Microporous metal-organic frameworks (MOFs) that display permanent porosity show great promise for a myriad of purposes. The potential applications of MOFs can be developed further and extended by encapsulating various functional species (for example, nanoparticles) within the frameworks. However, despite increasing numbers of reports of nanoparticle/MOF composites, simultaneously to control the size, composition, dispersed nature, spatial distribution and confinement of the incorporated nanoparticles within MOF matrices remains a significant challenge. Here, we report a controlled encapsulation strategy that enables surfactant-capped nanostructured objects of various sizes, shapes and compositions to be enshrouded by a zeolitic imidazolate framework (ZIF-8). The incorporated nanoparticles are well dispersed and fully confined within the ZIF-8 crystals. This strategy also allows the controlled incorporation of multiple nanoparticles within each ZIF-8 crystallite. The as-prepared nanoparticle/ZIF-8 composites exhibit active (catalytic, magnetic and optical) properties that derive from the nanoparticles as well as molecular sieving and orientation effects that originate from the framework material.
We report a low-cost, high-throughput scanning probe lithography method that uses a soft elastomeric tip array, rather than tips mounted on individual cantilevers, to deliver inks to a surface in a "direct write" manner. Polymer pen lithography merges the feature size control of dip-pen nanolithography with the large-area capability of contact printing. Because ink delivery is time and force dependent, features on the nanometer, micrometer, and macroscopic length scales can be formed with the same tip array. Arrays with as many as about 11 million pyramid-shaped pens can be brought into contact with substrates and readily leveled optically to ensure uniform pattern development.
Programmable assembly methods based upon the use of oligonucleotide-functionalized nanoparticles and sequence-specific assembly with complementary DNA have led to the development of a variety of fundamentally interesting materials and technologically significant detection systems. 1-3 The attractive feature of this approach to materials synthesis is that one can control the size, shape, and compositions of the individual nanoparticle building blocks as well as their spacing and periodicity within a macroscopic and, often times, polymeric structure through judicious choice of nanoparticle building block and DNA linkers. Most of the work in this area has focused on the use of isotropically functionalized particles since there are very few ways of selectively functionalizing different surface regions of an individual particle. However, if one could deliberately functionalize only one hemisphere or one distinct point on a particle in a general way, one could begin to introduce valency into such structures, thereby allowing greater control over the assembly process. 4A kinetic control approach, developed by Alivisatos and coworkers, allows one to functionalize nanoparticles with as few as one oligonucleotide per particle. 2b,5 This novel strategy introduces anisotropy into such particles and has enabled the assembly of dimer and trimer structures not attainable with the isotropically functionalized particles. Although this was an important step forward in nanoparticle functionalization, it has been limited to very small particles and typically leads to mixtures of products that must be separated by electrophoretic means. Here, we report a general strategy to functionalize a AuNP with two different types of oligonucleotides in a site-specific manner by using a magnetic sphere as a geometric restriction template (Scheme 1).Anisotropic functionalization of AuNPs was accomplished using a three-component assembly strategy (Scheme 1) consisting of the following: (1) magnetic microparticles (MMPs, 2.8 μm diameter polystyrene particles with iron oxide cores) functionalized with 3′thiol-terminated 30-mer oligonucleotides 1, (2) 3′-hydroxyl-modified "extension" oligonucleotides 2 that are complementary to half of the MMP oligonucleotides, and (3) AuNPs (13 nm, citrate-stabilized particles) densely functionalized with 3′-thiolated and 5′-phosphorylated 15-mer oligonucleotides 3 that are half-complementary to the other half of the MMP oligonucleotides. Standard methods were used to functionalize the MMPs and AuNPs with oligonucleotides (see Supporting Information). After combining the three components in the presence of a ligation buffer, they assembled to form complex 4 in which the oligonucleotide-modified MMP acts as a template to co-align the 3′-hydroxy group of the extension oligonucleotides with the 5′-phosphate group of the AuNP oligonucleotide. T4 DNA ligase was added to the reaction solution to catalyze the formation of a phosphodiester bond between the 3′-hydroxyl and the 5′-phosphate of the extension oligonucleotides ...
Aprotic Li-O batteries represent promising alternative devices for electrical energy storage owing to their extremely high energy densities. Upon discharge, insulating solid LiO forms on cathode surfaces, which is usually governed by two growth models, namely the solution model and the surface model. These LiO growth models can largely determine the battery performances such as the discharge capacity, round-trip efficiency and cycling stability. Understanding the LiO formation mechanism and controlling its growth are essential to fully realize the technological potential of Li-O batteries. In this review, we overview the recent advances in understanding the electrochemical and chemical processes that occur during the LiO formation. In the beginning, the oxygen reduction mechanisms, the identification of O/LiO intermediates, and their influence on the LiO morphology have been discussed. The effects of the discharge current density and potential on the LiO growth model have been subsequently reviewed. Special focus is then given to the prominent strategies, including the electrolyte-mediated strategy and the cathode-catalyst-tailoring strategy, for controlling the LiO growth pathways. Finally, we conclude by discussing the profound implications of controlling LiO formation for further development in Li-O batteries.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
customersupport@researchsolutions.com
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
This site is protected by reCAPTCHA and the Google Privacy Policy and Terms of Service apply.
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.