Navigation Links
Growth spurts

The veil is being lifted from the once unseen world of molecular activity. Not so long ago only the final products were visible and scientists were forced to gauge the processes behind those products by ensemble averages of many molecules. The limitations of that approach have become clear with the advent of technologies that allow for the observation and manipulation of single molecules. A prime example is the recent first ever direct observations in real-time of the growth of single nanocrystals in solution, which revealed that much of what we thought we knew is wrong.

Interim Berkeley Lab Director Paul Alivisatos and Ulrich Dahmen, director of Berkeley Lab's National Center for Electron Microscopy (NCEM), led a team of experts in nanocrystal growth and electron microscopy who combined their skills to observe the dynamic growth of colloidal platinum nanocrystals in solution with subnanometer resolution. Their results showed that while some crystals in solution grow steadily in size via classical nucleation and aggregation meaning monomer molecules collide and join together others grow in fits and spurts, driven by "coalescence events," in which small crystals randomly collide and fuse together into larger crystals. Despite their distinctly different growth trajectories, these two processes ultimately yield a nearly monodisperse distribution of nanocrystals, meaning the crystals are all approximately the same size and shape.

"Coalescence events have been previously observed in flask synthesis of colloidal nanocrystals and has been considered detrimental for achieving monodisperse colloidal nanocrystals," says Haimei Zheng, a chemist in Alivisatos' research group, who was the lead author on a paper that reported these results in the journal Science. "In our study, we found that coalescence events are frequently involved in the early stage of nanocrystal growth and yet monodisperse nanocrystals are still formed."

Says Alivisatos, a chemist who holds joint appointments with Berkeley Lab and the University of California at Berkeley where he is the Larry and Diane Bock professor of Nanotechnology, "This direct observation of nanocrystal growth trajectories revealed a set of pathways more complex than those previously envisioned and enables us to re-think the nanocrystal growth mechanism with an eye towards more controlled synthesis."

The Science paper was titled: "Observation of Single Colloidal Platinum Nanocrystal Growth Trajectories." Co-authoring this paper with Zheng, Alivisatos and Dahmen were Rachel Smith, Young-wook Jun and Christian Kisielowski.

Nanocrystals are projected to play important roles in a wide-ranging number of technologies including solar and fuel cell, catalysis, electronics and photonics, medicine, and imaging and sensing. The key to success will be the ability to synthesis nanocrystals with desired physical properties. This will require a much better understanding of colloidal nanocrystal growth mechanisms. While the past two decades have seen tremendous advances in the synthesis of semiconductor, metal and dielectric nanocrystals, these advances have generally been realized through trial and error chemistry. A much more directed and controlled approach to nanocrystal synthesis is needed.

A new technique known as "liquid cell in situ transmission electron microscopy," in which the powerful resolution capabilities of a transmission electron microscope (TEM) are brought to bear on a liquid cell that allows liquids to be observed inside a vacuum, enables the visualization of single nanoparticles in solution. The Berkeley researchers deployed this technique on NCEM's JEOL 3010 In-Situ microscope. Utilizing an electron beam operating at 300 kilovolts of energy, the JEOL 3010 provides outstanding specimen penetration and spatial resolution of about 8 angstroms through the thick liquid cell sample.

"The JEOL 3010 In-Situ Microscope is our best machine for imaging dynamic events, and at 300kV the electron beam has enough penetrating power to maintain high resolution, even when looking through a liquid confined between two thin solid windows," says NCEM director Dahmen. "Our resolution is significantly higher than any previous studies of this nature, which made it possible for us to measure the movement and growth of individual colloidal particles only a few nanometers in size."

Zheng, Dahmen, Alivisatos and their colleagues used the JEOL 3010 and liquid cells microfabricated from a pair of 100-micron-thick silicon wafers with 20 nanometer thick silicon nitride membrane windows to image the growth trajectories of platinum nanocrystals in solution. Platinum nanocrystals are an ideal system for such studies because their high electron contrast allows liquid-cell TEM imaging of individual particles. The JEOL 3010's electron beam was used to both trigger nucleation and drive crystal growth through reduction of the platinum cations.

"Video-rate acquisition allowed us to track nanocrystal growth trajectories from frame-to-frame," says Zheng. "This allowed us to observe that each nanocrystal can either grow steadily through the addition of monomers from solution or by merging with another nanocrystal in random coalescence events."

Zheng says it has been assumed that coalescence events would result in some crystals being much larger than others, a bad thing in that the physical properties of nanocrystals are so dependent upon size and shape that for many applications it is critical that monodispersed nanocrystals be produced during synthesis. Consequently, strategies such as the use of surfactants to coat nanocrystal surfaces have been adopted to avoid coalescence events.

"Our observations provide invaluable direct information on how nanocrystals grow and indicate how we might directly control nanocrystal synthesis for tailored properties," says Zheng. "Also, our in situ liquid cell TEM technique can be applied to other areas of research such as soft matter imaging and nanoparticle catalysis, and offers great potential for addressing many fundamental issues in materials science, chemistry and other fields of science."

Says Dahmen, "From a microscopist's point of view, the ability to observe nanoparticles in liquid solution opens new opportunities in an area that has traditionally been off-limits because electron microscopes require vacuum conditions. We can now see directly what before could only be surmised from the statistical behavior of the ensemble. It's like understanding traffic by watching individual cars instead of listening to the traffic report."


