Quantum dots (QDs) have attracted great attention due to their unique optical properties. High fluorescence efficiency is very important for their practical application. In this study, we report a simple and efficient strategy to enhance the photoluminescence of water-dispersed thiol-capped QDs using γ-radiation. Three kinds of QDs with different surface ligands and cores (MPA-CdTe, MPA-CdSe and Cys-CdTe) were fabricated and irradiated by high-energy γ-ray in an aqueous solution. Their photoluminescence intensities were significantly enhanced after irradiation, which were closely related to the radiation dose and the structure of QDs. The positions of the fluorescence emission peaks did not shift obviously after irradiation. The mechanism of photoluminescence enhancement was discussed based on the results of photoluminescence (PL) spectra, UV-visible light absorption (UV-vis) spectra, transmission electron microscope (TEM), X-ray diffraction (XRD) patterns, Fourier transform infrared (FT-IR) spectra and X-ray photoelectron spectroscopy (XPS). This method can be employed to uniformly treat large batches of QDs at room temperature and without other chemicals.Keywords:quantum dots;luminescence enhancement;γ-radiation;thiol-capped
Zhiguang Song,Shiyuan Cui,Cuiping Tang,Yong Chen,Deqing Liang,Sibo Wang
Polyvinylcaprolactam (PVCap) is an economic kinetic inhibitor for hydrate formation in pipelines during oil and gas transportation. However, its application is limited because of the low inhibition performance under certain conditions. In this work, a modified PVCap on its chain end is proposed. 2-amino-3-propionic acid mercapto-terminated polyvinyl caprolactam (PVCap-NH2-COOH) was synthesized and its performance as a KHI for methane hydrate formation was evaluated under different conditions. Results showed that the performance of PVCap-NH2-COOH as a KHI was better than that of PVCap at the same concentrations. Gas hydrate samples with 1 wt.% PVCap-NH2-COOH were measured using Raman spectroscopy, XRD, and cryo-SEM. PVCap-NH2-COOH had a selective action on a specific crystal surface of the hydrates and could prevent methane molecules from entering large cages. Its inhibition ability increased with the decrease in the occupancy rate of large cages. The morphology of the gas hydrate crystal changed from porous in a pure water system to a chaotic but compact structure state in the system with PVCap-NH2-COOH.Keywords:natural gas hydrate;formation;inhibition;modification
With significantly decreased light scattering and tissue autofluorescence , fluorescence imaging in the second near infrared (NIR-II, 1000-1700 nm) region has been heavily explored in biomedical field recently. Silver sulfide quantum dots (Ag 2 S QDs) with unique optical properties were one of the most classic NIR-II imaging probes. However, the Ag 2 S QDs for in vivo purpose were mainly obtain by oil phase-based high-temperature route at present. Here, we proposed a mild aqueous route to prepare NIR-II emissive Ag 2 S QDs for in vivo tumor imaging. Original Ag 2 S QDs was obtained by mixing sodium sulfide and silver nitrate in a thiol-terminated polyethylene glycol (mPEG-SH) solution. Treating the original Ag 2 S QDs with extra mPEG-SH ligands produced highly PEGyalted Ag 2 S QDs. These re-PEGylated Ag 2 S QDs exhibited much better blood circulation and tumor accumulation in vivo comparing with the original ones, which can serve as excellent tumor imaging probes. The whole-body blood vessel imaging of living mice was achieved with high resolution, the bio-distribution of these QDs were studied by NIR-II imaging as well. This work also highlighted the importance of ligand density for tumor targeting.
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