Metal-enhanced fluorescence (MEF) effect based on silver nanoparticles with different UV spectra on a surface carbon dot-based novel dry platform

In this work, to enhance the fluorescence quantum yield of carbon dots (CDs), a novel metal-enhanced fluorescence (MEF) structure was designed by decorating CDs on silver nanoparticle (AgNPs) film. The glass slide-AgNPs (GS-AgNPs) structure was fabricated using the electrostatic adsorption method, and the AgNPs-CDs structures were prepared by the direct drying method, which then formed the GS-AgNPs-CDs composite structure. In this structure, the MEF effect was found to be size dependent by changing the 5 types of AgNPs with different sizes. And the MEF effect also decreased as the distance between the AgNPs and CDs increased by using polyvinylpyrrolidone (PVP) to separate the AgNPs and CDs. This hybrid structure can be used as a fluorescence detection platform and the recorded fluorescence intensity of GS-AgNPs 428 nm-CDs achieved a maximum enhancement factor (EF) of 31.72. Considering the high enhancement factor, this system may become promising to find potential applications in biochemical assay fields.

Ratiometric fluorescence and smartphone-assisted sensing platform based on dual-emission carbon dots for brilliant blue detection

In this study, an innovative ratiometric fluorescence and smartphone-assisted visual sensing platform based on blue-yellow dual-emission carbon dots (BY-CDs) was constructed for the first time to determine brilliant blue. The BY-CDs was synthesized via a facile one-step hydrothermal process involving propyl gallate and o-phenylenediamine. The synthesized BY-CDs exhibit favorable water solubility and exceptional fluorescence stability. Under excitation at 370 nm, BY-CDs show two distinguishable fluorescence emission bands (458 and 558 nm). Upon addition of brilliant blue, the fluorescence intensity at 558 nm exhibited a significant quenching effect attributed to fluorescence resonance energy transfer (FRET), while the fluorescence intensity at 458 nm was basically unchanged. The prepared BY-CDs can effectively serve as a ratiometric nanosensor for determining brilliant blue with the ratio of fluorescence intensities at 458 and 558 nm (F458/F558) as response signal. In addition, the developed ratiometric fluorescence sensor exhibits a noticeable alteration in color from yellow to green under UV light with a wavelength of 365 nm upon addition of varying concentrations of brilliant blue, which provides the possibility of visual detection of brilliant blue by a smartphone application. Finally, the BY-CDs based dual-mode sensing platform successfully detected brilliant blue in actual food samples and achieved a desirable recovery rate. This study highlights the merits of fast, convenient, economical, real-time, visual, high accuracy, excellent precision, good selectivity and high sensitivity for brilliant blue detection, and paves new paths for the monitoring of brilliant blue in real samples.

Hydrogen peroxide enhanced glow-type chemiluminescence of hydrazine hydrate modified carbon quantum dots-potassium persulfate system

Most known chemiluminescence (CL) systems are flash-type that generate weak luminescence and decline quickly after dozens of seconds, while the glow-type CL systems have stable emission for an extended period to achieve accurate quantitation. In this work, a long-term CL system based on hydrazine-hydrate (N2H4·H2O) modified carbon quantum dots (N-CQDs) as a luminescent probe, with K2S2O8 and H2O2 as co-reactants, was proposed. The CL emission enhanced by H2O2 increased 18-fold more than that of N-CQDs and K2S2O8 direct reaction, and decayed by 5% of the maximum intensity over 700 s. In the reaction system, K2S2O8 and H2O2 co-reactants can promote each other to continuously generate corresponding radicals (•OH, O2•-, 1O2), which in turn trigger the CL emission of N-CQDs. This phenomenon was identified as the primary cause for the production of persistent CL. In addition, a stable and selective CL sensor based on the N-CQDs-K2S2O8-H2O2 CL enhancing system was developed for ascorbic acid quantitation in the linear range from 0.1 to 10.0 mM with a detection limit of 0.036 mM. The method has been applied to the analysis of tablet samples and holds potential in pharmaceutical analysis field.

Rapid detection of Hg2+ in an ON-OFF-ON process using N doped carbon dots

Contamination of ground water with pollutants released from various anthropogenic activities is a major concern due to its adverse effects on the environment and human health. Rapid and efficient detection of such pollutants is the first step toward remediation of the problem. Herein we report a two-point fluorescence turn OFF-ON detection method for Hg2+ ions using nitrogen doped carbon dots (NCDs). The NCDs obtained through solvothermal treatment of ammonium citrate tribasic in DMF at 190 °C for four hours exhibited a quantum yield of 9.67%. Hg2+ detection is demonstrated in two steps, first the quenching of the fluorescence of NCDs by Hg2+ and second the fluorescence recovery upon addition of ascorbic acid from different sources. A rapid filter paper-based detection device is demonstrated based on the principles developed.

Fabrication of bio-inspired carbon nanodot-corn starch nanocomposite films via extrusion process for sustainable active food packaging applications

In this study, carbon nanodot (CD)-corn starch (CS) nanocomposite films are fabricated for active food packaging applications. First, ginkgo biloba leaves (GBL) were used as a biomass-derived carbon precursor, and a facile hydrothermal method was employed to synthesise environmentally sustainable CDs. The GBL-derived carbon nanodots (gCDs) were then characterised and incorporated into a CS matrix via an extrusion process to fabricate the CS/gCD nanocomposite film. The effects of various gCD concentrations on the physicochemical and functional properties of CS/gCD composite films were systematically investigated. The gCD exhibited non-cytotoxic effect against human colorectal adenocarcinoma cell line (Caco-2) cells when exposed up to 1000 μg/mL. The incorporation of gCDs into the CS film improved its mechanical properties, with the toughness of the CS/gCD2% nanocomposite film exhibiting 198 % superiority compared to the CS film. In addition, the oxygen barrier and UV-blocking properties were significantly improved. Furthermore, the CS/gCD nanocomposite film significantly extended the shelf life of ω-3 oils owing to the superior antioxidant activity of the gCDs, exhibiting only 9 meq/kg during the 15-day storage period. Our results suggest that the developed CS/gCD active composite film is a promising candidate for environmentally sustainable solutions to enhance food shelf life and reduce food waste.

The synergistic effect of adsorption and Fenton oxidation for organic pollutants in water remediation: an overview

Water pollution from industrial sources presents a significant environmental challenge due to the presence of recalcitrant organic contaminants. These pollutants threaten human health and necessitate effective remediation strategies. This article reviewed the synergistic application of adsorption and Fenton oxidation for water treatment. Adsorption, a common technique, concentrates pollutants onto a solid surface, but offers limited degradation. Fenton oxidation, an advanced oxidation process (AOP), utilizes hydroxyl radicals for efficient organic compound breakdown. When adsorption and Fenton oxidation combine, adsorption pre-concentrates pollutants, boosting Fenton oxidation effectiveness. This review delves into the mechanisms and advantages of this integrated approach, highlighting its potential for enhanced removal of organic contaminants. The discussion encompasses the mechanisms of Fenton oxidation and the synergistic effects it has with adsorption. Additionally, various support materials employed in this combined process are explored, including carbon-based supports (activated carbon, graphene, carbon nanotubes and biochar), metal-organic frameworks (MOFs), and clays. Finally, the applicability of this approach to diverse wastewater streams, such as medical and industrial wastewater, is addressed. The review contains 105 references and summarizes the key findings and future perspectives for this promising water remediation technology.

