Doped Carbon Quantum Dots Research Articles

Nitrogen Doped Carbon Quantum Dots as Fluorescence "Turn-Off-On" Sensor for Detection of Fe3+ Ions and Ascorbic Acid in Moringa oleifera and Citrus Lemon.

In recent year, the uses of carbon quantum dots (CQDs) have increased in many fields. Herein we report, synthesis of fluorescent nitrogen doped carbon quantum dots (N-CQDs) by simple and ecofriendly hydrothermal method. The as-synthesized N-CQDs were characterized by various techniques and the quantum yield was also calculated. Then, application of N-CQDs were performed as a sensor for detection of ferric ions (Fe3+) based on static quenching mechanism (turn-off) which occurred due to formation of non-fluorescent complex between N-CQDs and Fe3+ ions. Interestingly, fluorescence intensity of quenched N-CQDs has been significantly recovered (turn-on) by addition of ascorbic acid (AA). The recovery mechanism is based on the redox reaction between Fe3+ ions and AA. Thus, N-CQDs has been used as fluorescence "turn-off-on" sensor for detection of Fe3+ ions and AA. Further this detection system is used for detecting Fe3+ ions in Moringa oleifera and AA in citrus lemon.

Enhancing nanomedicine with doped carbon quantum dots: a comprehensive review

Enhancing nanomedicine with doped carbon quantum dots: a comprehensive review

UV and blue light cut-off filters using phosphorus doped carbon quantum dots extracted from raw egg yolk

Abstract Using raw egg yolk and phosphoric acid, a simple hydrothermal treatment for synthesizing carbon quantum dots (CQDs) has been developed for the manufacture of UV and blue light-blocking filters. Several samples with different doping ratios of phosphoric acid were prepared. Namely: reference (REF.), 25%, 50%, 75% and 100%. The synthesized CQDs were embedded in polyvinyl alcohol (PVA) to produce blocking-light films with desired optical properties. Six films were prepared, one of which was PVA alone, and the other five samples were the prepared CQDs, with different phosphorus doping levels, mixed with PVA in a 1:1 ratio. We aimed to test the ability of these films to block ultraviolet rays and blue light. The experimental results revealed that the prepared films were able to block the blue light, emitted from a 450 nm blue LED, with blocking ratios of 7%, 17.5%, 27%, 30%, 37% and 70% for the films: PVA alone, REF., 25%, 50%, 75% and 100%, respectively. Moreover, it was found that these phosphorus-doped CQDs films can prevent destructive UV light with substantial value reaching 86%. These results suggest that carbon dots, derived from raw egg yolk, can be effectively applied to block harmful UV and blue lights.

Harnessing hetero-atom doped CQDs from Pyrostegia venusta for latent fingerprint and anti-counterfeit applications

The development of innovative techniques for latent fingerprint (LFP) analysis and anti-counterfeiting applications is crucial for addressing various societal challenges. Quantum dot (QD)-based fluorescent staining offers a promising approach due to its high sensitivity. However, the toxicity of traditional heavy metal-containing QDs necessitates the exploration of eco-friendly alternatives. This study presents a facile and environmentally sustainable method for synthesizing heteroatom (nitrogen, phosphorus, and potassium)-doped carbon quantum dots (N-P-K@CQDs) derived from the flower extract of Pyrostegia venusta. Characterization revealed spherical CQDs with an average size of approximately 4.7 nm, a quantum yield of 25 %, and excellent water solubility, photostability, and greenish-fluorescent properties. N-P-K@CQDs were incorporated into a cornstarch nanocomposite phosphor, which exhibited greenish fluorescence under UV excitation. The nanocomposite was utilized as a fluorescent marker for LFP analysis using a customized smartphone-based dactyloscope. Python-based image processing algorithms were employed to enhance and analyze the fluorescence images of the developed LFPs. Additionally; a proof-of-concept anti-counterfeiting tag was demonstrated using CQDs-based ink, enabling the detection of concealed security marks. The findings highlight the potential of eco-friendly N-P-K@CQDs as a versatile platform for both LFP analysis and anti-counterfeiting applications.

