In this study, the phase transition from tetragonal BiOBr to monoclinic Bi₄O₅Br₂ was regulated in the presence of branched polyethyleneimine (BPEI) containing massive amino groups via a hydrothermal route. Based on the crystal phase of the products obtained at different concentrations of the BPEI and Br⁻ sources, the relative concentration of BPEI (the concentration ratio of the BPEI and Br⁻ sources, BPEI/Br⁻) played the decisive role in this phase transition. In particular, a BPEI/Br⁻ value over 0.2 g mmol⁻¹ with excessive BPEI was critical for the phase transition. Further, a reasonable theory referring the synergistic effect of the “drag force” and facet recognition of excessive BPEI underlying this phase transition was confirmed through a series of systematically designed experiments. The protonated amino groups from excessive BPEI could not only act as a “drag force” to extract the bromine ions from the solid-state BiOBr nanosheets but also recognize the (001) facet of BiOBr, thereby distorting the tetragonal structure of the BiOBr nanosheets and forming monoclinic Bi₄O₅Br₂ nanosheets. This work provides a new insight and proof of the regulation of the phase transition of BiOBr to Bi₄O₅Br₂.

中文翻译：

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通过“拖曳力”和支链聚乙烯亚胺的刻面识别的协同效应来调节单斜晶Bi4O5Br2的相变

在这项研究中，在含有大量氨基的支链聚乙烯亚胺（BPEI）的存在下，通过水热途径调节了从四方BiOBr到单斜Bi ₄ O ₅ Br ₂的相变。基于在不同浓度的BPEI和Br所获得的产物的晶相^-源，BPEI（在BPEI和Br的浓度比的相对浓度^-源，BPEI /溴^- ）在该相变中的决定性作用。特别地，BPEI /溴^-超过0.2值g毫摩尔^-1BPEI过多对于相变至关重要。此外，通过一系列系统设计的实验，证实了一种合理的理论，该理论涉及“拖曳力”的协同效应和该相变背后的过多BPEI的方面识别。过量BPEI产生的质子化氨基不仅可以作为“拖拉力”从固态BiOBr纳米片中提取溴离子，而且可以识别BiOBr的（001）面，从而扭曲了BiOBr纳米片的四方结构，并且形成单斜Bi ₄ O ₅ Br ₂纳米片。这项工作为BiOBr到Bi ₄ O ₅ Br ₂的相变调控提供了新的见识和证据。。