Nanotechnology最新文献

There has been a lot of study and advancement in the area of carbon allotropes in the last several decades, driven by the exceptional and diverse physical and chemical characteristics of carbon nanomaterials. For example, nanostructured forms such as carbon nanotubes, graphene, and carbon quantum dots have the potential to revolutionize various industries [1-3]. The global scientific community continues to research in the field of creating new materials, particularly low-dimensional carbon allotropes such as carbon nanotubes (CNTs) and carbyne. Carbyne is a one-dimensional carbon allotrope with a large surface area, chemical reactivity, and gas molecule adsorption potential that makes it extremely sensitive to gases and electronic nose (E-nose) applications due to its linear sp-hybridized atomic chain structure. The primary objective of this work is to increase the sensitivity, selectivity, and overall efficiency of E-nose systems using a synergistic combination of carbyne-based sensing components with cutting-edge machine learning techniques. The exceptional electronic properties of carbyne, such as its high electron mobility and adjustable bandgap, enable rapid and specific adsorption of various gas molecules. Additionally, its significant surface area-to-volume ratio enhances the detection of trace concentrations. Our suggested advanced hybrid system utilises support vector machines (SVMs) and convolutional neural networks (CNNs) as sophisticated machine learning approaches to analyse data provided by carbyne sensors. These algorithms enhance the precision and durability of gas detection by effectively recognising intricate patterns and correlations in the sensor data. Empirical evidence suggests that E-nose systems based on carbyne have superior performance in terms of reaction time, sensitivity, and specificity compared to conventional materials. This research emphasises the revolutionary potential of carbyne in the advancement of next-generation gas sensing systems, which has significant implications for applications in environmental monitoring, medical diagnostics, and industrial process control. .

This paper presents the synthesis of mixed metal oxide (BaTiO3: ZnO) (B: Z) sensors with various molar ratios using a low- temperature hydrothermal method for dual sensing applications (gas and acceleration). The sensor developed with an equal molar ratio of 1B:1Z, showcases superior performance compared to unmixed and alternative mixed metal oxide sensors. This equilibrium in ratios optimally enhances synergistic effects between elements B and Z, resulting in improved sensing properties. Furthermore, it contributes to structural stability, enhancing performance in gas and acceleration sensing. A decreased band gap of 2.82eV and a rapid turn-on voltage of 0.18V were achieved. The acceleration performance of 1B:1Z sensor exhibits a maximum voltage of 2.62 V at a 10 Hz resonant frequency and an output voltage of 2.52 V at 1 g acceleration, achieving an improved sensitivity of 3.889 V/g. In addition, the proposed gas shows a notable sensor response of ~63.45% (CO) and 58.29% (CH4) at 10 ppm with a quick response time of 1.19s (CO) and 8.69s (CH4) and recovery time of 2.09s (CO) and 8.69s (CH4). Challenges in selectivity are addressed using machine learning, employing various classification algorithms. Linear Discriminant Analysis (LDA) achieves superior accuracy in differentiating between CO and CH4, reaching 96.6 % for CO and 74.6 % for CH4 at 10 ppm. Understanding these concentration-dependent trends can guide the optimal use of the sensors in different current applications. .

This study investigates the fluence-dependent evolution of gold nanoparticles formed through single nanosecond pulsed laser dewetting of a gold thin film on a fused silica substrate. By employing a well-defined Airy-like laser spatial profile and reconstructing SEM images across the irradiation spot into a panoramic view, we achieve a detailed continuous analysis of the nanoparticle formation process. Our morphological analysis, combined with finite element thermal simulations directly correlated with the applied fluence, identifies two distinct thresholds. The first threshold corresponds to the dewetting of the gold film at its melting point, resulting in large, sparse nanoparticles. The second threshold, where the substrate temperature reaches values near its melting point, leads to the formation of numerous small nanoparticles and a significant increase in coverage area. Notably, the formation of these small nanoparticles is attributed to substrate heating, which alters the interaction between the molten gold film and the substrate, increasing adhesion. Contact angle measurements of the nanoparticles confirm this change, revealing a shift in wettability, and highlighting the crucial role of substrate heating in modulating the interactions leading to nanoparticle formation. Our findings underscore the intricate interplay between laser fluence, material properties, and substrate interactions in pulsed laser dewetting, with the well-defined laser profile offering valuable insights into these dynamics.

