Shape-controlled Synthesis And Growth Mechanism Of Cuprous Oxide Crystals

The control ability of micro/nano-material synthesis directly affects the physical and chemical properties of function materials,so it is of great significance to investigate the growth habits of crystal.In this study,the growth mechanisms of hollow and solid Cu₂O polyhedral crystals were discussed,respectively;and a modle aimed at elaborating the relationship between the relative growth rate of low index crystal faces and shape of polygonal crystals in cubic crystal systems was firstly proposed,as follows.?1?Facile Synthesis of Hollow Cu₂O Polyhedron without Template or EtchantPreviously,hollow Cu₂O configurations have been fabricated with the use of template or etchant.However,in this study,simply mixing aqueous sodium dodecyl sulfate?SDS?,CuCl2,NaOH,and NH2OH·HCl in the order listed,Cu₂O polyhedron with empty interior arise,which is rarely reported.Observations made on the adding order of reactants and the the content of NaOH revealed that it was favourable to hollow Cu₂O polyhedron formation in case of introducing SDS firstly and keeping M?NaOH?:M?CuCl2?=<4.What's more,we have reason to attribute the formation of hollow polyhedron to acidic etching by HCl?from NH2OH·HCl?,instead of oxidative etching by O2.As the reaction was prolonged,the free Cu₂O growth units in the reaction solution were exhausted and the crystal stopped growing;at the same time,HCl etching was dominan,resulting in hollow structure as well as rough surface of the Cu₂O polyhedron.?2?Polyhedral Cu₂O Crystal: Morphology Evolution from Meshed Nanocube to SolidPreviously,the formation of polyhedral Cu₂O crystal is usually proposed like that the seed crystals grow outward following the relative growth rates?R values?along different directions?Inside-out Pattern?or that the surrounding building blocks aggregate toward the center followed by ripening?Outside-in Pattern?.However,in this study,simply mixing aqueous Cu?CH3COO?2,NaOH,and D-?+?-glucose in the order listed at 70 ? for a period,a distinct growth manner of Cu₂O polyhedron was observed based on carefully recording the solution color changes and the elaborate time-dependent SEM/TEM observations,which was referred to All-direction Pattern.More specifically,the initially formed Cu₂O nanoshuttles first self-aggregated into porous braided structure with well-defined cubic framework and then condensed into solid cube from all direction via consuming the surrounding fragments everywhere possible,rather than in gradient densification from inside-out or outside-in.After that,the solid cube fell into the common Outside-in Pattern,i.e.,adsorbing the surroundings followed by ripening.?3?Relative Growth Rate Model: Crystal Polyhedron Prediction and CalculationA model aimed at elaborating the relationship between the relative growth rate of low index crystal faces and shape of polygonal crystals in cubic crystal systems was firstly proposed via investigating the section lines left by?110?section cutting plane.By using this model,relative growth rate conditions of 14 polygonal crystals were successfully deduced,resulting in a {100}?{111}-{100}?{110} plot,which could be applied in crystallography:?i?predict the crystal morphology if giving the relative growth rate of the crystal faces;?ii?calculate the specific surface ratio of each face if giving the relative growth rate of the crystal faces;?iii?calculate the relative growth rate of the crystal faces if knowing the polyhedron shape,and so on.It's worth pointing out that the 14 polyhedral crystals are all enclosed by low index crystal faces:?1?cube,?2?angle-truncated cube,?3?cuboctahedron,?4?angle-truncated octahedron,?5?octahedron,?6?edge-angle-truncated cube,?7?perfect edge-angle-truncated cube,?8?angle-edge-truncated cube,?9?edge-truncated cube,?10?edge-angle-truncated octahedron,?11?perfect edge-angle-truncated octahedron,?12?angle-edge-truncated octahedron,?13?edge-truncated octahedron and?14?rhombic dodecahedron.