Sequential self-assembly for construction of Pt(II)-bridged [3]rotaxanes on gold nanoparticles

An effective self-assembly route for construction of Pt(II)-bridged [3]rotaxane functionalized gold nanoparticles was developed through a stepwise introduction of Pt(II) coordination and gold-thiol binding in turn. The sequential self-assembly process can be quantitatively controlled and directly monitored by the naked eye.     

A new Co(II)-metalloviologen-based electrochromic material integrated in thin multilayer films

A metallosupramolecular coordination polyelectrolyte prepared by the reaction of cobalt(II) with a novel bisterpyridine ligand has been assembled as the active component in electrochromic films by sequential deposition using electrostatic layer-by-layer self-assembly.     

Template-induced and molecular recognition directed hierarchical generation of supramolecular assemblies from molecular strands

The linear oligo-isophthalamide strand 1 undergoes a conformational reorganization upon binding of a cyanuric acid template as effector to afford a helical disklike object possessing radially disposed alkyl residues. Solvophobic and stacking interactions, in turn, drive a "second level" self-assembly of the templated structure, the stacking of the helical disks, to yield fibers as revealed by electron microscopy. These data provide insight into the interplay of the different structural and interactional features of the molecular components towards the formation of supramolecular fibers through sequential hierarchical self-assembly events and suggest design strategies for the effector-controlled generation of related supramolecular assemblies.     

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.     

Switch-peptides: controlling self-assembly of amyloid beta-derived peptides in vitro by consecutive triggering of acyl migrations

The sequential triggering (Soff --> Son) of O, N-acyl migrations (AcM) by chemical and enzymatic methods (Ti) in peptides containing structure-disrupting switch-elements, S (switch-peptides), offers a novel tool for studying in statu nascendi the onset and inhibition of polypeptide folding and self-assembly as a key process in degenerative diseases.     

Surface self-assembly of the cyanuric acid-melamine hydrogen bonded network

A hydrogen-bonded bimolecular network formed between cyanuric acid (CA) and melamine (M), CA x M, has been prepared by a surface-based self-assembly process; the monolayer CA x M network is prepared under ultra-high vacuum conditions either by sequential deposition of CA followed by M, or through simultaneous deposition of the component molecular species.     

聚环氧乙烷-g-聚己内酯两亲性接枝共聚物的合成及药物释放行为

通过环氧丙醇(GL)与环氧乙烷(EO)的阴离子顺序开环聚合制备了水溶性嵌段共聚物PEO-b-PGL, 以PGL嵌段每个重复单元的侧羟基为引发点进一步引发ε-己内酯(CL)的开环聚合, 合成了结构规整的以聚环氧乙烷(PEO)为主链的两亲性接枝共聚物(PEO-b-PGL-g-PCL). 研究了PEO-b-PGL-g-PCL在水相中的自组装行为, 采用稳态荧光探针法测定了胶束的临界胶束浓度(cmc). 以疏水性药物阿霉素(DOX)为模型药物, 研究了两亲性接枝共聚物的化学组成对药物的扩散释放以及降解释放行为的影响.     

Mineralomimetic sodalite- and muscovite-type coordination frameworks. Dynamic crystal-to-crystal interconversion processes sensitive to ion pair recognition

A flexible sodalite-type metal organic framework [Cu(pyrimidine-2-olate)2]n (1R) is obtained in a self-assembly process involving Cu2+ ions and pyrimidine-2-olate ligands. 1R suffers a series of sequential and reversible structural changes upon solid-liquid sorption processes of metal nitrates. The 1C-to-1O transformation occurs only with large cations.     

Hierarchical self-assembly of supramolecular spintronic modules into 1D- and 2D-architectures with emergence of magnetic properties

Hierarchical self-assembly of complex supramolecular architectures allows for the emergence of novel properties at each level of complexity. The reaction of the ligand components A and B with Fe(II) cations generates the [2x2] grid-type functional building modules 1 and 2, presenting spin-transition properties and preorganizing an array of coordination sites that sets the stage for a second assembly step. Indeed, binding of La(III) ions to 1 and of Ag(I) ions to 2 leads to a 1D columnar superstructure 3 and to a wall-like 2D layer 4, respectively, with concomitant modulation of the magnetic properties of 1 and 2. Thus, to each of the two levels of structural complexity generated by the two sequential self-assembly steps corresponds the emergence of novel functional features.     

