Graphene-Paper-Based Electrodes on Plastic and Textile Supports as New Platforms for Amperometric Biosensing

The possibility of exfoliating graphite into graphene sheets allows the researchers to produce a material, termed “graphene paper” (G-paper), conductive as graphite but more flexible and processable. G-paper is already used for electronic applications, like conductors, antennas, and heaters, outperforming metal conductors thanks to its high flexibility, lightness, chemical stability, and compatibility with polymeric substrates. Here, the effectiveness in the use of G-paper for the realization of electrodes on flexible plastic substrates and textiles, and their applicability as amperometric sensors are demonstrated. The performance of these devices is compared with commercial platforms made of carbon-based inks, finding that they outperform commercial devices in sensing nicotinamide adenine dinucleotide (NADH), a key molecule for enzymatic biosensing; the electrodes can achieve state-of-the-art sensitivity (107.2 μA mm−1 cm−2) and limit of detection (0.6 × 10−6 m) with no need of additional functionalization. Thanks to this property, the stable deposition of a suitable enzyme, namely lactate dehydrogenase, on the electrode surface is used as a proof of concept of the applicability of this new platform for the realization of a biosensor. The possibility of having a single material suitable for antennas, electronics, and now sensing opens new opportunities for smart fabrics in wearable electronic applications

Nanostructured Au/Ti bimetallic electrodes in selective anodic oxidation of carbohydrates

he anodic oxidation of species possessing potentially oxidisable functionalities has been studied on a non conventional electrode system based on a Ti substrate partially coated by electrodeposited Au nanoparticles. The results show that the electrocatalytic behaviour of the Au nanoparticles, in the frame of such a bimetallic system, is very different from that of pure Au. In particular, catalytic synergy between Au and Ti leads to the electro-oxidation of aldoses and aldehydes, while ketoses and monohydric alcohols result electrochemically inert. A different behaviour has been observed in the case of bulk Au surface: all the species under investigation undergo oxidation, so that no selectivity is activated. A correlation is found between the actual electroactivity and the nature of the functional group, when considered together with the chemical structure of the molecule

Voltammetric determination of hydrogen peroxide at high concentration level using a copper electrode

The determination of strong oxidizing species is of outmost importance in a number of practical applications. However, the currently available analytical tools should be improved in terms of reliability, automation, and costs. With this respect amperometric techniques are particularly promising candidates; nevertheless, the performance of conventional electrode materials, such as Au and Pt, are unsatisfactory, particularly in terms of resistance to fouling. In addition, electroanalytical methods and devices most commonly pay highest attention to the determination of similar analytes present in trace. On the other hand, the determination of high concentrations is of particular importance in industrial and environmental frames. Especially with reference to similar situations, the present paper reports the electrochemical behavior and analytical effectiveness of an alternative electrode material, namely Cu, in the presence of H2O2 at high concentrations (up to 0.5 M) and at different pH values. Furthermore, the behavior in real, harsh matrices, namely wastewater samples exhibiting different levels of chemical oxygen demand, is also reported. The results have been fruitfully employed in the development of an analytical procedure for the determination of H2O2 in similar matrices. A statistical treatment of the electrochemical responses suggests that the repeatability and reproducibility are well adequat

Behaviour of Ti electrode in the amperometric determination of high concentrations of strong oxidising species

The study of the capabilities of an unusual electrode material, namely, Ti, is presented: the amperometric determination of species showing responses that, on different materials, cannot be often profitably exploited, is proposed. H2O2 and HClO are successfully analysed, even at high concentrations. In similar conditions, which are quite common in industrial environments, these strong oxidising species are determined by time-consuming, off- or at-line, and multistep procedures. A complex real matrix, such as an industrial detergent, containing high H2O2 concentrations, has been taken as a meaningful study case to check the effectiveness of the electrode system and procedure proposed. Keywords: Amperometric sensor, Titanium electrode, Hydrogen peroxide, Hypochlorite ions, Strong oxidant

Preliminary evaluation of the use of a disposable electrochemical sensor for selective identification of Δ9-tetrahydrocannabinol and cannabidiol by multivariate analysis

The widespread diffusion of products deriving from Cannabis sativa L. led to the necessity of rapid and reliable methods for the identification of samples containing Δ9-tetrahydrocannabinol (THC), the psychoactive component of the plant, which imparts mental distortions and hallucinations. Although some efficient electrochemical sensors have been already proposed for such a purpose, they do not consider that the plant may also contain huge amounts of cannabidiol (CBD), which possesses an electroactive moiety quite similar to that of THC. The definition of both THC and CBD concentration is at the basis of discrimination between recreational-type and fibretype cannabis samples; detection of these species is not only important in vegetable samples but also in relevant commercial products and in biological fluids. We proposed here a screen-printed electrode coated with a layer of carbon black for the rapid identification of samples containing THC irrespectively of the simultaneous presence of CBD. The most performing carbon black typology used for such a purpose was chosen among various commercial products tested on the basis of preliminary tests performed on 1,3-dihydroxybenzene, constituting the redox active moiety of cannabinoids. The voltammetric responses collected in various solutions containing different amount of THC and CBD were initially elaborated by Principal Component Analysis, assessing the possibility of identifying samples with similar concentrations of THC irrespectively of the CBD concentration values, and vice-versa. Afterwards a preliminary Partial Last Square regression was performed to evaluate the possibility of a quantitative analysis of both THC and CBD. This approach suggests the possibility of using the sensor proposed to screen samples containing THC even in the presence of high amounts of CBD

