# Nova Scotia’s (Canada) Sona Nanotech and its gold nanoparticles move

I hope one day to have at least one piece on nanotechnology for each province, the Yukon, and the territories. Unfortunately, today (Nov. 2, 2016) will not be the day I add one previously unsung province, etc. to the list as Nova Scotia has previously graced this blog with a nanotechnology story (my June 5, 2016 posting).

The latest nano news from Nova Scotia is found in a Nov. 1, 2016 article by James Risdon for the Chronicle Herald,

A Nova Scotia biotech startup with big plans for its super-small, non-toxic gold particles is looking to move its lab facilities to Halifax and expand.

Andrew McLeod, Sona Nanotech Ltd.’s president and chief operating officer, said Tuesday the company is already looking for lab space in Halifax and wants to hire three additional employees to handle production, research and business development.

Sona Nanotech has two products, its Gemini and Omni gold particles, intended to be used in the health-care industry for such things as the treatment of cancer and diagnostic testing.

These particles are measured in nanometres.

“You’re talking about something that’s on the order of millionths of the width of a human hair,” said McLeod. [The comparison measurements I’ve seen most frequestion for a single nanometre is 1/50,000 or 1/60,000 or 1/100,000 of a hair.]

While other players make gold particles, Sona Nanotech has developed a way to make its products so that they are free of a toxic chemical ,and that’s opening doors for the Nova Scotia startup whose products can be used inside the human body.

There’s already talk of Sona Nanotech teaming up with an as-yet-unnamed Canadian organization for a cancer research project, but McLeod was tight-lipped about the details.

Congratulations to Sona Nano!

For anyone curious about the business aspects of the story, I recommend reading Risdon’s article in its entirety.

Sona Nanotech’s website can be found here,

Sona Nanotech Ltd. has leveraged its team’s unique knowledge and experience with novel surface chemistry methods and surfactants to create a disruptive leap forward in metallic nanoparticle technology.

Co-founders Dr. Gerrard Marangoni, Dr. Kulbir Singh, and Dr. Michael McAlduff recognized the role that gold nanoparticles can play in a variety of life sciences applications, e.g.,  in-vivo 3-D imaging, GNR-enabled diagnostic test products and other cutting edge medical applications.  Gold nanorods can be enabling technologies for non-invasive targeted cell, tumor, tissue and organ treatments such as photothermal cancer cell destruction, and location specific drug and pain treatment.

The Problem
Gold nanorods have been made to date with toxic CTAB [cationic surfactant cethyltrimetylammonium bromide] which makes them much less attractive for in-vivo medical applications.

The Solution
100% CTAB-FREE – Gemini™ and Omni™ Patent-Pending Gold Nanorods – from Sona Nanotech Ltd.

The Problem
For a given colour contrast, large gold nanospheres are not as stable or mobile as gold nanorods (dip tests).

The Solution
Stable, high loading capacity GNRs [gold nanorods] from Sona Nanotech offer a broad range of rich, high contrast test color options.

So, there you have it.

# Discovering why nanoscale gold has catalytic properties

Gold’s glitter may have inspired poets and triggered wars, but its catalytic prowess has helped make chemical reactions greener and more efficient. (Image courtesy of iStock/sbayram) [downloaded from http://www1.lehigh.edu/news/scientists-uncover-secret-gold%E2%80%99s-catalytic-powers

A Sept. 27, 2016 news item on phys.org describes a discovery made by scientists at Lehigh University (US),

Settling a decades-long debate, new research conclusively shows that a hierarchy of active species exists in gold on iron oxide catalysis designed for low temperature carbon monoxide oxidation; Nanoparticles, sub-nanometer clusters and dispersed atoms—as well as how the material is prepared—are all important for determining catalytic activity.

A Sept. 27, 2016 Lehigh University news release by Lori Friedman, which originated the news item, provides more information about the discovery that gold nanoparticles can be used in catalysis and about the discovery of why that’s possible,

Christopher J. Kiely calls the 1982 discovery by Masatake Haruta that gold (Au) possessed a high level of catalytic activity for carbon monoxide (CO) oxidation when deposited on a metal-oxide “a remarkable turn of events in nanotechnology”—remarkable because gold had long been assumed to be inert for catalysis.

Haruta showed that gold dispersed on iron oxide effectively catalyzed the conversion of harmful carbon monoxide into more benign carbon dioxide (CO2) at room temperatures—a reaction that is critical for the construction of fire fighters’ breathing masks and for removal of CO from hydrogen feeds for fuel cells. In fact, today gold catalysts are being exploited in a major way for the greening of many important reactions in the chemical industry, because they can lead to cleaner, more efficient reactions with fewer by-products.

Haruta and Graham J. Hutchings, who co-discovered the use of gold as a catalyst for different reactions, are noted as Thompson Reuters Citation Laureates and appear annually on the ScienceWatch Nobel Prize prediction list. Their pioneering work opened up a new area of scientific inquiry and kicked off a decades-long debate about which type of supported gold species are most effective for the CO oxidation reaction.

