Nano Today最新文献

Direct growth of large-area vertically stacked two-dimensional (2D) van der Waal (vdW) materials is a prerequisite for their high-end applications in integrated electronics, optoelectronics and photovoltaics. Currently, centimetre- to even metre-scale monolayers of single-crystal graphene (MLG) and hexagonal boron nitride (h-BN) have been achieved by epitaxial growth on various single-crystalline substrates. However, in principle, this success in monolayer epitaxy seems extremely difficult to be replicated to bi- or few-layer growth, as the full coverage of the first layer was believed to terminate the reactivity of those adopting catalytic metal surfaces. Here, we report an exceptional layer-by-layer chemical vapour deposition (CVD) growth of large size bi-layer graphene single-crystals, enabled by proximity catalytic activity from platinum (Pt) surfaces to the outermost graphene layers. In-situ growth and real-time surveillance experiments, under well-controlled environments, unambiguously verify that the growth does follow the layer-by-layer mode on open surfaces of MLG/Pt(111). First-principles calculations indicate that the transmittal of catalytic activity is allowed by an appreciable electronic hybridisation between graphene overlayers and Pt surfaces, enabling catalytic dissociation of hydrocarbons and subsequently direct graphitisation of their radicals on the outermost sp² carbon surface. This proximity catalytic activity is also proven to be robust for tube-furnace CVD in fabricating single-crystalline graphene bi-, tri- and tetra-layers, as well as h-BN few-layers. Our findings offer an exceptional strategy for potential controllable, layer-by-layer and wafer-scale growth of vertically stacked few-layered 2D single crystals.

Technological advances constantly set new challenges for materials development. The miniaturisation of electronic devices demands the migration of metallurgy from macro/micro to the nanoscale, thus requiring a re-definition of existing and classical concepts in this field. The present study reports on the behaviour of pure Cu nanowires with diameters ranging from 40 to 140 nm heated in a low-pressure environment within a transmission electron microscope. The response of Cu nanowires was investigated at different temperatures up to 1123 K and analysed using electron-microscopy techniques, revealing both volumetric and shape changes over time. Sublimation, with a steady-state length reduction of the nanowires, was identified as the dominant effect of such heating. Additionally, it was detected that sublimation occurred not only at temperatures above ≈ 1023 K, where Cu has a higher vapour pressure than the column pressure of the electron-microscope, but also at temperatures as low as 923 K. This behaviour is explained by the presence of active regions at sharply curved regions at the nanowire tip and the imbalance of evaporation and redeposition rates of Cu atoms due to the experimentally-induced loss of vapor atoms. The study of Cu nanowires at the nanoscale with the electron microscope facilitates the elucidation of some fundamental aspects of the emerging science of nanometallurgy.

Chemotherapy remains the core anticancer treatment for castration-resistant prostate cancer (CRPC). However, drug resistance still poses a major obstacle, leading to shorter survival times. Given the biosafety of porous Se@SiO₂ nanospheres in normal tissues, their combination with chemotherapeutic drugs has emerged as an effective treatment for cancer. It is unknown whether porous Se@SiO₂ nanospheres can protect CRPC cells from drug resistance. In our study, we synthesized porous Se@SiO₂ nanospheres and confirmed their characteristics in line with previous studies. We discovered that porous Se@SiO₂ nanospheres sensitize CRPC to docetaxel (DTX) treatment, both in vitro and in vivo. Mechanistically, the nanospheres induce dephosphorylation of autophagy-related 14 (ATG14) at Y357 by upregulating the expression of the cellular form of prostatic acid phosphatase (cPAP) protein, which prevents the induction of autophagy and the survival of prostate cancer cells after DTX treatment. Furthermore, there is a negative correlation between cPAP and autophagy in CRPC. Our results suggest that the combination of porous Se@SiO₂ nanospheres with DTX could be a potentially effective treatment for CRPC.

We present cryo-responsive dynamic fractal ice nano-nucleators (DF-INNs) for cryo-cancer therapy applications. Our development of DF-INNs leverages their structural advantages, which inherently maximizes the number of active sites for heterogeneous ice nucleation. Owing to their radially attached nanocrystalline structure, DF-INNs expose an extensive array of grain boundaries. The rapid precipitation and subsequent radial attachments of nanocrystallites promote the exposure of facets with high Miller indices, intrinsically strained, five-fold twinned nanocrystals, and increasing point defects due to kinetically-limited precipitation. This unique fractal structure culminates in the elevating of freezing temperature compared to Euclidean-shaped ice nucleators. Additionally, the branched fractal structure of DF-INNs facilitates heterogenic ice formation within its nanoconfined region, leading to the production of numerous self-similar small fractal fragments. This fragmentation is primarily driven by nanoconfinement-induced delayed ice nucleation, similar to frost heaving. The shear stress can be easily relieved through grain boundary sliding within the radially stacked DF-INN, making itself prone to cryo-responsive fragmentation. Such dynamic attributes significantly enhance ice nucleating activity, presenting a powerful strategy to increase the efficacy of cryotherapy by enhancing cellular ice formation and in vivo tumor coverage.

Horizontally aligned carbon nanotube (HACNT) arrays hold significant potential for various applications in nanoelectronics and material science. However, their high-throughput characterization remains challenging due to the lack of methods with both high efficiency and high accuracy. Here, we present a novel technique, Calibrated Absolute Optical Contrast (CAOC), achieved through the implementation of differential principles to filter out stray signals and high-resolution calibration to endow optical contrast with physical significance. CAOC offers major advantages over previous characterization techniques, providing consistent and reliable measurements of HACNT array density with high throughput and non-destructive assessment. To validate its utility, we demonstrate wafer-scale uniformity assessment by rapid density mapping. This technique not only facilitates the practical evaluation of HACNT arrays but also provides insights into balancing high throughput and high resolution in nanomaterial characterization.

