NiO photocathodes have been developed for photoelectrochemical (PEC) sensing. However, the development of NiO-based photoactive materials with higher performance is still being pursued to further improve the sensitivity of detection. In this article, we prepared a C-ZIF-8/NiO composite material photocathode composed of porous carbon derived from ZIF-8 (C-ZIF-8) and NiO, and utilized its enhanced PEC activity and amplification effect on chlorohemin (hemin) sensitization to achieve ultra-sensitive detection of lead ions (Pb2+). The introduction of C-ZIF-8 improved the charge transfer and light absorption ability of the composite material, and significantly increased the load of hemin on the photocathode, thereby enhancing the photocurrent response by 8 times. Based on the C-ZIF-8/NiO photocathode and in situ generated photosensitizer signal amplification strategy, ultra-sensitive detection of Pb2+ had been attained with a detection linear range of 10 pM to 5 nM and a detection limit of 2.6 pM. This study provides a new platform for high sensitivity detection of Pb2+, and extensive potential applications could be further expected.

MWCNT–COOH and Fc–COOH were integrated into the framework structure of a NiMOF, altering its electronic structure and generating lattice strain. The resulting MWCNT–NiMOF(Fc) exhibited excellent UOR and OER dual functional catalytic activity.

Metal-organic framework (MOF) materials exhibit unique advantages in adsorption, pre-enrichment and selective recognition of heavy metal ions due to their porous nature, tunable structure and ease of functionalization. However, due to the poor conductivity and electrochemical activity of most MOFs, their application in electrochemical sensing is limited. In this paper, an electroactive hybrid material rGO/UiO-bpy composed of UiO-bpy and electrochemically reduced graphene oxide (rGO) was prepared and has been successfully used in the electrochemical determination of lead ions (Pb2+). Interestingly, a reverse response relationship between the electrochemical signal of UiO-bpy and the concentration of Pb2+ was discovered in the experiment, which can be used to develop a novel on-off ratiometric sensing strategy for Pb2+ detection. To our knowledge, this is the first time that UiO-bpy has been used as both an improved electrode material for heavy metal ion detection and an internal reference probe for ratiometric analysis. This study is of great significance to expand the electrochemical application of UiO-bpy and develop innovative electrochemical ratiometric sensing strategies for Pb2+ determination.

Electrochemical sensing has unique advantages in developing on-site and online detection technologies for heavy metal ions (HMIs) due to its fast response, simple operation, high sensitivity, and portable instruments. The vigorous development of modern micro/nanomaterial preparation technology has provided greater space for improving the performance of electrochemical sensing platforms. In this work, a novel hetero-shelled hollow structure metal-organic framework (MOF) hybrid material (denoted as HCZ@UN) was prepared by adopting the hollow carbonized ZIF-8 (HCZ) as the substrate for growing UiO-66(Zr)-NH2 (UN), and subsequently used for efficient electrochemical detection of lead ions (Pb2+). The grown UN crystal particles were anchored on the HCZ hollow cages and showed nanometer size. The unique shell structure and nanometer size of UN created large specific surface area and rich accessible adsorption sites, which promoted the preconcentration of Pb2+. While the hollow carbon polyhedron structure of HCZ improved the dispersibility of UN and electron transfer ability of the material. These factors synergistically improved the detection sensitivity and sensing performance for Pb2+ determination with a wide linear range of 0.100-500 nM, a low detection limit of 0.0492 & PLUSMN; 0.00523 nM as well as good selectivity, repeatability and long-term stability. This paper provides a simple and effective method for the preparation of electroactive MOF functional materials, which is expected to inspire more interest in building other MOF-based materials with unique structure, high-performance and extensive application value.

Metal-organic frameworks (MOFs) have shown unique advantages and huge potential in heterogeneous catalysis such as photocatalysis due to their impressive physicochemical properties. However, the direct application in electrocatalysis are usually limited by their poor electrocatalysis performance. Herein, we present the synthesis of Ni/Co bimetallic organic framework with missing linkers of carboxyferrocene (NiCoMOF-Fc) on nickel foam (NF) by a facile protocol of one-step solvothermal method for the urea oxidation reaction (UOR) electrocatalysis. The integration of defect tailoring and bimetallic coupling effect changes the coordination environment of Ni active sites and optimizes the electronic structure, which significantly improves the electrocatalytic activity of the Ni-based MOF. The NiCoMOF-Fc modified NF exhibits excellent electrocatalytic performance towards UOR with high current density at low potential (140 mA cm-2 at 1.299 V vs. RHE and 782 mA cm-2 at 1.5 V vs. RHE), a small Tafel slope of 46.2 mV dec- 1 and good durability. In addition, a two-electrode electrolyser with NiCoMOF-Fc as the bifunctional catalyst for UOR and hydrogen evolution reaction (HER) has also been suc-cessfully constructed, which shows bright prospect of practical use.

