Stability of mixed-oxide titanosilicates: dependency on size and composition from nanocluster to bulk - CNRS - Centre national de la recherche scientifique Accéder directement au contenu
Article Dans Une Revue Nanoscale Année : 2018

Stability of mixed-oxide titanosilicates: dependency on size and composition from nanocluster to bulk

Résumé

Nanostructured titanosilicate materials based upon interfacing nano-TiO 2 with nano-SiO 2 have drawn much attention due to their huge potential for applications in a diverse range of important fields including gas sensing, (photo)catalysis, solar cells, photonics/optical components, tailored multi-(bio)functional supports and self-cleaning coatings. In each case it is the specific mixed combination of the two SiO 2 and TiO 2 nanophases that determines the unique properties of the final nanomaterial. In the bulk, stoichiometric mixing of TiO 2 with SiO 2 is limited by formation of segregated TiO 2 nanoparticles or metastable glassy phases and more controlled disperse crystalline mixings only occur at small fractions of TiO 2 (< 15 wt%). In order to more fully understand the stability nano-SiO 2 and nano-TiO 2 combinations with respect to composition and size, we employ accurate all-electron density functional calculations to evaluate the mixing energy in (Ti x Si 1-x O 2) n nanoclusters with a range of sizes (n = 2-24) having different titania molar fractions (x = 0-1). We derive all nanoclusters from a dedicated global optimisation procedure to help ensure that they are the most energetically stable structures for their size and composition. We also consider a selection of representative intimately mixed crystalline solid phase (Ti x Si 1-x O 2) bulk systems for comparison. In agreement with experiment, we find that intimate mixing of SiO 2 and TiO 2 in bulk crystalline phases is energetically unfavourable. Conversely, we find that SiO 2-TiO 2 mixing is energetically favoured in small (Ti x Si 1-x O 2) n nanoclusters. Following the evolution of mixing energy with nanocluster size and composition we find that mixing is most favoured in nanoclusters with a diameter of 1 nm with a TiO 2 molar fraction of 0.3-0.4. Thereafter, mixed nanoclusters with increasing size have progressively less negative mixing energies up to diameters of approximately 1.5 nm. We propose some chemical-structural principles to help rationale this energetically favourable nanoscale mixing. As a guide for
Fichier principal
Vignette du fichier
Revised_manuscript_FINAL_v2.pdf (3.1 Mo) Télécharger le fichier
Origine : Fichiers produits par l'(les) auteur(s)
Loading...

Dates et versions

hal-01823256 , version 1 (25-06-2018)

Identifiants

Citer

Andi Cuko, Monica Calatayud, Stefan T Bromley. Stability of mixed-oxide titanosilicates: dependency on size and composition from nanocluster to bulk. Nanoscale, 2018, 10 (2), pp.832 - 842. ⟨10.1039/c7nr05758j⟩. ⟨hal-01823256⟩
119 Consultations
221 Téléchargements

Altmetric

Partager

Gmail Facebook X LinkedIn More