Book excerpt: The book focuses on novel sensor materials and their environmental and healthcare applications, such as NO2 detection, toxic gas and biosensing, hydrazine determination, glucose sensing and the detection of toxins and pollutants on surfaces. Materials covered include catalytic nanomaterials, metal oxides, perovskites, zeolites, spinels, graphene-based gas sensors, CNT/Ni nanocomposites, glucose biosensors, single and multi-layered stacked MXenes, black phosphorus, transition metal dichalcogenides and P3OT thin films. Keywords: Toxic Gas Sensors, Biosensors, Nitrogen Dioxide Detection, Hydrazine Determination, Glucose Sensing, Catalytic Nanomaterials, Metal Oxides, Perovskites, Zeolites, Spinels, Graphene-based Gas Sensors, CNT/Ni Nanocomposites, Mxenes, Black Phosphorus, Transition Metal Dichalcogenides, P3OT Thin Films.