We present the one-dimensional optical-waveguiding crystal dithieno[3,2-a:2',3'-c]phenazine with ah igh aspect ratio,high mechanical flexibility,and selective self-absorbance of the blue part of its fluorescence (FL). While macrocrystals exhibit elasticity,m icrocrystals deposited at ag lass surface behave more like plastic crystals due to significant surface adherence,m aking them suitable for constructing photonic circuits via micromechanical operation with an atomic-forcemicroscopyc antilever tip.T he flexible crystalline waveguides displayoptical-path-dependent FL signals at the output termini in both straight and bent configurations,m aking them appropriate for wavelength-division multiplexing technologies. Ar econfigurable 2 2-directional coupler fabricated via micromanipulation by combining two arc-shaped crystals splits the optical signal via evanescent coupling and delivers the signals at two output terminals with different splitting ratios. The presented mechanical micromanipulation technique could also be effectively extended to other flexible crystals.
Self-recognition, self-selection, and dynamic self-organization are of fundamental importance for the assembly of all supramolecular systems, but molecular-level information is not generally accessible. We present direct examples of these critical steps by using scanning tunneling microscopy to study mixtures of complementary organic ligands on a copper substrate. The ligands coordinate cooperatively with iron atoms to form well ordered arrays of rectangular multicomponent compartments whose size and shape can be deliberately tuned by selecting ligands of desired length from complementary ligand families. We demonstrate explicitly that highly ordered supramolecular arrays can be produced from redundant ligand mixtures by molecular self-recognition and -selection, enabled by efficient error correction and cooperativity, and show an example of failed self-selection due to error tolerance in the ligand mixture, leading to a disordered structure.nanostructure ͉ scanning tunneling microscopy ͉ self-assembly ͉ surface chemistry ͉ organic molecule ligands S upramolecular self-organization, directed by information stored in molecular components and read out through their specific interactions, represents the pivotal operation in the spontaneous but controlled build-up of structurally organized and functionally integrated molecular systems (1). Metal-ligand coordination bonding is an effective strategy for strong, directional bonding to stabilize designed, self-assembled supramolecular architectures (2-5). Substrate-supported, 2D supramolecular coordination for efficient nanometer-scale patterning of solid surfaces has been demonstrated (6, 7). By selecting organic ligands with appropriate size, geometry, and binding moieties, specific tailored architectures can be produced across a substrate completely by self-assembly of the molecules. Such patterning of surfaces is of great interest for potential applications in surface nanofunctionalization, templated growth, and controlling 2D molecular nanoarrays. Molecular level insight has provided structural details of these systems, and here we explore multicomponent systems at that level to illustrate critical assembly requirements for these systems and (bio-)molecular systems in general.Self-selection occurs when the involved molecular components are sufficiently instructed to allow self-recognition and -assembly into discrete supramolecular architectures (8). Processes of modular self-assembly, dynamic self-organization, and self-selection are of fundamental importance for the assembly of all supramolecular systems, but molecular-level information is not generally accessible. Using scanning tunneling microscopy (STM), we address these issues by studying mixtures of complementary organic molecule ligands on a copper substrate that coordinate cooperatively with iron atoms to form regular arrays of rectangular multicomponent compartments. Ensembles of these complementary components serve as model systems to investigate the dynamic bottom-up self-organization process of modular ...
We report on theoretical and experimental work involving a particular molecular switch, an [Fecomplex, that utilizes a spin transition ("crossover"). The hallmark of this transition is a change of the spin of the metal ion, S Fe = 0 to S Fe = 2, at fixed oxidation state of the Fe ion. Combining density functional theory and first principles calculations, we demonstrate that within a single molecule this transition can be triggered by charging the ligands. In this process the total spin of the molecule, combining metal ion and ligands, crosses over from S = 0 to S = 1. Three-terminal transport through a single molecule shows indications of this transition induced by electric gating. Such an electric field control of the spin transition allows for a local, fast, and direct manipulation of molecular spins, an important prerequisite for molecular spintronics.
Nano/micro scale passive organic optical waveguides, which are self-assembled from tailor made organic molecules, are one of the less studied branches of organic photonics. This perspective article is primarily focused on the research work related to one dimensional (1D) passive organic optical waveguides. In the beginning, a brief theory of organic waveguides, recent works on active organic waveguides and attempts towards fabrication of integrated photonic components and circuits will be discussed. Later more focus will be given to passive organic wave guiding materials derived from 1D hexagonal submicrotubes, parallelepipedic nanotubes, shape shifting organic structures and paramagnetic tubes. By using laser ablation techniques, the polishing of organic tube tips, the precise control of the light propagation distance and the creation of multiple optical outputs will be discussed. This perspective also highlights some noteworthy applications of passive organic waveguides in remote sensing, excitation and defect identification. The end of this article concludes with the potential of passive organic optical waveguides in future organic nanophotonics.
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