Highly Efficient Red/NIR-Emissive Fluorescent Probe with Polarity-Sensitive Character for Visualizing Cellular Lipid Droplets and Determining Their Polarity.

Lipid droplets (LDs), which are ubiquitous organelles existing in almost all eukaryotic cells, have attracted a lot of attention in the field of cell biology over the last decade. For the biological study of LDs via fluorescence imaging, the superior LD fluorescent probes with environmental polarity-sensitive character are highly desired and powerful but are very scarce. Herein, we have newly developed such a kind of fluorescent probe named LDs-Red which enables us to visualize LDs and to further reveal their polarity information. This fluorescent probe displays the advantages of intense red/near-infrared emission, high LD staining specificity, and good photostability; thus, it would be very useful for LD fluorescence imaging application. As a result, the three-dimensional confocal imaging to visualize spatial distribution of LDs and the multicolor confocal imaging to simultaneously observe LDs and other cellular organelles have been realized using this new LD fluorescent probe. Furthermore, the polarity-sensitive emission character of this probe enables us to quantitatively determine the LD polarity via spectral scan imaging. Consequently, the cancer cells (HepG2, HeLa, and Panc02) displaying lower polarity of LDs than the normal cells (L929, U251, and HT22) have been systematically demonstrated. In addition, this polarity-sensitive probe displaying shorter fluorescence wavelengths in cancer cells than in normal cells has an important and potential ability to distinguish them.

Gold-Trisoctahedra-Coated Capillary-Based SERS Platform for Microsampling and Sensitive Detection of Trace Fentanyl.

A cost-effective and highly reproducible capillary-based surface-enhanced Raman scattering (SERS) platform for sensitive, portable detection and identification of fentanyl is presented. Through encapsulating gold trisoctahedra (Au TOH) in the capillary tube for the first time, the SERS platform was constructed by combining the superior SERS properties of Au TOH and the advantages of capillaries in SERS signal amplification, facile sample extraction, and portable trace analysis. The effects of the size and density of Au TOH on the SERS performance were investigated by experiments and simulations, which showed that the maximum SERS enhancement was obtained for Au TOH with the size of 75 nm when particle density reached 74.54 counts/µm2. The proposed SERS platform possesses good reproducibility with a relative standard deviation (RSD) of less than 5%. As a demonstration, the platform was applied to detect fentanyl spiked in aqueous solution and serum samples with a limit of detection (LOD) as low as 1.86 and 40.63 ng/mL, respectively. We also validated the feasibility of the designed platform for accurate identification of trace fentanyl adulterated in heroin at mass concentration down to 0.1% (10 ng in 10 µg total). Overall, this work advances more explorations on capillary-based SERS platform to benefit portable trace analysis.

Embedding Proteins within Spatially Controlled Hierarchical Nanoarchitectures for Ultrasensitive Immunoassay.

Modulating the precise self-assembly of functional biomacromolecules is a critical challenge in biotechnology. Herein, functional biomacromolecule-assembled hierarchical hybrid nanoarchitectures in a spatially controlled fashion are synthesized, achieving the biorecognition behavior and signal amplification in the immunoassay simultaneously. Biomacromolecules with sequential assembly on the scaffold through the biomineralization process show significantly enhanced stability, bioactivity, and utilization efficiency, allowing tuning of their functions by modifying their size and composition. The hierarchically hybrid nanoarchitectures show great potential in construction of ultrasensitive immunoassay platforms, achieving a three order-of-magnitude increase in sensitivity. Notably, the well-designed HRP@Ab2 nanoarchitectures allow for optical immunoassays with a detection range from picogram mL-1 to microgram mL-1 on demand, providing great promise for quantitative analysis of both low-abundance and high-residue targets for biomedical applications.

Smartphone-Assisted Robust Sensing Platform for On-Site Quantitation of 2,4-Dichlorophenoxyacetic Acid Using Red Emissive Carbon Dots.

