Reactions in elastomeric nanoreactors reveal the role of force on the kinetics of the Huisgen reaction on surfaces.

The force dependence of the copper-free Huisgen cycloaddition between an alkyne and a surface-bound azide was examined in elastomeric nanoreactors. These studies revealed that pressure and chain length are critical factors that determine the reaction rate. These experiments demonstrate the central role of pressure and surface structure on interfacial processes that are increasingly important in biology, materials science, and nanotechnology.

Beam pen lithography as a new tool for spatially controlled photochemistry, and its utilization in the synthesis of multivalent glycan arrays.

Herein, we describe how cantilever-free scanning probes can be used to deposit precursor material and subsequently irradiate the precursor to initiate polymerization, resulting in a 3D lithographic method wherein the position, height and diameter of each feature can be tuned independently. Specifically, acrylate and methacrylate monomers were patterned onto thiol terminated glass and subsequently exposed to UV light produced brush polymers by a photoinduced radical acrylate polymerization reaction. Here, we report the first examples of glycan arrays, comprised of methacrylate brush polymers that are side-chain functionalized with α-glucose, by this new lithographic approach. Their binding with fluorophore labeled concanavalin A (ConA) was assayed by fluorescence microscopy. The fluorescence of these brush polymers was compared to glycan arrays composed of monolayers of α-mannosides and α-glucosides prepared by combining polymer pen lithography (PPL) with the thiol-ene photochemical reaction or the copper-catalyzed azide-alkyne cycloaddition. At high ConA concentration, the fluorescence signal of the brush polymer was nearly 20 times greater than that of the glycan monolayers, and the brush polymer arrays had a detection limit nearly two orders of magnitude better than their monolayer counterparts. Because of the ability of this method to control precisely the polymer length, the relationship between limit of detection and multivalency could be explored, and it was found that the longer polymers (136 nm) are an order of magnitude more sensitive towards ConA binding than the shorter polymers (8 nm) and that binding affinity decreased systematically with length. These glycan arrays are a new tool to study the role of multivalency on carbohydrate recognition, and the photopolymerization route towards forming multivalent glycan scaffolds described herein, is a promising route to create multiplexed glycan arrays with nanoscale feature dimensions.

Covalently patterned graphene surfaces by a force-accelerated Diels-Alder reaction.

Cyclopentadienes (CPs) with Raman and electrochemically active tags were patterned covalently onto graphene surfaces using force-accelerated Diels-Alder (DA) reactions that were induced by an array of elastomeric tips mounted onto the piezoelectric actuators of an atomic force microscope. These force-accelerated cycloadditions are a feasible route to locally alter the chemical composition of graphene defects and edge sites under ambient atmosphere and temperature over large areas (∼1 cm(2)).

Matrix-assisted polymer pen lithography induced Staudinger Ligation.

The Staudinger Ligation has been combined with Polymer Pen Lithography to create patterns of fluorescent and redox-active inks with 1-micrometer scale feature diameters over centimeter-scale areas. This report presents a straightforward strategy to expand the scope of organic reactions employed in surface science.

Polymer pen lithography (PPL)-induced site-specific click chemistry for the formation of functional glycan arrays.

Polymer pen lithography (PPL) can be combined with the Cu(I) -catalyzed azide-alkyne click reaction to create molecular arrays with control over orientation and sub-1 µm feature sizes over cm(2) areas. The process has been applied to the deposition of carbohydrates to form functional glycochips.

A facile template approach to high-nuclearity silver(I) alkynyl clusters.

Peanut clusters: Anion templates are used in a facile approach for the synthesis of high-nuclearity silver clusters. The cluster nuclearity can be controlled by adjusting the size of the templating anions and by using different alkynyl ligands. The largest silver alkynyl cluster, which consists of 35 silver(I) centers in the shape of a peanut, has been prepared by using chromate anions as templates (see picture).

High-nuclearity silver clusters templated by carbonates generated from atmospheric carbon dioxide fixation.

Two high-nuclearity silver clusters have been prepared by reacting AgC(2)Bu(t) with AgBF(4) (or AgOTf) in the presence of TMEDA in air. The reaction takes up atmospheric CO(2) to give CO(3)(2-), which functions as a template for the formation of the cage compounds, whose nuclearities depend on the particular counteranions employed.

Snowman-like silver alkynyl cluster consolidated by templating chloride and peripheral trifluoroacetates.

A novel nonadecanuclear silver double cage was isolated, in which a square antiprism and a pentacapped pentagonal prism templated by a chloride ion share a tetragonal face to form a snowman-like cluster that is held together by bridging alkynyl groups and trifluoroacetates.