The zinc sulfide is an inorganic compound of formula ZnS, formed by Zn cationstwo+ and S anionstwo-. It is found in nature mainly as two minerals: wurtzite and sphalerite (or zinc blende), the latter being its main form.
Sphalerite is black in nature due to the impurities it presents. In pure form it has white crystals, while wurtzite has grayish-white crystals..
Zinc sulfide is insoluble in water. It can cause environmental damage, since it penetrates the soil and contaminates groundwater and its currents.
Zinc sulfide can be produced, among other reactions, by corrosion and neutralization.
By corrosion:
Zn + HtwoS => ZnS + Htwo
By neutralization:
HtwoS + Zn (OH)two => ZnS + 2HtwoOR
Zinc sulfide is a phosphorescent salt, which gives it the capacity for multiple uses and applications. In addition, it is a semiconductor and a photocatalyst.
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Zinc sulfide adopts crystalline structures governed by electrostatic attractions between the Zn cationtwo+ and the anion Stwo-. These are two: sphalerite or zinc blende, and wurzite. In both, the ions minimize the repulsions between ions of equal charges..
The zinc blende is the most stable in the terrestrial conditions of pressure and temperature; and wurzite, which is less dense, results from crystalline rearrangement due to increased temperature.
The two structures can coexist in the same ZnS solid at the same time although, very slowly, the wurzite will end up dominating.
The upper image shows the cubic unit cell centered on the faces of the zinc blende structure. The yellow spheres correspond to the anions Stwo-, and the gray ones to the Zn cationstwo+, located at the corners and in the centers of the cube faces.
Note the tetrahedral geometries around the ions. The zinc blende can also be represented by these tetrahedra, whose holes inside the crystal have the same geometry (tetrahedral holes).
Likewise, within the unit cells, the ZnS proportion is fulfilled; that is, a 1: 1 ratio. Thus, for each Zn cationtwo+ there is an anion Stwo-. In the image it may seem that gray spheres are abundant, but in reality, since they are in the corners and center of the cube's faces, they are shared by other cells.
For example, if you take the four yellow spheres that are inside the box, the "pieces" of all the gray spheres around it should equal (and do) four. Thus in the cubic unit cell there are four Zntwo+ and four Stwo-, fulfilling the stoichiometric ratio ZnS.
It is also important to emphasize that there are tetrahedral holes in front and behind the yellow spheres (the space that separates them from one another).
Unlike the structure of zinc blende, wurzite adopts a hexagonal crystal system (top image). This is less compact, so the solid has a lower density. The ions in wurzite also have tetrahedral surroundings and a 1: 1 ratio that agrees with the ZnS formula..
It can be presented in three ways:
-Wurtzite, with white and hexagonal crystals.
-Sphalerite, with greyish-white crystals and cubic crystals.
-As a white to grayish-white or yellowish powder, and cubic yellowish crystals.
1700º C.
Practically insoluble (0.00069 g / 100 ml at 18º C).
Insoluble in alkalis, soluble in dilute mineral acids.
Sphalerite 4.04 g / cm3 and wurtzite 4.09 g / cm3.
Has a hardness of 3 to 4 on the Mohs scale.
When it contains water, it slowly oxidizes to sulfate. In a dry environment it is stable.
When heated to high temperatures it emits toxic vapors of zinc and sulfur oxides.
The electron configuration of Zn is [Ar] 3d104stwo. By losing the two electrons of the 4s orbital it remains as the Zn cationtwo+ with their d orbitals filled. Therefore, since electronically Zntwo+ it is much more stable than Zn+, it only has a valence of +2.
Hence, it is omitted for the stock nomenclature, adding its valence enclosed in parentheses and with Roman numerals: zinc sulfide (II).
But there are other ways to call the ZnS in addition to the one already raised. In systematics, the number of atoms of each element is specified with the Greek numerators; with the only exception of the element to the right when it is only one. Thus, the ZnS is named as: monkeyzinc sulfide (and not monozinc monosulfide).
Regarding the traditional nomenclature, zinc having a single valence of +2 is added by adding the suffix -ico. Consequently, its traditional name results: zinc sulphideico.
-Sachtolith is a white pigment made with zinc sulfide. Used in caulks, mastics, sealants, undercoats, latex paints, and signage.
Its use in combination with ultraviolet light absorbing pigments, such as micro titanium or transparent iron oxide pigments, is necessary in weather resistant pigments.
-When ZnS is applied to latex or textured paints it has a prolonged microbicidal action.
-Due to its great hardness and resistance to breakage, erosion, rain or dust, it makes it suitable for exterior infrared windows or in aircraft frames.
-ZnS is used in the coating of rotors used in the transport of compounds, to reduce wear. It is also used in the production of printing inks, insulating compounds, thermoplastic pigmentation, flame resistant plastics and electroluminescent lamps..
-Zinc sulfide can be transparent, and can be used as a window for visible optics and infrared optics. Used in night vision devices, television screens, radar screens, and fluorescent coatings.
-ZnS with Cu doping is used in the production of electroluminescence panels. Also, it is used in rocket propulsion and gravimetry.
-Its phosphorescence is used to tint the clock hands and thus display the time in the dark; Also in paint for toys, in emergency signs and traffic warnings.
Phosphorescence allows a use of zinc sulfide in cathode ray tubes and X-ray screens to glow in dark spots. The color of the phosphorescence depends on the activator used.
-Sphalerite and wurtzite are broadband slit semiconductors. Sphalerite has a band cleft of 3.54 eV, while wurtzite has a band cleft of 3.91 eV.
-ZnS is used in the preparation of a photocatalyst composed of CdS - ZnS / zirconium - titanium phosphate used for the production of hydrogen under visible light.
-It acts as a catalyst for the degradation of organic pollutants. Used in the preparation of a color synchronizer in LED lamps.
-Its nanocrystals are used for ultrasensitive protein detection. For example, by emitting light from quantum dots of ZnS. It is used in the preparation of a combined photocatalyst (CdS / ZnS) -TiO2 for electrical production via photoelectrocatalysis.
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