Multifunctional Carbon Quantum Dots Research Articles

Adoption of self-exothermic reaction for synthesis of multifunctional carbon quantum dots: Applications to vincristine sensing and cell imaging

This work introduces an extremely easy method for preparing luminescent carbon dots (CDs) at ambient temperature using 1,2-naphthoquinone sulphonate and ethylenediamine as precursors via self-exothermic reaction without energy input. The as-obtained CDs have a high quantum yield (34.1 %), a production yield of 21.2 %, and a small size diameter (3.44 nm). Various techniques (NMR, TEM, EDX-mapping, XPS, XRD, FT-IR, fluorescence, and UV–visible spectroscopy) were used to characterize the prepared CDs. The CDs exhibited an excitation-independent emission with λex of 275 nm, demonstrating their homogeneity and high purity. The anticancer drug vincristine (VCR) quantitively quenched the fluorescent signal of the synthesized CDs, allowing their application as the first fluorescent nano-sensor to determine VCR. The quenching effect was linear within the range of 0.2–5.0 μg mL−1, enabling the determination of VCR in vials, plasma, and for content uniformity testing with a detection limit of 0.06 μg mL−1. Moreover, the synthesized CDs were employed as a bio-sensing platform to detect VCR in cancer cells owing to their good selectivity, excellent biocompatibility, minimal cytotoxicity, and high stability. The fabrication of CDs with excellent properties at room temperature under mild conditions paves the way for new advancements in the room temperature synthesis of CDs and offers a highly efficient alternative to traditional synthesis approaches.

Multifunctional nitrogen-sulfur codoped carbon quantum dots: Determining reduced glutathione, broad-spectrum antibacterial activity, and cell imaging

In this study, nitrogen-sulfur codoped carbon quantum dots (N-S/CQDs) with various functions and properties were synthesized through a one-step method utilizing citric acid and cysteine as reaction substrates. The fluorescence of N-S/CQDs can be specifically quenched by permanganate ion (MnO4−), and the quenched fluorescence can be recovered by the presence of reduced glutathione (GSH). A fluorescence sensing system based on N-S/CQDs@MnO4− was developed and successfully applied for the determination of GSH in pharmaceutical preparations. Additionally, N-S/CQDs demonstrated broad-spectrum antibacterial activity, with minimum inhibitory concentrations of 32 μg/ml against Staphylococcus aureus (gram-positive bacterium) and 64 μg/ml against Escherichia coli (gram-negative bacterium). N-S/CQDs also proved effective for cell imaging, exhibiting excellent biocompatibility. These findings underscore the multifunctional characteristics and promising application potential of N-S/CQDs. Furthermore, this study provides a solid foundation for the development of multifunctional carbon quantum dots and the expansion of their applications in various fields.

Carbon Quantum Dot-Functionalized Dermis-Derived Transparent Electronic Skin for Multimodal Human Motion Signal Monitoring and Construction of Self-Powered Triboelectric Nanogenerator.

Electronic skin (e-skin) is considered as a highly promising interface for human-computer interaction systems and wearable electronic devices. Through elaborate design and assembly of various materials, it possesses multiple characteristics similar to human skin, including remarkable flexibility, stretchability, sensitivity to temperature and humidity, biocompatibility, and efficient interfacial ion/electron transport capabilities. Here, we innovatively integrate multifunctional carbon quantum dots (CQDs), which exhibit conductivity, antibacterial properties, ultraviolet absorption, and fluorescence emission, with poly(acrylic acid) and glycerin (Gly) into a three-dimensional network structure of natural goatskin collagen fibers. Through a top-down design strategy enhanced by hydrogen bond reconstruction, we successfully fabricated a novel transparent e-skin (PAC-eSkin). This e-skin exhibited significant tensile properties (4.94 MPa of tensile strength and 263.42% of a maximum breaking elongation), while also possessing Young's modulus similar to human skin (2.32 MPa). It is noteworthy that the functionalized CQDs used was derived from discarded goat hair, and the addition of Gly gave PAC-eSkin excellent antifreezing and moisturizing properties. Due to the presence of ultrasmall CQDs, which creates efficient ion/electron transport channels within PAC-eSkin, it could rapidly sense human motion and physiological signals (with a gauge factor (GF) of 1.88). Furthermore, PAC-eSkin had the potential to replace traditional electrode patches for real-time monitoring of electrocardiogram, electromyogram, and electrooculogram signals, with a higher SNR (signal-to-noise ratio) of 25.1 dB. Additionally, the customizable size and shape of PAC-eSkin offer vast possibilities for the construction of single-electrode triboelectric nanogenerator systems. We have reason to believe that the design and development of this transparent e-skin based on CQDs-functionalized dermal collagen matrices can pave a new way for innovations in human-computer interaction interfaces and their sensing application in diverse scenarios.

