Nanocellulose Foam

You have probably held polystyrene cups (styrofoam cups) in your hands. It is a wonderful material for making disposable cups because it is light-weight, holds it shape well, and is an excellent insulator. All this means that you can fill a polystyrene cup with hot tea and drink from it without having it burn your hands. High school chemistry teachers are very fond of using polystyrene cups as "cup calorimeters" in the school laboratory. Unfortunately, polystyrene is not an environmentally friendly polymer, it doesn't break down, it is chemically inert, so persists in the environment.
Plant-based polymers which degrade in time, such as cellulose, could replace polystyrene if we can make a cellulose-based material with same properties as polystyrene.
Cellulose is a polysaccharide. It is composed of many glucose units joined together by ether bonds (glycosidic links). During acid hydrolysis these ether bonds (glycosidic links) are attacked and broken so that the final product of a complete reaction is a lot of glucose molecules. The reaction mechanism for the acid hydrolysis of cellulose is shown below:


If only some of the ether bonds (glycosidic links) within a cellulose polymer chain are attacked, then you could end up with shorter chains of glucose polymer, still enough glucose units in the chain to be considered cellulose. If these chains are only 5-20 nanometres wide (even though they may be several micrometres long) they will be referred to as nanocellulose.
Researchers at Washington State University have added polyvinyl alcohol, shown below:

to nanocellulose. Polyvinyl alcohol binds to the nanocellulose which stabilises the foam that can be  produced. This light-weight material is reported to be a better insulator than polystyrene foam (styrofoam) and "can support up to 200 times its weight without changing shape. It degrades well, and burning it doesn't produce polluting ash."

Suggested Further Reading:
Nanotechnology

Suggested Study Questions:

1. Convert the following measurements to metres (m):
   • 5 nm
   • 20 nm
   • 100 μm
   • 1000 μm
2.  Convert the following measurements to nanometres (nm)
   • 5 × 10^-9 m
   • 2.5 μm
   • 5.2 mm
   • 0.75 cm
3. Draw a section of cellulose polymer containing 6 glucose units. Circle the ether bonds (glycosidic links) in red.
4. Draw the results of acid hydrolysis if all the ether bonds (glycosidic links) in this section of cellulose polymer were broken.
5. Draw the results of acid hydrolysis on the section of cellulose polymer you drew for question 3 if only 2 new "molecules" are produced. Is there only one possible answer? If more than one answer is possible, how many possible answers can you think of?
6. Consider the structure of cellulose and of polyvinyl alcohol. Explain how polyvinyl alcohol can "bind with" cellulose. 
7. Explain why a nanocellulose foam can be stabilised by adding polyvinyl alcohol.
8. Consider the combustion of cellulose. Give the products for
   • complete combustion of cellulose
   • incomplete combustion of cellulose
9. Wood is composed largely of cellulose. When a wood log burns on a camp fire it produces a sooty flame. Explain why.
10. Explain why nanocellulose is unlikely to produce a sooty flame when it burns.

How long is a piece of string?

How long is a piece of string?
What units of length you use to measure a piece of string will depend on how long the string is.
If you are putting up a string of Christmas lights you might measure the length of the string in metres or centimetres.
But if you are measuring the length of string, or ribbon, to tie back your hair you might measure the length of string in centimetres or millimetres.
1 centimetre is a hundredth of a metre: 1 cm = 10^-2 m
1 millimetre is a thousandth of a metre: 1mm = 10^-3 m
The metre is the SI base unit of length.
On the other hand, if your piece of string is holding 2 atoms together in a molecule you are going to need a very tiny piece of string, less than a billionth of a metre. Which is why chemists use units of length like the nanometre (1nm = 10^-9 m), the Ångstrom (1 Å = 10^-10 m), and the picometre (1 pm = 10^-12 m).
You will need to be familiar with these units and be able to convert one unit of length into another, so AUS-e-TUTE has just added new tutorials, games, tests to help our members do this.
If you are not a member, you can access a "free-to-view" tutorial at https://www.ausetute.com.au/lengthconv.html

Graphene from Graphite

In 2004, University of Manchester researchers isolated graphene by applying sticky tape to a piece of graphite and peeling off a layer, then repeating the sticking and peeling process on this and subsequent layers until they had a layer that was just one carbon atom thick. The final 2-dimensional layer of carbon atoms is graphene. The structure of graphene is shown below:

The researchers, Professors Andre Geim and Kostya Novoselov were awarded the 2010 Nobel Prize in Physics.

