Carbon Dots Research Articles

A “performance-inheritance” strategy for achieving hydrophilic/hydrophobic fluorescent biomass-derived carbon dots through simple solvothermal treatments

It remains a challenge to obtain hydrophilic/hydrophobic materials with promising biocompatibility and environmental compatibility by simple methods. Herein, we designed a “performance-inheritance” strategy and for the first time constructed hydrophilic/hydrophobic fluorescent spirulina-derived carbon dots (CDs) through simple solvothermal treatments. The contact angle of hydrophobic CDs with near-infrared (NIR) fluorescence is 110°, while hydrophilic CDs with blue fluorescence is 19°. We further revealed that the NIR luminescence is derived from the chlorophyll structure, while blue fluorescence is from the surface states. Based on the hydrophilicity/hydrophobicity of CDs, a ratiometric sensor was constructed to detect water content in organic solutions. In addition, CDs with NIR emission have low toxicity and good biocompatibility, making them efficient probes for bioimaging. This strategy provides a simple method for the high value-added conversion of algae and a new perspective for the “design-preparation-application” of biomass-derived CDs with specific properties.

Utilization of Biodiesel Residue through Efficient Microwave-Assisted Synthesis of Carbon Quantum Dots: A Versatile Nanomaterial for Environmental Remediation

The rapid expansion of the biodiesel industry has substantially increased crude glycerol residue (CG) production, creating sustainability and economic challenges due to surplus glycerol generation. Conventional purification methods are costly and environmentally demanding, necessitating innovative strategies to utilize this residue effectively. This study innovates by exploring the microwave-assisted synthesis of carbon dots (CDs) from CG, exemplifying a shift toward sustainable biodiesel production by transforming the residue into a multifunctional material. CDs exhibited a nanometric spherical morphology of 2.6 ± 0.3 nm diameter verified by HRTEM analysis. The reduction of oxygen confirmed the transformation of CG into CDs–H bands and the formation of polyaromatic structures. The graphitic structures were verified by Raman spectroscopy, electron paramagnetic resonance, and X-ray diffraction. The quantum yield (QY) was calculated to be 1.3%. The multifunctionality of CDs has been proven in sensing and photocatalysis. In the sensor applications, the CDs demonstrated strong fluorescence quenching in the presence of Fe3+ and Cu2+ ions, with a limit of detection of 1.8 ± 0.01 and 4.0 ± 0.04 mg.L-1, respectively, indicating the potential use of CDs in detecting these ions in wastewater samples. When complexed with titanium dioxide (TiO2), the TiO2/CDs composite showed an extended photoresponse of TiO2 to the UV-visible region, improving the efficiency of photocatalytic reactions for Victoria Blue B (VBB) dye degradation (98% degradation after 150 min). This research highlights the potential of utilizing CG to produce versatile CDs, contribute to more sustainable biodiesel production, and offer promising applications in environmental sensing and photocatalysis.

Design and green synthesis of carbon Dots/Gold nanoparticles Composites and their applications for neurotransmitters sensing based on emission Spectroscopy

Changes in the neurotransmitters are indications for several diseases. Several sensors were reported for monitoring dopamine (DA), but the simple and accurate DA detection in biological samples still faces many challenges. The research proposal aims to develop an optical sensor for detecting neurotransmitters based on luminescence emission spectra in different biological samples. Carbon dots (CDs) were fabricated based on a green synthesis route. Then the prepared CDs were decorated with varying concentrations of gold nanoparticles (Au NPs). The synthesis process was optimized, and the obtained CDs/Au NPs nanocomposites were applied as neurotransmitters’ optical nanosensors. The optical nanosensor approach provides easy and sensitive multiplex analysis. A wide range of neurotransmitters was monitored. The developed sensor’s sensitivity, selectivity, and reproducibility were investigated. Au NPs act as CDs’ stabilizers, enhancing the emission effect, and scaffolds for binding DA with CDs’ surface. DA moieties bind to CDs through the interaction between the DA-NH2 groups and Au NPS. Due to electron transfer, the bonding of DA molecules leads to fluorescence quenching of AuNPs/CDs. The Au-CDs-based DA fluorescence showed high sensitivity with adetection limit, and limit quantification of 2.04 nM and 6.18 nM, respectively. Furthermore, the selectivity of the sensor was investigated in the presence of glucose, uric acid (UA), and ascorbic acid (AA), which showed no interference effect at 10 times higher concentrations. Moreover, the proposed sensor has been successfully utilized for DA detection in human serum samples with a high recovery efficiency between 98.83 % and 103.5 %.

