Research Statement

Statement of the major research accomplishments

Pauling proposed (PNAS 1930) that layered compounds (2D materials) with asymmetric structure along their a-axis, like chrysotile, and halloysite would bend spontaneously and form tubular structures (or scrolls). This proposition was vindicated later by Bates et al. (Science 1950), who first observed chrysotile nanotubes. Following the discovery of carbon fullerenes, Kroto proposed (Nature 1987) that (2D) graphite nanoparticles suffer inherent instability due to the dangling bonds of the rim atoms, forcing them to fold and close into fullerenes. This idea was extended to carbon nanotubes (Iijima, Nature 1991, 1993), which led Tenne to propose (Nature 1992, 1993, Science 1995) that, likewise, nanoparticles (NPs) of inorganic layered compounds, such as WS2 and MoS2 would suffer a similar instability forming hollow closed nanostructures i.e., inorganic nanotubes (INT) and fullerene-like (IF) nanoparticles. Subsequently, nanotubes and fullerene-like NPs of numerous 2D materials, including BN, NiCl2, Cs2O, Tl2O, NiClOH, TaS2, H2Ti3O7, V2O5 and many others were synthesized and studied experimentally. Many other kinds of nanotubes from 2D materials were studied in-silico. In recent years Tenne expanded this concept synthesizing nanotubes from a large class non-stoichiometric compounds with “misfit” layered structure (MLC), of the form (MX)1+y(TX2)m with (M = Sn, Pb, Sb, Bi, rare earths; T = Nb, Ta, Ti, V, Cr; X = S, Se; 0.08<y<0.28; m = 1-3). Here, both the Pauling mechanism (asymmetry along the a-axis) and healing of the rim’s dangling-bonds (the Kroto-Iijima-Tenne mechanism) operate conjointly leading to high yields of the nanotubes (see for example JPCL 2014; PNAS 2021). It can therefore be safely concluded that nanotubes and fullerene-like NPs are metastable (nano)phases of layered compounds (2D materials). They can be prepared from most of the elements in the periodic table and encompass thousands of compounds varying from insulators to semiconductors, metals and superconductors. Indeed, these (IF/INT) metastable nanophases are distinguishable by any physio-chemical analysis from their parent bulk 2D materials.

Tenne and his research team conceived new material-chemistry strategies to synthesize INT and IF from different classes of compounds with layered structure, including layered metal dichalcogenides, halides and oxides. For this purpose, he used variety of high temperature techniques, including chemical vapor transport (CVT), chemical vapor deposition (CVD), laser ablation; focused solar beam irradiation; electron beam; microwave, shockwaves to synthesize IF/INT nanostructures. In particular, careful study of the high-temperature conversion of metal oxide nanoparticles into sulfides (selenides) permitted the elucidation of a unique “surface-inwards” mechanism for the synthesis of IF/INT (JACS 1996, 1998, 2000) of WS2 (MoS2). Subsequently, borrowing concepts from (chemical) reactor engineering, he scaled-up the production of IF/INT of WS2 using fluidized bed reactor method. These studies paved the way for the commercialization of such nanoparticles for a variety of applications.

A new high-temperature materials chemistry strategies were developed for the controlled doping of IF/INT of WS2 (MoS2) with minute (<500 ppm) amounts of rhenium and niobium (JACS 2007; Angew. Chem. 2012; Particle 2018). The doping endowed the nanoparticles/nanotubes with negative and positive surface charge, respectively, allowing them facile dispersion in various liquids. Furthermore, hints for their transformation from the stable 2H (semiconductor) into the metastable 1T (metal) states, were obtained in Re-doped IF. The doped IF nanoparticles exhibited better catalytic properties towards hydrogen generation and also improved their tribological behavior, attributed to self-repulsion of the NPs. A few lucrative medical applications of the doped NPs, like coatings for catheters, were proposed for the doped NPs through his group research.