Graphene is a highly sought after material. It is stronger than steel, yet it is a million times thinner a strand of hair. It is also a better conductor than the copper commonly used for electrical wiring. In order to use graphene in consumer products it needs to be produced on a large scale and in commercial quantities. It is not commercially viable to spend large amounts of time peeling off layers from graphite using sticky tape to produce small quantities of graphene. So the race has been on to find a process that could be used commercially.

One method is to oxidize graphite using hazardous oxidizing agents like anhydrous sulfuric acid and potassium peroxide. A representation of a layer of this oxidized graphene from the stacked layers making up graphite is shown below:

Layers of oxidized graphene can then be separated chemically from the bulk graphite, but these processes take a long time, and, the product is not graphene but oxidized graphene which is not as conductive as pure graphene.

University of Connecticut (UConn) Professor Doug Adamson has found a new way to produce graphene based on its solubility. Graphene is insoluble in liquids like oil, hexane and water.
Imagine you have a jug containing some oil and some water. If you wait, the two liquids will separate out, forming two distinct layers as represented below:

The less dense oil will float on top of the more dense water. If you add graphite to the area where these two liquids meet (the interface), then the stacked layers of graphene sheets in the graphite spontaneously "unstack" and spread out to cover this interface. These trapped graphene sheets can be locked into place using a cross-linked polymer.

The researchers are now investigating how this graphene composite material could be used to desalinate brackish water.

Reference

1. Steven J. Woltornist, Andrew J. Oyer, Jan-Michael Y. Carrillo, Andrey V. Dobrynin, Douglas H. Adamson. Conductive Thin Films of Pristine Graphene by Solvent Interface Trapping. ACS Nano, 2013; 7 (8): 7062 DOI: 10.1021/nn402371c

Further Reading:

Allotropes Tutorial

Graphene and Fullerenes Tutorial

Nanotechnology Tutorial

Metallic Bonding Tutorial

Wetting Tutorial

Surface Tension Tutorial

Density Tutorial

Water as a Solvent (aqueous solutions) Tutorial

Suggested Study Questions

1. Explain why graphite is a good conductor of electricity.
2. Explain how the structure of graphene and graphite are:
• similar
• different
3. Explain why graphene is considered to be a 2-dimensional material but graphite is considered to be a 3-dimensional material.
4. Explain why graphene is a much better conductor of electricity than graphite.
5. What characteristics of graphene allow it to be peeled off in layers from bulk graphite. Explain your answer.
6. Explain why a mixture of oil and water will separate out into 2 distinct layers rather than forming a homogeneous mixture.
7. Consider the structure of graphene to explain the insolubility of graphene in:
• water
• oil
8. Explain why copper is a good conductor of electricity.
9. Discuss how the structures of copper and graphene are:
• similar 
• different
10. Explain why graphene is a much better conductor of electricity than copper.

Nanoparticles to Remove Coral Bleaching Oxybenzone

Sunblocks contain a number of different compounds including oxybenzone which acts as a UV filter. The skeletal structural formula of oxybenzone is shown below:

Oxybenzone is soluble in water.
Before you go snorkeling in the Great Barrier Reef to be amazed by the beautiful corals, fascinating fish and other exciting wonders, you smother yourself in sunblock. When you step into the water, the oxybenzone starts to dissolve. Unfortunately, oxybenzone contributes to coral bleaching, the killing off of the tiny, colourful zooxanthellae marine algae that live inside corals. The result is that the coral loses its colour and appears white, as if it has been bleached.

