Self-assembly of functional molecules into 1D crystalline nanostructures

Understanding Pathway Complexity of Organic Micro/Nanofiber Growth in Hydrogen-Bonded Coassembly of Aromatic Amino Acids

Rational engineering of one-dimensional (1D) self-assembled aggregates to produce desired materials for versatile functions remains a challenge. In this work, we report the noncovalent modulation of 1D aggregates at the micro/nanoscale using a coassembly protocol. Aromatic amino acids were employed as the model building blocks, and melamine (Mm) behaves as a modulator to form coassembly arrays with aromatic amino acids selectively. The selective self-assembly behavior between aromatic amino acids and Mm allows distinguishing and detecting Mm and aromatic amino acids from their analogues in macroscopic and microscopic scales. Dimensions and sizes of fibrous aggregates prepared from different amino acids show two opposite pathways from pristine assemblies to coassemblies induced by the addition of Mm. This pathway complexity could be controlled by the molecular conformation determined by α-positioned substituents. The developed hypothesis presents an excellent expansibility to other substrates, which may guide us to rationally design and screen 1D materials with different dimensions and sizes including the production of high-quality self-standing hydrogels.

Semiconducting Self-Assembled Nanofibers Prepared from Photostable Octafluorinated Bisanthene Derivatives

Bisanthene is an important class of small two-dimensional polycyclic aromatic hydrocarbons with a zigzag-edged graphene nanoribbon character. Therefore, the functionalization and deep understanding of the structure-property relationship of bisanthene would provide an effective design for small organic molecular devices. In this study, octa- and tetrafluorinated bisanthene derivatives were synthesized for investigating the effect of electronegative fluorine substitution on the structure and physical property of bisanthene. Firstly, the octafluorinated bisanthene derivative has a twisted structure due to the steric repulsion of fluorine atoms at the bay region. Secondly, the absorption and fluorescence peak maxima are blueshifted with an increase in the degree of fluorine substitution. Notably, a triisopropylsilylethynyl-substituted octafluorinated derivative (F8) exhibited strong fluorescence at 657 nm with high fluorescence quantum yield (84 %). Additionally, cyclic voltammograms indicate the positive effect of fluorine substitution on the high highest occupied molecular orbital energy level of the molecules; thus, F8 molecule exhibited a remarkably increased photostability. Finally, the self-assembled behavior of fluorinated compounds was investigated by scanning electron microscopy and X-ray diffraction analysis. Specifically, F8 self-assembled to form bundles of long semicrystalline nanofibers exhibiting hole-transporting properties (3.4×10^-3  cm²  V^-1  s^-1 ).

Preparation of Main-Chain Polymers Based on Novel Monomers with D-π-A Structure for Application in Organic Second-Order Nonlinear Optical Materials with Good Long-Term Stability

Main-chain nonlinear optical polymers based on novel chromophores with special structures presented good solubility in most of the organic solvents. Polymers PE-1 and PE-2 attained the thermal decomposition temperatures of 305 and 223 °C and glass transition temperatures of 113 and 108 °C, and exhibited only negligible decay in the SHG signal baked at 85 °C over hundreds of hours, respectively. The SHG coefficients of poled films from polymers PE-1 and PE-2 were 26.3 and 35.8 pm/V, respectively. These results indicated that this class of polymers can be used in the preparation of organic electro-optic devices.

Controlling the length of self-assembled nanotubes by sonication followed by polymer wrapping

In this work, we report that sonication, followed by polymer-wrapping, is an effective strategy to reduce the length of self-assembled nanotubes and suspend their propensity to self-heal into their elongated precursors.

One-minute self-assembly of millimetre-long DAST crystalline microbelts via substrate-supported rapid evaporation crystallization

We propose a substrate-supported rapid evaporation crystallization method to rapidly self-assemble microbelts of DAST, a benchmark organic NLO crystal. DAST microbelt formation depends on substrate properties and surfactant.

Temperature-Dependent Charge Transport through Individually Contacted DNA Origami-Based Au Nanowires

DNA origami nanostructures have been used extensively as scaffolds for numerous applications such as for organizing both organic and inorganic nanomaterials, studying single molecule reactions, and fabricating photonic devices. Yet, little has been done toward the integration of DNA origami nanostructures into nanoelectronic devices. Among other challenges, the technical difficulties in producing well-defined electrical contacts between macroscopic electrodes and individual DNA origami-based nanodevices represent a serious bottleneck that hinders the thorough characterization of such devices. Therefore, in this work, we have developed a method to electrically contact individual DNA origami-based metallic nanowires using electron beam lithography. We then characterize the charge transport of such nanowires in the temperature range from room temperature down to 4.2 K. The room temperature charge transport measurements exhibit ohmic behavior, whereas at lower temperatures, multiple charge transport mechanisms such as tunneling and thermally assisted transport start to dominate. Our results confirm that charge transport along metallized DNA origami nanostructures may deviate from pure metallic behavior due to several factors including partial metallization, seed inhomogeneities, impurities, and weak electronic coupling among AuNPs. Besides, this study further elucidates the importance of variable temperature measurements for determining the dominant charge transport mechanisms for conductive nanostructures made by self-assembly approaches.

Mechanism for Conducting Filament Growth in Self-Assembled Polymer Thin Films for Redox-Based Atomic Switches

The switching mechanisms of atomic switches based on poly(ethylene oxide) (PEO) are systematically investigated. By using self-assembled PEO and Ag-PEO thin films, stack-structured devices exhibit stable bipolar switching behavior over 10(3) cycles. Direct observation of filament growth behavior in planar-structured devices reveals the effects of the polymer thin-film morphology, and the presence of electrochemically active electrodes, on the switching characteristics.

