Manipulation of light flows in organic color-graded microstructures towards integrated photonic heterojunction devices

Printable Block Molecular Assemblies with Controlled Exciton Dynamics

Creating hierarchical molecular block heterostructures, with the control over size, shape, optical, and electronic properties of each nanostructured building block can help develop functional applications, such as information storage, nanowire spectrometry, and photonic computing. However, achieving precise control over the position of molecular assemblies, and the dynamics of excitons in each block, remains a challenge. In the present work, the first fabrication of molecular heterostructures with the control of exciton dynamics in each block, is demonstrated. Additionally, these heterostructures are printable and can be precisely positioned using Direct Ink Writing-based (DIW) 3D printing technique, resulting in programable patterns. Singlet excitons with emission lifetimes on nanosecond or microsecond timescales and triplet excitons with emission lifetimes on millisecond timescales appear simultaneously in different building blocks, with an efficient energy transfer process in the heterojunction. These organic materials also exhibit stimuli-responsive emission by changing the power or wavelength of the excitation laser. Potential applications of these organic heterostructures in integrated photonics, where the versatility of fluorescence, phosphorescence, efficient energy transfer, printability, and stimulus sensitivity co-exist in a single nanowire, are foreseen.

Organic Bilayer Heterostructures with Built-In Exciton Conversion for 2D Photonic Encryption

Organic multilayer heterostructures with accurate spatial organization demonstrate strong light-matter interaction from excitonic responses and efficient carrier transfer across heterojunction interfaces, which are considered as promising candidates toward advanced optoelectronics. However, the precise regulation of the heterojunction surface area for finely adjusting exciton conversion and energy transfer is still formidable. Herein, organic bilayer heterostructures (OBHs) with controlled face-to-face heterojunction via a stepwise seeded growth strategy, which is favorable for efficient exciton propagation and conversion of optical interconnects are designed and synthesized. Notably, the relative position and overlap length ratio of component microwires (LDSA /LBPEA = 0.39-1.15) in OBHs are accurately regulated by modulating the crystallization time of seeded crystals, resulting into a tailored heterojunction surface area (R = Loverlap /LBPEA = 37.6%-65.3%). These as-prepared OBHs present the excitation position-dependent waveguide behaviors for optical outcoupling characteristics with tunable emission colors and intensities, which are applied into two-dimensional (2D) photonic barcodes. This strategy opens a versatile avenue to purposely design OBHs with tailored heterojunctions for efficient energy transfer and exciton conversion, facilitating the application possibilities of advanced integrated optoelectronics.

Directional Self-Assembly of Facet-Aligned Organic Hierarchical Super-Heterostructures for Spatially Resolved Photonic Barcodes

Organic multicolor heterostructures with spatially resolved luminescent colors and identifiable patterns have exhibited considerable potential for achieving micro-/nanoscale photonic barcodes. Nevertheless, such types of barcodes reported thus far are exclusively based on a single heterostructure with limited coding elements. Here, a directional self-assembly strategy is proposed to achieve high-coding-capacity spatially resolved photonic barcodes through rationally constructing organic hierarchical super-heterostructures, where numerous subheterostructure blocks with flat hexagonal facets are precisely oriented with their specific facets via a reconfigurable capillary force. The building blocks were prepared through a one-pot sequential heteroepitaxial growth, which enables the effective modulation of the structural and color characteristics in coding structures. Significantly, a directional facet-to-facet attraction between particles via facet registration leads to the formation of well-defined 1D super-heterostructures, which contain multiple coding elements, thus providing a good platform for constructing the high-coding-capacity photonic barcodes. The results may be useful in fabricating organic hierarchical hybrid super-heterostructures for security labels and optical data recording.

