Electroactive Function Research Articles

Functionality Modulation Toward Thianthrene-based Metal-Free Electrocatalysts for Water Splitting.

The development of metal-free bifunctional electrocatalysts for hydrogen and oxygen evolution reactions (HER and OER) is significant but rarely demonstrated. Porous organic polymers (POPs) with well-defined electroactive functionalities show superior performance in hydrogen evolution reaction (HER) and oxygen evolution reaction (OER). Precise control of the active sites' local environment requires careful modulation of linkers through the judicious selection of building units. Here, a systematic strategy is introduced for modulating functionality to design and synthesize a series of thianthrene-based bifunctional sp2 C═C bonded POPs with hollow spherical morphologies exhibiting superior electrocatalytic activity. This precise structural tuning allowed to gain insight into the effects of heteroatom incorporation, hydrophilicity, and variations in linker length on electrocatalytic activity. The most efficient bifunctional electrocatalyst THT-PyDAN achieves a current density of 10 mA cm─2 at an overpotential (η10) of ≈65 mV (in 0.5 m H2SO4) and ≈283 mV (in 1 m KOH) for HER and OER, respectively. THT-PyDAN exhibits superior activity to all previously reported metal-free bifunctional electrocatalysts in the literature. Furthermore, these investigations demonstrate that THT-PyDAN maintains its performance even after 36 h of chronoamperometry and 1000 CV cycling. Post-catalytic characterization using FT-IR, XPS, and microscopic imaging techniques underscores the long-term durability of THT-PyDAN.

Multi‐scale structure engineering of covalent organic framework for electrochemical charge storage

AbstractCovalent organic frameworks (COFs), which are constructed by linking organic building blocks via dynamic covalent bonds, are newly emerged and burgeoning crystalline porous copolymers with features including programmable topological architecture, pre‐designable periodic skeleton, well‐defined micro‐/meso‐pore, large specific surface area, and customizable electroactive functionality. Those benefits make COFs as promising candidates for advanced electrochemical energy storage. Especially, for now, structure engineering of COFs from multi‐scale aspects has been conducted to enable optimal overall electrochemical performance in terms of structure durability, electrical conductivity, redox activity, and charge storage. In this review, we give a fundamental and insightful study on the correlations between multi‐scale structure engineering and eventual electrochemical properties of COFs, started with introducing their basic chemistries and charge storage principles. The careful discussion on the significant achievements in structure engineering of COFs from linkages, redox sites, polygon skeleton, crystal nanostructures, and composite microstructures, and further their effects on the electrochemical behavior of COFs are presented. Finally, the timely cutting‐edge perspectives and in‐depth insights into COF‐based electrode materials to rationally screen their electrochemical behaviors for addressing future challenges and implementing electrochemical energy storage applications are proposed.

Redox Polyelectrolytes with pH-Sensitive Electroactive Functionality in Aqueous Media

A framework of ferrocene-containing polymers bearing adjustable pH- and redox-active properties in aqueous electrolyte environments was developed. The electroactive metallopolymers were designed to possess enhanced hydrophilicity compared to the vinylferrocene (VFc) homopolymer, poly(vinylferrocene) (PVFc), by virtue of the comonomer incorporated into the macromolecule, and could also be prepared as conductive nanoporous carbon nanotube (CNT) composites that offered a variety of different redox potentials spanning a ca. 300 mV range. The presence of charged non-redox-active moieties such as methacrylate (MA) in the polymeric structure endowed it with acid dissociation properties that interacted synergistically with the redox activity of the ferrocene moieties to impart pH-dependent electrochemical behavior to the overall polymer, which was subsequently studied and compared to several Nernstian relationships in both homogeneous and heterogeneous configurations. This zwitterionic characteristic was leveraged for the enhanced electrochemical separation of several transition metal oxyanions using a P(VFc0.63-co-MA0.37)-CNT polyelectrolyte electrode, which yielded an almost twofold preference for chromium as hydrogen chromate versus its chromate form, and also exemplified the electrochemically mediated and innately reversible nature of the separation process through the capture and release of vanadium oxyanions. These investigations into pH-sensitive redox-active materials provide insight for future developments in stimuli-responsive molecular recognition, with extendibility to areas such as electrochemical sensing and selective separation for water purification.

