Single-step synthesis of N-doped carbon dots and applied for dopamine sensing, in vitro multicolor cellular imaging as well as fluorescent ink

Synthesis of Temperature Sensing Nitrogen-Doped Carbon Dots and Their Application in Fluorescent Ink

With the discovery of research, many properties of carbon dots are getting better and better. People have taken advantage of this and utilized them interspersed in various fields. In the present study, water-soluble nitrogen-doped carbon dots (N-CDs) with excellent optical and fluorescence thermal properties were prepared by the hydrothermal method using 4-dimethylaminopyridine and N,N'-methylenebisacrylamide as precursors. Co2+ has a selective bursting effect on the fluorescence of N-CDs. The fluorescence of N-CDs is selectively burst by Co2+, and the high sensitivity is good in the range of 0-12 μM with a detection limit of 74 nM. In addition, the good temperature response (reversible and recoverable fluorescence in the temperature range of 20~90 °C) and excellent optical properties of the N-CDs also make them new potentials in the field of fluorescent inks and temperature sensing.

High quantum yield carbon dots and nitrogen-doped carbon dots as fluorescent probes for spectroscopic dopamine detection in human serum

Recent advances in fluorescent carbon dots have shown great potential for the sensing of biological molecules. In this study, one-step hydrothermally synthesised carbon dots (CD) and nitrogen doped carbon dots (NCD) with high quantum yields of 54.29% and 89.82%, respectively, were investigated and demonstrated to be a reliable, cost-effective, and naked-eye fluorescent probe for the detection of dopamine, a neurotransmitter, in human serum fluids. The current study is well supported by a comprehensive synthesis approach and has been described utilizing a variety of microscopic and spectroscopic techniques. The discovered approach is time and pH dependent, and it provides a robust platform for specifically detecting aberrant dopamine levels using a fluorescence quenching mechanism. Dopamine detection limits for CD were calculated to be 5.54 μM for CD and 5.12 μM for NCD, respectively. The fluorescence quenching shows a linear continuous trend with a range within 3.3-500 μM and 3.3-400 μM of dopamine concentration for CD and NCD respectively. To further verify the sensitivity of CD and NCD as fluorescent probes, interference studies in the presence of different biological components were also studied and validated. This work shows that carbon-based nanomaterials and their doped nanostructures, due to their high fluorescence, have significant potential as fluorescent probes in neurological disease diagnosis as they display high selectivity, sensitivity and fast responses in the real time spectroscopic detection of dopamine in human fluid samples.

Bioresource-derived colloidal nitrogen-doped graphene quantum dots as ultrasensitive and stable nanosensors for detection of cancer and neurotransmitter biomarkers

Rapid and accurate detection of cancer and neurological diseases is a major issue that has received great attention recently to enable early therapy treatment. In this report, we utilize an atmospheric pressure microplasma system to convert a natural bioresource chitosan into nitrogen-doped graphene quantum dots (NGQDs) for photoluminescence (PL) based selective detection of cancer and neurotransmitter biomarkers. By adjusting the pH conditions during the detection, multiple biomolecules including uric acid (UA), folic acid (FA), epinephrine (EP), and dopamine (DA) can be simultaneously detected with high selectivity and sensitivity using a single material only. Linear relationships between the biomarker concentration and the PL intensity ratio are obtained starting from 0.8 to 100 μM with low limits of detection (LoDs) of 123.1, 157.9, 80.5, and 91.3 nM for UA, EP, FA, and DA, respectively. Our work provides an insight into the multiple biomarker detection using a single material only, which is beneficial for the early detection and diagnosis of cancer and neurological diseases, as well as the development of new drugs.

Efficient synthesis of yellow-green carbon quantum dots as a sensitive fluorescent probe of folic acid

Bright yellow-green carbon quantum dots (YGCDs) have been successfully synthesized by a simple and efficient hydrothermal method. Its luminescent absolute quantum yield reached 30.0% in 4 h, compared with that using common reported solvothermal method, the synthesis time was reduced more than 70% with tin oxide nano particles as a catalyst. Moreover, the fluorescence of YGCDs could be selectively quenched by folic acid (FA) molecules, and the relative fluorescence intensities of F/F0 was fitted perfectly in line decay curve versus the concentration of FA in the range of 2.0 × 10-8 mol/l ~ 1.0 × 10-5 mol/l (R2 = 0.9988). The detection limit of FA was below 2.0 × 10-8 mol/l, suggesting a promising fluorescent probe of folic acid.

Microplasma-Enabled Surfaced-Functionalized Silicon Quantum Dots for Label-Free Detection of Dopamine

Rapid and sensitive detection of dopamine (DA) is important for the diagnostics of neurological disorders and the development of new drugs. Here, we report microplasma synthesis of surfaced-functionalized silicon quantum dots (SiQDs) at ambient conditions. The synthesized SiQDs with useful properties including abundant surface functionalities, stable colloidal dispersion, and photoluminescence (PL) emission enable direct label-free detection of DA, providing a wide sensing range from 0.83 to 83.33 μM and a low detection limit of 0.32 μM. Our work provides a new direction for the synthesis of colloidal SiQDs and the understanding of SiQD-based PL probes for biomolecule sensing.

Microplasma-Tunable Graphene Quantum Dots for Ultrasensitive and Selective Detection of Cancer and Neurotransmitter Biomarkers

The effective and precise detection of cancer and neurotransmitter biomarkers including folic acid (FA), dopamine (DA), and epinephrine (EP) are essential for early detection and diagnosis of cancer and neurological disorders and for the development of new drugs. However, it remains challenging to detect FA, DA, and EP with high selectivity and sensitivity with a single material. Herein, we report a photoluminescence (PL)-based selective sensing of FA, DA, and EP with nitrogen-doped graphene quantum dots (NGQDs) synthesized from biocompatible chitosan under ambient conditions using atmospheric pressure microplasmas. By regulating the pH, the selective detection is achieved in broad ranges from 0.8 to 80 μM for FA and 0.4 to 100 μM for both DA and EP with the very low limits of detections of 81.7, 57.8, and 16.7 nM for FA, DA, and EP, respectively. The developed PL sensing method shows the high throughput of 5000 detections per hour. Moreover, highly stable colloidal NGQD dispersion with 100 μg/mL concentration for at least 100 PL detections is produced in 1 h by a single microplasma, and the process is scalable. The mechanisms of the outstanding performance are related to the enhanced, size-dependent π-π stacking attraction between the NGQDs and the pH-regulated chemical states of the analytes and the associated pH-specific photo-induced electron transfer and PL.

β-Cyclodextrin-capped ZnO-doped carbon dot as an advanced fluorescent probe for selective detection of dopamine

Selective and sensitive detection of dopamine in presence of other interfering biomolecules using β-cyclodextrin-capped ZnO-doped carbon dot.