Dynamic Epitaxial Growth of Organic Heterostructures for Polarized Exciton Conversion

Highly spatial and angular precision in epitaxial-growth process is crucial for constructing organic low-dimensional heterostructures (OLDHs) with the desired substructures, which remains significant challenge owing to the unpredicted location of complex heterogeneous nucleation. Herein, a dynamic epitaxial-growth approach is developed along the tailored longitudinal/horizontal directions to create diverse OLDHs with hierarchical architectures. The controlled morphology evolution of seed crystals from kinetic to thermodynamic species is achieved via incrementally increasing the crystallization time from 0 to 600 s. Accordingly, the kinetic and thermodynamic seed crystals respectively present the specific lattice-matching crystal-planes of (100) and (011), which facilitates the longitudinal epitaxial-growth (LG) process for triblock heterostructures, and the horizontal epitaxial-growth (HG) process for axial-branch heterostructures. The dominant core/shell heterostructures are prepared via both LG and HG processes with a crystallization time of ≈30 s. Significantly, these prepared OLDHs realize the rationally polarized exciton conversion for optical logic gate application through the exciton conversion and photon propagation at the heterojunction. This strategy provides an avenue for the precise synthesis of OLDHs with anisotropy optical characters for integrated optoelectronics.

Optical Signal Modulation in Photonic Waveguiding Heteroarchitectures with Continuously Variable Visible-To-Near-Infrared Emission Color

Photonic circuit systems based on optical waveguiding heteroarchitectures have attracted considerable interest owing to their potential to overcome the speed limitation in electronic circuits by modulating the optical signal at the micro- or nanoscale. However, controlling the parameters, including the wavelength and polarization of the light outcoupling, as well as the sequence among different building blocks, remains a key issue. Herein, supramolecular heteroarchitectures made by phosphorescent organometallic complexes of Pt, Pd, Cu, and Au are applied as photonic logic gates that show continuously variable emission colors from 475 to 810 nm, low waveguide losses down to 0.0077 dB µm^-1 , and remarkable excitation-light polarization-dependent photoluminescence with anisotropy ratios up to 0.68. The sequences among Pt, Pd, Au, and Cu building blocks in the heteroarchitectures are controlled by living supramolecular polymerization or crystallization-driven self-assembly synthetic approaches. The results indicate the prospects for using organometallic complexes and supramolecular synthetic approaches to prepare photonic circuit systems with tunable emission color and controllable sequences among different blocks that achieve modulation of the optical signal in the visible-to-near-infrared spectral region.

Lattice-mismatch-free growth of organic heterostructure nanowires from cocrystals to alloys

Organic heterostructure nanowires, such as multiblock, core/shell, branch-like and related compounds, have attracted chemists’ extensive attention because of their novel physicochemical properties. However, owing to the difficulty in solving the lattice mismatch of distinct molecules, the construction of organic heterostructures at large scale remains challenging, which restricts its wide use in future applications. In this work, we define a concept of lattice-mismatch-free for hierarchical self-assembly of organic semiconductor molecules, allowing for the large-scale synthesis of organic heterostructure nanowires composed of the organic alloys and cocrystals. Thus, various types of organic triblock nanowires are prepared in large scale, and the length ratio of different segments of the triblock nanowires can be precisely regulated by changing the stoichiometric ratio of different components. These results pave the way towards fine synthesis of heterostructures in a large scale and facilitate their applications in organic optoelectronics at micro/nanoscale.

The large-scale synthesis of organic heterostructure nanowires is challenging. Here, the authors report the synthesis of organic triblock nanowires via a lattice mismatch-free strategy.

Organic Branched Heterostructures with Optical Interconnects for Photonic Barcodes

Optical interconnects exhibit superior potential in the precise regulation of photon transmission for organic photonic circuits. However, the rational design of well-defined organic heterostructures toward active optoelectronics remains challenging. Herein, we designed organic branched heterostructures (OBHs) with accurate spatial organization for optical interconnection. Notably, the precise regulation of OBHs has been controllably achieved including the trunk morphologies and the branched microwire number. Significantly, these as-prepared OBHs inherently exhibit the multichannel coupling outputs and the excitation position-dependent waveguide characteristics, leading to various outcoupling signals with tunable intensity and emission colors. The optical interconnects are realized due to the occurrence of exciton conversion and photon propagation between branch and trunk at the heterojunction, benefiting the application possibilities of two-dimensional (2D) optical barcodes.

