Surface-induced self-assembly of dipeptides onto nanotextured surfaces

There is an increasing interest for the utilization of biomolecules for fabricating novel nanostructures due to their ability for specific molecular recognition, biocompatibility, and ease of availability. Among these molecules, diphenylalanine (Phe-Phe) dipeptide is considered as one of the simplest molecules that can generate a family of self-assembly based nanostructures. The properties of the substrate surface, on which the self-assembly process of these peptides occurs, play a critical role. Herein, we demonstrated the influence of surface texture and functionality on the self-assembly of Phe-Phe dipeptides using smooth silicon surfaces, anodized aluminum oxide (AAO) membranes, and poly(chloro-p-xylylene) (PPX) films having columnar and helical morphologies. We found that helical PPX films, AAO, and silicon surfaces induce similar self-assembly processes and the surface hydrophobicity has a direct influence for the final dipeptide structure whether being in an aggregated tubular form or creating a thin film that covers the substrate surface. Moreover, the dye staining data indicates that the surface charge properties and hence the mechanism of the self-assembly process are different for tubular structures as opposed to the peptidic film. We believe that our results may contribute to the control of surface-induced self-assembly of peptide molecules and this control can potentially allow the fabrication of novel peptide based materials with desired morphologies and unique functionalities for different technological applications.     

Photonic properties of hybrid colloidal crystals fabricated by a rapid dip-coating process

The enhancement of the capillarity fabrication of well-ordered two-dimensional (2D) and three-dimensional (3D) opal photonic crystal is described herein. The quality enhancement and the reduction of the fabrication time are improved by using core@soft adhesive shell (Silica@PolyButylAcrylate) particles dispersed in an organic solvent with a high boiling point. The hybridization by an elastomeric corona polymer, grafted from the SiO(2) surface, has offered adhesive properties naturally tunable by changing the polymer state from a solvated to a dry one. Such properties involve drastic changes of the self-assembly behavior and qualities. Their use, as elementary building blocks, for colloidal crystal fabrication have required a high withdrawal rate (up to 4000 μm s(-1)), i.e. involving a three order of magnitude reduction in time compared to a classic vertical deposition method (1 to 10 μm s(-1)) and a good control/prediction of the coating thickness can be tuned by varying the withdrawal rate and the particle concentration. In addition, an analysis of the 2D synthetic iridescence of the hybrid photonic crystal was performed under white light, revealing the adhesive shell bridge influence on the dissipation energy of cracks linked to the crystal quality and the photonic properties.     

Preparation of high-quality colloidal mask for nanosphere lithography by a combination of air/water interface self-assembly and solvent vapor annealing

Nanosphere lithography (NSL) has been regarded as an inexpensive, inherently parallel, high-throughput, materials-general approach to the fabrication of nanoparticle arrays. However, the order of the resulting nanoparticle array is essentially dependent on the quality of the colloidal monolayer mask. Furthermore, the lateral feature size of the nanoparticles created using NSL is coupled with the diameter of the colloidal spheres, which makes it inconvenient for studying the size-dependent properties of nanoparticles. In this work, we demonstrate a facile approach to the fabrication of a large-area, transferrable, high-quality latex colloidal mask for nanosphere lithography. The approach is based on a combination of the air/water interface self-assembly method and the solvent-vapor-annealing technique. It enables the fabrication of colloidal masks with a higher crystalline integrity compared to those produced by other strategies. By manipulating the diameter of the colloidal spheres and precisely tuning the solvent-vapor-annealing process, flexible control of the size, shape, and spacing of the interstice in a colloidal mask can be realized, which may facilitate the broad use of NSL in studying the size-, shape-, and period-dependent optical, magnetic, electronic, and catalytic properties of nanomaterials.     