Development of an electrochemical sensor based on carbon black for the detection of cannabidiol in vegetable extracts

A glassy carbon electrode chemically modified with a carbon black coating is proposed here for the rapid and portable determination of cannabidiol (CBD) in a commercial Cannabis seed oil and in fibre-type Cannabis sativa L. leaves. The mechanism of CBD oxidation was studied in relation to simpler phenyl derivatives bearing the same electroactive group, namely resorcinol and 2-methylresorcinol. These molecules also allowed us to determine the best conditions for the electrochemical detection of CBD, as to the pH value and to the best solvent mixture to use. Carbon black was chosen among nanostructured carbon-based materials owing to its outstanding features as an electrode modifier for analyte detection. The performance of the modified electrode was determined by flow injection analyses of standard solutions of CBD, obtaining a linear correlation between the oxidation current and the analyte concentration; the sensor response is characterised by suitable repeatability and reproducibility. The analysis of commercial products by the standard addition method allowed us to ascertain the accuracy of the sensor for the detection of CBD in real samples

Amperometric paper sensor based on Cu nanoparticles for the determination of carbohydrates

In the present article the development of a paper-based amperometric sensor for the determination of glucose and of the total carbohydrates is described. The motivation of the study lies in the necessity of novel low cost and fast methods for the determination of sugars in foodstuff; the commonly used procedures, in fact, often suffer from inaccuracy. To this aim, paper-based electrodes have been fabricated through the deposition of an electrically conductive ink based on Cu nanoparticles, graphite and polystyrene. In order to gain highest oxidation currents for glucose, i.e. to increase the sensitivity of the sensor, the composition of the ink has been optimised through a suitable experimental design. The performance of the paper-based system has been estimated in glucose, 0.1 M KOH solution. The estimated concentration value calculated from the calibration curve is ca. 10.4 mM (0.6 mM standard deviation) when a probe solution containing 10.1 mM glucose is used. In addition, the effectiveness of the system has been verified in real matrices, i.e. soft drinks: calibration curves lead to accurate estimation of the total carbohydrates concentration. On the basis of a suitable t-test, the probability of being wrong in rejecting the proper null hypothesis is lower than 1%

Development of an electrochemical sensor based on carbon black for the detection of cannabidiol in vegetable extracts

A glassy carbon electrode chemically modified with a carbon black coating is proposed here for the rapid and portable determination of cannabidiol (CBD) in a commercial Cannabis seed oil and in fibre-type Cannabis sativa L. leaves. The mechanism of CBD oxidation was studied in relation to simpler phenyl derivatives bearing the same electroactive group, namely resorcinol and 2-methylresorcinol. These molecules also allowed us to determine the best conditions for the electrochemical detection of CBD, as to the pH value and to the best solvent mixture to use. Carbon black was chosen among nanostructured carbon-based materials owing to its outstanding features as an electrode modifier for analyte detection. The performance of the modified electrode was determined by flow injection analyses of standard solutions of CBD, obtaining a linear correlation between the oxidation current and the analyte concentration; the sensor response is characterised by suitable repeatability and reproducibility. The analysis of commercial products by the standard addition method allowed us to ascertain the accuracy of the sensor for the detection of CBD in real samples

On the feasibility of a portable electrochemical measuring system for the on-site measurement of cannabinoids

Given the neuroprotective, anti-inflammatory, and analgesic properties of cannabidiol (CBD), many countries have recently legalized the use of fiber-type Cannabis products, including those known as 'Cannabis light'. Nonetheless, in freely commercialized products, it is not uncommon to find Δ9-tetrahydrocannabinol (THC), the principal psychoactive constituent of cannabis, in concentrations exceeding the legal limit. To determine whether a product is commercially viable, the THC/CBD ratio is typically analyzed using chromatographic techniques. However, chromatographic techniques have costs, complexity, and response times that prevent their in-situ use, making control actions much more expensive and ineffective. In this work, we report our preliminary activities aimed at verifying the possibility of performing in-situ analysis of cannabinoids in cannabis-derived products using an ad-hoc designed measuring system based on screen-printed electrodes modified with carbon black. The results obtained from preliminary tests comparing fiber cannabis (legal THC concentration) and recreational cannabis (illegal THC concentration) suggest that the proposed system can allow the effective and efficient in-situ analysis of cannabis-derived products

Synthesis, spectroscopic and electrochemical characterization of Co(II)-terpyridine based metallopolymer

A new oligothienyl-based metallopolymer including Co(terpyridine)2complex units is synthesised by electrochemical oxidation of the relevant monomer. The chemical structure of the polymer chains and the electronic interaction between the organic portions and the metal centres are investigated by spectroscopic (X-rays photoelectron spectroscopy included), electrochemical, and spectroelectrochemical techniques. Thanks to the low potential of the Co(III)/Co(II) redox couple in the Co(terpyridine)2complex and to the presence of oligothienyl spacer, strong electron interaction between the organic backbone and the metal centres have been demonstrated