X-ray induced photochromic (XP) materials, characterized by their radiation dose-dependent coloration properties, exhibit broad application potential in national defense and security, nuclear energy development and utilization, industrial nondestructive testing, and medical imaging. In recent years, scientists worldwide have developed diverse XP material systems, conducted in-depth investigations into their radiation-induced coloration mechanisms, and explored their specialized applications, highlighting the urgent need for a comprehensive review on their working principles and application domains. This article systematically summarizes the material systems exhibiting XP behavior, categorizing them based on chemical composition and coloration characteristics. Their advantages and limitations are comparatively analyzed, while their underlying mechanisms, such as color center formation and redox processes, are analyzed. Furthermore, their potential applications in X-ray detection, medical diagnostics, and industrial monitoring are introduced. Finally, their future research directions are proposed to develop new XP materials with enhanced performance and broader scenario adaptability. This review holds significant implications for guiding subsequent research on optimizing XP materials and accelerating their commercialization process, thereby facilitating the practical implementation of XP technologies.

Electrochromic (EC) smart windows utilizing a reversible metal electrodeposition device (RMED) offer a compelling alternative for dynamically regulating transmissions of optical and thermal energy. An EC device (ECD) is constructed by reversible metal electrodeposition (RME) of Bi/Cu on WO₃·xH₂O film electrodeposited onto fluorine-doped tin oxide (FTO) transparent conductive glass. The electrolyte consists of CuCl₂, BiCl₃, KCl and HCl aqueous solution, supplying necessary components for both electrochemical and electrodeposition processes. The ECD shows ability to rapidly transition between colorless and black states, which achieves a large optical modulation of 77.0% at 570 nm. In the black state, the ECD exhibits a near-zero transmittance in the wavelength range of 400-1100 nm while maintaining 96.6% of its initial optical modulation after coloration/bleaching cycling of 60000 s, exhibiting good cyclic stability. This RMED has relatively high stability under open-circuit voltage and also possesses excellent heat insulation performance. The results offer a solution to overcome the poor cyclic stability of RMEDs and improve the optical modulation of ECDs.

Electrochromic smart windows can regulate indoor light through modulating optical transmittance of electrochromic materials to realize energy-saving buildings. Amorphous tungsten oxide (WO₃) film fabricated by magnetron sputtering technology is the most likely to be industrialized due to its advantages of large-area and uniform deposition. However, electrochromic characteristics of the sputtered WO₃ film lag behind those of the solution-process approach due to inefficient ion transport arising from its intrinsically dense atomic structure. In this work, a strategy to develop microstructured magnetron-sputtered WO₃ films by introducing the buried porous electrodes to improve the optical modulation and response time was proposed. The results demonstrate that the porous sputtered WO₃ films prepared by this method exhibit significantly enhanced electrochromic characteristics compared with the dense WO₃ films. When thickness of the porous WO₃ increased to 300 nm, the optimized electrochromic characteristics were achieved, with a remarkable optical modulation of up to 79.08%, coloring and bleaching times of only 2.6 and 2.0 s, and a high coloring efficiency of 52.5 cm²/C. The improved performance is mainly attributed to synergistic effect of the porous indium tin oxide (ITO) electrode and the porous WO₃ film. The porous ITO electrode can increase the surface area with the increased WO₃ component and then increase electronic charges, facilitating the redox reaction process. Moreover, the porous WO₃ film offers a larger surface area for the electrolyte, increases reactive active sites and shortens ion diffusion pathway, which accelerates the ion diffusion and migration process, realizing efficient redox reactions and fast ion transport. This work provides an effective method for preparing high-performance micro- and nano-structured sputtered electrochromic films.