Identification of Skim Milk Electroacidification Fouling: A Microscopic Approach

The self-assembly film fabricated via the layer-by-layer technique was studied by the dynamic contact angle (DCA) method (wilhelmy plate method). The used polyelectrolytes are poly(diallyl-dimethylammonium chloride) (PDDA), poly(etheleneimine) (PEI), diphenylamine-4-diazonium-formaldehyde resin (DR), 2-nitro-N-methyl-4-diazonium-formaldehyde resin (NDR), and poly(sodium-p-styrenesulfonate) (PSS). For the self-assembly systems of PDDA/PSS, PEI/PSS, DR/PSS, and NDR/PSS, their individual contact angle fluctuates regularly with the fabrication of each layer, while the magnitude of different systems' contact angle depends on the participant polycation. The re-organization of components and the adjacent layer interpenetration are presented here to explain this phenomena. We also found that DR or NDR can adsorb itself via the layer-by-layer method to form multilayer film, and the hydrophobic interaction is put forward to effect this process. Moreover, the procedure of washing and drying after adsorption was studied and considered as a prerequisite for the successful fabrication, especially of the same charge carried components. Copyright 2001 Academic Press.     

Synthesis and Self-Assembly of Mixed-Graft Block Copolymers

Mixed-graft block copolymers (mGBCPs) consist of two or more types of polymeric side chains grafted on a linear backbone in a random, alternating, or pseudo-alternating sequence. They can phase-separate with the backbone serving as the interface of the blocks, and the side chains dominate their self-assembly behavior. mGBCPs are an accessible polymer architecture for exploring the idea of encoding polymer properties through the macromolecular architecture, as there are two distinct structural components that can be tuned: the backbone and the side chains. In this Concept article, the current literature on the synthesis of mGBCPs is reviewed, and the advantages and disadvantages of each synthetic method are noted. The self-assembly of mGBCPs is also discussed where possible. Finally, directions for future research on mGBCP synthesis and self-assembly are suggested.     

自组装方法与三维光子晶体制作

光子晶体,特别是三维光子晶体,可能成为信息处理和通信等领域的新型功能材料.光子晶体的制作方法可分为"自上而下"的物理方法和"自下而上"的化学自组装方法.化学自组装方法是制作三维光子晶体最为经济有效的方法.本文在阐述自组装方法的种类、一般过程、优点和不足等内容的基础上,分别分析和总结了带有各种功能缺陷的三维光子晶体的制作,这些缺陷主要包括线缺陷、面缺陷和点缺陷.从研究中可以看出,化学自组装方法通常需要结合其他方法才能实现缺陷的嵌入.近些年,三维光子晶体制作在材料选取、结构设计和方法改进等方面都有一些最新进展,本文对此进行了较为详尽的评述,并对我们课题组的研究进行了总结.最后对光子晶体的研究和制作方向进行了展望.     

Self-assembly of inorganic nanoparticle vesicles and tubules driven by tethered linear block copolymers

Controllable self-assembly of nanoscale building blocks into larger specific structures provides an effective route for the fabrication of new materials with unique optical, electronic, and magnetic properties. The ability of nanoparticles (NPs) to self-assemble like molecules is opening new research frontiers in nanoscience and nanotechnology. We present a new class of amphiphilic "colloidal molecules" (ACMs) composed of inorganic NPs tethered with amphiphilic linear block copolymers (BCPs). Driven by the conformational changes of tethered BCP chains, such ACMs can self-assemble into well-defined vesicular and tubular nanostructures comprising a monolayer shell of hexagonally packed NPs in selective solvents. The morphologies and geometries of these assemblies can be controlled by the size of NPs and molecular weight of BCPs. Our approach also allows us to control the interparticle distance, thus fine-tuning the plasmonic properties of the assemblies of metal NPs. This strategy provides a general means to design new building blocks for assembling novel functional materials and devices.     

