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Abstract Chiral assemblies have become one of the most active research areas due to their versatility, playing an increasingly important role in bio-detection, imaging and therapy. In this work, chiral UCNPs/CuxOS@ZIF nanoprobes are prepared by encapsulating upconversion nanoparticles (UCNPs) and CuxOS nanoparticles (NPs) into zeolitic imidazolate framework-8 (ZIF-8). The novel excited-state energy distribution-modulated upconversion nanostructure (NaYbF4@NaYF4: Yb, Er) is selected as the fluorescence source and energy donor for highly efficient fluorescence resonance energy transfer (FRET). CuxOS NP is employed as chiral source and energy acceptor to quench upconversion luminescence (UCL) and provide circular dichroism (CD) signal. Utilizing the natural adsorption and sorting advantages of ZIF-8, the designed nanoprobe can isolate the influence of other common disruptors, thus achieve ultra-sensitive and highly selective UCL/CD dual-mode quantification of H2S in aqueous solution and in living cells. Notably, the nanoprobe is also capable of in vivo intra-tumoral H2S tracking. Our work highlights the multifunctional properties of chiral nanocomposites in sensing and opens a new vision and idea for the preparation and application of chiral nanomaterials in biomedical and biological analysis.

Abstract 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.

Abstract 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.

Abstract The fast booming of wearable electronics provides great opportunities for intelligent gas detection with improved healthcare of mining workers, and a variety of gas sensors have been simultaneously developed. However, these sensing systems are always limited to single gas detection and are highly susceptible to the inference of ubiquitous moisture, resulting in less accuracy in the analysis of gas compositions in real mining conditions. To address these challenges, we propose a synergistic strategy based on sensor integration and machine learning algorithms to realize precise NH3 and NO2 gas detections under real mining conditions. A wearable sensing array based on the graphene and polyaniline composite is developed to largely enhance the sensitivity and selectivity under mixed gas conditions. Further introduction of backpropagation neural network (BP‐NN) and partial least squares (PLS) algorithms could improve the accuracy of gas identification and concentration prediction and settle the inference of moisture, realizing over 99% theoretical prediction level on NH3 and NO2 concentrations within a wide relative humidity range, showing great promise in real mining detection. As proof of concept, a wireless wearable bracelet, integrated with sensing arrays and machine‐learning algorithms, is developed for wireless real‐time warning of hazardous gases in mines under different humidity conditions.

Abstract The recent surge in demand for human–machine interaction (HMI), Internet of Things (IoTs), and artificial intelligence (AI) has created both opportunities and challenges for room‐temperature wearable gas sensors. These sensors serve as a source of perceptual information and can be easily integrated into wearable electronic devices due to their portability and miniaturization. In recent years, various types of wearable room temperature gas sensors have been developed for fields like environmental monitoring, healthcare, smart home, industrial security, food safety monitoring, and public security. These sensors not only adjust to the movements of human effortlessly but also have reduced power consumption. Therefore, room temperature wearable gas sensors hold great promise for the development of integrated intelligent gas sensing system worn on the human body. These sensors can be fabricated using various sensing materials to detect diverse target gases. This review provides a comprehensive summary of the preparation of sensing materials with extraordinary sensing capabilities at room temperature. Additionally, the article includes a brief discussion of the sensing mechanism, employing four models to explain it: oxygen adsorption, direct electron transfer, proton transfer, and ions conduction. Finally, this article discusses the various applications and future perspectives of room‐temperature wearable gas sensors.

Abstract In this study, Sb‐doped SnO2 nanosphere composite polypyrrole nanohybrid with different doping ratios (0–5 mol%, Sb:Sn) and composite ratios (0–30 mol%, Sb‐doped SnO2:polypyrrole) is synthesized by hydrothermal method and in situ chemical oxidation method. The flexible sensors are fabricated by drop‐casting the materials on polyamide substrate and gas sensing performances are investigated systematically at room temperature. The results show that the 3 at% Sb‐doped 20 mol% SnO2/polypyrrole nanohybrid exhibits excellent sensitivity (≈213% toward 100 ppm NH3) at room temperature, which are about 3 times as much as those of polypyrrole, as well as excellent selectivity and humidity resistance, reliable repeatability, and good robustness. The enhance sensing performance can be attributed to the formation of p‐n junction between conducting polymers and metal oxide semiconductor materials and the doping of Sb elements allows more electrons to transfer to polypyrrole, which further thickens the depletion layer and decreases hole concentrations in air. Therefore, Sb‐doped SnO2/polypyrrole nanohybrid may be a promising sensitive material for the design and manufacture of room temperature flexible ammonia gas sensors.

