Abstract:Novel fluorescent silicon quantum dots (Si-QDs) were synthesized by a one-step hydrothermal procedure using (3-aminopropyl)trimethoxysilane (APTES) as a silicon source and sodium ascorbate (SA) as a reducing agent.
“…The HR-TEM images display the high crystallinity of the SQDs, as evidenced by the distinct lattice fringes with 0.30 nm interplanar spacing, which is consistent with the (111) plane of diamond silicon 14 , 25 . It should be mentioned that the low contrast of the TEM and HR-TEM images is due to the extreme small dimensions of SQDs and also the low atomic weight of silicon compared to metallic or semiconductor quantum dots, which results in poor visualization 12 , 26 . Figure 2 TEM (left), diameter distributions (middle) and HR-TEM images (right) of SQD-heptene ( A ), SQD-phenanthrene ( B ), SQD-pyrene ( C ), and SQD-perylene ( D ).…”
Silicon Quantum Dots (SQDs) have recently attracted great interest due to their excellent optical properties, low cytotoxicity, and ease of surface modification. The size of SQDs and type of ligand on their surface has a great influence on their optical properties which is still poorly understood. Here we report the synthesis and spectroscopic studies of three families of unreported SQDs functionalized by covalently linking to the aromatic fluorophores, 9-vinylphenanthrene, 1-vinylpyrene, and 3-vinylperylene. The results showed that the prepared functionalized SQDs had a highly-controlled diameter by HR-TEM, ranging from 1.7–2.1 nm. The photophysical measurements of the assemblies provided clear evidence for efficient energy transfer from the fluorophore to the SQD core. Fӧrster energy transfer is the likely mechanism in these assemblies. As a result of the photogenerated energy transfer process, the emission color of the SQD core could be efficiently tuned and its emission quantum efficiency enhanced. To demonstrate the potential application of the synthesized SQDs for bioimaging of cancer cells, the water-soluble perylene- and pyrene-capped SQDs were examined for fluorescent imaging of HeLa cells. The SQDs were shown to be of low cytotoxicity
“…The HR-TEM images display the high crystallinity of the SQDs, as evidenced by the distinct lattice fringes with 0.30 nm interplanar spacing, which is consistent with the (111) plane of diamond silicon 14 , 25 . It should be mentioned that the low contrast of the TEM and HR-TEM images is due to the extreme small dimensions of SQDs and also the low atomic weight of silicon compared to metallic or semiconductor quantum dots, which results in poor visualization 12 , 26 . Figure 2 TEM (left), diameter distributions (middle) and HR-TEM images (right) of SQD-heptene ( A ), SQD-phenanthrene ( B ), SQD-pyrene ( C ), and SQD-perylene ( D ).…”
Silicon Quantum Dots (SQDs) have recently attracted great interest due to their excellent optical properties, low cytotoxicity, and ease of surface modification. The size of SQDs and type of ligand on their surface has a great influence on their optical properties which is still poorly understood. Here we report the synthesis and spectroscopic studies of three families of unreported SQDs functionalized by covalently linking to the aromatic fluorophores, 9-vinylphenanthrene, 1-vinylpyrene, and 3-vinylperylene. The results showed that the prepared functionalized SQDs had a highly-controlled diameter by HR-TEM, ranging from 1.7–2.1 nm. The photophysical measurements of the assemblies provided clear evidence for efficient energy transfer from the fluorophore to the SQD core. Fӧrster energy transfer is the likely mechanism in these assemblies. As a result of the photogenerated energy transfer process, the emission color of the SQD core could be efficiently tuned and its emission quantum efficiency enhanced. To demonstrate the potential application of the synthesized SQDs for bioimaging of cancer cells, the water-soluble perylene- and pyrene-capped SQDs were examined for fluorescent imaging of HeLa cells. The SQDs were shown to be of low cytotoxicity
“…This is in agreement with the (111) plane of diamond structured silicon 23 . It should be noted that the low resolution of the TEM and HR-TEM images is assigned to the ultra-small dimensions of these SQDs and the small atomic weight of the silicon atom compared to the counterpart metallic or semiconductor quantum dots, which is known to provide low-quality visualization 10 , 24 . Figure 2 TEM together with HR-TEM (left) and diameter distribution with photographs for solutions under UV (365 nm) irradiation (right) for Am-SQD-Per ( A ) and Urea-SQD-Per ( B ).…”
The superior optical properties of Silicon Quantum Dots (SQDs) have made them of increasing interest for a variety of biological and opto-electronic applications. The surface functionalization of the SQDs with aromatic ligands plays a key role in controlling their optical properties due to the interaction of the ligands with the electronic wave function of SQDs. However, there is limited reports in literature describing the impact of spacer groups connecting the aromatic chromophore to SQDs on the optical properties of the SQDs. Herein, we report the synthesis of two SQDs assemblies (1.6 nm average diameter) functionalized with perylene-3,4,9,10-tetracarboxylic acid diimide (PDI) chromophore through N-propylurea and propylamine spacers. Depending on the nature of the spacer, the photophysical measurements provide clear evidence for efficient energy and/or electron transfer between the SQDs and PDI. Energy transfer was confirmed to be the operative process when propylurea spacer was used, in which the rate was estimated to be ~2 × 109 s−1. On the other hand, the propylamine spacer was found to facilitate electron transfer process within the SQDs assembly. To illustrate functionality, the water soluble SQD-N-propylurea-PDI assembly was proven to be nontoxic and efficient for fluorescent imaging of embryonic kidney HEK293 cells and human bone cancerous U2OS cells.
“…These results indicated that the assemblies could not cause cancer death without irradiation and confirmed the low dark cytotoxicity of the C‐dot assemblies (Figure S3). These characteristics are similar to those of many other nanomaterials, such as GQDs and silicon nanoparticles . However, incubation with C‐dot assemblies under irradiation at 671 nm (2 W/cm 2 ) gradually decreased cell viability.…”
Constructing complex nanoarchitectures via self-assembly with nanoparticle building blocks is a practical strategy that produces nanostructures with properties that are absent in the individual unit. In this work, we used hydrophilic carbon dots (C-dots) as building blocks to form C-dot assemblies. Compared to the individual C-dot, the self-assembled C-dots showed about 30 nm red-shift of absorption, resulting in the 5.1% increasing of photothermal conversion efficiency upon a 671 nm laser irradiation. More importantly, the C-dot assemblies enable them can be efficiently uptaken by cancer cells. Meanwhile, in vitro study demonstrated the C-dot assemblies can efficiently kill cancer cells than that of individual C-dot upon irradiation for 5 min at equivalent C-dot concentration. Our study may provide a new strategy for the efficient photothermal therapy of cancer based on C-dots.
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