二氨基脲嘧啶作为前驱体, 经两步串联反应制备了两种具有不同配体结构的荧光碳点（CDs)。X射线光电子能谱与红外光谱分析揭示了两种碳点的配体结构特征。第一步所得的碳点（CDHB)具有尿嘧啶结构典型的氢键给体—NH和受体—CO基团特征。发射光谱表现出具浓度依赖性的波长红移特点, 同时该碳点对银和汞离子具有很强的亲和特性。第二阶段在碱性水解条件下, CDHB尿嘧啶配体易于转化为氨基和羧基等水溶性基团。该碳点（CDZW)在水相中没有任何聚集行为, 也没有发射波长浓度依赖特性。同时, 作为荧光传感器, CDZW显示对金属镍离子具有特异性荧光猝灭。总之, 可调控的结构特征与传感特性验证了一锅串联反应合成碳点的有效性, 为碳点的可控合成提供了新的合成范式。

A two-steps sequential reaction with diaminouracil as precursor was implemented to produce two types carbon dots(CDs) with distinctive ligands. The structural information of ligands on CDs in each step was obtained by XPS and FT-IR. It revealed that the carbon dots(denoted as CDHB) directly produced in first stage beard uracil moiety with typical hydrogen bond donor —NH and acceptor —CO. CDHB displayed concentration dependent emission bathochromic shift. In addition, the dots’ high affinity towards silver and mercury confirmed the presence of uracil receptor. In the second stage, it gradually converted to a form of dots with zwitterion symbol(denoted as CDZW). Under alkaline condition, uracil receptor converted to amine and carboxyl moieties in CDZW. The transformation of the receptor formed an aqueous solution of CDZW without any aggregate behavior. And no evident peak-shifted fluorescence was observed. When used as a fluorescent indicator, the CDZW displayed fluorescence turn-off upon the addition of nickel. Therefore, tailorable structures and binding properties of the two dots revealed the implement of one-pot sequential reactions, which provides a new access for controllable synthesis of carbon dots.