A "turn-on" fluorescence sensor for hydroquinone detection based on BSA doped carbon dots (BSA@CDs) from crawfish shells

By using crawfish shells as the precursor and hydrothermal synthesis, Bovine serum albumin doped carbon dots (BSA@CDs) were prepared without excessive chemical reagents. The relationship between the fluorescence properties of different BSA@CDs and BSA amount was investigated by variouscharacterization techniques. When the amount of BSA added was 30 %, the prepared BSA@CDs' quantum yield (QY) reached 25.01 %, which was the highest. Inner Filter Effect (IFE) suggested that Cr (VI) can selectively quench the fluorescence of BSA@CDs. Cr (VI) can be reduced to Cr (III) by Hydroquinone (HQ), thus recovering the fluorescence. Accordingly, using BSA@CDs as a probe, a "turn-on" fluorescence sensor applied in HQ determination was constructed. The linear range was 10-200 µmol/L and limit of detection (LOD) was 0.18 µmol/L. Further, it has been employed to the determination of HQ in both crawfish tail meat and aquaculture water with good performance.

g-C3N4-Based Photocatalytic Materials for Converting CO2 Into Energy: A Review

Environmental pollution management and renewable energy development are humanity's biggest issues in the 21st century. The rise in atmospheric CO2, which has surpassed 400 parts per million, has stimulated research on CO2 reduction and conversion methods. Presently, photocatalytic conversion of CO2 to valuable hydrocarbons enables the transformation of solar energy into chemical energy and offers a novel avenue for energy conversion while regulating the greenhouse effect. This is an ideal strategy for simultaneously addressing environmental issues and the energy crisis. Photocatalysts are essential to photocatalytic processes. Photocatalyst is the core of photocatalytic technology, and graphite carbon nitride (g-C3N4) has attracted much attention because of its nonmetallic characteristics, and it has the characteristics of low cost, tunable electronic structure, easy manufacture and strong reducibility. However, its activity is not only affected by external reaction conditions, but also by the band gap structure, physical and chemical stability, surface morphology and specific surface area of the photocatalyst it. In this paper, the application progress of g-C3N4-based photocatalytic materials in CO2 reduction is reviewed, and the modification strategies of g-C3N4-based catalysts to obtain better catalytic efficiency and selectivity in CO2 photocatalytic reduction are summarized, and the future development of this material is prospected.

Carbon quantum dots for the diagnosis and treatment of ophthalmic diseases

Carbon quantum dots (CQDs), an emerging nanomaterial, are gaining attention in ophthalmological applications due to their distinctive physical, chemical, and biological characteristics. For example, their inherent fluorescent capabilities offer a novel and promising alternative to conventional fluorescent dyes for ocular disease diagnostics. Furthermore, because of the excellent biocompatibility and minimal cytotoxicity, CQDs are well-suited for therapeutic applications. In addition, functionalized CQDs can effectively deliver drugs to the posterior part of the eyeball to inhibit neovascularization. This review details the use of CQDs in the management of ophthalmic diseases, including various retinal diseases, and ocular infections. While still in its initial phases within ophthalmology, the significant potential of CQDs for diagnosing and treating eye conditions is evident.

Photochromic Carbon Nanomaterials: An Emerging Class of Light-Driven Hybrid Functional Materials

Photochromic molecules have remarkable potential in memory and optical devices, as well as in driving and manipulating molecular motors or actuators and many other systems using light. When photochromic molecules are introduced into carbon nanomaterials (CNMs), the resulting hybrids provide unique advantages and create new functions that can be employed in specific applications and devices. This review highlights the recent developments in diverse photochromic CNMs. Photochromic molecules and CNMs are also introduced. The fundamentals of different photochromic CNMs are discussed, including design principles and the types of interactions between CNMs and photochromic molecules via covalent interactions and non-covalent bonding such as π-π stacking, amphiphilic, electrostatic, and hydrogen bonding. Then the properties of photochromic CNMs, e.g., in photopatterning, fluorescence modulation, actuation, and photoinduced surface-relief gratings, and their applications in energy storage (solar thermal fuels, photothermal batteries, and supercapacitors), nanoelectronics (transistors, molecular junctions, photo-switchable conductance, and photoinduced electron transfer), sensors, and bioimaging are highlighted. Finally, an outlook on the challenges and opportunities in the future of photochromic CNMs is presented. This review discusses a vibrant interdisciplinary research field and is expected to stimulate further developments in nanoscience, advanced nanotechnology, intelligently responsive materials, and devices.

Preparation and Application of a Sulfur-Doped Fluorescent Carbon Dots with Aggregation-Induced Emission Character

As a new type of zero-dimensional nanomaterial, carbon dots are widely applied in various fields. However, most of the carbon dots have aggregation fluorescence quenching properties, which limited their practical applications. In this study, a novel sulfur-doped carbon dots (S-CDs) was prepared by solvothermal method. The properties of the S-CDs in ethanol solution and in solid state were investigated respectively. The results showed that the S-CDs have an excited wavelength dependent emission of blue fluorescence in ethanol solution, and have orange fluorescence emission in solid state and composite films, indicating the prepared S-CDs has aggregation-induced emission (AIE) performance. The main reason was that the presence of S-S bonds and the intramolecular rotation of aromatic rings were limited in solid state, resulting in its emission of orange fluorescence. Furthermore, the S-CDs could be applied to identify fingerprints, anti-counterfeiting.

Facile synthesis of carbon dots via pyrolysis and their application in photocatalytic degradation of rhodamine B (RhB)

Carbon Quantum dot (CQDs) is one of the newest materials in carbon-based nanomaterials. It is pertinent to study the synthesis and the application of these carbon dots. Here we have studied the effect of precursor on the optical, morphological, and photocatalytic properties of CQDs. We have synthesized CQDs using pyrolysis method using the precursors citric acid, urea, polyethyleneimine. We have synthesized two samples: CQD-S1; synthesized using urea and polyethyleneimine, and CQD-S2; synthesized using citric acid and polyethyleneimine. In optical properties study two distinct peaks have been obtained at 243 nm and 345 nm for CQD-S1, and at 265 nm and 335 nm for CQD-S2. In fluorescence study, the maximum emission was found at excitation wavelength of 340 nm for CQD-S1 and at excitation wavelength of 350 nm for CQD-S2. In morphological studies, Transmission Electron Microscope (TEM) revealed particle size of sample CQD-S1 and CQD-S2 were 1.91 nm and 1.61 nm, respectively. EDX confirmed the elemental composition in both samples. The rhodamine B (RhB) dye degradation percentages in dark and under visible and UV light were found to 6, 13, and 98.4% respectively for CQD-S1. Similarly, dye degradation for CQD-S2 were 7, 11, and 99.63%, respectively. Effective degradation of photocatalysis performed under UV-light within 100 min using mineralization process.

Biocidal polymer derived near white light-emitting polymeric carbon particles for antibacterial and bioimaging applications

A growing antimicrobial crisis has increased demand for antimicrobial materials. It has become increasingly popular to convert polymeric macromolecules into polymeric carbon particles (PCP) in order to achieve highly biocompatible materials with unique properties as a result of the ability to synthesize nanomaterials of the right size and add value to existing stable polymers. This work presents the tuning of PCP for antibacterial application by combining a biocidal polymer with one-pot solvothermal synthesis. PCP displayed broad-spectrum antibacterial activity via various mechanisms, including inhibition of bacterial cell walls, ROS generation, and antibiotic resistance. Furthermore, these biocidal PCP were observed to show excitation-independent near-white light emission which on the other hand is generally possible due to mixed sizes, doping, and surface effects. As opposed to the parent biocidal polymer, PCP added ROS-mediated bactericidal activity, increased cytocompatibility, and nanofibers with anti-adhesive effects and potential of imaging bacterial cells.

