Tag Archives: gold

Not the same old gold: there’s a brand new phase

A Dec. 7, 2015 news item on ScienceDaily announces a new phase for gold has been identified,

A new and stable phase of gold with different physical and optical properties from those of conventional gold has been synthesized by Agency for Science, Technology and Research (A*STAR) researchers [1], Singapore, and promises to be useful for a wide range of applications, including plasmonics and catalysis.

Many materials exist in a variety of crystal structures, known as phases or polymorphs. These different phases have the same chemical composition but different physical structures, which give rise to different properties. For example, two well-known polymorphs of carbon, graphite and diamond, arranged differently, have radically different physical properties, despite being the same element.

Gold has been used for many purposes throughout history, including jewelry, electronics and catalysis. Until now it has always been produced in one phase ― a face-centered cubic structure in which atoms are located at the corners and the center of each face of the constituent cubes.

Now, Lin Wu and colleagues at the Institute of the A*STAR Institute of High Performance Computing have modeled the optical and plasmonic properties of nanoscale ribbons of a new phase of gold — the 4H hexagonal phase (…) — produced and characterized by collaborators at other institutes in Singapore, China and the USA. The team synthesized nanoribbons of the new phase by simply heating the gold (III) chloride hydrate (HAuCl4) with a mixture of three organic solvents and then centrifuging and washing the product. This gave a high yield of about 60 per cent.

Here’s an image supplied by the researchers,

The atomic structure of the new phase of gold synthesized by A*STAR researchers. Reproduced from Ref. 1 and licensed under CC BY 4.0 © 2015 Z. Fan et al.

The atomic structure of the new phase of gold synthesized by A*STAR researchers. Reproduced from Ref. 1 and licensed under CC BY 4.0 © 2015 Z. Fan et al.

A Dec. 2, 2015 A*STAR news release, which originated the news item, provides more details,

The researchers also produced 4H hexagonal phases of the precious metals silver, platinum and palladium by growing them on top of the gold 4H hexagonal phase.

The cubic phase looks identical when viewed front on, from one side or from above. In contrast, the new 4H hexagonal phase lacks this cubic symmetry and hence varies more with direction — a property known as anisotropy. This lower symmetry gives it more directionally varying optical properties, which may make it useful for plasmonic applications. “Our finding is not only is of fundamental interest, but it also provides a new avenue for unconventional applications of plasmonic devices,” says Wu.

The team is keen to explore the potential of their new phase. “In the future, we hope to leverage the unconventional anisotropic properties of the new gold phase and design new devices with excellent performances not achievable with conventional face-centered-cubic gold,” says Wu. The synthesis method also gives rise to the potential for new strategies for controlling the crystalline phase of nanomaterials made from the noble metals.

Here’s a link to and a citation for the paper,

Stabilization of 4H hexagonal phase in gold nanoribbons by Zhanxi Fan, Michel Bosman, Xiao Huang, Ding Huang, Yi Yu, Khuong P. Ong, Yuriy A. Akimov, Lin Wu, Bing Li, Jumiati Wu, Ying Huang, Qing Liu, Ching Eng Png, Chee Lip Gan, Peidong Yang & Hua Zhang. Nature Communications 6, Article number: 7684 doi:10.1038/ncomms8684 Published 28 July 2015

This is an open access paper.

Combining gold and palladium for catalytic and plasmonic octopods

Hopefully I did not the change meaning when I made the title for this piece more succinct. In any event, this research comes from the always prolific Rice University in Texas, US (from a Nov. 30, 2015 news item on Nanotechnology Now),

Catalysts are substances that speed up chemical reactions and are essential to many industries, including petroleum, food processing and pharmaceuticals. Common catalysts include palladium and platinum, both found in cars’ catalytic converters. Plasmons are waves of electrons that oscillate in particles, usually metallic, when excited by light. Plasmonic metals like gold and silver can be used as sensors in biological applications and for chemical detection, among others.

Plasmonic materials are not the best catalysts, and catalysts are typically very poor for plasmonics. But combining them in the right way shows promise for industrial and scientific applications, said Emilie Ringe, a Rice assistant professor of materials science and nanoengineering and of chemistry who led the study that appears in Scientific Reports.

“Plasmonic particles are magnets for light,” said Ringe, who worked on the project with colleagues in the U.S., the United Kingdom and Germany. “They couple with light and create big electric fields that can drive chemical processes. By combining these electric fields with a catalytic surface, we could further push chemical reactions. That’s why we’re studying how palladium and gold can be incorporated together.”