Dual-mode bioanalysis integrating photoelectrochemical (PEC) and other modes is emerging and allows signal cross-checking for more reliable results. Metal-organic frameworks (MOFs) have been shown to be attractive materials in various biological applications. This work presents the utilization of MOF encapsulation and stimuli-responsive decapsulation for dual-mode PEC and fluorescence (FL) bioanalysis. Photoactive dye methylene violet (MV) was encapsulated in zeolitic imidazolate framework-90 (ZIF-90) to form an MV@ZIF-90 hybrid material, and MV could be released by adenosine triphosphate (ATP)-induced ZIF-90 disintegration. The released MV not only had FL emission but also had a sensitization effect on the ZnIn2S4 (ZnInS) photoanode. Based on the MV-dependent sensitization effect and FL emission characteristic, a dual-mode PEC-FL strategy was established for ATP detection with low detection limits, that is, 3.2 and 4.1 pM for PEC and FL detection, respectively. This study features and will inspire the construction and implementation of smart MOF materials for dual-mode bioanalysis.

制备了NH2-UiO66和电化学还原氧化石墨烯(rGO)的混合材料NH2-UiO66/rGO,并将其成功地用于电化学同时检测镉离子(Cd2+)和铅离子(Pb2+).通过采用扫描电子显微镜(SEM)、X射线衍射和各种电化学技术对材料的形貌及其电化学性质进行了表征.结果表明:NH2-UiO66/rGO具有较NH2-UiO66明显改善的电化学性质.所构建的电化学传感平台在优化条件下可以实现对Cd2+和Pb2+的灵敏检测.此外,该传感器具有良好的选择性、重现性和稳定性,在实际样品检测中也具有广阔的应用前景.

As a typical carbon nanomaterial, graphene is frequently used as a modified material due to its excellent optical, electrical, and mechanical properties. Composite materials combining graphene with silicone rubber or silicone resin have significantly improved electrical, thermal, and mechanical properties compared with sole silicone rubber or silicone resin. This paper focused on the influence of graphene on the properties of silicone rubber and silicone resin in recent years. In addition, the application of graphene/silicone rubber composites in sensors and microwave absorption materials was also summarized. This review is expected to provide a systematic and fundamental understanding of the modification effect of graphene on silicone rubber and silicone resin, and look forward to the application of their composite materials in wearable electronic devices and other emerging fields, hope to inspire and perfect the future design of composites and expand their applications.

The development of selective electrochemical response materials and new detection strategies are the research focus in the field of heavy metal ion (HMI) electroanalysis. Herein, a Ni(II)-based metal-organic framework (NH2-Ni-MOF) was synthesized and functionalized by electrochemically active molecule of ferrocene (Fc) via post-synthesis modification. Based on the Fc-functionalized NH2-Ni-MOF (Fc-NH2-Ni-MOF), a novel electrochemical ratiometric sensing platform was developed and applied for the simultaneous determination of various HMIs. The prepared NH2-Ni-MOF exhibits nanoplate structure, which is conducive to increase accessible electrode area and expose more active sites, thus promoting the adsorption and pre-concentration of HMIs. The modification of Fc on MOF not only enhances the electrical conductivity of the MOF material, but also provides an internal reference signal for the ratiometric analysis. Due to the excellent characteristics of the Fc-NH2-NiMOF, the as-prepared ratiometric electrochemical sensing platform exhibits wide linear ranges (0.001 mu M to 2.0 mu M for lead ions (Pb2+), and 0.01 mu M to 2.0 mu M for copper ions (Cu2+) as well as cadmium ions (Cd2+)) and high sensitivity (the detection limit toward Cu2+, Pb2+ and Cd2+ is 6.3 nM, 0.2 nM and 7.1 nM, respectively). In addition, compared with the non-ratiometric strategy, the reproducibility of ratiometric analysis is significantly improved. The developed electrochemical method with high sensitivity, selectivity and reliability exhibits bright application prospects in the detection of real samples. Moreover, the electrochemical application of MOF materials has been effectively expanded.

