Combinatiorial method for surface-confined sensor desing and fabrication

The procedure for the combinatorial fabrication of new sensing materials for cations and anions based on self-assembled monolayers (SAM) is discussed. A library of different sensitive substrates is generated by sequential deposition of fluorophores and small ligand molecules onto an amino-terminated SAM coated glass. The preorganization provided by the surface avoids the need for complex receptor design, allowing for a combinatorial approach to sensing systems based on individually deposited small molecules. Additionally the sensing system has been miniaturized to the microscale using microcontact printing and integrating the sensory SAMs on the walls of microchannels

Silver containing nanostructures from hydrogen-bonded supramolecular scaffolds

International audienceThe self-organisation of silver-containing hydrogen-bonded rosette assemblies on highly oriented pyrolytic graphite (HOPG) surfaces is described. The introduction of silver atoms into the double rosette architecture was achieved using the affinity of silver cations for cooperative π-donors or cyano- functionalities on the double rosettes. Highly ordered 2-D nanorod domains with an inter-row spacing of 4-5 nm oriented in different directions were revealed by tapping-mode atomic force microscopy (AFM). This new and simple strategy for the creation of metal-containing supramolecular nanorod arrays that can act as well-defined surface-immobilized self-assembled scaffolds, will contribute to the development of functionalized nanoarchitectures via bottom-up approaches.The self-organisation of silver-containing hydrogen-bonded rosette assemblies on highly oriented pyrolytic graphite (HOPG) surfaces is described. The introduction of silver atoms into the double rosette architecture was achieved using the affinity of silver cations for cooperative π-donors or cyano- functionalities on the double rosettes. Highly ordered 2-D nanorod domains with an inter-row spacing of 4-5 nm oriented in different directions were revealed by tapping-mode atomic force microscopy (AFM). This new and simple strategy for the creation of metal-containing supramolecular nanorod arrays that can act as well-defined surface-immobilized self-assembled scaffolds, will contribute to the development of functionalized nanoarchitectures via bottom-up approaches

Conversion of a metastable superhydrophobic surface to an ultraphobic surface

Superhydrophobic surfaces in Wenzel and metastable wetting state were prepared and the conversion of such surfaces to ultraphobic surfaces was reported by the application of a fine-scale roughness. Silicon nitride substrates with hexagonally arranged pillars were prepared by micromachining. The two-scale roughness was achieved by coating these substrates with 60 nm silica nanoparticles. The surface was made hydrophobic by silanization with octadecytrichlorosilane (OTS). Wettability studies of the silicon nitride flat surface, silicon nitride pillars, and the surfaces with two-scale roughness showed that a two-scale roughness can effectively improve the hydrophobicity of surfaces with a higher apparent contact angle and reduced contact angle hysteresis when the original rough surface was in a metastable or Wenzel state. This study shows the pathway of converting a metastable hydrophobic surface to an ultraphobic surface by the introduction of a fine-scale roughness, which adds to the literature a new aspect of fine-scale roughness effect

Cross-Reactive Sensor Array for Metal Ion Sensing Based on Fluorescent SAMs\ud

Fluorescent self assembled monolayers (SAMs) on glass were previouslydeveloped in our group as new sensing materials for metal ions. These fluorescent SAMs arecomprised by fluorophores and small molecules sequentially deposited on a monolayer onglass. The preorganization provided by the surface avoids the need for complex receptordesign, allowing for a combinatorial approach to sensing systems based on small molecules.Now we show the fabrication of an effective microarray for the screening of metal ions andthe properties of the sensing SAMs. A collection of fluorescent sensing SAMs wasgenerated by combinatorial methods and immobilized on the glass surfaces of a custom-made 140 well microtiter-plate. The resulting libraries are easily measured and show variedresponses to a series cations such as Cu2+ , Co2+ , Pb2+ , Ca2+ and Zn2+ . These surfaces are notdesigned to complex selectively a unique analyte but rather they are intended to producefingerprint type responses to a range of analytes by less specific interactions. The unselectiveresponses of the library to the presence of different cations generate a characteristic patternfor each analyte, a “finger print” response.\u

Exploring the transferability of large supramolecular assemblies to the vacuum-solid interface

We present an interplay of high-resolution scanning tunneling microscopy imaging and the corresponding theoretical calculations based on elastic scattering quantum chemistry techniques of the adsorption of a gold-functionalized rosette assembly and its building blocks on a Au(111) surface with the goal of exploring how to fabricate functional 3-D molecular nanostructures on surfaces. The supramolecular rosette assembly stabilized by multiple hydrogen bonds has been sublimed onto the Au(111) surface under ultra-high vacuum conditions; the resulting surface nanostructures are distinctly different from those formed by the individual molecular building blocks of the rosette assembly, suggesting that the assembly itself can be transferred intact to the surface by in situ thermal sublimation. This unanticipated result will open up new perspectives for growth of complex 3-D supramolecular nanostructures at the vacuum-solid interface

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

Effect of Disorder on Ultrafast Exciton Dynamics Probed by Single Molecule Spectroscopy

We present a single-molecule study unraveling the effect of static disorder on the vibrational-assisted ultrafast exciton dynamics in multichromophoric systems. For every single complex, we probe the initial exciton relaxation process by an ultrafast pump-probe approach and the coupling to vibrational modes by emission spectra, while fluorescence lifetime analysis measures the amount of static disorder. Exploiting the wide range of disorder found from complex to complex, we demonstrate that static disorder accelerates the dephasing and energy relaxation rate of the exciton