ON-OFF Fluorescent Cyanine Dye Based on a Benzothiophenyl Rotor Enables Selective Illumination of G-Quadruplexes in Mitochondria.

Conventional cyanine dyes exist as "always-on" fluorescent probes leading to inevitable background signals which often limit their performance and scope of applications. To develop specific fluorescent probes with high sensitivity and robust OFF/ON switching for targeting G4s, we introduced aromatic heterocycles through conjugation with polymethine chains to construct a rotor-π system. Here, a universal strategy is presented to synthesize pentamethine cyanines with different aromatic heterocycle substituents on the meso-polymethine chain. In these probes, SN-Cy5-S is self-quenched in aqueous solution due to H-aggregation. The structure indicates that SN-Cy5-S with a flexible meso-benzothiophenyl rotor conjugated to the cyanine backbone matches adaptively with G-tetrad planes, enhancing π-π stacking and resulting in triggered fluorescence. This allows recognition of G-quadruplexes due to the synergy of disaggregation-induced emission (DIE) and inhibited twisted intramolecular charge-transfer effects. This combination leads to a robust lighting-up fluorescence response for c-myc G4 with superior fluorescence enhancement (98-fold), allowing for a low detection limit of 1.51 nM, which is much more sensitive than the previously reported DIE-based G4 probes (22-83.5 nM). In addition, the superior imaging properties and rapid internalization time (5 min) in mitochondria allow SN-Cy5-S to also have a high potential for mitochondrially targeting anti-cancer therapy.

Rapid photocatalytic reduction of hexavalent chromium over Z-scheme MgIn2S4/BiPO4 heterojunction: Performance, DFT calculation and mechanism insight.

The accumulation of highly fluid and biotoxic hexavalent chromium (Cr(VI)) impairs water ecosystems. It is urgent to quickly reduce Cr (VI) to trivalent chromium (Cr (III)) in wastewater. Hereby, Z-scheme MgIn2S4/BiPO4 heterojunction was prepared, and MB-30 (mass ratio of BiPO4 to composite) presented a rapid Cr(VI) (10 mg L-1) removal efficiency of 100% within 10 min, its kinetic rate constant was 9.0 and 30.1 folds that of MgIn2S4 and BiPO4, respectively. After four rounds, MB-30 maintained a high removal rate of 93.18% and stabilized crystal texture. First-principles calculations revealed that the formation of Z-scheme heterojunction could ameliorate charge generation, detachment, migration capability, and light utilization. Meanwhile, the coupling of S and O in the two components produced a tight S-O bond, which acted as an atomic-level access to promote carrier migration. The findings were consistent with the structure superiority and optical and electronic properties of MB-30. The Z-scheme pattern was substantiated based on multifarious experiments, which exhibited an elevated reduction potential while emphasizing the significance of interfacial chemical bond and the internal electric field (IEF) on carrier detachment and migration.

Modulating the electronic structure of ternary transition metal phosphide for enhanced hydrogen evolution activity.

Rationally designing ternary transition-metal phosphides (TMPs) for the hydrogen evolution reaction (HER) is desirable but remains a significant challenge. Herein, ternary FeCoNiP encapsulated in a porous carbon shell, coupled with N-doped carbon nanotubes (FeCoNiP@NCNTs) are synthesized via a simple pyrolysis-phosphatization strategy derived from FeCoNi-MOF-100@dicyandiamide. Because Co/Ni enters the FeP lattice, FeCoNiP@NCNTs show a favorable catalytic performance towards the HER with low overpotential values of 86.7 and 233.5 mV at 10 mA cm-2 in acidic and alkaline media, respectively, surpassing the HER performance of FeP@NCNTs, FeCoP@NCNTs, and FeNiP@NCNTs. Impressively, FeCoNiP@NCNTs display adequate acid-resistance capacity during the HER process, with nearly negligible decay due to the thin graphitized carbon shell structure with a thickness of 11.5-20.3 nm. The results of experiments, structural characterization, and density functional theory (DFT) calculations demonstrate that Co/Ni co-doping can modulate the adsorption and dissociation processes of H+ and downshift the d-band center of FeP. This work proposes a strategy for fabricating ternary TMP catalysts with heterogeneous structures for the HER.

