As-prepared Carbon Quantum Dots Research Articles

Lanthanide Functionalized Carbon Quantum Dots for White Light Emission, pH Sensing, and Co (II) Detection.

Carbon quantum dots (CQDs) with fluorescence emission have been widely studied for versatile applications, but facile tunability of the spectral properties of CQDs by doping remains to be further explored. Herein, employing lanthanide ion Eu3+ as a dopant and activator, a simple and efficient synthesis route for pure CQDs and Eu-CQDs was demonstrated using N, N-dimethylformamide, oleic acid, and oleylamine as precursors for carbon sources. In comparison, with the popular citric acid precursor, the as-prepared CQDs and Eu-CQDs exhibited an obviously smaller particle size (1.72 ± 0.29 nm) and a more uniform distribution. Through systematic optimization of Eu3+ doping for the Eu-CQD system, colorful light emissions in the visible range were first realized under excitation of ultraviolet (UV) ∼360 nm for promising application of UV-triggered light-emitting diodes. Most interestingly, this Eu-CQD solution with UV-excited colorful light emissions was utilized as a visual pH sensor, experimentally featuring good repeatabilities and stabilities (pH values switching between 7 and 14). Besides, the Eu-CQD solution exhibited highly sensitive detection characteristics for Co (II) ions. Due to the spectral overlapping, the quenching efficiency is as high as 96.3%, and the detection limit is obtained as 0.139 μM, which is much lower than the maximum concentration of Co (II) in the drinking water permitted by WHO. All of these relevant results significantly demonstrate the great potential of lanthanide doping in the multifunctionalization of CQDs for certain emerging applications like lighting, sensing, and detection.

Carbon Quantum Dots with High Photothermal Conversion Efficiency and Their Application in Photothermal Modulated Reversible Deformation of Poly(N-isopropylacrylamide) Hydrogel.

The fluorescence of carbon quantum dots (CQDs) has been paid a lot of attention, but its photothermal performance attracts less attention since preparing CQDs with high photothermal conversion efficiency (PCE) is a big challenge. In this work, CQDs with an average size of 2.3 nm and a PCE of up to 59.4% under 650 nm laser irradiation were synthesized by a simple one-pot microwave-assisted solvothermal method using citric acid (CA) and urea (UR) as the precursors and N,N-dimethylformamide as the solvent under an optimized condition (CA/UR = 1/7, 150 °C, and 1 h). The as-prepared CQDs were demonstrated to have unique surface chemical states; i.e., abundant pyrrole, amide, carboxyl, and hydroxyl groups were found on the surfaces of CQDs, which ensure a high PCE. These CQDs were introduced into a thermoresponsive poly(N-isopropylacrylamide) (PNIPAM) to form a CQDs@PNIPAM nanocomposite, and then, a bilayer hydrogel composed of CQDs@PNIPAM and polyacrylamide (PAM) was fabricated. The bilayer hydrogel can be reversibly deformed just by a light switching on/off operation. Based on the excellent photothermal performance, the developed CQDs are expected to be used in photothermal therapy, photoacoustic imaging, and other biomedical fields, and the CQDs@PNIPAM hydrogel nanocomposite is promising to be applied in intelligent device systems as a light-driven smart flexible material.

One-step green synthesis of in–situ functionalized carbon quantum dots from Tagetes patula flowers: Applications as a fluorescent probe for detecting Fe3+ ions and as an antifungal agent

