ACS Applied Nano Materials最新文献

We report the fabrication of an ultrathin, lossless, all-dielectric ferromagnetic film via the sequential deposition of TiO₂/Y₂O₃/MnO/ZnO (TYMZO) monolayers on silicon (100) substrates by using atomic layer deposition (ALD). The TYMZO films, with controlled thicknesses of 30, 60, and 100 nm, exhibit tunable optical and structural properties. Their composition and structural integrity were confirmed using spectroscopic ellipsometry, UV–vis spectrophotometry, X-ray photoelectron spectroscopy (XPS), and transmission electron microscopy (TEM). The extinction coefficient of TYMZO approached zero across the optical spectrum, attributed to the lossless optical properties of its constituent materials. Cross-sectional TEM analysis revealed amorphous phases in films deposited at a substrate temperature of 250 °C, with a well-defined film–substrate interface. The amorphous nature of the TYMZO film, coupled with atomic migration of Ti and Mn, facilitated the formation of ZnO, TiO, and Y₂O₃ clusters as well as the potential formation of Mn-ZnO and Ti-ZnO compounds, which are known for their anisotropic magnetic properties. Magnetic measurements confirmed anisotropic ferromagnetic behavior, likely resulting from Mn-ZnO and Ti-ZnO clusters with nonparallel easy axes. The TYMZO films on silicon exhibited exceptional absorption efficiency across a tunable range of wavelengths. This enhanced absorption is attributed to the localization of optical fields within the lossless TYMZO layer due to Fabry–Perot resonances, which are subsequently absorbed by the lossy silicon substrate. These findings demonstrate the potential of TYMZO films for advanced photonic and magnetic applications, combining lossless optical properties with tunable ferromagnetic behavior.

Ion-intercalated MoS₂ can enhance its electrochemical activity, electrical conductivity, and stability, which can be combined with other materials to meet specific application requirements, such as the fields of electrochemistry and microwave absorption. This study explored the modulation of electromagnetic characteristics of ion-intercalated MoS₂-based ternary FeCoNi alloy nanocomposites, in which MoS₂ provides more contact sites for an electromagnetic wave, and the heterogeneous interfaces formed by the heterogeneous structure can improve the stronger interface polarization to enhance the dielectric loss. In addition, by inserting nano-FeCoNi alloy particles into the interlayers of MoS₂, the FeCoNi alloy also enhanced the magnetic loss capabilities, in which the impedance matching of FeCoNi/MoS₂ composites was also regulated. The results show that the FeCoNi/MoS₂ composite achieved a minimum RL (RL_min) value of −54.73 dB at 4.20 GHz with a matching thickness of 3.29 mm, and the effective absorption bandwidth (EAB) was 4.72 GHz at a thickness of 1.32 mm. In addition, the radar cross section (RCS) and COMSOL simulation results verify the possibility of application. The study revealed the microwave loss mechanisms of the FeCoNi/MoS₂ heterostructured composites, providing insights for designing novel low-frequency absorbing materials.

The limited sensitivity of indium oxide (In₂O₃) gas-sensing materials for detection of hydrogen sulfide (H₂S) restricts their application in identifying meat spoilage. In this study, two-dimensional indium oxide nanosheets (In₂O₃-NS) with intrinsic defects were synthesized using an “egg-box” structure, which was formed by the interaction between sodium alginate and metal cations, combined with an ice-templating method and annealing process. The resulting In₂O₃-NS sensor demonstrated a response of 950 to 5 ppm of H₂S at its optimal operating temperature of 175 °C, with a detection limit as low as 100 ppb. Structural characterization and density functional theory calculations revealed that intrinsic defects in the In₂O₃-NS structure optimize the electron density distribution, providing additional adsorption sites for H₂S and significantly enhancing gas sensitivity. Furthermore, a system utilizing In₂O₃-NS sensors was developed to evaluate meat freshness by detecting H₂S emissions.

