N-doped Carbon Dots Research Articles

Machine learning integrated high quantum yield blue light carbon dots for real-time and on-site detection of Cr(VI) in groundwater and drinking water

The safety of groundwater and drinking water is directly related to the well-being of human beings and ecosystems. On-site monitoring and timely response to heavy metals in these water sources are crucial for water supply security. Fluorescent probes combined with machine learning technology have been applied to on-site detection of heavy metals. However, they were primarily focused on industrial-level detection and lacked the sensitivity required for detecting Cr(VI) in groundwater and drinking water. In this study, we developed an machine learning-integrated approach using high-quantum-yield (QY) N-doped blue-light carbon dots (N-BCDs) for instant detection of Cr(VI) in groundwater and drinking water. N-BCDs were synthesized within 3 min using a household microwave oven with citric acid and 1,2-diaminobenzene, resulting in a QY of approximately 90 %. The fluorescence of N-BCDs was quenched via the internal filter effect (IFE), enabling the detection of Cr(VI) within 1 min, with a detection limit of 0.1574 μg L−1 for Cr(VI) concentrations ranging from 0 to 60 μg L−1. We employed machine learning methods to determine Cr(VI) concentrations from simple shots, based on the red-green-blue (RGB) feature and Kmeans feature extraction. These features were input into four models (Ridge, XGB, SVR, and Linear), achieving a fitness of 95.2 %. Furthermore, the accuracies for Cr(VI) concentration identification in actual groundwater and drinking water were as high as 95.71 % and 96.81 %, respectively. Our work successfully extended the detection range of Cr(VI) to the μg level, significantly improving the practical applicability of the method and providing a new approach for on-site detection of Cr(VI) in groundwater and drinking water.

Development of a Modified Electrode with N-doped Carbon Dots for Electrochemical Determination of 17α-ethinylestradiol

This work aims to develop a modified electrode with N-doped carbon dots (CPE/N-CD) for the voltammetric detection of 17α-ethinylestradiol (EE2) in solution. N-doped carbon dot nanoparticles (N-CD) were synthesized using citric acid and urea as the nitrogen source. The N-doped carbon dots were characterized by absorption and emission spectroscopy in the ultraviolet and visible regions, electronic absorption spectroscopy in the infrared region, and Raman Spectroscopy, which showed evidence of the formation of the material. Electrochemical analyses were conducted utilizing Differential Pulse Voltammetry (DPV). After optimization of electrochemical parameters, a calibration plot was produced for the sensor, demonstrating a linear range of 0.01 to 0.80 μmol L-1 (R2 = 0.9969). Additionally, the sensor exhibited a detection limit (LOD) of 0.59 nmol L-1 and a quantification limit (LOQ) of 2.00 nmol L-1. The studies on reproducibility and repeatability revealed RSDs of 1.63% and 3.61% respectively. The results obtained using CPE/N-CD indicate that the developed electrode exhibits excellent analytical performance, making it suitable for identifying and quantifying EE2 in solution.

Selenium and nitrogen co-doped carbon dots with highly efficient electrochemiluminescence for ultrasensitive detection of microRNA

In this work, selenium and nitrogen co-doped carbon dots (SeN-CDs) possessing highly efficient electrochemiluminescence (ECL) and excellent biocompatibility were synthesized as a new emitter with S2O82− as a coreactant for constructing a biosensor to detect microRNA-221 (miRNA-221) sensitively. Notably, the SeN-CDs exhibited superior ECL performance compared with the N-doped CDs, in which selenium with excellent redox activity served as a coreaction accelerator for facilitating the electroreduction of S2O82− to significantly improve ECL efficiency. Furthermore, target-induced T7 exonuclease (T7 Exo)-assisted double cycle amplification strategy could convert traces of target miRNA-221 into large amounts of output DNA to capture three-dimensional (3D) nanostructures (DTN-Au NPs-DOX-Fc) loaded with large amounts of ECL signal quencher. The constructed biosensor could realize ultrasensitive detection of miRNA-221 and has a low detection limit reaching 2.3 aM, with a successful application to detect miRNA-221 in lysate of Hela and MHCC97-L cancer cell. This work explored a novel method to strengthen the ECL performance of CDs to construct an ECL biosensing platform with sensitive detecting of biomarkers and disease diagnosis.

