Carbon Quantum Dots Research Articles

Rapid determination of organophosphorus insecticides residue in fruit juice by a fluorescence sensor based on carbon quantum dots

Nitrogen doped carbon quantum dots (N-CQDs) were synthesized by a hydrothermal method. A fluorescence sensor for rapid determination of organophosphorus pesticides residue was developed using the N-CQDs based on acetylcholine enzyme inhibition. Cu2+ effectively quenched the strong fluorescence of N-CQDs, which could be recovered due to the complexation between copper ions and thiocholine, the hydrolysis product of acetylthiocholine catalyzed by acetylcholinesterase. Organophosphorus pesticides inhibited the activity of acetylcholinesterase, resulting in fluorescence quenching of N-CQDs. Fluorescence inhibiting efficiency depends on the concentration of the analytes, and therefore, the sensor could be used for quantitative analysis of organophosphorus pesticides residue. The average recoveries of the analytes ranged from 85.33 % to 110.67 % at the spiked concentrations of 0.015 mg/L, 0.04 mg/L and 0.1 mg/L, and the limits of detection were 2.89 ∼6.40 ng/mL. The developed method had the advantages of simple operation, fast speed, low cost, expensive apparatus-free, and environmental friendliness, which could be used for rapid screening of organophosphorus pesticides residue in real samples.

Nitrogen-doped carbon quantum dot regulates cell proliferation and differentiation by endoplasmic reticulum stress

ABSTRACT Quantum dots have diverse biomedical applications, from constructing biological infrastructures like medical imaging to advancing pharmaceutical research. However, concerns about human health arise due to the toxic potential of quantum dots based on heavy metals. Therefore, research on quantum dots has predominantly focused on oxidative stress, cell death, and other broader bodily toxicities. This study investigated the toxicity and cellular responses of mouse embryonic stem cells (mESCs) and mouse adult stem cells (mASCs) to nitrogen-doped carbon quantum dots (NCQDs) made of non-metallic materials. Cells were exposed to NCQDs, and we utilized a fluorescent ubiquitination-based cell system to verify whether NCQDs induce cytotoxicity. Furthermore, we validated the differentiation-inducing impact of NCQDs by utilizing embryonic stem cells equipped with the Oct4 enhancer-GFP reporter system. By analyzing gene expression including Crebzf, Chop, and ATF6, we also observed that NCQDs robustly elicited endoplasmic reticulum (ER) stress. We confirmed that NCQDs induced cytotoxicity and abnormal differentiation. Interestingly, we also confirmed that low concentrations of NCQDs stimulated cell proliferation in both mESCs and mASCs. In conclusion, NCQDs modulate cell death, proliferation, and differentiation in a concentration-dependent manner. Indiscriminate biological applications of NCQDs have the potential to cause cancer development by affecting normal cell division or to fail to induce normal differentiation by affecting embryonic development during pregnancy. Therefore, we propose that future biomedical applications of NCQDs necessitate comprehensive and diverse biological studies.

An Invisible Dermal Nanotattoo-Based Smart Wearable Sensor for eDiagnostics of Jaundice.

Despite substantial progress in the diagnosis of jaundice/hyperbilirubinemia as the most common disease and cause of hospitalization of newborns, on the eve of Industry/Healthcare 5.0, the development of accurate and reliable wearable diagnostic sensors for noninvasive smart monitoring of bilirubin (BIL) is still in high demand. Aiming to fabricate a smart wearable sensor for early diagnosis of neonatal jaundice and its therapeutic monitoring, we here report a fluorescent dermal nanotattoo that further coupled with an IoT-integrated wearable optoelectronic reader for minimally invasive, continuous, and real-time monitoring of BIL in interstitial fluid. Selective recovery of quenched fluorescence of the dermal tattoo sensor, composed of biocompatible dissolving/hydrogel microneedles loaded with fluorescent carbon quantum dots, upon blue light exposure used for jaundice phototherapy was utilized for highly selective BIL sensing. The fascinating features of our developed smart wearable tattoo sensor and its successful results with high correlation with blood BIL results make it a highly promising sensor for easy, minimally invasive, reliable, and smart eDiagnostics and continuous therapeutic eMonitoring of jaundice and other BIL-induced diseases at the point of care. We envision that the developed nanotattoo sensing bioplatform will inspire the development of future smart tattoo sensors in various diagnostic and monitoring scenarios.

