Incorporation of Tris (2, 2 '-bipyridine) ruthenium (II) in a Synthetic

Department of Applied Chemistry, Waseda University Ohkubo 3-4-1, Shinjuku-ku,. Tokyo 169-8555, Japan, and Kagami Memorial Laboratory for Materials ...
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Langmuir 2000, 16, 4202-4206

Incorporation of Tris(2,2′-bipyridine)ruthenium(II) in a Synthetic Swelling Mica with Poly(vinylpyrrolidone) Makoto Ogawa*,†,‡ PRESTO, Japan Science and Technology Corporation, and Department of Earth Sciences, Waseda University, Nishiwaseda 1-6-1, Shinjuku-ku, Tokyo 169-8050, Japan

Masashi Tsujimura§ and Kazuyuki Kuroda§,| Department of Applied Chemistry, Waseda University Ohkubo 3-4-1, Shinjuku-ku, Tokyo 169-8555, Japan, and Kagami Memorial Laboratory for Materials Science and Technology, Waseda University, Nishiwaseda 2-8-26, Shinjuku-ku, Tokyo 169-0051, Japan Received November 19, 1999. In Final Form: February 3, 2000 Tris(2,2′-bipyridine)ruthenium(II) ([Ru(bpy)3]2+)-fluortetrasilicic mica-poly(vinylpyrrolidone) intercalation compounds were prepared by the intercalation of poly(vinylpyrrolidone) into the presynthesized [Ru(bpy)3]2+-fluortetrasilicic mica intercalation compounds. The formation of the intercalation compounds was confirmed by the expansion of the interlayer space as well as the spectroscopic observations. Intercalation compounds with variable chemical compositions have been prepared, and the effect of the distribution of the intercalated [Ru(bpy)3]2+ on the luminescence has been discussed. The luminescence probe can be utilized for the study of clay-polymer interactions.

Introduction Intercalation of organic guest species into layered inorganic solids is a way of constructing ordered inorganicorganic assemblies with unique microstructures controlled by host-guest and guest-guest interactions.1 Intercalation of photoactive species into layered solids has been investigated to understand the nature of host-guest systems as well as to prepare novel photofunctional supramolecular systems, since the characteristics of the photoprocesses are sensitive to the environment where photoactive species are adsorbed.2 Tris(2,2′-bipyridine)ruthenium(II) (abbreviated as [Ru(bpy)3]2+) is one of the photoactive species studied most extensively because of its unique combination of chemical stability, capability of photosensitizing redox reactions, and photophysical properties.3 To construct functional supramolecular systems, which mimic natural photosynthetic systems, photoprocesses of [Ru(bpy)3]2+ in heterogeneous media have been investigated extensively.3,4 Along this line, photoprocesses of [Ru(bpy)3]2+ intercalated in layered solids, especially in smectites, have been reported.2,5-16 As reported for [Ru(bpy)3]2+-smectite sys* To whom correspondence should be addressed. † PRESTO, Japan Science and Technology Corporation. ‡ Department of Earth Sciences, Waseda University. § Department of Applied Chemistry, Waseda University. | Kagami Memorial Laboratory for Materials Science and Technology, Waseda University. (1) Alberti, G., Bein, T., Eds. Comprehensive supramolecular chemistry; Pergamon: Oxford, 1996; Vol. 7. Ogawa, M.; Kuroda, K. Bull. Chem. Soc. Jpn. 1997,70, 2593. (2) Ogawa, M.; Kuroda, K. Chem. Rev. 1995, 95, 399. (3) Kalyanasundaram, K. Photochemistry of Polypyridine and Porphyrin Complexes; Academic Press: London, 1992. (4) Thomas, J. K. J. Phys. Chem. 1987, 91, 267. (5) Thomas, J. K. Acc. Chem. Res. 1988, 21, 275. (6) Ghosh, P. K.; Bard, A. J. J. Phys. Chem. 1984, 88, 5519. (7) Vliers, D. P.; Schoonheydt, R. A.; de Schrijver, F. C. J. Chem. Soc., Faraday Trans. 1 1985, 81, 2009. (8) Vliers, D. P.; Collin, D.; Schoonheydt, R. A.; de Schryver, F. C. Langmuir 1986, 2, 165. (9) DellaGuardla, R. A.; Thomas, J. K. J. Phys. Chem. 1983, 87, 990.

