An embodiment provides a method for measuring fluoride concentration in an aqueous solution, including: preparing a polyethylene glycol (PEG) monomethyl ether to produce an ester; reacting the ester in the presence of ammoniated tetrahydrofuran to produce an amino polyethylene glycol; placing, in a solution comprising a benzaldehyde species with a phenol functional group and a carboxylic acid functional group, a 2,3,3-trimethylindolenine derivative to produce a hemicyanine with a phenol functional group and a carboxylic acid functional group; combining, in a polar aprotic solvent, the hemicyanine with the phenol functional group and carboxylic acid functional group with a 1,1-carbonyldiimidazole (CDI) and adding the amino-PEG to produce a hemicyanine-PEG; and creating a fluoride sensitive hemicyanine species by reacting the hemicyanine-PEG that contains a phenol functional group with a SiR3 species. Other embodiments are described and claimed.