Currently the synthesis of plasmonic nanoparticles for sensing applications mostly focuses on their shape because it is believed that nanoparticles with sharp tips provide higher sensitivities than those without. Herein, by measuring and analyzing the sensitivities of more than 74 types of nanoparticles of various shapes, sizes, and compositions, we found that, contrary to this common belief, the correlation between shape and sensitivity is much weaker than that between aspect ratio and sensitivity. Among all the parameters investigated here, including size, shape, composition, aspect ratio, crosssectional area, and initial plasmonic resonance frequency, the aspect ratio (R) is the key parameter that controls the nanoparticle sensitivity (S) following an empirical equation, S = 46.87R + 109.37. Other parameters have much less influence on the nanoparticle sensitivity to refractive index changes. The stronger dependence of the sensitivity on aspect ratio than on shape encourages us to reassess the current focus of nanoparticle synthesis chemistry. In addition, the S−R linear relationship determined here can be used as a design rule for future synthesis and fabrication of highly sensitive nanomaterials for chemical, biological, biomedical, and environmental sensing.
Block copolymer-based porous carbon fibers (PCFs) exhibit hierarchical porous structures, high surface areas, and exceptional electrochemical properties. However, the design of block copolymers for PCFs remains a challenge in advancing this type of fibrous material for energy storage applications. Herein, we have systematically synthesized a series of poly(methyl methacrylate-block-acrylonitrile) (PMMA-b-PAN) with well-controlled molecular weights and compositions to study the physical and electrochemical properties of PCFs. PCFs are synthesized via electrospinning, selfassembly, oxidation, and pyrolysis with no additives or chemical activation. By adjusting the molecular weights of polyacrylonitrile (PAN) and poly(methyl methacrylate) blocks, we have achieved tunable mesopore sizes ranging from 10.9 to 18.6 nm and specific capacitances varied from 144 to 345 F g −1 at 10 mV s −1 . Interestingly, regardless of the volume fraction of PAN, all the block copolymers produce hierarchical porous structures because of the self-assembly and cross-linking of PAN. Block copolymers with a PAN volume fraction of near 50% show the highest surface areas and gravimetric capacitances. The PCFs represent a new platform material with tunable specific surface areas, pore sizes, and electrochemical properties. This work has an immediate impact on designing block copolymers to create PCFs for applications in energy conversion and storage.
Pyrolysis temperature is an important processing parameter that determines the physical and electrochemical properties of block copolymer-based porous carbon fibers.
A new class of 3D functionally graded plasmonic materials and devices manufactured through 3D printing is presented. Up to eight different plasmonic inks are interwoven into a single functionally graded construct. Both continuous and discrete 3D gradients in plasmonic properties are realized. The approach is applied toward engineering of next‐generation plasmonic devices. Specifically, the manufacturing of a novel functionally graded plasmonic night‐vision contact lens is demonstrated.
After condensation with polystyrene oligomers, ultra-low-molecular-weight polyetherimide-based triblock copolymers form disordered nanostructures with domain sizes less than 8 nm.
Herein, a poly(vinylpyrrolidone) (PVP)-free method is described for synthesizing Ag nanoplates that have localized surface plasmon resonance in the near-infrared (NIR) range. Citrate-capped Ag spherical nanoparticles are first grown into small Ag nanoplates that resonate in the range of 500-800 nm. The small Ag nanoplates are used as seeds to further grow into large Ag nanoplates with a lateral dimension of 100-600 nm and a plasmon resonance wavelength of 800-1660 nm and above. The number of growth steps can be increased as desired. Without introducing additional citrate into the solutions of small Ag nanoplate seeds, large Ag nanoplates can be synthesized within minutes. The entire synthesis is completely PVP free, which promotes the nanoparticle growth along the lateral direction to form large Ag nanoplates. The multistep growth and the minimum usage of citrate are essential for the fast growth of high-aspect-ratio Ag nanoplates resonating in the NIR range.
State-of-the-art commercial light-reflecting glass is coated with a metalized film to decrease the transmittance of electromagnetic waves. In addition to the cost of the metalized film, one major limitation of such light-reflecting glass is the lack of spectral selectivity over the entire visible and near-infrared (NIR) spectrum. To address this challenge, we herein effectively harness the transmittance, reflectance, and filtration of any wavelength across the visible and NIR, by judiciously controlling the planar orientation of two-dimensional plasmonic silver nanoplates (AgNPs) in polymer nanocomposites. In contrast to conventional bulk polymer nanocomposites where plasmonic nanoparticles are randomly mixed within a polymer matrix, our thin-film polymer nanocomposites comprise a single layer, or any desired number of multiple layers, of planarly oriented AgNPs separated by tunable spacings. This design employs a minimal amount of metal and yet efficiently manages light across the visible and NIR. The thin-film plasmonic polymer nanocomposites are expected to have a significant impact on spectral-selective light modulation, sensing, optics, optoelectronics, and photonics.
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