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Synergistic interactions of cadmium-free quantum dots embedded in a photosensitised polymer surface: efficient killing of multidrug-resistant strains at low ambient light levels
摘要： Cadmium-free quantum dots (QD) were combined with crystal violet photosensitising dye and incorporated into medical grade polyurethane via a non-covalent dipping process known as ‘swell-encapsulation-shrink’. The antibacterial efficacy of the prepared quantum dot-crystal violet polyurethane substrates (QD + CV PU) was investigated under low power visible light illumination at similar intensities (500 lux) to those present in clinical settings. The antibacterial performance of QD + CV PU was superior to the constituent polymer substrates, eliminating ~99.9% of an environmental P. aeruginosa strain, a clinical P. aeruginosa strain from a cystic fibrosis patient and a clinical E. coli strain. The nature of the reactive oxygen species (ROS) involved in antibacterial activity of the QD + CV PU surface was investigated using ROS inhibitors and time-resolved optical spectroscopy. The photo-physical interaction of the green-emitting QDs with CV lead to a combination of Type I and II electron transfer and energy transfer processes, with the highly potent ROS singlet oxygen playing a dominant role. This study is the first to demonstrate highly efficient synergistic killing of clinical and environmental strains of intrinsically resistant and multi-drug resistant Gram-negative bacteria using light-activated surfaces containing biocompatible cadmium-free QDs and crystal violet dye at ambient light levels.
关键词： photodynamic therapy,antibacterial,reactive oxygen species,surfaces,quantum dots
更新于2025-09-23 15:21:01
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Stepped morphology on vicinal 3C- and 4H-SiC (0001) faces: A Kinetic Monte Carlo study
摘要： Stepped morphologies on vicinal 3C- and 4H-SiC (0001) surfaces with the miscut toward [1100] or [1120] directions have been studied with a three-dimensional kinetic Monte Carlo model. In the model, a three-dimensional lattice mesh was established based on the crystal lattice of 3C-and 4H-SiC to fix the positions of atoms and interatomic bonding. Periodic boundary conditions were applied in the lateral direction while helicoidal boundary conditions were used in the direction of crystal growth. Events, such as adatoms attachment, detachment and interlayer transport at the step edges, and adatoms adsorption and diffusion on the terraces were considered in the model. Effects of Ehrlich-Schwoebel barriers at downward step edges and incorporation barriers at upwards step edges were also considered. Moreover, the atoms of silicon and carbon were treated as the minimal diffusing species independently to achieve more elaborate information for the behavior of atoms in the crystal surface. The simulation results showed that multiple-height steps were formed on the vicinal 4H-SiC (0001) surfaces, whereas single bilayer-height stepped morphologies were observed on the vicinal 3C-SiC (0001) surfaces. Furthermore, zigzag shaped edges were observed for both of 3C- and 4H-SiC (0001) surfaces with the miscut toward [1120] direction. At last, the formation mechanism of the stepped morphology was also analyzed.
关键词： Computer simulation,Crystal morphology,Silicon Carbide,Surfaces,Kinetic Monte Carlo Model
更新于2025-09-23 15:21:01
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One-Step Generation of Reactive Superhydrophobic Surfaces via SiHCl <sub/>3</sub> -Based Silicone Nanofilaments
摘要： Superhydrophobic surfaces gain ever-growing attention because of their applicability in many (consumer) products/materials as they often display, among others, antifouling, anti-icing, and/or self-cleaning properties. A simple way to achieve superhydrophobicity is through the growth of silicone nanofilaments. These nanofilaments, however, are very often nonreactive and thus difficult to utilize in subsequent chemistries. In response, we have developed a single-step procedure to grow (SiHCl3-based) silicone nanofilaments with selective reactivity that are intrinsically superhydrophobic. The silicone nanofilaments could be further functionalized via Pt-catalyzed hydrosilylation of exposed Si?H moieties. These surfaces are easily obtained using mild conditions and are stable under hydrolytic conditions (neutral water, 24 h at 80 °C) while remaining highly transparent, which makes them well suited for optical and photochemical experiments.
