Electronic Properties of DNA Origami Nanostructures Revealed by In Silico Calculations

DNA origami is a pioneering approach for producing complex 2- or 3-D shapes for use in molecular electronics due to its inherent self-assembly and programmability properties. The electronic properties of DNA origami structures are not yet fully understood, limiting the potential applications. Here, we conduct a theoretical study with a combination of molecular dynamics, first-principles, and charge transmission calculations. We use four separate single strand DNAs, each having 8 bases (4 × G4C4 and 4 × A4T4), to form two different DNA nanostructures, each having two helices bundled together with one crossover. We also generated double-stranded DNAs to compare electronic properties to decipher the effects of crossovers and bundle formations. We demonstrate that density of states and band gap of DNA origami depend on its sequence and structure. The crossover regions could reduce the conductance due to a lack of available states near the HOMO level. Furthermore, we reveal that, despite having the same sequence, the two helices in the DNA origami structure could exhibit different electronic properties, and electrode position can affect the resulting conductance values. Our study provides better understanding of the electronic properties of DNA origamis and enables us to tune these properties for electronic applications such as nanowires, switches, and logic gates.

Sorption of Soil Carbon Dioxide by Biochar and Engineered Porous Carbons

CO2 is 45 to 50 times more concentrated in soil than in air, resulting in global diffusive fluxes that outpace fossil fuel combustion by an order of magnitude. Despite the scale of soil CO2 emissions, soil-based climate change mitigation strategies are underdeveloped. Existing approaches, such as enhanced weathering and sustainable land management, show promise but continue to face deployment barriers. We introduce an alternative approach: the use of solid adsorbents to directly capture CO2 in soils. Biomass-derived adsorbents could exploit favorable soil CO2 adsorption thermodynamics while also sequestering solid carbon. Despite this potential, previous study of porous carbon CO2 adsorption is mostly limited to single-component measurements and conditions irrelevant to soil. Here, we probe sorption under simplified soil conditions (0.2 to 3% CO2 in balance air at ambient temperature and pressure) and provide physical and chemical characterization data to correlate material properties to sorption performance. We show that minimally engineered pyrogenic carbons exhibit CO2 sorption capacities comparable to or greater than those of advanced sorbent materials. Compared to textural features, sorbent carbon bond morphology substantially influences low-pressure CO2 adsorption. Our findings enhance understanding of gas adsorption on porous carbons and inform the development of effective soil-based climate change mitigation approaches.

Minimizing Structural Heterogeneity in DNA Self-Assembled Dye Templating via DNA Origami-Tuned Conformations

With recent advances in DNA-templated dye aggregation for leveraging and engineering molecular excitons, a need exists for minimizing structural heterogeneity. Holliday Junction complexes (HJ) are commonly used to covalently template dye aggregates on their core; however, the global conformation of HJ is detrimentally dynamic. Here, the global conformation of the HJ is selectively tuned by restricting its position and orientation by using a sheet-like DNA origami construct (DOC) physisorbed on glass. The HJ arms are fixed with four different designed interduplex angles (IDAs). Atomic force microscopy confirmed that the HJs are bound to the surface of DOC with tuned IDAs. Dye orientation distributions were determined by combining dipole imaging and super-resolution microscopy. All IDAs led to dye orientations having dispersed distributions along planes perpendicular to the HJ plane, suggesting that stacking occurred between the dye and the neighboring DNA bases. The dye-base stacking interpretation was supported by increasing the size of the core cavity. The narrowest IDA minimizes structural heterogeneity and suggests dye intercalation. A strong correlation is found between the IDA and the orientation of the dye along the HJ plane. These results show that the HJ imposes restrictions on the dye and that the dye-DNA interactions are always present regardless of global conformation. The implications of our results are discussed for the scalability of dye aggregates using DNA self-assembly. Our methodology provides an avenue for the solid-supported single-molecule characterization of molecular assemblies templated on biomolecules─such as DNA and protein templates involved in light-harvesting and catalysis─with tuned conformations and restricted in position and orientation.

Trace Analysis of C4F7N Insulating Gas Mixtures by Spontaneous Raman Spectroscopy and Gas Chromatography

2,3,3,3-Tetrafluoro-2-(trifluoromethyl) propanenitrile (C4F7N) is being researched as an alternative to sulfur hexafluoride (SF6) for applications in gas-insulated switchgear. We independently assessed the effectiveness of gas chromatography-mass spectrometry (GC-MS) and a novel method of feedback-assisted multipass cavity spontaneous Raman spectroscopy (SRS) for the trace quantification of impurities in C4F7N and its related byproducts. A total of 14 gases were identified with estimated concentrations as low as 20 ppm (ppm) for C3F6 using GC-MS and 7.4 ppm for CH4 using SRS and as high as 500 ppm for CF4 using GC-MS and 1430 ppm for CO using SRS. While GC-MS is highly effective in selectively detecting and quantifying trace contaminants, it necessitates separate detectors for various gases, such as CH4 and H2. SRS succeeded in detecting CF4 and C2F6 at concentrations of 465 and 100 ppm, respectively, and in placing an upper bound of several hundred ppm for the other analytes. Crucially, SRS holds potential for portability-and thus for field applications-in gas-insulated switchgear equipment diagnostics.

Elucidating the Role of Reduction Kinetics in the Phase-Controlled Growth on Preformed Nanocrystal Seeds: A Case Study of Ru

This study demonstrates the crucial role of reduction kinetics in phase-controlled synthesis of noble-metal nanocrystals using Ru nanocrystals as a case study. We found that the reduction kinetics played a more important role than the templating effect from the preformed seed in dictating the crystal structure of the deposited overlayers despite their intertwined effects on successful epitaxial growth. By employing two different polyols, a series of Ru nanocrystals with tunable sizes of 3-7 nm and distinct patterns of crystal phase were synthesized by incorporating different types of Ru seeds. Notably, the use of ethylene glycol and triethylene glycol consistently resulted in the formation of Ru shell in natural hexagonal close-packed (hcp) and metastable face-centered cubic (fcc) phases, respectively, regardless of the size and phase of the seed. Quantitative measurements and theoretical calculations suggested that this trend was a manifestation of the different reduction kinetics associated with the precursor and the chosen polyol, which, in turn, affected the reduction pathway (solution versus surface) and packing sequence of the deposited Ru atoms. This work not only underscores the essential role of reduction kinetics in controlling the packing of atoms and thus the phase taken by Ru nanocrystals but also suggests a potential extension to other noble-metal systems.

Dedoping of Intraband Silver Selenide Colloidal Quantum Dots through Strong Electronic Coupling at Organic/Inorganic Hybrid Interfaces

Colloidal quantum dot (CQD) infrared (IR) photodetectors can be fabricated and operated with larger spectral tunability, fewer limitations in terms of cooling requirements and substrate lattice matching, and at a potentially lower cost than detectors based on traditional bulk materials. Silver selenide (Ag2Se) has emerged as a promising sustainable alternative to current state-of-the-art toxic semiconductors based on lead, cadmium, and mercury operating in the IR. However, an impeding gap in available absorption bandwidth for Ag2Se CQDs exists in the short-wave infrared (SWIR) region due to degenerate doping by the environment, switching the CQDs from intrinsic interband semiconductors in the near-infrared (NIR) to intraband absorbing CQDs in the mid-wave infrared (MWIR). Herein, we show that the small molecular p-type dopant 2,3,5,6-tetrafluoro-7,7,8,8-tetracyanoquinodimethane (F4-TCNQ) can be used to extract electrons from the 1Se state of MWIR active Ag2Se CQDs to activate their intrinsic energy gap in the SWIR window. We demonstrate quenching of the MWIR Ag2Se absorbance peak, shifting of nitrile vibrational peaks characteristic of charge-neutral F4-TCNQ, as well as enhanced CQD absorption around ∼2500 nm after doping both in ambient and under air-free conditions. We elucidate the doping mechanism to be one that involves an integer charge transfer akin to doping in semiconducting polymers. These indications of charge transfer are promising milestones on the path to achieving sustainable SWIR Ag2Se CQD photodetectors.