Rapid determination of organophosphorus insecticides residue in fruit juice by a fluorescence sensor based on carbon quantum dots

Nitrogen doped carbon quantum dots (N-CQDs) were synthesized by a hydrothermal method. A fluorescence sensor for rapid determination of organophosphorus pesticides residue was developed using the N-CQDs based on acetylcholine enzyme inhibition. Cu2+ effectively quenched the strong fluorescence of N-CQDs, which could be recovered due to the complexation between copper ions and thiocholine, the hydrolysis product of acetylthiocholine catalyzed by acetylcholinesterase. Organophosphorus pesticides inhibited the activity of acetylcholinesterase, resulting in fluorescence quenching of N-CQDs. Fluorescence inhibiting efficiency depends on the concentration of the analytes, and therefore, the sensor could be used for quantitative analysis of organophosphorus pesticides residue. The average recoveries of the analytes ranged from 85.33 % to 110.67 % at the spiked concentrations of 0.015 mg/L, 0.04 mg/L and 0.1 mg/L, and the limits of detection were 2.89 ∼6.40 ng/mL. The developed method had the advantages of simple operation, fast speed, low cost, expensive apparatus-free, and environmental friendliness, which could be used for rapid screening of organophosphorus pesticides residue in real samples.

Rapid detection of chlorpyrifos in miscellaneous beans based on nitrogen and phosphorus doped carbon quantum dots fluorescence probe

A fluorescent probe based on N, P-doped carbon quantum dots was established to detect chlorpyrifos. N, P-doped carbon quantum dots were prepared by one-step hydrothermal method with trisodium citrate, dipotassium hydrogen phosphate and urea. The sensing mechanism was based on the fluorescence quenching of N, P-doped carbon quantum dots by chlorpyrifos through internal filtering effect. The results indicated that the linear range was 0.025 ~ 25µg/mL with the detection limit of 0.0008µg/g under the optimal detection conditions. The method was applied to different miscellaneous beans with the recoveries of 90.2% ~ 105.7% and the relative standard deviations were less than 4.8%. The fluorescent probe has the advantages of economy, high efficiency, easy preparation and specificity.

A novel molecular imprinted polymer grafted on N, S Co-doped carbon quantum dots-based fluorescence sensor for chloramphenicol in food and clinical samples

Globally, antibiotic consumption surpasses thousands of tons on every year and even during this alarming state, the abundant traces of antibiotics have been found in the environment especially on water bodies and food producing creatures. The high accumulation of Chloramphenicol (CPL) may cause microbial resistance and lowering the general immunity. All these finding urges to develop a sensitive detection system for CPL. The present work describes the fabrication of Molecular Imprinted Polymer (MIP) grafted on Nitrogen and Sulfur doped Carbon Quantum Dots (N, S-CQDs) as a probe for the nanomolar level detection of CPL in food and clinical samples by using fluorescence technique. The developed N, S-CQDs based MIP sensor exhibits a bright fluorescence response and high recognition capability on CPL. The proposed sensor system has shown the detection limit of 7.65 nM and the linearity range was found between 0.24 μM and 26.1 μM. The real time consistency of the proposed sensor system has been verified by applying on clinical and food samples. Interestingly, we have received an excellent recovery varies from 97 % to 103 %. All these research outcomes further boost up the novel strategy to develop MIP based fluorescence probe for the detection of CPL.

NiFe-spinel oxides with nitrogen-doped carbon quantum dots for enhanced oxygen evolution activity

Designing efficient and stable electro-catalysts for non-precious metal oxygen evolution reactions (OER) is critical to solve the bottleneck of water splitting. The NiFe2O4/NCQDs composite electrode was fabricated by combining nitrogen doped carbon quantum dots (NCQDs) with NiFe2O4 spinel via a hydrothermal method, which showed brilliant OER catalytic performance by modifying on nickel foams (NF). The composites had petal-like structures, and the NiFe2O4 was epitaxially grown on the NF substrates with exposed sites, resulting in enhanced electron transport. The fluorescence quenching of NCQDs was accompanied by binding NCQDs with NiFe2O4, which indicated the energy barrier was greatly reduced during the electron transport as well as electro-catalysis. The higher intrinsic charge transfer was achieved, and the doping combination having a higher conductivity was confirmed. The electrochemical activity of NiFe2O4/NCQDs electrode in OER reaction was evaluated under alkaline conditions. The addition of NCQDs effectively enhanced the OER activity, and over-potentials were decreased from 330 mV to 270 mV at 10 mA cm−2 with Tafel slope lower (66 mV/dec) than counterparts. The NiFe2O4/NCQDs displayed long-term catalytic stability at 1.47 V. Therefore, a facile method for preparing NiFe2O4/NCQDs was developed which had characteristics of low cost, simple process and excellent OER activity.