Ternary two-dimensional (2D) material-based memristors have garnered significant attention in the fields of machine learning, neuromorphic computing due to their low power consumption, rapid learning, and synaptic-like behavior. Although such memristors often exhibit high ON/OFF ratios and exceptional pulse response characteristics, they have also to face some challenges concerning reusability and switching cycles, which arise from the filament instability issues. Here we propose a modulation strategy to improve performance of 2D-material memristors with synaptic and flexible features. By laser-modulating few-layer FePS₃, we induced the formation of conductive filaments, realized a major improvement in performance of the FePS₃memristors, achieving an ON/OFF ratio of nearly 10⁴, low power consumption at approximately 10^-7W of single switching operation, and maintaining stability even after over 500 cycles. The performance promotion has been ascribed to enhancement of conductive filament induced by laser-modulation. Furthermore, we have identified the effectiveness of our laser modulation under strain by building the high-performance flexible FePS₃memristor. Meanwhile, we discovered a novel strain-dominant erasure method for the flexible memristors. Our work confirms that laser modulation is a viable method for enhancing the performance of 2D material-based memristive devices.

Two-dimensional (2D) materials with unique physical, electronic, and optical properties have been intensively studied to be utilized for the next-generation electronic and optical devices, and the use of laser energy in the synthesis and modification of 2D materials is advantageous due to its convenient and fast fabrication processes as well as selective, controllable, and cost-effective characteristics allowing the precise control in materials properties. This paper summarizes the recent progress in utilizations of laser technology in synthesizing, doping, etching, transfer and strain engineering of 2D materials, which is expected to provide an insight for the future applications across diverse research areas.

The GaAs based diluted magnetic semiconductor, (Ga, Mn)As, with the unique advantage of manipulating the spin and charge was widely investigated in the scientific community and considered as a potential material for the spintronic devices. However, its Curie temperature (T_c), which is limited to around 200 K, hinders the research progress of diluted magnetic semiconductors for potential device applications. Herein, we propose an approach to prepare the MnGa nanoparticles embedded in (Ga, Mn)As matrix using the magnetron sputtering deposition of Mn on GaAs surface, followed by the nano-second pulsed laser annealing (PLA), which gives aT_cabove 400 K. We demonstrate that the MnGa nanoparticles are only formed in (Ga, Mn) As thin film during the nano-second PLA under a critical range of energy density (0.4-0.5 J cm^-2). The highest achieved coercivity, saturation magnetization and remanent magnetization are 760 Oe, 11.3 emu cm^-3and 9.6 emu cm^-3, respectively. This method for preparing the hybrid system of ferromagnetic metal/dilute magnetic semiconductor builds a platform for exploring the interesting spin transport phenomenon and is promising for the application of spintronic devices.

Evaporation power generators (EPGs) based on natural water evaporation can directly convert heat energy from the surrounding environment into electrical energy. Nevertheless, the commercialization of EPGs faces challenges due to the low charge generation and transport efficiency of single material systems, leading to unsatisfactory open-circuit voltages and short-circuit currents. Here, we systematically prepared molybdenum sulfide (MoS₂)/porous carbon nanofiber (PCNF) heterogeneous systems by electrospinning and hydrothermal methods. Electron microscope measurements have confirmed the uniform coating of high-crystalline quality MoS₂nanosheets on PCNF fabrics, and the uneven concave-convex surface increased the specific surface area. MoS₂covered PCNF fabrics retained excellent hydrophilicity, which was suitable for absorbing water and keeping the surface wet during long-term evaporation. Moreover, layered MoS₂with rich surface charge improved the charge transfer of the MoS₂/PCNF fabrics. As a result, the open-circuit voltage and short-circuit current of the EPGs fabricated with MoS₂/PCNF fabrics were enhanced to 0.25 V and 75μA, respectively, in comparison to those based on PCNF fabrics, which demonstrated that the MoS₂coatings improved the interaction area with water and the charge transfer effect of the EPGs. This heterogeneous combination strategy provides ideas for the preparation of high-performance EPG materials.

