Metal Salt Precursors Research Articles

Facile construction of a stable biomass-derived carbon-supported Al[sbnd]Zr composite with crystalline solid solution and Brønsted–Lewis dual acidity for efficient catalytic conversion of cellulose

Exploiting cellulose-derived levulinic acid (LA) in biorefinery has potential application prospects, and the development of efficient and stable catalysts is crucial yet challenging. In this study, a bimetallic synergy strategy was proposed to construct an efficient and durable solid acid catalyst with crystalline solid solution by a totally solid-phase method. Mechanical activation (MA)-treated precursor (metal salts, starch, and urea) was calcined to obtain a stable biomass-derived carbon (BC)-supported AlZr (MA-AZ/BC) composite, which was applied for catalytic conversion of cellulose to LA in aqueous-phase system. The results indicate that the synergistic effect of bimetallic crystalline solid solution and the existence of Brønsted–Lewis dual-acid sites in the MA-AZ/BC catalyst contributed to a cellulose conversion efficiency of 97.5 % and a LA yield of 67.1 %. Benefiting from the strong bimetal–support interaction, the MA-AZ/BC catalyst exhibited favorable stability and recoverability. On the basis of comprehensive analysis, a reaction mechanism of Brønsted–Lewis dual-acid sites for synergistic catalytic conversion of cellulose was proposed. This study provides a new idea for the rational design and environmentally friendly fabrication of functional BC-based catalysts for efficiently producing platform compounds derived from biomass.

Universal, Time-Cost-Effective, and Inside-Out Strategy for Synthesis of Plant-Based Flow Catalysis Microreactors.

The utilization of plant-based flow catalytic microreactors has been increasingly gaining traction in the fields of water treatment, energy generation, and biotechnological science due to their inherent channel structures, renewable properties, and environmentally friendly nature. The conventional outside-in strategy for synthesizing plant-based monolithic microreactors typically entails prolonged hydrothermal modification, extensive chemical usage, or energy-intensive equipment. The present study presents a universal inside-out strategy for the rapid synthesis of monolithic catalytic microreactors derived from plant materials. This approach enables the direct formation of catalytic metal nanoparticles within specific plant microchannels through regioselective deposition, resulting in reduced chemical usage and an accelerated process. Moreover, this method effectively minimizes the required catalyst dosage. In this process, the plant monolith's aligned, narrow, and accessible channels provided a higher contact area, shorter diffusion path, and abundant oxygen-containing functional groups for rapid transformation of metal salt precursors into catalytic metal nanoparticles with excellent dispersion. The inside-out strategy can be extended to various plant-based monoliths and diverse metal/metal oxide/MOF materials within the plant monolith, thereby offering a facile, time- and cost-effective universal approach for skillfully designing plant-based flow microreactors for a wide range of applications.

Mechanism of Co3O4-TiO2 Nanocomposite Formation with Enhanced Photocatalytic Performance

TiO2 nanotubes are tubular structures that have garnered significant attention in materials science and engineering due to their unique properties and diverse applications. In this study, highly ordered and well aligned TiO2 nanotubes were successfully synthesized through anodization of Ti foil in ethylene glycol (C2H6O2) containing ammonium fluoride (NH4F) and hydrogen peroxide (H2O2) at 60 V for 30 minutes. The effectiveness of TiO2 as a photocatalyst under solar light is limited by its wide band gap and high recombination rate of charge carriers. To address these limitations, TiO2 nanotubes were modified with cobalt oxide. The resulting Co3O4-TiO2 nanocomposite was synthesized using a wet impregnation technique, aiming to enhance the photocatalytic performance of TiO2 nanotubes across a broader range of the solar spectrum. The formation of Co3O4-TiO2 nanocomposite is by immersing the TiO2 nanotubes in the metal salt precursor solution of Co(NO3)2 for a certain soaking period. The soaking cycle was repeated a few times to ensure the deposition of cobalt oxide nanostructures on the TiO2 nanotube samples. This diffusion interstitial process via wet impregnation was time dependent, which altered the amount of cobalt loaded on the nanotube's surface. The addition of cobalt significantly improved the photodegradation activity of the nanotubes under visible light, outperforming bare TiO2 nanotubes. This enhancement is likely due to the cobalt acting as shallow traps, which effectively promote the separation of photogenerated charge carriers.

