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.

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.

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.

So, if you are not an AUS-e-TUTE member it will cost you nothing to view our new nanoparticles and nanotechnology tutorial at
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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.

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.
    

Nanoparticles in Sunscreens

Titanium dioxide and zinc oxide are currently used for sunscreens because they absorb and scatter light. University of Tennessee, Knoxville, scientists have found that nanoparticles found in ivy may protect skin from UV radiation at least four times better.

A yellowish material is secreted by the ivy to aid it in clinging to surfaces. Nanoparticles within this material create the ability for the vine leaves to hold almost 2 million more times than its weight as well as provide the ability to absorb and disperse light due to their large surface-to-volume ratio. Sunscreens made with ivy nanoparticles would probably not need to be re-applied after swimming because the nanoparticles are more adhesive, and, while metal-based sunscreens give the skin a white tinge, the ivy nanoparticles are virtually invisible.

The study indicates that ivy nanoparticles are less toxic to mammalian cells than small-scale metal oxides, have a limited potential to penetrate through human skin, and are easily biodegradable.

Reference:
University of Tennessee at Knoxville (2010, July 19). Nanoparticles in English ivy may hold the key to making sunscreen safer and more effective. ScienceDaily. Retrieved July 22, 2010, from http://www.sciencedaily.com­ /releases/2010/07/100719162955.htm

Study Questions

1. Write the formula for titanium dioxide and for zinc oxide.
2. Give the oxidation state (number) for titanium and zinc in the compounds above.
3. What is a nanoparticle?
4. Explain the term surface-to-volume ratio.
5. Why do nanoparticles have a large surface-to-volume ratio?
6. How is the scattering of light affected by differences in surface-to-volume ratio?
7. Why are titanium dioxide and zinc oxide the preferred metal oxides for use in sunscreens?
   

Growing Egg Shells

For a long time scientists have believed that a chicken egg shell protein called ovocledidin-17 (OC-17) played a part in the formation of egg shells. This protein is only found in the mineral region of the egg which is the hard part of the shell, and, it appears to influence the transformation of amorphous calcium carbonate into calcite crystals by acting as a catalyst for crystal growth.

Scientists have now created simulations to show how the protein binds to the amorphous calcium carbonate surface using two clusters of arginine residues located on two loops of the OC-17 protein and creating a chemical clamp to nano sized particles of calcium carbonate. While clamped in this way, the OC-17 protein encourages the nanoparticles of calcium carbonate to transform into calcite crystallites that form the tiny nucleus of crystals that can continue to grow on their own. When the crystal nucleus is sufficiently large to grow on its own, the OC-17 protein desorbs, or, falls off. This frees up the OC-17 protein to promote yet more crystallization.

Reference:
Colin L. Freeman, John H. Harding, David Quigley, P. Mark Rodger. Structural Control of Crystal Nuclei by an Eggshell Protein. Angewandte Chemie International Edition, 2010; 49 (30): 5135 DOI: 10.1002/anie.201000679

Study Questions

1. What are the elements common to all proteins?
2. Proteins are actually polymers. What is the name given to the monomers that make up a protein?
3. What kind of bond binds these monomers together within the protein?
4. What is the formula for arginine?
5. Would the "loops" referred to in reference to the structure of OC-17 be part of its primary, secondary or tertiary structure? Explain your answer.
6. What does the term amorphous mean?
7. How does amorphous calcium carbonate differ from calcite crystals?
8. What is the definition of a catalyst?
9. Do you think OC-17 could be accurately described as a catalyst? Explain your answer.
   

Gold Nanoparticle Dispersion

Queensland University of Technology (QUT) scientists have developed a new technique for dispersing metals in nanoparticle form throughout polymers or plastic materials.

The properties of metals change when they are in nano form. When nanoparticles are added to plastics, a new range of composite materials are formed.

When gold nanoparticles are added to paint, essentially a plastic, the intensity of colours and durability are increased.

Mixing gold nanoparticles with titanium dioxide, TiO₂, using a plastic mould makes a very efficient catalyst for water purification as the titania absorbs light, converting it into electricity which is then passed into the conductive gold.

Queensland University of Technology (2010, May 6). Gold nanoparticles promise to enrich everyday products. ScienceDaily. Retrieved May 8, 2010, from http://www.sciencedaily.com­ /releases/2010/05/100505092004.htm