Before getting to the latest about carbon dots, there’s something to be clarified (and it was news to me), a carbon dot is not a quantum dot. So says this 2020 paper, “Advances in carbon dots: from the perspective of traditional quantum dots” by Yanhong Liu, Hui Huang, Weijing Cao, Baodong Mao, Yang Liu, and Zhenhui Kang. Mater. Chem. Front., 2020,4, 1586-1613 First published March 17, 2020.
Quantum dots (QDs) have been the core concept of nanoscience and nanotechnology since their inception, and play a dominant role in the development of the nano-field. Carbon dots (CDots), defined by a feature size of <10 nm, have become a rising star in the crossover field of carbon materials and traditional QDs (TQDs). CDots possess many unique structural, physicochemical and photochemical properties that render them a promising platform for biology, devices, catalysis and other applications. …
This story is about carbon dots but you can find out more about quantum dots in my October 6, 2023 posting concerning the 2023 Nobel prizes; scroll down to the ‘Chemistry’ subhead.
Researchers at Concordia have developed a new system using tiny nanosensors called carbon dots to detect the presence of the widely used chemical glyphosate. Their research, titled “Ratiometric Sensing of Glyphosate in Water Using Dual Fluorescent Carbon Dots,” is published in Sensors.
Glyphosate is a pesticide found in more than 750 agricultural, forestry, urban and home products, including Monsanto’s popular weed-killer Roundup. It is also controversial: studies have linked its overuse to environmental pollution and cancer in humans. Its sale is banned or restricted in dozens of countries and jurisdictions, including Canada.
The researchers’ system relies on the carbon dots’ chemical interaction with glyphosate to detect its presence. Carbon dots are exceedingly small fluorescent particles, usually no more than 10 or 15 nanometres in size (a human hair is between 80,000 and 100,000 nanometres). But when they are added to water solutions, these nanomaterials emit blue and red fluorescence.
The researchers employed an analysis technique called a ratiometric self-referencing assay to determine glyphosate levels in a solution. The red fluorescence emitted by the carbon dots when exposed to varying concentrations of the chemical and different pH levels is compared with a control in which no glyphosate is present. In all the tests, the blue fluorescence remained unchanged, giving the researchers a common reference point across the different tests.
They observed that higher levels of glyphosate quenched the red fluorescence, which they accredited to the interaction of the pesticide with the carbon dots’ surface.
“Our system differs from others because we are measuring the area between two peaks—two fluorescent signatures—on the visible spectrum,” says Adryanne Clermont-Paquette, a PhD candidate in biology and the paper’s lead author. “This is the integrated area between the two curves. Ratiometric measurement allows us to ignore variables such as temperature, pH levels or other environmental factors. That allows us to just only look at the levels of glyphosate and carbon dots that are in the system.”
“By understanding the chemistry at the surface of these very small dots and by knowing their optical properties, we can use them to our advantage for many different applications,” says Rafik Naccache, an associate professor of chemistry and biochemistry and the paper’s supervising author.
Research assistants Diego-Andrés Mendoza and Amir Sadeghi, along with associate professor of biology Alisa Piekny, are co-authors.
Naccache says the technique is designed to detect minute amounts of the pesticide. The technique they developed is sensitive enough to be able to detect the presence of pesticide at levels as low as 0.03 parts per million.
“The challenge is always in the other direction, to see how low we can go in terms of sensitivity and selectivity,” he says.
There remains much work to be done before this technology can be used widely. But as Clermont-Paquette notes, this paper represents an important beginning.
“Understanding the interaction between glyphosate and carbon dots is a first step. If we are to move this along further, and develop it into a real-life application, we have to start with the fundamentals.”
The researchers are supported by funding from the Natural Sciences and Engineering Research Council of Canada.
For the first time in the 15 years this blog has been around, the Nobel prizes awarded in medicine, physics, and chemistry all are in areas discussed here at one or another. As usual where people are concerned, some of these scientists had a tortuous journey to this prestigious outcome.
The Nobel Assembly at Karolinska Institutet [Sweden]
has today decided to award
the 2023 Nobel Prize in Physiology or Medicine
Katalin Karikó and Drew Weissman
for their discoveries concerning nucleoside base modifications that enabled the development of effective mRNA vaccines against COVID-19
The discoveries by the two Nobel Laureates were critical for developing effective mRNA vaccines against COVID-19 during the pandemic that began in early 2020. Through their groundbreaking findings, which have fundamentally changed our understanding of how mRNA interacts with our immune system, the laureates contributed to the unprecedented rate of vaccine development during one of the greatest threats to human health in modern times.
Vaccines before the pandemic
Vaccination stimulates the formation of an immune response to a particular pathogen. This gives the body a head start in the fight against disease in the event of a later exposure. Vaccines based on killed or weakened viruses have long been available, exemplified by the vaccines against polio, measles, and yellow fever. In 1951, Max Theiler was awarded the Nobel Prize in Physiology or Medicine for developing the yellow fever vaccine.
Thanks to the progress in molecular biology in recent decades, vaccines based on individual viral components, rather than whole viruses, have been developed. Parts of the viral genetic code, usually encoding proteins found on the virus surface, are used to make proteins that stimulate the formation of virus-blocking antibodies. Examples are the vaccines against the hepatitis B virus and human papillomavirus. Alternatively, parts of the viral genetic code can be moved to a harmless carrier virus, a “vector.” This method is used in vaccines against the Ebola virus. When vector vaccines are injected, the selected viral protein is produced in our cells, stimulating an immune response against the targeted virus.
Producing whole virus-, protein- and vector-based vaccines requires large-scale cell culture. This resource-intensive process limits the possibilities for rapid vaccine production in response to outbreaks and pandemics. Therefore, researchers have long attempted to develop vaccine technologies independent of cell culture, but this proved challenging.
mRNA vaccines: A promising idea
In our cells, genetic information encoded in DNA is transferred to messenger RNA (mRNA), which is used as a template for protein production. During the 1980s, efficient methods for producing mRNA without cell culture were introduced, called in vitro transcription. This decisive step accelerated the development of molecular biology applications in several fields. Ideas of using mRNA technologies for vaccine and therapeutic purposes also took off, but roadblocks lay ahead. In vitro transcribed mRNA was considered unstable and challenging to deliver, requiring the development of sophisticated carrier lipid systems to encapsulate the mRNA. Moreover, in vitro-produced mRNA gave rise to inflammatory reactions. Enthusiasm for developing the mRNA technology for clinical purposes was, therefore, initially limited.