Application of ZIF-67 coated by N-doped carbon dots in dispersive solid phase extraction of several pesticides from fruit juices and its combination with dispersive liquid-liquid microextraction followed by GC-FID

Application of ZIF-67 coated by N-doped carbon dots in dispersive solid phase extraction of several pesticides from fruit juices and its combination with dispersive liquid-liquid microextraction followed by GC-FID

Determination of β2-Agonist Residues in Meat Samples by Gas Chromatography-Mass Spectrometry with N-Doped Carbon Dots in Molecular Sieves

A simple, effective, and highly sensitive analytical approach was created and applied in this study for the accurate measurement of three β2-agonist residues (clenbuterol, salbutamol, and ractopamine) in meat samples. In the course of the experiment, new adsorbent molecular sieves (ZMS)@nitrogen-doped carbon quantum dots (N-CQDs) composite materials were synthesized with the aid of hydrothermal synthesis. The composite adsorbent materials were prepared and characterized through scanning electron microscopy, transmission electron microscope, X-ray photoelectron spectroscopy, fluorescence, and zeta potential. Four determinants affecting the extraction and elution’s efficiency, such as the amount of adsorbent, the extraction time, desorption time, and the amount of extraction salt, were substantially optimized. The analytes were quantified by gas chromatography–mass spectrometry. Final results of the methodological validation reflected that the ZMS@N-CQDs composite materials were able to adsorb three β2-agonist residues well and had good reproducibility. In the meantime, all analytes indicated good linearity with coefficient of determination R2 ≥ 0.9908. The limit of detection was 0.7–2.0 ng·g−1, the limit of quantification varied from 2.4 to 5.0 ng·g−1, the precision was lower than 11.9%, and the spiked recoveries were in the range of 79.5–97.8%. To sum up, the proposed approach was quite effective, reliable, and convenient for the simultaneous analysis of multiple β2-agonist residues. Consequently, this kind of approach was successfully applied for the analysis of such compounds in meat samples.

Highly sensitive enantioselective spectrofluorimetric determination of R-/S-mandelic acid using l-tryptophan-modified amino-functional silica-coated N-doped carbon dots as novel high-throughput chiral nanoprobes

Amino-functional silica-coated N-doped carbon dots (NH2–SiO2-CDs) were covalently modified by l-tryptophan (chiral selector) by producing an amide bond between carboxyl groups of L-try and amino groups of NH2–SiO2-CDs to develop a novel high throughput chiral nanoprobes (L-try–CONH–SiO2-CDs) for highly sensitive and enantioselective quantification of S-/R-mandelic acid (S-/R-Man). The method showed a great difference between S- and R-isomers (enantioselectivity coefficient = 4.17) due to the ultra-stability of the Meisenheimer complex that was formed between S-isomer and nanoprobe (KS-Man/KR-man = 2122.7, where K is the binding-constant). At optimal experimental conditions, two linear ranges of 0.5–25.0 (LOD of 0.05 μM) and 0.5–22.0 μM (LOD of 0.27 μM) for S- and R-Man, respectively, along with an enhanced sensitivity toward S-isomer (about 5.7-fold higher than R-isomer) were attained. High selectivity for the determination of mandelic acid was achieved compared to metal ions, amino acids, and sugars that commonly coexist with it. Intra-day as well as inter-day assays, respectively, showed RSD values of about 3.2 and 3.9%. The mechanistic studies were performed for proving the enantioselective behavior of the developed nanoprobe. The method was then used for S-/R-mandelic acid determination in bio-samples. The figures of merit for the method were found to be better than those already reported for enantioselective detection of R-/S-Man.

1,10-Phenanthroline-5-amine derived N-doped carbon dots for long-lived visible-light-activated room temperature phosphorescence in the matrix and information encryption application

