In situ synthesis of copper metal-organic framework on paper-based device for dual-mode detection of volatile sulfur compounds in exhaled breath

Volatile sulfur compounds (VSCs) are considered as indicators of halitosis and precursors of periodontal diseases. Trace VSCs determination in-breath can provide noninvasive data for clinical diagnostics. In this work, a dual-mode colorimetric/ chemiluminescent (CL) paper-based device with a copper metal-organic framework (Cu-MOF) was developed for trace VSCs detection in exhaled breath. The Cu-MOF with 2,4,6-tris(4-carboxyphenyl)− 1,3,5-triazine (TATB) as a ligand was in situ synthesized on a paper surface by the solvothermal method. The porous Cu-TATB served as a gaseous confinement cavity to selectively capture and adsorb VSCs. When Cu-TATB reacted with VSCs, significant and sensitive color changes can be observed from aqua blue to greenish-brown. Also, the Cu-TATB had an excellent catalytic effect on the luminol-H2O2 CL system. The CL intensity was inhibited by VSCs because of sulfur in VSCs reacting with copper active sites in Cu-TATB to form CuS. In this way, dual-mode detection methods for VSCs in breath were established with limits of detection (LOD) of 0.2 µM for colorimetry and 8 nM for CL. This portable, low-cost and stable paper-based sensor realizes accurate and reproducible signals read-out and shows potential feasibility as a prospect sensor platform for exhaled breath analysis.