Nanotechnology Now

Our NanoNews Digest Sponsors

Heifer International

Wikipedia Affiliate Button

Home > Press > Nanocrystals Go Bare: Berkeley Lab Researchers Strip Material’s Tiny Tethers

Vials of ligand-free nanocrystals dispersed in solution for various applications, including energy storage, smart windows and LEDs.
Vials of ligand-free nanocrystals dispersed in solution for various applications, including energy storage, smart windows and LEDs.

Abstract:
Researchers with the U.S. Department of Energy (DOE)'s Lawrence Berkeley National Laboratory (Berkeley Lab) have discovered a universal technique for stripping nanocrystals of tether-like molecules that until now have posed as obstacles for their integration into devices. These findings could provide scientists with a clean slate for developing new nanocrystal-based technologies for energy storage, photovoltaics, smart windows, solar fuels and light-emitting diodes.

Nanocrystals Go Bare: Berkeley Lab Researchers Strip Material’s Tiny Tethers

Berkeley, CA | Posted on December 13th, 2011

Nanocrystals are typically prepared in a chemical solution using stringy molecules called ligands chemically tethered to their surface. These hydrocarbon-based or organometallic molecules help stabilize the nanocrystal, but also form an undesirable insulating shell around the structure. Efficient and clean removal of these surface ligands is challenging and has eluded researchers for decades.

Now, using Meerwein's salt—an organic compound also known by its tongue twisting moniker triethyloxonium tetrafluoroborate—a Berkeley Lab team has stripped away organic ligands tethered to nanocrystals, exposing a bare surface enabling nanocrystals to be used in a variety of applications.

"Our technique basically allows you to take any nanocrystal—metal oxides, metallic, semiconductors—and turn these into dispersions of ligand-free nanocrystal inks for spin or spray coating and even patterning using an ink jet printer," says Brett Helms, a staff scientist in the Organic and Macromolecular Synthesis Facility at Berkeley Lab's Molecular Foundry, a nanoscience research center. "What's more, they retain their structural integrity and exhibit more efficient transport properties in devices."

Many nanocrystals important for energy devices cannot withstand strong acids or oxidizing agents typically used to strip organic ligands—these nanocrystals simply dissolve. In this study, Helms and coworkers investigated atomistic details of the interaction between a lead selenide nanocrystal—a semiconductor material—and ligands surrounding its surface. The team then used chemical reagents based on Meerwein's salt to react with nanocrystals chemically to render these coordinating ligands incapable of re-binding to the surface, creating ‘naked' nanocrystals in solution or as a thin film on a support. This technique, Helms says, turned out to be exceedingly general.

"Our team has developed a general method of removing ligands on a nanocrystal to obtain "bare" nanocrystal surfaces," says Evelyn Rosen, a post-doctoral researcher working with Helms. "These bare nanocrystals may have unique properties themselves, but also enable the addition of new ligands to this bare surface as desired for some types of nanocrystals. Most significantly, this technique should expand the utility of nanocrystals by granting more control over the optimization of their properties."

To demonstrate the nanocrystals were genuinely stripped of their ligands, the team characterized thin films of ligand-coated and bare lead selenide nanocrystals with a new technique called nanoscale infrared spectroscopy, or nano-IR. In this technique, infrared light absorbed by the films is used to analyze excitations from specific molecular vibrations, such as the carbon-hydrogen bonds formed by ligands. Using nano-IR, the researchers found nanocrystals were uniformly bare across macroscopic distances, leading to an increase in electronic conductivity by several orders of magnitude when compared with unstripped nanocrystal films.

"This method is applicable in a truly universal fashion and makes it possible to use nanocrystals in a broad range of applications and in different environments," says Delia Milliron, Director of the Inorganic Nanostructures Facility at the Foundry and a coauthor on this study.

Indeed, Milliron adds, several Foundry users are already taking advantage of these nanocrystals for projects on energy storage and supercapacitor materials, which store energy like batteries but can be charged more rapidly.

"Having a robust yet simple procedure to process ‘activated' nanocrystals from solution over large areas, commensurate with the demands of a manufacturing process, is an important first step to integrating these exciting new materials into next generation energy-related devices," Helms adds. "We are leveraging this process broadly in our research and encourage potential collaborators to submit user proposals to the Molecular Foundry,"

Rosen is the lead author and Helms the corresponding author of a paper reporting this research in the journal Angewandte Chemie International Edition. The paper is titled "Exceptionally mild reactive stripping of native ligands from nanocrystal surfaces using Meerwein's salt." Co-authoring the paper with Rosen, Helms and Milliron were Raffaella Buonsanti, Anna Llordes and April Sawvel.

This work at the Molecular Foundry was supported by DOE's Office of Science.

####

About Berkeley Lab
The Molecular Foundry is one of five DOE Nanoscale Science Research Centers (NSRCs), national user facilities for interdisciplinary research at the nanoscale, supported by the DOE Office of Science. Together the NSRCs comprise a suite of complementary facilities that provide researchers with state-of-the-art capabilities to fabricate, process, characterize and model nanoscale materials, and constitute the largest infrastructure investment of the National Nanotechnology Initiative. The NSRCs are located at DOE’s Argonne, Brookhaven, Lawrence Berkeley, Oak Ridge and Sandia and Los Alamos National Laboratories. For more information about the DOE NSRCs, please visit science.energy.gov.

