Linearly Polarized Emission of an Organic Semiconductor Nanobelt

Rational Design of PDI-Based Linear Conjugated Polymers for Highly Effective and Long-Term Photocatalytic Oxygen Evolution

Constructed through relatively weak noncovalent forces, the stability of organic supramolecular materials has shown to be a challenge. Herein, the designing of a linear conjugated polymer is proposed through creating a chain polymer connected via bridging covalent bonds in one direction and retaining π-stacked aromatic columns in its orthogonal direction. Specifically, three analogs of linear conjugated polymers through tuning the aromatic core and its covalently linked moiety (bridging group) within the building block monomer are prepared. Cooperatively supported by strong π-π stacking interactions from the extended aromatic core of perylene and favorable dipole-dipole interactions from the bridging group, the as-expected high crystallinity, wide light absorption, and increased stability are successfully achieved for Oxamide-PDI (perylene diimide) through ordered molecular arrangement, and present a remarkable full-spectrum oxygen evolution rate of 5110.25 µmol g^-1  h^-1 without any cocatalyst. Notably, experimental and theoretical studies reveal that large internal dipole moments within Oxamide-PDI together with its ordered crystalline structure enable a robust built-in electric field for efficient charge carrier migration and separation. Moreover, density functional theory (DFT) calculations also reveal oxidative sites located at carbon atoms next to imide bonds and inner bay positions based on proven spatially separated photogenerated electrons and holes, thus resulting in highly efficient water photolysis into oxygen.

Pyridyl substitution at 2,6-positions of anthracene toward crystal polymorphs with distinct optical characteristics

As for molecular materials, packing motif plays a pivotal role in determining the optoelectronic characteristics, which can be tailored by not only molecular structures but also crystal polymorphs. However, it...

Organic semiconductor crystals

A comprehensive overview of organic semiconductor crystals is provided, including the physicochemical features, the control of crystallization and the device physics.

Preparation and Fluorescence Properties of Perylenediimide Nanodispersions Having a One-Dimensional π-Stacked Structure

We prepared stable nanodispersions of a fluorescent perylenediimide (PDI) derivative having long alkyl chains by nanosecond laser fragmentation of its microcrystalline powder in acetonitrile (ACN). The nanoparticles had cube-like or rod shapes with a mean size of 100 nm, and they dispersed stably for longer than 1 month. The prepared nanobricks exhibited absorption and fluorescence spectra characteristic of one-dimensional aggregates with cofacial stacking of PDI planes. Single-particle fluorescence measurements demonstrated that nanobricks had a well-aligned structure of one-dimensional columns of PDI. The aqueous dispersions were also fabricated by redispersing the prepared nanobricks, utilizing lipophilic interactions of surfactants having long alkyl chains. We examined the fluorescence properties of nanoparticles dispersed in ACN and in water, and observed amplified fluorescence quenching by the surface-adsorbed dye.

Donor–acceptor single cocrystal of coronene and perylene diimide: molecular self-assembly and charge-transfer photoluminescence

Organic semiconductor molecules, coronene and perylene diimide, form an alternate stacked cocrystal due to the strong donor–acceptor charge transfer interaction.

How does the interplay between bromine substitution at bay area and bulky substituents at imide position influence the photophysical properties of perylene diimides?

This article reports a comparative study on the photophysical properties of perylene diimides which caused by the interplay between bromine substitution at bay area and bulky substituents at imide position.

2,6-Di(thiophenyl)-1,5-dihydrodipyrrolopyrazine (DT-DPP) structural isomers as donor–acceptor–donor molecules and their optoelectronic investigation

We report the synthesis and characterization of two new D–A–D molecules via Pd catalyzed C–C and C–N coupling reactions. This illustrates the potential of DT-DPP for promising optoelectronic applications.

Large-size nanosheets of 9,10-bis(phenylethynyl)anthracene with high photoresponse and light emission anisotropy

Large-size single crystalline nanosheets of 9,10-bis(phenylethynyl)-anthracene were prepared by a facile solution process and were fully characterized.

