Persistent luminescence induced by near infra-red photostimulation in chromium-doped zinc gallate for in vivo optical imaging (original) (raw)
Related papers
Origin of the visible light induced persistent luminescence of Cr3+-doped zinc gallate
Journal of Physics and Chemistry of Solids, 2014
ZnGa 2 O 4 :Cr 3 þ (ZGO:Cr) is a very bright persistent phosphor able to emit a near infrared light for hours following a UV (band to band excitation) or visible (Cr 3 excitation) illumination. As such it serves as an outstanding biomarker for in vivo imaging. Persistent luminescence, due to trapping of electrons/holes at point defects, is studied here on a series of ZGO:Cr spinel compounds where the introduction of defects is controlled by varying the Zn/(Ga þ Cr) nominal ratio during synthesis. Simulation of Electron Paramagnetic Resonance spectra revealed up to six types of Cr 3 þ ions with different neighboring defects and correlated to four emission lines in low temperature photoluminescence spectroscopy. Of particular importance, three EPR signals were attributed to Cr 3 þ with a pair of neighboring Zn 0 Ga and Ga zn 1 antisite defects. They were identified to the emission line N2 that plays a key role in the persistent luminescence mechanism for both storage of visible excitation and persistent luminescence emission. A model is proposed whereby the local electric field at Cr 3 þ created by the two neighboring antisite defects triggers the electron-hole separation and trapping upon excitation of Cr 3 þ . The process is equivalent to a photoinduced electron transfer from a donor (here Zn 0 Ga ) to an acceptor (here Ga zn 1) observed in some molecular systems.
Long term in vivo imaging with Cr3+ doped spinel nanoparticles exhibiting persistent luminescence
Journal of Luminescence, 2016
Persistent luminescence is a singular property of some materials which are able to store the excitation or light irradiation energy at intrinsic traps or defects before slowly emitting lower energy photons within several hours. When such compounds are prepared as nanoparticles (NPs), when functionalization is realized to get colloidal materials well dispersed in aqueous medium, such nanoprobes open the use of the persistent luminescence for bioimaging applications. Recently, the numbers of in vivo applications increased with new modalities and new expectations. In this review, we focused our attention on the ZnGa 2 O 4 :Cr (ZGO:Cr) nanoparticles. When ZnGa 2 O 4 (ZGO), a normal spinel is doped with Cr 3+ ions, a high brightness persistent luminescence material with an emission spectrum perfectly matching the transparency window of living tissues is obtained. It allows in vivo mouse imaging with an excellent target-to-background ratio. One interesting characteristic of ZGO:Cr lies in the fact that its persistent luminescence can be excited with orange/red light, well below its band gap energy and in the transparency window of living tissues. This important property allows multiple re-excitations to perform long term bioimaging. Antisite defects of the direct spinel structure are assumed to provide shallow traps which store the excitation light. Charge release by room temperature thermal excitation and recombination center, here trivalent chromium, are responsible for the persistent luminescence. Following a primary excitation (UV or visible), one also observed that trapped charges can be released under 977 nm light stimulation for several spinel gallate materials, therefore increasing the modalities and the materials envisioned for in vivo excitation of these NPs.
Dalton transactions (Cambridge, England : 2003), 2015
Novel Cr(3+) doped zinc gallogermanate (ZGGO) nanoparticles with 697 nm near-infrared (NIR) super long afterglow were prepared via a hydrothermal method. Subsequently, a vacuum-annealing strategy was adopted to improve NIR afterglow in ZGGO:Cr(3+) nanoparticles. For the sample annealed at 800 °C, no variation in the particle size is observed, the persistent luminescence increases by an order of magnitude (∼14 times) and the NIR afterglow time reaches more than 15 hours relative to the as-prepared sample. After annealing at temperatures higher than 880 °C, the persistent luminescence of the nanoparticles is enhanced, but they show aggregated-surface behavior. Meanwhile, shallow and deep traps are generated, related to the antisite defects and VGe-Cr(3+)-VO defect clusters, respectively. Finally, we apply ZGGO:Cr(3+) persistent luminescence nanoparticles (PLNPs) to a human serum albumin (HSA) colloid solution, and more than 1 h of NIR persistent luminescence is detected under 320 nm e...