关键词： silicone nanofilaments,SiHCl3,PMMA,hydrosilylation,superhydrophobic surfaces
更新于2025-09-23 15:21:01
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On the Construction of Quasi-Diabatic Hamiltonians That Accurately Represent Ab Initio Determined Adiabatic Electronic States Coupled by Conical Intersections for Systems With on the Order of 15 Atoms. Application to Cyclopentoxide Photoelectron Detachment in the Full 39 Degrees of Freedom
摘要： We present, for systems of moderate dimension, a fitting framework to construct quasi-diabatic Hamiltonians that accurately represent ab initio adiabatic electronic structure data including the effects of conical intersections. The framework introduced here minimizes the difference between the fit prediction and the ab initio data obtained in the adiabatic representation, which is singular at a conical intersection seam. We define a general and flexible merit function to allow arbitrary representations and propose a representation to measure the fit-ab initio difference at geometries near electronic degeneracies. A fit Hamiltonian may behave poorly in insufficiently sampled regions, in which case a machine learning theory analysis of the fit representation suggests a regularization to address the deficiency. Our fitting framework including the regularization is used to construct the full 39-dimensional coupled diabatic potential energy surfaces for cyclopentoxy relevant to cyclopentoxide photoelectron detachment.
关键词： cyclopentoxide photoelectron detachment,quasi-diabatic Hamiltonians,ab initio electronic structure,potential energy surfaces,conical intersections
更新于2025-09-23 15:21:01
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Submicron laser-textured vents for self-cleaning injection molds
摘要： Clogging of venting slots in injection molds is a common maintenance problem caused by the degradation and the accumulation of gaseous and volatiles by-products of polymer melting. In this work, the effect of laser-induced periodic surface structures on the self-cleaning properties of venting slots is investigated. The degradation of poly(ethylene terephthalate) (PET) over different surfaces is characterized by reproducing the mechanisms that occurs in mold cavities when the air is pushed through the venting channel. An imaging technique is developed for the quantification of the sediment that deposits on sample surfaces due to condensation of by-products of PET melting. The experimental results indicate that the use of a multiscale texture minimizes the deposition of residues on the vent surface reducing it from 17.2 to 3.1%. A linear dependency between contact angle and clogging ratio indicates the efficacy of the model that explains vent self-cleaning properties considering their wetting properties.
关键词： applications,surfaces and interfaces,thermoplastics
更新于2025-09-23 15:21:01
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Imaging empty states on the Ge(100) surface at 12 K
摘要： Our understanding of bias-dependent scanning-tunneling-microscopy (STM) images is complicated not only by the multiplicity of the surface electronic structure, but also the manifold tunneling effects in probing semiconductor surfaces having directional dangling- and covalent-bond orbitals. Here we present a re?ned interpretation of empty-state STM images from the model semiconductor surface, Ge(100), on the basis of measurements at low temperature (12 K) combined with density-functional-theory calculations. In the lower-bias regime ((cid:2)1.6 V), the electron tunneling is found to occur predominantly in antibonding dangling-bond or/and dimer-bond states (π ? 2 , and σ ?) of Ge(100) at the surface-parallel wave vector k(cid:3) = 0, leading to the tunneling current maxima located directly on the dimer rows. At higher biases (e.g., at 2 V), the current maxima are shifted to the position in the troughs between the dimer rows, because the tunneling occurs ef?ciently in the π ? 2 states at k(cid:3) (cid:4)= 0 associated with the dimer-up atoms of two adjacent dimer rows, i.e., because of increased sideways tunneling. Thus, the empty-state STM images of Ge(100), albeit strongly bias-dependent, re?ect the dimer arrangement rather than the backbonds and surface resonances at all experimental conditions used. The results are also discussed in comparison with the counterpart system of Si(100).
关键词： STM,density-functional-theory,Ge(100),tunneling,semiconductor surfaces
更新于2025-09-23 15:21:01
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Reference Module in Chemistry, Molecular Sciences and Chemical Engineering || Electronic Structure of Oxide Ultrathin Layers on Metal Surfaces
摘要： Since about 35 years ago, the development of the electron microscopy and spectroscopy techniques has pushed the scienti?c community toward the fabrication of physical systems with a reduced “vertical” dimension, down to nanometer size and ultimately to the monolayer (ML) or single-atom thickness. Especially at the beginning, a requirement for these ultra-thin systems was that these should be grown on metallic or at least semiconducting substrates in order to exploit the enhanced resolution of surface science techniques available when working with conductive systems. Oxide systems were no exception to this trend, and systems made by one or very few oxide layers grown onto metallic substrates were indeed achieved and started to be thoroughly characterized.1,2 Another push to research on oxide ultra-thin ?lms was provided by semiconductor device technology, in which silicon chips are covered by a nanometer-size ?lm of amorphous silica, by the efforts in understanding metal corrosion, by the study of thin insulating oxide ?lms in storage devices, and by the study of oxide supports in heterogeneous catalysis. The ?eld however evolved independently of these initial drives especially as it became clear that the properties of these materials, such as transport and electronic structure, were strongly in?uenced by their detailed and unusual structure. Quite soon, in fact, it was realized that these systems in most cases were not a mere reproduction of the bulk oxides on a reduced scale, but represented completely new hybrid metal/oxide systems with novel structural and electronic properties, often with no counterpart in the bulk. This was unequivocally demonstrated when the atomistic structure of some of these phases was unveiled via the combined use of microscopy and computational characterization,3–5 which allowed researchers to investigate not only the novel structures thus produced, but also the corresponding electronic and spectroscopic properties in great detail. It was the birth of the ?eld of UltraThin Oxides (UTOx) on metal surfaces, whose theoretical or electronic structure description is the topic of this essay.
