Synthesis of a Magnetic Nanostructured Composite Sorbent Only from Waste Materials.

Water pollution is a big problem for the environment, and thus depollution, especially by adsorption processes, has garnered a lot of interest in research over the last decades. Since sorbents would be used in large quantities, ideally, they should be cheaply prepared in scalable reactions from waste materials or renewable sources and be reusable. Herein, we describe a novel preparation of a range of magnetic sorbents only from waste materials (sawdust and iron mud) and their performance in the adsorption of several dyes (methylene blue, crystal violet, fast green FCF, and congo red). The preparation is performed in a hydrothermal process and is thus easily scalable and requires little sophisticated equipment. The magnetic nanostructured materials were analyzed using FTIR, VSM, SEM/EDX, XRD, and XPS. For crystal violet as a pollutant, more in-depth adsorption studies were performed. It was found that the best-performing magnetic sorbent had a maximum sorption capacity of 97.9 mg/g for crystal violet (methylene blue: 149.8 mg/g, fast green FCF: 52.2 mg/g, congo red: 10.5 mg/g), could be reused several times without drastic changes in sorption behavior, and was easily separable from the solution by simply applying a magnet. It is thus envisioned to be used for depollution in industrial/environmental applications, especially for cationic dyes.

Iridium-Based Nanohybrids: Synthesis, Characterization, Optical Limiting, and Nonlinear Optical Properties.

The present work reports on the synthesis and characterization of iridium (Ir)-based nanohybrids with variable chemical compositions. More specifically, highly stable polyvinylpyrrolidone (PVP) nanohybrids of the PVP-IrO2 and PVP-Ir/IrO2 types, as well as non-coated Ir/IrO2 nanoparticles, are synthesized using different synthetic protocols and characterized in terms of their chemical composition and morphology via X-ray photoelectron spectroscopy (XPS) and scanning transmission electron microscopy (STEM), respectively. Furthermore, their nonlinear optical (NLO) response and optical limiting (OL) efficiency are studied by means of the Z-scan technique, employing 4 ns laser pulses at 532 and 1064 nm. The results demonstrate that the PVP-Ir/IrO2 and Ir/IrO2 systems exhibit exceptional OL performance, while PVP-IrO2 presents very strong saturable absorption (SA) behavior, indicating that the present Ir-based nanohybrids could be strong competitors to other nanostructured materials for photonic and optoelectronic applications. In addition, the findings denote that the variation in the content of IrO2 nanoparticles by using different synthetic pathways significantly affects the NLO response of the studied Ir-based nanohybrids, suggesting that the choice of the appropriate synthetic method could lead to tailor-made NLO properties for specific applications in photonics and optoelectronics.

Anticoagulant Properties of Coated Fe-Pd Ferromagnetic Shape Memory Ribbons.

Shape memory alloys, especially ferromagnetic shape memory alloys, are interesting new materials for the manufacturing of stents. Iron-palladium alloys in particular can be used to manufacture self-expanding temporary stents due to their optimum rate of degradation, which is between that of magnesium and pure iron, two metals commonly used in temporary stent research. In order to avoid blood clotting upon the introduction of the stent, they are often coated with anticoagulants. In this study, sulfated pectin, a heparin mimetic, was synthesized in different ways and used as coating on multiple iron-palladium alloys. The static and dynamic prothrombin time (PT) and activated partial thromboplastin time (APTT) of the prepared materials were compared to samples uncoated or coated with polyethylene glycol. While no large differences were observed in the prothrombin time measurements, the activated partial thromboplastin time increased significantly with all alloys coated with sulfated pectin. Aside from that, sulfated pectin synthesized by different methods also caused slight changes in the activated partial thromboplastin time. These findings show that iron-palladium alloys can be coated with anticoagulants to improve their utility as material for temporary stents. Sulfated pectin was characterized by nuclear magnetic resonance (NMR) and Fourier-transform infrared (FTIR) spectroscopy, and the coated alloys by scanning electron microscopy (SEM) and energy dispersive X-ray analysis (EDX).

Green Synthesis of Gold, Silver, Copper, and Magnetite Particles Using Poly(tartaric acid) Simultaneously as Coating and Reductant.

Poly(tartaric acid) is a relatively recently described polymer that can be easily synthesized and scaled up from a readily available renewable material (tartaric acid). This article demonstrates its use in a green synthesis of gold nanoparticles, silver nanoparticles, copper particles, and magnetite nanoparticles. In this case poly(tartaric acid) acts both as a reductant and as a coating agent. To our knowledge this is the first green synthesis of several different types of nanoparticles using only one reagent (polytartrate) as both reductant and coating. The resulting particles were analyzed by XRD, TEM/SEM, EDX, FTIR, DLS, zeta-potential, XPS, and UV/VIS spectroscopy. Preliminary studies of the thermal behavior of mixtures of different types of particles with poly(tartaric acid) were also conducted. The obtained particles show different sizes depending on the material, and the coating allows for better dispersibility as well as potential further functionalization, making them potentially useful also for other applications, besides the inclusion in polymer composites.

