Spectroelectrochemistry (SEC) has been used for more than 50 years, but this set of techniques has not been widely used for quantitative analysis. For many years, no commercial instruments were ...available, which made very difficult to spread the use of SEC. Nowadays, only the creativity of the researchers is required to exploit the capabilities of SEC. This review is written with the aim of showing the potential of SEC, mainly for analytical chemistry. Here, we explain what SEC is, how analytical responses can be obtained, why these techniques are useful for sensors, with a brief description of its advantages in use, and, finally, we try to show the challenges that must be addressed in the next years. SEC can resolve interesting analytical problems using the high amount of data provided by this intrinsic trilinear technique. Given the quantitative analysis point of view of this review, the discussion of the SEC techniques is focused on UV/Vis absorption, photoluminescence and Raman SEC.
Novel single-walled carbon nanotube press-transfer electrodes (SW-PTEs) for microfluidic sensing are proposed. In this approach, carbon nanotubes are press-transferred on poly(methyl methacrylate) ...(PMMA) substrates and are easily coupled to microfluidic chips and act as the exclusive transducer in electrochemical sensing. The detector design consisted of a press-transferred SW film (7 mm × 1 mm) positioned and centered on the PMMA substrate (33 mm × 9 mm). The analytical performance of the SW-PTEs was deeply evaluated using two commercial SWs sources and employing a mixture of dopamine and catechol as model analytes. Analyte detection was influenced by the volume of commercial SW dispersion used in the fabrication of SW-PTEs, with 5 mL taken from a dispersion of 0.5 mg/100 mL being the most favorable volume. In addition, excellent repeatability (relative standard deviation (RSD) of ≤7%, n = 5), interelectrodes reproducibility (RSD ≤ 9%, n = 5), and an extreme resistance to fouling were obtained even after 1 h of microchip analysis with RSD values of ≤4% and ≤9% (n = 15) for migration times and peak heights, respectively. Good sensitivity, remarkable signal-to-noise characteristics, and a well-defined linear concentration dependence (r ≥ 0.990) was also obtained, which allowed these novel detectors to be considered as valuable tools for quantitative analysis. Analytical characterization of the SW-PTEs by field-emission scanning electron microscopy (FESEM) revealed individual bundles of SWs that were highly ordered over the PMMA at the background where the SW bundles were embedded on the PMMA substrate, giving the electrode a high stability. Furthermore, the laboratory-fabricated SW-PTEs can be afforded in any laboratory since they do not require clean-room facilities and are highly compatible with microfluidic scale, mass production, and disposability. In addition, the proposed approach draws new and exciting horizons for electrochemical microfluidic sensing, such as the use of other pure or hybrid nanomaterials and also the possibilities to incorporate biomolecules for highly selective sensing.
Dual MBs-based amperometric immunoplatform developed for simultaneous RANKL and TNF determination, and applied to the analysis of serum samples from breast cancer patients diagnosed with different ...HER2 subtypes.
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•First immunoplatform for simultaneous determination of RANKL and TNF.•Sandwich immunoassays onto Neutravidin-MBs and amperometric detection at SPdCEs.•LOD values of 2.6 and 3.0 pg mL−1 for RANKL and TNF, respectively.•Accurate determination in serum samples from BC patients with different HER2 subtypes.•Analyses require 90 min and just 5 μL of human serum per biomarker.
This paper describes a dual immunosensor using neutravidin-functionalized magnetic microbeads (Neu-MBs) and dual screen-printed carbon electrodes (SPdCEs) for the simultaneous amperometric determination of two emerging biomarkers related to breast cancer (BC) and metastasis: Receptor Activator of Nuclear Factor-κB Ligand (RANKL) and Tumor Necrosis Factor alpha (TNF). In the implemented methodology, sandwich-type immunocomplexes, using biotinylated specific capture, detector antibodies and HRP-labeled secondary antibodies, are formed onto Neu-MBs. Electrochemical detection was performed by amperometry (−0.20 V vs. the Ag pseudo-reference) electrode using the H2O2/hydroquinone (HQ) system upon capturing the Neu-MBs modified with the sandwich immunocomplexes for each target biomarker on the corresponding working electrode (WE) of SPdCEs. The approach exhibits high sensitivity offering detection limits of 2.6 and 3.0 pg mL−1 for RANKL and TNF, respectively, using simple protocols and taking 90 min as assay time. The usefulness of the dual immunoplatform was tested by determining RANKL and TNF levels in 5 μL of human serum from healthy controls and BC patients diagnosed with different HER2 subtypes. Results showed a higher expression of both biomarkers in BC patients (38 and 17 % higher for RANKL and TNF, respectively) and were in agreement to those obtained using the ELISA methodologies for each target biomarker involving the same immunoreagents. The obtained results show the potential of this immunoplatform to improve the reliability of BC diagnosis using fast and cost-effective procedures.
