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Doughnut-Shaped Peptide Nano-Assemblies and Their Applications as Nanoreactors
Abstract
Doughnut-shaped nanoreactors, peptide nano-doughnuts, were self-assembled from peptides and organic Au salts. We demonstrated that monodisperse Au nanocrystals were synthesized inside the cavities of peptide nano-doughnuts by the reduction of Au ions and the size of the Au nanocrystal was controlled by the cavity dimension. The Au nanocrystals inside the nano-doughnuts were extracted by destroying the nano-doughnuts via long UV irradiation (>10 h). These features may allow the peptide nano-doughnuts to be applied in the fields of nanomaterial syntheses, controlled release systems, and drug delivery.
... Importantly, the protein surface is amenable to both genetic and chemical manipulation to impart specific functionalities by design and it is easily achievable due to presence of accessible amino, thiol, and carboxyl groups (Zeng et al., 2007;Kang et al., 2009). The self-assembled peptides nanodoughnuts serve as template nanoreactors for the preparation of gold nanoparticles (Djalali et al., 2003;Keren et al., 2003;Djalali et al., 2004) (Scheme 4). Monodisperse gold nanocrystals grew inside the template by the reduction of gold (III) salt to neutral gold atom (Djalali et al., 2004). ...
... The self-assembled peptides nanodoughnuts serve as template nanoreactors for the preparation of gold nanoparticles (Djalali et al., 2003;Keren et al., 2003;Djalali et al., 2004) (Scheme 4). Monodisperse gold nanocrystals grew inside the template by the reduction of gold (III) salt to neutral gold atom (Djalali et al., 2004). Free nanoparticles were isolated by the destruction of protein shell using UV irradiation and heating. ...
... Scheme 4. Scheme for the peptide nanodoughnut formation (Djalali et al., 2004). ...
Noble metal nanoparticles are important subjects in the field of nanotechnology. Various synthetic processes have been summarized and discussed for the preparation of noble metal nanoparticles of different sizes, shapes and solubility. Among them the colloidal fluids are most fascinating. The formation of nanoparticles starts by the reduction of metal salt and continue with the agglomeration of metal atoms to embryos, subnanoparticles and to premature metal nanoparticles. The existence of the microenvironments in the colloidal systems gives nanoparticles unique reactivity towards various molecules and additives. A soft template can be applied to synthesize noble metal nanoparticles in different-shaped biomolecules-based nanoreactors, micelles and liposomes. The size and shape of nanoparticles follows reactant feed composition, reaction conditions, presence or absence of template and type and concentration of reactants.
... The shell composition has also evolved from silica and polymer to many more functional materials such as metals, metal oxides, metal chalcogenides, and complex compounds. More importantly, the research community has quickly realized the fascinating properties associated with the unique hollow structures, such as large surface area, low density, and high loading capacity, and demonstrated a large variety of applications, including micro-/ nanoreactors, 36 53,72−80 and so forth. Because of the existence of a hollow cavity, the surface area of hollow structures is significantly larger while the density is much lower than that of their solid counterparts with the same composition and size. ...
... For example, Djalali et al. prepared monodisperse gold nanocrystals in doughnut-shaped peptide assemblies. 36 The nano-doughnuts were self-assembled from peptides and organic Au salts. Reducing gold ions led to the formation of gold nanocrystals inside the cavities of the peptide. ...
In this Review, we aim to provide an updated summary of the research related to hollow micro- and nanostructures, covering both their synthesis and their applications. After a brief introduction to the definition and classification of the hollow micro-/nanostructures, we discuss various synthetic strategies that can be grouped into three major categories, including hard templating, soft templating, and self-templating synthesis. For both hard and soft templating strategies, we focus on how different types of templates are generated and then used for creating hollow structures. At the end of each section, the structural and morphological control over the product is discussed. For the self-templating strategy, we survey a number of unconventional synthetic methods, such as surface-protected etching, Ostwald ripening, the Kirkendall effect, and galvanic replacement. We then discuss the unique properties and niche applications of the hollow structures in diverse fields, including micro-/nanocontainers and reactors, optical properties and applications, magnetic properties, energy storage, catalysis, biomedical applications, environmental remediation, and sensors. Finally, we provide a perspective on future development in the research relevant to hollow micro-/nanostructures.
... Various shapes of peptide/protein assemblies have been produced in biomaterials [44] . Monodisperse gold nanocrystals (AuNCs) grew 4 inside the cavities of peptide nano-doughnuts by the reduction of Au ions trapped in the cavities and the resulting AuNCs were extracted by destroying the nano-doughnuts via long UV irradiation[ Figure 3] [45] . Because the peptide nano-doughnuts already contained gol ions inside the cavities, Au nanocrystal synthesis was completed in a simpler process as compared to that of micelle nanoreactors. ...
... After those samples were dried on mica surfaces, the peptide nano-doughnuts without gold nanocrystals collapsed and displayed a deformed ring shape, whereas the peptide nano-doughnuts with gold nanocrystals inside the cavities showed a monodisperse and isotropic ring shape. Figure 3. Scheme for the peptide nanodoughnut formation [45] . ...
To manipulate the size of noble metal particles on a nanometer scale are priority subjects in the field of nanotechnology. So far various approaches have been developed to synthesize noble metal nanoparticles in controlled sizes and dimensions. Among them the colloidal systems become broadly used. These systems can be made up of several very different reactants and solvents: a continuous medium water or alkane, surfactant and precursor(s). In some systems the formation of (sub) nanoparticles is based on the supersaturation of solution by reactants. The existence of the microenvironments gives them a particular ability to modulate the chemical reactivity of the reactants due to their compartmentalization in different microenvironments. The size and shape of noble metal nanoparticles follow the feed composition of reactants in the precursor solution, the reaction conditions and concentration and type of reactants. Surface modification and functionalization is expected to increase the stability of nanoparticles and organize them to the assembly of higher order array conjugates. Various soft and hard templates can be applied to produce noble metal nanoparticles in different shaped nanoreactors. Monodisperse gold nano crystals can grow inside soft templates and the cavities of hard templates by the reduction of metal ions trapped in the cavities. The interesting optical properties of noble metal nanoparticles and their (bio)conjugates results from the strong absorption in the visible spectrum region, so called the surface plasmon absorption. Some noble metal nanoparticles have been studied for their antimicrobial potential and have proven to be antibacterial and antiviral agents.
... [6,7] Among the various self-assembled architectures of peptides, peptide nanotubes (PNTs) have been recognized as one of the most attractive one-dimensional nanostructures. [8] The peptide nanotube assemblies have shown diverse applications such as nanoreactors, [9] sensors, [10] light-harvesting systems, [11] artificial photosynthesis, [12] drug delivery [13] and antimicrobials. [14] In their pioneering work, Gazit and co-workers showed the selfassembly of PheÀ Phe dipeptide into distinct nanotubes and demonstrated the potential optoelectronic applications of the peptide nanotubes. ...
Development of miniaturized lab‐on‐chip devices for the detection of rapid and specific small molecule‐protein binding interactions at very low concentrations holds significant importance in drug discovery and biomedical applications. Here, the label‐free detection of small molecule‐protein interactions is reported on the surface functionalizable nanotubes of α,γ‐hybrid peptide helical foldamers using nanoscale capacitance and impedance spectroscopy. The 12‐helix conformation of the α,γ‐hybrid peptide observed in the single crystals, self‐assembled into nanotubes in an aqueous environment with exposed cysteine thiols for small molecule conjugation. The binding of streptavidin to the covalently linked biotin on the surface of nanotubes was detected at the picomolar concentrations. No change in the capacitance and impedance were observed in the absence of either immobilized biotin or protein streptavidin. The functionalizable hybrid peptide nanotubes reported here pave the way for the label‐free detection of various small molecule protein interactions at very low concentrations.
... Thus, many studies have been devoted to this field. The output of these investigations has led to benefit from these nanoscale structures in nanocomposites [3,4], nanoreactors [5], nanoribbons [6,7], nanoresonators [8,9], nanosensors [10,11], and nano-optics [12,13]. Nano-and microstructures are divided into different categories, such as nano-/microrods, nano-/microbeams, nano-/microshells, nano-/microbars, and nano-/microplates [14]. ...
This paper is devoted to the free torsional behavior of the nanorods containing noncircular cross sections. The rectangular cross section is chosen to be the case of the study. Three various boundary conditions, namely the clamped–clamped (C–C), clamped–free (C–F), and clamped–torsional spring (C–T) boundary conditions, are used to model the nanorod. Hamilton’s principle is utilized to derive the equation of motion along with associated boundary conditions. The derived equation is reformulated by Eringen’s nonlocal elasticity approach to exhibit the small-scale effect. An analytical method is established to discretize and analyze the equation of motion. The novelty of this work is the analysis of the torsional vibration in rectangular nanorods, which are not observed in previous works. For the results, the influences of the horizontal and vertical aspect ratios (a/b and b/a) (for C–C and C–F boundary conditions) and the influences of the nonlocal parameter and stiffness of the boundary spring (for C–T boundary condition) are illustrated schematically and tabularly.
... The molecular structures like as nucleotide chain (NC)-gold nanoparticles (NPs)-carbon nanotube (CNT) is an important stage in the understanding of interaction mechanism of a whole DNA or RNA molecule with NP and CNT[7][8][9][10][11][12][13][14][15][16][17][18]. Metallic nanoparticle of gold, silver, etc. are of great research interest in modern biomedical applications[19][20][21][22][23][24][25][26][27][28][29][30][31][32][33][34][35][36][37]. In recent experiments[29], for example, such nanoparticles have been used, which consisted of porous gold discs with a diameter of 400 nanometers. ...
Studying of molecular systems as single nucleotides, nucleotide and peptide chains, RNA and DNA interacting with metallic nanoparticles within a carbon nanotube matrix represents a great interest in modern research. In this respect it is worth mentioning the development of the electronics diagnostic apparatus, the biochemical and biotechnological application tools (nanorobotic design, facilities of drug delivery in a living cell), so on. In the present work using molecular dynamics (MD) simulation method the interaction process of small nucleotide chains (NCs) and elongated peptide chains with different sets of metallic nanoparticles (NPs) on a matrix from carbon nanotube (CNT) were simulated to study their mechanisms of encapsulation and folding processes. We have performed a series of the MD calculations with different NC,peptides-NP-CNT models that were aimed on the investigation of the peculiarities of NC,peptide-NP interactions, the formation of bonds and structures in the system, as well as the dynamical behavior in an environment confined by the CNT matrix.