Hollow closed nanooctahedra of MoS2 were hypothesized by Prof. Tenne to be the smallest fullerene-like nanoparticles, early on (Nature 1993, Adv. Mater. 1995). These unique nanoparticles could be produced by laser ablation (M. Heben and co-workers Nature 1999), arc discharge and more recently by solar ablation. Both theory and experiment show that the hollow MoS2 nanooctahedra are stable in the range of 3-7 nm (103-105 atoms, Angew. Chem. 2007, 2011). Being the smallest hollow closed polyhedra, they can be regarded as the inorganic analogues of C60, i.e. “the true inorganic fullerenes”. Such hollow nanooctahedra are likely to be common for numerous other layered compounds and exhibit new catalytic pathways.

Tenne first conjectured (Nature 1997) and later proved (PNAS 2011) that IF nanoparticles of MoS2 and WS2 would behave like nanoball-bearing exhibiting superior solid lubrication behavior. Not only this work offered a new lubrication mechanism, it also heralded a new lubrication technology useful for different tribological applications as well as for machining fluids and coatings with a few companies already manufacturing and marketing these products. Medical products based on his publications, e.g. Tribol. Lett. (2014) 55, 103 (2014) were proposed and being developed.

The unique mechanical properties of IF/INT of WS2 were elucidated through different kinds of studies. Exposure to shockwaves indicated that the IF NPs can withstand pressure waves of 21 PGa (Adv. Mater. 2005), offering them applications in self-protection; Tensile, bending and torsion tests of individual nanotubes (PNAS 2006; PRL 2008) revealed that they are as strong as 20 GPa (some four times stronger than Kevlar fibers) and can withstand stain of > 10% without failure. The mechanical robustness of these nanotubes offered them numerous applications, most importantly for reinforcing polymer nanocomposites. Indeed, polymer nanocomposites impregnated with up to 1 wt% IF/INT of WS2 and exhibiting improved mechanical, thermal and tribological behavior were developed offering preeminent applications. In particular, biocompatible and biodegradable polymers, such as PLLA, PVA and PPF, which are used in numerous medical technologies, food packaging and tissue engineering. Adding small amounts (< 1 wt%) of WS2 nanotubes, which exhibit also low toxicity, was shown to improve their mechanical robustness, substantially (see for example,, offering numerous opportunities for applications of IF/INT in biopolymer nanocomposites.

In collaboration with other research groups, he was able to confirm the unique quasi-1D behavior of WS2 nanotubes in optoelectronics. For instance, as superconductors exhibiting Little-Parks oscillations (Nature Comm. 2017); bulk photovoltaic effect (Nature 2019); strong coupling effect (Small 2020); second harmonic generation (Nano Lett. 2021) and for artificial vision and memory devices (Nature Comm. 2022, ibid. 2023). Nanotubes from the misfit compound (SmS)1.19TaS2 were recently shown to exhibit superconductivity at 4 K (Chem. Mater. 2022). These unique properties could make major contributions to quantum technologies, such as ultra-dense memory devices and quantum computing in the distant future. Recently, a significant bandgap tenability (2-1.5 eV) was achieved by his group, synthesizing W(SxSe1-x)2 nanotubes in the entire composition range (0 ≤x≤ 1) (JACS 2022).

Prof. Tenne mentored numerous (~70) students among which 5 females who themselves became professors in different universities. He has served in many national and international capacities, including chairing the MRS Kavli Young Investigator Award for the last few years and being Principal Editor of the MRS J. Mater. Res. (2002-2006). His public service epitomized in his chairing for the last 9 years the committee providing the triannual “State of Science Report in Israel” submitted to the Israeli government and the parliament (Knesset) in the name of the Israel Academy of Sciences (the latest submitted in February 2023). He received numerous prizes and recognitions, the latest being the EMET prize for excellence in research given by the Israeli Prime-minister (2020), the ACS Chemistry of Materials award (2023) and the von Hippel award, the highest recognition of the MRS. He is a member of the Israel Academy of Science and two other European Academies and Fellow of the MRS and the Royal Society of Chemistry.

In conclusion, the pioneering work of Prof. Tenne on nano-2D materials during the last >30 years resulted in a fascinating science and some major applications with numerous other applications on the horizon. It also spearheaded the modern research on nano-2D materials.