Tag Archives: gold nanoparticles

Synthesized nanoparticles with the complexity of protein molecules

Caption: The structure of the largest gold nanoparticle to-date, Au246(SR)80, was resolved using x-ray crystallography. Credit: Carnegie Mellon University

Carnegie Mellon University (CMU) researchers synthesized a self-assembled nanoparticle of gold as they built on their 2015 work described in my April 14, 2015 posting (Nature’s patterns reflected in gold nanoparticles). Here’s the latest from the team in a Jan. 23, 2017 news item on phys.org,

Chemists at Carnegie Mellon University have demonstrated that synthetic nanoparticles can achieve the same level of structural complexity, hierarchy and accuracy as their natural counterparts – biomolecules. The study, published in Science, also reveals the atomic-level mechanisms behind nanoparticle self-assembly.

The findings from the lab of Chemistry Professor Rongchao Jin provide researchers with an important window into how nanoparticles form, and will help guide the construction of nanoparticles, including those that can be used in the fabrication of computer chips, creation of new materials, and development of new drugs and drug delivery devices.

Caption: By resolving the structure of Au246, Carnegie Mellon researchers were able to visualize its hierarchical assembly into artificial solid. Credit: Carnegie Mellon University

A Jan.  23, 2017 CMU news release on EurekAlert, which originated the news item, expands on the theme,

“Most people think that nanoparticles are simple things, because they are so small. But when we look at nanoparticles at the atomic level, we found that they are full of wonders,” said Jin.

Nanoparticles are typically between 1 and 100 nanometers in size. Particles on the larger end of the nanoscale are harder to create precisely. Jin has been at the forefront of creating precise gold nanoparticles for a decade, first establishing the structure of an ultra-small Au25 nanocluster and then working on larger and larger ones. In 2015, his lab used X-ray crystallography to establish the structure of an Au133 nanoparticle and found that it contained complex, self-organized patterns that mirrored patterns found in nature.

In the current study, they sought to find out the mechanisms that caused these patterns to form. The researchers, led by graduate student Chenjie Zeng, established the structure of Au246, one of the largest and most complex nanoparticles created by scientists to-date and the largest gold nanoparticle to have its structure determined by X-ray crystallography. Au246 turned out to be an ideal candidate for deciphering the complex rules of self- assembly because it contains an ideal number of atoms and surface ligands and is about the same size and weight as a protein molecule.

Analysis of Au246’s structure revealed that the particles had much more in common with biomolecules than size. They found that the ligands in the nanoparticles self-assembled into rotational and parallel patterns that are strikingly similar to the patterns found in proteins’ secondary structure. This could indicate that nanoparticles of this size could easily interact with biological systems, providing new avenues for drug discovery.

The researchers also found that Au246 particles form by following two rules. First, they maximize the interactions between atoms, a mechanism that had been theorized but not yet seen. Second the nanoparticles match symmetric surface patterns, a mechanism that had not been considered previously. The matching, which is similar to puzzle pieces coming together, shows that the components of the particle can recognize each other by their patterns and spontaneously assemble into the highly ordered structure of a nanoparticle.

“Self-assembly is an important way of construction in the nanoworld. Understanding the rules of self-assembly is critical to designing and building up complex nanoparticles with a wide-range of functionalities,” said Zeng, the study’s lead author.

In future studies, Jin hopes to push the crystallization limits of nanoparticles even farther to larger and larger particles. He also plans to explore the particles’ electronic and catalytic power.

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

Emergence of hierarchical structural complexities in nanoparticles and their assembly by Chenjie Zeng, Yuxiang Chen, Kristin Kirschbaum, Kelly J. Lambright, Rongchao Jin. Science  23 Dec 2016: Vol. 354, Issue 6319, pp. 1580-1584 DOI: 10.1126/science.aak9750

This paper is behind a paywall.

Sniffing out disease (Na-Nose)

The ‘artificial nose’ is not a newcomer to this blog. The most recent post prior to this is a March 15, 2016 piece about Disney using an artificial nose for art conservation. Today’s (Jan. 9, 2016) piece concerns itself with work from Israel and ‘sniffing out’ disease, according to a Dec. 30, 2016 news item in Sputnik News,

A team from the Israel Institute of Technology has developed a device that from a single breath can identify diseases such as multiple forms of cancer, Parkinson’s disease, and multiple sclerosis. While the machine is still in the experimental stages, it has a high degree of promise for use in non-invasive diagnoses of serious illnesses.

The international team demonstrated that a medical theory first proposed by the Greek physician Hippocrates some 2400 years ago is true, certain diseases leave a “breathprint” on the exhalations of those afflicted. The researchers created a prototype for a machine that can pick up on those diseases using the outgoing breath of a patient. The machine, called the Na-Nose, tests breath samples for the presence of trace amounts of chemicals that are indicative of 17 different illnesses.

A Dec. 22, 2016 Technion Israel Institute of Technology press release offers more detail about the work,

An international team of 56 researchers in five countries has confirmed a hypothesis first proposed by the ancient Greeks – that different diseases are characterized by different “chemical signatures” identifiable in breath samples. …

Diagnostic techniques based on breath samples have been demonstrated in the past, but until now, there has not been scientific proof of the hypothesis that different and unrelated diseases are characterized by distinct chemical breath signatures. And technologies developed to date for this type of diagnosis have been limited to detecting a small number of clinical disorders, without differentiation between unrelated diseases.

The study of more than 1,400 patients included 17 different and unrelated diseases: lung cancer, colorectal cancer, head and neck cancer, ovarian cancer, bladder cancer, prostate cancer, kidney cancer, stomach cancer, Crohn’s disease, ulcerative colitis, irritable bowel syndrome, Parkinson’s disease (two types), multiple sclerosis, pulmonary hypertension, preeclampsia and chronic kidney disease. Samples were collected between January 2011 and June 2014 from in 14 departments at 9 medical centers in 5 countries: Israel, France, the USA, Latvia and China.

The researchers tested the chemical composition of the breath samples using an accepted analytical method (mass spectrometry), which enabled accurate quantitative detection of the chemical compounds they contained. 13 chemical components were identified, in different compositions, in all 17 of the diseases.

According to Prof. Haick, “each of these diseases is characterized by a unique fingerprint, meaning a different composition of these 13 chemical components.  Just as each of us has a unique fingerprint that distinguishes us from others, each disease has a chemical signature that distinguishes it from other diseases and from a normal state of health. These odor signatures are what enables us to identify the diseases using the technology that we developed.”

With a new technology called “artificially intelligent nanoarray,” developed by Prof. Haick, the researchers were able to corroborate the clinical efficacy of the diagnostic technology. The array enables fast and inexpensive diagnosis and classification of diseases, based on “smelling” the patient’s breath, and using artificial intelligence to analyze the data obtained from the sensors. Some of the sensors are based on layers of gold nanoscale particles and others contain a random network of carbon nanotubes coated with an organic layer for sensing and identification purposes.

The study also assessed the efficiency of the artificially intelligent nanoarray in detecting and classifying various diseases using breath signatures. To verify the reliability of the system, the team also examined the effect of various factors (such as gender, age, smoking habits and geographic location) on the sample composition, and found their effect to be negligible, and without impairment on the array’s sensitivity.

“Each of the sensors responds to a wide range of exhalation components,” explain Prof. Haick and his previous Ph.D student, Dr. Morad Nakhleh, “and integration of the information provides detailed data about the unique breath signatures characteristic of the various diseases. Our system has detected and classified various diseases with an average accuracy of 86%.

This is a new and promising direction for diagnosis and classification of diseases, which is characterized not only by considerable accuracy but also by low cost, low electricity consumption, miniaturization, comfort and the possibility of repeating the test easily.”

“Breath is an excellent raw material for diagnosis,” said Prof. Haick. “It is available without the need for invasive and unpleasant procedures, it’s not dangerous, and you can sample it again and again if necessary.”

Here’s a schematic of the study, which the researchers have made available,

Diagram: A schematic view of the study. Two breath samples were taken from each subject, one was sent for chemical mapping using mass spectrometry, and the other was analyzed in the new system, which produced a clinical diagnosis based on the chemical fingerprint of the breath sample. Courtesy: Tech;nion

There is also a video, which covers much of the same ground as the press release but also includes information about the possible use of the Na-Nose technology in the European Union’s SniffPhone project,

