New Understanding Could Result in More Efficient Organic Solar Cells

The goal of making cheap organic solar cells may have gotten a little more approachable with a new understanding of the basic science of charge separation presented in a paper published online today, February 3, in Nature Communications. 

Co-authored by Penn State electrical engineer Noel Giebink with lead author Bethany Bernardo, an undergraduate in his group, and colleagues at IMEC in Belgium, Argonne National Lab, Northwestern, and Princeton, the paper suggests design rules for making more efficient solar cells in the future.

Organic solar cells currently have a top efficiency of approximately 10 percent in the laboratory, much less than inorganic single crystal silicon. 

Read more here...

An electron wave function, indicated by orange shading, spreads across several nanocrystalline fullerene molecules in this representation of an organic solar cell heterojunction. Image Credit: Giebink, Penn State

 

Molecular Collisions Now Imaged Better Than Ever

Molecular physicists from Radboud University Nijmegen have produced images of the changes in direction of colliding nitrogen monoxide molecules (NO) with unprecedented sharpness. 

By combining a Stark decelerator with advanced imaging techniques, they were able to obtain very high resolution images of the collision processes. 

The results were published in Nature Chemistry on 9 February. 

Read more here...

Visualisation of the collisions between NO and helium (left) and NO and neon (right). The top images show the research results of Van de Meerakker and his colleagues; the bottom images show the visualised theoretical predictions of the collisions. Red indicates a high probability of change of direction; blue indicates a low probability. The small peaks show the diffraction oscillations (Credits: Image Courtesy of Nature Chemistry).

New study shows click chemistry could provide total chemical DNA synthesis

An interdisciplinary study led by Dr Ali Tavassoli, a Reader in chemical biology at the University of Southampton, has shown for the first time that 'click chemistry' can be used to assemble DNA that is functional in human cells, which paves the way for a purely chemical method for gene synthesis.

Writing in Angewandte Chemie International Edition Dr Tavassoli's team and his collaborators, Dr Jeremy Blaydes and Professor Tom Brown, show that human cells can still read through strands of DNA correctly despite being stitched together using a linker not found in nature.

Read more here...

Credit: University of Southampton

Phosphorene discovery positively impacts 2D electronics

US researchers have made phosphorus into an analogue of graphene, dubbed phosphorene, allowing practical electronic devices made from such two-dimensional materials. Peide Ye at Purdue University, US, and his co-workers show that phosphorene is the first native 2D electron-poor – or p-type – semiconductor. That’s important for making these flat materials into standard complementary metal-oxide semiconductor (CMOS) logic circuit elements, which Ye’s team has also achieved with phosphorene. ‘For device applications it’s fundamentally better than graphene,’ Ye says. Read more here...

The ridged structure of phosphorene explains the directional electrical performance dependence that Ye's team saw © Peide Ye

Process Holds Promise for Production of Synthetic Gasoline from Carbon Dioxide

A chemical system developed by researchers at the University of Illinois at Chicago can efficiently perform the first step in the process of creating syngas, gasoline and other energy-rich products out of carbon dioxide.

A novel “co-catalyst” system using inexpensive, easy to fabricate carbon-based nanofiber materials efficiently converts carbon dioxide to carbon monoxide, a useful starting-material for synthesizing fuels. The findings have been published online in advance of print in the journal Nature Communications.

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UIC researchers Amin Salehi-Khojin (seated), Bijandra Kumar and Mohammad Asadi. Photo: Roberta Dupuis-Devlin/UIC Photo Services

Reimer-Tiemann Reaction

The Reimer-Tiemann reaction is an organic reaction used to convert a phenol to an o-hydroxy benzalde-hyde using chloroform, a base, and acid work-up. 

The mechanism begins with abstraction of the proton from chloroform with the base to form a trichlorocarbanion which spontaneously loses a chloride ion to form a neutral dichlorocarbene.  

The base also deprotonates the phenol reagent which then attacks the carbene. 

A series of steps and a final acid work-up result in the o-hydroxy benzaldehyde product. For more click here.

Image Credit: chemistry.tutorvista.com

Credit: http://www.name-reaction.com/reimer-tiemann-reaction

Reaction Mechanism Animation

Credit: http://cd1.edb.hkedcity.net

Introduction to Rearrangement Reactions

Rearrangement reactions are really interesting. They can accompany many of the reactions we’ve previously covered such as substitution, addition, and elimination reactions. In fact, if you don’t look closely, sometimes you can miss the fact that a rearrangement reaction has occurred. Let’s look at a substitution reaction first. For more details click here.

Credit: http://www.masterorganicchemistry.com

Dye Chemistry

Look around you, at your clothes, the walls, the floor. Chances are that you see before you a riot of colour. Humans have been fascinated by colour for thousands of years and use colours to warn, to seduce and primarily to decorate. So, what about the chemistry behind the decoration? What makes one molecule coloured, and another not? Why do some clothes fade in the wash?

