As-prepared Carbon Dots Research Articles

Electrochemiluminescence of Carbon Dots and Nitrogen-Doped Carbon Dots from a Microwave-Assisted Method

This research focuses on the use of carbon dots (CDs) and nitrogen-doped carbon dots (NCDs) synthesized using a microwave-assisted method as electrochemiluminescence (ECL) luminophores. CDs have been synthesized using citric acid, while various concentrations of nitrogen-doped CDs have been successfully obtained by varying the amount of urea from 1 to 3 g with citric acid to produce NCD1, NCD,2 and NCD3. The ECL mechanism of CDs and NCDs on screen-printed electrodes has been studied using cyclic voltammetry (CV). ECL emission from as-prepared CDs and NCDs was observed in PBS with potassium persulfate (K2S2O8) as a co-reactant. The addition of potassium chloride (KCl) as a supporting electrolyte displays fast electroreduction of CDs and K2S2O8 to expedite the generation of CDs and peroxydisulfate radicals that simultaneously increase ECL intensity. Furthermore, as the concentration of nitrogen-doped CDs increases, so does the intensity of the ECL. NCD3 shows the highest ECL intensity by an increment of 86.4% in comparison to CDs in PBS with the addition of K2S2O8 and KCl. Finally, optimization of ECL measurement was carried out in terms of CV potential range, concentration of luminophore, supporting electrolyte, and co-reactant using NCD3 luminophore. The CV potential range at 0 to -2 V shows 50 mV of early CV reverse onset potential that resulted in an increase of 52.9% ECL intensity. Meanwhile, 30x dilution of NCD3, 0.1 M of supporting electrolyte KCl, and 0.1 M of co-reactant K2S2O8 show the optimum value to obtain high ECL intensity.

Multimodal optical detection, identification and reduction of Cr(VI) with carbon dots and its PVA/polyNIPAM spheres based 2D luminescent photonic structures

Multiple emissive carbon dots (CDs) were synthesized through a one-step solvothermal acid-assisted method using citric acid and urea. Three main emission bands were observed at ∼431 nm, ∼501 nm, and ∼622 nm, corresponding to excitation wavelengths of 360 nm, 430 nm, and 550 nm, respectively. Simultaneous detection through salient discernible features of three metal ions has been achieved. Emission of CDs with Fe(III) shows reduction in intensity at 360 nm and 550 nm wavelengths and an enhancement of photoluminescence (PL) intensity at an excitation wavelength of 430 nm. Al(III) revealed turn-on PL signals, along with a redshift when excited at 360 and 430 nm, and turn-off intensity at excitation of 550 nm. Under all the excitation wavelengths, Cr(VI) exhibits PL quenching accompanied with an additional red shift. This sensor enhances the accuracy and reliability of the probe through multiple distinctive and characteristic responses for all the three ions for which the probes were selective. Apart from the optical detection at a certain wavelength, the Cr(VI) reduction to the less toxic Cr(III) through as-prepared CDs could be monitored at three different excitation wavelengths. The Fe(III) and Cr(VI) detection in solid state has also been demonstrated through 2D luminescent photonic structures formed with CDs-PVA (poly-vinyl alcohol)-polyNIPAM (poly (N-isopropylacrylamide)) composites that can possibly be used for anticounterfeiting applications.

Carbon Dots: A Versatile Platform for Cu2+ Detection, Anti-Counterfeiting, and Bioimaging.

