- 标题
- 摘要
- 关键词
- 实验方案
- 产品
-
Effect of pre-existing nuclei on crystallization during laser welding of Zr-based metallic glass
摘要： In this study, experiments are carried out in laser welding of a Zr-based (Zr52.5Ti5Al10Ni14Cu17.9) bulk metallic glass (BMG), pre-existing nuclei nucleus density has significant influence on its crystallization behavior. Based on the classical nucleation/growth theory, it is concluded that a small amount of pre-existing nuclei in a BMG can shift the time-temperature-transformation (TTT) curve from a well-known ‘C-shape’ to a ‘ε-shape.’ This result provides fundamental understanding on why the shape of the TTT curve for a heating process is different from that for a cooling process for the same BMG. Two quality factors were defined as a measure of the effect of pre-existing nucleus density. By integrating the classical nucleation/growth theory with the heat transfer model, the evolution of crystalline phase during laser welding for a BMG with pre-existing nuclei was studied, and the modeling predictions compared favorably with the experimental results.
关键词： Crystallization,Nucleation and growth,Laser processing,Metallic glasses,Amorphous alloys
更新于2025-11-28 14:24:20
-
Targeting fluorescent nanodiamonds to vascular endothelial growth factor receptors in tumor
摘要： The increased expression of vascular endothelial growth factor (VEGF) and its receptors is associated with angiogenesis in a growing tumor, presenting potential targets for tumor-selective imaging by way of targeted tracers. Though fluorescent tracers are used for targeted in vivo imaging, the lack of photostability and biocompatibility of many current fluorophores hinder their use in several applications involving long-term, continuous imaging. To address these problems, fluorescent nanodiamonds (FNDs), which exhibit infinite photostability and excellent biocompatibility, were explored as fluorophores in tracers for targeting VEGF receptors in growing tumors. To explore FND utility for imaging tumor VEGF receptors, we used click-chemistry to conjugate multiple copies of an engineered single-chain version of VEGF site-specifically derivatized with trans-cyclooctene (scVEGF-TCO) to 140 nm FND. The resulting targeting conjugates, FND-scVEGF, were then tested for functional activity of the scVEGF moieties through biochemical and tissue culture experiments and for selective tumor uptake in Balb/c mice with induced 4T1 carcinoma. We found that FND-scVEGF conjugates retain high affinity to VEGF receptors in cell culture experiments and observed preferential accumulation of FND-scVEGF in tumors relative to untargeted FND. Microspectroscopy provided unambiguous determination of FND within tissue by way of the unique spectral shape of nitrogen-vacancy induced fluorescence. These results validate and invite the use of targeted FND for diagnostic imaging and encourage further optimization of FND for fluorescence brightness.
关键词： Vascular Endothelial Growth Factor,Oncology,Targeted Fluorescence Imaging,Nanodiamond,Angiogenesis
更新于2025-11-21 11:24:58
-
Zwitterionic near-infrared fluorophore-conjugated epidermal growth factor for fast, real-time, and target-cell-specific cancer imaging
摘要： Epidermal growth factor receptor (EGFR) is overexpressed in many types of cancers, which is associated with metastatic potential and poor prognosis in cancer patients. Therefore, development of EGFR-targeted sensitive imaging probes has been a challenge in tumor targeting, image-guided cancer surgery, patient-selective anti-EGFR therapy, and efficient targeted therapies. Methods: We synthesized a zwitterionic near-infrared fluorophore (ATTO655)-conjugated epidermal growth factor (EGF) as a novel activatable molecular probe. Fluorescence OFF/ON property and EGFR-targeting specificity of EGF-ATTO655 as well as its utility in real-time near-infrared (NIR) fluorescence imaging of EGFR-positive cancers were evaluated using in vitro and in vivo studies. Results: When conjugated to EGF, the fluorescence of ATTO655 quenched efficiently by photo-induced electron transfer (PET) mechanism between the conjugated dyes and nearby amino acid quenchers (tryptophan/tyrosine residues), which was stably maintained at physiological pH and in the presence of serum for at least 17 h. The fluorescence of EGF-ATTO655 turned on by receptor-mediated endocytosis and subsequent disintegration of EGF in EGFR-positive A431 cancer cells, thereby enabling specific and real-time fluorescence imaging of EGFR-positive cancer cells. Consequently, EGFR-positive tumors could be clearly visualized 3 h post-injection with a significantly high tumor-to-background ratio (TBR = 6.37). Conclusion: This PET mechanism-based OFF/ON type of EGF probe showed great potential for rapid, real-time, and target-cell-specific imaging of EGFR-overexpressing cancers in vitro and in vivo.
