Nitrogen-doped hollow carbon spheres as chemical vapour sensors

This study reports on low nitrogen content-doped hollow carbon spheres (N-HCSs) for use as chemical vapour sensors. The N-HCSs were prepared by a template-assisted chemical vapour deposition method followed by nitrogen doping in an ammonia atmosphere. Raman spectroscopy data displayed an increase in...

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Bibliographic Details
Published in:New journal of chemistry 2019-06, Vol.43 (22), p.8418-8427
Main Authors: Mutuma, Bridget K, Garcia-Martinez, Clara I, Dias, Rodrigo C, Matsoso, Boitumelo J, Coville, Neil J, Hümmelgen, Ivo A
Format: Article
Language:English
Subjects:
Acetone
Ammonia
Annealing
Carbon
Chemical sensors
Chemical vapor deposition
Chloroform
Dependence
Doping
Graphitization
Heat treatment
Humidity
Lactic acid
Methanol
Morphology
Nitrogen
Organic chemistry
Raman spectroscopy
Sensors
Thermal stability
Toluene
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Summary:This study reports on low nitrogen content-doped hollow carbon spheres (N-HCSs) for use as chemical vapour sensors. The N-HCSs were prepared by a template-assisted chemical vapour deposition method followed by nitrogen doping in an ammonia atmosphere. Raman spectroscopy data displayed an increase in the I D / I G ratio of the carbons upon N-doping indicating the creation of structural defects in the hollow carbon spheres (HCSs). The XPS results showed the N-HCSs had a very low N content (0.6 at%) comprising predominantly pyridinic-N (35%) and pyrrolic-N (48%) configurations. Annealed HCSs obtained by thermal annealing in Ar exhibited a lower I D / I G ratio and higher thermal stability than the N-HCSs. The HCSs-based sensors were exposed to varying concentrations of acetone, water, lactic acid, ammonia, toluene, chloroform and methanol vapours at room temperature. Low detection limits for toluene (15 ppm), lactic acid (12 ppm) and ammonia (6 ppm) were established for the N-HCSs-based sensors. The methanol sensitivity for the N-HCSs was recorded to be 5 times higher than that of related rGO based sensors. This was ascribed to the moderate degree of graphitization, hollow carbon morphology and the electron-rich N-HCS surface. Most importantly, the water dependency for the N-HCSs was lower than that of the un-doped HCSs. This indicated the effect of heat treatment and post-nitrogen doping of the HCSs in significantly lowering the humidity dependency of the carbon. Thus, the results suggested that the N-HCSs nanostructures are potential candidates for humidity-insensitive environmental sensing devices for the detection of various chemical vapours. The sensitivities of N-HCSs and annealed HCSs towards various analytes revealing a decrease in water sensitivity of the N-HCSs.
ISSN:1144-0546
1369-9261
DOI:10.1039/c9nj00628a