Properties and customization of sensor materials for biomedical applications.

Low-power chemo- and biosensing devices capable of monitoring clinically important parameters in real time represent a great challenge in the analytical field as the issue of sensor calibration pertaining to keeping the response within an accurate calibration domain is particularly significant (1–4). Diagnostics, personal health, and related costs will also benefit from the introduction of sensors technology (5–7). In addition, with the introduction of Registration, Evaluation, Authorization, and Restriction of Chemical Substances (REACH) regulation, unraveling the cause–effect relationships in epidemiology studies will be of outmost importance to help establish reliable environmental policies aimed at protecting the health of individuals and communities (8–10). For instance, the effect of low concentration of toxic elements is seldom investigated as physicians do not have means to access the data (11)

Carbon nanoparticulate films as effective scaffolds for mediatorless bioelectrocatalytic hydrogen oxidation

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Three-Phase Electrochemistry of a Highly Lipophilic Neutral Ru-Complex Having a Tridentate Bis(benzimidazolate)pyridine Ligand

Here we describe the synthesis and electrochemical testing of a heteroleptic bis(tridentate) ruthenium(II) complex [RuII(LR)(L)]0 (LR =2,6-bis(1-(2-octyldodecan)benzimidazol-2-yl)pyridine, L = 2,6-bis(benzimidazolate)pyridine). It is a neutral complex which undergoes a quasireversible oxidation and reduction at relatively low potential. The newly synthetized compound was used for studies of ion-transfer at the three-phase junction because of the sensitivity of this method to cation expulsion. The [RuII(LR)(L)]0 shows exceptional stability during cycling and is sufficiently lipophilic even after oxidation to persist in the organic phase also using very hydrophilic anions such as Cl−. Given its low redox potential and strong lipophilicity this compound will be of interest as an electron donor in liquid-liquid electrochemistry

Scanning electrochemical microscopy activity mapping of electrodes modified with laccase encapsulated in sol-gel processed matrix

Electrodes modified with sol-gel encapsulated laccase (isolated from Cerrena unicolor) exhibiting mediated or mediatorless bioelectrocatalytic dioxygen reduction activity were inspected using confocal laser scanning microscopy, atomic force microscopy and scanning electrochemical microscopy. Potential-driven leaching of the redox mediator 2,2'-azino-bis(3-ethylbenzothiazoline-6-sulfonate) from carbon ceramic electrodes covered by hydrophilic silicate-encapsulated laccase was detected during electrocatalytic action. Strongly non-homogeneous lateral distribution of the activity towards dioxygen reduction was found by redox competition mode of scanning electrochemical microscopy using a similar electrode with syringaldazine as redox mediator. Hydrogen peroxide formation at these electrodes is detected at potentials lower than 0.05 V. It is ascribed to the electrochemical oxygen reduction at the carbon material while laccase-catalyzed oxygen reduction occurs below 0.35 V without hydrogen peroxide formation. The scanning electrochemical microscopy images of electrodes consisting of single-walled carbon nanotubes non-covalently modified with pyrenesulfonate and laccase encapsulated in a sol-gel processed silicate film confirm direct electron transfer electrocatalysis in redox competition mode experiments and show that the enzyme is evenly distributed in the composite film. In conclusion scanning electrochemical microscopy proved to be useful for mapping of enzyme activity on different materials

Electrochemistry in an Optical Fiber Microcavity - Optical Monitoring of Electrochemical Processes in Picoliter Volumes

In this work, we demonstrate a novel method for multi-domain analysis of properties of analytes in volumes as small as picoliter, combining electrochemistry and optical measurements. A microcavity in-line Mach-Zehnder interferometer (µIMZI) obtained in a standard single-mode optical fiber using femtosecond laser micromachining was able to accommodate a microelectrode and optically monitor electrochemical processes inside the fiber. The interferometer shows exceptional sensitivity to changes in optical properties of analytes in the microcavity. We show that the optical readout follows the electrochemical reactions. Here, the redox probe (ferrocenedimethanol) undergoing reactions of oxidation and reduction changes the optical properties of the analyte (refractive index and absorbance) that are monitored by the µIMZI. Measurements have been supported by numerical analysis of both optical and electrochemical phenomena. On top of a capability of the approach to perform analysis in microscale, the difference between oxidized and reduced forms in the near-infrared can be clearly measured using the µIMZI, which is hardly possible using other optical techniques. The proposed multi-domain concept is a promising approach for highly reliable and ultrasensitive chemo- and biosensing

Near-Field and Far-Field Sensitivities of LSPR Sensors

International audienceThe present study compares the near-field and far-field sensitivities of localized surface plasmon resonance (LSPR) sensors. To put into evidence the difference between far-field and near-field sensors, optical extinction measurements have been performed on gold nanoparticle gratings coated with dielectric superstrates of varying thicknesses. The potential of LSPR sensors is usually considered to lie in the near-field regime. Therefore, a comparison of the near-field sensitivities for gold nanoparticle gratings and continuous gold films of 50 nm in thickness is provided. The difference in refractive index sensitivities of both sensors is discussed in relation with the decay length of the evanescent near-field. SPRs sensors are usually considered more sensitive than LSPRs in terms of the m factor, refractive index sensitivity. We argue that the m factor sensitivity can only be defined for thick (15--100 nm) superstrates; for thin superstrates (d < 15 nm), the decay length of the evanescent field must be taken into account to properly compare both sensors