Carbon dots (CDs) have garnered extensive interest in basic physical chemistry as well as in biomedical applications due to their low cost, good biocompatibility, and great aqueous solubility. However, the synthesis of multi-functional carbon dots has always been a challenge for researchers. Here, we synthesized novel CDs with a high quantum yield of 28.2% through the straightforward hydrothermal method using Diaminomaleonitrile and Boc-D-2, 3-diaminopropionic acid. The size, chemical functional group, and photophysical properties of the CDs were characterized by TEM, FTIR, XPS, UV, and fluorescence. It was demonstrated in this study that the prepared CDs have a high quantum yield, excellent photostability, and low cytotoxicity. Regarding the highly water-soluble property of CDs, they were proven to possess selective and sensitive behavior against Cu2+ ions (linear range = 0-9 μM and limit of detection = 1.34 μM). Moreover, the CDs were utilized in fluorescent ink in anti-counterfeiting measures. Because of their low cytotoxicity and good biocompatibility, the CDs were also successfully utilized in cell imaging. Therefore, the as-prepared CDs have great potential in fluorescence sensing, anti-counterfeiting, and bioimaging.

Detection of sulphur(II) of carbon dots synthesized from Gardenia residue.

The detection of anions using carbon dots (CDs) has received less attention compared to cations. Therefore, the present study aimed to develop a fluorescence sensor based on carbon dots (CDs) capable of detecting S2- in real water samples. The CDs were successfully prepared from the residues of a traditional Chinese herb, Gardenia, which emitted green photoluminescence (PL) under ultraviolet light irradiation. The as-prepared CDs were quasi-spherical in shape and ranged in size from 10 to 30 nm. Different detailed analyses proved that the CDs had good morphology, various functional groups, high water solubility, great optical features, and excellent stability under diverse environmental conditions. The ion detection showed that only Ag+ had the strongest fluorescence quenching effect on the CDs, however, the addition of S2- could recover their fluorescence. Based on these results, an "off-on" fluorescence sensor was achieved to selectively detect the concentration of S2- in real water samples with a limit of detection (LOD) of 39 μM, which further expanded the application of residues from traditional Chinese herbal medicine.

Dopamine inspired lignin-derived green emissive carbon dots for pH sensing and metal ions separation

Lignin is the most abundant, but underutilization polyphenolic material on the earth. In this paper, an integrated platform for pH sensing and ions separation was prepared from lignin to make use of this abundant bioresource. Demethylation of enzymatic hydrolysis lignin was first achieved to mimic the catechol structure of dopamine. The demethylated lignin was then converted into carbon dots by a facile hydrothermal treatment. The as-prepared carbon dots emit green fluorescence with enhanced quantum yield, and exhibited pH-responsive color changes from yellow-green to blue. When incorporated into a chitosan aerogel, the pH-responsive property of the carbon dots was intact, whereas the adsorption capacity of the aerogel for Cu2+ ions was noticeably improved, which was owed to the abundant oxygen containing functional groups and unique optical properties of the as-prepared carbon dots. This study provides a feasible approach to convert lignin into fluorescent nanomaterials for pH sensing and metal ions recovery from wastewater.

Fluorometric Determination of Fe3+ Ions using Carbon Dots Prepared from the Extract of Singapore Cherry

Background: The development of affordable and ecologically acceptable technologies for heavy metal detection and removal is required due to the rising levels of water and soil pollution. Carbon Dots (CDs) have emerged as a promising nanomaterial for heavy metal detection due to their unique properties. In this study, we report a simple and eco-friendly method to produce CDs using Muntingia calabura fruit extract as a precursor. Methods: The hydrothermal method produced a well-defined size, structure, and optical properties of CDs, which were analyzed by using various characterization techniques, including Field Emission Scanning Electron Microscopy (FE-SEM), Energy Dispersive X-ray Spectroscopy (EDS), Elemental mapping (E-map), UV-visible spectroscopy, X-ray diffraction (XRD), Fourier Transform Infrared spectroscopy (FT-IR), Photoluminescence (PL) spectroscopy, and Transmission Electron Microscopy (TEM). Additionally, Zeta potential and DLS analysis were used to characterize the CDs. Results: As-synthesized CDs exhibited strong fluorescence emission, making them suitable for the selective determination of Fe3+ ions. The detection limit was found to be 3.6 μM for Fe3+ ions, which highlighted the potential application of as-prepared CDs in environmental monitoring. Conclusion: The green synthesized CDs from Muntingia calabura fruit extract provided a sustainable approach for developing efficient nanoprobes for detecting Fe3+ ions in environmental and biological samples.

