Fluorescent Carbon Dots for Neurodegenerative Disorders

ZnCl2 Enabled Synthesis of Highly Crystalline and Emissive Carbon Dots with Exceptional Capability to Generate O2⋅–

Microwave enhanced carbon dots synthesis from eggshell membrane: Versatile applications in heavy metal ion sensing, strain free detection of fingerprints, UV shielding, food packing and anti-counterfeiting

Fluorescent carbon dots have the advantages of good chemical stability, low toxicity, and surface functionalization, which has caused concern. In recent years, polymer carbon dots synthesize by polymer polysaccharides have become a new research hotspot. In this paper, a chitosan-based fluorescent polymer carbon dot material is synthesized by hydrothermal method and used for drug-loading research. We choose chitosan-graft-polyethylene glycol monomethyl ether and citric acid derivatives as the carbon sources for the carbon dots, because chitosan and polyethylene glycol are both a carbon source for carbon dots and a passivation reagent for carbon dots. Then the quantum yield of the polymeric carbon dots is increased. Polymer carbon dots can also retain the molecular structure of polyethylene glycol and chitosan, providing favorable conditions for its application in drug loading. The structural characterization is performed on P(CS-g-mPEG-CA)CDs by IR, UV, X-ray diffraction, photoelectron spectroscopy, transmission electron microscopy and photoluminescence spectra and pH stability test is carried out. The results show that the synthesized P(CS-g-mPEG-CA)CDs has higher fluorescence quantum yield(66.81%), longer fluorescence lifetime(15.247 ns), and better pH stability. Using Doxorubicin as a model drug, a load study was conducted using this polymer carbon dot. The results show that if the degree of substitution of mPEG is 11.9%, the maximum loading rate of polymer carbon dots is 51.3% and the maximum drug release rate is 28.7%. In addition, we also found that drug loading and release could be controlled by the grafting rate of mPEG. In addition, the cytotoxicity of polymer carbon dots on nasopharyngeal carcinoma cells(CNE-2) is evaluated using an MTT assay. The study shows that there is no obvious cytotoxicity of blank P(CS-g-mPEG-CA)CDs, and that the survival rate of CNE-2 cells decreases with the increase of drug-loaded micelles. The results show that the P(CS-g-mPEG-CA)CDs have a certain application prospect in the aspects of fluorescence labeling, drug delivery, fluorescent tracer system and controlled release.

Fluorescent Carbon dots (CDs), a young member of Carbon nanomaterial family has gained a lot of research attention across the globe due to its highly luminescent emission properties, non-toxic behavior, stable emission properties and zero re-absorption losses. These dots have potential to replace the use of traditional semiconductor quantum dots in white light emitting devices. For successful application of these dots in White LEDs it is highly essential to synthesize luminescent CDs and CDphosphor with higher Quantum yields (QY). Immense research is going on across the globe in enhancing the optical properties of CDs and CD phosphor by proper surface functionalization and passivation of CD surface. In this paper we report successful fabrication of single system white light emitting CDs, CD phosphor and two different schemes to enhance the Quantum yield of fabricated CDs and CD phosphor by modifying the CD surface. The so fabricated CDs and CD phosphor emit white light under UV -illumination. Further the fabricated CDs and CD phosphor are characterized using UV-absorption emission spectroscopies and the quality of white light obtained from CDs and CD phosphor is characterized using CIE chromatic co-ordinates.

Carbon dots (CDs) are versatile fluorescent nanocrystalswith uniqueoptical and structural properties and are commonly used in biosensing,bioimaging, and biomolecule tagging studies. However, fluorescenceof CDs is brightest in the wavelength range of 430–530 nm,which overlaps with the autofluorescence range of many eukaryoticcells and makes CDs impractical for in vivo and in vitro imaging studies.Thus, the design of yellow-red emissive CDs with high quantum yieldis of importance. In this study, the quantum yield of traditionalyellow emissive CDs was enhanced by two different methods: (1) thesurface of traditional yellow emissive CDs passivated with a biomolecule,urea, through easy, rapid, inexpensive microwave assisted synthesismethods and (2) a fluorescent biomolecule, aflatoxin B1, used as anenergy donor for yellow emissive CDs. In the first method, the quantumyield of the CDs was enhanced to 51%. In the second method, an efficientenergy transfer (above 40%) from aflatoxin B1 to the CDs was observed.Our study showed that highly luminescent yellow emissive CDs can besynthesized by simple, rapid microwave assisted synthesis methods,and these CDs are potential candidates to sense aflatoxin B1. Furthermore,our results indicated that Aflatoxin B1 can be considered as an emissionbooster for CDs.

