Hierarchically nanoporous N-doped carbon nanowires (N-CWs) were prepared by a novel space-confinement-induced assembly strategy, for which nitrogen-enriched pyrimidine and anodic aluminium oxide (AAO) template bearing metal oxides are employed as precursor and nanoscale channels, respectively, and the Fe/Co metal oxide not only blocks the AAO surface from the original surface-templating carbonization, but also introduces nanoporosity with acid etching. Thus-obtained carbon nanowires composed of N-doped graphene-like carbon nanosheets not only contain a high N content (up to ∼12%), but also possess a hierarchically meso/microporous structure (∼1.3 cm3 g−1) with high specific surface area (∼455 m2 g−1). This protocol allows for the simultaneous optimization of graphitization, porous structure and surface functionalization. As a result, the prepared N-CWs demonstrate an attractive electrocatalytic capability towards oxygen reduction reaction (ORR). Specifically, in addition to the improved kinetic current density and overpotential, the N-CWs prepared at 700 °C show the optimized ORR performance with an electron-transfer number of ∼4.0, which very close to that of a commercial Pt/C catalyst.
Na Li,Jin-Gui Wang,Hui-Jing Zhou,Ping-Chuan Sun,Tie-Hong Chen
Single-crystal-like, hierarchically nanoporous silica SBA-1 particles were successfully fabricated by employing organic mesomorphous complexes of polyelectrolyte (poly(acrylic acid) (PAA)) and cationic surfactant (hexadecylpyridinium chloride (CPC)) as templates. By adjusting the amount of PAA in the synthesis, a series of silica particles with well-defined morphologies and well-ordered cubic Pm3̅n mesostructure were obtained. Both the mesostructure and well-defined morphology of the silica particles inherited those of the corresponding PAA/CPC mesomorphous complexes. The materials possess bimodal nanopores corresponding to the mesopore size of SBA-1 templated by surfactant micelles and secondary interstitial nanopores templated by phase-separated PAA with different domain sizes, respectively. Notably, the presence of a large amount of foamlike secondary nanopores did not disturb the single-crystal characteristic of the SBA-1 particles. By means of pore-expanding with 1,3,5-trimethylbenzene, the mesopore size of the SBA-1 could be easily tuned from 3.0 nm to 5.0 nm, and the secondary nanopore were enlarged to several hundreds of nanometers, while the morphology of the particles was not changed. Besides, using bridged organosilane as a precursor, a series of hierarchically nanoporous periodic mesoporous organosilicas (H-PMO) with well-defined morphology were fabricated. Because of the hierarchically nanoporous structure and inherent hydrophobic bridged-ethylene group, the H-PMO exhibited rapid adsorption rate and high adsorption capacity in enzyme and protein immobilization.
We reported a facile strategy to fabricate three dimensional (3D) hierarchical nanoporous Cu films via simple in-situ electrochemical alloying/dealloying approach in a choline chloride-ethylene glycol (ethaline) deep eutectic solvent (DES) containing zinc chloride. The fabrication process involved electrochemical formation of Cu-Zn surface alloys (alloying), and followed by in-situ selective etching of the active zinc element from the alloys (dealloying). Compared with those exerted from choline chloride-urea (reline) based DES, the resultant nanoporous Cu (NPC) films obtained in ethaline exhibited a hierarchical porous architecture with a tailorable channel/pore size distribution. The evolution of nanoporosity was found to be highly temperature and time dependent, suggesting a thermal activation process controlled by surface diffusion. For kinetics investigation, the surface diffusivities of self-assembled copper atoms at the hierarchical layers, and their corresponding activation energies have been evaluated. The as-prepared NPC showed a significant catalytic activity for reduction of nitrate with a linear detection range of 10–100 μM. A fairly high nitrate sensitivity of 3415 μA mM−1 cm−2 coupled with a low detection limit of 1.92 μM is achieved.
Conventional rigid patch antennas, constrained by high-permittivity substrates ( ε r > 3.0) with severe dielectric loss ( tanδ > 0.02), suffer from catastrophic performance degradation at elevated frequencies (>3 GHz) and inherent inflexibility that fundamentally prohibits their integration in wearable electronics. This work presents a breakthrough in synthesizing PMMA-reinforced polyimide aerogels (PIAs) via a 10-min ambient pressure drying (APD) strategy, enabling tunable porosity (>90%) and ultra-low dielectric constants ( ε r = 1.35, tanδ < 0.01). The incorporation of PMMA into the PI matrix endows the aerogel skeleton with outstanding mechanical resilience (tensile strength of 7.2 MPa and fracture energy of 45.8 kJ/m 2 ), while effectively suppressing capillary-induced shrinkage to below 2.1% during solvent evaporation. The synergistic interplay between PMMA encapsulation and APD-optimized solvent exchange yields a hierarchical nanoporous structure (30 nm average pore size) with exceptional thermal insulation (0.036 W/m·K). When deployed as a substrate for flexible Sub-6 GHz patch antennas, the aerogel exhibits 106% gain enhancement (9.92 dBi) and broad impedance bandwidth (3.862–3.941 GHz), outperforming conventional FR-4 substrates. This work establishes a scalable, low-cost paradigm for multifunctional aerogels in wearable electronics and high-frequency communication systems.
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