Fig. 2: Mechanistic investigation and characterization of ionoluminescence in nanodiamonds.
From: Quantifying nanodiamonds biodistribution in whole cells with correlative iono-nanoscopy
a Photoluminescence (PL) spectrum of nanodiamonds excited with a 532-nm laser. b Photoluminescence spectrum of nanodiamonds excited with a 405-nm laser. c Ionoluminescence (IL) spectrum of nanodiamonds excited with a beam of 1.6 MeV α-particles. d Illustration of α-particle-induced atomic ionization in producing secondary electrons (top), through energy deposition (ΔE) of the bombarding α-particles (energy of E0), and calculated energy distribution of the secondary electrons (bottom) in a nanodiamond. e Proposed mechanism of ionoluminescence through α-particle excitation. Process 1 represents NV-defect-assisted recombination which results in the emission of NV0 and NV¯. Process 2 represents interband recombination which results in the conversion of NV¯ to NV0 through ground-state ionization of NV¯, forming NV0 in its excited state of (NV0)*. f Time-resolved ionoluminescence measurement. Note that the instrumental response function (IRF) was determined by measuring the ionoluminescence response of a fast-decay material (Supplementary Fig. 5 and Note 3). g Relative ionoluminescence yield measurement. Note that the ionoluminescence yields of nanodiamonds, upconversion nanocrystals (NaYF4: Yb/Tm), CdSe/ZnS quantum dots (QDs), and fluorescein dyes (FITC-1907) were normalized with a perovskite-QDs scintillator (Supplementary Figs. 6 and 7 and Note 4). h Ionoluminescence intensity profile as a function of the accumulated fluence of α-particles, showing a considerable iono-bleaching resistance of the nanodiamonds. The inserted images, taken at different time intervals (5, 40, and 75 min), indicate that the emission brightness of the nanodiamonds remains essentially unaltered over time. Scale bars are 2 μm.
