Hydrothermal synthesis and characterization of nitrogen-doped fluorescent carbon quantum dots from citric acid and urea

Lai, Xinmin; Liu, Chang; He, Huan; Li, Junfeng; Wang, Li; Long, Qing; Zhang, Peicong; Huang, Yi

doi:10.1080/00150193.2020.1762435

Cited by 15 publications

(5 citation statements)

References 20 publications

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“…In this study, the strongest fluorescence was observed in the case of the longest treatment at the highest temperature (the 5-10 nm graphitic particles were found in the product by means of TEM), which is in seeming contradiction with the findings in [10]. However, the initial mixture compositions in these studies were strongly different: a large excess of urea in [10] and of citric acid in [11]. Therefore, the composition of the reaction mixture is another important factor affecting the process outcome.…”

Section: Introductioncontrasting

confidence: 73%

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Optical and Sensing Properties of Carbon Colloidal Particles Based on (Thio)urea and Citric Acid: Effect of the Components Ratio

et al. 2023

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Changing the composition of a precursors mixture is a powerful tool to tune the structure and properties of carbonaceous nanoparticles synthesized via the solvothermal route. We have addressed the influence of the ratio of urea or thiourea to citric acid during their solvothermal treatment in dimethylformamide on the optical and sensing properties of the obtained colloidal product. It has been found that the urea-derived products are more diverse in comparison with the thiourea-based ones. The excitation-dependent fluorescence of the products and their sensitivity to mercury(II) ions have been investigated; one to three types of fluorophores have been observed in the products depending on the composition. The nanoparticles prepared in excess of urea have been found more sensitive to the heavy metal, with the sensitivity of the long-wave emission band being superior.

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Section: Introductioncontrasting

confidence: 73%

“…Another study of a similar hydrothermal process (temperature 140-240 • C, duration 2-10 h, urea/citric acid mass ratio 1:223 to 1:22, aqueous solution) [11] has led to a somewhat different conclusion. Upon the synthesis, the product was filtered and subject to dialysis in order to remove large particles and low-molecular species.…”

Section: Introductionmentioning

confidence: 99%

Optical and Sensing Properties of Carbon Colloidal Particles Based on (Thio)urea and Citric Acid: Effect of the Components Ratio

et al. 2023

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“…An amount of 1 g of the prepared P. guajava leaves powder was taken in 60 mL DI water in a Teflon lined hydrothermal reactor of 100 mL capacity and was put in a hot air oven for 10 h [30][31][32] at different temperatures (160-200 °C). The obtained brownish-yellow liquid was then vacuum filtered through a 0.2 μm Nylon filter.…”

Section: Synthesis Of Cdsmentioning

confidence: 99%

Carbon Dots Derived from Waste Psidium Guajava Leaves for Electrocatalytic Sensing of Chlorpyrifos

2022

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Carbon dots (CDs) modified GCE was used for the electrochemical sensing of Chlorpyrifos (CHL). The hydrothermal synthesis (200 °C for 10 h) produced CDs of 3.7 nm using Psidium guajava leaves. Square wave voltammetry was employed for the determination of CHL and the electrokinetic parameters. The reduction of CHL involved an irreversible two‐electron process with heterogeneous reaction rate (k°) and formal potential (E°) of 1.21 s−1 and −1.34 V respectively. The modified GCEs exhibited good repeatability (RSD 4.7 %), reproducibility (RSD 1.17 %), and sensitivity (1.30 mA μM−1 cm−2). The detection limit and linear ranges were 1.5 nM and 0.01–1 μM, respectively. Electrochemical sensing of CHL was comparable with the HPLC (∼5 % variation).

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“…The FL sensors exhibite a visual response to rancid milk, and the FL color changed almost instantly (<5 s). Th paper-based method was more sensitive than the film-based method, with bett performance than the sensory evaluation, owing to the earlier detection of spoiled mil The sensing performance may depend on the FL brightness of the N-CQDs and th combination effect, involving N-CQDs and H + [34,35]. The N-CQDs, on paper, displaye excellent FL properties and the combination between H+ and the N-CQDs was mo On-site sensing is necessary for testing milk freshness during the milk production, processing and sales process.…”

Section: Fl-based Visual Assaymentioning

confidence: 99%

“…The paper-based method was more sensitive than the film-based method, with better performance than the sensory evaluation, owing to the earlier detection of spoiled milk. The sensing performance may depend on the FL brightness of the N-CQDs and the combination effect, involving N-CQDs and H + [34,35]. The N-CQDs, on paper, displayed excellent FL properties and the combination between H+ and the N-CQDs was more effective and complete than that on the starch-gel film.…”

Section: Fl-based Visual Assaymentioning

confidence: 99%

Easy-to-Use Visual Sensing System for Milk Freshness, Sensitized with Acidity-Responsive N-Doped Carbon Quantum Dots

Zhang

et al. 2022

Foods

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This study established a flexible and eye-readable sensing system for the easy-to-use, visual detection of milk freshness, using acidity-responsive N-doped carbon quantum dots (N-CQDs). N-CQDs, rich in amino groups and with characteristic acidity sensitivity, exhibited high relative quantum yields of 25.2% and an optimal emission wavelength of 567 nm. The N-CQDs fluorescence quenching upon the dissociated hydrogen ions (H+) in milk and their reacting with the amino groups produced an excellent linear relation (R2 = 0.996) between the fluorescence intensity and the milk acidity, which indicated that the fluorescence of the N-CQDs was highly correlated with milk freshness. Furthermore, a fluorescence sensor was designed by depositing the N-CQDs on filter-papers and starch-gel films, to provide eye-readable signals under UV light. A fluorescence colorimetric card was developed, based on the decrease in fluorescence brightness as freshness deteriorated. With the advantages of high sensitivity and eye readability, the proposed sensor could detect spoiled milk in advance and without any preprocessing steps, offering a promising method of assessing food safety.

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Hydrothermal synthesis and characterization of nitrogen-doped fluorescent carbon quantum dots from citric acid and urea

Cited by 15 publications

References 20 publications

Optical and Sensing Properties of Carbon Colloidal Particles Based on (Thio)urea and Citric Acid: Effect of the Components Ratio

Optical and Sensing Properties of Carbon Colloidal Particles Based on (Thio)urea and Citric Acid: Effect of the Components Ratio

Carbon Dots Derived from Waste Psidium Guajava Leaves for Electrocatalytic Sensing of Chlorpyrifos

Easy-to-Use Visual Sensing System for Milk Freshness, Sensitized with Acidity-Responsive N-Doped Carbon Quantum Dots

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