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Carbaryl as an important insecticide is always used in agricultures to achieve higher yields. So, rapid detection of carbaryl residues in agricultural products is very necessary due to its potential harm to human beings. Herein, a hollow covalent-organic frameworks (HCOFTFPB-DBD) gold nanoparticles (AuNPs) nanospheres was used to construct a sensitive electrochemical carbaryl biosensor. The surface of electrode modified by HCOFTFPB-DBD-AuNPs nanospheres was negatively charged and repelled the [Fe(CN)6]3-/4-. The acetylcholinesterase (AChE) immobilized on HCOFTFPB-DBD-AuNPs nanospheres catalyzed the hydrolysis of acetylcholine chloride to thiocholine (TCh). The obtained positively charged TCh was adsorbed on the electrode surface by Au-S, which made the electrode surface positively charged to adsorb the negatively charged [Fe(CN)6]3-/4-, showing enhanced oxidation current of [Fe(CN)6]3-/4-. After carbaryl was added, the oxidation current of [Fe(CN)6]3-/4-deceased because ChE activity were inhibited by carbaryl. So, the sensitive detection of carbaryl was achieved at a low potential, which resulted in a high selectivity. The biosensor had a detection limit of 0.38 μM, a linear range of 1.10 μM-40.0 μM, a sensitivity of 0.00863 mA μM−1and better performance in actual sample.

Fe3O4has the potential to be an alternative material for the anode of lithium-ion batteries (LIBs) due to its high theoretical capacity, cheapness, and environmental friendliness. However, its inevitable volume expansion and poor Li+storage dynamics due to small lattice spacing are disadvantages that severely limit its application. Here, Ce-Fe3O4nanoparticles with large lattice spacing and porous structure were obtained by inserting Ce with a large radius into Fe3O4lattice. Next, the Ce-Fe3O4nanoparticles was used as the core for the in-situ growth of COFLZU1to form Ce-Fe3O4@ COFLZU1. Finally, high-temperature calcination was carried out to obtain flexible nano-cages of nitrogen-doped porous carbon (NC)-covered Ce-Fe3O4(Ce-Fe3O4@NC). Flexible NC nanocages not only accommodate the volume expansion of Fe3O4but also increase the rate of Li+transport and provide space for Li+storage. The successful doping of Ce effectively increases the lattice spacing of Ce-Fe3O4, improving the space and efficiency of the embedded Li+. Compared with pure Fe3O4, Ce-Fe3O4exhibits better performance when applied to the anode of LIBs. Ce-Fe3O4@NC exhibits best electrochemical performance during lithium storage, with capacities of 662.2 and 923.7 mAh g−1after 500 cycles at current densities of 1000 mA g−1and 100 mA g−1. This strategy of Ce doping combined with flexible NC cladding offers options for the preparation of other core-shell type carbon nanocomposites.

The presence of Cd2+, Pb2+, Cu2+and Hg2+in drinking-water can be harmful to human health, even if their concentration is fairly low. Hence, it is significant to detect these heavy metal ions in sewage to evaluate the quality of water. Herein, amino-functionalized metal–organic frameworks (NH2-MIL-88(Fe)) embedded with graphitic carbon nitride (g-C3N4) nanosheets and acid-functionalized carbon nanotubes were prepared viaa one-pot synthesis. The composite can be directly modified on the surface of glass carbon electrodes without the assistance of Nafion or other binders. The modified glass carbon electrodes can be used to simultaneously detect Cd2+, Pb2+, Cu2+and Hg2+in water viasquare wave stripping voltammetry. The doping of g-C3N4in the composite, rich in N-containing functional groups, participates in the adsorption of metal ions on the surface of the electrodes. The porous composite provides accommodation room for metals generated by electro-reduction. The detection limit for Cd2+, Pb2+, Cu2+and Hg2+is 39.6 nM, 7.6 nM, 11.9 nM, and 9.6 nM, respectively. And the sensitivity for Cd2+, Pb2+, Cu2+and Hg2+is 0.0789 mA μM−1cm−2, 0.4122 mA μM−1cm−2, 0.2616 mA μM−1cm−2, and 0.3251 mA μM−1cm−2, respectively. This work not only enriches the functional design of Fe-MOF materials, but also develops a method for the determination of metal ions using the adsorption sites in g-C3N4.