Researchers have found a way to soak up the oxybenzone from the seawater using magnetite nanoparticles.

Magnetite, Fe₃O₄ , is a mineral made up of iron(II) and iron(III) oxides and is one of the main iron ores, that is, magnetite is mined in order to produce iron. Magnetite is ferromagnetic, that is, it is attracted to a magnet. It is the most magnetic naturally occurring mineral on Earth. If you could get the oxybenzone in the seawater to attach to magnetite nanoparticles then you could pull the oxybenzone out of the water using a magnet.

First, the researchers coated the magnetite nanoparticles with sodium oleate. The skeletal structural formula of sodium oleate is shown below:

Next, they oxidised the oleate coating to increase the number of hydroxyl (OH) functional groups:

Since oxybenzone can interact with other molecules via hydrogen bonds, magnetite nanoparticles  covered in a coating rich with hydroxyl functional groups increases the interactions between oxybenzone and the nanoparticles. Once the oxybenzone has hydrogen bonded to the nanoparticle coating, a magnet can be used to extract the particles from water.

Does it work?
One brave researcher applied sunblock, stepped into the ocean, waited 10 minutes, then collected a sample of the surrounding seawater. Back at the lab, chromatography was used to determine the concentration of oxybenzone in the water, 1.3 ppm. This is a disturbing result since it is known that the concentration needed to bleach coral is measured in parts per billion.
Next, the researchers prepared seawater samples. Some had no magnetite nanoparticles added, others had the nanoparticles added. Then they added 30 ppm oxybenzone to  all the samples. The concentration of oxybenzone in the samples with no nanoparticles did not change in an hour. In the samples that contained the nanoparticles, 95% of the  oxybenzone  was removed within the hour.

Reference
American Chemical Society. "Sopping up sunblock from oceans to save coral reefs." ScienceDaily. ScienceDaily, 21 August 2017.

Further Reading
Solutions Concepts
Water as a Solvent
Transition Metals (magnetism)
Fatty Acids
Carboxylic Acids
Nanoparticles and Nanotechnology
Parts per Million (ppm)
Chromatography
Experimental Design
Variables
2-Dimensional Structural Formula
Skeletal Structural Formula
Molecular Formula

Suggested Study Questions

1. For a molecule of oxybenzone:
• draw the 2-dimensional structural formula
• give the molecular formula
2. On the 2-dimensional structural formula of oxybenzone identify and name each functional group present.
3. Use diagrams to explain why oxybenzone is soluble in water.
4. Draw the 2-dimensional structural formula for oleic acid.
5. On your structural formula of oleic acid, identify and name the functional group(s).
6. Suggest a method by which you could change oleic acid into sodium oleate in the laboratory.
7. Suggest a method by which you could oxidise sodium oleate in the laboratory.
8. Explain the term "nanoparticle".
9. Why do you think the researchers chose nanoparticles of magnetite rather than bulk magnetite for this research?
10. Consider the description of the experiment used to determine the effectiveness of the magnetite nanoparticles in removing oxybenzone from seawater:
• What was the hypothesis being tested?
• What was the aim of the experiment?
• What variables need to be considered in this experiment?
• What is the independent variable in the experiment?
• What is the dependent variable in the experiment?
• Which variables are constant variables in the experiment?
• Why did the experimenters add nanoparticles to some samples but not to others?
• Write out a suitable method for this experiment.

Molecular Machines

People use machines to perform tasks that fall beyond our capacities.

Since the Industrial Revolution, the complexity and number of machines we use has increased.

At the Annual Meeting of the American Physical Society in 1959, physicist and 1965 Nobel Laureate in Physics, Richard Feynman talked about the possibility of building small machines from atoms.

He returned to this idea in a lecture in 1984 he asked, "How small can you make a machine?".

But by then Chemists had already taken the first tentative steps towards building molecular machines.

The 2016 Nobel Prize in Chemistry has been awarded to Jean-Pierre Sauvage, Sir J. Fraser Stoddart and Bernard L. Feringa, whose research has led to the development of molecular machines...