Green synthesis of biomass-derived carbon quantum dots for photocatalytic degradation of methylene blue

Water pollution, significantly influenced by the discharge of synthetic dyes from industries, such as textiles, poses a persistent global threat to human health. Among these dyes, methylene blue, particularly prevalent in the textile sector, exacerbates this issue. This study introduces an innovative approach to mitigate water pollution through the synthesis of nanomaterials using biomass-derived carbon quantum dots (CQDs) from grape pomace and watermelon peel. Utilizing the hydrothermal method at temperatures between 80 and 160 °C over periods ranging from 1 to 24 h, CQDs were successfully synthesized. A comprehensive characterization of the CQDs was performed using UV-visible spectroscopy, Fourier-transform infrared spectroscopy, dynamic light scattering, Raman spectroscopy, and luminescence spectroscopy, confirming their high quality. The photocatalytic activity of the CQDs in degrading methylene blue was evaluated under both sunlight and incandescent light irradiation, with measurements taken at 20 min intervals over a 2 h period. The CQDs, with sizes ranging from 1-10 nm, demonstrated notable optical properties, including upconversion and down-conversion luminescence. The results revealed effective photocatalytic degradation of methylene blue under sunlight, highlighting the potential for scalable production of these cost-effective catalytic nanomaterials for synthetic dye degradation.

Recent Progress of Fluorescent Carbon Dots and Graphene Quantum Dots for Biosensors: Synthesis of Solution Methods and their Medical Applications

In the fields of health and biology, fluorescent nanomaterials have emerged as highly potential and very useful candidates for use in biosensor applications. These typical highly powerful nanomaterials are carbon dots (CDs) and graphene quantum dots (GQDs) among many other metallic nanomaterials. In the context of medical biosensors, this review article investigates the techniques of synthesis, and many uses of these nanomaterials, the obstacles that they face, and the potential for their future. We cover the significance of fluorescent nanomaterials, their use in the medical field, as well as the several techniques of synthesis for CDs and GQDs, including ultrasonication, hydrothermal, electrochemical method, surface modification, and solvothermal. In addition, we also discuss their biomedical applications, which include biomolecule detection, disease diagnosis and examine the obstacles and prospective possibilities for development of ultra-bright, ultra-sensitive, and selective biosensors for use in in-vivo research.Fluorescent carbon dots and graphene quantum dots is synthesized by using several types of raw material and methods. These Carbon dots and graphene quantum dots are used in the medical field includes detection of biomaterials, detection of cancer, virus and mutation in DNA.

Green synthesis of yeast cell wall-derived carbon quantum dots with multiple biological activities

Hypothesis

Yeast cell walls are a sustainable biomass source containing carbon and other elements like phosphorus. Converting cell walls into valuable nanomaterials like carbon quantum dots (CQDs) is of interest.

Experiments

Cell walls from Saccharomyces cerevisiae were hydrothermally treated in 0.5 M H2SO4 to produce CQDs. Multiple analytical techniques were utilized to confirm phosphorus-doping (P-CQDs), characterize the fluorescence properties, determine quantum yield, and evaluate the sensing, antimicrobial, photocatalytic, and antioxidant capacities.

Findings

A successful synthesis of P-CQDs was achieved with strong blue fluorescence under UV excitation, 19 % quantum yield, and excellent stability. The P-CQDs showed sensitive fluorescence quenching in response to ferric ions with a 201 nM detection limit. Antibacterial effects against Escherichia coli and Staphylococcus aureus were demonstrated. P-CQDs also exhibited dye degradation under sunlight and antioxidant activity. So, the prepared P-CQDs displayed promising multifunctional capabilities for metal ion detection, disinfection, and environmental remediation. Further research is required to fully realize and implement the multifunctional potential of P-CQDs in real-world applications.

Non-enzymatic biosensor based on F,S-doped carbon dots/copper nanoarchitecture applied in the simultaneous electrochemical determination of NADH, dopamine, and uric acid in plasma

This work presents the synthesis and characterization of an innovative F,S-doped carbon dots/CuONPs hybrid nanostructure obtained by a direct mixture between F,S-doped carbon dots obtained electrochemically and copper nitrate alcoholic solution. The hybrid nanostructures synthesized were characterized by absorption spectroscopy in the Ultraviolet region (UV-vis), high-resolution transmission electron microscopy (HRTEM), X-ray photoelectron spectroscopy (XPS), and different electrochemical techniques. The fluoride and sulfur-doped carbon dots/CuONPs nanostructures were used to prepare a non-enzymatic biosensor on a printed carbon electrode, exhibiting excellent electrocatalytic activity for the simultaneous determination of NADH, dopamine, and uric acid in the presence of ascorbic acid with a detection limit of 20, 80, and 400 nmol L-1, respectively. The non-enzymatic biosensors were also used to determine NADH, dopamine, and uric acid in plasma, and they did not suffer significant interference from each other.

Carbon dots combined with phytosphingosine inhibit acid-induced demineralization of hydroxyapatite in vitro

OBJECTIVES

To study the effects of carbon dots (CDs), in combination with phytosphingosine (PHS), against acid-induced demineralization of hydroxyapatite in vitro.

METHODS

CDs were generated from citric acid and urea by microwave heating. Transmission electron microscope (TEM), FT-IR, and fluorescence intensity were used to characterize the CDs. A hydroxyapatite (HAp) model was used to investigate the protective effects of CDs, PHS, and their combinations with and without a salivary pellicle against acid-induced demineralization in vitro. Ca2+ release as a parameter to evaluate the inhibition of demineralization was measured by capillary electrophoresis. The interactions between CDs, PHS, and HAp discs were investigated using a fluorescence detector.

RESULTS

Uniform-sized CDs were synthesized, showing typical optical characteristics. CDs exhibited no inhibition of acid-induced demineralization in vitro, in contrast to PHS. Notably, a pre-coating of CDs increased the protective effects of PHS against acid-induced demineralization, which was not disturbed by the presence of a salivary pellicle and Tween 20. Scanning electron microscope (SEM) confirmed the binding and layers formed of both CDs and PHS to the HAp surfaces. Based on fluorescence spectra CDs binding to HAp seemed to be dependent on Ca2+ and PO43- interactions.

CONCLUSIONS

CDs combined with PHS showed protective effects against acid-induced demineralization of HAp discs in vitro.

Carbon Nanomaterial Fluorescent Probes and Their Biological Applications

Fluorescent carbon nanomaterials have broadly useful chemical and photophysical attributes that are conducive to applications in biology. In this review, we focus on materials whose photophysics allow for the use of these materials in biomedical and environmental applications, with emphasis on imaging, biosensing, and cargo delivery. The review focuses primarily on graphitic carbon nanomaterials including graphene and its derivatives, carbon nanotubes, as well as carbon dots and carbon nanohoops. Recent advances in and future prospects of these fields are discussed at depth, and where appropriate, references to reviews pertaining to older literature are provided.

Recent Advances in Nanomaterials for the Treatment of Acute Kidney Injury

Acute kidney injury (AKI) is a serious clinical syndrome with high morbidity, elevated mortality, and poor prognosis, commonly considered a "sword of Damocles" for hospitalized patients, especially those in intensive care units. Oxidative stress, inflammation, and apoptosis, caused by the excessive production of reactive oxygen species (ROS), play a key role in AKI progression. Hence, the investigation of effective and safe antioxidants and inflammatory regulators to scavenge overexpressed ROS and regulate excessive inflammation has become a promising therapeutic option. However, the unique physiological structure and complex pathological alterations in the kidneys render traditional therapies ineffective, impeding the residence and efficacy of most antioxidant and anti-inflammatory small molecule drugs within the renal milieu. Recently, nanotherapeutic interventions have emerged as a promising and prospective strategy for AKI, overcoming traditional treatment dilemmas through alterations in size, shape, charge, and surface modifications. This Review succinctly summarizes the latest advancements in nanotherapeutic approaches for AKI, encompassing nanozymes, ROS scavenger nanomaterials, MSC-EVs, and nanomaterials loaded with antioxidants and inflammatory regulator. Following this, strategies aimed at enhancing biocompatibility and kidney targeting are introduced. Furthermore, a brief discussion on the current challenges and future prospects in this research field is presented, providing a comprehensive overview of the evolving landscape of nanotherapeutic interventions for AKI.

