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Beilstein Journal of Nanotechnology (1)
International Journal of Alzheimer's Disease (1)
International Journal of Nanomedicine (1)
Scientific Reports (1)
Zhang, Hongzhou (4)
Fox, Daniel (2)
Chen, Yanhui (1)
D’Arcy, Deirdre M (1)
Faulkner, Colm C (1)
Giordani, Silvia (1)
Holmes, Justin D (1)
Inkielewicz-Stepniak, Iwona (1)
Leblanc, Roger M. (1)
Li, Wenzhi (1)
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Micic, Miodrag (1)
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O'Connell, Robert (1)
Radomski, Marek Witold (1)
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Santos-Martinez, Maria Jose (1)
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High throughput secondary electron imaging of organic residues on a graphene surface
Surface organic residues inhibit the extraordinary electronic properties of graphene, hindering the development of graphene electronics. However, fundamental understanding of the residue morphology is still absent due to a lack of high-throughput and high-resolution surface characterization methods. Here, we demonstrate that secondary electron (SE) imaging in the scanning electron microscope (SEM) and helium ion microscope (HIM) can provide sub-nanometer information of a graphene surface and reveal the morphology of surface contaminants. Nanoscale polymethyl methacrylate (PMMA) residues are visible in the SE imaging, but their contrast, i.e. the apparent lateral dimension, varies with the imaging conditions. We have demonstrated a quantitative approach to readily obtain the physical size of the surface features regardless of the contrast variation. The fidelity of SE imaging is ultimately determined by the probe size of the primary beam. HIM is thus evaluated to be a superior SE imaging technique in terms of surface sensitivity and image fidelity. A highly efficient method to reveal the residues on a graphene surface has therefore been established.
Nano-structuring, surface and bulk modification with a focused helium ion beam
Faulkner, Colm C
Beilstein Journal of Nanotechnology
We investigate the ability of a focused helium ion beam to selectively modify and mill materials. The sub nanometer probe size of the helium ion microscope used provides lateral control not previously available for helium ion irradiation experiments. At high incidence angles the helium ions were found to remove surface material from a silicon lamella leaving the subsurface structure intact for further analysis. Surface roughness and contaminants were both reduced by the irradiation process. Fabrication is also realized with a high level of patterning acuity. Implantation of helium beneath the surface of the sample is visualized in cross section allowing direct observation of the extended effects of high dose irradiation. The effect of the irradiation on the crystal structure of the material is presented. Applications of the sample modification process are presented and further prospects discussed.
EELS; EFTEM; helium ion microscopy; nanofabrication; TEM
The use of quartz crystal microbalance with dissipation (QCM-D) for studying nanoparticle-induced platelet aggregation
Santos-Martinez, Maria Jose
D’Arcy, Deirdre M
Holmes, Justin D
Radomski, Marek Witold
International Journal of Nanomedicine
Interactions between blood platelets and nanoparticles have both pharmacological and toxicological significance and may lead to platelet activation and aggregation. Platelet aggregation is usually studied using light aggregometer that neither mimics the conditions found in human microvasculature nor detects microaggregates. A new method for the measurement of platelet microaggregation under flow conditions using a commercially available quartz crystal microbalance with dissipation (QCM-D) has recently been developed. The aim of the current study was to investigate if QCM-D could be used for the measurement of nanoparticle-platelet interactions. Silica, polystyrene, and gold nanoparticles were tested. The interactions were also studied using light aggregometry and flow cytometry, which measured surface abundance of platelet receptors. Platelet activation was imaged using phase contrast and scanning helium ion microscopy. QCM-D was able to measure nanoparticle-induced platelet microaggregation for all nanoparticles tested at concentrations that were undetectable by light aggregometry and flow cytometry. Microaggregates were measured by changes in frequency and dissipation, and the presence of platelets on the sensor surface was confirmed and imaged by phase contrast and scanning helium ion microscopy.
platelet aggregation; nanoparticles; light aggregometer; quartz crystal microbalance with dissipation; scanning helium ion microscopy
Conjugated Quantum Dots Inhibit the Amyloid β (1–42) Fibrillation Process
Leblanc, Roger M.
International Journal of Alzheimer's Disease
Nanoparticles have enormous potential in diagnostic and therapeutic studies. We have demonstrated that the amyloid beta mixed with and conjugated to dihydrolipoic acid- (DHLA) capped CdSe/ZnS quantum dots (QDs) of size approximately 2.5 nm can be used to reduce the fibrillation process. Transmission electron microscopy (TEM) and atomic force microscopy (AFM) were used as tools for analysis of fibrillation. There is a significant change in morphology of fibrils when amyloid β (1–42) (Aβ (1–42)) is mixed or conjugated to the QDs. The length and the width of the fibrils vary under modified conditions. Thioflavin T (ThT) fluorescence supports the decrease in fibril formation in presence of DHLA-capped QDs.
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