Spectroelectrochemistry of Quantum Dots Garoz‐Ruiz, Jesus; Perales‐Rondon, Juan V.; Heras, Aranzazu ...
Israel journal of chemistry,
August 2019, 2019-08-00, 20190801, Letnik:
59, Številka:
8
Journal Article
Recenzirano
Odprti dostop
Spectroelectrochemistry (SEC) is a set of techniques with many advantages in the study and characterization of materials. Although SEC has not yet been widely used to study quantum dots (QDs), the ...information extracted from SEC experiments about these nanostructures is very useful. Most of the works that use SEC to study QDs are high‐quality pieces of research. This review intends to show how to perform SEC in an easy way and what information can be obtained using these techniques. Most of the examples shown in this review are related to semiconductor and carbon QDs. After a brief introduction, some optoelectronic properties of QDs and the main SEC techniques are described. The capabilities of SEC for the study of QDs are illustrated with examples extracted from literature. Finally, the needs of SEC to become a user‐friendly technique and its evolution to become more powerful are commented in the last section of the review.
UV/Vis absorption spectroelectrochemistry (SEC) is a multi-response technique that has been commonly used for the characterization of materials and the study of reaction mechanisms. However, it has ...been scarcely used for quantitative purposes. SEC allows us to obtain two analytical signals simultaneously, yielding a dual sensor in just one experiment. In the last years, our group has developed new devices useful for analysis. In this work, a SEC device in parallel configuration, based on optical fibers fixed on screen-printed electrodes, was used to determine isoprenaline in a commercial drug, using both, the electrochemical and the spectroscopic signals. In this commercial drug, isoprenaline is accompanied in solution by other compounds. Among them is sodium metabisulfite, an antioxidant that strongly interferes in the isoprenaline determination. A simple pretreatment of the drug sample by bubbling wet-air allows us to avoid the interference of metabisulfite. Here, we demonstrate again the capabilities of UV/Vis absorption SEC as double sensor for analysis and we propose a simple pretreatment to remove interfering compounds.
A flexible electrode system entirely constituted by single-walled carbon nanotubes (SWCNTs) has been proposed as the sensor platform for β-nicotinamide adenine dinucleotide (NADH) detection. The ...performance of the device, in terms of potential at which the electrochemical process takes place, significantly improves by electrochemical functionalization of the carbon-based material with a molecule possessing an o-hydroquinone residue, namely caffeic acid. Both the processes of SWCNT functionalization and NADH detection have been studied by combining electrochemical and spectroelectrochemical experiments, in order to achieve direct evidence of the electrode modification by the organic residues and to study the electrocatalytic activity of the resulting material in respect to functional groups present at the electrode/solution interface. Electrochemical measurements performed at the fixed potential of +0.30 V let us envision the possible use of the device as an amperometric sensor for NADH detection. Spectroelectrochemistry also demonstrates the effectiveness of the device in acting as a voltabsorptometric sensor for the detection of this same analyte by exploiting this different transduction mechanism, potentially less prone to the possible presence of interfering species.
A number of renewable energy systems require an understanding and correlation of material properties and photoelectrochemical activity on the micro to nanoscale. Among these, conducting polymer ...electrodes continue to be important materials. In this contribution, an ultrasensitive scanning electrochemical cell microscopy (SECCM) platform is used to electrodeposit microscale thin films of poly(3-hexylthiophene) (P3HT) on an optically transparent gold electrode and to correlate the morphology (film thickness and structural order) with photoactivity. The electrochemical growth of P3HT begins with a thin ordered film up to 10 nm thick, after which a second more disordered film is deposited, as revealed by micro-Raman spectroscopy. A decrease in photoactivity for the thicker films, measured in situ immediately following film deposition, is attributed to an increase in bulk film disorder that limits charge transport. Higher resolution ex situ SECCM phototransient measurements, using a smaller diameter probe, show local variations in photoactivity within a given deposit. Even after aging, thinner, more ordered regions within a deposit exhibit sustained enhanced photocurrent densities compared to areas where the film is thicker and more disordered. The platform opens up new possibilities for high-throughput combinatorial correlation studies, by allowing materials fabrication and high spatial resolution probing of processes in photoelectrochemical materials.
