Nitrogen, Copper, and Iodine Triple‐Doped Carbon Dots as a Dual‐Functional Probe for Chemiluminescence Detection of Nickel Ion and Tannic Acid

Jiaoyan Xie; Suqin Han

doi:10.1002/bio.70590

. 2026 Jul 24;41(7):e70590. doi: 10.1002/bio.70590

Nitrogen, Copper, and Iodine Triple‐Doped Carbon Dots as a Dual‐Functional Probe for Chemiluminescence Detection of Nickel Ion and Tannic Acid

Jiaoyan Xie ¹, Suqin Han ^1,^✉

PMCID: PMC13396972 PMID: 42494250

ABSTRACT

A new chemiluminescence (CL) method based on nitrogen, copper, and iodine triple‐doped carbon dots (N,Cu,I‐CDs) was developed for the rapid determination of nickel ion (Ni²⁺) and tannic acid (TA). The N,Cu,I‐CDs were synthesized via a one‐step hydrothermal method and exhibited uniform particle size, excellent water solubility, and favorable optical properties. Further studies revealed that the N,Cu,I‐CDs significantly enhanced the CL signal of the K₃Fe(CN)₆‐H₂O₂ system, while the introduction of Ni²⁺ or TA strongly suppressed the CL emission. Under optimal conditions, the CL intensity was linearly correlated with Ni²⁺ concentration over the range of 1.0–100.0 μM, with a limit of detection (LOD) of 0.08 μM. For TA, a linear range of 0.4–10.0 μM was obtained, with an LOD of 0.045 μM. The proposed method was successfully applied to the determination of Ni²⁺ in celery, spinach, and starch, and TA in tea, beer, and grape juice, with recoveries of 97.7%–107.0% and 95.0%–107.0%, respectively.

Keywords: chemiluminescence; food; N,Cu,I‐CDs; Ni²⁺ ; tannic acid

N,Cu,I‐CDs, synthesized by the hydrothermal method, showed a remarkable improvement for the weak CL of the K₃Fe(CN)₆‐H₂O₂ system, while the addition of Ni²⁺ or TA strongly suppressed the CL signal of the system. Under optimal conditions, the method was used for the determination of Ni²⁺ and TA in food samples. The mechanism of CL enhancement was investigated.

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1. Introduction

Nickel ions (Ni²⁺) play significant roles in industrial and biological contexts but also pose considerable toxicological risks. They are essential in stainless steel production and battery manufacturing and serve as a cofactor for microbial and plant enzymes. However, excessive Ni²⁺ exposure is associated with respiratory disorders and malignancies [1, 2], leading to its classification as a Group 1 carcinogen by the IARC [3]. Tannic acid (TA), a natural polyphenol widely used as an additive in medicine and food [4], exhibits beneficial antioxidant, anti‐inflammatory, and anticarcinogenic properties [5, 6]; nevertheless, excessive intake can cause adverse effects such as malnutrition, osteoporosis, and anemia [7]. Therefore, accurate monitoring of Ni²⁺ and TA in environmental, occupational, and food samples is essential to balance their utility against potential health risks.

Current analytical methods for Ni²⁺, including resonance light scattering (RLS) [8], colorimetry (CM) [9], electrochemistry (EC) [10], fluorescence (FL) [11, 12], and for TA, including EC [13], resonance Rayleigh scattering (RRS) [14], CM [15], and FL [16], offer high sensitivity but are often limited by complex sample pretreatment, sophisticated instrumentation, and time‐consuming procedures. These drawbacks hinder their practical application for rapid and simple analysis. Therefore, there is a growing demand for the development of simple and reliable analytical platforms that circumvent these conventional limitations.

The chemiluminescence (CL) method has attracted considerable interest due to its high sensitivity, simplicity, and wide linear range [17]. However, the CL intensity from the oxidation of inorganic molecules is inherently weak because of low quantum yields [18]. To overcome this limitation, signal amplification strategies are essential for practical analytical applications. Carbon dots (CDs), known for excellent photostability, low toxicity, and tunable optical properties, offer an effective means for CL enhancement. Heteroatom doping further improves their quantum yield and introduces abundant surface functional groups [19, 20, 21]. Several studies have demonstrated the utility of doped CDs in amplifying CL systems [22]. For example, Co,N‐CDs enhanced the CL signal of the H₂O₂‐NaIO₄ system for 3‐nitrotyrosine detection [23]; N‐CDs amplified the Ce (IV)‐Na₂S system for H₂S sensing [24]; and B,N‐CDs were shown to enhance the Ce (IV)‐SO₃ ²⁻ reaction for rifampicin determination [25].

