Chemistry - Quantum Dots
Alice in Wonderland, Rewritten
In 1865, 33-year-old Lewis Caroll wrote of Alice’s bewilderment at her shrinking figure after she took a tentative gulp from an inconspicuously labelled bottle. ‘Drink me,’ it coerced her, and the gullible young girl watched in horror as the world suddenly towered over her new dimensions. Whether or not she was aware of it, by shrinking to nanoscopic dimensions, Alice had almost entered the quantum world – and perhaps the story would’ve ended differently had she done so.
Nearly two hundred years later, this nanoworld – unexplored by young Alice, and feared by many modern chemists because of its tendency to not adhere to the rules of our ‘regular’ sized world – is still shrouded in mystery. But through brave conquests into the unknown, scientists are shining a light on the field, and opening doors (not unlike Alice!), previously thought to not even have keys.
The term ‘quantum dots’ contains a word that can easily intimidate passersby: quantum. Quantum mechanics, quantum physics, quantum numbers, these are all incredibly complex concepts that people study years upon years to grasp. But the idea of quantum dots, be it revolutionary as it is, does not have to be rocket science! So, where do we begin?
It is important to lay the ground rules for the playing field upon which quantum dots rest. Quantum dots are minuscule – ten million times smaller than an eyelash. They are composed of a few thousand atoms. Even in chemistry, where working with small amounts is not uncommon, this is considered incredibly small. They are nanocrystals, or nanoscale semiconductor particles, and because of their size, they display some unique properties. The way they behave is a result of the quantum mechanical effect, an idea that has long been stipulated to be true but has been difficult to prove. Quantum dots are made up of atoms, and similar to bulk material, they have all the same structure. A smaller quantum dot will have fewer atoms, and a bigger quantum dot will have more. But in every other aspect besides size, they will be identical twins.
The ‘particle-in-a-box’ concept is essential in understanding the unique properties of quantum dots. It is the idea that, by putting an electron into a smaller space, its wave function is compressed, and the electron will have more energy. This allows it to give more energy to a photon. So, how do we observe this in quantum dots? Smaller quantum dots, where electrons are forced into a smaller ‘box’ (a smaller particle size) will emit blue light because of their shorter wavelength and their higher energy, whereas bigger quantum dots, where electrons have more space and will therefore have a longer wavelength and less energy, will emit red light, and every size in between will emit a different, particular colour.
What is so revolutionary about this theoretical proposition is the fact that the optical property is size-dependent. Not only this property, thermal, electric, magnetic properties and more can all be controlled through alteration of size. Changing a property has never been this simple before.
“Theory will only take you so far.”
Robert J. Oppenheimer proclaimed this in response to an entirely different problem, that of the atomic bomb, but nowhere else does this quote better apply than in the case of the 2023 Chemistry Nobel Prize story. Up until the late 20th century, theory was all that chemists had to work with. Any efforts to prove this theory seemed a colossal task; the scale was ridiculously small, and the prerequisites for precision and accuracy were beyond scientists in the 1930s. And this is where the story truly begins.
Three people received the Chemistry Nobel Prize this year: Moungi G. Bawendi, Louis E. Brus, and Aleksey Yekimov. It was this combined effort of these three scientists that helped revolutionise nanochemistry.
The story begins in 1980, in what was then the Soviet Union. Aleksey Yekimov was studying semiconductors by shining light on the materials in order to deduce their absorbance. Through complete coincidence, this led to a monumental discovery (accidental discoveries occur more often than one may think!). Tiny crystals of copper chloride formed inside the coloured glass he was studying, and, just like theory had predicted, the colour of light they absorbed was entirely dependent on their size. Yekimov impatiently published his results, sensing he had touched upon a revolutionary concept.
On the other side of the Iron Curtain, Louis Brus was working on an entirely different project – utilising solar energy to make chemical reactions occur, using particles of cadmium sulphide in a solution. The smaller the particles of cadmium sulphide, the bigger the surface area on which chemical reactions could take place, therefore he worked with smaller and smaller particles until eventually he struck ‘gold’. Nanoparticles.
Brus left these particles on a lab bench and observed what scientists had predicted for years and what Aleksey Yekimov had encountered: their optical properties changed over time because they had gotten bigger. The bigger the particles, the more red they were. The smaller the particles, the more blue they were. This was the second major step in unlocking nanochemistry and exploring the size-dependent quantum effect.
But this was a very primitive method that did not allow for the refinement of nanocrystals in terms of quality, or the precise manipulation of their size. And that is where the third and final winner of the Nobel Chemistry Prize, Moungi G. Bawendi, comes in. In 1993, after much research and trial and error, Mr. Bawendi was able to inject substances into specific solvents (heated in order to form the desired amount of nanocrystals) and create nanocrystals of differing size and previously unthought-of precision.
The beauty of this discovery lies in what it unlocks. In mathematics, in formative education, students are taught of two axes: x and y. However, later on, a third dimension is introduced that changes everything: z. The discovery that properties can be changed based on size introduces a new axis in chemistry and in the periodic table, one earlier unimaginable. Scientists can now play with size when playing with elements.
Don’t be fooled by the complexity of the discovery into assuming that the problem is so deeply buried in chemistry that it is completely detached from the real world. This could not be further from the truth. If your television screen utilises QLED technology (the Q standing for quantum), you are already feeling the effects of this discovery. Moreover, quantum dots are now used in biochemistry, where they can be attached to biomolecules and, in the future, aid in tracking tumour tissue. Chemists are also using quantum dots to drive chemical reactions.