Abstract Developing open-shell singlet (OS) diradicals with high luminescent properties and exceptional single-molecule magnetoluminescence (ML) performance is extremely challenging. Herein, we propose a concept to enhance luminescent efficiency by adjusting the donor conjugation of OS diradicals, thereby achieving a highly luminescent diradical, DR1, with outstanding stability and making it a viable option for use in the emitting layer of organic light-emitting diodes (OLEDs). More importantly, the 0.5 wt%-DR1 doped film demonstrates significant single-molecule magnetoluminescence (ML) properties. A giant ML value of 210% is achieved at a magnetic field of 7 T, showing the great potential of DR1 in magneto-optoelectronic devices.

In this paper, a novel synthesis method is presented to design of a class of multi-section ultra-wideband (UWB) Wilkinson power dividers (WPDs) with an arbitrary power ratio. The proposed UWB-WPD topology consists of $N$ cascaded asymmetric coupled line sections (ACLSs) and $N$ isolation resistors. Through even- and odd-mode analysis, the proposed synthesis method is demonstrated with a few unique novelties as summarized: (1) It is for the first time proved that the first kind Chebyshev equal-ripple performance can be exactly realized by the cascaded transmission-line transformer without Hansen’s approximation; (2) It is also for the first time revealed that all the $S$ -parameters ( $S_{11}$ , $S_{21}$ , $S_{31}$ , $S_{22}$ , $S_{33}$ and $S_{32}$ ) of proposed WPD can achieve controllable in-band equal-ripple performance. To verify the effectiveness of proposed synthesis method, several design examples are presented and designed for demonstration of varied equal-ripple responses. Finally, two WPD circuits with $N = 3$ are fabricated, and the measured results well validate the predicted ones from proposed method.

Wearable transdermal iontophoresis offers advantages for patient-comfort when deploying epidermal diseases treatments but current self-powered iontophoresis based on energy harvesters is limited in the support of efficient long-term operation therapeutic administration. Here, the authors propose a simplified wearable iontophoresis patch with a built-in Mg battery for efficient and controllable transdermal delivery.

Abstract Metallic interface engineering is a promising strategy to stabilize Zn anode via promoting Zn2+ uniform deposition. However, strong interactions between the coating and Zn2+ and sluggish transport of Zn2+ lead to high anodic polarization. Here, we present a bio-inspired silk fibroin (SF) coating with amphoteric charges to construct an interface reversible electric field, which manipulates the transfer kinetics of Zn2+ and reduces anodic polarization. The alternating positively and negatively charged surface as a build-in driving force can expedite and homogenize Zn2+ flux via the interplay between the charged coating and adsorbed ions, endowing the Zn-SF anode with low polarization voltage and stable plating/stripping. Experimental analyses with theoretical calculations suggest that SF can facilitate the desolvation of [Zn(H2O)6]2+ and provide nucleation sites for uniform deposition. Consequently, the Zn-SF anode delivers a high-rate performance with low voltage polarization (83 mV at 20 mA cm−2) and excellent stability (1500 h at 1 mA cm−2; 500 h at 10 mA cm−2), realizing exceptional cumulative capacity of 2.5 Ah cm−2. The full cell coupled with ZnxV2O5·nH2O (ZnVO) cathode achieves specific energy of ~ 270.5/150.6 Wh kg−1 (at 0.5/10 A g−1) with ~ 99.8% Coulombic efficiency and retains ~ 80.3% (at 5.0 A g−1) after 3000 cycles.