In 2008, using electron microscopy technology that was not yet available in the 1980s and ’90 s, Hutchings, the director of the Cardiff Catalysis Institute at Cardiff University worked with Kiely, the Harold B. Chambers Senior Professor Materials Science and Engineering at Lehigh, examined the structure of supported gold at the nanoscale. One nanometer (nm) is equal to one one-billionth of a meter or about the diameter of five atoms.

Using what was then a rare piece of equipment—Lehigh’s aberration-corrected JEOL 2200 FS scanning transmission electron microscope (STEM)—the team identified the co-existence of three distinct gold species: facetted nanoparticles larger than one nanometer in size, sub-clusters containing less than 20 atoms and individual gold atoms strewn over the support. Because only the larger gold nanoparticles had previously been detected, this created debate as to which of these species were responsible for the good catalytic behavior.

Haruta, professor of applied chemistry at Tokyo Metropolitan University, Hutchings and Kiely have been working collaboratively on this problem over recent years and are now the first to demonstrate conclusively that it is not the particles or the individual atoms or the clusters which are solely responsible for the catalysis—but that they all contribute to different degrees. Their results have been published in an article in Nature Communications titled: “Population and hierarchy of active species in gold iron oxide catalysts for carbon monoxide oxidation.”

“All of the species tend to co-exist in conventionally prepared catalysts and show some level of activity,” says Kiely. “They all do something—but some less efficiently than others.”

Their research revealed the sub-nanometer clusters and 1-3nm nanoparticles to be the most efficient for catalyzing this CO oxidation reaction, while larger particles were less so and the atoms even less.  Nevertheless, Kiely cautions, all the species present need to be considered to fully explain the overall measured activity of the catalyst.

Among the team’s other key findings: the measured activity of gold on iron oxide catalysts is exquisitely dependent on exactly how the material is prepared. Very small changes in synthesis parameters  influence the relative proportion and spatial distribution of these various Au species on the support material and thus have a big impact on its overall catalytic performance.

A golden opportunity

Building on their earlier work (published in a 2008 Science article), the team sought to find a robust way to quantitatively analyze the relative population distributions of nanoparticles of various sizes, sub-nm clusters and highly dispersed atoms in a given gold on iron oxide sample. By correlating this information with catalytic performance measurements, they then hoped to determine which species distribution would be optimal to produce the most efficient catalyst, in order to utilize the precious gold component in the most cost effective way.

Ultimately, it was a catalyst synthesis problem the team faced that offered them a golden opportunity to do just that.

During the collaboration, Haruta’s and Hutchings’ teams each prepared gold on iron oxide samples in their home labs in Tokyo and Cardiff. Even though both groups nominally utilized the same ‘co-precipitation’ synthesis method, it turned out that a final heat treatment step was beneficial to the catalytic performance for one set of materials but detrimental to the other. This observation provided a fascinating scientific conundrum that detailed electron microscopy studies performed by Qian He, one of Kiely’s PhD students at the time, was key to solving. Qian He is now a University Research Fellow at Cardiff University leading their electron microscopy effort.

“In the end, there were subtle differences in the order and speed in which each group added in their ingredients while preparing the material,” explains He. “When examined under the electron microscope, it was clear that the two slightly different methods produced quite different distributions of particles, clusters and dispersed atoms on the support.”

“Very small variations in the preparation route or thermal history of the sample can alter the relative balance of supported gold nanoparticles-to-clusters-to-atoms in the material and this manifests itself in the measured catalytic activity,” adds Kiely.

The group was able to compare this set of materials and correlate the Au species distributions with catalytic performance measurements, ultimately identifying the species distribution that was associated with greater catalytic efficiency.

Now that the team has identified the catalytic activity hierarchy associated with these supported gold species, the next step, says Kiely, will be to modify the synthesis method to positively influence that distribution to optimize the catalyst performance while making the most efficient use of the precious gold metal content.

“As a next stage to this study we would like to be able to observe gold on iron oxide materials in-situ within the electron microscope while the reaction is happening,” says Kiely.

Once again, it is next generation microscopy facilities that may hold the key to fulfilling gold’s promise as a pivotal player in green technology.

Despite the link to the paper already in the news release, here’s one that includes a citation,

Identification of Active Gold Nanoclusters on Iron Oxide Supports for CO Oxidation by Andrew A. Herzing, Christopher J. Kiely, Albert F. Carley, Philip Landon, Graham J. Hutchings. Science  05 Sep 2008: Vol. 321, Issue 5894, pp. 1331-1335 DOI: 10.1126/science.1159639

This paper is currently behind a paywall but, if you can wait one year, free access can be gained if you register (for free) with Science.

# Producing catalytically active gold nanoparticles at absolute zero

A Sept. 8, 2016 news item on Nanowerk describes research into producing remarkably stable gold nanoparticles with catalytic capabilities (Note: A link has been removed),

An ultra-high-vacuum chamber with temperatures approaching absolute zero—the coldest anything can get—may be the last place you would expect to find gold. But a group of researchers from Stony Brook University (SBU) in collaboration with scientists at the Air Force Research Lab (AFRL) and the U.S. Department of Energy’s (DOE) Brookhaven National Laboratory have just demonstrated that such a desolate place is ideal for producing catalytically active gold nanoparticles.

