Solution-processed Er3+-Doped GeS2 chalcogenide glass films with NIR photoluminescence towards functional flexibility and integration.

Rare-earth doped chalcogenide films are major components in flexible and integrated photonic and optoelectronic devices for modern communication systems, metrology, and optical sensing. However, it is still challenging to develop a high concentration of rare-earth doping chalcogenide film with a smooth surface to realize efficient photoluminescence (PL). Here, we demonstrate that Er3+-doped GeS2 films are prepared by spin-coating based on a two-step dissolution process. Such a two-step process provides the high solubility of Er3+ in GeS2 films and exhibits efficient emission at ∼1.5 µm crossing the telecommunication C-band. The highest PL emission intensity is obtained in GeS2 films doped with 1.4 mol% of Er3+, and this PL in GeS2 films is reported for the first time. We propose adjustments of annealing parameters for improving the PL characteristics in such materials. Through the control precision of the heating rate and annealing temperature, the smooth surface of GeS2 films enables efficient photo-luminescence. This two-step dissolution-based strategy would pave a new path to design luminescent chalcogenide films for application in flexible and integrated optoelectronics and photonics.

Tunable broadband near-infrared luminescence in glass realized by defect-engineering.

Tunable broadband near-infrared (NIR)-luminescent materials play a crucial role as light sources and tunable fiber lasers in modern technologies such as high-capacity telecommunication, imaging, and remote sensing. Despite considerable effort in studying the luminescent materials doped with rare-earth or transition metal ions, it is still challenging to achieve tunable broadband emission in photonic materials, especially in glasses, for active-fiber applications. In the present work, such NIR emission is achieved by modifying oxygen-deficient structural defects (i.e., singly ionized oxygen vacancies (VO∙) in tellurium (Te)-doped germanate glass). The local glass chemistry around Te is controlled by engineering singly ionized oxygen vacancies (VO∙) in alkali-alumino-germanate glass. This enables fine-tuning of the configurations and chemical states of Te centers over a wide range of chemical states, from ionic states to neutrally charged clusters and to positively charged clusters, resulting in various intriguing luminescent behaviors (e.g., wavelength-tunable emission, great emission enhancement, bandwidth extension).

Unusual thermal response of tellurium near-infrared luminescence in phosphate laser glass.

We report an unusual thermal response of tellurium (Te) near-infrared (NIR) luminescence in phosphate laser glass, where the luminescence first increases and then decreases with heat-treatment temperatures increasing from 250°C to the glass transition temperature (Tg). This is followed by a distinct revival of Te NIR luminescence at temperatures above Tg. This result differs from the scenario in conventional rare-earth (Er3+, Nd3+, and Yb3+)-doped phosphate glasses, where the rare-earth NIR emission decreases with increasing heat-treatment temperature. The difference may originate from conversion between Te4 and other Te species, which depends on the evolution of the glass structure and molecular motion during the reheating processes, leading to unusual thermal response of Te NIR luminescence. The increase in Te4 clusters enhances Te NIR emission, indicating that Te NIR luminescence is assigned to the Te4 cluster, in contrast to previous studies. Heating and cooling cycles between 50°C and 250°C reveal strong dependence of the thermal degradation on glass structure. Te-doped phosphate laser glass with zero thermal degradation can be realized by stabilizing NIR luminescence center Te4 by adjusting the glass structure with reduced network crosslinking. The superior optical performance has been confirmed in our previous study that the NIR luminescence properties can be well maintained in Te-doped fiber. The findings indicate that Te-doped phosphate glass with unusual thermal responses can potentially be used in fiber laser devices.

Unusual anti-thermal degradation of bismuth NIR luminescence in bismuth doped lithium tantalum silicate laser glasses.

For application of bismuth laser glasses in either fiber amplifier or laser, their performance stability in long run should be understood especially in extreme conditions. However, so far, there are few reports on it. Here, we found, after the cycle experiments on heating and cooling, that the proper increase of lithium content in lithium tantalum silicate laser glass can lead to unusual anti-thermal degradation of bismuth NIR luminescence, which completely differs from the scenario in germanate glass. FTIR, 29Si MAS NMR spectra, absorption and dynamic photoluminescence spectra are employed to unravel how this happens. The results illustrate that it should be due to the decrease of polymerization of silicate glass network, which in turn allows the regeneration at 250°C, and therefore, the content increase of bismuth NIR emission centers. In the meanwhile, we noticed though Bi luminescence can be thermally quenched its peak does not shift along with temperature, which seldom appears in laser materials. The unique property might guarantee the unshift of Bi fiber laser wavelength once such glass was made into fiber devices even as the environmental temperature changes. The role of lithium is discussed in the evolution of glass structures, the suppression of glass heterogeneity, and the thermal stability of Bi luminescence, and it should be helpful to design homogeneous silicate laser glass with outstanding thermal stability.

