Nanotechnology最新文献

Thin silver oxide Ag_xO_yfilm (p-type) was deposited via DC magnetron sputtering onto n-type silicon substrate and integrated into a pn heterojunction architecture. Structural (XRD, XPS and EDX), optical ultraviolet-visible-near infrared and morphological analysis (SEM) of the Ag_xO_yfilm were investigated in detail. Electrical measurements revealed that the Ag_xO_y/n-Si pn heterojunction as a self-driven photodetector device exhibits a high photoresponse both in visible light and in UV, IR and yellow lights. It was also observed that under visible light the photocurrent increased with increasing light intensity, higher at higher intensities. Furthermore, the photodetector exhibits high sensitivity to the incident light of 365 nm with responsivity as 1061 mA W^-1for -1.5 V. The highest specific detectivity value for the conditions illuminated by LED with wavelength of 590 nm is 9.77 × 10¹²cm·Hz^1/2·W^-1(Jones) for zero bias. Experimental results show that the Ag_xO_y/n-Si heterojunction has great potential for practical applications as self-driven and high-performance photodetectors.

The use of atomic layer deposition (ALD) and molecular layer deposition (MLD) in energy sectors such as catalysis, batteries, and membranes has emerged as a growing approach to fine-tune surface and interfacial properties at the nanoscale, thereby enhancing performance. However, compared to the microelectronics field where ALD is well established on conventional substrates such as silicon wafers, employing ALD and MLD in energy applications often requires depositing films on unconventional substrates such as nanoparticles, secondary particles, composite electrodes, membranes with a wide pore size distribution, and two-dimensional materials. This review examines the challenges and perspectives associated with implementing ALD and MLD on these unconventional substrates. We discuss how the complex surface chemistries and intricate morphologies of these substrates can lead to non-ideal growth behaviors, resulting in inconsistent film properties compared to those grown on standard wafers, even within the same deposition process. Additionally, the review outlines the strengths and limitations of several characterization techniques when employed for ALD or MLD films grown on unconventional substrates, and it highlights a few example studies in which these growth methods have been applied for energy applications with a focus on energy storage. With ALD and MLD continuing to gain attention, this review aims to deepen the understanding of how to achieve controllable, predictable, and scalable deposition with atomic-scale precision, ultimately advancing the development of more efficient and durable energy devices.

In this study, the core-shell nanostructure of magnesium reinforced cobalt silicate@13X was synthesized by a two-step reaction using zeolite 13X as the initial silicate material and carrier, and the organic pollutant metronidazole was degraded by activating PMS. It was found that 6CoMg-13X had excellent and stable catalytic performance on PMS activation, with a degradation rate of 99.7% in 5 min and a removal rate of more than 99.4% after 5 cycles. Under hydrothermal conditions, 13X gradually dissolved into silicate anion under the action of urea, while Co2+ and Mg2+ reacted on 13X surface to form ultra-thin core-shell nanostructures, the calcination process further improves the stability of the catalyst while reducing cobalt leaching, after calcination, cobalt leaching is only 0.16 mg/L. In addition, the catalyst had high degradation rates for norfloxacin (NFA), 5-fluorouracil (FLU), tetracycline (TC) and Rhodamine B (RhB), which were 90.29%, 97.36%, 96.24% and 99.69%, respectively. EPR and quenching experiments indicated that SO4•- and 1O2 are the main active substances in the 6CoMg-13X-PMS system, and •OH and •O2- also play a certain role in the degradation system. This research provides a feasible solution for developing high performance cobalt-based environmental purification catalysts.

