Monitoring ultralow nitrogen dioxide (NO₂) concentrations is crucial for air quality management and public health. However, the existing NO₂ gas sensors have several defects, like high cost and power consumption, and exhibit poor selectivity. This study addresses these challenges by presenting a novel hexadecafluorinated iron phthalocyanine-reduced graphene oxide (FePcF₁₆-rGO) covalent hybrid sensor for NO₂ detection. This innovative approach, which overcomes the limitations of fabrication cost, energy efficiency, and gas selectivity, is a significant step forward in gas sensor technology. The sensor demonstrates exceptional sensitivity toward ultralow NO₂ concentrations (15.14% response for 100 ppb) with a rapid 60 s UV light-induced recovery. Additionally, the sensor exhibits high selectivity for NO₂, achieving a limit of detection (LOD) of 8.59 ppb. This approach paves the way for developing cost-effective, energy-efficient, and miniature NO₂ monitoring devices for improved environmental monitoring and enhanced safety in workplaces where NO₂ exposure is a concern.

Herein, a single-step production for the development of gas sensing devices from unsubstituted and hexadecafluorinated metal phthalocyanines (MPc, M = Fe²⁺ and Co²⁺) is explained. The preparation of sensor devices by the direct growth of nanowires on interdigitated electrodes by the vapor transport of the synthesized MPc precursors is discussed, emphasizing a single-step approach. Results using as-prepared devices for the detection of NH₃ and NO₂ in the ppb range are shown. In agreement with similar MPc sensing materials, response and recovery times fitted using a double-exponential model gave two rate constants: a short one, on the order of minutes for concentrations above 500 ppb, and a long one, on the order of hours. These rate constants are suitable for environmental monitoring of gases in recovery zones, where longer exposure times are critical in the sampling process. Our F₁₆FePc-NW sensor prototypes show a ∼10% normalized response toward NH₃ at 40 ppb for a measuring time of ∼2.5 h at room temperature and measurable responses to concentrations as low as 5 ppb, rendering them applicable to environmental studies.

Palladium phthalocyanine (PdPc) nanowires (NWs) were developed to achieve the gas sensing of NO₂ in the sub-parts-per-million (ppm) range. Non-substituted metal phthalocyanine are well known for their p-type semiconducting behavior, which is responsible for its gas-sensing capabilities. Nanofabrication of the PdPc NWs was performed by physical vapor deposition (PVD) on an interdigitated gold electrode (IDE). The coordination of palladium in the structure was confirmed with UV–Vis spectroscopy. Gas-sensing experiments for NO₂ detection were undertaken at different sensed gas concentrations from 4 ppm to 0.5 ppm at room temperature. In this work, the responses at different gas concentrations are reported. In addition, structural studies of the PdPc NWs with scanning electron microscopy (SEM) and electron-dispersive X-ray diffraction (EDS) are shown.

This study presents the fabrication and characterization of highly selective, room-temperature gas sensors based on ternary zinc oxide–molybdenum disulfide–titanium dioxide (ZnO-MoS₂-TiO₂) nanoheterostructures. Integrating two-dimensional (2D) MoS₂ with oxide nano materials synergistically combines their unique properties, significantly enhancing gas sensing performance. Comprehensive structural and chemical analyses, including scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDX), Raman spectroscopy, and Fourier transform infrared spectroscopy (FTIR), confirmed the successful synthesis and composition of the ternary nanoheterostructures. The sensors demonstrated excellent selectivity in detecting low concentrations of nitrogen dioxide (NO₂) among target gases such as ammonia (NH₃), methane (CH₄), and carbon dioxide (CO₂) at room temperature, achieving up to 58% sensitivity at 4 ppm and 6% at 0.1 ppm for NO₂. The prototypes demonstrated outstanding selectivity and a short response time of approximately 0.51 min. The impact of light-assisted enhancement was examined under 1 mW/cm² weak ultraviolet (UV), blue, yellow, and red light-emitting diode (LED) illuminations, with the blue LED proving to deliver the highest sensor responsiveness. These results position ternary ZnO-MoS₂-TiO₂ nanoheterostructures as highly sensitive and selective room-temperature NO₂ gas sensors that are suitable for applications in environmental monitoring, public health, and industrial processes.

The electrocatalytic reduction of carbon dioxide (CO₂) into added-value products is a promising alternative to completing the cycle of atmospheric CO₂. We report two new platinum complexes—a salen-like naphthalene (PtL1) and a hydroxy-substituted salpn naphthalene (PtL2)—that are capable of activating CO₂ to produce carbon monoxide (CO). The predominant keto tautomer of the non-innocent ligands was determined using DFT calculations and UV-Vis spectroscopy. The PtL2 complex has a CO Faradaic efficiency >40% in the presence of water as a sacrificial proton source at −2.5 V vs. Fc/Fc⁺. The addition of the hydroxy group in combination with water as a proton source decreased the reduction potential and increased the CO formation tenfold when compared to PtL1.

Surface modification of Cu foam electrode using a CoPc-MWCNT hybrid enhances CO₂RR while minimizing HER.