Table 3. FTIR vibration peaks and their corresponding functional group.

Vibration assignment	Functionalized graphene	Cysteamine treated graphene	Glutaraldehydetreated graphene	Enzyme coupled graphene
C-H deformation				673
C-H bending of arenes		847	864	775, 844, 872
N-O aliphatic		971	923	962
C-O stretch	1030, 1120	1112	1131	1124
C = S stretch		1049	1048	1040, 1089
C = O amide I bond				1192, 1296
O-H bending in plane	1385	1396		1336, 1382, 1403
Amide II bond		1487, 1592		1481, 1576
Amide I band			1643	1621
C = C asymmetric stretch			1934	1908
-N = C = O or C?C stretch		2088	2097, 2244	2099
O-H (acids) stretch		3028	2418, 2919	2916
O-H stretch	3436	3426	3428