A paper describing the first catalyst ever produced using their new method, called Helium Nanodroplet Deposition (HND), was recently published in the Journal of Physical Chemistry Letters (“Development of a New Generation of Stable, Tunable, and Catalytically Active Nanoparticles Produced by the Helium Nanodroplet Deposition Method”).

A Sept. 7, 2016 Brookhaven National Laboratory news release by Alexander Orlov and Karen McNulty Walsh, which originated the news item, describes the work in more detail,

As lead researcher Alexander Orlov of SBU explains, HND works by boiling gold atoms in a vacuum to produce a vapor. The vaporized gold is then “picked up” by an extremely cold jet stream of liquid helium droplets that act to literally strike gold clusters against a solid collector downstream. Upon striking the collector, the liquid helium droplets instantly evaporate releasing helium gas and leaving behind unprecedentedly pure and stable gold nanoparticles.

“This new method to produce active nanoparticles offers unique opportunities to create materials with unprecedented properties to solve energy and environmental problems,” Orlov said.  “Our Brookhaven and AFRL collaborators made it possible for our students to access the most unique facilities in the world, which made all the difference in our research.”

Qiyuan Wu, a graduate student working in Orlov’s laboratory and first author on the paper, performed much of the work to develop the method. Michael Lindsay and Claron Ridge of AFRL provided state-of-the-art facilities at Eglin Air Force Base, one of only a few places in the world with the capabilities required to generate the gold nanoparticles using the new technique. And a team at the Center for Functional Nanomaterials (CFN), a DOE Office of Science User Facility at Brookhaven Lab, used advanced imaging and characterization tools to study the nanoparticles’ catalytic activity.

Specifically, Brookhaven scientists Eric Stach and Dmitri Zakharov of the CFN and Shen Zhao, then a postdoctoral fellow working under Stach, developed a method to deposit the gold nanoparticles onto a “catalyst support” structure they use for characterizing the stability of other nanomaterials. They then studied the characteristics of the nanoparticles, including their stability under reaction conditions, using the Titan Environmental Transmission Electron Microscope at the CFN. Further characterization by Zhao and CFN staff member Dong Su using aberration-corrected Scanning Transmission Electron Microscopy allowed the SBU researchers to understand how the droplets form.

“This was part of a User project, that morphed into a collaboration,” said Stach, who leads the electron microscopy group at CFN. “It was a very nice study”—and an example of how the Office of Science User Facilities offer not just unique scientific equipment but also scientific expertise that can be essential to the success of a research project.

Nanoparticles are of high research interest due to their improved properties compared to bulk materials. They have revolutionized technologies aimed at improving sustainability such as fuel cells, photocatalysts, and solar panels. The gold nanoparticle catalysts produced in this study are capable of converting poisonous carbon monoxide gas into carbon dioxide gas, an essential reaction that occurs in the catalytic converters of cars to reduce pollution and lower impacts on the environment.

According to Orlov, the HND method is not limited to the production of gold nanoparticles, but can be applied to nearly all metals and can even produce challenging multi-metallic nanoparticles. The technique’s versatility and ability to produce clean and well-defined samples make it a powerful tool for the discovery of new catalysts and studying factors that affect catalyst performance.

The collaboration is currently researching how the parameters of HND can be adjusted to control catalyst performance.

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

Development of a New Generation of Stable, Tunable, and Catalytically Active Nanoparticles Produced by the Helium Nanodroplet Deposition Method by Qiyuan Wu, Claron J. Ridge, Shen Zhao, Dmitri Zakharov, Jiajie Cen, Xiao Tong, Eoghan Connors, Dong Su, Eric A. Stach, C. Michael Lindsay, and Alexander Orlov. J. Phys. Chem. Lett., 2016, 7 (15), pp 2910–2914 DOI: 10.1021/acs.jpclett.6b01305 Publication Date (Web): July 13, 2016

This paper is behind a paywall.

# Making magnetic rust behave like gold and the nanoscale

Researchers at the University of Georgia (US) have found a way to combine gold nanoparticles with magnetic rust nanoparticles for a hybrid structure that behaves with the properties of both types of nanoparticles. From a Sept. 15, 2016 news item on ScienceDaily,

Researchers from the University of Georgia are giving new meaning to the phrase “turning rust into gold”—and making the use of gold in research settings and industrial applications far more affordable.

The research is akin to a type of modern-day alchemy, said Simona Hunyadi Murph, adjunct professor in the UGA Franklin College of Arts and Sciences department of physics and astronomy. Researchers combine small amounts of gold nanoparticles with magnetic rust nanoparticles to create a hybrid nanostructure that retains both the properties of gold and rust.

A Sept. 15, 2016 University of Georgia news release by Jessica Luton, which originated the news item, expands on the theme,

“Medieval alchemists tried to create gold from other metals,” she said. “That’s kind of what we did with our research. It’s not real alchemy, in the medieval sense, but it is a sort of 21st century version.”

Gold has long been a valuable resource for industry, medicine, dentistry, computers, electronics and aerospace, among others, due to unique physical and chemical properties that make it inert and resistant to oxidation. But because of its high cost and limited supply, large scale projects using gold can be prohibitive. At the nanoscale, however, using a very small amount of gold is far more affordable.

