TITLE:
The Signatures of Acid Concentration on the Optical Band Gap and Associated Band Tails of Chitosan from Shrimp for Application in Optoelectronic Devices
AUTHORS:
Edwin Atego, John O. Agumba, Godfrey O. Barasa
KEYWORDS:
Chitosa, Optical Band Gap, Urbach Energy, Absorbance Spectrum, Tauc Plot
JOURNAL NAME:
Advances in Chemical Engineering and Science,
Vol.12 No.1,
December
9,
2021
ABSTRACT: Over the recent years, the global increase of electronic wastes from
electrical and electronic devices (e-wastes) has been on an alarming trend in
quantity and toxicity and e-wastes are
non-biodegradable resulting in its cumulative increase over time. Changes in
technology and unrestricted regional movement of electrical devices have facilitated
the generation of more e-wastes leading to high levels of air, soil and water
pollution. To address these challenges, biodegradable organic components such
as chitosan have been used to replace their inorganic counterparts for
optoelectronic device applications. However, in-depth knowledge on how such
materials can be used to tune the optical properties of their hybrid
semiconductors is unrivaled. Thus, systematic studies of the interplay between
the preparation methods and optical band
gap and Urbach energy of such organic components are vital. This study has thus
been dedicated to map out the effect of acid concentrations during
chitosan extraction on the corresponding optical band gap and Urbach energy
with a view to improving its applications in optoelectronic devices. The, 1.0 to
2.5 molar hydrochloric acid (HCl) was used for 12 hours at room temperature
during demineralization and 2.0 molar sodium hydroxide (NaOH) during
deprotonation processes. The absorbance spectrum of the samples was collected
by UV-Vis spectrophotometer and band gap energies were analyzed by performing
Tauc’s plot. This study revealed that the energy band gap of chitosan extracted
from 1 M HCl, 1.5 M HCl, 2.0 M HCl and 2.5 M HCl were 3.72 eV, 3.50 eV, 3.45 eV
and 3.36 eV respectively. Furthermore, the Urbach energy of chitosan extracted
from 1 M HCl, 1.5 M HCl, 2.0 M HCl and 2.5 M HCl were 0.60496 eV, 0.5292 eV, 4724
eV and 0.2257 eV, respectively.