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Synthesis of N,S co-doped carbon quantum dots – metal complex for the detection of fluoride (F−) ion in adults and Children’s toothpastes

  • Mutendu C. Kungwa , Olanrewaju A. Aladesuyi and Oluwatobi S. Oluwafemi ORCID logo EMAIL logo
Published/Copyright: December 23, 2025
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Green Processing and Synthesis
From the journal Green Processing and Synthesis Volume 14 Issue 1

Abstract

We herein report a simple and facile synthesis of N, S co-doped carbon quantum dots (N,S-CQDs) complexed with lead ions as a fluorescent nanoprobe for the detection of fluoride ions in adults’ and children’s toothpaste. The nanoprobe was prepared via a hydrothermal method using sodium sulphide, glutamine and citric acid as the sulphur, nitrogen and carbon precursors, respectively. The structural characterisation of the as-synthesised nanoprobe confirmed that the material is small, crystalline and spherical. The nanoprobe was sensitive and selective towards Pb2+ in the presence of other metal ions. In addition, the as-prepared nanoprobe/Pb2+ complex was sensitive and selective towards fluoride ions in the presence of other ions, with a detection limit of 78.03 nM. Furthermore, the as-synthesised material served as a nanoprobe for the detection of fluoride ions in commercial toothpaste with recoveries of 98.32–117.03 % in adult’s toothpaste and 103.24–111.88 % in kids’ toothpaste with RSD< 5 %, indicating its potential application in complex matrices.

Keywords: carbon quantum dot; fluorescent probe; dental caries; fluoride ion; lead ion

1 Introduction

Dental caries, more commonly recognised as tooth decay, poses a substantial worldwide public health issue that impacts people across various age groups and socioeconomic strata [1]. Caries in children can cause pain, loss of teeth, speech impediment, sleep disturbance, lack of concentration, and ultimately affect learning performance [2], 3]. Fluorine is a vital element that plays a critical role in the oral health of humans. It ensures the structural stability of the tooth by ensuring the continuous mineralisation of the enamel. The use of fluorinated dental products and the adequate intake of fluoride have been described as the best approach to prevent dental caries. Furthermore, the most common way of oral hygiene technique is the use of a toothbrush and toothpaste [4]. However, the effectiveness of toothpaste can vary based on its chemical composition, with fluoride being the main active ingredient that prevents tooth decay and strengthens the enamel [5]. Insufficient amount of fluoride in toothpaste can result in ineffective prevention of dental caries, while excess fluoride, on the other hand, is also counterproductive. This could result in fluorosis, [6] a condition that alters the appearance and strength of one’s teeth. Thus, the accurate monitoring of fluoride in toothpaste is important for its effectiveness in maintaining good oral hygiene and preventing dental caries. Currently, the determination of fluoride ions in toothpaste primarily relies on traditional analytical techniques such as ion-selective electrodes or spectrophotometry [7]. Although these methods are sensitive and reliable, they involve the use of costly equipment, trained personnel, and expensive reagents. Considering these limitations, the development of an alternative, sensitive, and dependable fluoride monitoring system is necessary for regulating the amount of fluoride in toothpaste. The use of fluorescent nanoprobes such as carbon quantum dots (CQDs) or its co-doping CQDs with different heteroatoms (N, S and P) has been extensively explored as selective metal and non-metal sensors in quantification analysis due to their outstanding properties such as water solubility, low toxicity, resistance to photobleaching, etc. [8], 9]. Though there have been a few reports showing the use of doped CQDs as a nanoprobe for non-metal ion detection however, reports on fluoride sensing, particularly in dental products, still need to be investigated. In this work, we reported the use of N,S CQDs/Pb2+ for the detection of fluoride ions in toothpaste. We employed the fluorescence “off-on” detection strategy using N,S-CQDs/Pb2+ by leveraging the interaction between Pb2+ and fluoride ions. This interaction occurs through the formation of an ionic bond between lead and fluorine, resulting in PbF2. The strong affinity is further explained by the fact that lead, as a relatively hard acid, preferentially binds to fluoride ions. This strong interaction resulted in the recovery of the quenched fluorescence of N,S CQDs/Pb2+. The nanoprobe/Pb2+ complex showed good selectivity for fluoride ions in the presence of interfering ions. The as-synthesized nanoprobe was subsequently used to determine the amount of fluoride ions present in toothpaste. Excellent recoveries of (98.32 %–117.03 %) and (103.24 %–111.88 %) were obtained for the adult and kids categories of toothpaste, respectively with RSD< 5 %. The result showed that this method is easy, and the developed material can accurately detect the fluoride ion in a complex matrix like toothpaste.

2 Materials and methods

2.1 Materials and reagents

l-Glutamine, sodium sulfide, citric acid, sodium chloride (NaCl), potassium chloride (KOH), mercury chloride (HgCl2), copper chloride (CuCl2), calcium chloride(CaCl2), Aluminum chloride(AlCl3), chromium chloride hexahydrate (CrCl3.6H2O), calcium nitrate tetrahydrate [Ca(NO3)2.4 H2O], sodium hydroxide (NaOH), sodium carbonate (Na2CO3), sodium sulfite (Na2SO3), sodium phosphate hydrate (Na3PO4.H2O) were purchased from Sigma Aldrich. All the chemicals used were of analytical grade and did not require any further processing.

