Composites of organic compounds and inorganic nanomaterials provide novel sensing platforms for high-performance sensor applications. The combination of the attractive functionalities of nanomaterials with polymers as an organic matrix offers promising materials with tunable electrical, mechanical, and chemisensitive properties. This review mainly focuses on nanocarbon/polymer composites as chemiresistors. We first describe the structure and properties of carbon nanofillers as reinforcement agents used in the manufacture of polymer composites and the sensing mechanism of developed nanocomposites as chemiresistors. Then, the design and synthesizing methods of polymer composites based on carbon nanofillers are discussed. The electrical conductivity, mechanical properties, and the applications of different nanocarbon/polymer composites for the detection of different analytes are reviewed. Lastly, challenges and the future vision for applications of such nanocomposites are described.

The present investigation deals with the fabrication of CO ₂ gas sensor based on La ₂ O ₃ /SnO ₂ metal-oxide material. In this paper, the sensitive material was prepared by La ₂ O ₃ /SnO ₂ nanopowder and the addition of 1 wt.% and 3 wt.% platinum (Pt) using high-speed ball milling method. The sensitive film prepared by sensitive powder was printed on alumina (Al ₂ O ₃ ) substrate by screen printing method. This film was characterized by X-Ray powder diffraction spectroscopy, and Field-emission scanning electron microscopy. As a result, the prepared 3 wt.% Pt/La ₂ O ₃ /SnO ₂ thick film sensitive paste exhibits a high sensitivity to increasing the CO ₂ gas concentration at 225 °C in air atmosphere.

The combination of graphene (G) and multi-walled carbon nanotubes (MWCNTs) creates three-dimensional hybrid structures particularly suitable as next-generation electrical interface materials. Nevertheless, efficient mixing of the nanopowders is challenging, unless previous disaggregation and eventual surface modification of both is reached. To avoid use of solvents and multistep purification process for synthesis of stable G/MWCNTs hybrids, herein, a novel dry method based on an air sonication process was used. Taking advantage from the vigorous turbulent currents generated by powerful ultrasonication in air that induces strong thermal convection or radiation to and from the particles, it simultaneously ensures disentanglement of the large MWCNT bundles and G exfoliation and their only mild surface modifications. By changing the ratio between MWCNTs and G, a range of hybrids was obtained, different in surface morphology and chemistry. These hybrids have shown great potential as sensing material for designing mass-based sensors for toxic gases and chemiresistor for vapors detection.

Thick film CO2 sensors were fabricated using La2O3/SnO2 loaded with Pt and in the unloaded form. The nano-crystalline powders of SnO2-La2O3-Pt synthesized by high speed ball milling method were screen-printed on alumina substrates. The resistance of fabricated sensors were measured against different CO2 concentration in the working temperature of 225 C. The composition that gives an acceptable resistivity for CO2 was in the 3wt.% ratio of Pt.

Both the electrical conductivity and tailored mechanical characteristics—showing flexibility and structural integrity—are key properties of polymer composites. In this work, a novel, simple, and water-based strategy for synthesizing rGO-MWCNT/polymer composites was developed. Namely, carbon nanofillers in a mixture of reduced graphene oxide (rGO) and multi-walled carbon nanotubes (MWCNTs) were incorporated in a waterborne methacrylic polymer matrix at loadings of 0.25, 0.5, and 1.0 wt.% nanofiller, and with rGO-to-MWCNT ratios of 10:1, 1:1, and 1:10 (w/w) at room temperature. Electrically conductive composites were obtained with all tested filler rates showing the highest conductivity (up to 8.2 × 10⁻³ Sm⁻¹) for the MWCNT-rich filler due to the formation of a segregated network of the filler in the matrix. The mechanical properties of the composites—characterized by their Young’s modulus and elongation at break—strongly depended on both the filler incorporation rate and the rGO:MWCNT ratio. For instance, soft and flexible composites were obtained by incorporating 0.25 wt.% of the MWCNT-rich filler, which increased the elongation at break from 154.2% (neat polymer) to 252.4%. Overall, this study emphasizes the sensitive interplay between carbon filler introduction incorporating conductivity and the fillers’ impact on the mechanical properties of a polymer composite, both necessitating careful optimization for applications, e.g., in flexible electronics.