Xiangdong Chai

X-ray photoelectron spectroscopy study of the synthesis of copper sulphide in Langmuir-Blodgett films

On the basis of work by Barraud et al. (A. Barraud et al., Mol. Cryst., Liq. Cryst., 134 (1986) 347), the process of H2S diffusion into Langmuir-Blodgett (LB) films of copper stearate and the formation of layers of copper sulphide with semiconducting properties were studied by X-ray photoelectron spectroscopy measurements. It was shown that the reaction rate is mainly controlled by the diffusion of H2S. Thus various non-stoichiometric products can be obtained by controlling the H2S pressure. At least two sulphur species were found in the product, the sulphur ion (S2-) and the sulphur molecular ion (S22-), and the S22-:S2- ratio seems to be related to the extent of reaction. Finally, the specific effect of the microenvironment of LB films and the characteristics of the reaction in the LB film are discussed.

Electrochemical deposition and photovoltaic properties of Nano-Fe2O3-incorporated polypyrrole films

Abstract Fe 2 O 3 nanoparticles, of which sizes vary from 4 to 40nm, were introduced into polypyrrole(PPy) films while pyrrole monomers were electrodeposited onto ITO electrodes. When measured in surface photovoltage spectroscopy(SPS), new photovoltaic behaviors were observed in both, cases containing small and large Fe 2 O 3 particles. In terms of band structure and polaron theory, together with the reference of absorption spectra, some principles involved were revealed.

Optical and electrical properties of organic-inorganic composite system

Abstract Anionic phthalocyanine sodium hydrogallium 4,4′,4″,4‴-tetrasulfonated phthalocyanine(GaTsPc) was used to modify the surface of a size-quantized particulate TiO 2 photoelectrode fabricated by electrostatic attraction. The photovoltaic features and interfacial electron transfer of the electrodes were studied by a photoelectrochemical method and surface photovoltage spectroscopy. The results indicate that the light absorption of phthalocyanine monomer makes more contribution to the photovoltaic response in the TiO 2 /GaTsPc composite electrode in spite of obvious aggregation occurring in composite electrode.

Temperature-dependent FTIR study of a supramolecular mesophase from the self-assembly of melamine and barbituric acid derivatives

A supramolecular mesophase was prepared from molecular recognition directed self- assembly of two complementary molecular components, namely 5-(4-dodecyloxy- benzylidene)-2,4,6-(1H,3H)-pyrimidinetrione and 4-amino-2,6-didodecylamino-1,3,5triazine. Differential scanning calorimetry measurements indicate a mesophase having liquid crystalline properties. Infrared studies suggest that not only hydrogen bonds but also pi-aromatic stacking and van der Waals interactions direct the formation of the mesophase.

Formation of mesophase by hydrogen bond directed self-assembly between barbituric acid and melamine derivatives

Abstract The 1:1 mesophase was formed through molecular self-assembly directed by hydrogen bonding between light active barbituric acid derivative, 5-[4-dodecyloxybenzylidene]-2, 4, 6,-(1H, 3H)-pyrimidinetrione (B) and melamine derivative, 4-amino-2, 6-didodecylamino-1, 3, 5-triazine (M). It was found through temperature-dependent IR spectra that there are three kinds of hydrogen bonds with different strength in this mesophase. When dispersed in chloroform, this mesophase shows a double helical structure.

Preparation of covalently modified organic–inorganic composite nanoparticles and their interfacial electron transfer researches

TiO 2 and α-Fe 2 O 3 nanoparticles were covalently coated with an organic chromophore monolayer, 4-(4-N,N-(dialkylamino) styrl pyridium using trimethoxyl (p-(chloromethyl) phenyl) silane as linkage molecules. The resulting composite particles were characterized by UV-vis, IR, X-ray photoelectron spectroscopy (XPS), and surface photovoltaic spectroscopy (SPS). All the results indicated the formation of the organic-inorganic hybrid structures. The photoinduced interfacial charge transfer in the composite particles were also detected by SPS under different external voltages imposed.

Aggregation behaviors of light-active barbituric acid molecular components in solution

Abstract Self-aggregation of light active barbituric acid derivatives and their self-assembly with melamine derivatives through hydrogen-bonding, π-aromatic stacking, and other weak interactions were studied by UV–visible absorption and fluorescence spectroscopy. PB12Me has the same fluorescence behavior as PB12 in chloroform though it cannot aggregate through a hydrogen-bond. AB12 and AB1 lead to different degrees of fluorescence splitting. When barbituric acid molecular components were self-assembled with melamine a similar splitting phenomenon was observed. It was shown that π-aromatic stacking resulted in the exclusive fluorescence changes and H-aggregates were formed in solution.

Improved surface photovoltaic response of nanoparticulate TiO2-pyridine derivative monolayer/n-Si(111) assembly

Abstract Nanoparticulate TiO 2 -pyridine derivative monolayer/n-Si(111) assembly was fabricated by Langmuir-Blodgett (LB) technique from 4-[4′-N,N-(didodecylamino) stryll pyridium (P II ), and its photovoltaic conversion properties were investigated by surface photovoltage spectroscopy. Sensitization effect of P II molecule as well as TiO 2 nanoparticle on n-Si(111) is observed, and the photovoltaic response of this assembly is about 20 times as high as that of n-Si(111).

Frontier orbital interactions of electron pushing and drawing substituents with ferrocenyl group

The frontier orbital interactions of electron pushing and drawing substituents with ferrocenyl group were analyzed based on the electrochemical, UV-visible spectral and spectroelectrochernical results of five ferrocene derivatives, R-Fc-A1(P1), A1-Fc-A1(PII), D-Fc-R (PIII), D-Fc-A1(PIV) and D-Fc-A2(PV) (R, CH2OH; A1 CHO; A2, CH = C(CN)2 and D, ((318H37)2N-C6&-CH = CH). It was found that there are strong interactions of the LUMO (π a* ) of electron drawing substituents with 1e2g (dry, dr2 - y2) and e2u(ϕ4u, ϕ5u) of the ferrocenyl group because the energy levels of πA * and e2g, e2u of (Cp-)2 are close, which lower not only the energy levels of bonded orbits πA *+[ϕ4u] and dx 2\t-y2 of PI, PII, PIV and PV obviously, but also those of their non-bonded orbit,dxy For PIII, PIV and PV, there are strong interactions of HOMO (πD) of the electron pushing substituent with lelu (ϕ2u, ϕ3u) of the ferrocenyl group because the levels of πD and eluof (Cp-)2 are close, which result in the formation of anti-bonded orbit, πD\t-[ϕ3u], and bonded orbit, ϕ3u +[πD].

A novel amphiphilic push-pull ferrocene derivative: Langmuir–Blodgett films and second-order optical nonlinearity

Abstract The Langmuir–Blodgett (LB) films built from the mixture of an amphiphilic push–pull ferrocene derivative ( P ) and behenic acid were investigated. Langmuir films of P diluted by behenic acid exhibit a very good cohesion and the mixed films can easily be transferred onto solid substrates. Linear dichroism UV-visible and IR spectroscopy measurements of the mixed LB multilayers confirm that the molecules ( P ) are oriented to the substrate. The nonlinear optical experiments on the mixed monolayer deposited on the CaF 2 slide showed that P displayed efficient optical second harmonic generation (SHG) with a molecular hyperpolarizability ( β ) as high as 6.0×10 -29 e.s.u.