Carbon Dots Hybrid Research Articles

Carbon Dots Hybrid Nanostructure-based Electrochemical Sensors: Applications in Determining Different Species in a Real Sample

Abstract: This overview describes the synthesis, characterization, and application of different carbon dots hybrid nanostructures obtained by chemical interaction between nanomaterials or nanomaterials bonded to another material, i.e. silicon (SiO2/Carbon dots-N), reduced graphene oxide (rGO/Carbon dots), multiwalled carbon nanotubes (MWCNTs/Carbon dots), nano magnetite (Carbon dots/Fe3O4), reduced graphene oxide and gold nanoparticles (rGO/Carbon dots/AuNPs), copper oxide (CuO/Carbon dots), and Carbon dots/Metallic NPs that were employed in the development of electrochemical (bio)sensors. The formation of different carbon dots hybrid nanostructures has been characterized by X-ray diffraction (XRD), Raman and ultraviolet- visible spectroscopy, atomic force microscopy (AFM), high-resolution transmission electron microscopy (HR-TEM), and electrochemical techniques. These carbon dots hybrid nanostructures have been used to modify the surface of glassy carbon and screen-printed electrodes and to determine various analytes, i.e., dopamine, uric acid, paracetamol, ephynefrin, dihydroxybenzenes, pesticides, endocrine disruptors, NADH, and other substances in real samples.

Detection of Organophosphorus Pesticides Using Silver-Coated Gold Nanoparticles

Plasmonic nanoparticles can provide great utility for the construction of advanced optical and electrical sensors. Herein, we present a versatile sensing strategy that can perform triple-mode detection of organophosphorus pesticides (OPPs) based on carbon dots (CDs)-participated silver deposition on gold nanoparticles (AuNPs). Simply, a hybrid system composed of AuNPs, CDs, and silver ions in phosphate-buffered saline (AuNPs/Ag+/CDs) is designed, and alkaline phosphatase (ALP) is used to catalytically produce l-ascorbic acid, which reduces silver ions to metallic silver on the surface of AuNPs. OPPs can simultaneously modulate triple optical signals, including light absorption, fluorescence, and Rayleigh scattering of the AuNPs/Ag+/CDs hybrid, by inhibiting the activity of ALP, and thus colorimetry, fluorescence, and resonance Rayleigh scattering methods for OPPs are established. Meanwhile, the mechanism of spectral change involved in the three optical signals is investigated in detail. In addition, the proposed detection system is used for the determination of OPPs in vegetables with satisfactory results. The nanohybrid-platform-integrated triple-signal readout provides not only approaches for OPPs detection but also insight for the development of optical sensors.

Design and Use of a Gold Nanoparticle-Carbon Dot Hybrid for a FLIM-Based IMPLICATION Nano Logic Gate.

The interest in nanomaterials resides in the fact that they can be used to create smaller, faster, and more portable systems. Nanotechnology is already transforming health care. Nanoparticles are being used by scientists to target malignancies, improve drug delivery systems, and improve medical imaging. Integration of biomolecular logic gates with nanostructures has opened new paths in illness detection and therapy that need precise control of complicated components. Most studies have used fluorescence intensity techniques to implement the logic function. Its drawbacks, mainly when working with nanoparticles in intracellular media, include fluctuations in excitation power, fluorophore concentration dependence, and interference from cell autofluorescence. We suggest using fluorescence lifetime imaging microscopy (FLIM) in order to circumvent these constraints. Designing a nanohybrid composed of gold nanoparticles (AuNPs) and red-emitting carbon dots (CDs) can be used to develop a FLIM-based logic gate that can respond to multiple input parameters. Our findings indicate a nanohybrid that can serve as a nano-computer to receive and integrate chemical and biochemical stimuli and produce a definitive output measured by FLIM. This can open a new research avenue for enhanced diagnostics and therapy that require complicated factor handling and precise control. The AuNPs are conjugated to CDs’ surfaces through a strong covalent linkage. The AuNP–CD nanohybrid shows fluorescence lifetime (FLT) quenching of pristine CDs after conjugation to AuNPs. The FLT was reduced from 3.61 ± 0.037 to 2.48 ± 0.040 ns. This quenched FLT can be recovered back by using trypsin as a recovering agent, giving us a reversible logic output. The FLT was recovered to 3.01 ± 0.01 ns after trypsin addition. This “on–off–on” response can be used to construct the IMPLICATION logic gate.