On-site quantitative analysis of pesticide is of significant importance for addressing serious public health issues in clinical, food, and environmental settings. Herein, we designed a novel smartphone-assisted sensing platform for on-site monitoring of 2,4-dichlorophenoxyacetic acid (2,4-D) based on carbon dots/cobalt oxyhydroxide nanosheet (CDs/CoOOH) composite. In this work, a red emissive CDs/CoOOH composite was proposed as a signal indicator for shielding background interference, enhancing anti-interference capability. 2,4-D as an inhibitor of alkaline phosphatase could specifically suppress the production of ascorbic acid, which restrained in situ etching of the CDs/CoOOH composite and further triggered the fluorescence response of the biosensor. By employing a lab-on-smartphone based device and self-designed application software, the fluorescence image was directly captured and analyzed with a sensitive detection limit of 100 µg L-1 for 2,4-D. Merging the CDs/CoOOH composite-based fluorometric system with the smartphone-assisted optical reader, such a cost-effective and portable platform provided a new sight for on-site monitoring of pesticide and expanded application prospect in the field of biological analysis.

Temperature-controlled resistive sensing of gaseous H2S or NO2 by using flower-like palladium-doped SnO2 nanomaterials.

Palladium-doped SnO2 nanomaterials, with palladium in fractions from 0 to 10 mol% were hydrothermally synthesized and characterized by XRD, FESEM, TEM, and XPS. Their gas sensing properties were studied in two temperature ranges of 75-95 °C and 160-210 °C. The sensor using 5 mol% Pd-doped SnO2 exhibits temperature-dependent sensing property. NO2 can be detected at 80 °C, while H2S is preferably detected at 180 °C. The response to 10 ppm H2S is 50 times higher than that of the undoped sample. Its detection limit is 500 ppb. For NO2, the sensor exhibited strong response and a lower detection limit of 20 ppb. In view of the selective detection of H2S and NO2 by regulating the temperature, palladium-doped SnO2 has great prospects in the detection of H2S and NO2. Graphical abstract Schematic of the gas sensing mechanism of the S-5% Pd doped SnO2.

Enhanced resistive acetone sensing by using hollow spherical composites prepared from MoO3 and In2O3.

Hollow sphere composites were synthesized by a template-free hydrothermal method from MoO3 and In2O3. The spheres have a typical size of 800 ± 50 nm and were characterized by XRD, FESEM, TEM, XPS. Gas sensors based on samples with different Mo/In composite ratios were fabricated and their gas sensing properties were studied. The results show that a Mo:In ratio of 1:1 in the composite gives the highest response, typically at a working temperature of 250 °C. The response increases to 38 when exposed to 100 ppm acetone at 250 °C. This is 13.6 times better than when using pure MoO3. The sensor shows improved selectivity, response, repeatability and long-term stability. Typical features include a large specific surface area, and high levels of chemisorbed oxygen and defective oxygen sites. The N-N heterojunction theory was used to explain the improvement of gas sensing performance. Graphical abstract Schematic presentation of MoO3 and In2O3 composites and response test graph for 100 ppm acetone. The sensor based on this composite exhibits a very high response (38) to acetone at 250 °C and very fast response time (2 s).

Highly Sensitive and Stable Multifunctional Self-Powered Triboelectric Sensor Utilizing Mo2CTx/PDMS Composite Film for Pressure Sensing and Non-Contact Sensing.

Sensors based on triboelectric nanogenerators (TENGs) are increasingly gaining attention because of their self-powered capabilities and excellent sensing performance. In this work, we report a Mo2CTx-based triboelectric sensor (Mo-TES) consisting of a Mo2CTx/polydimethylsiloxane (PDMS) composite film. The impact of the mass fraction (wt%) and force of Mo2CTx particles on the output performance of Mo-TES was systematically explored. When Mo2CTx particles is 3 wt%, Mo-TES3 achieves an open-circuit voltage of 86.89 V, a short-circuit current of 578.12 nA, and a power density of 12.45 µW/cm2. It also demonstrates the ability to charge capacitors with varying capacitance values. Additionally, the Mo-TES3 demonstrates greater sensitivity than the Mo-TES0 and a faster recovery time of 78 ms. Meanwhile, the Mo-TES3 also demonstrates excellent stability in water washing and antifatigue testing. This demonstrates the effectiveness of Mo-TES as a pressure sensor. Furthermore, leveraging the principle of electrostatic induction, the triboelectric sensor has the potential to achieve non-contact sensing, making it a promising candidate for disease prevention and safety protection.