In this study, citric acid (CA), ethylenediamine (EDA), CuCl₂·2H₂O, and KIO₃ were used as precursors to synthesize water‐soluble nitrogen (N), copper (Cu), and iodine (I) triple‐doped CDs (N,Cu,I‐CDs) via a one‐step hydrothermal method. The synthesized N,Cu,I‐CDs significantly enhanced the CL signal of the K₃Fe(CN)₆‐H₂O₂ system. Upon addition of Ni²⁺ or TA, the CL intensity of the N,Cu,I‐CDs‐K₃Fe(CN)₆‐H₂O₂ system was markedly suppressed, and the degree of suppression was positively correlated with the concentration of each analyte. On this basis, a novel CL method for the detection of Ni²⁺ and TA was developed (Scheme S1). The proposed method exhibited high sensitivity and excellent selectivity and was successfully applied to the determination of Ni²⁺ in celery, spinach, and starch, as well as TA in tea, beer, and grape juice, with satisfactory results.

2. Experimental

2.1. Reagents and Instruments

The reagents and instruments used in our work were listed in the Supporting Information.

2.2. Synthesis of N,Cu,I‐CDs

N,Cu,I‐CDs were synthesized via a one‐step hydrothermal process with slight modifications to a previously reported procedure [26]. KIO₃ (0.5 g), CA (1.0 g), EDA (0.1 mL), and CuCl₂·2H₂O (0.3 g) were added successively to 30 mL of water. The mixture was ultrasonicated, transferred to a polytetrafluoroethylene‐lined stainless steel autoclave, and heated at 180°C for 8 h. After cooling to room temperature, the resulting solution was filtered, centrifuged, and dialyzed to obtain the N,Cu,I‐CDs solution, which was stored at 4°C. For comparison, undoped CDs (n‐CDs, from CA), N‐doped CDs (N‐CDs, from CA and EDA), N,I‐doped CDs (N,I‐CDs, from CA, EDA and KIO₃), and N,Cu‐doped CDs (N,Cu‐CDs, from CA, EDA and CuCl₂·2H₂O) were prepared following the same procedure.

2.3. Preparation of Sample

All real samples, including celery, spinach, starch, tea, beer, and grape juice, were purchased from the local market. Celery and spinach were pretreated according to the literature method [27]. Briefly, the samples were washed with water, cut into pieces, dried at 60°C for 12 h, and ground with a mortar. The pretreated samples were then digested using a wet digestion method. Specifically, 5.0 g of celery, spinach, or starch samples was mixed with 30 mL of concentrated HNO₃ in a beaker and heated until the solution evaporated to near dryness. After cooling to room temperature, 20 mL of H₂O₂ was added, and the mixtures were continuously digested until dry. The residue was dissolved in 10 mL of water, transferred to a 25‐mL volumetric flask, and diluted to the mark with water. For tea samples, 2.5 g of tea was brewed in 100 mL of boiling water for 30 min, cooled to room temperature, filtered, and diluted to the mark in a 100 mL volumetric flask. Beer was directly diluted five‐fold, and grape juice was filtered and diluted 10‐fold prior to analysis. The concentration of Ni²⁺ in celery, spinach, and starch, as well as TA in tea, beer, and grape juice, was determined by the proposed CL method.

2.4. Process of CL Detection

A schematic of the flow injection (FI)‐CL system is illustrated in Figure 1. All reaction solutions were delivered to the flow cell via two peristaltic pumps and a six‐way injection valve. A mixture of N,Cu,I‐CDs and H₂O₂ was injected into the H₂O carrier stream, which then merged with the Ni²⁺ or TA stream. Subsequently, K₃Fe(CN)₆ was introduced, triggering the CL reaction and generating the CL signal. The CL signal was detected by a photomultiplier tube (PMT) at −600 V and recorded by a computer. The determination of Ni²⁺ or TA was based on the change in CL intensity, ΔI = I₀ − I, where I₀ and I are the CL signals in the absence and presence of Ni²⁺ or TA, respectively.

Schematic diagram of FI‐CL system. HV: negative high voltage; F: flow cell.

3. Results and Discussion

3.1. Optical Properties of N,Cu,I‐CDs

The optical properties of the synthesized N,Cu,I‐CDs were investigated by UV–vis absorption and FL spectroscopy. As shown in Figure 2a, the N,Cu,I‐CDs appeared brown under visible light and exhibited blue FL under 365‐nm UV light. The UV–vis absorption spectrum showed two distinct peaks at 220 and 335 nm, attributable to π–π* (C=C) and n–π* (C=O) transitions, respectively [28].

UV–vis spectrum (a) and FL spectra (b) of N,Cu,I‐CDs.

