Tag Archives: Arumugam Manikandan

Nanowires with fast infrared light (IR) response and more

An April 10, 2019 news item on Nanowerk points the way to improved high-speed communication with nanowires (Note: A link has been removed),

Chinese scientists have synthesized new nanowires with high carrier mobility and fast infrared light (IR) response, which could help in high-speed communication. Their findings were published in Nature Communications (“Ultra-fast photodetectors based on high-mobility indium gallium antimonide nanowires”).

Below, you will find an image illustrating the researchers’ work ,

Caption: The growth mechanism and fast 1550 nm IR detection of the single-crystalline In0.28Ga0.72Sb ternary nanowires Credit: HAN Ning

An April 10, 2019 Chinese Academy of Sciences news release (also on EurekAlert), which originated the news item, provides more detail,

Nowadays, effective optical communications use 1550 nm IR, which is received and converted into an electrical signal for computer processing. Fast light-to-electrical conversion is thus essential for high-speed communications.

According to quantum theory, 1550 nm IR has energy of ~ 0.8 eV, and can only be detected by semiconductors with bandgaps lower than 0.8 eV, such as germanium (0.66 eV) and III-V compound materials such as InxGa1-xAs (0.35-1.42 eV) and InxGa1-xSb (0.17-0.73 eV). However, those materials usually have huge crystal defects, which cause substantial degradation of photoresponse performance.

Scientists from the Institute of Process Engineering (IPE) of the Chinese Academy of Sciences, City University of Hong Kong (CityU) and their collaborators synthesized highly crystalline ternary In0.28Ga0.72Sb nanowires to demonstrate high carrier mobility and fast IR response.

In this study, the In0.28Ga0.72Sb nanowires (bandgap 0.69 eV) showed a high responsivity of 6000 A/W to IR with high response and decay times of 0.038ms and 0.053ms, respectively, which are some of the best times so far. The fast IR response speed can be attributed to the minimized crystal defects, as also illustrated by a high hole mobility of up to 200 cm2/Vs, according to Prof. Johnny C. Ho from CityU.

The minimized crystal defect is achieved by a “catalyst epitaxy technology” first established by Ho’s group. Briefly, the III-V compound nanowires are catalytically grown by a metal catalyst such as gold, nickel, etc.

“These catalyst nanoparticles play a key role in nanowire growth as the nanowires are synthesized layer by layer with the atoms well aligned with those in the catalyst,” said HAN Ning, a professor at IPE and senior author of the paper.

Here’s a link to and a citation for the paper,

Ultra-fast photodetectors based on high-mobility indium gallium antimonide nanowires by Dapan Li, Changyong Lan, Arumugam Manikandan, SenPo Yip, Ziyao Zhou, Xiaoguang Liang, Lei Shu, Yu-Lun Chueh, Ning Han & Johnny C. Ho. Nature Communicationsvolume 10, Article number: 1664 (2019) DOI: https://doi.org/10.1038/s41467-019-09606-y Published 10 April 2019

This paper is open access.

Glucose-sensing contact lens invented by US and Korean researchers

Blood tests for glucose levels may one day be a feature of the past according to an Oct. 3, 2016 news item on ScienceDaily,

Blood testing is the standard option for checking glucose levels, but a new technology could allow non-invasive testing via a contact lens that samples glucose levels in tears.

“There’s no noninvasive method to do this,” said Wei-Chuan Shih, a researcher with the University of Houston [UH] who worked with colleagues at UH and in Korea to develop the project, described in the high-impact journal Advanced Materials. “It always requires a blood draw. This is unfortunately the state of the art.”

A Sept. 27, 2016 UH news release (also on EurekAlert) by Jeannie Kever, which originated the news item, describes the proposed technology,

… glucose is a good target for optical sensing, and especially for what is known as surface-enhanced Raman scattering spectroscopy [also known as surface-enhanced Raman scattering or surface-enhanced Raman spectroscopy, and SERS], said Shih, an associate professor of electrical and computer engineering whose lab, the NanoBioPhotonics Group, works on optical biosensing enabled by nanoplasmonics.

This is an alternative approach, in contrast to a Raman spectroscopy-based noninvasive glucose sensor Shih developed as a Ph.D. student at the Massachusetts Institute of Technology. He holds two patents for technologies related to directly probing skin tissue using laser light to extract information about glucose concentrations.

The paper describes the development of a tiny device, built from multiple layers of gold nanowires stacked on top of a gold film and produced using solvent-assisted nanotransfer printing, which optimized the use of surface-enhanced Raman scattering to take advantage of the technique’s ability to detect small molecular samples.

Surface-enhanced Raman scattering – named for Indian physicist C.V. Raman [Raman scattering; SERS history begins in 1973 according to its Wikipedia entry], who discovered the effect in 1928 – uses information about how light interacts with a material to determine properties of the molecules that make up the material.

The device enhances the sensing properties of the technique by creating “hot spots,” or narrow gaps within the nanostructure which intensified the Raman signal, the researchers said.

Researchers created the glucose sensing contact lens to demonstrate the versatility of the technology. The contact lens concept isn’t unheard of – Google has submitted a patent for a multi-sensor contact lens, which the company says can also detect glucose levels in tears – but the researchers say this technology would also have a number of other applications.

“It should be noted that glucose is present not only in the blood but also in tears, and thus accurate monitoring of the glucose level in human tears by employing a contact-lens-type sensor can be an alternative approach for noninvasive glucose monitoring,” the researchers wrote.

“Everyone knows tears have a lot to mine,” Shih said. “The question is, whether you have a detector that is capable of mining it, and how significant is it for real diagnostics.”

In addition to Shih, authors on the paper include Yeon Sik Jung, Jae Won Jeong and Kwang-Min Baek, all with the Korea Advanced Institute of Science and Technology; Seung Yong Lee of the Korea Institute of Science and Technology, and Md Masud Parvez Arnob of UH.

Although non-invasive glucose sensing is just one potential application of the technology, Shih said it provided a good way to prove the technology. “It’s one of the grand challenges to be solved,” he said. “It’s a needle in a haystack challenge.”

Scientists know that glucose is present in tears, but Shih said how tear glucose levels correlate with blood glucose levels hasn’t been established. The more important finding, he said, is that the structure is an effective mechanism for using surface-enhanced Raman scattering spectroscopy.

Although traditional nanofabrication techniques rely on a hard substrate – usually glass or a silicon wafer – Shih said researchers wanted a flexible nanostructure, which would be more suited to wearable electronics. The layered nanoarray was produced on a hard substrate but lifted off and printed onto a soft contact, he said.

Here’s a link to and a citation for the paper,

Wafer Scale Phase-Engineered 1T- and 2H-MoSe2/Mo Core–Shell 3D-Hierarchical Nanostructures toward Efficient Electrocatalytic Hydrogen Evolution Reaction by Yindong Qu, Henry Medina, Sheng-Wen Wang, Yi-Chung Wang, Chia-Wei Chen, Teng-Yu Su, Arumugam Manikandan, Kuangye Wang, Yu-Chuan Shih, Je-Wei Chang, Hao-Chung Kuo, Chi-Yung Lee, Shih-Yuan Lu, Guozhen Shen, Zhiming M. Wang, and Yu-Lun Chueh. Advanced Materials DOI: 10.1002/adma.201602697 Version of Record online: 26 SEP 2016

© 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim

This paper is behind a paywall.