Interfaces Traitements Organisation et Dynamique des Systèmes

Electrochemiluminescence (ECL) is a powerful analytical technique that generates light through electrochemically induced reactions, enabling ultrasensitive biosensing and imaging of submicrometric objects. Conventional ECL systems, such as those using Ru(bpy)3 2⁺ and tri-n-propylamine (TPrA), require high applied potentials (oxidation at ∼1.4V versus Ag/AgCl), leading to electrode surface modification and parasitic reactions. Herein, we present a novel autocatalytic ECL mechanism that drastically lowers the triggering potential to -0.2V by exploiting the synergistic interplay between oxalate (C2O4 2-) and peroxydisulfate (S2O8 2-) radicals, mediated by Ru(NH3)6 3+ reduction. This system generates ECL without direct oxidation of the luminophore, but instead through a mild reduction process, relying on homogeneous radical reactions (SO4 • - and CO2 • -) to populate the Ru(bpy)3 2⁺* excited state. Experimental investigation at different Ru(NH3)6 3+/S2O8 2 -/C2O4 2 - concentration ratios, backed by finite element simulations, demonstrates the autocatalytic cycle's capability of exciting luminophores with a bandgap as high as 2.77eV (blue-emitting Ir(III) complex), while also showing a more stable ECL emission and achieving an emitting layer as thick as ∼4.8 ± 0.2µm. These findings establish a low-potential ECL pathway with a large emitting layer, extending the applicability of such nontoxic coreactants-historically limited by their short-lived radicals-and potentially paving the way for new frontiers in ECL.

Density functional theory (DFT) is the most widely and accepted model for calculating the electronic structure of physical systems, but practical applications rely on approximations to the (still) unknown exact exchange–correlation functional. We revisit here the main advances, families, and tipping points for the development of accurate expressions for the exchange–correlation functional, focusing on the historical evolution followed by DFT but also on the underlying reasons for that, while emphasizing both the theoretical foundations and the last methodological and technical developments (exemplified by deep-learned models). The latter are built by training a neural network on a very extended collection of molecular data, with the DM21, the aPBE0-ML, and the Skala functionals now available using such a strategy. This degree of development could have not been possible without the knowledge achieved so far, after more than half a century of investigations and applications of DFT to all kind of systems, and it is rooted on the traditional local (LDA), semi-local (GGA or meta-GGA) and non-local (hybrid and double-hybrid) functionals, which are still important pillars of DFT and are expected to coexist with deep-learned models, as well as on the creation of large and diverse datasets of nearly-exact reference results, which are also needed to train any of the deep-learned models envisioned.

In recent years, researchers have significantly increased their exploration of nanomaterials, primarily due to their exceptional and distinctive electrochemical properties. Hierarchical nanostructured materials have become a prevalent component in electrochemical sensors owing to their numerous advantages, including abundant open diffusion channels, diverse junction interfaces, and a highly exposed surface area. This review provides a comprehensive overview of the potential of hierarchical nanomaterials as electrode modifiers, highlighting their capacity to enhance device performance. The introduction section sets the context by addressing the challenges and recent advancements in the field of hierarchical nanomaterials, emphasizing their promise for electrochemical sensor applications, and outlining the diverse research directions that are currently being explored. In the following section, a range of strategies and techniques for synthesizing hierarchical nanomaterials are outlined, with an emphasis on the impact of various parameters on their properties. Subsequently, the characteristics and performance of diverse hierarchical nanomaterials as electrode modifiers for electrochemical sensor applications are examined. Ultimately, the primary aspects and challenges of hierarchical nanomaterials in the domain of electroanalysis are reported, followed by a discussion of their future development.

