Viologens (1,1 '-disubstituted-4,4 '-bipyridinium salts) are well-known redox-active molecules with broad applications in energy conversion and optoelectronics. However, their excited-state dynamics in the solid state remain largely unexplored. Here, we report fluorescence enhancement in crystalline viologen-based organic-inorganic hybrids under continuous photoirradiation, where photoluminescence (PL) intensity increases up to sixfold relative to the initial emission within seconds of excitation. Spectroscopic studies, X-ray crystallography, and DFT calculations reveal that the phenomenon is driven by photoinduced electron transfer (PIET) from anionic donors to viologen dications, generating long-lived radicals. The radicals are confirmed via Raman and X-ray photoelectron spectroscopies and quenched by heating, which accelerates their consumption. Re-irradiation restores the PL, indicating reversibility. This PIET-driven PL enhancement is tunable by structural modification and stable across a range of temperatures and environments. The reversible optical response enables potential applications in optical memory and data storage.

Bias-free photoelectrochemical devices provide a sustainable route for solar hydrogen production from alkaline seawater, however, the requirement for large potential for anodic oxygen evolution and undesired chloride oxidation in seawater limit their efficiency. By leveraging the low oxidation potential of hydrazine, a toxic pollutant, bias-free devices can achieve high-performance hydrogen production and simultaneous degradation of hydrazine, effectively avoiding chloride oxidation. Here, we design a self-powered artificial leaf device, comprising a perovskite photocathode integrated with a noble-metal-free oxide catalyst for direct solar hydrogen production and hydrazine oxidation. The device exhibits a high photocurrent density of 25 mA cm-2 and stability for 3 days under 1-sun illumination. Upscaling the artificial leaf device enables near-complete hydrazine degradation to below 1 ppb within ≈ 30 h under zero-bias operation. This study provides a scalable and sustainable approach for simultaneous hydrogen generation and pollutant removal, advancing the use of solar energy in environmental applications.

Kesterite Cu2ZnSnS4 (CZTS) is a promising material for solar energy harvesting due to its high absorption coefficient and favorable electrical properties. However, its performance as a photocathode for photo-electrochemical (PEC) water splitting is limited by deep defects and poor interfacial charge transport. While partial substitution of Zn with Cd has shown improvements in PEC performance by reducing antisite defects, the impact of fully substituting Zn with Cd in CZTS-based devices remains underexplored due to challenges in forming high quality films. This study successfully fabricates fully cadmium-substituted CZTS (Cu2CdSnS4, CCTS) films by precisely controlling the Cu/(Cd + Sn) ratio in the precursor solution. Films with a Cu/(Cd + Sn) ratio of 0.9 demonstrate optimal quality, achieving a photocurrent of 25 mA cm-2 at 0 VRHE and a half-cell solarto-hydrogen conversion efficiency of 4.36 %-among the highest reported for chalcogenide photocathodes. These results stem from a suitable band gap, reduced defect concentration, lower charge transfer resistance, and favorable interfacial band alignment, as supported by Density Functional Theory, impedance spectroscopy, and ultraviolet photoelectron spectroscopy. This work highlights the importance of compositional optimization in maximizing PEC performance of CCTS photocathodes, establishing CCTS as a leading candidate among emerging chalcogenides for solar water splitting applications.

This study presents the first comprehensive investigation of pyrene-based covalent organic frameworks (COFs) as bulk dopants in formamidinium lead iodide (FAPbI3) perovskite solar cells (PSCs). A series of three frameworks-sp2c-PyCOF, Im-PyCOF, and SH-PyCOF-were synthesized to systematically evaluate the effects of distinct linkage chemistries and Lewis-basic functionalities (-C≡N, -C = N-, and -SH) on perovskite optoelectronic performance. When incorporated into the perovskite precursor solution, the PyCOFs coordinate with undercoordinated Pb2 + sites, effectively passivating deep trap states and suppressing non-radiative recombination. Their extended π-conjugation further promotes efficient charge delocalization and transfer within the bulk perovskite. Consequently, PyCOF-doped PSCs demonstrated enhanced charge extraction and higher Fill Factors, achieving champion power conversion efficiencies of ∼19.5%, outperforming both undoped devices (17.75%) and pyrene-free COF controls. These findings establish π-conjugated pyrene COFs as a new class of multifunctional dopants that couple structural stability with optoelectronic tunability, offering a rational molecular design platform for the next-generation of high-performance and durable perovskite photovoltaics.

