Publications by authors named "Yuwen Zeng"

11 Publications

  • Page 1 of 1

Diameter Dependence of Water Filling in Lithographically Segmented Isolated Carbon Nanotubes.

ACS Nano 2021 Feb 29;15(2):2778-2790. Epub 2021 Jan 29.

Department of Chemical Engineering, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, United States.

Although the structure and properties of water under conditions of extreme confinement are fundamentally important for a variety of applications, they remain poorly understood, especially for dimensions less than 2 nm. This problem is confounded by the difficulty in controlling surface roughness and dimensionality in fabricated nanochannels, contributing to a dearth of experimental platforms capable of carrying out the necessary precision measurements. In this work, we utilize an experimental platform based on the interior of lithographically segmented, isolated single-walled carbon nanotubes to study water under extreme nanoscale confinement. This platform generates multiple copies of nanotubes with identical chirality, of diameters from 0.8 to 2.5 nm and lengths spanning 6 to 160 μm, that can be studied individually in real time before and after opening, exposure to water, and subsequent water filling. We demonstrate that, under controlled conditions, the diameter-dependent blue shift of the Raman radial breathing mode (RBM) between 1 and 8 cm measures an increase in the interior mechanical modulus associated with liquid water filling, with no response from exterior water exposure. The observed RBM shift with filling demonstrates a non-monotonic trend with diameter, supporting the assignment of a minimum of 1.81 ± 0.09 cm at 0.93 ± 0.08 nm with a nearly linear increase at larger diameters. We find that a simple hard-sphere model of water in the confined nanotube interior describes key features of the diameter-dependent modulus change of the carbon nanotube and supports previous observations in the literature. Longer segments of 160 μm show partial filling from their ends, consistent with pore clogging. These devices provide an opportunity to study fluid behavior under extreme confinement with high precision and repeatability.
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http://dx.doi.org/10.1021/acsnano.0c08634DOI Listing
February 2021

Highly Ordered Two-Dimensional MoS Archimedean Scroll Bragg Reflectors as Chromatically Adaptive Fibers.

Nano Lett 2020 May 29;20(5):3067-3078. Epub 2020 Apr 29.

Department of Chemical Engineering, Massachusetts Institute of Technology, Cambridge, Massachusetts 02141, United States.

Nanostructured fibers provide a basis for a unique class of multifunctional textiles, composites, and membrane applications, including those capable of chromatic modulating because of their high aspect ratio, surface area, and processing capability. Here in, we utilize two-dimensional (2D) materials including molybdenum disulfide (MoS) and hexagonal boron nitride (hBN) to generate single layer Archimedean scroll fibers, possessing cross sections formed from a single 2D molecular layer. Chemical vapor deposited (CVD) monolayer MoS (0.29-0.33% in volume) and 226-259 nm-thick poly(methyl methacrylate) (PMMA) were used to create Bragg reflector fibers, exploiting the anisotropic function, exhibiting reflection at 630-709 nm, and verifying the highly ordered nanoinclusions. The Bragg reflectors show a memory response to heating and cooling, which switches the reflection wavelength from 629 to 698 nm. We simulate the reflection and transmission spectra of MoS/PMMA and MoS/polydimethylsiloxane layered composites to provide the design of scroll fiber composites using the transfer matrix methods. Moreover, we demonstrate the incorporation of a few-layer CVD hBN into the scroll fiber composite that emits photons at 576 nm. The highly oriented layered structures extend the capability of the fiber nanocomposites to take advantage of anisotropic optical, electrical, and thermal properties unique to 2D materials.
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http://dx.doi.org/10.1021/acs.nanolett.9b05004DOI Listing
May 2020

Automatic Diagnosis Based on Spatial Information Fusion Feature for Intracranial Aneurysm.

IEEE Trans Med Imaging 2020 05 4;39(5):1448-1458. Epub 2019 Nov 4.

Timely and accurate auxiliary diagnosis of intracranial aneurysm can help radiologist make treatment plans quickly, saving lives and cutting costs at the same time. At present, Digital Subtraction Angiography (DSA) is the gold standard for the diagnosis of intracranial aneurysm, but as radiologists interpret those imaging sequences frame by frame, misdiagnosis might occur. The utilization of computer-aided diagnosis (CAD) can ease the burdens of radiologists and improve the detection accuracy of aneurysms. In this article, a deep learning method is applied to detect the intracranial aneurysm in 3D Rotational Angiography (3D-RA) based on a spatial information fusion (SIF) method, and instead of a 3D vascular model, 2D image sequences are used. Given the intracranial aneurysm and vascular overlap having similar feature in the most time, rather than focusing on distinguishing them in one frame, the morphological differences between frames are considered as major feature. In the training data, consecutive frames of every imaging time series are extracted and concatenated in a specific way, so that the spatial contextual information could be embedded into a single two-dimensional image. This method enables the time series with obvious correlation between frames be directly trained on 2D convolutional neural network (CNN), instead of 3D-CNN with huge computational cost. Finally, we got an accuracy of 98.89%, with sensitivity and specificity of 99.38% and 98.19%, respectively, which proves the feasibility and availability of the SIF feature.
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http://dx.doi.org/10.1109/TMI.2019.2951439DOI Listing
May 2020

