Chemistry of Materials: Impurity controlled crystal growth in low dimensional bismuth telluride

Impurity controlled crystal growth in low dimensional bismuth telluride

Sharifi, T., Yazdi, S., Costin, G., Apte, A., Coulter, G., Tiwary, C., and Ajayan, P.M.

Chemistry of Materials,


Topological insulators, such as layered Bi2Te3, exhibit extraordinary properties, manifesting profoundly only
at nanoscale thicknesses. However, it has been challenging to synthesize these structures with controlled thickness. Here,
control over the thickness of solvothermally grown Bi2Te3 nanosheets is demonstrated by manipulating the crystal growth
through selected and controlled impurity atom addition. By a comprehensive analysis of growth mechanism and the intentional
addition of Fe impurity, it is demonstrated that the nucleation and growth of few-layer nanosheets of Bi2Te3 can be
stabilized in solution. By optimizing the Fe concentration, nanosheets thinner than 6 nm, and as thin as 2 nm, can be
synthesized. Such thicknesses are smaller than the anticipated critical thickness for the transition of topological
insulators to the quantum spin Hall regime.


Sharifi, T., Yazdi, S., Costin, G., Apte, A., Coulter, G., Tiwary, C., and Ajayan, P.M. (2018). Impurity controlled crystal growth in low dimensional bismuth telluride. Chemistry of Materials, p. acs.chemmater.8b02548. doi: 10.1021/acs.chemmater.8b02548

RCMS: Scale distortion from pressure baselines as a source of inaccuracy in triple-isotope measurements

Laurence Y. Yeung, Justin A. Hayles, Huanting Hu, Jeanine L. Ash, and Tao Sun

Rapid Comm. Mass Spectrom. (2018)

doi: 10.1002/rcm.8247

Rationale: Isotope ratio measurements have become extremely precise in recent years, with many approaching parts‐per‐million (ppm) levels of precision. However, seemingly innocuous errors in signal baselines, which exist only when gas enters the instrument, might lead to significant errors. These “pressure‐baseline” (PBL) offsets may have a variety of origins, such as incoherent scattering of the analyte, isobaric interferences, or electron ablation from the walls of the flight tube. They are likely present in all but ultra‐high‐resolution instruments, but their importance for high‐precision measurements has not been investigated.

Methods: We derive the governing equations for the PBL effect. We compare the oxygen triple‐isotope composition of gases on three different mass spectrometers before and after applying a correction for PBLs to determine their effects. We also compare the composition of atmospheric O2 with that of several standard minerals (San‐Carlos Olivine and UWG‐2) on two high‐precision mass spectrometers and compare those results with the differences reported in the literature.

Results: We find that PBLs lead to stretching or compression of isotopic variations. The scale distortion is non‐mass‐dependent, affecting the accuracy of triple‐isotope covariations. The governing equations suggest that linear stretching corrections using traditional isotopic delta values (e.g., δ18O) are rigorous for PBL‐induced errors in pure gases. When the reference and sample gases are not comparable in composition or purity, however, a different correction scheme may be required. These non‐mass‐dependent errors are systematic and may have influenced previous measurements of triple‐isotope covariations in natural materials.

Conclusions: Accurate measurements of isotopic variations are essential to biogeochemistry and for testing theoretical models of isotope effects. PBLs are probably ubiquitous, contributing to the interlaboratory disagreements in triple‐isotope compositions of materials differing greatly in δ18O values. Moreover, they may lead to inaccurate determination of triple‐isotope compositions and fractionation factors, which has implications for isotopic studies in hydrology and biogeochemistry.

GCA: Core-mantle fractionation of carbon in Earth and Mars: The effects of sulfur

Tsuno, K., Grewal, D.S., Dasgupta, R. (2018). Core-mantle fractionation of carbon in Earth and Mars: The effects of sulfur. Geochimica et Cosmochimica Acta 238: 477-495.


Abstract: Constraining carbon (C) fractionation between silicate magma ocean (MO) and core-forming alloy liquid during early differentiation is essential to understand the origin and early distribution of C between reservoirs such as the crust-atmosphere,
mantle, and core of Earth and other terrestrial planets. Yet experimental data at high pressure (P)-temperature (T) on the
effect of other light elements such as sulfur (S) in alloy liquid on alloy-silicate partitioning of C and C solubility in
Fe-alloy compositions relevant for core formation is lacking. Here we have performed multi-anvil experiments at
6–13 GPa and 1800–2000 °C to examine the effects of S and Ni on the solubility limit of C in Fe-rich alloy liquid as well
as partitioning behavior of C between alloy liquid and silicate melt (Dc). The results show that C solubility in the alloy
liquid as well as Dc decreases with increasing in S content in the alloy liquid. Empirical regression on C solubility in
alloy liquid using our new experimental data and previous experiments demonstrates that C solubility significantly increases
with increasing temperature, whereas unlike in S-poor or S-free alloy compositions, there is no discernible effect of Ni on C
solubility in S-rich alloy liquid.
Our modelling results confirm previous findings that in order to satisfy the C budget of BSE, the bulk Earth C undergoing
alloy-silicate fractionation needs to be as high as those of CI-type carbonaceous chondrite, i.e., not leaving any room for
volatility-induced loss of carbon during accretion. For Mars, on the other hand, an average single-stage core formation at
relatively oxidized conditions (1.0 log unit below IW buffer) with 10–16 wt% S in the core could yield a Martian mantle with
a C budget similar to that of Earth’s BSE for a bulk C content of 0.25–0.9 wt%. For the scenario where C was delivered to
the proto-Earth by a S-rich differentiated impactor at a later stage, our model calculations predict that bulk C content in the
impactor can be as low as ~0.5 wt% for an impactor mass that lies between 9 and 20% of present day Earth’s mass. This value
is much higher than 0.05–0.1 wt% bulk C in the impactor predicted by Li et al. (Li Y., Dasgupta R., Tsuno K., Monteleone B.,
and Shimizu N. (2016) Carbon and sulfur budget of the silicate Earth explained by accretion of differentiated planetary
embryos. Nat. Geosci. 9, 781–785) because C-solubility limit of 0.3 wt% in a S-rich alloy predicted by their models is significantly
lower than the experimentally derived C-solubility of 1.6 wt% for the relevant S-content in the core of the impactor.