CTC-Race: Single-Cell Motility Assay of Circulating Tumor Cells from Metastatic Lung Cancer Patients

Distinctive subpopulations of circulating tumor cells (CTCs) with increased motility are considered to possess enhanced tumor-initiating potential and contribute to metastasis. Single-cell analysis of the migratory CTCs may increase our understanding of the metastatic process, yet most studies are limited by technical challenges associated with the isolation and characterization of these cells due to their extreme scarcity and heterogeneity. We report a microfluidic method based on CTCs' chemotactic motility, termed as CTC-Race assay, that can analyze migrating CTCs from metastatic non-small-cell lung cancer (NSCLC) patients with advanced tumor stages and enable concurrent biophysical and biochemical characterization of them with single-cell resolution. Analyses of motile CTCs in the CTC-Race assay, in synergy with other single cell characterization techniques, could provide insights into cancer metastasis.

Mitigating Illumination-, Leaf-, and View-Angle Dependencies in Hyperspectral Imaging Using Polarimetry

Automation of plant phenotyping using data from high-dimensional imaging sensors is on the forefront of agricultural research for its potential to improve seasonal yield by monitoring crop health and accelerating breeding programs. A common challenge when capturing images in the field relates to the spectral reflection of sunlight (glare) from crop leaves that, at certain solar incidences and sensor viewing angles, presents unwanted signals. The research presented here involves the convergence of 2 parallel projects to develop a facile algorithm that can use polarization data to decouple light reflected from the surface of the leaves and light scattered from the leaf's tissue. The first project is a mast-mounted hyperspectral imaging polarimeter (HIP) that can image a maize field across multiple diurnal cycles throughout a growing season. The second project is a multistatic fiber-based Mueller matrix bidirectional reflectance distribution function (mmBRDF) instrument which measures the polarized light-scattering behavior of individual maize leaves. The mmBRDF data was fitted to an existing model, which outputs parameters that were used to run simulations. The simulated data were then used to train a shallow neural network which works by comparing unpolarized 2-band vegetation index (VI) with linearly polarized data from the low-reflectivity bands of the VI. Using GNDVI and red-edge reflection ratio we saw an improvement of an order of magnitude or more in the mean error (ϵ) and a reduction spanning 1.5 to 2.7 in their standard deviation (ϵσ) after applying the correction network on the HIP sensor data.

Long-Term Robustness and Failure Mechanisms of Electrochemical Stripping for Wastewater Ammonia Recovery

Nitrogen in wastewater has negative environmental, human health, and economic impacts but can be recovered to reduce the costs and environmental impacts of wastewater treatment and chemical production. To recover ammonia/ammonium (total ammonia nitrogen, TAN) from urine, we operated electrochemical stripping (ECS) for over a month, achieving 83.4 ± 1.5% TAN removal and 73.0 ± 2.9% TAN recovery. With two reactors, we recovered sixteen 500-mL batches (8 L total) of ammonium sulfate (20.9 g/L TAN) approaching commercial fertilizer concentrations (28.4 g/L TAN) and often having >95% purity. While evaluating the operation and maintenance needs, we identified pH, full-cell voltage, product volume, and water flux into the product as informative process monitoring parameters that can be inexpensively and rapidly measured. Characterization of fouled cation exchange and omniphobic membranes informs cleaning and reactor modifications to reduce fouling with organics and calcium/magnesium salts. To evaluate the impact of urine collection and storage on ECS, we conducted experiments with urine at different levels of dilution with flush water, extents of divalent cation precipitation, and degrees of hydrolysis. ECS effectively treated urine under all conditions, but minimizing flush water and ensuring storage until complete hydrolysis would enable energy-efficient TAN recovery. Our experimental results and cost analysis motivate a multifaceted approach to improving ECS's technical and economic viability by extending component lifetimes, decreasing component costs, and reducing energy consumption through material, reactor, and process engineering. In summary, we demonstrated urine treatment as a foothold for electrochemical nutrient recovery from wastewater while supporting the applicability of ECS to seven other wastewaters with widely varying characteristics. Our findings will facilitate the scale-up and deployment of electrochemical nutrient recovery technologies, enabling a circular nitrogen economy that fosters sanitation provision, efficient chemical production, and water resource protection.

Conformational Preference of Lithium Polysulfide Clusters Li2Sx (x = 4-8) in Lithium-Sulfur Batteries

Structures are of fundamental importance for diverse studies of lithium polysulfide clusters, which govern the performance of lithium-sulfur batteries. The ring-like geometries were regarded as the most stable structures, but their physical origin remains elusive. In this work, we systematically explored the minimal structures of Li2Sx (x = 4-8) clusters to uncover the driving force for their conformational preferences. All low-lying isomers were generated by performing global searches using the ABCluster program, and the ionic nature of the Li···S interactions was evidenced with the energy decomposition analysis based on the block-localized wave function (BLW-ED) approach and further confirmed with the quantum theory of atoms in molecule (QTAIM). By analysis of the contributions of various energy components to the relative stability with the references of the lowest-lying isomers, the controlling factor for isomer preferences was found to be the polarization interaction. Notably, although the electrostatic interaction dominates the binding energies, it contributes favorably to the relative stabilities of most isomers. The Li+···Li+ distance is identified as the key geometrical parameter that correlates with the strength of the polarization of the Sx2- fragment imposed by the Li+ cations. Further BLW-ED analyses reveal that the cooperativity of the Li+ cations primarily determines the relative strength of the polarization.

Efficient Raman Lasing and Raman-Kerr Interaction in an Integrated Silicon Carbide Platform

Implementing stimulated Raman scattering in a low-loss microresonator could lead to Raman lasing. Here, we report the demonstration of an efficient Raman laser with >50% power efficiency in an integrated silicon carbide platform for the first time. By fine-tuning the free spectral range (FSR) of 43 μm-radius silicon carbide microresonators, the Stokes resonance corresponding to the dominant Raman shift of 777 cm-1 (23.3 THz) is aligned to the center of the Raman gain spectrum, resulting in a low power threshold of 2.5 mW. The peak Raman gain coefficient is estimated to be (0.75 ± 0.15) cm/GW in the 1550 nm band, with an approximate full width at half-maximum of (120 ± 30) GHz. In addition, the microresonator is designed to exhibit normal dispersion at the pump wavelength near 1550 nm while possessing anomalous dispersion at the first Stokes near 1760 nm. At high enough input powers, a Kerr microcomb is generated by the Stokes signal acting as the secondary pump, which then mixes with the pump laser through four-wave mixing to attain a wider spectral coverage. Furthermore, cascaded Raman lasing and the occurrence of multiple Raman shifts, including 204 cm-1 (6.1 THz) and 266 cm-1 (8.0 THz) transitions, are also observed. Finally, we show that the Stokes Raman could also help broaden the spectrum in a Kerr microcomb which has anomalous dispersion at the pump wavelength. Our example of a 100 GHz-FSR microcomb has a wavelength span from 1200 to 1900 nm with 300 mW on-chip power.

