Effect of PECVD deposition parameters on the DLC/PLC composition of a-C:H thin films

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Abstract

Hydrogenated amorphous carbon (a-C:H) thin films were synthesized on the surface of materials to improve mechanical, optical and chemical properties. In the present study, plasma enhanced chemical vapor deposition (PECVD) was performed to produce a-C:H films with PLC (polymer like carbon) and DLC (diamond like carbon) phases. The influences of the acetylene partial pressure and chamber pressure on the chemical structures of the products were evaluated by infrared reflection absorption spectroscopy (IRRAS) and Raman spectroscopy. Moreover, the morphology and thickness of the films were investigated by atomic force microscopy (AFM) and profilometry, respectively.

Translated abstract

Filmes finos de carbono amorfo hidrogenado (a-C:H) têm sido depositados na superfície de materiais para melhorar propriedades mecânicas, ópticas e químicas. Nesse estudo, foi empregado o sistema de deposição química assistida por plasma (PECVD) para sintetizar filmes de a-C:H com fases DLC (tipo diamante) e PLC (tipo polimérico). As pressões parciais de acetileno em argônio foram variadas e as estruturas dos produtos analisadas pela técnica de espectroscopia de reflexão-absorção no infravermelho (IRRAS) e Raman. Além disso, a morfologia e as espessuras dos filmes foram determinadas por microscopia de força atômica (AFM) e perfilometria, respectivamente.

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Visoltricin, a novel biologically active compound produced by Fusarium tricinctum.

A Visconti, M Solfrizzo (1995)

The major compound responsible for toxicity to Artemia salina of some Fusarium tricinctum strains has been isolated, and its structure has been elucidated by spectroscopical methods, i.e. UV, IR, MS, 1H-NMR and 13C-NMR. The novel compound, trivially named visoltricin, is the first imidazole derivative produced by Fusarium spp., and its structure has been established as the methyl ester of 3-[1-methyl-4-(3-methyl-2-butenyl)-imidazol-5yl]-2-propenoic acid (molecular formula C13H18N2O2; MW = 234.297). Visoltricin was toxic to A. salina larvae (LD50 = 8.5 x 10(-7) M), and inhibited the growth of six human tumour cell lines (out of 60 lines tested) at concentrations lower than 10(-5) M. Tested on rabbit eye it showed an interesting miotic activity similar to that of pilocarpine, a miotic agent largely used in the therapy of glaucoma. This biological activity could be explained in part by the anticholinesterase properties shown by visoltricin towards both human serum and pure enzymes (EC 3.1.1.7 and EC 3.1.1.8). Kinetics studies showed for visoltricin a mixed-type and reversible inhibition of the EC 3.1.1.7 enzyme with the competitive inhibition constant (Ki) = 1.9 x 10(-4) M.