Enhanced Localized Surface Plasmon Resonance Gas Sensing Using Metal-Organic Frameworks Combined With PEDOT: PSS Films

While localized surface plasmon resonance (LSPR) spectroscopy is highly sensitive to changes in refractive index (RI), its applications have traditionally been confined to larger biological entities. The detection of smaller molecules remains an important yet challenging objective for this method. As a representative case of small molecule detection, gas detection through changes in bulk RI presents a significant challenge for LSPR spectroscopy. In this letter, we report on the sensing of various gases using LSPR Au nano-urchin substrates. In preliminary experiments, although the substrates demonstrated rapid response and reversibility in gas detection, not all gases elicited a strong response. To further improve the response to gases, we encapsulated the nanoparticles with metal organic frameworks (MOF) materials. Given their excellence in gas adsorption, MOFs significantly enhanced the response sensitivity of the sensors fabricated in our experiments. The sensitivity increased several-fold for various types of gases, including ammonia, which was previously undetectable, now eliciting an effective response. Furthermore, since LSPR sensors lack selectivity in detection, we spin-coated a layer of PEDOT: PSS film onto the substrates. As a commonly used material in ammonia detection, the chemical interaction between PEDOT: PSS and ammonia enabled the sensor to exhibit better detection results for ammonia compared to other gases.