Prospects of nanoscience with nanocrystals

Colloidal nanocrystals (NCs, i.e., crystalline nanoparticles) have become an important class of materials with great potential for applications ranging from medicine to electronic and optoelectronic devices. Today's strong research focus on NCs has been prompted by the tremendous progress in their synthesis. Impressively narrow size distributions of just a few percent, rational shape-engineering, compositional modulation, electronic doping, and tailored surface chemistries are now feasible for a broad range of inorganic compounds. The performance of inorganic NC-based photovoltaic and light-emitting devices has become competitive to other state-of-the-art materials. Semiconductor NCs hold unique promise for near- and mid-infrared technologies, where very few semiconductor materials are available. On a purely fundamental side, new insights into NC growth, chemical transformations, and self-organization can be gained from rapidly progressing in situ characterization and direct imaging techniques. New phenomena are constantly being discovered in the photophysics of NCs and in the electronic properties of NC solids. In this Nano Focus, we review the state of the art in research on colloidal NCs focusing on the most recent works published in the last 2 years.

Preparation of n-type semiconducting polymer nanoarrays by covalent synthesis followed by crystallization

N-type semiconducting polymer nanoarrays derived from poly(perylenediimide-bridged silsesquioxanes) were prepared by in situ covalent synthesis followed by solution crystallization. Their crystallinity and polymer chain ordering support their photophysical behavior in solid state.

Fused arene-functionalized polyhedral oligomeric silsesquioxanes as thermoelectric materials

Two derivatives of fused-arene functionalized polyhedral oligomeric silsesquioxanes (POSS-ANT and POSS-PDI-POSS) were synthesized and their electronic properties were studied for organic-based thermoelectric devices.

Self-assembly of CdSe nanoplatelets into giant micrometer-scale needles emitting polarized light

We report on the self-assembly of colloidal CdSe nanoplatelets into micrometers long anisotropic needle-like superparticles (SPs), which are formed in solution upon addition of an antisolvent to a stable colloidal dispersion. Optical fluorescence microscopy, transmission electron microscopy, and small-angle X-ray scattering provide detailed structural characterization and show that each particle is composed of 10(6) nanoplatelets organized in highly aligned columns. Within the SPs, the nanoplatelets are stacked on each other to maximize the contact surface between the ligands. When deposited on a substrate, the planes of the platelets are oriented perpendicularly to its surface and the SPs exhibit polarized emission properties.

Covalent synthesis of perylenediimide-bridged silsesquioxane nanoribbons and their electronic properties

Perylenediimide-bridged silsesquioxane nanostructures were prepared by base catalyzed polymerization and their electronic properties were studied for organic photovoltaics.

Self-assembled pentacenequinone derivative for trace detection of picric acid

Pentacenequinone derivative 3 forms luminescent supramolecular aggregates both in bulk as well as in solution phase. In bulk phase at high temperature, long-range stacking of columns leads to formation of stable and ordered columnar mesophase. Further, derivative 3 works as sensitive chemosensor for picric acid (PA) and gel-coated paper strips detect PA at nanomolar level and provide a simple, portable, and low-cost method for detection of PA in aqueous solution, vapor phase, and in contact mode.

Construction of supramolecular self-assembled microfibers with fluorescent properties through a modified ionic self-assembly (ISA) strategy

Highly ordered supramolecular microfibers were constructed through a simple ionic self-assembly strategy from complexes of the N-tetradecyl-N-methylpyrrolidinium bromide (C(14)MPB) surface-active ionic liquid and the small methyl orange (MO) dye molecule, with the aid of patent blue VF sodium salt. By using scanning electron microscopy and polarized optical microscopy, the width of these self-assembled microfibers is observed to be about 1 to 5 μm and their length is from tens of micrometers to almost a millimeter. The (1)H NMR spectra of the microfibers indicates that the supramolecular complexes are composed of C(14)MPB and MO in equal molar ratio. The electrostatic, hydrophobic, and π-π stacking interactions are regarded as the main driving forces for the formation of microfibers. Furthermore, through characterization by using confocal fluorescence microscopy, the microfibers were observed to show strong fluorescent properties and may find potential applications in many fields.

