Co-porphyrin functionalized CVD graphene ammonia sensor with high selectivity to disturbing gases: hydrogen and humidity

Abstract

Recently low-power, small gas sensors have been strongly demanded to realize "super smart society." In particular, ammonia: NH 3 sensors are expected to be key devices for breath diagnosis. However, it is difficult for NH 3 sensors to obtain high selectivity against hydrogen: H 2 , since conventional metal-oxide gas sensors respond to any reducing gases. In this study, Co-porphyrin functionalized graphene sensors were fabricated, and selective NH 3 sensing was realized by the selective metal-ligand bond of Co with NH 3 . The sensor successfully detected sub-ppm NH 3 , while it showed no response to high concentration H 2 . Furthermore, we investigated the effect of humidity on the Co-porphyrin functionalized graphene NH 3 sensor. We demonstrated the detection of low concentration NH 3 even under rapid humidity changes. We considered that the key sensing mechanism of our sensor is charge transfer to graphene by the electronic structure change of Co-porphyrin-graphene complexes due to NH 3 adsorption on Co-porphyrin.

Stable Cobalt Porphyirn Ometed Type Small Molecule Sensor for the Sensitive and Selective Detection of Ammonia Gas at Room Temperature

“…Additionally, with deference to the entire sensing procedure, the excellent electrical conductivity of PCo, as well as the attraction of PCo, were promising due to the Co atom for active electron conduction throughout the sensing development process. Further, PCo contains a promising amount of sp 2 bonded carbons, vacancies, structural defects, and residual oxygen groups, and the Co atom's d‐electrons helps intra charge transfer is created an overlap between Co atom's d‐electrons and Po p‐electrons by a large wave function, the (d xz ) 2 (d yz ) 2 (d z 2 ) 1 (d x 2 − y 2 ) create a hole‐transporting matrix, [ 21,26 ] which also acts as a p‐type semiconductor. The absorbed NH 3 molecules in the sensing process were also capable of transferring electrons to the PCo surface, resulting in increased resistance.…”

A Review on Functionalized Graphene Sensors for Detection of Ammonia

“…Besides, porphyrins and phthalocyanines with different coordinated metals were used to functionalize graphene for improving the performance of the NH 3 sensors [ 104 ]. For example, the Co-porphyrin/CVD-G sensor showed six times greater response to NH 3 compared to non-functionalized graphene [ 105 ]. The Co-phthalocyanine/rGO sensor also showed a higher and faster response for low concentration of NH 3 (~2.5% and 45 s for 100 ppb NH 3 ) [ 106 ].…”

Functionalized Graphene Surfaces for Selective Gas Sensing

“…Recently, hybrid Co porphyrin (CoOEP–2,3,7,8,12,13,17,18-Octaethyl-21 H ,23 H -porphine cobalt(II))/CVD graphene were evaluated as gas sensing materials. 12 To functionalize the CVD graphene film, a saturated chloroform Co porphyrin solution was spin-coated onto a graphene sensor array ( Figure 3 a). Successful graphene functionalization was evidenced by the XPS measurements of the hybrids indicating characteristic features of pyrrole rings in Co porphyrin and C=C bonds in the graphene network.…”

“… (a) Schematic of a CoOEP/graphene sensor. 12 (b) Selectivity of CoOEP/graphene sensor for ammonia against hydrogen. Adapted with permission from ref ( 12 ).…”