Aspergillus Niger Derived Wrinkle-Like Carbon as Superior Electrode for Advanced Vanadium Redox Flow Batteries

The scarcity of high electrocatalysis composite electrode materials has long been suppressing the redox reaction of V(II)/V(III) and V(IV)/V(V) couples in high performance vanadium redox flow batteries (VRFBs). Herein, through ingeniously regulating the growth of Aspergillus Niger, a wrinkle-like carbon (WLC) material that possesses edge-rich carbon, abundant heteroatoms, and nature wrinkle-like structure is obtained, which is subsequently successfully introduced and uniform dispersed on the surface of carbon fiber of graphite felt (GF). This composite electrode presents a lower overpotential and higher charge transfer ability, as the codoped multiheteroatoms increase the electrocatalysis activity and the wrinkled structure affords more abundant reaction area for vanadium ions in the electrolyte when compared with the pristine GF electrode, which is also supported by the density functional theory (DFT) calculations. Hence, the assembled battery using WLC electrodes achieves a high energy efficiency of 74.5% for 300 cycles at a high current density of 200 mA cm-2 , as well as the highest current density of 450 mA cm-2 . The WLC material not only uncovers huge potential in promoting the application of VRFBs, but also offers referential solution to synthesis microorganism-based high-performance electrode in other energy storage systems.

Ferrocene anchored activated carbon as a versatile catalyst for the synthesis of 1,5-benzodiazepines via one-pot environmentally benign conditions

1,5-Benzodiazepine is considered as one of the central moieties in the core unit of most drug molecules. Construction of such moieties with a new C–N bond under solvent-free and mild reaction conditions is challenging. Herein, we present a benign protocol for one pot synthesis of 1,5-benzodiazepine derivatives by using ferrocene (FC) supported activated carbon (AC) as a heterogeneous catalyst. The catalyst FC/AC was characterized by several analytical and spectroscopic techniques to reveal its physicochemical properties and for structural confirmation. The synthesized catalyst FC/AC was explored for its catalytic activity in the synthesis of 1,5-benzodiazepines through condensation of o-phenylenediamine (OPDA) and ketones (aromatic and aliphatic) under solvent-free conditions. The robust 10 wt% FC/AC catalyst demonstrated appreciable activity with 99% conversion of diamines and 91% selectivity towards the synthesis of the desired benzodiazepine derivatives under solvent-free conditions at 90 °C in 8 h. Additionally, several reaction parameters such as catalyst loading, reaction temperature, effect of reaction time and effect of different solvents on selectivity were also studied and discussed in-depth. To understand the scope of the reaction, several symmetrical and unsymmetrical ketones along with different substituted diamines were tested with the synthesized catalyst. All prepared reaction products were obtained in good to efficient yields and were isolated and identified as 1,5-benzodiazepines and no side products were observed. The obtained catalyst characterization data and the activity studies suggested that, the synergetic effect occurred due to the uniform dispersion of ferrocene over the AC surface with numerous acidic sites which triggered the reaction of diamine and ketone to form the corresponding benzodiazepine derivative and the same was illustrated in the plausible mechanism. Furthermore, the synthesized catalyst was tested for leaching and recyclability, and the results confirmed that catalyst can be used for up to six consecutive cycles without much loss in the catalytic activity and its morphology which makes the process sustainable and economical for scale-up production. The present method offered several advantages such as an ecofriendly method, excellent yields, sustainable catalytic transformation, easy work-up and isolation of products, and quick recovery of catalyst.

1,5-Benzodiazepine is considered as one of the central moieties in the core unit of most drug molecules.

A Non-Enzymatic Sensor Based on Fc-CHIT/CNT@Cu Nanohybrids for Electrochemical Detection of Glucose

Herein, a composite structure, consisting of Cu nanoparticles (NPs) deposited onto carbon nanotubes and modified with ferrocene-branched chitosan, was prepared in order to develop a nonenzymatic electrochemical glucose biosensor ferrocene-chitosan/carbon nanotube@ Cu (Fc-CHIT/CNT@Cu). The elemental composition of the carbon nanohybrids, morphology and structure were characterized by various techniques. Electrochemical impedance spectroscopy (EIS) was used to study the interfacial properties of the electrodes. Cyclic voltammetry (CV) and chronoamperometry methods in alkaline solution were used to determine glucose biosensing properties. The synergy effect of Cu NPs and Fc on current responses of the developed electrode resulted in good glucose sensitivity, including broad linear detection between 0.2 mM and 22 mM, a low detection limit of 13.52 μM and sensitivity of 1.256 μA mM⁻¹cm⁻². Moreover, the modified electrode possessed long-term stability and good selectivity in the presence of ascorbic acid, dopamine and uric acid. The results indicated that this inexpensive electrode had potential application for non-enzymatic electrochemical glucose detection.

