Flash Nitrogen-Doped Carbon Nanotubes for Energy Storage and Conversion.

In recent years, nitrogen-doped carbons show great application potentials in the fields of electrochemical energy storage and conversion. Here, the ultrafast and green preparation of nitrogen-doped carbon nanotubes (N-CNTs) via an efficient flash Joule heating method is reported. The precursor of 1D core-shell structure of CNT@polyaniline is first synthesized using an in situ polymerization method and then rapidly conversed into N-CNTs at ≈1300 K within 1 s. Electrochemical tests reveal the desirable capacitive property and oxygen catalytic activity of the optimized N-CNT material. It delivers an improved area capacitance of 101.7 mF cm-2 at 5 mV s-1 in 1 m KOH electrolyte, and the assembled symmetrical supercapacitor shows an energy density of 1.03 µWh cm-2 and excellent cycle stability over 10 000 cycles. In addition, the flash N-CNTs exhibit impressive catalytic performance toward oxygen reduction reaction with a half-wave potential of 0.8 V in alkaline medium, comparable to the sample prepared by the conventional long-time pyrolysis method. The Zn-air battery presents superior charge-discharge ability and long-term durability relative to commercial Pt/C catalyst. These remarkable electrochemical performances validate the superiorities of the Joule heating method in preparing the heteroatom-doped carbon materials for wide applications.

Unveiling Superior Capacitive Behaviors of One-Pot Molten Salt-Engineered B, N Co-Doped Porous Carbon Sheets.

Heteroatom-doped porous carbon materials with distinctive surface properties and capacitive behavior have been accepted as promising candidates for supercapacitor electrodes. Currently, the researches mainly focus on developing facile synthetic method and unveiling the structure-activity relationship to further elevate their capacitive performance. Here, the B, N co-doped porous carbon sheet (BN-PCS) is constructed by one-pot pyrolysis of agar in KCl/KHCO3 molten salt system. In this process, the urea acts as directing agent to guide the formation of 2D sheet morphology, and the decomposition of KHCO3 and boric acid creates rich micro- and mesopores in the carbon framework. The specific capacitance of optimized BN-PCS reaches 361.1 F g-1 at a current density of 0.5 A g-1 in an aqueous KOH electrolyte. Impressively, the fabricated symmetrical supercapacitor affords a maximum energy density of 43.5 Wh kg-1 at the power density of 375.0 W kg-1 in 1.0 mol L-1 TEABF4 /AN electrolyte. It also achieves excellent long-term stability with capacitance retention of 91.1% and Columbic efficiency of 100% over 10 000 cycles. This study indicates one-pot molten salt method is effective in engineering advanced carbon materials for high-performance energy storage devices.

Biaxially-Strained Phthalocyanine at Polyoxometalate@Carbon Nanotube Heterostructure Boosts Oxygen Reduction Catalysis.

Iron phthalocyanine (FePc) with unique FeN4 site has attracted increasing interests as a promising non-precious catalyst. However, the plane symmetric structure endows FePc with undesired catalytic performance toward the oxygen reduction reaction (ORR). Here, we report a novel one-dimensional heterostructured ORR catalyst by coupling FePc at polyoxometalate-encapsulated carbon nanotubes (FePc-{PW12 }@NTs) using host-guest chemistry. The encapsulation of polyoxometalates can induce a local tensile strain of single-walled NTs to strengthen the interactions with FePc. Both the strain and curvature effects of {PW12 }@NT scaffold tune the geometric structure and electronic localization of FeN4 centers to enhance the ORR catalytic performance. As expected, such a heterostructured FePc-{PW12 }@NT electrocatalyst exhibits prominent durability, methanol tolerance, and ORR activity with a high half-wave potential of 0.90 V and a low Tafel slope of 30.9 mV dec-1 in alkaline medium. Besides, the assembled zinc-air battery demonstrates an ultrahigh power density of 280 mW cm-2 , excellent charge/discharge ability and long-term stability over 500 h, outperforming that of the commercial Pt/C+IrO2 cathode. This study offers a new strategy to design novel heterostructured catalysts and opens a new avenue to regulate the electrocatalytic performance of phthalocyanine molecules.

An Efficient and Stable Perovskite Solar Cell with Suppressed Defects by Employing Dithizone as a Lead Indicator.

The defects in perovskite films are one of the most non-negligible factors that can attenuate the performances of perovskite solar cell. This work fabricates defect-reduced perovskite film by using the lead indicator (dithizone) as an additive of perovskite functional layer. The dithizone can retard the crystallization rate of perovskite films, passivate the defects, and enhance the structure stability of perovskite by coordinating with lead atoms. As a result, the device doped with dithizone yields outstanding power conversion efficiency and stability.