•Water-solubility OH-MIL-53(Al) was prepared via a facile green and economic strategy.•OH-MIL-53(Al) displayed uniformly nanospheres and good crystalline structure.•OH-MIL-53(Al) as a multi-response sensor showed good performance.

A simple and large-scale strategy to prepare flexible graphene tape electrode (GTE) was proposed. The flexible GTE was prepared by a facile peeling method in which a piece of commercial graphite foil was first covered by a commercial acrylic transparent tape and then the transparent adhesive tape was quickly torn off from the graphite foil. Scanning electron microscopy results showed that some folded and wrinkled graphene layers stood up on the GTE surface to form three-dimensional (3D) porous graphene foam. The 3D porous flexible GTE was proposed as a novel supporting matrix to load Ni–Co nanoparticles (Ni-CoNPs) and glucose oxidase (GOD) as examples to test its applications for electrochemical glucose sensing. The Ni-CoNPs/GTE showed the linear range of 0.6 μM–0.26 mM and 1.360–5.464 mM with a detection limit of 0.16 μM. The GOD/AuNPs-CHIT/GTE had a linear range of 0.616–14.0 mM and a detection limit of 0.202 mM. These results were similar or superior to the printable electrodes by nanocarbon and electrodes modified with graphene, carbon nanotubes, or porous carbon materials, but the flexible GTE was more easier to prepare in large-scale and the 3D porous graphene foam were not easy to drop off from the tape because they were glued on acrylic transparent tape firmly. Therefore, the 3D porous flexible GTE should be promising candidates for electrochemical sensors and other electrochemical applications.

Luminescent nanoscale coordination polymers (NCPs) have been found to have promising potential application in sensing. Herein, novel luminescent Au nanoparticles (AuNPs)@Tb/adenosine monophosphate (AMP) NCP nanostructures were prepared by encapsulating AMP-functionalized AuNPs into Tb/AMP NCPs for the detection of 2,6-pyridinedicarboxylic acid (DPA). The as-prepared AuNPs@Tb/AMP NCP nanostructures were characterized by transmission electron microscopy, UV-vis absorbance spectroscopy, dynamic light scattering and luminescence spectroscopy. The results showed that the AuNPs@Tb/AMP NCP nanostructures were very stable in aqueous solutions. The coordination of DPA with Tb3+in the AuNPs@Tb/AMP NCP nanostructures by replacing the water molecules to form AuNPs@Tb/AMP NCPs–DPA caused intermolecular energy transfer from DPA to Tb3+, leading to the enhancement of the AuNPs@Tb/AMP NCP luminescence. The obtained AuNPs@Tb/AMP NCP nanostructures as a probe for the detection of DPA demonstrated high sensitivity and selectivity with a good linear range (10 nM to 10 μM) and a low detection limit (2.7 nM) which was well below the anthrax infectious dose.

A flexible nanocomposite of cobalt hexacyanoferrate (CoHCF) and commercial carbon cloth (CC) was prepared by facile electrodeposition of CoHCF on a flexible CC surface. As a kind of flexible integrated electrode without polymer binders, the flexible CC–CoHCF nanocomposites were directly used for nonenzymatic H2O2sensing. Several techniques such as scanning electron microscopy, energy dispersive X-ray spectroscopy, Fourier transform infrared spectroscopy and electrochemistry were employed for the characterization of the electrode. It was found that CoHCF nanoparticles (about 100 nm) uniformly deposited on the CC surface. Electrochemical experiments demonstrated that the flexible CC–CoHCF nanocomposite electrode exhibited good electrocatalytic activity towards the oxidation of H2O2. Based on the amperometric experiments, the proposed nonenzymatic sensor showed a linear response to H2O2detection in the range of 0.002–9.04 mM with a detection limit of 0.7 μM, which was superior to most of the previous results. Such a good result renders it a promising candidate for routine testing.

