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Nematic liquid crystals of bifunctional patchy spheres
摘要： Anisotropic interactions can bring about the formation, through self-assembly, of semi-?exible chains, which in turn can give rise to nematic phases for suitable temperatures and concentrations. A minimalist model constituted of hard cylinders decorated with attractive sites has been already extensively studied numerically. Simulation data shows that a theoretical approach recently proposed is able to properly capture the physical properties of these self-assembly–driven liquid crystals. Here, we investigated a simpler model constituted of bifunctional Kern-Frenkel hard spheres which does not possess steric anisotropy but which can undergo a istropic-nematic transition as a result of their self-assembly into semi-?exible chains. For this model we compare an accurate numerical estimate of isotropic-nematic phase boundaries with theoretical predictions. The theoretical treatment, originally proposed for cylinder-like particles, has been greatly simpli?ed and its predictions are in good agreement with numerical results. Finally, we also assess a crucial, and not obvious, hypothesis used in the theory, i.e. the ability of the Onsager trial function to properly model particle orientation in the presence of aggregation, that has not been properly checked yet.
关键词： nematic phases,semi-?exible chains,Kern-Frenkel hard spheres,Anisotropic interactions,self-assembly,Onsager trial function,isotropic-nematic transition
更新于2025-09-04 15:30:14
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Optical Simulations of Self-assembly Relevant Gold Aggregates: A Comparative Study
摘要： In this study, visible light extinction spectra of different gold nanoparticle assemblies were simulated using boundary element method (BEM) in order to investigate the optical properties of structures which determine the experimentally measured spectra during the self-assembly of the particles. Numerous different optically dominant particle arrangements can evolve depending on the underlying physicochemical mechanism of the clustering process itself: one-dimensional chains, two-dimensional arrays or three-dimensional clusters can be formed in the solutions or at interfaces. Experimentally the aggregation or clustering of gold nanoparticles can be conveniently followed by spectroscopic techniques due to the plasmon coupling related profound effect of particle aggregation on the visible extinction spectrum. However, the measured spectra usually contain the optical response of various aggregate structures. Additionally, small changes of the interparticle distance can have a significant impact on the frequency of the coupled mode. In order to assess the contribution of the different structures to the experimentally measurable extinction spectra during particle clustering, different model structures (chains, array and 3D-cluster) have been simulated, where the distance between the particles was varied as well.
关键词： 3D cluster,boundary element method,2D heptamer,self-assembly,optical simulations,nanoparticle chains,gold nanoparticles
更新于2025-09-04 15:30:14
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The self-assembly of DyF3 nanoparticles synthesized by chloride-based route
摘要： The series of DyF3 nanoparticles was synthesized for the first time by a chloride-based route, using the water-soluble dysprosium chloride hexahydrate as a precursor. The synthesized nanoparticles have sizes of 3 to 7 nm, which is the smallest reported size for DyF3 nanoparticles. The influence of precursor concentration in an aqueous solution prior to the chemical reaction on the size of nanoparticles was studied. The influence of microwave-assisted hydrothermal treatment was also studied. The analysis of transmission electron microscopy (TEM) data revealed no correlation between the size of synthesized nanoparticles and the concentration of the aqueous solution. The AC/DC magnetic susceptibility of DyF3 nanoparticles was measured. The dipolar ferromagnetic transition for this sample was not observed down to 1.8 K that can be possibly explained by onset of superparamagnetism. The self-assembly of DyF3 nanoparticles was observed for the first time by analysis of XRD and TEM data and the evidence of superlattice formation along (020) and (210) lattice planes over the size of 20–30 nm (4–5 nanoparticles) was obtained.
关键词： X-ray techniques,Self-assembly,Nanocrystalline materials,Colloidal processing,Crystal structure,Electron microscopy
更新于2025-09-04 15:30:14
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Fabrication of Metal–Organic Framework Thin Films Using Programmed Layer‐by‐Layer Assembly Techniques
摘要： Metal–organic frameworks (MOFs) are a rather new class of crystalline, nanoporous solids that are self-assembled from inorganic, metal or metal-oxo nodes and organic linkers. Powder MOFs are originally developed for gas storage and catalyst applications, but more recently, more advanced applications have used well-defined MOF thin films in electronic, photonic, and sensing devices. MOF thin films for targeted applications can be fabricated on appropriately functionalized substrates using a programmed layer-by-layer (LbL) assembly technique, which yields oriented, highly crystalline MOF thin films (surface-mounted MOFs, SURMOFs). The LbL assembly technique as well as the huge potential of SURMOFs is presented herein. Emerging SURMOF properties related to their heteroepitaxy, postsynthetic modification/crosslinking, lithography, and photoswitching are highlighted.
