Collector and binder-free high quality graphene film has been successfully synthesized by a simple filtration process. Electrochemical results indicate that the graphene film exhibits good rate and cycle behavior compared with the commercial mesocarbon microbeads (MCMB)/copper system. More importantly, after excluding the dead-weight copper collector, the gravimetric energy density could be enhanced to some extent. This may provide an alternative in the demand for higher energy density lithium-ion batteries.

Collector and binder-free high quality graphene film has been successfully synthesized by a simple filtration process. Electrochemical results indicate that the graphene film exhibits good rate and cycle behavior compared with the commercial mesocarbon microbeads (MCMB)/copper system. More importantly, after excluding the dead-weight copper collector, the gravimetric energy density could be enhanced to some extent. This may provide an alternative in the demand for higher energy density lithium-ion batteries.

We discovered an organic weak acid, 3,4,9,10-perylene tetracarboxylic acid (PTCA), confined on the electrode surface, revealing a reversible and ultrafast protonation/deprotonation non-Faradaic process but exhibiting analogous voltammetric peaks (capacitive peaks). A further synthesized PTCA–graphene supramolecular nanocomplex discloses a wide voltage window (1.2 V) and ultrahigh specific capacitance up to 143 F g–1 at an ultrafast charge–discharge density of 1000 A g–1 (at least 1 order of magnitude faster than present speeds). The capacitance retention maintained at 73% after 5000 cycles. This unique capacitive voltammetric behavior suggests a new type of charge-storage modes, which may offer a way for overcoming the present difficulties of supercapacitors.

•Both porous Si from rice husks and rGO have been introduced into the composite.•The composite exhibits good rate and cycling performance.•Waste material can be converted into potential sources for future technological applications.We report a new method for synthesizing reduced graphene oxide (rGO)-porous silicon composite for lithium-ion battery anodes. Rice husks were used as a as a raw material source for the synthesis of porous Si through magnesiothermic reduction process. The as-obtained composite exhibits good rate and cycling performance taking advantage of the porous structure of silicon inheriting from rice husks and the outstanding characteristic of graphene. A considerably high delithiation capacity of 907 mA h g−1 can be retained even at a rate of 16 A g−1. A discharge capacity of 830 mA h g−1 at a current density of 1 A g−1 was delivered after 200 cycles. This may contribute to the further advancement of Si-based composite anode design.

High stability of the signal and simplicity in fabrication of the device are the two important requirements in development of potentiometric sensors. A robust single-piece all-solid-state potassium-selective electrode (K-SPE) was developed by incorporating monolayer-protected Au clusters (MPCs) as advanced ion-to-electron transducers into a conventional ion-selective membrane (ISM). The extraordinary properties of MPCs such as high solubility, profound hydrophobicity and large capacitance make them quite suitable to be used in fabrication of single-piece electrodes (SPEs) with advanced performance. The developed KSPEs containing small amount of MPCs in the membrane showed a significant increase in the potential stability (12.9 μV/h), lower detection limit (10–6.1 M) and prolonged life time (high performance still after 3 weeks). The multi-valence MPCs in the membrane facilitated the ion-to-electron transduction and fast establishment of the potential equilibrium resulting in fast response time in potential measurements. The inserted MPCs did not cause any interference either in the potential formation process or in the selectivity of the ion-selective membrane.

Simple, portable analytical devices are entering our daily lives for personal care, clinical analysis, allergen detection in food, and environmental monitoring. Smartphones, as the most popular state-of-art mobile device, have remarkable potential for sensing applications. A growing set of physical-co-chemical sensors have been embedded; these include accelerometers, microphones, cameras, gyroscopes, and GPS units to access and perform data analysis. In this review, we discuss recent work focusing on smartphone sensing including representative electromagnetic, audio frequency, optical, and electrochemical sensors. The development of these capabilities will lead to more compact, lightweight, cost-effective, flexible, and durable devices in terms of their performances.简单便携的分析设备正走进我们生活的各个方面,如个人保健、医疗分析、食品安全以及环境监测。智能手机作为最普及的移动设备在分析测试方面最具潜力,现代手机带有越来越多的传感器:加速计、麦克风、摄像头、陀螺仪、定位器等可以方便地获得更多数据和信息。本文综述了移动设备在分析传感方面的应用,包括电磁传感、音频传感、光学传感以及电化学传感等,并总结了该领域的发展趋势。未来的移动传感设备会更加小巧、轻便、便宜、耐用且易携带。

