Detecting VOCs is essential in environmental monitoring and industrial safety, but existing optical sensors often rely on liquid crystals, zeolites, or nanoparticles. These materials are complicated to produce and often have slow response times.
Cellulose acetate offers an alternative. It’s biodegradable, optically transparent, chemically versatile, and forms stable films.
Its semi-polar nature and controlled moisture uptake make it particularly well-suited for VOC detection through swelling-induced changes in diffraction efficiency.
A Hologram in Polymer Film
The sensor was created by dissolving cellulose acetate in a solvent, along with acrylamide (monomer), MBA (crosslinker), TEA (photoinitiator), and erythrosine B (dye).
The solution was cast onto a glass substrate using a doctor blade and cured to form a thin photopolymer film.
A holographic transmission grating was then recorded using a two-beam interference setup with 532 nm laser light. The process was initiated in under a second and reached a diffraction efficiency of ~70 % within 17 seconds.
Sensing Mechanism and Optical Response
When exposed to VOC vapors, specifically acetone, isopropyl alcohol (IPA), and tetrahydrofuran (THF), the polymer matrix swells, altering the grating’s periodicity. This disrupts Bragg diffraction conditions, leading to a measurable drop in diffraction efficiency.
The sensor exhibited distinct sensitivity across the three compounds: acetone showed a 29.52 % decrease in diffraction efficiency, IPA showed a 12.09 % decrease, and THF showed a 15.90 % decrease.
Response times for each compound were fast. Results were obtained within 99 seconds for acetone, 202 seconds for IPA, and 170 seconds for THF.
Full recovery was achieved in all cases, with an average recovery time of 2.8 minutes.
The researchers simulated vapor diffusion using COMSOL, based on Fick’s law. They found that swelling ratios peaked at over 500 % at 2700 mol/m3 acetone concentration, aligning with experimental data.
Profilometry confirmed physical swelling: film thickness increased from 2.1 µm to 18 µm after acetone exposure, while surface roughness (Sa) nearly doubled.
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Optical microscopy also revealed structural changes in the polymer surface after exposure.
The sensor demonstrated higher selectivity for acetone over IPA and THF, with mean selectivity coefficients of 2.55 (acetone/IPA) and 2.08 (acetone/THF).
Reversibility testing across five sensing cycles showed consistent recovery, with minimal degradation in diffraction efficiency. Inter-sample reproducibility was also strong, with <6 % variation across independently prepared films.
Performance Summary
Compared to prior holographic VOC sensors, the cellulose acetate film resulted in:
- Rapid response and recovery
- Simplified, particle-free fabrication (~30 min)
- High diffraction efficiency
- Stable multi-cycle performance
- Material biodegradability and scalability
These are significant improvements compared to other systems, such as nanoparticle or layered material sensors, demonstrating the potential of cellulose acetate.
Toward Sustainable Sensing Platforms
This study demonstrates that biodegradable holographic films can serve as sensitive, rapid, and reusable VOC sensors.
With its straightforward fabrication and reliable performance, the cellulose acetate-based sensor shows promise for applications in environmental monitoring, industrial safety, and potentially even medical diagnostics, such as breath-based detection of VOC biomarkers.
Future work may explore enhancing selectivity through molecular binders like aptamers.
Journal Reference
Sharma K., et al. (2025). Holographically sensing of volatile organic compounds using cellulose acetate-based photopolymer film. Scientific Reports 15, 37757. DOI: 10.1038/s41598-025-06944-4