Optical materials based on molecular nanoparticles

A major part of contemporary nanomaterials research is focused on metal and semiconductor nanoparticles, constituted of extended lattices of atoms or ions. Molecular nanoparticles assembled from small molecules through non-covalent interactions are relatively less explored but equally fascinating materials. Their unique and versatile characteristics have attracted considerable attention in recent years, establishing their identity and status as a novel class of nanomaterials. Optical characteristics of molecular nanoparticles capture the essence of their nanoscale features and form the basis of a variety of applications. This review describes the advances made in the field of fabrication of molecular nanoparticles, the wide spectrum of their optical and nonlinear optical characteristics and explorations of the potential applications that exploit their unique optical attributes.

Quinoacridine derivatives with one-dimensional aggregation-induced red emission property

A new series of acceptor-donor-acceptor (A-D-A) type quinoacridine derivatives (1-3) with aggregation-induced red emission properties were designed and synthesized. In these compounds, the electron-withdrawing 2-(3,5-bis(trifluoromethyl)phenyl)acetonitrile groups act as electron-accepting units, while the alkyl-substituted conjugated core acts as electron-donating units. The restriction of intramolecular rotation was responsible for the AIE behavior of compounds 1-3. All compounds were employed as building blocks to fabricate one-dimensional (1-D) organic luminescent nano- or microwires based on reprecipitation or slow evaporation approaches. Morphological transition from zero-dimensional (0-D) hollow nanospheres to 1-D nanotubes has been observed by recording SEM and TEM images of aggregated sates of compound 2 in THF/H(2)O mixtures at different aging time. It was demonstrated that the synthesized compounds with different lengths of alkyl chains displayed different wire formation properties. The single-crystal X-ray analysis of compound 2 provided reasonable explanation for the formation of 1-D nano- or microstructures.

Fine-tuned nanostructures assembled from L-lysine-functionalized perylene bisimides

Controllable nanostructures with tunable dimensions were obtained via self-assembly of CBZ-L-lysine-functionalized tetrachloroperylene bisimides (4ClPBI-Lys). Depending on the nature of substitute, solvent polarity, and sample concentration, 4ClPBI-Lys could form nanosphere, nanowire, nanobelt, and nanosheet, which were found to have different degree of molecular ordering. The effects of substitution position with respect to L-lysine on 4ClPBI were also explored in terms of assembly nanostructures. Hydrogen bonding was important to promote formation of long-range ordering. The nanostructures of different assemblies were characterized using SEM, TEM, XRD, UV-vis, and FTIR spectroscopy. For each obtained supramolecular assembly, we also found that the molecular packing motif ultimately determined the corresponding devices' electronic properties.

Organogels based on J- and H-type aggregates of amphiphilic perylenetetracarboxylic diimides

Three new perylenetetracarboxylic diimide (PDI) compounds substituted with hydrophobic and/or hydrophilic groups at the two imide nitrogen positions, namely N,N'-di[N-(4-aminophenyl)-3,4,5-tris(2-(2-(2-methoxyethoxy)ethoxy)ethoxy)benzamide]-1,7-di(4-tert-butylphenoxy)perylene-3,4;9,10-tetracarboxylic diimide (1), N,N'-di[N-amido-3,4,5-tris(2-(2-(2-methoxyethoxy)ethoxy)ethoxy)benzamide]-1,7-di(4-tert-butylphenoxy)perylene-3,4;9,10-tetracarboxylic diimide (2), and N-amido-3,4,5-tris(2-(2-(2-methoxyethoxy)ethoxy)ethoxy)benzamide-N'-amido-3,4,5-tris(dodecyloxy)benzamide-1,7-di(4-tert-butylphenoxy)perylene-3,4;9,10-tetracarboxylate diimide (3), have been designed and prepared. The gelating abilities of them in different solvents have been investigated, and the results indicated that compounds 1 and 3 can form fluorescent gels whereas compound 2 cannot. The properties of the gels of compounds 1 and 3 have been investigated by UV-vis absorption and emission spectra. The results indicate that the gel of compound 1 is composed of H-aggregates, whereas the gel of compound 3 is composed of J-aggregates. The reversible transformation between gel and solution states induced by temperature change is observed. The structure of dried gel has been investigated by X-ray diffraction (XRD) experiments, and the morphology has been measured by atomic force microscopy (AFM). This research revealed successfully the crucial roles of amphiphilic properties and the side-chain conformations in controlling the gelating properties of PDI molecules. This information may be useful for the design of novel organogels based on perylenetetracarboxylic diimides.

