Synthesis Of Carbon Quantum Dots Research Articles

Green Synthesis of CQDs via the Trunks of Bauhinia purpurea as Fluorescence Probes for Rapid and Accurate Detection of Quinoline Yellow.

Carbon quantum dots (CQDs) were greenly synthesized via a single-step hydrothermal method, using the trunks of Bauhinia purpurea as the carbon source. They exhibited good dispersibility, water solubility, high sensitivity, and great stability with a spherical form and a particle size of 2.68 ± 0.32 nm. By utilizing the inner filter effect and dynamic quenching effect, the fluorescence quenching of CQDs can be induced to detect quinoline yellow. Detailed experimental results showed that the change rate of fluorescence intensity of CQDshadagood linearrelationshipwith varying concentrations of quinoline yellow (2-128 µmol/L). It can be clearly observed that the fluorescence quenching occurred within 1 min, its correlation coefficient (R2) is 0.9912, and the detection limit (DL) is 1.7884 μmol/L, substantially lower than the maximum concentration stipulated by the national standard of 209.5 µmol/L. Furthermore, quinoline yellow had been successfully detected in real beverage samples using CQDs, with the recovery rates of 90.6%-110.4% and the relative standard deviation (RSD) ≤ 6.3% and it also showed great anti-interference and selectivity. These findings indicate that the detected quinoline yellow of CQDs possess substantial promise for a wide range of applications within the detected artificial food colors field.

Efficient visible light-driven Photodegradation of malachite green dye using carbon quantum dots-MXene nanocomposite: Synthesis, characterization, and performance evaluation

BackgroundRemoval of azo dyes is one of important issue in water treatment studies and many of research works focused on it. Current work represents a simple and economical feasible to synthesize carbon quantum dots (CQDs) integrated with Ti3C2(OH)2 MXene nanocomposite (CQDs/MXene) for rapid photodegradation of Malachite green (MG) under visible light irradiation. In practice, CQDs were synthesized via a hydrothermal method from Petroselinum crispum leaves, while Ti3C2(OH)2 nanosheets resulted from a simple etching process of Ti3AlC2 using an alkaline solution (KOH with a trace amount of water). MethodsSubsequently, nanocomposites (CQDs/MXene) were prepared by a self-assembly process through sonication-assisted mixing process under ambient conditions. The prepared catalysts were characterized using various analyses like analysis employing field-emission scanning electron microscopy (FE-SEM), X-ray diffraction (XRD), and an energy dispersion X-ray (EDX) spectrometer to determine the chemical composition. The optimum measurement of this activity of the CQDs/MXene was attained through adjusting several constraints such as pH, dye concentration, amount of temperature and photocatalyst. Significant findingsThe kinetics of the degradation process were represented using the Langmuir–Hinshelwood model, with a rate constant (k) of 0.1382 min−1. This means that the degradation of MG dye follows a first-order reaction with respect to the dye concentration. In addition, the study also looked at the reusability of the prepared CQDs/MXene nanophotocatalyst and found that it exhibited outstanding stability after three reaction cycles. This suggests that the nanophotocatalyst is a promising material for efficient and sustainable degradation of MG dye. The nanocomposite displays high photocatalytic activity with the ability to reduce 96.1 % of the MG dye concentration after being exposed to 25 min of visible light.

Green Synthesis of Carbon Quantum Dots and Carbon Quantum Dot-Gold Nanoparticles for Applications in Bacterial Imaging and Catalytic Reduction of Aromatic Nitro Compounds

Green Synthesis of Carbon Quantum Dots and Carbon Quantum Dot-Gold Nanoparticles for Applications in Bacterial Imaging and Catalytic Reduction of Aromatic Nitro Compounds

Microwave Synthesis of Carbon Quantum Dots from Arabica Coffee Ground for Fluorescence Detection of Fe3+, Pb2+, and Cr3.

