Anion Exchange Process Research Articles

Removal of Per- and Polyfluoroalkyl Substances (PFAS) in fixed bed anion exchange reactors: Factors determining PFAS uptake capacity and models predicting PFAS breakthrough

Per- and polyfluoroalkyl substances (PFAS) are widespread contaminants with adverse environmental and public health effects. Anion exchange (IX) processes can effectively remove many PFAS from water. Objectives of this research were to (1) quantify the effects of PFAS structure and background water matrix constituents [dissolved organic matter (DOM) and major inorganic anions (bicarbonate, chloride, sulfate, and nitrate)] on PFAS uptake capacity of IX resins (KIX), and (2) develop models that predict PFAS breakthrough in packed bed IX columns from PFAS structure and background water matrix characteristics. Rapid small-scale column tests were conducted with two IX resins and 18 water matrices to determine breakthrough curves and KIX values for 23 PFAS. A quantitative structure-property relationship (QSPR) was developed that predicts KIX for different PFAS from a newly developed concept, the normalized chain length (NCL). NCL for each PFAS was calculated using a group contribution method, in which the contributions of PFAS structural fragments to NCL were normalized to that of -CF2-, which was assigned a value of 1.00. Relative to -CF2-, contributions of the structural fragments -O-, -CH2-, >CF-CF3, -CHF-, and -SO3H to NCL for the purposes of KIX prediction were 0.34, -1.87, 1.70, 0.00, and 3.65, respectively. DOM and nitrate adversely impacted PFAS removal, while chloride, sulfate, and bicarbonate, when added at concentrations of up to 3 meq/L above native background levels, had negligible effects on KIX. Based on the obtained water matrix effects, pseudo-single solute models were developed for the two tested IX resins, with which PFAS breakthrough curves for fixed bed IX columns can be predicted using only the NCL and the total organic carbon and nitrate concentrations of the influent water.

Heavy Metal-Based Toxic Oxo-Pollutants Sequestration by Advanced Functional Porous Materials for Safe Drinking Water.

ConspectusWater scarcity as a consequence of either environmental or economic actions is the most compelling global concern of the 21st century, as ∼2 billion people (26% of the total population) struggle to access safe drinking water and ∼3.6 billion (46% of the total population) lack access to clean water sanitation. In this context, groundwater pollution by toxic heavy metals and/or their oxo-pollutants, such as CrO42-, Cr2O72-, AsO43-, SeO32-, SeO42-, TcO4-, UO22+, etc., have been becoming rapidly growing global concerns. The severe toxicity upon bioaccumulation of these oxo-anions has prompted the US Environment Protection Agency (EPA) to mark these persistent and hazardous substances as priority pollutants. Additionally, the heavy-metal-based pollutants are difficult to transform into eco-friendly substances, thus presenting serious challenges toward human health and environmental preservation. To this end, the emergence of advanced functional porous materials (AFPMs), including metal-organic frameworks (MOFs), covalent organic frameworks (COFs), metal-organic polyhedrons (MOPs), porous organic polymers (POPs), etc., have presented extraordinary opportunities in material research and water treatment applications. The liberty in designing and structural tunability of AFPMs, facilitated by utilization of structure-encoded molecular building blocks, enables precise control over target-specificity and structure-property correlations. Bridging the gap between strategic material design and on-demand real-world application can facilitate the development of next-generation sorbents/ion-exchangers for efficient water treatment.In this Account, we summarize the recent advancements from our group toward the development of cutting-edge multifunctional ionic-porous sorbents, offering viable solutions toward providing clean and safe drinking water. Our vision allows us to comprehend this challenge through two strategic factors: efficient oxo-anion capture via ion-exchange and specific host-guest interactions via installation of modular functional groups. To provide an overview, we first highlight the different structural variants and coexistance of various toxic oxo-anions depending on the pH of the medium and their adverse effects. Next, we highlight the promising potential of water stable cationic MOFs toward selective remediation of toxic Cr(VI), Mn(VII), Tc(VI), Se(IV), Se(VI), U (VI), As(III), and As(V)-based toxic oxo-pollutants from water. In the subsequent sections, we summarize the target-specific design strategies and oxo-anion remediation performances of ionic porous organic polymers and hybrid functional porous materials. The key role of target-specific designability and/or structural fine-tuning of AFPMs toward preferential sorption of oxo-pollutants is systematically demonstrate. Particularly, the role of ion-exchange (anion-exchange) processes toward targeted oxo-pollutant capture by ionic AFPMs has been discussed in details. In several examples, the AFPMs were successful in reducing the toxic oxo-anion concentration levels lower than the permitted values for drinking water by the World Health Organizing Committee (WHO), showcasing their real-world applicability potency.Our contemporaneous endeavors in exploring ionic AFPMs for selective toxic oxo-anion sequestration may serve as a blueprint to researchers for future development of the next generation sorbent materials for energy-economically feasible water treatment methods.

