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IgG detection in human serum employing non-functionalized chromium doped zinc gallate nanoparticles
No full textInternational audienceChromium-doped zinc gallate (ZnGa2O4:Cr3 +) nanoparticles (ZGO) show promising potential for antigen immunodetection using persistent luminescence, thereby reducing autofluorescence interference. Recently, we have shown that ZGO prepared by hydrothermal treatment at 120°C for 24 h can be used for in vitro biodetection in simple media such as phosphate-buffered saline. In this study, we investigated the effect of the protocol used to synthesize these ZGO nanoparticles, using a hydrothermal treatment at 220°C for different durations (6 h, 12 h, and 24 h), followed by calcination at 500°C. The nanoparticle size determined by transmission electron microscopy after grinding and centrifugation was found to be around 15 nm. The persistent luminescence signal of the ZGO nanoparticles varied with the hydrothermal synthesis conditions. Moreover, in the presence of H2O2, these nanoparticles show a signal enhancement dependent on the hydrothermal duration, with a 12 h treatment showing the highest 8-fold luminescence increase in the presence of H2O2 produced by glucose oxidase mediated glucose degradation. Based on these results, these non-functionalized nanoparticles were successfully used to develop a persistent luminescence-based sandwich immunoassay for autofluorescence-free detection of antigens in undiluted human serum samples, using rabbit IgG as a model antigen. This study highlights the promising potential for biosensing applications of persistent ZGO nanophosphors for IgG detection in a complex medium (undiluted human serum), with a linear range from 1 ng mL−1 to 104 ng mL−1 and a limit of detection of 0.01 ng mL−1. The present optimization of ZGO nanophosphor synthesis offers promising prospects for medical diagnostics due to their increased sensitivity and ability to eliminate autofluorescence interference, as well as their ease of use, since no functionalization of the ZGO NPs is required before use
Boosting Effect of Encapsulated Polyoxometalates in the Photocatalytic CO 2 Reduction by MOF-545
No full textInternational audienceAchieving efficient photocatalytic CO2 reduction is a current complex challenge, requiring the development of strategies that optimize not only the capture of photons but also the photoinduced charge separation and electron transfer processes. In this pursuit, we have immobilized polyoxometalates (POMs), specifically [SiW12O40] 4-(SiW12) and [W10O32] 4-(W10), within the Zr-based porphyrinic metal-organic framework (MOF) MOF-545 catalytic material with the purpose of maximizing its CO2 photoreduction activity. The resulting SiW12@MOF-545 and W10@MOF-545 composites were fully characterized by various techniques (IR spectroscopy, powder X-ray diffraction, N2 adsorption isotherms, HADDF-STEM) to confirm the POM's incorporation via impregnation. These characterizations were complemented by simulations in order to locate the POM into the MOF's cavities and identify host/guest interactions. In photocatalytic conditions, i.e. under visible-light irradiation and in CH3CN/TEOA 20:1 solution, the two SiW12@MOF-545 and W10@MOF-545 composites reduced CO2 to formate with 100% selectivity at rates of 669 and 1239 mol gMOF -1 h -1 , respectively. Remarkably, W10@MOF-545 showed around a 3-fold increase in activity compared to its POM-free counterpart. DFT calculations suggest that both POM guests can accept photoexcited electrons from the porphyrin linkers of MOF-545, allowing increased lifetime of the photogenerated holes in the MOF upon illumination, thus boosting TEOA oxidation by the porphyrinic MOF for subsequent CO2 reduction. Moreover, the calculations unveil the origin of the observed superior overall catalytic activity of W10@MOF-545 over SiW12@MOF-545 due to stronger thermodynamic driving force for charge separation, providing rational guidelines for future design of efficient photocatalysts.</div
Extraction and chemical features of wood hemicelluloses: A review
No full textInternational audienceHemicelluloses have immense potential for applications in diverse fields, especially in polymeric materials. This review critically examines biomass treatment technologies, encompassing chemical, mechanical, and combined approaches to disrupt plant cell walls and enhance hemicellulose accessibility and solubility. The choice of a treatment method depends on factors like purpose, biomass composition, and economic and environmental considerations. Hemicelluloses extracted from wood are composed from up to 11 monomer units, most of them “neutral” monosaccharides (glucose, mannose etc.) but a couple “charged” (uronic acids). The average compositions of wood hemicelluloses change with the type of wood; the accuracy is not known. The content of “charged” monosaccharides may particularly suffer from underestimation due to strong hydrolysis. The chemical composition of intact wood hemicelluloses has never been determined: it is thus not known if hemicelluloses in wood are a mixture of several “simple” polysaccharides (such as glucomannans) or complex polysaccharides with up to 11 monomer units in the same macromolecule. Currently determined molecular weights (MW) of hemicelluloses range from 500 to 1,000,000 Da. The precision and accuracy of MWs are not known, primarily due to column inconsistency in analyzing anionic and neutral polymers. A combination of chromatography SEC methods and detectors is required for standardization
