DOI: 10.1002/chem.201406428

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Synthesis, Crystal Structure, and Colloidal Dispersions of Vanadium Tetrasulfide (VS4) Mariia N. Kozlova,*[a, b] Yuri V. Mironov,[a, b] Ekaterina D. Grayfer,[b] Anton I. Smolentsev,[a, b] Vladimir I. Zaikovskii,[a, c] Nadezhda A. Nebogatikova,[d] Tatyana Yu. Podlipskaya,[b] and Vladimir E. Fedorov*[a, b]

Abstract: Although many of the layered metal chalcogenides, such as MoS2, are well-studied, some other chalcogenides have received less attention by comparison. In particular, there has been an emerging interest in vanadium tetrasulfide (VS4), which displays useful properties as a component of hybrids. However, the synthetic methods and characteristics of individual VS4 are not yet well defined, and there is no report on its solution processability. Here we have synthesized VS4 by a simple and fast direct reaction between elements. Reinvestigation of the VS4 crystal structure yielded more precise atomic coordinates and interatomic distances,

thereby confirming the crystallization of VS4 in the monoclinic C2/c group and its quasi-1D chainlike structure. As the chains in VS4 are only bonded by weak van der Waals forces, we further demonstrate that bulk VS4 may be ultrasonically dispersed in appropriate solvents to form colloids, similarly to the layered chalcogenides. VS4 particles in colloids retain their phase identity and rod-shaped morphology with lengths in the range of hundreds of nanometers. Isopropanol dispersion exhibited the highest concentration and stability, which was achieved owing to the repulsion caused by high negative charges on the edges of the particles.

Introduction

Recently, nanomaterials based on vanadium chalcogenides such as layered 2D VS2[6] and chain-structured 1D VS4[7] have gained renewed interest. The most recent studies report growth of the VS4 phase on graphitic surfaces. In these works, VS4 has been synthesized from Na3VO4 and C2H5NS under hydrothermal conditions on different species (e.g., graphene oxide, carbon nanotubes, perylene-3,4,9,10-tetracarboxylic dianhydride). Graphene oxide was found to promote the formation of vanadium tetrasulfide most effectively. Such VS4-reduced graphene oxide nanocomposites exhibit good functional characteristics (high rate capability and cycling performance including mechanical flexibility) in devices for energy storage.[7] However, other than those recent studies, little information is available on this interesting compound. Naturally, VS4 occurs as a mineral named patronite, but its laboratory synthesis is insufficiently described. In a few works from several decades ago, VS4 was synthesized from V2S3 and sulfur by heating at 400 8C,[8] in some cases for as long as four months.[8a] The first single-crystal data were obtained on the samples synthesized by this method.[8a] Some papers reported low-temperature synthetic routes whereby VCl4 was treated with hexamethyldisilthiane, di-tert-butyl disulfide, di-tert-butyl sulfide, or hydrogen sulfide.[9] However, the resulting products were amorphous or had poor crystallinity. Finally, the phase diagram of the VS system was studied in detail more than twenty years ago.[10] According to these studies, VS4 is the phase of constant composition, which is stable up to 400 8C and melts incongruently at 400 8C. Thus, vanadium tetrasulfide can be obtained by the synthesis from elemental V and S when heated to 400 8C by using a small excess amount of

Transition-metal oxides[1] and chalcogenides[1, 2] with low-dimensional nature of the crystal lattice are the focus of abundant scientific literature, as they constitute promising materials for energy-storage systems and other areas. The most studied chalcogenide is MoS2,[2h, 3] a member of the family of layered dichalcogenides, which is appealing for use in lithium-ion batteries as cathode[4] as well as anode materials.[2b, 5]

[a] M. N. Kozlova, Dr. Y. V. Mironov, Dr. A. I. Smolentsev, Dr. V. I. Zaikovskii, Prof. V. E. Fedorov Novosibirsk State University 2 Pirogova Str., 630090 Novosibirsk (Russian Federation) E-mail: [email protected] [email protected] [b] M. N. Kozlova, Dr. Y. V. Mironov, Dr. E. D. Grayfer, Dr. A. I. Smolentsev, Dr. T. Y. Podlipskaya, Prof. V. E. Fedorov Nikolaev Institute of Inorganic Chemistry Siberian Branch of Russian Academy of Sciences 3 Akad. Lavrentiev Ave, 630090 Novosibirsk (Russian Federation) [c] Dr. V. I. Zaikovskii Boreskov Institute of Catalysis Siberian Branch of the Russian Academy of Sciences 5 Acad. Lavrentiev Ave., Novosibirsk, 630090 (Russian Federation) [d] N. A. Nebogatikova Rzhanov Institute of Semiconductor Physics Siberian Branch of the Russian Academy of Sciences 13 Acad. Lavrentiev Ave. Novosibirsk, 630090 (Russian Federation) Supporting information for this article is available on the WWW under http://dx.doi.org/10.1002/chem.201406428. It includes details on the Raman, UV/Vis, DLS, z potential, AFM, TEM, and SEM measurements. Chem. Eur. J. 2015, 21, 1 – 8