Development of Bifunctional Electrocatalyst for Overall Water Electrolysis: Vanadium and Phosphorus Dual-Doping Strategy on Ni3S2 Nanoneedle

Along with the rapid consumption of fossil fuels and serious environmental pollution, the development of renewable and clean energy has been receiving a lot of attention recently. Among the various renewable energy sources, hydrogen (H2) is considered as most promising substance in future energy society owing to its high gravimetric energy density and environmental friendliness. Electrochemical water electrolysis system is powerful strategy for high-purity hydrogen production without emission of any pollutants. It consists of two electrocatalytic reactions: oxygen evolution reaction (OER) and hydrogen evolution reaction (HER). However, the practical efficiency of water electrolysis is limited due to the intrinsically sluggish reaction kinetics of OER and HER. To date, the precious metal-based electrocatalysts such as RuO2 and Pt/C for OER and HER, respectively, were employed as state-of-the-art electrocatalyst to enhance the performance of water electrolysis. However, due to the high expense, mono-functionality, and unsatisfactory stability of the precious metal-based materials, research on bifunctional electrocatalysts with low cost and high activity has become an urgent topic. To date, numerous scientific endeavors have been dedicated to the advancement of highly efficient non-noble metal-based bifunctional electrocatalysts such as transition metal oxides, hydroxides, sulfides, carbides, nitrides, and phosphides. Among these, Ni3S2 has emerged as a particularly promising electrocatalyst for water splitting, garnering substantial attention owing to its high electric conductivity, rich redox property, abundance in the Earth's crust, and environmentally friendly characteristics. Nevertheless, the electrocatalytic activity of Ni3S2 lags behind that of noble metal counterparts. Therefore, elaborate modification of Ni3S2 catalyst should be conducted to further improve its intrinsic activity toward OER and HER. Among the various strategies, heteroatom doping into Ni3S2 structure could be adopted as powerful technique for enhancement of electrocatalytic performance. The homogeneously incorporated dopants not only generate lattice disorders but elaborately modulate the surface electronic property. Specifically, high-valent cation dopants such as vanadium and molybdenum can effectively mediate the change of chemical states of Ni active sites during the step-wise electrocatalytic procedure. Meanwhile, additionally introduced anion dopants, which have lower electronegativity compared with sulfur, can reduce the electron trapping phenomenon induced by excessive electron transfer from nickel to sulfur. Inspired by above features, we synthesized V and P co-doped Ni3S2 nanoneedles directly grown on nickel foam (V-Ni3S2-P/NF) through facile two-step preparation method. First, V doped Ni3S2 nanoneedles were homogeneously grown on NF (V-Ni3S2/NF) by hydrothermal process without use of nickel precursor. The vanadium ions promote the nucleation of Ni3S2 species and lead the preferential growth toward 1D direction during the hydrothermal reaction. After that, the V-Ni3S2/NF was annealed in the tube furnace with the NaH2PO2 as a phosphorus precursor under the Ar flow. Under the mild annealing condition, the PH3 gases generated from thermal decomposition of NaH2PO2 reacted with the V-Ni3S2 species. Consequently, the V-Ni3S2 was partially phosphidated into V-Ni3S2-P throughout anion exchange process. As a result, the V-Ni3S2-P/NF electrocatalyst exhibited excellent bifunctional activity toward both OER and HER compared with mono-doped and un-doped counterparts and precious metal-based electrocatalysts. Furthermore, the outstanding electrocatalytic performance of V-Ni3S2-P/NF was well-maintained over the 100 h of continuous operation under alkaline condition. This study will contribute to the development of efficient and cost-effective electrocatalysts for future energy conversion and storage technologies.

