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The development of efficient oil/water separation membranes is highly significant for reducing severe environmental pollution nowadays. Constructing hierarchical structures with double-scale roughness and inverted trapezoidal geometry is an alternative rational design to fabricate low oil-adhesive membranes. Based on this design concept, a Cu mesh vertically wrapped with novel microphone-like Cu-CAT-1 hierarchical microstructures with double-scale roughness was tactfully prepared by a local concentration effect, which was referred to as CCMOF. The CCMOF possessed superior anti-oil-fouling performance and an outstanding water-absorbing capacity (180.3% larger than that of the pristine Cu mesh) due to its ingenious microphone-like structures and its high affinity for water. Therefore, it could separate various types of oil/water mixtures with a considerably high flux of over 25,000 L m−2 h−1 and an extremely low oil content in filtrate of below 10 ppm. The design concept of this work offered a simple idea to design low oil-adhesive membranes for efficient oil/water separation.

It is an increasing need to explore advanced materials and technologies for CO2 capture to weaken its impact on the environment. For the first time, it is demonstrated that a suitable doping can dramatically increase CO2 adsorption capacity of negatively charged C3N nanosheets using density functional theory calculations. For example, the CO2 adsorption energy on 2e− negatively charged P doped C3N (P-C3N) nanosheet can reach −2.233 eV, which is about 600% larger than that on 2e− negatively charged C3N nanosheet. Additionally, the negatively charged P-C3N nanostructure exhibits good CO2/CH4, CO2/H2 and CO2/N2 selectivity. Therefore, P-C3N nanosheet may be a very promising negatively charge-regulated CO2 sorbent. More importantly, charge modulation strategies offer the potential for spontaneous, controllable CO2 storage and release. Furthermore, it is manifested that the increased interactions between CO2 and negatively charged P-C3N monolayer are attributed to the heterogeneous charge density distribution of P-C3N monolayer and the hybridization of p orbits of C and P atoms. These theoretical predictions could shed new light on designing feasible high-performance CO2 sorbents.

Exothermic oxidative dehydrogenation of propane (ODHP) to olefins is a promising alternative to industrialized direct dehydrogenation. However, it encounters a great challenge to control the olefin selectivity as the over-oxidation to produce carbon oxides (COx) is thermodynamically more favorable. In this work, graphitic carbon nitride was reported to be a new kind of metal-free catalyst for ODHP, obtaining high selectivity for propylene (74.7%) and ethylene (14.9%) at a given propane conversion of 12.8%. Based on the spectroscopic insights and in situ experiments, the carbonyl groups modified on the graphitic carbon nitride were affirmed as active sites. A feasible ODHP reaction pathway was hypothesized by density functional theory (DFT) in which two adjacent carbonyl groups on the edge of carbon nitride can activate two C–H bonds of propane simultaneously, thus avoiding the generation of free C3H7* radicals and leading to the high selectivity of light olefins.

Many biophysical and biochemical properties of pathogenic tissues are different from those of healthy tissues. These disease symptom‐associated properties include pH, reduction–oxidation conditions, enzyme generation and expression, blood glucose concentration, mechanical stiffness and strain, and temperature. Autonomous drug release that uses one or more of these disease symptom‐associated properties as the release trigger minimizes the delay in treatments and allows for the release of medications with precisely controlled amounts and with desired spatiotemporal patterns. Herein, a comprehensive assessment of current research progress on autonomous drug release systems (ADRS) is provided. The representative symptoms‐associated properties that can be potentially used as the endogenous stimuli are introduced. The autonomous drug systems that utilize these symptom‐associated signals as the endogenous stimulation signals are discussed, followed by the discussion of current challenges and opportunities in this field, as well as possible future directions in ADRS.

It is imperative to explore an accurate ppb-level acetone sensor for noninvasive detection of diabetes. In this work, two dimensional p-type MoS2 nanosheets are introduced on the surface of p-type ZnO derived from metal-organic frameworks (MOFs) to produce ZnO@MoS2 core/shell heterojunctions as a novel acetone sensor, showing a great enhancement of acetone response, about two orders of magnitude than that of pure ZnO derived from MOFs. For example, the ZnO@MoS2 exhibits about 80 times enhancement in response to 100 ppb acetone than that of pure ZnO. More importantly, this ZnO@MoS2 heterojunctions sensor exhibits an ultra-fast response/recovery to ultra-low concentration acetone (60 s/40 s @ 5 ppb), which is the best acetone sensing performance for the metal oxide-based materials reported to date. Moreover, the acetone sensing performances are negligibly affected by humidity and other gas, which is suitable for exhaled acetone detection. Finally, it is elucidated that the sharp increase of negative heterojunction interface resistance, ultra-fast gas diffusion rates in MoS2 nanosheets and strong interaction energy are key factors for the excellent acetone sensing properties of ZnO@MoS2. This work opens up a novel and efficient way for ultra-low concentration gas detection.

