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Multi-walled WS2 nanotubes (NTs) with lengths ranging from 2 to 65 μm and widths from 50 to 110 nm were synthesized in a horizontal quartz-made reactor by a process yielding NTs with aspect ratios (ARs) between ∼40 and >1000. The NTs obtained were thermally stable in air up to 400 °C but were oxidized within the temperature range 400–550 °C to produce yellow WO3 particles. Critically, 400 °C is well above the temperature used to mix additives with the majority of melt-processable polymers. The hydrophilic WS2 NTs were easily dispersed in poly(lactic) acid (PLA) using a twin-screw extruder, but the shear stresses applied during melt mixing resulted in chopping of the NTs such that the AR decreased by >95% and the tensile mechanical properties of the PLA were unchanged. Although the as-extruded unfilled PLA was >99% amorphous, the much-shortened WS2 NTs had a significant effect on the crystallization behavior of PLA, inducing heterogeneous nucleation, increasing the crystallization temperature (Tc) by ∼3 °C and the crystalline content by 15%, and significantly increasing the rate of PLA crystallization, producing smaller and more densely packed spherulites. The reduction in the AR and the nucleating effect of WS2 NTs for PLA are critical considerations in the preparation, by melt mixing, of composites of rigid 1D NTs and polymers, irrespective of the target application, including bone tissue engineering and bioresorbable vascular scaffolds.\ud \ud

In situ synchrotron X-ray scattering was used to reveal the transient microstructure of poly(L-lactide) (PLLA)/tungsten disulfide inorganic nanotubes (WS2NTs) nanocomposites. This microstructure is formed during the blow molding process (“tube expansion”) of an extruded polymer tube, an important step in the manufacturing of PLLA-based bioresorbable vascular scaffolds (BVS). A fundamental understanding of how such a microstructure develops during processing is relevant to two unmet needs in PLLA-based BVS: increasing strength to enable thinner devices and improving radiopacity to enable imaging during implantation. Here, we focus on how the flow generated during tube expansion affects the orientation of the WS2NTs and the formation of polymer crystals by comparing neat PLLA and nanocomposite tubes under different expansion conditions. Surprisingly, the WS2NTs remain oriented along the extrusion direction despite significant strain in the transverse direction while the PLLA crystals (c-axis) form along the circumferential direction of the tube. Although WS2NTs promote the nucleation of PLLA crystals in nanocomposite tubes, crystallization proceeds with largely the same orientation as in neat PLLA tubes. We suggest that the reason for the unusual independence of the orientations of the nanotubes and polymer crystals stems from the favorable interaction between PLLA and WS2NTs. This favorable interaction leads WS2NTs to disperse well in PLLA and strongly orient along the axis of the PLLA tube during extrusion. As a consequence, the nanotubes are aligned orthogonally to the circumferential stretching direction, which appears to decouple the orientations of PLLA crystals and WS2NTs.

Tungsten disulfide (WS2) nanotubes (NTs) are examined here as a filler for polylactide (PLA) for their ability to accelerate PLA crystallization and for their promising biocompatibility in relevant to biomedical applications of PLA-WS2 nanocomposites. In this work, we have studied the structural and thermal properties of PLA-WS2 nanocomposite films varying the concentration of WS2 NTs from 0 (neat PLA) to 0.6 wt%. The films were uniaxially drawn at 90 °C and annealed at the same temperature for 3 and 10 min. Using wide angle x-ray scattering, Raman spectroscopy and differential scanning calorimetry, we probed the effects of WS2 NT addition on the structure of the PLA films at various stages of processing (unstretched, stretching, annealing). We found that 0.6 wt% of WS2 induces the same level of crystallinity in as stretched PLA-WS2 as annealing in neat PLA for 10 min. These data provide useful insights into the role of WS2 NTs on the structural evolution of PLA-WS2 composites under uniaxial deformation, and extend their applicability to situations where fine tuning of PLA crystallinity is desirable.