... Since Ghadiri et al. [17] described a new class of organic nanotubes based on a cyclic peptide architecture, these structures have been used for the assembly of a variety of nano-ordered materials. A number of peptide-based nanomaterials have been prepared using different building blocks, including cyclic peptides with alternating D-and L-amino acids [17,23], peptide amphiphiles and peptide bolaamphiphiles [10], short peptides with alternating negatively and positively charged residues, and surfactant-like peptides [42], aromatic dipeptides [35], and hydrophobic dipeptides [18]. The molecular sequence can be carefully selected based on the expected interactions between the specific amino acids, such as β-sheet, aromatic stacking or alternating hydrophilic and hydrophobic interactions [51]. ...
L,L-diphenylalanine has been employed in the formation of self-assembled peptide nanotubes with great potential for the development of biosensors, molecular carriers, and optoelectronic devices. They are usually formed in an aqueous solution, and it is well known that water remains confined inside the structure. However, the role played by water in the overall stability of the nanotube is still unknown at the microscopic level. In this work, we investigate the stability of peptide structures after assembly due to the interaction with water molecules. We demonstrate, using molecular dynamics based on density functional tight-binding techniques, that water is fundamental in keeping the nanotube structure. It interacts with the nanotube walls as well as with other water molecules via hydrogen bonds keeping the structure stable. We identify and quantify the interaction between water and the relevant groups, and, upon increasing the solvent concentration, we show there is a transition region where there is a competition between the formation of water/water hydrogen bonds, and steric effects.
... Some recent examples are bolaform-mediated synthesis of tailored zeolite nanosheets with improved performance in targeted catalytic reactions (Liu et al., 2014) and templating of mesoporous silicon nanofibers, which can be used as anode materials for lithium-ion batteries (Xu et al., 2014). Furthermore, bolaforms have good interaction properties with several metals such as gold and silver and with their structural support, singleand multi-wall silver particle-coated nanotubes (Gao et al., 2006), gold nanocrystals (Djalali et al., 2004), and bionanotubes coated with cupper nanocrystals (Banerjee et al., 2003) can be obtained. ...
Bola-amphiphilic surfactants are molecules with fascinating properties. Their unique configuration consisting of a long hydrophobic spacer connecting two hydrophilic entities renders the molecule more water soluble than the average surfactant, but still allows formation of supramolecular structures. These properties make them extremely suitable for applications in in nanotechnology, electronics and gene and drug delivery. In general, these compounds are obtained by chemical synthesis. We report here an efficient microbial production process for the fully green synthesis of bolaform surfactants. A sophorolipid producing Starmerella bombicola yeast strain was disabled in its sophorolipid acetyltransferase and lactone esterase, which should logically result in synthesis of non-acetylated acidic sophorolipids; molecules with the classic amphiphilic structure. Surprisingly, also bolaform glycolipids were obtained, with an additional sophorose linked to the free carboxyl end of the acidic sophorolipids as confirmed by MS and NMR analysis. The obtained titres of 27.7 g/L total product are comparable to wild-type values, and the novel molecules account for at least 74% of this. Bola-amphiphile biosynthesis proved to be attributed to the promiscuous activity of both UDP-glucosyltransferases UGTA1 and UGTB1 from the core sophorolipid pathway displaying activity towards non-acetylated intermediates. The absence of acetyl groups seems to trigger formation of bolaform compounds starting from acidic sophorolipids. Hence, wild type Starmerella bombicola produces these compounds only at marginal amounts in general not reaching detection limits. We created a strain knocked-out in its sophorolipid acetyltransferase and lactone esterase able to produce these novel compounds in economical relevant amounts, opening doors for the application of biological derived bolaform structures. This article is protected by copyright. All rights reserved.
... As such, in addition to their use as reducing and/or capping agents to synthesize various nano-or microstructures, peptides can also act as versatile building blocks for peptide superstructures via self-assembly. [11][12][13][14][15][16] To date, researchers have produced various nano and/or microsized metals, metalloids, and semiconductor materials via biomimetic methods using peptides, including gold nanoparticles, silver nanoparticles, silica nanoparticles, calcium molybdate phosphor microparticles, and barium metatitanate precipitates. [6][7][8][17][18][19][20] In addition, a few gold-synthesizing peptides were isolated from cell-and phage-surface displayed techniques and were subsequently used to produce large, thin, hexagonal platelets, and smaller spherical gold nanoparticles by using repeating polypeptides, and 12.8 nm-sized gold nanoparticles by using A3 peptides, respectively. ...
Although biological synthesis methods for the production of gold structures by microorganisms, plant extracts, proteins, and peptide have recently been introduced, there have been few reports pertaining to controlling their size and morphology. The gold ion and peptide concentrations affected on the size and uniformity of gold plates by a gold-binding peptide Midas-11. The higher concentration of gold ions produced a larger size of gold structures reached 125.5 μm, but an increased amount of Midas-11 produced a smaller size of gold platelets and increased the yield percentage of polygonal gold particles rather than platelets. The mechanisms governing factors controlling the production of gold structures were primarily related to nucleation and growth. These results indicate that the synthesis of gold architectures can be controlled by newly isolated and substituted peptides under different reaction conditions.
... Research in the field of synthesis methodology of nanomaterials is mainly oriented in controlling their shape, size and composition. Each of these factors is a key factor in determining the properties of materials that lead to different technological applications 1,2 . ...
In this work we develop a simple technique to synthesize ZnO nanoparticles using zinc nitrate and KOH in aqueous solution. The precipitated compound was calcined and characterized by UV - Vis spectroscopy, transmission electron microscopy (TEM), and dynamic light scattering (DLS). The ZnO nanoparticles displayed characteristic Surface Plasmon Resonance peak at around 372 nm. Particle size distribution by dynamic light scattering technique (DLS) showed that the particles are in the range of 30±15 nm.
... [32][33][34][35] The various shapes of these nanostructures arise from a series of factors including hydrophobic interactions, hydrogen bonding, aromatic stacking, crystallization, steric effects, and electrostatic interaction. [36][37][38][39] Many studies have been conducted to generate nanomaterials using cyclic peptides, 40,41 amphiphiles, 42 bolaamphiphiles, 43 ionic peptides, 44 surfactant-like peptides, 45 and hydrophobic dipeptides. 46 Self-assembling peptide nanotubes formed by stacking cyclic peptides and stabilization by hydrogen bonds have attracted broad attention because of the potential ease with which they can be endowed with structural and functional properties. ...
While tremendous efforts have been spent in investigating scalable approaches for fabricating nanoparticles, less progress has been made in scalable synthesizing cyclic peptide nanoparticles and nanotubes, despite their great potential for broader biomedical applications. In this paper, tunable synthesis of self-assembled cyclic peptide nanotubes and nanoparticles using three different methods, phase equilibrium, pH-driven, and pH-sensitive methods were proposed and investigated. The goal is for scalable nanomanufacturing of cyclic peptide nanoparticles and nanotubes with different sizes in large quality by controlling multiple process parameters. Cyclo-(L-Gln-D-Ala-L-Glu-D-Ala-)2 was applied to illustrate the proposed ideas. In the study, mass spectrometry and high performance liquid chromatography were employed to verify the chemical structures and purity of the cyclic peptides. Morphology and size of the synthesized nanomaterials were characterized using atomic force microscopy and dynamic light scattering. The dimensions of the self-assembled nanostructures were found to be strongly influenced by the cyclic peptides concentration, side chains modification, pH value, reaction time, stirring intensity, and sonication time. This paper proposed an overall strategy to integrate all the parameters to achieve optimal synthesis outputs. Mechanisms about the self-assembly of the cyclic peptide nanotubes and nanoparticles under variable conditions and tunable parameters were discussed. This study contributes to scalable nanomanufacturing of cyclic peptide based self-assembled nanoparticles and nanotubes for broader biomedical applications.
... Interestingly, a structure of toroidal nanostructures was commonly found in many transmembrane proteins. Several research groups have designed and constructed self-assembled structure of toroid through amphiphilic block copolymers, DNAs, rod-coil amphiphiles, peptides and proteins (Butterfield and Lashuel, 2010;Huang et al., 2009;Yagai et al., 2008;Carlson et al., 2006;Djalali et al., 2004;Pochan et al., 2004;Jain and Bates, 2003). Therefore, selfassembly of rigid-flexible amphiphiles and synthetic peptidebased amphiphiles can be attractive to generate toroidal nano-structures. ...
The self-assembled structure of palm kernel oil-based (PKOEs) nano-emulsions have been shown a great potential used for parenteral drug delivery applications. Here, all-atom level molecular dynamics (MD) was applied to investigate the aggregation process of PKOEs based nano-emulsion system. The system was consisted of palm kernel oil-based ester (PKOEs) and dipalmitoylphosphatidylcholine (DPPC) in water. The ratio of all constituents was taken from the homogenous region of a ternary phase diagram determined experimentally. The molecules started to aggregate very rapidly from random configurations. A doughnut-like toroidal assembled structure formed at 50 ns with PKOEs surrounded by DPPC molecules. The structural and dynamics properties of the self-assembled doughnut-like toroidal aggregate were analysed using the principle moment of inertia, eccentricity and radius of gyration. The aggregation structures were compact with the average radius of gyration of 4.10 (±0.02) nm over the last 5 ns. Additionally, both hydrophobic and hydrophilic interactions were involved in aggregation process with a total solvent accessible surface area of 551.72 (±5.88) nm2.
... Это свойство активно используется при создании искусственных конструкций, имитирующих реальные биологические структуры. К этому классу наночастиц можно отнести вирусные нановекторы [18], различные однокомпонентные и мультикомпонентные липосомы, которые способны при определенных условиях формироваться из раствора смеси липидов [19][20][21], липидные нанотрубки [22], липидные наносферы [23][24][25], липидные наночастицы [26,27] и наноэмульсии [28,29], пептиды [30], хитозаны [31,32], наночастицы на основе нуклеиновых кислот [33]. ...