Magnetic Nanoclusters Increase the Sensitivity of Lateral Flow Immunoassays for Protein Detection: Application to Pneumolysin as a Biomarker for Streptococcus pneumoniae.

Lateral flow immunoassays for detecting biomarkers in body fluids are simple, quick, inexpensive point-of-care tests widely used in disease surveillance, such as during the coronavirus disease 2019 (COVID-19) pandemic. Improvements in sensitivity would increase their utility in healthcare, food safety, and environmental control. Recently, biofunctional magnetic nanoclusters have been used to selectively label target proteins, which allows their detection and quantification with a magneto-inductive sensor. This type of detector is easily integrated with the lateral flow immunoassay format. Pneumolysin is a cholesterol-dependent cytolysin and one of the most important protein virulence factors of pneumonia produced by Streptococcus pneumoniae. It is recognized as an important biomarker for diagnosis in urine samples. Pneumonia is the infectious disease that causes the most deaths globally, especially among children under five years and adults over 65 years, most of them in low- and middle-income countries. There especially, a rapid diagnostic urine test for pneumococcal pneumonia with high sensitivity and specificity would be helpful in primary care. In this work, a lateral flow immunoassay with magnetic nanoclusters conjugated to anti-pneumolysin antibodies was combined with two strategies to increase the technique's performance. First, magnetic concentration of the protein before the immunoassay was followed by quantification by means of a mobile telephone camera, and the inductive sensor resulted in detection limits as low as 0.57 ng (telephone camera) and 0.24 ng (inductive sensor) of pneumolysin per milliliter. Second, magnetic relocation of the particles within the test strip after the immunoassay was completed increased the detected signal by 20%. Such results obtained with portable devices are promising when compared to non-portable conventional pneumolysin detection techniques such as enzyme-linked immunosorbent assays. The combination and optimization of these approaches would have excellent application in point-of-care biodetection to reduce antibiotic misuse, hospitalizations, and deaths from community-acquired pneumonia.

Single-cell Raman micro-spectroscopy for tracking of carotenoids in cyanobacteria exposed to Mn and Zn doped ferrite nanoparticles.

Ferrite nanoparticles are increasingly produced and exploited as adsorbents for environmental pollutants. However, their impact on the aquatic microbiota such as cyanobacteria, are not yet investigated. Targeting the environmental monitoring context, in this paper we explored for the first time if any change in the carotenoid signal from cyanobacteria Coelomoron pussilum (AICB 1012) exposed to non-lethal doses of Mn and Zn doped ferrite nanoparticles (NPs) can be associated with the nano-aggression on single-cell level, using micro-Raman spectroscopy. UV-Vis absorption spectroscopy of the bulk culture and single-cell Raman microscopy showed that the carotenoid signal increases relative to the chlorophyll contribution upon exposure of the cells to the Mn-ferrite NPs throughout the 7 days of the experiment. The red-shift and broadening of the strongest carotenoid Raman band arising from (CC) stretching modes indicates the change of carotenoid profile towards increased amount of ß-carotene in answer to the NPs stress. The increase of this band intensity relative to the fluorescence background was also observed in Zn-ferrite NPs treatment. Using a simplified and rapid sample preparation procedure, electron microscopy in both transmission and scanning modes, showed greater coverage of the cells by the stable colloidal AgNPs than by the magnetic ferrite NPs. The latter mostly clumped together rather than adhering to the cells. The combined single-cell micro-Raman tracking of physiological response of the unicellular photosynthetic microorganisms coupled with electron microscopy approach to visualise cell-NPs interaction and the extracellular polymeric substance secretion holds the promise for rapid assessment of the NPs-induced environmental stress acting on the unicellular organisms.

Polydopamine--an organocatalyst rather than an innocent polymer.

Polydopamine (PDA) is easily available by oxidation of dopamine and is widely used for persistent coatings of various materials. It is hitherto considered to be inert in many interesting biomedical and other applications. Results presented here, reveal an unexpected behavior of polydopamine as an organocatalyst in direct aldol reactions under mild conditions. Evidence was found for dual catalysis making use of amino and phenolic hydroxy groups found in PDA. Thus scientists must be aware that PDA is not an innocent polymer and can cause unwanted side effects in important applications, such as in biomedicine or as supports in catalysis.