Stiffening of Metallic Gallium Particles by Entrapment of Organic

Subscriber access provided by Fudan University

Article

Stiffening of Metallic Gallium Particles by Entrapment of Organic Molecules Vijay Bhooshan Kumar, Olga Girshevitz, David Avnir, Aharon Gedanken, and Ze'ev Porat Cryst. Growth Des., Just Accepted Manuscript • DOI: 10.1021/acs.cgd.7b00032 • Publication Date (Web): 14 Mar 2017 Downloaded from http://pubs.acs.org on March 17, 2017

Just Accepted “Just Accepted” manuscripts have been peer-reviewed and accepted for publication. They are posted online prior to technical editing, formatting for publication and author proofing. The American Chemical Society provides “Just Accepted” as a free service to the research community to expedite the dissemination of scientific material as soon as possible after acceptance. “Just Accepted” manuscripts appear in full in PDF format accompanied by an HTML abstract. “Just Accepted” manuscripts have been fully peer reviewed, but should not be considered the official version of record. They are accessible to all readers and citable by the Digital Object Identifier (DOI®). “Just Accepted” is an optional service offered to authors. Therefore, the “Just Accepted” Web site may not include all articles that will be published in the journal. After a manuscript is technically edited and formatted, it will be removed from the “Just Accepted” Web site and published as an ASAP article. Note that technical editing may introduce minor changes to the manuscript text and/or graphics which could affect content, and all legal disclaimers and ethical guidelines that apply to the journal pertain. ACS cannot be held responsible for errors or consequences arising from the use of information contained in these “Just Accepted” manuscripts.

Crystal Growth & Design is published by the American Chemical Society. 1155 Sixteenth Street N.W., Washington, DC 20036 Published by American Chemical Society. Copyright © American Chemical Society. However, no copyright claim is made to original U.S. Government works, or works produced by employees of any Commonwealth realm Crown government in the course of their duties.

Page 1 of 17

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Crystal Growth & Design

Stiffening of Metallic Gallium Particles by Entrapment of Organic Molecules Vijay Bhooshan Kumar (1), Olga Girshevitz (1), David Avnir (2), Aharon Gedanken (1) and Ze’ev Porat (3, 4) * (1) Bar Ilan Institute for nanotechnology and advanced materials, Department of Chemistry, BarIlan University, Ramat-Gan 52900, Israel. (2) Institute of Chemistry and the Center for Nanoscience and Nanotechnology, the Hebrew University of Jerusalem, Jerusalem 91904, Israel (3) Division of Chemistry, Nuclear Research Center-Negev, Be’er Sheva 84190, Israel. (4) Institutes of Applied Research, Ben-Gurion University of the Negev, Be’er Sheva 84105, Israel. *Corresponding authors: [email protected] Tel: 972-8-6567449; Fax: 972-8-6567750 KEYWORDS: Gallium particles, XRD, PFM, stiffness measurements

ABSTRACT This work describes stiffness measurements of gallium particles that include entrapped organic molecules, using PeakForce Tapping® technology, particularly PeakForce QNM (Quantitative Nanomechanical) characterization. The composite particles were formed by ultrasonic irradiation of molten gallium in decane or in aqueous solutions of three organic compounds: phenanthroline, Congo red or crystal violet. It was found that the Ga particles formed in the aqueous solutions of the organic compounds demonstrated very similar stiffness values, regardless of the identity of the organic compound. Moreover, those stiffness values were ca. 5 times higher than the stiffness of the Ga particles formed in pure decane. We attribute the superior stiffness to the formation of hybrids in which the organic molecules were partially incorporated within the crystal lattice of the gallium particles. ACS Paragon Plus Environment


1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

1. INTRODUCTION Liquid metals are characterized by the largest surface tension of any ﬂuid, having high electrical conductivity and density 1–4. Metals such as bismuth, gallium, indium and lead were found to be applicable in various fields of science and technology, particularly in electronic and nuclear industries. Among these metals, gallium exhibits a wide range of temperatures in the liquid state due to its low melting point (29.8 oC) and high melting point (2237 oC), and the surface tension of liquid gallium was the subject or several studies