Superbroad visible to NIR photoluminescence from Bi+ evidenced in Ba2B5O9Cl: Bi crystal.

The nature of bismuth NIR luminescence is essential to develop the bismuth doped laser materials with high efficiency and desirable emission wavelength, and it, thereby, receives rising interests. Our previous work reported the Bi(0) luminescence from Ba2B5O9Cl: Bi with a lifetime of ~30 µs and the conversion of Bi(2+) to Bi(0). This work found indeed the conversion could be enabled in the compound by an in situ reduction technique and it, however, happens via an intermediate state of Bi(+). Once the ion of Bi(+) is stabilized and built into the compound, it can luminesce in a super broad spectral range from 600 to 1200 nm with a lifetime longer than 1 ms, due to the cascade transitions from (3)P2 and (3)P1 to (3)P0. This is completely different from Bi(0) and Bi(2+) in the compound, and it has never been noticed before. We believe this work can help us better understand the complex nature of bismuth luminescence.

Ultraflexible Temperature-Strain Dual-Sensor Based on Chalcogenide Glass-Polymer Film for Human-Machine Interaction.

Skin-like thermoelectric (TE) films with temperature- and strain-sensing functions are highly desirable for human-machine interaction systems and wearable devices. However, current TE films still face challenges in achieving high flexibility and excellent sensing performance simultaneously. Herein, for the first time, a facile roll-to-roll strategy is proposed to fabricate an ultraflexible chalcogenide glass-polytetrafluoroethylene composite film with superior temperature- and strain-sensing performance. The unique reticular network of the composite film endows it with efficient Seebeck effect and flexibility, leading to a high Seebeck coefficient (731 µV/K), rapid temperature response (≈0.7 s), and excellent strain sensitivity (gauge factor = 836). Based on this high-performance composite film, an intelligent robotic hand for action feedback and temperature alarm is fabricated, demonstrating its great potential in human-machine interaction. Such TE film fabrication strategy not only brings new inspiration for wearable inorganic TE devices, but also sets the stage for a wide implementation of multifunctional human-machine interaction systems.

Superflexible Inorganic Ag2 Te0.6 S0.4 Fiber with High Thermoelectric Performance.

Fiber-based inorganic thermoelectric (TE) devices, owing to the small size, light-weight, flexibility, and high TE performance, are promising for applications in flexible thermoelectrics. Unfortunately, current inorganic TE fibers are strictly constrained by limited mechanical freedom because of the undesirable tensile strain, typically limited to a value of 1.5%, posing a strong obstacle for further application in large-scale wearable systems. Here, a superflexible Ag2 Te0.6 S0.4 inorganic TE fiber is demonstrated that provides a record tensile strain of 21.2%, such that it enables various complex deformations. Importantly, the TE performance of the fiber shows high stability after ≈1000 cycles of bending and releasing processes with a small bending radius of 5 mm. This allows for the integration of the inorganic TE fiber into 3D wearable fabric, yielding a normalized power density of 0.4 µW m-1 K-2 under the temperature difference of 20 K, which is approaching the high-performance Bi2 Te3 -based inorganic TE fabric and is nearly two orders of magnitude higher than the organic TE fabrics. These results highlight that the inorganic TE fiber with both superior shape-conformable ability and high TE performance may find potential applications in wearable electronics.

High Seebeck Coefficient Inorganic Ge15Ga10Te75 Core/Polymer Cladding Fibers for Respiration and Body Temperature Monitoring.

Wearable thermal sensors based on thermoelectric (TE) materials with high sensitivity and temperature resolution are extensively used in medical diagnosis, human-machine interfaces, and advanced artificial intelligence. However, their development is greatly limited by the lack of materials with both a high Seebeck coefficient and superior anticrystallization ability. Here, a new inorganic amorphous TE material, Ge15Ga10Te75, with a high Seebeck coefficient of 1109 µV/K is reported. Owing to the large difference between the glass-transition temperature and initial crystallization temperature, Ge15Ga10Te75 strongly inhibits crystallization during fiber fabrication by thermally codrawing a precast rod comprising a Ge15Ga10Te75 core and PP polymer cladding. The temperature difference can be effectively transduced into electrical signals to achieve TE fiber thermal sensing with an accurate temperature resolution of 0.03 K and a fast response time of 4 s. It is important to note that after the 1.5 and 5.5 K temperatures changed repeatedly, the TE properties of the fiber demonstrated high stability. Based on the Seebeck effect and superior flexibility of the fibers, they can be integrated into a mask and wearable fabric for human respiration and body temperature monitoring. The superior thermal sensing performance of the TE fibers together with their natural flexibility and scalable fabrication endow them with promising applications in health-monitoring and intelligent medical systems.

