T. Šafarik, A. Karajić, S. Reculusa, P. N. Bartlett, N. Mano, A. Kuhn
Redox cycling (RC) is a powerful tool capable of amplifying faradaic currents in electroanalytical measurements, thus allowing an enhancement of sensitivity through fast multiple sequential oxidation and reduction reactions of a redox-active analyte. Present state-of-the-art RC devices are mostly based on planar electrode geometries either in 2D or 3D configurations, requiring cleanroom facilities and expensive microfabrication techniques. Here, we report the electrochemical elaboration and characterization of a three-dimensional coaxial macroporous twin-electrode, obtained by following a low-cost bottom-up approach. A nanoengineered highly organized porous material is the bases for the design of two threaded cylindrical porous gold microelectrodes with a gap in the micrometer range that can be fine-tuned. The potentials of the outer and inner electrodes are biased at values above and below the redox potential of the analyte so that a given molecule can participate several times in the electron exchange reaction by shuttling between both electrodes. The resulting signal amplification, combined with a straightforward synthesis strategy of the electrode architecture allows envisioning numerous (bio)electroanalytical applications.
S. M. Beladi-Mousavi, G. Salinas, L. Bouffier, N. Sojic, A. Kuhn
Spatial confinement of chemical reactions or physical effects may lead to original phenomena and new properties. Here, the generation of electrochemiluminescence (ECL) in confined free-standing 2D spaces, exemplified by surfactant-based air bubbles is reported. For that, the ultrathin walls of the bubbles (typically in the range of 100 - 700 nm) are chosen as a host where graphene sheets, acting as bipolar ECL-emitting electrodes are trapped and dispersed. The proposed system demonstrates that the required potential for the generation of ECL is up to three orders of magnitude smaller compared to conventional systems, due to the nanoconfinement of the potential drop. This proof-of-concept study demonstrates the key advantages of a 2D environment, allowing a wireless activation of ECL at rather low potentials, compatible with (bio)analytical systems.
Electrochemiluminescence (ECL) has been widely applied in imaging owing to its high signal-to-noise ratio, remarkable sensitivity, wide linear range, high spatio-temporal resolution and near-zero background light that distinguish it from other microscopic techniques and electrochemical methods. The imaging technology based on ECL has been used in the fields of immunosensing, pathological cell detection and drug analysis. Additionally, its simple operation and ability to detect dynamic processes and catalytic sites emphasize its potential in the field of material surface and interface research, biological analysis in vivo and cell visualization. At the same time, the emergence of a variety of nanomaterials and new microscopic analysis equipment has further promoted the development of high resolution ECL imaging technology. Firstly, this paper introduces the development of ECL technology and the mechanism of the main ECL systems. Then various forms of ECL imaging methods are further described. On this basis, the research progress of ECL imaging technology in the fields of single particle imaging, fingerprint structure analysis and single cell microscopic imaging is reviewed. Finally, the authors give their views about the prospects of ECL imaging technology.
G. Salinas, F. Malacarne, G. Bonetti, R. Cirilli, T. Benincori, S. Arnaboldi, A. Kuhn
Microfluidic valves based on chemically responsive materials have gained considerable attention in recent years. Herein a wireless enantio-responsive valve triggered by bipolar electrochemistry combined with chiral recognition is reported. A conducting polymer actuator functionalized with the enantiomers of an inherently chiral oligomer was used as bipolar valve to cover a tube loaded with a dye, and immersed in a solution containing chiral analytes. When an electric field is applied, the designed actuator shows a reversible cantilever-type deflection, allowing the release of the dye from the reservoir. The tube can be opened and closed by simply switching the polarity of the system. Qualitative results show the successful release of the colorant, driven by chirality and redox reactions occurring at the bipolar valve. The device works well even in the presence of chemically different chiral analytes in the same solution. These systems open up new possibilities in the field of microfluidics, including also controlled drug delivery applications.
Binxiao Li, Xuedong Huang, Yanwei Lu, Zihui Fan, Bin Li, Dechen Jiang, Neso Sojic and Baohong Liu
Direct imaging of single-molecule and its movement is of fundamental importance in biology, but challenging. Herein, aided by the nano-confinement effect and resultant high reaction activity within metal–organic frameworks (MOFs), the designed Ru(bpy)32+ embedded MOF complex (RuMOFs) exhibits bright electrochemiluminescence (ECL) emission permitting high-quality imaging of ECL events at single molecule level. By labeling individual proteins of living cells with single RuMOFs, the distribution of membrane PTK7 proteins at low-expressing cells is imaged via ECL. More importantly, the efficient capture of ECL photons generated inside the MOFs results in a stable ECL emission up to 1 h, allowing the in operando visualization of protein movements at the cellular membrane. As compared with the fluorescence observation, near-zero ECL background surrounding the target protein with the ECL emitter gives a better contrast for the dynamic imaging of discrete protein movement. This achievement of single molecule ECL dynamic imaging using RuMOFs will provide a more effective nanoemitter to observe the distribution and motion of individual proteins at living cells.
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