w, d(CH)], 1349 [vw, n(CN)], 1322 [vw, d(CH)], 1298 [vw, d(C±O±CH 2 ) [b]], 1196 [w, d(CO)], 1119 [m, n(C±C=O) [b]], 1053 [w, n(SiO)], 962 [w, n(WO)], 926 [w, n(WO)], 902 [w, n(WO)], 866 [w, n(WO)], 820 [w, n(WO)], 749 [w, n(WO)], 627 [vs, n(FeO)], 561 [vs, n(FeO)]. The BA ferrogels were prepared under the same conditions as the POM ferrogels but replacing POM by N,N¢-methylenebis(acrylamide) (BA) (0.017, 0.042, and 0.084 mol/L). The infrared data of a BA ferrogel with 0.017 M of BA and 5.5 % (volume fraction) of maghemite g-Fe 2 O 3 : IR (KBr): n = 1665 [s, n(CO) [a]], 1615 [s, d(NH)], 1448 [m, d(CH 2 )], 1414 [m, d(CH)], 1349 [m, n(CN)], 1322 [w, d(CH)], 1119 [vw, n(C±C=O) [b]], 627 [vs, n(FeO)], 561 [vs, n(FeO)]. Physical Measurements: The compound g-K 8 [SiW 10 O 36 ]×12H 2 O was prepared according to the literature [16]. Other reagents, [RSi(OMe) 3 ], and solvents were purchased from Aldrich and used as received. Elemental analyses were performed by the ªService central de microanalyses du CNRSº, Vernaison, France. The IR spectra (4000±250 cm ±1 ) were recorded on a Bio-Rad FTS 165 FTIR spectrometer with compounds and dried hydroferrogels sampled in KBr pellets. The volume fraction of magnetic particles in the different hydroferrogels and the particle sizes are deduced from magnetic measurements using a classical Foner device [17]. The rotational diffusion coefficient of particles is determined by the relaxation of birefringence. This method has already been described in the literature [15]. Transmission electron microscopy (TEM) (microscope JEOL 100 CX2) was performed on a microcoat of hydroferrogel deposited on a grid after microtomy. The gels are filmed with a charge coupled device (CCD) color camera (Vista, VPC 4130, UK). The degree of swelling of the hydroferrogel samples was characterized by the ratio m/m 0 , where m is the mass of the hydroferrogel sample swollen in aqueous solution and m 0 is the mass of the dry hydroferrogel.

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This work was partially funded by the European TMR project NAMITECH. M.B. and G.P. acknowledge support from the BMBF. The help of M. Kelsch with TEM and U. Waizmann with SEM investigations is greatly appreciated.

Langmuir−Blodgett films consisting of carbon single-walled nanotubes embedded in a surfactant matrix were prepared. Aqueous dispersions of single-walled nanotubes stabilized by lithium dodecyl sulfate were purified by a centrifugation step. The supernatant was spread onto a subphase containing a positively charged polyelectrolyte. AFM investigations of monolayers transferred onto hydrophobic silicon substrates revealed the presence of homogeneously dispersed single-walled nanotube bundles, as well as individual single-walled nanotubes, both of which are surrounded by micelle-like surfactant aggregates.

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A field-effect transistor (FET) with a channel length of ∼100 nm was constructed from a small number of individual V2O5 fibers of the cross section 1.5 nm×10 nm. At low temperature, the conductance increases as the gate voltage is changed from negative to positive values, characteristic of a FET with n-type enhancement mode. The carrier mobility, estimated from the low-field regime, is found to increase from 7.7×10−5 cm2/V s at T=131 K to 9.6×10−3 cm2/V s at T=192 K with an activation energy of Ea=0.18 eV. The nonohmic current/voltage dependence at high electric fields was analyzed in the frame of small polaron hopping conduction, yielding a nearest-neighbor hopping distance of ∼4 nm.

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