World's smallest ice cube created

The hexagonal structure characteristic of ice begins to form when 275 water molecules link up © Victoria Buch, Cristoph Pradzynski and Udo Buck

Ice crystals must contain at least 275 water molecules, say German chemists. This size limit has implications for any process that involves ice particles, from cloud formation to making the perfect gin and tonic.

To determine the smallest possible ice crystal, the German chemists, jointly led by Thomas Zeuch at the University of Göttingen and Udo Buck at the Max Planck Institute for Dynamics and Self-Organization in Göttingen, analysed various different size water clusters using mass spectrometry and infrared (IR) spectroscopy. 

They used mass spectrometry to determine the number of water molecules in each cluster, which ranged from 85 to 475, and IR spectroscopy to determine the structure of the water clusters.

Previous groups have struggled to perform both mass spectrometry and IR spectroscopy on such small clusters of water molecules. 

Zeuch and Buck managed it by doping the surface of the clusters with sodium atoms. 

These helped to ionise the water clusters for analysis by mass spectrometry, but because they were only present on the surface they didn’t alter the structure of the clusters, which could still be probed by IR spectroscopy.

IR spectroscopy records the specific IR frequencies absorbed by the chemical bonds in a molecule: the bonds in liquid water absorb at one frequency, while those in ice absorb at a slightly different one. 

So Zeuch and Buck simply looked for the smallest cluster that absorbed at the IR frequency characteristic of ice, finding the first evidence of ice-like absorption for clusters containing 275 molecules. 

This represents the start of the crystallisation process, which is more or less complete by the time you reach clusters with 475 water molecules.

‘We have determined the onset of crystallisation, which is the size where the inner core of the cluster becomes crystalline,’ explains Zeuch. ‘This is around 275 molecules. [By] adding more molecules the crystalline part of the cluster grows. For around 475 molecules, the cluster has become a nanocrystal showing the spectral features of ice. Thus, we have obtained a fully size-resolved picture of the gradual change between amorphous and crystalline ice.’

Smaller clusters are unable to crystallise into ice because there is simply not enough room for their water molecules to adopt the ice configuration, which is based around a central ring of six hydrogen-bonded water molecules. 

‘The hexagonal ice crystal needs, because of the underlying hydrogen bonds, a lot of space and, therefore, a minimum number of molecules is required to form it,’ Zeuch tells Chemistry World.

‘This study is of major scientific importance, but it’s also a significant development from an experimental point of view,’ says Christoph Salzmann, a physical chemist who studies crystalline materials, such as ice, at University College London. 

‘The experiments the authors have done are not easy; it’s a real achievement.’

Zeuch and Buck say that the same approach could be used to investigate the crystallisation process in other substances, such as alcohols. 

All of which bodes well for making the perfect gin and tonic.

REFERENCES

C C Pradzynski et al, Science, 2012, 337, 1529 (DOI: 10.1126/science.1225468)

Jon Evans

rsc.org

via 

@maxplanckpress

Researchers design 'smart' waterpumps for rural Africa

Researchers hope to harness mobile phone technology to improve water supplies in rural parts of  Africa

A team from the University of Oxford, in the United Kingdom, proposes installing handpumps containing devices that automatically send text messages to local water engineers whenever pumps break down or dry up.

The device, known as a waterpoint data transmitter, is fitted into handpump handles, and automatically monitors the number of strokes made when a pump is operated.

This data, which provides estimates of daily and seasonal demand, including critical under- or over-usage information, is then transmitted to a central hub — thus informing engineers, cheaply and regularly, of the need for repairs, and helping to ensure a constant flow of water.

The researchers will trial their idea, which is known as the 'Smart Handpumps' initiative, in 70 villages in Kenya next month (August). 

A prototype transmitter was successfully trialled in Zambia in 2011.

"We came up with the project in response to the widespread failure of hand pumps [largely because of wear and tear, and mechanical faults] and associated health and economic failure impacts on the 276 million Africans who do not have improved water services," lead researcher Rob Hope, a senior research fellow at the University of Oxford, told SciDev.Net.