Two-dimensional Covalent Organic Frameworks for Electrochromic Switching.

The electrochromic materials have received immense attention for the fabrication of smart optoelectronic devices. The alteration of the redox states of the electroactive functionalities results in the color change in response to electrochemical potential. Even though transition metal oxides, redox-active small organic molecules, conducting polymers, and metallopolymers are known for electrochromism, advanced materials demonstrating multicolor switching with fast response time and high durability are of increasing demand. Recently, two-dimensional covalent organic frameworks (2D COFs) have been demonstrated as electrochromic materials due to their tunable redox functionalities with highly ordered structure and large specific surface area facilitating fast ion transport. Herein, we have discussed the mechanistic insights of electrochromism in 2D COFs and their structure-property relationship in electrochromic performance. Furthermore, the state-of-the-art knowledge for developing the electrochromic 2D COFs and their potential application in next-generation display devices are highlighted.

Acid-directed preparation of micro/mesoporous heteroatom doped defective graphitic carbon as bifunctional electroactive material: Evaluation of trace metal impurity

Extensive research to explore cost-effective carbon materials as electrocatalysts and electrode materials for energy conversion and storage has been conducted in the recent literature. This raised a crucial question regarding the origin of this electrocatalytic activity from the heteroatom doping/ hierarchical porous defect-rich architecture and/ or the trace metal impurities introduced during synthesis/ inherent to the precursor. In this work, an insight into this issue is provided by considering a lignocellulosic biowaste, Euryale Ferox (foxnut) shells as a precursor to derive micro/ mesoporous defective graphitic carbon sheets by the phosphoric acid (H3PO4) dictated in-situ carbonization for oxygen reduction reaction (ORR) and supercapacitor applications. The sample synthesized at 900 °C (FP900) shows an onset potential of 0.98 V vs. reversible hydrogen electrode (RHE), ORR current density of 5.5 mA cm−2, and current stability of 93% (in 10 h measurement) in 0.1 M KOH. In addition, a symmetric supercapacitor device is assembled using the prepared material and the specific capacitance of 207.5 F g−1 at 1 A g−1 is obtained. An attempt to explain the origin of the electrochemical performance is made by establishing parallels with the physicochemical characterizations. The inherently doped heteroatoms give rise to electroactive functionalities and the wide enough pore size distribution improves the active sites utilization efficiency by enhancing the accessibility to electrolytic ions resulting in better electrochemical performance. Furthermore, the contribution from the intrinsic trace metal impurities is evaluated using X-ray fluorescence (XRF) spectroscopy. The presented research clarifies the non-contributing nature of trace metal species owing to the inaccessibility of active sites and lower abundance in F900 and FP900, respectively.

Thermally responsive reduced graphene oxide with electroactive functionality for controllable electroanalysis

A thermally responsive hybrid poly(NIPAm-b-BVIm[FcCOO])-rGO composed of block co-polymer poly(NIPAm-b-BVImBr), reduced graphene oxide (rGO) and electroactive anions was designed and synthesized to achieve electroactive functionality. It is the polymeric ionic liquids (PILs) segment in the block co-polymer that integrated the three different components into a whole hybrid. Such segment of PILs could not only promote the modification of polar PNIPAm onto the non-polar rGO by cation-π interaction, but also realize the immobilization of ferrocenecarboxylate anion (FcCOO−) via anion-exchange reaction. The PNIPAm moiety endowed the poly(NIPAm-b-BVIm[FcCOO])-rGO with thermal responsiveness, while the anion moiety provided additional electroactive function. It is noteworthy that the conformational change of PNIPAm segment upon different temperature could reveal or seal the redox probe of FcCOO−, thereby leading to a controllable expression of electroactivity switching by thermal stimuli. Owing to such regulation on surface property and conformation of PNIPAm segment, the modified electrode exhibited excellent thermally responsive electrocatalysis with reversible ‘ON-OFF’ effect toward the detection of ascorbic acid (AA), which led to two different catalytic states at the same electrode. The reversible electrocatalytic performance with switching capability of the poly(NIPAm-b-BVIm[FcCOO])-rGO/GCE is expected to have a broad application in the field of intelligent electrochemical sensors and devices.

