Supporting Information for
Study on the surfaceenergies and dispersibility of graphene oxide and its derivatives
Jinfengdai, Guojian Wang, Lang Ma,Chengken Wu
Further experimental details
IGC measurements and theory:
For the determination of thermodynamic surface parameters, the net retention volumeVn is computed according to Eq. (1):[1, 2]
(1)
(2)
Where F is the flow rate, tr and t0 are the retention and dead times respectively, p0 is thepressure at the flow meter, pw is the vapor pressure of water at the temperature of the flow meter (Tmeter), and the Tc is the column temperature. j is the James-Martin compressibility factor for the correction of gas compressibility when the column inlet (pi) and outlet (p0) pressure are different and it is given by Eq. (2)[1, 2]
According to Fowkers[3], the surface free energy of solid, , which can be considered to be a sum of a dispersive component, , due to van der Waals interactions, and a specific component, , such as acid–base interactions, hydrogen-bonding, or π-π stacking. The value of stationary phase is measured when n-alkanes are used as probes, and can be obtained according to Dorris and Gray method[4]. Where for n-alkanes is plotted against the number of carbon atoms of the probe, the can be determined from the slope of the resulting line. Then, the can be calculated using the following Eq. (3), as seen in Figure S2:
(3)
Where is the Avogadro constant, is the area of a –CH2– group (0.06 nm2) and the surface energy of a solid consisting of only –CH2– groups. The value of with temperature can be obtained by Eq. (4):
(4)
If the polar probes are injected, both dispersive and specific interactions are established with the solid surface, , being the adsorption free energy, defined by Eq. (5)[2, 5, 6]:
(5)
Where is the adsorption free energy of dispersive interaction; While is the specific interaction contributions to which reflects specific interaction (such as acid–base interactions, hydrogen-bonding, or π-π stacking) between chemical surface and probes. The value of is difficult to obtain through Dorris and Gray method. however, can be plotted against the molecular polarizabilities (PD) of the probes according to an approach defined by Dong et al.[7] The value of results from the distance between the value of polar probe and the straight n-alkanes line, as shown in Figure S3.
From these values, polar surface energies of solid () are calculated using the following Eq. (6)[8, 9] based on the theory of Good-Van Oss[10, 11]:
(6)
Where and are the acidic and basic parameters of the solid surface, respectively, and and are the acidic and basic parameters of the probe molecules, respectively. In our work, we adopted DCM and EtAc as a monopolar acidic probe and a monopolar basic probe, and their acidic and basic parameters (using as 0.0 mJ·m-2 and as 5.20 mJ·m-2; assuming to be 0.0 mJ·m-2 and to be 19.2 mJ·m-2) are provided.Consequently, the is determined according to Eq. (7)[10, 11]:
(7)
Once the and are obtained, the total surface energy () is calculated as following Eq. (8):
(8)
Tables
Table S1 The physicochemical properties of probes
Probe / (Å)2 / PD(cm3﹒mol-1)* / AN
(kJ﹒mol-1) / DN
(kJ﹒mol-1) / Specific
Character
C6 / 51.5 / 29.9 / - / - / neutral
C7 / 57.0 / 34.6 / - / - / neutral
C8 / 62.8 / 39.2 / - / - / neutral
C9 / 69.0 / 43.8 / - / - / neutral
DCM / 31.5 / 16.4 / 16.4 / 0 / acidic
EtAc / 48.0 / 22.2 / 6.3 / 71.7 / amphoteric (stongly basic)
THF / 45.0 / 20.0 / 2.1 / 84.4 / basic
* Molecular Deformation Polarizability
Table S2 EA, XPS data of samples
Sample / Element / EA (wt %) / XPS (at %)GO / C / 65.14 / 68.6
O / 33.35 / 31.0
N / 0.17 / 0.4
C/O / 2.60 / 2.21
COOH-GO / C / 68.94 / 72.4
O / 29.54 / 27.6
C/O / 3.11 / 2.62
EG-rGO / C / 79.87 / 83.3
O / 19.36 / 16.7
C/O / 5.50 / 4.98
rGO / C / 91.56 / 90.6
O / 6.91 / 8.2
N / 1.34 / 1.2
C/O / 17.67 / 11.0
Table S3 Quantitative comparison of C1s and O1s peaks for samples
Sample / C 1s (%) / O 1s (%)sp2/284.6eV / C-O/286.3eV / C=O/288.1eV / O-C/533.2eV / O=C/531.5eV
GO / 41.5 / 45.4 / 13.1 / 70.9 / 29.1
COOH-GO / 49.8 / 33.8 / 16.4 / 41.6 / 58.4
EG-rGO / 67.8 / 23.6 / 8.6 / 59.4 / 40.6
rGO / 72.8 / 7.1 / 3.4 / 48.9 / 51.1
Figures
Fig. S1 High resolution O1s XPS spectra of GO, COOH-GO, EG-rGO and rGO
Fig. S2 The plot of Vs. carbon number
Fig. S3 Determination of for polar probes by Dong`s method
Fig.S4 Dispersion states of GO, COOH-GO, EG-rGO and rGOversus the dispersive components (δD) of solvents
Fig. S5. AFM images of GO/DMF, COOH-GO/DMF, EG-rGO/NMP and rGO/NMP
References
1. Conder JR, Young. CL (1979) Physicochemical measurement by gas chromatography. John Wiley and Sons: Chichester.
2. Santos JMRCA, Guthrie JT (2005) Study of a core-shell type impact modifier by inverse gas chromatography. J Chromatogr A 1070(1-2): 147-154.
3. Fowkes FM (1964) Attractive forces at interfaces. Industrial & Engineering Chemistry 56(12): 40-52.
4. Dorris GM, Gray DG (1980) Adsorption of n-alkanes at zero surface coverage on cellulose paper and wood fibers. J Colloid Interface Sci 77(2): 353-362.
5. Laub RJ (1980) Physicochemical measurement by gas chromatography J High ResolutChromatogr 3(9): 486-486.
6. Santos JMRCA, Fagelman K, Guthrie JT (2002) Characterisation of the surface Lewis acid-base properties of poly(butylene terephthalate) by inverse gas chromatography. J Chromatogr A 969(1-2): 111-118.
7. Dong S, Brendlé M, Donnet JB (1989) Study of solid surface polarity by inverse gas chromatography at infinite dilution. Chromatographia 28(9-10): 469-472.
8. Traini D, Young P, Thielmann F, Acharya M (2008) The influence of lactose pseudopolymorphic form on salbutamol sulfate-lactose interactions in DPI formulations. Drug Dev Ind Pharm 34(9): 992-1001.
9. Das SC, Larson I, Morton DA, Stewart PJ (2010) Determination of the polar and total surface energy distributions of particulates by inverse gas chromatography. Langmuir 27(2): 521-523.
10. Van Oss C, Good R, Chaudhury M (1988) Additive and nonadditive surface tension components and the interpretation of contact angles. Langmuir 4(4): 884-891.
11. Van Oss CJ, Chaudhury MK, Good RJ (1988) Interfacial Lifshitz-van der Waals and polar interactions in macroscopic systems. Chem Rev 88(6): 927-941.