We reported the synthesis of graphenated-carbon nanotubes (G-CNTs) using a floating catalyst chemical vapour deposition (FCCVD) method and formed a bulk-cotton-like structure. The objectives of this work were to study the effect of the injection rate parameter of the carbon source on the formation of G-CNTs and CNTs and later to test them as an ammonia gas sensor. Ethanol, thiophene, and ferrocene were mixed and injected into FCCVD at 1150°C. The as-synthesized samples were then characterized using FESEM, HRTEM, TGA, Raman spectroscopy, XPS, and electrical conductivity measurement. We found that the injection rate of 5 ml/h was suitable for the formation of G-CNTs and a higher injection rate resulted in the formation of CNTs. Our measurement showed that the electrical conductivity response of G-CNTs was higher compared to that of CNTs. The gas-sensing performance of the gas sensor made of G-CNT materials also showed good response compared to that of CNTs. This experimental work paved the way for how we can selectively synthesize CNTs and G-CNTs via the FCCVD method, and G-CNTs have proven to be a better material for gas sensors.

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