Integrated Mixed Potential Gas Sensor with Efficient Structure for Discriminative Volatile Organic Compounds Detection.

Amid growing interest in the precise detection of volatile organic compounds (VOCs) in industrial field, the demand for highly effective gas sensors is at an all-time high. However, traditional sensors with their classic single-output signal, bulky and complex integrated structure when forming array often involve complicated technology and high cost, limiting their widespread adoption. Here, this study introduces a novel approach, employing an integrated YSZ-based (YSZ: yttria-stabilized zirconia) mixed potential sensor equipped with a triple-sensing electrode array, to efficiently detect and differentiate six types of VOCs gases. This innovative sensor integrates NiSb2O6, CuSb2O6, and MgSb2O6 sensing electrodes (SEs), which are sensitive to pentane, isoprene, n-propanol, acetone, acetic acid, and formaldehyde gases. Through feature engineering based on intuitive spike-based response values, it accentuates the distinct characteristics of every gas. Eventually, an average classification accuracy of 98.8% and an overall R-squared error (R2) of 99.3% for concentration regression toward six target gases can be achieved, showcasing the potential to quantitatively distinguish between industrial hazardous VOCs gases.

Multilayer Fluorine-Free MoBTx MBene with Hydrophilic Structural-Modulating for the Fabrication of a Low-Resistance and High-Resolution Humidity Sensor.

2D transition metal borides (MBenes) with abundant surface terminals hold great promise in molecular sensing applications. However, MBenes from etching with fluorine-containing reagents present inert -fluorine groups on the surface, which hinders their sensing capability. Herein, the multilayer fluorine-free MoBTx MBene (where Tx represents O, OH, and Cl) with hydrophilic structure is prepared by a hydrothermal-assisted hydrochloric acid etching strategy based on guidance from the first-principle calculations. Significantly, the fluorine-free MoBTx-based humidity sensor is fabricated and demonstrates low resistance and excellent humidity performance, achieving a response of 90% to 98%RH and a high resolution of 1%RH at room temperature. By combining the experimental results with the first-principles calculations, the interactions between MoBTx and H2O, including the adsorption and intercalation of H2O, are understood first in depth. Finally, the portable humidity early warning system for real-time monitoring and early warning of infant enuresis and back sweating illustrates its potential for humidity sensing applications. This work not only provides guidance for preparation of fluorine-free MBenes, but also contributes to advancing their exploration in sensing applications.

Pt Loading of Phosphorus-Doped Carbon Nanotube Aerogels in Fuel Cell-Type Gas Sensors for Ultrasensitive H2 Detection.

A phosphorus-doped carbon nanotube (CNT) aerogel as the support material was loaded with Pt nanoparticles in fuel cell-type gas sensors for ultrasensitive H2 detection. The high surface area of the CNT scaffold is favorable to providing abundant active sites, and the high electrical conductivity facilitates the transport of carriers generated by electrochemical reactions. In addition, the CNT aerogel was doped with phosphorus (P) to further enhance the conductivity and electrochemical catalytic activity. As a result, the fuel cell-type gas sensor using the Pt/CNT aerogel doped with the optimal P content as the sensing material shows considerable performance for H2 detection at room temperature. The sensor exhibits an ultrahigh response of -921.9 µA to 15,000 ppm of H2. The sensitivity is -0.063 µA/ppm, which is 21 times higher than that of the conventional Pt/CF counterpart. The sensor also exhibits excellent repeatability and humidity resistance, as well as fast response/recovery; the response/recovery times are 31 and 4 s to 3000 ppm of H2, respectively. The modulation of the structure and catalytic properties of the support material is responsible for the improvement of the sensor performance, thus providing a feasible solution for optimizing the performance of fuel cell-type gas sensors.

Mixed Potential Type Isoprene Sensor for the Application in Real-Time Monitoring of Biomarker Gases.