tems, the adsorbed [Ru(bpy)3]2+ ions tend to aggregate in the interlayer space (segregation) to cause effective excited-state deactivation.6 Accordingly, the organization of [Ru(bpy)3]2+ in a controlled manner on the surface of layered solids is currently being investigated to obtain photofunctional intercalation compounds.10,14,15,17 We have already reported the photoprocesses of the [Ru(bpy)3]2+ adsorbed on swelling mica-poly(vinylpyrrolidone) (abbreviated as PVP) intercalation compounds.17 The cointercalated PVP was forced to surround [Ru(bpy)3]2+ in close contact in the sterically limited interlayer spaces to cause luminescence shift and the suppression of self-quenching. However, since the intercalation compounds were prepared by the intercalation of [Ru(bpy)3]2+ to the presynthesized mica-PVP intercalation compound, some portion of the intercalated PVP deintercalates upon the intercalation of [Ru(bpy)3]2+. In this study, [Ru(bpy)3]2+-swelling mica-PVP intercalation compounds were prepared by the intercalation of PVP into the presynthesized [Ru(bpy)3]2+-mica intercalation compounds in order to avoid the deintercalation of PVP. Clay-polymer interactions have long been recognized.18 After the commercialization of clay-nylon hybrids, claypolymer hybrids have attracted new interest as possible candidates to replace conventional polymer materials.19 (10) Awaluddin, A.; DeGuzman, R. N.; Kumar, C. V.; Suib, S. L.; Burkett, S. L.; Davis, M. E. J. Phys. Chem. 1995, 99, 9886. (11) Schoonheydt, R. A.; de Pauw, P.; Vliers, D.; de Schryver, F. C. J. Phys. Chem. 1984, 88, 5113. (12) Colo´n, J. L.; Yang, C.-Y.; Clearfield, A.; Martin, C. R. J. Phys. Chem. 1988, 92, 5777. (13) Colo´n, J. L.; Yang, C.-Y.; Clearfield, A.; Martin, C. R. J. Phys. Chem. 1990, 94, 874. (14) Kumar, C. V.; Williams, Z. J. 1995 J. Phys. Chem. 99, 17632. (15) Jakubiak, R.; Francis, A. H. 1996 J. Phys. Chem. 100, 362. (16) Nakato, T.; Kusunoki, K.; Yoshizawa, K.; Kuroda, K.; Kaneko, M. J. Phys. Chem. 1995, 99, 17896. (17) Ogawa, M.; Inagaki, M.; Kodama, N.; Kuroda, K.; Kato, C. J. Phys. Chem. 1993, 97, 3819. (18) Theng, B. K. G. Formation and Properties of Clay-Polymer Complexes; Elsevier: Amsterdam, 1979. (19) See for example: Kawasumi, M.; Hasegawa, N.; Kato, M.; Usuki, A.; Okada, A. Macromolecules 1997, 30, 6333.

10.1021/la9915163 CCC: $19.00 © 2000 American Chemical Society Published on Web 03/21/2000

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In the present study, we investigated the possibility of clay-polymer hybrids as immobilizing media for photoactive species. Experimental Section Materials. Sodium fluortetrasilicic mica (abbreviated as NaTSM, the ideal composition is NaMg2.5Si4O10F2, Topy Ind. Co., the cation exchange capacity is 97 mequiv/100 g of host), which is a synthetic 2:1 type layered silicate20 and exhibits ion exchange and adsorptive properties similar to those of smectites,21,22 was used as the host material. Na-TSM was used after removing nonexpandable impurities by a dispersion-sedimentation method. [Ru(bpy)3]2+ chloride hexahydrate (Aldrich) and PVP (Mw ) 10 000, Tokyo Kasei Ind. Co.) were used as received. Sample Preparation. [Ru(bpy)3]2+-TSM intercalation compounds were prepared by cation exchange of Na-TSM with an ethanol solution of [Ru(bpy)3]2+ at room temperature for 1 day. The loading amount of [Ru(bpy)3]2+ varied from 0.1 to 2 mmol/ 100 g of TSM. The [Ru(bpy)3]2+-TSM intercalation compound was added to an aqueous solution of PVP and allowed to react at room temperature for 1 day. The product was separated by centrifugation and washed with ethanol. The amount of the added PVP was 1:1.5 (weight ratio of [Ru(bpy)3]2+-TSM intercalation compound:PVP). Characterization. X-ray powder diffraction patterns were obtained on a Mac Science M03XHF22 diffractometer using Mnfiltered Fe KR radiation. Visible absorption spectra were recorded on a Shimadzu UV-3101PC spectrophotometer. Steady-state luminescence spectra were recorded on a Hitachi F-4500 fluorospectrophotometer with the excitation wavelength of 475 nm. Luminescence lifetimes were measured by a single-photoncounting technique on a HORIBA NAES-700 time-correlated spectrophotometer equipped with a hydrogen lamp. To determine the composition of the products, thermogravimetry (TG) and CHN analysis were conducted. TG was performed on a Mac Science TG-DTA 2000S instrument at a heating rate of 10 °C min-1 with R-alumina as the standard. CHN analyses were performed on a Perkin-Elmer 2400 II instrument.

