Lesson video

Hello and welcome to this lesson on nanoparticles from the Unit Chemistry of carbon.

Throughout this unit we have discussed the varieties of different types of carbon nanostructures, but we are gonna talk about lots of different types of nanostructures in this lesson, not just those that are carbon-based.

By the end of the lesson that you should be able to compare the sizes of microscopic and submicroscopic particles using scientific notation, as well as discuss a variety of applications using nanoparticle technology.

Some keywords and phrases throughout today's lesson, one being nanometre, nanoparticle, standard form, nanoparticulate and surface area two volume ratio.

On the next slide are the definitions, but we're just gonna cover them as we go through the lesson.

So this lesson is split into two halves.

The first half looks at understanding nanoparticles, what they are, what their sizes are in relation to other things that we interact with in the world around us, as well as their applications and their risks.

So we're gonna start by looking at what nanoparticles are.

So scientists use what's known as the metric system to describe distances, volumes, any kind of measurement that we make within science, and kind of nanoparticles have one of the key prefixes that we use within the metric system, nano within their name.

And the reason we use that is because of how small particles are when we talk about them on the nano scale.

So hopefully you're familiar with the phrase kilometre and metre.

Kilometre is a thousand times greater than a metre.

You might be familiar with the term millimetre, micrometre, perhaps maybe not nanometre or picometre, but they follow the same vein, the idea that each step is a thousand times smaller than the step before them.

So if you want to kind of convert between these units, if we were gonna convert a kilometre into a metre or a kilometre into metres, should I say one kilometre is equal to a thousand metres or one metre is equivalent to 0.

001 kilometres.

And we can see as we go down that if we were to work in just the nanometre scale, sorry, if we were gonna work within metres for everything that we discussed, even things that are incredibly tiny at the nanometre scale, we'd be working with very large values.

So instead we are going to quote everything to nanometres.

So one nanometre is equivalent to 0.

000 000 001 metres.

Sometimes though, we may wish to quote things two metres rather than two nanometres or even picometres, and instead of giving all of those zeros, instead we will quote the number to standard form, the idea of having a value times 10 to the power of something.

And nanometres are one times ten to the power of minus nine, so that's nine zeroes before the one smaller than a metre.

Okay, so that's how the relationship, the ratio between metres and nanometres.

So here we have a query of, which of these is a correct conversion using the metric system? So one kilometre being equal to a hundred metres, one millimetre being equal to 0.

001 metres, one micrometre being, or micrometre being equal to 0.

01 metres and one picometre being equal to 0.

1 metres.

Which of these is correct? You might want to have a flick back to the previous slide to have a think about that.

Pause now if you need a bit of time and press play when you are ready.

Well, the answer is one millimetre is equivalent to 0.

001 metres.

This is a thousand times smaller.

Nanoscience, therefore is the study of structures that are in the nanometre region, specifically within 1 to 100 nanometres in size.

And any particles or structures that are within that size we call nanoparticles.

So just to put that into context, human DNA is about two nanometres wide, it's much longer than that, but the width is about two nanometres, and as we've said before, one nanometre is equivalent to one times ten to the power of minus nine metres is a billion times smaller than a metre.

There are lots of other types of particles that can be classified not as nanoparticles but as small microscale particles.

So we've got microparticles that exist on the microscale between micro and millie.

So that's one times ten to the minus six metres to one times ten to the minus three metres.

We've got fine particles that are not quite nanoparticles but too small to be microparticles.

They exist within one times ten to the minus nine and 2.

5 times 10 to the minus six.

And then coarse particles that are 2.

5 times 10 to the minus six metres to one times ten to the minus five metres in size.

So they're technically a type of microparticle.

Again, just to put that into context, we've got some plant cells here.

These are about 200 micrometres or micrometres long.

That's about two times 10 to the minus four metres.

So they would exist within the microparticle scale.

The size of different particles will lead to different physical and chemical properties and we're gonna talk about a few of them throughout this lesson.

So specifically, we can classify fine particles and coarse particles under what's known as a particulate matter scale.

So particulate matters are made of nanoparticles or nanoparticulate matters are made of nanoparticles, and this PM, the particulate matter scale measures a specific diameter of particles.

