New technique maps twin faces of smallest Janus nanoparticles

ScienceDaily (Sep. 28, 2011) — New drug delivery systems, solar cells, industrial catalysts and video displays are among the potential applications of special particles that possess two chemically distinct sides. These particles are named after the two-faced Roman god Janus and their twin chemical faces allow them to form novel structures and new materials.

However, as scientists have reduced the size of Janus particles down to a few nanometers in diameter -- about the size of individual proteins, which has the greatest potential for drug therapy -- their efforts have been hampered because they haven't had a way to accurately map the surfaces of the particles that they produce. This uncertainty has made it difficult to evaluate the effectiveness of these particles for various applications and to improve the methods researchers are using to produce them.

Now, a team of Vanderbilt chemists has overcome this obstacle by developing the first method that can rapidly and accurately map the chemical properties of the smallest of these Janus nanoparticles.

The results, published online this month in the German chemistry journal Angewandte Chemie, address a major obstacle that has slowed the development and application of the smallest Janus nanoparticles.

The fact that Janus particles have two chemically distinct faces makes them potentially more valuable than chemically uniform particles. For example, one face can hold onto drug molecules while the other is coated with linker molecules that bind to the target cells. This advantage is greater when the different surfaces are cleanly separated into hemispheres than when the two types of surfaces are intermixed.

For larger nanoparticles (with sizes above 10 nanometers), researchers can use existing methods, such as scanning electron microscopy, to map their surface composition. This has helped researchers improve their manufacturing methods so they can produce cleanly segregated Janus particles. However, conventional methods do not work at sizes below 10 nanometers.

The Vanderbilt chemists -- Associate Professor David Cliffel, Assistant Professor John McLean, graduate student Kellen Harkness and Lecturer Andrzej Balinski -- took advantage of the capabilities of a state-of-the-art instrument called an ion mobility-mass spectrometer (IM-MS) that can simultaneously identify thousands of individual particles.

The team coated the surfaces of gold nanoparticles ranging in size from two to four nanometers with two different chemical compounds. Then they broke the nanoparticles down into clusters of four gold atoms and ran these fragments through the IM-MS.

Molecules from the two coatings were still attached to the clusters. So, by analyzing the resulting pattern, the chemists showed that they could distinguish between original nanoparticles where the two surface compounds were completely separated, those where they were randomly mixed and those that had an intermediate degree of separation.

"There is no other way to analyze structure at this scale except X-ray crystallography," said Cliffel, "and X-ray crystallography is extremely difficult and can take months to get a single structure."

"IM-MS isn't quite as precise as X-ray crystallography but it is extremely practical," added McLean, who has helped pioneer the new instrument's development. "It can provide structural information in a few seconds. Two years ago a commercial version became available so people who want to use it no longer have to build one for themselves."

The research was funded in part by a grant from the National Institutes of Health.

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The above story is reprinted (with editorial adaptations by ScienceDaily staff) from materials provided by Vanderbilt University. The original article was written by David Salisbury.

Journal Reference:

Kellen M. Harkness, Andrzej Balinski, John A. McLean, David E. Cliffel. Nanoscale Phase Segregation of Mixed Thiolates on Gold Nanoparticles. Angewandte Chemie International Edition, 2011; DOI: 10.1002/anie.201102882

Note: If no author is given, the source is cited instead.

Disclaimer: Views expressed in this article do not necessarily reflect those of ScienceDaily or its staff.

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New technique maps twin faces of smallest Janus nanoparticles

ScienceDaily (Sep. 28, 2011) — New drug delivery systems, solar cells, industrial catalysts and video displays are among the potential applications of special particles that possess two chemically distinct sides. These particles are named after the two-faced Roman god Janus and their twin chemical faces allow them to form novel structures and new materials.

However, as scientists have reduced the size of Janus particles down to a few nanometers in diameter -- about the size of individual proteins, which has the greatest potential for drug therapy -- their efforts have been hampered because they haven't had a way to accurately map the surfaces of the particles that they produce. This uncertainty has made it difficult to evaluate the effectiveness of these particles for various applications and to improve the methods researchers are using to produce them.

Now, a team of Vanderbilt chemists has overcome this obstacle by developing the first method that can rapidly and accurately map the chemical properties of the smallest of these Janus nanoparticles.

The results, published online this month in the German chemistry journal Angewandte Chemie, address a major obstacle that has slowed the development and application of the smallest Janus nanoparticles.

The fact that Janus particles have two chemically distinct faces makes them potentially more valuable than chemically uniform particles. For example, one face can hold onto drug molecules while the other is coated with linker molecules that bind to the target cells. This advantage is greater when the different surfaces are cleanly separated into hemispheres than when the two types of surfaces are intermixed.

For larger nanoparticles (with sizes above 10 nanometers), researchers can use existing methods, such as scanning electron microscopy, to map their surface composition. This has helped researchers improve their manufacturing methods so they can produce cleanly segregated Janus particles. However, conventional methods do not work at sizes below 10 nanometers.

The Vanderbilt chemists -- Associate Professor David Cliffel, Assistant Professor John McLean, graduate student Kellen Harkness and Lecturer Andrzej Balinski -- took advantage of the capabilities of a state-of-the-art instrument called an ion mobility-mass spectrometer (IM-MS) that can simultaneously identify thousands of individual particles.

The team coated the surfaces of gold nanoparticles ranging in size from two to four nanometers with two different chemical compounds. Then they broke the nanoparticles down into clusters of four gold atoms and ran these fragments through the IM-MS.