The intrinsic driving force of semiconductor-based photocatalysts for separation and transfer of photoexcited charge carriers is still insufficient kinetically. The establishment and enhancement of an internal electric field within single particles are effective approaches to accelerate carrier migration with the introduction of symmetric breaking. In our work, a facet-selective doping strategy is proposed as the synergetic combination of the asymmetric facet effect and doping effect on truncated {100} and {110} SrTiO₃ single nanoparticles as the model, which is realized via facet-selective photodeposition and facet-domain doping methods. For {100} facets, Rh doping with aliovalent Rh³⁺ substituted for Ti⁴⁺ after Rh valence regulation leads to p-type transformation compared to pristine n-type {110} facets without doping, resulting in the opposite shift of the surface band bending direction within the space charge region. Due to facet-selective p-type transformation, surface electric fields contributed by anisotropic band bendings are aligned between the doped p-type {100} facet with downward bending and the undoped n-type {110} facet with upward bending. Therefore, the directional migration of electrons to {100} facets is boosted by the intensified facet-oriented electric field and the photocatalytic performance is improved (2-fold) for hydrogen evolution with ∼1.75% AQY at 400 nm consequently.

The two-dimensional/zero-dimensional (2D/0D) hybrid heterojunctions, based on transition-metal dichalcogenides (TMDCs), have attracted increasing attention in broadband photodetectors. As efficient light absorbers, the ultraviolet/near-infrared (UV/NIR)-absorbing quantum dots (QDs) can inject photocarriers into TMDCs, thereby extending the detection range of the photodetector. However, the QDs intended to broaden the spectral detection range do not effectively enhance the visible-light detection capabilities of TMDCs, resulting in a remaining deficient performance in the broadband photodetectors. Herein, we used activated ZnO QDs rich in surface oxygen vacancy defects to construct a high-performance broadband photodetector. By introducing surface oxygen vacancy defects as “self-doping” to adjust the band levels of ZnO, we achieved the heterojunction interface with efficient carrier separation. The photodetector exhibited a high responsivity of 1055.5 A/W and a high detectivity of 1.98 × 10¹¹ Jones. In particular, the photodetector demonstrated an ultrafast response time of 50 ns, surpassing that of most other 2D/0D hybrid photodetectors based on TMDCs. The innovative device design can provide an avenue for promoting the evolution of high-performance broadband devices based on 2D/0D hybrid heterojunctions.

Sulfur quantum dots (SQDs) hold immense promise for a wide range of applications due to their unique properties. However, the large-scale production of high-performance SQDs from readily available elemental sulfur remains a significant challenge. Herein, we report a simple yet effective approach to synthesizing highly fluorescent guanidyl SQDs (G-SQDs) with abundant guanidine groups on their surface. By employing a one-pot solvothermal process on an elemental sulfur-ethylenediamine mixture, using arginine as a stabilizer, we achieved a remarkable 12.7% conversion rate from elemental sulfur to G-SQDs. The resulting G-SQDs exhibit small and uniform size, excellent aqueous dispersibility, a high photoluminescence quantum yield of 60.2%, and low cytotoxicity. The presence of guanidine groups significantly enhances their antibacterial and antioxidant activities, making G-SQDs highly effective against both Gram-positive (e.g., S. aureus) and Gram-negative bacteria (e.g., E. coli). Moreover, their ABTS radicals scavenging efficiency is superior to that of other SQDs. These exceptional properties render G-SQDs highly suitable for applications in cell imaging, antibacterial treatments, and food preservation, as demonstrated in this study. Given their simple synthesis and superior performance, this work not only provides a cost-effective route for the production of high-performance SQDs but also promotes the efficient utilization of elemental sulfur resources.

The nanofluidic chip holds immense potential for applications in disease diagnosis, bioanalysis, and environmental detection due to its advantageous nanoscale size. The key component enabling the performance of a nanofluidic chip is the nanochannel. In this study, we fabricated controllable and consistent arrays of nanochannels, termed nanoripple structures, using an atomic force microscopy (AFM) probe reciprocal scanning approach. Furthermore, we successfully fabricated a nanofluidic chip with a nanochannel array by combining photolithography, transfer, and bonding techniques. We verified the feasibility of the prepared nanofluidic chip through ionic conduction experiments. Additionally, we compared the performance of the nanofluidic chip with a single channel to that of a chip with a nanochannel array through ionic conduction experiments to demonstrate the high sensitivity achieved by incorporating a nanochannel array. Moreover, we conducted DNA molecule detection experiments by modifying the nanochannel surface, which lays down the foundations for expanding applications of AFM-based Nanomachining technology in nanopore sensing.

