Design,synthesis, and self-assembly of optically active perylenetetracarboxylic diimide bearing two peripheral chiral binaphthyl moieties

An optically active perylenetetracarboxylic diimide (PTCDI) bearing two optically active binaphthyl moieties has been designed and synthesized. The self-assembly properties of these novel PTCDI derivatives in DMF/H₂O were systematically investigated by electronic absorption, circular dichroism (CD) spectra, IR spectroscopy, transmission electron microscopy (TEM), scanning electron microscopy (SEM), and X-ray diffraction (XRD) technique. Observation of CD signal in the whole absorption region of PTCDI chromophore, indicates effective chiral information transfer from the chiral binaphthyl units to the central PTCDI chromophore at molecular level. The intermolecular π–π interaction between PTCDI rings together with the additionally formed hydrogen bonds between the crown ether moieties of (S)-1 and additional water molecules and the chiral discrimination of periphery chiral side chains induces further intensified asymmetrical perturbation of the chiral binaphthyl units to the central PTCDI chromophore during the self-assembly process, resulting in the formation of right-handed helical arrangement of corresponding molecules in a stack of PTCDI chromophores in aggregates. In addition, the formed nanostructures were revealed to show good semiconducting properties.     

Effect of microwave power on the morphology and optical property of zinc oxide nano-structures prepared via a microwave-assisted aqueous solution method

The effect of the microwave power on the morphology and optical properties of zinc oxide nanostructures prepared using a microwave-assisted aqueous solution method has been investigated. The ZnO nanostructures were synthesized from zinc chloride and sodium hydroxide mixed aqueous solutions exposed for 5 min to microwave radiation at four different powers, namely 150, 450, 700 and 1000 W. The morphologies of the samples have been characterized by transmission electron microscope (TEM) and scanning electron microscope (SEM). The results showed that the power of microwave radiation influenced the shape and size of the synthesized nanostructures. It is also found that the average particle size of nanostructures decreased with decreasing microwave power. The results of X-ray diffraction (XRD) showed that all the as-prepared ZnO nanostructures are in crystalline form with high purity. The infrared (IR) spectra indicated that the as-prepared nano ZnO product can be used as infrared gas sensors such as an infrared carbon dioxide (CO₂) and/or CO sensor. Optical properties of the as-prepared ZnO nanostructures were investigated by UV–vis spectroscopy and showed that the optical properties of as-synthesized ZnO samples are sensitive to the variation of the power of microwave radiation.     

Tuning the morphology of chevron-type graphene nanoribbons by choice of annealing temperature

Bottom-up synthesis of graphene nanoribbons (GNRs) by surface-assisted polymerization and cyclodehydrogenation of specifically designed precursor monomers has been shown to yield precise edges and doping. Here we use a precursor monomer containing sulfur atoms to fabricate nanostructures on a Au(111) surface at different annealing temperatures. The nanostructures have distinct configurations, varying from sulfur-doped polymers to sulfur-doped chevron-type GNRs (CGNRs) and, finally, pristine graphene nanoribbons with specific edges of periodic five-member carbon rings. Non-contact atomic force microscopy provides clear evidence for the cleavage of C–S bonds and formation of pristine CGNRs at elevated annealing temperatures. First-principles calculations show that the CGNRs exhibit negative differential resistance.

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Conformational morphology of polyaniline grown on self-assembled monolayer modified silicon

Polyaniline (PANI) films with pyramidal shaped crystallites were prepared by self-organization on self-assembled monolayer (SAM) modified Si substrates. High-resolution atomic force microscopy (HR-AFM) shows that SAM has tridymite structural order and the PANI film has biphasic conformational morphology corresponding to face-on orientation and edge-on orientation. Order parameters obtained from power spectral density analysis of HR-AFM images of SAM and PANI films show that the pyramidal crystallites are in emeraldine salt (ES-I) form and the region between the crystallites is in emeraldine base (EB-II) form. The ordered lattice of PANI crystallites as observed by cross-sectional HR-TEM confirms its single crystalline nature as well as epitaxial growth. The heteroepitaxial growth of PANI is attributed to the structural order of interfacial SAM on Si.     

