Science China Materials最新文献

At present, the development of perovskite solar cells (PSCs) is progressing rapidly, but the issue of poor stability remains a significant challenge. Achieving a stable precursor solution is crucial for the large-scale production of high-quality PSC films. In this study, we successfully developed a strategy to improve the long-term stability of the precursor solution and improve device performance by employing 1-n-butyl-3-methylimidazolium di-n-butyl phosphate (BMIMBP) as an anti-aging additive. The BP⁻ component inhibits the reactivity of I⁻ and formamidinium ion through multiple chemical bonds, thereby stabilizing the precursor solution. In addition, the BMIM⁺ component, which contains an amino group, can form two-dimensional perovskite internally, further enhancing the device stability. This strategy provides valuable guidance for achieving long-term stability in solar cells.

Covalent organic framework (COF) materials have gained significant applications in electrocatalytic systems due to their structural diversity and tunable functionalities. Moreover, three-dimensional (3D) COFs exhibit multistage pore structures, exposing numerous open sites, which facilitate the oxygen reduction reaction (ORR) process. However, the advancement of 3D COFs for ORR has been hindered by challenges, including limited topologies, the scarcity of building blocks with the required reactivity and symmetries, and difficulties in determining crystalline structures. In this work, we utilized an 8-connectivity building unit and successfully constructed two isoreticular 3D COF materials, which exhibited exceptionally high catalytic activity for 2e⁻ oxygen reduction reaction without the addition of any metal or conductive support materials, nor the pyrolyzed process. The electrochemically active surface areas (ECSAs) of the two 3D COFs were found to be 17.19 and 12.18 mF/cm², respectively, which were significantly higher than those reported from other framework materials.

Exchange coupling within nanomagnetism is a rapidly evolving field with significant implications for that plays a crucial role in the development of magnetic nanomaterials. Manipulating exchange coupling interaction enables the magnetic systems to overcome limitations associated with size-dependent magnetic behavior within nano scale, thereby improving their magnetic properties and providing for superior performance in biomedical applications compared with single-phase magnetic materials. Understanding the underlying mechanism of exchange coupling and its impact on macroscopic magnetic properties is crucial for the design and application of such magnetic materials. This review provides an overview of recent advances in interfacial exchange coupling among different magnetic modalities—ferromagnetism, ferrimagnetism, and antiferromagnetism—based on core-shell magnetic nanoparticles (MNPs). Additionally, this review discusses micromagnetic simulations to gain insights into the relationship between the microscopic magnetic structure (size, shape, composition, and exchange coupling) and the resulting macroscopic properties. The controlled synthesis of MNPs is summarized, including one-step method and two-step method. The precise manipulation of interfacial characteristics is of great importance, albeit challenging, as it allows for the fine-tuning of magnetic properties tailored for specific applications. The review also explores potential applications of core-shell MNPs in magnetic resonance imaging, hyperthermia therapy, targeted drug delivery, and advanced neuromodulation.

Notably, the cleavage of Sn–C bonds in extreme-ultraviolet photoresists containing Sn-oxygen (oxo) clusters and the generation of free radicals upon exposure lead to the chemical linking of Sn-oxo cores and subsequent solubility shifts. The reactivities and migration patterns of the generated radicals substantially influence patterning outcomes, including sensitivity and resolution. Herein, two Snoxo clusters, Sn₄-Me-C₁₀ (with Sn–methyl) and Sn₄-Bu-C₁₀ (with Sn–butyl), were combined to balance the sensitivity and resolution of photoresists, leveraging the feedback regulation between methyl and butyl free radicals generated from Sn–C bond cleavage. During electron beam lithography exposure, sensitive butyl radicals produced by Sn₄-Bu-C₁₀ initiated reactions within Sn₄-Me-C₁₀, improving sensitivity. Subsequently, the unstable methyl and bulky adamantyl radicals generated by Sn₄-Me-C₁₀ quenched the excess butyl radicals, thus improving the resolution and exposure latitude. Thus, this method leveraging the feedback regulation of free radicals offers new insights into the design of sensitive metal oxide resists with enhanced resolution.

