Fabrication of Fluorescent Nanodots by Self-Crosslinking Ufasomes of Conjugated Linoleic Acid and Their Unique Fluorescence Properties

Abstract

Carbon dots (CDs), as a kind of carbonbased fluorescent nanodots (FNDs), not only retain the advantageous characteristics of carbon-based materials (e.g., low toxicity and biocompatibility) but also exhibit tunable fluorescence emission, low photobleaching, and undergo facile surface functionalization. Therefore, the prospect of applying these materials for analysis and detection, cell imaging, drug delivery, light-emitting devices, photocatalysis, biosensing, and cancer treatment is promising. Although the synthesis of carbon dots from green and renewable feedstocks as biomass carbon sources is possible, the controllability of the involved chemical reactions is poor, resulting in poor atom economy, low quantum yields, and, especially, extremely low yields of carbon dots. In addition, these disadvantages could lead to an increase in equipment requirements and could pose a safety risk because of the need for hydrothermal and solvothermal synthesis. Certain methods even require large amounts of acid/alkali, strong oxidants, or organic solvents, thereby complicating the postprocessing process and generating waste and emissions. This research aimed to implement a new idea, namely to "fabricate" rather than "synthesize" carbon-based FNDs from a certain kind of natural and small unsaturated molecule with surface activity relying on a self-assembling and self-crosslinking strategy in lieu of traditional approaches that involve uncontrollable reactions with unknown mechanisms including pyrolysis, dehydrolysis, polyconcensation, and carbonization. In this context, conjugated linoleic acid (CLA) has been studied extensively in our laboratory, and was found to have the self-assembly and self-crosslink characteristics required by the above innovative strategy. This motivated us to adopt CLA as a new carbon source in this study. First, CLA self-assembles into unsaturated fatty acid liposomes (ufasomes) in an aqueous solution of pH 8.6 at ambient temperature (15-25 °C), and then, the initiator Ammonium persulfate is added to induce self-crosslinking of the ufasomes at 80 °C to obtain firm and uniform nanoparticles. On this basis, the possibility of using them as FNDs is investigated. Consequently, FNDs based on self-crosslinked ufasomes (SCU-FNDs) are prepared in high FND yield of 73.9% after dialysis, with a consistent particle size (17 nm), a degree of self-crosslink (DSC) of 75%, and emission of bluish green fluorescence excited at 320 nm. Furthermore the "fabrication" route provided a clear solution of FNDs that could be applied directly without separation and purification and with no wasteful emissions, which is therefore beneficial for large-scale preparation. The experimental results showed that the fluorescence intensities of the SCU-FNDs are positively correlated with both the surface carboxyl groups and DSC results. A reasonable explanation for the former relationship is the effect of the restricted geometry of the ufasomes on the accumulation of oxygen atoms at the surface of FNDs, whereas the latter could be explai...

Hydrolysis mechanism of the cyclohexaborate anion: Unraveling the intricacies

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“…Therefore, when the solution is alkaline, the hydrolysis reaction of hexaborate ions tends to generate tetraborate ions and diborate ions, which is the best explanation for the fact that pentaborate is not found in the "dilution to salt" process. 12,52 Since the intermediates generated by the hydrolysis reaction of AM2 and AM4 are not conducive to further hydrolysis reactions, they will not be described in detail. The hydrolysis pathways of AM2 and AM4 are shown in Figures 8 and 9.…”

“…10,12,29,50,51 Some studies have pointed out that the salt dissolution effect of 4 ). 12,50,52 When the borate solution is acidic or neutral, the dimer borate ions generated by the hydrolysis reaction exist in the…”

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