Self-assembly Of Organic Molecules Research Articles

Self-assembled organic molecules with a fused aromatic ring as hole-transport layers for inverted perovskite solar cells: the effect of linkers on performance

Two D–π–A structured SAMs (FNE29 and DT-1) with different linkers are self-assembled onto the indium tin oxide (ITO) substrates as HTLs for inverted PSCs. The results indicate that the SAMs with large conjugated fused linkers have obvious advantages as HTLs because of its fast hole transfer.

A Molecular-Scale Understanding of Misorientation Toughening in Corals and Seashells.

Biominerals are organic-mineral composites formed by living organisms. They are the hardest and toughest tissues in those organisms, are often polycrystalline, and their mesostructure (which includes nano- and microscale crystallite size, shape, arrangement, and orientation) can vary dramatically. Marine biominerals may be aragonite, vaterite, or calcite, all calcium carbonate (CaCO3 ) polymorphs, differing in crystal structure. Unexpectedly, diverse CaCO3 biominerals such as coral skeletons and nacre share a similar characteristic: Adjacent crystals are slightly misoriented. This observation is documented quantitatively at the micro- and nanoscales, using polarization-dependent imaging contrast mapping (PIC mapping), and the slight misorientations are consistently between 1° and 40°. Nanoindentation shows that both polycrystalline biominerals and abiotic synthetic spherulites are tougher than single-crystalline geologic aragonite. Molecular dynamics (MD) simulations of bicrystals at the molecular scale reveal that aragonite, vaterite, and calcite exhibit toughness maxima when the bicrystals are misoriented by 10°, 20°, and 30°, respectively, demonstrating that slight misorientation alone can increase fracture toughness. Slight-misorientation-toughening can be harnessed for synthesis of bioinspired materials that only require one material, are not limited to specific top-down architecture, and are easily achieved by self-assembly of organic molecules (e.g., aspirin, chocolate), polymers, metals, and ceramics well beyond biominerals.

Fabrication of monolayer with aggregation-induced emission at the air/water interface

Existing methods for producing transparent fluorescent materials are adequate for small scale production but unsuitable for larger scales. Assistant Professor Kohei Iritani and his team at the Department of Applied Chemistry, School of Engineering, Tokyo University of Technology, Japan, are working to develop 2D monolayers to overcome this. These monolayers are formed by the self-assembly of organic molecules at the solid/liquid or air/water interface and monolayers with the aggregation-induced emission (AIE) effect have the potential to be used as transparent fluorescent materials. The researchers have been successful in synthesising various AIE molecules and have made attempts to form a monolayer using the Langmuir-Blodgett (LB) trough. The team established a method whereby if a monolayer could not be obtained, feedback was given to the molecular design and a process of trial and error was repeatedly performed while new molecules were synthesised. This led to the construction of a fluorescence monolayer that can be transferred to a glass substrate while maintaining fluorescence emission. In their work to construct a monolayer with AIE effect at the air/water interface the researchers are seeking to suppress intramolecular motion using a flat surface of water as a substrate and make it emit fluorescence by forming a monolayer.

Stimuli-Responsive Transformable Supramolecular Nanotubes.

Supramolecular nanotubes produced by self-assembly of organic molecules can have unique structural features such as a one-dimensional morphology with no branching, distinguishable inner and outer surfaces and membrane walls, or a structure that is hollow and has a high aspect ratio. Incorporation of functional groups that respond to external chemical or physical stimuli into the constituent organic molecules of supramolecular nanotubes allows us to drastically change the structure of the nanotubes by applying such stimuli. This ability affords an array of controllable approaches for the encapsulation, storage, and release of guest compounds, which is expected to be useful in the fields of physics, chemistry, biology, and medicine. In this article, I review the supramolecular nanotubes developed by our group that exhibit morphological transformations in response to pH, chemical reaction, light, temperature, or moisture.

Dosimetric gelator probes and their application as sensors

Supramolecular gels formed by the self-assembly of organic molecules are useful in many areas from materials to medicine. Of the different applications, exploitation of gels for the visual detection of analytes is a fairly recent trend in gel chemistry. Most of the gel-based sensors rely on non-covalent interactions between the gelator molecules and the added chemical analytes and therefore, often suffer from less selectivity and long response time. In this context, dosimetric gelator probes are superior to other gel-based sensors with high selectivity and fast response time. Unlike non-covalent binding sites, dosimetric gelators typically contain a reaction centre and undergo a specific chemical reaction selective to an analyte resulting in either formation or rupturing of covalent bonds. In this review, we provide an up-to-date report of various reaction-based gel systems applied for the sensing of analytes. We elaborately discuss the concept, design principles, self-assembly properties, and reaction mechanisms of such gelators. We also highlight the limitations, challenges, and the necessity of further exploration of dosimetric gels in this domain.