Adaptable Range-Separated Hybrids for the Description of Excited States: Tuning the Range Separation Parameter on Effective Charge Transfer Distance
No full textInternational audienceIn this contribution we describe a novel approach, rooted on Time Dependent Density Functional Theory (TD-DFT), enabling to adapt range separated hybrids (RSH) to correctly describe excited states of inter-and intra-molecular Charge Transfer (CT) character. Contrary to previous works enforcing the fulfillment of Koopmans' theorem, here the range-split parameter of RSHs is tuned so to constrain it in the range of distances corresponding to the hole-electron separation occurring in target CT states for the molecule of interest. The procedure proposed, while not requiring a fit but only an estimate of the CT distances for all excited states (ES) of interest, is not based on empirical adjustment and enables to find a system dependent range separation parameter optimal for the treatment of CT states while not deteriorating its performances with respect to low Hartree-Fock exchange global hybrids for the description of excited states of more local character. The results obtained for a series of CT compounds show the very good accuracy of this adaptative tuning procedure of RSHs and its potential for the exploration of the ES behavior of molecular systems.</div
Covalent POM-Ir hybrid assemblies: tuning redox properties for light-driven multiple charge accumulation
No full textInternational audienceThis study reports the synthesis, electrochemical characterization, and photophysical properties of two novel photoactive polyoxometalate (POM)-Ir photosensitizer hybrid assemblies. Under visible light irradiation in the presence of triethylamine and trifluoroacetic acid, the polyoxomolybdate-based dyad photoaccumulates the electrons via an efficient intramolecular photoinduced electron transfer process
Modelling proton transfer in [HEIM][TFSI] ionic liquid
No full textInternational audienceProtic ionic liquids, PILs, are promising materials for energy storage applications, in part due to their ability to decouple proton transport from ion diffusion. In this work, we model the proton transfer mechanism in 1-ethylimidazolium bis(trifluoromethanesulfonyl)imide ([HEIM][TFSI]) IL by means of Neural Network Force Field simulations. The latter are combined with classical polarizable molecular dynamics simulations to explore the structure and dynamics of the fully ionized system and Density Functional Theory calculations to estimate the energy barriers for the different proton transfer reactions. Our results show that proton transfer is indeed possible when doping the ionic liquid with an excess of deprotonated cations, but not with an excess of protonated anions. We highlight the importance of the formation of dimers between donor and acceptor species for the reaction to occur, and we identify the main driving factor for the reaction to be the energy cost for reaching a suitable coordination environment and form such dimers, which is higher than that for the transfer reaction
Conformational Changes of the ABC Transporter BmrA Depend on Membrane Curvature
No full textAbstract While mechanosensitive ion channels’ gating has been well documented, the effect of membrane mechanics, in particular membrane curvature, on the function of transporters remains elusive. Since conical shape transmembrane proteins locally deform membranes, conversely membrane bending could impact their conformations and their function. We tested this hypothesis using BmrA, a bacterial ABC exporter that exhibits large conformational changes upon ATP hydrolysis, switching between open and closed states with opposite V-shapes. After reconstitution in liposomes of different curvatures, and at two different temperatures, we showed that BmrA ATPase activity decreases by 2.9-fold when their diameter decreases from 125 to 29 nm. Moreover, using single-molecule FRET, we observed that the fraction of closed conformations is reduced in highly curved vesicles when adding ATP or non-hydrolysable AMP-PNP. Our results are well explained by a theoretical 2-states model including the effect of membrane mechanics on protein shape transition. Our work reveals that the functional cycle of conical transporters is curvature sensitive, to an extent depending on protein geometry. Significance Statement Biological membranes actively regulate protein function. While some ion channels are known to sense membrane tension, whether transporters also respond to mechanical cues was unknown. We show that the conical-shaped bacterial exporter BmrA is sensitive to membrane curvature, with both its activity and conformation landscape determined by the surrounding lipid bilayer. This reveals a previously unrecognized mechanism of mechanosensitivity, suggesting that membrane geometry and transporter shape are intrinsically coupled, providing a general principle of regulation across biological systems
