Improvement of optical properties of pH- sensitive nanolayers coating deposited using Layer-by-Layer technique

The focus of this paper is to investigate two different techniques to improve the optical properties of pH-sensitive nanolayers coating deposited using Layer-by-Layer (LbL) method. The two approaches studied in this work are: addition of salt into the polyion solutions and/or the use of different drying methods. As a case study, pH sensitive nanolayer coatings using Neutral Red as pH sensitive molecule and poly (acrylic acid) [PAA] as cross-linker are deposited on either a bare silica optical fiber or a glass slide using different salt concentrations and drying techniques. The optical properties of each coated sensor are measured and compared. It is shown that both methods can optimize the deposition process and improve the sensor sensitivity.