Treatment of vascular disease, from peripheral ischemia to coronary heart disease (CHD), is poised for transformation with the introduction of transient implants designed to "scaffold" regeneration of blood vessels and ultimately leave nothing behind. Improved materials could expand the use of these devices. Here, we examine one of the leading polymers for bioresorbable scaffolds (BRS), polylactide (PLA), as the matrix of nanocomposites with tungsten disulfide (WS2) nanotubes (WSNT), which may provide mechanical reinforcement and enhance radio-opacity. We evaluate in vitro cytotoxicity using vascular cells, flow-induced crystallization and radio-opacity of PLA-WSNT nanocomposites at low WSNT concentration. A small amount of WSNT (0.1 wt%) can effectively promote oriented crystallization of PLA without compromising molecular weight. And radio-opacity improves significantly: as little as 0.5 to 1 wt% WSNT doubles the radio-opacity of PLA-WSNT relative to PLA at 17 keV. The results suggest that a single component, WSNT, has the potential to increase the strength of BRS to enable thinner devices and increase radio-opacity to improve intraoperative visualization. The in vitro toxicity results indicate that PLA-WSNT nanocomposites are worthy of investigation in vivo. Although substantial further preclinical studies are needed, PLA-WSNT nanocomposites may provide a complement of material properties that may improve BRS and expand the range of lesions that can be treated using transient implants. STATEMENT OF SIGNIFICANCE: Bioresorbable Scaffolds (BRSs) support regeneration of arteries without permanent mechanical constraint. Poly-L-lactide (PLLA) is the structural material of the first approved BRS for coronary heart disease (ABSORB BVS), withdrawn due to adverse events in years 1-3. Here, we examine tungsten disulfide (WS2) nanotubes (WSNT) in PLA to address two contributors to early complications: (1) reinforce PLLA (enable thinner BRS), and (2) increase radiopacity (provide intraoperative visibility). For BRS, it is significant that WSNT disperse, remain dispersed, reduce friction and improve mechanical properties without additional chemicals or surface modifications. Like WS2 nanospheres, bare WSNT and PLA-WSNT nanocomposites show low cytotoxicity in vitro. PLA-WSNT show enhanced flow-induced crystallization relative to PLA, motivating future study of the processing behavior and strength of these materials.

Biodegradable polymers open the way to treatment of heart disease using transient implants (bioresorbable vascular scaffolds, BVSs) that overcome the most serious complication associated with permanent metal stents—late stent thrombosis. Here, we address the long-standing paradox that the clinically approved BVS maintains its radial strength even after 9 mo of hydrolysis, which induces a ∼40% decrease in the poly l-lactide molecular weight (Mn). X-ray microdiffraction evidence of nonuniform hydrolysis in the scaffold reveals that regions subjected to tensile stress during crimping develop a microstructure that provides strength and resists hydrolysis. These beneficial morphological changes occur where they are needed most—where stress is localized when a radial load is placed on the scaffold. We hypothesize that the observed decrease in Mn reflects the majority of the material, which is undeformed during crimping. Thus, the global measures of degradation may be decoupled from the localized, degradation-resistant regions that confer the ability to support the artery for the first several months after implantation.

Coronary Heart Disease (CHD) is one of the leading causes of death worldwide, claiming over seven million lives each year. Permanent metal stents, the current standard of care for CHD, inhibit arterial vasomotion and induce serious complications such as late stent thrombosis. Bioresorbable vascular scaffolds (BVSs) made from poly L-lactide (PLLA) overcome these complications by supporting the occluded artery for 3-6 months and then being completely resorbed in 2-3 years, leaving behind a healthy artery. The BVS that recently received clinical approval is, however, relatively thick (~150 μm, approximately twice as thick as metal stents ~80 μm). Thinner scaffolds would facilitate implantation and enable treatment of smaller arteries. The key to a thinner scaffold is careful control of the PLLA microstructure during processing to confer greater strength in a thinner profile. However, the rapid time scales of processing (~1 s) defy prediction due to a lack of structural information. Here, we present a custom-designed instrument that connects the strain-field imposed on PLLA during processing to in situ development of microstructure observed using synchrotron X-ray scattering. The connection between deformation, structure and strength enables processing-structure-property relationships to guide the design of thinner yet stronger BVSs. © 2018 by the authors.