An Interconnected Ternary MIn2 S4 (M=Fe, Co, Ni) Thiospinel Nanosheet Array: A Type of Efficient Platinum-Free Counter Electrode for Dye-Sensitized Solar Cells.

The ternary iron-group thiospinels of metal diindium sulfides (MIn2 S4 , M=Fe, Co, Ni) with a vertically aligned nanosheet array structure are fabricated through an in situ solvothermal method on F-doped tin oxide (FTO) substrates, which are employed as one type of platinum (Pt)-free counter electrodes (CEs) in structure-dependent dye-sensitized solar cells (DSSCs). A DSSC assembled with ternary CoIn2 S4 CE achieves an photoelectric conversion efficiency (PCE) of 8.83 %, outperforming than that of FeIn2 S4 (7.18 %) and NiIn2 S4 (8.27 %) CEs under full sunlight illumination (100 mW cm-2 , AM 1.5 G), which is also comparable with that of the Pt CE (8.19 %). Putting aside that the interconnected nanosheet array provides fast electron transfer and electrolyte diffusion channels, the highest PCE of CoIn2 S4 based DSSC results from its largest specific surface area (144.07 m2 g-1 ), providing abundant active sites and the largest electron injection efficiency from CE to electrolyte.

Moisture-Enabled Electricity from Hygroscopic Materials: A New Type of Clean Energy.

Water utilization is accompanied with the development of human beings, whereas gaseous moisture is usually regarded as an underexploited resource. The advances of highly efficient hygroscopic materials endow atmospheric water harvesting as an intriguing solution to convert moisture into clean water. The discovery of hygroelectricity, which refers to the charge buildup at a material surface dependent on humidity, and the following moisture-enabled electric generation (MEG) realizes energy conversion and directly outputs electricity. Much progress has been made since then to optimize MEG performance, pushing forward the applications of MEG into a practical level. Herein, the evolvement and development of MEG are systematically summarized in a chronological order. The optimization strategies of MEG are discussed and comprehensively evaluated. Then, the latest applications of MEG are presented, including high-performance powering units and self-powered devices. In the end, a perspective on the future development of MEG is given for inspiring more researchers into this promising area.

Armoring the cathode with starch gel enables Shuttle-Free Zinc-Iodine batteries.

Zinc-iodine batteries (ZIBs) have been recognized as a promising energy storage device due to their high energy density, low cost and environmental friendliness. However, the development of ZIBs is hindered by the shuttle effect of polyiodides which results in capacity degradation and poor cycling performance. Inspired by the ability of starch to form inclusion compounds with iodine, we propose to use a starch gel on the cathode to suppress the shuttle of polyiodides. Herein, porous carbon is utilized as a host for iodine species and provides an excellent conductive network, while starch gel is used as another host to suppress polyiodides shuttle, resulting in improved battery performance. The test results demonstrate that the conversion between I-/I2/I3- in the cathode and the effective inclusion role of starch suppress the shuttle of polyiodides during the charging process. Meanwhile, based on the electrochemical tests and theoretical DFT calculations, it is found that starch has a stronger ability to adsorb polyiodides compared to carbon materials, which enables effective confinement of polyiodides. The ZIBs used the cathode with starch gel exhibit high coulombic efficiency (>95 % at 0.2 A/g) and low self-discharge (86.8 % after resting for 24 h). This strategy is characterized by its simplicity, low cost and high applicability, making it significant for the advancement of high-performance ZIBs.

Synergistic γ-In2 Se3 @rGO Nanocomposites with Beneficial Crystal Transformation Behavior for High-Performance Sodium-Ion Batteries.

Crystal transformation of metal compound cathodes during charge/discharge processes in alkali metal-ion batteries usually generates profound impact on structural stability and electrochemical performance, while the theme in anode materials, which always occurs and completes during the first redox cycle, is rarely explored probably due to the fast transformation dynamics. Herein, for the first time, a unique crystal transformation behavior with slow dynamics in anode of sodium-ion batteries (SIBs) is reported, which further promotes electrochemical performance. Specifically, irreversible γ → ß crystal transformation of In2 Se3 is observed, induced by the persistent size degradation of In2 Se3 particles during repeated sodiation/desodiation, supported by a series of ex situ characterizations, such as HRTEM, XRD, and XPS of γ-In2 Se3 /reduced graphene oxide (γ-In2 Se3 @rGO) nanocomposite. The hybrid electrode shows ultrahigh long-term cycling stability (378 mA h g-1 at 1.0 A g-1 after 1000 cycles) and excellent rate capability (272 mA h g-1 at 20.0 A g-1 ). Full battery with Na3 V2 (PO4 )3 cathode also manifests superior performance, promising ß-In2 Se3 dominated electrode materials in high-power and long-life SIBs. The first-principle calculations suggest the crystal transformation enhances electric conductivity of ß-In2 Se3 and facilitates its accessibility to sodium. In combination with the synergistic effect between rGO matrix, substantially enhanced electrochemical performance is realized.