So we've got PM 2.

5 where particles have a maximum diameter of 2.

5 times 10 to the minus six, and we've got PM 10 where particles have a maximum diameter of 10.

So that's one times ten to the minus five 10 micrometres is the maximum diameter.

So which of these statements are correct? Which of these accurately describe particulate matter classifications? PM 2.

5 refers to particles with a maximum diameter larger than 2.

5 micrometres, PM 10 and PM 2.

5 classify particles based on their minimum possible diameter, PM 2.

5 are considered fine particles due to their size, and PM 10 refers to particulate matter with a maximum diameter of 10 micrometres.

Which of these are correct? Pause now, give it a bit of time and press play when you are ready to continue.

Well, the answers are the last two.

The top two are incorrect because it's not a maximum larger than 2.

5, the maximum is 2.

5 micrometres, and the PM 10 and PM 2.

5 don't classify based on minimum, they classify based on maximum possible size.

So the UK Government is different to obviously in lots of other governments around the world.

We're gonna focus mainly on the situation in the UK as that's where most of the students watching this probably will be based.

So the UK Government uses the term particulate matter to describe the mixture of solid particles, as well as liquid droplets in the air.

Particulate matter can either be human made or can be naturally occurring and some examples include things like dust, ash, sea-spray, and various other kind of pollen for instance, all classes as particular matter.

If you are wondering how particulate matter can be human made things like soot and other particles from the combustion of solid and liquid fuels as well as domestic heating and vehicle engines can be released into the air around us and has certain particle sizes.

Those of you who live in an area that has a lower emission zone, either London or some of the many other cities in the UK, which we'll talk a little bit about later, may be aware that at certain speed limits and types of vehicles are only allowed to drive in certain areas to limit the amount of particulate matter that is being released into the atmosphere.

One of the biggest misunderstandings that students have and other people have is that individual atoms are nanoparticles.

That's not quite true.

Most atoms, not all atoms are actually much smaller than nanoparticles.

The typical atom radius and bond length between atoms is roughly in the order of times 10 to the power of minus 10 metres.

That's almost 10 times smaller than the smallest nanoparticle.

Here we have something that is smaller than a nanoparticle.

This is an atoms, one of the first images we have of atoms using electron microscopes, and here we have a diagram representing the distance between two oxygen atoms that are bonded together in diatomic oxygen.

And again that distance is about 0.

3 nanometres, so a lot smaller than a typical nanoparticle.

A reminder that nanoscience refers to structures that are within one to 100 nanometres in size and we're gonna look at some coarse particles which include things like dust in this lesson.

They are too large, massive in comparison to nanoparticles.

There are at least 2,500 nanometres in size.

So of these, you might need to do some conversions, which of these values describes the size of something that could be classed as a nanoparticle? Pause now as you do those conversions and press play when you are ready to continue.

Only one of these is correct and that is our final answer, 20,000 picometres that is equivalent to about 20 nanometres.

A is way too large.

If it said one times ten to the minus nine metres, then perhaps maybe it would be able to be classed as a nanometre, a nanoparticle even.

However, it's too large, it's one times ten to the nine.

So that is one quintillion nanometres, it's way too large.

Two and half thousand micrometres is 2.

5 million nanometres and 0.

001 millimetres is a thousand nanometres.

They're all far too large.

So obviously the title is Understanding Nanoparticles, we're gonna focus mainly on nanoparticles and some have very interesting and unique properties, mostly down to their incredibly small size.

One of the main things that we need to take away from this lesson is the understanding that nanoparticles have an incredibly large surface area to volume ratio.

What that means is, is if we were to take a large sample of nanoparticles and stick them all together to make one large bulk substance that the surface area to volume ratio of the individual particles versus the one big bulk substance is much greater.

And we can see that represented here by taking a cube and cutting it up into eight separate pieces.

The total volume remains the same but the total surface area will increase and that's because the surface area on the inside is not able to be exposed when it's locked away inside a much larger substance.

So we're gonna look at some examples and then we're gonna do some maths.

So in this diagram we have a large cube and that cube is made up of 27 smaller blocks.

