Cleaning the world with sunscreen and pencils!

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About me

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Hello! I live in Lancaster, England.

I attend Chetham's School of Music in Manchester, where I study Biology, Chemistry, Maths, and Music.

I’ve been playing the Oboe and Piano for nearly a decade. Being involved in music allows one to appreciate people's dedication to their work, and serves as an inspiration to excel in what you love doing most. After being diagnosed with a damaging combination of RSI in my arm and a pharyngocele in my neck (inhibiting my playing ability), I decided to shift my focus onto dealing with the world's problems - 'If you don't solve them, who will?'

I feel I've been inspired by a great many scientists, though my favourites would have to be Oliver Sacks, Leonardo Da Vinci, and Einstein - working through adverse circumstances to achieve greatness.

Photocatalysts are extremely fascinating to me as they simply and effectively utilise the sun's energy to perform chemical reactions - I love how lots of simple things add up to make a big difference. I've found music is an excellent means of experimenting with these 'little things'; discovering new ways of approaching the fine details of phrasing and technique to create a unique performance.

Winning would give me the means to put my pollution-neutralising paint into action globally, whilst allowing me to fulfill my dream of going to MIT as an undergraduate; then hopefully to form a synergistic research company pooling minds from all backgrounds to make the world a better place.

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Question / Proposal

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How can we solve the problem of global pollution?

 

We all live with pollution every day of our lives. In the past, people tackled it with the assumption that earth's vast ecosystem will simply absorb the unbalance and 'everything'll be fine'... but with increasing globalisation and population levels, everyone is beginning to feel the strain.

View from my bedroom window - Manchester smog!


Attempts to remedy the issue, namely with Titanium Dioxide-coated building materials, have proven ineffective due to high cost and unscalability. I set out to find a way of improving Titanium Dioxide's properties, along with creating a cheap, easy-to-use paint-like coating that could be used by anyone, anywhere. This coating could break down pollutants anywhere where light was present.

Whilst doing some separate research on Graphene (because Graphene is awesome), I theorised that Graphene's superior electron transport mechanisms might help prohibit electron-hole recombination in TiO2. I looked extensively in the literature, and there seemed to be some interest in doping TiO2 with Graphene, as indeed it was good at prohibiting electron-hole recombination. I realised that this would allow the coating to be used indoors - increasing its applications. But to use Graphene in the water-based coating, I would have to use the soluble Graphene Oxide precursor, which can be photocatalytically reduced to Graphene. I wanted to find out (as no other research papers had) if Graphene Oxide could be reduced to Graphene after being applied to the intended substrate, just under ambient light.

See slides for more details.

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Research

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Previously, photocatalytic coatings have been based on Titanium Dioxide (or, as in Shrishti Asthana's project last year, ZnO). Numerous commercial coatings exist (self-cleaning glass etc), but they aren't very effective without complete saturation of the surface with TiO2 - my school building has 'self cleaning' glass... most people in the school thought the wrong coating had been put on - it has almost no effect whatsoever! 

 

Understandably, research is ongoing to find suitable doping agents to help TiO2 do its job. Silver is one of them - but Graphene has received the most interest. As mentioned earlier (see diagram in powerpoint) - Graphene's unique electron transport properties allow it to absorb TiO2's excited electrons and prohibit electron-hole recombination, a major problem in conventional TiO2. Despite extensive research, I couldn't find any papers using graphene-doped TiO2 in a paint-like form - assumingly because applying water-dispersed graphene straight onto the intended surface in the concentrations required for the coating would result in instant agglutination - rendering the paint useless. I decided to combine another paper's hint at photocatalytic graphene oxide reduction with that of Graphene-doped TiO2 - this would solve this problem of the graphene sheets sticking together before they've even been painted! See powerpoint for more details.


During the undertaking of my project, I visited Prof. Robert Dryfe at Manchester University just down the road. Whilst asking about my project, he mentioned another person in the department working on Graphene-enhanced Polymers. His research showed that Graphene enhances a polymer's strength massively. Shortly after reading a page on 'Electron Beam Processing' (knocking bits off polymer chains to stick them together - increases their abrasion resistance), I realised that I could use a similar technique (photocatalytic degradation) to achieve cross-linking. Utilising these concepts was critical for my coating to satisfy my aim of a coating that could be used anywhere.