Results By the reactions between Na-TSM and [Ru(bpy)3]2+, orange solids were obtained. The quantitative adsorption of the added [Ru(bpy)3]2+ was confirmed by the visible absorption spectra of the supernatants where the MLCT absorption band (at around 452 nm) of [Ru(bpy)3]2+ was not detected. The X-ray diffraction pattern of the sample at a loading amount of 1 mmol of [Ru(bpy)3]2+/100 g of TSM is shown in Figure 1b together with that of the original Na-TSM (Figure 1a). The basal spacing did not change by the reaction with [Ru(bpy)3]2+. Similar X-ray diffraction (XRD) results were obtained when the loading amounts varied (0.1, 0.2, 0.5, 1.0, and 2.0 mmol/100 g of TSM). Hereafter, the amount of the adsorbed [Ru(bpy)3]2+ is shown in parentheses as [Ru(bpy)3]2+(1 mmol)-TSM intercalation compound where 1 mmol indicates that the loaded amount of [Ru(bpy)3]2+ is 1 mmol/100 g TSM. Desorption of the preadsorbed [Ru(bpy)3]2+ was not observed by the reaction with PVP as evidenced by the absence of [Ru(bpy)3]2+ in the supernatant. The change in the XRD pattern of the [Ru(bpy)3]2+(1 mmol)-TSM intercalation compound after the reaction with PVP is shown in Figure 1. The basal spacing increased to 2.32 nm, indicating expansion of the interlayer space by ca. 1.3 nm. (The thickness of silicate layer of TSM is ca. 1.0 (20) Kitajima, K.; Daimon, N. Nippon Kagaku Kaishi 1974, 685; Nippon Kagaku Kaishi 1975, 991; Nippon Kagaku Kaishi 1976, 597; Soma, M.; Tanaka, A.; Seyama, H.; Hayashi, S.; Hayamizu, K. Clay Sci. 1990, 8, 1. (21) Theng, B. K. G. The Chemistry of Clay-Organic Reactions; Adam Hilger: London, 1974. (22) Van Olphen, H. An Introduction to Clay Colloid Chemistry, 2nd ed.; Wiley-Interscience: New York, 1977.

Figure 1. The X-ray powder diffraction patterns of (a) NaTSM and the [Ru(bpy)3]2+-TSM intercalation compound at the loading of 1 mmol/100 g of TSM, before (b) and after (c) the intercalation of PVP. Table 1. Amounts of Adsorbed Species, Basal Spacing, Luminescnece Maxima, and Average Distance of Intercalated Ru(bpy)32+ in the Interlayer Space of TSM for the Ru(bpy)32+-TSM-PVP Intercalation Compounds and the Ru(bpy)32+-TSM Intercalation Compounds amt of adsorbed basal lumin amt of Ru(bpy)32+, spacing, max, adsorbed PVP, av dist, mmol/100 g of TSM nm nm g/100 g of TSM nm 0.1 0.2 0.5 1 2

Ru(bpy)32+-TSM-PVP 2.29 589 2.29 589 2.29 590 2.32 588 2.42 593

0.1 0.2 0.5 1 2

Ru(bpy)32+-TSM 1.24 598 1.24 594 1.24 600 1.24 601 1.24 604

46 46 45 48 48

14 11 8.0 6.4 5.1

nm.) The basal spacing did not increase further even when larger amounts of PVP were added. Similar changes of the basal spacings by the reactions with PVP were observed for the [Ru(bpy)3]2+-TSM intercalation compounds with different [Ru(bpy)3]2+ amounts and the basal spacings are summarized in Table 1. The amounts of the adsorbed PVP, which are determined by subtracting the C content due to [Ru(bpy)3]2+ from the total C content obtained by the CHN analysis, are shown in Table 1. The observed luminescence maxima of the [Ru(bpy)3]2+ MLCT bands for the [Ru(bpy)3]2+-TSM intercalation compounds before and after the intercalation of PVP are summarized in Table 1. The loading amount of [Ru(bpy)3]2+ did not affect the wavelength of the luminescence maxima. After the intercalation of PVP, the luminescence maxima shifted toward shorter wavelength regions (around 589 nm). Luminescence lifetimes of the intercalated [Ru(bpy)3]2+ were measured at room temperature, and the lifetimes are summarized in Table 2. All the luminescence decay curves of the intercalation compounds were fitted by a double-exponential model, which is expressed as

