ACS Applied Nano Materials最新文献

Nitrogen dioxide (NO₂) is a hazardous air pollutant that poses significant threats to both human health and the environment. The development of NO₂ sensors with high sensitivity, exceptional selectivity, and ultralow detection limits is of critical scientific and practical importance. However, conventional metal oxide-based NO₂ sensors often suffer from inherent limitations, including high operating temperatures and relatively low sensitivity. Given that oxygen vacancies in metal oxides serve as active sites for NO₂ adsorption and facilitate charge transfer at the gas–solid interface, this study demonstrates the room-temperature sensing capabilities of two-dimensional (2D) SnO nanosheets with a high concentration of oxygen vacancies, achieved without external excitation (e.g., light). Notably, the sensor exhibits n-type behavior, attributed to free electrons originating from oxygen vacancies. More importantly, the proposed sensor outperforms pure SnO and other metal oxide-based sensors, achieving a remarkably low detection limit of 10 ppb and a record-high response value of 136.43 toward 800 ppb of NO₂. Furthermore, it demonstrates outstanding repeatability, exceptional selectivity, and long-term stability over two months. These findings highlight the feasibility of achieving ppb-level NO₂ detection at room temperature through morphological control and defect engineering, paving the way for the development of ultrasensitive and high-performance NO₂ sensors.

The escalating phenomenon of bacterial resistance has precipitated the exacerbation of maladies attributable to microbial infections, constituting a substantial menace to human health. Nanozymes can catalyze the production of large quantities of reactive oxygen species (ROS) and then destroy bacterial cells. Nevertheless, most nanozymes require H₂O₂, photothermal, and acidic environments to elicit an effective antibacterial response. In this study, a Fe–Cu bimetallic single-atom nanozyme (FeCu-SAN-SO₄²^-) was synthesized by high-temperature pyrolysis and sulfation using an environmentally friendly Cu-FeMOF as a precursor. The resulting FeCu-SAN-SO₄²^- exhibited excellent oxidase (OXD)-like activity due to the synergistic effect of Fe–Cu dual sites, the high specific surface area (202 m² g^–1), and mesopore distribution (11.08 nm). FeCu-SAN-SO₄²^- also overcame the pH limitation by introducing Brønsted acidic sites and demonstrated excellent temperature tolerance and storage stability compared with natural enzymes. At a concentration of 0.1 mg mL^–1, the killing rate against four strains of E. coli, S. aureus, A. hydrophila, and A. tarda reached a level exceeding 90% without needing external conditions. The high antibacterial efficacy of FeCu-SAN-SO₄²^- was mainly attributed to its efficient generation of ROS, predominantly O₂^–• and •OH radicals. These ROS further deprive electrons of bacterial cellular components, causing irreversible oxidative stress. This work provides an effective antimicrobial agent by enhancing the environmental tolerance of nanozymes, which has great potential for food preservation and clinical applications.

Room-temperature phosphorescence (RTP) materials play a crucial role in fields such as anticounterfeiting, bioimaging, and optoelectronics. Nevertheless, their application in antibacterial coatings remains scarce. Herein, we introduce a straightforward physical mixing approach to form nanomicelles. Amphiphilic molecular nanoengineered peptide-grafted hyperbranched polymers (NPGHPs) are employed to encapsulate organic phosphorescent molecules. By embedding these nanomicelles into the rigid matrix of chitosan (CS), the assembled material can easily achieve RTP emission. Both NPGHPs and CS can effectively kill bacteria, and CS exhibits excellent film-forming ability. The assembled material can be readily processed into antibacterial films with good breathability, thus expanding the application of RTP materials in the antibacterial field. The preparation of this antibacterial RTP material is simple, rapid, and versatile. The bulk material can be prepared in a short time, enabling its reliable application in anticounterfeiting, coatings, and antibacterial domains.

Rutile-type GeO₂ (r-GeO₂) is expected as a next-generation ultra-wide-band-gap oxide semiconductor with controllable p-type and n-type conduction. However, the existence of other polymorphs, such as α-quartz and amorphous phases, makes it challenging to grow a single-phase r-GeO₂ film. Here, we investigate the effect of growth temperature (T_g) and oxygen pressure (P_O2) on the phase stability of GeO₂ films grown on c-plane α-Al₂O₃ substrates by pulsed laser deposition and establish a growth phase diagram. The GeO₂ films deposited at 400 °C are amorphous, while (100)-oriented r-GeO₂ crystalline films are stabilized only under reducing conditions (P_O2 ≤ 0.1 Pa) within a T_g range of 500–600 °C due to severe re-evaporation at higher T_g. However, the deep defect states, which are detected by optical absorption in its band gap and probably related to oxygen vacancies (V_O), form in the r-GeO₂ films, and the amount of V_O increases under lower P_O2 conditions. On the other hand, increasing P_O2 suppresses both re-evaporation and V_O formation, but further higher P_O2 promotes amorphous phase growth simultaneously. The r-GeO₂ films with 6-fold-rotational columnar domains are grown epitaxially on c-plane Al₂O₃ substrates, with the amorphous phase forming in the gaps between the domains. Precise control of T_g and P_O2 is crucial for obtaining high-quality r-GeO₂ films, as there is a competition between re-evaporation and the formation of amorphous phase.