Due to the combined action of gas adsorption, surface diffusion and slippage, classical simulation approaches based on Darcy's law may not be appropriate for simulating shale gas flow in shale. In this work, a novel lattice Boltzmann (LB) model is proposed to study shale gas flow in a kerogen pore by introducing temperature dependent thickness of adsorption layer. The surface diffusion, which is caused by gradient of adsorption density, is considered as the slippage velocity on the surface of adsorption layer. The proposed LB model was adopted to simulate shale gas flow in a nano-pore. The results show that adsorption can significantly decrease the permeability of nano-pores. Surface diffusion improves the gas movement in nano-pores at lower pressure. With the decrease of pore size, the adsorbed layer had more impacts on gas permeability. Increasing temperature improves gas flow ability in nano-pores when pore size is less than 10nm. [Received: December 18, 2017; Accepted: May 2, 2018]

A tin oxide/diatomaceous earth (DE) composite was synthesized via the hydrothermal method without using a template or surfactant, and its humidity-sensing and controlling properties were investigated. The SnO2/DE composites have a special embedded structure, in which SnO2 nanoparticles are embedded in the DE porous frame. The optimal composites exhibit short response and recovery times (T = 3 and 8 s, respectively), and their response (S = 35.64) is 11.88 times higher than that of DE (S = 3). Furthermore, the optimal composite C-1:3 was tested to determine its humidity-controlling properties, which revealed that it possessed absorption (27 h, 12.04%) and desorption (5 h, 8.56%) characteristics. Regarding the selectivity, the C-1:3 sensor showed better sensing behavior to humidity than to NO2, NH3 and other gases. These beneficial properties of the composites are due to a honeycomb structure that endows the composite with a large specific surface area for adsorption of H2O molecules and allows charge transfer between the embedded SnO2 nanoparticles. The humidity-sensing mechanism is explained in detail by the Grotthuss proton transfer theory and density functional theory (DFT), which were used together with a Nyquist diagram to analyze the conditions of H2O adsorption. This study demonstrates a novel strategy for designing a material that can rapidly sense and control humidity and provides insights into the application of the composite in sensing and controlling environmental humidity at room temperature.

For the first time, Co-MOF-74 derived Co3O4/graphene heterojunction nanoscrolls (Co3O4/GNS) structure is synthesized by a simple one-step hydrothermal strategy and subsequent calcination process. Theoretically, the growth mechanism of Co3O4/GNS is revealed by molecular dynamic simulation, demonstrating that a high loading of Co-MOF-74 nanoparticles is needed for effective rolling of GO. The sensor based on Co3O4/GNS exhibits high response of 58.1 (34-fold enhancement compared with that of Co3O4), short response/recovery time of 12 s/66 s (157 s/200 s for Co3O4) toward 1 ppm acetone at 190 °C and superior selectivity, which are much better than those of most reported acetone sensors. Moreover, the Co3O4/GNS can even detect as low as 50 ppb acetone with a notable response (1.24). The appreciable response together with rapid response/recovery of Co3O4/GNS is attributed to the large heterojunction interface between Co3O4 and graphene nanoscroll and high-speed gas transfer pathways provided by nanoscroll. This unique structure design is believed to offer guidance for generalizable synthesis of metal oxide/GNS that can be effectively applied in the fields of ppb-level gas detection.

Using molecular dynamics simulations, we investigated the process of oil detachment from silica surface modified by carboxy groups in aqueous surfactant (cetyltriethylammonium bromide (CTAB)) solution. It is demonstrated that CTAB molecules promote the formation of water channel between oil molecules and silica surface, which is vital to the detachment of oil drop from silica surface. In this paper, the effects of temperature, surfactant concentration, and calcium ion concentration on the oil detachment from silica surface have been extensively examined. We find that appropriate temperature, surfactant concentration, and calcium ion concentration are crucial for improving oil detachment efficiency. Our study can provide a simple method to design and choose appropriate oil-displacing agents, which is important for its applications in oil recovery, ore floatation, detergency, printing fields, and so on.

Chloroplasts are essential organelles, in which genes have widely been used in the phylogenetic analysis of green plants. Here, we took advantage of the breadth of plastid genomes (cpDNAs) sequenced species to investigate their dynamic changes. Our study showed that gene rearrangements occurred more frequently in the cpDNAs of green algae than in land plants. Phylogenetic trees were generated using 55 conserved protein-coding genes including 33 genes for photosynthesis, 16 ribosomal protein genes and 6 other genes, which supported the monophyletic evolution of vascular plants, land plants, seed plants, and angiosperms. Moreover, we could show that seed plants were more closely related to bryophytes rather than pteridophytes. Furthermore, the substitution rate for cpDNA genes was calculated to be 3.3 × 10 − 10 , which was almost 10 times lower than genes of nuclear genomes, probably because of the plastid homologous recombination machinery.