Nano-calcium phosphate (nCaP) has potential applications in nanomedicine fields such as drug delivery, bioimaging, antibacterial treatment, and bone formation promotion. However, its distribution and metabolic patterns within the body are not yet fully understood and require further in-depth research. This study employs a rare earth europium ion fluorescence labeling method and uses tumor-bearing mice as a model to investigate the distribution and metabolism of two sizes of nCaP (nanodots NDs: (2.53±0.63) nm; nanoparticles NPs: (107.76±25.37) nm×(17.66±1.63) nm) in the liver, spleen, lung, kidney, and tumor tissue. The results showed that after tail vein injection of 200 μL with a mass concentration of 1.5 mg/mL nCaP into tumor-bearing nude rats for 4 h, CaP NPs were primarily distributed in the liver and spleen, accounting for 65.70% and 29.32%, respectively, with 3.83% in the lung, while only 0.84% and 0.32% in the kidney and tumor. This suggests that larger CaP NPs are more easily captured by phagocytes within the reticuloendothelial system (RES). In contrast, compared to CaP NPs, accumulation of CaP NDs in the liver, spleen, and lung decreased significantly by 89.40%, 87.00%, and 88.89%, respectively, while their accumulation in the kidney and tumor increased by 3.67 and 3.06 times. This indicates that smaller particle size facilitates CaP NDs in glomerular filtration for urinary excretion and enhances their tumor-targeting capability. The clearance rates (CLz) of CaP NDs in the liver, spleen, and lung were 6.60, 4.14, and 2.40 times higher than that of CaP NPs, respectively, and 42.29% in the kidney. This indicates that reduced size of CaP NDs facilitates rapid metabolism by phagocytes in the liver, spleen, and lung but also results in reabsorption in the renal tubules. In tumor, the CLz of CaP NDs decreased by 91.9%, much smaller than that of CaP NPs, suggesting that the smaller CaP NDs exhibit significantly enhanced tumor targeting and retention capability. In the meantime, a physiologically based pharmacokinetic (PBPK) model incorporating particle size factors was preliminarily established for tumor-bearing mice to simulate the distribution of nano-calcium phosphate. The model's predictive fit (R²) for CaP NDs and CaP NPs in tumor sites reached 0.925 and 0.827, respectively. This study provides promising support for understanding in vivo distribution and metabolic patterns of nCaP and applying potential in medicine.

Ammonia is a harmful atmospheric pollutant that poses serious threats to human health and ecological environment. Therefore, the development of low-energy, high-performance and real-time ammonia monitoring system is imperative. In this study, p-aminobenzene sulfonic acid (pABSA) modified MoO₃/polypyrrole (PPy) composite materials were successfully prepared using an in situ chemical oxidation polymerization method with MoO₃ and pyrrole monomer (Py) as raw materials and FeCl₃ as an oxidant, along with pABSA as an anionic surfactant. Microstructure of the materials was characterized to explore influence of pABSA-modified MoO₃/PPy composite materials on the gas sensing performance. The results demonstrate that at room temperature, the response value of pABSA-modified MoO₃/PPy composite material to a mass concentration of 1×10⁵ µg/L ammonia is 188%, which is ~8 times higher than that of pure PPy (22%), exhibiting excellent selectivity and stability. The enhancement in sensing performance can be attributed to the formation of a heterojunction between MoO₃ and PPy as well as surface modification by pABSA leading to increased mobile charge carriers on the material's surface.

Electrochromic materials with dynamic color change and optical modulation have potential applications in the fields of automotive anti-glare mirror, smart window, low-power display, and electronic paper, attracting worldwide attention. NiO and MnO₂ are typical anodic coloration materials with a comfortable neutral tone. However, the low transmittance of single NiO or MnO₂ films in bleaching states leads to small optical modulation. Herein, a porous nickel-manganese layered double hydroxide (NiMn-LDH) film with neutral color for visible electrochromic application was prepared. The NiMn-LDH films were grown directly on fluorine-doped tin oxide (FTO) conductive glass substrates by a one-step solvothermal method using NiCl₂·6H₂O and MnSO₄·H₂O as the raw materials. The crystalline phase and micromorphology of the as-grown NiMn-LDH films were characterized and the electrochromic and electrochemical performances were also investigated. The results indicate that the film grown by solvothermal method is composed of NiMn-LDH nanosheets with porous surface morphology, leading to a large optical modulation of 61.9% at 550 nm. The coloration and bleaching time are calculated to be 15.8 and 13.2 s, respectively. A high coloration efficiency of 63.1 cm²·C^-1 is also achieved for the as-grown NiMn-LDH nanosheet film. Meanwhile, the NiMn-LDH film electrode demonstrates good cycle stability, retaining 87.0% of its maximum optical modulation after 160 cycles. Furthermore, the NiMn-LDH film electrode delivers an area capacitance of 10.0 mF·cm^-2 at a current density of 0.1 mA·cm^-2. These results consolidate that the as-prepared NiMn-LDH film electrode is a promising candidate for both electrochromic and energy-storage applications.