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

Diagnosis and Classification of 17 Diseases from 1404 Subjects via Pattern Analysis of Exhaled Molecules by Morad K. Nakhleh, Haitham Amal, Raneen Jeries, Yoav Y. Broza, Manal Aboud, Alaa Gharra, Hodaya Ivgi, Salam Khatib, Shifaa Badarneh, Lior Har-Shai, Lea Glass-Marmor, Izabella Lejbkowicz, Ariel Miller, Samih Badarny, Raz Winer, John Finberg, Sylvia Cohen-Kaminsky, Frédéric Perros, David Montani, Barbara Girerd, Gilles Garcia, Gérald Simonneau, Farid Nakhoul, Shira Baram, Raed Salim, Marwan Hakim, Maayan Gruber, Ohad Ronen, Tal Marshak, Ilana Doweck, Ofer Nativ, Zaher Bahouth, Da-you Shi, Wei Zhang, Qing-ling Hua, Yue-yin Pan, Li Tao, Hu Liu, Amir Karban, Eduard Koifman, Tova Rainis, Roberts Skapars, Armands Sivins, Guntis Ancans, Inta Liepniece-Karele, Ilze Kikuste, Ieva Lasina, Ivars Tolmanis, Douglas Johnson, Stuart Z. Millstone, Jennifer Fulton, John W. Wells, Larry H. Wilf, Marc Humbert, Marcis Leja, Nir Peled, and Hossam Haick. ACS Nano, Article ASAP DOI: 10.1021/acsnano.6b04930 Publication Date (Web): December 21, 2016

Copyright © 2017 American Chemical Society

This paper appears to be open access.

As for SniffPhone, they’re hoping that Na-Nose or something like it will allow them to modify smartphones in a way that will allow diseases to be detected.

I can’t help wondering who will own the data if your smartphone detects a disease. If you think that’s an idle question, here’s an excerpt from Sue Halpern’s Dec. 22, 2016 review of two books (“Weapons of Math Destruction: How Big Data Increases Inequality and Threatens Democracy” by Cathy O’Neil and “Virtual Competition: The Promise and Perils of the Algorithm-Driven Economy” by Ariel Ezrachi and Maurice E. Stucke) for the New York Times Review of Books,

We give our data away. We give it away in drips and drops, not thinking that data brokers will collect it and sell it, let alone that it will be used against us. There are now private, unregulated DNA databases culled, in part, from DNA samples people supply to genealogical websites in pursuit of their ancestry. These samples are available online to be compared with crime scene DNA without a warrant or court order. (Police are also amassing their own DNA databases by swabbing cheeks during routine stops.) In the estimation of the Electronic Frontier Foundation, this will make it more likely that people will be implicated in crimes they did not commit.

Or consider the data from fitness trackers, like Fitbit. As reported in The Intercept:

During a 2013 FTC panel on “Connected Health and Fitness,” University of Colorado law professor Scott Peppet said, “I can paint an incredibly detailed and rich picture of who you are based on your Fitbit data,” adding, “That data is so high quality that I can do things like price insurance premiums or I could probably evaluate your credit score incredibly accurately.”

Halpern’s piece is well worth reading in its entirety.

Gold nanoparticles concentrate light so atomic bonds can be viewed

 Artist's impression light waves capable of revealing atomic bonds Credit: NanoPhotonics Cambridge/Bart deNijs

Artist’s impression light waves capable of revealing atomic bonds Credit: NanoPhotonics Cambridge/Bart deNijs

This research upends centuries of scientific thought according to a Nov. 10, 2016 news item on ScienceDaily,

For centuries, scientists believed that light, like all waves, couldn’t be focused down smaller than its wavelength, just under a millionth of a metre. Now, researchers led by the University of Cambridge have created the world’s smallest magnifying glass, which focuses light a billion times more tightly, down to the scale of single atoms.

If they’ve created is a ‘magnifying glass’ as they call it in the news item, then I suppose you could call the ‘pico-cavity’ mentioned in the following press release, a lens.

A Nov. 10, 2016 University of Cambridge press release (also on EurekAlert), which originated the news item, describes the research in more detail,

In collaboration with European colleagues, the team used highly conductive gold nanoparticles to make the world’s tiniest optical cavity, so small that only a single molecule can fit within it. The cavity – called a ‘pico-cavity’ by the researchers – consists of a bump in a gold nanostructure the size of a single atom, and confines light to less than a billionth of a metre. The results, reported in the journal Science, open up new ways to study the interaction of light and matter, including the possibility of making the molecules in the cavity undergo new sorts of chemical reactions, which could enable the development of entirely new types of sensors.

According to the researchers, building nanostructures with single atom control was extremely challenging. “We had to cool our samples to -260°C in order to freeze the scurrying gold atoms,” said Felix Benz, lead author of the study. The researchers shone laser light on the sample to build the pico-cavities, allowing them to watch single atom movement in real time.