A Route to Selective Arsenate Adsorption in Phosphate Solutions via Ternary Metal Biopolymer Composites

With the increased need for improved adsorbents for efficient water treatment, sodium alginate (NaAlg) and chitosan (Chi) represent promising platform biopolymers for the preparation of biocomposite adsorbents for the effective removal of waterborne oxyanion (arsenate (Asi) and orthophosphate (Pi)) contaminants. The TMCs were characterized by spectroscopy (infrared (IR), SEM with an energy dispersive X-ray (SEM-EDX)), point-of-zero-charge (PZC) measurements, and dye adsorption by employing p-nitrophenol at variable pH. Based on dye adsorption results, the adsorbent surface area (SA) was 271 m2/g for Al-TMC, 286 m2/g for Fe-TMC, and 311 m2/g for Cu-TMC. This indicates the role of adsorbent pore structure and swelling in water. Further, the role of either aluminum (Al), copper (Cu), or iron (Fe) for the preparation of TMCs for the selective Asi removal in the presence of Pi as a competitor anion was evaluated. While Al, Fe, and Cu coordinate to the biopolymer framework at C=O sites, only Fe coordinates to –NH2 sites. While Al coordinated via Al-O and interfacial hydroxy groups, Cu showed the formation of Cu2(OH)3NO3 in contrast to Fe, which observed FeOOH formation. Adsorption of Asi was highest for Al-TMC (80 mg/g), followed by Fe-TMC (77 mg/g) and Cu-TMC (31 mg/g). Adsorption of Pi was highest for Al-TMC (93 mg/g), followed by Fe-TMC (66 mg/g) and Cu-TMC (17 mg/g). While Al-TMC showed the highest adsorption capacity overall, only Fe-TMC (followed by Cu-TMC) showed strong arsenate selectivity over orthophosphate. The selectivity toward Asi in presence of Pi was determined and the binary separation factor (αt/c) and the selectivity coefficient (βt) were calculated, where Cu-TMC (αt/c = 6.1; βt = 4.4) and Fe-TMC (αt/c = 8.3; βt = 5.0) exceeded Al-TMC (αt/c = 1.5; βt = 1.2). This work contributes to the field of oxyanion-selective adsorbents via judicious selection of the metal salt precursor during the synthetic design of the ternary biocomposite systems, as demonstrated herein.

Exploring the Complex Chemistry and Degradation of Ascorbic Acid in Aqueous Nanoparticle Synthesis.

Ascorbic acid (AA) is the most widely used reductant for noble metal nanoparticle (NP) synthesis. Despite the synthetic relevance, its aqueous chemistry remains misunderstood, due in part to various assumptions about its reduction pathway which are insufficiently supported by experimental evidence. This study aims to provide an understanding of the complex chemistry associated with AA under aqueous conditions. We demonstrate that (i) AA undergoes appreciable degradation in alkaline solution on a timescale relevant to NP synthesis, (ii) contrary to popular belief, AA does not degrade into dehydroascorbic acid (DHA), nor is DHA the oxidized product of AA under noble metal NP synthetic conditions, (iii) DHA, which readily degrades under alkaline conditions, can also effectively reduce metal salt precursors to metal NPs, (iv) neither ascorbate nor dehydroascorbate act as surface capping agents post-synthetically on the NPs (v) AA degradation time greatly affects the morphology and polydispersity of the resultant NP. Results from our mechanistic investigation enabled us to utilize purposefully-aged reductants to achieve control over shape yield and monodispersity in the seed-mediated synthesis of Au nanorods. Our findings have important implications for achieving monodispersed products in the many metal NP synthesis reactions that make use of AA as a reducing agent.

Exploring the Complex Chemistry and Degradation of Ascorbic Acid in Aqueous Nanoparticle Synthesis

Ascorbic acid (AA) is the most widely used reductant for noble metal nanoparticle (NP) synthesis. Despite the synthetic relevance, its aqueous chemistry remains misunderstood, due in part to various assumptions about its reduction pathway which are insufficiently supported by experimental evidence. This study aims to provide an understanding of the complex chemistry associated with AA under aqueous conditions. We demonstrate that (i) AA undergoes appreciable degradation in alkaline solution on a timescale relevant to NP synthesis, (ii) contrary to popular belief, AA does not degrade into dehydroascorbic acid (DHA), nor is DHA the oxidized product of AA under noble metal NP synthetic conditions, (iii) DHA, which readily degrades under alkaline conditions, can also effectively reduce metal salt precursors to metal NPs, (iv) neither ascorbate nor dehydroascorbate act as surface capping agents post‐synthetically on the NPs (v) AA degradation time greatly affects the morphology and polydispersity of the resultant NP. Results from our mechanistic investigation enabled us to utilize purposefully‐aged reductants to achieve control over shape yield and monodispersity in the seed‐mediated synthesis of Au nanorods. Our findings have important implications for achieving monodispersed products in the many metal NP synthesis reactions that make use of AA as a reducing agent.

