Horizontal lifting method

The second way of preparing L-B monolayer structures, the horizontal lifting method, was introduced by Langmuir and Schaefer. In this method, a compressed monolayer first is formed at the water-air interface, and a flat substrate is then placed horizontally on the monolayer film. When the substrate is lifted and separated from the water surface, the monolayer is transferred onto the substrate, as depicted in Fig. 15(d). 

The surface pressure-area (tc-A) isotherm measurements and LB film transfer were performed with the use of a KSV 5000 minitrough (KSV Instrument Co., Finland) operated at a continuous speed for two barriers of 10 cm2/min at 20°C. The buffer used in the present work was composed of 10 mM MES, 2 mM ascorbic acid sodium salt, and a given concentration of salt or polymers (pH =7.0). The accuracy of the surface pressure measurement was 0.01 mN/m. Monolayers of the PS I were transferred at 10 mN/m on hydrophobic substrate surface by horizontal lifting method. 

The complex PS I multilayers can be obtained by the horizontal lifting method with well washing the substrate after each transfer. Figure 4d shows absorption spectra of five layers of PS I/PBV multilayer. Absorptions at 440 nm and 674 nm increase with the increase of layer numbers. Moreover, this multilayer exhibits quite strong stability in buffer solution. As shown in Figure 5, over 80 % PS I still remains in the multilayer after the PS I LB film coated substrate was immersed in the buffer for 1 h. 

Cationic ions and polyelectrolytes can stabilize the formation of the PS I monolayers at the air-water interface. These complex monolayers can be transferred onto the hydrophobic substrate surfaces by horizontal lifting method. The PS I/polyelectrolyte complex film may be used for the development of a biosystem for the studies on photoinduced electron transfer and for hydrogen evolution. 

Phthalocyanines (Pc) are attractive materials for their potential functions including the semiconductive behaviours in addition to the thermal and chemical stabilities. In particular, control of orientation of the Pc macrocycles in thin films is expected to provide novel molecular electronic devices. Previously, we have found that copper tetrakis(butoxycarbonyl) Pc is oriented nearly perpendicular to the surface and also the dipping direction in the LB films [46], while octa-alkyl Pc derivatives [H2Pc(R)8, CuPc(R)a R = CnH2n+i. n=7,9,11] take the orientation with Pc macrocycles nearly parallel to the plane of films deposited by the horizontal lifting method to form a non-alternating X-type film [47], as illustrated schematically in... 

Ten layers of DPPC (Tc = 42 °C) LB films were deposited on a QCM plate by a horizontal lifting method on one side and immersed in water. Typical time-courses of frequency changes of the DPPC-deposited QCM are shown in Figure 12. At 25 °C in the solid state below the Tc, DPPC LB films were stable and hardly swelled in water. However, the frequency gradually increased (mass decreased) at 50 °C (above the Tc) and reached equilibrium at AF = 450 50 Hz -Am = 575 50 ng), which is equivalent to the loss of 10 layers mass of the dry LB films. Frequency... 

As an extension of their previous work, the Tachibana group (82, 83) studied the collapse fragments that occur when monolayers of 12-hydroxystearic acid are compressed slowly (18 A /molecule hr) at surface areas of less than 21 A /molecule, the normal cross-sectional area of a hydrocarbon chain. The collapsed monolayers were transferred from the subphase to hydrophilic supports by a horizontal lifting method for electron microscopic observation, which revealed (Fig. 30) flat platelets when the sample was racemic and twisted... 

Fig. 11 Polarized absorption spectra of DNA /proflavine/2Ci8-glu-N LB films (88 layers) deposited by a vertical dipping method and b horizontal lifting method...

Variations on the vertical dipping technique have been utilized to construct films containing divalent metal ions. For example, the quartz crystal microbalance (QCM) has been used to evaluate the horizontal lifting method of CdSt LB Film construction (26). In this method, the QCM quartz plate was touched to monolayers compressed on a subphase and lifted horizontally. Y-type transfer (transfer ratio of 1) was demonstrated with two centrosymmetric monolayers deposited for each cycle. A combination of the vertical and horizontal dipping techniques has been utilized to prepare multilayer films from an amphiphilic porphyrin compound (27). 