Does the salt really matter? Impact of the counterion upon ECL signal

The incorporation of counterions into a variety of substances to control a number of their physiochemical properties is vital within a range of fields. Electrochemiluminescence (ECL) based sensors have grown in popularity in recent years with their employment observed across analytical and bioanalytical applications. ECL is typically concerned with the core electroactive functionality of the species of interest, with structural similarities commonly employed to determine the likelihood of a species ECL capability. However, to date no consideration has been given to the impact of different counterions toward an analytes ECL mechanism. Here we report for the first time how a simple alternation to a co-reactants counterion can significantly impact upon its recorded ECL response. Utilizing the tropane alkaloid scopolamine and its hydrobromide and hydrochloride salt forms, we have seen through interrogation with the traditional ruthenium luminophore, that replacement of the bromide anion for the chloride anion can reduce the electroactivity of the species. Direct comparison between the hydrobromide and hydrochloride salt forms relived differences in respect of their emission potentials and intensities. The impact of the salt form upon the ECL response has here been investigated, in respect to predicted concentrations. Results demonstrated how vastly different concentrations were obtained dependent upon the salt form present within the sample and that which was used to produce the calibration curve. The impact of this discovery will be of interest to the electrochemiluminescent and electroanalytical communities, and in particular forensic practitioners where electrochemical and ECL based sensors are of increasing interest. Ultimately the application of an ECL sensor within an analytical environment relies upon its accuracy and hence a thorough understanding of the phenomenon observed will only stand to widen the acceptance of ECL within the wider analytical community and increase its potential future applications.

Sustainable impact of tartaric acid as electron shuttle on hierarchical iron-incorporated biochar

Metal-biochar composite is considered as a promising alternative for future carbocatalysis in environmental decontamination. Nevertheless, unavoidable metal leaching impedes its scaling-up application and remains an environmental concern in the present scientific progress. Herein, a hierarchical Fe biochar (Fe/CBC) derived from cellulose was fabricated via a hydrothermal carbonization coupled with microwave irradiation and NH3 activation. Several exterior organic electron shuttles (i.e., ascorbic acid, oxalic acid, tartaric acid, and hydroquinone) were accommodated onto Fe/CBC to introduce more electroactive functionalities (i.e., C–O and C = O). In particular, comprehensive material characterization was performed to elaborate the physicochemical properties of tartaric acid-treated biochar catalyst (Fe/CBC-TA). Synergies of inherent hierarchical structure, well-developed carbon π-electron network, and accommodated electron shuttle could mitigate the Fe leaching from 2.44 to 0.578 mg L−1 in the peroxymonosulfate (PMS) activation system for catalytic degradation of bisphenol A. Based on the results of scavenging experiments and electron paramagnetic resonance (EPR) analysis, the catalytic mechanisms transformed from a one-phase pathway (mainly •OH) for the Fe/CBC system to a two-phase pathway (first phase: 1O2; second phase: •OH) for the Fe/CBC-TA system. The increased activation energy and improved catalyst recyclability of the Fe/CBC-TA in the redox reaction further pinpointed its environmental sustainability. Overall, this work offers new strategies to fabricate efficient metal-biochar catalyst and insights into its sustainable electrocatalysis.

