Room-temperature spin injection across a chiral perovskite/III-V interface.

Spin accumulation in semiconductor structures at room temperature and without magnetic fields is key to enable a broader range of optoelectronic functionality1. Current efforts are limited owing to inherent inefficiencies associated with spin injection across semiconductor interfaces2. Here we demonstrate spin injection across chiral halide perovskite/III-V interfaces achieving spin accumulation in a standard semiconductor III-V (AlxGa1-x)0.5In0.5P multiple quantum well light-emitting diode. The spin accumulation in the multiple quantum well is detected through emission of circularly polarized light with a degree of polarization of up to 15 ± 4%. The chiral perovskite/III-V interface was characterized with X-ray photoelectron spectroscopy, cross-sectional scanning Kelvin probe force microscopy and cross-sectional transmission electron microscopy imaging, showing a clean semiconductor/semiconductor interface at which the Fermi level can equilibrate. These findings demonstrate that chiral perovskite semiconductors can transform well-developed semiconductor platforms into ones that can also control spin.

Multivariate Bayesian Optimization of CoO Nanoparticles for CO2 Hydrogenation Catalysis.

The hydrogenation of CO2 holds promise for transforming the production of renewable fuels and chemicals. However, the challenge lies in developing robust and selective catalysts for this process. Transition metal oxide catalysts, particularly cobalt oxide, have shown potential for CO2 hydrogenation, with performance heavily reliant on crystal phase and morphology. Achieving precise control over these catalyst attributes through colloidal nanoparticle synthesis could pave the way for catalyst and process advancement. Yet, navigating the complexities of colloidal nanoparticle syntheses, governed by numerous input variables, poses a significant challenge in systematically controlling resultant catalyst features. We present a multivariate Bayesian optimization, coupled with a data-driven classifier, to map the synthetic design space for colloidal CoO nanoparticles and simultaneously optimize them for multiple catalytically relevant features within a target crystalline phase. The optimized experimental conditions yielded small, phase-pure rock salt CoO nanoparticles of uniform size and shape. These optimized nanoparticles were then supported on SiO2 and assessed for thermocatalytic CO2 hydrogenation against larger, polydisperse CoO nanoparticles on SiO2 and a conventionally prepared catalyst. The optimized CoO/SiO2 catalyst consistently exhibited higher activity and CH4 selectivity (ca. 98%) across various pretreatment reduction temperatures as compared to the other catalysts. This remarkable performance was attributed to particle stability and consistent H* surface coverage, even after undergoing the highest temperature reduction, achieving a more stable catalytic species that resists sintering and carbon occlusion.

Genesis of Nanogalvanic Corrosion Revealed in Pearlitic Steel.

Nanoscale, localized corrosion underpins billions of dollars in damage and material costs each year; however, the processes responsible have remained elusive due to the complexity of studying degradative material behavior at nanoscale liquid-solid interfaces. Recent improvements to liquid cell scanning/transmission electron microscopy and associated techniques enable this first look at the nanogalvanic corrosion processes underlying this widespread damage. Nanogalvanic corrosion is observed to initiate at the near-surface ferrite/cementite phase interfaces that typify carbon steel. In minutes, the corrosion front delves deeper into the material, claiming a thin layer of ferrite around all exposed phase boundaries before progressing laterally, converting the ferrite to corrosion product normal to each buried cementite grain. Over the following few minutes, the corrosion product that lines each cementite grain undergoes a volumetric expansion, creating a lateral wedging force that mechanically ejects the cementite grains from their grooves and leaves behind percolation channels into the steel substructure.

Tuning the Potential Energy Landscape to Suppress Ostwald Ripening in Surface-Supported Catalyst Systems.

Rational control of nanoparticle (NP) size distribution during operation is crucial to improve catalytic performance and noble metal sustainability. Herein, we explore the Ostwald ripening (OR) of metal atoms on zeolite surfaces by a coupled theoretical-experimental approach. Zeolites with the same structure (ZSM-5) but different concentrations of aluminum doped into the matrix were observed to yield systematic differences in supported nanoparticle size distributions. Our first-principles simulations suggest that NP stability at high temperature is governed by both geometric constraints and the roughness of the energetic landscape. Calculated adatom migration paths across the zeolite surface and desorption paths from the supported NPs lend insight into the modified OR sintering processes with the emergence of different binding configurations as the aluminum concentration increases from pristine to heavily doped ZSM-5. These findings reveal the potential for the rational design of support structures to suppress OR sintering.