Learn more in this edition of AUS-e-NEWS.

Visit http://www.ausetute.com.au/ausenews.html to subscribe to AUS-e-NEWS, AUS-e-TUTE's free quarterly newsletter.

Nanomaterials Monitoring Reactions

Syracuse University Chemists have designed a nanomaterial that changes colour when it interacts with ions and other small molecules during a chemical reaction which enables them to monitor the progress of chemical reactions qualitatively with the naked eye and quantitatively using simple instruments.

Many chemical reactions that occur in aqueous solution involve colourless species. In order to determine how fast the chemical reaction occurs,  Chemists have traditionally tried to "freeze" the reaction at certain points, purify the solution and determine the amounts of unreacted reactants and products produced present at each stage.
Syracuse University Chemists have taken a different route. They are using nanoparticles that react with the byproduct of a reaction. The nanoparticles they used are known as perovskites.
Perovskites are typically composed of metal ions and oxygen. The structure shown below is for a typical perovskite, calcium titanium oxide (CaTiO₃):

Each pale-blue titanium atom is surrounded by 6 red oxygen atoms. The darker-blue calcium atom occupies the space between titanium oxide octahedrons.
The perovskites the researchers used were a bit different to the one shown above. Metal ions were surrounded by halide ions rather than oxygen.
At the nanolevel, perovskites are photo-luminescent, that is, they emit light when "excited" by a laser or a lamp. The colour they emit is largely determined by the concentration of their ions in solution., and it is this property which the researchers used to monitor chemical reactions. It is also this property which is being in exploited in research into light emitting diodes (LEDs), lasers, photodetectors and solar cells.

In this study, perovskites were used to monitor an elimination reaction in which haloalkanes react to form alkenes, eliminating halide ions in the process.
At the start of the reaction, the perovskite fluoresces red.
As the reaction proceeds, halide ions are released which are absorbed by the perovskite nanoparticles, and the fluorescence colour changes from red to yellow to green.
When the fluorescence colour is green, the reaction is over.
The image on the right shows a control colour on the left, and on the right, the changing fluorescence colour of the reaction as it proceeds from 0 minutes at the top to 90 minutes at the bottom.

This technology is patent-pending at the University. In the words of Matthew Maye, Associate Professor of Chemistry, "Who knows, maybe in the future, every chemist will use a Syracuse-based perovskite for monitoring their reactions."

Reference:
Tennyson L. Doane, Kayla L. Ryan, Laxmikant Pathade, Kevin J. Cruz, Huidong Zang, Mircea Cotlet, Mathew M. Maye. Using Perovskite Nanoparticles as Halide Reservoirs in Catalysis and as Spectrochemical Probes of Ions in Solution. ACS Nano, 2016; DOI: 10.1021/acsnano.6b00806

Further Reading:
Nanotechnology: http://www.ausetute.com.au/nanotech.html
Reaction Rate: http://www.ausetute.com.au/reactrate.html
Ligands and Complex Ions: http://www.ausetute.com.au/ligands.html
Naming Haloalkanes: http://www.ausetute.com.au/namhaloa.html
Naming Alkenes: http://www.ausetute.com.au/namsenes.html
Substitution Reactions of Haloalkanes: http://www.ausetute.com.au/rxreacts.html
Dehydration of Alkanols: http://www.ausetute.com.au/dehydraol.html

Suggested Study Questions:

