Carbon Quantum Dots Research Articles

Comparison of toxic effects and underlying mechanisms of carbon quantum dots and CdSe quantum dots on Chromochloris zofingiensis from the chemical composition perspective

Quantum dots (QDs) are widely utilized semiconductor nanocrystal materials with both nanotoxicity and composition-related toxicity. To determine the toxicological impacts and underlying mechanisms of QDs with different compositions on microalgae, carbon QDs (CQDs) and CdSe QDs were used in the present study. Results showed that QDs composed of CdSe were more toxic than QDs composed of carbon, which inhibited cell growth, with reductions in chl b content, chlorophyll fluorescence parameters, and increases in lipids and starch (two major storage substances). In addition, CdSe QDs elevated reactive oxygen species (ROS), resulting in oxidative damage, while CQDs had little effect on antioxidants. Comparative transcriptome analysis showed that gene expression was accelerated by CdSe QDs, and there was a compensatory upregulation of porphyrin metabolism, potentially to support chlorophyll synthesis. In addition, an MYB transcription factor was predicted by weighted gene co-expression network analysis (WGCNA) to serve as regulator in nanoparticle toxicity, while glutathione peroxidase (GPX) and dual-specificity tyrosine phosphorylation regulated kinases 2/3/4 (DYRK2/3/4) may be key mediators of the composition-related toxicity of CdSe QDs. This study highlights the critical role of QDs’ composition in determining their impacts on aquatic microalgae, providing a theoretical reference for selecting appropriate QDs materials for various industrial applications.

Novel green CQDs/ZnO binary photocatalyst synthesis for efficient visible light irradiation of organic dye degradation for environmental remediation

The advancement of effective and sustainable water treatment depends on the creation of a highly active and controllable photocatalyst. A suitable site for increasing the activity of such a photocatalyst is the heterojunction. Organic dyes have become a major source of concern in recent years because they are so common in wastewater. Heavy metals have a high permanence in wastewater and may be carcinogenic. Low-waste, high-performance technologies are needed to remove organic dyes and heavy metals from wastewater. To determine their structural, photochemical, and optical properties, Carbon Quantum Dots (CQDs) (made from Tamarindus indica shell waste), ZnO (from Ficus Benghalensis), and CQDs/ZnO photocatalysts were synthesised using green route techniques, followed by calcination. Malachite Green (MG) and Methylene Blue (MB) are effectively photo-degraded by the synthesised CQDs, ZnO, and Green CQDs/ZnO Binary Photocatalyst under the irradiation of naturally occurring solar light. The maximum photocatalytic activity for MG and MB within 60 min was shown by the Green CQDs/ZnO Binary Photocatalyst, with 100 % and 100 %, respectively. The reduced rate of electron-hole recombination causes effective photocatalytic activity. According to experiments with free radical entrapment, O2 and h+ play an important role in photodegradation. The study thus presents a fresh approach to the synthesis of highly effective binary photocatalysts for their application in environmental remediation.

Impact of ternary nanocomposite In2O3/SnO2/F-CDs composition on low ppm NO2 sensing performance

Nitrogen dioxide (NO2) is a significant air pollutant with a notable environmental impact, necessitating precise monitoring. However, most existing NO2 sensing materials exhibit low sensitivity and require high-temperature operation. In this study, we employed a hydrothermal and co-precipitation method to synthesize a novel ternary nanocomposite, In2O3/SnO2 nanoparticles (NPs)/fluorine-doped carbon quantum dots (F-CDs). By varying the mass ratio of In2O3 to SnO2 NPs, we investigated the gas-sensing performance of the composite towards NO2. The results demonstrate that when the ratio of SnO2 and In2O3 reaches to 1 : 2, the 2-In2O3/SnO2/F-CDs gas sensor exhibited the highest response, excellent selectivity, and remarkable stability under ultraviolet (UV) light irradiation at room temperature (∼25 °C). Furthermore, the response of the 2-In2O3/SnO2/F-CDs gas sensor displayed a strong linear relationship with the concentration of NO2 gas. At a NO2 gas concentration of 3 ppm, the sensitivity was 238, which is significantly higher than that of In2O3/SnO2 NPs and In2O3 sensors. The response time and recovery time were measured at 62 s and 33 s, respectively. Finally, based on experimental characterization results and band structure analysis, we confirmed the promising effects of ternary nanocomposite in enhancing gas sensing.