Pineapple stem starch-based films incorporated with pineapple leaf carbon dots as functional filler for active food packaging applications

Pineapple leaf waste, a byproduct of agricultural processes, was used as a novel raw material to synthesize carbon dots (CDs) through a simple hydrothermal method. The CDs were subsequently incorporated into pineapple stem starch (PSS)-based active food packaging films. The characterization of the CDs and PSS-CDs films was conducted using various techniques, including UV-light spectroscopy, fluorescence spectroscopy, and transmission electron microscopy. The results revealed that the CDs measured 2.36 ± 0.33 nm and exhibited antioxidant and antibacterial activities. The addition of the CDs led to notable enhancements in both mechanical strength and UV-barrier properties. Thus, PSS-CDs packaging film was successfully prepared, with the incorporation of CDs enhancing the antioxidant and antimicrobial properties of the film, thereby extending the shelf-life of fresh pork.

High-specific capacitance, binder-free composite electrodes prepared from carbon dots embedded in copper oxide-nickel oxide nanowires grown on nickel foam for asymmetric supercapacitors

The binder-free electrodes based on CuO-NiO and sodium polyacrylate-derived carbon dots (CDs) composites were simply prepared on nickel foam in two steps: hydrothermal synthesis and thermal annealing. A specific capacitance as high as 635F g−1 (at 5 mV s−1) was achieved with the electrodes containing CDs embedded in the CuO-NiO nanowires, compared to only 468F g−1 for the CuO-NiO nanowire electrode without CDs, representing a 136 % improvement. To provide mechanistic insights on the supercapacitor performance, electrochemical analysis was carried out, and it was found that synergistic effects from CuO-NiO and CDs gave an optimum contribution of surface/diffusion processes of charge transfer. Asymmetric supercapacitor was also fabricated using activated carbon as a negative electrode and CDs/CuO-NiO@Ni-foam as a positive electrode, giving a 1.5 V, highest energy density of 20.3 Wh kg−1 at power density of 151.1 W kg−1. Due to simplicity and extraordinary performance, the binder-free CDs/CuO-NiO composite electrodes are potential candidates for the mainstream supercapacitors, and the strategy detailed in this work also provides an innovative, practical way for an electrode design for energy storage devices.

Carbon dot aggregates: a new strategy to promote corrosion inhibition performance of carbon dots

The corrosion of metal not only produces serious economic losses and environmental pollution but also threatens equipment safety. Carbon dots (CDs) exhibit outstanding inhibition properties to availably retard the corrosion of metal. However, the present CDs-based corrosion inhibitors still fail to fully exert the environmentally friendly and low-cost merits of CDs. To address this issue, CD aggregates (CDAs) prepared by low-cost and eco-friendly CDs are developed as novel corrosion inhibitors for the first time, and their corrosion inhibition mechanism is disclosed. Specifically, CDAs with excellent long-term dispersion stability are synthesized by solvothermal treatment of CDs formed by citric acid and urea. CDAs at only 200 mg/L provide a corrosion inhibition effect of 90.38% for Q235 carbon steel in 1 mol/L HCl solution, approximately 1.53 times higher than that of CDs (59.21%). Moreover, the corrosion inhibition mechanism of CDAs is proposed through the analysis of adsorption isotherm, examination of corrosion morphologies, and theoretical calculations. That is, CDAs physically and chemically adsorb on the carbon steel surface, mainly hindering its anodic reaction, thus retarding the corrosion of carbon steel. This research firstly verifies the corrosion inhibition potential of green and low-cost CDAs and provides a novel strategy to promote the corrosion inhibition performance of CDs, promoting the progress of aggregate-based corrosion inhibitors.

Innovative fluorescent ratiometric probe from Oolong tea dreg for highly sensitive bilirubin detection

Bilirubin, a crucial component in heme degradation, is formed during the breakdown of red blood cells in the liver and spleen. Elevated bilirubin levels are closely associated with jaundice and serve as markers for various blood and liver-related disorders. Detection of BR has been approached through various methods with fluorescent methods gaining prominence due to their exceptional sensitivity, rapid response, and precision. Among the fluorescence methods, carbon dots have emerged as versatile optical probes, known for their unique optical properties, low toxicity, and ease of synthesis. However, carbon dots typically exhibit a single emission peak, limiting accuracy due to vulnerability to external interferences. To overcome this limitation, probes featuring multiple independent emission signals are preferred. Chlorophyll, abundant in nature and sourced from biomass, is recognized for its safe and fluorescent properties, making it a secure choice for fluorescence-based sensing. This study introduces an innovative approach utilizing Oolong tea dreg as a source of chlorophyll for creating a fluorescent probe to detect bilirubin. Chlorophyll was partially converted into carbon dots using a combination of extraction and hydrothermal techniques, producing a ratiometric probe with two emission signals. The fluorescence of the probe was quenched in the presence of the bilirubin through the inner filter effect. The proposed probe exhibited outstanding selectivity and a low limit of detection (0.8 µM) for bilirubin. Furthermore, the probe demonstrated satisfactory recovery rates when tested with artificial urine and human urine samples.

Quaternary Ammonium Salt-Derived Carbon Dots for Antibacterial Efficacy and Tetracycline Sensing

Bacterial infections pose a significant threat to global health, necessitating the development of novel antibacterial materials. Tetracycline antibiotics (CTC, OTC, TC) are low-cost and widely abused in recent years. However, they were easily absorbed by the human body and long-term exposure to tetracycline could contribute to some adverse reactions and diseases. So there is a need for novel antimicrobial agents and a rapid, sensitive detection method of tetracycline antibiotics. In this study, we synthesized three carbon dots (CDs1, CDs2, CDs3) from quaternary ammonium salts via a hydrothermal method. Antibacterial assays against Staphylococcus aureus and Escherichia coli demonstrated their potent antibacterial activity with minimum inhibitory concentrations(MIC) determined as 39 μg/mL, 78 μg/mL, and 9.8 μg/mL, respectively. Notably, CDs3 exhibited the highest antibacterial effectiveness, attributed to its smaller size and higher chlorine content compared toCDs1 and CDs2. Additionally, CDs1, characterized by its high fluorescence quantum yield and stability, demonstrated remarkable specificity and robust anti-interference capabilities in detecting tetracycline antibiotics, including chlortetracycline (CTC), oxytetracycline (OTC), and tetracycline (TC). Leveraging the internal filtration effect mechanism, CDs1 exhibited detection limits of 0.18 μmol/L for CTC, 0.15 μmol/L for OTC, and 0.13 μmol/L for TC, respectively. The effectiveness of this detection method was further confirmed through validation in real milk samples, confirming the practical utility of CDs1 in food safety testing. The low toxicity of carbon dots were synthesized using a simple one-step hydrothermal method, which was fast, cost-effective, and easy to achieve large-scale production. Our findings underscore the potential of CDs derived from quaternary ammonium salts, demonstrating promising performance in antibacterial applications and providing insights into food safety testing methodologies.

Dracocephalum Moldavica L.-Derived carbon dots for effective periodontitis treatment via reprogramming energy metabolism in Macrophages

Dracocephalum Moldavica L. (DML), a Chinese traditional medicine rich in flavone compounds (e.g., tilianin), has shown antioxidant and anti-inflammatory potential for alleviating inflammatory disorders. However, the extraction of active ingredients of DML is complex, and these extracts usually act synergistically to treat inflammatory diseases. In this study, the carbon dots derived from DML (T-CDs) were rapidly prepared via the one-pot method and showed good performance in biocompatibility and free radical scavenging capacity. Then, the T-CDs were loaded into the hydrogel and applied to treat periodontitis. The in vivo experiments demonstrated that T-CDs could promote the inflammation resolution of and the alveolar bone reparation in the periodontitis model after periodontal injection. With further investigation, it could be found that T-CDs involved the alternative polarization of macrophage by rebalancing glycolysis and mitochondrial respiration. Overall, it was the first time DML had been used to prepare carbon dots with anti-inflammation. This study provided an effective drug candidate for the treatment of periodontitis and offered an in-depth understanding of the therapeutic mechanism of T-CDs in periodontitis through macrophage immunomodulation.

