*Proceeding Paper* **Study of a pH-Sensitive Hologram for Biosensing Applications †**

**Komal Sharma 1,2, Heena 1, Girish C. Mohanta 1,2 and Raj Kumar 1,2,\***

	- **\*** Correspondence: raj.optics@csio.res.in
	- † Presented at the International Conference on "Holography Meets Advanced Manufacturing", Online, 20–22 February 2023.

**Abstract:** Photopolymers are widely utilized as holographic recording media due to their ease of preparation and lack of wet chemistry post-processing. Holographic sensors constructed from a pH-sensitive photopolymer film have several applications in biosensors and the medical diagnostic field. However, the stability of photopolymer films in an aqueous medium is one of the most important challenges in their application for biosensing. Furthermore, the pH of the solution is another important parameter for biochemical reactions. In this work, we compared the pH sensitivity and stability of our holographic grating against two widely utilized classes of buffers; Phosphate Buffered Saline (PBS) and Tris-Acetate-EDTA (TAE) at two different pH values of 7.36 and pH 8.3, respectively. It was observed that a physiological pH (pH 7.4) had a negligible effect on the diffraction efficiency of the holographic sensor while it significantly deteriorated at a higher value of ~pH 8.3. This high sensitivity towards the minute pH difference of our holographic sensor could potentially be exploited for pH-based biosensing applications such as urea detection.

**Keywords:** holographic sensors; photopolymer film; biosensors; pH-sensing
