O. Monereo

Flexible sensor based on carbon nanofibers with multifunctional sensing features

Herein, we present the fabrication and characterization of a flexible gas sensor based on carbon nanofibers. The sensing device is composed of interdigitated silver electrodes deposited by inkjet printing on Kapton substrates, subsequently coated with carbon nanofibers as sensing element. Gas sensing response to CO, NH3 and humidity has been characterized in detail. Thermal, mechanical and electromagnetic radiation effects have also been studied and discussed from the point of view of the cross-sensitivity. The obtained results open the door for a new generation of flexible sensors with multifunctional sensing features, which are producible with scalable techniques based on low cost nanomaterials.

NO2 Measurements with RGB Sensors for Easy In-Field Test

We present a simple an inexpensive method to implement a Griess-Saltzman-type reaction that combines the advantages of the liquid phase method (high specificity, fast response time) with the benefits of a solid implementation (easy to handle). We demonstrate that the measurements can be carried out using conventional RGB sensors; circumventing all the limitations around the measurement of the samples with spectrometers. We also present a method to optimize the measurement protocol and target a specific range of NO2 concentrations. We demonstrate that it is possible to measure the concentration of NO2 from 50 ppb to 300 ppm with high specificity and without modifying the sensing elements.

Highly Specific and Wide Range NO2 Sensor with Color Readout

We present a simple and inexpensive method to implement a Griess-Saltzman-type reaction that combines the advantages of the liquid phase method (high specificity and fast response time) with the benefits of a solid implementation (easy to handle). We demonstrate that the measurements can be carried out using conventional RGB sensors; circumventing all the limitations around the measurement of the samples with spectrometers. We also present a method to optimize the measurement protocol and target a specific range of NO2 concentrations. We demonstrate that it is possible to measure the concentration of NO2 from 50 ppb to 300 ppm with high specificity and without modifying the Griess-Saltzman reagent.

Low-cost, low-power, heater-free solid state gas sensors based on pulsed self-heated nanostructures

Self-heating and pulsed self-heating operation modes are applied to the use of conductometric gas sensor devices. Self-heating is proven to occur in sensing active layers formed by large arrays of randomly deposited nanostructures, in particular, drop-casted carbon nanofibers. Using this methodology, cheaper gas sensor devices without heater can be fabricated. Moreover, the device power consumption is reduced by self-heating operation by at least two orders of magnitude. A temperature calibration, needed for non-controlled deposition techniques of the active film, is proposed. Self-heating and external heater operation is also compared and found to be equivalent. Pulsed self-heating mode is applied to further reduce the power consumption. A simple processed signal is obtained from pulsed operation, achieving high stability. Gas sensing characteristics are fully studied for both modes for humidity sensing as an example of application.

Sub-second humidity sensing using surface acoustic waves in electrospray-deposited carbon nanofiber and reduced graphene oxide structures

Propagation of surface acoustic waves in lithium niobate crystals with carbon nanofibers or reduced graphene oxide layers deposited by electrospray has been investigated. We show that the ambient air humidity variations affect the phase of the wave noticeably stronger than its amplitude. The response of both phase and amplitude to fast humidity changes is in the sub-second range. The capability of surface acoustic waves of monitoring the fast changes in nano-layer properties for sensing applications has been demonstrated.