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Tailoring of battery-type NiCo 2 O 4 with carbon-based materials for supercapacitors usually involves several steps, which require prolonged syntheses at high temperatures. Here, a facile one-step strategy is presented for the fabrication of a binder-free composite, made of NiO x decorated multi-walled carbon nanotubes (CNTs) and NiCo 2 O 4 nanoparticles on nickel foam to form a stable supercapacitor with high specific capacity. The process is based on the electrophoretic co-deposition of carboxylated-CNTs and NiCo 2 O 4 NPs, which were positively charged using Ni2+. The latter played a double role by stabilizing the nanomaterials and improving the electrochemical performance by decorating the nanomaterials with NiO x species. The well-dispersed NiCo 2 O 4 NPs in the highly conductive porous matrix of CNTs provide efficient electron transfer, high surface area and superior electrochemical performance, such as high charge storage, high rate delivery and good cycling stability. The nanocomposite film exhibited high specific capacitance of 1363 F gr−1 at 2 A gr−1, while retaining 82% of the capacitance at higher current density (20 A gr−1). The straightforward fabrication process and the excellent electrochemical activity are of generic nature and can be applied for assembling other well-structured carbon-based composites. [ABSTRACT FROM AUTHOR]

Abstract The sensing performance of a Langmuir-Blodgett monolayer was significantly improved by controlling the film organization at the air-water interface. Cellulose acetate (CA) and 4-tert-butylcalix [6]arene (calix) were co-spread and formed a Langmuir film, which was efficiently transferred onto a preoxidized gold electrode, Au ox. The modified gold electrode was applied as a fast, highly sensitive electrochemical sensing platform for the quantitative determination of a model molecule, dopamine (DA). The modified gold electrode, CA-calix/Au ox , demonstrated better recognition and sensing ability towards dopamine as compared with electrodes modified by a single component. Under the optimized conditions, the reduction peak currents at the CA-calix/Au ox increased linearly within the concentration range of dopamine from 5 to 100 and 100–7500 nM, and exhibited a very low limit of detection (LOD) of 2.54 nM (S/N = 3). These results suggest a simple, superior and efficient approach for the controllable rearrangement of Langmuir-Blodgett monolayers on a molecular level. The electroanalytical performance was optimized from the perspective of the electrode-electrolyte interface. Graphical abstract Image 1 Highlights • A mixed Langmuir layer composed of cellulose acetate, and the selectivity factor, calixarene, were co-spread at the air-water interface. • The Langmuir film was transferred onto a solid gold electrode and used as a means of electrochemically detecting dopamine. • The Langmuir-Blodgett based interface was carefully studied and exhibits superior electrochemical performance for the detection of dopamine. [ABSTRACT FROM AUTHOR]

Abstract Despite many efforts devoted to explore novel electrode materials for lithium ion hybrid supercapacitors, the obtainable long-life cycling of existing anode materials are still inadequate for promising applications. This report demonstrates a new nanocomposite with TiNb 2 O 7 network nanostructure in situ anchored onto the holey graphene, which is designed as anode material for lithium ion hybrid supercapacitors. Impressively, electrochemical analyses show that the good rate performance (capacity retention of 73.5% from 0.05 to 5 A g−1) and long cycle life up to 1000 cycles at 1 A g−1 (a capacity retention of 91.5%) are attained. Furthermore, the lithium ion hybrid supercapacitor device consisting of this nanocomposite and activated carbon exhibits excellent cycling stability (90.2% of initial capacity after 3000 cycles), high energy density of 86.3 W h kg−1 (at 237.7 W kg−1) and high power density of 3.88 kW kg−1 (at 28.7 W h kg−1). This study ascribes the unprecedented performance to the high conductive holey graphene with abundant mesopores, the uniformly distributed TiNb 2 O 7 network nanostructure and the synergetic effect between them. Based on these findings, the presented nanocomposite has great potential in high performance lithium ion hybrid supercapacitors. Graphical abstract Image 1 Highlights • A novel composite of TiNb 2 O 7 network nanostructure and holey graphene was fabricated. • The long-term life with 91.5% capacity retention after 1000 cycles was obtained. • The Li-HSC device exhibits high energy density and excellent cycling stability. [ABSTRACT FROM AUTHOR]

Tin-based metal oxides usually suffer from severe capacity fading resulting from aggregation and considerable volume variation during the charge/discharge process in lithium ion batteries. In this work, a novel nanocomposite (MTO/N-RGO) of hollow amorphous MnSnO 3 (MTO) nanoparticles and nitrogen-doped reduced graphene oxide (N-RGO) has been designed and synthesized by a two-step method. Firstly, the nitrogen-doped graphene nanocomposite (MTO/N-RGO-P) with MnSn(OH) 6 crystal nanoparticles was synthesized by a facile solvothermal method. Subsequently, the MTO/N-RGO nanocomposite was obtained through the post heat treatment of MTO/N-RGO-P. The designed heterostructure and well-combination of the hollow amorphous MTO and N-RGO matrix can accelerate the ionic and electronic transport, and simultaneously accommodate the aggregation and volume variation of MTO nanoparticles during the lithiation–delithiation cycles. The as-prepared hybrid of MTO and N-RGO (MTO/N-RGO) exhibits a high reversible capacity of 707 mAh g −1 after 110 cycles at 200 mA g −1 , superior rate capability, and long-term cyclic life with high capacity of 610 mAh g −1 over 1000 cycles at 400 mA g −1 . Superior capacity retention of 97.3% over 1000 cycles was obtained. This work opens new opportunities to fabricate the high-performance electrode materials with heterostructure for lithium storage systems, especially for novel multi-metal oxide based nanocomposites with high cycling stability. [ABSTRACT FROM AUTHOR]

The physicochemical property of chemically prepared graphene can be significantly changed due to the incorporating of heteroatoms into graphene. In this article, boron-doped graphene sheets are used as carbon substrates instead of graphene for loading polyaniline by in situ polymerization. Compared with the individual component and polyaniline/non-doped graphene, the sandwich-like polyaniline/boron-doped graphene exhibits remarkably enhanced electrochemical specific capacitance in both acid and alkaline electrolytes. In a three-electrode configuration, the hybrid has a specific capacitance about 406 F g −1 in 1 M H 2 SO 4 and 318 F g −1 in 6 M KOH at 1 mV s −1 . In the two-electrode system of a symmetric supercapacitor, this hybrid achieves a specific capacitance about 241 and 189 F g −1 at 0.5 A g −1 with a specific energy density around 19.9 and 30.1 Wh kg −1 , in the acid and alkaline electrolytes, respectively. The as-obtained polyaniline/boron-doped graphene hybrid shows good rate performance. Notably, the obtained electrode materials exhibit long cycle stability in both acid and alkaline electrolytes (∼100% and 83% after 5000 cycles, respectively). The improved electrochemical performance of the hybrid is mainly attributed to the introduction of additional p -type carriers in carbon systems by boron-doping and the well combination of pseudocapacitive conducting polyaniline. [ABSTRACT FROM AUTHOR]

Abstract: Organic compounds as functional materials have attracted much keen interest in the past three decades owing to their potential applications in science and technology. Currently, great efforts have been made in looking for suitable photo-responsive materials among the multifarious organic compounds. Herein we reported the photophysical properties of 2-furanylmethylene-aminoantipyrine (FMAAP), benzylideneaminoantipyrine (BIAAP) and cinnamilideneamino-antipyrine (CIAAP) studied by a combined experimental and theoretical investigation. Two-photon absorption measurements give the cross-section values of 1.350×10−50 cm4 s/photon for FMAAP, 1.046×10−50 cm4 s/photon for BIAAP and 2.047×10−50 cm4 s/photon for CIAAP. The calculated first-hyperpolarization values are of 2.303×10−30, 1.257×10−29, 2.889×10−29 cm5/esu for FMAAP, BIAAP and CIAAP, respectively. UV–vis spectroscopy technique further reveals that the studied compounds display long-range electron transfer characteristics by absorbing light of specific wavelengths of 294.5nm for FMAAP, 293.2nm for BIAAP and 303.1nm for CIAAP. All the results indicate that the studied compounds are promising candidates of functionally photo-responsive materials. [Copyright &y& Elsevier]