Room-temperature thermoelectric properties of heterostructures prepared by direct physical vapor deposition of Bi₂Se₃ nanostructures on carbon fullerenes (C60)-multiwalled carbon nanotubes (MWCNT) substrates were studied in relation to the C60/MWCNT wt % ratio in the substrate and compared with the properties of similar heterostructures fabricated using bare untreated p-type MWCNTs and nitrogen-doped n-type MWCNTs (nMWCNTs). It is found that Bi₂Se₃-C60-MWCNT heterostructures exhibit n-type conductance when the total wt % of the C60-MWCNT component does not exceed 10 wt %, and at optimal C60/MWCNT ratios the maximal power factor of ∼58 μW/mK² is reached, which exceeds previously reported maximal power factor values exhibited by Bi₂Se₃-MWCNT and Bi₂Se₃-nMWCNT heterostructures, as well as by C60-based hybrid thermoelectric materials, by factors of ∼11, ∼4, and ∼2, respectively. This effect was attributed to the cluster-like growth mechanism of Bi₂Se₃ on C60-MWCNT substrates different from that on bare MWCNTs, which was supported by the magnetoresistance studies of the Bi₂Se₃-C60-MWCNT heterostructures in the 2–300 K temperature range, and to the charge transfer between the Bi₂Se₃ and C60 molecules, resulting in the formation of a Bi₂Se₃-dominated heterostructure with enhanced Seebeck coefficient, reaching ∼−110 to −150 μV/K and electrical resistivity not exceeding 1 mΩ·m for optimal C60/MWCNT ratios, which is similar to or lower than that of Bi₂Se₃-MWCNT and Bi₂Se₃-nMWCNT heterostructures. In addition, bending tests performed for Bi₂Se₃-C60-MWCNT heterostructures with the best power factor showed that these structures are stable during 100 consecutive bending cycles down to a 4 mm radius. This work opens the path for significant improvement of thermoelectrical properties of topological insulator–carbon allotrope heterostructures by tuning their charge transport mechanism using different types and concentrations of carbon allotropes and for their application in flexible thermoelectrics.

Bilayered vanadium oxides (BVOs) are promising cathode materials for beyond-Li-ion batteries due to their tunable chemistries and high theoretical capacities. However, the large size of beyond-Li⁺ ions limits electrochemical cycling and rate capability of BVO electrodes. Recent reports of MXene-derived BVOs with nanoscale flower-like morphology have shown improved electrochemical stability at high rates up to 5C in nonaqueous lithium-ion batteries. Here, we report how morphological stabilization can lead to improved rate capability in potassium-ion batteries (PIBs) through the synthesis and electrochemical characterization of MXene-derived K-preintercalated BVOs (MD-KVOs), which were derived from two V₂CT_x precursor materials prepared using two different etching protocols. We show that the etching conditions affect the surface chemistry of the MXene, which plays a role in the MXene-to-oxide transformation process. MXene derived from a milder etchant transformed into a nanoflower MD-KVO with two-dimensional (2D) nanosheet petals (KVO-DMAE) while a more aggressive etchant produced a MXene that transformed into a MD-KVO with one-dimensional (1D) nanorod morphology (KVO-CMAE). Electrochemical cycling of the produced MD-KVOs after drying at 200 °C under vacuum (KVO-DMAE-200 and KVO-CMAE-200) in PIBs showed that electrochemical stability of MD-KVO at high rates improved through the morphological stabilization of 2D particles combined with the control of interlayer water and K⁺ ion content. Structure refinement of KVO-DMAE-200 further corroborates the behavior observed during K⁺ ion cycling, connecting structural and compositional characteristics to the improved rate capability. This work demonstrates how proper synthetic methodology can cause downstream effects in the control of structure, chemical composition, and morphology of nanostructured layered oxide materials, which is necessary for development of future materials for beyond-Li-ion battery technologies.

Vertically stacked 3D dynamic random-access memory (DRAM) with horizontal cells has emerged as a promising solution for next-generation high-density memory. In order to meet the next node requirement, the stacked period of a specific SiGe/Si superlattice (SL) needs to exceed more than 64. However, achieving ultrahigh-period SiGe/Si SLs with uniform strain and low defects remains a critical challenge. Here, we demonstrate the epitaxial growth of fully strained 100-period Si/Si_0.8Ge_0.2 (43/8 nm) SLs with a total thickness of 5 μm. The SLs exhibit exceptional tier-to-tier uniformity (σ_thickness ∼ 0.33, σ_Ge% ∼ 0.66), excellent crystallinity, sharp SiGe/Si interface (<3.3 nm), smooth surface (roughness <0.1 nm), and low threading dislocation density (<10⁷/cm²). To efficiently evaluate the electrical performance of stacked SLs, we propose an approach using planar n-MOSFETs fabricated on the top Si layer. Remarkably, these devices show consistent electrical properties across 5–100 periods, confirming the uniformity of electrical performance of individual Si layers across the entire stack, even for 100-period SLs. This work provides a scalable pathway toward high-performance 3D DRAM with significantly enhanced storage density.

