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Nitrogen-doped carbon dots from Brahmi (Bacopa monnieri): Metal-free probe for efficient detection of metal pollutants and methylene blue dye degradation

  • Kondetharayil Soman , Kuppusamy Kanagaraj , Nangan Senthilkumar , Saravanan Rajendran EMAIL logo , Turki Kh. Faraj , Abdulwahed Fahad Alrefaei , Natesan Thirumalaivasan , Thanigaivel Sundaram EMAIL logo , Arpita Roy , Rajan Verma , Sabu Thomas , Sreeraj Gopi EMAIL logo and Maximilian Lackner EMAIL logo
Published/Copyright: July 10, 2025
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Green Processing and Synthesis
From the journal Green Processing and Synthesis Volume 14 Issue 1

Abstract

Contaminants like heavy metals in water bodies pose serious risks to human health and ecosystems, often leading to acute and chronic disorders, including cancer and organ damage. Understanding water contamination is vital for sustainable development. A biosensor is a biocompatible, sustainable device that can detect heavy metal ions. To do this, we used a hydrothermal process to produce nitrogen-doped carbon dots (NCDs) from the plant Brahmi (Bacopa monnieri), given that Brahmi is a novel material for the synthesis of carbon dots and a medicinal plant. The nanoparticles’ size and morphology were analyzed using high-resolution transmission electron microscopy, field emission scanning electron microscopy, and dynamic light scattering techniques, while Raman spectroscopy, Fourier transform infrared spectroscopy), and X-ray diffraction spectroscopy were employed for sample characterization. Optical properties were studied using ultraviolet (UV) and fluorescence spectroscopy. The NCDs showed a high quantum yield of 15.7%, and demonstrated significant fluorescence quenching in the presence of Fe³⁺ and Ni²⁺ ions, with detection limits of 1.46 and 3.19 µmol·L−1, respectively. This rapid, accurate method offers a promising solution for detecting heavy metals in water and could be expanded to real water samples and photocatalytic degradation of methylene blue dye under UV light.

Keywords: Bacopa monnieri ; metal pollutant; nitrogen doped-carbon dots; bioremediation; biosensing, Ni2+ ; Fe3+

1 Introduction

According to United Nations sustainable development goals, clean water and sanitation is one of the pivotal elements in people’s well-being. Urbanization and new living conditions are creating contamination of main water bodies. People are aware of the gravity of water contamination and how momentous the proper identification and treatment of water have become. The current access to clean water, for a large number of communities and even countries, is expensive and unreliable, and developing nations cannot bear to use the advanced methodologies for water treatment. A cost-effective biosensor to detect heavy metals in water is therefore desperately needed. This is where the quantum dots (QDs) become important since they can be used as biosensors to find heavy metal ions contained in water. There are several metal-based QDs present such as cadmium, lead, and carbon-based graphene QDs (GQDs). However, they themselves contain toxic substances which constitute a menace to humans and limit the application of QDs. Also, the manufacture technique is quite complex [1,2], leading to expensive sensors. As a result, researchers have considered developing a novel technology; for this reason, carbon dots (CDs) are increasingly being used in biosensor applications. These are ideal nanoparticles because they are made from precursors that are found in nature and have favorable traits like biocompatibility, cytotoxicity, low cost, and ease of production. Also, CDs were found to possess antioxidant and antimicrobial activity. Due to their exquisite properties, CDs enter the biomedical domain fairly quickly which includes drug delivery, bioimaging of microorganisms, cancer cells, and neuro-cells [3], photodynamic therapy, and photothermal therapy [4]. CDs can be used in biosensing applications, due to their high quantum yield (QY) – a measurement of the optical property of CDs that indicates excitation-dependent photoluminescent emission – and stability towards light [5]. Chauhan et al. used a hydrothermal process to produce CDs from coconut coir, obtaining a 48% yield and favorable, low water solubility. They discovered that the excitation wavelength has an effect on the emission spectrum; the highest intensity of emission wavelength was reported to be 530 at 280 nm excitation wavelength. They used pH testing to check the stability of CDs, and the results showed that the CDs were sufficiently stable. Particularly, these CDs can be utilized as effective copper and cadmium metal ion detecting probes [6]. Pacquiao et al. used the same approach to produce CDs from mushrooms, which were then used to detect the presence of Cr6+. Initially, they got a QY of 11%, but surface passivation using tetraethylenepentamine increased the QY to 39% [7]. Chang et al. demonstrated a high QY of 42% CDs utilizing polygoni multiflori caulis as a precursor in 2021 [8]. They reported good characteristics, and their CDs were extremely sensitive to Fe3+ ions, with a detection limit of 0.025 µmol·L−1. The hydrothermal process was selected for synthesizing NCDs due to its simplicity, environmental friendliness, and ability to produce uniform, high-quality CDs [9]. This method’s long growth period ensures adequate carbonization, leading to high QY, enhanced surface functionality, and improved stability of the CDs [9].