Carbon dots hybrid for dual fluorescent detection of microRNA-21 integrated bioimaging of MCF-7 using a microfluidic platform

BackgroundMicroRNAs have short sequences of 20 ~ 25-nucleotides which are similar among family members and play crucial regulatory roles in numerous biological processes, such as in cell development, metabolism, proliferation, differentiation, and apoptosis.ResultsWe reported a strategy for the construction of a dual-emission fluorescent sensor using carbon dots (CDs) and confirmed their applications for ratiometric microRNA-21 sensing and bioimaging of cancer cells in a microfluidic device. The composition of blue CDs (B-CDs) and yellow CDs (Y-CDs) depicts dual-emission behavior which is centered at 409 and 543 nm under an excitation wavelength of 360 nm. With increasing microRNA-21 concentration, the robust and specific binding of DNA probe functionalized B-CDs to complementary microRNA-21 target induced perturbations of probe structure and led to changing fluorescence intensity in both wavelengths. Consequently, the ratio of turn-on signal to turn-off signal is greatly altered. With monitoring of the inherent ratiometric fluorescence variation (ΔF540nm/ΔF410nm), as-prepared BY-CDs were established as an efficient platform for ratiometric fluorescent microRNA-21 sensing, with a wide linear range of 0.15 fM to 2.46 pM and a detection limit of 50 aM.ConclusionsFurthermore, the proposed assay was applied for detecting microRNA-21 in dilute human serum samples with satisfactory recovery and also in MCF-7 cell lines in the range 3000 to 45,000 (cell mL−1) with a detection limit (3 cells in 10 μL), demonstrating the potential of the assay for clinic diagnosis of microRNA-associated disease. More importantly, the images revealed that MCF-7 cells well labeled with BY-CDs could exhibit the applicability of the proposed microfluidic system as an effective cell trapping device in bioimaging.Graphical

Design of an efficient fluorescent nanoplatform carrier for hydrophobic drugs along with green carbon dot: Possible application in cancer image-guided drug therapy

Nanotechnology has taken novel approaches to advance cancer therapeutic efficacy employing multifunctional nanocarriers with drug delivery and imaging function. In this work, we designed a biocompatible and affordable fluorescence nanocarrier called chitosan (CS)-carbon dot (CD) hybrid nanogel for cell imaging. The green CDs were synthesized using tomato juice through a simple single-step hydrothermal method. Chitosan polymer was used as a carrier for co-delivery CDs and the anti-cancer drug with low solubility, silibinin (Sil), to design the Sil-chitosan carbon dots hybrid nanogels (CCHNs) system. After optimizing the physicochemical properties of nanostructure by DLS, FTIR, FESEM, TEM, and UV-visible techniques, the successful uptake of the fluorescent nanoparticle conjugates into MCF-7 breast cancer cells occurred. Then we embedded CDs in chitosan nanogel. The resultant CCHNs demonstrated optical properties similar to free-CDs, a desirable size distribution (55.22 nm) with a positive surface charge, a suitable loading capacity for Sil (35%), and drug release vulnerable to pH changes. The fluorescent nanocarrier could transfer Sil to MCF-7 cancer cells without remarkable toxicity. The results of the fluorescent microscope indicated that after 4 h, the solid fluorescent signal was received from cells containing CCHNs compared to free CDs and confirmed the ability of hybrid nanogels to high cellular uptake. This study demonstrates a multifunctional nanocarrier containing therapeutic compounds and fluorescent agents that provide cellular imaging to enhance therapeutic efficacy.

