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Sensitive detection and effective removal of copper ions (Cu

Electrocatalytic hydrogen production from water is limited by sluggish kinetics and requires a highly overpotential of anodic oxygen evolution reaction (OER) and cathodic hydrogen evolution reaction (HER). NiFe double hydroxides (NiFe-LDH) bifunctional group catalyst is applied to OER/HER under alkaline conditions. The good chemical contact between LDH nanosheets grown in situ (NiFe-LDH) on nickel foam (NF) and nickel foam substrate improves the electrons and ions transportation in the reaction process, which is beneficial to promote the OER/HER. The results show only 464.6/219.4 mV overpotential (vs reversible hydrogen electrode (RHE)) at 100/10 mA cm−2 for OER/HER, respectively. The stability of D 0 (stands for NiFe-LDH/NF) was measured at 10 mA cm−2 worked continuously for 24 h, and it is found that D 0 exhibits excellent stable catalytic performance. This work opens up a simple way to design and prepare the efficient, low-cost, and easily synthetic earth-rich electrocatalysts.

Fabrication of high performance and low-cost nonprecious metal carbides for oxygen evolution reaction (OER) and hydrogen evolution reaction (HER) is significantly important. Herein, Ni and WC (Tungsten Carbide) nanoparticles embedded in carbon nanofibers (Ni-WC/CNFs) electrocatalysts were successfully synthesized by electrospinning followed by subsequent carbonization process. The morphology and composition of the Ni-WC/CNFs composite were characterized by using SEM and XRD analysis. Ni and WC nanoparticles were successfully uniformly dispersed on carbon nanofibers (CNFs). The Ni-WC/CNFs electrocatalysts exhibit excellent electrocatalytic activity towards OER and HER in 1.0 M KOH solutions. The experimental results show that the OER and HER overpotentials of Ni-WC/CNFs are 350 mV and 190 mV respectively when the current density is 10 mA cm−2. The excellent electrocatalytic properties of OER and HER are attributed to the synergistic effect between Ni and WC nanoparticles and the large electrochemically active surface area. This study provides a simple and feasible strategy for the development of bifunctional electrocatalysts with low cost and high activity.

In this study, cobalt-iron selenides embedded in porous carbon nanofibers (CoFe2Se4/PCF), derived from Prussian blue analogues, was prepared as a novel phenolic sensor. The obtained CoFe2Se4/PCF nanocomposites show three-dimensional (3D) networks nanostructures that can supply a desirable conductive network to accelerate electron transfer and avoid the aggregation of CoFe2Se4 nanoparticles. Electrochemical detection of hydroquinone (HQ), catechol (CC) and resorcinol (RS), at CoFe2Se4/PCF modified glassy carbon electrode (GCE) were researched. The results show the obtained 3D CoFe2Se4/PCF/GCE exhibits excellent electrochemical properties towards the simultaneous testing trace of HQ, CC and RS. The obtained electrode provides wide linear ranges of 0.5–200, 0.5–190 and 5–350 μM and low detection limit of 0.13, 0.15 and 1.36 μM for HQ, CC and RS, respectively. The as-prepared phenolic sensor displays satisfied selectivity and long-term storage stability. In addition, the constructed sensor can be used to determine HQ, CC and RS in actual samples.

