Facile Synthesis of PtP2 Nanocrystals as Highly Active Electrocatalysts for Methanol Oxidation.

Although significant efforts have been made in the past few decades, the development of affordable, durable, and effective electrocatalysts for direct methanol fuel cells (DMFCs) remains a formidable challenge. Herein, we present a facile and efficient phosphorization approach for synthesizing PtP2 intermetallic nanocrystals and utilize them as electrocatalysts in the methanol oxidation reaction (MOR). Impressively, the synthesized PtP2 nanocatalysts exhibit a mass activity of 2.14 mA µg-1 and a specific activity of 6.28 mA cm-2, which are 5.1 and 9.5 times higher than those achieved by the current state-of-the-art commercial Pt/C catalyst, respectively. Moreover, the PtP2 nanocatalysts demonstrate improved stability toward acidic MOR by retaining 92.1% of its initial mass activity after undergoing 5000 potential cycles, far surpassing that of the commercial Pt/C (38%). Further DMFC tests present a 2.7 times higher power density than that of the commercial Pt/C, underscoring their potential for application in methanol fuel cells. Density functional theory calculations suggest that the accelerated MOR kinetics and improved CO tolerance on PtP2 can be attributed to the attenuated binding strength of CO intermediates and the enhanced stability due to strong Pt-P interaction. To our knowledge, this is the first report identifying the MOR performance on PtP2 intermetallic nanocrystals, highlighting their potential as highly active and stable nanocatalysts for DMFCs.

Synthesis of amorphous trimetallic PdCuNiP nanoparticles for enhanced OER.

Metal phosphides with multi-element components and amorphous structure represent a novel kind of electrocatalysts for promising activity and durability towards the oxygen evolution reaction (OER). In this work, a two-step strategy, including alloying and phosphating processes, is reported to synthesize trimetallic amorphous PdCuNiP phosphide nanoparticles for efficient OER under alkaline conditions. The synergistic effect between Pd, Cu, Ni, and P elements, as well as the amorphous structure of the obtained PdCuNiP phosphide nanoparticles, would boost the intrinsic catalytic activity of Pd nanoparticles towards a wide range of reactions. These obtained trimetallic amorphous PdCuNiP phosphide nanoparticles exhibit long-term stability, nearly a 20-fold increase in mass activity toward OER compared with the initial Pd nanoparticles, and 223 mV lower in overpotential at 10 mA cm-2. This work not only provides a reliable synthetic strategy for multi-metallic phosphide nanoparticles, but also expands the potential applications of this promising class of multi-metallic amorphous phosphides.

How likely is septic shock to develop in a patient with Fournier's gangrene? A risk prediction model based on a 7-year retrospective study.

Background: Fournier's gangrene (FG) is a rare life-threatening form of necrotizing fasciitis. The risk factors for septic shock in patients with FG are unclear. This study aimed to identify potential risk factors and develop a prediction model for septic shock in patients with FG. Methods: This retrospective cohort study included patients who were treated for FG between May 2013 and May 2020 at the Sixth Affiliated Hospital, Sun Yat-sen University (Guangzhou, China). The patients were divided into a septic shock group and a non-septic shock group. An L1-penalized logistic regression model was used to detect the main effect of important factors and a penalized Quadratic Discriminant Analysis method was used to identify possible interaction effects between different factors. The selected main factors and interactions were used to obtain a logistic regression model based on the Bayesian information criterion. Results: A total of 113 patients with FG were enrolled and allocated to the septic shock group (n = 24) or non-septic shock group (n = 89). The best model selected identified by backward logistic regression based on Bayesian information criterion selected temperature, platelets, total bilirubin (TBIL) level, and pneumatosis on pelvic computed tomography/magnetic resonance images as the main linear effect and Na+ × TBIL as the interaction effect. The area under the ROC curve of the probability of FG with septic shock by our model was 0.84 (95% confidence interval, 0.78-0.95). The Harrell's concordance index for the nomogram was 0.864 (95% confidence interval, 0.78-0.95). Conclusion: We have developed a prediction model for evaluation of the risk of septic shock in patients with FG that could assist clinicians in identifying critically ill patients with FG and prevent them from reaching a crisis state.