A novel dual-function fluorescence sensor Eu/CDs@MOF-808 for the sensitive detection of adenosine triphosphate and uric acid

Designing and developing a reliable method for the detection of potential biomarker molecules are crucial for the early prevention and diagnosis of diseases. In this study, we present a novel functionalized metal–organic framework material (MOF-808) that is developed to construct ratiometric fluorescence sensing platforms (Eu/CDs@MOF-808) for the detection of adenosine triphosphate (ATP) and uric acid (UA). The fluorescent probe Eu/CDs@MOF-808 prepared through the in-situ encapsulation of fluorescent carbon dots (CDs) within the structure of MOF-808 exhibits excellent optical properties. Additionally, rare earth ions (Eu3+) are incorporated into the CDs@MOF-808 using a post-synthetic modification strategy. The presence of ATP significantly enhances the characteristic peak of carbon dots (CDs) at 440 nm, while the peak of Eu3+ at 614 nm remains relatively unchanged. Furthermore, the concentration of ATP exhibits a strong linear relationship with the ratiometric fluorescence intensity (F440/F614) in the concentration range of 0.5–450 μM, with a detection limit of 0.22 μM. Notably, the addition of uric acid (UA) to this fluorescence sensing platform leads to a marked reduction in the characteristic peak intensity of Eu3+, which results in a satisfactory linear relationship between the ratiometric fluorescence intensity and UA concentration in the concentration ranges of 0.04–300 μM and 300–650 μM, with a detection limit of 0.04 μM. Additionally, the fluorescent sensor has been successfully applied for the detection of ATP and UA in real serum and urine samples.

Robust polymer electrolytes with fast ion-transport nanochannels constructed by carbon dots for long lifespan Li metal batteries

As an anode material in energy storage systems, Li metal has exceptional merits, including high specific capacity, low density, and low redox potential. However, challenges such as lithium dendrites and unstable solid electrolyte interphase (SEI) hinder the practical application of lithium metal batteries (LMBs). Solid polymer electrolytes (SPEs), notably PVDF-HFP, are expected to overcome the above problems because of their mechanical merits and safe features, but their limited ion transportation behaviors result in insufficient ionic conductivity at room temperature. Herein, we invent an approach to prepare high performance electrolytes composed by porous PVDF-HFP and functionalized carbon dots (CDs). Such porous PVDF-HFP polymer membranes are created by a subtle phase inversion process, possessing a sponge-like structure, vertical lithium-ion transport channels and CDs decorated surfaces, thus able to uptake the liquid electrolyte (LE) to form gel polymer electrolytes (GPEs). The CDs fillers are produced in large scale with adjustable surface states, which can enhance Li salts disassociation to release free Li ions. As a result, the optimal conductivity of the as-prepared GPEs at room temperature is up to 8.7 mS cm−1 and the lithium transference number reaches 0.64. Our GPEs endow Li symmetric batteries with very stable SEI and long cycling life over 2200 h, and help realize high capacities and retention rates of the LMBs using LiFePO4(LFP) or LiCoO2(LCO) cathodes.

Highly efficient reduction of Cr(VI) from industries sewage using novel biomass-driven carbon dots modified TiO2 under sunlight

Hexavalent chromium (Cr(VI)) pollution poses a significant global environmental challenge, with current photocatalysts exhibiting limited efficiencies under natural sunlight, especially in neutral to alkaline conditions or at high Cr(VI) concentrations. In this study, amine-rich biomass-derived carbon dots (CDs) were synthesized from peanut shells and ethylenediamine via a hydrothermal method, combined with titanium dioxide (TiO2) to form a composite with a narrower band gap. This enhanced the electrostatic interactions with Cr(VI), thus improving photocatalytic performance. The composite (1 % CDs) effectively reduced 50 mg/L of Cr(VI) within 60 min under sunlight irradiation, demonstrating stable performance across various pH levels (3, 5, 7, and 9) and Cr(VI) concentrations (10 to 60 mg/L). Even after five cycles, the reduction efficiency remained high at 96.83 %. The composite also achieved reduction rates of 90.09 % and 89.01 % for domestic and electroplating wastewater, respectively, while exhibiting antibacterial properties. Free-radical scavenging experiments confirmed that electrons and holes were the primary active species driving the reduction. This work highlights the potential of the composites for efficient and stable Cr(VI) reduction in real-world water treatment applications.