Fabrication of γ-cyclodextrin-Based metal-organic frameworks as a carrier of cinnamaldehyde and its application in fresh-cut cantaloupes

Cinnamaldehyde (CA) is a promising antimicrobial agent for the preservation of fruits and vegetables due to its excellent antibacterial activity. The application is however, limited by its unstable and volatile properties. A biocompatible carbon dots hybrid γ-cyclodextrin-based metal organic framework (CD/MOF) was developed by the seed-mediated method to improve the encapsulation and sustained continuous release of CA. CD/MOF-0.5 exhibited a CA loading efficiency of 28.42% and a sustained release duration time of more than 15 days at 8 oC. The release kinetics results showed that the release behavior of CD/MOF-0.5 fitted well with the Korsmeyer–Peppas release kinetics model, indicating that its sustained release is mainly controlled by diffusion. Both the Fourier-transform infrared spectroscopy and X-ray photoelectron spectroscopy analyses revealed that CD/MOF-0.5 and CA molecules were linked by hydrogen bonds. Due to the high sustained release performance, CA-loaded CD/MOF-0.5 considerably inhibited the growth of Escherichia coli, hence preventing the spoilage of fresh-cut cantaloupes. CD/MOF-0.5/CA treatment also maintained the qualities of the fresh-cut cantaloupes, prolonging their edibility to five days. This work provides a promising strategy for the prevention of spoilage in food industry.

Mussel-inspired preparation of temperature-responsive polymer brushes modified layered double hydroxides@Pd/carbon dots hybrid for catalytic applications

A novel type of multicomponent nanocomposite of LDH@PDA@PNIPAM@Pd/carbon dots (CDs) was successfully constructed for highly efficient heterogeneous catalytic reduction from two-dimensional layer double hydroxide (LDH) nanosheet functionalized with thermo-responsive PNIPAM polymer brushes based on the mussel-inspired chemistry. CDs were used as a reductant and stabilizer by in situ loading metal Pd onto LDH@PDA@PNIPAM. Compared with LDH@PDA@PNIPAM@Pd catalyst without CDs modification, the designed LDH@PDA@PNIPAM@Pd/CDs nanohybrid catalyst had better catalytic reduction ability for various dyes and nitrophenol thanks to the synergistic catalytic effect between metal active center and CDs, LDH and their high dispersion stability. Especially, a good catalytic reduction activity was demonstrated for methylene blue (MB) with a high TOF (545.2 min−1). Furthermore, the nanohybrid presented interesting thermo-responsive catalytic property due to the existence of PNIPAM polymer chains. In addition, the prepared catalyst also exhibited outstanding catalytic property for the Knoevenagel condensation reaction. Our study provides a new way for the composite preparation of organic-inorganic hybrid materials by polymer and inorganic materials, and shows great potential in the field of catalytic applications.

Simple paper-based colorimetric and fluorescent glucose sensor using N-doped carbon dots and metal oxide hybrid structures

A new strategy for the fluorescent and colorimetric sensing of hydrogen peroxide (H2O2) and glucose based on the metal oxide – carbon-dot hybrid structure was investigated. The sensing system is related to the catalytic oxidation reaction of glucose-by-glucose oxidase (GOx) to H2O2. In this study, a metal oxide hybrid with nitrogen-doped carbon dots (MFNCDs) that showed intrinsic peroxidase-like activity was synthesized and used as a catalyst instead of GOx to oxidize 3,3′,5,5′-tetramethylbenzidine (TMB) to blue-emitting oxidized TMB (oxTMB) in the presence of hydrogen peroxide (H2O2). The fluorescence of MFNCDs/TMB at 405 nm was quenched in the presence of H2O2 through the inner filter effect (IFE) and electron transfer within MFNCDs, oxTMB, and glucose system. Therefore, the fluorescence and absorbance intensity can be applied to the quantitative determination of the concentration of H2O2 and glucose with a wide linear range. The detection limit for H2O2 and glucose based on the colorimetric method were as low as 84 nM and 0.41 μM, respectively. In contrast, the detection limit for H2O2 and glucose based on the fluorescent method were as low as 97 nM and 0.85 μM, respectively. Furthermore, the colorimetric readout on the paper device based on the changing color of the solution could also be integrated with a smartphone platform to conduct the on-site analysis of glucose without the use of the spectrometer. In addition, this dual sensor can be applied to detect glucose in real serum with highly accurate results, making it a good candidate for biosensor applications.

