Formation and stability of manganese-doped ZnS quantum dot monolayers determined by QCM-D and streaming potential measurements

Enhanced Antifouling Capability of In Situ-Grown Hydrophilic-Hydrophobic Nanodomains on Membrane Surface in the Ultralow Pressurized Ultrafiltration Process

Although hydrophilic modification of the membrane surface is widely adopted, polymeric membranes still suffer from irreversible fouling caused by hydrophilic components in surface water. Here, an ultrathin hydrogel layer (40 nm) with hydrophilic-hydrophobic textures was in situ grown onto the polysulfone ultrafiltration membrane surface using an organic-radical-initiated interfacial polymerization technique. The interfacial polymerization of hydrophilic and hydrophobic monomers ensured the molecular-scale distribution of hydrophilic and hydrophobic nanodomains on the membrane surface. These nanodomains, with their molecular lengths, facilitated dynamic repulsion interactions between the uniformly textured surface and foulant components with different degrees of hydrophilicity. Chemical force characterization confirmed that the adhesion force between the hydrophilic-hydrophobic textured membrane surface and foulants (dodecane, bovine serum albumin, and humic acid) was greatly reduced. Dynamic filtration experiments showed that a hydrophilic-hydrophobic textured membrane always possessed the largest water flux and the best antifouling performance. Furthermore, the foulant coverage ratio on the membrane surface was first evaluated by measuring changes in surface streaming potentials, which demonstrated a 69% reduction in the amount of foulant adhering to the hydrophilic-hydrophobic textured membrane surface. Therefore, the construction of hydrophilic-hydrophobic nanodomains on the membrane surface provides a promising strategy for alleviating membrane fouling caused by both hydrophobic and hydrophilic components during ultralow pressurized ultrafiltration processes.

Effect of the Anchoring Layer and Transport Type on the Adsorption Kinetics of Lambda Carrageenan

The kinetics of lambda carrageenan (λ-car) adsorption/desorption on/from anchoring layers under diffusion- and convection-controlled transport conditions were investigated. The eighth generation of poly(amidoamine) dendrimers and branched polyethyleneimine possessing different shapes and polydispersity indexes were used for anchoring layer formation. Dynamic light scattering, electrophoresis, streaming potential measurements, optical waveguide lightmode spectroscopy, and quartz crystal microbalance were applied to characterize the formation of mono- and bilayers. The unique combination of the employed techniques enabled detailed insights into the mechanism of the λ-car adsorption mainly controlled by electrostatic interactions. The results show that the macroion adsorption efficiency is strictly correlated with the value of the final zeta potentials of the anchoring layers, the transport type, and the initial bulk concentration of the macroions. The type of the macroion forming the anchoring layer had a minor impact on the kinetics of λ-car adsorption. Besides significance to basic science, the results presented in this paper can be used for the development of biocompatible and stable macroion multilayers of well-defined electrokinetic properties and structure.

Modification of Higher Alkanes by Nanoparticles to Control Light Propagation in Tapered Fibers

This study presents the doping of higher alkanes, namely, pentadecane (C15) and hexadecane (C16), with ZnS:Mn nanoparticles to create new types of in-line optical fiber sensors with unique optical properties. In this research, the phenomenon of light beam leakage out of the taper and its interaction with the surrounding materials is described. The fabricated new materials are used as cladding in a tapered optical fiber to make it possible to control the optical light beam. The manufactured sensor shows high sensitivity and fast response to the change in the applied materials. Results are presented for a wide optical range of 1200–1700 nm with the use of a supercontinuum source and an optical spectrum analyzer, as well as for a single wavelength of 800 nm, corresponding to the highest transmitted power. The results present a change in the optical property dependence on the temperature in the cooling and heating process. For all materials, the measurements in a climatic chamber are provided between 0 and 40 °C, corresponding to the phase change of the alkanes from solid to liquid. The addition of nanoparticles to the volume of alkanes is equal to 1 wt%. To avoid a conglomeration of nanoparticles, the anti-agglomeration material, Brij 78 P, is used.

Gold substrates of controlled roughness and electrokinetic properties formed by nanoparticle deposition

The kinetics of positively charged gold nanoparticle self-assembly on oxidized silicon substrates (wafers) under diffusion-controlled transport was studied using scanning electron microscopy (SEM) and atomic force microscopy (AFM). The latter technique allowed the roughness parameters of the monolayer (root mean square) to be determined as a function of the particle coverage. These results were adequately interpreted in terms of a theoretical model developed for surfaces covered by features of spherical shape considering the tip convolution effect. The stability and the electrokinetic characteristics (zeta potential) of the monolayers were also acquired using streaming potential measurements. It was shown that the inversion of the negative zeta potential of the bare substrate (overcharging) occurs at the particle coverage equal to 0.15, and for larger coverages positive zeta potential values were asymptotically attained. Additionally, the desorption kinetics of the particles was investigated by the streaming potential method, which confirmed the stability of the monolayers for a broad range of pHs. It was argued that these results enable to develop an efficient method for the preparation of gold sensors exhibiting a well-controlled surface roughness and electrostatic charge comprising both negative and positive values.

The Research Development of Quantum Dots in Electrochemical Energy Storage

Quantum dots, which are made from semiconductor materials, possess tunable physical dimensions and outstanding optoelectronic characteristics, and they have aroused widespread interest in recent years. In addition to applications in biomolecular analysis, sensors, organic photovoltaic devices, fluorescence, solar cells, photochemical reagents, light-emitting diodes, and catalysis, quantum dots have attracted mounting attention in the field of electrochemical energy storage owing to their size confinement and anisotropic geometry. In this review, a comprehensive summary is given and the research progress of the study of quantum dots for batteries and electrochemical capacitors in recent years, including their synthesis methods, micro/nanostructural features, and electrochemical performance, is appraised.