题目

麻烦翻译下Figure 1 displays the emission spectra
Figure 1 displays the emission spectra changes of QB upon
the addition of an increasing amount of Zn2+ and Cd2+. Free
QB showed weak fluorescence emission at 405 nm upon
excitation at 295 nm (ε ) 0.87 × 104 M-1 cm-1, Φ0 ) 0.057)
in buffer solution because of the efficient PET quenching
from the DPA moiety to the quinoline fluorophore. Remarkable
fluorescence enhancements were detected upon the
addition of Zn2+ and Cd2+, respectively. Upon binding Zn2+,
QB showed a larger emission red-shift of 53 nm from 405
to 458 nm with an isoemissive point at 400 nm (Figure 1a),
indicating that a promoted ICT process occurred with
consequent ratiometric fluorescent signals. The ratio of
emission intensities (F458 nm/F380 nm) varies from 0.6 to 12
and is saturated up to a molar ratio (QB/Zn2+) of 1:1 (Figure
1b). In contrast, upon binding Cd2+, only enhanced fluorescent
intensity (ΦCd ) 0.22) w

提问时间：2020-10-29

答案

图1示出了QB在添加数量逐渐增加的Zn2+和Cd2+时发射谱的变化.自由QB在于缓冲溶液中在295nm（ε＝0.87×104 M－1cm－1,Φ0＝0.057）下激励时,在405nm处显示出弱的荧光发射,因为从DPA分子部分到喹啉荧光团有效地PET猝灭.在添加Zn2+和Cd2+时,分别检测到明显的荧光增强.在结合Zn2+时,QB显示出53nm的较大红色偏移,从405到458nm,在400nm处有一个等发射点（图1a）,表明了由作为结果发生的比率荧光信号产生了得到促进的ICT过程.发射光强的比率（F458nm/F380nm）从0.6变到12,直至1：1的摩尔比（QB/Zn2＋）时饱和.与此相反,在结合Cd2+时,只观察到伴随较小波长偏移的增强的荧光光强（Φcd＝0.22）,而没有等发射点（图1c）,表明了传感器QB主要根据CHEF机理识别Cd2＋.如图1b、d所示的滴定曲线证明了高的结合亲和力12和Zn2+、Cd2+和QB之间1：1的络合物.
为了进一步了解QB对金属离子的传感性质,我们研究了CH3CN/H2O缓冲溶液中不同离子的荧光滴定（图2）.当添加Co2＋、Ni2＋、Cu2＋、Hg2＋、和Pb2＋等重金属离子时观察到
了猝灭效应,就像在其他喹啉—DPA基传感器上观察到的那样.添加Mg2＋、Ca2＋和Na＋对QB的发射不施加或几乎不施加影响,即使在高浓度（1mM）下也是如此.如预料的那样,在添加Zn2＋和Cd2＋时,都能检测到明显的荧光变化.QB对Zn2＋的选择性比率响应（F458nm/F380nm直至12）被清楚地观察到（图2b）,而且不受存在Mn2＋、Fe3＋、Mg2＋、Ca2＋、K＋和Na＋等离子的干扰（支持信息图S4和S5）.考虑在结合Cd2＋时明显的荧光增强,QB也可以用作CHEF Cd2＋选择性传感器.在这种情况下,其他金属的性状类似于在Zn2＋的情况下（支持信息图S3）.这些结果告诉我们,QB对Zn2＋和Cd2＋有良好的选择性.