BARC/PUB/2018/0330

 
 

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

 
     
 
Author(s)

Phule, A. D.; Ram, S.; Shinde, S. K.; Tyagi, A. K.; and others
(ApCD)

Source

Journal of Physics and Chemistry of Solids, 2018. Vol. 115: pp. 254-264

ABSTRACT

We report that a negative optical absorption arises in a sharp band at 325 nm (energy hν2) in a nanostructured silver (n-Ag) doped poly(vinylidene fluoride) (PVF2) in a hybrid nanocomposite of films (~100 μm thickness). Two polymorphs α- and β-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  103, i.e. a 30% value in the Ag-surface plasmon band 350–650 nm (hν1). An electron donor Ag (4d105s1) 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 (2–3 nm thickness). The IR phonon bands show how a α → β-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 hν2 = h(ν3  ν1). It absorbs light in a weak band at 210 nm (hν3) in a π → π* 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-convert

 
 
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