Tag Archives: #transistor

Ultrasensitive Transistor for Herbicide Detection in Water (Engineering)

A new polymer-based, solid-state transistor can more sensitively detect a weed killer in drinking water than existing hydrogel-based fluorescence sensor chips. The details were published in Chemistry-A European Journal.

University of Tokyo researchers have fabricated a tiny electronic sensor that can detect very low levels of a commonly used weed killer in drinking water. ©Institute of Industrial Science, the University of Tokyo

The sensor is a specially designed organic thin-film transistor based on semiconducting molecules of carboxylate-functionalized polythiophene (P3CPT). What’s special about this particular device is that, unlike other conjugated polymer-based sensors, this one is a solid-state device that can conduct an electric current when placed inside a fluid.

The device, designed by Tsuyoshi Minami of The University of Tokyo’s Institute of Industrial Science and colleagues, works by adding copper ions, which bind to the P3CPT molecules. When the device is placed in water that contains even the smallest amount of the herbicide glyphosate, the copper ions leave the P3CPT molecules to attach to the glyphosate molecules. This causes a detectable reduction in the flow of electric current through the device. Glyphosate is a commonly used weed killer in agriculture, and there are concerns that its presence in drinking water can be harmful to human health.

The scientists found that the device was so sensitive that it could detect as low as 0.26 parts per million of glyphosate in drinking water. The team compared their new device to a conventional fluorescence sensor chip, which was only capable of detecting down to 0.95 parts per million of glyphosate. To put this into perspective, the maximum allowable amount of glyphosate in drinking water, according to the United States Environmental Protection Agency, is 0.7 parts per million.

The scientists believe that the sensitivity of their device boils down to interactions occurring within individual polymer molecules and between neighbouring ones. Commonly used fluorescence sensors depend solely on interactions occurring within individual molecules.

“Our device could be a novel solid-state platform for sensing target molecules in aqueous media,” says Minami. The researchers are currently working on further developing their polythiophene-based sensors.

References: Dr. Yui Sasaki Koichiro Asano Dr. Tsukuru Minamiki Zhoujie Zhang Dr. Shin‐ya Takizawa Dr. Riku Kubota Prof. Dr. Tsuyoshi Minami, “A Water‐Gated Organic Thin‐Film Transistor for Glyphosate Detection: A Comparative Study with Fluorescence Sensing”, Chem. Eur. J. 2020, 26, 14525. https://chemistry-europe.onlinelibrary.wiley.com/doi/10.1002/chem.202003529

Provided by IIS, University of Tokyo

About Institute of Industrial Science (IIS), the University of Tokyo

Institute of Industrial Science (IIS), the University of Tokyo is one of the largest university-attached research institutes in Japan.

More than 120 research laboratories, each headed by a faculty member, comprise IIS, with more than 1,000 members including approximately 300 staff and 700 students actively engaged in education and research. Our activities cover almost all the areas of engineering disciplines. Since its foundation in 1949, IIS has worked to bridge the huge gaps that exist between academic disciplines and real-world applications.

Scientists Developed New Design Principles For Spin Based Quantum Materials (Quantum)

Northwestern University materials scientists have developed new design principles that could help spur development of future quantum materials used to advance (IoT) devices and other resource-intensive technologies while limiting ecological damage.

A crystal structure (left) and a visual model of the spin helix (right). Credit: Northwestern University

The study marks an important step in Rondinelli’s efforts to create new materials that are non-volatile, energy efficient, and generate less heat—important aspects of future ultrafast, low-power electronics and quantum computers that can help meet the world’s growing demand for data.

Rather than certain classes of semiconductors using the electron’s charge in transistors to power computing, solid-state spin-based materials utilize the electron’s spin and have the potential to support low-energy memory devices. In particular, materials with a high-quality persistent spin texture (PST) can exhibit a long-lived persistent spin helix (PSH), which can be used to track or control the spin-based information in a transistor.

Although many spin-based materials already encode information using spins, that information can be corrupted as the spins propagate in the active portion of the transistor. The researchers’ novel PST protects that spin information in helix form, making it a potential platform where ultralow energy and ultrafast spin-based logic and memory devices operate.

The research team used quantum-mechanical models and computational methods to develop a framework to identify and assess the spin textures in a group of non-centrosymmetric crystalline materials. The ability to control and optimize the spin lifetimes and transport properties in these materials is vital to realizing the future of quantum microelectronic devices that operate with low energy consumption.

The limiting characteristic of spin-based computing is the difficulty in attaining both long-lived and fully controllable spins from conventional semiconductor and magnetic materials. Their study will help future theoretical and experimental efforts aimed at controlling spins in otherwise non-magnetic materials to meet future scaling and economic demands.

Rondinelli’s framework used microscopic effective models and group theory to identify three materials design criteria that would produce useful spin textures: carrier density, the number of electrons propagating through an effective magnetic field, Rashba anisotropy, the ratio between intrinsic spin-orbit coupling parameters of the materials, and momentum space occupation, the PST region active in the electronic band structure. These features were then assessed using quantum-mechanical simulations to discover high-performing PSHs in a range of oxide-based materials.

The researchers used these principles and numerical solutions to a series of differential spin-diffusion equations to assess the spin texture of each material and predict the spin lifetimes for the helix in the strong spin-orbit coupling limit. They also found they could adjust and improve the PST performance using atomic distortions at the picoscale. The group determined an optimal PST material, Sr3Hf2O7, which showed a substantially longer spin lifetime for the helix than in any previously reported material.

Their approach provides a unique chemistry-agnostic strategy to discover, identify, and assess symmetry-protected persistent spin textures in quantum materials using intrinsic and extrinsic criteria. They proposed a way to expand the number of space groups hosting a PST, which may serve as a reservoir from which to design future PST materials, and found yet another use for ferroelectric oxides—compounds with a spontaneous electrical polarization. Their work will also help guide experimental efforts aimed at implementing the materials in real device structures.

This study has been republished from Science daily.

References: Xue-Zeng Lu, James M. Rondinelli. Discovery Principles and Materials for Symmetry-Protected Persistent Spin Textures with Long Spin Lifetimes. Matter, 2020; DOI: 10.1016/j.matt.2020.08.028 link: https://www.cell.com/matter/fulltext/S2590-2385(20)30455-0?_returnURL=https%3A%2F%2Flinkinghub.elsevier.com%2Fretrieve%2Fpii%2FS2590238520304550%3Fshowall%3Dtrue