Negative optical absorption and up-energy conversion in dendrites of nanostructured silver grafted with alpha/beta-poly(vinylidene fluoride) in small hierarchical structures

Abstract

We report that a negative optical absorption arises in a sharp band at 325 nm (energy h nu(2)) in a nanostructured silver (n-Ag) doped poly(vinylidene fluoride) (PVF2) in a hybrid nanocomposite of films (similar to 100 mu m thickness). Two polymorphs alpha- and beta-PVF2 are co-stretched through the n-Ag crystallites in dendrites of hierarchical structures. A critical 0.5 wt% n-Ag dosage promotes this band of extinction coefficient to be enhanced by as much as 2.009 x 10(3), i.e. a 30% value in the Ag-surface plasmon band 350-650 nm (h nu(1)). An electron donor Ag (4d(10)5s(1)) bonds to an electron accepter moiety CF2 of PVF2, it tunes a dielectric field and sets up an up-energy conversion of the plasmon band. The FESEM and HRTEM images reveal fcc-Ag dendrites entangled with in-built PVF2 surface layers (23 nm thickness). The IR phonon bands show how a alpha -> beta-PVF2 transformation propagates onto a nascent n-Ag surface and how it is raised-up in small steps of 0.1 wt% and up to 5.0 wt%. In a model scheme, we illustrate how a rigid core-shell of a capsule conducts a new transfer mechanism of the energy to a cold surface plasmon (core) in a coherent collision, so as to balance a net value h nu(2) = h(nu(3) - nu(1)). It absorbs light in a weak band at 210 nm (h nu(3)) in a pi -> pi* electron transition in the C=C bonds of the PVF2 (shell), and results in a negative absorption in a coherent excitation of the energy-carriers. A light-emitter on absorption over a wide range of wavelengths (200-650 nm) offers a unique type of energy-converter.