1. Explain the terms "qualitative" and  "quantitative".
2. Explain the term "reaction rate".
3. Explain the term "nanoparticle".
4. What property of nano-perovskite is being applied by the researchers in this article, and how does this property differ for bulk perovskite?
5. Explain how these perovskites can be used to monitor the reaction qualitatively.
6. Explain how you could use these perovskites to monitor the reaction quantitatively.
7. Discuss the differences between ethane, ethene (ethylene) and bromoethane.
8. Consider ethane and ethene (ethylene), which is likely to be more chemically reactive? Explain your answer.
9. Consider ethane and bromoethane. Which is likely to be more chemically reactive? Explain your answer.
10. Explain what is meant by the term "elimination reaction" as used in the article above.
11. What is the difference between and addition reaction, a substitution reaction and an elimination reaction? Give examples of each type of reaction.
12. Write a chemical reaction to represent the elimination of bromide ions from a bromoethane to produce ethene (ethylene). 
13. Consider the structure of CaTiO₃ given in the article. What is the name of the ligand?
14. Give the formula for the perovskite in which all the oxygen atoms have been replaced with bromine.
15. Could the same perovskite be used to monitor a chemical reaction in which water is eliminated from an alkanol to produce an alkene? Explain your answer.

Nano-zinc oxide and the Environment

Increasingly, we are making use of nanoparticles because of their unique properties compared to the same substance in bulk material. Many cosmetics, including sunscreens and sunblocks, now contain nanoparticles. When you go swimming or wash, these nanoparticles are washed off. Depending on where the nanoparticles are washed off, the waste water may directly enter a natural water system such as a river or ocean, it may end up in sewerage sludge, and it may eventually end up on land. What scientists do not know is just how many nanoparticles are entering the earth, air and water.

It is estimated that carbon nanotubes, which form part of a composite material in objects such as bicycle frames and tennis rackets, can take 10 years to breakdown and be released into the environment. On the other hand, about half of the cosmetic nanoparticles enter our waste water within one year.

Europe currently produces about 39,000 tons of nano-titanium dioxide per year, and it is estimated that the concentration of these nanoparticles in effected areas is now 61 micrograms per kilogram of ground. For humans, the maximum "safe" levels for exposure to these nanoparticles is set at:

• 2,500 mg/kg/day for oral exposure
• 2.4 mg/m³ for inhalation

While small amounts of zinc oxide are beneficial to plant growth, larger amounts can impair seed germination. Plants take up the free zinc ions in aqueous solution rather than the zinc oxide particles. This zinc becomes incorporated into the plants we eat. Zinc is an essential element in the human diet. The recommended dietary allowance of zinc for men is 11 mg/day, and for women is 8 mg/day. There are concerns that the increasing level of zinc in  plants may lead to accumulation of zinc in humans which will be detrimental to our health. Ingesting more than about 100 mg of zinc per day may lead to chronic toxicity.

Research into the environmental impact of nanoparticles, and their impact on plant and animal health, will continue for a long time.

Reference:
https://www.sciencedaily.com/releases/2016/05/160512084646.htm

Further reading
Nanotechnology: http://www.ausetute.com.au/nanotech.html
Graphene and Fullerenes: http://www.ausetute.com.au/graphene.html
Solutions Concepts: http://www.ausetute.com.au/solutions.html
Weight percent (w/w): http://www.ausetute.com.au/weightpc.html
Parts per MIllion (ppm): http://www.ausetute.com.au/partspm.html

Suggested Study Questions:

1. What is meant by the term "nanoparticle"?
2. If a nanoparticle of zinc oxide has a diameter of 20 nm, what is its diameter in:
   • metres
   • centimetres
   • millimetres
   • micrometres
3. Give an example of one property of bulk zinc oxide that is different to nanoparticles of zinc oxide.
4. Explain why zinc oxide nanoparticles are used in sunscreens.
5. What is a carbon nanotube?
6. Why are carbon nanotubes used in the production of bicycle frames?
7. Why are concentrations of titanium dioxide nanoparticles in soil given in units of micorgrams per kilogram of soil rather than in moles per litre?
8. Convert the following concentrations into parts per million (ppm)
   • 2,500 mg kg^-1
   • 2.4 mg m^-3
9. Using the recommended dietary allowance figures in the article, determine the mass in grams of zinc allowed for a:
   • 58 kg woman each day
   • 79 kg man each day
10. A typical vitamin pill contains 25 mg of zinc. By consuming 1 tablet per day, will the man or woman above exceed the recommended daily allowance of zinc?
11. 6 raw oysters contain 32 mg of zinc. How many oysters can the man and woman above eat before exceeding the recommended dietary allowance of zinc?
12. 85 g of cooked beef contains 7 mg of zinc. What mass of beef can the man and woman above ingest before exceeding the recommended dietary allowance of zinc.
13. 28 g of dry roasted cashews contain 1.6 mg of zinc. What mass of zinc, in grams, is present in 750 g bag of cashews?
14. 1/2 cup of cooked red kidney beans contain 0.9 mg of zinc. How many cups of red kidney beans would our man and woman above need to consume in order to achieve their recomended dietary allowance of zinc?
15. Do you think you should take a daily vitamin pill containing zinc? Justify your answer.