I(t) ) A1 exp(-k1t) + A2 exp(-k2t) where I(t) is luminescence intensity at time t, A1 and A2 are preexponential factors, and k1 and k2 are decay rate constants. The decay was fitted to a major long-lived

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Table 2. Luminescence Lifetimes and Relative Ratios of Fast (τ1) and Slow (τ2) Components Observed for the Ru(bpy)32+-TSM-PVP Intercalation Compounds and the Ru(bpy)32+-TSM Intercalation Compounds amt of adsorbed Ru(bpy)32+, mmol/100 g of TSM

τ1, ns

Q1, %

τ2, ns

Q2, %

12 9 13 13 11

1540 996 1040 1030 890

88 91 87 87 89

12 13 8 15 19

1090 901 744 789 675

88 87 92 85 81

2+-TSM-PVP

Ru(bpy)3 0.1 0.2 0.5 1 2 0.1 0.2 0.5 1 2

234 166 198 206 175 Ru(bpy)32+-TSM 171 187 103 176 156

Figure 2. Relationship between the basal spacings and the luminescence maxima of the MLCT band of the adsorbed [Ru(bpy)3]2+.

component (ca. 1000 ns, 90%) and a minor short-lived component (100-200 ns, 10%). Another observation to be noted is a luminescence shift during the hydration/dehydration. When the [Ru(bpy)3]2+(1 mmol)-TSM-PVP intercalation compound was stored in an atmosphere with relatively high humidity, the basal spacings increased to 2.58 nm from 2.32 nm. The increase in the basal spacing upon hydration shows the intercalation of water molecules into the interlayer space of TSM to alter the interlayer microenvironment from [Ru(bpy)3]2+-PVP to [Ru(bpy)3]2+-PVP-water. Since PVP is a hydrophilic polymer, water molecules can easily be intercalated into the interlayer space of the Ru(bpy)3]2+TSM-PVP intercalation compound. The MLCT luminescence band shifted toward longer wavelength regions upon the hydration from 588 to 598 nm. The amounts of the adsorbed water molecules were determined by thermogravimetry (TG) to be 2-10 mass % for the dehydrated and the hydrated samples, respectively. The relationship between the basal spacings and the luminescence maxima of the MLCT band of the adsorbed [Ru(bpy)3]2+ is shown in Figure 2. Discussion The added [Ru(bpy)3]2+ was quantitatively adsorbed into TSM as confirmed by the absence of [Ru(bpy)3]2+ in the supernatant. Since the basal spacing did not change by the reaction with [Ru(bpy)3]2+, the exact location of the adsorbed [Ru(bpy)3]2+ is difficult to determine from the X-ray diffraction pattern shown in Figure 1a. Either a

