What molecule am I?
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 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 (Wak艒, both in Japan) . Theoretical calculations showed that HfS2 was a viable candidate for low-power devices, leading the authors to assemble few-layer transistors using the graphene 鈥淪cotch Tape鈥� 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/渭m), which prompted the authors to assert that their results provided 鈥渢he basic information for experimental research of electron devices based on HfS2.鈥�
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 鈥渢he first direct electrical observation of the inverse charge-funnel effect enabled by deterministic and spatially resolved strain-induced electric fields.鈥� They showed that charges driven by these fields in the channel of a phototransistor 鈥攁 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 . 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 2 | H315鈥擟auses skin irritation |  |
| Serious eye damage, category 2A | H319鈥擟auses serious eye irritation | |
| Specific target organ toxicity, single exposure, respiratory tract irritation, category 3 | H335鈥擬ay cause respiratory irritation | |
*Globally Harmonized System (GHS) of Classification and Labeling of Chemicals. .
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 尾-辫颈苍别苍别2 (11 wt%); coming in at number three is 纬-迟别谤辫颈苍别苍别3 at 8 wt%.
A 1960 gas鈥搇iquid chromatography study of the composition of lemon oil by Richard A. Bernhard at the University of California, Davis, turned up several monoterpenes, . Bernhard鈥檚 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 (Krak贸w, Poland) published a comprehensive treatise on what they called the 鈥�Citrus limon (Lemon) Phenomenon鈥�. 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 .
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.鈥擡d.聽See this week's winter remedy.
This molecule was suggested by a reader. We present聽almost all of the molecules suggested by our readers.聽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! 鈥擡d.
Hafnium disulfide
fast facts
| CAS Reg. No. | 18855-94-2 |
| SciFindern name | Hafnium sulfide (HfS2) |
| Empirical formula | HfS2 |
| Molar mass | 242.62 g/mol |
| Appearance | Dark brown to purple-brown crystals or powder |
| Melting point | >2000 潞C (est.) |
| Water solubility | Insoluble |
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