Elastic Organic Crystals Based on Barbituric Derivative: Multi-faceted Bending and Flexible Optical Waveguide

Elastic organic single crystals with light-emitting and multi-faceted bending properties are extremely rare. They have potential application in optical materials and have attracted the extensive attention of researchers. In this paper, we reported a structurally simple barbituric derivative DBDT, which was easily crystallized and gained long needle-like crystals (centimeter-scale) in DCM/CH₃ OH (v/v=2/8). Upon applying or removing the mechanical force, both the (100) and (040) faces of the needle-like crystal showed reversible bending behaviour, showing the nature of multi-faceted bending. The average hardness (H) and elastic modulus (E) were 0.28±0.01 GPa and 4.56±0.03 GPa for the (040) plane, respectively. Through the analysis of the single crystal data, it could be seen that the van der waals (C-H⋅⋅⋅π and C-H⋅⋅⋅C), H-bond (C-H⋅⋅⋅O) and π⋅⋅⋅π interactions between molecules were responsible for the generation of the crystal elasticity. Interestingly, elastic crystals exhibited optical waveguide characteristics in straight or bent state. The optical loss coefficients measured at 627 nm were 0.7 dBmm^-1 (straight state) and 0.9 dBmm^-1 (bent state), while the optical loss coefficient (α) were 1.5 dBmm^-1 (straight state) and 1.8 dBmm^-1 (bent state) at 567 nm. Notably, the elastic organic molecular crystal based on barbituric derivative could be used as the candidate for flexible optical devices.

Programmable Rainbow-Colored Optofluidic Fiber Laser Encoded with Topologically Structured Chiral Droplets

Optofluidic lasers are emerging building blocks with immense potential in the development of miniaturized light sources, integrated photonics, and sensors. The capability of on-demand lasing output with programmable and continuous wavelength tunability over a broad spectral range enables key functionalities in wavelength-division multiplexing and manipulation of light-matter interactions. However, the ability to control multicolor lasing characteristics within a small mode volume with high reconfigurability remains challenging. The color gamut is also restricted by the number of dyes and emission wavelength of existing materials. In this study, we introduce a fully programmable multicolor laser by encapsulating organic-dye-doped cholesteric liquid crystal microdroplet lasers in an optofluidic fiber. A mechanism for tuning laser emission wavelengths was proposed by manipulating the topologically induced nanoshell structures in microdroplets with different chiral dopant concentrations. Precision control of distinctive lasing wavelengths and colors covering the entire visible spectra was achieved, including monochromatic lasing, dual-color lasing, tri-color lasing, and white colored lasing with tunable color temperatures. Our findings revealed a CIE color map with 145% more perceptible colors than the standard RGB space, shedding light on the development of programmable lasers, multiplexed encoding, and biomedical detection.

Organic Semiconductor-DNA Hybrid Assemblies

Organic semiconductors are photonic and electronic materials with high luminescence, quantum efficiency, color tunability, and size-dependent optoelectronic properties. The self-assembly of organic molecules enables the establishment of a fabrication technique for organic micro- and nano-architectures with well-defined shapes, tunable sizes, and defect-free structures. DNAs, a class of biomacromolecules, have recently been used as an engineering material capable of intricate nanoscale structuring while simultaneously storing biological genetic information. Here, the up-to-date research on hybrid materials made from organic semiconductors and DNAs is presented. The trends in photonic and electronic phenomena discovered in DNA-functionalized and DNA-driven organic semiconductor hybrids, comprising small molecules and polymers, are observed. Various hybrid forms of solutions, arrayed chips, nanowires, and crystalline particles are discussed, focusing on the role of DNA in the hybrids. Furthermore, the recent technical advances achieved in the integration of DNAs in light-emitting devices, transistors, waveguides, sensors, and biological assays are presented. DNAs not only serve as a recognizing element in organic-semiconductor-based sensors, but also as an active charge-control material in high-performance optoelectronic devices.

Organic micro/nanoscale materials for photonic barcodes

This review summarizes recent advances in micro/nanoscale photonic barcodes based on organic materials from the aspects of diverse optical encoding techniques.

