Carbon Dots from Dried German Chamomile Flower and Its Residual Biomass: Characteristics, Bioactivities, Cytotoxicity and Its Preservative Effect on the Refrigerated Precooked Baby Clam (Paphia undulata)

ZnCl2 Enabled Synthesis of Highly Crystalline and Emissive Carbon Dots with Exceptional Capability to Generate O2⋅–

Exploring the origin of emission is fundamental in the field of carbon dots (CDs). Due to the lack of suitable in situ probing techniques, it is necessary to explore effective alternative methods that can accurately reflect the relationship between the emission and the composition of the functional groups of CDs. Herein, we propose a new method of post-synthetic treatment of CDs by photo-oxidation to investigate the origin of emission for CDs. After the addition of a photo-oxidant into pre-prepared CDs under UV irradiation, the fluorescence of CDs can be regulated from the original orange emission to the final green emission due to the damage of original functional groups and the formation of new functional groups on CDs during the post-treatment process. The abundant dynamic information about the functional groups and emissions of CDs during the visible and ready-to-monitor post-treatment process makes it possible to quantitatively analyze the origin of the emission of CDs. Our results suggest that the emission sub-peaks at 560 nm and 600 nm relate to the CD surface-state-associated -NH3+ groups, while the emission sub-peak at 537 nm or 494 nm is associated with the CD surface-state-associated -OH groups or the CD surface-state-associated carbonyl groups (CO). Under UV irradiation, the CD surface-state-associated -NH3+ groups can be continuously converted into the CD surface-state-associated -OH groups and the CD surface-state-associated carbonyl groups (CO), leading to the changed emission color of CDs.

Carbon dots are regarded as a brand new class of nanostructures in the carbonaceous family that have piqued the curiosity of researchers in a wide range of bio applications. This work focuses on the synthesis and characterization of carbon dots, as well as their latent fingerprint detection and antibacterial/antifungal capabilities. Highly luminous carbon dots were prepared by optimizing simple hydrothermal carbonization settings at 180 °C for 12 h using lemon juice as a raw precursor. The resulting product was examined using Fourier transform infrared spectroscopy, scanning electron microscopy, energy dispersive X-ray analysis, X-ray diffractometery, and ultraviolet–visible spectrophotometer. The as-prepared carbon dots were found to be extremely bright when excited under ultraviolet light (λ = 365 nm). The presence of carbon and oxygen functionalities on the surface of the carbon dots was revealed by infrared spectrocopy. The diffraction pattern confirmed the amorphous structure of the carbon dots, with an average size of 7 nm determined using the Scherrer equation. The surface morphology analysis revealed that the carbon dots exhibited an aggregated form with irregular spherical shapes. The chemical structure examination validated the elemental makeup of the prepared lemon juice-based carbon dots. The detection of latent fingerprints on carbon dots under ultraviolet light yielded positive results. In addition, the obtained carbon dots displayed antifungal and antibacterial activity against tested pathogenic fungal and bacterial strains.

Carbon dots (CDs) are light-emitting nanoparticles that show great promise for applications in biology and medicine due to the ease of fabrication, biocompatibility, and attractive optical properties. Optical chirality, on the other hand, is an intrinsic feature inherent in many objects in nature, and it can play an important role in the formation of artificial complexes based on CDs that are implemented for enantiomer recognition, site-specific bonding, etc. We employed a one-step hydrothermal synthesis to produce chiral CDs from the commonly used precursors citric acid and ethylenediamine together with a set of different chiral precursors, namely, L-isomers of cysteine, glutathione, phenylglycine, and tryptophan. The resulting CDs consisted of O,N-doped (and also S-doped, in some cases) carbonized cores with surfaces rich in amide and hydroxyl groups; they exhibited high photoluminescence quantum yields reaching 57%, chiral optical signals in the UV and visible spectral regions, and two-photon absorption. Chiral signals of CDs were rather complex and originated from a combination of the chiral precursors attached to the CD surface, hybridization of lower-energy levels of chiral chromophores formed within CDs, and intrinsic chirality of the CD cores. Using DFT analysis, we showed how incorporation of the chiral precursors at the optical centers induced a strong response in their circular dichroism spectra. The optical characteristics of these CDs, which can easily be dispersed in solvents of different polarities, remained stable during pH changes in the environment and after UV exposure for more than 400 min, which opens a wide range of bio-applications.

