Latest ArticlesTraditional soft lithography based PDMS device fabrication requires complex procedures carried out in a clean room. Herein, we report a photolithography-free method that rapidly produces PDMS devices in 30 min. By using a laser cutter to ablate a tape, a male photoresist mold can be obtained within 5 min by a simple heating-step, which offers significant superiority over currently used photolithographybased method. Since it requires minimal energy to cut the tape, our fabrication strategy shows good resolution (~ 100 μm) and high throughput. Furthermore, the micro-mold height can be easily controlled by changing the tape types and layers. As a proof-of-concept, we demonstrated that the fabricated PDMS devices are compatible with biochemical reactions such as quenching reaction of KI to fluorescein and cell culture/staining. Collectively, our strategy shows advantages of low input, simple operation procedure and short fabrication time, therefore we believe this photolithography-free method could serve as a promising way for rapid prototyping of PDMS devices and be widely used in general biochemical laboratories.
CO2 is a representative prototype model in energy and environmental fields. Many factors for CO2 capture and activation have been investigated extensively but the research on the influence of thermal conductivity is still absence. We herein have calculated many properties, including dipole moment, electric structure, and adsorption energies, on Pt doped graphene and 2D BC3N2 substrates and served the thermal conductivity as the bridge. Our results have demonstrated that the lower (higher) thermal conductivity for 2D BC3N2 (graphene) corresponds to larger (lower) dipole moment, which is beneficial for CO2 activation (capture) process. Our research have not only revealed the dominant role of heat conductivity for CO2 capture and activation, but also paved the way for further catalyst design of various areas.
The activation of molecular oxygen is an important step in metal-catalyzed oxidation reactions and a hot subject for the research of gas-phase metal clusters. It is known that the Ag and Au clusters readily react with O2 when they have open shell electronic structures. Distinct from this, here we observed Cun− (n = 7−20) clusters of both open and closed shells possess high reactivity with O2 with few exceptions. In a combination with ab initio calculations, we demonstrate that the activation of O2 on the even- and odd-sized Cun− clusters follows the single and double electron transfer models, respectively. Such phenomenon of metal clusters with different basicity to activate oxygen is enabled by the leveling effect of spin accommodation. The activity of Cun− clusters is correlated to the HOMO level, and for the close-shell clusters is also governed by the vertical spin excitation energy (VSE). In encountering the attack of dioxygen, the activity of the copper cluster anions not only depends on their basicity to donate electrons, but also closely associated with the cluster sizes. Small copper clusters Cun− (n = 7−13) can dissociate O2 spontaneously, while large clusters require extra energies and display close relationship between the reaction rates and electronic vertical detachment energies (VDE). Our work illuminates a novel reaction mechanism between Cun− clusters and O2, which sheds light in manipulating the activity and stability of coinage clusters by controlling the spin and charge states.
Electrocatalysis plays an increasingly important role in converting atmospheric molecules (e.g., N2, CO2 and H2O) to value-added products (e.g., NH3, C2H4 and H2). However, developing a simple strategy for preparing catalysts with high performance for the effective conversion of clean energy is still full of challenges. Herein, we describe a straightforward, one-step reduction method to achieve the formation of Pt nanoparticles (NPs) and the vacancy engineering of TiO2–x nanofibers (NFs) simultaneously, which can be accomplished in 5 min. Furthermore, a Pt/TiO2–x nanofibrous aerogel (NA) with an ordered cellular architecture is prepared through a directional freezing technology. The Pt/TiO2–x NA with excellent mechanical properties can be made into a self-supporting electrode for electrocatalytic N2 reduction reaction (NRR), showing high NH3 yield rate (4.81 × 10–10 mol/s cm–2) and Faraday efficiency (14.9%) at –0.35 V vs. RHE.
The electrocatalytic methanol conversion is of importance in direct methanol fuel cell, biomass reforming, and hydrogen generation. To achieve a "carbon-neutral" target, CO2 byproducts derived from biofuels should be mitigated. In contrast to the complete oxidation of methanol to CO2, the selective oxidation of methanol to formate is a CO2-emission-free route without the generation of toxic CO intermediates. Herein, we present a highly active catalyst based on transition-metal disulfide nanosheet arrays supported on Ni foam for methanol conversion. Through composition screening, we find that the FeCoNi disulfide nanosheet exhibits a highly efficient and selective methanol-to-formate conversion. The surface reconstruction of this catalyst allows us to produce 0.66 mmol cm−2 h−1 of formate at low potential (1.40 V) with high faradaic efficiency of > 98%. This work offers a substantial composition tuning strategy to construct noble-metal-free active multi-metal sites for CO2-emission-free conversion of methanol to value-added formate.