A review on carbon quantum dot/semiconductor-based nanocomposites as hydrogen production photocatalysts.

Carbon quantum dots (CQDs) are discrete, quasi-spherical carbon nanoparticles with sizes below 10 nm. The properties of CQDs can be further enhanced by doping with elements such as nitrogen, phosphorous, sulphur, and boron or co-doping with heteroatoms such as nitrogen-phosphorous, nitrogen-sulphur, and nitrogen-boron. These excellent properties of CQDs can be utilized to enhance the photocatalytic performance of semiconductors. Therefore, in this review, we summarize different types of bare CQD-scaffolded semiconductors, both doped and co-doped, used for photocatalytic hydrogen production. Moreover, the detailed photocatalytic mechanism of CQD/semiconductor-based hydrogen production is reviewed. Recent progress in the design and development of CQD-based photocatalysts, along with the challenges involved, is comprehensively reviewed.

Axially Growing Carbon Quantum Ribbon with 2D Stacking Control for High-Stability Solar Cell.

Although power conversion efficiency (PCE) of solar cells (SCs) continues to improve, they are still far from practical application because of their complex synthesis process, high cost and inferior operational stability. Carbon quantum dots with high material stability and remarkable photoluminescence are successfully used in light-emitting diodes. A good light emitter should also be an efficient SC according to the photon balance in Shockley-Quieisser formulation, in which all excitons are ultimately separated. However, the finite quantum-sized sp2 domain leads to tight exciton bonding, and highly delocalized electron clouds in irregular molecular stacks form disordered charge transfer, resulting in severe energy loss. Herein, an axially growing carbon quantum ribbon (AG-CQR) with a wide optical absorption range of 440-850nm is reported. Structural and computational studies reveal that AG-CQRs (aspect ratio ≈2:1) with carbonyl groups at both ends regulate energy level and efficiently separate excitons. The stacking-controlled two-dimensional AG-CQR film further directionally transfers electrons and holes, particularly in AB stacking mode. Using this film as active layer alone, the SCs yield a maximum PCE of 1.22%, impressive long-term operational stability of 380h, and repeatability. This study opens the door for the development of new-generation carbon-nanomaterial-based SCs for practical applications.

A novel magnetoelastic biosensor consisting of carbon quantum dots/nitrocellulose membranes and NiFe2O4/ polylactic acid based on 3D printing for α2-macroglobulin detection

α2-macroglobulin (α2-M) have crucial clinical significance as a potent biomarker for diabetes nephropathy (DN). There is an increasing demand for rapid detection of α2-M. Herein, a magnetoelastic (ME) biosensor with a layered composite structure is developed for α2-M detection. Based on 3D printing, the basal layer of the biosensor is prepared as a grid structure fabricated by polylactic acid (PLA) doped with NiFe2O4. The conductivity of the biosensor was improved significantly due to the addition of multi-walled carbon nanotubes (MWCNTs). The biological site for capturing α2-M antigen was provided by the carbon quantum dots (CDs) coupled with anti-α-2M (anti-α2-M@CDs) in the nitrocellulose filter (NC) membrane. Meanwhile, the distribution of antibodies on the biosensor surface can be observed more directly due to the fluorescence characteristics of CDs. The biosensor in this work can realize multi-pattern recognition of fluorescent signal and electromagnetic signal. The results show that the limit of detection (LOD) was 0.506 ng/mL in the linear range from 10 ng/mL to 100 µg/mL and the linear equation of fitting curve is: y = 0.21 x - 0.15. The ME biosensors with a simple preparation method have advantages of high sensitivity, good stability and low LOD, showing the great potential for α2-M detection.

