Reproducible Ionization of Gold Nanospheres and Nanostars in Gelatin Sections

Abstract

Gold nanospheres were dispersed in gelatin sections (10–100 µm thickness) and their laser desorption/ionization (LDI) efficiencies of gold ions (Au+, Au2+, Au3+) under pulsed-laser irradiation were examined. The mass signal intensities were linear to the surface densities ranging from 6 × 104 to 6 × 106 particles/mm2. When the thickness of the sections was thinner than or equal to 50 µm, the LDI efficiency of gold nanospheres was independent of the thickness. Thus, the mass intensity was dependent on the surface densities of gold nanospheres in the gelatin sections. It was also found that the LDI efficiencies were affected by the concentration of gelatin solutions. Based on the high reproducibility of mass signals obtained from gelatin sections, the LDI efficiencies of star-shaped gold nanoparticles (gold nanostars) were also evaluated. It was found that the nanostars showed higher LDI efficiencies than gold nanospheres, but the enhancement was not more than 25%.

Anionic gold ions desorbed from gold nanorods and nanospheres

“…The dependence of the mass signal intensities on their volumes was consistent with the results presented in our previous paper discussing ionization properties of gold nanostars. 11 In our present work, gold nanorods with volumes smaller than 10 4 nm 3 showed mass signal intensities that were roughly 3 times larger than those of spherical particles having the same volumes; in contrast, larger nanorods and nanospheres showed comparable signal intensities.…”

“…The process for dispersing the nanorods was the same as that used in our previous paper. 11 The nanorods in gelatin solutions gave gold cations (Au + , Au2 + , and Au3 + ) quantitatively (see Fig. S6 in the supporting information).…”

“…To evaluate laser desorption/ionization efficiencies of the gold nanoparticles, the nanoparticles were dispersed in 10 wt% gelatin solutions. 11 The absorbance of the nanoparticle-gelatin solutions was kept constant (0.043 cm -1 at 355 nm), independent of the shapes and sizes of the gold nanoparticles. The concentration of gold atoms in the gelatin solutions was about 10 µM.…”

“…1,5,6 The ionization efficiency was dependent on the sizes and shapes of the gold nanoparticles. 6,11 Previous works have shown that gold nanoparticles could be a highly sensitive mass probe for investigating distribution using a conventional MALDI-MS instrument.…”