Abstract: Mobile counter anion exchange of electropolymerized polyaniline (PANI) films with the anions in acid solutions has been investigated by cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS), scanning electron microscopy, Raman, UV–vis, and fluorescence spectra. The studied acids include camphorsulfonic acid, p-toluene sulfonic acid, HCl, HClO4, H2SO4 and H3PO4. In two cases of small and large counter ions of PANI films, CV tests have been performed alternately three times in each of two electrolytes containing organic or inorganic acid. The investigation of electrochemical and spectrophotometric measurements reveals that large counter anions can be easily replaced by the small anions; and the reverse exchange also occurs, but shows very low efficiency. This indicates that the achieved anion exchange in both cases leads to the remarkable alteration in electrochemical behavior and electrical conductance of PANI films. This implies counter anions, whatever the original or redoping ones, play an important role in the electrical, electrochemical, even optical properties of PANI. However, the polymer morphology does not be changed after exchange tests. This allows us to point out a ‘morphology-memory’ effect which is very significant for the development and application of PANI films with the same morphology and different properties. [Copyright &y& Elsevier]

Abstract: A novel high-performance electrode material based on fibrillar polyaniline (PANI) doped with graphene oxide sheets was synthesized via in situ polymerization of monomer in the presence of graphene oxide, with a high conductivity of 10Scm−1 at 22°C for the obtained nanocomposite with a mass ratio of aniline/graphite oxide, 100:1. Its high specific capacitance of 531F/g was obtained in the potential range from 0 to 0.45V at 200mA/g by charge–discharge analysis compared to 216F/g of individual PANI. The doping and the ratio of graphene oxide have a pronounced effect on the electrochemical capacitance performance of the nanocomposites. [Copyright &y& Elsevier]

Abstract: The interactions of promethazine hydrochloride (PZH) with thiolated single-stranded DNA (HS-ssDNA) and double-stranded DNA (HS-dsDNA) self-assembled on gold electrodes have been studied electrochemically. The binding of PZH with ssDNA shows a mechanism containing an electrostatic interaction, while the mode of PZH interaction with dsDNA contains both electrostatic and intercalative bindings. The redox system belongs to the category of diffusion control approved by cyclic voltammetry (CV). The diffusion coefficients of PZH at the bare, HS-dsDNA and HS-ssDNA modified gold electrodes decrease regularly as 1.34×10−3 cm2 s−1, 1.04×10−3 cm2 s−1, 7.47×10−4 cm2 s−1, respectively. The electron transfer standard rate constant k s of PZH at bare gold, HS-ssDNA and HS-dsDNA modified electrodes are 0.419s−1, 0.131s−1, and 0.154s−1, respectively. The presence of adsorbed dsDNA results in a great increase in the peak currents of PZH in comparison with those obtained at a bare or ssDNA adsorbed gold electrode. The difference between interactions of PZH with HS-ssDNA and HS-dsDNA has been used for hybridization recognition of 14-mer DNA oligonucleotide. The peak current (i pa) of PZH is linearly proportional to the logarithmic concentration of complementary target DNA in the range from 2.0×10−9 molL−1 to 5.0×10−7 molL−1 with the detection limit of 3.8×10−10 molL−1. [Copyright &y& Elsevier]

A conventional resistance measured by two-point technique includes bulk and contact components. The contact resistance can be excluded by a four-point technique. A simultaneous use of the two- and four-point techniques allows to separate the total resistance between two electrodes for the contact and bulk parts. This approach has been used to analyze electrical coupling between metal electrodes of interdigitated structures and chemically sensitive coating formed by polyaniline (PANI). The polymer layers were deposited by electropolymerization on bare gold and platinum electrodes as well as on gold electrodes precoated by a self-assembled monolayer of 4-aminothiophenol. An exposure of the PANI films formed on interdigitated structures to gaseous HCl displays proportional changes of resistance measured by the two- and four- point techniques for platinum electrodes and for the precoated gold electrode, while a strong deviation from this proportionality was observed for the gold electrodes without precoating. The results demonstrate a high contribution of the contact resistance between PANI and bare gold electrodes into the resistance measured by the two-point technique. This contribution is small and therefore not measurable for bare platinum electrodes or for gold electrodes coated by 4-aminothiophenol. [Copyright &y& Elsevier]

Abstract: Poly (o-phenylenediamine) (PoPD) hollow multi-angular microrods have been synthesized at 10 °C via an interfacial process using ferric chloride and o-phenylenediamine (oPD) as starting materials. The chemical structure of the one dimensional (1D) superstructure is proved to be phenazine-like, and contains the benzenoid and quinoid imine units doped partly with Cl. Scanning electron microscopy (SEM) and transmission electron microscopy (TEM) observations indicate that the resulting superstructure of PoPD is built from hollow nanofibers aligned parallel to the fiber axis by van der Waals'' force. The possible formation mechanism of the structure has been proposed. [Copyright &y& Elsevier]

A stable and well-distributed nitrogen-doped graphene (NGE) is prepared by a simple and efficient hydrothermal method with a reducing-doping reagent of vitamin B3. Compared with NGE reduced by urea, vitamin B3 reduced NGE (NGE-N) show superior catalysis towards the electrochemical reduction of imidacloprid. The pyridine-N oxide induced in graphene sheets is considered enhancing the interaction between NGE-N and imidacloprid molecules. The NGE-N modified electrode is used in fast determination of imidacloprid with a low detection limit of 0.55 μM. [ABSTRACT FROM AUTHOR]

A simple and sensitive label-free electrochemical biosensor for nimodipine was fabricated by using nitrogen-doped graphene (NGE) modified electrode. The surface morphology and electron transfer behavior of the modified electrodes were studied by scanning electron microscopy and electrochemical impedance spectroscopy, respectively. The electrochemical behaviors of nimodipine at the modified electrodes were investigated by using cyclic voltammetry. On the basis of the excellent electrocatalytic activity of NGE, an obvious cathodic peak of nimodipine could be caused at the NGE modified glassy carbon electrode (GCE), moreover, the electrochemical signal was greatly enhanced compared with the undoped graphene modified GCE. Under the optimized conditions, the present sensor showed excellent performances for nimodipine detection including wide linear range of 0.02–3 μM, low detection limit (9.1 nM), good selectivity to the general coexisted interferences, etc. The proposed biosensor was also successfully applied to validate its capability for the analysis of nimodipine in tablets. The work would promote the potential application of NGE as an excellent material in fabricating electrochemical sensors for chemical or biochemical analysis. [ABSTRACT FROM AUTHOR]

Abstract: To improve the electrochemical properties of chemically synthesized graphene hybrids, nitrogen-doped (N-doped) graphene decorated with M(OH) x (M=FeO, Ni, Co) nanoparticles were fabricated by a one-pot method at a mild temperature (95°C). Urea plays an important role in the synthesis process; it not only acts as the reducing agent and doping agent for N-doped graphene, but also as a hydroxyl donor for the fabrication of metal hydroxides and oxide-hydroxide. With the help of N-doped graphene and urea, FeOOH nanorods, Co(OH)2 nanowires and flower-like Ni(OH)2 nanoparticles were grown on the graphene sheets. The N-doped graphene hybrids exhibited the significantly improved electrochemical performances compared to the undoped equivalents or the separate components. [Copyright &y& Elsevier]

