Photochemical reaction of organosilane self-assembled monolayer as studied by scanning probe microscopy

Abstract

Articles you may be interested inReversible work function changes induced by photoisomerization of asymmetric azobenzene dithiol selfassembled monolayers on gold Appl. Phys. Lett. 93, 083109 (2008); 10.1063/1.2969468 Micropatterning organosilane self-assembled monolayers with plasma etching and backfilling techniques J. Vac. Sci. Technol. B 23, 354 (2005); 10.1116/1.1861041Organosilane self-assembled monolayers directly linked to the diamond surfaces A photopatterning process of an alkylsilane self-assembled monolayer ͑SAM͒ using vacuum ultraviolet ͑VUV͒ light at 172 nm has been studied by characterizing the VUV-irradiated SAM surfaces through lateral force microscopy ͑LFM͒ and Kelvin-probe force microscopy ͑KFM͒. The SAM was formed from n-octadecyltrimethoxysilane on a Si substrate covered with a 2-nm thick oxide layer. Due to VUV irradiation in the presence of atmospheric oxygen, polar functional groups, e.g., COOH, were generated through photochemical oxidation of the SAM which was gradually etched. Finally, the SAM was completely removed from the VUV-irradiated region. Relative frictional forces and surface potentials of the VUV-irradiated regions at various irradiation dose rates were measured by LFM and KFM using the unirradiated regions on each sample as a reference. Changes in the surface chemical composition of the SAM could be measured by these scanning probe microscopic methods. The LFM contrast increased monotonically with the increase in the dose rate, while the surface potential contrast measured by KFM showed a characteristic feature. At a certain dose rate of 10-15 J/cm 2 , VUV-irradiated SAMs showed particularly lower surface potentials than the other SAM surfaces with different dose rates. This is most likely because COOH groups, which were considered negatively charged in part, had been accumulated on the surfaces. LFM and KFM measurements are promising in order to probe chemistries on organic thin films proceeding in small domains with a scale.

Enhanced flux in direct contact membrane distillation using superhydrophobic PVDF nanofibre membranes embedded with organically modified SiO2 nanoparticles

“…An increase in the size of the organically modified SiO 2 NPs and formation of uniform structures would be ascribed to the self‐assembled layer of the silane agent on the surface of the pristine SiO 2 NPs . Self‐assembled monolayers of ODTS, OTMS and Cl‐DMOS on SiO 2 surfaces has been reported previously .…”

“…Self‐assembled monolayers of ODTS, OTMS and Cl‐DMOS on SiO 2 surfaces has been reported previously . Although the determination of the additional layer formation was not conducted, the increase in size of the SiO 2 NPs as observed on TEM micrographs upon modification using the silane reagents indicated the formation of an additional layer as suggested by others …”

“…34 An increase in the size of the organically modified SiO 2 NPs and formation of uniform structures would be ascribed to the self-assembled layer of the silane agent on the surface of the pristine SiO 2 NPs. 35,36 Self-assembled monolayers of ODTS, OTMS and Cl-DMOS on SiO 2 surfaces has been reported previously. 26,27,36 Although the determination of the additional layer formation was not conducted, the increase in size of the SiO 2 NPs as observed on TEM micrographs upon modification using the silane reagents indicated the formation of an additional layer as suggested by others.…”

A review of nanoparticle‐enhanced membrane distillation membranes: membrane synthesis and applications in water treatment

“…The OTMS molecule is characterized by a long aliphatic carbon chain (CH 3 (CH 2 ) 17 ‐) where the anchor group is (‐Si‐OCH 3 ) 3 . Furthermore, the anchor groups on ODTS and Cl‐DMOS are (‐Si‐ClCH 2 ) 3 and (‐Si‐Cl 3 ) 3 , respectively . The anchor groups on OTMS are more hydrophobic due to the presence of bulky non‐polar CH 3 groups.…”

“…Furthermore, the anchor groups on ODTS and Cl-DMOS are (-Si-ClCH 2 ) 3 and (-Si-Cl 3 ) 3 , respectively. [68][69][70][71][72][73][74] The anchor groups on OTMS are more hydrophobic due to the presence of bulky non-polar CH 3 groups. The presence of strong electron withdrawing atoms such as chlorine and oxygen in Cl-DMOS and ODTS cause an uneven distribution of electrons, which could subsequently induce a minimal polarity on one end of the molecule, and slightly reduce its hydrophobicity.…”