Deciphering the Role of Oxygen in Materials for Heterogeneous Catalysis and Energy Storage: A Dive into the Oxygen K-Edge
No full textInternational audienceUnderstanding the structural and electronic properties of oxygen in materials is critical for advancing various technological applications, particularly in catalysis and energy storage. Oxygen species play a pivotal role in mediating reactions within metal-oxide systems, significantly influencing the reactivity and stability of catalysts. Insight into the electronic structure of oxygen, comprising hybridization and bonding with transition metals, provides a deeper understanding of catalytic processes and the efficiency of electrocatalysts. Additionally, oxygen’s involvement in electrochemical processes within batteries, particularly through anionic redox reactions, underscores its importance in developing efficient energy storage solutions. This review focuses on the use of two empirical parameters in O K-edge simulations, offering a guide on simulating observed O spectra for solid oxides. By bridging experimental fingerprints with theoretical approaches, an in-depth understanding of the spectra is provided. First, the theory defining the empirical parameters of the FDMNES code, “dilatorb” and “screening,” is presented. Then, the importance of studying the O K-edge is highlighted through a discussion of selected case studies. This highlights the essential role of oxygen K-edge experiments and simulations in advancing the understanding of catalytic and energy storage processes. By providing detailed insights into the electronic structure, bonding, and real-time transformations in (electro)catalysts, these techniques make significant contributions to material design and optimization
Chromium‐Doped Zinc Gallate Nanoparticles for Enhanced Enzyme‐Linked Immunosorbent Assay Sensitivity: Optimization of Synthesis and Functionalization Strategies for Ultra‐Low IgG Detection
No full textInternational audienceThe use of zinc gallate nanoparticles (ZnGa 2 O 4 :Cr 3+ ) (ZGO‐NPs) presents significant potential for improving the sensitivity in enzyme‐linked immunosorbent assays (ELISA). The persistent luminescence signal increase of these nanoparticles in the presence of hydrogen peroxide (H 2 O 2 ) offers advantages for the sensitive detection of biomolecules. Herein, different conditions of ZGO synthesis have been investigated by varying the hydrothermal reaction duration (6, 12, and 24 h) and examining its impact in the presence of H 2 O 2 . These nanoparticles have been integrated into ELISA assays, using as target antigen IgG. The lowest limit of detection (LOD) of 0.2 pg mL −1 is observed for ZGO‐NPs prepared during 12 h (ZGO2), and with a detection range from 1 to 1000 pg mL −1 . The impact of covalently functionalizing these nanoparticles has then been assessed. First using glucose oxidase (GOx) and the detection antibody (Ab D ) linked to PEGylated ZGO‐NPs, named ZGO‐GOx‐Ab D . Alternatively, only the detection antibody is linked to the PEG ZGO‐NPs, named ZGO‐Ab D . The results show a significant lowering of the LOD when using the functionalized ZGO2 NPs and also highlight the impact of the signal amplification by H 2 O 2 . Specifically, when using ZGO2‐GOx‐Ab D incubated with glucose to produce H 2 O 2 , or with ZGO2‐Ab D to which H 2 O 2 was added, the LODs are ≈98 and 56 fg mL −1 respectively, with detection ranges from 0.01 to 100 pg mL −1
High-entropy Tungsten-Based Oxide as Electrocatalyst and Potential Photo-electro-catalyst for H 2 Evolution
No full textInternational audienceHigh-entropy oxides (HEOx) have emerged as a promising class of materials for photocatalysis due to their unique properties and exceptional stability. This study investigates ( Co 0.2 Ni 0.2 Fe 0.2 Cu 0.2 Zn 0.2 )WO 4 HEOx material synthesized using a top-down approach. The material exhibits a single phase, a suitable band gap for visible light absorption, and a promising electrocatalyst for oxygen evolution reaction (OER) compared to their corresponding individual tungstates. Additionally, the initial tests for Photo-current and MB degradation show the potential for hydrogen (H 2 ) production, making HEOx potential catalysts for solar-driven H 2 generation. ΔS mix = RΣ x n lnx n</div