Porous silica and polymer monolith architectures as solid-state optical chemosensors for Hg²⁺ ions

We demonstrate a simple strategy to concoct a competent solid-state opto-chemosensor for the selective and sensitive visual detection of Hg²⁺ ions. The sensor fabrication involves the utilization of indigenously prepared mesoporous silica and polymer monoliths as probe anchoring templates and 8-hydroxy-7-(4-n-butylphenylazo) quinoline (HBPQ) as the chromo-ionophoric probe for Hg²⁺ sensing. Both the monoliths are designed with discrete structural and morphological features to serve as efficient host templates. The structural and surface features of the monoliths are characterized using p-XRD, TEM, SEM, SAED, EDAX, XPS, and N₂ isotherm analysis. The synergetic features of monolith structural hierarchy along with the probe's selective chelating ability enable rapid signal response and remarkable ion selectivity for Hg²⁺. The solid-state sensors evince a linear signal response from 0.6 to 150 μg/L for Hg²⁺ recognition, with superior data authenticity and replication that is preceded by an RSD value of ≤ 2.25% when tested with real water samples.Graphical abstract Mesoporous silica and polymer monolith architects hosting HBPQ probe molecules demonstrate an excellent visual sensing of ultra-trace (μg/L) Hg²⁺ in various water samples with a striking color transition from light orange to dark red upon complexation of probe with Hg²⁺. The solid-state sensors are Hg²⁺ ion selective, super-responsive, real-time applicable, and also reusable.