Particles organic films

Gill, P. S., T. E. Graedel, and C. J. Weschler, Organic Films on Atmospheric Aerosol Particles, Fog Droplets, Cloud Droplets, Raindrops, and Snowflakes, Rev. Geophys. Space Phys., 21, 903-920 (1983). 

The degree of compression of the film would be expected to alter its effects on uptake and evaporation from the particle. Thus, as organic films of linear-chain surfactants are compressed, they go through different stages, from a disordered 2-D gas-like phase at low... 

The possibility of such organic films being formed on aerosol particles in the atmosphere as well as on fog, cloud, and rain droplets and snowflakes has been discussed in detail by Gill and co-workers (1983). As seen from our earlier discussions on the types of organics that have been observed in both urban and nonurban aerosols, there is no question that surface-active species... 

There is some field evidence for the existence of organic films on the surfaces of particles. For example, Fig. 9.57 shows the results of electron microscopy of haze aerosol collected in Los Angeles (Husar and Shu, 1975). The droplets are wrinkled in appearance, and they suggest this is due to haze aerosol droplets being coated with an organic layer that collapsed when the water in the particle evaporated under vacuum. Husar and Shu propose that the wrinkled appearance is due to a nonvolatile layer of organics that shrunk after water evaporated from the particle during analysis ... 

Organic films may have some or all of the following effects (1) reduction of the rate of evaporation of water from the droplets, (2) inhibition of the transport of stable molecules and of highly reactive free radicals such as OH and HOz from the gas phase into the droplet, and (3) reduction of the efficiency with which the particles are scavenged by larger cloud and rain droplets (Gill et al., 1983). Thus, the presence of organic films may increase the lifetime of such particles in the atmosphere compared to those expected if the films were not present (Toossi and Novakov, 1985). 

Ziemann, P. J., and P. H. McMurry, Secondary Electron Yield Measurements as a Means for Probing Organic Films on Aerosol Particles, Aerosol Sci. Technol., 28, 77-90(1998). 

In addition to the blueshifling of the optical absorbance of Q-state semiconductor particles, a linear optical effect, there are nonlinear optical effects demonstrated by Q-state semiconductors. Two types have been observed by MCs prepared in organized films. One is the third harmonic generation or frequency tripling (44). A... 

Pankow (1994a,b) proposed that gaseous POPs also absorb into a liquid-like organic film on the particles. Liang and Pankow (1996), and Pankow (1999) found the sorptive capacity of environmental tobacco smoke (almost entirely organic matter) and urban air particles (about 20% organic matter) for n-alkanes and PAHs was nearly the same when normalized to the organic content of the particles. Gas absorption is expressed by ... 

The Pankow absorption model supposes that gaseous POPs partition into a liquid-like organic film on the aerosol. It uses P,s, the fraction of organic matter in the particle (fom), and the activity coefficient of the solute in the liquid film (yorJ. The latter is apt to vary substantially among different chemical classes of POPs. 

Replacing P with the octanol-air partition coefficient (Koa) improves the absorption model. Advantages of the Koa - based model are twofold Koa is directly measureable as a function of temperature, and the model depends on the ratio of activity coefficients of the solute in octanol and the organic film on the particle (yoct/ yom). This ratio is more likely to be constant among classes of compounds than yom alone. 

Gill, P.S., Graedel, T.E. and Weschler, C.J. (1983) Organic films on atmospheric aerosol-particles, fog droplets, cloud droplets, raindrops and snowflakes. Rev. Geophys., 21, 903-920. 

Semiconductor particles and films have been found to act as heterogeneous photocatalysts in a number of environmentally important reactions. Materials such as Ti02 and CdS have been found to be efficient in laboratory-scale pollution abatement systems, reducing both organic and inorganic pollutants/impurities to harmless species (see [1-35] and references therein). Photocatalysts have been shown to be useful for decomposition of O3 [36], destruction of bacteria [37-39] and viruses [40], purification of air [41], photosplitting of water [42,43] and clean-up of oil spills [44,45]. Photocat-... 

Another way to produce quantized electronic levels is the confinement of carriers in ultrathin organic films in a manner observed previously with inorganic semiconductors [557]. If a free particle (say electron) is completely confined to a layer of thickness Lz (by an infinite potential well) then the energies of the bound states are... 

The research on the structural behavior of emulsion polymers has been greatly influenced recently by colloid chemistry. Surface charges, particle morphology, film formation, flow properties, and interactions with organic solvents and monomers have been studied. Of particular... 

The inverse dependence of these ratios with particle size is also consistent with the organic film hypothesis. Since the iodine is bound... 

It is easy to chimge the polished poly Si hydrophobic surface to hydrc hilic surface by organic surfactant inclut g silica particles during water polish. Because, the wafin surfece was covered with organic film. This organic tilm was easy to remove by anode water rinse and spin dried. 

---