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Full Paper sulfur to ensure equilibrium with the liquid phase. To the best of our knowledge, however, this simple approach has received surprisingly little attention in the literature.[11] However, nanosized VS4 has only been described as a component of the aforementioned composites with reduced graphene oxide and related materials. To the best of our knowledge, no report exists on individual VS4 nanostructures. Considering that VS4 has linear chain fragments in its structure (Figure 1), we envisage that interchain interactions might be manipulated and weakened so that the bulk is broken into nanosized fragments following a top-down approach. It is known that separation of layers and exfoliation for layered compounds might be achieved through intercalation or exchange of molecules or ions, often helped by ultrasonic treatment.[12] Depending on the interaction strength between the host and guest, the guest molecules either stay fixed between layers to form an intercalated phase, or stabilize completely or partly separated host layers in dispersion. As for chain-structured compounds, their intercalation[13] or liquidphase dispersion[14] is less studied than layered systems; however, some examples might be found in the literature. Recently, we succeeded in transferring niobium trichalcogenides NbS3 and NbSe3, which display both 1D and 2D characteristics, into colloids by means of ultrasonic treatment in organic media.[15] Quasi-1D compounds M2Mo6X6 (M = Li, Na; X = Se, Te) completely or partly delaminate in organic solvents to form either true solutions or colloid dispersions. For example, Li2Mo6Se6 disperses in N-methylformamide and dimethyl sulfoxide into individual (Mo3Li3)11 chains,[14] whereas Na2Mo6Se6 forms col-

loids that contain rod-shaped particles. Other examples of chain-structured compounds that form solutions or colloids under certain conditions are KFeS2,[14a] thiophosphates NaV1xP2S6 (x = 0.16),[16] tellurophosphate K4P8Te4,[17] NaPdPS4 and RbPdPS4,[18] and others. Colloidal dispersions of layered or chain-structured compounds were successfully applied in the assembly of thin films and the preparation of multifunctional composites, new intercalation compounds, large-surface area catalysts, and so forth. It is therefore interesting to investigate VS4 in its bulk and nanosized state by applying modern characterization tools to fully exploit the potential of this material. In this work we perform a simple and convenient direct synthesis of VS4 powder and single crystals from vanadium and sulfur, reinvestigate its crystal structure, and demonstrate its dispersibility in organic media with the formation of stable colloids that contain VS4 nanorods.

Results and Discussion Crystal structure Vanadium tetrasulfide VS4, which occurs naturally as the mineral patronite, crystallizes in the monoclinic form. The crystal structure of patronite was solved a long time ago, and here we reexamine the structure of VS4 prepared synthetically by a simple direct reaction between elements. Several studies on the structure of vanadium tetrasulfide VS4 can be found in the literature. The earliest work[8a] reported only approximate unit-cell parameters and the space group, whereas two subsequent works[19] provided detailed information on the atomic arrangement. The structure is monoclinic and belongs to the C2 symmetry, which is expressed as the C2/c[8a] or I2/c[19] space groups in the literature. The transformation rule between these two crystallographic settings is aI = aC + cC, bI = bC, cI = cC. The unit-cell parameters obtained in the present work are a = 12.7131(6), b = 10.3532(6), c = 6.7494(4) , b = 110.825(1)8, with Z = 8 and space group C2/ c (Table 1). These can be transformed to the I2/c formation as follows: a’ = 12.0899(6), b’ = 10.3532(6), c’ = 6.7494(4) , b’ = 100.627(1)8, which is close to the previously reported data (Table 1). However, the non-standard I2/c space group is not commonly used since it is a left-handed system; in most cases, it is recommended to use the C2/c system to avoid any confusion, even if this system is less “orthogonal”. The assignment of the I2/c space group in the literature[19] was not well argued and cannot be considered unambiguous. For this reason, we make the assertion that the structure reported in the literature[19] has an erroneous space group. Some selected interatomic distances are listed in Table S1 of the Supporting Information. The polymeric structure of VS4 can be regarded essentially as quasi-one-dimensional with metal chains (Figure 1). The tetragonal-antiprismatic coordination of metal atoms in VS4 is generated through the right-angled planes (S4) to be formed by (S2)2 groups with the short SS distances of 2.0274(6) and 2.0386(6) . In metal chains, V2 pairs of V4 + ions with a VV

