Organisation in monolayers at the air–water interface of butadienyl dyes containing benzodithiacrown-ether or dimethoxybenzene

Colloids and Surfaces A: Physicochem. Eng. Aspects 264 (2005) 207–214

Organisation in monolayers at the air–water interface of butadienyl dyes containing benzodithiacrown-ether or dimethoxybenzene T.I. Sergeeva a,c,∗ , S.P. Gromov b , A.I. Vedernikov b , M.S. Kapichnikova b , M.V. Alfimov b , D. M¨obius c , S.Yu. Zaitsev a,d a

Institute of Bioorganic Chemistry, Russian Academy of Sciences, Miklukho-Maklaya Str. 16/10, Moscow 117871, Russia b Center Photochemistry, Russian Academy of Sciences, Novatorov Str. 7a, Moscow 117334, Russia c Abt. NanoBiophotonik, Max-Planck-Institut f¨ ur biophysikalische Chemie, D-37070 G¨ottingen Germany d Department of Organic and Biological Chemistry, Moscow State Academy of Veterinary Medicine and Biotechnology, Acad. Skryabina Str. 23, Moscow 109472, Russia Received 23 December 2004; received in revised form 8 April 2005; accepted 23 May 2005

Abstract The novel amphiphilic butadienyl dye, containing a dimethoxybenzene unit instead of benzocrown-ether moiety (dye 1) and the amphiphilic benzodithia-15-crown-5 butadienyl dye (dye 2) form stable insoluble monolayers on distilled water. In order to evaluate the influence of the ionophore size on the molecular organisation, the known amphiphilic benzodithia-18-crown-6 butadienyl dye (dye 3) has also been used. The monolayers have been characterized by surface pressure–area and surface potential–area isotherms as well as Brewster angle microscopy and reflection spectroscopy. Besides monomers of the dyes two types of associates exist in the pure dye monolayers, i.e. dimers and aggregates. The spectroscopic properties of the monomers were obtained by studying mixed monolayers of the dyes with the lipid dimyristoyl-phosphatidylcholin (DMPC). The dimers may be organised as head-to-tail dimers with the intermolecular distances 0.38, 0.45, and 0.49 nm for dyes 1, 2, and 3, respectively. According to the extended dipole model, we propose formation of aggregates in which the chromophores are parallel to each other with the same intermolecular distances as in the dimers, and the centers of their transition moments shifted by 0.95 nm (dye 1) and 1.2 nm (dyes 2 and 3). © 2005 Elsevier B.V. All rights reserved. Keywords: Monolayers; Crown-ether; Butadienyl dye; Aggregates

1. Introduction Amphiphilic crown-ether dyes are of great interest due to their ability to form monolayers, selectively bind cations, and photoreact. This polyfunctionality makes them particularly useful for the construction of various supramolecular systems [1], which may be used, e.g. for optically controlled extraction of ions, as elements of photo-switchable molecular devices, or as novel materials for recording, storing and, processing optical information [2]. During the last years, several studies on monolayers at the air–water interface as well as on Langmuir–Blodgett ∗

Corresponding author. Tel.: +49 551 2011497; fax: +49 551 2011085. E-mail address: [email protected] (T.I. Sergeeva).

0927-7757/$ – see front matter © 2005 Elsevier B.V. All rights reserved. doi:10.1016/j.colsurfa.2005.05.024

films of amphiphilic azobenzene crown-ethers have been published [3–7]. Our studies have focussed on amphiphilic crown-ether styryl dyes with various sizes of the polyether ring and various substitutions in the chromophoric part [8–13]. Monolayers of these materials may be used to prepare photosensitive films with the ability to selectively bind cations. Recently, we reported on the synthesis of a new amphiphilic butadienyl benzodithia-18-crown-6 dye and its iono-selective and photosensitive properties in monolayers [14]. Monolayers of that benzodithia-18-crown (denoted here as dye 3) are characterized by several different types of structures, such as monomers, dimers, small aggregates as well as complexes with cations [15]. The structural parameters of these species have not yet been determined.