Reversible Lifting of Surface Supported Lipid Bilayers with a Membrane-Spanning Nonionic Triblock Copolymer.

Neutron reflectometry was used to monitor structural variations in surface-supported dimyristoylphosphatidycholine (DMPC) bilayers induced by the addition of Triton X-100, a surfactant commonly used to aid solubilization of membrane proteins, and the coaddition of a membrane spanning nonionic amphiphilic triblock copolymer, (PEO117-PPO47-PEO117, Pluronic F98). Surfactant addition causes slight compression of the bilayer thickness and the creation of a distinct EO layer that increases the hydrophilic layer proximal to the supporting substrate (i.e., a water and EO gap between the lipid bilayer and quartz) to 6.8 ± 0.4 Å. Addition of the triblock copolymer into the DMPC:Triton X-100 bilayer increases the complexity of (broadens) the lipid phase transition, further compresses the bilayer, and continues to expand the proximal hydrophilic layer thickness. The observed structural changes are temperature dependent with transmembrane polymer insertion achieved at 37 °C, leading to a compressed membrane thickness of 39.2 ± 0.2 Å and proximal gap of 45.0 ± 0.2 Å. Temperature-driven exclusion of the polymer at 15 °C causes partitioning of the polymer into the proximal space generating a large hydrogel cushion 162 ± 16 Å thick. An intermediate gap width (10-27 Å) is achieved at room temperature (22-25 °C). The temperature-driven changes in the proximal hydrophilic gap dimensions are shown to be reversible, but thermal history causes variation in magnitude. Temperature-driven changes in polymer association with a supported lipid bilayer offer a facile means to reversibly control both the membrane characteristics as well as the separation between membrane and solid substrate.

Antimicrobial activity of water-soluble triazole phenazine clickamers against E. coli.

The antimicrobial potency of phenazine derivatives is attenuated by their inherently hydrophobic nature, complicating their use as antibiotic drugs. We have analyzed the cytotoxicity and mode of action of water-soluble bis-triazolyl phenazines against E. coli and a human epithelial (HaCat) cell line. We observed complete inhibition of bacterial growth over concentration ranges that do not affect the viability of human epithelial cells. Confocal fluorescence microscopy revealed a high degree of interaction between the phenazine compounds and E. coli, as well as evidence of membrane damage in phenazine-treated E. coli. Additional data suggests that the potency of these particular water-soluble phenazine compounds does not result from the production of reactive oxygen species, but rather from cytotoxic interference with metabolic electron-transfer cascades.

Aggregation and interaction of cationic nanoparticles on bacterial surfaces.

Cationic monolayer-protected gold nanoparticles (AuNPs) with sizes of 6 or 2 nm interact with the cell membranes of Escherichia coli (Gram-) and Bacillus subtilis (Gram+), resulting in the formation of strikingly distinct AuNP surface aggregation patterns or lysis depending upon the size of the AuNPs. The aggregation phenomena were investigated by transmission electron microscopy and UV-vis spectroscopy. Upon proteolytic treatment of the bacteria, the distinct aggregation patterns disappeared.

Antiandrogen gold nanoparticles dual-target and overcome treatment resistance in hormone-insensitive prostate cancer cells.

Prostate cancer is the most commonly diagnosed cancer among men in the developed countries.(1) One in six males in the U.S.(2) and one in nine males in the U.K.(3) will develop the disease at some point during their lifetime. Despite advances in prostate cancer screening, more than a quarter of a million men die from the disease every year(1) due primarily to treatment-resistance and metastasis. Colloidal nanotechnologies can provide tremendous enhancements to existing targeting/treatment strategies for prostate cancer to which malignant cells are less sensitive. Here, we show that antiandrogen gold nanoparticles--multivalent analogues of antiandrogens currently used in clinical therapy for prostate cancer--selectively engage two distinct receptors, androgen receptor (AR), a target for the treatment of prostate cancer, as well as a novel G-protein coupled receptor, GPRC6A, that is also upregulated in prostate cancer. These nanoparticles selectively accumulated in hormone-insensitive and chemotherapy-resistant prostate cancer cells, bound androgen receptor with multivalent affinity, and exhibited greatly enhanced drug potency versus monovalent antiandrogens currently in clinical use. Further, antiandrogen gold nanoparticles selectively stimulated GPRC6A with multivalent affinity, demonstrating that the delivery of nanoscale antiandrogens can also be facilitated by the transmembrane receptor in order to realize increasingly selective, increasingly potent therapy for treatment-resistant prostate cancers.

