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
This 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 electrophoretic 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 Mo6 clusters whereas ultra-violet (UV) and near infrared (NIR) filters were realized by using Nb6 or Ta6 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).
The high potential of [{Nb 6 Cl i 12 }L a 6 ] cluster-based building blocks as near-infrared radiation blockers for energy saving applications is exposed in the present paper (i = inner edge-bridging ligand, a = apical ligand of the Nb 6 ; L = H 2 O and/or Cl). To do so, a combined experimental and theoretical investigation of edge-bridged [{Nb 6 Cl i 12 }Cl a 6−x (H 2 O) x ] m+/0/n− cluster unit series (x = 0, 4, 6; m = 2, 3, 4; n = 2, 3, 4) has been carried out. By using the K 4 [{Nb 6 Cl i 12 }Cl a 6 ] starting solid-state precursor, we explored the behavior of the [{Nb 6 Cl i 12 }Cl a 6 ] 4− cluster unit during the different steps of its integration as a building block into a polyvinylpyrrolidone (PVP) matrix to form a glass coating composite denoted {Nb 6 Cl i 12 } m+ @PVP (m = 2 or 3). The optical, vibrational and redox properties [{Nb 6 Cl i 12 }Cl a 6−x (H 2 O) x ] m+/0/n− building blocks have been interpreted with the support of electronic structure calculations and simulation of properties. The chemical modifications and oxidation properties have been identified and studied thanks to various techniques in solution. Combining Raman and ultraviolet−visible spectroscopies, electrochemistry, and quantum chemical simulations, we bring new knowledge to the understanding of the evolution of the properties of the [{Nb 6 Cl i 12 }Cl a 6−x (H 2 O) x ] m+/0/n− cluster units as a function of the number of valence electron per cluster (VEC) and the nature of terminal ligands (x = 0, n = 4; x = 4, charge = 0; x = 6, m = 4). The fine understanding of the physical properties and vibrational fingerprints depending on the VEC and chemical modifications in solution are mandatory to master the processing of cluster-based building blocks for the controlled design and shaping of glass coating nanocomposites. On the basis of this acquired knowledge, [{Nb 6 Cl i 12 }Cl a 6−x (H 2 O) x ] m+/0/n− building blocks were embedded in a PVP matrix. The resulting {Nb 6 Cl i 12 } 2+ @PVP nanocomposite film shows excellent ultraviolet (UV, 280−380 nm) and near-infrared (NIR, 780−1080 nm) blocking ability (>90%) and a highly visible light transmittance thanks to the controlled integration of the {Nb 6 Cl i 12 } 2+ cluster core. The figures of merit (FOM) value of T vis /T sol (T vis = visible transmittance and T sol = solar transmittance) as well as the haze, clarity, and the NIR shielding values (S NIR ) were measured. After optimization of the integration process, a {Nb 6 Cl i 12 } 2+ @PVP nanocomposite on glass substrate has been obtained with a high FOM equal to 1.29. This high value places the transparent green olive {Nb 6 Cl i 12 } 2+ @PVP nanocomposites at the top system in the benchmark in the field of glass coating composites for energy-saving applications.
This 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 matrixes 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 is demonstrated. This review also provides a basic level of understanding how nanocomposites are characterized and processed using different technics 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.
Hexanuclear tantalum bromide cluster units [{Ta6Bri12}La6] (i = inner, a = apical, L = ligand OH or H2O) are embedded into SiO2 nanoparticles by a reverse microemulsion (RM) based method. [{Ta6Bri12}Bra2 (H2O)a4]·nH2O (noted TBH) and tetraethyl orthosilicate (TEOS) are used as the starting cluster compound and the precursor of SiO2, respectively. The RM system in this study consists of the n-heptane (oil phase), Brij L4 (surfactants), ethanol, TEOS, ammonia solution and TBH aqueous sol. The size and morphology of the product namely {Ta6Br12}@SiO2 nanoparticles are analyzed by HAADF-STEM and EDS mappings. The presence and integrity of {Ta6Br12} in the SiO2 nanoparticles are evidenced by EDS mapping, ICP-OES/IC and XPS analysis. The optical properties of {Ta6Br12}@SiO2 nanoparticles are analyzed by diffuse reflectance UV-vis spectroscopy, further evidencing the integrity of the embedded {Ta6Br12} and revealing their oxidation state. Both {Ta6Br12}2+ and {Ta6Br12}3+ are found in SiO2 nanoparticles, but the latter is much more stable than the former. The by-products in this RM-based synthesis, as well as their related factors, are also discussed.
Transparent optical thin films for energy saving application have recently gained substantial prominence for functional window processes. In this study, highly visible transparent nanocomposite films with ultraviolet (UV) and near-infrared...
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