Contact: Lynn Yarris
DOE/Lawrence Berkeley National Laboratory

Related biology technology :

1. AEterna Zentaris to Present at Upcoming Canaccord Adams 29th Annual Global Growth Conference
2. Orexigen(R) Therapeutics to Speak at Canaccord Adams Global Growth Conference
3. Shire plc: Core Portfolio of Products Delivers 20% Sales Growth
4. VIVUS to Present at the Canaccord Adams 29th Annual Global Growth Conference
5. Optimer Pharmaceuticals to Present at the Canaccord Adams 29th Annual Global Growth Conference
6. Cardium Announces New Orthobiologics Product Initiative Extending Gene Activated Matrix Technology to Deliver Bone Growth Factors
7. NovaBay(R) Pharmaceuticals to Present at Jesup & Lamont 2009 Growth Stock Conference
8. Histogen Hair Regrowth Clinical Trial Presented at ISHRS Annual Meeting
9. Growing Awareness and Increased Investments Lead to Growth of Biotechnology Applications in the Food & Beverage and Dietary Supplements Sector, Reveals Frost & Sullivan
10. Peregrine Pharmaceuticals to Present at the Jesup & Lamont 2009 Growth Stock & National Sales Conference
11. Sundia in Top 100 Fast-growth Outsourcing Companies in China
Post Your Comments:
Related Image:
Growth spurts
(Date:10/9/2015)... HERSHEY, Pa. and ROCKVILLE, ... Therapeutics, Inc. ("ITI"), a privately-held biotechnology company developing ... today announced that it has entered into an ... on LAMP-vax products for the treatment or prevention ... Upon execution of the agreement, Immunomic Therapeutics will ...
(Date:10/9/2015)... ... October 09, 2015 , ... ... the current methods of separating those cells from their surroundings for research, diagnostics, ... the cells. , To address this, Ann Arbor-based startup Akadeum Life Sciences ...
(Date:10/8/2015)... 8, 2015   Intrexon Corporation (NYSE: ... the appointment of Joseph L. Vaillancourt as ... Nir Nimrodi who continues in his role as ... endeavors to generate sustainable, biologically based solutions to environmental ... he held a variety of key roles including, Vice ...
(Date:10/8/2015)...  ATCC, the premier global biological materials resource and ... by The Michael J. Fox Foundation for Parkinson,s Research ... and biotechnology organizations committed to speed a cure for ... , and more than 5 million worldwide, have ... , and more than 5 million worldwide, have ...
Breaking Biology Technology:
... SANFORD, Maine, Jan. 31, 2012  Maine Manufacturing, LLC announced ... GE Healthcare granting Maine Manufacturing the exclusive right to ... line.  Maine Manufacturing, which has been manufacturing the FAST ... FAST Slides and accessories including FAST Quant, direct to ...
... Jan. 26, 2012 Life Technologies Corporation (NASDAQ: ... company,s presentations at the following upcoming investment conferences in ... Life Technologies will present at the Leerink Swann 2012 ... a.m. ET. Life Technologies will also present ...
... 2012  ZyGEM Corp. Ltd., a developer and marketer of ... nucleic acids, today announced that it has signed an ... DNA and RNA extraction kits.  SDL was established by ... as part of the Saudi Arabian government,s drive to ...
Cached Biology Technology:
(Date:10/8/2015)... 8, 2015 NXT-ID, Inc. ... a biometric authentication company focused on the growing ... smart wallet announces that revenues for the three ... compared with $113,00 for the three months ended ... ended September 30, 2015 were approximately $520,000. ...
(Date:10/6/2015)... LAKE CITY , Oct. 6, 2015 ... company, announced today that it has signed a contract ... monitoring services across the full range of sentences under ... Group,s President of the Americas. "This contract with the ... region of the US and advances our position as ...
(Date:10/2/2015)... DUBLIN , Oct. 02 2015 ... addition of the "Enforcing the Law Using ... ) has announced the addition of ... report to their offering. --> Research ... addition of the "Enforcing the Law Using ...
Breaking Biology News(10 mins):
... that ever walked the earthIndricotherium transouralicum, a hornless ... stood about eighteen feet high at the shoulderlived ... largest mammal that ever walked the earth Indricotherium ... approximately seventeen tons and stood about eighteen feet ...
... and other pathogens result in global crop losses of over ... Institution,s Department of Plant Biology developed a novel trick for ... organism. They discovered a novel family of pores that transport ... pores to access the plant sugar for food. The first ...
... , In the scorching summer heat of the Chihuahuan ... 97F (36C) while at the surface of the soil ... extreme temperatures, plants must utilize creative methods to not ... lethal conditions. This new work by Dr. Gretchen ...
Cached Biology News:
... The pPIC9K and pPIC3.5K vectors carry the ... Geneticin Reagent in Pichia. Spontaneous generation of ... resistance to increased levels of Geneticin Reagent. ... and screened for their level of resistance ...
... Clone/PAD: ZMD.478. Immunogen: Synthetic ... of the humanmouse and bovine Math-2. ... protein. Reactivity: Human Rat (positive ... rat B28 cell lysates and rat ...
solute carrier family 25, member 13 (citrin)...
Biology Products: