Rapid Synthesis of Carbon Dots by Hydrothermal Treatment of Lignin.
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ABSTRACT:
SUBMITTER: Chen W
PROVIDER: S-EPMC5456677 | biostudies-other | 2016 Mar
REPOSITORIES: biostudies-other
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Project description:The transformation of lignin with natural aromatic structure into value-added carbon dots (CDs) achieves a win-win situation for low-cost production of novel nanomaterials and reasonable disposal of biomass waste. However, it remains challenging to produce multi-emission CDs from biomass for advanced applications. Herein, a green and facile approach to preparing multi-emission CDs from alkali lignin via N and B co-doping is developed. The obtained N and B co-doped CDs (NB-CDs) show multi-emission fluorescence centers at 346, 428 and 514 nm under different excitations. As the doping amount of N and B increases, the fluorescence emission band gradually shifts to 428 and 514 nm, while that at 346 nm decreases. The fluorescence mechanism is explored through the research of the structure, composition and optical performance of NB-CDs in combination with density functional theory (DFT) calculations. It demonstrates that the effect of doping with B-containing functional groups on the fluorescence emission behavior is multivariate, which may be the crucial contribution to the unique multi-emission fluorescence of CDs. The multi-emission NB-CDs with prominent stability are applied for multilevel anti-counterfeiting printing. It provides a promising direction for the sustainable and advanced application of biomass-derived CDs, and the theoretical results highlight a new insight into the deep understanding of the multi-emission fluorescence mechanism.
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Project description:BackgroundCarbon dots (CDs) are widely used in cell imaging due to their excellent optical properties, biocompatibility and low toxicity. At present, most of the research on CDs focuses on biomedical application, while there are few studies on the application of microbial imaging.ResultsIn this study, B- and N-doped carbon dots (BN-CDs) were prepared from citric acid, ethylenediamine, and boric acid by microwave hydrothermal method. Based on BN-CDs labeling yeast, the dead or living of yeast cell could be quickly identified, and their growth status could also be clearly observed. In order to further observe the morphology of yeast cell under different lethal methods, six methods were used to kill the cells and then used BN-CDs to label the cells for imaging. More remarkably, imaging of yeast cell with ultrasound and antibiotics was significantly different from other imaging due to the overflow of cell contents. In addition, the endocytosis mechanism of BN-CDs was investigated. The cellular uptake of BN-CDs is dose, time and partially energy-dependent along with the involvement of passive diffusion. The main mechanism of endocytosis is caveolae-mediated.ConclusionBN-CDs can be used for long-term stable imaging of yeast, and the study provides basic research for applying CDs to microbiol imaging.
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Project description:Nitrogen and sulfur codoped carbon dots (NSCDs) were synthesized via a one-pot hydrothermal method, and citric acid, ethylenediamine, and methyl blue were used as precursors. The obtained NSCDs were spherical with an average size of 1.86 nm. The fluorescence emission spectra of the NSCDs were excitation independent and emitted blue fluorescence at 440 nm with an excitation wavelength at 350 nm. The quantum yield of the NSCDs was calculated to be 68.0%. The NSCDs could be constructed as fluorescent probes for highly selective and sensitive sensing mercuric (Hg2+) and hypochlorite (ClO-) ions. As the addition of Hg2+ or ClO- ions to the NSCDs, the fluorescence intensity was effectively quenched due to dynamic quenching. Under the optimal conditions, the linear response of the fluorescence intensity ranged from 0.7 μM to 15 μM with a detection limit of 0.54 μM and from 0.3 μM to 5.0 μM with a limit of detection of 0.29 μM for Hg2+ and ClO- ions, respectively. Finally, the proposed method was successfully used for quantifying Hg2+ and ClO- ions in spiked tap water samples.