"It is estimated that at any one time, one third of handpumps in rural Africa are not working. Unimproved water access is associated with 1.5 million unnecessary deaths of children under five," said Hope.

"Women and children spend close to 40 billion hours collecting water each year in Africa, and 448 million school days [are] lost because of unreliable water supplies," he added.

Julius Kabubi, an East African Commission risk reduction adviser, said that the initiative would particularly benefit arid and semi-arid areas, which require a constant water supply.

"A minor [pump] breakdown in a remote area can cause a well to be abandoned, and this is what the technology is trying to address," Kabubi said.

He added that for the project to be effective, it needed to work closely with mobile communication providers to ensure good signal coverage, as in some remote areas the mobile network coverage, upon which handpump technology depends, is not very strong.

Furthermore, Kabubi believes the initiative will work better if more water engineers — who are in low supply in Africa — receive traning

The researchers hope to expand the technology to other African countries, including Malawi, South Sudan and Zambia.

The project is funded by the UK Department for International Development (DFID).

Mercy Adhiambo

scidev.net

Innovation 'must consider water, energy and land jointly'

More technological innovation is needed to fight growing resource scarcity, but it will only be successful in achieving sustainable developmentif it considers the use of water, energy and land as interdependent issues, according to a European report.

Investment in innovation is required for sustainable agriculture, for achieving more efficient use of water and energy, and for rolling out renewable energy technologies, says the 'European Report on Development 2011–2012', funded by the European Commission and seven European states.

But failure to consider the three basic resources of water, energy and land as a 'nexus' — in which the use of one affects the availability of the other two — is leading to poor decisions that ultimately work against sustainable development, it says.

"We can no longer think about solving [resource] issues by tackling one problem at a time," said James Mackie, of the European Centre for Development Policy Management, which produced the report along with the UK's Overseas Development Institute (ODI) and the German Development Institute.

The third in an annual series, the report, subtitled 'Confronting Scarcity', combines two strands of emerging thought.

The first is that of absolute resource scarcity. Demand for energy and water is set to increase by 40 per cent in the next two decades, and demand for food — which will in turn be one of the factors increasing land demand — by 50 per cent. But there is not enough of these resources to meet the demand unless their management is transformed.

The second is that of the interconnectedness of resources, a phenomenon the authors believe is largely ignored in setting policy.

"This issue is becoming more acute because of the absolute shortages coming into play," Mackie told SciDev.Net.

"While much has been written about managing water, energy and land (WEL), few initiatives focus directly on the resource nexus," said the authors, who have been promoting the idea to national delegations to the UN Conference on Sustainable Development (Rio+20) taking place in Brazil next month (20–22 June).

The report cites an example in Bangladesh where open pit coal mining is cheap, but harms the environment and uses up land, whilst closed pit mining is more expensive, but requires less land and is environmentally friendly.

"A WEL nexus approach is more likely to choose the latter option," lead author Dirk Willem te Velde, of the ODI, told SciDev.Net.

Decisions about renewable energy technologies could also be influenced by this approach, the authors said, pointing out that "the average biomass energy source requires 70 times the water footprint of oil".

Such thinking should also be invoked in rolling out the UN Secretary-General Ban Ki Moon's initiative, Sustainable Energy for All, which aims to improve access to energy and the use of renewables.

The report's authors also call for institutions that govern access to land, water or energy, at local, national and regional levels, to be established, "or radically reformed", to take into account the WEL nexus.

They say that the European Union needs to improve the coherence of its policies for the developing world so that it considers scarcity on all three fronts.

Aisling Irwin

scidev.net

World Water Day 22 March 2012

 

http://www.fao.org/nr/water/ 

http://www.unwater.org/worldwaterday/ 

http://www.unwater.org/worldwaterday/downloads/WWD2012_BROCHURE_EN.pdf