3,4

. Liquid gallium and gallium alloys, under

small stress, exhibit a solid-like elastic response, which was explained by the oxidation of the metal when exposed to ambient atmosphere 5–7. Moreover, gallium, which is highly wetting when oxidized, becomes non-wetting on glass when oxidation is prevented.7 Xu et al. measured the surface tension with a pendant drop method and showed that the oxide skin generates a surface stress that mimics surface tension 6. High-temperature shear properties of molten metals under steady state have been found to exhibit non-Newtonian behavior 8. The incorporation of organic molecules in metals or on metal surfaces has recently gained much attention due to the potential applications in various areas such as catalysis, molecular switches and sensors, photovoltaics and energy materials.9–13. These interfaces synergistically combine the best features of two distinct component materials. For example, the electrical conductivity of the metal and the highly tunable properties of organic molecules. resulting in new functionalities that are not possessed by either of the materials separately.14 Recently, we reported on the formation of stable gallium micro- and nano spheres by ultrasonic cavitation of molten gallium in warm water 15,16. These particles were found to be spherical, in the size-range from tens of nanometers to several micrometers. Their surface was covered with crystallites of GaO(OH), and at least part of the spheres was found to be hollow. The GaO(OH) crystallites were the product of a sonochemical reaction between the Ga particles with oxygen and

ACS Paragon Plus Environment

Page 2 of 17

Page 3 of 17

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


OH radicals which are formed in water upon ultrasonic irradiation17. When the Ga particles were formed from aqueous solutions of some organic compounds such as phenanthroline or Congo red, it was found that certain amounts of the organic compounds were entrapped within the gallium particles 15. Some of the entrapped molecules leached out slowly upon immersion of the particles in pure water for several weeks. The molecules that stayed entrapped could be released by complete dissolution of the particles in HCl. Experiments with a chiral compound (tryptophan) showed that the organic molecules can also imprint chirality on the surface of the formed particles 18

. SEM images of the particles that were formed in solutions of organic compounds showed no

GaO(OH) crystallytes on their surface [9, 10]. A possible explanation could be that the organic compounds act as scavengers of the OH radicals and thus prevent their reaction with the gallium. Another possible explanation is that the attachment of these compounds on the outer surface might be a competing process to the crystal formation. PeakForce QNM is a quantitative AFM-based technique that allows simultaneous imaging of the structure and measurements of the adhesion and mechanical properties of the sample at high speed and high resolution 19. In this technique, the probe is oscillated in the vertical direction with amplitude of 100-300 nm at frequencies up to 2 kHz. The Z piezo is driven with a sinusoidal waveform in conventional force-distance (F-D) curves. The oscillating system enables direct force control of damaging lateral forces, which is important for the structural imaging of soft samples such as gallium particles. Moreover, adhesion and mechanical maps can be obtained by analysis of the individual force curves to generate to a much better resolution (up to 2048×2048 pixels) than in conventional force-volume (F-V) imaging (64 pixels×64 pixels). In PeakForce QNM the F-D curves are recorded at frequencies that are 3 orders of magnitude higher than in F-V imaging, and therefore the imaging speed is similar to that of topographic imaging, being faster than the conventional F-V imaging 20.



1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

The influence of organic dopants on the physical properties of solids has been reported in the literature. Recently Avnir et al. reported on metal-organic composites having remarkable physical and mechanical properties21. Kim et al. reported on a model system created by incorporation of amino acids such as glycine (Gly) and aspartic acid (Asp) in calcite. They demonstrated that the nano-indentation hardness increased with increasing the concentration of the amino acid content22. The current study describes comparative PFM measurements of the stiffness of the micron-size gallium particles that were formed in decane and in aqueous solutions of three organic compounds: phenanthroline, Congo red or crystal violet.