The development of DNA-based imaging techniques provides a promising way for theranostic applications. However, the dramatic chemical difference between DNA probes and therapeutics significantly hinders the construction of an ideal theranostic system for evaluation of therapeutic effects via in situ molecular imaging. In this work, we report a simple approach for the construction of a two-in-one DNA nanohybrid via one-step assembly of DNA probes and small molecular drugs, enabling evaluation of therapeutic effects via sensitive imaging of apoptosis-related mRNA. The nanohybrid was self-assembled from a rationally designed molecular beacon (MB) probe, doxorubicin (DOX, a chemotherapeutic drug) and Fe (II) ions through coordination interactions, which possesses anti-cancer effects from chemotherapeutics and the capability of efficient co-delivery of DNA probes without transfection agents. By tracking pro-apoptotic Bax mRNA expression with the MB, this system allows real-time monitoring of cell apoptotic process in response to drug treatment, enabling assessment of therapeutic effects of small molecular drugs. In addition, the approach is extended to the imaging of target microRNA in the drug treatment based on flexible DNA probe design, demonstrating the universality of this strategy. Moreover, the modular design of this DNA nanohybrid allows the introduction of photosensitizers into this system for efficient photodynamic therapy and simultaneous mRNA monitoring. This strategy expands the theranostic toolbox for the in situ evaluation of treatment response and screening anticancer drugs.

The in-depth blood-based proteomics is significantly limited owing to the intrinsic wide dynamic range of protein concentrations (over 10 orders of magnitude) and highly abundant proteins (albumin, etc.) in blood. Here, we developed a protein denaturation strategy to enhance the serum proteomic depth via nanoparticle-protein corona for enhanced non-small cell lung cancer (NSCLC) diagnosis. We developed an optimal denaturant panel consists of nature, 30 % acetonitrile, 40 % RapiGest, and 4 M urea respectively treated serum to form various nanoparticle-protein coronas with magnetic nanoparticles (MNPs). Based on this panel, we have identified 1846 proteins by profiling 172 NSCLC serum samples, significantly enhancing the depth of serum proteomics. Furthermore, we selected 15 key proteins with random forest algorithm to distinguish the benign and malignant nodules and achieved an ROC-AUC of 98.44 %. Differentially expressed protein-based pathway analysis revealed that metabolic and immune-related pathways were significantly enriched, in which apolipoproteins play pivotal role in the transfer from benign to malignant nodules. Our study demonstrated a facile serum denaturation strategy for enhanced depth of serum proteomics which will benefit the cancer biomarker discovery and diagnosis.

Electrochemical water splitting (EWS) is a pivotal method for sustainable hydrogen (H₂) generation, yet it faces challenges due to limited accessibility and high costs associated with precious metal electrocatalysts. Efforts in research have thus been directed toward developing cost-effective alternatives to drive widespread adoption. Transition metals (TMs) emerge as promising candidates to replace noble metal-based electrocatalysts in EWS, offering abundance and affordability. This review surveys recent advancements and innovative methodologies in designing TM-based electrocatalysts, focusing on strategies such as defect engineering of MXene. This approach demonstrates considerable potential in enhancing EWS technology. Moreover, the review underscores the necessity of comprehending the fundamental mechanisms and activity-limiting factors inherent in EWS. It advocates for catalyst engineering strategies, integration of theoretical calculations, and modern in situ characterization techniques to facilitate the commercialization of electrocatalysts for sustainable hydrogen production. By integrating recent progress and ongoing challenges, this review seeks to present insights into the frontier of TM-based electrocatalysts and their role in advancing the field of EWS toward a more sustainable future.

The precise control of nanomaterial microstructure at the atomic level relies on the comprehensive understanding of atomic structural transition during the fabrication process at the atomic level. The phase transition from protonated titanate to TiO₂ is a prevalent route to synthesize low dimensional TiO₂-based nanomaterials, which exhibit excellent photocatalytic, lithium-ion battery performances, while the detailed phase transition mechanism remains to be clarified due to lack of atomic-level in situ information. Herein, the atomic structural transitions from one-dimensional H₂Ti₃O₇ (HT) to TiO₂(B) and anatase TiO₂ (TB and TA) nanocrystals were revealed through in situ environmental transmission electron microscopy, which exhibited a two-step phase transition at 200–600 °C. (I) H₂Ti₃O₇ to TiO₂(B) transition began via an indirect pathway at ∼200 °C: The HT (200) interlayer dehydration occurred firstly with lattice shrinkage; Then TB discretely nucleated at the dehydrated H₂Ti₃O₇ nanotube wall with a crystallographic relationship of (200)_HT∥(200)_TB {[001]_HT∥[001]_TB}; At higher temperature, the separated nuclei grew up with defects and distorted crystal lattice among them, which then connected and jointed to a single crystalline TB nanotube by atomic rearrangement. (II) The further transition of TiO₂(B) to anatase TiO₂ occurred via a direct pathway above 400 °C: Scarce nucleation event of TA phase was observed, which generated within TB nanocrystal with a crystallographic relationship of (200)_TB∥(002)_TA {[001]_TB∥[010]_TA}. Once a TA nucleus formed, it grew up to a large crystal by consuming the neighbor TB nanocrystals. These findings may contribute to comprehensively understanding phase transition and precisely manipulating the atomic structure of one-dimensional TiO₂ nanocrystals.