The N,Cu,I‐CDs exhibited excitation‐dependent FL behavior, with the maximum excitation and emission wavelength at 370 and 485 nm, respectively (Figure 2b). As the excitation wavelength increased from 260 to 500 nm, the FL peak exhibited a redshift, with the FL intensity fluctuating, reflecting the influence of varying particle sizes and surface state distributions [29]. Characterization of the N,Cu,I‐CDs by TEM, XRD, FTIR, and XPS is presented in the Supporting Information (Figures S1 and S2).

3.2. CL Activity of N,Cu,I‐CDs as Sensitizer

The CL kinetic curves were recorded using a static injection method. As shown in Figure 3a, the N,Cu,I‐CDs induced the strongest CL emission in the K₃Fe(CN)₆‐H₂O₂ system. Weak CL emission was observed in both the N,Cu,I‐CDs‐H₂O₂ and K₃Fe(CN)₆‐N,Cu,I‐CDs mixed solutions, whereas no CL signal was detected for the K₃Fe(CN)₆‐H₂O₂ system alone. To further evaluate the origin of the CL enhancement, the effects of the precursors used for synthesizing N,Cu,I‐CDs (CA, EDA, KIO₃, CuCl₂, and their mixtures) on the K₃Fe(CN)₆‐H₂O₂ system were examined. None of these precursors affected the CL emission, indicating that the observed CL enhancement was specifically attributable to the N,Cu,I‐CDs rather than their precursors.

(a) CL kinetic curves of K₃Fe(CN)₆‐H₂O₂ system (1), N,Cu,I‐CDs‐H₂O₂ system (2), N,Cu,I‐CDs‐K₃Fe(CN)₆ system (3), N,Cu,I‐CDs‐K₃Fe(CN)₆‐H₂O₂ CL system (4), N,Cu,I‐CDs‐K₃Fe(CN)₆‐H₂O₂‐Ni²⁺ system (5), and N,Cu,I‐CDs‐K₃Fe(CN)₆‐H₂O₂‐TA system (6). (b) CL spectrum of N,Cu,I‐CDs‐K₃Fe(CN)₆‐H₂O₂ and FL spectrum of N,Cu,I‐CDs. (c) Effect of radical scavengers (1.0 mM) on the CL response.

Figure S3a presents the CL responses of various CDs, including n‐CDs, N‐CDs, N,Cu‐CDs, N,I‐CDs, and N,Cu,I‐CDs, in the K₃Fe(CN)₆‐H₂O₂ system. The results confirm the synergistic roles of N, Cu, and I in boosting the CL intensity. Specifically, nitrogen doping modulates the electronic structure of the carbon skeleton, creating defects and facilitating electron transfer [19, 20]. Iodine doping induces local dipoles and lattice distortion, promoting charge separation [20]. Copper acts as a redox‐active catalytic center (Cu²⁺/Cu⁺), accelerating reactive oxygen species decomposition and radical generation while facilitating electron transfer [21]. The triple synergy yields cooperative effects unattainable in single‐ or dual‐doped systems, enabling precise optical property tuning and enhanced catalytic activity [23, 24], which collectively result in significantly improved CL performance.

To obtain optimal CL emission, different mixing orders of the CL reagents were investigated. As shown in Figure S3b, the strongest signal was achieved when K₃Fe(CN)₆ was injected into the mixed N,Cu,I‐CDs‐H₂O₂ solution. When N,Cu,I‐CDs were injected into the mixture of K₃Fe(CN)₆‐H₂O₂, or when H₂O₂ was injected into the mixture of N,Cu,I‐CDs‐K₃Fe(CN)₆, the CL intensity decreased by approximately 94.2% and 94.0%, respectively. This marked reduction is possibly due to the premature reaction of K₃Fe(CN)₆ with H₂O₂ or N,Cu,I‐CDs before the addition of the third component.

3.3. Study on the Mechanism of CL Reaction

To investigate the unique CL phenomenon, the CL spectrum of the N,Cu,I‐CDs‐K₃Fe(CN)₆‐H₂O₂ system was measured and compared with the FL spectrum of N,Cu,I‐CDs excited at 480 nm (Figure 3b). Only one maximum emission peak was observed at 535 nm, which was consistent with the FL spectrum of the N,Cu,I‐CDs. The overlap between CL and FL spectra demonstrated that the major emitting specie was excited‐state N,Cu,I‐CDs (N,Cu,I‐CDs*), generated in the N,Cu,I‐CDs and K₃Fe(CN)₆‐H₂O₂ reaction system. Subsequently, radical scavenger tests were conducted to confirm the presence of radicals in the CL reaction. Four scavengers, namely ascorbic acid (AA), NaN₃, thiourea (TU), and nitroblue tetrazolium chloride (NBT), were tested. As shown in Figure 3c, the CL signal was strongly inhibited upon the addition of AA, suggesting that radical species played a key role in the generation of the emitting species [30]. NaN₃, a typical ¹O₂ scavenger, exhibited a weak quenching effect on the CL intensity, indicating that the CL did not originate from ¹O₂ [31] and further supporting that the N,Cu,I‐CDs served as the emissive species. Furthermore, the CL signals were greatly quenched by TU and NBT, which are trapping agents for ^•OH and ^•O₂ ⁻, respectively, demonstrating the essential roles of these radicals in the CL system [30].

