Metal-Breathing Bacteria Could Transform Electronics, Biosensors, and More
When the Shewanella oneidensis bacterium “breathes” in certain metal and sulfur compounds anaerobically, the way an aerobic organism would process oxygen, one of the materials it can produce is molybdenum disulfide, a material that could be used to enhance electronics, electrochemical energy storage, and drug-delivery devices. Shayla Sawyer, an associate professor of electrical, computer, and systems engineering at Rensselaer, has centered much of her research on the unique abilities of this bacterium. Her lab’s exploration in this area could be an important step toward developing a new generation of nutrient sensors that can be deployed on lakes and other water bodies. Compared with other anaerobic bacteria, one thing that makes Shewanella oneidensis particularly unusual and interesting is that it produces nanowires capable of transferring electrons. “That lends itself to connecting to electronic devices that have already been made,” Sawyer said. “So, it’s the interface between the living world and the manmade world that is fascinating.” Sawyer is available to talk about this unique and innovative area of research, and the potential to develop the next generation of electronics and sensors.
Areas of Expertise
Nano-Bio Optoelectronics
Sensor Development
Hybrid Nanomaterials
Ultraviolet Photodetectors
Biography
Shayla Sawyer is an associate professor in the Electrical, Computer, and Systems Engineering Department at Rensselaer Polytechnic Institute. Her Nano-Bio Optoelectronics research program expands the fundamental understanding, engineering processes, and potential applications of hybrid inorganic/organic materials for optoelectronic devices and sensors. This includes the fabrication of nanomaterials from bacteria, fabrication in a solution process, and the development of optoelectronic sensors and complimentary systems. The optoelectronic devices are comprised of hybrid inorganic/organic materials what may include semiconductor metal oxide nanostructures, conductive polymers, conductive nanostructures, and bio-chemical solutions. Her overall research goal is aimed at effectively fabricating and characterizing novel materials and sensors with consideration of systems that require sensitivity and/or selectivity to bring quantitative measurements in typically qualitative worlds. NSF Lighting Enabled Systems and Applications Research Center, NSF Divison of Biological Infrastructure, National Security Technologies/Department of Energy, NSF Division on Research and Learning, and the NSF GK-12 Community Situated Research Center are a few recent funding resources for her work.
A high performance UV–visible dual-band photodetector based on an inorganic Cs2SnI6 perovskite/ZnO heterojunction structure
Journal of Materials Chemistry C
Dali Shao, Weiguang Zhu, Guoqing Xin, Xueqing Liu, Tianmeng Wang, Sufei Shi, Jie Lian and Shayla Sawyer*a
2019-12-11
Inorganic metal halide (IMH) perovskites have recently emerged as highly promising optoelectronic materials due to their excellent material properties, including tunable direct bandgap, long carrier diffusion length, high carrier mobility and outstanding environmental stabilities. However, the performance of photodetectors fabricated from IMH perovskites so far is limited as compared to their counterparts based on organic–inorganic hybrid perovskites. In this work, we demonstrate a high performance ultraviolet–visible (UV–Vis) dual-band photodetector based on a Cs2SnI6/ZnO heterojunction structure. By adjusting the polarity of the applied bias voltage, the photodetector can switch between two operation modes: (1) UV–Vis dual-band detection mode and (2) visible-blind UV detection mode. High detectivity in both the UV (1.39 × 1012 Jones) and visible (5.88 × 1011 Jones) regions is achieved. In addition, this photodetector demonstrated a fast response speed with a rise and fall time on the order of milliseconds and a large linear dynamic range of 119 dB. The excellent performance of this photodetector originates from efficient charge separation at the heterojunction interfaces, which will be discussed in detail in terms of the energy band diagrams and carrier dynamics of the device. Our study demonstrates the great application potential of inorganic vacancy-ordered perovskites in high-performance heterojunction photodetectors.
Dali Shao, Weiguang Zhu, Guoqing Xin, Jie Lian, and Shayla Sawyer
2019-09-17
A heterojunction photodiode was fabricated from Bi doped Cs2SnCl6 nanoparticles (Cs2SnCl6:Bi NPs) spin-coated on an epitaxially grown GaN substrate. With the back illumination configuration, the heterojunction photodiode demonstrated excellent narrow-band UV sensing capability with a full wavelength of half maximum of 18 nm and a maximum detectivity of 1.2 × 1012 jones, which is promising for biomedical applications. In addition to the excellent narrow band UV sensitivity, the device also demonstrated a large linear dynamic range of 71 decibels (dB) and a fast photoresponse speed (a rise time of 0.75 μs and a fall time of 0.91 μs). The excellent performance is attributed to excellent carrier separation efficiency at the heterojunction interface and improved carrier collection efficiency through the multi-walled carbon nanotube (MWCNT) network. All the above advantages are of great importance for commercial deployment of perovskite-based photodetectors.