Urchin-like cobalt hydroxide coupled with N-doped carbon dots hybrid for enhanced electrocatalytic water oxidation

The electrocatalytic water splitting into oxygen (O2) and hydrogen (H2) is one of promising technique for addressing the problem of energy shortage. Owing to the sluggish reaction kinetics for oxygen evolution reaction (OER), it is urgent to explore efficient and inexpensive OER electrocatalytic materials. Herein, a highly efficient three-dimensional (3D) hybrid of anions (Cl− and CO32−) doped cobalt hydroxide catalyst coupled with nitrogen-doped carbon dots (Co(OH)2@NCDs) is reported via a simple in situ hydrothermal method. Interestingly, the additional mass ratio of NCDs in Co(OH)2 hybrid has strong influence on the morphology of as-prepared composites. The well-defined urchin-like Co(OH)2@NCDs composite exhibits superior OER performance, achieving the low overpotential (η) of 296 mV at 10 mA cm−2 and high durability in 1 M KOH solution. The urchin-like Co(OH)2@NCDs catalyst could achieve 29-fold electrochemical active surface area than that of the pure Co(OH)2. Additionally, after coupling with NCDs, analysis result shows new Co-N charge transfer channel is generated in hybrid and an optimized electronic environment is originated from the strong electronic interaction among Co atom and NCDs, which can provide efficient charge channels for the rapid electron transfer and further improve the intrinsic activity and promote the OER kinetics. The work may endow a new strategy for the construction of excellent transition metal-based hydroxide water oxidation electrocatalysts.

Application of molecularly imprinted polymers and dual-emission carbon dots hybrid for ratiometric determination of chloramphenicol in milk

Chloramphenicol (CLP) is a veterinary antibiotic that has been banned due to its severe side effects but it is still illegally used in animal husbandry. In this work, the fabrication of simple, fast-response and highly selective ratiometric probe for sensitive visual detection of CLP antibiotic at trace levels in both indoor and outdoor is reported. For the construction of the ratiometric fluorescence probe (mMIP@YBCDs), two kinds of different carbon dots with yellow emission (Y/CDs, 560 nm) and blue emission carbon dots (B/CDs, 440 nm) were used as target sensitive and as reference dyes respectively. Besides, molecularly imprinted mesoporous silica was used as a recognized part of the probe. Upon the addition of different concentrations of CLP, the fluorescence of Y/CDs was quenched significantly while the fluorescence intensity of B/CDs stayed constant which was accompanied by gradual fluorescence color change from yellow-to-blue. The ratiometric probe has a linear response in the range of 0.1–3 μgL−1 with a detection limit 0.035 μgL−1. The practicality of the ratiometric method was validated by the quantification of CLP in milk samples.

Palmitic acid–carbon dot hybrid vesicles for absorption of uric acid

Human health is always sensitive to the effect of toxin developed due to various reason like metabolic activities, excessive material uptake etc. in the body. Hence, there is a need to develop ways to remove such toxin. In this work, we successfully fabricated a Carbon dot–palmitic acid hybrid vesicles and demonstrated that it can absorb uric acid (UA) which is taken in this work as a model toxin. Interestingly, the nanohybrid was found to be efficient UA absorber (~ 80%) compare to pure palmitic acid vesicles (~ 60%) confirming the role of carbon dot in absorption and hence removal of uric acid. The electrostatic interaction operated between carbon dot and uric acid inside the palmitic acid vesicles is the prime factor for the UA absorption. Development of such nanohybrid vesicles system will lead to system which can be used as toxin removal from our body.

