Xing He

Catheter-related infections (CRIs) pose a significant threat to patient safety; therefore, the development of effective strategies to prevent and treat these infections is imperative. In this study, a photothermal system based on gold-silver nanoshell (AuAgNSh)-modified catheter surfaces was developed for the rapid eradication of the pathogenic bacterium Enterococcus faecalis (E. faecalis) using near-infrared (NIR) irradiation. The morphology and elemental composition of AuAgNShs were characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), energy-dispersive X-ray spectroscopy (EDX), and X-ray photoelectron spectroscopy (XPS). The optical and photothermal properties were acquired by ultraviolet-visible-near-infrared (UV-vis-NIR) spectroscopy and thermographic imaging with an IR camera, respectively. Bacterial survival studies on AuAgNSh-modified surfaces irradiated with and without NIR light were evaluated using a colony-formation assay. The results demonstrated that AuAgNSh-modified surfaces, when illuminated with NIR light, effectively killed E. faecalis on silicone surfaces in less than 10 min. The system is stable and reusable throughout multiple cycles and has the potential to serve as a rapid, localized adjunct to traditional antibiotic therapy for CRIs. By harnessing the thermal energy produced by AuAgNShs in response to NIR irradiation, this hyperthermia technique can potentially serve as a broad-spectrum antibiotic that kills adhered pathogens rapidly.

Plasmonic nanopipets, which are functionalized with plasmonic nanomaterials, are widely used in near-field spectroscopy to enhance the optical processes. The fabrication and screening processes of these nanopipets are critical for their intended applications. Here, an easy-to-implement fabrication scheme based on high-vacuum sputtered gold island films was reported. Additionally, the process of using surface-enhanced Raman spectroscopy (SERS) to evaluate the plasmonic enhancement of nanopipets was described for near-infrared laser excitation, and it could be readily applied to other optical windows. These results indicated that the reported plasmonic nanopipets can be used as Tip-SERS probes. Finally, the scanning ion-conductance microscopic tip-enhanced Raman spectroscopy was demonstrated with the optimized plasmonic nanopipet. Together with density functional theory simulation, the observed near-field Raman spectra were analyzed and assigned. These plasmonic nanopipets can be used to investigate a range of surface science problems in heterogeneous electrochemical interfaces, as well as in soft and biomimetic materials.

Colloidal plasmonic metasurfaces are emerging as versatile platforms for advancing nanophotonic applications, whose rational design of increasing complexity allows for tailoring and integrating advanced plasmonic and photonic optical properties. Traditional lithographic techniques limit crystallographic and chemical adaptability, hindering the dynamic tuning of optical properties. In this work, a template‐assisted self‐assembly approach for achieving plasmonic metasurfaces using colloidal silver nanoparticle arrays and a thin film of core–shell CdSe/ZnS quantum dots are demonstrated. This system leverages plasmonic surface lattice resonances to create open nanophotonic cavities that enhance the two‐photon excited emission process. The near‐field interactions within these nanophotonic structures offer spectral tunability and efficient light–matter coupling. Moreover, using synthetic nanoparticles enables the integration of a rich library in nanoparticles’ size, shape, and composition, positioning them as promising candidates for compact and scalable photonic devices targeting nonlinear optical processes, advanced sensing, and dynamic light manipulation.

Scanning ion conductance microscopy (SICM) is a powerful surface imaging tool used in the electrolytic environment. Tip-enhanced Raman spectroscopy (TERS) can give more information in addition to the morphology provided by the SICM by utilizing label-free Raman spectroscopy aided by the localized plasmonic enhancement from the metal-coated probes. In this study, the integration of SICM with TERS is demonstrated through employing a silver-coated plasmonic nanopipette. Leveraging a two-dimensional (2D) molybdenum disulfide (MoS₂) as a model system, the SICM-TERS enhancement factor was estimated to be ∼10⁵, supported by finite-difference time-domain (FDTD) simulation. Moreover, the subnanometer distance dependence SICM-TERS study reveals the tensile stress and structural changes caused by the nanopipette. These findings illustrate the potential of SICM-TERS for providing comprehensive morphological and chemical insights into electrolytic environments, paving the way for future investigations of electrocatalytic and biological systems.

