Publications by authors named "Zhiyuan Sun"

83 Publications

Topological Charge Pumping in Excitonic Insulators.

Phys Rev Lett 2021 Jan;126(2):027601

Department of Physics, Columbia University, 538 West 120th Street, New York, New York 10027, USA.

We show that in excitonic insulators with s-wave electron-hole pairing, an applied electric field (either pulsed or static) can induce a p-wave component to the order parameter, and further drive it to rotate in the s+ip plane, realizing a Thouless charge pump. In one dimension, each cycle of rotation pumps exactly two electrons across the sample. Higher dimensional systems can be viewed as a stack of one-dimensional chains in momentum space in which each chain crossing the Fermi surface contributes a channel of charge pumping. Physics beyond the adiabatic limit, including in particular dissipative effects is discussed.
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http://dx.doi.org/10.1103/PhysRevLett.126.027601DOI Listing
January 2021

Biomimetic Design of Mitochondria-Targeted Hybrid Nanozymes as Superoxide Scavengers.

Adv Mater 2021 Jan 22:e2006570. Epub 2021 Jan 22.

Key Laboratory of Bioactive Materials for the Ministry of Education, College of Life Sciences, State Key Laboratory of Medicinal Chemical Biology, Nankai University, Tianjin, 300071, China.

Development of enzyme mimics for the scavenging of excessive mitochondrial superoxide (O ) can serve as an effective strategy in the treatment of many diseases. Here, protein reconstruction technology and nanotechnology is taken advantage of to biomimetically create an artificial hybrid nanozyme. These nanozymes consist of ferritin-heavy-chain-based protein as the enzyme scaffold and a metal nanoparticle core as the enzyme active center. This artificial cascade nanozyme possesses superoxide dismutase- and catalase-like activities and also targets mitochondria by overcoming multiple biological barriers. Using cardiac ischemia-reperfusion animal models, the protective advantages of the hybrid nanozymes are demonstrated in vivo during mitochondrial oxidative injury and in the recovery of heart functionality following infarction via systemic delivery and localized release from adhesive hydrogels (i.e., cardiac patch), respectively. This study illustrates a de novo design strategy in the development of enzyme mimics and provides a promising therapeutic option for alleviating oxidative damage in regenerative medicine.
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http://dx.doi.org/10.1002/adma.202006570DOI Listing
January 2021

Nonlinear Spectroscopy of Collective Modes in an Excitonic Insulator.

Phys Rev Lett 2020 Dec;125(25):257601

Center for Computational Quantum Physics, Flatiron Institute, 162 Fifth Avenue, New York, New York 10010, USA.

The nonlinear optical response of an excitonic insulator coupled to lattice degrees of freedom is shown to depend in strong and characteristic ways on whether the insulating behavior originates primarily from electron-electron or electron-lattice interactions. Linear response optical signatures of the massive phase mode and the amplitude (Higgs) mode are identified. Upon nonlinear excitation resonant to the phase mode, a new in-gap mode at twice the phase mode frequency is induced, leading to a huge second harmonic response. Excitation of in-gap phonon modes leads to different and much smaller effects. A Landau-Ginzburg theory analysis explains these different behaviors and reveals that a parametric resonance of the strongly excited phase mode is the origin of the photoinduced mode in the electron-dominant case. The difference in the nonlinear optical response serves as a measure of the dominant mechanism of the ordered phase.
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http://dx.doi.org/10.1103/PhysRevLett.125.257601DOI Listing
December 2020

Hyperbolic Cooper-Pair Polaritons in Planar Graphene/Cuprate Plasmonic Cavities.

Nano Lett 2021 Jan 15;21(1):308-316. Epub 2020 Dec 15.

Department of Physics, Columbia University, New York, New York 10027, United States.

Hyperbolic Cooper-pair polaritons (HCP) in cuprate superconductors are of fundamental interest due to their potential for providing insights into the nature of unconventional superconductivity. Here, we critically assess an experimental approach using near-field imaging to probe HCP in BiSrCaCuO (Bi-2212) in the presence of graphene surface plasmon polaritons (SPP). Our simulations show that inherently weak HCP features in the near-field can be strongly enhanced when coupled to graphene SPP in layered graphene/hexagonal boron nitride (hBN)/Bi-2212 heterostructures. This enhancement arises from our multilayered structures effectively acting as plasmonic cavities capable of altering collective modes of a layered superconductor by modifying its electromagnetic environment. The degree of enhancement can be selectively controlled by tuning the insulating spacer thickness with atomic precision. Finally, we verify the expected renormalization of room-temperature graphene SPP using near-field infrared imaging. Our modeling, augmented with data, attests to the validity of our approach for probing HCP modes in cuprate superconductors.
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http://dx.doi.org/10.1021/acs.nanolett.0c03684DOI Listing
January 2021

Charge-Transfer Plasmon Polaritons at Graphene/α-RuCl Interfaces.

Nano Lett 2020 Dec 9;20(12):8438-8445. Epub 2020 Nov 9.

Department of Physics, Columbia University, New York, New York 10027, United States.

Nanoscale charge control is a key enabling technology in plasmonics, electronic band structure engineering, and the topology of two-dimensional materials. By exploiting the large electron affinity of α-RuCl, we are able to visualize and quantify massive charge transfer at graphene/α-RuCl interfaces through generation of charge-transfer plasmon polaritons (CPPs). We performed nanoimaging experiments on graphene/α-RuCl at both ambient and cryogenic temperatures and discovered robust plasmonic features in otherwise ungated and undoped structures. The CPP wavelength evaluated through several distinct imaging modalities offers a high-fidelity measure of the Fermi energy of the graphene layer: = 0.6 eV ( = 2.7 × 10 cm). Our first-principles calculations link the plasmonic response to the work function difference between graphene and α-RuCl giving rise to CPPs. Our results provide a novel general strategy for generating nanometer-scale plasmonic interfaces without resorting to external contacts or chemical doping.
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http://dx.doi.org/10.1021/acs.nanolett.0c03466DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7729890PMC
December 2020

Influence of Polylactide (PLA) Stereocomplexation on the Microstructure of PLA/PBS Blends and the Cell Morphology of Their Microcellular Foams.

