Dynamic Raman Spectroelectrochemistry of Single Walled Carbon Nanotubes modified electrodes using a Langmuir-Schaefer method

Spectroelectrochemistry, the future of visualizing electrode processes by hyphenating electrochemistry with spectroscopic techniques

Reviewing the future of electrochemistry combined with infrared, Raman, and nuclear magnetic resonance spectroscopy as well as mass spectrometry.

Interference of single walled carbon nanotubes (SWCNT) in the measurement of lipid peroxidation in aquatic organisms through TBARS assay

Nanomaterials (NM) exhibit unique properties due their size and relative area, but the mechanisms and effects in the living organisms are yet to be unfold in their totality. Potential toxicity mechanisms concerning NM as carbon nanotubes include oxidative stress generation. Several fluorimetric and colorimetric methods have been systematically used to measure NM toxicity, and controversial results have been reported. One of the problems can be related to the interference effects induced by NM, leading to artifacts that can lead to misleading conclusions. In present study, it was performed in vitro assays with two aquatic species: the zebrafish Danio rerio and the polychaete Laeonereis acuta to evaluate the potential interference capacity of single-wall carbon nanotubes (SWCNT) in a fluorometric method (TBARS assay) to measure lipid peroxidation. Obtained results indicated that gills and brain of zebrafish presented a lowered fluorescence only at extremely high concentrations (50 and 500mg/L). Determinations in anterior, middle, and posterior body regions of L. acuta showed a quite different pattern: high fluorescence at low SWCNT concentrations (0.5mg/L) and lowering at the highest (500mg/L). To eliminate matrix effect of biological samples, tests employing the standard for TBARS assay, 1,3,3-tetramethoxipropane, were run and the results showed again higher fluorescence values at low concentrations (0.5-5mg SWCNT/L), a technique artifact that could lead to misleading conclusions since higher fluorescence values implicate higher TBARS concentration, implying oxidative stress. Using the colorimetric FOX assay with cumene hydroperoxide as standard presented remarkable better results since no artifacts were observed in the same SWCNT concentration range that employed with the TBARS technique.

In-situ Evidence of the Redox-State Dependence of Photoluminescence in Graphene Quantum Dots

Changes in the optical properties of graphene quantum dots (GQD) during electrochemical reduction and oxidation were investigated by photoluminescence (PL) spectroelectrochemistry, which provided direct in situ evidence of the dependence of GQD luminescence on their redox state. We demonstrated that GQD PL intensity was enhanced upon reduction (quantum yield increased from 0.44 to 0.55) and substantially bleached during oxidation (quantum yield ∼0.12). Moreover, PL emission blue/red-shifted upon GQD reduction/oxidation, rendering information about electronic transitions involved in the redox processes, namely, the π → π* and the n → π* transitions between energy levels of the aromatic sp² domains and the functional groups, respectively. PL intensity changes during GQD reduction/oxidation resulted from a variation in structural changes in GQD as a result of charge injection, as corroborated by in situ Raman spectroelectrochemistry.

Optically transparent electrodes for spectroelectrochemistry fabricated with graphene nanoplatelets and single-walled carbon nanotubes

Hybrid optically transparent electrodes based on single-walled carbon nanotubes and graphene nanoplatelets have been fabricated. The new methodology can be used with other carbon nanomaterials.