These obstacles did not discourage the Hungarian biochemist Katalin Karikó, who was devoted to developing methods to use mRNA for therapy. During the early 1990s, when she was an assistant professor at the University of Pennsylvania, she remained true to her vision of realizing mRNA as a therapeutic despite encountering difficulties in convincing research funders of the significance of her project. A new colleague of Karikó at her university was the immunologist Drew Weissman. He was interested in dendritic cells, which have important functions in immune surveillance and the activation of vaccine-induced immune responses. Spurred by new ideas, a fruitful collaboration between the two soon began, focusing on how different RNA types interact with the immune system.
Karikó and Weissman noticed that dendritic cells recognize in vitro transcribed mRNA as a foreign substance, which leads to their activation and the release of inflammatory signaling molecules. They wondered why the in vitro transcribed mRNA was recognized as foreign while mRNA from mammalian cells did not give rise to the same reaction. Karikó and Weissman realized that some critical properties must distinguish the different types of mRNA.
RNA contains four bases, abbreviated A, U, G, and C, corresponding to A, T, G, and C in DNA, the letters of the genetic code. Karikó and Weissman knew that bases in RNA from mammalian cells are frequently chemically modified, while in vitro transcribed mRNA is not. They wondered if the absence of altered bases in the in vitro transcribed RNA could explain the unwanted inflammatory reaction. To investigate this, they produced different variants of mRNA, each with unique chemical alterations in their bases, which they delivered to dendritic cells. The results were striking: The inflammatory response was almost abolished when base modifications were included in the mRNA. This was a paradigm change in our understanding of how cells recognize and respond to different forms of mRNA. Karikó and Weissman immediately understood that their discovery had profound significance for using mRNA as therapy. These seminal results were published in 2005, fifteen years before the COVID-19 pandemic.
In further studies published in 2008 and 2010, Karikó and Weissman showed that the delivery of mRNA generated with base modifications markedly increased protein production compared to unmodified mRNA. The effect was due to the reduced activation of an enzyme that regulates protein production. Through their discoveries that base modifications both reduced inflammatory responses and increased protein production, Karikó and Weissman had eliminated critical obstacles on the way to clinical applications of mRNA.
mRNA vaccines realized their potential
Interest in mRNA technology began to pick up, and in 2010, several companies were working on developing the method. Vaccines against Zika virus and MERS-CoV were pursued; the latter is closely related to SARS-CoV-2. After the outbreak of the COVID-19 pandemic, two base-modified mRNA vaccines encoding the SARS-CoV-2 surface protein were developed at record speed. Protective effects of around 95% were reported, and both vaccines were approved as early as December 2020.
The impressive flexibility and speed with which mRNA vaccines can be developed pave the way for using the new platform also for vaccines against other infectious diseases. In the future, the technology may also be used to deliver therapeutic proteins and treat some cancer types.
Several other vaccines against SARS-CoV-2, based on different methodologies, were also rapidly introduced, and together, more than 13 billion COVID-19 vaccine doses have been given globally. The vaccines have saved millions of lives and prevented severe disease in many more, allowing societies to open and return to normal conditions. Through their fundamental discoveries of the importance of base modifications in mRNA, this year’s Nobel laureates critically contributed to this transformative development during one of the biggest health crises of our time.
Katalin Karikó was born in 1955 in Szolnok, Hungary. She received her PhD from Szeged’s University in 1982 and performed postdoctoral research at the Hungarian Academy of Sciences in Szeged until 1985. She then conducted postdoctoral research at Temple University, Philadelphia, and the University of Health Science, Bethesda. In 1989, she was appointed Assistant Professor at the University of Pennsylvania, where she remained until 2013. After that, she became vice president and later senior vice president at BioNTech RNA Pharmaceuticals. Since 2021, she has been a Professor at Szeged University and an Adjunct Professor at Perelman School of Medicine at the University of Pennsylvania.
Drew Weissman was born in 1959 in Lexington, Massachusetts, USA. He received his MD, PhD degrees from Boston University in 1987. He did his clinical training at Beth Israel Deaconess Medical Center at Harvard Medical School and postdoctoral research at the National Institutes of Health. In 1997, Weissman established his research group at the Perelman School of Medicine at the University of Pennsylvania. He is the Roberts Family Professor in Vaccine Research and Director of the Penn Institute for RNA Innovations.
The University of Pennsylvania messenger RNA pioneers whose years of scientific partnership unlocked understanding of how to modify mRNA to make it an effective therapeutic—enabling a platform used to rapidly develop lifesaving vaccines amid the global COVID-19 pandemic—have been named winners of the 2023 Nobel Prize in Physiology or Medicine. They become the 28th and 29th Nobel laureates affiliated with Penn, and join nine previous Nobel laureates with ties to the University of Pennsylvania who have won the Nobel Prize in Medicine.
Nearly three years after the rollout of mRNA vaccines across the world, Katalin Karikó, PhD, an adjunct professor of Neurosurgery in Penn’s Perelman School of Medicine, and Drew Weissman, MD, PhD, the Roberts Family Professor of Vaccine Research in the Perelman School of Medicine, are recipients of the prize announced this morning by the Nobel Assembly in Solna, Sweden.
After a chance meeting in the late 1990s while photocopying research papers, Karikó and Weissman began investigating mRNA as a potential therapeutic. In 2005, they published a key discovery: mRNA could be altered and delivered effectively into the body to activate the body’s protective immune system. The mRNA-based vaccines elicited a robust immune response, including high levels of antibodies that attack a specific infectious disease that has not previously been encountered. Unlike other vaccines, a live or attenuated virus is not injected or required at any point.
When the COVID-19 pandemic struck, the true value of the pair’s lab work was revealed in the most timely of ways, as companies worked to quickly develop and deploy vaccines to protect people from the virus. Both Pfizer/BioNTech and Moderna utilized Karikó and Weissman’s technology to build their highly effective vaccines to protect against severe illness and death from the virus. In the United States alone, mRNA vaccines make up more than 655 million total doses of SARS-CoV-2 vaccines that have been administered since they became available in December 2020.
Editor’s Note:The Pfizer/BioNTech and Moderna COVID-19 mRNA vaccines both use licensed University of Pennsylvania technology. As a result of these licensing relationships, Penn, Karikó and Weissman have received and may continue to receive significant financial benefits in the future based on the sale of these products. BioNTech provides funding for Weissman’s research into the development of additional infectious disease vaccines.
Science can be brutal
Now for the interesting bit: it’s in my March 5, 2021 posting (mRNA, COVID-19 vaccines, treating genetic diseases before birth, and the scientist who started it all),
Before messenger RNA was a multibillion-dollar idea, it was a scientific backwater. And for the Hungarian-born scientist behind a key mRNA discovery, it was a career dead-end.
Katalin Karikó spent the 1990s collecting rejections. Her work, attempting to harness the power of mRNA to fight disease, was too far-fetched for government grants, corporate funding, and even support from her own colleagues.
“Every night I was working: grant, grant, grant,” Karikó remembered, referring to her efforts to obtain funding. “And it came back always no, no, no.”
