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In this study, we are the first to observe the alignment behaviors of various assembling molecules with different feature sizes and shapes, including rod-, disc-, and column-shaped ...molecules, on zeolitic imidazolate framework-8 (ZIF-8) surfaces. Among the various rod-shaped 4-alkyl-4′-cyanobiphenyls (nCBs), those with short alkyl chains with less than nine hydrocarbons (e.g., 5CB, 6CB, 8CB, and 9CB) were vertically aligned on the ZIF-8 surface, while nCBs with long alkyl chains with more than 10 hydrocarbons (e.g., 10CB and 11CB) were randomly oriented on the surface. Unlike rod-shaped small molecules, the disc- and column-shaped molecules were randomly oriented on the ZIF-8 surface. A molecular dynamic simulation revealed that the vertical alignment of rod-shaped molecules on the ZIF-8 surface can be attributed to physical anchoring by the ZIF-8 micropores. Most portions of the alkyl chain of nCB with shorter alkyl chain lengths (n ≤ 9) can be inserted into the ZIF-8 aperture, while nCBs with longer alkyl chain lengths (n > 9) cannot be adequately anchored in the ZIF-8 aperture. According to these results, we believe that MOF materials with micropores can offer an effective tool for controlling the orientation of various functional small molecules.
The direct synthesis of inherently defect‐free, large‐area graphene on flexible substrates is a key technology for soft electronic devices. In the present work, in situ plasma‐assisted thermal ...chemical vapor deposition is implemented in order to synthesize 4 in. diameter high‐quality graphene directly on 10 nm thick Ti‐buffered substrates at 100 °C. The in situ synthesized monolayer graphene displays outstanding stretching properties coupled with low sheet resistance. Further improved mechanical and electronic performances are achieved by the in situ multi‐stacking of graphene. The four‐layered graphene multi‐stack is shown to display an ultralow resistance of ≈6 Ω sq−1, which is consistently maintained during the harsh repeat stretching tests and is assisted by self‐p‐doping under ambient conditions. Graphene‐field effect transistors fabricated on polydimethylsiloxane substrates reveal an unprecedented hole mobility of ≈21 000 cm2 V−1 s−1 at a gate voltage of −4 V, irrespective of the channel length, which is consistently maintained during the repeat stretching test of 5000 cycles at 140% parallel strain.
Averaged mobility of 42 GTO‐FET (field‐effect transistor) devices indicates high hole and electron mobilities of 21 000 and 12 000 cm2 V−1 s−1, respectively, at VGS = ± 4 V. The Ti–O–C interfacial layer indicated by the density functional theory‐predicted GTO model produces the unprecedented stretchability of the GTO‐FETs during 5000 cycles of parallel stretching of up to 140% strain.
Engineering the grain boundaries of crystalline materials represents an enduring challenge, particularly in the case of soft materials. Grain boundaries, however, can provide preferential sites for ...chemical reactions, adsorption processes, nucleation of phase transitions, and mechanical transformations. In this work, "soft heteroepitaxy" is used to exert precise control over the lattice orientation of three-dimensional liquid crystalline soft crystals, thereby granting the ability to sculpt the grain boundaries between them. Since these soft crystals are liquid-like in nature, the heteroepitaxy approach introduced here provides a clear strategy to accurately mold liquid-liquid interfaces in structured liquids with a hitherto unavailable level of precision.
We present aqueous dispersions of conjugated polymer nanowires (CPNWs) with improved light absorption properties aimed at aqueous-based applications. We assembled films of a donor–acceptor-type ...conjugated polymer and liquid crystalline 4-n-octylbenzoic acid by removing a cosolvent of their mixture solutions, followed by annealing of the films, and then formed aqueous-dispersed CPNWs with an aspect ratio >1000 by dispersing the films under ultrasonication at a basic pH. X-ray and spectroscopy studies showed that the polymer and liquid crystal molecules form independent domains in film assemblies and highly organized layer structures in CPNWs. Our ordered molecular assemblies in films and aqueous dispersions of CPNWs open up a new route to fabricate nanowires of low-band-gap linear conjugated polymers with the absorption maximum at 794 nm remarkably red-shifted from 666 nm of CPNWs prepared by an emulsion process. Our results suggest the presence of semicrystalline polymorphs β1 and β2 phases in CPNWs due to long-range π–π stacking of conjugated backbones in compactly organized lamellar structures. The resulting delocalization with a reduced energy bang gap should be beneficial for enhancing charge transfer and energy-conversion efficiencies in aqueous-based applications such as photocatalysis.
The main gas‐sensing mechanisms of 2D materials are surface charge transfer by analytes and Schottky barrier (SB) modulation at the interface between the metallic and semiconducting surfaces. In ...particular, dramatic differences in the gas‐sensing performances of 2D materials originate from SB modulation. However, SB sites typically exist only at the interface between the semiconducting channel material and the metal electrode. Herein, in situ formed multiple SBs in a single gas‐sensing channel are demonstrated, which are derived from the heterojunction of metallic Ti3C2 and semiconducting TiO2. In stark contrast with previous techniques, edge‐oxidized Ti3C2 flakes are synthesized by solution oxidation, allowing the uniform formation of TiO2 crystals on all flakes that comprise the gas sensing channel. Oxidized colloidal solutions are subjected to vacuum filtration to automatically form SB sites at the multiple inter‐flake junctions in both the outer surface and inner bulk regions of the film. The TiO2/Ti3C2 composite sensor shows 13.7 times higher NO2 sensitivity as compared with pristine Ti3C2 MXene, while the responses of the reducing gases are almost unchanged. The results suggest a new strategy for improving gas‐sensing performance by maximizing the density of SB sites through a simple method.
