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More bimetallic nanoparticles

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Two days ago, I noted that I’d never encountered bimetallic nanoparticles before reading about the ‘Christmas decorations’ created by a Mexico/US research team (my Dec. 6, 2010 posting). Live and learn. Here’s another bimetallic (gold and silver this time too) news item on Nanowerk,

Shrink Nanotechnologies, Inc. (“Shrink”), an innovative nanotechnology company developing products and licensing opportunities in the solar energy industry, medical diagnostics and sensors and biotechnology research and development tools businesses, announced today that Shrink’s MetalFluor™ technology was studied, reported on and made the front cover of the November issue of Applied Physics Letters (“Bimetallic nanopetals for thousand-fold fluorescence enhancements”). [the article is behind a paywall]

I was most interested to note that at least one of the authors is a researcher associated with the company that issued the news release trumpeting the article in Applied Physics Letters. From the news item on Nanowerk,

The Company’s technology and the work being performed by Dr. Michelle Khine, our scientific founder, continues to gain high praise from leading academic journals. [emphases mine] The studies relate to potential commercial applications of this technology. Of note, the article states, “Because we have a range of nanostructure and nanogap sizes, we can ensure that we can achieve huge fluorescent enhancements on our substrate. These advantages show great potential for low-cost biomedical sensing at single molecular levels at physiological concentrations.” The Company believes that this article is further evidence that certain medical diagnostics tests, a multi-billion dollar annual industry in the United States alone, can provide physicians, patients and other medical professionals with better results using lower quantities of specimens using MetalFluor™ technologies.

Here’s more about possible uses for the technology cited in the article in Applied Physics Letters (citation: Bimetallic nanopetals for thousand-fold fluorescence enhancements by Chi-Cheng Fu1, Giulia Ossato, Maureen Long, Michelle A. Digman, Ajay Gopinathan, Luke P. Lee, Enrico Gratton, and Michelle Khine in vol. 97, issue no. 20, Nov. 15, 2010),

Our method can be easily integrated with microfluidic devices to combine with high throughput lab-on-chip techniques. Importantly, because of–not in spite of–the “variability” in our substrate, we do not need to choose an esoteric dye such that it would match our plasmon resonance. Because we have a range of nanostructure and nanogap sizes, we can ensure that we can achieve huge fluorescence enhancements on our substrate. These advantages show great potential for low-cost biomedical sensing at single molecular levels at physiological concentrations.

The company Khine founded is very interesting from an organizational perspective (the news item on Nanowerk),

Shrink is a first of its kind FIGA™ organization. FIGA companies bring together diverse contributions from leaders in the worlds of finance, industry, government and academia. [emphases mine] Shrink’s solutions, including its diverse polymer substrates, nano-devices and biotech research tools, among others, are designed to be ultra-functional and mechanically superior in the solar energy, environmental detection, stem cell and biotechnology markets. The Company’s products are based on a pre-stressed plastic called NanoShrink™, and on a patent-pending manufacturing process called the ShrinkChip Manufacturing Solution™. Shrink’s unique materials and manufacturing solution represents a new paradigm in the rapid design, low-cost fabrication and manufacture of nano-scale devices for numerous significant markets.

I can’t make much of this academic/business hybrid but I am intrigued and will watch its progress with some interest. You can visit the Shrink Nanotechnologies website here.

Nano-sized Christmas decorations or creative writing?

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The opening line certainly caught my attention (from the Dec. 3, 2010 news item on Nanowerk),

They might just be the smallest Christmas tree decorations ever. Tiny spherical particles of gold and silver that are more than 100 million times smaller than the gold and silver baubles used to decorate seasonal fir trees have been synthesized by researchers in Mexico and the US.

I was expecting to see an image of these baubles on a nano -sized tree but I was doomed to disappointment.  The reference to Christmas decorations is a flight of fancy and the story rapidly progresses in another direction,

Writing in the December issue of the International Journal of Nanoparticles, materials engineer Xavier E. Guerrero-Dib, of the Universidad Autónoma de Nuevo León and colleagues there and at The University of Texas at Austin, describe the formation of gold, silver and alloyed, bimetallic nanoparticles just 25 nanometers in diameter. They used vitamin C, ascorbic acid, commonly found in tangerines, a favorite stocking filler in many parts of the world, and a soap-like, surfactant molecule known as cetyltrimethylammonium bromide, an antiseptic occasionally used in expensive cosmetics.

Reaction of silver nitrate and the gold compound chloroauric acid under these conditions led to successive reduction of the metals and the formation of different silver, gold and bimetallic nanoparticles. The precise structures of the nanoparticles were revealed using a high-resolution elemental mapping technique. The analysis shows the nanoparticles to have multiple layers, shells of gold within silver within gold, in the case of the bimetallic particles and some blending, or alloying, of the metals occurred.

I like how they kept the Christmas theme going with the reference to tangerines and stocking stuffers. As for the technology, this is the first time I’ve heard of silver and gold being combined to create a bimetallic particle.