As a new member of the group of promising 2D materials, MXene shows the advantages including metallic conductivity, high charge carrier mobility, tunable band gap, flexibility and diverse surface chemistry, favorable optical and mechanical properties. These unique properties have drawn huge attention, and research on MXene has been intensively conducted and innovative applications have been reported in various fields. At the same time, MXene/polymer nanocomposites have been developed, and many amazing results have been reported. However, overviews of the status and progress in this field are rare. In this paper, first, the preparation method and technical route of MXene/polymer nanocomposites are reviewed. It is found that solution mixing and in situ polymerization are the main preparation methods of the nanocomposites. Second, the properties of the composites are presented. It is shown that MXene can effectively improve the electrical, mechanical, and thermal characteristics of polymers. Then, innovative applications and representative results of the composites in the biomedical, sensing, energy, electromagnetic protection, and other fields are summarized. Finally, the development prospects and key challenges of the composites are listed concisely.

In biosensing and biophotonics, red/near-infrared fluorescent carbon dots (R-CDs) are attractive and deserve more attention. However, the synthesis and purification of R-CDs are time-consuming, impeding their industrial production and application on a large scale. We proposed a solvent-free method for reducing the number of raw materials used in the R-CD synthesis by utilizing the dehydration self-carbonation effect of the-HSO₃ group in the precursor. The synthesized R-CDs exhibit a quantum yield of 59% and an emission wavelength of 600–800 nm with only one raw material (3,4-diaminobenzenesulfonic acid) and without the addition of any extra precursors, solvents, catalysts, dehydration agent, or other additives. We hypothesized that the red/near-infrared emission was caused by carbon-nucleus conjugated structures formed during the dissociation of the –HSO₃ group at high temperatures. Additionally, the prepared R-CDs demonstrated a good response to the products of glucose oxidation, indicating glucose's sensing capability. Additionally, the synthesized R-CDs demonstrated excellent single-photon imaging of cells while being non-toxic, demonstrating their enormous potential in biophotonics. We believe that this simple and environmentally friendly R-CD synthesis can significantly accelerate industrialization and application.

Low-cost wireless temperature measurement has significant value in the food industry, logistics, agriculture, portable medical equipment, intelligent wireless health monitoring, and many areas in everyday life. A wireless passive temperature sensor based on PCB (Printed Circuit Board) materials is reported in this paper. The advantages of the sensor include simple mechanical structure, convenient processing, low-cost, and easiness in integration. The temperature-sensitive structure of the sensor is a dielectric-loaded resonant cavity, consisting of the PCB substrate. The sensitive structure also integrates a patch antenna for the transmission of temperature signals. The temperature sensing mechanism of the sensor is the dielectric constant of the PCB substrate changes with temperature, which causes the resonant frequency variation of the resonator. Then the temperature can be measured by detecting the changes in the sensor’s working frequency. The PCB-based wireless passive temperature sensor prototype is prepared through theoretical design, parameter analysis, software simulation, and experimental testing. The high- and low-temperature sensing performance of the sensor is tested, respectively. The resonant frequency decreases from 2.434 GHz to 2.379 GHz as the temperature increases from −40 °C to 125 °C. The fitting curve proves that the experimental data have good linearity. Three repetitive tests proved that the sensor possess well repeatability. The average sensitivity is $347.45\mathrm{KHz}/℃$ from repetitive measurements conducted three times. This study demonstrates the feasibility of the PCB-based wireless passive sensor, which provides a low-cost temperature sensing solution for everyday life, modern agriculture, thriving intelligent health devices, and so on, and also enriches PCB product lines and applications.

An aluminum nitride (AlN) based patch antenna-type high-temperature wireless passive sensor is reported to operate as both a sensor and an antenna, which integrates in situ measurement/sensing with remote wireless communication at the same time. The sensor is small, easy to manufacture, highly sensitive and has a high operating temperature; it can be used in high-temperature, chemically corrosive and other harsh environments. The sensing mechanism of the sensor, the dielectric constant of the AlN ceramic substrate, increases with rising temperature, which reduces the resonant frequency of the sensor. Thus, the temperature can be measured by detecting changes in the sensor’s resonant frequency. High-Frequency Simulation Structure (HFSS) software is used to determine the structure and size of the sensor, which is then fabricated using thick-film technology. The substrate of the sensor is AlN ceramic due to its outstanding thermal resistance at high temperature; and its conductors (the radiation patch and the ground under the substrate) are silver-palladium alloy sintered form silver–palladium paste. A vector network analyzer reveals that the sensor’s operating range extends to 700 °C. Furthermore, its resonant frequency decreases from 2.20 GHz to 2.13 GHz with increasing temperature from room temperature (25 °C) to 700 °C, with an absolute sensitivity of 104.77 KHz/°C. Our work verifies the feasibility of measuring high temperatures using AlN-based patch antenna wireless passive temperature sensors, and provides a new material and temperature sensitive structure for high-temperature measurement in harsh environments.

Pressure measurements in high-temperature applications, including compressors, turbines, and others, have become increasingly critical. This paper proposes an implantable passive LC pressure sensor based on an alumina ceramic material for in situ pressure sensing in high-temperature environments. The inductance and capacitance elements of the sensor were designed independently and separated by a thermally insulating material, which is conducive to reducing the influence of the temperature on the inductance element and improving the quality factor of the sensor. In addition, the sensor was fabricated using thick film integrated technology from high-temperature materials that ensure stable operation of the sensor in high-temperature environments. Experimental results showed that the sensor accurately monitored pressures from 0 bar to 2 bar at temperatures up to 800 °C. The sensitivity, linearity, repeatability error, and hysteretic error of the sensor were 0.225 MHz/bar, 95.3%, 5.5%, and 6.2%, respectively.