The researchers created eight-armed specks of gold and coated them with a gold-palladium alloy. The octopods proved to be efficient catalysts and sensors.

A Nov. 30, 2015 Rice University news release (also on EurekAlert), which originated the news item, expands on the theme,

“If you simply mix gold and palladium, you may end up with a bad plasmonic material and a pretty bad catalyst, because palladium does not attract light like gold does,” Ringe said. “But our particles have gold cores with palladium at the tips, so they retain their plasmonic properties and the surfaces are catalytic.”

Just as important, Ringe said, the team established characterization techniques that will allow scientists to tune application-specific alloys that report on their catalytic activity in real time.

The researchers analyzed octopods with a variety of instruments, including Rice’s new Titan Themis microscope, one of the most powerful electron microscopes in the nation. “We confirmed that even though we put palladium on a particle, it’s still capable of doing everything that a similar gold shape would do. That’s really a big deal,” she said.

“If you shine a light on these nanoparticles, it creates strong electric fields. Those fields enhance the catalysis, but they also report on the catalysis and the molecules present at the surface of the particles,” Ringe said.

The researchers used electron energy loss spectroscopy, cathodoluminescence and energy dispersive X-ray spectroscopy to make 3-D maps of the electric fields produced by exciting the plasmons. They found that strong fields were produced at the palladium-rich tips, where plasmons were the least likely to be excited.

Ringe expects further research will produce multifunctional nanoparticles in a variety of shapes that can be greatly refined for applications. Her own Rice lab is working on a metal catalyst to turn inert petroleum derivatives into backbone molecules for novel drugs.

Here’s a link to and a citation for the paper,

Resonances of nanoparticles with poor plasmonic metal tips by Emilie Ringe, Christopher J. DeSantis, Sean M. Collins, Martial Duchamp, Rafal E. Dunin-Borkowski, Sara E. Skrabalak, & Paul A. Midgley.  Scientific Reports 5, Article number: 17431 (2015)  doi:10.1038/srep17431 Published online: 30 November 2015

This is an open access paper,

Solid gold smoke?

Aerogels seem to enchant even scientists who sometimes call it ‘solid smoke’ (my Aug. 20, 2012 posting). This latest aerogel is made of gold according to a Nov. 25, 2015 news item on Nanowerk,

 A nugget of real 20 carats gold, so light that it does not sink in a cappuccino, floating instead on the milk foam – what sounds unbelievable has actually been accomplished by researchers from ETH Zurich. Scientists led by Raffaele Mezzenga, Professor of Food and Soft Materials, have produced a new kind of foam out of gold, a three-dimensional mesh of gold that consists mostly of pores. It is the lightest gold nugget ever created. “The so-called aerogel is a thousand times lighter than conventional gold alloys. It is lighter than water and almost as light as air,” says Mezzenga.

A Nov. 25, 2015 ETH Zurich press release (also on EurekAlert), which originated the news item, provides more information about the ‘gold smoke’,

The new gold form can hardly be differentiated from conventional gold with the naked eye – the aerogel even has a metallic shine. But in contrast to its conventional form, it is soft and malleable by hand. It consists of 98 parts air and only two parts of solid material. Of this solid material, more than four-fifths are gold and less than one-fifth is milk protein fibrils. This corresponds to around 20 carat gold.

Here’s what it looks like,

Caption: Even when it seems unbelievable: these are genuine photographs, in which nothing has been faked. E.g. the 20 carats gold foam is lighter than milk foam. Credit: Gustav Nyström and Raffaele Mezzenga / (copyright) ETH Zurich

Caption: Even when it seems unbelievable: these are genuine photographs, in which nothing has been faked. E.g. the 20 carats gold foam is lighter than milk foam.
Credit: Gustav Nyström and Raffaele Mezzenga / (copyright) ETH Zurich

The press release provides more technical details,

The scientists created the porous material by first heating milk proteins to produce nanometre-fine protein fibres, so-called amyloid fibrils, which they then placed in a solution of gold salt. The protein fibres interlaced themselves into a basic structure along which the gold simultaneously crystallised into small particles. This resulted in a gel-like gold fibre network.

“One of the big challenges was how to dry this fine network without destroying it,” explains Gustav Nyström, postdoc in Mezzenga’s group and first author of the corresponding study in the journal Advanced Materials. As air drying could damage the fine gold structure, the scientists opted for a gentle and laborious drying process using carbon dioxide. They did so in an interdisciplinary effort assisted by researchers in the group of Marco Mazzotti, Professor of Process Engineering.