2.2 Synthesis of the nanoprobe

The synthesis of the nanoprobe was carried out hydrothermally as described in our previous report [10] using Na2S, glutamine and CA as the sulphur, nitrogen and carbon precursors, respectively. Briefly, Na2S (9 mmol), glutamine (9 mmol), and citric acid (6 mmol) were placed in a beaker, then 30 mL of deionized water was added. The beaker was then placed on a magnetic stirrer at 450 rpm until an even solution was obtained. The transparent solution was transferred to a Teflon-lined stainless-steel autoclave, which was then sealed and heated at 200 °C for 4 h in the oven. After 4 h, the autoclave was taken out of the oven and allowed to cool gradually at ambient temperature overnight. To purify the obtained nanoprobe, the yellowish solution obtained after cooling was centrifuged at 950 rpm for 20 min, washed several times with n-butanol, and the supernatant was sieved using a 0.02 μm filter paper. This was followed by freeze-drying to produce solid crystals of the synthesised nanoprobe.

2.3 Characterisation of the as-synthesised nanoprobe

A JEOL JEM-2100 high-resolution transmission electron microscope (HRTEM), operated at an accelerating voltage of 200 kV was used to determine the morphology and the particle size. The fluorescence spectra were acquired using a PL spectrometer (RF-6000) while the lifetime measurement and quantum yield (QY) were obtained using FS5 spectrofluorometer (Edinburg Instruments). X-ray diffraction (XRD) measurements were performed using a Bruker D8 Advance diffractometer equipped with monochromatic CuKα1 radiation (λ = 1.5418 Å). The surface chemistry was analysed using a PerkinElmer Spectrum Two Fourier Transform Infrared (FTIR) instrument equipped with an attenuated total reflection (ATR) sample holder, scanning over a range of 400–4,000 cm−1.

2.4 Fluorescence sensing of metal ions using N,S-CQDs nanoprobe

A 60 μL of aqueous N,S-CQDs was added into individual cuvettes containing 3 mL of various ionic solutions, including NaCl, KOH, HgCl2, CuCl2, CaCl2, Pb(NO3)2, and CrCl3·6H2O. After an incubation period of approximately 5 min (to facilitate interaction between the N,S-CQDs and the metal ions), the fluorescence spectra were recorded. The photoluminescence intensity changes were then compared between the control sample (60 μL N,S-CQDs in 3 mL deionized water) and the respective N,S-CQDs/metal ion mixtures.

2.5 Fluorescent detection of fluoride ion and real sample analysis

The F− ion sensing was conducted by mixing 100 μL of N,S-CQDs solution with 3 mL of Pb2+ solution (100 μM) in a centrifuge tube. This N,S-CQDs/Pb2+ mixture was then transferred into separate cuvettes containing various fluoride ion standards, with the final volume adjusted to 3 mL. Fluorescence spectra of the resulting mixtures were recorded at an excitation wavelength of 350 nm. For selectivity studies, the same procedure was repeated using the mixture of F− and other anions (Cl−, Br−, I−, CO3 2−, PO4 −,NO3 −). For real sample analysis, 1 g of the adult toothpaste (Colgate herbal white) purchased from the Clicks store, Johannesburg, South Africa, was dissolved in 30 mL of deionised water, and the mixture was stirred at 70 °C for 3 h. The solution obtained was filtered with a 0.22 µm filter paper to remove the solids in the suspension. The suspension was further diluted to 100 mL with water. Thereafter, 1 mL of the suspension was added to 3 mL of N,S-CQDs/Pb2+ system, and the fluorescence intensity differences were recorded to assess the response of the N,S-CQDs/Pb2+ system to fluoride ions. The same experimental protocol was applied using a sample of children’s toothpaste (Jordan Junior).

3 Results and discussion

3.1 Optical properties of the N,S-CQDs

The optical properties of the as-synthesised N,S-CQDs were evaluated using UV–Vis absorption spectroscopy and photoluminescence spectroscopy. Figure 1a depicts the UV–Vis absorption spectrum of the as-synthesised N,S-CQDs. Two major absorption bands were observed at 225 nm and 330 nm. The peak at 225 nm can be attributed to a π-π* transition that arises due to the presence of the sp2-hybridised carbon domains, which serve as active electronic states of the CQDs. The peak at 330 nm can be attributed to n- π* transition due to excitonic transitions between the different energetically active states of the quantum dots, which are driven by the functional groups present on the surface of the N,S-CQDs [11]. Figure 1b shows the photoluminescent spectra of the as-synthesised N,S-CQDs at different excitation wavelengths (350–450 nm). The emission position of the N,S-CQDs red-shifted as the excitation wavelength increased, an indication of excitation-dependent emission. This phenomenon could be attributed to the surface defects experienced by the N,S-CQDs [12]. The as-synthesized nanoprobe exhibited a fluorescent quantum yield (QY) of 10.35 %. The photostability of the developed nanoprobe was studied by exposure to constant UV light for 7 h. The result showed that there was no significant change in the fluorescent intensity after the exposure, an indication of good photostability (Figure 2).

