Due to the biological importances of thiols, such as cysteine, homocysteine and glutathione, the development of optical probes for thiols has been an active research area in recent few years. This critical review focuses on the fluorescent or colorimetric sensors for thiols according to their unique mechanisms between sensors and thiols, including Michael addition, cyclization with aldehyde, cleavage of sulfonamide and sulfonate ester by thiols, cleavage of selenium–nitrogen bond by thiols, cleavage of disulfide by thiols, metal complexes-oxidation–reduction, metal complexes-displace coordination, nano-particles and others (110 references).

Fluorescent and colorimetric probes for detection of thiols

Superoxide ion (O2•–) is of great significance as a radical species implicated in diverse chemical and biological systems. However, the chemistry knowledge of O2•– is rather scarce. In addition, numerous studies on O2•– were conducted within the latter half of the 20th century. Therefore, the current advancement in technology and instrumentation will certainly provide better insights into mechanisms and products of O2•– reactions and thus will result in new findings. This review emphasizes the state-of-the-art research on O2•– so as to enable researchers to venture into future research. It comprises the main characteristics of O2•– followed by generation methods. The reaction types of O2•– are reviewed, and its potential applications including the destruction of hazardous chemicals, synthesis of organic compounds, and many other applications are highlighted. The O2•– environmental chemistry is also discussed. The detection methods of O2•– are categorized and elaborated. Special attention is given to the f...

Superoxide Ion: Generation and Chemical Implications

Blue luminescent nanocrystals (NCs) were prepared electrochemically from multiwalled carbon nanotubes (MWCNTs) for the first time. The carbon NCs were characterized by UV−vis, photoluminescence, Raman, XRD spectroscopy, and high-resolution transmission electron microscopy. The structure evolution of the MWCNTs during electrochemical treatments was monitored by SEM ex situ. Since the MWCNTs were formed with scrolled graphene layers, we propose that tetrabutyl ammonium (TBA) cations most probably intercalate into the gaps and the defects during electrochemical cycling and break the tubes near the defects.

An Electrochemical Avenue to Blue Luminescent Nanocrystals from Multiwalled Carbon Nanotubes (MWCNTs)

A review. Physicochem. properties of ionic liqs. are discussed. Chem. and electrochem. reactivity in ionic liqs. is described including electrode reactions, electrode reaction kinetics, electrosynthesis, etc.

Electrochemical reactivity in room-temperature ionic liquids.

Electrocatalysis at graphite and carbon nanotube modified electrodes: edge-plane sites and tube ends are the reactive sites

Analytical strategies for the detection of sulfide: a review

Analytical determination of homocysteine: a review

The electrochemical oxidation of N,N-dimethylphenylenediamine at glassy carbon electrodes in aqueous solution in the pH range 3-6 is shown to lead to currents which are considerably amplified in the presence of dissolved hydrogen sulfide. The mechanism of the electrode process is investigated and the reaction is shown to provide an attractive basis for the amperometric sensing of sulfide with an accessible range of ca. 3 to 150 muM (0.1 to 4.8 ppm).

The Electrochemical Analog of the Methylene Blue Reaction: A Novel Amperometric Approach to the Detection of Hydrogen Sulfide

Monitoring thiol concentrations within physiological fluids has risen to considerable importance within the biomedical communities as our appreciation of the various roles that these compounds can perform has increased. Their utilization as biomarkers for numerous clinical conditions has prompted considerable interest in the development of analytical protocols that enable speedy measurements to be made. As such, a large number of procedures have arisen. This perspective highlights the contexts where physiological thiol measurements are required and describes the basis of many of the current electrochemical approaches to their determination. The collation of information from a broad range of sources covering the major electrochemical approaches (direct, indirect, and post column/capillary detection) has been achieved and the salient points of each technique critically appraised. The various characteristics and limitations of the systems are compared and contrasted with the analytical parameters (matrix, methodology, detection limit etc) from each major grouping tabulated to aid direct comparison.

Electrochemical Determination of Thiols: A Perspective

The use of microdroplet modified electrodes provides a simple methodology with which to study the biphasic electrochemistry of a plethora of species, encouraging the use of such techniques to mimic emulsion media. Furthermore, since the droplets may be miniaturised, this approach may assist in the field of biomimetic electrochemistry. For these reasons, this paper reviews the voltammetry of electrodes modified with electrochemically active droplets. The primary focus of the review is of unsupported droplets, where electron transfer processes occur at the three phase boundary, the base circumference of the individual droplets (of a volume range spanning nine orders of magnitude, going from microlitre to femtolitre volumes). The voltammetry of such systems is categorised via a semi-quantitative appreciation of the voltammetric characteristics. Finally, several topical examples illustrating the potential of application of this technology are described.

Nathan S. Lawrence

Papers

Analytical strategies for the detection of sulfide: a review

Analytical determination of homocysteine: a review

The Electrochemical Analog of the Methylene Blue Reaction: A Novel Amperometric Approach to the Detection of Hydrogen Sulfide

Electrochemical Determination of Thiols: A Perspective

Electrochemistry of immobilised redox droplets: Concepts and applications