Charge Transfer in Self-Assembled Fullerene-Tetraphenylporphyrin Non-Covalent Multilayer

Self-assembly of organic molecules is a promising method for generating multilayer systems for fabrication of functional devices. In particular, fullerene (C60) and porphyrin molecules offer a variety of binding modes, including π–π interactions, dipole electrostatic attraction, and hydrogen bonding, to tailor the charge separation and charge recombination limiting device performance. Here, we investigate multilayer systems obtained by the sequential physical vapor deposition of C60 and tetraphenylporphyrin (H2TPP) layers, focusing on the effect of the interfaces on the charge transfer processes. Absorbance spectra indicate noncovalent-like π-stacking, with the increment of fullerene interfaces shifting the porphyrin Soret band toward the blue. Similarly, surface photovoltage measurements in the multilayer systems show that as the number of interfaces increases, so does the photogeneration of charge. Charge separation follows carrier generation given that the recombination time, associated to trap states, decreases. This behavior indicates that the Donor-Acceptor nature of the fullerene-porphyrin bilayer system is conserved, and even enhanced in the multilayer film, and that the number of interfaces aids to the formation of selective paths for charge carrier collection, demonstrating its potential in optoelectronic devices.

Continuum modelling of structure formation of biosilica patterns in diatoms

Formation of regularly structured silica valves of various diatom species is a particularly fascinating phenomenon in biomineralization. Intensive investigations have been devoted to elucidate the formation mechanisms of diatom valve structures. Phase-separation of species-specific organic molecules has been proposed to be involved in pattern formation, where the evolving organic molecule structures serve as template for silica formation. In the present work, using a continuum approach, we investigate the conditions under which silica structures of high regularity can develop within a phase separation model. In relation to previously reported in vitro experiments of silica formation, which revealed the important role of phosphate ions in the self-assembly of organic molecules, we propose a model where phase separation is coupled with a chemical reaction. We analyze the impact of the reaction of phosphate ions with organic molecules on the appearing morphology of the organic template. Two- and three-dimensional simulations of the development of regular stationary patterns are presented. The influence of a confined geometry and an interaction of organic molecules with the walls on pattern formation is also addressed. We expect that our approach will be relevant for experimental studies aiming at inducing structure formation under controlled in vitro conditions.

<em>SELF-ASSEMBLY</em> DI DNA SU SUPERFICIE: UNO STUDIO COMBINATO NANOLITOGRAFIA/SPETTROSCOPIA OTTICA

The self-assembly of organic molecules and biomolecules on inorganic surfaces is a complex process which results from the interplay between different interactions: molecule/molecule, molecule/surface, and molecule/solvent interactions. The interest in the study of molecular self-assembly derives from the possibility to obtain functionalized surfaces that exhibit the functional properties of the deposited (bio) molecules. Self-Assembled Monolayers (SAMs) are indeed widely used in biosensing. SAMs of organosulphur compounds on gold are among the most widely studied SAMs. In the following, a combined approach that couples scanning probe microscopy and spectroellipsometry is discussed and applied to the study of the morphological, mechanical and optical properties of SAMs of DNA single strands. DNA SAMs are a widely investigated system since they can be exploited for the design of DNA microarrays based on the hybridization between complementary DNA strands.

Mixing Behavior of Trimesic Acid with Pentacene at the Liquid–Solid Interface

The self-assembly of organic molecules on a solid surface presents a promising route toward the nanoscale-precision construction of functional patterns. In particular, using trimesic acid (TMA) and...

Novel Strategy for Organic Cocrystals of n-Type and p-Type Organic Semiconductors with Advanced Optoelectronic Properties.

Cocrystallization has been applied widely for material synthesis. Recently cocrystal of organic molecules has been developing rapidly, taking the advantages of the flexibility and self-assembly of organic molecules. Here we report an experimental study of a cocrystal of copper-phthalocyanines and fluorinated ones. We have grown the samples via the vapor-phase deposition of the mixture with different mass ratios from 1:13.5 to 6:1. As suggested by our scanning electron microscopy (SEM), X-ray diffraction (XRD), and Raman spectroscopy, new crystal structures and morphologies through our novel strategy for the cocrystallization of these molecules have been found. Our work will provide a solid foundation to systematically synthesize the cocrystal of phthalocyanine molecules with new crystal structures, thus providing the opportunity to advance material properties.