Preparation and application of DES doped carbon quantum dots for fluorescent chromium ions determination

ABSTRACT This paper uses orange peel and deep eutectic solvents as precursors to prepare DES-CQDs via one-step hydrothermal method. The average size of DES-CQDs is 5.5 nm, with abundant luminescent groups such as amino and hydroxyl groups on the surface. Under the excitation of ultraviolet light at 360 nm, blue fluorescence with a wavelength of 452 nm is emitted. In addition, to investigate the practical application effect of DES-CQDs, this study further used DES-CQDs as fluorescent sensor to detect Cr6+ ions in solutions. The results showed that Cr6+ exhibited a significant quenching effect on DES-CQDs, consistent with the quenching mechanism of static quenching and internal filtering effect, and the limit of detection was 3.2 nM. The recovery rates of Cr6+ spiked in four environmental samples are 94.27 ~ 100.51%, indicating that DES-CQDs can be used for the detection of Cr6+ in complex environmental samples.

Facile synthesis of yellow emissive heteroatom doped carbon quantum dots fluorescent probe with superior quantum yield for fast-track ionic detection in aqueous media

In this work, heteroatom (B and N) doped carbon quantum dots (CQDs) materials were synthesized via facile hydrothermal method using o-phenylenediamine (o-PD) as a nitrogen source and 3-aminophenyl boronic acid (3APBA) as a boron source. The synthesis parameters were optimized and optimal synthesis temperature and reaction time were 260 °C and 2 h, respectively. The chemical structures were characterized using various techniques. The experimental results showed that B,N co-doped CQDs had the strongest fluorescence intensity when the weight ratio of 3APBA:o-PD was 3:1 and showed a phenomenal quantum yield of 59% with high selectivity for Fe3+ and Hg2+ ions, with quenching constants 1.25 × 103 M–1 and 8.3 × 103 M–1, respectively. The high fluorescence quenching was attributed to the photoinduced electron transfer phenomenon, making it suitable for fluorescent sensing materials. Cytotoxicity data revealed synthesized materials are safe for biomedical applications within a 1–10 µg/mL concentration.

A new fabricated hetero-atom doped carbon quantum dots as a fluorescent probe for metronidazole determination using garlic and red lentils with microwave assistance.

Biocompatible and highly fluorescent phosphorus, nitrogen and sulfur carbon quantum dots (P,N,S-CQDs) were synthesized using a quick and ecologically friendly process inspired from plant sources. Garlic and red lentils were utilized as natural and inexpensive sources for efficient synthesis of the carbon-based quantum dots using green microwave-irradiation, which provides an ultrafast route for carbonization of the organic biomass and subsequent fabrication of P,N,S-CQDs within only 3 min. The formed P,N,S-CQDs showed excellent blue fluorescence at λem= 412 nm when excited at 325 nm with a quantum yield up to 26.4%. These fluorescent dots were used as a nano-sensor for the determination of the commonly used antibacterial and antiprotozoal drug, metronidazole (MTR). As MTR lacked native fluorescence and prior published techniques had several limitations, the proposed methodology became increasingly relevant. This approach affords sensitive detection with a wide linear range of 0.5-100.0μM and LOD and LOQ values of 0.14 μM and 0.42 μM, respectively. As well as, it is cost-effective and ecologically benign. The MTT test was used to evaluate the in-vitro cytotoxicity of the fabricated P,N,S-CQDs. The findings supported a minimally cytotoxic impact and good biocompatibility, which provide a future perspective for the applicability of these CQDs in biomedical applications.