Understanding the relationship between CO2 reduction reaction (CO2RR) performance and surface terminations of MXenes is crucial for designing effective electrocatalysts. This study explores the impact of common terminations on Mo2CTx using a computational hydrogen electrode (CHE) model integrated with a pseudo-microkinetic model (pseudo-MM). Unlike traditional CHE methods, CHE/pseudo-MM considers the energy differences of all steps, providing a comprehensive view of CO2RR mechanisms while reducing computational cost generated from calculating transitional state. The electrolyte is considered as acetonitrile with 1-ethyl-3-methylimidazolium tetra-fluoroborate (EMIMBF4) to inhibit the generation of hydrogen. Theoretical predictions reveal surface terminations dictate the selectivity of C1 products, whose proton is provided by EMIMBF4. The selectivity for fully-F, -O-and-OH-terminated Mo2CTx surfaces varies with the applied potential, as confirmed by experiments. Electrochemical CO2RR in acetonitrile with EMIMBF4 electrolyte confirms these predictions, showing that CH4 outperforms CO and gradually becomes the dominant product as the applied potential increases. These findings demonstrate the qualitative accuracy of the proposed CHE/pseudo-MM for predicting CO2RR selectivity, particularly for gaseous products, over Mo2CTx systems.

Achieving fully transparent electronic devices requires improving p-type transparent conducting materials (TCMs) to match their n-type counterparts. This study explores novel p-type TCMs using high-throughput screening via an automatic spray pyrolysis system. The performance of conducting wide bandgap chalcogenide based on CuS can be improved by incorporating various cations, with Mg emerging as the most promising candidate. The optimized CuS-Mg films exhibited superior transparency and conductivity, comparable to state-of-the-art p-type TCMs. Density functional theory (DFT) calculations linked the inverse correlation between transparency and conductivity to changes in Cu 3d and S 3p orbital coupling with varying Mg content. The best CuS-Mg composition demonstrated high hole concentration (5 × 1021 cm-3), low sheet resistance (266 Ω □-1), and high transparency (∼75%). The transmittance increased by ∼30% compared with pristine CuS. The successful application of a p-CuS-Mg/n-CdS heterojunction as a semi-transparent photodiode highlights its potential for smart displays and window-integrated electronics. This study demonstrates the value of combining experimental and theoretical methods for accelerated material discovery.

Chemically inert low-dimensional (CI LD) halogenometallate interfaces incorporating low-reactivity bulky cations could address the trade-off between efficiency and stability in perovskite solar cells (PSCs). However, their formation is hindered by the low reactivity of their bulky cations and solubility constraints of their precursors in orthogonal solvents compatible with underlying perovskites. Here we introduce a selective templating growth strategy that leverages conventional metastable LD interfaces as templates to drive the growth of more stable CI LD interfaces through an organic cation exchange process. Our prototype PSCs achieve efficiencies of 25.1% over an active area of 1.235 cm2-among the highest reported for 1-cm2 PSCs. The PSCs retain over 93% and 98% of their initial efficiency after 1,000 h of operation and 1,100 h of thermal ageing at 85 degrees C, respectively. The versatility of this strategy unlocks access to CI LD interfaces, paving the way for the development of more efficient and stable PSCs.

Electric-field manipulation of spin degrees of freedom is pivotal for next-generation spintronics, yet nonvolatile control at terahertz (THz) frequencies remains elusive. Here, we harness the quantum geometry of a Dirac semimetal, PtTe2, to achieve all-electrical tunability of THz spintronic emission under a constant magnetic field without field cycling or remanent magnetization. By integrating a ferroelectric substrate with a PtTe2/ferromagnetic heterobilayer, we electrically modulate the Fermi level and Berry curvature of PtTe2, thereby controlling its spin Hall conductivity in real time, yielding a 21% modulation of the THz emission amplitude. Density functional theory corroborates doping-driven shifts in Berry curvature that directly alter spin Hall conductivity, underscoring the key role of geometric phases in ultrafast spin-charge conversion. Our approach offers a low-complexity, energy-efficient, and nonvolatile route to tunable spin Hall THz devices, and we anticipate that these findings will open new avenues for harnessing quantum geometry in spin-based logic and ultrafast electronics.

