Double bubbles: a new structural motif for enhanced electron–hole separation in solids

Abstract

Electron-hole separation for novel composite systems comprised of secondary building units formed from different compounds is investigated with the aim of finding suitable materials for photocatalysis. Pure and mixed SOD and LTA superlattices of (ZnO)12 and (GaN)12, single-shell bubbles are constructed as well as core@shell single component frameworks composed of larger (ZnO)48 and (GaN)48 bubbles with each containing one smaller bubble. Enthalpies of formation for all systems are comparable with fullerenes. Hole and electron separation is achieved most efficiently by the edge sharing framework composed of (GaN)12@(ZnO)48 double bubbles, with the hole localised on the nitrogen within the smaller bubbles and the excited electron on zinc within the larger cages.

Double bubble secondary building units used as a structural motif for enhanced electron–hole separation in solids

“…All mixed double bubble systems have lower values of E g than the single bubble systems. Comparing our data with previous work [7], for each type of outer bubble E g is lowest when the inner bubble is comprised of SiC and greatest when it is comprised of ZnO.…”

“…Oxynitride materials that possess smaller band gaps have been investigated as a promising alternative to the semiconductor oxides [4] for water splitting and, recently, a promising photocatalyst has been proposed as a solid solution between ZnO and GaN [5]. We have previously reported a novel new structural motif for enhancing electron-hole separation, using so-called 'double bubble' secondary building units (SBU) of GaN and ZnO [6,7]. These motifs were constructed from previous computational simulations of nanoclusters that predicted bubble (or cage) architectures [8,9].…”

Structural, Electronic and Mechanical Properties of Few-layer Porous Nanosheet from Spheroidal Cage-like ZnO Polymorph

“…In this section, following our recent approach for theoretically predicting ZnO crystal hollow structures [14,[16][17][18], the secondary building blocks were chosen to be high in symmetries and large in HOMO-LUMO gap, which is generally believed as if criteria of stability [19,20]. Starting out from a three dimensional porous crystalline of SOD's ZnO phase, we engrave out it with layered patterns, leaving out the porous polymeric frame work NS of originated SOD cage-like spheroid cluster.…”

“…Nanoclusters, in particular cage-like spheroid, are of special interest since they offer a novel bottom-up mean of creating a large variety of structurally different materials without changing its common material composition such as metal oxides material compunds. Thus, beside the traditional experimental approach, many low-density structures/allotropes of ZnO have been predicted computationally from first principles theoretical calculation recently [6][7][8][9][10][11].…”

Heterostructures of GaN with SiC and ZnO enhance carrier stability and separation in framework semiconductors

“…In this paper, we propose that, by combining SiC, ZnO and GaN, the resulting composite heterostructures will possess the ability to readily generate separable and stable electron–hole pairs. We build on our previous work, in which we have devised novel structures that comprise secondary building units (SBU) of ‘perfect’ 24‐atom GaN, ZnO and SiC sodalite (β‐) cages and 96‐atom bubbles . Cage‐like molecular and extended structures including SiC have also been the topic of previous investigations .…”