It is a significant and challenging task to simultaneously detection of multiple heavy metal ions with convenience, sensitivity and reliability. Herein, a novel ratiometric electrochemical sensing method was established for the simultaneously detection of three main heavy metal ion pollutants (Cd2+, Pb2+ and Cu2+). The sensing platform was constructed by a composite of ferrocenecarboxylic acid functionalized metal-organic framework (MOF), Fc-NH2-UiO-66, and thermally reduced graphene oxide (trGNO), which was designated as trGNO/Fc-NH2-UiO-66. NH2-UiO-66 has porous structure and large specific surface area, which is beneficial to the adsorption and preconcentration of heavy metal ions. The introduction of trGNO and Fc improves the conductivity and electrochemical activity of the MOF material. Moreover, the signal of Fc can be used as internal reference to develop ratiometric detection, which greatly improves the reproducibility and reliability of electrochemical detection. Based on this ratiometric electrochemical sensing platform, the simultaneous, sensitive and reliable detection of Cd2+, Pb2+ and Cu2+ was realized. This work provides a new sensing platform for simultaneous detection of multiple heavy metal ions and greatly expands the application of UiO-66-type MOFs in electrochemical field.

采用酸刻蚀后处理制备了具有中空结构的UiO-66-NH2材料(P-UiO-66-NH2),并利用其构建电化学传感平台实现了对水溶液中铅离子(Pb2+)和铜离子(Cu2+)的同时电化学检测.采用扫描电子显微镜(SEM),透射电子显微镜(TEM)和各种电化学技术对材料的形貌及其电化学性质进行了表征.结果表明:P-UiO-66-NH2具有较UiO-66-NH2明显改善的电化学性质.基于P-UiO-66-NH2所构建的电化学传感平台,在优化条件下可实现对Pb2+和Cu2+的灵敏检测,检测限分别为0.020μmol·L-1(Pb2+)和0.030μmol·L-1(Cu2+).此外,该传感器还具有良好的选择性、重现性和稳定性,对实际样品中Pb2+和Cu2+的检测也表现出令人满意的结果.

Metal manic frameworks (MOFs) have unique advantages in adsorption and preconcentration of heavy metal ions due to their structure and composition characteristics, which make them show great potential in optical sensing of heavy metal ions. However, their applications in the field of electrochemical sensing is greatly limited because of their poor conductivity. In this work, a functionalized MOF composite, thermally reduced graphene oxide-Au nanoparticles-zeolitic imidazolate skeleton material (RGO-Au-ZIF-8), was fabricated. It exhibits much improved electrochemical properties compared with the pristine MOF. A novel electrochemical sensing platform was constructed based on it, and simultaneous detection of lead ions (Pb2+) and copper ions (Cu2+) in aqueous solution was realized. Specifically, the Au-ZIF-8 was prepared by adding polyvinylpyrrolidone (PVP)-stabilized Au nanoparticles (AuNPs) to the reaction solution of ZIF-8. The modification of AuNPs effectively improved the conductivity of the material. After compounding with RGO, the RGO-Au-ZIF-8 composite was prepared. The RGO was used as scaffold for the Au-ZIF-8 in the composite to increase the effective surface area of electrode and improve conductivity. The morphology and structure of the prepared materials were characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM) and UV-visible absorption spectroscopy (UV-Vis). The electrochemical properties of the modified electrodes were characterized by various electrochemical techniques. The experimental parameters, such as pH value of working solution, accumulation potential, accumulation time and composition ratio of Au-ZIF-8 to RGO were optimized. Under the optimized conditions, simultaneous and sensitive detection of Pb2+ and Cu2+ on the prepared electrochemical sensor was realized with the detection limits of 2.6 x 10(-9) and 7.8 x 10(-9) mol.L-1 for Pb2+ and Cu2+, respectively (S/N =3). The interference test showed that the electrochemical sensor has good selectivity for the detec tion of Pb2+ and Cu2+, and further electrochemical studies revealed that the designed sensor has excellent reproducibility and good stability. The result of recovery test indicated that the prepared electrochemical sensor has great potential in Pb2+ and Cu2+ detection in real water samples. This work provides a new platform for simultaneous, rapid and sensitive detection of heavy metal ions, and greatly expands the electrochemical applications of MOF materials.

