Orbital Angular Momentum from Self‐Assembled Concentric Nanoparticle Rings

Abstract

Some of these limitations-in particular, fabrication of small features and complex geometries-have been addressed with a hybrid approach, where simple lithographic templates guide the self-assembly of finer features. [1][2][3][4][5] Directed self-assembly (DSA) of block copolymers (BCPs) has successfully produced a variety of functional nanodevices, including capacitors, memory storage, and photonic crystals. [6][7][8] DSA of curved features, however, has not achieved the same level of success, despite the technological importance of ring and concentric ring patterns. Ring-based devices include zone plates, nanolenses, and optical ring resonators; certain memory storage devices, transistors, and sensors also use nanoscale ring features. [9][10][11][12][13][14][15] Compared to assembly along linear patterns, DSA of curved nanostructures has distinct requirements. In order for a lamellar or cylindrical BCP microdomain to form a ring, the polymer chains need to compress along the microdomain's inner edge and stretch along its outer edge. [16,17] This asymmetric distortion is energetically unfavorable. In solution, spontaneous formation of rings or toroids requires that the BCP blocks be chemically modified to experience self-attraction. [18,19] BCP rings and spirals have been observed within cylindrical confinement, though only a narrow set of BCP block ratios have been studied. [20][21][22][23] The confined BCP assemblies often exhibit structural degeneracy, typical of a system trapped far away from its free energy minimum state.Polymer nanostructures typically serve as etching masks for inorganic materials with the requisite electronic, magnetic, or optical properties. Alternatively, BCPs and inorganic nanoparticles (NPs) can be blended into nanocomposites, which offer additional advantages, including single-step fabrication and nanoparticle size-and arrangement-dependent properties. [24][25][26][27][28] Indeed, ordered nanocomposites with longrange alignment across one, two, and three dimensions have been obtained with DSA. However, curved features have been notably absent. Incorporated particles increase the bending moduli of their host microdomains, and thus increase the energy penalty associated with curved features. [29,30] To assemble successfully, the polymer matrix must accommodate Ring-shaped nanostructures can focus, filter, and manipulate electromagnetic waves, but are challenging to incorporate into devices using standard nanofabrication techniques. Directed self-assembly (DSA) of block copolymers (BCPs) on lithographically patterned templates has successfully been used to fabricate concentric rings and spirals as etching masks. However, this method is limited by BCP phase behavior and material selection. Here, a straightforward approach to generate ring-shaped nanoparticle assemblies in thin films of supramolecular nanocomposites is demonstrated. DSA is used to guide the formation of concentric rings with radii spanning 150-1150 nm and ring widths spanning 30-60 nm. When plasmonic nanoparticles are us...

Using Machine Learning to Predict and Understand Complex Self‐Assembly Behaviors of a Multicomponent Nanocomposite

“…[ 16 ] The system's ability to self‐regulate has proven useful in scalable fabrication of optical devices, and we expect the same principle could be applied to manufacture electronic, dielectric, and thermal transport devices. [ 3 ] The possible compositions and processing conditions of this ternary PS‐ b ‐P4VP(PDP)+NP blend occupy a tremendously large parameter space (Figure 1E). 2D slices along any pair of variables reveal complicated, interwoven interactions (Figure 1F,G).…”

“…The structure-dependent properties of nanocomposites have led to many functional devices, including energy storage, magnetic memory, optical lenses, and photonic crystals. [1][2][3][4] been applied across all areas of physical science: predicting molecular energy levels, streamlining chemical synthesis, and optimizing composite designs. [21][22][23][24] ML has also been used to predict the self-assembly of block copolymers, colloidal particles, and binary blends.…”

“…The structure‐dependent properties of nanocomposites have led to many functional devices, including energy storage, magnetic memory, optical lenses, and photonic crystals. [ 1–4 ] Currently, devices like these are designed and refined via many cycles of trial and error. The nanocomposite design process is particularly arduous because effective medium approximations do not accurately predict the properties of materials built from nanoscopic components.…”

In Situ and Ex Situ Studies of Ring-Like Assembly of Silica Nanoparticles in the Presence of Poly(propylene oxide)–Poly(ethylene oxide) Block Copolymers

“…Nanoparticle (NP) arrays have attracted great attention as they can exhibit fascinating collective properties different from those of individual NPs. , The ring-shaped NP arrays are of interest because of their unique electromagnetic properties, leading to applications in sensing, data storage, , and optical devices. , NP rings as two-dimensional structures were often fabricated on a solid substrate using electron-beam lithography , or templates, including cylindrical grooves, solid spheres, droplets, , bubbles, , and polymer films with nanosegregated structures . Fabricating NP rings in the liquid phase is desirable for producing bulk materials because free-standing NP rings can be obtained in relatively large quantities. ,− Magnetic NPs spontaneously assemble into rings owing to the flux-closure mechanisms. , Viral proteins, , polymer single crystals, and liquid–liquid phase separated nanodroplets were used as templates to arrange noble metal NPs in rings.…”