Carbon dots (CDs) have outstanding optical properties, biocompatibility, and photostability, making them attractive for imaging applications. A facile and green one-step hydrothermal synthesis method is proposed, which can be safely used in a wide range of applications such as chemical sensing, bioimaging, and optoelectronics. In this study, we report green synthesis of carbon dots from bitter orange juice (Citrus Aurantium) by hydrothermal treatment for the first time. We studied effects of time, temperature, and pH on fluorescence of CDs, characterized them using various spectroscopic and microscopic methods, and evaluated their toxicity to different cell lines. Identifying an optimum reaction condition of 180 ºC for 7 h heating gave CDs that showed pH-dependent fluorescence, with the largest fluorescence at a pH of 7.0. The CDs were 1-2 nm in size with a spherical morphology and negative surface charge. The CDs showed a high quantum yield of 19.9 %, reasonable photostability, excellent water solubility, and long fluorescence lifetime. A one step hydrothermal rout led to various hydrophilic functional groups on the surface of the CDs. Our results showed that the CDs were non-toxic over a large concentration range and effective for imaging of cells, indicating their potential as imaging probes in medical diagnostics and biosensor applications.

These days, carbon dots (CDs) are the rising stars of nanomaterials. Carbon dots (CDs) are small carbon nanoparticles with the same type of surface passivation (less than 10 nm in size). Researchers found C-dots by accident while purifying single-walled carbon nanotubes (SWCNTs) manufactured using the arc-discharge process. Toxic metal-based quantum dots are being replaced with carbon dots (QDs). Carbon dots are currently being prepared from a variety of natural resources in order to obtain self-passivated products at a reasonable cost. Because of their superior photo physical characteristics, biocompatibility, and low toxicity, carbon dots have prospective applications in bio sensing, bio imaging, and drug administration. Different synthetic processes, precursors, salient properties, and applications were reviewed in this review, as well as some future prospects, obstacles, and possible solutions for future development. Because of their tunable optical characteristics and better biocompatibility, luminous carbon-based nanomaterials have sparked a lot of scientific interest. Different light emission properties of carbon are discussed in this review. Distinct synthesis procedures have resulted in different carbon dots (CDs). Summarized here. The optical properties of CDs that haven't been synthesized yet surface doping and element doping can be used to further control it. CDs are being functionalized for an adjustable band gap. As a result of their luminescent with reduced cytotoxicity and tunable optical characteristics CDs have been thoroughly investigated in terms of their potential uses in biomedicine, such as analytical sensors, and instruments for bioimaging. Fluorescent carbon dots are a new type of nanomaterial from the carbon family. Green CDs, which have attracted a lot of attention from researchers because of their better water solubility, high biocompatibility, and eco-friendly nature when compared to chemically generated CDs, can be made from a variety of inexpensive and renewable resources. The presence of heteroatoms on the surface of green CDs in the form of amine, hydroxyl, carboxyl, or thiol functional groups, which can improve their physicochemical qualities, quantum yield, and likelihood of visible light absorption, eliminates the need for additional surface passivation.

Fluoride detection in water is a critical issue that has received extensive attention recently. Researchers have focused on developing practical and reliable methods for detecting Fluoride in water, and fluorescent carbon dots have emerged as a promising solution. These dots are easy to synthesise, highly fluorescent and stable, making them an ideal choice for this application. In this context, highly fluorescent boron-doped Carbon Dots (BCDs) were synthesised using Urea, Citric acid, and Boric acid via microwave synthesis. Characterisation of BCDSs was performed (Photoluminescence, HR-TEM, DLS, and FTIR), showing excellent optical properties (quantum yield = 55.4%), size (< 5nm). The BCDSs solution was used as a fluoride sensor probe using the 'turn-off-on' property. Ferric (Fe3+) solution was used to inhibit (turn-off) the fluorescence of the BCDs by forming BCDs-Fe3+ complex in the solution. The addition of a fluoride sample recovers the fluorescence (turn-on) by removing Fe3+ from the complex to form [FeF6]3-. Materials, BCDs, quencher volume and reaction time were optimised to develop a reliable fluoride sensing scheme, which included BCDs dilution, controlled turn-off by adjusting the volume of the quencher, and time dependence studies (2-15s). A chemometric model was generated through PLS analysis to study the influence of each optimisation on the sensing performance. The result is a highly reproducible and reliable method for detecting Fluoride in water, obtaining high linearity (R2 = 0.98), low error (RMSE = 0.7) and high sensitivity (LOD and LOQ of 0.69 and 2.10ppm, respectively) for a concentration range of 0-50ppm. Real samples were also analysed to get an overview of sensing performance. Overall, fluorescent BCDs-based and chemometric-assisted sensor optimisation schemes have shown great promise for F- detection in water. This breakthrough could open new pathways for optical-based sensor optimisations for other hazardous ions as well, which in turn have far-reaching implications for community's worldwide, helping to ensure safe and healthy drinking water for everyone.