Integration of jackfruit seed-derived carbon dots and electronic nose for a sensitive detection of formaldehyde vapor

The preparation of carbon dots from jackfruit seeds through a pyrolysis method at 280℃ and their use for the detection of formaldehyde were reported. The as-prepared carbon dots showed a high fluorescence efficiency with a quantum yield of 12.7% and excellent photostability and dispersibility in aqueous solution with a zeta potential of ‒62.5 mV. The integration of carbon dot thin film and a home-made optical electronic nose system possessed sensitivity towards formaldehyde vapor with a detection limit of 24.7%v/v across a linear range of 25%v/v to 100%v/v. Furthermore, the sensor showed the highest sensitivity towards formaldehyde against other volatile organic compounds through a strong interaction between the carbonyl groups and the carbon dots. Additionally, principal component analysis (PCA) was conducted to achieve quantitative measurements of formaldehyde content in different formaldehyde volume ratios with substantial variance. Due to the significance of methanol as a typical chemical precursor for the industrial manufacturing of formaldehyde, the quantitative analytical method is essential to determining formaldehyde or methanol concentration. The sensing ability of carbon dot film-integrated electronic nose towards formaldehyde in formaldehyde/methanol mixtures was measured to be 10.74%v/v in a linear range of 25%v/v to 100%v/v. The PCA showed orderly linear combinations of the data set, which can be potentially utilized to analyze formaldehyde and methanol content in industrial processes. The results indicate the significant potential of carbon dots and optical electronic nose system as an effective formaldehyde sensing platform. Potential applications include the quantification of formaldehyde from methanol conversion and determination of methanol contaminant in formaldehyde.

B and N Co-doped carbon dots for the ratiometric fluorescence detection of riboflavin and information security with room temperature phosphorescence

Matrix-free room temperature phosphorescence (RTP) materials have generated considerable interest in sensing, anti-counterfeiting and bioimaging due to long lifetime and large Stokes shift. However, spin-forbidden transition and non-radiative transition make RTP challenging to implement. In this work, matrix-free RTP carbon dots (CDs) co-doped with boron and nitrogen were prepared through the microwave-assisted strategy. The CDs realize RTP without any protective matrix. This may be attributed to the stable and rigid structure formed during the heating polymerization process, which can protect the triplet excited state from being quenched by oxygen and water in the air environment. The fluorescence and phosphorescence emission wavelength of the as-prepared CDs were observed at 532 nm and 596 nm with the excitation wavelength of 476 nm and 514 nm, respectively, showing a long afterglow lifetime of 735.3 ms. Nitrogen doping has a crucial effect on the luminescence of RTP, and the increase of nitrogen content facilitates the n-π* transition and improve the efficiency of intersystem crossing (ISC). Importantly, the ratiometric fluorescence method for determining riboflavin has been established based on the Förster resonance energy transfer (FRET) between the CDs (Donor) and riboflavin (Acceptor), with a linear relationship in the range of 9.52–85.71 μM and the limit of detection (LOD) of 19.9 nM. Additionally, the phosphorescent property of the CDs was exploited to demonstrate the potential applications in the field of information encryption.

A red fluorescent carbon dots with good water solubility for rapid detection of Al3+ in actual samples.

We developed a facile strategy for the fabrication of red fluorescent carbon nanodots (R-CDs) and demonstrated their applications for Al3+ sensing. Red-emission carbon dots (CDs) were synthesized using a simple hydrothermal treatment with citric acid and urea as precursors, manifesting intriguing red-emission behaviour at 610 nm. With increasing Al3+ concentration, the fluorescence band at 610 nm decreased gradually. Monitoring the intrinsic fluorescence variation (I610nm ), as-prepared CDs were developed as an effective platform for fluorescent Al3+ sensing, with a linear range of 0.5-60.0 μM and a detection limit of 3.0 nM. More importantly, R-CDs have been applied successfully to the analysis of Al3+ in actual samples with satisfactory recoveries in the range 97.12-102.05%, which indicated that obtained CDs could be implemented as an effective tool for the identification and detection of Al3+ in actual samples.