Each individual small cube has a side length of three metres.

So that means, sorry, each individual cube has a side length of one metre, meaning that the larger cube has a side length of three metres.

We can work out what the individual area of each of the faces are of the cube.

So each side length is three metres, it's a cube so each side is a square, so that's three times three metres.

That's distance times by height or distance times by length or length times by height depending on which way we look at this cube.

So three times three is nine metres squared.

There are six faces to a cube.

So that means the total surface area of this larger cube is nine metres squared times by six, which is 54 metres squared.

If we want to work out the volume, the volume is the length times by height, times by depth.

So that's three times three times three 'cause it's a cube which is 27 metres cubed.

So that gives us a surface area to volume ratio of 57 to 20 or 54 to 27, which can be simplified to two to one.

So basically the surface area is double the size of the volume.

If we take a a smaller cube, so we've taken one of the smaller cubes off of the side the length and the depth, we've now got a new side length of two metres.

New face area is two times two, which is four metres squared giving us a total surface area of four metres squared times six, which is 24 metres squared.

The volume is two times two times two 'cause that's the length times by height, times wide depth, and that gives us eight metres cubed, giving us a new surface area to volume ratio of 24 to 8, which can be simplified to three to one.

So the surface area is now three times greater than the volume.

And if we go all the way down to just one block, we've got a side length of one which gives us a face area of also one because one times one is one, so it's one metre squared.

We've got six faces, so one metre squared times six is six metres squared.

And the total volume again is the width times by the height, times by the depth, which is one times one times one, giving us a volume of one metre cubed.

That means now that the surface area is six times greater than the volume.

In comparison then, what we've done is by splitting up the larger material into the smaller particles, we've increased the total surface area.

Now that's really important because an increased surface area gives particles much more space to react.

You may have studied about rates of reaction in either biology or chemistry.

If you haven't, that will be covered in another lesson, but the greater the surface area, the faster a a substance can react because there's more surface to react with or it could be a catalyst.

So there is an increased rate of reaction 'cause there's a greater surface for the reaction to take place on.

So I'm gonna have a go at doing a calculation, bit like what we've just done and then I'm gonna ask you to do the same.

So I've got a cube here that has a side length of three metres.

The face area, so the area of one face is equivalent to two of the side length.

So times by itself, height times width if you will, so it's the side length squared.

Three squared is nine metres squared.

If I want to work out what the total surface area is, I need to times each of the face areas by six because there are six of them.

So nine metres squared times six is 54 metres cubed, sorry, 54 metres squared, and if I want to work out the volume, then the volume is equal to the side length cubed because we're times the height by the width, by the depth, all the same value.

So three square three cubed is 27 metres cubed.

That gives us a ratio of 57, sorry, 54 to 27, which we can simplify to 18 to 9, which can be simplified even further to 6 to 3, which we can simplify even further to 2 to 1.

Here are two cubes, one that has a side length of five millimetres and one that has a side length of 50 millimetres.

I'd like you to calculate the surface area to volume ratio for both.

Pause the video now, as you do so, use my example on the left hand side, the I do, once you do the you do, and when you're ready, press play.

So we're following the same steps.

The side length times the side length is 25 or 250 for the larger cube, the surface area is equivalent to the face areas to by six.

So 150 millimetres squared for the smaller cube or 1500, sorry, 15,000 millimetre squared for the larger cube, the volume is equivalent to the side length cubed.

So for volume for the small cube, that's 125 millimetres cubed, but for the larger cube that's 125,000 millimetres cubed giving us a surface area to volume ratio for the small cube of 6 to 5 and for the larger cube 6 to 50.

So the surface area in comparison to the volume is 10 times greater for the smaller cube than it is for the larger cube.

That means that we can draw a conclusion that as the side of a cube decreases by a factor of 10, the surface area to volume ratio also will change by a factor of 10, but it will increase in relation to the surface area.

I got a multiple choice question for you here.

So I'd like you to look at how the surface area to volume ratio changes when a bulk material is split into smaller nanoparticles.

Have a read through these, have a think about which ones are correct and pause the videos as you do so and press play when you are ready to continue.