Scale Effect of a Fluorescent Waveguide in Organic Micromaterials: A Case Study Based on Coumarin Microfibers

The classical method for evaluating the waveguide ability only focuses on the optical loss coefficient. However, for the micro- or submicroscale, an organic waveguide is demonstrated by the present study whose scale effect should not be neglected. We found that the optical loss coefficient increased remarkably when decreasing the sectional size of the microfibers. Furthermore, simulations based on Finite-Difference Time-Domain also demonstrated the size-dependent effect of the waveguide. Both the experimental and simulating results showed that the optical loss coefficient converges to a certain value, which means that the scale effect can be neglected as the sectional size is large enough. On the basis of the present study, we suggest that the scale-dependent effect on the sectional size of the waveguide should be investigated by evaluating the waveguide ability by the optical loss coefficient.

Self-Templated Assembly of AuI /AgI -Thiolate Sheets with Central Holes

Composite crystalline sheets of Au^I /Ag^I -thiolate with central holes are achieved by co-assembly of Ag^I -thiolate and Au^I -thiolate in one-pot without sacrificial template. Both Ag^I -thiolate and Au^I -thiolate can separately assemble to lamellar sheets with similar structures, which makes their co-assembly possible, while the differences in their assembly pathways make the co-assembly processes highly dynamic and complex. First, a core@shell structure with Ag^I -thiolate at the core was formed upon the mixing of the two, then the core@shell structure transformed to a hole@shell structure by dissociation of the core. Finally, some instable hole@shell structures further dissociated and grew on stable ones to generate holed Au^I /Ag^I -thiolate composite sheets, in which the two components neither have severe phase separation nor blend uniformly at atomic level. By tuning the feeding ratios, the average diameter of the holes can be controlled. Therefore, the work demonstrates the advantage of co-assembly technique in obtaining complex structurers. The holed sheets can further assemble to porous macroscopic materials and transform to composite metal nanoparticles by pyrolysis.

Hierarchical self-assembly of organic heterostructure nanowires

Organic heterostructures (OHSs) integrating the intrinsic heterostructure characters as well as the organic semiconductor properties have attracted intensive attention in material chemistry. However, the precise bottom-up synthesis of OHSs is still challenging owing to the general occurrence of homogeneous-nucleation and the difficult manipulation of noncovalent interactions. Herein, we present the rational synthesis of the longitudinally/horizontally-epitaxial growth of one-dimensional OHSs including triblock and core/shell nanowires with quantitatively-manipulated microstructure via a hierarchical self-assembly method by regulating the noncovalent interactions: hydrogen bond (−15.66 kcal mol⁻¹) > halogen bond (−4.90 kcal mol⁻¹) > π-π interaction (−0.09 kcal mol⁻¹). In the facet-selective epitaxial growth strategy, the lattice-matching and the surface-interface energy balance respectively facilitate the realization of triblock and core/shell heterostructures. This hierarchical self-assembly approach opens up avenues to the fine synthesis of OHSs. We foresee application possibilities in integrated optoelectronics, such as the nanoscale multiple input/out optical logic gate with high-fidelity signal.

Organic heterostructures attract attention in material chemistry but the precise bottom-up synthesis is still challenging. Herein the authors present a hierarchical self-assembly approach to synthesize one-dimensional organic heterostructures by regulating the noncovalent interactions.

One-Dimensional Programmable Polymeric Microfiber Waveguide with Optically Reconfigurable Photonic Functions

Programmable materials and reconfigurable photonic components, which can change their physicochemical properties and functionalities upon external stimuli, are a major topic of interest in modern science. However, most conventional reconfigurable photonic components rely heavily on mechanical deformation, restricting their application. Herein, a novel strategy based on a dynamically tunable fluorescence resonance energy transfer process to design and fabricate programmable fluorescent micropatterns within single polymer microfiber is proposed. A set of reconfigurable photonic components (including optical switchable waveguide systems, photonic analogies of diodes and transistors, as well as one-dimensional (1D) optical encoding) can be achieved within a single polymeric waveguide microfiber straightforwardly, in which such photonic components can be written, erased, and rewritten as 1D binary patterns with tailored external optical stimuli. These results might be of great fundamental value for the rational design of novel reconfigurable photonic devices with numerous potential applications in highly integrated optical communication components and optical computing devices.

