Abstract With the continuous advancement of microscopic imaging techniques, the motion of micro- and nanosized particles can be followed with increasing spatial and temporal accuracy. Analyzing the tracks of single particles enables one to address a broad range of scientific questions, e.g., the dynamics of active and passive (thermally driven) motion or the transport of particles in complex environments. While anisotropic motion, which is exhibited by the vast majority of biologically relevant particles (e.g., bacteria and viruses), has been amply studied in theoretical works, only little experimental data with single-particle resolution have been reported so far. In this study, fluorescence microscopy is used to follow the unconstrained motion of green-fluorescent protein (GFP)-labeled Salmonella enterica serovar Typhimurium (S. Typhimurium) in bulk. By decomposing the motion of individual bacteria into contributions parallel and perpendicular to the bacterial long axis, we introduce new scores that quantify the degree of motile activity and alignment with high throughput. We find that S. Typhimurium possesses a surprisingly broad spectrum of opening angles that range from full alignment of the bacterial long axis with the direction of translational motion to no alignment at all. Applied to mutants, in which motility-related proteins (the flagellins FljB and FliC) have been deleted, we find that wild-type (WT) and FliC-expressing S. Typhimurium exhibit very similar motility but differ significantly in the fraction of actively moving bacteria.
Abstract High-entropy rare-earth oxides (HE-REOs) offer a broad compositional space for tuning defect chemistry, lattice distortion, and local atomic environments, yet their controlled synthesis as monodisperse and structurally well-defined nanostructures remains challenging. Here, we report a colloidal approach for the synthesis of solution-dispersible, single-crystalline HE-REO nanoplatelets. The ultrathin two-dimensional nanoplatelets adopt a trigonal REO lattice that supports homogeneous multication incorporation across ternary to denary HE-REO compositions, and a simultaneous multication nucleation and growth pathway is demonstrated. Atomic-resolution imaging, combined with binary-type intensity classification, enables assessment of local chemical ordering, and increasing configurational entropy drives the system from a nearly random local structure toward a heteroelement-dominated short-range ordered state. High-entropy design further facilitates the incorporation of chemically dissimilar nonrare-earth cations, expanding the accessible miscibility window of REO nanostructures. Our work establishes colloidal synthesis as both a versatile route to monodisperse high-entropy oxide nanostructures and a model platform for probing and understanding entropy-governed behavior and functionality in high-entropy materials.
Abstract Precise synthesis and engineering of homogeneous anisotropic nanostructures are essential to realize their shape-dependent physicochemical properties for different applications. However, due to the difficulty in controlling factors influencing nucleation and growth, many reported anisotropic nanostructures exhibit substantial heterogeneity, particularly in their size and shape distributions. Current methods for assessing nanostructure heterogeneity, whether ensemble- or single-particle-based techniques, are limited in the types of readout information, resolution, and throughput. Although machine-learning-assisted microscopy approaches have facilitated nanomaterial heterogeneity characterization to a certain extent, strategies that transform microscopy images into quantitative morphology feature spaces for population-level heterogeneity analysis remain underexplored. Herein, a quantitative approach combining transmission electron microscopy (TEM) imaging with machine learning is demonstrated for delineating the projected morphological heterogeneity of anisotropic nanostructures. Following supervised pixel classification and thresholding, TEM images are converted to probability maps and image masks, from which a series of interpretable projected size- and shape-related morphological descriptors are extracted. Dimensionality reduction and unsupervised clustering are subsequently employed to analyze the acquired morphological feature space and identify putative nanostructure subpopulations based on morphological similarities or differences. Feature scoring is further performed to identify descriptors associated with variations among nanostructure subpopulations while considering correlations among related geometric parameters. This study establishes a machine-learning-augmented framework for quantitative and objective analysis of anisotropic nanostructure heterogeneity and provides a foundation for future integration with synthesis metadata and predictive modeling approaches.
