New nanomaterial acts as molecular thermometer

The layered material developed by KAUST specialists can act as an accurate temperature sensor using the same principle as in biological ion channels. The research results are published by ACS Nano.

Human cells have different proteins that act as channels for charged ions. In the skin, the ion channels rely on heat to control the flow of particles, which generates electrical signals that a person uses to measure ambient temperature.

Inspired by these biological sensors, KAUST researchers have prepared a titanium carbide compound (Ti3C2Tx) known as MXene.

MXenes is a class of two-dimensional inorganic compounds. These materials consist of layers several atom thick carbides, nitrides or carbonitrides of transition metals. Each layer is covered with negatively charged atoms such as oxygen or fluorine.

These groups act as separators separating adjacent nano-sheets, allowing water molecules to penetrate into interplanar channels. Channels between layers of MXene are already more than one nanometer.

The researchers used X-ray diffraction and scanning electron microscopy to study a new compound and found that adding water to the material slightly expands the channels between the layers. When the material touched the potassium chloride solution, the passages were large enough to allow positively charged potassium ions to pass through MXene, but blocked the passage of negative chlorine ions.

A team of scientists created a small device containing MXene and exposed one end to sunlight. MXenes are particularly effective in absorbing sunlight and converting this energy into heat. The resulting increase in temperature has induced water molecules and potassium ions to flow through the nano channels from cooler end to warmer end. This thermosmotic flow caused a voltage change comparable to that observed in temperature-sensitive biological ion channels. As a result, the device can reliably detect temperature changes of less than 1°C.