Advanced Materials Interfaces: Chromiteen: A New 2D Oxide Magnetic Material from Natural Ore

Chromiteen: A New 2D Oxide Magnetic Material from Natural Ore

Advanced Materials Interfaces, 2018, 1800549. Posted by Gelu Costin

Thakur Prasad Yadav,* Sharmila N. Shirodkar, Narumon Lertcumfu, Sruthi Radhakrishnan, Farheen N. Sayed, Kirtiman Deo Malviya, Gelu Costin, Robert Vajtai, Boris I. Yakobson,* Chandra Sekhar Tiwary,* and Pulickel M. Ajayan*

The absence of inherent magnetism in the family of 2D materials limits its application in magnetoelectric and magnetic storage media. Here, a simple scalable route for the synthesis of magnetic 2D material chromite (chromiteen) via sonication-assisted liquid-phase exfoliation is demonstrated. The (111) plane of the exfoliated chromite is found to be the most stable which is confirmed by its common occurrence in exfoliation. Further, the stability and dispersion are verified by ab initio density functional theoretical simulations. Magnetic measurements over a large temperature range of 4 K ≤ T ≤ 300 K confirm ferromagnetic/superparamagnetic order with nearly 40 times higher magnetic moment saturation in chromiteen compared to chromite. The results reveal that 2D chromiteen causes a change in the magnetic behavior with respect to chromite which could be ascribed to the increase in the lattice strain as well as a magnetic strain due to high ferromagnetic
fraction in 2D plane.

Yadav, T. P., Shirodkar, S. N., Lertcumfu, N., Radhakrishnan, S., Sayed, F. N., Malviya, K. D., … Ajayan, P. M. (2018). Chromiteen: A New 2D Oxide Magnetic Material from Natural Ore. Advanced Materials Interfaces, 1800549.

Nature Nanotechnology: Exfoliation of a non-van der Waals material from iron ore hematite

Exfoliation of a non-van der Waals material from iron ore hematite

Nature Nanotechnology, volume 13pages602–609 (2018), posted by Gelu Costin

Aravind Puthirath Balan 1,2,11, Sruthi Radhakrishnan1,11, Cristiano F. Woellner 3, Shyam K. Sinha4,
Liangzi Deng5, Carlos de los Reyes6, Banki Manmadha Rao7, Maggie Paulose7, Ram Neupane7,
Amey Apte1, Vidya Kochat1, Robert Vajtai 1, Avetik R. Harutyunyan8, Ching-Wu Chu5,9, Gelu Costin10,
Douglas S. Galvao3, Angel A. Martí6, Peter A. van Aken4, Oomman K. Varghese7, Chandra Sekhar Tiwary1*,
Anantharaman Malie Madom Ramaswamy Iyer1,2* and Pulickel M. Ajayan1*

With the advent of graphene, the most studied of all two-dimensional materials, many inorganic analogues have been synthesized
and are being exploited for novel applications. Several approaches have been used to obtain large-grain, high-quality
materials. Naturally occurring ores, for example, are the best precursors for obtaining highly ordered and large-grain atomic
layers by exfoliation. Here, we demonstrate a new two-dimensional material ‘hematene’ obtained from natural iron ore hematite
(α -Fe2O3), which is isolated by means of liquid exfoliation. The two-dimensional morphology of hematene is confirmed by
transmission electron microscopy. Magnetic measurements together with density functional theory calculations confirm the
ferromagnetic order in hematene while its parent form exhibits antiferromagnetic order. When loaded on titania nanotube
arrays, hematene exhibits enhanced visible light photocatalytic activity. Our study indicates that photogenerated electrons can
be transferred from hematene to titania despite a band alignment unfavourable for charge transfer.


Citation: Balan, A. P., Radhakrishnan, S., Woellner, C. F., Sinha, S. K., Deng, L., Reyes, C. D. L., … Ajayan, P. M. (2018). Exfoliation of a non-van der Waals material from iron ore hematite. Nature Nanotechnology, 13pages 602–609.


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