Tailoring plasmonic and electrostatic field effects to maximize solar energy conversion by bacteriorhodopsin, the other natural photosynthetic system.

We have explored the plasmonic field enhancement of current production from bacteriorhodopsin (bR) by maximizing the blue light effect, where the influx of blue photons absorbed by the long-lived M intermediate drastically shortens the time scale of the bR photocycle, leading to current enhancement. To this end, we used three approaches in our solution-based cell: (1) We improved the charge carrier separation in solution through the use of a proton-selective Nafion membrane. (2) We maximized the plasmonic surface field effects by selecting the capping polymer with minimum surface field screening and best nanoparticle stability. (3) We selected the plasmonic nanoparticle with the strongest plasmonic field whose surface plasmon resonance has the largest spectral overlap with the blue light absorbing M-intermediate. Theoretical models are used to explain experimental results, which show a 40 nm cuboidal nanoparticle capped with 55k PVP polymer to give the best photocurrent enhancement. Enhanced by this particle, bR in our Nafion membrane solution cell gave a photocurrent of 0.21 µA/cm(3), which is 5000 times larger than the published results for thin film bR electrochemical cells even with an applied bias. Additional possible enhancements are proposed.

TiO2 nanotube/CdS hybrid electrodes: extraordinary enhancement in the inactivation of Escherichia coli.

Titanium dioxide nanotubes offer distinct advantages over films of the same material in the production of hydroxyl radicals and subsequent inactivation of Escherichia coli in wastewater. However, their visible light absorption capabilities are limited. Semiconducting nanocrystals of cadmium sulfide have been used to increase the sensitivity of TiO(2) nanotubes to visible light. A small applied potential, using CdS-coated TiO(2) nanotube arrays, allowed for total inactivation of E. coli in hitherto record short time.

Mixed-Matrix Membranes Formed from Multi-Dimensional Metal-Organic Frameworks for Enhanced Gas Transport and Plasticization Resistance.

Mixed-matrix membranes (MMMs) formed by incorporating metal-organic frameworks (MOFs) into polymers have a general limitation in that the MOFs are typically formed into rather simple dimensionalities (such as 1D, 2D, or 3D). Each design approach has intrinsic-albeit independent-benefits, such as network percolation (1D), access to high-aspect ratios (2D), and ease of processability (3D). However, a design strategy is needed to combine multiple dimensionalities and, thereby, access the full range of transport and compositing benefits of these high-performance materials. Herein, a facile method to form multi-dimensional HKUST-1 nanoparticles is introduced by using a modulator to tune the MOF nucleation and growth mechanism. At 30 wt % multidimensional MOF loading, the MMM shows CO2 permeabilities of approximately 2500 Barrer, which represents a 2.5-fold increase compared to that of a pure polymer without a large loss of selectivity for CO2 /CH4 and CO2 /N2 . Additionally, almost no plasticization pressure response is observed for CO2 up to 750 psi, suggesting an unusual stability to high activity feeds.

Data on dielectric strength heterogeneity associated with printing orientation in additively manufactured polymer materials.

The following data describe the dielectric performance of additively manufactured polymer materials printed in various orientations for four common additive manufacturing techniques. Data are presented for selected commercial 3D printing materials fabricated using four common 3D printing techniques: Stereolithography (SLA), Fused Deposition Modeling (FDM), Selective Laser Sintering (SLS), and Polymer Jetting (PolyJet). Dielectric strengths are compiled for the listed materials, based on the ASTM D139 standard. This article provides data related to "Dielectric Strength Heterogeneity Associated with Printing Orientation in Additively Manufactured Polymer Materials" [1].

Fabrication of biosensing surfaces using adhesive polydopamine.

Dopamine can be induced to polymerize on a variety of substrates, providing a robust and bioinspired surface coating that can be used to tune substrate surface properties and to sequester other species at the interface. We first exploit the facile nature of this surface modification procedure to generate an array of polydopamine that, in conjunction with fluorescent tags, provides the ability to detect multiple protein targets simultaneously and with great specificity. We then demonstrate the use of polydopamine as a matrix to confine gold nanoparticles at the surface of glass and graphene substrates. The nanoparticles (NPs) are used to template further gold nanoparticle growth in situ at the interface; subsequent calcination to remove the polydopamine matrix and sinter the NPs generates a highly active surface enhanced Raman scattering surface that allows for sensitive molecular detection. These varied uses in surface modification/biosensing demonstrate the utility of polydopamine as a functional surface modification for control of physical and electronic properties at the interface.