Engineering the assembly of nanoscale objects into complex and prescribed structures requires control over their binding properties. Such control might benefit from a well-defined bond directionality, the ability to designate their engagements through specific encodings, and the capability to coordinate local orientations. Although much progress has been achieved in our ability to design complex nano-objects, the challenges in creating such nano-objects with fully controlled binding modes and understanding their fundamental properties are still outstanding. Here, we report a facile strategy for creating a DNA nanochamber (DNC), a hollow cuboid nano-object, whose bonds can be fully prescribed and complexly encoded along its three orthogonal axes, giving rise to addressable and differentiated bonds. The DNC can host nanoscale cargoes, which allows for the integration with functional nano-objects and their organization in larger-scale systems. We explore the relationship between the design of differentiated bonds and a formation of one-(1D), two-(2D), and three-(3D) dimensional organized arrays. Through the realization of different binding modes, we demonstrate sequence encoded nanoscale heteropolymers, helical polymers, 2D lattices, and mesoscale 3D nanostructures with internal order, and show that this assembly strategy can be applied for the organization of nanoparticles. We combine experimental investigations with computational simulation to understand the mechanism of structural formation for different types of ordered arrays, and to correlate the bonds design with assembly processes.

Directing the formation of nanoscale architectures from nanoparticles is one of the key challenges in designing nanomaterials with prescribed functions. Atomic systems, given their ability to form molecules and crystals via directional chemical bonds, provide an inspiration for establishing approaches where nanoparticles with designed anisotropic binding modalities can be assembled into nanoscale architectures. However, fabricating such nanoparticles has been challenging due to their small dimensions and limited ways for site-specific control of their surface. To this end, we present a molecular stamping (MOST) approach to pattern DNA-coated nanoparticles with molecules at the predefined positions on a nanoparticle surface. This patterning is realized by use of a rigid and coordinative DNA frame as a molecular stamping apparatus (MOST App). The MOST App transfers multiple types of molecular “inks”, DNA sequences, onto a nanoparticle surface and fixes these molecular inks into place to form a designed pattern. After a nanoparticle is released the from MOST App, it possesses single-molecule patches that can provide anisotropic bonds with distinctive affinities. We further use these stamped nanoparticles to assemble prescribed clusters, whose structure is determined by the locations of patches. Using electron microscopy and tomographic methods, we investigate the efficiency of cluster formation and the resulting spatial arrangements of nanoparticles. The presented approach provides a single-molecule and spatially determined control over nanoparticle functionalization for creating nanoparticles with designed placement of different molecules and for realizing a rational fabrication of nanomaterial architectures.

The detection of testosterone in aqueous solutions is a difficult task due to the low concentration levels that are relevant in environmental and physiological samples. Current analytical methods are expensive and/or complex. To address this issue, we fabricated a molecularly imprinted polymer (MIP) photonic film for the detection of testosterone in water. The films were obtained using colloidal crystals as templates for the pore morphology. Monodispersed silica particles with an average diameter 330 nm were used to obtain the colloidal crystal by vertical deposition. A solution of acrylic acid with testosterone as the imprinted template was infiltrated in the colloidal crystal and polymerized via bulk polymerization; the particles were then removed by acid etching and the testosterone eluted by a suitable solvent. The material was characterized by FTIR, swelling experiments and microscopy; MIPs were investigated by equilibrium rebinding, kinetics and reuse experiments. The results showed that the MIPs exhibited selectivity to the template, a 30-min equilibration time and stability after at least six cycles of use and regeneration. After incubation, the reflectance spectra of the films showed a shift of the Bragg diffraction peak that correlated with testosterone concentration in the 5–100 ppb range.