Figure 1. A view of the quasi-one-dimensional chains in the crystal structure of VS4.

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Full Paper pattern of a powder particle is satisfactorily indexed to the single-crystalline monoclinic phase of VS4 as shown in the inset of Figure 2a. According to energyParameter Ref. [8a] Ref. [19a] Ref. [19b] This work dispersive X-ray (EDX) data (Figure 2b), the V/S atomic ratio is close to 1:4. X-ray powder diffraction space group C2/c I2/c I2/c C2/c a [] 12.67 6.780(5) 6.775(5) 12.7131(6) data of VS4 is shown in Figure 2c. The experimental b [] 10.41 10.42(1) 10.42(1) 10.3532(6) data (upper curve) are in good agreement with the c [] 12.11 12.11(1) 12.11(1) 6.7494(4) data calculated from the single-crystal structure b [8] 148.37 100.8(2) 100.8(2) 110.825(1) (lower curve). The absence of intense extraneous reV [3] – 840.39 839.77 830.33(8) Z 8 8 8 8 flections in the experimental diffraction pattern indi2.83 2.83 2.83 2.867 1calcd [g cm3] cates that a single-phase product is formed. The 2 2 – 0.095 0.070 0.0161 R1 [F > 2s(F )] Raman spectrum of VS4 has not been described in – – – 0.0380 wR2(F2) the literature, therefore, we studied the vibrational GoF – – – 1.064 properties of VS4 in the range of 50–1000 cm1 (Figure 2d). There are seven intensive vibration modes lodistance 2.8534(5)  are formed; the V···V distance between cated at about 100, 140, 190, 280, 400, 690, and 990 cm1 and these pairs is 3.1918(5) . Such metal chains with alternating several low-intensive vibration modes in the VS4 Raman specsequences of short and long metal–metal distances together trum. The IR spectrum (Figure S1 in the Supporting Informawith the diamagnetism of the compound support the formation) is characterized by the band at 550 cm1 that corre1 1 tion of a VV metal bond (d –d coupled electrons) indicative sponds to the vibrations of SS groups, which correlates with of a Peierls insulator that is typical of d1 chain compounds. A the literature data.[9] quasi-one-dimensional character of the structure is defined by long interchain V···V distances (> 6.1 ) that lead to excessively Dispersion of VS4 in colloids slight interactions between the neighboring chains.[20] VS4 is an insoluble solid, and, to the best of our knowledge, no report exists on its conversion to the colloidal state. However, Characterization of bulk VS4 considering its structure (Figure 1), we figured that it could be dispersed in the liquid phase under some conditions. Bulk VS4 The powder sample is shaped as elongated crystals with lengths mostly in the range of 10–20 mm and widths below is composed of chainlike fragments bound by weak dispersive 2 mm as seen from the scanning electron microscopy (SEM) forces with interchain distances of more than 6.1 , which is image presented in Figure 2a. The fast Fourier transform (FFT) comparable to interlayer distances in dispersible layered VS2 (5.8 ) and MoS2 (6.7 ). We envisaged that solvent molecules could enter these wide interchain spaces and push them apart to some extent, as happens with interlayer spaces of layered materials. Motivated by the potential of VS4 colloids in the preparation of thin films and composites for energy storage and conversion, catalysis and sensing, and other areas, we attempted to disperse it in a number of organic solvents. We chose to test a number of easily available solvents with different properties (Table 2). Bulk VS4 was ultrasonically treated in a solvent, large undispersed particles were isolated from solution by settling, and the upper part of the colloidal dispersion was separated and examined by a set of methods. Figure 2. Characteristics of the VS4 powder sample: a) SEM image; inset: fast Fourier transform pattern with indexDispersions have a dark gray ing reflections with a [021] zone axis. b) EDX data. c) X-ray diffraction powder (upper curve) and data calculated or violet color if the concentrafrom single-crystal structure (lower curve). d) Raman spectrum. Table 1. Crystal data and structural refinement of VS4 in comparison with literature data.

