A new material that possesses high transparency in the visible and near infra-red (NIR) range and is also highly conducting could have promising application as transparent electrodes (TEs) in optoelectronic devices.

TEs are one of the critical components of optoelectronic devices and are based on materials that can be tuned to become simultaneously optically transparent and electrically conductive. These fundamentally contrasting attributes make it applicable in areas extending from energy generation and emission devices to gas sensors, low-emissivity windows, thermoelectric generators, and flat panel displays.

The most widely used TEs are based on metal oxide thin films like tin-doped indium oxide (ITO), fluorine-doped tin oxide (FTO), and aluminium-doped zinc oxide (AZO), with ITO extensively used for its high optical transparency in the visible range and low electrical resistivity.

Alongside the relatively low NIR transparency of the metal-oxide TEs, the scarcity, high cost and cytotoxicity of tin, toxicity of fluorine, and poor chemical stability of zinc oxide necessitate the development of new high-NIR transmittance TE with high visible transparency.

The development of infrared (IR) transparent electrodes (specifically in the near-infrared range) is crucial for improving the efficiency of certain optoelectronic devices and opening up applications in emerging areas like IR photodetectors, IR switching devices, sensors, and modulators for telecommunication.

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Researchers at IIT-Gandhinagar, have developed a material with high transparency in the visible and NIR range that is highly conducting. Moreover, its abundance (hence cost-effectiveness), non-cytotoxicity, and chemical inertness make it a promising alternative, says a press release.

Low-cost stroke diagnosis

Researchers at the Indian Institute of Technology, Mandi, in collaboration with PGIMER Chandigarh have developed a simple, portable and cost-effective device to detect and diagnose stroke caused by impaired blood flow to the brain.

Ischemic stroke caused by insufficient or interrupted blood supply to parts of the brain affects one in 500 Indians each year.

Surveys have shown that 10-15 per cent of all strokes affect people below 40 years of age. The efficient management and treatment of stroke depends upon early identification and diagnosis.

Currently, magnetic resonance imaging (MRI) and computer tomography (CT) techniques are considered the gold standard for ischemic stroke detection. While these are indeed reliable methods, they require considerable infrastructure and high cost, and are inaccessible to many in India — there is only one MRI service for every one million people in the country.

“We are working towards finding a low-cost diagnostic technique to precisely detect ischemic stroke at the point of care so that such tests can be used in rural, poor and remote areas.

“Our team has designed and developed a small wearable device that makes use of near-infrared spectroscopy to detect ischemic stroke.

“In this device, a near-infrared light emitting diode (NIRS LED) emits light in the range of 650 nm to 950 nm. This light interacts with the coloured components of the blood like haemoglobin and provides information on blood characteristics such as regional oxygen saturation, regional oxygen consumption, and regional blood volume index,” says Dr Shubhajit Roy Chowdhury, Associate Professor, IIT-Mandi.