NaNoparticulate delivery systeMs for targetiNg delivery of Nucleic acids to the cells T his review illustrates the recent advances on the design of nanoparticulate delivery systems (vectors) for the delivery of nucleic acids to target cells. Literature data on structural and functional features of viral, non-viral, nanostructured, and multimodality vectors have been analyzed. The potential future applications of nanoparticles in medicine, including their possible disadvantages and side effects have been discussed. ВВЕДЕНИЕ В настоящее время одним из глав-ных государственных приоритетов Российской Федерации стало развитие исследований наноматериалов и нано-структур и создание на их основе нано-технологий для перевода на новый мировой уровень многих отраслей про-мышленности, сельского хозяйства и социальной сферы. Направления работ в этой области связаны с исполь-зованием процессов самоорганизации и самосборки нанообъектов, использо-ванием квантовых свойств нанострук-тур и применением методов нанокон-струирования в информационных, химических, биологических и меди-цинских технологиях. Особой отраслью нанотехнологий, исследования в кото-рой признаны приоритетными во всем мире, является нанобиотехнология, базирующаяся на использовании био-логических наномолекул. Важнейшими задачами нанобио-технологии являются развитие новых методов инструментального исследова-ния живых систем, диагностики и лече-ния заболеваний: ранней диагностики рака, инфекционных, генетических заболеваний, – создание биосовмести-мых наноматериалов и нанолекарств. Ключевой проблемой, от которой зави-сит успешное развитие нанобиотехно-логии, является создание эффективных нанотранспортных систем доставки лекарственных препаратов в клетки. Решение этой задачи позволит уве-личить продолжительность действия лекарств, минимизировать побочные эффекты и, как следствие, повысить эффективность терапевтического лече-ния и способствовать развитию эколо-гически чистых процессов. В настоящем обзоре суммированы сведения об использовании достиже-ний нанотехнологии для направленного транспорта нуклеиновых кислот (ДНК, РНК и коротких олигонуклеотидов) в клетки. Рассмотрены нанотранспорт-ные системы доставки. Обсуждаются перспективы использования нано-частиц в медицине, включая оцен-ку возможных побочных эффектов их применения. ПРИНЦИПЫ АДРЕСНОЙ ДОСТАВКИ НУКЛЕИНОВЫХ КИСЛОТ В ТКАНИ И КЛЕТКИ-МИШЕНИ Уникальные особенности нуклеино-вых кислот (НК), такие как способ-ность к самоорганизации, самовоспро-изведению, молекулярному узнаванию мишени и возможность интеграции в клеточный геном, лежат в основе ген-ной терапии – лечения наследствен-ных, мультифакториальных и инфек-ционных заболеваний путем введения экзогенного генетического материала в клетки пациентов с целью направлен-ного изменения генетических дефектов или придания отдельным клеточным органеллам новых свойств.
... 48 Nanodoughnut forming self-assembled peptide bolaamphiphile was also used as a nanoreactor to synthesis Au nanocrystal. 49 The nanostructural transformation requires a stimulus, which can break weak non-covalent interactions and induces another supramolecular arrangement. The change in pH can tune the evolution of different nanostructures of bolaamphiphiles. ...
which has been through the Royal Society of Chemistry peer review process and has been accepted for publication. Accepted Manuscripts are published online shortly after acceptance, before technical editing, formatting and proof reading. Using this free service, authors can make their results available to the community, in citable form, before we publish the edited article. We will replace this Accepted Manuscript with the edited and formatted Advance Article as soon as it is available. You can find more information about Accepted Manuscripts in the Information for Authors. Please note that technical editing may introduce minor changes to the text and/or graphics, which may alter content. The journal's standard Terms & Conditions and the Ethical guidelines still apply. In no event shall the Royal Society of Chemistry be held responsible for any errors or omissions in this Accepted Manuscript or any consequences arising from the use of any information it contains. Abstract: Nanostructural transition of a small peptide bolaamphiphile via molecular self-assembly is a challenging task. Here, we report self-programmed morphological transformation from nanovesicles to nanofibers of a smart peptide bolaamphiphile in it's self-assembling hydrogel state. The nanostructural transition occurs based on the structural continuity of the β-sheet structures. The spectroscopic studies confirmed different molecular arrangements of two different nanostructures. Furthermore, the smart bolaamphiphile shows dose dependent cytotoxicity and cell-proliferation behaviour.
... Doughnut-shaped nano-structures (including nano-doughnuts, nano-rings, nano-toroïds and in particular the example of nano-wells), being a reach object for fundamental study of light localization at nanoscale, have also recently attracted attention due to their efficient use in nano-plasmonics, photochemistry, nano-rectors and sensors. Several successful approaches were developed to produce organic and inorganic doughnut-shaped nanostructures by chemical synthesis and self-assembling [16] as well as colloidal [17] and optical [18] lithography. However they are limited to fabrication of non-reshapeable nanostructures that makes them inefficient for the study of size-dependency of optical and photochemical properties of these structures and their applications to nanoreactors. ...
We show that an incoherent unpolarized single-beam illumination is able to
photoinduce nano-doughnuts on the surface of azopolymer thin films. We
demonstrate that individual doughnut-shaped nano-objects as well as clusters of
several adjacent nano-doughnuts can be formed and tailored with wide range of
typical sizes, thus providing a rich field for applications in nanophotonics
and photochemistry.
... Despite the relatively small numbers of studies, reports have shown that various types of self-assembling molecules can form toroidal nanostructures. Self-assembled toroidal nanostructures have been found in amphiphilic block copolymers, [14][15][16][17] surfactants, 18,19 DNAs, 20,21 rod-coil amphiphiles, [22][23][24][25] peptides, [26][27][28][29] proteins, [30][31][32] and other building blocks. 33, 34 In recent years, the amount of literature concerning the observation of self-assembled toroidal nanostructures, either serendipitously found or rationally designed, has increased. ...
Controlling nanostructural morphologies has been the subject of intensive research as nanostructures can display significantly different bioactivities depending on their physicochemical parameters. Toroidal proteins perform numerous important functions in biological systems. Recent studies show that toroidal nanostructures can be constructed by rationally designed self-assembling peptide building blocks.
Cyclic peptides (CPs) possess the ability to self-assemble into cyclic peptide nanotubes (CPNTs), which find extensive applications in nanotechnology. The formation and stability of these nanotubes are influenced by multiple factors. The present study explores the stability of CPNTs in various solvents with varying polarity, focusing on three specific peptide sequences: DK4, WL4, and DLKL2. Using molecular dynamics simulations, the effect of solvent polarity and peptide composition on the stability of CPNTs is assessed through the determination of electrostatic, van der Waals, and hydrogen-bonding interactions. The binding free energy between adjacent cyclic peptide rings is analyzed via MM/GBSA and MM/PBSA methods, revealing that DLKL2, an amphiphilic peptide, exhibits greater stability than DK4 and WL4 in nonpolar solvents. The introduction of leucine residues in DLKL2 reduces intramolecular hydrogen bonding and electrostatic interactions, promoting stronger interpeptide backbone hydrogen bonds and maintaining the nanotube’s structural integrity. Hydrogen bond lifetimes, computed using the corresponding time correlation function, indicate the longest-lasting hydrogen bonds occur in all the solvent environments except water, further contributing to the stability of DLKL2 nanotubes. Additionally, deformation from circularity in the peptide rings, analyzed using ellipticity values, highlights the degree of structural distortion across solvents, with DK4 showing the highest deviation due to stronger intramolecular interactions. These findings offer valuable insights into the roles of solvent and peptide composition in the self-assembly and stability of CPNTs, which have significant implications for their potential applications in nanotechnology and biomedicine.
Urea-cored pseudopeptides exhibit remarkable self-assembly to varying morphologies. Concentration-dependent studies revealed a series of morphological transformations from vesicles to toroids, and honeycomb-like architectures. The morphology dependent autofluorescence is another noteworthy...
Functional supramolecular materials exhibit important features including structural versatility and versatile applications. Here, this study reports the construction of unique hierarchically organized nanotoroids exhibiting fluorescence, photocatalytic, and sensing properties. The nanotoroids comprise of macrocyclic diacetylenes (MCDA) and 8‐anilino‐1‐naphthalene sulfonate (ANS), a negatively charged aromatic fluorescent dye. This study shows that the hierarchical structure of the nanotoroids consist of MCDA nanofibers formed by stacked diacetylene monomers as the basic units, which are further bent and aligned into toroidal organization by electrostatic and hydrophobic interactions with the ANS molecules. The amine moieties on the nanotoroids surface are employed for deposition of gold nanostructures – Au nanoparticles or Au nanosheets – which constitute effective platforms for photocatalysis and surface enhanced Raman scattering (SERS)‐based sensing.
Polymer self-assembly has become a reliable and versatile workhorse to produce polymeric nanomaterials. With appropriate polymer design and monomer selection, polymers can assemble into shapes and morphologies beyond well-studied spherical and cylindrical micellar structures. Steadfast access to anisotropic polymer nanoparticles has meant that the fabrication and application of 2D soft matter has received increasing attention in recent years. In this review, we focus on nanoscale polymer discs, toroids, and platelets: three morphologies that are often interrelated and made from similar starting materials or common intermediates. For each morphology, we illustrate design rules, and group and discuss commonly used self-assembly strategies. We further highlight polymer compositions, fundamental principles and self-assembly conditions that enable precision in bottom-up fabrication strategies. Finally, we summarise potential applications of such nanomaterials, especially in the context of biomedical research and template chemistry and elaborate on future endeavours in this space.
Metallic gold (Au) nanostructures have attracted attentions in various fields of materials science and electrical science in terms of catalysts, sensing systems, photonic devices, and drug delivery systems because of their characteristic physical, chemical, and biocompatible properties. Recently, Au nanostructures with near-infrared light absorbing properties have shown potential for applications such as biological imaging and thermotherapy in biotechnological fields. However, fabrication of Au nanostructures with complex shapes often requires the use of highly biotoxic substances such as surfactants and reducing agents. Peptides are promising compounds for controlling the shape of Au nanostructures by mineralization with several advantages for this purpose. In this highlight, we focus on the shapes with respect to the fabrication of Au nanostructures using biocompatible peptides. We classify the peptides that form Au nanostructures into three broad categories: those that bind Au ions, those that reduce Au ions, and those that control the direction of Au crystal growth. Then, we briefly summarize the correlations between peptide sequences and their roles, and propose future strategies for fabricating Au nanostructures using peptides for biotechnological applications.