Poly(L-lactide) (PLLA) is a semicrystalline, biocompatible and biodegradable polymer widely employed in many applications (food packaging, biomedical devices, drug delivery systems). This work deals with nanocomposites of PLLA and tungsten disulfide (WS2) nanotubes (NTs) as a novel material to obtain thinner and stronger bioresorbable vascular scaffolds. We studied the influence of WS2 NTs on the mechanical properties of PLLA-WS2 films. Polarized optical microscopy reveals a high degree of orientation of the polymer molecules in stretched films that further increases with a post-stretching annealing treatment. At the same time, X-ray diffraction (XRD) and Raman spectroscopy confirm enhancement of the crystallinity induced by the WS2 NTs. © 2018 Author(s).

In this work, FETs are used as a research tool to study charge carrier mobilities in PbS nanocrystals (NCs) thin-films employed as semiconducting layer in bottom-gate bottom-contact (BGBC) field-effect transistors (FETs). The as-synthesised NCs are surrounded by long alkyl chain ligands which act as electrical insulators. Therefore, a ligand exchange process with shorter molecules is necessary to enhance the free charges generation and transport. We used two different ligands: 1,2 ethandithiol (EDT) and 1,2,3,4-tetrabutylammonium iodide (TBAI) and studied the charge mobility of PbS NCs comparing the electrical characteristics of FETs made by exchanged NCs. We analysed also the contemporary presence of both exchanged nanocrystals on the device. All the transistors showed p-type transport behaviour, enhanced by an annealing process at 100 °C for 10 min. After this, only the TBAI-treated NCs devices showed a n-type transport, resulting in an ambipolar behaviour. Inkjet printing deposition techniques was also successfully used to deposit PbS-(TBAI) NCs and ambipolar devices were obtained. In addition, for printed devices it was found that it is possible to modulate the charge transport properties by applying surface treatment to the substrate with a pentafluorothiophenol (PFTP). Indeed in this case, the p-type transport was suppressed while n-type behaviour was induced.

POC polymer is an oxadiazole-carbazole copolymer we have previously synthetized and established as light emitting material in Organic Light Emitting Devices (OLEDs), although POC quantum yield emission efficiency and color purity still need to be enhanced. On the other hand, tris[2-phenylpyridinato-C2,N]iridium(III) (Ir(ppy)3) complexes, namely Ir(ppy)3 are among the brightest luminophores employed in green light emitting devices. Our aim, in this work, is to take advantage of Ir(ppy)3 bright emission by combining the Ir complex with blue emitting POC to obtain tunable light emitting composites over a wide range of the visible spectrum. Here we have investigated the optical proprieties POC based nanocomposites with different concentrations of Ir(ppy)3, ranging from 1 to 10 wt%. Both spectral and time resolved fluorescence measurements show an efficient energy transfer from the polymer to the dopants, resulting in white-emitting composites. The most intense and stable emission has been found when POC was doped with about 5 wt% concentration of Ir(ppy)3. © 2016 Elsevier B.V.