Ce-MOF/COF/carbon nanotube hybrid composite: Construction of efficient electrochemical immune platform for amplifying detection performance of CA125.

The combination of metal organic framework (MOF), covalent organic frameworks (COF) and carbon nanotube (CNT) forms a system due to their synergistic effect, thereby possessing the structural traits of individual components and exhibiting new properties. Herein, we successfully integrated terephthalonitrile-based-COF (TPN-COF)/CNT into the Ce-MOF, designed and synthesized Ce-MOF/TPN-COF/CNT hybrid material to construct a label-free immunosensor for specific detection of carcinomicantigen 125 (CA125). The synthesized composite exhibited abundant active sites and excellent electronic conductivity. As a result, more immunocomplex were immobilized to the carbon paste electrode (CPE) modified by Ce-MOF/TPN-COF/CNT owing to the hydrogen bonding and π-π interaction between triazine ring and trimesic acid ligand, leading to produce an amplified current response. The results of various instrument tests demonstrated that these structural advantages indeed contribute to the low detection limit of 0.000088 U/mL and wide linear range from 0.0001 U/mL to 100 U/mL for the CA125 immunosensor, which was superior to those of other proposed immunosensor. In addition, the constructed CA125 immunosensor exhibits good stability, repeatability, specificity, regeneration characteristics and acceptability in human serum. Therefore, MOF/COF/CNT composite holds promise as an electrode platform for building electrochemical immunosensors in the early diagnosis of cancer.

A novel pomegranate-inspired bifunctional electrode materials design for acetylcholinesterase biosensor and methanol oxidation reaction.

A pomegranate-inspired bifunctional electrode material based on Ni/NiO nanoparticle embedded in nitrogen-doped, partially graphitized carbon framework (Ni/NiO@NPGC) was designed and prepared for the construction of novel electrochemical biosensor and methanol oxidation reaction (MOR). Profiting from itsspecialstructureandfunction, Ni/NiO@NPGC was employed as a matrix immobilizing acetylcholinesterase (AChE) for methyl parathion (MP) sensor. The developed biosensor was proved to have wide linear range (1.0 × 10-14-1.0 × 10-8 g mL-1), low detection limit (3.5 × 10-15 g mL-1), and good stability for the determination of MP in practical samples. In addition, the Ni/NiO@NPGC electrode exhibited high electrocatalytic activity (specific activity 73.1 mA cm-2) and durability for the MOR in alkaline medium. The results were mainly attributed to the pomegranate-like architecture structure with pyridinic N and carbon frame of Ni/NiO@NPGC, which ensured the electrochemical activities of all nanoparticles and immobilization of enzyme. In addition, the metal oxide was well dispersed to prevent from self-agglomeration and kept mass transfer paths. The work provides a reference for the development of high-performance bifunctional electrode material for the biosensor and MOR.

Indium sulfide deposited MIL-53(Fe) microrods: Efficient visible-light-driven photocatalytic reduction of hexavalent chromium.

The ecosystems and human health were seriously threatened by hexavalent chromium (Cr(VI)) in wastewater. In this article, using the idea of the highly matched energy band structure between indium sulfide (In2S3) and MIL-53(Fe), a Type-II heterojunction has been constructed by loading In2S3 on MIL-53(Fe) microrod to overcome the fault like high recombination rates of photogenerated electron-holes of In2S3. The composite with 20:1 mass ratio of In2S3 to MIL-53(Fe) (IM-2) was adopted as an optimal sample for efficient photocatalytic Cr(VI) reduction under visible light. Various characterization techniques were used to verify the characteristics of composites and delved into the structure-effect relationship between this heterojunction and its activity. Results showed that the reaction rate constants of the photoreduction process over IM-2 was ~ 4 and 26 times higher than those of pure In2S3 and MIL-53(Fe), respectively, and the catalyst could maintain superior removal efficiency (88.6%) and steady crystal structure after four cycles. First-principles calculations further illustrated that the heterostructure formed between In2S3 and MIL-53(Fe) could effectively accelerate the separation of photogenerated electrons and holes, thus improving the photocatalytic reduction performance. Moreover, the active species analyses revealed that the superoxide radicals and electrons were mainly involved in the reduction of Cr(VI).

