Perovskite Nanocrystals In Situ Encapsulated in TiO2 Microspheres for Stable CO2 Photoreduction in Water.

Photoreduction of carbon dioxide (CO2) into fuels presents a promising approach to mitigate global warming and energy crises. Halide perovskite nanocrystals (NCs) with prominent optoelectronic properties have triggered substantial attention as photocatalysts but are limited by the charge recombination and instability. Here, we develop stable CsPbBr3/titania microspheres (TMs) by in situ growth of CsPbBr3 NCs inside mesoporous TMs through solid-state sintering, which significantly improves the stability of perovskite NCs, making them applicable in water with efficient CO2 photoreduction performance. Notably, the CsPbBr3/TMs demonstrates a 6.73- and 9.23-fold increase in the rate of CH4 production compared to TMs and CsPbBr3, respectively. The internal electric field facilitates S-scheme charge transfer, enhancing the separation of electron-hole pairs, as evidenced by X-ray photoelectron spectroscopy and electron paramagnetic resonance analysis, which is pivotal for the selective photoreduction of CO2. These insights pave the way for the design of CsPbBr3-based photocatalysts with superior efficiency and stability.

Ternary Rotational Polyanion Coupling Enables Fast Li Ion Dynamics in Tetrafluoroborate Ion Doped Antiperovskite Li2OHCl Solid Electrolyte.

Li-rich antiperovskite (LiRAP) hydroxyhalides are emerging as attractive solid electrolyte (SEs) for all-solid-state Li metal batteries (ASSLMBs) due to their low melting point, low cost, and ease of scaling-up. The incorporation of rotational polyanions can reduce the activation energy and thus improve the Li ion conductivity of SEs. Herein, we propose a ternary rotational polyanion coupling strategy to fasten the Li ion conduction in tetrafluoroborate (BF4-) ion doped LiRAP Li2OHCl. Assisted by first-principles calculation, powder X-ray diffraction, solid-state magnetic resonance and electrochemical impedance spectra, it is confirmed that Li ion transport in BF4- ion doped Li2OHCl is strongly associated with the rotational coupling among OH-, BF4- and Li2-O-H octahedrons, which enhances the Li ion conductivity for more than 1.8 times with the activation energy lowering 0.03 eV. This work provides a new perspective to design high-performance superionic conductors with multi-polyanions.

Damage-Free Silica Coating for Colloidal Nanocrystals Through a Proactively Water-Generating Amidation Reaction at High Temperature.

Silica is a promising shell coating material for colloidal nanoparticles due to its excellent chemical inertness and optical transparency. To encapsulate high-quality colloidal nanocrystals with silica shells, the silane coupling hydrolysis is currently the most effective approach. However, this reaction requires water, which often adversely affects the intrinsic physicochemical properties of nanocrystals. Achieving a damage-free silica encapsulation process to nanocrystals by hydrolysis is a huge challenge. Here, a novel strategy is developed to coat colloidal nanocrystals with a denser silica shell via a proactively water-generating reaction at high temperature. In this work, water molecules are continuously and proactively released into the reaction system through the amidation reaction, followed by in situ hydrolysis of silane, completely avoiding the impacts of water on nanocrystals during the silica coating process. In this work, water sensitive perovskite nanocrystals (CsPbBr3 ) are selected as the typical colloidal nanocrystals for silica coating. Notably, this high-temperature in situ encapsulation technology greatly improves the optical properties of nanocrystals, and the silica shells exhibit a denser structure, providing nanocrystals with better protection. This method overcomes the challenge of the influence of water on nanocrystals during the hydrolysis process, and provides an important reference for the non-destructive encapsulation of colloidal nanocrystals.

Removal of toxic metals using iron sulfide particles: A brief overview of modifications and mechanisms.

