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Molecular dynamics simulation of a Gold nanodroplet in contact with graphene
Materials Letters 178 (2016) 205–207
Contents lists available at ScienceDirect
Materials Letters journal homepage: www.elsevier.com/locate/matlet
Molecular dynamics simulation of a Gold nanodroplet in contact with graphene Jamal Davoodi n, Mitra Safaralizade, Mohsen Yarifard Department of Physics, University of Zanjan, P. O. Box 45195-313, Iran
art ic l e i nf o
a b s t r a c t
Article history: Received 1 October 2015 Accepted 2 May 2016 Available online 3 May 2016
The liquid Gold (Au) Nanodroplet spreading on a graphene substrate was studied by molecular dynamics (MD) simulation technique. The EAM interatomic potential and Tersoff many body potential have been used for Au-Au and C-C interactions respectively, and Lenard–Jones potential has been employed for Au-C interaction. The temperature of nanodroplet and substrate were controlled by Nose-Hoover thermostat in canonical ensemble. The cross-section snapshots of the nanodroplet were used to study contact angle and wettability of nanodroplet. Upon alteration of nanodroplet size is changed and no obvious effect on the contact angle was seen in the nanodroplet on the graphene surface. Moreover, we investigated effect of graphene temperature, the number of graphene layers and cooling rate of nanodroplet on the contact angle. Our MD results showed that the contact angle decreased with the increase of number of graphene layers and increased with increase of cooling rate and graphene temperature. It means that, the wettability of Au nanodroplet is independent of nanodroplet size and is dependent on substrate temperature and cooling rate. & 2016 Elsevier B.V. All rights reserved.
Keywords: Thermal properties Nanoparticles Contact angle Graphene
1. Introduction The spreading of droplet on the solid surfaces is a very important phenomenon due to its wide range of applications, including soldering, superhydrophobic surfaces in self-cleaning, spray painting, ink-jet printing, and biological sensors [1–4]. Contact angle is defined geometrically as the angle formed by a liquid droplet at the three phase boundary where a liquid, gas and solid intersect. It is a quantitative measure of the wetting of a solid by a liquid and can also be considered in terms of the thermodynamics of the materials by Young-Dupre equation [5]. Extensive studies have been carried out over the past few decades to investigate the wetting phenomena of a droplet on different surfaces. For instance, the sessile-drop technique has been extensively used to measure the contact angle in order to determine wettability [6,7]. In spite of intense research on graphene, only a few reports [8–11] have studied the interfacial behaviour between graphene and liquid, including the wetting properties of graphene, which could be important if graphene is to be used in conformal coatings. Since production graphene [12], and functionalization of graphene with metals interest has grown to control its intrinsic properties [13–16]. Gold is one of the most broadly used metals for n
Corresponding author. E-mail address: [email protected] (J. Davoodi).
http://dx.doi.org/10.1016/j.matlet.2016.05.013 0167-577X/& 2016 Elsevier B.V. All rights reserved.
a range of graphene applications, including biosensors [17], photoactive composites [18], making contacts to circuits and studying interfaces [19,20]. Notwithstanding the profound insight obtained into graphene-gold interface and its implications for nanoelectronics [16], diffusion and adsorption of gold nanoclusters on graphene and graphite [20–23] and wetting properties of graphene by Au are poorly understood and investigation of contact angle between Au and graphene is one of the key requirements to understand the nature of the interaction. In the present paper, we performed gold nanodroplet contactangle calculations on graphene sheet surface by molecular dynamics (MD) simulation.
2. Details of simulation The Spreading of gold nanodroplet on graphene surface was simulated using Embedded-atom model (EAM) interatomic potential for Au-Au interactions [24]. We carried out all MD simulations under the canonical ensemble using the LAMMPS package [25], employing the Tersoff many-body interatomic potential to model the energetic and dynamics of C-C atoms [26]. Lenard–Jones potentials were used for Au-C interactions [20]. We selected the size for approximately square graphenes to be 10 nm, such that the two sides were fixed. Periodic boundary conditions were applied in-plane, in both the x and y directions and mirror boundary condition in the vertical to graphene surface. Equations of motion
206
J. Davoodi et al. / Materials Letters 178 (2016) 205–207
were integrated via the velocity Verlet algorithm and time step of the simulation was set at 1 fs. The temperature of the nanodroplet and substrate were controlled by Nose-Hoover thermostat. At first, the solid Au nanoparticle with face-centred cubic structure was equilibrated during 200 ps at T ¼300 K. Following equilibration, the temperature was raised by 0.1 K at each temperature step. At each step that the temperature was increased, the system was reequilibrated for 1 ps. After melting, the nanodroplet was released to spread on graphene surface.