Zinc Oxide (ZnO) nanoparticles (NPs) have been synthesized by a simple chemical precipitation method. The effect of monoethanolamine (MEA) content in different solvents on ZnO NPs synthesis and their structural properties has been investigated. The NPs synthesized by using isopropanol (IPA) with 15 ml MEA as a stabilizer under the most favorable conditions (deposition time, td = 120 min, temperature = 60 °C) showed good structural properties. Synthesized NPs exhibited beneficial structural properties after annealing. The hexagonal wurtzite crystal structure of ZnO NPs was verified by XRD. Different models were used to calculate structural parameters such as crystallite size, strain, stress, and energy density for all the reflection peaks of XRD corresponding to ZnO lying in the range 2θ = 15⁰–80⁰. The crystallite size of the ZnO nanoparticles was found to be 50–60 nm. FTIR and EDX confirmed the presence of ZnO NPs in the samples. SEM micrograph of all the samples revealed that the grain sizes decrease gradually with the increase of the amount of MEA. UV–Visible diffuse reflectance spectroscopy results provide evidence that the ZnO NPs possess broader absorption bands, together with high band gap energy. The ZnO NPs synthesized with IPA solvent have the highest transmittance and band gap energy of 3.3eV. According to DLS data, various content of MEA stabilizer in solvent affects the hydrodynamic size of ZnO NPs.
Azacalixphyrins are used as building blocks to elaborate nanostructures with different shapes depending on the nature of the N-substituents. In this work, the formation of nanoribbons from N-alkyl azacalixphyrin 4, and nanodonuts from the N-aryl analogue 5, is presented and rationalized by molecular dynamics (MD) simulations. Indeed, MD revealed different modes of intermolecular interactions (defines as nodes-and-trails and nodes-and-thorns models) according to the nature of the N-substituents. Nanoribbons based on 4 results from the stackings of the azacalixphyrin cores along the vertical direction generate the nodes, while the van der Waals interactions between the N-C 8 H[Formula: see text] aliphatic chains generate the trails among the nodes along the ribbon. On the other hand, azacalixphyrin 5 self-assemblies into a nanodonut shape, in which the macrocyclic cores (nodes) stack along the horizontal plane while the 3,4,5-trimethoxyphenyl groups (thorns) point along the vertical direction towards the solvent where they establish a network of [Formula: see text]-[Formula: see text] interactions among their aromatic portions and H-bond interactions among the CH 3 O-groups and the solvent molecules, respectively.
The significant trend for the improvement of material’s performance is increasing of their surface area, pore volume and surface to volume ratio. That leads huge attention from various fields and scientists. Hollow nanomaterials are unique materials to evolve because of special attributions like surface area as these materials have wide surfaces than their solid counterparts. Synthesis of hollow nanomaterials (HNMs) is very challenging and important in the grown era of industrialization. The common synthetic strategies are hard-template, self-template, soft template, template free and simple methods. The characterization tools are scanning electron microscopy (SEM) and transmission electron microscopy (TEM). Hollow nanomaterials have wide range applications in catalysis, sensors, lithium ion batteries, water treatment, drug delivery, nanoreactors and dye sensitized solar cells etc. Herein we had summarized the strategies for preparation of HNMs and their applications.
Porous nanospheres have potential applications in reactions, catalysis and water treatment because of their high surface area, low density and high loading capacity. In this work, a reproducible and well-controlled way to fabricate hollow Polystyrene/Poly(divinylbenzene-co-methacrylic acid)@Fe3O4/Tannic [email protected] (PS/P(DVB-co-MAA)@Fe3O4/[email protected]) nanocomposites with high catalytic efficiency is developed. Firstly, hollow Polystyrene/Poly(divinylbenzene-co-methacrylic acid) (PS/P(DVB-co-MAA)) nanospheres with an open hole on the surface are produced by supercritical carbon dioxide (scCO2) rapid depressurization methodology. The consequence shows that structure of polymer nanospheres is controllable by altering the reactive conditions, like temperature, pressure, solvent ratio, degree of cross-linking and time. Secondly, the magnetic Fe3O4 and Ag nanoparticles are deposited onto the surface of hollow PS/P(DVB-co-MAA) nanospheres. The result indicates that hollow PS/P(DVB-co-MAA)@Fe3O4/[email protected] nanocomposites are highly efficient in degrading dyes, displaying that the apparent rate coefficients of methylene blue (MB), rhodamine B (RhB) and 4-nitrophenol (4-NP) reduction are 0.0090 s⁻¹, 0.0239 s⁻¹, and 0.0073 s⁻¹, respectively. Besides, hollow PS/P(DVB-co-MAA)@Fe3O4/[email protected] nanocomposites can be recycled at least seven times and show no significant loss in catalytic performance.
Homopolypeptide poly(γ-benzyl- l -glutamate) can self-assemble into fluorescent toroids following an end-to-end closure mechanism.
In recent years, toroidal nanostructures have become an appealing topic in nanoscience owing to their unique structure and promising applications. Among them, polymeric toroidal self-assemblies have attracted considerable attention because of their manipulability and diversity. Despite the substantial advances in the area of polymeric nanotoroids, the universal formation principles and functions of these toroids have not been sufficiently summarized. This article aims to review recent advances in the formation and function of polymeric nanotoroids. The significant role of theoretical simulations in revealing the formation mechanism and inherent structure of toroidal assemblies is emphasized. Additionally, a perspective on the challenges of this research field is addressed.
Toroids and helices are fundamental geometrical structures in nature. Polymers can self‐assemble into various nanostructures, including both toroids and helices; however, nanostructures combining toroidal and helical morphologies, i.e., helical toroids, are rarely observed. Herein, we report that a binary system containing polypeptide homopolymer and its block copolymer can hierarchically self‐assemble into uniform helical nanotoroids in solution. The formation of the helical toroids is a successive two‐step process. First, the homopolymers aggregate into fibrils and convolve into toroids, resembling the toroidal condensation of DNA chains. Second, the block copolymers self‐assemble on the homopolymer toroids resulting in helical surface patterns. Additionally, the chirality of the surface helical patterns can be varied by the chirality of the polypeptide block copolymers.
Toroids and helices are fundamental geometrical structures in nature. Polymers can self‐assemble into various nanostructures, including both toroids and helices; however, nanostructures combining toroidal and helical morphologies (that is, helical toroids) are rarely observed. A binary system is reported containing polypeptide homopolymer and its block copolymer, which can hierarchically self‐assemble into uniform helical nanotoroids in solution. The formation of the helical toroids is a successive two‐step process. First, the homopolymers aggregate into fibrils and convolve into toroids, thereby resembling the toroidal condensation of deoxyribonucleic acid (DNA) chains. Second, the block copolymers self‐assemble on the homopolymer toroids and result in helical surface patterns. Additionally, the chirality of the surface helical patterns can be varied by the chirality of the polypeptide block copolymers.
Formation of polymeric materials on the surface of supramolecular assemblies is rather challenging due to the often weak non‐covalent interactions between the self‐assembled template and the monomers before polymerization. We herein describe that the introduction of a supramolecular anion recognition motif, the guanidiniocarbonyl pyrrole cation (GCP), into a short Fmoc‐dipeptide 1 leads to self‐assembled spherical nanoparticles in aqueous solution. Onto the surface of these nanoparticles negatively charged diacetylene monomers can be attached which after UV polymerization lead to the formation of a polymer shell around the self‐assembled template. The hybrid supramolecular and polymeric nanoparticles demonstrated intriguing thermal hysteresis phenomenon. The template nanoparticle could be disassembled through the treatment with organic base which cleaved the Fmoc moiety on 1. This strategy thus showed that a supramolecular anion recognition motif allows the post‐assembly formation of polymeric nanomaterials from anionic monomers around a cationic self‐assembled template.
Light irradiation was found to trigger the self-assembly of a cyanostilbene-conjugated dialkyl glutamide from nanobelt to nanotoroids, which emitted inversed circularly polarized luminescence.
Biomineralization, the process by which biological systems direct the synthesis of inorganic structures from organic templates, is an exquisite example of nanomaterial self-assembly in nature. Its products include the shells of mollusks and the bones and teeth of vertebrates. By comparison, conventional inorganic synthesis techniques provide limited control over inorganic nanomaterial architecture. Inspired by biomineralization in nature, over the last two decades, the field of biotemplating has emerged as a new paradigm for inorganic nanomaterial assembly, wherein researchers seek to design novel nano-structures in which inorganic nanomaterial synthesis is directed from an underlying biomolecular template. Here, we review the motivation, mechanistic understanding, progress, and challenges for the field of biotemplating. We highlight the interdisciplinary nature of this field, and survey a broad range of examples of bio-templated engineering: ranging from strategies that exploit the inherent capabilities of proteins in nature, to genetically-engineered systems that unlock new capabilities for self-assembly with biomolecules. We illustrate that the use of biological materials as templates for inorganic self-assembly holds tremendous potential for nanomaterial engineering, with applications that range from electronics and energy to medicine.
The equipment of technical devices with biogenic adapter structures enables an effective integration of biofunctional units into advanced sensor, filtration, or catalytic layouts. Plant virus-derived self-organizing supramolecular complexes are among the most promising soft-matter adapters due to their multivalence on the nanometer scale, precise dimensions, high availability, and compatibility with routine conjugation chemistry. Bioengineering can tailor both the templates’ shapes and coupling sites, and has been applied here to develop nucleoprotein “nanorings” made of tobacco mosaic virus (TMV) building blocks. Short RNA-scaffolded four-turn helices of ≈68 protein subunits and ≈9 nm length, with 18 nm outer and 4 nm inner diameter, were generated efficiently in vitro. A structure-directing single-stranded 204 nts RNA containing the TMV origin of assembly yielded colloidal preparations of structural integrity and well-dispersed in a pH range from about 7 to 9. Two selectively addressable protein types with either an amino, or a thiol group accessible were combined in the ring-like objects, allowing dual covalent coupling of a fluorescent dye first, and to an isothiocyanate-(ITC)-covered substrate thereafter. Such precisely shaped nanoconstructs with distinct functional groups exposed in high surface densities offers novel opportunities as versatile adapter elements for the fabrication of extended bio/synthetic hybrid materials.