Abstract Overcoming the trade-off between proton conductance and gas crossover in conventional proton exchange membranes (PEMs) is imperative to realize thinner membranes with higher power density for reducing stack costs in next-generation fuel cells. However, reducing the thickness of state-of-the-art perfluorosulfonic acid (PFSA)-based PEMs typically leads to diminished mechanical strength and increased gas crossover, ultimately compromising durability. While incorporating a polytetrafluoroethylene (PTFE) reinforcement layer into PEMs (e.g., Nafion HP ∼22 μm thick with expanded PTFE reinforcement layer) provides an effective approach to improve mechanical strength, the integration of atomically thin two-dimensional (2D) materials with proton-selective lattice defects presents a promising route to mitigate gas crossover. Here, we systematically investigate the influence of integrating monolayer graphene synthesized via scalable chemical vapor deposition (CVD) with Nafion HP PEMs using two architectures: sandwich structures (HP|G|HP) and single-layer configurations (HP|G). Our results show that CVD graphene reduces H2 crossover by ∼30–40% while maintaining proton conductance and fuel cell performance comparable to control membranes (HP|HP and HP) as well as the benchmark fuel cell PEM Nafion N211 (∼25 μm thick). Our approach demonstrates that combining mechanically reinforced PEMs with atomically thin, proton-selective 2D layers offers a viable pathway to advance PEMs for next-generation energy conversion and storage applications.
Abstract The first critical steps of electroluminescence in quantum dot light-emitting diodes are the charge accumulation and transport processes upon the application of a driving voltage. Transient electroluminescence measurements with systematically varying offset voltages are carried out to separate out the capacitive charging effects from charge transport. Capacitive charging around the organic hole transport layer is shown to be the dominant contribution to the delay time between driving voltage application and the onset of electroluminescence. The minimum voltage required for light emission may be dictated by the capacitance of the hole transport layer when the electron injection barrier is small. Further implications of these findings are discussed.
Abstract Radically activated dynamic covalent bonds can enable reprocessable, thus more sustainable, polymeric materials, but conventional characterization approaches limit understanding of atomic-scale rearrangements. Specifically, the addition–fragmentation–transfer (AFT) pathway has been characterized by bulk-scale changes in mechanical properties; attempts to probe the exchange on a atomic scale are limited. Traditional spectroscopic methods cannot detect AFT because the overall bonding environment is unchanged before and after exchange with a very short-lived intermediate. To this end, this study uses fluorescence lifetime imaging microscopy (FLIM) to probe local AFT bond exchange via nondestructive characterization. Herein, allyl sulfide AFT in acrylate polymer thin films is monitored by FLIM over time, leveraging the sensitivity of fluorescence lifetime to nearby bond rearrangement through a series of control systems. Notably, FLIM reveals a continuing AFT cascade beyond the typical time scale when mechanical property change saturates. We anticipate applying these findings to other hard-to-access phenomena, as well as a mechanistic understanding of the environmental dependence of fluorescence lifetime.
Gold nanoparticles with complex anisotropic geometries offer unique opportunities for tailoring plasmonic near-fields beyond the limits of conventional nanorods. Here we combine photon-induced near-field electron microscopy (PINEM) and full-wave simulations to resolve plasmon hybridization and near-field localization in gold dog-bone nanoparticles and their dimers with and without conformal SiO2 shells. We demonstrate that the dog-bone geometry drives unconventional polarization-dependent field confinement, including pronounced tip-localized near-fields under both longitudinal and transverse excitation. Conformal SiO2 shells red-shift the plasmon resonances through dielectric screening and prevent charge-transfer coupling in adjacent dimers. Depending on the dimer orientation and excitation polarization, coupled structures exhibit distinct bonding- and antibonding-like hybridized modes as well as interparticle near-field channels. However, weakly interacting dimers retain largely independent particle responses with geometry-governed asymmetries. The close agreement between PINEM measurements and simulations establishes a direct picture of how shape, dielectric environment, and nanoscale coupling together define plasmonic modes in complex anisotropic nanoparticles. These findings provide design principles for engineering localized optical fields in plasmonic nanoscale structures.
