Journal of Materials Chemistry C最新文献

Wearable cuffless blood pressure sensing is essential for the monitoring of hypertension and its related cardiovascular diseases in an on-demand, timely, and comfortable manner. Measurement of the pulse transit time (PTT) has been the most employed technique to monitor blood pressure due to its noninvasiveness, low cost, and ease of device miniaturization. However, the existing PTT measurements rely on analyzing pulse and electrophysiological signals using discrete sensors that complicate the circuit design and signal processing. Herein, we report a wearable dual-mode sensor that can simultaneously monitor both the electrocardiogram and arterial pulse to simplify the measurement of the PTT. This was achieved by encapsulating a liquid metal pressure sensing circuit within the adhesive and conductive ionogel. The ionogel can not only be used for encapsulation but also as ionotronic electrodes for electrocardiogram recording, thus eliminating the use of multiple sensors in PTT sensing. We also integrated the dual-mode sensor into a printed circuit board to achieve wireless signal transmission based on Bluetooth. Upon wearing it on the wrist, the electrocardiogram and arterial pulse can be simultaneously collected. Based on these two signals, the PTT was measured to predict blood pressure, and the predicted results agree well with those of the commercial sphygmomanometer.

McCumber theory describes the relationship between the absorption and emission cross-sections of ionic luminescence centers and is frequently used for determining absorption and emission cross-sections. However, the present application method of this theory seems complicated and exposes some faultiness. In this work, we proposed a simple and reliable procedure for determining the absorption and emission cross-sections based on McCumber theory with the assistance of Einstein's A/B coefficient relationship. The route we proposed was applied to confirm the absorption cross-sections of the transitions from ⁴I_15/2 to ²H_11/2, ⁴S_3/2, ⁴F_9/2, ⁴I_11/2, and ⁴I_13/2 of Er³⁺ in the NaY(WO₄)₂ compound. The absorption cross-sections determined from our proposed route were compared with those derived from a traditional approach, and it was found that the results derived from our route are reliable. Moreover, the corresponding parameters in the McCumber theoretical expression are referenced for other Er³⁺-doped luminescent materials.

The delicate nature of the half-metallic ferromagnetic (HMF) properties in Heusler alloys is often compromised by inherent structural disorder within the systems. Fe₂VSi is a prime example, where such disorder prevents the realization of the theoretically proposed HMF state as the anti-site disorder leads to the formation of two anti-parallel magnetic lattices resulting in antiferromagnetic order. In this study, we propose an innovative and simple strategy to prevent this atomic disorder by replacing 50% of the magnetic element Fe by a large, isoelectronic, non-magnetic element: Ru. In this way, one of the magnetic sublattices of the antiferromagnetic lattice ceases to order while the ferromagnetic order is restored – an essential criterion for exhibiting HMF properties. Through various experimental measurements and theoretical calculations, we have shown that such partial replacement of Fe by Ru prevents the cross-site substitution of V/Si sites and the system regains its ferromagnetic order. Our theoretical calculations suggest that a perfect structural arrangement in Fe and Ru would have restored the HMF properties in FeRuVSi. However, the local atomic disorder of Fe and Ru was found to decrease the spin polarization value. The present work sheds light on the complex interplay between structural disorder and magnetic properties in Heusler alloys and provides insights for future design strategies in the pursuit of robust half-metallic ferromagnets.

