7th IMRMPT

Abstract

Abstract information

English title:	Study of Dodecylamine functionalized Graphene Oxide as a molecular surfactant in water/oil systems
Spanish title:	Estudio del �xido de Grafeno funcionalizado con Dodecilamina como surfactante molecular en sistemas agua/aceite
English abstract:	Graphene oxide (GO) is a derivative of graphene obtained from the oxidation and chemical exfoliation of graphite. Its lamellar structure is mainly conformed by carbons that change from sp2 hybridization (typical of graphene) to sp3 by covalent bonding with oxygen atoms coming from carbonyl, carboxyl, hydroxyl, and epoxide functional groups formed during the oxidation process (Dimiev & Tour, 2014). The presence of these functional groups randomly distributed in the basal plane and at the edges of GO gives it a hydrophilic character that favors its dispersion in polar solvents, however, GO is an amphiphilic material because it retains in its basal plane pristine graphene domains that are hydrophobic. Despite the amphiphilicity, the diffusion of GO sheets to the interface is slow and the surface/interfacial activity is low (Valtierrez-gaytan et al., 2017), however, this can be adjusted by modifying the oxidation degree, the sheet size, the pH and the salinity of the medium or by covalent functionalization with different molecules through oxygenated functional groups (He et al., 2013; Kim et al., 2010; Yang et al., 2018). Recently, studies have been published on the chemical functionalization of GO with alkylamines by amidation reactions with carboxylic acids at the edge of the sheets and nucleophilic substitution reactions with epoxides on the basal plane. Lin et al. and Shanmugharaj et al. obtained superhydrophobic GO surfaces with improved thermal stability after functionalization with octadecylamine and hexylamine(Lin et al., 2010; Shanmugharaj et al., 2013). Fei et al. evaluated the emulsifying properties of hexylamine, dodecylamine and octadecylamine functionalized GO by measurements of contact angle, emulsion volume, and average droplet diameter. They showed that these properties depended on the amphiphilicity of GO, since the wettability to oil increased with increasing alkyl chain length and the functionalized GOs formed water in oil Pickering emulsions stable over a wide pH range (Fei et al., 2016). Yang et al. studied the interfacial behavior of GO selectively functionalized with octylamine at a water/oil interface. They found that basal plane functionalization of GO has a greater effect on interfacial tension reduction compared to GO, edge-functionalized GO, and a traditional ionic surfactant (Yang et al., 2018). The interfacial properties of GO are fundamental to its application in many fields of science and engineering and are inevitably affected by functionalization. So far, there has been little research on these properties in dodecylamine functionalized GO. Therefore, in this work GO was synthesized by the modified Hummers method and functionalized with dodecylamine (GODDA) by amidation and nucleophilic substitution reactions. The obtained materials were characterized by Fourier Transform Infrared Spectroscopy (FTIR), Raman and Thermogravimetric Analysis (TGA). The dispersibility of GO and GODDA was evaluated in water and toluene by bottle test. The wettability of the materials was determined by measuring the material/water contact angle by the sessile drop method and the interfacial tension in toluene/material/water systems by the pendant drop method. The emulsifying properties in these systems were established and their colloidal stability in Pickering emulsions was evaluated by bottle test and Zeta potential at different pH. FTIR and Raman spectroscopies confirmed the synthesis and covalent functionalization of GO by amidation and nucleophilic substitution reactions. TGA analysis revealed that GODDA has a higher thermal stability. Bottle tests and contact angle measurements showed that GO functionalization increases its hydrophobic character and therefore its dispersibility in toluene. Interfacial tension and Zeta potential measurements showed that GODDA can act as a molecular surfactant at the water/toluene interface reducing the interfacial tension and forming stable Pickering emulsions at pH 2, 7 and 10. References Dimiev, A. M., & Tour, J. M. (2014). Mechanism of graphene oxide formation. ACS Nano, 8(3), 3060�3068. Fei, X., Xia, L., Chen, M., Wei, W., Luo, J., & Liu, X. (2016). Preparation and application of water-in-Oil emulsions stabilized by modified graphene oxide. Materials, 9(9). He, Y., Wu, F., Sun, X., Li, R., Guo, Y., Li, C., Zhang, L., Xing, F., Wang, W., & Gao, J. (2013). Factors that affect pickering emulsions stabilized by graphene oxide. ACS Applied Materials and Interfaces, 5(11), 4843�4855. Kim, J., Cote, L. J., Kim, F., Yuan, W., Shull, K. R., & Huang, J. (2010). Graphene oxide sheets at interfaces. Journal of the American Chemical Society, 132(23), 8180�8186. Lin, Z., Liu, Y., & Wong, C. P. (2010). Facile fabrication of superhydrophobic octadecylamine-functionalized graphite oxide film. Langmuir, 26(20), 16110�16114.