Excellent radiation resistance is a prerequisite for pressure-sensitive hydrogels to be used in high-energy radiation environments. In this work, tannic acid-modified boron nitride nanosheet (BNNS-TA) is first prepared as the radiation-resistant additive by a facile one-step ball milling of hexagonal boron nitride and tannic acid. Then, polyacrylamide (PAAm)-based pressure-sensitive hydrogel doped with BNNS-TA and Fe3+ ions is fabricated. The ternary BNNS-TA/Fe3+/PAAm hydrogel exhibits excellent compressive strength (at least four times the compressive strength of unfilled pure PAAm hydrogel), pressure-sensitive performance (gauge factor is up to 1.4), and performance recovery due to the combination of multiple intermolecular interactions, such as covalent crosslinking, hydrogen bonds, and ion coordination interactions. The BNNS-TA/Fe3+/PAAm hydrogel can be made as a pressure sensor installed in the control circuit or attached on the human body to detect human activities accurately. More importantly, the compressive strength and the pressure-sensitive performance of the BNNS-TA/Fe3+/PAAm hydrogel can be maintained after the hydrogel is irradiated by 60Co gamma-ray at an absorbed dose of 15 kGy. As a comparison, the compressive strength of the unfilled PAAm hydrogel is only a quarter of that before irradiation. This work not only reveals a facile method to achieve the preparation of chemically modified BNNS as a promising radiation-resistant additive but also provides a novel strategy for the development of pressure-sensitive hydrogel devices in radiation environments.
We demonstrate hole-transport-layer-free light-emitting diodes (LEDs) based on solution-processed multiple-quantum-well (MQW) perovskite. The MQW perovskite can self-assemble to a unique structure of vertically graded distribution with two-dimensional layered perovskite covered by three-dimensional-like perovskite at top, which can naturally form a barrier of electron transporting to the anode interface, thereby enhancing the charge capture efficiency. This leads to hole-transport-layer-free MQW perovskite LEDs reaching an external quantum efficiency (EQE) of 9.0% with emission peak at 528 nm, which is over 6 times of LEDs based on three-dimensional perovskite with the same device structure, representing the record EQE of hole-transport-layer-free perovskite LED.
In this paper, the crystallization behavior of a novel poly(monothiocarbonate), poly(trimethylene monothiocarbonate) (PTMMTC), was investigated and compared with its polycarbonate analogue, poly(trimethylene carbonate) (PTMC). It is found that PTMMTC exhibits strong crystallizability, while unstretched PTMC is amorphous. DSC and DMA results reveal that PTMMTC possesses higher glass transition temperature (Tg) and β-transition temperature (Tβ) than PTMC. Simulation based on density functional theory (DFT) shows that, the bond angle of C-S-C is evidently smaller than that of C-O-C, and thus a larger dipole moment. This leads to the stronger intermolecular interaction and more rigid chain conformation in PTMMTC, which is the origin of sulfur-substitution enhanced crystallization. The crystal structure of PTMMTC was preliminarily determined for the first time. PTMMTC has an orthorhombic crystal structure with a planar zig-zag chain conformation. The parameters of unit cell are a = 10.74 Å, b = 4.79 Å, and c (fiber axis) = 7.74 Å.
Lithium metal is deemed as an ideal anode material in lithium-ion batteries because of its ultrahigh theoretical specific capacity and the lowest redox potential. However, the rapid capacity attenuation and inferior security resulting from the dendritic lithium growth severely limit its commercialization. Herein a novel hybrid gel polymer electrolyte (GPE) based on electrospun lithium sulfonated polyoxadiazole (Li-SPOD) nanofibrous membrane swelled by lithium bis(trifluoromethanesulfonyl)imide (LiTFSI) ether liquid electrolyte is proposed to address the issue of lithium dendrites. The Li-SPOD membrane synthesized by a simple one-pot method exhibits excellent mechanical strength and thermal resistance due to its high molecular weight and rigid backbone. The electron-withdrawing oxadiazole ring and oxadiazole ring-Li+ complex, and N, O heteroatoms with lone pairs of electrons in Li-SPOD macromolecular chains facilitate the dissociation of -SO3Li group and Li+ transference. The hybrid Li-SPOD GPE exhibits both a high lithium-ion transference number (0.64) and high ionic conductivity (2.03 mS/cm) as well as superior interfacial compacity with lithium anodes. The LiFePO4-Li cell using this novel GPE can operate steadily at 2 C for 300 cycles, remaining a high discharge capacity of 125 mAh/g and dendrite-free anode. Remarkable performance improvements for the Li-Li and Cu-Li cells are also presented.
By the replacement of halogen anion, three new multifunctional organic-inorganic hybrid perovskites (thiomorpholinium)PbX3 (X = Cl, Br, I) were successfully synthesized and underwent reversible structural transformation above room temperature, accompanied by the anomalous change of dielectric constant. With the adjustment of the halogen anion from Cl to I in the inorganic skeleton, the space group is transformed from centrosymmetric space group P21/c ((thiomorpholinium)PbCl3) to chiral one P212121 ((thiomorpholinium)PbBr3, (thiomorpholinium)PbI3) at room temperature. The ordered-disordered transition of organic cations and the change of hydrogen bonds with the increase of temperature lead to above-room-temperature phase transitions. Ultraviolet absorption and second-harmonic generation (SHG) measurements confirmed that both the band gap and SHG activity of (thiomorpholinium)PbX3 (X = Cl, Br, I) crystals were tunable. The band gaps reveal a broadening trend with 3.532 eV, 3.410 eV and 3.175 eV along the Cl → Br → I series. This work provides an effective molecular design for multifunctional organic-inorganic perovskites.
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