A new colorimetric chemosensor for naked-eye detection and determination of cysteine (Cys) based on indicator displacement assay (IDA) was designed using 1-(2-pyridylazo)-2-naphthol (PAN). The indicator exchange occurred between PAN and Cys by the addition of Cys to the Cu(PAN)₂ complex, which is accomplished by an immediate visible color change from magenta to yellow, in the solution phase and paper-based test strips. The proposed method exhibits 0.35 μmol L⁻¹ detection limit and good linearity in the range of 2.25–42.91 μmol L⁻¹. Paper test strips presented a detection limit of 38.0 μmol L⁻¹, fabricating an easy to use test kit for compatible “in-the-field” detection of Cys. The computer image analysis of the paper test strips, obtained from the CMYK color analysis system, showed a linear increase in Y (yellow) intensity with enhancement in the Cys concentration of 50.0–550.0 μmol L⁻¹. Additionally, the absorption and color change obtained in this chemosensor operate as an “INHIBIT” logic gate considering Cu²⁺ and Cys as inputs. Eventually, based on such a fast, reversible, and reproducible signal, a molecular-scale sequential memory unit was designed displaying “Writing–Reading–Erasing–Reading” and “Multi-Write” behavior. The developed chemosensor presented a satisfactory repeatability, intermediate precision, and successful application for the selective determination of Cys in human biological fluids.

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使用1-（2-吡啶基偶氮）-2-萘酚（PAN）设计了一种基于指示剂位移测定（I​​DA）的用于裸眼检测和测定半胱氨酸（Cys）的比色化学传感器。通过将Cys添加到Cu（PAN）₂络合物中，在PAN和Cys之间发生指示剂交换，这是通过在溶液相和纸基测试条中从洋红色到黄色的立即可见颜色变化实现的。所提出的方法具有0.35μmolL ^-1的检出限，并且在2.25–42.91μmolL ^-1的范围内具有良好的线性。纸试纸的检测极限为38.0μmolL ^-1，制造了易于使用的测试套件，用于兼容的Cys的“现场”检测。从CMYK颜色分析系统获得的纸质测试条的计算机图像分析显示，Y（黄色）强度呈线性增加，并且Cys浓度提高了50.0–550.0μmolL ^-1。此外，考虑到Cu ^{2+的影响，}在该化学传感器中获得的吸收和颜色变化也可作为“抑制”逻辑门和Cys作为输入。最终，基于这种快速，可逆和可再现的信号，设计了一种分子级顺序存储单元，显示“写-读-擦除-读”和“多写”行为。研发的化学传感器具有令人满意的重复性，中等精度，并成功用于选择性测定人类生物流体中的Cys。

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