Table 3. Value of the Parameters of the Langmuir Fit (eq 3), Together with the Sensitivity to Analyte ConcentrationS_c and the LOD as Expressed by eq 1 and 2, Respectively; the Parameters Are Related to the Optical Sensing of the Hg²⁺ Ion by Bare Gold Thin Films, Gr/Au, and Gr/SiO₂/Au Heterostructures.

Interface	HMI	Sc(°/ppm)	LOD (ppm)	Δθmax	K (L mol–1)	R2
Au	Hg2+	1.4	5.2 × 10–3	0.044	7.2× 106	0.996
Gr/SiO2/Au	Hg2+	5.5	1.2 × 10–3	0.071	1.8 × 107	0.947
Gr/Au	Hg2+	9.8	0.7 × 10–3	0.079	3.1 × 107	0.975