Peptide Nanophotonics: From Optical Waveguiding to Precise Medicine and Multifunctional Biochips

Optical waveguiding phenomena found in bioinspired chemically synthesized peptide nanostructures are a new paradigm which can revolutionize emerging fields of precise medicine and health monitoring. A unique combination of their intrinsic biocompatibility with remarkable multifunctional optical properties and developed nanotechnology of large peptide wafers makes them highly promising for new biomedical light therapy tools and implantable optical biochips. This Review highlights a new field of peptide nanophotonics. It covers peptide nanotechnology and the fabrication process of peptide integrated optical circuits, basic studies of linear and nonlinear optical phenomena in biological and bioinspired nanostructures, and their passive and active optical waveguiding. It is shown that the optical properties of this generation of bio-optical materials are governed by fundamental biological processes. Refolding the peptide secondary structure is followed by wideband optical absorption and visible tunable fluorescence. In peptide optical waveguides, such a bio-optical effect leads to switching from passive waveguiding mode in native α-helical phase to an active one in the β-sheet phase. The found active waveguiding effect in β-sheet fiber structures below optical diffraction limit opens an avenue for the future development of new bionanophotonics in ultrathin peptide/protein fibrillar structures toward advanced biomedical nanotechnology.

Tailoring the structures and photonic properties of low-dimensional organic materials by crystal engineering

Low-dimensional organic materials have given rise to tremendous interest in optoelectronic applications, owing to their controllable photonic properties. However, the controlled-synthesis approaches for organic nano-/micro-architectures are very difficult to attain, because the weak interaction (van der Waals force) between the organic molecules cannot dominate the kinetic process of crystal growth. We report a simple method, which involves selective adhesion to the organic crystal plane by hydrogen-bonding interaction for modulating the crystal growth process, which leads either to the self-assembly of one organic molecule into two-dimensional (2D) microsheets with an obvious asymmetric light propagation or one-dimensional (1D) microrods with low propagation loss. The method of tailoring the structures and photonic properties for fabricating different micro-structures would provide enlightenment for the development of tailor-made mini-sized devices for photonic integrated circuits.

On-Nanowire Axial Heterojunction Design for High-Performance Photodetectors

We report the growth of high-quality CdS/CdSxSe1-x axial heterostructure nanowires (NWHs) via a temperature-controlled chemical vapor deposition method. Microstructural characterizations revealed that these NWHs have a single-crystalline structure with abrupt heterojunctions. Local photoluminescence and mapping near the heterojunctions show only two separated narrow band-edge emission bands from the two different adjacent semiconductors, further demonstrating the high-quality of these heterostructures. Moreover, the photodetector based on the single NWH shows a performance (higher responsivity (1.18 × 10(2) A/W), faster response speed (rise ∼68 μs, decay ∼137 μs), higher Ion/Ioff ratio (10(5)), higher EQE (3.1 × 10(4) %), and broader detection range (350-650 nm)) at room temperature superior to that of photodetectors based on single band gap nanostructures. This work suggests a much simpler route to achieve superior NWHs for applications in optoelectronic devices.

Photonic Applications of Metal-Dielectric Heterostructured Nanomaterials

Metal materials, supporting plasmon modes on their surface, can confine the optical field at deep subwavelength scale, which is desired for photonic integration. However, their intrinsic high Ohmic losses make it impossible to construct the whole circuit solely with the metal materials. Integrating the plasmonic components with dielectric materials may offer a solution to this dilemma. With outstanding active optical performance, these dielectric components not only can greatly reduce the optical losses of the entire circuits but also offer an efficient way to launch the surface plasmon polaritons through the evanescent field coupling or the direct exciton-plasmon conversion. Furthermore, the cooperative interaction between metal and dielectric materials would bring vast novel optical phenomena and functional photonic devices. In this review, the synergistic effects among metal and dielectric materials in various heterostructures as well as their related applications are highlighted. Comprehensive understanding on their synergistic interactions would offer useful guidance for the design and fabrication of the ultracompact novel optical devices.

