Materials Today Nano最新文献

Silver telluride (Ag_xTe) is a member of the chalcogenide family that comprises materials extensively used as solid electrolytes. Because of its high-ionic conductivity, low-optical bandgap, and excellent thermoelectric properties, Ag_xTe has been studied in many research fields, including optoelectronics and energy harvesting. Herein, Ag_xTe is proposed as the active channel for resistive random access memory (RRAM) showing complementary resistive switching (CRS) characteristics. Ag_xTe-based RRAM devices with an Ag/Ag_xTe/Au structure are fabricated on a glass substrate. Ag_xTe nanoparticles are synthesized using the colloidal method, and Ag_xTe thin films are prepared via spin coating of the synthesized nanoparticles dispersed in deionized water. The fabricated Ag_xTe-based RRAM device exhibits CRS characteristics without any additional built-in selectors or antiserial arrangement. This is attributed to the formation of the inversion of CF geometry and allows the fabrication of high-density crossbar arrays. The Ag_xTe RRAM device annealed at 200 °C exhibits a resistance on/off ratio of approximately 10² as well as stable retention (∼10⁴ s) and endurance (∼10³ cycles). This investigation proposes a new application of Ag_xTe, as a solid electrolyte, and a new strategy for the development of high-density crossbar RRAM architectures, for the first time.

The success in enhancing diamond by introducing nanotwins opens a new frontier in the development of superhard materials. However, the underlying hardening mechanism of nanotwinned diamond (nt-diamond) remains elusive and a persistent research focus. In this study, we employ first-principles calculations to unveil the performance enhancement in nt-diamond mediated by quantum confinement effect. This effect is characterized by the non-uniform valence charge density of C-C bonds near the twin boundary, leading to incomplete bond breakage at the onset of elastic instability and identified as the key factor in delaying cracking. These findings not only contribute to establishing the theory of hardness in superhard materials, but also suggest new avenues for enhancing their mechanical performance through the introduction of heterogeneous structures and dopant atoms aligned with the principle of quantum confinement effect.

Gastric ulcer, a chronic disease of the digestive system, presents a high incidence rate and poses significant health risks. It is closely associated with the excessive production of reactive nitrogen and oxygen species (RONS), inflammation and cell apoptosis. In this study, taxifolin (Tax)-iron nanozymes (Fe-Tax) was developed by conjugating Tax with iron ions (Fe³⁺), which exhibited the activities of catalase and superoxide dismutase in the gastrointestinal environment. Our results revealed that Fe-Tax nanozymes effectively scavenge RONS, mitigate oxidative damage, inflammation and cell apoptosis in vitro. Additionally, Fe-Tax could alleviate tissue inflammation and gastric mucosal damage by regulating NRF2, NF-κB, Bax/Bcl-2, and VEGF signal pathways in gastric ulcer ethanol-induced. Crucially, the Fe-Tax has been shown to have excellent biocompatibility in vitro and in vivo. Overall, this study developed Fe-Tax nanozymes with enzyme cascade reactions and provided a highly efficient strategy to prevent and alleviate gastric ulcers.

It is now well established that multi-principal element alloys (MPEAs) offer ample opportunities for exploring new compositions beyond those accessed previously by conventional alloys. However, there is one more realm of possibility presented by MPEAs that has not been touch upon thus far. Here we show that, different from conventional alloys based on a single host element, a given starting MPEA solid solution on its way towards equilibrium can take a rich variety of potential decomposition pathways via multi-stage phase separation, offering a wide range of composition destinations. If/when some of them are reached, assuming kinetically allowed, the multiple phase separation reactions one after another would lead to domains that are compositionally complex and spatially localized. This hypothetical scenario is demonstrated in this paper using a model that mimics Cr-Co-Ni MPEA, showing a preponderance of multiplicity even when assuming only fcc-based phases can form. The complex chemical heterogeneities created as such are expected to be an additional knob to turn for tuning spatially variable composition and chemical order and therefore mechanical properties. Our results thus advocate multiple phase separation possibilities with many potential paths and terminal chemical heterogeneities as yet another important characteristic that distinguishes MPEAs from conventional alloys.