small amount of the adsorbed [Ru(bpy)3]2+ locates at the external surface of silicate layer or the intercalated phase cannot be detected by the X-ray diffraction pattern due to the low contribution. By reaction with PVP, the basal spacings of the [Ru(bpy)3]2+-TSM intercalation compounds increased to ca. 2.3 nm, indicating the intercalation of PVP into the interlayer space of TSM. Since the minimum expansion of the interlayer space to accommodate [Ru(bpy)3]2+ was ca. 0.8 nm,23-25 the observed gallery heights (1.3 nm) of the products, which are determined by subtracting the thickness of silicate layer (1.0 nm) from the observed basal spacings, are large enough to accommodate [Ru(bpy)3]2+. The amounts of the adsorbed PVP after the washing (Table 1) were similar irrespective of the loading amounts of [Ru(bpy)3]2+. Thus, the [Ru(bpy)3]2+-TSM-PVP intercalation compounds with variable compositions have successfully been prepared by simply varying the synthetic conditions. The luminescence due to MLCT transition of the [Ru(bpy)3]2+ was observed in the emission spectra of the products. By the intercalation of PVP, the luminescence maxima shifted toward a shorter wavelength region. Similar luminescence blue shifts have been observed for the [Ru(bpy)3]2+-TSM-PVP intercalation compounds with different [Ru(bpy)3]2+ loadings (Table 1). Blue shifts of MLCT luminescence of the [Ru(bpy)3]2+ have been observed in various heterogeneous systems. Wheeler and Thomas observed a luminescence blue shift upon the adsorption of [Ru(bpy)3]2+ on colloidal silica.26 Blue shifts of the [Ru(bpy)3]2+ luminescence maxima have also been observed in silica and aluminosilica gels through sol-togel conversion and gel aging and drying.27 It was hypothesized that an increased possibility for relaxation in a more fluid state caused the spectral shifts. In the present [Ru(bpy)3]2+-TSM-PVP intercalation compounds, the cointercalated PVP are thought to surround [Ru(bpy)3]2+ rigidly to cause the spectral blue shifts. Colo´n and co-workers found a concentration dependence of the luminescence maxima for [Ru(bpy)3]2+ intercalated in zirconium phosphate sulfophenylphosphonate with different loadings and attributed the spectral shifts to a hydrocarbon-like environment both by neighboring bpy and by the hydrophobic nature of phenyl rings.13 In our previous paper on the intercalation of [Ru(bpy)3]2+ into the TSM-PVP intercalation compound,17 the luminescence maxima of the intercalated [Ru(bpy)3]2+ shifted gradually toward blue with the decrease in the loading of [Ru(bpy)3]2+, reflecting the variation in the microenvironments of the intercalated [Ru(bpy)3]2+. On the contrary, the luminescence maxima observed in the present study are almost constant (589 nm) irrespective of the [Ru(bpy)3]2+ loadings. Due to the lower concentration of [Ru(bpy)3]2+ in the present system, the intermolecular interactions are thought to be negligible if compared with those in the previous study. To understand the difference, the variation of the luminescence maxima was plotted against the average distance of the adsorbed [Ru(bpy)3]2+ in the interlayer space (Figure 3, the data obtained in the previous study17 are also included). The average distance of the adsorbed (23) Traynor, M. F.; Mortland, M. M.; Pinnavaia, T. J. Clays Clay Miner. 1978, 26, 318. (24) Berkheiser, V. E.; Mortland, M. M. Clays Clay Miner. 1977, 25, 105. (25) Ogawa, M.; Hashizume, T.; Kuroda, K.; Kato, C. Inorg. Chem. 1991, 30, 584. (26) Wheeler, J.; Thomas, J. K. J. Phys. Chem. 1982, 86, 4540. (27) Innocenzi, P.; Kozuka, H.; Yoko, T., J. Phys. Chem. B 1997, 101, 2285. Matsui, K.; Sasaki, K.; Takahashi, N. Langmuir 1991, 7, 2866.

Intercalation of Photoactive Species

Figure 3. Luminescence maxima as a function of the average distance of the intercalated [Ru(bpy)3]2+ in the interlayer space of TSM. Scheme 1 . Schematic Drawing for the [Ru(bpy)3]2+-TSM-PVP Intercalation Compounds

[Ru(bpy)3]2+ in the interlayer space (Scheme 1) has been determined by the gallery height, the ideal surface area (supposed to be 700 m2/g of clay,22 which is calculated based on the surface area of each cell), and the composition (Table 1). The wavelength of the luminescence maxima shifted toward shorter wavelength regions with decreasing the [Ru(bpy)3]2+ concentration when the [Ru(bpy)3]2+[Ru(bpy)3]2+ distance is shorter than 6 nm. On the contrary, the luminescence maxima did not change further when the average [Ru(bpy)3]2+-[Ru(bpy)3]2+ distance is longer than 6 nm. These observations indicate that the intermolecular interactions between adjacent [Ru(bpy)3]2+ are a possible factor for the observed luminescence shifts in addition to the host-guest interactions. The concentration quenching radius was reported to be 1.3 nm for [Ru(bpy)3]2+ synthesized within zeolite Y cages.28 The adsorbed sites of [Ru(bpy)3]2+ have been determined by the crystalline structures of host zeolites. In amorphous materials, the distribution can be controlled by changing the concentration of dispersed [Ru(bpy)3]2+. Nagai et al. reported the distance-dependent concentration quenching of [Ru(bpy)3]2+ dispersed in a polysiloxane film.29 Considering the excluded volume of the [Ru(bpy)3]2+, the quenching radius was determined to be 1.1 nm. The observed luminescence shifts as a function of the concentration of [Ru(bpy)3]2+ in the present [Ru(bpy)3]2+TSM-PVP system are thought to reflect the interprobe interactions in a larger separation. Although a more detailed explanation for the observed luminescence shifts is difficult at present, the luminescence shifts reflect the unique nature of the two-dimensional nanospace for guest organization. (28) Turbeville, W.; Robins, D. S.; Dutta, P. K. J. Phys. Chem. 1992, 96, 5024. (29) Nagai, K.; Takamiya, N.; Kaneko, M. J. Photochem. Photobiol. A: Chem. 1994, 84, 271.