Dark-red gold

The method chosen, in which the gold particles are crystallised directly during manufacture of the aerogel protein structure (and not, for example, added to an existing scaffold) is new. The method’s biggest advantage is that it makes it easy to obtain a homogeneous gold aerogel, perfectly mimicking gold alloys.

The manufacturing technique also offers scientists numerous possibilities to deliberately influence the properties of gold in a simple manner. ” The optical properties of gold depend strongly on the size and shape of the gold particles,” says Nyström. “Therefore we can even change the colour of the material. When we change the reaction conditions in order that the gold doesn’t crystallise into microparticles but rather smaller nanoparticles, it results in a dark-red gold.” By this means, the scientists can influence not only the colour, but also other optical properties such as absorption and reflection.

The new material could be used in many of the applications where gold is currently being used, says Mezzenga. The substance’s properties, including its lighter weight, smaller material requirement and porous structure, have their advantages. Applications in watches and jewellery are only one possibility. Another application demonstrated by the scientists is chemical catalysis: since the highly porous material has a huge surface, chemical reactions that depend on the presence of gold can be run in a very efficient manner. The material could also be used in applications where light is absorbed or reflected. Finally, the scientists have also shown how it becomes possible to manufacture pressure sensors with it. “At normal atmospheric pressure the individual gold particles in the material do not touch, and the gold aerogel does not conduct electricity,” explains Mezzenga. “But when the pressure is increased, the material gets compressed and the particles begin to touch, making the material conductive.”

Here’s a link to and a citation for the paper,

Amyloid Templated Gold Aerogels by Gustav Nyström, Maria P. Fernandez-Ronco, Sreenath Bolisetty, Marco Mazzotti, Raffaele Mezzenaga. Advanced Materials DOI: 10.1002/adma.201503465 First published: 23 November 2015

This paper is behind a paywall.

Gold, acetic acid, and proton shuttles

I think the information has been taken from Russian to English by a machine translator, as well, I’m not a chemist, so please bear with my interpretation. It seems that Russian researchers have determined why gold, inert at the macroscale, is a good catalyst at the nanoscale. From a July 28, 2015 news item on Azonano,

Being found mostly in the native state, gold is one of the oldest elements known to man. The affection to gold was determined by it’s unusual properties – heft, shine and ability to withstand oxidation and corrosion.

The combination of properties determined gold use in the jewelry and as a coinage metal. The ancient alchemists working with gold were struggled by utmost chemical resistance of this element – it did not react with concentrated acids or alkali solutions even at high temperatures. Actually, it is the chemical inertness that makes gold to appear in a native form and not as a part of a mineral.

Later analysis established that gold compounds can not only compete with traditional nickel and palladium-based catalysts in the common reactions, but to surpass them. Besides that, gold compounds often demonstrated principally novel types of reactivity compared to well-established catalysts. This allowed chemists to discover a bunch of new chemical reactions and predetermined a fascinating boom in gold catalysis that we have observed in the recent years.

A July 24, 2015 Institute of Organic Chemistry, Russian Academy of Sciences press release on EurekAlert, which also originated the news item, reveals more about the study,

Professor Ananikov and co-workers introduced gold into well-known catalytic system which led to dramatic change of the reactivity and furnished the formation of novel gold-containing complexes. The complexes appeared to be air stable and were isolated in the individual state. A single crystal X-Ray diffraction study ascertained the existence of unique structural motif in the molecule, which can not be explained within conventional mechanistic framework.

The study was carried out using both theoretical and experimental approaches. Dedicated labeling of the reagents allowed observation of molecular re-organizations. Variation of reaction conditions helped to estimate key factors governing the discovered transformation. In addition, computational study of the reaction provided the models of certain intermediate steps, which were invisible for experimental investigation. The theoretical data obtained was in excellent agreement with experiment, proposing the reaction mechanism, where a molecule of acetic acid serves as a proton shuttle, transferring the hydrogen atom between the reaction centers.

The belief of gold inactivity towards chemical transformations resulted in the fact, that organometallic chemistry of gold was developed significantly later compared to other coinage metals (like silver, nickel or copper). Today, our goal is to “introduce gold catalysis as a valuable practical tool in fine organic chemistry, competitive with other transition metal catalysts”, says Prof. Ananikov.