With the rapid development of wearable electronic, smart robot and health monitoring, there is a growing focus on flexible piezoresistive pressure sensors. Herein, a new strategy is proposed to prepare flexible piezoresistive pressure sensor with porous polydimethylsiloxane (PDMS) sponge as matrix and reduced graphene oxide (rGO) and multi-walled carbon nanotubes (MWCNTs) for the construction of dual-conductive network. The sensor exhibited excellent overall sensing performances (pressure detection range of 0–200 kPa, sensitivity of 1.62 kPa⁻¹ in 0–29 kPa and 0.41 kPa⁻¹ in 29–65 kPa, response/recovery time of 61/40 ms and 22,000 loading-unloading cycles at 0–15 % compressive strain). Meanwhile, the sensor was able to normally work in the range of 30–100 °C and affected little by temperature. In addition, the sensor was successfully applied for detecting various human motions as well as music recognition and identification. The piezoresistive pressure sensor has great application prospect in wearable devices, health monitoring, and human-machine interaction.

Hafnium oxide (HfO₂) has special technological significance due to its superior properties such as high dielectric constant (κ∼25), wide bandgap (∼5.7 eV), and superb thermal and chemical stabilities. Its room-temperature ferromagnetism and excellent CMOS technology compatibility make it a promising candidate for seamless CMOS-spintronics integration. Low-dimensional single-crystalline HfO₂ nanostructures, particularly one dimensional (1D) nanostructures, are expected to exhibit enhanced ferromagnetic properties due to large specific surface areas and potentially more surface defects. To date, the synthesis of single-crystalline HfO₂ 1D nanostructures has, however, remained elusive. Here, single-crystalline dopant-free HfO₂ nanostructures with notable morphologies, including HfO₂ 1D nanostructures, are grown using catalyst-assisted pulsed laser deposition. It is shown that Sn plays a crucial role in producing these 1D nanostructures by increasing both the VLS nucleation and growth rates. Magnetization measurements reveal room-temperature ferromagnetism in HfO₂ nanowires, contrasting with weak paramagnetic responses in HfO₂ nanostructured films. We also provide the first direct evidence of oxygen vacancies as the source of room-temperature ferromagnetism in HfO₂. To account for the observed magnetic property, we employ a modified bound magnetic polaron-band ferromagnetism hybrid model, which is also generally applicable to dopant-free nanostructures of other metal oxides. This work provides new insights into the growth of novel metal oxide 1D nanostructures and the design of new dilute magnetic semiconducting oxides for potential integrated CMOS-spintronics applications.

Proton therapy presents an appealing radiotherapy modality for the treatment of deeply-seated and unresectable tumors, but it still needs additional means to enhance the localization and efficiency of therapeutic action. Here we explore the use of elemental bismuth nanoparticles (Bi NPs) as sensitizers for proton therapy enhancement. Spherical Bi NPs were prepared by the method of pulsed laser ablation, followed by their coating with Pluronic polymer to stabilize them in a physiological environment. We observed efficient apoptotic cell death after proton irradiation at the Bragg peak, which was explained by high proton stopping power and low work function of Bi. The maximal effect was observed for 3 Gy radiation and 50 μg/mL NPs dose with 97 % inhibition of tumor cell clonogenic activity. The strong therapeutic effect was confirmed in vivo using aggressive Sa37 sarcoma tumors in mice. We observed 60 % inhibition of primary tumor growth with a decrease of metastatic potential in popliteal and axillary lymph nodes. Combined with X-ray contrast properties and radiosensitizing functionalities, the proposed concept of Bi NPs-enhanced proton therapy promises a major upgrade for cancer therapy.

