Study On The Preparation Of Carbon Dots And Their Application In The Biosensor

CDs, as a new type of carbon nano materials, has been widely used in various research fields due to its excellent performance. Compared with traditional semiconductor quantum dots, the CDs hace better optical properties, biocompatibility and environment friendliness. This makes the carbon can be widely used in biological imaging, nano sensing, photocatalysis, optoelectronic devices and other fields. In this paper, we prepared the CDs by microwave-assisted method. And then we prepared the GCDs based on the preparation of CDs and NCs, applying to the the intracellular ion detection, dual fluorescent imaging and the photocatalytic degradation of organic dye:(1) A unique photoluminescence carbon dots (CDs) with larger size were prepared by microwave-assisted method. Complex functional groups on the surface of the CDs facilitate the nanoparticles to form affinity with some metal ions. Taking advantage of the effective fluorescence quenching effect of K+, a highly sensitive CD-based fluorescence analytical system for label-free detection of K+with limit of detection (LOD)1.0×10-12 M was established. The concentrations of potassium ion in biological samples such as human serum are usually found at millimolar levels or even higher. The proposed method begins with a substantial dilution of the sample to place the K+ concentration in the dynamic range for quantification, which covers 3 orders of magnitude. This offers some advantages:the detection of K+ only needs very small quantities of biological samples, and the dilution of samples such as serum may effectively eliminate the potential interferences that often originate from the background matrix. The determined potassium levels were satisfactory and closely comparable with the results given by the hospital, indicating that this fluorescent probe is applicable to detection of physiological potassium level with high accuracy. Compared with other relative biosensors requiring modified design, bio-molecular modification or/and sophisticated instruments, this CD-based sensor is very simple, cost-effective and easy detection, suggesting great potential applications for successively monitoring physiological potassium level and the change in biological system.(2) In this study, we synthesized novel gold-carbon dots (GCDs) with unique properties by microwave-assisted method. The characterization of high-resolution transmission electron microscope (HRTEM), XRD, high-angle annular dark field scanning transmission electron microscope (HAADF-STEM), and energy dispersive spectrometer demonstrates the GCDs are composed of carbon and Au. Tiny Au clusters are dispersed in 2-nm-size carbon skeleton, which integrate the properties of typical CDs and gold nanoclusters (AuNCs), displaying fascinating peroxidase-like activity and single excitation/dual emission. Dual emission of the GCDs exhibits different fluorescent response to the target species enables the GCDs to be exploited for sensing and bioimaging. The highly photostable and biocompatible GCDs were applied to dual fluorescent imaging for breast cancer cells and normal rat osteoblast cells under a single excitation. Moreover, ratiometric fluorescence imaging was used to monitor Fe3+ level in normal rat osteoblast cells.(3) A sensitively colormetric assay for detection of Prostate Specific Antigen (PSA) based on the carbon dots nanocomposite mimic enzyme was developed, which enables the detection of a few molecules of PSA with the naked eye. The nanocomposite of AuNcs-CD label of an immunosorbent assay controls the growth of gold nanoparticles and generates coloured solutions with distinct tonality when the anti-PSA is present. Compared to traditional ELISA, our developed assay is very simple and has high sensitivity.(4) In this study, a type of carbon dots composite consisted of gold and carbon was prepared. A apatmer can specifically react with prostate cancer antigen was immobilized on the carbon dots composite. A sensitive analytical method for detection of Prostate Specific Antigen (PSA) was fabricated based on the change of resonance light scattering. The experiment results indicate that the PSA concentration in human serum samples of prostate cancer patients might be successfully detected. PSA concentration in the 0.01 ng/mL and 0.05 ng/mL range can be detected.(5) Fluorescent carbon dots (CDs) were prepared by hydrothermal synthesis method, which exhibits weak photocatalytic activity inrhodamine B (RhB) degradation under UV and visible light irradiation. The introduction of plasmonic nanoparticles, such as gold nanorods (GNRs), core-shell GNRs and spherical gold nanoparticles, can significantly enhanced photocatalytic activity in thedecomposition of RhB under wide spectrum (UV, visible, and near infrared light) irradiation comparedwith the pure CDs. The surface plasmon resonance (SPR) property of plasmonic nanoparticles facilitates to improve photocatalytic activity of CDs efficiently, implying the visible and infrared light (NIR) light of the sunlight can be efficiently used in this photocatalytic process. Moreover, a synergistic effect of UV and visible light on the photocatalytic activity of CDs/GNRs was observed. Such light-triggered plasmonic photocatalyst may bring new insight into the designing of highly efficient catalyst to make full use of sunlight to perform the photocatalytic applications in environmental pollution treatment.