By 1995, after six years on the faculty at the University of Pennsylvania, Karikó got demoted. [emphasis mine] She had been on the path to full professorship, but with no money coming in to support her work on mRNA, her bosses saw no point in pressing on.
She was back to the lower rungs of the scientific academy.
“Usually, at that point, people just say goodbye and leave because it’s so horrible,” Karikó said.
There’s no opportune time for demotion, but 1995 had already been uncommonly difficult. Karikó had recently endured a cancer scare, and her husband was stuck in Hungary sorting out a visa issue. Now the work to which she’d devoted countless hours was slipping through her fingers.
In time, those better experiments came together. After a decade of trial and error, Karikó and her longtime collaborator at Penn — Drew Weissman [emphasis mine], an immunologist with a medical degree and Ph.D. from Boston University — discovered a remedy for mRNA’s Achilles’ heel.
You can get the whole story from my March 5, 2021 posting, scroll down to the “mRNA—it’s in the details, plus, the loneliness of pioneer researchers, a demotion, and squabbles” subhead. If you are very curious about mRNA and the rough and tumble of the world of science, there’s my August 20, 2021 posting “Getting erased from the mRNA/COVID-19 story” where Ian MacLachlan is featured as a researcher who got erased and where Karikó credits his work.
Karikó’s daughter is a two-time gold medal Olympic athlete as the Canadian Broadcasting Corporation’s (CBC) radio programme, As It Happens, notes in an interview with the daughter (Susan Francia). From an October 4, 2023 As It Happens article (with embedded audio programme excerpt) by Sheena Goodyear,
Olympic gold medallist Susan Francia is coming to terms with the fact that she’s no longer the most famous person in her family.
That’s because the retired U.S. rower’s mother, Katalin Karikó, just won a Nobel Prize in Medicine. The biochemist was awarded alongside her colleague, vaccine researcher Drew Weissman, for their groundbreaking work that led to the development of COVID-19 vaccines.
“Now I’m like, ‘Shoot! All right, I’ve got to work harder,'” Francia said with a laugh during an interview with As It Happens host Nil Köksal.
But in all seriousness, Francia says she’s immensely proud of her mother’s accomplishments. In fact, it was Karikó’s fierce dedication to science that inspired Francia to win Olympic gold medals in 2008 and 2012.
“Sport is a lot like science in that, you know, you have a passion for something and you just go and you train, attain your goal, whether it be making this discovery that you truly believe in, or for me, it was trying to be the best in the world,” Francia said.
“It’s a grind and, honestly, I love that grind. And my mother did too.”
… one of her [Karikó] favourite headlines so far comes from a little blurb on the rowing website Row 2K: “Rowing Mom Wins Nobel.”
Nowadays, scientists are trying to harness the power of mRNA to fight cancer, malaria, influenza and rabies. But when Karikó first began her work, it was a fringe concept. For decades, she toiled in relative obscurity, struggling to secure funding for her research.
“That’s also that same passion that I took into my rowing,” Francia said.
But even as Karikó struggled to make a name for herself, she says her own mother, Zsuzsanna, always believed she would earn a Nobel Prize one day.
Every year, as the Nobel Prize announcement approached, she would tell Karikó she’d be watching for her name.
“I was laughing [and saying] that, ‘Mom, I am not getting anything,'” she said.
But her mother, who died a few years ago, ultimately proved correct.
Congratulations to both Katalin Karikó and Drew Weissman and thank you both for persisting!
This prize is for physics at the attoscale.
Aaron W. Harrison (Assistant Professor of Chemistry, Austin College, Texas, US) attempts an explanation of an attosecond in his October 3, 2023 essay (in English “What is an attosecond? A physical chemist explains the tiny time scale behind Nobel Prize-winning research” and in French “Nobel de physique : qu’est-ce qu’une attoseconde?”) for The Conversation, Note: Links have been removed,
“Atto” is the scientific notation prefix that represents 10-18, which is a decimal point followed by 17 zeroes and a 1. So a flash of light lasting an attosecond, or 0.000000000000000001 of a second, is an extremely short pulse of light.
In fact, there are approximately as many attoseconds in one second as there are seconds in the age of the universe.
Previously, scientists could study the motion of heavier and slower-moving atomic nuclei with femtosecond (10-15) light pulses. One thousand attoseconds are in 1 femtosecond. But researchers couldn’t see movement on the electron scale until they could generate attosecond light pulses – electrons move too fast for scientists to parse exactly what they are up to at the femtosecond level.
Harrison does a very good job of explaining something that requires a leap of imagination. He also explains why scientists engage in attosecond research. h/t October 4, 2023 news item on phys.org
The Royal Swedish Academy of Sciences has decided to award the Nobel Prize in Physics 2023 to
Pierre Agostini The Ohio State University, Columbus, USA
Ferenc Krausz Max Planck Institute of Quantum Optics, Garching and Ludwig-Maximilians-Universität München, Germany
Anne L’Huillier Lund University, Sweden
“for experimental methods that generate attosecond pulses of light for the study of electron dynamics in matter”
Experiments with light capture the shortest of moments
The three Nobel Laureates in Physics 2023 are being recognised for their experiments, which have given humanity new tools for exploring the world of electrons inside atoms and molecules. Pierre Agostini, Ferenc Krausz and Anne L’Huillier have demonstrated a way to create extremely short pulses of light that can be used to measure the rapid processes in which electrons move or change energy.
Fast-moving events flow into each other when perceived by humans, just like a film that consists of still images is perceived as continual movement. If we want to investigate really brief events, we need special technology. In the world of electrons, changes occur in a few tenths of an attosecond – an attosecond is so short that there are as many in one second as there have been seconds since the birth of the universe.
The laureates’ experiments have produced pulses of light so short that they are measured in attoseconds, thus demonstrating that these pulses can be used to provide images of processes inside atoms and molecules.
In 1987, Anne L’Huillier discovered that many different overtones of light arose when she transmitted infrared laser light through a noble gas. Each overtone is a light wave with a given number of cycles for each cycle in the laser light. They are caused by the laser light interacting with atoms in the gas; it gives some electrons extra energy that is then emitted as light. Anne L’Huillier has continued to explore this phenomenon, laying the ground for subsequent breakthroughs.
In 2001, Pierre Agostini succeeded in producing and investigating a series of consecutive light pulses, in which each pulse lasted just 250 attoseconds. At the same time, Ferenc Krausz was working with another type of experiment, one that made it possible to isolate a single light pulse that lasted 650 attoseconds.
The laureates’ contributions have enabled the investigation of processes that are so rapid they were previously impossible to follow.
“We can now open the door to the world of electrons. Attosecond physics gives us the opportunity to understand mechanisms that are governed by electrons. The next step will be utilising them,” says Eva Olsson, Chair of the Nobel Committee for Physics.
