There has been a long standing debate on the luminescence origination from carbon nanodots (CDs). Herein, we report the solvent dependent piezochromism of CDs by diamond anvil cells experiment. Red- and blue-shift piezochromism were observed in CDs with N,N-dimethylformamide and water as pressure transmitting medium (PTM) with increasing pressure from atmospheric pressure to 25 GPa, which were related to increased π-π stacking and protic-solvent-induced surface chemical structural changes, respectively. Based on theoretical modeling and structural analysis of hydrothermally treated CDs (h-CDs), the reversible and irreversible piezochromism from green emission to blue emission with water as PTM was attributed to pressure induced enhanced intermolecular hydrogen bonding and addition reaction between water molecules and surface electron withdrawing groups on the CDs, respectively. The decreased electron withdrawing ability of the surface chemical structures of CDs further affects their intrinsic luminescence. This work provides a new understanding of the piezochromic luminescence origination from CDs, which is related to the surface related intrinsic luminescence.

中文翻译：

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碳纳米点与表面相关的固有发光：溶剂依赖性压致变色。

关于源自碳纳米点（CD）的发光一直存在着长期的争论。在本文中，我们通过金刚石砧细胞实验报告了CD的溶剂依赖性压致变色现象。在N，N-二甲基甲酰胺和水作为压力传递介质（PTM）的CD中，随着压力从大气压增加到25 GPa，观察到红移和蓝移压致变色现象，这与π-π堆积增加和质子溶剂分别引起表面化学结构变化。根据水热处理CD（h-CD）的理论模型和结构分析，用水作为PTM，从绿色发射到蓝色发射的可逆和不可逆压致变色现象分别归因于压力诱导的分子间氢键增强以及CD上水分子与表面吸电子基团之间的加成反应。CD的表面化学结构的吸电子能力下降，进一步影响其固有发光。这项工作为源自CD的压致变色发光提供了新的认识，其与表面相关的固有发光有关。