Shedding light on the energy applications of emerging 2D hybrid organic-inorganic halide perovskites

Exploring the frontiers of X@MXene nanozymes: Synthesis, enhanced catalytic mechanism, and application in biomedical sensors

Biosensing technologies are facing increasingly urgent demands for highly sensitive and selective sensors. MXene, as a novel two-dimensional (2D) material, has emerged as an ideal candidate for sensors due to its ultrahigh conductivity and tunable surface functional groups. However, unmodified MXene lacks catalytic activity and specificity, limiting its applications. Surface-engineered X@MXene composites (X = metal oxides, aptamers, etc.) can significantly enhance catalytic activity and selectivity. This review systematically summarizes MXene synthesis strategies (HF etching, HF-free etching, vapor deposition, surface terminal group modulation), elucidates the regulatory mechanism of heterocomponents (X) on MXene catalytic pathways, analyzes its design principles in single-mode devices with different signal types (optical, electrical, colorimetric), and reveals the synergistic advantages of dual-mode sensors in sensitivity and anti-interference performance. This review provides theoretical guidance for designing high-performance MXene-based sensors, advancing their applications in precision medicine and intelligent monitoring.

Refractory Metal-Based MXenes: Cutting-Edge Preparation and Applications

Refractory metal-based MXenes refer to MXenes with M as a refractory metal. Due to their high conductivity, large specific surface area, multiple active sites, high photothermal conversion efficiency, adjustable surface groups, and controllable nanolayer spacing, they hold broad application prospects in various fields such as photoelectrocatalysis, biomedicine, water treatment, electromagnetic shielding, and sensors. The unique physical properties of refractory metal-based MXenes are related to their electronic and crystal structures. The interstitial layer causes the carbides to exhibit different behavior compared to the original metal. At the same time, different preparation methods have a great influence on the interlayer spacing and surface termination of refractory metal-based MXenes, thus affecting their performance. This review systematically summarizes the latest progress in the preparation methods and frontier applications of refractory metal-based MXenes, offering new insights for further development. Additionally, various characterization techniques and first-principles calculations are summarized, which are crucial for optimizing refractory metal-based MXenes for applications such as catalysis, energy storage, and sensors. In summary, the current challenges and future development prospects of refractory metal-based Mxenes are addressed, aiming to provide indispensable information for the intelligent design of 2D materials in the future.

A tellurium iodide perovskite structure enabling eleven-electron transfer in zinc ion batteries

The growing potential of low-dimensional metal-halide perovskites as conversion-type cathode materials is limited by electrochemically inert B-site cations, diminishing the battery capacity and energy density. Here, we design a benzyltriethylammonium tellurium iodide perovskite, (BzTEA)2TeI6, as the cathode material, enabling X- and B-site elements with highly reversible chalcogen- and halogen-related redox reactions, respectively. The engineered perovskite can confine active elements, alleviate the shuttle effect and promote the transfer of Cl- on its surface. This allows for the utilization of inert high-valent tellurium cations, eventually realizing a special eleven-electron transfer mode (Te6+/Te4+/Te2-, I+/I0/I-, and Cl0/Cl-) in suitable electrolytes. The Zn||(BzTEA)2TeI6 battery exhibited a high capacity of up to 473 mAh g-1Te/I and a large energy density of 577 Wh kg-1 Te/I at 0.5 A g-1, with capacity retention up to 82% after 500 cycles at 3 A g-1. The work sheds light on the design of high-energy batteries utilizing chalcogen-halide perovskite cathodes.