Conjugated polymer photocatalysts have been receiving extensive attention in the field of photocatalytic hydrogen evolution, owing to their tunable molecular structures and electronic properties. Herein, we report a hyperbranched conjugated polymer, containing thienothiophene and anthracene units (TT-Ant), synthesized via Pd(0) catalyzed Suzuki coupling. Its structural, photophysical and electrochemical features were investigated by using UV-vis and fluorescence spectroscopy, cyclic voltammetry (CV) and X-ray photoelectron spectroscopy (XPS). Photocatalytic hydrogen evolution tests, combining the material with two different additives, resulted in high hydrogen production rates from water. A steady state production rate of around 286 μmol g⁻¹ h⁻¹ for its hybridization with TiO₂ was recorded, which is more than 3 times that for pristine TiO₂ under the same conditions. Moreover, the combination of the polymeric material with platinum (1% wt) resulted in a maximum rate value of 700 μmol g⁻¹ h⁻¹. The surface properties of the latter combination before and after the reaction were studied by scanning electron microscopy (SEM) and transmission electron microscopy (TEM), which demonstrated successful Pt deposition on the surface of the polymer. This work may provide a new strategy to construct stable photocatalysts with thienothiophene and anthracene cores as active sites for efficient catalytic reactions in energy conversion applications.

Two donor–acceptor–donor (D–A–D) derivatives of benzothiadiazole (BTD) symmetrically functionalized with dihexylfluorene units serving as a linker between the BTD core and the thiophene (Th-FBTD) or bithiophene (2Th-FBTD) electron-donating groups were designed, synthesized and comprehensively characterized. Both compounds show high photoluminescence quantum yield (PLQY) both in solution and in the solid state. Th-FBTD demonstrates PLQY values of 82% and 96%, whereas 2Th-FBTD exhibits values of 74% and 97% in DCM and Zeonex, respectively. These compounds were employed as emissive dopants in multilayer solution-processed OLEDs, resulting in green electroluminescence with an emission peak at ca. 540 nm. The OLEDs display comparable performance, with a maximum external quantum efficiency of 3.5% for Th-FBTD and 2.8% for 2Th-FBTD. Both Th-FBTD and 2Th-FBTD undergo quasi-reversible electrochemical reduction and irreversible oxidation, giving stable electroactive polymer layers of bipolar character: p(Th-FBTD) and p(2Th-FBTD). The electrodeposited polymers undergo one-step reversible reduction and two-step reversible oxidation. Their electrochemical oxidation is accompanied by a reversible color change. Analysis of the optical density difference and coloration efficiency revealed improved electrochromic properties in both visible and near-infrared (NIR) ranges in p(2Th-FBTD) compared to that in p(Th-FBTD).

Winter sports have gained popularity in recent years. These sports and activities, however, come with some health concerns, particularly in harsh and extremely cold conditions. A self-heating, flexible, and smart conductive material that can monitor body health in extreme conditions would thus be highly desirable. Inspired by the structure of a spider-web, a flexible pressure sensor was developed by depositing a CNTs/CuS composite coating on a fabric surface with a cellulose-entangled structure constructed by hydroxypropyl methyl cellulose (HPMC). The obtained flexible pressure sensor demonstrated stable physiological signal detection and temperature insensitivity during photothermal heating, attributed to the water-retention capacity of HPMC. In addition, it exhibited excellent electrical conductivity (resistance of 10 Ω cm⁻¹), deicing (181s), sterilization (≈99.99%), UV resistance (UPF ≈ 13 926), environmental adaptability (−78 °C to 50 °C) and high sensitivity (13.25 ± 0.123 kPa⁻¹). This coating process can be applied to various garments, offering new possibilities for designing and preparing wearable multifunctional sensors.

The need for novel memory devices with low energy usage, strong reliability, and multi-level capacity is growing significantly nowadays. Among one of the promising candidates, hafnia (HfO₂)-based ferroelectric devices with a coercive field (E_c) designed for a multi-peak profile are known to provide stable multi-level capabilities in terms of suppressed device-to-device variations. In this study, a novel approach was demonstrated using a fixed charge method to realize a six-level ferroelectric cell. Using the Landau–Khalatnikov model, it is verified that the fixed charge in the ferroelectric device generated a bidirectional imprint field leading to separate E_c peaks. For experimental demonstration, tantalum oxide (TaO) and hafnium zirconium oxide (HZO) were employed as a fixed charge source and ferroelectric layer, respectively, to fabricate a HZO/TaO/HZO/TaO/HZO device. The imprint field created by positively charged oxygen vacancies at TaO/HZO interfaces shifted the switching properties of HZO layers, allowing the device to exhibit three distinct switching behaviors from the HZO layers. Therefore, the overall device showed a triple-peak E_c profile and corresponding six polarization states. Moreover, because of the preferential polarization switching within the shifted HZO layers, polarization states were well maintained over time. The findings of this work may provide a hint toward a scalable path for future memory solutions.