Carbon quantum dot-modified TiO2/SrTiO3 heterojunction for boosting photocatalytic CO2 reduction

An efficient carbon quantum dot (CQD)-modified TiO2/SrTiO3 heterojunction was constructed for photocatalytic CO2 reduction in this paper. Photogenerated electrons of SrTiO3 transferred to TiO2 via the transfer channel of CQDs for electron-hole recombination, while the photogenerated electrons migrated from TiO2 to CQDs to participate in the photocatalytic CO2 reduction reaction. Meanwhile, the up-conversion of CQDs enhanced the light harvesting ability of the catalyst and the CQDs enriched the active reaction sites. Due to the above advantages, the CO and CH4 produce rate over 0.1-CTS reached 54.9 and 35.9 μmol g−1 h−1, respectively, which was dramatically increased compared with pure TiO2 and pure SrTiO3. This work proposes a feasible strategy for integrating CQDs with TiO2 and SrTiO3 for the optimistic cooperative effect to obtain an effective catalyst for photocatalytic CO2 reduction.

Enhancing interfacial electron transfer and photoelectrochemical kinetics for efficient water-treatment strategy through N-doped carbon dots modified PhC2Cu

To improve the water environment quality, the development of an effective photocatalyst for pollutant removal was considered a promising strategy. The aim of the development of a novel photocatalyst PNC is pursued by modifying copper-phenylacetylide (PhC2Cu) with nitrogen-doped carbon quantum dots (N-CDs). Leading to a remarkable improvement in its light absorption capability, electron transfer efficiency and photoelectrochemical properties. Importantly, PNC possesses the characteristic of straightforward synthesis and demonstrates remarkable performance in the photodegradation of 99.87% sulfamethoxazole (SMX) within just 15 min, with a 3.95-fold increase in the photocatalytic rate. Analysis of the active substances revealed that 1O2, O2·‐, and h+ are the generated active species by PNC. Active sites and degradation pathways of SMX were explored through density functional theory (DFT) calculations and intermediate analysis. Key evidence regarding the direction of electron transfer within the system was obtained through in-situ irradiated X-ray (ISI-XPS) techniques. This study deepened our understanding of the electron transfer characteristics of phenylacetylene copper and provided new insights for the modification of photocatalysts.

Electrochemical sensing of hydroquinone using green synthesized nitrogen-doped carbon dots

Xenobiotic contaminants are dreadful to the environment. Hydroquinone is one of those toxins that need to be sensed using a nonenzymatic, environmentally friendly material. This was achieved by carbon quantum dots (CQDs) synthesized using hydrothermal supported by heteroatom doping using a bare glassy carbon electrode (GCE) electrochemically. The carbon dot’s largest active surface area of 0.13 cm2, better electron transfer capability, and doping enhance the functional groups and electrostatic interaction with a Limit of Detection (LOD) of 0.112 µM.

Synthesis and characterisation of tamarind seed husk-derived carbon quantum dots incorporated polypyrrole nanosphere composite for energy storage applications

ABSTRACT In this study, the green synthesis of Tamarind Seed Husk-derived carbon quantum dots (TCQDs) by using a facile one-step hydrothermal technique and Tamarind Seed Husk-derived carbon quantum dots/Polypyrrole nanosphere composites (TCQDs/PPy-NS) was synthesised by using the facile in-situ chemical polymerisation method. These results suggest that the TCQDs/PPy-NS composite electrode is a promising electrode for high-energy storage applications. The TCQDs/PPy-NS composite offers an effective supercapacitor electrode material by blending the superior electrical conductivity of TCQDs with the increased pseudocapacitive capacity of polypyrrole nanospheres (PPy-NS). The TCQDs/PPy-NS composite exhibits a specific capacity (Csp) of 400 Fg−1 at a current density (CD) of 2 Ag−1, and a solid-state flexible symmetric supercapacitor (SSC) was developed using the TCQDs/PPy-NS composite to meet an excellent power density (PD) of 1008.19 Wkg−1 at an energy density (ED) of 31.02 Whkg−1 It also demonstrated excellent cycling stability with a capacity retention and coulombic efficiency of 84.57% and 98.06% after 4000 cycles at 2 Ag−1 respectively. This remarkable flexibility and stability make the TCQDs/PPy-NS SSC device highly suitable for applications in wearable electronics and flexible energy storage systems.

