Thomas LaGrange

A Rhodium Nanoparticle–Lewis Acidic Ionic Liquid Catalyst for the Chemoselective Reduction of Heteroarenes

We describe a catalytic system composed of rhodium nanoparticles immobilized in a Lewis acidic ionic liquid. The combined system catalyzes the hydrogenation of quinolines, pyridines, benzofurans, and furan to access the corresponding heterocycles, important molecules present in fine chemicals, agrochemicals, and pharmaceuticals. The catalyst is highly selective, acting only on the heteroaromatic ring, and not interfering with other reducible functional groups.

Low-Dose Prostate Cancer Brachytherapy with Radioactive Palladium-Gold Nanoparticles

Prostate cancer (PCa) is one of the leading causes of death among men. Low-dose brachytherapy is an increasingly used treatment for PCa, which requires the implantation of tens of radioactive seeds. This treatment causes discomfort; these implants cannot be removed, and they generate image artifacts. In this study, the authors report on intratumoral injections of radioactive gold nanoparticles (Au NPs) as an alternative to seeds. The particles (103 Pd:Pd@Au-PEG and 103 Pd:Pd@198 Au:Au-PEG; 10-14 nm Pd@Au core, 36-48 nm hydrodynamic diameter) are synthesized by a one-pot process and characterized by electron microscopy. Administrated as low volume (2-4 µL) single doses (1.6-1.7 mCi), the particles are strongly retained in PCa xenograft tumors, impacting on their growth rate. After 4 weeks, a tumor volume inhibition of 56% and of 75%, compared to the controls, is observed for 103 Pd:Pd@Au-PEG NPs and 103 Pd:Pd@198 Au:Au-PEG NPs, respectively. Skin necrosis is observed with 198 Au; therefore, Au NPs labeled with 103 Pd only are a more advisable choice. Overall, this is the first study confirming the impact of 103 Pd@Au NPs on tumor growth. This new brachytherapy procedure could allow tunable doses of radioactivity, administered with smaller needles than with the current technologies, and leading to fewer image artifacts.

Irradiation-induced phase transformation in undeformed and deformed NiTi shape memory thin films by high-energy ion beams

Irradiation-induced transformations in sputter-deposited Ti-rich NiTi thin films have been investigated with special attention given to the effects of prior deformation on the response of martensite phase. Irradiation at low fluence was carried out at room temperature with Au ions at 350 MeV, such that the projected ion range greatly exceeded the film thickness and lattice damage was attributable mainly to electronic stopping effects (43 keV nm−1). Ion-beam modified microstructures were investigated using transmission electron microscopy, X-ray diffraction, and differential scanning calorimetry. Amorphous tracks were observed in both Ti2Ni precipitates and martensite. The track diameter and the amount of amorphization were larger in the pre-deformed sample as compared to the undeformed sample. In both cases the displacive transformation temperatures and transformation enthalpies were depressed by irradiation, but to a greater degree in the pre-deformed material. Similarly, the extent of austenitic and R-phase regions observed to surround individual ion tracks was substantially greater for the pre-deformed films. These observations are discussed in terms of differences between the deformed and undeformed cases with respect to microstructure.

Planar extrinsic biasing of thin film shape-memory MEMS actuators

Although slow and dissipative, sputtered thin-film shape-memory alloys like equiatomic titanium-nickel can exert a large ohmically-excited force displacement product when deployed in photolithographically micromachined actuators. They give energy densities far exceeding those typically produced by competing microactuator materials [1], and their size can probably be scaled down to the nanometer range (where the benefits of high surface to volume ratio are best exploited for speed and efficiency). But a large, energetic, and resettable actuation stroke is possible only if some agency has imparted a non-trivial initial plastic strain , of between one and five percent, to the martensite phase. Is not always obvious how this strain is to be achieved when discrete mechanical manipulation of the active element is difficult. Furthermore, for cyclic actuation, a resetting-force that periodically re-deforms the martensite during the cooling interval must arise naturally from mechanical elements in the design. Here, several methods responding these requirements are discussed in relation to various kinematic themes.