An Alloy Engineering Strategy toward Helical Microstructures of Achiral π-Conjugated Molecules for Circularly Polarized Luminescence.

Helical assembly has been demonstrated to efficiently facilitate the circularly polarized luminescence (CPL) performances, but the synthesis of micro- and nanohelices from rigid achiral π-conjugated compounds remains challenging due to the absence of bilayer structures or complementary hydrogen-bonding interactions. Here, we develop an alloying strategy for the realization of helical microstructures from achiral anthracene/anthracene derivatives with -/-axis modification or anthracene/tetracene derivatives with -/-axis modification via solution coassembly. Interestingly, two anthracene derivatives bearing asymmetric phenyl/phenylethynyl groups and symmetric phenylethynyl groups can assemble into spiral microribbons with a fractal branching pattern.

750 V Breakdown in GaN Buffer on 200 mm SOI Substrates Using Reverse-Stepped Superlattice Layers.

In this work, we demonstrated the epitaxial growth of a gallium nitride (GaN) buffer structure on 200 mm SOI (silicon-on-insulator) substrates. This epitaxial layer is grown using a reversed stepped superlattice buffer (RSSL), which is composed of two superlattice (SL) layers with different Al component ratios stacked in reverse order. The upper layer, with a higher Al component ratio, introduces tensile stress instead of accumulative compressive stress and reduces the in situ curvature of the wafer, thereby achieving a well-controlled wafer bow ≤ ±50 µm for a 3.

Fractal Branched Microwires of Organic Semiconductor with Controlled Branching and Low-Threshold Amplified Spontaneous Emission.

Fractals are quite normal in nature. However, fractal self-assembly of organic semiconductors remains challenging. Herein, we develop a facile solution assembly route to access organic microwires (MWs) comprising an oligo(-phenylenevinylene) derivative (OPV-A) with and without branching.

Cocrystallization tailoring radiative decay pathways for thermally activated delayed fluorescence and room-temperature phosphorescence emission.

Modulation of excited-state processes in binary organic cocrystals has been rarely explored so far. Here, we develop two charge-transfer (CT) cocrystal microrods with a 1 : 1 stoichiometric ratio where halogenated dibenzothiophene (DBT) compounds act as π-electron donors and 1,2,4,5-tetracyanobenzene (TCNB) acts as an acceptor. Unexpectedly, the cocrystal containing one bromine (Br) atom at the 3-position of DBT (3-BrTC) presents thermally activated delayed fluorescence (TADF), while the other one comprising one Br atom at the 4-position of DBT (4-BrTC) exhibits both TADF and room-temperature phosphorescence (RTP).

Vapor-Phase Living Assembly of π-Conjugated Organic Semiconductors.

In contrast to well-studied amphiphilic block copolymers (BCPs) and π-stacked dyes, living assembly of hydrophobic π-conjugated materials has not yet been explored to date. Using a microspacing physical vapor transport (PVT) technique, the prefabricated microrods of organic semiconductors involving 9,10-dicyanoanthracene (DCA, ) or its binary alloy () can act as seeds to initiate living homoepitaxial growth from their ends, giving elongated microrods with controlled length. Red-green-red tricolor fluorescent microrod heterostructures with low dispersity are further realized by living heteroepitaxial growth of microrod blocks on seed microrod tips.

Hyperbranched Microwire Networks of Organic Cocrystals with Optical Waveguiding and Light-Harvesting Abilities.

We report the synthesis of hyperbranched organic microwire (MW) networks comprising 1,4-bis(pentafluorostyryl)benzene (10Ft) and 9,10-bis(phenylethynyl)anthracene (BA) using a simple solution co-assembly route. Pure 10Ft or BA assemblies cannot produce such complex MW networks; in contrast with a binary cocrystal of 10Ft and BA with a 2:1 molar ratio ((2:1)10Ft:BA), which is formed via intermolecular arene-perfluoroarene (AP) interactions. A new generation of multiple MWs grow epitaxially on the previous generation of MWs to form MW arrays in which BA may also act as an intermediate product to facilitate the regeneration of (2:1)10Ft:BA.

Structural evolution from the CdSSe alloy to the CdS/CdSe core/shell in Cd(S and Se) composite quantum dots and its impact on the performance of sensitized solar cells.

CdSSe alloy and CdS/CdSe core/shell quantum dots (QDs) are widely studied in quantum dot solar cells (QDSSCs). However, to date, there have been no detailed comparative investigations into the cell performance between CdSSe alloy and CdS/CdSe core/shell structures prepared with the same preparation process. In this work, the performances of CdSSe alloy and CdS/CdSe core/shell QDSSCs, which are prepared with the same SILAR (successive ionic layer adsorption and reactions) process, are investigated in detail.