Spanish abstract:	El �xido de grafeno (GO) es un derivado del grafeno obtenido a partir de la oxidaci�n y exfoliaci�n qu�mica del grafito. Su estructura laminar est� conformada principalmente por carbonos que cambian de hibridaci�n sp2 (propia del grafeno) a sp3 por la uni�n covalente con �tomos de ox�geno provenientes de grupos funcionales carbonilo, carboxilo, hidroxilo y ep�xido formados durante el proceso de oxidaci�n (Dimiev & Tour, 2014). La presencia de estos grupos funcionales distribuidos aleatoriamente en el plano basal y en los bordes del GO le confieren un car�cter hidrof�lico que favorece su dispersi�n en solventes polares, sin embargo, el GO es un material anfif�lico porque conserva en su plano basal dominios pr�stinos del grafeno que son hidrof�bicos. A pesar de la anfifilicidad, la difusi�n de las hojas de GO hasta interfase es lenta y la actividad superficial/interfacial es baja (Valtierrez-gaytan et al., 2017), no obstante, esto puede ajustarse modificando el grado de oxidaci�n, el tama�o de la hoja, el pH y la salinidad del medio o por funcionalizaci�n covalente con diferentes mol�culas a trav�s de los grupos funcionales oxigenados (He et al., 2013; Kim et al., 2010; Yang et al., 2018). Recientemente, se han publicado estudios sobre la funcionalizaci�n qu�mica del GO con alquilaminas mediante reacciones de amidaci�n con los �cidos carbox�licos en los bordes de la hoja y reacciones de sustituci�n nucleof�lica con los ep�xidos del plano basal. Lin et al. y Shanmugharaj et al. obtuvieron superficies superhidrof�bicas de GO con una mejora en la estabilidad t�rmica despu�s de funcionalizarlo con octadecilamina y hexilamina (Lin et al., 2010; Shanmugharaj et al., 2013). Fei et al. evaluaron las propiedades emulsificantes del GO funcionalizado con hexilamina, dodecilamina y octadecilamina mediante medidas de �ngulo de contacto, volumen de emulsi�n y di�metro promedio de la gota. Demostraron que estas propiedades dependen de la anfifilicidad del GO, ya que la mojabilidad al aceite aument� con el aumento de la longitud de la cadena alqu�lica y los GO funcionalizados formaron emulsiones Pickering de agua en aceite estables en un amplio rango de pH (Fei et al., 2016). Yang et al. estudiaron el comportamiento interfacial del GO funcionalizado selectivamente con octilamina en una interfase agua/aceite. Descubrieron que la funcionalizaci�n del GO en el plano basal tiene un mayor efecto en la reducci�n de la tensi�n interfacial en comparaci�n con el GO, el GO funcionalizado en los bordes y un tensoactivo i�nico tradicional (Yang et al., 2018). Las propiedades interfaciales del GO son fundamentales para su aplicaci�n en muchos campos de la ciencia e ingenier�a e inevitablemente se ven afectadas por la funcionalizaci�n. Hasta ahora, ha sido poca la investigaci�n sobre estas propiedades en el GO funcionalizado con dodecilamina. Por lo tanto, en este trabajo se sintetiz� GO por el m�todo Hummers modificado y se funcionaliz� con dodecilamina (GODDA) mediante reacciones de amidaci�n y sustituci�n nucleof�lica. Los materiales obtenidos se caracterizaron por espectroscopia infrarroja con transformada de Fourier (FTIR), Raman y An�lisis Termogravim�trico (TGA). La dispersabilidad del GO y del GODDA se evalu� en agua y en tolueno mediante la prueba de botellas. Se determin� la mojabilidad de los materiales midiendo el �ngulo de contacto material/agua por el m�todo de la gota s�sil y la tensi�n interfacial en sistemas tolueno/material/agua por el m�todo de la gota colgante. Se establecieron las propiedades emulsificantes en estos sistemas y se evalu� su estabilidad coloidal en emulsiones Pickering mediante la prueba de botellas y el potencial Zeta a diferentes pH. Las espectroscopias FT-IR y Raman confirmaron la s�ntesis y funcionalizaci�n covalente del GO por reacciones de amidaci�n y sustituci�n nucleof�lica. El an�lisis TGA revel� que el GODDA tiene una mayor estabilidad t�rmica. La prueba de botellas y las mediciones del �ngulo de contacto mostraron que la funcionalizaci�n del GO aumenta su car�cter hidr�fobo y, por lo tanto, su dispersabilidad en tolueno. Las medidas de tensi�n interfacial y potencial Zeta mostraron que el GODDA puede actuar como un surfactante molecular en la interfase agua/tolueno reduciendo la tensi�n interfacial y formando emulsiones Pickering estables a pH 2, 7 y 10. Referencias Dimiev, A. M., & Tour, J. M. (2014). Mechanism of graphene oxide formation. ACS Nano, 8(3), 3060�3068. Fei, X., Xia, L., Chen, M., Wei, W., Luo, J., & Liu, X. (2016). Preparation and application of water-in-Oil emulsions stabilized by modified graphene oxide. Materials, 9(9). He, Y., Wu, F., Sun, X., Li, R., Guo, Y., Li, C., Zhang, L., Xing, F., Wang, W., & Gao, J. (2013). Factors that affect pickering emulsions stabilized by graphene oxide. ACS Applied Materials and Interfaces, 5(11), 4843�4855.
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Authors

Name	Institution	Email
Gladys Roc�o Cepeda Mar�n	Universidad Industrial de Santander	gladys2218392@correo.uis.edu.co
Rafael Cabanzo Hern�ndez	Universidad Industrial de Santander	rcabanzo@uis.edu.co
Brayan Arenas	Universidad Industrial de Santander	brayan.arenas@correo.uis.edu.co
Enrique Mej�a Ospino	Universidad Industrial de Santander	emejia@uis.edu.co

Presentation

Room:	Principal Room
Date:	June 8, 2023
Hour:	15:00 - 15:20

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7^th IMRMPT
Seventh International Meeting for Researchers in Materials and Plasma Technology

Previous editions:

        1st IMRMPT 2011
        2nd IMRMPT 2013
        3rd IMRMPT 2015
        4th IMRMPT 2017
        5th IMRMPT 2019
        5+1 IMRMPT 2021

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