Green Synthesis of Carbon Quantum dots Derived from Lycium barbarum for Effective Fluorescence Detection of Cr (VI) Sensing

Green and economical self-doped nitrogen-containing fluorescent carbon quantum dots (N-CQDs) were synthesized using a one-pot hydrothermal treatment method. The optical and structural properties of the N-CQDs were investigated in detail by UV-vis and fluorescence spectroscopy, X-ray diffraction (XRD) techniques, transmission electron microscopy (TEM), and high-resolution transmission electron microscopy (HRTEM). Fourier transform infrared spectroscopy (FT-IR), X-ray photoelectron spectroscopy (XPS) spectroscopy, and elemental analysis illustrate the surface function and composition of N-CQDs. N-CQDs emit a broad fluorescence between365 ̴ 465 nm and fluoresce most strongly at the excitation wavelength of 415 nm. Meanwhile, Cr (VI) could significantly burst the fluorescence intensity of N-CQDs. N-CQDs showed an excellent sensitivity and selectivity to Cr (VI), which exhibited good linearity in the range of 0 ̴ 40 µmol/L with a detection limit of 0.16 µmol/L. In addition, the mechanism of Fluorescence quenching of N-CQDs by Cr (VI) was investigated. This work well provides a research idea for the preparation of green carbon quantum dots from biomass and their use for the detection of metal ions.

Himalayan lichen biomass for green synthesis of silver nanocolloids: growth kinetics, effect of pH and metal sensing

Lichen is one of the most abundant non-vascular biomasses; however, a systematic study on the application of biomass in nanomaterial synthesis is very limited. In this study, an aqueous lichen extract was obtained from Hypotrachyna cirrhata, one of the most abundant Himalayan lichen biomasses, using a simple cold percolation method. The effects of extract-to-silver nitrate mixing ratio, pH and waiting time on the growth and stability of nanoparticles were systematically explored. The rate constant for bio-reduction was found to be 5.3 × 10-3 min-1. Transmission electron microscopy showed a narrow particle size distribution with a mean particle size of 11.1 ± 3.6 nm (n = 200). The X-ray diffraction and selected area electron diffraction techniques confirmed the formation of cubic crystals. The synthesized colloidal solution showed excellent response to Hg2+ and Cu2+ ions in spiked water samples. The limit of detection and calibration sensitivity for Hg2+ and Cu2+ ions were found to be 1 and 5 mg l-1 and 2.9 × 10-3 and 1.6 × 10-3 units ppm-1, respectively. These findings suggested that spherical silver nanoparticles with a narrow particle size distribution can be synthesized on a laboratory scale using an aqueous H. cirrhata lichen extract, and the colloidal solution can be used for the detection of selected heavy metals in water samples.

A ratiometric fluorescence amine sensor based on carbon quantum dot-loaded electrospun polyvinylidene fluoride film for visual monitoring of food freshness

A ratiometric fluorescence sensor based on dual-emission carbon quantum dots (CQD) was developed to real time monitor food spoilage. Two hydrophobic electrospun fluorescent films were developed using polyvinylidene fluoride (PVDF) as the film-forming polymer in combination with CQD as the fluorescent probe. The CQD/PVDF film and CQD@PVDF film enabled the analysis of TMA with limits of detection (LODs) of 1.04 μM and 2.1 μM, respectively, and they exhibited excellent stability at 4 °C. By these virtues, the CQD@PVDF film exhibited visible fluorescence color changes from yellow green to blue by real time and nondestructively sensing volatile amines generated from beef, pork and shrimp in a packaging system with high humidity. This strategy provided a simple but useful, non-destructive, robust, and platform to real time monitor food spoilage for intelligent food packaging.

Neglected negative effect of carbon quantum dots (CQDs) entering the ocean on marine organisms living in different water layers

Carbon quantum dots (CQDs) are well dispersed in water, but their potential risks in the marine environment have not been described. This study characterized CQDs and investigated their biological effects (including growth, photosynthesis and behavioural changes) in three marine organisms living in different water layers (the surface phytoplankton Phaeodactylum tricornutum and zooplankton Artemia salina and the benthic coral Zoanthus sp. at the bottom). The results showed that over 78 % of CQDs were suspended in seawater after 96 h. The biomass and photosynthesis of P. tricornutum were significantly affected, with a maximum reduction of 89.49 % in algal cells. CQDs accumulated in the intestinal tract of A. salina, reducing grazing and filtration rates by up to 71.88 % and 89.46 %, respectively. In contrast, CQD exposure had irreversible effects on the tentacle expansion behaviour of Zoanthus sp. This study helps clarify the environmental effects and ecological risks associated with the release of CQDs into the ocean.

Structural Features of Carbon Dots and Their Agricultural Potential

Carbon dots (CDs) have drawn attention due to their enticing physical, chemical, and surface properties. Besides, good conductivity, low toxicity, environmental friendliness, simple synthetic routes, and comparable optical properties are advantageous features of CDs. Further, recently, CDs have been explored for biological systems, including plants. Among biological systems, only plants form the basis for sustainability and life on Earth. In this Review, we reviewed suitable properties and applications of CDs, such as promoting the growth of agricultural plants, disease resistance, stress tolerance, and target transportation. Summing up the available studies, we believe that the applications of CDs are yet to be explored significantly for innovation and technology-based agriculture.

A Ratiometric Biosensor Containing Manganese Dioxide Nanosheets and Nitrogen-Doped Quantum Dots for 2,4-Dichlorophenoxyacetic Acid Monitoring

Nanomaterials are desirable for sensing applications. Therefore, MnO2 nanosheets and nitrogen-doped carbon dots (NCDs) were used to construct a ratiometric biosensor for quantification of 2,4-dichlorophenoxyacetic acid. The MnO2 nanosheets drove the oxidation of colorless o-phenylenediamine to OPDox, which exhibits fluorescence emission peaks at 556 nm. The fluorescence of OPDox was efficiently quenched and the NCDs were recovered as the ascorbic acid produced by the hydrolyzed alkaline phosphatase (ALP) substrate increased. Owing to the selective inhibition of ALP activity by 2,4-D and the inner filter effect, the fluorescence intensity of the NCDs at 430 nm was suppressed, whereas that at 556 nm was maintained. The fluorescence intensity ratio was used for quantitative detection. The linear equation was F = 0.138 + 3.863·C 2,4-D (correlation coefficient R2 = 0.9904), whereas the limits of detection (LOD) and quantification (LOQ) were 0.013 and 0.040 μg/mL. The method was successfully employed for the determination of 2,4-D in different vegetables with recoveries of 79%~105%. The fluorescent color change in the 2,4-D sensing system can also be captured by a smartphone to achieve colorimetric detection by homemade portable test kit.