Magnetic dopants are commonly employed to modify the characteristics of dilute magnetic quantum dots (DMQDs), resulting in a significant alteration in their magnetic ground state. A thorough investigation of the structural changes induced by the dopants during DMQD growth is pivotal to comprehending the magnetic state of the system. In this regard, we employed the well-established organometallic route to manufacture CdSe QDs with trace amounts of Co and Fe, and we halted their growth process at two different stages. Subsequently, we utilized high-resolution transmission electron microscopy, X-ray diffraction, X-ray photoelectron spectroscopy, photoluminescence, and vibrating sample magnetometry to examine the interplay between each structure and its magnetic properties. Our analyses reveal that Co ions form a β-Co(OH)₂ shell on the surface of the CdSe QD, changing the diamagnetism of the pure CdSe matrix into soft-ferromagnetism of the DMQD at a low magnetic field, accompanied by a substantial enhancement in photoluminescence, amounting to approximately 250% in comparison to the pure CdSe QDs. In contrast, Fe ions form a FeSe structure in the core of the CdSe QD, leading to a room-temperature ferromagnetic DMQD. Both DMQDs are potential candidates for quantum information storage and processing, enabling the development of advanced quantum technologies.

Nonlinear optical (NLO) crystals are of importance in modern lasers, high-precision micromachining, ultrahigh resolution photolithography and advanced scientific equipment. Herein, we have rationally obtained two new lead oxybromides, A₃[Pb₂Br₅(OOC(CH₂)₃COO)] (A = Rb, Cs), with a strong second-harmonic generation (SHG) response and large birefringence. Two neighboring highly distorted [PbBr₄O₂] polyhedrons with high polarizability and anisotropic polarization are bridged by the flexible glutarate group and one Br⁻ anion to form a large [Pb₂Br₇(OOC(CH₂)₃COO)] group. Interestingly, the large [Pb₂Br₇(OOC(CH₂)₃COO)] groups are induced by Rb⁺/Cs⁺ cations into an oriented alignment, leading to the effective superimposition of their microscopic second-order susceptibility and the enhancement of optical anisotropy. Notably, Rb₃[Pb₂Br₅(OOC(CH₂)₃COO)] exhibits good comprehensive NLO performance, including a strong phase-matching SHG response of 3.1 × KDP, a large birefringence of 0.207@546 nm, a wide high transparency window, easy growth of large single crystals, as well as good thermal stability up to 240 °C under an air atmosphere. On the basis of their crystal structures and theoretical calculations, their strong SHG responses mainly stem from the highly distorted [PbBr₄O₂] polyhedron. This research provides an effective strategy for the design and pursuit of high-performance NLO crystals in the future.

Pt(II) metal complexes are known for having strong intermolecular Pt⋯Pt interaction in the condensed phases, to which the associated metal–metal-to-ligand charge transfer (MMLCT) transition characteristics allowed the effective generation of long-wavelength emission down to the red and near-infrared region. To expand the scope of the designs, we synthesized three homoleptic Pt(II) complexes Pt(a), Pt(b), and Pt(c) using chelating naphthyridinyl pyrazolates, which exhibited efficient emission peaks centered at 681, 690 and 723 nm as the vacuum deposited thin film. Upon fabrication of OLED devices, device Pt(b) achieved emission centered at 676 nm, maximum EQE of 25.6% with suppressed efficiency roll-off. Furthermore, device Pt(c) exhibited emission peaking at 710 nm and a slightly inferior but still remarkable max. EQE of 17.8%, paving a basis for further exploration of these self-aggregated Pt(II) metal phosphors and optimization of relevant NIR OLED devices.