Fabrication Of Various Nanostructures Research Articles

Peptide Hydrogels and Nanostructures Controlling Biological Machinery.

Peptides are versatile building blocks for the fabrication of various nanostructures that result in the formation of hydrogels and nanoparticles. Precise chemical functionalization promotes discrete structure formation, causing controlled bioactivity and physical properties for functional materials development. The conjugation of small molecules on amino acid side chains determines their intermolecular interactions in addition to their intrinsic peptide characteristics. Molecular information affects the peptide structure, formation, and activity. In this Perspective, peptide building blocks, nanostructure formation mechanisms, and the properties of these peptide materials are discussed with the results of recent publications. Bioinstructive and stimuli-responsive peptide materials have immense impacts on the nanomedicine field including drug delivery, cellular engineering, regenerative medicine, and biomedicine.

Micro + Nano: Conserving the Gold Standard Microroughness to Nanoengineer Zirconium Dental Implants.

Zirconium has achieved popularity as a biomaterial for dental and orthopedic implants; however, its bioinertness can compromise implant-tissue integration, especially in compromised patient conditions. More recently, various nanoengineering strategies have been explored to enhance the bioactivity of Ti-based implants; however, nanoengineering of Zr-based implants has not been adequately explored. In this pioneering attempt, we report on the optimized fabrication of various nanostructures on microrough Zr surfaces and explore the influence of the underlying surface topography. In-depth optimization of electrochemical anodization (EA) is performed by tuning various parameters, including substrate topography, voltage/current and time, onto microrough (micromachined) and extremely rough Zr substrates, which represent clinically relevant implant surfaces. Variations of EA factors yielded various nanotopographies, including nanotubes, nanograss and nanotemplates, offering different topographical and chemical combinations. EA optimization and precise current-voltage recording was performed to arrive at clinically translatable and reproducible nanostructures on Zr surfaces. This study will pave the way toward the fabrication of the next generation of nanoengineered Zr-based orthopedic and dental implants.

Fabrication of nanoribbons by dielectrophoresis assisted cold welding of gold nanoparticles on mica substrate

Using alternating current electric fields, nanoribbons are fabricated from an aqueous suspension of gold nanoparticles (AuNPs) on mica substrate without resorting to further chemical functionalization of AuNPs. The potential and kinetic energies of AuNPs subjected to attractive forces from a mica substrate provide sufficient energy to pass the diffusion barrier of the gold atoms, which eventually leads to cold welding. A dielectrophoresis force exerted on polarizable particles in a non-uniform electric field contributes to the directed growth of the cold welding that occurs by adjusting the lattice structures of AuNPs. Depending on the concentration of the AuNP suspension, the frequency of the electric field, and the geometry of electrodes, various morphologies of nanoribbons are fabricated. It turns out that the welded region is nearly perfect to provide the same crystal orientation and strength as the rest of the nanostructures, which can be extensively utilized in the fabrication of various nanostructures.

Direct Formation of C-C Double-Bonded Structural Motifs by On-Surface Dehalogenative Homocoupling of gem-Dibromomethyl Molecules.

Conductive polymers are of great importance in a variety of chemistry-related disciplines and applications. The recently developed bottom-up on-surface synthesis strategy provides us with opportunities for the fabrication of various nanostructures in a flexible and facile manner, which could be investigated by high-resolution microscopic techniques in real space. Herein, we designed and synthesized molecular precursors functionalized with benzal gem-dibromomethyl groups. A combination of scanning tunneling microscopy, noncontact atomic force microscopy, high-resolution synchrotron radiation photoemission spectroscopy, and density functional theory calculations demonstrated that it is feasible to achieve the direct formation of C-C double-bonded structural motifs via on-surface dehalogenative homocoupling reactions on the Au(111) surface. Correspondingly, we convert the sp3-hybridized state to an sp2-hybridized state of carbon atoms, i. e., from an alkyl group to an alkenyl one. Moreover, by such a bottom-up strategy, we have successfully fabricated poly(phenylenevinylene) chains on the surface, which is anticipated to inspire further studies toward understanding the nature of conductive polymers at the atomic scale.

Rhombic-Shaped Nanostructures and Mechanical Properties of 2D DNA Origami Constructed with Different Crossover/Nick Designs.

