Papers by Keyword: Self-Assembly

Abstract: Industrial application of superhydrophobic surfaces is limited by the unsatisfactory mechanical properties of the material. Combining chemical etching and anodization terraced features containing aluminium oxide on different aluminium alloy surfaces were produced. After modified by fatty acid, the surfaces were superhydrophobic and they showed self-cleaning effect. The highest contact angle was obtained after forming hierarchical structures with a solution free of fluorine compounds; therefore, the process is considered eco-friendly. The alumina formed in the coating process promotes an improved corrosion resistance. The present study has three main objectives: to identify the molecules responsible for superhydrophobicity, the mechanism by which superhydrophobicity is produced, and consequently the influence of variables such as anodization time on the proposed processing method. We use time-of-flight secondary ion mass spectrometry (TOF-SIMS) and X-ray photoelectron spectroscopy (XPS) techniques to identify each compound involved in the final surface, by paying close attention to the analysis of the mechanism by which the chemical reaction proceeds. The morphology of the superhydrophobic surfaces was further observed by scanning electron microscope (SEM) and atomic force microscopy and was used to elucidate the effect of the anodization time in the properties of the superhydrophobic material.

Abstract: It will be discussed in this work how it is possible to produce latex films by evaporation induced self-assembly (EISA) process. Latex beads were synthesized in a cylindrical flask without N₂ flow. The polymerization process of styrene happens at water as solvent and with the presence of persulfate potassium as initiator. The final product was a dispersion of spherical nanometric particles (ɸ = 0.47 ± 0.06μm) whose concentration can be changed from 0.5 to 10% (V/V_o). These dispersions were spread on glassy substrates at 50°C over a square area (~1cm²) with control of solvent evaporation. The films are transparent and they show the formation of nanowire structures by scanning electron microscopy (SEM) characterization. Such structures were associated to high affinity of latex beads particles to form cylindrical arrangements due to presence of O₂ during their synthesis. It has been concluded that this self-assembly structure can be very worthy for generation of functional devices like sensors, solar cells and biomaterials.

Abstract: Zinc oxide (ZnO) nanorods were grown on the pre-seeded substrate using a facile, solution route technique. The multilayer self-assembly of polyaniline (PAni) and tetrasulphonated phthalocyanine (TSCuPc) on ZnO nanorods was monitored by FTIR, UV-Vis SEM and XRD. Infrared spectrum of the assembled layer showed peaks centered at 1589cm-1and 1504 cm-1, confirmed the presence of quinoid and benzenoid structures of PAni, while peaks centered at ~1165cm^-1and ~775cm^-1 provided evidence for the presence of TSCuPc species. Absorption spectra of the assembled layer show broadened peaks at ~600nm and ~700nm affirmed the presence of PAni and TSCuPc molecules. A linear increase in the absorbance level at these wavelengths was also observed upon increasing the number of bilayers. The surface modification of the ZnO nanorods after self-assembly was confirmed through SEM. The edges of the ZnO nanorods was observed to change from sharp to dull upon employing layer by layer deposition of PAni and TSCuPc. XRD pattern of the assembled layer showed broadened peaks at low 2Θvalues associated to the amorphous nature of the emeraldine base of PAni. Even so, the diffraction peaks in XRD patterns of ZnO nanorods and ZnO/(TSCuPc-PAni) multilayer have been indexed as hexagonally wurtzite structure. The multilayer deposition of PAni and TSCuPc on the surface of ZnO as monitored by UV-Vis spectroscopy and confirmed by FTIR, XRD, and SEM provides a new way of anchoring dye molecules without carboxylic moieties on the surface of metal oxides

Abstract: An organic nanocapsule was obtained by mixing zinc acetate powder into a peptide lipid dispersion in ethanol. The nanocapsule was mass-produced at a scale of over 100 g L^–1 within 1 h. Fourier transform infrared spectroscopy and scanning electron microscopy revealed that a zinc-peptide lipid complex was formed within 15 min, which subsequently transformed into a nanocapsule as a result of changes in the hydrogen bonding networks between the peptides. A variety of organic dyes could be encapsulated by simply adding them during the nanocapsule formation. We also confirmed their high stabilities in organic solvents, water-responsive morphological change, and resulting guest release. The water-responsive nanocapsule is expected to be useful in a variety of fields.

Abstract: A new amphiphilic bio-organic material was developed by conjugating the xanthine oxidase inhibitor, 2-amino-6-hydroxy-8-mercaptopurine (AMHP) with the naturally occurring polyphenol coumaric acid (CA). The formed product, AMHP-CA was allowed to self-assemble at a pH range of 4 through 8. Nanospheres or fibrous assemblies ranging upto micrometers in length were formed, depending upon growth conditions. Furthermore, it was found that the assemblies biomimetically formed gold nanoparticles on its surfaces resulting in AMHP-CA-AuNP hybrids. The DNA sensing ability of the AuNP bound AMHP-CA assemblies was investigated at varying concentrations by studying the changes in conformations of salmon milt DNA by CD spectroscopy and by examining live binding with surface plasmon resonance (SPR) analysis. AuNP bound AMHP-CA assemblies had significantly increased DNA sensing ability and SPR signal compared to binding interactions in the absence of AuNPs. Thus, in this study it was found that AMHP-CA-AuNP assemblies may function as biosensors for DNA detection.

