Green synthesis of carbon dots originated from Lycii Fructus for effective fluorescent sensing of ferric ion and multicolor cell imaging.

Green, economical and effective method was developed for synthesis of fluorescent carbon dots (CDs), using one-pot hydrothermal treatment of Lycii Fructus. Optical and structural properties of the CDs have been extensively studied by UV-visible and fluorescence spectroscopic, x-ray diffraction (XRD) techniques, transmission electron microscopy (TEM) and high resolution TEM (HRTEM). Surface functionality and composition of CDs has been illustrated by Fourier transform infrared spectroscopy (FTIR), x-ray photoelectron spectroscopy (XPS) spectra and elemental analysis. The fabricated CDs possess stable fluorescent properties. The fluorescent quantum yield of the CDs can reach 17.2%. The prepared CDs emitted a broad fluorescence between 415 and 545nm and their fluorescence was tuned by changing excitation wavelength. Meanwhile, the fluorescence intensity of the CDs could be significantly quenched by Fe3+ (turn-off). The CDs exhibit captivating sensitivity and selectivity toward Fe3+ with a linear range from 0 to 30μM and a detection limit of 21nM. The prepared CDs were successfully applied to the determination of Fe3+ in the urine samples, the water samples from the from the Yellow River and living HeLa (Henrietta Lacks) cells. Moreover, the low-toxicity and excellent biocompatibility of the CDs were evaluated through MTT assay on HeLa cells. The CDs were also employed as fluorescent probes for multicolor imaging of HeLa cells successfully.

Sun X ，He J ，Yang S ，Zheng M ，Wang Y ，Ma S ，Zheng H ... -  《-》

Nitrogen and sulfur co-doped highly luminescent carbon dots for sensitive detection of Cd (II) ions and living cell imaging applications.

In this work, we have developed a green, simple and fast one-pot microwave-assisted strategy for synthesis of nitrogen and sulfur co-doped fluorescent carbon dots (CDs) using scallion (SL) as the carbon source. Optical properties of the SL-CDs have been measured by UV-visible and fluorescent spectroscopy. The morphology of the prepared SL-CDs has been performed by transmission electron microscopy (TEM). Surface functionality and elemental composition of SL-CDs was analyzed by Fourier transform infrared spectroscopy (FTIR) and X-ray photoelectron spectroscopy (XPS) spectra. The photoluminescent (PL) quantum yield of the obtained scallion carbon dots (SL-CDs) can reach as high as 18.6%. We further demonstrated that the SL-CDs can be used as fluorescent probes for detection of Cd2+ ions with a high sensitivity and an excellent selectivity. Linear relationships between the variation of the luminescent intensity of the SL-CDs before and after exposing the Cd2+ ions versus the concentration of Cd2+ ions in the range of 0.1-3.0 μM and 5.0-30.0 μM. The detection limit of Cd2+ ions can reach 15.0 nM. Moreover, the as-prepared SL-CDs exhibit negligible or extremely low cytotoxicity, which makes them be able to be used as fluorescent probes for living cell imaging. Overall, the prepared SL-CDs have promising applications in sensing of Cd2+ ions and in vivo or in vitro bioimaging.

Gu D ，Hong L ，Zhang L ，Liu H ，Shang S ... -  《-》

Facile preparation and characterization of new green emitting carbon dots for sensitive and selective off/on detection of Fe(3+) ion and ascorbic acid in water and urine samples and intracellular imaging in living cells.

Carbon dots (CDs) have gained great attention as multifunctional materials because of their interesting properties and general applicability. However, there are some reports for the preparation of highly luminescent green-emitting CDs (G-CDs), although these reports seem not to be extensible. Herein, new G-CDs (quantum yield: 27.2%) were synthesized from a facile hydrothermal treatment of p-aminosalicylic acid and ethylene glycol dimethacrylate as both carbon and nitrogen source and cross-linking agent, respectively. The chemical composition and optical properties of the as-prepared G-CDs were successfully investigated using transmission electron microscopy, atomic force microscopy, dynamic light scattering, X-ray diffraction, energy dispersive X-ray spectroscopy, Fourier transform infrared spectroscopy and fluorescence and UV-vis spectroscopies. Interestingly, the fluorescence intensity of G-CDs was selectivity quenched by Fe3+ in the range of 0.05-10.0 µmol L-1, with a detection limit of 13.7 nmol L-1. Meanwhile, ascorbic acid found to reduce Fe3+ to Fe2+, thereby causing restoration of the fluorescence of G-CDs. The detection limit for ascorbic acid detection was estimated as 82.0 nmol L-1 over a linear range from 0.2 to 11.0 µmol L-1. Furthermore, the designed sensing platform was successfully utilized to the detection of Fe3+ and ascorbic acid in water and urine samples and to intracellular imaging without surface modification.

Shamsipur M ，Molaei K ，Molaabasi F ，Alipour M ，Alizadeh N ，Hosseinkhani S ，Hosseini M ... -  《-》

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.

Edison TN ，Atchudan R ，Sethuraman MG ，Shim JJ ，Lee YR ... -  《-》

Nitrogen-doped carbon dots originating from unripe peach for fluorescent bioimaging and electrocatalytic oxygen reduction reaction.

This paper reports the robust hydrothermal synthesis of nitrogen doped carbon dots (N-CDs) using the unripe fruit of Prunus persica (peach) as the carbon precursor and aqueous ammonia as the nitrogen source. The optical properties of synthesized N-CDs were characterized by ultraviolet visible (UV-Vis) and fluorescence spectroscopy techniques. The synthesized N-CDs were emitted blue light when excitated with a portable UV lamp. The materials with the optical properties were characterized further by high resolution transmission electron microscope (HRTEM), X-ray diffraction (XRD), Raman, Fourier transform infrared (FT-IR) and X-ray photoelectron spectroscopy (XPS). The mean size of the N-CDs was approximately 8nm, as calculated from the HRTEM image. The d-spacing of N-CDs, calculated using Bragg law, was approximately 0.21nm, which was consistent with the interlayer distance calculated from the HRTEM image. FT-IR spectroscopy and XPS revealed the presence of the phytoconstituents functionalities of peach fruit over the N-CDs surface and a high level of nitrogen doping on carbon dots (CDs) was confirmed by XPS studies. These results suggest that the unripe fruit extract of peach is an ideal candidate for the preparation of N-CDs. The resulting N-CDs showed excellent optical properties in water. The synthesized N-CDs exhibited a high fluorescence quantum yield and low cytotoxicity, and can be used as fluorescence imaging probes. In addition, the N-CDs were catalytically activite towards the oxygen reduction reaction (ORR). The N-CDs exhibited good catalytic activity in an alkaline medium (0.1M KOH) with a remarkable ORR of approximately 0.72V vs reversible hydrogen electrode (RHE), and O2 reduction follows mainly a 2 electron pathway by being reduced to hydrogen peroxide. The 2-electron reduction pathway is used in industry for H2O2 production.

Atchudan R ，Edison TNJI ，Lee YR 《-》