High-efficient synthesis of straw-derived carbon quantum dots for facilitating methanogenic performance in high-load co-digestion of food waste and excess sludge

Anaerobic digestion (AD), as a crucial technology for organic waste resource recovery, faces the challenge of low efficiency in converting high-load organic substance into biogas. In this study, high-load AD system with food waste and excess sludge as co-substrates was constructed. The effect and mechanism of carbon quantum dots (CQD) derived from straw in promoting the performance of AD systems have been studied. The oxidation pretreatment of straw with H2O2 and acetic acid increased the yield of hydrothermal synthesis CQD to approximately 40%. The effect of different CQD on CH4 yield performance was further explored. The cumulative CH4 yield performance of the fermenter was improved after adding CQD. The CQD synthesized from pretreated straw and the nitrogen-doped CQD synthesized using Chlorella as the nitrogen source showed competitive promotion performance, increasing cumulative CH4 yield by 17.71% and 8.87%, respectively. These CQD can effectively accelerate the degradation of dissolved organic matter and thus improve the CH4 yield performance, with the most significant effect of CQD synthesized from pretreated straw. Electrochemical analysis and the correlation analysis between microorganisms and performance parameters showed that these CQD established an electron conductive network to enhance the electron transfer of the system. This well conductive conditions enriched hydrogenotrophic methanogenic (Methanosarcina), electroactive bacteria (Clostridium_sensu_stricto_1), and hydrolytic-acidifying bacteria (norank_f__Bacteroidetes_vadinHA17). This study significantly enhanced the yield of straw-derived CQD through green methods, and deeply revealed the potential promoting mechanisms of biomass-derived CQD by investigating the correlation between system performance and microorganisms in high-load AD systems

Comprehensive evaluation of the nephrotoxicity of carbon quantum dots: Effects of the surface charge

Carbon quantum dots (CQDs) are garnering attention for their broad applications. This study offers a detailed evaluation of the biomedical safety and health risks of carbon quantum dots (CQDs) with different surface modifications, addressing a key gap in their safe application. It focuses on three CQD types: diammonium citrate-based (CQDs-A), spermidine trihydrochloride-based (CQDs-S), and a combination (CQDs-A/S), analyzing their physicochemical properties, cytotoxicity, oxidative stress, inflammatory responses, and nephrotoxicity. While all CQDs were under 10 nm, their biological impacts varied. Positively charged CQDs-S and CQDs-A/S showed significant cytotoxicity in HEK293 cells, inducing oxidative stress but not activating NLRP3 inflammasome, indicating a limited inflammatory response. Renal integrity remained unaffected, with stable zonula occludens 2 expression and unaltered renal markers. In vivo studies in BALB/c mice further supported the safety of CQDs, showing no organ damage or kidney pathology at high doses. The findings underscore the potential for safe biomedical use of CQDs, particularly when their retention time is minimized. This research makes a novel contribution by linking CQDs' surface charge to cytotoxic effects and oxidative stress, providing key insights into their safe use in biomedicine and filling a critical gap in nanoparticle toxicity studies.

A novel carbon quantum dot (CQD) synthesis method with cost-effective reactants and a definitive indication: Hot bubble synthesis (HBBBS)