Cross-linking diagram
https://drive.google.com/file/d/0B4utH-L16SafN1dxenBuSndlM0ZUMDNTdU90d3dJUG90TEtJ/edit?usp=sharing

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Method / Testing and Redesign

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All experiments shown in this project were performed in the school lab at Chetham's School of Music, 2\3 lunchtimes a week, over a period of 4 months.

Preparing Graphene Oxide solution

I started my project by obtaining some Graphene Oxide and TiO​​2 microparticles. I began by making up 250ml of 1mg\ml concentration of Graphene oxide, dispersed in distilled water over a period of 48 hours@320K on a lab stirrer. This became the 'GO Solution'. I had to be extra careful to make sure no impurities were present, as the GO nanoflakes easily clump around tiny impurities present, rendering them useless.


Preparing the composite

To prepare the composite solution, a 1mg/ml TiO2 microparticle dispersion was added to the 1mg/ml GO solution, making a 1mg/ml solution of composite - this was then stirred at high velocity on a magnetic stirrer for 10 minutes. This created the 'TiO2-GO composite solution'. See presentation for more details.

To prepare the photocatalytic sponges, I added the same cm3 solution as the volume of sponge into a plastic container, then compressed/released the sponge to encourage it to absorb the photocatalytic composite solution - which it did. To reduce the sponge, I later discovered that leaving it on the lab bench turns it black on its own, using the lab's ambient light.

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To perform the Ethanol Oxidation test, I simply performed the same process, but with ethanol and a post-dried/reduced sponge, simply squeezing out the oxidised ethanol into a test tube with Tollen's test already present. See presentation (slide12) for more details.


Producing the polymer composite

(see slide 14)

I started by adding Polyurethane to the composite mix. This turned out quite badly, presumably disrupting the hydrogen bonding (previously proven to help solvate TiO2), and causing a solid precipitate to form - I later found a use for this, but I still wanted to try different ways of making the polymer composite. I finally found that adding Graphene Oxide slowly to a fast-stirring Polyurethane-PVA-TiO2 composite solution actually caused a precipitate of any excess polymer, but leaving behind a stable composite solution - why this happens will be discussed in the 'Results' section.

To test the photocatalytic action of the polymer composite, I decided to observe the destruction of fish blood cells under a microscope (we were performing a fish dissection on the same day; it provided a quantitative method of observing the photocatalytic destruction). I added a homogenised fish tissue solution to the surface of a dried coating on a microscope slide, and took images of the same magnification before and after exposure to ambient and weak 6w UV lamp- the images shown in the results section/slide16 had been taken 15 minutes after each other.

To test the abrasion resistance of the coatings, I simply rubbed them repeatedly then observed changes under a microscope. Other tests used included the water test, running the slide under a tap then drying with a paper towel. 


Equipment used

  • Lab stirrer
  • Numerous conical flasks
  • Measuring cylinder
  • Metal spatula
  • Gloves
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Results

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See slides 9-18 for composite testing and results.

Polymer composite observations

Test 1

Added 5ml of Polyurethane to GO/TiO2 composite whilst stirring @320K. 
Test failed - polymer disrubted the GO/TiO2 interactions, causing the solution to form large clumps. I later found a use for these - see slide 15.

Test 2

Added 20ml GO solution to Polyurethane/TiO2 mix - test failed.

 

Test 3

I wondered if using a 'thinner' polymer i.e. one with less hydrogen bonding would help stabilize the solution. I added 20ml of GO to a fast-stirring mix of TiO2 and an excess of PVA (Elmer's glue). After 5 minutes stirring, I then added Polyurethane. This caused clumps to form in the solution! I turned the stirrer off, and it turned out they were actually excess polymer. The benefits of adding Polyurethane can be seen clearly with the strength test - 


These images shows micro-tears in the surface of a sample of the composite before adding Polyurethane.

