6/3/2013 Ultralong Gold Nanoparticles/Block Copolymers Hybrid Cylindrical Micelles

Paper:

Ultralong Gold Nanoparticles/Block Copolymers Hybrid Cylindrical Micelles: a Strategy Combining Surface Templated Self-Assembly and Rayleigh Instability

Jiangping Xu, Yutian Zhu, Jintao Zhu and Wei Jiang

Nanoscale, 2013, Accepted Manuscript
DOI: 10.1039/C3NR01296D
Received 14 Mar 2013, Accepted 20 May 2013
First published online 21 May 2013

Keywords: gold nanoparticles, Rayleigh instability, BCP TSA,

Dead Body: When NPs are synthesized in solution outside of the BCP, they can be bottom-up "encapsulated" or inserted into the polymer, but it is hard to achieve cylindrical micells of the NPs. Sometimes it can be achieved, but it takes a good bit of time. Locations and efficiency are difficult. Using top-down, Rayleigh instability can be also used to produce NP micelles, but isn't very reliable.

Solution: Use combined bottom-up and top-down: TSA of cylinderical BCP with Rayleigh breakup of gold nanowires.


What are the most interesting results: 

• Fine control over placement of NPs in center of cylindrical micelles, diameter of the NPs and cylindrical micelles.
• 7 days of stirring the PS-cylindrical-micelles with the AuNWs results in the AuNPs through Rayleigh breakdown.
• AuNPs increase in size to decrease interfacial energy
• Polymer shell around AuNWs is 10.1 nm +/- 2.1 nm, but total micelle diameter increase with # of NWs inside of it
• Diameter of AuNPs increase with # of AuNWs per micelle and density of AuNWs
• Diameter more polydisperse at high AuNW concentration, but more uniform at lower concentration
• The NPs are highly spatially concentrated in the center of the cylindrical micelles - see statistics
• Experimental values of NP diameter and inter-particle spacing aligns somewhat with theoretical values for Rayleigh breakup

What are the most interesting discussions: 

• BCP usually spherical domain, but AuNWs in self assembly help to make cylindrical micelles instead of spheres.
• DMF swells PAA more
• H2O interacts with PS and AuNWs, increasing their interaction - seem more on this discussion
• long AuNW to short AuNW to AuNP breakdown proceeds
• The density of AuNWs must be in correct range, not too low or too high
• Viscosity of the PS encapsulation of the Au is high, and therefore the characteristic breakup time for the NPs is larger than normally predicted.
• Without the PS shell, the AuNPs would coalesce into larger NPs, but the shell keeps them broken from Rayleigh instability

Materials used: 

oleylamine-capped AuNWs, PS-b-poly(acrylic acid) (144-b-22) (precipitation method: DMF/THF/H20 5:1:0.8,

How this applies to my work:

• Including NWs or NPs in the solution with solvent annealing can considerably change the final morphology
• NPs can evolve within the BCP after being infiltrated, and don't have to be infiltrated as the final form.
• How can this be used for bio, plasmonic, or further templating?
• Can you make a good sensor with this hybrid array?  If you have so many NPs in a material, can you see a significant UV/Vis shift?
• If the breakdown is fast enough, can you use the diameter of the NPs as an indicator of something bigger in the polymer or in the solvent annealing?

Applications:

Cited - Nanoelectronics, plasmonics, medicine delivery, thermal therapy

My own - sensors (either UV/Vis or measuring characteristics)