2. EXPERIMENTAL 2.1 Chemicals: Metallic gallium (>99.8%), decane (anhydrous, 99.98), and phenanthroline (99.98 % were purchased from Aldrich and used as received. Ar (99.999%) was used for degassing of water. Distilled water was obtained from a TREIONTM purification system. 2,2 Synthesis: Gallium particles were prepared in water, decane or in an aqueous solution of phenathroline, Congo red or crystal violet (ca. 10 mM each) by the following procedure: A weighted granule of gallium (0.5g) was inserted into a spherical test tube, which contained 12 ml of one of the liquids. It was heated in a water bath at 55oC for approximately 20 minutes to assure complete melting of the gallium, thus forming a separate liquid phase at the bottom of the test tube. The ultrasonic horn was dipped into the test tube with its end suspended ca. 2 cm above the liquid gallium. Irradiation of the system for 2-3 minutes caused dispersion of the molten gallium and formation of a grey suspension of micro- or nano- particles that precipitated slowly to the bottom of the test tube. The particles were separated by centrifugation, washed with water and dried.


Page 4 of 17

Page 5 of 17

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


2,3 Equipment: Peak-Force Microscopy imaging: PeakForce QNM (PeakForceTM Quantitative Nanonechanical Mapping) were done by using Bio FastScan Scanning Probe Microscope (Bruker corp., USA). These measurements were performed under ambient conditions (22.3 °C and 48% humidity). The microscope was covered with an acoustic hood to minimize vibrational noise. FastScan-C cantilevers (Bruker) with spring constants of 0.45 N/m were used. The fast scan direction was perpendicular to the cantilever long axis, and the images were captured in the retrace direction. Topographic height images and simultaneous phase, modulus, stiffness and adhesion maps were recorded at 512 x 512 pixels at 1 kHz. From the knowledge of the probe signal sensitivity (nm/V) and spring constant (nN/nm), raw deflection vs. displacement plots were converted into force vs. distance for comparing adhesion force vs. surface. All images were flattened and plane-fitted by using the NanoScope Analysis software (Bruker). Samples for each of these measurements were prepared by applying a small droplet of an aqueous suspension of the particles on a clean glass slide followed by drying under vacuum. The suspension was prepared by dispersion of a small quantity of the particles in water using an ultrasonic cleaning bath for 2 min. at 4 °C. X-ray diffraction (XRD) was performed with a high resolution Bruker D8 Advance or a Philips PW1050 X-ray diffractometer using Cu Kα radiation operating at 40 kV/30 mA with a 0.0019 step size and a 0.5 sec. step. All measurements were performed at very slow scan rates. Analysis of the diffractograms was done by the Rietveld’s refinement method using two programs: Powder Cell for Windows (PCW) and FullProf (FP).

3. RESULTS AND DISCUSSION SEM images of the particles that were obtained in the three media are shown in Fig. 1. The particles that were formed in pure water were covered with small crystallites which were



1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

identified by X-ray diffraction as GaO(OH) (Fig. 1A). These were formed by the reaction of the gallium particles with dissolved oxygen and OH radicals originated by some sonochemical decomposition of water. Much less of these crystallites were observed on the particles that were formed in an aqueous solution of phenanthroline whereas none were formed in decane (Fig 1b, c). SEM images of particles that were formed in aqueous solution of Congo red15 and tryptophan18 showed that they were also smooth. In a previous work we showed that ultrasonic formation of gallium particles in aqueous solution of tryptophan led to partial chiral imprinting of these molecules on the surface of the particles. Such imprinting can occur with other organic compounds as well, like phenanthroline or Congo red. Thus, the lack of crystallites on the surface of the gallium particles that were formed in the aqueous solution can be explained either by competing surface processes (imprinting vs. crystallization of GaO(OH)) or by scavenging of the OH. radicals by the dissolved organic compounds. Comparative examination of the five kinds of Ga particles by X-ray diffraction (Figure 2a and 2b) revealed that: (a) they were mostly crystalline but also somewhat amorphous. (b) The particles that were formed in pure water included crystalline GaO(OH), whereas no peaks for GaO(OH) could be observed in the XRD patterns for the particles that were formed in decane or in the aqueous solutions of the three organic compounds, in agreement with the SEM observation.


