Facile green and one-pot synthesis of seville orange derived carbon dots as a fluorescent sensor for Fe3+ ions

l-cysteine capped MoS2 QDs for dual-channel imaging and superior Fe3+ ion sensing in biological systems

MoS2 quantum dots (MQDs) with an average size of 1.9 ± 0.7 nm were synthesized using a microwave-assisted method. Absorbance studies confirmed characteristic transitions of MoS2, with absorption humps at 260-280 nm and 300-330 nm, and a band gap of 3.6 ± 0.1 eV. Fluorescence emission studies showed dominant blue and some green emissions under 315 nm excitation, with an absolute quantum yield of ∼9%. The MQDs exhibited fluorescence stability over time after repeated quenching cycles across various pH and media systems. In vitro toxicity tests indicated cytocompatibility, with around 80% cell survival at 1000 mg L-1. Confocal imaging demonstrated significant uptake and vibrant fluorescence in cancerous and non-cancerous cell lines. The MQDs showed strong selectivity towards Fe3+ ions, with a detection limit of 27.61 ± 0.25 nM. Recovery rates for Fe3+ in phosphate buffer saline (PBS) and simulated body fluid (SBF) systems were >97% and >98%, respectively, with a relative standard deviation (RSD) within 3%, indicating precision. These findings suggest that MQDs have high potential for diagnostic applications involving Fe3+ detection due to their fluorescence stability, robustness, enhanced cell viability, and dual-channel imaging properties.

Synthesis of Carbon Dots via Microwave-Assisted Process: Specific Sensing of Fe(III) and Antibacterial Activity

Carbon dots synthesized from a renewable and sustainable source of biomass have greater attention in the nanomaterial research field. In the present study, we adopted a facile and green synthesis of carbon dots from bio waste of pumpkin seeds using a one-pot microwave-assisted carbonization method. The synthesized carbon dots exhibit excellent photoluminescence properties with a bright blue emission peak at 399 nm and fluorescence quantum yield was about 9.5%. The optical properties and structure of carbon dots were examined using various spectroscopy techniques and the synthesized carbon practical size was about 4.37 nm and possessed good solubility in water. Carbon dots were used for the detection of Ferric ions in the water bodies and the interaction between Fe3+ ions and carbon dots was evaluated by fluorescence spectroscopy techniques. This method is a simple and selective detection of Fe3+ in the aqueous medium. Interestingly carbon dots also show good antibacterial activity at a very low concentration (1 mg/L) for effective control of E. coli 93% and Pseudomonas aeruginosa (81%), within 12 h.

Recent Progress in MOF-Aerogel Fabrication and Applications

Recent advancements in metal-organic frameworks (MOFs) underscore their significant potential in chemical and materials research, owing to their remarkable properties and diverse structures. Despite challenges like intrinsic brittleness, powdered crystalline nature, and limited stability impeding direct applications, MOF-based aerogels have shown superior performance in various areas, particularly in water treatment and contaminant removal. This review highlights the latest progress in MOF-based aerogels, with a focus on hybrid systems incorporating materials like graphene, carbon nanotube, silica, and cellulose in MOF aerogels, which enhance their functional properties. The manifold advantages of MOF-based aerogels in energy storage, adsorption, and catalysis are discussed, with an emphasizing on their improved stability, processability, and ease of handling. This review aims to unlock the potential of MOF-based aerogels and their real-world applications. Aerogels are expected to reshape the technological landscape of MOFs through enhanced stability, adaptability, and efficiency.

A Polycaprolactone-Capped ZnO Quantum Dots-Based Fluorometric Sensor for the Detection of Fe3+ Ions in Seawater

Fe3+ ion plays a very active role in life, agriculture, and industry. Human health and the environment are seriously affected by the abnormal presence or excess of this cation. Therefore, the development of a fast, reliable, sensitive, and simple fluorescent probe to detect this cation is crucial. In the present paper, polycaprolactone-capped zinc oxide quantum dots were prepared for the determination of Fe3+ ions. The proposed fluorescent chemosensor exhibited a fluorometric and strong quenching effect toward Fe3+ ions at two wavelengths (303 and 602 nm). The limit of detection (LOD) was calculated as 0.410, and 0.333µM at the mentioned wavelengths. Also, the binding stoichiometric ratio was calculated as 1:1 by Job's plot. The findings indicated that the PCL@ZnO colorimetric chemosensor could be successfully applied with reliable, and good accuracy for the detection of Fe3+ ions in real seawater samples.