Uniaxial Strain-Induced Stacking Order Change in Trilayer Graphene

The layer stacking order in two-dimensional heterostructures, like graphene, affects their physical properties and potential applications. Trilayer graphene, specifically ABC-trilayer graphene, has captured significant interest due to its potential for correlated electronic states. However, achieving a stable ABC arrangement is challenging due to its lower thermodynamic stability compared to the more stable ABA stacking. Despite recent advancements in obtaining ABC graphene through external perturbations, such as strain, the stacking transition mechanism remains insufficiently explored. In this study, we unveil a universal mechanism to achieve ABC stacking, applicable for understanding ABA to ABC stacking changes induced by any mechanical perturbations. Our approach is based on a novel strain engineering technique that induces interlayer slippage and results in the formation of stable ABC domains. We investigate the underlying interfacial mechanisms of this stacking change through computational simulations and experiments. Our findings demonstrate a highly anisotropic and significant transformation of ABA stacking to large and stable ABC domains facilitated by interlayer slippage. Through atomistic simulations and local energy analysis, we systematically demonstrate the mechanism for this stacking transition, that is dependent on specific loading orientation. Understanding such a mechanism allows this material system to be engineered by design compatible with industrial techniques on a device-by-device level. We conduct Raman studies to validate and characterize the formed ABC stacking, highlighting its distinct features compared to the ABA region. Our results contribute to a clearer understanding of the stacking change mechanism and provide a robust and controllable method for achieving stable ABC domains, facilitating their use in developing advanced optoelectronic devices.

Rh@Au Core-Shell Nanocrystals with the Core in Tensile Strain and the Shell in Compressive Strain

Bimetallic nanocrystals provide a versatile platform for utilizing the desired characteristics of two different elements within one particle. Core-shell nanocrystals, in particular, have found widespread use in catalysis by providing an ability to leverage the strains arising from the lattice mismatch between the core and the shell. However, large (>5%) lattice mismatch tends to result in nonepitaxial growth and lattice defects in an effort to release the strain. Herein, we report the epitaxial growth of Au on Rh cubic seeds under mild reaction conditions to generate Rh@Au truncated octahedra featuring a lattice mismatch of 7.2%. Key to the success was the use of small (4.5 nm) Rh cubes as seeds, which could homogeneously distribute the tensile strain arising from the epitaxial growth of a conformal, compressively strained Au shell. Further, delicate tuning of kinetic parameters through the introduction of NaOH and KBr into the synthesis allowed for a unique nucleation pattern that led to centrally located cores and a narrow size distribution for the product. A thorough investigation of the various possible highly strained morphologies was conducted to gain a full understanding of the system.

Cold Temperature Direct Air CO2 Capture with Amine-Loaded Metal-Organic Framework Monoliths

Zeolites, silica-supported amines, and metal-organic frameworks (MOFs) have been demonstrated as promising adsorbents for direct air CO2 capture (DAC), but the shaping and structuring of these materials into sorbent modules for practical processes have been inadequately investigated compared to the extensive research on powder materials. Furthermore, there have been relatively few studies reporting the DAC performance of sorbent contactors under cold, subambient conditions (temperatures below 20 °C). In this work, we demonstrate the successful fabrication of adsorbent monoliths composed of cellulose acetate (CA) and adsorbent particles such as zeolite 13X and MOF MIL-101(Cr) by a 3D printing technique: solution-based additive manufacturing (SBAM). These monoliths feature interpenetrated macroporous polymeric frameworks in which microcrystals of zeolite 13X or MIL-101(Cr) are evenly distributed, highlighting the versatility of SBAM in fabricating monoliths containing sorbents with different particle sizes and density. Branched poly(ethylenimine) (PEI) is successfully loaded into the CA/MIL-101(Cr) monoliths to impart CO2 uptakes of 1.05 mmol gmonolith-1 at -20 °C and 400 ppm of CO2. Kinetic analysis shows that the CO2 sorption kinetics of PEI-loaded MIL-101(Cr) sorbents are not compromised in the monoliths compared to the powder sorbents. Importantly, these monoliths exhibit promising working capacities (0.95 mmol gmonolith-1) over 14 temperature swing cycles with a moderate regeneration temperature of 60 °C. Dynamic breakthrough experiments at 25 °C under dry conditions reveal a CO2 uptake capacity of 0.60 mmol gmonolith-1, which further increases to 1.05 and 1.43 mmol gmonolith-1 at -20 °C under dry and humid (70% relative humidity) conditions, respectively. Our work showcases the successful implementation of SBAM in making DAC sorbent monoliths with notable CO2 capture performance over a wide range of sorption temperatures, suggesting that SBAM can enable the preparation of efficient sorbent contactors in various form factors for other important chemical separations.

Local Control of a Single Nitrogen-Vacancy Center by Nanoscale Engineered Magnetic Domain Wall Motion

Effective control and readout of qubits form the technical foundation of next-generation, transformative quantum information sciences and technologies. The nitrogen-vacancy (NV) center, an intrinsic three-level spin system, is naturally relevant in this context due to its excellent quantum coherence, high fidelity of operations, and remarkable functionality over a broad range of experimental conditions. It is an active contender for the development and implementation of cutting-edge quantum technologies. Here, we report magnetic domain wall motion driven local control and measurements of the NV spin properties. By engineering the local magnetic field environment of an NV center via nanoscale reconfigurable domain wall motion, we show that NV photoluminescence, spin level energies, and coherence time can be reliably controlled and correlated to the magneto-transport response of a magnetic device. Our results highlight the electrically tunable dipole interaction between NV centers and nanoscale magnetic structures, providing an attractive platform to realize interactive information transfer between spin qubits and nonvolatile magnetic memory in hybrid quantum spintronic systems.

Effect of Acidity on Ice Nucleation by Inorganic-Organic Mixed Droplets

Aerosol acidity significantly influences heterogeneous chemical reactions and human health. Additionally, acidity may play a role in cloud formation by modifying the ice nucleation properties of inorganic and organic aerosols. In this work, we combined our well-established ice nucleation technique with Raman microspectroscopy to study ice nucleation in representative inorganic and organic aerosols across a range of pH conditions (pH -0.1 to 5.5). Homogeneous nucleation was observed in systems containing ammonium sulfate, sulfuric acid, and sucrose. In contrast, droplets containing ammonium sulfate mixed with diethyl sebacate, poly(ethylene glycol) 400, and 1,2,6-hexanetriol were found to undergo liquid-liquid phase separation, exhibiting core-shell morphologies with observed initiation of heterogeneous freezing in the cores. Our experimental findings demonstrate that an increased acidity reduces the ice nucleation ability of droplets. Changes in the ratio of bisulfate to sulfate coincided with shifts in ice nucleation temperatures, suggesting that the presence of bisulfate may decrease the ice nucleation efficiency. We also report on how the morphology and viscosity impact ice nucleation properties. This study aims to enhance our fundamental understanding of acidity's effect on ice nucleation ability, providing context for the role of acidity in atmospheric ice cloud formation.

Designing Metasurfaces for Efficient Solar Energy Conversion

Metasurfaces have recently emerged as a promising technological platform, offering unprecedented control over light by structuring materials at the nanoscale using two-dimensional arrays of subwavelength nanoresonators. These metasurfaces possess exceptional optical properties, enabling a wide variety of applications in imaging, sensing, telecommunication, and energy-related fields. One significant advantage of metasurfaces lies in their ability to manipulate the optical spectrum by precisely engineering the geometry and material composition of the nanoresonators' array. Consequently, they hold tremendous potential for efficient solar light harvesting and conversion. In this Review, we delve into the current state-of-the-art in solar energy conversion devices based on metasurfaces. First, we provide an overview of the fundamental processes involved in solar energy conversion, alongside an introduction to the primary classes of metasurfaces, namely, plasmonic and dielectric metasurfaces. Subsequently, we explore the numerical tools used that guide the design of metasurfaces, focusing particularly on inverse design methods that facilitate an optimized optical response. To showcase the practical applications of metasurfaces, we present selected examples across various domains such as photovoltaics, photoelectrochemistry, photocatalysis, solar-thermal and photothermal routes, and radiative cooling. These examples highlight the ways in which metasurfaces can be leveraged to harness solar energy effectively. By tailoring the optical properties of metasurfaces, significant advancements can be expected in solar energy harvesting technologies, offering new practical solutions to support an emerging sustainable society.

