Fluorescent N-doped Carbon Dots Research Articles

Hydrothermal synthesis of N-doped carbon dots for selective fluorescent sensing and cellular imaging of cobalt(II)

Strongly blue fluorescent N-doped carbon dots (CDs) were synthesized by using citric acid (CA) as the carbon source and diethylenetriamine (DETA) as the nitrogen source using a one-step hydrothermal method. Several synthetic parameters, including the molar ratios of initial starting materials, the temperature and time of hydrothermal reaction, were investigated and optimized. The range and average value of the diameters of the resultant CDs were 1.2–4.0 nm and 2.3 nm, respectively. The synthesized CDs display fluorescence with excitation/emission maxima of 391/438 nm and a quantum yield of 58%. Fluorescence is quenched by Co(II) ions, and this effect was exploited to design a method for determination of Co(II) in water and to image it in living HeLa (cervical carcinoma) cells. The limit of detection and linear range of Co2+ using the synthesized CDs as fluorescence probe are 0.4 μmol·L−1 and 0–90 μmol·L−1, respectively. Due to the selective and sensitive response of Co2+, the CDs possess potential applications in biological labeling for the demands such as monitoring the distribution of vitamin B-12 or other cobalt-containing medicines in cells or organisms.

Biological and catalytic applications of green synthesized fluorescent N-doped carbon dots using Hylocereus undatus

In this work, a simple hydrothermal route for the synthesis of fluorescent nitrogen doped carbon dots (N-CDs) is reported. The Hylocereus undatus (H. undatus) extract and aqueous ammonia are used as carbon and nitrogen source, respectively. The optical properties of synthesized N-CDs are analyzed using UV–Visible (UV–Vis) and fluorescence spectroscopy. The surface morphology, elemental composition, crystallinity and functional groups present in the N-CDs are examined using high resolution transmission electron microscopy (HR-TEM) with energy dispersive spectroscopy (EDS), selected area electron diffraction (SAED), X-ray diffraction (XRD) and Fourier transform infrared (FT-IR) spectroscopy, respectively. The synthesized N-CDs emit strong blue fluorescence at 400nm under the excitation of 320nm. Further, the excitation dependent emission properties are also observed from the fluorescence of synthesized N-CDs. The HR-TEM results reveal that synthesized N-CDs are in spherical shape with average diameter of 2.5nm. The XRD pattern exhibits, the graphitic nature of synthesized N-CDs. The doping of nitrogen is confirmed from the EDS and FT-IR studies. The cytotoxicity and biocompatibility of N-CDs are evaluated through MTT assay on L-929 (Lymphoblastoid-929) and MCF-7 (Michigan Cancer Foundation-7) cells. The results indicate that the fluorescent N-CDs show less cytotoxicity and good biocompatibility on both L-929 and MCF-7 cells. Moreover, the N-CDs show excellent catalytic activity towards the reduction of methylene blue by sodium borohydride.

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.

Turn-off fluorescence sensor for the detection of ferric ion in water using green synthesized N-doped carbon dots and its bio-imaging

This paper reports turn-off fluorescence sensor for Fe3+ ion in water using fluorescent N-doped carbon dots as a probe. A simple and efficient hydrothermal carbonization of Prunus avium fruit extract for the synthesis of fluorescent nitrogen-doped carbon dots (N-CDs) is described. This green approach proceeds quickly and provides good quality N-CDs. The mean size of synthesized N-CDs was approximately 7nm calculated from the high-resolution transmission electron microscopic images. X-ray photoelectron spectroscopy and Fourier transform infrared spectroscopy revealed the presence of –OH, –NH2, –COOH, and –CO functional groups over the surface of CDs. The N-CDs showed excellent fluorescent properties, and emitted blue fluorescence at 411nm upon excitation at 310nm. The calculated quantum yield of the synthesized N-CDs is 13% against quinine sulfate as a reference fluorophore. The synthesized N-CDs were used as a fluorescent probe towards the selective and sensitive detection of biologically important Fe3+ ions in water by fluorescence spectroscopy and for bio-imaging of MDA-MB-231 cells. The limit of detection (LOD) and the Stern–Volmer quenching constant for the synthesized N-CDs were 0.96μM and 2.0958×103M of Fe3+ ions. The green synthesized N-CDs are efficiently used as a promising candidate for the detection of Fe3+ ions and bio-imaging.

