Photoluminescent carbon dots from 1,4-addition polymers

The controllable synthesis of multi-color carbon quantum dots modified by polythiophene and their application in fluorescence detection of Au3+ and Hg2

Herein, hydrothermal method was used to prepare a series of multi-color polythiophene modified carbon quantum dots. Under UV excitation, fluorescence their maximum emission wavelengths appear at 612 nm, 570 nm, and 540 nm respectively. The prepared CD-BTH and CD-BN can have specific detection of Au3+ and Hg2+ through fluorescence quenching effect. The detection limits for Au3+ are 3 nM and 5.4 nM respectively, and for Hg2+ are 23 nM and 90 nM respectively. CD-KN detects Au3+ specifically through fluorescence resonance, with a detection limit of 33 nM. Under the interference of other metal ions, three types of polythiophene modified quantum carbon dots exhibit excellent selectivity for the responsive ions. Meanwhile, this article also elucidates the law that as the electron withdrawing ability of the side chains of polythiophene derivatives increasing, the fluorescence emission peaks of the prepared polythiophene modified carbon dots shifts red and the fluorescence quantum yield is higher.

Synthesis of luminescent chitosan-based carbon dots for Candida albicans bioimaging

In this work, we used chitosan as a raw material to synthesize carbon dots using fast microwave carbonization. We studied the influence of the synthesis time, doping agent, and the molar ratio between the reactants on the quantum yield of carbon dots. Chitosan-based carbon dots displayed stable blue fluorescence emission with excitation-dependent behavior and quantum yield values ranging from 1.16 to 7.07 %. ANOVA results showed that the interaction factor between the doping agent and the molar ratio of the reactants was a significant combination to produce carbon dots with higher quantum yield. The presence of the doping agent improved the carbon dots optical properties by obtaining higher fluorescence intensity values. Confocal laser microscope images showed that the carbon dots internalized in the Candida albicans cellular membrane, exhibiting blue, green, and red emissions, acting as a promising agent for bioimaging.

A zeolite-based ship-in-a-bottle route to ultrasmall carbon dots for live cell labeling and bioimaging

Fluorescent carbon quantum dots (CQDs) are a new class of carbon nanomaterials that have excellent biocompatibility and low toxicity, useful for cell labeling and bioimaging. However, it is challenging to reproducibly create CQDs that are uniform and small in size with controlled toxicity and fluorescence properties, and this status quo hinders the practical application of CQDs, especially in vivo. In this report, CQDs with a uniform size of ∼1.53 ± 0.42 nm are synthesized via in situ pyrolysis of organics confined in the smallest-pore zeolite SAPO-20 with a micropore aperture of 0.28 nm. The ultrasmall fluorescent CQDs show a bright green fluorescence with a quantum yield (QY) of 16%, higher than that of most of the bare CQDs without any functionalization and maximum emission at 523 nm under the irradiation of xenon-light at an excitation wavelength of 470 nm. X-ray photoelectron spectroscopy (XPS) characterization confirms the presence of rich carboxyl and hydroxyl groups on the CQD surface containing N- and O-based functional groups. The synthesized CQDs with high QY and low cytotoxicity have been successfully used for cellular imaging with excellent biocompatibility.

Cross-Linked Polyamide Chains Enhanced the Fluorescence of Polymer Carbon Dots

Carbon dots (CDs) have attracted tremendous attention for their outstanding advantages in luminescence. Here, α-amino-substituted lysine derivatives with the determined chemical structure were employed as precursors to obtain bright and highly stable fluorescent CDs through a facile hydrothermal route. The relationships among the chemical structure of precursors, CD fluorescence, and particle size were investigated. The results indicated that increased numbers of functional groups in precursors could promote the degree of cross-linking and lead to a smaller size, better fluorescent properties, and stronger stability of CDs. The C-CDs that were prepared from lysine derivatives with most functional groups showed excitation-dependent dual excitation and dual emission (DE2), high-stability luminescence, strong resistance to photobleaching, and high selectivity to Fe3+ and could be used as a sensitive probe for Fe3+ detection.