Well, the answer is it increases because the surface area increases relative to the volume, the other statements are incorrect.

So a slightly longer task for you here, you've got a table that has various different entities and their sizes in a variety of different units.

I'd like you to work out what they are in nanometres and then I'd like you to write what they are in metres using standard form.

Please give all of your answers to two significant figures.

For the second task, I'd like you to calculate the surface area to volume ratio for a nanoparticle that is a cube with a side length of 15 nanometres and one that has a side length of 60 nanometres.

As you're doing those tasks, press pause on the video and press play when you're ready for the answers.

So for this first task you need to convert those into nanometres and then convert them into metres using the standard form.

And for the second task, you needed to work out what the surface area to volume ratio was for both of these different cubes, and you can see that the side length is four times greater for the large cube, and therefore because of that, because of that ratio we know of how increasing the side length affects the surface area to volume ratio.

We can see that the surface area to volume ratio for the larger cube is four times smaller than for the smaller cube.

So we've increased the side length by a factor of four, and so therefore the surface area to ratio has decreased by a factor of four.

Now we're gonna look at some of the applications of risks of nanoparticles and other particulate matter.

So we've already said that nanoparticles differ to bulk substances because they have a much higher surface area to volume ratio.

We've already said that that also affects their properties.

It also is very useful because it means that smaller quantities might be needed than for normal sized particles.

So we might not have to use as much in a chemical reaction.

Most nanoparticles that we use in chemistry are either made from metals, metal oxides, or silicates, however, some are also made from carbon.

Here are some images of some different silica-based nanoparticles and we've got some scales so that we can see that all of these are being compared to 20 nanometres.

So the one on the left is slightly larger and the one, sorry, slightly smaller and the one on the right is slightly larger.

Nanoparticles have lots of different applications, most nanoparticulate materials, however, we are still researching to find some really interesting uses for.

True or false then, the properties of nanoparticles are identical to those of the same materials in bulk form.

Well, that's false.

Here are two statements, I'd like you to choose the correct one.

So pause the video as you read through them and press play when you are ready to continue.

Well, the answer is A is because nanoparticles have a much higher surface area to volume ratio than bulk materials.

We're gonna look at some examples now.

So the first one is titanium dioxide, this is a very commonly talked about one.

Bulk titanium dioxide is a white solid.

We use it as a pigment in lots of different resources such as paint, and it's well known for its ability to absorb harmful UV radiation emitted from the sun.

In nanoparticulate form, we are able to use it to its advantage of absorbing UV radiation, but because it's such a small particle, because it's made of such small particles, we are able to use it in an application where we cannot see it, which is different to in the bulk form because it's a white powder, whereas in nanoparticulate form it's almost invisible.

So we use it in sunscreens and most modern-day sunscreens have, especially the ones that are kind of a fluid, that kind of a spray that you can't really see and it's a lot of clear and kind of colourless ones out there on the market these days, we use titanium dioxide nanoparticulates.

We can also use nanoparticles in electronics.

So we use gold and silver nanoparticles as conductive inks for printed on electronics.

Because of their small size, they allow the electronics to be very thin and very flexible.

So here we've got a bulk gold plated headphone jack.

So this is made up of bulk material.

This is not flexible and so would not be very useful in wearable electronics, whereas nanoparticles would be.

Silver nanoparticles are also known for their anti-microbial properties, meaning they can target bacteria and kill them, reducing odour, so they are used in things like medical dressings, deodorants, as well as sock fabrics.

Bulk silver is too large, it can't interact with bacteria and is not an effective microbial agents, but does have its own properties that are obviously very useful in other applications.

Another use for nanoparticles, which we've hinted at already, is they're used as catalysts in chemical reactions.

And again, that's down to their high surface area to volume ratio, providing more surfaces or more sites on the surface for reactions to occur, meaning reactions can occur faster and more efficient.

It can also mean because of their lower surface area to volume ratio, that we don't need to use as much of them as traditional catalysts.

Bulk catalysts, on the other hand, have a low surface area to volume ratio, makes them less efficient and slow in catalysing reactions.

