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Highly homogeneous nanostructured templates based on environmental friendly microemulsion for nanomaterials processing
Materials Letters 132 (2014) 346–348
Contents lists available at ScienceDirect
Materials Letters journal homepage: www.elsevier.com/locate/matlet
Highly homogeneous nanostructured templates based on environmental friendly microemulsion for nanomaterials processing Elena Adina Rogozea a, Nicoleta Liliana Olteanu a, Adrian Victor Crisciu b, Adina Roxana Petcu a, Maria Mihaly b,n a University POLITEHNICA of Bucharest, Research Centre for Environmental Protection and Eco-friendly Technologies, Polizu 1, RO-011061, Bucharest, Romania b University POLITEHNICA of Bucharest, Faculty of Applied Chemistry and Materials Science, Inorganic Chemistry, Physical Chemistry and Electrochemistry Department, Polizu 1, RO-011061, Bucharest, Romania
art ic l e i nf o
a b s t r a c t
Article history: Received 7 April 2014 Accepted 12 June 2014 Available online 19 June 2014
Highly homogeneous nanostructured templates in the system Water/Polyoxyethylene(4)lauryl ether (Brij 30)/Pinus Oil have been designed for nanomaterials processing by studying the phase behaviour and influence of several physico-chemical parameters such as water/oil ratio (R), water/alcohol ratio (r), temperature, surfactant concentration and nickel salt on the phase transition. A Winsor I-III-II inversion was promoted by using isopropanol cosolvent, at different r, from 1 to 10. For r ¼ 4, as the temperature is increased the Winsor II domain is enhanced subsequently, but no phase transition by temperature change has been revealed. While a narrowing of Winsor II microemulsion region has been noticed, as a result of Ni(II) salt addition by increasing the concentration, still no phase transitions promoted by their presence have been obtained. The Water/Isopropanol/Brij 30/Pinus Oil formulations are promoted as potential synthesis templates for both inorganic and organic materials or as an efficient extraction system for pollutants removal from aqueous media. & 2014 Elsevier B.V. All rights reserved.
Keywords: Highly homogeneous nanostructured templates Physico-chemical parameters Phase diagram Nanomaterials processing
1. Introduction Nanostructured materials are processed by many techniques like sol–gel, hydrothermal, chemical vapour deposition, electrodeposition, sonochemical [1–4], etc. Their drawback is the impossibility to avoid the functional nanoparticles agglomeration during the incorporation into different matrices. To prevent their agglomeration and to allow a homogeneous dispersion, working in microemulsion template is a feasible one pot procedure for nanomaterials processing [5–7].Microemulsions are macroscopically isotropic mixtures of a hydrophilic, a hydrophobic and an amphiphilic component [5]. A wide range of compositions depending on the properties of the oil and the surfactant can lead to different structures as oil-in-water (O/W), water-in-oil (W/O) droplets and bicontinuous structures. In excess of oil, the microemulsion coexists with an oil continuous phase forming Winsor I (WI) type and in excess of water it coexists with an aqueous continuous phase forming Winsor II (WII) type. In Winsor III (WIII)
n
Corresponding author. Tel./fax: þ 40 213154193. E-mail address: [email protected] (M. Mihaly).
http://dx.doi.org/10.1016/j.matlet.2014.06.072 0167-577X/& 2014 Elsevier B.V. All rights reserved.
