Nanotechnology最新文献

This paper demonstrates a significant advance in creating ultra-flat Si(100) surfaces suitable for low thermal budget device fabrication. This is achieved by a two-step pre-flash and protect (PFP) process that locks in an atomically flat surface that survives subsequent device processing steps. The first PFP step is a high-temperature flash in ultra-high vacuum (UHV) that creates an atomically flat surface. The second PFP step is a Piranha solution treatment that preserves the surface with a thin oxide shortly after removal from UHV. This oxide can then be easily removed with buffered oxide etchant (BOE) as needed during subsequent device fabrication. Following BOE, a surface with angstrom-level flatness is recovered, obviating the need for more aggressive thermal or chemical surface flattening processes. With this new process no aggressive chemical cleaning, such as RCA cleaning, is needed and no high-temperature surface cleaning or flattening is required for nanoscale device fabrication. This method offers promising opportunities for device fabrication and other applications that require clean and atomically flat Si(100) surfaces and low thermal budget device processing.

The efficiency of green hydrogen production via water splitting is typically hindered by the sluggish kinetics of the oxygen evolution reaction (OER). Here we investigate the performance of various nickel nanoclusters, deposited via a binder-free gas-phase method, as OER catalysts on two distinct porous platforms: commercial gas diffusion layers (GDL) for electrocatalysis and mesoporous TiO₂thin films for photoelectrocatalysis. For dark electrocatalysis on GDL, we find a non-linear relationship between catalyst loading and activity, where the lowest Ni loadings exhibited the highest specific activity. Trace iron impurities in the electrolyte dramatically enhanced the performance, leading to a 120-fold increase in specific current for the lowest loading samples through the in situ formation of highly active NiFe oxyhydroxide species. When integrated as co-catalysts on mesoporous TiO₂ photoanodes, Ni nanoclusters significantly improved photocurrents, with an optimal loading of 0.27-0.89 μg/cm². While Fe impurities also boosted photoelectrochemical performance at low Ni coverages, the effect was less pronounced and became detrimental at higher loadings. These findings underscore that the precise control of the catalyst loading and composition is decisive for designing scalable and highly efficient systems for water oxidation.

Ionic polymer metal composites (IPMCs) are widely used in flexible actuation and sensing. Traditional IPMCs employ the commercial Nafion film as the electrolyte films, suffering from low water uptake (WU), high modulus, and high cost. This study reports a water-resistant polyvinyl alcohol (PVA) electrolyte film with high WU and ion exchange capacity (IEC), using PVA as the matrix, sulfonic SiO2 nanocolloids as the fillers, and glutaraldehyde as the crosslinking agent. Physicochemical tests reveal that the PVA film containing 9 wt% sulfonic SiO2 nanocolloids exhibits better IPMC-related properties when compared to Nafion: 3.92 folds in WU, 1.14 folds in IEC, and 0.238 folds in elastic modulus. After spraying an electrode slurry containing poly(3,4-ethylenedioxythiophene) /poly(styrenesulfonate) dispersed multi-walled carbon nanotubes, the SiO2/PVA film IPMC actuator demonstrated exceptional electromechanical response. Under DC signal, it maintains a steady one-way deflection with a large swelling angle of 48.1 ° and no significant back relaxation. Under AC signals, it generates periodic deflections with outputted displacements up to 8.19 mm for 440 s; after water replenishment, the actuator remains a repeatable and reliable deflection without an evident displacement decay. The SiO2/PVA film IPMC actuator demonstrates outstanding stability and actuation performance, making it suitable for applications in bionic robotics and wearable electronics.

Quantum dots attract significant attention as one of the most promising colloidal nanocrystals with unique optical properties and potential applications for the next generation of display technology. In this paper, we evaluate the performance of CdZnSeS-based alloyed-shell quantum dots (QDs) for electroluminescence devices upon additional shell growth and ligand exchange. This includes core/shell (C/S) and core/shell/shell (C/S/S) QDs, whose latter includes an additional ZnS shell and octanethiol (OT) ligands. We present detailed characterizations of QDs using transmission electron microscopy, XRD, and various spectroscopic techniques and demonstrate their QD light emitting (QLEDs). We find the photoluminescence quantum yield of C/S/S QDs increased from 68.8% to 88.7% compared to C/S QDs whereas the emission linewidth narrows from 22.2 nm to 20.8 nm. QLEDs fabricated with C/S/S QDs exhibit a higher peak external quantum efficiency (EQE) of 4.1% and maximum luminance of 85 000 cd m^-2, compared to 2.3% EQE and 67 000 cd m^-2for C/S QLEDs. In this respect, the OT-assisted shell growth significantly improves the optical property of QDs and performance of QLEDs, likely attributed to the enhanced charge balance and increased radiative recombination rate.