Carbon quantum dots (CQDs) are carbon-based biocompatible quantum dots that have low toxicity, are more soluble in water, have broad application areas, and the surface modification of these can be performed easily. In this study, we present a new CQD synthesis method with cost-effective reactants that can be easily found in laboratories are used. Besides, there is a definitive indication (bubble) for CQD production, unlike the other methods in the literature. The purification method of the CQDs was also optimized in this study. In the beginning of the synthesis, 3 times centrifugation (x3 CF) of the mixture was performed and the optimization of the purification method indicated that x3 CF before 3 days of dialysis membrane tubing (x3 CF & 3 DM) resulted in the formation of the purest CQDs. The characterization of the CQDs was done utilizing UV–VIS spectrophotometer, Fourier Transfer Infrared Spectroscopy (FT-IR), Zetasizer, fluorescence microscopy, Dynamic Light Scattering (DLS), Scanning Electron Microscope (SEM), Energy Dispersive Spectroscopy (EDS), and Transmission Electron Microscopy (TEM). It was concluded that the CQD formation depends on the mixing of sulphuric acid:acetone (2:1) ratio in a hot (140-165 °C) and an inert environment, and bubble coverage of the mixture surface(30-60 s). The bubble formation due to the reaction between sulphuric acid and pure acetone at high temperatures gives the developed method’s name of “Hot Bubble Synthesis” (HBBBS).

Tannic Acid Carbon Dots with Both Antimicrobial Activity and Selectivity for Fe3+ Detection

AbstractIn the field of antimicrobial nanomaterials, biomass‐derived carbon quantum dots have attracted great attention from contemporary researchers due to their unique physicochemical properties and favorable biosafety. In this study, novel carbon quantum dots (CQDs) were synthesized from tannic acid by a one‐step hydrothermal method. The polymeric CQDs have good surface functionality and hydrophilicity with a large number of hydroxyl, carboxyl and amino functional groups. Antimicrobial experiments showed that CQDs had a good inhibitory effect on Gram‐negative Escherichia coli and Gram‐positive Staphylococcus aureus, as well as the drug‐resistant bacterium methicillin‐resistant Staphylococcus aureus. Scanning electron microscopy showed that the morphology of S.aureus cells treated with CQDs became shrivelled and irregular, the surface of E.coli cells protruded to form irregular vesicles, and the whole became shriveled up, whereas MRSA cells appeared to be depressed in the middle, and there was a residue of adherent CQDs on the cell surface. In addition, CQDs exhibit selective fluorescence bursting behavior for ferric ions and can be used as fluorescent probes for rapid, sensitive and selective detection of Fe3+. Therefore, CQDs not only possess good bacteriostatic properties, but also serve as fluorescent sensors for the detection of Fe3+. It can be used as a potential sensing array for selective detection of iron ions and bacterial abatement from contaminated water.

Mixed Systems of Quaternary Ammonium Foam Drainage Agent with Carbon Quantum Dots and Silica Nanoparticles for Improved Gas Field Performance.

Foam drainage agents enhance gas production by removing wellbore liquids. However, due to the ultra-high salinity environments of the Hechuan gas field (salinity up to 32.5 × 104 mg/L), no foam drainage agent is suitable for this gas field. To address this challenge, we developed a novel nanocomposite foam drainage system composed of quaternary ammonium and two types of nanoparticles. This work describes the design and synthesis of a quaternary ammonium foam drainage agent and nano-engineered stabilizers. Nonylphenol polyoxyethylene ether sulfosuccinate quaternary ammonium foam drainage agent was synthesized using maleic anhydride, sodium chloroacetate, N,N-dimethylpropylenediamine, etc., as precursors. We employed the Stöber method to create hydrophobic silica nanoparticles. Carbon quantum dots were then prepared and functionalized with dodecylamine. Finally, carbon quantum dots were incorporated into the mesopores of silica nanoparticles to enhance stability. Through optimization, the best performance was achieved with a (quaternary ammonium foam drainage agents)-(carbon quantum dots/silica nanoparticles) ratio of 5:1 and a total dosage of 1.1%. Under harsh conditions (salinity 35 × 104 mg/L, condensate oil 250 cm3/m3, temperature 80 °C), the system exhibited excellent stability with an initial foam height of 160 mm, remaining at 110 mm after 5 min. Additionally, it displayed good liquid-carrying capacity (160 mL), low surface tension (27.91 mN/m), and a long half-life (659 s). These results suggest the effectiveness of nanoparticle-enhanced foam drainage systems in overcoming high-salinity challenges. Previous foam drainage agents typically exhibited a salinity resistance of no more than 25 × 104 mg/L. In contrast, this innovative system demonstrates a superior salinity tolerance of up to 35 × 104 mg/L, addressing a significant gap in available agents for high-salinity gas fields. This paves the way for future development of advanced foam systems for gas well applications with high salinity.