Carbon dots (CDs) are a new class of nanomaterials exhibiting high biocompatibility, water solubility, functionality, and tunable fluorescence (FL) property. Due to the limitations of batch hydrothermal synthesis in terms of low CDs yield and long synthesis duration, this work aimed to increase its production capacity through a continuous flow reactor system. The influence of temperature and time was first studied in a batch reactor for glucose, xylose, sucrose and table sugar precursors. CDs synthesized from sucrose precursor exhibited the highest quantum yield (QY) (175.48%) and the average diameter less than 10 nm (~6.8 ± 1.1 nm) when synthesized at 220°C for 9 h. For a flow reactor system, the best condition for CDs production from sucrose was 1 mL min−1 flow rate at 280°C, and 0.2 MPa pressure yielding 53.03% QY and ~ 6.5 ± 0.6 nm average diameter (6.6 mg min−1 of CDs productivity). CDs were successfully used as ciprofloxacin (CP) nanocarrier for antimicrobial activity study. The cytotoxicity study showed that no effect of CDs on viability of L-929 fibroblast cells was detected until 1000 µg mL−1 CDs concentration. This finding demonstrates that CDs synthesized via a flow reactor system have a high zeta potential and suitable surface properties for nano-theranostic applications.

Cross-linked gelatin film enriched with green carbon quantum dots for bioactive food packaging

Low toxicity carbon dots are combating the disadvantages of quantum dots. The carbon dots find their applications in many fields due to their versatile nature. Four different types of carbon dots are present, according to the way of manufacturing and application the type is chosen. The water-soluble characteristics of carbon dots help them be involved in biomedicine applications. The optical properties of the carbon dots find applications as drug delivery, biosensors, LED, etc. The properties like fluorescence, photoluminescence, and phosphorescence are found in the carbon dots. The carbon dots occupy the tiny spot that exhibits different optical properties on excitation. The carbon dots excitation is mainly due to surface states. The characterization of surface states is very complex. The surface states contain the core structure of carbon and oxygen functional groups on the surfaces. The anions and cations formed from functional groups on excitation will recombine themselves. The functional groups are usually carboxyl and hydroxyl groups. The Π-collaborative network of the electronic structure contains many quantization levels which help the carbon dots to produce different wavelengths adapting to different applications. Due to the interference of the structure of the carbon dots, the entire property will vary. Doping of heteroatom methods is employed to enhance the fluorescence, and photoluminescence property carried out. They used N, S, P, and B heteroatoms singly and in combination to doping carbon dots. Here, the paper proposes the sulphur dioxide adsorption technique to enhance the optical properties of the carbon dots. The proposed method shows 8.5% efficiency in relative fluorescence intensity and 8% efficiency in terms of photoluminescence intensity.

Green synthesis of carbon dots from elm seeds via hydrothermal method for Fe3+ detection and cell imaging

Manipulating the chiroptical properties at the nanoscale is of great importance in stereoselective reactions, enantioseparation, self-assembly, and biological phenomena. In recent years, carbon dots have garnered great attention because of their favorable properties such as tunable fluorescence, high biocompatibility, and facile, scalable synthetic procedures. Herein, we report for the first time the unusual behavior of cyclic amino acids on the surface of carbon dots prepared via microwave-based carbonization. Various amino acids were introduced on the surface of carbon dots via EDC/NHS conjugation at room temperature. Circular dichroism results revealed that although most of the surface conjugated amino acids can preserve their chirality on negatively charged, "bare" carbon dots, the "handedness" of cyclic α-amino acids can be flipped when covalently attached on carbon dots. Moreover, these chiroptical carbon dots were found to interact with the cellular membrane or its mimic in a highly selective manner due to their acquired asymmetric selectivity. A comprehensive inhibitor study was conducted to investigate the pathway of cellular trafficking of these carbon dots. Overall, it was concluded that the chirality of the amino acid on the surface of carbon dots could regulate many of the cellular processes.

A self-quenching-resistant carbon dots powder with tunable solid-state fluorescence and their applications in light-emitting diodes and fingerprints detection

This research paper investigates the effect of functionalizing the surfaces of citric acid-synthesized carbon dots (CDs) with hyperbranched bis(methylol)propionic acid (bis-MPA) polyester hydroxyl polymers (HBPs) on their performance as electrode materials in a supercapacitor. Two types of HBPs with 16 and 64 peripheral hydroxyl groups were used to functionalize the CDs' oxygen-enriched surface. Here, CDs were used as electrode materials for the first time in symmetric supercapacitors without a composite material, and how surface modification affects the capacitance performance of CDs was investigated. Our results showed that the functionalization of green-emitting CDs with HBP resulted in the successful passivation of surface defects, which improved their stability and prevented further oxidation. The CDs with HBP passivation exhibited excellent electrochemical performance, with a high specific capacitance of 32.08 F g-1 at 0.1 A g-1 and good rate capability, indicating a faster ion transport rate at high current densities. Experimental EPR spectra of functionalized and non-functionalized CDs reveal distinct changes in g-factor values and line widths, confirming the impact of dangling bonds and spin-orbit interactions. The observed broader linewidth indicates a wider range of electron spin resonances due to energy-level splitting induced by spin-orbit coupling. The excellent electrochemical performance of CDs with HBP passivation can be attributed to the presence of oxygen-containing surface functional groups such as hydroxyl and carboxyl groups on their surfaces, which enhance the conductivity and charge transfer reactions. These results suggest that functionalization with polar HBPs is a promising strategy to enhance the electrochemical performance of CDs in supercapacitor applications.

