Hafnium disulfide

January 27, 2025
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Image of Hafnium disulfide 3D Image of Hafnium disulfide
Credit: (3-D image) Sci. Rep. 6, 22277 (2016).

Hafnium disulfide (HfS2) is an inorganic compound that consists of alternating layers of hafnium and sulfur (see 3-D image). It appears to have been first mentioned in the chemical literature in 1958 by Frederick Kenneth McTaggart* and A. David Wadsley at CSIRO1 (Canberra, Australia). In an extensive article, the authors described the preparation and characterization of the sulfides, selenides, and tellurides of the group 22 elements titanium, zirconium, and hafnium along with thorium sulfide.

In recent years, HfS2 has shown value in multiple electronics applications. In 2016, Toru Kanazawa at the Tokyo Institute of Technology and colleagues there and at Okayama University and RIKEN (Wakō, both in Japan) used the molecule in electronic devices for the first time. Theoretical calculations showed that HfS2 was a viable candidate for low-power devices, leading the authors to assemble few-layer transistors using the graphene “Scotch Tape” method, that is, micromechanical exfoliation in which the tape extracts atomically thin flakes of HfS2. The transistors had excellent properties (e.g., a drain current of 0.75 mA/μm), which prompted the authors to assert that their results provided “the basic information for experimental research of electron devices based on HfS2.”

Taking HfS2 farther, in 2018 Adolfo De Sanctis, Saverio Russo, and co-workers at the University of Exeter (UK) used an atomically thin sheet of HfS2 as a semiconductor to achieve “the first direct electrical observation of the inverse charge-funnel effect enabled by deterministic and spatially resolved strain-induced electric fields.” They showed that charges driven by these fields in the channel of a phototransistor led to a 350% enhancement in responsivity—a finding that could be useful in the design of highly efficient photovoltaic cells for generating solar power.

And in 2022, Chengwen Huang and Huangzhong Yu* at South China University of Technology, (Guangzhou) added to the advance of solar energy by using HfS2/hafnium diselenide2 (HfSe2) films in polymer solar cells (PSCs). HfS2/HfSe2 films have defects; but oxygen plasma treatment converts their surfaces to hafnium dioxide3 (HfO2), which passivates the defects and increases the conductivity of the films. According to the authors, the presence of HfO2 has other advantages that improve the efficiency of PSCs.

1. Commonwealth Scientific and Industrial Research Organisation, the Australian agency responsible for scientific research.
2. CAS Reg. No. 12162-21-9.
3. CAS Reg. No. 12055-23-1.

Hafnium disulfide hazard information

Hazard class**GHS code and hazard statement
Skin corrosion/irritation, category 2H315—Causes skin irritationChemical Safety Warning
Serious eye damage, category 2AH319—Causes serious eye irritationChemical Safety Warning
Specific target organ toxicity, single exposure, respiratory tract irritation, category 3H335—May cause respiratory irritationChemical Safety Warning

*Globally Harmonized System (GHS) of Classification and Labeling of Chemicals. Explanation of pictograms.

Winter Remedy Molecules

Using lemon-flavored cough drops, lemon juice in tea, and other traditional remedies that contain lemon make people feel better when they have coughs and colds. The two most common molecules in the essential oil of lemon (Citrus limon) are former Molecules of the Week (R)-limonene1 (70 wt%) and β-pinene2 (11 wt%); coming in at number three is γ-terpinene3 at 8 wt%.

A 1960 gas–liquid chromatography study of the composition of lemon oil by Richard A. Bernhard at the University of California, Davis, turned up several monoterpenes, including γ-terpinene. Bernhard’s study was followed by dozens of articles on the constituents of lemon and other citrus oils from the 1960s to the 1990s.

In 2020, Marta Klimek-Szczykutowicz, Agnieszka Szopa*, and Halina Ekiert at Jagiellonian University (Kraków, Poland) published a comprehensive treatise on what they called the “Citrus limon (Lemon) Phenomenon”. After reviewing the chemical composition, metabolomic studies, and biological activities of the main raw materials obtained from C. limon, the authors cited the scientifically proven therapeutic properties of lemon that include anti-inflammatory, antimicrobial, anticancer, and antiparasitic activity.

1. CAS Reg. No. 5989-27-5.
2. CAS Reg. No. 127-91-3.
3. CAS Reg. No. 99-85-4.

Winter Remedy Molecules

Throughout January, MOTW is featuring key components of natural substances that people use when they have coughs or runny noses.—Ed. See this week's winter remedy.

This molecule was suggested by a reader. We present almost all of the molecules suggested by our readers. If you have a molecule you would like us to consider, please send us a message. And thank you for your interest in Molecule of the Week! —Ed.


Hafnium disulfide
fast facts

CAS Reg. No.18855-94-2
SciFindern nameHafnium sulfide (HfS2)
Empirical
formula
HfS2
Molar mass242.62 g/mol
AppearanceDark brown to purple-brown crystals or powder
Melting point>2000 ºC (est.)
Water
solubility
Insoluble
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