The application generally describes devices, systems, and methods for determination of one or more analytes. Embodiments described herein may be useful as sensors for analytes such as explosives, chemical warfare agents, and/or toxins. In some cases, chemiresistor or chemFET sensor devices for monitoring volatile organics, especially chemical warfare agents such as sarin, are described. Some embodiments comprise functionalized carbon nanotube/conjugated polymer composites (6) as sensing material. In some embodiments, the polymer is poly(3-hexylthiophene), 3PHT, optionally substituted with calixarenes, or hexafluoroisopropanol susbstituted polythiophene, HFIP-PT. Biosensing embodiments are also described, as well as methods of manufacturing the devices.