Based on these results, a possible CL mechanism is proposed. Under alkaline conditions, K₃Fe(CN)₆ reacts with H₂O₂ to generate ^•O₂ ⁻ [32], which further reacts with excess H₂O₂ to produce ^•OH, catalyzed by trace iron species (e.g., Fe (CN)₆ ³⁻/Fe (CN)₆ ⁴⁻) [33, 34]. Meanwhile, H₂O₂ undergoes deprotonation to form HO₂ ⁻, which rapidly decomposes to generate large amount of ^•OH and ^•O₂ ⁻, owing to the peroxidase‐like catalytic activity of the N,Cu,I‐CDs [35]. Subsequently, ^•OH and K₃Fe(CN)₆ inject holes into the valence band of the N,Cu,I‐CDs, forming positively charged N,Cu,I‐CDs (h ⁺), whereas ^•O₂ ⁻ injects electrons into the conduction band, generating negatively charged N,Cu,I‐CDs (e−) [36]. The charged N,Cu,I‐CDs radials undergo electron–hole annihilation upon collision, leading to the formation of N,Cu,I‐CDs*. The subsequent return of electrons from the excited state to the ground state is accompanied by light emission.

To elucidate the mechanism by which Ni²⁺ and TA suppress the CL emission of the N,Cu,I‐CDs‐K₃Fe(CN)₆‐H₂O₂ system, the FL and UV–vis spectra of N,Cu,I‐CDs were investigated in the absence and presence of Ni²⁺. As shown in Figure S4a,b, both the FL intensity and the UV–vis absorbance of N,Cu,I‐CDs decreased after the addition of Ni²⁺, while the maximum emission and absorption wavelengths remained unchanged. This suggests that Ni²⁺ may disrupt the nanostructure of N,Cu,I‐CDs, thereby reducing the number of emissive species. The abundant surface functional groups of the N,Cu,I‐CDs, including carboxyl, hydroxyl, amino, and N‐containing heterocycles, are well‐established coordination sites for Ni²⁺ via electrostatic or chelation interactions [11, 37, 38, 39], accounting for the high selectivity towards Ni²⁺. Furthermore, the binding constant (K_b) between Ni²⁺ and the N,Cu,I‐CDs was calculated to be 1550 L mol⁻¹ from CL quenching titration data using the Stern‐Volmer equation (Figure S4c and Table S1), confirming a strong affinity that underlies the high selectivity.

As shown in Figure S4d, the UV–vis spectrum of the K₃Fe(CN)₆‐TA mixture was recorded and compared with those of TA and K₃Fe(CN)₆ alone. The absorption peak of TA at 275 nm disappeared, while the characteristic absorption of K₃Fe(CN)₆ at 420 nm decreased significantly, indicating a reaction between K₃Fe(CN)₆ and TA that consumed part of K₃Fe(CN)₆. Moreover, as a reducing substance, TA may scavenge ^•O₂ ⁻ and ^•OH radicals, thereby reducing the amount of free radicals and leading to a decrease in CL signal (Figure 3c).

3.4. CL Detection of Ni²⁺ and TA

The analytical performance of the proposed CL method for the detection of Ni²⁺ and TA was evaluated under optimized experimental conditions (Figure S5). As shown in Figure S6a,b, ΔI was linearly proportional to the logarithm of Ni²⁺ and TA concentrations. The linear ranges were 1.0–100.0 μM for Ni²⁺ and 0.4–10.0 μM for TA, with regression equations of ΔI = 1713.7 lg [Ni²⁺] + 279.8 (R ² = 0.9927) and ΔI = 3360.5 lg [TA] + 1151.2 (R ² = 0.9916), respectively. The limits of detection (LOD) were 0.08 μM for Ni²⁺ and 0.045 μM for TA, based on a signal‐to‐noise ratio of 3. The relative standard deviations (RSD) for 11 consecutive measurements of 10.0‐μM Ni²⁺ and 1.0‐μM TA were 0.85% and 0.92%, respectively, indicating good precision. A comparison of the proposed method with other reported methods for the determination of Ni²⁺ and TA is presented in Table S2.