Molybdenum disulfide (MoS 2 ) thin films are grown on p -type Si substrates by dc magnetron sputtering technique and MoS 2 /Si p – n junctions are fabricated. The typical oscillating modes of E 1 2g and A 1g are shown in the Raman spectrum of the MoS 2 film. Atomic force microscopy illustrates that the surface of the deposited MoS 2 film is composed of dense nano-level grains. The electrical characteristics of the junction are investigated. The current–voltage curves of the p – n junction show good rectifying characteristics and change dramatically with temperature. The fabricated junction exhibits obvious sensing properties to ammonia gas (NH 3 ) at room temperature. Especially, the sensing behaviors can be tuned by external electrical fields. In the forward voltage range, the currents increase significantly after the junction is exposed to NH 3 and the response increases with increasing voltage. The sensing performance is featured by a high sensitivity (∼769.2% toward 9000 ppm and ∼19.1% toward 200 ppm), and fast response and recovery (∼5.0 s). The response in reverse voltage range is contrary to that in forward voltage range and decreases with increasing the reverse voltage. We also study the dependence of the sensing response on NH 3 concentration. An almost linear correlation is obtained in the measured range of NH 3 concentration. The sensing mechanisms of the MoS 2 /Si p – n junction are proposed.

The salient practical application feature of an ideal supercapacitor is its ability to deliver high energy density stably even at ultrahigh power density. Therefore, a rational design of electrode materials is essentially required for achieving high current, energy and power densities. In this work, a special “in situ replicating” strategy is employed to fabricate double shell hollow carbon spheres with homogeneously doped heteroatoms. The KOH activation introduces micropores to the thin shells of the hollow carbon spheres. Materials characterizations show that these carbon spheres have such merits as large surface area, easy-accessible micropore surface with faradaic reaction sites, and high conductivity. All these result in ultrafast ion transport from electrolyte to the micropores in the carbon spheres and endow the carbon with outstanding capacitive performance, e.g., an unprecedentedly high specific capacitance of 270 F g−1 at a very high current density of 90 A g−1. Moreover, a high energy density of 11.9 Wh kg−1 at a respectable power density of 30,000 W kg−1 is achieved in 6 M KOH electrolyte.

Unconventional energy, such as shale oil and gas, opens up a new avenue for alleviating the pressure on the use of conventional energy, enabling a sustainable development of economy and industry. We firstly explored the mechanism of oil molecules transportation in a nano-sized shale channel by molecular dynamic simulations. It is demonstrated that the competition between the oil adsorption strength to the shale surface and the driving force from gas flooding (N2) plays the dominant role in the oil translocation process in the shale channel. The encapsulated oil molecules would be expelled by gas flooding when the gas pressure reaches a critical value. Besides, it is found that the pressure of the gas flooding, shale channel pore size, N2 amount, temperature and shale component all have an important effect on the translocation process of oil molecules inside the shale channel, whose oil-driving efficiency is characterized by oil displacement distance and oil displacement loss. This work lays a theoretical foundation to achieve effectively and efficiently exploiting oil. Besides, the result may shed light on explaining many industrial processes and natural phenomena in nano-sized channels, including viscous liquid transport or diffusion through membranes, energy conversion devices, biological molecules (hemoglobin, protein, DNA) translocation and so forth.

Using the first-principles density functional theory (DFT) and molecular dynamics (MD) simulations, we investigate the He separation performance of a porous C2N monolayer synthesized recently. The DFT calculations demonstrate that the porous C2N monolayer is stable enough to be used as a gas separation membrane and the porous C2N monolayer with a suitable pore size presents a surmountable energy barrier (0.13 eV) for He molecules passing through the membrane. Furthermore, the porous C2N monolayer shows an exceptionally high selectivity for He/Ne (Ar, CH4, CO2, N2, etc.) in a wide range of temperatures. Besides, using MD simulations we demonstrate that the porous C2N monolayer exhibits a He permeance of 1 × 107 GPU at room temperature, which is much higher than the value (20 GPU) in current industrial applications. Therefore, the porous C2N monolayer should be an excellent candidate for He separation from natural gas, due to its high selectivity and excellent permeability.

A solar cell based on the n-MoS2/i-SiO2/p-Si heterojunction is fabricated. The device exhibits a high power-conversion efficiency of 4.5% due to the incorporation of a nano-scale SiO2 buffer into the MoS2/Si interface. The present device architectures are envisaged as potentially valuable candidates for high-performance photovoltaic devices.

Self-supported sponge MnO2 nanotube monoliths (SMM) are synthesized via a hydrothermal method using commercial polyurethane foam as a sacrificial template. The SMM with its three-dimensional interconnected foam structure, macroporous channels, and mesoporous tube structure endow this novel material with a diversity of porous architectures and great promise for various applications involving sorbents, catalysts, ion exchange, and energy storage. As a proof of application, we have demonstrated that an SMM-based supercapacitor exhibits excellent capacitance behavior and rate capability.