Exploring highly active, inexpensive and robust electrocatalysts for oxygen reduction reaction (ORR) is of great significance as a competitive alternative to noble metal-based catalysts in energy conversion and storage devices. In the present study, we design a novel ORR electrocatalyst of iron-cobalt (FeCo) alloy nanoparticles embedded on N-doped porous carbon nanofibers (FeCo@PCNF-T) by electrospinning of [Polyacrylonitrile (PAN)/Prussian blue analogues/CaCO3] and post-calcination treatment. The obtained catalysts with bimetallic active sites show unique three-dimensional (3D) hierarchical meso/macropores structures. FeCo alloy nanoparticles are encapsulated into graphitic carbon that can increase stability and provide additional catalytic active sites. Under the optimized condition, FeCo@PCNF-800 displays excellent ORR electrocatalytic activity in alkaline solutions, with a more positive half-wave potential (E1/2 of 0.854 V vs RHE) and larger limited-diffusion current density (j of 6.012 mA cm−2) than those of 20 wt% Pt/C (E1/2 of 0.849 V and j of 5.710 mA cm−2). In addition, FeCo@PCNF-800 also exhibits comparable ORR electrocatalytic activity in acidic solutions to those of 20 wt% Pt/C with onset potential and half-wave potential as more positive as 0.843 V vs RHE and 0.739 V vs RHE, respectively. Moreover, FeCo@PCNF-800 exhibits excellent tolerance towards methanol, stability and a four-electron pathway in both basic and acidic solutions. The excellent ORR electrocatalytic activity performance of FeCo@PCNF-800 is attributed to the synergistic effect of the FeCo alloy nanoparticles and N-doped porous carbon nanofibers. The synergistic effect can improve the mass and charge transport capability and increase active sites of FeCo-N-C. Furthermore, this work offers a new insight for the reasonable design and development of efficient non-noble metal electrocatalysts for challenging electrochemical energy-related technologies.

In this work, a novel enzyme-free glucose and hydrogen peroxide (H2O2) sensor based on Ni3N nanoparticles on conductive 3D graphene aerogels (Ni3N/GA) has been successfully synthesized by using hydrothermal reaction, freeze-dried and then calcined under NH3 atmosphere. The obtained Ni3N/GA composites were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), nitrogen adsorption–desorption isotherms and electrochemical methods. The results show the obtained 3D Ni3N/GA composites exhibit excellent electrochemical performance toward glucose oxidation and H2O2 reduction with larger catalytic rate constant Kcat value of 3.75 × 103 M−1 s −1 and 1.24 × 103 M−1 s −1, respectively. As a glucose sensor, the obtained electrode provides a wide detection range of 0.1–7645.3 μM, fast response time within 3 s, high sensitivity of 905.6 μA mM-1 cm-2 and low detection limit of 0.04 μM. For detection of H2O2, this prepared sensor offers a wide detection range (5 μM–75.13 mM), fast response time (within 5 s), sensitivity (101.9 μA mM-1 cm-2) and low detection limit (1.80 μM). This enzyme-free glucose and H2O2 sensor display satisfactory selectivity, reproducibility and long-term storage stability. Additionally, the sensor can also be used for glucose and H2O2 detection in human blood serum. The results demonstrate that 3D GA nanostructures provide an enviable conductive network for efficient charge transfer and avoid Ni3N nanoparticles aggregation, which is advantageous for electrocatalytic applications.

Porphyrinic iron metal-organic framework (pFeMOF) was combined with different kinds of carbon matrices, including porous graphene (PG), ordered mesoporous carbon (OMC) and macroporous carbon (MPC) via a simple one-step hydrothermal method. The introduction of carbon substrates improves the electrical conductivity and stability of pFeMOF. The presence of carbon also reduces the size of pFeMOF crystallites, leading to more active sites. The catalysts were used to electrocatalysis of hydrogen evolution reaction (HER) and the reduction of hydrogen peroxide (H2O2). Electrochemical measurements show that pFeMOF/PG has better electrocatalytic efficiency than pFeMOF/OMC, pFeMOF/MPC and pFeMOF. The HER on pFeMOF/PG displays a small onset potential of −34.37 mV vs. reversible hydrogen electrode (RHE), a low Tafel slope of 73.06 mV dec−1, a small over-potential of 154.71 mV at 10 mA cm−2. The catalytic effect for H2O2 is also satisfied. The linearity range of H2O2 is as wide as 5–4310 μM, and the sensitivity is as high as 77.38 μA mM−1. Such splendid performances may be attributed to the crumpled structure of PG leading to evenly and smaller pFeMOF. Furthermore, abundant hierarchical pores of pFeMOF/PG result in larger electrochemically surface areas. Our work may provide a new approach to design efficient non-precious metal catalysts.

