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Hypercrosslinked pyrrole was synthesized via the Friedel-Crafts reaction and then carbonized to obtain urchin-like nitrogen-doped carbon (UNC). Ultrasmall iron oxide nanoparticles were then supported on UNC, and the composite was used to prepare an electrochemical sensor for detecting uric acid (UA) in human urine. Fe x O y /UNC was characterized and analyzed via scanning electron microscopy, transmission electron microscopy, energy dispersive spectrometry, X-ray diffraction, and X-ray photoelectron spectroscopy. A glassy carbon electrode (GCE) modified with Fe x O y /UNC was used as an electrochemical sensor to effectively identify UA. The electrochemical behavior of the Fe x O y /UNC-based UA sensor was studied using differential pulse stripping voltammetry, and the optimal conditions were determined by changing the amount of Fe x O y /UNC, pH of the buffer solution, deposition potential, and deposition time. Under optimal conditions, the Fe x O y /UNC-based electrochemical sensor detected UA in the range of 2-200 μM, where the limit of detection (LOD) for UA was 0.29 μM. Anti-interference experiments were performed, and the sensor was applied to the actual analysis of human urine samples. Urea, glucose, ascorbic acid, and many cations and anions present at 100-fold concentrations relative to UA did not strongly interfere with the response of the sensor to UA. The Fe x O y /UNC electrochemical sensor has high sensitivity and selectivity for uric acid in human urine samples and can be used for actual clinical testing of UA in urine., (Copyright © 2022 The Authors. Published by Elsevier B.V. All rights reserved.)

In the present work, irregular Cu nanoparticle-decorated boron-carbon-nitrogen (Cu-BCN) nanosheets were successfully synthesized. A Cu-BCN dispersion was deposited on a bare glassy carbon electrode (GCE) to prepare an electrochemical sensor (Cu-BCN/GCE) for the detection of chloramphenicol (CAP) in the environment. Cu-BCN was characterized using high-resolution scanning transmission electron microscopy (HRSTEM), scanning electron microscopy (SEM), X-ray diffraction (XRD) analysis, and X-ray photoelectron spectroscopy (XPS). The performance of the Cu-BCN/GCE was studied using electrochemical impedance spectroscopy (EIS), and its advantages were proven by electrode comparison. Differential pulse voltammetry (DPV) was used to optimize the experimental conditions, including the amount of Cu-BCN deposited, enrichment potential, deposition time, and pH of the electrolyte. A linear relationship between the CAP concentration and current response was obtained under the optimized experimental conditions, with a wide linear range and a limit of detection (LOD) of 2.41 nmol/L. Cu-BCN/GCE exhibited high stability, reproducibility, and repeatability. In the presence of various organic and inorganic species, the influence of the Cu-BCN-based sensor on the current response of CAP was less than 5%. Notably, the prepared sensor exhibited excellent performance in real-water samples, with satisfactory recovery.

Aqueous phase of bio-oil (APBO) is water-rich but also contains some sugar-derivatives and phenolics. APBO has little potential as feedstock for producing biofuel, but can be potentially used as medium for hydrothermal carbonization (HTC) of biomass. In this study, the HTC of lignin in APBO was conducted, aiming to probe the influence of the organics in APBO on property of the hydrochar. The results indicated that the organics in APBO cross-polymerized with lignin derivatives, resulted in the yield of hydrochar to exceed 100%. In addition, APBO promotes the deoxygenation but does not promote dehydrogenation. More aliphatic structures are generated in the hydrochar, reducing its thermal stability. In addition, the hydrochar from APBO also shows the improved combustion performance by lowering the activation energy and the ignition temperature (180 vs 240 °C)., (Copyright © 2022 Elsevier Ltd. All rights reserved.)

