1. INTRODUCTION

Construction of ordered and functional metal oxide filmswith nanometer-sized grains and thickness has attractedinterest in the field of materials research, because thesefilms may find desirable applications in heterogeneouscatalysis, electronic and photonic device fabrication, andsensor development.1–3 Films containing copper oxide havebeen noted for their unique properties, such as high temper-ature superconductivity,4–8 magnetic properties,9 improvedradiation cooling,10 and unique optical and electrical char-acteristics.11, 12 Numerous methods have been developedfor the preparation of thin copper oxide films, including,but not limited to, molecular beam epitaxy,13, 14 spin coat-ing,15 metal-organic chemical vapor deposition,16–18 andsol-gel chemistry.12 However, production of thin metal

Polyelectrolyte-Mediated Assembly of CopperPhthalocyanine Tetrasulfonate Multilayers and the Subsequent Production of Nanoparticulate

Copper Oxide Thin Films

Zarui Sara Chickneyan, Alejandro L. Briseno, Xiangyang Shi, Shubo Han, Jiaxing Huang,† and Feimeng Zhou*

Department of Chemistry and Biochemistry, California State University–Los Angeles,Los Angeles, California 90032, USA

An approach to producing films of nanometer-sized copper oxide particulates, based on polyelectro-lyte-mediated assembly of the precursor, copper(II)phthalocyanine tetrasulfonate (CPTS), is described.Multilayered CPTS and polydiallyldimethylammonium chloride (PDADMAC) were alternately assem-bled on different planar substrates via the layer-by-layer (LbL) procedure. The growth of CPTS mul-tilayers was monitored by UV-visible spectrometry and quartz crystal microbalance (QCM) measure-ments. Both the UV-visible spectra and the QCM data showed that a fixed amount of CPTS couldbe attached to the substrate surface for a given adsorption cycle. Cyclic voltammograms at theCPTS/PDADMAC-covered gold electrode exhibited a decrease in peak currents with the layer num-ber, indicating that the permeability of CPTS multilayers on the electrodes had diminished. Whenthese CPTS multilayered films were calcined at elevated temperatures, uniform thin films composedof nanoparticulate copper oxide could be produced. Ellipsometry showed that the thickness of cop-per oxide nanoparticulate films could be precisely tailored by varying the thickness of CPTS multi-layer films. The morphology and roughness of CPTS multilayer and copper oxide thin films werecharacterized by atomic force microscopy. X-ray diffraction (XRD) measurements indicated that thesethin films contained both CuO and Cu2O nanoparticles. The preparation of such copper oxide thinfilms with the use of metal complex precursors represents a new route for the synthesis of inorganicoxide films with a controlled thickness.

Keywords: Layer-by-Layer, Nanoparticulate Thin Films, Polyelectrolyte.

JOURNAL OF NANOSCIENCE AND NANOTECHNOLOGY

oxide films with a controllable thickness has been chal-lenging. Recently, sequential deposition and reaction at asubstrate surface has been purported as a remedy. The Fer-guson,19 Kunitake,20–23 and Mallouk24, 25 groups reporteda sol-gel-based technique, which permits tuning of titaniafilm thickness down to the nanometer range. Keszlerandand co-workers developed a method involving adsorptionof the ionic layer for a subsequent reaction to prepare crys-talline metal oxide thin films with a variable thickness.3, 26

An alternative and versatile strategy for fabricating func-tional films with nanometer thickness is the layer-by-layer(LbL) self-assembly technique. The LbL method, originallydeveloped to form films of oppositely charged polyelectro-lytes27 at a planar substrate or on a colloidal particle,28, 29

has been extended to prepare metal,30, 31 semiconductor,32–35

and metal oxide36–44 nanoparticulate thin films. The advan-tage of the LbL approach is that control of the film thick-ness can be realized by varying the layer deposition cycles,and the film composition can be varied by the selection

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*Author to whom correspondence should be addressed.†Department of Chemistry and Biochemistry, University of California–

Los Angeles, Los Angeles, CA 90095.

of different charged precursors and calcination condi-tions. Moreover, the method is straightforward and doesnot require a sophisticated apparatus. Thus it is highlycomplementary to bulk syntheses of metal or metal oxidenanoparticles for cases that are challenging and cost-ineffective. For instance, Caruso and co-workers45, 46 andFerguson and co-workers47 fabricated thin titania filmswith a finite and controllable thickness by employing tita-nium(IV)bis(ammonium lactato)dihydroxide as the pre-cursor. However, the preparation of nanometer-sized metaloxide films or other nanostructures with water-soluble andcharged metal complexes as precursors has not been widelyreported.