Stable and Bright Electroluminescent Devices utilizing Emissive 0D Perovskite Nanocrystals Incorporated in a 3D CsPbBr3 Matrix.

The 0D cesium lead halide perovskite Cs4 PbBr6 has drawn remarkable interest due to its highly efficient robust green emission compared to its 3D CsPbBr3 counterpart. However, seizing the advantages of the superior photoluminescence properties for practical light-emitting devices remains elusive. To date, Cs4 PbBr6 has been employed only as a higher-bandgap nonluminescent matrix to passivate or provide quantum/dielectric confinement to CsPbBr3 in light-emitting devices and to enhance its photo-/thermal/environmental stability. To resolve this disparity, a novel solvent engineering method to incorporate highly luminescent 0D Cs4 PbBr6 nanocrystals (perovskite nanocrystals (PNCs)) into a 3D CsPbBr3 film, forming the active emissive layer in single-layer perovskite light-emitting electrochemical cells (PeLECs) is designed. A dramatic increase of the maximum external quantum efficiency and luminance from 2.7% and 6050 cd m-2 for a 3D-only PeLEC to 8.3% and 11 200 cd m-2 for a 3D-0D PNC device with only 7% by weight of 0D PNCs is observed. The majority of this increase is driven by the efficient inherent emission of the 0D PNCs, while the concomitant morphology improvement also contributes to reduced leakage current, reduced hysteresis, and enhanced operational lifetime (half-life of 129 h), making this one of the best-performing LECs reported to date.

Deposition of Atomically Thin Pt Shells on Amorphous Palladium Phosphide Cores for Enhancing the Electrocatalytic Durability.

As an excellent electrocatalyst, platinum (Pt) is often deposited as a thin layer on a nanoscale substrate to achieve high utilization efficiency. However, the practical application of the as-designed catalysts has been substantially restricted by the poor durability arising from the leaching of cores. Herein, by employing amorphous palladium phosphide (a-Pd-P) as substrates, we develop a class of leaching-free, ultrastable core-shell Pt catalysts with well-controlled shell thicknesses and surface structures for fuel cell electrocatalysis. When a submonolayer of Pt is deposited on the 6 nm nanocubes, the resulting Pd@a-Pd-P@PtSML core-shell catalyst can deliver a mass activity as high as 4.08 A/mgPt and 1.37 A/mgPd+Pt toward the oxygen reduction reaction at 0.9 V vs the reversible hydrogen electrode and undergoes 50 000 potential cycles with only ∼9% activity loss and negligible structural deformation. As elucidated by the DFT calculations, the superior durability of the catalysts originates from the high corrosion resistance of the disordered a-Pd-P substrates and the strong interfacial Pt-P interactions between the Pt shell and amorphous Pd-P layer.

Gentle Materials Need Gentle Fabrication: Encapsulation of Perovskites by Gas-Phase Alumina Deposition.

Metal halide perovskites have attracted tremendous attention as promising materials for future-generation optoelectronic devices. Despite their outstanding optical and transport properties, the lack of environmental and operational stability remains a major practical challenge. One of the promising stabilization avenues is metal oxide encapsulation via atomic layer deposition (ALD); however, the unavoidable reaction of metal precursors with the perovskite surface in conventional ALD leads to degradation and restructuring of the perovskites' surfaces. This Perspective highlights the development of a modified gas-phase ALD technique for alumina encapsulation that not only prevents perovskites' degradation but also significantly improves their optical properties and air stability. The correlation between precise atomic interactions at the perovskite-metal oxide interface with the dramatically enhanced optical properties is supported by density functional theory calculations, which also underlines the widespread applicability of this gentle technique for a variety of perovskite nanostructures unbarring potential opportunities offered by combination of these approaches.

Interface Matters: Enhanced Photoluminescence and Long-Term Stability of Zero-Dimensional Cesium Lead Bromide Nanocrystals via Gas-Phase Aluminum Oxide Encapsulation.