In this research, for the first time, fluorescent carbon quantum dots (CQDs) synthesized by using a green, simple, and efficient one-step hydrothermal carbonization technique from Tagetes patula flowers as carbon precursors without using any toxic chemicals are reported. The as-prepared CQDs have been characterized by Transmission electron microscope (TEM), Field emission scanning electron microscopy with Energy dispersive X-ray spectroscopy (FESEM-EDX), UV–Visible spectroscopy, Raman spectroscopy, X-ray Diffraction (XRD), zeta potential analysis, Fourier-transform infrared spectroscopy (FTIR), fluorescence spectroscopy, and X-ray photoelectron spectroscopy (XPS). As analyzed by TEM and XRD analysis, it is observed that the as-synthesized CQDs are spherical having an average particle diameter of about 5.15 nm. The quantum yield (QY) of the CQDs was calculated and found to be 29.88%. The as-synthesized CQDs show an excellent fluorescence quenching behavior towards Fe3+ ions as compared to other metal ions. Therefore, CQDs were used as a sensing probe for detecting Fe3+ ions in a linear range of 0–4 μM and a limit of detection (LOD) of 0.32 μM. A comprehensive study has been conducted to show the effectiveness of the CQDs on the growth of rice plants (Oryza sativa) and the antifungal activities of CQDs on the mycelial growth of Magnaporthe oryzae (a plant pathogenic fungus).

The synthesis of fluorescent carbon quantum dots for tartrazine detection in food: a novel one-step microwave heating approach

Nowadays, carbon quantum dots (CDs) as semiconductor synthesized nanoparticles have become an attractive subject for lots of applications due to their remarkable features. In the current study, the highly fluorescent (FL) CDs with great characteristics were synthesized through a novel one-step microwave irradiation by citric acid monohydrate and urea as carbon precursors. The as-prepared CDs were quasi-spherical shape with an average diameter of 4.5 nm and emitted bright blue FL under ultraviolet light irradiation (UV). Furthermore, the synthesized CDs possessed different properties such as diverse functional groups, good sensitivity and selectivity, high water-solubility, low toxicity, and significant stability in various environmental conditions. The results indicated that the as-prepared CDs can be applied as a fluorescent probe for detection of different concentrations of tartrazine from 5 to 100 µM in food samples. In addition, the findings revealed that the good linear relationship was obtained between the FL intensity of CDs and different concentrations of tartrazine over the range of 5 to 100 µM with the detection limit of 2.58 µM.

Effect of Hydrothermal Conditions on Kenaf-Based Carbon Quantum Dots Properties and Photocatalytic Degradation

The development of biomass-based CQD is highly attentive to enhancing photocatalytic performance, especially in secondary or ternary heterogeneous photocatalysts by allowing for smooth electron-hole separation and migration. In this study, kenaf-based carbon quantum dots (CQD) were prepared. The main objective of the current work was to investigate temperature, precursor mass and time in hydrothermal synthesis treatment to improve the CQD properties and methylene blue photocatalytic degradation. Optimization of kenaf-based CQD for inclusion in hydrothermal treatment was analyzed. The as-prepared CQDs were characterized in detail by Fourier transform infrared (FTIR) spectroscopy, using a Hitachi TEM System (HT7830, RuliTEM, Tokyo, Japan), by photoluminescence (PL), and by ultraviolet-visible (UV-Vis) spectroscopy. It was found that C200-0.5-24 exhibits a higher photocatalytic activity of the methylene blue dye and optimized hydrothermal conditions of 200 °C, 0.5 g and 24 h. Therefore, novel kenaf-based CQD was synthesized for the first time and was successfully optimized in the as-mentioned conditions. During the hydrothermal treatment, precursor mass controls the size and the distribution of CQD nanoparticles formed. The C200-0.5-24 showed a clearly defined and well-distributed CQD with an optimized nanoparticle size of 8.1 ± 2.2 nm. Indeed, the C200-0.5-24 shows the removal rate of 90% of MB being removed within 120 min.

Photoluminescence Performance and Photocatalytic Activity of Modified Carbon Quantum Dots Derived from Pluronic F127.

