LiYF4 nanocrystals (NCs) doped with 1% and 10% of Yb3+ and capped with oleic-acid were synthesized via a previously reported and modified co-precipitation method. Size, morphology, composition, and colloidal stability of these NCs are reported with data obtained from TEM, XRD, TGA/DSC, XRF, and zeta potential techniques. TEM analysis shows a monodisperse size distribution, with the nanocrystal size of ~20 nm. Optical characterization is described using data collected from UV-Vis-NIR absorption spectrophotometry and photoluminescence spectroscopy. The excellent luminescence in the NIR-II spectral region makes these NCs potential candidate for bioimaging applications.
We have successfully synthesized lithium yttrium fluoride (YLF) nanocrystals doped with ytterbium. The Yb content was varied between 1% and 10%. The nanocrystals emit in near-infrared, with the emission spectrum extending from 960 nm to 1060 nm when excited with the 900 nm light. Strong anti-Stokes photoluminescence was observed when using excitation wavelengths ranging from 1010 nm to 1020 nm. The temperature-dependence of the anti-Stokes photoluminescence was measured over the range from 10 °C till 70 °C. These nanocrystals have a high potential to be used in optical cooling applications.
Colloidal quantum dots (QDs) emitting in the near-infrared (NIR) spectrum are of interest for many biomedical applications, including bioimaging, biosensing, drug delivery, and photodynamic therapy. However, a significant limitation is that QDs are typically highly cytotoxic, containing materials such as indium arsenide (InAs), cadmium, or lead, which makes prospects for their FDA approval for human treatment very unlikely. Previous work on QDs in the NIR has focused on indium arsenide or cadmium chalcogenide cores coated with cadmium sulfide shells or zinc sulfide shells. Lead-based nanoparticles, such as lead selenide (PbSe) or lead sulfide (PbS) are also popular materials used for NIR emission. However, these nanoparticles have also been shown to be cytotoxic. Coating these Pb-based QDs with a biocompatible shell consisting of tin chalcogenides, such as tin sulfide (SnS) or tin selenide (TnSe), could be a reasonable alternative to improve their biocompatibility and reducing their cytotoxicity. In this paper, we report on our recent studies of PbSe-core QDs with Sn-containing shells, including synthesis, structural characterization, and investigation of optical properties. Characteristics of these QDs synthesized under different conditions are described. We conclude that their synthesis is challenging and still requires further work to avoid shell oxidation.
CdSexS1-x/ZnS quantum dots (QDs) can cover a broader spectral range than the commonly used CdSe/ZnS QDs and are potentially useful as biomarkers for tagging cell lines such as HeLa, A549, and MCF-7 due to their high photoluminescence intensity and stability in solution. So far, there have been few studies of colloidal CdSexS1-x/ZnS QDs that would simultaneously investigate changes in a) the molar composition of QD cores, and b) the shell thickness, as well as the effects of these changes on the photoluminescence and quantum yield properties of the QDs. CdSeyS1-y QDs and CdSexS1-x/ZnS core/shell QDs were synthesized via a previously reported and modified hot-injection procedure and via a telescoping one-pot synthesis based on the modified hot-injection procedure. Size, morphology, composition, and colloidal stability of these QD core/shell systems is reported with data obtained from TEM, XRD, TGA, DSC, DLS, and zeta potential techniques. Optical characterization is described using data collected from UV-Vis absorption spectrophotometry and photoluminescence spectroscopy.
Anti-Stokes photoluminescence from colloidal CdSeS/ZnS quantum dots (QDs) is observed. The QDs were inserted into the core of wider-bandgap SiO2/Si3N4/SiO2 structure by thin film deposition and confirmed as promising nanoemitters for laser cooling due to efficient anti-Stokes emission. The nanoemitters were optically pumped by semiconductor lasers coupled to the waveguides using free-space optics. A direct evidence of local optical cooling in the waveguide structure has been demonstrated with a luminescence thermometry based on the detection of photoluminescence signal phase change versus power of the pumping laser, using a lock-in amplifier.
Colloidal quantum dots (QDs) emitting in the visible spectrum are of interest for many biomedical applications, including bioimaging, biosensing, drug delivery, and photodynamic therapy. However, a significant limitation is that QDs typically contain cadmium, which is highly cytotoxic and makes prospects for their FDA approval for human treatment very unlikely. Previous work on biocompatible QDs has focused on indium phosphide and zinc oxide as alternative materials for QDs. However, these nanoparticles have also been shown to be cytotoxic. High-efficiency luminescent ZnTe-based QDs could be a reasonable alternative to Cd-containing QDs. We started our recent studies of ZnTe core, zinc chalcogenide shell QDs with synthesis, structural characterization, and investigation of optical properties of ZnTe/ZnSe colloidal QDs that displayed a blue-green photoluminescence under UV excitation. In this paper, the characteristics of ZnTe/ZnS QDs are compared to those of ZnTe/ZnSe QDs. We conclude that ZnTe/ZnS QDs are appealing candidates for various biomedical applications instead of the currently prominent alternative: cadmium-chalcogenide core QDs.
Quantum dots (QDs) emitting in the visible are of interest for many biomedical applications, including bioimaging, biosensing, drug targeting, and photodynamic therapy. However, a significant limitation is that QDs typically contain cadmium, which makes prospects for their FDA approval very unlikely. Previous work has focused on InP and ZnO as alternative semiconductor materials for QDs. However, these nanoparticles have also been shown to be cytotoxic. High-efficiency luminescent ZnTe-based QDs could be a reasonable alternative to Cd-containing QDs. In this paper, we present preliminary results of our recent studies of ZnTe-based QDs, including their synthesis, structural characterization, and optical properties.
The human mouth is a host of a large gamut of bacteria species, with over 700 of different bacteria strains identified. Most of these bacterial species are harmless, some are beneficial (such as probiotics assisting in food digestion), but some are responsible for various diseases, primarily tooth decay and gum diseases such as gingivitis and periodontitis. Dental plaque has a complicated structure that varies from patient to patient, but a common factor in most cases is the single species of bacterium acting as a secondary colonizer, namely Fusobacterium nucleatum, while the actual disease is caused by a variety of tertiary colonizers. We hypothesize that destruction of a compound biofilm containing Fusobacterium nucleatum will prevent tertiary colonizers (oral pathogens) from establishing a biofilm, and thus will protect the patient from developing gingivitis and periodontitis. In this paper, we report on the effects of exposure of compound biofilms of a primary colonizer Streptococcus gordonii combined with Fusobacterium nucleatum to iron oxide nanoparticles as possible bactericidal agent.
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