Heterometallic MIL-125(Ti-Al) frameworks for electrochemical determination of ascorbic acid, dopamine and uric acid.

The detection of ascorbic acid (AA), dopamine (DA), and uric acid (UA) is not only of great significance in the areas of biomedicine and neurochemistry but also helpful in disease diagnosis and pathology research. Due to their diverse structures, designability, and large specific surface areas, metal-organic frameworks (MOFs) have recently caught considerable attention in the electrochemical field. Herein, a family of heterometallic MOFs with amino modification, MIL-125(Ti-Al)-xNH2 (x = 0%, 25%, 50%, 75%, and 100%), were synthesized and employed as electrochemical sensors for the detection of AA, DA, and UA. Among them, MIL-125(Ti-Al)-75%NH2 exhibited the most promising electrochemical behavior with 40% doping of carbon black in 0.1 M PBS (pH = 7.10), which displayed individual detection performance with wide linear detection ranges (1.0-6.5 mM for AA, 5-100 µM for DA and 5-120 µM for UA) and low limits of detection (0.215 mM for AA, 0.086 µM for DA, and 0.876 µM for UA, S/N = 3). Furthermore, the as-prepared MIL-125(Ti-Al)-75%NH2/GCE provided a promising platform for future application in real sample analysis, owing to its excellent anti-interference performance and good stability.

Recycling cobalt from spent lithium-ion batteries for designing the novel cobalt nitride followers: Towards efficient overall water splitting and advanced zinc-air batteries.

Although cobalt nitride (CoN)-based nanomaterials have been widely designed as advanced oxygen evolution reaction (OER), hydrogen evolution reaction (HER), and oxygen reduction reaction (ORR) catalysts, the continuous consumption of lithium-ion batteries (LIBs) has led to a high price of cobalt metal. Therefore, in the future, recycling valuable Co elements from spent devices and boosting their service efficiency will inevitably promote the utilization of Co-based materials in water splitting and zinc-air batteries (ZABs). Herein, we realize the Co recycling from spent LIBs by a simple hydrometallurgy method. Under the assistance of hexamethylenetetramine and polystyrene spheres, after the hydrothermal and pyrolysis treatment in the NH3 atmosphere, the as-reclaimed cobalt oxalates were successfully transformed into novel three-dimensional (3D) CoN nanoflowers (denoted as CoN NFs). Benefiting from the unique 3D flower-like architectures, intrinsic high conductivity, large surface area, uniformly dispersed CoN nanoparticles, and the synergistic effect between Co3N and CoO phases, the 3D flower-like CoN NFs exhibited excellent OER catalytic activity. The performance was much better than commercial RuO2 in the 1.0 M KOH solution. Furthermore, the CoN NFs-based water splitting cell needed a voltage of 1.608 V to achieve the current density of 10 mA cm-2, which is even 16 mV smaller than that of Pt/C||RuO2 benchmark (1.624 V). Meanwhile, the CoN NFs-derived ZAB exhibited a high peak power density of 107.3 mW cm-2 (vs. 103.2 mW cm-2 of Pt/C-RuO2-based ZAB) and a low charge-discharge voltage gap (0.93 V vs. 1.43 V of Pt/C-RuO2-based ZAB). Due to the excellent structural and elemental stabilities, the corresponding water splitting cell and ZAB had outstanding durability. This work successfully explored an advanced industrial chain from recycling Co metal in spent devices to designing the high-efficiency HER/OER/ORR electrocatalysts for advanced water splitting devices and ZABs. This will further promote the value-added utilization of valuable Co metal in various energy storage or conversion devices.

Synthesis of three-dimensional (3D) hierarchically porous iron-nickel nanoparticles encapsulated in boron and nitrogen-codoped porous carbon nanosheets for accelerated water splitting.