Room temperature phosphorescence (RTP) materials have received a lot of attention. However, it is still a challenge to realize the practical application of RTP excited under visible light. Herein, five different carbon dots (CDs) were prepared using 1,10-phenanthroline-5-amine (Aphen) as the co-carbon source and nitrogen source, and several polymer-based RTP films were prepared by simple doping. It was found that the phosphorescence emission behavior of polymer films was changed by the surface state structure of different CDs. Non-radiative transition of the triplet excitons of Aphen structure on the CDs surface was effectively inhibited by the hydrogen bonding interaction and the fixed domain-limiting effect of the polymer matrix. Meanwhile, the Aphen structure was bound to the CDs through covalent interaction, which further suppressed the molecular vibration, realizing the efficient organic RTP. The phosphorescence lifetime of the prepared ACCDs-PVA films reached 352.88 ms with a photoluminescence quantum yield of 36.7%. In addition, the dye RhB was co-doped in the ACCDs-PVA system to modulate the afterglow color of the materials via the triplet to single-state energy resonance transfer (TS-FRET) process. Finally, we also developed stable ACCDs-EPO RTP material by exploiting the dense three-dimensional network structure and hydrophobic property of the cured epoxy resin (EPO) matrix. The as-constructed long-lived RTP materials can be employed in information encryption.

Full-value preparation of biochar and 2D N-doped CDs@ZIF-L from fermentation residues for sensitive sensing tetracyclines in food samples

The use of thermal conversion to convert Chinese patent medicines (CPM) residues into porous carbon-based materials and carbon dots (CDs) has effectively resolved the challenges associated with resource waste and environmental pollution while enhancing the added value of CPM residues. In this study, biochar and N-doped CDs with high quantum yield (QY) were simultaneously prepared from fermentation residues by employing a hydrothermal carbonization method without any chemical reagents. The obtained biochar had remarkable adsorption capacity, with an iodine adsorption value of 693.22 mg g–1. The QY of N-doped CDs could reach to 36.17 % by the mean of self-doping due to the high nitrogen content of the fermentation residues. Considering the structural integrity and permeable porous structure of the two-dimensional leaf-like zeolitic imidazole framework (ZIF-L), N-doped CDs were encapsulated into ZIF-L to form novel fluorescent composites (N-doped CDs@ZIF-L). Moreover, N-doped CDs@ZIF-L as a novel fluorescent probe could be efficiently quenched in the presence of tetracycline (TC), doxycycline (DOC), and chlortetracycline (CTC) by static quenching and the inner filter effect. Notably, the fluorescent probe exhibited a good linear relationship with the TC, DOC, and CTC at 0–50, 0–50, and 0–45 μM, respectively, with limits of detection of 0.025, 0.033, and 0.027 μM, respectively. This probe could be employed to detect TC antibiotics in honey and milk, suggesting that it had the great potential for applications in environmental monitoring and food safety.

Zn anode surface engineering for stable zinc-ion batteries: Carbon dots incorporated mesoporous TiO2 as a coating layer

Uncontrolled Zn dendrites growth and sustained corrosion originating from severe interfacial reactions are the major shortcomings of Zn metal electrodes in aqueous zinc-ion batteries (ZIBs). In order to overcome these obstacles, we designed a protective coating layer to stabilize the zinc anode and regulate the Zn deposition simultaneously. This hybrid layer (TiO2/NCDs) is constructed by mesoporous TiO2 nanosheets and N-doped carbon dots (NCDs), which is prepared by a solvothermal growth under the control of NCDs. On one hand, the TiO2 layer immobilize water molecules effectively, preventing them from the parasitic reactions with Zn electrodes. On the other, NCDs with abundant functional groups (–OH, –COOH, –NH2) provide the zincophilic nucleation sites to endow a small deposition overpotential of 28 mV and guide Zn deposition into a petal structure. Owing to mesoporous protective coating layer, the Zn-TiO2/NCDs anode presents a low voltage hysteresis of 48 mV and a prolonged cycling lifespan of 1500 h at 5 mA cm−2 and 2.5 mAh cm−2. Moreover, aqueous ZIBs assembled with the Zn-TiO2/NCDs anode and the α-MnO2 cathode show outstanding reversibility and good cycling stability, whose capacity retention is up to 90% after 1000 cycles.

