A novel polymer composite with a small optical band gap: New approaches for photonics and optoelectronics

Abstract

In this article, a novel approach is presented for the preparation of small band-gap polymer composites. The intensity of the surface plasmon resonance (SPR) peak increased from 0.64 to 3.2 for the chitosan-silver nitrate sample containing 1 wt % titanium dioxide (TiO 2 ). In the cases of 3 and 5 wt % added TiO 2 particles, the SPR peak disappeared. A wide shift of the absorption coefficient from 4.36 to 0.93 eV was observed. The smallest optical band gap of about 0.98 eV was achieved for the sample containing 3 wt % TiO 2 filler. The wide shift in the optical band gap was interpreted on the bases of the formation of metal-induced gap states between the metallic silver particles and the TiO 2 structure. A novel approach was achieved that was an alternative method to Tauc's semi-empirical model for band-gap estimation. The optical dielectric loss parameter for the band-gap study was easily calculated and analyzed, whereas it unfolded a deep knowledge from the physics point of view. The established quantum mechanical expression revealed a strong relationship between the energy band gap and the optical dielectric loss parameter. The scanning electron microscopy results show the leakage of white aggregated silver particles and distinguishable intense peaks of metallic silver particles between 3 and 3.3 keV appearing in the energy-dispersive X-ray spectrum.

New Method for the Development of Plasmonic Metal-Semiconductor Interface Layer: Polymer Composites with Reduced Energy Band Gap

“…This may be related to the fact that the reduced silver nanoparticles attach to or enter the alumina structure. In our previous works, similar effect on the broadening of the SPR peaks due to the adsorption silver particles on TiO 2 structure has been observed [14]. This phenomenon can be more enlightened by study of band gap.…”

“…Again, from the quantum-mechanics viewpoint, the optical dielectric loss is also established to be correlated with electrons and the density of states near the Fermi energy level. Here, it is also shown that only certain electrons near the Fermi surface can participate to conduct once they absorb photon energies [14,28]. The type of electronic transition and the optical band gap can be determined by comparison of plots obtained from Tauc's equation to those of optical dielectric loss [14,25].…”

“…Polymers, such as CS, poly(ethylene oxide) (PEO), poly(2-ethyl-2-oxazoline) (POZ), and poly(vinyl pyrrolidone) (PVP), containing polar 2 Journal of Nanomaterials groups have been introduced as a polymer solvent for the silver salts to be dissolved [12]. Earlier works established that lone-pair electrons on the functional groups of polar polymers are responsible for the complexation and reduction of silver ions to silver nanoparticles [13][14][15][16]. This phenomenon (i.e., Ag + → AgO) limits the application of silver-based ionconducting polymer electrolytes in electrochemical devices [17,18].…”

“…This phenomenon (i.e., Ag + → AgO) limits the application of silver-based ionconducting polymer electrolytes in electrochemical devices [17,18]. However, this phenomenon may be beneficial for the preparation of polymer nanocomposites with small optical band gaps [14]. Alumina (Al 2 O 3 ) has recently received considerable attention in materials science because it is key material in many applications, such as metal-oxide semiconductor devices, dye-sensitized solar cells, and corrosion protection [19].…”

“…To precisely specify the types of electronic transition in the samples, optical dielectric loss must be examined. In our previous works [14,25], it is established that the optical dielectric loss is the only parameter that can be used successfully to study the optical band gap and identify the dominant type of electronic transition. Journal of Nanomaterials The optical dielectric function is reported to be closely correlated to the electron-photon interaction, connecting the solid electronic structure to the physical process of interband transition.…”