DES-driven sustainable dual valorization of lignocellulose into carbon dots and porous biochar for effective wastewater remediation

Deep eutectic solvents (DES) are renowned for their effectiveness in deconstructing lignocellulose and extracting lignin, yet the challenges lie in lignin condensation and the disposal of the DES remnants after pretreatment. To overcome these issues, this work proposed a holistic strategy utilizing deep eutectic solvent (DES)-driven lignocellulose deconstruction to upgrade lignocellulose into nitrogen-doped carbon dots (CDs) and iron-decorated porous carbons, serving as photocatalysts and adsorbents, respectively. These nitrogen-doped CDs via the choline chloride/FeCl3 DES pretreatment exhibited abundant nitrogen/oxygen functional groups, enhancing photocatalytic activities and facilitating effective charge separation and transfer. The photocatalytic efficiency of the CDs on dyes reached 97 % under acidic conditions primarily, and free radical quenching experiments indicated that singlet oxygen was the dominant oxidant species. Moreover, the adsorption capabilities of Fe-decorated porous carbons for Congo red reached 2432.3 mg·g−1, surpassing most existing carbon materials. The adsorption mechanism was due to a synergistic effect including physical adsorption, coordination, hydrogen bonding, electrostatic, and π-π interactions. This study proposed a synergetic conversion of DES and lignocellulose into functional carbon materials for wastewater remediation, which inspired the development of a green and cost-effective biorefinery.

Magnesium-Doped Carbon Quantum Dot Nanomaterials Alleviate Salt Stress in Rice by Scavenging Reactive Oxygen Species to Increase Photosynthesis.

Salt stress has strongly impacted the long-term growth of eco-friendly farming worldwide. By targeting the oxidative stress induced by salt, the utilization of biomass-derived carbon dots (CDs) that possess high-efficiency antioxidant properties, are nontoxic, and have excellent biocompatibility represents a viable and effective approach for enhancing the salt tolerance of plants. In this study, we blended magnesium oxide nanoparticles with carbon sources derived from durian shells to construct Mg-doped carbon dots (Mg-CDs) through a hydrothermal reaction. We demonstrated that the foliar application of 150 μg/mL Mg-CDs to rice plants after treatment with 100 mM salt effectively increased the plant height (9.52%), fresh weight (22.41%), dry weight (33.33%), K+ content (21.46%), chlorophyll content (36.21%), and carotenoid content (16.21%); decreased the malondialdehyde (MDA) (9.43%), Na+ (25.75%), H2O2 (17.50%), and O2•- contents (37.99%); and promoted the photosynthetic system and antioxidant activity. Transcriptome analysis revealed that Mg-CD pretreatment triggered transcriptional reprogramming in rice seedlings. The enrichment analysis of the Kyoto Encyclopedia of Genes and Genomes pathways based on trend groups of gene expression patterns of Profile 8 and Profile 15 indicated that priming with Mg-CDs activated stress signaling- and defense-related pathways, such as metabolic pathways, biosynthesis of secondary metabolites, and photosynthesis pathways. These activations subsequently prompted the expression of genes related to the mitogen-activated protein kinase signaling pathway, hormone signal transduction, the oxidative stress response, and the photosynthetic system. This study demonstrated that the use of Mg-CDs represents a potential strategy to increase plant salt tolerance, creating the possibility for the regulation of crop salinity stress and offering valuable advancements in sustainable agriculture.

Colorimetric and fluorometric sensing of polar E120 in juice and environmental water samples using mannitol-functionalized magnetic nanoparticles and nitrogen-doped carbon dots