Synergistic effects of caesium closo-dodecaborate on buried interface for efficient and stable perovskite solar cells.

The defects and strain of the buried SnO2/perovskite interface seriously affects the performances of n-i-p type perovskite solar cells. Herein, caesium closo-dodecaborate (B12H12Cs2) is introduced into buried interface to improve the device performances. B12H12Cs2 can passivate the bilateral defects of the buried interface, including the oxygen vacancy and uncoordinated Sn2+ defects on SnO2 side and the uncoordinated Pb2+ defects on perovskite side. Three-dimensional aromatic B12H12Cs2 can promote the interface charge transfer and extraction. [B12H12]2- can enhance the interface connection of buried interface by forming B-H---H-N dihydrogen bond and coordination bonds with metal ions. Meanwhile, the crystal properties of perovskite films can be improved and the buried tensile strain can be released by B12H12Cs2 due to the matched lattice between B12H12Cs2 and perovskite. In addition, Cs+ can diffuse into perovskite to reduce the hysteresis behavior by inhibiting the I- migration. Arising from the enhanced connection performances, passivated defects, improved perovskite crystallization, enhanced charge extraction, inhibited ions migration, released tensile strain at buried interface by B12H12Cs2, the corresponding devices yield a champion power conversion efficiency of 22.10% with enhanced stability. The stability of devices by B12H12Cs2 modification have been improved, and it can still maintain 72.5% of the original efficiency after 1440 h, while the control devices can only maintain 20% of the original efficiency after aging in air condition of 20-30% RH.

Ionic liquid-functionalized graphene for fabricating an amperometric acetylcholinesterase biosensor.

This work reports a sensitive amperometric biosensor for organophosphate pesticides (OPs) fabricated by modifying a glassy carbon electrode with acetylcholinesterase (AChE) immobilized on ionic liquid-functionalized graphene (IL-G). The functionalized graphene sheets had good dispersibility and long-term stability in various solvents. The as-prepared biosensor showed high affinity to acetylthiocholine (ATCl) with a Michaelis-Menten constant (K(m)) value of 0.77 mM. Furthermore, based on the inhibition by OPs of the enzymatic activity of the immobilized AChE, and using carbaryl as a model compound, the inhibition of carbaryl was proportional to its concentration ranging from 0.0025 to 0.48 and 0.48 to 1.42 µg mL(-1) with a detection limit of 0.8 ng mL(-1) (S/N = 3). The developed biosensor exhibited a good performance for OPs detection, including good reproducibility and acceptable stability, which provided a new and promising tool for the analysis of enzyme inhibitors.

Potassium nitrilotriacetate as a multifunctional modifier of the buried interface for hysteresis-reduced perovskite solar cells.

Potassium nitrilotriacetate (NTAK) was employed to modify the buried SnO2/perovskite interface. Benefiting from the coordination roles of carboxyl and amino groups, and the diffusion role of potassium ions, NTAK could enhance the bilateral connection, improve perovskite morphology, suppress non-radiation recombination, and reduce the hysteresis effect. The optimal device with NTAK modification achieved an effective power conversion efficiency of 21.02%. This was a successful attempt to improve the buried interface.

Multistrategy Preparation of Efficient and Stable Environment-Friendly Lead-Based Perovskite Solar Cells.

Perovskite solar cells (PSCs) have achieved huge success in power conversion efficiency (PCE) and stability. However, further improving the PCE of PSCs and stability is still a big challenge. Here, we attempt to improve the PCE and stability of PSCs using a functional additive named 3-mercaptopropyltriethoxysilane (SiSH) in the perovskite antisolvent. It is revealed that SiSH can release the stress in the film, reduce the defects, and inhibit lithium-ion migration and lead leakage. As a result, the target device achieves an efficiency enhancement from 20.80 to 22.42% as compared to the control device. Meanwhile, device stability is ameliorated after SiSH modification. Furthermore, new adsorbents are used to treat the leaked lead to make it comply with safe drinking water standards. This work provides an idea for developing multifunctional antisolvent additives and adsorbents for high PCE, long stability, and environment-friendly Pb-based PSCs.

