Publications by authors named "Sylvia Xin Li"

5 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.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1021/acsnano.0c08634DOI Listing
February 2021

Enhancing Lithium Insertion with Electrostatic Nanoconfinement in a Lithography Patterned Precision Cell.

ACS Nano 2019 Jul 5;13(7):8481-8489. Epub 2019 Jul 5.

Department of Electrical Engineering , Yale University , New Haven , Connecticut 06511 , United States.

The rapidly growing demand for portable electronics, electric vehicles, and grid storage drives the pursuit of high-performance electrical energy storage (EES). A key strategy for improving EES performance is exploiting nanostructured electrodes that present nanoconfined environments of adjacent electrolytes, with the goal to decrease ion diffusion paths and increase active surface areas. However, fundamental gaps persist in understanding the interface-governed electrochemistry in such nanoconfined geometries, in part because of the imprecise and variable dimension control. Here, we report quantification of lithium insertion under nanoconfinement of the electrolyte in a precise lithography-patterned nanofluidic cell. We show a mechanism that enhances ion insertion under nanoconfinement, namely, selective ion accumulation when the confinement length is comparable to the electrical double layer thickness. The nanofabrication approach with uniform and accurate dimensional control provides a versatile model system to explore fundamental mechanisms of nanoscale electrochemistry, which could have an impact on practical energy storage systems.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1021/acsnano.9b04390DOI Listing
July 2019

A nanofluidic ion regulation membrane with aligned cellulose nanofibers.

Sci Adv 2019 Feb 22;5(2):eaau4238. Epub 2019 Feb 22.

Department of Materials Science and Engineering, University of Maryland College Park, College Park, MD 20742, USA.

The advancement of nanofluidic applications will require the identification of materials with high-conductivity nanoscale channels that can be readily obtained at massive scale. Inspired by the transpiration in mesostructured trees, we report a nanofluidic membrane consisting of densely packed cellulose nanofibers directly derived from wood. Numerous nanochannels are produced among an expansive array of one-dimensional cellulose nanofibers. The abundant functional groups of cellulose enable facile tuning of the surface charge density via chemical modification. The nanofiber-nanofiber spacing can also be tuned from ~2 to ~20 nm by structural engineering. The surface-charge-governed ionic transport region shows a high ionic conductivity plateau of ~2 mS cm (up to 10 mM). The nanofluidic membrane also exhibits excellent mechanical flexibility, demonstrating stable performance even when the membrane is folded 150°. Combining the inherent advantages of cellulose, this novel class of membrane offers an environmentally responsible strategy for flexible and printable nanofluidic applications.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1126/sciadv.aau4238DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6386557PMC
February 2019

Direct Observation of Charge Inversion in Divalent Nanofluidic Devices.

Nano Lett 2015 Aug 30;15(8):5046-51. Epub 2015 Jun 30.

§Department of Electrical Engineering, Pennsylvania State University, State College, Pennsylvania 16801, United States.

Solid-state nanofluidic devices have proven to be ideal systems for studying the physics of ionic transport at the nanometer length scale. When the geometrical confining size of fluids approaches the ionic Debye screening length, new transport phenomena occur, such as surface mediated transport and permselectivity. Prior work has explored these effects extensively in monovalent systems (e.g., predominantly KCl and NaCl). In this report, we present a new characterization method for the study of divalent ionic transport and have unambiguously observed divalent charge inversion at solid/fluid interfaces. This observation has important implications in applications ranging from biology to energy conversion.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1021/acs.nanolett.5b01115DOI Listing
August 2015

Voltage gated ion and molecule transport in engineered nanochannels: theory, fabrication and applications.

Nanotechnology 2014 Mar 25;25(12):122001. Epub 2014 Feb 25.

Department of Electrical Engineering, Yale University, New Haven, CT 06520, USA.

Nanochannels remain at the focus of growing scientific and technological interest. The nanometer scale of the structure allows the discovery of a new range of phenomena that has not been possible in traditional microchannels, among which a direct field effect control over the charges in nanochannels is very attractive for various applications, since it offers a unique opportunity to integrate wet ionics with dry electronics seamlessly. This review will focus on the voltage gated ionic and molecular transport in engineered gated nanochannels. We will present an overview of the transport theory. Fabrication techniques regarding the gated nanostructures will also be discussed. In addition, various applications using the voltage gated nanochannels are outlined, which involves biological and chemical analysis, and energy conversion.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1088/0957-4484/25/12/122001DOI Listing
March 2014