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.

In this study, we report a simple and green method for the synthesis of l-tyrosine-stabilized silver (AgNPs) and gold nanoparticles (AuNPs) in aqueous medium under ambient sunlight irradiation. The nanoparticles (NPs) are characterized by UV–visible spectroscopy, high-resolution transmission electron microscopy (HR-TEM), Fourier transform infrared spectroscopy (FT-IR), cyclic voltammetry (CV), and dynamic light scattering (DLS) techniques. The size and shape of the metal NPs could be controlled by changing the concentration of the substrate, metal precursors, and pH of the medium. The synthesized AgNPs are found to be highly sensitive to Hg2+ and Mn2+ ions with the detection limit for both ions as low as 16 nM under optimized conditions. However AuNPs are found to be sensitive to Hg2+ and Pb2+ ions with a detection limit as low as 53 and 16 nM, respectively. The proposed method was found to be useful for colorimetric detection of heavy metal ions in aqueous medium.

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.

Flexible organic single crystals are evolving as new materials for optical waveguides that can be used for transfer of information in organic optoelectronic microcircuits.I ntegration in microelectronics of such crystalline waveguides requires downsizing and precise spatial control over their shape and sizea tt he microscale,h owever that currently is not possible due to difficulties with manipulation of these small, brittle objects that are prone to cracking and disintegration. Here we demonstrate that atomic force microscopy(AFM) can be used to reshape,r esizea nd relocate single-crystal microwaveguides in order to attain spatial control over their light output. Using an AFM cantilever tip,m echanically compliant acicular microcrystals of three N-benzylideneanilines were bent to an arbitrary angle,s liced out from ab undle into individual crystals,cut into shorter crystals of arbitrary length, and moved across and aboveasolid surface.W hen excited by using laser light, such bent microcrystals act as active optical microwaveguides that transduce their fluorescence,w ith the total intensity of transduced light being dependent on the optical path length. This micromanipulation of the crystal waveguides using AFM is non-invasive,a nd after bending their emissive spectral output remains unaltered. The approach reported here effectively overcomes the difficulties that are commonly encountered with reshaping and positioning of small delicate objects (the "thick fingers" problem), and can be applied to mechanically reconfigure organic optical waveguides in order to attain spatial control over their output in two and three dimensions in optical microcircuits.

Fabrication of microscale organic photonic integrated circuits (μ-OPIC) from two electronically different flexible crystals via a mechanophotonics approach is demonstrated here. The experiments focus on the mechanical micromanipulation of orange-emitting (E)-1-(4-(dimethylamino)-phenyl) iminomethyl-2-hydroxyl-naphthalene (DPIN) and green-emitting (E)-1-(4bromo)iminomethyl-2-hydroxyl-naphthalene (BPIN) crystals with atomic force cantilever tip. The flexibility of these crystals originate from molecular H-bonding, CH•••π, and π•••π stacking interactions. These mechanically compliant crystals form exceedingly bent and photonically relevant reconfigurable geometries during micromanipulation, including three μ-OPICs.Remarkably, these μ-OPICs operate through passive-, active-waveguiding and energy transfer mechanisms. Depending upon the crystal's electronic nature (either BPIN or DPIN) receiving the optical signal input, the circuit executes mechanism-selective and direction-specific optical outputs. The presented proof-of-principle concepts can be used to fabricate complex photonic circuits with diverse, flexible crystals performing multiple optical functions.