Oxide interfaces have enormous potential for future electronics with many applications, such as large spin Hall conductance, phase transitions, topological states, and superconductivity. However, previous investigations have predominantly focused on gigahertz frequencies; whilst the possibilities to fabricate devices operational at terahertz frequencies are demonstrated. A model solution is proposed employing 5d rare-earth, strontium iridate (SrIrO3) heterostructure with cobalt (Co) ultrathin layers. Femtosecond lasers are used to photoexcite the spins in Co, which super diffuse into the SrIrO3 layer to produce an ultrafast inverse spin Hall effect in sub-picosecond timescales. The devices exploit the external magnetic field and laser fluence to control the spin polarization from the Co layer and demonstrate a tailored spin Hall effect. These results thus pave paths for next-generation ultrafast oxide electronics offering possibilities for room temperature-based devices.

Cellulose is a versatile and sustainable biopolymer that can be used to make microparticles for various applications. However, its inherent crystallinity limits the surface access for sorption and functionalization. This study presents a one-step method for tuning the crystallinity and chain accessibility of cellulose microparticles using a reactive spray drying technique. The spray drying parameters (e.g., feed concentration, N2 gas flow rate, and cross-linker dosage) were optimized to produce spherical, porous microparticles with a size distribution ranging from 0.54 to 5.65 μm. Among these parameters, feed concentration and N2 gas flow rate were shown to have the greatest influence on the morphology and internal structure, while cross-linking reduced crystallinity and enhanced chain accessibility. The extent of the enhancement in the chain accessibility was directly linked to the epichlorohydrin cross-linker/glucose monomer (E/G) ratio in the feed solution. As a result, the improved chain accessibility led to greater solvent absorptivity, methylene blue adsorption, and dispersibility of the spray-dried cellulose microparticles compared to those of pristine cellulose. These findings highlight the potential of the method as a simple and scalable approach to producing cellulose microparticles with tunable properties.

Electron Transport Layer (ETL) is one of the most important and necessary components in perovskite solar cells (PSCs). The performance and stability of PSCs highly depend on the morphology, quality and electron transport characteristic of ETL. High-efficiency PSCs are typically fabricated via spin coating, a simple and reliable technique yielding highly uniform thin films, though its application to large-area processes remains challenging. Spray coating, already extensively adopted in industrial manufacturing, enables continuous large-scale production. The efficient SnO2-based layers exhibit a uniform and pinhole-free surface with high transmittance. Low temperature spraying process is suitable for a variety of substrates, can be used to make flexible devices. The implementation of in-situ hydrolysis-mediated nanocrystal precursor passivation enabled spray-deposited SnO2-NbOx ETLs to achieve power conversion efficiencies (PCE) of 23.07 % in rigid PSCs, while maintaining 21.36 % PCE in flexible perovskite solar cells (F-PSCs). SnO2-NbOx outperforms commercial SnO2 NCs by suppressing the energy barrier and reducing trap-state density at the perovskite/ETL buried interface. The environmental stability testing reveals a striking contrast between the two ETL materials, PSCs incorporating spray-coated SnO2-NbOx ETLs demonstrate remarkable durability, retaining 93.91 % of their initial PCE after 2000 h of aging, whereas their SnO2-based counterparts suffer significant degradation, preserving merely 62.75 % PCE under identical accelerated aging conditions. Meanwhile, the mechanical stability of the device based on spray-coated SnO2-NbOx is also improved.

Traditional 3D perovskites, being remarkably effective in solar cells and light-emitting diodes (LEDs), exhibit poor stability under illumination and moisture, limiting their real-life applications. Recent advancements in perovskite-based devices have utilized combinations of 2D and 3D perovskites to improve stability. However, high ion mobility can lead to the formation of quasi-2D phases at interfaces during fabrication, whose behavior remains unclear. Previous studies indicate that quasi-2D perovskites are less stable and may transform into 3D phases under illumination, but the underlying mechanisms have yet to be investigated. In this work, the light-induced transformation of quasi-2D phenylethylammonium cesium lead bromide PEA2Csn-1PbnBr3 n +1 perovskite is demonstrated to stable 3D CsPbBr3 perovskite. The process is initiated by light excitation, which triggers a reaction with surrounding moisture and oxygen molecules. PbO and Pb(OH)2 species form within the material which passivate defects and significantly enhance the photoluminescence and stability of the 3D phase. The simple synthesis method, followed by UV treatment, provides a direct method to stable and luminescent 3D perovskite, making it promising for solar cell, LEDs and photodetector applications.