A CNN-based prototype method of unstructured surgical state perception and navigation for an endovascular surgery robot.

Med Biol Eng Comput 2019 Sep 20;57(9):1875-1887. Epub 2019 Jun 20.

Key Laboratory of Convergence Biomedical Engineering System and Healthcare Technology, The Ministry of Industry and Information Technology, School of Life Science, Beijing Institute of Technology, No.5, Zhongguancun South Street, Haidian District, Beijing, 100081, China.

Performance of robot-assisted endovascular surgery (ES) remains highly dependent on an individual surgeon's skills, due to common adoption of master-slave robotic structure. Surgeons' skill modeling and unstructured surgical state perception pose prohibitive challenges for an autonomous ES robot. In this paper, a novel convolutional neural network (CNN)-based framework is proposed to address these challenges for navigation of an ES robot based on surgeons' skill learning. An operating action probability estimator is proposed by integrating a two-dimensional CNN, with which the features of a surgical state image are extracted and then directly mapped to the action probability. A one-dimensional CNN with multi-input is developed to recognize the guide wire operating force condition. An eye-hand collaborative servoing algorithm is proposed to combine the outputs of these two networks and to control the robot under a closed-loop architecture. A real-world ES robot is employed for data collection and task performance evaluation in laboratory condition. Compared with the state of the art, the CNN-based method shows its capability of adapting to different situations and achieves similar success rate and average operating time. Robotic operation performs similar operating trajectory and maintains similar level of operating force with manual operation. The CNN-based method can be easily extended to many other surgical robots. Graphical abstract A surgeon's guide wire operating skills in endovascular surgery (ES) is learned by the proposed CNN-based method. Then, the learned model is used for autonomous control of a ES robot with surgical state input (images and operating force).
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http://dx.doi.org/10.1007/s11517-019-02002-0DOI Listing
September 2019

Concerted nucleophilic aromatic substitutions.

Nat Chem 2018 09 16;10(9):917-923. Epub 2018 Jul 16.

Department of Chemistry & Chemical Biology, Harvard University, Cambridge, MA, USA.

Nucleophilic aromatic substitution (SAr) is one of the most widely applied reaction classes in pharmaceutical and chemical research, providing a broadly useful platform for the modification of aromatic ring scaffolds. The generally accepted mechanism for SAr reactions involves a two-step addition-elimination sequence via a discrete, non-aromatic Meisenheimer complex. Here we use C/C kinetic isotope effect (KIE) studies and computational analyses to provide evidence that prototypical SAr reactions in fact proceed through concerted mechanisms. The KIE measurements were made possible by a new technique that leverages the high sensitivity of F as an NMR nucleus to quantitate the degree of isotopic fractionation. This sensitive technique permits the measurement of KIEs on 10 mg of natural abundance material in one overnight acquisition. As a result, it provides a practical tool for performing detailed mechanistic analyses of reactions that form or break C-F bonds.
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http://dx.doi.org/10.1038/s41557-018-0079-7DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6105541PMC
September 2018

Trifluoromethyl Benzoate: A Versatile Trifluoromethoxylation Reagent.

J Am Chem Soc 2018 06 25;140(22):6801-6805. Epub 2018 May 25.

Key Laboratory of Organofluorine Chemistry, Center for Excellence in Molecular Synthesis, Shanghai Institute of Organic Chemistry , University of Chinese Academy of Sciences, Chinese Academy of Sciences , 345 Ling-Ling Road , Shanghai 200032 , China.

Trifluoromethyl benzoate (TFBz) is developed as a new shelf-stable trifluoromethoxylation reagent, which can be easily prepared from inexpensive starting materials using KF as the only fluorine source. The synthetic potency of TFBz is demonstrated by trifluoromethoxylation-halogenation of arynes, nucleophilic substitution of alkyl (pseudo)halides, cross-coupling with aryl stannanes, and asymmetric difunctionalization of alkenes. The unprecedented trifluoromethoxylation-halogenation of arynes proceeds smoothly at room temperature with the aid of a crown ether-complexed potassium cation, which significantly stabilizes the trifluoromethoxide anion derived from TFBz.
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http://dx.doi.org/10.1021/jacs.8b04000DOI Listing
June 2018

Silver-Mediated Trifluoromethylthiolation-Iodination of Arynes.

