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European Microscopy Congress 2016: Proceedings || Dispersion, dose and stability of semiconductor quantum dot biomarkers
摘要： Photoluminescent semiconductor nanoparticles or quantum dots have significant potential for medical imaging. For optimum performance however, the dispersion of the nanoparticulate material when suspended in delivery or incubation media, any transformation of the particles in the media, plus the nature and degree of uptake of the nanoparticles by a particular cell or organism all need to be understood. Analytical electron microscopy can play a vital role in assessing this complex inter-relationship, and we discuss here specific methods developed for this type of analysis. First, we will review the in vitro cellular uptake of commercially available CdSe/ZnS quantum dot nanoparticles with a coating specifically targeted for endocytic uptake (Invitrogen QTracker 705), dispersed in cell culture media and exposed to human osteosarcoma (U-2 OS) cells. We have examined these nanoparticles as-dispersed in cell culture media (t = 0 h), after 1 hour exposure to cells and after a round of cell division (t = 24 h). Transmission electron microscopy (TEM) has been used to assess the dispersion state of the nanoparticles in media after rapidly freezing suspensions to avoid drying artefacts [1], and in exposed cells which have been fixed and resin embedded [2]. The resin-embedded cells have been further examined using serial block face scanning electron microscopy (SBF-SEM), which enables quantification of nanoparticle loaded organelles in whole cell volumes for quantitative correlation to imaging flow cell cytometry [2]. From this we have measured probability densities for the number of quantum dots per agglomerate when in cell culture media and following uptake by cells in vitro [3, 4 and Figure 1 a-d]. Thus, we will discuss the agglomeration processes that occur both in suspension and during endocytosis. Second and looking forward, most commercially available semiconductor quantum dots currently contain cadmium although its health and environmental risks may limit exploitation. Thus, copper indium sulfide (CIS) quantum dots have been investigated as a potential replacement [5]. Aberration corrected STEM-EELS has identified some elemental separation of Cu and In within individual quantum dots [Figure 1 e-h], which may be the origin of an In-Cu anti-site defect state known to act as a donor in the radiative recombination pathway for chalcopyrite CIS quantum dots. We will report here on further analysis using a FEI Titan cubed Themis 300 G2 S/TEM to assess elemental distribution by STEM-EDX. Such analysis will enable additional characterisation of core-shell coatings (e.g. CIS/ZnS/ZnS:Al) designed to improve photo luminescent quantum yield while enhancing environmental stability of the particles.
关键词： quantum dots,SBF-SEM,dose,TEM
更新于2025-09-11 14:15:04
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European Microscopy Congress 2016: Proceedings || Laser induced yellowing of stonework: a combined TEM imaging and STEM-EELS study on model samples
摘要： Nd-YAG Q-Switched laser devices operating at 1064 nm have been considered in the 1990s as the most promising tool for cleaning stone sculptures, and more particularly eliminating indurated black gypsum crusts. However, the spreading of this laser technology has been undermined because of the yellow hue it occasionally conveys to the cleaned surfaces as seen on Figure 1. Especially in France, this yellowing effect is considered as a major esthetic issue by conservators and the laser technique has gradually disappeared from the restoration sites. This discoloration issue remains partly unexplained: a currently admitted hypothesis states that the iron containing compounds present in the black crusts would transform, upon laser irradiation, into yellow iron-rich nanophase(s) that would re-deposit on the cleaned substrate. To verify this hypothesis, model black crusts have been elaborated by mixing hematite α-Fe2O3 and gypsum CaSO4.2H2O in different proportions. The model crusts were irradiated using a Nd-YAG QS laser resulting in ablation of numerous particles in a visible smoke and the color of the samples shifted instantaneously from red to a bright yellow. Transmission electron microscopy (TEM) has been used to characterize the morphology of the nanostructures generated by the laser, both in the smoke and on the surface of the samples as observed in Figure 2. In addition, the chemical composition of the neo-formed nanophases was determined by aberration corrected scanning transmission electron microscopy in combination with electron energy loss spectroscopy (STEM-EELS) and high angle annular dark field imaging (HAADF) as seen on Figure 3. It was found that both the surface of the samples and the ablated micro-materials are covered by an irregular nano-film and by dispersed spherical nanoparticles, all containing iron and oxygen. These results ascertain the link between the yellowing effect and the presence of iron containing nanophases after irradiation.