Green synthesis of carbon dots from fish scales for selective turn off-on detection of glutathione.

Carbon dots as fluorescent probes were fabricated using readily available grass carp fish scales as the carbon source via one-step synthesis based on a pyrolytic reaction. The as-prepared grass carp fish scale carbon dots (GF-CDs) exhibited good biocompatibility and excellent optical properties with a high fluorescence quantum yield of 23.8%. Glutathione (GSH) is an essential small tri-peptide molecule present in every body cell and plays a crucial role in vivo and performs a wide range of biological functions. Ag+ can effectively quench the fluorescence of GF-CDs because of the electron transfer between GF-CDs and Ag+; however, the addition of GSH can significantly increase GF-CD-Ag+ fluorescence. Because of their combination with Ag+ and GSH, GF-CDs show selective fluorescence recovery. GF-CDs can serve as fluorescent probes for GSH detection. This detection method covered a wide linear range (1.6-36.0 μg mL-1) with the lowest detection limit of 0.77 μg mL-1 and manifested great advantages such as a short analysis time, good stability, repeatability, and ease of operation.

Synthesis of a new carbon dot magnetic nanocomposite (CDs@Fe3O4) from Crocus Cancellatus: Characterization and its photocatalytic degradation of fluorescein dye

Using a one-pot hydrothermal treatment of crocus cancellatus for the first time, a simple and very low-cost method for the synthesis of carbon dots (CDs) with well-distributed size was developed. To obtain better-quality performance of synthesized CDs, the temperature and time of the hydrothermal carbonization reaction of crocus were optimized simply. The as-prepared CDs exhibit exceptional advantages including low toxicity, high fluorescent, and satisfactory chemical stability. Magnetic nanocomposite CDs@Fe3O4 powders were synthesized using the synthesized CDs from crocus cancellatus to study the photocatalytic activity of fluorescein dye under sunlight. The synthesized CDs, Fe3O4, and magnetic nanocomposite were characterized using various techniques including XRD, EDX, SEM, BET, FTIR, VSM and HRTEM analysis. The microstructure images confirmed that CDs were encapsulated in porous magnetic Fe3O4 nanoparticles. The results show that the as-synthesized nanocomposite exhibited higher photocatalytic activity under sunlight compared to LED lamp illumination. The fluorescein dye concentration (45 µM) can be decreased by 94.4% within 60 min exposure to sunlight under optimum conditions using 15 mg of nanocomposite. After five recycles, the stability testing demonstrated that 15 mg of nanocomposite had strong photocatalytic activity by removing 75% of the dye.

Detection and elimination of tetracycline: Constructing multi-mode carbon dots for ultra-sensitive visual assay and CDs/TiO2 for photocatalytic degradation

Ultrasensitive detection and degradation of tetracycline (TC) has gained increasing attention owing to their inevitable detriments to human and ecosystem. Many studies have focused on mono-functional detection or degradation. However, the design of multi-functional materials is still a challenge. Till now, a novel protocol applied to the consecutive detection and complete degradation of TC are rarely successfully reported. Herein, we not only developed a multi-mode optical carbon dots (CDs) for ultra-sensitive sensing, but also further manufactured CDs/TiO2 photocatalyst that can degrade TC 100 %, completely eliminating the TC for the first time. The as-prepared CDs can selectively detect TC with low detection limit of 5.2 nM and 10.7 nM within only 40 s, accompanied by wide linear interval of 1.0–50.0 μM and 50.0–250.0 μM, respectively. Therefore, the fabricated point-of-care testing platform can realize “in-situ” visual detection rapidly and efficiently. Furthermore, a highly active CDs/TiO2 photocatalyst was prepared by rationally modifying CDs on TiO2 and exhibited almost 100 % degradation behavior towards TC within 70 min. The mechanism of fluorescence quenching and photocatalysis were lucubrated. Notably, our proposed protocol can drive consecutive detection and elimination towards tetracycline, which powerfully reduces the potential harm and provides a new strategy for the eradication of pollutants.

