Color Tuning in Garnet Oxides: The Role of Tetrahedral Coordination Geometry for 3 d Metal Ions and Ligand–Metal Charge Transfer (Band‐Gap Manipulation)

Abstract

We explored garnet-structured oxide materials containing 3d transition-metal ions (e.g., Co , Ni , Cu , and Fe ) for the development of new inorganic colored materials. For this purpose, we synthesized new garnets, Ca Sb Ga ZnO (I) and Ca Sb Fe ZnO (II), that were isostructural with Ca Te Zn O . Substitution of Co , Ni , and Cu at the tetrahedral Zn sites in I and II gave rise to brilliantly colored materials (different shades of blue, green, turquoise, and red). The materials were characterized by optical absorption spectroscopy and CIE chromaticity diagrams. The Fe -containing oxides showed band-gap narrowing (owing to strong sp-d exchange interactions between Zn and the transition-metal ion), and this tuned the color of these materials uniquely. We also characterized the color and optical absorption properties of Ca Te Zn Co O (0<x≤2.0) and Cd Te Zn Co O (0<x≤1.0), which display brilliant blue and green-blue colors, respectively. The present work brings out the role of the distorted tetrahedral coordination geometry of transition-metal ions and ligand-metal charge transfer (which is manifested as narrowing of the band gap) in producing brilliantly colored garnet-based materials.

Exploring the Corundum Structure as a Host for Colored Compounds – Synthesis, Structures, and Optical Studies of (MM′)3TeO6 (M = Mg, Mn, Co, Ni, Zn; M′ = Mg, Mn, Co, Ni, Cu)

“…2.00 eV (orange region) produces the complementary blue color of the material . Thus, the triplet band centered at approximately 2.00 eV can be assigned to the tetrahedral Co 2+ [ 4 A 2 (F)→ 4 T 1 (P)] transition , , . A small band at ca.…”

“…A small band at ca. 2.56 eV may be attributed to the transitions between the octahedral and tetrahedral sites , , …”

“…Of the many studies, the observations of the blue color in Mn 3+ ‐substituted YInO 3 and Co 2+ ‐substituted ZnMoO 4 as well as the different colors in copper‐substituted apatites and transition‐metal‐substituted MgTi 2 O 5 have shown much promise. Recently, we explored the distorted coordination geometries of transition elements in different hosts, which resulted in uniquely colored compounds . Continuing our efforts in this direction, we have now investigated the corundum‐related structure of the general formula (MM′) 3 TeO 6 (M = Mg, Mn, Co, Ni, Zn; M′ = Mg, Mn, Co, Ni, Cu).…”

Adding complexity to the garnet supergroup: monteneveite, Ca&lt;sub&gt;3&lt;/sub&gt;Sb&lt;sup&gt;5+&lt;/sup&gt;&lt;sub&gt;2&lt;/sub&gt;(Fe&lt;sup&gt;3+&lt;/sup&gt;&lt;sub&gt;2&lt;/sub&gt;Fe&lt;sup&gt;2+&lt;/sup&gt;)O&lt;sub&gt;12&lt;/sub&gt;, a new mineral from the Monteneve mine, Bolzano Province, Italy

“…2 ZnO 12 garnet (Bhim et al, 2017), in keeping with a content of tetrahedral divalent cations less than 1.00 atoms pfu. The presence of measurable quantities of divalent Fe at the Z site in a garnet structure is not too common, but it has been demonstrated with spectroscopic methods, both for synthetic material (e.g.…”

Finding high-quality metal ion-centric regions across the worldwide Protein Data Bank

“…Protein metal binding is part of many biochemical mechanisms including signal transduction, enzyme catalysis, and protein structural integrity [3–5]. The local protein structure environment around bound metal ions can provide clues to the biochemical and cellular function of the binding [6–8] and how sequence-based structural changes modulates metal binding [9,10]. However, the quality of 3D protein structural data around metal binding sites can vary dramatically from structure to structure, and especially from region to region [8,11].…”