A novel porphyrinic iron metal-organic framework (pFeMOF)-decorated ordered mesoporous carbon (OMC) was developed to detect hydrogen peroxide (H2O2) released from viable cells. The pFeMOF/OMC hybrid materials were synthesized via a simple one-step hydrothermal method. Fe (III) ion could coordinate with carboxylates of porphyrin groups strongly, leading to more stable MOFs. Because of the mimic peroxidase property of pFeMOF, amplified electrochemical signal could be obtained. The carbon skeleton of OMC revealed a function of restriction for the growth of pFeMOF crystallites, resulting in more active sites to reduce H2O2. The increased amount of mesopores brings faster diffusion. Moreover, the electrical conductivity and stability has been improved due to the introduction of OMC. The electrocatalytic reduction of H2O2 displayed two segments linearity range from 0.5 to 70.5 μM and 70.5 to 1830.5 μM, with high sensitivity of 67.54 μA mM−1 in the range of low concentration and 22.29 μA mM−1 of high concentration as well as a low limit of detection (LOD) as 0.45 μM. In addition, the pFeMOF/OMC/glassy carbon electrode (GCE) exhibited outstanding property to resist interference, long-term stability and repeatability. Due to these excellent analytical performances, the as-prepared biosensor was applied to detect H2O2 released from living cells with satisfactory outcome. These results display that this new nanocomposite has the potential to fabricate electrochemical sensing platform for nonenzymatic biosensing.

In this work, a novel porphyrinic metal-organic framework-based composite has been successfully synthesized by a simple one-step solvothermal method through growing Zr-PorMOF on macroporous carbon (MPC). Porphyrin-base MOFs combining the structural adjustable of MOFs and the specific catalytic activity of biomimetic catalysts play an important role in electrocatalysis. A series of characterization show that the roles of MPC as follow: (1) MPC could avoid the agglomeration of Zr-PorMOF particles and increase the specific surface area; (2) MPC could improve the electrochemical stability of Zr-PorMOF particles; (3) MPC could reduce the electron transfer resistance. Therefore, MPC plays the role of the conductive bridges to provide facile charge transport. The obtained Zr-PorMOF/MPC composites exhibit much better electrocatalytic activity for the reduction of hydrogen peroxide (H2O2) than the pristine Zr-PorMOF due to the synergy of Zr-PorMOF and MPC. This enzyme-free H2O2 sensor shows two linear relationships in the ranges 0.5–137 μM (R2 = 0.991, sensitivity = 66 μA mM−1) and 137–3587 μM (R2 = 0.993, sensitivity = 16 μA mM−1), with a low over-potential at −0.2 V, a fast response time within 1 s and a low limit of detection (LOD) of 0.18 μM. Moreover, Zr-PorMOF/MPC composites were used to simultaneously detect uric acid (UA), xanthine (XA) and hypoxanthine (HX). These three substances are degradation products of purine metabolism. In addition, Zr-PorMOF/MPC composites can be used to develop multifunctional biosensors.

Non-small cell lung cancer (NSCLC) is the most common type of lung cancer accounting for ~80% of lung cancer cases. According to novel research, numerous microRNAs (miRs) have been suggested to function as important regulators of cancer. In addition, the expression of miR-140-5p is decreased in patients with NSCLC. Therefore, it is important to further elucidate the role of miR-140-5p in NSCLC. Reverse transcription-quantitative polymerase chain reaction (RT-qPCR) was used in order to investigate the expression of miR-140-5p in NSCLC tissues and matched normal tissues and to determine miR-140-5p levels following transfection with mimics into A549 lung cancer cells. Targetscan software was used to predict the oncogene target of miR-140-5p. This analysis revealed that YES proto-oncogene 1 (YES1) includes a target site for miR-140-5p binding. The results revealed that YES1 is a potential target gene of miR-140-5p, and this was further confirmed by the results of luciferase reporter assays, which demonstrated that miR-140-5p directly targeted the predicted binding site in the 3′-untranslated region of YES1. Cell Counting Kit-8 (CCK-8) and flow cytometry assays were performed to determine the levels of cell viability and apoptosis. Western blot assays was performed to investigate the expression levels of YES1 and proteins associated with apoptosis in A549 cells following transfection. The results revealed that miR-140-5p expression was significantly downregulated in NSCLC tissues compared with matched normal tissues. The expression of miR-140-5p was significantly increased following transfection with miR-140-5p mimics. The results of CCK-8 and flow cytometry assays indicated that miR-140-5p inhibited proliferation and induced apoptosis of tumor cells. Western blot analysis and RT-qPCR revealed that YES1 and B-cell lymphoma 2 (Bcl-2) mRNA and protein expression levels were markedly decreased in A549 cells, while Bcl-2 associated X (Bax) and caspase-3 expression levels increased significantly following transfection with miR-140-5p mimics compared with the negative control group. In conclusion, miR-140-5p may induce apoptosis in A549 cells by targeting YES1 and regulating the expression of apoptosis-associated proteins Bcl-2, Bax and caspase-3.

