Supramolecular Science最新文献

The behavior of hot-electrons is very important for thin film electroluminescence (TFEL) devices. In SrS:Ce TFEL, the electrons in excited states of Ce³⁺ ions are easily to be ionized into conduction band under a high electric field, and are easily trapped by the ionized luminescent centers under a low electric field. In this paper, the dependence of ionization possibility on the field strength is studied and the emission wave forms were determined. The energy transfer process is discussed.

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 CaF₂ 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.

Organic electroluminescent (EL) devices with one layer of Alq(CH₃)₂ doped with poly(N-vinylcarbozle) (PVK) (Alq(CH₃)₂/PVK) as the EL-emitting layer sandwiched between indium tin-oxide (ITO) and aluminum electrodes have been fabricated by spin coating on to ITO. We found that two EL-peak intensities at the position of 520 nm from Alq(CH₃)₂ and at 470 nm from PVK change with different voltages applied to the organic EL devices. According to the analysis of the experimental results, it could be inferred that a charge transfer from Alq(CH₃)₂to PVK may take place in the Alq(CH₃)₂/PVK mixed film, leading to a much increased the EL intensity of the peak $\text{(λ=470}\text{nm}\text{)}$ from the PVK and a slight increase in the EL intensity of the peak $\text{(λ=520}\text{nm}\text{)}$ from Alq(CH₃)₂ with the voltage elevation at the higher voltages applied.

Self-assembled monolayers of 1-teradecanethiol on gold were characterized by means of FTIR-ATR measurements, XPS and contact angle measurements. Linear dichroism measurements using FTIR-ATR are used to estimate the orientation of the alkyl chains. An equation for calculating the orientation angles of the alkyls chains was deduced.

CdSe sensitized TiO₂ nanocrystalline solar cells were made with the participation of silicotungstic acid (STA) during the deposition of CdSe, the resulting Voc and Isc were 0.23 V cm^-2 and 10 mA cm^-2, respectively. The doping, time and microporous membrane effects were also discussed.

Surface pressure–area (π–A) isotherm characteristics of 5,10,15-(4-hydroxyphenyl)-20-(4-hexadecyloxyphenyl) porphyrin monolayers on both the water and TiO₂ hydrosol subphases, the UV–vis absorption and fluorescence spectra of the monolayers deposited onto CaF₂ substrates are investigated. π–A isotherms find that the porphyrin ring extends to lie more flat on a TiO₂ hydrosol surface than on a water surface. The UV–vis absorption spectra of the deposited monolayers prove that the porphyrin TiO₂ nanoparticle heterostructure assembly is formed, in which the J-aggregated effect of porphyrin is weakened, comparing with that in the monolayer deposited from water subphase. The fluorescence spectra show that the fluorescent emission quenching by the photoinduced electron transfer from the excited porphyrin molecule to TiO₂ nanoparticle, occurs under excitation in the Soret band region of porphyrin.

Molecular recognition directing self-assembly of two complementary molecular components, 5-(4-dodecyloxybenzylidene)-2,4,6-(1H,3H)-pyrimidinetrione (B) and 4-amino-2,6-didodecylamino-1,3,5-triazine (M), was found to form a mesoscopic supercoil structure with length of several tens of μm and diameter of ca. 300 nm. Fluorescence spectral studies show that it takes more than 1200 h for the self-assembling process to reach the equilibrium in chloroform. It was suggested that in this system with positive cooperation, at least two steps were involved in the self-assembling process. First, supramolecular tapes, cyclic hexamers, are formed based on the network of triple complementary hydrogen bonds between B and M. Second, π-aromatic stacking and van der Waals interactions drive further the assembling of tapes into more complex nanometric strand. The coiling of the strands results in the formation of the supercoil structure.

It is suggested that the appearance of Jordan blocks in the normal form of the recursion (transfer) matrix is responsible for high temperature superconductivity and related phenomena. Several published observations are discussed to support this idea. The draft of a quantum chemical theory is given for a more complete verification.

This study describes the fabrication sequence of a prototype device based on the assembly of copper-tetracyanoquinodimethane (Cu-TCNQ) crystallites in a specially designed and prepared electrode structure. The assembed Cu-TCNQ organometallic salt was synthesized by using the spontaneous electrolysis growth technique. The results of the electrical measurement on this device have clearly shown a typical rectifying characteristic. It is suggested that this rectifying phenomenon is mainly related with the Cu-TCNQ molecular homojuction formed by in-microregion contact.

Sodium 9,10-anthraquinone-2-sulfonate (AQS) binds to the double helical DNA with a high affinity, as deduced from the absorption and fluorescence spectral data. The results of absorption spectra, KI quenching studies, competitive binding studies, and thermal denaturation experiments suggested the intercalative binding of AQS into DNA bases.