Antifungal films for strawberry packaging using carbon quantum dots derived from lemon and onion juice via green hydrothermal method

Fungi are the prime concern since they cause post-harvest decay in fruits such as strawberries; the fungi motivate the need for new antifungal agents. Among all these nanoparticles, the carbon quantum dots (CQDs) show the most promising results for their use in food packaging applications. Lemon carbon quantum dots (LCQD), which is derived from lemon juice, and onion carbon quantum dots (OCQD), which is derived from onion juice, were synthesized using the one-step hydrothermal method. The synthesized materials were then characterized using a transmission electron microscope, X-ray diffraction, Fourier transform infrared spectroscopy, and ultraviolet-visible (UV-Vis) spectroscopy. LCQD and OCQD solutions were applied to fresh strawberries for the purpose of conducting studies on weight loss, decay, and shelf-life extension. The antifungal activity of both CQDs was assessed against Rhizopus sp., Penicillium sp., Candida albicans, Aspergillus sp., and Botrytis cinerea using the agar-well diffusion technique. The obtained average size was 4.33±1.67 nm for LCQDs and 3.34±1.72 nm for OCQDs. Strawberries packaged with OCQDs and LCQDs showed weight loss of 5.21%±1.03% and 8.14%±1.09% on the fourth day of observation, respectively, against 18.71%±2.2% by control. On the same day, the decay rate for OCQDs was 11%, 40% for LCQDs, and 96.65% for control. Both exhibited antifungal activity, with inhibition zones ranging from 12.6-44.5 mm for various fungi. OCQD exhibits higher activity packaging compared to LCQD due to their smaller size and superior antifungal activity against a variety of fungi.

Carboxylic Group Functionalized Carbon Quantum Dots inhibit Hen Egg White Lysozyme Amyloidogenesis, leading to the Formation of Spherical Aggregates with Reduced Toxicity and ROS Generation.

Proteinopathies are a group of diseases where the protein structure has been altered. These alterations are linked to the production of amyloids, which are persistent, organized clumps of protein molecules through inter-molecular interactions. Several disorders, including Alzheimer's and Parkinson's, have been related to the presence of amyloids. Highly ordered beta sheets or beta folds are characteristic of amyloids; these structures can further self- assemble into stable fibrils. Protein aggregation is caused by a wide variety of environmental and experimental factors, including mutations, high pH, high temperature, and chemical modification. Despite several efforts, a cure for amyloidosis has yet to be found. Due to its advantageous semi-conducting characteristics, unique optical features, high surface area-to-volume ratio, biocompatibility, etc., carbon quantum dots (CQDs) have lately emerged as key instruments for a wide range of biomedical applications. To this end, we have investigated the effect of CQDs with a carboxyl group on their surface (CQD-CA) on the in vitro amyloidogenesis of hen egg white lysozyme (HEWL). By generating a stable compound that is resistant to fibrillation, our findings show that CQD-CA can suppress amyloid and disaggregate HEWL. In addition, CQD-CA caused the creation of non-toxic spherical aggregates, which generated much less reactive oxygen species (ROS). Overall, our results show that more research into amyloidosis treatments, including surface functionalized CQDs, is warranted.

Interfacial Bi-O-C bonds and rich oxygen vacancies synergistically endow carbon quantum dot/Bi2MoO6 with prominent photocatalytic CO2 reduction into CO