3. Results and discussion For investigating the wetting, Au nanodroplet was released on graphene surface to spread. The force behind the spreading is interaction between Gold and Carbon atoms. The contact angle was determined from side-view image of the nanodroplet on graphene surface (Fig. 1). The size dependence of the contact angle of Au nanodroplet was investigated by varying the number of atoms in the nanodroplet. Fig. 2 shows the contact angle versus the number of atoms in the nanodroplet. As is seen, the contact angle remains unaffected by the size of nanodroplet approximately. Another useful parameter to examine was the temperature of graphene. Fig. 3 demonstrates the dependence of contact angle on the temperature of substrate without changing the number of gold atoms. It was observed that the contact angle varied from 113° to 145° with increasing substrate temperature from 0 to 4000 K. The reason for increasing is that surface tension decreases with the increase of temperature. The general trend is that surface tension decreases with the increase of temperature, reaching a value of 0 at the critical temperature. The contact angle ( θ ) can be considered in terms of the thermodynamics of the materials by Young's equation for the balance of surface tensions at the liquidgas-solid three phase from the following form
γgs = γls + γgl cos θ
Fig. 2. Contact angle versus number of Au atoms in the nanodroplet.
(1)
We see from Young's equation as temperature of substrate increases, the solid-gas ( γgs ) and solid-liquid ( γls ) interfacial tensions approach to zero and liquid-gas ( γgl ) interfacial remain constant. Therefore, the contact angle increases with graphene temperature. Cooling rate is another important parameter for wetting control in spreading process in industry. In order to explore the effect of cooling rate on the contact angle, during the spreading of nanodroplet on the substrate, the cooling rate of nanodroplet was changed. Our MD results for different cooling rate are illustrated in the Fig. 4. The contact angle is enhanced when the cooling rate is increased. It means that nanodroplet spreads better on the
Fig. 1. Cross-section snapshot of simulation for Au nanodroplet on graphene surface.
Fig. 3. Dependence of contact angle on substrate temperature.
Fig. 4. Contact angle of Au nanodroplet on graphene surface as a function of cooling rate.
J. Davoodi et al. / Materials Letters 178 (2016) 205–207
graphene with low cooling rate thus increasing wettability. Finally, the effect of number of graphene layers on the contact angle was investigated. The simulations identified the contact angles of 113°, 104°, 99° for one, two and three layers of graphene, respectively. The reason for decreasing is, when the number of substrate layers increase, the attractive force on the nanodroplet increase. Therefore, the number of graphene layers has a profound effect on wettability.
4. Conclusion The contact angles of Au nanodroplet on graphene surface were obtained by MD simulation technique. Decreasing cooling rate reduced the contact angle, indicating good wettability. Also, the results show that contact angle is approximately independent of the nanodroplet size and increasing graphene temperature enhanced the contact angle. It means that nanodroplet spreads better on the graphene with low substrate temperature. We examined contact angle value for one, two and three layers of graphene and found substrate with three layers has better wettability. However our results show low wettability of Au on graphene surface, which can be controlled by of cooling rate and substrate temperature.
