Tag: Materials Science

Over the past couple of days, I have been reviewing a series of Materials Science papers, all co-authored by the same group of researchers from the Universities of Lahore, Chakwal, and Sargodha in Pakistan. While reviewing them, one analytical technique kept standing out for unusual reasons.

Materials Science

Materials science studies the composition and structure of materials and how these determine their properties. It uses a range of different techniques, such as Scanning Electron Microscopy (SEM) or Transmission Electron Microscopy (TEM) to look at the compounds, X-ray Diffraction (XRD) to identify crystal structures, and calorimetry to study phase transitions. Many of these techniques sit at the intersection of physics and chemistry.

Coming from a molecular biology/microbiology background, I am not very familiar with these techniques or with what the expected results should look like. I am much more used to looking at photos of blots, gels, or tissues, so in my past searches for science integrity concerns, I have not really focused on materials science papers.

That changed thanks to the efforts of Reese Richardson and several other science sleuths, who created the Collection of Open Science Integrity Guides (COSIG). The collection currently contains dozens of guides explaining how to examine scientific papers for problems in general, but also on how to find problems in specific methods or fields, including those in materials science or statistics. As one of their slogans says: “Anyone can do forensic metascience“. These guides have helped me identify problems across a much broader range of analytical methods.

One technique covered in the COSIG guides is one that often appears in materials science papers: Energy-dispersive X-ray spectroscopy. And, as we will see below, some papers will claim to have produced some unbelievable results.

Energy-dispersive X-ray spectroscopy

Energy-dispersive X-ray spectroscopy (EDX or EDS) is a technique used to determine which elements are present in a material. When a sample is struck by an electron beam, it emits X-rays with energies characteristic of specific elements, enabling researchers to identify and quantify the material’s composition. The resulting spectrum shows peaks at energies corresponding to those elements.

Each element emits X-rays at specific, known energies, so the peaks that appear in an EDX spectrum occur at predictable positions. For example, carbon (C) will have a peak at 0.28 keV, nitrogen (N) at 0.39 keV, and oxygen (O) at 0.52 keV. Some elements might have multiple peaks, such as iron (Fe), with peaks around 0.7, 6.4, and 7.1 keV.

Below is an EDX spectrum of the mineral crust from a shrimp, taken from Wikimedia. We see the expected C peak around 0.3 keV, the O peak at 0.5 keV, and the Fe peaks at the expected positions. The Ka and Kb values behind the element labels indicate the electron shell (K, L, or M). The a/alpha denote the drop of an electron from the adjacent shell (e.g., L to K), while b/beta is an electron dropping two shells (e.g., M to K).

Common concerns with EDX plots

Several issues in EDX papers in scientific papers might indicate data alteration or fabrication.

As explained in the COSIG guide on EDX, the easiest problem to spot is the presence of peaks at unexpected positions. There is a useful look-up table from the Lawrence Berkeley National Laboratory. Even just remembering that the O peak should be around 0.5 keV and that C, N, and O, should appear in that order, is enough to find many problems. Also, the elements hydrogen (H) and helium (He) do not produce peaks in an EDX spectrum, so if you see those peaks in a published paper, that is another sign that the data might be made up.

A problematic set of papers from Pakistani researchers

Following up on a lead provided by another sleuth, I found more than 30 problematic papers [spreadsheet] by collaborating materials scientists from the Universities of Lahore, Chakwal, and Sargodha, published from 2016 to 2025. The papers have one author in common, Asif Mahmood, who held several Assistant and Associate Professor positions at the Universities of Lahore, Chakwal, and Rasul.

Professor Mahmood is currently listed at a Chairperson and Associate Professor at the Department of Pharmacy at Rasul University. While his Google Scholar profile still works, his ORCID account [pdf] appears to have been deactivated, and his ResearchGate page leads to a dead link.

His frequent co-authors are Rai Muhammad Sarfraz from the University of Sargodha, Hira Ijaz at Riphah International University, Nadiah Zafar at the University of Lahore, and Umaira Rehman at the University of Sargodha.

At least four papers by Asif Mahmood have been retracted [PubPeer posts here, here, here, and here], mostly for overlapping images. One of these retractions was covered by Retraction Watch.

Most of Mahmood et al.’s papers follow the same structure: synthesizing hydrogel nanocomposites for the oral delivery of certain drugs, then testing their physical and chemical features. The concerns in these papers vary from SEM photos found in multiple papers representing different studies, repetitive noise patterns in XRD plots, bar plots with identical error bars, to unrealistic EDX plots.

UnEDXpected EDX plots

Several EDX plots in these papers contain peaks at unexpected positions.

Here is a figure from Zafar et al., Saudi Pharmaceutical Journal (2023), where the O peak deviates from the expected 0.52 keV position, or even shows two peaks!

In Mahmood et al., J. Drug Delivery Sci Techn (2016), the peaks do not follow the expected C-N-O order. While the O peak is at the expected 0.52 keV, the C peak jumps around from the correct position at 0.28 keV to an impossible 1.8 keV in the bottom plot. Hydrogen (H) does not produce an X-ray peak, so the H peaks indicated at 2.6 keV in panel A or at 0 keV in panels B or C are quite unexpected.

This Hussain et al. paper published in Int J Biol Macromolecules (2022), has similar problems in its EDX plots, as shown below. The right plot shows C, N, and O peaks, but in the wrong order, the O peaks bounce around from 0.5 to 0.9 keV, and the peaks have a strange blocky appearance.

Six papers by Mahmood et al. describing various hydrogel materials for drug release unexpectedly contain very similar, wonky EDX plots. Note the incorrect order of C-N-O, overhanging peaks, and the same wavy lines on the right of the left and middle plots.

The EDX plots in this paper by Malatani et al., Gels (2023), DOI: 10.3390/gels9030187 have another disorderly set of C-N-O peaks, the O is found at the incorrect values, and peaks have strange serrated ‘shoulders’.

Even stranger EDX plots in this set were from Shabir et al., Polymer Bulletin (2025), DOI: 10.1007/s00289-025-05917-x [PubPeer]. The peaks in these EDX spectra look unexpectedly wobbly and serrated, with some peaks appearing to fall to the left. Some elemental peaks are at unexpected positions. For example, several peaks appear to have <0 (negative) values, which is unexpected. For example, the element Ca has expected peaks at 0.34, 3.7, and 4 keV, but these plots show peaks at >6 keV. Perhaps related to the incorrect peak positions is the unclear labeling of the X-axis, where the numbers 2, 4, and 6 do not always appear to correspond to a tick.

Perhaps the wonkiest EDX plot was found in Farya Shabir et al., Pharmaceutics (2023), DOI: 10.3390/pharmaceutics15010062. Although the peaks appear to be at the correct positions, they look like they were hand drawn after a couple too many Gin and Tonics.

Other problems:

The troubled EDX plots were not the only problem in this set of papers. Several papers contained X-ray diffraction (XRD) plots with unexpected duplicated noise and peaks.

Here are four papers by Mahmood et al. in which several histology images appear to have been reused, even though the hydrogels described in each paper differ.

There were many more problems in this set – currently standing at 38 papers. See the complete list here: [spreadsheet]