Different types of Nitrogen-doped CQDs loaded by CoP used as OER electrocatalysts

In recent years, CoP catalysts loaded with N-doped carbon dots (NCQDs) have gained attention as promising metal-free electrocatalysts due to their low cost, simple preparation process, and excellent electrocatalytic performance. However, few studies have investigated the effect of different types of nitrogen doping on the catalytic performance of NCQDs in electrocatalysis. In this study, NCQDs doped with graphite/amine N, pyridine N, and pyrrole/amine/pyridine N were prepared using various small molecule precursor systems, and control experiments were conducted with CQDs without nitrogen doping. Electrochemical tests demonstrated that nitrogen doping can enhance the electrocatalytic performance of the NCQDs. Notably, CoP modified with pyrrole/amine/pyridine N-doped CQDs (NCQDs-3) exhibited significantly improved electrocatalytic performance, the largest specific surface area, and the lowest charge transfer resistance. Pyridine N was found to increase structural defects, pyrrole N could supply electrons to create an electron-rich state in CoP, while amine and graphite N could reduce the bandgap. Furthermore, the Co-N-C covalent bonds between CoP and CQDs enhanced conductivity. Therefore, the electrochemical performance of the electrocatalyst was closely related to the synergy between the nitrogen atom doping mode.

High-throughput detection of mycophenolic acid in human plasma based on sensitive and rapid fluorescence nitrogen-doped carbon dots sensing platform

In this experiment, a water-soluble, nitrogen-doped yellow-green fluorescent N-doped carbon dots (N-CDs) were synthesized by one-step hydrothermal method using β-cyclodextrin as carbon source and L-phenylalanine as nitrogen source. The fluorescence quantum yield of the obtained N-CDs was as high as 9.96%, and the N-CDs exhibited photostability at different pH, ionic strength and temperature. The morphology of the N-CDs was approximately spherical with an average particle size of about 9.4 nm. Based on the fluorescence enhancement effect of mycophenolic acid (MPA) on N-CDs, a quantitative detection method of MPA was established. This method had good selectivity and high sensitivity for MPA. The fluorescence sensing system was applied to the detection of MPA in human plasma. The linear range of MPA were 0.06–3 μg·mL−1 and 3–27 μg·mL−1 with a detection limit of 0.016 μg·mL−1, and the recoveries were 97.03∼100.64 % with the RSDs of 0.13∼2.90 %. The interference experiment results showed that the interference of other coexisting substances, including Fe3+, can be ignored in the actual detection. Comparing the results measured by the established method with the EMIT method, it was found that the results obtained by the two methods were similar, and the relative error was within ± 5 %. This study provided a simple, rapid, sensitive, selective and effective method for the quantitative analysis of MPA, and was expected to be applied to clinical MPA blood concentration monitoring.

Facile synthesis of ultrathin g-C3N4 nanosheets modified with N-doped carbon dots: Enhanced photocatalytic hydrogen production activity and mechanism insight

In this study, nitrogen-doped carbon dots (NCDs) modified ultrathin carbon nitride (g-C3N4) nanosheets were synthesized by a simple secondary calcination method, which realizes efficient photocatalytic hydrogen production. The secondary calcination process can not only thermally exfoliate g-C3N4 into ultrathin nanosheets, but also uniformly anchor NCDs (∼3 nm) on the surface of g-C3N4. The photocatalytic results manifested that a very small amount of NCDs (0.5 wt%) loading on g-C3N4 could achieve a high photocatalytic hydrogen production rate (5.21 mmol g−1 h−1). The reasons for the enhanced photocatalytic activity were analyzed. The ultrathin g-C3N4 nanosheets facilitated the migration of photogenerated carriers. Moreover, NCDs/g-C3N4 exhibited enhanced visible light absorption owing to the up-conversion fluorescence effect of NCDs and the narrow band gap caused by the decoration of NCDs. Furthermore, NCDs as electron acceptors can promote carrier separation. This combination strategy provides a basis for the synthesis of inexpensive, metal-free, and efficient carbon-based photocatalysts.

An exploratory in N-doped carbon dots as green fluorescence probes for Hg(II) ions detection

ABSTRACT Carbon dots (CDs), as a fascinating carbon nanomaterial, have important applications in various fields due to their unique properties. The physical and chemical properties of CDs can be fine-tuned using heteroatom doping and surface functionalisation. Here, we synthesised N-doped carbon dots (N-CDs) by reacting Citric acid, which serve as the carbon core, with twenty amino acids under microwave irradiation. The fluorescence quenching of each amino acid doped CDs by Hg(II) ions was experimentally measured. Then the effect of the molecular features and chemical properties of amino acids on the fluorescence quenching of N-CDs by Hg(II) ions was investigated by using the quantitative structure–property relationship (QSPR) method. Applying different machine learning techniques including correlation-based and ReliefF algorithm feature selection approaches to choose relevant descriptors, multi-linear regression, and support vector machine to construct QSPR model, some reliable and predictive models were developed. Based on the variables used throughout the final QSPR models, hydrophobic interactions, in addition to hydrogen bonding interactions, can be considered a major factor governing the photoluminescence behaviour of different N-CDs quenched by Hg(II) ions. N-CDs derived from amino acids bearing larger hydrophobic surfaces show greater fluorescence quenching, indicating that a greater capacity to interact with Hg(II) metal ions resulting in further fluorescence quenching.

