Enhancement of polymer endurance to UV light by incorporation of semiconductor nanoparticles

Abstract

Improvement of polyvinyl alcohol stability against ultraviolet (UV) illumination is achieved by introducing cadmium sulfide (CdS) nanoparticles into the polymeric matrix. Enhancement of stability is analyzed by optical characterization methods. UV protection is achieved by diminishing the probability of photo-activated formation of defects in polymer. The sources of polymer protection are the lowering of the efficiency of polymer excitation via partial absorption of incident light by the embedded nanoparticles as well as the de-excitation of the macromolecules that have already absorbed UV quanta via energy drain to nanoparticles. Within the nanoparticles, the energy is either dissipated by conversion to the thermal energy or reemitted as visible-range photoluminescence quanta.

Size-Dependent Effects in Optically Detected Magnetic Resonance Spectra of CdS Nanocrystals

“…Similar PL of CdS nanoparticles has been repeatedly observed earlier and attributed to defect/surface states. 18,19,[23][24][25][27][28][29]45,46 As is seen in Figure 2a, as nanoparticle size decreases, the PL band remains in the same spectral region while its shape is somewhat modified. It should be noted that there is no regularity in the changes of PL shape; probably, the differences are caused by individual features of the studied ensembles of NCs.…”

Highly Flexible and Visibly Transparent Poly(vinyl alcohol)/Calcium Zincate Nanocomposite Films for UVA Shielding Applications As Assessed by Novel Ultraviolet Photon Induced Fluorescence Quenching

“…However, PVA is also known to undergo photochemical transformations under the influence of high energy radiations. 14 This distinctive feature of PVA can also affect the properties of PVA/nanofiller composites, since material characteristics of semiconductor, especially optical absorption, emission, and electronic conduction, are known to be influenced significantly by the extent of passivation of under coordinated surface atoms of the semiconductor by organic ligands in addition to the chemical nature of passivating entities. 15 Calcium zincate (Ca 0.2 Zn 0.8 O) semiconductors with its wide band gap energies are totally transparent in the visible regions and are excellent UVA shielding materials owing to their direct band gap absorptions.…”