Additive Engineering for Stable and Efficient Dion-Jacobson Phase Perovskite Solar Cells

Because of their better chemical stability and fascinating anisotropic characteristics, Dion-Jacobson (DJ)-layered halide perovskites, which owe crystallographic two-dimensional structures, have fascinated growing attention for solar devices. DJ-layered halide perovskites have special structural and photoelectronic features that allow the van der Waals gap to be eliminated or reduced. DJ-layered halide perovskites have improved photophysical characteristics, resulting in improved photovoltaic performance. Nevertheless, owing to the nature of the solution procedure and the fast crystal development of DJ perovskite thin layers, the precursor compositions and processing circumstances can cause a variety of defects to occur. The application of additives can impact DJ perovskite crystallization and film generation, trap passivation in the bulk and/or at the surface, interface structure, and energetic tuning. This study discusses recent developments in additive engineering for DJ multilayer halide perovskite film production. Several additive-assisted bulk and interface optimization methodologies are summarized. Lastly, an overview of research developments in additive engineering in the production of DJ-layered halide perovskite solar cells is offered.

The Effects of Mono- and Bivalent Linear Alkyl Interlayer Spacers on the Photobehavior of Mn(II)-Based Perovskites

Mn(II)-based perovskite materials are being intensively explored for lighting applications; understanding the role of ligands regarding their photobehavior is fundamental for their development. Herein, we report on two Mn (II) bromide perovskites using monovalent (perovskite 1, P1) and bivalent (perovskite 2, P2) alkyl interlayer spacers. The perovskites were characterized with powder X-ray diffraction (PXRD), electron spin paramagnetic resonance (EPR), steady-state, and time-resolved emission spectroscopy. The EPR experiments suggest octahedral coordination in P1 and tetrahedral coordination for P2, while the PXRD results demonstrate the presence of a hydrated phase in P2 when exposed to ambient conditions. P1 exhibits an orange-red emission, while P2 shows a green photoluminescence, as a result of the different types of coordination of Mn(II) ions. Furthermore, the P2 photoluminescence quantum yield (26%) is significantly higher than that of P1 (3.6 %), which we explain in terms of different electron-phonon couplings and Mn-Mn interactions. The encapsulation of both perovskites into a PMMA film largely increases their stability against moisture, being more than 1000 h for P2. Upon increasing the temperature, the emission intensity of both perovskites decreases without a significant shift in the emission spectrum, which is explained in terms of an increase in the electron-phonon interactions. The photoluminescence decays fit two components in the microsecond regime-the shortest lifetime for hydrated phases and the longest one for non-hydrated phases. Our findings provide insights into the effects of linear mono- and bivalent organic interlayer spacer cations on the photophysics of these kinds of Mn (II)-based perovskites. The results will help in better designs of Mn(II)-perovskites, to increase their lighting performance.

Roles of Organic Ligands in Ambient Stability of Layered Halide Perovskites

The combination of organic ligands and inorganic Pb-I frameworks in layered perovskites has bestowed upon them high structural tunability and stability, while their microscopic degradation mechanism remains unclear. Here, we found the key role of ligands in intrinsic structural stability and the consequent morphological evolution in layered perovskites during long-term ambient aging based on (GA)(MA)nPbnI3n+1 (GA = guanidinium, = 4) and (BDA)(MA)n-1PbnI3n+1 (BDA = 1,4-butanediammonium, < n > = 4) perovskites. The BDA-based perovskites have a low intrinsic stability due to high crystal formation energy (ΔH), which are prone to hydration during ambient aging. We overserved changed crystal orientation from perpendicular to parallel, a delayed charge populating time from <1 ps to >50 ps, an inhibited carrier transfer kinetics between quantum wells, an increase of 0.9 μs of charge carrier transport time and a decrease of 1.2 μs of charge carrier lifetime in the BDA-based film during ambient aging, which accounts for a large power-conversion efficiency (PCE) loss (14.2% vs 11.2%). By contrast, the GA ligand increases the intrinsic structural stability of perovskites, which not only yields an initial PCE as high as 20.0% but also helps retain excellent optoelectronic properties during aging. Therefore, only a slight PCE loss (20.0% vs 19.1%) was observed. Our work reveals the key role of organic-inorganic interaction affecting the intrinsic structural stability and optoelectronic properties, and provides a theoretical basis for the future design of stable and efficient optoelectronic devices.