Layer‐by‐Layer Assembly of Polyelectrolyte and Nanoparticles, Monitored by Capillary Electrophoresis

Abstract

Layer-by-layer (LBL) assembly is a versatile nanofabrication technique, and investigation of its kinetics is essential for understanding the assembly mechanism and optimizing the assembly procedure. In this work, the LBL assembly of polyelectrolyte and nanoparticles were monitored in situ by capillary electrophoresis (CE) for the first time. The assembly of poly(diallyldimethylammonium chloride) (PDDA), and gold nanoparticles (AuNPs) on capillary walls causes surface-charge neutralization and resaturation, and thus yields synchronous changes in the electroosmotic flow (EOF). The EOF data show that formation of multilayers follows first-order adsorption kinetics. On the basis of the fit results, influencing factors, including number of layers, concentration of materials, flow rate, and size of AuNPs, were investigated. The stability and robustness of the assembled coatings were also characterized by CE. It was found that degradation of PDDA layers follows first-order chemical kinetics, while desorption of AuNPs takes place in a disorderly manner. The substrate strongly affects assembly of the underlying layer, while this effect is rapidly screened with increasing number of layers. Furthermore, we demonstrate that the EOF measuring step does not disturb LBL assembly, and the proposed method is reliable and rugged. This work not only studies in detail the LBL adsorption/desorption process of polyelectrolyte and nanoparticles, but also offers an alternative tool for monitoring multilayer buildup. It may also reveal the potential of CE in fields other than analytical separation.

Permanent gold nanoparticle coatings on polyelectrolyte multilayer modified capillaries for open-tubular capillary electrochromatography

“…It should be noted that in the column preparation process, the time for nega- tively charged AuNPs to stay in the capillary was 12 h, while that for positively charged AuNPs was only 30 min. Nevertheless, the surface coverage of the Type I column is still higher than that of Type III even though recent research showed that the adsorption of AuNPs onto a PEM coated capillary wall is a slow process that needs at least 1 h to reach saturation of the AuNPs [36,46]. Thus, this experimental result also indicates that the adsorption rate of DMAP capped AuNPs onto the PEM coated capillary wall is very fast.…”

CE of inorganic species – A review of methodological advancements over 2009–2010

“…CZE 138, 139, MEKC 139, or CE using a polymer additive as sieving medium 140. Likewise, CE in different modes can be utilized to verify the conjugation of quantum dots with proteins 141, ligand molecules 142, and antibodies 143; to separate nanoparticles of TiO 2 and Al 2 O 3 from a mixed suspension 144 or gold nanoparticles (Au‐NP) at trace concentrations following reversed electrode‐polarity stacking 145, 146; to characterize differently functionalized bifunctional Fe 2 O 3 –SiO 2 nanoparticles 147 or the ligand‐protected Au‐NP 148; to monitor the assembly of a polyelectrolyte and Au‐NP on capillary walls 149 etc. Perhaps the most interesting example over the reviewed period concerns the CE‐ICP‐MS assaying of free and albumin‐bound Au‐NP in human urine 150.…”

Chiral Separations Using Heparin and Polyelectrolyte Multilayers in Capillary Electrophoresis

“…This deposition technique results in a multilayer complex that is predominantly stabilized by strong electrostatic interactions. [13] Many studies have been performed to better understand the adsorption and formation of PEM systems in a capillary [13][14][15][16][17][18][19][20][21] and the specific effects of various system variables, including: (1) the type of polyelectrolyte, [22][23][24][25] (2) ionic strength, [18,24,[26][27][28] (3) dynamics of counterions, [29,30] and (4) short range interactions, [24,31] on the properties of useful PEM systems. These reports have established a wide range of useful conditions for developing PEM systems with widely varied properties.…”