Although hybrid perovskite-based devices have made significant advances in terms of device performance, long-term stability remains a major challenge to widespread implementation. A unified understanding of the complexity describing the degradation of these types of materials is absent, and in this work, one common hybrid perovskite material, methylammonium lead iodide (MAPI), is used as a vehicle to show how a unified understanding can be achieved using complementary characterization techniques. This work uses low-dose in situ electron microscopes with electric fields ranging from 2.5 to 5 V/μm in a scanning electron microscope before focusing on the lower fields of 1.25 and 2.5 V/μm, where an electric threshold is identified. The results demonstrate that material loss is initiated at the MAPI grain boundaries near the negative electrode interface, where MA+ is reduced. Above the electrochemical threshold, extensive material volatilization and amorphous layer formation were detected, accompanied by significant PL quenching. High-field solid-state MAS NMR and materials modeling indicate that the MAPI decomposition process is a simultaneous combination of iodine migration, vacancy formation, and organic cation decomposition. The 1H MAS NMR data from the as-synthesized MAPI show direct evidence of preexisting iodine vacancies that induce the formation of CH3NH2, forming possible dative coordination to the lead framework positions. Subsequent data from MAPI degraded under exposure to electric fields (1.25 and 2.50 V/μm) directly demonstrate the presence of decomposition products such as NH4I, CH3I, and CH2I2 through pinhole formation at the electrochemical threshold and more widespread damage induced above this threshold. The methodology presented here can be applied to investigate other hybrid perovskite materials through direct spin coating on the corresponding substrates, deepening our understanding and providing insights for improved device stability.

In this study, we synthesized a new category of materials, 2D Cr2X3 (where X = S, Se, and Te), using an APCVD method. By leveraging the same space group and identical exposed facets of the as-synthesized Cr2X3 nanoflakes, we compared their catalytic performance for HER and electrical properties to unveil the contribution of electrical conductivity in the overall performance. A descending trend in HER activities from Cr2X3 to Cr2Se3, and Cr2Te3 was found, as evidenced by the increasing overpotentials and decreasing current densities at the same over -potential. Interestingly, electrical properties showed an improving trend from Cr2S3 to Cr2Se3, and Cr2Te3, as revealed by IDS-VG and IDS-VDS tests based on FET devices, respectively. The primary factor affecting overall catalytic performance was found to be intrinsic catalytic activities rather than electrical properties, as supported by DFT calculations. These insights emphasize that the focus of harnessing intrinsic catalytic activities when exploring 2D electrocatalysts.

There is currently no agreement on the degradation mechanisms for PA6 as a result of mechanical recycling. In this study, PA6 was extruded five times to simulate mechanical melt recycling process. Both virgin PA6 and the extruded PA6 were characterised to determine the predominant degradation mechanism. Melt flow rate (MFR) increases with increasing number of extrusion passes suggesting a reduction in melt viscosity due to mechanical processing. Gel permeation chromatography (GPC) results confirmed a reduction in molecular weight from 18,600 g/mol to 13,100 g/mol. Chain ends titration showed a decrease in the concentration of both the amine and carboxyl chain ends after the fifth extrusion. There were no changes to the chemical structure of the virgin PA6 and extruded PA6 observed from the Fourier transform infra-red (FTIR) and Nuclear magnetic resonance (NMR) spectra. X-ray photoelectron spectroscopy (XPS) showed a reduction in the C–N peak area supporting the scission of the N-alkylamide bond. The increase in the O=C–N peak area suggests that chain recombination via branching is possible. The shorter chains have higher mobility, and this gives rise to an increase in the crystallisation rate as seen from the differential scanning calorimeter (DSC) thermograms. The appearance of the γ phase after the fifth extrusion was identified in the DSC melting endotherms. The understanding of the degradation process of recycled PA6 will enable targeted modifications involving the incorporation of additives in the recycling process to ensure good mechanical properties in the recycled polymer.

Adsorption of inert small molecules has always been challenging, and hence, these molecules are generally difficult to remove from solution. In this work, we demonstrated a significant improvement (>25 times) in the adsorption of an inert small molecule, urea, using a hierarchical material design, which remarkably outperformed the simple chemical functionalization of the substrate. To illustrate this point, we employed two-dimensional (2D) materials such as Ti3C2Tx MXene as the adsorbent "substrate" which has a high potential for efficient urea removal. In particular, Cu-functionalized MXene, with Cu valency between 0 and +1 exhibited superior urea adsorption performance compared to pristine MXene. However, due to the strong van der Waals forces, MXene has a propensity to aggregate, leading to the loss of active sites for urea adsorption. To address this, cellulose nanocrystals were introduced as they have dual functionalities, namely, to prevent aggregation and preserve active sites for adsorption of urea. These nanocrystals are small, rigid, and hydrophilic, facilitating their interaction with hydrophilic groups on the MXene surface. Porous hydrogel macrobeads prepared using alginate cross-linked with calcium ions yielded a hierarchical structure with nanosized MXene-cellulose moieties distributed within the millimeter beads. Besides serving as mechanical support, the cellulose nanocrystals can be further surface-functionalized with enhanced interaction with chemical groups such as polydopamine to boost the adsorption properties. Each component in the hydrogel composite synergistically enhanced the interaction with urea and promoted adsorption. Consequently, the composite hydrogel exhibited a remarkable enhancement in urea adsorption capacity from 6.7 to 354.4 mg/g in aqueous solution, while a maximum adsorption capacity (Q(max)) of 115.1 mg/g was observed in simulated dialysate solution due to the increased surface area available for urea adsorption. The development of this hydrogel composite consisting of Cu-functionalized MXene, functionalized cellulose nanocrystals, and alginate cross-linked with calcium showcased its potential as a highly efficient and versatile material for effective urea adsorption in both aqueous and simulated dialysate solutions.