Hemostatic and hepatoprotective bioactivity of Junci Medulla Carbonisata-derived Carbon Dots

AIM

To explore the hemostatic and hepatoprotective bioactivity of Junci Medulla Carbonisata-derived Carbon Dots (JMC-CDs).

MATERIALS & METHODS

The JMC-CDs were characterized using transmission electron microscopy, HPLC, Fourier transform IR, UV, fluorescence and x-ray photoelectron spectroscopy. The hemostatic effect of JMC-CDs was evaluated and confirmed by trauma hemorrhagic animal models and internal hemorrhage animal model induced by Deinagkistrodon acutus venom.

RESULTS

The JMC-CDs ranged in diameter from 1.0 to 8 nm and had a yield of 0.12%. Moreover, JMC-CDs not only possessed remarkable hemostatic efficacy but could also prevent hemorrhage-induced liver injury, as demonstrated by the reduced serum levels of biochemical indicators of liver damage such as aspartate aminotransferase, alanine amino transferase, alkaline phosphatase, total bilirubin and direct bilirubin.

CONCLUSION

The JMC-CDs may have great potentials in clinical practice.

Haemostatic bioactivity of novel Schizonepetae Spica Carbonisata-derived carbon dots via platelet counts elevation

Schizonepetae Spica Carbonisata (SSC) has pronounced haemostatic effects for hundreds of years and has been acknowledged in the 2015 Pharmacopoeia of the People's Republic of China (PPRC) as a haemostatic charcoal drug. However, after years of efforts, the underlying mechanism and the material basis is still less defined. In this research, we developed a novel CDs derived from SSC (SSC-CDs) with an average diameter of 1.29-6.87 nm and a quantum yield of 6.31%. SSC was prepared using a modified pyrolysis method and no further modification and external surface passivation agent is required. With abundant surface groups, SSC-CDs showed distinct solubility and bioactivity. In this study, we innovatively used the Deinagkistrodon acutus (D. acutus) venom model as well as the classical haemorrhagic animal model to evaluate the haemostatic bioactivity of SSC-CDs. The results indicated that SSC-CDs had outstanding haemostatic bioactivity and might inhibit the haemorrhagic activity via PLT elevation. According to the results of this study and our previous work, we discovered that CDs derived from different kinds of charcoal drugs presented similarities and differences in the structural feature, physicochemical property and bioactivity. In order to further explore the self-bioactivities, we first named this kind of CDs as "Chinese Medicine charcoal drug nanoparticles" (CMNP). These results may not only provide evidence for further researches of self-bioactivities of CDs but give new insights into potential biomedical and healthcare applications of CDs, therefore, make contributions to future drug discovery.

Novel carbon dots derived from Schizonepetae Herba Carbonisata and investigation of their haemostatic efficacy

Schizonepetae Herba Carbonisata (SHC) has been used in traditional Chinese medicine (TCM) to treat haemorrhagic diseases for more than 1000 years. However, little information is available on its haemostatic components and mechanism. In this study, we developed novel water-soluble carbon dots (CDs) in aqueous extracts of SHC for the first time and a modified pyrolysis method was used to prepare the SHC using Schizonepetae Herba (SH) as the sole precursor. The SHC-CDs were characterized using transmission electron microscopy (TEM), high-resolution TEM (HRTEM), Fourier transform infrared (FT-IR), ultraviolet-visible (UV-Vis) and fluorescence spectroscopy, X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD) and high-performance liquid chromatography (HPLC). Furthermore, the CDs with a quantum yield (QY) around 2.26% exhibited no toxicity within approximately 0.84 mg/mL in the CCK-8 assay. More interestingly, tail haemorrhaging and liver haemorrhaging experiments showed that CDs-treated mice had significantly shorter bleeding time than did normal saline (NS)-treated control group. Coagulation assays suggested that SHC-CDs could stimulate the extrinsic blood coagulation system and activate the fibrinogen system. These results suggested that SHC-CDs possess a remarkable haemostatic property, which provides evidence to support the further investigation of the considerable potential and effective material basis of TCM.

