ACS Applied Nano Materials最新文献

Designing a material with simultaneous microwave and sound absorption abilities is highly desired to mitigate electromagnetic radiation and noise pollution. However, their further development is highly challenging due to their totally different mechanisms of energy conversion. Here, we fabricate an ultralight and porous composite aerogel composed of cotton-derived nanofibrillated cellulose and MXene (f-Ti₃C₂T_X) nanosheets by directional freeze-drying technology, toward simultaneous microwave and sound absorption. The honeycomb-like biomimetic microstructure of obtained composite aerogel not only allows unidirectional transmission for incident microwaves and sound waves but also induces strong energy attenuation and high conductive loss due to assembled f-Ti₃C₂T_X nanosheets. Moreover, the f-Ti₃C₂T_X content and density of the composite aerogel are further regulated to enable precise tunability of the microstructure and dielectric properties, contributing to optimal microwave absorption ability and high sound absorption capacity at the same time. The high-efficiency absorption covers the whole X band with a RC_min of −44.9 dB at a thickness of 6.35 mm, while the average sound absorption coefficient reaches 0.82 at a thickness of 30 mm in the frequency range from 1000 to 6300 Hz. This study offers a facile and sustainable approach to achieving controllable microwave and sound absorption for the targeted applications.

Fluorescence nanodiamonds (FNDs) containing negatively charged nitrogen vacancy (NV^–) centers promise sensors for electromagnetic fields, temperatures, and chemical potential in sub-micro- and nanoscales. Nevertheless, handling separative FND particles for such an objective is quite challenging. We report in this paper an approach to separate FNDs into trapped microdroplets for optically detected magnetic resonance (ODMR). We form microscale aqueous droplets on a droplet-based microfluidic chip for separating and trapping FNDs. We estimate the average encapsulated FND population through the proportion of FND-containing droplets in the total generated droplets. These droplets are separately trapped in 80 × 80 μm² trap cells. We developed a home-built detection system for exciting fluorescence and detecting ODMR for FND particles entrapped in an individual droplet. To the best of our knowledge, this work is the first for the ODMR detection of FNDs trapped in separative microdroplets. In this initiative study, we obtain ODMR spectra of the contrast of 0.07 to 0.15%. The zero-field splitting (ZFS) of the electron spin triplet of the nano NV ensemble is extracted from the ODMR spectra with the standard deviations among 0.2–0.5 MHz. The technique we develop here presents a potential platform separating FNDs in microdroplets for single-particle analysis, delivery, and traceable measurements of electromagnetic fields, temperatures, and chemical potentials.

Cathodic protection is one of the effective methods for metal protection, but it faces issues such as the use of an external power supply or the need for repeated charging. The self-powered metal corrosion prevention system based on triboelectric nanogenerator (TENG) is a viable solution to address the power supply issues in traditional methods. However, the low surface charge density of traditional triboelectric materials poses a challenge to the practical application of TENGs. Herein, we successfully modulated the dielectric constant and surface roughness of poly(vinyl chloride) (PVC) by incorporating Bi₂Ti₂O₇ nanoparticles, and fabricated a Bi₂Ti₂O₇/PVC composite triboelectric material with a surface charge density of 711 μC/m², which is 108% higher than that of pure PVC film. The 1.5 wt % Bi₂Ti₂O₇/PVC-based TENG can generate alternating current (AC) signals up to 416 V and a current of 55 μA, and it only requires 13 s to charge a 1000 μF capacitor from 0 to 3 V. Furthermore, the device maintains good operational stability after 20 h of continuous operation. The self-powered metal corrosion protection system based on 1.5 wt % Bi₂Ti₂O₇/PVC composite film can effectively protect iron sheet and 45 steel sheet in simulated seawater. This research not only offers a reference for the creation of triboelectric materials with high surface charge density but also demonstrates the application of high-performance TENG in metal corrosion protection systems.