In the present study, a copper phthalocyanine tetrasul-fonate (CPTS) (molecular structure shown in Scheme I)was used as a precursor and sequentially adsorbed withpolydiallyldimethylammonium chloride (PDADMAC) toa solid substrate to prepare thin copper oxide nanoparticu-late films. These two oppositely charged constituents couldbe LbL assembled. The multilayer buildup was confirmedby UV-visible spectrophotometer, quartz crystal micro-balance (QCM), and electrochemical measurements. Aftercalcination at an elevated temperature, nanoparticulate cop-per oxide thin films were formed. The thickness and mor-phology of these films were characterized by ellipsometryand atomic force microscopy (AFM), and the compositionof the copper oxide nanoparticles formed in the films wasdetermined by X-ray diffraction (XRD). Because the LbLapproach allows nanometer-scale control of film thick-ness by variation of the adsorption cycles of CPTS andPDADMAC, fine-tuning of the copper oxide film thick-ness becomes feasible. This approach may be extended toprepare a variety of metal oxide thin films.

2. EXPERIMENTAL DETAILS

2.1. Materials

CPTS and PDADMAC (MW � 200,000) were obtainedfrom Aldrich. NaCl was purchased from Fisher. Hexa-amineruthenium(III)chloride (Aldrich) was used as received.Water used in all experiments was prepared in a three-stage Millipore Milli-Q Plus 185 purification system.

2.2. Preparation of CPTS Multilayer Films

2.2.1. Quartz Substrates

Thin, alternating PDADMAC/CPTS films were LbL-assembled on quartz substrates (Hellma, Germany), cleanedby soaking in a 5:1:1 (vol%) H2O/H2O2/NH3 mixture at70 °C for 10 min (RCA protocol),48, 49 and rinsed with acopious amount of water. The first layer of PDADMAC wasadsorbed to the negatively charged quartz surface by immer-sion of the quartz substrate in a 1 mg/ml PDADMAC solu-tion (containing 0.5 M NaCl) for 15 min. The PDADMAC-covered substrates were rinsed with water three times,followed by drying under a gentle stream of N2. CPTS wasthen attached to the PDADMAC layer by immersion of thePDADMAC-modified quartz substrate in a CPTS solutionof different concentrations. These processes were repeatedto produce the multilayered films. The LbL growth of CPTSmultilayers was monitored by a UV-visible spectrophoto-meter (SLM-AMINCO, model 3000).

2.2.2. Silicon Wafers and Gold Surfaces

Silicon wafers (111) were treated by the RCA protocoldescribed above. Thin films containing PDADMAC/CPTSmultilayers were assembled on the silicon wafers. Gold-coated glass slides were also used for the multilayer depo-sition. The gold substrates were prepared by sputtering30 nm of gold with a 0.5-nm-thick chromium underlayeronto thin glass slides (Fisher Scientific), with a Kurt J.Lesker coater (model 108; Clairton, PA). The gold surfacewas treated with a piranha solution (30% H2O2 and 70% con-centrated H2SO4) and rinsed thoroughly with water beforePDADMAC and CPTS adsorption. CAUTION: Piranhasolution reacts violently with organic solvents and is a skinirritant. Extreme caution should be exercised when handlingpiranha solution.

2.2.3. QCM Electrodes

AT-cut 9.995-MHz crystals (ICM Technologies, OklahomaCity, OK) with both sides coated with gold films wereemployed for PDADMAC/CPTS multilayer formation. Thecrystal surface could again be cleaned with a piranha solu-tion. Frequency measurements were carried out with anICM oscillator and a PM6680B counter/timer (Fluke Corp.,Everett, WA).

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Scheme I. Molecular structures of copper(II)phthalocyanine tetrasul-fonate (CPTS) and polydiallyldimethylamonium chloride (PDADMAC).