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Further, we have synthesized a novel amphiphilic benzodithia-15-crown-5 butadienyl dye (denoted here as dye 2) and shown that it forms stable monolayers at the air–water interface [16]. Surface pressure–area and surface potential–area isotherms provided evidence for the formation of complexes of dye 2 with Hg2+ cations from the aqueous subphase and non-specific interactions with K+ [16]. However, the spectroscopic properties of dye 2 including an analysis of the molecular organisation in monolayers at the air–water interface have not yet been described. In order to rationalize the behavior of the two crown-ether dyes, we investigated a novel amphiphilic butadienyl dye, containing a dimethoxybenzene unit instead of benzocrownether part (dye 1). This reference dye is unable to form complexes with particular cations and, therefore, is particularly suited for a comparative monolayer study with dyes 2 and 3, containing benzodithia-15-crown-5 and benzodithia18-crown-6, respectively. The aim of this work is to propose appropriate models for the organisation of these dyes in monolayers at the air–water interface. Such models will be the basis to analyze the behavior of the dye monolayers on aqueous solutions of various salts that will be discussed in a separate publication due to the large amount of experimental data.

aldehyde (5, 51 mg, 0.27 mmol) in anhydrous ethanol (12 mL) was refluxed for 120 h and then cooled to 5 ◦ C. A precipitate formed that was filtered, washed with cold ethanol (2 mL × 3 mL), and dried in air to yield dye 1 as a black powder (55 mg, 37%); mp = 188–191 ◦ C; 1 H NMR (Bruker DRX500 spectrometer, CDCl3 , 30 ◦ C) δ: 0.89 (t, 3H, Me, J 6.7); 1.22–1.39 (m, 28H, 14CH2 ); 1.50 (m, 2H, CH2 CH2 CH2 N); 1.90 (m, 2H, CH2 CH2 N); 3.85 (s, 3H, MeO); 3.98 (s, 3H, MeO); 4.63 (m, 2H, CH2 N); 6.65 (d, 1H, H(5 ), J 8.6); 7.01 (br.d, 1H, H(6 ), J 8.6); 7.25 (d, 1H, H(d), J 15.3); 7.27 (br.s, 1H, H(2 )); 7.54 (m, 2H, H(a), H(c)); 7.64 (m, 2H, H(4), H(6)); 7.70 (m, 1H, H(5)); 7.87 (dd, 1H, H(b), J 14.4, J 11.1); 7.95 (d, 1H, H(7), J 8.0). Elemental analysis calculated for C37 H54 ClNO6 S (676.4): C, 65.71; H, 8.05; N, 2.07%; found: C, 65.61; H, 8.17; N, 2.08%. The syntheses of the amphiphilic benzodithia-15-crown-5 butadienyl dye (dye 2) and of the benzodithia-18-crown-6 butadienyl dye (dye 3) have been described earlier [16,14], respectively.

2. Experimental section 2.1. Materials The new amphiphilic dimethoxyphenyl butadienyl dye (dye 1) was prepared by the condensation reaction of 2-methyl-3-octadecylbenzothiazolium perchlorate (4) with dimethoxycinnamaldehyde (5) in moderate yield.

The syntheses of the initial heterocyclic salt 4 and of the cinnamaldehyde 5 have been described previously [2,17]. Dye 3 was thoroughly characterized by 1 H NMR spectroscopy and elemental analysis. According to the NMR spectra, the dye was obtained in the E,E-configuration (3 JH(a),H(b) = 14.4 Hz and 3 JH(c),H(d) = 15.3 Hz) and the strans-conformation (3 JH(b),H(c) = 11.1 Hz). 2.1.1. Synthesis of 2-[(1E,3E)-4-(3,4-dimethoxyphenyl)1,3-butadienyl]-3-octadecyl-1,3-benzothiazol-3-ium (dye 1) A solution of 2-methyl-3-octadecylbenzothiazolium perchlorate (4, 111 mg, 0.22 mmol) and 3,4-dimethoxycinnam-

The water was purified with a Milli-Q filtration unit of Millipore Corp. (specific resistance 18 M cm, surface tension 72.7 mN/m at 20 ◦ C).

2.2. Methods The surface pressure–molecular area (π–A) and surface potential–molecular area (V–A) isotherms of dye monolayers were recorded on a rectangular trough (dimensions 11 cm × 36 cm × 1 cm) made from poly(tetrafluoroethylene) equipped with a 20 mm wide filter paper Wilhelmy balance and a vibrating plate condenser (with Pt plate, operating at 400 Hz, 1.5 cm diameter). Usually, 35 ␮L of the 1 mM dye solution in chloroform was spread onto water (21 ◦ C), and the monolayers were compressed by moving the barrier with constant speed reducing the surface area by about 16.1 cm2 /min.