High-Sensitivity and Extreme Environment-Resistant Sensors Based on PEDOT:PSS@PVA Hydrogel Fibers for Physiological Monitoring.

The rapid development of flexible electronic devices has caused a boom in researching flexible sensors based on hydrogels, but most of the flexible sensors can only work at room temperature, and they are difficult to adapt to extremely cold or dry environments. Here, the flexible hydrogel fibers (PEDOT:PSS@PVA) with excellent resistance to extreme environments have been prepared by adding glycerin (GL) to the mixture of poly(vinyl alcohol) (PVA) and poly 3,4-dioxyethylene thiophene:polystyrene sulfonic acid (PEDOT:PSS) because GL molecules can form dynamic hydrogen bonds with an elastic matrix of PVA molecules. It is found that the prepared sensor exhibits very good flexibility and mechanical strength, and the ultimate tensile strength can reach up to 13.76 MPa when the elongation at break is 519.9%. Furthermore, the hydrogel fibers possess excellent water retention performance and low-temperature resistance. After being placed in the atmospheric environment for 1 year, the sensor still shows good flexibility. At a low temperature of -60 °C, the sensor can stably endure 1000 repeated stretches and shrinks (10% elongation). In addition to the response to a large strain, this fiber sensor can also detect extremely small strains as low as 0.01%. It is proved that complex human movements such as knuckle bending, vocalization, pulse, and others can be monitored perfectly by this fiber sensor. The above results mean that the PEDOT:PSS@PVA fiber sensor has great application prospects in physiological monitoring.

In situ lead oxysalt passivation layer for stable and efficient perovskite solar cells.

A Rb2SO4 additive is employed to passivate the Pb2+ defects in a perovskite film by forming PbSO4in situ, which can cover the surface and grain boundaries of the perovskite to ensure that the film is not decomposed by moisture. Finally, a device based on the Rb2SO4 modification achieved an enhanced power conversion efficiency (22.25%) and long-term stability.

Intercalation pseudo-capacitance behavior of few-layered molybdenum sulfide in various electrolytes.

The insertion and de-insertion of ions in layered materials are important processes during the energy storage. The investigation on the preparation and electrochemical properties of layered materials attracts a lot of attention. Here, few-layered MoS2 nanosheets are prepared by solvothermally treating ammonium tetrathiomolybdate ((NH4)2MoS4) in the presence of hydrazine and cetyltrimethylammonium bromide (CTAB). The structure and electrochemical properties of few-layered MoS2 have been characterized and explored in detail. The results show that ions intercalation causes an interlayer spacing change of the obtained MoS2, and that the prepared few-layered MoS2 exhibits fairly good specific capacitance (330.8 F g-1 at 2.0 A g-1), a high rate capability (specific capacitance can still retain 256 F g-1 at 40 A g-1) and good cycle stability (capacitance can retain 88.8 % over 5000 cycles). Furthermore, different from most of the current literatures in which MoS2's capacitance is generally attributed to electric double-layer capacitance, the relationships between current responses and scan rates uncover that few-layered MoS2's capacitance mainly comes from intercalation pseudo capacitance. The result of this work predicts that few layered-MoS2 can be developed as a promising electrode material for energy storage.

Using Stretchable PPy@PVA Composites as a High-Sensitivity Strain Sensor To Monitor Minute Motion.

With the rapid development of flexible and wearable electronic devices, research on high-sensitivity strain sensors has been attracting much attention. Here, glutaraldehyde is used as a cross-linking reagent to precross-link poly(vinyl alcohol); then FeCl3·6H2O is added into the precross-linked poly(vinyl alcohol) to obtain composite films of FeCl3@PVA after gelatinization and freeze drying. Elastic conductive films of polypyrrole@poly(vinyl alcohol) (PPy@PVA) are prepared by immersing FeCl3@PVA into a solution of pyrrole in acetonitrile and water to complete the polymerization in situ. The effects of the concentrations of glutaraldehyde and FeCl3·6H2O on the film's structure and properties have been studied in detail; the results show that the strain sensor prepared from the optimized film has excellent stretchability (strain up to 309.5%), mechanical property (tensile strength of 32.8 MPa), and relatively high sensitivity (gauge factor can reach 5.07 under 1.0% strain). It can be used to detect various tiny physiological signals, for example, detecting the number of pulse beats, bending of the knuckles at different frequencies, and recognizing the pronunciation of different words by vocal cord vibration. These good properties mean that this kind of PPy@PVA strain sensor has great application prospects in physiological monitoring.

