Template-assisted Self-assembly Research Articles

A Comparative Study on the Self-Assembly of Peptide TGV-9 by In Situ Atomic Force Microscopy.

Previous studies of amyloid diseases reported that the aggregating proteins share a similar conserved peptide sequence which can form the cross-β-sheet-containing nanostructures like nanofilaments. The template-assisted self-assembly (TASA) of peptides on inorganic substrates with different hydrophilicity could be an alternative approach to shed light on the fibrillization mechanism of proteins/peptides in vivo. To figure out the effect of interfaces on amyloid aggregation, we herein employed in situ atomic force microscopy (AFM) to investigate the self-assembling of a Parkinson disease-related core peptide sequence (TGV-9) on a hydrophobic liquid-solid interface via real-time observation of the dynamic fibrillization process. The results show that TGV-9 forms one-dimensional nanostructures on the surface of highly ordered pyrolytic graphite (HOPG) with three preferred growth orientations, which are consistent with the atomic lattice of HOPG, indicating an epitaxial growth or TASA. Conversely, the nanostructures formed in bulk solution can be free-standing nanofilaments, and the fibrillization mechanism is different from that on HOPG. These results could not only deepen the understanding of the protein/peptide aggregation mechanism but also benefit for the early diagnosis and clinic treatment of related diseases.

Graphite-Templated Amyloid Nanostructures Formed by a Potential Pentapeptide Inhibitor for Alzheimer's Disease: A Combined Study of Real-Time Atomic Force Microscopy and Molecular Dynamics Simulations.

Self-assembly of peptides is closely related to many diseases, including Alzheimer's, Parkinson's, and prion diseases. Understanding the basic mechanism of this assembly is essential for designing ultimate cure and preventive measures. Template-assisted self-assembly (TASA) of peptides on inorganic substrates can provide fundamental understanding of substrate-dependent peptides assemble, including the role of hydrophobic interface on the peptide fibrillization. Here, we have studied the self-assembly process of a potential pentapeptide inhibitor on the surface of highly oriented pyrolytic graphite (HOPG) using real time atomic force microscopy (RT-AFM) as well as molecular dynamics (MD) simulation. Experimental and simulation results show nanofilament formation consisting of β-sheet structures and epitaxial growth on HOPG. Height analysis of the nanofilaments and MD simulation indicate that the peptides adopt a lying down configuration of double-layered antiparallel β-sheets for its epitaxial growth, and the number of nanofilament layers is concentration-dependent. These findings provide new perspective for the mechanism of peptide-based fibrillization in amyloid diseases as well as for designing well-ordered micrometrical and nanometrical structures.

Template-assisted self-assembly of diblock copolymer micelles for non-hexagonal arrays of Au nanoparticles

We report the construction of non-hexagonal arrays of nanoparticles by the template-assisted self-assembly of polystyrene-block-poly(4-vinylpyridine) copolymer micelles.

Antimony nanoparticles anchored in three-dimensional carbon network as promising sodium-ion battery anode

A novel composite with antimony (Sb) nanoparticles anchored in three-dimensional carbon network (denoted as SbNPs@3D-C) is successfully synthesized via a NaCl template-assisted self-assembly strategy, followed by freeze-drying and one-step in-situ carbonization. The three-dimensional interconnected macroporous carbon framework can not only stabilize the architecture and buffer the volume expansion for Sb nanoparticles, but also provide high electrical conductivity for the whole electrode. Consequently, as a sodium-ion battery anode, the SbNPs@3D-C delivers a high reversible capacity (456 mAh g−1 at 100 mA g−1), stable cycling performance (94.3% capacity retention after 500 cycles at 100 mA g−1) as well as superior rate capability (270 mAh g−1 at 2000 mA g−1). When compared with commercial Sb particles, the SbNPs@3D-C exhibits dramatically enhanced electrochemical performance. Free from expensive template sources and complex manipulation, this work might shed some light on the synthesis of low-cost and high-performance materials for the next “beyond lithium” battery generation.

Microfabrication for a polystyrene quadrupole by template-assisted self-assembly

Abstract It has been widely known that colloidal particles and their arrayed structures play a critical role in various fields because of their versatility. Based on an expectation that quadrupole microstructures would display unique optical characteristics, we focused on the fabrication process for quadrupole structures composed of colloidal particles. The quadrupole structures consisted of polystyrene particles (PSt) with a 1.0 μm diameter were formed by applying the integrated approach with a top-down method and a bottom-up method (i.e., template-assisted self-assembly). Microhole arrays with two different shapes—circular holes and square holes—were fabricated on a Si substrate by using electron beam lithography and reactive ion etching. These top-down processes were followed by a bottom-up process that the Si substrate with fabricated microhole arrays was withdrawn from a PSt aqueous solution. With the microhole arrays as a guide, the PSt particles were forced to array the specific structures in the microholes due to the capillary force and Van der Waals force acting on the particles and substrate. By controlling the solvent drying process, the yield of quadrupole structure was reached approximately 80% in over 300 microholes. Additionally, the distance between two neighboring particles consisting of quadrupole structures could be controlled by the sizes of the microholes, and the obtained particle configurations could be removed onto an adhesive tape.