In this study, carbon quantum dots (CQDs), which were synthesized from arabica coffee ground-derived activated carbon, have been successfully employed as a fluorescence sensor to detect Fe3+ ions. CQDs were fabricated using microwave heating for 5-10 min, which emitted vibrant blue light at 455 nm when exposed to excitation at 365 nm. Dynamic light scattering (DLS) analysis revealed that the average size of CQDs was 10.12 nm with a quantum yield of 6.01%. Fluorescence detection was developed for sensing Fe3+, Pb2+, and Cr3+ ions. The addition of the three metal ions resulted in a decrease in the fluorescence (FL) intensity of the CQDs, with the addition of Fe3+ ions demonstrating a more significant decrease in FL compared to the addition of both Cr3+ and Pb2+ ions. The results indicated that the CQDs synthesized from activated carbon of arabica coffee waste performed as a selective fluorescent detector for Fe3+ ions, with a detection limit of 0.27 μM.

Photoluminescent Carbon Quantum Dots from Dichrostachys glomerata Pods with Antioxidant and Cu2+ Chelating Properties

AbstractThis work presents the facile and single‐step hydrothermal synthesis of carbon quantum dots (CQDs) using the Dichrostachys glomerata extract as raw material. CQDs with the highest photoluminescence (PL) were obtained after heating the extract in 4 M NaOH at 200 °C for 7 h. The obtained CQDs exhibit an average size of ca. 4.7 nm, a green‐yellow PL emission independent on the excitation wavelength with contributions located at 478 and 562 nm, a monoexponential decay of their PL lifetime and a PL quantum yield of 18 %. These results indicate that the surface functionalization of sp2 clusters in CQDs is uniform. The antioxidant properties of CQDs were also investigated. CQDs can effectively reduce free radicals like superoxide or oxidants like KMnO4. Moreover, CQDs show a high Cu2+ chelating activity, which is attributed to the abundant carboxylate functions on their surface and may therefore be of high interest in therapeutic applications related to Cu2+ ions overload.

Synthesis of carbon quantum dots based on quinoa straw and their application in alkali metal ions detection

Synthesis of carbon quantum dots based on quinoa straw and their application in alkali metal ions detection

A facile, green synthesis of carbon quantum dots from folium cycas for rapid and sensitive determination of Fe3+ and cell imaging

In this study, biomass-derived carbon quantum dots (CQDs) were synthesized by an one-step hydrothermal method using folium cycas as a carbon source. By optimizing the reaction conditions, the fluorescence quantum yield of CQDs was obtained to be as high as 8.91%, and strong blue emission light was emitted. The characterization results showed that the CQDs were quasi-spherical with an average particle size of 2.69 ± 0.08 nm and contained a large number of hydrophilic functional groups with excellent water solubility and photostability. The CQDs showed high selectivity and sensitivity for the detection of Fe3+, with a low limit of detection of 0.72 μM and a wide linear range of 0–200 μM. The practical applicability of the CQDs was further established by carrying out Fe3+ detection in environmental sample analysis. Besides, CQDs have been successfully applied to in vitro cell imaging and bioimaging. The final by-product of the hydrothermal reaction, biochar, is used for dye adsorption. This work identifies the importance of using a relatively green process and an inexpensive biomass precursor to produce high-quality CQDs that hold a promising future for use in metal ion detection, bioimaging, and practical sensing applications.

Synthesis of carbon quantum dots via electrochemically-induced carbon dioxide nanobubbles exfoliation of graphite for heavy metal detection in wastewater

Carbon quantum dots (CQDs) offer significant promise across industries due to their distinctive optical properties and strong biocompatibility. However, conventional synthesis methods frequently need more precision in controlling nanoparticle size, shape, and uniformity, limiting their versatility in diverse applications. Therefore, this study introduced an innovative approach to synthesising CQDs by combining electrochemical techniques with carbon dioxide (CO2) nanobubbles, circumventing the need for conventional surfactant-based exfoliation. According to the findings, the synthesised CQDs exhibited remarkable properties, including a high quantum yield of 26.17% and an average particle size of 2.24 ± 1.07 nm. Such characteristics render them exceptionally suitable for portable sensors for heavy metal detection in wastewater. Moreover, the investigation revealed the outstanding selectivity of the synthesised CQDs, particularly towards iron (Fe3+) ions, but demonstrated limited reactivity towards lead (Pb2+) and copper (Cu2+) ions. The novel approach also generated non-toxic CQD under the supply of CO2 nanobubbles, which offers a scalable avenue for developing advanced materials for various applications, including sensors for heavy metal ion detection in wastewater. The conventional synthesis method that relied on sodium dodecyl sulphate (SDS) surfactants without CO2 nanobubbles yielded CQDs with a significantly lower quantum yield of 11.2%. In short, incorporating CO2 nanobubbles with electrochemical techniques enhanced quantum yield and superior control over the size and shape of the synthesized CQDs. This novel method successfully produced CQDs with scalable distinct morphologies and provided a new understanding of the CQD synthesis mechanism, with potential applications in portable sensing for environmental monitoring and water quality management.

