Laser-induced synthesis

Nanocomposite Si-C-N ternary UFPs have been synthesized for aiming at improving the properties of the final powders, increasing safety, and lowering the production cost. In the laser-induced synthesis, many gaseous mixtures are used as reactants, such as hexamethyl-disilazane ((CH3)3SiNHSi(CH3)3) (68,69), methyl-amine (CH3NH2), and dimethylamine ((CH3)2NH) (70-72). 

The focus of this chapter has been on the synthesis of new catalysts by parallel and combinatorial methods. Another aspect important to the development of new catalysts by these methods is the screening of these large libraries. We will not attempt to cover this topic comprehensively but do feel it is necessary to summarize some of the approaches that have been taken. Methods for screening libraries can be divided into both serial and parallel methods. Generally, the serial methods are adaptations of standard methods that allow for rapid individual analysis of each member of a library. Serial approaches for the analysis of libraries can be as simple as use of an auto sampler on a GC or HPLC system or as advanced as laser-induced resonance-enhanced multiphoton ionization of reaction products above the head-space of a catalyst (16) or microprobe sampling MS (63). The determination of en-antioselectivity in catalysis is a particular problem. Reetz et al. (64) reported the use of pseudoenantiomers and MS in the screening of enantioselective catalysis while Finn and co-workers (65) used diastereoselective derivatization followed by MS to measure ee. 

The synthesis of a new near-infrared cyanine dye was monitored by CE and fluorescence detection. The chemicals structure of the dye and its synthetic precursor are depicted in Fig. 3.165. The analysis of the dye was realized in fused-silica capillaries of 75 and 100 /an i.d. The total and effective lengths of capillaries were 75 and 60 cm, respectively. The separation voltage was 30 kV and separations were carried out at ambient temperature. The running buffer was 2.5 mM Na2B407 (pH = 9.2). A near-infrared laser-induced fluorescence detector was applied. Electropherograms illustrating the separation of the dye are shown in Fig. 3.166. 

Figure 8.1.12 shows a schematic illustration of laser-induced CVC (63). For the synthesis of silicon nitride, the reaction between silane (SiH,) and ammonia... 

Table 8.1.6 Processing Conditions for the Synthesis of Silicon Nitride UFPs by a Laser-induced CVC...

Laser-induced CVC has been applied to the synthesis of UFPs of novel materials such as BN from the BCl3-NH3 system (75) and CVNV from the C2H2-N20-NH3 system (76). 

Plasma chemical synthesis Laser induced reaction... 

Toshiyuki O., Yasuhiro I. and Kenkyu R.K., Synthesis of Sn02, VO2 and V2O3 fine particles by laser-induced vapor-phase reaction. J. Photopolym Sci. Technol. 10(1997) pp. 211-216. 

All these modified purine nucleosides have the advantage that they are readily converted to fluorescent building blocks for solid-phase DNA synthesis or to 5 -triphosphates for enzymatic DNA synthesis. Such compounds are useful for single DNA molecule detection in solution by laser-induced fluorescence as well as for single DNA molecule sequencing. 

Tremendous fundamental research especially in the CVD technologies and precursor synthesis extends the applicability to some new area. These technologies include metal-organic CVD (MOCVD), plasma-enhanced CVD, photo CVD and laser induced CVD etc. The advancement of the synthesis technology provides new precursors to deposit a variety of materials with high purity. 

K. Kitahama, K. Hirata, H. Nakamatsu, S. Kawai, N. Fujimori, T. Imai, H. Yoshino, and A. Doi, Synthesis of diamond by laser-induced chemical vapor deposition, Appl Phys. Lett, 49 634 (1986)... 

Y. Goto, and H. Nagai, Synthesis of diamond films by laser-induced chemical vapor deposition, in Laser- and Particle-Beam Chemical Processes on Surfaces Symposium, (A. W. Johnson, G. L. Loper, and T. W. Sigmon, eds.), Pittsburgh, PA, MRS, pp. 213-218 (1989)... 

Fluorescently labeled libraries can be used to facilitate detection during selections. Laser-induced fluorescence (LIF) detection is orders of magnitude more sensitive than UV-absorbance detection making it much easier to reliably observe peaks for the unbound sequences during selections. Fluorescent labels are easily incorporated at the 5 end of ssDNA during initial synthesis. Fluorescent... 

Phillips HM, Li Y, Bi X, Zhang B (1996) Reactive pulsed laser deposition and laser induced crystallization of SnO transparent conducting thin films. Appl Phys A 63 347-351 Pique A, Auyeung RCY, Stepnowsk JL, Weir DW, Arnold CB, McGiU RA, Chrisey DB (2003) Laser processing of polymer thin films for chemical sensor applications. Surf Coat Technol 163-164 293-299 Randhaw H (1991) Review of plasma-assisted deposition processes. Thin Solid Films 196 329-349 Risti M, Ivanda M, Popovi S, Musi S (2002) Dependence of nanocrystaUine SnO particle size on synthesis route. J Non-Crystal Solids 303 270-280... 

Carbothermal nitridation of silica, including rice huUs Diimide synthesis Vapor-phase synthesis Plasmachemical synthesis Laser-induced reactions Pyrolysis of organosilicon compounds... 

Lee J., Zhang Q.W., Saito F. Synthesis of nano-sized lanthanum oxyfluoride powders by mechanochemical processing. J. Alloys Comp. 2003 348 214-219 Liberman V., Rothschild M., Sedlacek J.H.C., Uttaro R.S., Grenville A., Bates A.K., Van Peski C. Excimer-laser-induced degradation of fused silica and calcium fluoride for 193-mn lithographic applications. Opt. Lett. 1999 24 58-60... 

R Alexandrescu, E BorseUa, S Botti, MC Cesile, S Martelli, R Giorgi, S Turtu, G Zappa. Synthesis of Tie and SiC/TiC nanocrystalline powders by gas-phase laser-induced reaction. J Mater Sci 32 5629, 1997. 

---