3.5. Selectivity for Ni²⁺ and TA

To evaluate the practical applicability of the proposed method, interference from coexisting species was examined prior to the detection of Ni²⁺ and TA in real samples. Various potential interfering substances were mixed with 10.0‐μM Ni²⁺ or 2.0‐μM TA solutions, respectively, and then added to the N,Cu,I‐CDs‐K₃Fe(CN)₆‐H₂O₂ system, after which the CL intensity was measured. Table S3 lists the tolerable concentration ratios of the interfering substances that caused a relative error of less than 5%. These results confirm that the proposed CL sensor based on the N,Cu,I‐CDs‐K₃Fe(CN)₆‐H₂O₂ system exhibits excellent selectivity for the determination of Ni²⁺ and TA.

We further compared the CL responses of n‐CDs, N‐CDs, N,Cu‐CDs, N,I‐CDs, and N,Cu,I‐CDs (Figure S3a) toward Ni²⁺ and TA, respectively, in the K₃Fe(CN)₆‐H₂O₂ system. The N,Cu,I‐CDs system exhibited the highest discrimination ratio, confirming that the triple‐doping configuration is essential for achieving superior selectivity, a feature unattainable with single or dual doping.

3.6. Ni²⁺ and TA Analysis in Real Samples

The Ni²⁺ contents in starch, celery, spinach, as well as the TA contents in tea, beer, and grape juice, were further determined using the standard addition method to evaluate the applicability of the proposed method for real sample analysis. The results are summarized in Tables S4 and S5. The recoveries for Ni²⁺ in starch, celery, and spinach ranged from 97.7% to 107.0%, and those for TA in tea, beer, and grape juice ranged from 95.0% to 107.0%. These result demonstrate that the proposed CL method is effective for the sensitive detemination of Ni²⁺ and TA in real samples.

4. Conclusion

In this study, N,Cu,I‐CDs were synthesized and demonstrated to significantly amplify the CL intensity of the K₃Fe(CN)₆‐H₂O₂ system, leading to the development of a new CL system. The luminophore was identified as excited N,Cu,I‐CDs. The system exhibited sensitive and selective responses to Ni²⁺ and TA based on their inhibitory effects, enabling the successful determination of both analytes in real samples. This strategy highlights the potential of multi‐heteroatom‐doped CDs as versatile CL signal amplifiers, which may be extended to the detection of other inhibitors.

Author Contributions

Jiaoyan Xie: investigation, data curation, conceptualization, writing – original draft. Suqin Han: methodology, resources, supervision, writing – review and editing.

Funding

The authors have nothing to report.

Conflicts of Interest

The authors declare no conflicts of interest.

Supporting information

SCHEME S1 Schematic illustration of the N,Cu,I‐CDs‐K₃Fe(CN)₆‐H₂O₂ CL system for detection of Ni²⁺ and TA.

FIGURE S1: TEM image (a), size distribution histogram spectrum (b), XRD pattern (c), and FTIR spectrum (d) of N,Cu,I‐CDs.

FIGURE S2: (a) XPS survey spectrum of N,Cu,I‐CDs and (b–f) XPS high‐resolution of C 1s, N 1s, O 1s, Cu 2p, I 3d of N,Cu,I‐CDs.

FIGURE S3: (a) CL intensity of the K₃Fe(CN)₆‐H₂O₂ toward various CDs. (b) CL kinetic curves of the N,Cu,I‐CDs‐K₃Fe(CN)₆‐H₂O₂ system with different reagents mixing orders: (1) N,Cu,I‐CDs injected into the mixture of K₃Fe(CN)₆ and H₂O₂.

FIGURE S4: (a) FL spectra of N,Cu,I‐CDs with 0 μM (1), 10.0 μM (2), 50.0 μM (3), and 100.0 μM (4) Ni²⁺. (b) UV–vis spectra of N,Cu,I‐CDs (1) and N,Cu,I‐CDs‐Ni²⁺ (2). (c) Double‐logarithmic plot of log[(I₀ − I)/I] versus log[Ni²⁺] for the calculation of binding constant (K_b). (d) UV–vis spectra of TA (1), K₃Fe(CN)₆ (2), and K₃Fe(CN)₆‐TA (3).

FIGURE S5: Effects of the concentration of N,Cu,I‐CDs (a), NaOH (b), K₃Fe(CN)₆ (c), and H₂O₂ (d) on the CL intensity.

FIGURE S6: Linear relationship between CL intensity and Ni²⁺ (a) and TA (b).

TABLE S1: Binding parameters for Ni²⁺ interaction with N,Cu,I‐CDs derived from CL quenching data.

TABLE S2: The comparison of analytical performance of different methods for the determination of Ni²⁺ and TA.