Nanofibrous Carbon Multifunctional Smart Scaffolds for Simultaneous Cell Differentiation and Dopamine Detection.

Advances in stem-cell therapy rely on new, multifunctional smart scaffolds (MSS) to promote growth while simultaneously characterizing stem cells undergoing selective differentiation. Nondestructive cell characterization techniques, such as electrochemical detection of lineage-specific metabolites, play a critical role in translational stem-cell therapy by providing clinicians with real-time information to evaluate cell-readiness for transplant. However, electrochemical sensors that provide biophysical cues capable of guiding cell fate, while preserving electroactive functionality, remain unavailable. In this work, a carbon MSS is fabricated by pyrolyzing polyacrylonitrile (PAN) with optimal multiwalled carbon nanotube (MWCNT) loading to optimize electrochemical activity and with a tunable surface to promote cell growth and organization. Carbon MSS is used to (1) enhance the morphology and differentiation of mouse neural stem/progenitor cells (mNSPCs) derived from different regions of the developing brain and (2) simultaneously detect a neurotransmitter, dopamine, from a model dopaminergic cell line growing on the electrode. The study presents a carbon multifunctional smart scaffold for advancing stem-cell therapy toward clinically relevant applications.

Template-assisted construction of N,O-doped mesoporous carbon nanosheet from hydroxyquinoline-Zn complex for high-performance aqueous symmetric supercapacitor

Developing porous carbon materials with open accessibility and electro-active functionalities is essential for the enhancement of supercapacitive performance such as energy density and rate capability. Herein, for the first time, a hydroxyquinoline-Zn complex was adopted to fabricate N,O co-doped mesoporous carbon using a template-assisted method for morphology construction. We used sheet-like Mg(OH)2 as template to achieve nanosheet morphology and as agent to preserve oxygenic functionality. Meanwhile, the zinc oxide self-generated upon carbonization acts as template for mesopore formation. The ZnMgC973 nanosheet obtained under optimized conditions is rich in mesoporosity, displaying large surface area (816 m2/g), high electro-active functionalities (17.6 atom% of O and 4.4 atom% of N) and homogenous distribution of elements. Benefited from these unique features, ZnMgC973 is a promising candidate for energy storage. When applied as electrode of aqueous symmetric supercapacitor in 1.0 M Na2SO4, ZnMgC973 works excellently well within the working voltage of 0–2 V, displaying large capacitance retention of 72% at current density from 1 to 20 A/g, maximum energy density of 30.6 Wh/kg at power density of 2000 W/kg (maintaining 20.5 Wh/kg at high power density of 39 620 W/kg), and 96% capacitance retention after 10 000 continual charge/discharge cycles.

Adding an electroactive response to 3D printed materials: Printing a piezoelectret

Electrets have been increasingly investigated for their high piezoelectric sensitivity for sensing and energy harvesting applications, but fabricating complex 3D structures for optimum performance has remained challenging. 3D printing capabilities have likewise become a mature manufacturing technology widely used for end-user customization and rapid prototyping, but limitations on materials and geometries have complicated the incorporation of electroactive structures. In this paper, the first completely 3D printed porous piezoelectret is demonstrated. These samples were structured using standard infill patterns commonly used in 3D printing, allowing easy incorporation with current 3D printing technology. Pores generated by fused-filament fabrication (FFF) are characterized, charged, and the resultant piezoelectret activity measured. Analytical electromechanical models are used to understand and compare the measured charge density and piezoelectric coefficients. The piezoelectric coefficient is found to increase strongly with decreasing infill percentages. An average piezoelectric d33 coefficient of 87 pC N−1 is achieved for 5 % infill samples and is found to be stable for a period of at least 2 weeks, competitive with many other state-of-the-art single-pore piezoelectretic materials. These results provide a first step in using 3D printing techniques to optimize and integrate piezoelectrets into parts, allowing a useful new electroactive functionality for additive manufacturing.