A novel glucose biosensor was developed based on a 4-amino thiophenol/Au nanoparticle/glucose oxidase (GOD)–horseradish peroxidase (HRP)/6-mercapto-1-hexanol-11-mercaptoundecanoic acid/Au electrode. The modified electrode could be used to detect glucose based on the polymerization of aniline induced by HRP and H2O2which was produced by the reduction of O2accompanied by the oxidation of glucose into gluconic acid viaGOD. With the increase of glucose, more H2O2molecules were produced and then a growing number of polyaniline (PANI) molecules were formed on the modified electrode surface, which resulted in the decrease of peak current of Fe(CN)63−/4−because the formed PANI hindered the electron transfer of Fe(CN)63−/4−toward the electrode surface. Based on the decrease of peak current of Fe(CN)63−/4−, the glucose concentration could be determined accurately and selectively. The resulted biosensor exhibited a wide linear range from 16.5 μM to 10.0 mM, a high sensitivity of 41.78 μA mM−1cm−2and good selectivity. The glucose biosensor exhibits some advantages over the traditional GOD electrodes in terms of a close to zero applied potential. Moreover, the used electrode might be used as a H2O2sensor due to its good electrocatalytic response for H2O2.

In this work, the spherical porous MOF-5 microstructures supported by three-dimensional (3D) kenaf stem-derived porous carbon (KSC) (denoted as MOF-5/3D-KSC) composites were constructed for ascorbic acid (AA) sensing. The formation of MOF-5/3D-KSC was verified by scanning electron microscopy, X-ray powder diffraction and energy dispersive X-ray spectroscopy. The results showed that spherical porous MOF-5 microstructures were evenly arrayed on the surface of 3D-KSC viaa simple one-step hydrothermal method, which could greatly increase the effective surface area, stability and active sites. The MOF-5/3D-KSC composites were directly used to prepare integrated MOF-5/3D-KSC electrodes for AA sensing, and the integrated electrodes showed better performance for AA detection than traditional enzyme-based sensors and nonenzymatic sensors. The sensor exhibited good stability, wide linear range (0.7 μM to 11.5 mM) and low detection limit (0.24 μM). Hence, the MOF-5/3D-KSC composites could be a potential material for sensing platforms.

A simple and industrially scalable approach to prepare porous carbon (PC) with high surface areas as well as abundant nitrogen element as anode supporting materials for lithium-ion batteries (LIBs) was developed. Herein, the N-doped PC was prepared by carbonizing crawfish shell, which is a kind of food waste with abundant marine chitin as well as a naturally porous structure. The porous structure can be kept to form the N-doped PC in the pyrolysis process. The N-doped PC-Co3O4nanocomposites were synthesized by loading Co3O4on the N-doped PC as anode materials for LIBs. The resulting N-doped PC-Co3O4nanocomposites release an initial discharge of 1223 mA h g–1at a current density of 100 mA g–1and still maintain a high reversible capacity of 1060 mA h g–1after 100 cycles, which is higher than that of individual N-doped PC or Co3O4. Particularly, the N-doped PC-Co3O4nanocomposites can be prepared in a large yield with a low cost because the N-doped PC is derived from abundant natural waste resources, which makes it a promising anode material for LIBs.

A novel nonenzymatic glucose sensor was constructed based on anthill-like Cu@carbon nanocomposites which were derived from a Cu-based metal organic framework by a simple thermolysis method. The final nanocomposites were characterized by scanning electron microscopy, thermogravimetric analysis, X-ray powder diffraction and electrochemical techniques. The results showed that the derived nanocomposites maintained the morphology of the original materials upon thermolysis, while the produced Cu nanoclusters were embedded in three-dimensional carbon frameworks and presented an anthill-like structure. Since the final products gave a sufficiently large specific surface area, good catalytic activity towards the oxidation of glucose and appropriate pores for electrolyte transfer, the resultant glucose sensor based on the anthill-like Cu@carbon nanocomposites showed a wide linear range of 0.2–8.0 mM and a low detection limit of 29.8 μM. The low cost, simple preparation and good catalytic activity of anthill-like Cu@carbon nanocomposites render them promising candidates as electrode materials for the construction of novel nonenzymatic sensors.