TABLE S3: Effects of interfering species for the determination of Ni²⁺ and TA.

TABLE S4: Determination results of Ni²⁺ in real samples.

TABLE S5: Determination results of TA in real samples.

BIO-41-e70590-s001.docx^{(1.3MB, docx)}

Data Availability Statement

The data that support the findings of this study are available from the corresponding author upon reasonable request.

References

1. Denkhaus E. and Salnikow K., “Nickel Essentiality, Toxicity, and Carcinogenicity,” Critical Reviews in Oncology/Hematology 42 (2002): 35–56, 10.1016/S1040-8428(01)00214-1. [DOI] [PubMed] [Google Scholar]
2. Zhao J., Shi X., Castranova V., and Ding M., “Occupational Toxicology of Nickel and Nickel Compounds,” Journal of Environmental Pathology, Toxicology and Oncology 28 (2009): 177–208, 10.1615/jenvironpatholtoxicoloncol.v28.i3.10. [DOI] [PubMed] [Google Scholar]
3. Li J., Hou C., Huo D., et al., “Detection of Trace Nickel Ions With a Colorimetric Sensor Based on Indicator Displacement Mechanism,” Sensors and Actuators B: Chemical 241 (2017): 1294–1302, 10.1016/j.snb.2016.09.191. [DOI] [Google Scholar]
4. Wang J., Chen X. L., Chen Y., Qin F., and Yang H. F., “Pharmacological Effects and Mechanisms of Tannic Acid,” Biomedicine & Pharmacotherapy 154 (2022): 113561, 10.1016/j.biopha.2022.113561. [DOI] [PubMed] [Google Scholar]
5. Baer‐Dubowska W., Szaefer H., Majchrzak‐Celińska A., and Krajka‐Kuźniak V., “Tannic Acid: Specific Form of Tannins in Cancer Chemoprevention and Therapy‐Old and New Applications,” Current Pharmacology Reports 6 (2020): 28–37, 10.1007/s40495-020-00211-y. [DOI] [Google Scholar]
6. Khan N. S., Ahmad A., and Hadi S. M., “Anti‐Oxidant, Pro‐Oxidant Properties of Tannic Acid and Its Binding to DNA,” Chemico‐Biological Interactions 125 (2000): 177–189, 10.1016/S0009-2797(00)00143-5. [DOI] [PubMed] [Google Scholar]
7. Chung K. T., Wong T. Y., Wei C. I., Huang Y. W., and Lin Y., “Tannins and Human Health: A Review,” Critical Reviews in Food Science and Nutrition 38 (1998): 421–464, 10.1080/10408699891274273. [DOI] [PubMed] [Google Scholar]
8. Pimsin N., Kongsanan N., Keawprom C., et al., “Ultratrace Detection of Nickel (II) Ions in Water Samples Using Dimethylglyoxime‐Doped GQDs as the Induced Metal Complex Nanoparticles by a Resonance Light Scattering Sensor,” ACS Omega 6 (2021): 14796–14805, 10.1021/acsomega.1c00190. [DOI] [PMC free article] [PubMed] [Google Scholar]
9. Joseph S., Somkuwar P., Menon G. G., et al., “Smartphone‐Assisted Colorimetric Detection of Nickel (II) Ions Using a Novel Benzothiazole–Quinoline Dyad in Semi‐Aqueous Media,” Analytical Methods 17 (2025): 265–274, 10.1039/d4ay01574f. [DOI] [PubMed] [Google Scholar]
10. Selvolini G. and Marrazza G., “On Spot Detection of Nickel and Cobalt From Exhausted Batteries by a Smart Electrochemical Sensor,” Talanta 253 (2023): 123918, 10.1016/j.talanta.2022.123918. [DOI] [PubMed] [Google Scholar]
11. Gu C., Jiao Y., Gao Y., Liu X., and Qian T., “Synthesis of Nitrogen‐Doped Fluorescent Carbon Dots for Determination of Nickel Ions and Morin From Aqueous Solution Simultaneously,” Microchemical Journal 200 (2024): 110317, 10.1016/j.microc.2024.110317. [DOI] [Google Scholar]
12. Wang X., Cheng S., Liu C., et al., “A Novel Ratiometric Fluorescent Probe for the Detection of Nickel Ions in the Environment and Living Organisms,” Science of the Total Environment 840 (2022): 156445, 10.1016/j.scitotenv.2022.156445. [DOI] [PubMed] [Google Scholar]