Polymers (Basel) 2020 Oct 15;12(10). Epub 2020 Oct 15.

Queen Mary University of London Engineering School, Northwestern Polytechnical University, Xi'an 710129, China.

Polylactide foaming materials with promising biocompatibility balance the lightweight and mechanical properties well, and thus they can be desirable candidates for biological scaffolds used in tissue engineering. However, the cells are likely to coalesce and collapse during the foaming process of polylactide (PLA) due to its intrinsic low melt strength. This work introduces a unique PLA stereocomplexation into the microcellular foaming of poly (l-lactide)/poly (butylene succinate) (PLLA/PBS) based on supercritical carbon dioxide. The rheological properties of PLA/PBS with 5 wt% or 10 wt% poly (d-lactide) (PDLA) present enhanced melt strength owing to the formation of PLA stereocomplex crystals (sc-PLA), which act as physical pseudo-cross-link points in the molten blends by virtue of the strong intermolecular interaction between PLLA and the added PDLA. Notably, the introduction of either PBS or PDLA into the PLLA matrix could enhance its crystallization, while introducing both in the blend triggers a decreasing trend in the PLA crystallinity, which it is believed occurs due to the constrained molecular chain mobility by formed sc-PLA. Nevertheless, the enhanced melt strength and decreased crystallinity of PLA/PBS/PDLA blends are favorable for the microcellular foaming behavior, which enhanced the cell stability and provided amorphous regions for gas adsorption and homogeneous nucleation of PLLA cells, respectively. Furthermore, although the microstructure of PLA/PBS presents immiscible sea-island morphology, the miscibility was improved while the PBS domains were also refined by the introduction of PDLA. Overall, with the addition of PDLA into PLA/10PBS blends, the microcellular average cell size decreased from 3.21 to 0.66 μm with highest cell density of 2.23 × 10 cells cm achieved, confirming a stable growth of cells was achieved and more cell nucleation sites were initiated on the heterogeneous interface.
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http://dx.doi.org/10.3390/polym12102362DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7602427PMC
October 2020

Lipolysis by downregulating miR-92a activates the Wnt/β-catenin signaling pathway in hypoxic rats.

Biomed Rep 2020 Oct 4;13(4):33. Epub 2020 Aug 4.

Biology Center, China Institute of Sport Science, Beijing 100061, P.R. China.

The aim of the present study was to investigate the role of miR-92a in lipid metabolism in hypoxic rats. Microarray analysis and reverse transcription-quantitative (RT-q)PCR were used to detect changes in the mRNA expression levels of miR-92a in the epididymal fat of hypoxic and normoxic rats. The downstream target mRNA of miR-92a was predicted using bioinformatics analysis and verified using a dual luciferase reporter assay. Changes in the expression of frizzled (Fzd)10 and c-Myc in the epididymal fat were detected using RT-qPCR and western blotting. Microarray analysis and RT-qPCR results showed that the expression of miR-92a was significantly lower in the fat tissues of the hypoxic rats compared with the normoxic rats. The results of the dual luciferase reporter assay showed that the target gene of miR-92a was Fzd10, which is an acceptor in the Wnt pathway. Fzd10 expression was upregulated in the hypoxic rats. The mRNA expression levels of c-Myc, which is located downstream of the Wnt pathway, was increased significantly. The increase in the mRNA and protein expression levels of Fzd10 and c-Myc may be associated with miR-92a downregulation. Downregulation of miR-92a in-turn may result in lipolysis through the regulation of the Wnt/β-catenin signaling pathway, and thus weight loss in the rats.
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http://dx.doi.org/10.3892/br.2020.1340DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7418506PMC
October 2020

Femtosecond exciton dynamics in WSe optical waveguides.

Nat Commun 2020 Jul 16;11(1):3567. Epub 2020 Jul 16.

Department of Physics, Columbia University, New York, NY, 10027, USA.

Van-der Waals (vdW) atomically layered crystals can act as optical waveguides over a broad range of the electromagnetic spectrum ranging from Terahertz to visible. Unlike common Si-based waveguides, vdW semiconductors host strong excitonic resonances that may be controlled using non-thermal stimuli including electrostatic gating and photoexcitation. Here, we utilize waveguide modes to examine photo-induced changes of excitons in the prototypical vdW semiconductor, WSe, prompted by femtosecond light pulses. Using time-resolved scanning near-field optical microscopy we visualize the electric field profiles of waveguide modes in real space and time and extract the temporal evolution of the optical constants following femtosecond photoexcitation. By monitoring the phase velocity of the waveguide modes, we detect incoherent A-exciton bleaching along with a coherent optical Stark shift in WSe.
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http://dx.doi.org/10.1038/s41467-020-17335-wDOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7367278PMC
July 2020

Stress Response Simulated by Continuous Injection of ACTH Attenuates Lipopolysaccharide-Induced Inflammation in Porcine Adrenal Gland.

Front Vet Sci 2020 26;7:315. Epub 2020 Jun 26.

Co-innovation Center for Sustainable Forestry in Southern China, College of Forestry, Nanjing Forestry University, Nanjing, China.