Preparation of self-assembled zinc oxide nanoparticles multilayer films under ultrasonic irradiation

Zinc oxide nanoparticles were synthesized and self-assembled on the reactive surface of a glass slide functionalized with (3-mercaptopropyl)-trimethoxysilane under ultrasonic irradiation. The structure, morphology, and optical property of the zinc oxide nanoparticles were investigated by TEM, XRD, and UV-vis spectroscopy. The functionalized glass slide was soaked in an aqueous solution which dispersed zinc oxide nanoparticles under ultrasonic irradiation. Zinc oxide multilayer films grew up to several layers (up to 5 layers) depending on the immersion time. The self-assembled zinc oxide nanoparticles multilayer films were characterized using UV-vis spectroscopy and SEM. Ultrasonic irradiation was an efficient method to make multilayer films on the functionalized glass slide with zinc oxide nanoparticles.     

Tuning morphology and fluorescence of aggregated nanostructures of derived perylene diimide molecules

In this paper, we report on the self-assembly of water-soluble N,N'-di(N,N'-dimethyl-dodecane-1, 12-diamide)-perylene-3,4,9,10-tetracarboxylic diimide (PDDoAM) in formic acid and chloride salts for producing varied nano-aggregates with different optical properties. Interestingly, the self-assembly can lead to nanocubic, microsheet and "tower-like" nanostructures respectively, as demonstrated by Scanning Electron Microscopy (SEM) images. The optical properties of molecular aggregates were investigated by means of Confocal Raman Microscopy, indicating the morphologies and fluorescence of these nanomaterials are dependent on acids, acid concentrations and casting methods.     

Texture and morphology of pulse plated zinc electrodeposits

Zinc coatings were deposited under pulse-current plating conditions from an acidic sulphate bath on low-carbon steel cathodes. The effect of the (peak) deposition current density, duty cycle and pulse frequency on the microstructural texture and morphology of the deposits was studied by X-ray diffractometry and scanning electron microscopy. The zinc films consisted of crystallites having an average size controlled by deposition current density, and oriented mostly with basal (00.2) and high index (10.3), (10.4), (10.5) pyramidal planes parallel to the surface. Pulse plating resulted in coatings which were microstructurally different to those prepared under similar conditions by direct current deposition. Texture and grain size modification is illustrated. The effect of pulse current is explained in terms of enhanced nucleation and inhibited growth.     

Tuning the morphology and molecular orientation of copper hexadecafluorophthalocyanine thin films by solvent annealing

We present a detailed investigation of the molecular orientation transition and resulting morphology of copper hexadecafluorophthalocyanine (F₁₆CuPc) thin films induced by solvent annealing. The F₁₆CuPc molecules reorganize from small spherical or fibre-like crystals to large-size ribbon crystals which then dominate the resulting film properties. This reorganization and the formation of the ribbon crystals are closely related to the evaporation of solvent molecules and Ostwald ripening. The resulting thin films demonstrate morphological and structural characteristics with significant potential for application in high-performance organic electronic devices.     

Growth mechanism and ultraviolet-light emission of the self-assembled complex of MgO nanostructures

Bulk-quantity net-like nanodendrites and four-fold hierarchical nanostructures were synthesized by direct thermal evaporation and oxidation of metallic Mg powder. Their formation mechanism is explained using the self-catalytic vapor-liquid-solid mechanism together with dendritic-crystal epitaxial growth mechanism. Four-branch and eight-branch nanodendrites were also detected. The photoluminescence spectrum reveals that the peak with the maximum intensity is centered at about 3.16 eV (392 nm). Through Gaussian fitting, a strong and narrow ultraviolet-light emission peak centered at 3.16 eV (392 nm) and a relatively weak but broad blue-light emission band centered at 2.74 eV (453 nm) were observed in the photoluminescence emission spectrum, which are respectively attributed to the recombination luminescence of the F+ and F centers (belonging to oxygen-vacancy related defect levels) in the MgO nanostructures. In addition, another very weak and broad red-infrared emission band can also be detected, which is probably due to the relaxation luminescence of impurity levels in the MgO nanostructures.     