A ratiometric fluorescence sensing system for rapid detection of glyphosate in miscellaneous beans

To establish a ratiometric fluorescence sensing system for the detection of glyphosate, nitrogen-sulfur doped carbon quantum dots nano-fluorescent probe was prepared by one-step hydrothermal method. At an excitation wavelength of 360 nm, the emission peak with maximum fluorescence intensity was obtained at 470 nm. The generation of 2.3-diaminophenazine by o-phenylenediamine oxidation produces a new fluorescence emission peak at 570 nm and a decrease in fluorescence at 470 nm. The fluorescence peaks at 470 and 570 nm form a ratio state. In the presence of glyphosate, reduces the oxidation of 2.3-diaminophenazine, this results in enhanced fluorescence at 470 nm and weakened fluorescence at 570 nm. Under the best conditions, the ratiometric fluorescence sensing system has good selectivity, the linear at glyphosate concentrations of 0.005–10 µg/mL, the limit of detection was 2.88 µg/kg, the limit of quantitation was 4.07 µg/kg. In addition, it is worth mentioning that this developed sensing system has shown good detection performance in 10 miscellaneous samples, the simple, efficient, and highly sensitive ratiometric fluorescence detection sensing strategy is provided.

Investigating the effect of nitrogen and chlorine Co–doped carbon quantum dots in phenazine and quinoxaline sensitized solar cells

We investigated five dyes for dye-sensitized solar cells (DSSCs) relying upon derivatives of phenazine and quinoxaline and also studied their optical characteristics and the influence of functional groups such as (-CH3, -NO2, -C = O, -CN, and -OH) on these characteristics. When the prepared dyes are directly used at DSSCs, 9-Nitrobenzo[a]phenazin-5-ol (3b) dye device showed an improved Jsc (0.288 mA cm−2), Voc (0.437 V), FF (0.446), and η (0.056 %) than the sensitized solar cells by other dyes. In the following, nitrogen-doped carbon quantum dot and nitrogen, chlorine co-doped carbon quantum dot are used to improve the performance of DSSCs. The results showed that the device sensitized using the sensitizer (5-hydroxybenzo[α]phenazin-9-yl)(phenyl) methanone (3c)/NCQD has the highest photovoltaic efficiency with Jsc (0.979 mA cm−2), Voc (0.465 V), FF (0.370), and η (0.168 %). The N and Cl co-doped carbon dots were synthesized with a green approach to improve the performance of solar cells by the co-sensitization method. This approach is improving the efficiency of DCSSs with a simple, eco-friendly, and low-cost technique. Among the prepared sensitizers, (5-hydroxybenzo[α]phenazin-9-yl)(phenyl) methanone (3c)/N, Cl-CQD demonstrates the highest photovoltaic efficiency with Jsc (1.31 mA cm−2), Voc (0.495 V), FF (0.466), and η (0.303 %). FT-IR, XRD, 13C NMR, 1H NMR, TEM, EDS-Map, AFM, DLS, and PL studies were used to confirm the structure of the synthesized dyes and quantum dots.

Nitrogen and zinc doped carbon quantum dots for rapid and accurate detection of mercury ions in cosmetics

Rapid and reliable detection technologies for mercury ion in cosmetics are critical for public health. In this study, we synthesized nitrogen and zinc doped carbon quantum dots (N, Zn-CDs) with bright and stable fluorescence using the hydrothermal method. Structure characterization reveals the abundant oxygen- and nitrogen-containing functional groups on the surface of N, Zn-CDs, which readily coordinate with Hg2+, resulting in fluorescence quenching. Basing on this, a rapid and simple quantitative analysis method for Hg2+ detection was designed. By optimizing the detection conditions, a good linear relationship in the range of 0 to 10 μM and a low detection limit of 0.023 μM were achieved. Besides, interference tests demonstrate the presence of other metal ions does not interfere with Hg2+ detection. When detecting Hg2+ in four types of cosmetics spiked with the ion, the sensor achieved recovery rates of 98.27 %, 110.03 %, 100.90 %, and 108.80 %, respectively, with relative standard deviations all under 6.90 %, demonstrating its capability to identify Hg2+ in complex matrices. This research offers a novel approach for the rapid and accurate detection of mercury in cosmetics.

