A Chemistry movie

Good Chemistry 

88 min

A movie

http://www.imdb.com/title/tt0496306/

Electrodes for Solar cells,

Sustainable Electrodes for Solar Cells
by John Emsley

To generate solar energy, a solar cell must have an electrode that is transparent. Currently there are two materials which meet this requirement: indium tin oxide (ITO), which is the preferred one, and fluorine tin oxide (FTO), which is less effective. However, indium is rare and has to be extracted from zinc and lead ores, of which it is a minor component; production is less than 500 tons a year.

ITO and FTO are not without their drawbacks. They lack transparency with respect to the infrared region of the spectrum, and this restricts their ability to gather a wider range of solar energy. They are unstable in the presence of acids and bases, and their metal ions are prone to diffusing into the polymer layers thereby reducing efficiency. Unless they are structurally perfect they suffer from current leakage.

The figures below are from an interview with coauthor Hideo Hosono, in regards to paper #1. Click figures for a larger view & description.

Graphene, on the other hand, appears to have none of these drawbacks—and it is cheap and sustainable. Graphene films are transparent, electrically conducting, and can be made ultra-thin. Paper #9 describes such an electrode, and one that is suitable for solid-state dye-sensitized solar cells which harvest light over a wider range of the spectrum. What is particularly important for these titanium dioxide based solar cells is that the graphene films are chemically more stable, especially to strong acids. The paper comes from the Max Planck Institute for Polymer research at Mainz, Germany.

Graphene sheets are produced from graphite starting with the acid oxidation of graphite flakes. The oxygen-containing groups which are formed make the product dispersible in water in which it can be exposed to ultrasonification to separate it into thinner sheets. These are then deposited on to a substrate such as quartz, and this is done by simply dipping in the hot solution. The thickness of the film can be varied by changing the temperature of the aqueous medium.

The graphite oxide so obtained is an insulator but can be reduced by heating to high temperatures in an atmosphere of argon and hydrogen gas. (The absence of oxygenated groups in the product was evidenced by IR spectroscopy.) The resulting graphene film was tens of layers thick. One such film, which was 10 nm in width, was observed to have transmittance of 71% at a wavelength of 500 nm which may be lower than that of ITO’s 90% and FTO’s 82%. However, compared to ITO and FTO, the graphene film is transparent to IR radiation. The films have a conductivity of 550 S cm^-1 which compares to that of graphite’s 1250 S cm^-1 and so they have the potential to act as electrodes.

Currently leading the research at the Max Planck Institute are Xinliang Feng and Klaus Müllen, and their recent papers suggest more exciting developments. In Nanotechnology (Y.Y. Liang, et al., 20[43]: no 434007, 2009) the group reports an improved way of making the films which involves using acetylene in the reduction of the graphite oxide, a method which not only repairs defects within the sheets but also increases the conductivity to 1425 S cm^-1 while still maintaining high optical transmittance.

In Advanced Materials (Q. Su, et al., 21[31]: 3191-5, 2009) they report the inclusion of large aromatic donor and acceptor molecules to functionalize the graphene. This approach stabilizes the graphene in aqueous dispersion and also enables it to be deposited in monolayer and double-layer on substrates in large quantities. When the graphene is then heated at around 1000^° C, the aromatic molecules repair holes in the film, thereby contributing to an improved conductivity of 1314 S cm^-1which now exceeds that of ordinary graphene.

As Xinliang Feng tells Science Watch: "Our work is possibly the most attractive application of graphene in future electronics. We are currently improving the quality of graphene film in terms of transmittance and conductivity, because these are the crucial parameters for the window electrode replacement of traditional ITO. I think that we are leading in this area of large scale and cheap synthesis of transparent graphene electrodes. If graphene electrodes can be fabricated by easy and cheap methods in large quantities, then a big market for them can be expected."

Qucik Guide to Organic Chemistry, fundamentals and reactions

Topics covered include: 
- organic compounds, formulas isomers 
- nomenclature intermolecular forces 
- chemical bonding in organic compounds 
- spectroscopy instrumental methods 
- thermodynamics 
- quantum mechanical model: Mo theory 
- and much more 

ORGANIC CHEMISTRY REACTIONS:

This guide is packed with useful and up-to-date information. 

