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1. Hybrid Ag–LiNbO 3 nanocomposite thin films with tailorable optical properties

   https://doi.org/10.1039/D0NA00975J  

   Huang, Jijie ; Zhang, Di ; Qi, Zhimin ; Zhang, Bruce ; Wang, Haiyan ( February 2021 , Nanoscale Advances)

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   Ag nanostructures exhibit extraordinary optical properties, which are important for photonic device integration. Herein, we deposited Ag–LiNbO 3 (LNO) nanocomposite thin films with Ag nanoparticles (NPs) embedded into the LNO matrix by the co-deposition of Ag and LNO using a pulsed laser deposition (PLD) method. The density and size of Ag NPs were tailored by varying the Ag composition. Low-density and high-density Ag–LNO nanocomposite thin films were deposited and their optical properties, such as transmittance spectra, ellipsometry measurement, as well as angle-dependent and polarization-resolved reflectivity spectra, were explored. The Ag–LNO films show surface plasmon resonance (SPR) in the visible range, tunable optical constants and optical anisotropy, which are critical for photonic device applications. 

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2. Plasmonic Response of Light-Activated, Nano-Gold Doped Polymers

   https://doi.org/10.1557/adv.2019.286  

   Andriolo, Jessica M. ; Joseph, McKenzie L. ; Brockway, Molly C. ; Skinner, Jack L. ( January 2019 , MRS Advances)

   Abstract Incorporation of metallic nanoparticles (NPs) in polymer matrix has been used to enhance and control dissolution and release of drugs, for targeted drug delivery, as antimicrobial agents, localized heat sources, and for unique optoelectronic applications. Gold NPs in particular exhibit a plasmonic response that has been utilized for photothermal energy conversion. Because plasmonic nanoparticles typically exhibit a plasmon resonance frequency similar to the visible light spectrum, they present as good candidates for direct photothermal conversion with enhanced solar thermal efficiency in these wavelengths. In our work, we have incorporated ∼3-nm-diameter colloidal gold (Au c ) NPs into electrospun polyethylene glycol (PEG) fibers to utilize the nanoparticle plasmonic response for localized heating and melting of the polymer to release medical treatment. Au c and Au c in PEG (PEG+Au c ) both exhibited a minimum reflectivity at 522 nm or approximately green wavelengths of light under ultraviolet-visible (UV-Vis) spectroscopy. PEG+Au c ES fibers revealed a blue shift in minimum reflectivity at 504 nm. UV-Vis spectra were used to calculate the theoretical efficiency enhancement of PEG+Au c versus PEG alone, finding an approximate increase of 10 % under broad spectrum white light interrogation, and ∼14 % when illuminated with green light. Au c enhanced polymers were ES directly onto resistance temperature detectors and interrogated with green laser light so that temperature change could be recorded. Results showed a maximum increase of 8.9 °C. To further understand how gold nanomaterials effect the complex optical properties of our materials, spectroscopic ellipsometry was used. Using spectroscopic ellipsometry and modeling with CompleteEASE® software, the complex optical constants of our materials were determined. The complex optical constant n (index of refraction) provided us with optical density properties related to light wavelength divided by velocity, and k (extinction coefficient) was used to show the absorptive properties of the materials. 

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3. Effect of polymer–nanoparticle interactions on solvent-driven infiltration of polymer (SIP) into nanoparticle packings: a molecular dynamics study

   https://doi.org/10.1039/c9me00148d  

   Venkatesh, R. Bharath ; Zhang, Tianren ; Manohar, Neha ; Stebe, Kathleen J. ; Riggleman, Robert A. ; Lee, Daeyeon ( March 2020 , Molecular Systems Design & Engineering)