Low-temperature CO poisoning of Pt-based catalysts remains a persistent issue during the start-up of automotive three-way catalysts and at the operation temperatures of polymer electrolyte membrane fuel cells. Hence, we have investigated the low-temperature CO oxidation behavior of Pt/ZnO catalysts composed of size-controlled, 2–4 nm large Pt particles and 8–20 nm wide hexagonal ZnO nanorods. Carbon monoxide conversion abruptly escalated as soon as it reached ∼10%, approaching 100% at temperatures as low as 110 °C in a 1/20/79 CO/O₂/He feed. The onset of CO conversion shifted by ca. 70 °C in a 5/5/90 CO/O₂/He feed, indicating that it is very sensitive to the CO/O₂ reactant ratio. At lower temperatures, the activation of O₂ on the Pt particles was strongly inhibited by CO, pointing to a Langmuir–Hinshelwood-type reaction mechanism. Kinetic analyses of the temperature dependence suggest that the generation of vacant Pt sites for O₂ activation is the oxidation rate-limiting process at the lowest temperatures, while O₂ activation at Pt sites and/or its subsequent reaction with CO becomes rate-determining at higher temperatures. CO turnover frequencies amounted to τ ≈ 0.05 s^–1 at 100 °C in the 1/20/79 feed and τ ≈ 0.29 s^–1 at 190 °C in the 5/5/90 CO/O₂/He feed. Reductive pretreatment of the catalysts increased the metallic character of the Pt particles with a concomitant enhancement of the CO turnover frequencies. Infrared spectroscopic analyses revealed that CO is more strongly activated at metallic than at positively charged Pt sites. Still, the effect of reductive treatment on CO activation is minor in comparison to the impact of CO inhibition on O₂ activation. Therefore, the generation of accessible Pt sites for O₂ activation via reactive removal of CO is a key to low-temperature efficiency improvement of Pt catalysts for CO oxidation.

Bismuth oxyiodide (BiOI), a two-dimensional material, is well known for its photocatalytic and photovoltaic properties owing to its low bandgap, efficient charge separation, and suitable work function that facilitates various photocatalytic reactions. However, the performance of BiOI depends on the synthetic methods, as they dictate the growth directions and overall quality of the nanosheets or crystals produced. Herein, we investigated the morphology and the charge-separated character in the photoexcited states of the BiOI nanocrystals/sheets produced from alternative synthetic routes such as hydrothermal, ball milling, and hand grinding methods by using electroabsorption (E-A) spectroscopy. The optical band gaps, absorption, and E-A spectra of BiOI are shown to be sensitive to the synthetic method. The E-A spectra of BiOI nanocrystals/sheets embedded in poly(methyl methacrylate) (PMMA) matrix measured at the second harmonic of the applied field were simulated by using integral method analysis to estimate the changes in electric dipole moment and polarizability following photoexcitation. From the analysis, it is found that BiOI nanosheets prepared using a hand grinding method with a [001] orientation have much larger charge-separated character in the photoexcited states than those in the nanoparticles prepared from hydrothermal and ball milling methods with a [110] orientation, implying the excellent photoelectronic performance in BiOI nanosheets prepared by the hand grinding method in comparison with BiOI nanoparticles prepared by other methods. The present finding may open the gateway for the development of the specific BiOI material, which is suitable for photocatalysis and photodynamic therapy.

Solution-processed photodetectors have attracted significant research interest due to their multimodal functionalities, ease of fabrication, and compatibility with various substrates. However, these devices often face challenges such as limited performance and slow response times. This study reports the development of a zero-bias photodetector employing a p–n junction heterostructure that combines environmentally benign copper tin sulfide (Cu₂SnS₃, CTS) with low-temperature-processed TiO₂ nanorods. CTS, a nontoxic and earth-abundant chalcogenide, was deposited onto hydrothermally synthesized TiO₂ nanorods via chemical bath deposition, resulting in a robust and efficient CTS/TiO₂ heterostructure. XRD analysis revealed the rutile phase of TiO₂ and the mixed tetragonal-wurtzite phases of Cu₂SnS₃. The heterojunction demonstrated broad spectral absorption across the UV–visible range, with TiO₂ (3.1 eV) absorbing primarily UV light and Cu₂SnS₃ (1.75 eV) effectively covering the visible spectrum. I–V characteristics depicted a nonlinear relationship, indicating the presence of a built-in potential at the p–n junction, which enhances photocurrent generation under illumination. Notably, the detector operates efficiently at 0 V, highlighting its self-powered capability. Temporal response analysis revealed rapid rise and fall times (∼40 ms), emphasizing the potential of this solution-processed heterostructure for fast and reliable photodetection. The detector exhibited excellent performance metrics, including a low dark current (477 nA), high photocurrent (15.7 μA), high ON/OFF ratio (33), and high responsivity (50 mA/W). The nanorod heterostructure architecture offers conformable junction between Cu₂SnS₃ and TiO₂ and thereby offers an efficient pathway for photocarrier collection. The demonstrated CTS-TiO₂ nanorod detector is promising for the development of sustainable photodetectors for various potential applications, viz., environmental monitoring, medical diagnostics, and portable electronics.

