Substitution Route Research Articles

Clarifying the contrasting effects of limestone fillers in cement-based materials is crucial for the sustainable valorisation of quarry by-products. This study investigates the influence of three limestone fillers – quarry limestone dust (2985 cm²/g), commercial limestone filler (4690 cm²/g), and laboratory-ground limestone powder (4073 cm²/g) – on the rheological and mechanical properties of cement mortar. Two substitution strategies were considered: replacing sand (0–20%) with quarry limestone dust and laboratory-ground powder, and replacing cement (0–30%) with commercial filler. Quarry dust substitution reduces workability with little effect on strength, but washing and superplasticiser restore consistency. In contrast, cement replacement with commercial filler improves workability but decreases strength. Laboratory-ground limestone powder from washed sand, with finer particles and higher purity confirmed by XRD and FTIR, exhibited a nucleation effect and increased strength by 32.7% at 7 days. These results demonstrate that the impact of limestone fillers is governed by their origin, fineness, and substitution route, offering insights for optimising mortar formulation and enabling efficient utilisation of quarry by-products without compromising performance.

Simple isovalent substitution route enhancing energy storage performance of linear dielectric ceramics

Peracetic acid (PAA)-based advanced oxidation processes (AOPs) have shown broad application prospects in organic wastewater treatment. Alkoxy radicals including CH3COO• and CH3COOO• are primary reactive species in PAA-AOP systems; however, their reaction mechanism on attacking organic pollutants still remains controversial. In this study, a Co(II)/PAA homogeneous AOP system at neutral pH was constructed to generate these two alkoxy radicals, and their different reaction mechanisms with a typical emerging contaminant (sulfacetamide) were explored. Dynamic electron distribution analysis was applied to deeply reveal the radical-meditated reaction mechanism based on molecular orbital analysis. Results indicate that hydrogen atom abstraction is the most favorable route for both CH3COO• and CH3COOO• attacking sulfacetamide. However, both radicals cannot react with sulfacetamide via the radical adduct formation route. Interestingly, the single-electron transfer reaction is only favorable for CH3COO• due to its lower ESUMO. In comparison, CH3COOO• can react with sulfacetamide via a similar radical self-sacrificing bimolecular nucleophilic substitution (SN2) route owing to its high ESOMO and easy escape of unpaired electrons from n orbitals of O atoms in the peroxy bond. These findings can significantly improve the knowledge of reactivity of CH3COO• and CH3COOO• on attacking organic pollutants at the molecular orbital level.

Improving the up/down-conversion luminescence via cationic substitution and dual-functional temperature sensing properties of Er3+ doped double perovskites

Yttrium substituted Co–Cu–Zn nanoferrite: A synergetic impact of Y3+ on enhanced physical properties and photocatalysis

BackgroundThe radiofluorinated levodopa analogue 6-[18F]F-l-DOPA (3,4-dihydroxy-6-18F-l-phenylalanine) is a commonly employed radiotracer for PET/CT imaging of multiple oncological and neurological indications. An unusually large number of different radiosyntheses have been published to the point where two different Ph. Eur. monographs exist depending on whether the chemistry relies on electrophilic or nucleophilic radiosubstitution of appropriate chemical precursors. For new PET imaging sites wishing to adopt [18F]FDOPA into clinical practice, selecting the appropriate production process may be difficult and dependent on the clinical needs of the site.MethodsData from four years of [18F]FDOPA production at three different clinical sites are collected and compared. These three sites, Aarhus University Hospital (AUH), Odense University Hospital (OUH), and Herlev University Hospital (HUH), produce the radiotracer by different radiosynthetic routes with AUH adopting an electrophilic strategy, while OUH and HUH employ two different nucleophilic approaches. Production failure rates, radiochemical yields, and molar activities are compared across sites and time. Additionally, the clinical use of the radiotracer over the time period considered at the different sites are presented and discussed.ResultsThe electrophilic substitution route suffers from being demanding in terms of cyclotron operation and maintenance. This challenge, however, was found to be compensated by a production failure rate significantly below that of both nucleophilic approaches; a result of simpler chemistry. The five-step nucleophilic approach employed at HUH produces superior radiochemical yields compared to the three-step approach adopted at OUH but suffers from the need for more comprehensive synthesis equipment given the multi-step nature of the procedure, including HPLC purification. While the procedure at OUH furnishes the lowest radiochemical yield of the synthetic routes considered, it produces the highest molar activity. This is of importance across the clinical applications of the tracer discussed here, including dopamine synthesis in striatum of subjects with schizophrenia and congenital hyperinsulinism in infants.ConclusionFor most sites either of the two nucleophilic substitution strategies should be favored. However, which of the two will depend on whether a given site wishes to optimize the radiochemical yield or the ease of the use.

