User:Hayden6226
 ZnS powders containing different concentrations of sulfur vacancies[1]
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| Identifiers | |
3D model (JSmol)
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PubChem CID
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| Properties | |
| ZnS | |
| Molar mass | 97.474 g/mol |
| Density | 4.090 g/cm3 |
| Melting point | 1,850 °C (3,360 °F; 2,120 K) (sublime) |
| negligible | |
| Band gap | 3.54 eV (cubic, 300 K) 3.91 eV (hexagonal, 300 K) |
Refractive index (nD)
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2.3677 |
| Structure | |
| see text | |
| Tetrahedral (Zn2+) Tetrahedral (S2−) | |
| Thermochemistry | |
Std enthalpy of
formation (ΔfH⦵298) |
−204.6 kJ/mol |
| Hazards | |
| NFPA 704 (fire diamond) | |
| Flash point | Non-flammable |
| Safety data sheet (SDS) | ICSC 1627 |
| Related compounds | |
Other anions
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Zinc oxide Zinc selenide Zinc telluride |
Other cations
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Cadmium sulfide Mercury sulfide |
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
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Zinc sulfide (or zinc sulphide) is an inorganic compound with the chemical formula of ZnS. This is the main form of zinc found in nature, where it mainly occurs as the mineral sphalerite. Although this mineral is usually black because of various impurities, the pure material is white, and it is widely used as a pigment. In its dense synthetic form, zinc sulfide can be transparent, and it is used as a window for visible optics and infrared optics.
Structure
[edit]
ZnS exists in two main crystalline forms. This dualism is an example of polymorphism. In each form, the coordination geometry at Zn and S is tetrahedral. The more stable cubic form is known also as zinc blende or sphalerite. The hexagonal form is known as the mineral wurtzite, although it also can be produced synthetically.[2] The transition from the sphalerite form to the wurtzite form occurs at around 1020 °C.
Applications
[edit]Luminescent material
[edit]
Zinc sulfide, with addition of a few ppm of a suitable activator, exhibits strong phosphorescence. The phenomenon was described by Nikola Tesla in 1893,[3] and is currently used in many applications, from cathode-ray tubes through X-ray screens to glow in the dark products. When silver is used as activator, the resulting color is bright blue, with maximum at 450 nanometers. Using manganese yields an orange-red color at around 590 nanometers. Copper gives a longer glow, and it has the familiar greenish glow-in-the-dark. Copper-doped zinc sulfide ("ZnS plus Cu") is used also in electroluminescent panels.[4] It also exhibits phosphorescence due to impurities on illumination with blue or ultraviolet light.
Optical material
[edit]Zinc sulfide is also used as an infrared optical material, transmitting from visible wavelengths to just over 12 micrometers. It can be used planar as an optical window or shaped into a lens. It is made as microcrystalline sheets by the synthesis from hydrogen sulfide gas and zinc vapour, and this is sold as FLIR-grade (Forward Looking Infrared), where the zinc sulfide is in a milky-yellow, opaque form. This material when hot isostatically pressed (HIPed) can be converted to a water-clear form known as Cleartran (trademark). Early commercial forms were marketed as Irtran-2 but this designation is now obsolete.
Pigment
[edit]Zinc sulfide is a common pigment, sometimes called sachtolith. When combined with barium sulfate, zinc sulfide forms lithopone.[5]
Catalyst
[edit]Fine ZnS powder is an efficient photocatalyst, which produces hydrogen gas from water upon illumination. Sulfur vacancies can be introduced in ZnS during its synthesis; this gradually turns the white-yellowish ZnS into a brown powder, and boosts the photocatalytic activity through enhanced light absorption.
