Nanorod-polymer composites

Huynh WU Dittmer JJ Teclemariam N Milliron DJ Altvisatos AP Barnham KWJ, Charge transport in hybrid nanorod-polymer composite photovoltaic cells, Rhys. Rev. B, 2003, 67, 115326. 

Cahn-Hilliard Brownian Dynamics Model of Nanorod Polymer Composites... 

Recently, there have been a nirmber of reviews on polymer nanocomposites within this relatively broad topic, there is one specific area that has not, however, been extensively examined namely, mixtures involving nanoscopic rods and polymers. Here, we focus on nanorod polymer composites, where nanoscale rod-like particles are blended with homopolymers, polymer blends, or diblock copolymers. The spatial organization of nanorods within a polymeric material can have a dramatic effect on the composites maaoscopic properties. By elucidating these stracture-property correlations, researchers can pave the way to manipulating morphologies to aeate materials with superior performance and develop... 

Figure 1 The morphology of nanorod polymer composites. The contour plot depicts the order parameter of the CH-BD model and reveals the morphology of the polymer blend. The black lines represent the position and orientation of the nanorods, (a) The early-time droplet morphology of a phase-separating polymer blend is shown, with no inclusions present. Inset, the dispersion of nanorods in a homopolymer is depicted, (b) Combining the phase separation dynamics of the polymer blend and the dispersion of nanorods results in a bicontinuous structure.

As an example of how the LSM can be applied to nanorod polymer composites, we take the morphological information shown in Figure 1 and use this as the input into this mechanical model. Figure 2 shows both the normal stress and strain fields for the randomly dispersed rods in Figure 1(a) and the... 

To investigate the electrical properties of nanorod polymer composites, we can use a finite difference approximation of the continuum equations for electrical transport. The condition for the conservation of current, J, in a closed electrical circuit is V-J = 0. The current density and electric field are related through Ohm s law, J = GE, where G is the conductivity. Therefore, the conservation of current is... 

The high aspect ratio of nanorods can facilitate charge transport, while the handgap can he tuned by vaiying the nanorod radius. This enables the absorption spectmm of the devices to be tailored to overlap with the solar emission spectmm, whereas traditionally polymer absorption has been limited to only a small fraction of the incident solar irradiation. At present, the nanorods in polymer solar cells are typically incorporated into a homopolymer matrix. An alternative to this approach is to incorporate the nanorods into either a polymer blend or diblock copolymer system. The photovoltaic properties of nanorod polymer composites could potentially be improved due to the percolation of nanorods, and the presence of continual electrical pathways, from the DA interfaces to the electrodes. To test this hypothesis, we use the distribution of nanorods from the self-assembled stmcture in Figure 1(b) as the input into a drift-diffusion model of polymer photovoltaics. 

We now couple the GH-BD model of nanorod polymer composites with the above photovoltaic model. In particular, we feed the morphology from Figure 1(b) into the drift-diffusion model and elucidate the photovoltaic properties of this self-assembled stmcture. Figure 4 shows the exciton, electron, and hole concentrations in the device. 

Figure 4 Photovoltaic performance of a nanorod polymer composite. The morphology from our simulation of nanorods corralled into the phase-separating polymer blend is fed into a photovoltaic model. The (a) exciton concentrations, (b) electron concentrations, and (c) hole concentrations are depicted. Despite the nanoscale dimensions (and, therefore, high exciton dissociation rates) and the bicontinuous nature of the morphology, the rods do not provide a continuous pathway for charge transport to the electrodes. Anisotropic ordering of the nanorods in the vertical direction is expected to significantly improve the power conversion efficiencies of these devices.

There has been extensive work on core/shell nanoparticles where the core is magnetic Fe304, PbS and the shell is a polymer that provides biocompatibility and long-term stability [121]. PbS particles are formed in a Pb(AOT)2/polymer composite [122], according to whether this has an ordered layer structure or not, nanorods or spherical particles are obtained. 

In a recent pubHcation, Alivisatos and co-workers reported the making of hybrid nanorods-polymer solar cells and their properties [122]. These solar cells were made by spin casting of a solution of both poly(3-hexylthiophene) (hole acceptor) and CdSe nanorods (electron acceptor) onto indium tin oxide glass substrates coated with poly(ethylene dioxythiophene) doped with polystyrene sulfonic acid and aluminum as a top contact. Nanorods have been used in composites so as to improve the carrier mobiHty. Indeed, the latter can be high for some inorganic semiconductors, but it is typically extremely low for conjugated polymers [123]. The use of the nanorods suppHes an interface for the charge transfer as well as a direct path for electrical transport. Also, because of their anisotropy, self-assembly of these nanorods is observed by electron microscopy. It shows... 

One-dimensional nanostructured polymer composite materials include nanowires, nanorods, nanotubes, nanobelts, and nanoribbons. Compared to the other three dimensions, the first characteristic of one-dimensional nanostructure is its smaller dimension structure and high aspect ratio, which could efficiently transport electrical carriers along one controllable direction, thus is highly suitable for moving charges in integrated nanoscale systems (Tran et al., 2009). The second characteristic of one-dimensional nanostructure is its device function, which can be exploited as device elements in many kinds of nanodevices. With a rational synthetic design, nanostructures with different diameters/... 

C. J. Murphy and C. J. Orendorff, Alignment of gold nanorods in polymer composites and on polymer surfaces. Advanced Materials, 17(18), 2173-2177 (2005). 

Figure 3 Current density in (a) nanorod homopoiymers composites and (b) nanorods corraiied in a poiymer biend structure. The nanorods are taken to be 100 times more conductive than the polymer and the perco-iating supramoiecuiar structure in (b) results in higher current densities and a more conductive composite.

PP-g-MA) silicate nanocomposites and intercalated thermoset silicate nanocomposites for flame-retardant applications were characterised by XRD and TEM [333], XRD, TEM and FTIR were also used in the study of ID CdS nanoparticle-poly(vinyl acetate) nanorod composites prepared by hydrothermal polymerisation and simultaneous sulfidation [334], The CdS nanoparticles were well dispersed in the polymer nanorods. The intercalation of polyaniline (PANI)-DDBSA (dodecylbenzene-sulfonate) into the galleries of organo-montmorillonite (MMT) was confirmed by XRD, and significantly large 4-spacing expansions (13.3-29.6A) were observed for the nanocomposites [335],... 

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