Mixed matrix membranes (MMMs), possessing high porosity, have received extensive attention for gas sensing applications. However, those with high flexibility and significant sensitivity are rare. In this work, we report on the fabrication of a novel membrane, using Cu₃(HHTP)₂ MOF (Cu-MOF) embedded in a polymer matrix. A solution comprising a homogenous suspension of poly-vinyl alcohol (PVA) and ionic liquid (IL), and Cu-MOF solid particles, was cast onto a petri dish to obtain a flexible membrane (215 μm in thickness). The sensor membrane (Cu-MOF/PVA/IL), characterized for its structure and morphology, was assessed for its performance in sensing against various test gases. A detection limit of 1 ppm at 23 °C (room temperature) for H₂S was achieved, with a response time of 12 s. Moreover, (Cu-MOF/PVA/IL) sensor exhibited excellent repeatability, long-term stability, and selectivity towards H₂S gas. The other characteristics of the (Cu-MOF/PVA/IL) sensor include high flexibility, low cost, low-power consumption, and easy fabrication technique, which nominate this sensor as a potential candidate for use in practical industrial applications.

Self-assembled gold nanoparticles (Au-NPs) possess distinctive properties that are highly desirable in diverse nanotechnological applications. This study meticulously explores the size-dependent behavior of Au-NPs under an electric field, specifically focusing on sizes ranging from 5 to 40 nm, and their subsequent assembly into 2D monolayers on an n-type silicon substrate. The primary objective is to refine the assembly process and augment the functional characteristics of the resultant nanostructures. Utilizing a multifaceted analytical approach encompassing X-ray diffraction (XRD) and scanning electron microscopy (SEM) with energy-dispersive X-ray spectroscopy (EDXS), atomic force microscopy (AFM), and COMSOL multiphysics simulation, this work yields comprehensive insights. Results reveal that the electric field and nanoparticle size critically influence assembly dynamics due to variations in surface energy and electrostatic interactions. Larger Au-NPs (20, 30, and 40 nm) experience enhanced dipolar interactions and more substantial polarizability, enabling more efficient alignment and organization under an applied electric field. This leads to the formation of structured, uniform monolayers with minimal vacancies and smoother surfaces. In contrast, smaller Au-NPs (5, 10, and 15 nm) exhibit lower polarizability, which hampers alignment and promotes clustering and voids. XRD analysis delineates notable disparities in peak intensities and positions: smaller Au-NPs exhibit diminished (111) peak intensities, indicative of uneven distribution and crystallinity, whereas larger particles manifest higher intensities and well-defined peaks across multiple crystallographic planes. SEM images portray diverse surface coverages with AFM corroborating that larger Au-NPs achieve uniform and continuous monolayers with minimal height variations. COMSOL simulations substantiate these findings by illustrating the efficient alignment and settling of larger Au-NPs under the electric field. This study bridges critical gaps in understanding how nanoparticle size modulates assembly dynamics and the resultant properties of 2D Au-NP monolayers, offering pivotal insights into engineering advanced nanostructured materials tailored to specific applications in electronics, coatings, photonics, and catalysis.

Analyzing acetone in the exhaled breath as a biomarker has proved to be a non-invasive method to detect diabetes in humans with good accuracy. In this work, a Bi-gallate MOF doped into a chitosan (CS) matrix containing an ionic liquid (IL) was fabricated to detect acetone gas with a low detection limit of 10 ppm at an operating temperature of 60 °C and 5 V operating bias. The sensor recorded the highest response to acetone in comparison to other test gases, proving its high selectivity along with long-term stability and repeatability. The sensor also exhibited ultra-fast response and recovery times of 15 ± 0.25 s and 3 ± 0.1 s, respectively. Moreover, the sensor membrane also exhibited flexibility and ease of fabrication, making it ideal to be employed as a real-time breath analyzer.

Developing new materials for energy and environment-related applications is a critical research field. In this context, organic and metal–organic framework (MOF) materials are a promising solution for sensing hazardous gases and saving energy. Herein, a flexible membrane of the zeolitic imidazole framework (ZIF-67) mixed with a conductivity-controlled chitosan polymer was fabricated for detecting hydrogen sulfide (H₂S) gas at room temperature (RT). The developed sensing device remarkably enhances the detection signal of 15 ppm of H₂S gas at RT (23 °C). The response recorded is significantly higher than previously reported values. The optimization of the membrane doping percentage achieved exemplary results with respect to long-term stability, repeatability, and selectivity of the target gas among an array of several gases. The fabricated gas sensor has a fast response and a recovery time of 39 s and 142 s, respectively, for 15 ppm of H₂S gas at RT. While the developed sensing device operates at RT and uses low bias voltage (0.5 V), the requirement for an additional heating element has been eliminated and the necessity for external energy is minimized. These novel features of the developed sensing device could be utilized for the real-time detection of harmful gases for a healthy and clean environment.