Green synthesis and multifunctional properties of Cu/NiO nanocomposites using Commelina benghalensis leaf extract

This study presents the green synthesis and multifunctional properties of Cu/NiO nanocomposites (NCs) fabricated with varying ratios (90:10, 80:20, and 70:30) using Commelina benghalensis leaf extract. X-ray diffraction (XRD) analysis confirmed the polycrystalline nature of the NCs, revealing crystallite sizes of 13.62, 13.22, and 7.14 nm. Scanning electron microscopy (SEM) showed rod-shaped and agglomerated particles with sizes ranging from 17.64 to 22.97 nm. Energy-dispersive X-ray spectroscopy (EDX) verified the elemental composition of copper, nickel, oxygen, and carbon. UV–visible spectroscopy determined the energy band gaps to be in the range of 1.24–1.56 eV. Fourier-transform infrared spectroscopy (FT-IR) indicated the presence of bioactive compounds responsible for the reduction of precursor metal salts. The Cu/NiO NCs exhibited remarkable antimicrobial activity, with the 90:10 ratio showing the highest zones of inhibition at 32.76 ± 0.23 mm, 18.66 ± 0.33 mm, and 14.36 ± 0.32 mm against Bacillus subtilis, Staphylococcus aureus, and Escherichia coli, respectively. Additionally, the 70:30 Cu/NiO NCs demonstrated superior antioxidant activity, with a radical scavenging efficiency of 83.22%, closely approaching that of ascorbic acid (96.98%). Photocatalytic evaluations revealed that the NCs were highly effective in degrading environmental pollutants, achieving 97.69% degradation of malachite green and 96.52% of congo red under UV light irradiation. The novelty of this work lies in the use of Commelina benghalensis leaf extract as a sustainable and eco-friendly reducing and stabilizing agent for synthesizing Cu/NiO NCs, offering a green alternative to conventional methods. The synergistic effects between Cu and NiO in the different compositions (90:10, 80:20, and 70:30) enhanced the overall antimicrobial and photocatalytic activities, highlighting their potential for environmental remediation applications.

Antioxidant, antiglycation, and antibacterial of copper oxide nanoparticles synthesized using Caesalpinia Sappan extract.

Synthesis of metal nanoparticles using plant extracts is environmentally friendly and of increasing interest. However, not all plant extracts can meet successfully on the synthesis. Therefore, searching for the high potential extracts that can reduce the metal salt precursor in the synthesis reaction is essential. The present study explores the synthesis of copper oxide nanoparticles (CuONPs) using Caesalpinia sappan heartwood extract. Phytochemical analysis and determination of the total phenolic content of the extract were performed before use as a reducing agent. Under the suitable synthesized condition, a color change in the color of the solutions to brown confirmed the formation of CuONPs. The obtained CuONPs were confirmed using ultraviolet-visible spectroscopy, photon correlation spectroscopy, X-ray diffraction, scanning electron microscope, energy dispersive X-ray, and Fourier transform infrared analysis. The synthesized CuONPs investigated for antioxidant, antiglycation, and antibacterial activities. CuONPs possessed antioxidant activities by quenching free radicals with an IC50 value of 63.35 µg/mL and reducing activity with an EC range of 3.19-10.27 mM/mg. CuONPs also inhibited the formation of advanced glycation end products in the bovine serum albumin/ribose model with an IC50 value of 17.05 µg/mL. In addition, CuONPs showed inhibition of human pathogens, including Gram-positive Staphylococcus aureus and Gram-negative Escherichia coli, and prevention of biofilm formation and biofilm eradication, with maximum inhibition of approx. 75%. Our findings suggest that C. sappan extract can be used to obtain highly bioactive CuONPs for the development of certain medical devices and therapeutic agents.

