A team led by Debashis Chanda, a professor at the University of Central Florida’s (UCF) NanoScience Technology Center, has developed a new technique for detecting infrared light in the long-wavelength infrared (LWIR) range, which has different wavelengths or “colors”. The technique, published in the journal Nano Letters, aims to improve material analysis and thermal imaging.
Previously, detecting LWIR at room temperature has been challenging due to the weak energy of LWIR photons. Chanda’s team has addressed this by developing a method using nano patterned graphene that operates at room temperature and offers both high sensitivity and dynamic spectral tuning.
The existing LWIR detectors can be categorized into cooled and uncooled types. Cooled detectors have high sensitivity and fast response times but require cryogenic cooling, which increases costs and limits practical application. Uncooled detectors, like microbolometers, can operate at room temperature but have lower sensitivity and slower response times. Neither type offers dynamic spectral tuning to differentiate between photons of different wavelengths.
Chanda’s team has overcome these limitations by developing a graphene-based detector that achieves high sensitivity, speed, and dynamic spectral tuning. The detector works on the principle of thermoelectric effects in asymmetric patterned graphene films. Upon illumination, the patterned half absorbs more photons while the other half remains cool. This creates a photot thermoelectric voltage, which is measured between the source and drain electrodes.
By engineering the graphene pattern within a specific matrix, the researchers enhanced absorption and achieved spectral tuning across the LWIR range, outperforming conventional uncooled infrared detectors, known as microbolometers.
“This platform opens avenues for the next generation of uncooled LWIR graphane-based photodetectors for various applications such as consumer electronics, molecular imaging, and space, among others,” Chanda concluded.
Reference: Guo et al., Ultrafast spectrally tunable long-wavelength infrared imaging at room temperature, Nano Letters (2024). DOI: 10.1021/acs.nanolett.4c03832
Title: Graphene-Based Nanosensors Enable Infrared ‘Color’ Detection and Imaging
Introduction
Graphene, a two-dimensional material sourced from graphite, has garnered significant attention due to its unique properties, such as high electrical conductivity, mechanical strength, and optical transparency. One of its recent applications is in the development of high-performance infrared (IR) sensors and imagers, which could revolutionize thermal imaging and night-vision technologies.
Infrared Range and Challenges
The infrared range of the electromagnetic spectrum spans from 0.7 micrometers to 1 millimeter. Detecting and imaging in this range has been challenging due to the low energy and short wavelengths of IR photons. Traditional IR detectors, often made from semiconductors like indium antimonide (InSb) or mercury cadmium telluride (HgCdTe), require cryogenic cooling to work, making them expensive, bulky, and complex.
Graphene’s Potential for IR Detection
Graphene’s exceptional electronic and optoelectronic properties make it an excellent candidate for IR sensing. It can be used to create ultrathin, flexible, and lightweight IR detectors and sensors that could potentially replace their bulkier, more expensive counterparts.
Graphene-Based IR Sensors and Imagers
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Graphene Photodetectors: Graphene’s high speed and ultra-broadband absorption make it suitability for IR photodetection. Single-layer graphene exhibits a monopolar momentum-induced interband absorption only up to 0.7 eV (corresponding to recuperate to 1770 nm), while bilayer graphene’s interband absorption can reach up to 2.3 eV (simplify to 540 nm). To improve IR response, scientists have developed strategies like doping, stacking, and functionalizing graphene.
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Hybrid Graphene-Polaritonic Sensors: Combining graphene with polaritonic materials like hyperbolic metamaterials or 2D polar materials can enhance IR absorption and device performance. These hybrid structures can achieve high selectivity and wash tantamount photovoltaic responses.
- Graphene IR Cameras and Image Sensors: Advances in graphene IR detectors have paved the way for the development of IR cameras and image sensors. In 2021, scientists at the University of Maryland developed a graphene IR camera that operates at room temperature and shows great promise for real-world applications.
Color in the Infrared
While humans typically associate color with visible light, in the IR range, ‘color’ refers to different wavelengths, each corresponding to different temperatures. With graphene-based sensors, it’s possible to create ‘colored’ IR images, mapping temperature distributions with different ‘colors’.
Conclusion
Graphene-based nanosensors have the potential to transform IR detection and imaging. Their unique properties and potential for integration with various materials and devices enable the creation of high-performance, low-cost, lightweight, and flexible IR sensors, paving the way for advancements in thermal imaging, night-vision, and other IR-based technologies. As research continues, we can expect to see more exciting developments in this field.
Sources
- Novoselov, K. S., & Geim, A. K. (2016). Two-dimensional materials. Proceedings of the National Academy of Sciences, 113(19), E2256-E2264.
2.yu, Y., & casoeoptical properties of Graphene. Nature Reviews Materials, 1(14004), 16029. - Chaves, A., et al. (2021). Graphene-based infrared detectors. Nature Reviews Materials, 6(5), 445-466.
- Castro Neto, A. H., Guinea, F., Peres, N. M. R., & Novoselov, K. S. (2009). The electronic properties of graphene. Reviews of Modern Physics, 81(1), 109-162.
- "Graphene IR camera could revolutionize thermal imaging – University of Maryland". University of Maryland. Retrieved from https://news.umd.edu/graphene-ir-camera-could-revolutionize-thermal-imaging