A multifunctional carbon quantum dot overcoming the BBB for modulating amyloid aggregation and scavenging reactive oxygen species

The abnormal aggregation of β-amyloid (Aβ), the accumulation of reactive oxygen species (ROS), and the presence of the blood-brain barrier (BBB) cause the prevention and treatment of Alzheimer's disease (AD) extremely difficult. In this study, we report multifunctional carbon quantum dots (CQDs) with red emission (RCQDs) for targeting Aβ42, modulating Aβ42 aggregation, overcoming the BBB, and scavenging ROS. RCQDs demonstrate exceptional targeting affinity for Aβ42 species, and exhibit high inhibition and disaggregation efficiencies against Aβ42 aggregates. Moreover, RCQDs possess outstanding scavenging abilities against the ROS in cells, thus resulting in the mitigation of cellular oxidative damages. RCQDs also exhibited strong penetration through the BBB in both in vitro and in vivo models, highlighting their potential for brain-targeted treatment. Further investigations using primary microglial cells confirm the anti-neuroinflammation properties of RCQDs. This study unprecedently demonstrates the therapeutic potential of unmodified pure CQDs for overcoming the BBB, targeting Aβ42 species, modulating Aβ42 aggregation and scavenging ROS, offering a promising candidate for the treatment of AD.

Multifunctional carbon quantum dots decorated self-healing hydrogel for highly effective treatment of superbug infected wounds

Rapid healing of wounds infected by bacteria, especially multidrug-resistant bacteria, is a common clinical challenge. Local bacterial infection causes excessive reactive oxygen species (ROS) that further induce oxidative stress and inflammatory responses, which impairs cell migration, angiogenesis and delays cutaneous regeneration. Herein, we designed a novel type of carbon quantum dots (CQDs) derived from herbal medicines. The CQDs are able to against gram-positive bacteria including methicillin-resistant Staphylococcus aureus (MRSA), and possessed SOD-like as well as CAT-like activities for scavenging ROS. The biocompatible CQDs could protect HUVECs migration and angiogenesis from oxidative stress damage. Moreover, the expression of NO and pro-inflammatory cytokines (TNF-α and IL-6) of LPS-induced macrophages could be downregulated by the CQDs. Besides, the self-healing hydrogel decorated with multifunctional CQDs were prepared via the reaction between OSA and CMCS through Schiff base linkage for better wound management. The CQDs/hydrogel could continuously eliminate bacteria and scavenge ROS to modulate the complex oxidative stress microenvironment. The results of animal experiments demonstrated that the CQDs/hydrogel exerted the effects of eliminating MRSA, anti-inflammation, and promoting angiogenesis, which was manifested in enhancing wound healing, epithelial regeneration and collagen disposition. Therefore, the CQDs/hydrogel is excellent candidate for MRSA-infected skin wound healing.

Multifunctional Carbon Quantum Dots: Iron Clearance and Antioxidation for Neuroprotection in Intracerebral Hemorrhage Mice.

Iron overload and oxidative stress are pivotal in the pathogenesis of brain injury secondary to intracerebral hemorrhage (ICH). There is a compelling need for agents that can chelate iron and scavenge free radicals, particularly those that demonstrate substantial brain penetration, to mitigate ICH-related damage. In this study, we have engineered an amine-functionalized aspirin-derived carbon quantum dot (NACQD) with a nominal diameter of 6-13 nm. The NACQD possesses robust iron-binding and antioxidative capacities. Through intrathecal administration, NACQD therapy substantially reduced iron deposition and oxidative stress in brain tissue, alleviated meningeal inflammatory responses, and improved the recovery of neurological function in a murine ICH model. As a proof of concept, the intrathecal injection of NACQD is a promising therapeutic strategy to ameliorate the ICH injury.

