Ternary Nanocomposites Based on Oxidized Carbon Nanohorns as Sensing Layers for Room Temperature Resistive Humidity Sensing

Abstract

This paper presents the relative humidity (RH) sensing response of a resistive sensor employing sensing layers based on a ternary nanocomposite comprising graphene oxide-oxidized carbon nanohorns-polyvinylpyrrolidone (GO-CNHox–PVP), at 1/1/1, 1/2/1, and 1/3/1 w/w/w mass ratios. The sensing structure is composed of a silicon substrate, a SiO2 layer, and interdigitated transducers (IDT) electrodes, on which the sensing layer is deposited via the drop-casting method. The morphology and the composition of the sensing layers are investigated through scanning electron microscopy (SEM) and RAMAN spectroscopy. The RH sensing capability of each carbonaceous nanocomposite-based thin film was analyzed by applying a current between the two electrodes and by measuring the voltage difference when varying the RH from 0% to 100% in humid nitrogen. The sensors have a room temperature response comparable to that of a commercial humidity sensor and are characterized by a rapid response, excellent linearity, good sensitivity, and recovery time. The manufactured sensing devices’ transfer functions were established, and we extracted the response and recovery times. While the structures with GO/CNHox/PVP at 1/1/1 ratio (w/w/w) had the best performance in terms of relative sensibility, response time, and recovery time, the sensors employing the GO/CNHox/PVP nanocomposite at the 1/2/1 ratio (w/w/w) had the best linearity. Moreover, the ternary mixture proved to have much better sensing properties compared to CNHox and CNHox-PVP-based sensing layers in terms of sensitivity and linearity. Each component of the ternary nanocomposites’ functional role is explained based on their physical and chemical properties. We analyzed the potential mechanism associated with the sensors’ response; among these, the effect of the p-type semiconductor behavior of CNHox and GO, correlated with swelling of the PVP, was dominant and led to increased resistance of the sensing layer.

Ternary Holey Carbon Nanohorns/TiO2/PVP Nanohybrids as Sensing Films for Resistive Humidity Sensors

“…For instance, Figure 7b shows Raman spectra recorded in four different positions of the CNHox/TiO 2 /PVP = 2/1/1 (w/w/w) film plotted in red, grey, green, and blue colors. It can be observed that three active Raman bands (D, G, and 2D) were recorded at the wavenumbers of 1318.3, 1591.9, and 2627.8 cm −1 , which confirms the presence of the nanocarbonic material (CNHox) [27,30,34]. One can also identify specific anatase TiO 2 bands as follows: E g1 mode at 149.1 cm −1 (very sharp and intense in all the samples, except for 1/1/1), B 1g at 397.6 cm −1 , A 1g at 513.9 cm −1 , and E g3 at 634.7 cm −1 [47][48][49].…”

“…Holey carbon nanohorns (CNHox), a type of carbon nanohorns with increased hydrophilicity, have proven to be promising alternatives as a sensitive coating within the design of the RH chemoresistors [27]. Moreover, binary nanocomposites such as CNHox/PEG-PPG-PEG (poly (ethylene glycol)-poly block (propylene glycol)-poly block (ethylene glycol), CNHox/PVP (polyvinylpyrrolidone), and ternary nanocomposites from the type CNHox/GO (graphene oxide)/PVP were successfully explored as sensing layers for RH monitoring [28][29][30][31].…”

Quaternary Holey Carbon Nanohorns/SnO2/ZnO/PVP Nano-Hybrid as Sensing Element for Resistive-Type Humidity Sensor

“…[32][33][34]. Among these types of materials, one can mention, inter alia, graphene oxide [35][36][37], carbon nanotubes [38][39][40], amorphous carbon [41], nanodiamond [42,43], nanocones [44], fullerenes and their derivatives [45,46], carbon nanocoils [47], holey carbon nanohorns (CNHox) and their nanocomposites [48][49][50][51][52][53][54][55], hydrogenated amorphous carbon [56], oxidized carbon nanoonions [57][58][59][60], carbon quantum dots [61].…”

Road Map of Semiconductor Metal-Oxide-Based Sensors: A Review

“…H + or H 3 O + ions produced by the dissociation of adsorbed water on the surface are the conduction mechanism in metal-oxide-based humidity sensors. Recent works [ 226 , 227 ] studied and described the adsorption of water on metal oxide surfaces and the mechanism of sensing water vapor. As a result of water adsorption on metal oxide surfaces, humidity decreased the sensitivity of metal oxide sensors ( Figure 15 ) [ 228 , 229 ].…”