Ultraviolet encryption information storage using hydrophobic poly(ε-caprolactone)/carbon quantum dot composite film

Luminescent poly(ε-caprolactone)/nitrogen-doped carbon quantum dots (PCL/N-CQDs) film with the function of information protection and encryption was realized based on the fluorescent N-CQDs. The N-CQDs were synthesized from citric acid with urea as a dopant for the enhancement of fluorescent properties. The facilely prepared composite film retained the hydrophobic nature of PCL and achieved the enhanced mechanical property. The appropriate crystallization temperature and degree of crystallinity of PCL provide the film with opaque characteristics at room temperature, rendering it an ideal carrier for carrying information. The information encryption and decryption are achieved through ionoprinting technique, exploiting the ability of Fe3+ ions to quench the fluorescence of N-CQDs, allowing for the encryption of designed information on the film’s surface. With its opaque, hydrophobic, and photoluminescent properties, the PCL/N-CQDs composite film holds significant promise for applications in information encryption.

Mechanistic Insights of Neuroprotective Efficacy of Verapamil-Loaded Carbon Quantum Dots against LPS-Induced Neurotoxicity in Rats.

Alzheimer's disease (AD) is a neurodegenerative disease that badly impacts patients and their caregivers. AD is characterized by deposition of amyloid beta (Aβ) and phosphorylated tau protein (pTau) in the brain with underlying neuroinflammation. We aimed to develop a neuroprotective paradigm by loading verapamil (VRH) into hyaluronic acid-modified carbon quantum dots (CQDs) and comparing its effectiveness with the free form in an AD-like model in rats induced by lipopolysaccharide (LPS). The experimental rats were divided into seven groups: control, LPS, CQDs, early free VRH (FVRH), late FVRH, early verapamil carbon quantum dots (VCQDs), and late VCQDs. Characterizations of VCQDs, the behavioral performance of the rats, histopathological and immunohistochemical changes, some AD hallmarks, oxidative stress biomarkers, neuro-affecting genes, and DNA fragmentation were determined. VRH was successfully loaded into CQDs, which was confirmed by the measured parameters. VRH showed enhancement in cognitive functions, disruption to the architecture of the brain, decreased Aβ and pTau, increased antioxidant capacity, modifiable expression of genes, and a decline in DNA fragmentation. The loaded therapy was superior to the free drug. Moreover, the early intervention was better than the late, confirming the implication of the detected molecular targets in the development of AD. VRH showed multifaceted mechanisms in combating LPS-induced neurotoxicity through its anti-inflammatory and antioxidant properties, thereby mitigating the hallmarks of AD. Additionally, the synthesized nanosystem approach exhibited superior neuroprotection owing to the advantages offered by CQDs. However, finding new actionable biomarkers and molecular targets is of decisive importance to improve the outcomes for patients with AD.

Wood-supported nitrogen-doped carbon quantum dot @Cu2O composites for efficient photocatalytic degradation of dye wastewater

Wood-supported nitrogen-doped carbon quantum dot @Cu2O composites for efficient photocatalytic degradation of dye wastewater

A green method for the preparation of carbon quantum dots from yellow lupin peel waste for spectrofluorometric determination of nirmatrelvir

The COVID-19 pandemic has highlighted the urgent need for effective antiviral agents. One such promising drug is nirmatrelvir (NIRMA), which has demonstrated the ability to inhibit viral replication and reduce hospitalization and mortality rates. In the field of analytical chemistry, carbon quantum dots (CQDs) derived from fruit peel waste have gained attention for their eco-friendly and cost-effective properties. In this study, CQDs were synthesized from the peel biomass waste of yellow lupin and utilized for the spectrofluorometric determination of NIRMA in pharmaceutical tablets. The proposed method offers simplicity and speed compared to existing methods. The synthesis process involved washing and grinding the peel waste, followed by heating in propylene glycol and purification using a dialysis membrane. The resulting CQD solution showed fluorescence at an emission wavelength of 411 nm upon excitation at 325 nm. The validation of the method, including linearity, range, limit of detection and quantification, accuracy, precision, and robustness, was conducted following ICH guidelines. The fluorescence intensities exhibited a linear relationship with increasing NIRMA concentration in the range of 15–150 µg/mL. The limit of detection found to be 4.0 μg/mL, with %relative standard deviations ≤ 1.46. This spectrofluorometric method represents a novel approach for the determination of NIRMA using CQDs derived from yellow lupin peel waste.