Supramolecular hybrids of carbon dots and dihydroartemisinin for enhanced anticancer activity and mechanism analysis.

Dihydroartemisinin (DHA) has been regarded as a potential anticancer agent in recent years. Nevertheless, the clinical applications of DHA are seriously restricted as a result of its intrinsic characteristics, such as poor water solubility, instability, and fast clearance. Herein, a type of fluorescent nanoparticles was successfully fabricated via supramolecular assembling of carbon dots (CDs) and DHA. The formulated CDs-DHA fluorescent nanoparticles not only significantly improve the solubility and stability of DHA, but also possess favorable biocompatibility and pH-dependent drug release behavior. In particular, the hybrids of CDs and DHA as nanocarriers can effectively promote the endocytosis of DHA and exhibit enhanced antitumor effects compared with free DHA in vitro and in vivo. In addition, we also explore the possible action mechanism of CDs-DHA through flow cytometric assay, transfection and western blot analysis. The results indicate that CDs-DHA nanoparticles suppress the progression of hepatic carcinoma through inducing apoptosis and inhibiting glucose metabolism, and the mechanism is related to the downregulation of PKM2 expression and the suppression of the Akt/mTOR signaling pathway, which may provide a potential therapeutic target for hepatic carcinoma treatment. This work emphasizes the great potential of utilizing CDs as a safe and convenient platform to deliver DHA for efficient cancer therapy, and the study on the anticancer mechanism can also offer theoretical support for the clinical application of DHA.

Heterogeneous nucleation and synthesis of carbon dots hybrid Zr-based MOFs for simultaneous recognition and effective removal of tetracycline

Abstract Discharged tetracycline (TC) seriously threatens human health and environmental safety. Herein, we developed a novel 3D flower-on-sheet structure of Zr-metal organic framework adsorbent with the assistant of N,S co-doped carbon dots as heterogeneous nucleation (UiO-67/NSC) for selective and effective removal of TC residue from contaminated water. Functional groups of UiO-67/NSC acts as a tentacle to identify TC molecules, and TC-adsorbed NSC can be separated easily by incorporating in UiO-67 structure. Hierarchical UiO-67/NSC exhibited excellent recognition performance with a wide sensitive range (0.08–20.0 mg/L) and low detection limit (0.063 mg/L) for TC. Particularly, vertically oriented 2D nanosheets in UiO-67/NSC alleviate the diffusion barrier and enhance mass transfer between adsorption sites and TC molecules, endowing it with an ability that can improve the TC adsorption capacity of parent UiO-67 to 427.35 mg/g. UiO-67/NSC with 0D structure has no significant toxic effect on human cells (HepG2 and Caco-2), which demonstrate the prepared hybrid structure is safety in practical application. Our data indicate the great potential of UiO-67/NSC as an innocuous, bifunctional, smart adsorbent for the effective detection and removal of TC residues, and we not only provide a rational design of advanced metal organic framework-based hierarchical adsorbents, but also shed light on an available method to toxic antibiotic residue recognition and water remediation.

Fabrication and electrochemically-modulated optical properties of viologen and carbon dots hybrid glass composite films

The electrochemical manipulation of optical properties will be essential in engineering next generation intelligent displays, wearable devices, and smart sensors. The rational design of electrochemically-modulated optical materials, especially those with multiple regulatory capacities, remains an unmet research challenge. We present here an optical composite, featuring multiple electrochemically-modulated properties, prepared through an electrochemistry-assisted hydrolytic crosslinking reaction between electroactive viologen and fluorescent carbon dots. Upon the electrochemical manipulation of the redox states of the viologen moieties, the resultant composite film exhibits interesting multistage regulated chromism with great color contrast, moderate switching rates, good coloration efficiency, and enhanced cycling stability. We demonstrate a unique sequential multistage regulated electrofluorochromism resulting from the inner filter effect and synergistic interplay between the electroactive viologen units and the fluorescent carbon dots. Furthermore, this optical composite reveals electrogenerated chemiluminescence with acceptable electrochemiluminescence intensity, attributed to the intrinsic behavior of carbon dots.