•A novel two electrode flow photoelectron–chemical system (two-EPCS) has been successfully developed.•Shortcomings of liquid reference electrode has been completely avoided in this two-EPCS.•Such two-EPCS is applied for detection of global antioxidant capacity in food.•The microfluidic chip technique has been developed for antioxidant capacity assay based on this two-EPCS.•The two-EPCS is a universal platform, which does not depend on selected optoelectronic materials.Recently, a flow photoelectrochemical cell has been first developed and applied to assay global antioxidant capacity in our group. Yet, shortcomings of liquid reference electrode such as sample contaminations from the leaking of the reference solution, mechanically fragile, temperature and light sensitivity, etc. are significant restrictions for integration and miniaturization of photoelectrochemical sensing instruments, which have greatly limited their practical applications. Bearing these problems, in this work a novel two electrode flow photoelectron–chemical system (two-EPCS) has been developed for detection of antioxidant capacity. It is noteworthy that the electrochemical modulation-free mode (detection at the potential of 0.0 V) is performed, which has greatly simplified the analysis process and will result in significant simplifications of the instrument integrations. During the sample analysis, both standard antioxidants and commercial beverages were detected. Results evaluated from the two-EPCS are well agreed with those of the traditional three-EPCS at low potentials. By unloading of the reference electrode, it is of great convenience to design a novel photoelectrochemical microfluidic chip based on the two-EPCS, which has also been successfully applied for antioxidant capacity assay. It is satisfactory that comparable detection concentration range and sensitivity were accomplished by applying the microfluidic chip technique. Moreover, the two-EPCS is verified to be a universal platform which does not depend on selected optoelectronic materials but pervasive for general photocatalysts. Such a two-EPCS should be considered as a feasible alternative to the three-EPCS, which will become a promising candidate for industrial and commercial photoelectrochemical sensing instrument integrations in the future.In this article, a two electrode flow photoelectrochemical system (two-EPCS) was designed for detection of antioxidant capacity. Based on the technique of two-EPCS, a photoelectrochemical microfluidic chip was constructed for assaying antioxidant capacity, which opens a door for high-throughput photoelectrochemical sensing in industrial and biomedical applications

The local molecular environment is a critical factor which should be taken into account when measuring single-molecule electrical properties in condensed media or in the design of future molecular electronic or single molecule sensing devices. Supramolecular interactions can be used to control the local environment in molecular assemblies and have been used to create microenvironments, for instance, for chemical reactions. Here, we use supramolecular interactions to create microenvironments which influence the electrical conductance of single molecule wires. Cucurbit[8]uril (CB[8]) with a large hydrophobic cavity was used to host the viologen (bipyridinium) molecular wires forming a 1:1 supramolecular complex. Significant increases in the viologen wire single molecule conductances are observed when it is threaded into CB[8] due to large changes of the molecular microenvironment. The results were interpreted within the framework of a Marcus-type model for electron transfer as arising from a reduction in outer-sphere reorganization energy when the viologen is confined within the hydrophobic CB[8] cavity.Keywords: cucurbituril; host−guest complexes; single molecule conductance; STM; viologen

High quality graphitized graphene has been successfully synthesized by solid-exfoliation of graphite and a subsequent wet chemical process. The as-obtained graphene exhibits charge–discharge behaviour quite different from that of reduced graphene oxide and shows enhanced cycling and rate performance compared with commercial mesocarbon microbeads (MCMBs) for lithium ion batteries.

Herein, a novel photoelectrochemical platform with WS2/TiO2 composites as optoelectronic materials was designed for selective detection of o-diphenol and its derivatives without any biomolecule auxiliary. First, catechol was chosen as a model compound for the discrimination from resorcinol and hydroquinone; then several o-diphenol derivatives such as dopamine, caffeic acid, and catechin were also detected by employing this proposed photoelectrochemical sensor. Finally, the mechanism of such a selective detection has been elaborately explored. The excellent selectivity and high sensitivity should be attributed to two aspects: (i) chelate effect of adjacent double oxygen atoms in the o-diphenol with the Ti(IV) surface site to form a five/six-atom ring structure, which is considered as the key point for distinction and selective detection. (ii) This selected WS2/TiO2 composites with proper band level between WS2 and TiO2, which could make the photogenerated electron and hole easily separated and results in great improvement of sensitivity. By employing such a photoelectrochemical platform, practical samples including commercial clinic drugs and human urine samples have been successfully performed for dopamine detection. This biomolecule-free WS2/TiO2 based photoelectrochemical platform demonstrates excellent stability, reproducibility, remarkably convenient, and cost-effective advantages, as well as low detection limit (e.g., 0.32 μmol L–1 for dopamine). It holds great promise to be applied for detection of o-diphenol kind species in environment and food fields