关键词： Oxide Ultrathin Layers,Electronic Structure,UltraThin Oxides,Metal Surfaces,UTOx
更新于2025-09-23 15:21:01
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Antireflective Transparent Oleophobic Surface by Non-Interacting Cavities
摘要： Oleophobic surfaces have been so far realized using complex micro-scale and nano-scale re-entrant geometries where primary and secondary structures or overhang geometries are typically required. Here we propose a new design to create them with non-interacting cavities. The suspension of liquid droplets relies on the mechanism of compression of air under the meniscus leading to stable composite oil-air-solid interfaces. To demonstrate the concept, we make oleophobic surfaces, with contact angle for oleic acid of about 130o (and Hexadecane about 110o), using both micro-holes in silicon and nano-holes in glass. Thanks to the subwavelength dimensions and antireflection effect of the nano-holes, the glass substrate also shows a high degree of optical transparency with optical transmission exceeding that of the initial bare substrate. Crockmeter tests without any significant change of morphology, optical and wetting properties after more than 500 passes also confirm the high mechanical durability of the nano-hole surface. The results indicate the possibility of using the proposed oleophobic surfaces for a wide range of applications, including self-cleaning transparent windows, windshields for automobiles and aircrafts.
关键词： Antireflective,cavities,Transparent surface,nanostructured optical surfaces,Oleophobic,self-cleaning,Micro-Nano manufacturing,surface wetting
更新于2025-09-23 15:21:01
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BiOCl Nanoplates Decorated on g-C3N4 for Enhanced Photocatalytic Activities
摘要： A facile solvothermal method has been successfully developed for the preparation of BiOCl/g-C3N4 nanocomposite using sodium dodecyl benzene sulfonate as the surfactant. The results revealed that BiOCl nanoplates with thickness below 5 nm and widths of 20~30 nm were uniformly dispersed on the surface of g-C3N4 nanosheets, indicating the formation of a close contact between the BiOCl and g- C3N4. The catalytic activity of the obtained BiOCl/g-C3N4 composite has been evaluated by the degradation process of rhodamine B under visible light irradiation. It has been demonstrated that the catalytic activity of BiOCl/g-C3N4 composite was significantly enhanced compared with the bare component due to the synergistic effect between BiOCl and g-C3N4.
关键词： BiOCl,Nanocomposite,Surfaces,Photocatalyst,g-C3N4
更新于2025-09-23 15:21:01
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Enhanced brightness of a laser-driven x-ray and particle source by microstructured surfaces of silicon targets
摘要： The production of intense x-ray and particle sources is one of the most remarkable aspects of high energy laser interaction with a solid target. Wide application of these laser-driven secondary sources requires a high yield, which is partially limited by the amount of laser energy absorbed by the target. Here, we report on the enhancement of laser absorption and x-ray and particle flux by target surface modifications. In comparison to targets with flat front surfaces, our experiments show exceptional laser-to-target performance for our novel cone-shaped silicon microstructures. The structures are manufactured via laser-induced surface structuring. Spectral and spatial studies of reflectance and x-ray generation reveal significant increases of the silicon Ka line and a boost of the overall x-ray intensity, while the amount of reflected light decreases. Also, the proton and electron yields are enhanced, but both temperatures remain comparable to those of flat foil targets. We support the experimental findings with 2D particle in cell simulations to identify the mechanisms responsible for the strong enhancement. Our results demonstrate how custom surface structures can be used to engineer high power laser-plasma sources for future applications.
关键词： particle source,laser absorption,laser-driven x-ray,microstructured surfaces,x-ray generation,silicon targets
更新于2025-09-23 15:19:57