Radical-Induced Generation of Small Silver Particles in SPEEK/PVA Polymer Films and Solutions:  UV−Vis, EPR, and FT-IR Studies

Abstract

The present study is centered on the processes involved in the photochemical generation of nanometer-sized Ag particles via illumination at 350 nm of aqueous solutions and cross linked films containing sulfonated poly(ether ether ketone) and poly(vinyl alcohol). Optical and electron paramagnetic resonance experiments, including electron nuclear double resonance data, proved conclusively that the photogenerated chromophore exhibiting a band with lambda(max) = 565 nm is an alpha-hydroxy aromatic (ketyl) radical of the polymeric ketone. This reducing species was produced by illumination of either solutions or films, but the radical lifetime extended from minutes in the fluid phase to hours in the solid. Direct evidence is presented that this long-lived chromophore reduces Ag(I), Cu(II), and Au(III) ions in solution. A rate constant of k = 1.4 x 10(3) M(-)(1) s(-)(1) was obtained for the reduction of Ag(+) by the ketyl radical from the post-irradiation formation of Ag crystallites. FTIR results confirmed that the photoprocess yielding polymeric ketyl radicals involves a reaction between the macromolecules. The photochemical oxidation of the polymeric alcohol, as well as the formation of light-absorbing macromolecular products and polyols, indicates that the sulfonated polyketone experienced transformations similar to those encountered during illumination of the benzophenone/2-propanol system.

Photopatterning of PMMA Films with Gold Nanoparticles: Diffusion of AuCl4− Ions

“…Alexandrov et al 9 reported the diffusion coefficient (D) of gold atoms in PMMA matrix at 348 K as 2 × 10 -7 cm 2 s -1 , which is quite large compared to other reports about diffusion of metal atoms in polymers. For example, in a detailed paper about diffusion of metal atoms in polymers by Faupel et al, 10 the corresponding diffusion coefficients are given for gold atoms in different polymer matrices (like BPA-PC and TMC-PC) at temperatures about 500 K. These reported values are in the range of 10 , smaller by about 7 orders of magnitude. In contrast to several studies on metal atoms, no corresponding reports are available dealing with diffusion of metal ions (i.e., AuCl 4 -) in polymer matrices.…”

Synthesis, characterisation and antibacterial activity of PVA/TEOS/Ag-Np hybrid thin films

“…Incorporation of silver nanoparticles in PVA polymer matrix could provide antibacterial activity, which is highly desirable in medical field. Various methods including solvent evaporation, electron radiation, UV light, thermal annealing, and in situ chemical reduction have been proposed for the synthesis of materials based on PVA/silver nanoparticles [17][18][19][20][21][22][23][24][25][26][27][28] which yields different morphology and sizes of silver depending on the preparation method. PVA is very sensitive towards moisture and as a result reduces the film strength [16] that is highly undesirable of the films used for biomedical applications.…”

Photoinduced antimicrobial polymer blends with benzophenone as a functional additive

“…However, the antibacterial functions of PVA/BP films are due to formation of triplet radicals and potential production of H 2 O 2 . Photoirradiated BP is well known to attract H atoms from suitable hydrogen donors such as amines or alcohol (i.e., PVA) and form corresponding benzophenone ketyl (BPK) radicals 22. And when exposed to oxygen, the BPK radicals rapidly reoxidize to form BP with an accompanying formation of H 2 O 2 22, 23.…”