Organic multicomponent microparticle libraries.

Multimetallic nanostructures can be synthesized by integrating up to seven or eight metallic elements into a single nanoparticle, which represent a great advance in developing complex multicomponent nanoparticle libraries. Contrary, organic micro- and nanoparticles beyond three π-conjugated components have not been explored because of the diversity and structural complexity of molecular assemblies. Here, we report a library of microparticles composed of an arbitrary combination of four luminescent organic semiconductors.

Color- and Dimension-Tunable Light-Harvesting Organic Charge-Transfer Alloys for Controllable Photon-Transport Photonics.

An electron donor/acceptor pair comprising perylene (Pe) and 9,10-dicyanoanthracene (DCA) was specifically designed to construct organic charge-transfer (CT) alloys via weak CT interaction through a solution co-assembly route. By adjusting the molar ratio between Pe and DCA, we achieve color- and dimension-tunable CT alloy assemblies involving one-dimensional (1D) (DCA) (Pe) (0 ≤ x ≤10 %) microribbons and two-dimensional (2D) (Pe) (DCA) (0 ≤ y ≤5 %) nanosheets as a consequence of energy transfer from DCA or α-Pe to Pe-DCA CT complex. Importantly, dimension-related optical waveguiding performances are also revealed: continuously adjustable optical loss in 1D (DCA) (Pe) microribbons and successive conversion from isotropic waveguide to anisotropic waveguide in 2D (Pe) (DCA) nanosheets.

Heat-treatment-induced development of the crystalline structure and chemical stoichiometry of a CuS counter electrode, and the influence on performance of quantum-dot-sensitized solar cells.

Recently, various phases of CuS (1 ≤ x ≤ 2) were extensively explored as superb counter electrode (CE) materials for quantum dot-sensitized solar cells (QDSSCs). Herein, hexagonal covellite CuS (HC-CuS) with hierarchical nanostructure was grown on porous Ti substrates by chemical bath deposition, and then heat treated in the temperature range of 150-450 °C under N atmosphere. The reaction process and the evolution of morphology, composition and crystalline structure of CuS with the variation of heat treatment temperature were studied by XRD, SEM, EDX, TEM and XPS.

Epitaxial Growth of Nanorod Meshes from Luminescent Organic Cocrystals via Crystal Transformation.

Two-dimensional (2D) nanorod meshes made of benzoperylene-1,3-dicyanotetrafluorobenzene (BP-1,3-DTFB) were formed via crystal transformation of the pre-existing BP microsheets. The transformation was driven by a cooperative effect of intermolecular charge-transfer and arene-perfluoroarene interactions. Epitaxial growth of cyan-emitting BP-1,3-DTFB nanorod meshes was directed by small lattice mismatch between BP and BP-1,3-DTFB, followed by the consumption of BP and the formation of BP-1,3-DTFB.

Two-dimensional C nano-meshes via crystal transformation.

Developing a rational and general approach towards complex two-dimensional (2D) nanostructures represents potential promising applications in a wide variety of fields, such as electronics, catalysis, and energy conversion. However, the synthesis of 2D nanoscale superstructures remains a great challenge because of the great difficulty in arranging the growth units in a rational manner. Here, we develop a simple yet effective solution-phase strategy to achieve hexagonal mesh networks made of aligned nanorods which are obtained via crystal transformation of 2D C60 microplates.

Complex assembly from planar and twisted π-conjugated molecules towards alloy helices and core-shell structures.

Integrating together two dissimilar π-conjugated molecules into controlled complex topological configurations remains a largely unsolved problem owing to the diversity of organic species and their respective different assembly features. Here, we find that two structurally similar organic semiconductors, 9,10-bis(phenylethynyl)anthracene (BA) and 5,12-bis(phenylethynyl)naphthacene (BN), co-assemble into two-component helices by control of the growth kinetics as well as the molar ratio of BA/BN. The helical superstructures made of planar and twisted bis(phenylethynyl) derivatives can be regarded as (BA)(BN) alloys, which are formed due to compatible structural relationship between BA and BN.

Solvatomechanical Bending of Organic Charge Transfer Cocrystal.

We report here a new ternary solvated (perylene-TCNB)·2THF cocrystal, which can transform into binary perylene-TCNB cocrystal reversibly by successive desorption or absorption of THF solvent. As a consequence, macroscopic mechanical bending would be realized when repeated stimulation with THF solvent. The present results clearly demonstrated that solvent induced mechanical bending is driven by structural change at the molecular scale.