Figure 1: Optical properties of the as-synthesised N,S-CQDs. (a) Absorption spectrum of the synthesised N,S-CQDs and (b) photoluminescent spectra at different excitation wavelengths.
Figure 1:

Optical properties of the as-synthesised N,S-CQDs. (a) Absorption spectrum of the synthesised N,S-CQDs and (b) photoluminescent spectra at different excitation wavelengths.

Figure 2: Photostability of the developed N,S-CQDs.
Figure 2:

Photostability of the developed N,S-CQDs.

3.2 Structural properties of the N,S-CQDs

The HRTEM micrograph (Figure 3a) shows that the synthesised nanoprobe exhibits a spherical morphology with uniform dispersion. The particle size distribution (inset) indicates an average diameter of 3.45 ± 0.86 nm. The presence of distinct lattice fringes (inset), with a measured spacing of 0.23 nm, confirms the nanocrystalline nature of the material and corresponds to the (002) lattice planes of graphite. The XRD analysis (Figure 3b) shows a broad diffraction peak centered at 2θ = 21.55°, characteristic of the (002) graphite lattice plane, indicating a low graphitic carbon structure [13].

Figure 3: TEM and XRD analysis. (a) TEM micrograph (inset: Lattice spacing and size distribution), (b) XRD pattern of the as-synthesised N,S-CQDs and (c) FTIR spectrum.
Figure 3:

TEM and XRD analysis. (a) TEM micrograph (inset: Lattice spacing and size distribution), (b) XRD pattern of the as-synthesised N,S-CQDs and (c) FTIR spectrum.

The FTIR spectrum (Figure 3c) shows distinct vibrational bands, including a broad peak at 3,201 cm−1 corresponding to O–H stretching vibrations. Additionally, a peak at 2,973 cm−1 is attributed to N–H stretching vibrations associated with conjugated amide groups. Absorption bands at 1,666 cm−1 and 1,582 cm−1 correspond to C–O and C–NH groups, respectively. Additionally, peaks at 1,408 cm−1 and 1,293 cm−1 are attributed to C–S stretching and C–OH vibrations, indicating the successful synthesis of the N,S-CQDs [14].

3.3 Fluorescence detection of Pb2+ (fluorescent sensing and selectivity evaluation)

The fluorescence responses of N,S-CQDs were investigated under optimised conditions. (100 μL N,S-CQDs and 100 μM Pb2+) in the presence of various metal ions. Figure 4a, shows that the fluorescence intensity of the N,S-CQDs reduces appreciably in the presence of Pb2+ ions compared to other metal ions. The extent of fluorescence intensity reduction was dependent on the concentration of the analyte., as shown in Figure 4b. The appreciable reduction in the presence of Pb2+ ions could be attributed to the strong coordination between the functional groups on the surface of the nanoprobe and Pb2+ ions [15]. Complex formation arising from this coordination distorts the activity and arrangement of electrons. Consequently, causing a non-radiative recombination of electron-hole pairs and ultimately resulting in a decreased fluorescence intensity [16], [17], [18]. A clear linear relationship was observed between the reduction in the fluorescence intensity of N,S-CQDs and increasing concentrations of Pb2+ standards (0–50 μM), as depicted in Figure 4c. This correlation conforms to the Stern–Volmer equation (1), indicating a dynamic quenching mechanism. The linear fit yielded a high coefficient of determination (R2 = 0.9766), confirming the reliability of the response and the potential of N,S-CQDs as a sensitive probe for Pb2+ detection.

(1) Fo / F = K sv C + 1

Figure 4: Selectivity study towards Pb2+. (a) PL intensity bar chart of the N,S-CQDs in the presence of various metal ions. (b) PL spectra of the nanoprobe in the presence of Pb2+ standards (0–50 μM) (c) Stern-Volmer linear plot (0–50 μM) (d) PL intensity bar chart of the N,S-CQDs in the presence of interfering ion metal ions.
Figure 4:

Selectivity study towards Pb2+. (a) PL intensity bar chart of the N,S-CQDs in the presence of various metal ions. (b) PL spectra of the nanoprobe in the presence of Pb2+ standards (0–50 μM) (c) Stern-Volmer linear plot (0–50 μM) (d) PL intensity bar chart of the N,S-CQDs in the presence of interfering ion metal ions.

The K sv-is the Stern-Volmer constant, C is the concentration of the quencher ion (Pb2+), F and Fo are the PL intensities of the nanoprobe in the presence and absence of Pb2+ ions, respectively. By calculating the limit of detection (LOD) using the formula 3SD/S; where SD is the standard deviation of the blank and S is the slope of the calibration curve, LOD was calculated to be 1.3 μM, indicating high sensitivity of the N,S-CQDs toward Pb2+ ions.

To evaluate the selectivity of the synthesised nanoprobe towards Pb2+, the fluorescence responses were recorded for mixtures containing the nanoprobe and various potentially interfering metal ions (Figure 4d). The result shows that the presence of other metal ions has no significant impact on the fluorescence response of the nanoprobe compared to Pb2+, indicating that the synthesised material is highly selective towards Pb2+.