关键词： EELS,TEM,STEM,nano materials,iron,yellowing,laser
更新于2025-09-11 14:15:04
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European Microscopy Congress 2016: Proceedings || Structural transformations revealed by in-situ HRTEM observations
摘要： With the recent advance of In-Situ Transmission Electron Microscopy (In-Situ TEM), it has become a very essential technique to understand the structure-property relationships of materials. Here, we demonstrate that the formation mechanism of 1D-Si nanowires is initiated by the atom intrusion into the Si lattice at the interfaces, and the formation process is advanced by the atom intrusion into the Si lattice at the interfaces. The formation mechanism of 1D-Si nanowires is also discussed by the thermodynamic analysis. It is found that the 1D-Si nanowires are formed at the triple junction at the interfaces, and the formation process is advanced by the atom intrusion into the Si lattice at the interfaces. The formation mechanism of 1D-Si nanowires is also discussed by the thermodynamic analysis.
关键词： formation mechanism,atom intrusion,In-Situ TEM,thermodynamic analysis,1D-Si nanowires
更新于2025-09-11 14:15:04
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Erbium doped anatase TiO2 nanoparticles for photovoltaic applications
摘要： Doping of rare earth metal erbium (Er) into the nanocrystalline titanium dioxide (TiO2) was identified to enhance the performance of photocatalytic and photovoltaic applications. Herein, TiO2 was doped with different concentrations of erbium through hydrothermal method and then employed to photocatalytic and photovoltaic applications. XRD, FT-IR, TEM, AFM, UV–visible DRS and photocatalytic measurements were carried out to examine the impact of erbium doping on TiO2. The photovoltaic study revealed that the Er doped TiO2 exhibited the better power conversion efficiency with high short-circuit current density (Jsc) and open-circuit voltage (Voc). This enhancement may be due to the reduced charge recombination, increased dye absorption ability and fast photoelectron injection.
关键词： TEM,Photovoltaic,XRD,FT-IR,Er doped TiO2,Photocatalytic
更新于2025-09-11 14:15:04
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Kinking effects and transport properties of coaxial BN-C nanotubes as revealed by <i>in situ</i> transmission electron microscopy and theoretical analysis
摘要： The insights into transport behavior and the effects of bending on heterostructures constructed from boron nitride (BN) and carbon (C) nanotubes are important for their flexible device applications because the two systems have equally excellent mechanical but completely different electrical properties. In this work, coaxial BN–C nanotubes have been fabricated and their intrinsic transport properties, as well as structural and electrical response to bending deformation, are studied inside a high-resolution transmission electron microscope. Ballistic, diffusive, and hopping transports within different tube length ranges have been observed. When bending deformation was applied to the tubes, although severe kinking becomes apparent, their transport properties are not notably affected. Meanwhile, both theoretical and experimental analyses confirm that the kink positions depend on the ratio of tube diameter to its length. Possible formation of quantum dots, directly within the kink areas, was predicted through calculations of electron density redistribution between nanotube walls at bending.
关键词： bending deformation,transport properties,BN-C nanotubes,in situ TEM,quantum dots
更新于2025-09-11 14:15:04
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Optical and structural investigation of synthesis ZnO/Ag Nanoparticles prepared by laser ablation in liquid
摘要： ZnO/Ag nanoparticle was synthesis by using pulsed laser ablation in liquid with various Ag doped at a time of 1, 3, and 5 min. Characterization was carried out with UV–Vis (UV–Visible) Spectrometer, PL 325 (Photoluminescence 325) spectrometer, XRD (X-Ray di?raction), and TEM (transmission electron microscopy). The enhancement of dopant time, the band gap value decrease from 3,021 eV to 2,781 eV and the wavelength peak position was shifted to the red shift which can transform the structure of ZnO nanoparticles and can be applied as food packaging in the future.
关键词： TEM,ZnO/Ag nanoparticles,Laser ablation,Photoluminescence,Band gap
更新于2025-09-11 14:15:04
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Synthesis of gold nanoparticles by pulsed laser-assisted reduction of aqueous gold precursor
摘要： In this paper, colloidal gold nanoparticles (GNPs) were synthesized by Nd:YAG (λ = 1064 nm) pulsed laser-assisted reduction (PLAR) of aqueous [AuCl4]?. In this process, during laser ablation of a Mo target in DI water, a [AuCl4]? precursor solution was being added dropwise in situ. UV–Vis absorption spectra showed distinct plasmonic absorption bands at 209 and 530 nm corresponding to Mo nanoparticles (NPs) and GNPs, respectively. Furthermore, no significant conversion for [AuCl4]? was found when it was added to aged Mo NPs or when it was irradiated in the lack of the Mo target. Using transmission electron microscope (TEM) images, it was found that precursor concentration and laser-ablation time can affect the population or size of GNPs. In PLAR with a small amount of KI solution in water, the GNPs size increases to ~ 50 nm via an iodine-induced particle fusion mechanism. The reduction mechanism was discussed based on metastable species intercation, producing the cavitation bubble during laser ablation.
