Fabrication of Octahedral Tantalum Cluster Film by Electrophoretic Deposition

The octahedral Ta6Br14.8H2O cluster, one of the [M6Li12La6]n- octahedrons (M= Nb, Ta; Li= halogen, La= halogen or chalcogen), exhibits interesting oxido-reduction properties in solution1. The application of the [Ta6Bri12]2+ cores has been potentially studied in biotechnologies2, optical devices3, photovoltaic cells4 and catalysis5. Originating from the expectation to block the UV and NIR light on low-emissivity window, the Ta6Br14.8H2O cluster thin film on ITO glass has been fabricated by electrophoretic deposition (EPD) process, a fairly rapid and low cost two-step process well-known for ceramic shaping, conductive surface coating and easily scalable to industrial level. The interesting characteristic has been recognized that the green [Ta6Bri12]2+ cores (adsorbing Ultra-Visible range) easily transfers to brown [Ta6Bri12]3+/4+ cores (absorbing near-infrared range) when dissolved in different solvents. Therefore, selecting the medium and optimizing the concentration of water in solvent to obtain the green homogeneous suspension with high dissolution is the main purpose of study. Considering the green color and transmittance of solution, as well as FE-SEM surface morphology of the green film, 0.02 mL H2O per mL acetone was selected as the optimal ratio to obtain the green transparent suspension and possibility to fabricate the green film by EPD process. However, the [Ta6Bri12]2+ green film has been essentially incorporated with poly vinyl pyrrolidone (PVP) in order to improve the dispersion of Ta6Br14.8H2O clusters inside the suspension and effectively prevent the performance of new [Ta6Bri12]3+/4+ clusters (brown-color) by oxidizing reactions. Reference [1] A. Vogler et al., Inorg. Chem., 1983, 23 (10), 1360. [2] J. Knablein et al., J. Mol. Biol., 1997, 270, 1. [3] S. Cordier et al., J. Inorg. Organomet. Polym., 2015, 25, 189. [4] A. Renaud et al., Chemistry Select., 2016, 1, 2284. [5] A. Barras et al., Appl. Catal. B: Environ., 2012, 123,

Élaboration de revêtements transparents à base de clusters de métaux de transition pour le blocage des rayonnements proche-infrarouge

The antagonism between growing global energy needs and the obligation to slow the global warming is one of the challenges humanity faces. In order to ensure sufficient thermal comfort, the housing, automotive or agricultural buildings sectors are major energy consumers. To reduce these needs, one of the proposed solutions aims to improve the thermal insulation of these buildings through the use of innovative materials. One of the major objectives is to improve the insulation of the windows which represent a significant part of the energy losses. The research described in this thesis has made it possible to develop transparent materials for visible solar radiation while being effective shields against ultraviolet and near-infrared radiation. Such materials are the result of the combination between transition metal cluster patterns having desired absorption properties and a host matrix for shaping these materials (processability). The syntheses as well as the methodology for modulating the absorption and integration properties of clusters in different sol-gel or polymer matrices are presented. Of particular interest is the relationship between the structure of cluster pattern and their absorption properties through comparisons between experimental studies and quantum chemistry studies using density functional theory (DFT). In fine, the increase in the level of understanding of the structure-absorption properties of the clusters studied will make it possible to consider the study of new compositions for even more efficient materials in the future for solar control.L'antagonisme entre les besoins croissants d'énergie au niveau mondial et l'obligation de ralentir le réchauffement climatique fait partie des défis auquel l'humanité fait face. Dans le but d'assurer un confort thermique suffisant, les domaines de l'habitat, de l'automobile ou encore des bâtiments agricoles consomment de grandes quantités d'énergie. Pour réduire ces besoins, une des solutions proposées vise à améliorer l'isolation thermique de ces bâtiments grâce à l'utilisation de matériaux innovants. Un des objectifs majeurs est d'améliorer l'isolation des fenêtres qui représentent une partie importante des pertes énergétiques. Les recherches décrites dans cette thèse ont permis de développer des matériaux transparents aux rayonnements solaires visibles tout en étant des boucliers efficaces contre les rayonnements ultra-violets et proche-infrarouges. De tels matériaux sont le fruit de la combinaison entre des motifs à clusters de métaux de transition présentant des propriétés d'absorption recherchées et une matrice hôte permettant la mise en forme de ces matériaux (processabilité). La synthèse, ainsi que la méthodologie de modulation des propriétés d'absorption et d'intégration des clusters dans différentes matrices de type sol-gel ou polymères sont présentées. Un intérêt tout particulier est porté sur les relations qui s'établissent entre la structure des motifs à clusters et leurs propriétés d'absorption grâce aux comparaisons faites entre des études expérimentales et des études de chimie quantique utilisant la théorie de la fonctionnelle de la densité (DFT). In fine, l'augmentation du niveau de compréhension des relations structures-propriétés d'absorption des motifs à clusters étudiés permettra d'envisager l'étude de nouvelles compositions pour des matériaux encore plus efficaces à l'avenir pour le contrôle solaire