Diamond like carbon (DLC) film was a promising candidate for microelectromechanical system (MEMS) piezoresistive sensors owing to its excellent mechanical properties and sensitivity. The effects of carrier transport behavior and the role of operating conditions (such as temperature, humidity, etc.) on piezoresistive performance of metal-doped DLC were still unclear. In this work, Ti doped diamond like carbon (Ti-DLC) films with Ti atom fraction ranging from 0.43% to 4.11% were prepared using high-power pulse magnetron sputtering, where the high-throughput conception was introduced for film deposition. Effects of the doped Ti content on microstructure, electrical behavior and piezoresistive properties of the films were studied under various humidity environments. The results indicated that the doped Ti atoms were uniformly dissolved in the diamond like carbon matrix, accompanying typical amorphous characteristics for the Ti-DLC films regardless of Ti atom fraction changing from 0.43% to 4.11%. Furthermore, all the Ti-DLC films demonstrated distinct semiconductor feature, where the electrical resistivity was reduced with the increase of temperature in the range of 200-350 K. Particularly, the carrier transport was dominated by Mott type conduction with three-dimensional range hopping conduction from 200 to 270 K, while the thermal activation transport served as the conductive mechanism in the temperature range of 270-350 K. For the Ti-DLC films, the highest gauge factor (GF) was 95.1, and GF value increased with increasing relative humidity from 20% to 80%. This can be explained from reduction of the average distance between conductive cluster by introducing Ti atoms and a change in electrical resistance caused by adsorption of water molecules.

Advanced ink printing techniques, such as printing and coating, have overcome the limitations of traditional manufacturing methods, allowing for rapid prototyping of films and electronic devices with sophisticated structures and specific functions. These techniques hold enormous potential in wearable smart identification, energy storage, electromagnetic shielding and absorption, touch display, and so on. The key to printing advanced energy and electronic devices lies in the development of cutting-edge functional inks and their corresponding printing technologies. MXene, a family of two-dimensional compounds composed of transition metal carbides, nitrides, or carbonitrides, was discovered in 2011. MXene exhibits remarkable physical and chemical properties, including high conductivity, pronounced hydrophilicity, and diverse surface chemistry, which has garnered significant attention within the research community and made it particularly suitable as inks in printing applications. Conducting research on the printing behavior and mechanisms of MXene inks is crucial not only for achieving high-precision patterns but also for establishing a solid foundation for manufacturing techniques that can precisely create multiscale, multimaterial and multifunctional films, and electronic devices. This article begins with a brief discussion of MXene flakes’ synthesis and colloidal stability, followed by a detailed examination of its rheological characteristics, printable ink formulation, and printing methods. Additional, special attention is given to the latest advances of MXene ink in energy, health, and sensing applications. The perspective concludes with a summary of current research challenges and future directions in this area, offering new perspectives and insights for researchers.

In recent years, pressure sensors have been widely applied in the fields of smart wearable textile, health detection, and electronic skin. The emergence of the two-dimensional nanomaterial MXene has brought a brand-new breakthrough for pressure sensing. Ti₃C₂T_x is the most popular studied MXene in the field of pressure sensing and shows good mechanical, electrical properties, excellent hydrophilicity, and extensive modifiability, enabling it an ideal material for pressure sensing. Hence, researchers have conducted a lot of explorations and studies on design and application of MXene in pressure sensors in recent years. Herein, the preparation technologies and antioxidant methods are summarized. Design of MXene-based microstructures is also introduced, including aerogels/porous structural materials, hydrogels, flexible substrates, and films, which are beneficial to improve the response range, sensitivity, and flexibility of pressure sensors, and promote the rapid development of pressure sensors. The mechanisms of MXene pressure sensors are further broached, including piezoresistive, capacitive, piezoelectric, triboelectric, battery typed and nanofluidic. MXene has been applied in a wide range of sensors for various mechanisms due to its excellent characteristics. Finally, the chance and challenge in the synthesis, properties, and pressure sensing performance of MXene materials are prospected.

