The Impact of Cr3+ Doping on Temperature Sensitivity Modulation in Cr3+ Doped and Cr3+, Nd3+ Co-doped Y3Al5O12, Y3Al2Ga3O12, and Y3Ga5O12 Nanothermometers.

Karolina Elzbieciak,Lukasz Marciniak

doi:10.3389/fchem.2018.00424

Karolina Elzbieciak, Lukasz Marciniak

Open Access

https://doi.org/10.3389/fchem.2018.00424

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Abstract

A new approach to enhance the sensitivity of transition metal ion based nanocrystalline luminescent thermometer is presented. It was shown that the increase of Cr3+ concentration in three types of garnet host namely Y3Al5O12, Y3Ga5O12, and Y3Al2Ga3O12 allows for significant enhancement of their performance in non-contact thermometry. This phenomenon is related to the weakening of the crystal field strength due to enlargement of average Cr3+-O2− distance at higher Cr3+ concentrations. By increasing Cr3+ concentration from 0.6 to 30%, the sensitivity increased by over one order of magnitude from S = 0.2%/°C to S = 2.2%/°C at 9°C in Y3Al2Ga3O12 nanocrystals. Moreover, it was found that due to the Cr3+ → Nd3+ energy transfer in the Cr3+, Nd3+ co-doped system, the usable Cr3+ concentration, for which its emission can be detected, is limited to 10% while the sensitivity at −50°C was doubled (from 1.3%/°C for Y3Al2Ga3O12:10%Cr3+ to 2.2%/°C Y3Al2Ga3O12:10%Cr3+, 1%Nd3+ nanocrystals).

Highlights

It was shown that the increase of the Cr3+ concentration causes elongation of the average Cr3+-O2− distance leading to the reduction of the crystal field strength in Y3Al2Ga3O12, Y3Ga5O12 and Y3Al5O12 nanocrystals
The relative sensitivity of 4T2→4A2 to 2E→4A2 emission intensity increases from S = 0.2%/◦C for 0.06%Cr3+ to S = 2.2%/◦C for 30%Cr3+ at 9◦C in Y3Al2Ga3O12 nanocrystals, from S = 0.027%/◦C for 0.5%Cr3+ to S = 2.7% for 10%Cr3+ at −105◦ C in Y3Al5O12 nanocrystals, and from S = 0.14%/◦C for 0.5%Cr3+ to S = 2% for 10%Cr3+ at −78◦C in Y3Ga5O12 nanocrystals
In the case of Nd3+ co-doped nanocrystals, due to the Cr3+→Nd3+ energy transfer, the usable concentration range of Cr3+ dopants is strongly reduced and no evidence of Cr3+ emission was found above 10% of Cr3+

Summary

Introduction

In response to the requirements imposed by technology, micro/nanoelectronics or photonics as well as by biomedical applications, new approaches to the luminescent nanothermometers (LNTs) have to be proposed to secure fast and accurate temperature sensing with submicrometer spatial resolution, and highly sensitive temperature readout (Brites et al, 2012; Jaque and Vetrone, 2012; Chen et al, 2016; del Rosal et al, 2016a,b; Dramicanin, 2016; Marciniak et al, 2016b; Suo et al, 2017; Wang et al, 2017; Gao et al, 2018; Liao et al, 2018; Liu et al, 2018; Malysa et al, 2018; Runowski et al, 2018; Zhong et al, 2018). Analysis of the emission spectra of Y3Al2Ga3O12:Cr3+ for different dopant concentration obtained upon 450 nm excitation, clearly indicates that at higher Cr3+ concentration the broad 4T2→4A2 emission band localized at around 870 nm increase its intensity in respect to the 2E→4A2 band at 692 nm (Figure 2B). In order to obtain self-referenced luminescent thermometer based of the Cr3+ emission intensity the examined nanocrystals with different Cr3+ concentration were co-doped with 1% Nd3+ ions.

Results

Conclusion