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CeO2 nanoparticles possess catalytic activity for hydrolysis of organophosphates such as paraoxon and nerve agents used in chemical warfare. Intoxication with these highly toxic compounds can occur directly through inhalation or dermal contact and lead to rapid and severe consequences including death. It is therefore necessary to have effective means of skin decontamination, and CeO2 nanoparticles are promising. In this study, a wide range of CeO2 nanoparticles were synthesized and their efficiency against paraoxon degradation was evaluated. Nanocubes (NC), nanorods (NR), nano-octahedra (NO), and nanopolyhedra (NPO) were studied along with nanoparticles obtained after calcination (NC*, NR*, NO*, and nanotruncated octahedra NTO*). Results show an influence of calcination, specific surface area, and crystal facets with higher activity for {111} facets compared to {100} facets. pH also impacted POX degradation rates, with higher pH accelerating the degradation. In vitro tests using the Franz cell method demonstrated the skin decontamination efficacy of the CeO2 nanoparticles. NC* exhibited lower efficiency, possibly due to smaller surface area and limited {100} facet degradation. The most efficient nanoparticles were NR* and NO* followed by NTO* consistently with their degradation efficiency and specific surface area. Notably, NR* and NO* performed comparably to FE (Fuller's earth), the standard powder skin decontaminant on battlefield. Unlike FE that can only adsorb paraoxon, CeO2 nanoparticles can neutralize it into safer byproducts. This study highlights the interest of CeO2 nanoparticles and the influence of their physicochemical properties on organophosphorus compound degradation and cutaneous decontamination. [ABSTRACT FROM AUTHOR]

The incorporation of luminescent lanthanide complexes in inorganic matrices opens appealing possibilities in the rational upstream conception of new luminescent materials with easier recyclability. In this regard, the influence of SBA‐15 mesoporous silica, as a host matrix, on the photophysical properties of europium‐trisdipicolinate cesium salt is investigated. The lanthanide complex can be completely and reversibly adsorbed on the silica, using incipient wetness impregnation (IWI) in WATER, without the need of anchoring groups or covalent bonding on the silica surface. This specific procedure allows the homogeneous dispersion of the lanthanide complex into the host silica matrix. Appropriately assessing the photophysical properties of the targeted luminescent material proved remarkably challenging, demanding utmost caution, particularly due to the strong scattering of the mesoporous matrices. Additionally, while the observations confirm an important increase of luminescence lifetimes of lanthanide complexes upon integration into these mediums, this variation is attributed to the differing refractive indexes and not to specific surface interactions or confinement effect. Indeed, it appeared that previous literature precedents depicted erroneous exhalations of the complexes intrinsic quantum yield due to the repeated use of erroneous refractive index values. In the meantime, the luminance of these materials under UV irradiation improves drastically in comparison to what is obtained with the physical dispersion of micro‐crystals of the lanthanide complex onto silica. It is demonstrated that this improvement is due to a reduced inner filter effect in the adsorbed samples. In this regard, IWI of lanthanide complexes in the mesoporous matrices method could be of interest in the development of recyclable emitting layers, less demanding in terms of emitter quantity. [ABSTRACT FROM AUTHOR]

A multifunctional hybrid gel based on cellulose nanofibrils (CNFs) was developed by grafting on its surface stearyl acrylate (PSA) and gadolinium-(III) fluoride nanoparticles (GdF3 NPs) via Cu0-mediated surface-initiated radical polymerization (SET-LRP) while encapsulating antimicrobial peptides in it. GdF3 NPs were first surface-modified with 11-phosphonoundecyl acrylate (PDA) to participate in the SET-LRP and cross-linked the grafted polymer-modified CNF. Several characterizations of the hybrid material (GdF3–PSA-CNF) were carried out, such as Fourier transform infrared (FTIR) spectroscopy, thermogravimetric analysis (TGA), rheology, and microscopic analyses. The grafted PSA and cross-linked GdF3 NPs created sophisticated networks in the CNF-based gel, presenting outstanding rheological properties and promising three-dimensional (3D) printability of this hybrid material (GdF3–PSA-CNF). The nanostructures of GdF3 NPs and their incorporated CNF species were characterized via small-angle X-ray scattering (SAXS). In addition, due to the unique intrinsic property of the GdF3 nanoparticles, properties for magnetic resonance imaging (MRI) of GdF3–PSA-CNF were investigated, showing the potential application as a contrast agent. Finally, the encapsulation of the antimicrobial peptides added another function to the hybrid material, evaluated by an antimicrobial test against methicillin-resistant Staphylococcus aureus (MRSA) in vitro. [ABSTRACT FROM AUTHOR]

Exposure to organophosphorus compounds, in military conflicts or terrorist acts, requires an emergency procedure including the availability of efficient decontamination systems. Systems based on nanosized cerium(IV) oxide (CeO2) are highly promising candidates. CeO2 is a heterogeneous catalyst for the degradation of the organophosphorus compounds such as VX agent or sarin. While the synthesis method influences the physicochemical characteristics of the nanoparticle surface and thus their degradation activity, we have compared the degradation activity of nanosized CeO2 powders commercially available, or developed using different synthesis processes, namely hydrothermal process, photochemistry and laser ablation in liquids. The degradation activity was evaluated in vitro by measuring the degradation kinetics of paraoxon organophosphate. A quenching of the degradation activity is observed on the as-produced particles with a surface pollution, especially when organic molecules with carboxylate ion R–COO− are involved in the synthesis process. In contrast, laser-generated nanoparticles in ultra-pure water show the best activity, while the sample presents the lowest specific surface area. After annealing, almost all samples present a clean surface and the degradation activity is mainly driven by the specific surface area. We propose a figure of merit including the particle activity for the degradation of paraoxon, the production costs and the production time. Indeed, the two last parameters are essential to assess the relevance of each method in view of marketing. [ABSTRACT FROM AUTHOR]

The local optical field enhancement which can occur at the end of a nanometer-size metallic tip has given rise to both increasing interest and numerous theoretical works on near-field optical microscopy. In this article we report direct experimental observation of this effect and present an extensive study of the parameters involved. Our approach consists in making a "snapshot" of the spatial distribution of the optical intensity in the vicinity of the probe end using photosensitive azobenzene-containing films. This distribution is coded by optically induced surface topography which is characterized in situ by atomic force microscopy using the same probe. We perform an extensive analysis of the influence of several experimental parameters. The results are analyzed as a function of the illumination parameters (features of the incident laser beam, exposure time, illumination geometry) as well as the average tip-to-sample distance and tip geometry. The results obtained provide substantial information about the tip's field. In particular, they unambiguously demonstrate both the nanometric spatial confinement of the tip field and the evanescent nature of the nanosource excited at the tip's end. Most of the experimental results are illustrated by numerical calculations based on the finite element method and commented using the literature on the subject. Additionally, we discuss the origin of the optically induced topography on a nanometer scale and present some preliminary results of the apertureless near-field optical lithography based on local field enhancement. Our approach constitutes a useful tool to investigate the near-field of apertureless probes and should enable the optimization of the nanosource for any experiment requiring local optical excitation of the matter. [ABSTRACT FROM AUTHOR]

Discusses the mechanisms of a remanent alignment of polarizable molecules dispersed in a solid gel matrix when submitted to powerful, femtosecond, linearly polarized, optical pulses emitted from a dye laser. Optical memory effect in doped gel matrices; Description on the temporal structure of the excitation pulses; Polarization directions of the auxiliary pulses studied.