In the new study published this summer in the Journal of Physical Chemistry C, the researchers used solution chemistry to reduce gold ions into a metallic gold structure using sodium citrate. In this process, if other ingredients-rust in this case-are present in the reaction pot during the transformation process, the metallic gold structures nucleate and grow on these “ingredients,” otherwise known as supports.

“We are really excited to share our new discoveries. When researchers are looking at gold as a potential material for research, we talk about how expensive gold is. For the first time ever, we’ve been able to create a new class of cheaper, highly efficient, nontoxic, magnetically reusable hybrid nanomaterials that contain a far more abundant material-rust-than the typical noble metal gold,” said Murph, who is also a principal scientist in the National Security Directorate at the Savannah River National Laboratory in Aiken, South Carolina.

When materials are broken down in size to reach nanometer scale dimensions-1-100 nanometers, which is approximately 100,000 times smaller than the diameter of human hair-these substances can take on new properties. For example, bulk gold does not display catalytic properties; however, at the nanoscale, gold is an efficient catalyst, accelerating chemical change for many reactions including oxidation, hydrogen production or reduction of aromatic nitro compounds.

Gold nanoparticles of different sizes and shapes display different colors when impinged by light because they absorb and scatter light at specific wavelengths, known as plasmonic resonances. These plasmonic resonances are of particular interest for biological applications. If someone shines light on the gold nanoparticles, the absorbed light can be converted to heat in the surrounding media, and if bacteria or cancerous cells are in the vicinity of such gold nanoparticles, they can be destroyed by using light of appropriate wavelength. This phenomenon is known as photothermal therapy.

By replacing some of the nano-gold with magnetic nano-rust, researchers show that the hybrid gold and rust nanostructures are able to photothermally heat the surrounding media as efficiently as pure gold nanoparticles, even with a significantly smaller concentration of gold.

“In a way, we’ve done a little better than alchemy,” said George Larsen, co-investigator and postdoctoral researcher in the Group for Innovation and Advancements in Nano-Technology Sciences at the Savannah River National Laboratory, “because these new hybrid nanoparticles not only behave better than gold in some cases, but also have magnetic functionality.”

Murph and her team looked at three different shapes of hybrid nanoparticles in this research-spheres, rings and tubes.

“A differently shaped nanoparticle means that the atoms are arranged differently-into cubes, hexagons or triangles, for example,” she said. “A different atom arrangement means different packing densities, spacing between atoms, defects, surface area and surface energies. Different shapes lead to an increased atom area that is exposed to catalyze a chemical reaction. Scientifically speaking, different shape means different crystallographic facets and surface energy that could lead to higher catalytic activity and different catalytic products.

“The results of our research showed that the ring- and tube-shaped hybrid nanoparticles proved to be better catalytic materials than the sphere-shaped nanoparticles because of the way the atoms are arranged in the structure at this nanoscale. More importantly, the hybrid nanoparticles of gold and rust are better catalysts than gold nanoparticles alone, even with a significantly smaller amount of gold.

When these different shaped hybrid nanoparticles were exposed to light of specific wavelength, the spheres heated the solution up to slightly higher temperatures than the ring- or tube-shaped nanoparticles.

“This could have a variety of biological applications such as tracking, drug delivery or imaging inside the body,” Murph said. “If you feed these gold nanoparticles to bacteria and shine the light on them, you could destroy these by just using light.”

The hybrid structures could also be used for new application [sic], such as sensing, hyperthermia treatment, environmental cleaning and protection medical imaging applications including magnetic resonance imaging contrast agents, product detection and manipulation.

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

Multifunctional Hybrid Fe2O3-Au Nanoparticles for Efficient Plasmonic Heating by Simona E. Hunyadi Murph, George K. Larsen, Robert J. Lascola. Journal of Visualized Experiments, 2016; (108) DOI: 10.3791/53598

This paper/video appears to be open access.

# Counteracting chemotherapy resistance with nanoparticles that mimic salmonella

Given the reputation that salmonella (for those who don’t know, it’s a toxin you don’t want to find in your food) has, a nanoparticle which mimics its effects has a certain cachet. An Aug. 22, 2016 news item on Nanowerk,

Researchers at the University of Massachusetts Medical School have designed a nanoparticle that mimics the bacterium Salmonella and may help to counteract a major mechanism of chemotherapy resistance.

Working with mouse models of colon and breast cancer, Beth McCormick, Ph.D., and her colleagues demonstrated that when combined with chemotherapy, the nanoparticle reduced tumor growth substantially more than chemotherapy alone.

Credit: Rocky Mountain Laboratories,NIAID,NIHColor-enhanced scanning electron micrograph showing Salmonella typhimurium (red) invading cultured human cells.

An Aug. 22, 2016 US National Institute of Cancer news release, which originated the news item, explains the research in more detail,

A membrane protein called P-glycoprotein (P-gp) acts like a garbage chute that pumps waste, foreign particles, and toxins out of cells. P-gp is a member of a large family of transporters, called ATP-binding cassette (ABC) transporters, that are active in normal cells but also have roles in cancer and other diseases. For instance, cancer cells can co-opt P-gp to rid themselves of chemotherapeutic agents, severely limiting the efficacy of these drugs.