See powerpoint slide 14 for successful TiO2-Polyurethane-PVA-GO composite coating. No tears can be made on that coating without rubbing with a coin.


Other coatings without 6W UV exposure have less strength in the water test - when drying with a paper towel, they peel off the surface easily. Those with treatment are much more hardy, though they are still slightly weaker when very damp. 
What must be noted is the shade of white they take - Polyurethane is known to be waterproof, so it must be assumed that the white shade is due to the PVA. Scope for investigation would be getting the ratios of PVA right to reduce this effect as much as possible.

These results support the hypothesis that reducing GO by exposure to light does turn it back into insoluble Graphene. They also suggest that cross-linking is formed - the coating's abrasion resistance increases when 'curing' with UV light. 

It must be noted that the strength of the UV used (6 watts) is far below that received in direct sunlight - a UV lamp was used to ensure a constant source of light (Manchester is famous for its rain). In a real-world situation, ambient light would be enough to reduce the GO and 'cure' the Polyurethane.

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Conclusion / Report

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Project overview

The results show that TiO2 does indeed reduce Graphene Oxide to Graphene under ambient light, whilst inducing cross-linking in the polymer composite (when Polyurethane is added). This supports my hypothesis. 

My findings suggested that the coating is much stronger, more efficient, and cheaper than the TiO2 catalysts currently in use today. 

 

List of applications for each coating type

  • Sponge
    ​
    ​ - Oxidation of compounds in batch reactor (water purification, glucose>ethanol oxidation, etc)
     - Water purification (full oxidation) in batch reactor, floating in sea/river etc
     - Air purification; huge surface area of sponge allows for long contact time with polluted air, ensuring more compounds are removed

  • Sand
     - Some use possible in water filtration, (better removal of heavy metals) - but quite expensive to produce.

  • Surface paint
     - Removal of all microorganisms from surfaces via radical-induced destruction - scope for investigation on dust mite egg removal from carpets
     - Degradation of polluting compounds e.g. dirt etc on its surface
     - Degradation/elimination of polluting gases (i.e. on outside of buildings)
     - Tunable hydrophobic/hydrophilic properties

  • Powder
     - Offers an easier distribution method for worldwide water sanitizing - simply pour the powder into the required container, leave out in the sun, and voilà - clean water.
     - Much higher S.A.:volume ratio than other forms of the photocatalyst

 

There are, however, small deficiencies in the experimental process - as I was limited to the equipment available commercially/in the school laboratory, the accuracy of the results could have been improved by using modern equipment/procedures etc.

Despite this, the project shows scope for easy implementation in rural and industrial areas, due to its ease of use, relatively cheap manufacture and efficiency. 

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Bibliography, References and Acknowledgements

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References 

Photocatalytic reduction of Graphene oxide - http://pubs.acs.org/doi/abs/10.1021/nn800251f

Graphene adding strength to the polymer, and problems with RGO (reduced graphene oxide) coagulation - https://www.physics.purdue.edu/quantum/files/CarbonNano/nature04969.pdf

TiObehaviour - http://image.sciencenet.cn/olddata/kexue.com.cn/blog/admin//images/upfiles/200710117325893655.pdf

Reduction of Polyurethane's photocatalytic degradation by protective Graphene - http://www.hindawi.com/journals/isrn.polymer.science/2013/514617/

Polyurethane cross-linking - 
http://www.bayercoatings.de/BMS/DB-RSC/BMS_RSC_CAS.nsf/id/COEN_What_is_UV__EB_radiation_curing

Thanks to - 

Paul Pryzybyla - Head of Science, Chetham's School of Music, for being incredibly patient and supportive in supervising the undertaking of my project.

Ambrose Henderson - Biology teacher, Chetham's School of Music, for his microscopy assistance.

Julian Blundell, Physics teacher, Chethams's School of Music, for moral support!

Prof. Robert Dryfe - Professor of Chemistry, Manchester University, for various chats about the project.

And finally, David Kong - Lab Technician, Chetham's School of Music, for supplying the chemicals and technical know-how to use the equipment in this project. 

 

All experiments in this project were carried out in the Chemistry Lab, Chetham's School of Music. 

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