Two stories today in ScienceDaily point to different nanotech applications that could enable a solar solution to our energy problems—one including the use of self-repairing nanosystems. “Converting Sunlight To Cheaper Energy” describes the use of photoactive nanoscale systems to develop molecular electronics. Organic molecules and fullerenes will be used to make inexpensive photovoltaics and light emitting diodes:

Organic photovoltaics and organic LEDs are made up of thin films of semiconducting organic compounds that can absorb photons of solar energy. Typically an organic polymer, or a long, flexible chain of carbon-based material, is used as a substrate on which semiconducting materials are applied as a solution using a technique similar to inkjet printing.

…[South Dakota State University] scientists plan to use the variable band gap polymers to build multi-junction polymer solar cells or photovoltaics.

These devices use multiple layers of polymer/fullerene films that are tuned to absorb different spectral regions of solar energy.

Ideally, photons that are not absorbed by the first film layer pass through to be absorbed by the following layers.

The devices can harvest photons from ultraviolet to visible to infrared in order to efficiently convert the full spectrum of solar energy to electricity.

SDSU scientists also work with organic light-emitting diodes focusing on developing novel materials and devices for full color displays.

…The new technology will make it easy to insert lights into walls or ceilings. But instead of light bulbs, the lighting apparatus of the future may look more like a poster…

The second story describes how scientists are not only trying to exploit biology’s 3.7 billion year-old system for harvesting the sun’s energy, but planning to mimic it with artificial self-assembling and self-repairing nanodevices. From “Bacteria Power: Future For Clean Energy Lies In ‘Big Bang’ Of Evolution“:

Dramatic progress has been made over the last decade understanding the fundamental reaction of photosynthesis that evolved in cyanobacteria 3.7 billion years ago, which for the first time used water molecules as a source of electrons to transport energy derived from sunlight, while converting carbon dioxide into oxygen.

The light harvesting systems gave the bacteria their blue (”cyano”) colour, and paved the way for plants to evolve by “kidnapping” bacteria to provide their photosynthetic engines, and for animals by liberating oxygen for them to breathe, by splitting water molecules. For humans now there is the tantalising possibility of tweaking the photosynthetic reactions of cyanobacteria to produce fuels we want such as hydrogen, alcohols or even hydrocarbons, rather than carbohydrates.

Progress at the research level has been rapid, boosting prospects of harnessing photosynthesis not just for energy but also for manufacturing valuable compounds for the chemical and biotechnology industries. Such research is running on two tracks, one aimed at genetically engineering real plants and cyanobacteria to yield the products we want, and the other to mimic their processes in artificial photosynthetic systems built with human-made components. Both approaches hold great promise and will be pursued in parallel, as was discussed at a recent workshop focusing on the photosynthetic reaction centres of cyanobacteria, organised by the European Science Foundation (ESF).

…Among promising contenders discussed at the ESF conference was the idea of an artificial leaf that would simulate not just photosynthesis itself but also the ability of plants to regenerate themselves. This could be important, since the reactions of photosynthesis are destructive, dismantling the protein complexes where they take place, which therefore need regular reconstruction. Under a microscope, chloroplasts, the sub-cellular units where photosynthesis take place, resemble a permanent construction site, and even artificial systems would probably need some form of regenerative capability.

A future aim therefore is to build an artificial leaf-like system comprised of self-assembling nanodevices that are capable of regenerating themselves — just as in real plants or cyanobacteria. “Fundamental breakthroughs in these directions are expected on a time scale of 10 to 20 years and are recognized by the international science community as major milestones on the road to a renewable fuel,” said [Eva Mari Aro, the vice-chair of the ESF conference].

I found it particularly interesting that the researchers are thinking beyond simple nanodevices to harvest solar energy and considering self-repairing “leaf” systems in a 10-20 year time frame.
—Jim

Advanced nanotech would benefit from the ability to engineer atomically precise structures on nanoparticles. In a step in that direction, UK scientists have developed a combined computational and experimental method to determine how specific peptides self-assemble on the surface of a gold nanoparticle—in particular how closely spaced on the surface of the nanoparticle the peptides have to be to form chemical bonds. Via ScienceDaily, a news release from UK Biotechnology and Biological Sciences Research Council (includes images and molecular dynamics animations) “Scientists overcome nanotech hurdle“:

When you make a new material on a nanoscale how can you see what you have made? A team lead by a Biotechnology and Biological Sciences research Council (BBSRC) fellow has made a significant step toward overcoming this major challenge faced by nanotechnology scientists. With new research published today (13 August) in ChemBioChem [abstract], the team from the University of Liverpool, The School of Pharmacy (University of London) and the University of Leeds, show that they have developed a technique to examine tiny protein molecules called peptides on the surface of a gold nanoparticle. This is the first time scientists have been able to build a detailed picture of self-assembled peptides on a nanoparticle and it offers the promise of new ways to design and manufacture novel materials on the tiniest scale — one of the key aims of nanoscience.

Engineering new materials through assembly of complex, but tiny, components is difficult for scientists. However, nature has become adept at engineering nanoscale building blocks, e.g. proteins and RNA. These are able to form dynamic and efficient nanomachines such as the cell’s protein assembly machine (the ribosome) and minute motors used for swimming by bacteria. The BBSRC-funded team, led by Dr Raphaël Lévy, has borrowed from nature, developing a way of constructing complex nanoscale building blocks through initiating self-assembly of peptides on the surface of a metal nanoparticle. Whilst this approach can provide a massive number and diversity of new materials relatively easily, the challenge is to be able to examine the structure of the material.

Using a chemistry-based approach and computer modelling, Dr Lévy has been able to measure the distance between the peptides where they sit assembled on the gold nanoparticle. The technique exploits the ability to distinguish between two types of connection or ‘cross-link’ — one that joins different parts of the same molecule (intramolecular), and another that joins together two separate molecules (intermolecular). As two peptides get closer together there is a transition between the two different types of connection. Computer simulations allow the scientists to measure the distance at which this transition occurs, and therefore to apply it as a sort of molecular ruler. Information obtained through this combination of chemistry and computer molecular dynamics shows that the interactions between peptides leads to a nanoparticle that is relatively organized, but not uniform. This is the first time it has been possible to measure distances between peptides on a nanoparticle and the first time computer simulations have been used to model a single layer of self-assembled peptides.

Dr Lévy said: “As nanotechnology scientists we face a challenge similar to the one faced by structural biologists half a century ago: determining the structure with atomic scale precision of a whole range of nanoscale materials. By using a combination of chemistry and computer simulation we have been able to demonstrate a method by which we can start to see what is going on at the nanoscale.

“If we can understand how peptides self-assemble at the surface of a nanoparticle, we can open up a route towards the design and synthesis of nanoparticles that have complex surfaces. These particles could find applications in the biomedical sciences, for example to deliver drugs to a particular target in the body, or to design sensitive diagnostic tests. In the longer term, these particles could also find applications in new generations of electronic components.”

Professor Nigel Brown, BBSRC Director of Science and Technology, said: “Bionanotechnology holds great promise for the future. We may be able to create stronger, lighter and more durable materials, or new medical applications. Basic science and techniques for working at the nanoscale are providing the understanding that will permit future such applications of bionanotechnology.”

—Jim