Page 6 of 17

Page 7 of 17

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


Figure 1. SEM images of Ga particles formed by ultrasonic irradiation in (a) water (b) decane, (c) aqueous solution of 9 mM phenanthroline.

Figure 2: A. XRD patterns of Ga particles formed in (a) aqueous solution of phenanthroline (b) aqueous solution of crystal violet (c) aqueous solution of Congo red, (d) decane (e) pure water. B. Enlargement of the section marked in (A) (vide infra).

PFM is a quantitative AFM-based technique that allows simultaneous imaging of the structure and measurements of the mechanical properties and adhesion of the Ga particles to the surface. Comparative stiffness measurements were done with Ga particles that prepared in decane and in aqueous solution of the three organic compounds: phenanthroline, Congo red and crystal violet. Examples for height-profile AFM images of such particles are shown in Fig. 3a and 3b, and their stiffness maps are shown in Figs. 3c, d, for the Ga particles formed in aqueous solution of phenanthroline and in decane, respectively. The F-D curves for the particles that were formed in the three aqueous solutions are almost overlapping, regardless of the identity of the entrapped compound, whereas the image for the Ga particles that formed in decane is different (Fig. 3e). The stiffness measurements were done for 3-5 particles of each kind, each particle measured once or twice. The results for all four kinds of particles are presented in Table 1, from which the



1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Page 8 of 17

average stiffness values, the standard deviations and the measurement uncertainty were calculated.

Figure 3: AFM images of gallium particles that were formed in (a) aqueous solution of phenathroline (b) decane. (c, d) AFM Tapping mode images of these particles after stiffness measurement. (e) F-D curves obtained from the different kinds of particles in the PFM measurements. Scale bar for all images: 500 nm.

An attempt to measure the stiffness of particles that were formed in pure water and were coated with GaO(OH) was not successful due to charging effect of the GaO(OH) crystallites on the surface of Ga particles. As a result, Ga spheres covered with GaO(OH) were attached to the AFM tip and thus measurement was not possible. Table 1: The results of stiffness measurements of the gallium particles Stiffness (mN) particle

1

2

3

4

5

1

33

29

31

37

33

2

34

33

33

35

31

ave.

33.5

31

32

origin Ga formed in decane

36

32


ave. (mN)

33

sd

unc.*

1.7

2.1

Page 9 of 17

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


aqueous

1

152

150

179

145

149

2

156

152

178

132

171

ave.

154

151

178.5

138.5

169

158

14

17.4

1

148

138

149

161

146

148

7.4

9.2

1

139

143

186

--

--

156

21.3

52.9

phenanthroline aqueous Congo red aqueous crystal violet

* Based on student’s t for 95% confidence level.

Several observations are apparent from these results: a) Good repeatability of the results for the particles that were measured twice. b) Good agreement between the results of the 3 or 5 particles of each kind. c) Remarkable proximity between the average results of particles that were formed in the solutions of the three organic compound. d) A prominent difference between the stiffness results of the Ga particles that were formed in decane to those formed in the three solutions of the organic compounds (Fig. 4). The first two observations demonstrate the credibility of the measurements whereas the latter observations demonstrate the difference between Ga particles that were formed in decane to those formed in the aqueous solutions of the various organic compounds, regardless of their nature.



