Nanotechnology最新文献

With the rapid development of the Internet of Things, sustainable energy supply and wireless transmission of distributed wireless sensor nodes have become a challenge. In recent years, self-powered wireless sensing technologies (SWSTs) combining triboelectric nanogenerators (TENG) and wireless solutions have been proposed to address the issues of energy harvesting and wireless transmission. This review systematically summarizes the research advances in SWSTs based on TENG, and compares the advantages and disadvantages of different technologies. In addition, challenges and expectations for future TENG-based SWSTs are discussed as well.

In lithium-sulfur batteries (LSBs), the dissolution of lithium polysulfides (LiPSs) triggers the shuttle effect to lose active materials irreversibly, leading to the fast deterioration of electrochemical performance. Rational designs on the separator membrane could mitigate the shuttle effect. However, the development of efficient separators economically remains a challenging task, aggressively limiting the commercial use of LSBs. This work reports the engineering of commercial molybdenum diselenides (MoSe₂) flakes to mitigate the shuttle effect of LSBs, by forming rich Se vacancies via a potassium (K) intercalation and de-intercalation reaction. The Se vacancy in MoSe_xflakes significantly enhances the adsorption capacity of LiPSs and accelerates the Li⁺diffusion kinetics, thereby alleviating the shuttle effect and enhancing the energy storage performance. This directly improves the energy storage performance of the LSBs by incorporating the MoSe_xflakes into the separator membrane, giving a high capacity retention rate of 94.6% at 2 C after 500 cycles, with a reversible specific capacity as high as 452 mAh g^-1. This work offers a new strategy for the design and synthesis of vacancy rich transition metal chalcogenides for high-performance LSBs and beyond.

Anti-ambipolar transistors (AATs) are considered as a breakthrough technology in the field of electronics and optoelectronics, which is not only widely used in diverse logic circuits, but also crucial for the realization of high-performance photodetectors. The anti-ambipolar characteristics arising from the gate-tunable energy band structure can produce high-performance photodetection at different gate voltages. As a result, this places higher demands on the parametric driving range (ΔV_g) and peak-to-valley ratio (PVR) of the AAT. Here, we demonstrate a high-performance photodetector with anti-ambipolar properties based on a van der Waals heterojunction of MoTe₂/MoS₂. Flexible modulation of carrier concentration and transport by gate voltage achieves a driving voltage range ΔV_gas high as 38.4 V and a PVR of 1.6 × 10². Most importantly, MoTe₂/MoS₂exhibits a pronounced gate-tunable photoresponse, which is attributed to the modulation of photogenerated carrier transport by gate voltage. The MoTe₂/MoS₂heterojunction photodetector exhibits excellent performance, including an impressive responsivity of 17 A W^-1, a high detectivity of 4.2 × 10¹¹cm Hz^1/2W^-1, an elevated external quantum efficiency of 4 × 10³%, and a fast response time of 21 ms. Gate-tunable photodetectors based on MoTe₂/MoS₂heterostructures AAT have potential to realize optoelectronic devices with high performance, providing a novel strategy to achieve high-performance photodetection.

Over the past few decades, significant efforts have been dedicated to advancing technologies for the removal of micropollutants from water. Achieving complete pure water with a single treatment process is challenging and nearly impossible. One promising approach among various alternatives is adopting hybrid technology, which is considered as a win-win technology. It utilizes the advantages of each technique, resulting in the enhancement of wastewater treatment. This pioneering idea is designed to significantly enhance water quality, addressing real-world implementation hurdles, and offer a promising solution to the worldwide issue of water scarcity. This review assesses the merits and drawbacks of the hybrid photocatalytic membrane technology employed in wastewater treatment. Notably, this hybrid process not only improves the membrane filtration capacity and permeates water quality but also enhances the antifouling performance of the membrane. However, it is crucial to acknowledge potential drawbacks, such as membrane structure degradation and photocatalytic activity loss in nanoparticles during the operation period. While improvements in wastewater treatment efficiency are evident, there remains ample room for further enhancements. The review summarizes the future directions and challenges of implementing such an integrated system.

This study investigates simple acetylenes substituted with phenylurea as a constant H-bonding unit (Alk-R) and varied hydrophobic units (R = H, Phenyl (Ph), phenylacetylene (PA), Ph-NMe₂) to understand self-assembly properties driven by synergistic non-covalent interactions. Our observations reveal hierarchical self-assembled fibrillar networks with luminescent needles, fibers, and flowers on nano- to micro-meter scales. Subtle changes in substituents led to significant differences: H, Ph, PA, and Ph-NMe₂produced needle-like crystals, dendritic nanofibers, microflakes, and no self-assembly, respectively.Alk-Ph-NMe₂likely did not self-assemble due to reduced hydrophobic interactions and steric hindrance. Interestingly,Alk-Phexhibited a uniform spherulitic pattern and effectively gelled organic solvents and water. This luminescent gel demonstrated multifunctionality, including white light emission when doped with rhodamine-B dye and adsorption of organic cationic dyes (methylene blue and crystal violet) from water. This study offers valuable insights into balancing interactions to achieve desired hierarchical networks and understand material properties, guiding future molecular design.

Color centers are promising single-photon emitters owing to their operation at room temperature and high photostability. In particular, using nanodiamonds as a host material is of interest for sensing and metrology. Furthermore, being a solid-state system allows for incorporation to photonic systems to tune both the emission intensity and photoluminescence (PL) spectrum and therefore adapt the individual color center to desired properties. We show successful coupling of a single nanodiamond hosting silicon-vacancy color centers to a plasmonic double bowtie antenna structure. To predict the spectrum of the coupled system, the PL spectrum of the silicon vacancy centers was measured before the coupling process and convoluted with the antenna resonance spectrum. After transferring the nanodiamond to the antenna the combined spectrum was measured again. The measurement agrees well with the calculated prediction of the coupled system and therefore confirms successful coupling.