The removal of phosphate from aqueous solutions using two nano-structures: copper oxide and carbon tubes

The removal of phosphate from water is vital in controlling eutrophication. Adsorption is one of the most popular technologies for removing phosphate. In this study, two types of nanoparticles (NPs), namely carbon nanotubes (CNTs) and copper oxide (CuO), were used and their phosphate removal potential was investigated. The physical and chemical properties of the two NPs were systematically studied using X-ray diffraction (XRD), scanning electron microscopy (SEM), FTIR, energy-dispersive X-ray (EDX), and BET methods. The image analyses of SEM indicated that CuO NPs and CNTs were nano-structured aggregates with mean diameters of about 85.0 and 22.2 nm, respectively. The sorption kinetic data were better described by the pseudo-second-order equation indicating its chemisorption nature. The equilibrium sorption data were well fitted into the Freundlich model for CNTs but for CuO, sorption data were better fitted into Langmuir isotherm model. The phosphate sorption capacities without the presence of competing anions were 15.4 and 23.9 mg/g (PO₄ ^3?-P) for CNTs and CuO, respectively. Besides, the competing anions (Cl^?, NO₃ ^?, and humic acid) decreased the phosphate removal of CNTs and CuO. The negative values of the Gibbs’ free energy change (ΔG°) demonstrated the spontaneous nature of the sorption process in both sorbents, while the positive values of the enthalpy change (ΔH°) indicated that the sorption process was endothermic in nature. Overall, the results of this study suggest that CuO NPs and CNTs in a single solution have the potential to act as effective sorbents of phosphate under optimum conditions, respectively.     

Influence of aqueous hexamethylenetetramine on the morphology of self-assembled SnO2 nanocrystals

The present report details the effects of synthesis time, concentrations of hexamethylenetetramine (HMTA) and precursor tin (II) chloride solutions on the self-assembly of SnO₂ nanocrystals. High-resolution electron microscopy images revealed that the structures were made of randomly attached SnO₂ nanocrystals with sizes in between ∼2 and 5 nm. X-ray photoelectron spectroscopy (XPS) showed that the Sn3d region was characterized by the spin-orbit splitting of the Sn3d_5/2 ground state at ∼487.6 eV and by the Sn3d_3/2 excited state at ∼496.1 eV, which was attributed to the Sn⁺⁴ oxidation state of the SnO₂ samples. We also found that the self-assembly could be achieved only with aqueous tin (II) chloride solution, and not with aqueous stannic (IV) chloride solution. A plausible growth mechanism is proposed in order to analyze the distinctive self-assembly of SnO₂ nanocrystals in the presence of aqueous HMTA solution.     

原卟啉IX锌-聚乳酸的合成及表征

血红素用硫酸亚铁-氯化氢的氯仿-甲醇溶液处理,制得原卟啉IX二甲酯。原卟啉IX二甲酯水解得到原卟啉IX,再与乙酸锌反应制得原卟啉IX锌。然后,利用原卟啉IX锌上的羧基,在脱水剂DCC和催化剂HOBt的作用下,与聚乳酸端基的氨基发生酰胺化反应,制备得到了原卟啉IX锌-聚乳酸。UV-Vis光谱、IR和1 H-NMR分析表明,卟啉环脱除铁离子和络合锌离子过程中乙烯基保持稳定。采用GPC测试分子量及分子量分布。结果表明,酰胺化反应近似按照投料比进行反应。     

Electric driven molecular switching of asymmetric tris(phthalocyaninato) lutetium triple-decker complex at the liquid/solid interface

Molecular structures are known to significantly impact the adsorption and assembling behavior of the adsorbates on surfaces. Precise control of the molecular orientation and ordering will enable us to tailor the physical and chemical properties of the molecular architectures. In this work, we present a strategy of attaching functional groups with dissimilar adsorption and assembling characteristics to the top and bottom phthalocyaninato moieties of a triple-decker complex, and orientational-dependent ordering of such molecules at the liquid/solid interface has been identified, which is attributed to the interaction of the intrinsic molecular dipole with the external electric field. In addition, isomerization of the noncentrosymmetric tris(phthalocyaninato) lutetium triple-decker complex has been revealed directly with STM and further confirmed by theoretical simulation. This approach provides a possible way for the preparation of organic films with switchable electronic and/or interface properties with external field.     

Role of self-assembled gold nanodots in improving the electrical and optical characteristics of zinc oxide films

We have studied the effect of embedding nanocrystalline Au particles on the electrical and optical characteristics of ZnO films. Au-embedded epitaxial ZnO films were deposited on (0001) sapphire substrates with a pulsed laser deposition technique. The crystalline quality of both the ZnO matrix and Au nanoparticles was investigated by X-ray diffraction and transmission electron microscopy. Composite films were characterized by photoluminescence, optical absorption, and low-temperature electrical resistivity measurements. Photoluminescence spectra of theses films showed a sharp excitonic peak at 3.22 +/- 0.05 eV without any signature of green band emission. Electrical resistivity measurements showed these films to be highly conducting, with a room-temperature resistivity of 3.4 +/- 0.2 m omega-cm.     

