Miyuki Kuramori

Atomic force microscopic observation of a dialkylmelamine monolayer on barbituric acid

A monolayer of 2-amino-4,6-di(dodecylamino)-1,3,5-triazine 1 transferred from barbituric acid solution onto a mica plate is observed by atomic force microscopy (AFM) to show regularly arrayed terminal methyl groups of 1 as a result of hydrogen-bond networking.

Morphology and molecular orientation and structure of Langmuir–Blodgett films of chlorophyll a studied by atomic force microscopy and UV–VIS and IR spectroscopies

Atomic force microscopy (AFM), scanning electron microscopy (SEM) and UV–VIS absorption and IR spectroscopies have been used to investigate the morphological and molecular structure of Langmuir–Blodgett (LB) films of the title compound (Chl-a). The AFM and SEM measurements reveal that the surface of the LB films are very smooth and consist of rigid and condensed monolayers. The tilt angle of the chlorin plane in a six-monolayer LB film of Chl-a has been calculated to be 35° between the normal of the chlorin plane and the substrate normal and 44° between the dipping direction and projection of the normal of the chlorin plane, from measurements of its polarized UV–VIS spectra. Band frequencies in the 1750–1400 cm −1 region of the IR spectra of one-, six- and ten-monolayer (ML) LB films of Chl-a suggest that Chl-a exists in a five-coordinated monomer in the films, irrespective of the number of monolayers. Comparison of IR transmission and reflection–absorption spectra of 6 ML LB films of Chl-a indicates that the chlorin plane and the ester and keto CO groups are tilted considerably with respect to the surface normal. LB films of pheophytine a (Phe-a) have also been studied for comparison. Comparison of the UV–VIS and IR spectra of the LB films of Chl-a and Phe-a show that pheophytinization occurs little in the LB films of Chl-a. High-performance liquid chromatography (HPLC) examination has supported this conclusion. All the experiments carried out in the present study suggest that Chl-a molecules in the LB films are oriented in an orderly manner with face-to-face packing of the chlorin rings.

Control of molecular ordering in guanidinium-functionalized monolayer by carboxylate template molecules

Electron diffraction studies of a [(dioctadecyl)carbamoylmethyl]guanidinium toluene-p-sulfonate (DG) monolayer reveal that the regularity of the molecular arrangement and the size of crystalline domains are controlled through binding of aqueous α,ω-dicarboxylates with various spacer lengths.

Nanotribology of behenic acid monolayer and its aggregation state

Abstract The tribological properties of behenic acid monolayers in CS and L 2 phases were investigated on the basis of scanning probe microscopic observations. The lateral (friction) force of the monolayers in CS and L 2 phases increased consistently with applied force. The increment in CS phase comes from an increase in contact area between a probe and the monolayer owing to elastic deformation, while that in L 2 phase does from not only increase in contact area owing to plastic deformation but wear of the monolayer. The lateral force of the monolayer in CS phase was independent of the scan velocity. On the other hand, the monolayer in L 2 phase exhibited the scan velocity dependence of the lateral force. The difference in tribological properties of the monolayer is attributable to the static mechanical properties of elasticity and plasticity which are governed by the molecular packing in monolayer.

Effect of binding state between hydrophilic and hydrophobic portions on aggregation structure of monolayer

Abstract The effect of molecular structure of anionic (2CnPOH (n=12, 16)) amphiphiles with dialkyl chains that bind with the hydrophilic group only through ether bond and cationic (2CnN+2C (n=18, 22)) amphiphiles with dialkyl chains that directly bind with the hydrophilic group without a spacer on aggregation structure of amphiphile monolayers was investigated on the basis of π-A isotherm measurement and electron diffraction (ED) analysis. π-A Isotherms of the 2C12POH and 2C18N+2C monolayers exhibited a plateau region, whereas those of the 2C16POH and 2C22N+2C monolayers did a sharp rise in surface pressure with decreasing surface area. ED analysis revealed that 2C12POH, 2C18N+2C and 2C22N+2C monolayers were in an amorphous state even at higher surface pressures. On the other hand, the 2C16POH monolayer was in a crystalline hexagonal state in which the degree of molecular aggregation is low. Noncrystallization of the 2C12POH, 2C18N+2C and 2C22N+2C monolayers and the low degree of molecular aggregation of the 2C16POH monolayer may be attributed to the molecular aggregation by distantness between dialkyl chains in their parallel alignment due to binding between the hydrophilic and hydrophobic portions without or through only one spacer.

Structural and morphological studies on Langmuir-Blodgett films of pheophytine a by ultraviolet–visible and infrared spectroscopies and atomic force microscopy

Abstract The structure concerning the molecular aggregation in Langmuir-Blodgett (LB) films of pheophytine a (Phe- a ) has been studied by ultraviolet–visible (UV–Vis) and infrared (IR) spectroscopies and their morphology has been delineated by atomic force microscopy (AFM). UV–Vis spectra were measured for a chloroform (CHCl 3 ) solution of Phe- a , cast film from the CHCl 3 solution and six-layer LB films of Phe- a prepared in air and argon (Ar) atmospheres. A comparison of these UV–Vis spectra indicates the existence of two kinds of aggregates of Phe- a in the cast and LB films. One has a Qy band at 683 nm and another has a corresponding band at 700 nm. Soret bands of the cast and LB films also show a marked broadening. It is suggested from the UV–Vis measurements that the LB film prepared in the Ar atmosphere includes the aggregate with the 700 nm band at the highest ratio among the three kinds of films. On the other hand, the IR spectra of the solution, and cast and LB films resemble each other, suggesting that Phe- a exists in a monomer in them. Therefore, it seems that the aggregates are composed of stacked Phe- a monomers with a π – π interaction. AFM images for the LB films of Phe- a prepared in the air and Ar atmosphere reveal that they have very smooth and flat surface.

Phase Separation for Langmuir Monolayer in Binary System Based on a π-A Isotherm Measurement

The mixing behavior of binary monolayer of fatty acid was investigated on the basis of π-A isotherm measurements. The (palmitic acid(C16)/arachidic acid(C20)) and (C20/lignoceric acid(C24)) mixed monolayers were in a miscible state, whereas the (C16/C24) mixed monolayer was an immiscible state. The (C16/behenic acid(C22)) and (stearic acid(C18)/C24) mixed monolayers were in an incomplete miscible state. The dependence of mixing behavior on the difference in the number of methylene group between components in monolayer is probably due to an enthalpic contribution based on the difference in cohesive energy between the monolayer components.