PMID- 27143102
OWN - NLM
STAT- PubMed-not-MEDLINE
DCOM- 20180521
LR  - 20220317
IS  - 1520-5827 (Electronic)
IS  - 0743-7463 (Linking)
VI  - 32
IP  - 20
DP  - 2016 May 24
TI  - Colloidal Stability of Graphene Oxide: Aggregation in Two Dimensions.
PG  - 5058-68
LID - 10.1021/acs.langmuir.6b01012 [doi]
AB  - Colloidal stability of graphene oxide (GO) is studied in aqueous and organic 
      media accompanied by an improved aggregation model based on 
      Derjaguin-Landau-Verwey- Overbeek (DLVO) theory for ultrathin colloidal flakes. 
      It is found that both magnitude and scaling laws for the van der Waals forces are 
      affected significantly by the two-dimensional (2D) nature of GO. Experimental 
      critical coagulation concentrations (CCC) of GO in monovalent salt solutions 
      concur with DLVO theory prediction. The surface charge density of GO is largely 
      affected by pH. However, theoretical calculations and experimental observations 
      show that the colloidal stability of the 2D colloids is less sensitive to the 
      changes in the surface charge density compared to the classical picture of 3D 
      colloids. The DLVO theory also quantitatively predicts the colloidal stability of 
      reduced GO (rGO). The origin of lower stability of rGO compared to GO is rooted 
      in the higher van der Waals forces among rGO sheets, and particularly, in the 
      removal of negatively charged groups, and possibly formation of some cationic 
      groups during reduction. GO also exfoliates in the polar organic solvents and 
      results in stable dispersions. However, addition of nonpolar solvents perturbs 
      the colloidal stability at a critical volume fraction. Analyzing the aggregation 
      of GO in mixtures of different nonpolar solvents and N-methyl-2-pyrrolidone 
      proposed that the solvents with dielectric constants of less than 24 are not able 
      to host stable colloids of GO. However, dispersions of GO in very polar solvents 
      shows unexpected stability at high concentration (>1 M) of salts and acids. The 
      origin of this stability is most probably solvation forces. A crucial parameter 
      affecting the ability of polar solvents to impart high stability to GO is their 
      molecular size: the bigger they are, the higher the chance for stabilization.
FAU - Gudarzi, Mohsen Moazzami
AU  - Gudarzi MM
AD  - Department of Polymer Engineering and Colour Technology, Amirkabir University of 
      Technology , Tehran 15875-4413, Iran.
LA  - eng
PT  - Journal Article
DEP - 20160510
PL  - United States
TA  - Langmuir
JT  - Langmuir : the ACS journal of surfaces and colloids
JID - 9882736
EDAT- 2016/05/05 06:00
MHDA- 2016/05/05 06:01
CRDT- 2016/05/05 06:00
PHST- 2016/05/05 06:00 [entrez]
PHST- 2016/05/05 06:00 [pubmed]
PHST- 2016/05/05 06:01 [medline]
AID - 10.1021/acs.langmuir.6b01012 [doi]
PST - ppublish
SO  - Langmuir. 2016 May 24;32(20):5058-68. doi: 10.1021/acs.langmuir.6b01012. Epub 
      2016 May 10.