One-Step synthesis of nanosized Cu-Ag films using atmospheric pressure plasma jet

Thin films of copper-silver (Cu-Ag) composed of nanosized particles were successfully synthesised and deposited on glass and carbon substrates under various metal ratios in a single step using an atmospheric pressure plasma jet (APPJ) system. This rapid synthesis and deposition technique only requires very low power input (20 W) and rudimentary solutions of metal salt precursors and DI water without additives, pretreatment, or post-treatment process. Successful Cu-Ag alloying was observed, with excellent compositional and deposition area control. Strongly adherent films can be formed on conductive and non-conductive substrate, making APPJ an ideal and sustainable approach for large-scale deposition of multi-component thin metallic films. A comprehensive characterisation of Cu-Ag alloys deposited using APPJ and their potential use as electrocatalytic CO2 reduction catalysts is discussed.

One-pot approach for acoustic directed assembly of metallic and composite microstructures by metal ion reduction

Acoustic-directed assembly is a modular and flexible bottom-up technique with the potential to pattern a wide range of materials. Standing acoustic waves have been previously employed for patterning preformed metal particles, however, direct patterning of metallic structures from precursors remains unexplored. Here, we investigate utilization of standing waves to exert control over chemical reaction products, while also exploring their potential in the formation of multi-layered and composite micro-structures. Concentric micro-structures of gold and silver were obtained by introducing a metal precursor salt and a reducing agent into a cylindrical piezoelectric resonator that also served as a reservoir. In addition, we introduce an innovative approach to directly fabricate metallic multi-layer and composite structures by reducing different metal ions or adding nanoparticles during the reduction step. We showcased our method through the fabrication of layered structures, incorporating a combination of gold and silver, as well as structures composed of silver and hematite nanoparticles. The produced structures were characterized through both surface and cross-sectional analyses, revealing the influence of the acoustic field on the mesostructure as well. This innovative approach is promising for production of complex microstructures with enhanced functionality and controlled properties.

Explosive Leidenfrost-Droplet-Mediated Synthesis of Monodispersed High-Entropy-Alloy Nanoparticles for Electrocatalysis.

High-entropy-alloy nanoparticles (HEA NPs) exhibit promising potential in various catalytic applications, yet a robust synthesis strategy has been elusive. Here, we introduce a straightforward and universal method, involving the microexplosion of Leidenfrost droplets housing carbon black and metal salt precursors, to fabricate PtRhPdIrRu HEA NPs with a size of ∼2.3 nm. The accumulated pressure within the Leidenfrost droplet triggers an intense explosion within milliseconds, propelling the carbon support and metal salt rapidly into the hot solvent through explosive force. The exceptionally quick temperature rise ensures the coreduction of metal salts, and the dilute local concentration of metal ions limits the final size of the HEA NPs. Additionally, the explosion process can be fine-tuned by selecting different solvents, enabling the harvesting of diverse HEA NPs with superior electrocatalytic activity for alcohol electrooxidation and hydrogen electrocatalysis compared to commercial Pt (Pd) unitary catalysts.

In-situ immobilization strategy for single-atom iron sites to enhance oxygen reduction reaction in Zn–air batteries and microbial fuel cells

A straightforward and environmentally friendly approach was utilized to synthesize single-atomic Fe–N–C catalyst. In-situ immobilization of Fe3+ during the formation of polydopamine (PDA) and ZIF-8 in aqueous solution effectively prevent metal agglomeration. The mutual promotion of PDA and aqueous solution constructed the hybrid-level porous hollow structure in P–FeNC. This method extends the solution scope from organic solution system to water solution, thus providing fascinating opportunities for investigating metal-N-C catalyst by in-situ mixing various metal salt precursor and dopamine. The optimal P–FeNC catalyst demonstrates superlative oxygen reduction reaction (ORR) performance, with the half-wave potentials (E1/2) of 0.886 V, 0.79 V, and 0.72 V in 0.1 M KOH, 0.5 M H2SO4, and 0.05 M PBS solutions, which exceeded commercial 20 wt% Pt/C. The combinatorial impacts of highly dense FeN4 active sites and interconnected hierarchical mesopores/macropores are presumed to underpin the observed enhancement in ORR performance. Further evaluations show that the power densities of P–FeNC equipped zinc-air battery (ZAB) and microbial fuel cell (MFC) are 460 mW/cm2 and 3083 ± 10 mW/m2, respectively. This study confirms the feasibility to design the innovative single-atom catalyst in aqueous solution and provides constructive ideas to employ the high-performance P–FeNC electrocatalyst in ZABs and MFCs.