Bioresource-derived multifunctional carbon quantum dots as a fluorescence and electrochemical sensing platform for picric acid and noncytotoxic food storage application

This work deals with the synthesis of facile, water-soluble, and blue-emitting carbon quantum dots (CQDs) from Plumbago indica leaves by a hydrothermal method with a quantum yield of 16 %. The biomass Plumbago indica leaves exhibit several advances such as easy availability, cost-effectiveness, non-toxic, green source, and not requiring any sophisticated techniques to develop the sensor. The optical, morphological, structural, and compositional properties of the CQDs were confirmed by various characterization methods. As a fluorescent probe, CQDs exhibited good linear response to picric acid (PA) with a limit of detection (LOD) of 18 nM. The sensing mechanism involves a combination of static quenching and fluorescence resonance energy transfer (FRET). In the electrochemical sensing method, the differential pulse voltammetric (DPV) technique was performed using a CQD-modified gold electrode with a LOD of 0.35 nM for PA. Using fresh carrots as a model sample, the antioxidant activity of PVA, CQD, and a PVA-CQD mixture was qualitatively determined. The in vitro cytotoxicity analysis of CQDs by MTT assay using the L6 cell line confirmed its non-toxic behaviour. This work is noteworthy because it offers a new attempt to identify toxic PA from biomass-derived precursor material and finds future applications in the food industry.

A Dual‐Function Carbon Quantum Dot Fluorescent Probe for the Detection of Fe3+ and Sunset Yellow

AbstractThere are few researches on the application of multifunctional carbon quantum dots (CQDs) in analysis and detection. In this study, carbon quantum dots (CQDs) with dual‐function detection were synthesized by the one‐step hydrothermal method with citric acid as the carbon source and o‐phenylendiamine as the nitrogen source to detect Fe3+ and sunset yellow. The morphology of the prepared CQDs and the surface functional groups were characterized using TEM, FTIR, XPS, UV‐Vis spectroscopy, and fluorescence spectrophotometer. The results show that the morphology of CQDs is nearly spherical and well dispersed, with a particle size range of 1.24∼6 nm and the average particle size was 3.23 nm. The surface of the CQDs has hydrophilic groups, such as OH, −COOH and −NH2. CQDs exhibited good acid and alkali resistance, salt resistance, and photobleaching resistance under different conditions. The detection limits of CQDs for Fe3+ and sunset yellow were 1.52 μM and 0.812 μM, respectively. The recoveries of actual samples were 96.65 %∼104.85 % and 95.4 %∼104.55 %, with relative standard deviations (RSDs) of less than 6 %. Therefore, CQDs can be employed as dual‐function fluorescent probes in the practical detection of samples and have promising application prospects.

Green synthesis of multifunctional carbon quantum dots: An approach in cancer theranostics.

Carbon quantum dots (CQDs) have gained significant growing attention in the recent past due to their peculiar characteristics including smaller size, high surface area, photoluminescence, chemical stability, facile synthesis and functionalization possibilities. They are carbon nanostructures having less than 10nm size with fluorescent properties. In recent years, the scientific community is curiously adopting biomass precursors for the preparation of CQDs over the chemical compounds. These biomass sources are sustainable, eco-friendly, inexpensive, widely available and convert waste into valuable materials. Hence in our work the fundamental understating of diverse fabrication methodologies of CQDs, and the types of raw materials employed in recent times, are all examined and correlated comprehensively. Their unique combination of remarkable properties, together with the ease with which they can be fabricated, makes CQDs as promising materials for applications in diverse biomedical fields, in particular for bio-imaging, targeted drug delivery and phototherapy for cancer treatment. The mechanism for luminescence is of considerable significance for leading the synthesis of CQDs with tunable fluorescence emission. Therefore, it is aimed to explore and provide an updated review on (i) the recent progress on the different synthesis methods of biomass-derived CQDs, (ii) the contribution of surface states or functional groups on the luminescence origin and (iii) its potential application for cancer theranostics, concentrating on their fluorescence properties. Finally, we explored the challenges in modification for the synthesis of CQDs from biomass derivatives and the future scope of CQDs in phototherapy for cancer theranostics.

Microwave-assisted green synthesis of multi-functional carbon quantum dots as efficient fluorescence sensor for ultra-trace level monitoring of ammonia in environmental water

This study reports a facile green preparation of self-assembled multi-functional carbon quantum dots (CQDs) via direct pyrolysis technique coupled with microwave-assisted synthesis using Ziziphus Mauritiana stone biomass (as a bio-resource precursor). The synthesized multi-functional CQDs was characterized using FT-IR, XRD, XPS, TEM, and fluorescence spectroscopy techniques. The results exhibit that the prepared CQDs are spherical-shaped with an average diameter of 2–4 nm and showed bright bluish-green emissions property with stable dispersion and high photostability in the aqueous medium. Furthermore, the emission properties of CQDs were examined by quenched with ammonia (NH3) and other molecules in aqueous media. Results indicated that the developed CQDs showed effective fluorescent for the selective and sensitive detection (sensor) of NH3 with a detection limit of 10 nM. Thus, the presented procedure is a simple, low-cost, efficient, chemical-free synthesis of CQDs and can be applied as selective and sensitive (sensor) monitoring of NH3 concentration in aquatic environmental samples.