Bulk-like molybdenum disulfide (MoS2) thin films were deposited on Si substrates using a dc magnetron sputtering technique and n-MoS2/p-Si junctions were fabricated at room temperature (RT) and 400 °C, respectively. The typical oscillating modes of E12g and A1g were shown in the Raman spectra of the as-grown MoS2 films. Atomic force microscopy illustrated that the surfaces of the films were composed of dense nanoscale grains and scanning electron microscopy revealed the existence of large quantities of pores in the surface. The current–voltage curves of the junctions showed obvious rectifying characteristics due to the energy-band bending near the interface of MoS2/Si. The fabricated junctions exhibited humidity-dependent electrical properties. Compared with the one with the MoS2 film deposited at RT, the junction fabricated at 400 °C showed much more obvious sensing properties to humid gas. In particular, the sensitivity of the device could be tuned by external electrical fields. In the forward voltage range, the currents increased significantly after the junction was exposed to humid conditions. The response increased with increasing voltage and reached a saturated value after V = 1.9 V. The sensing performance featured high sensitivity, fast response and recovery. The junction current in the reverse voltage range decreased under the humid condition. This was contrary to that in the forward voltage range. We also studied the dependence of the sensing response on humidity levels. An almost linear correlation was obtained in the measured range of humidity levels. The sensing mechanisms of the MoS2/Si heterojunction were proposed.

In this paper, we have studied Fe-doping of nanostructured tungsten trioxide (WO3) and its pronounced effect in promoting the photoelectrochemical (PEC) water splitting performance. Vertically aligned Fe-doped WO3 nanoflakes on fluorine-doped tin oxide (FTO) were synthesized via the hydrothermal method. An X-ray photoelectron spectroscopy (XPS) analysis confirmed the Fe(3+) substitution at the W(6+) site in the prepared films. Broadened visible light absorption was observed in doped films, likely due to the formation of extra band states through doping. The Fe-doping was shown to greatly improve the PEC water splitting performance of WO3. More specifically, the 2 mol% Fe-doped WO3 achieved a photocurrent density of 0.88 mA cm(-2) at 1.23 V versus RHE, approximately 30% higher than that of the undoped WO3 (0.69 mA cm(-2) at 1.23 V versus RHE). This enhancement was attributed to the reduced band gap and the doping-enhanced charge carrier density as confirmed by the absorption spectra and the Mott-Schottky plots, respectively. Finally, first-principles density functional theory (DFT) calculations confirmed that the formation of oxygen vacancies was favored after Fe-doping, contributing to the increased charge carrier density in slightly doped films.

A series of diaminoalkane-intercalated graphenes (DIGs) are successfully synthesized by intercalating graphite oxide with diaminoalkanes, followed by a reduction process using hydrazine as a reductant at room temperature. The as-prepared intercalated graphite oxides (DIGOs) and their reduced products are characterized using a variety of approaches such as X-ray diffraction, Fourier transform infrared spectroscopy, Raman spectroscopy and elemental analysis. Electrochemical tests show that the specific capacitances of DIGOs and DIGs decrease with the increase of the interlayer distance, and that the DIGs possess larger capacitance than DIGOs after hydrazine reduction. The ion diffusion in the DIGOs/DIGs follows pseudo-second-order kinetics and is dominated mainly by their pore sizes.

MnO2/graphene nanosheets/MnO2 (MGM) is fabricated by a facile and effective ethanol-assisted graphene-sacrifice reduction method. The morphology and structure of the MGM are examined by scanning electron microscopy, transmission electron microscopy, X-ray diffraction and X-ray photoelectron spectroscopy. The MGM is used as a dielectric filler to prepare MGM/Polyvinylidene composites by solution casting and hot pressing. The MGM/Polyvinylidene composites exhibit excellent dielectric properties (dielectric constant is 2360, dielectric loss is 2.0) near the percolation threshold at 1 kHz which are better than that of most carbon/polymer composites. The excellent dielectric properties originate from the poor conductive MnO2 layers which not only ensure good dispersion of graphene nanosheets in the Polyvinylidene fluoride but also act as inter-particle barriers to prevent direct contact of the graphene nanosheets.

A series of Pd/TiO2/SiO2/Si multilayers were produced using magnetron sputtering method. It is found that H2 molecules have dramatic effect on the current–voltage (I–V) characteristics of the Pd/TiO2/SiO2/Si multilayers at room temperature (RT). When Pd/TiO2/SiO2/Si multilayer is exposed to H2, the Pd film quickly reacts with H2 and forms palladium hydride which results in transferring more electrons from the Pd film to TiO2 film. Therefore, the I–V characteristic of Pd/TiO2/SiO2/Si multilayer was greatly changed when exposed to H2. For example, a Pd/TiO2/SiO2/p-Si multilayer can show a high response (∼2431%) to 1% H2 with appreciable short response time of 13 s and recovery time of 4 s at RT. Besides, it is demonstrated that Si substrate has a great effect on the H2 response of Pd/TiO2/SiO2/Si multilayers. When exposed to H2 the current of Pd/TiO2/SiO2/p-Si multilayer at −0.5 V greatly decreases while the current of Pd/TiO2/SiO2/n-Si multilayer greatly increase, which can be understood by their energy band structures.