Molecules from the two coatings were still attached to the clusters. So, by analyzing the resulting pattern, the chemists showed that they could distinguish between original nanoparticles where the two surface compounds were completely separated, those where they were randomly mixed and those that had an intermediate degree of separation.

"There is no other way to analyze structure at this scale except X-ray crystallography," said Cliffel, "and X-ray crystallography is extremely difficult and can take months to get a single structure."

"IM-MS isn't quite as precise as X-ray crystallography but it is extremely practical," added McLean, who has helped pioneer the new instrument's development. "It can provide structural information in a few seconds. Two years ago a commercial version became available so people who want to use it no longer have to build one for themselves."

The research was funded in part by a grant from the National Institutes of Health.

Recommend this story on Facebook, Twitter,
and Google +1:

Other bookmarking and sharing tools:

Story Source:

The above story is reprinted (with editorial adaptations by ScienceDaily staff) from materials provided by Vanderbilt University. The original article was written by David Salisbury.

Journal Reference:

Kellen M. Harkness, Andrzej Balinski, John A. McLean, David E. Cliffel. Nanoscale Phase Segregation of Mixed Thiolates on Gold Nanoparticles. Angewandte Chemie International Edition, 2011; DOI: 10.1002/anie.201102882

Note: If no author is given, the source is cited instead.

Disclaimer: Views expressed in this article do not necessarily reflect those of ScienceDaily or its staff.

View the original article here

As Congress Fusses Over Climate Semantics, the U.S. Faces a Weather Satellite Gap

Weather monitoring is vital, but don't mention the C-word
NPOESS Engineers begin integration of the Medium resolution Visible and Infra-red Imager or VIIRS into the NPOESS Preparatory Project NASA/Ball Aerospace

This year has seen some phenomenally bizarre weather, from deadly tornadoes ripping through the Midwest and South to historic snowmelt-related flooding on the Mississippi River. Most hurricane forecasters are saying it’s about to get worse — the National Oceanic and Atmospheric Administration projected Thursday that the Atlantic basin is likely to see 12 to 18 named storms this season.

Amid all this, the country’s future weather prediction capabilities could be stymied by a battle in Washington.

During the budget battle earlier this spring, Congress cut funding for a new polar-orbiting satellite, which is designed to monitor atmospheric temperatures and pressure, severe weather, fires and other manmade and natural disasters, and to provide continuous climate data. If it does not get built, the country faces a satellite gap, which could affect forecasters’ ability to predict the weather.

The key word here is climate.

“Weather is apolitical, but climate is unfortunately not,” Bill Sullivan, a director at Raytheon Intelligence and Information Systems and program manager for the new satellite, said in an interview.

Click here to launch a gallery of images of NASA's NPP satellite

NOAA Administrator Jane Lubchenco said at a news conference Thursday that the agency’s satellite program is in limbo.

This is at least the fourth time in the past few years that a climate-monitoring project has fallen victim to either terrible luck or bad politics. First the Orbiting Carbon Observatory failed to reach orbit, then NASA’s aerosol-monituring Glory mission also died during launch. Last month we told you about the Deep Space Climate Observatory, languishing in a box in Maryland. Now a satellite called JPSS is in danger of losing its funding.

Here’s a bit of history: Until last year, NASA, NOAA and the Department of Defense were going to share a brand-new polar-orbiting satellite called the National Polar Orbiting Operational Environmental Satellite System (NPOESS). But after a few years of planning and design work, the government decided the military and civilian agencies didn’t play well together and divorced the project, giving the DOD its own satellite. The existing civilian project, called NPP for NPOESS Preparatory Project, will serve NASA and NOAA only, and is planned for launch in October. It just completed a thermal test.

It is supposed to have a companion successor called the Joint Polar Satellite System, and NOAA requested $1.06 billion in this year’s budget to build it. Then the federal budget stalemate happened, and everything was funded at 2010 levels as Congress and the White House wrangled.

“The message that was getting to Congress was that NOAA needed a billion dollars to do climate research,” said Sullivan, who is Raytheon’s program manager for the JPSS. As a result, the funding was not approved.

Since the funding cuts, NOAA — and contractors like Raytheon — have started marketing the satellite's weather forecasting abilities, not just its utility in informing climate models.

Polar-orbiting satellites can provide global weather coverage, which is useful when trying to make future weather predictions. Geostationary satellites, like the ones that provide the satellite radar imagery on your local news, only look at a specific section of the planet. The National Weather Service needs both sets of data to complete accurate forecasting.

NPP is a new polar-orbiting satellite that will replace NOAA’s previous orbiters, Sullivan said. It will circle the Earth 512 miles above the surface, completing about 14 orbits every day.

“We’re going to see just a huge increase in the amount of data that can be collected ... NPP provides an enormous amount of capability that is currently not on orbit,” Sullivan said.

NPP will have a life span of about five years, at which point JPSS should be ready to replace it. Sullivan said NOAA needs funding this year for construction so the JPSS project doesn’t fall behind schedule. NOAA is hoping the project will get funding this year, but it looks doubtful, Sullivan said. Meanwhile, the agency is preparing for a budget battle next year, he said.

"If the program doesn't get funded at the appropriate level in 2012, it will fall behind, which is bad for all of us," he said.

“Not having satellites and not applying their latest capabilities could spell disaster,” said NOAA's Lubchenko. “We are likely looking at a period of time a few years down the road where we will not be able to do severe storm warnings and long-term weather forecasts that people have come to expect today.”

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