The total mass deposited at the QCM crystal surface canbe calculated from the cumulative frequency change withthe Sauerbrey equation.50 For a 9.995-MHz QCM crystalwith an electrode area of 0.196 cm2, the relationshipbetween the adsorbed mass (�m) of each PDADMAC andCPTS layer and the change in the resonant frequency (�F)is given by

�m(ng) � �0.86 � �F(Hz) (1)

2.3. Formation of Copper Oxide Films

PDADMAC/CPTS multilayer films coated onto siliconwafers were calcined at 500 °C under N2 for 4 h and O2 for8 h. We selected 500 °C to calcine the CPTS multilayerfilms to produce the copper oxide nanoparticulate films(mixtures of Cu2O and CuO, vide infra). To completelyform CuO, a higher temperature (e.g., 900 °C) must beused.51 The outermost layer of these films was kept asPDADMAC to avoid the adsorption of sodium ions fromthe solution (which could lead to sodium oxide formationduring the calcination step). The resultant films were sub-sequently characterized by contact angle, AFM, ellipsome-try, and XRD measurements.

2.4. Electrochemical Measurements

A CHI 440 electrochemical workstation (CH Instruments;Austin, TX) was used for the voltammetric experiments.Gold films covered with PDADMAC/CPTS films servedas the working electrode, and a Pt flag and a Ag/AgCl elec-trode were employed as the auxiliary and reference elec-trodes, respectively. A phosphate buffer (pH 7.8) solutionwith 1 mM Ru(NH3)6

3� was purged with nitrogen for3 min before the voltammetric measurement.

2.5. Contact Angle

Contact angles at multilayered PDADMAC/CPTS filmsbefore and after calcination were measured with a contactangle meter (KSV Instruments, Monroe, CT). Measure-ments were performed on several portions of each siliconwafer. Values reported here are the averages of at leastnine measurements.

2.6. Atomic Force Microscopy

AFM measurements were conducted with an AFM equippedwith a magnetic alternating current (MAC) mode (MolecularImaging, Phoenix, AZ). Both contact and MAC modeswere used for the characterization of PDADMAC/CPTSfilms before and after calcinations. Images of multilayerfilms of PDADMAC/CPTS on silicon wafers were obtainedwith an oscillating frequency of 25 kHz and a driver cur-rent of 30 � 5 A.

2.7. Ellipsometry

Ellipsometric measurements were carried out on a picome-ter (Beaglehole Instruments, Wellington, New Zealand).The measuring wavelength was selected to be 550 nm by fil-tration of the light from a halogen lamp. The angle of inci-dence was set at 75°, which is near the Brewster angle of thesilicon substrate. The thickness is statistically averaged overan 8 � 8 mm area. Calculations of the film thickness werebased on a film model consisting of silicon (refractive indexn � 3.865, absorption coefficient k � 0.020), polymer (n �1.68, k � 0), and air (n � 1, k � 0).46, 52

2.8. X-Ray Diffraction

XRD measurements were performed with a v–2v diffrac-tometer (Crystal Logic) with Cu-Ka radiation. Scans weretaken in the range of 2v, 10–100°, at 0.10° or 0.05° inter-vals, and with 3-s count times.

3. RESULTS AND DISCUSSION

3.1. Formation of PDADMAC/CPTS Multilayer Films

The LbL assembly of PDADMAC and CPTS thin filmswas performed on quartz substrates. The absorption spec-tra (Fig. 1) are characteristic of the phthalocyanine ligandcomplexed to copper and agree well with previously re-ported absorption spectra.53 Hence the plot of absorbanceat 226 nm vs. the layer number (inset of Fig. 1) shows thestepwise increase only at the even number. CPTS alsoabsorbs in the visible range with peaks at 611 nm and691 nm (data not shown), and, in principle, one can useeither of the two peaks to monitor the growth of the multi-layer thin films. We envision that the use of the peaks at611 nm and 691 nm would produce similar plots. How-

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Fig. 1. UV-visible spectra of PDADMAC/CPTS multilayer filmsassembled on quartz substrates. The CPTS concentration used for the filmpreparation was 0.1 M. The inset shows a plot of the CPTS absorbancevalues at 226 nm as a function of the layer number. The odd layer numbercorresponds to PDADMAC and the even layer number to CPTS.

ever, these peaks are weaker and less sensitive for moni-toring the film growth. PDADMAC does not show anyappreciable absorption within the wavelength range. Notethat after each PDADMAC layer deposition, the absorbanceat 226 nm decreased, suggesting that CPTS was partiallydissolved from the surface. Such behavior has been reportedfor LbL-assembled composite films in which one com-ponent is a low-molecular-weight compound (e.g., a dyemolecule).48, 54–56 The partial loss is due both to the rel-atively weak electrostatic force between small chargedspecies and the polyelectrolytes and to the higher mobilityof small species. This partial loss can be compensated forby the incorporation of more CPTS through a few addi-tional adsorption cycles.

We also investigated the relationship between the CPTSloading and the CPTS concentration used for the film prepa-ration. Figure 2 plots the absorbance values at 226 nm ofthe PDADMAC/CPTS multilayers assembled, with differ-ent CPTS concentrations as a function of layer number.As can be seen, all of the PDADMAC/CPTS multilayersshowed a gradual increase in absorbance (at 226 nm) forall of the concentrations studied. Partial loss of the CPTSprecursor was also observed for all cases. With the increasein CPTS concentration, greater amounts of CPTS can beloaded. We found that 0.1 M CPTS was an optimal con-centration for constructing quality films without large con-sumption of the CPTS precursor.

The growth of PDADMAC/CPTS multilayer thin filmswas also monitored by QCM. Figure 3 shows the frequencydecrease (��F) at the QCM electrode caused by theattachment of PDADMAC and CPTS. The QCM frequencydecreases incrementally with the layer number, demon-strating the possibility of fine control over the extent ofprecursor loading. The average frequency decreases foreach PDADMAC and CPTS layer are 47 � 21 Hz and 76 �6 Hz, respectively. The former corresponds to a mass in-crease of 40 � 18 ng and the latter to 65 � 5 ng. Inasmuch

as the mass increase of CPTS after each consecutivePDADMAC adsorption cycle was quite steady, the smalldecline in the CPTS absorbance implies that the partialloss of the precursor is insignificant and the remainingCPTS precursor still results in the deposition of additionalPDADMAC layers.

To understand the influence of the layer number on thecompactness of the multilayered films, voltammetric exper-iments were carried out to assess the permeability of a smallcharged redox ion, Ru(NH3)6

3�. Figure 4 shows an overlayof four voltammograms at gold electrodes coated with 0, 4,8, and 12 bilayers of PDADMAC/CPTS. The voltammo-grams at the unmodified electrode exhibited the typical dif-fusion-controlled reversible waves of Ru(NH3)6

3�. Whenfour layers were deposited on the gold electrode, the peakcurrents decreased only slightly, suggesting that there were

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Fig. 2. Absorbance values of PDADMAC/CPTS multilayer films assem-bled with different CPTS concentrations, plotted as a function of layernumber.

Fig. 3. Frequency decreases arising from the LbL assembly ofPDADMAC and CPTS (concentration � 0.1 M) layers at QCM elec-trodes. The even layer numbers correspond to the CPTS adsorption andthe odd layer numbers to the PDADMAC adesorption.

Fig. 4. Cyclic voltammograms of 1 mM Ru(NH3)63+ in a phosphate

buffer solution at gold electrodes coated with 0 (a), 4 (b), 8 (c), and 12 (d)layers of PDADMAC/CPTS. The scan rate employed was 0.1 V/s; arrowsindicate the scan directions.

still abundant pores present in the films. The overall voltam-metric behavior is similar to what would be observable atthe ensemble of many small conductive sites.57 However,when the layer number increased to 8 and 12 layers, theshapes of the voltammograms became significantly differ-ent, showing responses resembling those at microelectrodes.Such a change is clearly indicative of the transition from anelectrode modified with a porous film to that covered withmuch more compact films. As a result, only a small numberof pores allow the Ru(NH3)6

3� to permeate the films and toapproach the underlying electrode. The voltammetric wavesof Ru(NH3)6