The application of biomass-based carbon materials in electrode materials are usually subject to their deficient adsorption sites as well as sluggish diffusion of electrolyte ions. Herein, flower-like carbons are obtained from the heavy fraction of bio-oil with the auxiliary of Hydrogen-bonded frameworks (HOFs) crystals. During the co-carbonization of the both, the HOFs crystals are removed on account of its poor stability, which directs the formation of flower-like morphology and generates the penetrable meso/macropores across petal-like carbon nanosheets. In addition, the pyrolysis gases serve as the agents for activation to enrich the active sites without the further activation. The degree of graphitization and the contents of pyridine nitrogen for carbon materials could be flexibly adjusted with the contents of HOFs. Owing to the beneficial 3D flower-like structure, high specific surface area (1076 m 2 /g), large pore volume (2.59 cm 3 /g), and rational N species, the assembled Zn//BH-4 hybrid supercapacitor reaches a superior energy density of 117.5 Wh/kg at 890 W/kg and maintains 60.7 Wh/kg even at 16.2 kW/kg., Competing Interests: Declaration of Competing Interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2021 Elsevier Inc. All rights reserved.)

In this study, an iron-doped metal-organic framework (MOF) Fe/ZIF-8 was synthesized from ZIF-8 at room temperature. Direct carbonization of Fe/ZIF-8 under a nitrogen atmosphere produced nanoporous nitrogen doped carbon nanoparticles decorated with Fe component (Fe/NC). The Fe/NC exhibited a large surface area (1221.185 m 2  g -1 ) and narrow pore-size distribution (3-5 nm). The nanoporous Fe/NC components along with Nafion were used to modify a glassy carbon electrode for the electrochemical determination of chloramphenicol and metronidazole via linear sweep voltammetry. Under optimal conditions, the reduction peak currents (observed at -0.237 V and -0.071 V vs. Ag/AgCl) of these analytes increased linearly with increasing chloramphenicol and metronidazole concentrations in the range of 0.1-100 μM and 0.5-30 μM, with the detection limits estimated to be 31 nM and 165 nM, respectively. This result was attributed to the large surface area, porous structure, high nitrogen content, and as well as the electrocatalytic effect of Fe atoms embeded in the carbon support. The proposed sensor was used for chloramphenicol and metronidazole analysis in samples, providing satisfactory results., (Copyright © 2020 Elsevier Inc. All rights reserved.)

Pursuing nonprecious doped carbon with Pt-like electrocatalytic N 2 H 4 oxidation activity for hydrazine fuel cells (HzFCs) remains a challenge. Herein, we present a Fe/N-doped carbon (Fe-NC) catalyst with mesopore-rich channel and highly dispersed Fe-N sites incorporated in N-doped carbon, as an analogue of hydrazine dehydrogenase (HDH), showing the structure-dependent activity for electrocatalytic oxidation of N 2 H 4 . The maximal turnover frequency of the N 2 H 4 oxidation reaction (HzOR) over the Fe-N sites (62870 h -1 ) is 149-fold that over the pyridinic-N sites of N-doped carbon. The Fe mass activity of HzOR and maximal power density of HzFCs driven by Fe-NC approximately surpass those of Pt/C by 2.3 and 2.2 times, respectively. Theoretical calculation reveals that the Fe-N sites improve the dehydrogenation process of HzOR-related intermediates. One of the roles of the mesoporous structure in Fe-NC resembles that of a substrate channel in HDH for enhancing the transport of N 2 H 4 besides exposing Fe-N sites and improving storage capacity of HzOR-related species.

In this study, ordered mesoporous carbon (OMC) was synthesized by applying a soft template method, and its mesoporous structure was characterized by scanning electron microscopy, transmission electron microscopy, and nitrogen adsorption-desorption techniques. X-ray diffraction and Raman spectroscopic analyses were conducted to demonstrate the high graphitization and topological defects at the sample surface. An electrochemical sensor based on an OMC-modified glassy carbon electrode (OMC/GCE) was constructed to detect aristolochic acids (AAs) using cyclic voltammetry and linear sweep voltammetry. The dependence of the experimental parameters including solution pH, scan rate, and accumulation time were examined and optimized. Under the optimal conditions, the response of OMC/GCE was linear over wide concentration ranges of AAs (0.6-10 μM and 10-50 μM), with sensitivities of -1.77 and -0.31 μA/μM, respectively. The limit of detection was calculated to be 0.186 μM (at S/N = 3). Furthermore, the proposed OMC/GCE was applied to detect AAs in Asarum sieboldini and the content of AAs was calculated to be 8.9 μg/g with high accuracy and precision. In addition, the modified electrode also exhibited good selectivity, reproducibility, and stability. Therefore, the OMC/GCE can be used as a platform for the determination of AAs., (Copyright © 2019 Elsevier B.V. All rights reserved.)

