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[Display omitted] • Gelation of chitosan dissolved in an alkaline aqueous solution was investigated. • Ethanol-water mixtures were employed as the coagulant for the APS processes. • Gelling film in the ethanol-containing coagulant was in-situ characterized by OCT. • Film morphology was analyzed by combining OCT and network-based modeling. • Internal rejection of particles was correlated with the morphological formation. Gelation of chitosan dissolved in an alkali/urea aqueous solution promotes the mechanistic diversity of forming a membrane via aqueous phase separation (APS), which is conceptualized to highlight the advantages of using environmentally friendly solvents. When aimed at deepening the knowledge of regulating the structural formation, the alkaline dope of chitosan was employed in this study to investigate how the presence of ethanol in the coagulant could regulate the gelation behavior in APS and thereby change the particle-trapping mechanism. Both the gelling films and the particle-filtering membranes were in-situ characterized by optical coherence tomography (OCT) to compare the film-formation kinetics and the morphological variations in the resulting porous substructures, respectively. It was revealed that the ethanol-containing coagulant could induce the shrinkage of the gelling film and thereby favor the transverse coalescence of polymer-rich phases; that is, increasing the content of ethanol in the coagulant (over a range less than a critical value to avoid film deformation) would give rise to more tortuous substructures (for effectively capturing particles) primarily owing to the lower connectivity in the transverse direction. The theoretical analysis was supported by numerically evaluating the topological analog. This study not only confirms effectiveness of the ethanol-based regulation, but also establishes a paradigm for fabricating membranes with tailored topological characteristics. [ABSTRACT FROM AUTHOR]

Precipitating polymer in a completely aqueous environment is conceptualized as a process of aqueous phase separation (APS) and lends itself to the environmentally friendly fabrication of membranes. In an effort to effectively regulate the morphological formation in APS, it is of fundamental concern to elucidate how asymmetry can be developed in the absence of an unbalanced exchange of the 'nonsolvent' and solvent. Therefore, technical modifications were made by this study to essentially improve the in-situ characterization based on optical coherence tomography (OCT). In particular, a process of APS was modeled by passively contacting an acidic aqueous dope of chitosan with another aqueous solution of sodium hydroxide in a mini-coagulation bath, where the OCT scan was implemented in a high speed mode to capture the onset and evolution of gelation at the coagulant-dope interface with a temporal resolution of 6.25 ms. The quantitative analysis indicated that the gelation could be initiated at the interface in a period shorter than ∼10 ms and evolved in an oscillating way; a skin layer with a smaller critical size would be formed by damping the interfacial oscillations. This study not only sheds light on the APS-based fabrication of membranes, but also establishes a novel paradigm for in-situ characterizing the film formation via an OCT-based approach. [Display omitted] • Formation of asymmetry in APS was modeled by the gelation of chitosan. • OCT was used to in-situ characterize the initial gelation occurring at the interface. • Passive contact was employed to eliminate the delay resulting from immersion. • High speed scan mode enabled achieving a temporal resolution of 6.25 ms. • Interfacial oscillations in the gelation were correlated with the skin rejection. [ABSTRACT FROM AUTHOR]

Highlights: [•] l-Cys CdS:Eu QDs were first successfully synthesized in aqueous solution. [•] The synthesized l-Cys CdS:Eu QDs exhibit higher photoluminescent intensity and bright a strong yellow emission. [•] The as-prepared QDs could be used as fluorescence probes to detect Hg2+ ions in aqueous media. [ABSTRACT FROM AUTHOR]

Abstract: In this study, we report the synthesis of PbS quantum dots (QDs) using an aqueous route with three different ligands: thioglycolic acid (TGA), 3-mercaptopropionic acid (MPA), l-Cysteine (l-Cys) as the capping molecule. Fourier transform infrared (FT-IR) spectrometry analysis demonstrates that PbS QDs are capped with these three capping ligands through the coordination. The influences of various experimental variables, on the growth rate and luminescent properties of the obtained QDs have been systematically investigated. Experimental results indicate that the capping ligands and pH value plays a crucial role in determining the growth rate and optical properties of obtained PbS QDs. Furthermore, the stability of l-Cys-capped QDs was compared with the TGA and MPA capped QDs were investigated. Experimental results indicate that the l-Cys-capped QDs show better chemical stability than those capped by TGA and MPA. The synthesized l-Cys-capped PbS QDs were characterized by high-resolution transmission electron microscopy (HRTEM) and X-ray diffraction (XRD), the results indicate that the QDs were about 8nm in size and dispersed well with a rock salt crystalline structure. [Copyright &y& Elsevier]

Abstract: In this study, we report the synthesis of PbS quantum dots (QDs) using an aqueous route with l-cysteine (l-Cys) as the capping ligands. The as-prepared PbS QDs were characterized by high resolution transmission electron microscopy (HRTEM) and X-ray diffraction (XRD), the results indicated that the QDs were about 7nm in size and dispersed well. There was l-Cys on the surface of QDs, which was confirmed by Fourier transform infrared (FT-IR) spectrometry. Various synthesis parameters affecting on the photoluminescent (PL) properties of the PbS QDs were discussed in detail. These parameters include the reaction time, the molar ratio of l-Cys/Pb or S/Pb, pH value and different sulfur source compounds. Furthermore, we found the as-synthesized QDs were still keeping highly PL properties not only in their original solution but also in deinoized (DI) water and phosphate buffer saline (PBS) solution during the period of 30 days, which indicated that the l-Cys capped PbS QDs could be important to the application in biomedical field in the future. [Copyright &y& Elsevier]