Growing mechanization has released higher concentrations of toxic metals in water and sediment, which is a critical concern for the environment and human health. Recent studies show that naturally occurring and synthetic iron sulfide particles are efficient at removing these hazardous pollutants. This review seeks to provide a concise summary of the evolution in the production of iron sulfide particles, specifically nanoparticles, through the years. This review presents an outline of the synthesis process for the most dominant forms of iron sulfide: mackinawite (FeS), pyrite (FeS2), pyrrhotite (Fe1-x S), and greigite (Fe3S4). The review confirms that both natural forms of iron sulfide and modified forms of iron sulfide are highly effective at removing different heavy metals and metalloids from water. Concurrently, this review reveals the interaction mechanism between toxic metals and iron sulfide, along with the impact of conditions for remedy and rectification. None the less, modifications and future investigations into the synthesis of novel iron sulfides, their use to adsorb diverse environmental pollutants, and their fate after injection into polluted aquifers, remain crucial to maximizing pollution control.

Interface defects repair of core/shell quantum dots through halide ion penetration.

The interface defects of core-shell colloidal quantum dots (QDs) affect their optoelectronic properties and charge transport characteristics. However, the limited available strategies pose challenges in the comprehensive control of these interface defects. Herein, we introduce a versatile strategy that effectively addresses both surface and interface defects in QDs through simple post-synthesis treatment. Through the combination of fine chemical etching methods and spectroscopic analysis, we have revealed that halogens can diffuse within the crystal structure at elevated temperatures, acting as "repairmen" to rectify oxidation and significantly reducing interface defects within the QDs. Under the guidance of this protocol, InP core/shell QDs were synthesized by a hydrofluoric acid-free method with a full width at half-maximum of 37.0 nm and an absolute quantum yield of 86%. To further underscore the generality of this strategy, we successfully applied it to CdSe core/shell QDs as well. These findings provide fundamental insights into interface defect engineering and contribute to the advancement of innovative solutions for semiconductor nanomaterials.

Fluorine Passivation Inhibits "Particle Talking" Behaviors under Thermal and Electrical Conditions of Pure Blue Mixed Halide Perovskite Nanocrystals.

Owing to outstanding optoelectronic properties, lead halide perovskite nanocrystals (PNCs) are considered promising emitters for next-generation displays. However, the development of pure blue (460-470 nm) perovskite nanocrystal light-emitting diodes (PNC-LEDs), which correspond to the requirements of Rec. 2020 standard, lag far behind that of their green and red counterparts. Here, pure blue CsPb(Br/Cl)3 nanocrystals with remarkable optical performance are demonstrated by a facile fluorine passivation strategy. Prominently, the fluorine passivation on halide vacancies and strong bonding of Pb-F intensely enhance crystal structure stability and inhibit "particle talking" behaviors under both thermal and electrical conditions. Fluorine-based PNCs with high resistance of luminescence thermal quenching retain 70% of photoluminescent intensity when heated to 343 K, which can be attributed to the elevated activation energy for carrier trapping and unchanged grain size. Fluorine-based PNC-LEDs also exhibit stable pure blue electroluminescence (EL) emission with sevenfold promoted luminance and external quantum efficiencies (EQEs), where the suppression of ion migration is further evidenced by a lateral structure device with applied polarizing potential.

A simple method for the synthesis of copper nanoparticles from metastable intermediates.

Copper nanoparticles have attracted a wide attention because of their low cost and high specific surface area. At present, the synthesis of copper nanoparticles has the problems of complicated process and environmentally unfriendly materials like hydrazine hydrate and sodium hypophosphite that would pollute water, harm human health and may even cause cancer. In this paper, a simple and low-cost two-step synthesis method was used to prepare highly stable and well-dispersed spherical copper nanoparticles in solution with a particle size of about 34 nm. The prepared spherical copper nanoparticles were kept in solution for one month without precipitation. Using non-toxic l-ascorbic acid as the reducing and secondary coating agent, polyvinylpyrrolidone (PVP) as the primary coating agent, and NaOH as the pH modulator, the metastable intermediate CuCl was prepared. Due to the characteristics of the metastable state, copper nanoparticles were rapidly prepared. Moreover, to improve the dispersibility and antioxidant, the PVP and l-ascorbic acid were used to coat the surface of copper nanoparticles. Finally, the mechanism of the two-step synthesis of copper nanoparticles was discussed. This mechanism mainly relies on the two-step dehydrogenation of l-ascorbic acid to obtain copper nanoparticles.

Inverted semitransparent perovskite nanocrystal light-emitting diodes with a conjugated polymer as an electron transport layer.