Topics covered include: 
- features of an organic reaction 
- kinetics reaction mechanism 
- organic acid base 
- benzene/arene, alkyne alcohol 
- aromatic alcohol haloalkane 
- halohydrin ether 
- aldehyde ketone 
- carboxylic acid ester 
- amine amide acid 
- organic polymer 
- and much more


Download from here
http://depositfiles.com/files/mriz7y6xs
http://depositfiles.com/files/w8mn036fr

Colorful periodic table

What is Chemistry,,, DNA

Reactions........

Grignards Reactions, Additions to carbonyl bond........

additions along carbon and oxygen double bonds

Sweeeeetest Compound,,, Lugduname

This compound is 220,000 times sweetener than table suger called sucrose. while sacchrine is 300 times sweetener than Table suger

Worst smell compound,, ethyl mercaptan

Most bitter compound.. Bitrex or Denatonium Benzoate

The Nobel Prize in Chemistry 2010 Richard F. Heck, Ei-ichi Negishi, Akira Suzu

The Nobel Prize in Chemistry 2010 was awarded jointly to Richard F. Heck, Ei-ichi Negishi and Akira Suzuki 
"for palladium-catalyzed cross couplings in organic synthesis"




visit at 
http://nobelprize.org/nobel_prizes/chemistry/laureates/2010/#


Speech

This year’s Nobel Laureates in Chemistry are rewarded for a method to link carbon atoms together, and this method has provided chemists with an efficient tool to create new organic molecules. The Laureates have utilised the metal palladium to couple two carbons to one another under mild conditions and with high precision.

Organic molecules contain the element carbon, where carbon atoms are bound to each other to form long chains and rings. Carbon-carbon bonds are a prerequisite for all life on earth and they are found in proteins, carbohydrates and fats. Plants and animals mainly consist of organic molecules in which carbon atoms bind to each other, and we human beings, we who have gathered here today, are to a large extent built up by carbon-carbon bonds. In living organisms bonds between carbon atoms are created via Nature’s own pathways utilising various enzyme systems.

To create new organic molecules in an artificial manner that can be used as medicines, plastics, and various other materials, we need new efficient methods for synthesising carbon-carbon bonds in our laboratories.

Looking back in history we find that the German chemist Kolbe synthesised the first carbon-carbon bond in 1845. Since then a number of methods for the synthesis of bonds between carbon atoms have been developed of which several have been awarded with a Nobel Prize. This year’s Nobel Prize in Chemistry is the fifth that rewards the synthesis of carbon-carbon bonds.

Richard Heck’s pioneering work from 1968 – 1972 laid the foundation for palladium-catalysed formation of carbon-carbon bonds. He coupled two rather unreactive molecules to one another with the aid of palladium. One of these is a molecule with a handle, e.g. bromobenzene and the other has a double bond and is called an olefin. In 1977, Ei-ichi Negishi reported a mild method to couple one of Heck’s unreactive molecules to a carbon bound to zinc with the aid of palladium. Two years later, in 1979, Akira Suzuki found that the corresponding palladium-catalysed coupling of an unreactive molecule such as bromobenzene to a carbon bound to boron could be made under very mild conditions.

Carbon is stable and carbon atoms do not easily react with one another. Earlier methods used by chemists to bind carbon atoms together were therefore based upon various techniques for rendering carbon more reactive. Such methods worked when creating simple molecules, but when synthesising more complex molecules chemists ended up with too many unwanted by-products in their test tubes. The palladium-catalysed cross coupling solved that problem and provided chemists with a more precise and efficient tool to work with. In the Heck reaction, Negishi reaction, and Suzuki reaction, the carbon atoms meet on a palladium atom. When the carbon atoms meet on a palladium atom, chemists do not need to activate the carbon atom to the same extent. This entails fewer by-products and a more efficient reaction.

The palladium-catalysed cross couplings have been used for large-scale industrial manufacturing of, for example, pharmaceuticals, agricultural chemicals, and organic compounds that are used by the electronic industry.

Professors Heck, Negishi and Suzuki:
You are being awarded the Nobel Prize in Chemistry for palladium-catalysed cross couplings in organic synthesis and with these achievements you have provided organic chemists with efficient and useful methods for synthesizing compounds that were previously difficult to obtain. On behalf of the Royal Swedish Academy of Sciences, I wish to convey to you our warmest congratulations and I now ask you to step forward to receive your Nobel Prizes from the hands of His Majesty the King.

Introducing chemistry

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