We theoretically investigate the electronic transport properties of three-terminal ballistic junctions based on bilayer phosphorene nanoribbons, subjected to a uniform perpendicular electric field. We exploit the intrinsic anisotropy of phosphorene by considering different edge terminations for the nanoribbons that form such junctions, namely normal armchair, normal zigzag, skewed armchair, and skewed zigzag. Unlike bilayer graphene, the Bernal-stacked bilayer phosphorene, when subjected to an inversion symmetry breaking, such as the application of a perpendicular electric field, exhibits a semiconductor to metal transition, whereas in AB-stacked bilayer graphene, one observes a gap opening and a metal to semiconductor transition instead. Thus, by adopting this electric-field-controlled band gap strategy for bilayer phosphorene, we demonstrate the possibility of modulating the current flowing through bilayer-BP-based Y-junctions, redirecting it to one or both output terminals under specific conditions. The role played on the electron conductance and probability density currents by the different Y-junction constituents is also explored, and such results are interpreted in light of nanoribbons' dispersion relations. In this sense, the proposed system acts as a nanoscale switching device, and its current modulation effect can be used to develop phosphorene-based logic gates with a large on/off current ratio, benefiting from the material's high carrier mobility.

Increased emissions of volatile organic compounds (VOCs) are prone to cause health issues like cancer and central nervous system disorders, making the development of efficient VOCs-sensing materials crucial. Monolayer α-AsN, a 2D V-V binary material with a wrinkled honeycomb structure, features better environmental stability (higher cohesive energy than black phosphorus, BP) and tunable electrical properties (unlike single-target VOC-sensing TMDs). It overcomes flaws of existing 2D sensors (BP's poor stability, TMDs' narrow selectivity) while retaining high surface-to-volume ratio, and shows superior adsorption efficiency and selectivity for alcohol VOCs versus BP and acetone-specialized Janus TMDs. However, its VOCs-sensing performance remains uninvestigated. This study employed density functional theory (DFT) and nonequilibrium Green's function to systematically investigate the adsorption and sensing behaviors of monolayer α-AsN toward the five VOCs. Electronic localization function (ELF) analysis confirmed physical adsorption (no chemical bonding) between α-AsN and all VOCs. Among the tested VOCs, methanol and ethanol exhibited the highest adsorption energy and density (ethanol slightly higher), with ultra-low detection limits (7.69×10^-4p.p.b. for methanol and 4.88×10^-5p.p.b. for ethanol). Critically, methanol adsorption reduced α-AsN's current by 30%, while ethanol increased it by 100%. These findings demonstrate that monolayer α-AsN holds great application potential for the selective detection of methanol and ethanol.

ZnO, anintrinsic n-typesemiconductor, has attracted considerable attention in optoelectronics. However, its application in broadband photoresponsivity is limited by its wide band gap. In this study, polyol-synthesized silver nanoparticles (Ag NPs) with controlled size were used to enhance the performance of n-type ZnO nanorods (NRs) and p-type Si heterojunction (ZnO NRs/Si) photodetectors (PDs). Photoluminescence spectra confirmed that the broadband emissions of the ZnO NRs, originating from crystal defects, efficiently overlapped with the localized surface plasmon resonance of the Ag NPs. Under illumination and a reverse bias voltage of 4.0 V, the photocurrent (I_ph) of the detectors increased from 2.2 × 10^-5-2.39 × 10^-4after Ag NP decoration of the ZnO NRs. TheI_ph/I_darkratio of the pristine ZnO NRs/Si device was determined to be 5.5, which increased to 100 in the presence of the Ag NPs. The plasmonic-enhanced PD (Ag-decorated ZnO NRs/Si) exhibited broader and stronger spectral photoresponsivity from the UV-Vis to the NIR range. Responsivity and detectivity values of 0.39 A W^-1and 2 × 10^-11cm.Hz^1/2W^-1at 372 nm, and 0.42 A W^-1and 4.2 × 10^-11cm.Hz^1/2W^-1at 420 nm, were observed for this device. Overall, plasmon-enhanced ZnO NRs/Si PDs demonstrated enhanced broadband UV-Vis-NIR spectral response with high photocurrent values.

