A rolling-circle-amplification method was developed to produce DNA hydrogels with horseradish-peroxidase-like catalytic capability. The catalytic hydrogel exhibits highly improved stability at elevated temperatures or during a long-term storage. Integrated with glucose oxidase, the complex hydrogel can be applied to the sensitive and reliable detection of glucose.

Recently, smart DNA hydrogels, which are generally formed by the self-assembly of oligonucleotides or through the cross-linking of oligonucleotide-polymer hybrids, have attracted tremendous attention. However, the difficulties of fabricating DNA hydrogels limit their practical applications. We report herein a novel method for producing pH-responsive hydrogels by rolling circle amplification (RCA). In this method, pH-sensitive cross-linking sites were introduced into the polymeric DNA chains during DNA synthesis. As the DNA sequence can be precisely defined by its template, the properties of such hydrogels can be finely tuned in a very facile way through template design. We have investigated the process of hydrogel formation and pH-responsiveness to provide rationales for functional hydrogel design based on the RCA reaction.

Serious freshwater shortage and environmental pollution boost the rapid development of solar-driven water production. Although improved evaporation rate has achieved in recent years, undesirable impurity (e.g., pollutant components) can also be inevitably evaporated and collected as impurity in produced freshwater. This work reports new ultra-light threedimensional (3D) aerogels assembled by hierarchical Al 2 O 3 /TiO 2 nanofibers and reduced graphene oxide (RGO) for exciting synchronized solar-driven evaporation and water purification. Hydrophilic Al 2 O 3 /TiO 2 fibrous channels linked up the graphene hot-spots and water body for sufficient water supply and bulk water insulation. Meanwhile, featured with thermal insulation effect, the Al 2 O 3 /TiO 2 nanofibers effectively locked the converted heat with less energy loss from sunlight. The introducing of Al 2 O 3 /TiO 2 nanofibers into RGO aerogel led to the effective interfacial evaporation for a more rapid water evaporation rate (2.19 kg • m −2 • h −1 , normalized to evaporation area including both top and side surface), which was 36% higher than that of pristine RGO aerogel. Moreover, simultaneous with the strong steam generation, Al 2 O 3 /TiO 2 nanofibers in situ removed the pollutants within steam by photodegradation, achieving polluted wastewater purification with high contaminant removal ratio of 91.3%. Our work on coupling Al 2 O 3 /TiO 2 nanofibers into photothermal aerogel provides attractive solutions for the challenges of clean water scarcity and serious environmental pollution.

Recently, there has been strong interest in flexible and wearable electronics to meet the technological demands of modern society. Environmentally-friendly and scalable electronic textiles is a key area that is still significantly underdeveloped. Here, we describe a novel strain sensor composed of aligned cellulose acetate (CA) nanofibers with belt-like morphology and a reduced graphene oxide (RGO) layer. The unique spatial alignment, microstructure and wettability of CA nanofibrous membranes facilitate their close contact with deposited GO colloids. After a portable and fast hot-press process within 700 s at 150 °C, the GO on CA membrane can be facilely reduced to a conductive RGO layer. Moreover, the connection among contiguous CA nanofibers and the interaction between the GO and CA substrate were both highly enhanced, resulting in superior mechanical strength with Young's modulus of 1.3 GPa and small sheet resistance lower than 10 kΩ. Therefore, the conductive RGO/CA membrane was successfully utilized as a strain sensor in a broad deformation range and with versatile deformation types. Moreover, the distinctive mechanical strength under different stretch angles endowed the well-aligned RGO/CA film with intriguing sensitivity against stress direction. Such a cost-effective and environmentally-friendly method can be easily extended to the scalable production of graphene-based flexible electronic textiles.

The growth and disaggregation of hydrogen-bonded layer-by-layer (LbL) multilayers based on poly­(methacrylic acid) (PMAA) and poly­(N-vinyl­caprolactam) (PVCL) are studied depending on pH, NaCl concentration, and PVCL molar mass. Whereas multilayer growth is essentially insensitive to salt and PVCL molar mass, the critical pH for disaggregation strongly depends on salt concentration. The PMAA/PVCL multilayers are then used as sacrificial compartments for the release of LbL nanostructures in biocompatible close-to-neutral 0.15 M NaCl aqueous conditions. We particularly demonstrate the liberation of LbL nanotubes grown inside the nanopores of templating polymer membranes without having to dissolve the membrane template in nonbiocompatible organic solvents and show that the amount of released nanotubes is close to the amount of noncrossing nanopores in the membrane.

No abstract

New N‐doped reduced graphene oxide (N‐RGO) meshes are facile fabricated by selective etching of 3–5 nm nanopores, with controllable doping of N dopants at an ultrahigh N/C ratio up to 15.6 at%, from pristine graphene oxide sheets in one‐pot hydrothermal reaction. The N‐RGO meshes are illustrated to be an efficient metal‐free catalyst toward hydrogenation of 4‐nitrophenol, with new catalytic behaviors emerging in following three aspects: (i) tunable kinetics following pseudofirst order from commonly observed pseudozero order; (ii) strikingly improved activity with 26‐fold increased rate constant (1.0 s−1 g−1 L); (iii) no induction time required prior to reaction due to depressed back conversion, and dramatically decreased apparent activation energy (Ea) (17 kJ mol−1). The origin of these new catalytic properties can be assigned to the synergetic effects between graphitic N doping and structural defects arising from nanopores. Deeper understanding unveils that the concentration of graphitic N is inverse proportion to Ea, while the pyrrolic N has no impact on this reaction, and oxygenate groups hampers it. The porous nature allows the N‐RGO meshes to conduct catalyze reactions in continuous flow fashion.

Fragile TiO2 nanofibers was functionalized with good structural integrity, flexibility, and foldability, by depressing the sintering of nanocrystallites, enabling PM capture and in situ elimination via a “one-stone-two-birds” approach.