Oxide-Free Gadolinium Nanocrystals with Large Magnetic Moments

Among the elements in the periodic table, gadolinium (Gd) has the highest number of unpaired electrons. However, the potential of this rare-earth metal has not yet been fully realized due to challenges in its chemical synthesis, namely, its high reduction potential, leading to the formation of oxides with suboptimal properties. This problem is also prevalent with other lanthanides, severely limiting their uses in industry. Herein, a fabrication approach along with a reduction process and appropriate capping have been developed to produce oxide-free, stable gadolinium nanoparticles. We demonstrate broad tunability of the particle size while maintaining remarkably narrow size distributions (<5%). The nanoconstructs displayed the highest magnetization measured to date for Gd, 206 emu/g Gd at 2 K along with a record high per particle nuclear magnetic resonance (NMR) transverse relaxivity (r(2)) of 2.7 x 10(8) mM(-1) s(-1), which corresponds to the highest per-particle r2 relaxivity reported for any T-2 contrast agents to date. Unlike traditional approaches, this process can be extended to produce oxide-free nanoconstructs of other lanthanides, making them accessible for technological or biomedical applications

Active Metal Template Synthesis and Thermal Actuation of a Nanohoop [c2]Daisy Chain Rotaxane

Molecules and materials that demonstrate large amplitude responses to minor changes in their local environment play an important role in the development of new forms of nanotechnology. Molecular daisy chains are a type of a mechanically interlocked molecule that are particularly sensitive to such changes where, in the presence of certain stimuli, the molecular linkage enables muscle-like movement between a reduced-length contracted form and an increased-length expanded form. To date, all reported syntheses of molecular daisy chains are accomplished via passive-template methods, resulting in a majority of structures being switchable only through the addition of an exogenous stimuli such as metal ions or changes in pH. Here, we describe a new approach to these structural motifs that exploits a multi-component active-metal template synthesis to mechanically interlock two pi-rich nanohoop macrocycles into a molecular daisy chain which we show can be actuated through simple thermal changes.</p

Templated Synthesis of End-Functionalized Graphene Nanoribbons through Living Ring-Opening Alkyne Metathesis Polymerization.

Atomically precise bottom-up synthesized graphene nanoribbons (GNRs) are promising candidates for next-generation electronic materials. The incorporation of these highly tunable semiconductors into complex device architectures requires the development of synthetic tools that provide control over the absolute length, the sequence, and the end groups of GNRs. Here, we report the living chain-growth synthesis of chevron-type GNRs (cGNRs) templated by a poly-(arylene ethynylene) precursor prepared through ring-opening alkyne metathesis polymerization (ROAMP). The strained triple bonds of a macrocyclic monomer serve both as the site of polymerization and the reaction center for an annulation reaction that laterally extends the conjugated backbone to give cGNRs with predetermined lengths and end groups. The structural control provided by a living polymer-templated synthesis of GNRs paves the way for their future integration into hierarchical assemblies, sequence-defined heterojunctions, and well-defined single-GNR transistors via block copolymer templates

4-D Flow Control in Porous Scaffolds: Toward a Next Generation of Bioreactors.

Tissue engineering (TE) approaches that involve seeding cells into predetermined tissue scaffolds ignore the complex environment where the material properties are spatially inhomogeneous and evolve over time. We present a new approach for controlling mechanical forces inside bioreactors, which enables spatiotemporal control of flow fields in real time. Our adaptive approach offers the flexibility of dialing-in arbitrary shear stress distributions and adjusting flow field patterns in a scaffold over time in response to cell growth without needing to alter scaffold structure. This is achieved with a multi-inlet bioreactor and a control algorithm with learning capabilities to dynamically solve the inverse problem of computing the inlet pressure distribution required over the multiple inlets to obtain a target flow field. The new method constitutes a new platform for studies of cellular responses to mechanical forces in complex environments and opens potentially transformative possibilities for TE

Templated Synthesis of End-Functionalized Graphene Nanoribbons through Living Ring-Opening Alkyne Metathesis Polymerization.

Atomically precise bottom-up synthesized graphene nanoribbons (GNRs) are promising candidates for next-generation electronic materials. The incorporation of these highly tunable semiconductors into complex device architectures requires the development of synthetic tools that provide control over the absolute length, the sequence, and the end groups of GNRs. Here, we report the living chain-growth synthesis of chevron-type GNRs (cGNRs) templated by a poly-(arylene ethynylene) precursor prepared through ring-opening alkyne metathesis polymerization (ROAMP). The strained triple bonds of a macrocyclic monomer serve both as the site of polymerization and the reaction center for an annulation reaction that laterally extends the conjugated backbone to give cGNRs with predetermined lengths and end groups. The structural control provided by a living polymer-templated synthesis of GNRs paves the way for their future integration into hierarchical assemblies, sequence-defined heterojunctions, and well-defined single-GNR transistors via block copolymer templates