One-pot hydrothermal green synthetic approach of fluorescent carbon dots as optical probes for 2-nitrophenol

The pursuit of a cost-effective and green synthetic approach to chemical sensors and their application in the sensing of toxic and harmful substances is a never-ending exercise for scientists and researchers. Preparation of fluorescent carbon dots (C-dots) from biomass using water as a solvent and a hydrothermal autoclave to provide the required synthesis temperature offers a cheap and environmentally friendly synthetic approach. Herein, we report a faster, less costly and ecofriendly hydrothermal synthetic approach of carbon dots from Citrullus vulgaris peels as a precursor. The as-prepared carbon dots exhibited hydroxyl, carbonyl and amide functional groups on the surface and an amorphous structure with a particle size distribution of 1.7–3.0 nm. Moreover, the carbon dots displayed intense blue emission fluorescence at 470 nm after excitation at 400 nm. The as-prepared carbon dots demonstrated effective application without further modification towards the selective and sensitive optical recognition of 2-nitrophenol used in the manufacture of explosives. A limit of detection of 2.28×10−7 M was achieved, and no fluorescence quenching was observed in the presence of other nitroaromatic and benzene derivatives indicating excellent selectivity towards 2-nitrophenol. Finally, further studies are required to investigate the potential for the as-prepared carbon dots to monitor nitroaromatic pollutants in real environmental systems.

Carbon dots-based fluorescent probe for the detection of imidacloprid residue in leafy vegetables

Consumption of leafy vegetables with excessive imidacloprid (IMI) can cause serious harm to the human body. To achieve rapid IMI detection, a carbon dots (CDs)-based fluorescent (FL) probe was hydrothermally prepared using O-phenylenediamine as the precursor. The morphology, particle size distribution, crystal structure, optics and chemical bond state of the as-prepared CDs were characterized. The mechanism of the CDs in detecting IMI was investigated by Fourier transform infrared spectroscopy, and the CDs’ selectivity, stability, sensitivity, and actual sample recovery were tested. The CDs showed good selectivity, stability, and anti-interference ability. Under optimum conditions, there was a strong linear relationship between the FL intensity of the CDs and the IMI concentration in the range of 0.037–0.2 mg/L. The detection limit was 0.00187 mg/kg. The CDs were successfully applied to detect IMI in lettuce, cole, spinach, and pakchoi with spiked recoveries between 81.026% and 106.803% and a relative standard deviation between 0.001 and 0.027%.

Facile preparation of carbon dots with multicolor emission for fluorescence detection of ascorbic acid, glutathione and moisture content

The nitrogen-doped carbon dots (N-CDs) with multicolor emission (green, yellow, and red) were fabricated with naphthalenetetracarboxylic dianhydride as carbon precursor, and different alkylamines as passive agents. The structures of the as-prepared carbon dots were confirmed by the Fourier transform infrared (FT-IR) spectrum, X-ray photoelectron spectroscopy (XPS) spectra, transmission electron microscopy (TEM), Raman spectra, and X-ray diffraction (XRD) pattern. The characterized results and UV–vis absorption spectrum demonstrated that the luminescence variations of different CDs were probably attributed to the difference of N-related states, oxygen-containing groups, and oxidation degree in the CDs structure. Moreover, the green emitting CDs (G-CDs) could be utilized as fluorescent probe for ascorbic acid (AA) detection with detection limit (LOD) of 5 μM. The yellow emitting CDs (Y-CDs) could be used to detect glutathione (GSH) in the range of 1–70 μM with LOD of 0.07 μM. The red emitting CDs (R-CDs) could detect the water content in THF, DMF, acetone, and EtOH with LODs of 0.44%, 0.31%, 0.55% and 0.55%, respectively. Remarkably, G-CDs and Y-CDs can distinguish AA and GSH respectively with high selectivity and accuracy. Finally, the fluorescent probes based on G-CDs and Y-CDs were successfully applied for the AA and GSH determination in vitamin C tablet, grapefruit juice, and GSH whitening serum samples with high reliability and feasibility, which provided the guidance for the selection of AA and GSH supplements.