Two-dimensional transition metal carbon/nitride MXenes show promising applications in various fields due to their remarkable electrical and mechanical properties. Recently, the research of high performance MXenes nanocomposites (including one-dimensional fibers, two-dimensional films and three-dimensional blocks) has made remarkable progress. However, the mechanical properties are still far lower than the intrinsic mechanical properties of MXenes nanosheets, mainly due to the key scientific problems of voids, misalignment of MXenes nanosheets and weak interfaces. In order to solve the above problems, the intrinsic mechanical properties of MXenes nanosheets are firstly discussed in this work, then the development of high performance MXenes nanocomposites are summarized, and the latest research progress of high performance MXenes nanocomposites is discussed in detail, including how to eliminate void, improve the orientation of MXene nanosheets and enhance the interface interaction. Meanwhile, the applications of high performance MXenes nanocomposites in the fields of electric heating, thermal camouflage, electromagnetic shielding, sensing and energy storage are introduced. Finally, the challenges and future development directions of high performance MXenes nanocomposites are proposed.

Brain-inspired neuromorphic computing refers to simulation of the structure and functionality of the human brain via the integration of electronic or photonic devices. Artificial synapses are the most abundant computation element in the brain-inspired system. Memristors are considered to be ideal devices for artificial synapse applications because of their high scalability and low power consumption. Based on Ohm’s law and Kirchhoff’s law, memristor crossbar arrays can perform parallel multiply-accumulate operations in situ, leading to analogue computing with greatly improved speed and energy efficiency. Oxides are most widely used in memristors due to the ease of fabrication and high compatibility with CMOS processes. This work reviews the research progress of oxide memristors for brain-inspired computing, mainly focusing on their resistance switching mechanisms, device structures and performances. These devices fall into three categories: electrical memristors, memristors controlled via both electrical and optical stimuli, and all-optically controlled memristors. The working mechanisms of electrical memristors are commonly related to microstructure change and Joule heat that are detrimental to device stability. The device performance can be improved by optimizing device structure and material composition. Tuning the device conductance with optical signals can avoid microstructure change and Joule heat as well as reducing energy consumption, thus making it possible to address the stability problem. In addition, optically controlled memristors can directly response to external light stimulus enabling integrated sensing-computing-memoring within single devices, which are expected to be used for developing next-generation vision sensors. Hence, the realization of all-optically controlled memristors opens a new window for research and applications of memristors.

Wearable instruments are functional devices that can be worn on human body, sensing, transmitting and processing body or environmental information in real time, and show broad application prospects in medical health, especially artificial intelligence, sports and entertainment. With the development of wearable instruments, various flexible sensors have emerged. Flexible mechanical sensors based on piezoelectric effect have attracted much attention because of their advantages of wide sensing frequency, fast response, good linearity, and self-power supply. However, traditional piezoelectric materials are mostly brittle ceramics and crystalline materials, which limit their application in flexible devices. With the deepening of research, more and more flexible piezoelectric materials and piezoelectric composites continue to emerge, injecting new development vitality into flexible wearable mechanical devices. This article mainly summarizes the cutting-edge progress of flexible wearable piezoelectric devices, including piezoelectric principle, preparation and performance improvement methods of flexible piezoelectric materials. In addition, the main application directions of flexible wearable piezoelectric devices, including medical health and human-computer interaction, as well as the challenges and opportunities encountered, are summarized.

The outbreak of corona virus disease 2019 (COVID-19) has aroused great attention around the world. SARS-CoV-2 possesses characteristics of faster transmission, immune escape, and occult transmission by many mutation, which caused still grim situation of prevention and control. Early detection and isolation of patients are still the most effective measures at present. So, there is an urgent need for new rapid and highly sensitive testing tools to quickly identify infected patients as soon as possible. This review briefly introduces general characteristics of SARS-CoV-2, and provides recentl overview and analysis based on different detection methods for nucleic acids, antibodies, antigens as detection target. Novel nano-biosensors for SARS-CoV-2 detection are analyzed based on optics, electricity, magnetism, and visualization. In view of the advantages of nanotechnology in improving detection sensitivity, specificity and accuracy, the research progress of new nano-biosensors is introduced in detail, including SERS-based biosensors, electrochemical biosensors, magnetic nano-biosensors and colorimetric biosensors. Functions and challenges of nano-materials in construction of new nano-biosensors are discussed, which provides ideas for the development of various coronavirus biosensing technologies for nanomaterial researchers.