Modulation of oxygen vacancy concentration of Nb 2 O 5 anode, arising from quantitative regulation of oxygen content in the precursor, is developed, revealing the relationship between the oxygen vacancy concentration and kinetics for Li-ion storage. In addition, the integrated binder-free electrode with appropriate oxygen vacancies and highly conductive N-doped carbon porous framework results in improved kinetics for the anode of Li-ion capacitors. [Display omitted] • Oxygen vacancy concentration of Nb 2 O 5 @NC anode is quantitative regulation. • Revealing relationship between oxygen vacancy concentration and kinetics of Li-ion storage. • Nb 2 O 5 @NC binder-free electrode is constructed via electrophoretic deposition. • Binder-free electrode further improves kinetics for the anode of Li-ion capacitors. Introducing appropriate oxygen vacancies (OVs) improves the integral conductivity of the Nb 2 O 5 anode of Li-ion capacitors (LICs). Whereas a few recent studies link the OVs level and the kinetics of Nb 2 O 5 , the quantitative relationship between the OVs and the performance of Nb 2 O 5 remains elusive. Herein, we show that the OVs concentration in Nb 2 O 5 can be quantitatively manipulated by regulating the oxygen content in niobium complex (NbL) precursors, thus controlling the kinetics of the Nb 2 O 5 -based anode. The OVs concentration is inversely proportional to the oxygen content in the NbL, where it facilitates the electronic transfer and the Li-ion migration of Nb 2 O 5 with optimal introduction. In addition, the ligand in the NbL can also be used as a sacrificial template for creating an N-doped carbon coating wrapping Nb 2 O 5 nanoparticles with OVs to further improve the electronic conductivity of the composite. This was followed by depositing the NbL nanoparticles via electrophoretic deposition for assembling binder-free electrodes. The integrated electrode-based LICs deliver 76 μWh cm−2 at 550 μW cm−2 and retain 94 % of the capacity after 5000 cycles. This work provides a new recognition for the design of metal oxide electrodes with fast kinetics for LICs from material modification to electrode material assembly. [ABSTRACT FROM AUTHOR]

Highlights: [•] CoMoO4/Graphene composites were prepared via one-step hydrothermal method. [•] The composites have high surface/body ratios and large electroactive regions. [•] The composites present better electrochemical properties than pure-CoMoO4. [•] The composite achieves a capacitance of 394.5Fg−1 at 1mVs−1. [ABSTRACT FROM AUTHOR]

Abstract: A novel conducting poly (N-phenyl-2-naphthylamine) (PPBNA) film was successfully electropolymerized by direct anodic oxidation of its monomer N-phenyl-2-naphthylamine in boron trifluoride diethyl etherate. The prepared PPBNA films showed good redox activity and structural stability even in concentrated sulfuric acid. The impedance spectra of PPBNA films demonstrated that the electron transfer resistance was around 80Ω. The fluorescent results indicated that the emission band of PPBNA was red-shifted about 30nm in comparison with that of the monomer. The fluorescent spectra exhibited that the monomer and PPBNA films were excellent blue-light-emitting and blue-green-light-emitting material, respectively. [ABSTRACT FROM AUTHOR]

Abstract: The optical properties of electrochemically polymerized N-methylaniline are changed in the presence of gaseous hydrogen chloride. This effect was used for preparation of chemical sensors with transduction based on surface plasmon resonance. The interaction of hydrogen chloride with a two nm layer of poly-(N-methylaniline) on gold leads to the shift of the surface plasmon resonance. The analysis of the resonance spectra demonstrates that the effect is caused by an increase of the imaginary component of the refractive index; a minor contribution is also provided by film condensation leading to an increase of the real component of the refractive index and a decrease in the thickness. The effect is selective and quasi-reversible. The concentration dependence of the gas effect obeys Langmuir''s adsorption isotherm with a reciprocal value of the binding constant of 850 ± 160ppm. [Copyright &y& Elsevier]

The utility of TiO 2 as an anode for lithium-ion storage is hindered by low conductivity and sluggish ionic diffusion. Here, the 2D N-doped carbon-wrapped TiO 2 (TiO 2 @NC) composite with a thickness of 5.5 nm derived from the 2D metal-organic framework was designed. This composite consisting of TiO 2 nanoparticles embedded in ultrathin N-doping carbon was used to address the rate and cyclability of Li-ion batteries. The 2D nanosheet morphology obtained from Ti 8 O 8 (OH) 4 (BDC-NH 2) 6 （NH 2 -MIL-125 (Ti)）effectively increases the specific surface area and shortens the electron/ion transport pathway. The chemical bond of Ti-C-O between TiO 2 nanocrystals and N-doping carbon further improve conductivity. Due to its unique structure, the produced TiO 2 @NC composite shows excellent cyclability with a reversible capacity of 110 mAh g–1 after 2000 cycles at 0.5 A g–1. Furthermore, the 2D TiO 2 @NC exhibits outstanding rate performance (71 mAh g–1 at 5 A g–1) compared to bulk TiO 2 @NC. This general concept can be extended to the development of metal oxide materials based on insertion mechanisms, such as Nb 2 O 5. • The 2D TiO 2 @N-doping carbon composite with a thickness of 5.5 nm is prepared. • Solvent-dependent variation of morphology NH 2 -MIL-125(Ti) MOF is investigated. • The TiO 2 nanocrystals embedded in ultrathin N-doping carbon nanosheets via chemical bonding. • The TiO 2 @N-doping carbon composite shows excellent lithium-ion storage performances. [ABSTRACT FROM AUTHOR]

The repeated outbreaks of coronavirus disease 2019 (COVID-19) have seriously threatened human health and economic development. Therefore, it is still significant to explore an efficient method for severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) detection. Herein, we designed a dual-mode colorimetric and fluorescent immunosensor based on Fe2+ doped ZIF-67 derivatives-based composites, Pt nanoparticles loaded on CoFe nanoparticles embedded porous carbon-nitrogen hexahedron (CoFe/NC@Pt), for detecting SARS-CoV-2 nucleocapsid protein. The doping of Fe2+ generated bimetallic CoFe nanoparticles and formed more defects after pyrolysis. Meanwhile, the peroxides-like activity significantly improved owning to the synergistic effect of Co and Fe nanoparticles. Furthermore, loaded Pt nanoparticles not only provided more active sites, but also could couple antibodies by modifying functional groups. CoFe/NC@Pt exhibited good peroxidase-like activity and could catalyze the oxidation of 3,3′,5,5′-tetramethylbenzidine (TMB) to blue oxides in the presence of H 2 O 2 , generating visible color signals. While the oxTMB could quench the fluorescence of carbon dots through inner filter effect, thereby providing fluorescent signals. The limit of detection were 0.022 ng/mL (colorimetric) and 0.018 ng/mL (fluorescent). And the specificity of the immunosensor was verified by comparing with other interferents. Therefore, this dual-mode immunosensor with good performance provided a reliable strategy for diagnosis of COVID-19. [Display omitted] • A dual-mode colorimetric and fluorescent immunosensor based on CoFe/NC@Pt nanozyme. • CoFe/NC@Pt exhibited good peroxidase-like activity. • The quenching mechanism of CDs was inner filter effect. • The accuracy of the sensor was improved by mutual authentication of double signals. [ABSTRACT FROM AUTHOR]