Large scale anomalous patterns of muscovite mica discovered by atomic force microscopy.

Muscovite mica is a widely used substrate because of its flatness. The large scale anomalous patterns of muscovite have been discovered by atomic force microscopy (AFM). These patterns distribute around the defects of the muscovite surface. By using different imaging modes and analyzing functions of AFM, these extraordinary patterns are thoroughly characterized, and it was revealed that some selected regularly aligned patterns mimic 2-D orthorhombic crystal systems surrounding the regular structure. However, such patterned nanostructures have no effects on the template-assisted self-assembly (or epitaxial growth) of a disease-related peptide GAV-9.

Mechanical properties and cytotoxicity of nanoplate-like hydroxyapatite/polylactide nanocomposites prepared by intercalation technique

Hydroxyapatite (HAp) in the forms of fiber, needle, and whisker has been employed as fillers in polymer composites. Herein, nanoplate-like HAp synthesized by template-assisted self-assembly was used to reinforce polylactide (PLA) nanocomposites via the solution intercalation method. Dynamic and static mechanical properties and cytotoxicity of the as-prepared HAp/PLA nanocomposites were assessed in addition to characterizations by XRD, FTIR, and TGA. XRD analysis confirms the formation of exfoliated structure in the HAp/PLA nanocomposites. The HAp/PLA nanocomposites exhibit better static and dynamic mechanical properties than unreinforced PLA. Furthermore, the HAp/PLA nanocomposite with an optimum HAp content of 20wt% (20HAp/PLA) demonstrates not only the best mechanical performance but also the highest thermal stability among the nanocomposite samples. Cell studies using a mouse fibroblast cell line (L929) suggest that 20HAp/PLA shows excellent biocompatibility, which makes it a promising material for biomedical applications.

Aligned gold nanobowl arrays: their fabrication, anisotropic optical response and optical grating applications

Aligned Au nanobowl arrays on a flexible film with specific optical properties were obtained by combining template-assisted self-assembly and colloidal lithography.

Strongly coupled plasmonic modes on macroscopic areas via template-assisted colloidal self-assembly.

We present ensembles of surface-ordered nanoparticle arrangements, which are formed by template-assisted self-assembly of monodisperse, protein-coated gold nanoparticles in wrinkle templates. Centimeter-squared areas of highly regular, linear assemblies with tunable line width are fabricated and their extinction cross sections can be characterized by conventional UV/vis/NIR spectroscopy. Modeling based on electrodynamic simulations shows a clear signature of strong plasmonic coupling with an interparticle spacing of 1–2 nm. We find evidence for well-defined plasmonic modes of quasi-infinite chains, such as resonance splitting and multiple radiant modes. Beyond elementary simulations on the individual chain level, we introduce an advanced model, which considers the chain length distribution as well as disorder. The step toward macroscopic sample areas not only opens perspectives for a range of applications in sensing, plasmonic light harvesting, surface enhanced spectroscopy, and information technology but also eases the investigation of hybridization and metamaterial effects fundamentally.

Plasmon-enhanced upconversion luminescence in single nanophosphor-nanorod heterodimers formed through template-assisted self-assembly.

We demonstrate plasmonic enhancement of upconversion luminescence in individual nanocrystal heterodimers formed by template-assisted self-assembly. Lithographically defined, shape-selective templates were used to deterministically coassemble single Au nanorods in proximity to single hexagonal (β-phase) NaYF4:Yb(3+),Er(3+) upconversion nanophosphors. By tailoring the dimensions of the rods to spectrally tune their longitudinal surface plasmon resonance to match the 977 nm excitation wavelength of the phosphors and by spatially localizing the phosphors in the intense near-fields surrounding the rod tips, several-fold luminescence enhancements were achieved. The enhancement effects exhibited a strong dependence on the excitation light's polarization relative to the rod axis. In addition, greater enhancement was observed at lower excitation power densities due to the nonlinear behavior of the upconversion process. The template-based coassembly scheme utilized here for plasmonic coupling offers a versatile platform for improving our understanding of optical interactions among individual chemically prepared nanocrystal components.