References [1] M.F. Arenas, V.L. Acoff, Contact angle measurements of Sn-Ag and Sn-Cu leadfree solders on copper substrates, J. Electron. Mater. 13 (2004) 1452–1458. [2] Y. Son, C. Kim, D.H. Yang, et al., Spreading of an inkjet droplet on a solid surface with a controlled contact angle at low Weber and Reynolds numbers, Langmuir 24 (2008) 2900–2907. [3] H. Yang, P. Jiang, Self-cleaning diffractive macroporous films by doctor blade coating, Langmuir 26 (2010) 12598–12604. [4] B. Bhushan, Y.C. Jung, K. Koch, Self-cleaning efficiency of artificial superhydrophobic surfaces, Langmuir 25 (2009) 3240–3248. [5] T. Young, An essay on the cohesion of fluids, Philos. Trans. R. Soc. Lond. 95
207
(1805) 65–87. [6] H.K. Kim, H.K. Liou, K.N. Tu, Morphology of instability of the wetting tips of eutectic SnBi, eutectic SnPb, and pure Sn on Cu, J. Mater. Res. 10 (1995) 497–504. [7] A.P. Xian, Wetting of Si-Al-O-N ceramic by Sn-5at% Ti-X ternary active solder, Mater. Sci. Eng. B 25 (1994) 39–46. [8] S. Wang, Y. Zhang, N. Abidi, et al., Wettability and surface free energy of graphene films, Langmuir 25 (2009) 11078–11081. [9] J. Rafiee, M.A. Rafiee, Z.Z. Yu, et al., Superhydrophobic to superhydrophilic wetting control in graphene films, Adv. Mater. 22 (2010) 2151–2154. [10] F. Yavari, C. Kritzinger, C. Gaire, et al., Tunable band gap in graphene by the controlled adsorption of water molecules, Small 6 (2010) 2535–2538. [11] J. Rafiee, X. Mi, H. Gullapalli, et al., Wetting transparency of graphene, Nat. Mater. 11 (2012) 217–222. [12] K.S. Novoselov, A.K. Geim, S.V. Morozov, et al., Electric field effect in atomically thin carbon films, Science 306 (2004) 666–669. [13] S. Huh, J. Park, K.S. Kim, et al., Selective n-type doping of graphene by photopatterned gold nanoparticles, ACS Nano 5 (2011) 3639–3644. [14] Y. Shi, K.K. Kim, A. Reina, et al., Work function engineering of graphene electrode via chemical doping, ACS Nano 4 (2010) 2689–2694. [15] R. Muszynski, B. Seger, P.V. Kamat, Decorating graphene sheets with gold nanoparticles, J. Phys. Chem. C 112 (2008) 5263–5266. [16] R.S. Sundaram, M. Steiner, H.Y. Chiu, et al., The graphene-gold interface and its implications for nanoelectronics, Nano Lett. 11 (2011) 3833–3837. [17] W. Hong, H. Bai, Y. Xu, et al., Preparation of gold nanoparticle/graphene composites with controlled weight contents and their application in biosensors, J. Phys. Chem. C 114 (2010) 1822–1826. [18] G. Williams, B. Seger, P.V. Kamat, TiO2-graphene nanocomposites. UV-assisted photocatalytic reduction of graphene oxide, ACS Nano 2 (2008) 1487–1491. [19] Z. Lee, K.J. Jeon, A. Dato, et al., Direct imaging of soft–hard interfaces enabled by graphene, Nano Lett. 9 (2009) 3365–3369. [20] W.D. Luedtke, U. Landman, Slip diffusion and lévy flights of an adsorbed gold nanocluster, Phys. Rev. Lett. 82 (1999) 3835–3838. [21] L.J. Lewis, P. Jensen, N. Combe, et al., Diffusion of gold nanoclusters on graphite, Phys. Rev. B 61 (2000) 16084–16090. [22] P. Jensen, A. Clement, L.J. Lewis, Diffusion of nanoclusters, Comput. Mater Sci. 30 (2004) 137–142. [23] S. Malola, H. Häkkinen, P. Koskinen, Gold in graphene: in-plane adsorption and diffusion, Appl. Phys. Lett. 94 (2009) 043106. [24] S.M. Foiles, M.I. Baskes, M.S. Daw, Embedded-atom-method functions for the fcc metals Cu, Ag, Au, Ni, Pd, Pt, and their alloys, Phys. Rev. B 33 (1986) 7983–7991. [25] S. Plimpton, Fast parallel algorithms for short-range molecular dynamics, J. Comp. Phys. 117 (1995) 1–19. [26] J. Tersoff, Modeling solid-state chemistry: interatomic potentials for multicomponent systems, Phys. Rev. B 39 (1989) 5566–5568.