Competition between Arene-Perfluoroarene and Charge-Transfer Interactions in Organic Light-Harvesting Systems.

Two typical types of luminescent organic cocrystals comprising pyrene-octafluoronaphthalene (pyrene-OFN) and pyrene-1,2,4,5-tetracyanobezene (pyrene-TCNB) were developed by a simple supramolecular assembly strategy. The cocrystals exhibit distinct optical properties because of their different intermolecular interaction modes; that is, arene-perfluoroarene (AP) and charge-transfer (CT) interactions. Unexpectedly, a pyrene-TCNB system with strong CT interactions was incorporated into a pyrene-OFN host as a robust guest to generate white-light emission (WLE).

Facet-Selective Growth of Organic Heterostructured Architectures via Sequential Crystallization of Structurally Complementary π-Conjugated Molecules.

In contrast to those for their polymeric counterparts, the controlled construction of organic heterostructured architectures derived from π-conjugated organic molecules has been rare and remains a great challenge. Herein, we develop a simple single-step solution strategy for the realization of organic heterostructures comprising coronene and perylene. Under a sequential crystallization process, an efficient doping step for coronene and perylene domains enables their perfect lattice matching, which facilitates facet-selective epitaxial growth of perylene domains on both the tips and the side surfaces of the preformed seed microwires by manipulating the growth pathways of the two pairs of materials.

Constructing luminescent particle/MOF composites by employing polyvinylpyrrolidone-modified organic crystals as seeds.

We develop a novel and facile chemical reaction route to modulate the crystallization process of luminescent zinc 8-hydroxyquinoline (Znq) particles. Polyvinylpyrrolidone (PVP)-modified octahedral Znq micro- and nano-crystals were used as seeds to construct two distinct hybrid structures, i.e.

Hierarchically porous Pd nanospheres: facile synthesis and their application in HCOOH electrooxidation.

With the help of rhodamine B base (RBB), novel Pd nanospheres were synthesized by a facile one-step approach. Owing to their hierarchically porous characteristics, these nanospheres exhibited highly catalytic activity for HCOOH electrooxidation (∼1.84 times and 1.

Two-dimensional optical waveguiding and luminescence vapochromic properties of 8-hydroxyquinoline zinc (Znq2) hexagonal microsheets.

Two-dimensional (2D) hexagonal microsheets of 8-hydroxyquinoline zinc (Znq2) were synthesized readily via a mixed solvent induced self-assembly method. The 2D optical waveguiding properties of the microsheets have been clearly revealed by both fluorescence microscopy and confocal microscopy. In addition, the reversible vapochromic properties of the microsheets have also been demonstrated when the Znq2 is exposed to HCl and NH3 vapors.

White-light emitting microtubes of mixed organic charge-transfer complexes.

Self-assembled microtubes of mixed charge-transfer (CT) complexes comprising TCNB and naphthalene can be constructed with pyrene as dopant by an etching-assisted CT-induced interaction. Highly efficient Förster resonance energy transfer (FRET) from the excited naphthalene-TCNB to pyrene-TCNB molecules is obtained in mixed CT complex microtubes. White-light emissive CT complex microtubes can be formed by adjusting the dopant concentration and serve as an active optical waveguide.

Fullerene hollow microspheres prepared by bubble-templates as sensitive and selective electrocatalytic sensor for biomolecules.

We developed an electrocatalytic sensor based on C(60) hollow microspheres for highly sensitive and selective detection of dopamine (DA) in the presence of ascorbic acid (AA), and uric acid (UA) in the presence of l-cysteine (RSH). The hollow microspheres of C(60) with a diameter controllable in the range of 0.5 to 1.

Orange-blue-orange triblock one-dimensional heterostructures of organic microrods for white-light emission.

1D triblock hetrostructures with striping patterns have been synthesized by doping 1,3-diphenyl-2-pyroline (DP) microrods with 4-(dicyanomethylene)-2-methyl-6-(p-dimethylaminostyryl)-4H-pyran (DCM) molecules selectively at both ends. The middle stripe of triblock microds emit the blue light, while both ends emit orange light due to the efficient FET from excited DP to DCM molecules (right inset). Although triblock microrods show microarea heterogeneity in the striping pattern, they generate macroscopic high-quality white-light emission (WLE) in both the colloidal suspension (left inset) and the solid state with a photoluminescence efficiency as high as 36 +/- 5%.