Despite a recent shift toward methylammonium (MA)‐free lead‐halide perovskites for perovskite solar cells, high‐efficiency formamidinium lead iodide (FAPbI3) devices still often require methylammonium chloride (MACl) as an additive, which evaporates away during the annealing process. In this article, it is shown that the residual MA+, however, triggers thermal instability. To investigate the possibility of an optimal concentration of MA+ that may improve thermal stability, the intrinsic thermal stability of pure FA, FA‐rich, MA‐rich, and pure MA perovskite films (FA1−xMAxPbI3, FAMA) is studied. The results show that the thermal stability of FAMA perovskites decreases with more MA+, under degradation conditions that isolate the intrinsic thermal stability of the material (i.e., without moisture and oxygen effects). X‐ray diffraction (XRD), proton‐transfer‐reaction time‐of‐flight mass spectrometry (PTR‐ToF‐MS), photoluminescence (PL) and UV–visible spectroscopy, and depth‐profiling X‐ray Photoelectron Spectroscopy (XPS) are employed to show that the observed trend is mainly due to the decomposition of the MA+ cation, as opposed to other effects such as the precursor solvent and film morphologies. It is also found that the surfaces of these FAMA films are MA+ rich, although this phenomenon does not appear to affect thermal stability. Finally, it is demonstrated that this trend is unaffected by the presence of Spiro‐OMeTAD atop the film, and thus solar cell devices should preserve this trend.

Organic electrochemical transistor (OECT)-based electronic devices, known for their high transconductance and low power consumption, have garnered significant attention within the field of electrophysiology and logic circuits. Nevertheless, high-performing and stable n-type depletion-mode OECTs are highly desired to enable the implementation of more sophisticated information processing and integrated device functionalities. In this work, an n-type depletion-mode OECT based on poly(benzodifurandione) (PBFDO) is evaluated with respect to its operational stability in aqueous media. We observe that large anions effectively facilitate the dedoping process of PBFDO, resulting in a significant enhancement of its drain current ON/OFF ratio (similar to 10(3)). The optimized PBFDO-OECTs show high normalized transconductance of 223 +/- 43 S/cm, ultrafast transient speed of 45 mu s, and high ON/OFF ratio of 10(3) when gated in sodium hexafluorophosphate aqueous electrolyte, capable of detecting high-resolution electrophysiological signals as well as integrating seamlessly into logic circuits, including NAND and NOR gates. Moreover, the blend of n-type PBFDO and p-type poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) for construction of a fully depletion-mode ambipolar transistor is demonstrated. Our work significantly improves the operational stability and the ON/OFF ratio of PBFDO-OECT, overcoming the performance mismatch between n-type and its counterpart p-type materials and advancing the prospects of integrated OECT in next-generation electronics.

Empowering soft robots with the ability to perceive will greatly improve human-machine interaction, enabling autonomous robotic systems. However, integrating additional sensing components into soft actuators poses significant challenges, particularly in terms of adhesion and stiffness matching. Here, we present a novel dual-functional thermal-sensing actuator (TSA) with conductive polymer ionogel electrodes. This TSA leverages ion diffusion for thermal sensing and electrochemical actuation, all within a single device. One remarkable feature of this TSA is its ability to not only sense temperature through heat conduction upon contact, but also remotely sense thermal radiation, especially from the human body. We further designed a sensing-actuation smart control system and demonstrated robotic hands, bionic butterflies and flytraps that exhibit autonomous and programmable responses when approached by a human hand. This work represents a pioneering effort in integrating thermal sensing and actuation functions within a single device. It not only facilitates proprioceptive actuation but also offers fresh insights for the development of autonomous robots.