Hydrochemical characterization and health risk assessment of different types of water bodies in Fenghuang Mountain Area, Northeast China.

Groundwater, as an essential resource, holds significant importance for human production and livelihoods. With the deterioration of the water environment, the issue of groundwater quality has become an urgent international concern. This study focused on the Fenghuang Mountain Area (FMA) and collected a total of 41 sets of samples including pore groundwater (PGW), fissure groundwater (FGW), karst groundwater(KGW), and river water(RW). Hydrochemical analysis methods were employed to identify the hydrochemical characteristics and controlling factors. The entropy-weighted water quality index (EWQI) and health risk assessment model were utilized to assess the groundwater quality and nitrate health risk, respectively. The results indicated that the dominant anion and cation in both groundwater and surface water in the FMA were HCO3- and Ca2+, respectively, with the main hydrochemical type being HCO3-Ca. Groundwater and surface water in the FMA were primarily controlled by rock weathering process, with ion concentrations influenced mainly by the dissolution of halite, sylvite, carbonates (calcite and dolomite), silicates, and gypsum, as well as by reverse anion exchange process. PGW was significantly affected by agricultural activities, with NO3- concentration closely related to human activities. The water quality of FGW was relatively good, with Class I and Class II water accounting for the highest proportion, reaching 84.62%. The high-value area of EWQI in PGW was influenced by human activities. The impact of nitrate health risk on children was significantly greater than on adults, with FGW having the lowest health risk and PGW having the highest health risk. The research results can provide important guarantees for the rational development and utilization of water resources in the FMA and the sustainable development of the economy in Northeast China.

Precise Control Light Emission of PVDF-CH3NH3PbBr3-xClx Nanocrystalline Films Using a Cl-(CH3OH)n System.

Methylammonium lead halide perovskites with highly efficient pure-color or white-light generation have gained increasing scientific interest and promote the development of a great commercial opportunity in displays, lighting, and other applications. However, the poor stabilities, lead toxicity, and unfriendly solvents and ligands in the growth process severely restrict their commercial application. Here, we proposed a green method for preparing uniform and stable polymer-encapsulated photoluminescence (PL) tunable CH3NH3PbBr3-xClx NC thin films at room temperature. Utilizing the swelling effect between alcohol compounds and organic polymers and the ionization of NaCl in methanol solution, the anion exchange process can be achieved rapidly within 7 min. Moreover, the PL wavelengths of the CH3NH3PbBr3-xClx NCs films were precisely tuned with steps as fine as 2 nm. Experimental results showed that NaCl dissolved in methanol solution can form Cl-(CH3OH)n, which brings ionized Cl into the polymer-encapsulated CH3NH3PbBr3 NCs film for CH3NH3PbBr3-xClx NCs film growth. Based on the swelling and anion exchange dynamics, a modified NaCl-CH3OH-MABr solution system was developed to trigger CH3NH3PbBr3-xClx NCs film PL emission tuning from 528 to 463 nm with several-fold intensity enhancement. The realization of precisely controlled photoluminescence from the perovskite nanocrystal film would have wide applications in the optical and imaging fields.

Perovskite Quantum Heterostructure Constructed by Halide Mixing between a Single CsPbI3 Nanocrystal and an Individual CsPbBr3 Microplate.

