Thermochromic Luminescent Nanomaterials Based on Mn⁴⁺/Tb³⁺ Codoping for Temperature Imaging with Digital Cameras

Abstract

A new thermographic nanocrystalline Sr 4 Al 14 O 25 :Mn 4+ ,Tb 3+ phosphor was developed, and the concentrations of both dopants and the synthesis conditions were optimized. The combination of the thermally quenched luminescence from the Mn 4+ ions to the almost temperature-independent emission from Tb 3+ provides a sensitive luminescent thermometer ( S R = 2.8%/°C at 150 °C) with strong emission color variability. In addition, a figure of merit for this luminescence thermochromism was proposed, as the relative sensitivities of the x and y CIE coordinates, which for this phosphor reaches at 150 °C S R ( x ) = 0.6%/°C and S R ( y ) = 0.4%/°C, respectively. Noncontact thermal imaging was demonstrated with this phosphor using a single consumer digital camera and exploiting the ratio of red (R) and green (G) channels of the RGB images, thereby confirming the high application potential of Sr 4 Al 14 O 25 :Mn 4+ ,Tb 3+ nanocrystals for thermal sensing and mapping.

A single-band ratiometric luminescent thermometer based on tetrafluorides operating entirely in the infrared region

“…In order to intentionally design highly temperature-sensitive luminescent thermometer, the phosphor properties and performance, as well as the temperature readout methodology must be further optimized. Until recently, 6 classes of thermometers were distinguished, among which mainly those, in which the temperature-dependent parameter was based on the luminescence intensity ratio (LIR) of two emission bands of phosphors was utilized as a thermometric parameter [7][8][9][10][11][12][13][14] .…”

mOptical Sensing for the Internet of Things: A Smartphone‐Controlled Platform for Temperature Monitoring

“…Moreover, the emission color temperature dependence was explored a step further, as the color variation was also quantified using photographic records from a digital camera in the RGB color system, complementing the analysis of spectral data to in CIE 1931 color coordinates ( Figure ). [ 101 ] This is a representative example that quantifies emission color through remote captured images even though the full temperature range is very broad and outside the expected working regime for a smartphone. Nonetheless, as luminescence thermometry is a noncontact method, it is feasible to consider the use of a smartphone, illustrating its use for temperature sensing in more extreme scenarios.…”

From quencher to potent activator – Multimodal luminescence thermometry with Fe3+ in the oxides MAl4O7 (M = Ca, Sr, Ba)

“…Therefore, currently conducted works on TM-based luminescent thermometers aim at an enhancement of the emission intensity in the NIR range [12][13][14] . Among the most prominent candidates so far are the 3d 3 ions Cr 3+ and Mn 4+ doped into oxidic host compounds [15][16][17][18] . However, also several other TM ions show intense NIR luminescence with large a large response to small temperature changes [19][20][21][22][23][24][25][26][27][28] .…”