Volatile organic compounds are a class of widespread air pollutants that are increasingly impacting anthropized environments. Due to the potential toxic effects associated with many of these compounds, the development of inexpensive and effective sensors for in situ detection, both indoor and outdoor, is of paramount technological importance to mitigate human exposure and develop appropriate intervention strategies. However, portable technologies are typically designed to quantify known pollutants, while qualitative measurements often require complex sampling and laboratory analyses. In this study, we propose a dual-detection photonic sensor based on polymeric microcavities doped with emitting nanocrystals, capable of identifying various volatile compounds in vapor phase. The sensor consists of a lattice of altenated sub-micrometric layers of cellulose acetate and poly(N-vinylcarbazole), with a periodic structure interrupted by an engineered defect layer doped with core-shell CdSe/ZnS quantum dots. The response to different analytes can be detected through both transmittance and photoluminescence measurements, with distinct features arising from the specific chemical and physical interactions between the sensor components and the pollutants.

Zero-standby power sensors are crucial for enhancing the safety and widespread adoption of hydrogen (H₂) technologies in chemical processes and sustainable energy applications, given the flammability of H₂ at low concentrations. Here, we report an event-driven hydrogen sensing system utilizing palladium (Pd)-based micromechanical cantilever switches. The detection mechanism relies on strain generation in the Pd layer, which undergoes reversible volume expansion upon hydrogen adsorption. Our experimental and simulation results demonstrate that the bistable micromechanical switch-based sensor generates a wake-up signal with activation time depending on hydrogen concentration in the target environment while always remaining active for events without any standby power consumption under normal conditions. The H₂ adsorption-induced subsequent switching of the multi-cantilever-based switch configuration on the sensor resulted in the quasi-quantification of hydrogen concentrations. The reported zero-standby power sensor's operational lifetime is limited by the frequency of detection events and exposure to concentrations exceeding hydrogen's flammability limit. This work advances the development of high-density, maintenance-free sensor networks for large-scale deployment with Internet of Things devices, enabling unattended continuous monitoring of hydrogen generation, transportation, distribution, and end-user applications.

Electrical energy and chemical energy play an important role in developing the emerging intelligent vehicle and artificial intelligence. Essentially, in well-designed energy devices, they can be converted with each other and stored based on electrochemical reactions. Since the eventual performance relates closely with the physiochemical properties of the electrode catalysts, it is crucial to tune their microstructure to enhance the reaction kinetics and performance of energy devices. Benefitted from its superb spatial distribution of exsolved nanoparticles and uniquely anchored architecture, exsolution is a robust technique to improve performance for energy conversion and storage. Here, we review the characteristics and mechanisms of exsolution to provide solid knowledge on rationally designing and fabricating of novel exsolution-derived energy products with excellent properties. Moreover, to trigger inspirations to create new types of energy devices and widen the application window, the recent advances in the exsolution application in energy areas covering fuel cells, electrolysers and batteries, and the fundamental principles of the exsolution effect on tuning their performance are comprehensively reviewed and analyzed. Lastly, the potential directions to further improve the energy devices' performance are discussed.

Cellulose, one of the most versatile and abundant biopolymers in nature, has been employed by humans for thousands of years in diverse applications, such as renewable energy resources, structural materials, and fabric constituents. Cellulose nanocrystals (CNCs), obtained through the acidic hydrolysis of cellulose-based materials including wood, cotton, and additional sources, have attracted significant attention in areas, for example, energy storage, cosmetics, and medical devices. CNCs can spontaneously assemble into a cholesteric liquid crystal phase, which exhibits distinctive properties including biodegradability, high surface area, low cost, excellent mechanical strength, and surface functionality. Modifying the surfaces of CNCs or embedding CNCs with other materials enables novel cellulose-based composites for advanced technologies and applications. This review systematically outlines the preparation of cellulose-based liquid crystals (LCs), highlights the structural color regulation, photonic properties manipulation, and potential applications. Specifically, stimuli responsiveness, for example, temperature-responsiveness, humidity-responsiveness, pressure-responsiveness, tension-responsiveness, electricity-responsiveness, magnetic force-responsiveness and the optical properties of cellulose-based LCs (circularly polarized light modulation and circularly polarized phosphorescence properties) are demonstrated. Furthermore, the applications of cellulose-based LCs for gas detection, anticounterfeiting, multicolor separation, multifunctional E-skin, and advanced fabrics are also reviewed. Finally, this review concludes with the remaining challenges and perspectives for unleashing new possibilities in the development of high-performance multiple-responsive cellulose-based LCs.

