The structural tailoring of Pt-based catalysts into 1D nanowires for oxygen reduction reactions (ORR) has been a focus of research. Mo(CO)6 is commonly used as a morphological modifier to form nanowires, but it is found that it inevitably leads to Mo doping. This doping introduces unique electrochemical signals not seen in other Pt-based catalysts, which can directly reflect the stability of the catalyst. Through experiments, it is demonstrated that Mo doping is detrimental to ORR performance, and theoretical calculations have shown that Mo sites that are inherently inactive also poison the ORR activity of the surrounding Pt. Therefore, a novel gas-assisted technique is proposed to replace Mo(CO)6 with CO, which forms ultrafine nanowires with an order of magnitude increase in length, ruling out the effect of Mo. The catalyst performs at 1.24 A mgPt -1, 7.45 times greater than Pt/C, demonstrating significant ORR mass activity, and a substantial improvement in stability. The proton exchange membrane fuel cell using this catalyst provides a higher power density (0.7 W cm-2). This study presents a new method for the preparation of ultra-long nanowires, which opens up new avenues for future practical applications of low-Pt catalysts in PEMFC.

The transport of ions through biological ion channels is regulated not only by their structural characteristics but also by the composition of the phospholipid membrane, which serves as a carrier for nanochannels. Inspired by the modulation of ion currents by lipid membrane composition, exemplified by the activation of the K+ channel of Streptomyces A by anionic lipids, we present a biomimetic nanochannel system based on combining DNA nanotechnology with two-dimensional graphene oxide (GO) nanosheets. By designing multibranched DNA nanowires, we assemble programmable DNA scaffold networks (DSNs) on the GO surface to precisely control membrane composition. Modulating the DSN layers from one to five enhances DNA composition, yielding a maximum 12-fold enhancement in ion current, primarily due to charge effects. Incorporating DNAzymes facilitates reversible modulation of membrane composition, enabling cyclic conversion of ion current. This approach offers a pathway for creating devices with highly efficient, tunable ion transport, applicable in diverse fields like mass transport, environmental protection, biomimetic channels, and biosensors.

We introduce the FlexoSERS sensor, which is notable for its high stretchability, sensitivity, and patternability. Featuring a hierarchically oriented jellyfish-like architecture constructed from stretchable gold nanowires, this sensor provides an ultrasensitive SERS signal even under 50% strain, with an enhancement factor (EF) of 3.3 × 1010. Impressively, this heightened performance remains consistently robust across 2,500 stretch-release cycles. The integration of nanowires with 3D-printed hydrogel enables a customizable FlexoSERS sensor, facilitating localized sweat collection and detection. The FlexoSERS sensor successfully detects and quantifies uric acid (UA) in both artificial and human sweat and functions as a pH sensor with repeatability and sensitivity across a pH range of 4.2-7.8, enabling real-time sweat monitoring during exercise. In summary, the rational architectural design, scalable fabrication process, and hydrogel integration collectively position this nanowire-based FlexoSERS sensor as a highly promising platform for customizable wearable sweat diagnostics.

Long nanowires offer an increased surface area for biomolecule immobilization, facilitating enhanced binding capacity and sensitivity in the detection of target analytes. However, robust long-nanowire fabrication remains a significant challenge. In this paper, we developed a novel construction of a micro chemical pen (MCP), called a clean-assisted micro chemical pen (CAMCP), for robust long-nanowire fabrication. CAMCP, based on localized hydrodynamic flow confinement, was conducted by incorporating a clean phase to effectively dissolve aggregated silver particles in the aspiration channel\'s shell, thereby enhancing the MCP\'s longevity by 60.84%, allowing for an 840 μm extension in nanowire patterning capability. A 4600-aspect ratio (length:1200 μm, width: 260 nm) nanowire was fabricated by CAMCP and utilized as a nanowire sensor, showing a 39.7% increase in IgA detection sensitivity compared to a 3000-aspect ratio sensor. Furthermore, the longer nanowire sensor exhibited enhanced signal responses, a higher signal-to-noise ratio, and a lower limit of detection (LOD). The preponderant bioassay performances of the longer nanowire sensor in bioassays, facilitated by CAMCP, open up its possibilities for chemical-synthesis nanowires (NWs) in ultrasensitive biodetection.