Polymers in Carbon Dots: A Review

Carbon dots (CDs) have been widely studied since their discovery in 2004 as a green substitute of the traditional quantum dots due to their excellent photoluminescence (PL) and high biocompatibility. Meanwhile, polymers have increasingly become an important component for both synthesis and modification of CDs to provide polymeric matrix and enhance their PL property. Furthermore, critical analysis of composites of CDs and polymers has not been available. Herein, in this review, we summarized the use of polymers in the synthesis and functionalization of CDs, and the applications of these CDs in various fields.

Microwave assisted green synthesis of fluorescent N-doped carbon dots: Cytotoxicity and bio-imaging applications

A fast and facile microwave approach for the synthesis of fluorescent nitrogen-doped carbon dots (N-CDs) is reported. The N-CDs were hydrothermally synthesized using l-ascorbic acid (AA) and β-alanine (BA) as the carbon precursor and the nitrogen dopant, respectively. The morphology of synthesized N-CDs was characterized by high resolution transmission electron microscopy (HR-TEM) and the elemental composition was analyzed using elemental mapping method. The crystallinity and graphitation of N-CDs were examined by X-ray diffraction (XRD) and Raman spectroscopy. The doping of nitrogen over the carbon dots (CDs) was revealed by attenuated total reflection conjunction with Fourier transform infrared (ATR-FTIR) spectroscopy and X-ray photo electron spectroscopy (XPS). The optical properties of synthesized N-CDs were examined by UV-Visible (UV-Vis) and fluorescence spectroscopy. The synthesized N-CDs emit strong blue fluorescence at 401nm under excitation of 325nm. The excitation dependent emission property of synthesized N-CDs was exposed from fluorescence results. The quantum yield of synthesized N-CDs is about 14% against the reference quinine sulfate. The cytotoxicity of synthesized N-CDs on Madin-Darby Canine Kidney (MDCK) and HeLa cells were evaluated through Cell Counting Kit-8 (CCK-8) cytotoxicity assay. The results implied that the fluorescent N-CDs showed less cytotoxicity, further which was successfully applied as a staining probe for the confocal imaging of MDCK and HeLa cells.

One-pot synthesis and control of aqueous soluble and organic soluble carbon dots from a designable waterborne polyurethane emulsion

Carbon dots (CDs) have a wide range of applications and have drawn great interest in the recent decade. The fabrication and control of CDs with different solubilities are still urgent problems for their practical use. In this paper, aqueous soluble and organic soluble CDs (ACDs, OCDs) were produced by one-pot hydrothermal treatment of a designable waterborne polyurethane (WPU) emulsion. The difference in the solubility and fluorescence of these two kinds of CDs was attributed to the various functional groups on the surface, which were derived from the different segment fragments formed by hydrothermal treatment of a block polymer. It was found that the yields of the ACDs and OCDs could be regulated by means of selecting different soft segments in WPU. The more hydrophobic soft segments could result in an increase of the OCDs and a decrease of the ACDs. While the soft segments were hydrophilic or hydrolysable under hydrothermal conditions, only ACDs were obtained. The ACDs had good fluorescence and showed low cytotoxicity for use in multicolour bio-imaging. The OCDs processed good solubility in a wide range of organic solvents and were suitable for preparing fluorescent composite films with polymers.

Carbogenic nanodots derived from organo-templated zeolites with modulated full-color luminescence

Dual modulated luminescence of carbogenic nanodots derived from zeolites has been acquired by controlling the concentration and pH value of CND aqueous dispersions.

Hydrophilic N-doped carbogenic nanodots (denoted as CNDs) have been prepared from a N-methylpiperazine-templated zeolite precursor by calcination and NaOH treatment. The isolated CNDs exhibit tunable photoluminescence according to the concentration and pH value of aqueous dispersions of the CNDs. Fine-tuning of the fluorescence emission wavelength across the entire visible spectrum can be easily achieved by varying the concentration of the CND dispersions. Meanwhile, both the emission wavelength and intensity of the photoluminescence can be tuned by controlling the pH value of the CND dispersion. The pyrolysis of organic templates confined in nanoporous zeolites represents a new approach to controlling the optical properties of CNDs, which may open more opportunities in applications such as multimodal sensing and full-color displays.

