A New Radio Frequency Plasma Oxygen Primary Ion Source on Nano Secondary Ion Mass Spectrometry for Improved Lateral Resolution and Detection of Electropositive Elements at Single Cell Level

Abstract

An important application field of secondary ion mass spectrometry at the nanometer scale (NanoSIMS) is the detection of chemical elements and, in particular, metals at the subcellular level in biological samples. The detection of many trace metals requires an oxygen primary ion source to allow the generation of positive secondary ions with high yield in the NanoSIMS. The duoplasmatron oxygen source is commonly used in this ion microprobe but cannot achieve the same quality of images as the cesium primary ion source used to produce negative secondary ions (C(-), CN(-), S(-), P(-)) due to a larger primary ion beam size. In this paper, a new type of an oxygen ion source using a rf plasma is fitted and characterized on a NanoSIMS50L. The performances of this primary ion source in terms of current density and achievable lateral resolution have been characterized and compared to the conventional duoplasmatron and cesium sources. The new rf plasma oxygen source offered a net improvement in terms of primary beam current density compared to the commonly used duoplasmatron source, which resulted in higher ultimate lateral resolutions down to 37 nm and which provided a 5-45 times higher apparent sensitivity for electropositive elements. Other advantages include a better long-term stability and reduced maintenance. This new rf plasma oxygen primary ion source has been applied to the localization of essential macroelements and trace metals at basal levels in two biological models, cells of Chlamydomonas reinhardtii and Arabidopsis thaliana.

SIMS imaging in neurobiology and cell biology

“…20 In addition, the instrument can be equipped with both O À and Cs + primary ion beams which are highly focused and energetic, so both positive and negative ions can be imaged. A spatial resolution of $50 nm can be achieved; 21 however, to obtain sufficient signals of the secondary ions from biological samples (e.g. lipids), a lateral resolution of $100 nm is more commonly used.…”

Pyrenoidal sequestration of cadmium impairs carbon dioxide fixation in a microalga

“…NanoSIMS 50 L (CAMECA, Gennevilliers, France) was used to perform SIMS analysis. This device was equipped with a primary Cs + ion source (lateral resolution down to 50 nm) for the mapping of electronegative elements and with a novel O − RF plasma primary ion source enabling a high sensitivity for electropositive elements combined to a high lateral resolution (40 nm lateral resolution) (Malherbe et al, ). The seven parallel electron multiplier detectors equipped on the NanoSIMS 50 L instrument allowed detection of seven elements at the same time.…”

GGR Biennial Critical Review: Analytical Developments Since 2014

“…The new source has a better current density and long‐term stability, and lateral resolution down to 37 nm (Malherbe et al . ). One application of the new source was the imaging of trace elements in single cells (Penen et al .…”

“…This new ion probe is based on the earlier model Cameca 1280‐HR, but with a new RF plasma oxygen source that allows an enhanced beam density (Malherbe et al . , Liu et al . in press), an automated sample height adjustment and 10 12 Ω resistor Faraday cups.…”