Designing two-dimensional (2D) porous carbon nanosheets is a promising strategy for enhancing the water-splitting activities of non-noble metal catalysts. In this study, we developed a novel method for synthesizing the novel three-dimensional (3D) hierarchically porous iron-nickel (FeNi) nanoparticles encapsulated in boron (B) and nitrogen (N)-codoped porous carbon nanosheets (denoted as FeNi@BNPCNS). Owing to the advantages of morphology and structure of B and N, 10.31 atom % of B/N active centers were successfully doped into the optimal FeNi@BNPCNS-800 nanosheets. FeNi@BNPCNS-800 exhibited better hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) electrocatalytic activities than control catalysts in an alkaline solution. However, the HER and OER electrocatalytic activities of FeNi@BNPCNS-800 were slightly lower than 20 wt% Pt/C and RuO2. The FeNi@BNPCNS-800||FeNi@BNPCNS-800 electrolyzer achieved 10 mA cm-2 at 1.514 V, which was 73 mV lower than that of 20 wt% Pt/C||RuO2 electrolyzer (1.587 V). The perfect 3D honeycomb-like architectures, abundant mesopores/defects, and abundant electrocatalytic active sites were attributed to the outstanding water-splitting performances of FeNi@BNPCNS-800 nanosheets. This study provides an efficient strategy for the large-scale, rapid, and low-cost fabrication of 2D porous carbon nanosheets without using any template, surfactant, or expensive raw material, thus presenting a simple approach to design advanced non-noble metal electrocatalysts for water splitting.

Universal Fully Integrated Wearable Sensor Arrays for the Multiple Electrolyte and Metabolite Monitoring in Raw Sweat, Saliva, or Urine.

Fully integrated wearable sensors are capable of dynamically, directly, and independently tracking biomarkers in raw noninvasive biofluids without any other equipment or accessories by integrating the unique on-body monitoring feature with the special complete functional implementation attribute. Sweat, saliva, and urine are three important noninvasive biofluids, and changes in their biomarkers hold great potential for revealing physiological conditions. However, it is still a challenge to design single fully integrated wearable sensor arrays (FIWSAs) that are universally able to concurrently measure electrolytes and metabolites in three of the most common noninvasive biofluids including sweat, saliva, and urine. Here, we propose the first single universal FIWSAs for wirelessly, noninvasively, and simultaneously measuring various metabolites (i.e., uric acid) and electrolytes (i.e., Na+ and H+) in raw sweat, saliva, or urine under subjects' exercise by integrating the specifically designed microfluidic, sensing, and electronic modules in a seamless manner. We evaluate its utility for noninvasive gout management in healthy subjects and in gout patients through a purine-rich meal challenge and with a medicine-treatment control, respectively. Noninvasive monitoring of multiple electrolytes and metabolites in a variety of raw noninvasive biofluids via such single universal FIWSAs may enrich the understanding of the biomarkers' levels in the body and would also facilitate self-health management.

Carboxyl induced ultrahigh defects and boron/nitrogen active centers in cobalt-embedded hierarchically porous carbon nanofibers: The stable oxygen reduction reaction catalysis in acid.

Transition metal-nitrogen-carbon (MNC) type catalysts have been considered a promising alternative to noble metals for oxygen reduction reaction (ORR) electrocatalysis. Nevertheless, poor stabilities of MNC catalysts in acidic solutions limit their commercialization. In this study, we design and synthesize novel three-dimensional (3D) cobalt (Co) nanoparticles encapsulated in ultrahigh content of boron (B) and nitrogen (N) -doped hierarchically porous carbon nanofibers (denoted as Co@BN-PCNFs) by carbonizing the 3D acetic acid/cobalt nitrate/4-hydroxybenzeneboronic acid/polyvinylpyrrolidone precursor networks woven using electrospinning method under a nitrogen atmosphere. The optimal Co@BN-PCNFs-900 catalyst has abundant micro/mesopores and numerous topological defects and exhibits the largest surface area. Under the synergistic effect of oxygen-containing acetic acid molecules and the electrospinning technology, 5.87 at.% of B and 5.91 at.% of N atoms were doped into carbon nanofibers. Specifically, B/N electrocatalytic active centers (including BC3, pyridinic-N/CoNC, pyrrolic-N, and graphitic-N) of approximately 8.70 at.% were successfully introduced into the skeletons of Co@BN-PCNFs-900. In 0.1 M KOH, the ORR onset potential (Eonset) and half-wave potential (E1/2) of Co@BN-PCNFs-900 were âˆ¼ 64 and âˆ¼ 63 mV, respectively, more positive than those of 20 wt% Pt/C. Additionally, in 0.5 M H2SO4, the ORR Eonset and E1/2 values of Co@BN-PCNFs-900 were only âˆ¼ 11 and âˆ¼ 7 mV, respectively, more negative than those of 20 wt% Pt/C. As the 3D hierarchically porous architectures, topological carbon edges, BC3, and partial NC/CoNC are relatively stable, the Co@BN-PCNFs-900 exhibits excellent stability toward ORR catalysis in both acidic and basic media. These favorable properties of Co@BN-PCNFs-900 nanofibers make them the best non-noble metal-based carbonaceous electrocatalysts for ORR in acidic electrolytes.

