Multi-Functional and Flexible Nano-Silver@MXene Heterostructure-Decorated Graphite Felt for Wearable Thermal Therapy.

Wearable heaters with multifunctional performances are urgently required for the future personal health management. However, it is still challengeable to fabricate multifunctional wearable heaters simultaneously with flexibility, air-permeability, Joule heating performance, electromagnetic shielding property, and anti-bacterial ability. Herein, silver nanoparticles (AgNPs)@MXene heterostructure-decorated graphite felts are fabricated by introducing MXene nanosheets onto the graphite felts via a simple dip-coating method and followed by a facile in situ growth approach to grow AgNPs on MXene layers. The obtained AgNPs@MXene heterostructure decorated graphite felts not only maintain the intrinsic flexibility, air-permeability and comfort characteristics of the matrixes, but also present excellent Joule heating performance including wide temperature range (30-128 °C), safe operating conditions (0.9-2.7 V), and rapid thermal response (reaching 128 °C within 100 s at 2.7 V). Besides, the multifunctional graphite felts exhibit excellent electromagnetic shielding effectiveness (53 dB) and outstanding anti-bacterial performances (>95% anti-bacterial rate toward Bacillus subtilis, Escherichia coli and Staphy-lococcus aureus). This work sheds light on a novel avenue to fabricate multifunctional wearable heaters for personal healthcare and personal thermal management.

Self-wavelength shifting in two-dimensional perovskite for sensitive and fast gamma-ray detection.

Lead halide perovskites have recently emerged as promising X/γ-ray scintillators. However, the small Stokes shift of exciton luminescence in perovskite scintillators creates problems for the light extraction efficiency and severely impedes their applications in hard X/γ-ray detection. Dopants have been used to shift the emission wavelength, but the radioluminescence lifetime has also been unwantedly extended. Herein, we demonstrate the intrinsic strain in 2D perovskite crystals as a general phenomenon, which could be utilized as self-wavelength shifting to reduce the self-absorption effect without sacrificing the radiation response speed. Furthermore, we successfully demonstrated the first imaging reconstruction by perovskites for application of positron emission tomography. The coincidence time resolution for the optimized perovskite single crystals (4 × 4 × 0.8 mm3) reached 119 ± 3 ps. This work provides a new paradigm for suppressing the self-absorption effect in scintillators and may facilitate the application of perovskite scintillators in practical hard X/γ-ray detections.

Sub-Nanosecond 2D Perovskite Scintillators by Dielectric Engineering.

Perovskite materials have demonstrated great potential for ultrafast scintillators with high light yield. However, the decay time of perovskite still cannot be further minimized into sub-nanosecond region, while sub-nanosecond scintillators are highly demanded in various radiation detection, including high speed X-ray imaging, time-of-flight based tomography or particle discrimination, and timing resolution measurement in synchrotron radiation facilities, etc. Here, a rational design strategy is showed to shorten the scintillation decay time, by maximizing the dielectric difference between organic amines and Pb-Br octahedral emitters in 2D organic-inorganic hybrid perovskites (OIHP). Benzimidazole (BM) with low dielectric constant inserted between [PbBr6 ]2- layers, resulting in a surprisingly large exciton binding energy (360.3 ± 4.8 meV) of 2D OIHP BM2 PbBr4 . The emitting decay time is shortened as 0.97 ns, which is smallest among all the perovskite materials. Moreover, the light yield is 3190 photons MeV-1 , which is greatly higher than conventional ultrafast scintillator BaF2 (1500 photons MeV-1 ). The rare combination of ultrafast decay time and considerable light yield renders BM2 PbBr4 excellent performance in γ-ray, neutron, α-particle detection, and the best theoretical coincidence time resolution of 65.1 ps, which is only half of the reference sample LYSO (141.3 ps).

Multifunctional MoSe2 @MXene Heterostructure-Decorated Cellulose Fabric for Wearable Thermal Therapy.

A booming demand for wearable electronic devices urges the development of multifunctional smart fabrics. However, it is still facing a challenge to fabricate multifunctional smart fabrics with satisfactory mechanical property, excellent Joule heating performance, highly efficient photothermal conversion, outstanding electromagnetic shielding effectiveness, and superior anti-bacterial capability. Here, a MoSe2 @MXene heterostructure-based multifunctional cellulose fabric is fabricated by depositing MXene nanosheets onto cellulose fabric followed by a facile hydrothermal method to grow MoSe2 nanoflakes on MXene layers. A low-voltage Joule heating therapy platform with rapid Joule heating response (up to 230 °C in 25 s at a supplied voltage of 4 V) and stable performance under repeated bending cycles (up to 1000 cycles) is realized. Besides, the multifunctional fabric also exhibits excellent photothermal performance (up to 130 °C upon irradiation for 25 s with a light intensity of 400 mW cm-2 ), outstanding electromagnetic interference shielding effectiveness (37 dB), and excellent antibacterial performances (>90% anti-bacterial rate toward Escherichia coli, Bacillus subtilis, and Staphylococcus aureus). This work offers an efficient avenue to fabricate multifunctional wearable thermal therapy devices for mobile healthcare and personal thermal management.