Zinc oxide
[CAS# 1314-13-2]

Identification

• Classification: API >> Special medicine >> Dermatology medication
• Name: Zinc oxide
• Synonyms: Zinc white; C.I. pigment white 4
• Molecular Formula: ZnO
• Molecular Weight: 81.39
• CAS Registry Number: 1314-13-2 (8051-03-4)
• EC Number: 215-222-5
• SMILES: O=[Zn]

Properties

• Density: 5.6
• Melting point: 1975 °C
• Water solubility: 1.6 mg/L (29 °C)

Safety Data

• Hazard Symbols: GHS09 Warning
• Risk Statements: H400-H410
• Safety Statements: P273-P391-P501

Hazard Classification

Hazard	Class	Category Code	Hazard Statement
Acute hazardous to the aquatic environment	Aquatic Acute	1	H400
Chronic hazardous to the aquatic environment	Aquatic Chronic	1	H410
Reproductive toxicity	Repr.	1A	H360
Acute toxicity	Acute Tox.	4	H332
Acute toxicity	Acute Tox.	4	H302
Specific target organ toxicity - repeated exposure	STOT RE	2	H373
Specific target organ toxicity - single exposure	STOT SE	1	H370
Skin irritation	Skin Irrit.	2	H315
Eye irritation	Eye Irrit.	2	H319
Specific target organ toxicity - single exposure	STOT SE	3	H335
Reproductive toxicity	Repr.	2	H361
Specific target organ toxicity - repeated exposure	STOT RE	1	H372
Carcinogenicity	Carc.	1A	H350
Serious eye damage	Eye Dam.	1	H318
Skin sensitization	Skin Sens.	1	H317
Acute toxicity	Acute Tox.	2	H300
Acute toxicity	Acute Tox.	2	H330
Skin corrosion	Skin Corr.	1B	H314
Germ cell mutagenicity	Muta.	2	H341

Discovery and Applications

Zinc oxide (ZnO) is a white inorganic compound with numerous industrial applications, known for its semiconductor properties and uses in fields ranging from electronics to pharmaceuticals. This versatile material has been utilized since ancient times for its medicinal properties, particularly in soothing skin irritations and as a key component in calamine lotion. The historical use of zinc oxide was primarily for its healing effects, as it provides a protective barrier on the skin and has mild antimicrobial properties. It was also used as a pigment in ancient paintings and ointments.

Zinc oxide occurs naturally as the mineral zincite, but due to its rarity, most of the ZnO used today is synthetically produced. The French process is the most common method of production, involving the vaporization of metallic zinc and its subsequent oxidation to zinc oxide powder. This method ensures a high purity of the material, which is essential for its many applications. Another method, the American process, involves reducing zinc ores with carbon and oxidizing the product with air. These processes have enabled the large-scale use of ZnO in modern industries.

One of the most critical applications of zinc oxide is in the electronics industry. As a semiconductor with a wide bandgap, ZnO is widely used in the production of varistors, surge protectors, and UV light-emitting diodes. Its ability to absorb ultraviolet light makes it valuable in optoelectronic devices, while its transparency to visible light allows it to be used in transparent electronics and sensors. Furthermore, the development of zinc oxide nanostructures has expanded its use in nanotechnology, including solar cells and biosensors.

In the cosmetics industry, zinc oxide is a key ingredient in sunscreens. Its ability to block both UVA and UVB radiation makes it an effective physical sunblock. Unlike chemical sunscreens, which absorb UV radiation, ZnO reflects and scatters harmful rays. It is also a common component in skin care products for treating conditions like acne and diaper rash due to its soothing and protective properties. In these applications, zinc oxide acts as a barrier to moisture, promoting skin healing.

Zinc oxide is widely used in the rubber industry, especially in the vulcanization process. It serves as an activator, helping to strengthen rubber by forming cross-links between polymer chains. This process significantly improves the durability and elasticity of rubber products, making ZnO essential in the manufacture of tires, seals, and hoses. The ceramics industry also benefits from zinc oxide’s fluxing properties, which help reduce the melting point of glazes and improve the strength and appearance of ceramics.

In medicine, zinc oxide continues to be valued for its role in topical ointments and creams. Its antimicrobial and anti-inflammatory effects make it ideal for treating minor wounds, burns, and skin irritations. The compound forms a protective layer over the skin, preventing moisture loss and promoting healing. Moreover, zinc oxide’s potential in advanced biomedical applications, such as drug delivery systems, is being actively researched due to its biocompatibility.

Zinc oxide also finds use in environmental applications, particularly in pollution control. Its photocatalytic properties enable the breakdown of organic pollutants in water and air, making it a candidate for environmental remediation technologies. This application is part of the ongoing effort to find sustainable solutions to industrial pollution.

In conclusion, zinc oxide’s broad range of applications, from traditional medicinal uses to advanced electronics and environmental technologies, highlights its importance as an industrial and scientific material. Its unique chemical and physical properties ensure its continued relevance in various industries, with future innovations likely to expand its role even further.

References

1987. Clinical performance of three endodontic sealers. Endodontics & Dental Traumatology, 3(4).
DOI: 10.1111/j.1600-9657.1987.tb00621.x

2023. Impact of Cu Doping on ZnO Nanoparticles Phyto-Chemically Synthesized for Improved Antibacterial and Photocatalytic Activities. Nanotechnology Convergence in Africa.
DOI: 10.1007/978-94-024-2194-1_5

2000. Heterogeneous photocatalytic decomposition of halosubstituted benzyl alcohols on semiconductor particles in aqueous media. Chemosphere, 41(8).
DOI: 10.1016/s0045-6535(99)00554-8