3� eventually become indiscernible when lay-ers higher than 14 were deposited on the electrode (data notshown). The decrease in permeability of PDADMAC/CPTSmultilayers with the layer number is similar to that ofpoly(allylamine hydrochloride)/poly(styrene sulfonate) mul-tilayers investigated by Bruening et al.58, 59 We also foundthat there was an abrupt decline in the peak currents whenthe layer number exceeded 6. Such nonlinearity could beattributed to the different structure in the first two bilayerscompared with the rest of the film, a behavior noted in pre-vious reports.58–61

3.2. Structural Characterization of PDADMAC/CPTSMultilayers and Subsequent Copper Oxide Films

In a previous study, copper phthalocyanine was used as aprecursor to prepare copper oxide thin films by chemicalbeam epitaxy. In this study, we chose CPTS as the pre-cursor because of its multiple charges and water solubil-ity. Both of these factors make the LbL procedure forassembling the multilayered films straightforward. ThePDADMAC/CPTS multilayer films were characterized bycontact angle, ellipsometry, and AFM measurements beforeand after calcination, and the composition of the final filmswas examined by XRD.

We measured the contact angles of PDADMAC/CPTSmultilayer films (the outermost layer being PDADMAC)before calcination to be 30 � 1°. After calcination, thecontact angle increased to 42 � 3°. Such an increase isindicative of the change in the film composition, suggest-ing the conversion from a more hydrophilic surface(PDADMAC) to a more hydrophobic surface (copper oxide,as shown by the XRD spectrum presented below).

Calcination should also cause a change in the thicknessof the multilayered PDADMAC/CPTS films because of thecombustion of the PDADMAC polymer and the organicligands of CPTS at a high temperature (500 °C). Such athickness change can be conveniently measured by ellip-sometry. Table I lists the change in the PDADMAC/CPTSfilm thickness with the layer number before and after calci-nation. Films with layer numbers of 11, 21, and 41 havethicknesses of 11, 27, and 45 nm, respectively. These datacorrelate well with the cumulative values of the total num-ber of PDADMAC (each layer � 1.4 � 0.2 nm) and CPTS(each layer � 0.8 � 0.1 nm) layers. After calcination, the

thickness of PDADMAC/CPTS multilayer films decreasedand the extent of the decrease was found to be dependent onthe layer number. A PDADMAC/CPTS film of 11 layersdecreased to 9.1 nm, and the 41-layer counterpart dimin-ished to 29.8 nm. We believe that the formation of nano-crystalline copper oxide granules in the final film mightresult from the calcination of the CPTS when a polyelec-trolyte layer serves as the interlayer. PDADMAC may some-how reduce the rate of copper oxide particle formation.The layer dependence of the thickness change implies thatfewer PDADMAC layers would not significantly hinder thecopper oxide particle formation, whereas more layers couldlimit the particle growth. However, the latter effect is par-tially offset by the fact that more layers of PDADMACwould also incorporate a larger amount of CPTS complex.As a consequence, a thicker copper oxide film can be pro-duced. It thus becomes clear that, by judicious optimizationof the layer number and the amount of precursor loading,thin metal oxide films with controlled thickness can be pre-pared with this methodology.

The morphologies of the multilayered PDADMAC/CPTS films before and after calcination were examined byAFM. Figure 5 shows AFM images of three PDADMAC/

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Table I. Thickness and root-mean-square roughness of PDADMAC/CPTS multilayer films before and after calcination.

Root-mean-squareroughness (nm)a Thickness (nm)b

Layer Before After Before Afternumber calcination calcination calcination calcination

11 1.62 0.76 11.4 9.121 6.96 1.85 27.4 21.441 10.10 2.26 45.0 29.8

aEllipsometric measurements.bAFM measurements over a 3 mm � 3 mm area of each sample.

Fig. 5. AFM images of PDADMAC/CPTS multilayer films with layernumbers of 11 (a), 21 (c), and 41 (e). Images (b), (d), and (f) represent thethin copper oxide films formed after calcination of the PDADMAC/CPTSfilms with the corresponding layer number.