Modification and performance enhancement of P3HT:PCBM based organic solar cells incorporated with phosphorus doped carbon quantum dots

We demonstrate a strategy to improve the performance of organic solar cells (OSCs) by phosphorous doped CQDs (P-CQDs). The presence of P-CQDs P3HT:PCBM layer (1 vol% of P-CQDs) enhanced photon harvesting in the UV region and emitting visible light, the PCE was increased from 2.19% to 2.48% and champion device provided a FF of 55.34%. The incorporation of P-CQDs leads to effective photons harvesting ability and collection/transport of charge carriers. The optical absorption and crystallinity of photoactive layer improved with the incorporation of P-CQDs. The larger grain size distribution were obtained with P-CQDs additive helping to better charge extraction.

Fluorescent nanozyme based dual-channel lipopolysaccharide sensing

The release of lipopolysaccharide (LPS) during the proliferation and death of bacterial growth could cause acute versatile disorders like anaphylaxis and multiple organ failure. Analysis methods with high sensitivity and selectivity are expected to be developed to replace the limuluslysatetest. Classical colorimetric method was equipped with portable visualization but limited with low sensitivity, while incredibly sensitive fluorescence sensing strategy suffered from negligible selectivity. Delicate design of the dual channels analysis would make the ends of such dilemma based on a fluorescent nanozyme of iron doped carbon quantum dots (Fe-CQDs) with both excellent fluorescence and peroxidase-mimic catalytic activity. Accordingly, a complementary dual channel analytical platform of LPS was prepared. The excellent peroxidase-like activity imparted the dominant selectivity for LPS (available under 6 interferences), while the powerful fluorescence property endowed the excellent sensitivity with the limit of detection (LOD) of an unprecedented level (0.0023 EU/mL). Our study has broadened a new path for design of efficient analytical methods via complementway.

Wearable, disposable and non-enzymatic fluorescence nanosensor for monitoring sweat glucose through smartphone

The promise of non-invasive health monitoring has fuelled the development of wearable biosensors for in situ detection of biological analytes in sweat. This paper presents a new fluorescent nanosensor probe based on boric acid functionalized and heteroatom doped carbon quantum dots (CQDs) embedded in paper-based analytical devices and integrated with a hydrophilic cotton thread-based microfluidic channel for the development of a flexible, wearable, biocompatible, and biodegradable sweat sensor for real-time measurement of sweat glucose concentration via smartphone readout. The morphological, physiochemical, compositional, crystallinity, and optical properties of nanosensors were extensively investigated. CQD particle sizes were found to be widely dispersed, ranging from 2.6 to 7.1 nm, with an average diameter of 4.38 nm. A dual response via fluorescence and colorimetric change was demonstrated for on-site sweat glucose monitoring using a smartphone camera to capture images in RGB (red, green, and blue) format and analyse them simultaneously by a customized android app, with quantitative results displayed on the smartphone. The limit of detection value for in situ measurement of sweat glucose concentration was 1.40 to 2.00 μM (25.25 to 36.13 μg/dL) and the limit of quantification value was 4.67 to 6.69 μM (84.16–120.44 μg/dL) in the pH range of 4.5 to 7.5. The developed sensor's performance metrics were validated using a standard clinical technique, which indicates strong correlation between two methods with Pearson correlation coefficient values of 0.83 and 0.80 for non-diabetic and type- II diabetes patients, respectively. Besides, interference, spike, and recovery studies were carried out with recovery rates ranging from 96.5 to 105.8 %, demonstrating good repeatability and reproducibility. Furthermore, feasible fluorescence quenching processes have been explored. In addition, the disposable and biodegradable nature of the nanosensor probe was studied by throwing it into the soil in the natural environment, where it dissolves almost spontaneously after three weeks.

