The results of studies of the formation of various titanium-based nanoparticles by laser ablation of a titanium rod in liquid environments comprised of water, ethanol, 2-propanol, and n-hexane are reported. The effect of fluence on nanoparticle characteristics was studied by ablation with a 532 nm Nd:YAG operating at 10 Hz, showing that mean particle size and the size distribution increase with increasing laser intensity. The solvent plays a crucial role in the nature of the nanoparticles, as solvent components are incorporated into the nanoparticles during formation. Titanium nanoparticles formed in oxygen-rich solvents incorporate oxygen, while those formed in a carbon-rich environment are found to contain carbon. The nanoparticles created in their respective liquid environments are very stable, maintain their character over time, and remain in solution for months after creation.

1,3-Bis(diethylphosphino)propane (depp) protected gold clusters are synthesized and studied via electrospray ionization mass spectrometry. An undecagold cluster, [Au11(depp)4Cl2]+, is observed under soft ionization conditions and is found to persist in solution for at least 1 month. The importance of the Cl ligands is discussed in terms of the electron-donating nature of the depp ligands, and we contrast the core−ligand interactions observed here with those found in the previously reported [Au11(dppp)5]3+ (where dppp = 1,3-bis(diphenylphosphino)propane). The experimental observations are supported by density functional theory calculations, which suggest that the dppp ligand is a better electron acceptor than depp. Further calculations illustrate some of the subtleties that emerge when attempting to model core−ligand interactions on small clusters. The results demonstrate that a degree of caution is merited when making ligand approximations for modeling of monolayer-protected nanoparticles.

Previous work by Kirby and co-workers revealed a significant acceleration of the rate of hydrolysis of p-nitrophenyl phosphate by added dipolar solvents such as DMSO. Activation parameters and kinetic isotope effects have been measured to ascertain the origin of this effect. The generality of this phenomenon was examined with a series of esters with more basic leaving groups. Computational analyses of the effects of desolvation of dianionic phosphate monoesters were carried out, and the possible effect of the transfer from water to the active site of alkaline phosphatase was modeled. The results are consistent with a desolvation-induced weakening of the P-O ester bond in the ground state. Other aryl phosphate esters show similar rate accelerations at high fractions of DMSO, but phenyl and methyl phosphates do not, and their hydrolysis reactions are actually slowed by these conditions.

Laser Ablation / Transition Metals / Nanoparticles / Zirconium / ColloidsWe report the results of the ablation of a zirconium rod in isopropyl alcohol employing a titanium sapphire femtosecond laser system operated at sub-800 nm wavelengths with a fluence of 2 mJ/pulse and a 10 Hz pulse rate. Ablation of zirconium was investigated under two different focal regimes, resulting in ablation with different power densities. Optimally, the femtosecond laser system produces pulses of 100 femtoseconds; however, experiments were also performed in which the temporal nature of the femtosecond pulse was adjusted by stretching the pulse to minimize supercontinuum formation. The resultant nanoparticles displayed size distributions with mean values of 12 to 15 nm. Optical activity of zirconium nanoparticles is addressed.