Multifunctional carbon quantum dots as a theranostic nanomedicine for fluorescence imaging-guided glutathione depletion to improve chemodynamic therapy

To minimize unwanted reactions with high concentrations of reduced glutathione (GSH) in the tumor microenvironment (TME) during chemodynamic therapy (CDT), a simple and effective strategy was developed to fabricate a TME stimuli-responsive theranostic nanomedicine (Fe-CD) for fluorescence imaging-guided GSH depletion and cancer therapy by combining fluorescent imaging carbon dots (CD) and Fe(III). Introducing Fe(III) into Fe-CD not only quenched the fluorescence of CD while reacting with and consuming intracellular GSH for fluorescence imaging of the depletion of GSH but also provided a source of metal ions to generate more abundant hydroxyl radicals (•OH) with hydrogen peroxide (H2O2) through the Fenton reaction to improve CDT. Fe-CD showed promising •OH generation under H2O2 to effectively degrade methylene blue in vitro and obviously activate the green fluorescence of the reactive oxygen species (ROS) probe in cells. Benefiting from the fluorescence enhancement in response to TME stimulation, Fe-CD greatly enhanced CDT cytotoxicity while monitoring successful GSH depletion by fluorescence imaging. Fe-CD has the potential to act as a theranostic nanomedicine for fluorescence imaging-guided GSH depletion to amplify CDT.

Synthesis of Multi-Functional Carbon Quantum Dots for Targeted Antitumor Therapy.

Carbon dots are nano-sized photoluminescence materials which have good biocompatibility and low cytotoxicity, while the previously synthesized carbon dots lack tumor targeting capability and therapy function so that it cannot achieve the purpose of diagnosis and treatment. Herein, a new kind of multi-functional carbon dots (GFCDs) is promising to be applied in tumor cells imaging and clinical targeted therapy. Gallic acid (GA) was used as the carbon resource and antitumor active molecule, folic acid (FA) was used as the nitrogen resource and tumor targeting molecule, and citric acid monohydrate (CA) was used as the auxiliary carbon source. Multi-functional GACDs were synthesized by a simple one-step microwave-assisted procedure and analyzed with UV - vis spectrophotometer, fourier transform infrared spectrometer, transmission electron microscopy and X-ray photoelectron spectrometer. Results show that the diameter of GFCDs is about 3nm. And GFCDs are pale-yellow under natural light which turn blue under 360nm UV lamp. Besides ester bond is the connecting mode between functional molecules. In addition, the results of in vitro cell imaging experiments and in vivo antitumor experiments demonstrate the targeting imaging and antitumor abilities towards Hela cells. The synthesis route and properties of GFCDs.

Carbon quantum dots-embedded electrospun antimicrobial and fluorescent scaffold for reepithelialization in albino wistar rats.

A prosthetic scaffold development using fluorescent nanofiber is reported for an enhanced reepithelialization in wistar albino rats. In this study, a novel approach was followed to construct the biocompatible fluorescent nanofiber that will be helpful to monitor the tissue regeneration process. Here, a multifunctional carbon quantum dots (CQDs)-embedded electrospun polyacrylonitrile (PAN) nanofiber was fabricated and characterized using standard laboratory techniques. The biodegradation ability was assessed by simulated body fluid thereby analyzing porosity and water absorption capacity of the material. The fluorescent scaffold was tested for cytotoxicity and antimicrobial activity using bacterial and fibroblast cells and fluorescent stability was analyzed by bioimaging of animal and bacterial cells. Tissue regeneration capability of the developed scaffold was evaluated using wistar albino rats. Unlike biomicking scaffolds, the CQDs-embedded PAN-based substrate has given dual support by enhancing reepithelialization without growth factors and acted as an antimicrobial agent to provide contamination free tissue regeneration. Scaffolds were examined by using histostaining techniques and scanning electron microscopy to observe the reepithelialization in the regenerated tissues. The novel approach for developing infection free soft tissue regeneration was found to be phenomenal in scaffold development.