Simultaneous synthesis of carbon quantum dots and porous carbon using one step hydrothermal method for supercapacitor applications

The present work reports a one-step hydrothermal carbonization process used to simultaneously produce carbon quantum dots and porous carbon. The synthesized materials were characterized by using a Fourier transform infrared spectrometer (FT-IR) to study the chemical interactions, the optical properties were studied with the help of UV-visible absorption spectroscopy, and the morphology analysis of CQDs and porous carbon was examined using FESEM, in which spherical morphology confirms the formation of CQDs, while XRD confirms the amorphous nature of the porous carbon. The application of CQDs and porous materials is evaluated as a supercapacitor material by using the cyclic voltammetry technique. The specific capacitance of porous carbon was 161.33 Fg−1 at 0.01mVs−1 scan rate. This makes CQDs and porous carbon a promising candidate for applications in energy storage devices such as supercapacitors.

Microwave-assisted synthesis of carbon quantum dots and their integration with TiO2 nanotubes for enhanced photocatalytic degradation

This study demonstrates the successful synthesis of carbon quantum dots (CQDs) using the microwave method. Additionally, the hydrothermal method is employed to synthesize CQDs-decorated TiO2 nanotubes (CQDs@TNT) from CQDs decorated TiO2 (CQDs@TiO2). The CQDs induce the quantum confinement effect, observed by employing fluorescence spectroscopy (FL). The decoration of CQDs also results in a 2.92 eV reduction in the band gap in CQDs@TNT. X-ray photoelectron spectroscopy (XPS) reveals the elemental composition of both CQDs and TiO2, including TiO, CO, Ti-O-C, CC, and CO bonds. XRD spectroscopy confirms a reduction in crystallite size and negative microstrain due to compressive strength. The degradation study demonstrates the remarkable photocatalytic activity and stability of CQDs@TNT in the presence of tetracycline (TC) as the target pollutant under simulated visible light. The time dependence of the photodegradation of TC is also studied, and the system is found to be following pseudo second-order kinetics.

Hybrid cross-linking for the synthesis of highly tough fluorescent alginate fibers

The limited mechanical performance and functional constraints of alginate fibers significantly impede their development in the context of professional research. To address the aforementioned issues, this study initially utilized polyethyleneimine (PEI) and citric acid to synthesize carbon quantum dots (CD) with surface amino functionalization. Subsequently, in a sodium alginate (SA) solution, CD and vinyl silicon-based nanoparticles (VSNP) were co-introduced. Utilizing the abundant hydroxyl and carboxyl groups in polysaccharides, stable interactions were achieved with CD and VSNP. Incorporating a dynamic hydrogen-bonded crosslinking network among CD, VSNP and SA, the establishment of a calcium alginate (CA) ionically crosslinked network is facilitated via calcium-sodium ion exchange. Additionally, the interwoven and interlocked structure between the aforementioned dual networks was established. Employing a wet spinning process, the synergistic multiple dynamic energy dissipation mechanisms significantly enhance the mechanical performance. Fluorescent alginate fibers (CA/VSNP/CD) were prepared. The tensile strength was 3.81 cN/dtex, and the elongation at break was 13.16%. Compared to pure CA fibers, there were respective increases of 95.38% and 82.02%. Simultaneously, the fibers exhibit excitation-dependent emission characteristics. This work lays the foundation for potential applications of fluorescent alginate fibers in environmental monitoring, chemical sensors, dynamic anti-counterfeiting, and biomedical fields.