A novel nonenzymatic glucose sensor was prepared based on a Cu coralloid granule/polyaniline (PANI)/reduced graphene oxide (rGO) nanocomposite modified glassy carbon electrode (GCE). The PANI nanowire array/rGO nanocomposite was synthesized by using an in situchemical oxidative polymerization method, and then was cast onto a GCE surface. Cu coralloid granules were constructed on PANI/rGO/GCE by constant potential deposition. The Cu/PANI/rGO nanocomposite was characterized by scanning electron microscopy, X-ray energy dispersive spectroscopy, X-ray powder diffraction and Fourier transform infrared spectroscopy. The electrochemical and electrocatalytic behaviors of the Cu/PANI/rGO/GCE towards glucose oxidation were evaluated by cyclic voltammograms, electrochemical impedance spectroscopy, chronoamperometry and amperometric method. The amperometric response of Cu/PANI/rGO/GCE showed high catalytic activity towards the oxidation of glucose with a wide linear range of 0.01–9.66 mM, high sensitivity of 603.59 μA cm−2mM−1and low detection limit of 1.34 μM (S/N= 3).

The metal–organic coordination polymers with tunable structures and properties have been rapidly emerging as very important functional materials. In this work, we prepared terbium (Tb3+)-based coordination polymer nanoparticles (CPNPs) by employing adenine (Ad) as bridging ligands. The CPNPs was further used as a receptor reagent for ciprofloxacin (CF) detection in aqueous solution. Addition of CF induces a typical emission of Tb3+due to the formation of Ad/Tb-CF complex and the sensitization of CF. The fluorescent intensity of Tb3+was enhanced linearly with increasing the CF concentration from 60 nM to 14 μM. The detection limit for CF in aqueous solution is 60 nM. The Ad/Tb CPNPs was successfully applied to detect CF in tablet and urine samples and showed a satisfactory result. Compared with other methods, the proposed method is advantageous because that it provides a very simple strategy for CF detection, which does not require complicated sample pretreatment processes or special reaction media. The proposed strategy could be contributed to expand the potential applications of lanthanide coordination polymers in biological and environmental fields.

Hierarchical Cu–Co–Ni nanostructures (Cu–Co–Ni NSs) attached to carbon nanofibers (CNFs) modified glassy carbon electrode (GCE) was prepared by electrodeposition. Scanning electron microscopy results indicated that many hierarchical Cu–Co–Ni NSs were formed and uniformly dispersed on the CNFs/GCE surface. The electrochemical behavior and electrocatalytic performance of the Cu–Co–Ni NSs/CNFs/GCE towards the oxidation of glucose were evaluated by cyclic voltammograms, chronoamperometry and amperometric methods. The results revealed that Cu–Co–Ni NSs/CNFs/GCE has a good electrocatalytic activity for glucose oxidation and could be used as a nonenzymatic glucose sensor. The sensor showed an acceptable linear range from 0.01 to 4.30 mM with a sensitivity of 104.68 μA mM cm−2, and a detection limit of 3.05 μM (S/N= 3). The good catalytic activity, high sensitivity, good selectivity and stability rendered the Cu–Co–Ni NSs/CNFs/GCE to be a promising electrode for constructing a nonenzymatic glucose sensor.

A glucose biosensor was developed based on cytochrome c(Cyt c) and glucose oxidase (GOD) co-entrapped on gold nanoparticles (AuNPs)–chitosan (CHIT) nanocomposites which were constructed on glassy carbon electrode (GCE) by one-step electrodeposition. The surrounding Cyt caround GOD provided a biocompatible microenvironment to keep GOD's biological activity. Simultaneously, the AuNPs–CHIT nanocomposites provided a roughened surface with large surface-to-volume ratio to greatly amplify the surface coverage of GOD–Cyt cmolecules and good conductivity to realize the direct electron transfer (DET) of GOD. The biosensor showed a wide detection range, low detection limit, good stability and high sensitivity. Thus, this study not only successfully achieved DET of GOD, but also constructed satisfactory point-of-care glucose monitoring.

