Probe decorated porous silica and polymer monoliths as solid-state optical sensors and preconcentrators for the selective and fast recognition of ultra-trace arsenic ions

In this work, we manifested a new approach in designing solid-state colorimetric sensors for the selective optical sensing of As3+. The sensor fabrication is modulated using, (i) a cubic mesopores of ordered silica monolith, and (ii) a bimodal macro-/meso-porous polymer monolith, as hosting templates that are immobilized with a tailor-made chromoionophoric probe (DFBEP). The surface morphology and structural dimensions of the monolith templates and the sensor materials are characterized using p-XRD, XPS, FE-SEM-EDAX, HR-TEM-SAED, FT-IR, TGA, and BET/BJH analysis. The sensing components such as pH, probe content, sensor dosage, kinetics, temperature, analyte concentration, linear response range, selectivity, and sensitivity are optimized to arrive at the best sensing conditions. The silica and polymer-based monolithic sensors show a linear spectral response in the concentration range of 2–300 and 2–200 ppb, with a detection limit of 0.87 and 0.75 ppb for As3+, respectively. The real-time ion-monitoring propensity of the sensors is tested with spiked synthetic and real water samples, with a recovery efficiency of ≥99.1% (RSD ≤1.57%). The sensors act as both naked-eye optical sensors and preconcentrators, with a response time of ≤2.5 min. The molecular and photophysical properties of the DFBEP-As3+ complex are studied by TD-DFT calculations, using the B3LYP/6–31G (d,p) method. [Display omitted] •Ordered pore networks of silica and polymer-based monolith templates are prepared.•An indigenous chromoionophoric molecular probe is synthesized for As3+ ion-sensing.•The probe anchored monolith templates act as solid-state colorimetric ion-sensors.•The optodes offer exclusive selectivity in capturing ultra-trace levels of As3+.•The proposed optical sensors are fast responsive, benign, reusable, and durable.