Critical assessment of the evidence for striped nanoparticles

• Published in: PloS one 2014-11, Vol.9 (11), p.e108482-e108482
• Main Authors: Stirling, Julian, Lekkas, Ioannis, Sweetman, Adam, Djuranovic, Predrag, Guo, Quanmin, Pauw, Brian, Granwehr, Josef, Lévy, Raphaël, Moriarty, Philip
• Format: Article
• Language: English
• Subjects: Artefacts; Astronomy; Biology and Life Sciences; Computer and Information Sciences; Computer simulation; Data acquisition; Data analysis; Data processing; Electron microscopy; Engineering and Technology; Gold; Gold - chemistry; Ligands; Magnetic resonance; Magnetic resonance spectroscopy; Materials science; Mathematical models; Metal Nanoparticles - analysis; Metal Nanoparticles - chemistry; Metal Nanoparticles - ultrastructure; Microscopy; Microscopy, Electron, Transmission; Microscopy, Scanning Tunneling; Monte Carlo simulation; Nanoparticles; Nanoparticles - analysis; Nanoparticles - chemistry; Nanoparticles - ultrastructure; Neutron scattering; NMR; Nuclear magnetic resonance; Particle physics; Particulates; Physical chemistry; Physical Sciences; Physics; Protocol (computers); Resonance scattering; Scanning tunneling microscopy; Short term memory; Spectroscopy; Transmission electron microscopy
• ISSN: 1932-6203; 1932-6203
• DOI: 10.1371/journal.pone.0108482

There is now a significant body of literature which reports that stripes form in the ligand shell of suitably functionalised Au nanoparticles. This stripe morphology has been proposed to strongly affect the physicochemical and biochemical properties of the particles. We critique the published evidence for striped nanoparticles in detail, with a particular focus on the interpretation of scanning tunnelling microscopy (STM) data (as this is the only technique which ostensibly provides direct evidence for the presence of stripes). Through a combination of an exhaustive re-analysis of the original data, in addition to new experimental measurements of a simple control sample comprising entirely unfunctionalised particles, we show that all of the STM evidence for striped nanoparticles published to date can instead be explained by a combination of well-known instrumental artefacts, or by issues with data acquisition/analysis protocols. We also critically re-examine the evidence for the presence of ligand stripes which has been claimed to have been found from transmission electron microscopy, nuclear magnetic resonance spectroscopy, small angle neutron scattering experiments, and computer simulations. Although these data can indeed be interpreted in terms of stripe formation, we show that the reported results can alternatively be explained as arising from a combination of instrumental artefacts and inadequate data analysis techniques.