关键词： photo-induced electron transfer,Epidermal growth factor,real-time cancer imaging,tumor-specific targeting
更新于2025-11-21 11:24:58
-
Wnt signaling induces neurite outgrowth in mouse retinal ganglion cells
摘要： Wingless-type (Wnt) signaling pathways mediate axonal growth and remodeling in the embryonic optic nerve, brain and spinal cord. Recent studies demonstrated that the canonical Wnt/β-catenin signaling pathway also induces axonal regeneration after injury in the optic nerve of adult animals. However, the molecular mechanisms of Wnt-mediated axonal growth are not well understood. Additionally, because Wnt signaling is stimulated in neurons as well as neighboring non-neuronal cells, the cell type(s) responsible for Wnt-induced axonal regeneration are not known. The objectives of this study were to investigate potential mechanisms and target cells of Wnt3a stimulated neurite growth using primary retinal ganglion cell (RGC) cultures. We demonstrated that Wnt3a ligand induced dose-dependent increases in average neurite length and number of neurites in RGCs. QPCR analysis of candidate mediators showed that Wnt3a-dependent neurite growth was associated with lower expression of Ripk1 and Ripk3 genes. Additionally, inhibiting Ripk1 signaling with Necrostatin-1s led to increased neurite number per cell but not increased neurite length. Therefore, Ripk signaling may be involved in mediating the effects of Wnt3a on neurite number but Ripk activity does not seem to be required for Wnt3a-dependent regulation of neurite length. This study shows that RGCs are direct cellular targets of Wnt3a-induced axonal growth, and we identified a novel association between Wnt signaling and Rip kinases in neurite formation.
关键词： retina,Ripk1,axon,retinal ganglion cell,neurite growth,Wnt signaling
更新于2025-11-21 11:24:58
-
Study on the element segregation and Laves phase formation in the laser metal deposited IN718 superalloy by flat top laser and gaussian distribution laser
摘要： The element segregation, Laves phase formation, and mechanical properties of the laser metal deposited IN718 superalloy by the flat top laser beam (FTLB) and gaussian distribution laser beam (GDLB) are studied. It is found that the Laves phase formation in the gaussian distribution laser deposited IN718 (GDLD-IN718) is substantially higher than that in the flat top laser deposited IN718 (FTLD-IN718). The higher production of the Laves phase in the GDLD-IN718 contributes to the higher microhardness and lower tensile strength (about 20% reduction) of the as-deposited IN718 than that of the FTLD-IN718. The element redistribution behavior in the laser rapid solidification under both of the lasers are also studied through the finite element simulation. The results show that the severe laser energy concentration in the center of the GDLB produces higher molten pool temperature, lower horizontal thermal gradient to vertical thermal gradient ratio (GX/GZ) of the solid-liquid interface. These typical thermal characteristic of the GDLB generated molten pool eventually results in a lower redistribution coefficient of the alloying elements and as a result, the interdendritic element segregation and Laves phase formation are dramatically improved in the GDLD-IN718. The present comparative study proves that the FTLB is more superior for the laser additive manufacturing than that of the GDLB.
关键词： Dendritic growth,Laser metal deposition,Element segregation,Redistribution coefficient,Laves phase
更新于2025-11-21 11:18:25
-
Hexagonal Boron Nitride Growth on Cu-Si Alloy: Morphologies and Large Domains
摘要： Controllable synthesis of high-quality hexagonal boron nitride (h-BN) is desired toward the industrial application of 2D devices based on van der Waals heterostructures. Substantial efforts are devoted to synthesize h-BN on copper through chemical vapor deposition, which has been successfully applied to grow graphene. However, the progress in synthesizing h-BN has been significantly retarded, and it is still challenging to realize millimeter-scale domains and control their morphologies reliably. Here, the nucleation density of h-BN on Cu is successfully reduced by over two orders of magnitude by simply introducing a small amount of silicon, giving rise to large triangular domains with maximum 0.25 mm lateral size. Moreover, the domain morphologies can be modified from needles, tree patterns, and leaf darts to triangles through controlling the growth temperature. The presence of silicon alters the growth mechanism from attachment-limited mode to diffusion-limited mode, leading to dendrite domains that are rarely observed on pure Cu. A phase-field model is utilized to reveal the growing dynamics regarding B-N diffusion, desorption, flux, and reactivity variables, and explain the morphology evolution. The work sheds lights on the h-BN growth toward large single crystals and morphology probabilities.
