Chemical Detectors Using Nano Sensors

Before going into the intricacies of the topic it is essential for us to know about what a chemical detector is and what its functionality is. Chemical detecting equipment detects the harmful chemical agents present in the atmosphere. Having done with this, it detects the type of the agent and the area in which it is spread over. It also performs an important task of finding of the extent of contamination i.e. the degree to which the atmosphere has been polluted by the agents. For an equipment to be a good detector, it has to accomplish all the above mentioned tasks in the least possible time.

#-Link-Snipped-#Conventionally, these equipments needed power from an external source such as a battery to function accordingly. But today, with the advent of the nanosensors, the conventional batteries can be done away with and the equipment can work without a battery. The painstaking efforts of the Lawrence Livermore researchers have borne a fruit after all. The nanosensors being used in the process in turn depend on the semiconductor nanowires. Nanowires are basically threadlike structures which has the diameter of the order of 10 raised to (-9) and length as per the requirement. The Quantum mechanical effects become prominent at such small scales and hence these wires are also called as “quantum wires”.

Now when we talk about the working principle, it goes as follows. The nanosensors are triggered by the interaction between the chemical agents and the semiconducting nanowire surfaces. This causes the stimulation of an electric charge between either the two ends of the wire or the exposed and unexposed part of the wire. The battery less sensor was tested for different types of platforms out of which one was zinc oxide and silicon using ethanol solvent as the detecting agent. From the observations it was found that the voltage across the nanowires changed a bit when ethanol solvent was placed on the detector. It was also noticed that the rise in the electric voltage was instantaneous but the voltage dropped slowly as the ethanol began to evaporate. The same test was carried out with “hexane” as a solvent instead of ethanol. Again a voltage was seen. It was thus concluded that the detector responded to various type of molecules of the chemical agents.

A total of 15 different organic solvents were tried and different values of voltages were seen and recorded. This voltage signifies the type of solvent and the level of concentration of the gas in the atmosphere. More or less the same response was obtained when the solvents were tested for the silicon sensors. Nevertheless, the voltage drops using silicon sensors were very much different than that observed using zinc oxide sensors. A step further in this direction would be detection of somewhat more complex molecules coming from the explosives. The advantage of this detector over the battery powered detector is that it is simple to operate, highly sensitive and quickly detects various types of molecules. Owing to these advantages, these sensors can easily be deployed in the battlefields and in times of wars.

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