Contents lists available at ScienceDirect
Materials Letters journal homepage: www.elsevier.com/locate/matlet
Molecular dynamics simulation of a Gold nanodroplet in contact with graphene Jamal Davoodi n, Mitra Safaralizade, Mohsen Yarifard Department of Physics, University of Zanjan, P. O. Box 45195-313, Iran
art ic l e i nf o
a b s t r a c t
Article history: Received 1 October 2015 Accepted 2 May 2016 Available online 3 May 2016
The liquid Gold (Au) Nanodroplet spreading on a graphene substrate was studied by molecular dynamics (MD) simulation technique. The EAM interatomic potential and Tersoff many body potential have been used for Au-Au and C-C interactions respectively, and Lenard–Jones potential has been employed for Au-C interaction. The temperature of nanodroplet and substrate were controlled by Nose-Hoover thermostat in canonical ensemble. The cross-section snapshots of the nanodroplet were used to study contact angle and wettability of nanodroplet. Upon alteration of nanodroplet size is changed and no obvious effect on the contact angle was seen in the nanodroplet on the graphene surface. Moreover, we investigated effect of graphene temperature, the number of graphene layers and cooling rate of nanodroplet on the contact angle. Our MD results showed that the contact angle decreased with the increase of number of graphene layers and increased with increase of cooling rate and graphene temperature. It means that, the wettability of Au nanodroplet is independent of nanodroplet size and is dependent on substrate temperature and cooling rate. & 2016 Elsevier B.V. All rights reserved.
Keywords: Thermal properties Nanoparticles Contact angle Graphene
1. Introduction The spreading of droplet on the solid surfaces is a very important phenomenon due to its wide range of applications, including soldering, superhydrophobic surfaces in self-cleaning, spray painting, ink-jet printing, and biological sensors [1–4]. Contact angle is defined geometrically as the angle formed by a liquid droplet at the three phase boundary where a liquid, gas and solid intersect. It is a quantitative measure of the wetting of a solid by a liquid and can also be considered in terms of the thermodynamics of the materials by Young-Dupre equation [5]. Extensive studies have been carried out over the past few decades to investigate the wetting phenomena of a droplet on different surfaces. For instance, the sessile-drop technique has been extensively used to measure the contact angle in order to determine wettability [6,7]. In spite of intense research on graphene, only a few reports [8–11] have studied the interfacial behaviour between graphene and liquid, including the wetting properties of graphene, which could be important if graphene is to be used in conformal coatings. Since production graphene [12], and functionalization of graphene with metals interest has grown to control its intrinsic properties [13–16]. Gold is one of the most broadly used metals for n
Corresponding author. E-mail address: [email protected] (J. Davoodi).
http://dx.doi.org/10.1016/j.matlet.2016.05.013 0167-577X/& 2016 Elsevier B.V. All rights reserved.
a range of graphene applications, including biosensors [17], photoactive composites [18], making contacts to circuits and studying interfaces [19,20]. Notwithstanding the profound insight obtained into graphene-gold interface and its implications for nanoelectronics [16], diffusion and adsorption of gold nanoclusters on graphene and graphite [20–23] and wetting properties of graphene by Au are poorly understood and investigation of contact angle between Au and graphene is one of the key requirements to understand the nature of the interaction. In the present paper, we performed gold nanodroplet contactangle calculations on graphene sheet surface by molecular dynamics (MD) simulation.
2. Details of simulation The Spreading of gold nanodroplet on graphene surface was simulated using Embedded-atom model (EAM) interatomic potential for Au-Au interactions [24]. We carried out all MD simulations under the canonical ensemble using the LAMMPS package [25], employing the Tersoff many-body interatomic potential to model the energetic and dynamics of C-C atoms [26]. Lenard–Jones potentials were used for Au-C interactions [20]. We selected the size for approximately square graphenes to be 10 nm, such that the two sides were fixed. Periodic boundary conditions were applied in-plane, in both the x and y directions and mirror boundary condition in the vertical to graphene surface. Equations of motion
206
J. Davoodi et al. / Materials Letters 178 (2016) 205–207
were integrated via the velocity Verlet algorithm and time step of the simulation was set at 1 fs. The temperature of the nanodroplet and substrate were controlled by Nose-Hoover thermostat. At first, the solid Au nanoparticle with face-centred cubic structure was equilibrated during 200 ps at T ¼300 K. Following equilibration, the temperature was raised by 0.1 K at each temperature step. At each step that the temperature was increased, the system was reequilibrated for 1 ps. After melting, the nanodroplet was released to spread on graphene surface.