It is extremely important to design stimuli-responsive biomimetic supramolecular materials. Such type of materials require molecular monomers with multiple functionalities. Perylene diimide (PDI) has been considered as one of the most versatile building block units for supramolecular architecture. However, most of the reported PDI derivatives work in organic media, whereas their application in aqueous systems is a challenge due to the pronounced hydrophobicity of their perylene backbones. Here, we report a water-soluble amino-imidazole-armed perylene diimide (AIA-PDI) dye that discloses reversible supramolecular structure and fluorescence emission conversion upon external pH-stimulation. Such characteristics offer a gap of PDI derivatives in the fabrication of a pH-responsive biomimetic system. Successful application for glucose detection, as a proof of concept, further demonstrates this PDI derivative's biological suitability in pH-responsive systems.

•One nanosheet organic anode material (Na2C8H4O4) for SIBs is successfully prepared.•The nanosheet Na2C8H4O4 exhibits much improved electrochemical properties in comparison to the bulk one.•The reasons of improvement are disclosed by ex-situ FTIR, SEM and EIS.•One new one-step desodiation mechanism is found in the Na2C8H4O4 nanosheet system.Recently, room temperature sodium ion batteries (SIBs) have been considered as one of the optimal alternatives for lithium ion batteries although there are still many challenges to be solved. At the present stage, the research priorities for SIBs still focus on the development of various electrode materials to meet the applicability. In this communication, we have controllably prepared a superior anode material (disodium terephthalate, Na2C8H4O4) with nanosheet-like morphology, which exhibits much improved electrochemical properties in terms of larger reversible capacity (248 mA h/g vs. 199 mA h/g), higher rate capabilities (for instance, 1.55 times the bulk material at 1250 mA/g) and better cycling performance (105 mA h/g vs. 60 mA h/g after 100 cycles at 250 mA/g) in comparison with the bulk one prepared at the similar system without the addition of polar solvent dimethylformamide. More importantly, it is further disclosed that, these enhanced performances could be mainly due to the new one-step desodiation mechanism and optimized ionic/electronic transfer pathways in the nanosheet system through the analyses of ex-situ infrared spectra, cyclic voltammogram, galvanostatic curves, scanning electron microscope images and electrochemical impedance spectroscopy.

The antioxidants in biological organisms can scavenge excess free radicals and effectively reduce oxidative stress, which protects DNA, protein and lipids in the human body from damage, thus preventing diseases from being induced. Therefore, it is particularly significant to assay the antioxidant capacities of our habitual foods during dietary evaluation. Herein, ultrathin graphitic carbon nitride (utg-C3N4)/TiO2 composites have been introduced as sensing elements into a photoelectrochemical platform with a thin layer structured flow-cell, for the real-time assay of the global antioxidant capacity in practical samples. In this system, the two-dimensional utg-C3N4 nanosheet/TiO2 nanoparticle composite material provided a much better optoelectronic function than the individual materials. In comparison with previous reports, this photoelectrochemical strategy shows considerable advantages, including excellent anti-interference properties, a high level of stability and reproducibility, and it is also proved to be the most prompt, convenient and cost-effective method for antioxidant capacity detection up to now. Moreover, utilizing theoretical and experimental examinations, we revealed its photoelectrochemical sensing mechanism in depth. It is proposed that the developed method will pave the way for the development of excellent antioxidant assays with the advantages of photoelectrochemistry and fluidic cells . It is expected to be further applied in food quality inspections and health guides, as well as in other fields.

Along with the challenges of wet-chemically preparing graphene-based nanohybrids, for example easy aggregation, low-stability in solution environment and insufficient loading amount, here we report the preparation and application of a type of π-conjugated molecule, perylenetetracarboxylic acid di-imide (PDI)-functionalized graphene material with high density of gold nanoparticles (AuNPs). In this nanohybrid, the PDI molecule comprises five-connected benzene rings and positively charged terminals composed of two symmetrical imidazole rings and amine groups, which offers the intrinsic driving force for π–π interactions with graphene and also serves as the active sites for immobilization of AuNPs. Transmission electron microscopy results demonstrated that AuNPs were uniformly dispersed and densely covered the PDI-functionalized graphene compared to the control experiment without PDI. To prove its biological application, the Au–PDI–graphene nanohybrid was chosen as a sensing material for fabricating a label-free electrochemical impedance hairpin DNA (hpDNA) biosensor for detection of human immunodeficiency virus 1 gene. When hpDNA was hybridized, it exhibited a sensitive electrochemical impedance variation on an Au–PDI–graphene modified electrode. This fabricated hpDNA biosensor reveals a wide linear detection range and a relatively low detection limit. Thanks to its high stability and efficient electrochemical impedance sensitivity, this nanohybrid would offer a broad range of possible DNA sequences for specific applications in biodiagnostics and bionanotechnology.