“Our models suggested that individual atoms sticking out might act as tiny lightning rods, but focusing light instead of electricity,” said Professor Javier Aizpurua from the Center for Materials Physics in San Sebastian in Spain, who led the theoretical section of this work.

“Even single gold atoms behave just like tiny metallic ball bearings in our experiments, with conducting electrons roaming around, which is very different from their quantum life where electrons are bound to their nucleus,” said Professor Jeremy Baumberg of the NanoPhotonics Centre at Cambridge’s Cavendish Laboratory, who led the research.

The findings have the potential to open a whole new field of light-catalysed chemical reactions, allowing complex molecules to be built from smaller components. Additionally, there is the possibility of new opto-mechanical data storage devices, allowing information to be written and read by light and stored in the form of molecular vibrations.

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

Single-molecule optomechanics in “picocavities” by Felix Benz, Mikolaj K. Schmidt, Alexander Dreismann, Rohit Chikkaraddy, Yao Zhang, Angela Demetriadou, Cloudy Carnegie, Hamid Ohadi, Bart de Nijs, Ruben Esteban, Javier Aizpurua, Jeremy J. Baumberg. Science  11 Nov 2016: Vol. 354, Issue 6313, pp. 726-729 DOI: 10.1126/science.aah5243

This paper is behind a paywall.

The character of water: both types

This is to use an old term, ‘mindblowing’. Apparently, there are two types of the liquid we call water according to a Nov. 10, 2016 news item on phys.org,

There are two types of liquid water, according to research carried out by an international scientific collaboration. This new peculiarity adds to the growing list of strange phenomena in what we imagine is a simple substance. The discovery could have implications for making and using nanoparticles as well as in understanding how proteins fold into their working shape in the body or misfold to cause diseases such as Alzheimer’s or CJD [Creutzfeldt-Jakob Disease].

A Nov. 10, 2016 Inderscience Publishers news release, which originated the news item, expands on the theme,

Writing in the International Journal of Nanotechnology, Oxford University’s Laura Maestro and her colleagues in Italy, Mexico, Spain and the USA, explain how the physical and chemical properties of water have been studied for more than a century and revealed some odd behavior not seen in other substances. For instance, when water freezes it expands. By contrast, almost every other known substance contracts when it is cooled. Water also exists as solid, liquid and gas within a very small temperature range (100 degrees Celsius) whereas the melting and boiling points of most other compounds span a much greater range.

Many of water’s bizarre properties are due to the molecule’s ability to form short-lived connections with each other known as hydrogen bonds. There is a residual positive charge on the hydrogen atoms in the V-shaped water molecule either or both of which can form such bonds with the negative electrons on the oxygen atom at the point of the V. This makes fleeting networks in water possible that are frozen in place when the liquid solidifies. They bonds are so short-lived that they do not endow the liquid with any structure or memory, of course.

The team has looked closely at several physical properties of water like its dielectric constant (how well an electric field can permeate a substance) or the proton-spin lattice relaxation (the process by which the magnetic moments of the hydrogen atoms in water can lose energy having been excited to a higher level). They have found that these phenomena seem to flip between two particular characters at around 50 degrees Celsius, give or take 10 degrees, i.e. from 40 to 60 degrees Celsius. The effect is that thermal expansion, speed of sound and other phenomena switch between two different states at this crossover temperature.

These two states could have important implications for studying and using nanoparticles where the character of water at the molecule level becomes important for the thermal and optical properties of such particles. Gold and silver nanoparticles are used in nanomedicine for diagnostics and as antibacterial agents, for instance. Moreover, the preliminary findings suggest that the structure of liquid water can strongly influence the stability of proteins and how they are denatured at the crossover temperature, which may well have implications for understanding protein processing in the food industry but also in understanding how disease arises when proteins misfold.

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

On the existence of two states in liquid water: impact on biological and nanoscopic systems
by L.M. Maestro, M.I. Marqués, E. Camarillo, D. Jaque, J. García Solé, J.A. Gonzalo, F. Jaque, Juan C. Del Valle, F. Mallamace, H.E. Stanley.
International Journal of Nanotechnology (IJNT), Vol. 13, No. 8/9, 2016 DOI: 10.1504/IJNT.2016.079670

This paper is behind a paywall.

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

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

Copyright © 2016 American Chemical Society

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.

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.