These days, carbon dots (CDs) are the rising stars of nanomaterials. Carbon dots (CDs) are small carbon nanoparticles with the same type of surface passivation (less than 10 nm in size). Researchers found C-dots by accident while purifying single-walled carbon nanotubes (SWCNTs) manufactured using the arc-discharge process. Toxic metal-based quantum dots are being replaced with carbon dots (QDs). Carbon dots are currently being prepared from a variety of natural resources in order to obtain self-passivated products at a reasonable cost. Because of their superior photo physical characteristics, biocompatibility, and low toxicity, carbon dots have prospective applications in bio sensing, bio imaging, and drug administration. Different synthetic processes, precursors, salient properties, and applications were reviewed in this review, as well as some future prospects, obstacles, and possible solutions for future development. Because of their tunable optical characteristics and better biocompatibility, luminous carbon-based nanomaterials have sparked a lot of scientific interest. Different light emission properties of carbon are discussed in this review. Distinct synthesis procedures have resulted in different carbon dots (CDs). Summarized here. The optical properties of CDs that haven’t been synthesized yet surface doping and element doping can be used to further control it. CDs are being functionalized for an adjustable band gap. As a result of their luminescent with reduced cytotoxicity and tunable optical characteristics CDs have been thoroughly investigated in terms of their potential uses in biomedicine, such as analytical sensors, and instruments for bioimaging. Fluorescent carbon dots are a new type of nanomaterial from the carbon family. Green CDs, which have attracted a lot of attention from researchers because of their better water solubility, high biocompatibility, and eco-friendly nature when compared to chemically generated CDs, can be made from a variety of inexpensive and renewable resources. The presence of heteroatoms on the surface of green CDs in the form of amine, hydroxyl, carboxyl, or thiol functional groups, which can improve their physicochemical qualities, quantum yield, and likelihood of visible light absorption, eliminates the need for additional surface passivation.

In this study, carbon dots (CDs) synthesized by hydrothermal method with amino-rich surface exhibit tunable fluorescence across entire visible range by simply controlling the concentration. A comprehensive comparison has been performed for the first time between concentration-induced aggregation of the single-type CDs and electrostatic-induced agglomeration of opposite-charged CDs in terms of their fluorescence properties. Experimental results show that both the aggregation of CDs and internal absorption filtration are possible causes of the concentration-dependent fluorescence emission. Subsequently, the inter distance of adjacent CDs in their aggregates was enlarged by forming rigid double-stranded DNA (dsDNA) between adjacent CDs through base pairing. It is clear that the contact of CDs induces the changes of fluorescence emission and light absorption. Through a better understanding of the mechanisms behind concentration-induced multicolor emission, this work can provide a novel strategy to develop the advanced applications of CDs.

Carbon dots (CDs) are a class of nanobiomaterials with significant potential in bone regeneration. Their excellent biocompatibility, tunable fluorescence, high stability, low toxicity, and abundant functional groups make CDs promising candidates for efficient drug delivery and bone tissue regeneration. CDs contribute to targeted drug release, enhance osteogenic differentiation, and interact with cellular components to facilitate bone formation. Recent research highlights the roles of CDs in scaffold-based approaches, offering controlled drug delivery and real-time bioimaging capabilities. This review provides a comprehensive overview of CDs in bone regeneration, with a focus on their synthesis, functionalization, and biomedical applications. It begins by exploring CD synthesis methods, physicochemical properties, and mechanisms of action. Next, it discusses CD-based drug delivery systems and their applications in bone regeneration. Finally, the review highlights the challenges and future perspectives in optimizing CDs for enhanced therapeutic outcomes.

Cancer is one of the global health threats and several developed therapies are undergoing evolution with advancements in nanotechnology and awareness of tumor microenvironments. Low-dimensional carbon-based nanomaterials like carbon dots (CDs) and their derivatives have the potential of treating cancer at the preclinical level. Zero-dimensional CDs are unique in their physical, chemical, and biomedical properties. Characteristics such as high surface area, broad absorption spectrum, high hydrophilicity, tunable fluorescence, photo-stability, and biocompatibility are significant in healthcare applications like fluorescence sensing, imaging, and drug delivery. As a photosensitizer, CDs produce reactive oxygen species under light and convert light energy to heat as a photothermal agent. Thus, CDs have applications in photodynamic therapy or photothermal therapy (PTT) of cancer. In this chapter, the functionalized CDs and their synthetic approaches are discussed to provide photothermal aspects of CDs. The mechanism of PTT and scope of therapeutic efficacy of CD-based phototheranostic is highlighted. An insight into the challenges of limiting the clinical application of CDs is provided to prompt advances in phototherapy.