No abstract

Could one manipulate nanoscale building blocks using chemical reactions like molecular synthesis to yield new supra-nanoscale objects? The precise control over the final architecture might be challenging due to the size mismatch of molecularly scaled reactive functional groups and nanoscale building blocks, which limits a control over the valence and specific locations of reaction spots. Taking advantage of programmable octahedral DNA frame, we report a facile approach of engineering chemical reactions between nanoscale building blocks toward formation of controlled nanoarchitectures. Azide and alkyne moieties were specifically anchored onto desired vertices of DNA frames, providing chemically reactive nanoconstructs with directionally defined valence. Akin to the conventional molecular reactions, the formation of a variety of nanoscale architectures was readily achieved upon mixing of the frames with the different reactive valence and at different stoichiometric ratios. This strategy may open a door for a programmable synthesis of supra-nanoscale structures with complex architectures and diversified functions.

“Single-atom” catalysts (SACs) have demonstrated excellent activity and selectivity in challenging chemical transformations such as photocatalytic CO2 reduction. For heterogeneous photocatalytic SAC systems, it is essential to obtain sufficient information...

A series of supported ReO x catalysts were synthesized by incipient-wetness impregnation of perrhenic acid onto one component (Al2O3 and SiO2) and surface-modified mixed-oxide supports (SiO2/Al2O3, Al2O3/SiO2, and ZSM-5 (Si/Al = 15)), characterized with in situ molecular spectroscopy (Raman, DRIFTS, UV–vis, and XAS), and chemically probed (ammonia chemisorption, C2H4/C4H8-titration, C3H6-TPSR, and steady-state propylene self-metathesis). The initial dehydrated surface rhenia species were coordinated to the oxide supports as isolated Re7+O4 sites. For the Al-containing supports, dioxo surface (O)2Re­(−O)2 sites appear to be the preferred coordination. The number of activated surface ReO x sites during metathesis is determined by the oxide support ligands (3% ReO x /ZSM-5 > 3% ReO x /5% AlO x /SiO2 > 3% ReO x /5% SiO x /Al2O3 > 3% ReO x /Al2O3 ≈ 3% ReO x /SiO2). The specific activity (TOF) is also controlled by the oxide support ligands (3% ReO x /Al2O3 > 3% ReO x /5% SiO x /Al2O3 ≫ 3% ReO x /ZSM-5 ≈ 3% ReO x /5% AlO x /SiO2 ≫ 3% ReO x /SiO2). The overall propylene metathesis activity (N × TOF), however, is dominated by the number of activated sites (N). Consequently, the enhanced overall activity of surface ReO x supported on SiO2–Al2O3 mixed-oxide supports is related to the greater number of activated surface ReO x sites. The overall propylene metathesis activity was not related to the local surface ReO4 molecular structure or the strength of the Brønsted acid site, since the same rhenia structures appeared to be present on all of the active catalysts and the strengths of the Brønsted acid sites were comparable for all of the active catalysts, respectively.

A series of supported 3% MoO x catalysts were synthesized by incipient-wetness impregnation of a 5–15% TaO x surface-modified γ-Al2O3 support. The catalysts were characterized by in situ spectroscopies (diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS), Raman, UV–vis, X-ray absorption spectroscopy (XAS)) and multiple chemical probes (C2H4/C4H8 titration, C3H6-TPSR, steady-state propylene metathesis, NH3-IR adsorption). The supported tantalum oxide phase was present as surface TaO x sites on the γ-Al2O3 support that capped the Al2O3 surface hydroxyls. The change in available surface hydroxyls caused the subsequent anchoring of MoO x species to occur at different surface hydroxyls. This shifted the anchoring of MoO x species from basic (Al-OH) to neutral (Al2-OH) to more acidic (Al3-OH) surface hydroxyls as well as perturbation of the remaining alumina surface hydroxyls by the surface TaO x sites. The TaO x surface-modified γ-Al2O3 support increased the number of activated surface MoO x sites (Ns) by ∼6× and the turnover frequency (TOF) by ∼10×, resulting in an increased activity of ∼60×. It was found that the specific anchoring surface hydroxyls rather than the extent of oligomerization of the surface MoO x sites control the number of activated MoO x sites and TOF for propylene metathesis. No relationships between the nature of the surface Lewis/Brønsted acid sites and Ns and TOF were found to be present.