Spherical and dendritic CdS@TiO 2 hollow double-shelled nanoparticles (HDNPs) with visible light photocatalytic activity were synthesized via sol–gel and wet-chemical approach respectively. The morphology, composition, size of the nanoparticles and crystal structure of the synthesized CdS@TiO 2 HDNPs were characterized by XRD, TEM, and SAED. The results showed that morphologies and crystalline phases of as-prepared CdS@TiO 2 HDNPs mainly depended on the synthesis conditions such as temperature and pressure. Compared with the typical core–shell of PS@TiO 2 and PS@CdS, CdS@TiO 2 HDNPs, their photocatalytic activity was obviously enhanced with maximum degradation efficiency of RhB as high as 99.9%.

Heterojunctions are very promising structures due to their hybrid properties, which are usually obtained via a multistep growth process. However, in this paper, WO

A novel sandwich-like composite with ultrathin CoAl-layered double hydroxide (LDH) nanoplates electrostatically assembled on both sides of two-dimensional polypyrrole/graphene (PG) substrate has been successfully fabricated using facile hydrothermal techniques. The PG not only serves as an excellent conductive and structural scaffold to enhance the transmission of electrons and prevent aggregation of CoAl-LDH nanoplates but also contributes to the enhancement of the specific capacitance. Owing to the homogeneous dispersion of CoAl-LDH nanoplates and its intimate interaction with PG substrate, the resulting CoAl-LDH/PG nanocomposite material exhibits excellent capacitive performance, for example, enhanced gravimetric specific capacitance (864 F g–1 at 1 A g–1 ), high rate performance (75% retention at 20 A g–1), and excellent cycle life (almost no degradation in supercapacitor performance after 5000 cycles) in aqueous KOH solution. Furthermore, the assembled asymmetric capacitor is able to deliver a superh...

Development of high-performance sorbents is extremely significant for CO

The sliding behavior of interwalls between double-walled carbon nanotubes (DWCNTs) is studied by molecular dynamics (MD) simulations. The results show that a platinum (Pt) nanowire (NW) is able to push out a single wall from the DWCNT. The pushout process is strongly dependent on the match level of the NW radius and the inner wall CNT radius. The match radius of the Pt NW and the inner CNT wall will form perfect single-walled CNT (SWCNT) and Pt/CNT core/shell nanostructure. In addition, the bonding interactions between the Pt NW and the CNT are also studied. The shear stress between the Pt NW and CNT is in megapascal magnitude. The chirality has little effect on the interfacial bonding and the shear stress between the Pt NW and the CNT. This study will shed light on the understanding of the lubrication mechanism of the multi-walled CNT and the metal NWs in realistic situations.

In this paper, a facile and elegant Green Chemistry method for the synthesis of SnO

The SnO

In this work, we investigate the dynamics mechanism of oil transportation in nanochannel using molecular dynamics simulations. It is demonstrated that the interaction between oil molecules and nanochannel has a great effect on the transportation properties of oil in nanochannel. Because of different interactions between oil molecules and channel, the center of mass (COM) displacement of oil in a 6-nm channel is over 30 times larger than that in a 2-nm channel, and the diffusion coefficient of oil molecules at the center of a 6-nm channel is almost two times more than that near the channel surface. Besides, it is found that polarity of oil molecules has the effect on impeding oil transportation, because the electrostatic interaction between polar oil molecules and channel is far larger than that between nonpolar oil molecules and channel. In addition, channel component is found to play an important role in oil transportation in nanochannel, for example, the COM displacement of oil in gold channel is very few due to great interaction between oil and gold substrate. It is also found that nano-sized roughness of channel surface greatly influences the speed and flow pattern of oil. Our findings would contribute to revealing the mechanism of oil transportation in nanochannels and therefore are very important for design of oil extraction in nanochannels. Electronic supplementary material The online version of this article (doi:10.1186/s11671-017-2161-2) contains supplementary material, which is available to authorized users.

