Single-molecule photobleaching probes the exciton wave function in a multichromophoric system

Ajuts: This work has been supported by the EC Program IHP- 99 (HPMF-CT-2002-01698)The exciton wave function of a trichromophoric system is investigated by means of single molecule spectroscopy at room temperature. Individual trimers exhibit superradiance and loss of vibronic structure in emission spectrum, features proving exciton delocalization. We identify two distinct photodegradation pathways for single trimers upon sequential photobleaching of the chromophores. The rate of each pathway is a measure for the contribution of the separate dyes to the collective excited state of the system, in this way probing the wave function of the delocalized exciton

Novel Supramolecular Nanoparticles Derived From Cucurbit[7]uril and Zwitterionic Surfactants

Binding constants, Log K ≈ 6.6 M-1, and NMR characterization of the complexes formed by sulfobetaines and cucurbit[7]uril (CB7) support the electrostatic interaction as major driving force. This very strong binding motif is cross-linked by additional CB7 molecules resulting in the formation of supramolecular nanoparticles (SNPs) with an average diameter of 172 nm and negative surface potential. The time course evolution of the particle size and the surface potential suggests the very fast formation of an amorphous aggregate that absorbs additional amount of sulfobetaine. These aggregates afford very stable (more than two weeks) nanoparticles in aqueous dispersion. The reversibility of the sulfobetaine/CB7 host:guest complexes allows SNPs disaggregation by adding a competitive guest as shown by treatment with tetraethylammonium chloride. The addition of this competitive cation triggers a SNPs to micelle transition. The potential application of these nanoparticles as drug delivery vehicles was investigated by using carboxyfluorescein. These experiments revealed that upon externally induced disruption of the SNPs (by tetraethylammonium chloride) the fluorescent dye was trapped into micellar aggregates that can be further disrupted by cyclodextrin additionhttp://www.usc.es/Financial support from Ministerio de Economia y Competitividad of Spain (projects CTQ2014-55208-P, CTQ2017-84354-P, CTQ2014-59646-R and MAT2015-67458-P), Xunta de Galicia (GR 2007/085; IN607C 2016/03 and Centro singular de investigación de Galicia accreditation 2016-2019, ED431G/09) and the European Union (European Regional Development Fund – ERDF), is gratefully acknowledged. J.M. received a Ramón y Cajal (RYC-2013- 13784) and a starting grant from the ERC (DYNAP677786)S

A simple approach to sensor discovery and fabrication on self-assembled monolayers on glass

Self-assembled monolayers (SAMs) on glass were used as a platform to sequentially deposit fluorophores and small molecules for ion sensing. The preorganization provided by the surface avoids the need for complex receptor design, allowing for a combinatorial approach to sensing systems based on small molecules. The resulting libraries are easily measured and show varied responses to a series of both cations and anions. This technology is transferable from the macro- to the microscale both via microcontact printing (CP), where the fluorophore is printed onto a glass surface, and via direct attachment of the fluorophore to microchannel walls. The ease of miniaturization of this technology may make the generation of a wide variety of simple yet efficient microarrays possible