Copper metallic nanoparticles capped with PEGylated PAMAM-G3 dendrimers for the catalytic reduction of low solubility nitroarenes of pharmaceutical interest

Determination of copper and cobalt in different tea samples at trace levels by FAAS after preconcentration with a novel iron PAMAM-OH-encapsulated magnetic nanoparticle as SPE sorbent

Environmental contamination caused by heavy metals is a significant global concern. The presented study investigated the efficiency of iron PAMAM-OH encapsulated magnetic nanoparticles (Fe-MNP-G2-OH) as sorbent for the preconcentration of copper and cobalt from tea samples. High metal-chelating ethylenediamine core polyamidoethanol generation-2 (PAMAM-G2-OH) was encapsulated with iron oxide (Fe3O4) to synthesize the sorbent. Limit of detection (LOD) values for copper and cobalt extracted and detected by the developed Fe-MNP-G2-OH -SPE-FAAS method were 0.52 and 1.1 μg L-1, respectively. There were 230- and 101-fold improvement in detection limits for copper and cobalt, respectively, when compared to direct FAAS measurement. The percent recovery results for the analytes in green and black tea samples ranged from 93 to 107%, with low relative standard deviation (%RSD) values. The synthesis of nanoparticle was carried out through a unique method, which was characterized by thermogravimetric analysis (TGA), scanning electron microscope (SEM), and Fourier transform infrared spectroscopy (FTIR) methods. The analytical results demonstrated the applicability and effectiveness of Fe-MNP-G2-OH nanoparticles on the preconcentration of copper and cobalt from tea samples and the developed method is suitable for the trace detection of heavy metals by FAAS method. To the best our knowledge, this is the first study where copper and cobalt in green and black tea samples were extracted by Fe-MNP-G2-OH adsorbent and precipitation of the adsorbent during its synthesis was carried out in acetone medium rather than aqueous one.

Gold nanoparticle-decorated earth-abundant clay nanotubes as catalyst for the degradation of phenothiazine dyes and reduction of 4-(4-nitrophenyl)morpholine

In the present work, halloysite nanotubes modified with gold nanoparticles (AuNPs-HNT) are successfully prepared by wet chemical method for the catalytic degradation of phenothiazine dyes (azure B (AZB) and toluidine blue O (TBO)) and also cleaner reduction of 4-(4-nitrophenyl)morpholine (4NM) in the sodium borohydride (NaBH4) media. The catalyst is formulated by modifying the HNT support with a 0.964% metal loading using the HNT supports modified with 3-aminopropyl-trimethoxysilane (APTMS) coupling agent to facilitate the anchoring sites to trap the AuNPs and to prevent their agglomeration/aggregation. The AuNPs-HNT catalyst is investigated for structural and morphological characterization to get insights about the formation of the catalyst for the effective catalytic reduction of dyes and 4NM. The microscopic studies demonstrate that AuNPs (2.75 nm) are decorated on the outer surface of HNT. The as-prepared AuNPs-HNT catalyst demonstrates AZB and TBO dye degradation efficiency up to 96% in 10 and 11 min, respectively, and catalytic reduction of 4NM to 4-morpholinoaniline (MAN) is achieved up to 97% in 11 min, in the presence of NaBH4 without the formation of any by-products. The pseudo-first-order rate constant (K1) value of the AuNPs-HNT catalyst for AZB, TBO, and 4NM were calculated to be 0.0078, 0.0055, and 0.0066 s-1, respectively. Moreover, the synthesized catalyst shows an excellent reusability with stable catalytic reduction for 7 successive cycles for both the dyes and 4NM. A plausible mechanism for the catalytic dye degradation and reduction of 4NM by AuNPs-HNT catalyst is proposed as well. The obtained results clearly indicate the potential of AuNPs-HNT as an efficient catalyst for the removal of dye contaminants from the aquatic environments and cleaner reduction of 4NM to MAN, insinuating future pharmaceutical applications.

Catalytic Neutralization of Water Pollutants Mediated by Dendritic Polymers

Radially polymerized dendritic compounds are nowadays an established polymer category next to their linear, branched, and cross-linked counterparts. Their uncommon tree-like architecture is characterized by adjustable internal cavities and external groups. They are therefore exceptional absorbents and this attainment of high concentrations in their interior renders them ideal reaction media. In this framework, they are applied in many environmentally benign implementations. One of the most important among them is water purification through pollutant decomposition. Simple and composite catalysts and photo-catalysts containing dendritic polymers and applied in water remediation will be discussed jointly with some unconventional solutions and prospects.