Fabrication of manganese borate/iron carbide encapsulated in nitrogen and boron co-doped carbon nanowires as the accelerated alkaline full water splitting bi-functional electrocatalysts.

With high prices of precious metals (such as platinum, iridium, and ruthenium) and transition metals (such as cobalt and nickel), the design of high-efficiency and low-cost non-precious-metal-based catalysts using iron (Fe) and manganese (Mn) metals for hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) are critical for commercial applications of water splitting devices. In the study, without using any template or surfactant, we successfully designed novel cross-linked manganese borate (Mn3(BO3)2) and iron carbide (Fe3C) embedded into boron (B) and nitrogen (N) co-doped three-dimensional (3D) hierarchically meso/macroporous carbon nanowires (denoted as FexMny@BN-PCFs). Electrochemical test results showed that the HER and OER catalytic activities of Fe1Mn1@BN-PCFs were close to those of 20 wt% Pt/C and RuO2. For full water splitting, (-) Fe1Mn1@BN-PCFs||Fe1Mn1@BN-PCF (+) cell achieved a current density of 10 mA cm-2 at a cell voltage of 1.622 V, which was 14.2 mV larger than that of (-) 20 wt% Pt/C||RuO2 (+) benchmark. The synergistic effect of 3D hierarchically meso/macroporous architectures, excellent charge transport capacity, and abundant active centers (cross-linked Mn3(BO3)2/Fe3C@BNC, BC3, pyridinic-N, MNC, and graphitic-N) enhanced the water splitting catalytic activity of Fe1Mn1@BN-PCFs. The (-) Fe1Mn1@BN-PCFs||Fe1Mn1@BN-PCF (+) cell exhibited excellent stability owing to the superior structural and chemical stabilities of 3D hierarchically porous Fe1Mn1@BN-PCFs.

A Bifunctional Fully Integrated Wearable Tracker for Epidermal Sweat and Wound Exudate Multiple Biomarkers Monitoring.

Fully integrated wearable electronics that combine the extraordinary feature of incessant and on-body operation with the distinctive external equipment-free trait are the ultimate goal of modern wearables. Epidermal sweat and wound exudate, as two noninvasively accessible biofluids on/surrounding the skin, reflect underlying health conditions. However, the design of universal wearable sensors with the bifunctional capability to monitor both epidermal secretions is still a challenge. Here, a single bifunctional fully integrated wearable tracker for wirelessly, simultaneously, and dynamically in situ measuring multiple epidermal sweat or wound exudate biomarkers is propos. Considering the electrolytes (e.g., Na+ , K+ , and H+ ) and metabolites (e.g., uric acid (UA)) levels in sweat or wound exudate may correlate with health or wound conditions, the dynamic and skin-on tracking of the biomarkers of Na+ , K+ , pH, and UA levels in sweat under subjects' exercise and in wound exudate during subjects' wound healing are performed through the seamless integration of microfluidic, sensing, and electronic modules. Its applicability is evaluated for noninvasive hyperuricemia management in hyperuricemia/healthy subjects through a purine-rich intake test and for wound management in subjects' infected wounds through a control medical treatment.

Single-Step and Room-Temperature Synthesis of Laser-Induced Pt/VC Nanocomposites as Effective Bifunctional Electrocatalysts for Hydrogen Evolution and Oxygen Evolution Reactions.

The development of cost-effective Pt-based electrocatalysts is of great scientific and industrial significance for improving the electrocatalytic activity of hydrogen evolution (HER) and oxygen evolution (OER) reactions for overall water splitting. In this work, unlike traditional furnace pyrolysis, we report the rapid and single-step room-temperature synthesis of Pt/VC nanocomposites with a three-dimensional (3D) network porous structure by laser irradiation technology. The resultant Pt-based composite (Pt/VC-2.84) could be applied to HER under different pH conditions. In particular, the content of Pt in Pt/VC-2.84 is only 2.84 wt %, which is far lower than that in the advanced HER electrocatalyst with the Pt content of 20 wt % (commercial 20 wt % Pt/C). In addition, Pt/VC-2.84 exhibits a boosted higher OER activity and stability than RuO2 in an alkaline medium. Most importantly, electrocatalytic results reflect that Pt/VC-2.84 reveals superior activity and stability toward overall water splitting.

