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Chapter 6: The Essential Role of Electrode Materials in ECL Applications
No full textElectrochemiluminescence (ECL) is a phenomenon that occurs in the proximity of the electrode
surface, since the radicals involved in the formation of the light-emitting excited states are generated
after an electrochemical stimulus. The choice of the electrode material is crucial for the light
generation, because it influences the kinetic of the heterogeneous electron transfer reaction. For this
reason, the deep understanding of the whole ECL system, of the relative target application under
development, is of fundamental importance for the proper choice of the electrode material. In the
present chapter, different electrode materials are reported for different ECL applications, ranging
from noble gold electrodes, through transparent electrodes for ECL and microscopy techniques
combination, to carbon-based electrodes, which present fast kinetics for coreactant oxidation. Their
electrochemical behaviour and their ECL efficiencies have been reported mainly with
[Ru(bpy)3]2+/TPrA coreactant system in “oxidative-reduction” mechanism, but other coreactants
have been used, such as peroxydisulfate and benzoyl peroxide in “reductive-oxidation” mechanism.
A comprehensive and exhaustive electrochemical study of the above-written materials will be
presented in the next pages
Nanoelectrode Arrays Fabricated by Thermal Nanoimprint Lithography for Biosensing Application
Full text linkElectrochemical sensors are devices capable of detecting molecules and biomolecules in solutions and determining the concentration through direct electrical measurements. These systems can be miniaturized to a size less than 1 μm through the creation of small-size arrays of nanoelectrodes (NEA), offering advantages in terms of increased sensitivity and compactness. In this work, we present the fabrication of an electrochemical platform based on an array of nanoelectrodes (NEA) and its possible use for the detection of antigens of interest. NEAs were fabricated by forming arrays of nanoholes on a thin film of polycarbonate (PC) deposited on boron-doped diamond (BDD) macroelectrodes by thermal nanoimprint lithography (TNIL), which demonstrated to be a highly reliable and reproducible process. As proof of principle, gliadin protein fragments were physisorbed on the polycarbonate surface of NEAs and detected by immuno-indirect assay using a secondary antibody labelled with horseradish peroxidase (HRP). This method allows a successful detection of gliadin, in the range of concentration of 0.5–10 μg/mL, by cyclic voltammetry taking advantage from the properties of NEAs to strongly suppress the capacitive background signal. We demonstrate that the characteristics of the TNIL technology in the fabrication of high-resolution nanostructures together with their low-cost production, may allow to scale up the production of NEAs-based electrochemical sensing platform to monitor biochemical molecules for both food and biomedical applications
Electrochemiluminescence as emerging microscopy techniques
No full textThe use of electrochemiluminescence (ECL), i.e., chemiluminescence triggered by electrochemical stimulus, as emitting light source for microscopy is an emerging approach with different applications ranging from the visualization of nanomaterials to cell mapping. In this trend article, we give an overview of the state of the art in this new field with the purpose to illustrate all the possible applications so far explored as well as describing the mechanism underlying this transduction technique. The results discussed here would highlight the great potential of the combination between ECL and microscopy and how this marriage can turn into an innovative approach with specific application in analytical sciences. [Figure not available: see fulltext.]