3.4 Fluorescent detection of fluoride ion

The strong interaction between Pb2+ and F− inspires the determination of fluoride in actual toothpaste samples based on the ‘off-on’ mode of the fluorescence. The fluorescence response of N,S-CQDs/Pb2+ in the presence of different fluoride concentrations is shown in Figure 5a. The results show that the fluorescence intensity of the N,S-CQDs/Pb2+ was restored gradually in the presence of fluoride ions under controlled experimental conditions (pH 6, 5 min incubation). The extent of fluorescence recovery was proportional to fluoride ion concentration, indicating that the N,S-CQDs/Pb2+ can effectively function as a nanoprobe for fluoride ions. The recovered fluorescence can be attributed to the electrostatic bond that exists between Pb2+ and F− ion, resulting in the formation of PbF2 and thus preventing non-radiative recombination. Furthermore, lead, being a moderately strong acid, will show a preference for bonding with a hard base, such as the fluoride ion. A linear relationship (Figure 5b) exists between the recovered fluorescence intensity of the N,S-CQDs/Pb2+ and the various F− standards (0–16 µM), n = 3 for each concentration. A calculated limit of detection (LOD) of 78.03 nM and a limit of quantification (LOQ) of 259.84 nM was obtained using the formula LOD =  3 SD S and LOQ =  10 SD S , respectively (Where SD is the standard deviation of the blank N,S-CQDs and S is the slope of the calibration curve). The selectivity experiment in Figure 5c shows that the N,S-CQDs/Pb2+ system was more selective to fluoride ion compared to other anions evaluated (SO3 2−, OH−, PO4 3−, NO3 −, CO3 2− and F−). In addition, when a mixture of fluoride ions and these interfering anions was added to solutions of the N–S-CQDs + Pb2+ system, the result shows a similar recovery in fluorescent intensity to that obtained using F− ion alone (Figure 5d). This further indicates the selectivity of the nanoprobe towards F− amidst interfering ions. A comparative summary of different nanosensors used for fluoride ion (F−) detection is presented in Table 1.

Figure 5: Flourescence recovery via flouride ion. (a) PL spectra of N,S-CQDs in the presence of F− standards (b) plot of change in fluorescence recovery against F− concentration. Selectivity assessment of N,S-CQDs/Pb2+ towards F− (c) with other non-metals (d) amidst interfering ions.
Figure 5:

Flourescence recovery via flouride ion. (a) PL spectra of N,S-CQDs in the presence of F− standards (b) plot of change in fluorescence recovery against F− concentration. Selectivity assessment of N,S-CQDs/Pb2+ towards F− (c) with other non-metals (d) amidst interfering ions.

Table 1:

Comparison of the as-synthesised fluorescent probe with existing methods for fluoride (F−) detection.

Nanosensor Real sample applied LOD (nM) Ref.
Silyl-capped pyrene Toothpaste 140 [20]
2-(2′-hydroxyphenyl)benzothiazole (HBT) Water and toothpaste 3.8 [21]
QT-AuNPs/Al3+ Toothpaste and mouthwash 7,500 [22]
Ceria@zirconia nanocages–xylenol orange colorimetric smartphone sensor Toothpaste 0.1 ppm [23]
Chitosan functionalised N-CD nanocomposite Toothpaste 10 [24]
N,S-CQDs/Pb2+ Toothpaste 78.03 This work

The fluorescent lifetime were measured to be 5.235 ns, 3.62 ns, and 3.59 ns, for N,S-CQDs, N,S-CQDs/Pb2+ and N,S-CQDs/Pb2+ + F−, respectively, while the absorption spectra show that no new absorption peaks were formed (Figure 6). These indicate the quenching mechanism to be dynamic [19].

Figure 6: Quenching mechansim. (a) Fluorescence lifetime decay profiles of N,S-CQDs, N,S-CQDs in the presence of Pb2+, and N,S-CQDs in the presence of Pb2+ and F−. (b) UV–Vis absorption spectra of N,S-CQDs, N,S-CQDs + Pb2+, and N,S-CQDs + Pb2+ + F−.
Figure 6:

Quenching mechansim. (a) Fluorescence lifetime decay profiles of N,S-CQDs, N,S-CQDs in the presence of Pb2+, and N,S-CQDs in the presence of Pb2+ and F−. (b) UV–Vis absorption spectra of N,S-CQDs, N,S-CQDs + Pb2+, and N,S-CQDs + Pb2+ + F−.

3.5 Real sample analysis

In real sample analysis, the standard addition method was used to determine the amount of fluoride ions in the toothpaste. The results show that the amount of fluoride ions in the adult toothpaste (Colgate herbal white) exceeded that of the kids’ (Jordan junior) (Table 2). Furthermore, excellent recoveries of 98.32 %–117.03 % (adult) and 103.24 %–111.88 % (kids) with low RSD (< 5) were experienced when detected samples of both toothpaste categories were spiked with fluoride standards. The result obtained validates the accuracy and reliability of the as-prepared nanoprobe.

Table 2:

The amount of Fluoride ions in adult and kids’ toothpaste and the recovery % after spiking with fluoride ion standard.