In this work, a novel enzyme-free glucose and hydrogen peroxide (H

YF3:Eu3+ nanofibers, polyaniline (PANI) and ferroferric oxide (Fe3O4) nanoparticles (NPs) were incorporated into polyvinyl pyrrolidone (PVP) and electrospun into Janus nanofibers with YF3:Eu3+ nanofibers/PVP as one half side and PANI/Fe3O4/PVP as the other half side. The morphology and properties of the final products were investigated in detail by X-ray diffractometry, scanning electron microscopy, transmission electron microscopy, energy dispersive spectrometry, Hall effect measurement system, fluorescence spectroscopy, vibrating sample magnetometry and UV–Vis spectroscopy. The results reveal that the [YF3:Eu3+/PVP]//[PANI/Fe3O4/PVP] trifunctional Janus nanofibers possess excellent electrical conduction, magnetism and fluorescence due to their peculiar isolated nanostructure. Fluorescence emission peaks of Eu3+ are observed in the [YF3:Eu3+/PVP]//[PANI/Fe3O4/PVP] Janus nanofibers and assigned to the 5D0 → 7F1 (587, 595 nm), 5D0 → 7F2 (614, 622 nm), and the 5D0 → 7F1 magnetic-dipole transition at 595 nm is the predominant emission peak. The electrical conductivity reaches up to the order of 10−4 S cm−1. The luminescent intensity, electrical conductivity and saturation magnetization of the Janus nanofibers can be respectively tunable by adjusting respective amounts of YF3:Eu3+ nanofibers, PANI and Fe3O4 NPs. The new type trifunctional Janus nanofibers have many potential applications in the fields of electromagnetic interference shielding, microwave absorption, molecular electronics and biomedicine. More importantly, this design concept and construct technology is of universal significance to fabricate other multifunctional nanostructures.

Y2 O3 :Eu3+ nanoparticles (NPs), polyaniline (PANI), and Fe3 O4 NPs are incorporated into polymethyl methacrylate (PMMA) and electrospun into [Y2 O3 :Eu3+ /PMMA]//[PANI/Fe3 O4 /PMMA] Janus nanobelts with Y2 O3 :Eu3+ /PMMA as one half side and PANI/Fe3 O4 /PMMA as the other. The morphology and properties of the final products are investigated in detail by X-ray diffraction (XRD), scanning electron microscopy (SEM), optical microscopy (OM), energy-dispersive spectrometry (EDS), Hall effect measurements, fluorescence spectroscopy, vibrating sample magnetometry (VSM), and UV/Vis spectroscopy. The results reveal that the [Y2 O3 :Eu3+ /PMMA]//[PANI/Fe3 O4 /PMMA] trifunctional Janus nanobelts possess excellent electrical conductivity, magnetism, and fluorescence owing to their special nanostructure. Fluorescence emission peaks of Eu3+ are observed in the Janus nanobelts. The electrical conductivity reaches the order of 10-4 S cm-1 . The luminescent intensity, electrical conductivity, and saturation magnetization of the Janus nanobelts can be tuned by adjusting the respective amounts of Y2 O3 :Eu3+ NPs, PANI, and Fe3 O4 NPs. The flexible luminescent-electrical-magnetic trifunctional Janus nanobelts have many potential applications. More importantly, this design concept and construct technology is of universal significance for the fabrication of other multifunctional nanostructures.