The O–H, N–H, C–H, and COO functionalities that make up the surface of CD can be enhanced by additional doping, which could lead to a higher rate of fluorescence quenching, i.e., the material's fluorescence intensity being reduced [10]. Metal-free CDs are a type of carbon-based nanomaterial known for their biocompatibility, photoluminescence, and low toxicity. In environmental monitoring, they are widely used as sensors for detecting metal ions and pollutants due to their sensitivity and selective interaction with contaminants. In medical applications, CDs serve as bioimaging agents, drug delivery systems, and have potential in cancer diagnostics and therapy owing to their excellent biocompatibility and low toxicity profile. This is the most important aspect of the CDs use in biosensing and the relevant application. Of late, the increase in the number of publications emphasizes the importance of a low-cost biosensor.

In this study, we synthesized nitrogen-doped CDs (NCDs) by using a medicinal plant, Brahmi (Bacopa Monnieri), as a precursor. It has been used as ayurvedic medicine for many years, and its therapeutic properties have been reported [10,18]. Because of its antioxidant and anti-inflammation properties, Brahmi is utilized for a variety of purposes. There are bioactive molecules in Brahmi that can function as natural dopants and affect the surface functionalization. Because of its abundance of bioactive surface groups, it may have additional biological activities like antioxidant or antimicrobial capabilities. While past studies on CDs in biosensing emphasize their optical properties and low toxicity, they often overlook long-term stability and specificity in complex environments. Our work addresses these gaps by focusing on metal-free CDs, enhancing stability and selectivity in diverse conditions, thus providing a more sustainable and targeted approach to biosensing applications.

Many heavy metal ion detections employing CDs have long been reported [9,11]; however, Ni2+ ion detection is yet to be published. The innovative aspect of this work is the synthesis of CDs from Brahmi, as well as the selective detection of Ni2+ ions by this carbon nanomaterial. We conducted morphological, spectroscopic, and optical analyses here. This work helps to understand the effect of doping on QY. We were also interested in how this fluorescence property influences the detection of heavy metal ions; therefore, we conducted a metal sensing investigation. As a result, we obtained an outstanding result for detecting Fe3+ and Ni2+ ions. Figure 1 illustrates a schematic representation of the synthesis procedure of NCDs and metal ion sensing.

Figure 1 Graphical representation of NCDs synthesis (left) and Ni2+ and Fe3+ iron probing (right).
Figure 1

Graphical representation of NCDs synthesis (left) and Ni2+ and Fe3+ iron probing (right).

2 Materials and methods

2.1 Materials

The medicinal plant Brahmi was collected from a local garden. The chemicals lead(ii) acetate (anhydrous), zinc oxide (grade “Hi-LR Himedia”), titanium(iv) dioxide, and dialysis membrane-150, LA401-5MT were purchased from HiMedia (Mumbai, India). Ammonium solution and iron(iii) oxide were purchased from Empura. Cupric sulfate pentahydrate and silver nitrate were purchased from Sigma Aldrich. Nickel sulfate and quinine sulfate were purchased from Spectrum and Kemphasol, respectively. All the solutions were made using ultrapure water.

2.2 Synthesis of NCDs from Brahmi

The raw material Brahmi was collected from a local garden, identity-checked, and then thoroughly washed to remove dead leaves and dirt. A grinding machine was used to produce a thick green-colored juice. This juice was then filtered and underwent centrifugation for 20 min at 5,000 rpm and was again passed through the filter. 25 mL of this juice was mixed with 1 mL of ammonium solution, and this mixture was kept in an autoclave for 16 h at 120°C [12]. After that step, the solution was removed from the oven and allowed to cool at room temperature, followed by centrifugation and passing through the filtration process to remove unreacted particles. This solution was finally subjected to a dialysis process, through a dialysis membrane for 3 days. Finally, the authors obtained a dark brown colored liquid containing the NCDs. It was stored below 8°C for further characterization.

2.3 Characterization techniques

The morphological study and particle size distribution were analyzed using Transmission electron microscopy (TEM) from JEOL JEM 2100 (LaB6 Type) at 200 kV. Transmission electron microscopy (TEM) from JEOL JEM 2100 (LaB6 Type) at 200 kV and a field emission scanning electron microscope (FE-SEM) using a MALA3 XMH model (TESCAN BRONO s.r.o., Czech Republic) were used to analyze the morphological study and particle size distribution. The dynamic light scattering (DLS) device HORBIA SZ-100 was used for particle size analysis with a measuring range of 0.3 nm to 8.0 μm. The X-ray diffraction (XRD) patterns were determined using an X-ray spectrometer (Rigaku mini flex bench tops) equipped with a graphite monochromator. For Raman spectroscopic analysis of NCDs, we used an Alpha300RA AFM (WITec GmbH, Ulm, Germany) and RAMAN spectrometer with 532 nm diode-pumped solid-state laser. Fluorescence spectrum analysis has been done using a Perkin Elmer Spectrum Two, and the wavenumber ranges from 400 to 4,000 cm−1. Shimadzu UV-2600 was used to analyze the absorbance spectra of NCDs in the range of 200–800 nm and fluorescence emission spectra were obtained from a Shimadzu RF-6000 spectro-fluorophotometer.