CPTS multilayer films deposited on Si(111) single crystalwafers and the corresponding copper oxide films. In gen-eral, both the grain sizes and the roughness of the filmscalcined from a smaller number of PDADMAC/CPTS lay-ers were found to be less than those from a larger numberof layers. The root mean square (RMS) roughnesses ofthese films with layer numbers 11 (Fig. 5a), 21 (Fig. 5b),and 41 (Fig. 5c) were 1.62 nm, 6.96 nm, and 10.1 nm,respectively. Compared with films containing multilayersof PDADMAC and PSS (polystyrene sulfonate sodiumsalt), these PDADMAC/CPTS multilayers appear to besmoother.60, 61 Such a difference in the film morphologiescould be ascribed to the difference in charges betweenCPTS and PSS (many more charges reside on the long PSSbackbone). Caruso and co-workers have also investigatedthe influence of charge density of PDADMAC-NMVA(N-methyl-N-vinylacetamide) copolymer on the multilayerfilm morphology61 and found that when the PDADMAC-NMVA copolymer charge density is above a critical value,multilayered films with a greater roughness are produced.

After calcination, nanoparticulate copper oxide filmswere prepared. The RMS roughness in the AFM images ofnanoparticulate films derived from 11, 21, and 41 layers ofPDADMAC/CPTS films decreased drastically, indicatingthe removal of the organic constituents during the calcina-tion (Table I). It can be seen that the morphology of cop-per oxide films is quite uniform and the uniformity of thenanometer-sized particles depends on the number ofPDADMAC/CPTS multilayers (Fig. 5b, d, and f). Filmsderived from 11 layers are composed of particles with adiameter of 116 � 13 nm with a RMS roughness of0.76 nm, whereas films produced from 21 and 41 layers ofPDADMAC/CPTS contain grain particles with diametersof 169 � 12 nm and 237 � 32 nm with RMS roughnessesof 1.85 and 2.26 nm, respectively. The increase in the par-ticle diameters may have originated from the incorporationof greater amounts of the CPTS precursor with more layernumbers.

XRD measurements were performed to determine thecomposition of films produced from calcination of themultilayered PDADMAC/CPTS films. In a typical XRDpattern (Fig. 6), both CuO and Cu2O phases can be found.Peaks at 33.1°, 61.3°, and 82.5° are associated with thereflection of CuO (JCPDS file no. 44-0706), whereas peaksat 52.5° and 69.6° can be attributed to the reflection ofCu2O (JCPDS file no. 05-0667). Note that the reflectionpeak at 69.6° is overlapped with the Si signal from theunderlying silicon wafer (69.2°, 400 reflection). Hence thecalcination of the multilayered PDADMAC/CPTS filmsproduced nanoparticulate films composed of CuO andCu2O phases. We have also carried out a UV-visible mea-surement of the calcined thin films and found no absorp-tion peaks characteristic of the CPTS precursor (data notshown), suggesting that the calcination of the multilayerfilms has converted the as-prepared films to copper oxidenanoparticulate thin films. The formation of Cu2O could

result from incomplete oxidation during the calcinationstep.

4. CONCLUSIONS

This work demonstrates that CPTS can be assembled on aplanar substrate with the sequential adsorption of a poly-electrolyte (i.e., PDADMAC) as the interlayer and can serveas a precursor to form nanocrystalline copper oxide thinfilms. PDADMAC and CPTS can be adsorbed to quartz,silicon, or gold surfaces via the LbL procedure, and the for-mation of the multilayered films was verified by UV-visiblespectrometric, quartz crystal microbalance, and electro-chemical measurements. The results show that the LbL pro-cedure can precisely control the amount of precursor load-ing in the multilayered film structure, and the compactnessbecomes greater with a thicker multilayer. XRD spectrashow that calcination of these multilayered films at an ele-vated temperature leads to the formation of thin films con-taining both CuO and Cu2O. Both ellipsometric and AFMmeasurements were employed for characterizing multi-layered PDADMAC/CPTS and copper oxide films. Thefilm thickness and surface roughness were found to bedependent on the PDADMAC/CPTS layer number. Smallercopper oxide grains with a smoother morphology were ob-tained with a smaller number of PDADMAC/CPTS layers,illustrating that fine control of both the copper oxide filmthickness and morphology can be accomplished by varia-tion of the PDADMAC/CPTS layer number before the cal-cination step. The approach described here may provide analternative route for the preparation of nanocrystalline metaloxide thin films; it is relatively straightforward and does notrequire stringent synthetic procedures involving a sophisti-cated apparatus and expensive precursors.