The photocatalytic degradation of organic dyes in waste water using carbon quantum dots (CQDs) remains a hot topic due to the importance of environmental protection. However, identifying suitable carbon resources and successful surface modification are still challenging. Herein, the hydrothermal method and surface modification of ammonia and thionyl chloride were applied to synthesize CQDs with different surface groups using PEO106PPO70PEO106 (Pluronic F127) as a carbon source. The average particle size of the as-prepared CQDs was in the range of 2.3-3.5 nm. The unmodified CQDs had the highest relative photoluminescence intensity, while all as-prepared CQDs exhibited abnormal photoluminescence located outside the scope of the visible spectrum. Interestingly, CQDs modified with ammonia achieved a degradation rate of 99.13% (15 d) for 50 mg/L indigo carmine solution, while CQDs modified with thionyl chloride reached a degradation rate of 97.59% (15 d) for light green SF yellowish solution. Therefore, in this work, two typical organic dyes can be effectively photocatalytically degraded by as-prepared CQDs, with suitable surface modification.

A potential forecast of carbon quantum dots (CQDs) as an ultrasensitive and selective fluorescence probe for Hg (II) ions sensing

Carbon quantum dots (CQDs) are remarkable nanomaterials owing to their auspicious aspects. Herein, we synthesized highly green fluorescent CQDs via a one-step facile hydrothermal method using a chicken feather as a carbon source. The synthesized CQDs have an average particle size of ∼ 5 ± 1 nm in diameter with a quantum yield of ∼ 77.2 %. As-prepared CQDs are directly used as a fluorescent probe for the sensitive and selective detection of Hg2+ ions with a detection limit of ∼ 6.2 nM. Interestingly, the above results suggested that the synthesized CQDs as a potential candidate for Hg2+ sensing application.

Targeted ginkgo kernel biomass precursor using eco-friendly synthesis of efficient carbon quantum dots for detection of trace nitrite ions and cell imaging

• Carbon quantum dots (CQDs) is prepared based on hydrothermal approach using ginkgo kernels as the carbon source. • The CQDs exhibited the excellent selectivity and sensitivity for nitrites. • The CQDs can be successfully used to perform biological imaging in MCF7 cell. Carbon quantum dots (CQDs) are useful in medical imaging and detection of toxins in food. In this work, efficient CQDs are prepared from ginkgo kernels by a hydrothermal reaction. The size distribution of the CQDs is both uniform and narrow, with an average particle diameter of 2.7 nm. We realise a quantum yield of 37.8% from our CQDs. Moreover, the CQDs have high selectivity and sensitivity to NO 2 − , with the linear ranges of 0.50–50 μmol/L, and its limit of detection is 0.15 μmol/L, this developed method was applied to detect NO 2 − in corn sausage, ham sausage, preserved Szechuan pickle, and hot dog, whose concentration of nitrite were further confirmed by high performance liquid chromatograph. Furthermore, the as-prepared CQDs not only have low toxicity and benign biocompatibility, but also display strong blue fluorescence. Therefore, the CQDs can be used for cell imaging of MCF7 cells. Our results indicate that the proposed CQDs based on ginkgo kernel biomass have great potential for cell imaging and NO 2 − detection.

Green synthesized carbon quantum dots from maple tree leaves for biosensing of Cesium and electrocatalytic oxidation of glycerol

Carbon quantum dots (CQDs) synthesized from biological sources play a significant role in biomedical and environmental applications, including bioimaging, biosensing, metal ions detection and electrocatalytic oxidations. Herein, we synthesized blue-emitting carbon quantum dots using maple tree leaves via a one-step hydrothermal process to detect Cesium ions selectively. The synthesized CQDs' functional group composition, morphology, and pH stability was analytical and morphologically investigated. The maple leaves derived carbon quantum dots (M-CQDs) exhibited blue fluorescence, and their sizes ranged from 1 to 10 nm. They exhibited emission at 445 nm upon excitation at 360 nm. M-CQDs PL intensity was highly stable for about 100 d without any changes and confirmed that the as-prepared CQDs could be used as a probe for Cesium ion sensing. M-CQDs were effectively used as Cesium sensing probes based on the electron transfer process and simultaneously used as a catalyst for glycerol electrooxidation. The PL intensity of M-CQDs was quenched while adding the varies concentration of Cesium ions in the linear range from 100 μM to 100 nM with the detection limit of (LOD) 160 nM, simultaneously electrocatalytic oxidation of glycerol showed an onset potential of 1.32 V at a current density of 10 mA/cm2.

