Powders and Films

Sorption isotherms, measurements of the weight of water adsorbed by a protein sample tis a function of the partial pressure of water in the vapor phase at constant temperature, are among the earliest descriptions of protein hydration [for references to early work, see Bull and Breese (1968a) and McLaren and Rowen (1951)]. 

A typical isotherm, for lysozyme, is shown in Fig. 1. There is a knee at 0.05—0.1 h (g of water per g of protein, mass ratio) and a strong upswing to the isotherm near 0.25 h. Sorption measurements on model polymers and chemically modified proteins (see Watt and D Arcy, 1976  

Rochester and Westerman, 1976a,b, 1977 and references cited therein) suggested the molecular basis for the sigmoidal shape of the isotherm. Below the knee water interacts principally with ionizable protein groups. In the plateau region, between 0.1 and 0.25 h, water binds to polar sites. Above 0.25 h water condenses onto the weakest binding sites of the protein surface to complete the hydration process, and at sufficiendy high water content (water partial pressure) the system passes into the solution state. 

Methods of measurement have been reviewed (Kuntz and Kauzmann, 1974 McLaren and Rowen, 1951 Poole and Finney, 1986). Hydration levels are often established by isopiestic equilibration of protein samples against concentrated salt or sulfuric acid solutions of known water vapor pressure. A difficulty with this method is the long equilibration time, possibly several days, which is likely a consequence of the sample size (typically 100 mg or larger). Wilkinson et al. (1976) have described an automated sorption isotherm device transducers are used for the measurement of vapor pressure and sample weight. Gascoyne and Pethig (1977) used a resonating quartz crystal microbalance to study the hydration of bovine serum albumin and other proteins. Rao and Bryan (1978) 

The mass rado h is commonly used in describing protein hydration. Hydration, however, should depend more closely on protein surface than on volume or mass. Most of the data described in this review are for small globular proteins, for which weight and surface-based measures should be similar. Comparisons of proteins of much different size may need to take into account surface area, compactness, and domain size. 

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The ease of sample handling makes Raman spectroscopy increasingly preferred. Like infrared spectroscopy, Raman scattering can be used to identify functional groups commonly found in polymers, including aromaticity, double bonds, and C bond H stretches. More commonly, the Raman spectmm is used to characterize the degree of crystallinity or the orientation of the polymer chains in such stmctures as tubes, fibers (qv), sheets, powders, and films... 

Chiu, C. Y. Chiang, A. S. T. Chao, K. J. 2006. Mesoporous silica powders and films—Pore size characterization by krypton adsorption. Microporous Mesoporous Mater. 91 244-253. 

Sample Preparation. PBS-MP20, obtained in powder form from Mead Chemical Co., was the primary source of the samples used in this study. A portion of the MP20 powder was dissolved in 2-methoxyethyl acetate (Mead Chemical) and films were spin-coated on silicon wafers. Films were baked at 120 C for 1 hour prior to irradiation. MP20 samples, both in powder and film form, were irradiated under vacuum at 30 C in a Co source. Films were spun from methoxyethyl acetate solutions of the irradiated powders. These films were also baked at 120 C for 1 hour. The above procedure created two types of degraded MP20 samples (1) those irradiated in film form and (2) those irradiated in powder form. The first type of films were designated as IF-type films. Films spun from solutions of the irradiated powders were designated as IP-type films. 

Sensitization of Ti02 powders and films for water photolysis is still an attractive and as yet unsolved problem in the construction of an artificial photosynthetic system for creating energy sources from solar energy and water. 

The first commercial application of photocatalysts has started to clean our environment by Ti02 powders and films. In order to utilize photocatalysts for solar energy conversion, sensitization of large bandgap semiconductors is important. The most difficult task for an artificial photosynthetic system is to establish visible light-induced charge separation with minimum back charge recombination. 

Application of metal alkoxides for the preparation of niobates and tanta-lates in the form of both powders and films has been first performed by Dand-liker [475]. In our study of hydrolysis of LiOEt andNb(OEt)5 solutions in anhydrous EtOH, it was demonstrated that although the freshly prepared powder is amorphous for X-ray, it already contains microcrystallites of LiNb03 [1778]. In addition to conventional techniques, the properties ofthe powder in the course of thermal treatment were studied by the second harmonic generation ofthe laser beam, which is a sensitive technique for detection ofnoncen-trosymmetric phase the first signal was registered at 350°C. 