Design and optimization of a Cr(VI)-Selective Electrode based on a polymeric ß-cyclodextrin membrane modified with sulfur donor groups

This work presents the design and optimization of a new Cr(VI)-selective electrode. The new sensor is based on modifying a glassy carbon electrode with carbon quantum dots, ß-cyclodextrin, and carbon disulfide. The carbon quantum dots aided the electrical properties of the glassy carbon by improving charge transfer; the electropolymerization of ß-cyclodextrin resulted in a polymeric membrane that functions as a recognition element when modified by adding sulfur donor groups to its structure. Modifying the membrane with sulfur atoms gave the sensor excellent selectivity toward Cr(VI) ions. The electrode synthesis was optimized using a 23 factorial design; the factors studied were pH, the number of cycles in the electropolymerization, and the presence or absence of carbon nanoparticles. Eight different electrodes were constructed, and their potentiometric response to different concentrations of Cr(VI) was evaluated for all of them. The analysis of variance of the experimental design found no significant effect of any factor on the response. However, it suggests a strong interaction between the three factors studied. The sensor that presented the best analytical parameters was synthesized at pH 5 and 50 consecutive cycles in the presence of carbon quantum dots. This new electrode, with its response times of 40 s at different concentrations of the metal ion, exhibiting a slope of (66.0 ± 2.1) mV decade−1 and a detection limit of (5.2 ± 0.1)x10−7 mol L−1, can be used at pH between 0 and 3 without the effect of hydronium ions. The proposed electrode has good reproducibility and excellent selectivity against various metal ions and has significant advantages over other analysis methods. Its cost, ease of construction, easy handling, ease of operation, ease of storage and transportation, as well as good performance, short response time, and high selectivity make this electrode a valuable tool for easy, fast, and reliable monitoring of Cr(VI) in water samples, contributing to the safety and health of our environment.

Metolachlor Detection in Grain Using N‐Doped Carbon Quantum Dots and the Intramolecular Charge Transfer Effect

Herein, nitrogen is doped into carbon quantum dots (N‐CQDs) using a hydrothermal method for the rapid detection of metolachlor in grain. The morphological features, elemental compositions, and optical properties of the N‐CQDs are then analyzed and investigated using transmission electron microscopy, X‐ray photoelectron spectroscopy, and fluorescence spectroscopy, respectively. Based on the principle of intramolecular charge transfer, a fluorescent probe is constructed for the rapid detection of metolachlor. Under optimal experimental conditions, the fluorescence intensity change values of the N‐CQDs and metolachlor concentration have a good linear relationship when the concentration of metolachlor is in the range of 0.0125−2.5 μg mL−1. An evaluation of the method shows that the method has good selectivity, reproducibility, and stability, with a limit of detection of 1.63 μg kg−1 and a limit of quantification of 3.92 μg kg−1. The spiked recoveries of six real samples are tested using a spiked recovery assay that yielded spiked recoveries in the range of 105.05−87.13%, and their relative standard deviations (n = 3) ranged from 4.62% to 0.61%, indicating that the method can be used for detection in actual samples with good precision and stability.

Novel Carbon Quantum Dots Precisely Trigger Ferroptosis in Cancer Cells through Antioxidant Inhibition Synergistic Nanocatalytic Activity.

High levels of glutathione (GSH) are an important characteristic of malignant tumors and a significant cause of ineffective treatment and multidrug resistance. Although reactive oxygen species (ROS) therapy has been shown to induce tumor cell death, the strong clearance effect of GSH on ROS significantly reduces its therapeutic efficacy. Therefore, there is a need to develop new strategies for targeting GSH. In this study, novel carbon quantum dots derived from gentamycin (GM-CQDs) were designed and synthesized. On the basis of the results obtained, GM-CQDs contain sp2 and sp3 carbon atoms as well as nitrogen oxygen groups, which decrease the intracellular levels of GSH by downregulating SLC7A11, thereby disrupting redox balance, mediating lipid peroxidation, and inducing ferroptosis. Transcriptome analysis demonstrated that GM-CQDs downregulated the expression of molecules related to GSH metabolism while significantly increasing the expression of molecules related to ferroptosis. The in vivo results showed that the GM-CQDs exhibited excellent antitumor activity and immune activation ability. Furthermore, because of their ideal biological safety, GM-CQDs are highly promising for application as drugs targeting GSH in the treatment of malignant tumors.