Enhancing the Interfacial Stability of the Li2S-SiS2-P2S5 Solid Electrolyte toward Metallic Lithium Anode by LiI Incorporation.

Chalcogenide solid-state electrolytes (SEs) have been regarded as promising candidates for lithium dendrite suppression due to their high ionic conductivity, suitable mechanical strength, and large Li+ ion transference number. However, the wide applications of SEs in pragmatic all-solid-state batteries are still retarded by their limited interface stability, which leads to lithium dendrite growth and formation of interphase with high resistance. In addition, the interphase evolution mechanism between SEs and metallic Li anodes remains unclear. Herein, this work demonstrates that the interfacial stability of Li2S-SiS2-P2S5 SEs can be effectively enhanced by tuning the interphase through LiI incorporation. This strategy contributes to a high ionic conductivity of the SEs and electronic insulation interphase containing LiI. Thus, the 70(60Li2S-28SiS2-12P2S5)-30 LiI SEs prepared by melt-quenching exhibit a high ionic conductivity of 1.74 mS cm-1 at room temperature and a larger critical current density of 1.65 mA cm-2 at 65 °C. The cycling life of the symmetric Li|SEs|Li cell is up to 200 h without significant resistance growth at 0.1 mA cm-2 at room temperature. This enhanced interface stability is revealed to originate from the in situ-formed LiI within the interphase, which prevents continual SEs degradation and suppresses lithium dendrite growth. This work provides a vital understanding of interphase evolution, which is valuable for designing SEs with long cycling stability.

D2h-Symmetric Tetratellurium Clusters in Silicate Glass as a Broadband NIR Light Source for Spectroscopy Applications.

Broadband near-infrared (NIR) light sources present attractive opportunities for potential applications in high-capacity telecommunication, temperature sensing, energy conversion, and NIR spectroscopy. While significant effort has been spent on materials doped with rare-earth and transition-metal ions, the achievement of these materials with ultrabroadband NIR emission and desired wavelength region remains a long-standing challenge, especially operating in the spectral region between 700 and 1300 nm. Here, such emission is developed in tellurium (Te) cluster-doped silicate glass for the first time. Furthermore, the mechanism of the NIR luminescence due to D2h-symmetric tetratellurium (Te4) clusters is identified by density functional theory (DFT) calculations. For intense luminescence, a model for the generation and stabilization of Te clusters by tailoring topological cages via adjustment of the Na2O and Al2O3 contents and by optimizing the content of the dopant is proposed. Various stable Te clusters embedded into glass exhibit intense visible (Vis) to NIR broadband luminescence (400-1300 nm) with a spectral gap of 900 nm. In a demonstration experiment, a light-emitting diode (LED) device is fabricated from Te cluster-doped glass. This study opens a new opportunity for Te cluster-doped glass as a broadband NIR light source for spectroscopy applications.

[Effect of etomidate on hemodynamics in elderly and shock patients during general anesthesia induction].

OBJECTIVE: To investigate the effect of etomidate on the hemodynamics in elderly and shock patients during general anesthesia induction. METHODS: Totally 100 elderly patients or patients with hemorrhagic shock (ASA II -III ) undergoing surgery were studied. Anesthesia was induced with 4 microg/kg of fentanyl, 0.1 mg/kg of vecuronium and 0.2-0.3 mg/kg of etomidate, and the mean arterial blood pressure (MAP), heart rate (HR), stroke volume (SV), stroke index (SI), cardiac output (CO), cardiac index (CI), cardiac acceleration index (ACI), left cardiac work (LCW), and left cardiac work index (LCWI) were recorded using thoracic electrical bioimpedance (TEB) hemodynamic monitoring system before induction and at 1, 2 and 3 min after etomidate injection as well as at 3 min after intubation. RESULTS: After etomidate injection, MAP, HR, SV, SI, CO, CI, ACI, LCW and LCWI were decreased significantly as compared with those before induction (P<0.05). MAP, HR, CO, CI and ACI at 3 min after intubation were higher than those before induction (P<0.05), and the other indices resumed the baseline level. The amplitudes of such changes in the recorded indices was below 20% of the baseline level in the course of anesthesia induction. CONCLUSION: Cardiovascular hemodynamics may vary slightly during the course of induction with etomidate, which is an ideal drug for anesthesia induction for elderly or shock patients with unstable hemodynamics.