Ion migration is significantly enhanced in lead-halide perovskites with a soft crystal lattice, which can promote the formation of a heterogeneous interface between two such materials with different halide-anion compositions. Here we have deposited a single CsPbI3 nanocrystal (NC) on top of an individual CsPbBr3 microplate to create a mixed-halide CsPbBrxI3-x (0 < x < 3) NC by means of the anion exchange process. The formation of a CsPbBrxI3-x/CsPbBr3 heterostructure is confirmed by the much-enlarged geometric volume of the CsPbBrxI3-x NC as compared to the original CsPbI3 one, as well as by its capability of receiving photogenerated excitons from the CsPbBr3 microplate with a larger bandgap energy. The quantum nature of this heterostructure is reflected from single-photon emission of the composing CsPbBrxI3-x NC, which can also be bulk-like during phase segregation to demonstrate a red shift in the photoluminescence peak that is opposite to the common trend observed in smaller-sized mixed-halide NCs.

Emerging Mo-doped MgAl-LDH lamellar/carbon nanotubes as 3D sustainable nanohybrid for designing a durable smart anti-corrosion composite

This paper focused on the utilization of 3D hybrid nanocomposites composed of layered double hydroxides (L) containing sodium molybdate (SM), which are chemically bonded with functionalized multi-walled carbon nanotubes (FCN), as nanocarriers for smart corrosion prevention. The SM molecules were loaded into the L, and L/FCN nanocarriers by an anion exchange process, and then the 3 synthesized nanoparticles (L, SM-L, and SM-L/FCN) were characterized. Based on the electrochemical impedance spectroscopy (EIS) and potentiodynamic polarization (PD) tests' outcomes, the maximum corrosion prevention efficiency (about 90.88 %) belongs to the SM-L/FCN nano reservoir containing saline extract. Additionally, for the epoxy phase, the EIS results (on the intact and scratched specimens) revealed a significant diminish in the chloride and water penetration into the epoxy coating during 63 days of immersion for intact and 24 h for scratched states. EIS results indicated the enhancement of the charge transfer resistance (Rct) of the scratched coatings, from 17.42 kΩ.cm2 for the EP sample to 72.47 kΩ.cm2 for the SM-L/FCN/EP one in long immersion times, revealing the self-repairing behavior of the designed coating. The results of intact coating revealed that the Log (|Z|0.01 Hz) value reached 10.63 in long immersion time indicating a decreased occurrence of coating disbondment attributed to the electrolyte infiltration and corrosion of the underlying metal substratum. According to the pull-off and cathodic disbonding tests results, there was an enhancement in adhesion (51.5 % decrease in loss of adhesion strength, & a 52 % decline in diameter of cathodic disbondment), and a strong interaction between the interface of epoxy and substratum. According to the mechanical tests (tensile and DMTA) results the incorporation of L and FCN nanoparticles into the SM-L/FCN sample enhanced the nanocomposite's mechanical properties. The tensile test showed an increase in ultimate tensile strength (σUTS) and elongation at break (Ɛb) of 130.61 % and 107.59 %, respectively, compared to the pure epoxy (EP) sample. Additionally, the dynamic mechanical thermal analysis (DMTA) test indicated a 144 % increase in crosslinking density for the SM L/FCN sample compared to the neat epoxy.

Highly Efficient and Selective Extraction of Gold from Thiosulfate Leaching Solution Using Functionalized Dicationic Ionic Liquids.