Electrode Effect on Ferroelectricity in Free-Standing Membranes of PbZr0.2Ti0.8O3

We report the effects of screening capacity, surface roughness, and interfacial epitaxy of the bottom electrodes on the polarization switching, domain wall (DW) roughness, and ferroelectric Curie temperature (TC) of PbZr0.2Ti0.8O3 (PZT)-based free-standing membranes. Singe crystalline 10-50 nm (001) PZT and PZT/La0.67Sr0.33MnO3 (LSMO) membranes are prepared on Au, correlated oxide LSMO, and two-dimensional (2D) semiconductor MoS2 base layers. Switching the polarization of PZT yields nonvolatile current modulation in the MoS2 channel at room temperature, with an on/off ratio of up to 2 × 105 and no apparent decay for more than 3 days. Piezoresponse force microscopy studies show that the coercive field Ec for the PZT membranes varies from 0.75 to 3.0 MV cm-1 on different base layers and exhibits strong polarization asymmetry. The PZT/LSMO membranes exhibit significantly smaller Ec, with the samples transferred on LSMO showing symmetric Ec of about -0.26/+0.28 MV cm-1, smaller than that of epitaxial PZT films. The DW roughness exponent ζ points to 2D random bond disorder dominated DW roughening (ζ = 0.31) at room temperature. Upon thermal quench at progressively higher temperatures, ζ values for PZT membranes on Au and LSMO approach the theoretical value for 1D random bond disorder (ζ = 2/3), while samples on MoS2 exhibits thermal roughening (ζ = 1/2). The PZT membranes on Au, LSMO, and MoS2 show TC of about 763 ± 12, 725 ± 25, and 588 ± 12 °C, respectively, well exceeding the bulk value. Our study reveals the complex interplay between the electrostatic and mechanical boundary conditions in determining ferroelectricity in free-standing PZT membranes, providing important material parameters for the functional design of PZT-based flexible nanoelectronics.

Insight into the Isoreticularity of Li-MOFs for the Design of Low-Density Solid and Quasi-Solid Electrolytes

Isoreticularity in metal organic frameworks (MOFs) allows the design of the framework structure and tailoring the pore aperture at the molecular level. The optimal pore volume, long-range order of framework expansion, and crystallite size (grain size) could enable improving Li-ion conduction, thereby providing a unique opportunity to design high-performance solid and quasi-solid electrolytes. However, definitive understanding of the pore aperture, framework expansion, and crystallite size on the Li-ion conduction and its mechanism in MOFs remains at the exploratory stage. Among the different MOF subfamilies, Li-MOFs created by the isoreticular framework expansion using dicarboxylates of benzene, naphthalene, and biphenyl building blocks emerge as low-density porous solids with exceptional thermal stability to study the solid-state Li+ transport mechanisms. Herein, we report the subtle effect of the isoreticularity in Li-MOFs on the performance of solid and quasi-solid-state Li+ conduction, providing new insight into Li+ transport mechanisms in MOFs for the first time. Our experimental and computational results show that the reticular design on an isostructural extended framework structure with the optimal pore aperture and crystallite size can influence the Li+ conductivity, exhibiting comparable ionic conductivities to solid polymer electrolytes at room temperature. Aligning with the computational studies, our experimental absorption spectral traces of solid electrolytes prepared by encapsulating lithium salt (LiClO4) and the plasticizer (ethylene carbonate) with Li-MOFs confirm the participation of the free and bound states of Li+ in a pore filling-driven ion conduction mechanism. We postulate that porous channels of Li-MOFs aid free Li+ to move through the pores via a vehicle-type mechanism, in which the pore-filled plasticizer acts as a carrier for mobile Li+ while the framework's functional sites transport the bound state of Li+ via an ion hopping mechanism from one crystallite site to another. Our computational studies performed on the Li+ conduction pathway validated the postulated pore filling mechanism and confirmed the involvement of bridging complexes, formed by binding Li+ onto the framework's functional sites as well as to the pore-filled ethylene carbonates. The Li+ diffusion energy barrier profiles along with the respective conformational changes during the diffusion of Li+ in solid electrolytes prepared from Li-BDC MOF and Li-NDC MOF strongly support the cooperative movement of Li+ ions via ion hopping along the framework's edges and vehicle-type transfer, involving the pore-filled plasticizer. Our findings suggest that cooperative function of the optimal pore volume, framework expansion, and crystallite size play a unique role in Li-ion conduction, thereby providing design guidelines for the low-density solid and quasi-solid electrolytes.

Synthesis, Characterization, and Magnetic Properties of Lanthanide-Containing Paramagnetic Ionic Liquids: An Evan's NMR Study

The present study focuses on the synthesis and characterization of lanthanide-containing paramagnetic ionic liquids (ILs), [CnC1Im]3[MCl3X3] (n = 4, 6, and 8; M = Gd, Dy, and Ho; X = Br and Cl), derived from 1-alkyl-3-methylimidazolium anions. These paramagnetic ILs exhibit low vapor pressure, high thermal stability, physiochemical stability, and tunability, along with significant magnetic susceptibility, making them of interest in advanced material applications that may take advantage of neat liquids with magnetic susceptibility. Structural and physical properties were determined using FTIR, 1H NMR, DSC, and TGA. The room temperature density and viscosity of the iron paramagnetic ILs were also reported. Accompanying this report of paramagnetic IL products, we reintroduce and highlight Evan's NMR technique, an accessible magnetic susceptibility measurement technique that can utilize any available proton NMR to characterize the magnetic susceptibility of ILs. This work demonstrates the robustness of Evan's technique by demonstrating the ability to account for the IL water content, a common issue for hygroscopic materials, during the measurement of magnetic susceptibility. A detailed comparison of the ILs is presented, with dysprosium- and holmium-containing paramagnetic ILs exhibiting the highest magnetic susceptibility reported for mononuclear ILs reported to date. These materials have been studied with an eye on applications for mass transfer, eventually seeking to optimize magnetic susceptibility and viscosity using magnetic field gradients to move paramagnetic ILs carrying solute or heat. The study of paramagnetic ILs is important not only for understanding the magnetic properties of these materials but also for potential applications in areas such as magnetic resonance imaging, biomedicine, environmental remediation, and mass transfer. These unique materials have the potential to bring about new advances and technologies in the fields of materials science and analytical chemistry.

New Horizons in Near-Zero Refractive Index Photonics and Hyperbolic Metamaterials

The engineering of the spatial and temporal properties of both the electric permittivity and the refractive index of materials is at the core of photonics. When vanishing to zero, those two variables provide efficient knobs to control light-matter interactions. This Perspective aims at providing an overview of the state of the art and the challenges in emerging research areas where the use of near-zero refractive index and hyperbolic metamaterials is pivotal, in particular, light and thermal emission, nonlinear optics, sensing applications, and time-varying photonics.

Time-Resolved Mid-Infrared Photothermal Microscopy for Imaging Water-Embedded Axon Bundles

Few experimental tools exist for performing label-free imaging of biological samples in a water-rich environment due to the high infrared absorption of water, overlapping with major protein and lipid bands. A novel imaging modality based on time-resolved mid-infrared photothermal microscopy is introduced and applied to imaging axon bundles in a saline bath environment. Photothermally induced spatial gradients at the axon bundle membrane interfaces with saline and surrounding biological tissue are observed and temporally characterized by a high-speed boxcar detection system. Localized time profiles with an enhanced signal-to-noise, hyper-temporal image stacks, and two-dimensional mapping of the time decay profiles are acquired without the need for complex post image processing. Axon bundles are found to have a larger distribution of time decay profiles compared to the water background, allowing background differentiation based on these transient dynamics. The quantitative analysis of the signal evolution over time allows characterizing the level of thermal confinement at different regions. When axon bundles are surrounded by complex heterogeneous tissue, which contains smaller features, a stronger thermal confinement is observed compared to a water environment, thus shedding light on the heat transfer dynamics across aqueous biological interfaces.

