Organic Single-Crystalline Ribbons of a Rigid "H"-type Anthracene Derivative and High-Performance, Short-Channel Field-Effect Transistors of Individual Micro/Nanometer-Sized Ribbons Fabricated by an "Organic Ribbon Mask" Technique

An asymmetric naphthalimide derivative for n-channel organic field-effect transistors

A novel asymmetric naphthalimide derivative (IZ0) is synthesized and high electron mobility of 0.072 cm²V⁻¹s⁻¹and 0.22 cm²V⁻¹s⁻¹are achieved for IZ0 film and single crystal-based transistors, respectively.

Anisotropy of the n-type charge transport and thermal effects in crystals of a fluoro-alkylated naphthalene diimide: a computational investigation

The anisotropy of the n-type charge transport of a fluoro-alkylated naphthalene diimide is investigated in the framework of the non-adiabatic hopping mechanism. Charge transfer rate constants are computed within the Marcus-Levich-Jortner formalism including a single effective mode treated quantum-mechanically and are injected in a kinetic Monte Carlo scheme to propagate the charge carrier in the crystal. Charge mobilities are computed at room temperature with and without the influence of an electric field and are shown to compare very well with previous measurements in single-crystal devices which offer a superior substrate for testing molecular models of charge transport. Thermally induced dynamical effects are investigated by means of an integrated computational approach including molecular dynamics simulations coupled to quantum-chemical evaluation of electronic couplings. It is shown that charge transport occurs mainly in the b,c crystallographic plane with a major component along the c axis which implies an anisotropy factor in very good agreement with the observed value.

Charge-transfer complex crystal based on extended-π-conjugated acceptor and sulfur-bridged annulene: charge-transfer interaction and remarkable high ambipolar transport characteristics

A single crystal of a novel mixed-stack donor-acceptor complex formed by a tetracyanoquinodimethane derivative with an extended π-conjugated system and a sulfur-bridged annulene displays the highest ambipolar transport behavior among donor-acceptor complexes reported with electron and hole mobilities reaching up to 0.24 and 0.77 cm(2) V(-1) s(-1) , respectively.

Integrated prototype nanodevices via SnO₂ nanoparticles decorated SnSe nanosheets

Hybrid materials made from all inorganic components are intriguing in many fields, because they have shown in-depth potential use for electronic and optoelectronic applications including solar cells, gas sensors, photodetectors, and field effect transistors. Hybrid materials made from SnO₂ nanoparticles on SnSe nanosheets have been synthesized via a facile, lost-cost and safe solution method, and have been demonstrated as promising multifunctional materials in various prototype devices, including gas sensors, photodetectors, and field effect transistors.

Porphyrin nanoassemblies via surfactant-assisted assembly and single nanofiber nanoelectronic sensors for high-performance H₂O₂ vapor sensing

Porphyrins are recognized as important π-conjugated molecules correlating supramolecular chemistry, nanoscience, and advanced materials science. So far, as their supramolecular nanoassemblies are addressed, most efforts focus on the photo- or opto-related subjects. Beyond these traditional subjects, it is strongly desired to develop advanced porphyrin nanoassemblies in some other new topics of paramount importance. By means of a surfactant-assisted assembly, we herein show that porphyrins of different central metal ions, 5,10,15,20-tetra(4-pyridyl)-21H,23H-porphine (H2TPyP), zinc 5,10,15,20-tetra(4-pyridyl)-21H,23H-porphine (ZnTPyP), and oxo-[5,10,15,20-tetra(4-pyridyl)porphyrinato]titanium(IV) (TiOTPyP), could be organized to form irregular aggregates, short nanorods, and long yet straight nanofibers, respectively. Remarkably, in terms of an organic ribbon mask technique, we show that such long yet straight TiOTPyP nanofibers could be integrated into single nanofiber-based two-end nanoelectronics. Such simple nanodevices could serve as high-performance sensors of a satisfactory stability, reproducibility, and selectivity for an expeditious detection of vapor-phase H2O2. This provides a new alternative for a fast sensing of vapor-phase H2O2, which is currently an important issue in the fields of anti-terrorism, industrial healthcare, etc. In contrast to the traditional investigations focusing on the photo- or opto-related topics, our work endows porphyrin nanostructures with new opportunities as advanced nanomaterials in terms of portable yet high-performance nanoelectronic sensors, which is an issue of general concern in modern advanced nanomaterials.

Near-equilibrium chemical vapor deposition of high-quality single-crystal graphene directly on various dielectric substrates

By using near-equilibrium chemical vapor deposition, it is demonstrated that high-quality single-crystal graphene can be grown on dielectric substrates. The maximum size is about 11 μm. The carrier mobility can reach about 5650 cm(2) V(-1) s(-1) , which is comparable to those of some metal-catalyzed graphene crystals, reflecting the good quality of the graphene lattice.

Single-molecule electronics: from chemical design to functional devices

The use of single molecules in electronics represents the next limit of miniaturisation of electronic devices, which would enable to continue the trend of aggressive downscaling of silicon-based electronic devices.