Toroidal structures based on self-assembly of predesigned building blocks are well established in literature however, spontaneous self-organization to prepare such structures has never been reported thus far. Here, organic-inorganic hybrid microtoroids synthesized by simultaneous coordination-driven assembly of amphiphilic molecules and hydrophilic polymers are reported. Mixing amphiphilic molecules with iron(III) chloride and hydrophilic polymers in water leads, within minutes, to the formation of star-like nanostructures. A spontaneous self-organization of these nanostructures is then triggered to form stable hybrid microtoroids. Interestingly, the toroids exhibit anisotropic hierarchical growth giving rise to a layered toroidal framework. These microstructures are mechanically robust and can act as templates to host metallic nanoparticles such as gold and silver. Understanding the nature of spontaneous assembly driven by multiple non-covalent interactions can help explain the well-ordered complexity of many biological organisms in addition to expanding the available tools to mimic such structures at a molecular level.
The self-assembly of tris(phenylisoxazolyl)benzene 1b with photochemically addressable azobenzene moieties produced toroidal nanostructures, the formation and dissociation of which were reversibly regulated upon photoirradiation. 1b displayed a mesogenic behavior. In the solution, the stacked assemblies along with their C3 axes were formed. In the mesophase, two molecules of 1b most likely adopted the antiparallel arrangement to stabilize the columnar organization. This assembling behavior most likely triggered the development of the supramolecular toroidal nanostructures.
Exerting control over the size, morphology, and complexity of metal and semiconductor nanoparticles and nanostructures is a requisite for exploring novel phenomena, and the potential applications of these nanomaterials. Bottom-up colloidal chemistry syntheses can benefit from using biomolecules as active elements to influence the formation of inorganic nanoparticles. In this review, we will discuss how three main biomolecule types, (namely DNA; amino acids, peptides, and proteins; and enzymes), can affect the growth of metal and semiconductor nanoparticles. We will present and discuss the templating and non-templating roles of those biomolecules, featuring key aspects and prospects of biomolecule-assisted metal and semiconductor nanoparticle growth.
The past few years have witnessed the development of non-spherical metal nanoparticles with complex morphologies, which offer tremendous potential in materials science, chemistry, physics and medicine. Covering all important aspects and techniques of preparation and characterization of metal nanoparticles with controlled morphology and architecture, this book provides a sound overview - from the basics right up to recent developments. Renowned research scientists from all over the world present the existing knowledge in the field, covering theory and modeling, synthesis and properties of these nanomaterials. By emphasizing the underlying concepts and principles in detail, this book enables researchers to fully recognize the future research scope and the application potential of the complex-shaped metal nanoparticles, inspiring further research in this field. Reviews. "Complex-shaped Metal Nanoparticles: Bottom-Up Syntheses and Applications is an extremely useful reference, whether the reader is interested in synthesis, application or theory of complex-shaped nanoparticles." From Platninum Metal Reviews.
Peptides are intriguing building blocks for a variety of applications in bionanotechnology. They can self-assemble into many forms of nanostructures. In this chapter, we focus on peptide nanofibers and nanotubes. Their design principles are presented and their applications as tissue engineering scaffolds, drug delivery vehicles and therapeutics are illustrated. We also describe the nanofibers derived from a novel class of ultrashort self-assembling peptides. These ultrashort self-assembling peptides contain three to seven natural aliphatic amino acids and can form hydrogels with biocompatibility, high thermal stability and high mechanical strength. They hold great potential for various biotechnological and industrial applications.
Dichloromethane liquid droplets containing a cobalt dipyrromethene timer deposited on a graphite surface were found to form coffee ring, toroid ring, or volcano dot structures due to the redistribution of the solute during solvent evaporation. The shapes and size distributions. of the ring structures, depended on the drying temperature. The shape differences were attributed to the fact that the solvent evaporation rate controlled the self-assembly process that yielded the coffee stain and pinhole structures.
In this thesis, interaction of ferritin with transition metal ions and chelates is studied. First, a simple method for synthesizing gold nanoparticles stabilized by horse spleen apoferritin (HSAF) was reported using NaBH4 or 3-(N-morpholino)propanesulfonic acid (MOPS) as the reducing agent. The average particle diameters were 3.6 and 15.4 nm for NaBH4-reduced and MOPS-reduced Au-HSAF, respectively. NaBH4-reduced Au-HSAF was much more effective than MOPS-reduced Au-HSAF in catalyzing the reduction of 4-nitrophenol by NaBH4, based on the greater accessibility of the NaBH4-reduced gold particle to the substrate. Methods for studying ferritin-gold nanoparticle assemblies may be readily applied to other protein-metal colloid systems. Second, the binding interactions between HSAF and three recombinant apoferritins and two commonly employed gadolinium magnetic resonance imaging (MRI) contrast agents were investigated. The anionic Gd(DTPA)2- complex was undetectable in apoferritin solutions after dialysis, indicating little protein-binding interaction. However, the non-ionic Gd(DTPA-BMA) complex bound to all apoferritins tested, producing remarkable relaxivity enhancements as well as inhibition of iron mineralization. Serum ferritin binding and dysregulation of iron mineralization may have medical significance, particularly in patients with impaired kidney function.
Target drug delivery methodology is becoming increasingly important to overcome the shortcomings of conventional drug delivery absorption method. It improves the action time with uniform distribution and poses minimum side effects, but is usually difficult to design to achieve the desire results. Economically favorable, environment friendly, multifunctional, and easy to design, hybrid nanomaterials have demonstrated their enormous potential as target drug delivery vehicles. A combination of both micelles and nanoparticles makes them fine target delivery vehicles in a variety of biological applications where precision is primarily required to achieve the desired results as in the case of cytotoxicity of cancer cells, chemotherapy, and computed tomography guided radiation therapy.
Self-assembled supramolecular structures of peptide derivatives often reflect a kinetically trapped state rather than the thermodynamically most favoured structure, which presents a challenge when trying to elucidate the molecular design rules for these systems. In this article we use thermodynamically controlled self-assembly, driven by enzymatic condensation of amino acid derivatives, to elucidate chemical composition/nanostructure relationships for four closely related Fmoc-dipeptide-methyl esters which form hydrogels; SF, SL, TF and TL. We demonstrate that each of the four systems self-assemble to form extended arrays of beta-sheets which interlock via pi-stacking of Fmoc-moieties, yet with subtle differences in molecular organisation as supported by rheology, fluorescence emission spectroscopy, infrared spectroscopy, X-ray diffraction analysis and molecular mechanics minimisation.
Achiral amphiphiles with hydroxylated oxanorbornane head groups showed specific morphological characteristics and hierarchical preferences depending upon the nature of lipophilic units. Detailed SEM studies showed that twisted ribbon-like aggregates are characteristic of mono-alkoxyaryl lipids with hydrocarbon chain length in the range of C10-C13; these systems also had a preference towards lamellar arrangement. Asymmetric packing of these lipids is a unique occurrence and shows that presence of molecular chirality is not an absolute requirement for curvature effects in their supramolecular assemblies. Aryl units in these systems were found important for the observed morphological preferences which became evident from comparative studies involving simple long chain esters without this moiety. Single crystal X-ray diffraction analysis of one of the lipids from the latter group gave finer details of strong and weak secondary interactions which operate during their assembly process. Introduction of more than one alkyl chain on the aromatic ring caused a notable shift in the packing propensity towards columnar arrangement. Most of these cone-shaped molecules were found to give doughnut-shaped aggregates from acetone solution through the intermediary of fibrous structures which was confirmed through SEM, TEM and AFM studies.
Toroidal nanostructures are symmetrical ring-shaped structures with a central internal pore. Interestingly, in nature, many transmembrane proteins such as β-barrels and α-helical bundles have toroidal shapes. Because of this similarity, toroidal nanostructures can provide a template for the development of transmembrane channels. However, because of the lack of guiding principles for the construction of toroids, researchers have not widely studied the self-assembly of toroidal nanostructures as compared with the work on other supramolecular architectures. In this Account, we describe our recent efforts to construct toroidal nanostructures through the self-assembly of rationally designed building blocks. In one strategy for building these structures, we induce interfacial curvatures within the building blocks. When we laterally graft a bulky hydrophilic segment onto a p-oligophenyl rod or β-sheet peptides, the backbones of the self-assembled structures can bend in response to the steric effect of these large side groups, driving the p-oligophenyl rod or β-sheet peptides to form nanosized toriods. In another strategy, we can build toroids from bent-shaped building blocks by stacking the macrocycles. Aromatic segments with an internal angle of 120° can associate with each other in aqueous solution to form a hexameric macrocycle. Then these macrocycles can stack on top of each other via hydrophobic and π-π interactions and form highly uniform toroidal nanostructures. We provide many examples that illustrate these guiding principles for constructing toroidal nanostructures in aqueous solution. Efforts to create toroidal nanostructures through the self-assembly of elaborately designed molecular modules provide a fundamental approach toward the development of artificial transmembrane channels. Among the various toroids that we developed, a few nanostructures can insert into lipid membranes and allow limited transport in vesicles.
This review describes the state-of-the-art scientific developments of bolaamphiphilic molecules composed of two hydrophilic headgroups connected by a hydrophobic chain in the middle of the molecule. In contrast to previous review articles, this review focuses on the discussion of the bolaamphiphilic molecules from assembly to applications in various fields. The main principles of the assembly structures of bolaamphiphilic molecules are discussed, both at interfaces, including air/water and liquid/solid, and in solutions. Since different interactions exist among hydrophilic or polar head groups of the molecules, and the complexity of different hydrophobic, van der Waals, π–π interactions, etc., between the chains, the assembly structures of the bolaamphiphilic molecules in the solution are more complicated and are therefore discussed in more detail. Finally, current applications for several important structures and assembly mechanisms of the molecules are introduced.