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Dye monolayers were characterized by Brewster angle microscopy (BAM) [18,19] using a MiniBAM (NFT G¨ottingen) equipped with a laser diode, emission wavelength 660 nm. Reflection spectra of dye monolayers at constant monolayer area were measured under normal incidence of light with a modified spectrometer of the type described earlier [20,21] and plotted as the difference R of the reflectivities of the monolayer-covered water surface and the bare water surface. To avoid any possible photoreactions of the dyes, all experiments were conducted in a laboratory illuminated only by red light. Reflection spectra were analyzed on a wave number scale by non-linear curve fitting using Origin 6.1. The range from 375 to 700 nm or 400 to 700 nm was used, to avoid contributions from the weak band at about 340–360 nm. This band was excluded from the analysis because of the low signal-tonoise ratio at short wavelengths and the instrument cut off at 300 nm.

3. Results and discussion 3.1. Isotherms and Brewster angle microscopy of the dye monolayers on water In this chapter, we compare the isotherms and monolayer topography of the three butadienyl dyes (dyes 1–3). The π–A and V–A isotherms of the dyes on water are shown in Fig. 1a and b, respectively, curves 1–3. Several important facts may be extracted from these isotherms. (1) The area per molecule increases with the size of the crown-ether moiety. For example, the areas at a surface pressure of π = 35 mN/m, when all monolayers are in a condensed phase but did not yet collapse, are about 0.31, 0.52, and 0.65 nm2 for dyes 1, 2, and 3, respectively. The areas at collapse pressure (Ak ) are increasing in the same order. (2) The smaller crown-ether moiety leads to the formation of a mechanically more stable monolayer, since the collapse pressure is highest for dye 1 (πk = 55 mN/m) and lowest for dye 3 (πk = 41 mN/m). (3) The increase of the size of the crown-ether moiety from dye 2–3, i.e. the increase by one CH2 O CH2 unit leads not only to an increase of the area per molecule but also to qualitative changes of the π–A isotherms. For example, the isotherm of dye 2 exhibits besides a liquidcondensed state (Fig. 1a, curve 2), as in the case of dye 3 (Fig. 1a, curve 3), also a liquid-expanded state in the range of 0.78 nm2 > A > 0.64 nm2 and surface pressures π < 20 mN/m. (4) The V–A isotherms of all dyes show a similar behavior (Fig. 1b). For all three dyes at a large surface area of 1.6 nm2 the values for the surface potential are between 200 and 300 mV, due to the positively charged benzothiazolium group. At π = 35 mN/m, the values of V are

Fig. 1. Surface pressure–area isotherms (a) and surface potential–area isotherms (b) of monolayers of dye 1 (curves 1), dye 2 (curves 2) and dye 3 (curves 3) on water; 21 ◦ C.

between 600 and 700 mV. From the surface potential, the normal component µn of the effective molecular dipole moment (within the medium) may be calculated according to the Helmholtz equation: µn = VAε0 Here, ε0 is the permittivity of the vacuum. Due to different molecular areas at the surface pressure π = 35 mN/m, the normal components µn of the effective dipole moments increase in the series from dye 1 to 3 with 0.09, 0.15, and 0.18 D. The contribution to the total effective dipole moment of a positively charged head group as in the case of eicosylammonium monolayers on water has been estimated to be 0.14 D [22]. The total effective dipole moment in that case has been determined to be 0.48 D. Therefore, contributions of the dipole moments of the terminal methyl group of the hydrocarbon chains as well as of other dipoles in the molecule play an important role. The difference between the dipole moments of dye 1 (without the macrocycle) and 2, and 3 (with macrocycles differing in size) may reflect a contribution of the hetero-atoms of the macrocycles to the total effective dipole moment as well as a slightly different molecular packing of the chromophores. The V–A isotherm of dye 2 increases in two steps (Fig. 1b, curve 2) with a transition region between 0.85 and 0.75 nm2 marking the phase transition between the liquid-

