Noble-Nanoparticle-Decorated Ti(3)C(2)T(x) MXenes for Highly Sensitive Volatile Organic Compound Detection

[Image: see text] Two-dimensional transition-metal carbides and nitrides (MXenes) have been regarded as promising sensing materials because of their high surface-to-volume ratios and outstanding electronic, optical, and mechanical properties with versatile transition-metal and surface chemistries. However, weak gas-molecule adsorption of MXenes poses a serious limitation to their sensitivity and selectivity, particularly for trace amounts of volatile organic compounds (VOCs) at room temperature. To deal with these issues, Au-decorated MXenes are synthesized by a facile solution mixing method for room-temperature sensing of a wide variety of oxygen-based and hydrocarbon-based VOCs. Dynamic sensing experiments reveal that optimal decoration of Au nanoparticles (NPs) on Ti(3)C(2)T(x) MXene significantly elevates the response and selectivity of the flexible sensors, especially in detecting formaldehyde. Au–Ti(3)C(2)T(x) gas sensors exhibited an extremely low limit of detection of 92 ppb for formaldehyde at room temperature. Au–Ti(3)C(2)T(x) provides reliable gas response, low noise level, ultrahigh signal-to-noise ratio, high selectivity, as well as parts per billion level of formaldehyde detection. The prominent mechanism for Au–Ti(3)C(2)T(x) in sensing formaldehyde is elucidated theoretically from density functional theory simulations. The results presented here strongly suggest that decorating noble-metal NPs on MXenes is a feasible strategy for the development of next-generation ultrasensitive sensors for Internet of Things.