system three phases are present, where the microemulsion is in equilibrium with both excess aqueous and organic phases and in Winsor IV (WIV) only one microemulsion phase is formed. WIV microemulsion was especially employed in the synthesis of inorganic [6,8], organic [7,9] and hybrid nanostructures [7,10], like nanoparticles (even below 10 nm) and composites. Although it was less exploited, the WII microemulsion could be used for inorganic nanoparticles preparation when water-in-oil (W/O) droplets form hydrophilic nanotemplates for the synthesis processes [6,11,12]. Moreover, the WII microemulsion templates were applied in the recovery of metallic cations from aqueous media, followed by their recycling as nanoparticles in one pot procedure, at large scale [5]. WI microemulsion systems might be used in extraction processes from organic media and organic nanoparticles synthesis [7,13], since oil-in-water nanodroplets act as appropriate containers where hydrophobic compounds can be processed. This paper is the first attempt to investigate the phase behaviour of microemulsions systems stabilised by non-ionic surfactant (Brij 30) with non-aqueous solvents, like Pinus Oil (PO), that has the benefit of using environmental-friendly compounds. The low toxicity, corrosion level and limited persistence in environment of PO are important advantages for its use in environmentally
E.A. Rogozea et al. / Materials Letters 132 (2014) 346–348
347
friendly systems. Also PO is a phenol disinfectant that is mildly antiseptic, relatively inexpensive and widely available. Surfactant, Brij 30, based on fatty acids is biodegradable and has low toxicity. As the medium-chain alcohols might be the most efficient cosolvents, the isopropyl alcohol acts as a co-solvent [13,14], being water miscible. Since there are several parameters that promote phase transitions in microemulsions systems, the influence of water/oil ratio (R), water/alcohol ratio (r), temperature, surfactant concentration and Ni (II) salt concentration on the phase behaviour of Water (W)/Brij 30/PO system based on phase diagrams are discussed. In this way the nanostructure corresponding to specific applications can be tailored by simply choosing the right microemulsion system.
2. Experimental section Chemicals: 5-bromo-N-(4,5-dihydro-1H-imidazol-2-yl)quinoxalin-6-amine 99% (Pinus Oil (PO)) was obtained from FARES BIO VITAL Laboratories, Romania, Brij 30 and Iso-C3-ol 99.5% were purchased from SIGMA-ALDRICH, Nickel(II) Nitrate Hexahydrate 98.5% and bromothymol blue dye (BTB) from MERCK. The water used was deionized and double distilled. Phase diagrams construction: In order to find out the region where the microemulsion is formed, pseudo-ternary phase diagrams were constructed using the surfactant titration method [15]. The samples were taken in sealed test tubes and shaken vigorously using a magnetic stirrer to ensure proper mixing and then kept in a thermostatic device at desired temperature. For different r and temperature the phase transitions were observed by direct visual inspection using BTB as colour indicator (Supporting information).
Fig. 1. The pseudo-ternary diagrams in Water/Iso-C3-ol/Brij 30/PO system, for different water: alcohol ratios, r.
3. Results and discussion Since the temperature, the surfactant and metallic salt concentration present a significant influence on the phase transitions in the Water/Brij 30/PO system, the results are reported by drawing prismatic phase diagrams. The co-solvent influence on the phase equilibrium: Generally, the use of a single surfactant is unlikely to reduce the interfacial tension between oil and water to form stable microemulsions, and therefore the addition of co-solvent is required [16]. Herein a series of systems of Water/Iso-C3-ol/Brij 30/PO for different water/ iso-C3-ol ratio, r ¼1; 2; 3; 4; 6; 8; 10 at 298 K were studied. A better insight on the conditions of microemulsions formulation, in terms of composition and phase changes is provided by a three dimensional phase diagram of Water/Iso-C3-ol/Brij 30/PO pseudo-ternary system (Fig. 1). One can see that compared to the system without alcohol (Supporting information), the addition of various amounts of Iso-C3-ol in the Water/Brij 30/PO system led to the development of extended areas of WII phases on a large range of surfactant concentrations (5/10% (w/w)). Increasing the alcohol content, for r o3, the WII area decreases and a WI region appears, which also occurs for high r values (6 and 8). For r ¼6, all desired WI, WII, WIII and WIV microemulsions are obtained. Since all types of microemulsions are developed and no phase inversion have been noticed, one can assume that the co-solvent tunes the curvature at water/oil interface by changing the polarity of hydrophilic or hydrophobic phase or both and not by changing the surfactant direct packing towards phase inversion. The influence of temperature on the phase equilibrium: The stability of the non-ionic Water/Iso-C3-ol/Brij 30/PO microemulsion system is studied over a temperature range from 278 to 333 K, since the increase of temperature is known to change the phase
Fig. 2. The phase transitions promoted by temperature changes on Water/Iso-C3ol/Brij 30/PO system.