The two-dimensional polymerization and reaction at the solid/liquid interface has caused considerable attention in recent years because of its fundamental importance and many potential applications. Scanning tunneling microscopy (STM) provides the possibility for the observation and manipulation of polymerization and reaction occurring at the solid/liquid interface at the atomic level. Two-dimensional polymerization and reaction could be induced by external stimuli, such as electrochemistry-induced, STM tip-induced, or light-induced. The polymerization at the solid/liquid interface is the focus of this review, including the mechanism of polymerization and characterization of structural and electrical properties of the resulting polymers. Finally, the outlooks for developments in this field are described.

Two kinds of two-dimensional (2D) covalent-organic frameworks (COF) were used to construct a sandwich-type electrochemical immunosensor for a proof-of-concept study. Vinyl-functionalized COFTab-Dva could be linked with Ab1 by the thiol–ene “click” reaction. Electroactive COFTFPB-Thi was modified with gold nanoparticles (AuNPs) to ensure the successful connection with Ab2 through Au–S bond. Meanwhile, electroactive COFTFPB-Thi was used to as signal probe to realize both the detection of carcinoembryonic antigen (CEA) and the amplification of detection signal. In detection process of the sandwich-type electrochemical immunosensor, glassy carbon electrode (GCE) was modified with 2D COFTab-Dva first then connected with Ab1 by the thiol–ene “click” reaction, next quantitative CEA was captured, followed by specificially capturing signal probe of Ab2/AuNPs/COFTFPB-Thi where AuNPs acted as nanocarriers of Ab2 and COFTFPB-Thi served as the signal producers. As the amount of CEA was increased, the amount of signal probe captured to the electrode was also increased, and the peak signal intensity of the redox reaction of COFTFPB-Thi was enhanced accordingly. Thus, the quantitative detection of CEA could be realized according to the peak signal intensity of electroactive COFTFPB-Thi. The electrochemical immunosensor owned wide detection range of 0.11 ng/mL-80 ng/mL, low detection limit of 0.034 ng/mL and good practicability. This study opens up a new revelation for quantitative detection of CEA using electroactive COF as enhanced signal probe.

A novel sensor have been constructed by layer‐by‐layer hybridizing phosphomolybdate (POM) and poly(ferrocenylsilane) (PFS) on a cysteamine modified gold electrode. The properties and performance of the sensor have been measured by electrochemistry and atomic force microscopy in detail. The results showed that the constructed multilayers modified gold electrode combined the properties of POM and PFS, and exhibited good electrocatalytic ability to a series of inorganic ions, including BrO$\rm{ {_{3}^{-}}}$, IO$\rm{ {_{3}^{-}}}$, NO$\rm{ {_{2}^{-}}}$, Fe3+, ascorbic acid and SO$\rm{ {_{3}^{2-}}}$. The well catalytic activity of the sensor was ascribed to the porous structure of hybrid POM‐PFS multilayer. The resulted sensor exhibited extremely fast amperometric response, low detection limit, high selectivity and wide linear range to these analyses.

A controllable silver nanoparticle aggregate system has been synthesized by adding different amounts of ethanol to cetyltrimethylammonium bromide (CTAB) capped silver nanoparticles (Ag-nps), which could be used as highly efficient surface-enhanced Raman scattering (SERS) active substrates. This ethanol-induced aggregation can be attributed to preferential dissolution of CTAB into ethanol, which leads a partial removal of the protective CTAB layer on Ag-nps. The optical and morphological properties of these aggregates under various volumes of ethanol were explored via UV−vis spectroscopy and atomic force microscopy. Two common probe molecules, Rhodamine 6G (R6G) and 4-aminothiophenol (4-ATP) were used for testing the SERS activity on these substrates at very low concentrations. It was found that the SERS enhancement ability is dependent on the ethanol volume used. The SERS enhancement factors of 4-ATP were estimated to be as large as 8.1 × 108for b2vibration modes and 6.8 × 106for a1vibration modes. Good stability of the substrates was demonstrated by measuring the Raman activity with time. The optimized SERS-active substrate with the largest enhancement ability shown in this study could be used to detect double-strand DNA. The great advantage for this SERS-based DNA detection is that a dye label is not needed. It showed the potential of this Ag-nps aggregate system as a convenient and powerful SERS-active substrate for DNA detection.