N-butanol (C4H9OH) is a volatile organic compound (VOC) that is susceptible to industrial explosions. It has become imperative to develop n-butanol sensors with high selectivity and fast response and recovery kinetics. CdS/Ag2S composite nanomaterials were designed and prepared by the solvothermal method. The incorporation of Ag2S engendered a notable augmentation in specific surface area and a consequential narrow band gap. The CdS/Ag2S-based sensor with 3% molar ratio of Ag2S, operating at 200 °C, demonstrated a remarkably elevated response (S = Ra/Rg = 24.5) when exposed to 100 ppm n-butanol, surpassing the pristine CdS by a factor of approximately four. Furthermore, this sensor exhibited notably shortened response and recovery times, at a mere 4 s and 1 s, respectively. These improvements were ascribed to the one-dimensional single-crystal nanorod structure of CdS, which provided an effective path for expedited electron transport along its axial dimension. Additionally, the electron and chemical sensitization effects resulting from the modification with precious metal sulfides Ag2S were the primary reasons for enhancing the sensor response. This work can contribute to mitigating the safety risks associated with the use of n-butanol in industrial processes.

With the development of gas sensor arrays and computational technology, machine olfactory systems have been widely used in environmental monitoring, medical diagnosis, and other fields. The reliable and stable operation of gas sensing systems depends heavily on the accuracy of the sensors outputs. Therefore, the realization of accurate gas sensor array fault diagnosis is essential to monitor the working status of sensor arrays and ensure the normal operation of the whole system. The existing methods extract features from a single dimension and require the separate training of models for multiple diagnosis tasks, which limits diagnostic accuracy and efficiency. To address these limitations, for this study, a novel fault diagnosis network based on multi-dimensional feature fusion, an attention mechanism, and multi-task learning, MAM-Net, was developed and applied to gas sensor arrays. First, feature fusion models were applied to extract deep and comprehensive features from the original data in multiple dimensions. A residual network equipped with convolutional block attention modules and a Bi-LSTM network were designed for two-dimensional and one-dimensional signals to capture spatial and temporal features simultaneously. Subsequently, a concatenation layer was constructed using feature stitching to integrate the fault details of different dimensions and avoid ignoring useful information. Finally, a multi-task learning module was designed for the parallel learning of the sensor fault diagnosis to effectively improve the diagnosis capability. The experimental results derived from using the proposed framework on gas sensor datasets across different amounts of data, balanced and unbalanced datasets, and different experimental settings show that the proposed framework outperforms the other available methods and demonstrates good recognition accuracy and robustness.

Abstract Environmentally friendly degradable sensors with both hazardous gases and pressure efficient sensing capabilities are highly desired for various promising applications, including environmental pollution monitoring/prevention, wisdom medical, wearable smart devices, and artificial intelligence. However, the transient gas and pressure sensors based on only identical sensing material that concurrently meets the above detection needs have not been reported. Here, we present transient all-MXene NO2 and pressure sensors employing three-dimensional porous crumpled MXene spheres prepared by ultrasonic spray pyrolysis technology as the sensing layer, accompanied with water-soluble polyvinyl alcohol substrates embedded with patterned MXene electrodes. The gas sensor achieves a ppb-level of highly selective NO2 sensing, with a response of up to 12.11% at 5 ppm NO2 and a detection range of 50 ppb–5 ppm, while the pressure sensor has an extremely wide linear pressure detection range of 0.14–22.22 kPa and fast response time of 34 ms. In parallel, all-MXene NO2 and pressure sensors can be rapidly degraded in medical H2O2 within 6 h. This work provides a new avenue toward environmental monitoring, human physiological signal monitoring, and recyclable transient electronics.

Abstract Analysis and design of a wideband bandstop filter with multi‐transmission zeros (TZs) and reflection zeros (RZs) are presented. The proposed topology consists of N‐1 shunt open‐circuited stubs (OCSs) cascaded through N‐sections of transmission lines, and two M‐sections of OCSs are shunted at two output ports, respectively. After complicated mathematical analysis, the numbers of TZs and RZs are determined by section numbers M and N. By using the proposed algorithm, equal ripples with controllable ripple levels can be realized in the passband. Although the ripples in the stopband have different levels, each ripple level can be designed independently. As the proposed algorithm can design the positions of TZs and RZs, upper and lower attenuation rates can be increased dramatically. Therefore, compared with former works, the proposed work provides enhanced sharp‐rejection and simultaneously maintains wide stopband performance. For verification, two experimental circuits are fabricated, and the proposed design theory and algorithm are well verified by the measured frequency response.