Turning indium oxide into high-performing electrode materials via cation substitution strategy: Preserving single crystalline cubic structure of 2D nanoflakes towards energy storage devices

Ionic liquid-modified silica-coated magnetite (Fe3O4@SiO2-IL) nanoparticles were synthesized using co-precipitation, silylation, and substitution routes, and finally immobilized on talc sheets by electrostatic interactions. The prepared Fe3O4@SiO2-IL/Talc nanocomposite was characterized by FTIR, XRD, VSM, SEM, and TEM techniques. The nanocomposite was used for adsorption of cationic methylene blue (MB) dye from the aqueous media. The effect of operating parameters, namely initial MB concentration, solution pH, and contact time on the removal rate, was investigated. Electrostatic interactions between MB ions and active sites of the nanocomposite allowed fast adsorption and nanocomposite showed higher adsorption capacity towards MB ions than talc, and Fe3O4@SiO2-IL alone. It was also found that Fe3O4@SiO2-IL/Talc nanocomposite could be used in multiple cycles using environmentally benign ethanol as a solvent. As a result, this study presents a synthesis of novel nanocomposite adsorbent for the removal of harmful organic compounds from the aqueous media, followed by easy separation and possible reuse.

An efficient route for promoter incorporation into a single phase zM precursor has been demonstrated, which enables the maximum utilization of the promotional action for methanol synthesis.

The diffusion of lithium ions decoupled from a solid polymer electrolyte matrix is the key for high-energy electrochemical devices with the safety needed for commercial use. This Letter reports how the ion mobility in a single-phase hybrid polyelectrolyte (SPHP) matrix can be tuned by changing an inorganic coordinating atom from silicon (Si) to germanium (Ge). Nuclear Magnetic Resonance (NMR) results show that the lithium ion activation barrier in the polyelectrolyte with Si can be modulated from 0.26 eV to the unprecedented value of 0.12 eV in the polyelectrolyte with Ge. Density functional theory is used to show that the electronic structures of both polymers are very different, although their chemical structures are very similar, except for the coordinating atom. This simple chemical substitution route will certainly increase the interest in these polymers for applications in electrochemical devices.

The transition from a linear to a circular economy is essential to reduce the environmental burden of our society. A key issue is to prevent a shift of the environmental burdens and take the consequences of a decision into account, for example based on a consequential life cycle assessment (LCA). However, limited practical guidance is available on how to implement consequential LCA in the context of the construction sector. Therefore, the aim of this study is twofold. First, to quantify the potential environmental and burdens of introducing circular design alternatives for internal wall assemblies to the Belgian market. Second, to review the methodological implications on the results of a consequential LCA with a particular focus on consistently identifying marginal suppliers and substitution routes, acknowledging the time dependence and closed-loop nature of the design alternatives.In total seven wall assemblies are assessed over a period of 60 years, with a refurbishment every 15 year.The results show that a low life cycle impact can be achieved for assemblies that are designed to be used again and have a higher initial impact, such as a plywood boarding connected reversibly to a demountable metal frame substructure, as well as for assemblies with no possibilities for direct reuse that have a low initial impact, such as a drywall system with a wooden substructure. Further, regarding the methodological scenarios on marginal supplier identification, the range of possible outcomes is however much larger for the demountable wall assemblies than for the conventional ones.

Nucleophilic-functionalized β-cyclodextrin-polyethersulfone structures from facile lamination process as nanoporous membrane active layers for wastewater post-treatment: Molecular implications

A dual mechanism for direct benzene catalytic hydroxylation is described. Experimental studies and DFT calculations have provided a mechanistic explanation for the acid-free, Tp x Cu-catalyzed hydroxylation of benzene with hydrogen peroxide (Tp x = hydrotrispyrazolylborate ligand). In contrast with other catalytic systems that promote this transformation through Fenton-like pathways, this system operates through a copper-oxyl intermediate that may interact with the arene ring following two different, competitive routes: (a) electrophilic aromatic substitution, with the copper-oxyl species acting as the formal electrophile, and (b) the so-called rebound mechanism, in which the hydrogen is abstracted by the Cu-O moiety prior to the C-O bond formation. Both pathways contribute to the global transformation albeit to different extents, the electrophilic substitution route seeming to be largely favoured.

