Polyvinylpyrrolidone solution preparation

A sample experiment of Ag+iedueing inthe polyvinylpyrrolidone solution as a stabilizer was carried out to determine a possible size of the reduced silver particles. It is found that the silver particle diameter in freshly prepared sols does not exceed 10-15 nm. 

Nanomaterials are a new class of research material that have been tested for enzyme immobilization. Sawicka et al. measured urea concentration by using nanocomposite fibers of urease and polyvinylpyrrolidone (PVP) [146]. Biocomposite nanotibers were prepared by electrospinning a solution in which urease and PVP were dissolved, leading to improvement in response time and sensitivity. 

Figure 96.1 The PVP-I complex. Povidone-iodine (PVP-I), a complex of the polymer polyvinylpyrrolidone and iodine, is a water-soluble powder containing 10% iodine. The available iodine content in the preparation varies from 0.05 to 1%. PVP-I solutions used for disinfection of the skin or wounds have a 1 % iodine content.

Reetz et al. reported on catalytically active solvent-stabilized colloids in propylene carbonate, which were prepared electrochemically or by thermal decomposition of [Pd(OAc)2 assisted by ultrasound. The colloidal particles had sizes of 8 to 10 nm, as determined by TEM. After addition of aryl bromide, styrene, and base to the colloid solution, satisfactory conversions were obtained within reaction times of 5-20 h. Isolation of the particles stabilized by propylene carbonate was not possible, however [16]. The same authors also reported Suzuki and Heck reactions with electrochemically prepared Pd or Pd/Ni colloids stabilized by tetraalkylammonium, as well as polyvinylpyrrolidone (PVP)-stabilized palladium colloids prepared by hydrogen reduction (Table 1) [17]. It was assumed that the reaction occurs on the nanopartide surfaces. 

Composites with one-dimensional structure can also be fabricated by template-free method. They are formed via an in situ synthetic process. For instance, Ag/PPy nanocables have been prepared through the redox reaction between pyrrole and silver nitrite in aqueous solution in the presence of polyvinylpyrrolidone. During the reaction process, the formation of Ag nanowires and the polymerization of a pyrrole sheath were proceeded simultaneously. The as-synthesized Ag/PPy nanocables displayed a coaxial nanostructure with a dark core and a lighter sheath (Fig. 4.3I-J) (Chen et al., 2005). The diameter of the Ag nanowire core was about 20 nm, while the outer diameter of PPy sheath reached about 50 nm. 

Blends or composites were also prepared especially by Hirano in the same way as mentioned previously for chitin [63], Other systems were proposed in the literature and listed previously [1, 2], Some of them are described in detail, for example, chitosan/ polyamide 6 and chitosan/polyamide 66 [119,120], chitosan/cellulose using a common solvent [121,122], chitosan/poly(oxyethylene) (POE) [123], chitosan/polyvinylpyrrolidone (PVP), chitosan/polyvinyl alcohol (PVA) [123,124], chitosan/polycaprolactone [124-126], chitosan/ collagen [127], chitosan/PHB [128], and chitosan/cellulose fibres [129]. In some case, the polymers are crosslinked in the blends [130]. Hydrogels or films have been prepared by mixing chitosan solution with monomers, initiator and cross-linker followed by copolymerization [131,132]. 

PC is the material used for preparing the majority of commercially available track-etched membranes. It is characterized by high sensitivity to tracking and it does not require UV sensitization. However, PC is soluble in organic solvents and has low wettability in aqueous solutions. Its hydrophilicity can be increased by impregnation with polyvinylpyrrolidone (29). 

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