Mn2+-activated dual-wavelength emitting materials toward wearable optical fibre temperature sensor

Abstract

Photothermal sensing is crucial for the creation of smart wearable devices. However, the discovery of luminescent materials with suitable dual-wavelength emissions is a great challenge for the construction of stable wearable optical fibre temperature sensors. Benefiting from the Mn2+-Mn2+ superexchange interactions, a dual-wavelength (530/650 nm)-emitting material Li2ZnSiO4:Mn2+ is presented via simple increasing the Mn2+ concentration, wherein the two emission bands have different temperature-dependent emission behaviours, but exhibit quite similar excitation spectra. Density functional theory calculations, coupled with extended X-ray absorption fine structure and electron-diffraction analyses reveal the origins of the two emission bands in this material. A wearable optical temperature sensor is fabricated by incorporating Li2ZnSiO4:Mn2+ in stretchable elastomer-based optical fibres, which can provide thermal-sensitive emissions at dual- wavelengths for stable ratiometric temperature sensing with good precision and repeatability. More importantly, a wearable mask integrated with this stretchable fibre sensor is demonstrated for the detection of physiological thermal changes, showing great potential for use as a wearable health monitor. This study also provides a framework for creating transition-metal-activated luminescence materials.

Interstitial Li+ Occupancy Enabling Radiative/Nonradiative Transition Control toward Highly Efficient Cr3+-Based Near-Infrared Luminescence

“…Cr 3+ with a 3d 3 electron configuration is considered an ideal emitting center for broadband NIR emission because of its broad absorption in blue/red light regions and tunable broadband NIR emission at ∼720–1200 nm depending on the crystal-field strength. , Moreover, this type of Cr 3+ emission can be easily achieved by doping Cr 3+ in a weak crystal-field environment. Broadband NIR emission can be observed via Eu 2+ , Mn 2+ , or Ni 2+ doping, which was only obtained in some limited structures. − Therefore, the current attention is mainly focused on Cr 3+ -activated NIR phosphors. Some of the high-efficiency (internal quantum efficiency (IQE) > 85%) Cr 3+ -doped NIR emission phosphors for LEDs have been developed, such as Ca 3 Sc 2 Si 3 O 12 :Cr 3+ (IQE = 92.3%), Gd 3 Sc 2 Ga 3 O 12 :Cr 3+ (IQE = 98.6%), Ga 2– x Sc x O 3 :Cr 3+ (99%), GaTaO 4 :Cr 3+ (IQE = 91%), etc.…”

Ultrasensitive Optical Thermometry via Inhibiting the Energy Transfer in Zero-Dimensional Lead-Free Metal Halide Single Crystals

“…Self-referencing optical thermometry based on the correlation between the temperature and fluorescence intensity ratio (FIR) of dual-band emission luminous materials is an ongoing area of interest in temperature detection research. − It can be applied to detect small-size, fast-moving objects or provide real-time biological temperature monitoring as a result of its high sensitivity, great spatial resolution, and non-invasively fast response. − The technique calls for luminescent materials possessing two or more luminescence peaks and responding to temperature differently. In this aspect, rare earth ions with two thermally coupled levels (TCLs) are particular attractive to researchers.…”

A Mild‐Stimuli‐Responsive Fluorescent Molecular System Enables Multilevel Anti‐Counterfeiting and Highly Adaptable Temperature Monitoring

“…[ 5–7 ] Compared to conventional physical (e.g., mercury, ethanol) and electronic (e.g., thermocouple) thermometers, luminescence thermometers possess distinct merits of visualization, non‐invasiveness, fast response, and particularly can work in an electromagnetic circumstance, and provide high spatial and thermal resolutions. [ 8–10 ]…”

“…[5][6][7] Compared to conventional physical (e.g., mercury, ethanol) and electronic (e.g., thermocouple) thermometers, luminescence thermometers possess distinct merits of visualization, non-invasiveness, fast response, and particularly can work in an electromagnetic circumstance, and provide high spatial and thermal resolutions. [8][9][10] Over the last few decades, organic luminescent materials with responses to one or more external "triggers," such as light, [11,12] heat, [13,14] mechanical force [15,16] and chemical vapors, [17,18] have gained increasing attention owing to their potentials for a variety of applications. [19] The feature of adjustable fluorescence color changes on demand endows the smart materials with an encoding capacity, as well as an easily decodable property through visualized patterns.…”