Buckyballs and Nanotubes

Want to know more about graphene and fullerenes?
Need to know the properties and uses of graphene, buckminsterfullerene an carbon nanotubes?

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Nanotechnology and Nanoparticles

What is nanotechnology?
What is a nanoparticle?
How are the properties of nanoparticles different to the properties of bulk material?
What makes nanoparticles special?
How do you make nanoparticles?
Are nanoparticles safe?

Hey! You ask really good questions!
AUS-e-TUTE not only provides some really good answers, but we also have games to play and test questions to answer on this topic ..... and ......when you answer a test question you get immediate feedback and a worked solution if you need it.

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Borospherene

A molecule containing 60 carbon atoms in a cage-like spherical shape was first produced in 1985 and was called buckminsterfullerene, or bucky-ball. The structure is like a soccer ball, made up of 20 hexagons and 12 pentagons.
A bucky-ball is shown on the right. Each blue sphere represents a carbon atom, and each cream-coloured line represents a covalent bond between 2 carbon atoms.
One of the reasons that scientists are very interested in buckminsterfullerene is because of its ability to hold atoms of different elements inside the cage-like structure. This could enable bucky-balls to be used to deliver drugs in the body, or to store atoms such as hydrogen.

In 1991, scientists discovered that carbon atoms can also form nanotubes, and in 2004, sheets of carbon atoms just 1 atom thick known as graphene were discovered.

But can atoms other than carbon make these kinds of 3-dimensional networks at the nanometre level?

Researchers from Brown University, Shanxi University and Tsinghua University in China have shown that a cluster of 40 boron atoms forms a hollow molecular cage similar to a carbon buckyball. It's the first experimental evidence that a boron cage structure does indeed exist.
This boron cage, called borospherene, isn't quite as spherical as its carbon cousin. Rather than a series of five- and six-membered rings formed by carbon, borospherene consists of 48 triangles, 4 seven-sided rings and 2 six-membered rings. Several atoms stick out a bit from the others, making the surface of borospherene somewhat less smooth than a buckyball.

Because of the electron deficiency of boron, borospherene is likely to bond well with hydrogen. So these tiny boron cages could serve as safe houses for hydrogen molecules.

Reference:
Brown University. "Researchers discover boron 'buckyball'." ScienceDaily. ScienceDaily, 13 July 2014. .

Further Reading:
Graphene
Molecular Formula
Allotropes

Suggested Study Questions:

1. Write the molecular formula for buckminsterfullerene given the information in the article above.
2. How many covalent bonds does each carbon atom in buckminsterfullerene make?
3. Do you expect buckminsterfullerene to be soluble or insoluble in water? Explain your answer.
4. Draw a representation of graphene.
5. How many covalent bonds does each carbon atom make in graphene?
6. Do you expect graphene to conduct electricity? Explain your answer.
7. Write the molecular formula for borospherene based on the information provided in the article.
8. In the pictorial representation of borospherene given above, what do each of the following represent:
   • red spheres
   • yellow lines
9. In what ways are the structures of bucky-balls and borospherene similar?
10. In what ways are the structures of bucky-balls and borospherene different?