The pandemic outbreak of COVID-19 has posed a threat to public health globally, and rapid and accurate identification of the viruses is crucial for controlling COVID-19. In recent years, nanomaterial-based electrochemical sensing techniques hold immense potential for molecular diagnosis with high sensitivity and specificity. In this review, we briefly introduced the structural characteristics and routine detection methods of SARS-CoV-2, then summarized the associated properties and mechanisms of the electrochemical biosensing methods. On the above basis, the research progress of electrochemical biosensors based on gold nanomaterials, oxide nanomaterials, carbon-based nanomaterials and other nanomaterials for rapid and accurate detection of virus were reviewed. Finally, the future applications of nanomaterial-based biosensors for biomolecular diagnostics were pointed out.

Flexible sensors have wide applications in various fields such as biomedicine, environmental monitoring and smart wearable devices, as they can adapt to diverse complex environments and curved surfaces. This study aimed to develop resilient and flexible oxygen sensors based on fluorescence quenching. A flexible oxygen sensing component was prepared, comprising aluminum silicate fibers as the support, polydimethysiloxane (PDMS) as the matrix, and platinum tetrakis pentafluorophenyl porphyrin (PtTFPP) as the oxygen probe. The component exhibited superhydrophobicity with a water contact angle of 152°, which was beneficial for maintaining integrity in humid atmospheres and aqueous solutions. It showed the fluorescence quenching effect towards gaseous oxygen and dissolved oxygen in water, which could be well fitted by the Stern-Volmer equation with K_SV constants of 0.020 h·Pa^-1 for the gaseous oxygen and 2.94 L·mmol^-1 for the dissolved oxygen. The component also demonstrated good reversibility and fast response in rapidly altered atmosphere, with a response time of 0.9 s from nitrogen switching to oxygen and a recovery time of 2.7 s from oxygen switching to nitrogen. Additionally, the PtTFPP-PDMS component displayed remarkable stability concerning its relative fluorescence intensity and water contact angle even after exposure to 100 ℃ steam for 15 h, soaking in pH 1-10 aqueous solutions, and enduring 400 bending cycles. The aluminum silicate fiber-supported PtTFPP-PDMS film developed in this study exhibited excellent fluorescent oxygen sensing properties and stability, making it a promising candidate for oxygen sensors, and suitable for determination of gaseous and dissolved oxygen in challenging environments.

Mechanoluminescent (ML) materials, due to their unique mechanical-to-optical energy conversion, hold significant promise in stress sensing and are poised to become the next generation of visual strain-sensing materials. Currently, expanding ML material systems and enhancing their performance remain focal points of research. In this study, a series of Tb³⁺-doped green ML phosphors was synthesized using BaSrGa₄O₈ matrix (hexagonal crystal system, space group P6₃, with a non-centrosymmetric structure) via high-temperature solid-state synthesis. These materials emitted bright green light under various mechanical excitations (tension, compression, and torsion). Clear note mappings were observed by writing B, S, G, O, T, and b on the prepared ML elastomer with a glass rod. By analyzing the colormap, the stress conditions during the writing process could be traced. This is the first observation of ML phenomenon in the above-mentioned matrix doping system. Under 254 nm ultraviolet (UV) excitation, BaSr_1-xGa₄O₈: xTb³⁺ phosphors exhibited bright green emission at 543 nm, which was attributed to ⁵D₄-⁷F₅ transition of Tb³⁺, and shared the same luminescent center as ML. The samples continued to display strong long persistent luminescence after UV irradiation was removed. By combining ML, photoluminescence (PL), and long persistent luminescence (LPL) with thermoluminescence (TL) analysis, further insights into their intrinsic connections were elucidated. In conclusion, this study broadens the range of high-performance ML material systems, showcasing potential applications in visual strain sensing, information security, and anti-counterfeiting.