In this study, mannitol-functionalized magnetic nanoparticles (MMNPs) as a unique nanosorbent and N-doped fluorescent carbon dots (N-CDs) as a cost-effective nanosensor were created and utilized, for the first time, for dispersive micro-solid-phase extraction (Dµ-SPE) to determine carmine (E120) dye in water samples and juices. The modification of the magnetic nanoparticles with mannitol was designed to enhance the responsive potential for adsorption of the polar E120 dye from complex sample matrices through electrostatic interaction. The as-fabricated N-CDs fluorescent probe exhibited a high fluorescence quantum yield (Φs) of 43.1 %, allowing for accurate fluorometric detection of E120 dye. The as-synthesized MMNPs nanosorbent and fluorescent N-CDs nanoprobe were characterized by Scanning electron microscopy (SEM), X-ray diffraction (XRD), Fourier Transform Infrared Spectroscopy (FT-IR), Transmission electron microscopy (TEM), Energy Dispersive X-ray (EDX), Thermogravimetric analysis (TGA), and Vibrating-sample magnetometer (VSM). Density Functional Theory (DFT) studied the E120 dye structure using Gaussian 09 to explore the interactions between E 120 dye molecules and MMNPs/N-CDs. The impact of the critical adsorption and detection experimental factors was investigated and adjusted. A minimal amount of MMNPs nanosorbent (150 mg) is sufficient for E120 extraction in an acceptable time of 15 min. Furthermore, with a high determination coefficient, the adsorption characteristics fit with the models of Langmuir isotherm and first-order kinetics. The adsorption capacity (qe) of the as-fabricated MMNPs was 87.7 mg.g−1. After adsorption, E120 dye was fluorometrically analyzed using nitrogen-doped carbon dots as a fluorescent nanosensor via the inner filter effect (IFE) mechanism. Under the optimized conditions, the proposed fluorometric procedures showed a linear increase in the fluorescence ratio with increasing the E120 concentration in the range of 1.0 – 160.0 μg.mL−1 with detection (LOD) and quantitation (LOQ) limits of 0.27 and 0.83 μg.mL−1, respectively. The relative standard deviation (%RSD) did not exceed 2.34 %. The proposed methodology was successfully applied to determine E120 dye in juice and environmental water samples with % recovery ranged from 89.2-106.1 % and 92.9–107.2 %, respectively offering a reliable and environmentally friendly alternative to traditional detection methods with potential applications across various industries.

In situ green synthesis of Rosa sterilis-based carbon dots for Fe3+ fluorescent sensing in baijiu

Baijiu is susceptible to contamination by Fe3+ during brewing and storage, and it is crucial to select a convenient method for the detection of Fe3+. In this work, we developed a one-step hydrothermal in situ green synthesis of blue fluorescent carbon dots (RS-CDs) from Rosa sterilis. A series of characterization of RS-CDs was carried out, and it was found that RS-CDs derived from biomass materials were environmentally friendly and low toxic, with an average particle size of 2.75 nm, a graphitic structure, and a surface rich in functional groups related to C, N, and O atoms. In addition, the PL of RS-CDs exhibited excitation-dependent behavior. The emission center was redshifted from 448 nm to 530 nm at excitation wavelengths ranging from 320 nm to 460 nm. After investigating the selectivity of RS-CDs for different metal ions, we found that RS-CDs had the highest quenching efficiency for Fe3+ and exhibited a static quenching mechanism. The LOD was 0.959 μM in the linear range of 0-140 μM. In addition, RS-CDs were successfully used for the detection of Fe3+ in four kinds of basic flavor baijiu, as well as in different containers for storage of baijiu. The study demonstrated that Rosa sterilis can be used to produce green and low-cost CDs, and the prepared RS-CDs can be conveniently, rapidly and selectively detected Fe3+ in the baijiu system, which is of potential application.

Functional composite films incorporating triphala-derived carbon dots for extending chicken preservation

Triphala-based carbon dots (T-CDs) were successfully prepared using a simple one-step hydrothermal method. T-CDs were characterized by absorbance, fluorescence, Fourier-transform infrared, X-ray photoelectron spectroscopy, and high-resolution transmission electron microscopy. T-CDs showed bright blue fluorescence at 434 nm upon excitation at 360 nm. Functional composite films were prepared using poly(vinyl alcohol) and gelatin mixture by incorporating T-CDs and applied as a packaging film to extend the shelf life of chicken. The antibacterial activity of T-CDs against Listeria monocytogenes and Staphylococcus aureus was evaluated using well diffusion and colony count methods. T-CDs were evenly dispersed throughout the PVA/Gel solution to form a dense and uninterrupted film. They also formed strong bonds with polymer chains, which improved the tensile strength of the film from 32.44 to 42.70 MPa. Furthermore, the presence of T-CDs significantly enhanced the UV-blocking ability of the PVA/Gel films, achieving 99.7 % for UV-B and 97.2 % for UV-A. In addition, the PVA/Gel/T-CDs composite films showed excellent antioxidant, antimicrobial and UV-barrier properties, extending the shelf life of chicken. Therefore, the PVA/Gel/T-CDs composite films showed great potential as an active food packaging material to extend the shelf life and preserve the visual quality of packaged meat.