[Display omitted] • Au@CeO 2 @Pt nanoenzymes exhibited an outstanding peroxidase-like activity. • A colorimetric-fluorescent dual-mode assay for SARS-CoV-2 was constructed. • The immunosensor achieved detection in simulated samples with satisfactory results. Developing powerful alternatives to natural enzymes has been a target pursued by researchers, and nanozymes are considered to be the best candidate due to their unique advantages of high stability, high activity, and easy modification. In this study, the multishell complexes of Au@CeO 2 @Pt nanozymes were successfully synthesized which exhibited an excellent intrinsic peroxidase-like ability to oxidize 3,3′,5,5′-tetramethylbenzidine (TMB), and resulting in a visible colorimetric signal. Interestingly, due to the internal filtration effect, the blue-emitting oxidized TMB (oxTMB) can also quench the red-emitting light from bimetallic AuAg nanoclusters. Based on the above properties, a kind of robust immunoassay for target protein detection was established. The dual-mode immunoassay is more accurate for SARS-CoV-2 detection on account of the reciprocal corroboration of the signals. More importantly, the immunoassay had high sensitivity with a low limit of detection and excellent recovery rates in simulated urine/saliva samples. Therefore, it is highly anticipated the immunoassay based on the newly developed nanozyme became an accurate instrument for diagnosing SARS-CoV-2 in the biomedical field. [ABSTRACT FROM AUTHOR]

Oxygen reduction reaction (ORR) plays a key role in the application of fuel cells. Here, we used shaddock peel to fabricate a set of N, P dual-doped hierarchical porous carbons, abbreviated as NPSPs, where the carbons were carbonized, activated and dual-doped via a simple one-step pyrolyzation. Contrast results indicate the contents of pyridinic-N, graphitic-N and P–C species increase with the rising of temperatures, and the temperature also affects the degree of graphitization, surface area, morphology, thus influences the ORR performance. More importantly, the NPSP-900 demonstrates an outstanding ORR activity with a comparable half-wave potential (0.83 V vs. RHE) and higher current density with respect to commercial Pt/C, following 4e transfer pathway. Our work illustrates that NPSP-900 is a promising cathode for fuel cells because of its simple preparation, waste utilization, excellent ORR performance, good methanol tolerance and superior stability. Image 1 • One-step pyrolysis can accomplish carbonization, activation and N,P-dual doping. • NPSPs own hierarchical porous structures with high BET surface areas. • Higher temperature can enhance ORR activities with improved doping N/P species. • NPSP-900 owns a close ORR activity compared with Pt/C, following 4e transfer way. • NPSP-900 shows a remarkable methanol tolerance and superior stability. [ABSTRACT FROM AUTHOR]

An electrochemical sensor based on a glassy carbon electrode (GCE) modified by three-dimensional graphene (3D-GE) and polyglutamic acid (PGA) was developed to quantitatively detect Amoxicillin (AMX), a worldwide used antibiotic. AMX response at PGA/3D-GE/GCE involving the transfer of one electron and an equal number of protons were determined using electrochemical approaches. Density functional theory simulations were performed to give insights on the reaction mechanism of AMX on the surface of the modified electrode. When the optimization of the experimental conditions was completed, the linear range of AMX was 2–60 μM. Besides, the detection limit was calculated as 0.118 μM (S/N = 3). And the modified electrode could detect the concentration of the AMX in human urine samples. Overall, the developed PGA/3D-GE/GCE for determination of AMX shows great potentials in practice. Image 1 • A friendly and sensitive method for the determination of amoxicillin was developed. • Polyglutamic acid/three-dimensional porous graphene (PGA/3D-GE) was used for the modification of electrode. • A new reaction mechanism of amoxicillin was proposed by combining computational simulation with electrochemical methods. [ABSTRACT FROM AUTHOR]

• The discarded and cheap mulberry leaves was used to prepare bacterial cellulose. • The as-prepared composite shows good antimicrobial properties and biocompatibility. • The composite may be potential application in wound dressings. It's long been understood that antimicrobial properties are one of the most important function in the field of biomedicine. In this thesis, we introduce a new technique to functionalize bacterial cellulose (BC) with antimicrobial properties by in situ method. We design a series of experiments on hydrolyzing mulberry leaves and exploring the methods of fermenting and purifying to obtain a BC complex with antimicrobial properties. Meanwhile, the anti-bacterial performances of MH-BC (fermented by the mulberry leaves acid hydrolysate fermentation medium) were evaluated with Escherichia coli and Staphylococcus aureus , and the experimental results showed that the MH-BC have excellent anti-bacterial activities. Considering the excellent biocompatibility of MH-BC towards hMSCs, we expect that this antibacterial functional BC composite will find potential applications in biomedicine and regenerative medicine. [ABSTRACT FROM AUTHOR]

A dual-doping strategy was applied to fabricate the novel electrode materials. For the first time, the spinel hybrids of nanosized Ni x Co 1−x Fe 2 O 4 with N-doped graphene (N x -NG) were synthesized by a hydrothermal co-precipitation method. The size of Ni x Co 1−x Fe 2 O 4 (N x) nanoparticles on N-doped graphene can be tuned with the regulation of Ni/Co content. Among these nanocomposites, the Ni 0.4 Co 0.6 Fe 2 O 4 nanoparticles with the smallest average size of 10 nm are uniformly anchored on the N-doped graphene. The electrochemical characterizations display that the N 0.4 -NG exhibits the best electrochemical lithium storage performance compared to other five nanocomposites. It delivers a high capacity of 1367.0 mA h g−1 at the first discharge process，and the reversible capacity retention of 87% (2nd to 50th) at 0.1 A g−1. The excellent electrochemical performance of N 0.4 -NG can be owing to the small size of nanoparticles and its well-combination with N-doped graphene, which provide the large surface area and promote the ion/electron transfer rate. The synergistic effect resulted from the strong interaction between N 0.4 and N-doped graphene is contributed to the enhanced electrochemical performance of N 0.4 -NG. This study not only extends graphene-based electrode materials for lithium ion battery, but also promotes the development of energy resources. Unlabelled Image • A spinel hybrid of nanosized Ni x Co 1-x Fe 2 O 4 with N-doped graphene was fabricated. • Size of Ni x Co 1−x Fe 2 O 4 nanoparticles was tuned with the regulation of Ni/Co content. • A reversible capacity of 785.2 mA h g−1 of N 0.4 -NG after 50 cycles was obtained. [ABSTRACT FROM AUTHOR]

Abstract A novel fluorescent sensor based on g-C 3 N 4 nanofibers for the sensitive detection of dopamine (DA) has been proposed. We synthesized g-C 3 N 4 nanofibers by directly hydrolyzing bulk g-C 3 N 4 in the alkaline atmosphere (3 M NaOH). The obtained ultrathin g-C 3 N 4 nanofibers were verified by characterizations of Transmission electronic microscope (TEM), X-ray diffractometer (XRD), Fourier transformation-infrared (FT-IR) and X-ray photoelectron spectroscopy (XPS). It was found that the fluorescence intensity of g-C 3 N 4 nanofibers was obviously quenched by DA. Fluorescence resonance energy transfer (FRET) between DA and g-C 3 N 4 nanofibers led to the fluorescence reduction of g-C 3 N 4 nanofibers. The fluorescent probe based on g-C 3 N 4 nanofibers exhibits linear responses to the concentration of DA in the range from 0 to 4 μM and 4 to 20 μM, the limit of detection is 17 nM. The fluorescent probe shows excellent stability, good selectivity with its application in serums. Graphical Abstract Unlabelled Image Highlights • A rapid and sensitive approach for detection of DA has been reported. • The developed probe exhibits excellent stability and good selectivity. • The proposed g-C 3 N 4 nanofibers probe has been presented for DA detection in human serums. [ABSTRACT FROM AUTHOR]

Abstract A rapid and sensitive, non-enzymatic electrochemical detection of hydrogen peroxide (H 2 O 2) is of utmost importance for diagnosis and treatment of related diseases in clinical purpose. To meet this requirement, we report a simple and robust microwave-assisted synthetical route via prepared Gd 2 O 3 nanoparticles decorated reduced graphene oxide nanocomposite (Gd 2 O 3 NPs@RGO) modified electrode for non-enzymatic H 2 O 2 detection. The composition and morphological formation were characterized by using XRD, FT-IR, XPS, FESEM, and HRTEM. The impedance and cyclic voltammetry exhibit tremendous electrocatalytic capability and superior performance toward H 2 O 2 reduction. A sensitive and reproducible amperometric H 2 O 2 sensor was fabricated which was able to detect concentration as low as 1.57 nM. The method worked well even in clinical and biological samples, which indicates the reliability of the method in real time analysis. [ABSTRACT FROM AUTHOR]