In recent years, copper iodide (CuI) is an emerging p-type wide bandgap semiconductor with high intrinsic Hall mobility, high optical absorption and large exciton binding energy. However, the spectral response and the photoelectric conversion efficiency are limited for CuI-based heterostructure devices, which is related to the difficulty in fabrication of high-quality CuI thin films on other semiconductors. In this study, a p-CuI/n-Si photodiode has been fabricated through a facile solid-phase iodination method. Although the CuI thin film is polycrystalline with obvious structural defects, the CuI/Si diode shows a high weak-light sensitivity and a high rectification ratio of 7.6×10⁴, indicating a good defect tolerance. This is because of the unilateral heterojunction behavior of the formation of the p⁺n diode. In this work, the mechanism of photocurrent of the p⁺n diode has been studied comprehensively. Different monochromatic lasers with wavelengths of 400, 505, 635 and 780 nm have been selected for testing the photoresponse. Under zero-bias voltage, the device is a unilateral heterojunction, and only visible light can be absorbed at the Si side. On the other hand, when a bias voltage of -3 V is applied, the photodiode is switched to a broader “UV-visible” band response mode. Therefore, the detection wavelength range can be switched between the “Visible” and “UV-visible” bands by adjusting the bias voltage. Moreover, the obtained CuI/Si diode was very sensitive to weak light illumination. A very high detectivity of 10¹³-10¹⁴ Jones can be achieved with a power density as low as 0.5 μW/cm², which is significantly higher than that of other Cu-based diodes. These findings underscore the high application potential of CuI when integrated with the traditional Si industry.

In recent years, humidity sensors have attracted widespread attention from researchers in fields such as food safety and soil monitoring. Traditional humidity sensors exhibit the advantages of good stability and high sensitivity. However, most humidity sensing systems convert humidity signals into recognizable waveforms through wired connections and large external devices, making it impossible to achieve real-time visual monitoring of changes in humidity information. Currently, direct conversion of humidity information into visible color signals by eyes provides an ideal solution to the aforementioned problems but still lacks intelligent monitor capacity. This study integrated humidity sensors and electrochromic devices (ECDs) to prepare an intelligent visual humidity monitoring system. By converting humidity signals into voltage signals to drive ECDs, stable and reversible color change in the system could be achieved. The ECDs were prepared using tungsten trioxide (WO₃) as the negative electrode and zinc foil (Zn) as the positive electrode. Based on the output voltage of the humidity sensor, it achieves transitions between different working states, thereby generating color signals that can be observed by the naked eyes. Electrochemical performance and electrochromic performance of ECDs were tested and characterized by using a UV-visible spectrophotometer and an electrochemical workstation. Subsequently, the performance of the conditioning circuit was analyzed using an oscilloscope and a humidity generation platform. The results show that the intelligent electrochromic humidity indicator has good stability and rapid response performance, where the coloring time and fading time are only 7.5 s and 4.5 s, respectively. After 300 cycles, the optical modulation (ΔT) is basically maintained the same as the initial value, and the retention rate can reach more than 95%. Therefore, this visual humidity indication system which possesses novel design and simple structure has promising broad application in fields such as artificial intelligence and intelligent agriculture.

Photochromic windows are considered an effective and energy-efficient smart window due to their simple structure, passive light modulation, and zero-energy input. However, the research on photochromic smart windows has rarely addressed the mid-infrared (MIR) bands, which greatly limits energy-saving efficiency. Here, we report that rare-earth oxygen-containing hydrides (ReO_xH_y) films grown on ITO substrates have the ability to be broadband modulated. The developed photochromic smart window is capable of automatically adjusting emissivity by sensing light intensity while maintaining visible and near-infrared (NIR) modulation (ΔT_sol = 35.1%, ΔT_lum = 37%, and Δε_{8-13 μm} = 0.12). We also achieved one-step preparation of GdO_xH_y with improved stability by optimising the preparation atmosphere. The photochromic mechanism was analyzed by comprehensive characterization. In conclusion, this passive and synergistic modulation method across the visible-NIR-MIR is expected to greatly advance the field of photochromic smart windows.