DNA origami methods enable the fabrication of various nanostructures and nanodevices, but their effective use depends on an understanding of their structural and mechanical properties and the effects of basic structural features. Frequency-modulation atomic force microscopy is introduced to directly characterize, in aqueous solution, the crossover regions of sets of 2D DNA origami based on different crossover/nick designs. Rhombic-shaped nanostructures formed under the influence of flexible crossovers placed between DNA helices are observed in DNA origami incorporating crossovers every 3, 4, or 6 DNA turns. The bending rigidity of crossovers is determined to be only one-third of that of the DNA helix, based on interhelical electrostatic forces reported elsewhere, and the measured pitches of the 3-turn crossover design rhombic-shaped nanostructures undergoing negligible bending. To evaluate the robustness of their structural integrity, they are intentionally and simultaneously stressed using force-controlled atomic force microscopy. DNA crossovers are verified to have a stabilizing effect on the structural robustness, while the nicks have an opposite effect. The structural and mechanical properties of DNA origami and the effects of crossovers and nicks revealed in this paper can provide information essential for the design of versatile DNA origami structures that exhibit specified and desirable properties.

Depth analysis of molecular orientation induced by nanoimprint graphoepitaxy

The nanoimprint process is a useful technique for the fabrication of various nanostructures on functional materials without the use of any etching processes. We previously confirmed that the molecular orientation of a photo-crosslinkable liquid crystalline polymer (PLCP) was induced by nanoimprinting using a process called nanoimprint graphoepitaxy. In this work, we repeat the previous O2 reactive ion etching processing and molecular orientation evaluation to examine the depth profile of the unidirectional molecular orientation that is induced by nanoimprint graphoepitaxy. The results obtained indicate that the initial PLCP film thickness affects the resulting unidirectional molecular orientation depth.

Advanced Colloidal Lithography Beyond Surface Patterning

This Review presents an overview of recent development of colloidal lithography (CL) and its applications in fabrication of various nanostructures consisted of orderly arranged, dots, holes, bowls, cones, pillars, rings, shells and triangles. These structures have been widely exploited in various fields, including plasmonics, optics, wettability, sensors, solar cells, organic light‐emitting diode (OLEDs), biology and many others. The recent successes in the technical applications of the nanostructures fabricated via CL will be summarized. Hopefully, the present review will inspire more ingenious designs and execution of CL for advanced, smart applications.

Ultrasound-assisted anodization of aluminum in oxalic acid

Porous anodic alumina is an important nanoscale template for fabrication of various nanostructures. We report a new ultrasound-assisted anodization process in oxalic acid. Under the continuous irradiation of ultrasound, the one-step-anodized sample has a smooth and clean surface, and two-step-anodization brings ordered porous anodic alumina with higher growth rate of 52 μm/h. The ultrasound applied during the anodization can clean the surface and enhance the nanopore growth since it can accelerate the oxide dissolving on the electrolyte/oxide interface. The ultrasound-assisted anodization may be utilized for other anodizations.

Peptide Mesocrystals as Templates to Create an Au Surface with Stronger Surface‐Enhanced Raman Spectroscopic Properties

The design and fabrication of various nanostructures with predefined geometry and composition is a big challenge of nanotechnology. Here we demonstrate an Au nanoflake film replicated from a self-assembled, well-ordered, dipeptide flower-like hierarchical architecture. Such morphology can give rise to useful and remarkable surface-enhanced Raman spectroscopy (SERS) properties. We obtained these nanostructures by using a scaffold of flake-built spherical dipeptide aggregations. Gold nanoparticles were sputtered on the surface of as-assembled dipeptide by an etching system. After removing the dipeptide templates by ethanol, a metal crust was left with a morphology similar to that of the dipeptide hierarchical structure. The different steps within the process were monitored by using electron microscopy, energy-dispersive spectrum (EDS) analysis and atomic force microscopy (AFM). Cyclic voltammetry and Raman spectra were employed to prove the SERS effect of the obtained Au substrates. The enhancement factor is estimated to be about 10(4) for 4-mercaptobenzoic acid (4-MBA) molecules on the Au nanoflake surfaces.

Probing Temperature on a Microfluidic Chip with Thermosensitive Conjugated Polymer Supramolecules

Owing to the unique self- assembled state and the poly(ene-yne) backbone structure, the conjugated polymer displays a phase transition upon environ-mental perturbations, and this results in a brilliant blue-to-red color change in most cases. Unlike other conjugated polymers which require tedious multistep modification processes, PDA can be readily prepared from diacetylene supramolecules in an aqueous-friendly environment by UV irradiation (Scheme 1). In addition, amphiphilic nature of the diacetylene monomer allows fabrication of various nanostructures including nano-tubes, nanowires, nanovesicles, nanohelices, and nanoribbons.The apparent blue-to-red color transition of PDA has served as a foundation for the construction of many colorimetric che-mosensors for the detection of target molecules of interest such as DNAs, proteins, ions, and volatile organic compounds (VOCs).