Tuning electrical properties of graphite oxide by plasma

The electrical properties of graphite oxide (GO) can be tuned consecutively by treating samples with ammonia and hydrogen plasma. When altering ammonia plasma time from 10 to 4.5 min, large area (greater than 100×100 μm²), n-type, ambipolar and p-type semiconducting reduced graphite oxide (RGO) sheets could be obtained. The highest mobilities of the electron and hole are 5.41 and 2.10 cm² V⁻¹ s⁻¹ at low operational voltage (3 or -3 V, respectively). When treating a GO film with hydrogen:argon (9:1) plasma, high conductivity RGO was obtained with conductivity around 630 S cm⁻¹. It is anticipated that this study could pave the way towards carbon-based electronics.

Anisotropic photoresponse properties of single micrometer-sized GeSe nanosheet

Micrometer-sized single-crystal GeSe nanosheets have been synthesized by a solution method. The single GeSe nanosheet exhibits novel anisotropic photoresponse properties in two photodetectors based on individual nanosheet. The on/off switching ratio of the photodetector perpendicular to the nanosheet is 3.5 times higher than that parallel to the nanosheet.

Coaxial organic p-n heterojunction nanowire arrays: one-step synthesis and photoelectric properties

Organic/organic single-crystal coaxial p-n heterojunction nanowire arrays consisting of p-type copper phthalocyanine (CuPc) and n-type 5,10,15,20-tetra(4-pyridyl)-porphyrin (H(2)TPyP) are fabricated through a one-step physical vapor transport (PVT) process. Each single junction wire revealed high photodependent rectifying and sensitive photoresponsive characteristics in devices of light-controlled diodes and photoswitches. The typical photovoltaic device based on a single p-n junction exhibited a high open-circuit voltage (Voc) of 0.64 V.

High performance n-type single crystalline transistors of naphthalene bis(dicarboximide) and their anisotropic transport in crystals

High-performance n-type organic single crystal transistors of a naphthalene diimide are demonstrated. The accomplished transistors exhibit electron mobility as high as 0.7 cm(2) V(-1) s(-1). The anisotropic charge transport in the elongated hexagonal crystals of the naphthalene diimide is also explored. The transport anisotropy along different directions is at least 1.6 (mobility ratio).

Uniform hexagonal graphene flakes and films grown on liquid copper surface

Unresolved problems associated with the production of graphene materials include the need for greater control over layer number, crystallinity, size, edge structure and spatial orientation, and a better understanding of the underlying mechanisms. Here we report a chemical vapor deposition approach that allows the direct synthesis of uniform single-layered, large-size (up to 10,000 μm(2)), spatially self-aligned, and single-crystalline hexagonal graphene flakes (HGFs) and their continuous films on liquid Cu surfaces. Employing a liquid Cu surface completely eliminates the grain boundaries in solid polycrystalline Cu, resulting in a uniform nucleation distribution and low graphene nucleation density, but also enables self-assembly of HGFs into compact and ordered structures. These HGFs show an average two-dimensional resistivity of 609 ± 200 Ω and saturation current density of 0.96 ± 0.15 mA/μm, demonstrating their good conductivity and capability for carrying high current density.

Molecular crystal lithography: a facile and low-cost approach to fabricate nanogap electrodes

A novel cost-efficient and facile technique, molecular crystal lithography, to fabricate nanogap electrodes efficiently is reported. The gap width of the electrodes can be tuned from ∼9 nm to several micrometers. Organic field-effect transistors based on the nanogap electrodes all exhibit a high performance, indicating the effectiveness and practicability of molecular crystal lithography for mass production of nanogap electrodes.

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.

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.

Self-assembled single-crystal polyaniline microplates and their anisotropic electrical transport property

Self-assembly of two-dimensional (2D) structures from functional molecules is of great scientific importance. Herein, using a typical linear conducting polymer, polyaniline as building blocks, 2D single crystalline microplates are successively produced. The structure of 2D microplates is clearly defined by selected area electron diffraction, X-ray diffraction, and Raman spectroscopy. Owing to the anisotropic arrangement of linear conjugated PANI molecules, the microplate shows a typical anisotropic electrical transport property.

Ag nanoparticles/PPV composite nanofibers with high and sensitive opto-electronic response

The novel Ag nanoparticles/poly(p-phenylene vinylene) [PPV] composite nanofibers were prepared by electrospinning. The transmission electron microscope image shows that the average diameter of composite fibers is about 500 nm and Ag nanoparticles are uniformly dispersed in the PPV matrix with an average diameter of about 25 nm. The Fourier transform infrared spectra suggest that there could be a coordination effect to a certain extent between the Ag atom and the π system of PPV, which is significantly favorable for the dissociation of photoexcitons and the charge transfer at the interface between the Ag nanoparticle and the PPV. The Au top electrode device of the single Ag/PPV composite nanofiber exhibits high and sensitive opto-electronic responses. Under light illumination of 5.76 mW/cm2 and voltage of 20 V, the photocurrent is over three times larger than the dark current under same voltage, which indicates that this kind of composite fiber is an excellent opto-electronic nanomaterial.

