Surface functionality and optical properties impact of phenol red dye on mesoporous silica matrix for fiber optic pH sensing

Phenol red dye (PR) functionalized mesoporous silica matrix nano-structures/nano-tubes (MSNs) are synthesized by sol-gel method for pH sensing. FE-SEM analysis revealed formation of different nano objects (i.e. nano-clusters and nano-tubes) with defined pores, which are arranged into bunch of nanotubes after PR encapsulation. AFM analysis shows the crack-free dense matrices films with low average surface roughness and thickness. XRD and FT IR exhibited the interaction/bonding of phenolic anchoring groups of PR with silica. HRTEM analysis confirms the formation of crystalline nano-tubes after PR encapsulation within silica matrix. TGA/DTA analysis shows PR dye interacts efficiently within the silica matrix species from 300 degrees C-1000 degrees C. N-2 adsorption isotherms confirms the meso-porous nature of the PR encapsulated silica matrix have high surface area value of 434 m(2)/g with a pore volume of 0.96 cm(3) /g. UV-vis analysis exhibited that silica matrix has transmission of 84% at 550 nm and 1.36 refractive index. However, transmission is reduced to 79% whilst refractive index increased to 1.37 at 550 nm after PR encapsulation. Coated fiber optic displayed dynamic range of 1-10 pH with fast response time (<50 s). In conclusion, these structural, physicochemical, thermal and optical characteristics of synthesized PR encapsulated silica matrix film could serve as a prototype sensing device model leading to functional benefits in pH stimuli response behavior of opto-chemical devices and optical characteristics. (C) 2018 Published by Elsevier B.V.