2.4 Calculation of QY

One of the most important factors to evaluate CDs fluorescent stability and application is their QY, which is simple to ascertain using Eq. 1.

(1) QY S = ( F S A R QY S ) / ( F R A S )

where QYS, F S, and A S stands for the quantum yield, integrated fluorescence emission, and absorbance of the sample, and QYR, F R, and A R stand for quantum yield, integrated fluorescent emission, and absorbance of the reference. Quinine sulfate (CAS no. 130-95-0) is used as the reference material, and its QY is 54% in a 0.1 N solution of H2SO4 [13].

2.5 Metal ion detection

For the metal ion detection analysis, 500 µM metal ion solutions were prepared for each metal salt. Then, 1 mL of synthesized NCDs was added to the metal ion solution, and after a few minutes, the solution was subjected to fluorescent microscopic analysis to check the fluorescent quenching of NCDs by comparing with the intensities of pure NCDs and a solution with NCDs and metal ions [10]. To analyze the concentration dependence on fluorescent quenching, the concentration of metal ions was varied from 50 to 500 µM.

3 Results and discussion

Prepared CDs were characterized by various techniques and was used based on their utility. Generally, TEM analysis provides crucial insights into the morphological structure and particle size distribution of CDs, directly aligning with the research objective of understanding nanoparticle formation. FTIR helps identify surface functional groups, offering important information on the chemical composition and bonding of the CDs. Spectroscopic analysis, such as ultraviolet-visible (UV-Vis) and XPS, reveals electron-level distribution and surface states, essential for characterizing optical properties. Fluorescence spectroscopy is the primary technique for evaluating the photoluminescence behavior of the CDs, which is key to their application in sensing and bioimaging.

Initially, the morphology and the particle size of synthesized NCDs are calculated using high resolution-transmission electron microscopy (HR-TEM) and is shown in Figure 2a and b. The NCDs are spherical in shape, with an average particle size distribution range of 2.54–3.27 nm and a d-spacing of 0.24 nm (the minimum distance between two parallel planes of atoms), as determined by this analysis. These findings can be compared to the study by Atchudan et al., who reported on NCDs [14]. They obtained NCDs with a particle size of the same range as that of our studies, and QY is relatively high in this study, at 15.76%.

Figure 2 (a) and (b) HR-TEM image of NCDs, (c) FE-SEM of NCDs, and (d) DLS analysis.
Figure 2

(a) and (b) HR-TEM image of NCDs, (c) FE-SEM of NCDs, and (d) DLS analysis.

The FE-SEM analysis of this study gives an excellent illustration of NCDs morphology. Figure 2c depicts the FE-SEM image, which demonstrates the spherical shape of the produced NCDs and gives support to the TEM report. The DLS analysis is shown in Figure 2d. The mean diameter of the nanoparticle was found to be 2.54 nm with a monodisperse distribution.

Figure 3a shows the FTIR spectra of NCDs, which are used to identify the surface functional groups of NCDs, with distinctive absorption bands appearing at 3,261 cm−1 for O–H and N–H stretching vibrations, while 2,176 and 1,080 cm−1 represent the C═N and C–O bonds, respectively, and 1,634 cm−1 for C═C or NH2 stretching vibrations. Furthermore, a considerable number of aromatic alkoxy groups are allocated to bands in the 1,050–1,360 cm−1 range [15].

Figure 3 (a) FTIR spectrum and (b) XRD pattern of NCDs.
Figure 3

(a) FTIR spectrum and (b) XRD pattern of NCDs.

All of the foregoing findings show that hydroxyl and carboxylic groups are present on the surface of NCDs, which enhances the optical and surface properties of NCDs. Figure 3b shows the XRD pattern of the NCDs. The broad peak verifies the amorphous nature of CDs and is detected at 2θ = 23°. Using the Bragg equation, the d spacing obtained was 0.39, which is close to the d spacing value obtained from HR-TEM analysis. The amorphous character of NCDs is caused by an increase in the d spacing value. These results are consistent with NCDs made from Chionanthus retusus fruit extract [14,16].

(2) n λ = 2 d sin θ

where the value of n is 1, the incident X-ray wavelength is λ = 1.54 Å, and the angle between the incident rays and the surface of the materials is θ. Figure 4a shows the emission peak at 434 nm, which corresponds to a 320 nm excitation wavelength. Under ambient light, the diluted NCDs aqueous solution appears pale yellow, but when exposed to UV–light (λ = 365 nm), it turns to a highly strong blue color. Excitation-dependent emission spectra of NCDs are shown in Figure 4b, and the excitation wavelengths ranged from 320 to 550 nm in this experiment [17]. The surface functionalities of NCDs have a considerable number of electronic states, which causes this excitation-dependent emission characteristics [18]. The graph shows that by varying the excitation wavelength, the peak centers were red shifted (Figure 4b). These findings can be compared to the NCDs studies by Zulfajri et al., where highest fluorescence intensity was obtained at 350 nm excitation wavelength, and the maximum intensity was reported here at 360 nm [19].There is no significant emission peak after 550 nm [20].