We reported a simple method to synthesize gold nanoparticles (NPs) by photoreducing HAuCl4in acetic acid solution in the presence of type I collagen. It was found that the collagen takes an important role in the formation of gold NPs. The introduction of collagen made the shape of the synthesized gold nanocrystals change from triangular and hexangular gold nanoplates to size-uniform NPs. On the other hand, thanks to the special characters of collagen molecules, such as its linear nanostructure, are positively charged when the pH < 7, and the excellent self-assembly ability, photoreduced gold NPs were assembled onto the collagen chains and formed gold NPs films and networks. A typical probe molecule, 4-aminothiophenol, was used to test the surface-enhanced Raman scattering activity of these gold NPs films and networks and the results indicated good Raman activity on these substrates.

Didodecyldimethylammonium bromide (DDAB) lipid bilayer-protected gold nanoparticles (AuNPs), which were stable and hydrophilic, were synthesized by in situ reduction of HAuCl4 with NaBH4 in an aqueous medium in the presence of DDAB. As-prepared nanoparticles were characterized by UV−vis spectra, transmission electron microscopy, dynamic light scattering analysis, and X-ray photoelectron spectroscopy. All these data supported the formation of AuNPs. Fourier transform infrared spectroscopy (FTIR) and differential thermal analysis/thermogravimetric analysis data revealed that DDAB existed in a bilayer structure formed on the particle surface, resulting in a positively charged particle surface. The FTIR spectra also indicated that the DDAB bilayer coated on the surface of AuNPs was probably in the ordered gel phase with some end-gauche defects. On the basis of electrostatic interactions between such AuNPs and anionic polyelectrolyte poly(sodium 4-styrenesulfonate) (PSS), we successfully fabricated (PSS/AuNP)n multilayers on a cationic polyelectrolyte poly(ethylenimine) coated indium tin oxide substrate via the layer-by-layer self-assembly technique and characterized as-formed multilayers with UV−vis spectra and atomic force microscopy.

An effective approach to the nucleation and growth of nanoparticles was performed for forming polyoxometalate based nanoparticles: TBAB3–PMo12TBAB tetrabutylammonium bromide, PMo12 12-molybdophosphoric anions in multilayer films. The polyelectrolyte matrix was constructed by layer-by-layer self-assembly technology. The nucleation and growth of PMo12nanoparticles was achieved by alternately dipping the precursor films into PMo12and TBAB solutions, in which TBAB was employed as precipitator. Repeating the above process of absorption and precipitation of PMo12anions, the PMo12nanoparticles were of controllable synthesis in the multilayer films. The variation of the size and morphology of PMo12nanoparticles was accomplished by increasing adsorption and precipitation cycle number, which was detected by transmission electron microscopy and scanning electron microscopy. The growth process, composition, and surface topography of the multilayer films containing PMo12nanoparticles were investigated by UV–Vis spectroscopy, Fourier transform infrared FTIR spectroscopy, and atomic force microscopy AFM. The electrochemical properties were studied through cyclic voltammograms when the substrate was indium–tin oxide and the films presented good stability and similar electrochemical behavior to that of PMo12in aqueous solution.

We demonstrate the pH-induced assembly of 2-mercaptosuccinic acid-functionalized silver nanoparticles (MSA–Ag NPs) in the absence of hard or soft template. Two-dimensional (2D) and three-dimensional (3D) networks of silver NPs were achieved by tuning pH of the medium. The assembly process was monitored using atomic forces microscopy. The key factor affects the formation of network of silver NPs may be intermolecular hydrogen bonding between two carboxylic acid groups of MSA on two adjacent silver NPs.

A simple method has been developed to assemble gold nanoparticles to generate 1D assemblies by the assistance of silver ions. The lengths of nanoparticle chains can be controlled by adjusting the content of silver ions in the system. The assembly procedure of gold nanoparticles chains requires no template. The gold nanoparticle chains were characterized using TEM and XPS techniques.

A highly organized phenyl-capped teraniline (PC-teraniline) film at the molecular level was fabricated on carbon surfaces by electrochemical reduction of diazonium salts. Cyclic voltammetry (CV), scanning tunneling microscopy (STM) and X-ray photoelectron spectroscopy (XPS) were employed for the characterization of the film.