Nanocrystalline Mn-doped ZnO of compositions Zn1–x Mn x O (0 ≤ x ≤ 0.08) has been synthesised by chemical route for uniform substitution of Mn in Zn site and then sintered at 1300 °C. Systematic investigations show the effect of Mn doping level and the sintering temperature on the structural, electrical and magnetic properties of ZnO. The average size of the nanocrystalline particles is in the order of 30–50 nm, whereas the grain sizes of the sintered specimen are of the order of few microns. Substitution of Mn in ZnO has been confirmed from the X-ray diffraction peak shift. A few peaks related to secondary phases of MnO have been observed in the X-ray diffraction patterns of the doped samples. ZnO and Mn-doped ZnO show Ohmic behavior and increased resistivity value with the increasing concentration of Mn. Effect of Mn concentration in ZnO has also been reflected in the dielectric constant and dielectric loss values. All the sintered samples show paramagnetic behavior even though the presence of MnO with oxygen vacancies is evident in X-ray photoelectron spectroscopic study.

On the occasion of Professor Takashi Tatsumi’s retirement and winning of the Alwin Mittasch Prize, some of his main achievements in zeolite catalysis are summarized, with a focus on the design, synthesis, and catalytic application of new titanosilicate catalysts. He and his co-workers succeeded in the direct synthesis of the MWW-type titanosilicate, Ti-MWW, by employing boric acid in the synthesis and thereafter developed a dry gel conversion method for boron-reduced Ti-MWW as well as a secondary isomorphous substitution route for boron-free Ti-MWW molecular sieves. In particular, the postsynthetic conversion involved a reversible structure interchange between three-dimensional silicalite and a two-dimensional layered precursor. Taking advantage of the structural diversity of the layered MWW zeolite precursor, phase-delaminated Ti-MMW and interlayer expanded Ti-MWW were also prepared. Using hydrogen peroxide as an oxidant, the Ti-MWW/H2O2 system was highly efficient for liquid-phase oxidation of a variety of substrates, particularly the epoxidation of alkenes and ammoximation of ketones. Some of the Ti-MWW-catalyzed reactions have already led to or are becoming practical catalytic technologies in industrial practice. Several other recent achievements in the synthesis and catalytic applications of other titanosilicates, zeolitic hydrid materials, and solid acid zeolite catalysts are also briefly summarized.

Sequential desilication–isomorphous substitution route to prepare mesostructured silica nanoparticles loaded with ZnO and their photocatalytic activity

The reaction of PhCOCH2Cl with OH– gave the expected α‐substituted alcohol (PhCOCH2OH) in addition to three dimer products. To clarify whether the substitution product is formed by direct SN2 or via carbonyl addition, the reaction of PhCOCH2Cl and OMe– was examined. The reaction gave two products, PhCOCH2OH as the major product after acid hydrolysis and PhCOCH2OMe as the minor product. An electron‐withdrawing substituent on the phenyl ring enhanced the overall reactivity and gave more alcohol than ether. It was concluded that the alcohol was formed via carbonyl addition‐epoxidation route, whereas the ether was formed by the direct substitution route. Copyright © 2012 John Wiley & Sons, Ltd.

Stereoselective synthesis of an iodinated resveratrol analog: Preliminary bioevaluation studies of the radioiodinated species

Pd-catalyzed amination as an alternative to nucleophilic aromatic substitution for the synthesis of N-alkyltacrines and analogs

Bu(3)SnH/1,1'-azobis(cyclohexanecarbonitrile) (ACN)-mediated five, six, and seven-membered double alkyl radical cyclizations onto imidazo[5,4-f]benzimidazole and imidazo[4,5-f]benzimidazole are described. The quinone derivatives evaluated show selective toxicity towards human cervical (HeLa) and prostate (DU145) cancer cell lines (with negligible toxicity towards a normal human cell line, GM00637). Only the Fremy oxidation of the 6-aminoimidazo[5,4-f]benzimidazole gave iminoquinone, which showed high specificity towards the prostate cancer cell line (DU145).