Layered metal dichalcogenides (LMDs) semiconducting materials have recently attracted tremendous attention as high performance gas sensors due to unique chemical and physical properties of thin layers. Here, three-dimensional SnS

By use of grand canonical Monte Carlo calculations, we study the effects of sulfur doping and humidity on the performance of graphite split pore as an adsorbent for CO

Supporting Information for Surface Effect on Oil Transportation in Nanochannel: A Molecular Dynamics Study. (DOCX 225 kb)

A ultrahigh performance humidity sensor based on graphene oxide (GO)/poly(diallyldimethylammonium chloride) (PDDA) nanocomposite film was reported in this paper. The multilayered film of GO/PDDA was fabricated on a polyimide substrate using layer-by-layer self-assembly technique. The structures of the self-assembled films were characterized by scanning electron microscopy (SEM) and X-ray diffraction (XRD). The humidity sensing behaviors of the film sensor were investigated at room temperature over a wide range of 11–97% relative humidity. Unprecedented response of up to 265,640% was demonstrated for the presented sensor when exposed to varying relative humidity levels, which is better than that of the best conventional humidity sensor. Furthermore, the presented sensor exhibited ultrafast response and recovery times capable of monitoring human breath. Moreover, the possible humidity sensing mechanism of the proposed sensor was discussed by using complex impedance spectra and bode diagrams. This measurement results observed highlight the layer-by-layer self-assembled graphene oxide/polyelectrolyte film is a candidate material for constructing humidity sensors.

Low surface area carbon materials, derived from pyrolyzing biomass or polymers, often possess high areal capacitances. However, the well-accepted pseudocapacitance introduced by heteroatoms could not explain this phenomenon without doubt. In order to explore the nature of the energy storage mechanism in these low surface area carbon materials, we prepared a series of laver-based carbon materials by regulating the heteroatom contents and investigated their electrochemical performance. Combining the results of advanced pore structure analyses and electrochemical measurements, we disclose that the presence of ultramicropores, which could not be probed by adsorbates such as nitrogen gas or argon, but are accessible to carbon dioxide or electrolyte ions, plays a most dominant role in the high capacitance of low surface area carbon materials. In this contribution, the previously accepted viewpoint that the capacitance is mainly derived from heteroatoms undergoing Faradaic reactions is challenged.

We provide a one-step hydrothermal reaction to modify graphite powders (GPs) and prepare hydroxyl modified GPs/poly(vinylidene fluoride) (PVDF) composites which have excellent dielectric properties using high conductivity, low cost GPs as raw material. Fourier transform infrared spectroscopy (FT-IR) and X-ray photoelectron spectroscopy (XPS) showed that hydroxyl groups had been introduced to the surface of GPs. Scanning electron microscopy (SEM) showed that the hydroxyl modified GPs had better dispersion in the polymer matrix than the GPs. An ultra-high dielectric constant of more than 5.1 × 103 (dielectric loss is about 3.0) was obtained for the hydroxyl modified GPs/PVDF near the percolation threshold at 1 kHz. The hydroxyl modified GPs/PVDF composites exhibited better dielectric properties than most carbon/polymer composites. POLYM. COMPOS., 2014. © 2014 Society of Plastics Engineers

In this study, amorphous (K,Na)NbO 3 (KNN) lead free thin films were deposited on (100) silicon substrate via RF magnetron sputtering, and the humidity sensitive properties of these films have been firstly studied. The humidity sensors based on these KNN films show a giant capacitive response of 95% at 25 Hz in the RH range 33–95% and a great linear relationship between capacitance and relative humidity (RH). The humidity sensing mechanism of amorphous KNN films was well described, and its high performance was correlated to a large amount of intrinsic hydrophilic groups K–O and Na–O bonds as well as the rough structure on the amorphous film surfaces, thereby, accelerating the adsorption and desorption of multi-physisorbed water molecules. This conclusion was further confirmed by a comparison studies between KNN amorphous film and bulk ceramics (response time: 1.0 min vs. >10 min; recovery time: 2.0 min vs. 7 min).

Graphene nanoribbons (GNRs) have been of great interest in a wide range of device applications for their novel physical, electronic and spin transport properties. Here we study the hydrogen (H2) sensing properties of GNRs decorated with palladium (Pd) nanoparticles by a one-step chemical modification and reduction process. A novel Pd-GNR film/SiO2/Si structure was fabricated by transferring a Pd-GNR film onto a heavily doped Si substrate with a native oxide layer. It is demonstrated that the Pd-GNR film/SiO2/Si structure exhibits highly enhanced responses to H2 than the pristine Pd-GNR film at parts-per-million (ppm) concentration levels at room temperature. For example, the Pd-GNR film/SiO2/p-Si structure shows an excellent response (ΔR/Rair) of ∼94% to 100 ppm H2 in air. The sensing mechanism was proposed to explain these H2 sensing characteristics based on p–n junction theory. Our findings demonstrate the incorporation of nanoparticles in GNR-based gas sensors through chemical functionalization and present a novel strategy for the application of GNRs in high performance gas sensors.