Plasmonic semiconductors are arising as potential photocatalysts for the artificial synthesis of green ammonia. However, plasmon excitation-generated hot carriers on a single nanoparticle are easily recombined, leading to low photoconversion efficiency, and energetic defects make plasmonic semiconductors subject to unexpected changes, limiting post-engineering. Here, we developed a plasmonic semiconductor p-n junction by in situ growing p-type Cu3BiS3 in n-type Bi2S3 nanorods by an ion exchange method. The formation of plasmonic semiconductor heterojunctions was verified through high-resolution transmission electron microscopy, Mott-Schottky tests, valence band spectroscopy, and X-ray diffraction (XRD). Additionally, the rapid transfer of hot carriers between the heterojunctions was investigated using transient absorption spectroscopy. The plasmonic p-n junction shows strong localized surface plasmon resonance absorption in the near-infrared range and delivers a 61 times enhancement of the ammonia production rate under full spectrum irradiation in pure water. It can achieve an apparent quantum efficiency of 0.45% at 400 nm and 0.16% at 1000 nm. In situ Fourier-transform infrared (FTIR) reveal that the plasmonic semiconductor heterojunction promotes the nitrogen chemisorption and activation. Using ultrafast transient absorption spectroscopy, we found that localized surface plasmon resonance (LSPR) induced hot carriers can be efficiently injected from plasmonic Cu3BiS3 to non-plasmonic Bi2S3, with sufficient energy to drive water oxidation. We further confirmed that photothermal effects have little contribution to the photocatalytic performance in the water-particle suspension system. The present study shows a potential strategy utilizing plasmonic semiconductors made of earth-abundant elements for green ammonia synthesis. .

Zero-dimensional quantum dots (QDs) and their hybrid structures having been rapidly developed are reshaping the design and performance of next generation ultrafast electronic and optoelectronic devices. The high-performance metrics achievable in photodetectors, solar cells, transistors, and other application areas can be realized through the use of QDs with their tunable electronic and optical properties. Recent advances in the synthesis of QD hybrid structures, where QDs are incorporated within other nanostructure dimensions (1D nanowires, 2D materials), have dramatically increased charge carrier mobility, lowered recombination rates, and resulted in highly controlled interfacial properties. Synergistic effects between these hybrid configurations are exploited, including improved charge separation and enhanced exciton dissociation, which are very important for having ultrafast response times and greater sensitivity. Advanced fabrication techniques such as chemical vapor deposition and solution based self-assembly, QD hybrids can be fabricated with highly controlled interfaces and optimal energy band alignments. Further, computational simulations such as density functional theory (DFT) and time dependent DFT have provided further insights into the charge dynamics and electronic interactions in these hybrid systems for guidance on their design and application. The potential of QD-based hybrid architectures in addressing future information processing demands is demonstrated in this work, setting the stage for the development of high-speed, low-power devices in communications, sensing, and renewable energy technologies.

Metasurfaces (MSs), two-dimensional arrays of engineered nanostructures, have revolutionized optics by enabling precise manipulation of electromagnetic waves at subwavelength scales. These platforms offer unparalleled control over amplitude, phase, and polarization, unlocking advanced applications in imaging, communication, and sensing. Among them, plasmonic MSs stand out for their ability to exploit surface plasmon resonances (SPRs)-collective electron oscillations at metal-dielectric interfaces. This phenomenon enables extreme light confinement and field enhancement, leading to highly efficient light-matter interactions. The remarkable sensitivity of SPR to refractive index variations makes plasmonic MSs ideal for detecting minute biochemical and environmental changes with exceptional precision. Additionally, their tunable SPR characteristics enhance multifunctionality, enabling adaptive and real-time sensing. By leveraging these advantages, plasmonic MSs address critical challenges in modern sensing, driving breakthroughs in biomedical diagnostics, environmental monitoring, and chemical detection. This perspective explores recent advancements in plasmonic MSs, emphasizing flexible, multifunctional designs and the transformative role of artificial intelligence in optimizing performance and enabling real-time data analysis.

The optical response manipulation of two-dimensional materials is crucial for designing and optimizing high-performance optoelectronic devices. Previously, optical modulation in two-dimensional semiconductors primarily relied on adjusting carrier density through optical excitation or charge injection using the energy band-filling effect. Recently, twist angle has been found to tune the optical and optoelectronic properties of van der Waals structure, but its impact on the transient optical response remains unexplored. Herein, we demonstrate that twist angle can effectively regulate carrier behaviors by tracing the evolution of optical responses in twisted bilayer WS₂from 0° to 60°. Both Raman and PL spectra consistently show that the optical responses of WS₂bilayers are highly dependent on the twist angle. Exciton behavior and phonon modes exhibit similarity at twist angles near 0° and 60°, but significantly change as the angle approaches 30°. Moreover, the impact of the twist angle on the transient optical responses was carefully investigated using a femtosecond pump-probe technique. The results reveal a significant decrease in carrier thermalization/relaxation time and exciton formation/recombination time at the WS₂bilayers with twist angle of ∼31.0°, as compared to twist angles of ∼2.9° and ∼58.9°, which can be attributed to the accumulation of intralayer carriers due to weakened interlayer coupling. These results demonstrate that twist angle can effectively modulate the optical response of twisted 2D materials. Our study elucidates the dynamic carrier behavior in twisted bilayer WS₂and provides new insights for designing future optoelectronic and photonic devices.