The high reduction potential of generated electrons in ZnS contributes to efficient water reduction without requiring noble metal co-catalysts. However, ZnS is prone to severe photocorrosion under illumination, leading to decreased long-term stability. The addition of other materials like sodium sulfide (Na2S) is commonly used to mitigate this, though this method can compromise sustainability due to the consumption of these extra materials.[6]
Degradation of organic pollutants
[edit]Zinc sulfide has been extensively studied for its application in degrading organic pollutants such as dyes in wastewater. The generated electrons and holes from photons can react with water and oxygen to produce reactive species capable of breaking down complex organic molecules. Studies have shown that ZnS exhibits degradation rates comparable to or better than those of titanium dioxide. However, corrosion remains a significant challenge, many times resulting in the formation of zinc sulfate and other byproducts.[6]
Carbon dioxide reduction
[edit]Zinc sulfide has also been explored for photocatalytic carbon dioxide reduction to produce different chemicals like formic acid and methanol. The high reduction potential of ZnS supports electron transfer for these reactions. While this is impressive in theory, the low absorption for CO2 and the prevalence of recombination processes hinder efficiency, limiting the application primarily to academic research.[6]
Semiconductor properties
[edit]Both sphalerite and wurtzite are intrinsic, wide-bandgap semiconductors. These are prototypical II-VI semiconductors, and they adopt structures related to many of the other semiconductors, such as gallium arsenide. The cubic form of ZnS has a band gap of about 3.54 electron volts at 300 kelvins, but the hexagonal form has a band gap of about 3.91 electron volts. ZnS can be doped as either an n-type semiconductor or a p-type semiconductor.
The morphology of zinc sulfide nanostructures in particular can be controlled through synthesis techniques, leading to forms like quantum dots and nanowires. This structural flexibility impacts the surface energy and electron behavior, enhancing its suitability for applications that require specific surface interactions, such as sensors and photocatalysis.
ZnS is known for its chemical stability and relatively low solubility, which make it durable for extended use. In addition, its reactivity, especially at nanoscale levels, enables modifications like doping with metals to alter its electronic properties for more specialized applications such as photovoltaics.[7]
A major obstacle in using ZnS as a photocatalyst is its susceptibility to photocorrosion, which leads to the formation of zinc oxide, sulfur, hydrogen, and zinc sulfate, reducing its effectiveness over time. This corrosion can be increased by the presence of oxygen which alters the reaction pathways and subsequently increases the rate of degradation. Methods such as doping with transition metals like cobalt and immobilizing ZnS on support materials have been studied to enhance stability and reduce photocorrosion.[6]
History
[edit]The phosphorescence of ZnS was first reported by the French chemist Théodore Sidot in 1866. His findings were presented by A. E. Becquerel, who was renowned for the research on luminescence.[8] ZnS was used by Ernest Rutherford and others in the early years of nuclear physics as a scintillation detector, because it emits light upon excitation by x-rays or electron beam, making it useful for X-ray screens and cathode-ray tubes.[9] This property made zinc sulfide useful in the dials of radium watches.
Production
[edit]Zinc sulfide is usually produced from waste materials from other applications. Typical sources include smelter, slag, and pickle liquors.[5] As an example, the synthesis of ammonia from methane requires a priori removal of hydrogen sulfide impurities in the natural gas, for which zinc oxide is used. This scavenging produces zinc sulfide:
- ZnO + H2S → ZnS + H2O
Laboratory preparation
[edit]Crude zinc sulfide can be produced by igniting a mixture of zinc and sulfur.[10] More conventionally, ZnS is prepared by treating a mildly acidic solution of Zn2+ salts with H2S:[11]
- Zn2+ + S2− → ZnS
This reaction is the basis of a gravimetric analysis for zinc.[12]
One other commonly used method for nanocrystallites specifically is colloid chemistry, which offers precise control over the particle size through reaction conditions such as the concentration of starting materials, choice of solvents, and stabilizing agents. In this process, capping agents like thioglycerol bind covalently to the surface atoms of ZnS nanoparticles, preventing their combination and ensuring the extraction of stable, free-standing powders that can be redissolved in solvents.[13]
A different approach involves the preparation of ZnS nanoparticles by using zinc acetate and sodium sulfide, with solvents like dimethylformamide (DMF) and stabilizers such as 1-thioglycerol. The controlled addition of reagents and pH adjustment is essential to form particles of different sizes. This method results in nanocrystallites that exhibit the cubic (sphalerite) structure and are stable under atmospheric conditions, with properties suited for optoelectronic and photocatalytic applications.[13]
References
[edit]- ^ Wang, Gang; Huang, Baibiao; Li, Zhujie; Lou, Zaizhu; Wang, Zeyan; Dai, Ying; Whangbo, Myung-Hwan (2015). "Synthesis and characterization of ZnS with controlled amount of S vacancies for photocatalytic H2 production under visible light". Scientific Reports. 5: 8544. Bibcode:2015NatSR...5E8544W. doi:10.1038/srep08544. PMC 4339798. PMID 25712901.
