Multi-sensing Platform Based on Two-Dimensional Monoelement Germanane.

Covalently functionalized germanane is a novel type of fluorescent probe that can be employed in material science and analytical sensing. Here, we developed a fluorometric sensing platform based on methyl-functionalized germanane (CH 3 Ge) for gas (humidity and ammonia) sensing, pH (1-9) sensing, and anti-counterfeiting. A luminescence (red-orange) is seen when a gas molecule intercalates into the interlayer space of CH 3 Ge and the luminescence disappears upon deintercalation. This allows for direct detection of gas absorption via fluorometric measurements of the CH 3 Ge. Structural and optical properties of CH 3 Ge with intercalated gas molecules are investigated by density functional theory. To demonstrate real-time and on-the-spot testing, we first precisely quantified absorbed gas molecules (humidity and ammonia) by CH 3 Ge using a smartphone camera with an installed color intensity processing application (APP). Further, CH 3 Ge film was integrated into real food packets (e.g., fish and milk) to monitor the shelf life of perishable foods. The band gap changes and optical response of CH 3 Ge to various gas molecules were examined using density functional theory calculations. Finally, CH3Ge-based rewritable paper was applied in water jet printing to illustrate the potential for secret communication with quick coloration and good reversibility by water evaporation. This article is protected by copyright. All rights reserved.