Abstract In this letter, a novel wideband bandstop filter with controllable equal‐ripple response is newly presented. The proposed topology consists of two cascaded transmission lines and three open‐circuited stubs, where, one two‐section OS is shunted between two transmission lines, two three‐section OSs are shunted at two output ports, respectively. By using the proposed design approach, both passband and stopband provide controllable equal‐ripple responses independently, where there are five transmission zeros and six reflection zeros in a single period of frequency domain. For demonstration, an experimental BSF centered at 2 GHz with 20‐dB FBW 129.5% and 30‐dB stopband rejection is designed and fabricated. The simulations and measurements agree with the design theory very well.

In this paper, a parallel transmission-line transformer with complex terminal loads is introduced for dual-frequency design. Through analyzing the different cases of complex terminal loads conditions, there are four different mapping patterns of designable regions on the Electrical Length-Electrical Length (EL-EL) plane. By adding an extra vertical Frequency Ratio (FR) axis, a novel 3D cube can be created on the FR-EL-EL coordinate system, then the designable ranges of frequency ratio can be easily drawn in this 3D cube. Therefore, the visible 3D mapping approach is newly reported for matching the complex terminal load of parallel transmission-line transformer at two different frequencies. For the certain pattern, a clearly boundary could be drawn to distinguish the designable and undesignable ranges. For verification, two examples are designed, fabricated and measured. Simulated and measured results are matched very well.

Abstract Aqueous all‐polymer proton batteries (APPBs) consisting of redox‐active polymer electrodes are considered safe and clean renewable energy storage sources. However, there remain formidable challenges for APPBs to withstand a high current rate while maximizing high cell output voltage within a narrow electrochemical window of aqueous electrolytes. Here, a capacitive‐type polymer cathode material is designed by grafting poly(3,4‐ethylenedioxythiophene) (PEDOT) with bioinspired redox‐active catechol pendants, which delivers high redox potential (0.60 V vs Ag/AgCl) and remarkable rate capability. The pseudocapacitive‑dominated proton storage mechanism illustrated by the density functional theory (DFT) calculation and electrochemical kinetics analysis is favorable for delivering fast charge/discharge rates. Coupled with a diffusion‐type anthraquinone‐based polymer anode, the APPB offers a high cell voltage of 0.72 V, outstanding rate capability (64.8% capacity retention from 0.5 to 25 A g−1), and cycling stability (80% capacity retention over 1000 cycles at 2 A g−1), which is superior to the state‐of‐the‐art all‐organic proton batteries. This strategy and insight provided by DFT and ex situ characterizations offer a new perspective on the delicate design of polymer electrode patterns for high‐performance APPBs.

Carbon monoxide (CO) is one of the most toxic gases to human life. Therefore, the effective monitoring of it down to ppb level is of great significance. Herein, a series of In2O3 nanofibers modified with Au or Pd species or simultaneous Au and Pd species have been prepared by electrospinning combined with a calcination process. The as-obtained samples are applied for the detection of CO. Gas-sensing investigations indicate that 2 at% Au and 2 at% Pd-co-modified In2O3 nanofibers exhibit the highest response (21.7) to 100 ppm CO at 180 °C, and the response value is ~8.5 times higher than that of pure In2O3 nanofibers. More importantly, the detection limit to CO is about 200 ppb with a response value of 1.23, and is obviously lower than that (6 ppm) of pure In2O3 nanofibers. In addition, the sensor also shows good stability within 19 days. These demonstrate that co-modifying In2O3 nanofibers with suitable amounts of Pd and Au species might be a meaningful strategy for the development of high-performance carbon monoxide gas sensors.

In this paper, a novel synthetization approach is proposed for filter-integrated wideband impedance transformers (ITs). The original topology consists of N cascaded coupled line sections (CLSs) with 2N characteristic impedance parameters. By analyzing these characteristic impedances, a Chebyshev response can be derived to consume N + 2 design conditions. To optimize the left N − 2 variable parameters, CLSs were newly substituted by transmission lines (TLs) to consume the remaining variable parameters and simplify the circuit topology. Therefore, there are totally 2N − N − 2 substituting possibilities. To verify the proposed approach, 25 cases are listed under the condition of N = 5, and 7 selected cases are compared and discussed in detail. Finally, a 75–50 Ω IT with 100% fractional bandwidth and 20 dB bandpass return loss (RL) is designed and fabricated. The measured results meet the circuit simulation and the EM simulation accurately.

Herein, formaldehyde sensors based on gallium-doped In2O3 inverse opal [...]