Detection of azo dyes using carbon dots from olive mill wastes

Azo dyes are widely spread in our day life, being heavily used in cosmetics, healthcare products, textile industries, and as artificial food colorants. This intense industrial activity, which inherently includes their own production, inexorably leads to uncontrolled release of dyes into the environment. As emerging pollutants, their detection, particularly in water systems, is a priority. Herein, a fluorescence-based method was employed for the sensitive and selective detection of anionic and neutral azo dyes. Carbon dots (CDs) synthesized from wet pomace (WP), an abundant semi-solid waste of olive mills, were used as probes. An outstanding capability for detection of azo dyes methyl orange (MO) and methyl red (MR) in aqueous solutions was disclosed, which reached a limit of detection (LOD) of 151 ppb for MO. The selectivity of WP-CDs for the anionic azo dye (MO) was established through competitive experiments with other dyes, either anionic (indigo carmine) or cationic (fuchsin, methylene blue, and rhodamine 6G); perchlorate salts of transition metal cations (Cu(II), Co(II), Fe(II), Fe(III), Hg(II), and Pb(II)); and sodium salts of common anions (NO3-, CO32-, Cl-, and SO42-). Evidence has been collected that supports static quenching as the main transduction event underlying the observed quenching of the probe's fluorescence, combined with a dynamic resonance energy transfer (RET) mechanism at high MO concentrations.info:eu-repo/semantics/publishedVersio

Kinetic Criteria for Optimal Thermally Activated Delayed Fluorescence in Photoluminescence and in Electroluminescence

A complete set of criteria for the classification, design, and selection of optimal thermally activated delayed fluorescence (TADF) emitters, for both photoluminescence and electroluminescence applications, is presently unavailable. In this work, and as a contribution toward this aim, a detailed characterization of TADF photophysical kinetics is presented, contrasting TADF in photoluminescence and TADF in electroluminescence. Two different types of TADF are identified: One-way and two-way TADF. It is shown that, for a given efficiency, one-way TADF allows lower rates of reverse intersystem crossing, an aspect that may be significant with respect to stability and roll-off issues. Graphical and quantitative indicators of singlet–triplet interconversion and photophysical efficiency are obtained and applied to the photoluminescence of eosin, coronene, and fullerenes and to the electroluminescence of several TADF emitters specifically designed for organic light emitting diodes. Relations for the photoluminescence TADF onset temperature and for the electroluminescence internal quantum efficiency are also derived

Finding value in wastewaters from the cork industry: carbon dots synthesis and fluorescence for hemeprotein detection

Valorisation of industrial low-value waste residues was preconized. Hence, carbon dots (C-dots) were synthesized from wastewaters of the cork industry—an abundant and a_ordable, but environmentally-problematic industrial e_uent. The carbon nanomaterials were structurally and morphologically characterised, and their photophysical properties were analysed by an ensemble of spectroscopy techniques. Afterwards, they were successfully applied as highly-sensitive fluorescence probes for the direct detection of haemproteins. Haemoglobin, cytochrome c and myoglobin were selected as specific targets owing to their relevant roles in living organisms, wherein their deficiencies or surpluses are associated with several medical conditions. For all of them, remarkable responses were achieved, allowing their detection at nanomolar levels. Steady-state and time-resolved fluorescence, ground-state UV–Vis absorption and electronic circular dichroism techniques were used to investigate the probable mechanisms behind the fluorescence turn-o_ of C-dots. Extensive experimental evidence points to a static quenching mechanism. Likewise, resonance energy transfer and collisional quenching have been discarded as excited-state deactivating mechanisms. It was additionally found that na oxidative, photoinduced electron transfer occurs for cytochrome c, the most electron-deficient protein Besides, C-dots prepared from citric acid/ethylenediamine were comparatively assayed for protein detection and the di_erences between the two types of nanomaterials highlighted.info:eu-repo/semantics/publishedVersio