The ever-increasing use of antibiotics and the accumulation of antibiotic waste in ecosystems are expediting antimicrobial resistance (AMR). Our next-generation antibiotics should aim for a different antimicrobial mechanism that is less conducive to AMR, a wider therapeutic window tolerant to drug titration, and a quicker deactivation strategy responsive to environmental stimuli. Membrane-active antimicrobials (MAAs) have the potential to thwart AMR, but the lipophilicity of current MAAs gives rise to their broad-spectrum cytotoxicity. Here, we show that biological nanoparticles, such as cyclodextrin and phytoglycogen, can be transformed into potent MAAs with low cytotoxicity by grafting them with hydrophilic polymer brushes. In service, these hydrophilic nanoantibiotics kill bacteria by inducing pore formation exclusively on microbial membranes rich in negative curvature lipids, a bactericidal mode less likely to incur AMR. After service, they are degraded and deactivated by biomass recycling enzymes that are abundant in ecosystems. This study illuminates a new paradigm to combat AMR with hydrophilic and eco-friendly membrane-active antibiotics derived from biological nanoparticles.
Substitutional or interstitial metal-cation dopants in CeO2 play key roles in catalytic, sensing, and energy applications. Cation dopants with a valency less than 4+ create charge-compensating oxygen vacancies in the lattice that boost ionic conductivity and act as reactant adsorption/dissociation sites. These cation dopants also modify the optical properties of CeO2, enabling the normally high-bandgap oxide to more effectively harvest visible light. In this perspective, we highlight the key progress made using dopants in CeO2 and the challenges that remain. We briefly summarize common roles that cation dopants play in the CeO2 lattice, including how their speciation and solubility affect materials properties. We also report how the structural and optical properties of CeO2 aerogels vary when doped with transition metals (Co, Ni) or lanthanides (Y, La, Gd, Tb, Ho, and Er), thereby providing a rare look at the effects of a diverse group of dopants on a single morphologically fixed system.
Diagnostic sensor development and clinical translation lag, in part, due to a lack of rapid, high-throughput screening methodologies. Optimization of high-throughput sensor development and deployment will likely help in expediting tools toward the clinic. To address this issue, we optimized high-throughput screening parameters using a near-infrared (NIR-II) plate reader attached to an external probe for in vivo testing. We assessed spectroscopy parameters to improve the speed and precision in screening a single-walled carbon nanotube (SWCNT)-based optical sensor. To do so, we assessed the appropriate well-plate specifications, including laser power, excitation wavelength, exposure time, and focal height parameters for SWCNT-based optical sensor development. We also used the plate reader to screen fluorescent SWCNTs that were endocytosed by a macrophage cell line. We then performed NIR probe spectroscopy to assess SWCNTs embedded within a methylcellulose hydrogel. Finally, we used the NIR probe to measure the SWCNT center wavelength and intensity from live immunocompetent mice. We anticipate that this framework may be broadly applicable to the development of near-infrared nanosensors with the potential for more rapid clinical diagnostic translation.
Photocatalytic hydrogen (H2) evolution offers a promising solution to environmental pollution and the global energy crisis. Among different photocatalysts, graphitic carbon nitride (g-C3N4), most known as melon in the literature, is distinguished by its availability, large surface area, low cost, and unique optical and electrical properties. However, the efficiency of pristine g-C3N4 is limited by rapid electron-hole recombination, presence of charged trapped states and high charge transference resistance. To overcome these challenges, we used a facile magnetron sputtering technique to load Cu and Pt single atoms onto g-C3N4, confirmed by AC-STEM, XPS, ICP-OES, and XAS characterizations. This approach not only overcomes the problems related to the charge carrier dynamics of the pristine graphitic carbon nitride but also ensures uniform, contamination-free deposition and high distribution of single atoms, thereby optimizing photocatalytic performance. Under solar irradiation (AM 1.5G) for 5 h, the Cu and Pt-loaded g-C3N4 demonstrated significantly improved photocatalytic activity, achieving H2 accumulated values of 93 μmol and 173 μmol, respectively, compared to only 0.3 μmol for pristine g-C3N4. For comparison, Pt and Cu nanoparticles (NPs)- loaded g-C3N4 samples were also prepared, achieving H2 accumulation values of 86.3 and 24.3 μmol, respectively, compared to pristine g-C3N4. However, these values are lower than those of Pt and Cu single-atom-loaded samples. The enhanced H2 evolution performance is attributed to the deposition of metal single atoms acting as electron traps and active catalytic sites, thus improving electron-hole separation. These findings highlight the potential of sputter depositing single-atom to overcome the inherent limitations of g-C3N4, paving the way for more efficient and scalable hydrogen production systems.