Perovskite nanocrystals have attracted much attention due to their unique optical and electronic properties. Much progress has also been made in the development of light-emitting diodes based on perovskite nanocrystals in the past years. However, compared with the widely reported opaque perovskite nanocrystal light-emitting diodes, semitransparent perovskite nanocrystal light-emitting diodes are rarely studied, which affects the potential application of perovskite nanocrystals in the translucent display field in the future. Here, poly[(9,9-bis(3'-(N,N-dimethylamino)propyl)-2,7-fluorene)-alt-2,7-(9,9-dioctylfluorene)] (PFN), a conjugated polymer, was used as an electron transport layer to fabricate the inverted opaque and semitransparent perovskite light-emitting diodes. The maximum external quantum efficiency and luminance were improved from 0.13% and 1041 cd m-2 to 2.07% and 12 540 cd m-2, respectively, through device optimization in opaque light-emitting diodes. The corresponding semitransparent device also demonstrated high transmittance (average 61% from 380 to 780 nm) and high brightness of 1619 and 1643 cd m-2 for the bottom and top sides, respectively.

Sequential exposures of single walled carbon nanotubes and heavy metal ions to macrophages induce different cytotoxicity.

The probability of occupational exposure rises with the increasing production and biomedical application of carbon nanotubes (CNTs). Thus, the risk of co-exposure of nanomaterials with environmental pollutants is also increasing. Although many studies have focused on the combined toxicity of nanomaterials and pollutants, more attention has been paid to the toxicity of nanomaterials after adsorbing pollutants or the toxicity of nanomaterials and pollutants exposed simultaneously. Few studies have been conducted on the toxicity and toxicity mechanisms of nanomaterials and environmental pollutants following sequential exposure. In this study, we employed THP-1 cells to investigate how pristine single walled CNTs (p-SWCNTs) and oxidized single walled CNTs (SWCNT-COOHs) pretreatments at a non-lethal dose of 10 µg/mL affect cell responses to metal ions (i. e., Pb2+, Cu2+, and Cr(VI)). We found that p-SWCNTs caused more significant damage to cell membrane integrity than SWCNT-COOHs, which led to higher metallothionein (MT) levels and increased transport of metal ions into cells. Pretreatment of p-SWCNTs in cells significantly increased the cytotoxicity of Pb2+, Cu2+, and Cr(VI) by 2-4-fold, whereas SWCNT-COOHs pretreated cells showed no noteworthy changes in response to heavy metals, which were further confirmed by the cellular reactive oxygen species (ROS) assays. These findings indicate that understanding the effects of the exposure sequence of engineered nanomaterials and environmental pollutants on their toxicity provides an excellent complement to combined toxicity evaluation.

A Novel Strategy to Enhance the Photostability of InP/ZnSe/ZnS Quantum Dots with Zr Doping.

Plentiful research of InP semiconductor quantum dots (QDs) has been launched over the past few decades for their excellent photoluminescence properties and environmentally friendly characteristics in various applications. However, InP QDs show inferior photostability because they are extremely sensitive to the ambient environment. In this study, we propose a novel method to enhance the photostability of InP/ZnSe/ZnS QDs by doping zirconium into the ZnS layer. We certify that Zr can be oxidized to Zr oxides, which can prevent the QDs from suffering oxidation during light irradiation. The InP/ZnSe/ZnS:Zr QDs maintained 78% of the original photoluminescence quantum yields without significant photodegradation under the irradiation of LED light (450 nm, 3.0 W power intensity) for 14 h, while conventional InP/ZnSe/ZnS QDs dramatically decreased to 29%.

Modulating Electron Conducting Properties at Lithium Anode Interfaces for Durable Lithium-Sulfur Batteries.