The ratiometric method allows the measurement of ratio changes between two signals, which can reduce the detection signal fluctuations caused by distinct background conditions and greatly improve the reproducibility and reliability of detection. However, in contrast with the emerging dual excitation or dual emission dyes applied in ratiometric luminescence measurement, only a few internal reference probes have been exploited for ratiometric electrochemical detection. In this paper, a gold nanoparticles@carbonized resin nanospheres composite with thermally reduced graphene oxide as scaffold (AuNPs@CRS-TrGNO) has been fabricated, and the AuNPs embedded in the CRS were first used as an internal reference probe for ratiometric electrochemical detection. The detachment and aggregation of AuNPs is suppressed by embedding in the CRS, so its redox signal is very stable, which provides feasibility for ratiometric detection. Moreover, the embedment of AuNPs, carbonization of resin spheres, and hybridization with TrGNO all have played positive roles in improving the charge transfer rate, which leads to excellent electrochemical performance of the composite. Based on these characteristics of the AuNPs@CRS-TrGNO, a new ratiometric electrochemical detection platform was constructed, and copper ions (Cu2+) in simulated seawater were successfully detected. This ratiometric method has the advantages of simple design and convenient operation, and obviously it improves the reproducibility and reliability of the electrochemical sensor.

近年来,工业快速发展使得我国水污染现象日趋严重,其中,重金属离子含量超标是造成水污染的重要原因.因此,发展简便、快速、灵敏的重金属离子检测技术非常重要.电化学检测方法具有操作简单、制备成本低、灵敏度高和易于微型化等优点,在重金属离子检测中具有重要应用价值.基于热还原氧化石墨烯(TrGNO)-金纳米颗粒(AuNPs)复合材料构筑高性能电化学传感器平台,采用电化学方法实现对铜离子(Cu2+)的简便、快速、灵敏检测.采用透射电子显微镜和各种电化学技术对纳米复合材料及其修饰电极进行了形貌表征和电化学测试,并对材料制备和测试条件进行了优化.结果表明,通过TrGNO与AuNPs的有效复合,所制备的纳米复合材料具有增大的电极表面积和优异的导电性,有利于提高对Cu2+的电化学检测灵敏度.线性检测范围为1.0×10-6～5.0×10-4 mol/L,检测限可达8.5×10-7 mol/L.

The demand of precise assay of nucleic acids and other bioanalytes has been increasing enormously in various areas including point-of-care diagnostics, military, environmental monitoring and so on. Compared with other nucleic acid biosensors, the electrochemical nucleic acid biosensors possess a range of merits like amenable miniaturization, low costs and high sensitivity. Ratiometric electrochemical nucleic acid biosensors can overcome the inherent systematic errors of conventional electrochemical biosensors and enhance the reproducibility and credibility. This short review (with 81 refs.) summarizes the evolvements made in the area of nucleic acid-based biosensors based on ratiometric (electrochemiluminescent, electrochemical and photoelectrochemical) readout in the past few years. Many of the methods discussed here are based on the use of advanced nanomaterials such as quantum dots, graphitic carbon nitrides, graphene oxide, C-dots, gold nanoparticles, metal-organic frameworks, and respective nanohybrids. Three sections (on electrochemiluminescence, classical electrochemical and emerging photoelectrochemical systems) demonstrate the merits of ratiometric assays in various applications. The review ends with a section with conclusions and a discussion of future perspectives.

Conventional epoxy resin fails as corrosion protection in long-term soaking in water as pores are developing. Here, a modified epoxy coating with enhanced corrosion resistance was fabricated by impregnation with functionalized reduced graphene oxide-hydrophobic ionic liquid (RGO-IL) nano composites. The modified RGO was characterized by scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FT-IR), electrochemical impedance spectroscopy and simulated immersion experiments. Compared to epoxy resin (ER) coatings without RGO-IL nano composites, the ER with RGO nano composites showed higher hydrophobicity in contact angle tests. In electrochemical experiments on Q235 substrates coated with the RGO-IL/ER composite, enhanced barrier properties and excellent corrosion protection was found. A more hydrophobic interface was built, and the nano composite material of RGO-IL was easy to prepare and cost efficient. We speculated that the presence of the ionic liquids also improves the dispersion properties of RGO in ER, and thereby further improving its barrier effect. In addition, the hydrophobic ionic liquid itself had a hindrance to water molecules and chloride ions. The highlight of our work is the combination of the corrosion inhibition of the hydrophobic ionic liquids with the barrier effect of RGO.