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The above-mentioned idea was supported by the luminescence lifetimes (Table 2). Lifetimes observed for the long-lived component (ca. 1000 ns) were comparable to those observed for the [Ru(bpy)3]2+ adsorbed on hectorite30 and zirconium phosphate sulfophenylphosphonate.13 As to the longer-lived components, there is a general tendency toward longer lifetimes with decreasing the loading amount of [Ru(bpy)3]2+, suggesting the decreased possibility of self-quenching at lower [Ru(bpy)3]2+ loading. A similar tendency with [Ru(bpy)3]2+ loading has been observed for the [Ru(bpy)3]2+-zirconium phosphate system.14 The lifetimes observed for the [Ru(bpy)3]2+-TSMPVP system were longer than those for the [Ru(bpy)3]2+TSM system, confirming that the coadsorbed PVP suppress the self-quenching of [Ru(bpy)3]2+. Another characteristic feature of the present [Ru(bpy)3]2+-TSM-PVP system is the luminescence shift during hydration (luminescence maximum at 598 nm) and dehydration (luminescence maximum at 588 nm). Luminescence shifts have been observed upon hydration/ dehydration when [Ru(bpy)3]2+ was adsorbed on a zeolite Y31 and an ion-exchange resin.32 Incavo and Dutta explained the blue shifts of [Ru(bpy)3]2+ luminescence upon dehydration as the lack of solvation of the excited state led to destabilization and increase in energy.31 In the present system, the basal spacing decreased upon the dehydration (from 2.6 to 2.3 nm). After the removal of the adsorbed water molecules, the remaining PVP were thought to surround the intercalated [Ru(bpy)3]2+ more rigidly to cause the spectral shifts. Thus, the luminescence characteristics of [Ru(bpy)3]2+ were successfully controlled by organizing [Ru(bpy)3]2+ in the interlayer space of a layered silicate together with PVP. In other words, the luminescence probe is applicable to the study of the clay-polymer interactions. The preparation of various silicate-polymer hybrids has been reported;18,19 however, the mechanisms of the complexation and the microstructures at clay-polymer interfaces are still controversial. The application of a luminescence probe for the clay-polymer systems is worth investigating as a way to elucidate the clay-polymer interactions. Although the luminescence shifts observed for the present systems are not so large if compared with those reported for the previous host-guest systems,14,16,30 systematic study using various polymers may lead to different spectroscopic results. Cationic luminescence probes are useful for this purpose since desorption of the probe during the intercalation of polymer is not plausible. Judging from the present results on the concentration dependence of the [Ru(bpy)3]2+ luminescence, the concentration of the luminescence probe should be very low to minimize probeprobe interactions in order to apply the luminescence probe for clay-polymer systems. The stability of the probe is another factor to be considered. Since the adsorbed [Ru(bpy)3]2+ is stable in the temperature range up to 200 °C, [Ru(bpy)3]2+ is a promising probe for the study on the clay-polymer interactions. Further studies are being made in order to control the distribution of the guest species (luminescent species) in a controlled manner in clay-polymer intercalation compounds as well as to apply luminescence probes for other clay-polymer hybrid systems. (30) Kuykendall, V. G.; Thomas, J. K. J. Phys. Chem. 1990, 94, 4224. (31) Incavo, J. A.; Dutta, P. K. J. Phys. Chem. 1990, 94, 3075. (32) Masschelen, A.; Mesmaeker, K. A.; Willsher, C. J.; Wilkinson, F. J. Chem. Soc., Faraday Trans. 1991, 87, 259.

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Conclusions [Ru(bpy)3]2+-TSM-PVP intercalation compounds were prepared by the intercalation of PVP into the presynthesized [Ru(bpy)3]2+-TSM intercalation compounds. The luminescence characteristics of the products as well as chemical analysis and X-ray diffraction studies provide important information on the distribution of the intercalated [Ru(bpy)3]2+. When the loading amount of [Ru-

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(bpy)3]2+ was lower than 1 mmol/100 g of clay, the intermolecular interactions are negligible. Acknowledgment. The present work was partially supported by Waseda University as a Special Project Research. LA9915163