Herein, Co-MOF arrays were used as a precursor to fabricate hierarchical catalysts. Heterostructure Co-MOF/Co(OH)₂and Co(OH)₂micro-nano sheet arrays were fabricated by etching treatment in ultrapure water for different time. When treated for 60 min, infrared spectrum and x-ray diffraction (XRD) pattern indicate that there is the co-existence of Co-MOF and Co(OH)₂. After etching for 120 min, the scanning electron microscopy image reveals three-dimensional hierarchical micro-nano sheet arrays, the energy dispersive x-ray spectrum and XRD analysis indicate pure Co(OH)₂phase with high crystallinity. Their glucose sensing performance is systematically explored by cyclic voltammetric and amperometrici-tcurves. The linear ranges of Co-MOF/Co(OH)₂and Co(OH)₂micro-nano sheet arrays are 0.05-2.2 mM (R²= 0.999) and 0.05-5.8 mM (R²= 0.999), their corresponding sensitivities are 1040μA mM^-1cm^-2and 884μA mM^-1cm^-2, respectively. Good glucose sensing performance of Co(OH)₂micro-nano sheet arrays is attributed to its unique three-dimensional array structure which guarantees the sufficient diffusion of electrolyte and effective contact between glucose molecule and active sites. Further, the obtained hierarchical Co(OH)₂electrode possesses good selectivity, stability, repeatability and practical detection ability.

This study presents the development of a frequency-controlled drug delivery platform employing gold (Au)-melittin (Mel) conjugates loaded onto titanium dioxide nanocylinders (TiO_₂NCs) decorated with magnetic (M) nanoparticles (NPs). TiO_₂NCs were synthesized via a multi-step anodization and sonication process, providing a high surface-area scaffold for drug loading, while MNPs enabled magnetically-responsive behavior. AuNPs were functionalized with Mel, a potent antimicrobial and anticancer peptide, to enhance its stability and minimize cytotoxicity. The resulting Au-Mel-loaded MNP-TiO_₂NCs exhibited controlled drug release in response to alternating magnetic fields, with peak release occurring within 10 min under stimulation frequencies ranging from 10 Hz to 10 000 Hz. FTIR, TEM, EDX, and zeta potential analyses confirmed successful conjugation and integration of all components.In vitroantibacterial assays demonstrated effective inhibition ofE. coliby magnetically released Au-Mel, while cytotoxicity tests indicated selective activity against HepG2 liver cancer cells with minimal impact on HEK293 cells. This nanoplatform offers a promising solution for dual antibacterial and anticancer therapy with spatiotemporal control via external magnetic fields.

Tellurium (Te) has recently gained attention due to its unique one-dimensional helical chain crystal structure and promising optoelectronic and thermoelectric properties. In this study, we investigate the influence of substrate temperature (296 K-326 K) on the structural and electrical characteristics of ∼20 nm Te films deposited via vacuum thermal evaporation on Si/SiO_₂substrates. Morphological analysis using atomic force microscopy and high-resolution transmission electron microscopy revealed correlation between the substrate temperature and the changes in the structure from trapezoidal to elongated stick-like features. X-ray diffraction and Raman spectroscopy demonstrated that the Te chains were predominantly oriented parallel to the substrate surface atT_S= 326 K. The chain length and packing density were dependent onT_S. Spatially resolved current-voltage measurements show a strong temperature-dependent decrease of the in-plane charge transport, whereas higher-temperature films were characterized by an increased lateral resistance. Scanning Kelvin probe microscopy measurements further reveal surface potential differences of ∼0.6 V between samples. These results demonstrate that small variations in substrate temperature can significantly modulate nanoscale morphology and electrical transport, providing a route to engineer Te-based thin-film devices with tailored performance.