Shape-Tailored Colloidal Molecules Obtained by Self-Assembly of Model Gold Nanoparticles with Flexible Polyelectrolyte

Abstract

ABSTRACT.We study the effect of citrate to gold molar ratio (X) on the size of citrated gold nanoparticles (AuNPs). This dependence is still a matter of debate for X  3 where the polydispersity is yet minimized. Indeed, there is no consensus between experiments proposed so far for comparable experimental conditions. Nonetheless, the sole available theoretical prediction has never been validated experimentally in this range of X. We show unambiguously using 3 techniques (UV-Vis spectroscopy, dynamic light scattering and transmission electronic microscopy), 2 different synthetic approaches (Direct, Inverse) and 10 X values for each approach that AuNPs' size decay as a monoexponential with X. This result is, for the first time, in agreement with the sole available theoretical prediction by Kumar et al. on the whole studied range of X.2

Self-Assembly of Gold Nanoparticles with Oppositely Charged, Long, Linear Chains of Periodic Copolymers

“…1 Indeed, it has been shown that the electrostatic complexation of cationic gold NPs (AuNPs) with DNA enables to assemble a finite number of NPs in stable linear nanostructures in water by simple mixing. 14 Similar results were then reported with silica NPs 15 and other polyelectrolytes such as chitosan, 16,17 hyaluronic acid, 18,19 polystyrene sulfonate 20 and polylysine. 18 However, as shown theoretically 21 and experimentally 18 , the interparticle distance within these assemblies is governed by the electrostatic interactions.…”

Role of the ratio of biopolyelectrolyte persistence length to nanoparticle size in the structural tuning of electrostatic complexes

“…The past decade has witnessed great progress in NP self-assembly, yet the quantitative prediction of the architecture of NP ensembles remains a challenge. Hierarchical organizations can be triggered in solution by various mechanisms, such as van der Waals attraction [8], polymerization of functionalized NPs [9,10], lock-and-key binding, depletion [11], magnetic field [12], and electrostaticinteractions [13][14][15] to initiate the self-assembly from the NP level to the mesoscopic one.Among them, the association of charged NPs induced by complexation with (bio)polyelectrolytes (PELs) of opposite charge is a simple fast, robust, cost-efficient (bio)-process that can lead to new nano-objects, also called electrostatic complexes.In spite of this large interest, none systematic work has been undergone considering a quite simple aspect as far as chains are concerned: the effect of rigidity of the chain, namely its persistence length, which in a sensible approach, can be compared with the NP size. First approaches have been published: in a preliminary communication [13], we described the complexation between model negatively charged spherical silica NPs with radius R~10 nm and chitosan, a natural polyelectrolyte bearing positive charges with a semi-rigid backbone characterized by an intrinsic persistence length of L p~9 nm, using a combination of cryo-TEM, light, small-angle neutron and X-rays scattering.…”

Structure of nanoparticle‐polyelectrolyte complexes: Effects of polyelectrolyte characteristics and charge ratio

“…15,16 Mesoscale assemblies of polyelectrolytes (PEs) and nanocolloids (nanoparticles [NPs], proteins, macroions) into micellar [17][18][19][20] and rodlike [21][22][23] structures have been reported 24 alongside demonstrations of close-packed assembly of charged NPs using PEs. [25][26][27][28][29][30] Such approaches provide an alternative route to create supramolecular NP assemblies that are typically created via DNA grafting-mediated self-assembly, [31][32][33][34][35][36] lithography, [37][38][39][40] and evaporation-based assembly [40][41][42][43] which lack scalability and have high costs associated with their production. 40 Use of PEs to create NP assemblies can potentially overcome these limitations and provide a cost-effective alternative for the bulk production of such architectures.…”

“…Electrostatic interaction‐driven self‐assembly of charge‐bearing macromolecules and nanocolloids has garnered recent attention owing to their applications in diverse areas such as protein encapsulation, 1,2 delivery 1,3 and purification, 4–6 diagnostics, 7 biosensing, 8–10 water treatment, 11,12 catalysis 13,14 and mesoporous zeolite synthesis 15,16 . Mesoscale assemblies of polyelectrolytes (PEs) and nanocolloids (nanoparticles [NPs], proteins, macroions) into micellar 17–20 and rod‐like 21–23 structures have been reported 24 alongside demonstrations of close‐packed assembly of charged NPs using PEs 25–30 . Such approaches provide an alternative route to create supramolecular NP assemblies that are typically created via DNA grafting‐mediated self‐assembly, 31–36 lithography, 37–40 and evaporation‐based assembly 40–43 which lack scalability and have high costs associated with their production 40 .…”

“…Use of PEs to create NP assemblies can potentially overcome these limitations and provide a cost‐effective alternative for the bulk production of such architectures. Moreover, this approach also allows for tunability of the emerging structure through facile variations of the PE characteristics (backbone and ionic group chemistry, size, persistence length, charge density, and concentration), NP attributes (morphology, charge, and concentration) and solvent characteristics (ionic strength, pH, and temperature) 29,30,44 . However, this multiparameter space also makes it challenging to predict the mesoscale structure and properties of the PE‐NP assemblies.…”