Polar CsPbBr3-based Dion-Jacobson hybrid for promising UV photodetection.

An unprecedented CsPbBr3-based polar Dion-Jacobson type bilayered hybrid, (2meptH2)CsPb2Br7 (1, where 2mept = 2-methyl-1,5-diaminopentane), has been reported. Polarization could benefit the charge transport to induce low Ntrap. 1 exhibits a large on/off ratio (∼103), fast response time (∼200 µs) and high photodetectivity (∼109 Jones) for promising UV photodetection.

The Applications of Polymers in Solar Cells: A Review.

The emerging dye-sensitized solar cells, perovskite solar cells, and organic solar cells have been regarded as promising photovoltaic technologies. The device structures and components of these solar cells are imperative to the device's efficiency and stability. Polymers can be used to adjust the device components and structures of these solar cells purposefully, due to their diversified properties. In dye-sensitized solar cells, polymers can be used as flexible substrates, pore- and film-forming agents of photoanode films, platinum-free counter electrodes, and the frameworks of quasi-solid-state electrolytes. In perovskite solar cells, polymers can be used as the additives to adjust the nucleation and crystallization processes in perovskite films. The polymers can also be used as hole transfer materials, electron transfer materials, and interface layer to enhance the carrier separation efficiency and reduce the recombination. In organic solar cells, polymers are often used as donor layers, buffer layers, and other polymer-based micro/nanostructures in binary or ternary devices to influence device performances. The current achievements about the applications of polymers in solar cells are reviewed and analyzed. In addition, the benefits of polymers for solar cells, the challenges for practical application, and possible solutions are also assessed.

Study on the interaction of porphyrin with G-quadruplex DNAs.

Interactions of 5,10,15,20-Tetrakis(N-propylpyridinium-4-yl)-21H,23H-porphyrin (TPrPyP4) with dimer hairpin (G4T4G4)2 and parallel four-stranded (TG4T)4 G-quadruplex DNAs in Na+-containing buffer were studied. The results show that two TPrPyP4 molecules bind to both G-quadruplexes by a noncooperative and nonequivalent binding mode, and there are one high affinity site and one low affinity site, the respective binding constants are 8.06 x 10(8) and 1.13 x 10(6) M(-1) for (G4T4G4)2-TPrPyP4, 8.04 x 10(7) and 9.08 x 10(5)M(-1) for (TG4T)4-TPrPyP4. TPrPyP4 presents two lifetimes of about 5.8 and 12.0 ns in the complexes of G-quadruplexes-TPrPyP4. The primary results suggest that two TPrPyP4 molecules bind to both G-quadruplexes by terminal stacking and outside binding mode.

Synthesis and characterization of water-insoluble and water-soluble dibutyltin(IV) porphinate complexes based on the tris(pyridinyl)porphyrin moiety, their anti-tumor activity in vitro and interaction with DNA.

The water-insoluble and water-soluble organotin(IV)porphinate complexes based on the tris-(4-pyridinyl)porphyrin and tris(N-methyl-4-pyridiniumyl)porphyrin moieties were synthesized and characterized by elemental analysis, (1)H NMR, IR and electrospray ionization mass spectra. The in vitro activity of the compounds against P388 leukemia and A-549 was determined. The results show that the anti-tumor activities of organotin(IV)porphinate is related to the water solubility of the compounds and the central ion in the porphyrin ring. The interaction between the water-soluble dibutyltin(IV) porphinate (7 and 10) complexes and DNA has been investigated. The result shows that compounds 7 and 10 cause DNA hypochromism measured by A(260), a slight increase in the viscosity of the DNA, and an increase in the melting point of DNA by 2.9 and 1.6 degrees C, respectively at DNA(base)/Drug(Por) ratios of 60. The binding constants to DNA were 1.35+/-0.16 x 10(7) M(-1) (7) and 1.45+/-0.12 x 10(6) M(-1) (10) determined using EB competition method based on the porphyrin concentration, which is 20 and five times greater than that of precursor porphyrins [5-p,o-(carboxy)methoxyphenyl-10,15,20-tris(N-methyl-4-pyridiniumyl)] porphyrin (p,o-tMPyPac) to DNA. Electrophoresis test shows that the compounds cannot cleave the DNA. According to the electrophoresis test result and all the above results, the cytotoxic activity against P388 and A-549 tumor cells appears not to come from the cleavage of DNA caused by the compounds but from the high affinity of compounds to DNA.