Development of three-dimensional (3D) hierarchical micro/nanostructures with large surface area, better permeability and structural stability is an effective strategy for pursuing high performance of supercapacitors. Herein, we report a 3D hierarchical PANI micro/nanostructure (H-PANI) as super capacitor electrode material. The H-PANI has excellent electrical conductivity and unique porous structure, which could promote rapid charge transfer and ion diffusion. The as-prepared H-PANI electrode shows a relatively high specific capacitance of 520 Fg(-1) at a current density of 0.5 A g(-1) (with a specific capacity of 416 C g(-1), for a potential window of 0.8 V), and exhibits excellent rate capability (65% specific capacitance retains from 0.5 to 50 A g(-1)). The electrochemical performance of this hierarchical structured electrode material shows great improvement compared with that of the simple structured PANI prepared in this paper. Notably, the H-PANI was delicately synthesized by simply adjusting the ionic strength and temperature of the regular dilute polymerization reaction system of PANI with no need of any templates or organic structure directing reagents, which made the preparation process simple and low-cost. This study will provide a new perspective for development of much wider variety of PANI materials for supercapacitor applications. (C) 2016 Elsevier Ltd. All rights reserved.

Polymer inorganic nanosheet composites hold great promise in electrochemical sensing applications by improving the electrochemical performance and increasing the surface area. In this work, a reductively treated thin layer molybdenum disulfide nanosheet-poly(xanthurenic acid) (rTLMoS(2)-PXa) composite have been facilely prepared through a one-step electrosynthesis procedure. The TLMoS2 was used as building block for the construction of the composite with the PXa coated on it. The composite modified electrode possesses improved electron transfer capability and exhibits good electrochemical sensing performance towards several heterocyclic and aromatic ring compounds (2'-deoxyguanosine-5'-triphosphate trisodium salt, dGTP, bisphenol A, BPA and 2,4,6 -trinitrotoluene, TNT), which have good affinity to the electroactive PXa and never or rarely been analyzed by MoS2-based sensing platform. This research provides a new electrochemical sensing platform for simple and sensitive detection of dGTP, BPA and TNT, and further extends the application of MoS2 in the field of electrochemical sensing. (C) 2015 Elsevier Ltd. All rights reserved.

Recently, functional composites based on chemically modified graphenes(CMGs) and nanostructured conducting polymers have attracted wide interest in the field of electrochemical biosensing. However, comprehensive studies of the effects of various CMGs on the electrochemical properties and biosensing performance of the resulting composites are scarce. In this work, for the first time), we fabricated, and deeply evaluated three composites composed of CMGs and sulfonic acid-doped polyaniline nanofiber (namely, CMG SPAN composites). The CMGs (involving the unreduced form and reduced forms prepared by different reduction routes) were chosen to show the effects of reduction and different preparation routes on the morphologies, electrochemical properties, and DNA biosensing performances of the composites. Notably, the self-redox signals of SPAN in these composites were significantly enhanced and were used for rapid, direct, and label free DNA detection. Moreover, a preliminary study of the capacitive characteristics of the thermally-reduced graphene oxide SPAN composite was concluded at the end of this work, Owing to the potential benefits of the composite in a supercapacitor that were surprisingly observed in this research. The findings of this work Will provide useful guides for better understanding of the interaction between CMG and SPAN and for the future development of high-performance functional materials for electrochemical sensors/biosensors and supercapacitors.

Until now, morphology effects of 2-dimensional or 3-dimensional graphene nanocomposites and the effect of material composition on the biosensors have been rarely reported. In this paper, the various nanocomposites based on graphene oxide and self-doped polyaniline nanofibres for studying the effect of morphology and material composition on DNA sensitivity were directly reported. The isolation and dispersion of graphene oxide were realized via intercalated self-doped polyaniline and ultrasonication, where the ultrasonication prompts the aggregates of graphite oxide to break up and self-doped polyaniline to diffuse into the stacked graphene oxide. Significant electrochemical enhancement has been observed due to the existence of self-doped polyaniline, which bridges the defects for electron transfer and, in the mean time, increases the basal spacing between graphene oxide sheets. Different morphologies can result in different ssDNA surface density, which can further influence the hybridization efficiency. Compared with 2-dimensional graphene oxide, self-doped polyaniline and other morphologies of nanocomposites, 3-dimensional graphene oxide-self-doped polyaniline nanowalls exhibited the highest surface density and hybridization efficiency. Furthermore, the fabricated biosensors presented the broad detection range with the low detection limit due to the specific surface area, a large number of electroactive species, and open accessible space supported by nanowalls.