On modern farms, animals are at high risk of bacterial invasion due to environmental stress factors. The adrenal gland is the terminal organ of the stress response. The crosstalk between adrenal endocrine stress and innate immune response is critical for the maintenance of immune homeostasis during inflammation. Thus, it's important to explore whether stresses play a pivotal role in lipopolysaccharide (LPS)-induced inflammatory response in the porcine adrenal gland. Thirty-days-old Duroc × Landrace × Large White crossbred piglets (12 ± 0.5 kg) were randomly allocated into four groups in a 2 × 2 factorial arrangement of treatments, including ACTH pretreatment (with or without ACTH injection) and LPS challenge (with or without LPS injection). Each group consisted of six male piglets. The results showed that our LPS preparation alone induced mRNA expressions of IL-1β, IL-6, TNF-α, IL-10, COX-2, TLR2, TLR4, and GR ( < 0.05). ACTH pretreatment downregulated the TLR2 mRNA and IL-6 protein level induced by our LPS preparation significantly ( < 0.05) by one-way ANOVA analysis. Treatment with LPS alone extremely significantly decreased ssc-miR-338 levels ( < 0.01). Interaction of ACTH × LPS was significant for cNOS level ( = 0.011) and ssc-miR-338 expression ( = 0.04) by two-way ANOVA analysis. The LPS treatment significantly downregulated cNOS levels ( < 0.01), which was significantly attenuated by ACTH pretreatment ( < 0.05). Lipopolysaccharide alone did not affect ssc-miR-146b expression levels compared to that in the vehicle group. However, ACTH pretreatment in combination with LPS significantly increased this micro-RNA expression ( < 0.05). TLRs 1-10 were all expressed in adrenal tissue. The LPS challenge alone induced remarkable compensatory mitochondrial damages at the ultrastructural level, which was alleviated by ACTH pretreatment. Accordingly, ACTH pretreatment was able to block LPS-induced secretion of local adrenal cortisol ( < 0.05). Taken together, our results demonstrate that ACTH pretreatment seems to attenuate LPS-induced mitochondria damage and inflammation that decreased cNOS activity in the adrenal gland and ultimately returned local adrenal cortisol to basal levels at 6 h post LPS injection.
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http://dx.doi.org/10.3389/fvets.2020.00315DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7333078PMC
June 2020

Effects of dietary fish meal replacement by fermented moringa (Moringa oleifera Lam.) leaves on growth performance, nonspecific immunity and disease resistance against Aeromonas hydrophila in juvenile gibel carp (Carassius auratus gibelio var. CAS III).

Fish Shellfish Immunol 2020 Jul 28;102:430-439. Epub 2020 Apr 28.

Co-Innovation Center for Sustainable Forestry in Southern China, Nanjing Forestry University, 159 Longpan Road, Nanjing, Jiangsu, 210037, PR China. Electronic address:

This study was aimed to evaluate the effects of partial replacement of fish meal by fermented moringa leaves (FMLs) on growth performance, serum biochemistry, antioxidant status, nonspecific immunity, and resistance against Aeromonas hydrophila in juvenile gibel carp (Carassius auratus gibelio var. CAS III). Four isonitrogenous and isoenergetic balanced diets, including three FML diets (substituting 20%, 40%, 60% of the fish meal in basal diet, F20, F40 and F60, respectively) and a basal diet (a diet containing 10% fish meal) were used. Each diet was randomly allocated to four fish groups (F20, F40, F60 and control) reared in a recirculating system. After 50 days of the feeding trial, fish were challenged by A. hydrophila. The result revealed that final mean body weight (FBW), weight gain rate (WGR), specific growth rate (SGR), feed efficiency (FE) and survival rate (SR) were significantly increased (P < 0.05) in F20 and F40 groups compared with the control group. Decreased hepatosomatic index (HSI), body crude lipid, serum aspartate transaminase (AST) and serum alanine aminotransferase (ALT) activities, and increased serum alkaline phosphatase (AKP) and serum glutathione peroxidase (GPx) activities were observed in F40 and F60 groups compared with the control and F20 groups. All FMLs-supplemented groups increased (P < 0.05) serum superoxide dismutase (SOD), catalase (CAT) and lysozyme activities, complement component 3 (C3) and serum immunoglobulin M (IgM) concentration, or decreased serum malondialdehyde (MDA) and protein carbonyl (PCC) contents (P < 0.05). After the challenge test, the significant downregulation of toll-like receptors2 (TLR2), tumor necrosis factor-α (TNF-α), interleukin (IL)-1β and IL-8 mRNA transcription levels was observed in spleens of FMLs supplemented groups. Dietary F40 and F60 showed higher (P < 0.05) relative percent survival (RPS) (48.72% and 43.59%, respectively) against A. hydrophila infection than control. These results indicate that, as a dietary fish meal substitute, FMLs enhance the growth, and antioxidant and immune response, and regulate the expression of immune-related genes and increase disease resistance against A. hydrophila via TLR2 pathway in gibel carp, with greatest effects of 40% fish meal substitution.
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http://dx.doi.org/10.1016/j.fsi.2020.04.051DOI Listing
July 2020

A Novel Model System for Understanding Anticancer Activity of Hypoxia-Activated Prodrugs.

Mol Pharm 2020 06 11;17(6):2072-2082. Epub 2020 May 11.

Key Laboratory of Bioactive Materials, Ministry of Education, College of Life Sciences, and State Key Laboratory of Medicinal Chemical Biology, Nankai University, Tianjin 300071, China.

Reports on the comprehensive factors for design considerations of hypoxia-activated prodrugs (HAPs) are rare. We introduced a new model system composed of a series of highly water-soluble HAPs, providing a platform to comprehensively understand the interaction between HAPs and hypoxic biosystems. Specifically, four kinds of new HAPs were designed and synthesized, containing the same biologically active moiety but masked by different bioreductive groups. Our results demonstrated that the activity of the prodrugs was strongly dependent on not only the molecular structure but also the hypoxic tumor microenvironment. We found the presence of a direct linear relationship between cytotoxicity of the HAPs and the reduction potential of whole molecule/oxygen concentration/reductase expression. Moreover, limited blood vasculature in hypoxic regions was also a critical barrier for effective activation of the HAPs. This study offers a comprehensive insight into understanding the design factors required for HAPs.
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http://dx.doi.org/10.1021/acs.molpharmaceut.0c00232DOI Listing
June 2020

Exploring Factors Influencing Injury Severity of Vehicle At-fault Accidents: A Comparative Analysis of Passenger and Freight Vehicles.

Int J Environ Res Public Health 2020 02 12;17(4). Epub 2020 Feb 12.

Institute of Transportation Engineering and Geomatics, Tsinghua University, Beijing 100084, China.

