Abstract Magnetic nanoparticles (MNPs) that can support both magnetic particle imaging (MPI) and magnetic resonance imaging (MRI) are attractive for dual-modal imaging because they combine the quantitative, background-free tracer detection of MPI with the anatomical contrast of MRI. However, the MPI- and MRI-relevant performance of ferrite nanoparticles is strongly governed by core size, composition, magnetic relaxation, and biological environment. Here, we report a comparative study of four lab-synthesized, quasi-cubic MNP formulations: 30 nm Fe3O4 nanoparticles (F1), 10 nm Fe3O4 nanoparticles (F2), 30 nm Zn0.4Fe2.6O4 nanoparticles (Z1), and 10 nm Zn0.4Fe2.6O4 nanoparticles (Z2). The morphological, physicochemical, cytocompatibility, and cellular uptake properties of these nanoparticles were systematically characterized. Magnetic particle spectroscopy (MPS) was used as an MPI-relevant screening method to compare the dynamic magnetization responses of these nanoparticles under excitation fields in both water and agar phantoms. Z1 produced the strongest mass-normalized harmonic amplitudes under 7.75 kHz excitation in both water and agar phantoms, identifying it as the highest signal formulation for MPI applications. Agar embedding generally reduced the harmonic amplitudes, consistent with restriction of Brownian rotation and demonstrating that physical confinement can strongly affect the MPI-relevant tracer response. Among the 10 nm formulations, Z2 generated stronger absolute harmonic signals than F2 under both conditions and produced the second-highest harmonic amplitudes in the agar phantom. T1-weighted MRI phantom imaging further confirmed concentration-dependent signal attenuation. Z2 and F2 generated more localized hypointense contrast under T1-weighted imaging conditions, while Z1 and F1 generated susceptibility-related signal loss extending beyond the physical boundaries of the inclusions at equivalent nanoparticle concentrations. This spatially extended hypointensity can obscure boundary definition and complicate quantitative signal-intensity analysis. Overall, these findings clarify how core size and Zn substitution regulate the magnetic, biological, MPI-relevant, and MRI-relevant behavior of ferrite nanoparticles and identify Z2 as a promising balanced tracer candidate for dual-modal MPI-MRI imaging.
Abstract PFAS coatings impart strong water and oil repellency on materials, but their environmental persistence necessitates sustainable alternatives. The development of alternative chemistries is hindered by limited mechanistic understanding of how molecular structure and surface organization govern intrinsic water and oil wettability. Here, a machine learning-driven molecular dynamics (MD) simulation framework was developed to predict and rationalize the intrinsic water and oil wettability of PFAS coatings on nylon for both water and oil. By systematically sampling PFAS head group types (−CHO, −COOH, −OH, and −SO3H), chain lengths from C1–C7, surface packing densities (1.42–4.65 nm–2), and both linear and branched isomers, a comprehensive database of MD-derived contact angles was constructed. A data-efficient, error-driven refinement strategy enables accurate prediction of water and oil contact angles with mean absolute errors below 3° for linear PFAS and below 5° for branched isomers. Analysis shows that intrinsic water and oil repellency peaks at intermediate packing densities rather than at the highest packing density. Moreover, water repellency depends more on chain length than oil repellency, and head group chemistry strongly modulates these effects. Oil contact angles are typically ∼10–20° lower than water contact angles, consistent with experimental observations. This work provides molecular-level insight into the intrinsic water and oil wettability of PFAS coatings and establishes a data-driven framework that may support the future rational design and screening of environmentally benign, non-PFAS coating chemistries.