Neuropathic pain is a chronic condition that often requires long-term management, with opioids frequently being the primary option for severe pain relief. Capsaicin, a natural analgesic, holds promise for chronic pain management but is limited by its hydrophobicity, low tissue affinity, and short half-life. In this study, we developed a magnetic field-responsive nanodrug for the on-demand delivery of capsaicin, overcoming these limitations. We utilize iron oxide magnetic nanoparticles (MNPs) functionally coated with thermoresponsive poly(oligo (ethylene glycol) methyl ether methacrylate) (POEGMA). POEGMA nanocoatings on MNPs serve as capsaicin reservoirs. Upon alternating magnetic field (AMFs) exposure, MNPs dissipate heat locally, which triggers the thermodynamic response of their POEGMA nanocoating for capsaicin release. We studied the passive and AMFs-controlled release of capsaicin from MNPs. Then, we investigated the nanodrug for regulating the pain receptor TRPV1, endogenously expressed in primary rat hippocampal neurons, using calcium ion influx as an ion channel activity indicator. Finally, we assessed the biological impact of the nanodrug through cell viability and reactive oxygen species production. We showed that AMFs-induced release of one dose of capsaicin enhances TRPV1 receptors in more than 75% of hippocampal neurons, which would translate to an increased pain sensitivity. However, tonic capsaicin treatment (more than 3 doses of AMFs-induced release) desensitizes TRPV1 in more than 90% of neurons, which would result in analgesic effects. Importantly, the nanotherapy has no detrimental effects on neuronal health. The nanodrug developed here offers a promising mechanism-driven alternative for chronic pain management by enabling wireless and on-demand control of pain receptors.

Selective enrichment and isolation of polar phenolic acid compounds from the complex matrix of traditional Chinese medicine Salvia miltiorrhiza (Danshen) is challenging yet highly desirable due to their excellent pharmacological activities on cardiovascular and cerebrovascular systems. However, owing to their polar and ionic characteristics, trace levels of phenolic acid compounds, and the complexity of traditional Chinese medicine matrices, the selectivity and adsorption capacity of conventional separation media remain limited. Therefore, the rational design of efficient and selective extractants is crucial. In this study, a phenylboronic acid-functionalized microporous organic network (p-PBA-MON), with nanoscale porosity (1.2 nm) and a high surface area (437.6 m² g^–1), was synthesized and employed as an adsorbent for the selective and efficient enrichment of the phenolic acid compound salvianolic acid B (SAB) from Salvia miltiorrhiza. A monomer containing phenylboronic acid groups was chosen to construct p-PBA-MON, forming specific five- or six-membered cyclic esters with cis-diol groups in SAB and providing synergistic π–π and hydrogen bonding sites. This results in the selective adsorption of SAB with ultrafast adsorption kinetics (<20 min, C₀ = 50 mg L^–1) and high adsorption capacity (217.4 mg g^–1). The synthesized p-PBA-MON tolerates the influences of ionic strength and humic acid and can be reused at least five times without a decrease in adsorption capacity. This study introduces an efficient adsorbent for the selective enrichment and separation of polar SAB from complex traditional Chinese medicine samples. This advancement could significantly extend the application of MON in the extraction and purification of active substances from Chinese medicine and promote its development in the separation of complex samples.

Noble metal nanostructures have attracted substantial interest due to their unique optical properties, particularly their localized surface plasmon resonance (LSPR), which enables significant near-field electromagnetic enhancements. Among these, bowtie nanoantennas (BNAs) stand out for their strong plasmonic coupling at nanogap regions, making them highly effective in applications such as surface-enhanced Raman scattering (SERS). However, the limited hotspot area and potential scattering losses at peak enhancement wavelengths remain challenges for practical applications. To address these limitations, we designed and investigated a notch metal–insulator–metal bowtie nanoantenna (MIM-BNA) structure. Ge materials were horizontally integrated into conventional Ag-BNA nanostructures, and notched silver nanorods were strategically placed in the nanogap region to disrupt the geometric symmetry, thereby inducing Fano resonance. This approach successfully coupled bright (dipole mode of the nanorod array) and dark plasmonic modes (antisymmetric mode of the MIM-BNA), enhancing the electric field at the Fano dip wavelength. Further analysis explored the effects of material composition, stacking configurations, and nanorod arrays on near-field enhancement. Our findings demonstrate that the MIM-BNA structure significantly improves the near-field effect, provides more flexible adjustment of the operating wavelength within the visible and near-infrared (NIR) light spectrum, and expands the hotspot area compared to traditional BNAs, providing a promising platform for advanced SERS applications and other plasmonic technologies.