A novel ratiometric design of microfluidic paper-based analytical device for the simultaneous detection of Cu2+ and Fe3+ in drinking water using a fluorescent MOF@tetracycline nanocomposite

The regular and on-site monitoring of ions in drinking water is essential for safeguarding public health, ensuring high water quality, and preserving the ecological balance of aquatic ecosystems. Thus, developing a portable analytical device for the rapid, cost-effective, and visual on-site detection of multiple environmental pollutants is notably significant. In the present work, a novel ratiometric microfluidic paper-based analytical device (μPAD) was designed and developed for the simultaneous detection of Fe3+ and Cu2+ ions in water samples taking advantages from built-in masking zone. The μPAD was functionalized with a greenish-yellow fluorescent Zn-based metal-organic framework@tetracycline (FMOF-5@TC) nanocomposite, and the ratiometric design was based on the change in emission color from greenish yellow (FMOF-5@TC) to blue (FMOF-5). The μPAD consisted of one sample zone linked to two detection zones via two channels: the first channel was for the detection of both ions, while the second was intended for detecting only Cu2+ ions and comprised a built-in masking zone to remove Fe3+ ions prior to reaching the detection zone. The corresponding color changes were recorded with the aid of a smartphone and RGB calculations. The linear ranges were 0.1-80 μM for Cu2+ and 0.2-160 μM for Fe3+, with limits of detection of 0.027 and 0.019 μM, respectively. The simple μPAD design enabled the simultaneous detection of Cu2+ and Fe3+ ions in drinking water samples with excellent accuracy and precision, with spike recoveries of 81.28-96.36% and 83.01-102.33% for Cu2+ and Fe3+, respectively.

Fabrication of P and N Co-Doped Carbon Dots for Fe3+ Detection in Serum and Lysosomal Tracking in Living Cells

Doping with heteroatoms allows the retention of the general characteristics of carbon dots while allowing their physicochemical and photochemical properties to be effectively modulated. In this work, we report the preparation of ultrastable P and N co-doped carbon dots (PNCDs) that can be used for the highly selective detection of Fe³⁺ and the tracking of lysosomes in living cells. Fluorescent PNCDs were facilely prepared via a hydrothermal treatment of ethylenediamine and phytic acid, and they exhibited a high quantum yield of 22.0%. The strong coordination interaction between the phosphorus groups of PNCDs and Fe³⁺ rendered them efficient probes for use in selective Fe³⁺ detection, with a detection limit of 0.39 μM, and we demonstrated their practicability by accurately detecting the Fe³⁺ contents in bio-samples. At the same time, PNCDs exhibited high lysosomal location specificity in different cell lines due to surface lipophilic amino groups, and real-time tracking of the lysosome morphology in HeLa cells was achieved. The present work suggests that the fabrication of heteroatom-doped CDs might be an effective strategy to provide promising tools for cytology, such as organelle tracking.

A comprehensive review on multi-colored emissive carbon dots as fluorescent probes for the detection of pharmaceutical drugs in water

Exposure to constituent hazardous chemicals in medical products has become a threat to environmental health across the globe. Excessive medication and the mishandling of pharmaceutical drugs can lead to the increased presence of chemicals in the aquatic environment, causing water pollution. Only a few nanomaterials exist for the detection of these chemicals and they are limited in use due to their adverse toxicity, instability, cost, and low aqueous solubility. In contrast, carbon dots (C-dots), a member of the family of carbon-based nanomaterials, have various beneficial properties including excellent biocompatibility, strong photoluminescence, low photobleaching, tunable fluorescence, and easy surface modification. Herein, we summarize recent advancements in various synthetic strategies for high-quality tunable fluorescent C-dots. The root of fluorescence has been briefly explained via the quantum confinement effect, surface defects, and molecular fluorescence. The surface functional moieties of C-dots have been investigated in depth to recognize the various types of pharmaceutical drugs that are used for the treatment of patients. The modulation of C-dot fluorescence in the course of their interactions with these drugs has been carefully explained. Different types of interaction mechanisms behind the C-dot fluorescence alteration have been discussed. Finally, the challenges and future perspectives of C-dots have been proposed for the vibrant field development of C-dot-based drug sensors.

