Surface UV irradiation

Krotkov, N. A., P. K. Bhartia, J. R. Herman, V. Fioletov, and J. Kerr, Satellite Estimation of Spectral Surface UV Irradiance in the Presence of Tropospheric Aerosols. 1. Cloud-Free Case, J. Geophys. Res., 103, 8779-8793 (1998). 

Krotkov, N.A., Bhartia P.K, Herman J.R., Fioletov V. And Kerr J., Satellite estimation of spectral surface UV irradiance in the presence of tropospheric aerosols 1. Cloud free case, J. Geopys. Res., 103,8779-... 

Electrochemical reactions with use of a sacrificial cathode [121], which have not yet been reported in relation to phthalocyanine, could have theoretical success in the synthesis of PcM. The cathode dissolution takes place due to the action of free radicals formed in solution near the cathode surface [121] in the case of the synthesis of Pc (which is formed on the cathode surface), UV irradiation of the reaction mixture could serve as a source of free radicals. 

Figure 18 UV photopatterning method. The molecular structure of a photocleavable SAM formed on glass surfaces. UV irradiation through masks placed on top of SAM-modified microchannels leads to the production of hydrophilic carboxylate groups in the irradiated regions (Zhao et al, 2001).

Surface modification of iPP in vapwurs of halogen compounds (Novak Chodak, 2001 Novak Chodak, 2001 Kharitonov, 2000 Novak Chodak, 2001 Hruska Lepot, 2000 Carstens et al., 2000) under UV irradiation represents an efficient method for the increase of the adhesive properties. The ptresented method is based on the influence of the UV radiation and vapours of phosphoiyl chloride on the iPP surface. UV-irradiation results in a faster decomposition of the halogen compwimd and leads to the UV-oxidation of the surface of polymer. Surface modification of iPP vapours of phosphoryl chloride imder UV irradiation... 

If the diacetylene is solid-state polymerized, dissolved and respread on the subphase, a monolayer is produced with much lower 11 and viscosity than the corresponding surface polymerized material. This illustrates the fact that in some cases polymer properties can be strongly influenced by the polymerization mode, and if specific material parameters are required, it may be an advantage to use one polymerization technique in preference to another. However, in contrast, almost identical U-A behaviour has been reported for structure (10) with n = 12, m = 8 when polymerized on the subphase surface (UV irradiation for 1 h at a surface pressure of 10 mN m under a nitrogen atmosphere), and when prepolymerized in solution (using 2,2 -azoisobutyronitrile in toluene at 60 for 20 h) [27]. This emphasises the difficulty in predicting polymer properties each material system will exhibit characteristic behaviour, depending not solely on the molecular structure, but also on primary factors such as the mode of polymerization and the specific experimental conditions. 

UV irradiation on a polymer surface produces chemical modification as well as wettability and bondability improvement. It causes chain scission and oxidation on polymer surfaces. -iven in the presence of an inert gas [45]. Carbonyls are found to be introduced onto polyethylenes on UV irradiation. Sivram et al. [46] have used photochemical treatments for surface modification of polymers. They have generated surfaces of vaying surface energies by simple organic reactions. 

When the films were treated in either an oxygen plasma environment or under UV/ozone irradiation, the rates of oxidation were faster for the plasma process. Irradiation of chitosan solution showed that UV/ozone induces depolymerization. In both plasma and UV/ozone reactions, the main active component for surface modification was UV irradiation at a wavelength below 360 nm [231]. 

To date, numerous radical-induced hydrosilylations of terminal olefins or acetylenes have been reported for the H-terminated Si(l 11) surfaces. These reactions are mainly performed by using thermal conditions, UV irradiation, or electrochemistry. More recently, a very mild method was developed for the attachment of high-quality organic monolayers on crystalline silicon surfaces. 

E.coli recA y.luxCDABE strain were grown for 16-18 hours at 37°C in LB-broth in the presence of 20 pg/ ml of ampicillin. Immediately before the experiment the culture was diluted 1 20 by fresh culture medium and incubated until early log-phase. The grown biomass was mixed with AR solutions in final concentrations of ICfs, ICH n ICfs M, with used for their dilution with distilled water (control) and incubated for 60 minutes. The luminescence intensity of UV-irradiated E.coli recA lux and intact specimens were registered by plate bioluminometer LM OIT (Immimotech, Czech Rep.) in a real time. The number of viable cells was determined from the colony-forming units (CFU) on a surface of a LB-agar after the subsequent incubation within 24 hours at 37 °C. A quantitative estimation of an induction of the SOS-system calculated on formula... 

