Pentafluorophenyl Ester-Functionalized Nanoparticles as a Versatile Platform for Selective and Covalent Inter-nanoparticle Coupling

Preparing chemically selective nanoparticle (NP) building blocks to make robust structures from different NP compositions often requires complex hetero-bifunctional ligand pairs that have limited scalability and versatility. Here we describe pentafluorophenyl ester-functionalized nanoparticles (PFP-NPs) as versatile building blocks for covalent inter-NP coupling. This approach allows for a rapid and dense grafting of PFP-functionalized Au NPs onto several types of amine-functionalized NPs (metals, semiconductors, and insulators) and selective identification of amine-functionalized quantum dots (QDs) in solution. Such simple yet efficient inter-NP reactions suggest the suitability of PFP-NPs as a versatile functional platform for numerous NP-based applications

Novel Zwitterionic Copolymers with Dihydrolipoic Acid: Synthesis and Preparation of Nonfouling Nanorods

We report the synthesis of hydrophilic, zwitterionic copolymers containing pendent disulfide and dithiol groups along a phosphorylcholine methacrylate backbone. These novel copolymers were prepared by controlled free radical copolymerization of methacryloyloxyethyl phosphorylcholine (MPC) and the methacrylate of lipoic acid (LA), using reversible addition–fragmentation chain transfer (RAFT) polymerization, followed by reduction of the disulfides to give dihydrolipoic acid (DHLA) pendent groups. Poly­(MPC-<i>co</i>-DHLA) proved useful for surface functionalization of gold nanorods (Au NRs), resulting in removal of the cationic surfactant stabilizing layer present initially on the Au NRs. Au NRs coated with poly­(MPC-<i>co</i>-DHLA) proved stable against challenging conditions, and resisted cyanide ion digestion. Au NRs coated with poly­(MPC-<i>co</i>-DHLA) also showed nonfouling properties resulting from their surface coating, and the noncytotoxicity of these structures was confirmed in the presence of live cells. The novel polymer materials and the methodology we describe hold promise for enabling new opportunities that utilize surface-coated metallic and semiconductor nanostructures in both materials and biological applications

Elucidating the Impact of Molecular Structure on the ¹⁹F NMR Dynamics and MRI Performance of Fluorinated Oligomers

To understand molecular factors that impact the performance of polymeric ¹⁹F magnetic resonance imaging (MRI) agents, a series of discrete fluorinated oligoacrylates with precisely defined structure were prepared through the combination of controlled polymerization and chromatographic separation techniques. These discrete oligomers enabled thorough elucidation of the dependence of ¹⁹F NMR and MRI properties on molecular structure, for example, the chain length. Importantly, the oligomer size and dispersity strongly influence NMR dynamics (<i>T</i>₁ and <i>T</i>₂ relaxation times) and MR imaging properties with higher signal-to-noise ratio (SNR) observed for oligomers with longer chain length and shorter <i>T</i>₁. Our approach enables an effective pathway and thus opportunities to rationally design effective polymeric ¹⁹F MR imaging agents with optimized molecular structure and NMR relaxivity

Collective excitations in superfluid he-3-type fermi systems

The investigation is concerned with superfluid He-3-type Fermi liquid. The aim of the work is to study a spectrum of collective excitations in superfluid phases of helium-3 in the external electric and magnetic fields. The spectrum of collective excitations has been first calculated. The influence of the electric field on a spectrum in B-phase has been studied. The results obtained give a possibility of interpreting ultrasound experiments in superfluid helium-3. The field of application covers physics of the condensed stateAvailable from VNTIC / VNTIC - Scientific & Technical Information Centre of RussiaSIGLERURussian Federatio

Highly Conductive Ribbons Prepared by Stick–Slip Assembly of Organosoluble Gold Nanoparticles

Precisely positioning and assembling nanoparticles (NPs) into hierarchical nanostructures is opening opportunities in a wide variety of applications. Many techniques employed to produce hierarchical micrometer and nanoscale structures are limited by complex fabrication of templates and difficulties with scalability. Here we describe the fabrication and characterization of conductive nanoparticle ribbons prepared from surfactant-free organosoluble gold nanoparticles (Au NPs). We used a flow-coating technique in a controlled, stick–slip assembly to regulate the deposition of Au NPs into densely packed, multilayered structures. This affords centimeter-scale long, high-resolution Au NP ribbons with precise periodic spacing in a rapid manner, up to 2 orders-of-magnitude finer and faster than previously reported methods. These Au NP ribbons exhibit linear ohmic response, with conductivity that varies by changing the binding headgroup of the ligands. Controlling NP percolation during sintering (<i>e.g.</i>, by adding polymer to retard rapid NP coalescence) enables the formation of highly conductive ribbons, similar to thermally sintered conductive adhesives. Hierarchical, conductive Au NP ribbons represent a promising platform to enable opportunities in sensing, optoelectronics, and electromechanical devices

A Versatile and Efficient Strategy to Discrete Conjugated Oligomers

An efficient and scalable strategy to prepare libraries of discrete conjugated oligomers (<i><i>Đ</i></i> = 1.0) using the combination of controlled polymerization and automated flash chromatography is reported. From this two-step process, a series of discrete conjugated materials from dimers to tetradecamers could be isolated in high yield with excellent structural control. Facile and scalable access to monodisperse libraries of different conjugated oligomers opens pathways to designer mixtures with precise composition and monomer sequence, allowing exquisite control over their physical, optical, and electronic properties

Simple Benchtop Approach to Polymer Brush Nanostructures Using Visible-Light-Mediated Metal-Free Atom Transfer Radical Polymerization

The development of an operationally simple, metal-free surface-initiated atom transfer radical polymerization (SI-ATRP) based on visible-light mediation is reported. The facile nature of this process enables the fabrication of well-defined polymer brushes from flat and curved surfaces using a “benchtop” setup that can be easily scaled to four-inch wafers. This circumvents the requirement of stringent air-free environments (i.e., glovebox), and mediation by visible light allows for spatial control on the micron scale, with complex three-dimensional patterns achieved in a single step. This robust approach leads to unprecedented access to brush architectures for nonexperts

Controlled Formation and Binding Selectivity of Discrete Oligo(methyl methacrylate) Stereocomplexes

The triple-helix stereocomplex of poly­(methyl methacrylate) (PMMA) is a unique example of a multistranded synthetic helix that has significant utility and promise in materials science and nanotechnology. To gain a fundamental understanding of the underlying assembly process, discrete stereoregular oligomer libraries were prepared by combining stereospecific polymerization techniques with automated flash chromatography purification. Stereocomplex assembly of these discrete building blocks enabled the identification of (1) the minimum degree of polymerization required for the stereocomplex formation and (2) the dependence of the helix crystallization mode on the length of assembling precursors. More significantly, our experiments resolved binding selectivity between helical strands with similar molecular weights. This presents new opportunities for the development of next-generation polymeric materials based on a triple-helix motif

A Versatile and Scalable Strategy to Discrete Oligomers

A versatile strategy is reported for the multigram synthesis of discrete oligomers from commercially available monomer families, e.g., acrylates, styrenics, and siloxanes. Central to this strategy is the identification of reproducible procedures for the separation of oligomer mixtures using automated flash chromatography systems with the effectiveness of this approach demonstrated through the multigram preparation of discrete oligomer libraries (<i><i>Đ</i></i> = 1.0). Synthetic availability, coupled with accurate structural control, allows these functional building blocks to be harnessed for both fundamental studies as well as targeted technological applications