The present paper reported on the analysis of structural defects and their influence on the red-emitting γ-Al2O3:Mn4+,Mg2+ nanowires using positron annihilation spectroscopy (PAS). The nanowires were synthesized by hydrothermal method and low-temperature post-treatment using glucose as a reducing agent. X-ray diffraction (XRD), scanning electron microscopy (SEM), photoluminescence (PL), and photoluminescence excitation (PLE) were utilized, respectively, for determining the structural phase, morphology and red-emitting intensity in studied samples. Three PAS experiments, namely, positron annihilation lifetime (PAL), Doppler broadening (DB), and electron momentum distribution (EMD), were simultaneously performed to investigate the formations of structural defects in synthesized materials. Obtained results indicated that the doping concentration of 0.06% was optimal for the substitution of Mn4+ and Mg2+ to two Al3+ sites and the formation of oxygen vacancy (VO)-rich vacancy clusters (2VAl + 3VO) and large voids (~0.7 nm) with less Al atoms. Those characteristics reduced the energy transfer between Mn4+ ions, thus consequently enhanced the PL and PLE intensities. Moreover, this optimal doping concentration also effectively controlled the size of nanopores (~2.18 nm); hence, it is expected to maintain the high thermal conductivity of γ-Al2O3 nanowire-phosphor. The present study, therefore, demonstrated a potential application of γ-Al2O3 nanowire-phosphor in fabricating the high-performance optoelectronic devices.

Nanomechanical resonators can serve as ultrasensitive, miniaturized force probes. While vertical structures such as nanopillars are ideal for this purpose, transducing their motion is challenging. Pillar-based photonic crystals (PhCs) offer a potential solution by integrating optical transduction within the pillars. However, achieving high-quality PhCs is hindered by inefficient vertical light confinement. Here, we present a full-silicon photonic crystal cavity based on nanopillars as a platform for applications in force sensing and biosensing areas. Its unit cell consists of a silicon pillar with a larger diameter at its top portion than at the bottom, which allows vertical light confinement and an energy band gap in the near-infrared range for transverse-magnetic polarization. We experimentally demonstrate optical cavities with Q factors exceeding 103, constructed by inserting a defect within a periodic arrangement of this type of pillars. Each nanopillar naturally behaves as a nanomechanical cantilever, making the fabricated geometries excellent optomechanical (OM) photonic crystal cavities in which the mechanical motion of each nanopillar composing the cavity can be optically transduced. These geometries display enhanced mechanical properties, cost-effectiveness, integration possibilities, and scalability. They also present an alternative in front of the widely used suspended Si beam OM cavities made on silicon-on-insulator substrates.

BACKGROUND: In recent years, environmental pollution has attracted widespread global attention. Among them, environmental problems caused by heavy metal pollution pose a serious threat to human health and ecosystems. Mercury is a common heavy metal pollutant with high toxicity and wide distribution. Excessive intake of Hg2+ can cause permanent and severe damage to the nervous system, respiratory system, and kidneys in the human body. Therefore, developing both accurate and fast detection methods for Hg2+ is of great significance.
RESULTS: A sensitive Hg2+ colorimetric sensor is designed based on PtNi nanowires (NWs) and Pt NWs with peroxidase-mimetic activity. PtNi NWs and Pt NWs catalyze the reaction of 3,3\', 5,5\'-tetramethylbenzidine (TMB) with hydrogen peroxide (H2O2) to produce blue oxidized TMB (oxTMB). The specific interaction of Pt-Hg significantly inhibits the peroxidase-mimetic activity of PtNi NW and Pt NW nanozymes, resulting in a lighter blue color. It is worth noting that compared with specific activity (SA) of Pt NWs (3.31 U/mg), PtNi NWs own superior SA (10.43 U/mg), which inevitably leads to a wider linear range of Hg2+ analysis (1 nM-200 μM) and a lower detection limit (0.6748 nM) for PtNi NWs-based colorimetric sensor, versus linear range (4 nM-5 μM) and LOD of 1.198 nM for Pt NWs-based colorimetric sensor, which are far below the Hg2+ threshold (10 nM) for drinking water set by the US Environmental Protection Agency.
CONCLUSIONS: The two nanozyme colorimetric sensors have been successfully used for the evaluation of Hg2+ in complex river water and tap water. Due to the advantages of simple operation, fast response, and high sensitivity, colorimetric sensors have broad application prospects in environmental monitoring.