The high cost and limited natural abundance of platinum hinder its widespread applications as the oxygen reduction reaction (ORR) electrocatalyst for fuel cells. Carbon-supported materials containing metals such as Fe or Co as well as nitrogen have been proposed to reduce the cost without obvious lowering the performance compared to Pt-based electrocatalysts. In this work, based on the pyrolyzed corrin structure of vitamin B12 on the simultaneously reduced graphene support (g-VB12), we construct an efficient oxygen reduction electrocatalyst with very positive half-wave potential (only ∼30 mV deviation from Pt/C), high selectivity (electron transfer number close to 4) and excellent durability (only 11 mV shift of the half-wave potential after 10000 potential cycles). The admirable performance of this electrocatalyst can be attributed to the homogeneous distribution of abundant Co–Nx active sites, and a well-defined three-dimensional mesoporous structure of the N-doped graphene support. The high activity and long-term stability of the low cost g-VB12 make it a promising ORR electrocatalyst in alkaline fuel cells.

Optical absorption, as the fundamental requirement of photocatalysts, still has immense space for development. Herein, we design a novel kind of red Ag/AgCl photocatalyst, by which a large improvement of visible-light harvesting was obtained. These strongly coloured semiconductor materials can be facilely prepared using a versatile glycerol-mediated method and exhibit a uniform coaxial tri-cubic morphology. The enhancement of optical absorption is not only ascribed to the synergy of Ag and AgCl but also attributed to the Mie scattering effect due to the distinct morphology. As expected, the as-prepared red Ag/AgCl photocatalysts exhibit highly enhanced photocatalytic activities in the degradation of organic dyes, reduction of hexavalent chromium and conversion of CO2 into liquid hydrocarbon fuels. By means of theoretical calculations, furthermore, this work provides an in-depth perspective for understanding the physical photocatalytic mechanism of the red Ag/AgCl system and should stimulate the development of silver halide-based photocatalysts for the exploitation and utilization of solar energy.

We report a new method for controlling H- and J-stacking in supramolecular self-assembly. Graphene nanosheets act as structure inducers to direct the self-assembly of a versatile organic dye, perylene into two distinct types of functional nanostructures, i.e. one-dimensional nanotubes via J-stacking and two-dimensional branched nanobuds through H-stacking. Graphene integrated supramolecular nanocomposites are highly stable and show significant enhancement of photocurrent generation in these two configurations of photosensing devices, i.e. solid-state optoelectronic constructs and liquid-junction solar cells.

To make alloying anodes be practicability for lithium-ion batteries, graphene-incorporation has been demonstrated as one of the most effective strategies. However, successive lithiation/delithiation would usually lead to the detachment and self-aggregation of active alloying nanoparticles and graphene. Herein, an oxygen-bonds-bridging (Sn–O–C) Sn/graphene (Sn–O–G) micro/nanocomposite, in which Sn particles are in the ultrasmall scale of <3 nm and embedded in graphene-based microspheres, was prepared via an in-situ co-reduction procedure. Electrochemical tests demonstrated that the Sn–O–G exhibited much improved Li-storage properties in terms of high reversible capacity (1246 mA h/g at 50 mA/g), superior high-rate capabilities (220 mA h/g at 16 A/g) and long-term cycle life (410 mA h/g after 2000 cycles at 4 A/g) in comparison to the Sn/graphene (Sn/G) prepared from the similar procedures just without the presence of Sn–O–C bonds. Because of the same morphology, size and microstructures of both Sn-based anodes, it is speculated that such enhanced properties of Sn–O–G should be benefited from the Sn–O–C bonds. In order to answer “Do the bridging oxygen bonds between active Sn nanodots and graphene improve the Li-storage properties?”, several ex-situ technologies were employed to track the physicochemical and electrochemical variation of Sn–O–G electrodes, revealing the reversibility of breaking/re-formation and durability of Sn–O–C bonds during the successive Li-insertion/extraction. Therefore, the answer is “YES”.Download full-size image

Simple, portable analytical devices are entering our daily lives for personal care, clinical analysis, allergen detection in food, and environmental monitoring. Smartphones, as the most popular state-of-art mobile device, have remarkable potential for sensing applications. A growing set of physical-co-chemical sensors have been embedded; these include accelerometers, microphones, cameras, gyroscopes, and GPS units to access and perform data analysis. In this review, we discuss recent work focusing on smartphone sensing including representative electromagnetic, audio frequency, optical, and electrochemical sensors. The development of these capabilities will lead to more compact, lightweight, cost-effective, flexible, and durable devices in terms of their performances.

