Structure and Photonic Properties of a Perylenediimide Monolayer Assembled by the Langmuir-Blodgett Technique.

The photonic responses of densely packed dye molecule assemblies are strongly dependent on their organization and environment. The precise control of molecular orientations and distances relative to the substrate and to each other is thus a key point in the design of photonic molecular materials. Herein, we report the preparation of a homogeneous and well-organized single monolayer of the perylenediimide (PDI) derivative by means of the Langmuir-Blodgett technique. Its optical properties disclose an intense charge-transfer excitonic absorption band related to important intermolecular coupling. Furthermore, an important immunity to photobleaching is observed for such a molecular assembly. The dipolar orientations of the molecules along the substrate have been unambiguously determined by angle-of-incidence-resolved polarized absorption and back-focal-plane fluorescence mapping. In addition, time-resolved spectroscopy reveals a fast two-dimensional diffusion of excitons consistent with strong π-stacking of adjacent PDI molecules.

Design, synthesis, and characterization of protein origami based on self-assembly of a brick and staple artificial protein pair.

A versatile strategy to create an inducible protein assembly with predefined geometry is demonstrated. The assembly is triggered by a binding protein that staples two identical protein bricks together in a predictable spatial conformation. The brick and staple proteins are designed for mutual directional affinity and engineered by directed evolution from a synthetic modular repeat protein library. As a proof of concept, this article reports on the spontaneous, extremely fast and quantitative self-assembly of two designed alpha-repeat (αRep) brick and staple proteins into macroscopic tubular superhelices at room temperature. Small-angle X-ray scattering (SAXS) and transmission electron microscopy (TEM with staining agent and cryoTEM) elucidate the resulting superhelical arrangement that precisely matches the a priori intended 3D assembly. The highly ordered, macroscopic biomolecular construction sustains temperatures as high as 75 °C thanks to the robust αRep building blocks. Since the α-helices of the brick and staple proteins are highly programmable, their design allows encoding the geometry and chemical surfaces of the final supramolecular protein architecture. This work opens routes toward the design and fabrication of multiscale protein origami with arbitrarily programmed shapes and chemical functions.

Coherent two-beam steering of delocalized nonlinear photoluminescence in a plasmon cavity.

We aim at controlling the spatial distribution of nonlinear photoluminescence in a shaped micrometer-size crystalline gold flake. Interestingly, the underlying surface plasmon modal landscape sustained by this mesoscopic structure can be advantageously used to generate nonlinear photoluminescence (nPL) in remote locations away from the excitation spot. By controlling the modal pattern, we show that the delocalized nonlinear photoluminescence intensity can be redistributed spatially. This is first accomplished by changing the polarization orientation of the pulsed laser excitation in order to select a subset of available surface plasmon modes within a continuum. We then propose a second approach to redistribute the nPL within the structure by implementing a phase control of the plasmon interference pattern arising from a coherent two-beam excitation. Control and engineering of the nonlinear photoluminescence spatial extension is a prerequisite for deploying the next generation of plasmonic-enabled integrated devices relying on hot carriers.