ZnS–ZnO Heterostructure Nanorings Grown under a Possible Early Earth Atmosphere

Abstract

We synthesize ZnS–ZnO heterostructure nanorings at ∼680 °C under carrier gases with various [CO2]/[N2] ratios simulating an anoxic and weakly reduced atmosphere on early Earth. The synthesized nanorings consist of a ZnS–ZnO bilayered stem, ZnO teeth, and ZnS wing-like structures between the teeth and the ZnS layer. O atoms are supplied through the decomposition of CO2 presumably catalyzed by the ZnS surface. The respective growth directions of ZnS and ZnO layers in the stem are [0001] and [011̅1], and ZnO teeth are directed outward from the ring. The nanorings are structurally different from ZnS–ZnO nanorings having inward-directed teeth, which were grown under an oxygen-containing ambient environment. Contrary to the assumption of sulfide dominance including ZnS and MnS while disregarding oxygen-containing minerals such as ZnO on early Earth, we show that ZnS–ZnO nanorings, which are more advantageous in CO2 reduction efficiency, could be formed.

Photoinduced Self-Organization in “Semiconductor World”: Part I. from Protophotosynthesis to Protomembranes

“…ZnS and ZnO nanoparticles are also used as photocatalysts, both individually and together [184][185][186]. Apart from the potential of pure sulfide mineral semiconductors, it was also shown that mixed heterostructures based on ZnS and ZnO may be formed at high temperatures in an anoxic and weakly reduced atmosphere of the early Earth, and would possess a higher abiogenic photocatalytic activity in the CO2 reduction [187]. Pyrites [188,189] are another example of mineral structures with semiconductor and photocatalytic properties (including non-iron compounds -cattierite CoS2 [190,191], vaesit NiS2 [192,193] and others, often localized in paragenesis, in contact with autochthonous metals in the deposit [194,195]).…”