Sandwich-like electrode with tungsten nitride nanosheets decorated with carbon dots as efficient electrocatalyst for oxygen reduction

Developing efficient and cost-effective oxygen reduction reaction (ORR) catalysts for fuel cells is quite necessary but still full of challenges. In this study, tungsten nitride nanosheets (WN NSs) decorated with nitrogen-containing carbon dots hybrid materials are developed using a facile two-step route. Specifically, a sandwich-like porous electrode, which contains a N-doped carbon layer encapsulated with uniform carbon dots (N-CDs) and a sheet-like WN for both-side formation of N-CDs, is obtained and designed as a novel type of ORR catalysts (denoted as N-CDs@WN). The N-CDs@WN hybrid shows superior catalytic activity via a four-electron pathway and demonstrates excellent stability over long periods of time and resistance to methanol. The excellent electrocatalytic properties of N-CDs@WN hybrids benefited from a hierarchical structure with large specific area, numerous active sites, and synergistic effect between CDs and WN that can facilitate the conductivity and mass transfer during the ORR process. Compared to other carbon dots-based nanocomposites, our facile synthetic route for N-CDs@WN not only presents the advantages of being relatively green, simple, and cost-effective but also is an attractive alternative for the electrocatalyst in the non-precious ORR.

Hybrids of carbon dots with subunit B of ricin toxin for enhanced immunomodulatory activity

Although Ricin toxin binding subunit B (RTB) can promote the activation of macrophages and modulate the cell-mediated immunity, its applications are severely limited due to the intrinsic properties of proteins, like poor stability and low efficacy of cellular uptake. In this work, the stable nanoparticles were prepared by supramolecular assembling of carbon dots (CDs) and RTB. The formed CDs-RTB possesses robust stability and can protect RTB against enzymatic hydrolysis. More importantly, CDs-RTB can promote macrophages proliferation, improve the generation of NO, IL-6 and TNF-α in RAW264.7 cells and increase the expression of mRNA, indicating the enhanced immunomodulatory activity of CDs-RTB. This work highlights the potential of using CDs as a simple and stable platform to assemble RTB and effectively promotes the application of RTB as the immunostimulant.

Polymer-carbon dot hybrid structure for a self-rectifying memory device by energy level offset and doping.

A strategy for self-rectifying memory diodes based on a polymer–carbon dot hybrid structure, with a configuration of rGO/PEDOT : PSS/carbon dots/MEH-PPV/Al, has been proposed. The fabricated device exhibits a rectification of 103 in the rectification model and an ON/OFF current ratio of 121 in the memory model. The rectifying behavior was attributed to an energy level offset between the electrodes and the bilayer polymers and the memory effect was induced by carrier trapping of carbon dots within the polymers.

Supramolecular hybrids of carbon dots with doxorubicin and their cellular trafficking

Supramolecular hybrids of carbon dots with doxorubicin and their cellular trafficking

Supramolecular hybrids of carbon dots with doxorubicin: synthesis, stability and cellular trafficking

Functional nanoparticles were successfully prepared from carbon dots (CDs) and doxorubicin (Dox) via supramolecular interactions.

Co-assembled hybrids of proteins and carbon dots for intracellular protein delivery.

A general and simple strategy for intracellular protein delivery was developed by co-assembling carbon dots and proteins. Compared to free proteins, this delivery system can protect proteins against enzymatic hydrolysis and effectively deliver EGFP into HeLa cells.