A highly sensitive fluorescence nanosensor for determination of amikacin antibiotics using composites of carbon quantum dots and gold nanoparticles

Amikacin is an aminoglycoside antibiotic widely used to treat various bacterial infections in humans. However, elevated concentrations of amikacin can damage the cochlear nerve. Thus, accurate and rapid amikacin detection is crucial. In this study, we developed an "on-off" fluorescence nanosensor for highly sensitive amikacin determination based on a composite of carbon quantum dots (CQDs) and gold nanoparticles (AuNPs). The method quenches CQD fluorescence (turn-off) when they bind to AuNPs but restores it (turn-on) when amikacin binds and releases the CQDs. Adding Cu2+ enhances sensitivity by cross-linking amikacin-coated AuNPs. Under optimal conditions (pH 4, 1 mM Na2SO4, 1 mM CuSO4), the method achieved a low detection limit of 3.5 × 10-11 M (0.02 ppb), a wide linear range (10-10 to 10-8 M), high precision (RSD < 5 %), and a rapid 2-minute response time. Exceptional selectivity was observed over other antibiotics. The CQDs/AuNPs-based sensor successfully detected amikacin in pharmaceutical and surface water samples. This approach offers a fast on-site analytical method for amikacin detection, with potential applications in clinical and environmental settings.

Green, facial zinc doped hydrothermal synthesis of cinnamon derived fluorescent carbon dots (Zn-Cn-CDs) for highly selective and sensitive Cr6+ and Mn7+ metal ion sensing application

Carbon dots have demonstrated a great potential as luminescent nanoparticles in energy, drug delivery, sensors, and various biomedical applications as well as environmental pollutants and water analysis. Although, such nanoparticles appear to exhibit low toxicity compared to other semiconductor and metal based luminescent nanomaterials. Today, we know that toxicity of carbon dots (CDs) strongly depends on the protocol of fabrication. The various dopants or heteroatoms have been used to enhance the optical and physicochemical properties. In this work, zinc doped aqueous fluorescent Zn-Cn-CDs have been synthesized from cinnamon by hydrothermal synthesis method. The synthesized Zn-Cn-CDs were confirmed for their physicochemical properties by using various characterization techniques viz. UV-Vis. and spectrofluorometer for optical properties, Fourier transform infrared spectroscopy (FTIR) and XRD, as well as TEM and XPS, was done for morphological and chemical analysis. The successfully synthesized Zn-Cn-CDs showed outstanding optical performance for metal ion sensing applications. The developed heteroatom doped Zn-Cn-CDs as a fluorescent probe exhibited higher selectivity and sensitivity for Cr6+ and Mn7+ metal ions. The obtained results showed a better linear range with excellent limit of detection (LOD) 3.97 µg/mL and 2.05 µg/mL for Cr6+ and Mn7+ metal ions respectively. The low cost, simple and highly fluorescent probe can be effectively applicable for development of environmental pollutants sensing purposes.

Nanoscale Hotspot-Induced Emitters in DNA Origami-Assisted Nanoantennas

We report the observation of hotspot-induced emitters and photoluminescence enhancement of up to 42-fold from DNA origami-assisted plasmonic dimer nanoantennas upon excess polarized laser illumination. The presence of DNA and laser polarization alignment along the dimer axis are critical for the generation of bright emitters responsible for the observed PL increase. The emission spectrum reveals characteristic Raman peaks of amorphous carbon, suggesting the formation of carbon-based emitters in the nanoantenna due to the plasmonic hotspots at the longitudinal antenna resonance.

Bandgap tailoring and enhancing the aromatization in cysteine-based carbon dots

Cysteine, as a non-aromatic precursor, was used to produce Nitrogen (N) and Sulfur (S) sources for preparing N, S-doped carbon dots (CDs) with tunable luminescence emission. Despite the tremendous investigations, the photoluminescence (PL) mechanism of CDs is still unclear due to its complex core-shell structure, variety of surface functional groups, and structure dependency. This study focuses on controlling aromatization and graphitization processes during the hydrothermal synthesis on CDs by using Citric Acid (CA) and Ammonium persulfate. Detailed characterizations by FTIR spectroscopy, XPS, and HR-TEM are provided to suggest both chemical and bandgap structures. Results reveal that the red-shift of PL occurred due to the graphitization and increasing content of graphitic nitrogen in the core, as well as the Pyridinic and Amine groups creating sub-bands on the surface. These findings resolve the controversy on the PL mechanism of Cysteine-based CDs and provide a general guide for increasing the aromatization and graphitization degree from non-aromatic precursors which clarify the mechanism exploration and structural analysis of other types of CDs.

Properties of Carbon Dots versus Small Molecules from "Bottom-up" Synthesis

A major challenge in the "bottom-up" solvothermal synthesis of carbon dots (CDs) is the removal of small-molecule byproducts, noncarbonized polyamides, or other impurities that confound the optical properties. In previously reported benzene diamine-based CDs, the observed fluorescence signal already has been shown to arise from free small molecules, not from nanosized carbonized dots. Here we have unambiguously identified the small-molecule species in the synthesis of CDs starting with several isomers of benzene diamine by directly matching their NMR, mass spectrometry, and optical data with commercially available small organic molecules. By combining dialysis and chromatography, we have sufficiently purified the CD reaction mixtures to measure the CD size by TEM and STM, elemental composition, optical absorption and emission, and single-particle blinking dynamics. The results can be rationalized by electronic structure calculations on small model CDs. Our results conclusively show that the purified benzene diamine-based CDs do not emit red fluorescence, so the quest for full-spectrum fluorescence from isomers of a single precursor molecule remains open.

Colorimetric and fluorescence dual-mode pH sensor based on nitrogen-doped carbon dots and its diverse applications

A dual-mode pH sensor based on nitrogen-doped carbon dots (N-CDs) with the source of o-phenylenediamine and tryptophan has been constructed. Under the stimulation of pH, the N-CDs exhibited prominent both color and fluorescence changes, leading to the rarely discovered colorimetric and fluorescent dual-readouts for the evaluation of pH. The mathematic relationship was established between pH and fluorescence intensity of N-CDs, and between pH and the UV-Vis absorbance ratio at 630 nm and 488 nm of N-CDs, respectively, over a quite broad pH range of 2.2 to 12.0. Multiple techniques are used to explore the dual-mode pH-responsive mechanism, and the preliminary explanation is put forward. The experimental results show that the N-CDs have visualized pH sensing applicability for actual samples, including various water samples and HeLa cell. Furthermore, the N-CD ink is developed for successful information encryption and anti-counterfeiting. This work might provide valuable insights into the sensing mechanism of CDs, and the application potential of CDs in broader fields.

Revealing the Adverse Impact of Additive Carbon Material on Microorganisms and Its Implications for Biogas Yields: A Critical Review

Biochar could be a brilliant additive supporting the anaerobic fermentation process. However, it should be taken into account that in some cases it could also be harmful to microorganisms responsible for biogas production. The negative impact of carbon materials could be a result of an overdose of biochar, high biochar pH, increased arsenic mobility in the methane fermentation solution caused by the carbon material, and low porosity of some carbon materials for microorganisms. Moreover, when biochar is affected by an anaerobic digest solution, it could reduce the biodiversity of microorganisms. The purpose of the article is not to reject the idea of biochar additives to increase the efficiency of biogas production, but to draw attention to the properties and ways of adding these materials that could reduce biogas production. These findings have practical relevance for organizations seeking to implement such systems in industrial or local-scale biogas plants and provide valuable insights for future research. Needless to say, this study will also support the implementation of biogas technologies and waste management in implementing the idea of a circular economy, further emphasizing the significance of the research.