Figure 20.3 Digital photographs of sol-gel-derived materials monoliths, powders, and films. (See color insert.)...

Heat curing epoxy systems may consist of one or two components. The nomenclature is similar to that employed with the room temperature curing adhesives (e.g., resin component, curing agent component, 2Ksystem, etc.). Many heat curing epoxy adhesives systems are liquids or pastes. However, heat curing systems also can be processed into solid adhesive forms (e.g., powders and films). This chapter describes the paste and liquid formulations solid adhesive forms are considered separately in Chap. 13. 

Rare earth silicates exhibit potential applications as stable luminescent materials for phosphors, scintillators, and detectors. Silica and silicon substrates are frequently used for thin films fabrication, and their nanostructures including monodisperse sphere, NWs are also reliable templates and substrates. However, the composition, structure, and phase of rare earth silicates are rather complex, for example, there are many phases like silicate R2SiOs, disilicate R2Si207 (A-type, tetragonal), hexagonal Rx(Si04)602 oxyapatite, etc. The controlled synthesis of single-phase rare earth silicate nanomateriais can only be reached with precisely controlled experimental conditions. A number of heat treatment based routes, such as solid state reaction of rare earth oxides with silica/silicon substrate, sol-gel methods, and combustion method, as well as physical routes like pulsed laser ablation, have been applied to prepare various rare earth silicate powders and films. The optical properties of rare earth silicate nanocrystalline films and powders have been studied. 

Figure 8.15 Powder and film regions at 100 W. Adapted from Ref. 9.

Sasisekharan (1959a) has recently published a more detailed X-ray diffraction study of powders and films of poly-L-proline II, including an analysis of optical diffraction data. This elegant study confirms in all essential details the structure proposed by Cowan and McGavin. 

Figure 2. The NGR spectra of the composite powder and film at room temperature.

Sensitizing nanolayers are prepared with the thickness equal to the nanocrystal size d [5], and by using special techniques for nanocrystal ordering [6]. Initial silica, optical glasses (Fig. 1), alumina, crystals, powders, and films produced in standard ways were tested as substrate, matrice components and reference samples. A part of the samples was y-irradiated at room temperature (RT) [4]. 

Figure 3. PL of pure silica glass (KU), powder and films (left). NLO spectra of film composition with KU substrate, CaFi-matrix and CdSe nanocrystals, detected before (1) and after y-irradiation (2) (right).

Mechanistic conclusions from the work on gold and silver are facilitated by the low exchange activity of these metals. Therefore, Hirota s (45) research with nickel powders and films—showing a high exchange activity—do not provide very important data in this respect consequently only brief mention of these results will be made here. 

This work gives results about the characterisation of Sn02 materials, pure and W -added, prepared via a sol-gel route. The materials were characterised as powders or thick films using a variety of techniques. The powder and thick film morphology was analysed by TEM, HRTEM and SEM, the powder texture by volumetric measurements. Powders and films made by regularly shaped and nano-sized particles, even after thermal treatments at 850 °C were obtained. Electrical and FT-IR spectroscopic measurements were employed on films and powders, respectively. Electrical and FT-IR measurements show that W lowers the response of the tin oxide towards CO, but enhances its ability to sense NO2. The surface species formed by CO and NO2 interaction were carefiilly investigated by FT-IR spectroscopy. 

It can be used on polymers In chip, film, or powder form, and amounts required are small. In the range 10 to 50 mg for powders and film, and up to 100 mg for fibers or chips. 

The authors have studied the effect of polymer powders and films on corrosion rate of steels and their physical-chemical properties in aqua solutions of electrolytes. The experimental method was as follows. 

Figure 2.8 X-Ray diffraction pattern for (powder and film) a-chitin. Source Reproduced with permission from Gonzalez-Campos JB, Prokhorov E, Luna-Barcenas G, Mendoza-Galvan A, Sanchez IC, Nuno-Donlucas SM, Garcia-Gaitan B, Kovalenko Y. J Polym Sci B Polym Phys 2009 47 932 [5]. Copyright 2009 John Wiley and Sons, Inc.

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