Fac-Alq3 and mer-Alq3 nano/microcrystals with different emission and charge-transporting properties

Comparison of a dimeric and a monomeric indium-quinolinato complex: synthesis, structure and photoluminescence

Two indium(iii) complexes, mer-[In(Ox)₃]·2H₂O (1) and [In₂(Ox)₂Cl₂-μ-[κ²-O,O′-(Ox)₂]]·C₇H₈ (2) (Ox = 8-hydroxyquinolinate), were synthesized and characterised for comparison by NMR, X-ray diffraction and photoluminescence.

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.

Room-Temperature Phosphorescence and Low-Energy Induced Direct Triplet Excitation of Alq3 Engineered Crystals

Crystal engineering is a practical approach for tailoring material properties. This approach has been widely studied for modulating optical and electrical properties of semiconductors. However, the properties of organic molecular crystals are difficult to control following a similar engineering route. In this Letter, we demonstrate that engineered crystals of Alq₃ and Ir(ppy)₃ complexes, which are commonly used in organic light-emitting technologies, possess intriguing functional properties. Specifically, these structures not only process efficient low-energy induced triplet excitation directly from the ground state of Alq₃ but also can show strong emission at the Alq₃ triplet energy level at room temperatures. We associate these phenomena with local deformations of the host matrix around the guest molecules, which in turn lead to a stronger host-guest triplet-triplet coupling and spin-orbital mixing.

Fine Fabrication and Optical Waveguide Characteristics of Hexagonal tris(8-hydroxyquinoline)aluminum(Ⅲ) (Alq3) Crystal

Herein, we reported on the precise growth and optical waveguide characteristics of hexagonal tris(8-hydroxyquinoline)aluminum(Ⅲ) (Alq3) micro-crystals (MCs). The hexagonal Alq3 MCs were prepared using surfactant-assisted assembly growth with the help of cetyltrimethylammoniumbromide (CTAB), in which the crystallization occurred as a result of molecular assembly and packing. Also, we adjusted the molar ratio of Alq3 and CTAB for the control degree of crystallization. The formation and structure of Alq3 MCs were investigated using field-emission scanning electron microscopy and X-ray diffraction pattern experiments, respectively. The solid-state laser confocal microscope-photoluminescence spectra and charge-coupled device images for the Alq3 MCs were measured to study the luminescence efficiency and colors, respectively. The optical waveguide performance of the hexagonal Alq3 MCs was measured for each side direction. According to our results, crystalline Alq3 micro-crystals are promising materials for application to the development of optical communication devices.

Growth and Brilliant Photo-Emission of Crystalline Hexagonal Column of Alq₃ Microwires

We report the growth and nanoscale luminescence characteristics of 8-hydroxyquinolinato aluminum (Alq₃) with a crystalline hexagonal column morphology. Pristine Alq₃ nanoparticles (NPs) were prepared using a conventional reprecipitation method. Crystal hexagonal columns of Alq₃ were grown by using a surfactant-assisted self-assembly technique as an adjunct to the aforementioned reprecipitation method. The formation and structural properties of the crystalline and non-crystalline Alq₃ NPs were analyzed with scanning electron microscopy and X-ray diffraction. The nanoscale photoluminescence (PL) characteristics and the luminescence color of the Alq₃ single NPs and their crystal microwires (MWs) were evaluated from color charge-coupled device images acquired using a high-resolution laser confocal microscope. In comparison with the Alq₃ NPs, the crystalline MWs exhibited a very bright and sharp emission. This enhanced and sharp emission from the crystalline Alq₃ single MWs originated from effective π-π stacking of the Alq₃ molecules due to strong interactions in the crystalline structure.

Low loss optical waveguiding in large single crystals of a thiophene-based oligomer

Active optical waveguides based on functional small organic molecules in micro/nano regime have attracted great interest for their potential applications in high speed miniaturized photonic integrations.

Assembly of four 8-quinolinate-based multinuclear complexes: the effect of substituents on core structures and photoluminescence properties

Four multinuclear complexes with different core structures are synthesized. The core structures and photoluminescence properties of M(ii)–quinolinate complexes are controlled by the different substituent groups of ligands.

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

Two types of organic particle/MOF structures, i.e. Znq₂@ZIF-8 core–shell and multiple Znq₂ particles on each ZIF-8, can be constructed by modulating the Znq₂–ZIF-8 interfacial energy with PVP.

Multistimuli-Responsive Luminescence of Naphthalazine Based on Aggregation-Induced Emission

Stimuli-responsive luminescent materials, which are dependent on changes in physical molecular packing modes, have attracted more and more interest over the past ten years. In this study, 2,2-dihydroxy-1,1-naphthalazine was synthesized and shown to exhibit different fluorescence emission in solution and solid states with characteristic aggregation-induced emission (AIE) properties. A remarkable change in the fluorescence of 2,2-dihydroxy-1,1-naphthalazine occurred upon mechanical grinding, heating, or exposure to solvents. According to the characterization by solid-state fluorescence spectroscopy, X-ray crystallography, differential scanning calorimetry, and X-ray powder diffraction, the fluorescence change could be attributed to transitions between two structurally different polymorphs. These significant properties could also give 2,2-dihydroxy-1,1-naphthalazine more potential applications as a multifunctional material.

Structures and photoluminescence properties of Alq3 1D materials prepared by an extremely facile solution method

The formation processes of Alq₃ rods and the performance of photoluminescence.

Five 8-hydroxyquinolinate-based coordination polymers with tunable structures and photoluminescent properties for sensing nitroaromatics

Five coordination polymers with different structures have been prepared. The tunable structures and photoluminescent properties for sensing nitroaromatics in five polymers were observed.

Anomalous variation of electrical transport property and amorphization in dense Alq3

The experimental results indicate that the Al–oxine interaction can also be believed to be significant for the electrical transport properties of dense Alq₃.

Structural and luminescence modulation in 8-hydroxyquinolinate-based coordination polymers by varying the dicarboxylic acid

Using dicarboxylic acids as secondary auxiliary ligands, six coordination polymers are synthesized under solvothermal conditions. These polymers exhibited disparate fluorescence emission bands and lifetimes due to their different metal centers and supramolecular structures.

Six Zn(ii) and Cd(ii) coordination polymers assembled from a similar binuclear building unit: tunable structures and luminescence properties

Six coordination polymers with different structures have been prepared. The tunable structures and photoluminescence properties were observed due to their different metal centers and supramolecular structures.

Conformal and highly luminescent monolayers of Alq3 prepared by gas-phase molecular layer deposition

The gas-phase molecular layer deposition (MLD) of conformal and highly luminescent monolayers of tris(8-hydroxyquinolinato)aluminum (Alq3) is reported. The controlled formation of Alq3 monolayers is achieved for the first time by functionalization of the substrate with amino groups, which serve as initial docking sites for trimethyl aluminum (TMA) molecules binding datively to the amine. Thereby, upon exposure to 8-hydroxyquinoline (8-HQ), the self-limiting formation of highly luminescent Alq3 monolayers is afforded. The growth process and monolayer formation were studied and verified by in situ quartz crystal monitoring, optical emission and absorption spectroscopy, and X-ray photoelectron spectroscopy. The nature of the MLD process provides an avenue to coat arbitrarily shaped 3D surfaces and porous structures with high surface areas, as demonstrated in this work for silica aerogels. The concept presented here paves the way to highly sensitive luminescent sensors and dye-sensitized metal oxides for future applications (e.g., in photocatalysis and solar cells).