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Project description:Nitrogen-doped carbon dots (N-CDs) were synthesized using a one-pot hydrothermal treatment with citric acid in the presence of polyethylenimine. Transmission electron microscopy analysis revealed that the N-CDs were monodispersed and quasi-spherical with an average size of ~2.6 nm. Under ultraviolet irradiation the N-CDs emitted a strong blue luminescence with a quantum yield as high as 51%. Moreover, the N-CDs exhibited a negligible cytotoxicity and could be applied as efficient nanoprobes for real-time imaging of live cells. In addition, the ability of the N-CDs to cross the blood-brain barrier (BBB) in a concentration-dependent manner was demonstrated using an in vitro BBB model. Therefore, these PEI-passivated N-CDs with real-time live-cell imaging and BBB-penetration capabilities hold promise for traceable drug delivery to the brain.
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Project description:The emerging carbon quantum dots (CQDs) have been attracting significant attention for their prominent fluorescence, excellent stability and outstanding biocompatibility. Here, we report a facile one-step synthesis of highly fluorescent CQDs by using phthalic acid and triethylenediamine hexahydrate as precursors through a simple microwave-assisted method. The reaction time needed is only 60?s, which is less time-consuming than most previous reports. The phthalic acid with a benzene ring can improve the photoluminescence properties of CQDs as it can provide foreign sp2 conjugating units, and then finally result in long-wavelength emission. The synthesized CQDs were fully characterized by transmission electron microscopy, X-ray photoelectron spectroscopy and Fourier transform infrared spectroscopy. Besides, the impacts of different freed ratio on physical and chemical properties of CQDs were investigated in detail. The prepared CQDs exhibited strong green fluorescence with a broad maximum emission wavelength. The quantum yields of the CQDs can reach 16.1% in aqueous solution and they were successfully used in cell imaging with good biocompatibility. Moreover, in solid state, the CQDs with the feed ratio of 1?:?0.5 showed a strong green-yellow fluorescence which may have great potential to fabricate optoelectronic devices. Furthermore, the prepared CQDs also showed high pH sensitivity and can act as a fluorescence nanosensor for pH sensing.
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Project description:Porous carbon has been widely used for many applications e.g., adsorbents, catalysts, catalyst supports, energy storage and gas storage due to its outstanding properties. In this paper, characteristics of porous carbon prepared by carbonization of lignin from various biomasses are presented. Various biomasses, i.e., mangosteen peel, corncob and coconut shell, were processed using ethanol as an organosolv solvent. The obtained lignin was characterized using a Fourier transform infrared (FTIR) spectrophotometer and a viscosimeter to investigate the success of extraction and lignin properties. The results showed that high temperature is favorable for the extraction of lignin using the organosolv process. The FTIR spectra show the success of lignin extraction using the organosolv process because of its similarity to the standard lignin spectra. The carbonization process of lignin was performed at 600 and 850 °C to produce carbon from lignin, as well as to investigate the effect of temperature. A higher pyrolysis temperature will produce a porous carbon with a high specific surface area, but it will lower the yield of the produced carbon. At 850 °C temperature, the highest surface area up to 974 m2/g was achieved.
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Project description:Abstract As an emerging building unit, carbon dots (CDs) have been igniting the revolutionaries in the fields of optoelectronics, biomedicine, and bioimaging. However, the difficulty of synthesizing CDs in aqueous solution with full?spectrum emission severely hinders further investigation of their emission mechanism and their extensive applications in white light emitting diodes (LEDs). Here, the full?color?emission CDs with a unique structure consisting of sp3?hybridized carbon cores with small domains of partially sp2?hybridized carbon atoms are reported. First?principle calculations are initially used to predict that the transformation from sp3 to sp2 hybridization redshifts the emission of CDs. Guided by the theoretical predictions, a simple, convenient, and controllable route to hydrothermally prepare CDs in a single reaction system is developed. The prepared CDs have full?spectrum emission with an unprecedented two?photon emission across the whole visible color range. These full?color?emission CDs can be further nurtured by slight modifications of the reaction conditions (e.g., temperature, pH) to generate the emission color from blue to red. Finally a flexible LEDs with full?color emission by using epoxy CDs films is developed, indicating that the strategy affords an industry translational potential over traditional fluorophores. A novel multi?color?emissive carbon dots (CDs) with two?photon fluorescence are developed in aqueous solution for the first time by slight modifications of the reaction conditions. Theoretical calculations combined with experiments show that the photoluminescence mechanism of the multi?color?emissive CDs is the size change and the conversion of sp3 to sp2 hybridization.
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