Smartphone-based portable device for rapid and sensitive pH detection by fluorescent carbon dots

SummaryProtons are highly related to cell viability during physiological and pathological processes. Developing new probes to monitor the pH variation could be extremely helpful to understand the viability of cells and the cell death study. Carbonized polymer dots (CPDs) are superior biocompatible and have been widely applied in bioimaging field. Herein, a new type of extreme-pH suitable CPDs was prepared from citric acid and o-phenylenediamine (CA/oPD-CPDs). Due to the co-existence of hydrophilic and hydrophobic groups, CA/oPD-CPDs tend to aggregate in neutral condition with a dramatic decrease of fluorescence, but disperse well in both acidic and alkaline conditions with brighter emission. This specialty enables them to selectively illuminate lysosomes in cells. Moreover, CA/oPD-CPDs in the cytoplasm could serve as a sustained probe to record intracellular pH variation during apoptosis. Furthermore, CA/oPD-CPDs present a continuous fluorescence increase upon 2-h laser irradiation in living cells, underscoring this imaging system for long-term biological recording.

Fluorescent carbon dots (CDs) were efficiently synthesized by a one-step microwave-assisted method using diphenylamine as a carbon precursor. The obtained CDs exhibit high stability and strong water solubility. Under UV irradiation, these CDs could emit bright green photoluminescence. These synthesized CDs have an average diameter of 1.8 nm (±0.46) and quantum yield (QY) as high as 44.69% using rhodamine-B as a reference. The CDs’ intensity can be quantitatively quenched by Hg2+ and Fe3+ ions with high sensitivity and low LOD about 9.58 nM and 22.27 nM, respectively, indicating that the CDs sensors can be potentially applied for Hg2+ and Fe3+ detection in aqueous solutions.

In recent times, carbon dots have emerged as new fluorescent probes. The unique electronic and physical properties of carbon dots find significant applications in different fields like sensing, cell-imaging, catalysis, medicine etc. The intriguing fluorescence, cytocompatibility and nontoxicity of carbon dots are considered for their use in biological science also. The inherent fluorescence of carbon dots is dependent on their structure, method of synthesis etc. However, the fluorescence of carbon dots is known to improve through different chemical manipulation techniques. Among them, doping of heteroatoms like nitrogen, boron, phosphorous, sulphur etc. has made a mark as an interesting protocol to improve the emissive property of carbon dots. In this review, the recent processes of doping have been discussed along with the application of doped carbon dots in different fields.

A sensitive and reversible sensing platform based on fluorescent carbon dots (CDs) allowing capture and detection of metal ions is of significance for developing diagnostic probes and in-situ environmental-monitoring. Here, a simple and effective method for converting biomass lignin into fluorescent CDs is developed. The obtained CDs, with stable fluorescence and excellent water solubility, are fabricated as unique model biosensors to access the metal-induced quenching mechanism. It is demonstrated that selective fluorescence quenching behaviors of lignin CDs are firstly found related to the valence-state of metal ions. Moreover, a reversible control of CDs fluorescence is realized by introducing reducing agents. This novel biosensor and the approach to quenching mechanism may evoke new insight in designing ions-sensor and monitoring biologic redox signal.

Microwave synthesis of carbon dots in ten choline chloride-based deep eutectic solvents: Effect of solvent molecular structure on carbon dots fluorescence and sensing properties

Heterogeneity in the fluorescence of carbon dots (CDs) has been hard to figure out so far. This could potentially be related to structural factors, size or intermediate fluorophores, especially when employing the bottom‐up synthesis. Herein, we unveil the origin of fluorescence and spectral heterogeneity of CDs using a simple dynamic method. This work reports the room light‐excited green fluorescence and dual‐emissive N‐doped CDs synthesized using a hydrothermal method. Studies were carried out considering the factors of fluorescence phenomena, such as excitation‐independent emission, fluorescent impurities, aggregation and solvation dynamics. The new steady‐state, Excitation‐resolved area‐normalized emission spectroscopy (ERANES) and ensemble measurements, including time‐resolved studies reveal that a heterogeneous environment exists in the ground state. Eventually, the results show the existence of core, edge and surface states in the CDs. Additionally, the fluorescence characteristics depend on the structural functionalization that occurs in both the intrinsic and extrinsic states of the CDs and it is proven that this does not violate the Kasha‐Vavilov rule. Although a highly purified material could still exhibit heterogeneity due to the ensemble emissive states and structural variations. Our results provide insights into the enduring debates about fluorescence and a deeper understanding of the structure‐ property relationship of CDs.