To overcome these challenges, researchers enhanced chitosan with graphene oxide (GO) and titanium dioxide. These additions improve conductivity, increase surface area, and provide active sites for gas interaction, key for building more efficient sensors.
The goal was to create and test a chitosan-GO-TiO2 nanocomposite that could reliably detect carbon dioxide (CO2), methane (CH4), and water vapor (H2O). These gases are relevant to environmental monitoring, industrial safety, and humidity control.
Biodegradable Chitosan
Chitosan is structurally similar to cellulose, with some hydroxyl groups swapped out for amino groups. These functionalities allow chitosan to interact with different gas molecules, but it doesn't have the sensitivity and selectivity required for sensors.
By integrating graphene oxide, with its high surface area and abundant oxygen-containing groups, and titanium dioxide, the functionalized chitosan is able to easily adsorb gases and remain stable despite a changed chemical makeup.
Previous studies have shown that hybrid films combining chitosan with such nanomaterials improve mechanical strength, electrical conductivity, and selectivity. This new research builds on that foundation, using computational modeling and lab-based experiments to understand and test how the nanocomposite behaves at the molecular level.
Dual Experimental Approach
The team used density functional theory (DFT) simulations and other experimental techniques to assess the composite's potential. The DFT calculations were used to predict electronic properties like dipole moments, the HOMO-LUMO energy gap, and reactivity, all of which are important for understanding how well the material interacts with different gases.
They also applied Non-Covalent Interaction (NCI) and Quantum Theory of Atoms in Molecules (QTAIM) analyses to map the types and strengths of gas-molecule interactions, focusing particularly on weak forces like hydrogen bonds and van der Waals interactions.
Having assessed the chitosan composites' potential as sensors, the team produced the material using a modified Hummers method. They mixed the chitosan, titanium dioxide, and graphene oxide in solution and cast the resulting solution onto sensor substrates.
After production, the researchers used Fourier Transform Infrared (FTIR) spectroscopy to confirm the presence of key functional groups and interactions. Finally, the material was exposed to the target gases under ambient conditions to assess changes in electrical or optical signals.
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Clear Responses to Methane and Moisture
The findings clearly showed that adding GO and TiO2 to chitosan significantly altered the material’s electronic properties. The HOMO-LUMO energy gap decreased, indicating enhanced conductivity, an important factor for responsive sensors. The improved reactivity measures suggested better charge transfer, increasing the likelihood of gas detection.
Methane and water vapor emerged as the gases with the strongest and most favourable interactions, as confirmed by both computational adsorption energies and experimental data. These gases showed more negative adsorption energy values, indicating strong but reversible binding. This is ideal for sensors that need to reset after each use.
There was less sensitivity to carbon dioxide, however, which interacted more weakly with the nanocomposite. FTIR results supported these findings, revealing the functional groups involved in gas binding matched those predicted in the models.
Importantly, the interactions were primarily physical rather than chemical, which means the sensor doesn’t degrade or lose performance over time, which indicates the material would be resilient to repeated, long-term use.
A Greener Path for Gas Sensors
The study confirms that the Cs/GO/TiO2 nanocomposite offers real potential as a multi-gas sensor, particularly for detecting methane and water vapor. The results suggest, through a combination of theoretical modelling and lab testing, that this biopolymer-based material is effective, environmentally responsible, and economically viable.
Its ability to operate under ambient conditions, without permanent material changes, gives it strong appeal for use in environmental monitoring, industrial safety systems, and moisture-sensitive applications
Journal Reference
El-Srougy A.G., et al. (2025). Application of Cs/GO/TiO2 as a gas sensor. Scientific Reports 15, 31182. DOI: 10.1038/s41598-025-14525-8, https://www.nature.com/articles/s41598-025-14525-8