Aggregated films

Spano, F. C. 2006. Excitons in conjugated oligomer aggregates, films and crystals. Annu. Rev. Phys. Chem. 57 217-243. 

Fig. 2.2 Schematic diagram showing the probable steps involved in the hydroxide mechanism. A Diffusion of hydroxide colloidal particles to the substrate, where they adhere (B) and react with S ions (either generated homogeneously in solution or catalyzed by the hydroxide surface). This reaction results in exchange of the hydroxide by sulphide, probably starting at the surface of the colloid and proceeding inward (C). This reaction will occur both at the surface-adsorbed colloids and at those dispersed in the solution. Reaction will continue (as long as the supply of sulphide continues) until most of the hydroxide is converted to sulphide (D) eventually the primary particles of CdS will adhere to each other to form an aggregated film (E) usually the nonadsorbed particles will also aggregate and precipitate out of the solution.

Ikeda, I. Tsuji, T. Okahara, M., (1988) Synthesis of amphiphilic crown ethers and their ability to form molecular aggregation film. Kenkyu Hokoku - Asahi Garasu Kogyo Gijutsu Shoreikai 53, 311-315 [Chem. Abstr. 112 98500],... 

Figure 14. The spectral dependence of the xerographic sensitivity of the nonaggregated homogeneous dye-polymer film, the aggregated film, and the aggregated and sensitized film. The sensitivity is the reciprocal of the energy required for a photodischarge from 500 to 250 V. (Reprinted with permission from Ref. [31].)...

Keywords dynamic light scattering, fractal aggregates, filmed silica, particle size, simulation... 

Shown in Fig. 6 is the dependence of molecular flux on polymer film thickness. The observed inverse correlation is characteristic of permeation-controlled transport. In other words, fluxes are limited by rates of diffusion through the film rather than partitioning from the solution to the film. Similar behavior has been observed for molecular aggregate films. 

Fig. 3. The spectral change of the J-aggregated film PIC2-18 at sample heating...

Fig. 22. The absorption spectra change of the J-aggregated films PIC-closo-hydrodecaborate headed (cooled), doped with TEA at a dye-TEA mole ratio of 1 4 (a), expanded scale (b), expanded scale PIC2-2 in polymer anethole (c)...

It should be noted that the experimental spectra are not corrected for double passage of light through the sample. Losses of light to double reflection and absorption of dye film must be considered in order to obtain the true value of the optical density in our optical setup. For this, the reflectance spectrum of J-aggregated PIC 2-18 film was measured (Fig. 25). The corrected optical density of J-aggregated film D(Xcor)=log [Io/(fo--A-R)] was calculated by solving the quadratic equation for the absorption coefficient obtained from the formula for the measured optical density D(A) ... 

Fig. 25. Reflectance spectrum (1) and absorption s(>ectrum calculated taking into account reflectance of the sample (2), J-aggregated film of PIC 2-18...

Fig. 27. The absorption spectra of the PIC2-2 iodide and closo-hexahydrodecaborate J-aggregated films...

Fig. 28. The cubic susceptibility dispersion curves for the PIC J-aggregated films with -BioHJa 1 0,5 (a) and BioHio -1 0,5 (b)...

The luminescence kinetics decay for J-aggregated film was measured to estimate the values of the characteristic times of excited state relaxation. The luminescence decay of the J-aggregated thin film in the maximum of the J-aggregate luminescence A=590 nm at the excitation in J-peak maximum A 574 nm at temperature 94°K is shown in fig. 30. 

The laser radiation intensity dependence on the non-linear transmission of the J-aggregated film sample was calculated for the obtained specified model parameters for the intensity change in the range 1023-1025 quant/cm2 in the maximums of the induced non-linear bleaching and darkening as shown in fig. 31b. 

These polymers were insulators in their pristine state. However, ion-implantation of their aggregated films using a Kr+ source at energy of 190 keV and ion flux of 0.12... 

Table 2. Electrical conductivities of the l rypton-implanted aggregated films of the heterocyclic ladder and pseudo-ladder rigid-rod polymers.

Foaming capability relates to both foam formation and foam persistence. Surface tension lowering is necessary, but not sufficient. Other important factors include surface elasticity, surface viscosity and disjoining pressure [60]. Considering stability to aggregation, film thinning and bubble coalescence, the factors favouring foam stability can be summarized as follows ... 

There are several molecular scenarios for the delivery of miceUe-bound reactants into adsorbed surfactant films on electrodes. One possibility is dissociation (Eq. 17) followed by entry of the reactant into the aggregate film on the electrode, orientation near the surface, and electron transfer. Making the analogy between these latter processes and the adsorption rates of 3, entry into the films and orientation is expected to occur on a miUisecond timescale. 

It has been postulated that the formation of thick, multilayer protein films plays an important role in determining the friction coefficient of artificial hip implants. Albumin is sensitive to many factors including heat, protein concentration, salt concentration, and pH, and aggregates through hydro-phobic interactions in solution over time to form solid, insoluble particles. These particles are then deposited on the surface. Under the conditions used in this study, no deposition of protein to form a thick, aggregated film could be observed, either with AFM or with fluorescence imaging. It has been shown elsewhere that protein films with an average... 

Table 4. Electrical conductivities of the Krypton-Implanted Aggregated Films of Rigid-Rod Polymers ...

In a related phenomenon, the spectral shifts which accompany aggregation-deaggregation have been reported as a basis of yet another erasable medium.24 The active layer consists of discrete particles of a cocrystalline complex of a pyrylium dye with a polymer such as polycarbonate. Pulsed irradiation of this aggregated film resulted in an instantaneous deaggregation process which was accompanied by a hypsochromic shift of about 100 nm. The recording mechanism is believed to be thermal and a thermal erasure (reaggregation of the dye-polymer complex) was also demonstrated. 

The LB films from the self-aggregated film were subjected to alkali-metal doping. Superconducting transition was suggested by the low-magnetic-field microwave signal from potassium doped [339] or rubidium doped films [340]. 

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