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Full Paper ment with previous observations on other chalcogenides, such as MoS2[21] and NbS3.[15a] At the same time, N-methylpyrrolidone (NMP), a well-established solvent for layered materials, did not produce any dispersion of chain-structured VS4. The resulting dispersions were investigated by UV/Vis spectroscopy (Figure 3b). According to the obtained data, the value of the VS4 concentration in dispersions obeys the equation A/l = aC, in which A = absorbance, l = length of the cell, a = extinction coefficient, and C = concentration of the dispersion. For example, the isopropanol dispersion shows a linear dependence of the absorption (at 760 nm) on the dispersion concentration (Figure 3c); the extinction coefficient a was 1.62 L mg1 m1). The applicability of this equation for colloidal dispersions of several materials, such as MoS2, WS2, and BN, was shown in the work.[12c] UV/Vis spectra of VS4 dispersions demonstrate the large absorption in the region of 400–1100 nm, whereas the experimental spectrum looks superimposed on the background and decreases in the area of large wavelengths. We suppose that this background is responsible for the scattering of light by particles manifested in the Tyndall effect (shown in Figure 3a). To prove this, we plotted the spectra on a log/log scale (see Figure S3 in the Supporting Information). From the logarithmic graph, one can observe a linear decrease in the area of large wavelengths (800–1100 nm) of the spectrum taken with the isopropanol dispersion. Such behavior of the spectrum is consistent with the pattern of light scattering determined by the Rayleigh formula (characteristic dependence is A  ln). The obtained coefficient of a linear dependence n is equal to 1.38 for isopropanol and to 1.66 for acetonitrile dispersions, which is consistent with the model of Mie scattering (the expected value of n is in the range from 1 to 4).[12c] Various VS4 dispersions are stable for tens and hundreds of hours (up to two weeks). Aggregated precipitate can be easily redispersed by short sonication. Analysis of the z potential was performed to determine the stability of the colloids. The measurements carried out on the isopropanol dispersion showed that the VS4 particles were negatively charged with a z potential of 34 mV. This surface charge results in electrostatic repulsion between VS4 particles and ensures the stability of the colloid. Note that when an electrolyte such as KCl was added to the colloid, precipitation began shortly afterward (but not immediately, probably owing to the relatively low solubility of KCl in isopropanol). This observation provides further evidence of a charge-stabilized dispersion. This negative charge might be generated on the edges of the VS4 species owing to the rupture of VS bonds during sonication. The average effective hydrodynamic diameters of VS4 particles in the dispersions were estimated using dynamic light scattering (DLS). For isopropanol dispersions this value was found to be about 175 nm (Figure 4a). Atomic force and transmission electron microscopy (AFM and TEM) studies were carried out to understand the structure, size, and morphology of the VS4 particles in colloids. According to AFM observations (Figure 4b), when the solvent evaporates, particles tend to stick together, thus indicating high surface tension. Particles tend to collect in “islands” and “coral reefs”,

Table 2. Concentrations of VS4 dispersed in common solvents.[a] Solvent

VS4 concentration [mg L1]

water EtOH EtOH/water (1:1 v/v) iPrOH CH3CN DMF DMSO NMP acetone

no dispersion, no wettability 174 219 316 78 187 37 no dispersion poor dispersion

[a] The data were obtained by a weighing method and are averaged from not less than three trials each.

tion is low (Figure 3a and Figure S2 in the Supporting Information). As a criterion of the dispersive ability of a solvent, the value of the concentration of the material in the dispersion was estimated. To determine the dispersion concentrations, a weighing method was used. The exact amount of dispersion was filtered on a Whatman Anodisc membrane filter with a pore size of 0.02 mm, then the resulting film was dried and weighed. The highest concentration was reached for isopropanol dispersion (about 310 mg L1; Table 2). Also, an ethanol/ water mixture produced good dispersions, being more effective than ethanol or water individually, which was in agree-

Figure 3. Characteristics of VS4 colloidal dispersions: a) Photograph of the dispersion of VS4 in isopropanol; the trace of the laser pointer demonstrates the Tyndall effect. b) UV/Vis spectra of the VS4 dispersions in the following solvents: 1) iPrOH, 2) EtOH, 3) DMF, 4) CH3CN, 5) DMSO. c) Calibration line for the dispersion of VS4 in isopropanol. Correlation dependence between the concentration of the VS4/iPrOH dispersion and the value of the absorption band at 760 nm per cell length. Inset: Absorption spectra for isopropanol dispersions of VS4 that have different concentrations prepared by dilution.