1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Page 10 of 17

Fig. 4: Comparative presentation of the average stiffness results for the gallium particles that were formed in decane and aqueous solutions of phenanthroline, Congo red and crystal violet. The error bars represent the uncertainties based on the standard deviation. The lack of any effect related to the nature of the entrapped organic molecules on the stiffness of the particles and the large difference with respect to the decane-formed Ga particles may be explained by the incorporation of the organic compounds within the crystal lattice of gallium, forming gallium-organic molecules hybrids. Such a phenomenon was recently described by Pokroy and coworkers, who incorporated various amino acids into crystals of zinc oxide23, calcite24 and gold25, and found that the dimensions of lattice constants increased as a result. In these three cases the crystals were grown in solutions containing the amino acids, which were found to be incorporated within the products. The metallic gold was formed by polyol reduction of HAuCl4 with simultaneous and spontaneous incorporation of the amino acids. The product was a hybrid nano-composite gold crystals, composed of an inorganic host with an organic constituent. Examination of the products by high-resolution powder XRD revealed that the diffraction peaks were slightly shifted to smaller angles, corresponding to crystal-lattice


Page 11 of 17

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


expansion. This was the first report on the incorporation of organic molecules within the lattice of a metal single crystal25. In our work, crystalline particles of gallium were formed from the molten amorphous metal by acoustic cavitation, induced by ultrasonic energy. Here, too, the incorporation of the organic matter could occur simultaneously with the crystallization of gallium. Examination of the dried particles by XRD (Fig. 2B) showed that the gallium was mostly crystalline. Enlargement of the strongest signal at 2θ≈30° revealed slight shifts (0.2 °) of the signals for the particles formed in the presence of the three organic molecules to higher angels. Although the direction of the shift is opposite to that observed by Pokroy et al., it indicates that the crystal lattice of gallium has slightly changed as a result of the interaction with the organic molecules. Moreover, the same signal for gallium particles that were formed in decane showed a slight shift of 0.1 ° to the opposite direction with respect to the others, which means an opposite effect on the crystal lattice. In a previous work, describing the entrapment of these organic substances within gallium particles, we found that their concentrations in the aqueous solutions decreased by 24-32% after sonication, as measured by UV-vis. spectrometry. After separation by centrifugation, the particles were rinsed 2-3 times with water, immersed in pure water for four weeks for leaching measurements and then dissolved in HCl. Measuring the concentrations of phenanthroline and Congo red in the rinsing water, in the leaching solutions and after total dissolution of the particles enabled us to make a molar balance for each compound. Large parts of the “missing” substances were found in the rinsing water, which may come from absorbed or imprinted molecules, whereas the rest of the organic molecules were entrapped within the particles and leached out slowly or remained inside. The idea of incorporation of organic molecules within the crystal lattice of the metal opens a third possibility for the location of these molecules in the gallium particles.



1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Page 12 of 17

The higher stiffness of the Ga particles that include entrapped organic molecules may be related to the smaller unit cell (a= 0.4523 nm, b=0.7661 nm, c=0.4524 nm) of the orthorhombic system, which is more difficult to be compacted, in contrast to the Ga formed in decane that shows larger "blown" unit cells (Table 2). The lack of stiffness differences in the presence of the three organic molecules is a result of the almost equal dimensions of the lattices with these entrapped molecules. The difference between the reduced lattice dimensions in our case to the expansion of the cell dimension in the presence of amino acids, reported by Chen25, can be explained by the different distributions of the entrapped molecules. The amino acids are indeed entrapped in the metallic lattice whereas in our case most of the molecules are located on the surface of the Ga particle and only a small amount is entrapped inside the crystal lattice. Moreover, larger amounts of adsorbed or imprinted molecules on the surface might further squeeze the dimensions of the unit cell. A qualitative estimation of the relationship between the amount of entrapped molecules to the lattice dimensions and stiffness can be done by varying the concentrations of the organic compounds in the starting solutions and measuring the stiffness in each case. This will be done in a future work.

