Effects Of Carbon Quantum Dots Research Articles

Magnetic photocatalytic nano-semiconductors prepared from carbon quantum dots compounded with copper ferrate and their application in dye wastewater treatment

To investigate new and potent photocatalytic materials for organic pollutants, in this work, copper ferrate (CuFe2O4) nanoparticles were synthesized by sol-gel combustion method and then combined with the microwave synthesis method to prepare CQDs/CuFe2O4, which was used for the degradation of methylene blue (MB) dye. Firstly, scanning electron microscopy (SEM), X-ray diffraction (XRD), transmission electron microscopy (TEM), photoluminescence spectroscopy (PL), UV–visible diffuse reflectance spectroscopy (UV–vis DRS), and electrochemistry were employed to validate the composite effect of CQDs/CuFe2O4. The MB removal (99.86%) was maximized under the optimal conditions (1.5% CQDs/CuFe2O4, 10 mg/L, pH 7.0). Meanwhile, the recycling performance after magnet adsorption and recovery and the effects of carbon quantum dots (CQDs) dosing (0.5% ∼ 3%), dye concentration (10 mg/L ∼ 30 mg/L), and pH (3.0 ∼ 11.0) on the degradation of MB dye by the CQDs/CuFe2O4 system were comprehensively investigated. Finally, based on the findings of the free radical scavenging experiments, the photocatalytic mechanism is proposed that the high catalytic activity of CQDs/CuFe2O4 is owed to its high specific surface area, narrow bandgap, and multiple active sites. On account of the introduction of the CQDs, the rate of electron mobility is improved and carrier complexation is reduced. In conclusion, the present work provides an effective photocatalytic system for removing organic pollutants by CQDs/CuFe2O4 composites at room temperature under neutral conditions.

Carbon quantum dots as immune modulatory therapy in a Sjögren's syndrome mouse model.

The objective of the study was to evaluate the therapeutic effects of carbon quantum dots (CQDs) in immunomodulation on non-obese diabetic (NOD) mice, as the model for Sjögren's syndrome (SS). Carbon quantum dots were generated from Setaria viridis via a hydrothermal process. Their toxic effects were tested by cell viability and blood chemistry analysis, meanwhile therapeutic effects were investigated in NOD mice in the aspects of saliva flow, histology, and immune cell distribution. Carbon quantum dots, with rich surface chemistry and unique optical properties, showed non-cytotoxicity in vitro or no damage in vivo. Intravenously applied CQDs alleviated inflammation in the submandibular glands in NOD mice after 6-week treatments. The inflammatory area index and focus score were significantly decreased in CQD-treated mice. Besides, the levels of anti-SSA and anti-SSB were decreased in the presence of CQDs. The stimulated saliva flow rates and weight of submandibular glands were significantly increased in CQD-treated mice by reducing the apoptosis of cells. The CD3+ and CD4+ T cells distributed around the ducts of submandibular glands were significantly decreased, while the percentage of Foxp3+ cells was higher in CQD-treated mice than that in the control group. Our findings suggest that CQDs may ameliorate the dysregulated immune processes in NOD mice.

Inhibitory effects of carbon quantum dots towards hen egg white lysozyme amyloidogenesis through formation of a stable protein complex

Proteins, under certain circumstances such as defective quality control mechanism, mutations and altered environmental conditions, undergo misfolding and assemble into highly ordered beta-sheet structured fibrillar aggregates called amyloid fibrils. Formation of amyloid is seen in most of the protein linked degenerative diseases like Alzheimer's disease, Parkinson's disease, Huntington's disease, Type II diabetes mellitus and many more. Amyloid fibril forms via intermediate state(s), and is known to follow a nucleated condensation polymerization mechanism. Though extensive research is being carried out towards finding a therapeutic solution to the amyloidosis, an effective treatment to these diseases still remains elusive and also the mechanism of amyloidogenesis largely remains unclear. In recent times, carbon quantum dots (CQDs) are gaining the attention of researchers due to their semi-conductive nature, excellent physio-chemical properties, high surface to volume ratio, optical properties and mainly bio-compatibility. In the current study, we have synthesized CQDs from commonly available kitchen spice mix and explored their role in amyloidogenesis using hen egg white lysozyme (HEWL) as a model protein. The results clearly demonstrate the amyloid inhibitory as well as disaggregation potential of CQD by forming a stable complex with HEWL and thereby increasing the energy barrier for the aggregation process.

PHOTOCATALYTIC PROPERTIES OF CoO/g-C3N4 NANOCOMPOSITES MODIFIED BY CARBON QUANTUM DOT

A CQDs/CoO/g-C3N4 nanocomposite used for photocatalytic degradation was designed and fabricated in this paper. The effects of carbon quantum dots (CQDs) content and synthesis temperature on photocatalytic properties of nanocomposites were studied. The results show that the solar energy utilization efficiency of CQDs/CoO/g-C3N4 nanocomposite is twice that of pure g-C3N4 when the content of CQDs is 4.5 wt%. The improvement of photocatalytic performance of nanocomposite is mainly attributed to the synergistic effect of the junction/interface between g-C3N4, CoO and CQDs.