In this study, we developed a sensitive electrochemical sensor for the detection of chloramphenicol (CAP). An iron-nitrogen co-doped ordered mesoporous carbon-silicon nanocomposite (Si-Fe/NOMC) was prepared as follows. First, an SBA-15 surface was treated with an iron and nitrogen co-doped carbon framework obtained from the polymerization of ethylenediamine and carbon tetrachloride via the hard templating method. The mixture was then carbonized at a high temperature (900℃). Finally, the Si-Fe/NOMC modified electrode was fabricated, and employed as a high-performance electrochemical sensor to trace the CAP in drug samples using the large surface area of the hetero-atoms iron, nitrogen and silicon co-doped in the porous structure. Cyclic voltammetry and differential pulse voltammetry tests were determine to assess the efficiency of the sensor. Under optimized conditions, the sensor exhibited rapid current response for CAP in a phosphate buffer solution PBS with pH 7.5. The linear concentration of CAP ranged from 1 μM to 500 μM, with a limit of detection of 0.03 μM (S/N = 3). Furthermore, the electrochemical sensor was used to detect CAP in eye drop samples with satisfactory results., (Copyright © 2018 Elsevier B.V. All rights reserved.)

We report on a novel sensing platform for H2O2 and glucose based on immobilization of palladium-helical carbon nanofiber (Pd-HCNF) hybrid nanostructures and glucose oxidase (GOx) with Nafion on a glassy carbon electrode (GCE). HCNFs were synthesized by a chemical vapor deposition process on a C60-supported Pd catalyst. Pd-HCNF nanocomposites were prepared by a one-step reduction free method in dimethylformamide (DMF). The prepared materials were characterized by transmission electron microscopy (TEM), X-ray diffraction (XRD), scanning electron microscopy (SEM), and Raman spectroscopy. The Nafion/Pd-HCNF/GCE sensor exhibits excellent electrocatalytic sensitivity toward H2O2 (315 mA M(-1) cm(-2)) as probed by cyclic voltammetry (CV) and chronoamperometry. We show that Pd-HCNF-modified electrodes significantly reduce the overpotential and enhance the electron transfer rate. A linear range from 5.0 μM to 2.1 mM with a detection limit of 3.0 μM (based on the S/N = 3) and good reproducibility were obtained. Furthermore, a sensing platform for glucose was prepared by immobilizing the Pd-HCNFs and glucose oxidase (GOx) with Nafion on a glassy carbon electrode. The resulting biosensor exhibits a good response to glucose with a wide linear range (0.06-6.0 mM) with a detection limit of 0.03 mM and a sensitivity of 13 mA M(-1) cm(-2). We show that small size and homogeneous distribution of the Pd nanoparticles in combination with good conductivity and large surface area of the HCNFs lead to a H2O2 and glucose sensing platform that performs in the top range of the herein reported sensor platforms.

A new ordered mesoporous carbon (OMC) modified pyrolytic graphite electrode (PGE) was prepared to investigate electrochemical behavior of the anticancer drug tirapazamine (TPZ). Compared to the bare PGE, the modified electrode showed an excellent electrochemical response to TPZ. The anodic peak current (I(pa)) of TPZ at the OMC/PGE is 180-fold higher than that of the bare PGE. The I(pa) is proportional with TPZ concentration in the range of 5.0 x 10(-11) to 1.5 x 10(-5) mol L(-1). The linear regression equations are I(pa) (microA)=0.0000044+16.928C(TPZ) (micromolL(-1)), with a detection limit (S/N=3) of 2.0 x 10(-11) mol L(-1). This proposed method can be potentially used for ultrasensitive electrochemical sensing of TPZ in physiological condition.