Table 2: The lattice parameter of Ga particles obtained from the XRD plot. Medium

Latice parameter (nm)

Crystal type

Water

a= 0.4523, b=0.7661 , c=0.4524

Orthorhombic

Decane

a=0.4552, b=0.7670, c=0.4541

Orthorhombic

Aq. phenanthroline, crystal violet

a=0.4520, b=0.7643, c=0.4512

Orthorhombic


Page 13 of 17

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


4. CONCLUSIONS Ultrasonically-formed Ga particles in aqueous solutions of three organic compounds (phenanthroline, Congo red and crystal violet) were found to exhibit 5-fold larger stiffness values with respect to Ga particles that were similarly formed in pure decane. Moreover, these values were almost identical, regardless of the identity of the compound. In previous works we have shown that such organic compounds interacted with the formed Ga particles, either as adsorbed/imprinted molecules on their surface or entrapped within them. The enhanced stiffness measured in this work for the organic-gallium composited raised the possibility that the organic molecules could be entrapped within the crystal lattice of gallium and thus affect the stiffness of the material. Such inclusion of organic molecules within the crystal lattice of metallic gold has been reported in the literature.

ACKNOWLEDGEMENT The authors thank Ms. Meharav and Ms. Ortal of the Department of Chemistry at the Bar-Ilan University for their help with the PeakForce QNM measurement.

REFERENCES (1)

Spells, K. E. The Determination of the Viscosity of Liquid Gallium over an Extended Nrange of Temperature. Proc. Phys. Soc. 2002, 48, 299–311.

(2)

Alchagirov, B. B.; Mozgovoi, A. G. The Surface Tension of Molten Gallium at High Temperatures. High Temp. 2005, 43, 791–792.

(3)

Abbaschian, G. J. Surface Tension of Liquid Gallium. J. Less-Common Met.



1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Page 14 of 17

1975, 40, 329–333.

(4)

Hardy, S. C. The Surface Tension of Liquid Gallium. J. Cryst. Growth 1985, 71, 602–606.

(5)

Larsen, R. J.; Dickey, M. D.; Whitesides, G. M.; Weitz, D. a. Viscoelastic Properties of Oxide-Coated Liquid Metals. J. Rheol. (N. Y. N. Y). 2009, 53, 1305.

(6)

Xu, Q.; Oudalov, N.; Guo, Q.; Jaeger, H. M.; Brown, E. Effect of Oxidation on the Mechanical Properties of Liquid Gallium and Eutectic Gallium-Indium Effect of Oxidation on the Mechanical Properties of Liquid. Phys. Fluids 2012, 24, 603101-1–18.

(7)

Dickey, M. D.; Chiechi, R. C.; Larsen, R. J.; Weiss, E. A.; Weitz, D. A.; Whitesides, G. M. Eutectic Gallium-Indium (EGaIn): A Liquid Metal Alloy for the Formation of Stable Structures in Microchannels at Room Temperature. Adv. Funct. Mater. 2008, 18, 1097–1104.

(8)

Jeyakumar, M.; Hamed, M.; Shankar, S. Rheology of Liquid Metals and Alloys. J. Nonnewton. Fluid Mech. 2011, 166, 831–838.

(9)

Liu, W.; Tkatchenko, A.; Scheffler, M. Modeling Adsorption and Reactions of Organic Molecules at Metal Surfaces. Acc. Chem. Res. 2014, 47, 3369– 3377.

(10) Tautz, F. S. Structure and Bonding of Large Aromatic Molecules on Noble Metal Surfaces: The Example of PTCDA. Prog. Surf. Sci. 2007, 82, 479–520. (11) Morgenstern, K. Switching Individual Molecules by Light and Electrons: From Isomerisation to Chirality Flip. Prog. Surf. Sci. 2011, 86, 115–161. (12) Lu, W.; Lieber, C. M. Nanoelectronics from the Bottom Up. Nat. Mater. 2007, 6, 841–850. (13) Waser, R.; Aono, M. Nanoionics-Based Resistive Switching Memories. Nat. Mater. 2007, 6, 833–840.