There are potential applications in many different areas. In electronics, for example, it is important to understand and control how electrons behave in a material. Attosecond pulses can also be used to identify different molecules, such as in medical diagnostics.
Pierre Agostini. PhD 1968 from Aix-Marseille University, France. Professor at The Ohio State University, Columbus, USA.
Ferenc Krausz, born 1962 in Mór, Hungary. PhD 1991 from Vienna University of Technology, Austria. Director at Max Planck Institute of Quantum Optics, Garching and Professor at Ludwig-Maximilians-Universität München, Germany.
Anne L’Huillier, born 1958 in Paris, France. PhD 1986 from University Pierre and Marie Curie, Paris, France. Professor at Lund University, Sweden.
Three scientists have won the Nobel Prize in physics Tuesday for giving us the first split-second glimpse into the superfast world of spinning electrons, a field that could one day lead to better electronics or disease diagnoses.
The award went to French-Swedish physicist Anne L’Huillier, French scientist Pierre Agostini and Hungarian-born Ferenc Krausz for their work with the tiny part of each atom that races around the centre, and that is fundamental to virtually everything: chemistry, physics, our bodies and our gadgets.
Electrons move around so fast that they have been out of reach of human efforts to isolate them. But by looking at the tiniest fraction of a second possible, scientists now have a “blurry” glimpse of them, and that opens up whole new sciences, experts said.
“The electrons are very fast, and the electrons are really the workforce in everywhere,” Nobel Committee member Mats Larsson said. “Once you can control and understand electrons, you have taken a very big step forward.”
L’Huillier is the fifth woman to receive a Nobel in Physics.
L’Huillier was teaching basic engineering physics to about 100 undergraduates at Lund when she got the call that she had won, but her phone was on silent and she didn’t pick up. She checked it during a break and called the Nobel Committee.
Then she went back to teaching.
Agostini, an emeritus professor at Ohio State University, was in Paris and could not be reached by the Nobel Committee before it announced his win to the world
Krausz, of the Max Planck Institute of Quantum Optics and Ludwig Maximilian University of Munich, told reporters that he was bewildered.
“I have been trying to figure out since 11 a.m. whether I’m in reality or it’s just a long dream,” the 61-year-old said.
Last year, Krausz and L’Huillier won the prestigious Wolf prize in physics for their work, sharing it with University of Ottawa scientist Paul Corkum [emphasis mine]. Nobel prizes are limited to only three winners and Krausz said it was a shame that it could not include Corkum.
Corkum was key to how the split-second laser flashes could be measured [emphasis mine], which was crucial, Krausz said.
Congratulations to Pierre Agostini, Ferenc Krausz and Anne L’Huillier and a bow to Paul Corkum!
For those who are curious. a ‘Paul Corkum’ search should bring up a few postings on this blog but I missed this piece of news, a May 4, 2023 University of Ottawa news release about Corkum and the 2022 Wolf Prize, which he shared with Krausz and L’Huillier,
There was a little drama where this prize was concerned, It was announced too early according to an October 4, 2023 news item on phys.org and, again, in another October 4, 2023 news item on phys.org (from the Oct. 4, 2023 news item by Karl Ritter for the Associated Press),
Oops! Nobel chemistry winners are announced early in a rare slip-up
The most prestigious and secretive prize in science ran headfirst into the digital era Wednesday when Swedish media got an emailed press release revealing the winners of the Nobel Prize in chemistry and the news prematurely went public.
The Royal Swedish Academy of Sciences has decided to award the Nobel Prize in Chemistry 2023 to
Moungi G. Bawendi Massachusetts Institute of Technology (MIT), Cambridge, MA, USA
Louis E. Brus Columbia University, New York, NY, USA
Alexei I. Ekimov Nanocrystals Technology Inc., New York, NY, USA
“for the discovery and synthesis of quantum dots”
They planted an important seed for nanotechnology
The Nobel Prize in Chemistry 2023 rewards the discovery and development of quantum dots, nanoparticles so tiny that their size determines their properties. These smallest components of nanotechnology now spread their light from televisions and LED lamps, and can also guide surgeons when they remove tumour tissue, among many other things.
Everyone who studies chemistry learns that an element’s properties are governed by how many electrons it has. However, when matter shrinks to nano-dimensions quantum phenomena arise; these are governed by the size of the matter. The Nobel Laureates in Chemistry 2023 have succeeded in producing particles so small that their properties are determined by quantum phenomena. The particles, which are called quantum dots, are now of great importance in nanotechnology.
“Quantum dots have many fascinating and unusual properties. Importantly, they have different colours depending on their size,” says Johan Åqvist, Chair of the Nobel Committee for Chemistry.
Physicists had long known that in theory size-dependent quantum effects could arise in nanoparticles, but at that time it was almost impossible to sculpt in nanodimensions. Therefore, few people believed that this knowledge would be put to practical use.
However, in the early 1980s, Alexei Ekimov succeeded in creating size-dependent quantum effects in coloured glass. The colour came from nanoparticles of copper chloride and Ekimov demonstrated that the particle size affected the colour of the glass via quantum effects.
A few years later, Louis Brus was the first scientist in the world to prove size-dependent quantum effects in particles floating freely in a fluid.
In 1993, Moungi Bawendi revolutionised the chemical production of quantum dots, resulting in almost perfect particles. This high quality was necessary for them to be utilised in applications.
Quantum dots now illuminate computer monitors and television screens based on QLED technology. They also add nuance to the light of some LED lamps, and biochemists and doctors use them to map biological tissue.
Quantum dots are thus bringing the greatest benefit to humankind. Researchers believe that in the future they could contribute to flexible electronics, tiny sensors, thinner solar cells and encrypted quantum communication – so we have just started exploring the potential of these tiny particles.
Proving yet again that scientists can have a bumpy trip to a Nobel prize, an October 4, 2023 news item on phys.org describes how one of the winners flunked his first undergraduate chemistry test, Note: Links have been removed,
Talk about bouncing back. MIT professor Moungi Bawendi is a co-winner of this year’s Nobel chemistry prize for helping develop “quantum dots”—nanoparticles that are now found in next generation TV screens and help illuminate tumors within the body.
But as an undergraduate, he flunked his very first chemistry exam, recalling that the experience nearly “destroyed” him.
The 62-year-old of Tunisian and French heritage excelled at science throughout high school, without ever having to break a sweat.
But when he arrived at Harvard University as an undergraduate in the late 1970s, he was in for a rude awakening.
This year’s prize recognizes Moungi Bawendi, Louis Brus and Alexei Ekimov for the discovery and development of quantum dots. For many years, these precisely constructed nanometer-sized particles – just a few hundred thousandths the width of a human hair in diameter – were the darlings of nanotechnology pitches and presentations. As a researcher and adviser on nanotechnology [emphasis mine], I’ve [Dr. Andrew Maynard] even used them myself when talking with developers, policymakers, advocacy groups and others about the promise and perils of the technology.