Monitoring of isoprene in exhaled breath is expected to provide a noninvasive and painless method for dynamic monitoring of physiological and metabolic states during exercise. However, for real-time and portable detection of isoprene, gas sensors have become the best choice for gas detection technology, which are crucial to achieving the goal of anytime, anywhere, human-centered healthcare in the future. Here, we first report a mixed potential type isoprene sensor based on a Gd2Zr2O7 solid electrolyte and a CdSb2O6 sensing electrode, which enables sensitive detection for isoprene with sensitivities of -21.2 mV/ppm and -65.8 mV/decade in the range of 0.05-1 and 1-100 ppm. The sensing behavior of the sensor follows the mixed potential sensing mechanism and was further verified by the electrochemical polarization curves. The significant differentiation between the sensor response to exhaled breath of healthy individuals and simulated breath containing different concentrations of isoprene demonstrates the potential of the sensor for the detection of isoprene in exhaled breath. Simultaneously, monitoring of isoprene during exercise signifies the feasibility of the sensor in dynamic monitoring of physiological indicators, which is not only of great significance for optimizing training and guiding therapeutic exercise intervention in sporting scenarios but also expected to help further reveal the interaction between exercise, muscle, and organ metabolism in medicine.

Portable and Hand-Held Ammonia Gas Sensor Enables Noninvasive Prediagnosis of Helicobacter pylori Infection.

Disease diagnosis of Helicobacter pylori (Hp) through human exhaled breath analysis has attracted considerable attention. However, conventional methods, such as carbon 13 (13C) breath test and infrared spectrometers, are facing the challenge of achieving portability and reliability synchronously. Herein, we report a portable and hand-held Hp analyzer using a bimetallic PtRu@SnO2-based gas sensor for the prediagnosis of Hp infection, which is based on detecting ammonia (NH3) as a potential biomarker in exhaled breath. Owing to the surface functionalization through highly catalytically active bimetallic PtRu nanoparticles (NPs) prepared by a photochemical reduction strategy, the PtRu@SnO2-based sensor exhibits high sensitivity and selectivity toward trace-level (200 ppb) NH3 even at high-humidity surroundings (80% RH). Consequently, the designed portable and hand-held Hp analyzer makes the accurate determination of NH3 at 800 ppb in exhaled breath. The tuning of energy band structure and electrical characteristics and the catalytic modulation of NH3 oxidation by PtRu NPs are proposed to be the reasons behind the enhanced NH3 gas-sensing performance, as confirmed by in situ analysis using an online MKS MultiGas 2030 FTIR gas analyzer. This work paves the way for the prediagnosis of Hp infection using a metal oxide gas sensor.

A Wearable Self-Charging Electroceutical Device for Bacteria-Infected Wound Healing.

The prolonged wound-healing process caused by pathogen infection remains a major public health challenge. The developed electrical antibiotic administration typically requires metal electrodes wired to a continuous power supply, restricting their use beyond clinical environments. To obviate the necessity for antibiotics and an external power source, we have developed a wearable synergistic electroceutical device composed of an air self-charging Zn battery. This battery integrates sustained tissue regeneration and antibacterial modalities while maintaining more than half of the initial capacity after ten cycles of chemical charging. In vitro bacterial/cell coculture with the self-charging battery demonstrates inhibited bacterial activity and enhanced cell function by simulating the endogenous electric field and dynamically engineering the microenvironment with released chemicals. This electroceutical device provides accelerated healing of a bacteria-infected wound by stimulating angiogenesis and modulating inflammation, while effectively inhibiting bacterial growth at the wound site. Considering the simple structure and easy operation for long-term treatment, this self-charging electroceutical device offers great potential for personalized wound care.

Mixed Potential Type Acetone Sensor with Ultralow Detection Limit for Diabetic Ketosis Breath Analysis.

