Periodic Reporting for period 1 - GREBOS (Green Borophene Sensing)
Período documentado: 2023-03-01 hasta 2025-02-28
Air and water pollution are two of the most serious environmental issues worldwide, causing serious threats to human health and ecosystems. Nitrogen compounds such as nitrogen oxides (NOₓ) and nitrates are especially damaging, being linked to respiratory diseases, acid rain and water eutrophication. Monitoring these pollutants, particularly at low concentrations, is crucial to enforce environmental policies and to reduce harmful exposures. However, current monitoring systems are often based on bulky, costly and energy-intensive technologies that are unsuitable for large-scale deployment or real-time monitorization.
In this context, the GREBOS project aims to contribute to address this urgent need by developing new sensing devices that are affordable, scalable, and capable of detecting these harmful compounds in both air and water matrixes. This research aligns with strategic EU objectives like the Horizon Europe framework and the European Green Deal, both emphasizing the goal of achieving cleaner air and water by 2030.
To do this, GREBOS explores borophene, a novel 2D nanomaterial composed of boron atoms. Borophene shows very promising properties for sensing, including very high surface area, tunable electronic properties, and high chemical reactivity. Also, thanks to its electron-deficient nature, borophene can strongly interact with pollutant molecules while operating at room temperature. This is translated into a considerable reduction of the power requirements, a key point for developing dense sensor networks in urban or remote areas. Yet, practical applications have been limited by issues like oxidation of the borophene surface and interference of ambient moisture.
GREBOS aims to contribute towards the development of low-powered, affordable, and highly sensitive sensors by pursuing the following objectives:
1. Design a green synthesis route for borophene using liquid-phase exfoliation, avoiding complex, costly and energy-intensive methods like molecular beam epitaxy.
2. Functionalize the borophene by plasma methods (e.g. fluorine doping) to enhance the sensing performance and nanomaterial properties.
3. Develop novel sensors to detect nitrogen-based pollutants in gas (e.g. NO2) and water (e.g. nitrates) matrixes.
4. Investigate the sensing mechanisms through advanced characterization, to bridge theoretical predictions with experimental observations.
The GREBOS project contributes to some EU policy goals, including the Zero Pollution Action Plan, by offering new tools for environmental monitoring. Its interdisciplinary approach combining nanomaterials science, electronics, and environmental monitoring helps pave the way for the next generation of smart, miniaturized and sustainable sensors. These efforts support the UN Sustainable Development Goals (SDGs) 3, 6, and 11, and the expected benefits range from improved public health to cleaner cities and better industrial technology.
In this context, the GREBOS project aims to contribute to address this urgent need by developing new sensing devices that are affordable, scalable, and capable of detecting these harmful compounds in both air and water matrixes. This research aligns with strategic EU objectives like the Horizon Europe framework and the European Green Deal, both emphasizing the goal of achieving cleaner air and water by 2030.
To do this, GREBOS explores borophene, a novel 2D nanomaterial composed of boron atoms. Borophene shows very promising properties for sensing, including very high surface area, tunable electronic properties, and high chemical reactivity. Also, thanks to its electron-deficient nature, borophene can strongly interact with pollutant molecules while operating at room temperature. This is translated into a considerable reduction of the power requirements, a key point for developing dense sensor networks in urban or remote areas. Yet, practical applications have been limited by issues like oxidation of the borophene surface and interference of ambient moisture.
GREBOS aims to contribute towards the development of low-powered, affordable, and highly sensitive sensors by pursuing the following objectives:
1. Design a green synthesis route for borophene using liquid-phase exfoliation, avoiding complex, costly and energy-intensive methods like molecular beam epitaxy.
2. Functionalize the borophene by plasma methods (e.g. fluorine doping) to enhance the sensing performance and nanomaterial properties.
3. Develop novel sensors to detect nitrogen-based pollutants in gas (e.g. NO2) and water (e.g. nitrates) matrixes.
4. Investigate the sensing mechanisms through advanced characterization, to bridge theoretical predictions with experimental observations.
The GREBOS project contributes to some EU policy goals, including the Zero Pollution Action Plan, by offering new tools for environmental monitoring. Its interdisciplinary approach combining nanomaterials science, electronics, and environmental monitoring helps pave the way for the next generation of smart, miniaturized and sustainable sensors. These efforts support the UN Sustainable Development Goals (SDGs) 3, 6, and 11, and the expected benefits range from improved public health to cleaner cities and better industrial technology.
GREBOS project advanced in the synthesis, characterization, and sensor applications of borophene. It successfully achieved a working synthesis process based on optimized liquid-phase exfoliation, a top-down approach, producing borophene flakes with high crystallinity and lateral sizes between 50 and 100 nm. Most importantly, the synthesis method developed is straightforward, inexpensive and adaptable to larger scale production. Unlike traditional methods, our method avoids ultra-high vacuum systems and enables the obtention of large quantities of nanomaterial, making it more practical for industrial applications.
The borophene layers obtained showed a β-rhombohedral crystal structure, with average interlayer spacing of 4.9 Å. This entire synthesis was done using isopropanol (IPA), which is low in toxicity and relatively safe to handle. Besides, since water vapor is known to interfere with air quality sensors, a superficial fluorine doping (about 5 wt%) was introduced via plasma, known for its hydrophobic nature. The doping process altered the surface chemistry of borophene while retaining its crystallinity.