Elaboration of transparent coatings based on metal atom clusters for the blocking of near-infrared radiations

L'antagonisme entre les besoins croissants d'énergie au niveau mondial et l'obligation de ralentir le réchauffement climatique fait partie des défis auquel l'humanité fait face. Dans le but d'assurer un confort thermique suffisant, les domaines de l'habitat, de l'automobile ou encore des bâtiments agricoles consomment de grandes quantités d'énergie. Pour réduire ces besoins, une des solutions proposées vise à améliorer l'isolation thermique de ces bâtiments grâce à l'utilisation de matériaux innovants. Un des objectifs majeurs est d'améliorer l'isolation des fenêtres qui représentent une partie importante des pertes énergétiques. Les recherches décrites dans cette thèse ont permis de développer des matériaux transparents aux rayonnements solaires visibles tout en étant des boucliers efficaces contre les rayonnements ultra-violets et proche-infrarouges. De tels matériaux sont le fruit de la combinaison entre des motifs à clusters de métaux de transition présentant des propriétés d'absorption recherchées et une matrice hôte permettant la mise en forme de ces matériaux (processabilité). La synthèse, ainsi que la méthodologie de modulation des propriétés d'absorption et d'intégration des clusters dans différentes matrices de type sol-gel ou polymères sont présentées. Un intérêt tout particulier est porté sur les relations qui s'établissent entre la structure des motifs à clusters et leurs propriétés d'absorption grâce aux comparaisons faites entre des études expérimentales et des études de chimie quantique utilisant la théorie de la fonctionnelle de la densité (DFT). In fine, l'augmentation du niveau de compréhension des relations structures-propriétés d'absorption des motifs à clusters étudiés permettra d'envisager l'étude de nouvelles compositions pour des matériaux encore plus efficaces à l'avenir pour le contrôle solaire.The antagonism between growing global energy needs and the obligation to slow the global warming is one of the challenges humanity faces. In order to ensure sufficient thermal comfort, the housing, automotive or agricultural buildings sectors are major energy consumers. To reduce these needs, one of the proposed solutions aims to improve the thermal insulation of these buildings through the use of innovative materials. One of the major objectives is to improve the insulation of the windows which represent a significant part of the energy losses. The research described in this thesis has made it possible to develop transparent materials for visible solar radiation while being effective shields against ultraviolet and near-infrared radiation. Such materials are the result of the combination between transition metal cluster patterns having desired absorption properties and a host matrix for shaping these materials (processability). The syntheses as well as the methodology for modulating the absorption and integration properties of clusters in different sol-gel or polymer matrices are presented. Of particular interest is the relationship between the structure of cluster pattern and their absorption properties through comparisons between experimental studies and quantum chemistry studies using density functional theory (DFT). In fine, the increase in the level of understanding of the structure-absorption properties of the clusters studied will make it possible to consider the study of new compositions for even more efficient materials in the future for solar control

From Solid-State Cluster Compounds to Functional PMMA-Based Composites with UV and NIR Blocking Properties, and Tuned Hues

New nanocomposite materials with UV-NIR blocking properties and hues ranging from green to brown were prepared by integrating inorganic tantalum octahedral cluster building blocks prepared via solid-state chemistry in a PMMA matrix. After the synthesis by the solid-state chemical reaction of the K4[{Ta6Bri12}Bra6] ternary halide, built-up from [{Ta6Bri12}Bra6]4− anionic building blocks, and potassium cations, the potassium cations were replaced by functional organic cations (Kat+) bearing a methacrylate function. The resulting intermediate, (Kat)2[{Ta6Bri12}Bra6], was then incorporated homogeneously by copolymerization with MMA into transparent PMMA matrices to form a brown transparent hybrid composite Ta@PMMAbrown. The color of the composites was tuned by controlling the charge and consequently the oxidation state of the cluster building block. Ta@PMMAgreen was obtained through the two-electron reduction of the [{Ta6Bri12}Bra6]2− building blocks from Ta@PMMAbrown in solution. Indeed, the control of the oxidation state of the Ta6 cluster inorganic building blocks occurred inside the copolymer, which not only allowed the tuning of the optical properties of the composite in the visible region but also allowed the tuning of its UV and NIR blocking properties

High performance {Nb5TaX12}@PVP (X = Cl, Br) cluster-based nanocomposites coatings for solar glazing applications

International audienceThe development of highly ultraviolet (UV) and near-infrared (NIR) absorbent transparent coatings is an important enabling technology and area of research for environmental sustainability and energy conservation. Different amounts of K-4[{Nb5TaXi (12)}X-a (6)] cluster compounds (X = Cl, Br) dispersed into polyvinylpyrrolidone matrices were prepared by a simple, nontoxic and low-cost wet chemical method. The resulting solutions were used to fabricate visibly transparent, highly UV and NIR absorbehniques (op by drop casting. The properties of the solution and films were investigated by complementary techniques (optical absorption, electrospray ionization mass spectrometry and Raman spectroscopy). The UV and NIR absorption of such samples strongly depended on the concentration, dispersion and oxidation state of the [{Nb5TaXi (12)}X-a (6)] nanocluster-based units. By varying and controlling these parameters, a remarkable improvement of the figures of merit T-L/T-E and S-NIR for solar-glazing applications was achieved compared to the previous results on nanocomposite coatings based on metal atom clusters