Thiosulfate leaching has been regarded as a promising alternative to cyanidation, but it still faces the challenge of the recovery of low content of gold from high concentrations of thiosulfate solutions. Liquid-liquid extraction is a method to address this issue but is still limited by the use of volatile and toxic organic solvents. To overcome this limitation, this work synthesized some functionalized dicationic ionic liquids (DILs) to serve as extraction solvents for the recovery of the gold-thiosulfate complex, [Au(S2O3)2]3-, from thiosulfate solutions. Experimental results indicated that the DILs showed higher extraction rates toward [Au(S2O3)2]3- compared with their monocationic-based counterparts, likely due to the stronger electrostatic interaction between the dications of the ILs and [Au(S2O3)2]3-. The transfer of [Au(S2O3)2]3- from the water phase to the IL phase was identified as an anion exchange and endothermic process. The rate of extraction was limited by the anion exchange process occurring at the IL-water interface. The extraction ability of ILs highly depended on the type of anion; specifically, the ILs with anions that had strong hydrogen-bonding ability exhibited high extraction ability toward [Au(S2O3)2]3-. Finally, DILs proved effective in the recovery of [Au(S2O3)2]3- from an actual gold leaching solution and exhibited high selectivity toward coexisting ions, indicating their potential as environmentally friendly solvents for gold recovery.

Nanoconfinement regulation of La-Mg LDH/Ti3C2TX (T = O, OH) for effective removal of fluoride: Membrane fabrication and mechanism revelation

The present study utilized a nanoconfinement-regulated La-Mg LDH/Ti3C2TX (T = O, OH) adsorbent to achieve efficient fluoride removal. The modified adsorbent effectively increased the surface area and active sites of the material through controlled intercalation of La-Mg LDH into the Ti3C2TX gaps. The La-Mg LDH/Ti3C2TX composite was found to exhibit superior suitability for pseudo-second-order kinetics and conformed well to the Langmuir model. Under initial conditions of a fluoride ion concentration of 200 mg/L, pH 7, and a temperature of 298 K, the adsorption capacity was determined to be 139.860 mg/g. The adsorption of fluoride was primarily governed by electrostatic interactions and anion exchange processes. The La-Mg LDH/Ti3C2TX adsorbent with nanoconfinement regulation had the best adsorption effect on fluoride ions, and fluoride ions were more inclined to be adsorbed at the interface of La-Mg LDH/Ti3C2TX. Furthermore, facile fabrication of La-Mg LDH/Ti3C2TX membrane was achievable. Membrane filtration experiments demonstrated that the defluorination efficiency was significantly influenced by the thickness of membrane, water velocity, and solution pH. The membrane processing capacity was 11526 L/m3 when the membrane thickness was 9 mm and the flow rate was 10 mL/min. The present study offers novel insights into the development of defluorinated materials.

Hot-Injection Synthesis of Cesium Lead Halide Perovskite Nanowires with Tunable Optical Properties.

Metal halide perovskite semiconductors have emerged as promising materials for various optoelectronic applications due to their unique crystal structure and outstanding properties. Among different forms, perovskite nanowires (NWs) offer distinct advantages, including a high aspect ratio, superior crystallinity, excellent light absorption, and carrier transport properties, as well as unique anisotropic luminescence properties. Understanding the formation mechanism and structure-property relationship of perovskite NWs is crucial for exploring their potential in optoelectronic devices. In this study, we successfully synthesized all-inorganic halide perovskite NWs with high aspect ratios and an orthorhombic crystal phase using the hot-injection method with controlled reaction conditions and surface ligands. These NWs exhibit excellent optical and electrical properties. Moreover, precise control over the halogen composition through a simple anion exchange process enables the tuning of the bandgap, leading to fluorescence emission, covering a wide range of colors across the visible spectrum. Consequently, these perovskite NWs hold great potential for efficient energy conversion and catalytic applications in photoelectrocatalysis.

Hydroxide Ion Conduction through Viologen-Based Covalent Organic Frameworks (vCOFs): An Approach toward the Advancement.