Controllable generation of ZnO/ZnCo2O4 arising from bimetal-organic frameworks for electrochemical detection of naphthol isomers.

The development of a rapid and low concentration detection method for naphthol isomers is of great significance for protecting human health and environmental safety due to their high toxicity and strong corrosivity. Here, we reported a novel hollow ZnO/ZnCo2O4 material derived by adjusting the molar ratio of Zn/Co of bimetal-organic frameworks (BMOFs) and its application for simultaneous detection of 1-naphthol (1-NAP) and 2-naphthol (2-NAP) by electrochemical methods. The oxidation peak currents of 1-NAP and 2-NAP on a ZnO/ZnCo2O4 modified carbon paste electrode (ZnO/ZnCo2O4/CPE) depended linearly on their concentrations in the range of 0.4-50 µM and 0.06-40 µM with detection limits of 0.13 and 0.02 µM, respectively. Their electrooxidation at the ZnO/ZnCo2O4/CPE was a one-electron and one-proton process. These excellent performances could be driven by the high conductivity and number of active sites as well as the unique structure of ZnO/ZnCo2O4. The tactic may shed light on developing new electrodes for fast and efficient electrochemical detection of naphthol isomers.

Metal composite oxides Bi2MoO6/IL membrane as matrix for constructing ultrasensitive electrochemical immunosensor.

In the process of diagnosis and disease monitoring, it is important to quickly and easily detect protein biomarkers. The strategy reported here is an attempt to prepare Bi2MoO6 nanomaterial with new three-dimensional holes morphology surrounded by rod and sheet to construct a simple and sensitive sensing platform, where Bi2MoO6/ionic liquid (IL) composite was modified on the carbon paste electrode (CPE). In order to monitor the assembly process of human IgG immunosensors, a plurality of electrochemical tests such as cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS) was executed. The obtained BSA/anti-IgG/GA/Bi2MoO6/IL-CPE displayed prominent conductivity and high sensitivity in detecting human immunoglobulin G (human IgG). Under the optimal experimental conditions, the results by differential pulse voltammetry (DPV) showed that the constructed label-free IgG immunosensor can detect IgG in the range of 0.01 to 1000 ng mL-1, and limit of detection (LOD) was 4 pg mL-1. The immunosensor displayed good performances including selectivity, reproducibility, and stability. Based on preliminary experiments, Bi2MoO6 and its composite materials are very promising for the construction of a variety biosensors for the analysis of other biological substances. Graphical abstract.

Dispersive solid-phase extraction based on MoS2/carbon dot composite combined with HPLC to determine brominated flame retardants in water.

The method based on the dispersive solid-phase extraction (DSPE) by novel molybdenum disulfide modified with carbon dot (MoS2/CD) composite combined with high-performance liquid chromatography (HPLC) was developed for the determination of three brominated flame retardants (BFRs), including tetrabromobisphenol A (TBBPA), tetrabromobisphenol A bisallylether (TBBPA-BAE), and tetrabromobisphenol A bis(2,3-dibromopropyl ether) (TBBPA-BDBPE). Owing to the stacked planar structure and large surface area of MoS2, a large number of CDs can be easily loaded on the surface of MoS2. Benefiting from good dispersing capability of MoS2, similar density with analytes, and hydrogen bonds between CDs and the target analytes, the CDs on the surface of MoS2 as sorbent for the DSPE procedure exhibited good extraction performance. Under optimal conditions, application of the developed method to analyze BFRs from real water samples resulted in good recovery values ranging from 80 to 91% with relative standard deviation (RSD) values lower than 6.5%. Limits of detection (LODs) were in the range of 0.01-0.06 µg/L. The result above showed that the method has potential for the extraction and detection of trace-level BFRs from real water sample. Graphical abstract Owing to the stacked planar structure and large surface area of MoS2, a large number of CDs can be easily loaded on the surface of MoS2. Benefiting from good dispersing capability of MoS2, similar density with analytes, and hydrogen bonds between CDs and the target analytes, the prepared MoS2/CD composites as sorbent for the DSPE procedure exhibited good extraction performance. Accordingly, the extraction yield of BFRs was improved, which was favorable to its accurate determination in sample.

