Experimental benchmark data for Monte Carlo simulated radiation effects of gold nanoparticles. Part I: Experiment and raw data analysis

Abstract

Electron emission spectra of gold nanoparticles (AuNPs) after photon interaction were measured over the energy range between 50 eV and 9500 eV to provide reference data for Monte Carlo radiation-transport simulations. Experiments were performed with the HAXPES spectrometer at the PETRA III high-brilliance beamline P22 at DESY (Hamburg, Germany) for photon energies below and above each of the gold L-edges, that is, at 11.9 keV, 12.0 keV, 13.7 keV, 13.8 keV, 14.3 keV, and 14.4 keV. The study focused on a sample with gold nanoparticles with an average diameter of 11.0 nm on a thin carbon foil. Additional measurements were performed on a sample with 5.3 nm gold nanoparticles and on reference samples of gold and carbon foils. Further measurements were made to calibrate the photon flux monitor, to characterize the transmission function of the electron spectrometer, and to determine the size of the photon beam. This allowed the determination of the absolute values of the spectral particle radiance of secondary electrons per incident photon flux. The paper presents the experimental and raw data analysis procedures, reviews the data obtained for the nanoparticle samples, and discusses their limitations.

A simulation study on the radiosensitization properties of gold nanorods

“…This energy range could correspond to the most probable M 4 NN and M 5 NN Auger transitions, producing electrons with energies ranging from 1.6 to 2.1 keV. The energy range for the third Auger group generally falls between 5 and 10 keV, with L 3 MM (5-8 keV) and L 2 MM (9-10 keV) transitions being the predominant transitions, as outlined by Rabus et al (2023). Finally, the fourth group of Auger electrons has energies ranging from 70 to 90 keV.…”

Experimental benchmark data for Monte Carlo simulated radiation effects of gold nanoparticles. Part II: comparison of measured and simulated electron spectra from gold nanofoils

“…The sample preparation and experimental procedure were described in detail in [30] and are only briefly reported here. The measurements were performed at the PETRA III undulator beamline P22 at DESY (Hamburg, Germany).…”

“…The measurements were made at 15°grazing incidence of the photon beam for six photon energies slightly below and above each of the gold L-edges, that is, 11.9 keV, 12.0 keV, 13.7 keV, 13.8 keV, 14.3 keV, and 14.4 keV. The rationale for using these energies was the relevance of the Au L-shell Auger electrons for local dose enhancement in the first few micrometers around a AuNP [30]. A 15°grazing-incidence angle was chosen to achieve a larger irradiated area (and thus to a better signal-to-noise ratio).…”

“…The measured spectra were normalized to photon flux (measured with a monitor of calibrated response) and corrected for the energy dependent transmission of the spectrometer to obtain the particle radiance of electrons per incident photon, that is, the average number of electrons per energy interval, solid angle, and surface area. The data analysis procedure was described in detail in the first part of the paper [30].…”

“…The present project was started with the aim of providing experimental benchmark data for Monte Carlo simulations of the radiation effects of AuNPs and thus indirectly for the electron cross section data implemented in the codes. The motivation and background of the study, the experimental procedures and data analysis methodology, as well as the results for the AuNP samples, were described in the first part of the paper [30]. In this second part of the paper, comparisons of the measured data for gold (Au) foils with Monte Carlo simulations using the Penelope code and Geant4-DNA are presented.…”