Facile Synthesis of Green Fluorescent Carbon Dots and Their Application to Fe3+ Detection in Aqueous Solutions

Carbon dots (CDs), a class of fluorescent nanomaterials, have attracted widespread attention from researchers. Because of their unique chemical properties, these high-quality fluorescent probes are widely used for ion and molecule detection. Excess intake of many ions or molecules can cause harm to the human body. Although iron (in the form of Fe3+ ions) is essential for the human body, excess iron in the human body can cause many diseases, such as iron poisoning. In this study, we have synthesized fluorine and nitrogen co-doped carbon dots (FNCDs) by a hydrothermal method. These FNCDs exhibited good stability, selectivity, and anti-interference ability for Fe3+. Fe3+ could be detected in the range of 0.2-300 μM, and their detection limit is up to 0.08 μM. In addition, the recovery and relative standard deviation measured by the standard addition recovery method were not higher than 107.5% and 1.1%, respectively, indicating that FNCDs have good recovery and accuracy for Fe3+ detection.

pH-induced highly sensitive fluorescence detection of urea and urease based on carbon dots-based nanohybrids

Carbon quantum dots (CDs) have become one of the most popular fluorescent materials due to their intriguing performance, which are favored by many fields. However, it is difficult to synthesize CDs with high quantum yield by the simple synthesis methods. In this paper, we fabricated CDs- silicon (SiO₂) spheres composites via a versatile hydrothermal route. The prepared BCD-SiO₂ composites exhibited an approximately 10-fold increase in the fluorescence intensity over that of BCDs. At the same time, the purification path was simplified by the facile separation of SiO₂ spheres. The prepared BCD-SiO₂ composites were used to fabricate a special sensing platform for the ultrasensitive detection of urea and urease, with detection limits of 1.67 μM and 0.002 mg/mL, respectively. Furthermore, this strategy was successfully applied to the detection of real samples. This result shows that as-prepared BCDs-SiO₂ composites are promising for broad application to biological analysis.

Sustainable and Green Synthesis of Waste-Biomass-Derived Carbon Dots for Parallel and Semi-Quantitative Visual Detection of Cr(VI) and Fe3

Carbon dot (CD)-based multi-mode sensing has drawn much attention owing to its wider application range and higher availability compared with single-mode sensing. Herein, a simple and green methodology to construct a CD-based dual-mode fluorescent sensor from the waste biomass of flowers of wintersweet (FW-CDs) for parallel and semi-quantitative visual detection of Cr(VI) and Fe3+ was firstly reported. The FW-CD fluorescent probe had a high sensitivity to Cr(VI) and Fe3+ with wide ranges of linearity from 0.1 to 60 µM and 0.05 to 100 µM along with low detection limits (LOD) of 0.07 µM and 0.15 µM, respectively. Accordingly, the FW-CD-based dual-mode sensor had an excellent parallel sensing capacity toward Cr(VI) and Fe3+ with high selectivity and strong anti-interference capability by co-using dual-functional integration and dual-masking strategies. The developed parallel sensing platform was successfully applied to Cr(VI) and Fe3+ quantitative detection in real samples with high precision and good recovery. More importantly, a novel FW-CD-based fluorescent hydrogel sensor was fabricated and first applied in the parallel and semi-quantitative visual detection of Cr(VI) and ferrous ions in industrial effluent and iron supplements, further demonstrating the significant advantage of parallel and visual sensing strategies.