Chiral Monolayers with Achiral Tetrapod Molecules on Highly Oriented Pyrolytic Graphite

The self-assembly of organic molecules at the surface of highly oriented pyrolytic graphite (HOPG) is a promising process for constructing molecular-scale architectures. However, selectable organic...

Non-covalently self-assembled organic molecules graphene aerogels to enhance supercapacitive performance

Organic molecules electrodes with high electrochemical reversibility has enormous potential in energy storage. Here, benz[a]anthracene-7, 12-quinone (BAQ) and 2, 5-dihydroxy-p-benzoquinone (DHBQ) are anchored on reduced graphene oxide (rGO) [BAQ (DHBQ)/rGO] by non-convent method to form the porous 3D dry aerogels. The optimal BAQ (DHBQ)/rGO electrode materials display capacitance all in excess of 400 F g−1 at current density of 1 A g−1 and an excellent rate capability in 1 M H2SO4 electrolyte. And BAQ/rGO and DHBQ/rGO are used respectively as the negative and positive electrode to fabricate the asymmetric supercapacitor (ASC), which achieves high energy density of 30.33 Wh kg−1 with power density of 802.9 W kg−1. Finally, 47 light-emitting diode (LED) bulbs aligned in a ‘NWNU’ shape are lit by two ASCs device in series, demonstrating its outstanding energy storage performance. Moreover, density functional theory (DFT) calculations are employed to understand the adsorption orientations, binding interactions and charge storage mechanism of BAQ on rGO surface, elucidating the superior electrochemical performance of the tested organic molecule electrode. In short, quinones non-covalently modified graphene is a promising and effective strategy for energy storage devices in future.

Growth of a highly ordered inhomogeneous kinetically trapped molecular monolayer

It is often assumed that the self-assembly of organic molecules on a noble-metal surface results in a structure that is in thermodynamic equilibrium. Here, using scanning tunnel microscopy, we observe instead a highly ordered metastable striped monolayer phase of zinc tetraphenylporphyrin, self-assembled at 300 K on Ag(100). The usually reported stable square phase is found only after higher-temperature annealing. We use a statistical mechanical model to reveal a possible molecular mechanism for this process, in which the competition of molecule and substrate interactions at the growth front leads to the growth of a kinetically trapped inhomogeneous ordered structure. Our proposed mechanism rests only on simple features of molecular geometry and interactions, and the resulting principles could be used to promote particular outcomes of growth in other examples of molecular assembly at surfaces.

The Partner Does Matter: The Structure of Heteroaggregates of Acridine Orange in Water.

Self-assembly of organic molecules in aqueous solutions is governed by a delicate entropy/enthalpy balance. Even small changes in their intermolecular interactions can cause critical changes in the structure of the aggregates and their spectral properties. The experimental results reported here demonstrate that protonated cations of acridine orange, acridine, and acridin-9-amine form stable J-heteroaggregates when in water. The structures of these aggregates are justified by the homonuclear 1H cross-relaxation nuclear magnetic resonance (NMR). The absorption and fluorescence of these aggregates deviate characteristically from the known H-homoaggregates of the protonated cations of acridine orange. The latter makes acridine orange a handy optical sensor for soft matter studies.

Chiral crystal-like droplets displaying unidirectional rotational sliding.

The self-assembly of organic molecules into supramolecular materials with structural ordering beyond the nanometre scale is challenging. Here, we report the spontaneous self-assembly of a chiral discotic triphenylene derivative into millimetre-sized droplets. The structure of the droplets is characterized by high positional and orientational ordering and a three-dimensional integrity similar to that of single crystals. Notwithstanding, these assemblies slide when placed on a vertical substrate demonstrating their fluid nature. X-ray imaging shows that during the sliding process the internal crystal-like structure is maintained and that the droplets undergo clockwise or counterclockwise unidirectional rotation, depending on the chirality of their molecular components. Rheological measurements suggest that this rotational behaviour might result from the distinct yield stress between the (R)- and (S)-enantiomers. Overall, our findings demonstrate that molecular chirality can determine the movement direction of a supramolecular structure, thus expanding the fundamental understanding of the structure and dynamics of soft materials.