关键词： large domain,boron nitride,growth,morphology,chemical vapor deposition
更新于2025-11-21 11:18:25
-
Heterogeneous Growth of Continuous ZIF-8 Films on Low-Temperature Amorphous Silicon
摘要： Thin amorphous silicon films, deposited at low temperature by Inductively Coupled Plasma Chemical Vapor Deposition, have, for the first time, been employed as substrate for ZIF-8 growth. In order to investigate the role of the surface chemistry on the nucleation process, films have also been grown on other silicon-based substrates such as H-terminated Si(100), SiO2 and quartz. Film preparation was carried out at room temperature using a mixed Zn nitrate and imidazole solution in methanol or ethanol. Using methanol, continuous ZIF-8 films were obtained on amorphous Si and H-terminated Si(100), while less homogeneous films were formed on the other surfaces. In ethanol, slower growth rates occurred and thinner films, compared to the ones in methanol, were obtained. These slower rates highlight the different effects of the four surfaces on the growth process. These differences have been related to the silanol density of the surfaces and to the Lewis basic strength which affect imidazole moiety deprotonation. H-terminated Si(100) and amorphous Si turned out to be the most reactive surfaces, whereas on quartz and, especially, on SiO2 reactivity was much lower. Experimental results have been validated by the DFT modelling of the proton exchange, which takes place between the imidazole group and the surface. Finally, the VOCs adsorption capability of ZIF-8 films grown on amorphous silicon has been evaluated through temperature desorption experiments.
关键词： a-Si layer,ZIF-8 coating,growth mechanisms,VOCs adsorption,surface chemistry
更新于2025-11-21 11:03:25
-
One-step growth of reduced graphene oxide on arbitrary substrates
摘要： Reduced graphene oxide (rGO) has inherited the outstanding electronic, optical, thermal and mechanical properties of graphene to a large extent, while maintaining sufficient chemically active sites. Therefore, it has attracted a great deal of research attention in the fields of energy storage, electronics, photonics, catalysis, environmental engineering, etc. Currently, the most popular way to prepare rGO is to reduce graphene oxide, which is obtained by modified Hummer methods using tedious treatments in a harsh environment, to rGO flakes. Industrial applications demand advanced preparation methods that can mass produce highly uniform rGO sheets on arbitrary substrates. In this work, a one-step growth process is introduced that utilizes cellulose acetate as a precursor, without any catalysts, to produce uniform ultrathin rGO films on various substrates and free-standing rGO powders. Systematic spectroscopic and microscopic studies on the resulting rGO are performed. Prototypes of electronic and optoelectronic devices, such as field effect transistors (FETs), photodetectors, and humidity sensors, are fabricated and tested, demonstrating the intriguing applications of our rGO materials across a wide range of fields.
关键词： electronic devices,reduced graphene oxide,one-step growth,cellulose acetate,optoelectronic devices
更新于2025-11-21 11:03:25
-
Selective Growth of Ordered Hexagonal InN Nanorods
摘要： Well-ordered and vertically aligned InN nanorods with high aspect ratio are synthetized by hydride vapor phase epitaxy (HVPE) using the selective area growth (SAG) approach. The growth occurs through the apertures of a SiNx masked Ga-polar GaN/c-Al2O3 template for adjusted growth temperature and V/III ratio. The nanorods exhibit a hexagonal shape without any rotation around the growth axis. The wurtzite structure and the high crystalline quality of InN nanorods are confirmed by X-ray diffraction (XRD) as well as by high-resolution transmission electron microscopy (HR-TEM). Only few stacking faults are identified at the bottom part of the nanorods. Photoluminescence (PL) displays an emission peak centered at 0.77 eV which agrees with the band gap of InN. These promising achievements, which go far beyond the existing InN growth limitations, pave the way towards the integration of pure InN in future devices
关键词： Selective Area Growth,Hydride Vapor Phase Epitaxy,Indium Nitride,Nanorods
更新于2025-11-21 11:03:13
-
Template growth of Au/Ag nanocomposites on phosphorene for sensitive SERS detection of pesticides
摘要： We report template growth and dense packing of noble metallic nanoparticles on few-layer phosphorene for sensitive SERS detection. Phosphorene obtained by electrochemical exfoliation serves as both the template and reductant in the fabrication of noble metallic nanoparticles which are dispersed on phosphorene without aggregation or pile-up. The BP/Ag/Au and BP/Au/Ag nanocomposites with a nanogap structure exhibit excellent SERS sensitivity and reproducibility with respect to Rhodamine 6G (R6G). The BP/Au/Ag nanocomposite is further utilized as the SERS substrate for the detection of two fungicides, thiabendazole and thiram, and detection limits of 10-7 and 10-8 M are achieved. Template growth of Au/Ag nanocomposites is demonstrated to be a green strategy for the fabrication of SERS substrates and has large potential in applications such as pesticide detection.
关键词： template growth,nanocomposites,phosphorene,SERS
更新于2025-11-21 11:01:37