Carbon dots: a novel platform for biomedical applications

Carbon dots (CDs) are a recently synthesised class of carbon-based nanostructures known as zero-dimensional (0D) nanomaterials, which have drawn a great deal of attention owing to their distinctive features, which encompass optical properties (e.g., photoluminescence), ease of passivation, low cost, simple synthetic route, accessibility of precursors and other properties. These newly synthesised nano-sized materials can replace traditional semiconductor quantum dots, which exhibit significant toxicity drawbacks and higher cost. It is demonstrated that their involvement in diverse areas of chemical and bio-sensing, bio-imaging, drug delivery, photocatalysis, electrocatalysis and light-emitting devices consider them as flawless and potential candidates for biomedical application. In this review, we provide a classification of CDs within their extended families, an overview of the different methods of CDs preparation, especially from natural sources, i.e., environmentally friendly and their unique photoluminescence properties, thoroughly describing the peculiar aspects of their applications in the biomedical field, where we think they will thrive as the next generation of quantum emitters. We believe that this review covers a niche that was not reviewed by other similar publications.

Simultaneous removal of heavy metal ions using carbon dots-doped hydrogel particles

Heavy metal ions (HMI) have attracted worldwide concern due to their serious environmental pollution which led to the risk of health conditions. From Red Malus floribunda fruits, nitrogen-doped carbon dots (N-CDs) were prepared, followed by hybrid-spherical shaped hydrogel particles (CGCDs) were prepared. The prepared CGCDs were utilized as adsorbents for HMI-(Hg(II), Cd(II), Pb(II), and Cr(III)) from water. N-CDs with about 4.0 nm in diameter were characterized by various techniques such as field emission-scanning electron microscopy (FE-SEM) and attenuated total reflection-fourier transform infrared spectroscopy (ATR-FTIR) that confirm the presence of nitrogen, oxygen, and carbon functionalities. The prepared spherical CGCDs were characterized very well before it was used as HMI adsorbents. The sizes of the CGCDs were ranges between 20 and 300 μm and the degree of swelling was calculated as 1320 %. ATR-FTIR and X-ray diffraction analyses reveal the presence of N-CDs in CGCDs. Further, FE-SEM confirms the spherical shape morphology of CGCDs. Three different concentrations of HMI solutions were 500 mg/L, 1000 mg/L, and 1500 mg/L. Hg(II) adsorbed proficiently by CGCDs in single metal ion systems with ~72 % and almost complete removal of Hg(II) ions (99 %) in multiple metal ion systems was observed. Moreover, all metal ions Hg(II), Cd(II), Pb(II), and Cr(III) were efficiently (>70 %) removed in multiple systems by CGCDs. After HMI adsorption experiments, the elemental mapping from FE-SEM and X-ray photoelectron spectroscopy studies conveys the presence of HMI on CGCDs. This suggests that CGCDs would be a suitable adsorbent for the simultaneous removal of multiple HMI from wastewater.

Carbon Dots: Synthesis, Properties and Applications

Carbon dots (CDs) are known as the rising star of carbon-based nanomaterials and, by virtue of their unique structure and fascinating properties, they have attracted considerable interest in different fields such as biological sensing, drug delivery, photodynamic therapy, photocatalysis, and solar cells in recent years. Particularly, the outstanding electronic and optical properties of the CDs have attracted increasing attention in biomedical and photocatalytic applications owing to their low toxicity, biocompatibility, excellent photostability, tunable fluorescence, outstanding efficient up-converted photoluminescence behavior, and photo-induced electron transfer ability. This article reviews recent progress on the synthesis routes and optical properties of CDs as well as biomedical and photocatalytic applications. Furthermore, we discuss an outlook on future and potential development of the CDs based biosensor, biological dye, biological vehicle, and photocatalysts in this booming research field.

Dual-excitation and dual-emission carbon dots for Fe3+ detection, temperature sensing, and lysosome targeting

Dual-excitation and dual-emission carbon dots (CDs) have been prepared by simple one-step hydrothermal treatment of p-phenylenediamine and 5-aminosalicylic acid. The as-prepared CDs emit bright green fluorescence under excitation at 320-400 nm and bright orange fluorescence under excitation at 490-560 nm. Interestingly, the CDs can be employed as a dual-excitation and dual-emission fluorescent probe for Fe³⁺ detection in aqueous solution and living cells. Furthermore, the obtained CDs can function as a promising dual-excitation and dual-emission temperature sensor. Additionally, the CDs can be utilized for lysosomal targeting.