Template‐Assisted Self‐Assembly: Alignment, Placement, and Arrangement of Two‐Dimensional Mesostructured DNA–Silica Platelets

In the same direction: Two-dimensional mesostructured DNA–silica platelets were horizontally or vertically aligned on unpatterned substrate surfaces using “bottom-up” self-assembly. Through template-assisted self-assembly, vertically aligned DNA–silica platelets were selectively placed in the grooves and on the protuberances and with a parallel arrangement near the edges on patterned surfaces.

Solvent‐Free Directed Patterning of a Highly Ordered Liquid Crystalline Organic Semiconductor via Template‐Assisted Self‐Assembly for Organic Transistors

Highly ordered organic semiconductor micropatterns of the liquid-crystalline small molecule 2,7-didecylbenzothienobenzothiophene (C10 -BTBT) are fabricated using a simple method based on template-assisted self-assembly (TASA). The liquid crystallinity of C10 -BTBT allows solvent-free fabrication of high-performance printed organic field-effect transistors (OFETs).

Colloidal Surface Assemblies: Nanotechnology Meets Bioinspiration

AbstractThis Feature Article discusses two biomimetic aspects of functional particle surface assembly: the fabrication of biologically inspired structures from particles and the arrangement of particles on biomimetic templates. The first part discusses the creation of primary patterns by convective assembly and adsorption of particles that can be modified by a combination of etching and growth steps. Resulting structures mimic moth eyes, Lotus leaves, and the Gecko's adhesive structures, for example. The second part focusses on template assisted self‐assembly (TASA) of particles. Herein, biological examples are inspiring in terms of structure formation related processes, rather than in terms of functionality. Template formation is a major bottleneck TASA. It is illustrated how bio‐inspired wrinkling processes help overcoming this problem and can be employed for forming highly ordered functional nanoparticle assemblies.

Directed Self-Assembly Lithography and Its Application Based on Simulation Approach

The directed self-assembly (DSA) technology of block copolymers is a candidate for next-generation lithography. The computation model of this lithography can assist in overcoming its challenges. In this paper, a template-assisted self-assembly (DSA graphoepitaxy) is modeled and simulated in a molecular scale to reduce the process complexity. For a full simulation, the template fabrication and DSA process are modeled and simulated to evaluate the impact of the process parameters on the pattern profile. Simulation results similar to the experimental results allow the prediction of the self-assembled patterns of the confined block polymers.

Nanoscale Shuffling in a Template-Assisted Self-Assembly of Binary Colloidal Particles

We have fabricated a square lattice array of sub-micrometer fluorescent (red and green) polystyrene particles. The particles were each embedded into small pits fabricated on a silicon substrate by electron beam lithography, through the drying process of an aqueous suspension containing equal amounts of the two species. We indexed 0 and 1 for each red and green particle, respectively, and then obtained a one-dimensional bit sequence by the successive reading of the indices in a predetermined manner. We evaluated the randomness of the bit sequence by using the improved FIPS 140-2 statistical test suite. Consequently, we found that the bit sequences do not have any non-randomness. The particle array was obtained by a very simple process, i.e., the drying of a suspension, but the particle distribution pattern was definitely unpredictable and irreproducible, and the number of possible patterns was tremendously large. The signal--i.e., the color of the particle--does not deteriorate within a practical timescale under various conditions, such as in an electric field, in a magnetic field, in air or water, on a solid matrix, and so on, which means that a small tip with the particle pattern can be installed in miscellaneous object, including electronic products, plastic credit cards, currency bills, and so on. Therefore, this particle array is applicable to a nanoscale identification tag or a one-time pad encryption tip.

Designing and fabricating of surface-enhanced Raman scattering substrate with high density hot spots by polyaniline template-assisted self-assembly

In general, the procedures for producing a high density hot spots structure should be stable, inexpensive, and easy to make. It still remains a grand challenge to assemble silver or gold nanoparticles (Au NPs) with well-defined hot spots for SERS detection. In this study, we present a very simple method for designing and fabricating a surface-enhanced Raman scattering (SERS) substrate with high density hot spots, using large area positively charged polyaniline (PANI) nanofibers as template to assemble negatively charged Au NPs. In order to obtain the optimized SERS-active substrates, different experiments to synthesize diverse Au/PANI with different sizes of Au NPs from about 50, 30 to 15 nm were carried out. The results revealed that the PANI nanofibers were fully coated by the ~15 nm Au NPs, forming a high density Au/PANI SERS substrate. The results evidence that we can obtain stable and sensitive SERS measurements.