Toothpaste type Sample Detected (mg/kg) Added (mg/kg) Found (mg/kg) Recovery (%) RSD (%)
Adult 1 0.0389 0.0380 0.090 117.03 3.14
2 0.0359 0.0950 0.136 104.21 1.26
3 0.0369 0.190 0.223 98.32 4.82
Kids 1 0.0276 0.0380 0.0733 111.88 3.90
2 0.0258 0.095 0.1262 104.44 1.49
3 0.0264 0.190 0.2234 103.24 2.56

  1. RSD-relative standard deviation.

4 Conclusions

In this study, we reported hydrothermal synthesis of N,S-CQDs using environmentally benign precursors (Na2S, citric acid and glutamine). TEM analysis reveals the developed material is spherical, small and crystalline with an average particle size of 3.45 ± 0.86 nm. The N,S-CQDs/Pb2+ complex showed good sensitivity and selectivity towards F− ions with a limit of detection (LOD) and limit of quantification (LOQ) values of 78.03 nm and 259.84, respectively. The lifetime and absorption results pointed towards a dynamic quenching mechanism. This newly developed material also served as a highly effective nanoprobe for detecting F− ions in commercial adult and kids toothpastes with excellent discoveries and low relative standard deviations (RSD). The result obtained validates the accuracy and reliability of the as-prepared nanoprobe. Thus, making it a potentially valuable material for the swift and accurate detection of F− ions in complex systems.

Corresponding author: Oluwatobi S. Oluwafemi, Department of Chemical Sciences, University of Johannesburg, P.O. Box 17011, Doornfontein 2028, Johannesburg, South Africa; and Centre for Nanomaterials Science Research, University of Johannesburg, Johannesburg, South Africa, E-mail:

Funding source: National Research Foundation

Award Identifier / Grant number: 129290 and 230509103956

  1. Research funding: The authors would like to thank the National Research Foundation (N.R.F) under its Competitive Programme for Rated Researchers (CPRR), Grants Nos. 129290 and 230509103956; the University of Johannesburg (URC); and the Faculty of Science (FRC) for their financial support.

  2. Authors contribution: Mutendu Kungwa: Investigation, methodology, writing original draft, formal analysis. Olanrewaju Aladesuyi: Supervision, review and editing, methodology, validation, formal analysis. Oluwatobi Oluwafemi: Conceptualisation, Funding acquisition, supervision, methodology, writing-review and editing, validation, project administration.

  3. Conflict of Interest: The authors state no conflict of interest.

  4. Data Availability statement: The datasets generated during and/or analysed during the current study are available from the corresponding author on reasonable request.

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Received: 2025-08-17
Accepted: 2025-11-20
Published Online: 2025-12-23

© 2025 the author(s), published by De Gruyter, Berlin/Boston

This work is licensed under the Creative Commons Attribution 4.0 International License.