The study of real samples is more complicated than the study of other systems. However, the inherent advantages of UV–vis absorption spectroelectrochemistry should overcome some difficulties related ...to direct measurements in complex matrices. For this reason, a singular spectroelectrochemistry device has been fabricated and validated. The novel cell is based on single-walled carbon nanotubes, which are filtered and subsequently press-transferred on a polyethylene terephthalate support using a stencil with a custom design. With this new methodology, working, counter, and reference electrodes are completely flat on the surface, where two optical fibers are fixed in a long optical path length configuration. To demonstrate the usefulness of this device and the power of spectroelectrochemistry techniques to solve problems of the current world, this device is used to quantitatively detect the concentration of ascorbic acid in a complex matrix such as a fruit, directly, without any previous sample pretreatment. The ease to fabricate the device, the advantages related to its use, and the excellent results obtained not only with univariate but also with multivariate analysis, shed more light on the analysis of samples as they occur in nature. According to the particular features of this cell, to the best of our knowledge this is the first spectroelectrochemical sensor that can be inserted directly in a biological matrix, laying the groundwork to perform in vivo measurements in a near future.
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•Bidimensional Spectroelectrochemistry is used for quantitative analysis.•The best spectroelectrochemistry configuration is easily selected.•Interferences can be avoided using the ...most suitable experimental setup.•Good figures of merit for epinephrine were obtained using parallel configuration.
This work demonstrates how the way a chemical system is sampled plays a key role in spectroelectroanalysis, illustrated by the quantification of an analyte in presence of an antioxidant compound. For this purpose, bidimensional spectroelectrochemistry experiments were performed using epinephrine as the model analyte and ascorbic acid as antioxidant and interfering compound, as a proof of concept. This is the first time that three calibration curves are obtained simultaneously on a single spectroelectrochemistry data set, one for the electrochemical signal and two for the optical responses in normal and parallel configurations. The differences between the two optical arrangements, that are related to the diffusion process which is an essential feature for the spectroelectrochemical detection of compounds, have been experimentally demonstrated. As can be observed, the spectral signal in parallel configuration allows us to obtain the best analytical results, since in this configuration only the first micrometers of the solution adjacent to the electrode surface are sampled, thus removing the interfering effect of the antioxidant compound. This fact does not occur with either the electrochemical signal or the spectral response in normal configuration. Furthermore, it has been shown that the parallel configuration provides better results than the normal configuration in terms of sensitivity. In summary, epinephrine is successfully detected in a simple and effective way, even in the presence of a direct antioxidant compound such as ascorbic acid at different concentrations levels, which makes spectroelectrochemistry a good choice for quantitative analysis.
The amount of qualitative and quantitative information provided by a UV–vis absorption spectroelectrochemistry (SEC) experiment is sometimes wasted. However, almost all electrochemical and ...spectroscopic data can provide valuable information. In this spirit, the main objective proposed in this work is the quantitative resolution of catechol/dopamine (CAT/DA) and dopamine/epinephrine (DA/EP) mixtures, using spectroelectrochemical sensors in long optical path length arrangement based on bare optical fibers in parallel configuration with respect to carbon nanotubes or screen-printed electrodes. These compounds show extremely similar electrochemical and spectroscopic responses at high acidic pH, being impossible to determine their concentrations in the mixtures just using univariate regression models. To our knowledge, the SEC ability to resolve complex mixtures has never been demonstrated before with signals with this degree of overlapping. The quantitative analysis of these mixtures is possible using multivariate regression analysis of a set of time-resolved spectroelectrochemical data with a powerful statistical tool such as parallel factor analysis (PARAFAC). PARAFAC enables us to extract all the information from the experiments, allowing us to quantify the different analytes in mixtures of varying concentrations with excellent results. This milestone for spectroelectroanalysis illustrates the expected capabilities of SEC and demonstrates experimentally the potential of this technique for sensing of biomolecules.
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•Homemade carbon nanotube electrodes or commercial screen-printed electrodes are used.•Bare optical fibers in parallel configuration offer excellent quantitative results.•Catechol/dopamine and dopamine/epinephrine mixtures in varying amounts are resolved.•These compounds show very similar electrochemical and optical signals at acidic pH.•Spectroelectrochemistry combined with PARAFAC is very useful for analysis.
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