Authors:
Yuwen Zeng Jinbo Hu

Org Lett 2016 Feb 5;18(4):856-9. Epub 2016 Feb 5.

Key Laboratory of Organofluorine Chemistry, Shanghai Institute of Organic Chemistry, Chinese Academy of Sciences , 345 Lingling Road, Shanghai 200032, China.

A one-pot trifluoromethylthiolation-iodination of arynes with trifluoromethylthiosilver (AgSCF3) and 1-iodophenylacetylene is described. This protocol allows rapid construction of o-trifluoromethylthiolated arene building blocks in moderate yields. These products were found to be excellent precursors for Yagupolskii-Umemoto-type electrophilic trifluoromethylation reagents.
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http://dx.doi.org/10.1021/acs.orglett.6b00142DOI Listing
February 2016

Recent Advances in the One-Step Synthesis of Distally Fluorinated Ketones.

Chemistry 2016 Mar 22;22(10):3210-3223. Epub 2015 Dec 22.

Key Laboratory of Organofluorine Chemistry, Shanghai Institute of Organic Chemistry, Chinese Academy of Sciences, 345 Ling-Ling Road, Shanghai, 200032, P. R. China.

Fluorinated ketones are intriguing compounds in synthetic chemistry and life science-related fields. The development of efficient methodologies to obtain these compounds is of significant importance and has therefore attracted considerable attention. This Minireview highlights recent progress made in the synthesis of fluorine-containing ketones, with an emphasis on those methods in which the construction of carbonyl groups is synergetic with distal (β-, γ-, δ-, etc.) incorporation of fluorine atoms or fluorinated groups.
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http://dx.doi.org/10.1002/chem.201504036DOI Listing
March 2016

Diphenyliodonium-Catalyzed Fluorination of Arynes: Synthesis of ortho-Fluoroiodoarenes.

Angew Chem Int Ed Engl 2015 Sep 23;54(37):10773-7. Epub 2015 Jul 23.

Key Laboratory of Organofluorine Chemistry, Shanghai Institute of Organic Chemistry, Chinese Academy of Sciences, 345 Ling-Ling Road, Shanghai 200032 (China).

Described is a one-pot vicinal fluorination-iodination of arynes at room temperature. The diphenyliodonium salt proved to be a privileged catalyst for this nucleophilic fluorination process using CsF as a fluorine source, and a subsequent facile electrophilic iodination with C4 F9 I was also found to be crucial to ensure the efficient fluorination. This new synthetic protocol has a broad substrate scope under mild reaction conditions.
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http://dx.doi.org/10.1002/anie.201503308DOI Listing
September 2015

Silver-catalyzed formal insertion of arynes into Rf-I bonds.

Authors:
Yuwen Zeng Jinbo Hu

Chemistry 2014 Jun 29;20(23):6866-70. Epub 2014 Apr 29.

Key Laboratory of Organofluorine Chemistry, Shanghai Institute of Organic Chemistry, Chinese Academy of Sciences, 345 Ling-Ling Road, Shanghai, 200032 (P.R. China).

An unprecedented silver-catalyzed formal insertion of arynes into Rf-I (Rf = CF3, C2F5) bonds has been developed. This protocol provides easy access to various ortho-perfluoroalkyl iodoarenes under mild conditions. In this insertion reaction, an ionic atom-transfer reaction of RfI occurs, and a silver-mediated metathesis process is involved in the efficient transfer of the electropositive iodine atom.
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http://dx.doi.org/10.1002/chem.201402846DOI Listing
June 2014

Silver-mediated trifluoromethylation-iodination of arynes.

J Am Chem Soc 2013 Feb 18;135(8):2955-8. Epub 2013 Feb 18.

Key Laboratory of Organofluorine Chemistry, Shanghai Institute of Organic Chemistry, Chinese Academy of Sciences, 345 Ling-Ling Road, Shanghai 200032, China.

An unprecedented silver-mediated vicinal trifluoromethylation-iodination of arynes that quickly introduces CF(3) and I groups onto aromatic rings in a single step to give o-trifluoromethyl iodoarenes has been developed. A new reactivity of AgCF(3) has been revealed, and 2,2,6,6-tetramethylpiperidine plays an important role in this difunctionalization reaction.
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http://dx.doi.org/10.1021/ja312711cDOI Listing
February 2013