Influence of the deposition parameters on the morphology and electrical conductivity of PANI/PSS self-assembled films

The influence of deposition parameters, namely polymer concentration and pH of the deposition solution, cleaning, and drying steps on the morphology and electrical characteristics of polyaniline and sulfonated polystyrene (PANI/PSS) nanostructured films deposited by the self-assembly technique is evaluated by UV–Vis spectroscopy, optical and atomic force microscopy, and electrical resistance measurements. It is found that stirring the cleaning solution during the cleaning step is crucial for obtaining homogenous films. Stirring of the cleaning solution also influences the amount of PANI adsorbed in the films. In this regard, the drying process seems to be less critical since PANI amount and film thickness are similar in films dried with N₂ flow or with an absorbent tissue. It is observed, however, that drying with N₂ flow results in rougher films. As an additional point, an assessment of the influence of the deposition method (manual versus mechanical) on the film characteristics was carried out. A significant difference on the amount of PANI and film thickness between films prepared by different human operators and by a homemade mechanical device was observed. The variability in film thickness and PANI adsorbed amount is smaller in films mechanically assembled.     

Field emission from zinc oxide nanotowers: the role of the top morphology

Arrays of novel nanometer-scale tower-shaped structures of zinc oxide (ZnO nanotowers) were synthesized by a simple thermal evaporation method. Due to the difference in fabrication conditions, ZnO nanotowers with similar body structure but different top morphologies were obtained. These ZnO nanotowers with different top morphologies showed obvious disparity in field emission, despite their overall field enhancement factor and density being the same. The nanotowers with the sharpest top had the lowest turn-on and threshold electric field. This disparity is attributed to the different local field enhancement factors at the nanotower tops, which were calculated both from the field emission data and by simulation. The above results have demonstrated the essential importance of the top morphology of a ZnO nanostructure in field emission.     

Identification of complex sound sources produced by gear units

Noise source visualisation represents an important tool for technical acoustics. Many techniques of noise source visualisation have been developed, based on a specific noise source in a specific type of acoustic environment. A new visualisation method of complex noise sources is presented, using an acoustic camera and a new algorithm. Different transient acoustical phenomena can be noted. Additionally, a new family of biorthogonal wavelets is applied to determine fault in gears. The new wavelets are a generalisation of biorthogonal wavelet systems. Smoothness is controlled independently in the analysis. For the optimisation of the synthesis bank, discrete finite variation is used. Differentiability is measured, for which a large number of vanishing wavelet moments is necessary, in favour of a smoothness measure based on the fact that a finite depth of the filter bank tree is in most case related to practical applications.     

Electronic and thermal properties of compounds bearing diimide,azomethine and triphenylamine units

New triphenylamine containing azomethine diimides and two kinds of poly(azomethine imide)s, i.e., linear and branched were synthesized. These compounds were prepared from two diamines, that is, N,N′-bis(4-amino-2,3,5,6-tetramethylphenyl)phtalene-1,2,4,5-dicarboximide (DAPhDI), N,N′-bis(5-aminonaphtalen)naphthalene-1,4,5,8-dicarboxyimide (DANDI-2) and 4-formyltriphenylamine, 4,4′-diformyltriphenylamine and 4,4′,4″-triformyltriphenylamine. The structures of the compounds were characterized by means of FTIR, ¹H NMR spectroscopy and elemental analysis; the results show an agreement with the proposed structure. Thermal properties of prepared azomethine diimides and polymers were evaluated by thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC). Obtained compounds exhibited high thermal stability with 5% weight-loss temperatures above 390 °C. Azomethine diimides exhibited glass-forming properties with high glass-transition temperatures 216 and 308 °C. Optical properties of the prepared compounds were investigated by UV–vis and photoluminescence (PL) measurements. All compounds emitted blue light in NMP solution and in solid state as blend with PMMA. The electrochemical properties, that is, orbital energies and resulting energy gap were estimated based on cyclic voltammetry (CV). All synthesized material showed reversible reduction process, furthermore AzPhDI and AzNDI showed partially reversible oxidation process. Electrochemical band gap was found in the range 1.23–1.70 eV. Low molecular weight model compounds were tested as bipolar host materials in blue phosphorescent organic light emitting diodes (OLEDs). The devices exhibited turn-on voltages of about 5.5 V and maximum brightness of 40–220 cd/m².