It is well-established that the structures dominate the properties. Inspired by the highly contorted and crumpled maxilloturbinate inside dog nose, herein an artificial nanostructure, i.e., 3D crumpled graphene-based nanosheets, is reported with the simple fabrication, detailed characterizations, and efficient gas-sensing applications. A facile supramolecular noncovalent assembly is introduced to modify graphene with functional molecules, followed with a lyophilization process to massively transform 2D plane graphene-based nanosheets to 3D crumpled structure. The detailed morphological characterizations reveal that the bioinspired nanosheets exhibit full consistency with maxilloturbinate. The fabricated 3D crumpled graphene-based sensors exhibit ultrahigh response (Ra/Rg = 3.8) toward 10 ppm of NO2, which is mainly attributed to the specific maxilloturbinate-mimic structure. The sensors also exhibit excellent selectivity and sensing linearity, reliable repeatability, and stability. Interestingly, it is observed that only 4 mg of graphene oxide (GO) raw materials can produce more than 1000 gas sensors, which provides a new insight for developing novel 3D biomimetic materials in large-scale gas sensor production.Keywords: crumpled graphene nanosheets; dog noses; lyophilization; NO2 sensors; supramolecular modification;

In this work, we report the formation of a supramolecular assembly of graphene with a donor–π-acceptor (D–π-A) molecule to detect low concentration NO2. 5-Aminonaphthalene-1-sulfonic acid (ANS) was used herein to π–π stack with reduced graphene oxide (rGO), the resulting π-conjugated bridge being linked by a donor unit (–NH2) and an acceptor unit (–SO3H). The prepared ANS-rGO shows the highest response (Ra/Rg = 13.2 to 10 ppm NO2) so far among the reported organic molecule modified graphene materials, and excellent selectivity and reliable reversibility at room temperature. Furthermore, as revealed through the charge density difference calculation, it is the effective enhancement of charge transfer between ANS and graphene that should be responsible for the sharp improvement of NO2 gas response of the material. Thus, for the first time, we demonstrate that supramolecular assembly of a D–π-A molecule and graphene provides a facile and effective approach to fabrication of high performance graphene-based gas sensors.

Bio-calcification, known as microbiologically induced calcium precipitation, is an important process of the global carbon cycle. A large number of microorganisms exhibit this ability, including cyanobacteria. Even though the process was realized a long time ago, the detailed mechanism is still unclear. In this paper, we investigate the key role of extracellular carbonic anhydrase during bio-calcification of Synechocystis sp. FACHB 898. Detailed studies revealed that the precipitation of CaCO3 was significantly hindered when the function of extracellular carbonic anhydrase in Synechocystis sp. was inhibited. Furthermore, the reduction of calcium concentration in solution was significantly correlated with the reduction of bicarbonate concentration as 1:2. The results suggested that extracellular carbonic anhydrase of cyanobacteria enhanced CaCO3 precipitation from calcium and bicarbonate through facilitating the proton consumption during transformation of bicarbonate to carbon dioxide.

One of the key processes of photosynthesis is to control the influx of atmospheric carbon dioxide (CO2). Ion channels fulfill this process by regulating the opening and closing of stomatal pores in plants’ leaves. Inspired by this natural process, we have developed an amidine-modified gas-responsive system that closely mimics stomatal pores: CO2 rather than the variation in the pH value directly modulates the conductance state of the channel. The CO2-activated chemical reaction of amidine groups is reversible and produces an excess surface charge on the pore walls of asymmetric nanochannels, which makes the ions pass preferentially through the nanochannels in one direction relative to the conductance in the other direction, resulting in a significant ion current rectification. Furthermore, the influence of the different molecular conformation of the amidine-containing molecules on the current is investigated and discussed. The conclusive simulation of our system based on the Poisson and Nernst–Planck (PNP) model is also in good agreement with the experimental results. Accordingly, we have successfully mimicked the mechanism of stomatal closure in plants with our gas-activated nanosystem.