Many research efforts are focused toward significant improvements of polymeric solar cells efficiency, energy harvesting range, time, and environmental stability. Particular attention is given to hybrid organic/inorganic composites constituted of polymer/lead chalcogenides (PbS and PbSe) nanocrystals (NCs) to extend the spectral sensitivity of cells to near-infrared wavelengths. In this work we report the synthesis and characterization of PbS nanocrystals with absorption edge at 984 nm. The nanocrystals have a cubic crystal structure and size of about 2 nm as found by X-ray diffraction analysis. They were combined with poly(3-hexylthiophene) (P3HT) polymer to obtain P3HT:PbS blends with different PbS loadings. A post-deposition ligand exchange on PbS NCs by 1,2-ethanedithiol (EDT) allowed a better interaction between polymer and nanocrystals as showed by fluorescence measurements. The P3HT:PbS blends were deposited and treated by a layer by layer spin coating process and used as active layer in solar cells having structure glass/ITO/PEDOT:PSS/blend/Al. The major result obtained for this hybrid system is an increase of PCE by about two orders of magnitude with respect to analogous reported cells where a post-deposition ligand exchange was performed.

The prospect of exploiting quantum dots (QDs) properties (tunable absorption spectrum, multiple exciton generation) while maintaining the flexible structure of polymer systems opens new possibilities in the photovoltaic field. Although charge transport dynamics in pristine polymer and QDs systems have been quite well established lately, a complete understanding of the charge transfer process between QDs and polymers when they are in blends is still lacking. In this work we used static and ultrafast fluorescence spectroscopy together with Atomic force Microscopy (AFM) to study the exciton dynamics in polymer/QDs films. Specifically we used poly(3-hexylthiophene) (P3HT) as the hole conducting donor material and the core shell CdSe(ZnS) QDs as the electron acceptor material. The QDs surface has been treated with two different capping ligands treatments: one based on the use of pyridine and the other one on hexanoic acid. The influence of the two different methods on the exciton dynamics and on the morphology will also be discussed. Blends containing differently treated P3HT/CdSe(ZnS) wt% ratios have been prepared producing films having uniform morphology and good intermixing, as proved by AFM measurements. Ultrafast fluorescence decays allowed us to compare the exciton dynamics in the polymer pristine respect to the treated P3HT/CdSe(ZnS) films. Efficient fluorescence quenching has been shown by both kind of blends respect to the pure polymer. © 2014 The Authors.

Blends of conductive polymer poly(3-hexylthiophene) (P3HT) and size controlled MoS2 nanotubes (NTs) were prepared focusing on procedures which do not alter the electrical and optical properties of nanotubes, i.e., without surfactants. After disassembly of as-grown hedgehog-like self-assemblies of the MoS2 NTs, relatively homogeneous dispersions of the NTs in P3HT were prepared. Thin films of these blends were prepared via spin coating. The NTs were found efficiently wetted by the P3HT and nearly completely immersed in the films. The surface structure was composed of pure P3HT lamellae. Photoluminescence spectra taken on P3HT/MoS2 NT thin films revealed a quenching effect, which depends on the concentration of NTs. Results of optical microscopy and spectroscopy investigations, scanning tunnelling microscopy and scanning electron microscopy studies are shown.

The integration of semiconductor nanoparticles (NPs) into a polymeric matrix has the potential to enhance the performance of polymer-based solar cells taking advantage of the physical properties of NPs and polymers. We synthesize a new class of CdS-NPs-based active layer employing a low-cost and low temperature route compatible with large-scale device manufacturing. Our approach is based on the controlled in situ thermal decomposition of a cadmium thiolate precursor in poly(3-hexylthiophene) (P3HT). The casted P3HT:precursor solid foils were heated up from 200 to 300 °C to allow the precursor decomposition and the CdS-NP formation within the polymer matrix. The CdS-NP growth was controlled by varying the annealing temperature. The polymer:precursor weight ratio was also varied to investigate the effects of increasing the NP volume fraction on the solar cell performances. The optical properties were studied by using UV–Vis absorption and photoluminescence (PL) spectroscopy at room temperature. To investigate the photocurrent response of P3HT:CdS nanocomposites, ITO/P3HT:CdS/Al solar cell devices were realized. We measured the external quantum efficiency (EQE) as a function of the wavelength. The photovoltaic response of the devices containing CdS-NPs showed a variation compared with the devices with P3HT only. By changing the annealing temperature the EQE is enhanced in the 400–600 nm spectral region. By increasing the NPs volume fraction remarkable changes in the EQE spectra were observed. The data are discussed also in relation to morphological features of the interfaces studied by Focused Ion Beam technique.