Acknowledgments: Valuable discussions with MatthewC. Traub (California Institute of Technology) are appre-

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Fig. 6. XRD pattern of the films prepared by calcination of multilayeredPDADMAC/CPTS films.

ciated. Financial support from Donors of the PetroleumResearch Funds administered by the American ChemicalSociety (grant 37899-AC5), the NSF-CRUI (grant DBI-9978806), and a NIH-SCORE subproject (GM 08101) isgratefully acknowledged.

References and Notes

1. J. H. Fendler and Y. Tian, in Nanoparticles and NanostructuredFilms, edited by J. H. Fendler, Wiley-VCH, Weinheim, Germany(1998), pp. 429–456.

2. J. M. Marshall, N. Kirov, and A. Vavrek, Electronic, Optoelectronicand Magnetic Thin Films, Wiley, New York (1995).

3. S. Park, B. L. Clark, D. A. Keszler, J. P. Bender, J. F. Wager, T. A.Reynolds, and G. S. Herman, Science 297, 65 (2002).

4. J. B. Forsyth, P. J. Brown, and B. M. Wanklyn, J. Phys. C: SolidState Phys. 21, 2917 (1988).

5. B. N. Roy and T. Wright, Crystal Res. Tech. 31, 1039 (1996).6. A. Parretta, M. K. Jayaraj, A. D. Nocera, S. Loreti, L. Quercia, and

A. Agati, Phys. Status Solidi A 155, 399 (1996).7. B. Raveau, C. Michel, M. Herview, and D. Groult, Crystal Chemistry

of High Tc Superconducting Copper Oxides, Springer-Verlag, Berlin(1991).

8. C. P. Poole, T. Datta, H. A. Farach, M. M. Rigney, and C. R. Sanders,Copper Oxide Superconductors, Wiley, New York (1988).

9. M. Sohma and K. Kawaguchi, J. Magn. Magn. Mater. 126, 295(1993).

10. R. A. MacGill, S. A. A. Anders, R. A. Castro, M. R. Dickinson,K. M. Yu, and I. G. Brown, Surf. Coat. Technol. 78, 168 (1996).

11. M. T. S. Nair, L. Guerrero, O. L. Arenas, and P. K. Nair, Appl. Surf.Sci. 150 143 (1999).

12. S. C. Ray, Sol. Energy Mater. Sol. Cells 68, 307 (2001).13. E. F. A. Machler, E. Fritsch, J. G. Bednorz, H. Berke, J. R. Huber,

and J. P. Locquet, Appl. Phys. Lett. 71, 710 (1997).14. A. Brazdeikis, U. O. Karlsson, and A. S. Flodstrom, Thin Solid Films

281–282, 57 (1996).15. H. Y. Bae and G. M. Choi, Sens. Actuators, B 55, 47 (1999).16. G. G. Condorelli, G. Malandrino, and I. Fragala, Chem. Mater. 6,

1861 (1994).17. G. G. Condorelli, G. Malandrino, and I. L. Fragalà, Chem. Vap.

Deposition 3, 237 (1999).18. G. G. Condorelli, G. Malandrino, and I. L. Fragalà, Chem. Vap.

Deposition 5, 21 (1999).19. E. R. Kleinfeld and G. S. Ferguson, Mater. Res. Soc. Symp. Proc.

351, 419 (1994).20. T. Yonzawa, H. Matsune, and T. Kunitake, Chem. Mater. 11, 33

(1999).21. I. Ichinose, T. Kawakami, and T. Kunitake, Adv. Mater. 10, 535

(1998).22. I. Ichinose, H. Senzu, and T. Kunitake, Chem. Mater. 9, 1296 (1996).23. I. Ichinose, H. Senzu, and T. Kunitake, Chem. Lett. 831 (1996).24. M. Fang, C. H. Kim, B. R. Martin, and T. E. Mallouk, J. Nanoparticle

Res. 1, 43 (1999).25. N. I. Kovtyukhova, E. V. Buzaneva, C. C. Waraksa, B. R. Martin,

and T. E. Mallouk, Chem. Mater. 12, 383 (2000).