Breath analysis using gas sensors is an emerging method for disease screening and diagnosis. Since it is closely related to the lipid metabolism and blood ketone concentration of the body, the detection of acetone content in exhaled breath is helpful for the screening and monitoring of diabetes and ketosis. The development of an acetone sensor with high selectivity, stability, and low detection limit has been the research focus for this purpose. Here, we developed a mixed potential type acetone sensor based on Gd2Zr2O7 solid electrolyte and CoSb2O6 sensing electrode. The developed sensor exhibits an extremely low detection limit of 10 ppb, enabling linear detection for acetone in an extremely wide range of 10 ppb-100 ppm. The good results of systematic evaluation on selectivity, repeatability, and stability prove the superior reliability of the sensor, which is a prerequisite for the application in actual breath detection. The ability of the sensor to distinguish healthy people from diabetic ketosis patients was confirmed by using the sensor to detect the breath of healthy people and diabetic patients, proving the feasibility of the sensor in the diagnosis and monitoring of diabetic ketosis.

Self-Healing, Laminated, and Low Resistance NH3 Sensor Based on 6,6',6″-(Nitrilotris(benzene-4,1-diyl))tris(5-phenylpyrazine-2,3-dicarbonitrile) Sensing Material Operating at Room Temperature.

With the rapid development of the concept of the Internet of Things (IoT), gas sensors with the function of simulating the human sense of smell became irreplaceable as a key element. Among them, ammonia (NH3) sensors played an important role in respiration tests, environmental monitoring, safety, and other fields. However, the fabrication of the high-performance device with high stability and resistance to mechanical damages was still a challenge. In this work, polyurethane (PU) with excellent self-healing ability was applied as the substrate, and the sensor was designed from new sensitive material design and device structure optimization, through applying the organic molecule with groups which could absorb NH3 and the laminated structure to shorten the electronic transmission path to achieve a low resistance state and favorable sensing properties. Accordingly, a room temperature flexible NH3 sensor based on 6,6',6″-(nitrilotris(benzene-4,1-diyl))tris(5-phenylpyrazine-2,3-dicarbonitrile) (TPA-3DCNPZ) was successfully developed. The device could self-heal by means of a thermal evaporation assisted method. It exhibited a detection limit of 1 ppm at 98% relative humidity (RH), as well as great stability, selectivity, bending flexibility, and self-healing properties. The improved NH3 sensing performance under high RH was further investigated by complex impedance plots (CIPs) and density functional theory (DFT), attributing to the enhanced adsorption of NH3. The TPA-3DCNPZ based NH3 sensors proved to have great potential for application on simulated exhaled breath to determine the severity of kidney diseases and the progress of treatment. This work also provided new ideas for the construction of high-performance room temperature NH3 sensors.

A Mg Battery-Integrated Bioelectronic Patch Provides Efficient Electrochemical Stimulations for Wound Healing.

Bioelectronic patches hold promise for patient-comfort wound healing providing simplified clinical operation. Currently, they face paramount challenges in establishing long-term effective electronic interfaces with targeted cells and tissues due to the inconsistent energy output and high bio interface impedance. Here a new electrochemical stimulation technology is reported, using a simple wound patch, which integrates the efficient generation and delivery of stimulation. This is realized by employing a hydrogel bioelectronic interface as an active component in an integrated power source (i.e., Mg battery). The Mg battery enhances fibroblast functions (proliferation, migration, and growth factor secretion) and regulates macrophage phenotype (promoting regenerative polarization and down-regulating pro-inflammatory cytokines), by providing an electric field and the ability to control the cellular microenvironment through chemical release. This bioelectronic patch shows an effective and accelerated wound closure by guiding epithelial migration, mediating immune response, and promoting vasculogenesis. This new electrochemical-mediated therapy may provide a new avenue for user-friendly wound management as well as a platform for fundamental insights into cell stimulation.

Pattern Recognition with Temperature Regulation: A Single YSZ-Based Mixed Potential Sensor Classifies Multiple Mixtures of Isoprene, n-Propanol, and Acetone.

