Finding Value in Wastewaters from the Cork Industry: Carbon Dots Synthesis and Fluorescence for Hemeprotein Detection

Abstract

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 affordable, but environmentally-problematic industrial effluent. 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-off 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 an 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 differences between the two types of nanomaterials highlighted.

Luminescent Carbon Dots from Wet Olive Pomace: Structural Insights, Photophysical Properties and Cytotoxicity

“…In all cases, the emission maximum is maintained at 426 nm ( Figure S12b ). A great PL stability is observed for WP-CDs-5 between pH 1 and ~8, a characteristic that is shared with the CDs obtained from the wastewaters of olive mills [ 26 ] and cork factories [ 27 ]. Upon increasing the pH above this value, the fluorescence drops abruptly, reaching only 45% of the pristine emission at pH 11.6 ( Figure S12c PL intensity in most reported CDs is highly sensitive to pH changes.…”

“…The synthesis of CDs from several biomass wastes has been accomplished in the last few years [ 17 , 18 , 19 , 20 ]. Examples include the use of wastepaper [ 21 ], wheat straw [ 22 ], food waste [ 23 ], tobacco leaves [ 24 ], rice residues [ 25 ], and wastewaters from olive mills [ 26 ] and the cork industry [ 27 ]. Besides our own investigations [ 26 ], research focused on olive mill wastes for preparing CDs is scarce but has been pursued by other groups.…”

A Continuously Tunable Full-Color Emission Nitrogen-Doped Carbon Dots and for Ultrasensitive and Highly Selective Detection of Ascorbic Acid

“…When we measured the average fluorescence lifetime of F-NCDs, the calculated average (amplitude-weighted) lifetime was reduced from 10.2 ns to 7.68 ns with the addition of AA, suggesting that the presence of AA reduced the average lifetime of F-NCDs significantly (Figure 13b). Above all, these findings revealed that the fluorescence quenching mechanism of F-NCDs/AA system was dynamic [30,41,42]…”

Carbon Dots Synthesis from Coffee Grounds, and Sensing of Nitroanilines

“…Carbon-based nanomaterials, particularly carbon dots (C-dots) have attracted the researchers interest due their excellent luminescence, photostability and biocompatibility, encouraging their use in several fields such as biomedicine, sensing, (photo)catalysis and optoelectronics [1][2][3][4][5].…”

“…C-dots can be prepared by a variety of methods (top-down and bottom-up approaches), using a great diversity of carbon sources [2]. Use of several types of wastes, either from industrial or forest origin, for C-dots production has been achieved [3,4,[6][7][8]. Coffee is one of the most consumed brews all over the world, generating large amounts of waste.…”