Graphical abstract Highlights • Mn doped Co 3 O 4 (Mn x Co y O) deposited on NF presents mesoporous nanoneedle structure. • Mn 1.5 Co 0.75 O/NF shows remarkable capacitance retention of 104% after 10,000 cycles. • The assembled ASC shows high energy density of 10.63 Wh kg−1 (at 14.7 kW kg−1). Abstract Long–term cycling stability is an important criterion and big challenge for pseudocapacitive materials. Ultra-stable manganese doped Co 3 O 4 mesoporous nanoneedles were synthesized via one-step hydrothermal reaction followed by annealing grown on nickel foam (noted as Mn x Co y O/NF, x + y = 2.25) for supercapacitors. The Mn doping in Co 3 O 4 was confirmed by several techniques. Among various Mn x Co y O/NF electrodes, the Mn 1.5 Co 0.75 O/NF demonstrated the superior electrochemical performance, with an excellent cycling stability of 104% capacitance retention after 10 000 charge–discharge cycles at 6 A g−1, as well as a good capability (668.4 F g−1 at 1 A g−1 compared to that of undoped Co 3 O 4 which is 201.3 F g−1). Moreover, the assembled asymmetric supercapacitor based on Mn 1.5 Co 0.75 O/NF//graphene performs a high energy density of 25.88 Wh kg−1 (at 359.5 W kg−1) and a high power density of 14.7 kW kg−1(at 10.63 Wh kg−1). The improved electrochemical properties are mainly owing to the enhanced intrinsic conductivity and electrochemical activity of Co 3 O 4 after doped with appropriate Mn concentration. The three-dimensional nanostructure of mesoporous nanoneedle array grown on NF also provides short ion diffusion path and large active surface areas, contributing to the high rate performance and high energy density. This study may offer a new approach to fabricate the unique 3D nanostructured electrode materials based on doped metal oxides for supercapacitors with long-term cycling stability and high energy density. [ABSTRACT FROM AUTHOR]

Abstract Oxygen reduction reaction (ORR) and Lithium storage both play the key roles in energy conversion and storage devices. Here, we report a honeycomb-like nitrogen-doped carbon derived from enteromorpha algae (N-EA), using a one-step pyrolysis process at only 600 °C to simultaneously achieve doping, carbonization and activation. After anchoring CoFe 2 O 4 on N-EA, CoFe 2 O 4 /N-EA, not only inherits the high surface area, porous structure, active nitrogen species from N-EA, but also benefits from the active sites and high theoretical specific capacity of Li storage from CoFe 2 O 4. The synergistic effect makes CoFe 2 O 4 /N-EA an alternative catalyst to commercial Pt/C for ORR with superior activity and stability. Moreover, CoFe 2 O 4 /N-EA exhibits a remarkable cycle performance with a 100% capacity retention (∼900 mAh g−1) after 500 cycles at 0.5 A g−1. Green preparation, waste utilization, good ORR performance and Li storage property of CoFe 2 O 4 /N-EA could make it a promising candidate for fuel cells and LIBs. [ABSTRACT FROM AUTHOR]

Highlights • Graphene oxide (GO) hydrogel was induced by synergistic effect of pyrrole and Co2+. • S and N are doped in graphene framework with doping/reducing agent of L -Cysteine. • 3D-sturctrue are obtained via evaporation induced drying without freeze-drying. • The 3D S/N-co-doped graphene show enhanced response for hydroquinone and catechol. Abstract Herein, a three-dimensional self-assembled hydrogel of graphene oxide sheets induced by pyrrole and Co2+ is described. Controlled shrinkage and sulfur/nitrogen co-doping occurred in the subsequent hydrothermal process. The obtained 3D sulfur/nitrogen co-doped graphene was further dried through direct evaporation, without freeze-drying. SEM images demonstrated a surface 3D structure with high roughness and composed of interconnected sheets. This newly fabricated 3D sulfur/nitrogen co-doped graphene was used in the simultaneous detection of catechol and hydroquinone with low detection limits of 0.28 and 0.15 μM, respectively. [ABSTRACT FROM AUTHOR]

Graphical abstract The novel electrode materials, NiO ultrathin nanosheets anchored to two types of needle-like NiCo 2 O 4 and slice-like NiCo 2 O 4 on carbon cloth (CC), are synthesized by a simple two-step method. Both as-prepared hierarchical electrodes deliver high specific capacitance and excellent cycling performance, which show the potential of its practical application. Highlights • A new strategy for designing freestanding hierarchical structure of CC/NiCo 2 O 4 @NiO. • The electrodes show high specific capacitance and excellent cycle stability. • The capacitive contributions are leading roles in both kinds of electrodes. • All-solid-state asymmetric supercapacitors deliver high energy and power density. Abstract To fabricate free-standing electrodes with hierarchical structured redox-type metal oxides has become a wise strategy for the development of high-performance energy storage systems. Two types of NiCo 2 O 4 with needle-like and slice-like morphologies act as the conducting cores and hydrothermally grow on carbon cloth (CC/NiCo 2 O 4 -N and CC/NiCo 2 O 4 -S). The mesoporous NiO ultrathin nanosheets further are anchored on the surface of the two types of CC/NiCo 2 O 4 to form the novel high-performance electrodes (CC/NiCo 2 O 4 -N@NiO and CC/NiCo 2 O 4 -S@NiO). Particularly, the formation mechanism of NiO ultrathin nanosheets is proposed. The two integrated electrodes of CC/NiCo 2 O 4 -N@NiO and CC/NiCo 2 O 4 -S@NiO exhibit high specific capacitance of 921.9 and 852.9 mF/cm2 (or 709.1 and 775.1F/g) at 2 mA/cm2, respectively and excellent long cycling lifespan (both 100% retention after 10,000 cycles). The assembled asymmetric supercapacitors, CC/NiCo 2 O 4 -N@NiO//graphene and CC/NiCo 2 O 4 -S@NiO//graphene, can still deliver the high energy density and power density, and possess excellent cycling stability (95.2% and 92.3% retention after 10,000 cycles, respectively). Our work not only provides an attractive strategy and a two-step facile method for construction of hierarchical electrodes based on ultrathin NiO sheets and nanostructured NiCo 2 O 4 , but also offers a strategy for high-performance supercapacitors. [ABSTRACT FROM AUTHOR]

Highlights • A novel NC-Ti 3 C 2 T x hybrid has been synthesized. • NC-Ti 3 C 2 T x hybrid exhibits quick charge/discharge rate up to 3.0 V s−1. • NC-Ti 3 C 2 T x hybrid exhibits higher specific capacitance of 82.8 F g−1 at 1.0 A g−1. • The hybrid exhibits excellent cycling stability (100% retention after 5000 cycles). Abstract The MXenes with excellent chemical and physical properties are novel and promising electrode materials for supercapacitors. However, aggregation and restacking of MXene sheets limit material's electrochemical performance. Here, we report a method to prevent MXene sheets from restacking and significantly improved electrochemical capability of Ti 3 C 2 T x MXene by intercalating with N-doped carbon (NC) introduced from ZIF-8. Ti 3 C 2 T x MXene sheets were prepared by etching Ti 3 AlC 2 powder in HF, then ZIF-8/Ti 3 C 2 T x composite was prepared, followed by annealing in H 2 /Ar atmosphere. Benefited from higher specific surface area and electron conductivity, the obtained NC-Ti 3 C 2 T x hybrid shows the quick charge/discharge rate up to 3.0 V s−1, little IR drop at 50.0 A g−1, higher specific capacitance of 82.8 F g−1 at 1.0 A g−1 (about 210% of the origin), and 100% retention in capacitance after 5000 cycles. This new and effective approach efficiently enhanced the electrochemical performance of Ti 3 C 2 T x MXenes and improved them as one of auspicious electrode materials in future energy storage devices. [ABSTRACT FROM AUTHOR]