behaviour of the surfactant [17] due to the decreasing hydration level of polyoxyethylene chains. This explains why the curvature at the interface is reversed from convex to planar, towards oil or convex towards water, as the surfactant has the same behaviour with any of the two components (water and oil). The phase diagram is depicted in Fig. 2, for water: iso-C3-ol ratio r ¼4 corresponding to a sufficiently large WII domain, appropriate for extended depollution and synthesis applications. No phase inversion temperature (PIT) was noticed in Water/Brij 30/ PO/iso-C3-ol systems (Fig. 2). While at 278 K a single phase microemulsion, WIV, is obtained at temperatures above 283 K, WII areas subsequently increase with temperature and higher surfactant content is required. These results are especially useful for applications of the Water/ Iso-C3-ol/Brij 30/PO microemulsions system as extraction media at
348
E.A. Rogozea et al. / Materials Letters 132 (2014) 346–348
All types of microemulsion (WI, WII, WIII and WIV) were obtained by varying the water/Iso-C3-ol ratio, r, from 1 to 10. No phase transitions in water/Iso-C3-ol/Brij 30/PO system was noticed by temperature change and/or Ni(II) salt addition, but a narrowing of WII microemulsions region could be observed as the additives concentration increased. The Water/Iso-C3-ol/Brij 30/PO formulations are recommended as potential synthesis templates for both inorganic or organic nanoparticles [6,7] or as an efficient extraction system for pollutants removal from aqueous media such as Ni(II) and CV [15]. One can conclude that the phase behaviour of the water/IsoC3-ol/Brij 30/PO system remains almost unaltered at different temperatures and concentrations of additives, revealing the stability of the system in such environments.
Acknowledgements The work has been funded by the Sectorial Operational Program Human Resources Development 2007-2013 of the Ministry of European Funds through the Financial Agreement POSDRU/159/ 1.5/S/134398. The authors thank the support of this work from the Program: Cooperation in Priority Fields–PNII, developed with the support of ANCS, CNDI-UEFISCDI, Romania, in the project CHALKRESTORE, PN-II-PT-PCCA-2011-3.2-052, Contract no. 222/2-11. Fig. 3. The phase changes promoted by adding different Ni(II) concentrations on water/Iso-C3-ol/(Brij 30)/PO system.
environmental temperature, over a long period of time, from spring to autumn [17]. The influence of Ni(II) salt on the phase equilibrium: Since the phase transitions as well as the morphology of microemulsion templates are influenced by electrolytes [8], Ni(II) salt was employed to investigate the effect of the ionic strength of the aqueous phase over a range between 0.1 and 10 g/L on the Pinus oil based microemulsions (Fig. 3) at 298 K and r ¼4. Two microemulsions systems are formed in all cases, namely WIV and WII. At concentrations lower than 1 g/L, no influence of Ni(NO3)2 on phase transitions in water/Iso-C3-ol/Brij 30/PO system have been noticed knowing that, for uncharged non-ionic surfactants, the salt does not significantly influence the phase behaviour [15]. However, at high salt concentration (over 1 g/L), the solubility of surfactant in water decreases and thus the equilibrium of WII microemulsion is disturbed and the WII area became smaller. Furthermore, the formation of WII microemulsion requires large amounts of surfactant, over 10% (w/w), since the salt and surfactant molecules join together at the water/oil interface, preventing surfactant self-assembling in spherical nanometric aggregates. The hydrophobic interactions between surfactant molecules are reduced and the enhancement of W/O aggregates results as the number of molecules from the oil phase surface is low. Thereby, a reduction of water volume in equilibrium with microemulsion phase volume is induced, but this water/Iso-C3-ol/Brij 30/PO system is still able to clean wastewaters volumes of 6/15 times more than the microemulsion phase used for metallic cations removal [10]. 4. Conclusion Various environmental friendly nanostructure templates based on Water/Iso-C3-ol/Brij 30/PO could be designed for nanomaterials processing deppending on water/oil ratio (R), water/alcohol ratio (r), temperature, surfactant concentration and nickel salt.