Construction of Nanowire Heterojunctions: Photonic Function-Oriented Nanoarchitectonics

Nanophotonics has received broad research interest because it may provide an alternative opportunity to overcome the fundamental limitations of electronic circuits. So far, diverse photonic functions, such as light generation, modulation, and detection, have been realized based on various nano-materials. The exact structural features of these material systems, including geometric characteristics, surface morphology, and material composition, play a key role in determining the photonic functions. Therefore, rational designs and constructions of materials on both morphological and componential levels, namely nanoarchitectonics, are indispensable for any photonic device with specific functionalities. Recently, a series of nanowire heterojunctions (NWHJs), which are usually made from two or more kinds of material compositions, were constructed for novel photonic applications based on various interactions between different materials at the junctions, for instance, energy transfer, exciton-plasmon coupling, or photon-plasmon coupling. A summary of these works is necessary to get a more comprehensive understanding of the relationship between photonic functions and architectonics of NWHJs, which will be instructive for designing novel photonic devices towards integrated circuits. Here, photonic function oriented nanoarchitectonics based on recent breakthroughs in nanophotonic devices are discussed, with emphasis on the design mechanisms, fabrication strategies, and excellent performances.

Organic nanophotonic materials: the relationship between excited-state processes and photonic performances

Organic active nanophotonics: excited-state coupled photonic behaviours strongly determine the optical performances of organic nanomaterials. The photonic actions and related material properties can be well controlled by tailoring the intra/inter-molecular excited-state processes.

"H"-like Organic Nanowire Heterojunctions Constructed from Cooperative Molecular Assembly for Photonic Applications

"H"-like organic nanowire heterojunctions with two parallel 2-acetyl-6-dimethylamino-naphthalene wires vertically bridged by one 2,4,5-triphenylimidazole wire are prepared via cooperative molecular assembly in liquid phase. The exciton conversion at the junction interfaces is beneficial for the design of multichannel light-controlled photo-switches. The results provide better understanding of molecular assembly toward specific structures and open up new prospects for the creation of novel photonic materials.

From molecular design and materials construction to organic nanophotonic devices

CONSPECTUS: Nanophotonics has recently received broad research interest, since it may provide an alternative opportunity to overcome the fundamental limitations in electronic circuits. Diverse optical materials down to the wavelength scale are required to develop nanophotonic devices, including functional components for light emission, transmission, and detection. During the past decade, the chemists have made their own contributions to this interdisciplinary field, especially from the controlled fabrication of nanophotonic molecules and materials. In this context, organic micro- or nanocrystals have been developed as a very promising kind of building block in the construction of novel units for integrated nanophotonics, mainly due to the great versatility in organic molecular structures and their flexibility for the subsequent processing. Following the pioneering works on organic nanolasers and optical waveguides, the organic nanophotonic materials and devices have attracted increasing interest and developed rapidly during the past few years. In this Account, we review our research on the photonic performance of molecular micro- or nanostructures and the latest breakthroughs toward organic nanophotonic devices. Overall, the versatile features of organic materials are highlighted, because they brings tunable optical properties based on molecular design, size-dependent light confinement in low-dimensional structures, and various device geometries for nanophotonic integration. The molecular diversity enables abundant optical transitions in conjugated π-electron systems, and thus brings specific photonic functions into molecular aggregates. The morphology of these micro- or nanostructures can be further controlled based on the weak intermolecular interactions during molecular assembly process, making the aggregates show photon confinement or light guiding properties as nanophotonic materials. By adoption of some active processes in the composite of two or more materials, such as energy transfer, charge separation, and exciton-plasmon coupling, a series of novel nanophotonic devices could be achieved for light signal manipulation. First, we provide an overview of the research evolution of organic nanophotonics, which arises from attempts to explore the photonic potentials of low-dimensional structures assembled from organic molecules. Then, recent advances in this field are described from the viewpoints of molecules, materials, and devices. Many kinds of optofunctional molecules are designed and synthesized according to the demands in high luminescence yield, nonlinear optical response, and other optical properties. Due to the weak interactions between these molecules, numerous micro- or nanostructures could be prepared via self-assembly or vapor-deposition, bringing the capabilities of light transport and confinement at the wavelength scale. The above advantages provide great possibilities in the fabrication of organic nanophotonic devices, by rationally combining these functional components to manipulate light signals. Finally, we present our views on the current challenges as well as the future development of organic nanophotonic materials and devices. This Account gives a comprehensive understanding of organic nanophotonics, including the design and fabrication of organic micro- or nanocrystals with specific photonic properties and their promising applications in functional nanophotonic components and integrated circuits.

