Hierarchical Series of Ligands with Controlled HLB for Different  Types of Sensory Systems

To solve challenging problems of environmental and health monitoring, the development of highly selective and sensitive sensory systems for detection of metal ions in aqueous media is required. With this aim in mind, hierarchical series of modular receptors with controlled hydrophilic-lipophilic balance (HLB) were developed and their sensory properties were implemented in colorimetric and film systems of different types. Amphiphilic ligands of these hierarchical series are composed of 9,10-anthraquinone signalling moiety linked via amino groups to a receptor subunit bearing amide and diethoxyphosphoryl groups and decorated by two hydrophobic alkoxy chains. Binding of environmentally relevant metal ions by these amphiphilic chromoionophores with variable HLB were studied in solution, monolayers, Langmuir-Blodgett films, polymer films and test strips using electron absorption spectroscopy, surface balance technique, in situ fiber-optic absorption-reflection spectroscopy, surface plasmon resonance spectroscopy (SPRS) and scanning electron microscopy. Molecular architecture of studied ligands provides an appropriate orientation of the planar anthraquinone moiety at the interface that allows to prevent p-stacking of the molecules in the films. Conservative behavior of these amphiphilic modular compounds having bulky polar moieties and a significantly different length of alkyl chains in sensory monolayers was observed. Kinetic and thermodynamic parameters of the complexation of various metal ions by ligand monolayers immobilized onto a gold support were calculated using SPR-sensorgrams. The efficiency of this design strategy was demonstrated by the development of highly sensitive sensory systems for detection of mercury and copper ions in aqueous media.