Ratiometric Optical Thermometer Based on Dual Near-Infrared Emission in Cr³⁺-Doped Bismuth-Based Gallate Host

Abstract

Detailed spectroscopic analysis of the electronic configuration of Cr3+ in Bi2Ga4O9 is reported. The material exhibits unique luminescent properties arising from the crystal field experienced by Cr3+, with simultaneous strong sharp and broadband near-infrared emissions from the 2E and 4T2 excited states, in a wide range of temperature. The system displays dual near-infrared emission characterized by a remarkable thermal sensitivity over the whole explored range of temperatures, reaching a value of 0.7 %•K-1 in the physiological range. Moreover, the possibility to absorb and emit in the first biological window, allows to consider the system as a new promising candidate for ratiometric fluorescent thermal sensing in biotechnological applications

Non‐Rare‐Earth K2XF7:Mn4+ (X = Ta, Nb): A Highly‐Efficient Narrow‐Band Red Phosphor Enabling the Application in Wide‐Color‐Gamut LCD

“…Huang−Rhys parameter S gives account for the strength of the electron−phonon coupling, which can be expressed by the following expressions: where E( 4 T 2 ) and E( 4 T 2 ) ZPL are the energy at maximum and that at ZPL for Mn 4+ : 4 A 2 → 4 T 2 in the 10 K PLE spectrum, and determined as 21664 cm −1 and 20177 cm −1 , respectively (the first vibronic transition of 4 T 2 is set as ZPL); I 0 and I ZPL represent the integrated areas of the total intensity and the ZPL intensity for Mn 4+ : 2 E→ 4 A 2 in the 10 K PL spectrum. S( 4 T 2 ) in K 2 NbF 7 and K 2 TaF 7 are both calculated as ∼2.78, while S( 2 E) in K 2 NbF 7 and K 2 TaF 7 are calculated as ∼1.27 and ∼1.22, respectively.…”

“…Huang−Rhys parameter S gives account for the strength of the electron−phonon coupling, which can be expressed by the following expressions: [47,48]…”

Toward tunable and bright deep‐red persistent luminescence of Cr3+ in garnets

“…It is worth noting that the value estimated for Dq/B is an average one representative of the crystal field strength for the cation. In fact, the real crystal field strength consists of a distribution of values reflecting the fluctuation of the cation‐anion distance induced by the lattice vibrations and local variations of the host structure . According to the Tanabe‐Sugano ( d 3 ) diagram given in Figure (B), there is a cross‐point region between the energy levels of 4 T 2 ( 4 F) and 2 E ( 2 G) representing the intermediate crystal field region.…”

“…In fact, the real crystal field strength consists of a distribution of values reflecting the fluctuation of the cation-anion distance induced by the lattice vibrations and local variations of the host structure. 30 According to the Tanabe-Sugano (d 3 ) diagram 31 given in Figure 1(B), there is a cross-point region between the energy levels of 4 T 2 ( 4 F) and 2 E ( 2 G) representing the intermediate crystal field region. When the value of Dq/B is small (in the weak crystal field condition), the emission of Cr 3+ is mainly due to the 4 T 2 ( 4 F)?…”

Toward temperature‐dependent Bi3+‐related tunable emission in the YVO4:Bi3+ phosphor

“…Because of the vital role of phosphor in the pc‐wLEDs technology, a lot of UV‐ and blue‐converted phosphors that base on rare‐earth (RE; eg, Eu 2+ , Tb 3+ , Sm 3+ , Eu 3+ , Ce 3+ , Pr 3+ , etc) and non‐RE (eg, Bi 2+ , Mn 2+ , Mn 4+ , Bi 3+ , Cr 3+ , etc) ions doping are developed over the past years. Among these phosphors, RE‐doped phosphors exhibit a lot of sticky problems, for example, the limited absorption ability in UV/blue region (<10 nm; eg, Tb 3+ , Eu 3+ , Sm 3+ , Pr 3+ , etc) and the light reabsorption due to the broad excitation bands in the visible spectral region (eg, Eu 2+ , Ce 3+ , Dy 3+ , etc).…”