3. Results and discussion For investigating the wetting, Au nanodroplet was released on graphene surface to spread. The force behind the spreading is interaction between Gold and Carbon atoms. The contact angle was determined from side-view image of the nanodroplet on graphene surface (Fig. 1). The size dependence of the contact angle of Au nanodroplet was investigated by varying the number of atoms in the nanodroplet. Fig. 2 shows the contact angle versus the number of atoms in the nanodroplet. As is seen, the contact angle remains unaffected by the size of nanodroplet approximately. Another useful parameter to examine was the temperature of graphene. Fig. 3 demonstrates the dependence of contact angle on the temperature of substrate without changing the number of gold atoms. It was observed that the contact angle varied from 113° to 145° with increasing substrate temperature from 0 to 4000 K. The reason for increasing is that surface tension decreases with the increase of temperature. The general trend is that surface tension decreases with the increase of temperature, reaching a value of 0 at the critical temperature. The contact angle ( θ ) can be considered in terms of the thermodynamics of the materials by Young's equation for the balance of surface tensions at the liquidgas-solid three phase from the following form
γgs = γls + γgl cos θ
Fig. 2. Contact angle versus number of Au atoms in the nanodroplet.
(1)
We see from Young's equation as temperature of substrate increases, the solid-gas ( γgs ) and solid-liquid ( γls ) interfacial tensions approach to zero and liquid-gas ( γgl ) interfacial remain constant. Therefore, the contact angle increases with graphene temperature. Cooling rate is another important parameter for wetting control in spreading process in industry. In order to explore the effect of cooling rate on the contact angle, during the spreading of nanodroplet on the substrate, the cooling rate of nanodroplet was changed. Our MD results for different cooling rate are illustrated in the Fig. 4. The contact angle is enhanced when the cooling rate is increased. It means that nanodroplet spreads better on the
Fig. 1. Cross-section snapshot of simulation for Au nanodroplet on graphene surface.
Fig. 3. Dependence of contact angle on substrate temperature.
Fig. 4. Contact angle of Au nanodroplet on graphene surface as a function of cooling rate.
J. Davoodi et al. / Materials Letters 178 (2016) 205–207
graphene with low cooling rate thus increasing wettability. Finally, the effect of number of graphene layers on the contact angle was investigated. The simulations identified the contact angles of 113°, 104°, 99° for one, two and three layers of graphene, respectively. The reason for decreasing is, when the number of substrate layers increase, the attractive force on the nanodroplet increase. Therefore, the number of graphene layers has a profound effect on wettability.
4. Conclusion The contact angles of Au nanodroplet on graphene surface were obtained by MD simulation technique. Decreasing cooling rate reduced the contact angle, indicating good wettability. Also, the results show that contact angle is approximately independent of the nanodroplet size and increasing graphene temperature enhanced the contact angle. It means that nanodroplet spreads better on the graphene with low substrate temperature. We examined contact angle value for one, two and three layers of graphene and found substrate with three layers has better wettability. However our results show low wettability of Au on graphene surface, which can be controlled by of cooling rate and substrate temperature.
