Solid-state optical sensing of ultra-trace Hg2+ ions using chromoionophoric probe anchored silica monolithic architectures

In this work, we manifest the fabrication of a simple, portable, and benign solid-state sensor for the quantification of toxic Hg2+ ions through ocular colorimetric sensing. The sensor fabrication is modulated through solgel process using two different block-polymer surfactants (PEO and F108) for the formation of mesoporous silica monolithic designs that are immobilized with tailor-made probe molecules. The crack-free porous silica monoliths are structurally engineered to form, (i) highly ordered honey-combed 3D cubic, and (ii) disoriented worm-like mesopore structures that facilitates homogeneous probe anchoring through constrained spatial orientations for the selective detection of ultra-trace Hg2+ ions. The monolithic sensor materials are characterized by FE-SEM, HR-TEM, p-XRD, SAED, EDAX, XPS, FT-IR, TGA, and N-2 isotherm analysis. For ensuring unambiguous ion-sensing, analytical parameters such as solution pH, temperature, kinetics, probe concentration, sensor quantity, linear signal response, matrix tolerance, the limit of detection (L-D), and quantification (L-Q) are optimized. The L-D and L-Q values for probe anchored PEO-MSM based sensor are 0.61 & 2.05 ppb and for probe anchored F108-MSM based sensor are 0.22 & 0.72 ppb, respectively, in the corresponding linear response range of 0 - 100 ppb and 0 - 50 ppb of Hg2+, which has been validated by real-time analysis of natural water samples.