One-step microwave-assisted preparation of oxygen-rich multifunctional carbon quantum dots and their application for Cu2+-curcumin detection

Carbon quantum dots (CQDs), owing to its unique optical properties, have achieved tremendous progress for the detection of different metal ions, organic small molecules, macromolecules, etc. Here we synthesized fluorescent CQDs by a simple one-step microwave-assisted method using 3,4-Dihydroxy-l-phenylalanine (levodopa) as the carbon resource. The CQDs proved to be a multifunctional probe which can be used for detection of various species including copper ion, biothiols and curcumin, via different mechanisms. The selective detection of copper ion was obtained by fluorescence quenching and the mechanism was proved to be static quenching by electrostatic interaction. The fluorescence of levoCQDs-Cu2+ system can be recovered by biothiols (GSH, Cys and Hcy), implying levoCQDs-Cu2+ system can also be applied for biothiols detection. The excitation spectrum of levoCQDs had a good overlap with the absorption peak of curcumin, making it as a suitable curcumin probe by fluorescence quenching via inner filter effect (IFE). Furthermore, the levoCQDs can also track the formation of Cu2+-Curcumin complexes by restoring the fluorescence of the CQDs in levoCQDs and Cu2+-Curcumin system, and this feature may be exploited in the mechanism study of Cu2+-Curcumin in the treatment of Alzheimer's disease. The fluorescent levoCQDs were finally used for Cu2+ and curcumin detection in some real samples including different types of environmental water samples and human serum samples, providing a convenient strategy to monitor Cu2+and curcumin in environmental and biological samples.

Waste chimney oil to nanolights: A low cost chemosensor for tracer metal detection in practical field and its polymer composite for multidimensional activity

Proper waste disposal from household and restaurants is becoming an important and recurring waste-management concern. Herein, a method of upcycling of waste kitchen chimney oil has been adopted to prepare fluorescent multifunctional carbon quantum dots. These nanodots showed superior biocompatibility, excellent optical properties, water solubility and high yield. Preparation of C-dots from highly abundant carbon source of waste refusals is highly effective in commercial aspect as well as in reducing the immense environmental pollution. The C-dots showed quasi-spherical size obtained from high resolution transmission electron microscopy (HRTEM) having an abundance of 1–4 nm in size. The ease of water dispersibility of the nanodots is a mere reflection of their surface polarity which has been supported by Fourier transformed infrared spectroscopy (FTIR) and X-ray photoelectron spectroscopy (XPS). In the field of practical acceptability, the C-dots have been experimented to sense Fe3+ ion in a wide range of concentration (1 nM to 600 μM) with a detection limit of 0.18 nM which can be termed as ‘tracer metal chemosensor’. Moreover, the prepared carbon dots were also tested against inter-cellular Fe3+ ion sensing probe. Lastly, we also fabricate the biopolymer‑carbon dots composite for fluorescent marker ink and light emitting polymer film.

Synthesis of lanthanum doped carbon dots for detection of mercury ion, multi-color imaging of cells and tissue, and bacteriostasis

This work describes a hydrothermal method for the preparation of multi-functional carbon quantum dots of the type La-CQDs. The La-CQDs are 4.3±0.3nm in diameter and have a good dispersion and exhibit excellent emission property and high stability, as well as excitation-dependent emission behavior with typical excitation/emission peaks at 350/460nm. They can also be used as an effective fluorescent probe for the quenchometric determination of mercury ion in aqueous solution with a detection limit of 0.1µM. The particles are readily internalized by liver epithelial HepG2 cells and enable multi-color fluorescence imaging by displaying green and red emission if excited with 488 and 543nm light, respectively. Intravenous injection of the quantum dots in nude mice, in turn, enabled tissue imaging. The La-CQDs possess abundant phosphate, hydroxyl, pyridinic, pyridine-like and pyrrole-like nitrogen groups. Therefore, they can exhibit strong fluorescence, improve the accuracy as an optical monitoring code both in vitro and in vivo, and enhance blood compatibility. In vitro investigations show that La-CQDs do not exhibit significant apoptotic effects on NIH3T3 cells even at a high concentration (2.5mg/mL) while they exhibit improved antibactericidal capacity of the La-CQDs against gram-positive S. aureus and gram-negative E. coli bacteria was also observed. No apparent pathological damages are observed in all organs during the 30-day period, which suggests that La-CQDs do not produce detectable long-term toxicological responses.