Developing the photocatalysts with the low charge-transfer resistance and fast charge kinetics is crucial to photocatalytic CO2 reduction into hydrocarbon fuels. Herein, we depict the interfacial Bi-O-C bond-bridged carbon quantum dot (CD)/oxygen vacancy-rich Bi2MoO6 (VOR-BMO) Ohmic junction photocatalysts. They were constructed by in-situ anchoring carbon quantum dots (CDs) onto the VOR-BMO hierarchical petal-like structures (HPs), which are self-assembled from numerous nanosheet subunits. Experimental analysis together with density functional theory (DFT) calculations indicate that the Bi-O-C bonds can provide the atomic-level interfacial channels, and introducing rich oxygen vacancies (VOs) into the BMO HPs can induce the enhanced built-in electric field (IEF) of the Ohmic heterojunction formed between VOR-BMO HPs and CDs, synergistically contributing the eminent charge transfer kinetics, so as to sharply boost the separation and transfer of the photoinduced electrons of VOR-BMO HPs into CDs with a near-zero resistance; Besides, the CD/VOR-BMO heterostructures can not only change the endoergic rate-determining step of VO-poor (VOP)-BMO HPs (i.e., CO* desorption to form CO) to an exoergic reaction process, thus promoting the CO* desorption from the photocatalyst surface, but also decrease the overall activation energy barrier. Consequently, in the presence of H2O vapor with no sacrificial agent, the optimum photocatalyst (CD/VOR-BMO-1.2) exhibits the fantabulous performances of CO2 photoreduction into CO with the production rate and selectivity of 60.00 μmol·g−1·h−1 and near 100 %, respectively. Such performances are comparable with the most recently reported photocatalysts for CO2 conversion. The study offers a valid strategy that harnesses the synergistic effect of the interfacial chemical bonds and Vo-induced enhanced IEF to design the high-efficiency photocatalysts for both energy and environmental applications.

Carbon quantum dots composite for enhanced selective detection of dopamine with organic electrochemical transistors

A compact organic electrochemical transistors (OECT) sensor enriched with carbon quantum dots (CQDs) was developed to enhance the transconductance of an electropolymerized poly(3,4-ethylenedioxythiophene) (PEDOT) film, enabling the precise and selective detection of dopamine (DA). Accurate monitoring of DA levels is critical for diagnosing and managing related conditions. Incorporating CQDs, we have achieved a remarkable up to threefold increase in current at the DA detection peak in differential pulse voltammetry. This enhancement showcases superior selectivity even in the presence of high concentrations of interferents like uric acid and ascorbic acid. This material significantly boosts the sensitivity of OECTs for DA detection, delivering an amperometric response with a detection limit of 55 nM and a broader detection range (1 − 500 µM). Our results underscore the potential of low-dimensional carbonaceous materials in creating cost-effective, high-sensitivity devices for detecting DA and other biomolecules. This breakthrough sets the stage for the development of next-generation biosensors for point-of-care diagnostics.Graphical

Rapid detection of chlorpyrifos in miscellaneous beans based on nitrogen and phosphorus doped carbon quantum dots fluorescence probe

A fluorescent probe based on N, P-doped carbon quantum dots was established to detect chlorpyrifos. N, P-doped carbon quantum dots were prepared by one-step hydrothermal method with trisodium citrate, dipotassium hydrogen phosphate and urea. The sensing mechanism was based on the fluorescence quenching of N, P-doped carbon quantum dots by chlorpyrifos through internal filtering effect. The results indicated that the linear range was 0.025 ~ 25µg/mL with the detection limit of 0.0008µg/g under the optimal detection conditions. The method was applied to different miscellaneous beans with the recoveries of 90.2% ~ 105.7% and the relative standard deviations were less than 4.8%. The fluorescent probe has the advantages of economy, high efficiency, easy preparation and specificity.

Size and chemistry of 1–2 layer graphene nanosheets at the transition into photoluminescence and assembly with large shifts from blue to red emission