Nobel Prize countdown

As students head back to the class room for a new term of exciting learning, the scientific community is gearing up for a major annual event, the announcement of the Noble Prizes.
With just days to go before the Nobel Prize in Chemistry is to be announced, there is much discussion (and possibly even a bit of betting) about who is likely to be this year's laureate.

Among the contenders this year are:

• Louis E. Brus (Columbia University) for the discovery of colloidal semiconductor nanocrystals (quantum dots)
• Akira Fujishima (University of Tokyo) for the discovery of photocatalytic properties of titanium dioxide (the Honda-Fujishima Effect)
• Masatake Haruta (Tokyo Metropolitan University) and Graham J. Hutchings (Cardiff University) for their discoveries of catalysis by gold

Quantum dots are semiconductors, but their electronic properties are related to the size and shape of the individual crystals. In general, the smaller a crystal is, the more energy is needed to excite the dot, which means that more energy is released when the crystal returns to its ground state. It is hoped that quantum dots will lead to practical quantum computing and increase the efficiency of photovoltaic cells. Quantum dots are being used in preference to some dyes in biological analyses because quantum dots are brighter and more stable.

While working on his Ph.D in 1967, Akira Fujishima exposed a titanium dioxide electrode to strong light and discovered that this catalyzed the decomposition of water into hydrogen and oxygen. This became known as the Honda-Fujishima Effect (Professor Kenichi Honda was Akira Fujishima's supervisor). Finding cheap, effective methods for providing hydrogen would enable the development of hydrogen as fuel.

In the 1980's Masatake Haruta showed that colloidal gold, gold clusters with diameters of 5 nanometers or less, could catalyze reactions involving oxygen gas.
Graham J Hutchings has extended the number of reactions  we now know of that can be catalyzed by gold. Hutchings has shown that primary alcohols can be oxidized to aldehydes using a gold-palladium/titanium dioxide combination without the need for a solvent. He has also developed the rapid synthesis of hydrogen peroxide, H₂O₂, from hydrogen and oxygen  without the formation of water as a by-product.

Molecular Motor

The Guinness World Record for the smallest electric motor currently stands at 200 nanometers, a human hair is about 300 times wider! Now Chemists at Tufts University's School of Arts and Sciences say they have developed the world's first single molecule electric motor, just 1 nanometer in diameter.

The molecular motor was produced when a butyl methyl sulfide molecule had been placed on a conductive copper surface and given an electrical charge. This sulfur-containing molecule had carbon and hydrogen atoms radiating off to form what looked like two arms, with four carbons on one side and one on the other. These carbon chains were free to rotate around the sulfur-copper bond.

The team determined that by controlling the temperature of the molecule they could directly impact the rotation of the molecule. Temperatures around 5 K, or about -450ºF, proved to be the ideal to track the motor's motion. The motor spins much faster at higher temperatures

Reference
Heather L. Tierney, Colin J. Murphy, April D. Jewell, Ashleigh E. Baber, Erin V. Iski, Harout Y. Khodaverdian, Allister F. McGuire, Nikolai Klebanov, E. Charles H. Sykes. Experimental demonstration of a single-molecule electric motor. Nature Nanotechnology, 2011; DOI: 10.1038/NNANO.2011.142

Further Reading
SI Unit Conversions
Temperature Conversions
Nomenclature
Molecule Polarity
Intermolecular Forces
Molecular Mass (formula weight) Calculations
Percentage Composition
Empirical and Molecular Formula

Study Questions:

1. Convert 200 nanometers to a diameter in
   • meters
   • micrometers
   • millmeters
   • decimeters
2. Form the information in the article above:
   • What is the diameter of a human hair in nanometers?
   • What is the size ratio of the molecular motor to a human hair?
3. Convert the following temperatures:
   • 5K to ^oC
   • 0K to ^oC
   • 100^oC to K
   • 25^oC to K
     
4. On the molecular structure of butyl methyl sulfide:
   • identify the butyl group
   • identify the methyl group
5. For a molecule of butyl methyl sulfide:
   • write the molecular formula
   • give the empirical formula
     
   • calculate the molecular mass
   • calculate the percentage composition
     
   
   
6. Is butyl methyl sulfide a polar or non-polar molecule? Explain your answer.
7. Do you expect butyl methyl sulfide to be water soluble? Explain your answer.
   