In this work, a simple approach to prepare luminescent poly(3-hexylthiophene)–CdS nanocomposites to be employed in organic light emitting devices (OLED) devices is reported. The nucleation and growth of CdS nanoparticles were obtained by the thermolysis of a single Cd and S precursor dispersed in the polymer at three different temperatures of annealing: 240, 265, and 300°C. In this way, it was possible to compare the properties of nanocomposites containing nanoparticles with different sizes. X-ray diffraction and transmission electron microscopy analyses confirmed the formation of CdS nanoparticles and gave information about the size, distribution, and morphology of the nanoparticles; monodispersive and very small nanoparticles with diameters below 2.5 nm were obtained at 240°C. The application of such nanocomposites as emitting layers in OLED devices is discussed. Enhanced electrooptical properties were observed for the device containing the nanocomposite annealed at 240°C with respect to the pure polymer based device. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011

Thin films of zirconium oxynitride (ZrNO) and titanium oxynitride (TiNO) have been deposited onto Si(100) substrates at room temperature by radiofrequency magnetron sputtering in an argon–oxygen–nitrogen atmosphere. Single oxynitride layers have been stacked to obtain a multilayer structure. The film structure has been determined by X-ray diffraction while compositional analysis has been performed by X-photoelectrons spectroscopy. Structural analysis has shown that TiNO can be represented as a cubic structure where oxygen atoms replace nitrogen ones while ZrNO can be described as a cubic ZrO2 where nitrogen atoms replace oxygen ones. Besides the main peak, the multilayer films show satellite peaks, proving the formation of the stacked structure. The final films stoichiometry has been explained by a growth model. It establishes that in TiNO films the nitrogen vacancies filling by reactive reactions with oxygen atoms is favourite while for ZrNO films the oxygen vacancies filling by energetic nitrogen atoms is more likely to happen. The different behaviour between TiNO and ZrNO is further confirmed during the multilayer growth.

In this work chemical sensors based on polyaniline and on polyaniline/graphenenanosheets bilayer were prepared by dip coating. Their morphology and volatile organic compounds (VOCs) sensing behavior were compared. In particular, the devices were investigated in presence of VOCs as limonene and ethanol. Furthermore the devices were characterized under relative humidity. Bilayer samples, exposed to limonene, show a higher relative response respect to only polyaniline, encouraging the graphene use in VOCs sensor devices. © Springer International Publishing Switzerland 2015.

Cadmium sulfide nanoparticles embedded in a polystyrene matrix (CdS/PS) were successfully prepared by in situ thermolysis of a cadmium thiolate precursor dispersed in the polymer. The heat-induced formation of cadmium sulfide was studied by thermogravimetric analysis and differential thermal analysis, while the chemistry of the reaction forming the CdS/PS compound was investigated by nuclear magnetic resonance and X-ray photoelectron spectroscopy. The structural characterization was performed by X-ray diffraction and transmission electron microscopy. The CdS nanocrystals are single crystals of cubic phase (zincblende structure) of spherical shape. The average diameter of the nanocrystals embedded in the polystyrene matrix achieved by our synthesis process is as small as 2.5 ± 0.5 nm. Room temperature UV–VIS absorption spectra exhibit a shoulder at 412 nm that is consistent with the presence of CdS nanocrystals of ∅ ≈ 2 nm. The role of the polymer on the nanoparticle growth was also discussed.

Resistivity measurements in external applied magnetic field up to 8.5T have been performed on Bi2Sr2CuO6+δ/CaCuO2 superconducting superlattices obtained by MBE. The magnetic field (H) vs. temperature (T) phase diagrams have been determined and the experimental data have been compared with that obtained in the case of Bi2Sr2CuO6+δ thin films deposited with the same technique. A reduction of the anisotropy has been obtained in the case of the superlattices with respect to the case of Bi2Sr2CuO6+δ thin films and a three dimensional behavior has been observed by paraconductivity measurements.

