Morphological control to precisely tailor the energy absorption bands of plasmonic particles is improving constantly, with efforts to improve the monodispersity of the designed particles leading to sharper plasmonic features in controlled spectral regions. Transitioning these highly tailored plasmonic additives into a robust polymer composite platforms while retaining their specified plasmonic features has proven challenging, with the elevated temperatures and mechanical forces involved in composite manufacturing resulting in particle agglomeration and morphology alterations. In this work, thermally stable protecting layers are developed onto tailored silver nanoplate (Ag-NPL) plasmonic additives to facilitate their survivable processing at elevated temperature. The produced coatings allow for their implementation in a facile, low-cost method to produce uniform dichroic optical polarizers based on the protected Ag-NPLs in a polymer matrix. Nanocomposites are obtained through an extrusion and injection molding process, which is shown to induce alignment of anisotropic particles based on sheer forces. As the optical position of the resonances is dependent on the morphology of the additive, and unlike other methods where the anisotropy in the NP is induced in situ, our method can be easily adapted to varying optical regimes by modifying the size and shape of the initial additive. Furthermore, the method presented in this work forgoes the need for a polymer stretching alignment mechanism which enables the ability to use various types of anisotropic particles with visible and near-infrared operating regimes.

Evaluation and prediction of multicomponent diffusion in polymers is an important area of research since it occurs in several fields associated with mass transport including membrane separations, preparation of polymer films, and material decontamination. The functional dependence of the diffusivity on the composition in a multicomponent system is critical for accurately predicting transport in these processes. Here, the composition dependent diffusivity of 2,5-lutidine in polyurethane with acetonitrile as a co-penetrant was experimentally determined using Fourier transform infrared spectroscopy (FTIR) to acquire differential sorption curves for lutidine across the composition space and fitting a multicomponent diffusion model to the data. The free volume theory of diffusion was used to develop a mathematical expression for the composition-dependent diffusivity, and shows good agreement with the experimental data for both single and multicomponent cases. The lutidine diffusivity was found to vary up to two orders of magnitude with ACN concentration, and the importance of capturing this dependence quantitatively is highlighted by applying the multicomponent diffusion model with the best-fit values to predict previously published data for lutidine desorption from polyurethane.

A fundamental understanding of chemical interactions and transport mechanisms that result from introducing multiple chemical species into a polymer plays a key role in the development and optimization of membranes, coatings, and decontamination formulations. In this study, we explore the solvent-assisted desorption of a penetrant (2,5-lutidine) in polyurethane with aprotic (acetonitrile) and protic (methanol) solvents. Chemical interactions between solvent, penetrant, and polymer functional groups are characterized via time-resolved Fourier transform infrared spectroscopy (FTIR) during single and multicomponent exposures. For both solvents, an increase in the extraction rate of the penetrant is observed when the solvent is applied during desorption. Inspection of the FTIR spectra reveals two potential mechanisms that facilitate the enhanced desorption rate: (1) penetrant/solvent competition for hydrogen donor groups on the polymer backbone and (2) disruption of the self-interaction (cohesive forces) between neighboring polymer chains. Finally, the aprotic solvent is found to generate an order of magnitude greater desorption rate of the penetrant, which is attributed to a greater disruption of the self-interaction during penetrant desorption compared to the protic solvent and the inability of an aprotic solvent to form larger and potentially slower penetrant-solvent complexes.

Emerging nanoplasmonics utilizing asymmetric core-shell architectures present opportunities to precisely control the plasmon position and signal amplification within a single particle. In particular, asymmetric gold nanorods, assembled into a “matryoshka” structure (gold nanorod core, silica spacer shell, and outer gold shell) have the unique ability to enhance and precisely manipulate the plasmonic signature when compared to single gold nanorods via the generation of hybridized plasmonic modes. Currently, the fundamental understanding of the impact of the gold nanorod matryoshka dimensional parameters on the subsequent resonance behavior is incomplete. In this work, we elucidate the structural-hybridized resonance relationship of gold nanorod nanomatryoshka designs by experimentally varying the key geometrical properties; including silica spacer thickness, gold nanorod core size, and gold shell thickness/continuity.