Self-Assembled Au Nanoelectrodes: Enabling Low-Threshold-Voltage HfO2-Based Artificial Neurons

Filamentary-type resistive switching devices, such as conductive bridge random-access memory and valence change memory, have diverse applications in memory and neuromorphic computing. However, the randomness in filament formation poses challenges to device reliability and uniformity. To overcome this issue, various defect engineering methods have been explored, including doping, metal nanoparticle embedding, and extended defect utilization. In this study, we present a simple and effective approach using self-assembled uniform Au nanoelectrodes to controll filament formation in HfO2 resistive switching devices. By concentrating the electric field near the Au nanoelectrodes within the BaTiO3 matrix, we significantly enhanced the device stability and reduced the threshold voltage by up to 45% in HfO2-based artificial neurons compared to the control devices. The threshold voltage reduction is attributed to the uniformly distributed Au nanoelectrodes in the insulating matrix, as confirmed by COMSOL simulation. Our findings highlight the potential of nanostructure design for precise control of filamentary-type resistive switching devices.

Time-Resolved Temperature Mapping Leveraging the Strong Thermo-Optic Effect in Phase-Change Materials

Optical phase-change materials are highly promising for emerging applications such as tunable metasurfaces, reconfigurable photonic circuits, and non-von Neumann computing. However, these materials typically require both high melting temperatures and fast quenching rates to reversibly switch between their crystalline and amorphous phases: a significant challenge for large-scale integration. In this work, we use temperature-dependent ellipsometry to study the thermo-optic effect in GST and use these results to demonstrate an experimental technique that leverages the thermo-optic effect in GST to enable both spatial and temporal thermal measurements of two common electro-thermal microheater designs currently used by the phase-change community. Our approach shows excellent agreement between experimental results and numerical simulations and provides a noninvasive method for rapid characterization of electrically programmable phase-change devices.

Molecular van der Waals Fluids in Cavity Quantum Electrodynamics

Intermolecular van der Waals interactions are central to chemical and physical phenomena ranging from biomolecule binding to soft-matter phase transitions. In this work, we demonstrate that strong light-matter coupling can be used to control the thermodynamic properties of many-molecule systems. Our analyses reveal orientation dependent single molecule energies and interaction energies for van der Waals molecules. For example, we find intermolecular interactions that depend on the distance between the molecules R as R-3 and R0. Moreover, we employ ab initio cavity quantum electrodynamics calculations to develop machine-learning-based interaction potentials for molecules inside optical cavities. By simulating systems ranging from 12 H2 to 144 H2 molecules, we observe varying degrees of orientational order because of cavity-modified interactions, and we explain how quantum nuclear effects, light-matter coupling strengths, number of cavity modes, molecular anisotropies, and system size all impact the extent of orientational order.

Resonant Anti-Reflection Metasurfaces for Infrared Transmission Optics

A fundamental capability needed for any transmissive optical component is anti-reflection, yet this capability can be challenging to achieve in a cost-effective manner over longer infrared wavelengths. We demonstrate that Mie-resonant photonic structures can enable high transmission through a high-index optical component, allowing it to function effectively over long-wavelength infrared wavelengths. Using silicon as a model system, we demonstrate a resonant metasurface that enables a window optic with transmission up to 40% greater than that of unpatterned Si. Imaging comparisons with unpatterned Si and off-the-shelf germanium optics are shown as well as modulation transfer function measurements, showing excellent performance and suitability for imaging applications. Our results show how resonant photonic structures can be used to improve optical transmission through high-index optical components and highlight their possible use in infrared imaging applications.

Trainable Bilingual Synaptic Functions in Bio-enabled Synaptic Transistors

The signal transmission of the nervous system is regulated by neurotransmitters. Depending on the type of neurotransmitter released by presynaptic neurons, neuron cells can either be excited or inhibited. Maintaining a balance between excitatory and inhibitory synaptic responses is crucial for the nervous system's versatility, elasticity, and ability to perform parallel computing. On the way to mimic the brain's versatility and plasticity traits, creating a preprogrammed balance between excitatory and inhibitory responses is required. Despite substantial efforts to investigate the balancing of the nervous system, a complex circuit configuration has been suggested to simulate the interaction between excitatory and inhibitory synapses. As a meaningful approach, an optoelectronic synapse for balancing the excitatory and inhibitory responses assisted by light mediation is proposed here by deploying humidity-sensitive chiral nematic phases of known polysaccharide cellulose nanocrystals. The environment-induced pitch tuning changes the polarization of the helicoidal organization, affording different hysteresis effects with the subsequent excitatory and inhibitory nonvolatile behavior in the bio-electrolyte-gated transistors. By applying voltage pulses combined with stimulation of chiral light, the artificial optoelectronic synapse tunes not only synaptic functions but also learning pathways and color recognition. These multifunctional bio-based synaptic field-effect transistors exhibit potential for enhanced parallel neuromorphic computing and robot vision technology.

Quantification of Particle Filtration Using a Quartz Crystal Microbalance Embedded in a Microfluidic Channel

To quantify colloidal filtration, a quartz crystal microbalance (QCM) with a silicon dioxide surface is embedded on the inner surface of a microfluidic channel to monitor the real-time particle deposition. Potassium chloride solution with micrometer-size polystyrene particles simulating bacterial strains flows down the channel. In the presence of intrinsic Derjaguin-Landau-Verwey-Overbeek (DLVO) intersurface forces, particles are trapped by the quartz surfaces, and the increased mass shifts the QCM resonance frequency. The method provides an alternative way to measure filtration efficiency in an optically opaque channel and its dependence on the ionic concentration.

Enabling High Precision Gradient Index Control in Subsurface Multiphoton Lithography

Multiphoton lithography inside a mesoporous host can create optical components with continuously tunable refractive indices in three-dimensional (3D) space. However, the process is very sensitive at exposure doses near the photoresist threshold, leading previous work to reliably achieve only a fraction of the available refractive index range for a given material system. Here, we present a method for greatly enhancing the uniformity of the subsurface micro-optics, increasing the reliable index range from 0.12 (in prior work) to 0.37 and decreasing the standard deviation (SD) at threshold from 0.13 to 0.0021. Three modifications to the previous method enable higher uniformity in all three spatial dimensions: (1) calibrating the planar write field of mirror galvanometers using a spatially varying optical transmission function which corrects for large-scale optical aberrations; (2) periodically relocating the piezoelectrically driven stage, termed piezo-galvo dithering, to reduce small-scale errors in writing; and (3) enforcing a constant time between each lateral cross section to reduce variation across all writing depths. With this new method, accurate fabrication of optics of any index between n = 1.20 and 1.57 (SD < 0.012 across the full range) was achieved inside a volume of porous silica. We demonstrate the importance of this increased accuracy and precision by fabricating and characterizing calibrated two-dimensional (2D) line gratings and flat gradient index lenses with significantly better performance than the corresponding control devices. As a visual representation, the University of Illinois logo made with 2D line gratings shows significant improvement in its color uniformity across its width.

Understanding the Catalytic Active Sites of Crystalline CoSbxOy for Electrochemical Chlorine Evolution

The chlorine evolution reaction (CER) is a key reaction in electrochemical oxidation (EO) of water treatment. Conventional anodes based on platinum group metals can be prohibitively expensive, which hinders further application of EO systems. Crystalline cobalt antimonate (CoSbxOy) was recently identified as a promising alternative to conventional anodes due to its high catalytic activity and stability in acidic media. However, its catalytic sites and reaction mechanism have not yet been elucidated. This study sheds light on the catalytically active sites in crystalline CoSbxOy anodes by using scanning electrochemical microscopy to compare the CER catalytic activities of a series of anode samples with different bulk Sb/Co ratios (from 1.43 to 2.80). The results showed that Sb sites served as more active catalytic sites than the Co sites. The varied Sb/Co ratios were also linked with slightly different electronic states of each element, leading to different CER selectivities in 30 mM chloride solutions under 10 mA cm-2 current density. The high activity of Sb sites toward the CER highlighted the significance of the electronic polarization that changed the oxidation states of Co and Sb.