Triggering of Apoptosis in Osteosarcoma 143B Cell Line by Carbon Quantum Dots via the Mitochondrial Apoptotic Signal Pathway.

Objectives Carbon-based nanomaterials have gained attention in the field of biomedicine in recent years, especially for the treatment of complicated diseases such as cancer. Here, we report a novel carbon-based nanomaterial, named carbon quantum dots (CQDs), which has potential for cancer therapy. We performed a systematic study on the effects of CQDs on the osteosarcoma 143B cell line in vitro and in vivo. Methods Cell counting assay, the neutral red assay, lactic dehydrogenase assay, and fluorescein isothiocyanate (FITC) Annexin V/Propidium iodide (PI) were used to detect the cytotoxicity and apoptosis of CQDs on the 143B cell line. Intracellular reactive oxygen species (ROS) were detected by the oxidation-sensitive fluorescent probe 2′,7′-dichlorofluorescein diacetate. The JC-10 assay was used to detect the mitochondrial membrane potential (MMP) of 143B cells incubated with CQDs. The effects of CQDs on the 143B cell line were evaluated by Western blot and immunofluorescence analysis of apoptosis-related proteins Bax, Bcl-2, cytochrome-C, caspase-3, cleaved-caspase-3, PARP1, and cleaved-PARP1. Male tumor-bearing BALB/c nude mice were used to investigate the antitumor effects of CQDs, and the biosafety of CQDs in vivo was tested in male BALB/c mice by measuring weight changes, hematology tests, and histological analyses of major organs. Results CQDs exhibited a high cytotoxicity and induced apoptosis toward the 143B cell line. CQDs can also significantly increase the intracellular level of ROS and lower the mitochondrial membrane potential levels of 143B cells. CQDs increase apoptotic protein expression to induce apoptosis of 143B cells by triggering the mitochondrial apoptotic signaling pathway. The tumor volume in the CQD-treated mice was smaller than that in the control group, the tumor volume inhibition rate was 38.9%, and the inhibitory rate by tumor weight was 30.1%. All biosafety test indexes were within reference ranges, and neither necrosis nor inflammation was observed in major organs. Conclusions CQDs induced cytotoxicity in the 143B cell line through the mitochondrial apoptotic signaling pathway. CQDs not only showed an antitumor effect but also high biocompatibility in vivo. As a new carbon-based nanomaterial, CQDs usage is a promising method for novel cancer treatments.

Synergistic Enhancement Effects of Carbon Quantum Dots and Au Nanoclusters for Cathodic ECL and Non‐enzyme Detections of Glucose

AbstractIn this study, we found that glucose enhance electrochemiluminescence (ECL) intensity of both Au nanoclusters (Au NCs) and carbon quantum dots (CQDs) with K2S2O8 as the co‐reactants. The enhancing effects by Au NCs and CQDs were overlapped, enabling the detection of glucose. The increased ECL intensity of glucose was linear with the logarithm of concentrations of glucose in the range of 50 μM–3.0 mM, and the limit of detection is 20 μM. Anti‐interruption ability was achieved, and ascorbic acid, urea, and uric acid had little influence to glucose detection. This method realized the direct detection of glucose by enhancing ECL of Au NCs and CQDs, which was fast and economic, possessing potential applications for glucose detection in human serum.

Preparation and Performance of Radiata-Pine-Derived Polyvinyl Alcohol/Carbon Quantum Dots Fluorescent Films.

In this study, the low-cost processing residue of Radiata pine (Pinus radiata D. Don) was used as the lone carbon source for synthesis of CQDs (Carbon quantum dots) with a QY (The quantum yield of the CQDs) of 1.60%. The CQDs were obtained by the hydrothermal method, and +a PVA-based biofilm was prepared by the fluidized drying method. The effects of CQDs and CNF (cellulose nanofibers) content on the morphology, optical, mechanical, water-resistance, and wettability properties of the PVA/CQDs and PVA/CNF/CQDs films are discussed. The results revealed that, when the excitation wavelength was increased from 340 to 390 nm, the emission peak became slightly red-shifted, which was induced by the condensation between CQDs and PVA. The PVA composite films showed an increase in fluorescence intensity with the addition of the CNF and CQDs to polymers. The chemical structure of prepared films was determined by the FTIR spectroscopy, and no new chemical bonds were formed. In addition, the UV transmittance was inversely proportional to the change of CQDs content, which indicated that CQDs improved the UV barrier properties of the films. Furthermore, embedding CQDs Nano-materials and CNF into the PVA matrix improved the mechanical behavior of the Nano-composite. Tensile modulus and strength at break increased significantly with increasing the concentration of CQDs Nano-materials inside the Nano-composite, which was due to the increased in the density of crosslinking behavior. With the increase of CQDs content (>1 mL), the water absorption and surface contact angle of the prepared films decreased gradually, and the water-resistance and surface wettability of the films were improved. Therefore, PVA/CNF/CQDs bio-nanocomposite films could be used to prepare anti-counterfeiting, high-transparency, and ultraviolet-resistant composites, which have potential applications in ecological packaging materials.