Hydrothermal Synthesis of Carbon Quantum Dots from Persimmons as Probe for Determination of Ferric Ions.

Local natural persimmons were used as a new precursor to synthesize carbon quantum dots (CQDs) by a brief and environment friendly strategy, hydrothermal method. The as-prepared CQDs were characterized by transmission electron microscopy, Fourier transform infrared spectroscopy, Ultraviolet-visible spectroscopy, as well as fluorescence spectrophotometer. The average diameter of CQDs was 2.5±0.5 nm with spherical shape and exhibited blue fluorescence with the maximum emission wavelength at 438 nm and excitation wavelength at 345 nm. The influences of pH and ionic strength on CQDs fluorescence were evaluated. Moreover, the CQDs were used for determination of Fe3+ by blue fluorescence quenching as the result of the interaction between Fe3+ and -OH, -COOH on the CQDs surfaces. The proposed CQDs displayed high selectivity and sensitivity of Fe3+ in comparison with other metal ions. Therefore, a good linear relationship was established with the Fe3+ concentration in the range of 0.6-400 μM. The correlation coefficient of the calibration curve was 0.996. The detection limit of the method was 0.56 μM. Eventually, the CQDs made from persimmons were used for determination of Fe3+ in actual water sample with satisfactory results and gave recoveries between 95.66% and 99.90%. The relative standard deviation was 1.20%-1.86%. The results demonstrated the potential towards diverse applications of the local persimmons.

Facile synthesis of yellowish-green emitting carbon quantum dots and their applications for phoxim sensing and cellular imaging

In this work, we reported the first use of a novel fluorescent probe for phoxim detection based on yellowish-green emissive carbon quantum dots (CQDs). By facile one-pot hydrothermal treatment of citric acid and p-phenylenediamine, the CQDs with yellowish-green luminescence were synthesized. The sensing mechanism is based on the quenching effect of phoxim on the fluorescence emission of CQDs by inner filter effect (IFE). The CQDs showed a good sensitivity and selectivity to phoxim detection and dual good linear relationships were provided in the concentration ranges of 1–10 μM and 10–98 μM, associated with the limit of detection of 0.09 μM. The proposed assay has been allowed to detect phoxim in real samples with satisfying recoveries ranging from 93 to 105.9%. Furthermore, due to the low cytotoxicity and excellent biocompatibility, the as-prepared CQDs was successfully used for cell imaging, demonstrating the considerable potential applications of such CQDs in biological field.

Green synthesis of carbon quantum dots from corn stalk shell by hydrothermal approach in near-critical water and applications in detecting and bioimaging

Carbon quantum dots (CQDs) have diverse outstanding properties and potential application, but there are not many reports on the preparation of CQDs from agricultural waste without any addition of chemical reagent. Herein, a facile, economical and environmental route was developed for green synthesis of CQDs from corn stalk shell by hydrothermal approach in near-critical water. It’s worth noting that this method converted the biomass, which is regarded as agricultural wastes, into the carbon nano-materials with brilliant potential. The prepared CQDs present the great fluorescence property, the remarkable stability and biocompatibility, demonstrating this method is appreciate to produce the CQDs. The as-prepared CQDs can be employed in detecting and bioimaging domain, displaying distinctive potential for application. The superiorities of low-cost, renewability and sustainability drive the synthesis and applications of CQDs derived from biomass.