Storage of Visible Light for Long-Lasting Phosphorescence in Chromium-Doped Zinc Gallate
Chemistry of Materials, 2014
ZnGa 2 O 4 :Cr 3+ presents near-infrared long-lasting phosphorescence (LLP) suitable for in vivo bioimaging. It is a bright LLP material showing a main thermally stimulated luminescence (TSL) peak around 318 K. The TSL peak can be excited virtually by all visible wavelengths from 1.8 eV (680 nm) via d−d excitation of Cr 3+ to above ZnGa 2 O 4 band gap (4.5 eV− 275 nm). The mechanism of LLP induced by visible light excitation is entirely localized around Cr N2 ion that is a Cr 3+ ion with an antisite defect as first cationic neighbor. The charging process involves trapping of an electron−hole pair at antisite defects of opposite charges, one of them being first cationic neighbor to Cr N2 . We propose that the driving force for charge separation in the excited states of chromium is the local electric field created by the neighboring pair of antisite defects. The cluster of defects formed by Cr N2 ion and the complementary antisite defects is therefore able to store visible light. This unique property enables repeated excitation of LLP through living tissues in ZnGa 2 O 4 :Cr 3+ biomarkers used for in vivo imaging. Upon excitation of ZnGa 2 O 4 :Cr 3+ above 3.1 eV, LLP efficiency is amplified by band-assistance because of the position of Cr 3+4 T 1 ( 4 F) state inside ZnGa 2 O 4 conduction band. Additional TSL peaks emitted by all types of Cr 3+ including defect-free Cr R then appear at low temperature, showing that shallower trapping at defects located far away from Cr 3+ occurs through band excitation.
Journal of Solid State Chemistry, 2019
ZnGa 2 O 4 :Cr 3+ nanophosphors with an average crystallite size of 5 nm were prepared by a combustion method. We observed changes in the luminescence properties compared with the micro-crystalline system, such as a high brightnessemission band at 696 nm and a decrease in the persistent luminescence decay time for the near-infrared emission. The system does not show a change in the band gap. The emission intensity for the broad band with near-infrared emission was very high under excitation with both UV and visible wavelengths. The system presents good stability in colloidal suspensions in water and phosphatebuffered saline, which were found to conserve the luminescence properties. The system is non-toxic and shows applications for in vivo optical imaging due to the rather high penetration depth of near-infrared radiation into human tissue. Its small crystallite size enables it to enter cells for bioimaging, exhibit good dispersion in a biological environment and resist photobleaching.
NIR-Persistent Luminescence Nanoparticles for Bioimaging, Principle and Perspectives
Near Infrared-Emitting Nanoparticles for Biomedical Applications, 2020
The development of nanoparticles for NIR imaging and diagnostics is an area of considerable interest. Among the different imaging modalities, optics emerged has an interesting technique since it is a non-invasive, cheap imaging technique allowing real time imaging. In-vitro, this technique is very useful, however in-vivo fluorescence imaging suffers from suboptimal signal-to-noise ratio, which is caused by the strong tissue autofluorescence under constant external excitation. To address this limitation, novel types of optical nanoprobes are actually being developed in the deep red/near infrared (NIR) range and among them, persistent luminescence nanoparticles (PLNPs), with long lasting near-infrared luminescence capability. These NPs allow optical imaging to be performed in an excitation-free and consequently autofluorescence-free manner. This chapter will first introduce the physical phenomenon associated to the long luminescence delay of such nanoprobes, from minutes to hours after ceasing the excitation, and will then highlight the tools used in physico-chemistry laboratories to characterize these nanoparticles with a focus on the ZnGa2O4 nanoparticles which are widely studied over the world. Then their biocompatibility will be mentioned and finally the evaluation in term of new advances for in-vivo bioimaging theranostics nanoprobes will be presented. We will conclude this chapter by envisioning perspectives for such nanomaterials.
Nanomaterials
Near-infrared (NIR) persistent luminescence (PersL) materials have demonstrated promising developments for applications in many advanced fields due to their unique optical properties. Both high-temperature solid-state (SS) or hydrothermal (HT) methods can successfully be used to prepare PersL materials. In this work, Zn1.33Ga1.34Sn0.33O4:0.5%Cr3+ (ZGSO:0.5%Cr3+), a newly proposed nanomaterial for bioimaging, was prepared using SS and HT methods. The results show the crystal structure, morphology and optical properties of the samples that were prepared using both methods. Briefly, the crystallite size of the ZGSO:0.5%Cr3+ prepared using the SS method is ~3 µm, and as expected, is larger than materials prepared using the HT method. However, the growth process used in the hydrothermal environment promotes the formation of ZGSO:0.5%Cr3+ with more uniform shapes and smaller sizes (less than 500 nm). Different diameter ranges of nanoparticles were obtained using HT and ball milling (BM) m...
Chemistry (Weinheim an der Bergstrasse, Germany), 2015
Ultra-small ZnGa2 O4 :Cr(3+) nanoparticles (6 nm) that exhibit near-infrared (NIR) persistent luminescence properties are synthesized by using a non-aqueous sol-gel method assisted by microwave irradiation. The nanoparticles are pegylated, leading to highly stable dispersions under physiological conditions. Preliminary in vivo studies show the high potential for these ultra-small ZnGa2 O4 :Cr(3+) nanoparticles to be used as in vivo optical nanotools as they emit without the need for in situ excitation and, thus, avoid the autofluorescence of tissues.