The lithium (Li) ion and electron diffusion behaviors across the actual solid electrolyte interphase (SEI) play a critical role in regulating the Li nucleation and growth and improving the performance of lithium-sulfur (Li-S) batteries. To date, a number of researchers have pursued an SEI with high Li-ion conductivity while ignoring the Li dendrite growth caused by electron tunneling in the SEI. Herein, an artificial anti-electron tunneling layer with enriched lithium fluoride (LiF) and sodium fluoride (NaF) nanocrystals is constructed using a facile solution-soaking method. As evidenced theoretically and experimentally, the LiF/NaF artificial SEI exhibits an outstanding electron-blocking capability that can reduce electron tunneling, resulting in dendrite-free and dense Li deposition beneath the SEI, even with an ultrahigh areal capacity. In addition, the artificial anti-electron tunneling layer exhibits improved ionic conductivity and mechanical strength, compared to those of routine SEI. The symmetric cells with protected Li electrodes achieve a stable cycling of 1500 h. The LiF/NaF artificial SEI endows the Li-S full cells with long-term cyclability under conditions of high sulfur loading, lean electrolyte, and limited Li excess. This study provides a perspective on the design of the SEI for highly safe and practical Li-S batteries.

Thermal Percolation of Antiperovskite Superionic Conductor into Porous MXene Scaffold for High-Capacity and Stable Lithium Metal Battery.

Lithium metal battery is considered an emerging energy storage technology due to its high theoretical capacity and low electrochemical potential. However, the practical exploitations of lithium metal batteries are not realized because of uncontrollable lithium deposition and severe dendrite formation. Herein, a thermal percolation strategy is developed to fabricate a dual-conductive framework using electronically conductive Ti3 C2 Tx MXene aerogels (MXAs) and Li2 OHCl antiperovskite superionic conductor. By melting Li2 OHCl at a low temperature, the molten antiperovskite phase can penetrate the MXA scaffold, resulting in percolative electron/ion pathways. Through density functional theory calculations and electrochemical characterizations, the hybridized lithiophilic (MXA)-lithiophobic (antiperovskite) interfaces can spatially guide the deposition of lithium metals and suppress the growth of lithium dendrites. The symmetric cell with MXA-antiperovskite electrodes exhibits superior cycling stability at high areal capacities of 4 mAh cm-2 over 1000 h. Moreover, the full cell with MXA-antiperovskite anode and high-loading LiFePO4 cathode demonstrates high energy and power densities (415.7 Wh kgcell -1 and 231.0 W kgcell -1 ) with ultralong lifespans. The thermal percolation of lithium superionic conductor into electronically conductive scaffolds promises an efficient strategy to fabricate dual-conductive electrodes, which benefits the development of dendrite-free lithium metal anodes with high energy/power densities.

Stable Lead-Free Tin Halide Perovskite with Operational Stability >1200 h by Suppressing Tin(II) Oxidation.

Sn-based perovskites are the most promising alternative materials for Pb-based perovskites to address the toxicity problem of lead. However, the development of SnII -based perovskites has been hindered by their extreme instability. Here, we synthesized efficient and stable lead-free Cs4 SnBr6 perovskite by using SnF2 as tin source instead of easily oxidized SnBr2 . The SnF2 configures a fluorine-rich environment, which can not only suppress the oxidation of Sn2+ in the synthesis, but also construct chemically stable Sn-F coordination to hinder the electron transfer from Sn2+ to oxygen within the long-term operation process. The SnF2 -derived Cs4 SnBr6 perovskite shows a high photoluminescence quantum yield of 62.8 %, and excellent stability against oxygen, moisture, and light radiation for 1200 h, representing one of the most stable lead-free perovskites. The results pave a new pathway to enhance the optical properties and stability of lead-free perovskite for high-performance light emitters.

Suppressing thermal quenching of lead halide perovskite nanocrystals by constructing a wide-bandgap surface layer for achieving thermally stable white light-emitting diodes.

Lead halide perovskite nanocrystals as promising ultrapure emitters are outstanding candidates for next-generation light-emitting diodes (LEDs) and display applications, but the thermal quenching behavior of light emission has severely hampered their real-world applications. Here, we report an anion passivation strategy to suppress the emission thermal quenching behavior of CsPbBr3 perovskite nanocrystals. By treating with specific anions (such as SO4 2-, OH-, and F- ions), the corresponding wide-bandgap passivation layers, PbSO4, Pb(OH)2, and PbF2, were obtained. They not only repair the surface defects of CsPbBr3 nanocrystals but also stabilize the phase structure of the inner CsPbBr3 core by constructing a core-shell like structure. The photoluminescence thermal resistance experiments show that the treated sample could preserve 79% of its original emission intensity up to 373 K, far superior to that (17%) of pristine CsPbBr3. Based on the thermally stable CsPbBr3 nanocrystals, we achieved temperature-stable white LED devices with a stable electroluminescence spectrum, color gamut and color coordinates in thermal stress tests (up to 373 K).