Morphological modulation of iron carbide embedded nitrogen-doped hierarchically porous carbon by manganese doping as highly efficient bifunctional electrocatalysts for overall water splitting.

In the development of water splitting, the sluggish electrocatalytic kinetics of the hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) have restricted their energy conversion efficiencies. Along with the continuous rise in the prices of noble metals and transition metals (such as cobalt and nickel), constructing high-efficiency HER/OER catalysts based on low cost transition metals, such as iron and manganese, is becoming more meaningful in developing industrialized water splitting devices. In this paper, in the absence of a template or active agent, three-dimensional, hierarchically porous FexMny nanoparticles (NPs) were embedded and nitrogen-doped carbon materials (denoted as FexMny@NC; x:y, representing the molar ratio of Fe:Mn) were successfully prepared via pyrolysis of corresponding precursors containing different metallic salt components. Various morphological, structural, and chemical characterization analysis demonstrate that at an Fe:Mn molar ratio of 3:1, the optimal Fe3Mn1@NC material shows high graphitization degree, rich mesoporous structures, a large surface area, and abundant carbon defects/edges, which promote the uniform dispersion of pyridinic-N (pyridinic-N-metal), graphitic-N, carbon oxygen bonds (CO), manganese oxide (MnO) nanocrystals, and Fe3C NPs-embedded, N-doped carbon sheet (Fe3C@NC) active sites. In alkaline conditions, the HER onset potentials (Eonset) and potentials recorded at 10 mA cm-2 (E10) of the optimal Fe3Mn1@NC are just 84.8 and 156 mV more negative than those of 20 wt% platinum carbon (Pt/C). Meanwhile, the OER Eonset and E10 values of the optimal Fe3Mn1@NC are just 8 and 18.7 mV more positive than those of RuO2. Furthermore, optimized Fe3Mn1@NC catalysts were assembled into a water splitting cell, where the catalytic current density achieves 10 mA cm-2 at a low voltage of 1.6287 V (with superior catalytic stability), which is just 24.9 mV higher than that of the (-) 20 wt% Pt/C||RuO2 (+) benchmark (1.6038 V) under the same conditions. This work describes the regulating efficiency of Mn toward growing mesopores and opens new possibilities for the development of novel carbonaceous catalysts with excellent hydroxide catalytic efficiencies based on low cost Mn/Fe elements.

Laser-enabled flexible electrochemical sensor on finger for fast food security detection.

Today's rampant abuse of antibiotics and lean meat powder disturbs environment and threatens public human health. Therefore, fast in-site detection of antibiotics or lean meat powder residue could avoid potential risks. In this work, flexible graphene electrodes (FGE) were easily and facilely patterned and prepared by CO2 laser at room environment, which was coupled with a portable electrochemical analyzer for electronic signal transmission. Laser-enabled flexible electrochemical sensor on finger can be used for rapid real-time in-site electrochemical identification of chloramphenicol (CAP), clenbuterol (CLB) and ractopamine (RAC) in meat. The electrochemical response of CAP, CLB and RAC is investigated with the limit of detection of 2.70, 1.29 and 7.81 µM and the linear range of 10-200, 5-80 and 25-250 µM in phosphate buffer saline (PBS) pH 7.0, correspondingly. The minimum detection concentrations of CAP, CLB and RAC were 20, 10 and 30 µM, respectively, in actual samples of pork. And the minimum detection concentrations of CAP, CLB and RAC were 10, 5 and 25 µM in milk, respectively. Such an integrated sensing platform enriches application of sensors on finger in food security and provides information that prevents drug containments from entering food chain.

Laser-assisted coupling of nitrogen-doped carbon-coated molybdenum/molybdenum dioxide rods for efficient pH-universal hydrogen evolution electrocatalysis.

Herein, a simple and fast laser-assisted coupling method is used for preparation of rod-like carbon-coated Mo/MoO2 hybrids at room temperature and air environment. Under high energy of laser and reductive atmosphere caused by precursor decomposition, Mo-polydopamine complex-wrapped MoO3 rods are quickly converted into nitrogen-doped carbon-coated Mo/MoO2 rods. Carbon-coated Mo/MoO2 exhibits high surface area, uniform metal dispersion and appealing hydrogen evolution reaction (HER) catalytic performance in a wide pH range. Carbon-coated Mo/MoO2 shows overpotential of 134, 108 and 164 mV to deliver current density of 10 mA cm-2 under alkaline, acidic and neutral solution, respectively. Theoretical calculation demonstrates that combination of Mo and MoO2 into Mo/MoO2 composite favors the dissociation of water and adsorption of hydrogen. This study not only provides a high-efficiency strategy for preparation of electrocatalysts but also give guidance for development of hybrid electrocatalysts for HER.