Incorporation of Chiral Frustrated Lewis Pair into Metal-Organic Framework with Tailored Microenvironment for Heterogeneous Enantio- and Chemoselective Hydrogenation

The development of efficient heterogeneous catalysts with multiselectivity (e.g., enantio- and chemoselectivity) has long been sought after but with limited progress being made so far. To achieve enantio- and chemoselectivity in a heterogeneous system, as inspired by enzymes, we illustrate herein an approach of creating an enzyme-mimic region (EMR) within the nanospace of a metal-organic framework (MOF) as exemplified in the context of incorporating a chiral frustrated Lewis pair (CFLP) into a MOF with a tailored pore environment. Due to the high density of the EMR featuring the active site of CFLP and auxiliary sites of the hydroxyl group/open metal site within the vicinity of CFLP, the resultant EMR@MOF demonstrated excellent catalysis performance in heterogeneous hydrogenation of α,β-unsaturated imines to afford chiral β-unsaturated amines with high yields and high enantio- and chemoselectivity. The role of the hydroxyl group/open metal site in regulating chemoselectivity was proved by the observation of a catalyst-substrate interaction experimentally, which was also rationalized by computational results. This work not only contributes a MOF as a new platform for multiselective catalysis but also opens a promising avenue to develop heterogeneous catalysts with multiselectivity for challenging yet important transformations.

Tuning Ionic Conductivity in Fluorite Gd-Doped CeO2-Bixbyite RE2O3 (RE = Y and Sm) Multilayer Thin Films by Controlling Interfacial Strain

Interfacial strain in heteroepitaxial oxide thin films is a powerful tool for discovering properties and recognizing the potential of materials performance. Particularly, facilitating ion conduction by interfacial strain in oxide multilayer thin films has always been seen to be a highly promising route to this goal. However, the effect of interfacial strain on ion transport properties is still controversial due to the difficulty in deconvoluting the strain contribution from other interfacial phenomena, such as space charge effects. Here, we show that interfacial strain can effectively tune the ionic conductivity by successfully growing multilayer thin films composed of an ionic conductor Gd-doped CeO2 (GDC) and an insulator RE2O3 (RE = Y and Sm). In contrast to compressively strained GDC-Y2O3 multilayer films, tensile strained GDC-Sm2O3 multilayer films demonstrate the enhanced ionic conductivity of GDC, which is attributed to the increased concentration of oxygen vacancies. In addition, we demonstrate that increasing the number of interfaces has no impact on the further enhancement of the ionic conductivity in GDC-Sm2O3 multilayer films. Our findings demonstrate the unambiguous role of interfacial strain on ion conduction of oxides and provide insights into the rational design of fast ion conductors through interface engineering.

Increased Crystal Field Drives Intermediate Coupling and Minimizes Decoherence in Tetravalent Praseodymium Qubits

Crystal field (CF) control of rare-earth (RE) ions has been employed to minimize decoherence in qubits and to enhance the effective barrier of single-molecule magnets. The CF approach has been focused on the effects of symmetry on dynamic magnetic properties. Herein, the magnitude of the CF is increased via control of the RE oxidation state. The enhanced 4f metal-ligand covalency in Pr4+ gives rise to CF energy scales that compete with the spin-orbit coupling of Pr4+ and thereby shifts the paradigm from the ionic ζSOC ≫ VCF limit, used to describe trivalent RE-ion, to an intermediate coupling (IC) regime. We examine Pr4+-doped perovskite oxide lattices (BaSnO3 and BaZrO3). These systems are defined by IC which quenches orbital angular momentum. Therefore, the single-ion spin-orbit coupled states in Pr4+ can be chemically tuned. We demonstrate a relatively large hyperfine interaction of Aiso = 1800 MHz for Pr4+, coherent manipulation of the spin with QM = 2ΩRTm, reaching up to ∼400 for 0.1Pr:BSO at T = 5 K, and significant improvement of the temperature at which Tm is limited by T1 (T* = 60 K) compared to other RE ion qubits.

Effect of Dust and Hot Spots on the Thermal Stability of Laser Sails

Laser sails propelled by gigawatt-scale ground-based laser arrays have the potential to reach relativistic speeds, traversing the solar system in hours and reaching nearby stars in years. Here, we describe the danger interplanetary dust poses to the survival of a laser sail during its acceleration phase. We show through multiphysics simulations how localized heating from a single optically absorbing dust particle on the sail can initiate a thermal runaway process that rapidly spreads and destroys the entire sail. We explore potential mitigation strategies, including increasing the in-plane thermal conductivity of the sail to reduce the peak temperature at hot spots and isolating the absorptive regions of the sail that can burn away individually.

Deep Learning-Based Prediction of Contact Maps and Crystal Structures of Inorganic Materials

Crystal structure prediction is one of the major unsolved problems in materials science. Traditionally, this problem is formulated as a global optimization problem for which global search algorithms are combined with first-principles free energy calculations to predict the ground-state crystal structure of a given material composition. These ab initio algorithms are currently too slow for predicting complex material structures. Inspired by the AlphaFold algorithm for protein structure prediction, herein, we propose AlphaCrystal, a crystal structure prediction algorithm that combines a deep residual neural network model for predicting the atomic contact map of a target material followed by three-dimensional (3D) structure reconstruction using genetic algorithms. Extensive experiments on 20 benchmark structures showed that our AlphaCrystal algorithm can predict structures close to the ground truth structures, which can significantly speed up the crystal structure prediction and handle relatively large systems.

Optical engineering of PbS colloidal quantum dot solar cells via Fabry-Perot resonance and distributed Bragg reflectors

A tradeoff between light absorption and charge transport is a well-known issue in PbS colloidal quantum dot (CQD) solar cells because the carrier diffusion length in PbS CQD films is comparable to the thickness of CQD film. We reduce the tradeoff between light absorption and charge transport by combining a Fabry-Perot (FP) resonator and a distributed Bragg reflector (DBR). A FP resonance is formed between the DBR and a dielectric-metal-dielectric film as a top transparent electrode. A SiO₂-TiO₂ multilayer is used to form a DBR. The FP resonance enhances light absorption near the resonant wavelength of the DBR without changing the CQD film thickness. The light absorption near the FP resonance wavelength is further boosted by coupling the FP resonance with the high reflectivity of the Ag-coated DBR. When the FP resonance and DBR are combined, the power conversion efficiency (PCE) of PbS CQD solar cells increases by 54%. Moreover, the DBR assisted FP resonance enables a very thin PbS layer to absorb near infrared light four times more. The overall PCE of the thin PbS CQD solar cell increases by 24% without sacrificing the average visible transmittance (AVT). Our results show how to overcome the inherence problem of the CQD and develop a semi-transparent solar cell where the wavelength-selective absorption and the transparency for visible light are important.

Non-Markovian Hole Excess Noise in Avalanche Amorphous Selenium Thin Films

Enhancing the signal-to-noise ratio in avalanche photodiodes by utilizing impact ionization gain requires materials exhibiting low excess noise factors. Amorphous selenium (a-Se) as a wide bandgap at ∼2.1 eV, a solid-state avalanche layer, demonstrates single-carrier hole impact ionization gain and manifests ultralow thermal generation rates. A comprehensive study of the history dependent and non-Markovian nature of hot hole transport in a-Se was modeled using a Monte Carlo (MC) random walk of single hole free flights, interrupted by instantaneous phonon, disorder, hole-dipole, and impact-ionization scattering interactions. The hole excess noise factors were simulated for 0.1-15 μm a-Se thin-films as a function of mean avalanche gain. The hole excess noise factors in a-Se decreases with an increase in electric field, impact ionization gain, and device thickness. The history dependent nature of branching of holes is explained using a Gaussian avalanche threshold distance distribution and the dead space distance, which increases determinism in the stochastic impact ionization process. An ultralow non-Markovian excess noise factor of ∼1 was simulated for 100 nm a-Se thin films corresponding to avalanche gains of 1000. Future detector designs can utilize the nonlocal/non-Markovian nature of the hole avalanche in a-Se, to enable a true solid-state photomultiplier with noiseless gain.