Figure 4 (a) Fluorescence microscopy of NCDs, (b) Excitation-dependent PL intensity of NCDs, (c) UV spectroscopy, and (d) Raman spectroscopy.
Figure 4

(a) Fluorescence microscopy of NCDs, (b) Excitation-dependent PL intensity of NCDs, (c) UV spectroscopy, and (d) Raman spectroscopy.

The UV-vis absorption spectrum of the NCDs in Figure 4c shows two strong absorption bands, which are typical of an aromatic system’s absorption. The n–π* transition with C═N bonds is responsible for the first absorption band, which was found at 214 nm [21]. At 267 nm, the π–π* transition with C═C bonds for aromatic sp2 hybridization was detected, which is related to the second characteristic absorption peak. These NCDs appear pale yellow in natural light and blue under 365 nm UV irradiation. Raman spectroscopy provides vital information on the structural defects, degree of graphitization, and vibrational modes of CDs, aiding in the understanding of their molecular structure and carbon backbone, which is crucial for tuning their optical and electronic properties. Figure 4d illustrates the Raman spectrum of NCDs, which indicates a D-band at 1,353 cm−1, demonstrating the presence of sp2 hybridized carbon systems, and a G-band at 1,573 cm−1 represents the sp3 hybridization [22]. The ID/IG (D band to G band intensity ratio) values were used to determine the graphitization of carbon nanostructured materials. Because of the strong fluorescence background, the ID/IG value is 0.86, and the intensity ratio of the D to the G-band suggests that the synthesized NCDs had a mild graphitic character. This ID/IG ratio is also a measure of defects in the carbon nanomaterials. These results closely correspond to the findings of authors who have systematically studied the ID/IG ratio [23].

4 Metal ion detection

The test was carried out using various metal ions: Ag+, Zn2+, Ti4+, Pb2+, Ni2+, Fe3+, and Cu2+ in the presence of NCDs at a concentration of 500 µM. Figure 5a shows the fluorescence quenching of NCDs in the presence of these metal ions. Each of these metal ion shows different photoluminescence (PL) intensities, but in Figure 5a nickel and iron PL graphs show a deep quenching of NCDs fluorescence [24,25].

Figure 5 (a) Fluorescence quenching analysis of metal ions Ag+, Zn2+, Ti4+, Pb2+, Ni2+, Fe3+, and Cu2+ at a concentration of 500 µm and (b) quenching comparison of Ag+, Zn2+, Ti4+, Pb2+, Ni2+, Fe3+, and Cu2+.
Figure 5

(a) Fluorescence quenching analysis of metal ions Ag+, Zn2+, Ti4+, Pb2+, Ni2+, Fe3+, and Cu2+ at a concentration of 500 µm and (b) quenching comparison of Ag+, Zn2+, Ti4+, Pb2+, Ni2+, Fe3+, and Cu2+.

The quenching rate of NCDs is depicted in the diagram in Figure 5b. Functionalities seen on the surface of NCDs are too responsible for this quenching mechanism. The metal ion contained in the NCDs was shown to have a strong affinity by these surface functions. Figure 6a shows how the concentration of Fe3+ ions affect the quenching rate here varied the concentration of metal ion from 50 to 500 µM. From this graph it is very clear that increasing the concentration of metal ion decreased the fluorescent intensity. Figure 6b also shows the same analysis of Ni2+ ions [26]. From these two graphical representations, 500 µM shows the high fluorescent intensity of quenching. Upon addition of metal ions to CDs, the fluorescence quenching in CDs may occur due to multiple factors like photoinduced electron transfer, energy transfer, charge transfer, and aggregation, leading to the complete decay of their luminescence.

Figure 6 Quenching rate analysis at varying concentrations (a) Fe3+ ions and (b) Ni2+ ions. The fluorescent intensity ratios of NCDs versus the concentrations of (c) Fe3+ ions and (d) Mn2+ ions.
Figure 6

Quenching rate analysis at varying concentrations (a) Fe3+ ions and (b) Ni2+ ions. The fluorescent intensity ratios of NCDs versus the concentrations of (c) Fe3+ ions and (d) Mn2+ ions.

The interaction between fluorescence intensity and metal ion concentrations is shown linearly in Figure 6c and d. The obtained R 2 value of 0.9722 for Fe3+ ions and 0.971 for Ni2+ ions indicated good linearity in the outcome. It is determined that the Fe3+ ion’s limit of detection (LOD) is 1.46 and the LOD of Ni2+ ions is 3.19.

Table 1 compares the LOD (limit of detection) value of CDs synthesized from various raw materials. NCDs generated in this study had an excellent LOD value for Fe3+ ion detection when compared to CDs prepared from blueberry [29] and l-glutamic acid [31]. The value of the other reports in the table is comparable to that of our findings. Ni2+ detection studies are few in the literature; however, CDs synthesized from imidazole [26] reported Ni2+ detection with a LOD of 0.93 mM, which is greater than our findings. The performance of a biosensor is good with lower LOD values and these findings demonstrated that, this sensing probe is an excellent tool for detecting Ni2+ and Fe3+ ions.