Gelatin Carbon Dots Interaction with Nitrosyl Ruthenium Complex: Fluorescence Quenching and Chemiluminescence Mechanisms

Carbon dots (CDs) exhibit luminescence, biocompatibility, and higher water solubility. This material has been developed for biological applications, specifically in bioimaging. In this work, the gelatin carbon dots (CDg) was obtained from commercial gelatin using a hydrothermal method in domestic microwave, and the suppression fluorescent mechanism were enhanced by the addition of the [RuII(bdq)(NO)(tpy)]3+ (Rubdq-NO+) complex ion. After purification through a dialysis bag, the resulting CDs (CDg) exhibit fluorescent emission at 400 nm and maintained fluorescence stability in an aqueous solution (pH = 7) for 30 days under 5 ◦C. Fluorescence quenching studies revealed an electrostatic interaction between the negative charge from CDg (δ =  - 20 mV) and the positively charged nitrosyl (NO+) ligand of the ruthenium complex (Rubdq-NO+), resulting in quenching of the CDg fluorescence due to the inner filter effects (IFE). The chemiluminescence reaction of CDg and Rubdq-NO-CDg in presence of norepinephrine (NOR) were evaluated. NOR in PBS are liable to undergo spontaneous oxidation to quinone form (NOR-quinone). CDg are believed interact with NOR-quinone and an electron transfer occur obtained CDg+ accompanied to green emission fluorescence (520 nm). While for Rubdq-NO-CDg in presence of NOR, the green emission occurs accompanied by NO0 release using DAF-2 probe.

Carbon dots and their interactions with recognition molecules for enhanced nucleic acid detection

Carbon Dots (C-dots) have exceptional fluorescence and incident wavelength alteration capabilities because of their π-π* electron transitions between the surface-trapped charges. They have clear, considerate and cost-effective applications in the domain of bio-sensing, optical imaging, medical diagnostics, fluorescence chemotherapy, forensics, and environmentology. Advances in the production process of C-dots can change their optical and chemical characteristics, allowing them to interact with a variety of chemicals and ions that can be exploited for the DNA detection in point-of-care devices. In the current scenario of pathogenic disease prevention, metagenomics and industrial processes, alternative genetic material identification is critical. This review focuses on the existing carbon dots-based DNA detection technologies and their interactions with other components such as metallic salts, dyes, and biological chemicals based on their surface charge distribution (positive or negative) employed in the DNA diagnostic devices and biosensors with their operating mechanism regarding their target component. These intriguing scientific discoveries and technologies will be extensively examined to translate them into real-world solutions which will have a significant societal and economic impact on overall well-being and innovation.

Carbon Nanomaterial-Based Hydrogels as Scaffolds in Tissue Engineering: A Comprehensive Review

Carbon-based nanomaterials (CBNs) are a category of nanomaterials with various systems based on combinations of sp2 and sp3 hybridized carbon bonds, morphologies, and functional groups. CBNs can exhibit distinguished properties such as high mechanical strength, chemical stability, high electrical conductivity, and biocompatibility. These desirable physicochemical properties have triggered their uses in many fields, including biomedical applications. In this review, we specifically focus on applying CBNs as scaffolds in tissue engineering, a therapeutic approach whereby CBNs can act for the regeneration or replacement of damaged tissue. Here, an overview of the structures and properties of different CBNs will first be provided. We will then discuss state-of-the-art advancements of CBNs and hydrogels as scaffolds for regenerating various types of human tissues. Finally, a perspective of future potentials and challenges in this field will be presented. Since this is a very rapidly growing field, we expect that this review will promote interdisciplinary efforts in developing effective tissue regeneration scaffolds for clinical applications.

Assessment of biomass-derived carbon dots as highly sensitive and selective templates for the sensing of hazardous ions

Access to safe drinking water and a hygienic living environment are the basic necessities that encourage healthy living. However, the presence of various pollutants (especially toxic heavy metal ions) at high concentrations in water renders water unfit for drinking and domestic use. The presence of high concentrations of heavy-metal ions (e.g., Pb2+, Hg2+, Cr6+, Cd2+, or Cu2+) greater than their permissible limits adversely affects human health, and increases the risk of cancer of the kidneys, liver, skin, and central nervous system. Therefore, their detection in water is crucial. Due to the various benefits of "green"-synthesized carbon-dots (C-dots) over other materials, these materials are potential candidates for sensing of toxic heavy-metal ions in water sources. C-dots are very small carbon-based nanomaterials that show chemical stability, magnificent biocompatibility, excitation wavelength-dependent photoluminescence (PL), water solubility, simple preparation strategies, photoinduced electron transfer, and the opportunity for functionalization. A new family of C-dots called "carbon quantum dots" (CQDs) are fluorescent zero-dimensional carbon nanoparticles of size < 10 nm. The green synthesis of C-dots has numerous advantages over conventional chemical routes, such as utilization of inexpensive and non-poisonous materials, straightforward operations, rapid reactions, and renewable precursors. Natural sources, such as biomass and biomass wastes, are broadly accepted as green precursors for fabricating C-dots because these sources are economical, ecological, and readily/extensively accessible. Two main methods are available for C-dots production: top-down and bottom-up. Herein, this review article discusses the recent advancements in the green fabrication of C-dots: photostability; surface structure and functionalization; potential applications for the sensing of hazardous anions and toxic heavy-metal ions; binding of toxic ions with C-dots; probable mechanistic routes of PL-based sensing of toxic heavy-metal ions. The green production of C-dots and their promising applications in the sensing of hazardous ions discussed herein provides deep insights into the safety of human health and the environment. Nonetheless, this review article provides a resource for the conversion of low-value biomass and biomass waste into valuable materials (i.e., C-dots) for promising sensing applications.

Using 19F NMR to Investigate Cationic Carbon Dot Association with Per- and Polyfluoroalkyl Substances (PFAS)

There is much concern about per- and polyfluoroalkyl substances (PFAS) based on their environmental persistence and toxicity, resulting in an urgent need for remediation technologies. This study focused on determining if nanoscale polymeric carbon dots are a viable sorbent material for PFAS and developing fluorine nuclear magnetic resonance spectroscopy (19F NMR) methods to probe interactions between carbon dots and PFAS at the molecular scale. Positively charged carbon dots (PEI-CDs) were synthesized using branched polyethyleneimine to target anionic PFAS by promoting electrostatic interactions. PEI-CDs were exposed to perfluorooctanoic acid (PFOA) to assess their potential as a PFAS sorbent material. After exposure to PFOA, the average size of the PEI-CDs increased (1.6 ± 0.5 to 7.8 ± 1.8 nm) and the surface charge decreased (+38.6 ± 1.1 to +26.4 ± 0.8 mV), both of which are consistent with contaminant sorption. 19F NMR methods were developed to gain further insight into PEI-CD affinity toward PFAS without any complex sample preparation. Changes in PFOA peak intensity and chemical shift were monitored at various PEI-CD concentrations to establish binding curves and determine the chemical exchange regime. 19F NMR spectral analysis indicates slow-intermediate chemical exchange between PFOA and CDs, demonstrating a high-affinity interaction. The α-fluorine had the greatest change in chemical shift and highest affinity, suggesting electrostatic interactions are the dominant sorption mechanism. PEI-CDs demonstrated affinity for a wide range of analytes when exposed to a mixture of 24-PFAS, with a slight preference toward perfluoroalkyl sulfonates. Overall, this study shows that PEI-CDs are an effective PFAS sorbent material and establishes 19F NMR as a suitable method to screen for novel sorbent materials and elucidate interaction mechanisms.