Ultra small carbon dots from Crocus cancellatus as a highly fluorescence probe for synthetic Ponceau 4R dye sensing in food samples

In this work, for the first time, natural Crocus cancellatus was adopted for the green, low-cost, and simple synthesis of highly fluorescent ultra-small carbon dots (CDs) with well-distributed size using a one-pot hydrothermal treatment. As-synthesized CDs are used as fluorescence sensing probe for quantitative analysis of Ponceau 4R (E124) synthetic food dye, which is widely used. However, excessive consumption of Ponceau 4R poses potential health risks. To obtain better-quality performance of as-synthesized CDs, the time and temperature of the hydrothermal carbonization reaction of crocus were optimized simply. The as-prepared carbon dots exhibit exceptional advantages including excellent fluorescence, satisfactory chemical stability, low toxicity, and excellent biocompatibility. It produced a strong blue fluorescence when irradiated with UV light at 365 nm, which was subsequently effectively employed for Ponceau 4R sensing based on the quenching of fluorescence. The as-prepared CDs was characterized by EDX, XRD, FTIR, SEM, HRTEM, UV–Visible absorption spectrophotometry, and fluorescence. The effects of carbon dots fluorescence emission wavelength, CDs quantity, pH value, and reaction time were investigated to detect Ponceau 4R under optimum conditions. The synthesized carbon dot's fluorescence intensity allowed quantitative determination of Ponceau 4R in the linear range of 60–6000 nM with a detection limit of 40 nM that is lower than all previously published methods. Several soft drink samples were used to validate the potential use of this new fluorescent probe for P4R detection in actual samples with good precision and accuracy.

Dual Optical Sensing of Al3+ and Hg2+ Using Carbon Dots Synthesized from Biomass

This study aimed to use a simple, low-cost and eco-friendly microwave-assisted method for the synthesis of carbon dots-based fluorescent sensor that can detect more one target analyte in aqueous media. Herein, we report the synthesis of carbon dots (CDs) from peels of an indigenous and abundant wild fruit called wild medlar (Vangueria infausta). Functional groups such as hydroxyl (–OH) and carbonyl (C=O) were revealed on the surface of the as-prepared carbon dots using Fourier transform infrared spectroscopy (FTIR). The as-prepared CDs exhibited an amorphous structure and a broad distribution of particle size with an average size of 10 nm. In addition, the as-prepared CDs demonstrated excellent hydrophilicity and intense blue photoluminescence under UV light at 365 nm. The water-soluble CDs were employed for the detection of Al[Formula: see text] using a ‘turn on’ mechanism and Hg[Formula: see text] using a ‘turn off’ mechanism. Addition of increasing concentration of Al[Formula: see text] resulted in an increase in the fluorescence intensity of the as-prepared CDs while addition of increasing concentration of Hg[Formula: see text] resulted in quenching of the fluorescence intensity of CDs. The lowest limit of detection (LOD) for Al[Formula: see text] and Hg[Formula: see text] ions in aqueous media was determined at 817 nM and 612 nM, respectively. Furthermore, the as-prepared CDs have excellent selectivity towards Al[Formula: see text] and Hg[Formula: see text] among other potential metal ion interferences. Practical application of the as-prepared CDs towards detection of Al[Formula: see text] and Hg[Formula: see text] in tap water revealed good recovery rates of 86.0% to 87.4% and 96.4% to 106.5%, respectively. Therefore, this work has demonstrated a potent strategy for potential application of this nanoprobe towards dual detection of Al[Formula: see text] and Hg[Formula: see text] in aqueous samples.