One of the chief impediments to the wider adoption of nanocomposites is the challenge of maintaining nanoscale features while employing bulk preparative techniques. Nanoparticle fillers may tend to aggregate or become destabilized during processing at temperatures required to process engineering thermoplastics. We report a study where nanoparticles of varying aspect ratios were stabilized with robust shells and then compounded using a laboratory scale extruder. Optical plaques were produced via injection molding, and the resultant nanocomposites were assessed for their optical and morphological properties.

: In this work we demonstrated a new methodology to create asymmetric magnetic nanorods with a plasmonically active gold outer shell. The multistage approach involves the synthesis of a precursor iron (III) oxide-hydroxide (FeOOH) nanorod, where the incorporation of a protective silica (SiO2) shell allows for the material/morphology to survive hydrothermal treatment and subsequent transition to magnetically responsive iron (II, III) oxide (Fe3O4). On the magnetic nanorodSiO2 particle, a thin gold layer is grown to directly introduce tailorable plasmonic properties. This approach is demonstrated applicable to both spherical and asymmetric morphologies, allowing the hybrid materials to be readily engineered for precise magnetic and plasmonic responses.

Manipulation of the electronic and optical properties of plasmonic nanomaterials offers unique and exciting opportunities for several fields including opto-electronics, bio-medical engineering and photovoltaics. In particular, gold nanorods (GNR) represent a class of plasmonic nanomaterials that provide tunable optical properties from the visible to the near infrared regime. Herein, we have developed a highly effective method to prepare polymer nanocomposites (PNCs) doped with GNR additives utilizing extrusion and injection molding. A key outcome is that the process is amenable to scalable manufacturing and can produce highly reproducible PNCs with excellent optical properties. The resultant PNCs display good particle dispersion, minimal aggregation and a high retention of the optical properties as confirmed by UV-Vis spectroscopy and transmission electron microscopy. The nano-additives are incorporated into different thermoplastics to demonstrate the versatility of this method for different matrices and to demonstrate stability over the extrusion processing temperature range (235-335 degrees C). Furthermore, the tractability of this method is demonstrated by incorporating GNRs with different morphologies (aspect ratio, stabilizing layer, etc.). Finally, partial flow-induced alignment is demonstrated, the degree of which is modulated by the length and monodispersity of the GNR nano-additive. Ultimately, we report an optimized methodology to produce high quality GNR-PNCs with tailorable optical properties that can be adapted for scalable manufacturing.

The transition of highly functional nanomaterials into scalable composite manufacturing processes often leads to the deterioration of the desired nanomaterial properties. In this work, selective coating methodologies are employed to protect optically-tailored nanoplasmonic materials against the high temperature/high shear environments associated with extrusion and injection molded polymer nanocomposites. Optically tuned plasmonic nanomaterials including silver nanoplates, gold nanorods, gold nanostars, and noble metal shells have been produced with tailored resonances across the visible and nIR spectrum. Protective coatings are created on the materials, including PEG, polymer stabilizers, and silica shells, to enhance the survivability of the nanomaterial's morphology/physical properties during high-stress processing conditions. The stability and thermal effects of the processing on the additives is fully investigated, and the methods are optimized to allow for the creation of plasmonic polymer nanocomposites that preserve their tailored resonance properties at elevated processing temperatures. An additional focus will be presented towards coupling the plasmon energy to hybridized RAMAN tags and chromophore molecules in the developed composites.

Nanoscale engineering of noble metal particles has provided numerous material configurations to selectively confine and manipulate light across the electromagnetic spectrum. Transitioning these materials to a composite form while maintaining the desired resonance properties has proven challenging. In this work, the successful integration of plasmon-focusing gold nanostars (GNSs) into polymer nanocomposites (PNCs) is demonstrated. Tailored GNSs are produced with over a 90% yield and methods to control the branching structures are shown. A protective silica capping shell is employed on the nanomaterials to facilitate survivability in the high temperate/high shear processing parameters to create optically-tuned injection molded PNCs. The developed GNS PNCs possess dichroic scattering and absorption behavior, opening up potential applications in the fields of holographic imaging, optical filtering and photovoltaics.