Synthesis and characterization of coprecipitated layered NCM oxide as cathode for sodium-ion batteries: Kinetics and hydrodynamics studies

Interest in the development of high-performance sodium-ion batteries (SIBs) as a sustainable alternative to lithium-ion batteries (LIBs) for emerging energy storage systems has motivated to delve into a novel approach for the synthesis of layered transition metal oxide (LTMO) type cathode for SIBs batteries. In this study, we introduce novel chemical synthesis method that diverges from traditional methodologies reported till date. Rather than relying on sulfur, nitrate, or acetate metal precursor salts, we employ metal carbonate salt coupled with oxalic acid as a chelating agent, and sodium carbonate as a precipitating agent. This novel chemistry enhances the microstructure of the cathode material inherited from its precursor exhibiting spherical morphology, influence on the electrochemical properties, bestowing the material with high specific capacity, extended cycle life, and an elevated charge–discharge rate. The primary focus of this work centers on a comprehensive investigation of the hydrodynamic and kinetics aspects of the co-precipitation reaction, guided by the principles of chemical engineering. The effects of key parameters such as impeller speed, impeller type, and scale-up effects on the co-precipitation process have been systematically explored. This research introduces insights into optimizing reaction conditions such as pH, reaction temperature, metal precursor salt ratio, precipitating agent, through rigorous experimentation and characterization reports. The notable effect of precipitating agent on morphology has been demonstrated by electron microscopy images. The kinetics study shows the activation energy of 8.9 kJ mol−1 depicts the reaction is controlled by mass transfer resistance and to overcome this effect, impeller type and speed plays significant role and experimentation results shows the axial mixing pattern created by pitched blade impeller is effective to improvise electrochemical properties. The synthesized cathode material exhibits remarkable electrochemical properties, including tap density of approximately 1.3 g cc−1 with reversible capacity of 215 mAh g−1, along with excellent cyclic stability (90 %) over 60 cycles. Furthermore, it shows the high energy density up to 1300 Wh/L and a rapid charge–discharge rate. These findings contribute to the advancement of SIBs technology and offer promising prospects for future researchers to efficient development of high-performance energy storage solutions.

Laser writing of memristive logic gates and crossbar arrays

Memristor-based logic circuits are gaining a lot of attention due to the potential for high logic density hardware and novel in-memory computing applications. Readily available methods for fabricating of memristor logic structures that are suitable for integration with conventional computer hardware are a growing need. This work presents a direct laser writing process capable of rapidly fabricating memristor logic circuits by laser irradiation of metal salt precursor solutions. Planar memristor patterns are fabricated, and their I–V response is characterized. Boolean logic gates are fabricated from planar memristor pairs that exhibit low programming voltages and rapid switching. Cu/Cu2O/Cu and Ag/Cu2O/Cu memristors are also fabricated in crossbar arrays, showing the ability to be programmed to multiple resistance states through ultrashort voltage pulses. The devices also show the potential to have high endurance and nonvolatile resistance state retention.

Does the rate of metal salt precursor addition during ZIF-8 nanoparticles preparation affect their morphology?: Application in dye adsorption

Zeolitic imidazolate framework (ZIF)-8 nanoparticles demonstrate excellent physicochemical properties, which make them suitable for a variety of applications. However, their scale-up manufacturing requires insight into the rate of addition of precursors. This study investigates the impact of Zn salt precursor rate of addition to an organic linker solution on the morphology and size of ZIF-8 nanoparticles, and their potential for the adsorptive removal of dyes (cationic and anionic). ZIF-8 nanoparticles were produced with a molar ratio of Zn/2-methyl imidazole (Hmim)/H2O at 1/36/2206 by varying the flow rate of Zn precursor at 5, 10, 15, 20, and 25 mL/min into the Hmim solution. The physicochemical properties of the synthesized ZIF-8 nanoparticles were assessed using microscopy, analytical, and spectroscopy techniques. Owing to different flow rates of the precursor, variations in the ZIF-8 particles’ size and morphology were observed. It was found that the optimum flow rate was 15 mL/min (named Z-15), resulting in particle size of 261 nm, with a high specific surface area, thermal stability, and a substantially high yield of ∼89%. Furthermore, the dye adsorption studies, performed using Z-15 NPs, resulted in high methylene blue (∼82%) and methyl orange (∼76%) removal efficiency. The adsorption performance was maintained with dye-spiked simulated wastewater. The superior dye adsorption capacity of the ZIF-8 nanoparticles could be attributed to their microporous characteristics. Thus, this study demonstrates that the rate of addition of Zn precursor in the synthesis of ZIF-8, indeed, affects both their morphology and size, and the resulting nanoparticles exhibit promising adsorption performance toward dyes.