Given the diverse scientific and technological applications of gold nanoparticles (Au NPs), understanding the impact of macromolecular additives on the distribution of size, shape, and composition is crucial to ensure reproducibility and lower production cost. In situ measurement of the evolution of these distributions challenges current techniques; however, it is critical for in-line manufacturing controls. Using mild Au(I) reduction by tert-butylamine-borane in toluene, the utility and limitations of SAXS, UV/Vis spectroscopy, and TEM are considered by comparing the mean nanoparticle size, size distribution, and relative number density. Individually, these techniques are insufficient to follow these parameters through the initial process of nucleation and growth; either providing insufficient information on the number of particles (UV/Vis), introducing artifacts (TEM), or not providing a unique solution for the shape of the distribution (SAXS). However, when used in conjunction, especially SAXS calibrated with TEM of reaction aliquots, the time evolution of these parameters can be quantified. For the single-phase Au NP synthesis with Au(I) and mild reductants, four distinct experimental regions are revealed that entail two growth mechanisms, which complement previous discussions of single-mode growth kinetics. The kinetics of Au(I):borane reactions are dependent on the Au precursor/reductant ratio and the thiol capping agent length, when reductant concentration is low. The final reaction products exhibit an LSW size distribution.
The study of enzymatically triggered self-assembly of aromatic peptide amphiphiles has become increasingly popular in recent years and has lead to a variety of nanoscale architectures. As hydrophobic interactions have been recognised as a major driving force in their self-assembly, typically, the peptide components are found to be hydrophobic in nature, containing aromatic or aliphatic amino acid residues. In this article, we use subtilisin triggered self-assembly of four closely related Fmoc-dipeptide amphiphiles with terminal hydrophilic amino acid residues, YT, YS, YN and YQ, in order to introduce a new functionality to the self-assembled systems, and determine the influence of each amino acid side chain. We use microscopy techniques, rheology, fluorescence, FTIR and CD to demonstrate differences in molecular assembly, mechanical properties and nanoscale architecture as a direct result of the subtle molecular variance of each system. We demonstrate that the amino acid side chain in position two directly affects the molecular packing abilities in the supramolecular structure, with YT, YS and YN forming nanoscale fibres with mechanical properties being linked to the functionality of the amino acid side chain, and YQ forming spherical structures due to steric effects associated with the glutamine side chain prohibiting the adoption of the typical π–β assembly.
The peptide nano-rings containing Au nanoparticles inside their cavities were self-assembled on dithiol SAMs patterned as an array by AFM-based nanolithography. The peptide nano-rings were aligned as a line on these SAMs, and Au formed lines with the spacing between these nanoparticles as the peptide nano-rings functioned as spacers. This type of array fabrication will provide improved tunability in their optical properties of resulting nanoparticle-assembled arrays. In addition, optimization of the inter-particle distance of nanoparticles in the array with various spacers may allow one to design new types of photonic crystals with desired optical properties.
The interaction of tetrachloroauric anion (AuCl4-) and hydrophobic poly(amidoamine) dendrimers (PAMAM) with terminal methyl ester groups was investigated in ethyl acetate by UV-vis and IR spectroscopies. Three possible types of interaction are suggested: (a) ion pair formation between AuCl4- and protonated tertiary amine of PAMAM, (b) chelation of Au(III) by one (or two) tertiary amine(s) and two terminal methyl ester groups, and (c) chelation of Au(III) by two tertiary amines and two adjacent amide groups of the dendrimer. Au-PAMAM nanocomposites were synthesized by reducing the AuCl4--PAMAM complex with dimethylamine borane. The structure of the nanocomposites is supposed to be of exterior or mixed type. These Au-PAMAM nanocomposites exhibit a weak surface plasmon band in the range of 480 to 500 nm.
Structural types of dendrimer nanocomposites have been studied and the respective formation mechanisms have been described, with illustration of nanocomposites formed from poly(amidoamine) PAMAM dendrimers and zerovalent metals, such as gold and silver. Structure of {(Au(0)) n− PAMAM} and {(Ag(0)) n− PAMAM} gold and silver dendrimer nanocomposites was found to be the function of the dendrimer structure and surface groups as well as the formation mechanism and the chemistry involved. Three different types of single nanocomposite architectures have been identified, such as internal (‘I’), external (‘E’) and mixed (‘M’) type nanocomposites. Both the organic and inorganic phase could form nanosized pseudo-continuous phases while the other components are dispersed at the molecular or atomic level either in the interior or on the surface of the template/container. Single units of these nanocomposites may be used as building blocks in the synthesis of nanostructured materials. Peer Reviewed http://deepblue.lib.umich.edu/bitstream/2027.42/43294/1/11051_2004_Article_211595.pdf
We discuss a nanoengineering approach for supramolecular chemistry and self assembly. The collective properties and biofunctionalities of molecular ensembles depend not only on individual molecular building blocks but also on organization at the molecular or nanoscopic level. Complementary to "bottom-up" approaches, which construct supramolecular ensembles by the design and synthesis of functionalized small molecular units or large molecular motifs, nanofabrication explores whether individual units, such as small molecular ligands, or large molecules, such as proteins, can be positioned with nanometer precision. The separation and local environment can be engineered to control subsequent intermolecular interactions. Feature sizes as small as 2 x 4 nm(2) (32 alkanethiol molecules) are produced. Proteins may be aligned along a 10-nm-wide line or within two-dimensional islands of desired geometry. These high-resolution engineering and imaging studies provide new and molecular-level insight into supramolecular chemistry and self-assembly processes in bioscience that are otherwise unobtainable, e.g., the influence of size, separation, orientation, and local environment of reaction sites. This nanofabrication methodology also offers a new strategy in construction of two- and three-dimensional supramolecular structures for cell, virus, and bacterial adhesion, as well as biomaterial and biodevice engineering.
Traditional methods for fabricating nanoscale arrays are usually based on lithographic techniques. Alternative new approaches rely on the use of nanoscale templates made of synthetic or biological materials. Some proteins, for example, have been used to form ordered two-dimensional arrays. Here, we fabricated nanoscale ordered arrays of metal and semiconductor quantum dots by binding preformed nanoparticles onto crystalline protein templates made from genetically engineered hollow double-ring structures called chaperonins. Using structural information as a guide, a thermostable recombinant chaperonin subunit was modified to assemble into chaperonins with either 3 nm or 9 nm apical pores surrounded by chemically reactive thiols. These engineered chaperonins were crystallized into two-dimensional templates up to 20 microm in diameter. The periodic solvent-exposed thiols within these crystalline templates were used to size-selectively bind and organize either gold (1.4, 5 or 10nm) or CdSe-ZnS semiconductor (4.5 nm) quantum dots into arrays. The order within the arrays was defined by the lattice of the underlying protein crystal. By combining the self-assembling properties of chaperonins with mutations guided by structural modelling, we demonstrate that quantum dots can be manipulated using modified chaperonins and organized into arrays for use in next-generation electronic and photonic devices.
Proteins, through their unique and specific interactions with other macromolecules and inorganics, control structures and functions of all biological hard and soft tissues in organisms. Molecular biomimetics is an emerging field in which hybrid technologies are developed by using the tools of molecular biology and nanotechnology. Taking lessons from biology, polypeptides can now be genetically engineered to specifically bind to selected inorganic compounds for applications in nano- and biotechnology. This review discusses combinatorial biological protocols, that is, bacterial cell surface and phage-display technologies, in the selection of short sequences that have affinity to (noble) metals, semiconducting oxides and other technological compounds. These genetically engineered proteins for inorganics (GEPIs) can be used in the assembly of functional nanostructures. Based on the three fundamental principles of molecular recognition, self-assembly and DNA manipulation, we highlight successful uses of GEPI in nanotechnology.
The combination of their electronic properties and dimensions makes carbon nanotubes ideal building blocks for molecular electronics.
However, the advancement of carbon nanotube–based electronics requires assembly strategies that allow their precise localization
and interconnection. Using a scheme based on recognition between molecular building blocks, we report the realization of a
self-assembled carbon nanotube field-effect transistor operating at room temperature. A DNA scaffold molecule provides the
address for precise localization of a semiconducting single-wall carbon nanotube as well as the template for the extended
metallic wires contacting it.
With recent interest in seeking new biologically inspired device-fabrication methods in nanotechnology, a new biological approach was examined to fabricate Cu nanotubes by using sequenced histidine-rich peptide nanotubes as templates. The sequenced histidine-rich peptide molecules were assembled as nanotubes, and the biological recognition of the specific sequence toward Cu lead to efficient Cu coating on the nanotubes. Cu nanocrystals were uniformly coated on the histidine-incorporated nanotubes with high packing density. In addition, the diameter of Cu nanocrystal was controlled between 10 and 30 nm on the nanotube by controlling the conformation of histidine-rich peptide by means of pH changes. Those nanotubes showed significant change in electronic structure by varying the nanocrystal diameter; therefore, this system may be developed to a conductivity-tunable building block for microelectronics and biological sensors. This simple biomineralization method can be applied to fabricate various metallic and semiconductor nanotubes with peptides whose sequences are known to mineralize specific ions.
Hollow tubular structures of molecular dimensions perform diverse biological functions in nature. Examples include scaffolding and packaging roles played by cytoskeletal microtubules and viral coat proteins, respectively, as well as the chemical transport and screening activities of membrane channels. In the preparation of such tubular assemblies, biological systems make extensive use of self-assembling and self-organizing strategies. Owing to numerous potential applications in areas such as chemistry, biology, and materials science considerable effort has recently been devoted to preparation of artificial nanotubular structures. This article reviews design principles and the preparation of synthetic organic nanotubes, with special emphasis on noncovalent processes such as self-assembly and self-organization.
Flat silver nanocrystals have been synthesized by using a soft chemical procedure that involves mixing two reverse micellar solutions. The resulting “nanodisks” display highly anisotropic optical properties attributed to their shape anisotropy. A dark-field TEM image of such a nanodisk, illustrating its single crystal nature, is shown in the Figure.