Alkaline fuel cells rely on the movement of hydroxide anions (OH-) for their operation, yet these anions face challenges in efficient conduction due to their limited diffusion coefficient and substantial mass compared to proton (H+) transport. Within the covalent organic framework structure, ordered channels offer a promising solution for the OH- ion transport. Herein, we synthesized a cationic covalent organic framework (vTAPA) via the solvothermal-assisted Zincke reaction. vTAPA showcases excellent stability in harsh basic solution (12 M) and a wide range of pH. This framework facilitates OH- conduction through its one-dimensional network through the anion exchange process. We employed various tertiary ammonium salts (tetramethyl, tetraethyl, and tetrabutyl ammonium hydroxide) to exchange trapped anionic chloride ions inside the vTAPA structure with OH- ions. The density functional theory (DFT) study exhibited that the anion exchange process is very favorable, as the vTAPA framework offers preferable interaction sites for OH- ions. The impact of steric hindrance from these tertiary ammonium salts on the OH- conduction performance was extensively investigated. Butyl@vTAPA exhibited a high OH- ion conductivity of 1.05 × 10-4 S cm-1 at 90 °C under 98% relative humidity (RH). Our uniquely designed cationic covalent organic frameworks (COF) created a platform for a preferential transport network of hydroxide ions, and this is the first report of directly used COFs for hydroxide ion conduction without any vigorous postsynthetic modification.

Spatially Resolved Anion Diffusion and Tunable Waveguides in Bismuth Halide Perovskites.

Bismuth halide perovskites are widely regarded as nontoxic alternatives to lead halide perovskites for optoelectronics and solar energy harvesting applications. With a tailorable composition and intriguing optical properties, bismuth halide perovskites are also promising candidates for tunable photonic devices. However, robust control of the anion composition in bismuth halide perovskites remains elusive. Here, we established chemical vapor deposition and anion exchange protocols to synthesize bismuth halide perovskite nanoflakes with controlled dimensions and variable compositions. In particular, we demonstrated the gradient bromide distribution by controlling the anion exchange and diffusion processes, which is spatially resolved by time-of-flight secondary ion mass spectrometry. Moreover, the optical waveguiding properties of bismuth halide perovskites can be modulated by flake thicknesses and anion compositions. With a unique gradient anion distribution and controllable optical properties, bismuth halide perovskites provide new possibilities for applications in optoelectronic devices and integrated photonics.

Reticular access to triptycene-based cationic metal–organic frameworks for protein-bound uremic toxins sorption

P-cresyl sulfate (pCS) and indoxyl sulfate (IS), a class of protein-bound uremic toxins, cannot be effectively cleared through hemodialysis treatment due to their strong binding to human serum albumin, posing a potential risk of cardiovascular disease in patients with chronic renal failure. Herein, we designed and prepared novel cationic metal–organic frameworks (MOFs), denoted as ZJU-X18, for the efficient removal of pCS and IS. A triptycene-based rigid trigonal prismatic ligand was utilized to link with Ag+ to yield a rare 4-fold interpenetrated MOF with abundant hydrophobic channels, affording high sorption capacity, excellent selectivity, and decent recyclability toward uremic toxins. Furthermore, the anion-exchange process between ZJU-X18 and uremic toxins is verified through density functional theory (DFT) calculations. This study provides a proactive example of the rational design of cationic MOFs from the perspective of reticular chemistry and demonstrates their promising application in uremia treatment.

Bismuthene@ZnAlBi LDHs structure as a novel nanosorbent for efficient uptake of arsenic (V)