Using molecular dynamics simulations, it is shown that N-doped porous graphene membrane can efficiently separate CO2 from the CO2/CH4 mixture. The effects of pore rim modifications, N-doping sites, initial gas pressure, and feed gas compositions on CO2 separation performance of N-doped porous graphene membrane are also examined. It is found that gas permeability increases with increasing initial gas pressure or the feed gas percentages. Pore rim modifications with nitrogen atoms (pyridinic N) can significantly improve the selectivity of CO2 over CH4 owing to the enhanced electrostatic interactions compared to the unmodified one, and the all-N-modified pore-16 shows the highest CO2 selectivity over CH4 (~29). Doping N atoms on the graphene sheets (quaternary N) has little effect on the CO2 selectivity. Our study demonstrates that the N-doped porous graphene is an excellent candidate for CO2 separation, which may be beneficial for the realization of a low carbon society.

C4H nanotube (C4HNT) which is a novel kind of hydrogenated carbon nanotubes (CNTs) has gradually attracted much attention due to its unique structure and potential applications. In this work, we systematically studied the mechanical properties of C4HNT using classical molecular dynamics and molecular mechanics simulations. It is found that C4HNT can bear much greater radial pressure than CNT. For example, the collapse pressure of (10, 0) C4HNT can reach 25 GPa, which is more than 4 times that of (10, 0) CNT (6 GPa). However, hydrogenation weakens the value of Young’s modulus of CNT, and leads to the descent of axial strength of CNT. Besides, it is demonstrated that the collapse pressure of C4HNT decreases with increasing tube diameter while the Young’s modulus of C4HNT is independent of tube diameter. And the tube number, chirality, length have no effect on the axial and radial mechanical properties of C4HNT. The results show that C4HNT has much better radial mechanical properties than CNT so that C4HNT m...

Enteromorpha prolifera (E.prolifera), an ocean biomass, was used as raw materials to prepare active carbons by a two-step strategy (pre-carbonization followed by chemical activation). The as-prepared active carbons have been characterized by a variety of means such as N2 adsorption, field emission scanning electron microscope, transmission electron microscope, Raman spectroscopy. The results showed that the carbons have large surface area and developed porosity with micro-meso hierarchical pore texture. As evidenced by electrochemical measurements, the specific capacitance of the carbons can reach up to 296 F g−1. More importantly, the carbons can maintain a high capacitance of up to 152 F g−1 at a very high current density of 30 A g−1, highlighting the promise of the carbons for high power applications.

The influence of oxygen molecule (O2) on the hydrogen storage process of Li-doped graphene has been investigated using the density functional theory (DFT) simulation. The results show that, the existence of the O2 has a large influence on the hydrogen storage process of Li-doped graphene. Under the condition of coadsorption, each Li atom can only adsorb 3 H2 (4 H2 can be adsorbed without O2) with a theoretical storage density of 2.6 wt.%.

It is demonstrated that the fluorine-modified porous graphene membrane has excellent selectivity for CO2/N2 separation by using molecular dynamic (MD) simulations. We also investigated in detail the mechanism of the fluorine-modified porous graphene membrane for CO2/N2 separation by using first-principles simulations. We find that the diffusion barriers for CO2 and N2 to pass through the pore-22 (with 22 carbon atoms drilled out) graphene membrane are relatively small, which indicates that the pore-22 has a low selectivity for CO2/N2 separation. After fluorine modification, the diffusion barrier for CO2 to pass through decreases to 0.029 eV, while the diffusion barrier for N2 greatly increases to 0.116 eV. Therefore, N2 gets more difficult, while CO2 gets easier to penetrate through the fluorine-modified pore-22. The fluorine-modified pore-22 porous graphene shows a great enhancement of selectivity for CO2/N2 separation, which is consistent with the MD results. Our studies show that first-principles simul...

First-principle density functional theory (DFT) calculation and molecular dynamic (MD) simulation are employed to investigate the hydrogen purification performance of two-dimensional porous graphene material (PG-ESX). First, the pore size of PG-ES1 (3.2775 Å) is expected to show high selectivity of H2 by DFT calculation. Then MD simulations demonstrate the hydrogen purification process of the PG-ESX membrane. The results indicate that the selectivity of H2 over several other gas molecules that often accompany H2 in industrial steam methane reforming or dehydrogenation of alkanes (such as N2, CO, and CH4) is sensitive to the pore size of the membrane. PG-ES and PG-ES1 membranes both exhibit high selectivity for H2 over other gases, but the permeability of the PG-ES membrane is much lower than the PG-ES1 membrane because of the smaller pore size. The PG-ES2 membrane with bigger pores demonstrates low selectivity for H2 over other gases. Energy barrier and electron density have been used to explain the difference of selectivity and permeability of PG-ESX membranes by DFT calculations. The energy barrier for gas molecules passing through the membrane generally increase with the decreasing of pore sizes or increasing of molecule kinetic diameter, due to the different electron overlap between gas and a membrane. The PG-ES1 membrane is far superior to other carbon membranes and has great potential applications in hydrogen purification, energy clean combustion, and making new concept membrane for gas separation.