关键词： lithography,photoswitching,MOF thin film,layer-by-layer assembly,heteroepitaxy
更新于2025-09-04 15:30:14
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Synthesis of (BiSe) <sub/> 1+ <i>δ</i> </sub> (Bi <sub/>2</sub> Se <sub/>3</sub> ) <sub/> 1+ <i>γ</i> </sub> (BiSe) <sub/> 1+ <i>δ</i> </sub> TiSe <sub/>2</sub> by Directed Self-Assembly of a Designed Precursor
摘要： The synthesis, structure and properties of a new three constituent heterostructure containing BiSe, Bi2Se3, and TiSe2 layers, each with a different structural motif, is reported. (BiSe)1+δ(Bi2Se3)1+γ(BiSe)1+δTiSe2, where δ and γ are the misfit parameters representing the differences in the in-plane packing density of the constituents, forms via a self-assembly process during low-temperature annealing from precursors with a range of compositions and repeat period thicknesses. This indicates that the compound exists in a relatively broad and deep free-energy minima in the energy landscape. The formation was followed as a function of annealing temperature using X-ray diffraction to determine optimum annealing temperatures and stability range. High-resolution electron microscopy images revealed the layering sequence of the constituents and a supercell within the BiSe layers created by periodic anti-phase boundaries. Temperature dependent electrical transport measurements show unexpected changes in carrier mobility and concentration relative to (BiSe)1.15TiSe2. This study suggests that new ternary and multinary phases containing fragments of known binary phases can be synthesized via precursors that mimic the desired product and that the properties of these new phases with ultrathin constituent thicknesses will probably be different from that expected based on composite behavior.
关键词： X-ray diffraction,electron microscopy,heterostructure,BiSe,self-assembly,TiSe2,Bi2Se3,electrical transport
更新于2025-09-04 15:30:14
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Printing Birefringent Figures by Surface Tension-Directed Self-Assembly of a Cellulose Nanocrystal/Polymer Ink Components
摘要： Photonic printing on transparent substrates using emerging synthetic photonic crystals is in high demand, especially for anti-fraud applications. However, photonic printing is faced with grand challenges including lack of the full invisibility of printed patterns before stimulation or after stimuli removal and absence of the long-lasting stability. Natural anisotropic crystal structures and artificially molecularly arranged polymers show an optically anisotropic property known as birefringence. Crystalline cellulose is the most abundant birefringent bio-crystal on the earth. Here, we introduce a printing method based on using a cellulose nanocrystal/polymer ink that is governed by surface evaporation phenomenon and divided surface tension forces to direct the self-assembly of ink components at the nanoscale and print 3D birefringent micro-figures on transparent substrates. This type of printing is from now on referred to as Birefringent Printing (BP). Unlike previously reported photonic crystal printing methods, this method is accurate, has high-contrast, is virtually impossible to forge and at the same time is very simple, inexpensive and non-toxic.
关键词： polymer ink,cellulose nanocrystal,directed self-assembly,birefringence,surface tension,invisible printing
更新于2025-09-04 15:30:14
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[IEEE 2018 IEEE International Conference on Manipulation, Manufacturing and Measurement on the Nanoscale (3M-NANO) - Hangzhou, China (2018.8.13-2018.8.17)] 2018 IEEE International Conference on Manipulation, Manufacturing and Measurement on the Nanoscale (3M-NANO) - Precisely Lateral Alignment of Gold Nanorods Array via Hydrophilic-Hydrophobic Pattern
摘要： A simple strategy which combines the controlled solvent evaporation and hydrophilic-hydrophobic pattern to allow assembling gold nanorods (GNRs) on a flat substrate with arbitrary shapes in this work. Soft polydimethylsiloxane (PDMS) template as a pattern transfer stamp were utilized and transferred the structures onto the substrate successfully. By tuning the structures and sizes of templates, oriented large area lateral aligned GNRs arrays were fabricated as expected. Scan electron microscopy (SEM) images revealed that GNRs had been precisely placed as expected and the assembly is uniform.
关键词： hydrophilic-hydrophobic pattern,gold nanorods,self-assembly,solvent evaporation,micro-array
更新于2025-09-04 15:30:14
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Flexible silver nanowire transparent conductive films prepared by an electrostatic adsorption self-assembly process
摘要： In this work, we reported a facile approach to fabricate silver nanowire (AgNW) networks on ?exible substrates. Through immersing the modi?ed poly (ethylene terephthalate) with positively charged functional group into the AgNW dispersion with anionic dispersant, a ?exible AgNW transparent conductive ?lm was formed by electrostatic adsorption self-assembly process. Even without a post-treatment process, the as-prepared ?exible AgNW ?lms exhibited excellent optoelectrical property, low surface roughness and high reliability. It was shown that the insulating dispersant on AgNWs could be effectively removed by an ion bombardment method and then greatly decreased the sheet resistance of AgNW networks. Because of the nature of spontaneous adsorption, this preparation method can be suitable for an arbitrary shaped substrate, which will broaden the application of AgNW conductive ?lms in optoelectronic devices.
关键词： self-assembly,transparent conductive ?lms,silver nanowire,electrostatic adsorption,flexible substrates
更新于2025-09-04 15:30:14