Photoluminescent thermometry based on europium-activated calcium sulphide

Spotlight on Luminescence Thermometry: Basics, Challenges, and Cutting-Edge Applications

Luminescence (nano)thermometry is a remote sensing technique that relies on the temperature dependency of the luminescence features (e.g., bandshape, peak energy or intensity, and excited state lifetimes and risetimes) of a phosphor to measure temperature. This technique provides precise thermal readouts with superior spatial resolution in short acquisition times. Although luminescence thermometry is just starting to become a more mature subject, it exhibits enormous potential in several areas, e.g., optoelectronics, photonics, micro- and nanofluidics, and nanomedicine. This work reviews the latest trends in the field, including the establishment of a comprehensive theoretical background and standardized practices. The reliability, repeatability, and reproducibility of the technique are also discussed, along with the use of multiparametric analysis and artificial-intelligence algorithms to enhance thermal readouts. In addition, examples are provided to underscore the challenges that luminescence thermometry faces, alongside the need for a continuous search and design of new materials, experimental techniques, and analysis procedures to improve the competitiveness, accessibility, and popularity of the technology.

Indwelling blood compatible chemical sensors

Progress in surgery has frequently been preceded by progress in technology. Thus positive clinical results may be anticipated with the emerging use of catheter-tip chemical probes. In these devices, the sensor is based on fluorometric or colorimetric sensing, coupled via a fiberoptic light guide to the external environment, or the potentiometric determination of ionic species via catheter-tip ISFET devices. The stages of development for these devices range from laboratory formulations, with some in vitro testing, to limited clinical experience with production prototype models. Advantages reported for the fiberoptic-based devices include no electrical interference, no reference electrode requirement, potentially low-cost fabrication, O2 tension analysis capability, and the possibility of multi-wave-length determinations to improve stability. Disadvantages of the fiberoptic-based probes include ambient light and temperature sensitivity, long-term instability of some reagents, halocarbon anesthetic sensitivity, slow response time, limited dynamic range, and trade-offs between amount of reagent phase, quenching of probe radiation, and stability. The semiconductor-based devices respond only to ionic species but feature the possibility of determining multiple species in a single-chip, low-cost fabrication, on-chip signal processing, clinically useful frequency response, robust design, and long shelf life. Disadvantages are as follows: long-term instability in situ, requirement for a reference electrode, ambient light and temperature sensitivity, and interference (in some cases) by competing ions, necessitating signal compensation. Both types of probes require treatment to avoid fouling of the probe surface and danger to the patient from thromboembolism. Some approaches to resolution of the outstanding problems are outlined. It appears that, given the current pace of industrial development, several of these probes will become a clinical reality in the near future.

Fiber-optic sensors for biomedical applications

In this article the development of fiber-optic sensors for biomedical applications is reviewed. Light-carrying fibers are potentially useful in oximetry, dye dilution measurements, laser-Doppler velocimetry, and fluorometry; as physical sensors of temperature, pressure, and radiation; and as chemical sensors of pH, partial pressure of blood gases, and glucose. Emphasis is placed on the principles and ideas used in the various devices rather than on detailed descriptions or critical discussions.