This Ultrathin Sensor Could Save Your Lungs – and the Climate
Atomically thin device developed by scientists at Berkeley Lab and UC Berkeley could turn your smartphone into a supersmart gas sensor
By Theresa Duque
Nitrogen dioxide, an air pollutant emitted by fossil fuel-powered cars and gas-burning stoves is not only bad for the climate – it’s bad for our health. Long-term exposure to NO2 has been linked to increased heart disease, respiratory diseases such as asthma, and infections.
Nitrogen dioxide is odorless and invisible – so you need a special sensor that can accurately detect hazardous concentrations of the toxic gas. But most currently available sensors are energy-intensive as they usually must operate at high temperatures to achieve suitable performance.
An ultrathin sensor, developed by a team of researchers from Berkeley Lab and UC Berkeley, could be the answer.
In their paper published in the journal Nano Letters, the research team reported an atomically thin “2D” sensor that works at room temperature and thus consumes less power than conventional sensors.
The researchers say that the new 2D sensor – which is constructed from a monolayer alloy of rhenium niobium disulfide – also boasts superior chemical specificity and recovery time.
Unlike other 2D devices made from materials such as graphene, the new 2D sensor electrically responds selectively to nitrogen dioxide molecules, with minimal response to other toxic gases such as ammonia and formaldehyde. Additionally, the new 2D sensor is able to detect ultralow concentrations of nitrogen dioxide of at least 50 parts per billion, said Amin Azizi, a postdoctoral scholar from UC Berkeley and lead author of the current study.
Once a sensor based on molybdenum disulfide or carbon nanotubes has detected nitrogen dioxide, it can take hours to recover to its original state at room temperature. “But our sensor takes just a few minutes,” Azizi said.
The new sensor isn’t just ultrathin – it’s also flexible and transparent, which makes it a great candidate for wearable environmental-and-health-monitoring sensors. “If nitrogen dioxide levels in the local environment exceed 50 parts per billion, that can be very dangerous for someone with asthma, but right now, personal nitrogen dioxide gas sensors are impractical.” Azizi said. Their sensor, if integrated into smartphones or other wearable electronics, could fill that gap, he added.
Berkeley Lab postdoctoral researcher and co-author Mehmet Dogan relied on the Cori supercomputer at the National Energy Research Scientific Computing Center (NERSC), a supercomputing user facility at Berkeley Lab, to theoretically identify the underlying sensing mechanism.
Alex Zettl and Marvin Cohen, faculty scientists in Berkeley Lab’s Materials Sciences Division and professors of physics at UC Berkeley, co-led the study.
Charged Up: Scientists Find New Pathway to Harnessing the Sun for a Clean Energy Future
Berkeley Lab co-led collaboration with DESY and TU Freiberg brings us a step closer to more efficient photovoltaics and solar fuel systems
By Theresa Duque
In the past 50 years, scientists have made great advances in photovoltaic technologies that convert sunlight into electricity, and artificial photosynthesis devices that convert sunlight and water into carbon-free fuels. But the current state-of-the-art of these clean energy sources still lack the efficiency to compete with electricity or transportation fuel derived from petroleum.
Now, scientists at Berkeley Lab, DESY, the European XFEL, and the Technical University Bergakademie Freiberg, Germany, have reported in Nature Communications their discovery of a hidden charge-generating pathway that could help researchers develop more efficient ways to convert sunlight into electricity or solar fuels like hydrogen.
With help from DESY’s free-electron laser FLASH, the researchers shone ultrashort infrared and X-ray laser flashes on a copper-phthalocyanine:fullerene (CuPc:C60) material to study the charge generation mechanisms with a time resolution of 290 femtoseconds (290 quadrillionths of a second).
Combining the ultrashort pulses of light with a technique called time-resolved X-ray photoemission spectroscopy (TRXPS) allowed the researchers to observe and count in real time how many of the infrared photons absorbed by CuPc:C60 formed useful separate charges, and how many of the absorbed photons only led to heating the material.
Their unique approach unveiled an unknown pathway in CuPc:C60 that turns up to 22% of absorbed infrared photons into separate charges, said Oliver Gessner, a senior scientist in Berkeley Lab’s Chemical Sciences Division and co-author of the current study.
Previous studies of CuPc:C60 typically assessed the system’s efficiency by measuring the total amount of charges or hydrogen or oxygen produced when using the material in a photovoltaic or photocatalytic device. “That, however, only tells you how efficient the entire process is, from the light absorption until water is split,” Gessner said. “But there’s a lot that’s happening in between in these systems that isn’t well understood – and if we don’t understand these in-between steps, we can’t develop more efficient light harvesting systems. Our study will help people develop better models and theories so we can get there.”
India Can Boost Clean Energy and Double Its Power Supply by 2030
Berkeley Lab-led team of researchers finds that higher targets for wind an solar would come at a comparable cost to fossil fuel sources
By Christina Nunez
India has set ambitious targets for renewable power, with plans to quintuple its current wind and solar energy capacity by 2030. The country’s transition away from fossil fuels will have a significant impact on global climate efforts, since it is the world’s third-largest greenhouse gas emitter – although its per capita emissions are below the global average.
A new study recently published in the Proceedings of the National Academy of Sciences from researchers at Berkeley Lab, UC Santa Barbara, and UC Berkeley shows India can aim even higher with its renewable energy goals. By increasing its clean power capacity from the current target of 450 gigawatts within the next decade to 600 gigawatts, the nation can hold its greenhouse gas emissions from the electricity sector at 2018 levels while nearly doubling the supply of electricity to meet economic development needs. The costs, the researchers demonstrated, would be comparable to those of a fossil fuel-dominated grid.
“We found that high renewable energy targets can be cost-effective for India, thanks to falling prices,” said UC Santa Barbara assistant professor and Berkeley Lab faculty scientist Ranjit Deshmukh. “The key to achieving the lowest costs lies in finding the right mix on the electric grid.”
Using computer models, the research team, which also included Duncan Callaway of UC Berkeley, examined the electricity and carbon mitigation costs needed to reliably operate India’s grid in 2030 for a variety of wind and solar targets.
Under current goals, two-thirds of India’s added renewable electricity would come from solar and the rest from wind. But because of India's weather and electricity demand patterns, a target that leans more heavily on wind power will lead to lower costs, the study found.
India will still need resources to meet electricity demand during times when both sun and wind levels are too low, the researchers noted.
“Costs for energy storage on the grid are falling rapidly, making it a viable option in the near term,” said Amol Phadke, a Berkeley Lab staff scientist. “To avoid investments in new coal power plants, deploying battery storage will be essential.”