Boosting Plant Photosynthesis with Carbon Dots: A Critical Review of Performance and Prospects

Artificially augmented photosynthesis in nano-bionic plants requires tunable nano-antenna structures with physiochemical and optoelectronic properties, as well as unique light conversion capabilities. The use of nanomaterials to promote light capture across photosystems, primarily by carbon dots, has shown promising results in enhancing photosynthesis through tunable uptake, translocation, and biocompatibility. Carbon dots possess the ability to perform both down and up-light conversions, making them effective light promoters for harnessing solar energy beyond visible light wavelengths.This review presents and discusses the recent progress in fabrication, chemistry, and morphology, as well as other properties such as photoluminescence and energy conversion efficiency of nano-antennas based on carbon dots. The performance of artificially boosted photosynthesis is discussed and then correlated with the conversion properties of carbon dots and how they are applied to plant models. The challenges related to the nanomaterial delivery and the performance evaluation practices in modified photosystems, consideration of the reliability of this approach, and the potential avenues for performance improvements through other types of nano-antennas based on alternative nanomaterials are also critically evaluated. It is anticipated that this review will stimulate more high-quality research in plant nano-bionics and provide avenues to enhance photosynthesis for future agricultural applications.

Dual metal ion (Fe3+ and As3+) sensing and cell bioimaging using fluorescent carbon quantum dots synthesised from Cynodon dactylon

In this study, water dispersible fluorescent carbon quantum dot (CQD) has been synthesised, having an average size of 8.6 ± 0.4 nm using Cynodon dactylon (CD) following microwave assisted green synthetic one-step method. As-prepared CQD fluoresces strongly at 444 nm having a quantum yield of 1% in water when excited at 350 nm. This fluorescence of CQD is sensitive toward As3+ and Fe3+ metal ions. These CQD are utilized for dual metal ion fluorescence sensing; turn-on fluorescence sensing for As3+ and turn-off fluorescence sensing for Fe3+ ions. Limit of detection for As3+ and Fe3+ ions has been found to be 19 nM and 0.10 μM respectively, which is the lowest value reported for As3+ without any functionalization. The adsorption kinetics of As3+ and Fe3+ ions on CQD have been examined using pseudo-first-order-kinetic model revealing that physical adsorption is dominant over chemical processes in this work. For 0.41 g/L and 1.90 g/L dose of CQD, the equilibrium adsorption capacity was found to be 1.57 × 10-6 mg/g, 2.91 × 10-7 mg/g, and 1.01 × 10-5 mg/g, 1.69 × 10-6 mg/g respectively for As3+ and Fe3+ ions. Despite having low quantum yield in water, as-prepared CQD showed low cytotoxicity and good tolerance against photodegradation of biological cells at concentrations lower than 62.5 μg/mL and when the cells are illuminated up to 12 h. Owing to this, the synthesised CQD have been utilized as fluorescent probes for in itro cell imaging.

Multicolor Photoluminescent Carbon Dots à La Carte for Biomedical Applications

Dual-emission fluorescence probes that provide high sensitivity are key for biomedical diagnostic applications. Nontoxic carbon dots (CDs) are an emerging alternative to traditional fluorescent probes; however, robust and reproducible synthetic strategies are still needed to access materials with controlled emission profiles and improved fluorescence quantum yields (FQYs). Herein, we report a practical and general synthetic strategy to access dual-emission CDs with FQYs as high as 0.67 and green/blue, yellow/blue, or red/blue excitation-dependent emission profiles using common starting materials such as citric acid, cysteine, and co-dopants to bias the synthetic pathway. Structural and physicochemical analysis using nuclear magnetic resonance, absorbance and fluorescence spectroscopy, Fourier-transform infrared spectroscopy, and X-ray photoelectron spectroscopy in addition to transmission electron and atomic force microscopy (TEM and AFM) is used to elucidate the material's composition which is responsible for the unique observed photoluminescence properties. Moreover, the utility of the probes is demonstrated in the clinical setting by the synthesis of green/blue emitting antibody-CD conjugates which are used for the immunohistochemical staining of human brain tissues of glioblastoma patients, showing detection under two different emission channels.

Synthesis, properties and mechanism of carbon dots-based nano-antibacterial materials

Antibiotics play an important role in the treatment of diseases, but bacterial resistance caused by their widespread and unreasonable use has become an urgent problem in clinical treatment. With the rapid advancement of nanoscience and nanotechnology, the development of nanomedicine has been transformed into a new approach to the problem of bacterial resistance. As a new type of carbon-based nanomaterial, carbon dots (CDs) have attracted the interest of antibacterial researchers due to their ease of preparation, amphiphilicity, facile surface functionalization, and excellent optical properties, among other properties. This article reviewed the synthesis methods and properties of various CDs and their composites in order to highlight the advancements in the field of CDs-based antibacterial agents. Then we focused on the relationship between the principal properties of CDs and the antibacterial mechanism, including the following: (1) the physical damage caused by the small size, amphiphilicity, and surface charge of CDs. (2) Photogenerated electron transfer characteristics of CDs that produce reactive oxygen species (ROS) in themselves or in other compounds. The ability of ROS to oxidize can lead to the lipid peroxidation of cell membranes, as well as damage proteins and DNA. (3) The nano-enzyme properties of CDs can catalyze reactions that generate ROS. (4) Synergistic antibacterial effect of CDs and antibiotics or other nanocomposites. Finally, we look forward to the challenges that CDs-based nanocomposites face in practical antibacterial applications and propose corresponding solutions to further expand the application potential of nanomaterials in the treatment of infectious diseases, particularly drug-resistant bacterial infections.

EGTA-Derived Carbon Dots with Bone-Targeting Ability: Target-Oriented Synthesis and Calcium Affinity

The bone-targeting mechanism of clinic bisphosphonate-type drugs, such as alendronate, risedronate, and ibandronate, relies on chelated calcium ions on the surface of the bone mineralized matrix for the treatment of osteoporosis. EGTA with aminocarboxyl chelating ligands can specifically chelate calcium ions. Inspired by the bone-targeting mechanism of bisphosphonates, we hypothesize that EGTA-derived carbon dots (EGTA-CDs) hold bone-targeting ability. For the target-oriented synthesis of EGTA-CDs and to endow CDs with bone targeting, we designed calcium ion chelating agents as precursors, including aminocarboxyl chelating agents (EGTA and EDTA) and bisphosphonate agents (ALN and HEDP) for the target-oriented synthesis of aminocarboxyl-derived CDs (EGTA-CDs and EDTA-CDs) and bisphosphonate-derived CDs (ALN-CDs and HEDP-CDs) with high synthetic yield. The synthetic yield of EGTA-CDs reached 87.6%. Aminocarboxyl-derived CDs and bisphosphonate-derived CDs retain the chelation ability of calcium ions and can specifically bind calcium ions. The chemical environment bone-targeting value coordination constant K and chelation sites of EGTA-CDs were 6.48 × 104 M-1 and 4.12, respectively. A novel method was established to demonstrate the bone-targeting capability of chelate-functionalized carbon dots using fluorescence quenching in a simulated bone trauma microenvironment. EGTA-CDs exhibit superior bone-targeting ability compared with other aminocarboxyl-derived CDs and bisphosphonate-derived CDs. EGTA-CDs display exceptional specificity toward calcium ions and better bone affinity than ALN-CDs, suggesting their potential as novel bone-targeting drugs. EGTA-CDs with strong calcium ion chelating ability have calcium ion affinity in simulated body fluid and bone-targeting ability in a simulated bone trauma microenvironment. These findings offer new avenues for the development of advanced bone-targeting strategies.