Gas sensors integrated with machine learning algorithms have aroused keen interest in pattern recognition, which ameliorates the drawback of poor selectivity on a sensor. Among various kinds of gas sensors, the yttria-stabilized zirconia (YSZ)-based mixed potential-type sensor possesses advantages of low cost, simple structure, high sensitivity, and superior stability. However, as the number of sensors increases, the increased power consumption and more complicated integration technology may impede their extensive application. Herein, we focus on the development of a single YSZ-based mixed potential sensor from sensing material to machine learning for effective detection and discrimination of unary, binary, and ternary gas mixtures. The sensor that is sensitive to isoprene, n-propanol, and acetone is manufactured with the MgSb2O6 sensing electrode prepared by a simple sol-gel method. Unique response patterns for specific gas mixtures could be generated with temperature regulation. We chose seven algorithm models to be separately trained for discrimination. In order to realize more accurate discrimination, we further discuss the selection of suitable feature parameters and its reasons. With temperature regulation coefficients which are easily available as feature input to model, a single sensor is verified to achieve elevated accuracy rates of 95 and 99% for the discrimination of seven gases (three unary gases, three binary gas mixtures, and one ternary gas mixture) and redefined six gas mixtures. This article provides a potential new approach via a mixed potential sensor instead of a sensor array that could provide a wide application prospect in the field of electronic nose and artificial olfaction.

Wearable Gas Sensor Based on Reticular Antimony-Doped SnO2/PANI Nanocomposite Realizing Intelligent Detection of Ammonia within a Wide Range of Humidity.

Wearable gas sensors demonstrate broad potential for environmental monitoring and breath analysis applications. Typically, they require a highly stable and high-performance flexible gas sensing unit that can work with a small, flexible circuit to enable real-time accurate concentration analysis and prediction. This work proposes a flexible gas sensor using antimony-doped tin dioxide composite polyaniline as the sensing material for room-temperature ammonia detection over a wide humidity range. The sensor exhibits high sensitivity (response value at 33.1 toward 100 ppm ammonia at 70% relative humidity), excellent selectivity, and good long-term and mechanical stability. The increased sensitivity is due to a reduction in the hole concentration of polyaniline in air, achieved through compositing and doping. Subsequently, regression analysis equations are developed to establish the relationship between the gas concentration and sensor response under varying environmental humidity conditions. The sensor was integrated with a small, low-power circuit module to form a wearable smart bracelet with signal acquisition, processing, and wireless transmission functions, which could achieve early and remote warning of gas leakage in different humidity environments. This research demonstrates a promising approach to designing high-performance, high-stability, and flexible gas sensors and their corresponding wireless sensing systems.

Machine Learning-Assisted Volatile Organic Compound Gas Classification Based on Polarized Mixed-Potential Gas Sensors.

The performance of electrochemical gas sensors depends on the reactions at the three-phase boundary. In this work, a mixed-potential gas sensor containing a counter electrode, a reference electrode, and a sensitive electrode was constructed. By applying a bias voltage to the counter electrode, the three-phase boundary can be polarized. The polarization state of the three-phase boundary determined the gas-sensitive performance. Taking 100 ppm ethanol vapor as an example, by regulating the polarization state of the three-phase boundary, the response value of the sensor can be adjusted from -170 to 40 mV, and the sensitivity can be controlled from -126.4 to 42.6 mV/decade. The working temperature of the sensor can be reduced after polarizing the three-phase boundary, lowering the power consumption from 1.14 to 0.625 W. The sensor also showed good stability and short response-recovery time (3 s). Based on this sensor, the Random Forest algorithm reached 99% accuracy in identifying the kind of VOC vapors. This accuracy was made possible by the ability to generate several signals concurrently. The above gas-sensitive performance improvements were due to the polarized three-phase boundary.

Reply to the Comment on "Understanding the Increasing Trend of Sensor Signal with Decreasing Oxygen Partial Pressure by a Sensing-Reaction Model Based on O2- Species".

In our recent work (ACS Sens.2022, 7, 1095-1104), Mirabella et al. provided comments on our publication, mainly focusing on the controversy between the oxygen vacancy model and the ionosorbed model and the related derivation based on the law of mass action. Herein we explain the correlation between the ionosorption model and the oxygen vacancy model and provide a brief introduction of our view on these two models. Moreover, a more detailed derivation about the law of mass action is provided to explain the relationship between surface electron concentration, oxygen partial pressure, adsorbed oxygen density, and oxygen vacancy density.