Appendix A. Supporting information Supplementary data associated with this article can be found in the online version at http://dx.doi.org/10.1016/j.matlet.2014.06.072. References [1] Duraes L, Oliveira O, Benedini L, Costa BFO, Bej AM, Portugal A. J Phys Chem Solids 2011;72:678–84. [2] Fang L, Zu X, Liu C, Li Z, Peleckis G, Zhu S, et al. J Alloys Compd 2010;491:679–83. [3] Bhatia R, Prasad V. Solid State Commun 2010;150:311–5. [4] Bang JH, Suslick KS. J Adv Mater 2010;22:1039–59. [5] Stubenrauch C. Microemulsions – background, new concepts, applications, perspectives. United Kingdom: Wiley; 2009. [6] Mihaly M, Comanescu AF, Rogozea AE, Vasile E, Meghea A. Mater Res Bull 2011;46:1746–53. [7] Mihaly M, Rogozea A, Comanescu A, Vasile E, Meghea A. J Optoelectron Adv Mater 2010;10:2097–105. [8] Chen Q, Shen X, Gao H. J Colloid Interface Sci 2007;308:491–9. [9] Holzinger D, Kickelbick G. Chem Mater 2003;15:4944–8. [10] Sahraoui B, Pranaitis M, Iliopoulus K, Mihaly M, Comanescu AF, Moldoveanu M, et al. Appl Phys Lett 2011;99:2433041–3. ́ ́ [11] Martınez-Rodrı guez RA, Vidal-Iglesias FJ, Solla-Gullón J, Cabrera CR, Feliu JM. J Am Chem Soc 2014;136:1280–3. [12] Fathi H, Kelly JP, Vasquez VR, Graeve OA. Langmuir 2012;28:9267–74. [13] Gupta S. Curr Sci 2011;101:174–88. [14] El Maghraby GM. Int J Pharm 2008;355:285–92. [15] Fleancu MC, Olteanu NL, Rogozea AE, Crisciu AV, Pincovschi I, Mihaly M. Fluid Phase Equilib 2013;337:18–25. [16] Palazzo G, Lopez F, Giustini M, Colafemmina G, Ceglie A. J Phys Chem B 2003;107:1924–31. [17] Warisnoicharoen W, Lansley AB, Lawrence MJ. Int J Pharm 2000;198:7–27.
Contents lists available at ScienceDirect
Materials Letters journal homepage: www.elsevier.com/locate/matlet
Highly homogeneous nanostructured templates based on environmental friendly microemulsion for nanomaterials processing Elena Adina Rogozea a, Nicoleta Liliana Olteanu a, Adrian Victor Crisciu b, Adina Roxana Petcu a, Maria Mihaly b,n a University POLITEHNICA of Bucharest, Research Centre for Environmental Protection and Eco-friendly Technologies, Polizu 1, RO-011061, Bucharest, Romania b University POLITEHNICA of Bucharest, Faculty of Applied Chemistry and Materials Science, Inorganic Chemistry, Physical Chemistry and Electrochemistry Department, Polizu 1, RO-011061, Bucharest, Romania
art ic l e i nf o
a b s t r a c t
Article history: Received 7 April 2014 Accepted 12 June 2014 Available online 19 June 2014
Highly homogeneous nanostructured templates in the system Water/Polyoxyethylene(4)lauryl ether (Brij 30)/Pinus Oil have been designed for nanomaterials processing by studying the phase behaviour and influence of several physico-chemical parameters such as water/oil ratio (R), water/alcohol ratio (r), temperature, surfactant concentration and nickel salt on the phase transition. A Winsor I-III-II inversion was promoted by using isopropanol cosolvent, at different r, from 1 to 10. For r ¼ 4, as the temperature is increased the Winsor II domain is enhanced subsequently, but no phase transition by temperature change has been revealed. While a narrowing of Winsor II microemulsion region has been noticed, as a result of Ni(II) salt addition by increasing the concentration, still no phase transitions promoted by their presence have been obtained. The Water/Isopropanol/Brij 30/Pinus Oil formulations are promoted as potential synthesis templates for both inorganic and organic materials or as an efficient extraction system for pollutants removal from aqueous media. & 2014 Elsevier B.V. All rights reserved.
