A novel multifunctional semiconducting polymer dot (Pdots)/pyrogallic acid (PA) system was successfully established for fluorescence sensing of urea, urease, and pesticides. The Pdots/PA system was pH controllable, emitting strong fluorescence at pH 6.0. However, in an alkaline environment, PA transformed into its quinone structure, which is an efficient fluorescence quencher, resulting in fluorescence quenching of the Pdots/PA system. Furthermore, urea was hydrolyzed in the presence of urease, releasing hydroxyl groups that transformed PA into its quinone structure, resulting in fluorescence quenching of the Pdots/PA system. Therefore, a sensitive detection method for urea and urease was developed. The limits of detection for urea and urease were 0.02 mM and 0.08 U L⁻¹, respectively. Pesticides, such as dimethoate, were able to inhibit the urease activity, resulting in recovery of the fluorescence intensity of the Pdots/PA system. Therefore, the fluorescence turn-on detection of pesticides could be also achieved. A satisfactory result was obtained when using the system to detect pesticides in fruit and vegetable samples.

中文翻译：

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在新型半导体聚合物/邻苯二甲酸中的pH值控制的荧光变化以及尿素，脲酶和农药的多功能传感策略

成功建立了一种新型的多功能半导体聚合物点（Pdots）/邻苯二酸（PA）系统，用于尿素，脲酶和农药的荧光传感。Pdots / PA系统可控制pH，在pH 6.0时发出强荧光。但是，在碱性环境中，PA转变为醌结构，这是一种有效的荧光猝灭剂，导致Pdots / PA系统发生荧光猝灭。此外，尿素在尿素酶的存在下被水解，释放出羟基，该羟基将PA转化为醌结构，从而导致Pdots / PA系统的荧光猝灭。因此，开发了一种灵敏的尿素和脲酶检测方法。尿素和尿素酶的检出限为0.02 mM和0.08 UL ^-1， 分别。农药（如乐果）能够抑制脲酶活性，从而恢复了Pdots / PA系统的荧光强度。因此，还可以实现农药的荧光开启检测。使用该系统检测水果和蔬菜样品中的农药时，获得了满意的结果。