Moisés Canle

Environmental Applications of Excitation-Emission Spectrofluorimetry: An In-Depth Review I

Abstract: This review attempts to cover the principles and environmental applications of excitation-emission spectrofluorimetry (EES). The article is divided into two parts and each part is divided into several sections. The first part includes the following: Introduction, advantages and drawbacks of EES, comparative EES versus other techniques, factors influencing EES signals, representation of EES spectra, relationships and changes in intensity of fluorescence, multivariate calibration combined with EES, quenching of fluorescence, and conclusions. Theoretical and practical considerations are included, and the possibilities and limitations are evaluated. The second part is devoted to the environmental applications of EES: Characterization of chromophoric dissolved organic matter (CDOM) in drinking waters, rivers, fog water, lakes, oceans, leachates, wastewaters, sludge, bioreactor membrane foulants and soils; characterization of extracellular polymeric substances in sluges; study of interactions between CDOM and organic pollutants in soils; and quantification of organic pollutants in waters and soils. This part includes the pretreatment of samples, and the environmental applications of the technique are discussed, including its application to biorremediation of wastewaters. More than 500 references (focusing mainly on the last 10 years) from all kinds of journals (environment, analytical chemistry, biotechnology) have been critically reviewed and included in this article.

Selective Insertion of Sulfur Dioxide Reduction Intermediates on Graphene Oxide

Graphite microparticles (d50 6.20 μm) were oxidized by strong acids, and the resultant graphite oxide was thermally exfoliated to graphene oxide sheets (MPGO, C/O 1.53). Graphene oxide was treated with nonthermal plasma under a SO2 atmosphere at room temperature. The XPS spectrum showed that SO2 was inserted only as the oxidized intermediate at 168.7 eV in the S 2p region. Short thermal shocks at 600 and 400 °C, under an Ar atmosphere, produced reduced sulfur and carbon dioxide as shown by the XPS spectrum and TGA analysis coupled to FTIR. MPGO was also submitted to thermal reaction with SO2 at 630 °C, and the XPS spectrum in the S 2p region at 164.0 eV showed that this time only the nonoxidized episulfide intermediate was inserted. Plasma and thermal treatment produced a partial reduction of MPGO. The sequence of thermal reaction followed by plasma treatment inserted both sulfur intermediates. Because oxidized and nonoxidized intermediates have different reactivities, this selective insertion would allow the addition of selective types of organic fragments to the surface of graphene oxide.