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The counterions of polydiallyldimethylammonium (PDADMA) coatings were altered by incubation in aqueous solutions of different electrolytes. Oil de‐wetting on the resulting polycationic surfaces upon water action exhibited a straightforward connection with the Jones–Dole viscosity B‐coefficient (Bη) sign of surface counteranions. Upon water action, surface counteranions with negative Bη render PDADMA coatings oil‐adhering, but those with positive Bη furnish PDADMA coatings with excellent self‐cleaning. The oil‐adhering PDADMA surfaces can become self‐cleaning upon water action in response to the Bη of surface counteranions sign‐switching with increasing water temperature. Courtesy of surface counter‐anions with Bη>0, self‐cleaning PDADMA coatings enable not only conversion of conventional meshes into self‐cleaning membranes for oil/water separation, but also regioselective maneuver of oil flow on polycationic surfaces according to the Bη sign of surface counteranions patterned atop. [ABSTRACT FROM AUTHOR]

Abstract: Hydrophobic reduced graphene oxides (rGOs) were generated in agarose hydrogel beads (AgarBs) by NaBH4 reduction of graphene oxides (GOs) initially loaded in the AgarBs. The resulting rGO‐loaded AgarBs were able to effectively adsorb organic compounds in water as a result of the attractive hydrophobic force between the rGOs in the AgarBs and the organic compounds dissolved in aqueous media. The adsorption capacity of the rGOs was fairly high even toward reasonably water‐soluble organic compounds such as rhodamine B (321.7 mg g−1) and aspirin (196.4 mg g−1). Yet they exhibited salinity‐enhanced adsorption capacity and preferential adsorption of organic compounds with lower solubility in water. Such peculiar adsorption behavior highlights the exciting possibility for adopting an adsorption strategy, driven by hydrophobic forces, in practical wastewater treatment processes. [ABSTRACT FROM AUTHOR]

In this work, uniform, quasi-spherical gold nanoparticles (Au NPs) with sizes of 31-577 nm are prepared via one-pot seeded growth with the aid of tris-base (TB). Distinct from the seeded growth methods available in literature, the present method can be simply implemented by subsequently adding the aqueous dispersion of the 17 nm Au-NP seeds and the aqueous solution of HAuCl4 into the boiling aqueous TB solution. It is found that at the optimal pH range, the sizes of the final Au NPs and their concentrations are simply controlled by either the particle number of the Au seed dispersion or the concentration of the HAuCl4 solution, while the latter enables us to produce large Au NPs at very high concentration. Moreover, as-prepared Au NPs of various sizes are coated on glass substrates to test their surface-enhanced Raman scattering (SERS) activities by using 4-aminothiophenol (4-ATP) molecules as probes, which exhibit 'volcano type' dependence on the Au NP sizes at fixed excitation wavelength. Furthermore, the Au NPs with sizes of ≈97 and 408 nm exhibit the largest SERS enhancement at the excitation wavelength of 633 and 785 nm, respectively. [ABSTRACT FROM AUTHOR]

Monodisperse,quasi-spherical silver nanoparticles (Ag NPs) withcontrolled sizes have been produced directly in water via adding theaqueous solutions of the mixtures of AgNO3and sodium citrateto boiling aqueous solutions of ascorbic acid (AA). Different compounds,including NaCl, NaBr, KI, Na2SO4, Na2CO3, Na2S, and Na3PO4, are added to the AgNO3/citrate mixture solutions toform new silver compounds with fairly low solubility in water, whichare used as precursors instead of soluble Ag+ions to synthesizeAg NPs via AA/citrate reduction. This enables us not only to producemonodisperse, quasi-spherical Ag NPs but also to tune the sizes ofthe resulting NPs from 16 to 30 nm according to the potential of newsilver precursors as well as the concentrations of anions. [ABSTRACT FROM AUTHOR]