Cesium lead halide perovskite nanocrystals (PNCs), while possessing facile chemical synthesis routes and high photoluminescence (PL) properties, are still challenged by issues of instability and degradation. Although atomic layer deposition (ALD) of metal oxides has been one of the common encapsulation approaches for longer term stability, its application inevitably resulted in severe loss of emission efficiency and at times partial loss of structural integrity of perovskites, creating a bottleneck in its practical viability. We demonstrate a nondestructive modified gas-phase technique with codeposition of both precursors trimethylaluminum and water to dramatically enhance the PL emission in zero-dimensional (0D) Cs4PbBr6 PNCs via alumina encapsulation. X-ray photoelectron spectroscopy analysis of Cs4PbBr6 films reveals the alumina deposition to be accompanied by elemental composition changes, particularly by the reduction of the excessive cesium content. Ab initio density functional theory simulations further unfold that the presence of excess Cs on the surface of PNCs leads to decomposition of structural [PbBr6]4- octahedra in the 0D perovskite lattice, which can be prevented in the presence of added hydroxyl groups. Our study thus unveils the pivotal role of the PNC surface composition and treatment in the process of its interaction with metal oxide precursors to control the PL properties as well as the stability of PNCs, providing an unprecedented way to use the conventional ALD technique for their successful integration into optoelectronic and photonic devices with improved properties.

Dynamical Interconversion between Excitons and Geminate Charge Pairs in Two-Dimensional Perovskite Layers Described by the Onsager-Braun Model.

Time-resolved photoluminescence (PL) and femtosecond transient absorption (TA) spectroscopy are employed to study the photoexcitation dynamics in a highly emissive two-dimensional perovskite compound (en)4Pb2Br9·3Br with the ethylene diammonium (en) spacer. We find that while the PL kinetics is substantially T-dependent over the whole range of studied temperatures T ∼ 77-350 K, the PL quantum yield remains remarkably nearly T-independent up to T ∼ 280-290 K, appreciably decreasing only at higher temperatures. Considerable differences are also revealed between the TA spectra and the responses to the excitation power at low and at room temperatures. Numerical solutions of Onsager-Braun-type kinetic-diffusion equations illustrate that the salient features of the experimental observations are consistent with the picture of a T-dependent dynamic interplay between tightly bound emissive excitons and larger-size, loosely bound, nonemissive geminate charge pairs arising already at earlier relaxation times. The geminate pairs play the role of "reservoir" states providing a delayed feeding into the emitting excitons, thus giving rise to the longer-time PL decay components and accounting for a stable PL output at lower temperatures. At higher temperatures, the propensity for thermal dissociation of excitons and bound pairs increases, leading subsequently to the precipitous decrease of the PL.

Mg Doped CuCrO2 as Efficient Hole Transport Layers for Organic and Perovskite Solar Cells.

The electrical and optical properties of the hole transport layer (HTL) are critical for organic and halide perovskite solar cell (OSC and PSC, respectively) performance. In this work, we studied the effect of Mg doping on CuCrO2 (CCO) nanoparticles and their performance as HTLs in OSCs and PSCs. CCO and Mg doped CCO (Mg:CCO) nanoparticles were hydrothermally synthesized. The nanoparticles were characterized by various experimental techniques to study the effect of Mg doping on structural, chemical, morphological, optical, and electronic properties of CCO. We found that Mg doping increases work function and decreases particle size. We demonstrate CCO and Mg:CCO as efficient HTLs in a variety of OSCs, including the first demonstration of a non-fullerene acceptor bulk heterojunction, and CH3NH3PbI3 PSCs. A small improvement of average short-circuit current density with Mg doping was found in all systems.

Miniature temperature sensor with germania-core optical fiber.

A miniature all-fiber temperature sensor is demonstrated by using a Michelson interferometer formed with a short length of Germania-core, silica-cladding optical fiber (Ge-fiber) fusion-spliced to a conventional single-mode fiber (SMF). Thanks to the large differential refractive index of the Ge-fiber sensing element, a reasonably small free spectral range (FSR) of 18.6 nm is achieved even with an as short as 0.9 mm Ge-fiber that may help us increase the measurement accuracy especially in point sensing applications and, at the same time, keep large measurement temperature range without overlapping reading problem. Experimental results show that high sensitivity of 89.0 pm/°C is achieved and the highest measurement temperature is up to 500°C.