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Low-power gas sensors that can be used in IoT (Internet of Things) systems, consumer devices, and point-of-care devices will enable new applications in environmental monitoring and health protection. We fabricated a monolithic chemiresistive gas sensor by integrating a micro-lightplate with a 2D sensing material composed of single-layer graphene and monolayer-thick TiO2. Applying ultraviolet (380 nm) light with quantum energy above the TiO2 bandgap effectively enhanced the sensor responses. Low (<1 μW optical) power operation of the device was demonstrated by measuring NO2 gas at low concentrations, which is typical in air quality monitoring, with an estimated limit of detection < 0.1 ppb. The gas response amplitudes remained nearly constant over the studied light intensity range (1–150 mW/cm2) owing to the balance between the photoinduced adsorption and desorption processes of the gas molecules. The rates of both processes followed an approximately square-root dependence on light intensity, plausibly because the electron–hole recombination of photoinduced charge carriers is the primary rate-limiting factor. These results pave the way for integrating 2D materials with micro-LED arrays as a feasible path to advanced electronic noses.

Miniature and low-power gas sensing elements are urgently needed for a portable electronic nose, especially for outdoor pollution monitoring. Hereby we prepared chemiresistive sensors based on wide-area graphene (grown by chemical vapor deposition) placed on Si/Si3N4 substrates with interdigitated electrodes and built-in microheaters. Graphene of each sensor was individually functionalized with ultrathin oxide coating (CuO-MnO2, In2O3 or Sc2O3) by pulsed laser deposition. Over the course of 72 h, the heated sensors were exposed to randomly generated concentration cycles of 30 ppb NO2, 30 ppb O3, 60 ppb NO2, 60 ppb O3 and 30 ppb NO2 + 30 ppb O3 in synthetic air (21% O2, 50% relative humidity). While O3 completely dominated the response of sensors with CuO-MnO2 coating, the other sensors had comparable sensitivity to NO2 as well. Various response features (amplitude, response rate, and recovery rate) were considered as machine learning inputs. Using just the response amplitudes of two complementary sensors allowed us to distinguish these five gas environments with an accuracy of ~ 85%. Misclassification was mostly due to an overlap in the case of the 30 ppb O3, and 30 ppb O3 + 30 ppb NO2 responses, and was largely caused by the temporal drift of these responses. The addition of recovery rates to machine learning input variables enabled us to very clearly distinguish different gases and increase the overall accuracy to ~94%.

Gas sensors play a critical role in safety assurance, environmental monitoring, and health diagnostics, requiring high sensitivity, fast response, and low power consumption—especially in portable applications. This study presents graphene‐based chemiresistive gas sensors fabricated on MEMS microheaters and functionalized with atomically thin layers of vanadium pentoxide or copper‐manganese oxide. In these heterostructures, the metal oxide serves as the gas receptor while graphene functions as the transducer. Operated in a pulsed heating mode (115–205 °C for 0.05–1 s every 10 s), the sensors demonstrated ultra‐low power consumption ranging from 13 to 520 µW. Ammonia (NH3), a hazardous industrial gas and a biomarker in exhaled breath, is used as the target analyte. Transient conductance profiles at 4–32 ppm NH3 are analyzed using machine learning. Feature extraction via discrete Fourier transform and prediction using a compact neural network enables NH3 concentration estimation within 10–20 s, achieving a mean absolute error below 1% (or below 0.1 ppm at low concentrations). Despite the raw signal's sensitivity to relative humidity (RH), the model accurately predicts NH3 concentrations without RH data. The highest accuracy and humidity robustness are achieved using signals from two sensors with different oxide coatings. Ultra‐low power graphene‐based MEMS gas sensors functionalized with vanadium pentoxide or copper‐manganese oxide are reported. Operated in pulsed heating mode, the sensors produce transient conductance profiles analyzed via discrete Fourier transform and compact neural networks. This approach enables rapid, humidity‐resilient NH3 quantification with sub‐ppm accuracy. The method is scalable and well‐suited for portable diagnostics and environmental monitoring applications.

Plant resource sharing mediated by mycorrhizal fungi has been a subject of recent debate, largely owing to the limitations of previously used isotopic tracking methods. Although CdSe/ZnS quantum dots (QDs) have been successfully used for in situ tracking of essential nutrients in plant-fungal systems, the Cd-containing QDs, due to the intrinsic toxic nature of Cd, are not a viable system for larger-scale in situ studies. We synthesized amino acid-based carbon quantum dots (CQDs; average hydrodynamic size 6 ± 3 nm, zeta potential −19 ± 12 mV) and compared their toxicity and uptake with commercial CdSe/ZnS QDs that we conjugated with the amino acid cysteine (Cys) (average hydrodynamic size 308 ± 150 nm, zeta potential −65 ± 4 mV) using yeast Saccharomyces cerevisiae as a proxy for mycorrhizal fungi. We showed that the CQDs readily entered yeast cells and were non-toxic up to 100 mg/L. While the Cys-conjugated CdSe/ZnS QDs were also not toxic to yeast cells up to 100 mg/L, they were not taken up into the cells but remained on the cell surfaces. These findings suggest that CQDs may be a suitable tool for molecular tracking in fungi (incl. mychorrhizal fungi) due to their ability to enter fungal cells.