Abstract Peri-implant infections remain a major cause of implant failure, motivating the development of multifunctional titanium surfaces capable of preventing bacterial colonization while preserving implant performance. Herein, a chitosan/poly-l-lysine (CH-PLL) bilayer coating was engineered on hydroxyl-rich titanium surfaces generated by hydrothermal treatment (HT) or plasma electrolytic oxidation (PEO). We hypothesized that the CH-PLL bilayer would establish a stable cationic interface capable of impairing early bacterial adhesion and modulating polymicrobial biofilm development, whereas the PEO substrate would provide superior mechanical and electrochemical stability. Surface characterization confirmed successful bilayer formation and showed that PLL functionalization increased positive surface charge and hydrophilicity while improving tribological and electrochemical performance, with the PEO@CH-PLL coating exhibiting a friction coefficient of ∼0.01 and significantly enhanced corrosion resistance (P < 0.05). Accordingly, PLL-coated surfaces reduced bacterial adhesion by 3.9 and 3.1 log CFU for Staphylococcus aureus and Escherichia coli, respectively. Against a saliva-derived polymicrobial biofilm, the coating reduced the total bacterial burden by ∼1.8 log while suppressing disease-related peri-implant pathogens. Importantly, these antibacterial effects were accompanied by preserved protein adsorption and enhanced preosteoblastic activity after 7 days. Collectively, these findings demonstrate that combining a stable cationic CH-PLL interface with a PEO-generated oxide layer provides a multifunctional titanium surface integrating biofilm control with improved mechanical, electrochemical, and biological performance.
Abstract One-dimensional (1D) nanostructured materials offer distinctive physical and chemical properties suitable for advanced energy applications. Among these, 1D lepidocrocite-type TiO2 (1DL), recently discovered, has shown potential in batteries, water splitting, wastewater treatment, and polymer composites, among others. In this study, we report on the combination of 1DL with an in situ formed metal–organic framework (MOF), specifically ZIF-8, to produce a hierarchically porous ZIF-8/1DL composite. X-ray diffraction (XRD) confirms the successful in situ formation of ZIF-8 in the presence of 1DL. In the composite, the average ZIF-8 size is ∼30 nm, that is smaller than that observed in conventional bulk syntheses that typically yield micron-scale crystals. Zeta-potential measurements indicate electrostatic interactions between positively charged ZIF-8 particles and negatively charged 1DL, which stabilize the composite. Transmission electron microscopy (TEM) and energy-dispersive X-ray spectroscopy (EDS) mapping show a relatively uniform distribution of ZIF-8 on 1DL surfaces. Nitrogen adsorption–desorption analyses reveal a substantial increase in specific surface area from 20 m2 g–1 for 1DL to 501 m2 g–1 for ZIF-8/1DL, together with the coexistence of micropores and newly generated mesopores. Electrochemical evaluation in lithium–sulfur (Li–S) batteries indicates enhanced Li-ion transport in the composite compared with 1DL alone. These findings highlight the utility of 1DL as a structural framework for MOF-based nanocomposites and provide a pathway to hierarchical designs for energy-storage applications.
Abstract This work reports a comprehensive investigation of the structural, morphological, and local-scale evolution of molybdenum oxides (MoOx) derived from a chelated precursor obtained via thermal decomposition of molybdenum(II) acetate. By systematically controlling annealing temperature and atmosphere, we demonstrate a clear pathway for phase and morphology engineering across the Mo–O system. Under oxidizing conditions, α-MoO3 microbelts are stabilized up to 800 °C and undergo a morphology-driven transformation into nanosheets without phase alteration. In contrast, vacuum annealing induces reduction processes, leading to the formation of β-MoO3 and its subsequent irreversible transformation into MoO2. The β-MoO3 → MoO2 transition is probed at the atomic scale using time-differential perturbed angular correlation (TDPAC) spectroscopy with the 111In(111Cd) probe nucleus over the temperature range 25–600 °C. The evolution of the hyperfine parameters reveals two distinct regimes associated with progressive local ordering and with the emergence of a likely associated with probable MoO2-related environment, characterized by a quadrupole frequency of ∼149 MHz. Correlation analysis and hierarchical clustering provide quantitative evidence of an irreversible transition above 600 °C. Structural characterization after TDPAC measurements as a function of temperature confirms the predominance of monoclinic MoO2 (∼90%) with residual β-MoO3, establishing a direct link between local hyperfine signatures and macroscopic phase composition. These results highlight the critical role of atmosphere in dictating phase transformation pathways and demonstrate that TDPAC is a powerful tool for resolving early stage local structural evolution. The findings provide a robust framework for the rational design of MoOx-based materials with tunable structural, electronic, and catalytic properties.