Two-dimensional bismuthene material is characterized with promising and superior optical, electrical and other characteristics. The application of 2D-bismuthene or its composites in water remediation of As(V) was not previously investigated. Consequently, embedded bismuthene into zinc aluminum bismuth-layered double hydroxide (ZnAlBi LDHs-embedded-Biene) was simply fabricated as a novel nanosorbent. Bismuthene (Biene) was prepared by bottom up hydrothermal reaction, while ZnAlBi LDHs was synthesized by a coprecipitation method followed by hydrothermal treatment process. Characterization of ZnAlBi LDHs-embedded-Biene referred to a crystalline mesoporous structure of globular particles with 5–8 nm. It was confirmed that the nanosorbent exterior surface is functionalized with metal oxides and metal oxyhydroxide, while exchangeable carbonate anion existed in the nanosorbent inner layer. Therefore, arsenate uptake was favored by both exterior electrostatic attraction and anion exchange processes. The highest uptake capacity of As(V) by ZnAlBi LDHs-embedded-Biene was detected at pH 3 and contact time 30 min providing 94.67% removal by using 5 mg L−1 As(V) concentration. The ionic strength factor proved a good selectivity of the nanosorbent toward As(V) ions. Thermodynamic behavior of interaction between As(V) and nanosorbent was emphasized as exothermic and spontaneous process, while the kinetic evaluation indicated that the pseudo-second order was the best-fitting expression. The application of ZnAlBi LDHs-embedded-Biene in the adsorptive uptake process of As(V) ions from various water samples referred to elevated uptake percentages as 93.29% and 90.52% by 5 mg L−1 and 10 mg L−1 As(V), respectively. The adsorbed As(V) onto ZnAlBi LDHs-embedded-Biene exhibited excellent recyclability and re-usage up to five cycles to affirm that the designed ZnAlBi LDHs-embedded-Biene has a great prospect for utilization in water purification from As(V).

Sustainable smart coatings of chitosan and LDH loaded with natural inhibitors for corrosion protection of Mg AZ31 alloy

In this study, sustainable smart coatings based on chitosan and layered double hydroxides (LDH), loaded with natural anions, were developed to enhance the corrosion resistance of AZ31 magnesium alloy. The LDH was synthesized using the co-precipitation method, loaded with natural inhibitors (vanillate, gallate and citrate anions) by an anion exchange process and characterized by various techniques, such as scanning electron microscopy (SEM), Fourier-transform infrared spectroscopy (FTIR), X-ray diffraction (XRD) and thermogravimetric analysis. The kinetics of inhibitor release was investigated at different pH and the results show higher rates as the pH increases. The corrosion resistance offered by the sustainable smart coatings was determined by electrochemical impedance spectroscopy and hydrogen evolution tests, while the coating morphology, before and after the corrosion tests, was analyzed by SEM and optical microscopy, respectively. All of the results demonstrated that the smart coating containing gallate ions significantly improved the corrosion resistance of AZ31 magnesium alloy.

Cover Image

The cover image shows the ligand mediated anion exchange (LMAE) process from CsPbBr3 QDs to CsPbI3 QDs. The incorporation of N‐Acetyl‐L‐cysteine creates more halogen vacancies in CsPbBr3 QDs, which provides sufficient adsorption sites for I‐ ions, leading to the acceleration of anion exchange. Benefiting from the synergistic‐LMAE process, high PLQY of 97% and remarkable stability of CsPbI3 QDs are obtained. image

Synthesis of Silane Functionalized LDH-Modified Nanopowders to Improve Compatibility and Enhance Corrosion Protection for Epoxy Coatings.

Novel modified Zn-Al LDH/epoxy coatings are synthesized and applied to steel substrates, providing active corrosion protection and improved barrier properties. This protective coating is made by combining Epon 828 as a polymer matrix with modified layered-double-hydroxy (LDH) nanoparticles acting as corrosion inhibitor containers. To synthesize the coatings, nitrate was intercalated into Zn-Al-LDH layers through an aqueous co-precipitation method to obtain Zn-Al LDH-NO3, and decavanadate replaced nitrate within the LDH layers through an anion exchange process to obtain Zn-Al LDH-(V10O28)6-. The intercalated LDH was functionalized by silanization with (3-aminopropyl)triethoxysilane (APTES) to increase the compatibility of the LDH inhibitor nanocontainers with epoxy resin and produce a protective coating. To protect the mild steel substrate, functionalized LDH nanopowders were dispersed into the epoxy resin, mixed with a polyamide hardener (Epikure 3571), and applied and cured to the metal surface. Surface morphology, structure, and chemical composition were determined for the modified LDH nanopowders using scanning electron microscopy, energy-dispersive X-ray analysis, X-ray diffraction, infrared spectroscopy, X-ray photoelectron spectroscopy, and thermogravimetric analysis. Corrosion protection of the coating system was studied using long-term immersion testing and potentiodynamic polarization studies in a 3.5 wt.% NaCl solution.