This paper reports the synthesis of a novel cardo type polyimide PI(BTDA–BAPF–DMMDA) based on 3,3′,4,4′-benzophenone-tetracarboxylic dianhydride (BTDA), 9,9′-bis (4-aminophenyl) fluorine (BAPF) and 4,4′-biamino-3,3′-dimethyldiphenyl-methane (DMMDA) using the low temperature solution copolymerization method, and cardo polyimide/TiO2 mixed matrix membranes (MMMs) were prepared by blending of TiO2 sol and the PI solution. The incorporation of the cardo groups was achieved through the reaction between the free –COOH of polyamide acid (PAA) and the –NH2 of the BAPF. The chemical structure and physical properties of membrane material were characterized using FTIR, 1H NMR, DSC and XRD. Results showed that the MMMs containing 24 wt% of TiO2 sol were nano-composite membranes with strong interactions between inorganic TiO2 phase and organic PI phase. Compared with PI(BTDA–DMMDA) membrane, the addition of BAPF and TiO2 greatly improved the gas separation properties of cardo PI membranes and MMMs. The gas permeation (PO2) and ideal separation factor (aO2/N2) of the cardo polyimide PI/TiO2 membrane with a BAPF: BTDA molar ratio of 0.15:1 and TiO2 content of 24 wt% were 4.5 Barrer and 15.8 respectively, which were a respective 9.4 and 4.6 times higher than that of the PI(BTDA–DMMDA) membrane. The PO2 and aO2/N2 of the cardo polyimide/TiO2 MMMs prepared in this work were beyond Robeson’s trade-off upper bound, highly promising for future gas separation application.

As wastewater remediation becomes a global concern, the development of innovative advanced oxidation processes for wastewater treatment is still a major challenge. With regard to its fast removal rate and environmental compatibility, plasma technology is considered as a promising remediation technology for water remediation. The principles of electrical plasma with liquids for pollutant removal and the reactors of various electrical discharge types are outlined in this review. To improve energy efficiency, combination of plasma technology with catalysts has attracted significant attention. The present review is concerned about present understanding of the mechanisms involved in these combined processes. Further on, detailed discussions are given of the effects of various factors on the performance of pulsed electrical plasma technology in water treatment processes. Finally, special attention is paid to the future challenges of plasma technology utilized for industrial wastewater treatment.

The uniform low density ZnS microtube arrays with a large diameter of up to 1 um are prepared for the first time via a three-step approach. ZnO microrod arrays are first hydrothermally grown on fluorinated tin oxide glass as a sacrificial template, which are converted to ZnO/ZnS core/shell structures subsequently through a sulfidation process, ZnS microtube arrays are then obtained by selectively etching of ZnO cores. The unique properties of this large diameter and low density ZnS tube array are demonstrated by comparing it with those of small diameter and high density ZnS tube array for use in the hybrid film photoelectrode of dye-sensitized solar cells.

Photoelectrochemical water splitting is an ideal method for hydrogen production due to its potential on high efficiency, simplicity and environmental friendliness. Photocatalysts are one of crucial parts for Photoelectrochemical water splitting, whilst most photocatalysts own insufficient hydrogen evolution efficiency due to narrow solar spectrum absorption range or low quantum efficiency. Herein, we first prepare Fe2O3 nanorod arrays by solvothermal method and then in-situ synthesize a hierarchical flower-like nickel ferrite/hematite heterojunction via facile solution quenched method. The as-prepared samples are characterized by X-Ray Powder Diffraction, X-ray photoelectron spectroscopy, scanning electron microscope, transmission electron microscope, Raman spectra and UV–vis absorption spectra. Morphological characterization shows nickel ferrite flower petal layer forms surrounding hematite stamens. This flower-like structure exhibits excellent light absorption properties (extending over 850 nm) with band gap at 1.73–1.88 eV, which is evidently narrower than that of pure hematite at 2.1 eV (about 600 nm). Its hydrogen evolution rate is 24 times higher than that of pure hematite.

Smart sensing devices with high reliability and self-powered features are critical in future generation wearable applications. In this paper, we reported for the first time a room temperature Au-MoSe2 composite ammonia (NH3) sensor driven by a novel flexible piezoelectric nanogenerator (PENG) based on two-dimensional (2D) semiconductor MoS2 flake. Moreover, we also demonstrated the MoS2-based PENG device attached to the human body for harvesting diverse body motion energy, demonstrating its strong potential for applications in wearable devices. A series of characterizations of 2D piezoelectric semiconductor MoS2 and Au-MoSe2 sensing materials were carried out. The Au-MoSe2 composite-based ammonia sensor with MoS2 PENG showed a higher response (Va/Vg = 29 @ 100 ppm NH3) toward NH3 than that of MoSe2 counterpart (Va/Vg = 25 @ 100 ppm NH3). And it has superior selectivity and outstanding long-term stability. Moreover, the sensor also has a fast response/recovery time (18 s/16 s) towards 20 ppm NH3. Finally, the enhanced sensing mechanism of Au-MoSe2 composite toward NH3 was discussed by using first-principle calculations based on density functional theory.