Preparation of salicylic acid nano-protectant with dual synergistic mechanism: High direct fungicidal activity and plant defence toward cotton Verticillium wilt

Nanomaterials exhibit a wide range of potential applications in agricultural field. Here we construct a series of nano-protectants based on one model plant elicitor salicylic acid (SA) and six types of nanomaterials, including mesoporous silica nanosphere (MSN), mesoporous Fe3O4 nanosphere (Fe3O4), carbon quantum dot (CQD), polylactic acid-glycolic acid copolymer (PLGA), star polycation (SPc) and hydrophilic and lipophilic diblock polymer (HLDP), and explore the best nanomaterial for plant disease control. Our results demonstrate that the HLDP-SA nano-protectant displays the best control effects on cotton Verticillium wilt caused by one of the most notorious soil-borne fungi (Verticillium dahliae). The HLDP self-assembles with SA via electrostatic interaction into HLDP-SA nano-protectant, which changes the morphology of SA from needle-like particles to spherical particles. The loading efficiency of HLDP toward SA is calculated to be 49.28%, and the plant uptake of HLDP-loaded SA significantly increases by 3–4 times. HLDP-SA nano-protectant can suppress the spore germination of V991 strain with the spore germination rate of merely 2%, and its colony diameter is significantly decreased by 64.9%. Our transcriptome data demonstrate that the HLDP-SA nano-protectant accelerates the delivery and translocation of exogenous substances into V. dahliae, which exhibits the highest direct fungicidal activity via inhibiting the metabolism and weakening the pathogenicity. Meanwhile, its enhanced plant uptake with better adhesion performance on leaves amplifies the plant defense induced by SA via accelerating the biosynthesis of plant secondary metabolites, such as SA, abscisic acid (ABA) and gossypol. This study provides a powerful nanomaterial with dual synergistic mechanism for designing nano-protectant with high fungicidal activity and amplified plant defense.

Nitrogen-doped carbon quantum dots as antimicrobial agents against gram-positive Bacillus subtilis and Staphylococcus aureus under visible white light-emitting diode

Carbon nanomaterials, such as carbon quantum dots (CQDs), are excellent candidates for antibacterial agent development as they are cost-effective. Nitrogen-doped CQDs (N-doped CQDs) exhibit antibacterial activity against gram-positive bacteria. However, investigation of N-CQDs and their efficacy against the selected bacterial strains under visible light irradiation has not been carried out. Here, we aimed to evaluate N-CQDs for their efficacy as a photosensitizer for antimicrobial photodynamic therapy (aPDT). N-CQDs were synthesized using the hydrothermal method with 1,3,6-trinitropyrene (TNP) as the nitrogen and carbon source. Antimicrobial tests of N-CQDs were conducted against gram-positive (Bacillus subtilis NCIB 3610, Staphylococcus aureus Newman, and S. aureus USA300) and gram-negative (Escherichia coli K12) bacteria at different concentrations (0–100 mg/L). The N-CQDs exerted a moderate growth-inhibitory effect on gram-positive bacteria in the dark. However, in the presence of white light generated using 20-W light-emitting diode, N-CQDs could completely kill the bacteria at a low concentration of 20 mg/L. The minimal inhibitory concentration of N-CQDs for the two S. aureus strains (Newman and USA300) was 20 mg/L under light conditions, whereas that for B. subtilis was 100 mg/L. The results demonstrate that N-CQDs may be used as a photosensitizer in aPDT and as an antibacterial agent.

The resistance switching performance of the memristor improved effectively by inserting carbon quantum dots (CQDs) for digital information processing

The resistance switching performance of the memristor improved effectively by inserting carbon quantum dots (CQDs) for digital information processing