In this work, we studied energetic and optical proprieties of a polyester-containing oxadiazole and carbazole units that we will indicate as POC. This polymer is characterized by high photoluminescence activity in the blue region of the visible spectrum, making it suitable for the development of efficient white-emitting organic light emission devices. Moreover, POC polymer has been combined with two red emitters InP/ZnS quantum dots (QDs) to obtain nanocomposites with wide emission spectra. The two types of QDs have different absorption wavelengths: 570 nm [InP/ZnS(570)] and 627 nm [InP/ZnS(627)] and were inserted in the polymer at different concentrations. The optical properties of the nanocomposites have been investigated and compared to the ones of the pure polymer. Both spectral and time resolved fluorescence measurements show an efficient energy transfer from the polymer to QDs, resulting in white-emitting nanocomposites. © Springer Science+Business Media Dordrecht 2013.

The properties of hybrid composites result from a complex cooperation between the organic and inorganic species constituting the nanocomposites. A continuous, increasing demand of the detailed knowledge of such properties at the nanoscale has contributed to the development of the characterization techniques. The chapter provides an overview on two specific characterization tools widely used in nanocomposites research: X-ray scattering (XRS) and Solid-State Nuclear Magnetic Resonance spectroscopy (SSNMR). We briefly describe some fundamentals of both the methods and present several relevant results from the literature in this field. Specific emphasis is devoted to nanoparticle polymer nanocomposites and polymer-layered silicate nanocomposites.

TiN/ZrN multilayers coatings have been deposited using a reactive R. F. magnetron sputtering process. Nitride layers with different sputtering conditions have been stacked in order to obtain superlattices having different preferred orientations. The deposition rate has been considered as independent parameter which changes the energy and the momentum transfer of the backscattered particles, influencing films structure evolution.

We deposited thin layers of CdS and ZnS nanoparticles embedded in a thermoplastic cyclo-olephin copolymer (COC) with elevated optical transparency and highly bio-compatible. The nanoparticles were obtained by thiolate precursors previously dispersed in the polymer upon thermal treatment at temperatures ranging between 200 and 300 Celsius degrees depending on the desired size. The precursor/polymer solutions were spin coated in order to get thin films. The samples were mainly characterised by X-ray reflectivity (XRR) and by High Resolution Transmission Electron Microscopy (HRTEM) analyses. The HRTEM measurements showed that the nanoparticles have quasi-spherical shape without evident microstructural defects. The size of the nanoparticles depends on the annealing temperature, e.g. at 232 Celsius degrees the size of the CdS nanoparticles is about 4-5 nm., 15 pages, 5 figures. E-MRS IUMRS ICEM 2006 Spring Meeting, Nice (France); oral presentation. Mater. Sci. Eng. C, in press

We report on the optimization of the thermolytic synthesis of cadmium sulfide (CdS) nanoparticles in a polystyrene (PS) matrix. The annealing conditions were tuned on the basis of the indications coming from solid state 113 Cd and 13 C Nuclear Magnetic Resonance (NMR) experiments. 113 Cd NMR provided direct evidence of CdS nanoparticles formation. Semi-quantitative 13 C NMR experiments demonstrated that good quality samples are obtained by heating up precursor/polystyrene films to 270 °C in vacuum. X-ray diffraction (XRD) and wide angle X-ray scattering (WAXS) experiments revealed structural details of CdS nanoparticles, their average size ranging from 1 to more than 7 nm as a function of the annealing conditions.

