Elaine DiMasi’s research while affiliated with Brookhaven National Laboratory and other places

The interactions of mixtures of anionic and amphoteric surfactants with sugar amphiphiles were studied via high throughput small angle x-ray scattering (SAXS). The sugar amphiphile was composed of Caprate, Caprylate, and Oleate mixed ester of methyl glucoside, MeGCCO. Optimal surfactant interactions are sought which have desirable physical properties, which must be identified in a cost effective manner that can access the large phase space of possible molecular combinations. X-ray scattering patterns obtained via high throughput SAXS can probe a combinatorial sample space and reveal the incorporation of MeGCCO into the micelles and the molecular associations between surfactant molecules. Such data make it possible to efficiently assess the effects of the new amphiphiles in the formulation. A specific finding of this study is that formulations containing comparatively monodisperse and homogeneous surfactant mixtures can be reliably tuned by addition of NaCl, which swells the surfactant micelles with a monotonic dependence on salt concentration. In contrast, the presence of multiple different surfactants destroys clear correlations with NaCl concentration, even in otherwise similar series of formulations.

The interactions of mixtures of anionic and amphoteric surfactants with sugar amphiphiles were studied via high throughput small angle x-ray scattering (SAXS). The sugar amphiphile was composed of Caprate, Caprylate, and Oleate mixed ester of methyl glucoside, MeGCCO. Optimal surfactant interactions are sought which have desirable physical properties, which must be identified in a cost effective manner that can access the large phase space of possible molecular combinations. X-ray scattering patterns obtained via high throughput SAXS can probe a combinatorial sample space and reveal the incorporation of MeGCCO into the micelles and the molecular associations between surfactant molecules. Such data make it possible to efficiently assess the effects of the new amphiphiles in the formulation. A specific finding of this study is that formulations containing comparatively monodisperse and homogeneous surfactant mixtures can be reliably tuned by addition of NaCl, which swells the surfactant micelles with a monotonic dependence on salt concentration. In contrast, the presence of multiple different surfactants destroys clear correlations with NaCl concentration, even in otherwise similar series of formulations.

We report on the implications of the design of a Soft Matter Interfaces beamline, a long energy range canted in-vacuum undulator (IVU) beamline at National Synchrotron Light Source II, based on comparison of geometrical ray-tracing and partially coherent x-ray wavefront propagation simulation software packages, namely, SHADOW and Synchrotron Radiation Workshop (SRW). For SHADOW, we employed an SRW-generated source file which simulated spectral angular distribution and apparent source characteristics of radiation produced by a 2.8 m long IVU with a 23 mm period and allowed us to realistically estimate the beam intensity at the sample positions. We highlight the necessity to use realistic mirror surface profiles with expected slope errors as opposed to “standard” built-in SHADOW surface error options. The beamline performances at three different x-ray photon energies: 20358 eV, 10778 eV, and 2101 eV, under different focusing conditions, have been studied. We compare beamline simulations performed with both software packages. In particular, we stress that the neglect of wavefront diffraction effects in geometrical ray-tracing approach results in significant discrepancies in beam spot size and beam shape, the correct assessments of which are crucial in determining the future performance of an instrument.

Helium implantation from transmutation reactions is a major cause of embrittlement and dimensional instability of structural components in nuclear energy systems. Development of novel materials with improved radiation resistance, which is of the utmost importance for progress in nuclear energy, requires guidelines to arrive at favorable parameters more efficiently. Here, we present a methodology that can be used for the design of radiation tolerant materials. We used synchrotron X-ray reflectivity to nondestructively study radiation effects at buried interfaces and measure swelling induced by He implantation in Cu/Nb multilayers. The results, supported by transmission electron microscopy, show a direct correlation between reduced swelling in nanoscale multilayers and increased interface area per unit volume, consistent with helium storage in Cu/Nb interfaces in forms that minimize dimensional changes. In addition, for Cu/Nb layers, a linear relationship is demonstrated between the measured depth-dependent swelling and implanted He density from simulations, making the reflectivity technique a powerful tool for heuristic material design.

We report the synthesis and nanostructural development of polycrystalline and single crystalline LiFePO4 (LFP) nanostructures using a solvothermal media (i.e., water–tri(ethylene glycol) mixture). Crystal phase and growth behavior were monitored by powder and synchrotron X-ray diffraction, as well as transmission electron microscopy (TEM), while particle morphologies were examined using scanning electron microscopy (SEM). Initially, thin (100 nm) platelets of Fe3(PO4)2·8H2O (vivianite, VTE) formed at short reaction times followed by the nucleation of LFP (20 nm particles) on the metastable VTE surfaces. Upon decrease in pH, primary LFP nanocrystals subsequently aggregated into polycrystalline diamond-like particles via an oriented attachment (OA). With increasing reaction time, the solution pH further decreased, leading to a dissolution–recrystallization process (i.e., Ostwald ripening, OR) of the oriented polycrystalline LFP particles to yield evenly sized, single crystalline LiFePO4. Samples prepared at short reaction durations demonstrated a larger discharge capacity at higher rates compared with the single crystalline particles. This is due to the small size of the primary crystallites within larger secondary LiFePO4 particles, which reduced the lithium ion diffusion path while subsequently maintaining a high tap density. Understanding the relationship between solution conditions and nanostructural development as well as performance revealed by this study will help to develop synthetic guidelines to enable efficient lithium ion battery performance.

During mineralization, the hard outer magnetite-containing shell of the radular teeth of Cryptochiton stelleri undergoes four distinct stages of structural and phase transformations: (i) the formation of a crystalline α-chitin organic matrix that forms the structural framework of the non-mineralized teeth, (ii) the templated synthesis of ferrihydrite crystal aggregates along these organic fibers, (iii) subsequent solid state phase transformation from ferrihydrite to magnetite, and (iv) progressive magnetite crystal growth to form continuous parallel rods within the mature teeth. The underlying α-chitin organic matrix appears to influence magnetite crystal aggregate density and the diameter and curvature of the resulting rods, both of which likely play critical roles in determining the local mechanical properties of the mature radular teeth.

Many biological materials are known for their remarkable structural complexity as well as their impressive mechanical properties. The ultrahard abrasion-resistant radular teeth of the chitons are one such example and members of this group of mollusks, studied by David Kisailus and co-workers on page 2908, have the surprising capacity to erode away the rocky substrates on which they graze for algae. The foreground image depicts the anterior end of the conveyor belt-like radula that contains the magnetite-rich teeth and the background image depicts the oriented rod-like aggregates of magnetic nanoparticles that comprise the material.

Systematic changes in the exocyclic substiution of core phthalocyanine platform tune the absorption properties to yield commercially viable dyes that function as the primary light absorbers in organic bulk heterojunction solar cells. Blends of these complementary phthalocyanines absorb a broader portion of the solar spectrum compared to a single dye, thereby increasing solar cell performance. We correlate grazing incidence small angle x-ray scattering structural data with solar cell performance to elucidate the role of nanomorphology of active layers composed of blends of phthalocyanines and a fullerene derivative. A highly reproducible device architecture is used to assure accuracy and is relevant to films for solar windows in urban settings. We demonstrate that the number and structure of the exocyclic motifs dictate phase formation, hierarchical organization, and nanostructure, thus can be employed to tailor active layer morphology to enhance exciton dissociation and charge collection efficiencies in the photovoltaic devices. These studies reveal that disordered films make better solar cells, short alkanes increase the optical density of the active layer, and branched alkanes inhibit unproductive homogeneous molecular alignment.