The assembled structure of the heptane bolaamphiphile, bis(N-alpha-amido-glycylglycine)-1,7-heptane dicarboxylate, displays a sensitivity to the acidity of a solution. At pH 4, the heptane bolaamlihiphile grows to a crystalline tubule in two weeks. At pH 8, a helical ribbon structure is formed in one week. The degree of carboxylic acid protonation was used to control the final assembled structures since the structures are determined by the strengths of the amide-amide and carboxylic acid dimer hydrogen bonds. Direct structural transformation between tubules and helical ribbons was also confirmed as a function of pH using optical microscopy and Raman microscopy. Conversion from the helical ribbons to the tubules occurs within one day, while the reverse conversion, from the tubules to the helical ribbons, is ten times slower.
The synthesis and characterization of well-dispersed, CoFe2O4 nanoparticles within a polymer matrix at room temperature are reported. Comparable inorganic synthetic methods require heating at high temperatures in order to produce this particular mixed-metal oxide composition. Our modification of prior reported templating schemes using block copolymers consists of introducing a mixture of metal salts to a polymer solution before any microphase separation of the block copolymer constituents can occur, thus allowing fast diffusion of metals to the functional polymer backbone. The diblock copolymer matrix was synthesized using ring-opening metathesis polymerization of norbornene derivatives. The self-assembly of the mixed-metal oxide within the polymer template was achieved at room temperature by introducing a mixture of FeCl3 and CoCl2 into one of the functional polymer blocks and by subsequent processing of the copolymer by wet chemical methods to substitute the chlorine atoms with oxygen. CoFe2O4 nanoparticles were thus formed within the spherical microphase-separated morphology of the diblock copolymer, which serves as the templating medium. Transmission electron microscopy, Fourier transform infrared spectroscopy, and wide-angle X-ray diffraction were used to characterize the nanocomposite morphology, oxide chemical composition, and process of oxide formation.
We developed a novel method to immobilize proteins at a specific location on nanotubes. In this report, avidin was immobilized only at the ends of peptide nanotubes using Au nanocrystals as protective masks on the sidewalls of nanotubes. While the Au nanocrystal-masked nanotubes adsorbed avidin on their entire surfaces, the chemical etching of the Au nanocrystal masks removed avidin molecules from the sidewalls, but avidin at the nanotube ends remained bound. The chemical etching process did not denature avidin and the nanotube ends could recognize and immobilize onto the complimentary biotin SAMs.
Avidin-coated peptide tubules, protein tubules, were anchored onto biotin-incorporated self-assembled monolayers (SAMs) on Au substrates and assembled as bridges between the SAMs. The patterned biotin-SAM/Au substrates were placed in a citric acid solution (pH 6) with the protein tubules. After 12 h, the avidin tubules were immobilized on the biotin-SAMs and some of the tubules bridged the patterned biotin-SAMs. No avidin tubules were found to attach onto the glass region between the biotin-SAM/Au substrates. This result shows that the protein tubules have potential to serve as connecting wires for microelectronics.
Palladium nanoparticles (2−3 nm in diameter) have been prepared within covalently functionalized poly(propylene imine) (PPI) dendrimers, and the resulting composite materials are shown to be effective for Heck coupling reactions. Two novel concepts are demonstrated in this report. The first concept involves the incorporation of Pd0 nanoparticles into PPI dendrimers covalently functionalized with perfluorinated polyether chains on their periphery. The second concept involves the first example of a carbon−carbon coupling reaction catalyzed by a dendrimer-templated nanomaterial, specifically, the catalytic heterocoupling between nonactivated aryl halides and n-butylacrylate mediated by the dendrimer-encapsulated catalysts. These reactions were carried out in a homogeneous fluorous/organic reaction phase at elevated temperature, and the catalyst was recovered by cooling to room temperature and concomitant phase separation. The catalyst was found to be catalytically active at a reaction temperature of only 90 °C in the absence of toxic phosphines, and it was 100% selective for the production of n-butyl-trans-formylcinnamate with unoptimized isolated yields up to 70%. The recovered catalysts retained a significant fraction of the original activity, comparable to coordination complex catalysts that use a similar catalyst recovery system.
Methacryloyl end-functionalized block copolymers consisting of styrene and vinyl-2-pyridine were polymerized to poly(block co-macromonomer)s with a much higher main chain than side chain degree of polymerization. Like homo-polymacromonomers these molecules exhibit the structure of cylindrical brushes. Since the vinylpyridine block is coupled to the polymerizable group, the resulting cylindrical macromolecules exhibit a core of vinylpyridine and a shell of polystyrene, thus forming an amphipolar core−shell cylindrical macromolecule. The core−shell character of the molecules was demonstrated by HRTEM utilizing selective positive staining for the core and for the core and the shell. The core of the cylindrical brushes was loaded with HAuCl4 in toluene or methylene chloride followed by reduction of the noble metal salt by the electron beam, by UV light, or by chemical reducing agents. Depending on the amount of complexed noble metal ions and the reduction conditions, either a linear array of noble metal cluster or a continuous nanowire is formed most probably within the core of the cylindrical brushes. The resulting metal nanowires are much longer than the individual core−shell macromolecules which is caused by a yet unexplained specific end-to-end aggregation of the cylindrical polymers upon loading with HAuCl4.
A new family of oligopeptide-based bolaamphiphiles, glycylglycine- (1a−h), glycylglycylglycine- (2a−b), sarcosylsarcosine- (3), l-prolyl-l-proline- (4), glycylsarcosylsarcosine- (5), and glycyl-l-prolyl-l-proline (6)-based bolaamphiphiles with a dicarboxylic headgroup at each end, has been synthesized. The oligopeptide fragments were linked via amide bond to a long-chain α,ω-dicarboxylic acid as a hydrocarbon spacer. Self-assembling properties of these bolaamphiphiles in water have been studied by light and cryogenic temperature transmission electron microscopy, infrared spectroscopy, and pH titration. Only sodium or potassium salts (acid soap) of the bolaamphiphiles 1a, 1c, 1e, 2a, and 2b produced well-defined microtubes of 1−3-μm diameter with closed ends. All the tubes encapsulated a number of vesicular assemblies inside the aqueous compartment. The tube formation strongly depends on the connecting alkylene chain length, the alkylene even−odd carbon numbers, and constituent amino acid residues. Vectorial formation of acid−anion dimers and loose interpeptide hydrogen-bond networks are responsible for the microtube self-assembly. The atomic force microscopic observation of the microtube made of 1e revealed a distorted hexagonal arrangement of the headgroups on the surface. A self-assembling model and the tube formation mechanism are also discussed from the viewpoint of proton-triggered self-assembly.
Organized multilayers of nanoparticles (9-, 20-, and 45-nm-diameter silica or 12-nm magnetite) and glucose oxidase (GOx) were assembled in alternation with oppositely charged polyelectrolytes on 420-nm latex particles. Stepwise growth of the multilayer films on latex was confirmed by microelectrophoresis and transmission electron microscopy. The inclusion of silica layers on latex yields a higher surface area, resulting in greater GOx adsorption and thereby increasing the catalytic activity of the bioreactor. The bioactivity was proportional to the core surface area and also to the number of GOx layers in the shells. Also, the presence of magnetic nanoparticles allows self-stirring of the nanoreactors with a rotating magnetic field and enhances its productivity. The ensemble of GOx and fluorescent dyes in the shells demonstrated the correlation between Ru-bpy fluorescence and glucose concentration in solution.
The size of in situ prepared silver nanoparticles and the overall metal concentration within poly(acrylic acid) (PAA) and poly(allylamine hydrochloride) (PAH) multilayer films are systematically controlled through multilayer processing conditions. Carboxylic acid groups in the PAH/PAA-based multilayers bind silver cations by ion exchange with the acid protons. Subsequent reduction forms metallic nanoparticles. Because PAA has a pH-dependent degree of ionization, the multilayer film can be fabricated with different concentrations of free acid groups that are available to bind silver cations depending on the multilayer assembly pH. We show that nanoparticle size and silver concentration, examined through a combination of UV−visible spectroscopy, transmission electron microscopy, and elemental analysis, can be controllably increased by reducing the assembly pH of PAH/PAA-based multilayers. Nanoparticles with diameters of 2 to 4 nm at volume fractions of 4 to 8% are obtained for multilayers assembled from PAA and PAH solution pHs of 4.5 to 2.5. Furthermore, since the metal-binding carboxylic acid groups are reprotonated upon nanoparticle formation, the synthesis methodology can be repeatedly cycled to incorporate more silver cations. Up to five cycles of silver cation exchange and reduction have been accomplished to produce nanoparticles with average diameters up to 9 nm at a volume fraction of 24%.
This paper describes the first method for making nanodisks having similar aspect ratios and differing by their size. Flat, single-crystal silver nanodisks in equilibrium with spheres are produced using colloidal solutions. The nanodisk size is tuned by the relative amount of reducing agent involved in the synthesis whereas their aspect ratios remain the same order of magnitude. The 3D nanodisk shape is determined by transmission electronic microscopy using the weak-beam dark-field technique. These nanodisks characterized by such anisotropic shapes exhibit several plasmon resonance modes observed in the UV−visible range.
Stratified amide-containing self-assembled monolayers (SAMs) provide opportunities for investigating the fundamental dependence of supramolecular structure upon molecular constitution. We report a series of amide-containing alkanethiol SAMs (Cn-1AT/Au, n = 9, 11−16, 18) in which the hydrophobic overlayer thickness is systematically varied and the thickness of the polar region is held constant. The results from X-ray photoelectron spectroscopy, contact angle goniometry, reflective IR spectroscopy, and electrochemical measurements provide a consistent structural picture of the series. The amide underlayers in all the SAMs are well-ordered and extensively hydrogen bonded. However, the alkyl chains are disordered below n = 15. Comparison of the assembly structures shows that the chain length threshold for alkyl ordering is several methylenes higher than in n-alkanethiol SAMs. This indicates that alkyl chains adjacent to an amide underlayer are destabilized as compared to n-alkanethiols and that the amide underlayer destructively interferes with alkyl close packing as compared to the Au(111)−sulfur template. However, the amide regions of the SAMs are all well-ordered, showing that the amide sublayer acts as a “template” that is independent of alkyl chain length. The amide region dominates over gold−sulfur epitaxy in establishing the structure of these assemblies, and the amide−alkyl boundary provides an example of a “rigid−elastic” buried organic interface. Implications of these studies for molecular control of bulk properties, lipid-linked protein structure and function, buried organic interfaces in other systems, rationally designed ordered multilayers, and hybrid supramolecular systems are discussed.
