Nanotechnology最新文献

The performance of silver nanowire (AgNW) network flexible transparent electrodes is limited by large contact resistance, making it necessary to perform nanowelding to improve conductivity of the network. However, not all nanowire junctions can be welded. Our work indicates that the welding kinetics between nanowires depend on the crossing angle, with higher surface diffusion velocity prone to welding and fracture at nanowire junctions of crossing angles close to 90 degrees. The impact of nanowire crossing angles on the welding process makes it difficult to achieve simultaneous welding of random AgNWs networks. To address this issue, we adopted an improved Meyer rod coating method to prepared a cross-aligned nanowire network based on a layer-by-layer assembly strategy. Compared to randomly distributed AgNWs networks (11.17 Ω sq^-1, 85.2%), the cross-aligned AgNWs network achieved simultaneous welding of nanowire junctions during thermal annealing, further enhancing the optoelectronic performance (10.8 Ω sq^-1, 90.3%) of the AgNWs network, resulting in a superior figure of merit value of 421.

MXenes [two-dimensional (2D) transition-metal carbides, nitrides and carbonitrides] are gaining significant interest as alternative electrocatalysts for the hydrogen evolution reaction due to their excellent properties such as high electrical conductivity, large surface area and chemical stability. MXenes are traditionally synthesized using hydrofluoric acid (HF), which raises safety and environmental concerns due to its highly corrosive and toxic nature. HF introduces fluoride functional groups on the surface of MXenes, and these have been reported to have a detrimental effect on electrocatalysis. As a result, there is growing interest in developing MXenes through non-fluoride routes. Here, we report room-temperature, HF-free, wet-chemical synthesis of MXene using a mixture of hydrogen peroxide and chromium chloride. The newly prepared CH-MXenes possess hydrophilic functionalities (-Cl, -OH and =O). Key advantages of the CH route over HF-based synthesis include the elimination of an additional delamination step, the prevention of MXene restacking via chloride functionalities and the consistent production of high-quality 2D MXenes with a reproducible flake size (∼650 nm). These CH-MXenes exhibit a high surface area, excellent conductivity and enhanced chemical stability, making them suitable for various energy and other applications.

Bovine serum albumin-capped gold nanoclusters (AuNC@BSA) are ionic, ultra-small, and eco-friendly nanomaterials that exhibit red fluorescence emission. Upon modification, these nanomaterials can serve as imaging probes with multimodal functionality. Owing to their nanoscale properties, AuNC@BSA-based nanomaterials can be readily endocytosed by cells for imaging. With the increasing interest in cell therapy, extracellular vesicles (EVs) have attracted considerable attention from researchers; however, effective methods for imaging EVs remain limited. Although several studies have explored imaging strategies for cells and EVs using compounds, nuclear pharmaceuticals, nanoparticles, or genetic constructs, the use of AuNC@BSA-based nanomaterials for labeling EVs and their parental cells has rarely been discussed, with even less attention paid to their multimodal potential. To address this gap, we utilized three types of AuNC@BSA-based derivatives: AuNC@BSA, AuNC@BSA-Gd, and AuNC@BSA-Gd-I. Our findings demonstrate that these derivatives can effectively label both cells and EVs using a simple direct labeling approach, which is particularly notable for EVs, as they typically require more complex labeling procedures. Furthermore, the multimodal potential of labeled cells and EVs was evaluated, revealing their capabilities for multimodal imaging. In summary, this study presents an effective strategy for labeling EVs and their parental cells using multimodal nanomaterials. These findings will contribute to accelerating the development of drug delivery systems, cell- and EV-based therapies, and advanced imaging strategies.

Herein, we synthesized anisotropic silica nanoparticles (AISNPs) with organic amines with different structures. Monoamines and diamines with distance between amine groups shorter thanca.4 Å have been observed to facilitate the formation of isotropic silica nanoparticles (ISNPs). AISNPs were synthesized with diamines with distance between amine groups longer thanca.4 Å and linear structures of triamines. Non-linear structures with amine groups positioned in a triangular configuration and the cage-like structure of tetra-amines directed the formation of ISNPs. It has been speculated that the formation of AISNPs would be due to the spherical primary particles connecting by organic amines with two or more amine groups with distances between them longer thanca.4 Å. On the contrary, the formation of ISNPs would be attributed to the adsorption of two amine groups on the same primary particles, or to steric hindrance that prevent their connection.

