Temperature dependence of afterglow in zirconia and its optically-stimulated luminescence by bone-through irradiation for biological temperature probe

Abstract

Development of minimally invasive and site-selective biological temperature sensing is quite importantin medical field. This study presents a novel temperature sensing technique based on afterglow and optically-stimulated luminescence (OSL). The dependence of afterglow photoluminescent intensity on the environmental temperature of zirconia (Zro 2 ) phosphor is examined to validate its use as a sensing probe. In addition, assuming the measurement in deep-part of human body, we have applied the information gathered from our validation to observe oSL from the Zro 2 by irradiation with near-infrared laser through a bone sample. This study demonstrates an alternative medical application of phosphor, and introduces an elemental-technology for the temperature sensing.Body temperature is main vital sign, which is closely related to immune system and metabolism. A technique for biological temperature monitoring is a powerful tool for medical treatment and monitoring human health. In addition, targeted temperature management has the potential to reduce the risk of brain dysfunction after a head injury and cardiopulmonary arrest. Although clinical thermometers and thermography are non-invasive, the methods measure the temperature on the surface of body. The gold standard for measuring temperature in critically ill patients is the Swan-Ganz catheter (Suppl. Fig. S1). The catheter must be inserted into the body in order to monitor the temperature at the desired location. Consequently, there is a need for accessible and minimally invasive temperature sensing methods which can monitor local internal temperature.Optical/spectroscopic measurement is recognized to be a minimally invasive and contactless method, and particularly, fluorescent and afterglow phenomena have been attempted to utilize for sensing-/imaging-applications so far 1-5 . Quantum-dots and fluorescent polymers have been proposed as temperature sensors for cell-imaging due to the relationship between temperature and fluorescence intensity/lifetime 1,2 . The observation of these effects is only possible with the magnification of a microscope. Chermont et al. developed a bio-imaging technique using afterglow phosphor of Eu 2+ , Dy 3+ , Mn 2+ -tri-doped Ca 0.2 Zn 0.9 Mg 0.9 Si 2 O 6 6 . Their study results inspired us to use the afterglow phenomenon to measure the temperature within the human body. In this manuscript, the fundamental measurements necessary to validate the use of the decay curve in the afterglow phosphor to measure temperature are presented. In addition, optically-stimulated luminescence (OSL) phenomena was also considered as irradiation of near-infrared (NIR) laser light would enable site-selective photoluminescence (PL), making it possible to obtain temperature information at internal sites in the human body.www.nature.com/scientificreports www.nature.com/scientificreports/ line. This departure was probably due to a partial electron-release from a deeper-trapping site corresponding to the peak F with peak at ~353 K. The pre-heating process is an eff...

Repetitive afterglow in zirconia by pulsed near-infrared irradiation toward biological temperature sensing

“…The moderate decay after pulsed irradiation is regarded as an AG process because the irradiation was stopped in this term. This leads us to consider that AG decay curves induced by OSL exhibit similar behavior to AG properties previously reported, i.e., the lifetime decreases as the environmental temperature of ZrO 2 increases 9 , 13 . Furthermore, we could confirm the rapid PL increase of over 100 times caused by repetitive irradiation (Fig.…”

“…According to the TL measurement, thermally treated ZrO 2 is reported to exhibit several peaks due to several kinds of electron-trapping sites 10 – 12 . We have also confirmed six primary TL peaks, peaks A–F, with peaks E and F appearing around/above room temperature, attributed to AG and OSL, respectively 9 . The ZrO 2 sample treated at 1400 °C for 6 h exhibits AG after ultraviolet (UV)-light exposure (254 nm), followed by OSL visually observed at the NIR-laser-irradiated spot (inset).…”

“…The ZrO 2 sample treated at 1400 °C for 6 h exhibits AG after ultraviolet (UV)-light exposure (254 nm), followed by OSL visually observed at the NIR-laser-irradiated spot (inset). However, the presence of multiple peaks complicates the analysis of AG decay curves 9 . Therefore, prior to the TL measurement, we pre-heated the ZrO 2 sample at 323 K for 2.5 h to release electrons trapped in trapping sites, appearing below room temperature, i.e., de-trapping.…”

“…Our research group has proposed a new temperature sensing concept for deep parts of the human body based on AG and OSL and then demonstrated a basic principle for temperature determination by the AG decay curve using a chemically-stable and harmless oxide, namely, zirconia (ZrO 2 ), as a sensing probe 9 . In addition, external laser stimulation with a wavelength (~ 650–1000 nm) in the NIR region, which has relatively high transmittance to biological tissue (i.e., biological window), enables site-selective and arbitrary-timing measurements, and we have also been able to observe OSL by irradiating a bone sample with a continuous-wave NIR-laser 9 . Meanwhile, continuous irradiation is regarded as an external source of energy in terms of temperature rise and resulting in thermal damage in biological tissue.…”

Optically Stimulated Luminescence Phosphors: Principles, Applications, and Prospects

“…The energy levels of defects in the bandgap close to the CB minimum and VB maximum are regarded as electron and hole traps. The big and small [ 191] Tb 3+ , Hf 4+ 544 442 - [ 192] LiCaPO 4 Ce 3+ 369 Blue LED 0.6, 0.9 [ 193] LiNbO 3 Pr 3+ 620 980 - [ 194] Ca 4 Ti 3 O 10 Pr 3+ , Y 3+ 612 980 0.9-0.98 [ 195] LiTaO 3 Bi 3+ 430 808/980 0.55-1.16 [ 196] ZrO 2 -480 808/980 - [ 197] SrMoO 4 --470 0.9-1.95 [ 198] BeO Na + , Tb 3+ , Gd 3+ -470 - [ 199] Na + , Dy 3+ , Er 3+ 250 470 - [ 200] LiMgPO Tm 3+ 460 energy differences between the defect energy level and CB/VB differ the deep and shallow traps. [205,206] Though the incorporation of an activator can affect the intrinsic traps or even cause new traps, an effective way is to properly codope with a different ion to introduce the traps intentionally.…”