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Fig. 2. BAM images (5.134 mm × 6.869 mm) of monolayers of dye 1 (a, c) and dye 2 (b, d) on distilled water at surface pressure 10 mN/m (a, b) and 20 mN/m (c, d); 21 ◦ C (the concentric elliptical rings are interference fringes caused by dust particles on the optical components).

expanded and -condensed states upon compression. Since the V–A isotherm of dye 1 exhibits a similar behavior (Fig. 1b, curve 3), we conclude, that there is a phase transition, although at rather small surface pressure. This interpretation is also supported by Brewster angle microscopy (BAM) images. The monolayers of 1 and 2 are non-homogeneous at surface pressures up to 20 mN/m as typical for the coexistence of two phases (Fig. 2a and b). Monolayers of dye 1 exhibit homogeneous regions mixed with “star”-shaped domains of varying brightness indicating an in-plane anisotropy (Fig. 2a). Monolayers of dye 2 consist of very small bright domains surrounded by dark liquid-expanded phase (Fig. 2b). Monolayers of dye 3 show a similar behavior [14]. At surface pressures π > 20 mN/m all monolayers become homogeneous within the resolution limits (about 5 ␮m) of the MiniBAM as shown for dye 1 in Fig. 2c and dye 2 in Fig. 2d. 3.2. Reflection spectra of dye monolayers on water The reflection spectra of the three dyes in monolayers at the air–water interface at the surface pressure π = 10 mN/m

are similar to each other (Fig. 3a), with maxima at about 444 nm and values of FWHM of about 100 nm in the case of dye 1 and 70 nm for dyes 2 and 3. All spectra are asymmetrical and differ considerably from those in acetonitrile solution. In solution, where dye monomers are present only, the absorption band maxima are at about 460 nm and FWHM values are about 98 nm, see Fig. 4, dotted (dye 1) dashed (dye 2), and dash-dotted (dye 3) curves. This indicates, that other species besides monomers contribute to the reflection spectra shown in Fig. 3a. For further analysis a measurement of the monomer spectra of the dyes in monolayers would be required. To achieve this, we measured spectra of mixed monolayers of the dyes with dimyristoyl-phosphatidyl-cholin (DMPC) as a matrix, at different molar ratios. Starting with the molar ratio of dye:DMPC = 1/5, the spectra did not change upon further increase of the lipid fraction. The spectra of the mixed monolayers are quite similar for all three dyes (Fig. 4, curves 1–3). Here, the reflectivity has been normalized with respect to the surface density of the dye, i.e. Rn = R·A. Since the maxima of the spectra are at about 465 nm and FWHM is about 97 nm, very similar to the corresponding values obtained for the spectra in solution, we attribute the reflection spectra of

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Fig. 3. Reflection spectra of monolayers at surface pressure 10 mN/m of dye 1 (curves 1), dye 2 (curves 2) and dye 3 (curves 3) on water (a); least-squares fit of three Gaussian functions to the reflection spectrum of dye 1 and their superposition (dashed line) (b); reflection spectra normalized to surface density, Rn = R·A (c).

these mixed monolayers to the dye monomers. Further, the reflection spectra provide information on the average orientation of the transition moments. The normalized reflection at the maximum, Rn,max , is calculated [23] according to: ∆Rn,max /nm2 = 2.303 × 1.66 × 10−7


Ri forient εmax /L mol−1 cm−1

Fig. 4. Reflection spectra of dye 1 (curve 1), dye 2 (curve 2) and dye 3 (curve 3) in mixed monolayers with DMPC at the air–water interface, molar ratio dye:DMPC = 1:5, at surface pressure 1 mN/m; absorption spectra of the dyes in acetonitrile solution (c = 3.3 × 10−5 M, 5 mm cuvette): dye 1 (dotted), dye 2 (dashed), dye 3 (dash-dotted).