A phenol contains a six-membered, conjugated, aromatic ring bound to a hydroxyl group. These molecules are important in biomedical studies, aromatic food preparation, and petroleum engineering. Traditionally, phenols have been measured with several analytical techniques such as UV-VIS spectroscopy, fluorescence, liquid chromatography, and mass spectrometry. These assays provide for relatively high sensitivity and selectivity measurements, but they suffer from relatively low spatiotemporal resolution, low biocompatibility, long analysis time, high cost, and complex sample treatment. Recently, electrochemistry has served as a viable alternative to the measurement of phenols. In this study, we utilized carbon fiber microelectrodes (CFMEs) with fast-scan cyclic voltammetry for the sensitive and selective measurement of phenols. We tested four common phenolic compounds: phenol, 2-methylaminophenol (2-MAP), 4-methylaminophenol (4-MAP), and 3-hydroxybenzoic acid (3-HBA). We found that phenol, 2-MAP, 4-MAP, and 3-HBA were all partially adsorption and diffusion controlled to the surface of the CFMEs and that all four molecules could be detected with repeated injections. Structural differences led to varied sensitivities amongst the four phenols, and we were able to co-detect and differentiate the phenols in complex solutions with dopamine and serotonin. Lastly, we measured the phenols in simulated urine with a high percent recovery. These assays demonstrate enhanced electrochemical measurement of phenols, which will create more effective diagnostics for these complex molecules to help elucidate their mechanistic properties and ultimate significance in a biological context.

In this paper we investigate the electrical response response of amorphous complex oxide memristors under different electrical stimulation. With the help of transmission electron microscopy and energy dispersive x-ray spectroscopy, we observed that those devices stimulated with voltage display strong cationic segregation at the nanoscale together with the partial crystallization of the oxide layer. On the other hand, devices stimulated with current maintain their amorphous character with no significative chemical changes. Our analysis also shows that current stimulation leads to a more stable memristive response with smaller cycle-to-cycle variations. These findings could contribute to the design of more reliable oxide-based memristors and underscore the crucial effect that has type of electrical stimulation applied to the devices has on their integrity and reliability.

The processes of electrochemical deposition of Ni on vertically aligned GaAs nanowires (NWs) grown by molecular-beam epitaxy (MBE) using Au as a growth catalyst on n-type Si(111) substrates were studied. Based on the results of electrochemical deposition, it was concluded that during the MBE synthesis of NWs the self-induced formation of conductive channels can occur inside NWs, thereby forming quasi core-shell NWs. Depending on the length of the channel compare to the NW heights and the parameters of electrochemical deposition, the different hybrid metal-semiconductor nanostructures, such as Ni nanoparticles on GaAs NW side walls, Ni clusters on top ends of GaAs NWs, core-shell GaAs/Ni NWs, were obtained.

Quantum dots (QDs) have shown great application potential in a variety of optoelectronic devices due to their unique optoelectronic properties, especially playing a key role in the development of quantum dot light-emitting diodes (QLEDs). Inorganic ligands, including metal or non-metal chalcogenides, oxoanions, halides, and metal cations, play crucial roles in the synthesis, stabilization, and functionalization of QDs. Compared to long-chain organic ligands, inorganic ligands are shorter and possess higher electron mobility, which facilitates their application in high-performance QLEDs. This review explores the mechanisms of ligand exchange, classifies the types of inorganic ligands, and discusses their impact on the properties of QDs. Special attention is given to the latest research developments in inorganic ligand QDs for LEDs and their prospective applications in optoelectronics. This review highlights the versatility and efficacy of inorganic ligands, showcasing their potential to revolutionize QLED technology for future high-resolution displays and efficient optoelectronic devices.

We report here the reversibility and bistability of the switching behavior in an azobenzene derivative induced by the bias applied by a scanning-tunneling microscopy (STM) tip, at low temperature and in ultra-high vacuum environment. Thiscis-to-transandtrans-to-cisswitching were observed during STM imaging in either polarity at +2 V or -2 V, on a sub-second time scale. This results in a blinking effect visible on STM images, corresponding to the reversible switching of the azobenzene molecule under the applied STM bias through an electric field induced process.