Redox- and EPR-Active Graphene Diiron Complex Nanocomposite

A mixed valence diiron(II/III) complex with the ligand 2,6-bis{bis[(2-pyridinylmethyl)amino]methyl}phenol (bppH) has been covalently anchored onto graphene using a mild in situ microwave-assisted diazonium coupling through an aryl amino precursor and isoamyl nitrite. A dinuclear iron complex is then formed by complexation of the grafted bppH-graphene material with iron(II) in the presence of dioxygen. X-ray photoelectron spectroscopy (XPS), atomic force microscopy, cyclic voltammetry, scanning transmission electron microscopy, energy-dispersive X-ray spectroscopy, and electron paramagnetic resonance (EPR) spectroscopy confirm the formation of the anchored ligand and derivative diiron complexes. Semiquantitative XPS analysis shows an average bppH ligand bulk loading of 0.33 mmol/g, corresponding to a significant 20.7 wt % of the functionalized material consisting of grafted moieties. EPR measurements reveal the existence of a strong isotropic S = 1/2 spin center associated with the graphene lattice, together with a much weaker S = 5/2 signal, associated with the iron(III) center of the grafted complex. The grafted complex is redox-active with surface-confined Fe^IIFe^II → Fe^IIFe^III (+0.56 V vs NHE), Fe^IIFe^III → Fe^IIIFe^III (+0.73 V), and Fe^IIIFe^III → Fe^IIIFe^IV (+0.95 V) redox processes accessible, with an estimated surface coverage of 58 pmol cm^-2 established from the electrochemical measurements.

Impedimetric ultrasensitive detection of chloramphenicol based on aptamer MIP using a glassy carbon electrode modified by 3-ampy-RGO and silver nanoparticle

In this research work, a biosensor with a dual recognition system was fabricated and founded on a combination of aptasensing and the molecular imprinting union of the chloramphenicol (CAP) selective detection. CAP, is an antibiotic, was applied in veterinary and human in order to treat gram-positive and gram-negative infections. It is worth mentioning that CAP residue brings about earnest side effects on human health. According to this, in this sensing system, 3-aminomethyl pyridine functionalized graphene oxide (GO) (3-ampy-RGO) has been coated on the surface of GCE. Afterwards, the silver nanoparticle (AgNPs) was coated on the 3-ampy-RGO/GCE and, then, the CAP complex-amino-aptamer (NH₂-Apt[CAP]) was attached to the AgNP/3-ampy-RGO/GCE using a kind of bonding formation of Ag-N. In this sense, it is worth noting that the resorcinol electropolymerization around the complex of aptamer/CAP would confine the complex and, then, retain the aptamer. Following the CAP removal, the MIP cavity, as it was supposed, synergistically acted with that of the embedded aptamer in order to construct a nanohybrid receptor. Interestingly, the double exact property of the molecular imprinting polymers and aptamers led to the superb sensing properties. In the mentioned system it was illustrated that the linear range was from 1.0 pM to 1.0 nM with the detection limit of 0.3 pM; consequently, as observed, it was better than or as good as other similar assays. Moreover, the mentioned system whose activity was observed in the various interferences presence showed great selectivity in detected the CAP. Finally, the designed sensor exhibited outstanding results when applied to detect CAP in milk samples.

Bidirectional charge-transfer behavior in carbon-based hybrid nanomaterials

In recent years there has been a growing interest in finding materials revealing bidirectional charge-transfer characteristics, that is, materials behaving as an electron donor or an acceptor in the presence of redox and photoactive addends, for optoelectronic applications. In this respect, carbon-based nanostructures, such as graphene and carbon nanotubes, have emerged as promising nanomaterials for the development of hybrid systems for bidirectional charge transfer, whose behaviour can be switched from donor-type to acceptor-type by simply changing the electroactive counterpart to which they are anchored. In this review we provide an overview of the main advances that have been made over the past few years in carbon-based hybrid architectures involving different types of carbon nanostructures and photosensitizers. In particular, carbon nanotube and graphene-based hybrid systems will be highlighted.