In the most popular NaYF₄:Yb/Er upconversion nanoparticles (UCNPs), the red emission is attributed to four potential excitation routes encompassing two- and three-photon excitation processes. Consequently, this red emission typically exhibits a super-quadratic dependency on near-infrared (NIR) excitation intensity, with the nonlinear order n being dependent on the individual contributions (C_is) of these four excitation routes. Notably, the C_is values are not constant but significantly impacted by the surface quenching of the UCNPs, leading to a decrease in the n value. However, a quantitative assessment of these variable C_is has not been undertaken, hindering a comprehensive understanding of the quenching effect on the UC mechanisms. In this work, we prepare four NaYF₄:Yb/Er nanocrystal samples with varying degrees of surface quenching, achieving through the modulation of particle size and core-shell structure. We quantitatively evaluate the C_is values and identify the primary excitation route responsible for the red emission. Our results reveal that the contribution of three-photon excitation increases from 7% in the 30 nm bare core to 74% in 90 nm core with shell at an excitation intensity of 200 mW cm⁻². This observation high-lights the impact of surface quenching suppression. Furthermore, we discover that the quenching effect operates by reducing the lifetimes of the Yb³⁺²F_5/2 and Er³⁺⁴S_3/2 levels, while enhancing the NIR emission intensity ratio of the Er³⁺⁴I_13/2 → ⁴I_15/2 transition to the Yb³⁺²F_5/2 → ²F_7/2 transition. Our findings provide physical insights into the excitation mechanisms underlying the red UC emission in NaYF₄:Yb/Er UCNPs.

The development of solid-state materials with switchable luminescence in response to stimuli remains a challenge, especially for organic materials. While crystal water significantly impacts the absorption spectra of organic crystals, it is unclear whether the emission spectra of organic luminescent materials can be systematically manipulated by water. In this study, we successfully obtained curcumin monohydrate (Form X), a channel-type hydrate exhibiting crystallization-induced emission (CIE) at 608 nm (orange fluorescence), which contrasted with the conventional forms of aggregation-caused quenching (ACQ). Thermal treatment induced the release of hydration water, resulting in a new anhydrate (Form IV) that emitted yellow-green fluorescence with the emission peak at 575 nm. Additionally, this approach can be used to track the absorption of curcumin crystals following subcutaneous or intramuscular delivery. The hydratemediated single-crystal-to-single-crystal transition (SCSC) and its associated luminescence transition were reversible and responsive to temperature, offering a green approach for synthesizing and designing aggregation-induced-emission (AIE)-based intelligent luminescent devices for detecting air humidity or drug absorption.

Negative temperature coefficient (NTC) thermistor plays a crucial role in science research and engineering applications for precise temperature monitoring. Although great progress has been achieved in NTC materials, enhancing sensitivity and maintaining this high sensitivity along with linearity across extensive temperature ranges remain a significant challenge. In this study, we introduce a diamond-based thermistor (DT) characterized by its outstanding sensitivity, swift response time, and broad temperature monitoring capabilities. The temperature constant B for this DT, measured from 30 to 300°C (B_30/300), achieves an exceptional value of 8012 K, which notably exceeds the temperature sensing capabilities of previously reported NTC thermistors within this extensive range. Moreover, diamond’s unique thermal conductivity and stability significantly boost the response speed and durability of the DT, offering substantial advantages over traditional ceramic thermistors. The enhanced temperature-sensitive properties of the DT are attributed to the presence of impurity elements in polycrystalline diamond. Impedance analysis indicates a hopping conduction mechanism, likely involving C-H or C-N dipoles at the diamond grain boundaries. This study marks a significant leap forward in diamond thermistor technology and sheds light on the mechanisms of thermal active conduction in diamond materials.