Corrosion protective properties of epoxy coating containing tetraaniline modified nano-α-Fe2O3

In this study, a self-healing epoxy coating containing tetraaniline modified α-Fe2O3 (TAFe) was prepared for corrosion protection of Q235 steel. The TAFe particles were synthesized using bio-inspired catechol chemistry and the evaluation of the corrosion resistant benefits of TAFe as additive in the epoxy coating were conducted. The time-dependent corrosion protective ability of the epoxy composite coating containing TAFe applied on Q235 carbon steel were characterized by electrochemical techniques such as EIS and LEIM. Characterization of corrosion layer was done by SEM and XRD after removing coatings after 70 days of immersion in 3.5 wt% NaCl solution. Findings of corrosion measurements confirmed the existence of a small amount TAFe (0.7 wt%) resulted in improvement of corrosion protective properties of steel during corrosion process compared with neat epoxy coating and the coating with 0.7 wt% non-modified Fe2O3. Moreover, surface techniques showed compact passivated iron oxide layer beneath the coatings and presence of different metallic oxide phases for coatings. The corrosion protective enhancement of composite coating could be ascribed to electroactive function of tetraaniline layer on α-Fe2O3.

Functional Protection of Exfoliated Black Phosphorus by Noncovalent Modification with Anthraquinone.

Few and monolayer black phosphorus (phosphorene) is currently an intensively researched material. Shear exfoliated black phosphorus (BPSE) nanosheets were functionalized with the redox active antraquinone (AQ) that can provide additional charge storage capacity. The noncovalent interaction of BP with AQ occurs due to van der Waals interactions. X-ray photoelectron spectroscopy results show that AQ coverage of BPSE nanosheets led to a stabilization against BPSE degradation. Electrochemistry of the BPSE-AQ shows that AQ is stably anchored onto BPSE and exhibits redox peaks stable for more than 100 cycles. The surface coverage by AQ on BPSE is estimated to be 1.25 nmol AQ/mg BP and electron-transfer rate constant ( kET) of 33 s-1. Furthermore, the proposed modification greatly increases the gravimetric capacitance of BPSE-AQ with respect to the starting BPbulk. Such coating of BP not only protects BP from degradation but also brings electroactive functionality to this two-dimensionally layered material.

Electrochemical Evaluation of Sweet Sorghum Fermentable Sugar Bioenergy Feedstock

Although sweet sorghum is a promising feedstock for bioenergy and biobased products, sweet sorghum-based biorefineries in the U.S. are still in the planning or pilot-scale stages. Accurate, rapid, and inexpensive metrology is known to streamline (bio)refining operations and drive the return on investment. In this study, new cyclic voltammetry (CV)-based methods were developed to rapidly classify sweet sorghum fermentable sugar feedstocks for electroactive functionalities. In addition to providing industrial QA/QC protocols, developed methods could be used to screen for the pest-resistant cultivars containing redox-active antifeedants (e.g., flavonoids, alkaloids, and aconitic acid), enabling germplasm development for a sustainable feedstock supply chain. Developed CV methods were tested on five male (Atlas, Chinese, Dale, Isidomba, and N98) and three female (N109B, N110B, and N111B) inbred lines and their hybrids (23 cultivars total) planted in April, May, and June of 2015 in Georgia, and harvested at the...

