CARBON QUANTUM DOTS (CQDS) from RAMBUTAN and PANDAN LEAVES for CU2+ DETECTION

Herein, we present the rapid synthesis of mono-dispersed carbon quantum dots (C-QDs) via a single-step microwave plasma-enhanced decomposition (MPED) process. Highly-crystalline C-QDs were synthesized in a matter of 5 min using the fenugreek seeds as a sustainable carbon source. It is the first report, to the best of our knowledge, where C-QDs were synthesized using MPED via natural carbon precursor. Synthesis of C-QDs requires no external temperature other than hydrogen (H2) plasma. Plasma containing the high-energy electrons and activated hydrogen ions predominantly provide the required energy directly into the reaction volume, thus maximizing the atom economy. C-QDs shows excellent Photoluminescence (PL) activity along with the dual-mode of excitation-dependent PL emission (blue and redshift). We investigate the reason behind the dual-mode of excitation-dependent PL. To prove the efficacy of the MPED process, C-QDs were also derived from fenugreek seeds using the traditional synthesis process, highlighting their respective size-distribution, crystallinity, quantum yield, and PL. Notably, C-QDs synthesis via MPED was 97.2% faster than the traditional thermal decomposition process. To the best of our knowledge, the present methodology to synthesize C-QDs via natural source employing MPED is three times faster and far more energy-efficient than reported so far. Additionally, the application of C-QDs to produce the florescent lysozyme protein crystals “hybrid bio-nano crystals” is also discussed. Such a guest–host strategy can be exploited to develop diverse and complex "bio-nano systems". The florescent lysozyme protein crystals could provide a platform for the development of novel next-generation polychrome luminescent crystals.

Sustainable synthesis of carbon quantum dots from banana peel waste using hydrothermal process for in vivo bioimaging

Green synthesis of biomass-derived carbon quantum dots as fluorescent probe for Fe3+ detection

Green synthesis of carbon quantum dots from wasted enzymatic hydrolysis lignin catalyzed by organic acids for UV shielding and antioxidant fluorescent flexible film

Hydrothermal synthesis of carbon quantum dots (CQDs) from natural biomass is a green and sustainable route for CQDs applications in various fields. In this work, the preparation and characterization of CQDs based on quinoa saponin were investigated. The optimum synthetic conditions determined by orthogonal experiments were as follows: 2 g quinoa saponin powder and 0.04 mol ethylenediamine reacted at 200°C for 10 h. The relative fluorescence quantum yield (QY = 22.2%) can be obtained, which is higher than some results reported in the literatures. The prepared CQDs had a small and uniform size (∼2.25 nm) and exhibited excitation wavelength-dependent blue light emission behavior. The CQDs displayed excellent sensitivity for Co2+ detection along with good linear correlation ranging from 20 to 150 µM and the detection limit of 0.49 µM. The CQDs prepared in this experiment were successfully implanted into soybean sprouts for fluorescence imaging. The sprouts could grow healthily even soaked in the CQDs solution for two weeks, demonstrating the low toxicity of the CQDs. The advantages of the CQDs, such as low cost, ease of manufacture, nontoxicity, and stability, have potential applications in many areas such as metal ion detection and biosensing.

Biomass-based carbon quantum dots (CQDs) have become a significant carbon materials by their virtues of being cost-effective, easy to fabricate and low in environmental impact. However, there are few reports regarding using cyanobacteria as a carbon source for the synthesis of fluorescent CQDs. In this study, the low-cost biomass of cyanobacteria was used as the sole carbon source to synthesize water-soluble CQDs by a simple hydrothermal method. The synthesized CQDs were mono-dispersed with an average diameter of 2.48 nm and exhibited excitation-dependent emission performance with a quantum yield of 9.24%. Furthermore, the cyanobacteria-derived CQDs had almost no photobleaching under long-time UV irradiation, and exhibited high photostability in the solutions with a wide range of pH and salinity. Since no chemical reagent was involved in the synthesis of CQDs, the as-prepared CQDs were confirmed to have low cytotoxicity for PC12 cells even at a high concentration. Additionally, the CQDs could be efficiently taken up by cells to illuminate the whole cell and create a clear distinction between cytoplasm and nucleus. The combined advantages of green synthesis, cost-effectiveness and low cytotoxicity make synthesized CQDs a significant carbon source and broaden the application of cyanobacteria and provide an economical route to fabricate CQDs on a large scale.