Alkyl chain length dependent morphology and emission properties of the organic micromaterials based on fluorinated quinacridone derivatives

The fluorinated quinacridone derivatives N,N'-dialkyl-2,9-difluoroquinacridone (Cn-DFQA, n = 4, 8, 10, 16) with different alkyl chains were used as building blocks to assemble luminescent micromaterials. It was demonstrated that the morphology and emission of the Cn-DFQA-based micromaterials strongly depended on their alkyl chain length. C4-DFQA and C8-DFQA showed stronger tendency to form 1-D microstructures, while C10-DFQA and C16-DFQA displayed the aggregation properties to form diamond and hexagonal platelike microcrystals, respectively. The photoluminescent (PL) spectra of Cn-DFQA (n = 4, 8, 10, 16) in THF dilute solutions displayed approximate profiles with a sharp emission peak at 533 nm and a shoulder at 573 nm, while the PL spectra of the Cn-DFQA-based micromaterials exhibited obviously red-shift emission bands at 622 nm for C4-DFQA, 627 nm for C8-DFQA, 614 nm for C10-DFQA, and 613 nm for C16-DFQA, respectively. The single-crystal X-ray structures of four Cn-DFQA compounds have been studied. In the C4-DFQA and C8-DFQA single crystals, there are 1-D molecular columns based on the intermolecular pi...pi and hydrogen bonding interactions. In the single crystals of C10-DFQA and C16-DFQA, the molecules assembled into 2-D molecular sheets based on the hydrogen bonds and C-H...pi interactions. The molecular packing structures provide a reasonable explanation for the alkyl chain length dependent morphologies and emission properties of fluorinated quinacridone micromaterials.

Organic supernanostructures self-assembled via solution process for explosive detection

Three different polymorphic crystalline structures, including microbelts and flowerlike supernanostructures, were obtained via a simple solution process by utilizing different solvents from an oligoarene derivative. Explosive chemosensors based on these self-assembled organic crystalline nanostructures were successfully fabricated. The differences in the structures on the microscopic level and in the film morphologies led to dramatic enhancements of the explosive detection speed. With the evolution of structures from the netted 1D microbelts to the flowerlike supernanostructures, the detection speed of the chemosensors for DNT and TNT was improved by more than 700 times. Our discovery demonstrates that the morphology control through self-assembly provides a new platform to utilize organic crystalline microstructures for chemosensors, optoelectronics, biosensors and bioelectronics, and so forth.

One-dimensional self-assembly of planar pi-conjugated molecules: adaptable building blocks for organic nanodevices

