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

Oscillator-Based Volatile Detection System Using Doubly- Clamped Micromechanical Resonators

AbstractIn this paper, we demonstrate a functionalized and resonant piezo-actuated volatile sensor which is interfaced by electronics for frequency shift detection. Enhanced signal sensing is achieved via the effective feed-through capacitance cancellation scheme. The closed-loop oscillator, realized with off-the-shelf components, attains a frequency stability of 2.7Hz for the 1.8MHz resonant mode of the gas sensor. The sensor was exposed to pulses of water and ethanol vapor mixtures, yielding a temporary dip in resonance frequency as well as volatile-specific recovery times

Interactions between directly and parametrically driven vibration modes in a micromechanical resonator

The interactions between parametrically and directly driven vibration modes of a clamped-clamped beam resonator are studied. An integrated piezoelectric transducer is used for direct and parametric excitation. First, the parametric amplification and oscillation of a single mode are analyzed by the power and phase dependence below and above the threshold for parametric oscillation. Then, the motion of a parametrically driven mode is detected by the induced change in resonance frequency in another mode of the same resonator. The resonance frequency shift is the result of the nonlinear coupling between the modes by the displacement-induced tension in the beam. These nonlinear modal interactions result in the quadratic relation between the resonance frequency of one mode and the amplitude of another mode. The amplitude of a parametrically oscillating mode depends on the square root of the pump frequency. Combining these dependencies yields a linear relation between the resonance frequency of the directly driven mode and the frequency of the parametrically oscillating mode.Comment: 5 pages, 4 figure

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

Synthesis beyond the molecule

Weak, noncovalent interactions between molecules control many biological functions. In chemistry, noncovalent interactions are now exploited for the synthesis in solution of large supramolecular aggregates. The aim of these syntheses is not only the creation of a particular structure, but also the introduction of specific chemical functions in these supramolecules

Gas sensing with vertical functionalized InAs nanowire arrays

Nanowires show great promise for use in next generation (bio-)chemical sensing devices because of their high surface to volume ratio enabling efficient modulation of their current by charges or dipoles present at the surface. Here, we present a gas sensing device based on vertical InAs nanowire arrays grown without metal catalyst particles. The nanowires are contacted ohmically in their as-grown locations using an air bridge construction, leaving the nanowire surface free for gas adsorption. Noise measurements were performed to determine the measurement resolution for gas detection. The bare devices show sensitivity to NO\2 concentrations well below 75 ppb at room temperature. We furthermore find that these nanowires can be functionalized with metalloporphyrins resulting in sensitivity to both NO\2 and NO concentrations below 75 ppb