The synthesis of silver and gold metal nanospherical particles stabilized by the fourth-generation poly(amido amine) (G4 PAMAM) dendrimer is reported. The reduction of silver nitrate and sodium tetrachloroaurate in the presence of the PAMAM dendrimer having terminal amine groups results in the formation of stable, water-soluble nanoparticles. The formation and size of the particles have been determined from the UV−vis plasmon absorption band and transmission electron microscopic (TEM) analyses. The average particle sizes are (6.2 ± 1.7)−(12.2 ± 2.9) nm for silver and are (3.2 ± 0.7)−(7.3 ± 1.5) nm for gold, depending on the metal ion-to-dendrimer terminal amine ratio (M:D) used. Thus, dendrimer-protected silver particles are substantially larger than the gold particles synthesized in similar systems. Nanoparticles prepared at 0.25:1 and lower M:D ratios are stable for a long period of time. A TEM study of the morphology also shows a short-ranged hexagonal arrangement of particles in a monolayer onto the carbon-coated copper TEM grid. Detailed particle size analysis studies by TEM support the possibility that the terminal amino groups of the dendrimers take part in the stabilization of the nanoparticles. The evidence from X-ray photoelectron spectroscopic and Fourier transform infrared absorption spectroscopic investigations confirms the valence state of the gold and the encapsulation by the dendrimer.
Neutralization of iron salts in aqueous solutions of κ-carrageenan and cellulose sulfate results in iron oxyhydroxide–polysaccharide
hybrid colloids with unusual pH stability up to pH 13. It is shown that both polysaccharides form a tight polymer layer surrounding
the inorganic particles, which in the case of κ-carrageenan is cross-linked by helical domains forming a self-assembled nanoreactor.
The stabilized iron oxyhydroxide particles can undergo further reactions, for example, it is possible by a chemical reaction
to produce stabilized magnetite particles. Repetition of the loading/neutralization steps in the reaction results in hybrids
with iron contents much higher than the stoichiometric balance of iron and functional groups of the polymer (greater than
100% Fe/SO4
−). This combination of high iron content with a natural polysaccharide stabilizer makes these colloids interesting for a number
of applications, for example, for nutritional purposes or as contrasting agents for tomography.
Nature has provided us with a range of reactive nanoscale platforms, in the form of protein cage architectures such as viral capsids and the cages of ferritin-like proteins. Protein cage architectures have clearly demarcated exterior, interior, and interface surfaces consisting of precisely located chemical functionalities. In the present work, we demonstrate that the small heat shock protein (MjHsp) cage from Methanococcus jannaschii is a new and versatile nanoscale platform whose exterior and interior surfaces are amenable to both genetic and chemical modification. Wild type and genetic mutants of the Hsp cage are shown to react with activated fluorescein molecules in a site specific manner. In addition, the 12 nm Hsp cage serves as a size constrained reaction vessel for the oxidative mineralization of iron, resulting in the formation of monodispersed 9 nm iron oxide nanoparticles. These results demonstrate the utility of the Hsp cage to serve as a nanoscale platform for the synthesis of both soft (organic) and hard (inorganic) materials.
We have used the pH-induced self-assembly of a peptide-amphiphile to make a nanostructured fibrous scaffold reminiscent of
extracellular matrix. The design of this peptide-amphiphile allows the nanofibers to be reversibly cross-linked to enhance
or decrease their structural integrity. After cross-linking, the fibers are able to direct mineralization of hydroxyapatite
to form a composite material in which the crystallographic c axes of hydroxyapatite are aligned with the long axes of the fibers. This alignment is the same as that observed between
collagen fibrils and hydroxyapatite crystals in bone.
Weakly ferromagnetic cobalt nanoparticles can assemble spontaneously into nanosized "bracelets" when dispersed in organic solvents containing resorcinarenes as surfactants. Bracelet self-assembly occurs in solution and is directed by magnetic dipolar interactions, whereas nanoparticle rings with larger diameters are produced by evaporation-driven flow on wetted surfaces.
Several self-assembling peptide and protein systems that form nanotubes, helical ribbons and fibrous scaffolds have recently emerged as biological materials. Peptides and proteins have also been selected to bind metals, semiconductors and ions, inspiring the design of new materials for a wide range of applications in nano-biotechnology.
In the past decade, colloidal solutions have been assumed to be very efficient templates for controlling particle size and shape. A large number of groups have used reverse micelles to control the size of spherical nanoparticles. This makes it possible to determine the various parameters involved in such processes, and demonstrates that nanoparticles can be considered to be efficient nanoreactors. However, some discrepancies arise. There are few reports concerning the control of particle shape, and it is still rather difficult to determine the key parameters, such as the adsorption of salts and other molecules, and the synthesis procedure. Here, we discuss these controls of the size and shape of inorganic nanomaterials.
Dependent on the relative particle core size, two distinct types of particle topologies in block copolymer/nanocrystal blends have been identified, that is, the localization of particles along the intermaterial dividing surface or at the center of the respective polymer domain. In ternary systems consisting of block copolymer and two different-sized nanocrystal species, the distinct morphological types are conserved, resulting in autonomous size-selective separation and organization of the respective nanocrystals within alternating arrays and sheets.
A new biological approach to fabricate Au nanowires was examined by using sequenced peptide nanotubes as templates. The sequenced histidine-rich peptide molecules were assembled on nanotubes, and the biological recognition of the sequenced peptide selectively trapped Au ions for the nucleation of Au nanocrystals. After Au ions were reduced, highly monodisperse Au nanocrystals were grown on nanotubes. The conformations and the charge distributions of the histidine-rich peptide, determined by pH and Au ion concentration in the growth solution, control the size and the packing density of Au nanocrystals. The diameter of Au nanocrystal was limited by the spacing between the neighboring histidine-rich peptides on nanotubes. A series of TEM images of Au nanocrystals on nanotubes in the shorter Au ion incubation time periods reveal that Au nanocrystals grow inside the nanotubes first and then cover the outer surfaces of nanotubes. Therefore, multiple materials will be coated inside and outside the nanotubes respectively by controlling doping ion concentrations and their deposition sequences. It should be noted that metallic nanocrystals in diameter around 6 nm are in the size domain to observe a significant conductivity change by changing the packing density, and therefore this system may be developed into a conductivity-tunable building block.
Dip-pen nanolithography (DPN) is becoming a popular technique to "write" molecules on a surface by using the tip of an atomic force microscope (AFM) coated with the desired molecular "ink". In this work, we demonstrate that poly-histidine-tagged peptides and proteins, and free-base porphyrins coated on AFM probes, can be chelated to ionized regions on a metallic nickel surface by applying an electric potential to the AFM tip in the DPN process. DPN has been accomplished in the Tapping Mode of AFM, which creates many possible applications of positioning and subsequently imaging biomolecules, especially on soft surfaces.
Azobenzene-functionalized nanotubes recognized and attached onto well-defined complementary regions of thiolated alpha-CD SAM/Au substrates via host-guest molecular recognition. The binding between the azobenzene nanotubes and the alpha-CD SAM/Au substrates was controlled by UV irradiation. The light-induced attachment-detachment of the azobenzene nanotubes on the alpha-CD SAMs was reversible. Some of the nanotubes were capable of interconnecting two Au substrates. This smart building block may be applied to build photoactive nanometer-sized mechanical switches in electronics.
The disassembly of dendritic structures was realized by a cascade cleavage reaction triggered by an initially stimulated group in the dendrimer periphery. A depolymerizable backbone was engineered into prototypical dendritic structures. Evidence for the completion of the disassembly process is provided by the absorbance peak of the p-nitrophenoxide ion that was intentionally installed at the focal point of the dendrons. Observation of the UV spectra during the disassembly process supports a stepwise cascade cleavage proceeding from the periphery into the core.
A small de novo designed peptide (MAX3) is described that exhibits complete thermoreversible self-assembly into a hydrogel network. Importantly, a prerequisite to hydrogelation is that the peptide must first fold into a conformation conducive to self-assembly. At ambient temperature, MAX3 is unfolded, resulting in a low viscosity aqueous solution. On increasing the temperature, the peptide undergoes a unimolecular folding event, affording an amphiphilic beta-hairpin that consequently self-assembles into a hydrogel network. Increasing the temperature serves to dehydrate the nonpolar residues of the unfolded peptide and trigger folding via hydrophobic collapse. Cooling the resultant hydrogel results in beta-hairpin unfolding and consequent complete dissolution of the hydrogel. The temperature at which folding and consequent self-assembly into a rigid hydrogel occur can be tuned by altering the hydrophobicity of the peptides.
The versatility of the branched macromolecules known as dendrimers is being exploited in various ways - explosively so, in the context of their application as potential drug-delivery systems.
The new biological approach was examined to fabricate shape-controlled Ag nanocrystals grown directly on surfaces, inspired by nature that various shapes of nanocrystals are produced accurately and reproducibly in biological systems. Here we demonstrate the direct growth of hexagon-shaped Ag nanocrystals on sequenced peptide-coated nanotubes via biological recognition. When the peptide, Asn-Pro-Ser-Ser-Leu-Phe-Arg-Tyr-Leu-Pro-Ser-Asp, recognizing and effecting the Ag nanocrystal growth on the (111) face, was sequenced and incorporated onto template nanotube surfaces, the biomineralization of Ag ions on the nanotubes led the isotropic hexagon-shaped Ag nanocrystal coating under pH control of the growth solution. Multiple Ag nanocrystal shapes were observed when the peptide mineralized Ag ions without the template nanotubes, and therefore the template nanotube has a significant influence on regulating the majority of Ag nanocrystals into the hexagonal shape. This biological approach, using specific peptide sequences on surfaces to control nanocrystal shapes, may be developed as a simple and economical method to produce building blocks with desired physical properties for new generation of electronics, sensors, and optical devices.
- Bong D. T.