For the borophene characterization, the project employed a wide range of techniques, including: i) High-Resolution Transmission Electron Microscopy (HRTEM), ii) X-Ray Photoelectron Spectroscopy (XPS), iii) Field-Effect Scanning Electron Microscope (FESEM), iv) X-Ray Diffraction (XRD) and v) X-ray absorption spectroscopy (XAS) at Solaris Synchrotron facilities (Krakow, Poland). These allowed for a deep understanding of the structure and electronic behavior of the nanomaterial.
In parallel, the sensing performance has been studied. GREBOS project developed a resistive gas sensor that successfully detected trace amounts of NO2, achieving a limit of detection (LOD) of 23 ppb, well below the EU air quality limits. Notably, the borophene sensitivity was increased by 50% in humid conditions, which is particularly useful for developing sensors for real-world settings. Besides, the borophene synthesized was implemented in electrochemical devices for nitrate detection in water samples. This was especially relevant since nitrates often result as subproducts from NO2 deposition in water bodies, providing a consistent sensing strategy across air and water phases.
The borophene layers obtained showed a β-rhombohedral crystal structure, with average interlayer spacing of 4.9 Å. This entire synthesis was done using isopropanol (IPA), which is low in toxicity and relatively safe to handle. Besides, since water vapor is known to interfere with air quality sensors, a superficial fluorine doping (about 5 wt%) was introduced via plasma, known for its hydrophobic nature. The doping process altered the surface chemistry of borophene while retaining its crystallinity.
For the borophene characterization, the project employed a wide range of techniques, including: i) High-Resolution Transmission Electron Microscopy (HRTEM), ii) X-Ray Photoelectron Spectroscopy (XPS), iii) Field-Effect Scanning Electron Microscope (FESEM), iv) X-Ray Diffraction (XRD) and v) X-ray absorption spectroscopy (XAS) at Solaris Synchrotron facilities (Krakow, Poland). These allowed for a deep understanding of the structure and electronic behavior of the nanomaterial.
In parallel, the sensing performance has been studied. GREBOS project developed a resistive gas sensor that successfully detected trace amounts of NO2, achieving a limit of detection (LOD) of 23 ppb, well below the EU air quality limits. Notably, the borophene sensitivity was increased by 50% in humid conditions, which is particularly useful for developing sensors for real-world settings. Besides, the borophene synthesized was implemented in electrochemical devices for nitrate detection in water samples. This was especially relevant since nitrates often result as subproducts from NO2 deposition in water bodies, providing a consistent sensing strategy across air and water phases.
GREBOS has achieved progress beyond the state of the art by developing new borophene-based gas sensors and performing a novel superficial doping using plasma treatments. Most notably, GREBOS has demonstrated the development of an inexpensive, straightforward and scalable synthesis method of borophene via ultrasonication-assisted liquid-phase exfoliation. This contrasts with most borophene research, which remains theoretical or dependent on expensive and small-scale synthesis methods.
The borophene produced in GREBOS project had smaller flake sizes than previously reported for sensing, which in combination with the optimized properties, allowed for unprecedented detection limits of NO2 using this nanomaterial. Also, it was shown that humidity, often a drawback in gas sensing, actually enhanced the sensor sensitivity, a finding that may help solve a known barrier for borophene sensors development.
In terms of surface doping, GREBOS was the first to experimentally introduce fluorine to borophene using plasma treatment, providing a clean and tunable method to change its surface without chemical reagents. This will be particularly valuable for improving both selectivity and long-term stability.
The project also made efforts to close the gap between theory and experiments. Many theoretical papers do not consider in their models some critical experimental challenges like surface oxidation, which in practice can drastically change the borophene properties. Through a dedicated review, GREBOS helped in identifying these inconsistencies and offered possible solutions to overcome these experimental bottlenecks.
In summary, GREBOS responds to societal and environmental needs by proposing borophene sensors that work at room temperature, reducing the energy consumption, cost and device complexity. The results are highly promising for the development of in-field sensors, but further research is needed to ensure longer-term stability and selectivity before commercialization.
The borophene produced in GREBOS project had smaller flake sizes than previously reported for sensing, which in combination with the optimized properties, allowed for unprecedented detection limits of NO2 using this nanomaterial. Also, it was shown that humidity, often a drawback in gas sensing, actually enhanced the sensor sensitivity, a finding that may help solve a known barrier for borophene sensors development.
In terms of surface doping, GREBOS was the first to experimentally introduce fluorine to borophene using plasma treatment, providing a clean and tunable method to change its surface without chemical reagents. This will be particularly valuable for improving both selectivity and long-term stability.
The project also made efforts to close the gap between theory and experiments. Many theoretical papers do not consider in their models some critical experimental challenges like surface oxidation, which in practice can drastically change the borophene properties. Through a dedicated review, GREBOS helped in identifying these inconsistencies and offered possible solutions to overcome these experimental bottlenecks.
In summary, GREBOS responds to societal and environmental needs by proposing borophene sensors that work at room temperature, reducing the energy consumption, cost and device complexity. The results are highly promising for the development of in-field sensors, but further research is needed to ensure longer-term stability and selectivity before commercialization.