The doors this discovery has opened up are endless – it has provided the nanoworld another dimension, and has begun to demystify a field shrouded in mystery. This breakthrough will no doubt lead to an avalanche of discoveries, and the world is impatiently waiting to begin the next chapter in nanochemistry.
Biology - mRNA COVID-19
With around 95% protection against the infamous virus and an astounding over 13 billion globally administered doses, the rapid and efficient catering of the COVID-19 vaccines highlight the role of the crucial discoveries fabricated by the 2023 Nobel Prize Award winners, Katalin Karikó and Drew Weissman.
Produced around 15 years prior to the COVID-19 breakout, Karikó, the 13th woman to win the award, and Weissman, led some remarkable scientific research that formed the foundation for the extraordinary speed with which vaccines against the coronavirus were manufactured. Not to mention that they also paved the way for the defence against innumerable vastly threatening diseases.
In order to comprehend the discoveries produced by prominent scientists, it is essential to understand that cells possess several defence mechanisms to defend us from any potential health-menacing intruders. Namely, our cells possess the innate ability to detect and demolish any unfamiliar material, which, through a series of biological processes, leads to an inflammatory response.
The eminent researchers discovered that Dendritic cells, which are involved in protecting us against pathogens, possessed the ability to correctly recognize in vitro transcribed mRNA, an artificially synthesised molecule involved in protein production, as foreign material. This subsequently led to the arousal of an inflammatory response. This reaction, albeit practical and beneficial in the short-term for making repairments in damaged tissues, can minimise the vaccine’s effectiveness and could potentially lead to perilous side effects. This led the scientists to probe deeper into the heart of this phenomenon to ultimately comprehend why in vitro transcribed mRNA triggered this reaction whereas it did not in RNA from mammalian cells. The conclusion generated was that the two mRNA types did not share identical characteristics.
Eventually, the experiments conducted shed light on these differences. Specifically, they discovered that on numerous occasions, mammalian RNA possessed chemical alterations in its bases. Therefore, because the fabricated mRNA lacked these chemical modifications, the body considered these as foreign, which subsequently triggered the immune response. To test this, Karikó and Weissman carried out a series of experiments in which they produced several mRNA alternatives, each with a unique variation in its chemical properties and then dispatched them to dendritic cells. Their outcome showcased a notable improvement in inflammatory responses when these chemically disparate mRNA molecules were injected.
This groundbreaking discovery illuminated the countless ways that cells acknowledge and react to various mRNA types, which has been paramount in making mRNA more useful in the medical world. Namely, it has been essential for the creation of mRNA vaccines, which are typically rapid and cheap to fabricate. In addition to this, mRNA vaccines are usually praised for their ability to be quickly modified and altered to adjust to new variants or versions of emerging viruses. Combined, all of these advantages enabled the fast and thoroughly efficient assembly of the COVID-19 vaccine in less than a year.
Economics - Women's Labour Market Outcomes
According to the 2023 Economics Science Nobel prize winner, Claudia Goldin's research about the gender difference in the labour market for women, we can understand the factors that influenced women to be employed in work and the reasons for the difference in wages in work. She also explained how the percentage of married women in work changed from the end of the 18th century up to the end of the 20th century. However, the trend was not a straight increasing line, but rather a U-shape curve.
One factor that Claudia Goldin pointed out that affected women in work was “social expectations”, which was a major factor in the past. Women were expected to leave their workplace after marriage or the birth of a child. Hence, when they were making their educational and career choices, they were influenced by those expectations, which limited their success to go further. Nowadays, women are treated the same as men in education, and through research, most women were proven to be smarter than men. However, women were still earning less than men. Claudia Goldin showed that the main reason behind this was discrimination and parenthood effects.
Discrimination resulted in women being paid less, because they were seen as having less ability compared to men. In deeper research, Claudia Goldin found an interesting fact: “between the end of 19th century and 1940, pay discrimination increased and at the same time earning gaps between women and men decreased.” The cause of this being that before the end of the 19th century, workers were paid based on the amount of output, and women needed to put time into domestic work, so their productivity in industries was less than men. After the new legislation that introduced the monthly wage paying system, women and men were paid the same, but the “equal” only remained until the parenthood effect. When a child is born, the mother puts more time and effort into child care, so they decrease their time at work. This restricts them from having higher wages and achieving higher success. As we can see, marriage is mostly the factor that influences women in work, so Claudia Goldin looked closer at married women in work in the last 200 years.
Around 1790, the primary sector was the major sector for people to work, where they worked in agriculture. The modern society thought that most married women were only engaged in domestic work, but this was not the case. Even though they need to take care of the housework, they also need to help with their husband’s work, mostly agriculture. Therefore, Claudia Goldin suggested that at that period, around 60% of married women worked both at home and outside. Surprisingly, Claudia Goldin found that the number of married women in work largely decreased in the 19th century, the Industrial Revolution. It was difficult for women to balance between work and home and society expected women to be a “wife” and “mother”. Then, the percentage of married women in work increased in the 20th century, due to the equal and higher quality of education, changing expectations and contraceptive pills. Education helped them study and achieve a better job, while the change in social expectations led them to make their own choices for their future. The contraceptive pill made a great impact on the lives of women. They were able to plan their future, when to have a child, and put their effort into work in recent years.
Claudia Goldin was able to conclude that there was a relationship between women in work and economic growth.
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