Phase transitions are crucial for tuning the physical properties of two-dimensional (2D) materials, as well as developing their high-performance device applications. Here, we reported the observation of a semiconducting-to-metallic-like phase transition in palladium diselenide (PdSe₂) by oxygen plasma treatment. Benefiting from the excellent compatibility of plasma treatment with the conventional microfabrication process, local phase transition in PdSe₂ allows for the realization. Such locally patterned metallic-like phase regions can serve as contacts in the corresponding transistors, which significantly reduce the Schottky barrier height, thus improving the device performance. Furthermore, we observe an improvement of photocurrent response when using the metallic-like regions as contacts. Our study provides a strategy to tune the properties as well as develop high-performance devices of PdSe₂, thereby extending the applications of plasma technology in 2D materials and their devices.

Electroless copper deposition is a pivotal process in the electronics industry, facilitating the formation of Cu films on nonconductive polymer substrates without the need for external electric sources by promoting redox reactions on catalysts. However, achieving large-scale, uniform Cu film deposition with high peel strength while minimizing catalyst costs poses significant challenges for industrial applications. In this study, we propose replacing polyvinylpyrrolidone (PVP)-capped Pd (PVP-Pd) with PVP-capped Ag (PVP-Ag) nanocatalysts, which offer superior catalytic performance and cost-effectiveness. Our findings demonstrate that PVP-Ag nanocatalysts effectively catalyze the oxidation of common reducing agents like formaldehyde, without the hydrogen embrittlement issues typically associated with traditional Pd nanocatalysts. This prevents the formation of nonuniform and low-ductility Cu films. Additionally, we develop a surface treatment method involving cationic-π interactions and hydrogen-bonding formation using cationic polyacrylamide (CPAM) polymer on liquid crystal polymer (LCP) substrates. This method facilitates the cross-linking of CPAM with PVP-Ag nanoparticles, creating a strong anchoring effect between Cu films and LCP substrates. Our results indicate that this approach ensures the formation of large-scale 10 × 10 cm² Cu films with high uniformity and enhances peel strength to levels exceeding the industrial standard of 800 gf cm^–1, with values up to 875 gf cm^–1.

Cellulose nanopaper, a kind of thin film mainly constructed from nanocellulose, has gained much attention due to its lightweight and excellent mechanical properties compared to the plastic substrates, showing great potential in the design of electronic devices. Understanding the surface confinement effect of the cellulose nanocrystal (CNC) is essential for tuning the mechanical properties of cellulose nanopaper. Here, an all-atom molecular dynamics simulation is used to systematically investigate the surface confinement effect and size effect at the nanoscale on the dynamics and mechanical properties of CNC. The introduction of free surfaces leads to a reduction in the density and an increase in the molecular mobility in the zones near free surfaces. The interfacial zone thickness estimated from the Debye–Waller factor gradient exhibits a different variation trend with increasing CNC chain length from that estimated from the density gradient, indicating a decoupling relationship between structure and dynamics variations in the interfacial zone. Moreover, the elastic moduli of CNC exhibit power scaling laws with the density and Debye–Waller factor, while a linear scaling law is observed between elastic moduli and the normalized interfacial zone thickness. The local molecular stiffness distribution further reveals that the enhanced modulus of CNC with increasing chain length is attributed to a reduction in the contribution of the interfacial zone on the mechanical properties. Our study provides fundamental insights into the influence of the interfacial zone on the dynamical and mechanical properties of CNC at a molecular level, shedding light on the design of high-performance electronic devices.

The removal of heavy metal ions (HMIs) from polluted environments is crucial for safeguarding public health and improving water quality. This study investigates the HMI adsorption capabilities of a tetragonal graphene nanobowl (TGNB), an sp²-hybridized carbon-based nanomaterial, in wastewater. The negative cohesive energy of −6.75 eV and real vibrational frequencies confirm that the TGNB structure is stable and can occur naturally. The nanobowl exhibited an energy gap of 1.148 eV, revealing its semiconducting nature. Using density functional theory calculations, the adsorption behavior of TGNB for Ni(ii) and As(iii) ions was explored in an aqueous medium. The optimized TGNB structure showed adsorption energies of −3.07 eV for Ni(ii) and −13.10 eV for As(iii), causing significant structural deformation. The interaction of HMIs with TGNB resulted in substantial changes in the energy gap and work function, suggesting its applicability in HMI detection and monitoring in wastewater. The negative entropy change confirms the thermodynamic stability of all the complexes. Strong, partially covalent, as well as van der Waals interactions were observed between TGNB and HMIs. The adsorption process was exothermic and spontaneous, with strong interactions confirmed for most complexes. These findings demonstrate the potential of TGNB as an efficient stable nanomaterial for HMI detection and removal from wastewater.