High-Efficiency Semitransparent Light-Emitting Diodes with Perovskite Nanocrystals.

Artificial intelligence offers new opportunities for translucent displays. However, achieving translucent light-emitting diodes (LEDs) with high efficiency and high color purity remains a challenge. Here, we propose a strategy of using an alkali metal/inert metal (calcium/silver) bilayer metal electrode as a top electrode and perovskite nanocrystals as an emitter layer in the device structure, which allows us to not only fabricate excellent opaque LEDs but also manufacture highly efficient semitransparent LEDs with high color purity, total brightness (over 7000 cd m-2), total external quantum efficiency (over 12%), and 56% transmittance around 520 nm. This is the highest external quantum efficiency report about semitransparent LED based on perovskite materials or inorganic quantum dots so far, which presents great application potential in the field of translucent display with high color purity and wide color gamut.

Simultaneous reduction and sequestration of hexavalent chromium by magnetic ß-Cyclodextrin stabilized Fe3S4.

In this study, ß-Cyclodextrin (CD) modified Fe3S4 nanomaterials were synthesized by a one-step facile strategy and investigated for the removal of Cr(VI). The resulted CD-Fe3S4 exhibited enhanced removal efficiency toward Cr(VI) than bared Fe3S4 with a maximum capacity of 220.26 mg·g-1 as the molar ratio of CD-to-Fe3S4 at 0.2. The effective performance of CD-Fe3S4 toward Cr(VI) could well maintain under oxic conditions and a wide pH range of aqueous solution. A high selectivity for Cr(VI) was achieved in the presence of coexisting cations and anions. More significantly, a single treatment step of CD-Fe3S4 effectively removed chromium from actual electroplating wastewater to the detection limit of 0.004 mg·L-1 that far below the WHO limitation of Cr (VI) (<0.05 mg·L-1) combing with the rapid magnetic separation without adjusting the pH value of wastewater at 7. The effective removal of Cr (VI) by CD-Fe3S4 involved a complex process of surface adsorption/reduction, and solution homogenous reduction and subsequent sequestration of Cr(III) achieving the effective removal of aqueous total Cr. The superior Cr (VI) removal capability and facial separation of CD-Fe3S4 attained its prominent potential application as an effective material for the Cr(VI) removal.

Magnetic Adsorbents for Wastewater Treatment: Advancements in Their Synthesis Methods.

The remediation of water streams, polluted by various substances, is important for realizing a sustainable future. Magnetic adsorbents are promising materials for wastewater treatment. Although numerous techniques have been developed for the preparation of magnetic adsorbents, with effective adsorption performance, reviews that focus on the synthesis methods of magnetic adsorbents for wastewater treatment and their material structures have not been reported. In this review, advancements in the synthesis methods of magnetic adsorbents for the removal of substances from water streams has been comprehensively summarized and discussed. Generally, the synthesis methods are categorized into five groups, as follows: direct use of magnetic particles as adsorbents, attachment of pre-prepared adsorbents and pre-prepared magnetic particles, synthesis of magnetic particles on pre-prepared adsorbents, synthesis of adsorbents on preprepared magnetic particles, and co-synthesis of adsorbents and magnetic particles. The main improvements in the advanced methods involved making the conventional synthesis a less energy intensive, more efficient, and simpler process, while maintaining or increasing the adsorption performance. The key challenges, such as the enhancement of the adsorption performance of materials and the design of sophisticated material structures, are discussed as well.

An overview of generic tools for information-theoretic secrecy performance analysis over wiretap fading channels.

