Platinum diselenide

Platinum diselenide

Names
Other names Platinum(IV) selenide Sudovikovite
Identifiers
CAS Number	12038-26-5 Y
3D model (JSmol)	Interactive image
PubChem CID	101946448
InChI InChI=1S/Pt.2Se Y Key: JTPDXCIVXNLRFP-UHFFFAOYSA-N Y
SMILES [Se]=[Pt]=[Se]
Properties
Chemical formula	PtSe2
Molar mass	353.03 g·mol−1
Appearance	opaque metallic yellowish white
Density	9.54
Melting point	decomposes
Solubility in water	insoluble
Band gap	0 (bulk) 1.3 eV monolayer
Structure
Crystal structure	space group P3m1 164 hexagonal
Lattice constant	a = 3.728[1], c = 5.031
Coordination geometry	octahedral
Related compounds
Other anions	platinum disulfide platinum ditelluride PtSeTe PtSSe
Other cations	palladium diselenide NiSeTe
Related platinum selenides	Luberoite Pt5Se4
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
N (what is YN ?)
Infobox references

Platinum diselenide is a transition metal dichalcogenide (TMDC) consisting of the metal platinum and the non-metal selenium with the formula PtSe₂. Being a layered substance, PtSe₂ can be split into thin layers down to three atoms thick called monolayers. PtSe₂ is a semimetal or semiconductor depending on thickness.

Formation

Minozzi was the first to report synthesising platinum diselenide from the elements in 1909.^[2]

Platinum diselenide can be formed by heating thin foils of platinum in selenium vapour at 400°C.^[3][4]

A platinum 111 surface exposed to selenium vapour at 270°C forms a monolayer of PtSe₂.^[5]

In addition to these selenization methods, PtS₂ can be made by precipitation in water solution of Pt(IV) treated with hydrogen selenide, or by heating platinum tetrachloride with elemental selenium.^[2]

Natural occurrence

Platinum diselenide occurs naturally as the mineral Sudovikovite. It was named after Russian petrologist, N.G. Sudovikov who lived from 1903 to 1966. The mineral's hardness is 2 to 21/2. Sudovikovite was found in the Srednyaya Padma mine, Velikaya Guba uranium-vanadium deposit, Zaonezhie peninsula, Karelia Republic, Russia.^[6]

Properties

Platinum diselenide forms crystals in the cadmium iodide structure. This means that the substance forms layers. Each of the monolayers has a central bed of platinum atoms, with a sheet of selenium atoms above and below. This structure is also called "1T" and has an trigonal structure. The layers are only weakly bonded together, and it is possible to exfoliate layers to bilayers or monolayers.^[7]

In bulk the material is semi-metallic, but as a monolayer it is a semiconductor.^[7] The conductivity of the bulk material is 620,000 S/m.^[8]

The XPS spectrum shows a peak at 72.3 eV from Pt 4f core, and also has peaks from Pt 5p_3/2^[7] and Se 3d_3/2 and 3d_5/2 at 55.19and 54.39 eV.^[5]

Phonon vibrations are designated by the infrared active A_2u (Se vibrating out of plane opposite to Pt), E_u (in layer vibration, Se opposite to Pt), and Raman active A_1g (Se top and bottom atoms moving out of plane in opposite directions 205 cm⁻¹), and E_g (In plane, top and botom Se atoms moving opposite 175 cm⁻¹). In the Raman spectrum, the A_1g is lessened when stimulated emissions polarised perpendicular to the incoming rays are measured. The E_g mode is red-shifted when more layers are stacked. (166 cm⁻¹ for bilayer and 155 cm⁻¹ for bulk material) The A_1g emission only has a slight change when thickness varies.^[7]

The band gap is calculated as 1.2 eV for monolayers, and 0.21 eV for bilayers. For a trylayer or thicker the substance loses a bandgap and becomes semimetallic.^[5]

PtSe₂ can change its conductance in the presence of particular gases, such as nitrogen dioxide. Within a few seconds, NO₂ absorbs on the surface of the PtSe₂ material and lowers the resistance. When the gas is absent, high resistance returns again in about a minute.^[3]

The Seebeck coefficient of PtSe₂ is 40 μV/K.^[9]

Although platinum diselenide is nonmagnetic, when there are up to 10% platinum vacancies and it is put under 5% strain it is predicted to become ferromagnetic.^[10]

Monolayers of platinum diselenide show helical spin texture, which is not expected for centrosymmetric materials such as this. This property could be due to a local dipole induced Rashba effect. It means that PtSe₂ is a potential spintronics material.^[11]

Reactions

Water can physisorb to the surface of platinum dielenide with an energy of −0.19 eV, and similarly for oxygen with energy −0.13 eV. Water and oxygen do not react at toom temperature, because significant energy would be required to break apart the molecules.^[8]

Comparison

Palladium diselenide has a different modified pyrite structure. Palladium ditelluride has a similar structure to platinum diselenide.^[12] Platinum disulfide is a semiconductor, and platinum ditelluride is metallic in nature.

More complex substances with platinum and selenium also exist, including the quaternary chalcogenides Rb₂Pt₃USe₆ and Cs₂Pt₃USe₆^[13]

Jacutingaite is a ternary platinum selenide HgPtSe₃.^[14]

Use

Platinum diselenide is proposed for use as a mid-infra red detector superior to black phosphorus in durability in air. Also it can work as a catalyst, and can be built into field effect transistors.^[8]

Combined with graphene it van be a photocatalyst, converting water and oxygen to reactive hydroxyl radical and superoxide. This reaction works when photons produce holes and electrons. The holes can neutralise hydroxide to make hydroxyl, and the electrons attach to oxygen to make superoxide. These reactive species can mineralise organic matter.

References