The origins of nanotechnology predate Bawendi, Brus and Ekimov’s work on quantum dots – the physicist Richard Feynman speculated on what could be possible through nanoscale engineering as early as 1959, and engineers like Erik Drexler were speculating about the possibilities of atomically precise manufacturing in the the 1980s. However, this year’s trio of Nobel laureates were part of the earliest wave of modern nanotechnology where researchers began putting breakthroughs in material science to practical use.
Quantum dots brilliantly fluoresce: They absorb one color of light and reemit it nearly instantaneously as another color. A vial of quantum dots, when illuminated with broad spectrum light, shines with a single vivid color. What makes them special, though, is that their color is determined by how large or small they are. Make them small and you get an intense blue. Make them larger, though still nanoscale, and the color shifts to red.
There’s also an October 4, 2023 overview article by Tekla S. Perry and Margo Anderson for the IEEE Spectrum about the magazine’s almost twenty-five years of reporting on quantum dots
Image credit: Brandon Palacio/IEEE Spectrum
Your Guide to the Newest Nobel Prize: Quantum Dots
What you need to know—and what we’ve reported—about this year’s Chemistry award
It’s not a long article and it has a heavy focus on the IEEEE’s (Institute of Electrical and Electtronics Engineers) the road quantum dots have taken to become applications and being commercialized.
Congratulations to Moungi Bawendi, Louis Brus, and Alexei Ekimov!
This research into using waste products from microbreweries comes from Québec, from a June 22, 2022 news item on ScienceDaily,
For a few years now, spent grain, the cereal residue from breweries, has been reused in animal feed. From now on, this material could also be used in nanotechnology! Professor Federico Rosei’s team at the Institut national de la recherche scientifique (INRS) has shown that microbrewery waste can be used as a carbon source to synthesize quantum dots. The work, done in collaboration with Claudiane Ouellet-Plamondon of the École de technologie supérieure (ÉTS), was published in the Royal Society of Chemistry’s journal RSC Advances
Often considered as “artificial atoms”, quantum dots are used in the transmission of light. With a range of interesting physicochemical properties, this type of nanotechnology has been successfully used as a sensor in biomedicine or as LEDs in next generation displays. But there is a drawback. Current quantum dots are produced with heavy and toxic metals like cadmium. Carbon is an interesting alternative, both for its biocompatibility and its accessibility.
An eco-responsible approach
The choice of brewery waste as a source material came from Daniele Benetti, a postdoctoral fellow at INRS, and Aurel Thibaut Nkeumaleu, the master’s student at ÉTS who conducted the work. Basically, they wanted to carry out various experiments using accessible materials. This is how the scientists came to collaborate with the Brasseurs de Montréal to obtain their cereal residues.
“The use of spent grain highlights both an eco-responsible approach to waste management and an alternative raw material for the synthesis of carbon quantum dots, from a circular economy perspective,” says Professor Rosei.
The advantage of using brewery waste as a source of carbon quantum dots is that it is naturally enriched with nitrogen and phosphorus. This avoids the need for pure chemicals.
“This research was a lot of fun, lighting up what we can do with the beer by-products,” says Claudiane Ouellet-Plamondon, Canada Research Chair in Sustainable Multifunctional Construction Materials at ÉTS. “Moreover, ÉTS is located on the site of the former Dow brewery, one of the main breweries in Quebec until the 1960s. So there is a historical and heritage link to this work.”
An accessible method
In addition to using biobased material, the research team wanted to show that it was possible to produce carbon quantum dots with common means. The scientists used a domestic microwave oven to carbonize the spent grain, resulting in a black powder. It was then mixed with distilled water and put back into the microwave oven. A passage in the centrifuge and advanced filtration allowed to obtain the quantum dots. Their finished product was able to detect and quantify heavy metals, as well as other contaminants that affect water quality, the environment and health.
The next steps will be to characterize these carbon quantum dots from brewery waste, beyond proof of concept. The research team is convinced that this nanotechnology has the potential to become sophisticated detection sensors for various aqueous solutions, even in living cells.
About the study
The paper “Brewery spent grain derived carbon dots for metal sensing,” by Aurel Thibaut Nkeumaleu, Daniele Benetti, Imane Haddadou, Michael Di Mare, Claudiane Ouellet-Plamondon, and Federico Rosei, was published on April 14, 2022, in the Royal Society of Chemistry journal RSC Advances. The study was supported by the Natural Sciences and Engineering Research Council of Canada (NSERC), the Quebec Centre for Advanced Materials (QCAM) and the Canada Research Chairs.
About INRS INRS is a university dedicated exclusively to graduate level research and training. Since its creation in 1969, INRS has played an active role in Québec’s economic, social, and cultural development and is ranked first for research intensity in Québec. INRS is made up of four interdisciplinary research and training centres in Québec City, Montréal, Laval, and Varennes, with expertise in strategic sectors: Eau Terre Environnement, Énergie Matériaux Télécommunications, Urbanisation Culture Société, and Armand-Frappier Santé Biotechnologie. The INRS community includes more than 1,500 students, postdoctoral fellows, faculty members, and staff.
Here’s a link to and a citation for the paper,
Brewery spent grain derived carbon dots for metal sensing by Aurel Thibaut Nkeumaleu, Daniele Benetti, Imane Haddadou, Michael Di Mare, Claudiane M. Ouellet-Plamondon and Federico Rosei. RSC Adv., 2022,12, 11621-11627 DOI: https://doi.org/10.1039/D2RA00048B First published: 14 Apr 2022
This is a little outside my comfort zone but here goes anyway. From a December 23, 2020 news item on phys.org (Note: Links have been removed),
Osaka City University scientists have developed mathematical formulas to describe the current and fluctuations of strongly correlated electrons in quantum dots. Their theoretical predictions could soon be tested experimentally.
Theoretical physicists Yoshimichi Teratani and Akira Oguri of Osaka City University, and Rui Sakano of the University of Tokyo have developed mathematical formulas that describe a physical phenomenon happening within quantum dots and other nanosized materials. The formulas, published in the journal Physical Review Letters, could be applied to further theoretical research about the physics of quantum dots, ultra-cold atomic gasses, and quarks.
At issue is the Kondo effect. This effect was first described in 1964 by Japanese theoretical physicist Jun Kondo in some magnetic materials, but now appears to happen in many other systems, including quantum dots and other nanoscale materials.
Normally, electrical resistance drops in metals as the temperature drops. But in metals containing magnetic impurities, this only happens down to a critical temperature, beyond which resistance rises with dropping temperatures.