Vacancy Engineering to Regulate Photocatalytic Activity of Polymer Photosensitizers for Amplifying Photodynamic Therapy against Hypoxic Tumors.

Polymer photosensitizers (PPSs) with the distinctive properties of good light-harvesting capability, high photostability, and excellent tumor retention effects have aroused great research interest in photodynamic therapy (PDT). However, their potential translation into clinic was often constrained by the hypoxic nature of tumor microenvironment, the aggregation-caused reduced production of reactive oxygen species (ROS), and the tedious procedure of manufacture. As a powerful and versatile strategy, vacancy engineering possesses the unique capability to effectively improve the photogenerated electron efficiency of nanomaterials for high-performance O2 and ROS production. Herein, by introducing vacancy engineering into the design of PPSs for PDT for the first time, we synthesized a novel PPS of Au-decorated polythionine (PTh) nanoconstructs (PTh@Au NCs) with the unique integrated features of distinguished O2 self-evolving function and highly efficient ROS generation for achieving the greatly enhanced PDT efficacy toward hypoxic tumor both in vitro and in vivo. The incorporation of Au into PTh leads to the special PTh-Au heterostructure-induced sulfur vacancies in PTh@Au NCs, which results in an efficient electron-hole separation performance and also plays a key role in a long lifetime of free electrons and holes. Accordingly, an ∼2- to 3-fold ROS generation and an ∼1.5-fold increase of O2 self-supply than the pure PTh nanoparticles (NPs) were obtained even under hypoxic conditions upon exposure to 650 nm light. By combining such superior ROS generation and O2 self-supply performances with the outstanding cellular internalization and tumor accumulation capacities, an advanced antitumor effect with the achievement of almost complete hypoxic tumor elimination in vivo or 88% cell destruction in vitro was acquired by the PTh@Au NCs. In addition, the distinctive facile one-step redox strategy for PTh@Au NCs synthesis compared to the reported PPSs for PDT also makes it beneficial for potential practical application. The first introduction of vacancy engineering concept into PPSs in the field of PDT proposed in this work offers a new strategy for the development and design highly efficient PPSs for PDT applications.

MOF-derived hollow NiCo2O4/C composite for simultaneous electrochemical determination of furazolidone and chloramphenicol in milk and honey.

Herein, bimetallic Co/Ni-MOF derived hollow NiCo2O4@C composite modified glassy carbon electrode (NiCo2O4@C/GCE) is constructed and applied to simultaneously detect furazolidone (FZD) and chloramphenicol (CAP) for the first time. Scanning electron microscopy, transmission electron microscopy, X-ray diffraction, nitrogen adsorption-desorption and X-ray photoelectron spectroscopy confirm that NiCo2O4@C has hollow and mesoporous structure, abundant carbon matrixes, sufficient oxygen defects and mixed-valence metallic elements. These advantages make NiCo2O4@C/GCE show distinguished electrocatalytic performance toward the simultaneous determination of FZD and CAP. The NiCo2O4@C/GCE shows wide linear ranges of 0.5-240 µM for FZD and 0.5-320 µM for CAP, low limit of detection of 8.47 nM for FZD and 35 nM for CAP. The mechanism studies show that reductions of FZD and CAP on NiCo2O4@C/GCE are both four-electron and four-proton processes. Moreover, the sensor obtains desirable recoveries for the simultaneous determination of FZD (95.85%-103.9%) and CAP (95.72%-104.4%) in milk and honey by standard addition method.

Laser conversion of biomass into porous carbon composite under ambient condition for pH-Universal electrochemical hydrogen evolution reaction.