A simple approach for improving the photovoltaic efficiency of organic solar cells through polymer modification via anion exchange as the interlayer

A simple anion exchange was used to synthesize polyelectrolytes based on naphthalene diimide (NDI), which were then applied as a cathode interlayer in organic solar cells (OSCs). These polyelectrolytes can be dissolved in alcohols and produce a beneficial interface dipole due to the ionic functionality in the side chain. The PCE of the OSC utilizing PFN-NDI-OH as the cathode interlayer showed an enhancement compared to the pristine ZnO-based device, increasing from 8.79 % to 8.91 %. This improvement can be attributed to the polar nature of PFN-NDI-OH, which facilitates a strong adhesion between the inorganic metal oxide and the organic active layer. The device with PFN-NDI-OTs exhibited an enhanced PCE of up to 9.41 % due to the size of the counteranion was found to be related to the PCE, as converting the hydroxide to a tosylate anion increased the PCE, with the larger size of the tosylate anion playing a role in enhancing the Jsc. These results indicate that these polyelectrolytes are a promising candidate for use as a cathode interlayer in OSCs, with the additional advantage of being able to improve interfacial properties through a simple anion exchange process without time-consuming purification steps.

Retarding anion exchanges in lead halide perovskite nanocrystals by ligand immobilization.

CsPbX3 (X = Cl-, Br-, I-) perovskite nanocrystals (PNCs) undergo rapid anion exchange, allowing easy bandgap tuning across the entire visible range. However, despite being highly luminescent, the same facile anion exchange process poses significant challenges for their use in tandem optoelectronic devices and white light-emitting diodes (WLEDs). This anion exchange occurs primarily due to the dynamic nature of loosely bound oleylamine ligands on the surface of the PNCs. The mobility of these loosely bound ligands is a key factor in the rapid anion exchange, suggesting that immobilizing these ligands could effectively inhibit the process. To address this, we report a unique approach involving the immobilization of ligands through crosslinking. By crosslinking the ligands on the surface of the PNCs, we can significantly retard the anion exchange process. Our research demonstrates that the anion exchange process can be effectively slowed down by carefully controlling the extent of ligand immobilization. Furthermore, our findings provide the reaction kinetics of anion exchange retardation in CsPbX3 NCs through ligand immobilization by plasma treatment.

Structural and optical control through anion and cation exchange processes for Sn-halide perovskite nanostructures.

Metal halide perovskite nanostructures, characterized by their ionic nature, present a compelling avenue for the tunability of dimensions and band gaps through facile compositional transformations involving both cationic and anionic exchange reactions. While post-synthetic ion-exchange processes have been extensively explored in Pb-halide perovskite nanocrystals, the inherent instability of Sn2+ has limited the exploration of such processes in Sn-halide perovskite nanostructures. In this study, we present a straightforward cation exchange process wherein 2D [R-NH3]2SnX4 Ruddlesden-Popper (RP) nanostructures with n = 1 transition to 3D ASnX3 nanocrystals at room temperature with the addition of A-cation oleate. In addition, anion exchange processes have been demonstrated for both 2D [R-NH3]2SnX4 RP nanostructures and 3D nanocrystals, showcasing transitions between iodide and bromide counterparts. Furthermore, we have fabricated a thin film of 2D [R-NH3]2SnX4 RP nanostructures for cation exchange, wherein A-cation diffusion through a liquid-solid interface facilitates the transformation into a 3D ASnX3 crystal. This investigation underscores the versatility of ion exchange processes in engineering the composition of Sn-halide perovskite nanostructures and, consequently, modulating their optical properties.