Scientists were eventually able to show that, at very low temperatures near absolute zero, electron spins become entangled with the magnetic impurities, forming a cloud that screens their magnetism. The cloud’s shape changes with further temperature drops, leading to a rise in resistance. This same effect happens when other external ‘perturbations’, such as a voltage or magnetic field, are applied to the metal.
Teratani, Sakano and Oguri wanted to develop mathematical formulas to describe the evolution of this cloud in quantum dots and other nanoscale materials, which is not an easy task.
To describe such a complex quantum system, they started with a system at absolute zero where a well-established theoretical model, namely Fermi liquid theory, for interacting electrons is applicable. They then added a ‘correction’ that describes another aspect of the system against external perturbations. Using this technique, they wrote formulas describing electrical current and its fluctuation through quantum dots.
Their formulas indicate electrons interact within these systems in two different ways that contribute to the Kondo effect. First, two electrons collide with each other, forming well-defined quasiparticles that propagate within the Kondo cloud. More significantly, an interaction called a three-body contribution occurs. This is when two electrons combine in the presence of a third electron, causing an energy shift of quasiparticles.
“The formulas’ predictions could soon be investigated experimentally”, Oguri says. “Studies along the lines of this research have only just begun,” he adds.
The formulas could also be extended to understand other quantum phenomena, such as quantum particle movement through quantum dots connected to superconductors. Quantum dots could be a key for realizing quantum information technologies, such as quantum computers and quantum communication.
Scientists used equipment at the Canadian Light Source (CLS; synchrotron in Saskatoon, Saskatchewan, Canada) in the quest for better glowing dots on your television (maybe computers and telephones, too?) screen. From an August 20, 2020 news item on Nanowerk,
There are many things quantum dots could do, but the most obvious place they could change our lives is to make the colours on our TVs and screens more pristine. Research using the Canadian Light Source (CLS) at the University of Saskatchewan is helping to bring this technology closer to our living rooms.
An August 19, 2020 CLS news release (also received via email) by Victoria Martinez, which originated the news item, explains what quantum dots are and fills in with technical details about this research,
Quantum dots are nanocrystals that glow, a property that scientists have been working with to develop next-generation LEDs. When a quantum dot glows, it creates very pure light in a precise wavelength of red, blue or green. Conventional LEDs, found in our TV screens today, produce white light that is filtered to achieve desired colours, a process that leads to less bright and muddier colours.
Until now, blue-glowing quantum dots, which are crucial for creating a full range of colour, have proved particularly challenging for researchers to develop. However, University of Toronto (U of T) researcher Dr. Yitong Dong and collaborators have made a huge leap in blue quantum dot fluorescence, results they recently published in Nature Nanotechnology.
“The idea is that if you have a blue LED, you have everything. We can always down convert the light from blue to green and red,” says Dong. “Let’s say you have green, then you cannot use this lower-energy light to make blue.”
The team’s breakthrough has led to quantum dots that produce green light at an external quantum efficiency (EQE) of 22% and blue at 12.3%. The theoretical maximum efficiency is not far off at 25%, and this is the first blue perovskite LED reported as achieving an EQE higher than 10%.
Dong has been working in the field of quantum dots for two years in Dr. Edward Sargent’s research group at the U of T. This astonishing increase in efficiency took time, an unusual production approach, and overcoming several scientific hurdles to achieve.
CLS techniques, particularly GIWAXS [grazing incidence wide-angle X-ray scattering] on the HXMA beamline [hard X-ray micro-analysis (HXMA)], allowed the researchers to verify the structures achieved in their quantum dot films. This validated their results and helped clarify what the structural changes achieve in terms of LED performance.
“The CLS was very helpful. GIWAXS is a fascinating technique,” says Dong.
The first challenge was uniformity, important to ensuring a clear blue colour and to prevent the LED from moving towards producing green light.
“We used a special synthetic approach to achieve a very uniform assembly, so every single particle has the same size and shape. The overall film is nearly perfect and maintains the blue emission conditions all the way through,” says Dong.
Next, the team needed to tackle the charge injection needed to excite the dots into luminescence. Since the crystals are not very stable, they need stabilizing molecules to act as scaffolding and support them. These are typically long molecule chains, with up to 18 carbon-non-conductive molecules at the surface, making it hard to get the energy to produce light.
“We used a special surface structure to stabilize the quantum dot. Compared to the films made with long chain molecules capped quantum dots, our film has 100 times higher conductivity, sometimes even 1000 times higher.”
This remarkable performance is a key benchmark in bringing these nanocrystal LEDs to market. However, stability remains an issue and quantum dot LEDs suffer from short lifetimes. Dong is excited about the potential for the field and adds, “I like photons, these are interesting materials, and, well, these glowing crystals are just beautiful.”
Here’s a link to and a citation for the paper,
Bipolar-shell resurfacing for blue LEDs based on strongly confined perovskite quantum dots by Yitong Dong, Ya-Kun Wang, Fanglong Yuan, Andrew Johnston, Yuan Liu, Dongxin Ma, Min-Jae Choi, Bin Chen, Mahshid Chekini, Se-Woong Baek, Laxmi Kishore Sagar, James Fan, Yi Hou, Mingjian Wu, Seungjin Lee, Bin Sun, Sjoerd Hoogland, Rafael Quintero-Bermudez, Hinako Ebe, Petar Todorovic, Filip Dinic, Peicheng Li, Hao Ting Kung, Makhsud I. Saidaminov, Eugenia Kumacheva, Erdmann Spiecker, Liang-Sheng Liao, Oleksandr Voznyy, Zheng-Hong Lu, Edward H. Sargent. Nature Nanotechnology volume 15, pages668–674(2020) DOI: https://doi.org/10.1038/s41565-020-0714-5 Published: 06 July 2020 Issue Date: August 2020
This paper is behind a paywall.
If you search “Edward Sargent,” he’s the last author listed in the citation, here on this blog, you will find a number of postings that feature work from his laboratory at the University of Toronto.
An August 5, 2019 news item on Nanowerk announces a new technology for detecting killer bacteria (Note: A link has been removed),
A combination of off-the-shelf quantum dots and a smartphone camera soon could allow doctors to identify antibiotic-resistant bacteria in just 40 minutes, potentially saving patient lives.
Staphylococcus aureus (golden staph), is a common form of bacterium that causes serious and sometimes fatal conditions such as pneumonia and heart valve infections. Of particular concern is a strain that does not respond to methicillin, the antibiotic of first resort, and is known as methicillin-resistant S. aureus, or MRSA.
Recent reports estimate that 700 000 deaths globally could be attributed to antimicrobial resistance, such as methicillin-resistance. Rapid identification of MRSA is essential for effective treatment, but current methods make it a challenging process, even within well-equipped hospitals.
Soon, however, that may change, using nothing except existing technology.
