Urease has been covalently immobilized on a 3-D networking silica gel (SG) using dimethyldichlorosilane (DMDCS) as second generation silane coupling reagent and m-nitroaniline as linker component in a robust methodology and subsequently characterized as [{Si­(OSi)4(H2O)0.05}205.2] n=4{OSi­(CH3)2–NH–C6H4–NN-urease}·282.5H2O (molecular mass 263 445 g or 263.4 kDa). Selective coupling of tyrosine residue with an identifiable m-nitroaniline modified SG unit prevents enzyme–enzyme cross-linking leading to enhancement of enzymatic activity. The material worked at room temperature and its activity (luminescent and ammonia releasing efficiency) was enhanced by 3-fold (for both synthetic and real sample) compared to native enzyme values at neutral pH. Up to 30 days and 30 cycles, this 3-fold activity remains as such but reduces gradually to native enzyme level after 60 days and 60 cycles of reuse.

By the use of a new silane coupling reagent, dimethyldichlorosilane (DMDCS), effective and instantaneous immobilization of 8-hydroxyquinoline (HQ) on an inorganic carrier (silica gel, SG) has been carried out for the facile synthesis of an extractor material (composition: {Si­(OSi) p=4(H2O) x=0.16} n=11[−Si­(CH3)2–NH–C6H4–NN–HQ] z=4·25H2O; molar mass: 4010.3 g/mol). The material (thermal stability: ≤100 °C; chemical stability: ≤8 M HNO3) possesses a high Brunauer–Emmett–Teller surface area (BET-SAFe(III): 1170 m2·g–1), an appreciable preconcentration factor (PFFe(III): 145.1), and high breakthrough capacity (BTCFe(III): column exchange capacity, 269 μmol·g–l; Langmuir Q 0, 278.6 μmol·g–1) for Fe­(III). Along with these discernible analytical qualities, a high level of reusability (<800 cycles @ 95% recovery) reflects the material warranty. Fe­(III), present as [Fe­(OH)­(H2O)5]2+ at the recommended pH (1.90 ± 0.15), binds at the highest occupied molecular orbital (HOMO) of the sorbent (η = 7.69 eV) through hard–soft binding with an appreciable binding energy (−14.2 eV). The breakthrough capacity (BTC: 269–278.6 μmol·g–1) was found to be the product of the amount of extractor HOMO (280 μmol·g–1) and the degree of polymerization of the adsorbed metal ion, x (i.e., BTC = [amount of HOMOextractor (μmol·g–1)] × x for monomeric (x = 1) and polymeric (x > 1) species). The findings reveal substantial improvement of Weetall–Hill immobilization of chelating ligands on inorganic carriers.

nCA anchored to SSG surface generates 121 μM g−1 H-bonded metal-trapping cores with 10-fold increase in surface area for selective uptake of {Th2(OH)2(H2O)2}6+.

Sorption–desorption equilibration, {extractor-HOMO}:{H3O}+ + {metal-species}n+ ⇄ {extractor-HOMO}:{metal-species}n+ + {H3O}+, an eventual ion-pair complexation controlled by {H3O}+.

Under optimum sorption conditions, FSG–PAN forms 1 : 1 ‘ion pairs’ with {Be3O(OH)2}2+, {Al3(OH)3(H2O)2}6+ and {(UO2)2(OH)2(H2O)7}2+.