almost fourfold compared to CN-8 without shell confined (0.403 mg/L to 0.120 mg/L). The catalytic stability is also greatly improved, confirming the dominant role of heterogeneous catalysis in the HYSCN/PMS system. HYSCN exhibits excellent catalytic performance compared to a solid structure (SCSCN), demonstrating the significance of hollow structures. Mechanism study found that HO•, SO4•- and 1O2 induced in HYSCN/PMS system and the relative contributions were distinguished and quantified by stoichiometric methods. The UPLC-Q-TOF-MS/MS was used to identify the CBZ degraded intermediate products and the possible degradation pathway was proposed. This study will provide theoretical guidance for reducing metal leaching and improving catalytic stability in the PMS activation.

Effect of Tie Bars on Axial Compressive Behavior of Round-Ended Rectangular CFST Stub Columns.

Round-ended rectangular concrete-filled steel tube (RRCFST) columns are prone to local buckling that are close to straight steel plates when used as piers of a bridge and affect its long-term use. In order to solve this problem, tie bars were used in this research to stiffen RRCFST columns. Eleven specimens with tie bars and three specimens without tie bars were tested to analyze influences of cross-sectional aspect ratio, longitudinal spacing, limb numbers and diameter of the tie bar on failure model, confined effect, bearing capacity and ductility of RRCFST stub columns. Finite element models (FEM) with different concrete constitutive models for rectangular and circle parts were established and validated to reveal the mechanism of the constrained effect of tie bars. Experimental and FEM results show that the local buckling scope was decreased and gradually moved to middle height with decreased longitudinal spacings tie bars. The addition of tie bars in RRCFST columns with large aspect ratios slightly enhanced the ultimate bearing capacity, the diameter of tie bars changing from 8 mm to 12 mm greatly enhanced displacement and energy ductility by 58.4% and 85.1%, respectively. However, more tie bars (e.g., two or three limbs) utilization could not further improve the bearing capacity and failure mode. While, the tie bars had very limited contribution to bearing capacity and ductility for RRCFST columns with small aspect ratios, because the outer steel tubes already individually provided for enough confinement on inner concrete. By considering different concrete confined models for rectangular and round-ended parts, an analytical model was proposed and validated to predict the ultimate bearing load for RRCFST stub columns with tie bars.

A molecularly imprinted nanoreactor with spatially confined effect fabricated with nano-caged cascaded enzymatic system for specific detection of monosaccharides.

Glucose oxidase (GOx), traditionally regarded as an oxidoreductase with high ß-D-glucose specificity, has been widely applied as sensing probe for ß-D-glucose detection. However, it is found that the specificity of GOx is not absolute and GOx cannot decern ß-D-glucose among its isomers such as xylose, mannose and galactose. The existence of the other monosaccharides in sensing system could compromise the sensitivity for ß-D-glucose, therefore, it is of great urgency to achieve the highly specific catalytic performance of GOx. Herein, porous metal-organic frameworks (MOF) are prepared as the host matrix for immobilization of both GOx and bovine hemoglobin (BHb), obtained a cascaded catalytic system (MOF@GOx@BHb) with both enhanced GOx activity and peroxidase-like activity owing to the spatially confined effect. Then, using ß-D-glucose as both template molecules and substances, hydroxyl radicals are produced continuously and applied for initiating the polymerization of molecular imprinting polymers (MIPs) on the surface of MOF@GOx@BHb. Impressively, the obtaining molecularly imprinted GOx (noted as MOF@GOx@BHb-MIPs) achieves the highly sensitive and specific detection of ß-D-glucose in the concentration range of 0.5-20 µM with the LOD = 0.4 µM (S/N = 3) by colorimetry. Similarly, MOF@GOx@BHb-MIPs are subsequently obtained using mannose, xylose and galactose as template molecules, respectively, and also show satisfied specific catalytic activity towards corresponding templates, indicating the effectiveness of the proposed strategy to achieve highly specific catalytic performance of GOx.