Page 15 of 17

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


(14) Xu, Y.; Hofmann, O. T.; Schlesinger, R.; Winkler, S.; Frisch, J.; Niederhausen, J.; Vollmer, A.; Blumstengel, S.; Henneberger, F.; Koch, N.; et al. Space-Charge Transfer in Hybrid Inorganic-Organic Systems. Phys. Rev. Lett. 2013, 111, 1–5. (15) Kumar, V. B.; Koltypin, Y.; Gedanken, A.; Porat, Z. Ultrasonic Cavitation of Molten Gallium in Water: Entrapment of Organic Molecules in Gallium Microspheres. J. Mater. Chem. A 2014, 2, 1309. (16) Kumar, V. B.; Gedanken, A.; Kimmel, G.; Porat, Z. Ultrasonic Cavitation of Molten Gallium: Formation of Micro- and Nano-Spheres. Ultrason. Sonochem. 2014, 21, 1166–1173. (17) Kumar, V. B.; Gedanken, A.; Porat, Z. Facile Synthesis of Gallium Oxide Hydroxide by Ultrasonic Irradiation of Molten Gallium in Water. Ultrason. Sonochem. 2015, 26, 340–344. (18) Kumar, V. B.; Mastai, Y.; Porat, Z.; Gedanken, A. Chiral Imprinting in Molten Gallium. New J. Chem. 2015, 39, 2690–2696. (19) García, R. Dynamic Atomic Force Microscopy Methods; 2002; Vol. 47. (20) Derjaguin, B. V; Muller, V. M.; Toporov, Y. U. P. Effect of Contact Deformation on the Adhesion of Particles. J. Colloid Interface Sci. 1975, 52, 105–108. (21) Avnir, D. Molecularly Doped Metals. Acc. Chem. Res. 2014, 47, 579–592. (22) Kim, Y.-Y.; Carloni, J. D.; Demarchi, B.; Sparks, D.; Reid, D. G.; Kunitake, M. E.; Tang, C. C.; Duer, M. J.; Freeman, C. L.; Pokroy, B.; et al. Tuning Hardness in Calcite by Incorporation of Amino Acids. Nat. Mater. 2016, in press, DOI: 10.1038/nmat4631. (23) Brif, A.; Ankonina, G.; Drathen, C.; Pokroy, B. Bio-Inspired Band Gap Engineering of Zinc Oxide by Intracrystalline Incorporation of Amino Acids. Adv. Mater. 2014, 26, 477–481.



1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

(24) Borukhin, S.; Bloch, L.; Radlauer, T.; Hill, A. H.; Fitch, A. N.; Pokroy, B. Screening the Incorporation of Amino Acids into an Inorganic Crystalline Host: The Case of Calcite. Adv. Funct. Mater. 2012, 22, 4216–4224. (25) Chen, L.; Polishchuk, I.; Weber, E.; Fitch, A. N.; Pokroy, B. Hybrid Gold Single Crystals Incorporating Amino Acids. Cryst. Growth Des. 2016, 16, 2972–2978.


Page 16 of 17

Page 17 of 17

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


For Table of Contents Use Only Title: Stiffening of Metallic Gallium Particles by Entrapment of Organic Molecules Authors:

Vijay Bhooshan Kumar (1), Olga Girshevitz (1), David Avnir (2), Aharon Gedanken (1)

and Ze’ev Porat (3, 4)

Synopsis:

This work compares the stiffness of micrometric gallium particles which were formed by ultrasonic cavitation in various liquid media. It was found that formation of Ga in aqueous solutions of various organic compounds yielded remarkably stiffer particles than those formed in decane. We attribute the superior stiffness to the formation of hybrids in which the organic molecules were incorporated within the crystal lattice of the gallium.


Stiffening of Metallic Gallium Particles by Entrapment of Organic

Recommend Documents