In previous work, Dr. McCormick and her colleagues serendipitously discovered that Salmonella enterica, a bacterium that causes food poisoning, decreases the amount of P-gp on the surface of intestinal cells. Because Salmonella has the capacity to grow selectively in cancer cells, the researchers wondered whether there was a way to use the bacterium to counteract chemotherapy resistance caused by P-gp.

“While trying to understand how Salmonella invades the human host, we made this other observation that may be relevant to cancer therapeutics and multidrug resistance,” explained Dr. McCormick.

Salmonella and Cancer Cells

To determine the specific bacterial component responsible for reducing P-gp levels, the researchers engineered multiple Salmonella mutant strains and tested their effect on P-gp levels in colon cells. They found that a Salmonella strain lacking the bacterial protein SipA was unable to reduce P-gp levels in the colon of mice or in a human colon cancer cell line. Salmonella secretes SipA, along with other proteins, to help the bacterium invade human cells.

The researchers then showed that treatment with SipA protein alone decreased P-gp levels in cell lines of human colon cancer, breast cancer, bladder cancer, and lymphoma.

Because P-gp can pump drugs out of cells, the researchers next sought to determine whether SipA treatment would prevent cancer cells from expelling chemotherapy drugs.

When they treated human colon cancer cells with the chemotherapy agents doxorubicin or vinblastine, with or without SipA, they found that the addition of SipA increased drug retention inside the cells. SipA also increased the cancer cells’ sensitivity to both drugs, suggesting that it could possibly be used to enhance chemotherapy.

“Through millions of years of co-evolution, Salmonella has figured out a way to remove this transporter from the surface of intestinal cells to facilitate host infection,” said Dr. McCormick. “We capitalized on the organism’s ability to perform that function.”

A Nanoparticle Mimic

It would not be feasible to infect people with the bacterium, and SipA on its own will likely deteriorate quickly in the bloodstream, coauthor Gang Han, Ph.D., of the University of Massachusetts Medical School, explained in a press release. The researchers therefore fused SipA to gold nanoparticles, generating what they refer to as a nanoparticle mimic of Salmonella. They designed the nanoparticle to enhance the stability of SipA, while retaining its ability to interact with other proteins.

In an effort to target tumors without harming healthy tissues, the researchers used a nanoparticle of specific size that should only be able to access the tumor tissue due to its “leaky” architecture. “Because of this property, we are hoping to be able to avoid negative effects to healthy tissues,” said Dr. McCormick. Another benefit of this technology is that the nanoparticle can be modified to enhance tumor targeting and minimize the potential for side effects, she added.

The researchers showed that this nanoparticle was 100 times more effective than SipA protein alone at reducing P-gp levels in a human colon cancer cell line. The enhanced function of the nanoparticle is likely due to stabilization of SipA, explained the researchers.

The team then tested the nanoparticle in a mouse model of colon cancer, because this cancer type is known to express high levels of P-gp. When they treated tumor-bearing mice with the nanoparticle plus doxorubicin, P-gp levels dropped and the tumors grew substantially less than in mice treated with the nanoparticle or doxorubicin alone. The researchers observed similar results in a mouse model of human breast cancer.

There are concerns about the potential effect of nanoparticles on normal tissues. “P-gp has evolved as a defense mechanism” to rid healthy cells of toxic molecules, said Suresh Ambudkar, Ph.D., deputy chief of the Laboratory of Cell Biology in NCI’s Center for Cancer Research. It plays an important role in protecting cells of the blood-brain barrier, liver, testes, and kidney. “So when you try to interfere with that, you may create problems,” he said.

The researchers, however, found no evidence of nanoparticle accumulation in the brain, heart, kidney, or lungs of mice, nor did it appear to cause toxicity. They did observe that the nanoparticles accumulated in the liver and spleen, though this was expected because these organs filter the blood, said Dr. McCormick.

Moving Forward

The research team is moving forward with preclinical studies of the SipA nanoparticle to test its safety and toxicity, and to establish appropriate dosage levels.

However, Dr. Ambudkar noted, “the development of drug resistance in cancer cells is a multifactorial process. In addition to the ABC transporters, other phenomena are involved, such as drug metabolism.” And because there is a large family of ABC transporters, one transporter can compensate if another is blocked, he explained.

For the last 25 years, clinical trials with drugs that inhibit P-gp have failed to overcome chemotherapy resistance, Dr. Ambudkar said. Tackling the issue of multidrug resistance in cancer, he continued, “is not something that can be solved easily.”

Dr. McCormick and her team are also pursuing research to better characterize and understand the biology of SipA. “We are not naïve about the complexity of the problem,” she said. “However, if we know more about the biology, we believe we can ultimately make a better drug.”

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

A Salmonella nanoparticle mimic overcomes multidrug resistance in tumours by Regino Mercado-Lubo, Yuanwei Zhang, Liang Zhao, Kyle Rossi, Xiang Wu, Yekui Zou, Antonio Castillo, Jack Leonard, Rita Bortell, Dale L. Greiner, Leonard D. Shultz, Gang Han, & Beth A. McCormick. Nature Communications 7, Article number: 12225  doi:10.1038/ncomms12225 Published 25 July 2016

This paper is open access.