Gold nanoparticles were self-assembled to the modified glassy carbon electrode (GC) with cysteamine (CA) to prepare the nano-Au/CA/GC modified electrode. The electrochemical behavior of epinephrine (EP) on the modified electrode was explored with cyclic voltammetry (CV) and differential pulse voltammetry (DPV). Epinephrine gave a pair of redox peaks at E(pa)=0.190 mV and E(pc)=-0.224 mV (versus SCE), respectively. The nano-Au/CA/GC modified electrode shows an excellent electrocatalytic activity for the oxidation of EP. The modified electrode could be used to determine EP in the presence of ascorbic acid (AA). The response of catalytic current with EP concentration shows a linear relation in the range of 1.0 x 10(-7) to 5.0 x 10(-4) mol L(-1) with the correlation coefficient of 0.998. The detection limit is 4.0 x 10(-8) mol L(-1). The modified electrode exhibited a good reproducibility, sensitivity and stability for the determination of EP injection.

In this study, bowl‐shaped N‐doped hollow carbon sphere‐containing mesoporous nanomaterials (BNHC) were used for the ultrasensitive electrochemical detection of isoprenaline (ISOP). The linear ranges of the BNHC‐based sensor were as follows: 0.05 – 15 μM; 15 – 70 μM, with the limit of detection (LOD) of 6.8 nM. And the BNHC‐based electrochemical sensor showed a good current response to ISOP and maintained 95.6 % of the initial current after 30 days of storage. Notably, when the BNHC‐modified sensor was used to detect the actual ISOP injection and urine samples, the sensor exhibited satisfactory recovery. [ABSTRACT FROM AUTHOR]

• It shows good selectivity for phosphate and easy liquid–solid separation. • The preparation of lanthanum-carbon composite nanoparticles by spark ablation is novel, and environmental friendliness. • Using central composite design method established a model to predict phosphorus removal effect in lake water. Eutrophication in water, such as rivers or lakes, is becoming increasingly serious. Controlling the phosphate concentration in such waters is the key to solving the eutrophication problem. The use of adsorption methods to limit the level of phosphate in aqueous solutions has the advantages of cost-effectiveness, ease of operation, and selectivity. In this study, a modified polypropylene (PP) membrane was used as the platform for the in-situ deposition of lanthanum-carbon (La-C) composite nanoparticles. Uniform lanthanum (La) and carbon (C) aerosols were deposited on the PP film using spark ablation, and the combined hydrothermal method was used to synthesise the nano-confinement crystal PP-La-C (PLC) for phosphorus removal in an aquatic environment. Because of the nanoconfinement of the PLC, particle agglomeration deactivation was effectively solved, and the doping of C changed the shape of La(OH) 3 from particles to ultrafine nano-fibres, which resulted in a larger surface area and more abundant active sites, and the overall adsorption performance was improved. The addition of C reduced the cost, and La proved to be the main active site for phosphate capture. The adsorption test revealed a significant adsorption capability of 194.1 mg⋅P⋅g−1. Three variables, such as reaction time, dose, and original phosphate concentration, were selected and a model for predicting lake water phosphate removal efficiency was developed using the central composite design method. When PLC was used to treat water samples from Lake Qilu (Yunnan, China), the observed removal rate of total phosphorus was 94 %, which is consistent with the model prediction. A series of characterisations established that ligand exchange and multilayer adsorption were the main mechanisms of phosphorus removal. [ABSTRACT FROM AUTHOR]

Developing highly active nonprecious‐metal catalysts for the oxygen reduction reaction (ORR) is of great significance for reducing the cost of fuel cells. 3D‐ordered porous structures could substantially improve the performance of the catalysts because of their excellent mass‐diffusion properties and high specific surface areas. Herein, ordered porous ZIF‐67 was prepared by forced molding of a polystyrene template, and Co‐supported, N‐doped, 3D‐ordered porous carbon (Co‐NOPC) was obtained after further carbonization. Co‐NOPC exhibited excellent performance for the ORR in an alkaline medium with a half‐wave potential of 0.86 V vs. reversible hydrogen electrode (RHE), which is higher than that of the state‐of‐the‐art Pt/C (0.85 V vs. RHE). Moreover, the substantially improved catalytic performance of Co‐NOPC compared with Co‐supported, N‐doped carbon revealed the key role of its hierarchical porosity in boosting the ORR. Co‐NOPC also exhibited a close‐to‐ideal four‐electron transfer path, long‐term durability, and resistance to methanol penetration, which make it promising for large‐scale application. [ABSTRACT FROM AUTHOR]