It is highly desirable to develop durable and advanced electrocatalysts for pH-universal hydrogen evolution reaction (HER). While it makes much progress so far, the development of an environmental-friendly and cost-effective method to upgrade earth-abundant biomass into high value-added products still remains a major challenge. Thermal pyrolysis method which requires high pyrolysis temperature and long synthesis period is considered as a general method for preparation of carbon-based electrocatalysts. In view of this, ruthenium, nitrogen co-doped porous carbon (Ru@CN) is synthesized by laser conversion method at room temperature using cheap and renewable biomass honey as green carbon source. By controlling the loading of Ru and laser power, the electrocatalytic activities of as-prepared electrocatalysts can be adjusted effectively. Because of the advantage of rich Ru0 and Ru-N sites, the synthesized 0.04-Ru@CN-6 with Ru loading amount of 2.66 wt% exhibits a preferable electrocatalytic activity toward HER under all-pH conditions. Especially in alkaline solution, the optimal 0.04-Ru@CN-6 exhibits a small overpotential (11 mV) at 10 mA cm-2 current density, which is even much better than commercial 20 wt% Pt/C (37 mV). This strategy reported here may be a feasible and unique approach to synthesis and design of high-performance as well as cost-effective all-pH HER electrocatalyst.

Ultrasensitive simultaneous voltammetric determination of 4-aminophenol and acetaminophen based on bimetallic MOF-derived nitrogen-doped carbon coated CoNi alloy.

Simultaneous electrochemical determination of 4-aminophenol (4-AP) and acetaminophen (ACOP) is crucial due to their high toxicity when are overused. Herein, a novel electrocatalyst of nitrogen-doped carbon coated CoNi alloy (CoNi@CN) is derived from bimetallic CoNi(BDC)2(DABCO) for the first time. A series of characterizations demonstrate that composite has been successfully synthesized, and all elements are evenly distributed in the catalyst. The optimal sensor based on Co1Ni1@CN-700 exhibits two wide linear responses for 4-AP (0.05-60 µM and 60-250 µM) and ACOP (0.05-40 µM and 40-150 µM) with the lowest detection limit of 5.2 nM and 3.8 nM compared with current known reports. Moreover, the sensor has superior reproducibility, selectivity and stability. In addition, the wonderful recoveries also are obtained when sensor is used to detect 4-AP and ACOP in real samples, illustrating that electrochemical sensor has great prospect in the clinical application.

MOF-818 metal-organic framework-reduced graphene oxide/multiwalled carbon nanotubes composite for electrochemical sensitive detection of phenolic acids.

Herein, a novel bimetallic MOF-818@reduced graphene oxide/multiwalled carbon nanotubes (RGO/MWCNTs) composite was successfully synthesized by a facile solvothermal method. Characterized by scanning electron microscopy, X-ray diffraction, N2 adsorption-desorption isotherm, X-ray photoelectron spectroscopy and electrochemical measurements, MOF-818@RGO/MWCNTs composite possesses hierarchical porous structures, good electrical conductivity and abundant active sites. The MOF-818@RGO/MWCNTs/GCE exhibits excellent electrocatalytic activity to phenolic acid compounds: caffeic acid (CA), chlorogenic acid (CGA) and gallic acid (GA). The sensor shows two linear ranges from 0.2 to 7 µM and 7-50 µM with a high sensitivity of 12.89 µA/µM for the detection of CA, a low detection limit of 5.7 nM and an excellent sensitivity of 12.50 µA/µM in the ranges of 0.1-3 µM and 3-20 µM for CGA detection, as well as a comparable electrochemical performance for GA. The sensor was used to detect CA, CGA and GA in biological samples and the results of quantitative recoveries for each compounds were satisfactory. We envision that the proposed strategy may stimulate extensive explorations of bimetallic MOFs with more active sites for the development of sensitive electrochemical sensors.

Preparation of a novel Ni-MOF and porous graphene aerogel composite and application for simultaneous electrochemical determination of nitrochlorobenzene isomers with partial least squares.

Metal-organic framework Ni2(BDC)2(DABCO) (Ni-MOF)/porous graphene aerogel (PGA) composites were fabricated for the first time. The introduction of PGA enhances conductivity of Ni-MOF, prevents Ni-MOF from accumulating, reduces the size of Ni-MOF, and increases the pore size of composites, which improve the electrocatalytic activity of Ni-MOF@PGA-2. The prepared sensors based on Ni-MOF@PGA-2 composite show the highest catalytic current towards electroreduction of 2-nitrochlorobenzene (2-NCB), 3-nitrochlorobenzene (3-NCB), and 4-nitrochlorobenzene (4-NCB) at around - 0.61 V, - 0.56 V, and - 0.57 V (vs. Ag/AgCl) with respect to other sensors. The reaction mechanisms also are discussed. Under optimized experiment conditions, the Ni-MOF@PGA-2/GCE displays the widest linear range (6-1260, 4-980, and 2-1280 µM for 2-NCB, 3-NCB, and 4-NCB, respectively) for determination of individual nitrochlorobenzene isomers (NCBIs) compared to that of recent reports, and relatively low detection limit (0.093, 0.085, and 0.051 µM for 2-NCB, 3-NCB, and 4-NCB, respectively). More importantly, three NCBIs in the mixture were for the first time simultaneously determined by combining differential pulse voltammetry (DPV) based on Ni-MOF@PGA-2/GCE with partial least squares (PLS) chemometrics modeling method. The proposed method was evaluated towards the determination of NCBI mixtures in tap water and Jing lake water, and satisfactory recoveries were obtained. Graphical abstract.