Three MOF-Templated Carbon Nanocomposites for Potential Platforms of Enzyme Immobilization with Improved Electrochemical Performance.

An efficient and facile metal-organic framework (MOF)-template strategy for preparing carbon nanocomposites has been developed. First of all, a series of metal ions, including Fe3+, Zr4+, and La3+, were respectively connected with 2-aminoterephthalate (H2ATA) to form three metal-organic frameworks (MOFs) and then three novel MOF-derived materials were obtained by annealing them at 550 °C under N2 atmosphere. The morphologies and microstructure results showed that they still retained the original structure of MOFs and formed carbon-supported metal oxide hybrid nanomaterials. Interestingly, it was found that La-MOF-NH2 and its derived materials were first reported, which had wool-ball-like structure formed by many streaky-shaped particles intertwining each other. Furthermore, these MOF-derived materials were all successfully used as effective immobilization matrixes of acetylcholinesterase (AChE) to construct biosensors for the detection of methyl parathion. Especially, [La-MOF-NH2]N2 with wool-ball-like structure not only provided more active sites of multicontents to increase AChE immobilization amount but also facilitated the accessibility of electron transfer and shorten their diffusion length on the surface of electrode. Under optimal conditions, the biosensor based on [La-MOF-NH2]N2 displayed the widest linear range of 1.0 × 10-13-5.0 × 10-9 g mL-1 and the lowest detection limit of 5.8 × 10-14 g mL-1 in three biosensors. This study illustrates the feasibility and the potential of a series of MOF-derived materials for biosensors with improved electrochemical performance.

Synthesis of reticulated hollow spheres structure NiCo2S4 and its application in organophosphate pesticides biosensor.

Electrode materials play a key role in the development of electrochemical sensors, particularly enzyme-based biosensors. Here, a novel NiCo2S4 with reticulated hollow spheres assembled from rod-like structures was prepared by a one-pot solvothermal method and its formation mechanism was discussed. Moreover, comparison of NiCo2S4 materials from different experiment conditions as biosensors was investigated by electrochemical impedance spectroscopy (EIS) and differential pulse voltammetry (DPV), and the best one that was reticulated hollow spheres assembled from rod-like structures NiCo2S4 has been successfully employed as a matrix of AChE immobilization for the special structure, superior conductivity and rich reaction active sites. When using common two kinds of organophosphate pesticides (OPs) as model analyte, the biosensors demonstrated a wide linear range of 1.0×10-12-1.0×10-8gmL-1 with the detection limit of 4.2×10-13gmL-1 for methyl parathion, and 1.0×10-13-1.0×10-10gmL-1 with the detection limit of 3.5×10-14gmL-1 for paraoxon, respectively. The proposed biosensors exhibited many advantages such as acceptable stability and low cost, providing a promising tool for analysis of OPs.

Exploiting multi-function Metal-Organic Framework nanocomposite Ag@Zn-TSA as highly efficient immobilization matrixes for sensitive electrochemical biosensing.