With the extinction coefficient εmax = 0.45818 × 105 L mol−1 cm−1 , the reflectivity of the air–water interface at normal incidence Ri = 0.02, and Rn,max = 0.052 × 10−2 nm2 the orientation factor forient = 1.48 is obtained in the case of dye 2. This value is close to the value 1.5 that is characteristic for an orientation of the transition moments in the monolayer plane with statistical distribution around the surface normal. To analyze the monolayer spectra of the pure dyes, nonlinear curve fitting of Gauss functions to the measured spectra on the energy scale (disregarding the small band in the UV) was used, including the monomer with the band position (λmax = 465 nm) and width (FWHM = 97 nm) fixed, however adjustable intensity. The analysis revealed, that two additional species with their relative strengths independent of the surface pressure coexist with the monomer in the dye monolayers at the air–water interface. An example using the reflection spectrum of dye 1 (from Fig. 3a) is shown in Fig. 3b with the three Gaussian functions as well as their superposition (dashed line). The fit parameters for all dyes are listed in Table 1. Since two characteristic parameters of species II (λmax = 465 nm and FWHM = 97 nm) have been chosen according to the spectra of the monomers as in the mixed monolayers, species II represents the monomers. Species I and III will be assigned after model calculations in Section 3.3.

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Table 1 Analysis of the reflection spectra shown in Fig. 3a Dye

1 2 3

Species I

Species II

Species III

λm (nm)

FWHM (nm)

Fraction (%)

λm (nm)

FWHM (nm)

Fraction (%)

λm (nm)

FWHM (nm)

Fraction (%)

425 434 438

66 50 47

33 41 41

465 465 465

97 97 97

54 51 51

535 558 558

88 94 98

13 8 8

Results of non-linear curve fitting of three Gaussian functions for dyes 1-3 including the monomer (species II) with the band position (λmax = 465 nm) and width (FWHM = 97 nm) fixed, however adjustable intensity.

Like in the case of the mixed monolayers, the reflection spectra normalized with respect to dye surface density, i.e. Rn = R·A, may be used to get information on the average orientation of the transition moments. These normalized spectra of the monolayers of dyes 1, 2, and 3 at a surface pressure of 10 mN/m, are shown in Fig. 3c. However, the situation is more complicated here than in the case of the mixed monolayers where no other species were present besides the monomer. Therefore, we have taken the integrals of Rn instead of the value Rn,max assuming that the total intensity is independent of the presence of different associates of the dyes. With these integrals we obtain in case of dye 2 at the surface pressure of 10 mN/m the orientation factor forient = 1.20 which indicates a tilt of the transition moments with respect to the surface normal. The average tilt angle ϑ is calculated [24] according to: forient = (3/2) sin2 ϑ The average tilt angle ϑ = 63.4◦ is obtained with forient = 1.20. With increasing surface pressure, the tilt angle decreases, i.e. the transition moments become increasingly titled, reaching the angle ϑ = 56.4◦ with respect to the surface normal at π = 30 mN/m (spectra not shown here). 3.3. Model calculations To characterize species I (blue-shifted with respect o the monomer) and species III (red-shifted) we used the extended dipole model approximation of H. Kuhn and co-workers [25]. In the extended dipole model, the transition moment of the dye molecule is replaced by the classical extended dipole with length l and charge +q and −q. It is assumed that the transition moment is oriented parallel to the long axis of the dye molecule as in the case of cyanine dyes with two longchain substituents [25]. We assume here, that the transition dipole length of all dye molecules is l = 1.1 nm. First, we calculated the interaction integrals Jij between two dipoles arranged parallel to each other with an inter-

Scheme 1.

molecular distance d, see Scheme 1. The ␲-electron system is represented by the rectangle and the macrocycle by the circle. The transition dipole extends just beyond the oxygen atoms linked to the benzene ring. The X-ray structure of crystals of the non-amphiphilic analog of dye 3 (with methyl instead of octadecyl) clearly shows that the quaternary nitrogen of one molecule interacts with the macrocycle of the neighbour [26]. For realistic values of d the calculated integrals are positive corresponding to a blue-shift of the band with respect to the monomer. Therefore, we attribute the blue-shifted bands (species I) to the formation of dimers, e.g. head-to-tail. The best agreement between the experimental blue shifts, obtained from non-linear curve fitting of the reflection spectra (Table 1) and the calculated shifts was obtained at the intermolecular distances 0.38, 0.45, and 0.49 nm for dyes 1, 2, and 3, respectively (Table 2). The fact that the intermolecular distance d diminishes with diminishing crown-ether size is reasonable, since steric hindrance reducing the interactions between two adjacent molecules should become less for smaller crownether ring and in the absence of the macrocycle. The calculated integrals Jij need to have relatively large negative values to explain the experimental red shifts of about 93 nm with respect to the monomer band. In our case, this is achieved, when the dye molecules are arranged in small aggregates consisting of several molecules (Scheme 2). The molecules in the aggregates are parallel to each other with an intermolecular distance d and the centers adjacent dipoles shifted by distance s. The results of the calculations are listed