Magnesium oxide (MgO) is a prototypical model for oxide-water interfaces and a technologically relevant material in catalysis, environmental remediation, and corrosion-resistant coatings. Here, the dissolution behavior and morphology evolution of MgO smoke nanocubes are investigated in aqueous media while simultaneously monitoring the self-adjusting solution pH under three initial conditions: distilled water (pH ≈ 6.4), mildly acidic HCl solution (pH = 6), and alkaline NaOH solution (pH = 11). Time-resolved TEM reveals that dissolution initiates preferentially at (110) edges, drives a progressive transition from cubic to truncated cubes and finally octahedral morphologies exposing (111) facets, and is accompanied by brucite [Mg-(OH)2] formation whose extent depends on particle size and pH. Upon immersion in distilled water or a mildly acidic solution, the suspension pH rapidly rises to ≈11-12 within minutes, whereas this abrupt pH change is not observed when MgO is introduced directly into an already alkaline medium (pH 11). A subsequent quasi-stationary regime with pH maintained at 11-12 persists for days, showing that the vast majority of the observed morphological transformations in these systems actually proceed under strongly alkaline rather than nominally neutral or mildly acidic conditions. To rationalize these observations, density functional theory calculations are performed for ideal and defect-containing low-index MgO surfaces under H+-rich conditions, including protonated Mg-vacancy (VMgH2) defects relevant to nonoxidative dissolution. The calculations reveal a strong pH dependence of defective surface energies, pronounced anisotropy in the thermodynamic driving force for dissolution, and higher Mg2+ extraction barriers for compact (100) than for more open (110) and (111) terminations, consistent with the experimentally observed facet-dependent kinetics. These results present a unified, pH-dependent picture of MgO dissolution and morphology evolution in water, clarify that earlier "neutral" dissolution studies actually probed alkaline conditions, and offer guidelines for controlling MgO stability and Mg-(OH)2 formation in aqueous media. They highlight how self-adjusted local pH and defect chemistry regulate dissolution, shape transformation, and passivation of oxide nanomaterials at solid-liquid interfaces relevant to environmental and energy-related (electro)-chemical systems.
Chalcogen vacancies in monolayer transition metal dichalcogenides (TMDs), such as WS2, play a crucial role in various applications ranging from optoelectronics and catalysis to quantum information science (QIS), making their identification and control essential. This study focuses on the WS2 single vacancy and vacancy pairs. Using first-principles computations, we investigate their thermodynamic stabilities and electronic structures. We identify an "on-top" divacancy configuration where two vacancies sit on top of each other to be the only energetically stable complex with a binding energy of 160 meV. We compute a small difference in electronic structure with a shift of the unoccupied state by 140 meV for the divacancy complex and make note of a similar shift observed experimentally.
Integrating therapeutic proteins into lipid-based nanocarriers remains challenging due to fundamental incompatibilities between hydrophilic protein surfaces and lipophilic carrier matrices. Here, we demonstrate that controlled hydrophobic ion pairing (HIP) using lysozyme-sodium dodecyl sulfate (SDS) at stoichiometric ratios simultaneously improves thermal stability during pharmaceutical processing and lipid compatibility for nanocarrier integration. Building on our previous molecular characterization of lysozyme-SDS complexes, we investigated their application in nanostructured lipid carrier (NLC) formulations for oral protein delivery. SDS complexation preserved lysozyme enzymatic activity at processing-relevant temperatures and increased apparent lipid miscibility by 50% in both solid and liquid pharmaceutical lipid excipients. This enhanced compatibility translated directly into superior NLC performance, with complexed lysozyme achieving a 4-fold higher encapsulation efficiency (79.6 ± 1.8% vs 18.4 ± 4.3% for native protein) with improved batch-to-batch reproducibility. In simulated gastrointestinal conditions, lysozyme-SDS NLCs demonstrated sustained intestinal release (87.2 ± 16.5% over 6 h) with 67.5 ± 7.5% enzymatic activity retained compared to only 15.2 ± 3.0% activity for native lysozyme formulations. Mechanistic analysis from differential scanning calorimetry and crystallinity measurements showed that SDS complexation induces a molten globule-like protein state that reduces lipid packing (56.8% vs 68.6% crystallinity for native lysozyme), enabling superior matrix integration while maintaining biological function. These findings establish that controlled surface modification through HIP provides a systematic approach to overcome protein-lipid incompatibilities, offering a generalizable framework for developing lipid-based protein therapeutics.
