The stepwise construction of a novel kind of self-assembled organic/inorganic multilayers based on multivalent supramolecular interactions between guest-functionalized dendrimers and host-modified gold nanoparticles has been developed, yielding supramolecular layer-by-layer assembly. The deposition process was monitored by surface plasmon resonance spectroscopy. Further characterization of the multilayer films was performed by means of UV/vis absorption spectroscopy, which showed a linear increase in absorption with the number of bilayers. The growth of the gold nanoparticle plasmon absorption band corresponded to approximately a dense monolayer of gold nanoparticles per bilayer. Ellipsometry and atomic force microscopy (AFM) scratching experiments were used to measure the development of the film thickness with the number of bilayers, confirming linear growth and a thickness increase of approximately 2 nm/bilayer.

No abstract

The transfer of functional molecules onto self-assembled monolayers (SAMs) by means of soft and scanning-probe lithographic techniques-microcontact printing (muCP) and dip-pen nanolithography (DPN), respectively-and the stability of the molecular patterns during competitive rinsing conditions were examined. A series of guests with different valencies were transferred onto beta-cyclodextrin- (beta-CD-) terminated SAMs and onto reference hydroxy-terminated SAMs. Although physical contact was sufficient to generate patterns on both types of SAMs, only molecular patterns of multivalent guests transferred onto the beta-CD SAMs were stable under the rinsing conditions that caused the removal of the same guests from the reference SAMs. The formation of kinetically stable molecular patterns by supramolecular DPN with a lateral resolution of 60 nm exemplifies the use of beta-CD-terminated SAMs as molecular printboards for the selective immobilization of printboard-compatible guests on the nanometer scale through the use of specific, multivalent supramolecular interactions. Electroless deposition of copper on the printboard was shown to occur selectively on the areas patterned with dendrimer-stabilized gold nanoparticles.

Various patterning strategies have been developed to create hybrid nanostructures of dendrimers and gold nanoparticles on cyclodextrin self-assembled monolayers (CD SAMs) based on multiple supramolecular interactions using a layer-by-layer (LBL) approach. A lack of specificity of the adsorption of the dendrimer prevented the use of LBL assembly on chemically patterned SAMs, which were prepared by microcontact printing (μCP) or nanoimprint lithography (NIL). Nanotransfer printing (nTP) and nanoimprint lithography solved that problem and resulted in patterned LBL assemblies on the CD SAMs. nTP was achieved by LBL assembly on a PDMS stamp followed by transfer onto a full CD SAM. NIL-prepared PMMA patterns provided patterned CD SAMs and functioned as a physical mask for LBL assembly. For these methods, differences in thickness of the LBL assemblies were observed when compared to LBL assembly on full CD SAMs. These differences were shown not to originate from rinsing or lift-off procedures, but probably from differences in wetting.

Host vesicles composed of amphiphilic ␤-cyclodextrin CD1 recognize metal-coordination complexes of the adamantyl-functionalized ethylenediamine ligand L via hydrophobic inclusion in the ␤-cyclodextrin cavities at the vesicle surface. In the case of Cu(II) and L, the resulting coordination complex was exclusively CuL2, and the interaction with the host vesicles was intravesicular, unless the concentration of metal complex and vesicles was high (>0.1 mM). In the case of Ni(II) and L, a mixture was formed consisting of mainly NiL and NiL2, the interaction with the host vesicles was effectively intervesicular, and addition of the guest-metal complex resulted in aggregation of the vesicles into dense, multilamellar clusters even in dilute solution [1 M Ni(II)]. The metal-L complex could be eliminated by a strong chelator such as EDTA, and the intervesicular interaction could be suppressed by a competitor such as unmodified ␤-cyclodextrin. The result from this investigation is that the strongest metal-coordination complex [Cu(II) with L] binds exclusively intravesicularly, whereas the weakest metal-coordination complex [Ni(II) with L] binds predominantly intervesicularly and is the strongest interfacial binder. These experimental observations are confirmed by a thermodynamic model that describes multivalent orthogonal interactions at interfaces.self-assembly ͉ vesicles ͉ cyclodextrins M ultivalent, noncovalent interactions at the interface of cell membranes are involved in a variety of biological processes such as cell-cell signaling, pathogen identification, and inflammatory response (1). Multivalent binding events have collective properties that are qualitatively and quantitatively different from the contributing monovalent interactions. For example, multivalent interactions lead to higher binding affinities and can afford larger contact areas between surfaces (1-3). Multivalency can be conveniently described by an effective concentration (C eff ) term that represents a probability of interaction between two interlinked reactive or complementary entities and symbolizes the concentration of one of the reacting or interacting functionalities as experienced by its counterpart (4, 5). Versatile model systems to investigate multivalent noncovalent interactions at the dynamic interface between cell membranes and the surrounding aqueous solution include self-assembled monolayers (SAMs) (6-11), nanoparticles (12-14), solid-supported lipid bilayers (15, 16), and bilayer vesicles (17-19).Metal-ligand coordination has been exploited to generate complex molecular architectures with specific topology, high stability, and original properties in aqueous solution (16,20,21). The N-nitrilotriacetic acid-histidine interaction is particularly interesting in a biological context. N-nitrilotriacetic acidfunctionalized lipids (22, 23) and SAMs (24, 25) have been used to immobilize proteins through multivalent interactions. In a comparable approach, the multivalent binding of Cu(II) ions to a membrane-bound dansyl-ethylenediamine conjugat...