Synthesis of fluorescent nitrogen-doped carbon dots from dried shrimps for cell imaging and boldine drug delivery system

Fluorescent N-doped carbon dots were synthesized using dried shrimps as precursors and rationally fabricated as a traceable drug delivery system for the targeted delivery of boldine to human breast cancer cells (MCF-7 cells).

Fluorescent N-Doped Carbon Dots as in Vitro and in Vivo Nanothermometer.

The fluorescent N-doped carbon dots (N-CDs) obtained from C3N4 emit strong blue fluorescence, which is stable with different ionic strengths and time. The fluorescence intensity of N-CDs decreases with the temperature increasing, while it can recover to the initial one with the temperature decreasing. It is an accurate linear response of fluorescence intensity to temperature, which may be attributed to the synergistic effect of abundant oxygen-containing functional groups and hydrogen bonds. Further experiments also demonstrate that N-CDs can serve as effective in vitro and in vivo fluorescence-based nanothermometer.

Fluorescent N-doped carbon dots for both cellular imaging and highly-sensitive catechol detection

N-doped carbon dots (NCDs) obtained by one-step reflux treatment of C3N4 with ethane diamine possess good water dispersibility, strong visible fluorescence, low toxicity, proton adsorption capacity, and photo-induced electron-accepting/donating abilities. Based on these unique properties, we demonstrate that the obtained NCDs can be used as a good fluorescent probe for cellar imaging without any further functionalization. Further, the NCDs are combined with laccase (LAC) to form NCDs–laccase (NCD–LAC) hybrids, which are sensitive, stable, and of low cost for the precise detection of catechol and catechol derivatives.

One-step synthesis of robust nitrogen-doped carbon dots: acid-evoked fluorescence enhancement and their application in Fe3+ detection

Robust and highly fluorescent N-doped carbon dots (CDs) are obtained from a hybrid source, alginic acid and ethanediamine.

Hydrophilic and blue fluorescent N-doped carbon dots from tartaric acid and various alkylol amines under microwave irradiation.

The desired control of particle size, doping element composition, and surface structure of carbon dots (CDs) are vital for understanding the fluorescence mechanism and exploring their potential applications. Herein, nitrogen-doped CDs (N-doped CDs) have been synthesized with tartaric acid and various alkylol amines (monoethanolamine, biethanolamine and triethanolamine) under microwave irradiation. A systematic investigation was performed to characterize the N-doped CDs. It is found that with increasing nitrogen proportion, the fluorescent quantum yield and lifetime of N-doped CDs increases, whereas cell toxicity decreases. In other words, N-doped CDs synthesized by tartaric acid and monoethanolamine have the highest nitrogen content, the highest fluorescent quantum yield, the longest lifetime and the lowest cell toxicity. A corresponding mechanism has been proposed. Moreover, as-synthesized N-doped CDs have been applied for selectively detecting the Fe(3+) ion and writing letters as a fluorescent ink.

One-step catalase controllable degradation of C3N4 for N-doped carbon dot green fabrication and their bioimaging applications.

Water-soluble fluorescent N-doped carbon dots (N-C dots) obtained by enzyme catalyzed degradation of C3N4 show high stability, good biocompatibility, and can be promising candidates for bioimaging.

One-step ultrasonic synthesis of fluorescent N-doped carbon dots from glucose and their visible-light sensitive photocatalytic ability

Water-soluble fluorescent N-doped carbon dots (NCDs) were synthesized by a facile one-pot ultrasonic reaction between glucose and ammonium hydroxide. Besides exhibiting strong luminescence in the visible-to-near infrared range, the obtained NCDs displayed clear upconversion photoluminescence properties. Moreover, the NCDs showed excellent photocatalytic property in the photodegradation of methyl orange under visible light.