above. Organic crystals are one of the strong contenders for nanophotonic applications due to the impressive advantages they offer, such as tailor-made synthesis, engineered flexibility, chirality, optical (linear and nonlinear) properties, high photoluminescence efficiency, lightweight, easy processability (solution or sublimation), and relatively high refractive index, n (n = √ε; where ε is the dielectric permittivity of the materials). [1] The customized synthesis of building block molecules offers fine-tuning of the optical absorbance and emission from ultraviolet (UV) to near-infrared (NIR) region of the electromagnetic spectrum by anchoring specific electron donor (D) and electron acceptor (A) groups to π-conjugated molecular backbone of varying lengths. Organic crystals with D and A functional groups also provide nonlinear optical (NLO) emissions (via multiphoton excitation process) depending upon the molecular symmetry and solid-state molecular packing (centrosymmetric/nonsymmetric). Besides, the polar and non-polar nature of the functional groups allows varying solubility of the organic compounds in a range of solvents facilitating solution processability. Depending upon the degree of solubility, organic compounds can be processed into microstructures (of various dimensions and sizes) suitable for nano-/micro-photonic applications using solvent-assisted selfassembly or crystal growth technique. Sublimation is also an alternative clean method to process organic compounds into crystalline microstructures. [2c] Naturally, most of the organic crystals are stiff, and they reveal their fragility when subjected to external stress beyond a specific limit. Therefore, until now, most of the devices fabricated with organic crystalline materials are rigid. [8] However, future "intelligent" technologies mandate flexible devices. The forecasted market for such devices is expected to touch over $70 billion by 2026. [9] Crystals with unusual mechanical flexibility (reversible) will open new avenues for applications in flexible organic electronics and photonic devices. [10-13] On the other hand, the rarity of the flexible crystal is one of the major impediment to the advancement of flexible nano-/micro-photonic device components. Seamless integration of a flexible crystal in a microcircuit needs precise spatial control of crystal position and its geometry. [13] However, the dearth of appropriate micromanipulation technique (mechanical or optical trapping) is a significant impediment to the shaping of flexible microcrystals for circuit applications.
We have fabricated nearly monodispersed nanocrystalline sheet waveguides from a well-known red emitting meso-tetratolylporphyrin molecule (1) by following a bottom-up solvent assisted self-assembly technique. The nano-sheets thickness is in the range of 110-180 nm. Localized laser illumination showed excitation position dependent exciton polariton (653 and 719 nm) propagation behavior of the sheets. The spatially resolved fluorescence spectra of the sheets showed optical modes at the input and output points, indicating cavity effect. Additionally, because of the reabsorption of the 653 nm emission, the nanosheets also act as wave length filter by cutting off the 653 nm photons from reaching the output end.
This article focuses on an innovative one‐pot fabrication of organic/inorganic hybrid parallepipedic tubes with rectangular cavities displaying multicolor luminescence. Firstly, using a novel back‐to‐back coupled 2,6‐di‐pyrazol‐1‐ylpyridine ligand, blue‐emitting several‐micrometer‐long (ca. 50 μm) parallepipedic organic nanotubes with rectangular cavities were fabricated in THF/water via supramolecular (H‐bonding and π–π stacking) and solvent‐assisted self‐assembly. Secondly, in the same pot, the ligand molecules available on the surface of the ligand nanotubes were reacted with Eu(tta)3 molecules at the solid/liquid interface to form a layer of red‐emitting Eu(III) complex coating on the inner and outer surface of the tubes. The resultant organic/inorganic hybrid parallepipedic nanotubes fabricated using this novel bottom‐up one‐pot technique display tricolor (blue–red–purple) luminescence, i.e., blue and red dual emission from the organic ligand and the Eu(III) complex, respectively, and a purple color due to the mixing of the two colors. This simple technique signifies an innovative and important method in the development of bottom‐up nanotechnology of multiluminescent organic/inorganic hybrid nanotubes.
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