The objective of this study is to find factors influencing the injury severity of vehicle at-fault accidents in Shenyang (China), and discuss the commonalities and differences between passenger and freight vehicle accidents. We analyzed 1647 traffic accidents from 2015 to 2017, in which motor vehicles were fully or mainly responsible, including 1164 traffic accidents caused by passenger vehicles and 483 traffic accidents caused by freight vehicles. Twenty influencing factors from the aspects of accident, driver, time, space and environmental attributes are analyzed to find their statistical connection with injury severity using the binary logistic regression model. For passenger vehicles, five influencing factors (side collision; illegal act while driving; hit-and-run; season and administrative division), showed statistically significant correlations with the injury severity. For freight vehicles, three influencing factors (illegal act while driving; season and administrative division), showed statistically significant correlations with the injury severity. Illegal act while driving is the only common influencing factor for the injury severity of both passenger and freight vehicle accidents. Side collision and hit-and-run are significant influencing factors for the injury severity of passenger vehicle accidents, but not for freight vehicle accidents. Season and administrative division present different results on influencing passenger and freight vehicle accidents. Based on these results, measures including driver education and road infrastructure improvement could be implemented to reduce the injury severity of accidents in passenger and freight vehicles.
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http://dx.doi.org/10.3390/ijerph17041146DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7068512PMC
February 2020

Hypoxia-tropic nanozymes as oxygen generators for tumor-favoring theranostics.

Biomaterials 2020 02 18;230:119635. Epub 2019 Nov 18.

Key Laboratory of Bioactive Materials, Ministry of Education, College of Life Sciences, and State Key Laboratory of Medicinal Chemical Biology, Nankai University, Tianjin, 300071, China; Joint Laboratory of Nanozymes, College of Life Sciences, Nankai University, Tianjin, 300071, China. Electronic address:

Oxygen deficiency is the main obstacle of hypoxia-related theranostics, thus this is a considerable amount of research focusing on the development of methods to supply oxygen by taking advantage of hypoxia-responsive properties of nanoparticles. However, strategies to properly penetrate hypoxic regions by the nanoparticles remains an unmet challenge. In this work, a biomimetic nanozyme capable of possessing catalase-like activity and the efficient direct penetration of hypoxic areas in tumor tissues was developed to supply oxygen based on catalytic tumor microenvironment-responsive reaction, providing substantial tumor hypoxia relief with nearly 3-fold reduction compared to untreated tumor tissues. To demonstrate the advantages of the nanozymes in overcoming hypoxia, a theranostic nanosystem model composed of the core/shell nanozymes and aggregation-induced emission (AIE) molecules was designed. The nanosystem was able to present multi-modal imaging of tumors and modulated the tumor microenvironment for improved photodynamic therapy (PDT) by cascade reactions of therapeutic effector molecules, thereby providing significantly enhanced therapeutic benefits in inhibiting tumor growth and lung metastasis of orthotopic breast cancer. This conceptual study showed the multifaceted features of biomimetic nanozymes as tumor therapeutics and demonstrated the encouraging potential for modulating hypoxia as an application for tumor theranostics.
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http://dx.doi.org/10.1016/j.biomaterials.2019.119635DOI Listing
February 2020

Photoenhanced metastable c-axis electrodynamics in stripe-ordered cuprate LaBaCuO.

Proc Natl Acad Sci U S A 2019 Oct 16;116(40):19875-19879. Epub 2019 Sep 16.

Department of Physics, University of California San Diego, La Jolla, CA 92093;

Quantum materials are amenable to nonequilibrium manipulation with light, enabling modification and control of macroscopic properties. Light-based augmentation of superconductivity is particularly intriguing. Copper-oxide superconductors exhibit complex interplay between spin order, charge order, and superconductivity, offering the prospect of enhanced coherence by altering the balance between competing orders. We utilize terahertz time-domain spectroscopy to monitor the c-axis Josephson plasma resonance (JPR) in LaBaCuO (x = 0.115) as a direct probe of superconductivity dynamics following excitation with near-infrared pulses. Starting from the superconducting state, c-axis polarized excitation with a fluence of 100 μJ/cm results in an increase of the far-infrared spectral weight by more than an order of magnitude as evidenced by a blueshift of the JPR, interpreted as resulting from nonthermal collapse of the charge order. The photoinduced signal persists well beyond our measurement window of 300 ps and exhibits signatures of spatial inhomogeneity. The electrodynamic response of this metastable state is consistent with enhanced superconducting fluctuations. Our results reveal that LaBaCuO is highly sensitive to nonequilibrium excitation over a wide fluence range, providing an unambiguous example of photoinduced modification of order-parameter competition.
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http://dx.doi.org/10.1073/pnas.1908368116DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6778182PMC
October 2019

High-throughput LC-MS quantitation of cell culture metabolites.

Biologicals 2019 Sep 7;61:44-51. Epub 2019 Aug 7.

Large Molecules Analytical Development, BioTherapeutics Development, Janssen Research & Development, LLC, Malvern, PA, 19355, USA. Electronic address:

Monitoring cell culture metabolites, including media components and cellular byproducts, during bio manufacturing is critical for gaining insights into cell growth, productivity and product quality. Historically, cell culture metabolite analysis was a complicated process requiring several orthogonal methods to cover the large number of metabolites with diverse properties over wide concentration ranges. These off-line analyses are time consuming and not suitable for real time bioreactor monitoring. In this study, we present a high-throughput LC-MS method with a 17-min cycle time that is capable of simultaneously monitoring 93 cell culture metabolites, including amino acids, nucleic acids, vitamins, sugars and others. This method has high precision and accuracy and has been successfully applied to the daily profiling of bioreactors and raw material qualification. Information obtained in these studies has been used to identify limiting amino acids during production, which guided adjustments to the feed strategy that prevented the potential misincorporation of amino acids. This type of metabolite profiling can be further utilized to build predictive process models for adaptive feedback control and pave the road for continuous manufacturing and real-time release testing.
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http://dx.doi.org/10.1016/j.biologicals.2019.07.003DOI Listing
September 2019

ZIPK mediates endothelial cell contraction through myosin light chain phosphorylation and is required for ischemic-reperfusion injury.