Abstract Sandwich-like ZIF-8 nanocrystal derived N-doped carbon decorated graphene sheets are developed through in-situ growth and followed by a thermal annealing treatment. The sandwich-like N-doped carbon decorated graphene sheets (NCGs) contain graphene substrate and the carbon nanoparticles with 30–50 nm in size. The sandwich-like NCGs generate a large specific surface area of 816.4 m2 g−1. With the high surface area and nitrogen doping, the as-fabricated NCGs as electrode materials for supercapacitor exhibit high specific capacitance of 225.0 F g−1 at 0.5 A g−1, an enhanced rate capability and excellent electrochemical stability with 96.8% retention after 10000 cycles even at 10 A g−1. The symmetry supercapacitor based on NCGs delivers an energy density of 12.7 Wh kg−1 at a specific power of 447 W kg−1. When the power density increases to 15126 W kg−1, the energy density can still keep 6.5 W h kg−1. Furthermore, the symmetry supercapacitor shows an excellent cycle stability with 96.6% capacitance retention at 2 A g−1 after 10000 cycles. Graphical abstract Image 1 [ABSTRACT FROM AUTHOR]

The ability to generate more apparent specific heat release at lower temperatures is the future trend of ammonium perchlorate (AP)-based composite solid propellants. To achieve this goal, the development of highly active catalysts for improving the thermal decomposition properties of AP is essential and challenging. Herein, three-dimensional hierarchically ordered porous carbon (3D HOPC) is employed as catalyst to improve AP thermal decomposition though synthesizing a series of AP/HOPC nanocomposites with different AP loading amount. In these nanocomposites, AP nanocrystals (26.2–69.0 nm) are successfully space-confined into the 3D HOPC scaffold and form the compact interfacial contact. Owing to the synergistic effect of the well-connected 3D hierarchically ordered porous structure, the good electrical and thermal conductivity, as well as the size effect of AP nanocrystals, 3D HOPC demonstrates excellent catalytic activity for AP thermal decomposition in decreasing the high-temperature decomposition temperature from 440.9 to 315.4 °C, lowering the activation energy from 176.4 ± 18.8 kJ/mol to 130.8 ± 5.3 kJ/mol, and unprecedentedly increasing the heat release from 371 ± 11 J/g to 3765 ± 10 J/g. It can be foreseen that 3D HOPC is an attractive catalyst for AP thermal decomposition, which may open new potential for high energy application of carbon-based materials as catalysts for AP-based solid propellants. [ABSTRACT FROM AUTHOR]

A novel electrochemical sensor based on nitrogen doped graphene (NGE) and palygorskite (Pal) for the simultaneous detection of hydroquinone (HQ) and catechol (CT) has been proposed. Pal is particularly pointed out for its appreciable specific surface area and reactive-OH groups on its surface. Acid treatment Pal demonstrated better physico-chemical properties, which are propitious to electrochemical sensor construction. The introduction of NGE not only improved the poor conductivity of Pal but also served as an excellent adherent matrix. The modified electrode demonstrated the enhanced redox peak currents of HQ and CT with good discrimination. Under optimized conditions, the linear ranges for HQ and CT were 2–50 μM and 1–50 μM, with detection limit (LOD) of 0.8 μM and 0.13 μM, respectively. The result designates that the Pal/NGE composite promises to be a new eco-friendly modified material for sensor fabrication. [ABSTRACT FROM AUTHOR]

A fast and sensitive electrochemical sensor for simultaneous determination of ascorbic acid (AA) and acetaminophen (AP) was proposed based on g-C 3 N 4 nanofibers (h-CN) doped poly(3,4-ethylenedioxy-thiophene) (PEDOT) composite. PEDOT/h-CN hybrid film was directly deposited on glass carbon electrode (GCE) by in-situ electropolymerization. The incorporation of h-CN and PEDOT brought out enhanced electro-catalytic activity and additional binding sites for AA and AP, which could be ascribed to the synergetic effect between h-CN and PEDOT. Under the optimal experimental condition, the oxidation peak currents of AA and AP give linear response over the range of 4–20 μM, 20–1800 μM and 1–10 μM, 10–50 μM, respectively. The detection limit of the modified electrode was calculated to be 1.51 μM for AA and 0.49 μM for AP (S/N = 3). The electrochemical experiments also suggested that PEDOT/h-CN modified electrode was feasible practice for quantitative detection of AA and AP. [ABSTRACT FROM AUTHOR]

The electrochemical properties of NCM cathodes with various conductive additives have been comparatively studied in this work. The conductive additives are porous graphene/carbon black (SG), carbon black/conductive graphite (SK), carbon black (SC), and conductive graphite (KS), respectively. The results suggest that the NCM electrode with SG conductive additive shows the best rate performance, which exhibits a discharge capacity of 78 mAh g −1  at the current density of 2000 mA g −1 in the voltage range of 2.5–4.1 V versus lithium electrode, that is ∼1.7 times higher than that of NCM electrode with SK additive. The electrochemical impedance spectra (EIS) results reveal that the NCM electrode with SG addition has the lowest charge transfer resistance. On this basis, the structural evolution of NCM material with SG conductive additive in the first charge process has been studied via an in situ synchrotron X-ray diffraction technique (XRD). The XRD patterns show that a thorough phase transition from hexagonal H1 to hexagonal H2 occurs at the voltage of 4.3 V, and the diffraction peaks of (0 1 8)/(1 1 0) splits gradually, representing the extraction of lithium from the ordered layer-structured NCM materials. [ABSTRACT FROM AUTHOR]

[Display omitted] • Fluorescent quantitative detection of Cu2+ realized by L-cysteine modified ZnS. • The formation of ground state complexes is verified by experiments and simulations. • Fluorescence quenching mechanism of the probe by Cu2+ revealed by simulation. L-cysteine (L-Cys) capped ZnS fluorescent probe (L-ZnS) were synthesized by binding ZnS nanoparticles in situ with L-Cys, the fluorescence intensity of L-ZnS increased more than 3.5 times than that of ZnS due to the cleavage of S–H bonds and the formation of Zn–S bonds between the thiol group of L-Cys and ZnS. The addition of copper ions (Cu2+) can effectively quench the fluorescence of L-ZnS to realize the rapid detection of trace Cu2+. The L-ZnS showed high sensitivity and selectivity to Cu2+. The LOD (limit of detection) of Cu2+ was as low as 7.28 nM and linearity in the concentration range of 3.5–25.5 μM. Meanwhile, for the first time, electron localization function (ELF), bond order density (BOD), and natural adaptive orbital (NAdO) analysis in the Multiwfn wavefunction program based on density functional theory were carried out to probe the binding sites and binding mode of L-Cys with Cu2+, it indicated that the deprotonated carboxyl oxygen atoms of L-Cys had the lowest electrostatic potential (ESP) and provided lone pair electrons to coordinate with Cu2+ to form non-luminescent ground state complexes, which led to fluorescence quenching of L-ZnS. From the microscopic point of view of atoms, the mechanism of fluorescence enhancement of L-Cys capped ZnS and the mechanism of fluorescence quenching after adding Cu2+ were revealed in depth, the theoretical analysis results were accordance with the experiments. [ABSTRACT FROM AUTHOR]

