Preparation of Carbon Dots with High-Fluorescence Quantum Yield and Their Application in Dopamine Fluorescence Probe and Cellular Imaging

Haitao Lin,Jun Huang,Liyun Ding

doi:10.1155/2019/5037243

Abstract

Carbon dots represent a kind of fluorescent nanomaterial and have broad application prospects in the field of biosensing and optoelectronics. Here, we explored carbon dots with a high-fluorescence quantum yield rate synthesized from L-cysteine and citric acid by the microwave-assisted method. The characteristics of the carbon dots were studied using a transmission electron microscope, an X-ray diffractometer, X-ray photoelectron spectra, a UV-Vis absorption spectrometer, a FTIR spectrometer, and a fluorescence spectrophotometer. The obtained carbon dots exhibited a high-fluorescence quantum yield (up to 85%), which is due to the combination of amidogens and sulfydryl with carbon dots, and hence bring the improved fluorescence property. We used carbon dots for in vitro imaging of CRL-5822 cells and human umbilical vein endothelial cells, which showed the low inhibitory rate (0.8%) of cells for 48 h with good biocompatibility demonstrated by the cell viability assay. The image of cells can be observed clearly under UV light. The Stern-Volmer equation was introduced to describe the quenching effect between the fluorescence intensity of carbon dots and the concentration of aqueous dopamine (DA).

Highlights

Carbon dots are “zero-dimensional” nanoparticles with carbon structures [1]
The High-resolution transmission electron microscopy (HRTEM) picture illustrates that the carbon core is well crystallized, with interlattice spacing around 0.31 nm, corresponding to the (002) interplanar distances in the carbon materials with turbostratic disorder and to the shoulder peak at 25 degrees in the XRD pattern of carbon dots as shown in Figure S1 [17]
It is shown that the C 1s peaks at 284.4 eV, 286.2 eV, and 288.3 eV corresponded to C-C, C-O/C-N, and C=O, respectively [2]. These results were in consonance with those of FTIR spectometry, demonstrating that the common hydrophilic groups such as amidogen, carboxylic, and hydroxyl from the precursor were immobilized on the edge of the synthesized carbon dots

Summary

Introduction

As a relatively new member in the big family of fluorescent materials, carbon dots have drawn ever-increasing attention for their promising properties, such as high chemical stability, low blinking, and good biocompatibility [2, 3]. These characteristics have been exploited for a range of applications including chemical sensing, bioimaging, biolabelling, biomedicine [4], photocatalytic energy conversion [5], and as nanocarriers for gene delivery [6]. Low cytotoxicity, one of the key features of carbon dots, makes them of promising significance in the field of in vivo and in vitro biology. The fluorescence wavelength of the carbon dots is dependent on the excitation wavelength in certain ranges, making them more flexible in applications

Methods

Results

Conclusion