The silicon nanowire field-effect transistor (SiNW FET) has been developed for over two decades as an ultrasensitive, label-free biosensor for biodetection. However, inconsistencies in manufacturing and surface functionalization at the nanoscale have led to poor sensor-to-sensor consistency in performance. Despite extensive efforts to address this issue through process improvements and calibration methods, the outcomes have not been satisfactory. Herein, based on the strong correlation between the saturation response of SiNW FET biosensors and both their feature size and surface functionalization, we propose a calibration strategy that combines the sensing principles of SiNW FET with the Langmuir-Freundlich model. By normalizing the response of the SiNW FET biosensors (ΔI/I0) with their saturation response (ΔI/I0)max, this strategy fundamentally overcomes the issues mentioned above. It has enabled label-free detection of nucleic acids, proteins, and exosomes within 5 min, achieving detection limits as low as attomoles and demonstrating a significant reduction in the coefficient of variation. Notably, the nucleic acid test results exhibit a strong correlation with the ultraviolet-visible (UV-vis) spectrophotometer measurements, with a correlation coefficient reaching 0.933. The proposed saturation response calibration strategy exhibits good universality and practicability in biological detection applications, providing theoretical and experimental support for the transition of mass-manufactured nanosensors from theoretical research to practical application.

Intracellular detection and imaging of microRNAs (miRNAs) with low expression usually face the problem of unsatisfactory sensitivity. Herein, a novel dual-function DNA nanowire (DDN) with self-feedback amplification and efficient signal transduction was developed for the sensitive detection and intracellular imaging of microRNA-155 (miRNA-155). Target miRNA-155 triggered catalytic hairpin assembly (CHA) to generate plenty of double-stranded DNA (dsDNA), and a trigger primer exposed in dsDNA initiated a hybridization chain reaction (HCR) between four well-designed hairpins to produce DDN, which was encoded with massive target sequences and DNAzyme. On the one hand, target sequences in DDN acted as self-feedback amplifiers to reactivate cascaded CHA and HCR, achieving exponential signal amplification. On the other hand, DNAzyme encoded in DDN acted as signal transducers, successively cleaving Cy5 and BHQ-2 labeled substrate S to obtain a significantly enhanced fluorescence signal. This efficient signal transduction coupling self-feedback amplification greatly improved the detection sensitivity with a limit of detection of 160 aM for miRNA-155, enabling ultrasensitive imaging of low-abundance miRNA-155 in living cells. The constructed DDN creates a promising fluorescence detection and intracellular imaging platform for low-expressed biomarkers, exhibiting tremendous potential in biomedical studies and clinical diagnosis of diseases.

In recent years, 1D nanostructure-based devices have achieved widespread usage in various fields, such as sensors, energy harvesters, transistors, and electrodes owing to their exceptional and distinct properties. The pioneering work of Dr. R. S. Wagner at Bell Laboratories in 1964 introduced the vapor-liquid-solid (VLS) process, a powerful synthesis method. Since then, numerous synthesis techniques, including sol-gel, hydrothermal, chemical vapor deposition (CVD), physical vapor deposition (PVD), and more, have been developed. These methods have enabled researchers to effectively control the shape (length and diameter) and material properties of nanowires. However, it was only about two decades ago that nanowires started to be widely utilized as key components in functional devices, primarily due to the lack of proper integration methods. Although dozens of integration techniques have been developed, none have emerged as a predominant choice, with each method presenting its own set of advantages and limitations. Therefore, this work aims to categorize these methods based on their working principles and provide a comprehensive summary of their pros and cons. Additionally, state-of-the-art devices that capitalize on the integration of 1D nanomaterials are introduced.