Oil-water interfacial self-assembly: a novel strategy for nanofilm and nanodevice fabrication

How to integrate individual nanostructures into macroscopic thin films has become one of the most intriguing fields in nanoscience and nanotechnology due to the unique properties and important applications of these functional films. Since being discovered in 2004, oil-water interfacial self-assembly of nanostructures has become a novel strategy for fabrication of nanofilms. It is a powerful bottom-up approach for film fabrication due to the low cost and high efficiency, and is simple and universal for almost all low-dimensional nanostructures. In this article, we provide a critical review of the state-of-the-art research activities in this burgeoning self-assembly strategy. We first discuss the thermodynamic mechanism of the oil-water interfacial self-assembly, then the self-assembly of various low-dimensional nanostructures including nanoparticles, one-dimensional (1D) nanostructures, two-dimensional (2D) nanostructures at an oil-water interface developed so far to fabricate high-quality nanofilms. Finally, we present some progress on the construction of functional nanofilm-based nanodevices from this novel strategy based on our research. We conclude this review with critical comments on advantages and the experimental challenges, and further propose the future research and development of this self-assembly strategy for nanodevice construction (105 references).     

Multicomponent submicron features of biomolecules created by voltage controlled deposition from a nanopipet

We have used a nanopipet as a nanopen to locally and controllably deposit complex biomolecules, including antibodies and DNA, onto a surface to create multicomponent and functional submicron features. Key advantages of this method are that the biomolecules are always in solution and the applied voltage provides fine control of the delivery down to the single molecule level. Two consecutive cycles of deposition, to produce spatially varying features with different biological properties, were demonstrated with fluorescently labeled antibodies or biotin. This approach combines "top-down" fabrication, using the nanopen for local application, and "bottom-up" fabrication, using molecular recognition for self-assembly at defined positions, and opens up new possibilities in nanotechnology.     

An improved convective self-assembly method for the fabrication of binary colloidal crystals and inverse structures

We report an improved convective self-assembly method for the fabrication of highly ordered, crack-free binary colloidal crystals (BCCs) and the associated inverse structures in large domains at length scales of several centimeters. With this method, BCCs can be fabricated in a non-close packed pattern and binary inverse opal films can be obtained over a centimeter scale. The presence of tetraethyl orthosilicate (TEOS) sol in the self-assembly system was found to play a significant role in the resultant structures. The pseudostop band positions are adjustable via varying the number ratio of small to large polystyrene (PS) spheres. At a given TEOS-to-PS ratio, the binary inverse opal film thickness was controllable by varying the colloidal volume fraction with an upper thickness threshold (>16 layers).     

Radiation-induced synthesis and cryo-TEM characterization of silver nanoshells on linoleate spherical micelles

We combine the self-assembly properties of amphiphilic molecules with the radiolysis method to produce specific sizes and shapes of metallic nano-objects. Radiolysis is used to synthesize core--shell structures consisting of nanometric linoleate spherical micelles as the core and silver as the shell. The validity of the technique is asserted by cryoelectron microscopy, which is an adequate technique for low density contrasts and core--shell structures. The shells are found to be homogeneous with a size of a few nanometers. Images are used to bring forward the hypothesis of the fabrication process.     

Directing the self-assembly of nanocrystals beyond colloidal crystallization

This article gives an overview of recent progress in the self-assembly of nanocrystals. Classic self-assembly of nanocrystals, so-called colloidal crystallization driven by van der Waals interactions, is highlighted first with an emphasis on the recent realization of binary colloidal crystals. Next, new developments in the integration of nanocrystals into clusters based on electrostatic interactions, hydrogen bonding and dipole-dipole interactions are summarized, shedding light on the defined control of the interactions between the nanocrystals. Finally, the fabrication of heterogenous nanocrystals, obtained via either phase selective modification at the water/oil interface or facet-selective crystal growth on non-spherical nanocrystals is discussed. These last materials may provide significant building blocks for mimicking molecular self-assembly.     

Hybrid one-dimensional nanostructures: one-pot preparation of nanoparticle chains via directed self-assembly of in situ synthesized discrete Au nanoparticles

The fabrication of well-defined one-dimensional (1D) arrays is becoming a challenge for the development of the next generation of advanced nanodevices. Herein, a simple concept is proposed for the in situ synthesis and self-assembly of gold nanoparticles (AuNPs) into 1D arrays via a one-step process. The results demonstrated the formation of nanoparticle chains (NPC) with high aspect ratio based on discrete Au nanoparticles stabilized by short thiol ligands. A model was proposed to explain the self-assembly based on the investigation of several parameters such as pH, solvent, temperature, and nature of the ligand on the 1D assembly formation. Hydrogen bonding was identified as a key factor to direct the self-assembly of the hybrid organic-inorganic nanomaterials into the well-defined 1D nanostructures. This simple and cost-effective concept could potentially be extended to the fabrication of a variety of hybrid 1D nanostructures possessing unique physical properties leading to a wide range of applications including catalysis, bionanotechnology, nanoelectronics, and photonics.     

