Laser irradiation synthesis

All 60 C-atoms of Cjq are incorporated in the CgoHjo polycyclic aromatic hydrocarbon (PAH) 6, for which an efficient synthesis was developed [153], Laser irradiation of 6 at 337 nm induces hydrogen loss and the formation of CgQ, as detected by mass spectrometry (Scheme 1.6). Control experiments with C-labeled material and with the C48H24 homologue of 6 verified that the C50 is formed by a molecular transformation directly from the C50H30 PAH and not by fragmentation and recombination in the gas phase. 

UFPs of the Fe-N system can be synthesized from iron pentacarbonyl Fe(CO)s] and NH3 as reactants by a IOOO-W continuous wave C02 laser irradiation. The NH, gas is the absorbent of the laser beam in this case. At the lower synthesis temperature, below 650°C, UFPs of y -Fe4N with particle size of 10-25 nm grew dominantly. Above 1150°C, however, the growth of y-Fe UFPs with larger particle size of 30-100 nm was predominant (73). Iron carbonitride (lCN) UFPs were also synthesized from the ternary reactants of Fe(CO)s, NH3, and C2H i. The structure oflCN UFPs was hexagonal with e-Fe3(N,C) phase. A large saturation magnetization up to 142 emu/g was obtained and was ascribed to the carbon layer on 1CN UFPs (74). 

Bromo- and iodo-substituted nucleotides are useful as affinity labels for proteins that interact with nucleic acids (Figure 5-9). Precursors for the synthesis of such affinity labels are commercially available as phosphoramidites, which can be used in conventional DNA or RNA synthesis to incorporate the label at the desired position in an oligonucleotide. Photoactivation is carried out using long wavelength UV light, for bromo-derivatives by laser irradiation at 305 nm (NeCl-laser), and for iodo-derivatives at 325 nm (HeCd-laser) (Willis et al. 1993). 

In addition to chemical methods variety of physical methods has been employed for the synthesis of AuNPs. UV irradiation is used to improve the quality of the AuNPs when it is used in synergy with micelles or seeds [32,33], Near-IR laser irradiation provokes an enormous size growth of thiol-stabilized AuNPs [34], The presence of an ultrasonic field (200 kHz) allowed the control of the rate of AuC14" reduction in an aqueous solution containing only a small amount of 2-propanol and the sizes of the formed AuNPs are controlled by varying the parameters such as the temperature of the solution, the intensity of the ultrasound, and the positioning of the reactor [35,36], Sonochemistry was also used for the synthesis of AuNPs within the pores of silica and for the synthesis of Au/Pd bimetallic particles [37,38], Radiolysis has been used to control the size of AuNPs [39], Laser photolysis has been used to form AuNPs in block copolymer micelles. Laser ablation is another technique of AuNP synthesis that has been used under various conditions whereby size control can be induced by the laser [40,41],... 

Using a developed method, laser irradiation of colloidal mixtures of the three metals, these authors dispersed Au/Ag/Pd nanoparticles with average diameters 4.4 1.5 nm. These tri-metallic nanoparticles were assessed for activity in the synthesis of nabumetone [4-(6-methoxy-2-naphthalenyl)-2-butanone], a non-steroidal anti-inflammatory drug that has greater activity than aspirin and is comparable to naproxen and indomethacin. The 0.45-mol% Au/Ag/Pd was sufficient to catalyse the coupling of the 3-buten-2-ol... 

In this review, in addition to more detailed experimental data for the synthesis of polyynes by laser ablation of graphite in solutions, new data for Indonesian and Australian coals are reported. In the experiments for graphite, besides benzene, toluene, and hexane used in our previous report [6], cyclohexane and methanol are used as solvents. It is known that long C2 F2 polyynes are generated by laser ablation of graphite in an F-containing gas [10]. Therefore, such F-containing solvents as hexafluorobenzene, perfluorooctane, and perfluorodecaline are also used as new solvents. The absorbances of polyynes in each solvent are measured not only at 355 nm laser irradiation reported previously [6] but also at 266, 532, and... 

Other procedures start with formyl derivatives which react under basic conditions via hydrogen cyanide to provide 1,3,5-triazine.20 A very simple synthesis of 1,3,5-triazine uses an orlhofor-mate and ammonium acetate (see Houben-Weyl, Vol. E5, p 119). 1,3,5-Triazine has been identified in a laser-irradiated hydrogen cyanide sample in the vapor phase at 293 K and a pressure of lOOTorr.126... 

Still relatively unexplored, but potentially a large application field of ordered mesoporous materials is optics and electronics. Marlow et al. succeeded in the synthesis of ordered mesoporous silica fibers doped with a rhodamin laser dye [38]. Upon laser irradiation the waveguide effect reported earlier [27] led to amplification by stimulated emission along the fiber axis. The light emitted from the ends of the fibers was spectrally narrowed and highly directional. The effect observed can be described as a mirrorless lasing which can be useful in the construction of optical circuits. 

Although, photolysis, radiolysis and laser irradiation have also been applied for metal nanoparticles synthesis, they are oflimited application value due to the need for low concentrations [208-210]. 

E. D Anna et al. Synthesis of thin films of semiconductor and refractory metal nitrides by laser irradiation of solid samples in ambient gas. Thin Solid Films 1992, 218, 224-225. 

Synthesis and nonlinear optical characterization of a two-photon absorbing organic dye, trans-4-(dimethylamino)-4 -[N-ethyl-N-(2-hydroxyethyl)amino]stilbene (DMAHAS), were reported [49]. Linear absorption, single-photon-induced fluorescence, and two-photon-induced fluorescence of DMAHAS were experimentally studied. This dye showed a moderate two-photon absorption cross section of a2 = 0.91 X 10-46 cm s/photon at 532 nm as shown by an open aperture Z-scan technique. DMAHAS also showed strong two-photon-induced blue fluorescence of 432 nm when pumped with 800 nm laser irradiation. 

Yingfeng G, Pedraza AJ. (2004) Synthesis, Characterization and modeling of self-organized nanostructure arrays generated by laser irradiation. Proc Mat Res Soc Symp 818 Ml 1.47. 

Recent research work by Museur et al. showed UV-laser-assisted nucleation of boron nitride nanorods from hexagonal boron nitride (h-BN). Pallets of h-BN powder were used as the target compound for the synthesis and they were subjected to a UV-laser irradiation in their ablation regime for laser pulse duration in picoseconds domain. The ambient gas pressure was kept relatively high (above 500 bar) and oxygen pressure was below 0.2 mbar. The appearance of the nanorods was noticed typically with the pulse duration of 5 ps or shorter. 

The synthesis of MNCGs can be obtained by sol-gel, sputtering, chemical vapor-deposition techniques. Ion implantation of metal or semiconductor ions into glass has been explored since the last decade as a useful technique to produce nanocomposite materials in which nanometer sized metal or semiconductor particles are embedded in dielectric matrices [1,2,4,23-29]. Furthermore, ion implantation has been used as the first step of combined methodologies that involve other treatments such as thermal annealing in controlled atmosphere, laser, or ion irradiation [30-32]. 

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