Inorganic—Carbon Nanomaterial Composites for Chemical Sensing

Carbon nanomaterials have been demonstrated to be excellent transducer materials for chemical sensing. Their high surface to volume ratio, high conductivity, and nanoscale dimensions allow them to be incorporated into miniaturized, low power consumption devices. The attachment of receptors to carbon nanomaterials as an analyte recognition layer is crucial for achieving selective and sensitive chemical sensing. The hybridization of carbon nanomaterials with metals, metal oxides, and other inorganic materials has created a new class of materials, inorganic—carbon nanomaterial composites. These composites seek to combine the properties of inorganic materials with the aforementioned properties of carbon nanomaterials. The surface chemistry and electronic structure of these composites are important for various applications, including chemical sensing. In this work we describe the synthesis and characterization of novel inorganic—carbon nanomaterial composites. Attachment of the inorganic materials to the carbon nanomaterial layer was achieved through both covalent and noncovalent methods. Characterization of these composites was performed with electron microscopy, X-ray diffraction, photoelectron spectroscopy, fluorescence spectroscopy, Raman spectroscopy, electrical measurements, and gas adsorption measurements. Most of the described inorganic—carbon nanomaterial composites were incorporated into chemiresistor devices for chemical gas sensing. The indium oxide/single-walled carbon nanotube composite was found to be sensitive to volatile organic compounds such as ethanol and acetone, while the carbon nitride/reduced graphene oxide composite was sensitive to inorganic gases such as oxygen and carbon dioxide. The sensing mechanisms for these inorganic—carbon nanomaterial composites are explored and discussed. A new photoredox sensing mechanism was demonstrated for the carbon nitride/reduced graphene oxide composite. Tuning the electronic structure of carbon nitride/reduced graphene oxide with copper nanoparticles was found to change the sensor sensitivity toward carbon dioxide. Through hybridization of carbon nanomaterial with new inorganic materials like zeolitic imidazolate frameworks (ZIF) and carbon nitride, we have shown that carbon nanomaterial composites can achieve new properties such as microporosity and photoexcited charge carriers, respectively. Combining these properties with those of carbon nanomaterials will benefit a variety of applications including chemical sensors, (photo)electrocatalysts, and energy storage devices, among others.