In general, fabrication of well-defined organic nanowires or nanobelts with controllable size and morphology is not as advanced as for their inorganic counterparts. Whereas inorganic nanowires are widely exploited in optoelectronic nanodevices, there remains considerable untapped potential in the one-dimensional (1D) organic materials. This Account describes our recent progress and discoveries in the field of 1D self-assembly of planar pi-conjugated molecules and their application in various nanodevices including the optical and electrical sensors. The Account is aimed at providing new insights into how to combine elements of molecular design and engineering with materials fabrication to achieve properties and functions that are desirable for nanoscale optoelectronic applications. The goal of our research program is to advance the knowledge and develop a deeper understanding in the frontier area of 1D organic nanomaterials, for which several basic questions will be addressed: (1) How can one control and optimize the molecular arrangement by modifying the molecular structure? (2) What processing factors affect self-assembly and the final morphology of the fabricated nanomaterials; how can these factors be controlled to achieve the desired 1D nanomaterials, for example, nanowires or nanobelts? (3) How do the optoelectronic properties (e.g., emission, exciton migration, and charge transport) of the assembled materials depend on the molecular arrangement and the intermolecular interactions? (4) How can the inherent optoelectronic properties of the nanomaterials be correlated with applications in sensing, switching, and other types of optoelectronic devices? The results presented demonstrate the feasibility of controlling the morphology and molecular organization of 1D organic nanomaterials. Two types of molecules have been employed to explore the 1D self-assembly and the application in optoelectronic sensing: one is perylene tetracarboxylic diimide (PTCDI, n-type) and the other is arylene ethynylene macrocycle (AEM, p-type). The materials described in this project are uniquely multifunctional, combining the properties of nanoporosity, efficient exciton migration and charge transport, and strong interfacial interaction with the guest (target) molecules. We see this combination as enabling a range of important technological applications that demand tightly coupled interaction between matter, photons, and charge. Such applications may include optical sensing, electrical sensing, and polarized emission. Particularly, the well-defined nanowires fabricated in this study represent unique systems for investigating the dimensional confinement of the optoelectronic properties of organic semiconductors, such as linearly polarized emission, dimensionally confined exciton migration, and optimal pi-electronic coupling (favorable for charge transport). Combination of these properties will make the 1D self-assembly ideal for many orientation-sensitive applications, such as polarized light-emitting diodes and flat panel displays.

Alq3 nanorods: promising building blocks for optical devices

Monodisperse Alq3 nanorods with hexagonal-prism-like morphology are produced via a facile, emulsion based synthesis route. The photoluminescence of individual nanorods differs from the bulk material. These nanorods are promising building blocks for novel optical devices.

Perylenediimide nanowires and their use in fabricating field-effect transistors and complementary inverters

Perylenetetracarboxyldiimide (PTCDI) nanowires self-assembled from commercially available materials are demonstrated as the n-channel semiconductor in organic field-effect transistors (OFETs) and as a building block in high-performance complementary inverters. Devices based on a network of PTCDI nanowires have electron mobilities and current on/off ratios on the order of 10(-2) cm2/Vs and 10(4), respectively. Complementary inverters based on n-channel PTCDI nanowire transistors and p-channel hexathiapentacene (HTP) nanowire OFETs achieved gains as high as 8. These results demonstrate the first example of the use of one-dimensional organic semiconductors in complementary inverters.

Colloid Chemical Reaction Route to the Preparation of Nearly Monodispersed Perylene Nanoparticles: Size-Tunable Synthesis and Three-Dimensional Self-Organization

By employing a colloid chemical reaction method we demonstrate the preparation of organic nanoparticles composed of perylene molecules (PeNPs) based on the reduction of perylene perchlorate by Br- anions in the presence of cetyl trimethyl ammonium bromide (CTA+Br-) in acetonitrile. A discrete nucleation event, followed by a slower controlled growth on the existing particles, is identified during formation of PeNPs. By changing the growth parameters, such as the monomer concentration and the method of injection, quasi-spherical PeNPs with controllable sizes from 25 to 90 nm could be obtained. The homogeneous solution phase of this method makes it capable of large-scale synthesis of PeNPs with a size distribution (<10%) that is improved by formation of a protective layer of CTA+ around the PeNPs. The three-dimensional, hierarchical self-organization of 25-nm PeNPs building blocks is observed to form nanobelts and square nanorods, possibly templated by the CTA+ lamellar micelle structures in acetonitrile. Spectroscopic results reveal two kinds of trends in the development of the optical properties of perylene as they evolve from the molecular to the bulk phase in the nanometer range. The so-called size dependence is evidenced by a switch from Y-type to E-type excimers as the size of the PeNPs increased from 25 to 90 nm. As the 25-nm PeNPs organize into nanobelts or square nanorods the oscillator strength of the Y-type excimers is relatively enhanced. That is, collective phenomena develop as the proximal particles interact in the glassy solids. Our very recent results indicate that this colloid chemical reaction method can also be applied to other organic compounds.