Table 1

Comparison of limit of detection values of biosensors made from CDs

Sl. no. Carbon precursor Metal ions Linear range LOD (µM) Ref.
1 Wheat straw Fe3+ 0–250 μM 1.95 [27]
2 Oxidized cellulose Fe3+ 0–100 μM 1.14 [28]
3 Blueberry Fe3+ 12.5–100 μM 9.97 [29]
4 Food waste Fe3+ 12.5–100 μM 32 [30]
5 CDs from l-glutamic acid Fe3+ 0–50 μM 4.64 [31]
6 CDs from graphite Fe3+ 1–100 μM 1 [32]
8 Cellulose fibers Fe3+ 25–250 μM 0.96 [33]
9 CD-imidazole Ni2+ 6–100 (mM) 0.93 (mM) [26]
10 Poa pratensis Fe3+ 5–25 μM 1.4 [34]
11 Bacopa monnieri (this work) Fe3+ 5–500 μM 1.46 This work
Bacopa monnieri (this work) Ni2+ 5–500 μM 3.19 This work

4.1 Real sample analysis: Determination of Fe3+ and Ni2+ ion levels in real water samples

For the purpose of exploring the possible benefits and realistic application of the generated NCDs to actual/real samples (which were collected from various water sources), the levels of Fe3+ and Ni2+ ions were measured in seven real-world water samples: drinking water, tap water, well water, bore well water, river water, sea water, and two waste water samples. Before being used, all obtained water samples were filtered three times with qualitative filter paper, and the initial concentrations of Fe3+ and Ni2+ ions were measured. Fe3+ and Ni2+ ions were added in increments of 20, 40, and 60 mm to the aforementioned water samples using the usual addition method to measure the concentration of these two ions. The data obtained demonstrate that NCDs enable good recovery in the measurement of spiking Fe3+ and Ni2+ ion concentrations (Table 2).

Table 2

Analytical results for the detection of Fe3+ and Ni2+ ions in five practical samples

Sample Metal ion determined (μM)a Metal ion added (μM) Metal ion expected (μM) Metal ion found (μM)a Recovery (%)
For Ni 2+ ions
Drinking water 0.39 ± 0.3 10 10.39 10.42 ± 0.3 100.3
20 20.39 20.35 ± 0.2 99.8
30 30.39 30.31 ± 0.4 99.7
Tap water 1.13 ± 0.5 10 11.13 11.18 ± 0.5 100.5
20 21.13 20.37 ± 0.3 96.4
30 31.13 31.07 ± 0.8 99.8
Well water 2.21 ± 0.2 10 12.21 12.12 ± 0.5 99.3
20 22.21 22.22 ± 0.4 100
30 32.21 31.16 ± 0.7 96.7
Bore well water 2.43 ± 0.3 10 12.43 12.11 ± 0.5 97.4
20 22.43 22.47 ± 0.3 100.2
30 32.43 32.12 ± 0.6 99
River water #1 2.76 ± 0.2 10 12.76 12.68 ± 0.8 99.4
20 22.76 22.74 ± 0.9 99.9
30 32.76 32.79 ± 0.5 100
Sea water 3.12 ± 0.7 10 13.12 13.08 ± 0.4 99.7
20 23.12 23.14 ± 0.3 100.1
30 33.12 33.04 ± 0.7 99.8
Waste water #1 7.97 ± 0.9 10 17.97 17.99 ± 0.4 100.1
20 27.97 27.91 ± 0.7 99.8
30 37.97 37.99 ± 0.2 100.1
Waste water #2 8.44 ± 0.9 10 18.44 18.45 ± 0.4 100.1
20 28.44 28.40 ± 0.5 99.9
30 38.44 38.45 ± 0.3 100
For Fe 3+ ions
Drinking water 5.47 ± 0.4 10 15.47 15.48 ± 0.4 100
30 35.47 35.44 ± 0.5 99.9
50 55.47 55.49 ± 0.2 100
Tap water 6.62 ± 0.5 10 16.62 16.63 ± 0.5 100
30 36.62 36.68 ± 0.3 100.2
50 56.62 56.58 ± 0.2 99.9
Well water 8.33 ± 0.9 10 18.33 18.0 ± 0.5 98.2
30 38.33 38.35 ± 0.3 100.1
50 58.33 58.12 ± 0.2 99.6
Bore well water 9.72 ± 0.3 10 19.72 19.12 ± 0.5 97.0
30 39.72 39.74 ± 0.3 100.1
50 59.72 59.67 ± 0.4 99.9
River water #1 10.13 ± 0.4 10 20.13 20.19 ± 0.6 100.3
30 40.13 39.11 ± 0.7 97.5
50 60.13 60.09 ± 0.8 99.9
Sea water 10.91 ± 0.7 10 20.91 20.95 ± 0.4 100.2
30 40.91 40.89 ± 0.3 100
50 60.91 60.10 ± 0.5 98.7
Waste water #1 12.72 ± 0.9 10 22.72 22.82 ± 0.4 100.4
30 42.72 42.54 ± 0.7 99.6
50 62.72 62.76 ± 0.3 100.1
Waste water #2 13.22 ± 0.4 10 23.22 20.23 ± 0.8 87.1
30 43.22 43.27 ± 0.4 100.1
50 63.22 63.24 ± 0.3 100

aMean value ± standard deviation (n = 3).