Flexible and gel-free dry electrophysiological electrodes offer excellent alternatives to the benchmark with better skin conformality and dispensing with the hydrogel electrolyte layer, where the integrity of recorded signals highly depends on the resilience of this layer. However, the implicit complex fabrication methods and resource-intensive nature of existing dry electrodes, designed for single use, necessitate additional technological innovations. This paper presents an original integration of inkjet-printing, graphene, and poly-(ethylene terephthalate) (PET) substrates to create flexible, inexpensive, and reusable dry electrodes for monitoring human physiological biopotential signals, including ECG, EEG, EOG, and EMG. The electrodes exhibited high electrical conductivity (80 Ω/□) and maintained their performance even after 100 cyclic bends. Additionally, they demonstrated robust signal collection even 90 days postfabrication, with reusability and strong graphene-substrate bonding verified through Scotch tape experiments. Assessing against gel-based commercial electrodes, a 99.34% correlation ratio was obtained from the recorded ECG signals. Similarly, a correlation ratio of 95.14 ± 4.75% was achieved with 10 diverse participants. The capability of these electrodes to effectively record neural signals in practical applications was demonstrated in real-time detection of sleep and drowsiness in car drivers. These findings highlight the potential of inkjet-printed graphene electrodes in advancing wearable health monitoring technologies.
A crucial tool in the design of multicomponent nanoheterostructures is the ability to carry out reactions with site-specificity. Here, we examine the interplay of two site-specific postsynthetic transformationstellurium anion exchange followed by cadmium cation exchange on Cu2‑xS nanorodsto reveal how, together, they create numerous new nanoheterostructures with various interfaces and chemical components. By varying the temperature of the initial exchange, we obtained Cu2‑xS/Cu2‑xTe structures with varying numbers of Cu2‑x Scores and thicknesses of Cu2‑xTe shells. We then subjected these Cu2‑xS/Cu2‑xTe nanoheterostructures to either low- or high-temperature cadmium exchange. While many different factors dictating the position of cation exchange have been identified, here we find that differences in the ease of ion diffusion through Cu2‑xS and Cu2‑xTe direct the incoming Cd2+ toward reaction with Cu2‑xS. This straightforward site preference for cation exchange, coupled with the ability to modulate the extent of tellurium and cadmium exchange, is used to create several distinctive nanostructure patterns. In particular, we demonstrate that the regioselectivity of Te2- anion exchange on Cu2‑xS nanorods can be leveraged to produce distinct templates for cation exchange, resulting in a library of nontrivial nanoheterostructures. The demonstration of such a variety of different copper/cadmium chalcogenide structures shows that consecutive anion and cation exchanges offer new routes to novel materials.
Resistive-switching random-access memory (RRAM) has gained a great deal of attention as an emerging memory suitable for massive data storage media and synaptic device applications. For low-power operation capability, eliminating the necessity of current compliance, tunneling oxide can be inserted as a tunneling layer in the conventional RRAM devices. In this work, we have systematically investigated the effects of SiO2 tunneling layer and its formation method on the reliability of a Si3N4-based RRAM device. The tunneling oxide layers were deposited by plasma-enhanced chemical vapor deposition (PECVD) and medium-temperature oxidation (MTO) and compared to a single-layer reference device. The devices with tunneling layers demonstrated reduced state current, and the device prepared by MTO exhibited superior endurance and retention. All of the devices demonstrated space-charge-limited current conduction in the high-resistance state. X-ray photoelectron spectroscopy revealed that the MTO oxide layer was chemically more stable, resulting in a difference in endurance characteristics.
