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Artifical leaf could be a green source of hydrogen
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satellite links it used took too long to send sensor data to base – so people had often disappeared by the time an alert was raised. The radar has been modified and satellite links abandoned in favour of fast ground-based microwave links, says Tim Peters, Boeing’s SBInet project chief. The project moves to its deployment phase in mid-2010, when 17 permanent towers near Tucson will be turned on. Magnetic sensors will be added to detect vehicle movements and weapons, too. CBP is also trialling Predator drones on the border to feed surveillance pictures into SBInet. IAI is a partner in the EU’s Transportable Autonomous Patrol for Land Border Surveillance (TALOS) programme, which eschews static ground sensors and border walls in favour of the aforementioned bug-eyed robots – replete with humansensing radar – and aerial drones. TALOS is needed because the expanded 27-nation EU has a porous eastern border that it cannot afford to monitor conventionally, says Agnieszka Spronska of the Industrial Research Institute for Automation and Measurements (PIAP), based in Warsaw, Poland. PIAP is leading the 10-nation TALOS consortium, which is spending €20 million on developing the architecture for a mobile network of ground robots, drones and the command centres from which they are run. “TALOS will be very scalable depending on the terrain – you can use as much of it as you need without static elements,” says Spronska. More than one ground robot will approach people, she says, as groups often split up. But where does this deepprobing 24/7 surveillance technology leave residents who are living near borders, in terms of privacy? “We protect the camera and sensor systems from any kind of illegal or unauthorised use,” says Borkowski. “But it is indeed a balancing act. People are right -Walls alone won’t seal US borders– to be asking such questions.” ■
Artificial leaves could be future source of energy HIDDEN detail in the natural world could hold the key to future sources of clean energy. So say materials scientists who have created an artificial leaf that can harness light to split water and generate hydrogen. Plant leaves have evolved over millions of years to catch the energy in the sun’s rays very efficiently. They use the energy to produce food, and the central step in the process involves splitting water molecules and creating hydrogen ions. By mimicking the machinery plants use to do this, it is possible to create a miniature hydrogen factory, says Tongxiang Fan of The State Key Laboratory of Metal Matrix Composites at Shanghai Jiao Tong University, China. “Using sunlight to split water molecules and form hydrogen fuel is one of the most promising tactics for kicking our carbon habit,” he says. The idea is not new, but until now researchers have focused on trying to modify or mimic the molecules directly involved in splitting hydrogen. “We’d like to adopt an entirely different concept, to mimic photosynthesis by copying the elaborate architectures of green leaves,” Fan says. Fan and his colleagues used several types of leaves as a template, including the grape-leaved anemone (Anemone vitifolia). First, they treated the leaves with dilute
hydrochloric acid, allowing them to replace magnesium atoms – which form a crucial part of plants’ photosynthetic machinery – with titanium (see illustration). Then they dried the leaves and heated them to 500 °C to burn away most of the remaining plant material. This left a crystallised titanium dioxide framework plus many of the leaves’ natural structures. Titanium dioxide is commonly used in solar
“Mimicking the machinery plants use to capture sunlight can create a mini hydrogen factory”
Plant power Harnessing a plant’s photosynthetic machinery could lead to an efficient way of producing hydrogen Leaves are treated with dilute acid to replace the magnesium in chlorophyll’s porphyrin ring with hydrogen The leaves are treated with titanium trichloride, which replaces hydrogen with titanium Remaining plant material is burned away, leaving a crystallised titanium dioxide scaffold that preserves much of the leaves' natural structure
CREDIT: PASIEKA/SPL
from the fence. So says Mark Borkowski, who directs the SBInet project for the US Customs and Border Protection (CBP) agency in Washington DC. The idea is that robotic cameras will zoom in automatically on any activity detected by radar or sensors. “Then we classify the event to gauge our response: is it just a stray cow? A person? If so, are they carrying weapons or maybe drugs?” says Borkowski. “We’re not foolish enough to think a fence alone will work: we know people can build ramps and cut through it.” A prototype SBInet system, based on nine temporary towers, has been tested on a 45-kilometre stretch of the US-Mexico border near Sasabe, Arizona, for the past three years. Called Project 28, it had problems: the X-band radar produced too much signal clutter from the ground, making it tough to detect human activity. And the
cells to enhance their efficiency, and in the leaf it catalyses the splitting of water molecules. The leaf retained features such as the lens-like cells at its surface, which catch light coming from any angle, and veins that help guide light deeper into the leaf. The replicas also captured very fine detail, including structures called thykaloids, which increase the surface area available for photosynthesis and are just 10 nanometres thick. It is these features which make the artificial leaves so efficient at generating hydrogen, Fan says. The team immersed the artificial leaves in a solution containing 20 per cent methanol – which acts as a catalyst – and zapped them with nearultraviolet visible light. Compared with a commercially available form of titanium dioxide called P25 that can be used to create hydrogen, the artificial leaves absorbed more than twice as much light, and gave off more than three times as much hydrogen, Fan reports (Advanced Materials, DOI: 10.1002/adma.200902039). The work is a “good beginning”, says Chinnakonda Gopinath of the National Chemical Laboratory in Pune, India. “Complex structures found in leaves should be utilised further for enhancement in light harvesting.” Mason Inman ■ 9 January 2010 | NewScientist | 21