Wavelength-dependent effects of carbon quantum dots on the photocatalytic activity of g-C3N4 enabled by LEDs

Although the photocatalytic activity of g-C3N4 can be evidently enhanced by implanting 0-dimensional (0D) carbon quantum dots (CQDs), the enhancement mechanism, especially the relationship between the role of CQDs and photo-excitation wavelength, remained largely unclear. Herein, 0D/2D CQDs/g-C3N4 heterostructures were fabricated for sulfamethazine (SMZ) photodegradation under both polychromatic (simulated daylight, 380 ≤ λ ≤ 780 nm) and monochromatic light (395, 410, 425, 435, 455, 475 and 500 nm) emitting from wavelength-tunable LEDs. We confirmed the promotional role of CQDs as a donor-sensitizer-acceptor to facilitate the charge separation and enhance light absorption. Further investigation showed that CQDs even exerted opposite effects in g-C3N4 photocatalytic activity under different excitation wavelengths: i) inhibition (380 ≤ λ ≤ 410 nm), ii) transition (410 < λ ≤ 425 nm), and iii) promotion (425 < λ ≤ 780 nm). Such oscillating behavior was attributed to the competition between synergistic effect and down-conversion fluorescent property of CQDs. The inherently versatile role of CQDs was among the first revealed, which was largely ignored in previous studies. Moreover, water quality parameters (pH, HCO3−, Br−, Cl−, NO3−, and SO42−) showed complicated impacts, and potentially improved the photocatalytic performance in actual water matrices. This study is of referential significance for developing LED-based photocatalysis technology for water decontamination, especially when CQDs are incorporated to improve the performance.

Effects of carbon quantum dots (CQD) on the energy storage capacity of a novel synthesized short-chain dyad

Abstract The present paper deals with the photophysical and time resolved spectroscopic investigations performed on the pristine short chain dyad, (E)-4-(((9H-fluorene-2-yl)imino)methyl)-N,Ndimethylaniline (NNDMBF) and its nanocomposite forms with CQD or NCQD. The experimental results with dyad-CQD (or NCQD) demonstrate that more than 80% trans structure of the ground state dyad could be protected in the environment of CQD (or NCQD) even on photoexcitation. Formations of elongated trans- conformers show in favor of efficient energy-storage systems. The stability of extended conformation has been hinted to be due to combination of surface coverage and surface trap effects, the later process seems to be the dominating one.

Effects of Carbon Quantum Dots on Aquatic Environments: Comparison of Toxicity to Organisms at Different Trophic Levels.

Carbon quantum dots (CQDs) have high hydrophilicity, high cell permeability, and are frequently used in water-based and biorelated applications, yet studies concerning the ecological risks of CQDs in aquatic environments are largely insufficient. In the present study, the toxicity of CQDs to zebrafish ( Danio rerio), zooplankton ( Daphnia magna), and phytoplankton ( Scenedesmus obliquus) were assessed for the first time. The results indicated that CQDs (up to 200 mg/L) could be depurated by D. rerio with negligible toxicity. In comparison, CQDs induced mortality and immobility in D. magna with a 48-h EC50 value and LC50 value of 97.5 and 160.3 mg/L, respectively. In S. obliquus, CQDs inhibited photosynthesis and nutrition absorption in a dose- and time-dependent manner, and the growth of algae was also inhibited with a 96-h EC50 value of 74.8 mg/L, suggesting that S. obliquus, the lowest trophic level in this study, was most sensitive to CQDs exposure. Further investigations revealed that CQDs induced an increase in oxidative stress in algae cells and a decrease in pH value of an algae medium, indicating that oxidative stress and water acidification may be the mechanisms underlying the toxicity of CQDs to S. obliquus.

Carbon Quantum Dots as Fluorescent Probes for Imaging and Detecting Free Radicals in C. elegans.