Mesoscopic Fabric Sheet Racks and Blocks as Catalysts with Efficiently Exposed Surfaces for Methanol and Ethanol Electrooxidation

Electrode designs based on sheet racks and blocks with multidiffuse groove spaces and enriched active sites and scales would promote the commercial applications of electroactive materials. A facile one‐pot hydrothermal approach is reported to synthesize mesoscopic porous Co3O4 or hybrid graphene (GO)/Co3O4 sheet‐on‐sheet racks and blocks. Three basic types of sheet scalability racks can be built in vertical and nonstacked edge orientations, such as neat micro/nanogroove rooms, butterfly wing scales, and wall groves, leading to highly exposed surface converges and sites. In particular, the stacked GO/Co3O4 sheet‐on‐sheet blocks (GO/Co3O4 blocks) can be oriented in vertical tower buildings. The atomic structures of the developed Co3O4 catalysts are dominant along the highly dense {112/111} interfaces and single crystal {111} and {112} facets. The electrochemical performance of the mesoscopic porous Co3O4 catalyst toward methanol and ethanol electrooxidation is evaluated in alkaline conditions. The mesoscopic hybrid GO/Co3O4 racks reveal superior catalytic activity in terms of oxidation currents and onset potentials, indicating the effect of the synergetic role of active Co3+ sites along the densely exposed {112} facets, graphene counterparts, and hierarchically nonstacked sheet racks on the electroactive functionality. Results indicate that the mesoscopic GO/Co3O4 sheet catalyst is suitable for highly efficient electrochemical reactions.

Energy harvesting based on soft material of dielectric elastomers: Status, trends and challenges

As a kind of new soft electroactive function materials (EAP), dielectric elastomers (DE) show great potentials in harvesting energy from human bodies or the nature, due to its good flexibility, large deformation, high specific energy density and many other advantages. This paper makes a review of the research status and main progress on energy harvesting based on dielectric elastomers, including its behavior mechanism and model description, the influence of material property to energy harvesting performance, DE generator (DEG) structure design, circuit design, as well as the development and application of related prototype products. Then, the main problems and challenges existing in current research are analyzed. At last, this paper makes a outlook for the development trend and research priorities on DE-based energy harvesting.

Redox-active electrolyte supercapacitors using electroactive ionic liquids

Here we present redox ionic liquid supercapacitors (RILSCs) which use electrolytes made from ionic liquids modified with an electroactive function to increase the energy density of activated carbon electrodes via faradaic reactions. More specifically, two different ionic liquids were made by modifying either the imidazolium cation or the bis(trifluoromethanesulfonyl)imide anion with ferrocene in order to determine the importance of the electroactive ion's polarity. The functionalization of an ionic liquid with ferrocene led to high concentrations of redox moieties in the electrolyte (2.4M) and a large maximum operating voltage (2.5V). An energy density of up to 13.2Wh per kg (both electrodes) was obtained which represents an 83% increase vs. the unmodified ionic liquid. When the ionic liquid's anion is modified with ferrocene, the self-discharge at the positive electrode is fully suppressed due to the deposition of a film on the electrode. The results presented herein demonstrate that electroactive ionic liquids constitute a promising alternative to conventional solute in solvent electrolytes found in energy storage devices, and are particularly well-suited for redox-active electrolyte supercapacitors.

Impact of Aromatic Extension on the Electrochemical Properties of Lithium Carboxylates As Negative Organic Electrode for Lithium-Ion Battery

