Graphene‐Enhanced 3D Chemical Mapping of Biological Specimens at Near‐Atomic Resolution

Abstract

The direct imaging of individual atoms within the cellular context holds great potential for understanding the fundamental physical and chemical processes in organisms. Here, a novel approach for imaging of electrically insulated biological cells by introducing a graphene encapsulation approach to "disguise" the low-conductivity barrier is reported. Upon successful coating using a water-membrane-based protocol, the electrical properties of the graphene enable voltage pulsing field evaporation for atom probe tomography (APT). Low conductive specimens prepared from both Au nanoparticles and antibiotic-resistant bacterial cells have been tested. For the first time, a significant graphene-enhanced APT mass resolving power is also observed confirming the improved compositional accuracy of the 3D data. The introduction of 2D materials encapsulation lays the foundation for a breakthrough direction in specimen preparation from nanomembrane and nanoscale biological architectures for subsequent 3D near-atomic characterization.physical and chemical properties. [1][2][3][4][5][6][7][8] Atom probe tomography (APT), the only technique offering 3D chemical measurements with near atomic resolution, has recently demonstrated its unique capability as a biological imaging tool to mammalian [9] and bacterial cells. [10] However, the broader application of APT to the field is largely limited by the challenges in the sample preparation and the nonconductivity of biological specimens. A requirement of APT experiments is that the specimen material must be shaped into a sharp needle, typically with a tip radius less than 75 nm. By applying a positive voltage to the specimen under ultrahigh vacuum and cryogenic conditions, this tip geometry allows the generation of the sufficient electric field intensity to cause field ionization and evaporation of surface atoms. Controlled voltage pulsing allows the evaporation of individual and molecular ions that eventually reach a position sensitive detector. The impact positions and sequence of hits are employed to reconstruct their original position within the specimen and the time of flight is utilized to determine the atomic species. [11,12] In order to maintain a field density Cellular ImagingThe ORCID identification number(s) for the author(s) of this article can be found under https://doi.

Direct Imaging of Liquid–Nanoparticle Interfaces with Atom Probe Tomography

“…22 Highly packed Au + (197 Da) ions are detected within a confined region, which represents a single AuNP. 14 H + (1 Da) ions are distributed across both the W and solution volume due to background H + residuals in the vacuum, 30,31 similar with H2 + and H3 + . In the following three repeats of APT imaging with the same batch of AuNP solution, no significant changes of ionic species have been identified in the acquired mass spectra, as shown in Figure S2.…”

“…Recently, graphene has been employed to coat insulated specimens for voltage-pulsed APT imaging, 14 due to its outstanding conductivity and mechanical properties. Imaging liquid specimens has also been proved to be feasible with minimal damages to unravel the protein structure.…”

Atom probe analysis of electrode materials for Li-ion batteries: challenges and ways forward

“…The recent efforts around specimen coating using only a few graphene sheets 50,56,57 demonstrates that even very thin conductive layer can achieve the necessary increase in conductivity and sufficient shielding to enable APT analysis. These species may simply neutralise dangling bonds for instance or modify the very local conduction properties, enabling surface conductivity, i.e.…”

New frontiers in atom probe tomography: a review of research enabled by cryo and/or vacuum transfer systems

“…More recently, Adineh et al developed a unique approach to sandwich biological materials (e.g., metal nanoparticles and bacterial cell culture) between a tungsten needle tip and a graphene coating [ 45 ]. This was accomplished by lowering a small-diameter metal ring with a suspended droplet of biomaterial sample with a graphene film floating on top, over a tungsten needle tip.…”