Interfacial self-transportation via controlled wettability transition for directed self-assembly

Wettability transition is a significant responsive mechanism which is widely applied to construct smart materials and systems. The broad-spectrum responsiveness of the wettability transition makes it a promising way to expand innovative applications. Here, we develop a track-guided self-transportation system mediated by sequential wettability transition accompanied with capillary transportation. Alkaline fuel is loaded into polydimethylsiloxane (PDMS) cuboid to trigger the wettability transition of distributed superhydrophobic tracks laid in shallow water. After the wettability transition, the induced capillary force can propel the repetitive track-to-track transportation of PDMS. Importantly, the spacing between adjacent tracks is rationally designed based on multiple factors including threshold of wettability transition, diffusion kinetics and capillary interaction. Furthermore, the track-guided transportation system is applied to realize directed self-assembly of multiple PDMS building blocks for designated configuration, which increases the complexity and intelligence of self-assembly systems.     

Measurement of Ibuprofen Binding to Mixed Monolayers Containing β-Cyclodextrin Active Sites

A molecular imprinting method involving a three-step sequential self-assembly procedure was applied to prepare gold electrodes responsive towards ibuprofen. The electrode modified with the cyclodextrin derivative binds ferrocene to form an electroactive complex with the ferrocene oxidation current decreasing in the presence of ibuprofen in the solution. The competition of ferrocene and ibuprofen for the cyclodextrin cavities in the monolayer provided a means for the determination of the binding constants of ibuprofen with two derivatives of lipoylamide β-cyclodextrin of different hydrophobicity.     

Self-Assembled Bilayers on Indium-Tin Oxide (SAB-ITO) Electrodes: A Design for Chromophore-Catalyst Photoanodes

A novel approach for creating assemblies on metal oxide surfaces via the addition of a catalyst overlayer on a chomophore monolayer derivatized surface is described. It is based on the sequential self-assembly of a chromophore, [Ru(bpy)(4,4'-(PO(3)H(2)bpy)(2))](2+), and oxidation catalyst, [Ru(bpy)(P(2)Mebim(2)py)OH(2)](2+), pair, resulting in a spatially separated chromophore-catalyst assembly.     

Kinetic stages of single-component colloidal crystallization

To harness the full potential of colloidal self-assembly, the dynamics of the transition between colloids in suspension to a colloidal crystalline film should be better understood. In this report, the structural changes during the self-assembly process in a vertical configuration for colloids in the size range 200-400 nm are monitored in situ, using the transmission spectrum of the colloidal assembly treated as an emergent photonic crystal. It is found that there are several sequential stages of colloidal ordering: in suspension, with a larger lattice parameter than the solid state, in a close-packed wet state with solvent in the interstices, and, finally, in a close-packed dry state with air in the interstices. Assuming that these stages lead continuously from one to another, we can interpret colloidal crystallization as being initiated by interparticle forces in suspension first, followed by capillary forces. This result has implications for identifying the optimum conditions to obtain high-quality nanostructures of submicrometer-sized colloidal particles.     

Design and synthesis of asymmetric acyclic phospholipid bolaamphiphiles

[structure: see text] A synthetic route was devised for the generation of asymmetric lipid bolaamphiphiles through the sequential esterification of an alkyldioic acid, bearing distinct terminal protecting groups, with propanylamine and lyso-phosphatidylcholine headgroups. Bolaamphiphile self-assembly was investigated in solvent mixes of varying polarity by nuclear magnetic resonance (NMR) and Fourier transform-infrared (FT-IR) spectroscopy, as well as in water by cryo-high-resolution scanning electron microscopy (cryo-HRSEM). We anticipate that asymmetric lipid bolaamphiphiles will provide facile building blocks for engineering a variety of unique membrane-mimetic structures.     