Green synthesis of carbon quantum dots from teak leaves biomass for in situ precipitation and regenerative-removal of methylene blue-dye.

The objective of this study was to completely eliminate environmentally harmful cationic organic dye from aqueous solutions using the one-step ultrasonication method, renowned for its energy efficiency, user-friendliness, and minimal requirement for chemical resources, making it particularly suitable for large-scale applications. To achieve effective environmental remediation, we employed carbon dots derived from teak leaf biomass (TBCDs) layered with graphene oxide. We conducted a thorough characterization of the TBCDs using UV-vis spectroscopy (with absorption peaks at λmax = 208 and 276nm), FTIR spectroscopy (confirming the presence of various functional groups including -OH, -CH, C = O, COO-, C-O-C, and = C-H), Raman spectroscopy (with bands at 1369cm-1 (D-Band) and 1550cm-1 (G-Band), and an intensity ratio (ID/IG) = 0.88, indicating structural defects correlated with the sp3 hybridization sites on the TBCDs), XRD analysis (indicating an amorphous nature of particles), HRTEM imaging (showing homogeneous dispersal of TBCDs with typical sizes ranging from 2 to 10nm), FESEM analysis (showing a flat surface and minuscule particles), and Zeta potential analysis (revealing a surface charge peak at -51.0mV). Our adsorption experiments yielded significant results, with a substantial 50.1 % removal rate and an impressive adsorption capacity of 735.2mg g-1. Theoretical adsorption parameters were rigorously analyzed to understand the adsorption behavior, surface interactions, and mechanisms. Among these models, the Langmuir isotherm in conjunction with pseudo-second-order kinetics provided an exceptional fit (with R2 values closer to 1) for our system. The Gibbs free energy (ΔG) was found to be negative at all temperatures, indicating the spontaneity of the reaction. Regarding mechanism, electrostatic attraction ((+ve) MB dye + (- ve) TBCDs), π-π stacking adsorption facilitated by the graphitic structure, formation of multiple hydrogen bonds due to polar functional groups, and a pore-filling mechanism wherein the cationic MB dye fills the pores of TBCDs with graphene oxide layers, forming an adduct were identified. Furthermore, we demonstrated the regenerative capacity of our system by effectively extracting and recovering the MB dye (with a regeneration rate of 77.1%), utilizing ethyl alcohol as the solvent. These findings not only provide valuable insights into the adsorption capabilities of TBCDs but also highlight the potential of our approach in the recovery of expensive cationic organic dye compounds from polluted environments.

Green synthesized carbon quantum dots as chemiluminescence sensor for sulfanilamide detection

N–S co-doped quantum carbon dots (N–S-CQD) were synthesized using a hydrothermal method with Artemisia annua L. as a precursor and dl-cysteine as the nitrogen-sulfur source. N–S-CQD can enhance the chemiluminescence (CL) intensity of KMnO4 system, while sulfanilamide (SA) is capable of significantly inhibit the CL intensity of KMnO4-(N–S-CQD) system. Based on this finding, we developed a novel CL method for the determination of SA. Under the optimal conditions, SA could be accurately determined in the concentration range of 50–1600 μM with a limit of detection of 0.22 μM. The investigation of potential interferences and recovery rates confirmed the method's suitability for assessing biomass samples.

One-pot Microwave Synthesis of Cobalt, Nitrogen, and Sulfur Co-Doped Carbon Quantum Dots for Efficient Monosodium Glutamate Determination in Food Samples