关键词： Mo target,Nd:YAG laser,TEM,UV–Vis absorption,Pulsed laser-assisted reduction,Gold nanoparticles,KI solution
更新于2025-09-11 14:15:04
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Coaxial waterjet-assisted laser drilling of film cooling holes in turbine blades
摘要： Film cooling holes (FCHs) of nickel-based single crystal turbine blades were drilled by 532 nm Nd:YVO4 nanosecond laser in coaxial waterjet-assisted environment. Microstructure of the side wall of the FCHs was mainly investigated by means of transmission electron microscopy. The average thickness of heat affected zone (HAZ) around FCHs decreases with increasing of water flow rate. The main phase within HAZ evolves from β-NiAl to β-NiAl + γ-Ni with the increase in the water flow rate. Some γ-Ni particles in the HAZ twined along (111) plane. A small portion of the FCHs are free of HAZ when drilled by coaxial waterjet-assisted laser drilling at a laminar water flow rate ≥ 3.1 m/s. There are no processing-induced defects including HAZ, microcrack, and phase transformation around the FCHs when drilled at the water flow rate ≥ 5.1 m/s. The FCHs with high surface quality can be drilled by the coaxial waterjet-assisted laser drilling. Finally, effects of fluid water on drilling quality of the FCHs were discussed.
关键词： turbine blades,film cooling holes,Coaxial waterjet-assisted laser drilling,heat affected zone (HAZ),transmission electron microscopy (TEM)
更新于2025-09-11 14:15:04
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Investigation of Biochemical Alterations in Ischemic Stroke Using Fourier Transform Infrared Imaging Spectroscopy—A Preliminary Study
摘要： Objective: Brain damage, long-term disability and death are the dreadful consequences of ischemic stroke. It causes imbalance in the biochemical constituents that distorts the brain dynamics. Understanding the sub-cellular alterations associated with the stroke will contribute to deeper molecular understanding of brain plasticity and recovery. Current routine approaches examining lipid and protein biochemical changes post stoke can be difficult. Fourier Transform Infrared (FTIR) imaging spectroscopy can play a vital role in detecting these molecular alterations on a sub-cellular level due to its high spatial resolution, accuracy and sensitivity. This study investigates the biochemical and molecular changes in peri-infract zone (PIZ) (contiguous area not completely damaged by stroke) and ipsi-lesional white matter (WM) (right below the stroke and PIZ regions) nine weeks post photothrombotic ischemic stroke in rats. Materials and Methods: FTIR imaging spectroscopy and transmission electron microscopy (TEM) techniques were applied to investigate brain tissue samples while hematoxylin and eosin (H&E) stained images of adjacent sections were prepared for comparison and examination the morphological changes post stroke. Results: TEM results revealed shearing of myelin sheaths and loss of cell membrane, structure and integrity after ischemic stroke. FTIR results showed that ipsi-lesional PIZ and WM experienced reduction in total protein and total lipid content compared to contra-lesional hemisphere. The lipid/protein ratio reduced in PIZ and adjacent WM indicated lipid peroxidation, which results in lipid chain fragmentation and an increase in olefinic content. Protein structural change is observed in PIZ due to the shift from random coil and α-helical structures to β-sheet conformation. Conclusion: FTIR imaging bio-spectroscopy provide novel biochemical information at sub-cellular levels that be difficult to be obtained by routine approaches. The results suggest that successful therapeutic strategy that is based on administration of anti-oxidant therapy, which could reduce and prevent neurotoxicity by scavenging the lipid peroxidation products. This approach will mitigate tissue damage in chronic ischemic period. FTIR imaging bio-spectroscopy can be used as a powerful tool and offer new approach in stroke and neurodegenerative diseases research.
关键词： photothrombotic stroke,Fourier transform infrared (FTIR) imaging spectroscopy,transmission electron microscope (TEM),brain ischemia
更新于2025-09-11 14:15:04
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Mode Composite Coplanar Waveguide
摘要： In this paper, a mode composite coplanar waveguide (MCCPW) is proposed and studied. The MCCPW can be regarded as a combination of a quasi-coplanar waveguide and a substrate integrated waveguide (SIW). In this composite structure, the center conductor of the quasi-coplanar waveguide serves as the SIW supporting TE10 mode, while the TEM mode operates in the quasi-coplanar waveguide part. The characteristics and design method of the MCCPW are analyzed and illustrated in this work. The MCCPW is fabricated together with two transition structures to demonstrate its integration capability further with other planar circuits. The MCCPW is a single layer structure, and it has the advantages of joint structure and mode composition, which make it a possible solution for multifunction and multiband application systems. The measured and the simulated results agree well with each other, and good transition performances are achieved.
关键词： structure sharing,TEM mode,quasi-coplanar waveguide (QCPW),multiband,TE10 mode,substrate integrated waveguide (SIW),Mode composite coplanar waveguide (MCCPW)
更新于2025-09-11 14:15:04