Heterostructure design has been employed for electrocatalytic water splitting, nevertheless, the correlation between charge distribution at the active sites and the electrochemical processes remains ambiguous. In this study, bifunctional nanoarrayed CoP/Co₃O₄ nanosheets on carbon cloth (CC) heterostructure nanoparticles were systematically synthesized to enhance electrical transmission at the interface. The CoP/Co₃O₄ coupling CC substrate increases the electron transport efficiency and prevents catalyst aggregation and corrosion during catalytic operations. The synthesized materials exhibited expected hydrogen evolution reaction/oxygen evolution reaction (HER/OER) performance under alkaline circumstances, attaining 10 mA cm^–2 with overpotentials of 58 and 273 mV, respectively. Meanwhile, just 1.61 V is required for the two-electrode configuration to attain 10 mA cm^–2, exceeding earlier recorded Co₃O₄-based electrocatalysts. Experimental and density functional theory (DFT) studies confirm that CoOOH/Co₃O₄ functions as the true active site for the reconstructive formation of CoP/Co₃O₄, hence diminishing the adsorption energy of the intermediate and accelerating the reaction kinetics. This technique is anticipated to facilitate efficient charge transfer in water splitting and be applicable to other energy transformation processes.

Boron nitride nanotubes (BNNTs) are promising materials for next-generation technologies owing to their exceptional physicochemical properties, including outstanding chemical and thermal stabilities, and their neutron absorption capability derived from boron. However, dispersion is essential for the effective utilization of BNNTs. BNNTs have hydrophobic surfaces and strong van der Waals interactions, hindering their dispersion in water and various organic solvents. Dispersion techniques rely on strong physical and chemical treatments, which may damage the material and degrade its properties. Herein, we investigate a graft polymerization technique using electron-beam irradiation to functionalize BNNTs under various conditions of acrylic acid (AAc) concentration, Mohr’s salt concentration, and absorbed dose. We analyze the correlations between these conditions and their effects on the grafting yield. Subsequently, we employ X-ray photoelectron spectroscopy and Fourier-transform infrared spectroscopy to elucidate the grafting mechanism of pristine BNNTs and poly(acrylic acid) (PAAc)-grafted BNNTs (PAAc-g-BNNTs). Furthermore, we evaluate the improved dispersibility and dispersion stability of the grafted BNNTs in water using ultraviolet–visible spectroscopy and zeta potential measurements. Additionally, we assess the dispersion behaviors of the pristine BNNTs and PAAc-g-BNNTs in 15 different solvents. We estimate the solubility range using the Hansen solubility parameter to confirm enhanced dispersion in various solvents. We believe our approach has high potential for applications such as the heatsink polymer composite, catalyst support, piezoelectric sensor in aerospace, electronics, and biotechnology fields.

Porphyrins with earth-abundant transition metals are appealing catalysts for the CO₂ electrochemical reduction reaction (CO₂ERR). However, their wider applications are often limited by aggregation and instability. Herein, a facile thermal treatment was employed to convert metal porphyrins into metal nanoparticles embedded in nitrogen-rich carbon nanomaterials. It was found that Ni nanoparticles derived from Ni porphyrins show a high selectivity of 93% toward CO with an exceptional onset overpotential of 320 mV, while Co nanoparticles derived from Co porphyrins exhibit a selectivity of 16% only as well as a high overpotential of 730 mV. The above contrast indicates that the derived metal nanoparticles exert huge effects on the selectivity and activity. Density functional theory (DFT) calculations reveal that metal nanoparticles would alter the energy barriers of the CO₂ERR and the competitive hydrogen evolution reaction (HER), both of which jointly affect the catalytic selectivity. The findings here provide not only a better understanding of the relationship between catalytic metal sites and selectivity but also deeper insights into the design of advanced catalysts for CO₂ERR.