Comparative physiological and anatomical responses of Tagetes erecta L. and Zinnia elegans Jacq. seedlings to AgNO3 and ZnSO4 metals and their nanoparticles

Heavy metals (HMs) pose a significant ecological risk due to their enduring presence in the ecosystem. They become more prevalent as a result of urbanization and industrialization, disrupting critical functions of plant life such as photosynthesis, seedling growth, and germination. Understanding the impact of HMs and nanoparticle exposure on plants is crucial for developing effective strategies to mitigate their potential hazards. Therefore, an effort was made to elucidate the impact of biosynthesized Ag NPs (nanoparticles) and ZnO NPs versus their precursor metal salts, AgNO3 and ZnSO4, respectively on two Asteraceous plants, Mexican marigold (Tagetes erecta L.) and Zinnia (Zinnia elegans Jacq.) in hydroponic solution by monitoring the changes in photosynthetic pigments and their associated photochemistry of photosystem II along with the anatomical attributes. In the present study, two concentrations (50 μM and 100 μM) for each treatments viz., AgNO3, Ag NPs, ZnSO4 and ZnO NPs were given to the seedlings. Metal salts were found to be more toxic than their nanoparticles, and this was manifested in terms of reduction in photosynthetic pigments, especially chlorophylla content (by 32% in marigold and 27% in Zinnia upon exposure to 100 µM of AgNO3, respectively) in both test seedlings. Reduction in chlorophyll fluorescence parameters was also found under metal as well as nanoparticle toxicity. In contrast, energy flux parameters such as absorption of photon per active reaction centre (ABS/RC), trapped energy flux per active reaction centre (TR0/RC), electron transport flux per active reaction centre (ET0/RC) and energy dissipation flux per active reaction centre (DI0/RC) increased significantly to cope with stress toxicity. Similarly, metals and nanoparticles also distorted the anatomy of the root and leaf, and the effect was more intense under AgNO3 treatment than with ZnSO4 in Zinnia. In conclusion, Zinnia seedlings were more resilient towards all the tested conditions, which might be attributed to their adaptability to various environmental factors, indicating their potential for thriving in diverse climates.

Effect of accompanying anion on the formation pathway and photocatalytic performance of metal-modified hydrothermal carbon

Metal modification can elevate the photocatalytic ability of hydrothermal carbonization carbon (HTCC), but the effect of accompanying anions in precursor metal salts is unclear. Taking Ca2+, Mn2+, Fe3+, Zn2+, and Ni2+ as metal examples, HTCCs modified with metal chloride and metal nitrate were fabricated through a simple hydrothermal process using glucose as raw material. The photocatalytic performance for sulfamethoxazole (SMX) removal by chloride catalyzed HTCC was superior to its nitrate modified counterpart. Zn2+ catalysis was profitable for surface C = O generation and furan polymerization, which promoted the SMX removal by hydrothermal carbon via a photosensitization-like mechanism. In ZnCl2 catalyzed system, the promotion effect of Zn2+ was not influenced by anion due to Cl- absence in glucose transformation. While in Zn(NO3)2 catalyzed system, less levulinic acid (LA) led to less surface C = O, and NO3–, the powerful oxidant under acidic conditions was reduced to –NH2, which interrupted the original polymerization route of 5-hydroxymethylfurfural (HMF) by participating in the pseudo-Michael reaction, leading to the low polymerization of hydrothermal carbon, and these changes decreased the photocatalytic performance of nitrate-modified HTCCs, thus counteracting the promotion effect of Zn2+.