Abstract: A novel one-step method has been carried out for synthesizing high-quality rhodium nanoparticle-loaded carbon nanofibers (nano-Rh/CNF) for the first time by using an electrospinning technology. The new hybrid material shows high electrocatalytic activity for hydrazine oxidation and can be potentially used for the amperometric sensing of hydrazine with high sensitivity and good selectivity. [Copyright &y& Elsevier]

The authors describe a method for synthesis of a nanomaterial consisting of porous carbon encapsulated Mg-Al-Si alloy (denoted as Mg-Al-Si@PC) nanocluster. The nanocluster was synthesis by a solvothermal reaction, followed by high-temperature annealing. The nanoclusters were used as a novel immobilization platform for electrochemical sensing of rutin. The electrochemical behavior of rutin at a modified electrode was investigated by cyclic voltammetry and differential pulse voltammetry. The modified electrode demonstrates a high electrocatalytic activity toward rutin oxidation at a relatively low working potential (0.6 vs. Ag/AgCl). Under optimal conditions, the sensor has a linear response in the 1–10 μM rutin concentration range, and a 0.01 μM lower detection limit (at an S/N ratio of 3). It was successfully applied to the quantification of rutin in pharmaceutical tablets, and satisfactory results were obtained. Furthermore, the results correspond with those with the standard method and with the amounts indicated by the producer, respectively. [ABSTRACT FROM AUTHOR]

A spatial separation strategy was proposed to fabricate an N/S co-doped carbon nanobox embedded with an asymmetrically coupled Fe-Co pair-site, which exhibited exceptional electrocatalytic activities. [Display omitted] • Fe-Co pair-site confined in N/S co-doped carbon nanobox. • The electronic interaction between Fe and Co facilitates charge redistribution. • This nanoreactor as an efficient ORR-OER electrocatalyst in rechargeable ZAB. The fabrication of a remarkably efficient iron-metal-based pair-site, constrained within carbon support, presents a significant and intricate undertaking, primarily attributable to the propensity of proximate metallic entities to amalgamate into the alloy state. In response to this challenge, a spatial segregation approach was conceptualized, aiming to synthesize an N/S co-doped carbon nanobox hosting an asymmetrically coupled Fe-Co pair-site. This engineered nanostructure manifested remarkable electrocatalytic properties, notably featuring a superb half-wave potential of 0.903 V for the oxygen reduction reaction (ORR) and a commendable overpotential of 0.296 V at 10 mA/cm2 for the oxygen evolution reaction (OER). Additionally, a homemade Zn-air battery incorporating this nanohybrid catalyst demonstrated a discharge capacity of 737 mAh/g, a specific maximum power density of 239 mW/cm2 as well as notable durability. Work-function calculations suggested that the electronic interaction between Fe and Co phases, along with the synergetic catalysis of N/S co-doped carbon substrate, could facilitate charge redistribution at the interface, create abundant active sites, and optimize the adsorption–desorption energy of oxygen species on the active center, thus markedly reducing the ORR/OER catalytic reaction barriers. These findings highlight a new strategy for designing and synthesizing efficient bifunctional carbon-based catalysts for energy storage and conversion devices. [ABSTRACT FROM AUTHOR]

