Semiconductor and Metal Nanoparticle Formation on Polymer Spheres Coated with Weak Polyelectrolyte Multilayers

Abstract

We report the in situ formation of semiconductor and metal nanoparticles (NPs) on colloid particles precoated with weak polyelectrolyte multilayers. Poly(acrylic acid) (PAA)/poly-(allylamine hydrochloride) (PAH) multilayers were assembled on the colloid spheres by the layer-by-layer technique and by exploiting copper ions as templating entities, as demonstrated by us earlier (Adv. Funct. Mater. 2003, 13, 929). Metal sulfide and metallic nanoparticles (NPs) were formed within PAH/PAA multilayers assembled on the polymer spheres by the adsorption of metal ions onto uncompensated functional groups of the polyelectrolytes (carboxylate or ammonium moieties), followed by reaction with hydrogen sulfide or sodium borohydride. Coating architectures comprising single or multi-shell NP layers were prepared, depending on the combination and sequence of weak and strong polyelectrolytes used for confining nanoparticle formation. The presence of the NPs within the polyelectrolyte matrixes was confirmed by UV-vis spectroscopy, energy-dispersive X-ray analysis, and transmission electron microscopy. We demonstrate that the method used permits the formation of organicinorganic heterostructures incorporating a diverse range of NPs, ranging from sulfides such as PbS to metals such as gold.

Self‐Assembling Nanoparticles at Surfaces and Interfaces

“…[95, 105a] Nanoparticles, such as Fe 3 O 4 , Au@SiO 2 , and CdTe, have been coated on colloidal microspheres, with the possibility of functionalizing the microsphere surfaces. [95,208,209] For example, polystyrene spheres, coated a few hundred nanometers by poly(diallyldimethylammonium chloride) (PDDA), can be covered with a controllable shell of SiO 2 nanoparticles. [95] Furthermore, Lee et al achieved assembly of CdTe nanoparticles with gold NCs using a thin layer of poly(ethyleneglycol) (PEG).…”

Influence of assembly pH on compression and Ag nanoparticle synthesis of polyelectrolyte multilayers

“…However, the compression makes the polycations and polyanions more closer, thus more physical entanglement of the polymers and electrovalent bonds are formed, leading to a denser structure of the multilayers [7]. On the other hand, in the PEI(PSS-MA/PDADMAC) 7 multilayers the Ag + can only complex with the protonated carboxyl groups to form COO À Ag + conjugates [23], which are then reduced to the Ag nanoparticles in the NaBH 4 solution. These facts explain the results that fewer Ag nanoparticles are formed in the compressed multilayers.…”

“…During the synthesis process, the Ag + ions first complex with the carboxylic acid groups, then were reduced into nanoparticles by NaBH 4 . After Ag + ions were reduced, a fraction of carboxyl groups in the multilayers were released, leading to the increase of ionization degree of the carboxylic acid groups in the water at neutral pH [23]. The polyelectrolyte molecules thus adopt a more flat conformation.…”

Synthesis and spectral properties of starch capped CdS nanoparticles in aqueous solution

“…Over the past 10 years extensive research has been carried out in the field of nanometer-size semiconductor particles [1][2][3][4], because they often exhibit different properties from those of the corresponding bulk semiconductor. For example, due to the quantum confinement effect, semiconductor nanoparticles show unique physical and chemical properties, such as size-dependent band-gap shifts.…”