FASEB J 2019 08 10;33(8):9062-9074. Epub 2019 Jun 10.

Jiangsu Key Laboratory for Molecular and Medical Biotechnology, College of Life Sciences, Nanjing Normal University, Nanjing, China.

The paracellular gap formed by endothelial cell (EC) contraction is fundamental for endothelium permeability, but the mechanism underlying EC contraction has yet to be determined. Here, we identified the zipper-interacting protein kinase (ZIPK) as the kinase for EC contraction and myosin light chain (MLC) phosphorylation. Inhibition of ZIPK activity by pharmacological inhibitors and small interfering RNAs led to a significant decrease in the mono- and diphosphorylation of MLCs along with a contractile response to thrombin, suggesting an essential role of ZIPK in EC paracellular permeability. To assess the role of ZIPK , we established mouse lines with conditional deletion of gene. The endothelium-specific deletion of led to embryonic lethality, whereas the UBC-Cre-mediated deletion of by tamoxifen induction at adulthood caused no apparent phenotype. The induced deletion of significantly inhibited ischemia-reperfusion-induced blood-brain barrier dysfunction and neuronal injuries from middle cerebral artery occlusion and reperfusion, as evidenced by reduced infarct and edema volume, attenuated Evans blue dye leakage, and improved neuronal behavior. We thus concluded that ZIPK and its phosphorylation of MLC were required for EC contraction and ischemic neuronal injuries. ZIPK may be a prospective therapeutic target for stroke.-Zhang, Y., Zhang, C., Zhang, H., Zeng, W., Li, S., Chen, C., Song, X., Sun, J., Sun, Z., Cui, C., Cao, X., Zheng, L., Wang, P., Zhao, W., Zhang, Z., Xu, Y., Zhu, M., Chen, H. ZIPK mediates endothelial cell contraction through myosin light chain phosphorylation and is required for ischemic-reperfusion injury.
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http://dx.doi.org/10.1096/fj.201802052RRRDOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6662964PMC
August 2019

Broad-band high-gain room temperature photodetectors using semiconductor-metal nanofloret hybrids with wide plasmonic response.

Nanoscale 2019 Mar;11(13):6368-6376

Department of Applied Physics, the Hebrew University, Jerusalem, Edmond J. Safra Campus, Givat Ram, Jerusalem, 91904, Israel.

Semiconducting nanowires are widely studied as building blocks for electro-optical devices; however, their limited cross-section and hence photo-response hinder the utilization of their full potential. Herein, we present an opto-electronic device for broad spectral detection ranging from the visible (VIS) to the short wavelength infra-red (SWIR) regime, using SiGe nanowires coupled to a broadband plasmonic antenna. The plasmonic amplification is obtained by deposition of a metallic nanotip at the edge of a nanowire utilizing a bottom-up synthesis technique. The metallic nanotip is positioned such that both optical plasmonic modes and electrical detection paths are coupled, resulting in a specific detectivity improvement of ∼1000 compared to conventional SiGe NWs. Detectivity and high gain are also measured in the SWIR regime owing to the special plasmonic response. Furthermore, the temporal response is improved by ∼1000. The fabrication process is simple and scalable, and it relies on low-resolution and facile fabrication steps with minimal requirements for top-down techniques.
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http://dx.doi.org/10.1039/c9nr00385aDOI Listing
March 2019

Strain-Energy Release in Bent Semiconductor Nanowires Occurring by Polygonization or Nanocrack Formation.

ACS Nano 2019 Mar 1;13(3):3730-3738. Epub 2019 Mar 1.

Department of Materials Science and Engineering , Northwestern University , 2220 Campus Drive , Evanston , Illinois 60208-3108 , United States.

Strain engineering of semiconductors is used to modulate carrier mobility, tune the energy bandgap, and drive growth of self-assembled nanostructures. Understanding strain-energy relaxation mechanisms including phase transformations, dislocation nucleation and migration, and fracturing is essential to both exploit this degree of freedom and avoid degradation of carrier lifetime and mobility, particularly in prestrained electronic devices and flexible electronics that undergo large changes in strain during operation. Raman spectroscopy, high-resolution transmission electron microscopy, and electron diffraction are utilized to identify strain-energy release mechanisms of bent diamond-cubic silicon (Si) and zinc-blende GaAs nanowires, which were elastically strained to >6% at room temperature and then annealed at an elevated temperature to activate relaxation mechanisms. High-temperature annealing of bent Si-nanowires leads to the nucleation, glide, and climb of dislocations, which align themselves to form grain boundaries, thereby reducing the strain energy. Herein, Si nanowires are reported to undergo polygonization, which is the formation of polygonal-shaped grains separated by grain boundaries consisting of aligned edge dislocations. Furthermore, strain is shown to drive dopant diffusion. In contrast to the behavior of Si, GaAs nanowires release strain energy by forming nanocracks in regions of tensile strain due to the weakening of As-bonds. These insights into the relaxation behavior of highly strained crystals can inform the design of nanoelectronic devices and provide guidance on mitigating degradation.
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http://dx.doi.org/10.1021/acsnano.9b01231DOI Listing
March 2019

Optical signatures of Dirac nodal lines in NbAs.

Proc Natl Acad Sci U S A 2019 01 17;116(4):1168-1173. Epub 2018 Dec 17.

Department of Physics, Columbia University, New York, NY 10027.

Using polarized optical and magneto-optical spectroscopy, we have demonstrated universal aspects of electrodynamics associated with Dirac nodal lines that are found in several classes of unconventional intermetallic compounds. We investigated anisotropic electrodynamics of [Formula: see text] where the spin-orbit coupling (SOC) triggers energy gaps along the nodal lines. These gaps manifest as sharp steps in the optical conductivity spectra [Formula: see text] This behavior is followed by the linear power-law scaling of [Formula: see text] at higher frequencies, consistent with our theoretical analysis for dispersive Dirac nodal lines. Magneto-optics data affirm the dominant role of nodal lines in the electrodynamics of [Formula: see text].
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http://dx.doi.org/10.1073/pnas.1809631115DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6347680PMC
January 2019

Influence Factors on Injury Severity of Traffic Accidents and Differences in Urban Functional Zones: The Empirical Analysis of Beijing.

