Photon-avalanche-like upconversion in NdAl3(BO3)4 nanoparticles excited at 1064 nm

Abstract

We report efficient non-resonant ground state excitation at 1064 nm of trivalent neodymium (Nd 3+ ) ions in stoichiometric neodymium aluminum borate NdAl 3 (BO 3 ) 4 nanoparticles, which are crystalline and, besides the large content of Nd 3+ ions, present excellent photoluminescence properties. Up-conversions (UCs) were observed and the energy pathways identified, as starting by multi-phonon assisted ground state absorption ( 4 I 9/2 → 4 F 3/2 ) and excited state absorption ( 4 I 11/2 → 4 F 3/2 ) with the population of the 4 I 11/2 level by thermal coupling with the ground state. The excited state 4 I 11/2 is also populated by relaxations of the Nd 3+ increasing the population of the 4 F 3/2 level. Cross-relaxation among two Nd 3+ ions ( 4 F 3/2 , 4 I 9/2 )→( 4 I 15/2 , 4 I 15/2 ) with subsequent phonon emission leads to two ions at the 4 I 11/2 level every iteration triggering a photon avalanche mechanism which greatly enhances the efficiency of the UCs. Ladder thermal excitation 4 F 3/2 →[ 4 F 5/2 , 2 H 9/2 ]→[ 4 F 7/2 , 4 S 3/2 ]→ 4 F 9/2 was achieved, and the ground state relaxation from these levels provided emission at 880 nm, 810 nm, 750 nm, and 690 nm, respectively. Energy transfer UCs (Auger) between Nd 3+ ions at the 4 F 3/2 level allowed population of the [ 2 G 3/2 , 4 G 7/2 ] from which relaxations to the 4 I 9/2 , 4 I 11/2 , and 4 I 13/2 states provided emissions around 536 nm, 600 nm, and 660 nm, respectively. Associated to the nonradiative relaxations, we observed the heating of the nanoparticles (22 °C to 240 °C) with subsequent thermal enhancement of the frequency UCs due to the redistribution of population among coupled energy levels of the Nd 3+ ions. The present results have potential applications in super-resolution imaging and nanothermometry.

High-Pressure Synthesis of Rare-Earth Borate-Nitrate Crystals for Second Harmonic Generation

“…The corresponding multiphoton excitation is then followed by radiative 4 F 3/2 → 4 I 9/2 transitions, which release the near-infrared emission at ∼880 nm. Such an unconventional UC mechanism, which involves an excited-state resonance absorption of the laser radiation at 1064 nm along the 4 I 11/2 → 4 F 3/2 transition, in combination with thermal coupling of the 4 I 11/2 level to the ground state, was recently reported for Nd 3+ -doped up-converting nanoparticles , …”

“…The corresponding multiphoton excitation is then followed by radiative 4 F 3/2 → 4 I 9/2 transitions, which release the near-infrared emission at ∼880 nm. Such an unconventional UC mechanism, which involves an excited-state resonance absorption of the laser radiation at 1064 nm along the 4 I 11/2 → 4 F 3/2 transition, in combination with thermal coupling of the 4 I 11/2 level to the ground state, was recently reported for Nd 3+ -doped up-converting nanoparticles 44,45 In this context, it is worth mentioning that the 532 nm SHG emission might directly populate the higher excited level 4 G 7/2 of the Nd atom, thus leading to photoluminescence. However, we emphasize that the 880 nm emission observed in the optical trapping experiments was mediated by the above-discussed UC process.…”

Laser-Induced Broadband White Emission of NdAlO3 Nanocrystals in Alcohols

“…Although some reports suggest a purely thermal origin for LIWE, 28,44,45 luminescent thermometry, 8,42 deviation from the Stefan−Boltzmann law, 13 and the fact that this emission was observed in liquid N 2 46 indicate otherwise. Recently, a photon avalanche-like mechanism was proposed for nonresonant excitation of Nd-containing materials at 1064 nm; 35,36 however, since in the present case a resonant excitation was used, photon avalanche is unlikely. Instead, these results might indicate that electron ejection is the main initiator for LIWE since the threshold is higher when electron ejection is more difficult.…”

“…For NdAlO 3 in vacuum, the shape of the emission can be described of a very broad band comprising the whole visible range with the presence of several well-defined bands. Two different explanations are given in the literature: Nd 3+ reabsorption ,,− and the Nd 3+ avalanche-like mechanism. − Although in methanol small drops in intensity can be seen, when immersed in the other alcohols the well-defined structure disappeared, resulting in only a broadband typical of other materials, ,,, and had a very high resemblance to the LaAlO 3 in vacuum. For this reason, it seems likely that Nd 3+ reabsorptions or avalanche-like emissions are broadened due to interactions with the solvent appearing as a single broadband.…”

Advancements in excited state absorption-based luminescence thermometry

“…Another work presenting a ratiometric measurement based on the mutual intensity of two emission bands was reported in 2020 by Silva et al (Table 4) 55 , who focused mainly on the characterization of the photon-avalanche-like process of Nd 3+ ions. Previously, the use of the ESA of Nd 3+ ions for luminescence thermometry by studying the absolute intensity of a single band (Marciniak et al 19 ) or the ratio of the intensity of a single band at two different excitations (Trejgis et al 39 ) was described.…”