Preparation of graphene/poly(2-acryloxyethyl ferrocenecarboxylate) nanocompositeviaa “grafting-onto” strategy

This article reports the construction of GS-PAEFC nanohybrids with excellent dispersibility and redox-responsibilityviaATNRC chemistry.

Polyaniline-Stabilized Intertwined Network-like Ferrocene/Graphene Nanoarchitecture for Supercapacitor Application

The present work highlights the effective H-π interaction between metallocenes (ferrocene; Fc) and graphene and their stabilization in the presence of polyaniline (PANI) through π-π interactions. The PANI-stabilized Fc@graphene nanocomposite (FcGA) resembled an intertwined network-like morphology with high surface area and porosity, which could make it a potential candidate for energy-storage applications. The relative interactions between the components were assessed through theoretical (DFT) calculations. The specific capacitance calculated from galvanostatic charging/discharging indicated that the PANI-stabilized ternary nanocomposite exhibited a maximum specific capacitance of 960 F g^- at an energy density of 85 Wh Kg^-1 and a current density of 1 A g^- . Furthermore, electrochemical impedance spectroscopy (EIS) analysis confirmed the low internal resistance of the as-prepared nanocomposites, which showed improved charge-transfer properties of graphene after incorporation of Fc and stabilization with PANI. Additionally, all electrodes were found to be stable up to 5000 cycles with a specific capacitance retention of 86 %, thus demonstrating the good reversibility and durability of the electrode material.

Chemical functionalization and characterization of graphene-based materials

This review offers an overview on the chemical functionalization, characterization and applications of graphene-based materials.

Donor-acceptor graphene-based hybrid materials facilitating photo-induced electron-transfer reactions

Graphene research and in particular the topic of chemical functionalization of graphene has exploded in the last decade. The main aim is to increase the solubility and thereby enhance the processability of the material, which is otherwise insoluble and inapplicable for technological applications when stacked in the form of graphite. To this end, initially, graphite was oxidized under harsh conditions to yield exfoliated graphene oxide sheets that are soluble in aqueous media and amenable to chemical modifications due to the presence of carboxylic acid groups at the edges of the lattice. However, it was obvious that the high-defect framework of graphene oxide cannot be readily utilized in applications that are governed by charge-transfer processes, for example, in solar cells. Alternatively, exfoliated graphene has been applied toward the realization of some donor-acceptor hybrid materials with photo- and/or electro-active components. The main body of research regarding obtaining donor-acceptor hybrid materials based on graphene to facilitate charge-transfer phenomena, which is reviewed here, concerns the incorporation of porphyrins and phthalocyanines onto graphene sheets. Through illustrative schemes, the preparation and most importantly the photophysical properties of such graphene-based ensembles will be described. Important parameters, such as the generation of the charge-separated state upon photoexcitation of the organic electron donor, the lifetimes of the charge-separation and charge-recombination as well as the incident-photon-to-current efficiency value for some donor-acceptor graphene-based hybrids, will be discussed.

Modulation of cell behaviors by electrochemically active polyelectrolyte multilayers

In addition to the topographical features and chemical properties of substrates, the mechanical properties are known as a vital regulator of cellular processes such as adhesion, proliferation, and migration, and have received considerable attention in recent years. In this work, electrochemical redox multilayers made of ferrocene-modified poly(ethylenimine) (PEI-Fc) and deoxyribonucleic acid (DNA) with controlled stiffness were used to investigate the effects of the mechanical properties of multilayers on fibroblast cell (NIH/3T3) behaviors. Redox PEI-Fc plays an essential role in inducing swelling in multilayers under an electrochemical stimulus, resulting in distinct changes in the stiffness of the multilayers. The Young’s modulus varied from 2.05 to 1.07 MPa for the (PEI-Fc/DNA) multilayers by changing the oxidation time of the electrochemical treatment. We demonstrated that the adhesion, proliferation, and migration of fibroblast cells depended on the multilayers’ stiffness. These results indicate that cell behaviors can be precisely controlled by electrochemical treatment, which provides a new way to prepare thin films with tunable mechanical properties with potential biomedical applications.