Int J Environ Res Public Health 2018 12 3;15(12). Epub 2018 Dec 3.

Institute of Transportation Engineering, Tsinghua University, Beijing 100084, China.

The objective of this study was to identify influence factors on injury severity of traffic accidents and discuss the differences in urban functional zones in Beijing. A total of 3982 sets of accident data in Beijing were analyzed from the perspective of whole city and different urban functional zones. From the aspects of accident attribute, occurrence time, infrastructure, management status, and environmental condition, the influence factors set of injury severity of traffic accidents in Beijing are set up in this paper, which include 17 influence factors. Based on Pearson's chi-squared test, factors are preselected. On the basis of binary logistic regression analysis, the impact of the value of influence factors on injury severity of traffic accidents is calibrated. Based on classification and regression tree analysis, the impact of influence factors is analyzed. Through Pearson's chi-squared test and binary logistic regression analysis, it is found that there are similarities and differences among different urban functional zones. There are two common influence factors, including accident type and cross-section position, and six personalized influence factors, including lighting conditions, visibility, signal control, road physical isolation facility, occurrence period and road type, and the other nine weak influence factors. The results of binary logistic regression analysis and classification and regression tree analysis are basically the same. The factors that should be paid attention to in different urban functional zones and the value of the factors that need special attention are determined by synthesizing two methods.
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http://dx.doi.org/10.3390/ijerph15122722DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6313644PMC
December 2018

[Change of bacterial community structure during cellulose degradation by the microbial consortium].

Sheng Wu Gong Cheng Xue Bao 2018 Nov;34(11):1794-1808

Heilongjiang Provincial Engineering Technology Research Center of Straws Resources Utilization, Heilongjiang Provincial Key Laboratory of Environmental Microbiology and Recycling of Agro-Waste in Cold Region, College of Life Science and Biotechnology, Heilongjiang Bayi Agricultural University, Daqing 163319, Heilongjiang, China.

In order to clarify dynamic change of microbial community composition and to identify key functional bacteria in the cellulose degradation consortium, we studied several aspects of the biodegradation of filter papers and rice straws by the microbial consortium, the change of substrate degradation, microbial biomass and pH of fermentation broth. We extracted total DNA of the microbial consortium in different degradation stages for high-throughput sequencing of amplicons of bacterial 16 S rRNA genes. Based on the decomposition characteristics test, we defined the 12th, 72nd and 168th hours after inoculation as the initial stage, peak stage and end stage of degradation, respectively. The microbial consortium was mainly composed of 1 phylum, 2 classes, 2 orders, 7 families and 11 genera. With cellulose degradation, bacteria in the consortium showed different growth trends. The relative abundance of Brevibacillus and Caloramator decreased gradually. The relative abundance of Clostridium, Bacillus, Geobacillus and Cohnella increased gradually. The relative abundance of Ureibacillus, Tissierella, Epulopiscium was the highest in peak stage. The relative abundance of Paenibacillus and Ruminococcus did not change obviously in each stage. Above-mentioned 11 main genera all belonged to Firmicutes, which are thermophilic, broad pH adaptable and cellulose or hemicellulose degradable. During cellulose degradation by the microbial consortium, aerobic bacteria were dominant functional bacteria in the initial stage. However, the relative abundance of anaerobic bacteria increased gradually in middle and end stage, and replaced aerobic bacteria to become main bacteria to degrade cellulose.
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http://dx.doi.org/10.13345/j.cjb.180061DOI Listing
November 2018

Liposomes encapsulated dimethyl curcumin regulates dipeptidyl peptidase I activity, gelatinase release and cell cycle of spleen lymphocytes in-vivo to attenuate collagen induced arthritis in rats.

Int Immunopharmacol 2018 Dec 5;65:511-521. Epub 2018 Nov 5.

The School of Pharmaceutical Engineering and Life Science, Changzhou University, Jiangsu 213164, China; The School of Medicine, the University of Southampton, Southampton SO16 6YD, UK. Electronic address:

Rheumatoid arthritis (RA) is an autoimmune disease and characterized by the excessive cell proliferation, abnormal cell cycle of lymphocytes and synovial cells. The therapeutic effects of curcumin in active RA patients were reported, but limited by its insolubility and rapid systemic elimination. Dimethyl curcumin (DiMC) is a metabolically stable analogue of curcum with anti-inflammatory property. In this study, liposomes encapsulated dimethyl curcumin (Lipo-DiMC) was prepared to improve the bioavailability and metabolic-stability; collagen induced arthritis (CIA) rat model was employed to investigate the effects of Lipo-DiMC treatments during CIA progress. Physical assessments and routine-blood-test were performed. Fresh spleen lymphocytes were isolated from normal, CIA and Lipo-DiMC-treated CIA rats; flow-cytometry for cell-cycle analysis, western-blotting for intracellular signal pathway protein expressions, gelatin-zymography for matrix-metalloproteases 2/9 (MMP-2/9) and GF-AFC for dipeptidyl-peptidase I (DPPI) activity assay. Compared with untreated CIA rats, Lipo-DiMC treatments relieved paw-swellings, suppressed the increments of immunocytes numbers and inhibited DPPI and MMP-2/9 over-activity in blood. Lipo-DiMC adjusted CIA-induced cell cycle dysfunction at G0/G1-phase and S-phase of spleen lymphocytes for CIA rats. The intracellular expression-trends of P38, P21, Bcl-2, JNK-1 and DPPI of spleen lymphocytes were observed during CIA progress with and without Lipo-DiMC administrations. Lipo-DiMC exhibited its therapeutic functions by attenuating CIA development in rats, associated with down-regulating CIA-induced lymphocytes numbers, inhibiting over-expressed of DPPI and MMP-2/9, and adjusting cell cycles. These findings provide a new insight into the mechanism of Lipo-DiMC treatment in CIA rat model and suggest that Lipo-DiMC could be considered as a potential drug for RA treatment.
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http://dx.doi.org/10.1016/j.intimp.2018.10.039DOI Listing
December 2018

Charge Separation at Mixed-Dimensional Single and Multilayer MoS/Silicon Nanowire Heterojunctions.