Optical absorption, as the fundamental requirement of photocatalysts, still has immense space for development. Herein, we design a novel kind of red Ag/AgCl photocatalyst, by which a large improvement of visible-light harvesting was obtained. These strongly coloured semiconductor materials can be facilely prepared using a versatile glycerol-mediated method and exhibit a uniform coaxial tri-cubic morphology. The enhancement of optical absorption is not only ascribed to the synergy of Ag and AgCl but also attributed to the Mie scattering effect due to the distinct morphology. As expected, the as-prepared red Ag/AgCl photocatalysts exhibit highly enhanced photocatalytic activities in the degradation of organic dyes, reduction of hexavalent chromium and conversion of CO2 into liquid hydrocarbon fuels. By means of theoretical calculations, furthermore, this work provides an in-depth perspective for understanding the physical photocatalytic mechanism of the red Ag/AgCl system and should stimulate the development of silver halide-based photocatalysts for the exploitation and utilization of solar energy.

High quality graphitized graphene has been successfully synthesized by solid-exfoliation of graphite and a subsequent wet chemical process. The as-obtained graphene exhibits charge–discharge behaviour quite different from that of reduced graphene oxide and shows enhanced cycling and rate performance compared with commercial mesocarbon microbeads (MCMBs) for lithium ion batteries.

The antioxidants in biological organisms can scavenge excess free radicals and effectively reduce oxidative stress, which protects DNA, protein and lipids in the human body from damage, thus preventing diseases from being induced. Therefore, it is particularly significant to assay the antioxidant capacities of our habitual foods during dietary evaluation. Herein, ultrathin graphitic carbon nitride (utg-C3N4)/TiO2 composites have been introduced as sensing elements into a photoelectrochemical platform with a thin layer structured flow-cell, for the real-time assay of the global antioxidant capacity in practical samples. In this system, the two-dimensional utg-C3N4 nanosheet/TiO2 nanoparticle composite material provided a much better optoelectronic function than the individual materials. In comparison with previous reports, this photoelectrochemical strategy shows considerable advantages, including excellent anti-interference properties, a high level of stability and reproducibility, and it is also proved to be the most prompt, convenient and cost-effective method for antioxidant capacity detection up to now. Moreover, utilizing theoretical and experimental examinations, we revealed its photoelectrochemical sensing mechanism in depth. It is proposed that the developed method will pave the way for the development of excellent antioxidant assays with the advantages of photoelectrochemistry and fluidic cells . It is expected to be further applied in food quality inspections and health guides, as well as in other fields.

Along with the challenges of wet-chemically preparing graphene-based nanohybrids, for example easy aggregation, low-stability in solution environment and insufficient loading amount, here we report the preparation and application of a type of π-conjugated molecule, perylenetetracarboxylic acid di-imide (PDI)-functionalized graphene material with high density of gold nanoparticles (AuNPs). In this nanohybrid, the PDI molecule comprises five-connected benzene rings and positively charged terminals composed of two symmetrical imidazole rings and amine groups, which offers the intrinsic driving force for π–π interactions with graphene and also serves as the active sites for immobilization of AuNPs. Transmission electron microscopy results demonstrated that AuNPs were uniformly dispersed and densely covered the PDI-functionalized graphene compared to the control experiment without PDI. To prove its biological application, the Au–PDI–graphene nanohybrid was chosen as a sensing material for fabricating a label-free electrochemical impedance hairpin DNA (hpDNA) biosensor for detection of human immunodeficiency virus 1 gene. When hpDNA was hybridized, it exhibited a sensitive electrochemical impedance variation on an Au–PDI–graphene modified electrode. This fabricated hpDNA biosensor reveals a wide linear detection range and a relatively low detection limit. Thanks to its high stability and efficient electrochemical impedance sensitivity, this nanohybrid would offer a broad range of possible DNA sequences for specific applications in biodiagnostics and bionanotechnology.