4.2 Photocatalytic activity of MB under UV light

In photocatalysis, a chemical reaction is accelerated by visible, infrared, or UV light while a photocatalyst is present to absorb light and change reaction partners. For instance, light can be harvested by CDs via chemical transformation, excitation, and direct absorption. Methylthioninium chloride, commonly called methylene blue (CA No. 61-73-4), is a salt used as a dye and as a medication, with the formula C16H18ClN3S. The photocatalytic degradation of methylene blue in the presence of NCDs has been used to evaluate under UV light (Figure 7).

Figure 7 Photocatalytic degradation of methylene blue. UV absorption spectra of methylene blue and prepared NCDs in the UV light at different time intervals (20–180 min).
Figure 7

Photocatalytic degradation of methylene blue. UV absorption spectra of methylene blue and prepared NCDs in the UV light at different time intervals (20–180 min).

Upon increasing the time, the methylene blue absorption peaks are decreased, which indicates the dye is degraded in the presence of NCDs. It is an interesting application, which uses the prepared NCDs to treat the polluted dye water.

5 Conclusion

Water contamination has caused a decrease in aquatic biodiversity and a rise in hazardous drinking water. Clean water is critical for ecological balance and public health. Biosensing with the novel NCDs reported here is an efficient method for detecting the presence of Fe3+ and Ni2+ ions in bodies of water. The obtained LOD value for Fe3+ ion is 1.46 μM, which is lower than the permissible level advised by the US Environmental Protection Agency, and the LOD value of Ni2+ is 3.19 μM, which is lower than previously reported. Further, we extend the potential utility of the produced NCDs for the detection of metal ions in various water sources as real sample analysis and sensor for photocatalytic dye degradation of methylene blue dye. This work demonstrates the potential for low-cost, heavy-metal free sensors for Fe3+ and Ni2+ in water, and its efficacy in different water samples could be demonstrated. In future CDs have the potential to combine with other semiconductors for high-efficiency hydrogen production. They can improve the efficiency of solar-to-hydrogen conversion in photocatalytic water splitting. In waste water, organic pollutants such as dyes and medications can be greatly broken down by CDs. This has the potential to improve the industrial waste water treatment and air purification systems. Moreover, they are capable of cleaning up dangerous substances like poisonous heavy metals and oil spills.

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Acknowledgments

We extend our appreciation to the Researchers Supporting Project at King Saud University, Riyadh, Saudi Arabia, for funding this research project, (Fund no. RSP2025R218).

  1. Funding information: This research was funded by Researchers Supporting Project at King Saud University, Riyadh, Saudi Arabia, Fund no. RSP2025R218.

  2. Author contributions: Kondetharayil Soman and Nangan Senthilkumar: writing – original draft, resources, investigation, data curation, and conceptualization. Kuppusamy Kanagaraj and Natesan Thirumalaivasan: writing – original draft, resources, and formal analysis. Turki Kh. Faraj and Abdulwahed Fahad Alrefaei: project administration and investigation. Arpita Roy and Rajan Verma: formal analysis, data curation, and conceptualization. Sabu Thomas, Saravanan Rajendran, Thanigaivel Sundaram, Sreeraj Gopi, and Maximilian Lackner: writing – review and editing, visualization, validation, supervision, resources, and conceptualization.

  3. Conflict of interest: Authors state no conflict of interest.

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

References

[1] Hu L, Zhang C, Zeng G, Chen G, Wan J, Guo Z, et al. Metal-based quantum dots: synthesis, surface modification, transport and fate in aquatic environments and toxicity to microorganisms. RSC Adv. 2016;6:78595–610.10.1039/C6RA13016JSearch in Google Scholar

[2] Qiu J, Li D, Mou X, Li J, Guo W, Wang S, et al. Effects of graphene quantum dots on the self‐renewal and differentiation of mesenchymal stem cells. Adv Healthc Mater. 2016;5:702–10.10.1002/adhm.201500770Search in Google Scholar PubMed

[3] Zheng M, Ruan S, Liu S, Sun T, Qu D, Zhao H, et al. Self-targeting fluorescent carbon dots for diagnosis of brain cancer cells. ACS Nano. 2015;9:11455–61.10.1021/acsnano.5b05575Search in Google Scholar PubMed

[4] Bao X, Yuan Y, Chen J, Zhang B, Li D, Zhou D, et al. In vivo theranostics with near-infrared-emitting carbon dots—highly efficient photothermal therapy based on passive targeting after intravenous administration. Light: Sci Appl. 2018;7:91.10.1038/s41377-018-0090-1Search in Google Scholar PubMed PubMed Central

[5] Hong WT, Yang HK. Luminescent properties of carbon dots originated from pine pollen for anti-counterfeiting application. Opt Laser Technol. 2022;145:107452.10.1016/j.optlastec.2021.107452Search in Google Scholar