Keywords: Highly homogeneous nanostructured templates Physico-chemical parameters Phase diagram Nanomaterials processing
1. Introduction Nanostructured materials are processed by many techniques like sol–gel, hydrothermal, chemical vapour deposition, electrodeposition, sonochemical [1–4], etc. Their drawback is the impossibility to avoid the functional nanoparticles agglomeration during the incorporation into different matrices. To prevent their agglomeration and to allow a homogeneous dispersion, working in microemulsion template is a feasible one pot procedure for nanomaterials processing [5–7].Microemulsions are macroscopically isotropic mixtures of a hydrophilic, a hydrophobic and an amphiphilic component [5]. A wide range of compositions depending on the properties of the oil and the surfactant can lead to different structures as oil-in-water (O/W), water-in-oil (W/O) droplets and bicontinuous structures. In excess of oil, the microemulsion coexists with an oil continuous phase forming Winsor I (WI) type and in excess of water it coexists with an aqueous continuous phase forming Winsor II (WII) type. In Winsor III (WIII)
n
Corresponding author. Tel./fax: þ 40 213154193. E-mail address: [email protected] (M. Mihaly).
http://dx.doi.org/10.1016/j.matlet.2014.06.072 0167-577X/& 2014 Elsevier B.V. All rights reserved.
system three phases are present, where the microemulsion is in equilibrium with both excess aqueous and organic phases and in Winsor IV (WIV) only one microemulsion phase is formed. WIV microemulsion was especially employed in the synthesis of inorganic [6,8], organic [7,9] and hybrid nanostructures [7,10], like nanoparticles (even below 10 nm) and composites. Although it was less exploited, the WII microemulsion could be used for inorganic nanoparticles preparation when water-in-oil (W/O) droplets form hydrophilic nanotemplates for the synthesis processes [6,11,12]. Moreover, the WII microemulsion templates were applied in the recovery of metallic cations from aqueous media, followed by their recycling as nanoparticles in one pot procedure, at large scale [5]. WI microemulsion systems might be used in extraction processes from organic media and organic nanoparticles synthesis [7,13], since oil-in-water nanodroplets act as appropriate containers where hydrophobic compounds can be processed. This paper is the first attempt to investigate the phase behaviour of microemulsions systems stabilised by non-ionic surfactant (Brij 30) with non-aqueous solvents, like Pinus Oil (PO), that has the benefit of using environmental-friendly compounds. The low toxicity, corrosion level and limited persistence in environment of PO are important advantages for its use in environmentally
E.A. Rogozea et al. / Materials Letters 132 (2014) 346–348
347
friendly systems. Also PO is a phenol disinfectant that is mildly antiseptic, relatively inexpensive and widely available. Surfactant, Brij 30, based on fatty acids is biodegradable and has low toxicity. As the medium-chain alcohols might be the most efficient cosolvents, the isopropyl alcohol acts as a co-solvent [13,14], being water miscible. Since there are several parameters that promote phase transitions in microemulsions systems, the influence of water/oil ratio (R), water/alcohol ratio (r), temperature, surfactant concentration and Ni (II) salt concentration on the phase behaviour of Water (W)/Brij 30/PO system based on phase diagrams are discussed. In this way the nanostructure corresponding to specific applications can be tailored by simply choosing the right microemulsion system.
2. Experimental section Chemicals: 5-bromo-N-(4,5-dihydro-1H-imidazol-2-yl)quinoxalin-6-amine 99% (Pinus Oil (PO)) was obtained from FARES BIO VITAL Laboratories, Romania, Brij 30 and Iso-C3-ol 99.5% were purchased from SIGMA-ALDRICH, Nickel(II) Nitrate Hexahydrate 98.5% and bromothymol blue dye (BTB) from MERCK. The water used was deionized and double distilled. Phase diagrams construction: In order to find out the region where the microemulsion is formed, pseudo-ternary phase diagrams were constructed using the surfactant titration method [15]. The samples were taken in sealed test tubes and shaken vigorously using a magnetic stirrer to ensure proper mixing and then kept in a thermostatic device at desired temperature. For different r and temperature the phase transitions were observed by direct visual inspection using BTB as colour indicator (Supporting information).