References [1] M.F. Arenas, V.L. Acoff, Contact angle measurements of Sn-Ag and Sn-Cu leadfree solders on copper substrates, J. Electron. Mater. 13 (2004) 1452–1458. [2] Y. Son, C. Kim, D.H. Yang, et al., Spreading of an inkjet droplet on a solid surface with a controlled contact angle at low Weber and Reynolds numbers, Langmuir 24 (2008) 2900–2907. [3] H. Yang, P. Jiang, Self-cleaning diffractive macroporous films by doctor blade coating, Langmuir 26 (2010) 12598–12604. [4] B. Bhushan, Y.C. Jung, K. Koch, Self-cleaning efficiency of artificial superhydrophobic surfaces, Langmuir 25 (2009) 3240–3248. [5] T. Young, An essay on the cohesion of fluids, Philos. Trans. R. Soc. Lond. 95
207
(1805) 65–87. [6] H.K. Kim, H.K. Liou, K.N. Tu, Morphology of instability of the wetting tips of eutectic SnBi, eutectic SnPb, and pure Sn on Cu, J. Mater. Res. 10 (1995) 497–504. [7] A.P. Xian, Wetting of Si-Al-O-N ceramic by Sn-5at% Ti-X ternary active solder, Mater. Sci. Eng. B 25 (1994) 39–46. [8] S. Wang, Y. Zhang, N. Abidi, et al., Wettability and surface free energy of graphene films, Langmuir 25 (2009) 11078–11081. [9] J. Rafiee, M.A. Rafiee, Z.Z. Yu, et al., Superhydrophobic to superhydrophilic wetting control in graphene films, Adv. Mater. 22 (2010) 2151–2154. [10] F. Yavari, C. Kritzinger, C. Gaire, et al., Tunable band gap in graphene by the controlled adsorption of water molecules, Small 6 (2010) 2535–2538. [11] J. Rafiee, X. Mi, H. Gullapalli, et al., Wetting transparency of graphene, Nat. Mater. 11 (2012) 217–222. [12] K.S. Novoselov, A.K. Geim, S.V. Morozov, et al., Electric field effect in atomically thin carbon films, Science 306 (2004) 666–669. [13] S. Huh, J. Park, K.S. Kim, et al., Selective n-type doping of graphene by photopatterned gold nanoparticles, ACS Nano 5 (2011) 3639–3644. [14] Y. Shi, K.K. Kim, A. Reina, et al., Work function engineering of graphene electrode via chemical doping, ACS Nano 4 (2010) 2689–2694. [15] R. Muszynski, B. Seger, P.V. Kamat, Decorating graphene sheets with gold nanoparticles, J. Phys. Chem. C 112 (2008) 5263–5266. [16] R.S. Sundaram, M. Steiner, H.Y. Chiu, et al., The graphene-gold interface and its implications for nanoelectronics, Nano Lett. 11 (2011) 3833–3837. [17] W. Hong, H. Bai, Y. Xu, et al., Preparation of gold nanoparticle/graphene composites with controlled weight contents and their application in biosensors, J. Phys. Chem. C 114 (2010) 1822–1826. [18] G. Williams, B. Seger, P.V. Kamat, TiO2-graphene nanocomposites. UV-assisted photocatalytic reduction of graphene oxide, ACS Nano 2 (2008) 1487–1491. [19] Z. Lee, K.J. Jeon, A. Dato, et al., Direct imaging of soft–hard interfaces enabled by graphene, Nano Lett. 9 (2009) 3365–3369. [20] W.D. Luedtke, U. Landman, Slip diffusion and lévy flights of an adsorbed gold nanocluster, Phys. Rev. Lett. 82 (1999) 3835–3838. [21] L.J. Lewis, P. Jensen, N. Combe, et al., Diffusion of gold nanoclusters on graphite, Phys. Rev. B 61 (2000) 16084–16090. [22] P. Jensen, A. Clement, L.J. Lewis, Diffusion of nanoclusters, Comput. Mater Sci. 30 (2004) 137–142. [23] S. Malola, H. Häkkinen, P. Koskinen, Gold in graphene: in-plane adsorption and diffusion, Appl. Phys. Lett. 94 (2009) 043106. [24] S.M. Foiles, M.I. Baskes, M.S. Daw, Embedded-atom-method functions for the fcc metals Cu, Ag, Au, Ni, Pd, Pt, and their alloys, Phys. Rev. B 33 (1986) 7983–7991. [25] S. Plimpton, Fast parallel algorithms for short-range molecular dynamics, J. Comp. Phys. 117 (1995) 1–19. [26] J. Tersoff, Modeling solid-state chemistry: interatomic potentials for multicomponent systems, Phys. Rev. B 39 (1989) 5566–5568.