Curauá-derived carbon dots: Fluorescent probes for effective Fe(III) ion detection, cellular labeling and bioimaging

This study reports the generation of curauá-derived carbon dots (C-dots) and their suitability for Fe(III) detection, bioimaging and FACS analysis. C-dots were generated from curauá (Ananas erectifolius) fibers by a facile one-step hydrothermal approach. They exhibited graphite-like structure with a mean diameter of 2.4 nm, high water solubility, high levels of carboxyl and hydroxyl functional groups, excitation-dependent multicolor fluorescence emission (in the range 450 nm - 560 nm) and superior photostability. C-dots were highly selective and effective for the detection of ferric Fe(III) ion in an aqueous medium with a detection limit of 0.77 μM in the linear range of 0-30 μM, a value much lower than the guideline limits proposed by the World Health Organization (WHO). In biological cell systems, C-dots were very well tolerated by B16F1 mouse melanoma and J774.A1 mouse macrophages cell lines, both of which effectively internalized C-dots in their cytoplasmic compartment. Finally, C-dots were effective probes for long-term live cell imaging experiments and multi-channel flow cytometry analysis. Collectively, our findings demonstrate that curauá-derived C-dots serve as versatile and effective natural products for Fe(III) ion sensing, labeling and bioimaging of various cell types. This study adds novel C-dots to the library of carbon-based probes and paves the way towards a sustainable conversion of a most abundant biomass waste into value-added products.

A Fluorescence Switching Sensor for Sensitive and Selective Detections of Cyanide and Ferricyanide Using Mercuric Cation-Graphene Quantum Dots

This study aims to use graphene quantum dots (GQDs) as a fluorescence switching sensor (turn on-off) for the simultaneous detection of cyanide (CN-) and ferricyanide [Fe(CN)6]3- in wastewater samples. The GQDs were synthesized by pyrolyzing solid citric acid. The intrinsic blue color of the solution was observed under ultraviolet irradiation. The fluorescence spectrum was maximized at both excitation and emission wavelengths of 370 and 460 nm, respectively. The fluorescence intensity of GQDs decorated with Hg2+ (turn-off mode as the starting baseline) could be selectively turned on in the presence of CN- and once back to turn-off mode by [Fe(CN)6]3-. The fluorescence switching properties were used to develop a fluorescence turn-on-off sensor that could be used to detect trace amounts of CN- and [Fe(CN)6]3- in water samples. For highly sensitive detection under optimum conditions (Britton-Robinson buffer solution in the pH range of 8.0-9.0, linearity ranges of 5.0-15.0 μM (R 2 = 0.9976) and 10.0-50.0 μM (R 2 = 0.9994), respectively, and detection limits of 3.10 and 9.48 μM, respectively), good recoveries in the ranges of 85.89-112.66% and 84.88-113.92% for CN- and [Fe(CN)6]3-, respectively, were recorded. The developed methods were successfully used for the simultaneous and selective detection of CN- and [Fe(CN)6]3- in wastewater samples obtained from local municipal water reservoirs.

Natural source of carbon dots from part of a plant and its applications: a review

Carbon dots (CDs) are carbon nanoparticles with a size of less than 10 nm, and are synthesized from various sources; they have been of great interest to scientists worldwide due to their unique optical, electrical, and chemical properties. Sources of carbon are inexpensive and can be classified as a renewable natural resources. Many researchers use CDs because of their low toxicity, better water solubility, high biocompatibility, and stable photoluminescence. The simple methods for producing CDs are hydrothermal and use inexpensive equipment, have low energy consumption, simple manipulation, and one-step preparation. Since the discovery of CDs, researchers have used them in various applications such as sensing, bioimaging, drug delivery, and catalysis. In this review, CDs synthesized from natural resources such as samples from herbs, roots, leaves, flowers, and fruit and some applications are described. This review provides a summary of carbon dots that is expected to provide further information for development of new CDs.