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Full Paper inates in the effects of ultrasound on the solid/liquid system. It is generally supposed that the formation, growth, and implosive collapse of bubbles (known as cavitation), which creates high local temperature and pressure in the solution, is responsible for exfoliation of layered materials. However, when the bubbles collapse on the solid surface itself, they directly damage it by shockwaves.[22] It should be possible to control and direct these two effects by adjusting sonication parameters such as power, frequency, time, and so forth, but this will require future studies. Finally, to ensure that the VS4 nanorods preserved their phase identity, VS4 films with thicknesses from 0.2 to 2 mm were obtained by filtration of dispersions and characterized by powder diffraction and Raman spectroscopy. XRD data for the films made from isopropanol dispersions contain the signals that correspond to the VS4 phase (Figure 5a). XRD patterns for thin films made from other solvents can be found in Figure S4 of the Supporting Information. The change in the ratio of peak intensities of film samples compared to bulk VS4 confirms the texture of the films. Raman spectra of the films contain all the same vibration modes characteristic of bulk VS4 (Figure 5 and Figure S5 in the Supporting Information). These data prove that the rods that form the films are of the VS4 phase, therefore, they keep their structure relatively undamaged.

Figure 4. Investigation of VS4 particle sizes in isopropanol dispersion: a) DLS monomodal distribution of hydrodynamic diameters; b) AFM image in lateral-force mode and their profile; c) TEM image; and d) HRTEM image.

whereas the degree of loose particles is small even at high dilution. Single particles have rod-type or elongated plate shapes; the particle in Figure 4b has a height of about 10 nm, and a length and width of approximately 300 and 100 nm, correspondingly (Figure 4b). HRTEM proves that the nanorods retain good crystallinity (Figure 4d). TEM images also show elongated crystals with lengths of up to hundreds of nanometers (Figure 4c). Interestingly, nanorods tend to align themselves in an end-to-end fashion. Such self-assembly of VS4 nanorods deposited on a TEM grid might be due to the peculiarities of their edges, such as unsatisfied valences of the vanadium atom or functional groups attached to it. This brings about the question as to how the bulk VS4 is converted into dispersed nanorods. The rodlike morphology of the VS4 particles implies that the bulk is preferentially defragmented by separation of weakly bonded chains.[2k] However, the rods deposited from dispersion are not only narrower but also much shorter than in the parent bulk. This means that cutting of the particles perpendicular to the rod axis occurs as well. When the rods are cut, dangling bonds and/or surface charge are generated. Also, solvent molecules might interact chemically with these broken edges, especially given that sonolysis can generate highly active species in solution. Therefore, nanorod edges should be responsible for the surface charge manifested in the high value of the z potential of colloids. Also, the peculiar arrangement of nanorods in TEM experiments might be a consequence of specific interactions of functionalized nanorod edges. Such fragmentation in different directions as a result of ultrasonic treatment is usually observed for other 1D and 2D materials as well: Carbon nanotubes can be not only debundled, but cut into shorter ones; exfoliated layered chalcogenides and graphene usually have limited lateral dimensions. This phenomenon origChem. Eur. J. 2015, 21, 1 – 8

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Figure 5. Characteristics of thin films prepared by filtration of a VS4/iPrOH dispersion: a) XRD pattern of the film (curve 1) in comparison with calculated data (curve 2). The black star indicates the reflection of filter material. b) Raman spectra of the VS4 film (curve 1) and VS4 crystals obtained through high-temperature reaction (curve 2).

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Full Paper Conclusion

Characterization X-ray powder diffraction patterns for solid samples (powders and films) were collected using a Philips PW 1830/1710 automated diffractometer (CuKa radiation, graphite monochromator, silicon plate as an external standard). X-ray diffraction intensity measurements performed for the single crystal with dimensions of 0.25  0.07  0.05 mm3 were carried out using a Bruker-Nonius X8 APEX area-detector diffractometer at 150(2) K using graphite-monochromated MoKa radiation (l = 0.71073 ). The standard data-collection strategy (f scan of narrow frames) was used; 1779 reflections were measured, of which 947 were unique (Rint = 0.0122) and 880 were observed with I > 2s(I). Semiempirical absorption corrections were applied using SADABS.[23] The structure was solved by direct methods and refined by full-matrix least-squares on F2 using the SHELXTL software package.[23] Final R factors were: R1 = 0.0161 for 880 observed reflections, wR2 = 0.0380 and GoF = 1.064 for all reflections with 47 refined parameters. Minimum and maximum residual electron densities were 0.408 and 0.293 e 3, respectively.

