Laser-induced Marangoni convection in the presence of surfactant monolayers

Autor(es)

Gugliotti‚ M. ; Baptista‚ M.S. ; Politi‚ M.J.

• Tipo de documento: Artigo Científico
• Fonte: Langmuir; v. 18, n. 25, p. 9792-9798, 2002.

Resumo

Marangoni convection was induced by laser heating in shallow layers of solutions of crystal violet in ethylene glycol and water. Single- and double-beam instrumentations were developed for monitoring the deformation generated on the solution surfaces and to detect the influence of surfactants. In the single-beam configuration, the depression of the liquid surface acted as a converging lens, focusing the reflected beam, and the magnitude of the lens effect was measured as in a classical thermal lens experiment. In the double-beam configuration, the depression of the surface was induced by a pump beam, and the deflection of a probe beam reflected on the surface near the deformed region was monitored by a position sensor detector. The influence of surfactants as hexadecanol, DPPC, and cardiolipin was studied by forming monolayers on the surface of the solutions. The results showed that the lens effect, as well as the deflection of the probe beam, can be suppressed by a small amount of surfactant deposited on the solutions surfaces. The high sensitivity of the instruments enabled the detection of the point at which the suppression first occurs, which is close to the G-LE transition of the monolayers. In all cases the surface healing was explained taking into account the Gibbs-Marangoni effect, and the possible correlations with other phenomena involving surface deformations were briefly discussed. (AU)

• Processo FAPESP: 01/08708-5 - A influência de surfactantes na movimentação de líquidos induzida por gradientes de tensão superficial
• Beneficiário: Marcos Eduardo Sedra Gugliotti
• Modalidade de apoio: Bolsas no Brasil - Pós-Doutorado
• Processo FAPESP: 98/02757-0 - Processos fotoquímicos e fotofísicos no desenvolvimento de novos materiais
• Beneficiário: Mario José Politi
• Modalidade de apoio: Auxílio à Pesquisa - Temático