A novel multi-function Metal-Organic Framework composite Ag@Zn-TSA (zinc thiosalicylate, Zn(C7H4O2S), Zn-TSA) was synthesized as highly efficient immobilization matrixes of myoglobin (Mb)/glucose oxidase (GOx) for electrochemical biosensing. The electrochemical biosensors based on Ag@Zn-TSA composite and ionic liquid (IL) modified carbon paste electrode (CPE) were fabricated successfully. Furthermore, the properties of the sensors were discussed by cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS) and amperometric current-time curve, respectively. The results showed the proposed biosensors had wide linear response to hydrogen peroxide (H2O2) in the range of 0.3-20,000 µM, to nitrite (NO2(-)) for 1.3 µM-1660 µM and 2262 µM-1,33,000 µM, to glucose for 2.0-1022 µM, with a low detection limit of 0.08 µM for H2O2, 0.5 µM for NO2(-), 0.8 µM for glucose. The values of the apparent heterogeneous electron transfer rate constant (ks) for Mb and GOx were estimated as 2.05 s(-1) and 2.45 s(-1), respectively. Thus, Ag@Zn-TSA was a kind of ideal material as highly efficient immobilization matrixes for sensitive electrochemical biosensing. In addition, this work indicated that MOF nanocomposite had a great potential for constructing wide range of sensing interface.

Fabric phase sorptive extraction: Two practical sample pretreatment techniques for brominated flame retardants in water.

Sample pretreatment is the critical section for residue monitoring of hazardous pollutants. In this paper, using the cellulose fabric as host matrix, three extraction sorbents such as poly (tetrahydrofuran) (PTHF), poly (ethylene glycol) (PEG) and poly (dimethyldiphenylsiloxane) (PDMDPS), were prepared on the surface of the cellulose fabric. Two practical extraction techniques including stir bar fabric phase sorptive extraction (stir bar-FPSE) and magnetic stir fabric phase sorptive extraction (magnetic stir-FPSE) have been designed, which allow stirring of fabric phase sorbent during the whole extraction process. In the meantime, three brominated flame retardants (BFRs) [tetrabromobisphenol A (TBBPA), tetrabromobisphenol A bisallylether (TBBPA-BAE), tetrabromobisphenol A bis(2,3-dibromopropyl)ether (TBBPA-BDBPE)] in the water sample were selected as model analytes for the practical evaluation of the proposed two techniques using high-performance liquid chromatography (HPLC). Moreover, various experimental conditions affecting extraction process such as the type of fabric phase, extraction time, the amount of salt and elution conditions were also investigated. Due to the large sorbent loading capacity and unique stirring performance, both techniques possessed high extraction capability and fast extraction equilibrium. Under the optimized conditions, high recoveries (90-99%) and low limits of detection (LODs) (0.01-0.05 µg L(-1)) were achieved. In addition, the reproducibility was obtained by evaluating the intraday and interday precisions with relative standard deviations (RSDs) less than 5.1% and 6.8%, respectively. The results indicated that two pretreatment techniques were promising and practical for monitoring of hazardous pollutants in the water sample. Due to low solvent consumption and high repeated use performance, proposed techniques also could meet green analytical criteria.

Environmentally Friendly Method: Development and Application to Carbon Aerogel as Sorbent for Solid-Phase Extraction.

We developed two simple, fast, and environmentally friendly methods using carbon aerogel (CA) and magnetic CA (mCA) materials as sorbents for micro-solid-phase extraction (µ-SPE) and magnetic solid-phase extraction (MSPE) techniques. The material performances such as adsorption isotherm, adsorption kinetics, and specific surface area were discussed by N2 adsorption-desorption isotherm measurements, ultraviolet and visible (UV-vis) spectrophotometry, scanning electron microscopy (SEM), and high resolution transmission electron microscopy (HR-TEM). The experimental results proved that the heterogeneities of CA and mCA were well modeled with the Freundlich isotherm model, and the sorption process well followed the pseudo-second-order rate equation. Moreover, plant growth regulators (PGRs) such as kinetin (6-KT), 6-benzylaminopurine (6-BA), 2,4-dichlorophenoxyacetic acid (2,4-D), and uniconazole (UN) in a reservoir raw water sample were selected as the evaluation of applicability for the proposed µ-SPE and MSPE techniques using high performance liquid chromatography (HPLC). The experimental conditions of two methods such as the amount of sorbent, extraction time, pH, salt concentration, and desorption conditions were studied. Under the optimized conditions, two extraction methods provided high recoveries (89-103%), low the limits of detection (LODs) (0.01-0.2 µg L(-1)), and satisfactory analytical features in terms of precision (relative standard deviation, RSD, 1.7-5.1%, n=3). This work demonstrates the feasibility and the potential of CA and mCA materials as sorbents for µ-SPE and MSPE techniques. Besides, it also could serve as a basis for future development of other functional CAs in pretreatment technology and make them valuable for analysis of pollutants in environmental applications.

