Two birds with one stone: Visual colorful assessment of dipicolinic acid and Cu2+ by Ln-MOF hybrid attapulgite nano-probe

• A bifunctional nano-probe was constructed through one-step method. • It can realize visual assessment of DPA and Cu 2+. • It was highly desirable for environmental security. • Thin-filmed sensor indicated good visual assessment for DPA and Cu 2+. The poor solubility of Ln-MOF fluorescent nano-probe in water significantly limited their practical application. At the same time, the determination of target analytes is mostly carried out in buffer solution, but the preparation of buffer solution and pH calibration often bring inconvenience to the test. In this work, a bifunctional fluorescent nano-probe (ATP@Eu:Tb-MOF) was constructed at room temperature through one-step method using inorganic nanoclays ATP and Ln-MOF, which recognized anthrax biomarker DPA and Cu 2+ in commercially pure drinking water. This nano-probe achieved visual detection of DPA with ultra-high sensitivity (LOD-DPA = 8.82 nM), excellent selectivity to DPA isomers and high reliability in the detection of DPA released by Bacillus subtilis . In addition, the probe can also selectively detect Cu 2+ through the “turn-off” pathway with a high sensitivity (LOD-Cu 2+ = 6.94 nM). Intelligent visual monitoring was realized by fast reading and analyzing the RGB values of the color changing images of the paper-based nano-probe using smartphone color scanning APP. Furthermore, thin-film-based luminescent nanoprobe can also make excellent visual color assessment of DPA and Cu 2+ , and advanced logic gate circuit analytical devices were also designed.