Alpha and deuteron irradiation effects on silica nanoparticles

Abstract

We present an experimental investigation\ud focused on the effects of alpha and deuteron irradiation on\ud different silica nanoparticles. The study has been devoted\ud also to characterize the induced point defects and the\ud eventual structural modifications to evaluate the effects of\ud the different irradiation source in comparison with the bulk\ud materials. After irradiation up to about 10^16 ions cm^-2, we\ud performed electron paramagnetic resonance (EPR), photoluminescence\ud (PL), infrared (IR) absorption, Raman, and\ud atomic force microscopy (AFM) measurements. We found\ud that the two types of irradiation qualitatively induce comparable\ud effects. Furthermore, irradiation generates the socalled\ud twofold coordinated Si and the H(I) point defects,\ud originating from the reaction of the former with hydrogen\ud atoms. The occurrence of these defects is a not trivial and\ud interesting finding due to its connection to irradiationinduced\ud oxygen deficiency, not yet evidenced by other\ud irradiation of silica nanoparticles. We also detected the\ud E'Si paramagnetic centers and found that their lineshape at\ud the highest fluence, independently from the nanoparticles\ud size and irradiation source, is different from the one\ud observed in the bulk. Furthermore, the integral of the E0Si\ud signal does not depend significantly on the nanoparticles\ud size differing from previous irradiation with b-ray of the\ud same nanoparticles. AFM images indicate the absence of\ud significant radiation induced sintering between the nanoparticles\ud in the plan orthogonal to the irradiation direction\ud suggesting the absence of morphological changes, whereas\ud IR measurements suggest the occurrence of some structural\ud modifications in all the nanoparticles, which consist in the\ud decrease of the peak value of the Si–O–Si angle distribution.\ud Finally, irradiation effects are induced not uniformly\ud along the irradiation direction, as supported also by micro-\ud Raman investigation of an irradiated bulk silica material\ud and simulations of ions penetration profiles. These results\ud suggest the occurrence of some irradiation effects due to\ud light ion bombardment specific of nanoparticles

Extremely rapid isotropic irradiation of nanoparticles with ions generated in situ by a nuclear reaction

“…Modification with energetic ions thus represents a key approach to the creation of a variety of functional nanostructured materials, which has enabled advances in numerous research fields. In optics, this approach is used to create lattice point defects, including vacancies, color centers 3 , 4 , and single-photon emitters 5 . In nanoscience, researchers have used modification with energetic ions to fabricate and tailor new types of materials 1 , 2 , 6 , 7 , including magnetic 8 , semiconductor 9 , and carbon 10 nanomaterials.…”

“…Compared to heavier ions, their range in materials is much higher 2 and they cause less damage 13 . For example, irradiation with α particles or He + ions has been used for tuning of the optical, electric, and magnetic properties of various nanomaterials—including graphene 14 , carbon 15 , and boron nitride 13 nanotubes; semiconductors; 16 magnetic nanoparticles; 17 silica; 4 and polymers 18 .…”