Constructing a hierarchical heterogeneous composite is deemed as an effective way to solve the current problems of metal oxides as lithium ion batteries’ anodes. In this work, we simultaneously designed the heterogeneous component and structure of the novel hybrid based on Kirkendall effect. The composite was composed of quasi-hexagonal Cu 1.5 Mn 1.5 O 4 nanoplates as a shell and CuO with voids as a core. The hybrids were characterized by using XRD, FTIR, TEM and SEM. It was found that the heating rate greatly influences the combination form of Cu 1.5 Mn 1.5 O 4 and CuO. The quasi-hexagonal Cu 1.5 Mn 1.5 O 4 nanoplates were assembled into branch-like shell decorated on the CuO surface under the low heating rate. However, the high heating rate led to a compact Cu 1.5 Mn 1.5 O 4 shell, although the shell was also assembled by quasi-hexagonal nanoplates. The reasonable formation mechanism of the unique component and structure was proposed. Such a hybrid with the branch-like shell exhibited the best lithium storage performance. The improved electrochemical performance can be attributed to the unique component and structure. Typically, the inside voids can alleviate the volume change and the hierarchical shell can provide much contact and reaction sites. This work not only opens a new view in constructing heterogeneous hybrid with unique structure by Kirkendall effect, but also can be expanded for many other structure-based applications, such as energy storage, sensors, and heterogeneous catalysts. [ABSTRACT FROM AUTHOR]

To enhance the energy density of supercapacitors, an asymmetric supercapacitor was prepared by well-matched graphene@MnO 2 nanosheets (G@MnO 2 ) as cathode material and porous graphene as anode material. The hierarchical MnO 2 ultrathin nanosheets uniformly decorating on graphene sheets were prepared by polyaniline-assisted growth method. The obtained G@MnO 2 composite can provide fast electron transfer rate and efficient space to decrease the length of ion diffusion during energy storage. Therefore, the G@MnO 2 electrode exhibits a high specific capacitance reaching 245.0 F g −1 at 0.5 A g −1 , 74.5% of retention ratio at 20 A g −1 . Meanwhile the assembled asymmetric supercapacitor delivers a high energy density of 30.6 W h kg −1 , and a remarkable energy density of 7.9 W h kg −1 at ultrahigh power density of 11,804 W kg −1 due to the well-assembly of G@MnO 2 and porous graphene with the similar capacitance and rate performance. Moreover, the asymmetric supercapacitor also shows an excellent cycle life with 8.5% loss of the initial specific capacitance after 10,000 cycles. The excellent electrochemical performance of the asymmetric supercapacitor of G@MnO 2 //porous graphene makes it an attractive candidate for high power and energy storage systems. [ABSTRACT FROM AUTHOR]

A newly fabricated nitrogen-doped graphene (NGE) supported hemin composite was prepared with facile one-pot method deriving from graphene oxide. Hemin was directly anchored on the surface of NGE during the N-doping process with doping-reducing agent of 2-aminopyridine. XPS results revealed the nitrogen doping of graphene and the integration of Hemin with NGE, and the hemin-N C (H-NGE) composite was characterized with TEM and SEM. The peroxidase-like activity of hemin maintained, displaying fast redox property. The H-NGE also exhibited remarkable electrocatalysis towards O 2 and H 2 O 2 reduction due to the high-speed charge-transfer between hemin and the modified electrode. The good electroactivity of NGE and the excellent synergic effect enables an enhanced electrochemical performance. Based on the well-designed H-NGE, the electrocatalytic H 2 O 2 determinations was monitored amperometrically with a low detection limit (0.092 μM). [ABSTRACT FROM AUTHOR]

A fast, ultrasensitive electrochemical sensing platform based on graphitic carbon nitride-electrochemically deposited-poly(3,4-ethylenedioxythiophene) (g-C 3 N 4 -E-PEDOT) composite was constructed by in-situ electropolymerization and applied for the quantitative determination of acetaminophen (AP). E-PEDOT was introduced as the conducting matrix for developing g-C 3 N 4 composite to complement the poor conductivity disadvantage of g-C 3 N 4 . The strong affinity and synergetic effect between g-C 3 N 4 and E-PEDOT, which were analyzed by PM6 computational calculation, highly improved the electron transfer property and remarkably enhanced the electrochemical catalytic activity of the composite. The g-C 3 N 4 -E-PEDOT modified glassy carbon electrode (GCE) demonstrated better electrocatalytic activity towards the oxidation of AP than bare, g-C 3 N 4 and E-PEDOT modified ones. Under the optimized conditions, the oxidation peak currents at the g-C 3 N 4 -E-PEDOT/GCE increased linearly in the concentration range of AP from 0.01 to 2 μM and 2–100 μM, and an ultra-low limit of detection (LOD) of 34.28 nM was obtained (S/N = 3). In addition, the g-C 3 N 4 -E-PEDOT/GCE was successfully applied for the AP determination in the clinical human serum, and also exhibited excellent selectivity, reproducibility and stability. Except the novel AP determination approach, moreover, this work provided a new electrochemical application angle of graphitic carbon nitride theoretically as well as experimentally. [ABSTRACT FROM AUTHOR]

A self-template method is developed for hierarchically yolk-shelled NiCo 2 O 4 spheres (YS-NiCo 2 O 4 ) through a controlled hydrolysis process and followed by a thermal annealing treatment. The yolk-shelled NiCo 2 O 4 spheres possess out-shell consisting of hundreds of ultrathin sheets with 3–5 nm in thickness and solid yolk composing of a large number of nanoparticles. The YS-NiCo 2 O 4 generates a large specific surface area of 169.6 m 2 g −1 . Benefit from the large specific surface area and rich oxygen vacancy, the as-fabricated YS-NiCo 2 O 4 as electrode materials for supercapacitor exhibits high specific capacitance of 835.7 F g −1 at 0.5 A g −1 , an enhanced rate capability and excellent electrochemical stability with 93% retention after 10,000 cycles even at 10 A g −1 . Moreover, a hybrid supercapacitor combined with YS-NiCo 2 O 4 and graphene shows a high energy density of 34.7 Wh kg −1 at the power density of 395.0 W kg −1 at 0.5 A g −1 , even at 20 A g −1 , the hybrid supercapacitor still delivers the energy density of about 12.1 Wh kg −1 and the power density of 11697 W kg −1 . The desirable performance of yolk-shelled NiCo 2 O 4 suggests it to be a promising material as supercapacitor electrodes. [ABSTRACT FROM AUTHOR]

A new furfuran-based rhodamine B fluorescent probe ( RBFF ) has been designed and synthesized, and its sensing behavior towards various metal ions was evaluated via UV–vis and fluorescence spectroscopic techniques. RBFF exhibits a highly sensitive and selective “turn-on” fluorescent response toward Fe 3+ ion and a fluorescence “turn-off” response when added B 4 O 7 2− to the RBFF -Fe 3+ in the EtOH/H 2 O solution (1:1, v/v, HEPES, 1 mM, pH 7.20). The detection limit of RBFF for Fe 3+ was calculated to be 0.025 μM. The fluorescence microscopy experiment suggested that RBFF could also be served as a biological fluorescence probe for the detection of Fe 3+ in human cervical carcinoma cells (HeLa). [ABSTRACT FROM AUTHOR]