Abstract: In this work, BaTiO₃ nanoparticles were synthesized through hydrothermal method. The powder obtained from the hydrothermal process (as-synthesized powder) was calcined at 1000 °C. The phase formation and morphology of the as-synthesized and calcined powders were studied using X-ray diffraction (XRD), thermogravimetric (TGA) and differential scanning calorimetry (DSC) analyzer, and transmission electron microscope (TEM). The XRD data showed that the as-synthesized powder is partially amorphous. Upon calcining the powder at 1000 °C, highly crystalline BaTiO₃ with tetragonal structure was obtained. As shown by TGA and DSC analysis, the precursor powder was completely transformed into BaTiO₃ at 1000 °C. The presence of BaCO₃ as an impurity phase in the powder is due to the lack of Ba²⁺ / Ti^3+/4+. Transmission electron microscope images showed that the particle size of the as-synthesized powder increased after calcination due to crystal growth. In addition, nanocubes with the average size of around 11.66 nm were obtained as a result of the calcination compared to the ellipsoid like particles of the as-synthesized powder.

Abstract: In this work, for the first time, chlorogenic acid, a natural phytochemical, was conjugated to a lactoferrin derived antimicrobial peptide sequence RRWQWRMKKLG to develop a self-assembled template. To mimic the components of extracellular matrix, we then incorporated Type I Collagen, followed by a sequence of aggrecan peptide (ATEGQVRVNSIYQDKVSL) onto the self-assembled templates for potential applications in ligament tissue regeneration. Mechanical properties and surface roughness were studied and the scaffolds displayed a Young’s Modulus of 169 MP and an average roughness of 72 nm respectively. Thermal phase changes were studied by DSC analysis. Results showed short endothermic peaks due to water loss and an exothermic peak due to crystallization of the scaffold caused by rearrangement of the components. Biodegradability studies indicated a percent weight loss of 27.5 % over a period of 37 days. Furthermore, the scaffolds were found to adhere to fibroblasts, the main cellular component of ligament tissue. The scaffolds promoted cell proliferation and displayed actin stress fibers indicative of cell motility and attachment. Collagen and proteoglycan synthesis were also promoted, demonstrating increased expression and deposition of collagen and proteoglycans. Additionally, the scaffolds exhibited antimicrobial activity against Staphylococcus epidermis bacteria, which is beneficial for minimizing biofilm formation if potentially used as implants. Thus, we have developed a novel biocomposite that may open new avenues to enhance ligament tissue regeneration.

Abstract: This paper presents a three-dimensional dynamic model of laser controlled dynamic self-assembly of nanostructure. A phase field model is employed to study the surface fabrication of silicon which is induced by the laser. The mechanism of the surface fabrication is that the heating effect enhances surface diffusion mobility results in atoms outward flow. The computational model systematically integrate for high reliability of the whole analysis, the experimental and simulated measurements have been quantitatively investigated. A semi-implicit Fourier spectral scheme is applied for high efficiency and numerical stability. The performed simulations suggest a substantial potential of the presented model, which provides a reliable technology of nanostructure fabrications on the surface of silicon.

Abstract: Most bacteria and all archaea possess as outermost cell envelope so called surface-layers (S-layers). These layers were formed by self-assembling proteins having a number of habitat depending interesting intrinsic properties. As example, S-layers from bacterial isolates recovered from heavy metal contaminated environments have outstanding metal binding properties and are highly stable. Thus they selectively bind several metals with different affinity. For using S-layer proteins for metal bioremediation and recycling three aspects of the metal-interactions with S-layer proteins must be taken into account. First, S-layers possess different functionalities, e.g. carboxyl, phosphoryl groups, binding toxic metals and metalloids, like U(VI) and As(V), nonspecifically depending on pH. Second, precious metals like Au and Pd are likewise nonspecifically bound to functional groups, but presumably covalently, making the binding irreversible. Third, intrinsic specifically bound metals, e.g. Ca²⁺, are needed for native protein folding, self-assembly, and the formation of highly-ordered lattices. Their binding sites also allow selective binding of chemical-equal elements including the trivalent rare earth elements, possessing comparable ionic radii. Thus this study combines older and recently generated results regarding the metal dependent binding behavior of the S-layer proteins. It enables the development of biohybrid materials for the separation, removal or recovery of strategic relevant metals from natural occurring or industrial waste waters using pH-value as regulating parameter for selective metal binding and also conceivably release.

Abstract: This report deals with a simple and efficient method to develop hybrid carbon nanoparticles (Nps) employing Multi-walled carbon nanotubes (MWCNTs) and Fullerene nps. Fullerene nps were self-assembled via Ultrasonicated Liquid-Liquid Precipitation. Surface treated MWCNTs were entangled with fullerene nps during the process of assembling of the fullerene nps. Fullerene nps are formed by reaction between two solutions, one is the saturated solution which contains dissolved fullerene and other solution is a rough alcohol. This reaction increases the concentration of carbon in the solution and leads to super saturate hence self-assembling into nanoparticles. The obtained hybrid nanoparticles sizes were in the range of 100 nm to 300 nm with entangled mwcnts and were confirmed by characterization using SEM, Raman, UV-Vis, XRD, and DLS.