Nanomaterials最新文献

The rapid advancement of 3D packaging technology has emerged as a key solution to overcome the scaling-down limitation of advanced memory and logic devices. Redistribution layer (RDL) fabrication, a critical process in 3D packaging, requires the use of polyimide (PI) films with thicknesses in the micrometer range. However, these polyimide films present surface topography variations in the range of hundreds of nanometers, necessitating chemical-mechanical planarization (CMP) to achieve nanometer-level surface flatness. Polyimide films, composed of copolymers of pyromellitimide and diphenyl ether, possess strong covalent bonds such as C-C, C-O, C=O, and C-N, leading to inherently low polishing rates during CMP. To address this challenge, the introduction of Fe(NO₃)₃ into CMP slurries has been proposed as a polishing rate accelerator. During CMP, this Fe(NO₃)₃ deformed the surface of a polyimide film into strongly positively charged 1,2,4,5-benzenetetracarbonyliron and weakly negatively charged 4,4'-oxydianiline (ODA). The chemically dominant polishing rate enhanced with the concentration of the Fe(NO₃)₃ due to accelerated surface interactions. However, higher Fe(NO₃)₃ concentrations reduce the attractive electrostatic force between the positively charged wet ceria abrasives and the negatively charged deformed surface of the polyimide film, thereby decreasing the mechanically dominant polishing rate. A comprehensive investigation of the chemical and mechanical polishing rate dynamics revealed that the optimal Fe(NO₃)₃ concentration to achieve the maximum polyimide film removal rate was 0.05 wt%.

Surface-enhanced Raman scattering (SERS) technology has important applications in many fields, such as biomedicine, environmental monitoring, and food safety. Plasmonic nanocavities have the ability to superdiffract localized light and enhance light-matter interactions. As a key SERS active substrate, research on plasmonic nanocavities has made significant progress regarding the enhancement mechanism, the utilization of hotspots for the detection of specific molecular groups, and practical applications. However, challenges related to improving the enhancement factor of nanocavity SERS, enhancing the stability and reproducibility of hotspots, and enabling the detection of single-molecule layers remain. In this study, we adopt a bottom-up approach to construct a silver microplate-molecule-multi-sized silver nanosphere nanoparticle-on-mirror (NPoM) nanocavity and achieve the efficient stable enhancement of Raman scattering from 4-mercaptobenzoic acid and biphenyl-4,4'-dithiol molecules via the electromagnetic mechanism. By characterizing the fabricated nanocavity using dark-field scattering and micro-confocal Raman scattering, we observed that the Raman scattering intensity in the NPoM nanocavity was enhanced by a factor of 10³ compared to that of individual silver nanospheres. Furthermore, we achieved the efficient stabilization of SERS by precisely tuning the size of the silver nanospheres to match their resonance frequency with the Raman shift of the target molecules. This approach offers a valuable reference for the detection of various single-molecule layers and demonstrates significant potential for applications in biosensing and chemical analysis.

Fires at the wildland-urban interface (WUI) result in the release of ash into the atmosphere that can be transported for long distances and deposited on land and in oceans. Wildfire ash has the potential to increase phytoplankton biomass in the open ocean by providing both major nutrients and trace metals. However, fires that originate at the WUI contain potentially toxic concentrations of metals such as Ti, Cr, Cu, Pb, and Zn, especially in coastal oceans close to WUI fires, where ash deposition rates are high. Here, we investigated the impact of fire ash from different sources originating from vegetation, structures, and vehicles on growth of the diatom Thalassiosira weissflogii (T. weissflogii). The diatom was exposed to ash suspensions containing equimolar concentrations of 10 and 50 µM Fe. The concentration of potentially toxic metals (e.g., Ti, Cu, and Zn) in the exposure suspensions decreased following the order vehicle ash suspension > structural ash suspension > vegetation ash suspension. Growth rates (GR) of T. weissflogii were between 0.44 d^-1 and 0.52 d^-1 in the controls, and varied with ash types, following the order vegetation (GR = 0.40 d^-1 to 0.48 d^-1) > vehicle (GR = 0.06 d^-1 to 0.46 d^-1) > structure (GR = 0.02 d^-1 to 0.31 d^-1) ash. Two ash samples (A 131 and A136) completely inhibited the growth of T. weissflogii, possibly due to high Ti, Cu, and Zn concentrations in the form of (nano)particles. Overall, this study showed that structural and vehicle ash, with high concentrations of potentially toxic metals, significantly suppress the growth of T. weissflogii, whereas vegetation ash with high concentrations of Fe and Mn but low concentrations of potentially toxic metals had no significant beneficial or suppressive effect. High concentrations of the metals Ti, Cu, and Zn in the form of nano(particles) in structural and vehicle ash are possible sources of toxicity to diatom growth. This study provides valuable insights into the potential impacts of WUI fires on aquatic ecosystems and can inform management strategies aimed at reducing these impacts.