Nitrogen-doped carbon dots for doxorubicin-targeted delivery and two-photon cell imaging

Nitrogen (N) doped CDs (N-CDs) were prepared using citric acid and hexamethylenetetramine by a one-step hydrothermal method, characterized by transmission electron microscopy (TEM), Powder X-ray Diffractometer (PXRD), Nuclear Magnetic Resonance (13C NMR), X-ray photoelectron spectroscopy (XPS), Fourier transform infrared (FT-IR), and ultraviolet–visible (UV–vis) absorption spectra. The doping mechanism and drug-loading characteristics of N-CDs were also studied. The results showed that N-CDs had both down- and up-conversion fluorescence properties and the average particle size was about 4.28 nm. N-CDs could be used as a drug carrier for doxorubicin (DOX) (N-CDs-DOX) via the formation of the NC bond, and the drug-loading rate of N-CDs-DOX was 35.88%. The N-CDs-DOX had pH-targeted properties and low cytotoxicity. In vitro release of N-CDs-DOX belonged to the Weibull model and Fick diffusion. The results showed that N-CDs could deliver DOX successfully, and collocate with DOX in the SH-SY5Y cells through two-photon imaging. The N-CDs-DOX system had sustained-release and pH-targeted properties. N-CDs were expected to deliver a type of drugs containing CO group and be used in cancer treatment.

Highly enhanced photoluminescence and suppressed blinking of N-doped carbon dots by targeted passivation of amine group for mechanistic insights and Vis-NIR excitation bioimaging application

Carbon dots (CDs) have attracted extensive attention owing to their attractive optical properties, small size, low cost, and good biocompatibility. However, there are still challenges in unequivocally unraveling the photoluminescence (PL) origin and the structure-function relationship associated with the surface groups of CDs. Herein, we have successfully enhanced the PL efficiency of GA/N-CDs by targeted passivation of the amine groups of N-doped CDs (N-CDs) with glutaraldehyde (GA), to facilitate their bioimaging applications under one-photon and two-photon excitations. In particular, we have systematically investigated the regulation effects of this surface modification on the optical properties, exciton dynamics, and blinking behavior using steady-state and time-resolved spectroscopies, and single-particle fluorescence imaging microscopes. The effective passivation of the amine surface group of N-CDs not only regulates the energy levels and properties of surface states, but importantly activates an additional emissive center via an aldehyde-amine condensation reaction. Meanwhile, the hydrogen bonding interactions between GA and the related surface groups of N-CDs further restrain the non-radiative exciton relaxations. This synergetic effect greatly enhances the PL efficiency of two separate emission centers and the photostability of GA/N-CDs. Moreover, the photoblinking of N-CDs is significantly suppressed and the two-photon excitation PL property is also markedly increased after the surface modification, endowing GA/N-CDs the outstanding performances for fluorescence bioimaging under Vis-NIR excitations. Our findings contribute to mechanistic insights into the correlation between photophysical properties and surface states/groups, as well as demonstrate an effective post-modification strategy to improve the PL efficiency and stability of carbon-based dots.

Carbon Dots-Biomembrane Interactions and Their Implications for Cellular Drug Delivery.

The effect of carbon dots (CDs) on a model blayer membrane was studied as a means of comprehending their ability to affect cell membranes. Initially, the interaction of N-doped carbon dots with a biophysical liposomal cell membrane model was investigated by dynamic light scattering, z-potential, temperature-modulated differential scanning calorimetry, and membrane permeability. CDs with a slightly positive charge interacted with the surface of the negative-charged liposomes and evidence indicated that the association of CDs with the membrane affects the structural and thermodynamic properties of the bilayer; most importantly, it enhances the bilayer's permeability against doxorubicin, a well-known anticancer drug. The results, like those of similar studies that surveyed the interaction of proteins with lipid membranes, suggest that carbon dots are partially embedded in the bilayer. In vitro experiments employing breast cancer cell lines and human healthy dermal cells corroborated the findings, as it was shown that the presence of CDs in the culture medium selectively enhanced cell internalization of doxorubicin and, subsequently, increased its cytotoxicity, acting as a drug sensitizer.

