Controllable Assembly and Separation of Colloidal Nanoparticles through a One‐Tube Synthesis Based on Density Gradient Centrifugation

Abstract

Self-assembly of gold nanoparticles into one-dimensional (1D) nanostructures with finite primary units was achieved by introducing a thin salt (NaCl) solution layer into density gradient before centrifugation. The electrostatic interactions between Au nanoparticles would be affected and cause 1D assembly upon passing through the salt layer. A negatively charged polymer such as poly(acrylic acid) was used as an encapsulation/stabilization layer to help the formation of 1D Au assemblies, which were subsequently sorted according to unit numbers at succeeding separation zones. A centrifugal field was introduced as the external field to overcome the random Brownian motion of NPs and benefit the assembly effect. Such a facile "one-tube synthesis" approach couples assembly and separation in one centrifuge tube by centrifuging once. The method can be tuned by changing the concentration of interference salt layer, encapsulation layer, and centrifugation rate. Furthermore, positively charged fluorescent polymers such as perylenediimide-poly(N,N-diethylaminoethyl methacrylate) could encapsulate the assemblies to give tunable fluorescence properties.

Perylene Bisimide Dyes with up to Five Independently Introduced Substituents: Controlling the Functionalization Pattern and Photophysical Properties Using Regiospecific Bay Substitution

“…Subsequent bay substitution with different substituents employing S N Ar reactions has been reported on a few special occasions only. ,, Similarly, since the first synthesis of tetrachloro-PTCAs in 1988, , bay substitution with four identical substituents on tetrachloro-PBIs has been reported almost exclusively. There are only a few exceptions in the literature where substitution of one, ,, two, , or three chlorines has been executed. Substitution of two chlorines has been achieved by Würthner et al and Fernández Lázaro et al .…”

Novel Metal Nanomaterials and Their Catalytic Applications

“…For example, when the temperature was below 60 °C, the catalytic reactions almost did not happen, while when the temperature was increased to 80 °C, the conversion was correspondingly increased to 9.8%; the most suitable temperature was 100 °C, and the yield of epoxidation product was 85.0%. It is worth noting that the FePt@Cu NWs could be recycled several times without any apparent catalytic degradation, the reason for which is mainly that the FePt@Cu nanostructure was retained as before and no significant loss of catalytic activity was observed which is similar to most metal nanocatalysts [28,29,30].…”

One-Step Direct Amination of Nanodiamond Surface and Facile Separation by Viscosity Gradient Centrifugation

“…Recently, density gradient centrifugation has a high degree of controllability due to the separation system. It is universal and efficient for the separation and purification of nanomaterials with different morphologies, different sizes and different synthetic systems, and becomes an efficient separation method for nanomaterials [14][15][16][17][18] . Large nanoparticles are usually denser than liquid media and are therefore suitable for separation by differences in settling velocity [19][20][21] .…”