Researchers create 'nanoflowers' for energy storage, solar cells

October 11, 2012 by Matt Shipman
The GeS "nanoflowers" have petals only 20-30 nanometers thick, and provide a large surface area in a small amount of space. The structures hold promise for next-generation energy storage devices and solar cells. Credit: Linyou Cao, North Carolina State University

(Phys.org)—Researchers from North Carolina State University have created flower-like structures out of germanium sulfide (GeS) – a semiconductor material – that have extremely thin petals with an enormous surface area. The GeS flower holds promise for next-generation energy storage devices and solar cells.

"Creating these GeS nanoflowers is exciting because it gives us a huge surface area in a small amount of space," says Dr. Linyou Cao, an assistant professor of at NC State and co-author of a paper on the research. "This could significantly increase the capacity of batteries, for instance, since the thinner structure with larger surface area can hold more lithium ions. By the same token, this GeS flower structure could lead to increased capacity for , which are also used for energy storage."

To create the flower structures, researchers first heat GeS powder in a furnace until it begins to vaporize. The vapor is then blown into a cooler region of the furnace, where the GeS settles out of the air into a layered sheet that is only 20 to 30 nanometers thick, and up to 100 micrometers long. As additional layers are added, the sheets branch out from one another, creating a floral pattern similar to a marigold or carnation.

"To get this structure, it is very important to control the flow of the GeS vapor," Cao says, "so that it has time to spread out in layers, rather than aggregating into clumps."

GeS is similar to materials such as graphite, which settle into neat layers or sheets. However, GeS is very different from graphite in that its atomic structure makes it very good at absorbing solar energy and converting it into useable power. This makes it attractive for use in , particularly since GeS is relatively inexpensive and non-toxic. Many of the materials currently used in solar cells are both expensive and extremely toxic.

Explore further: A potential treatment for gastric motility disorders

More information: The paper, "Role of Boundary Layer Diffusion in Vapor Deposition Growth of Chalcogenide Nanosheets: The Case of GeS," is published online in the journal ACS Nano. pubs.acs.org/stoken/nanotation/pipe/abs/10.1021/nn303745e

Abstract
We report a synthesis of single crystalline two-dimensional (2D) GeS nanosheets using vapor deposition processes, and show that the growth behavior of the nanosheet is substantially different from those of other nanomaterials and thin films grown by vapor depositions. The nanosheet growth is subject to strong influences of the diffusion of source materials through the boundary layer of gas flows. This boundary layer diffusion is found to be the rate-determining step of the growth under typical experimental conditions, evidenced by a substantial dependence of the nanosheet's size on diffusion fluxes. We also find that high quality GeS nanosheets can only grow in the diffusion-limited regime, as the crystalline quality substantially deteriorates when the rate-determining step is changed away from the boundary layer diffusion. We establish a simple model to analyze the diffusion dynamics in experiments. Our analysis uncovers an intuitive correlation of diffusion flux with the partial pressure of source materials, the flow rate of carrier gas, and the total pressure in synthetic setup. The observed significant role of boundary layer diffusions in the growth is unique for nanosheets. It may be correlated to the high growth rate of GeS nanosheets, ~3-5 [micrometer]/min, which is one order of magnitude higher than other nanomaterials (such as nanowires) and thin films. This fundamental understanding on the effect of boundary layer diffusions may generally apply to other chalcogenide nanosheets that can grow rapidly. It can provide useful guidance for the development of general paradigms to control the synthesis of nanosheets.

Related Stories

A potential treatment for gastric motility disorders

June 10, 2009

GES or pacing has been under investigation as a potential therapy for gastrointestinal motility disorders. Conventionally, GES is performed using a single pair of electrodes or single-channel GES. However, few studies have ...

Nanocables could lead to more powerful lithium-ion batteries

January 28, 2010

(PhysOrg.com) -- By itself, titanium dioxide (TiO2) is a very poor electrode. Electrons move very slowly through the material - so slowly, in fact, that it can take years to fill a millimeter-thick piece of TiO2. However, ...

Organic 2-D films could lead to better solar cells

April 12, 2011

(PhysOrg.com) -- Solar cells made from organic materials are inexpensive, lightweight and flexible, but their performance lags behind cells that contain silicon or other inorganic materials. Cornell chemist William Dichtel ...

Graphite + water = the future of energy storage

July 15, 2011

A combination of two ordinary materials – graphite and water – could produce energy storage systems that perform on par with lithium ion batteries, but recharge in a matter of seconds and have an almost indefinite ...

Recommended for you

Reshaping the solar spectrum to turn light to electricity

July 28, 2015

When it comes to installing solar cells, labor cost and the cost of the land to house them constitute the bulk of the expense. The solar cells—made often of silicon or cadmium telluride—rarely cost more than 20 percent ...

Could stronger, tougher paper replace metal?

July 24, 2015

Researchers at the University of Maryland recently discovered that paper made of cellulose fibers is tougher and stronger the smaller the fibers get. For a long time, engineers have sought a material that is both strong (resistant ...

Wafer-thin material heralds future of wearable technology

July 27, 2015

UOW's Institute for Superconducting and Electronic Materials (ISEM) has successfully pioneered a way to construct a flexible, foldable and lightweight energy storage device that provides the building blocks for next-generation ...

2 comments

Adjust slider to filter visible comments by rank

Display comments: newest first

antialias_physorg
not rated yet Oct 12, 2012
I'm betting it is this sort of 'self assembly' into complex structures which will most impact the products of the near to mid-term future.

Creating these GeS nanoflowers is exciting because it gives us a huge surface area in a small amount of space

I sometimes wonder how much surface area one could get from thin slices of aerogel as a substrate for CVD of GeS or even Si - and whether it would be cost effective.
PPihkala
not rated yet Oct 12, 2012
Nice structure. Now the question is can they grow these in industrially relevant quanties and prices.

Please sign in to add a comment. Registration is free, and takes less than a minute. Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.