ACS Materials Au最新文献

The integration of fluorinated benzothiadiazole (FBT) into donor-acceptor (D-A) copolymers represents a major advancement in the field of organic solar cells (OSCs). The fluorination process effectively fine-tunes the energy levels, reduces the highest occupied molecular orbital levels, and enhances the open-circuit voltages of the polymers. Furthermore, fluorination improves molecular packing and crystallinity, which significantly boosts the charge transport and overall device performance. This review provides a detailed analysis of the progress made with FBT-based polymers in OSCs, classifying these materials according to their copolymerization units. It discusses the design strategies and structure-property relationships that have emerged as well as the current challenges and future directions for optimizing these polymers. By offering a comprehensive overview of the existing research, this review aims to facilitate the development of high-performance FBT-based organic photovoltaic materials, ultimately contributing to the advancement of sustainable energy solutions.

Lanthanide materials with a 4f⁷ electron configuration (⁸S_7/2) offer an exciting system for realizing multiple addressable spin states for qubit design. While the ⁸S_7/2 ground state of 4f⁷ free ions displays an isotropic character, breaking degeneracy of this ground state and excited states can be achieved through local symmetry of the lanthanide and the choice of ligands. This makes Eu²⁺ attractive as it mirrors Gd³⁺ in exhibiting the ⁸S_7/2 ground state, capable of seven spin-allowed transitions. In this work, we identify Eu₂(P₂S₆) and Eu₂(P₂Se₆) as viable candidates for optically addressable spin states. The materials feature paramagnetic behavior at 2.0 ≤ T ≤ 400 K and μ₀ H = 0.01 and 7 T. The field-dependent magnetization M(H) curve reveals a single-ion spin with effective magnetic moments comparable to the expected magnetic moment of Eu²⁺. Seven well-defined narrow peaks in the excitation and emission spectra of Eu²⁺ are resolved. Phonon contributions to the Eu²⁺ spin environment are evaluated through heat capacity measurements. Insights into how the spin-polarized band structure and density of states of the materials influence the physical properties are described by using density functional theory calculations. These results present a foundational study of Eu₂(P₂S₆) and Eu₂(P₂Se₆) as a feasible platform for harnessing the spin, charge, orbital, and lattice degrees of freedom of Eu²⁺ for qubit design.

Electronics have evolved significantly with the development of semiconductor materials and devices, with emerging areas such as organic and flexible electronics showing great promise, particularly in applications such as wearable devices and environmental sensors. Since the discovery of conducting polymers in the late 1970s, organic electronics have paved the way for innovations such as organic field-effect transistors (OFETs), organic light-emitting diodes (OLEDs), and organic solar cells (OPVs). Recent advances have focused on nanostructuring techniques to enhance device properties, such as charge mobility and luminescence efficiency. The growing concern for sustainability has also led to the exploration of biodegradable organic electronics as a potential solution to electronic waste. This perspective briefly discusses the impact of nanostructuring on the performance of both conventional and biodegradable organic devices, exploring the challenges and opportunities associated with using alternative substrates like paper. This perspective emphasizes the importance of understanding molecular organization at the nanoscale to optimize device performance and ensure stability under practical conditions.

Of the few weberite-type Na-ion cathodes explored to date, Na₂Fe₂F₇ exhibits the best performance, with capacities up to 184 mAh/g and energy densities up to 550 Wh/kg reported for this material. However, the development of robust structure-property relationships for this material is complicated by its tendency to form as a mixture of metastable polymorphs, and transform to a lower-energy Na _y FeF₃ perovskite compound during electrochemical cycling. Our first-principles-guided exploration of Fe-based weberite solid solutions with redox-inactive Mg²⁺ and Al³⁺ predicts an enhanced thermodynamic stability of Na₂Mg _x Fe_2-x F₇ as the Mg content is increased, and the x = 0.125 composition is selected for further exploration. We demonstrate that the monoclinic polymorph (space group C2/c) of Na₂Fe₂F₇ (Mg0) and of a new Mg-substituted weberite composition, Na₂Mg_0.125Fe_1.875F₇ (Mg0.125), can be isolated using an optimized synthesis protocol. The impact of Mg substitution on the stability of the weberite phase during electrochemical cycling, and on the extent and rate of Na (de)intercalation, is examined. Irrespective of the Mg content, we find that the weberite phase is retained when cycling over a narrow voltage window (2.8-4.0 V vs Na/Na⁺). Over a wider voltage range (1.9-4.0 V), Mg0 shows steady capacity fade due to its transformation to the Na _y FeF₃ perovskite phase, while Mg0.125 displays more reversible cycling and a reduced phase transformation. Yet, Mg incorporation also leads to kinetically limited Na extraction and a reduced overall capacity. These findings highlight the need for the continued compositional optimization of weberite cathodes to improve their structural stability while maximizing their energy density.