Current trends in the detection and removal of heavy metal ions using functional materials

The shortage of freshwater resources caused by heavy metal pollution is an acute global issue, which has a great impact on environmental protection and human health. Therefore, the exploitation of new strategies for designing and synthesizing green, efficient, and economical materials for the detection and removal of heavy metal ions is crucial. Among the various methods for the detection and removal of heavy ions, advanced functional systems including nanomaterials, polymers, porous materials, and biomaterials have attracted considerable attention over the past several years due to their capabilities of real-time detection, excellent removal efficiency, anti-interference, quick response, high selectivity, and low limit of detection. In this tutorial review, we review the general design principles underlying the aforementioned functional materials, and in particular highlight the fundamental mechanisms and specific examples of detecting and removing heavy metal ions. Additionally, the methods which enhance water purification quality using these functional materials have been reviewed, also current challenges and opportunities in this exciting field have been highlighted, including the fabrication, subsequent treatment, and potential future applications of such functional materials. We envision that this tutorial review will provide invaluable guidance for the design of functional materials tailored towards the detection and removal of heavy metals, thereby expediting the development of high-performance materials and fostering the development of more efficient approaches to water pollution remediation.

Red emitting carbon dots: surface modifications and bioapplications

Quantum dots (QDs), and carbon quantum dots (CDs) in particular, have received significant attention for their special characteristics. These particles, on the scale of several nanometers, are often produced using simple and green methods, with naturally occurring organic precursors. In addition to facile production methods, CDs present advantageous applications in the field of medicine, primarily for bioimaging, antibacterial and therapeutics. Also, CDs present great potential for surface modification through methods like doping or material mixing during synthesis. However, the bulk of current literature focuses on CDs emitting in the blue wavelengths which are not very suitable for biological applications. Red emitting CDs are therefore of additional interest due to their brightness, photostability, novelty and deeper tissue penetration. In this review article, red CDs, their methods of production, and their biological applications for translational research are explored in depth, with emphasis on the effects of surface modifications and doping.

Microwave-assisted one-step synthesis of water-soluble manganese-carbon nanodot clusters

Using metal coordination to assemble carbon nanodots (CND) into clusters can enhance their photophysical properties for applications in sensing and biomedicine. Water-soluble clusters of CNDs are prepared by one-step microwave synthesis starting from ethylenediaminetetraacetic acid, ethylenediamine and MnCl2·4H2O as precursors. Transmission electron microscopy and powder X-Ray diffraction techniques indicate that the resulting clusters form spherical particles of 150 nm constituted by amorphous CNDs joined together with Mn ions in a laminar crystalline structure. The nanomaterial assemblies show remarkable fluorescence quantum yields (0.17-0.20) and magnetic resonance imaging capability (r1 = 2.3-3.8 mM-1.s-1). In addition, they can be stabilized in aqueous solutions by phosphate ligands, providing a promising dual imaging platform for use in biological systems.

Fabrication of FRET based nano sensor from biomass-derived fluorescent carbon quantum dots and naphthalimide for ratiometric detection of nitric oxide: To examine nitrite levels in meat samples

Nitric oxide (NO) is a ubiquitous, gaseous, free radical signaling molecule which plays a key role in physiological and pathological processes. Literature reports revealed that the conventional methods such as colorimetry, electron paramagnetic resonance (EPR), electrochemical etc. to detect NO are costly, time consuming and lack resolution, particularly in aqueous or biological system. Thus, in this context, herein we have developed covalently linked biomass derived carbon quantum dots (CQDs) and naphthalimide based nano sensor system for FRET based ratiometric detection of nitric oxide (NO) in pure aqueous media. The CQDs derived from orange peels were characterized using UV-visible absorption, fluorescence spectroscopy, PXRD, TEM, FT-IR and zeta potential studies. Further, the obtained CQDs were functionalized with amine functionality, and subsequently linked with naphthalimide derivative (5) using terephthaldehyde through covalent bond formation. The conjugation of naphthalimide (5) and functionalized CQDs was studied using DLS, zeta potential, FT-IR and time resolved fluorescence spectroscopy. The excitation of developed nano sensor system at λ_ex 360 nm results in fluorescence emission at λ_em 530 nm which establishes the FRET pair between the CQDs and naphthalimide unit. However, in the presence of NO, the observed FRET pair abolishes due to the cleavage of NO susceptible imine bond. The developed sensor demonstrates high selectivity towards NO with limit of detection (LOD) and limit of quantification (LOQ) of 15 nM and 50 nM respectively. Further, the developed sensor system was also utilized for indirect detection of nitrite (NO₂^-) in food samples for food safety and monitoring.

Highly Efficient Messenger RNA Transfection of Hard-to-Transfect Cells using Carbon Nanodots

Although messenger RNA (mRNA)-based therapeutics opened up new avenues for treating various diseases, intracellular delivery of mRNA is still challenging, especially to hard-to-transfect cells. For successful mRNA therapy, the development of a delivery vehicle that can effectively transport mRNA into cells is essential. In this study, we synthesized carbon nanodots (CNDs) as an efficient mRNA delivery vehicle via a one-step microwave-assisted method. CNDs easily formed complexes with mRNA molecules by electrostatic interactions, and the gene delivery performance of CNDs was highly effective in hard-to-transfect cells. Considering their outstanding transfection ability, CNDs are expected to be further applied for mRNA-based cellular engineering.

Synthesis, properties and potential applications of photoluminescent carbon nanoparticles: A review

Photoluminescent-carbon nanoparticles (PL-CNPs) are a new class of materials that received immense interest among researchers due to their distinct characteristics, including photoluminescence, high surface-to-volume ratio, low cost, ease of synthesis, high quantum yield, and biocompatibility. By exploiting these outstanding properties, many studies have been reported on its utility as sensors, photocatalysts, probes for bio-imaging, and optoelectronics applications. From clinical applications to point-of-care test devices, drug loading to tracking of drug delivery, and other research innovations demonstrated PL-CNPs as an emerging material that could substitute conventional approaches. However, some of the PL-CNPs have poor PL properties and selectivity due to the presence of impurities (e.g., molecular fluorophores) and unfavourable surface charges by the passivation molecules, which impede their applications in many fields. To address these issues, many researchers have been paying great attention to developing new PL-CNPs with different composite combinations to achieve high PL properties and selectivity. Herein, we thoroughly discussed the recent development of various synthetic strategies employed to prepare PL-CNPs, doping effects, photostability, biocompatibility, and applications in sensing, bioimaging, and drug delivery fields. Moreover, the review discussed the limitations, future direction, and perspectives of PL-CNPs in possible potential applications.

Design and development of molten metal nanomaterials using sonochemistry for multiple applications

Molten metals have prospective applications as soft fluids with unique physical and chemical properties, yet materials based on them are still in their infancy and have great potential. Ultrasonic irradiation of molten metals in liquid media induces acoustic cavitation and dispersion of the liquid metal into micrometric and nanometric spheres. This review focuses on the synthesis of mmetallic materials via sonochemistry from molten metals with low melting point (< 420 ᴼC): Ga, Hg, In, Sn, Bi, Pb, and Zn, which can be melted in organic or inorganic media or water and of aqueous solutions of metallic ions to form two immiscible liquid phases. Organic molecule entrapment, polymer solubilization, chiral imprinting, and catalyst incorporation within metals or metallic particles were recently developed to provide novel hybrid nanomaterials for several applications including catalysis, fuel cells, and biomass-to-biofuel conversion. In all cases where molten metal was sonicated in an organic solvent, in addition to a solid precipitant, an interesting supernatant was obtained that contained metal-doped carbon dots (M@C-dots). Some of these M@C-dots were found to exhibit highly effective antimicrobial activity, promote neuronal tissue growth, or have utility in lithium-ion rechargeable batteries. The economic feasibility and commercial scalability of molten metal sonochemistry attract fundamental interest in the reaction mechanisms, as the versatility and controllability of the structure and material properties invite exploration of various applications.