Impact of Co impregnation on 3D printed alumina supports for Fischer-Tropsch synthesis

3D printing of catalyst has made a significant headway the past decade. Very often metal species on 3D printed supports are being used in catalysis. However, there is no standardized method of impregnation of 3D printed structures. In this work, the impact of the step in the production process where the impregnation is done was studied. Cobalt on alumina catalyst structures were synthesized using direct ink writing (DIW), characterized and tested in Fischer-Tropsch synthesis. Three different impregnation methods were tested (A) incipient wetness impregnation of the structure after printing (B) adding the metal salt precursor to the printing recipe and (C) impregnation of the alumina powder before printing. The catalysts exhibited significant differences in final properties, including pore volume in the fibers of the structure, cobalt nanoparticle size and metal-support interaction. When using the catalysts in Fischer-Tropsch synthesis, the activity of the catalyst impregnated after printing, was more than double the one with the metal salt in the print paste. The difference in conversion showed a clear correlation with the reducibility of the metal species measured with H2-TPR.

Synthesis and ecotoxicity screening of reusable, magnetically harvestable metal oxide/hydroxide nanocomposites for safe and sustainable removal and recovery of phosphorus from wastewater

This study assesses the ecotoxicological hazard and suggests measures to improve the ecosafety of 10 highly-efficient metal oxide/hydroxide nanocomposite adsorbents for phosphorus removal/recovery from wastewater using the marine bacterium Vibrio fischeri - an ecotoxicological test organism commonly used for the screening of chemicals which is especially sensitive to zinc. Nanocomposites were synthesized through simple co-precipitation of two-, three- and four-valent metal precursors (Ca2+, Mg2+, Zn2+, Fe3+, Zr4+) at different molar ratios, and characterized with laser diffraction, ICP-OES, XRD and SEM. Among these, the pilot-scale tested ZnFeZr-6:1:1-oxyhydroxide was modified by reducing the zinc-fraction to minimize the leaching of harmful Zn2+. The presence of Zn, however, makes the materials technologically powerful by improving the adsorbent selectivity towards phosphate and the material reusability. Composites stability (d50 < 10 μm) was investigated in deionized water and 2% NaCl (V. fischeri test medium) addressing agglomeration, settling and solubilization (releasing metal ions and/or potentially hazardous nanoparticles). All composites, their filtered supernatants and precursor metal salt solutions were evaluated for their toxic potency (half-effective concentration, EC50 and minimum bactericidal concentration, MBC) using 30-min kinetic bioluminescence inhibition test (ISO-21338:2010) and 24-h viability assay with bacteria V. fischeri. Only the Zn-containing composites showed inhibitory effects to Vibrio fischeri. Those with highest zinc-fraction (ZnFeZr-18:5:1; ZnFeZr-10:1:1) were classified “harmful” (EC50 < 100 mg/L), thus environmentally unsafe for engineering applications. The ZnFeZr-6:1:1 (EC50 = 118 mg/L, MBC = 250 mg/L) proved assumingly safe once deposited on magnetic particles ZnFeZr-6:1:1@MPs (EC50 = 1123 mg/L, MBC > 1000 mg/L). All other composites without Zn were non-toxic to Vibrio fischeri.

Porous Poly(ionic Liquid) Membrane with Metal Nanoparticle Gradient: A Smart Actuator for Visualizing Chemical Reactions.

Poly(ionic liquid) (PIL)-based porous membranes are extensively investigated as soft polymer actuators. While PILs have shown significant advancements in membrane fabrication and stabilization of metal nanoparticles (MNPs), research on integrating MNPs into porous membranes to achieve actuation behavior under multiple stimuli is limited. Herein, this work presents a new paradigm for designing a porous PIL-polyacrylic acid (PAA) membrane with a distinct MNP gradient via a top-bottom diffusion approach involving a metal salt precursor solution and NaBH4 as a reducing agent. The strong binding sites provided by PILs, combined with the gradient distribution of -COO- groups across the membrane cross-section, play a significant role in controlling the MNPs' gradient distribution. Interestingly, the MNPs within the membrane display excellent catalytic activity in exothermic reactions such as H2O2 decomposition, dissipating uneven heat that quickly permeates the membrane network. This induces asymmetrical swelling of polymer chains, resulting in rapid membrane bending. Furthermore, such MNP-loaded membrane could serve as a portable test paper for visually monitoring H2O2. This advancement paves the way for the development of intricate smart actuation materials and expands their practical applications in various real-life scenarios.