The proton exchange membrane fuel cells (PEMFC) have been developed mainly as a power source for vehicles, power generation and consumer electronics since they combine high energy conversion efficiency at relatively low temperatures without pollutants emission in the environment. An electrode for a PEMFC is a layered structure composed by a catalyst layer deposited on a porous carbon substrate. The substrate is usually covered by a diffusion layer that enhances the gas and water flow. Platinum nanoparticles supported by carbon microparticles are commonly employed as catalyst layer. In this work an extreme ultra-low loading of Pt catalyst (< 0.02 mg/cm2) has been deposited by magnetron sputtering on gas diffusion electrodes, with different carbon supports (Vulcan and SuperP), in order to enhance the activity of PEM fuel cells. The morphology (shape and grain size) and microstructure have been studied combining field emission scanning electron microscopy (FEG-SEM), grazing incidence synchrotron x-ray diffraction (GIXRD) and x-ray photoelectron spectroscopy (XPS). The results presented here concern the evolution of the cluster size and shape after the ageing, induced by cyclic voltammetry for methanol oxidation reaction.

We performed a temperature and doping-dependent study of in-plane dc resistivity (IDCR) on molecular beam epitaxy grown ${\mathrm{Bi}}_{2}{\mathrm{Sr}}_{2}\mathrm{Ca}{\mathrm{Cu}}_{2}{\mathrm{O}}_{8+\ensuremath{\delta}}$ thin films. By analyzing the temperature dependence of normal state IDCR as a function of doping level, we show that long-known $T$-linear dependence of normal state IDCR occurs not at the optimal doping $(p=0.16∕\mathrm{Cu})$ but at an overdoping of $p=0.19∕\mathrm{Cu}$, which coincides with the recently proposed putative quantum critical point. This observation suggests that $p=0.19$ may be a sample-independent critical doping level at least for bilayer cuprate systems.

A thiolate precursor was dispersed in a polymer solution and a precursor/polymer film was obtained by casting. Thermal annealing of the precursor/polymer film leads to the formation of a nanocomposite of nanometer-sized CdS dispersed in the polymer (thermolytic process). Different polymers were used as matrix material; in particular we employed a cyclo-olefin copolymer for its good optical properties and extremely low water absorption. After annealing with a temperature between 230 and 250°C in vacuum (pressure of about 6×10−3 mbar) the CdS nanoparticles are found to be crystalline with a diameter of about 2nm in size. The nanoparticle size can be increased up to 15nm by annealing at higher temperatures (300°C). The details of the structural properties of the nanocomposite films have been investigated by small and wide angle x-ray scattering (SAXS and WAXS, respectively). A simple dependence of the nanoparticle dimensions on the annealing temperature was found. Furthermore, SAXS measurements indicate that the separation between the nanoparticles compares with their diameter.

CdS nanoparticles of different sizes were synthesised in poly(N-vinylcarbazole) and studied in device structures glass/indium tin oxide (ITO)/PVK:CdS/Al. Electrical bistability and negative differential resistance (NDR) effects were observed in the current-voltage characteristics. In addition, the devices showed a considerable enhancement of the current magnitude. A dependence of the current conduction on the nanoparticle size and size distribution in the polymer was studied through electrical impedance measurements. The study revealed the importance of the charge effects of the nanoparticles resulting in a bistable behavior. A resonant tunneling current model was proposed to explain the NDR and its relation with the nanoparticle size and size distribution.

We investigated the growth of CdS nanoparticles in polymer films by means of ex-situ and in-situ x-ray scattering experiments using synchrotron radiation. The CdS nanoparticles were synthesized by thermal decomposition of a Cd thiolate precursor dispersed in a cyclic olefin copolymer. The films were deposited by spin coating. Grazing incidence diffraction (GID) reveals the Bragg reflections of the CdS nanoparticles. In-situ diffraction and grazing incidence small angle scattering (GISAXS) experiments were recorded during the thermal treatment of the precursor/polymer films from room temperature up to 250°C. The diffraction curves show that the initial precursor structure is soon lost at 100°C. Correspondingly, the GISAXS data show a peak at a momentum transfer value q ∼ 0.2Å−1 that shifts towards smaller values with the temperature. Under UV excitation the films show photoluminescence in the range 400 – 700 nm.