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The direct, clean, and unbiased transduction of molecular recognition into a readable and reproducible response is the biggest challenge associated to the use of synthetic receptors in sensing. All possible solutions demand the mastering of molecular recognition at the solid-liquid interface as prerequisite. The socially relevant issue of screening amine-based illicit and designer drugs is addressed by nanomechanical recognition at the silicon-water interface. The methylamino moieties of different drugs are all first recognized by a single cavitand receptor through a synergistic set of weak interactions. The peculiar recognition ability of the cavitand is then transferred with high fidelity and robustness on silicon microcantilevers and harnessed to realize a nanomechanical device for label-free detection of these drugs in water., (© 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.)

A chiral organic-inorganic hybrid material, based on a porous silicon surface functionalized with a chiral cavitand, was designed and synthesized. The affinity of this device in water toward a bromine-marked alkyl-ammonium salt has been evaluated using XPS detection. UV and CD measurements highlight the enantioselective extraction from a racemic mixture in water of the S-enantiomer of the selected guest (ee ≥ 80%).

A supramolecular approach for the specific detection of sarcosine, recently linked to the occurrence of aggressive prostate cancer forms, has been developed. A hybrid active surface was prepared by the covalent anchoring on Si substrates of a tetraphosphonate cavitand as supramolecular receptor and it was proven able to recognize sarcosine from its nonmethylated precursor, glycine, in water and urine. The entire complexation process has been investigated in the solid state, in solution, and at the solid-liquid interface to determine and weight all the factors responsible of the observed specificity. The final outcome is a Si-based active surface capable of binding exclusively sarcosine. The complete selectivity of the cavitand-decorated surface under these stringent conditions represents a critical step forward in the use of these materials for the specific detection of sarcosine and related metabolites in biological fluids.

We have combined the metal-coordinating features of phenanthroline with the remarkable complexing properties of tetraphosphonate (Tiiii) cavitands towards N-methylammonium salts with the aim of assembling novel luminescent ternary complexes. The formation of such complexes was first tested in solution: the charged sarcosine derivative 1, bearing a phenanthroline moiety, was complexed by the cavitand Tiiii- A, followed by coordination of EuIII-tris(β-diketonate) complex 2. The occurrence of the self-assembly has been proven by NMR spectroscopy, mass spectrometry and photophysical measurements. The transfer of this binding protocol to the surface showed the complete orthogonality of these interactions, as verified by control experiments on complexation-inactive surfaces. The formation of the ternary complexes on the silicon surface was monitored by means of X-ray photoelectron spectroscopy and luminescence spectroscopy. The emission properties of the silicon-bound Si-Tiiii- B·1·2 and the corresponding ternary complex Tiiii- A·1·2 in solution are similar, which indicates that the transfer of the self-assembly process onto silicon does not significantly perturb the EuIII coordination environment. The self-assembly protocol illustrated here can be extended to a wide variety of lanthanide ions and can be implemented for applications in sensing, bioimaging and optoelectronic devices. [ABSTRACT FROM AUTHOR]

Selective and reversible complexation of halogen-tagged aromatic VOCs by a quinoxaline cavitand-decorated Si surface is demonstrated. The specific host–guest interactions of the Si-bonded receptors are proved to be responsible of the surface recognition properties, while extracavity non specific adsorptions are totally suppressed compared to the bulk material. [ABSTRACT FROM AUTHOR]

A Si(1 00) surface featuring molecular recognition properties was obtained by covalent functionalization with a tetraphosphonate cavitand (Tiiii), able to complex positively charged species. Tiiii cavitand was grafted onto the Si by photochemical hydrosilylation together with 1-octene as a spatial spectator. The recognition properties of the Si-Tiiii surface were demonstrated through two independent analytical techniques, namely XPS and fluorescence spectroscopy, during the course of reversible complexation-guest exchange-decomplexation cycles with specifically designed ammonium and pyridinium salts. Control experiments employing a Si(100) surface functionalized with a structurally similar, but complexation inactive, tetrathiophosphonate cavitand (TSiii,) demonstrated no recognition events. This provides evidence for the complexation properties of the Si-Thu surface, ruling out the possibility of nonspecific interactions between the substrate and the guests. The residual Si-O- terminations on the surface replace the guests' original counterions, thus stabilizing the complex ion pairs. These results represent a further step toward the control of self-assembly of complex supramolecular architectures on surfaces. [ABSTRACT FROM AUTHOR]