The synthesis of cobalt, nitrogen and sulfur co doped carbon quantum dots (Co-NS-CQDs) has become a subject of significant research interest. These CQDs were produced using a single-step microwave method, which is considered environmentally friendly, and the entire process was completed in just 90 seconds. In this synthesis, citric acid was utilized as the carbon source, methionine served as the source for both nitrogen and sulfur, and cobaltous acetate was used to introduce cobalt ions into the CQDs structure. The synthesized carbon quantum dots (CQDs) exhibit a narrow size distribution and a high quantum yield of 51.5%, which is notably superior to non-metal-doped CQDs with a yield of 38%. Characterization of these CQDs was performed using different techniques such as transmission electron microscopy (TEM), high-resolution TEM (HRTEM), Fourier transformation infrared spectroscopy (FTIR), energy dispersive X-ray analysis (EDX), X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS). The developed CQDs have blue luminescence at emission wavelength 438 nm after excitation at 350 nm. Different factors affecting the CQDs synthesis including dialysis duration, reaction time and reaction temperature. These CQDs were utilized as a probe for the detection of monosodium glutamate (MSG) in various food products. The intensity of the fluorescence of the CQDs showed a direct and linear increase with the concentration of MSG within the range of 25–250 µg/mL. The detection and quantitation limits for MSG were 2.78 µg/mL and 8.44 µg/mL, respectively. Additionally, the developed method is environmentally friendly, as confirmed by assessments using the analytical Eco scale, Green Analytical Procedure Index (GAPI), and Analytical Greenness calculator (Agree). The proposed method presents several advantages over other reported methods in terms of convenience, rapid response, and attainment of accurate and precise results.

Biocompatible carbon quantum dots as versatile imaging nanotrackers of fungal pathogen - Candida albicans.

Aim: The development of carbon quantum dots (C-QDs) as nanotrackers to understand drug-pathogen interactions, virulence and multidrug resistance. Methods: Microwave synthesis of C-QDs was performed using citric acid and polyethylene glycol. Further, in vitro toxicity was evaluated and imaging applications were demonstrated in Candida albicans isolates. Results: Well-dispersed, ultrasmall C-QDs exhibited no cyto/microbial/reactive oxygen species-mediated toxicity and internalized effectively in Candida yeast and hyphal cells. C-QDs were employed for confocal imaging of drug-sensitive and -resistant cells, and astudy of theyeast-to-hyphal transition using atomic force microscopy in Candida was conductedfor the first time. Conclusion: These biocompatible C-QDs have promising potential as next-generation nanotrackers for in vitro and in vivo targeted cellular and live imaging, after functionalization with biomolecules and drugs.

Layer-by-layer assembly of nanotheranostic particles for simultaneous delivery of docetaxel and doxorubicin to target osteosarcoma.

Osteosarcoma (OS) is a rare form of primary bone cancer, impacting approximately 3.4 × 106 individuals worldwide each year, primarily afflicting children. Given the limitations of existing cancer therapies, the emergence of nanotheranostic platforms has generated considerable research interest in recent decades. These platforms seamlessly integrate therapeutic potential of drug compounds with the diagnostic capabilities of imaging probes within a single construct. This innovation has opened avenues for enhanced drug delivery to targeted sites while concurrently enabling real-time monitoring of the vehicle's trajectory. In this study, we developed a nanotheranostic system employing the layer-by-layer (LbL) technique on a core containing doxorubicin (DOXO) and in-house synthesized carbon quantum dots. By utilizing chitosan and chondroitin sulfate as polyelectrolytes, we constructed a multilayered coating to encapsulate DOXO and docetaxel, achieving a coordinated co-delivery of both drugs. The LbL-functionalized nanoparticles exhibited an approximate size of 150 nm, manifesting a predominantly uniform and spherical morphology, with an encapsulation efficiency of 48% for both drugs. The presence of seven layers in these systems facilitated controlled drug release over time, as evidenced by in vitro release tests. Finally, the impact of the LbL-functionalized nanoparticles was evaluated on U2OS and Saos-2 osteosarcoma cells. The synergistic effect of the two drugs was found to be crucial in inducing cell death, particularly in Saos-2 cells treated with nanoparticles at concentrations higher than 10 μg/ml. Transmission electron microscopy analysis confirmed the internalization of the nanoparticles into both cell types through endocytic mechanisms, revealing an underlying mechanism of necrosis-induced cell death.