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  5. Development of a green and rapid ethanol-based HPLC assay for aspirin tablets and feasibility evaluation of domestically produced bioethanol in Thailand as a sustainable mobile phase
  6. A facile biodegradation of polystyrene microplastic by Bacillus subtilis
  7. Enhanced synthesis of fly ash-derived hydrated sodium silicate adsorbents via low-temperature alkaline hydrothermal treatment for advanced environmental applications
  8. Impact of metal nanoparticles biosynthesized using camel milk on bacterial growth and copper removal from wastewater
  9. Preparation of Co/Cr-MOFs for efficient removal of fleroxacin and Rhodamine B
  10. Applying nanocarbon prepared from coal as an anode in lithium-ion batteries
  11. Improved electrochemical synthesis of Cu–Fe/brass foil alloy followed by combustion for high-efficiency photoelectrodes and hydrogen production in alkaline solutions
  12. Precipitation of terephthalic acid from post-consumer polyethylene terephthalate waste fractions
  13. Biosynthesized zinc oxide nanoparticles: Multifunctional potential applications in anticancer, antibacterial, and B. subtilis DNA gyrase docking
  14. Anticancer and antimicrobial effects of green-synthesized silver nanoparticles using Teucrium polium leaves extract
  15. Green synthesis of eco-friendly bioplastics from Chlorella and Lithothamnion algae for safe and sustainable solutions for food packaging
  16. Optimizing coal water slurry concentration via synergistic coal blending and particle size distribution
  17. Green synthesis of Ag@Cu and silver nanowire using Pterospermum heterophyllum extracts for surface-enhanced Raman scattering
  18. Green synthesis of copper oxide nanoparticles from Algerian propolis: Exploring biochemical, structural, antimicrobial, and anti-diabetic properties
  19. Simultaneous quantification of mefenamic acid and paracetamol in fixed-dose combination tablet dosage forms using the green HPTLC method
  20. Green synthesis of titanium dioxide nanoparticles using green tea (Camellia sinensis) extract: Characteristics and applications
  21. Pharmaceutical properties for green fabricated ZnO and Ag nanoparticle-mediated Borago officinalis: In silico predications study
  22. Synthesis and optimization of gemcitabine-loaded nanoparticles by using Box–Behnken design for treating prostate cancer: In vitro characterization and in vivo pharmacokinetic study
  23. A comparative analysis of single-step and multi-step methods for producing magnetic activated carbon from palm kernel shells: Adsorption of methyl orange dye
  24. Sustainable green synthesis of silver nanoparticles using walnut septum waste: Characterization and antibacterial properties
  25. Efficient electrocatalytic reduction of CO2 to CO over Ni/Y diatomic catalysts
  26. Greener and magnetic Fe3O4 nanoparticles as a recyclable catalyst for Knoevenagel condensation and degradation of industrial Congo red dye
  27. Recycling of HDPE-giant reed composites: Processability and performance
  28. Fabrication of antibacterial chitosan/PVA nanofibers co-loaded with curcumin and cefadroxil for wound healing
  29. Cost-effective one-pot fabrication of iron(iii) oxychloride–iron(iii) oxide nanomaterials for supercapacitor charge storage
  30. Novel trimetallic (TiO2–MgO–Au) nanoparticles: Biosynthesis, characterization, antimicrobial, and anticancer activities
  31. Green-synthesized chromium oxide nanoparticles using pomegranate husk extract: Multifunctional bioactivity in antioxidant potential, lipase and amylase inhibition, and cytotoxicity
  32. Therapeutic potential of sustainable zinc oxide nanoparticles biosynthesized using Tradescantia spathacea aqueous leaf extract
  33. Chitosan-coated superparamagnetic iron oxide nanoparticles synthesized using Carica papaya bark extract: Evaluation of antioxidant, antibacterial, and anticancer activity of HeLa cervical cancer cells
  34. Antioxidant potential of peptide fractions from tuna dark muscle protein isolate: A green enzymatic approach
  35. Clerodendron phlomoides leaf extract-mediated synthesis of selenium nanoparticles for multi-applications
  36. Optimization of cellulose yield from oil palm trunks with deep eutectic solvents using response surface methodology
  37. Nitrogen-doped carbon dots from Brahmi (Bacopa monnieri): Metal-free probe for efficient detection of metal pollutants and methylene blue dye degradation
  38. High energy density pseudocapacitor based on a nanoporous tungsten(VI) oxide iodide/poly(2-amino-1-mercaptobenzene) composite
  39. Green synthesized Ag–Cu nanocomposites as an improved strategy to fight multidrug-resistant bacteria by inhibition of biofilm formation: In vitro and in silico assessment study
  40. In vitro evaluation of antibacterial activity and associated cytotoxicity of biogenic silver nanoparticles using various extracts of Tabernaemontana ventricosa
  41. Fabrication of novel composite materials by impregnating ZnO particles into bacterial cellulose nanofibers for antimicrobial applications
  42. Solidification floating organic drop for dispersive liquid–liquid microextraction estimation of copper in different water samples
  43. Kinetics and synthesis of formation of phosphate composites from low-grade phosphorites in the presence of phosphate–siliceous shales and oil sludge
  44. Removal of minocycline and terramycin by graphene oxide and Cr/Mn base metal–organic framework composites
  45. Microfluidic preparation of ceramide E liposomes and properties
  46. Therapeutic potential of Anamirta cocculus (L.) Wight & Arn. leaf aqueous extract-mediated biogenic gold nanoparticles
  47. Antioxidant-rich Micromeria imbricata leaf extract as a medium for the eco-friendly preparation of silver-doped zinc oxide nanoparticles with antibacterial properties
  48. Influence of different colors with light regime on Chlorella sp., biomass, pigments, and lipids quantity and quality
  49. Experimental vibrational analysis of natural fiber composite reinforced with waste materials for energy absorbing applications
  50. Green synthesis of sea buckthorn-mediated ZnO nanoparticles: Biological applications and acute nanotoxicity studies
  51. Production of liquid smoke by consecutive electroporation and microwave-assisted pyrolysis of empty fruit bunches
  52. Synthesis of MPAA based on polyacrylamide and gossypol resin and applications in the encapsulation of ammophos
  53. Application of iron-based catalysts in the microwave treatment of environmental pollutants
  54. Enhanced adsorption of Cu(ii) from wastewater using potassium humate-modified coconut husk biochar
  55. Adsorption of heavy metal ions from water by Fe3O4 nano-particles
  56. Green synthesis of parsley-derived silver nanoparticles and their enhanced antimicrobial and antioxidant effects against foodborne resistant bacteria
  57. Unwrapping the phytofabrication of bimetallic silver–selenium nanoparticles: Antibacterial, Anti-virulence (Targeting magA and toxA genes), anti-diabetic, antioxidant, anti-ovarian, and anti-prostate cancer activities
  58. Optimizing ultrasound-assisted extraction process of anti-inflammatory ingredients from Launaea sarmentosa: A novel approach
  59. Eggshell membranes as green carriers for Burkholderia cepacia lipase: A biocatalytic strategy for sustainable wastewater bioremediation
  60. Research progress of deep eutectic solvents in fuel desulfurization
  61. Enhanced electrochemical synthesis of Ni–Fe/brass foil alloy with subsequent combustion for high-performance photoelectrode and hydrogen production applications
  62. Valorization of baobab fruit shell as a filler fiber for enhanced polyethylene degradation and soil fertility
  63. Valorization of Agave durangensis bagasse for cardboard-type paper production circular economy approach
  64. Green priming strategies using seaweed extract and citric acid to improve early growth and antioxidant activity in lentil
  65. Synthesis of N,S co-doped carbon quantum dots – metal complex for the detection of fluoride (F−) ion in adults and Children’s toothpastes
  66. Review Article
  67. Sustainable innovations in garlic extraction: A comprehensive review and bibliometric analysis of green extraction methods
  68. Natural sustainable coatings for marine applications: advances, challenges, and future perspectives
  69. Integration of traditional medicinal plants with polymeric nanofibers for wound healing
  70. Rapid Communication
  71. In situ supported rhodium catalyst on mesoporous silica for chemoselective hydrogenation of nitriles to primary amines
  72. Special Issue: Valorisation of Biowaste to Nanomaterials for Environmental Applications
  73. Valorization of coconut husk into biochar for lead (Pb2+) adsorption
  74. Corrigendum
  75. Corrigendum to “An updated review on carbon nanomaterials: Types, synthesis, functionalization and applications, degradation and toxicity”
https://doi.org/10.1515/gps-2025-0105
Keywords for this article
carbon quantum dot; fluorescent probe; dental caries; fluoride ion; lead ion
Creative Commons
BY 4.0