   
   
   

Catalysis by Gold Nanoclusters

Since the early 1980s, experiments have indicated that gold nanoparticles exhibit unexpected catalytic activity towards many industrially important chemical reactions that involve activation of atomic bonds inside oxygen or hydrocarbon molecules. Room-temperature formation of carbon dioxide, CO₂, from carbon monoxide, CO, and oxygen molecule, O₂, is one of the most extensively studied processes. A number of different factors have been suggested to contribute to the ability of gold particles to activate the O-O bond, which is considered to be the key reaction step.

Finnish scientists recently exposed monolayer-thick gold clusters to a variable number of oxygen molecules. It was found that even one gold cluster can effectively adsorb multiple oxygen molecules at the boundaries of the cluster, simultaneously weakening, stretching, the O-O bond by transferring electrons to the oxygen molecules. Taking into account the effects of temperature and ambient pressure, the calculations predicted that the oxygen molecules will completely dissociate and the oxygen and gold atoms will form one-dimensional alternating chains at the cluster boundary. The oxygen atoms in these chains are negatively charged and the gold atoms positively charged, creating a system that is reminiscent of a one-dimensional gold-oxide chain. These chains are expected to be the highly catalytically active part towards conversion of carbon monoxide to carbon dioxide at room temperature.

At room temperature and pressure, it appears that gold can catalyse an oxidation reaction by first oxidizing itself to gold oxide, which seems to contradict the known properties of gold in the macroscopic level.

References

1. Pentti Frondelius, Hannu Häkkinen and Karoliina Honkala. Formation of Gold(I) Edge Oxide at Flat Gold Nanoclusters on an Ultrathin MgO Film under Ambient Conditions. Angewandte Chemie International Edition, 2010; DOI: 10.1002/anie.201003851
2. X. Lin, N. Nilius, H.-J. Freund, M. Walter, P. Frondelius, K. Honkala, H. Häkkinen. Quantum Well States in Two-Dimensional Gold Clusters on MgO Thin Films. Physical Review Letters, 2009; 102 (20) DOI: 10.1103/PhysRevLett.102.206801

Further Reading
Naming Compounds
Writing Formula
Balancing Chemical Equations
Oxidation States
Transition Metals
Energy Profiles
Reaction Rate

Study Questions:

1. Write a balanced chemical equation for the formation of carbon dioxide from carbon monoxide and oxygen.
2. For the reaction above, what other possible steps in the reaction mechanism could be rate determining steps?
3. Why do you think that scientists believe that the activation of the O-O bond is the key reaction step in the reaction mechanism for this reaction?
4. What is meant by the term catalysis?
5. Why is gold described as a catalyst for the reaction described in the article?
   
6. What is meant by the term dissociate?
7. Describe how oxygen molecules can dissociate.
8. What is meant by the term oxidize?
9. Given the position of gold in the Periodic Table, what oxidation states are possible?
10. Give the formula for two possible oxides of gold.
11. Name each of the oxides above.
    

Graphane and Quantum Dots

Graphene is a honeycomb-like form of carbon that is just one atom thick. Graphane is produced when hydrogen atoms are added to both sides of the graphene matrix, making graphane an insulator.

Rice University scientists have discovered that the strategic extraction of hydrogen atoms from a two-dimensional sheet of graphane opens up hexagonal spaces of pure graphene that look and act like quantum dots. Quantum dots interact with light and magnetic fields in unique ways and can be used for chemical sensors, solar cells, medical imaging and nanoscale circuitry.

Reference:
Abhishek K. Singh, Evgeni S. Penev, Boris I. Yakobson. Vacancy Clusters in Graphane as Quantum Dots. ACS Nano, 2010; : 100513111745088 DOI: 10.1021/nn1006072