Uniform and hydrophilic carbon quantum dots (C-QDs) were synthesized by calcination and NaOH treatment from an organo-templated zeolite precursor. The color of luminescence was determined by the concentration of C-QDs. These variable-color C-QDs were applied for the first time in the imaging of Caenorhabditis elegans (C. elegans) as a model organism. The effects of C-QDs and possible behavioral changes in C. elegans were evaluated under treatment conditions. We could clearly observe distribution of C-QDs in C. elegans from the fluorescence images. Furthermore, we observed significant and detectable fluorescence quenching of the C-QDs by free radicals in C. elegans. Our work affirms that C-QDs can be developed as imaging probes and as potential fluorescent quantitative probes for detecting free radicals.

Impact of carbon quantum dots on dynamic properties of BSA and BSA/DPPC adsorption layers

The effects of carbon quantum dots (CQDs) on the dynamic properties of bovine serum albumin (BSA) were investigated using pendant drop profile analysis method. Moreover, the effects of CQDs on the competitive adsorption of BSA and dipalmitoyl phosphatidylcholine (DPPC) were examined. CQDs reduce the fluorescence intensity of BSA and cause a red shift in fluorescence emission. The quenching constant at pH 4.3 is almost twice as large as that of the value obtained at pH 6.0. A small amount of CQDs does not influence the dynamic surface adsorption properties of BSA molecules. As the CQD concentration increases, a gradual increase in adsorption rate of BSA molecules is observed. Moreover, the addition of CQDs results in a significant transition of kinetic dependencies of surface elasticity of BSA solution when the CQD concentration exceeds a critical value. The appearance of the maximum surface elasticity value is probably attributed to the formation of tails and loops. When the dynamic surface properties are dominated by BSA molecules, the effects of CQDs on the surface properties of BSA/DPPC mixture are similar to those of BSA alone. However, when the surface film mainly consists of DPPC, CQDs can obviously change the interfacial properties of DPPC monolayer.

Radioprotective effect of ultra-small carbon quantum dots in mice in vivo

Objective To study the radioprotective effects of ultra-small carbon quantum dots (CQDs) in mice in vivo, and to reveal the protective mechanism, as well as to study the body immune response to CQDs and the toxicity in vivo. Methods Mice were injected with different concentrations of CQDs solution. Mice models of systemic radiation injury were constructed by high dose gamma rays radiation. The 30-days survival rate, bone marrow DNA, femoral bone marrow nucleated cells (BMNC), tissue superoxide dismutase (SOD) and malondialdehyde (MDA) were measured to evaluate the radioprotective effects of CQDs, and to investigate the possible protective mechanism. The toxicity of CQDs in vivo was studied by measuring the changes of body weight, liver index and spleen index before and after injections of CQDs in mice. Results CQDs showed obvious radioprotective effects on mice in vivo. Compared with the control group, the 30-days survival rate of irradiated mice treated with CQDs increased from 0% to 40%. CQDs could effectively reduce the hematopoietic system damages caused by radiation, and increase the level of bone marrow DNA, femur BMNC, liver and lung SOD, as well as reduce the production of MDA in liver and lung. The results of immunological reaction tests showed that CQDs had less toxicity in vivo and did not trigger the body immune response. Conclusions CQDs has tremendous application prospects in the field of radiation protection. This study can provide new ideas for the application of new nano-materials in medical field. Key words: Carbon quantum dots; Radiation protection; In vivo toxicity

Angiogenic Profiling of Synthesized Carbon Quantum Dots.

A simple method was employed for the synthesis of green luminescent carbon quantum dots (CQDs) from styrene soot. The CQDs were characterized by transmission electron microscopy, X-ray photoelectron spectroscopy, Fourier transform infrared, and Raman spectroscopy. The prepared carbon quantum dots did not show cellular toxicity and could successfully be used for labeling cells. We also evaluated the effects of carbon quantum dots on the process of angiogenesis. Results of a chorioallantoic membrane (CAM) assay revealed the significant decrease in the density of branched vessels after their treatment with CQDs. Further application of CQDs significantly downregulated the expression levels of pro-angiogenic growth factors like VEGF and FGF. Expression of VEGFR2 and levels of hemoglobin were also significantly lower in CAMs treated with CQDs, indicating that the CQDs inhibit angiogenesis. Data presented here also show that CQDs can selectively target cancer cells and therefore hold potential in the field of cancer therapy.

Quantitative and real-time effects of carbon quantum dots on single living HeLa cell membrane permeability.

The interaction between carbon quantum dots (CQDs) and a single living cell was explored in real time. Here, we provide the quantitative data on the permeability of the HeLa cell membrane in the presence of CQDs with different surface functional groups (CQDs terminated with -OH/-COOH (CQD-OH), -PEG (CQD-PEG), and -NH2 (CQD-NH2)). Although these CQDs have very low toxicity towards HeLa cells, they still increase the cell membrane permeability by 8%, 13%, and 19% for CQD-PEG, CQD-OH, and CQD-NH2, respectively, and this kind of permeability was irreversible. These observations are valuable for promoting the bio-applications of carbon nanostructures in living systems.