Gas bubbles, commonly used in medical ultrasound (US), witness advancements with nanobubbles (NB), providing improved capabilities over microbubbles (MB). NBs offer enhanced penetration into capillaries and the ability to extravasate into tumors following systemic injection, alongside prolonged circulation and persistent acoustic contrast. Low-frequency insonation (<1 MHz) with NBs holds great potential in inducing significant bioeffects, making the monitoring of their acoustic response critical to achieving therapeutic goals. We introduce a US-guided focused US system comprising a one-dimensional (1D) motorized rotating imaging transducer positioned within a low-frequency therapeutic transducer (center frequencies of 105 and 200 kHz), facilitating precise monitoring of NB cavitation activity in three-dimensional (3D) and comparison with MBs. Passive cavitation detection (PCD) revealed frequency-dependent responses, with NBs exhibiting significantly higher stable and inertial cavitation doses compared to MBs of the same gas volume when excited at a center frequency of 105 kHz and peak negative pressures ranging from 100 to 350 kPa. At 200 kHz, MBs showed higher cavitation doses than NBs. PCD showed that 105 kHz enhanced both NBs' and MBs' oscillations compared to 200 kHz. The system was further used for 3D passive acoustic mapping (PAM) to provide spatial resolution alongside PCD monitoring. Two-dimensional PAM was captured for each rotation angle and used to generate a complete 3D PAM reconstruction. Experimental results obtained from a tube phantom demonstrated consistent contrast PAM full-width half-maximum (FWHM) as a function of rotation angle, with similar FWHM between MBs and NBs. Frequency-selective PAM maps distinguished between stable and inertial cavitation via the harmonic, ultraharmonic and broadband content, offering insights into cavitation dynamics. These findings highlight NBs' superior performance at lower frequencies. The developed 3D-PAM technique with a 1D transducer presents a promising technology for real-time, noninvasive monitoring of cavitation-based US therapies.

In this study, we demonstrate the formation of a self-assembled microgel double layer on an electrode surface, utilizing the ability to form electro-responsive, reversible inclusion complexes between microgels modified with ferrocene and β-cyclodextrin in these systems. The bottom layer was based on microgels containing ferrocene moieties and derivatives of cysteine. The presence of the amino acid derivative enabled the formation of the well-packed monolayer on the gold surface through chemisorption, while ferrocene was responsible for electroactivity. The addition of βCD-modified microgel led to the formation of the second monolayer, ultimately creating the double layer. Our investigation focuses on the electrochemically controlled formation and deformation processes of the double microgel layer.

Ion migration in semiconductor devices is facilitated by the presence of point defects and has a major influence on electronic and optical properties. It is important to understand and identify ways to mitigate photoinduced and electrically induced defect-mediated ion migration in semiconductors. In this Perspective, we discuss the fundamental mechanisms of defect-mediated ion migration and diffusion as understood through atomistic simulations. The discussion covers a variety of case studies from the literature, with a special focus on metal halide perovskites, important materials for solar absorption and related optoelectronic applications. Tuning the perovskite composition and dimensionality and applying systematic strains are identified as ways to suppress phase segregation and ion migration. This Perspective delves into first-principles modeling approaches for defect migration and diffusion, presenting detailed case studies on the diffusion of defects and dopants in CdTe, hydrogen impurities in halide perovskites, and halogen migration in hybrid perovskites and emphasizing the importance of organic cations. The discussion further extends to accelerating the prediction of migration pathways and barriers through machine learning approaches, particularly the application of crystal-graph neural networks. By combining theoretical insights with practical case studies, this Perspective aims to provide an understanding of defect-mediated ion migration and suggestions for next-generation semiconductor discovery while considering ion migration suppression as one of many design objectives.