Metals exhibit nonequilibrium electron and lattice subsystems at transient times following femtosecond laser excitation. In the past four decades, various optical spectroscopy and time-resolved diffraction methods have been used to study electron–phonon coupling and the effects of underlying dynamical processes. Here, we take advantage of the surface specificity of reflection ultrafast electron diffraction (UED) to examine the structural dynamics of photoexcited metal surfaces, which are apparently slower in recovery than predicted by thermal diffusion from the profile of absorbed energy. Fast diffusion of hot electrons is found to critically reduce surface excitation and affect the temporal dependence of the increased atomic motions on not only the ultrashort but also sub-nanosecond times. Whereas the two-temperature model with the accepted physical constants of platinum can reproduce the observed surface lattice dynamics, gold is found to exhibit appreciably larger-than-expected dynamic vibrational amplitudes of surface atoms while keeping the commonly used electron–phonon coupling constant. Such surface behavioral difference at transient times can be understood in the context of the different strengths of binding to surface atoms for the two metals. In addition, with the quantitative agreements between diffraction and theoretical results, we provide convincing evidence that surface structural dynamics can be reliably obtained by reflection UED even in the presence of laser-induced transient electric fields.

Revived attention in black phosphorus (bP) has been tremendous in the past decade. While many photoinitiated experiments have been conducted, a cross-examination of bP’s photocarrier and structural dynamics is still lacking. In this article, we provide such analysis by examining time-resolved data acquired using optical transient reflectivity and reflection ultrafast electron diffraction, two complementary methods under the same experimental conditions. At elevated excitation fluences, we find that more than 90% of the photoinjected carriers are annihilated within the first picosecond (ps) and transfer their energy to phonons in a nonthermal, anisotropic fashion. Electronically, the remaining carrier density around the band edges induces a significant interaction that leads to an interlayer lattice contraction in a few ps but soon diminishes as a result of the continuing loss of carriers. Structurally, phonon–phonon scattering redistributes the energy in the lattice and results in the generation of out-of-plane coherent acoustic phonons and thermal lattice expansion. Their onset times at ∼6 ps are found to be in good agreement. Later, a thermalized quasi-equilibrium state is reached following a period of about 40–50 ps. Hence, we propose a picture with five temporal regimes for bP’s photodynamics.

Thermal conductance across a solid-solid interface requires an atomic- or molecular-level understanding, especially when a system is in a non-equilibrium state and/or consists of nanosized materials with prominent differences in structures, properties, and vibrational behaviors. Here, we report the lattice dynamics of graphite-supported molecular thin films of ethanol, whose layers exhibit in-plane hydrogen-bonded chains and out-of-plane van der Waals stacking with clear structural anisotropy. The direct structure-probing method of ultrafast electron diffraction reveals a surprising temperature difference of more than 400 K at pico- to sub-nanosecond times across the graphite-ethanol interface, yet the temporal behavior signifies a reasonably large thermal boundary conductance. This apparent conflict in a non-equilibrium condition can be resolved by considering the coupling of out-of-plane motions, instead of the commonly used temperature-based model, at transient times for energy transport across the interface separated by van der Waals interactions with mismatched unit sizes and no strong bonds. The importance of spatiotemporally resolved structural dynamics at the atomic or molecular level is emphasized.

Soft carbon is a promising anode material for potassium‐ion batteries due to its favorable properties such as low cost, high conductivity, stable capacity, and low potential platform. Polyvinyl chloride, as a white pollutant, is a soft carbon precursor that can be carbonized at varying temperatures to produce soft carbons with controllable defect and crystal structures. This work investigates the effect of carbonization temperature on the crystalline structures of the obtained soft carbons. In situ Raman spectroscopy was used to elucidate the adsorption‐intercalation charge storage mechanism of potassium ions in soft carbons. Soft carbons prepared at the temperature of 800 °C have a defect‐rich, short‐range ordered structure, which provides optimal intercalation and adsorption sites for potassium ions, resulting in a satisfactory capacity of 302 mAh g⁻¹. This work presents new possibilities for designing soft carbon materials from recycling plastics for potassium‐ion batteries.

To assess the potential optoelectronic applications of metal‐halide perovskites, it is critical to have a detailed understanding of the nature and dynamics of interactions between carriers and the polar lattices. Here, the electronic and structural dynamics of bismuth‐based perovskite Cs₃Bi₂I₉ are revealed by transient reflectivity and ultrafast electron diffraction. A cross‐examination of these results combined with theoretical analyses allows the identification of the major carrier–phonon coupling mechanism and the associated time scales. It is found that carriers photoinjected into Cs₃Bi₂I₉ form self‐trapped excitons on an ultrafast time scale. However, they retain most of their energy, and their coupling to Fröhlich‐type optical phonons is limited at early times. Instead, the long‐lived excitons exert an electronic stress via deformation potential and develop a prominent, sustaining strain field as coherent acoustic phonons in 10 ps. From sub‐ps to ns and beyond, a similar extent of the atomic displacements is found throughout the different stages of structural distortions, from limited local modulations to a coherent strain field to the Debye–Waller random atomic motions on longer times. The current results suggest the potential use of bismuth‐based perovskites for applications other than photovoltaics to take advantage of the carriers’ stronger self‐trapping and long lifetimes.