Tagetes erecta as an organic precursor: synthesis of highly fluorescent CQDs for the micromolar tracing of ferric ions in human blood serum

The present article illustrates the green synthesis of novel carbon quantum dots (CQDs) from biomass viz. Tagetes erecta (TE), and subsequently fabrication of a metal ion probe for the sensing of Fe³⁺ in real samples. TE-derived CQDs (TE-CQDs) have been synthesized by a facile, eco-friendly, bottom-up hydrothermal approach using TE as a carbon source. The successful synthesis and proper phase formation of the envisaged material has been confirmed by various characterization techniques (Raman, XRD, XPS, TEM, and EDS). Notably, the green synthesized TE-CQDs show biocompatibility, good solubility in aqueous media, and non-toxicity. The as-synthesized TE-CQDs show an intense photoluminescence peak at 425 nm and exhibit excitation dependent photoluminescence behavior. The proposed TE-CQD-based probe offers a remarkable fluorescence (FL) quenching for Fe³⁺ with high selectivity (K_q ∼ 10.022 × 10¹³ M⁻¹ s⁻¹) and a sensitive/rapid response in a linear concentration range 0–90 μM (regression coefficient R² ∼ 0.99) for the detection of Fe³⁺. The limit of detection (LOD) of the probe for Fe³⁺ has been found as 0.37 μM in the standard solution. It has further been applied for the detection of Fe³⁺ in real samples (human blood serum) and displays good performance with LOD ∼ 0.36 μM. The proposed TE-CQD-based ion sensing probe has potential prospects to be used effectively in biological studies and clinical diagnosis.

TE-CQDs synthesized via the hydrothermal method for the detection of Fe³⁺ in HBS.

Lysosome-targeted carbon dots for colorimetric and fluorescent dual mode detection of iron ion, in vitro and in vivo imaging

In this work, a colorimetric and fluorescent dual mode sensor based on lysosome-targeted CDs has been desirably implemented to identify Fe³⁺ fluctuations in vitro and in vivo. By simple one-pot hydrothermal carbonization of dried field mint, yellow-fluorescent CDs were directly fabricated without the assistance of other reagents and hold exceptional stability, superior biocompatibility as well as ultra-low cytotoxicity. Results indicated that as-prepared CDs can provide a rapid, reliable, and highly selective recognition of Fe³⁺ with a linear range of 0 μM-400 μM and a detection limit of 0.037 μM. Impressively, it was found that as-developed CDs can successfully target lysosome with high colocalization coefficient (0.85) and responds to fluctuations of Fe³⁺ in living cells. Further, acquired CDs was ingeniously devoted to Escherichia coli imaging. Besides, obtained CDs was eventually utilized to track the variation of Fe³⁺ in vivo system. A preliminary research expresses that as-synthesized CDs can function as an effective tool to detect Fe³⁺ in vitro and in vivo and thus indicates the promising applicability for disease detection in physiology and pathology in the future.

Green Sources Derived Carbon Dots for Multifaceted Applications

For the past decade, the Carbon dots (CDs) a tiny sized carbon nanomaterial are typically much attentive due to their outstanding properties. Nature is a fortune of exciting starting materials that provides many inexpensive and renewable resources which have received the topmost attention of researchers because of non-hazardous and eco-friendly nature that can be used to prepare green CDs by top-down and bottom-up synthesis including hydrothermal carbonization, microwave synthesis, and pyrolysis due to its simple synthetic process, speedy reactions and clear-cut end steps. Compared to chemically derived CDs, green CDs are varied by their properties such as less toxicity, high water dispersibility, superior biocompatibility, good photostability, bright fluorescence, and ease of modification. These nanomaterials are a promising material for sensor and biological fields, especially in electrochemical sensing of toxic and trace elements in ecosystems, metal sensing, diagnosis of diseases through bio-sensing, and detection of cancerous cells by in-vitro and in-vivo bio-imaging applications. In this review, the various synthetic routes, fluorescent mechanisms, and applications of CDs from discovery to the present are briefly discussed. Herein, the latest developments on the synthesis of CDs derived from green carbon materials and their promising applications in sensing, catalysis and bio-imaging were summarized. Moreover, some challenging problems, as well as upcoming perspectives of this powerful and tremendous material, are also discussed.

Fluorescence quenching mechanism and the application of green carbon nanodots in the detection of heavy metal ions: a review

This review article highlights the quenching mechanism and applications of green CNDs for the detection of metal ions.