Researchers from Macquarie University and the University of New South Wales, both in Australia, have demonstrated a proof-of-concept device that uses bacterial DNA to identify the presence of Staphylococcus aureus positively in a patient sample – and to determine if it will respond to frontline antibiotics.
In a paper published in the international peer-reviewed journal Sensors and Actuators B: Chemical the Macquarie University team of Dr Vinoth Kumar Rajendran, Professor Peter Bergquist and Associate Professor Anwar Sunna with Dr Padmavathy Bakthavathsalam (UNSW) reveal a new way to confirm the presence of the bacterium, using a mobile phone and some ultra-tiny semiconductor particles known as quantum dots.
“Our team is using Synthetic Biology and NanoBiotechnology to address biomedical challenges. Rapid and simple ways of identifying the cause of infections and starting appropriate treatments are critical for treating patients effectively,” says Associate Professor Anwar Sunna, head of the Sunna Lab at Macquarie University.
“This is true in routine clinical situations, but also in the emerging field of personalised medicine.”
The researchers’ approach identifies the specific strain of golden staph by using a method called convective polymerase chain reaction (or cPCR). This is a derivative of a widely -employed technique in which a small segment of DNA is copied thousands of times, creating multiple samples suitable for testing.
Vinoth Kumar and colleagues then subject the DNA copies to a process known as lateral flow immunoassay – a paper-based diagnostic tool used to confirm the presence or absence of a target biomarker. The researchers use probes fitted with quantum dots to detect two unique genes, that confirms the presence of methicillin resistance in golden staph
A chemical added at the PCR stage to the DNA tested makes the sample fluoresce when the genes are detected by the quantum dots – a reaction that can be captured easily using the camera on a mobile phone.
The result is a simple and rapid method of detecting the presence of the bacterium, while simultaneously ruling first-line treatment in or out.
Although currently at proof-of-concept stage, the researchers say their system which is powered by a simple battery is suitable for rapid detection in different settings.
“We can see this being used easily not only in hospitals, but also in GP clinics and at patient bedsides,” says lead author, Macquarie’s Vinoth Kumar Rajendran.
This work comes from the King Abdullah University of Science and Technology (KAUST; Saudi Arabia). From a June 27, 2019 news item on Nanowerk (Note: A link has been removed),
Some of the vast amount of wasted energy that machines and devices emit as heat could be recaptured using an inexpensive nanomaterial developed at KAUST. This thermoelectric nanomaterial could capture the heat lost by devices, ranging from mobile phones to vehicle engines, and turn it directly back into useful electricity (Advanced Energy Materials, “Low-temperature-processed colloidal quantum dots as building blocks for thermoelectrics”).
The nanomaterial is made using a low-temperature solution-based production process, making it suitable for coating on flexible plastics for use almost anywhere.
“Among the many renewable energy sources, waste heat has not been widely considered,” says Mohamad Nugraha, a postdoctoral researcher in Derya Baran’s lab. Waste heat emitted by machines and devices could be recaptured by thermoelectric materials. These substances have a property that means that when one side of the material is hot and the other is cold, an electric charge builds up along the temperature gradient.
Until now, thermoelectric materials have been made using expensive and energy-intensive processes. Baran, Nugraha and their colleagues have developed a new thermoelectric material made by spin coating a liquid solution of nanomaterials called quantum dots.
The team spin coated a thin layer of lead-sulphide quantum dots on a surface and then added a solution of short linker ligands that crosslink the quantum dots together to enhance the material’s electronic properties.
After repeating the spin-coating process layer by layer to form a 200-nanometer-thick film, gentle thermal annealing dried the film and completed fabrication. “Thermoelectric research has focused on materials processed at very high temperatures, above 400 degrees Celsius,” Nugraha says. The quantum-dot-based thermoelectric material is only heated up to 175 degrees Celsius. This lower processing temperature could cut production costs and means that thermoelectric devices could be formed on a broad range of surfaces, including cheap flexible plastics.
The team’s material showed promising thermoelectric properties. One important parameter of a good thermoelectric is the Seebeck coefficient, which corresponds to the voltage generated when a temperature gradient is applied. “We found some key factors leading to the enhanced Seebeck coefficient in our materials,” Nugraha says.
The team was also able to show that an effect called the quantum confinement, which alters a material’s electronic properties when it is shrunk to the nanoscale, was important for enhancing the Seebeck coefficient. The discovery is a step toward practical high-performance, low-temperature, solution-processed thermoelectric generators, Nugraha says.
Years ago I was asked about carbon sequestration and nanotechnology and could not come up with any examples. At last I have something for the next time the question is asked. From a June 11, 2019 news item on ScienceDaily,
University of Colorado Boulder researchers have developed nanobio-hybrid organisms capable of using airborne carbon dioxide and nitrogen to produce a variety of plastics and fuels, a promising first step toward low-cost carbon sequestration and eco-friendly manufacturing for chemicals.
By using light-activated quantum dots to fire particular enzymes within microbial cells, the researchers were able to create “living factories” that eat harmful CO2 and convert it into useful products such as biodegradable plastic, gasoline, ammonia and biodiesel.
“The innovation is a testament to the power of biochemical processes,” said Prashant Nagpal, lead author of the research and an assistant professor in CU Boulder’s Department of Chemical and Biological Engineering. “We’re looking at a technique that could improve CO2 capture to combat climate change and one day even potentially replace carbon-intensive manufacturing for plastics and fuels.”
The project began in 2013, when Nagpal and his colleagues began exploring the broad potential of nanoscopic quantum dots, which are tiny semiconductors similar to those used in television sets. Quantum dots can be injected into cells passively and are designed to attach and self-assemble to desired enzymes and then activate these enzymes on command using specific wavelengths of light.
Nagpal wanted to see if quantum dots could act as a spark plug to fire particular enzymes within microbial cells that have the means to convert airborne CO2 and nitrogen, but do not do so naturally due to a lack of photosynthesis.
By diffusing the specially-tailored dots into the cells of common microbial species found in soil, Nagpal and his colleagues bridged the gap. Now, exposure to even small amounts of indirect sunlight would activate the microbes’ CO2 appetite, without a need for any source of energy or food to carry out the energy-intensive biochemical conversions.
“Each cell is making millions of these chemicals and we showed they could exceed their natural yield by close to 200 percent,” Nagpal said.
The microbes, which lie dormant in water, release their resulting product to the surface, where it can be skimmed off and harvested for manufacturing. Different combinations of dots and light produce different products: Green wavelengths cause the bacteria to consume nitrogen and produce ammonia while redder wavelengths make the microbes feast on CO2 to produce plastic instead.
The process also shows promising signs of being able to operate at scale. The study found that even when the microbial factories were activated consistently for hours at a time, they showed few signs of exhaustion or depletion, indicating that the cells can regenerate and thus limit the need for rotation.