Since BaTi40g and Na2TieOi3 have a pentagonal prism tunnel and a rectangular tunnel structure, respectively, we have paid attention to the role of the tunnel structures in photocatalysis. A barium titanate, Ba4Tii303o, in a series of Ba-Ti titanates was chosen as a representative with non-tunnel structure, and we have compared the photocatalytic activity and the ability for the production of surface radical species with uv irradiation between the tunnel and the non-tunnel titanates. 

Laser microprobe MS (LMMS) can be used for direct analysis of normal-phase HPTLC plates [802,837]. Kubis et al. [802] used polyamide TLC plates polyamide does not interfere with compound identification by the mass spectrum, owing to its low-mass fragment-ions (m/z < 150). LMMS is essentially a surface analysis technique, in which the sample is ablated using a Nd-YAG laser. The UV irradiation desorbs and ionises a microvolume of the sample the positive and negative ions can be analysed by using a ToF mass spectrometer. The main characteristics of TLC-LMMS are indicated in Table 7.84 [838],... 

UV light in a second step. In later work reported by Tazuke, Kimura et al. (6-8) successful photograftings on the polymer surface of thin films (polyethylene, polypropylene and polystyrene) were achieved with various monomers. In this work, grafting was induced by UV irradiation through the film which was in contact with a solution containing initiator and monomer. The method is slow and - in addition to surface grafting - large amounts of homopolymer are formed. 

Method (1) is a slow process which requires several minutes of UV-irradiation for grafting a surface layer of an acrylic monomer onto the polymer substrate. 

Method (2) is a fast and efficient process which requires only 5 to 10 sec. UV-irradiation for surface grafting of the polymer substrate. About 2/3 of the polymer formed is grafted (about 1/3 is homopolymer). 

In our study we have found that UV-light greatly accelerates the rate of ozone attack at the polypropylene surface. Presented results were undertaken to determine mechanism of the photo-oxidation of polypropylene surface upon UV-irradiation of polymer films in ozone. 

The carbonyl index obtained from transmission and ATR spectra of PP films UV-irradiated (L2) in ozone shows that the concentration of carbonyl groups at the surface is 8 times higher than in a bulk. 

The most obvious change in an oxidation of the PP surface results in an increase in the wettability of the polymer. The PP shows a great decrease in contact angle with water or water/alcohol (3 1) after treatment with ozone or ozone-UV irradiation or atomic oxygen (Table 1). 

A PP sample after ozonization in the presence of UV-irradiation becomes brittle after 8 hrs of exposure, whereas the same effect in ozone is noticeable after 50-60 hours.Degradation of polymer chain occurs as a result of decomposition of peroxy radicals. The oxidation rapidly reaches saturation, suggesting the surface nature of ozone and atomic oxygen against of PP as a consequence of limited diffusion of both oxygen species into the polymer. Ozone reacts with PP mainly on the surface since the reaction rate and the concentration of intermediate peroxy radicals are proportional to the surface area and not the weight of the polymer. It has been found that polyethylene is attacked only to a depth of 5-7 microns (45). 

Polyvinyl chloride has been modified by photochemical reactions in order to either produce a conductive polymer or to improve its light-stability. In the first case, the PVC plate was extensively photochlorinated and then degraded by UV exposure in N2. Total dehydrochlorination was achieved by a short Ar+ laser irradiation at 488 nm that leads to a purely carbon polymer which was shown to exhibit an electrical conductivity. In the second case, an epoxy-acrylate resin was coated onto a transparent PVC sheet and crosslinked by UV irradiation in the presence of both a photoinitiator and a UV absorber. This superficial treatment was found to greatly improve the photostability of PVC as well as its surface properties. 

When the photostabilization of a polymer material is to be obtained through such a surface treatment process, it is all important to make sure that the protective effect will last throughout the service life and therefore to ensure a long-term adhesion of the coating onto the substrate. This can be best achieved by promoting a grafting reaction between the two elements (20). For that purpose, the photoinitiator was partly incorporated in the top layer of the PVC plate by a surface treatment with an acetone solution. Upon UV-irradiation of the resin-coated sample, the following reactions are expected to occur ... 

We have investigated the photochemical behavior of polymer 1 under various conditions in air and found that UV irradiation of the thin liquid films with a thickness of less than 10 pm, indeed produced transparent solid films. However, when the films with a thickness of 100 pm were irradiated with a mercury lamp, cross-linking leading to the solid films occurred only on the surface of the films, but inside remained as liquid after prolonged irradiation. In thses cases, tha surface of the films was found to be slightly opaque. Therefore, most of the light would not be transmitted to the inside of the films. 

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