External template-assisted self-assembly: design and synthesis of the [MoOS3Cu3]+ based supramolecular polymeric clusters

Four novel heterothiometallic cluster polymers based on a [MoOS3Cu3] unit have been synthesized by the solution self-assembly of 4,4′-bipy (4,4′-bipy = bpy) with [NH4]2MoS2O2 and CuX (X = I, Br, or SCN) in the presence of different organic cation-templates [DMI]·I, [C6(Mim)2]·Br2, [C3(Mim)2]·Br2, and [BBP]·Br2: Compounds {[MoOS3Cu3I(μ-bpy)2.5]·2.5DMF}∞ (1), {[MoOS3Cu3I(μ-bpy)2.5] ·DMF}∞ (2), and {[MoOS3Cu3Br(μ-bpy)2.5]·2.5DMF}∞ (3) are isomorphous neutral 3D 4-fold interpenetrating architectures with a (6, 4) node, while polymer [MoOS3Cu3(NCS)(μ-bpy)2.5]∞ (4) is a 3D architecture with a (64 82) net displaying self-interpenetrating features. All of them have been characterized by single-crystal X-ray diffraction, elemental analysis, IR, TGA, and UV-vis. The results may provide fascinating insights into the template effect on the construction of the cluster-based coordination polymers.

External Template-Assisted Self-Assembly:Design and Synthesis of 4,4′-bipy-Based Mo(W)/Cu/S Heterothiometallic Polymeric Clusters Directed by 1,1′-Bis(pyridinium)methylene Cation

Organic cation-templated self-assembly of 4,4′-bipy (4,4′-bipy = bpy) with [NH4]2MS2O2 (M = Mo, W) and CuX (X = Cl, NCS) in the present of 1,1-bis(pyridinium)methylene [bpm = 1,1′-bis(pyridinium)methylene] resulted in four novel neutral heterothiometallic cluster polymers based on tetranuclear [Mo/WOS3Cu3] unit: [MOS3Cu3Cl(μ-bpy)2·Sol]n (M = Mo, Sol = 1.3DMF·5.5H2O 1; M = W, Sol = 1.5DMF·8.2H2O 2), [MoOS3Cu3(NCS)(bpy)(μ-bpy)2·DMF]n (3), and [WOS3Cu3(NCS)(μ-bpy)2.5·3DMF]n (4). Polymer 1 or 2 crystallizes in the Fddd space group with a 2-fold interpenetrating (10,3)-b net, which presents a 3-connected 3D heterothiometallic polymer assembled with bidentate organic bridging ligands. Polymer 3 crystallizes in the space group P1 with a 2D noninterpenetrating network with (6,3) topology in which [MoOS3Cu3(bpy)] units are interconnected via three single or double Cu-μ-bpy-Cu bridges. Polymer 4 crystallizes in the space group C2/c with a (64 82) net, which displays the first self-interpenetrating network in hetero...

Template-assisted self-assembly of individual and clusters of magnetic nanoparticles

The deliberate control over the spatial arrangement of nanostructures is the desired goal formany applications such as, for example, in data storage, plasmonics or sensor arrays. Herewe present a novel method to assist the self-assembly process of magnetic nanoparticles.The method makes use of nanostructured aluminum templates obtained after anodizationof aluminum discs and the subsequent growth and removal of the newly formedalumina layer, resulting in a regular honeycomb-type array of hexagonally shapedvalleys. The iron oxide nanoparticles, 20 nm in diameter, are spin-coated onto thesurface of honeycomb nanostructured Al templates. Depending on the size, eachhexagon site can host up to 30 nanoparticles. These nanoparticles form clusters ofdifferent arrangements within the valleys, such as collars, chains and hexagonallyclosed islands. Ultimately, it is possible to isolate individual nanoparticles. Thestrengths of the magnetic interaction between particles in a cluster are probedusing the memory effect known from the coupled state in superspin glass systems.

Highly ordered defect arrays of 8CB (4′-n-octyl-4-cyano-biphenyl) liquid crystal via template-assisted self-assembly

A synthetic rod-like smectic liquid crystal containing a rigid aromatic group and semi-fluorinated chains generates well-ordered toroidal structures called toric focal conic domains (TFCDs) as self-assembling building blocks when confined within rectangular micro-channels. However, in the case of common smectic liquid crystals with alkyl-terminated chains, the ordered arrangement of TFCDs is challenging work because of their high mobility and low elasticity. Here, we present a simple method to fabricate highly mono-dispersed periodic patterns using the most commonly used smectic liquid crystal, 8CB (4′-n-octyl-4-cyano-biphenyl), by changing the geometry of confined microchannel with a controlled surface polarity. This is attributed to the combining effects between antagonistic surface anchoring conditions and precisely directed molecular orientation onto inclined side walls of a trapezoidal channel. Furthermore, size and ordering of arrays of 8CB can be simply controlled by varying the feature dimension of bottom width (l) and depth (h) in the trapezoid-shaped channel. The use of 8CB will generalize fabrication of the spatial arrangement of TFCD arrays for future nanotechnology and liquid crystal research.