“We were very surprised that it worked as elegantly as it did,” Nagpal said. “We’re just getting started with the synthetic applications.”
The ideal futuristic scenario, Nagpal said, would be to have single-family homes and businesses pipe their CO2 emissions directly to a nearby holding pond, where microbes would convert them to a bioplastic. The owners would be able to sell the resulting product for a small profit while essentially offsetting their own carbon footprint.
“Even if the margins are low and it can’t compete with petrochemicals on a pure cost basis, there is still societal benefit to doing this,” Nagpal said. “If we could convert even a small fraction of local ditch ponds, it would have a sizeable impact on the carbon output of towns. It wouldn’t be asking much for people to implement. Many already make beer at home, for example, and this is no more complicated.”
The focus now, he said, will shift to optimizing the conversion process and bringing on new undergraduate students. Nagpal is looking to convert the project into an undergraduate lab experiment in the fall semester, funded by a CU Boulder Engineering Excellence Fund grant. Nagpal credits his current students with sticking with the project over the course of many years.
“It has been a long journey and their work has been invaluable,” he said. “I think these results show that it was worth it.”
A pollination biologist from Stellenbosch University in South Africa is using quantum dots to track the fate of individual pollen grains. This is breaking new ground in a field of research that has been hampered by the lack of a universal method to track pollen for over a century.
In an article published in the journal Methods in Ecology and Evolution this week, Dr Corneile Minnaar describes this novel method, which will enable pollination biologists to track the whole pollination process from the first visit by a pollinator to its endpoint – either successfully transferred to another flower’s stigma or lost along the way.
Despite over two hundred years of detailed research on pollination, Minnaar says, researchers do not know for sure where most of the microscopically tiny pollen grains actually land up once they leave flowers: “Plants produce massive amounts of pollen, but it looks like more than 90% of it never reaches stigmas. For the tiny fraction of pollen grains that make their way to stigmas, the journey is often unclear–which pollinators transferred the grains and from where?”
Starting in 2015, Minnaar decided to tread where many others have thus far failed, and took up the challenge through his PhD research in the Department of Botany and Zoology at Stellenbosch University (SU).
“Most plant species on earth are reliant on insects for pollination, including more than 30% of the food crops we eat. With insects facing rapid global decline, it is crucial that we understand which insects are important pollinators of different plants–this starts with tracking pollen,” he explains.
He came upon the idea for a pollen-tracking method after reading an article on the use of quantum dots to track cancer cells in rats (https://doi.org/10.1038/nbt994). Quantum dots are semiconductor nanocrystals that are so small, they behave like artificial atoms. When exposed to UV light, they emit extremely bright light in a range of possible colours. In the case of pollen grains, he figured out that quantum dots with “fat-loving” (lipophilic) ligands would theoretically stick to the fatty outer layer of pollen grains, called pollenkitt, and the glowing colours of the quantum dots can then be used to uniquely “label” pollen grains to see where they end up.
The next step was to find a cost-effective way to view the fluorescing pollen grains under a field dissection microscope. At that stage Minnaar was still using a toy pen from a family restaurant with a little UV LED light that he borrowed from one of his professors. “I decided to design a fluorescence box that can fit under a dissection microscope. And, because I wanted people to use this method, I designed a box that can easily be 3D-printed at a cost of about R5,000, including the required electronic components.” (view video at https://youtu.be/YHs925F13t0
[or you can scroll down to the bottom of this post]
So far, the method and excitation box have proven itself as an easy and relatively inexpensive method to track individual pollen grains: “I’ve done studies where I caught the insects after they have visited the plant with quantum-dot labelled anthers, and you can see where the pollen is placed, and which insects actually carry more or less pollen.” But the post-labelling part of the work still requires hours and hours of painstaking counting and checking: “I think I’ve probably counted more than a hundred thousand pollen grains these last three years,” he laughs.
As a postdoctoral fellow in the research group of Prof Bruce Anderson in the Department of Botany and Zoology at Stellenbosch University, Minnaar will continue to use the method to investigate the many unanswered questions in this field.
A May 21, 2018 news item on phys.org announces some intriguing work borne of a UK-India research collaboration,
Nanoparticles derived from tea leaves inhibit the growth of lung cancer cells, destroying up to 80% of them, new research by a joint Swansea University and Indian team has shown.
The team made the discovery while they were testing out a new method of producing a type of nanoparticle called quantum dots. These are tiny particles which measure less than 10 nanometres. A human hair is 40,000 nanometres thick.
Although nanoparticles are already used in healthcare, quantum dots have only recently attracted researchers’ attention. Already they are showing promise for use in different applications, from computers and solar cells to tumour imaging and treating cancer.
Picture: Size comparison of quantum dots with football and with human hair, in nanometers.
Quantum dots can be made chemically, but this is complicated and expensive and has toxic side effects. The Swansea-led research team were therefore exploring a non-toxic plant-based alternative method of producing the dots, using tea leaf extract.
Tea leaves contain a wide variety of compounds, including polyphenols, amino acids, vitamins and antioxidants. The researchers mixed tea leaf extract with cadmium sulphate (CdSO4) and sodium sulphide (Na2S) and allowed the solution to incubate, a process which causes quantum dots to form. They then applied the dots to lung cancer cells.
The researchers found:
Tea leaves are a simpler, cheaper and less toxic method of producing quantum dots, compared with using chemicals, confirming the results of other research in the field.
Quantum dots produced from tea leaves inhibit the growth of lung cancer cells. They penetrated into the nanopores of the cancer cells and destroyed up to 80% of them. This was a brand new finding, and came as a surprise to the team.
The research, published in “Applied Nano Materials”, is a collaborative venture between Swansea University experts and colleagues from two Indian universities.
Picture: microscope images of A549 lung cancer cells: left, untreated; right, treated with quantum dots
Dr Sudhagar Pitchaimuthu of Swansea University, lead researcher on the project, and a Ser Cymru-II Rising Star Fellow, said:
“Our research confirmed previous evidence that tea leaf extract can be a non-toxic alternative to making quantum dots using chemicals.
The real surprise, however, was that the dots actively inhibited the growth of the lung cancer cells. We hadn’t been expecting this.
The CdS quantum dots derived from tea leaf extract showed exceptional fluorescence emission in cancer cell bioimaging compared to conventional CdS nanoparticles.
Quantum dots are therefore a very promising avenue to explore for developing new cancer treatments.
They also have other possible applications, for example in anti-microbial paint used in operating theatres, or in sun creams.”
Dr Pitchaimuthu outlined the next steps for research:
“Building on this exciting discovery, the next step is to scale up our operation, hopefully with the help of other collaborators. We want to investigate the role of tea leaf extract in cancer cell imaging, and the interface between quantum dots and the cancer cell.
We would like to set up a “quantum dot factory” which will allow us to explore more fully the ways in which they can be used.”