This study reports the supramolecular assembly of a silver nanoparticle-naphthalene-1-sulphonic acid-reduced graphene oxide composite (Ag-NA-rGO) and its utilization to fabricate a highly sensitive and selective gas sensor. The prepared supramolecular assembly acted not only as a non-covalent functionalization platform (π–π interaction) but was also an excellent scaffold to fabricate a highly sensitive and selective low concentration NO2 gas sensor. The prepared composites were characterized using several techniques, which revealed that the graphene sheets were dispersed as ultrathin monolayers with a uniform distribution of silver nanoparticles. The fabricated multilevel structure exhibited an excellent sensing performance, i.e. 2.8 times better, towards 10 ppm NO2 compared to the NA-rGO and rGO based sensors. Apart from its high sensitivity, superior reversibility and selectivity, the prepared supramolecular assembly exhibited an outstanding linear response over the large concentration range from 1 ppm to 10 ppm. The obtained results demonstrate that the prepared supramolecular assembly holds great potential in the fabrication of efficient and effective low-concentration NO2 gas sensors for practical applications.

An electric-field induced technique has been successfully utilized to control the phase separation and the interfaces of semiconductor–insulator composite film, which provided a new research approach for scientists working in related fields.

Conjugated polymer (CP) multilayer films with higher conductivity have been constructed by electric-field induced LBL assembly technique. Single component has been selected in the alternate deposition process, which not only provides a universal approach for CP films fabrication but also broadens the applicable scope of LBL assembly technique.

This paper reports the supramolecular fabrication of polyelectrolyte-modified reduced graphene oxide (rGO) nanocomposites and their applications towards NO2 gas sensors. To prepare the composite materials for sensing applications, rGO was used as a template which was readily prepared through the reduction of hydrazine hydrate. By using a facile and effective supramolecular assembly (SA) method, two nanocomposites, i.e. poly(allylamine hydrochloride)–rGO (PAH–rGO) and polystyrenesulfonate-rGO (PSS–rGO) were prepared and efficiently used as effective materials to fabricate highly sensitive and stable NO2 gas sensors. The prepared nanocomposites were examined using several techniques which confirmed the successful formation of PAH–rGO and PSS–rGO nanocomposites. By detailed sensing experiments, it was found that both PSS–rGO and PAH–rGO nanocomposites exhibited strong gas sensing response, good stability and favorable reversibility for the detection of NO2 gas. Finally, NO2 gas sensing mechanisms, based on the utilization of specific nanocomposites, were also discussed and presented in this paper.

We report the fabrication and detailed characterization of an ultrafast responsive, excellently stable and reproducible humidity sensor based on a supramolecularly modified graphene composite. The fabricated humidity sensors exhibited a response and recovery time of less than 1 s, which is the lowest among the values found in the literature. In addition, various sensing performances of the fabricated humidity sensors were studied in detail, and the corresponding kinetic model and mechanism have also been deduced and described.

•Gibbsite nanoplatelets were assembled on their basal plane to form (001)-textured films.•Textured alumina ceramics were prepared by sintering textured gibbsite films without addition of α-alumina seeds.•Both pseudomorphic and topotactic aspects were exploited in bulk form instead of individual nanoparticulate size.•Direct XRD evidence of the topotactic dehydroxylation from gibbsite to α-alumina is presented in this work.In this paper, textured alumina ceramics were prepared from dehydroxylation of gibbsite films and the pseudomorphic and topotactic nature of the dehydroxylation of textured gibbsite films has been investigated. First, the precursor film with a (001)-textured structure was obtained via vacuum filtration deposition of diluted aqueous suspensions of gibbsite nanoplatelets. Subsequently, (001)-textured α-alumina ceramics were successfully achieved by sintering of the deposited gibbsite films without addition of α-alumina seeds. The Scanning Electron Microscope (SEM) and X-ray Diffraction (XRD) results show that, during the phase transition from gibbsite to α-alumina, both layered morphology and crystal's axis orientation have been retained to a considerable extent. For the first time, a direct XRD evidence of gibbsite topotactic dehydroxylation to the α-alumina phase is presented. It is believed that the method described here exploits gibbsite's pseudomorphic and topotactic dehydroxylation, not on individual particles scale but on a bulk form. The resulting structure can be considered as inorganic scaffolds which can have applications for fabrication of dense, textured alumina-based ceramics and other layered/textured nanocomposites.