Halide perovskites (HPs) are emerging as key materials in the fight against global warming with well recognized applications, such as photovoltaics, and emergent opportunities, such as photocatalysis for methane removal and environmental remediation. These current and emergent applications are enabled by a unique combination of high absorption coefficients, tunable band gaps, and long carrier diffusion lengths, making them highly efficient for solar energy conversion. To address the challenge of discovery and optimization of HPs in huge chemical and compositional spaces of possible candidates, this perspective discusses a comprehensive strategy for screening HPs through automated high-throughput and combinatorial synthesis techniques. A critical aspect of this approach is closing the characterization loop, where machine learning (ML) and human collaboration play pivotal roles. By leveraging human creativity and domain knowledge for hypothesis generation and employing ML to test and refine these hypotheses efficiently, we aim to accelerate the discovery and optimization of HPs under specific environmental conditions. This synergy enables rapid identification of the most promising materials, advancing from fundamental discovery to scalable manufacturability. Our ultimate goal of this work is to transition from laboratory-scale innovations to real-world applications, ensuring that HPs can be deployed effectively in technologies that mitigate global warming, such as in solar energy harvesting and methane removal systems.

High-entropy alloys (HEAs) have become pivotal materials in the field of catalysis, offering unique advantages due to their diverse elemental compositions and complex atomic structures. Recent advances in computational techniques, particularly density functional theory (DFT) and machine learning (ML), have significantly enhanced our understanding and design of HEAs for use in catalysis. These innovative atomistic simulations shed light on the properties of HEAs, enabling the discovery and optimization of catalysis materials for solid-solution structures. This Perspective discusses recent studies that illustrate the progress of HEAs in catalysis. It offers an overview of the properties, constraints, and prospects of HEAs, emphasizing their roles in catalysis to enhance catalytic activity and selectivity. The discussion underscores the capabilities of HEAs as multifunctional catalysts with stable structures. The presented insights aim to inspire future computational and experimental efforts to address the challenges in fine-tuning HEAs properties for improved catalytic performance.

We report on the analysis of oxygen vacancies (OVs) content and ordering of Sr_2-x Ca _x Fe₂O_6-δ perovskites and explain how OVs change the electrical conductivity and oxygen evolution catalytic activity of these compounds. The structure and OV content are tuned by controlling the A-site composition and the reaction atmosphere. X-ray diffraction (XRD) and thermogravimetric analysis (TGA) are used to identify the crystal structures and to quantify bulk oxygen vacancy contents. Our analysis shows that OV content and crystal structure govern the electronic transport properties of the Sr_2-x Ca _x Fe₂O_6-δ system. The electrical conductivity of oxygen-deficient perovskites (ODPs) is significantly higher than those in brownmillerites (by at least 2 orders of magnitude). Seebeck coefficient measurements identified that the Sr-rich ODPs and brownmillerites are p-type semiconductors, while Ca-rich brownmillerites are either insulators (within the experimental temperature range) or p-type semiconductors at lower temperatures (<750 K). Electrical conductivity of p-type semiconductors (Sr-rich compounds) reduces with higher OV content, and in brownmillerites with x ≥ 1.25, a transition to n-type semiconductor is observed at temperatures above 750 K. Our analysis shows that the hole and electron concentrations are similar in these brownmillerites, indicating major contributions from ionic transport. Finally, we show how oxygen deficiency alters the electrical conductivity and catalytic activity of the Sr_2-x Ca _x Fe₂O_6-δ system in noncomplementary ways.