One possible way to promote the bond-selective chemical-reactions by frequency-modulated lasers

It is proposed in this paper that we can use frequency-modulated (FM) lasers to realize bond-selective chemical reactions or to raise the efficiency of molecular isotope separation. Examples are given for HF molecule and the C–H bond in some hydrocarbons.

Mechanism study of femtosecond laser induced selective metallization (FLISM) on glass surfaces

We investigate the mechanism of selective metallization on glass surfaces with the assistance of femtosecond laser irradiation followed by electroless plating. Irradiation of femtosecond laser makes it possible to selectively deposit copper microstructures in the irradiated area on glass surfaces coated with silver nitrate films. The energy-dispersive X-ray (EDX) analyses reveal that silver atoms are produced on the surface of grooves formed by laser ablation, which serve as catalysis seeds for subsequent electroless copper plating. (C) 2008 Elsevier B.V. All rights reserved.

Selective metallization on insulator surfaces with femtosecond laser pulses

We report selective metallization on surfaces of insulators ( glass slides and lithium niobate crystal) based on femtosecond laser modification combined with electroless plating. The process is mainly composed of four steps: (1) formation of silver nitrate thin films on the surfaces of glass or crystal substrates; (2) generation of silver particles in the irradiated area by femtosecond laser direct writing; (3) removal of unirradiated silver nitrate films; and (4) selective electroless plating in the modified area. We discuss the mechanism of selective metallization on the insulators. Moreover, we investigate the electrical and adhesive properties of the copper microstructures patterned on the insulator surfaces, showing great potential of integrating electrical functions into lab-on-a-chip devices. (C) 2007 Optical Society of America.

Harmonic Millimeter Wave Generation and Frequency Up-Conversion Using Optical Injection Locking and Brillouin Selective Sideband Amplification

Harmonic millimeter wave (mm-wave) generation and frequency up-conversion are experimentally demonstrated using optical injection locking and Brillouin selective sideband amplification (BSSA) induced by stimulated Brillouin scattering in a 10-km single-mode fiber. By using this method, we successfully generate third-harmonic mm-wave at 27 GHz (f(LO) - 9 GHz) with single sideband (SSB) modulation and up-convert the 2GHz intermediate frequency signal into the mm-wave band with single mode modulation of the SSB modes. In addition, the mm-wave carrier obtains more than 23 dB power gain due to the BSSA. The transmission experiments show that the generated mm-wave and up-converted signals indicate strong immunity against the chromatic dispersion of the fibers.

Calibration of an audio-frequency ion trap mass spectrometer

A method for calibration of an audio-frequency (AF) ion trap mass spectrometer is described. The method is proposed to surmount the obstacle that there is a lack of a proper calibrant for mass spectrometers in the mass-to-charge ratio (m/z) range of 10(6) to 10(10). To calibrate such mass spectra, we determine the point of ejection, q(eject), on the stability diagram of the ion trap operated in a mass-selective axial instability mode. This is accomplished by measuring the radial secular frequencies (and therefore, the m/z value) of a single trapped particle using a light scattering method, followed by monitoring the action of particle ejection in real time to obtain the q(eject). A delayed ejection with q(eject) = 0.949 +/- 0.004 is found at a trap driving frequency of Ohm/2pi = 200-600Hz. Theoretical analysis for the origin of the delayed ejection indicates that the delay is predominantly resulted from the existence of multipole components in the fields due to trap imperfections. Inclusion of -3% of the octopole with respect to the basic quadrupole field can satisfactorily account for our observations. An m/z accuracy approaching 0.1% is attainable after proper calibration of the AF ion trap mass spectrometer. (Int J Mass Spectrom 214 (2002) 63-73) (C) 2002 Elsevier Science B.V. All rights reserved.

Selective hydrogenation of citral catalyzed with palladium nanoparticles in CO2-in-water emulsion

CO2-in-Water (C/W) emulsion was formed by using a nonionic surfactant of poly (ethylene oxide)-poly (propylene oxide)-poly (ethylene oxide) (P123), and palladium nanoparticles were synthesized in situ in the present work. The catalytic performance of Pd nanoparticles in the C/W emulsion has been discussed for a selective hydrogenation of citral. Much higher activity with a turnover frequency (TOF) of 6313 h(-1) has been obtained in this unique C/W emulsion compared to that in the W/C microemulsion (TOF, 23 h(-1)), since the reaction was taking place not only in the surfactant shell but also on the inner surface of the CO2 core in the C/W emulsion. Moreover, citronellal was obtained with a higher selectivity for that it was extracted to a supercritical carbon dioxide (scCO(2)) phase as formed and thus its further hydrogenation was prohibited. The Pd nanoparticles could be recycled several times and still retain the same selectivity, but it showed a little aggregation leading to a slight decrease in conversion.

Selective crystallization of BaF2 under a compressed Langmuir monolayer of behenic acid

Selective crystallization of BaF2 crystals under a compressed Langmuir monolayer of behenic acid [CH3(CH2)(20)COOH] has been studied by using X-ray diffraction, X-ray photoelectron spectroscopy, scanning electron microscopy, and energy-dispersive X-ray analysis. It was found that, in the absence of a monolayer, three kinds of crystals (Ba2ClF3, BaClF, and BaF2) can be obtained by mixing BaCl2 with a NH4F solution. However, in the presence of the monolayer of behenic acid, only BaF2 crystals appear at the monolayer-subphase interface and crystals have a special crystal face (100). During this process of crystallization, the monolayer plays a very important role and acts as a template that can preferentially select a special crystal and a special crystal face. The above results can be explained in terms of a specific molecular interaction between ions and the headgroups of the monolayer and specific electrostatic, geometric, and stereochemical interactions at the organic-inorganic interface.