Epitactically Interpenetrated High Quality ZnO Nanostructured Junctions on Microchips Grown by the Vapor−Liquid−Solid Method

The usability of nanostructures in electrical devices such as gas sensors critically depends on the ability to form high quality contacts and junctions, at least in a two terminal setup. For the fabrication of various nanostructures, vapor−liquid−solid (VLS) growth is meanwhile a widely spread and very efficient technique for many semiconductors. However, as already demonstrated in the literature, forming contacts with the VLS grown structures to utilize them in a device is typically tedious. Either the substrate material has to be the same, such as the VLS material, or a laborious procedure has to be used to connect one side with the other. As a strikingly simple alternative approach, we report that the ability of VLS grown nanostructures to interpenetrate each other in a homoepitactical manner can be used to form a connecting bridge between two gold contact lines on a microchip. Other methods of direct growth are already established, but they lead only to a touching of the nanowires and not to interpenetration. The ZnO interpenetration junctions can be directly used as electrical devices, and just as a proof of principle, they were employed as UV-light dependent resistor, field effect transistor (FET), or gas sensor.

Colloidal Lithography—The Art of Nanochemical Patterning

Nanochemical printmaking: Colloidal lithography paves a powerful nanochemical way for patterning on planar substrates and microparticles. The feature size can easily be scaled down to 100 nm by reducing the diameter of the microspheres and the feature shape diversified by the crystalline structure of a colloidal crystal mask, the mask etching time, the incidence angle of the vapor beam, and the mask registry (the azimuth angle of the vapor beam). Colloidal lithography relies on using colloidal crystals as masks for etching and deposition, and allows fabrication of various nanostructures on planar and non-planar substrates with low-cost, high-throughput-processing, large fabrication area, and a broad choice of materials. The feature size can easily shrink by decreasing the microsphere diameter in the colloidal mask. The feature shape can be diversified by varying the crystal structure of the colloidal mask, etching the mask, altering the incidence angle of the vapor beam, and stepwise manipulation of the mask registry. This nanochemical patterning strategy paves a complementary way to conventional top-down lithography. This focus review provides an overview of the principle of colloidal lithography, and surveys the recent developments as well as outlining the future challenges.

Fabrication and structural control of anodic alumina films with inverted cone porous structure using multi-step anodizing

Porous anodic alumina (PAA) film has recently attracted much attention as a key material for the fabrication of various nanostructures. In this study, a multi-step anodization and leaching process was employed to produce three-dimensional nanometer scale structured film. During the leaching process, the porous alumina film was dipped in phosphoric acid solution for pore widening. Each anodization process was followed by this leaching process. This method produced alumina film with multi-step structure. Meanwhile, with five-step film production, the structure showed inverted cone structure. We produced the low aspect ratio pores of this structure, which would be applicable for fabrications of nanomaterials. In addition, the aspect ratio was controlled by changing the anodization duration.

Fabrication of nanostructures on Si(1 0 0) and GaAs(1 0 0) by local anodic oxidation

Atomic force microscopes have become useful tools not only for observing surface morphology and nanostructure topography but also for fabrication of various nanostructures itself. In this paper, the application of AFM for fabrication of nanostructures by local anodic oxidation (LAO) of Si(1 0 0) and GaAs(1 0 0) surfaces is presented. A special attention is paid to finding relations between the size of oxide nanolines (height and half-width) and operational parameters as tip-sample voltage and tip writing speed. It was demonstrated that the formation of silicon oxide lines obeys the Cabrera–Mott theory, i.e. the height of the lines grow, linearly with tip-sample voltage and is inversely proportional to logarithm of tip writing speed. As for GaAs substrates, the oxide line height grows linearly with tip-sample voltage as well but LAO exhibits a certain deviation from this theory. It is shown that the selective chemical etching of Si or GaAs ultrathin films processed by LAO makes it possible to use these films as nanolithographic masks for further nanotechnologies, e.g. fabrication of metallic nanostructures by ion-beam bombardment. The ability to control LAO and tip motion can be utilized in fabrication of complex nanostructures finding their applications in nanoelectronic devices, nanophotonics and other high-tech areas.