Michele Back

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

The increasing interest in the development of ratiometric optical thermal sensors has led to a wide variety of new systems with promising properties. Among them, singly-doped ratiometric thermometers were recently demonstrated to be particularly reliable. With the aim to discuss the development of an ideal optical thermal sensor, a combined experimental and theoretical insight into the spectroscopy of the Bi₂Ga₄O₉:Cr³⁺ system is reported showing the im

Abstract The design of effective optical systems featuring high thermal sensitivity able to discriminate ever smaller variations of temperature in noncontact mode is of critical importance to face the challenges brought by the modern‐day technological revolution. If from one hand, the ratiometric optical thermometers based on Boltzmann distribution are demonstrated to be characterized by a unique reliability, on the other hand, robust performances in different environments are highly desired for

Luminescence Boltzmann thermometry is one of the most reliable techniques used to locally probe temperature in a contactless mode. However, to date, there is no report on cryogenic thermometers based on the highly sensitive and reliable Boltzmann-based ⁴T₂ → ⁴A₂/²E → ⁴A₂ emission ratio of Cr³⁺. On the basis of structural information of the local HfO₆ octahedral site we demonstrated the potential of

Abstract The performance of luminescent Cr 3+ ‐doped thermometers is strongly influenced by the locally surrounding ligand field. A universal relationship between the thermometric performance and structural/chemical parameters is highly desirable to drive the development of effective Cr 3+ ‐based thermal sensors avoiding trial‐and‐error procedures. In this view, as prototypes, the electronic structure and the thermometric performance of Cr 3+ ‐doped α‐Ga 2 O 3 and β‐Ga 2 O 3 polymorphs are compa

The development of noncontact thermometers with self-control to specific temperatures to be used as control markers with an additional degree of reliability is a challenge in the field of thermal sensors. Herein, a strategy exploiting the wide tunability of an intrinsic feature of oxide perovskites such as the phase-transition temperature to design a new class of ratiometric luminescent thermometers is introduced. The structural and optical response to the thermal stimuli of LaGaO₃:Nd

Highly sensitive Boltzmann thermometry by double-layered Bi₂SiO₅:Yb³⁺,Tm³⁺@SiO₂ hollow nanoparticles with exceptional thermometric performances and biocompatibility are demonstrated.

The development of nanomaterials with high sensitivity to external stimuli such as temperature is critical to investigate the driving force of not only biological processes but also catalytic mechanisms in extreme environments. However, the instability of nano-objects at high temperatures and different environments is a serious drawback limiting often their real use. This is particularly severe in the case of bismuth-based compounds, making the development of highly stable bismuth-based nanosyst

After more than a century of studies on the optical properties of Bi3+ ions, the assignment of the nature of the emissions and the bands of the absorption spectra remain ambiguous. Here, we report an insight into the spectroscopy of Bi3+-activated CaMO3 perovskites (M = Zr, Sn, and Ti), discussing the factors driving the metal-to-metal charge transfer and sp → s2 transitions. With the aim to figure out the whole scenario, a combined experimental and theoretical approach is employed. The comparis

The energy transfer process between Tb³⁺ and Eu³⁺ ions in water-dispersible CaF₂ nanocrystals prepared using a simple process is reported. Fine colour control and long excited state lifetimes make the nanosystem suitable for biosensing applications.

The enhancement of the low absorption cross section and widening of the absorption range of the RE ions in the UV-blue region is still a challenge to develop optical systems with high performance. In this work we synthesized Bi- and Er-codoped Y2O3 nanocrystals by means of Pechini type sol–gel process. X-ray powder diffraction (XRPD) and transmission electron microscopy (TEM) were performed to evaluate the nanocrystalline particle size and phase. Photoluminescence investigation in the UV–vis and

Bismuth-based (nano)materials have been attracting increasing interest due to appealing properties such as high refractive indexes, intrinsic opacity, and structural distortions due to the stereochemistry of 6s² lone pair electrons of Bi³⁺. However, the control over specific phases and strategies able to stabilize uniform bismuth-based (nano)materials is still a challenge. In this study, we employed the ability of bismuth to lower the melting point of silica to introduce a

Understanding the role played by the material chemistry to increase the pressure sensitivity of new optical pressure probes is of great scientific interest. After almost 50 years from the first proposal as an optical pressure sensor, the R-line emission of ruby (α-Al2O3:Cr3+) is still the standard pressure probe used for the diamond anvil cell experiments in worldwide laboratories. Besides the fundamental importance of developing new materials able to discriminate pressure variations with high s

In the field of novel applications involving upconverting processes, the determination of new strategies for realizing emission-tunable nanomaterials is a challenge. In this work the design of Y³⁺ and Er³⁺ codoped bismuth oxide-based upconverting nanoparticles is presented, evidencing that the active role of the matrix allows for the emission selectivity with chromaticity control. The bandgap of the bismuth oxide-based host can be manipulated in the range of 0.65 eV, conseq