The graphitic carbon nitride (g-C₃N₄) is an important optoelectronic and photocatalytic material; however, its application is limited by the high recombination rate of the electron-hole (e^--h⁺) pairs. In this work, we reported a novel strategy combining two-step annealing treatment and ionic-liquid (IL) gating technology for effectively regulating the properties of g-C₃N₄, especially largely reducing the recombination rate of the e^--h⁺pairs, which is evidenced by a remarkable reduction of the photoluminescence (PL) intensity. Firstly, g-C₃N₄samples with typical layered structure were obtained by annealing melamine with temperature of 600 °C. Further annealing of the samples at 600 °C with much longer time (from 4 h to 12 h) were found to effectively reduce the imperfections or defects, and thus the PL intensity (49% reduction). This large reduction of PL intensity is attributed to the improved interconnection of triazine units, the shortened charge transfer diffusion distances, and the reduced interlayer spacing, which facilitate electron relocation on the g-C₃N₄surface. Secondly, by post-treating the annealed sample with IL, the PL intensities were found to be further reduced, mainly due to the passivation of charged defect centers by IL. Additionally, applying an external electric field in an IL environment can significantly enhance the charged defect passivation. Overall, by utilizing electric field-controlled IL gating, defect states in g-C₃N₄were passivated, leading to a significant reduction in PL intensity and an extension of PL lifetime, thereby effectively decreasing the e^--h⁺recombination rate in the material. This study demonstrates a new approach for defect passivation, providing insights and strategies for modulating properties of advanced materials such as g-C₃N₄.

HfO₂-based ferroelectric (FE) thin films have gained considerable interest for memory applications due to their excellent properties. However, HfO₂-based FE films face significant reliability challenges, especially the wake-up and fatigue effects, which hinder their practical application. In this work, we fabricated 13.5 nm-thick Al-doped Hf_0.5Zr_0.5O₂(HZO) films with both uniform (UD) and optimized (OD) Al distributions, systematically investigating the effects of Al doping distribution on their FE and endurance performances. After optimizing the Al distribution, the OD samples exhibit significantly enhanced ferroelectricity, with a robust remnant polarization (2P_r) of 53.7μC cm^-2. Besides, compared to the undoped and UD HZO films, the OD samples exhibit enhanced dielectric performance, with lower leakage currents and higher breakdown voltages, suggesting that the optimized distribution suppresses oxygen vacancy generation and mitigates defect formation. Furthermore, the OD samples maintain a large 2P_rof 40.4μC cm^-2after 10^8,which can be rejuvenated back to 50.7μC cm^-2by higher voltage cycling. The enhanced dielectric performances and reversible phase transitions during cycling underline the potential of Al-doped HZO films with optimized distribution as reliable, long-endurance FE materials, advancing the development of HfO₂-based FE devices for future memory applications.

The current work focuses on the synthesis and control of cubic vs monoclinic phase structures of Sm₂O₃via., cost-effective solution-based sol-gel technique. The structural analysis of the as-synthesized Sm₂O₃powder reveals the phase-change from initial mixture of cubic and monoclinic phases (82:18) to almost cubic phase (96:4), with increase of polyethylene glycol 600 additive from 2% to 25% respectively. The dark-current of the films made from as-synthesized Sm₂O₃powder revealed no measurable current, indicates its high defect tolerance against growth conditions. The multi-walled carbon nanotubes (MWCNT) are added as conducting scaffold into Sm₂O₃insulating matrix, to facilitate carrier transport for light-generated carriers, upon UV exposure. The dark-current of the photodetectors increased from nano-ampere to milli-ampere range with increase in MWCNT weight concentration from 1% to 10% respectively. A nominal photo-to-dark current ratio (PDCR) of around 2 is observed for different MWCNT concentrations in Sm₂O₃on glass substrates, upon UV light exposure. The PDCR is further increased to a maximum of 5.6 with the increase in grain-structure of Sm₂O₃within the nanocomposite via., substrate-engineering. The observed PDCR of 5.6 is the first reported value (to the best of our knowledge) for Sm₂O₃-based nanocomposite material towards deep-UV photodetector applications. The experimental results suggest incorporation of conductive nanocomposites into ultra-wide bandgap oxide semiconductor materials seems to be a feasible and promising approach for the design of future cost-effective deep-UV photodetectors.

The accurate estimation of the temperature distribution of the GaN based power devices and optimization of the device structure is of great significance to possibly solve the self-heating problem, which hinders the further enhancement of the device performances. We present here the operando temperature measurement with high spatial resolution using Raman spectroscopy of AlGaN/GaN high electron mobility transistors (HEMTs) with different device structures and explore the optimization of the device thermal design accordingly. The lateral and depth temperature distributions of the single-finger HEMT were characterized. The channel temperature and self-heating effect of the device under different bias voltages were investigated. By incorporating the two-dimensional electrothermal simulation, the hotspot position can be clearly observed under the gate edge near the drain side. The channel temperature of the multi-finger HEMT was further measured and the experiment results were in agreement with the three-dimensional finite element analysis simulation results. The device structure of the multi-finger device, including the gate width, gate pitch, structure layout, substrate materials, and thickness, were then theoretically optimized to improve the heat dissipation. The peak channel temperature of the device can be reduced by 70 °C when the substrate is substituted from silicon carbide to a single crystalline diamond. These results are of great interest for the thermal management of GaN HEMT power devices and further device performance improvement.