13. Haššo M., Sarakhman O., Đurđić S., Stanković D., and Švorc L., “Advanced Electrochemical Platform for Simple and Rapid Quantification of Tannic Acid in Beverages Using Batch Injection Analysis With Amperometric Detection,” Journal of Electroanalytical Chemistry 942 (2023): 117578, 10.1016/j.jelechem.2023.117578. [DOI] [Google Scholar]
14. Shi Y., Yang L., Zhu J., et al., “Resonance Rayleigh Scattering Technique for Simple and Sensitive Analysis of Tannic Acid With Carbon Dots,” Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy 173 (2017): 817–821, 10.1016/j.saa.2016.10.054. [DOI] [PubMed] [Google Scholar]
15. Xue Y., Ma X., Feng X., et al., “Temperature‐Derived Purification of Gold Nano‐Bipyramids for Colorimetric Detection of Tannic Acid,” ACS Applied Nano Materials 6 (2023): 11572–11580, 10.1021/acsanm.3c01593. [DOI] [PMC free article] [PubMed] [Google Scholar]
16. Yang H., He L., Pan S., Liu H., and Hu X., “Nitrogen‐Doped Fluorescent Carbon Dots for Highly Sensitive and Selective Detection of Tannic Acid,” Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy 210 (2019): 111–119, 10.1016/j.saa.2018.11.029. [DOI] [PubMed] [Google Scholar]
17. Giokas D. L., Vlessidis A. G., Tsogas G. Z., and Evmiridis N. P., “Nanoparticle‐Assisted Chemiluminescence and Its Applications in Analytical Chemistry,” TrAC Trends in Analytical Chemistry 29 (2010): 1113–1126, 10.1016/j.trac.2010.07.001. [DOI] [Google Scholar]
18. Chen H., Li R., Li H., and Lin J. M., “Plasmon‐Assisted Enhancement of the Ultraweak Chemiluminescence Using Cu/Ni Metal Nanoparticles,” Journal of Physical Chemistry C 116 (2012): 14796–14803, 10.1021/jp303092d. [DOI] [Google Scholar]
19. Xu Q., Kuang T., Liu Y., et al., “Heteroatom‐Doped Carbon Dots: Synthesis, Characterization, Properties, Photoluminescence Mechanism and Biological Applications,” Journal of Materials Chemistry B 4 (2016): 7204–7219, 10.1039/C6TB02131J. [DOI] [PubMed] [Google Scholar]
20. Kou X., Jiang S., Park S. J., and Meng L. Y., “A Review: Recent Advances in Preparations and Applications of Heteroatom‐Doped Carbon Quantum Dots,” Dalton Transactions 49 (2020): 6915–6938, 10.1039/d0dt01004a. [DOI] [PubMed] [Google Scholar]
21. Lin L., Luo Y., Tsai P., Wang J., and Chen X., “Metal Ions Doped Carbon Quantum Dots: Synthesis, Physicochemical Properties, and Their Applications,” TrAC Trends in Analytical Chemistry 103 (2018): 87–101, 10.1016/j.trac.2018.03.015. [DOI] [Google Scholar]
22. Shen C. L., Lou Q., Liu K. K., Dong L., and Shan C. X., “Chemiluminescent Carbon Dots: Synthesis, Properties, and Applications,” Nano Today 35 (2020): 100954, 10.1016/j.nantod.2020.100954. [DOI] [Google Scholar]
23. Delnavaz E. and Amjadi M., “A Chemiluminescence Probe Enhanced by Cobalt and Nitrogen‐Doped Carbon Dots for the Determination of a Nitrosative Stress Biomarker,” Microchimica Acta 188 (2021): 278, 10.1007/s00604-021-04932-9. [DOI] [PubMed] [Google Scholar]
24. Yuan X., Yan S., Wei C., Zhang Y., Su Y., and Lv Y., “Strong Enhancement of the Chemiluminescence of Cerium (IV)‐Na₂S System by Mono‐Dispersed N‐CDs Generated In Situ,” Microchemical Journal 189 (2023): 108560, 10.1016/j.microc.2023.108560. [DOI] [Google Scholar]
25. Shokri R. and Amjadi M., “Boron and Nitrogen Co‐Doped Carbon Dots as a Chemiluminescence Probe for Sensitive Assay of Rifampicin,” Journal of Photochemistry and Photobiology, A: Chemistry 425 (2022): 113694, 10.1016/j.jphotochem.2021.113694. [DOI] [Google Scholar]
26. Yin Q., Yang X., Yang L., Yang D., Yang Y., and Zhu Y., “Cu, I‐Doped Carbon Dots as Simulated Nanozymes for the Colorimetric Detection of Morphine in Biological Samples,” Analytical Biochemistry 680 (2023): 115313, 10.1016/j.ab.2023.115313. [DOI] [PubMed] [Google Scholar]
