Acid Oxidation of Muskmelon Fruit for the Fabrication of Carbon Dots with Specific Emission Colors for Recognition of Hg²⁺ Ions and Cell Imaging

Abstract

In this study, water-soluble emissive carbon dots (CDs) are effectively fabricated with specific optical properties and colors by acid oxidation of muskmelon (Cucumis melo) fruit, which are termed as C. melo CDs (CMCDs). The fluorescence properties of CMCDs were tuned by controlling the experimental conditions that allow them to emit different colors, that is, blue (B-), green (G-), and yellow (Y-) CMCDs, with different emission wavelengths at 432, 515, and 554 nm when excited at 342, 415, and 425 nm, respectively. The fabricated multicolor-emissive CDs were confirmed by various analytical techniques. The sizes of B-, G-, and Y-CMCDs were found to be ∼3.5, ∼4.3, and ∼5.8 nm, respectively. The as-prepared CMCDs display stable emissions with quantum yields of 7.07, 26.9, and 14.3% for the three CMCDs, which could act as a promising probe for the selective detection of Hg2+ ions. Upon the addition of Hg2+ ions, the fluorescence intensity of G-CMCDs at 515 nm was quenched largely than that of B- and Y-CMCDs. The spectroscopic results display that the G-CMCDs acted as a sensor for the detection of Hg2+ ions with a wide linear range from 1.0 to 25 μM (R2 = 0.9855) with a detection limit of 0.33 μM. This method was successfully applied to detect Hg2+ ions in biological and water samples. The fabricated multicolor-emissive CMCDs possess the cell (Cunninghamella elegans, Aspergillus flavus, and Rhizoctonia solani) imaging property, suggesting the biocompatible nature for multicolor imaging of various cells.

Hydrothermal synthesis of blue‐green emitting carbon dots based on the liquid products of biodegradation of coal

“…Figure 3B displays the optimal excitation and emission wavelength was at 328 nm and 442 nm, respectively. Furthermore, as shown in Figure 3C the resultant CDs solution possessed an obvious excitation‐dependent PL property, which is attributed to numerous chromophore or fluorophore systems with aromatic and oxidation groups are present 46,56 …”

“…Furthermore, as shown in Figure 3C obvious excitation-dependent PL property, which is attributed to numerous chromophore or fluorophore systems with aromatic and oxidation groups are present. 46,56 In Figure 3D, the time-resolved single-photon counting spectroscopy of the prepared CDs is shown. The timeresolved PL decay exhibits a bi-exponential decay function with an average lifetime of 4.96 ns, which included two components of the fast decay time τ 1 of 2.07 ns (35.2%), and the long decay time τ 2 of 7.85 ns (64.8%).…”

“…Up to the present, many biomass carbon sources have been used to prepare CDs such as eggs, fruits, milk, petals, vegetation, starch, waste and by-products, and so on. [46][47][48][49] Coal biodegradation refers to the use of fungi, bacteria, and actinomycetes, and other microorganisms to achieve the dissolution, degradation, liquefaction, or gasification of coal. This technology realizes the clean utilization of coal and has a broad prospect in the comprehensive utilization of low-rank coal (especially lignite and peat).…”

“…Therefore, the carbon source of biomass materials is important for the preparation of heteroatom doped CDs with high luminescence efficiency. Up to the present, many biomass carbon sources have been used to prepare CDs such as eggs, fruits, milk, petals, vegetation, starch, waste and by‐products, and so on 46‐49 …”

Detection of Melamine Based on the Fluorescence Changes of Nitrogen-Doped Carbon Dots

“…Carbon dots were widely used in heavy metal ions, photocatalysis, LED, and sensing because of its simple synthesis, low cost, low toxicity, and high specificity [25,26]. In order to detect melamine, a fluorescence resonance energy transfer system between carbon dots and gold nanoparticles was established by Li [27].…”