Nanochannel-Controlled Synthesis of Ultrahigh Nitrogen-Doping Efficiency on Mesoporous Fe/N/C Catalysts for Oxygen Reduction Reaction.

Designing appropriate methods to effectively enhance nitrogen-doping efficiency and active-site density is essential to boost the oxygen reduction reaction (ORR) activity of non-platinum Fe/N/C-type electrocatalysts. Here, we propose a facile and effective strategy to design a mesopore-structured Fe/N/C catalyst for the ORR with ultrahigh BET surface area and outstanding conductivity via nanochannels of molecular sieve-confined pyrolysis of Fe2+ ions coordinated with 2,4,6-tri(2-pyridyl)-1,3,5-triazine complexes as a novel precursor with the stable coordination effect. Combining the nanochannel-confined effect with the stable coordination effect can synergistically improve the thermal stability and stabilize the nitrogen-enriched active sites, and help to control the loss of active N atoms during pyrolysis process and to further obtain a high active-site density for enhancing the ORR activity. The as-prepared Fe/N/C electrocatalyst has exhibited excellent catalytic activity with an onset potential of ~ 0.841 V (versus RHE) closely approaching the Pt/C catalyst and high long-term stability in alkaline electrolyte. Besides, low-hydrogen peroxide yield (< 6.5%) and high electron transfer number (3.88-3.94) can be found on this catalyst, indicating that it is a valuable substitute for traditional Pt/C catalysts. This work paves a new way to design high-performance Fe/N/C electrocatalysts and deepens the understanding of active site and ORR catalysis mechanism.

Morphology-Tailored Gold Nanoraspberries Based on Seed-Mediated Space-Confined Self-Assembly.

Raspberry-like structure, providing a high degree of symmetry and strong interparticle coupling, has received extensive attention from the community of functional material synthesis. Such structure constructed in the nanoscale using gold nanoparticles has broad applicability due to its tunable collective plasmon resonances, while the synthetic process with precise control of the morphology is critical in realizing its target functions. Here, we demonstrate a synthetic strategy of seed-mediated space-confined self-assembly using the virus-like silica (V-SiO2) nanoparticles as the templates, which can yield gold nanoraspberries (AuNRbs) with uniform size and controllable morphology. The spikes on V-SiO2 templates serve dual functions of providing more growth sites for gold nanoseeds and activating the space-confined effect for gold nanoparticles. AuNRbs with wide-range tunability of plasmon resonances from the visible to near infrared (NIR) region have been successfully synthesized, and how their geometric configurations affect their optical properties is thoroughly discussed. The close-packed AuNRbs have also demonstrated huge potential in Raman sensing due to their abundant "built-in" hotspots. This strategy offers a new route towards synthesizing high-quality AuNRbs with the capability of engineering the morphology to achieve target functions, which is highly desirable for a large number of applications.

Mn-N-C Nanoreactor Prepared through Heating Metalloporphyrin Supported in Mesoporous Hollow Silica Spheres.

Mesoporous hollow silica spheres have been drawing tremendous interest due to their special structure and properties and potential applications. Here we synthesized a nanoreactor via ship-in-bottle method, encapsulated with Mn-N-C by heating manganese porphyrin in nanocages of mesoporous hollow silica spheres. And manganese porphyrin is first encapsulated and confined in the hollow spheres. The nanoreactors are investigated through transmission electron microscopy (TEM) and high angle annular dark field scanning TEM (HAADF-STEM) as well as nitrogen adsorption-desorption isotherms. The results demonstrate that the mesoporous hollow spheres with well-defined morphology hold large pore volumes (0.29-0.46 cm3 g-1), high specific surface areas (428-600 m2 g-1) and uniform pore sizes (4.0 nm). In addition, the ethylbenzene oxidation is conducted in order to explore the catalytic performance of the nanoreactors. And the nanoreactors are observed to possess remarkable catalytic activity and attractive stability for ethylbenzene oxidation, which should be ascribed to the special architectures and confined effect.