Self-assembly of organic molecules for bioimaging and cancer therapy

Self-assembly of organic molecules for bioimaging and cancer therapy

Ruthenium nanoparticles stabilized by mercaptan and acetylene derivatives with supercapacitor application

Ruthenium nanoparticles (RuHT, RuPET and RuPA) were prepared by hydrazine hydrate reduction of RuCl3 and stabilized by the self-assembly of organic molecules (hexanethiol, phenylethanethiol and phenylacetylene). The sizes of these Ru nanoparticles were carried out by transmission electron microscopic measurement, with the average core sizes of 2.8 ± 0.6 nm, 3.1 ± 1.2 nm, and 3.1 ± 1.1 nm, respectively. The structures and properties of these Ru nanoparticles were further examined and verified by UV–vis, FTIR, 1HNMR, XPS and fluorescent measurements. The performance of the supercapacitor was characterized by cyclic voltammetry, constant-current charge-discharge, and electrochemical impedance spectroscopy. Ru nanoparticles showed enhanced supercapacitor behaviors as compared with blank electrodes. The Ru nanoparticles for supercapacitors in the H2SO4 electrolyte exhibited areal capacitances of 347.8, 304.9 and 229.1 mF cm−2 for RuPET, RuPA and RuHT at a scan rate of 10 mV s−1, and specific capacitances for 344.4, 249.3, 230.0 F g−1 for RuPET, RuPA and RuHT at a current density of 0.5 A g−1, respectively. The interfacial bonding between ruthenium and the outlayer organic ligands and varied ratio of ruthenium in high valence might be the reasonable explanation for the capacitance difference.

Stimuli-responsive hydroxyapatite liquid crystal with macroscopically controllable ordering and magneto-optical functions

Liquid crystals are mostly formed by self-assembly of organic molecules. In contrast, inorganic materials available as liquid crystals are limited. Here we report the development of liquid-crystalline (LC) hydroxyapatite (HAp), which is an environmentally friendly and biocompatible biomineral. Its alignment behavior, magneto-optical properties, and atomic-scale structures are described. We successfully induce LC properties into aqueous colloidal dispersions of rod-shaped HAp by controlling the morphology of the material using acidic macromolecules. These LC HAp nanorod materials are macroscopically oriented in response to external magnetic fields and mechanical forces. We achieve magnetic modulation of the optical transmission by dynamic control of the LC order. Atomic-scale observations using transmission electron microscopy show the self-organized inorganic/organic hybrid structures of mesogenic nanorods. HAp liquid crystals have potential as bio-friendly functional materials because of their facile preparation, the bio-friendliness of HAp, and the stimuli-responsive properties of these colloidal ordered fluids.

The growth and assembly of organic molecules and inorganic 2D materials on graphene for van der Waals heterostructures

The unique properties of graphene have made it a promising material for integration in future electronic applications. The idealized surface of graphene, atomically-flat and without dangling bonds, offers the opportunity to understand the assembly of organic and inorganic molecules to form a wide range of ordered architectures and functional graphene-based heterostructures. In this review, we summarize recent progress in the growth of hierarchical nanostructures on graphene. The self-assembly of organic molecules and inorganic two-dimensional (2D) layers on graphene for the construction of various types of heterostructures are highlighted. Van der Waals interactions between the assembled molecules and graphene are shown to allow the formation of highly-ordered structures with preferred molecular orientations and stacking configurations that circumvent the strict lattice-matching requirements in traditional epitaxial growth. Finally, we briefly discuss representative applications of graphene-based heterostructures in electronic and optoelectronics.

Ruthenium nanoparticles stabilized by mercaptan and acetylene derivatives with supercapacitor application

Ruthenium nanoparticles (RuHT, RuPET and RuPA) were prepared by hydrazine hydrate reduction of RuCl3 and stabilized by the self-assembly of organic molecules (hexanethiol, phenylethanethiol and phenylacetylene). The sizes of these Ru nanoparticles were carried out by transmission electron microscopic measurement, with the average core sizes of 2.84?±?0.55 nm, 3.06?±?1.22 nm, and 3.10?±?1.08 nm, respectively. The structures and properties of these Ru nanoparticles were further examined and verified by UV–vis, FTIR, 1HNMR, XPS and fluorescent measurements. The performance of the supercapacitor was characterized by cyclic voltammetry and constant-current charge-discharge analysis. Ru nanoparticles exhibited enhanced supercapacitor behaviors as compared with blank electrodes. The Ru nanoparticles for supercapacitors in the H2SO4 electrolyte exhibited areal capacitances of 347.8, 304.9 and 229.1 mF?cm-2 for RuPET, RuPA and RuHT at a scan rate of 10?mV?s-1, and specific capacitances for 344.4, 249.3, 230.0?F?g-1 for RuPET, RuPA and RuHT at a current density of 0.5?A?g-1, respectively. The interfacial bonding between ruthenium and the outlayer organic ligands and varied ratio of ruthenium in high valence might be the reasonable explanation for the capacitance difference.