Retraction Watch

Tracking retractions as a window into the scientific process

Authors pull Science paper on molecular wires for “inappropriate data handling”

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pic.mag.current-issueThis week’s issue of Science includes a retraction of a highly cited paper about manipulating the current in a string of molecules with a magnet, after an investigation by the co-authors revealed “inappropriate data handling” by the first author.

According to the note, the co-authors’ suspicions arose when they tried to follow-up on the data. Following a “thorough investigation,” they concluded that first author Rabindra N. Mahato had handled the data in such a way that they could no longer trust the conclusions. In the end, Mahato agreed to the retraction.

Here’s more from the note:

Our report “ultrahigh magnetoresistance at room temperature in molecular wires” presents measurements on onedimensional molecular chains confined inside the nanochannels of zeolite L crystals. In these measurements, we observed signals that were interpreted as an exceptionally large (~1000%) response of the conductance through the molecular chains to an external magnetic field of a few millitesla. The explanation of the results was based on a room-temperature Pauli spin blockade effect, intrinsic to the hopping transport through the molecules. The observed magnetic field scale of a few millitesla could be explained by the typical magnitude of the random nuclear magnetic field in the molecular environment. The shape of the conductance versus magnetic field dependence was found to be in close agreement with similar curves observed in bulk organic semiconductors, in which the effect is referred to as “organic magnetoresistance” or “OMAR.” The exceptionally large effect in our case was ascribed to the one-dimensional nature of electron transport along the molecular chains.

In follow-up research by some of the coauthors, suspicion arose with regard to data collected by the first author Rabindra N. Mahato, which led to a thorough investigation by the co-authors. This investigation has revealed inappropriate data handling by Dr. Mahato, such that the experimental results are not accurately represented in the paper. This makes it, in our eyes, impossible to solidly underpin the conclusions made in the report. All co-authors have therefore concluded that the paper should be immediately retracted. Dr. Mahato has agreed to this Retraction.

Mahato is currently an assistant professor at Jawaharlal Nehru University in New Delhi.

When the findings were released, they were featured in that week’s Science podcast, in which corresponding author Wilfred van der Wiel explained the results in detail. They were also included in a press release from The Eindhoven University of Technology in The Netherlands:

Researchers of MESA+, the research institute for nanotechnology of the University of Twente, in cooperation with researchers of the University of Strasbourg and Eindhoven University of Technology, are the first to successfully create perfect one-dimensional molecular wires of which the electrical conductivity can almost entirely be suppressed by a weak magnetic field at room temperature. The underlying mechanism is possibly closely related to the biological compass used by some migratory birds to find their bearings in the geomagnetic field. This spectacular discovery may lead to radically new magnetic field sensors, for smartphones for example.

Van der Wiel, at the University of Twente in The Netherlands, reinforced to us the note’s explanation for why the authors became suspicious of the data:

In follow-up research, we had difficulties reproducing the results of Dr. Mahato in our own lab.

We also asked him if he knew anything more about the nature of the “inappropriate data handling:”

As stated in the Retraction, the data handling was such that the experimental results are not accurately represented in the paper. This makes it, in the eyes of all co-authors, impossible to solidly underpin the conclusions made in the report.

The paper has been cited 41 times since it was published in 2013, earning it a designation of “highly cited” from Thomson Scientific’s Web of Knowledge.

We’ve reached out to Science and Mahato.

Hat tip: Justin Bahl

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