Fig. 1. The pseudo-ternary diagrams in Water/Iso-C3-ol/Brij 30/PO system, for different water: alcohol ratios, r.
3. Results and discussion Since the temperature, the surfactant and metallic salt concentration present a significant influence on the phase transitions in the Water/Brij 30/PO system, the results are reported by drawing prismatic phase diagrams. The co-solvent influence on the phase equilibrium: Generally, the use of a single surfactant is unlikely to reduce the interfacial tension between oil and water to form stable microemulsions, and therefore the addition of co-solvent is required [16]. Herein a series of systems of Water/Iso-C3-ol/Brij 30/PO for different water/ iso-C3-ol ratio, r ¼1; 2; 3; 4; 6; 8; 10 at 298 K were studied. A better insight on the conditions of microemulsions formulation, in terms of composition and phase changes is provided by a three dimensional phase diagram of Water/Iso-C3-ol/Brij 30/PO pseudo-ternary system (Fig. 1). One can see that compared to the system without alcohol (Supporting information), the addition of various amounts of Iso-C3-ol in the Water/Brij 30/PO system led to the development of extended areas of WII phases on a large range of surfactant concentrations (5/10% (w/w)). Increasing the alcohol content, for r o3, the WII area decreases and a WI region appears, which also occurs for high r values (6 and 8). For r ¼6, all desired WI, WII, WIII and WIV microemulsions are obtained. Since all types of microemulsions are developed and no phase inversion have been noticed, one can assume that the co-solvent tunes the curvature at water/oil interface by changing the polarity of hydrophilic or hydrophobic phase or both and not by changing the surfactant direct packing towards phase inversion. The influence of temperature on the phase equilibrium: The stability of the non-ionic Water/Iso-C3-ol/Brij 30/PO microemulsion system is studied over a temperature range from 278 to 333 K, since the increase of temperature is known to change the phase
Fig. 2. The phase transitions promoted by temperature changes on Water/Iso-C3ol/Brij 30/PO system.
behaviour of the surfactant [17] due to the decreasing hydration level of polyoxyethylene chains. This explains why the curvature at the interface is reversed from convex to planar, towards oil or convex towards water, as the surfactant has the same behaviour with any of the two components (water and oil). The phase diagram is depicted in Fig. 2, for water: iso-C3-ol ratio r ¼4 corresponding to a sufficiently large WII domain, appropriate for extended depollution and synthesis applications. No phase inversion temperature (PIT) was noticed in Water/Brij 30/ PO/iso-C3-ol systems (Fig. 2). While at 278 K a single phase microemulsion, WIV, is obtained at temperatures above 283 K, WII areas subsequently increase with temperature and higher surfactant content is required. These results are especially useful for applications of the Water/ Iso-C3-ol/Brij 30/PO microemulsions system as extraction media at
348
E.A. Rogozea et al. / Materials Letters 132 (2014) 346–348
All types of microemulsion (WI, WII, WIII and WIV) were obtained by varying the water/Iso-C3-ol ratio, r, from 1 to 10. No phase transitions in water/Iso-C3-ol/Brij 30/PO system was noticed by temperature change and/or Ni(II) salt addition, but a narrowing of WII microemulsions region could be observed as the additives concentration increased. The Water/Iso-C3-ol/Brij 30/PO formulations are recommended as potential synthesis templates for both inorganic or organic nanoparticles [6,7] or as an efficient extraction system for pollutants removal from aqueous media such as Ni(II) and CV [15]. One can conclude that the phase behaviour of the water/IsoC3-ol/Brij 30/PO system remains almost unaltered at different temperatures and concentrations of additives, revealing the stability of the system in such environments.
