Gas Sensors Based on Locally Heated Multiwall Carbon Nanotubes Decorated with Metal Nanoparticles

Abstract

We report the design and fabrication of microreactors and sensors based on metal nanoparticle-decorated carbon nanotubes. Titanium adhesion layers and gold films were sputtered onto Si/SiO2substrates for obtaining the electrical contacts. The gold layers were electrochemically thickened until 1 μm and the electrodes were patterned using photolithography and wet chemical etching. Before the dielectrophoretic deposition of the nanotubes, a gap 1 μm wide and 5 μm deep was milled in the middle of the metallic line by focused ion beam, allowing the fabrication of sensors based on suspended nanotubes bridging the electrodes. Subsequently, the sputtering technique was used for decorating the nanotubes with metallic nanoparticles. In order to test the as-obtained sensors, microreactors (100 μL volume) were machined from a single Kovar piece, being equipped with electrical connections and 1/4′′ Swagelok-compatible gas inlet and outlets for controlling the atmosphere in the testing chamber. The sensors, electrically connected to the contact pins by wire-bonding, were tested in the 10−5to 10−2 W working power interval using oxygen as target gas. The small chamber volume allowed the measurement of fast characteristic times (response/recovery), with the sensors showing good sensitivity.

A review on recent advances of CNTs as gas sensors

“…In this review, examples of metal nanoparticle-modified gas sensors have been introduced by Penza et al (2010) and Leghrib et al (2010). Recently, Savu et al (2015) also has shown another approach to fabricating gas sensors based on CNTs decorated with metal (Ti and Cu) nanoparticles through a sputtering technique. MWCNTs were suspended on two opposing gold terminals connected to an electrical supply and were deposited by a DEP method.…”

Carbon Nanotube‐Based Chemical Sensors

“…Since the pioneering work reporting on the response of a CNTFET for ammonia and NO 2 exposures, there have been a large number of studies on the use of carbon nanotubes for sensing gases and vapors . The subject coverage includes a wide range of topics: types of nanotubes (SWCNTs, MWCNTs), doping/coating/metal loading/functionalization strategies, different gases and vapors, different transduction approaches (electrical, optical, etc.…”

A Review of Implementing ADC in RFID Sensor

“…A previous microreactor containing one CNT microsensor inside has already been fabricated following the same directions explained, but without any embedded electronics, being all measurements made from outside [22,59].…”

“…Oxidized silicon substrates (1), gold patterned electrodes (2), wire bonding connections (3), and the gap with DEP deposited carbon nanotubes (4) compose the device. The inset shows a closer view of the CNTs deposited between the gold electrodes[22].…”