Design synthesis of polypyrrole-Co3O4 hybrid material for the direct electrochemistry of Hemoglobin and Glucose Oxidase.

We designed and synthesized a novel organic-inorganic hybrid material polypyrrole-Co3O4 (Ppy-Co3O4), then mixed it with ionic liquid (IL) to form stable composite films for the immobilization of Hemoglobin (Hb) and Glucose Oxidase (GOD). The combination of Ppy and Co3O4 as well as IL created a platform with exceptional characteristics, and the content of Ppy had an effect on the direct electron transfer (DET) of Hb/GOD. Notably, when weight percentage of pyrrole monomer was 20%, the heterogenous electron transfer rate constant (ks) for Hb and GOD was estimated to be 1.71s(-1) and 1.67s(-1), respectively. In the meantime, electrochemical and spectroscopic measurements showed that Hb/GOD remained their bioactivity, and achieved fast electron transfer on the Ppy-Co3O4/IL composite film modified electrode. Furthermore, the Ppy-Co3O4/IL/Hb composite film modified electrode was used as a biosensor, and exhibited a long linear range and lower detection limit to H2O2. The apparent Michaelis-Menten constant (Km) was found to be 0.53mM. The sensing design based on the Ppy-Co3O4 hybrid material was demonstrated to be effective and promising in developing protein and enzyme biosensors.

Determination of fungicides in sediments using a dispersive liquid-liquid microextraction procedure based on solidification of floating organic drop.

A dispersive liquid-liquid microextraction procedure based on solidification of floating organic droplet has been investigated for the determination of fungicides (cyprodinil, difenoconazole, myclobutanil, and spiroxamine) in sediments by HPLC with diode array detection. In the overall extraction process, the extraction solvents can be separated easily from the sample solution, and the experiment time was shortened. Moreover, several parameters such as the type and volume of the extraction solvent and dispersive solvent, centrifugal speed, extraction time, and salt effect that affect the extraction efficiencies of the target fungicides were studied and optimized. Under the optimized conditions, the LOD for the target analytes were in the range of 0.1-0.5 µg/g. Satisfactory recoveries of the target analytes in the sediment samples were 81.00-99.00%, with RSDs (n = 5) that ranged from 1.8 to 6.5%. Finally, the simple, sensitive, and environmentally friendly method was successfully applied to determine the target fungicides in actual sediment samples.

The interaction of plant-growth regulators with serum albumin: molecular modeling and spectroscopic methods.

The affinity between two plant-growth regulators (PGRs) and human serum albumin (HSA) was investigated by molecular modeling techniques and spectroscopic methods. The results of molecular modeling simulations revealed that paclobutrazol (PAC) could bind on both site I and site II in HSA where the interaction was easier, while uniconazole (UNI) could not bind with HSA. Furthermore, the results of fluorescence spectroscopy, three-dimensional (3D) fluorescence spectroscopy and circular dichroism (CD) spectroscopy suggested that PAC had a strong ability to quench the intrinsic fluorescence of HSA. The binding affinity (Kb) and the amounts of binding sites (n) between PAC and HSA at 291 K were estimated as 2.37×10(5) mol L(-1) and 1, respectively, which confirm that PAC mainly binds on site II of HSA. An apparent distance between the Trp214 and PAC was 4.41 nm. Additionally, the binding of PAC induced the conformational changes of disulfide bridges of HSA with the decrease of α-helix content. These studies provide more information on the potential toxicological effects and environmental risk assessment of PGRs.