Two-dimensional (2D) materials, particularly transition metal dichalcogenides (TMDs), have gathered significant attention due to their interesting electrical and optical properties. Among TMDs, monolayers of WSe₂exhibit a direct band gap and high exciton binding energy, which enhances photon emission and absorption even at room temperature. This study investigates the electronic and optical properties of WSe₂monolayers when they are mechanically transferred to indium tin oxide (ITO) substrates. ITO is a transparent conducting electrode (TCE) used in many industrial optoelectronic applications. Samples were mechanically transferred under ambient conditions, consequently trapping an adsorbate layer of atmospheric molecules unintentionally between the monolayer and the substrate. To reduce the amount of adsorbates, some samples were thermally annealed. Atomic force microscopy confirmed the presence of the adsorbate layer under the TMD and its partial removal after annealing. X-ray photoelectron spectroscopy confirmed the presence of carbon species among the adsorbates even after annealing. Photoluminescence measurements show that WSe₂remains optically active on ITO even after annealing. Moreover, the luminescence intensity and energy are affected by the amount of adsorbates under the WSe₂monolayer. Scanning tunnelling spectroscopy reveals that the TMD monolayer is n-doped, and that its band edges form a type I band alignment with ITO. Surface potential measurements show a polarity change after annealing, indicating that polar molecules, most likely water, are being removed. This comprehensive study shows that a TCE does not quench WSe₂luminescence even after a prolonged thermal annealing, although its optical and electronic properties are affected by unintentional adsorbates. These findings provide insights for better understanding, controlling, and design of 2D material heterostructures on TCEs.

We have studied repositioning of carvedilol (an antihypertensive drug) incorporated into MCM-41 mesoporous silica. The repositioning proposes a reduction in the slow pace of discovery of new drugs, as well as toxicological safety and a significant reduction in high research costs, making it an attractive strategy for researchers and large pharmaceutical companies. We obtained MCM-41 bytemplatesynthesis and functionalized it by post-synthesis grafting with aminopropyltriethoxysilane (APTES) only or with folic acid (FA), which gave MCM-41-APTES and MCM-41-APTES-FA, respectively. We characterized the materials by scanning and transmission electron microscopy, zeta potential (ZP) measurements, Fourier transform infrared absorption spectroscopy, x-ray diffractometry, nitrogen gas adsorption, and CHNS elemental analysis. We quantified the percentage of drug that was incorporated into the MCM-41 materials by thermogravimetric analysis and evaluated their cytotoxic activity in non-tumor human lung fibroblasts and the tumor human melanoma and human cervical adenocarcinoma cell lines by XTT salt reduction (2,3-bis-(2-methoxy-4-nitro-5-sulfophenyl)-2H-tetrazolium-5-arboxanilide). The x-ray diffractograms of the MCM-41 materials displayed low-angle peaks in the 2θrange between 2° and 3°, and the materials presented type IV nitrogen adsorption isotherms and H2 hysteresis typical of the MCM-41hexagonal network. The infrared spectra, the charge changes revealed by ZP measurements, and the CHN ratios obtained from elemental analysis showed that MCM-41 was amino-functionalized, and that carvedilol was incorporated into it. MCM-41-APTES incorporated 23.80% carvedilol, whereas MCM-41 and MCM-41-APTES-FA incorporated 18.69% and 12.71% carvedilol, respectively. Incorporated carvedilol was less cytotoxic to tumor and non-tumor cells than the pure drug. Carvedilol repositioning proved favorable and encourages further studies aimed at reducing its cytotoxicity to non-tumor cells. Such studies may allow for larger carvedilol incorporation into drug carriers or motivate the search for a new drug nanocarrier to optimize the carvedilol antitumoral activity.

Molybdenum dioxide (MoO₂) is regarded as a potential anode for lithium-ion batteries due to its highly theoretical specific capacity. However, its further application in lithium-ion battery is largely limited by insufficient practical discharge capacity and cyclic performance. Here, MoO₂nanoparticles are in-situ grown on three-dimensional nitrogen doped carbon nanotubes (NCNTs) on nickel foam substrate homogeneously using a simple electro-deposition method. The unique structural features are favorable for lithium ions insertion and extraction and charge transfer dynamics at electrode/electrolyte interface. As a proof of concept, the as-synthesized nanocomposites have been employed as anode for lithium-ion battery, exhibiting a reversible and significantly improved discharge capacity of ∼517 mA h g^-1at the current density of 150 mA g^-1as well as superior cycle and rate performance. The first-principle calculations based on density functional theory and electrochemical impedance spectroscopy results demonstrate a reduced energy barrier of lithium ions diffusion, improved lithium storage behavior, reduced structure collapse, and significantly enhanced charge transfer kinetics in MoO₂/NCNTs nanocomposites with respect to MoO₂powder. The excellent performance makes as-prepared MoO₂/NCNTs nanocomposites promising binder-free anode for high performance lithium-ion batteries. This work also provides important theoretical insights for other state-of-the-art batteries design.