Simultaneous detection of carbon dioxide (CO₂) and oxygen (O₂) has attracted considerable interest since CO₂ and O₂ play key roles in various industrial and domestic applications. In this study, a new approach based on a fluorescence ratiometric referencing method was reported to develop an optical dual sensor where platinum (II) meso-tetrakis(pentafluorophenyl)porphyrin (PtTFPP) complex used as the O₂-sensitive dye, CdSe/ZnS quantum dots (QDs) combined with phenol red used as the CO₂-sensitive dye, and CdSe/ZnS QDs used as the reference dye for the simultaneous detection of O₂ and CO₂. All the dyes were immobilized in a gas-permeable matrix poly (isobutyl methacrylate) (PolyIBM) and subjected to excitation using a 380 nm LED. The as-obtained distinct fluorescence spectral intensities were alternately exposed to analyte gases to observe changes in the fluorescence intensity. In the presence of O₂, the fluorescence intensity of the Pt (II) complex was considerably quenched, while in the presence of CO₂, the fluorescence intensity of QDs was increased. The corresponding ratiometric sensitivities of the optical dual sensor for O₂ and CO₂ were approximately 13 and 144, respectively. In addition, the response and recovery for O₂ and CO₂ were calculated to be 10 s/35 s and 20 s/60 s, respectively. Thus, a ratiometric optical dual gas sensor for the simultaneous detection of O₂ and CO₂ was successfully developed. Effects of spurious fluctuations in the intensity of external and excitation sources were suppressed by the ratiometric sensing approach.

Mid-infrared plasmonic metasurfaces have attracted significant interest for a wide range of applications. While conventional metals are commonly used in plasmonic metasurfaces, metallic transition-metal dichalcogenides with high carrier densities and infrared plasmonic response have emerged as attractive alternatives. Here, we demonstrate the mid-infrared TaSe ₂ plasmonic metasurfaces with periodic hole arrays. It is observed that two plasmonic resonance modes in mid-infrared frequency range are supported in the TaSe ₂ metasurface. The simulated electromagnetic field distributions reveal that the two plasmonic resonances represent a fundamental (1, 0) mode and a higher-order (1, 1) mode. By increasing the array period, a continuous redshift of the resonance frequency is observed for each mode, consistent with the inverse scaling predicted by the grating coupling condition. The demonstrated results will advance the development of 2D-material-based mid-infrared photonic devices as a promising platform for applications in thermal emission control, molecular sensing, and infrared detection.

The realization of quantum light sources is crucial for advancing quantum technologies. Two‐dimensional van der Waals (vdW) materials offer a compelling platform for ultracompact entangled photon‐pair sources due to their strong optical nonlinearities and relaxed phase‐matching constraints. Here, the generation of entangled photon pairs from vdW NbOI ₂ flakes on Au film via spontaneous parametric down‐conversion (SPDC) process is demonstrated. The observed inverse relationship between second‐order correlation function and pump power and the linear relationship between coincidence rate and pump power confirm the characteristic features of SPDC process. Furthermore, the measured polarization‐dependent coincidence rate shows the anisotropic entangled photon‐pair emission in NbOI ₂ crystal. The dependence of coincidence rate on flake thickness is characterized by considering both optical interference and the phase‐matching effects. The demonstrated results open new avenues for the development of on‐chip integrated quantum photonic devices for applications in quantum state engineering, quantum communication, and quantum information processing.