In this study, the chitin and chitosan were extracted from shrimp shell through two-steps acid and alkaline treatment. The shrimp shell was deproteinized by 1 M of sodium hydroxide and demineralised by 1%, 2%, 3%, 4% and 5% of hydrochloric acid, respectively. The produced chitin was characterized by FTIR and FESEM. FTIR depicted that the chitin extracted from shrimp shell was in a-chitin isomorph. The surface morphology of chitin was found to increase with an increase in acid concentration. The chitosan film with rod-like micro-structure was produced when dissolved in 2% of acetic acid. It was shown that chitosan with 65% of DD was successfully produced using this chemical route.
Conventional piezoelectric materials from piezoceramic and polymer are non-renewable and could be toxic in nature, which limit its application in biomedical application. Chitosan, which is a natural polysaccharide, has the potential to be used as piezoelectric biomaterial which may provide the solution for toxicity, non-biodegradability and non-biocompatibility issues of conventional piezoelectric materials. Chitosan may be produced sustainably through extraction from fungal cell walls. This study aims to characterize chitosan extracted from fungi Aspergillus oryzae for piezoelectric application. A. oryzae was cultivated on modified Sabouraud dextrose broth medium. Alkaline treatment was performed on fungal biomass using 1 M NaOH for extraction and deacetylation of chitosan at 100 °C for 1 hour. Fourier transform infrared spectroscopy results showed that the broad absorption band that corresponds to hydrogen bonded O-H stretching vibrations overlapped with N-H stretching band. X-ray diffraction analysis confirmed the semicrystalline nature of the chitosan sample. Piezoelectric properties can be attributed to intrinsic molecular polarization arising from the noncentrosymmetric crystal structure.
The electrochemical performance of Al-air cell employing seawater and NaCl electrolyte of various concentrations has been investigated. The open circuit voltage and discharge capacity of the cell correlate well with the electrolyte conductivity data. Using 4 M NaCl electrolyte which possesses the highest conductivity, the Al-air cell registers an open circuit potential (OCV) of 1.1 V and demonstrates discharge capacity of 250 mAh, rated at 1 mA. Upon employing seawater, the OCV reduced to 0.68 V and discharge capacity decreased to 150 mAh. However, utilizing an exposed cell configuration which mitigates the hydroxide gel water binding effect, the Al-air seawater cell performance is greatly enhanced until almost compatible to Al-air cell employing 4 M NaCl.
Improvement in sensing layer properties of quartz crystal microbalance (QCM) sensors are crucial in developing gas sensors with high sensitivity and selectivity. In this work, we study the use of chitosan thin film as the sensing layer on a QCM sensor to identify the presence of volatile organic compounds specifically isopropyl alcohol (IPA). The effect of chitosan dissolved in different acetic acid concentrations towards QCM overlay with chitosan sensing performance were studied. Characterization work on chitosan thin film at different acetic acid concentrations (1.0, 1.5, 2.0, 2.5% (v/v)) were performed by using FTIR and FESEM. Higher acid concentration led to a higher degree of protonation which results in a more progressive solubilization of chitosan and promotes smoother film. For chitosan layer dissolved in 2% acetic acid , the highest resonance frequency shift (99.3 Hz) was observed during the adsorption of the analyte gas molecules on QCM sensors. This can be explained by the increase in chitosan solubility and protonation. This indicates that difference acid concentration in chitosan dissolution affects the sensing performance during the presence of the analyte gas.
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