Here’s a link to and a citation for the paper,

Carboxylic Group-Assisted Proton Transfer in Gold-Mediated Thiolation of Alkynes by Sergey S. Zalesskiy, Victor N. Khrustalev, Alexandr Yu. Kostukovich, and Valentine P. Ananikov. Organometallics, Article ASAP DOI: 10.1021/acs.organomet.5b00210 Publication Date (Web): July 22, 2015

Copyright © 2015 American Chemical Society

This paper is behind a paywall.

At a distance of less than a light wave, nanocamera takes pictures

A July 17, 2014 University of Illinois College of Engineering news release (also on EurekAlert) features a research breakthrough,

How is it possible to record optically encoded information for distances smaller than the wavelength of light?

Researchers at the University of Illinois at Urbana-Champaign have demonstrated that an array of novel gold, pillar-bowtie nanoantennas (pBNAs) can be used like traditional photographic film to record light for distances that are much smaller than the wavelength of light (for example, distances less than ~600 nm for red light). A standard optical microscope acts as a “nanocamera” whereas the pBNAs are the analogous film.

Here’s an image the researchers have provided to illustrate their work,

We demonstrate the plasmonic equivalent of photographic film for recording optical intensity in the near field. The plasmonic structure is based on gold bowtie nanoantenna arrays fabricated on SiO2 pillars. We show that it can be employed for direct laser writing of image data or recording the polarization structure of optical vector beams.[downloaded from http://pubs.acs.org/doi/abs/10.1021/nl501788a]

We demonstrate the plasmonic equivalent of photographic film for recording optical intensity in the near field. The plasmonic structure is based on gold bowtie nanoantenna arrays fabricated on SiO2 pillars. We show that it can be employed for direct laser writing of image data or recording the polarization structure of optical vector beams.[downloaded from http://pubs.acs.org/doi/abs/10.1021/nl501788a]

The news release describes the technique,

“Unlike conventional photographic film, the effect (writing and curing) is seen in real time,” explained Kimani Toussaint, an associate professor of mechanical science and engineering, who led the research. “We have demonstrated that this multifunctional plasmonic film can be used to create optofluidic channels without walls. Because simple diode lasers and low-input power densities are sufficient to record near-field optical information in the pBNAs, this increases the potential for optical data storage applications using off-the-shelf, low-cost, read-write laser systems.”

“Particle manipulation is the proof-of-principle application,” stated Brian Roxworthy, first author of the group’s paper, “Multifunctional Plasmonic Film for Recording Near-Field Optical Intensity,” published in the journal, Nano Letters. “Specifically, the trajectory of trapped particles in solution is controlled by the pattern written into the pBNAs. This is equivalent to creating channels on the surface for particle guiding except that these channels do not have physical walls (in contrast to those optofluidics systems where physical channels are fabricated in materials such as PDMS).”

To prove their findings, the team demonstrated various written patterns—including the University’s “Block I” logo and brief animation of a stick figure walking—that were either holographically transferred to the pBNAs or laser-written using steering mirrors (see video).

The news release concludes with,

“We wanted to show the analogy between what we have made and traditional photographic film,” Toussaint added. “There’s a certain cool factor with this. However, we know that we’re just scratching the surface since the use of plasmonic film for data storage at very small scales is just one application. Our pBNAs allow us to do so much more, which we’re currently exploring.”

The researchers noted that the fundamental bit size is currently set by the spacing of the antennas at 425-nm. However, the pixel density of the film can be straightforwardly reduced by fabricating smaller array spacing and a smaller antenna size, as well as using a more tightly focusing lens for recording.

“For a standard Blu-ray/DVD disc size, that amounts to a total of 28.6 gigabites per disk,” Roxworthy added. “With modifications to array spacing and antenna features, it’s feasible that this value can be scaled to greater than 75 gigabites per disk. Not to mention, it can be used for other exciting photonic applications, such as lab-on-chip nanotweezers or sensing.”

“In our new technique, we use controlled heating via laser illumination of the nanoantennas to change the plasmonic response instantaneously, which shows an innovative but easy way to fabricate spatially changing plasmonic structures and thus opens a new avenue in the field of nanotech-based biomedical technologies and nano optics,”  said Abdul Bhuiya, a co-author and member of the research team.

Here’s a link to and a citation for the paper,

Multifunctional Plasmonic Film for Recording Near-Field Optical Intensity by Brian J. Roxworthy, Abdul M. Bhuiya, V. V. G. Krishna Inavalli, Hao Chen, and Kimani C. Toussaint , Jr. Nano Lett., Article ASAP DOI: 10.1021/nl501788a Publication Date (Web): July 14, 2014
Copyright © 2014 American Chemical Society

This paper is behind a paywall.