N-doped graphene has been widely researched as metal-free electrocatalyst and electrode material of energy storage devices but the effect of heteroatom species and topographic defects on these applications was rarely reported. We successfully prepared dual (N, S) or ternary heteroatoms (N, S, P)-doped graphene by simple hydrothermal and then carbonization treatment. Compared to singly N doping, multiple heteroatom species dopant is beneficial to positively move onset potential, approach four electron catalytic pathway in oxygen reduction reaction (ORR) due to the synergistic effect. The emerging topographic defects induced by removing heteroatoms and oxygen at high temperature also act as efficient active sites for positively shifting onset potential. Meanwhile, the porous ternary heteroatoms-doped graphene possesses a good capacitive performance such as high gravimetric capacitance (196.4 Fg −1 at 1 Ag -1 ), high retained rate (92.7%), 98% retention over 2000 recycling. The excellent capacitive properties derive from large specific surface area (943.5 m 2 g -1 ), mesoporous structure, particularly the important role of abundant dopants of multiple heteroatom species. Therefore, we demonstrated the effect of heteroatom species and topographic defects on electrocatalyzing ORR and capacitive performance. [ABSTRACT FROM AUTHOR]

[Display omitted] • Three-dimensionally ordered mesoporous NiCo 2 O x @CeO y was developed by a hard template method. • Ce-doping can effectively adjust the electronic structure and bonding configuration of NiCo 2 O x electrode material. • The hollow cubic structure has high permeability and excellent bearing capacity. • The designed architecture has high specific surface area and abundant paths for electron/ion transport. • The NiCo 2 O x @CeO y //AC exhibits superior activity and stability for asymmetric supercapacitors. From the perspective of nano science and nanotechnology, it is very interesting and important to develop a reasonable and practical synthesis route of nanomaterials for production and life. Here, we develop a strategy of hollow cubic metal oxide nanocages. The method was inspired by Pearson's Hard-Soft-Acid-Base (HSAB) theory, and nanocages with excellent performance were prepared by coordination etching and optimization of reaction conditions. Firstly, Cu 2 O nanocubes were prepared by redox reaction at room temperature. Then, the hollow cubic NiCo 2 O x /CeO y nanocages were obtained by HSAB theory and cerium doping. The nanomaterial has a specific capacitance of up to 1976 F/g at the current density of 1 A/g. In addition, the asymmetric supercapacitor (ASC) prepared with hollow cubic NiCo 2 O x /CeO y nanocage as cathode and active carbon as anode exhibits an energy density as high as 37.1 Wh kg−1 at the power density of 375 W kg−1. The capacitance retention rate of the device is 91.5 % after 10,000 cycles. The device can be charged to light up LED lights. These excellent electrochemical properties, due to their unique structure and synergistic effect between materials, indicate the potential application value of hollow cubic NiCo 2 O x /CeO y nanocages in high-performance supercapacitors. [ABSTRACT FROM AUTHOR]

[Display omitted] • DMI form organic layers on the surface of zinc sheets by plane adsorption. • The addition of DMI disrupts the hydrogen bond network in the electrolyte. • DMI molecules regulate the solvation sheath structure of Zn2+ in the electrolyte. • The addition of DMI optimize the deposition behavior of Zn2+ on different substrates. The cycle life of aqueous Zn-metal batteries is greatly challenged due to the formation of Zn dendrites on the electrode surface and side reactions. Herein, an effective tactic against the above problems was proposed by adding 1,3-dimethyl-2-imidazolidinone (DMI) to the ZnSO 4 electrolyte to form an inert organic layer on the surface of the zinc foil, and the protective mechanism of DMI molecules on the surface of zinc poles was discussed by density functional theory. The formation of this inert layer can protect the zinc foil from being eroded by H 2 O, homogenize the electric field on the electrode surface and inhibit the formation of dendrites. The addition of DMI also destroys the original hydrogen bond network in the system and suppresses the side reaction problem caused by the Grotthuss mechanism. This new electrolyte can effectively improve the cycle performance of different half-batteries. In ZnSO 4 -DMI-05 electrolyte, the Zn||Zn cell achieved stable cycling for 2400 h at a current density of 1.0 mA cm−2 (1.0 mAh cm−2). Furthermore, it was applied to a Zn||VS 2 full cell and cycled for 600 cycles at a current density of 1 A/g, achieving a coulombic efficiency (CE) of 99.97 % and a capacity retention rate of 95.33 %. This organic additive enables ultrastable and reversible deposition of zinc ions on different types of substrates in an aqueous environment, providing a promising approach for the development of aqueous zinc-metal batteries. [ABSTRACT FROM AUTHOR]

The global corona virus disease 2019 (COVID-19) has been announced a pandemic outbreak, and has threatened human life and health seriously. Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), as its causative pathogen, is widely detected in the screening of COVID-19 patients, infected people and contaminated substances. Lateral flow assay (LFA) is a popular point-of-care detection method, possesses advantages of quick response, simple operation mode, portable device, and low cost. Based on the above advantages, LFA has been widely developed for detecting SARS-CoV-2. In this review, we summarized the articles about the sandwich mode LFA detecting SARS-CoV-2, classified according to the target detection objects indicating genes, nucleocapsid protein, spike protein, and specific antibodies of SARS-CoV-2. In each part, LFA is further classified and summarized according to different signal detection types. Additionally, the properties of the targets were introduced to clarify their detection significance. The review is expected to provide a helpful guide for LFA sensitization and marker selection of SARS-CoV-2. [Display omitted] • LFA as a simple user friendly tool is widely employed for SARS-CoV-2 detection. • Present review focus on latest developments in LFAs to detect SARS-CoV-2. • Sensitization strategies and marker properties are beneficial to further research. [ABSTRACT FROM AUTHOR]

Highly uniform Mn 3 O 4 /CuO@TiO 2 submicroboxes with hollow and core – shell structure have been synthesized for the first time by a facile and feasible multi-step method. A detail formation mechanism has been proposed based on the chemical and structural characterization, which consists of the part self sacrificing, in situ growth, etching, in situ hydrolysis coating and heat treatment process. The unique firm hollow core – shell structure of Mn 3 O 4 /CuO@TiO 2 made itself exhibit an enhanced lithium storage performance compared to the hollow Mn 3 O 4 /CuO. The TiO 2 coatings not only reinforce the hollow structure but also improve the conductivity, which result in the improved electrochemical performance. Typically, a specific capacity of 583 mA h g −1 (92.8% of the theoretical capacity of 628 mA h g −1 ) and 97.1% capacity retention (compared with the 2nd discharge capacity) after 150 cycles at 0.2 A g −1 were obtained from the hollow core – shell Mn 3 O 4 /CuO@TiO 2 . This work not only provides a promising strategy to solve the rapid capacity fading and large structure damage of metal oxides but also makes a contribution to the design and synthesis of metal oxides with hollow or core – shell structures for various structure-based applications, such as gas sensors, catalysis and energy storage. [ABSTRACT FROM AUTHOR]

Rhodamine B (RhB) is a kind of basic dye that is harmful to human health. Because RhB is cheap and abundant, it is easy to add it illegally to foods as a colorant. This paper used surface-enhanced Raman spectroscopy (SERS) and core-shell satellite structure Ag@SiO2-Au nanoparticles to detect RhB. We used the prepared Ag@SiO 2 -Au nanoparticles as SERS substrate to detect the ethanol solution of RhB. The silica shell protected Ag from oxidation and agglomeration and provided a large specific surface area for modified Au nanoparticles. The "hot spots" generated between metal nanoparticles can significantly enhance the Raman intensity of RhB. At the excitation wavelength of 532 nm, the SERS intensity of RhB at 1647 cm−1 has a linear relationship with the logarithm of RhB concentration in the range of 10−4-10−7 M and the limit of detection (LOD) can reach 5 × 10−9 M. Experiments verified the uniformity and stability of SERS substrate, ideal intensity can still obtain after SERS substrate stored for four weeks. Finally, we confirmed the reusability of the SERS substrate. After washing with anhydrous ethanol, the reused SERS substrate still had an enhanced effect on RhB. The prepared substrate can be used to detect actual samples with satisfactory recovery. The above results showed that Ag@SiO 2 -Au NPs could use as a sensitive, uniform, stable, and low-cost SERS substrate to detect trace RhB. [Display omitted] [ABSTRACT FROM AUTHOR]