Bacterial infections pose a major threat to human health as well as livestock production. Traditional antibiotics face significant limitations in the complex in vivo environment, including toxic side effects, non-specific accumulation, and poor pharmacokinetic profiles, posing considerable challenges to effective antibacterial therapy. In this context, intelligent peptide-based nanomaterials (IPBNs), which can specifically respond to pathological features or external stimuli to target the infection microenvironment are becoming emerging alternatives in the field of antibacterial therapy. However, a comprehensive summary of recent advances in IPBNs for antibacterial applications is still lacking. To this end, we first introduce the non-covalent interactions that drive the stimuli-responsive behavior of IPBNs. Subsequently, the response mechanisms and design strategies of IPBNs for different stimuli, including endogenous stimuli, exogenous stimuli, and multiple stimuli, are systematically discussed. In addition, a description of applications related to antimicrobial therapy is included. Finally, the biological properties, challenges, and future development trends of IPBNs are discussed. Overall, this review provides a comprehensive overview of IPBNs from the perspectives of design, mechanisms, properties and applications, aiming to promote more development work and explore their potential in fields such as biomedicine and animal husbandry.

Hydrogels are widely studied for their stimuli-responsive properties. They adapt to external stimuli, including physical, chemical and biological ones. To enhance adaptability in complex environments, multi-responsive hydrogels have been developed, which either react to multiple stimuli independently or cooperatively (multistimuli-response) or exhibit multiple responses triggered by single or multiple stimuli (multi-response). Their properties depend on polymer type, molecular weight, cross-linking, and water content, which affect mechanical behavior and response. To address their inherent fragility, polymer-inorganic nanocomposite hydrogels integrate the advantages of both components, yielding enhanced functionalities. Among various nanofillers, smectites have been extensively studied for improving mechanical strength and responsiveness. Polymer-smectite nanocomposite hydrogels exhibit enhanced elasticity, toughness, thermal stability, gas barrier properties, and responsiveness to external stimuli, expanding their applications in biomedical engineering, environmental remediation, and smart materials. This review discusses the fundamentals of polymer-smectite nanocomposite hydrogels, their design strategies, and the role of smectite in enabling multi-responsive behavior. The classification based on the site of responsiveness (polymer network and smectite) is presented, highlighting the important role of smectite in controlling the response and potential applications. Finally, challenges are addressed, emphasizing smectite's role in advancing next-generation smart materials.

Metal halide perovskites are recognized for their solution processability and high luminescent efficiency. Their broad optoelectronic applications are however challenged by their high sensitivity to the environment, a consequence of their ionic nature and low formation energy. Nevertheless, this sensitivity allows for a range of luminescent responses to different stimuli, positioning them as a novel class of responsive materials. This review aims to elucidate the flexible and diverse luminescence responses in metal halide perovskites while highlighting their significance for future information-related applications. It begins by introducing the working principles of responsive luminescent metal halide perovskites, followed by discussions on their changes in luminescence color, intensity, and lifetime in response to various stimuli, along with further elaboration on their emerging applications in sensing, anti-counterfeiting, and information encryption. It concludes by summarizing the challenges and providing perspectives on the future development of this exciting field.

Micro- and nanomotors (MNMs) are minuscule devices capable of independently navigating and executing designated functions within micro- and nanoscale domains. MNMs are emerging as a promising category of drug delivery vehicles, capable of transforming disease microenvironment chemical or external energy into mechanical force, facilitating their self-propelled motion. In recent years, MNMs have showcased immense promise in the field of biomedicine, especially in the treatment of diseases. This review first explores the design principles of the propulsion and operation of MNMs, and then highlights the remarkable capabilities of MNMs in various biomedical applications, including cardiovascular disease, gastrointestinal disease, wound sealing and hemostasis, central nervous system disease, bladder disease, antimicrobial applications, and cancer therapy. Finally, the review discusses the challenges and future opportunities in the biomedical application of MNMs.