Nanogermanium is a material that has great potential for technological applications, and doped and alloyed Ge nanocrystals (NCs) are actively being considered. New alloys and compositions are possible in colloidal synthesis because the reactions are kinetically rather than thermodynamically controlled. Most of the Group V elements have been shown to be n-type dopants in Ge to increase carrier concentration; however, thermodynamically, Bi shows no solubility in crystalline Ge. Bi-doped Ge NCs were synthesized for the first time in a microwave-assisted solution route. The oleylamirie capping ligand can be replaced by dodecanethiol without loss of Bi. A positive correlation between the lattice parameter and the concentration of Bi content (0.5-2.0 mol %) is shown via powder X-ray diffraction and selected area electron diffraction. X-ray photoelectron spectroscopy, transmission electron microscopy (TEM), scanning TEM, and inductively coupled plasma-mass spectroscopy are consistent with the Bi solubility up to 2 mol %. The NC size increases with increasing amount of bismuth iodide employed in the reaction. Absorption data show that the band gap of the Bi-doped Ge NCs is consistent with the NC size. This work shows that a new element can be doped into Ge NCs via a microwave assisted route in amounts as high as 1-2 mol %, which leads to increased carriers. Colloidal chemistry provides an inroad to new materials not accessible via other means.

Herein we report the electroless deposition of Ge onto sacrificial Ag nanoparticle (NP) templates to form hollow Ge NPs. The formation of AgI is a necessary component for this reaction. Through a systematic study of surface passivating ligands, we determined that tri-n-octylphosphine is necessary to facilitate the formation of hollow Ge NPs by acting as a transport agent for GeI2 and the oxidized Ag(+) cation (i.e., AgI product). Annular dark-field (ADF) scanning transmission electron microscopy (STEM) imaging of incomplete reactions revealed Ag/Ge core/shell NPs; in contrast, completed reactions displayed hollow Ge NPs with pinholes which is consistent with the known method for dissolution of the nanotemplate. Characterization of the hollow Ge NPs was performed by transmission electron microscopy, ADF-STEM, energy-dispersive X-ray spectroscopy, UV-vis spectrophotometry, and Raman spectroscopy. The galvanic replacement reaction of Ag with GeI2 offers a versatile method for controlling the structure of Ge nanomaterials.

: The main goal of the research project is to develop and test a novel class of dual-threat theranostic nanoparticles for targeted imaging and hyperthermic therapy of prostate cancer. These particles consist of both silicon (for hyperpolarized magnetic resonance imaging, (MRI) and superparamagnetic iron oxide (for hyperthermic therapy). Preliminary results show that simple mixtures between the two particles still allow for hyperpolarized MRI to take place, albeit with a slightly broadened 29Si NMR lineshape. The first batch of particles has been completed and physically characterized (tunneling electron microsopy, dispersive x-ray spectroscopy) and shown a viable coupling between the silicon (approximately 300 nm) and iron oxide (approximately 5 nm), with the iron oxide attaching to the surface of the silicon. A small-scale hyperthermia device that induces therapeutic heating in the nanoparticles has been acquired and set up. The next steps include hyperpolarizing this first batch of particles and testing their hyperthermic effect, then applying to gelatin phantoms and prostate cancer mouse models.

The Zintl phases with nominal compositions Na4Si4, Rb7NaSi8, and A12Si17 (A = K, Rb, Cs) were utilized as precursors in the synthesis of silicon nanoparticles (Si NPs). The present study characterizes and compares the yields of Si NPs synthesized from Na4Si4, Rb7NaSi8, and A12Si17 (A = K, Rb, Cs). Na4Si4 and Rb7NaSi8 Zintl phases consist of anionic silicon tetrahedra stabilized by group I cations. The A12Si17 (A = K, Rb, Cs) Zintl phases that contain [Si9](4-) and [Si4](4-) clusters have been speculated to be more soluble than the A4Si4 (A = Na, Rb, Cs) Zintl phases that contain solely [Si4](4-) clusters due to the lower charge density of the [Si9](4-) cluster. The Zintl phases were reacted with NH4Br in dimethylformamide (DMF) and subsequently capped with allylamine. The Si NPs were characterized by transmission electron microscopy (TEM), energy-dispersive spectroscopy (EDS), UV-vis, and photoluminescence (PL) spectrophotometry. Furthermore, the Si yields were characterized by inductively coupled plasma mass spectrometry (ICP-MS) to evaluate if the reactions of [Si9](4-) cluster containing Zintl phases resulted in higher yields of Si NPs. The yield of Si increased with larger or mixed alkali metal Zintl phases, leading to the conclusion that Coulombic interactions between the cations and anions affect the Zintl phase's reactivity. The size of the Si NPs also increased with larger and mixed alkali metal cations, resulting in similar NP concentrations regardless of the starting material. With respect to ease of synthesis and yield, Na4Si4 remains the most practical precursor for the solution synthesis of Si NPs; however, the larger and mixed alkali metal precursors show promise for further development.