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The rapidly increasing interest in Ge-based nanostructures is motivated by important advantages of this material compared to other semiconductors commonly investigated in the broad field of nanotechnology. Ge nanoparticles are promising materials for many applications such as photovoltaics, transistors, light emitting devices, bioimaging, and energy storage devices.Due to the strong covalent bonding nature, synthesis of high-quality Ge nanoparticles with uniform size, well-defined morphology, composition, and surface chemistry is a main scientific challenge in the colloidal chemistry community and finding a reliable, scalable, cost-effective, and environmentally friendly synthetic route is of key importance for their further applications. Besides technical interest, access to defined nanoscale structures and compositions is also essential for uncovering their intrinsic properties and expanding the chemistry of group 14 nanomaterials. In this dissertation, both direct synthetic methods and post transformation approaches are explored for rational synthesis of germanium-based nanomaterials with great control of the size, shape, and composition. The detailed reaction mechanisms are revealed through a systematic study on the reaction conditions such as temperature, precursor concentrations, reaction time, etc. Amorphous solid Ge nanoparticles and hollow Ge nanoparticles are synthesized via galvanic replacement reaction with Ag NPs serving as a sacrificial template. Ag@Ge core-shell nanoparticles with controlled shell thickness are also successfully synthesized as an intermediate. Their structural, optical, and electrical properties have been investigated in detail by high-angle annular dark-field scanning transmission electron microscopy (HAADF-STEM) and transmission electron microscopy (TEM), and supported by UV-Vis, Powder X-ray Diffraction (XRD), Energy-dispersive X-ray spectroscopy (EDS), etc. In addition, we provide an in situ method to observe the phase transition

The rapidly increasing interest in Ge-based nanostructures is motivated by important advantages of this material compared to other semiconductors commonly investigated in the broad field of nanotechnology. Ge nanoparticles are promising materials for many applications such as photovoltaics, transistors, light emitting devices, bioimaging, and energy storage devices.Due to the strong covalent bonding nature, synthesis of high-quality Ge nanoparticles with uniform size, well-defined morphology, composition, and surface chemistry is a main scientific challenge in the colloidal chemistry community and finding a reliable, scalable, cost-effective, and environmentally friendly synthetic route is of key importance for their further applications. Besides technical interest, access to defined nanoscale structures and compositions is also essential for uncovering their intrinsic properties and expanding the chemistry of group 14 nanomaterials. In this dissertation, both direct synthetic methods and post transformation approaches are explored for rational synthesis of germanium-based nanomaterials with great control of the size, shape, and composition. The detailed reaction mechanisms are revealed through a systematic study on the reaction conditions such as temperature, precursor concentrations, reaction time, etc. Amorphous solid Ge nanoparticles and hollow Ge nanoparticles are synthesized via galvanic replacement reaction with Ag NPs serving as a sacrificial template. Ag@Ge core-shell nanoparticles with controlled shell thickness are also successfully synthesized as an intermediate. Their structural, optical, and electrical properties have been investigated in detail by high-angle annular dark-field scanning transmission electron microscopy (HAADF-STEM) and transmission electron microscopy (TEM), and supported by UV-Vis, Powder X-ray Diffraction (XRD), Energy-dispersive X-ray spectroscopy (EDS), etc. In addition, we provide an in situ method to observe the phase transition

RationaleThe mechanisms underlying atrial fibrillation (AF), the most common clinical arrhythmia, are poorly understood. Nucleoplasmic Ca2+ regulates gene expression, but the nature and significance of nuclear Ca2+-changes in AF are largely unknown.ObjectiveTo elucidate mechanisms by which AF alters atrial-cardiomyocyte nuclear Ca2+ ([Ca2+]Nuc) and CaMKII (Ca2+/calmodulin-dependent protein kinase-II)-related signaling.Methods and resultsAtrial cardiomyocytes were isolated from control and AF dogs (kept in AF by atrial tachypacing [600 bpm × 1 week]). [Ca2+]Nuc and cytosolic [Ca2+] ([Ca2+]Cyto) were recorded via confocal microscopy. Diastolic [Ca2+]Nuc was greater than [Ca2+]Cyto under control conditions, while resting [Ca2+]Nuc was similar to [Ca2+]Cyto; both diastolic and resting [Ca2+]Nuc increased with AF. IP3R (Inositol-trisphosphate receptor) stimulation produced larger [Ca2+]Nuc increases in AF versus control cardiomyocytes, and IP3R-blockade suppressed the AF-related [Ca2+]Nuc differences. AF upregulated nuclear protein expression of IP3R1 (IP3R-type 1) and of phosphorylated CaMKII (immunohistochemistry and immunoblot) while decreasing the nuclear/cytosolic expression ratio for HDAC4 (histone deacetylase type-4). Isolated atrial cardiomyocytes tachypaced at 3 Hz for 24 hours mimicked AF-type [Ca2+]Nuc changes and L-type calcium current decreases versus 1-Hz-paced cardiomyocytes; these changes were prevented by IP3R knockdown with short-interfering RNA directed against IP3R1. Nuclear/cytosolic HDAC4 expression ratio was decreased by 3-Hz pacing, while nuclear CaMKII phosphorylation was increased. Either CaMKII-inhibition (by autocamtide-2-related peptide) or IP3R-knockdown prevented the CaMKII-hyperphosphorylation and nuclear-to-cytosolic HDAC4 shift caused by 3-Hz pacing. In human atrial cardiomyocytes from AF patients, nuclear IP3R1-expression was significantly increased, with decreased nuclear/nonnuclear HDAC4 ratio. MicroRNA-26a was predicted to target ITP