Acknowledgements The work has been funded by the Sectorial Operational Program Human Resources Development 2007-2013 of the Ministry of European Funds through the Financial Agreement POSDRU/159/ 1.5/S/134398. The authors thank the support of this work from the Program: Cooperation in Priority Fields–PNII, developed with the support of ANCS, CNDI-UEFISCDI, Romania, in the project CHALKRESTORE, PN-II-PT-PCCA-2011-3.2-052, Contract no. 222/2-11. Fig. 3. The phase changes promoted by adding different Ni(II) concentrations on water/Iso-C3-ol/(Brij 30)/PO system.
environmental temperature, over a long period of time, from spring to autumn [17]. The influence of Ni(II) salt on the phase equilibrium: Since the phase transitions as well as the morphology of microemulsion templates are influenced by electrolytes [8], Ni(II) salt was employed to investigate the effect of the ionic strength of the aqueous phase over a range between 0.1 and 10 g/L on the Pinus oil based microemulsions (Fig. 3) at 298 K and r ¼4. Two microemulsions systems are formed in all cases, namely WIV and WII. At concentrations lower than 1 g/L, no influence of Ni(NO3)2 on phase transitions in water/Iso-C3-ol/Brij 30/PO system have been noticed knowing that, for uncharged non-ionic surfactants, the salt does not significantly influence the phase behaviour [15]. However, at high salt concentration (over 1 g/L), the solubility of surfactant in water decreases and thus the equilibrium of WII microemulsion is disturbed and the WII area became smaller. Furthermore, the formation of WII microemulsion requires large amounts of surfactant, over 10% (w/w), since the salt and surfactant molecules join together at the water/oil interface, preventing surfactant self-assembling in spherical nanometric aggregates. The hydrophobic interactions between surfactant molecules are reduced and the enhancement of W/O aggregates results as the number of molecules from the oil phase surface is low. Thereby, a reduction of water volume in equilibrium with microemulsion phase volume is induced, but this water/Iso-C3-ol/Brij 30/PO system is still able to clean wastewaters volumes of 6/15 times more than the microemulsion phase used for metallic cations removal [10]. 4. Conclusion Various environmental friendly nanostructure templates based on Water/Iso-C3-ol/Brij 30/PO could be designed for nanomaterials processing deppending on water/oil ratio (R), water/alcohol ratio (r), temperature, surfactant concentration and nickel salt.
Appendix A. Supporting information Supplementary data associated with this article can be found in the online version at http://dx.doi.org/10.1016/j.matlet.2014.06.072. References [1] Duraes L, Oliveira O, Benedini L, Costa BFO, Bej AM, Portugal A. J Phys Chem Solids 2011;72:678–84. [2] Fang L, Zu X, Liu C, Li Z, Peleckis G, Zhu S, et al. J Alloys Compd 2010;491:679–83. [3] Bhatia R, Prasad V. Solid State Commun 2010;150:311–5. [4] Bang JH, Suslick KS. J Adv Mater 2010;22:1039–59. [5] Stubenrauch C. Microemulsions – background, new concepts, applications, perspectives. United Kingdom: Wiley; 2009. [6] Mihaly M, Comanescu AF, Rogozea AE, Vasile E, Meghea A. Mater Res Bull 2011;46:1746–53. [7] Mihaly M, Rogozea A, Comanescu A, Vasile E, Meghea A. J Optoelectron Adv Mater 2010;10:2097–105. [8] Chen Q, Shen X, Gao H. J Colloid Interface Sci 2007;308:491–9. [9] Holzinger D, Kickelbick G. Chem Mater 2003;15:4944–8. [10] Sahraoui B, Pranaitis M, Iliopoulus K, Mihaly M, Comanescu AF, Moldoveanu M, et al. Appl Phys Lett 2011;99:2433041–3. ́ ́ [11] Martınez-Rodrı guez RA, Vidal-Iglesias FJ, Solla-Gullón J, Cabrera CR, Feliu JM. J Am Chem Soc 2014;136:1280–3. [12] Fathi H, Kelly JP, Vasquez VR, Graeve OA. Langmuir 2012;28:9267–74. [13] Gupta S. Curr Sci 2011;101:174–88. [14] El Maghraby GM. Int J Pharm 2008;355:285–92. [15] Fleancu MC, Olteanu NL, Rogozea AE, Crisciu AV, Pincovschi I, Mihaly M. Fluid Phase Equilib 2013;337:18–25. [16] Palazzo G, Lopez F, Giustini M, Colafemmina G, Ceglie A. J Phys Chem B 2003;107:1924–31. [17] Warisnoicharoen W, Lansley AB, Lawrence MJ. Int J Pharm 2000;198:7–27.