Continuous productions of highly fluorescent carbon dots and enriched polymer nanofibers via microfluidic techniques

Carbon dots (CDs) have shown great promise in various fields owing to their fascinating properties. However, most of high-performance CDs are usually synthesized upon intermittent operations, which are difficult to produce continuously in batch. In this regard, we develop a robust aluminum-based microfluidic chip reaction platform with imbibition-injection cycle feeding and ease of scale-up production, allowing the rapid and continuous synthesis of highly fluorescent CDs. The as-prepared CDs possess excellent optical properties, including high photoluminescence (PL) quantum yield (QY) of 71%, narrow full width at half maximum (FWHM) of 65 nm by optimizing the parameters of reaction. Combined with electro-microfluidic spinning, the continuous production of fluorescent enriched CDs/polymer nanofibers could further be realized. CDs/thermoplastic polyurethane (TPU) and CDs/polyamide 6,6 (PA66) nanofibers are prepared to exhibit enhanced mechanical properties with tensile strength 2.9 and 4.1 times higher than those of the pure polymer matrix, respectively. This work contributes a new kind of microfluidic chip for nanomaterial synthesis, and paves a way toward rapid and continuous preparation of high-performance CDs and CDs/polymers nanofiber films by microfluidic techniques.

Multifaceted Carbon Dots: toward pH-Responsive Delivery of 5-Fluorouracil for In Vitro Antiproliferative Activity.

The synthesis of smart hybrid material to assimilate diagnosis and treatment is crucial in nanomedicine. Herein, we present a simple and facile method to synthesize multitalented blue-emissive nitrogen-doped carbon dots N@PEGCDs. The as-prepared carbon dots N@PEGCDs show enhanced biocompatibility, small size, high fluorescence, and high quantum yield. The N@PEGCDs are used as a drug carrier for 5-fluorouracil (5-FU) with more release at acidic pH. Furthermore, the mode of action of drug-loaded CD (5FU-N@PEGCDs) has also been explored by performing wound healing assay, DCFDA assay for ROS generation, and Hoechst staining. The drug loaded with carbon dots showed less toxicity to normal cells compared to cancer cells, making it a perfect candidate to be studied for designing next-generation drug delivery systems.

Pyridinic-N-rich carbon dots in IFE-based Turn-off Fluorometric detection of nerve agent Mimic- Diethyl chlorophosphate and multicolor cell imaging.

Fluorometric sensors for the detection of nerve agent mimics have received a lot of interest nowadays due to their high sensitivity and selectivity, ease of operation, and real-time monitoring. Pyridinic-N-rich carbon dots (NCDs) prepared through microwave-assisted pyrolysis of l-Malic acid and urea have been explored first time in this work as a novel turn-off fluorescent probe for the sensitive and selective detection of diethyl chlorophosphate (DCP), a nerve agent mimic. The as-prepared carbon dots contained a large amount of pyridinic nitrogen on their surface, which can modulate the photoluminescence properties of the NCDs. The blue emissive NCDs possessed both excitation wavelength-dependent and independent emission behavior. The detection of DCP was premised on quenching of the fluorescence emission intensity of NCDs in the presence of similar chemical reagents (e.g., trimethyl phosphate, triethyl phosphate, triethyl phosphonoacetate, triphenyl phosphate, diphenyl phosphate, tributyl phosphate). Fluorescence quenching of the NCDs in the presence of DCP has been attributed to the inner filter effect (IFE). From the linear Stern-Volmer plot (R2=0.9992), the limit of detection (LOD) was found to be 84μM for sensing DCP for the concentration ranging between 3 and 15mM. The biocompatibility of NCDs was assessed through cytotoxicity assay on MDA-MB-231 breast cancer cells. Fluorescence imaging demonstrated that NCDs have low cytotoxicity and can be employed successfully in cell imaging.