Anchor carbon dots inside NH2-MIL-88B via ship-in-a-bottle strategy for dual signal enhancement in colorimetric-fluorescent sensors

The increase in oxytetracycline (OTC) pollution has become a significant risk to ecological stability and human health because of excessive use. Therefore, developing a precise and reliable sensor for trace OTC detection is critical. In this work, a dual-mode sensor of colorimetric-fluorescent (CL-FL) with dual signal-on was developed for OTC detection. Firstly, a novel carbon dots encapsulating in cavities of MOFs composite (CDs@NH2-MIL-88B) was constructed by the ship-in-a-bottle approach, which enhanced peroxidase-like activity and fluorescent intensity. Further, combining with surface molecularly imprinted polymer (MIP), the dual-mode sensor was constructed to develop selectivity (CDs@NH2-MIL-88B@rMIP). Finally, the dual signal enhancement mechanism of the sensor comes from the interaction between OTC and identifying binding site involving strong hydrogen bonding and metal complexation from imprinted cavity and CDs@NH2-MIL-88B, respectively. The prepared sensor has a linear detection range of 1.00 × 10-9 - 1.00 × 10-5M with the limit of detection (LOD) of 1.47 × 10-10M for the CL mode and a detection range of 1.00 × 10-11 -1.00 × 10-7M with the LOD of 1.84 × 10-12M for the FL mode. Meanwhile, the sensor shows high sensitivity, accuracy and reliability in OTC detection. Overall, this work provides a promising CL-FL dual-mode sensing systems with signal-on in the detection of antibiotics and other hazardous pollutants.

Dual "Turn-On" Fluorescent and Colorimetric Sensing of Permanganate Based on Yellow Carbon Dots.

Existing permanganates (MnO4 -) sensing methods suffered from the poor selectivity, restricted solubility, and/or less desirable signaling mechanisms (e.g., "turn-off" processes), resulting in the false positive result. In this work, an effective "turn-on" fluorescence method for MnO4 - detection in aqueous media was proposed via yellow fluorescence carbon dots (Y-CDs) with the maximum emission peak of 553 nm. Upon the introduction of MnO4 -, the fluorescence of Y-CDs increased significantly due to the enhanced surface passivation degree and intramolecular charge transfer. In the range of 0.1-10 μM, the fluorescence ratio (F/F0) is proportional to the MnO4 - ions concentration, realizing the "turn-on" fluorescence sensing of MnO4 -. On the other hand, utilizing the significant color change of Y-CDs by MnO4 - ions, the colorimetric analysis can also be established for MnO4 - assay. Compared with other probes, the analysis results obtained by bimodal sensing tactics of fluorescent and colorimetric can be mutually verified to improve the reliability and meet the sensing needs of targets in complex environments.

Fluorescence Sensing of Glutathione Based on the In-Situ Growth of Carbon Dots-Manganese Dioxide Nanosheets

Blue fluorescent carbon dots with high purity were synthesized through a one-step hydrothermal method using citric acid and ethylenediamine as raw materials and then purification by column chromatography. In-situ controllable synthesis was used to prepare carbon dots-manganese dioxide (CDs-MnO2) nanosheets, with carbon dots as the seed, potassium permanganate as the manganese source and sodium citrate as the reducing agent. The as-prepared nanosheets were characterized by transmission electron microscopy, absorption spectroscopy, and fluorescence spectroscopy. It was found that MnO2 can be degraded by Glutathione (GSH) through a redox reaction, which restores the fluorescence of CDs. A new method for determining GSH was constructed using CDs-MnO2 fluorescence sensing. The method is simple and sensitive, with linear ranges of 0.1-5 μM and 10-60 μM, respectively, and a lowest detection limit of 0.034 μM. The method was successfully used for the determination of GSH in human serum, with satisfactory recoveries in the range of 98.9-100.1%.