Electrofluorochromic molecules share the unique property that their fluorescence changes as a function of their oxidation state. This makes them interesting from a fundamental perspective as molecular dyads are designed and synthesized to tune the interplay of electrochemical and luminescent properties of molecules. Electrofluorochromic systems also find applications in sensing because a fluorescent signal can be detected with high sensitivity. Moreover, in the recent years the interest in redox-switchable fluorescent polymers has strongly increased due to their applicability in display devices. Here, we review electrofluorochromic molecules and polymers; we emphasize their structures and functional principles and point to specific applications.@en

We report a strategy for the fabrication of a new type of electrochemical nanogap transducer. These nanogap devices are based on signal amplification by redox cycling. Using two steps of electron-beam lithography, vertical gold electrodes are fabricated side by side at a 70 nm distance encompassing a 20 attoliter open nanogap volume. We demonstrate a current amplification factor of 2.5 as well as the possibility to detect the signal of only 60 analyte molecules occupying the detection volume. Experimental voltammetry results are compared to calculations from finite element analysis.@en

We propose a new geometry for nanogap electrochemical sensing devices. These devices consist of two closelyspaced side-by-side electrodes which work under redox cycling conditions. Usingfinite element simulations,we investigate the effects of different geometric parameters on the redox cycling signal amplification to gaininsight into the electrochemical sensing performance of the device design. This will allow optimizing the sensorperformance of devices to be fabricated in the future@en

We report a novel, simple and cheap generator-collector electrode system, employing platinum leaves, with micron-sized pores and typically 100-300. nm thickness, sandwiched with a porous track etch membrane spacer with typically 30. nm diameter pores. The electrode assembly is sealed into a polymer lamination pouch with one side 2. mm diameter exposed to electrolyte solution. The generator electrode with sweeping potential (top or bottom electrode) shows transient current with high capacitive current component. The collector electrode with fixed potential shows well-defined steady state current response at low potential sweep rates. The fabricated device shows good performance in monitoring both 1,1'-ferrocenedimethanol oxidation and proton reduction redox processes. Oxygen sensor signals are assigned to a lowering of the steady state proton reduction current.@en

The post-synthetic modification (PSM) of two amino-MOFs with glucose oxidase is reported in this study. The multi-step approach preserved the MOFs' structure and allowed the production of enzyme-functionalized MOFs (MOFs@GOx), which retained the enzymatic activity and showed selective properties for glucose.@en

Electrochemical sensing is considered as one of the most powerful analytical detection techniques. Electrochemical methods have fast response time, high sensitivity and selectivity, and can be performed at low cost. Their inherent ease of miniaturization have made them so popular in recent years. Hence, electrochemical sensors have diverse applications including pathological, clinical, and environmental analyses. Miniaturization of analytical devices plays an important role in the sensor development studies. Miniaturized electrochemical sensors open up opportunities toward faster, more sensitive, more user friendly (ease to use) and portable systems compared to the traditional cumbersome bulky electrochemical cells. Thanks to the recent advances in nano/micro fabrication techniques, scaling down the electrode size to micro and even nano dimensions and developing “lab on a chip” technology is achievable and is considered as a hot topic in electrochemistry. Traditional electrochemical cells are composed of three electrodes: a working electrode, a reference electrode and a counter electrode. However, in this thesis the main focus is on the dual- electrode systems, where two closely spaced working electrodes are placed next to each other. Hence the events at each electrode can be affected by the other one. These two electrodes can be biased independently and the current of each can be detected separately. Biasing one of the electrodes in an oxidizing potential (according to a desired redox active analyte) and the other in a reducing potential, results in a repeated successive oxidation and reduction of analyte species on the two electrode surfaces. Accordingly, the current at each electrode is amplified which leads to a higher sensitivity. Reducing the gap size between the electrodes can further enhance the sensitivity and amplification factor (the ratio between the limiting current in dual electrode mode and the current in a single electrode mode) of the device. @en

In nanofluidic electrochemical sensors based on redox cycling, zeptomole quantities of analyte molecules can be detected as redox-active molecules travel diffusively between two electrodes separated by a nanoscale gap. These sensors are employed to study the properties of multiferrocenylic compounds in nonpolar media, 2,3,4-triferrocenylthiophene and 2,5-diferrocenylthiophene, which display well-resolved electrochemically reversible one-electron transfer processes. Using stochastic analysis, we are able to determine, as a function of the oxidation states of a specific redox couple, the effective diffusion coefficient as well as the faradaic current generated per molecule, all in a straightforward experiment requiring only a mesoscopic amount of molecules in a femtoliter compartment. It was found that diffusive transport is reduced for higher oxidation states and that analytes yield very high currents per molecule of 15 fA.@en

Interference or crosstalk of coexisting redox species results in overlapping of electrochemical signals, and it is a major hurdle in sensor development. In nanogap sensors, redox cycling between two independently biased working electrodes results in an amplified electrochemical signal and an enhanced sensitivity. Here, we report new strategies for selective sensing of three different redox species in a nanogap sensor of a 2 fL volume. Our approach relies on modulating the electrode potentials to define specific potential windows between the two working electrodes; consequently, specific detection of each redox species is achieved. Finite element modeling is employed to simulate the electrochemical processes in the nanogap sensor, and the results are in good agreement with those of experiments.@en