We've already looked at before, carbon nanotubes and fullerenes.

These are nanoparticles, they fit within the scale of nanoparticles and there are thoughts, ideas, suggestions that we might be able to use fullerenes as drug delivery devices.

As we know they already have high tensile strength due to their sort of long length, small diameter that's nanotubes, and they're also excellent thermal and electrical conductors.

True or false then, only titanium dioxide nanoparticles can absorb harmful ultraviolet radiation and that's why they're used in sunscreen.

That's false.

Here are two statements why, I'd like you to pause the video whilst you think about this and then press play when you are ready to continue.

Well, the answer is B, using nanoparticles allows UV protection with invisible coverage for aesthetic appeal so it's preferable for sunscreens.

Bulk titanium oxide is also able to absorb harmful ultraviolet radiation.

So we're kind of asking the question of is it just the nanoparticles? No, there are other substances that can also absorb them even in bulk form, that's not the reason why we use them in sunscreen.

The reason why we use the nanoparticles, it's 'cause they're almost invisible to the human eye.

Why do we use silver nanoparticles in deodorants? Have a read through these and press pause as you do so and press play when you're ready to continue.

The answer is B, they have antimicrobial properties.

They don't enhance the deodorant's fragrance, but they may limit the body odour by killing off harmful bacteria that produce that odour.

They don't improve the deodorant texture and application and they aren't necessarily cheaper than using bulk silver.

True or false, carbon nanotubes are valued in electronics for their high tensile strength and poor conductivity.

That is a false statement.

Here are two statements below to help justify that.

So have a read through, pause as you do so and press play when you're ready to continue.

Well, the answer is, A, carbon nanotubes have high tensile strength and are excellent thermal and electrical conductors.

The statement above says that they are poor conductors, which is not true.

Okay, so nanoparticles seem great so far, we talked about lots of excellent uses of them, however, they've not really been around for very long.

They're relatively new, they're not very well-researched, and so we don't really know what all the potential risks are to nanoparticles.

There are potentials that nanoparticles could be absorbed into our bodies, they could enter our cells, and they could potentially catalyse dangerous reactions within the body.

Nanoparticles as we know are incredibly small.

They are small enough to pass through cell membranes and there are concerns that if inhaled, nanoparticles could be absorbed by cells in our lungs.

So here we can see a diagram showing the alveoli in our lungs.

We've got a nice electron microscope image here of the alveoli in mouse lung or in mice lungs, and we can see here that they are kind of several thousand nanometres in size.

They're quite large in comparison to nanoparticles.

So nanoparticles can very easily cross through those membranes.

There are also concerns that nanoparticles could pass through cell membranes in our intestines after ingestion, and once inside those cells, again, they could catalyse harmful reactions.

Or there is concern that if they are in the environment, they could carry toxic substances bound to their surfaces inside our cells.

And again, we can see here that the kind of the scale of the microvilli in our intestines are much larger than nanoparticles.

So again, those nanoparticles could very easily cross into those cell membranes.

So true or false, nanoparticles are safe for human health and the environment because they're used in medical treatments and in electronic devices.

Well, that statement is false.

I want you to read through these two statements to justify why.

Pause now and as you do so, press play when you're ready to continue.

Well, the answer is B, we don't know what the effects are, so we can't say for certain that they will enter our cells and they will then cause damage.

We'll have to give a much broader answer, a much broader suggestion that the long-term effects are unknown, not fully understood, but this could happen.

So these are some larger particulates then.

So that's us looking at nanoparticles.

We can now look at some larger particles.

So these are particles that could have a maximum size of two and a half micrometres or ten micrometres.

And so the short-term effects versus the long-term effects are quite widely known.

And this is the reason why a lot of councils in the UK have started to introduce these low emission zones to reduce the amount of dangerous particulate matter that can enter our atmosphere.

I'll give you some chance to read through this if you want to, I'll give you a few highlights here.

So we've got PM 2.

5 short-term effects are, just worsens any known respiratory diseases, could cause some breathing discomfort, but over long term, so repeated exposure over a long period of time has been linked to premature death, reducing lung function, making breathing harder or causing even more difficult adverse health problems. Whereas for PM 10, what we know in the short term, it worsens respiratory diseases potentially leading to hospitalisation.