ACS Appl Mater Interfaces 2018 May 4;10(19):16760-16767. Epub 2018 May 4.

Layered two-dimensional (2-D) semiconductors can be combined with other low-dimensional semiconductors to form nonplanar mixed-dimensional van der Waals (vdW) heterojunctions whose charge transport behavior is influenced by the heterojunction geometry, providing a new degree of freedom to engineer device functions. Toward that end, we investigated the photoresponse of Si nanowire/MoS heterojunction diodes with scanning photocurrent microscopy and time-resolved photocurrent measurements. Comparison of n-Si/MoS isotype heterojunctions with p-Si/MoS heterojunction diodes under varying biases shows that the depletion region in the p-n heterojunction promotes exciton dissociation and carrier collection. We measure an instrument-limited response time of 1 μs, which is 10 times faster than the previously reported response times for planar Si/MoS devices, highlighting the advantages of the 1-D/2-D heterojunction. Finite element simulations of device models provide a detailed understanding of how the electrostatics affect charge transport in nanowire/vdW heterojunctions and inform the design of future vdW heterojunction photodetectors and transistors.
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http://dx.doi.org/10.1021/acsami.8b03133DOI Listing
May 2018

In vitro photodynamic inactivation effects of benzylidene cyclopentanone photosensitizers on clinical fluconazole-resistant Candida albicans.

Photodiagnosis Photodyn Ther 2018 Jun 4;22:178-186. Epub 2018 Apr 4.

Department of Laser Medicine, Chinese PLA General Hospital, Beijing 100853, China. Electronic address:

Background: The incidence of Candida infections has increased for various reasons, including, the more frequent use of immunosuppresants or broad-spectrum antibiotics. Photodynamic inactivation (PDI) is a promising approach for treating localized Candida infections.

Methods: The PDI efficacies of three benzylidene cyclopentanone-based (BCB) photosensitizers (PSs: P1, P2 and Y1) against three fluconazole-resistant C. albicans (cal-1, cal-2, and cal-3) and one control C. albicans (ATCC 90028), respectively, were evaluated using an established plate dilution method. The binding of PSs to C. albicans was determined by fluorescence spectroscopy. The mechanism of antifungal PDI was investigated using confocal laser scanning microscopy (CLSM) and transmission electron microscopy (TEM).

Results: Three BCB PSs all bound rapidly to C. albicans. After incubation with PSs for 30 min and irradiation with a 532 nm laser for 10 min (40 mW cm, 24 J cm), the fungicidal activity was achieved as 7.5 μM for P1 and P2, and 25 μM for Y1. CLSM confirmed that P1 and Y1 were located in intracellular components, including mitochondria, while P2 bound to the protoplast exterior and failed to enter the cells. TEM revealed the damage of mitochondria ultrastructures after P1- or Y1-mediated PDI, consistenting with the CLSM results. However, most cells became edematous, enlarged or deformation after P2-mediated PDI.

Conclusions: The three BCB PSs all have remarkable PDI effects on C. albicans. The best effect is obtained by P1, which has one cationic charge with a proper lipophilicity. The respective subcellular localization of the three PSs led to different PDI mechanisms.
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http://dx.doi.org/10.1016/j.pdpdt.2018.04.001DOI Listing
June 2018

Template-Assisted Scalable Nanowire Networks.

Nano Lett 2018 04 30;18(4):2666-2671. Epub 2018 Mar 30.

Laboratoire des Matériaux Semiconducteurs , École Polytechnique Fédérale de Lausanne, EPFL , 1015 Lausanne , Switzerland.

Topological qubits based on Majorana Fermions have the potential to revolutionize the emerging field of quantum computing by making information processing significantly more robust to decoherence. Nanowires are a promising medium for hosting these kinds of qubits, though branched nanowires are needed to perform qubit manipulations. Here we report a gold-free templated growth of III-V nanowires by molecular beam epitaxy using an approach that enables patternable and highly regular branched nanowire arrays on a far greater scale than what has been reported thus far. Our approach relies on the lattice-mismatched growth of InAs on top of defect-free GaAs nanomembranes yielding laterally oriented, low-defect InAs and InGaAs nanowires whose shapes are determined by surface and strain energy minimization. By controlling nanomembrane width and growth time, we demonstrate the formation of compositionally graded nanowires with cross-sections less than 50 nm. Scaling the nanowires below 20 nm leads to the formation of homogeneous InGaAs nanowires, which exhibit phase-coherent, quasi-1D quantum transport as shown by magnetoconductance measurements. These results are an important advance toward scalable topological quantum computing.
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http://dx.doi.org/10.1021/acs.nanolett.8b00554DOI Listing
April 2018

Universal linear and nonlinear electrodynamics of a Dirac fluid.

Proc Natl Acad Sci U S A 2018 03 12;115(13):3285-3289. Epub 2018 Mar 12.

Department of Physics, University of California, San Diego, La Jolla, CA 92093.

A general relation is derived between the linear and second-order nonlinear ac conductivities of an electron system in the hydrodynamic regime of frequencies below the interparticle scattering rate. The magnitude and tensorial structure of the hydrodynamic nonlinear conductivity are shown to differ from their counterparts in the more familiar kinetic regime of higher frequencies. Due to universality of the hydrodynamic equations, the obtained formulas are valid for systems with an arbitrary Dirac-like dispersion, ranging from solid-state electron gases to free-space plasmas, either massive or massless, at any temperature, chemical potential, or space dimension. Predictions for photon drag and second-harmonic generation in graphene are presented as one application of this theory.
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http://dx.doi.org/10.1073/pnas.1717010115DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5879671PMC
March 2018

Nanoscale Mapping and Spectroscopy of Nonradiative Hyperbolic Modes in Hexagonal Boron Nitride Nanostructures.