You probably can’t poison yourself by eating too many nanoparticles

Researchers, Ingrid Bergin in the Unit for Laboratory Animal Medicine, at the University of Michigan in Ann Arbor and Frank Witzmann in the Department of Cellular and Integrative Physiology, at Indiana University School of Medicine, in Indianapolis, have stated that ingesting food and beverage (translated by me from the more scientific description) with nanoparticles (at today’s current levels) is unlikely to prove toxic. A June 26, 2013 Inderscience news release on EurekAlert describes the researchers’ research and their conclusions,

Writing in a forthcoming issue of the International Journal of Biomedical Nanoscience and Nanotechnology, researchers have compared existing laboratory and experimental animal studies pertaining to the toxicity of nanoparticles most likely to be intentionally or accidentally ingested. Based on their review, the researchers determined ingestion of nanoparticles at likely exposure levels is unlikely to cause health problems, at least with respect to acute toxicity. Furthermore, in vitro laboratory testing, which often shows toxicity at a cellular level, does not correspond well with in vivo testing, which tends to show less adverse effects.

Ingrid Bergin in the Unit for Laboratory Animal Medicine, at the University of Michigan in Ann Arbor and Frank Witzmann in the Department of Cellular and Integrative Physiology, at Indiana University School of Medicine, in Indianapolis, explain that the use of particles that are in the nano size range (from 1 billionth to 100 billionths of a meter in diameter, 1-100 nm, other thereabouts) are finding applications in consumer products and medicine. These include particles such as nano-silver, which is increasingly used in consumer products and dietary supplements for its purported antimicrobial properties. Nanoparticles can have some intriguing and useful properties because they do not necessarily behave in the same chemical and physical ways as non-nanoparticle versions of the same material.

Nanoparticles are now used as natural flavor enhancers in the form of liposomes and related materials, food pigments and in some so-called “health supplements”. They are also used in antibacterial toothbrushes coated with silver nanoparticles, for instance in food and drink containers and in hygienic infant feeding equipment. They are also used to carry pharmaceuticals to specific disease sites in the body to reduce side effects. Nanoparticles actually encompass a very wide range of materials from pure metals and alloys, to metal oxide nanoparticles, and carbon-based and plastic nanoparticles. Because of their increasing utilization in consumer products, there has been concern over whether these small scale materials could have unique toxicity effects when compared to more traditional versions of the same materials.

Difficulties in assessing the health risks of nanoparticles include the fact that particles of differing materials and shapes can have different properties. Furthermore, the route of exposure (e.g. ingestion vs. inhalation) affects the likelihood of toxicity. The U.S. researchers evaluated the current literature specifically with respect to toxicity of ingested nanoparticles. They point out that, in addition to intentional ingestion as with dietary supplements, unintentional ingestion can occur due to nanoparticle presence in water or as a breakdown product from coated consumer goods. Inhaled nanoparticles also represent an ingestion hazard since they are coughed up, swallowed, and eliminated through the intestinal tract.

Based on their review, the team concludes that, “Ingested nanoparticles appear unlikely to have acute or severe toxic effects at typical levels of exposure.” Nevertheless, they add that the current literature is inadequate to assess whether nanoparticles can accumulate in tissues and have long-term effects or whether they might cause subtle alterations in gut microbial populations. The researchers stress that better methods are needed for correlating particle concentrations used for cell-based assessment of toxicity with the actual likely exposure levels to body cells. Such methods may lead to better predictive value for laboratory in vitro testing, which currently over-predicts toxicity of ingested nanoparticles as compared to in vivo testing.

The researchers focused specifically on ingestion via the gastrointestinal tract which I take to mean that they focused largely on nanoparticles in food (eaten) and liquid (swallowed).