Tuning intermolecular non-covalent interactions for nanowires of organic semiconductors

Anthracene and its derivatives are used to demonstrate a simple way to cast assemble nanowires of organic semiconductors with tuning of intermolecular non-covalent interactions by molecular design. The tuning of intermolecular interactions could be achieved by (i) decreasing intermolecular hydrophobic interactions by linking hydrophilic side chains to anthracene rings, (ii) increasing intermolecular interaction for self-assembly with the assistance of hydrogen bonds, and (iii) enhancing molecular π-π interaction by increasing the conjugated dimension of the compounds.

Micro- and nanocrystals of organic semiconductors

Organic semiconductors have attracted wide attention in recent decades, resulting in the rapid development of organic electronics. For example, the solution processibility of organic semiconductors allows researchers to use unconventional deposition methods (such as inkjet printing and stamping) to fabricate large area devices at low cost. The mechanical properties of organic semiconductors also allow for flexible electronics. However, the most distinguishing feature of organic semiconductors is their chemical versatility, which permits the incorporation of functionalities through molecular design. However, key scientific challenges remain before organic electronics technology can advance further, including both the materials' low charge carrier mobility and researchers' limited knowledge of structure-property relationships in organic semiconductors. We expect that high-quality organic single crystals could overcome these challenges: their purity and long-range ordered molecular packing ensure high device performance and facilitate the study of structure-property relationships. Micro- and nanoscale organic crystals could offer practical advantages compared with their larger counterparts. First, growing small crystals conserves materials and saves time. Second, devices based on the smaller crystals could maintain the functional advantages of larger organic single crystals but would avoid the growth of large crystals, leading to the more efficient characterization of organic semiconductors. Third, the effective use of small crystals could allow researchers to integrate these materials into micro- and nanoelectronic devices using a "bottom-up" approach. Finally, unique properties of crystals at micro- and nanometer scale lead to new applications, such as flexible electronics. In this Account, we focus on organic micro- and nanocrystals, including their design, the controllable growth of crystals, and structure-property studies. We have also fabricated devices and circuits based on these crystals. This interdisciplinary work combines techniques from the fields of synthetic chemistry, self-assembly, crystallography, and condensed matter physics. We have designed new molecules, including a macrocycle and polyaromatic compounds that self-assemble in a predictive manner into regular high-quality crystals. We have examined how the structure, particularly pi-pi interactions, determines the crystal growth and how the external conditions affect the crystal morphology. We have developed new methods, such as the gold wire mask, the organic ribbon mask, and the gold layer stamp techniques, to fabricate high-performance devices based on the small crystals and investigate their anisotropic charge transport properties. In addition, we have demonstrated small-crystal organic circuits that function with high performance and ultralow power consumption. We expect that organic micro- and nanocrystals have a bright future in organic electronics.

Nanogap electrodes

Nanogap electrodes (namely, a pair of electrodes with a nanometer gap) are fundamental building blocks for the fabrication of nanometer-sized devices and circuits. They are also important tools for the examination of material properties at the nanometer scale, even at the molecular scale. In this review, the techniques for the fabrication of nanogap electrodes, the preparation of assembled devices based on the nanogap electrodes, and the potential application of these nanodevices for analysis of material properties are introduced. The history, the research status, and the prospects of nanogap electrodes are also discussed.

From allenes to tetracenes: Syntheses, structures, and reactivity of the intermediates

Each step of the conversion of a series of 9-alkynyl-9H-fluorenes into the corresponding fluorenylidene-allenes that dimerize and proceed sequentially via head-to-tail and tail-to-tail dialkylidene-cyclobutanes, en route to electroluminescent tetracenes, has been characterized X-ray crystallographically. Allenes possessing substituents of very different electronic and steric character, such as aryl, halogeno, silyl, phosphino, and ferrocenyl, exhibit novel and unexpected reactivity patterns. The silyl-allenes dimerize to yield 1,2-bis(fluorenylidene)cyclobutanes of intrinsic C2 symmetry as a result of the overlapping fluorenylidenes with their large wingspans. Thermal rearrangement of a bis(fluorenyl)-bis(trimethylsilyl)-diallene generates the tetrabenzo-quatercyclopentadiene, C60H36, which represents 60 % of the C60 framework. An attempt to isolate a "push-pull" allene, whose central carbon possesses carbene character, was made by incorporating a cation-stabilizing substituent (ferrocenyl) and an aromatic anionic moiety (fluorenide) at the termini. However, the allene underwent facile dimerization to the very heavily congested 3,4-di(spirofluorenyl)-1,2-bis(ferrocenyl-chloromethylene)cyclobutane that exhibits a very long (1.65 Å) C(3)-C(4) bond. Extension of this chemistry to dibenzosuberenylidene-allenes led to a straightforward route to the hitherto difficultly available dibenz[c,d,h]azulene system. Moreover, the reaction of 5-phenylethynyl-5H-dibenzo[a,d]cyclohepten-5-ol with dicobalt octacarbonyl yielded, surprisingly, the first isolated example of a (μ-alkyne)Co2(CO)5(η2-alkene)complex, the long-sought first intermediate in the proposed mechanism of the Pauson-Khand reaction (PKR).