Organic–Inorganic Heterointerfaces for Ultrasensitive Detection of Ultraviolet Light
Nano Letters
Dali Shao, Jian Gao, Philippe Chow, Hongtao Sun, Guoqing Xin, Prachi Sharma, Jie Lian, Nikhil A. Koratkar, Shayla Sawyer
2015-05-04
The performance of graphene field-effect transistors is limited by the drastically reduced carrier mobility of graphene on silicon dioxide (SiO2) substrates. Here we demonstrate an ultrasensitive ultraviolet (UV) phototransistor featuring an organic self-assembled monolayer (SAM) sandwiched between an inorganic ZnO quantum dots decorated graphene channel and a conventional SiO2/Si substrate. Remarkably, the room-temperature mobility of the chemical-vapor-deposition grown graphene channel on the SAM is an order-of-magnitude higher than on SiO2, thereby drastically reducing electron transit-time in the channel. The resulting recirculation of electrons (in the graphene channel) within the lifetime of the photogenerated holes (in the ZnO) increases the photoresponsivity and gain of the transistor to ∼108 A/W and ∼3 × 109, respectively with a UV to visible rejection ratio of ∼103. Our UV photodetector device manufacturing is also compatible with current semiconductor processing, and suitable for large volume production.
Cl‐Doped ZnO Nanowire Arrays on 3D Graphene Foam with Highly Efficient Field Emission and Photocatalytic Properties
Small
Dali Shao, Jian Gao, Guoqing Xin, Yiping Wang, Lu Li, Jian Shi, Jie Lian, Nikhil Koratkar, Shayla Sawyer
2015
An environmentally friendly, low‐cost, and large‐scale method is developed for fabrication of Cl‐doped ZnO nanowire arrays (NWAs) on 3D graphene foam (Cl‐ZnO NWAs/GF), and investigates its applications as a highly efficient field emitter and photocatalyst. The introduction of Cl‐dopant in ZnO increases free electrons in the conduction band of ZnO and also leads to the rough surface of ZnO NWAs, which greatly improves the field emission properties of the Cl‐ZnO NWAs/GF. The Cl‐ZnO NWAs/GF demonstrates a low turn‐on field (≈1.6 V μm−1), a high field enhancement factor (≈12844), and excellent field emission stability. Also, the Cl‐ZnO NWAs/GF shows high photocatalytic efficiency under UV irradiation, enabling photodegradation of organic dyes such as RhB within ≈75 min, with excellent recyclability. The excellent photocatalytic performance of the Cl‐ZnO NWAs/GF originates from the highly efficient charge separation efficiency at the heterointerface of Cl‐ZnO and GF, as well as improved electron transport efficiency due to the doping of Cl. These results open up new possibilities of using Cl‐ZnO and graphene‐based hybrid nanostructures for various functional devices.
High responsivity, fast ultraviolet photodetector fabricated from ZnO nanoparticle–graphene core–shell structures
Nanoscale
Dali Shao, Mingpeng Yu, Hongtao Sun, Tao Hu, Shayla Sawyer
2013
We report a simple, efficient and versatile method for assembling metal oxide nanomaterial–graphene core–shell structures. An ultraviolet photodetector fabricated from the ZnO nanoparticle–graphene core–shell structures showed high responsivity and fast transient response, which are attributed to the improved carrier transport efficiency arising from graphene encapsulation.
High responsivity, fast ultraviolet photodetector fabricated from ZnO nanoparticle–graphene core–shell structures
Nanoscale
Dali Shao, Mingpeng Yu, Hongtao Sun, Tao Hu, Shayla Sawyer
2013
We report a simple, efficient and versatile method for assembling metal oxide nanomaterial–graphene core–shell structures. An ultraviolet photodetector fabricated from the ZnO nanoparticle–graphene core–shell structures showed high responsivity and fast transient response, which are attributed to the improved carrier transport efficiency arising from graphene encapsulation.
Enhanced ultraviolet sensitivity of zinc oxide nanoparticle photoconductors by surface passivation
Optical Materials
Liqiao Qin, Christopher Shing, Shayla Sawyer, Partha S Dutta
2011
Zinc oxide nanoparticles were created by a top-down wet-chemical etching process and then coated with polyvinyl-alcohol (PVA), exhibiting sizes ranging from 10 to 120 nm with an average size approximately 80 nm. The PVA layer provides surface passivation of zinc oxide nanoparticles. As a result of PVA coating, enhancement in ultraviolet emission and suppression of parasitic green emission is observed. Photoconductors fabricated using the PVA coated zinc oxide nanoparticles exhibited a ratio of ultraviolet photo-generated current to dark current as high as 4.5 × 104, 5 times better than that of the devices fabricated using uncoated ZnO nanoparticles.
