Blue Fluorescent Carbon Dots Research Articles

Semi-quantitative and visual assay of copper ions by fluorescent test paper constructed with dual-emission carbon dots.

A novel, simple and effective dual-emissive fluorescent probe for the sensitive and selective detection of Cu(ii) has been developed by mixing blue carbon dots and orange carbon dots, with a sensitive detection limit of 7.31 nM. The blue fluorescence can be selectively quenched by Cu(ii), while the orange fluorescence is a internal reference, resulting in a distinguishable fluorescence color change from blue to orange under a UV lamp. Meanwhile, its as-prepared text paper provides a convenient and simple approach for the visual detection of Cu(ii) and successfully applied in real water samples, with a dose-discerning ability as low as 50 nM. The methodology reported here opens a novel pathway toward the real applications of fluorescent test papers.

A colorimetric paper sensor for visual detection of mercury ions constructed with dual-emission carbon dots

A ratiometric fluorescence nanosensor has been developed by mixing blue fluorescent carbon dots and red fluorescent carbon dots, where the blue fluorescence can be selectively quenched by Hg2+, while the red fluorescence is an internal reference.

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.

Fluorescent turn-off competitive immunoassay for biotin based on hydrothermally synthesized carbon dots

Blue fluorescent carbon dots (C-Dots) were synthesized by a hydrothermal process using citric acid and polyethylene-polyamines as the precursors. The C-dots display strong fluorescence, excellent water solubility, good biocompatibility, and possess many amino groups on their surface. Biotin was linked to the amino groups, and the resulting biotinylated C-dots were applied in a binding assay where they compete with free biotin (vitamin B7; coenzyme R) for binding to streptavidin immobilized on superparamagnetic Dynabeads®. After incubation and magnetic separation, the fluorescence intensity of immobilized biotinylated C-dots released from the beads is inversely proportional to the concentration of biotin in the 0.5 to 100 ng·mL−1 concentration range. The detection limit is 0.1 ng·mL−1. Conceivably, the method may be further extended to the determination of biotinylated biomolecules.

Blue and cyan fluorescent carbon dots: one-pot synthesis, selective cell imaging and their antiviral activity

Two types of carbon dots were prepared by using the powder of young barley leaves as the precursor, which have the capability of selective cell imaging and antiviral activity.

Pollen derived blue fluorescent carbon dots for bioimaging and monitoring of nitrogen, phosphorus and potassium uptake in Brassica parachinensis L.

Carbon dots (CDs), synthesized from biological sources, have attracted attention in bioimaging and bioscience due to their low cytotoxicity, water-soluble nature, and biocompatibility.

A facile synthesis of water-soluble carbon dots as a label-free fluorescent probe for rapid, selective and sensitive detection of picric acid

In this work, novel water-soluble and blue fluorescent carbon dots (C-dots) were synthesized using one-pot hydrothermal method with malonic acid and urea, and were then used as a label-free fluorescent probe for selective, sensitive, and rapid determination of picric acid (PA). The sizes of the as-prepared C-dots were mainly distributed in the range of 1.5–3.0nm with an average diameter of 2.5nm. Moreover, the C-dots displayed blue fluorescence with an emission peak at 395nm (320nm excitation), which also showed good stability and anti-photobleaching ability. Interestingly, the fluorescence of C-dots could be selectively quenched by PA within 10s. Based on this phenomenon, a label-free fluorescence assay was proposed for specific determination of PA. The fluorescence intensity of probe showed a linear response to PA in the concentration range of 0.1 to 26.5μM with a low detection limit of 51nM (S/N=3). Finally, the resultant fluorescent probe was successfully applied to the detection of PA in real water samples.

Amino acid functionalized blue and phosphorous-doped green fluorescent carbon dots as bioimaging probe

Thermal coupling between citric acid and Na-salt of glycine, l-valine and l-isolucine produced blue emitting carbon dots (CDs) and in presence of NaH2PO4, produced green emitting phosphorous doped CDs (PCDs), which were utilized for cell imaging.

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.

Carbon dots as a luminescence sensor for ultrasensitive detection of phosphate and their bioimaging properties.

Highly blue fluorescence carbon dots were synthesized by one-step hydrothermal treatment of potatoes. The as-obtained C-dots have been applied to bioimaging of HeLa cells, which shows their excellent biocompatibility and low cytotoxicity. The results reveal that C-dots are promising for real cell imaging applications. In addition, the carbon dots can be utilized as a probe for sensing phosphate.

Biodistribution study of carbogenic dots in cells and in vivo for optical imaging

Blue fluorescent carbon dots (C-dots) were synthesized and evaluated for their cytotoxicity and also for their optical imaging performance. The results showed that the C-dots could enter into the Hela cells in 15 min incubation and the uptake increased rapidly from 15 min to 2 h. In cytotoxicity study, C-dots were biocompatible and nontoxic to three human cells including two cancer cells (Hela and SMCC-7721) and one normal cell (HEK 293) in concentrations up to 500 μg/mL. Since the endocytic interference factors, including NaN3, MβCD, sucrose, and low temperature, could not play an inhibitory effect on C-dots entering into cells, the direct nonendocytic pathway for C-dots was speculated. The C-dots showed encouraging cell-imaging applications in vitro and in vivo. They entered into cells without any further functionalization, and the fluorescence property of these particles can be used for fluorescence-based cell-imaging applications.

Electron transfer quenching by nitroxide radicals of the fluorescence of carbon dots

Blue fluorescent carbon dots (CDs) were synthesized by a microwave assisted one-step procedure without surface passivation. The intermolecular interactions between the CDs and nitroxide radicals in aqueous and aprotic solution were investigated. The fluorescence of the CDs was found to be efficiently quenched by the paramagnetic nitroxide radical. A SOMO (singly occupied molecular orbital) facilitated electron transfer was proposed to account for the quenching of the fluorescence of the CDs in the CD@TEMPO conjugate, formed via electrostatic interactions between the negatively charged CDs and the cationic 4-amino-2,2,6,6-tetramethylpiperidine-N-oxide free radical (4-AT). Covalently spin-labeled CDs by the paramagnetic nitroxide radical yield a weakly fluorescent spin-labeled conjugate (CD–TEMPO), which exhibits sensitive fluorescence and electron spin resonance (ESR) bimodal response towards ascorbic acid (AA) at the μM level. The fluorescence intensity of the spin-labeled CDs was also found to be sensitive to paramagnetic factors and thus establishes its promising potential for constructing a bimodal responsive sensor with off–on fluorescence and on–off ESR signaling for the detection of antioxidants and carbon-centered radicals.