Three-dimensional (3D) carbon from the assembly of low-dimensionally isolated segments have attracted much attention as these carbon materials not only inherit the superiorities of individual building blocks but also acquire new synergic effects. However, it remains a big issue to assemble isolated carbon segments into a 3D carbon superstructure by a facile strategy. Herein, the spheroidizing growth of hydrothermal carbon as an assembly drive and in situ formed melamine cyanurate nanosheets as structure-directing agent are combined to design and assemble B, N and O co-doped carbon flower as a promising cathode for Zn2+ hybrids supercapacitors. The flower-like carbon exhibits large nanosheets area, interlinked conductive network, nanoscale architecture and rich electroactive sites. Boron doping enhances the chemical adsorption of SO 4 2− onto the carbon cathode surface and the reaction between oxygen dopant and Zn ions added additional capacity for Zn-ion supercapacitors. The resulting device achieves an energy density of 119.7 Wh/kg at 890 W/kg and maintains 63.5 Wh/kg even at a power density of 16.5 kW/kg. [Display omitted] • A flower-like carbon material was prepared for Zn-ion supercapacitors. • In situ formed melamine cyanurate directed the formation of flakiness carbon. • The flakiness carbon was assembled into flower-like carbon by spheroidizing drive. • The boron enhanced the chemical adsorption of anions onto the cathode surface. • The electrochemical reaction between C-O and Zn2+ improved pseudocapacitance. [ABSTRACT FROM AUTHOR]

Abstract Herein, electrochemically sluggish polymeric carbon nitride (PCN) is successfully introduced into NiCo 2 O 4 to form hybrids of NiCo 2 O 4 and PCN, in which PCN nanosheets are regarded as a substrate to promote the nucleation and subsequent in-situ growth of NiCo 2 O 4 nanosheets. The surface of as-prepared hybrids are rich in Ni and Co ions in low and high valence state, respectively. In addition, the hybrids exhibit more hydrophilic compared with that of pristine NiCo 2 O 4 due to its higher amounts of hydroxyl group. It has been found that the nitrogen species originated from PCN nanosheets tend to bond with the metal ions and electrolyte used, resulting in tuning the electronic structural states and coupling effects with NiCo 2 O 4 nanosheets. Owing to these structural characteristics, the electrochemical performance as faradaic electrode materials and long-term stability of optimized hybrid is much superior to the bare NiCo 2 O 4 nanosheets. Graphical abstract The vertically growth of NiCo 2 O 4 on PCN nanosheets substrate with 3D open frameworks synthesized here is beneficial for facilitating electrolyte ions transport and electron trapping, thus boosting the supercapacitor performance of NiCo 2 O 4. Image 1 Highlights • NiCo 2 O 4 -PCN samples were prepared via a facile and scalable strategy. • The NiCo 2 O 4 -PCN-40 exhibited much higher supercapacitor performance than that of pure NiCo 2 O 4. • The PCN nanosheets can promote the nucleation and subsequent in-situ growth of NiCo 2 O 4 nanosheets in oriented way. • The presence of PCN can tune the electronic structural states and coupling effects with NiCo 2 O 4 nanosheets. [ABSTRACT FROM AUTHOR]

Heteroatom doping, involving the introduction of atoms with distinct electronegativity into carbon materials, has emerged as an effective approach to optimize their charge distribution. In this study, we designed a strategy to synthesize in-situ Mn, N co-doped carbon nanospheres (Mn-NC) through the polycondensation of 2,6-diaminopyridine and formaldehyde in synchronization with Mn2+ chelation to form Mn-polytriazine precursor, followed by calcination to form carbonaceous solid. Then Mn-NC was fabricated into a capacitive deionization (CDI) electrode for the selective removal of uranium ions (U (VI)), which is commonly found in radioactive water. Interestingly, Mn-NC exhibited good selectivity for UO 2 2+ capture with a demonstrated adsorption capacity of approximately 194 mg/g @1.8 V. The systematic analysis of the adsorption mechanism of UO 2 2+ revealed that N dopants within Mn-NC can coordinate with the U (VI) ions, thereby facilitating the removal process. Our study presents a straightforward and convenient strategy for removing UO 2 2+ ions by harnessing the coordination effect, eliminating the requirement for pore size control. [Display omitted] • Trace Mn in N doped carbon can boost charge density and adsorption energy. • Mn–N–C adsorbs UO 2 2+ ions by coordination interaction with high selectivity. • This material has a good adsorption capacity of 194 mg/g @1.8 V. [ABSTRACT FROM AUTHOR]