27. Nakhaei J. M., Jamali M. R., Sohrabnezhad S., and Rahnama R., “In‐Syringe Solvent‐Assisted Dispersive Solid Phase Extraction Followed by Flame Atomic Absorption Spectrometry for Determination of Nickel in Water and Food Samples,” Microchemical Journal 144 (2019): 88–92, 10.1016/j.microc.2018.08.063. [DOI] [Google Scholar]
28. Teng X. Y., Ma C. G., Ge C. J., et al., “Green Synthesis of Nitrogen‐Doped Carbon Dots From Konjac Flour With “Off–On” Fluorescence by Fe³⁺ and L‐Lysine for Bioimaging,” Journal of Materials Chemistry B 2 (2014): 4631–4639, 10.1039/c4tb00368c. [DOI] [PubMed] [Google Scholar]
29. Sun Y. P., Zhou B., Lin Y., et al., “Quantum‐Sized Carbon Dots for Bright and Colorful Photoluminescence,” Journal of the American Chemical Society 128 (2006): 7756–7757, 10.1021/ja062677d. [DOI] [PubMed] [Google Scholar]
30. Dong S., Yuan Z., Zhang L., Lin Y., and Lu C., “Rapid Screening of Oxygen States in Carbon Quantum Dots by Chemiluminescence Probe,” Analytical Chemistry 89 (2017): 12520–12526, 10.1021/acs.analchem.7b03711. [DOI] [PubMed] [Google Scholar]
31. Chen H., Wang Q., Shen Q., et al., “Nitrogen Doped Graphene Quantum Dots Based Long‐Persistent Chemiluminescence System for Ascorbic Acid Imaging,” Biosensors and Bioelectronics 91 (2017): 878–884, 10.1016/j.bios.2017.01.061. [DOI] [PubMed] [Google Scholar]
32. Wierzchowski J., Slawinska D., and Slawinski J., “Carbonate and Superoxide Ion‐Radicals as Intermediates in the Chemiluminescence of the Ferricyanide‐Hydrogen Peroxide Redox System,” Zeitschrift für Physikalische Chemie, Neue Folge 148 (1986): 197–214, 10.1524/zpch.1986.148.2.197. [DOI] [Google Scholar]
33. Koppenol W. H., “Reactions Involving Singlet Oxygen and the Superoxide Anion,” Nature 262 (1976): 420–421, 10.1038/262420a0. [DOI] [PubMed] [Google Scholar]
34. Flitter W., Rowley D. A., and Halliwell B., “Superoxide‐Dependent Formation of Presence of Hydroxyl Radicals in the Iron Salts: What Is the Physiological Iron Chelator?,” FEBS Letters 158 (1983): 310–312, 10.1016/0014-5793(83)80602-4. [DOI] [Google Scholar]
35. He L., Jiang Z. W., Li W., Li C. M., Huang C. Z., and Li Y. F., “In Situ Synthesis of Gold Nanoparticles/Metal–Organic Gels Hybrids With Excellent Peroxidase‐Like Activity for Sensitive Chemiluminescence Detection of Organophosphorus Pesticides,” ACS Applied Materials & Interfaces 10 (2018): 28868–28876, 10.1021/acsami.8b08768. [DOI] [PubMed] [Google Scholar]
36. Zheng Y., Zhang D., Shah S. N. A., Li H., and Lin J. M., “Ultra‐Weak Chemiluminescence Enhanced by Facilely Synthesized Nitrogen‐Rich Quantum Dots Through Chemiluminescence Resonance Energy Transfer and Electron Hole Injection,” Chemical Communications 53 (2017): 5657–5660, 10.1039/C7CC02041D. [DOI] [PubMed] [Google Scholar]
37. Almaquer F. E. P., Ricacho J. S. Y., and Ronquillo R. L. G., “Simple and Rapid Colorimetric Sensing of Ni (II) Ions in Tap Water Based on Aggregation of Citrate‐Stabilized Silver Nanoparticles,” Sustainable Environment Research 29 (2019): 23, 10.1186/s42834-019-0026-3. [DOI] [Google Scholar]
38. Li Y., Liu C., Chen M., et al., “Solvent‐Free Preparation of Tannic Acid Carbon Dots for Selective Detection of Ni²⁺ in the Environment,” International Journal of Molecular Sciences 23 (2022): 6681, 10.3390/ijms23126681. [DOI] [PMC free article] [PubMed] [Google Scholar]
39. Shah M. T., Balouch A., and Alveroglu E., “Sensitive Fluorescence Detection of Ni²⁺ Ions Using Fluorescein Functionalized Fe₃O₄ Nanoparticles,” Journal of Materials Chemistry C 6 (2018): 1105–1115, 10.1039/C7TC04298A. [DOI] [Google Scholar]

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