Table 2.
Graphene oxide (GO)/support material characterization techniques (gas separation applications) a.
| Characterization Approach | Measurements | References | Major Findings |
|---|---|---|---|
| SEM (FE-SEM) | Size and distribution of the GO flakes | [2,3,4,5,41] | GO particle size of 0.1–20 µm |
| TEM | Thinness and curliness of the GO nanosheets | [2,5,41] | Effectiveness of the method of exfoliation |
| AFM | Surface morphology and depth profile of the GO membrane | [2,3,4,5,34,41] | Thickness of a single GO layer of 0.7–0.9 nm |
| XPS | Surface chemical composition | [3,4,5] | Density of different bonds, e.g., C = C (28.04%), C–C (13.79%), C = O (27.11%), C–O (14.62%), O–C = O (12.52%) |
| XRD | Amount of GO content and curvature in the polymeric support for GO membranes | [4,5,41] | GO has a peak 2θ at 11.1° |
| FTIR | Analysis of the functional groups | [4,5,41] | Functional groups in the form of stretching vibrations of different bonds, e.g., O–H (3400 cm−1), C = O (1720 cm−1), C = C skeletal (1620 cm−1), C–O carboxyl (1390 cm−1), C–O epoxy (1195 cm−1), and C–O alkoxy (1035 cm−1) |
| Raman spectroscopy | Structural integrity of the GO membrane | [3,4,5,41] | GO powder: G band at 1585 cm−1 and D band at 1338 cm−1 |
| WCA | Wettability of the GO membrane | [5] | GO membrane WCA of 46.7 ± 1.1° |
| DLS | Particle size distribution | [34] | Particle size distribution of the GO membrane, e.g., 10 µm (30%), 20 µm (40%) |
| TGA | Weight percentage of GO or a GO–polymer composite with variation in temperature | [41] | Weight percentage of GO or a GO–polymer composite at different temperatures |
a SEM, scanning electron microscopy; FE-SEM, field emission scanning electron microscopy; TEM, transmission electron microscopy; AFM, atomic force microscopy; XPS, X-ray photoelectron spectroscopy; XRD, X-ray diffraction; FTIR, Fourier-transform infrared spectroscopy; WCA, water contact angle; DLS, dynamic light scattering; TGA, thermogravimetric analysis.