Heavy metals ions (HMI), if not properly handled, used and disposed, are a hazard for the ecosystem and pose serious risks for human health. They are counted among the most common environmental ...pollutants, mainly originating from anthropogenic sources, such as agricultural, industrial and/or domestic effluents, atmospheric emissions, etc. To face this issue, it is necessary not only to determine the origin, distribution and the concentration of HMI but also to rapidly (possibly in real-time) monitor their concentration levels in situ. Therefore, portable, low-cost and high performing analytical tools are urgently needed. Even though in the last decades many analytical tools and methodologies have been designed to this aim, there are still several open challenges. Compared with the traditional analytical techniques, such as atomic absorption/emission spectroscopy, inductively coupled plasma mass spectrometry and/or high-performance liquid chromatography coupled with electrochemical or UV-VIS detectors, bio- and biomimetic electrochemical sensors provide high sensitivity, selectivity and rapid responses within portable and user-friendly devices. In this review, the advances in HMI sensing in the last five years (2016-2020) are addressed. Key examples of bio and biomimetic electrochemical, impedimetric and electrochemiluminescence-based sensors for Hg
, Cu
, Pb
, Cd
, Cr
, Zn
and Tl
are described and discussed.
There is a growing interest in the technological transfer of highly performing electrochemical sensors within portable analytical devices for the in situ monitoring of environmental contaminants, ...such as perfluorooctanesulfonic acid (PFOS). In the redesign of biomimetic sensors, many parameters should be taken into account from the working conditions to the electrode surface roughness. A complete characterization of the surface modifiers can help to avoid time-consuming optimizations and better interpret the sensor responses. In the present study, a molecularly imprinted polymer electrochemical sensor (MIP) for PFOS optimized on gold disk electrodes was redesigned on commercial gold screen-printed electrodes. However, its performance investigated by differential pulse voltammetry was found to be poor. Before proceeding with further optimization, a morphological study of the bare and modified electrode surfaces was carried out by scanning electron microscopy–energy-dispersive X-ray spectrometry (SEM–EDS), atomic force microscopy (AFM) and profilometry revealing an heterogeneous distribution of the polymer strongly influenced by the electrode roughness. The high content of fluorine of the target-template molecule allowed to map the distribution of the molecularly imprinted polymer before the template removal and to define a characterization protocol. This case study shows the importance of a multi-analytical characterization approach and identify significant parameters to be considered in similar redesigning studies.
This paper describes the analysis of two near-spherical metallic inclusions partially incorporated within two Roman raw glass slags in order to elucidate the process that induced their formation and ...to determine whether their presence was related to ancient glass colouring processes. The theory of metallic scraps or powder being used in Roman times for glass-making and colouring purposes is widely accepted by the archaeological scientific community, although the assumption has been mainly based on oral traditions and documented medieval practices of glass processing. The analysis of the two inclusions, carried out by X-ray computed tomography, electrochemical analyses, and scanning electron microscopy, revealed their material composition, corrosion and internal structure. Results indicate that the two metallic bodies originated when, during the melting phase of glass, metal scraps were added to colour the material: the colloidal metal-glass system reached then a supersaturation condition and the latter ultimately induced metal expulsion and agglomeration. According to the authors' knowledge, these two inclusions represent the first documented and studied finds directly associated with the ancient practise of adding metallic agents to colour glass, and their analysis provides clear insights into the use of metallic waste in the glass colouring process.
•Small target analyte detection with nano-film coated D-shaped fiber.•Perfluorooctanoic acid detection via lossy mode resonance phenomenon.•Label-free optical sensing strategies based-on delipidated ...human serum albumin.
The determination of per- and polyfluoroalkyl substances (PFAS) in environmental samples, such as drinking waters, requires the design of high performing and versatile sensing strategies. Label-free biosensing platforms based on specialty fiber optics are a valid option to face this challenge. Among them, lossy mode resonance (LMR) fiber optic biosensors are showing remarkable performance in terms of detection limit, selectivity, and reproducibility. The detection of small molecules, such as perfluorooctanoic acid (PFOA), can be achieved with the help of well-designed biological recognition layers. In this study, the biosensing potentialities of a label-free LMR-assisted optical platform based on nanocoated fibers are investigated. Delipidated human serum albumin (hSA) was used as biological recognition layer for PFOA in aqueous solution. Different fiber functionalization protocols based on the covalent immobilization of hSA were tested. The conformational changes related to the formation of hSA/PFOA complex were followed via optical monitoring of LMR spectral shift, showing a trend that can be modeled with Langmuir adsorption isotherm. These results confirmed the potentiality of LMR-based fiber biosensors for the detection of small molecules, such as PFOA, in synthetic samples.
The ageing behavior of phenol formaldehyde (PF) foam, a material increasingly used in modern-contemporary art, was investigated by a multi-analytical approach. PF foams with open- and closed-cell ...structures were selected and analyzed in their unaged and naturally indoor-aged state by employing optical microscopy (OM) and fiber optical reflectance spectroscopy (FORS) for assessing their morphology and color alteration. Micro-Fourier transform infrared spectroscopy (μ-FTIR) was used for determining chemical changes and oxidation processes, and the acidity was monitored by pH measurements. The results clearly showed the extreme sensitivity of both open- and closed-cell PF foams to conditions typically found in indoor museums. OM indicated that the cells of the foams are prone to disrupt, and a tendency towards a red color shift was observed with FORS. μ-FTIR revealed the formation of quinone groups resulting from oxidation reactions. Finally, a slight decrease in the acidity was found by pH measurements.