Orientation modulation of a synthetic polypeptide in self-assembled monolayers: a TOF-SIMS study

Structure and orientation of molecules are key properties of functionalized surfaces. Using time-of-flight secondary ion mass spectrometry (TOF-SIMS), here we investigate how to modulate these parameters upon the immobilization process varying the conditions of self-assembly. The molecule of interest, a template-assembled synthetic protein (TASP), consists of a central peptide ring with orthogonally arranged residues. Thioalkane chains allow the directed self-assembly of the molecule on a gold surface; four serine residues on the opposite side of the ring can be used as anchoring sites for various functional sensing molecules. The TASP conformation and its orientation in self-assembled monolayers (SAMs) play a central role for the accessibility of these serine residues. To study the influence of the self-assembly conditions, two series of samples were prepared. Pure TASP monolayers of different surface densities are compared to mixed TASP/alkanethiol monolayers prepared by sequential adsorption varying sequence and particular incubation times as well as by coadsorption modifying incubation times and TASP/alkanethiol mass ratios. Switching the TASP orientation from a state where the molecules are lying flat on the surface to an upright orientation turned out to be possible by inserting the TASP into a preformed alkanethiol monolayer of an appropriate surface density. This study demonstrates that TOF-SIMS is an excellent tool not only to investigate the surface composition, but also the molecular structure of functionalized surfaces.     

High fidelity sorting of remarkably similar components via metal-mediated assembly

Subtle differences in ligand coordination angle and rigidity lead to high fidelity sorting between individual components displaying identical coordination motifs upon metal-mediated self-assembly. Narcissistic self-sorting can be achieved between highly similar ligands that vary minimally in rigidity and internal coordination angle upon combination with Fe(ii) ions and 2-formylpyridine. Selective, sequential cage formation can be precisely controlled in a single flask from a mix of three different core ligands (and 33 total components) differing only in the hybridization of one group that is uninvolved in the metal coordination process.     

3D flower-like Y(2)O(3):Eu(3+) nanostructures: template-free synthesis and its luminescence properties

In this work, a facile route using simple hydrothermal reaction and sequential calcinations to synthesize 3-dimensional flower-like Y(2)O(3):Eu(3+) nanoarchitectures without employing templates or matrix for self-assembly is presented. The flower-like nanostructures are composed of nanosheets with thickness of about 30 nm, which is verified by the field-emission electron microscopy (FESEM). Influencing factors such as the dosage of reactants, the solvent, and pH are systematically investigated. The time-dependent experiments indicate a self-assembly mechanism. This method is also applicable in the preparation of other lanthanide oxides. The PL spectra of the as-synthesized Y(2)O(3):Eu(3+) are systematically studied. Both the Eu(3+) concentration and the calcinations temperature have great effect on the luminescence intensity of (5)D(0)-(7)F(2) transition. The decay curve of the (5)D(0) transition shows that the lifetime of the as-obtained Y(2)O(3):Eu(3+) is about 2.4 ms.     

Temperature Control of Sequential Nucleation–Growth Mechanisms in Hierarchical Supramolecular Polymers

Upon cooling in solution, chiral triarylamine tris-amide unimers produce organogels by stacking into helical supramolecular polymers, which subsequently bundle into larger fibers. Interestingly, circular dichroism, vibrational circular dichroism, and AFM imaging of the chiral self-assemblies revealed that monocolumnar P-helical fibrils formed upon fast cooling, whereas bundled M-superhelical fibers formed upon slow cooling. The mechanistic study of this structural bifurcation reveals the presence of a strong memory effect, reminiscent of a complex stepwise combination of primary and secondary nucleation-growth processes. These results highlight the instrumental role of sequential self-assembly processes to control supramolecular architectures of multiple hierarchical order.     

2D supramolecular assemblies of benzene-1,3,5-triyl-tribenzoic acid: temperature-induced phase transformations and hierarchical organization with macrocyclic molecules

Two-dimensional supramolecular honeycomb networks with cavities of an internal diameter of 2.95 nm were formed by the self-assembly of 4,4',4' '-benzene-1,3,5-triyl-tribenzoic acid (BTA) on a Ag(111) surface at room temperature. Annealing to higher temperatures resulted in two sequential phase transformations into closer-packed supramolecular arrangements. The phase transformations are associated with stepwise deprotonation of the carboxylic acid groups. The voids of the honeycomb network of BTA have a suitable size for the construction of hierarchical structures with guest molecules. Single molecules of the macrocyclic compound mt-33 were successfully confined inside 2D nanocavities of the honeycomb networks and released when the phase was transformed to the close-packed structure.