The NU-MRSEC Super-Seed team has developed a method to process imine-linked 2D COF powders into thin films via reversible exfoliation. The COF powder is treated with strong acids, which causes each layer to become positively charged. This charged form is exfoliated in solvents with gentle sonication, which provides a suspension of nanosheets.
Semiconductors with both magnetic and optoelectronic properties are relevant for novel spintronic devices. With the aim of discovering new magnetic semiconductors, NU-MRSEC IRG-2 performed synthesis investigations on mixed halide-chalcogenides, resulting in the discovery of the new compound BaFMn0.5Te.
Since 2003 we have successfully partnered with universities in Southern Africa, specifically the National University of Lesotho and the University of Pretoria, to bring faculty members to the LRSM every summer to participate in collaborative research projects with our faculty. Often the students of faculty members are invited to join as well to gain research experience. This was the case with Mopeli Fabiane (top picture), who originally came as a lecturer, then a graduate student, and now continues to visit as a researcher with his Ph.D. The program started with 2-3 faculty/students visiting each summer and now this summer, 2019, will support 7 visitors (6 faculty and 1 student).
Our team designed a protein-based RGG material capable of self-assembly into micron size condensates that can be genetically encoded and expressed to form membranelles organelles in living cells. RGG is an intrinsically disordered peptide that coacervates to form a dynamic protein phase through weak, multivalent interactions.
This work reports the first experimental realization of nanoparticles templated at the interface of liquid crystals into reconfigurable, periodic structures. We establish that nanoparticles can segregate into highly ordered stripes, with tunable organization and thickness, forming the basis for the assembly of patchy colloids and nanowires. Our technique is advantageous over other methods, as the resultant assemblies can dynamically respond to changes within the underlying liquid crystal.
Shenoy group in the IRG led a study on the multiaxial behavior of collagen networks. When stretched, the network models exhibited drastic contractions transverse to the direction of loading (yellow arrows in the top left image). The networks exhibited an anomalous Poisson effect, with apparent Poisson’s ratios larger than 1. Experiments validated this result and showed increases of apparent Poisson’s ratio with decreasing collagen concentration (top right image).
This IRG focuses on the mechanical behavior of disordered materials, particularly beyond the onset of yield. The Figure shows recent advances in using Machine Learning (ML) methods to characterize the local structural environment of disordered materials with respect to susceptibility for particulate rearrangements using a quantity called softness. (A-D) shows an analysis of a polycrystalline material (created via Molecular Dynamic simulations) using ML and the concept of softness [1]. The Figure shows that softness (bright spots in D) is able to capture rearrangements measured as shown by colored particles in (C). This approach correctly identifies crystalline and grain boundary regions as having low values and high variability of softness, respectively. We also extended the concept of softness to anisotropic particles [2] (E). Similar predictive performance to isotropic particles is observed and a recursive feature elimination (RFE) method is introduced to better understand how softness arises from particular structural aspects that can be systematically tuned e.g. by particle aspect ratio. Indeed, longer particles lead to different global flow patterns for a pillar under compression (F).
Materials synthesis is a complex process that depends not only on thermodynamic stability, but also on kinetic factors, advances in synthesis techniques, and the availability of precursors. This complexity makes the development of a general theory for predicting synthesizability extremely difficult.
To enable ambient processing and study of indium selenide, NU-MRSEC IRG-1 has developed a mixed-dimensional organic/inorganic passivation scheme based on n-methyl-2-pyrrilodone (NMP) seeded atomic layer deposited (ALD) alumina that provides a pinhole-free encapsulation layer that preserves the intrinsic electronic properties of the underlying InSe.
In this work, molecular self-assembly of highly polarizable PAE molecules was used to create reconfigurable dielectric layers whose capacitance changes with illumination. Upon ultraviolet optical illumination, the PAE molecules undergo a photoisomerization from an extended trans geometry to a compact cis geometry, which can be reversed upon illumination at longer wavelengths.