Graphene oxide (GO) significantly enhances cement hydration at the nanoscale; however, its tendency to complex and agglomerate with Ca²⁺ in cement paste remains an unresolved issue. To improve the dispersibility and enhance the reinforcing effect of GO in cement paste, polycarboxylate (PC) superplasticizer was used to disperse GO (PC@GO). This study uniquely divided PC into two parts, with one modifying GO and the other acting as a water-reducing agent, to explore the effects on GO dispersion and analyze the rheological, carbon emission, mechanical, and hydration properties of cement paste. The experimental results show that the dispersion of GO modified by PC was improved, resulting in a significant enhancement in the performance of the cement paste containing PC@GO. The flexural and compressive strength of cement paste containing PC@GO₄ cured for 7 days increased by 23.7% and 12.6%, respectively, meanwhile, the carbon-to-strength ratio (CI) decreased by 14.8%. In addition, the hydration acceleration period shortened by 7.50%, and the water absorption and porosity of the cement paste containing PC@GO₄ decreased by 35.2% and 45.3%, respectively. Incorporating PC@GO into cement paste significantly enhances the dispersion of GO, substantially improves its mechanical properties, and positions it as a promising solution for the development of high-performance cementitious materials.

This review paper explores the emerging field of conversion cathode materials, which hold significant promises for advancing the performance of lithium-ion (LIBs) and lithium-sulfur batteries (LSBs). Traditional cathode materials of LIBs, such as lithium cobalt oxide, have reached their limits in terms of energy density and capacity, driving the search for alternatives that can meet the increasing demands of modern technology, including electric vehicles and renewable energy systems. Conversion cathodes operate through a mechanism involving complete redox reactions, transforming into different phases, which enables the storage of more lithium ions and results in higher theoretical capacities compared to conventional intercalation materials. This study examines various conversion materials, including metal oxides, sulfides, and fluorides, highlighting their potential to significantly enhance energy density. Despite their advantages, conversion cathodes face numerous challenges, such as poor conductivity, significant volume changes during cycling, and issues with reversibility and stability. This review discusses current nanoengineering strategies employed to address these challenges, including nano structuring, composite formulation, and electrolyte optimization. By assessing recent research and developments in conversion cathode technology, this paper aims to provide a comprehensive overview of their potential to revolutionize lithium-ion batteries and contribute to the future of energy storage solutions.

With the ongoing development of electronic devices, there is an increasing demand for new semiconductors beyond traditional silicon. A key element in electronic circuits, complementary metal-oxide semiconductor (CMOS), utilizes both n-type and p-type semiconductors. While the advancements in n-type semiconductors have been substantial, the development of high-mobility p-type semiconductors has lagged behind. Recently, tellurium (Te) has been recognized as a promising candidate due to its superior electrical properties and the capability for large-area deposition via vacuum processes. In this work, an innovative approach involving the addition of a metal-capping layer onto Te thin-film transistors (TFTs) is proposed, which significantly enhances their electrical characteristics. In particular, the application of an indium (In) metal-capping layer has led to a dramatic increase in the field-effect mobility of Te TFTs from 2.68 to 33.54 cm²/Vs. This improvement is primarily due to the oxygen scavenger effect, which effectively minimizes oxidation and eliminates oxygen from the Te layer, resulting in the production of high-quality Te thin films. This progress in high-mobility p-type semiconductors is promising for the advancement of high-performance electronic devices in various applications and industries.

Interface-passivated graphene/silicon Schottky junction solar cells have demonstrated promising features with improved stability and power conversion efficiency (PCE). However, there are some misunderstandings in the literature regarding some of the working mechanisms and the impacts of the silicon/insulator interface. Specifically, attributing performance improvement to oxygen vacancies and characterizing performance using Schottky barrier height and ideality factor might not be the most accurate or appropriate. This work uses Al₂O₃ as an example to provide a detailed discussion on the interface ALD growth of Al₂O₃ on silicon and its impact on graphene electrode metal-insulator-semiconductor (MIS) solar cells. We further suggest that the current conduction in MIS solar cells with an insulating layer of 2 to 3 nm thickness is better described by direct tunneling, Poole-Frenkel emission, and Fowler-Nordheim tunneling, as the junction voltage sweeps from negative to a larger forward bias. The dielectric film thickness, its band offset with Si, and the interface roughness, are key factors to consider for process optimization.