[6] Chauhan P, Dogra S, Chaudhary S, Kumar R. Usage of coconut coir for sustainable production of high-valued carbon dots with discriminatory sensing aptitude toward metal ions. Mater Today Chem. 2020;16:100247.10.1016/j.mtchem.2020.100247Search in Google Scholar

[7] Pacquiao MR, de Luna MDG, Thongsai N, Kladsomboon S, Paoprasert P. Highly fluorescent carbon dots from enokitake mushroom as multi-faceted optical nanomaterials for Cr6+ and VOC detection and imaging applications. Appl Surf Sci. 2018;453:192–203.10.1016/j.apsusc.2018.04.199Search in Google Scholar

[8] Chang D, Zhao Z, Niu W, Shi L, Yang Y. Iron ion sensing and in vitro and in vivo imaging based on bright blue-fluorescent carbon dots. Spectrochim Acta Part A: Mol Biomol Spectrosc. 2021;260:119964.10.1016/j.saa.2021.119964Search in Google Scholar PubMed

[9] Atchudan R, Edison TNJI, Perumal S, Muthuchamy N, Lee YR. Hydrophilic nitrogen-doped carbon dots from biowaste using dwarf banana peel for environmental and biological applications. Fuel. 2020;275:117821.10.1016/j.fuel.2020.117821Search in Google Scholar

[10] Wei LF, Chen CY, Lai CK, Thirumalaivasan N, Wu SP. A nano-molar fluorescent turn-on probe for copper (II) detection in living cells. Methods. 2019;168:18–23.10.1016/j.ymeth.2019.04.023Search in Google Scholar PubMed

[11] Singh J, Kaur S, Lee J, Mehta A, Kumar S, Kim K-H, et al. Highly fluorescent carbon dots derived from Mangifera indica leaves for selective detection of metal ions. Sci Total Environ. 2020;720:137604.10.1016/j.scitotenv.2020.137604Search in Google Scholar PubMed

[12] Sachdev A, Gopinath P. Green synthesis of multifunctional carbon dots from coriander leaves and their potential application as antioxidants, sensors and bioimaging agents. Analyst. 2015;140:4260–9.10.1039/C5AN00454CSearch in Google Scholar PubMed

[13] Yu J, Song N, Zhang Y-K, Zhong S-X, Wang A-J, Chen J. Green preparation of carbon dots by Jinhua bergamot for sensitive and selective fluorescent detection of Hg2+ and Fe3+. Sens Actuators B: Chem. 2015;214:29–35.10.1016/j.snb.2015.03.006Search in Google Scholar

[14] Atchudan R, Kishore SC, Gangadaran P, Edison TNJI, Perumal S, Rajendran RL, et al. Tunable fluorescent carbon dots from biowaste as fluorescence ink and imaging human normal and cancer cells. Environ Res. 2022;204:112365.10.1016/j.envres.2021.112365Search in Google Scholar PubMed

[15] Atchudan R, Edison TNJI, Mani S, Perumal S, Vinodh R, Thirunavukkarasu S, et al. Facile synthesis of a novel nitrogen-doped carbon dot adorned zinc oxide composite for photodegradation of methylene blue. Dalton Trans. 2020;49:17725–36.10.1039/D0DT02756ASearch in Google Scholar PubMed

[16] Jin H, Gui R, Wang Y, Sun J. Carrot-derived carbon dots modified with polyethyleneimine and nile blue for ratiometric two-photon fluorescence turn-on sensing of sulfide anion in biological fluids. Talanta. 2017;169:141–8.10.1016/j.talanta.2017.03.083Search in Google Scholar PubMed

[17] Ramezani Z, Qorbanpour M, Rahbar N. Green synthesis of carbon quantum dots using quince fruit (Cydonia oblonga) powder as carbon precursor: application in cell imaging and As3+ determination. Colloids Surf A: Physicochem Eng Asp. 2018;549:58–66.10.1016/j.colsurfa.2018.04.006Search in Google Scholar

[18] Shahraki HS, Bushra R, Shakeel N, Ahmad A, Ahmad M, Ritzoulis C. Papaya peel waste carbon dots/reduced graphene oxide nanocomposite: from photocatalytic decomposition of methylene blue to antimicrobial activity. J Bioresour Bioprod. 2023;8:162–75.10.1016/j.jobab.2023.01.009Search in Google Scholar

[19] Zulfajri M, Sudewi S, Damayanti R, Huang GG. Rambutan seed waste-derived nitrogen-doped carbon dots with l-aspartic acid for the sensing of Congo red dye. RSC Adv. 2023;13:6422–32.10.1039/D2RA07620ASearch in Google Scholar

[20] Shen J, Shang S, Chen X, Wang D, Cai Y. Facile synthesis of fluorescence carbon dots from sweet potato for Fe3+ sensing and cell imaging. Mater Sci Eng: C. 2017;76:856–64.10.1016/j.msec.2017.03.178Search in Google Scholar PubMed

[21] Huang H, Lv J-J, Zhou D-L, Bao N, Xu Y, Wang A-J, et al. One-pot green synthesis of nitrogen-doped carbon nanoparticles as fluorescent probes for mercury ions. RSC Adv. 2013;3:21691–6.10.1039/c3ra43452dSearch in Google Scholar