Inorganic/organic doped carbon aerogels as biosensing materials for the detection of hydrogen peroxide.

In this article, three different inorganic/organic doped carbon aerogel (CA) materials (Ni-CA, Pd-CA, and Ppy-CA) were, respectively, mixed with ionic liquid (IL) to form three stable composite films, which were used as enhanced elements for an integrated sensing platform to increase the surface area and to improve the electronic transmission rate. Subsequently, the effect of the materials performances such as adsorption, specific surface area and conductivity on electrochemistry for myoglobin (Mb) was discussed using N2 adsorption-desorption isotherm measurements, scanning electron microscopy (SEM), and electrochemical impedance spectroscopy (EIS). Moreover, they could act as sensors toward the detection of hydrogen peroxide (H2O2) with lower detection limits (1.68 µM, 1.02 µM, and 0.85 µM, for Ni-CA/IL/Mb-CPE, Pd-CA/IL/Mb-CPE, and Ppy-CA/IL/Mb-CPE, respectively) and smaller apparent Michaelis-Menten constants KM. The results indicated that the electroconductibility of the doped CA materials would become dominant, thus playing an important role in facilitating the electron transfer. Meanwhile, the synergetic effect with [BMIm]BF4 IL improved the capability of the composite inorganic/organic doped CA/IL matrix for protein immobilization. This work demonstrates the feasibility and the potential of a series of CA-based hybrid materials as biosensors, and further research and development are required to prepare other functional CAs and make them valuable for more extensive application in biosensing.

Ultrasonic-electrodeposition of hierarchical flower-like cobalt on petalage-like graphene hybrid microstructures for hydrazine sensing.

A facile, one-pot ultrasonic electrochemical method to synthesize hierarchical cobalt (Co)-nanoflowers on petalage-like graphene (GE) was developed. The hybrid microstructures were successfully evaluated as a new material for highly sensitive determination of hydrazine (N(2)H(4)). Scanning electron microscopic measurements displayed that the synthesized Co-GE exhibited a related hierarchical structure of a petalage-like GE homogeneous distribution as a matrix for the growth of smooth nanosheets-assembled Co nanoflowers. Co-GE was confirmed by energy dispersive X-ray spectrograms. Electrochemical methods were adopted to characterize the sensing properties of Co-GE towards the electrocatalytic oxidation of N(2)H(4) at 0.15 V in 0.1 M pH 7.0 sodium phosphate buffered saline. The sensor displayed a broad linearity of 0.25-370 µM and 370 µM to 2.2 mM with a relatively low detection limit of 0.1 µM (S/N = 3) and a response time of less than 3 s. Furthermore, the sensor showed outstanding sensitivity and reproducibility.

Direct electrochemistry of hemoglobin immobilized in chitosan-room temperature ionic liquid film and application in its interaction with 3,4'-bis-(4-hydro-3-xycoumarin)-2,5-hexanediol.

The direct electrochemistry of hemoglobin (Hb) and application in its interaction with 3,4'-bis-(4-hydro-3-xycoumarin)-2,5-hexanediol (HCH) based on the Hb immobilized in chitosan-room temperature ionic liquid film were investigated by means of cyclic voltammetry, differential pulse voltammetry and amperometry. The binding ratio m and binding constant between HCH and Hb were estimated as 2 and 3.46 M(-1), respectively. The amperometric response showed a linear dependence on the concentration of HCH with the detection limit of 0.06 µM. In addition, the amperometry was a novel method in the field of binding studies and might be taken into account for future binding studies. At last a sensitive and convenient electrochemical method was proposed for the determination of HCH.