Table 2 Dimers of the amphiphilic dyes; structural parameters and comparison of calculated and experimentally observed shifts with respect to the monomer band Dye

Oscillator strength

Transition moment (10−29 Cm)

q (10−20 C)

d (nm)

Jij (10−19 J)

λ (nm) calculated

λ (nm) experim.

1 2 3

1.12 1.13 1.17

4.1 4.1 4.17

3.73 3.90 3.97

0.38 0.45 0.49

+0.194 +0.151 +0.133

−39 −31 −27

−40 −31 −27

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Table 3 Aggregates of the amphiphilic dyes; structural parameters and comparison of calculated and experimentally observed shifts with respect to the monomer band for 7 and ∞ chromophores, respectively, in the aggregate Dye

d (nm)

S (nm)

Number of molecules

Jij (10−19 J)

λ (nm) calculated

λ (nm) experimental

1 2 3

0.38 0.45 0.50

0.95 1.2 1.2

7/∞ 7/∞ 7/∞

−0.2552/−0.4044 −0.2360/−0.3671 −0.2138/−0.3391

50/74 46/68 42/64

70 93 93

(project 2001-0267) and Deutsche Forschungsgemeinschaft, Germany (project 436 RUS 113/686). D.M. wants to thank the Fonds der Chemischen Industrie, Germany, for financial support.

Scheme 2.

in Table 3. With the reasonable parameters (distance s and number of molecules in the aggregate), the calculated shifts of the band of species III with respect to the monomer band differ somewhat from the observed shifts. However, the structural models proposed here for the dimer (species I) and aggregates (species III) of the three amphiphilic dyes in pure monolayers at the air–water interface seem to be appropriate.

4. Conclusions Dyes 1–3 form stable insoluble monolayers at the air–water interface. The area per molecule increases with the size of the macrocycle. Monolayers of dyes 1–3 on water consist of three species: monomer, dimer, and small aggregates. The dimers, characterized by a band shifted to shorter waves with respect to the monomer band, are organised as head-to-tail dimers with the intermolecular distances 0.38, 0.45, and 0.49 nm for dyes 1, 2, and 3, respectively. In small aggregates that give rise to a band shifted to longer waves with respect to the monomer, the transition moments are parallel to each other with the same intermolecular distances as in the dimers, however, the centers of the transition moments are shifted by a distance of 0.95 nm (dye 1), and 1.5 nm (dyes 2 and 3). These small aggregates, according to our estimates, consist of four to seven molecules.

Acknowledgments The authors are grateful to Dr. T. Jovin, Dr. Andreas Schoenle, and W. Zeiß (Max-Planck-Institut f¨ur biophysikalische Chemie, G¨ottingen, Germany) for valuable discussions and technical assistance. Some parts of this work have been supported by grants from the Russian Foundation for Basic Research (Russia, projects 00-03-33238, 00-0332898, 00-03-32159, 01-03-32474, 02-03-04003), INTAS

