From Impure to Purified Silver Nanoparticles: Advances and Timeline in Separation Methods

AgNPs have exceptional characteristics that depend on their size and shape. Over the past years, there has been an exponential increase in applications of nanoparticles (NPs), especially the silver ones (AgNPs), in several areas, such as, for example, electronics; environmental, pharmaceutical, and toxicological applications; theragnostics; and medical treatments, among others. This growing use has led to a greater exposure of humans to AgNPs and a higher risk to human health and the environment. This risk becomes more aggravated when the AgNPs are used without purification or separation from the synthesis medium, in which the hazardous synthesis precursors remain unseparated from the NPs and constitute a severe risk for unnecessary environmental contamination. This review examines the situation of the available separation methods of AgNPs from crude suspensions or real samples. Different separation techniques are reviewed, and relevant data are discussed, with a focus on the sustainability and efficiency of AgNPs separation methods.

Study of the properties of Ce3+-doped fluoride nanophosphors: phase composition, morphology, luminescence

To date, nanophosphors have found application in various fields, one of which is medicine. These phosphors were developed with the aim to become one of the components of a drug for photodynamic therapy of oncological diseases. The aim of this work was to study the effect of the duration, environment, and stabilizers of solvothermal synthesis on the microstructure and luminescent properties of the YF3:Ce nanophosphor. The solvothermal synthesis technique was carried out in three different media: water, ethanol, and ethylene glycol. The optimal duration of the synthesis was also determined (the synthesis was carried out at a temperature of 200°C for 4…20 hours). The dependence of the YF3 luminescence on the phase composition and the solvothermal synthesis medium was studied. Using SEM, the morphology and particle size of YF3:Ce phosphors were studied depending on different stabilizers (polyethylene glycol, polyethyleneimine, polyvinylpyrrolidone). The luminescence intensity of YF3:Ce and Na(Y1,5Na0,5)F6:Ce samples was compared.

Synthesis of Hierarchical MOR-Type Zeolites with Improved Catalytic Properties

Hierarchical MOR-type zeolites were synthesized in the presence of hexadecyltrimethylammonium bromide (CTAB) as a porogen agent. XRD proved that the concentration of CTAB in the synthesis medium plays an essential role in forming pure hierarchical MOR-type material. Above a CTAB concentration of 0.04 mol·L−1, amorphous materials are observed. These hierarchical mordenite possess a higher porous volume compared to its counterpart conventional micrometer crystals. Nitrogen sorption showed the presence of mesoporosity for all mordenite samples synthesized in the presence of CTAB. The creation of mesopores due to the presence of CTAB in the synthesis medium does not occur at the expense of zeolite micropores. In addition, mesoporous volume and BET surface seem to increase upon the increase of CTAB concentration in the synthesis medium. The Si/Al ratio of the zeolite framework can be increased from 5.5 to 9.1 by halving the aluminum content present in the synthesis gel. These synthesized hierarchical MOR-type zeolites possess an improved catalytic activity for n-hexane cracking compared to large zeolite crystals obtained in the absence of CTAB.

Synthesis of Vertically Aligned Porous Silica Thin Films Functionalized by Silver Ions

In this work, we have developed a chemical procedure enabling the preparation of highly ordered and vertically aligned mesoporous silica films containing selected contents of silver ions bonded inside the mesopore channels via anchoring propyl-carboxyl units. The procedure involves the electrochemically assisted self-assembly co-condensation of tetraethoxysilane and (3-cyanopropyl)triethoxysilane in the presence of cetyltrimethylammonium bromide as a surfactant, the subsequent hydrolysis of cyano groups into carboxylate ones, followed by their complexation with silver ions. The output materials have been electrochemically characterized with regard to the synthesis effectiveness in order to confirm and quantify the presence of the silver ions in the material. The mesostructure has been observed by transmission electron microscopy. We have pointed out that it is possible to finely tune the functionalization level by controlling the co-condensation procedure, notably the concentration of (3-cyanopropyl)triethoxysilane in the synthesis medium.

Fabrication of Zinc-Iron-Aluminum Layered Double Hydroxides with Controlled Micromorphology in a Tailored Aqueous - Organic Synthesis Medium

Micromorphology characteristics of layered double hydroxides are important to establish their performances to act as adsorbents and catalysts/photocatalysts. Herein, we report the fabrication of ZnFeAl layered double hydroxides (LDHs) (defined by a molar ratios Zn/Fe/Al 2/0.5/0.5), in a tailored aqueous-organic synthesis medium, by using the coprecipitation method. The nature of the organic solvent (e.g.: ethanol, ethyl acetate, glycerol and toluene) was used as a controlled variable for obtaining specific morphology characteristics of ZnFeAl. XRD, FTIR, UV-Vis-DR spectroscopy and SEM microscopy have been used to characterize the structural, optical and textural features of ZnFeAl. Results show that the controlled aqueous-organic synthesis medium established important changes in the structural features and the micromorphology characteristics (e.g.: particle sizes and their interconnection patterns) of ZnFeAl, as indicated by the results of XRD and SEM analyses. The FTIR spectra revealed that most of the interlayer anions are carbonate, even though the initial salts precursors contain nitrates or sulfates anions. Furthermore, the UV-Vis-DR results underline that the band gaps of the LDH derived oxides changed in a significant manner, as a function of the nature of the organic solvent. Such that, ZnFeAl prepared in the presence of ethanol and ethyl acetate show band gap values lower than 3 eV and thus could be better activated under visible light. These results should be inspiring for fabricating layered double hydroxides with a controlled micromorphology for specific applications for environmental cleanup.

Talc-like hybrids: influence of the synthesis

Adding water to the synthesis medium leads to the formation of hybrids with low polycondensation, high crystallinity and high thermal stability.

Synthesis of 2D cobalt oxide nanosheets using a room temperature liquid metal

A RT liquid metal based on Ga can be used as a synthesis medium for creation of 2D nanosheets of cobalt oxide via expulsion of the sheets from the liquid metal surface into an acidic aqueous solution. The 2D nanosheets are shown to be active for OER.