An advanced hollow bimetallic carbide/nitrogen-doped carbon nanotube for efficient catalysis of oxygen reduction and hydrogen evolution and oxygen evolution reaction.

Rational design and synthesis of multifunctional electrocatalysts with high-efficient activity and robust stability toward the oxygen reduction reaction (ORR), hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) are highly desirable, but remain a challenging step. Herein, a novel hollow bimetallic carbide/nitrogen-doped carbon nanotube (Co6Mo6C2@NCNT) is successfully synthesized through the simple pyrolysis of polypyrrole (PPy)-supported metal-organic framework (MOF) composite. Remarkable characteristics of the large surface area, hollow and porous structure, rich active sites and synergistic effect between Co6Mo6C2 and NCNT arouse high catalytic efficiency. Notably, the Co6Mo6C2@NCNT presents excellent ORR catalytic activity (a high half-wave potential of 0.875 V vs. reversible hydrogen electrode (RHE) and diffusion-limited current density of 6.22 mA cm-2) via a four-electron pathway, together with outstanding stability and methanol tolerance over commercial Pt/C in 0.1 M KOH solution. The composite also exhibits superior HER performance, delivering a low overpotential of 122.14 mV at current density of 10 mA cm-2, as well as good catalytic performance for OER in 1.0 M KOH solution. This work may provide some insight in design multifunctional electrocatalysts derived from MOF with advanced performance for sustainable energy technologies.

DUT-67 and tubular polypyrrole formed a cross-linked network for electrochemical detection of nitrofurazone and ornidazole.

The cross-linked network of DUT-67/tubular polypyrrole (T-PPY) composites was first synthesized by in-situ growth zirconium - based metal-organic frameworks (DUT-67) with T-PPY. The introduction of T-PPY effectively increases conductivity of DUT-67/T-PPY composites, weakens accumulation of the DUT-67, and exposes more active sites of DUT-67. DUT-67/T-PPY/GCE manifests increased electrocatalytic activity toward reduction of nitrofurazone and ornidazole compared with DTU-67. A novel electrochemical sensor based on DUT-67/T-PPY was established to effectively detect two anti-infective drugs, respectively. Under optimized experimental conditions, the proposed sensor shows a wider linear range for nitrofurazone that is composed by two line segments (9.08-354.08 µM and 354.08-1004.04 µM). Meanwhile, the sensor also displays a linear response to ornidazole in the range of (0.7-100.5 µM and 100.5-250.4 µM) as well as a low LOD as 0.25 µM (S/N = 3). The proposed sensor was used for the detection of nitrofurazone and ornidazole in actual samples, and the satisfactory results were acquired. This research provides an efficient strategy for fabricating novel electrochemical sensor based on cross-linked network structure of T-PPY and MOFs.

A laser-engraved wearable sensor for sensitive detection of uric acid and tyrosine in sweat.

Wearable sweat sensors have the potential to provide continuous measurements of useful biomarkers. However, current sensors cannot accurately detect low analyte concentrations, lack multimodal sensing or are difficult to fabricate at large scale. We report an entirely laser-engraved sensor for simultaneous sweat sampling, chemical sensing and vital-sign monitoring. We demonstrate continuous detection of temperature, respiration rate and low concentrations of uric acid and tyrosine, analytes associated with diseases such as gout and metabolic disorders. We test the performance of the device in both physically trained and untrained subjects under exercise and after a protein-rich diet. We also evaluate its utility for gout monitoring in patients and healthy controls through a purine-rich meal challenge. Levels of uric acid in sweat were higher in patients with gout than in healthy individuals, and a similar trend was observed in serum.