Nano Lett 2018 03 21;18(3):1628-1636. Epub 2018 Feb 21.

Department of Mechanical Engineering , Vanderbilt University , 101 Olin Hall , Nashville , Tennessee 37212 , United States.

The inherent crystal anisotropy of hexagonal boron nitride (hBN) provides the ability to support hyperbolic phonon polaritons, that is, polaritons that can propagate with very large wave vectors within the material volume, thereby enabling optical confinement to exceedingly small dimensions. Indeed, previous research has shown that nanometer-scale truncated nanocone hBN cavities, with deep subdiffractional dimensions, support three-dimensionally confined optical modes in the mid-infrared. Because of optical selection rules, only a few of the many theoretically predicted modes have been observed experimentally via far-field reflection and scattering-type scanning near-field optical microscopy (s-SNOM). The photothermal induced resonance (PTIR) technique probes optical and vibrational resonances overcoming weak far-field emission by leveraging an atomic force microscope (AFM) probe to transduce local sample expansion caused by light absorption. Here we show that PTIR enables the direct observation of previously unobserved, dark hyperbolic modes of hBN nanostructures. Leveraging these optical modes and their wide range of angular and radial momenta could provide a new degree of control over the electromagnetic near-field concentration, polarization in nanophotonic applications.
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http://dx.doi.org/10.1021/acs.nanolett.7b04476DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6140337PMC
March 2018

No differences in brain microstructure between young KIBRA-C carriers and non-carriers.

Oncotarget 2018 Jan 16;9(1):1200-1209. Epub 2017 Dec 16.

Department of Radiology, Qilu Hospital of Shandong University, Jinan 250012, China.

KIBRA rs17070145 polymorphism is associated with variations in memory function and the microstructure of related brain areas. Diffusion kurtosis imaging (DKI) as an extension of diffusion tensor imaging that can provide more information about changes in microstructure, based on the idea that water diffusion in biological tissues is heterogeneous due to structural hindrance and restriction. We used DKI to explore the relationship between KIBRA gene polymorphism and brain microstructure in young adults. We recruited 100 healthy young volunteers, including 53 TT carriers and 47 C allele carriers. No differences were detected between the TT homozygotes and C-allele carriers for any diffusion and kurtosis parameter. These results indicate KIBRA rs17070145 polymorphism likely has little or no effect on brain microstructure in young adults.
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http://dx.doi.org/10.18632/oncotarget.23348DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5787430PMC
January 2018

Doping of Self-Catalyzed Nanowires under the Influence of Droplets.

Nano Lett 2018 01 5;18(1):81-87. Epub 2017 Dec 5.

Department of Electronic and Electrical Engineering, University College London , London WC1E 7JE, United Kingdom.

Controlled and reproducible doping is essential for nanowires (NWs) to realize their functions. However, for the widely used self-catalyzed vapor-liquid-solid (VLS) growth mode, the doping mechanism is far from clear, as the participation of the nanoscale liquid phase makes the doping environment highly complex and significantly different from that of the thin film growth. Here, the doping mechanism of self-catalyzed NWs and the influence of self-catalytic droplets on the doping process are systematically studied using beryllium (Be) doped GaAs NWs. Be atoms are found for the first time to be incorporated into NWs predominantly through the Ga droplet that is observed to be beneficial for setting up thermodynamic equilibrium at the growth front. Be dopants are thus substitutional on Ga sites and redundant Be atoms are accumulated inside the Ga droplets when NWs are saturated, leading to the change of the Ga droplet properties and causing the growth of phase-pure zincblende NWs. This study is an essential step toward the design and fabrication of nanowire devices.
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http://dx.doi.org/10.1021/acs.nanolett.7b03366DOI Listing
January 2018

1-D Metal Nanobead Arrays within Encapsulated Nanowires via a Red-Ox-Induced Dewetting: Mechanism Study by Atom-Probe Tomography.

Nano Lett 2017 12 10;17(12):7478-7486. Epub 2017 Nov 10.

Department of Materials Science and Engineering, Northwestern University , 2220 Campus Drive, Evanston, Illinois 60208-3108, United States.

Metal nanoparticle arrays are excellent candidates for a variety of applications due to the versatility of their morphology and structure at the nanoscale. Bottom-up self-assembly of metal nanoparticles provides an important complementary alternative to the traditional top-down lithography method and makes it possible to assemble structures with higher-order complexity, for example, nanospheres, nanocubes, and core-shell nanostructures. Here we present a mechanism study of the self-assembly process of 1-D noble metal nanoparticles arrays, composed of Au, Ag, and AuAg alloy nanoparticles. These are prepared within an encapsulated germanium nanowire, obtained by the oxidation of a metal-germanium nanowire hybrid structure. The resulting structure is a 1-D array of equidistant metal nanoparticles with the same diameter, the so-called nanobead (NB) array structure. Atom-probe tomography and transmission electron microscopy were utilized to investigate the details of the morphological and chemical evolution during the oxidation of the encapsulated metal-germanium nanowire hybrid-structures. The self-assembly of nanoparticles relies on the formation of a metal-germanium liquid alloy and the migration of the liquid alloy into the nanowire, followed by dewetting of the liquid during shape-confined oxidation where the liquid column breaks-up into nanoparticles due to the Plateau-Rayleigh instability. Our results demonstrate that the encapsulating oxide layer serves as a structural scaffold, retaining the overall shape during the eutectic liquid formation and demonstrates the relationship between the oxide mechanical properties and the final structural characteristics of the 1-D arrays. The mechanistic details revealed here provide a versatile tool-box for the bottom-up fabrication of 1-D arrays nanopatterning that can be modified for multiple applications according to the RedOx properties of the material system components.
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http://dx.doi.org/10.1021/acs.nanolett.7b03391DOI Listing
December 2017