Analysis of PEG-lipid anchor length on lipid nanoparticle pharmacokinetics and activity in a mouse model of traumatic brain injury

Traumatic brain injury (TBI) affects millions of people worldwide, yet there are currently no therapeutics that address the long-term impairments that develop in a large portion of survivors. Lipid nanoparticles (LNPs) are a promising therapeutic strategy that may address the molecular basis of TBI pathophysiology. LNPs are the only non-viral gene delivery platform to achieve clinical success, but systemically administered formulations have only been established for targets in the liver. In this work, we evaluated the pharmacokinetics and activity of LNPs formulated with polyethylene glycol (PEG)-lipids of different anchor lengths when systemically administered to a mouse model of TBI. We observed an increase in LNP accumulation and activity in the injured brain hemisphere compared to the uninjured contralateral brain hemisphere. Interestingly, transgene expression mediated by LNPs was more durable in injured brain tissue compared to off-target organs when compared between 4 and 24 hours. The PEG-lipid is an important component of LNP formulation necessary for the stable formation and storage of LNPs, but the PEG-lipid structure and content also has an impact on LNP function. LNP formulations containing various ratios of PEG-lipid with C18 (DSPE-PEG) and C14 (DMG-PEG) anchors displayed similar physicochemical properties, independent of the PEG-lipid compositions. As the proportion of DSPE-PEG was increased in formulations, blood circulation times of LNPs increased and the duration of expression increased. We also evaluated diffusion of LNPs after convection enhanced delivery (CED) in healthy brains and found LNPs distributed >1 mm away from the injection site. Understanding LNP pharmacokinetics and activity in TBI models and the impact of PEG-lipid anchor length informs the design of LNP-based therapies for TBI after systemic administration.

Virtual reality as a means to explore assistive technologies for the visually impaired

Visual impairment represents a significant health and economic burden affecting 596 million globally. The incidence of visual impairment is expected to double by 2050 as our population ages. Independent navigation is challenging for persons with visual impairment, as they often rely on non-visual sensory signals to find the optimal route. In this context, electronic travel aids are promising solutions that can be used for obstacle detection and/or route guidance. However, electronic travel aids have limitations such as low uptake and limited training that restrict their widespread use. Here, we present a virtual reality platform for testing, refining, and training with electronic travel aids. We demonstrate the viability on an electronic travel aid developed in-house, consist of a wearable haptic feedback device. We designed an experiment in which participants donned the electronic travel aid and performed a virtual task while experiencing a simulation of three different visual impairments: age-related macular degeneration, diabetic retinopathy, and glaucoma. Our experiments indicate that our electronic travel aid significantly improves the completion time for all the three visual impairments and reduces the number of collisions for diabetic retinopathy and glaucoma. Overall, the combination of virtual reality and electronic travel aid may have a beneficial role on mobility rehabilitation of persons with visual impairment, by allowing early-phase testing of electronic travel aid prototypes in safe, realistic, and controllable settings.

Exosomes trapping, manipulation and size-based separation using opto-thermo-electrohydrodynamic tweezers

Owing to the heterogeneity of exosomes in size and biomolecular composition, there is a need for new approaches for trapping, manipulating, and sorting of single exosomes in solution. Due to their small size ranging from 30 nm to 150 nm and their relatively low refractive index, their stable trapping using optical tweezers has been met with challenges. Trapping exosomes in an optical trap requires nearly 100 mW of input power, which predisposes them to photo-induced damage and membrane rupture at the laser focus. Here, we report a high stability opto-thermo-electrohydrodynamic tweezer for the stable stand-off trapping of single exosomes based on a concentric nanohole array (CNA) using laser illumination and an a.c. field. The CNA system generates two regions of electrohydrodynamic potentials several microns away from the laser focus where single exosomes are trapped. We demonstrate the rapid trapping within seconds, and selective dynamic manipulation of exosomes based on size using only 4.2 mW of input laser power. The proposed platform opens up a promising approach for stabilizing single exosomes in solution and controlling their distribution based on size without the risk of photo-induced damage.

Multiphysics Modeling of Plasmon-Enhanced All-Optical Helicity-Dependent Switching

In this work, we propose a multiphysics approach to simulate all-optical helicity-dependent switching induced by the local hot spots of plasmonic nanostructures. Due to the plasmonic resonance of an array of gold nanodisks, strong electromagnetic fields are generated within the magnetic recording media underneath the gold nanodisks. We construct a multiphysics framework considering the opto-magnetic and opto-thermal effects, and then model the magnetization switching using the Monte Carlo method. Our approach bridges the gap between plasmonic nanostructure design and magnetization switching modeling, allowing for the simulation of helicity-dependent, nanoscale magnetization switching in the presence of localized surface plasmons.

Shaping a Soft Future: Patterning Liquid Metals

This review highlights the unique techniques for patterning liquid metals containing gallium (e.g., eutectic gallium indium, EGaIn). These techniques are enabled by two unique attributes of these liquids relative to solid metals: 1) The fluidity of the metal allows it to be injected, sprayed, and generally dispensed. 2) The solid native oxide shell allows the metal to adhere to surfaces and be shaped in ways that would normally be prohibited due to surface tension. The ability to shape liquid metals into non-spherical structures such as wires, antennas, and electrodes can enable fluidic metallic conductors for stretchable electronics, soft robotics, e-skins, and wearables. The key properties of these metals with a focus on methods to pattern liquid metals into soft or stretchable devices are summari.

Tunable Radio Frequency Antenna Based on Phase Change Materials

In conventional communication systems, dedicated tunable circuit elements are used to realize different functions and achieve performance metrics. For example, tuning the center frequency or the input impedance of an antenna in a radio frequency (RF) system is performed by complex impedance-matching circuits. In this paper, the antenna utilizes the temperature-induced irreversible mechanical deformation of a shape memory alloy (SMA) as a natural way to tune the antenna's shape and configuration, thereby providing inherent tunability without bulky circuit elements. This paradigm of material programming for impedance tuning of an SMA-based antenna is validated by both numerical simulation and measurements.

Machine Learning Enables Prediction of Halide Perovskites' Optical Behavior with >90% Accuracy

The composition-dependent degradation of hybrid organic-inorganic perovskites (HOIPs) due to environmental stressors still precludes their commercialization. It is very difficult to quantify their behavior upon exposure to each stressor by exclusively using trial-and-error methods due to the high-dimensional parameter space involved. We implement machine learning (ML) models using high-throughput, in situ photoluminescence (PL) to predict the response of Cs _y FA_1-y Pb(Br _x I_1-x )₃ while exposed to relative humidity cycles. We quantitatively compare three ML models while generating forecasts of environment-dependent PL responses: linear regression, echo state network, and seasonal autoregressive integrated moving average with exogenous regressor algorithms. We achieve accuracy of >90% for the latter, while tracking PL changes over a 50 h window. Samples with 17% of Cs content consistently showed a PL increase as a function of cycle. Our precise time-series forecasts can be extended to other HOIP families, illustrating the potential of data-centric approaches to accelerate material development for clean-energy devices.