satellite links it used took too long to send sensor data to base – so people had often disappeared by the time an alert was raised. The radar has been modified and satellite links abandoned in favour of fast ground-based microwave links, says Tim Peters, Boeing’s SBInet project chief. The project moves to its deployment phase in mid-2010, when 17 permanent towers near Tucson will be turned on. Magnetic sensors will be added to detect vehicle movements and weapons, too. CBP is also trialling Predator drones on the border to feed surveillance pictures into SBInet. IAI is a partner in the EU’s Transportable Autonomous Patrol for Land Border Surveillance (TALOS) programme, which eschews static ground sensors and border walls in favour of the aforementioned bug-eyed robots – replete with humansensing radar – and aerial drones. TALOS is needed because the expanded 27-nation EU has a porous eastern border that it cannot afford to monitor conventionally, says Agnieszka Spronska of the Industrial Research Institute for Automation and Measurements (PIAP), based in Warsaw, Poland. PIAP is leading the 10-nation TALOS consortium, which is spending €20 million on developing the architecture for a mobile network of ground robots, drones and the command centres from which they are run. “TALOS will be very scalable depending on the terrain – you can use as much of it as you need without static elements,” says Spronska. More than one ground robot will approach people, she says, as groups often split up. But where does this deepprobing 24/7 surveillance technology leave residents who are living near borders, in terms of privacy? “We protect the camera and sensor systems from any kind of illegal or unauthorised use,” says Borkowski. “But it is indeed a balancing act. People are right -Walls alone won’t seal US borders– to be asking such questions.” ■
Artificial leaves could be future source of energy HIDDEN detail in the natural world could hold the key to future sources of clean energy. So say materials scientists who have created an artificial leaf that can harness light to split water and generate hydrogen. Plant leaves have evolved over millions of years to catch the energy in the sun’s rays very efficiently. They use the energy to produce food, and the central step in the process involves splitting water molecules and creating hydrogen ions. By mimicking the machinery plants use to do this, it is possible to create a miniature hydrogen factory, says Tongxiang Fan of The State Key Laboratory of Metal Matrix Composites at Shanghai Jiao Tong University, China. “Using sunlight to split water molecules and form hydrogen fuel is one of the most promising tactics for kicking our carbon habit,” he says. The idea is not new, but until now researchers have focused on trying to modify or mimic the molecules directly involved in splitting hydrogen. “We’d like to adopt an entirely different concept, to mimic photosynthesis by copying the elaborate architectures of green leaves,” Fan says. Fan and his colleagues used several types of leaves as a template, including the grape-leaved anemone (Anemone vitifolia). First, they treated the leaves with dilute
hydrochloric acid, allowing them to replace magnesium atoms – which form a crucial part of plants’ photosynthetic machinery – with titanium (see illustration). Then they dried the leaves and heated them to 500 °C to burn away most of the remaining plant material. This left a crystallised titanium dioxide framework plus many of the leaves’ natural structures. Titanium dioxide is commonly used in solar
“Mimicking the machinery plants use to capture sunlight can create a mini hydrogen factory”
Plant power Harnessing a plant’s photosynthetic machinery could lead to an efficient way of producing hydrogen Leaves are treated with dilute acid to replace the magnesium in chlorophyll’s porphyrin ring with hydrogen The leaves are treated with titanium trichloride, which replaces hydrogen with titanium Remaining plant material is burned away, leaving a crystallised titanium dioxide scaffold that preserves much of the leaves' natural structure
CREDIT: PASIEKA/SPL
from the fence. So says Mark Borkowski, who directs the SBInet project for the US Customs and Border Protection (CBP) agency in Washington DC. The idea is that robotic cameras will zoom in automatically on any activity detected by radar or sensors. “Then we classify the event to gauge our response: is it just a stray cow? A person? If so, are they carrying weapons or maybe drugs?” says Borkowski. “We’re not foolish enough to think a fence alone will work: we know people can build ramps and cut through it.” A prototype SBInet system, based on nine temporary towers, has been tested on a 45-kilometre stretch of the US-Mexico border near Sasabe, Arizona, for the past three years. Called Project 28, it had problems: the X-band radar produced too much signal clutter from the ground, making it tough to detect human activity. And the
cells to enhance their efficiency, and in the leaf it catalyses the splitting of water molecules. The leaf retained features such as the lens-like cells at its surface, which catch light coming from any angle, and veins that help guide light deeper into the leaf. The replicas also captured very fine detail, including structures called thykaloids, which increase the surface area available for photosynthesis and are just 10 nanometres thick. It is these features which make the artificial leaves so efficient at generating hydrogen, Fan says. The team immersed the artificial leaves in a solution containing 20 per cent methanol – which acts as a catalyst – and zapped them with nearultraviolet visible light. Compared with a commercially available form of titanium dioxide called P25 that can be used to create hydrogen, the artificial leaves absorbed more than twice as much light, and gave off more than three times as much hydrogen, Fan reports (Advanced Materials, DOI: 10.1002/adma.200902039). The work is a “good beginning”, says Chinnakonda Gopinath of the National Chemical Laboratory in Pune, India. “Complex structures found in leaves should be utilised further for enhancement in light harvesting.” Mason Inman ■ 9 January 2010 | NewScientist | 21