Tunable Luminescent Carbon Nanospheres with Well-Defined Nanoscale Chemistry for Synchronized Imaging and Therapy

In this work, we demonstrate the significance of defined surface chemistry in synthesizing luminescent carbon nanomaterials (LCN) with the capability to perform dual functions (i.e., diagnostic imaging and therapy). The surface chemistry of LCN has been tailored to achieve two different varieties: one that has a thermoresponsive polymer and aids in the controlled delivery of drugs, and the other that has fluorescence emission both in the visible and near-infrared (NIR) region and can be explored for advanced diagnostic modes. Although these particles are synthesized using simple, yet scalable hydrothermal methods, they exhibit remarkable stability, photoluminescence and biocompatibility. The photoluminescence properties of these materials are tunable through careful choice of surface-passivating agents and can be exploited for both visible and NIR imaging. Here the synthetic strategy demonstrates the possibility to incorporate a potent antimetastatic agent for inhibiting melanomas in vitro. Since both particles are Raman active, their dispersion on skin surface is reported with Raman imaging and utilizing photoluminescence, their depth penetration is analysed using fluorescence 3D imaging. Our results indicate a new generation of tunable carbon-based probes for diagnosis, therapy or both.

Facile Microwave-Assisted Solid-Phase Synthesis of Highly Fluorescent Nitrogen-Sulfur-Codoped Carbon Quantum Dots for Cellular Imaging Applications

Carbon quantum dots (CQDs) have recently attracted significant attention for both their fundamental science and technological applications as a new class of fluorescent zero-dimensional nanomaterials with a size below 10 nm. However, the reported methods of synthesis were generally less suitable for the large-scale production of the CQDs with high-fluorescent quantum yield (QY). In the paper, a novel one-pot microwave-assisted drying synthesis approach was presented to prepare CQDs with high QY of 61.3 % for the first time. The production yield of CQDs was 35±3 % in weight. The as-prepared CQDs were characterized by various techniques such as TEM, AFM, XRD, XPS, FTIR spectroscopy, UV/Vis absorption spectroscopy, and fluorescence spectroscopy. The results showed that the high QY of CQDs was largely attributed to the dual doping of nitrogen and sulphur into CQDs. Such CQDs were then used as live-cell imaging reagents due to their high QY, good water dispersibility, fine biocompatibility, high photostability, and low cytotoxicity.

Scale-Up Synthesis of Fragrant Nitrogen-Doped Carbon Dots from Bee Pollens for Bioimaging and Catalysis

Fragrant nitrogen-doped carbon dots of gram scale can be prepared from commercial bee pollens by a hydrothermal process. These carbon dots of 1-2 nm in size show promising applications in cellular imaging and catalysis/photocatalysis.

A General Method Towards Efficient Synthesis and Fluorescence Tuning of Carbon Black-Derived Carbon Dots via Controlled Liquid Oxidization

Efficient synthesis and controlled modification of carbon dots (CDs) with tuneable properties on the basis of facile technical routes are of great significance for user-defined applications as well as more insightful understanding of the unique fluorescence from carbon nanomaterials. In this work, we report an improved nitric acid oxidization method towards low-cost and rapid preparation of fluorescent CDs. This is achieved by using industrial carbon black specimens as the precursor and implementing a reduced pressure distillation for the purpose of eliminating excessive acids. Unexpectedly, the product exhibits an interesting dual luminescence behaviour with tuneable characteristics that differs from all previously reported CDs. The strongest emissions at fixed or varied excitations can be simultaneously tuned from blue to green or yellow by simply prolonging the time of acid oxidization. These emissions show distinct stabilities in acid and alkaline environments, thereby making the resultant CDs very promising candidates for pH probes. It is further revealed that this simple synthesis and fluorescence tuning strategy is also applicable to CDs from other carbon blacks.

Sensing applications of luminescent carbon based dots

Carbon based dots (CDs) including carbon quantum dots and graphene quantum dots exhibit unique luminescence properties, such as photoluminescence (PL), chemiluminescence (CL) and electrochemiluminescence (ECL).