DNA-Based Nanoswitches: Insights into Electrochemiluminescence Signal Enhancement
Full text linkElectrochemiluminescence (ECL) is a powerful transduction technique that has rapidly gained importance as a powerful analytical technique. Since ECL is a surface-confined process, a comprehensive understanding of the generation of ECL signal at a nanometric distance from the electrode could lead to several highly promising applications. In this work, we explored the mechanism underlying ECL signal generation on the nanoscale using luminophore-reporter-modified DNA-based nanoswitches (i.e., molecular beacon) with different stem stabilities. ECL is generated according to the "oxidative-reduction"strategy using tri-n-propylamine (TPrA) as a coreactant and Ru(bpy)32+ as a luminophore. Our findings suggest that by tuning the stem stability of DNA nanoswitches we can activate different ECL mechanisms (direct and remote) and, under specific conditions, a "digital-like"association curve, i.e., with an extremely steep transition after the addition of increasing concentrations of DNA target, a large signal variation, and low preliminary analytical performance (LOD 22 nM for 1GC DNA-nanoswtich and 16 nM for 5GC DNA-nanoswitch). In particular, we were able to achieve higher signal gain (i.e., 10 times) with respect to the standard "signal-off"electrochemical readout. We demonstrated the copresence of two different ECL generation mechanisms on the nanoscale that open the way for the design of customized DNA devices for highly efficient dual-signal-output ratiometric-like ECL systems
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Nanoelectrode Arrays Fabricated by Thermal Nanoimprint Lithography for Biosensing Application
No full textElectrochemical sensors are devices capable of detecting molecules and biomolecules in solutions and determining the concentration through direct electrical measurements. These systems can be miniaturized to a size less than 1 μm through the creation of small-size arrays of nanoelectrodes (NEA), offering advantages in terms of increased sensitivity and compactness. In this work, we present the fabrication of an electrochemical platform based on an array of nanoelectrodes (NEA) and its possible use for the detection of antigens of interest. NEAs were fabricated by forming arrays of nanoholes on a thin film of polycarbonate (PC) deposited on boron-doped diamond (BDD) macroelectrodes by thermal nanoimprint lithography (TNIL), which demonstrated to be a highly reliable and reproducible process. As proof of principle, gliadin protein fragments were physisorbed on the polycarbonate surface of NEAs and detected by immuno-indirect assay using a secondary antibody labelled with horseradish peroxidase (HRP). This method allows a successful detection of gliadin, in the range of concentration of 0.5-10 μg/mL, by cyclic voltammetry taking advantage from the properties of NEAs to strongly suppress the capacitive background signal. We demonstrate that the characteristics of the TNIL technology in the fabrication of high-resolution nanostructures together with their low-cost production, may allow to scale up the production of NEAs-based electrochemical sensing platform to monitor biochemical molecules for both food and biomedical applications
Enhancing electrochemiluminescence intensity through emission layer control
No full textElectrochemiluminescence (ECL), an intriguing luminescent phenomenon induced by electrochemical stimulation, has evolved from studying electron transfer reactions to a powerful analytical method and imaging technique. ECL can be generated through annihilation or co-reactant methods, with recent advancements integrating it into imaging devices for diverse applications. This review traces the evolution of ECL from its early applications to recent developments in imaging technology. Notably, the utilization of charge-coupled devices (CCD) and electron multiplying charge-coupled devices (EMCCD) in ECL microscopy has revolutionized imaging capabilities, making it a cost-effective option for point-of-care testing. The review explores the heterogeneous ECL mechanism, emphasizing its limitations and challenges in visualizing objects away from the electrode surface. The synergy between ECL and microscopy is highlighted, showcasing its diverse applications and contributions to understanding ECL mechanisms and improving its use in biological contexts. Finally, the review encapsulates innovative approaches in material design, surface modification, and electrode architecture, providing a comprehensive overview of strategies to control the active layer of the ECL and advance ECL microscopy
Variations on the Author
Full text link“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
A perspective on the potential impact of microplastics and nanoplastics on the human central nervous system
No full textHumans are constantly exposed to microplastics and nanoplastics (MNPs). Although significant gaps remain in our understanding of their adverse effects on human health, it is increasingly evident that MNPs can penetrate physiological barriers and accumulate in various locations within the human body. Analytical limitations in tracking and measuring nanoplastics in physiological media may persist for several years before we can accurately detect these particles in the human body and establish a clear link between exposure to them and associated hazards. In addition to the few studies that have emerged recently, our knowledge of chemicals with properties similar to those of MNPs, as well as other types of nanomaterials, suggests that MNPs may cross the blood-brain barrier (BBB) and potentially induce damage to the human central nervous system. Here, we provide an overview of the limited number of studies available on this topic and present a perspective on the potential pathways through which MNPs may penetrate the BBB. We also discuss the main mechanisms by which MNPs could potentially impact the central nervous system (CNS), with a focus on neurodegenerative diseases such as Alzheimer's disease (AD), Parkinson's disease (PD), multiple sclerosis (MS), and amyotrophic lateral sclerosis (ALS). This information could contribute to the development of tailored studies exploring the negative effects of MNPs on the CNS
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