Articles in the same Issue

  1. Research Articles
  2. Optimized green synthesis of silver nanoparticles from guarana seed skin extract with antibacterial potential
  3. Green adsorbents for water remediation: Removal of Cr(vi) and Ni(ii) using Prosopis glandulosa sawdust and biochar
  4. Green approach for the synthesis of zinc oxide nanoparticles from methanolic stem extract of Andrographis paniculata and evaluation of antidiabetic activity: In silico GSK-3β analysis
  5. Development of a green and rapid ethanol-based HPLC assay for aspirin tablets and feasibility evaluation of domestically produced bioethanol in Thailand as a sustainable mobile phase
  6. A facile biodegradation of polystyrene microplastic by Bacillus subtilis
  7. Enhanced synthesis of fly ash-derived hydrated sodium silicate adsorbents via low-temperature alkaline hydrothermal treatment for advanced environmental applications
  8. Impact of metal nanoparticles biosynthesized using camel milk on bacterial growth and copper removal from wastewater
  9. Preparation of Co/Cr-MOFs for efficient removal of fleroxacin and Rhodamine B
  10. Applying nanocarbon prepared from coal as an anode in lithium-ion batteries
  11. Improved electrochemical synthesis of Cu–Fe/brass foil alloy followed by combustion for high-efficiency photoelectrodes and hydrogen production in alkaline solutions
  12. Precipitation of terephthalic acid from post-consumer polyethylene terephthalate waste fractions
  13. Biosynthesized zinc oxide nanoparticles: Multifunctional potential applications in anticancer, antibacterial, and B. subtilis DNA gyrase docking
  14. Anticancer and antimicrobial effects of green-synthesized silver nanoparticles using Teucrium polium leaves extract
  15. Green synthesis of eco-friendly bioplastics from Chlorella and Lithothamnion algae for safe and sustainable solutions for food packaging
  16. Optimizing coal water slurry concentration via synergistic coal blending and particle size distribution
  17. Green synthesis of Ag@Cu and silver nanowire using Pterospermum heterophyllum extracts for surface-enhanced Raman scattering
  18. Green synthesis of copper oxide nanoparticles from Algerian propolis: Exploring biochemical, structural, antimicrobial, and anti-diabetic properties
  19. Simultaneous quantification of mefenamic acid and paracetamol in fixed-dose combination tablet dosage forms using the green HPTLC method
  20. Green synthesis of titanium dioxide nanoparticles using green tea (Camellia sinensis) extract: Characteristics and applications
  21. Pharmaceutical properties for green fabricated ZnO and Ag nanoparticle-mediated Borago officinalis: In silico predications study
  22. Synthesis and optimization of gemcitabine-loaded nanoparticles by using Box–Behnken design for treating prostate cancer: In vitro characterization and in vivo pharmacokinetic study
  23. A comparative analysis of single-step and multi-step methods for producing magnetic activated carbon from palm kernel shells: Adsorption of methyl orange dye
  24. Sustainable green synthesis of silver nanoparticles using walnut septum waste: Characterization and antibacterial properties
  25. Efficient electrocatalytic reduction of CO2 to CO over Ni/Y diatomic catalysts
  26. Greener and magnetic Fe3O4 nanoparticles as a recyclable catalyst for Knoevenagel condensation and degradation of industrial Congo red dye
  27. Recycling of HDPE-giant reed composites: Processability and performance
  28. Fabrication of antibacterial chitosan/PVA nanofibers co-loaded with curcumin and cefadroxil for wound healing
  29. Cost-effective one-pot fabrication of iron(iii) oxychloride–iron(iii) oxide nanomaterials for supercapacitor charge storage
  30. Novel trimetallic (TiO2–MgO–Au) nanoparticles: Biosynthesis, characterization, antimicrobial, and anticancer activities
  31. Green-synthesized chromium oxide nanoparticles using pomegranate husk extract: Multifunctional bioactivity in antioxidant potential, lipase and amylase inhibition, and cytotoxicity
  32. Therapeutic potential of sustainable zinc oxide nanoparticles biosynthesized using Tradescantia spathacea aqueous leaf extract
  33. Chitosan-coated superparamagnetic iron oxide nanoparticles synthesized using Carica papaya bark extract: Evaluation of antioxidant, antibacterial, and anticancer activity of HeLa cervical cancer cells
  34. Antioxidant potential of peptide fractions from tuna dark muscle protein isolate: A green enzymatic approach
  35. Clerodendron phlomoides leaf extract-mediated synthesis of selenium nanoparticles for multi-applications
  36. Optimization of cellulose yield from oil palm trunks with deep eutectic solvents using response surface methodology