Reinvestigation of the crystal structure of VS4 undertaken in this study proved that VS4 synthesized by the simple interaction of elements crystallizes in the monoclinic C2/c space group. We have further shown for the first time that the bulk VS4, chain-structured quasi-1D material can be transferred into colloidal dispersions by means of ultrasonic treatment in common organic solvents, similarly to layered compounds. VS4 in colloids exists in the form of negatively charged rod-shaped particles with lengths on the order of hundreds of nanometers. The most effective solvent was isopropanol as it allowed for good stability (over ten days), the highest concentration (about 310 mg L1), ease of processing owing to the low boiling point, and preservation of the phase composition in the films formed from this dispersion. Our results contribute to the growing number of reports on colloids of quasi-1D compounds and open up opportunities for the fabrication of thin films and composites with other dispersible materials for prospective use in energy storage and conversion, catalysis and sensing, and other applications.

Further details of the crystal structure investigation(s) can be obtained from the Fachinformationszentrum Karlsruhe, 76344 Eggenstein-Leopoldshafen, Germany (fax: (+ 49)7247-808-666; e-mail: [email protected]) on quoting the depository number CSD428285.

Experimental Section

Acknowledgements

Synthesis of VS4

This work was supported the Russian Scientific Foundation (project 14-13-00674). The authors would like to thank Dr. I. A. Pyshnaya for z-potential measurements.

A mixture of high-purity powdered elemental vanadium and sulfur with a stoichiometry of V/S = 1:4.1 was loaded into a quartz ampoule, and the ampoule was evacuated until the residual pressure reached 102 torr. The ampoule was sealed, heated to 400 8C, and kept at this temperature for ten days. Then the ampoule was cooled with the furnace. After opening, the excess amount of sulfur was evacuated under dynamic vacuum at 200 8C. The final product (VS4) looked like a well-crystallized material. EDX data: V/S = 21:78 at %. Single crystals suitable for X-ray diffraction to solve the crystal structure were manually separated from the reaction mixtures.

Keywords: chain structures · colloids · sulfur · vanadium · Xray diffraction [1] S. Balendhran, S. Walia, H. Nili, J. Z. Ou, S. Zhuiykov, R. B. Kaner, S. Sriram, M. Bhaskaran, K. Kalantar-zadeh, Adv. Funct. Mater. 2013, 23, 3952 – 3970. [2] a) C. N. R. Rao, A. Nag, Eur. J. Inorg. Chem. 2010, 4244 – 4250; b) G. D. Du, Z. P. Guo, S. Q. Wang, R. Zeng, Z. X. Chen, H. K. Liu, Chem. Commun. 2010, 46, 1106 – 1108; c) C. H. Lai, M. Y. Lu, L. J. Chen, J. Mater. Chem. 2012, 22, 19 – 30; d) X. Huang, Z. Y. Zeng, H. Zhang, Chem. Soc. Rev. 2013, 42, 1934 – 1946; e) M. R. Gao, Y. F. Xu, J. Jiang, S. H. Yu, Chem. Soc. Rev. 2013, 42, 2986 – 3017; f) M. Chhowalla, H. S. Shin, G. Eda, L.-J. Li, K. P. Loh, H. Zhang, Nat. Chem. 2013, 5, 263 – 275; g) D. Ovchinnikov, A. Allain, Y.-S. Huang, D. Dumcenco, A. Kis, ACS Nano 2014, 8, 8174 – 8181; h) C. N. R. Rao, U. Maitra, U. V. Waghmare, Chem. Phys. Lett. 2014, 609, 172 – 183; i) W. Z. Teo, E. L. K. Chng, Z. Sofer, M. Pumera, Chem. Eur. J. 2014, 20, 9627 – 9632; j) X. Chia, A. Ambrosi, D. Sedmidubsky´, Z. Sofer, M. Pumera, Chem. Eur. J. 2014, 20, 17426 – 17432; k) J. Ma, X. Liu, X. Cao, S. Feng, M. E. Fleet, Eur. J. Inorg. Chem. 2006, 519 – 522. [3] T. Stephenson, Z. Li, B. Olsen, D. Mitlin, Energy Environ. Sci. 2014, 7, 209 – 231. [4] a) Y. Miki, D. Nakazato, H. Ikuta, T. Uchida, M. Wakihara, J. Power Sources 1995, 54, 508 – 510; b) C. Julien, S. I. Saikh, G. A. Nazri, Mater. Sci. Eng. B 1992, 15, 73 – 77. [5] J. Xiao, D. W. Choi, L. Cosimbescu, P. Koech, J. Liu, J. P. Lemmon, Chem. Mater. 2010, 22, 4522 – 4524. [6] J. Feng, X. Sun, C. Wu, L. Peng, C. Lin, S. Hu, J. Yang, Y. Xie, J. Am. Chem. Soc. 2011, 133, 17832 – 17838. [7] a) C. S. Rout, B. H. Kim, X. Xu, J. Yang, H. Y. Jeong, D. Odkhuu, N. Park, J. Cho, H. S. Shin, J. Am. Chem. Soc. 2013, 135, 8720 – 8725; b) X. Xu, S. Jeong, C. S. Rout, P. Oh, M. Ko, H. Kim, M. G. Kim, R. Cao, H. S. Shin, J. Cho, J Mater Chem. A 2014, 2, 10847 – 10853; c) J. Y. Pandurangan Mohan, Anirudha Jena, Hyeon Suk Shin, DOI: 10.1016/j.jssc.2014.06.031 2014; d) W. Guo, D. Wu, Int. J. Hydrogen Energy 2014, 39, 16832 – 16840.