The chemical basis of colours is the reason many people choose to do chemistry. The basis of this project is the chemistry behind fabric dyes- what are they? What are the origins of dyes? How are they made? What affects the way they attach to different fibres?

The search for highly coloured, colour fast dyes has fuelled major industry from ancient times right up to the present, from the Roman dye factories at Tyre, to modern chemical companies such as ICI. Nowadays, the chemist with a knowledge of organic chemistry is at the forefront of new dye development, altering the structures of known dyes, and inventing new ones.

For more click here.

Credit: http://www.chm.bris.ac.uk/webprojects2002

Carbocations

Carbocations are species bearing a formal "+" charge on carbon. The have sp² hybridization and trigonal planar geometry, with an empty p orbital on carbon, perpendicular to the plane containing the substituents (see diagrams shown to the right). Carbocations are "hypovalent" species, inasmuch as they have only three shared pairs of electrons around carbon, instead of the usual four. Of course, this incomplete octet around carbon makes carbocations very unstable and very reactive. Nevertheless, carbocations are known to be formed as intermediates in many types of organic reactions. For more details click here.

Courtesy: Dr. Thomas H. Eberlein, Penn State University

Racemic mixture

In chemistry, a racemic mixture, or racemate (pronounced /reɪˈsimeɪt/), is one that has equal amounts of left- and right-handed enantiomers of a chiral molecule. The first known racemic mixture was "racemic acid", which Louis Pasteur found to be a mixture of the two enantiomeric isomers of tartaric acid. For more details click here.

 

Courtesy: http://www.princeton.edu

Reactions of Alkanes

The alkanes and cycloalkanes, with the exception of cyclopropane, are probably the least chemically reactive class of organic compounds. Despite their relative inertness, alkanes undergo several important reactions that are discussed in the following section. For more click here.

Courtesy: Dr. William Reusch, http://www2.chemistry.msu.edu

Modern Strategies in Organic Catalysis

Enantioselective organocatalysis has become a field of central importance for the asymmetric synthesis of chiral molecules. In the last ten years alone, this field has grown at an extraordinary pace from a small collection of chemically unique reactions to a thriving area of general concepts, atypical reactivities, and widely applicable reactions. Moreover, novel modes of substrate activation have been achieved using organic catalysts that can now deliver unique, orthogonal, or complementary selectivities in comparison to many established metal-catalyzed transformations. For more details click here.

Image courtesy of Prof. D. Savoia

Courtesy: Dr. Gérald Lelais, Professor D. W. C. MacMillan, http://www.princeton.edu

Molecular Orbital Concepts

The overlap of the two atomic orbitals (AO’s) results in the formation of two molecular orbitals (MO’s), one of which is lower in energy than the original AO’s (the bonding MO or BMO) and the other higher in energy than the original AO’s (the antibonding MO or ABMO). For more Click Here.

http://www.chem.ufl.edu

Courtesy:  http://research.cm.utexas.edu

Enols, Enolates and Tautomerism

enols are compounds that have alcohol groups, -OH, substituted directly onto alkenes, C=C, hence "alkene-ols" or enols.

Enolates are the conjugate bases or anions of enols (like alkoxides are the anions of alcohols) and can be prepared using a base.

Click here for more

 Courtesy: Dr. Ian Hunt, Department of Chemistry, University of Calgary

Markovnikov's Rule

This is an empirical rule based on Markovnikov's experimental observations on the addition of hydrogen halides to alkenes.

The rule states that : "when an unsymmetrical alkene reacts with a hydrogen halide to give an alkyl halide, the hydrogen adds to the carbon of the alkene that has the greater number of hydrogen substituents, and the halogen to the carbon of the alkene with the fewer number of hydrogen substituents"

Courtesy: Dr. Ian Hunt, Department of Chemistry, University of Calgary

Aromatic Substitution Reactions

The chemical reactivity of benzene contrasts with that of the alkenes in that substitution reactions occur in preference to addition reactions. Find out more details here.

Courtesy: http://www2.chemistry.msu.edu

Organoboron Chemistry

Boron in Organic Synthesis

Courtesy: WINPLT, http://www.chem.wisc.edu

Great art in a test tube

2010 Nobel Prize in Chemistry: Creating Complex Carbon-Based Molecules Using Palladium

New ways of linking carbon atoms together has allowed scientists to make medicines and better electronics. (Credit: iStockphoto/Liang Zhang)

 Courtesy: http://www.nobelprize.org

Ester Chemistry

Esters are derived from carboxylic acids. A carboxylic acid contains the -COOH group, and in an ester the hydrogen in this group is replaced by a hydrocarbon group of some kind. This could be an alkyl group like methyl or ethyl, or one containing a benzene ring like phenyl. Click here for more details.

Courtesy: Jim Clark, http://www.chemguide.co.uk