Here’s a link to and citation for the paper,

Nanoparticle toxicity by the gastrointestinal route: evidence and knowledge gaps by Ingrid L. Bergin; Frank A. Witzmann.  Int. J. of Biomedical Nanoscience and Nanotechnology, 2013 Vol.3, No.1/2, pp.163 – 210.  DOI: 10.1504/IJBNN.2013.054515

I think the abstract further helps to understand the research focus,

The increasing interest in nanoparticles for advanced technologies, consumer products, and biomedical applications has led to great excitement about potential benefits but also concern over the potential for adverse human health effects. The gastrointestinal tract represents a likely route of entry for many nanomaterials, both directly through intentional ingestion or indirectly via nanoparticle dissolution from food containers or by secondary ingestion of inhaled particles. Additionally, increased utilisation of nanoparticles may lead to increased environmental contamination and unintentional ingestion via water, food animals, or fish. The gastrointestinal tract is a site of complex, symbiotic interactions between host cells and the resident microbiome. Accordingly, evaluation of nanoparticles must take into consideration not only absorption and extraintestinal organ accumulation but also the potential for altered gut microbes and the effects of this perturbation on the host. The existing literature was evaluated for evidence of toxicity based on these considerations. Focus was placed on three categories of nanomaterials: nanometals and metal oxides, carbon-based nanoparticles, and polymer/dendrimers with emphasis on those particles of greatest relevance to gastrointestinal exposures.

The article is behind a paywall.

I last mentioned Frank Witzmann here in a May 8, 2013 posting titled, US multicenter (Nano GO Consortium) study of engineered nanomaterial toxicology.

Tooth tattoos at Tufts University

In spring 2012, there was a fluttering in the blogosphere about tooth tattoos with the potential for monitoring dental health. As sometimes happens, I put off posting about the work until it seemed everyone else had written about it (e.g. Mar. 30, 2012 posting by Dexter Johnson for his Nanoclast blog on the IEEE website) and there was nothing left for me to say.  Happily, the researchers at Tufts University (where part of this research [Princeton University is also involved] is being pursued) have released more information in a Nov. 1, 2012 news article by David Levin,

The sensor, dubbed a “tooth tattoo,” was developed by the Princeton nanoscientist Michael McAlpine and Tufts bioengineers Fiorenzo Omenetto, David Kaplan and Hu Tao. The team first published their research last spring in the journal Nature Communications.

The sensor is relatively simple in its construction, says McAlpine. It’s made up of just three layers: a sheet of thin gold foil electrodes, an atom-thick layer of graphite known as graphene and a layer of specially engineered peptides, chemical structures that “sense” bacteria by binding to parts of their cell membranes.

“We created a new type of peptide that can serve as an intermediary between bacteria and the sensor,” says McAlpine. “At one end is a molecule that can bond with the graphene, and at the other is a molecule that bonds with bacteria,” allowing the sensor to register the presence of bacteria, he says.

Because the layers of the device are so thin and fragile, they need to be mounted atop a tough but flexible backing in order to transfer them to a tooth. The ideal foundation, McAlpine says, turns out to be silk—a substance with which Kaplan and Omenetto have been working for years.

By manipulating the proteins that make up a single strand of silk, it’s possible to create silk structures in just about any shape, says Omenetto, a professor of biomedical engineering at Tufts. Since 2005, he’s created dozens of different structures out of silk, from optical lenses to orthopedic implants. Silk is “kind of like plastic, in that we can make [it] do almost anything,” he says. “We have a lot of control over the material. It can be rigid. It can be flexible. We can make it dissolve in water, stay solid, become a gel—whatever we need.”

Omenetto, Kaplan and Tao created a thin, water-soluble silk backing for McAlpine’s bacterial sensor—a film that’s strong enough to hold the sensor components in place, but soft and pliable enough to wrap easily around the irregular contours of a tooth.

To apply the sensor, McAlpine says, you need only to wet the surface of the entire assembly—silk, sensor and all—and then press it onto the tooth. Once there, the silk backing will dissolve within 15 or 20 minutes, leaving behind the sensor, a rectangle of interwoven gold and black electrodes about half the size of a postage stamp and about as thick as a sheet of paper. The advantage of being attached directly to a tooth means that the sensor is in direct contact with bacteria in the mouth—an ideal way to monitor oral health.

Because the sensor doesn’t carry any onboard batteries, it must be both read and powered simultaneously through a built-in antenna. Using a custom-made handheld device about the size of a TV remote, McAlpine’s team can “ping” that antenna with radio waves, causing it to resonate electronically and send back information that the device then uses to determine if bacteria are present.

The sensor (A), attached to a tooth (B) and activated by radio signals (C), binds with certain bacteria (D). Illustration: Manu Mannoor/Nature Communications (downloaded from http://now.tufts.edu/articles/tooth-tattoo)

In addition to its potential for  monitoring dental health, the tooth tattoo could replace some of the more invasive health monitoring techniques (e.g., drawing blood), from the Tufts University article,

In addition to monitoring oral health, Kugel [Gerard Kugel, Tufts professor of prosthodontics and operative dentistry and associate dean for research at Tufts School of Dental Medicine] believes the tooth tattoo might be useful for monitoring a patient’s overall health. Biological markers for many diseases—from stomach ulcers to AIDS—appear in human saliva, he says. So if a sensor could be modified to react to those markers, it potentially could help dentists identify problems early on and refer patients to a physician before a condition becomes serious.

