July 14, 2017 Honeycomb type ZnO nanostructure. Credit: Indian Institute of Science

Researchers at the Indian Institute of Science (IISc) have developed a highly sensitive, low-cost nanosensor that can quickly detect minute changes in carbon monoxide (CO) levels, with potential applications in environmental pollution monitoring.

The team used a novel fabrication technique that leaves out lithography, a time-consuming and expensive process, to construct a honeycomb-like nanostructure made up of zinc oxide. The sensor was able to detect a difference in CO level as low as 500 parts per billion and selectively respond to CO even in the presence of other gases. The non-lithography technique also significantly cuts down the time and cost involved in making nanostructured gas sensors.

The study was carried out by Chandra Shekhar Prajapati, postdoctoral fellow, and Navakanta Bhat, Chair & Professor, Centre for Nano Science and Engineering (CeNSE), IISc, along with researchers at the KTH Royal Institute of Technology, Sweden.

"The size of the sensor itself is less than 1 mm," says Bhat. "If you combine it with the rest of the signal processing electronics and a small display, it may not be more than a couple of cm. This can be integrated with a cell phone or a small device at every traffic signal which can transmit the data to your cell phone through Bluetooth."

Conventional micro-machined CO sensors have a flat layer of zinc oxide, a metal oxide semiconductor, through which current flows. When exposed to CO, the resistance of the layer changes, affecting the amount of current flowing through. How much the resistance changes can be mapped to how much CO there is.

Creating nanostructures on flat zinc oxide improves the sensitivity, as the area available for gas interaction increases. However, making these nanosensors using traditional lithographya time-consuming, multi-step process in which metal oxide templates are etched on a light-sensitive materialrequires sophisticated equipment.

Instead, the researchers used tiny beads of polystyrene that arrange themselves into a closely packed layer when spread on an oxidized silicon surface. When zinc oxide is added, it settles into the hexagonal gaps between the beads. When the beads are then "lifted off," what remains is a 3-D honeycomb of zinc oxide, with a much larger surface area available for gas interaction than a flat plate.

The technique could cost significantly less than lithography-based methods, the researchers say. "You can buy a packet of these micron-sized polystyrene beads on the market for Rs. 4000-5000, which can be used to create nanostructures on thousands of sensors. This results in significant cost reduction compared to traditional lithography-based techniques to form such honeycombs," says Prajapati. In addition, the process only takes a few minutes, while lithography-based multi-step methods can take a few hours, he adds.

For environmental applications, gas sensors need to be both highly sensitive (detect very low levels) and selective (detect a specific gas in the presence of other gases). The researchers developed sensors with varying honeycomb wall width, and found that the one with the smallest width (~100 nm) was able to detect a change of even 500 parts per billion in CO concentration. When tested with a mixture of gases, the sensor also showed a distinctly greater response for CO.

The polystyrene-based method can be used to develop similar honeycomb nanostructures for other metal oxides to detect other gases, the researchers say. "What we have is a generic platform. You can do the same nano-structuring for different metal oxide semiconductor sensors," says Bhat.

Bhat and his team have been working on developing miniature sensors for air quality monitoring for several years. They previously developed a hybrid sensor array to detect four different gases simultaneously.

Explore further: Improved fire detection with new ultra-sensitive, ultraviolet light sensor

More information: C.S. Prajapati et al, Honeycomb type ZnO nanostructures for sensitive and selective CO detection, Sensors and Actuators B: Chemical (2017). DOI: 10.1016/j.snb.2017.06.070

A new study published today in Scientific Reports has discovered that a material traditionally used in ceramics, glass and paint, can be manipulated to produce an ultra-sensitive UV light sensor, paving the way for improved ...

(PhysOrg.com) -- Unlike many conventional chemical detectors that require an external power source, Lawrence Livermore researchers have developed a nanosensor that relies on semiconductor nanowires, rather than traditional ...

Professor Il-Doo Kim in the Department of Materials Science and Engineering at Korea Advanced Institute of Science and Technology (KAIST) is developing ultrasensitive and highly selective gas sensors to diagnose diseases ...

Scientists from the Semenov Institute of Chemical Physics of the Russian Academy of Sciences (ICP RAS) and the Moscow Institute of Physics and Technology (MIPT) have demonstrated that sensors based on binary metal oxide nanocomposites ...

RMIT University researchers have created wearable sensor patches that detect harmful UV radiation and dangerous, toxic gases such as hydrogen and nitrogen dioxide.

Pollutants emitted by factories and car exhausts affect humans who breathe in these harmful gases and also aggravate climate change up in the atmosphere. Being able to detect such emissions is a critically needed measure.

A little fluorine turns an insulating ceramic known as white graphene into a wide-bandgap semiconductor with magnetic properties. Rice University scientists said that could make the unique material suitable for electronics ...

Scientists from the Swiss Nanoscience Institute and the University of Basel have succeeded in coupling an extremely small quantum dot with 1,000 times larger trumpet-shaped nanowire. The movement of the nanowire can be detected ...

For more than 60 years, researchers have tried to successfully cryopreserve (or freeze) the embryo of zebrafish, a species that is an important medical model for human health. In a new study, researchers at the University ...

Antibiotic resistance is a growing problem, especially among a type of bacteria that are classified as "Gram-negative." These bacteria have two cell membranes, making it more difficult for drugs to penetrate and kill the ...

Visualizing biological cells under a microscope was just made clearer, thanks to research conducted by graduate student Yifei Jiang and principal investigator Jason McNeill of Clemson University's department of chemistry.

Early phase Northwestern Medicine research has demonstrated a potential new therapeutic strategy for treating deadly glioblastoma brain tumors.

Please sign in to add a comment. Registration is free, and takes less than a minute. Read more

Read the original post:

Low-cost CO sensor developed using nanoscale honeycomb structures - Phys.Org