# Generating clean fuel with individual gold atoms

A July 22, 2016 news item on Nanowerk highlights an international collaboration focused on producing clean fuel,

A combined experimental and theoretical study comprising researchers from the Chemistry Department and LCN [London Centre for Nanotechnology], along with groups in Argentina, China, Spain and Germany, has shed new light on the behaviour of individual gold atoms supported on defective thin cerium dioxide films – an important system for catalysis and the generation of clean hydrogen for fuel.

A July ??, 2016 LCN press release, which originated the news item, expands on the theme of catalysts, the research into individual gold atoms, and how all this could result in clean fuel,

Catalysis plays a vital role in our world; an estimated 80% of all chemical and materials are made via processes which involve catalysts, which are commonly a mixture of metals and oxides. The standard motif for these heterogeneous catalysts (where the catalysts are solid and the reactants are in the gas phase) is of a high surface area oxide support that is decorated with metal nanoparticles a few nanometres in diameter. Cerium dioxide (ceria, CeO2) is a widely used support material for many important industrial processes; metal nanoparticles supported on ceria have displayed high activities for applications including car catalytic converters, alcohol synthesis, and for hydrogen production. There are two key attributes of ceria which make it an excellent active support material: its oxygen storage and release ability, and its ability to stabilise small metal particles under reaction conditions. A recent system that has been the focus of much interest has been that of gold nanoparticles and single atoms with ceria, which has demonstrated high activity towards the water-gas-shift reaction, (CO + H2O —> CO2 + H2) a key stage in the generation of clean hydrogen for use in fuel cells.

The nature of the active sites of these catalysts and the role that defects play are still relatively poorly understood; in order to study them in a systematic fashion, the researchers prepared model systems which can be characterised on the atomic scale with a scanning tunnelling microscope.

Figure: STM images of CeO2-x(111) ultrathin films before and after the deposition of Au single atoms at 300 K. The bright lattice is from the oxygen atoms at the surface – vacancies appear as dark spots

These model systems comprised well-ordered, epitaxial ceria films less than 2 nm thick, prepared on a metal single crystal, upon which single atoms and small clusters of gold were evaporated onto under ultra-high-vacuum (essential to prevent contamination of the surfaces). Oxygen vacancy defects – missing oxygen atoms in the top layer of the ceria – are relatively common at the surface and appear as dark spots in the STM images. By mapping the surface before and after the deposition of gold, it is possible to analyse the binding of the metal atoms, in particular there does not appear to be any preference for binding in the vacancy sites at 300 K.

Publishing their results in Physical Review Letters, the researchers combined these experimental results with theoretical studies of the binding energies and diffusion rates across the surface. They showed that kinetic effects governed the behaviour of the gold atoms, prohibiting the expected occupation of the thermodynamically more stable oxygen vacancy sites. They also identified electron transfer between the gold atoms and the ceria, leading to a better understanding of the diffusion phenomena that occur at this scale, and demonstrated that the effect of individual surface defects may be more minor than is normally imagined.

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

Diffusion Barriers Block Defect Occupation on Reduced CeO2(111) by P.G. Lustemberg, Y. Pan, B.-J. Shaw, D. Grinter, Chi Pang, G. Thornton, Rubén Pérez, M. V. Ganduglia-Pirovano, and N. Nilius. Phys. Rev. Lett. Vol. 116, Iss. 23 — 10 June 2016 2016DOI:http://dx.doi.org/10.1103/PhysRevLett.116.236101 Published 9 June 2016

This paper is behind a paywall.

# Gold nanoparticles and two different collective oscillations

An April 27, 2016 news item on phys.org describes research into gold nanoparticles and Surface Plasmon Resonance at Hokkaido University and the University of Tsukuba (Japan),

The research group of Professor Hiroaki Misawa of Research Institute for Electronic Science, Hokkaido University and Assistant Professor Atsushi Kubo of the Faculty of Pure and Applied Sciences, University of Tsukuba, have successfully observed the dephasing time of the two different types of collective motions of electrons generated on the surface of a gold nanoparticle for the first time in the world, by combining a laser that emits ultrashort light pulses with a photoemission electron microscope.

An April 26, 2016 Hokkaido University press release, which originated the news item, explains further,

When gold is reduced to the size in nanometer scale, its color is red instead of gold. When gold nanoparticles are exposed to light, the collective oscillations of electrons existing on the localized surface of the gold causes red light to be strongly absorbed and dispersed.

This phenomenon is called Surface Plasmon Resonance. The red color of stained glass is also a result of this phenomenon. Recently, gold nanoparticles have been widely used in various fields, such as application in pregnancy tests.

This collective oscillations of electrons on the surface of gold nanoparticles caused by light was considered to be a phenomenon that sustained only for an extremely short time, and difficult to measure due to this shortness.

Our research group developed a methodology to measure the dephasing time of the collective oscillations of electrons occurring on the surface of gold nanoparticles by combining a laser that emits ultrashort light pulses of a few femtoseconds (1 femtosecond: 1´10-15 seconds), and a photoemission electron microscope in high spatial resolution.

