Dual-mode detection sensor based on nitrogen-doped carbon dots from pine needles for the determination of Fe3+ and folic acid

Green biosynthesis of carbon quantum dots from lotus seed plumules for folic acid detection and bioimaging applications

This study introduces a novel green hydrothermal synthesis approach using lotus seed plumules to prepare carbon quantum dots (L-CQDs) and systematically evaluates their potential applications in folic acid (FA) detection and bioimaging. L-CQDs, enriched with phytochemical constituents such as alkaloids and flavonoids, exhibit superior optical properties, biocompatibility, and low toxicity. For FA detection, L-CQDs demonstrated high sensitivity and specificity, achieving a limit of detection (LOD) of 0.27 μM with a binding constant (KSV ​) of 4271.04 L·mol-1. Their practical applicability was confirmed through successful FA detection in human serum samples. Investigations into fluorescence lifetime, NMR, and zeta potential revealed that the interaction between L-CQDs and FA followed a static quenching mechanism, forming stable complexes. Both in vitro and in vivo experiments validated their low toxicity and biosafety, alongside significant imaging capabilities. These findings establish L-CQDs as efficient and multifunctional fluorescent probes for FA detection and biomedical research.

Ratiometric fluorescent and smartphone-assisted dual-mode sensor for folic acid determination based on N-Nb2C QDs/CQDs

Accurate detection of folic acid (FA) content in foods is crucial for guiding dietary supplementation and mitigating risks associated with deficiency or overdose. However, most current methods have limitations in on-site visual detection. This study addresses this gap by developing a dual-mode ratiometric fluorescent and smartphone-assisted sensor (N-Nb2C QD/CQDs). The internal filter effect between the sensor and FA significantly changed the fluorescence intensity ratio and produced continuous fluorescence color changes. The fluorescence color was converted to RGB values using smartphone, enabling visual and quantitative determination of FA. Under optimal parameters, the linear ranges for detecting FA were found to be 0.1-400 and 0.1-350 μM for fluorescence spectrometer and smartphone-assisted sensor. The detection limits were 87 and 189 nM, respectively. Furthermore, the sensor was successfully applied to direct visual identification of FA in samples of orange juice, oatmeal and urine, indicating the possibility of its practical application.

Facile synthesis of N-doped graphene quantum dots as a fluorescent sensor for Cr(vi) and folic acid detection

The development of stable fluorescent sensors for toxic pollutants and drugs is meaningful to the environment and public health. In this work, nitrogen-doped graphene quantum dots (N-GQDs) were facially synthesized by a one-step hydrothermal method using soluble starch and l-arginine as carbon and nitrogen sources in pure water at 190 °C for 4 h. The as-synthesized N-GQDs were well characterized and displayed blue fluorescence emission at 445 nm with excellent pH stability, salt tolerance, thermostability, photobleaching resistance and reproducibility. Moreover, N-GQDs could serve as an "on-off" sensor for selective detection of Cr(vi) and folic acid with low detection limit (0.80 and 2.1 μM), good linear correlation over wide linear range (0-50 μM and 0-200 μM) as well as short response time (<10 s). The practical applications of N-GQDs for Cr(vi) and folic acid detection in actual samples were further investigated and showed acceptable recoveries (92-105%) with relative standard deviations less than 5%. These results indicated that this N-GQDs-based sensor could be a potential alternative for Cr(vi) and folic acid detection in the fields of environmental monitoring and drug analysis.

Recent Progress in Folic Acid Detection Based on Fluorescent Carbon Dots as Sensors: A Review

Folic acid (FA) is a water-soluble vitamin found in diverse natural sources and is crucial for preserving human health. The risk of health issues due to FA deficiency underscores the need for a straightforward and sensitive FA detection methodology. Carbon dots (CDs) have gained significant attention owing to their exceptional fluorescence performance, biocompatibility, and easy accessibility. Consequently, numerous research studies have concentrated on developing advanced CD fluorescent probes to enable swift and precise FA detection. Despite these efforts, there is still a requirement for a thorough overview of the efficient synthesis of CDs and their practical applications in FA detection to further promote the widespread use of CDs. This review paper focuses on the practical applications of CD sensors for FA detection. It begins with an in-depth introduction to FA and CDs. Following that, based on various synthetic approaches, the prepared CDs are classified into diverse detection methods, such as single sensing, visual detection, and electrochemical methods. Furthermore, persistent challenges and potential avenues are highlighted for future research to provide valuable insights into crafting effective CDs and detecting FA.

Applications of Functionalized Carbon-Based Quantum Dots in Fluorescence Sensing of Iron(III)

Iron, an essential trace element exhibits detrimental effects on human health when present at higher or lower concentration than the required. Therefore, there is a pressing demand for sensitive and selective detection of Fe3+ in water, food etc. Unfortunately, in several instances, the traditional approaches suffer from a number of shortcomings like complicated procedures, limited sensitivity, poor selectivity and more expensive and time consuming. The scope of optical tuning and excellent photophysical properties of carbon- based nanomaterials like carbon dots (C-dots) and graphene dots (g-dots) have made them promising optical sensors of metal ions. Moreover, high surface area, superior stability of such materials contributes towards the fruitful development of sensors. The present review offered critical information on the fabrication and fluorimetric applications of these functional nanomaterials for sensitive and selective detection of Fe3+. An in-depth discussion on fluorescent C-dots made from naturally occurring materials and chemical techniques were presented. Effect of doping in C-dots was also highlighted in terms of improved fluorescence response and selectivity. In a similar approach g-dots were also discussed. Many of these sensors exhibited great selectivity, superior sensitivity, high quantum yield, robust chemical and photochemical stability and real-time applicability. Further improvement in these factors can be targeted to develop new sensors.

Natural Nitrogen-Doped Carbon Dots Obtained from Hydrothermal Carbonization of Chebulic Myrobalan and Their Sensing Ability toward Heavy Metal Ions

Chebulic Myrobalan is the main ingredient in the Ayurvedic formulation Triphala, which is used for kidney and liver dysfunctions. Herein, natural nitrogen-doped carbon dots (NN-CDs) were prepared from the hydrothermal carbonization of Chebulic Myrobalan and were demonstrated to sense heavy metal ions in an aqueous medium. Briefly, the NN-CDs were developed from Chebulic Myrobalan by a single-step hydrothermal carbonization approach under a mild temperature (200 °C) without any capping and passivation agents. They were then thoroughly characterized to confirm their structural and optical properties. The resulting NN-CDs had small particles (average diameter: 2.5 ± 0.5 nm) with a narrow size distribution (1-4 nm) and a relatable degree of graphitization. They possessed bright and durable fluorescence with excitation-dependent emission behaviors. Further, the as-synthesized NN-CDs were a good fluorometric sensor for the detection of heavy metal ions in an aqueous medium. The NN-CDs showed sensitive and selective sensing platforms for Fe3+ ions; the detection limit was calculated to be 0.86 μM in the dynamic range of 5-25 μM of the ferric (Fe3+) ion concentration. Moreover, these NN-CDs could expand their application as a potential candidate for biomedical applications and offer a new method of hydrothermally carbonizing waste biomass.