In this work, a simple, continuous and completely green method based on microflow technique is demonstrated for the synthesis of carbon quantum dots (CQDs) from diverse bio‐based precursors. CQDs prepared from milk is illustrated as a case study to show the process feasibility. Crystalline fluorescent CQDs of 12.53% quantum yield and good stability are synthesized by the approach, even at 120°C. Systematic experiments further suggest their optical properties, bandgap energy, and fluorescence lifetime are closely related to the synthesis temperature. The maximum production rate of the CQDs was 51.1 mg/h at 180°C. Cytotoxicity and cellular imaging tests against 3T3 cells reveal the CQDs possess high biocompatibility, and can penetrate cell membranes and display bright fluorescence. The process versatility is investigated by expanding the precursor to watermelon juice, orange juice, and soy milk, indicating successful synthesis of small‐sized CQDs of low cytotoxicity and strong photoluminescence by the technique.

Comprehensive investigation of Prunus armeniaca for natural green synthesis of carbon quantum dots; Applications as fluorescent nano-probes for ramipril.

In this study, hydrothermal method was used to prepare carbon quantum dots from the natural apple juice and electrochemical synthesis method was used to prepare carbon quantum dots from graphite. The effect of synthesis type and current intensity on fluorescence and structural properties of the prepared carbon quantum dots was investigated. TEM and FTIR techniques were used for chemical and morphological study of carbon quantum dots. The synthesized carbon quantum dots were used for modification of the surface of the glassy carbon electrode and were used as an electrochemical sensor to measure Letrozole. According to the results, the sizes of apple juice-based carbon quantum dots were 5–10 nm and the sizes of graphite-based carbon quantum dots were 1–5 nm. With the increase and the intensity of the applied current in the electrochemical synthesis method, the particle size became larger and their fluorescence intensity decreased. The FTIR results confirmed the synthesis of the carbon quantum dots and the corresponding functional groups. Modified electrodes with a variety of carbon quantum dots showed a good response to Letrozole. The prepared sensor showed a good selectivity for Letrozole compared to similar drug (Clomifene). The sensitivity of the optimal sensor to Letrozole was 0.111 (A/M) while to Clomifene drug was 0.041 (A/M). The sensor was able to measure Letrozole in the concentration range of 1–12 × 5−5 M and the detection limit was 1.85 × 5−5 M. The results showed that the designed sensor with the appropriate recovery percentage can measure Letrozole in real drug samples.

Kilogram-scale synthesis of carbon quantum dots for hydrogen evolution, sensing and bioimaging

Synthesis of carbon quantum dots from Broccoli and their ability to detect silver ions

One-step microwave-assisted synthesis of fluorescent carbon quantum dots for determination of ascorbic acid and riboflavin in vitamin supplements

Eco-friendly and sustainable synthesis of carbon quantum dots from waste sulfuric acid of alkylation

One-pot hydrothermal synthesis and characterization of carbon quantum dots (CQDs)

Background: The synthesis of carbon quantum dots (CQDs) from Basella alba L. fruit using the hydrothermal method is investigated for heavy-metal detection. CQDs have gained significant attention due to their unique properties, including high photoluminescence, biocompatibility, and low toxicity. The utilization of natural sources such as Basella alba L. fruit for CQDs synthesis offers an eco-friendly and cost-effective approach. Methods: In this study, Basella alba L. fruit was chosen as a precursor for CQDs synthesis due to its abundance and potential for heavy-metal adsorption. The hydrothermal method was employed as it provides a simple and efficient route for CQDs synthesis. The process involves the hydrolysis and carbonization of the fruit extract under controlled temperature and pressure conditions. The resulting CQDs were characterized using various techniques such as UV-visible spectroscopy, FE-SEM, EDS, E-mapping, DLS, Zeta potential, PL spectroscopy, and FTIR. Results: UV-Vis confirmed the presence of CQDs via the observation of a distinct absorption peak. EDS spectrum revealed the formation of CQDs and other groups of elements present with it, which contribute to their stability and interaction with heavy metals. FESEM images showed that the synthesized CQDs possessed a uniform size distribution and exhibited a well-defined crystalline structure. The synthesized CQDs were then evaluated for heavy-metal detection. In addition, due to their unique surface properties and interaction with heavy metals, CQDs acted as an effective sensor. A series of experiments were conducted to investigate the sensitivity and selectivity of the CQDs towards various metal ions. The results demonstrated the superior performance of the synthesized CQDs in detecting Fe3+ ions, exhibiting high sensitivity and selectivity by quenching fluorescence when interacting with Fe3+ ions. Conclusion: The successful synthesis of CQDs from Basella alba L. fruit is reported. The characterization results confirmed the formation of CQDs with desirable properties for Fe3+ ions detection. The obtained CQDs demonstrated promising potential as efficient and eco-friendly sensors for Fe3+ ions detection in environmental and biomedical samples.