Preparation of colloidal dispersions VS4 powder (50 mg) was added to a solvent (30 mL) in covered glass vials and sonicated in an ultrasound bath for 3 h. The following solvents were tested: isopropanol (iPrOH), ethyl alcohol (EtOH), dimethylformamide (DMF), acetonitrile (CH3CN), dimethyl sulfoxide (DMSO), water, EtOH/water (1:1 v/v), acetone, and N-methylpyrrolidone (NMP). Exfoliation of bulk VS4 in organic solvents was carried out in a Sapphire ultrasonic bath (ultrasound power 150 W, frequency 35 kHz). The resulting mixtures were allowed to settle for 15 h. The colloidal dispersions were dark gray in color. The upper portions of the colloidal dispersions were separated and examined by a set of methods.

Preparation of films using colloidal dispersions To establish the nature of the nanoparticles that form colloidal dispersions, the dispersions were filtered through a Whatman Anodisc membrane filter with a pore size of 0.02 mm. The films prepared on the membranes were washed with ethanol and dried at 70 8C for 1 h. Film thicknesses were estimated using their mass, VS4 crystallographic density, and the formula for the area of a circle.

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Full Paper [8] a) B. Pedersen, Acta Chem. Scand. 1959, 13, 1050; b) S. J. Hibble, R. I. Walton, D. M. Pickup, J. Chem. Soc. Dalton Trans. 1996, 2245 – 2251; c) G. Brauer, Handbook of Preparative Inorganic Chemistry Vol. 2, Academic Press, London, 1965, p. 1275. [9] A. Bensalem, D. M. Schleich, Inorg. Chem. 1991, 30, 2052 – 2055. [10] a) M. Yokoyama, M. Yoshimura, M. Wakihara, S. Somiya, M. Taniguchi, J. Solid State Chem. 1985, 60, 182 – 187; b) J. F. Smith, Binary Alloy Phase Diagrams, 3rd ed.,(Ed. T. B. Massalski) 1990, pp. 3292 – 3295. [11] G. Brauer, Handbuch der Praparativen Anorganischen Chemie in drei Banden, 1981. [12] a) V. Nicolosi, M. Chhowalla, M. G. Kanatzidis, M. S. Strano, J. N. Coleman, Science 2013, 340, 1226419; b) A. O’Neill, U. Khan, J. N. Coleman, Chem. Mater. 2012, 24, 2414 – 2421; c) J. N. Coleman, M. Lotya, A. O’Neill, S. D. Bergin, P. J. King, U. Khan, K. Young, A. Gaucher, S. De, R. J. Smith, I. V. Shvets, S. K. Arora, G. Stanton, H.-Y. Kim, K. Lee, G. T. Kim, G. S. Duesberg, T. Hallam, J. J. Boland, J. J. Wang, J. F. Donegan, J. C. Grunlan, G. Moriarty, A. Shmeliov, R. J. Nicholls, J. M. Perkins, E. M. Grieveson, K. Theuwissen, D. W. McComb, P. D. Nellist, V. Nicolosi, Science 2011, 331, 568 – 571. [13] T. Li, Y.-H. Liu, B. Chitara, J. E. Goldberger, J. Am. Chem. Soc. 2014, 136, 2986 – 2989. [14] a) A. Jacobson in Mater. Sci. Forum, Vol. 152, Trans. Tech. Publ., 1994, pp. 1 – 12; b) J. M. Tarascon, F. J. DiSalvo, C. H. Chen, P. J. Carroll, M. Walsh, L. Rupp, J. Solid State Chem. 1985, 58, 290 – 300; c) J. H. Golden, F. J. DiSalvo, J. M. J. Frechet, Chem. Mater. 1995, 7, 232 – 235. [15] a) V. E. Fedorov, S. B. Artemkina, E. D. Grayfer, N. G. Naumov, Y. V. Mironov, A. I. Bulavchenko, V. I. Zaikovskii, I. V. Antonova, A. I. Komonov,

