Fig. 3. (a)–(e) Fluorescence intensity of BSA–SqNP hybrid nanosensors in the 480 (λ ex@380 nm) and 700 nm (λ ex@640 nm) region at different pH conditions. The active pH range for different ratios is indicated by the shadow color. (f) A pictorial representation of the construction of the narrow range tunable pH sensors with different ratios of BSA and SqNPs and the corresponding pH sensitivity range within a unit of one pH scale. (g) Photograph of BSA–SqNP hybrids with ratios of 10 : 1, 7 : 1 and 3 : 1 filled in wells of pH 5.0–8.0 in a microwell plate under UV illumination (365 nm).