A versatile method to rapidly synthesize high quality gold nanorods through the use of a microwave terminated growth process is presented. Traditional nanorod growth procedures require lengthy growth periods in addition to the use of additional materials/steps to terminate growth, including extra reagents, precise control of reagent concentrations, and tuning of environmental factors such as temperature or pH. Utilizing brief, high power microwave irradiation exposure, one can improve the nanorod monodispersity and achieve a significant reduction in the level of nanoparticle impurities within the sub-30 min growth regime without the need of additional reagents or pH adjustments. In addition to the increased synthesis efficiency, microwave-terminated gold nanorods yielded an increase in the longitudinal: transverse plasmon peak ratios, signifying a reduction in nanoparticle impurities with samples treated at 24 min versus traditional 24 h growth procedures without microwave termination. Utilizing the microwave methodology also yields an improved homogeneity of the produced rods as shown with a narrower spectral full width at half maximum compared to traditionally grown gold nanorods.

: The stability of gold nanorods (GNRs) is essential for their integration into functional materials. In this work, the stability of GNRs in organic and aqueous solvents is improved by using various stabilizing layers. The retention of the optical properties of the GNRs is confirmed by ultraviolet-visible and zeta-potential measurements. Additionally, 3 different methods are applied to achieve self-assembly of GNRs onto copper grids. Ultimately, these studies demonstrate the versatility and stability of GNRs with regard to their use in integrated functional systems.

Selective radial growth of gold nanorods with tailored optical absorption control between 550–850 nm.

Intrinsically conducting polymers belong to a class of organic polymers with intriguing electronic and physical properties specifically for electro-optical applications. Significant interest into doped polyaniline (PAni) can be attributed to its high conductivity and environmental stability. Poor dissolution in most solvents has thus far hindered the successful integration of PAni into commercial applications, which in turn, has led to the investigations of various deposition and acidic doping methods. Physical vapor deposition methods, including D.C. magnetron sputtering and vacuum thermal evaporation, have shown exceptional control over physical film properties (thickness and morphology). However, resulting films are less conductive than films deposited by conventional methods (i.e., spin and drop casting) due to interruption of the hyperconjugation of polymer chains. Specifically, vacuum thermal evaporation requires a postdoping process, which results in incorporation of impurities and oxidation of surface moieties. In this contribution, thermally evaporated films, sequentially doped by vacuum evaporation of an organic acid (camphorsulfonic acid, CSA) is explored. Spectroscopic evidence confirms the successful doping of PAni with CSA while physical characterization (atomic force microscopy) suggests films retain good morphology and are not damaged by the doping process. The procedure presented herein also combines other postpreparation methods in an attempt to improve conductivity and/or substrate adhesion.

Nanohole arrays exhibit unique surface plasmon resonance (SPR) characteristics according to hole periodicity, diameter, and excitation wavelength (λSPR). This contribution investigates the SPR characteristics and surface sensitivity of various nanohole arrays with the aim of tuning the parameters for optimal sensing capability. Both the Bragg surface plasmons (SPs) arising from diffraction by the periodic holes and the traditional propagating SPs are characterized with emphasis on sensing capability of the propagating SPs. Several trends in bulk sensitivity and penetration depth were established, and the surface sensitivity was calculated from bulk sensitivity and penetration depth of the SPs for different analyte thicknesses. Increased accuracy and precision in penetration depth values were achieved by incorporating adsorbate effects on substrate permittivity. The optimal nanohole array conditions for highest surface sensitivity were determined (820 nm periodicity, 0.27 diameter/periodicity, and λSPR = 1550 nm), which demonstrated an increase in surface sensitivity for the 10 nm analyte over continuous gold films at their optimal λSPR (1300 nm) and conventional visible λSPR (700 nm).