[22] Zhou J, Sheng Z, Han H, Zou M, Li C. Facile synthesis of fluorescent carbon dots using watermelon peel as a carbon source. Mater Lett. 2012;66:222–4.10.1016/j.matlet.2011.08.081Search in Google Scholar

[23] Arul V, Sethuraman MG. Hydrothermally green synthesized nitrogen-doped carbon dots from Phyllanthus emblica and their catalytic ability in the detoxification of textile effluents. ACS Omega. 2019;4:3449–57.10.1021/acsomega.8b03674Search in Google Scholar PubMed PubMed Central

[24] Dineshkumar R, Murugan N, Rani JA, Arthanareeswari M, Kamaraj P, Devikala S, et al. Synthesis of highly fluorescent carbon dots from Plectranthus amboinicus as a fluorescent sensor for Ag+ ion. Mater Res Express. 2019;6:104006.10.1088/2053-1591/ab3a7bSearch in Google Scholar

[25] Thirumalaivasan N, Venkatesan P, Wu SP. Highly selective turn-on probe for H2S with imaging applications in vitro and in vivo. N J Chem. 2017;41(22):13510–5.10.1039/C7NJ02869ESearch in Google Scholar

[26] Gong Y, Liang H. Nickel ion detection by imidazole modified carbon dots. Spectrochim Acta Part A: Mol Biomol Spectrosc. 2019;211:342–7.10.1016/j.saa.2018.12.024Search in Google Scholar PubMed

[27] Yuan M, Zhong R, Gao H, Li W, Yun X, Liu J, et al. One-step, green, and economic synthesis of water-soluble photoluminescent carbon dots by hydrothermal treatment of wheat straw, and their bio-applications in labeling, imaging, and sensing. Appl Surf Sci. 2015;355:1136–44.10.1016/j.apsusc.2015.07.095Search in Google Scholar

[28] Liu Z, Chen M, Guo Y, Zhou J, Shi Q, Sun R. Oxidized nanocellulose facilitates preparing photoluminescent nitrogen-doped fluorescent carbon dots for Fe3+ ions detection and bioimaging. Chem Eng J. 2020;384:123260.10.1016/j.cej.2019.123260Search in Google Scholar

[29] Aslandaş AM, Balcı N, Arık M, Şakiroğlu H, Onganer Y, Meral K. Liquid nitrogen-assisted synthesis of fluorescent carbon dots from Blueberry and their performance in Fe3+ detection. Appl Surf Sci. 2015;356:747–52.10.1016/j.apsusc.2015.08.147Search in Google Scholar

[30] Podder A, Thirumalaivasan N, Chao YK, Kukutla P, Wu SP, Bhuniya S. Two-photon active fluorescent indicator for detecting NADH dynamics in live cells and tumor tissue. Sens Actuators B: Chem. 2020;324:128637.10.1016/j.snb.2020.128637Search in Google Scholar

[31] Yu J, Xu C, Tian Z, Lin Y, Shi Z. Facilely synthesized N-doped carbon quantum dots with high fluorescent yield for sensing Fe3+. N J Chem. 2016;40:2083–8.10.1039/C5NJ03252KSearch in Google Scholar

[32] Nguyen V, Yan L, Si J, Hou X. Femtosecond laser-assisted synthesis of highly photoluminescent carbon nanodots for Fe3+ detection with high sensitivity and selectivity. Opt Mater Express. 2016;6:312–20.10.1364/OME.6.000312Search in Google Scholar

[33] Yang G, Wan X, Su Y, Zeng X, Tang J. Acidophilic S-doped carbon quantum dots derived from cellulose fibers and their fluorescence sensing performance for metal ions in an extremely strong acid environment. J Mater Chem A. 2016;4:12841–9.10.1039/C6TA05943KSearch in Google Scholar

[34] Krishnaiah P, Atchudan R, Perumal S, Salama E-S, Lee YR, Jeon B-H. Utilization of waste biomass of Poa pratensis for green synthesis of N-doped carbon dots and its application in detection of Mn2+ and Fe3+. Chemosphere. 2022;286:131764.10.1016/j.chemosphere.2021.131764Search in Google Scholar PubMed

Received: 2024-08-16
Accepted: 2024-12-02
Published Online: 2025-07-10

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

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

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https://doi.org/10.1515/gps-2024-0182
Keywords for this article
Bacopa monnieri; metal pollutant; nitrogen doped-carbon dots; bioremediation; biosensing, Ni2+; Fe3+
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. Review Article
  48. Sustainable innovations in garlic extraction: A comprehensive review and bibliometric analysis of green extraction methods
  49. Rapid Communication
  50. In situ supported rhodium catalyst on mesoporous silica for chemoselective hydrogenation of nitriles to primary amines
  51. Special Issue: Valorisation of Biowaste to Nanomaterials for Environmental Applications
  52. Valorization of coconut husk into biochar for lead (Pb2+) adsorption
  53. Corrigendum
  54. Corrigendum to “An updated review on carbon nanomaterials: Types, synthesis, functionalization and applications, degradation and toxicity”
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