Lawrence Berkeley National Laboratory addresses the world’s most urgent scientific challenges by advancing sustainable energy, protecting human health, creating new materials, and revealing the origin and fate of the universe. Founded in 1931, Berkeley Lab’s scientific expertise has been recognized with 12 Nobel prizes. The University of California manages Berkeley Lab for the U.S. Department of Energy’s Office of Science. For more, visit www.lbl.gov.

For more information, please click here

Contacts:
Aditi Risbud
(510)486-4861

Copyright © Berkeley Lab

If you have a comment, please Contact us.

Issuers of news releases, not 7th Wave, Inc. or Nanotechnology Now, are solely responsible for the accuracy of the content.

Bookmark:
Delicious Digg Newsvine Google Yahoo Reddit Magnoliacom Furl Facebook

Related Links

For more information about the Molecular Foundry visit the Website at:

Related News Press

News and information

Tuning into quantum: Scientists unlock signal frequency control of precision atom qubits July 16th, 2018

Nano-kirigami: 'Paper-cut' provides model for 3D intelligent nanofabrication July 13th, 2018

UMBC researchers develop nanoparticles to reduce internal bleeding caused by blast trauma July 13th, 2018

Oxford Instruments’ 22 Tesla superconducting magnet system commissioned at the UAM, making it the most intense magnetic field available outside a large international facility July 12th, 2018

Laboratories

Carbon is the new black: Researchers use carbon nanotubes to develop clothing that can double as batteries July 10th, 2018

NIST Researchers Simulate Simple Logic for Nanofluidic Computing June 30th, 2018

Cleaning or Etching Items with Unique Geometries Requires Specialized Expertise June 27th, 2018

Carbon nanotube optics poised to provide pathway to optical-based quantum cryptography and quantum computing: Researchers are exploring enhanced potential of carbon nanotubes for unique applications June 18th, 2018

Tripling the Energy Storage of Lithium-Ion Batteries: Scientists have synthesized a new cathode material from iron fluoride that surpasses the capacity limits of traditional lithium-ion batteries June 14th, 2018

Display technology/LEDs/SS Lighting/OLEDs

DNA drives design principles for lighter, thinner optical displays: Lighter gold nanoparticles could replace thicker, heavier layered polymers used in displays’ back-reflectors June 27th, 2018

Nanomaterials could mean more algae outbreaks for wetlands, waterways: High tech metal particles may inadvertently take a toll on aquatic life June 26th, 2018

Govt.-Legislation/Regulation/Funding/Policy

Tuning into quantum: Scientists unlock signal frequency control of precision atom qubits July 16th, 2018

Nano-kirigami: 'Paper-cut' provides model for 3D intelligent nanofabrication July 13th, 2018

Carbon is the new black: Researchers use carbon nanotubes to develop clothing that can double as batteries July 10th, 2018

High-power electronics keep their cool with new heat-conducting crystals July 6th, 2018

Discoveries

Tuning into quantum: Scientists unlock signal frequency control of precision atom qubits July 16th, 2018

Nano-kirigami: 'Paper-cut' provides model for 3D intelligent nanofabrication July 13th, 2018

UMBC researchers develop nanoparticles to reduce internal bleeding caused by blast trauma July 13th, 2018

Barium ruthenate: A high-yield, easy-to-handle perovskite catalyst for the oxidation of sulfides July 13th, 2018

Announcements

Tuning into quantum: Scientists unlock signal frequency control of precision atom qubits July 16th, 2018

Nano-kirigami: 'Paper-cut' provides model for 3D intelligent nanofabrication July 13th, 2018

UMBC researchers develop nanoparticles to reduce internal bleeding caused by blast trauma July 13th, 2018

Barium ruthenate: A high-yield, easy-to-handle perovskite catalyst for the oxidation of sulfides July 13th, 2018

Energy

NIST Researchers Simulate Simple Logic for Nanofluidic Computing June 30th, 2018

Northwestern researchers achieve unprecedented control of polymer grids: Materials could find applications in water purification, solar energy storage, body armor June 22nd, 2018

Physicists devise method to reveal how light affects materials: The new method adds to the understanding of the fundamental laws governing the interaction of electrons and light June 15th, 2018

Tripling the Energy Storage of Lithium-Ion Batteries: Scientists have synthesized a new cathode material from iron fluoride that surpasses the capacity limits of traditional lithium-ion batteries June 14th, 2018

Battery Technology/Capacitors/Generators/Piezoelectrics/Thermoelectrics/Energy storage

Carbon is the new black: Researchers use carbon nanotubes to develop clothing that can double as batteries July 10th, 2018

NIST Researchers Simulate Simple Logic for Nanofluidic Computing June 30th, 2018

BNAs improve performance of Li-ion batteries June 27th, 2018

Northwestern researchers achieve unprecedented control of polymer grids: Materials could find applications in water purification, solar energy storage, body armor June 22nd, 2018

Solar/Photovoltaic

Northwestern researchers achieve unprecedented control of polymer grids: Materials could find applications in water purification, solar energy storage, body armor June 22nd, 2018

Team achieves two-electron chemical reactions using light energy, gold May 15th, 2018

Hematene joins parade of new 2D materials: Rice University-led team extracts 3-atom-thick sheets from common iron oxide May 8th, 2018

Harvesting clean hydrogen fuel through artificial photosynthesis May 3rd, 2018

NanoNews-Digest
The latest news from around the world, FREE



  Premium Products
NanoNews-Custom
Only the news you want to read!
 Learn More
NanoStrategies
Full-service, expert consulting
 Learn More











ASP
Nanotechnology Now Featured Books




NNN

The Hunger Project