Template-directed self-assembly of 10-microm-sized hexagonal plates

This article presents a strategy for the fabrication of ordered microstructures using concepts of design inspired by molecular self-assembly and template-directed synthesis. The self-assembling components are 4-microm-thick hexagonal metal plates having sides 10 microm in length ("hexagons"), and each template consists of a 4-microm-thick circular metal plate surrounding a central cavity, the perimeter of which is complementary in shape to the external edges of a two-dimensional, close-packed array of hexagons. The hexagons and templates (collectively, "pieces") were fabricated via standard procedures and patterned into hydrophobic and hydrophilic regions using self-assembled monolayers (SAMs). Templated self-assembly occurs in water through capillary interactions between thin films of a nonpolar liquid adhesive coating the hydrophobic faces of the pieces. The hexagons tile the cavities enclosed by the templates, and the boundaries of the cavities determine the sizes and shapes of the assemblies. Curing the adhesive with ultraviolet light furnishes mechanically stable arrays having well-defined morphologies. By allowing control over the structures of the resulting aggregates, this work represents a step toward the development of practical methods for microfabrication based on self-assembly.     

Spatiotemporal dynamics of self-assembled structures in enzymatically induced agonistic and antagonistic conditions

Predicting and designing systems with dynamic self-assembly properties in a spatiotemporal fashion is an important research area across disciplines ranging from understanding the fundamental non-equilibrium features of life to the fabrication of next-generation materials with life-like properties. Herein, we demonstrate a spatiotemporal dynamics pattern in the self-assembly behavior of a surfactant from an unorganized assembly, induced by adenosine triphosphate (ATP) and enzymes responsible for the degradation or conversion of ATP. We report the different behavior of two enzymes, alkaline phosphatase (ALP) and hexokinase (HK), towards adenosine triphosphate (ATP)-driven surfactant assembly, which also results in contrasting spatiotemporal dynamic assembly behavior. Here, ALP acts antagonistically, resulting in transient self-assemblies, whereas HK shows agonistic action with the ability to sustain the assemblies. This dynamic assembly behavior was then used to program the time-dependent emergence of a self-assembled structure in a two-dimensional space by maintaining concentration gradients of the enzymes and surfactant at different locations, demonstrating a new route for obtaining ‘spatial’ organizational adaptability in a self-organized system of interacting components for the incorporation of programmed functionality.

We have shown ATP-driven spatiotemporally distinct self-organization pattern of a surfactant in a two-dimensional space using enzymes, demonstrating a new route for obtaining ‘spatial’ organizational adaptability among interacting components.     

Self-assembly of various guest substrates in natural cellulose substances to functional nanostructured materials

Biological organisms are produced from self-assembly of highly ordered functional units and are inherently complex and hierarchical, possessing macro-to-nanoscale features. It is a facile, low-cost and environmentally benign short-cut to artificial functional materials with unique multilevel structures and morphologies employing biological substances as platform for the self-assembly of various guest substrates. This review summarizes the recent advances in the fabrication of nanostructured materials with designed properties and functionalities by means of self-assembly of different guest substrates (such as metal oxide thin films, small molecules, polymers, biomacromolecules, nanoparticles, carbon nanotubes and colloidal spheres) on the surfaces of cellulose nanofibers of bulk natural cellulose substances. The combination of the specific chemical properties of the guest substrates and the unique physical features of the natural cellulose substances sheds new light on the design and syntheses of new functional nanomaterials.     