- ^ Wells, A. F. (1984), Structural Inorganic Chemistry (5th ed.), Oxford: Clarendon Press, ISBN 0-19-855370-6.
- ^ Tesla, Nikola (1894). "The Inventions, Researches, and Writings of Nikola Tesla". Internet Archive. p. 290. Retrieved 2 January 2024.
- ^ Karl A. Franz, Wolfgang G. Kehr, Alfred Siggel, Jürgen Wieczoreck, and Waldemar Adam "Luminescent Materials" in Ullmann's Encyclopedia of Industrial Chemistry 2002, Wiley-VCH, Weinheim. doi:10.1002/14356007.a15_519
- ^ a b Gerhard Auer, Peter Woditsch, Axel Westerhaus, Jürgen Kischkewitz, Wolf-Dieter Griebler and Marcel Liedekerke "Pigments, Inorganic, 2. White Pigments" in Ullmann's Encyclopedia of Industrial Chemistry 2009, Wiley-VCH, Weinheim. doi:10.1002/14356007.n20_n01
- ^ a b c d Lange, Thomas; Reichenberger, Sven; Ristig, Simon; Rohe, Markus; Strunk, Jennifer; Barcikowski, Stephan; Schlögl, Robert (2022-02-01). "Zinc sulfide for photocatalysis: White angel or black sheep?". Progress in Materials Science. 124: 100865. doi:10.1016/j.pmatsci.2021.100865. ISSN 0079-6425.
- ^ Sadovnikov, Stanislav I. (2019-06-01). "Synthesis, properties and applications of semiconductor nanostructured zinc sulfide". Russian Chemical Reviews. 88 (6): 571–593. doi:10.1070/RCR4867. ISSN 0036-021X.
- ^ Sidot, T. (1866). "Sur les propriétés de la blende hexagonale". Compt. Rend. 63: 188–189.
- ^ Greenwood, Norman N.; Earnshaw, Alan (1984). Chemistry of the Elements. Oxford: Pergamon Press. p. 1405. ISBN 978-0-08-022057-4.
- ^ Coustal, R. (1931). "Étude de la Phosphorescence du Sulfure de Zinc I. - La Méthode par Explosion". Journal de Chimie Physique. 28: 277–298. Bibcode:1931JCP....28..277C. doi:10.1051/jcp/1931280277.
- ^ F. Wagenknecht; R. Juza (1963). "Zinc Sulfide". In G. Brauer (ed.). Handbook of Preparative Inorganic Chemistry, 2nd Ed. Vol. 2pages=1075. NY,NY: Academic Press.
- ^ Mendham, J.; Denney, R. C.; Barnes, J. D.; Thomas, M. J. K. (2000), Vogel's Quantitative Chemical Analysis (6th ed.), New York: Prentice Hall, ISBN 0-582-22628-7
- ^ a b Nanda, J.; Sapra, Sameer; Sarma, D. D.; Chandrasekharan, Nirmala; Hodes, Gary (2000-04-01). "Size-Selected Zinc Sulfide Nanocrystallites: Synthesis, Structure, and Optical Studies". Chemistry of Materials. 12 (4): 1018–1024. doi:10.1021/cm990583f. ISSN 0897-4756.
External links
[edit]
- Zinc and Sulfur at The Periodic Table of Videos (University of Nottingham)
- Composition of CRT phosphors
- University of Reading, Infrared Multilayer Laboratory optical data
- [1] melting point