Charge Dynamics of a CuO Thin Film on Picosecond to Microsecond Timescales Revealed by Transient Absorption Spectroscopy

Understanding the mechanism of charge dynamics in photocatalysts is the key to design and optimize more efficient materials for renewable energy applications. In this study, the charge dynamics of a CuO thin film are unraveled via transient absorption spectroscopy (TAS) on the picosecond to microsecond timescale for three different excitation energies, i.e., above, near, and below the band gap, to explore the role of incoherent broadband light sources. The shape of the ps-TAS spectra changes with the delay time, while that of the ns-TAS spectra is invariant for all the excitation energies. Regardless of the excitations, three time constants, τ₁ ∼ 0.34-0.59 ps, τ₂ ∼ 162-175 ns, and τ₃ ∼ 2.5-3.3 μs, are resolved, indicating the dominating charge dynamics at very different timescales. Based on these observations, the UV-vis absorption spectrum, and previous findings in the literature, a compelling transition energy diagram is proposed. Two conduction bands and two defect (deep and shallow) states dominate the initial photo-induced electron transitions, and a sub-valence band energy state is involved in the subsequent transient absorption. By solving the rate equations for the pump-induced population dynamics and implementing the assumed Lorentzian absorption spectral shape between two energy states, the TAS spectra are modeled which capture the main spectral and time-dependent features for t > 1 ps. By further considering the contributions from free-electron absorption during very early delay times, the modeled spectra reproduce the experimental spectra very well over the entire time range and under different excitation conditions.

Engineered Nonviral Protein Cages Modified for MR Imaging

Diagnostic medical imaging utilizes magnetic resonance (MR) to provide anatomical, functional, and molecular information in a single scan. Nanoparticles are often labeled with Gd(III) complexes to amplify the MR signal of contrast agents (CAs) with large payloads and high proton relaxation efficiencies (relaxivity, r1). This study examined the MR performance of two structurally unique cages, AaLS-13 and OP, labeled with Gd(III). The cages have characteristics relevant for the development of theranostic platforms, including (i) well-defined structure, symmetry, and size; (ii) the amenability to extensive engineering; (iii) the adjustable loading of therapeutically relevant cargo molecules; (iv) high physical stability; and (v) facile manufacturing by microbial fermentation. The resulting conjugates showed significantly enhanced proton relaxivity (r1 = 11-18 mM-1 s-1 at 1.4 T) compared to the Gd(III) complex alone (r1 = 4 mM-1 s-1). Serum phantom images revealed 107% and 57% contrast enhancements for Gd(III)-labeled AaLS-13 and OP cages, respectively. Moreover, proton nuclear magnetic relaxation dispersion (1H NMRD) profiles showed maximum relaxivity values of 50 mM-1 s-1. Best-fit analyses of the 1H NMRD profiles attributed the high relaxivity of the Gd(III)-labeled cages to the slow molecular tumbling of the conjugates and restricted local motion of the conjugated Gd(III) complex.

Ligand Decomposition during Nanoparticle Synthesis: Influence of Ligand Structure and Precursor Selection

Aliphatic amine and carboxylic acid ligands are widely used as organic solvents during the bottom-up synthesis of inorganic nanoparticles (NPs). Although the ligands' ability to alter final NP properties has been widely studied, side reactivity of these ligands is emerging as an important mechanism to consider. In this work, we study the thermal decomposition of common ligands with varying functional groups (amines and carboxylic acids) and bond saturations (from saturated to polyunsaturated). Here, we investigate how these ligand properties influence decomposition in the absence and presence of precursors used in NP synthesis. We show that during the synthesis of inorganic chalcogenide NPs (Cu₂ZnSnS₄, Cu _x S, and SnS _x ) with metal acetylacetonate precursors and elemental sulfur, the ligand pyrolyzes, producing alkylated graphitic species. Additionally, there was less to no ligand decomposition observed during the sulfur-free synthesis of ZnO and CuO with metal acetylacetonate precursors. These results will help guide ligand selection for NP syntheses and improve reaction purity, an important factor in many applications.

Single-Walled Zeolitic Nanotubes: Advantaged Supports for Poly(ethylenimine) in CO2 Separation from Simulated Air and Flue Gas

Previous research has demonstrated that amine polymers rich in primary and secondary amines supported on mesoporous substrates are effective, selective sorbent materials for removal of CO₂ from simulated flue gas and air. Common substrates used include mesoporous alumina and silica (such as SBA-15 and MCM-41). Conventional microporous materials are generally less effective, since the pores are too small to support low volatility amines. Here, we deploy our newly discovered zeolite nanotubes, a first-of-their-kind quasi-1D hierarchical zeolite, as a substrate for poly(ethylenimine) (PEI) for CO₂ capture from dilute feeds. PEI is impregnated into the zeolite at specific organic loadings. Thermogravimetric analysis and porosity measurements are obtained to determine organic loading, pore filling, and surface area of the supported PEI prior to CO₂ capture studies. MCM-41 with comparable pore size and surface area is also impregnated with PEI to provide a benchmark material that allows for insight into the role of the zeolite nanotube intrawall micropores on CO₂ uptake rates and capacities. Over a range of PEI loadings, from 20 to 70 w/w%, the zeolite allows for increased CO₂ capture capacity over the mesoporous silica by ∼25%. Additionally, uptake kinetics for nanotube-supported PEI are roughly 4 times faster than that of a comparable PEI impregnated in SBA-15. It is anticipated that this new zeolite will offer numerous opportunities for engineering additional advantaged reaction and separation processes.

Assessing the bio-stability of microRNA-146a conjugated nanoparticles via electroanalysis

The number of diabetics is increasing worldwide and is associated with significant instances of clinical morbidity. Increased amounts of reactive oxygen species (ROS) and proinflammatory cytokines are associated with the pathogenesis of diabetic wounds and result in a significant delay in healing. Our previous studies have shown the ability of a cerium oxide nanoparticle (CNP) formulation conjugated with the anti-inflammatory microRNA miR146a (CNP-miR146a) to enhance the healing of diabetic wounds. The observed therapeutic activity exceeded the combined efficacies of the individual conjugate components (CNPs and miR146a alone), suggesting a synergistic effect. The current study evaluates whether the previously observed enhanced activity arises from increased agent delivery (simple nanocarrier activity) or is specific to the CNP-miR146a formulation (functional, bio-active nanomaterial). Comparison with miR146a conjugated gold (bioactive, metal) and silica (bioinert, oxide) nanoparticles (AuNPs and SiO₂NPs) was performed in the presence of H₂O₂, as an analogue to the high levels of ROS present in the diabetic wound environment. Electrochemical studies, materials characterization, and chemical assays showed limited interaction of AuNP-miR146a with H₂O₂ and instability of SiO₂NP-miR146a over time. In contrast, and in support of our prior results, CNP-miR146a displayed chemical stability and persistent ROS scavenging ability. Furthermore, it was determined that CNPs protect miR146a from oxidative damage under prolonged exposure to H₂O₂, whereas AuNPs and SiO₂NPs were shown to be ineffective. Overall, these results reinforce the ability of CNPs to stabilize and protect miRNA while exhibiting robust antioxidant properties, suggesting that therapeutic activity observed in related earlier studies is not limited to a facile nanocarrier function.

Cavity-Enhanced 2D Material Quantum Emitters Deterministically Integrated with Silicon Nitride Microresonators

Optically active defects in 2D materials, such as hexagonal boron nitride (hBN) and transition-metal dichalcogenides (TMDs), are an attractive class of single-photon emitters with high brightness, operation up to room temperature, site-specific engineering of emitter arrays with strain and irradiation techniques, and tunability with external electric fields. In this work, we demonstrate a novel approach to precisely align and embed hBN and TMDs within background-free silicon nitride microring resonators. Through the Purcell effect, high-purity hBN emitters exhibit a cavity-enhanced spectral coupling efficiency of up to 46% at room temperature, exceeding the theoretical limit (up to 40%) for cavity-free waveguide-emitter coupling and demonstrating nearly a 1 order of magnitude improvement over previous work. The devices are fabricated with a CMOS-compatible process and exhibit no degradation of the 2D material optical properties, robustness to thermal annealing, and 100 nm positioning accuracy of quantum emitters within single-mode waveguides, opening a path for scalable quantum photonic chips with on-demand single-photon sources.