3-Aminophenylboronic acid-functionalized molybdenum disulfide quantum dots for fluorescent determination of hypochlorite

Development of fluorescence sensor based on molecularly imprinted carbon quantum dots for sensitive and selective detection of rutin

A sensitive and selective fluorescence sensor for rutin was successfully developed. The sensor was fabricated from highly fluorescent nitrogen-boron co-doped carbon quantum dots (N,B-CDs) coated with mesoporous silica molecularly imprinted polymer (MIP). Rutin was detected by this sensor (N,B-CDs @ MIP) with a linear range of 0.08-30 μM and a detection limit as low as 0.05 μM, under optimal conditions. Meanwhile, the usefulness of the developed sensor was evaluated in samples of lake water, orange, and honey with satisfactory recoveries.

Microwave synthesis of molybdenum disulfide quantum dots and the application in bilirubin sensing

Molybdenum disulfide quantum dots (MoS2QDs) is a new type of graphite like nanomaterial, which exhibited well chemical stability, unique fluorescence characteristics, and excellent biocompatibility. The conventional hydrothermal synthesis of MoS2generally requires a long-term reaction at high temperature and high pressure. Herein, we have developed a simple and fast MoS2QDs synthesis scheme using microwave heating, and further modified the surface of MoS2QDs using 3-aminophenylboronic acid. The 3- aminophenylboronic acid modified MoS2QDs (B-MoS2QDs) were further coated by a zinc-based metal-organic backbone (ZIF-8) in a solution containing zinc ions and 2-methylimidazolium. The constructed nanohybrid B-MoS2@ZIF-8 were successfully applied to the visualization and rapid detection of bilirubin based on the ratiometric fluorescence changes. The linear range for bilirubin detection is 0.2-75 μmol·l-1, and detection limit is 0.017 μmol·l-1.

"Turn-on-off" Fluorescent Probes Based on Carbon Nanoparticles for Hypochlorite and Fe2+ Detection

The identification of ClO- and iron ions in water medium is a difficult task and has been one of the hot issues in analytical chemistry. For this objective, we synthesized carbon nanoparticles (CNPs) through a solvothermal reaction between 1, 3, 5-trimesic acid and o-phenylenediamine, which served as a sequential fluorescent probe for ClO- and Fe2+ ions. The obtained CNPs were spherical particles with a diameter of 26.5 nm, exhibiting excellent fluorescence stability under a wide pH range, high ionic strength, and UV irradiation. Interestingly, the fluorescence of CNPs was selectively enhanced in the presence of ClO-, and the resultant enhanced emission was extremely quenched by Fe2+. In view of this, a "turn-on-off" fluorescent probe was established, which possessed wonderful sensitivity and selectivity for quantitative analysis of ClO- and Fe2+, with corresponding detection limits of 0.15 µM and 0.088 µM, respectively. In addition, the practicality and viability of the developed probe were validated by quantifying ClO- and Fe2+ in tap water and river water.

N-aminomorpholine-functionalized bromine-doped carbon dots for hypochlorous acid detection in foods and imaging in live cells

Hypochlorous acid (HClO) is used in food preservation. However, excessive HClO can deteriorate nutritional composition of food, compromise its quality, and potentially induce various diseases. Consequently, the development of multifunctional fluorescent probes for the sensitive and selective detection of HClO is highly anticipated for food safety. In this work, we designed a nanoprobe using N-aminomorpholine (AM)-functionalized bromine-doped carbon dots (Br-CDs-AM) for sensing HClO. This nanoprobe exhibits pH stability, strong resistance to photobleaching, superior long-term photostability (12 weeks), high sensitivity (19.3 nM), and an ultrarapid response (8 s) for detecting HClO residues in food matrices with percentage recovery (96.5 %-108 %) and RSDs less than 5.34 %. In addition, extremely low cytotoxicity and outstanding biocompatibility enable the nanoprobe to be used primarily for lysosome tracking and rapidly visualizing HClO in live cells. Thus, this study provides a new pathway to design unconventional nanoprobes for food safety assessment and subcellular organelle-specific imaging HClO.

Alendronate-Functionalized Graphene Quantum Dots as an Effective Fluorescent Sensing Platform for Arsenic Ion Detection

Alendronate-functionalized graphene quantum dots (ALEN-GQDs) with a quantum yield of 57% were synthesized via a two-step route: preparation of graphene quantum dots (GQDs) by pyrolysis method using citric acid as the carbon source and post functionalization of GQDs via a hydrothermal method with alendronate sodium. After careful characterization of the obtained ALEN-GQDs, they were successfully employed as sensing materials with superior selectivity and sensitivity for the detection of nanomolar levels of arsenic ions (As(III)). According to the mechanistic investigation, arsenic ions can quench the fluorescence intensity of ALEN-GQDs through metal-ligand interaction between the As(III) ions and the surface functional groups of the fluorescent probe. This probe provided a rapid method to monitor As(III) with a wide detection range (44 nM-1.30 µM) and a low detection limit of 13 nM. Finally, to validate the applicability, this novel fluorescent probe was successfully applied for the quantitative determination of As(III) in rice and water samples.

Rapid and ratiometric fluorescent detection of hypochlorite by glutathione functionalized molybdenum disulfide quantum dots

We proposed a rapid and ratiometric fluorescent detection method for hypochlorite by glutathione functionalized molybdenum disulfide quantum dots (G-MoS₂ QDs). The G-MoS₂ QDs were obtained through a hydrothermal method and the maximum fluorescence intensity was obtained at 430 nm under excitation of 360 nm. The fluorescence of G-MoS₂ QDs at 430 nm can be weakened by curcumin through the inner filter effect, meanwhile the fluorescence of curcumin at 540 nm appeared. Hypochlorite can fast oxidize curcumin and weaken the inner filter effect, thus the fluorescence of curcumin at 540 nm decreased and the fluorescence of G-MoS₂ QDs at 430 nm increased. This process takes only 30 s at room temperature. This is the rationale behind our rapid ratiometric fluorescent detection model for hypochlorite. Two linear detection ranges for hypochlorite are obtained with concentration from 1 to 20 μM and 20 to 30 μM, the limit of detection (LOD) was 11.5 nM. The standard spike recovery tests on milk and tap water samples showed satisfactory results, which extended the application of G-MoS₂ QDs in the field of ratiometric fluorescence detection assays.