“The mouth is a window to the rest of the body,” Kugel says. “You can spot a lot of potential health problems through saliva, and it’s a much less invasive way to do diagnostic tests than drawing blood.”

Before monitoring of any type can take place, there is at least one major hurdle still be overcome. Humans are quite sensitive to objects being placed in their mouths. According to one of the researchers, we can sense objects that are 50 to 60 microns wide, about the thickness piece of paper, and that may be too uncomfortable to bear.

H/T Nov. 9, 2012 news item on Nanowerk for pointing me towards the latest information about these tooth tattoos.

Nano art and a solution for space junk from New Zealand

I don’t hear much about New Zealand usually but two items popped up on the radar yesterday. There’s a nano art exhibit opening on Aug. 11, 2010 in Christchurch at Our City O-Tautahi, corner of Worcester Boulevard and Oxford Terrace. Admission is free. More from the news item on Voxy,

A new exhibition at Our City O-Tautahi merges art with the atom in an effort to explain nanotechnology.

Nanotechnology, one of the key technologies of the 21st Century, is probably the least understood despite being well on its way to becoming an integral part of our everyday lives.

Now the University of Canterbury and the MacDiarmid Institute for Advanced Material and Nanotechnology, in collaboration with artists and scientists, is offering a better understanding of nanotechnology through art.

Their exhibition: The Art of Nanotechnology at Our City O-Tautahi from Wednesday 11 August through to Friday 10 September presents intriguing nanotechnology images and art inspired by nanotechnology.

Researchers from around New Zealand were asked to enter the most interesting images from their work in a competition, and the best images are displayed in the exhibition. The MacDiarmid Institute for Advanced Materials and Nanotechnology, which is a government-funded Centre of Research Excellence, kindly donated $2000 in prizes.

Alongside these images are works from artists Claire Beynon (in a collaboration with biologist Sam Bowser), Nicola Gibbons, Sue Novell and Robyn Webster. These artists attempt to shed light on the incredible and tiny new worlds of nanotechnology. Each have selected one little corner of a vast subject, and examined it up close, just as a scientist uses a microscope.

This is one of a series of events being put on by the University of Canterbury this August. You can read more here.

Space junk

As for the space junk item, that comes from an article by Kit Eaton in Fast Company. 1992 was the first I heard that outer space was in fact a floating junk yard. For example, when satellites and other space equipment stop functioning, it’s easier to send a new model up then try and repair them. I imagine that in the 18 years since the situation has gotten worse. Amongst other ideas on how to clean things up, there’s this one (from the Fast Company article, The Most Beautiful Way to Clean Up Space Junk: A Giant GOLD Balloon),

Dr. Kristen Gates has one idea, and it’s beautiful and simple. It’s dubbed GOLD–the Gossamer Orbit Lowering Device–and it’s just been revealed at the “Artificial and Natural Space Debris” session of the AIAA Astrodynamics Specialists Conference.

GOLD is not much more than a football-field sized balloon (made of gossamer-thin but super-tough material, a little like solar sails) that is flown into orbit deflated in a suitcase-sized box and then fastened to a dead satellite. It’s then inflated to maximum size, and the huge bulk of the balloon massively increases the atmospheric drag that satellites experience up there in the void. This drag is due to the rare molecules of gas that hover around above the fringe of the atmosphere, and it’s the same drag that resulted in the premature deorbiting of the famous Skylab satellite in the 1970s, when the mechanics of orbital drag weren’t as well understood. The drag acts to slow a satellite in its orbital path, and then simple orbital mechanics means the satellite descends into the atmosphere where the denser air heats it to the point it burns up.

I guess gold is my other theme for this post.

There’s gold in them thar nano hills; study on nanotechnology practices; robot actresses in Korea

The World Gold Council has released a paper, Gold for Good: gold and nanotechnology in the age of innovation which highlights the many benefits of using gold nanoparticles in areas ranging from medicine to the environment. From the news item on Azonano,

The report, which was produced in conjunction with Cientifica Ltd, the world’s leading source of global business and investor intelligence about nanotechnologies, demonstrates how gold nanoparticles offer the potential to overcome many of the serious issues facing mankind over the coming decades.