In this paper, a simple and fast (4 days) procedure to synthesize colloidal gibbsite nanoplatelets (NPTs) from a single aluminum alkoxide (aluminum sec-butoxide) as precursor is presented. The introduction of a preheating step accelerated the precursor’s hydrolysis/peptization and considerably shortened the overall reaction time while the acid concentration affected the uniformity of the platelets shape. This procedure was successfully exploited to rapidly produce gibbsite platelets of controllable sizes by combination with the seeded growth method. The use of a single alkoxide precursor induced high growth rates and allowed a fast control of the platelets size over a wide range (nano- to microscale after only three growth steps). No signs for size limitation were observed. The dehydroxylation sequence of the as-synthesized NPTs was systematically investigated. Thermally stable chi-alumina NPTs, pseudomorphs of the parent gibbsite platelets, with a micro/mesoporous structure and high specific surface area, were obtained. The synthesized gibbsite NPTs can efficiently adsorb Methyl Orange dye in wastewater treatment with removal efficiency up to 94.8%.Keywords: gibbsite nanoplatelets; high surface area; MO dye removal; pseudomorphic dehydroxylation; seeded growth; size control;

An amidine-based fluorescent chemosensor has been prepared and is sensitive to the viscosity increase of ionic liquid formed during a specialized reaction of amidine groups with CO2, which provides a facile and visible way to detect and sense CO2. It has been found that the greener fluorescent chemosensor has unique sensitivity to CO2, extraordinarily high water-resistance and no problem of carbon monoxide-interfering.

A polyethylene oxide-b-polystyrene (PEO-b-PS) block copolymer incorporating UV-crosslinkable coumarin groups in the PS block self-assembled into a cylindrical structure with PEO cylinders perpendicular to the film surface, which exhibited excellent CO2 separation properties. The block copolymer was successfully synthesized by atom transfer radical polymerization (ATRP). The molecular characterization of the diblock copolymer was performed with 1H nuclear magnetic resonance (NMR) and gel permeation chromatography (GPC). The UV-crosslinking of the film was monitored by UV-vis absorption spectroscopy. The cylindrical phase structure was confirmed by transmission electron microscopy (TEM). Gas permeation properties of CO2, N2 and He were determined at different temperatures varying from 20 °C to 70 °C. Both the CO2 permeation flux and total gas selectivity increased with increasing temperature. The maximum of CO2 permeance at 70 °C was 20400 × 10−6 cm3 cm−2 s−1 cmHg−1, and gas selectivity over He and N2 was 20.1 and 27.7, respectively. It was concluded that the functional block units and self-assembled microphase structures synergetically played key roles in the high performance of the membrane.

A polyethylene oxide-b-polystyrene (PEO-b-PS) block copolymer incorporating UV-crosslinkable coumarin groups in the PS block self-assembled into a cylindrical structure with PEO cylinders perpendicular to the film surface, which exhibited excellent CO2 separation properties. The block copolymer was successfully synthesized by atom transfer radical polymerization (ATRP). The molecular characterization of the diblock copolymer was performed with 1H nuclear magnetic resonance (NMR) and gel permeation chromatography (GPC). The UV-crosslinking of the film was monitored by UV-vis absorption spectroscopy. The cylindrical phase structure was confirmed by transmission electron microscopy (TEM). Gas permeation properties of CO2, N2 and He were determined at different temperatures varying from 20 °C to 70 °C. Both the CO2 permeation flux and total gas selectivity increased with increasing temperature. The maximum of CO2 permeance at 70 °C was 20400 × 10−6 cm3 cm−2 s−1 cmHg−1, and gas selectivity over He and N2 was 20.1 and 27.7, respectively. It was concluded that the functional block units and self-assembled microphase structures synergetically played key roles in the high performance of the membrane.

An electric-field induced technique has been successfully utilized to control the phase separation and the interfaces of semiconductor–insulator composite film, which provided a new research approach for scientists working in related fields.