In this work we study the surface enhanced Raman scattering (SERS) produced by hierarchical nanostructures obtained by coupling different anisotropic nanomaterial of two SERS active metals, namely Ag ...nanostars (AgNSs) and Au nanowires (AuNWs). Ag nanostars (AgNSs) are prepared, by a two-step one-pot synthesis by reduction of AgNO3 with hydroxylamine, trisodium citrate and NaOH. AuNWs are obtained by electroless templated synthesis in track-etched polycarbonate membranes with following etching of the template. The two precursors are bound together by bridging with the bifunctional cysteamine molecule, obtaining AgNS@AuNW hierarchical structures. Benzenethiol (BT) is adsorbed on the nanostructured material and used as SERS probe to study the amplification of Raman signals. Experimental results indicate significantly larger Raman enhancement when BT is adsorbed onto the AgNS@AuNW in comparison to AuNWs alone or decorated with quasi-spherical silver nanoparticles obtaining AgNP@AuNW. Digital simulations performed by the boundary element method agree with the experimental findings, showing higher number of hot spots and significantly higher SERS enhancements for AgNS@AuNW versus AuNWs or AgNSs or AgNP@AuNW.
Electrochemical methods for nitrate detection are very attractive since they are suitable for in-field and decentralized monitoring. Copper electrodes are often used to this aim as this metal ...presents interesting electrocatalytic properties towards nitrate reduction. In this research, we study improvements in the electrochemical analysis of nitrate in natural water and food by taking advantage of the detection capabilities of ensembles of copper nanowire electrodes (CuWNEEs). These electrodes are prepared via template electrodeposition of copper within the nanopores of track-etched polycarbonate (PC) membranes. A critical step in the preparation of these sensors is the removal of the template. Here, we applied the combination of chemical etching with atmospheric plasma cleaning which proved suitable for improving the performance of the nanostructured copper electrode. Analytical results obtained with the CuWNEE sensor for nitrate analyses in river water samples compare satisfactorily with those achieved by standard chromatographic or spectroscopic methods. Experimental results concerning the application of the CuWNEEs for nitrate analysis in food samples are also presented and discussed, with focus on nitrate detection in leafy vegetables.
This paper presents a previously unexplored biosensing strategy for detecting gliadin which exploits the crosslinking of gliadin with collagen, catalyzed by transglutaminase at the interfacial ...electron transfer rate, on a modified electrode. The process is monitored by electrochemical impedance spectroscopy using a glassy carbon electrode coated with a collagen layer. To validate the specificity of the response as well as to eliminate possible interferences from other proteins, such as soy protein or casein, the captured gliadin is further reacted with a specific anti-gliadin antibody. Changes in charge transfer resistance, measured from the Nyquist plots, scale linearly with the gliadin concentration in the range 5–20 mg/L, a range suitable for testing the gliadin concentration in gluten-free food commodities.
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•An enzymatic strategy for capturing gliadin on collagen is proposed•The cross-linking between collagen, gliadin and transglutaminase is monitored by electrochemical impedance spectroscopy•The modified electrode allows gliadin detection in the 5-20 mg/L range, i.e. below the limit for gluten free-products•The specificity of the analysis is assured by reacting gliadin with collagen and anti-gliadin antibody
The numerous advantages of disposable and screen-printed electrodes (SPEs) particularly in terms of portability, sensibility, sensitivity and low-cost led to the massive application of these ...electroanalytical devices. To limit the electronic waste and recover precious materials, new recycling processes were developed together with alternative SPEs fabrication procedures based on renewable, biocompatible sources or waste materials, such as paper, agricultural byproducts or spent batteries. The increased interest in the use of eco-friendly materials for electronics has given rise to a new generation of highly performing green modifiers. From paper based electrodes to disposable electrodes obtained from CD/DVD, in the last decades considerable efforts were devoted to reuse and recycle in the field of electrochemistry. Here an overview of recycled and recyclable disposable electrodes, sustainable electrode modifiers and alternative fabrication processes is proposed aiming to provide meaningful examples to redesign the world of disposable electrodes.
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•An overview of renewable disposable electrodes from paper-based and CDtrodes to plastic waste-based SPEs is provided.•Greener routes to the synthesis of electrode modifiers or the realization of disposable electrodes are described.•Recycling strategies and waste disposal must be integral part of this new outlook on sensors and biosensor development.
A combination of electrochemistry and luminescence methods was exploited to obtain information on the electrochemical activity and homogeneity of Nafion Langmuir−Blodgett films. The redox behavior of ...the Ru(bpy)3 2+ probe incorporated in the Nafion film was monitored by epifluorescence microscopy. The photoluminescent images, recorded by a charge-coupled device (CCD) camera, reflect the distribution of the probe in the film, which resulted as very uniform, particularly in comparison with spin-coated films. Apparent diffusion coefficients (D app) determined by cyclic voltammetry for films of less than 10 layers are in the range of 1 × 10−12 to 8 × 10−12 cm2 s−1, that is, 2 orders of magnitude lower than values reported in the literature for spin-coated Nafion films. The application to the electrode of a potential able to oxidize the luminescent Ru(bpy)3 2+ to the nonluminescent Ru(bpy)3 3+ switched off the photoluminescence with a response time that for the LB films was much shorter than that for the spin-coated ones. Experimental evidence and calculations indicate that lowering of the film thickness down to the nanometric level is very effective in shortening the switching time, notwithstanding the lowering of the D app value in LB films.
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