SiV-containing microcrystals of diamond are synthesised by using high-pressure high-temperature treatment of a mixture of pertinent organic-inorganic precursors. Photoluminescence of SiV defects were investigated with the aim to use the microcrystals for optical temperature sensing in near infrared at room temperature based on temperature-dependent shift of the 740 nm zero-phonon line of SiV photoemission.

In present work it was attempted to prepare luminescent TiO2:Sm3+ microprobes embedded into low density polyethylene (LDPE) films for real-time non-intrusive detection of oxygen contamination in plastic film of food packages with a long term goal of streamlining the quality control mechanisms in food packaging process. The luminescence of TiO2:Sm3+ has previously been reported to be a usable for optical sensing of O2 and other gases [1]. In current work we also show that its thermal stability makes it especially suitable for thermo polymer industry as it can withstand required thermal treatments encountered in different polymer processing stages without losing its ability to function as an O2 probe. Sol–gel-prepared TiO2:Sm3+ microparticles were embedded into LDPE by direct mixing [2] and hot pressing the polymer in molten state. The optical response of the doped films to various O2 ambient concentrations are reported in comparison to pristine TiO2:Sm3+ powder. The shortcomings in the sensor performance due to poor oxide particle size control must be paid attention in the future.

Low-power gas sensors that can be used in IoT (Internet of Things) systems, consumer devices, and point-of-care devices will enable new applications in environmental monitoring and health protection. We fabricated a monolithic chemiresistive gas sensor by integrating a micro-lightplate with a 2D sensing material composed of single-layer graphene and monolayer-thick TiO[sub.2] . Applying ultraviolet (380 nm) light with quantum energy above the TiO[sub.2] bandgap effectively enhanced the sensor responses. Low (<1 μW optical) power operation of the device was demonstrated by measuring NO[sub.2] gas at low concentrations, which is typical in air quality monitoring, with an estimated limit of detection < 0.1 ppb. The gas response amplitudes remained nearly constant over the studied light intensity range (1–150 mW/cm[sup.2] ) owing to the balance between the photoinduced adsorption and desorption processes of the gas molecules. The rates of both processes followed an approximately square-root dependence on light intensity, plausibly because the electron–hole recombination of photoinduced charge carriers is the primary rate-limiting factor. These results pave the way for integrating 2D materials with micro-LED arrays as a feasible path to advanced electronic noses.

The invention of electrospinning has solved the problem of producing micro- and nanoscaled metal oxide fibres in bulk quantities. However, until now no methods have been available for preparing a single nanofibre of a metal oxide. In this work, the direct drawing method was successfully applied to produce metal oxide (SnO 2 , TiO 2 , ZrO 2 , HfO 2 and CeO 2 ) fibres with a high aspect ratio (up to 10 000) and a diameter as small as 200 nm. The sol-gel processing includes consumption of precursors obtained from alkoxides by aqueous or non-aqueous polymerization. Shear thinning of the precursors enables pulling a material into a fibre. This rheological behaviour can be explained by sliding of particles owing to external forces. Transmission (propagation) of light along microscaled fibres and their excellent surface morphology suggest that metal oxide nanofibres can be directly drawn from sol precursors for use in integrated photonic systems.

Low-power gas sensors that can be used in IoT (Internet of Things) systems, consumer devices, and point-of-care devices will enable new applications in environmental monitoring and health protection. We fabricated a monolithic chemiresistive gas sensor by integrating a micro-lightplate with a 2D sensing material composed of single-layer graphene and monolayer-thick TiO . Applying ultraviolet (380 nm) light with quantum energy above the TiO bandgap effectively enhanced the sensor responses. Low (<1 μW optical) power operation of the device was demonstrated by measuring NO gas at low concentrations, which is typical in air quality monitoring, with an estimated limit of detection < 0.1 ppb. The gas response amplitudes remained nearly constant over the studied light intensity range (1-150 mW/cm ) owing to the balance between the photoinduced adsorption and desorption processes of the gas molecules. The rates of both processes followed an approximately square-root dependence on light intensity, plausibly because the electron-hole recombination of photoinduced charge carriers is the primary rate-limiting factor. These results pave the way for integrating 2D materials with micro-LED arrays as a feasible path to advanced electronic noses.

An enhanced Raman scattering from a thin layer of adenine molecules deposited on graphene substrate was detected. The value of enhancement depends on the photon energy of the exciting light. The benzene ring in the structure of adenine molecule suggests π-stacking of adenine molecule on top of graphene. So, it is proposed that the enhancement in the adenine Raman signal is explained by the resonance electron transfer from the Fermi level of graphene to the lowest unoccupied molecular orbital (LUMO) level of adenine.