Gold nanoparticles exhibit a variety of unique properties which, when harnessed and manipulated effectively, lead to materials whose uses are both far-ranging in their potential and cost effective. This report explores the many different applications that are being developed across the fields of health, environment and technology.

I found the report a useful (and rosy) overview of gold nanoparticles, their various benefits, and their potential for business investors as to be expected when one of the report’s authors is Tim Harper of the TNT Blog and principal of Cientifica. The report can be found here.

Michael Berger over at Nanowerk has written up a spotlight feature on a study about safety practices in  nanotechnology laboratories that was published in Feb. 2010 in Nature Nanotechnology.  From Nanowerk,

Published in the February issue of Nature Nanotechnology (“Reported nanosafety practices in research laboratories worldwide”), Jesus Santamaria, who heads the Nanostructured Films and Particles (NFP) Group at the University of Zaragoza, and his team have conducted an online survey to identify what safety practices researchers are following in their own labs.

“The results of our survey indicate that environmental health and safety practice in many research laboratories worldwide is lacking in several important aspects, and several reasons may contribute to this” Santamaria tells Nanowerk. “Toxicity of nanomaterials is a complex subject because it depends on multiple factors including size, surface area, chemical composition, shape, aggregation, surface coating and solubility. Furthermore, most published research emphasizes acute toxicity and mortality, rather than chronic exposure and morbidity.”

Meanwhile, Andrew Maynard at 2020 Science has written up a pointed critique. From Andrew,

Out of all those researchers surveyed who thought the materials they were using might become airborne at some stage, 21% didn’t use any form of “special protection” and 30% didn’t use respiratory protection.  Yet there is no way of telling from the survey whether “special protection” (the authors’ terminology) was needed, or indeed whether any respiratory protection was needed.  A researcher handling small amounts of fumed silica for example – used as a food additive amongst other places – might well handle it using established lab safety procedures that are entirely adequate and don’t include the use of a respirator – in this survey they would be classed in the category of “most researchers” not using “suitabe personal and laboratory protection.”

Unfortunately the Nature Nanotechnology article is behind a paywall but it is worth looking at Andrew’s critique both for the insight it gives you into laboratory practices and for a better understanding of the problems posed by the questions in the survey. Properly framing questions and the answers respondents get to choose from is one of the most difficult aspects of creating a questionnaire.

Andrew never mentions it and I can’t get past the paywall to find out but the questionnaire (or instrument as it’s often called) should have been tested before it was used. I suspect it was not. That said, testing won’t necessarily identify all the problems once you start dealing with a larger sample but it should help.

I have a couple of other comments. I didn’t see any mention of demographic information. For example, are they more careful in smaller labs or does lab size make any difference in safety processes? Does age or experience as a researcher have an impact? Are chemists more careful than physicists? Are men more careful than women or vice versa?

My second comment has to do with self-selected respondents. Why did these people respond to a survey? Generally, if you are surveying people about an issue, the most likely to respond are the ones who feel most strongly about the issue and this can give you a false picture of the general population. In other words, your sample is not generalizable. I don’t think that’s necessarily the situation here but it is a factor that needs to be taken into account. I would expect most social scientists (I gather the Spanish team is not composed of social scientists) to use a number of instruments and not just a self-reporting survey although that may be the first step as more work is undertaken.

I should mention the GoodNanoGuide as sharing handling and safety practices are the reasons this site was developed by the International Council on Nanotechnology (ICON). From their website,

The GoodNanoGuide is a collaboration platform designed to enhance the ability of experts to exchange ideas on how best to handle nanomaterials in an occupational setting.

Now for something completely different, Korean robot actresses. From the news item on physorg.com,

EveR-3 (Eve Robot 3) starred in various dramas last year including the government-funded “Dwarfs” which attracted a full house, said Lee Ho-Gil, of the state-run Korea Institute of Industrial Technology.

The lifelike EveR-3 is 157 centimetres (five feet, two inches) tall, can communicate in Korean and English, and can express a total of 16 facial expressions — without ever forgetting her lines. Lee acknowledged that robot actresses find it hard to express the full gamut of emotions and also tend to bump into props and fellow (human) actors. But he said a thespian android was useful in promoting the cutting-edge industry.

Here’s a shot of the robot actress as Snow White (from physorg.com where you can see a larger version if you wish),

Courtesy of the Korean Institute of Technology, Eve Robot 3 in costume for Robot Princess and 7 Dwarfs

That’s it.