π-Conjugated polymer anisotropic organogel nanofibrous assemblies for thermoresponsive photonic switches

The present work demonstrates one of the first examples of π-conjugated photonic switches (or photonic wave plates) based on the tailor-made π-conjugated polymer anisotropic organogel. New semicrystalline segmented π-conjugated polymers are designed with rigid aromatic oligophenylenevinylene π-core and flexible alkyl chain along the polymer backbone. These polymers are found to be self-assembled as semicrystalline or amorphous with respect to the number of carbon atoms in the alkyl units. These semicrystalline polymers produce organogels having nanofibrous morphology of 20 nm thickness with length up to 5 μm. The polymer organogel is aligned in a narrow glass capillary, and this anisotropic gel device is further demonstrated as photonic switches. The glass capillary device behaves as typical λ/4 photonic wave plates upon the illumination of the plane polarized light. The λ/4 photonic switching ability is found to be maximum at θ = 45° angle under the cross polarizers. The orthogonal arrangements of the gel capillaries produce dark and bright spots as on-and-off optical switches. Thermoreversibility of the polymer organogel (also its xerogel) was exploited to construct thermoresponsive photonic switches for the temperature window starting from 25 to 160 °C. The organic photonic switch concept can be adapted to large number of other π-conjugated materials for optical communication and storage.

Controlled synthesis of organic nanophotonic materials with specific structures and compositions

Organic nanomaterials have drawn great interest for their potential applications in high-speed miniaturized photonic integration due to their high photoluminescence quantum efficiency, structural processability, ultrafast photoresponse, and excellent property engineering. Based on the rational design on morphological and componential levels, a series of organic nanomaterials have been controllably synthesized in recent years, and their excitonic/photonic behaviors has been fine-tuned to steer the light flow for specific optical applications. This review presents a comprehensive summary of recent breakthroughs in the controlled synthesis of organic nanomaterials with specific structures and compositions, whose tunable photonic properties would provide a novel platform for multifunctional applications. First, we give a general overview of the tailored construction of novel nanostructures with various photonic properties. Then, we summarize the design and controllable synthesis of composite materials for the modulation of their functionalities. Subsequently, special emphasis is put on the fabrication of complex nanostructures towards wide applications in isolated photonic devices. We conclude with our personal viewpoints on the development directions in the novel design and controllable construction of organic nanomaterials for future applications in highly integrated photonic devices and chips.

Tailoring the self-assembled structures and photonic properties of organic nanomaterials

Organic nanomaterials have attracted more and more attention for their applications in nano-photonics due to their high photoluminescence quantum efficiencies, color tunabilities, and size-dependent optical properties. With the distinctive features of photoluminescence, waveguiding and dimensional confinement, different organic nanostructures, such as 0D nanoparticles, 1D nanowires and 2D nanosheets, have a significant influence on their photonic properties. Therefore, it is of great importance and scientific interest to develop the strategy for tailoring the self-assembled structures with specific photonic behaviors in desired manners. In this mini review, we give a brief review of the recent work on the control of self-assembled organic nanostructures, and the tunable photonic properties of the predetermined structures.

Organic nanophotonics: from controllable assembly of functional molecules to low-dimensional materials with desired photonic properties

The tutorial review aims to provide an insight into the relationship among opto-functional molecules, controllable assembly, diverse nanostructures and photonic properties, which can further guide the function-oriented design and synthesis of low-dimensional materials for integrated photonic devices.