Marcin Opallo

Reduction and Functionalization of Graphene Oxide Sheets Using Biomimetic Dopamine Derivatives in One Step

An easy and environmentally friendly chemical method for the simultaneous reduction and noncovalent functionalization of graphene oxide (GO) using dopamine derivatives is described. The reaction takes place at room temperature under ultrasonication of an aqueous suspension of GO and a dopamine derivative. X-ray photoelectron spectroscopy, FT-IR spectroscopy, and cyclic voltammetry characterizations revealed that the resulting material consists of graphene functionalized with the dopamine derivative. This one-step protocol is applied for simultaneous reduction and functionalization of graphene oxide with a dopamine derivative bearing an azide function. The chemical reactivity of the azide function was demonstrated by a postfunctionalization with ethynylferrocene using the Cu(I) catalyzed 1,3-dipolar cyloaddition.

Medium effect in the electroreduction of nitromesitylene

Abstract One-electron reduction of nitromesitylene ★★ to the corresponding radical anion has been studied at a hanging mercury drop electrode in various perchlorate salt solutions in five organic solvents: dimethylsulfoxide, dimethylacetamide, propylene carbonate, hexamethylphosphoramide and N -methylformamide. Standard redox potentials, diffusion coefficients, standard rate constants and transfer coefficients have been evaluated from cyclic voltammetry measurements. The results obtained are compared with the literature data for dimethylformamide and acetonitrile solutions. The standard rate constants were found to depend on the cation of the supporting electrolyte as well as on the solvent. It is shown that the rate constants corrected for both ion-pair formation and the double layer effect cannot be described by classical theories of heterogeneous electron transfer. It is shown that the dynamic dielectric properties of the solvent, described by the dielectric relaxation time, influence the rate of the heterogeneous charge transfer. The greater the dielectric relaxation time of the solvent, the smaller is the reaction rate.

Nitrogen doped graphene nanosheet supported platinum nanoparticles as high performance electrochemical homocysteine biosensors

Functional carbon nanomaterials are significantly important for the development of high performance sensitive and selective electrochemical biosensors. In this study, graphene supported platinum nanoparticles (GN-PtNPs) and nitrogen doped graphene supported platinum nanoparticles (N-GN-PtNPs) were synthesized by a simple chemical reduction method and explored as high performance nanocatalyst supports, as well as doped nanocatalyst supports, toward electrochemical oxidation of homocysteine (HCY) for the first the time. Our studies demonstrate that N-doped graphene supported PtNPs show higher electrocatalytic activity for HCY with an experimental detection limit of 200 pM. Moreover, N-doped graphene supported Pt was demonstrated to have excellent selectivity in the electrochemical oxidation of HCY i.e., the detection of HCY is successful in the presence of a 20-fold excess of ascorbic acid (AA). The practical application of N-doped graphene supported PtNP materials is effectively shown for the determination of HCY in both human blood serum and urine samples, by differential pulse voltammetry under optimized conditions. Our findings conclude that N-doped graphene supported PtNPs can be developed as a high performance and versatile nano-electrocatalyst for electrochemical biosensor applications.

Self-powered biosensor for ascorbic acid with a Prussian blue electrochromic display

We report on the development of a nanocarbon based anode for sensing of ascorbic acid (AA). The oxidation of AA on this anode occurs at a quite low overpotential which enables the anode to be connected to a biocathode to form an ascorbic acid/O2 biofuel cell that functions as a self-powered biosensor. In conjunction with a Prussian blue electrochromic display the anode can also work as a truly self-powered sensor. The oxidation of ascorbic acid at the anode leads to a reduction of the Prussian blue in the display. The reduced form of Prussian blue, called Prussian white, is transparent. The rate of change from blue to colourless is dependent on the concentration of ascorbic acid. The display can easily be regenerated by connecting it to the biocathode which returns the Prussian blue to its oxidized form. In this way we have created the first self-powered electrochromic sensor that gives quantitative information about the analyte concentration. This is demonstrated by measuring the concentration of ascorbic acid in orange juice. The reported quantitative read-out electrochromic display can serve as a template for the creation of cheap, miniturizable sensors for other relevant analytes.

Sensitive sugar detection using 4-aminophenylboronic acid modified graphene.

A sensitive electrochemical active interface for sugar sensing based on the specific boronic acid-diol binding was established. The sensing matrix was formed by stirring a suspension of graphene oxide (GO) with 4-aminophenylboronic acid (APBA). The resulting composite consists of a water insoluble precipitate of reduced graphene oxide (rGO) with APBA incorporated into the rGO matrix. Differential pulse voltammetry (DPV) on glassy carbon electrodes modified with rGO/APBA was used for the detection of fructose, mannose and glucose. The fabricated sensor exhibited a wide linear range with detection limits of 100 nM for fructose, and around 800 nM for mannose and glucose.