Synthetic refinement of graphene photoluminescence remains challenging because underlying characteristics have not been well understood from polydisperse mixtures of different sizes and surface chemistries. Here, we isolate and characterise different populations of 1–2 layer graphene (1-2LG) each with narrow size range. Small 1-2LG nanosheets down to 25 nm size remained black and non-luminescent with N. and O. additions at their edges, whereas 15 nm nanosheets transitioned into photoluminescence, while retaining substantial sp2 carbon of graphene. Positively-charged amine modifications overcame the repulsion between nanosheets from the negative zeta potential of sp2 graphene faces in water and allowed assembly of similarly-sized nanosheets with large red shifts (>150 nm) taking blue emission into the red. However, more extensive edge modification into carboxyl groups and neutral amides built negative charge at the edges. Together with smaller nanosheet size and reduced sp2 carbon, red shifts were weakened by half in these isolates, which were most modified and more like graphene oxide and carbon quantum dots. N addition to form amines at nanosheet edges, while avoiding O atom addition and carboxyl groups, presents as a simple refinement for synthesis of self-assembling graphene quantum dots with multi-colour emission, which also retain sp2 carbon properties of graphene.

Co3O4/CQDs composite for selective ammonia detection in exhaled human breath analysis

Co3O4 was synthesized using electrospinning method and different amounts of carbon quantum dots (CQDs) were subsequently doped into the Co3O4 matrix via grinding, resulting in Co3O4/CQDs composite materials with various ratios. Gas sensing tests revealed that the resulting composite Co3O4/CQDs sensors exhibited excellent performance at a low temperature of 50°C, with outstanding selectivity towards ammonia gas and rapid response and recovery characteristics. Specifically, response and recovery time for 50 ppm ammonia gas were 14 s and 164 s, respectively. The outcomes of the exhalation simulation test utilizing sensors composed of this material demonstrate that the sensor's response to simulated chronic kidney disease breath closely approximates that of pure biological samples (1.08), exceeding the average response value of healthy exhaled breath samples (1.0). This demonstrates the sensor's capability to differentiate between healthy individuals and chronic kidney disease patients despite significant water vapor and carbon dioxide interference. This study provides valuable insights for the development of more efficient ammonia sensors and their role in the early detection of chronic kidney disease.

Preparation of Carbon Quantum Dot with Copper Nanoparticles Using Mugwort Leaves as Carbon Source to Construct FRET Fluorescent Sensor for Melamine Detection

AbstractCarbon quantum dots (CQDs) have gained extensive attention due to their excellent properties and wide applications. In this study, we selected the common Chinese herb mugwort as the carbon source and employed the microwave heating method to synthesize CQDs with a quantum yield of 13.54 %. These CQDs exhibited blue fluorescence under UV light irradiation. Furthermore, we constructed a fluorescence resonance energy transfer (FRET) mechanism by combining CQDs with copper nanoparticles (CuNPs) for the detection of melamine. The detection limit for melamine was determined to be 0.83 nmol/L, with a linear range of 1–100 nmol/L. The results demonstrated the potential of this sensing system for the sensitive and selective detection of melamine.

Nitrogen and Sulfur Co-Doped Carbon Quantum Dots as Fluorescent Nanosensors for Determination of Two Tetracycline Antibiotics in Dosage Forms and Human Plasma: Compliance With Greenness Metrics.

In this study, a novel, sensitive, and cost-effective spectrofluorimetric approach was established for the estimation of two important tetracycline antibiotics, tetracycline and doxycycline, without any pre-treatment procedures or harsh reaction conditions, for the first time. The proposed methodology is based on the quantitative quenching effect of each tetracycline and doxycycline on the native fluorescence of nitrogen and sulfur co-doped carbon quantum dots (NS-CQDs). A simple and ultrafast approach was applied to synthesize NS-CQDs using thiosemicarbazide and citric acid as starting materials after incubation in a microwave for only 1 min. Utilizing an excitation wavelength of 360 nm, NS-CQDs showed maximum emission peak at 430 nm. Calibration curves revealed excellent linearity within the ranges of 1.0-10.0 and 0.8-12.0 μg/mL with detection limits of 0.20 and 0.09 μg/mL for tetracycline and doxycycline, respectively. Due to the method's high sensitivity and selectivity, the proposed approach was applied for the determination of the studied drugs in their capsules and human plasma samples with high %recoveries. The developed approach was validated according to ICHQ2(R2) guidelines. GAPI and AGREE metric tools were used to verify the method's greenness and eco-friendliness, suggesting its use as a green substitute for the analysis of the studied drugs.