We don't fully understand the long-term effects, but we think they could be linked to again, some serious long-term lung problems. So a lot of sources of PM 2.

5 come from human-made emissions on road vehicles and industrial activities.

There are some natural sources of them as well.

And you can see here some data from 2010, so this was about 14 years ago now, shows where the highest concentration of those PM 2.

5 particles are.

You can see kind of where it's green, there's slightly lower concentration, where it's purple and red, they are the highest concentrations.

Incidentally, the green areas are below the acceptable levels according to the World Health Organisation, so that's good.

I mean, the World Health Health Organisation suggests that ideally they should be lower, but they are under their definition of acceptable levels.

And anywhere that is dark orange, red or purple are considerably greater than the World Health Organization's recommended daily exposure levels.

And so hopefully that kind of makes sense as to why councils in the UK and across Europe are trying to reduce the amount of emissions.

So some cities in the UK have what's known as a designated clean air zone, and there are some listed on the screen now.

And you can see here an example sign from Bradford in the UK highlighting to road users that they are entering a clean air zone.

Vehicles that don't meet certain emission criteria may have to pay to drive on the roads in these areas, and the same is true in London in what's known as the low emissions zone or the ultra low emission zone, which has faced some controversy from locals in London over recent years due to kind of the levels of taxation that some people feel are being imposed on them for having older vehicles.

In Scotland there are low emission zones in Glasgow with many more planned in other cities, but Wales and Northern Ireland currently have no charging clean air zones and as far as I've done my research, no plans to introduce any any anytime soon.

So which statements about PM 2.

5 are true then? Have a read through these and pause the video, as you do so and press play when you are ready to continue.

Well, the answer is B, long-term exposure to PM 2.

5 is linked to severe health issues, and PM 2.

5 causes the greatest proportion of adverse effects in comparison between PM 2.

5 and PM 10.

What is the purpose of establishing clean air zones or low emission zones in UK cities? So there's some statements here.

Have a read through them, press pause as you read through them and press play when you are ready to continue.

Well, the answer is C, to reduce traffic flow and mitigate noise and air pollution.

There are obviously some cynics and some controversies out there of people trying to potentially limit people's movement through the cities or to perhaps just line the pockets of councils, but the main aim of these procedures is to reduce traffic flow and to mitigate noise and air pollution.

So we've got two questions here.

One that asks about titanium dioxide nanoparticles and asks you to explain how the properties makes them suitable for the applications, and then we've got a question here, considering the potential risks associated with nanoparticles.

I'm gonna give you some time to have a go at these questions.

So pause the video now once you do this and then press play when you're ready for the answers.

Question one asks you to explain how the properties, so titanium dioxide nanoparticles absorb ultraviolet radiation from the sun and they have an incredibly small size, so they appear transparent or invisible to the human eye.

So therefore, they provide UV protection without leaving a white residue behind like traditional sunscreens.

Silver nanoparticles are antimicrobial or antibacterial and because of their large surface area to volume ratio, increases the contact with bacteria inhibiting bacterial growth, reducing death.

So some risks of inhaling nanoparticles include that they could enter our cells which could trigger harmful internal reactions, or transport toxic substances into our cells.

How might society address the use of nanoparticles? Well, they might address the use by asking or pushing for more research into their long-term effects that will in turn lead to improving industry safety and therefore hopefully increase public awareness of the benefits and risks so they can make an informed decision.

So well done on those questions.

In this lesson, we've covered the idea that the prefix is milli, micro, nano, and pico in that order subdivided metre into smaller and smaller divisions.

Nanoparticles are 1 to 100 nanometres in size and are larger than atoms and molecules.

We've talked about how the smaller particle, the bigger its surface area to volume ratio, and how nanotubes are very small and extremely strong fibres that are thermal and electrical conductors.

We've talked about how nanoparticles have many applications and new applications for nanoparticulate materials are an important area for research.

I've really enjoyed going through this lesson with you today, and I look forward to seeing you in future lessons.

Thank you very much.

Bye-Bye.