Properties and molecular structure of carbon quantum dots derived from empty fruit bunch biochar using a facile microwave-assisted method for the detection of Cu2+ ions

Carbon quantum dots (CQD) have received considerable attention due to its advantageous characteristics of highly fluorescent nature and good biocompatibility. In this study, CQD were successfully prepared from empty fruit bunch (EFB) biochar, a renewable and sustainable resource using a facile microwave-assisted method in just minutes. The structures, morphology, and functional groups of CQD were analysed by HRTEM, FTIR and XPS analysis. CQD displayed bright blue emission upon exposure to UV irradiation. The maximum fluorescence emission of CQD was detected at 420 nm throughout the excitation wavelength 280 nm. To obtain optimum molecular structure of CQD, density functional theory (DFT) calculations were carried out using 6-31G(d) basis set which also includes a comparison of three exchange correlation functions such as B3LYP, CAM-B3LYP and wB97XD. These functionals were used to calculate the ground state molecular structure of CQD. The HOMO-LUMO gap obtained from 6 to 31G(d)/B3LYP was around 6.4 eV and is closer to the experimental band gap of 4.4 eV compared to CAM-B3LYP and wB97XD. The fluorescence quenching effect was observed when Cu 2+ ions were added into CQD solution. The experiment results showed that the as-prepared CQD have a sensitive response to Cu 2+ ions in the concentration range of 0–400 μM. This work not only provides insight into the properties and molecular structure of CQD obtained via a facile and scalable method, but also shows potential of a fluorescence sensor for metal ions detection. • Facile and rapid microwave synthesis of CQD. • Theoretical FTIR and HOMO-LUMO gap values were compared. • Optimum molecular structure of CQD was determined by DFT. • Outstanding fluorescence response characteristics of CQD for Cu 2+ ions.

Synthesis of Novel Fluorescent Carbon Quantum Dots From Rosa roxburghii for Rapid and Highly Selective Detection of o-nitrophenol and Cellular Imaging.

A novel carbon quantum dots (CQDs) were successfully synthesized by one-step hydrothermal reaction using Rosa roxburghii as a biomass-based precursor. The CQDs have an average size of 2.5 nm and a narrow size distribution. They display strong blue fluorescence with a quantum yield of 24.8% and good biocompatibility. Notably, these CQDs were capable of detecting trace o-nitrophenol in surface water and sewage with high sensitivity and specificity. The linear range is 0.08–40 μmol/L, and the limit of detection is 15.2 nmol/L. Furthermore, this CQDs was successfully applied for o-nitrophenol analysis in river water and sewage samples. Additionally, Hep3B cells, a human hepatocellular carcinoma cell line, can be easily imaged with high resolution using the as-prepared CQDs as nanoprobes. These results reveal that the as-prepared CQDs have potential applications for detecting o-nitrophenol and cell imaging.

Carbon-dot-based ratiometric fluorescent probe of intracellular zinc ion and persulfate ion with low dark toxicity.

Metal ions and anions play significant roles in biological systems and industrial processes, therefore it is important to develop good fluorescent probes to detect metal ions and anions. Here, N,O-co-doped carbon quantum dots (CDs) that could detect Zn2+ via a ratiometric fluorescence method were fabricated. The reaction between the as-prepared CDs and zinc acetate gave the composite CDs-Zn, in which fluorescence changed ratiometrically upon addition of S2 O8 2- . With change in excitation light, the emission peaks of the CDs and CDs-Zn were kept fixed while intensity changed. CDs and CDs-Zn exhibited good photostability, thermal stability, selectivity, and strong anti-interference ability. In addition, CDs and CDs-Zn displayed low dark toxicity under physiological temperatures. Ratiometric fluorescence imaging of intracellular Zn2+ and S2 O8 2- was carried out in living HeLa cells for both of these probes. Compared with reported ratiometric fluorescent hybrid nanosensors based on organic dyes and inorganic nanomaterials, the as-prepared CDs and CDs-Zn had low toxicity, and were easy to synthesize.