Enrichment of MnO2 Nanoparticles with Different N-Doped Carbon Dots as a Robust H2O2 Sensor: a Comparative Study

Enrichment of MnO2 Nanoparticles with Different N-Doped Carbon Dots as a Robust H2O2 Sensor: a Comparative Study

In-situ coupling of N-doped carbon dots with manganese hexacyanoferrate as a cathode material for aqueous zinc-ion batteries

Prussian blue analogs (PBAs) are a competitive class of aqueous Zn-ion batteries (AZIBs) cathode materials with an ideal three-dimensional open structure for rapid insertion and removal of Zn2+. Meanwhile, PBAs have the advantages of high working voltage and a simple synthesis process. However, these materials are inherently poor in electrical conductivity and are susceptible to structural collapse during cycling. These defects affect the performance of zinc storage in this type of material. Here, the integration of zero-dimensional nitrogen-doped carbon dots (NCDs) and in-situ grown manganese hexacyanoferrate (MnHCF) affords the MnHCF/NCDs cathode materials, which are applied to AZIBs. The introduction of NCDs modifies the active component of MnHCF effectively. Meanwhile, NCDs significantly enhance the overall electrical conductivity and structural stability of the composites and also provide abundant active sites for electrochemical reactions. Benefiting from these merits, the MnHCF/NCDs composite exhibits an excellent electrochemical zinc storage performance. It has a high discharge-specific capacity of 131.2 mAh g−1 at 50 mA g−1 and has outstanding cycling stability of 91% capacity retention after 1000 cycles at 1000 mA g−1. The electrochemical performance of PBAs-based cathodes for AZIBs may be improved using the straightforward and efficient method presented in this work.

Synthesis of Up-Conversion Fluorescence N-Doped Carbon Dots with High Selectivity and Sensitivity for Detection of Cu2+ Ions

Carbon dots have drawn extensive attention in the detection of metal ions with good stability, excellent biocompatibility and low toxicity. Meanwhile, the quantum yield, response rate and the detection mechanism for Cu2+ ions are vital to their development and application. To obtain more selective and sensitive materials to detect Cu2+ ions, N-doped carbon dots (DN-CDs) were synthesized by a one-step hydrothermal method using citric acid as the carbon source and diethylenetriamine (DETA) as the nitrogen source. The obtained DN-CDs exhibited stable and intense blue light emission and special near-infrared up-conversion fluorescence at 820 nm, attributed to the effect of introducing N atoms into the structure of carbon dots. Due to the dynamic quenching of the DN-CDs by Cu2+ ions, the fluorescence intensity (λex = 820 nm) of DN-CDs was quantitatively decreased in the presence of Cu2+ ions. The DN-CDs had a rapid response within 3 min. The DN-CD system exhibited a linear relationship with a concentration range from 2.5 to 50 µM and low detection limit (LOD) of 42 nM. After careful investigation, an interesting conclusion was proposed: N-doped CDs with N/O = 1:1 or higher with relatively abundant N atoms prefer to detect Cu2+ ions while those with N/O = 1:2 or lower prefer to detect Fe3+ ions.

Rapid and sensitive determination of Piroxicam by N-doped carbon dots prepared by plant soot

Piroxicam (PX) as a nonsteroidal anti-inflammatory drug (NSAID) can be effectively used for anti-inflammatory and analgesia. However, overdoses may induce side effects such as gastrointestinal ulcers and headaches. Therefore, the assay of piroxicam has considerable significance. In this work, nitrogen-doped carbon dots (N-CDs) was synthesized for PX detection. The fluorescence sensor was fabricated by hydrothermal method with plant soot and ethylenediamine. The strategy exhibited a detection range of 6–200 μg/mL and 250–700 μg/mL with the limited detection of 2 μg/mL. The mechanism of the PX assay base on the fluorescence sensor was the process of electron transfer between the PX and N-CDs. The assay subsequently demonstrated could be successfully used in actual sample. The results indicated that the N-CDs could be a superior candidate nanomaterial for piroxicam monitoring in the healthcare product industry.