When measured by this technique, the different dephasing times of the two different collective oscillations, namely dipole and quadrupole surface plasmon modes, could be resolved and identified as 5 femtoseconds and 9 femtoseconds, respectively.

Research using gold nanoparticles as optical antennae to harvest light for photovoltaic cell and an artificial photosynthesis system that can split water to obtain hydrogen is progressing. The successful measurement of the dephasing time of the collective oscillations of electrons is considered to be a useful guideline in developing these systems.

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

Dissecting the Few-Femtosecond Dephasing Time of Dipole and Quadrupole Modes in Gold Nanoparticles Using Polarized Photoemission Electron Microscopy by Quan Sun†, Han Yu, Kosei Ueno, Atsushi Kubo, Yasutaka Matsuo, and Hiroaki Misawa. ACS Nano, 2016, 10 (3), pp 3835–3842 DOI: 10.1021/acsnano.6b00715Publication Date (Web): February 15, 2016

This paper appears to be open access.

# Black gold: ultralight, high density nanoporous gold

South Korean researchers have found a way to fabricate a new kind of gold nanoparticle according to a March 28, 2016 news item on ScienceDaily,

A new material is more solid and 30 percent lighter than standard gold, scientists report. In their study, the team investigated grain boundaries in nanocrystalline np-Au and found a way to overcome the weakening mechanisms of this material, thereby suggesting its usefulness.

A March 28, 2016 Ulsan National Institute of Science and Technology (UNIST) press release (also on EurekAlert) by Chorok Oh, which originated the news item, provides more information,

A team of Korean research team, led by Professor Ju-Young Kim (School of Materials Science and Engineering) of Ulsan National Institute of Science and Technology (UNIST), South Korea has recently announced that they have successfully developed a way to fabricate an ultralight, high-dense nanoporous gold (np-Au).

In a new paper, published in Nano Letters on March 22, the team reported that this newly developed material, which they have dubbed “Black Gold” is twice more solid and 30% lighter than standard gold.

According to Prof. Kim, “This particular nanoporous gold has a 100,000 times wider surface when compared to standard gold. Moreover, due to its chemically stablity, it is also harmless to humans.”

The surfaces of np-Au are rough and the metal loses its shine and eventually turns black when they are at sizes less than 100 nanometres (nm). This is the reason that they are called “Black Gold”.

In their study, the team investigated grain boundaries in nanocrystalline np-Au and found a way to overcome the weakening mechanisms of this material, thereby suggesting its usefulness.

The team used a ball milling technique to increase the flexural strength of the three gold-silver precursor alloys. Then, using free corrosion dealloying of silver from gold-silver alloys, they were able to achieve the nanoporous surface. According to the team, “The size of the pores can be controlled by the temperature and concentration of nitrate.” Moreover, they also note that this crack-free nanoporous gold samples are reported to exhibit excellent durability in three-point bending tests.

Prof. Kim’s team notes, “Ball-milled np-Au has a much greater density of two-dimensional defects than annealed and prestrained np-Au, where intergranular fracture is preferred.” They continue, “Therefore, the probable existence of grain boundary opening in the highest tensile region is attributed to the flexural strength of np-Au.”

They suggest that this newly developed technique can be also applied to many other metal, as the np-Au produced by this technique have shown increased strength and durability while still maintaining the good qualities of standard gold.

This means that this technique can be also used in other technologies, like catalytic-converting as observed by platinum, the automobile catalyst and palladium, the hydrogen sensor catalyst.

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

Weakened Flexural Strength of Nanocrystalline Nanoporous Gold by Grain Refinement by Eun-Ji Gwak and Ju-Young Kim. Nano Lett., Article ASAP DOI: 10.1021/acs.nanolett.6b00062 Publication Date (Web): March 16, 2016

This paper is behind a paywall.

# Mass production of nanoparticles?

With all the years of nanotechnology and nanomaterials research it seems strange that mass production of nanoparticles is still very much in the early stages as a Feb. 24, 2016 news item on phys.org points out,

Nanoparticles – tiny particles 100,000 times smaller than the width of a strand of hair – can be found in everything from drug delivery formulations to pollution controls on cars to HD TV sets. With special properties derived from their tiny size and subsequently increased surface area, they’re critical to industry and scientific research.

They’re also expensive and tricky to make.

Now, researchers at USC [University of Southern California] have created a new way to manufacture nanoparticles that will transform the process from a painstaking, batch-by-batch drudgery into a large-scale, automated assembly line.

A Feb. 24, 2016 USC news release (also on EurekAlert) by Robert Perkins, which originated the news item, offers additional insight,

Consider, for example, gold nanoparticles. They have been shown to easily penetrate cell membranes without causing any damage — an unusual feat given that most penetrations of cell membranes by foreign objects can damage or kill the cell. Their ability to slip through the cell’s membrane makes gold nanoparticles ideal delivery devices for medications to healthy cells or fatal doses of radiation to cancer cells.

However, a single milligram of gold nanoparticles currently costs about $80 (depending on the size of the nanoparticles). That places the price of gold nanoparticles at$80,000 per gram while a gram of pure, raw gold goes for about \$50.

“It’s not the gold that’s making it expensive,” Malmstadt [Noah Malmstadt of the USC Viterbi School of Engineering] said. “We can make them, but it’s not like we can cheaply make a 50-gallon drum full of them.”