<strong class="journal-contentHeaderColor">Abstract.</strong> Mineral dust absorbs and scatters solar and infrared radiation, thereby affecting the radiance spectrum at the surface and top-of-atmosphere and the atmospheric heating rate. While half of the outgoing thermal radiation is emitted in the far infrared (FIR, 15&ndash;100 &mu;m), knowledge of the optical properties and thermal radiative effects of dust is currently limited to the mid-infrared region (MIR, 3&ndash;15 &mu;m). In this study we performed pellet spectroscopy measurements to evaluate the MIR and FIR contribution to dust absorbance and explore the variability and spectral diversity of the dust signature within the 2.5&ndash;25 &mu;m range. Thirteen dust samples re-suspended from parent soils with contrasting mineralogy were investigated, including low and mid latitude dust (LMLD) sources in Africa, America, Asia, and Middle East, and high latitude dust (HLD) from Iceland. Results show that the absorbance of dust in the FIR up to 25 &mu;m is comparable in intensity to that in the MIR. Also, spectrally different absorption (position and shape of the peaks) is observed for HLD compared to LMLD, due to differences in mineralogical composition. Corroborated with the few available literature data on absorption properties of natural dust and single minerals up to 100 &mu;m wavelength, these data suggest the relevance of MIR and FIR interactions to the dust radiative effect for low to high latitude sources. Furthermore, the dust spectral signatures in the MIR and FIR could potentially be used to characterise the mineralogy and differentiate the origin of airborne particles based on infrared remote sensing observations.

Nitrophenyl layers of varying thicknesses were grafted onto an arc-melted Ti 35 Zr 25 Nb 25 (MoTa) 15 high-entropy alloy via electrochemical reduction of 4-nitrobenzenediazonium tetrafluoroborate. A fluorescent peptide derived from bone morphogenetic protein 2 (BMP-2) was then covalently tethered to these films. Electrochemical corrosion behaviour was assessed in 0.1 M NaCl by potentiodynamic polarisation and electrochemical impedance spectroscopy. Grafted nitrophenyl films reduced the corrosion current density ( I corr ) by more than 10-fold and diminished anodic current densities by over 1550-fold, while shifting the corrosion potential ( E corr ) to more positive values. Subsequent BMP-2 coupling further increased the resistive impedance of the coating and eliminated diffusion-limited (Warburg) behaviour. These results demonstrate that, for the Ti 35 Zr 25 Nb 25 (MoTa) 15 alloy in chloride media, sequential nitrophenyl grafting and peptide immobilisation yield a robust, corrosion-resistant and biofunctional surface.

Photodynamic Therapy (PDT), which involves the combined action of a drug and its activation by suitable light, is a particularly attractive novel cancer therapy method due to less systemic side effects. However, the delivery and accumulation of the PDT drug into cancer cells is still problematic. Here, by using μ-scale molecular dynamic simulations combined with quantum mechanics/molecular mechanics approaches, we examine the behavior of a PDT drug functionalized with a folic acid unit targeting the folate receptor α (FR-α), which is overexpressed in ovarian cancer cells. We show that the PDT drug forms a stable complex with the folate receptor, albeit slightly disrupting the main interaction patterns as compared to the parent folate ligand. Furthermore, we also show that the optical properties of the PDT drug are not altered by its interaction with the protein. Our results confirm that coupling with folate is an attractive strategy for selective active delivery of PDT agents.

Coupling electrochemistry with opticaltechniques gives in-depthinsights into the interfacial processes in action. In that context,fluorescence confocal laser scanning microscopy (F-CLSM) enables anelectrode surface characterization with spatial resolution in thelateral plane (xy) as well as in the axial direction(z), perpendicular to the electrode surface. However,like most optical techniques, fluorescence microscopy has intrinsiclimitations, notably in terms of resolution and sensitivity, whichare investigated in this contribution by conducting F-CLSM experimentswith two disk electrodes of different sizes: a large microelectrode(LME, Ø = 250 μm) and a much smaller so-called ultramicroelectrode(UME, Ø = 18 μm). We demonstrated that the diffusion layersof both microelectrodes can be imaged with sufficient resolution andsensitivity to be quantitatively compared with the simulated concentrationprofiles. This work highlights the intrinsic technical challengesassociated with this kind of coupled experiments, and it discussesthe conditions that should be fulfilled to obtain reliable resultsat the microscale. These results pave the way toward reaction layerimaging down to micrometric resolution and could help decipher complexelectrochemical reactions possibly involving transient species.