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It is found that the TiO2 ultrafine particles (UFP) coated with a layer of stearic acid radicals had a significant red shift of their absorption band edge and clear photoluminescence at room temperature (RT), which are in contrast with that of bulk TiO2 and naked TiO2 UFP. It was concluded that these results are related to the self-trapped exciton absorption due to the interfacial dipole layer of stearic acid radicals on the TiO2 UFP surface.

Three kinds of amphiphilic oligomers, poly(maleic acid) with octadecanol ester (PMAO) with 2.0:1, 3.7:1, and 6.0:1 between the carboxylic groups and the hydrocarbon chains, were synthesized and have been used as a matrix to form and grown the quantum-sized PbS. Pure Y-type PbPMAO Langmuir-Blodgett (LB) films were prepared at a dipping speed of 4.0 cm/min and surface pressure of 18 mN/m. The results from Fourier tranform IR spectroscopy and X-ray diffraction measurements showed that an ordered structure was obtained from the PbPMAO LB films. The quantum-sized PbS particles were prepared by exposure of PbPMAO LB films to H 2S and nanoparticulate PbS monolayers were formed without destroying the layered structure. The result from structured UV-vis absorption spectra shows that the PbS particles within the LB matrix are relatively monodispersed. It was found that the PbS within PMAO LB films indicated a larger blue shift of the optical absorption edge with the decrease of the ratio between the carboxylic groups and the hydrocarbon chains. Meanwhile, it can be deduced that the size of the aggregate of the sulfides within PMAO LB films is smaller than that formed in stearic acid LB films. The observed absorption peaks showed similarity with the monomolecular PbS.

Langmuir and Langmuir−Blodgett (LB) films of two kinds of C60 derivatives with the substituents which have methoxycarbonyl (C60(I)) and a carboxylic group (C60(II)) were investigated, respectively. The photovoltaic behaviors and charge-transfer process of their LB films on n-type Si substrates and their powders were studied by surface photovoltage spectra (SPS). For the electronic effect caused by different electron-withdrawing groups, they exhibited different photovoltaic behaviors, and the reverse response values of SPS were obtained when the C60-derivatives powders contact with indium tin oxide substrates. The reason was that the relatively strong electron-withdrawing substituent shifted the molecular orbital levels to lower energy, which caused the opposite surface band bending. When deposited on n-Si substrates, the two kinds of C60-derivative LB films both exhibited the same increment on the direct transition of n-Si. Furthermore, the structural characterization of C60(II) LB film was studied in detail by measuring the π−A isotherm, FTIR, and small-angle X-ray diffraction. It revealed that this kind of C60 derivative formed micellar aggregates. The hydrophobic cores of the C60 moiety gave an actual cluster with the hydrophilic substituents sticking out.

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