aLaboratoire de Réactivité et Chimie des Solides (LRCS), Université de Picardie Jules Verne CNRS UMR7314, 80039 Amiens Cedex b Institut de Chimie de Picardie (ICP), Université de Picardie Jules Verne CNRS FR3085, 80039 Amiens Cedex c Réseau sur le Stockage Electrochimique de l’Energie (RS2E), FR CNRS 3459 The integration of organic-based electrode materials in lithium-ion batteries has aroused keen interest for the last years as it combines a set of advantages against inorganic as lower toxicity, easier recyclability or it takes the advantage of the rich versatility offered by the organic chemistry. This latter can give the promise for tunable redox potentials and kinetic properties1 , 2 , 3. As recently developed, a lot of questions are still pending about the reactivity of these organic compounds, in particular the relationship between the structure and the electrochemical properties. The most promising electroactive function as negative electrode is currently the lithium carboxylate, proposed first by our lab through the di-lithiated terephthalic acid4. Although the different electrochemical tests vs lithium and integration of the materials in batteries testify of the credibility of using organic electrodes, less is placed on the understanding of the structure/reactivity relationship for which it is nonetheless crucial to guide the experimentalist towards the synthesis of higher performance organic electrodes. With this aim, we will carefully expose our recent findings on the role of the spacer between the two carboxylates. For this, a new series of molecules have been developed in our group by changing the extent of π conjugation in the aromatic core unit separating the two electroactive functions. The first in the list is the di-lithium-2,6-Naphthalene dicarboxylate (Li2-NDC) which has a theoretical capacity of 235 mAh.g-1 (Fig. 1)5. Compared to the simpler phenyl core unit (Li2-BDC)with same textural properties, we showed a greater electrochemical performances in terms of power rate capability (Fig. 2). Based on this first result, we have developed a hyper-conjugated organic compound based on the tetralithium perylen-3,4,9,10-tetracarboxylate (Li4-PTC). This perylen core unit with high extended π conjugation offers a remarkable high rate capability to the carboxylate redox active functions as a result from the greater stabilization of the radical anion state. More than 120 mAh.g-1 gravimetric capacity over one hundred cycles at 5C rate was achieved without engineering any electrode formulation (Fig.3)6 This contribution will contain more details about the development of our materials and will give an insight about the relationship between structure of the core unit and electrochemical properties of the electrode material (eg. redox potential, power, capacity retention…).

Synthesis of electroactive and biodegradable multiblock copolymers based on poly(ester amide) and aniline pentamer

A new family of multiblock copolymers (PEA-b-AP) based on poly(ester amide) (PEA) and aniline pentamer (AP) with the unique properties of being both electroactive and biodegradable was synthesized via a two-stage active solution polycondensation. The new synthesis approach proceeded smoothly, and avoided the complicated purification steps for separating the intermediate products. The molecular weight of PEA blocks was regulated by varying the nucleophilic/electrophilic monomers feed ratios. The chemical structures of the copolymers were confirmed by both IR and NMR spectra. UV-Vis spectroscopy indicated that the copolymers possessed of the intrinsic electroactivity of AP blocks, and showed three reversible oxidation states. The copolymers had lower degradation rates than the PEA homopolymers with similar molecular weight, and their degradation rates were greatly affected by the proportion of AP blocks. In vitro cell culture studies of the PEA-b-APs revealed that they facilitated the proliferation of RSC96 Schwann cells and displayed a good biocompatibility. These biodegradable copolymers with electroactive function may have great potential for use as nerve repair and regeneration scaffold materials in tissue engineering. © 2013 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2013, 51, 4722–4731

Graphene-Orange II composite nanosheets with electroactive functions as label-free aptasensing platform for “signal-on” detection of protein

The combination of novel nanomaterials and biomolecule recognition units is promising in developing sensitive biosensors. This paper presents a facile approach for the preparation of water-soluble electroactive dye-Orange II functionalized graphene nanosheets (O-GNs). The successful attachment of Orange II on the surface of graphene nanosheets not only prevents the agglomeration of the as-formed graphene nanocomposite in aqueous media, but also endows graphene nanosheets with excellent electroactive property. Integrating the unique properties of the as-prepared O-GNs (high conductivity, high specific surface area and electroactive function) with high affinity and specificity of aptamer, a new label-free electrochemical biosensing concept is demonstrated for the “signal-on” detection of targets such as thrombin and lysozyme. The present O-GNs-based aptasensor exhibits good current response to the above proteins. The linear ranges for thrombin and lysozyme are 1.0×10−12–4.0×10−10M and 5.0×10−12–7.0×10−10M, with the detection limit of 3.5×10−13M and 1.0×10−12M, respectively. In contrast to the common laborious and expensive labeling approaches, the present O-GNs based aptasensing process is highly simple, cost-efficient and does not need labeling and modification of aptamers or introduce additional electrochemical probes.