Chem. Eur. J. 2015, 21, 1 – 8

www.chemeurj.org

These are not the final page numbers! ÞÞ

[16] [17]

[18]

[19]

[20] [21] [22] [23]

M. V. Medvedev, J. Mater. Chem. C 2014, 2, 5479 – 5486; b) S. B. Artemkina, T. Y. Podlipskaya, A. I. Bulavchenko, A. I. Komonov, Y. V. Mironov, V. E. Fedorov, Colloids Surf. A 2014, 461, 30 – 39. S. Coste, E. Gautier, M. Evain, M. Bujoli-Doeuff, R. Brec, S. Jobic, M. G. Kanatzidis, Chem. Mater. 2003, 15, 2323 – 2327. I. Chung, J.-H. Song, M. G. Kim, C. D. Malliakas, A. L. Karst, A. J. Freeman, D. P. Weliky, M. G. Kanatzidis, J. Am. Chem. Soc. 2009, 131, 16303 – 16312. S. Coste, J. Hanko, M. Bujoli-Doeuff, G. Louarn, M. Evain, R. Brec, B. Alonso, S. Jobic, M. G. Kanatzidis, J. Solid State Chem. 2003, 175, 133 – 145. a) I. B. R. Allmann, A. Kutoglu, H. Roesch, E. Hellner, E. Naturwissenschaften 1964, 51, 263 – 264; b) R. A. A. Kutoglu, Neues Jahrbuch fuer Mineralogie. Monatshefte (1972) 339 – 345, 1972. V. E. Fedorov, Chalcogenides of transition metals. Quasi-one-dimensional compounds, Science, Novosibirsk, 1988. K.-G. Zhou, N.-N. Mao, H.-X. Wang, Y. Peng, H.-L. Zhang, Angew. Chem. Int. Ed. 2011, 50, 10839 – 10842; Angew. Chem. 2011, 123, 11031 – 11034. G. Cravotto, P. Cintas, Chem. Eur. J. 2010, 16, 5246 – 5259. S. V. Bruker AXS Inc. APEX2 (Version 1.08), SADABS (Version 2.11), SHELXTL (Version 6.12). Bruker Advanced X-ray Solutions, Madison, Wisconsin, USA (2004).

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FULL PAPER & Crystal Structures

Don’t spare the rod: VS4 was synthesized and thoroughly characterized in the bulk and as single crystals, thereby proving its crystallization in the monoclinic C2/c group, its quasi-1D chain structure, and its dispersibility in solvents with the formation of stable colloidal dispersions that contain negatively charged rod-shaped particles (see figure).

M. N. Kozlova,* Y. V. Mironov, E. D. Grayfer, A. I. Smolentsev, V. I. Zaikovskii, N. A. Nebogatikova, T. Y. Podlipskaya, V. E. Fedorov* && – && Synthesis, Crystal Structure, and Colloidal Dispersions of Vanadium Tetrasulfide (VS4)

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 2015 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim

ÝÝ These are not the final page numbers!

Synthesis, crystal structure, and colloidal dispersions of vanadium tetrasulfide (VS4).

Although many of the layered metal chalcogenides, such as MoS2, are well-studied, some other chalcogenides have received less attention by comparison...
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