On one-dimensional self-assembly of surfactant-coated nanoparticles

Nanometer-sized metal and semiconductor particles possess novel properties. To fully realize their potential, these nanoparticles need to be fabricated into ordered arrays or predesigned structures. A promising nanoparticle fabrication method is coupled surface passivation and self-assembly of surfactant-coated nanoparticles. Due to the empirical procedure and partially satisfactory results, this method still represents a major challenge to date and its refinement can benefit from fundamental understanding. Existing evidences suggest that the self-assembly of surfactant-coated nanoparticles is induced by surfactant-modified interparticle interactions and follows an intrinsic road map such that short one-dimensional (1D) chain arrays of nanoparticles occur first as a stable intermediate before further assembly takes place to form higher dimensional close-packed superlattices. Here we report a study employing fundamental analyses and Brownian dynamics simulations to elucidate the underlying pair interaction potential that drives the nanoparticle self-assembly via 1D arrays. We find that a pair potential which has a longer-ranged repulsion and reflects the effects of surfactant chain interdigitation on the dynamics is effective in producing and stabilizing nanoparticle chain arrays. The resultant potential energy surface is isotropic for dispersed nanoparticles but becomes anisotropic to favor the growth of linear chain arrays when self-assembly starts.     

A nanoengineering approach to regulate the lateral heterogeneity of self-assembled monolayers

Using a scanning probe lithography method known as nanografting in conjunction with knowledge of self-assembly chemistry, regulation of the heterogeneity of self-assembled monolayers (SAMs) is demonstrated. While nanografting in single-component thiols produces areas of SAMs with designed geometry and size, nanofabrication in mixed thiol solution yields segregated domains. The reaction mechanism in nanografting differs significantly from self-assembly in mix-and-grow methods, as proven in systematic studies reported in this article and a companion paper of theoretical calculations of the nanografting process. Knowledge of the reaction pathways enables development of methods for shifting the interplay between the kinetics and thermodynamics in SAM formation, and thus the heterogeneity of mixed SAMs. By varying fabrication parameters, such as shaving speed, and reaction conditions, such as concentration and ratio of the components, the lateral heterogeneity can be adjusted ranging from near molecular mixing to segregated domains of several to tens of nanometers.     

A hierarchical self-assembly route to three-dimensional polymer-quantum dot photonic arrays

We demonstrate a new hierarchical self-assembly strategy for the formation of photonic arrays containing quantum dots (QDs), in which sequential self-assembly steps introduce organization on progressively longer length scales, ranging from the nanoscale to the microscale regimes. The first step in this approach is the self-assembly of diblock copolymers to form block ionomer reverse micelles (SA1); within each micelle core, a single CdS QD is synthesized to yield the hybrid building block BC-QD. Once SA1 is completed, the hydrophobic BD-QD building blocks are blended with amphiphilic block copolymer stabilizing chains in an organic solvent; water addition induces secondary self-assembly (SA2) to form quantum dot compound micelles (QDCMs). Finally, aqueous dispersions of QDCMs are slowly evaporated to induce the formation of three-dimensional (3D) close-packed arrays in a tertiary self-assembly step (SA3). The resulting hierarchical assemblies, consisting of a periodic array of hybrid spheres each containing multiple CdS QDs, exhibit the collective property of a photonic stop band, along with photoluminescence arising from the constituent QDs. A high degree of structural control is possible at each level of organization by judicious selection of experimental variables, allowing various parameters governing the collective optical properties, including QD size, nanoparticle spacing, and mesocale periodicity, to be independently tuned. The resulting control over optical properties via successive self-assembly steps should provide new opportunities for hierarchical materials for QD lasers and all-optical switching.     

胶体刻蚀——纳米结构化表面的构筑与应用

综述了近年来胶体刻蚀领域的研究进展, 分别讨论了基于胶体微粒和胶体晶体为模板的可控沉积与可控刻蚀及在固体平面基质、曲面基质和气液界面等不同基质上构筑结构化表面的方法. 同时还探讨了利用胶体刻蚀方法形成的微纳结构在光、电、磁以及表面润湿和生物学等方面的应用.