This mixture forms a monolayer at the air-water interface. This monolayer is then transferred on a substrate (glass, quartz, CaF2) by a horizontal lifting method. The neutral films so obtained are oxidized, that is, doped , in situ with gaseous bromine or by galvanostatic electrochemical oxidation at constant current (261). The RT conductivity of the films is 30 S cm 1, and they behave as a metal down to 200 K, below which temperature the behavior remains quasimetallic. However, after aging in vacuum, the film behaves like a semiconductor from RT down to 10 K. 

CH, horizontal lifting method V, vertical dipping method. dSilver paste was used as electrodes. 

Y. Okahata, K. Ariga, K. Tanaka, Evaluation of a Horizontal Lifting Method of Langmuir-Blodgett Films Using a Quartz-Crystal Microbalance , Thin Solid Films, 210,702(1992)... 

Zhang. G. Kuwahara, Y. Wu. J. Akai-Kasaya, M. Saito, A. Aono. M. Scanning tunneling microscopy observation of binary monolayers of 10.12-tricosadiynoic acid and stearic acid deposited by horizontal lifting method. Surf. Sci. 2001. 476, L254-L258. 

Amphiphilic dmit complexes with various ammonium cations and central metal cations (mCn-M, Fig 1) were synthesized, according to procedures described previously [22]. 1 1 mixtures with eicosanoic acid formed monolayers on pure water. The monolayers were deposited on hydrophobized solid substrates by the horizontal lifting method. Gold electrodes (gap distance 0.1 mm) were formed, by vacuum deposition, before the transfer of monolayers. The conductivity of the films was measured for a 20-layer sample by dc 2-probe or 4-probe method after oxidation. The oxidation of the LB films was performed by two different methods oxidation by bromine gas and electro-oxidation. The latter was achieved by a constant-current method in 0.1 mol/L LiC104 aqueous solution. 

We designed an amphiphilic molecule, in which three functional parts are involved azobenzene as the switching unit, an alkyl chain as the transmission unit, and a TCNQ charge transfer salt as the working unit (APT(8-12), Fig. 3). The molecule is assembled in an ordered array by a horizontal lifting method on a solid substrate. In this arrangement, the cis-trans photoisomerization of azobenzene induces the reversible change in the lateral conductivity of the LB film. 

The amphiphilic polyaniline derivative (degree of polymerization > 20), prepared by the chemical polymerization method with (NH4)2S20s in THF and 2 mol 1" HCl solution was used. More than 200 layers of the polyaniline derivative were prepared by transferring the monolayer on the HCl (0.1 mol 1 ) subphase onto polyester, gold- or ITO-deposited polyester and silated glass substrates at a surface pressure of 20-25 mNm" by the horizontal lifting method. 

Fig.l shows the schematic diagram to prepare the PC-LB films on the ITO substrate by the horizontal lifting method. A monolayer of stearic acid was deposited on the ITO substrate at first and then X-type layers of palmitoyl cellulose LB film were built up at a trough temperature of 290 K. The degree of substitution (DS) of the palmitoyl cellulose have been reported elsewhere. 

Fig. I Schematic diagram to prepcire the palmitoyl cellulose Langmuir-Blodgett film on the ITO substrate by the horizontal lifting method.

Conductive LB films of polythiophene were first reported using poly(3-dodecylthiophene) soluble in chloroform [268]. The polymer formed a stable monolayer which was transferred to solid substrates using the horizontal lifting method. The conductivity after ioding doping was 0.5 S/cm. The imdoped film showed a third order optical susceptibility of 10 esu (Figure 14.39). 

A soluble polyaniline derivative was prepared by the chemical polymerisation of 2-octadecylaniline. The monolayer of this compound on an aqueous HCl subphase was fabricated into LB film by the horizontal lifting method. Highly anisotropic conductivity was obtained after iodine doping (<7 il0 S/cm,... 

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