Reducing Humidity Response of Gas Sensors for Medical Applications: Use of Spark Discharge Synthesis of Metal Oxide Nanoparticles

Abstract

The application of gas sensors in breath analysis is an important trend in the early diagnostics of different diseases including lung cancer, ulcers, and enteric infection. However, traditional methods of synthesis of metal oxide gas-sensing materials for semiconductor sensors based on wet sol-gel processes give relatively high sensitivity of the gas sensor to changing humidity. The sol-gel process leading to the formation of superficial hydroxyl groups on oxide particles is responsible for the strong response of the sensing material to this factor. In our work, we investigated the possibility to synthesize metal oxide materials with reduced sensitivity to water vapors. Dry synthesis of SnO2 nanoparticles was implemented in gas phase by spark discharge, enabling the reduction of the hydroxyl concentration on the surface and allowing the production of tin dioxide powder with specific surface area of about 40 m2/g after annealing at 610 °C. The drop in sensor resistance does not exceed 20% when air humidity increases from 40 to 100%, whereas the response to 100 ppm of hydrogen is a factor of 8 with very short response time of about 1 s. The sensor response was tested in mixtures of air with hydrogen, which is the marker of enteric infections and the marker of early stage fire, and in a mixture of air with lactate (marker of stomach cancer) and ammonia gas (marker of Helicobacter pylori, responsible for stomach ulcers).

Aerosol Jet Printing of Silver Lines with A High Aspect Ratio on A Heated Silicon Substrate

“…Among the existing printing methods, aerosol jet printing is the most promising technology because it allows the formation of functional elements with a minimum lateral size of up to 10 microns [7][8][9] both on flat and curved substrates [10,11]. This technology has been applied for the manufacture of transistors [12], sensors [13][14][15], solar cells [16], microheaters [17], microantennas [18,19] and interconnects [20]. Previous studies of this technology relied mainly on the formation of thin-film microstructures due to the need for the manufacture of planar electronic devices.…”

Synthesis of Nanoparticles by Spark Discharge as a Facile and Versatile Technique of Preparing Highly Conductive Pt Nano-Ink for Printed Electronics

“…Experiments on the formation of narrow (about 30 μm) and conductive Pt lines were performed in order to optimize the parameters of nano-ink for AJP process [ 67 , 68 ]. Such lines are in demand as high-temperature and corrosion-resistant elements of various printed sensors [ 47 , 48 , 69 ]. The formation of Pt lines was carried out using the technology of AJP on a heat-resistant alumina substrate.…”

“…Platinum is a noble metal with excellent catalytic properties and high chemical stability [ 42 , 43 ]. In printed technologies, platinum is promising for the manufacture of corrosion-resistant current-carrying contacts [ 44 , 45 ], elements of gas [ 46 , 47 ], temperature [ 48 , 49 ] and biological [ 50 , 51 ] sensors. In our experiments, platinum nanoparticles (PtNPs) were synthesized by spark generator during electrical erosion of platinum electrodes in an atmosphere of Ar, N 2 , and air.…”

Gas sensing properties of individual SnO2 nanowires and SnO2 sol–gel nanocomposites

“…The effect of superficial hydroxy groups on the sensor cross-sensitivity to humidity was investigated in detail in [52]. It was shown that the application of tin dioxide materials synthesized by spark discharge and characterized as having a reduced concentration of superficial hydroxy groups resulted in a significantly decreased parasitic humidity response of the sensing material.…”