  37. Nitrogen-doped carbon dots from Brahmi (Bacopa monnieri): Metal-free probe for efficient detection of metal pollutants and methylene blue dye degradation
  38. High energy density pseudocapacitor based on a nanoporous tungsten(VI) oxide iodide/poly(2-amino-1-mercaptobenzene) composite
  39. Green synthesized Ag–Cu nanocomposites as an improved strategy to fight multidrug-resistant bacteria by inhibition of biofilm formation: In vitro and in silico assessment study
  40. In vitro evaluation of antibacterial activity and associated cytotoxicity of biogenic silver nanoparticles using various extracts of Tabernaemontana ventricosa
  41. Fabrication of novel composite materials by impregnating ZnO particles into bacterial cellulose nanofibers for antimicrobial applications
  42. Solidification floating organic drop for dispersive liquid–liquid microextraction estimation of copper in different water samples
  43. Kinetics and synthesis of formation of phosphate composites from low-grade phosphorites in the presence of phosphate–siliceous shales and oil sludge
  44. Removal of minocycline and terramycin by graphene oxide and Cr/Mn base metal–organic framework composites
  45. Microfluidic preparation of ceramide E liposomes and properties
  46. Therapeutic potential of Anamirta cocculus (L.) Wight & Arn. leaf aqueous extract-mediated biogenic gold nanoparticles
  47. Antioxidant-rich Micromeria imbricata leaf extract as a medium for the eco-friendly preparation of silver-doped zinc oxide nanoparticles with antibacterial properties
  48. Influence of different colors with light regime on Chlorella sp., biomass, pigments, and lipids quantity and quality
  49. Experimental vibrational analysis of natural fiber composite reinforced with waste materials for energy absorbing applications
  50. Green synthesis of sea buckthorn-mediated ZnO nanoparticles: Biological applications and acute nanotoxicity studies
  51. Production of liquid smoke by consecutive electroporation and microwave-assisted pyrolysis of empty fruit bunches
  52. Synthesis of MPAA based on polyacrylamide and gossypol resin and applications in the encapsulation of ammophos
  53. Application of iron-based catalysts in the microwave treatment of environmental pollutants
  54. Enhanced adsorption of Cu(ii) from wastewater using potassium humate-modified coconut husk biochar
  55. Adsorption of heavy metal ions from water by Fe3O4 nano-particles
  56. Green synthesis of parsley-derived silver nanoparticles and their enhanced antimicrobial and antioxidant effects against foodborne resistant bacteria
  57. Unwrapping the phytofabrication of bimetallic silver–selenium nanoparticles: Antibacterial, Anti-virulence (Targeting magA and toxA genes), anti-diabetic, antioxidant, anti-ovarian, and anti-prostate cancer activities
  58. Optimizing ultrasound-assisted extraction process of anti-inflammatory ingredients from Launaea sarmentosa: A novel approach
  59. Eggshell membranes as green carriers for Burkholderia cepacia lipase: A biocatalytic strategy for sustainable wastewater bioremediation
  60. Research progress of deep eutectic solvents in fuel desulfurization
  61. Enhanced electrochemical synthesis of Ni–Fe/brass foil alloy with subsequent combustion for high-performance photoelectrode and hydrogen production applications
  62. Valorization of baobab fruit shell as a filler fiber for enhanced polyethylene degradation and soil fertility
  63. Valorization of Agave durangensis bagasse for cardboard-type paper production circular economy approach
  64. Green priming strategies using seaweed extract and citric acid to improve early growth and antioxidant activity in lentil
  65. Synthesis of N,S co-doped carbon quantum dots – metal complex for the detection of fluoride (F−) ion in adults and Children’s toothpastes
  66. Review Article
  67. Sustainable innovations in garlic extraction: A comprehensive review and bibliometric analysis of green extraction methods
  68. Natural sustainable coatings for marine applications: advances, challenges, and future perspectives
  69. Integration of traditional medicinal plants with polymeric nanofibers for wound healing
  70. Rapid Communication
  71. In situ supported rhodium catalyst on mesoporous silica for chemoselective hydrogenation of nitriles to primary amines
  72. Special Issue: Valorisation of Biowaste to Nanomaterials for Environmental Applications
  73. Valorization of coconut husk into biochar for lead (Pb2+) adsorption
  74. Corrigendum
  75. Corrigendum to “An updated review on carbon nanomaterials: Types, synthesis, functionalization and applications, degradation and toxicity”
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