A fluid situation

At this time, the process of manufacturing a nanoparticle typically involves a technician in a chemistry lab mixing up a batch of chemicals by hand in traditional lab flasks and beakers.

The new technique used by Brutchey [Richard Brutchey of the USC Dornsife College of Letters, Arts and Sciences] and Malmstadt instead relies on microfluidics — technology that manipulates tiny droplets of fluid in narrow channels.

“In order to go large scale, we have to go small,” Brutchey said.

Really small.

The team 3-D printed tubes about 250 micrometers in diameter, which they believe to be the smallest, fully enclosed 3-D printed tubes anywhere. For reference, your average-sized speck of dust is 50 micrometers wide.

They they built a parallel network of four of these tubes, side-by-side, and ran a combination of two nonmixing fluids (like oil and water) through them. As the two fluids fought to get out through the openings, they squeezed off tiny droplets. Each of these droplets acted as a micro-scale chemical reactor in which materials were mixed and nanoparticles were generated. Each microfluidic tube can create millions of identical droplets that perform the same reaction.

This sort of system has been envisioned in the past, but it hasn’t been able to be scaled up because the parallel structure meant that if one tube got jammed, it would cause a ripple effect of changing pressures along its neighbors, knocking out the entire system. Think of it like losing a single Christmas light in one of the old-style strands — lose one and you lose them all.

Brutchey and Malmstadt bypassed this problem by altering the geometry of the tubes themselves, shaping the junction between the tubes such that the particles come out a uniform size and the system is immune to pressure changes.

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

Flow invariant droplet formation for stable parallel microreactors by Carson T. Riche, Emily J. Roberts, Malancha Gupta, Richard L. Brutchey & Noah Malmstadt. Nature Communications 7, Article number: 10780 doi:10.1038/ncomms10780 Published 23 February 2016

This is an open access paper.

# A nanoparticle ‘printing press’

This research comes from Montréal, Canada via a Jan. 7, 2016 McGill University news release (also on EurekAlert*),

Gold nanoparticles have unusual optical, electronic and chemical properties, which scientists are seeking to put to use in a range of new technologies, from nanoelectronics to cancer treatments.

Some of the most interesting properties of nanoparticles emerge when they are brought close together – either in clusters of just a few particles or in crystals made up of millions of them. Yet particles that are just millionths of an inch in size are too small to be manipulated by conventional lab tools, so a major challenge has been finding ways to assemble these bits of gold while controlling the three-dimensional shape of their arrangement.

One approach that researchers have developed has been to use tiny structures made from synthetic strands of DNA to help organize nanoparticles. Since DNA strands are programmed to pair with other strands in certain patterns, scientists have attached individual strands of DNA to gold particle surfaces to create a variety of assemblies. But these hybrid gold-DNA nanostructures are intricate and expensive to generate, limiting their potential for use in practical materials. The process is similar, in a sense, to producing books by hand.

Enter the nanoparticle equivalent of the printing press. It’s efficient, re-usable and carries more information than previously possible. In results reported online in Nature Chemistry, researchers from McGill’s Department of Chemistry outline a procedure for making a DNA [deoxyribonucleic acid] structure with a specific pattern of strands coming out of it; at the end of each strand is a chemical “sticky patch.”  When a gold nanoparticle is brought into contact to the DNA nanostructure, it sticks to the patches. The scientists then dissolve the assembly in distilled water, separating the DNA nanostructure into its component strands and leaving behind the DNA imprint on the gold nanoparticle. …

The researchers have made an illustration of their concept available,

Credit: Thomas Edwardson

“These encoded gold nanoparticles are unprecedented in their information content,” says senior author Hanadi Sleiman, who holds the Canada Research Chair in DNA Nanoscience. “The DNA nanostructures, for their part, can be re-used, much like stamps in an old printing press.”

The news release includes suggestions for possible future applications,

From stained glass to optoelectronics

Some of the properties of gold nanoparticles have been recognized for centuries.  Medieval artisans added gold chloride to molten glass to create the ruby-red colour in stained-glass windows – the result, as chemists figured out much later, of the light-scattering properties of tiny gold particles.

Now, the McGill researchers hope their new production technique will help pave the way for use of DNA-encoded nanoparticles in a range of cutting-edge technologies. First author Thomas Edwardson says the next step for the lab will be to investigate the properties of structures made from these new building blocks. “In much the same way that atoms combine to form complex molecules, patterned DNA gold particles can connect to neighbouring particles to form well-defined nanoparticle assemblies.”

These could be put to use in areas including optoelectronic nanodevices and biomedical sciences, the researchers say. The patterns of DNA strands could, for example, be engineered to target specific proteins on cancer cells, and thus serve to detect cancer or to selectively destroy cancer cells.

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

Transfer of molecular recognition information from DNA nanostructures to gold nanoparticles by Thomas G. W. Edwardson, Kai Lin Lau, Danny Bousmail, Christopher J. Serpell, & Hanadi F. Sleiman. Nature Chemistry (2016)  doi:10.1038/nchem.2420 Published online 04 January 2016

This paper is behind a paywall.