Organic Field-Effect Transistor Memory Device Based on an Integrated Carbon Quantum Dots/Polyvinyl Pyrrolidone Hybrid Nanolayer

In this work, we present a pentacene-based organic field-effect transistor memory (OFETM) device, which employs one-step microwave-assisted hydrothermal carbon quantum dots (CQDs) embedded in a polyvinyl pyrrolidone (PVP) matrix, to form an integrated hybrid nanolayer as the charge trapping layer. The as-prepared CQDs are quasi-spherical amorphous C, with sizes ranging from 5 to 20 nm, with a number of oxygen-containing groups and likely some graphite-like domains that produce CQDs with excellent electron-withdrawing characteristics. The incorporation of CQDs into PVP dielectric materials results in a bidirectional storage property. By optimizing the concentration of CQDs embedded into the PVP matrix, the OFETM shows excellent memory characteristics with a large memory window of 8.41 V under a programming/erasing (P/E) voltage of ± 60 V and a retention time of up to 104 s.

Phytochemical properties and antioxidant activity of Echinops persicus plant extract: green synthesis of carbon quantum dots from the plant extract

Echinops persicus is a species of Echinops that can be found in Europe and western Asia especially in Iran. In this paper, the phytochemical properties of Echinops persicus were thoroughly investigated and studied. In this way, total amounts of flavonoid, tannins, phenols, carotenoids, saponins, alkaloids, and anthocyanin were measured by various analytical methods. The major phenolic and flavonoid content was found in the root acetone and flower ethanolic extract of the plant. Also, major saponins and carotenoid contents was found in root and leaf of the plant. These measurements were also performed for root, leaf, and flower of the plant in various solvent extracts. The results indicated that Echinops persicus is a rich source of secondary metabolites. Also, the plant extract demonstrated a considerable antiradical activity, which evaluated qualitatively as well as quantitatively. The largest capacity to neutralize DPPH radicals was found for root water extract of Echinops persicus plant. Finally, the possibility of the plant extract was evaluated for the green preparation of carbon quantum dots (CQDs). As-prepared CQDs were characterized by TEM, HRTEM, UV–Vis, XRD, and EDX analyses.

Facile synthesis of novel carbon quantum dots from biomass waste for highly sensitive detection of iron ions

In this work, some common and inexpensive biomass waste were used as carbon sources including orange peel, ginkgo biloba leaves, paulownia leaves and magnolia flower to prepare biomass carbon quantum dots (CQDs) by using a facile hydrothermal process. These biomass CQDs exhibited the advantages of homogeneous particle size, superior water solubility and stability, similar optical properties and surface functional group. The fluorescence quenching effect was observed when Fe3+ ions were added into CQDs solution. The experiment results showed that the as-prepared CQDs have a sensitive response to Fe3+ ions in the concentration range of 0.2−100 μM, and the limit of detection (LOD) could as low as 0.073 μM. More importantly, practical applications for the detection Fe3+ ions in pond water acquired satisfactory recoveries (94 %–108 %). Therefore, this work not only provided a new way for reusages of biomass waste, but also provided a novel alternative sensor for Fe3+ ions detection in real-world.

Preparation of multicolored carbon quantum dots using HNO3/HClO4 oxidation of graphitized carbon

Abstract

Sensitive Optical Probe for Hydrogen Peroxide Using Carbon Quantum Dots Synthesized by Glutathione

Herein, we present the one-pot synthesis of carbon quantum dots (CQDs) using glutathione and used for the optical detection of hydrogen peroxide (H2O2). Unlike as reported in other literatures, the detection of H2O2 is free of using any additional chromogenic agents or metal ions. The CQDs are synthesized using glutathione by one-pot hydrothermal at 180∘C. The as-prepared CQDs exhibit good fluorescence response toward H2O2 without involving extra chromogenic substances. The addition of 300[Formula: see text][Formula: see text]M H2O2 to CQDs induces the quenching of fluorescence, besides the yellow becomes colorless. The decrease in the fluorescence is attributed to the polymeric structure of CQDs disbanded by H2O2. In addition, the practical application of the present method was verified by determining H2O2 in human urine samples.