Formulation of double nanoemulsions based on pH-sensitive carboxymethyl cellulose /Starch copper doped carbon quantum dots for quercetin controlled release

Nanocomposite Hydrogels are versatile and adaptable in drug delivery, suitable for various administrations. They offer prolonged and regulated drug release which makes them valuable in targeting cancer treatments. This study used the water/oil/water approach to construct a drug nanocarrier. It encapsulated hazelnut oil, serving as a protective and organic membrane that enveloped the nanocarrier and regulated drug release. Quercetin (QC), a potent flavonoid with potential therapeutic applications, faces challenges due to its hydrophobic nature and poor solubility. This approach presents a novel approach to enhance QC's solubility and stability by integrating it with copper carbon quantum dots (Cu-CQDs) into a pH-sensitive carboxymethyl cellulose (CMC) and starch-based hydrogel nanocomposite. This system aims to improve QC delivery while minimizing adverse effects. The nanocomposite exhibited exceptional drug loading and encapsulation efficiencies of 47.00 % ± 0.45 and 86.25 % ± 0.75, respectively, ranking among the top-reported values for similar systems. Fourier-transform infrared spectroscopy (FTIR) was used to examine molecular interactions. X-ray diffraction (XRD) assessment demonstrated the presence of components beneficial for drug solubility enhancement at 2Θ = 17–24°, where QC's crystalline peaks are absent from the CMC/Starch/Cu-CQDs@QC XRD pattern. A particle size of 151.57 ± 37 nm is optimized for selectively targeting cancer cells, minimizing interaction with healthy cells, as revealed through DLS assessment. Morphological characteristics analyzed by FE-SEM support this observation as well. Zeta potential measurement (+38.8 mV) highlights nanocarrier stability. CMC/Starch/Cu-CQDs@QC displayed remarkable cytotoxicity against cancerous cells, reducing U87-MG cell viability to 48 % while maintaining high cell viability (92 %) for normal L929 cells. These results emphasize the promise of this nanocomposite as a QC drug delivery system by indicating improved anticancer efficacy with fewer adverse effects.

Waterborne epoxy composite coating containing N,S-doped carbon dots for enhancing corrosion resistance

In order to construct waterborne epoxy composite coating with enhanced anti-corrosive performance, the development of efficient additives with good compatibility with adhesive resin and good interaction with steel matrix is of significance. Herein, we adapted two heteroatom (N and S) doped carbon quantum dots, namely ACDs and LCDs, as eco-friendly anti-corrosion components to mix with water-based epoxy resin (WP) to prepare the CDs/WP composite coating. Compared with the ACDs/WP composite, the LCDs/WP composite exhibited a better performance because it contained more functional groups such as carboxyl and hydroxyl on the surface of LCDs, which not only made the system denser but also facilitated the multi-anchor coordination and adsorption on carbon steel. Following immersing in a 3.5 wt% NaCl solution for 28 d, the impedance modulus of LCDs/WP surpassed 109 Ω cm2, exhibiting approximately three orders of magnitude higher values compared to pure WP coatings. The inhibition efficiency was improved by 96.9%. The facile synthesis of LCDs coupled with excellent anti-corrosive properties of LCDs/WP composites, provides a new way for developing anti-corrosion coating materials.

Ultra-trace Ag doped carbon quantum dots with peroxidase-like activity for the colorimetric detection of glucose

Carbon quantum dots (CQDs) have significant applications in nanozymes. However, previous studies have not elucidated the structure–activity relationship and enzyme mechanism. In this study, we employed a one-step microwave method to synthesize ultra-trace Ag-doped carbon quantum dots (Ag-CQDs). In the presence of hydrogen peroxide (H2O2), we used the oxidative coupling reaction of 3,3′,5,5′-tetramethylbenzidine (TMB) to evaluate the intrinsic peroxidase-like activity, kinetics, and mechanism of Ag-CQDs. The trace amount of doped Ag (1.64 %) facilitated electron transfer from the CQDs interior to the surface. The electron transfer triggered the peroxide activity of CQDs, producing hydroxyl radical (·OH), which oxidized the colorless TMB to blue-colored TMB (oxTMB). By coupling with glucose oxidase (GOx), the Ag-CQDs/H2O2/TMB system has been used for colorimetric glucose determination. The system demonstrated a low detection limit (0.17 µM), wide linear range (0.5–5.5 µM), and satisfactory results when fruit juice was analyzed. This study reports a feasible method for the colorimetric detection of glucose by synthesizing ultra-trace Ag-doped carbon quantum dots with peroxidase‐mimicking activity.