Film electrode prepared from oppositely charged silicate submicroparticles and carbon nanoparticles for selective dopamine sensing

Film electrodes prepared from oppositely charged silicate submicroparticles and carbon nanoparticles was applied for selective dopamine sensing. Mesoporous silicate submicroparticles with tetraalkylammonium functionalities were prepared by sol-gel method. They were immobilised on an indium tin oxide film surface together with phenylsulphonated carbon nanoparticles by layer-by-layer method: alternative immersion into their suspensions. As it is shown by scanning electron microscopy the obtained film is composed of silicate submicroparticles covered by carbon nanoparticles. The nanoparticulate film is stable and its electroactive surface is significantly larger than substrate. Accumulation of redox active cations indicates that only fraction charged functionalities of carbon nanoparticles are employed in film formation. The obtained electrode exhibits catalytic properties towards dopamine oxidation and its interferences as ascorbic acid, uric acid and acetaminophen. This allows for selective determination of tenth micromolar concentration of dopamine in the presence of these interferences at milimolar level. The detection limit and linear range were determined to 0.1 × 10⁻⁶ mol dm⁻³ and 0.3-18 × 10⁻⁶ mol dm⁻³ respectively.

Radiative and nonradiative electron transfer in donor–acceptor phenoxazine and phenothiazine derivatives

Abstract Radiative and nonradiative electron transfer (exemplified by the CT fluorescence and nonradiative charge recombination process in the singlet manifold, respectively) in a series of donor–acceptor phenoxazine and phenothiazine derivatives is reported. An analysis of the CT fluorescence leads to the quantities relevant for the radiative electron transfer in the Marcus inverted region. Using a nonadiabatic theory of electron transfer and the latter parameters, the rate constants for nonradiative electron transfer can be predicted. Electronic coupling elements V 0 between the 1 CT state and the ground state obtained from the radiative rates are in agreement with those calculated from the simple LCAO MO model which assumes that V 0 are mainly determined by the interactions between the atoms forming the A–D bond.

Functionalized carbon nanoparticles, blacks and soots as electron-transfer building blocks and conduits.

Functionalized carbon nanoparticles (or blacks) have promise as novel active high-surface-area electrode materials, as conduits for electrons to enzymes or connections through lipid films, or as nano-building blocks in electroanalysis. With previous applications of bare nanoblacks and composites mainly in electrochemical charge storage and as substrates in fuel cell devices, the full range of benefits of bare and functionalized carbon nanoparticles in assemblies and composite (bio)electrodes is still emerging. Carbon nanoparticles are readily surface-modified, functionalized, embedded, or assembled into nanostructures, employed in bioelectrochemical systems, and incorporated into novel electrochemical sensing devices. This focus review summarizes aspects of a rapidly growing field and some of the recent developments in carbon nanoparticle functionalization with potential applications in (bio)electrochemical, photoelectrochemical, and electroanalytical processes.

Recent Developments of Nanostructured Electrodes for Bioelectrocatalysis of Dioxygen Reduction

The recent development of nanostructured electrodes for bioelectrocatalytic dioxygen reduction catalysed by two copper oxidoreductases, laccase and bilirubin oxidase, is reviewed. Carbon-based nanomaterials as carbon nanotubes or carbon nanoparticles are frequently used for electrode modification, whereas there are only few examples of biocathodes modified with metal or metal oxide nanoparticles. These nanomaterials are adsorbed on the electrode surface or embedded in multicomponent film. The nano-objects deposited act as electron shuttles between the enzyme and the electrode substrate providing favourable conditions for mediatorless bioelectrocatalysis.

Thiol–Yne Click Reactions on Alkynyl–Dopamine‐Modified Reduced Graphene Oxide

The large-scale preparation of graphene is of great importance due to its potential applications in various fields. We report herein a simple method for the simultaneous exfoliation and reduction of graphene oxide (GO) to reduced GO (rGO) by using alkynyl-terminated dopamine as the reducing agent. The reaction was performed under mild conditions to yield rGO functionalized with the dopamine derivative. The chemical reactivity of the alkynyl function was demonstrated by post-functionalization with two thiolated precursors, namely 6-(ferrocenyl)hexanethiol and 1H,1H,2H,2H-perfluorodecanethiol. X-ray photoelectron spectroscopy, UV/Vis spectrophotometry, Raman spectroscopy, conductivity measurements, and cyclic voltammetry were used to characterize the resulting surfaces.