A novel graphene oxide (GO)-based pH sensor was designed and prepared through covalently attaching a zwitterionic betaine molecule onto a GO surface. This betaine-modified GO (BMGO) exhibited high water solubility and low toxicity. In aqueous media, BMGO displayed increased fluorescence in acidic conditions and decreased fluorescence in basic conditions. BMGO possesses a pH sensing range from 4 to 12 with excellent reversibility, quick response and high stability. With its high sensitivity and robustness, BMGO can be used to monitor the pH of intracellular contents, as demonstrated through cell imaging.

中文翻译：

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低毒荧光纳米探针适用于感测生物环境中的pH值变化

通过将两性离子甜菜碱分子共价附着在GO表面上，设计并制备了一种基于氧化石墨烯（GO）的新型pH传感器。该甜菜碱改性的GO（BMGO）表现出高水溶性和低毒性。在水性介质中，BMGO在酸性条件下显示增加的荧光，而在碱性条件下显示减少的荧光。BMGO具有4到12的pH感应范围，具有出色的可逆性，快速响应和高稳定性。BMGO具有高灵敏度和耐用性，可用于监测细胞内内容物的pH，如通过细胞成像所证明的那样。