Ti3C2 MXene thin films with in situ formed multiple Schottky barriers (SBs) are synthesized by employing a solution‐based oxidation method, selectively forming TiO2 nanocrystals at the edge sites of each individual MXene sheet. Gas sensors based on the TiO2/Ti3C2 heterostructure show a highly enhanced gas response toward nitrogen dioxide gas resulting from SB modulation.
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•A method to fabricate continuous hydrophobic/oleophilic RGO/ZIF-8 nanocoating on polymeric foam.•Selective oil absorption with an absorption capacity of 15–35 g/g depending on the ...viscosity of organic solvents.•Ultrafast hexane flux up to 800,000 Lm−2 h−1 and no water flux during vacuum filtration.•Universal method to fabricate metal-organic frameworks on polymeric foam.
Continuous ZIF-8/reduced graphene oxide (RGO) nanocoating is fabricated by growing ZIF-8 on RGO-coated polyurethane (PU) foam. Surface modification of PU foam can be easily achieved by immersing the PU foam in GO solution, followed by mild thermal treatment to turn the GO layer into RGO layer. Adhesion between polymer foam and ZIF-8 layer was enhanced by the inserted RGO layer because oxygen-containing groups of RGO could interact with Zn2+ precursor of ZIF-8 localizing the layer growth preferentially on the surface of RGO. The synergetic hydrophobic/oleophilic properties of RGO and ZIF-8 enable selective oil absorption of PU foam with an absorption capacity of 15–35 g/g depending on the viscosity of organic solvents. Most of all, the ZIF-8/RGO coated PU foam can filter organic solvent selectively via vacuum filtration, showing ultrafast hexane flux up to 800,000 Lm−2 h−1 and no water flux.
Use of Cu and Cu+ is one of the most promising approaches for the production of C2 products by the electrocatalytic CO2 reduction reaction (CO2RR) because it can facilitate CO2 activation and CC ...dimerization. However, the selective electrosynthesis of C2+ products on Cu0Cu+ interfaces is critically limited due to the low electrocatalytic production of ethanol relative to ethylene. In this study, a novel porous Cu/Cu2O aerogel network is introduced to afford high ethanol productivity by the electrocatalytic CO2RR. The aerogel is synthesized by a simple chemical redox reaction of a precursor and a reducing agent. CO2RR results reveal that the Cu/Cu2O aerogel produces ethanol as the major product, exhibiting a Faradaic efficiency (FEEtOH) of 41.2% and a partial current density (JEtOH) of 32.55 mA cm−2 in an H‐cell reactor. This is the best electrosynthesis performance for ethanol production reported thus far. Electron microscopy and electrochemical analysis results reveal that this dramatic increase in the electrosynthesis performance for ethanol can be attributed to a large number of Cu0Cu+ interfaces and an increase of the local pH in the confined porous aerogel network structure with a high‐surface‐area.
A Cu/Cu2O interconnected porous aerogel network exhibits remarkably high selectivity and productivity in ethanol electrosynthesis from CO2 (41.2% and 32.55mA cm−2 in an H‐cell). This high performance arises from a large population of Cu0Cu+ interfaces in the confined porous structure with a high surface area. This aerogel electrocatalyst is thought to be an appealing model for the commercial electrosynthesis of ethanol from CO2.
Abstract
The main gas‐sensing mechanisms of 2D materials are surface charge transfer by analytes and Schottky barrier (SB) modulation at the interface between the metallic and semiconducting ...surfaces. In particular, dramatic differences in the gas‐sensing performances of 2D materials originate from SB modulation. However, SB sites typically exist only at the interface between the semiconducting channel material and the metal electrode. Herein, in situ formed multiple SBs in a single gas‐sensing channel are demonstrated, which are derived from the heterojunction of metallic Ti
3
C
2
and semiconducting TiO
2
. In stark contrast with previous techniques, edge‐oxidized Ti
3
C
2
flakes are synthesized by solution oxidation, allowing the uniform formation of TiO
2
crystals on all flakes that comprise the gas sensing channel. Oxidized colloidal solutions are subjected to vacuum filtration to automatically form SB sites at the multiple inter‐flake junctions in both the outer surface and inner bulk regions of the film. The TiO
2
/Ti
3
C
2
composite sensor shows 13.7 times higher NO
2
sensitivity as compared with pristine Ti
3
C
2
MXene, while the responses of the reducing gases are almost unchanged. The results suggest a new strategy for improving gas‐sensing performance by maximizing the density of SB sites through a simple method.
Abstract
Use of Cu and Cu
+
is one of the most promising approaches for the production of C
2
products by the electrocatalytic CO
2
reduction reaction (CO
2
RR) because it can facilitate CO
2
...activation and CC dimerization. However, the selective electrosynthesis of C
2+
products on Cu
0
Cu
+
interfaces is critically limited due to the low electrocatalytic production of ethanol relative to ethylene. In this study, a novel porous Cu/Cu
2
O aerogel network is introduced to afford high ethanol productivity by the electrocatalytic CO
2
RR. The aerogel is synthesized by a simple chemical redox reaction of a precursor and a reducing agent. CO
2
RR results reveal that the Cu/Cu
2
O aerogel produces ethanol as the major product, exhibiting a Faradaic efficiency (FE
EtOH
) of 41.2% and a partial current density (
J
EtOH
) of 32.55 mA cm
−2
in an H‐cell reactor. This is the best electrosynthesis performance for ethanol production reported thus far. Electron microscopy and electrochemical analysis results reveal that this dramatic increase in the electrosynthesis performance for ethanol can be attributed to a large number of Cu
0
Cu
+
interfaces and an increase of the local pH in the confined porous aerogel network structure with a high‐surface‐area.
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