Self-assembly of Janus Au:Fe₃O₄branched nanoparticles. From organized clusters to stimuli-responsive nanogel suprastructures

Abstract

Janus nanoparticles offer enormous possibilities through a binary selective functionalization and dual properties. Their self-assembly has attracted strong interest due to their potential as building blocks to obtain molecular colloids, supracrystals and well-organized nanostructures that can lead to new functionalities. However, this self-assembly has been focused on relatively simple symmetrical morphologies, while for complex nanostructures this process has been unexplored. Here, we study the assembly of plasmonic-magnetic Janus nanoparticles with a branched (nanostar)sphere morphology.The branched morphology enhances their plasmonic properties in the near-infrared region and therefore their applicability, but at the same time constrains their self-assembly capabilities to obtain more organized or functional suprastructures. We describe the self-assembly of these nanoparticles after amphiphilic functionalization. The role of the nanoparticle branching, as well as the size of the polymercoating, is explored. We show how the use of large molecular weight stabilizing polymers can overcome the anisotropy of the nanoparticles producing a change in the morphology from small clusters to larger quasi-cylindrical nanostructures. Finally, the Janus nanoparticles are functionalized with a thermoresponsive elastin-like recombinamer. These nanoparticles undergo reversible self-assembly in the presence of free polymer giving rise to nanoparticle-stabilized nanogel-like structures with controlled size, providing the possibility to expand their applicability to multi-stimuli controlled self-assembly. † Electronic supplementary information (ESI) available: TEM images of nanoparticles and assemblies, UV-Vis spectra of functionalization and self-assembly, MALDI-TOFF and DSC of ELR, Cryo-TEM of thermo-responsive assemblies, photothermal heating prole and UV-Vis. See

3D Printed Microfluidic Device for Magnetic Trapping and SERS Quantitative Evaluation of Environmental and Biomedical Analytes

“…The same nanostar ensemble was used to calculate the SERS enhancements when excited at 785 nm, as shown in Figure S1b. One can see that the JMNSs tips act as hotspots , enhancing the local field by several orders of magnitudes without the need for aggregating them as is the case with spherical plasmonic nanoparticles. , The advantages provided by the magnetic properties of JMNSs were reported in previous studies. ,,, …”

“… 34 , 35 The advantages provided by the magnetic properties of JMNSs were reported in previous studies. 36 , 45 , 46 , 48 …”

“…34,35 The advantages provided by the magnetic properties of JMNSs were reported in previous studies. 36,45,46,48 3D Printed Microfluidic Device. A 3D printed microfluidic device was herein designed integrating a section in which the particles would accumulate under the effect of a magnetic field gradient.…”

Patchy metal nanoparticles with polymers: controllable growth and two-way self-assembly

“…37 As a result, distinct properties between the covered and exposed NP surfaces can potentially provide directional interparticle interactions to assemble patchy NPs. 25 While asymmetric patches with various chemical compositions can guide self-assembly as reported recently, [38][39][40] there is very limited controllability over the balance of attractive and repulsive interparticle interactions that play a key role in determining the self-assembly outcomes.…”

Photo-Responsive Self-Assembly of Plasmonic Magnetic Janus Nanoparticles

“…By tuning the pH, the electrostatic repulsion among the Fe 3 O 4 cores of the DNPs was adjusted, hence enabling the efficient switching between the assembled and disassembled states over several cycles . Even though several interesting reports demonstrate the self-assembly of DNPs, other stimuli such as photo-response remain unexplored. − …”