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MU professor develops new applications for platinum nanoparticles

Gangopadhyay works on a computer.

C.W. LaPierre Chair Professor Shubhra Gangopadhyay’s platinum nanoparticle research stems from initial National Science Foundation funding to create the platinum nanoparticles in sub-2 nanometer size through a tilted-target-sputtering technique.

MU electrical and computer engineering Professor Shubhra Gangopadhyay and her research group have been investigating applications of platinum nanoparticles, recently publishing a pair of papers on new ways to utilize the materials.

The paper “Barrier Modification of Metal-contact on Silicon by Sub-2 Nanometer Platinum Nanoparticles and Thin Dielectrics” was published in Scientific Reports and shows how the platinum nanoparticles can be used to achieve perfect Ohmic contact between metals and semiconductors. “Neutron detection with integrated sub-2 nanometer platinum nanoparticles and B enriched dielectrics — a direct conversion device” was published in Sensing and Bio-Sensing Research and illustrates how the materials can be used to create a complementary metal-oxide-semiconductor process-compatible, direct conversion solid-state neutron detection device.

Haisheng Zheng, a graduate research assistant in Gangopadhyay’s lab, was lead author on the papers, and Gangopadhyay was the corresponding author.

The research stems from initial National Science Foundation funding to create the platinum nanoparticles in sub-2 nanometer size through a tilted-target-sputtering technique. Gangopadhyay previously published a paper in which these particles were used in explosive sensors, another of the particles’ applications.

The barrier modification paper came about from an idea to tackle one of the biggest efficiency problems in electronic devices: increasing their efficiency by improving the flow of current between metal-semiconductor contacts. It is a critical need as devices of all kinds continue to pack more components in tinier spaces.

“One of the biggest problems with all devices, including solar cells, is the contact resistance between semiconductors and metals,” Gangopadhyay said. “Part of the current is lost because of the resistance of these contacts. We’re using these particles as current injection hotspot and reduce the barrier so we can reduce the resistance of contacts and make a better interface.”

Neutron detection also is a crucial current area of study. When such devices are exposed to neutrons, they generate charges, which is a signal that neutrons are present. Gangopadhyay and her team developed a way to store those charges in order to detect the amount of neutrons the sensor is exposed to without having to destroy the devices, which many current devices do.

“What we’re saying is once you destroy it, it’s a one time thing,” she said. “In our case, selectively, we can keep collecting, and every time it generates a charge, we can store it and access the information either on site or remotely. Or we can remove it completely and reuse. It’s more programmable, not by destroying but by moving the charge in and out of the system.

“Because it’s collecting and keeping it in memory, let’s say there is a truck with trace amounts of nuclear material which generates neutrons. Let’s say you have this detector… this will keep charging the device cumulatively so that at some point you will be able to detect [the neutrons present in the materials in the truck]. It keeps collecting the information. It’s very sensitive.”

Additionally, Gangopadhyay’s sensor has the added benefit of allowing the user to read the information remotely, allowing researchers to keep their distance in potentially dangerous situations. It also provides versatility in terms of use with certain types of equipment.

Gangopadhyay thanked John Brockman from the MU Research Reactor and Assistant Professor Mark Lee of the Department of Chemistry for their assistance with the neutron detection project.

“This work is not possible if we don’t have MURR. You need a neutron source to calibrate your detector,” she said. “If we didn’t have collaboration with chemistry — we needed materials with boron for converting neutron into a measureable quantity — [it would not have been possible].”

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