Solid-state chemiresistive gas sensors have attracted a lot of researchers’ attention during the last half-century thanks to their ability to detect different gases with high sensitivity, low power consumption, low cost, and high portability. Among the most promising sensitive materials, carbon nanotubes (CNTs) have attracted a lot of interest due to their large active surface area (in the range of 50–1400 m²/g, depending on their composition) and the fact that they can operate at room temperature. In this study, single-walled carbon nanotube (SWCNT)-based sensing films were prepared and deposited by spray deposition for the fabrication of gas sensors. For the deposition, various SWCNTs were prepared in deionized water with the addition of specific surfactants, i.e., carboxymethyl cellulose (CMC) and sodium dodecyl sulfate (SDS), which act as dispersing agents to create a suitable ink for deposition. This study aims to elucidate the possible differences in the sensing performance of the fabricated devices due to the use of the two different surfactants. To achieve this goal, all the devices were tested versus ethanol (C₂H₅OH), carbon monoxide (CO), nitrogen dioxide (NO₂), and ammonia (NH₃). The produced devices demonstrated high selectivity towards NH₃ and NO₂. The different sensors, prepared with different deposition thicknesses (from 0.51 nm to 18.41 nm), were tested in dry and wet conditions (40% humidity), highlighting an enhanced response as a function of relative humidity. In addition, sensor performance was evaluated at different working temperatures, showing the best performance when heated up to 150 °C. The best sensing conditions we found were against NO₂, sensors with 10 layers of deposition and an operating temperature of 150 °C; in this condition, sensors showed high responses compared those found in the literature (62.5%—SDS-based and 78.6%—CMC-based). Finally, cross-sensitivity measurements showed how the produced sensors are good candidates for the practical and selective detection of NO₂, even in the presence of the most important interfering gases identified, i.e., NH₃.

Molecular catalysts based on coordination complexes for the generation of hydrogen via photochemical water splitting exhibit a large versatility and tunability of the catalytic properties through chemical functionalization. In the present work, we report on light-driven hydrogen production in an aqueous solution using a series of cobalt polypyridine complexes as hydrogen evolving catalysts (HECs) in combination with CuInS₂@ZnS quantum dots (QDs) as sensitizers, and ascorbate as the electron donor. A peculiar trend in activity has been observed depending on the substituents present on the polypyridine ligand. This trend markedly differs from that previously recorded using [Ru(bpy)₃]²⁺ (where bpy = 2,2’-bipyridine) as the sensitizer and can be ascribed to different kinetically limiting pathways in the photochemical reaction (viz. protonation kinetics with the ruthenium chromophore, catalyst activation via electron transfer from the QDs in the present system). Hence, this work shows how the electronic effects on light-triggered molecular catalysis are not exclusive features of the catalyst unit but depend on the whole photochemical system.

Electrolyte-gated field-effect transistors (EG-FETs) are widely used in the growing field of biochemical sensing applications, due to their manifold advantages, such as large specific capacitance, low operating voltage, and intrinsic signal amplification. In this work, carbon nanotube EG-FET (EG-CNTFET)-based sensors for ammonium (NH ⁺ ₄ ) detection are reported. The active semiconducting single-walled carbon nanotube (CNTs) layer was manufactured through a cost-effective and scalable spray deposition technique. To achieve high-quality semiconducting networks, the CNT ink was optimized. Atomic force microscopy analysis was used to optimize the CNT concentration and significantly reduce the post-treatment time from the previously reported 12 h to 1 h. The optimized ink was then used to fabricate EG-CNTFETs first on standard rigid Si/SiO ₂ substrate and then on flexible polyimide foils. Both devices showed typical p-type behavior with an on-off ratio in the order of magnitude of 1×10 ³ A/A. Furthermore, as proof of concept, we demonstrated the detection of the NH ⁺ ₄ ions with EG-CNTFETs fabricated on a flexible substrate and functionalized with nonactin ion-selective membrane. The calibration curve of the fabricated sensors showed a linear detection range for ammonium from 0.01mM to 10mM, covering the entire range of physiological concentrations of interest, with an average sensitivity of 0.346 μA/decade and a 94.35% coefficient of determination.

Biophotonics has gained significant interest in recent years due to its potential in medical theranostic applications, with nano‐materials emerging as key enablers for advancing optical and electronic functionalities in biological environments. In this study, conjugated polymer nanoparticles (CP‐NPs), namely regio‐regular poly(3‐hexylthiophene) (P3HT), [6,6]‐phenyl C61‐butyric acid methyl ester (PCBM), and their blend (P3HT:PCBM), are exploited as nano‐materials for biophotonic applications. The CP‐NPs, obtained via a nanoprecipitation method, showed an average size of ca. 180 nm. Their optoelectrical properties indicate visible absorbance (350–600 nm) and red/near infra‐red (NIR, 650–900 nm) emission, demonstrating their suitability for biophotonic applications, in particular in biohybrid interfaces where effective light absorption and emission in biological environments are crucial. Interestingly, under light stimulation, the photocurrent response of the CP‐NPs in electrolyte solution (phosphate‐buffered saline, PBS) showed a stable and reproducible signal (current density ranging from 0.18 to 7 nA cm ⁻² ) thereby enhancing their potential for bio‐sensing/stimulation. Simulations of CP‐NPs interactions with biological fluids (i.e., PBS) under light stimulation showed distinct carrier generation and transport behaviors, with P3HT‐NPs exhibiting consistent charge generation (up to 3 × 10 ²⁰ nA cm ⁻³ ). These findings demonstrate that CP‐NPs are promising for biophotonic applications, such as photothermal therapy, due to their efficient charge transport, UV‐vis absorption, NIR emission, and controlled interactions with biological environments.

Chemoresistive gas sensors are surely one of the easiest and most commonly used methods to monitor the presence of different polluting gases. Nevertheless, there are still several challenges to overcome in order for these sensors to be widely used. In particular, the selectivity and sensitivity of chemoresistive gas sensors towards a wide range of analytes need to be improved. This is why new sensing materials capable of detecting different analytes in a sensitive and selective manner are being investigated. In this regard, this work is focused on the development and characterization of a new sensing material based on the quantum dot (QD) core–shell of CuInS₂/ZnO (CIS-ZO). Optimized films of the QD core–shell of CIS-ZO were integrated into a micro-electromechanical system (MEMS)-based gas sensor platform, showing excellent sensing performance versus different gases and especially towards ethanol (C₂H₅OH).