We prepared gold nanoparticles in an aqueous solution of sodium dodecyl sulfate (SDS), which were introduced inside a vacuum as a continuous liquid flow (liquid beam). When the particles in the liquid beam were irradiated with a nanosecond laser pulse, ions were ejected from the liquid beam into the vacuum. We analyzed massto-charge ratios of the ions by time-of-flight mass spectrometry. Gold cluster ions, Au n + , and their hydrated ions, Au n + (H 2 O) m (n, m ) 1, 2, 3, ...), were observed. The action spectrum of the cluster ions, showing the abundance of the ions against wavelength of the excitation laser pulse, does not accord with the optical absorption spectrum of the gold nanoparticles but agrees well with the component of the interband transition. This finding indicates that gold nanoparticles were ionized as a result of repetitive photoexcitation-relaxation cycles.
Boron nitride (BN) nanosheets/polysiloxane composites were fabricated under nano pulse width electric field to enhance the anisotropic alignment of BN nanosheets in a viscous matrix. BN nanosheets have unique physical and thermal properties and exhibit semiconducting behavior with a wide band gap comparing to carbon graphite. However the researches over one dimensional arrangement of BN nanosheets with application of the electric field are limited. The difficulty of modifying the BN surface with electrophilic metal particles or organic functional groups due to its remarkable chemical inertness is one of the reasons. In this study, we attempted to fabricate anisotropic aligned BN nanosheets in a viscous polysiloxane matrix without surface modification of BN nanosheets by using nano pulse width electricity. The electric responses of various nanodimensional BN nanoparticles were compared by zeta potential. Two kinds of polysiloxane pre-polymers were used to compare the viscosity effects of the polymer matrix. The anisotropic alignment of none-modified BN nanosheets inside polysiloxane can be controlled with variation of the shape and dimension of BN nanosheets, electrodes, DC electric fields, and by application of nano pulse width electricity.
We investigated solvation structures of I(-) on and below a surface of an aqueous solution by photodetachment spectroscopy. An aqueous solution of an alkali halide was introduced to the vacuum as a continuous liquid flow (liquid beam), and the liquid beam was irradiated with a UV laser pulse. The intensity of electrons emitted from the surface by the laser excitation was measured as a function of wavelength (photodetachment spectroscopy), and we obtained absorption spectrum of I(-) on and below the solution surface. From the absorption spectrum, we found that I(-) starts to appear on the solution surface as the bulk NaI concentration increases. Similar concentration dependence was observed for the KI solution. We also found that I(-) located inside the solution is pushed to the surface, when NaCl is added to the solution. These changes are explained in terms of the difference in the polarizability of halide ions.
We investigated solvation structures of I− and Na+ on an aqueous solution surface by photodetachment spectroscopy and mass spectrometry. An aqueous solution of NaI was introduced into the vacuum as a continuous liquid flow (liquid beam), and the liquid beam was irradiated with a UV laser pulse. The abundance of electrons emitted by the laser excitation was measured as a function of wavelength (photodetachment spectroscopy). For a concentrated aqueous solution of NaI, we observe an absorption peak at longer wavelengths than the charge-transfer-to-solvent band of I− in solution. This feature is assigned to the photoabsorption of I− at the surface. This finding indicates that when the concentration of NaI is high (>1.0 M), I− exists on the solution surface. The identity of the ion clusters ejected from the liquid beam following selective laser excitation of I− on the surface or I− inside the solution was revealed by mass spectrometry. The mass spectra show that Na rich clusters are formed when I− inside the solution is excited, whereas Na rich clusters are hardly formed by the excitation of surface I−. These findings lead us to conclude that Na+ does not exist on the surface of the NaI aqueous solution.
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