In this work, we developed 3D ionic liquid (IL) functionalized graphene assemblies (GAs) decorated by ultrafine RuCu alloy nanoparticles (RuCu-ANPs) via a one-step synthesis process, and integrated it into a microfluidic sensor chip for in situ electrochemical detection of NO released from living cells. Our findings have demonstrated that RuCu-ANPs on 3D IL-GA exhibit high density, uniform distribution, lattice-shaped arrangement of atoms, and extremely ultrafine size, and possess high electrocatalytic activity to NO oxidation on the electrode. Meanwhile, the 3D IL-GA with hierarchical porous structures can facilitate the efficient electron/mass transfer at the electrode/electrolyte interface and the cell culture. Moreover, the graft of IL molecules on GA endows it with high hydrophilicity for facile and well-controllable printing on the electrode. Consequently, the resultant electrochemical microfluidic sensor demonstrated excellent sensing performances including fast response time, high sensitivity, good anti-interference ability, high reproducibility, long-term stability, as well as good biocompatibility, which can be used as an on-chip sensing system for cell culture and real-time in situ electrochemical detection of NO released from living cells with accurate and stable characteristics in physiological conditions.

To meet the application requirements for structural components in Gen-IV nuclear reactors, it is essential to improve the high-temperature mechanical properties of 25Ni-20Cr (S35140) austenitic stainless steel. In this research, an improved austenitic stainless steel (N-S35140), derived from S35140 steel, was investigated. The scanning transmission electron microscopy (STEM) results indicate that the addition of titanium (Ti) microalloying elements to S35140 steel led to the precipitation of new strengthening nano phases, including M(C, N), MC, MN and Ti(C, N), in N-S35140. These precipitates effectively compensated for the loss of high-temperature strength resulting from the substantial reduction in carbon content. During the in situ transmission electron microscopy (TEM) compressive process at room temperature, the yield strength of N-S35140 steel is 618.4 MPa. At room temperature, the tensile strength of N-S35140 steel is 638.5 MPa, with a yield strength of 392.8 MPa and an elongation of 32.7%, which surpasses those of S35140 steel at room temperature. N-S35140 steel exhibits a tensile strength of 330.6 MPa, a yield strength of 228.2 MPa, and an elongation of 51.4% during the in situ scanning electron microscopy (SEM) tensile test conducted at 650 °C. As a consequence, the improved N-S35140 steel demonstrates significantly enhanced mechanical properties compared to the original S35140 steel, positioning it as a promising candidate for structural components in Gen-IV nuclear reactors.

To develop an efficient drug delivery system, we co-entrapped superparamagnetic Fe₃O₄ and the chemotherapeutic drug doxorubicin (DOX) in oleoyl-chitosan (OC) to prepare DOX-entrapped magnetic OC (DOX-MOC) nanoparticles (NPs) through ionic gelation of OC with sodium tripolyphosphate (TPP). The NPs provide magnetically targeted delivery of DOX in cancer therapy. Using folic acid (FA)-grafted OC, FA-conjugated DOX-entrapped magnetic OC (FA-DOX-MOC) NPs were prepared similarly for FA-mediated active targeting of cancer cells with overexpressed folate receptors. Considering DOX loading and release, the best conditions for preparing DOX-MOC NPs were an OC:TPP mass ratio = 1:4 and OC concentration = 0.2%. These spherical NPs had a particle size of ~250 nm, 87.9% Fe₃O₄ content, 53.1 emu/g saturation magnetization, 83.1% drug encapsulation efficacy, and 2.81% drug loading efficiency. FA did not significantly change the physico-chemical characteristics of FA-DOX-MOC compared to DOX-MOC, and both NPs showed pH-dependent drug release behaviors, with much faster release of DOX at acidic pH values found in endosomes. However, FA could enhance the intracellular uptake of the NPs and DOX accumulation in the nucleus. This active targeting effect led to significantly higher cytotoxicity towards U87 cancer cells. These results suggest that FA-DOX-MOC NPs can efficiently deliver DOX for controlled drug release in cancer therapy.