   Naturally occurring nanocomposites like nacre owe their exceptional mechanical properties to high loadings of platelets that are bridged by small volume fractions of polymers. Polymer infiltration into dense assemblies of nanoparticles provides a powerful and potentially scalable approach to manufacture bio-inspired nanocomposites that mimic nacre's architecture. Solvent-driven infiltration of polymers (SIP) into nanoparticle packings formed on top of glassy polymer films is induced via capillary condensation of a solvent in the interstitial voids between nanoparticles (NP), followed by plasticization and transport of polymers into the liquid-filled pores, leading to the formation of the nanocomposite structure. To understand the effect of polymer–nanoparticle interactions on the dynamics of polymer infiltration in SIP, we perform molecular dynamics simulations. The mechanism of polymer infiltration and the influence of interactions between polymer and NPs on the dynamics of the process are investigated. Depending on the strength of interaction, polymer infiltration either follows (a) dissolution-dominated infiltration where plasticized polymer chains remain solvated in the pores and rapidly diffuse into the packing or (b) adhesion-dominated transport where the chains adsorb onto the nanoparticle surface and move slowly through the nanoparticle film as a well-defined front. A non-monotonic trend emerges as the adhesion strength is increased; the infiltration of chains becomes faster with the co-operative effect of adhesion and dissolution as adhesion increases but eventually slows down when the polymer–nanoparticle adhesion dominates. 

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4. Collective multipole oscillations direct the plasmonic coupling at the nanojunction interfaces

   https://doi.org/10.1073/pnas.1909416116  

   Hooshmand, Nasrin ; El-Sayed, Mostafa A. ( September 2019 , Proceedings of the National Academy of Sciences)

   We present a systematic study of the effect of higher-multipolar order plasmon modes on the spectral response and plasmonic coupling of silver nanoparticle dimers at nanojunction separation and introduce a coupling mechanism. The most prominent plasmonic band within the extinction spectra of coupled resonators is the dipolar coupling band. A detailed calculation of the plasmonic coupling between equivalent particles suggests that the coupling is not limited to the overlap between the main bands of individual particles but can also be affected by the contribution of the higher-order modes in the multipolar region. This requires an appropriate description of the mechanism that goes beyond the general coupling phenomenon introduced as the plasmonic ruler equation in 2007. In the present work, we found that the plasmonic coupling of nearby Ag nanocubes does not only depend on the plasmonic properties of the main band. The results suggest the decay length of the higher-order plasmon mode is more sensitive to changes in the magnitude of the interparticle axis and is a function of the gap size. For cubic particles, the contribution of the higher-order modes becomes significant due to the high density of oscillating dipoles localized on the corners. This gives rise to changes in the decay length of the plasmonic ruler equation. For spherical particles, as the size of the particle increases (i.e., ≥80 nm), the number of dipoles increases, which results in higher dipole–multipole interactions. This exhibits a strong impact on the plasmonic coupling, even at long separation distances (20 nm). 

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5. Effect of vapor phase ethylenediamine crosslinking of matrimid on alcohol vapor sorption and diffusion

   https://doi.org/10.1002/app.44771  

   Stanford, John P. ; Pfromm, Peter H. ; Rezac, Mary E. ( March 2017 , Journal of Applied Polymer Science)

   This work examines the sorption, diffusion, and polymer relaxation behavior for water and C1‐C7 alcohol vapors at 30  °C in ethylenediamine vapor‐phase crosslinked Matrimid. Ethylenediamine is sufficiently volatile that crosslinking can occur by exposing the polymeric film to saturated vapor, in contrast to more conventional means of dissolving the crosslinker in a solvent and immersing the polymeric film in the solution. The vapor‐phase exposure method avoids the use of additional solvent and undesired solvent‐induced swelling. Sorption isotherms demonstrate that water and C1‐C5 alcohols do not appreciably differ for unmodified and crosslinked Matrimid; however, an approximate 90% reduction in sorption was determined for hexanol and heptanol. A minor impact on diffusion coefficients for water, methanol, and ethanol was observed, while those of propanol and butanol were reduced over an order of magnitude. Relaxation kinetics were similarly unchanged for water and C1‐C3 alcohols, while being significantly reduced for butanol and higher alcohols. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci.2017,134, 44771.

    

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