Physical layer security (PLS) has been proposed to afford an extra layer of security on top of the conventional cryptographic techniques. Unlike the conventional complexity-based cryptographic techniques at the upper layers, physical layer security exploits the characteristics of wireless channels, e.g., fading, noise, interference, etc., to enhance wireless security. It is proved that secure transmission can benefit from fading channels. Accordingly, numerous researchers have explored what fading can offer for physical layer security, especially the investigation of physical layer security over wiretap fading channels. Therefore, this paper aims at reviewing the existing and ongoing research works on this topic. More specifically, we present a classification of research works in terms of the four categories of fading models: (i) small-scale, (ii) large-scale, (iii) composite, and (iv) cascaded. To elaborate these fading models with a generic and flexible tool, three promising candidates, including the mixture gamma (MG), mixture of Gaussian (MoG), and Fox's H-function distributions, are comprehensively examined and compared. Their advantages and limitations are further demonstrated via security performance metrics, which are designed as vivid indicators to measure how perfect secrecy is ensured. Two clusters of secrecy metrics, namely (i) secrecy outage probability (SOP), and the lower bound of SOP; and (ii) the probability of nonzero secrecy capacity (PNZ), the intercept probability, average secrecy capacity (ASC), and ergodic secrecy capacity, are displayed and, respectively, deployed in passive and active eavesdropping scenarios. Apart from those, revisiting the secrecy enhancement techniques based on Wyner's wiretap model, the on-off transmission scheme, jamming approach, antenna selection, and security region are discussed.

Li-Rich Antiperovskite/Nitrile Butadiene Rubber Composite Electrolyte for Sheet-Type Solid-State Lithium Metal Battery.

Lithium-rich antiperovskites (LiRAPs) hold great promise to be the choice of solid-state electrolytes (SSEs) owing to their high ionic conductivity, low activation energy, and low cost. However, processing sheet-type solid-state Li metal batteries (SSLiB) with LiRAPs remains challenging due to the lack of robust techniques for battery processing. Herein, we propose a scalable slurry-based procedure to prepare a flexible composite electrolyte (CPE), in which LiRAP (e.g., Li2OHCl0.5Br0.5, LOCB) and nitrile butadiene rubber (NBR) serve as an active filler and as a polymer scaffold, respectively. The low-polar solvent helps to stabilize the LiRAP phase during slurry processing. It is found that the addition of LOCB into the NBR polymer enhances the Li ion conductivity for 2.3 times at 60°C and reduces the activation energy (max. 0.07 eV). The as-prepared LOCB/NBR CPE film exhibits an improved critical current of 0.4 mA cm-2 and can stably cycle for over 1000 h at 0.04 mA cm-2 under 60°C. In the SSLiB with the sheet-type configuration of LiFePO4(LFP)||LOCB/NBR CPE||Li, LFP exhibits a capacity of 137 mAh/g under 60 at 0.1°C. This work delivers an effective strategy for fabrication of LiRAP-based CPE film, advancing the LiRAP-family SSEs toward practical applications.

Configuring solid-state batteries to power electric vehicles: a deliberation on technology, chemistry and energy.

Solid-state batteries (SSBs) have been widely regarded as a promising electrochemical energy storage technology to power electric vehicles (EVs) that raise battery safety and energy/power densities as kernel metrics to achieve high-safety, long-range and fast-charge operations. Governments around the world have set ambitious yet imperative goals on battery energy density; however, sluggish charge transport and challenging processing routes of SSBs raise doubts of whether they have the possibility to meet such targets. In this contribution, the battery development roadmap of China is set as the guideline to direct how material chemistries and processing parameters of SSBs need to be optimized to fulfill the requirements of battery energy density. Starting with the identification of bipolar cell configurations in SSBs, the blade cell dimension is then selected as an emerging cell format to clarify weight breakdown of a solid NCM523||Li cell. Quantifying energy densities of SSBs by varying key cell parameters reveals the importance of active material content, cathode layer thickness and solid-electrolyte-separator thickness, whereas the thicknesses of the lithium metal anode and bipolar current collector have mild impacts. Even in the pushing conditions (200 µm for the cathode layer and 20 µm for the solid electrolyte separator), high-nickel ternary (NCM) cathodes hardly meet the expectation of the battery development roadmap in terms of gravimetric energy density at a cell level, while lithium- and manganese-rich ternary (LM-NCM) and sulfur cathodes are feasible. In particular, solid lithium-sulfur batteries, which exhibit exciting gravimetric energy density yet inferior volumetric energy density, need to be well-positioned to adapt diverse application scenarios. This analysis unambiguously defines promising battery chemistries and establishes how key parameters of SSBs can be tailored to cooperatively follow the stringent targets of future battery development.