To advance polydimethylsiloxane (PDMS)-supported silver nanowires (Ag NWs) based flexible and transparent electrodes (AgNWs/PDMS), innovative patterning techniques are essential for enabling large-area fabrication with cost-effective reusability features. Here, we introduce a metal assisted chemical etching (MACE) protocol for patterning Si wafers, allowing the repetitive fabrication of large-sized AgNWs/PDMS electrodes with controlled penetration depth for the first time. To the best of our knowledge, MACE technology has not previously been employed for fabricating AgNWs/PDMS electrodes. Through the careful selection of etchant, etching time, and suitably doped Si wafers (n-type and p-type), the resulting AgNWs/PDMS electrodes offer favorable optical, electrical and flexiblity characteristics. The electrodes deliver a sheet resistance of 18 Ω‧sq⁻¹ at 88 % transmittance (550 nm) while retaining 93.18 % transmittance with only a 7 Ω‧sq⁻¹ resistance increase after 10,000 bending cycles (3 mm). The penetration depth control offered by this method ensures impressive mechanical durability without additional post-processing. Moreover, the etched Si wafers can be reused multiple times, reducing overall costs. The sizes of AgNWs/PDMS electrodes produced using this method depend entirely on the Si wafer size, allowing scalability by employing larger wafers. As a proof-of-concept, we also demonstrate the fabrication of a robust, flexible, electrochromic zinc ion battery utilizing the AgNWs/PDMS electrodes developed in this study.

Long-term thermal exposure-induced γ′ coarsening strongly influences the mechanical properties of Ni-base superalloys and high/medium entropy alloys (H/MEAs), which has long been of scientific and industrial concern. In revealing the coarsening behavior, a great deal of theorical research has been made over several decades. One major advance is the development of Ostwald ripening kinetics theories, which allows for a quantitative description of γ′ coarsening kinetics. Nowadays, there have been two types of theorical models in wide acceptance, which advocate the matrix-diffusion controlled (LSW-family models) and trans-interface-diffusion controlled (TIDC model) kinetics mechanisms, respectively. Both of them have been validated in experiments and computational simulations. Besides, another major advance is the theorical revelation of the particle morphology evolution as γ′ coarsening, by means of energetic calculations and phase-field simulations. It has been shown that the morphological evolution depends on the combined effects of interfacial energy, elastic strain energy, and elastic interaction energy. The latter two generally play a dominate role in particle shape changes and regular spatial rearrangements, respectively. Based on these theories, the γ′ coarsening kinetics and morphological evolution patterns in Ni-base superalloys and H/MEAs has been clearly revealed and compared in many studies. Herein, we present a review on the development of these γ′ coarsening theories and their applications. This is not only instructive for alloy design and failure prevention, but also informative for further theorical extensions.

The mitochondrial energy metabolic reprogramming of tumors leads to the hypoxic, acidic, and immunosuppressive microenvironment. To regulate the reprogrammed mitochondrial energy metabolism and the abnormal tumor microenvironment (TME) intracellularly and extracellularly, herein, we purposely constructed the metabolic regulating and immunological activating nanocomposites (NCs) formed by the manganese dioxide (MnO₂) nanoparticles loaded with lactate oxidase (LOX), dichloroacetic acid (DCA) and SR-717, camouflaged by the cell membrane of tumors. After the NCs targeting to the tumors, the loaded DCA inhibited the glycolysis and triggered the produced pyruvate into mitochondria for further degradation. DCA also reduced the amount of CD39 and CD73, thereby promoting the accumulation of ATP intracellularly. The cascade of MnO₂ and LOX catalyzed the lactate to pyruvate together with oxygen for the relief of the hypoxic and immunosuppressive TME. The regulation of the mitochondrial metabolism together with the degradation of lactate contributed to activating the immune cells. Meanwhile, the loaded SR-717 together with the release of Mn²⁺ activated the cyclic guanosine monophosphate adenosine monophosphate synthase/interferon gene stimulator signaling pathway for efficient antitumor effects and immunotherapy. Taken together, the designed multifunctional nanocomposites realized an effective tumor immunotherapy by regulating the reprogrammed mitochondrial energy metabolism intracellularly, relieving the abnormal TME and activating the innate antitumor immunological effects extracellularly. Our work established an approach to the enhanced immunotherapy by regulating the reprogrammed metabolism for efficient cancer treatment.