Noriko Horimoto

Ejection mechanism of molecules and neutral clusters from liquid beam under irradiation of IR laser

Abstract Resorcinol molecules and those solvated with solvent water molecules were isolated in the gas phase from a liquid beam of an aqueous solution of resorcinol by resonant vibrational excitation of solvent water molecules under IR-laser irradiation. The spatial distribution of the ejected species at various delay times from the IR-laser irradiation indicates that two different isolation mechanisms operate: One dominates in a time range shorter than ∼1 μs (early-time domain), and the other in a time range longer than ∼1 μs (late-time domain). A time-dependent measurement of the liquid-beam profile by optical diffraction shows that the beam has a smooth surface in the early-time domain, whereas in the late-time domain the surface roughness overweighs the wavelength of the illumination laser.

Additive-free size-controlled synthesis of gold square nanoplates using photochemical reaction in dynamic phase-separating media.

Ultrafast phase separation of water and 2-butoxyethanol mixture was induced by nanosecond IR laser pulse irradiation. After a certain delay time, a UV laser pulse was introduced to induce photoreduction of aurate ions, which led to the formation of gold nanoparticles in dynamic phase-separating media. The structure and size of the nanoparticles varied depending on the delay time between the IR and UV pulses. For a delay time of 5 and 6 μs, gold square plates having edge lengths of 150 and 100 nm were selectively obtained, respectively. With a delay time of 3 μs, on the other hand, the size of the square plates varied widely from 100 nm to a few micrometers. The size of the gold square plates was also varied by varying the total irradiation time of the IR and UV pulses. The size distribution of the square plates obtained under different conditions suggests that the growth process of the square plates was affected by the size of the nanophases during phase separation. Electron diffraction patterns of the synthesized square plates showed that the square plates were highly crystalline with a Au(100) surface. These results showed that the nanophases formed during laser-induced phase separation can provide detergent-free reaction fields for size-controlled nanomaterial synthesis.

Electronic Structure and Dynamics of Solute Molecules on Solution Surfaces by Use of Liquid Beam Multiphoton Ionization Mass Spectrometry

A gas-liquid interface (liquid surface) is an important subject of investigation; chemical and physical properties of molecules on a solution surface are different from those in the liquid and in the gas [1, 2, 3, 4, 5, 6, 7, 8]. The specificity arises mainly from the fact that molecules on the liquid surface are not completely surrounded with the constituent molecules and hence are subject to asymmetric forces. The asymmetry in the force manifests itself in the chemical composition [9, 10, 11, 12, 13], the orientation of surface molecules [14,15], and dynamical behaviors such as molecular relaxation [16] and chemical reactivity, especially, ion-molecule reactions [17, 18].