The facile synthesis and optical waveguide properties of single-crystal 1,2,3,4,5-pentaphenyl-1,3-cyclopentadiene microrods

Single-crystalline 1,2,3,4,5-pentaphenyl-1,3-cyclopentadiene (PPCP) microrods were prepared using a facile solution process.

Shape-controlled synthesis of platinum octaethylporphyrin crystalline aggregates modulated by versatile ionic liquids

ILs-mediated solution self-assembly was exploited to produce the well-defined single-crystalline PtOEP microwires, which had highly sensitive photo-response and active optical waveguide characteristics.

Structure advantage and peroxidase activity enhancement of deuterohemin-peptide–inorganic hybrid flowers

Hybridizing deuterohemin-peptide (DhHP-6) with copper phosphate to form hybrid flowers was prepared for preventing DhHP-6 aggregation.

Anion-controlled morphologies and photophysical features of organic microcrystals by solid-phase anion exchange reactions

Anions play key roles in controlling the morphologies of organic microcrystals fabricated by simple and green solid-phase anion exchange reactions.

Synthetic self-assembled homogeneous network hydrogels with high mechanical and recoverable properties for tissue replacement

Homogeneous network hydrogels with high mechanical and recoverable properties for tissue replacement are prepared by one-pot free radical polymerization.

Morphology-dependent low macroscopic field emission properties of titania/titanate nanorods synthesized by alkali-controlled hydrothermal treatment of a metallic Ti surface

One-dimensional (1D) and two-dimensional (2D) titania/titanate nanostructures are fabricated directly on a self-source metallic titanium (Ti) surface via in situ surface re-construction of a Ti substrate using potassium hydroxide (KOH) under a hydrothermal (HT) condition. The effect of temperature and the concentration of KOH on the variations in morphology and titania-to-titanate phase changes are studied and explained in detail. A growth model is proposed for the formation process of the platelet-to-nanorod conversion mechanism. The field emission (FE) properties of titania/titanate nanostructures are studied, and the effects of the morphologies (such as 1D nanorods, 2D nanoplatelets, and a mixture of 1D nanorods and 2D platelets) on the FE properties of the samples are investigated. The samples depict a reasonable low turn-on field and emission stability. The FE mechanism is observed to follow standard Fowler-Nordheim (FN) electron tunneling. The geometrical field enhancement factor (β) is measured to be very high, and is compared with theoretical values calculated from various existing models to explore the feasibility of these models. The surface modification of metallic Ti by a simple non-lithographic bottom-up method and the low-macroscopic FE properties can provide a potential alternative to field emission displays for low-power panel technology.

High aspect ratio conjugated polymer nanowires for high performance field-effect transistors and phototransistors

We synthesized a highly crystalline DPP-based polymer, DPPBTSPE, which contained 1,2-bis(5-(thiophen-2-yl)selenophen-2-yl)ethene as a planar and rigid electron donating group. High- and low-molecular weight (MW) DPPBTSPE fractions were collected by Soxhlet extraction and were employed to investigate their unique charge transport properties in macroscopic films and single crystalline polymer nanowire (SC-PNW), respectively. The low-MW polymer could provide well-isolated and high aspect ratio SC-PNWs, in which the direction of π-π stacking was perpendicular to the wire growing axis. The field effect transistors made of SC-PNWs exhibited remarkably high carrier mobility of 24 cm(2) V(-1) s(-1). In addition, phototransistors (PTs) made of SC-PNW showed very high performance in terms of photoresponsivity (R) and photoswitching ratio (P). The average R of the SC PNW-based PTs were in the range of 160-170 A W(-1) and the maximum R was measured at 1920 A W(-1), which is almost three orders higher than that of thin film-based PT device.

Controllable growth of organic nanostructures from 0D to 1D with different optical properties

Controllable nano/microstructures from 0D to 1D were fabricated by adjusting the growth rate. The difference in symmetry between two molecules results in distinct self-assembly behaviours and different optical properties.

Solvothermal synthesis of 1D nanostructured Mn2O3: effect of Ni2+ and Co2+ substitution on the catalytic activity of nanowires

In this paper, cation modified one dimensional Mn₂O₃ nanowires were synthesized via a solvothermal synthesis and calcination free from the template-assisted method.

Fabrication and physical properties of self-assembled ultralong polymer/small molecule hybrid microstructures

The present work showed a novel approach to fabricate polymer/small molecule hybrid microstructures, and the transport characteristics and morphologies of the as-fabricated wires with different ratios of the two different components.

Development and cell imaging applications of a novel fluorescent probe for Cu2+

A reactivity-based fluorescent probe was utilized to selectively detecting Cu²⁺ in aqueous solution and living cell.

Morphology-controlled assembly and enhanced emission of fluorescence in organic nanospheres and microrods based on 1,2-diphenyl-4-(4-dibenzothienyl)phenyl-1,3-cyclopentadiene

Fluorescent organic micro/nanostructures of 1,2-diphenyl-4-(4-dibenzothienyl)phenyl-1,3-cyclopentadiene have been prepared via controlling the solvent composition.

Solvent-induced self-assembly synthesis of ultralong single crystalline organic NiOEP nanowires with high photoconductivity

We develop a facile approach for the one-step growth of ultralong and high-quality NiOEP nanowires in a large area, through a solvent-induced self-assembly method without using any structure directing agents.