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| Names | |
|---|---|
| Other names trizinc diphosphide | |
| Identifiers | |
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3D model (JSmol) | |
| ChemSpider |
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| ECHA InfoCard | 100.013.859 |
| EC Number |
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| UNII | |
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| Properties | |
| Zn3P2 | |
| Molar mass | 258.12 g/mol |
| Appearance | dark gray |
| Odor | characteristic[2] |
| Density | 4.55 g/cm3 |
| Melting point | 1,160 °C (2,120 °F; 1,430 K) |
| reacts | |
| Solubility | insoluble inethanol, soluble inbenzene, reacts withacids |
| Band gap | 1.4-1.6 eV (direct)[3] |
| Structure | |
| Tetragonal,tP40 | |
| P42/nmc, No. 137 | |
a = 8.0785 Å,c = 11.3966 Å[4] | |
Formula units (Z) | 8 |
| Hazards | |
| Occupational safety and health (OHS/OSH): | |
Ingestion hazards | Fatal, acutely toxic |
Inhalation hazards | High |
| GHS labelling:[2] | |
  | |
| Danger | |
| H260,H300 | |
| P223,P231+P232,P264,P270,P280,P301+P310,P321,P330,P335+P334,P370+P378,P402+P404,P405,P501 | |
| NFPA 704 (fire diamond) | |
| Lethal dose or concentration (LD, LC): | |
LD50 (median dose) | Oral 42.6 mg/kg (Rat) 12 mg/kg (Rat) Dermal 1123 mg/kg (Rat) 2000 mg/kg (Rabbit)[2] |
| Safety data sheet (SDS) | ThermoFisher Scientific, revised 02/2020[2] |
Except where otherwise noted, data are given for materials in theirstandard state (at 25 °C [77 °F], 100 kPa). | |
Zinc phosphide (Zn3P2) is aninorganicchemical compound. It is a grey solid, although commercial samples are often dark or even black. It is used as arodenticide.[5] Zn3P2 is aII-Vsemiconductor with a direct band gap of 1.5eV[6] and may have applications inphotovoltaic cells.[7] A second compound exists in the zinc-phosphorus system,zinc diphosphide (ZnP2).
Zinc phosphide can be prepared by the reaction ofzinc withphosphorus; however, for critical applications, additional processing to removearsenic compounds may be needed.[8]
Another method of preparation include reacting tri-n-octylphosphine withdimethylzinc.[9]
Zinc phosphide reacts with water to produce highly toxicphosphine (PH3) andzinc hydroxide (Zn(OH)2):
Zn3P2 has a room-temperaturetetragonal form that converts to acubic form at around 845 °C.[10] In the room-temperature form there are discrete P atoms, zinc atoms are tetrahedrally coordinated and phosphorus six coordinate, with zinc atoms at 6 of the vertices of a distorted cube.[11]
The crystalline structure of zinc phosphide is very similar to that ofcadmium arsenide (Cd3As2),zinc arsenide (Zn3As2) andcadmium phosphide (Cd3P2). These compounds of theZn-Cd-P-As quaternary system exhibit full continuous solid-solution.[12]
Zinc phosphide is an ideal candidate for thin film photovoltaic applications, for it has strong optical absorption and an almost ideal band gap (1.5eV). In addition to this, both zinc and phosphorus are found abundantly in the Earth's crust, meaning that material extraction cost is low compared with that of other thin filmphotovoltaics. Both zinc and phosphorus are also nontoxic, which is not the case for other common commercial thin film photovoltaics, likecadmium telluride.[13]
Researchers at theUniversity of Alberta were the first to successfully synthesize colloidal zinc phosphide. Before this, researchers were able to create efficientsolar cells from bulk zinc phosphide, but their fabrication required temperatures greater than 850 °C or complicated vacuum deposition methods. By contrast, colloidal zinc phosphidenanoparticles, contained in a zinc phosphide "ink", allows for inexpensive, easy large-scale production, by means of slot-die coating or spray coating.[14]
The testing and development of these zinc phosphide thin films is still in its early stages, but early results have been positive. Prototype heterojunction devices fabricated from zinc phosphide nanoparticle ink exhibited a rectification ratio of 600 andphotosensitivity with an on/off ratio near 100. These are both acceptable suitability benchmarks for solar cells. Development still needs to be made on optimizing the nanoparticle ink formation and device architecture before commercialization is possible, but commercial spray-on zinc phosphide solar cells may be possible within ten years.[15]
Metal phosphides have been used asrodenticides. A mixture of food and zinc phosphide is left where the rodents can eat it. The acid in the digestive system of the rodent reacts with the phosphide to generate toxicphosphine gas. This method of vermin control has possible use in places where rodents are immune to other common poisons. Other pesticides similar to zinc phosphide arealuminium phosphide andcalcium phosphide.
Zinc phosphide is typically added to rodent baits in amount of around 0.75-2%. Such baits have a strong, pungentgarlic-like odor characteristic of phosphine liberated byhydrolysis. The odor attracts rodents, but has a repulsive effect on other animals; However, birds, notablywild turkeys, are not sensitive to the smell. The baits have to contain sufficient amount of zinc phosphide in sufficiently attractive food in order to kill rodents in a single serving; a sublethal dose may cause aversion towards zinc phosphide baits encountered by surviving rodents in the future.
Rodenticide-grade zinc phosphide usually comes as a black powder containing 75% of zinc phosphide and 25% ofantimony potassium tartrate, anemetic to cause vomiting if the material is accidentally ingested by humans or domestic animals. However, it is still effective against rats, mice, guinea pigs and rabbits, none of which have a vomiting reflex.[17]
The New ZealandEnvironmental Protection Authority has approved the import and manufacture of Microencapsulated Zinc Phosphide (MZP Paste) for the ground control ofpossums. The application was made by Pest Tech Limited, with support from Connovation Ltd,Lincoln University and theAnimal Health Board. It will be used as an additional vertebrate poison in certain situations. Unlike1080 poison, it cannot be used for aerial application.[18]
Zinc phosphide is highly toxic, especially when ingested or inhaled. The reason for its toxicity is the release of phosphorus compounds, usuallyphosphine, when it reacts with water and acids. Phosphine is very toxic and, with trace amounts ofP2H4,pyrophoric. Phosphine is also denser than air and may remain close to the ground without sufficientventilation.