Nanowires (NWs) of III-V semiconductors provide a promising platform for the development of electronic and photonic components of integrated circuits. For the development of complex NW-based devices, it is crucial to precisely study structural, electronic, and optical properties at the nanoscale. Scanning tunneling microscopy (STM) is commonly used to achieve such precision. In this work we optimize the tunneling contact parameters in an ultrahigh vacuum STM (at room temperature) for reproducible high-quality topographic imaging of conductive GaP NWs, especially promising for photonic integrated circuits. Two methods were employed for transferring NWs onto auxiliary conducting substrates: ultrasonication in liquid (deionized water or isopropyl alcohol) followed by drop casting and mechanical scratching. Five substrate materials were tested: highly oriented pyrolytic graphite, single crystal silicon wafers, thin films of nickel, indium tin oxide and gold. The experimental results showed that the tunneling contact parameters, substrate material, and transfer method significantly affect the quality of STM images. It was found that bias voltages of 7-10 V, tunneling current up to 400 pA, and image recording rates in the range of 500-1500 nm/s were optimal, with nickel-coated substrates providing the best stability and image quality. Potentially harmful procedures for NW and substrate surfaces, such as ion treatment and high-temperature annealing, were avoided during the sample preparation. The results expand the understanding of STM studies of NWs and their applications in electronic and photonic devices.

Gate-all-around (GAA) nanosheet field-effect transistors (FETs) have significantly advanced nanoscale device technology by mitigating short-channel effects. These GAA structures are becoming essential in sub-3nm technology and are evolving into complementary FETs. Despite the reduction in variability achieved by multi-gate structures, random discrete dopants (RDDs) in source and drain regions continue to pose challenges. This study addresses the local variability induced by RDDs, particularly in the source and drain extensions in GAA nanosheet FETs. Through statistical quantum transport simulations under a ballistic approximation, we investigate parameters such as spacer length, channel width, and channel thickness. The results show that RDDs in the source and drain extensions cause not only threshold voltage variation but also increase resistance and reduce ON-state current. GAA nanosheet FETs with a 3 nm×10 nm cross-sectional channel and 5 nm spacer length exhibit 10% reduction in ON-state current compared to the ideal device, along with a standard deviation (variability) of 0.35 µA. Mitigation of these effects requires the use of thin, wide, and large cross-section nanosheets and short spacer lengths.

Graphene Oxide (GO) is a two-dimensional (2D) nanomaterial largely exploited in many fields. Its preparation, usually performed from graphite in an oxidant environment, generally affords two-dimensional layers with a broad size distribution, with overoxidation easily occurring. Here, we investigate the formation, along the Hummers synthesis of GO, of carbon nanoparticles isolated from GO and characterized through morphological and spectroscopic techniques. The purification methodology here applied is based on dialysis and results highly advantageous, since it does not involve chemical processes, which may lead to modifications in the composition of GO layers. Using a cross-matched characterization approach among different techniques, such as XPS, cyclic voltammetry and fluorescence spectroscopy, we demonstrate that the isolated carbon nanoparticles are constituted by layers that are highly oxidized at the edges and are stacked due to π-π interaction among their aromatic basal planes and H-bonded via their oxidized groups. These results, while representing a step forward in the comprehension of the structure of long-debated carbon debris in GO, strongly point to the introduction of dialysis as an indispensable step toward the preparation of more controlled and homogeneous GO layers and to its use for the valorization of low molecular weight GO species as luminescent carbon nanoparticles. .