Synthesis of carbon quantum dots from waste Phaseolus vulgaris for the development of a fluorescence sensing probe to detect plasticizer in cookies

Dibutyl phthalate (DBP) is a commonly used plasticizer in the fabrication of various packaging materials, however upon exposure, it poses significant health and environmental hazards. These plasticizers consist of low-molecular-weight components, which permeate easily into the food matrix. Hence, the development of a cost-effective detection technique is necessary for the detection and monitoring of DBP. Therefore, this research focuses on the utilization of broken Phaseolus vulgaris-derived carbon quantum dots (PV-CQDs) as a fluorescent probe for the detection of DBP in cookies. Herein, PV-CQDs were synthesized through a hydrothermal reaction, which exhibited a blue color under UV-luminescence and localized surface plasmon resonance spectrum at 238 and 270 nm. The highest fluorescence emission intensity was recorded at 428 nm. The resulting PV-CQDs exhibited an average particle size of 1.22 ± 0.05 nm and prominent peaks obtained during infrared spectroscopy were found to be of carboxylic and hydroxyl functional groups, respectively. Transmission electron microscopy and energy dispersive spectroscopy analyses confirmed the spherical morphology and elemental composition, which include C (58.05% by weight) and O (41.92% by weight), respectively. The topographical height profile of the PV-CQDs was observed by atomic force microscopy and it was found to be approximately 100 µm with a thickness of 2.9 µm . The inherent fluorescence of CQDs demonstrated notable quenching efficiency when exposed to varying concentrations of 0.1, 0.2, 0.3, 0.4, 0.5, 1, 5, and 10 µM of DBP residue, resulting in a linear relationship with a high detection sensitivity of 3.19634 µM. Furthermore, the developed method was successfully implemented to determine DBP in cookies, achieving recovery rates within the range of 97–99%. Thus, the rapid sensing capabilities of CQDs could be highlighted as their promising potential for the detection of DBP in food products.

Controllable and large-scale synthesis of carbon quantum dots for efficient solid-state optical devices

Carbon quantum dots (C-dots) showed excellent structure-tunable optical properties, mainly composed of carbon, nitrogen and oxygen. They have been used for various types of solid-state optical devices. Due to the photoluminescence quenching caused by aggregation, it is a challenge to produce high quantum yield and large Stokes shift C-dots via controllable and simple approaches. In this work, we demonstrated a microwave assisted heating approach for the high-quality C-dots production with ten grams scale per batch in less than 4 min. The addition of metal cation promoted the formation of the foam-structure by forming carboxyl-metal-amine complex, enabling the spatial confined growth of the C-dots in a solid-state, contributing to the high quantum yield (QY) of 73% with a Stokes shift of 0.65 eV. By tuning the structure of the C-dots, excitation dependent and independent photoluminescent (PL) behavior were achieved because of the formation of the different types of energy states evidenced by transient PL and femtosecond transient absorption spectroscopy. These optical properties enable the C-dots to be successfully integrated in luminescent solar concentrators (LSCs), having an external optical efficiency of 3.0% and a power conversion efficiency of 1.3% (225 cm2) and an excitation-dependent high-level anticounterfeiting fluorescent code, showing a great potential for solid-state optical system.

Recent advancements towards the green synthesis of carbon quantum dots as an innovative and eco-friendly solution for metal ion sensing and monitoring

An overview of the importance of green chemistry in synthesizing fluorescent carbon quantum dots as an effective tool for metal ion sensing is discussed. Various synthesis methods and mechanisms involved in metal ion sensing using CQDs are presented.

Room temperature cost-effective synthesis of carbon quantum dots for fluorescence pattern recognition of metal ions.

Herein, a type of low-consuming carbon quantum dot (CD) has been synthesized at room temperature in just 45 minutes via Schiff base reaction between o-phthalaldehyde (OPA) and polyethyleneimine (PEI). These CDs are pH-dependent, so a novel label-free florescent sensor array can be constructed by utilizing buffers with various pH levels, which leads to distinctive fluorescence response patterns upon being challenged with metal ions for their pattern recognition. The results demonstrate that large-scale detection of metal ions can be achieved with as little as 3 types of sensors. Additionally, the sensors are able to discriminate between various metal ion concentrations and mixtures of different metal ions. The technique demonstrates potential uses in water quality monitoring by promising straightforward, quick, sensitive, and potent discrimination of metal ions.