A review on functional nanoarchitectonics nanocomposites based on octahedral metal atom clusters (Nb-6, Mo-6, Ta-6, W-6, Re-6): inorganic 0D and 2D powders and films

International audienceThis review is dedicated to various functional nanoarchitectonic nanocomposites based on molecular octahedral metal atom clusters (Nb-6, Mo-6, Ta-6, W-6, Re-6). Powder and film nanocomposites with two-dimensional, one-dimensional and zero-dimensional morphologies are presented, as well as film matrices from organic polymers to inorganic layered oxides. The high potential and synergetic effects of these nanocomposites for biotechnology applications, photovoltaic, solar control, catalytic, photonic and sensor applications are demonstrated. This review also provides a basic level of understanding how nanocomposites are characterized and processed using different techniques and methods. The main objective of this review would be to provide guiding significance for the design of new high-performance nanocomposites based on transition metal atom clusters

Extended Study on Electrophoretic Deposition Process of Inorganic Octahedral Metal Clusters Advanced Multifunctional Transparent Nanocomposite Thin Films

International audienceThis review paper summarizes our very recent works on the synthesis of multifunctional transparent nanocomposite thin films or coatings based on metal atom clusters by an electro-phoretic deposition (EPD) process. Eight different octahedral atom clusters with niobium, molybdenum or tantalum as metallic cores were used to prepare highly transparent thin films in the visible. Green, yellow, orange, red and brown colored films were successfully fabricated by coating on a transparent conductive oxide glass substrate. Transparent nanocomposite films with prominent luminescent properties were obtained by using Mo 6 clusters whereas ultraviolet (UV) and near infrared (NIR) filters were realized by using Nb 6 or Ta 6 clusters. The EPD process appears to be a new strategy to fabricate highly transparent , homogeneous and colored nanocomposite thin films and coatings for smart windows and solar technologies in a very short time (<90 s)

Controlling the Deposition Process of Nanoarchitectonic Nanocomposites Based on {Nb(6-x)Ta(x)X(i)(12)}(n+) Octahedral Cluster-Based Building Blocks (X(i) = Cl, Br; 0 ≤ x ≤ 6, n = 2, 3, 4) for UV-NIR Blockers Coating Applications

International audienceThe antagonism between global energy needs and the obligation to slow global warming is a current challenge. In order to ensure sufficient thermal comfort, the automotive, housing and agricultural building sectors are major energy consumers. Solar control materials and more particularly, selective glazing are part of the solutions proposed to reduce global energy consumption and tackle global warming. In this context, these works are focused on developing new highly ultraviolet (UV) and near-infrared (NIR) absorbent nanocomposite coatings based on K(4)[{Nb(6-x)Ta(x)X(i)(12)}X(a)(6)]. (X = Cl, Br, 0 ≤ x ≤ 6) transition metal cluster compounds. These compounds contain cluster-based active species that are characterized by their strong absorption of UV and NIR radiations as well as their good transparency in the visible range, which makes them particularly attractive for window applications. Their integration, by solution processes, into a silica-polyethylene glycol or polyvinylpyrrolidone matrices is discussed. Of particular interest is the control and the tuning of their optical properties during the integration and shaping processes. The properties of the solutions and films were investigated by complementary techniques (UV-Vis-NIR spectrometry, ESI-MS, SEM, HRTEM, etc.). Results of these works have led to the development of versatile solar control coatings whose optical properties are competitive with commercialized material

ITO@SiO2 and ITO@{M6Br12}@SiO2 (M = Nb, Ta) nanocomposite films for ultraviolet-near infrared shielding

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New ultra-violet and near-infrared blocking filters for energy saving applications: fabrication of tantalum metal atom cluster-based nanocomposite thin films by electrophoretic deposition

International audienceThis study reports the first integration of inorganic tantalum octahedral metal atom clusters into multifunctional nanocomposite coating materials and devices for window technology and energy saving applications. [Ta6Br12i](n+) (n = 2, 3 or 4) cluster-based high visible transparency UV and NIR filters are realized. Green and brown colored films are fabricated by coating on an indium-doped tin oxide glass substrate by electrophoretic deposition, an industrialized solution process. The efficiency in energy saving of the new UV-NIR filters was estimated by the determination of different figure of merit (FOM) values, such as Tvis, Tsol and Tvis/Tsol (Tsol = solar transmittance and Tvis = visible transmittance), and the color coordinates (x, y, z and L*a*b). The Tvis/Tsol ratio is equal to 1.25 for the best films. Such values are evidence of a higher energy saving efficiency than most of the inorganic composites reported in the literature. These promising results pave the way for the use of transition metal clusters as a new class of nanocoatings in energy saving window-based applications