26. B. L. Clark and D. A. Keszler, Inorg. Chem. 40, 1724 (2001).27. G. Decher, Science 277, 1232 (1997).28. E. Donath, G. B. Sukhorukow, F. Caruso, S. A. Davis, and H.

Möhwald, Angew. Chem Int. Ed. 37, 2201 (1998).29. F. Caruso, R. A. Caruso, and H. Mohwald, Science 282, 1111 (1998).30. Y. J. Liu, Y. X. Wang, and R. O. Claus, Chem. Phys. Lett. 298, 315

(1998).31. T. Cassagneau and F. Caruso, Adv. Mater. 14, 732 (2002).32. J. H. Fendler, Chem. Mater. 13, 3196 (2001).33. T. Cassagneau, T. E. Mallouk, and J. H. Fendler, J. Am. Chem. Soc.

120, 7848 (1998).34. T. Cassagneau, J. H. Fendler, and T. E. Mallouk, Langmuir 16, 241

(2000).35. A. L. Rogach, D. S. Koktysh, M. Harrison, and N. A. Kotov, Chem.

Mater. 12, 1526 (2000).36. A. Rosidian, Y. J. Liu, and R. O. Claus, Adv. Mater. 10, 1087 (1998).37. N. A. Kotov, I. Dekany, and J. H. Fendler, J. Phys. Chem. 99, 13065

(1995).38. N. A. Kotov, T. Haraszti, L. Turi, G. Zavala, R. E. Geer, I. Dekany,

and J. H. Fendler, J. Am. Chem. Soc. 119, 6821 (1997).39. I. Ichinose, H. Tagawa, S. Mizuki, Y. Lvov, and T. Kunitake,

Langmuir 14, 187 (1998).40. Y. Lvov, K. Ariga, M. Onda, I. Ichinose, and T. Kunitake, Langmuir

13, 6195 (1997).41. F. Caruso, A. S. Susha, and M. H. M. Giersig, Adv. Mater. 11, 950

(1999).42. R. A. Caruso, A. Susha, and F. Caruso, Chem. Mater. 13, 400 (2001).43. F. Caruso, M. Spasova, A. Susha, M. Giersig, and R. A. Caruso,

Chem. Mater. 13, 109 (2001).44. F. Caruso, Adv. Mater. 13, 11 (2001).45. F. Caruso, X. Shi, R. Caruso, and A. Susha, Adv. Mater. 13, 740

(2001).46. X. Shi, T. Cassagneau, and F. Caruso, Langmuir 18, 904 (2002).47. J. H. Rouse and G. S. Ferguson, Adv. Mater. 14, 151 (2002).48. C. Tedeschi, F. Caruso, H. Mowald, and S. Kirstein, J. Am. Chem.

Soc. 122, 5841 (2000).49. W. Kern, Semicond. Int. 94 (1984).50. G. Sauerbrey, Z. Phys. 155, 206 (1959).51. E. A. Lawton, J. Phys. Chem. 62, 384 (1958).52. H. Brunner, T. Vallant, U. Mayer, and H. Hoffmann, Langmuir 12,

4614 (1996).53. Y. M. Lvov, G. N. Kamau, D. L. Zhou, and J. F. Rusling, J. Colloid

Interface Sci. 212, 570 (1999).54. K. Ariga, Y. Lvov, and T. Kunitake, J. Am. Chem. Soc. 119, 2224

(1997).55. M. Linford, M. Auch, and H. Mohwald, J. Am. Chem. Soc. 120, 178

(1998).56. S. Das and A. J. Pal, Langmuir 18, 458 (2002).57. J. J. Harris and M. L. Bruening, Langmuir 16, 2006 (2000).58. G. Decher, Y. Lvov, and J. Schmitt, Thin Solid Films 244, 772

(1994).59. N. G. Hoogeveen, M. A. Cohen Stuart, and G. J. Fleer, Langmuir 12,

3675 (1996).60. R. A. MaAloney, M. Sinyor, V. Dudnik, and M. C. Goh, Langmuir

17, 6655 (2001).61. B. Schoeler, G. Kumaraswamy, and F. Caruso, Macromolecules 35,

889 (2002).

Received: . Revised/Accepted: .

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