Combustion synthesis of TiO2/C composites for enhanced photocatalytic H2O2 production and solar steam evaporation efficiency

In this work, a simple combustion method was proposed for the controllable synthesis of TiO2/C composites, which can achieve both the efficient solar water evaporation at the interface and photocatalytic H2O2 production. Structural and morphological characteristic indicated the co-existence of carbon quantum dots and amorphous carbon, which were well distributed on the surface of the TiO2. TiO2/C composites displayed the enhanced visible light absorption and the rapid separation of photogenerated electron-hole pairs. TiO2/C-10 exhibited an excellent photocatalytic H2O2 production activity of 3068.46 μmol/g/h under simulated solar irradiation. Besides, its water evaporation rate reach up to 5.81 kg·m−2·h−1 under the simulated solar irradiation.

Hybridizing engineering strategy of decatungstate III: Transition metal modified carbon quantum dot-regulated photo-catalytic oxidation performance of decatungstate

The selective oxidation of hydrocarbons (RH) by dioxygen (O2) is a very important method for industrial production of bulk oxygen-containing compounds, However, due to the high chemical inertness of RH and O2, achieving this reaction under mild conditions still faces significant challenges. This paper discloses an efficient hybridizing engineering (HE) strategy of decatungstate (DT) with 3d transition metal ions (Mn+=Ni2+, Co2+ or Cu2+)-modified carbon quantum dots (Mn+/CQD) as the dopants. Compared to pure CQD, The Mn+/CQD can more efficiently combine with DT anion to fabricate a high-quality hybrid via electrostatic interactions, thereby bestowing the hybrid with an enhanced visible light response especially the separation efficiency of photo-generated charge pairs. Furthermore, the above hybridization effects of Mn+/CQD on DT anion can be fine-tuned and gradually improved with a change of the metal ion from Cu2+, Co2+ to Ni2+, along with a continuous enhancement of the hybrid's photo-catalytic efficiency in the visible light- triggered selective oxidation of ethylbenzene with O2 in acetonitrile. The best Ni2+/CQD-doped TBADT can achieve ca. 48% ethylbenzene conversion and 87.6% acetophenone selectivity in the presence of 2 M HCl, and it also shows a much higher photo-catalytic activity for the photo-oxidation of toluene, cyclohexane and benzyl alcohol compared to pure TBADT. The HE strategy with Mn+/CQDs as the cationized hybridizers is much superior to that with pure CQD or Ni2+ as the hybridizer in hoisting the photo-catalytic performance of DT.

Fluorescence switching sensor for sensitive detection of curcumin/Mn2+ using biomass carbon quantum dots: A combination of experimental and theoretical insights

Compared to high-performance liquid chromatography, capillary electrophoresis, and electrochemical analysis, fluorescent carbon dots derived from biomass materials have garnered significant attention due to their non-toxic, eco-friendly, and renewable advantages. In this research, CQDs-NH2 was synthesized in one step by hydrothermal method using banana peel as biomass carbon source and ethylenediamine (EDA) as dopant. The blue fluorescence of CQDs-NH2 was found to be quenched by the addition of curcumin through the synergistic effect of static quenching and internal filtering effect (IFE). The response to curcumin showed good linearity in the concentration range of 1-15μM with a limit of detection (LOD) of 18.56nM. The fluorescence of CQDs-NH2 was partially restored in the presence of curcumin and Mn2+, leading to the establishment of a curcumin@CQDs-NH2 switch sensor for the detection of Mn2+ in the linear range of 5-60μM with a LOD of 20.35nM. Furthermore, density functional theory (DFT) calculations suggest that the interaction between Mn2+ and curcumin is stronger than the interaction between Mn2+ and functionalized CQDs (f-CQDs), elucidating the introduction of Mn2+ disrupts the interaction between curcumin and CQDs-NH2, leading to the restoration of CQDs-NH2 fluorescence. Finally, the CQDs-NH2 fluorescence switch sensor demonstrated high accuracy and precision in liquid food and water quality testing with recoveries ranging from 95.19% to 105.54%.