References [1] H. Kuhn, D. M¨obius, Monolayer assemblies, in: B.W. Rossiter, R.C. Baetzold (Eds.), Investigations of Surfaces and Interfaces, vol. IXB, 2nd ed., Wiley, New York, 1993, p. 375. [2] S.P. Gromov, M.V. Alfimov, Russ. Chem. Bull. 46 (1997) 611 (English Translation). [3] H. Huesmann, J. Maack, D. M¨obius, J.F. Biernat, Sens. Actuators B 29 (1995) 148. [4] L.M. Goldenberg, J.F. Biernat, M.C. Petty, Langmuir 14 (1998) 1236. [5] I. Zawisza, R. Bilewicz, E. Luboch, J.F. Biernat, Supramol. Chem. 12 (2000) 123. [6] I. Zawisza, R. Bilewicz, M.R. Moncelli, R. Guidelli, J. Electroanal. Chem. 509 (2001) 31. [7] H. Huesmann, H. Fujiwara, E. Luboch, J. Biernat, D. M¨obius, J. Inclusion Phenom. Macrocycl. Chem. 49 (2004) 181. [8] S.Y. Zaitsev, V.P. Vereschetin, S.P. Gromov, O.A. Fedorova, M.V. Alfimov, H. Huesmann, D. M¨obius, Supramol. Sci. 4 (1997) 519. [9] S.Y. Zaitsev, S.P. Gromov, O.A. Fedorova, E.A. Baryshnikova, V.P. Vereschetin, W. Zeiß, H. Huesmann, M.V. Alfimov, D. M¨obius, Colloids Surf. A 131 (1998) 325. [10] S.Y. Zaitsev, V.P. Vereschetin, E.A. Baryshnikova, S.P. Gromov, O.A. Fedorova, M.V. Alfimov, H. Huesmann, D. M¨obius, Thin Solid Films 329 (1998) 821. [11] S.Y. Zaitsev, T.I. Sergeeva, E.A. Baryshnikova, W. Zeiss, D. M¨obius, O.V. Yescheoulova, S.P. Gromov, O.A. Fedorova, M.V. Alfimov, Mater. Sci. Eng. C 8–9 (1999) 469. [12] S.Y. Zaitsev, E.A. Baryshnikova, T.I. Sergeeva, S.P. Gromov, O.A. Fedorova, O.V. Yescheoulova, M.A. Alfimov, S. Hacke, W. Zeiss, D. M¨obius, Colloids Surf. A 171 (2000) 283. [13] S.Y. Zaitsev, E.A. Baryshnikova, T.I. Sergeeva, S.P. Gromov, O.A. Fedorova, O.V. Yescheoulova, M.V. Alfimov, S. Hacke, W. Zeiss, D. M¨obius, Thin Solid Films 372 (2000) 230. [14] T.I. Sergeeva, S.Y. Zaitsev, M.S. Tsarkova, S.P. Gromov, A.I. Vedernikov, M.V. Alfimov, T.S. Druzhinina, D. M¨obius, J. Colloid Interf. Sci. 265 (2003) 77. [15] T.I. Sergeeva, S.P. Gromov, A.I. Vedernikov, M.S. Kapichnikova, M.V. Alfimov, V.-T. Lieu, D. M¨obius, M.S. Tsarkova, S.Y. Zaitsev, Colloids Surf. A 255 (2005) 201. [16] S.Y. Zaitsev, T.I. Sergeeva, D. M¨obius, A.I. Vedernikov, M.S. Kapichnikova, S.P. Gromov, M.V. Alfimov, Mendeleev Commun. 2004 (2004) 199. [17] A.I. Vedernikov, S.P. Gromov, Synth. Stuttgart 6 (2001) 889. [18] S. H´enon, J. Meunier, Rev. Sci. Instrum. 62 (1991) 936. [19] D. H¨onig, D. M¨obius, J. Phys. Chem. 95 (1991) 4590. [20] H. Gr¨uniger, D. M¨obius, H. Meyer, J. Chem. Phys. 79 (1983) 3701.

214

T.I. Sergeeva et al. / Colloids and Surfaces A: Physicochem. Eng. Aspects 264 (2005) 207–214

[21] M. Orrit, D. M¨obius, U. Lehmann, H. Meyer, J. Chem. Phys. 85 (1986) 4966. [22] V. Vogel, D. M¨obius, J. Colloid Interf. Sci. 126 (1988) 408. [23] M.T. Mart´ın, I. Prieto, L. Camacho, D. M¨obius, Langmuir 12 (1996) 6554. [24] J.M. Pedrosa, M.T. Mart´ın Romero, L. Camacho, D. M¨obius, J. Phys. Chem. 106 (2002) 2583.

[25] V. Czikkely, H.D. F¨orsterling, H. Kuhn, Chem. Phys. Lett. 6 (1970) 207. [26] S.P. Gromov, A.I. Vedernikov, E.N. Ushakov, L.G. Kuz’mina, A.V. Feofanov, V.G. Avakyan, A.V. Churakov, Y.S. Alaverdyan, E.V. Malysheva, M.A. Alfimov, J.A.K. Howard, B. Eliasson, U.G. Edlund, Helv. Chim. Acta 85 (2002) 60.