Hybrid Nanocomposite Thin Films Research Articles

Experimental investigations on NO2 sensing of pure ZnO and PANI–ZnO composite thin films

In the present work, comparative investigations on NO2 gas sensing properties of the hybrid nanocomposite thin films of polyaniline (PANI), ZnO and PANI–ZnO towards NO2 gas at room temperature have been reported.

Hybrid nanocomposite thin films deposited by emulsion-based resonant infrared matrix-assisted pulsed laser evaporation for photovoltaic applications

Emulsion-based, resonant infrared matrix-assisted pulsed laser evaporation (RIR-MAPLE) was used to deposit CdSe nanoparticle films and hybrid nanocomposite films comprising colloidal CdSe nanoparticles embedded in a low band gap polymer, poly[2,6-(4,4-bis-(2-ethylhexyl)-4H-cyclopenta[2,1-b;3,4-b′]dithiophene)-alt-4,7-(2,1,3-benzothiadiazole)] (PCPDTBT). We show that, in contrast to traditional MAPLE deposition, the CdSe nanoparticle film deposited by emulsion based RIR-MAPLE is contiguous and uniform, and it maintains the optical properties of the nanoparticle solution. Moreover, we show that the RIR-MAPLE deposited PCPDTBT/CdSe hybrid nanocomposite film exhibits a relatively random and uniform distribution of CdSe nanoparticles without the significant phase segregation that is observed in hybrid nanocomposite films deposited by spin-casting. Finally, hybrid organic solar cells based on nanocomposite films deposited by the RIR-MAPLE technique were fabricated and characterized, showing 0.4% power conversion efficiency. This is the first demonstration of a polymer–nanoparticle hybrid organic solar cell fabricated by a MAPLE-related technique.

Nonvolatile organic field-effect transistors memory devices using supramolecular block copolymer/functional small molecule nanocomposite electret.

Organic field-effect transistors (OFETs) memory devices based on hybrid nanocomposite electret were fabricated by cooperative supramolecular polystyrene-block-poly(4-vinylpyridine) (PS-b-P4VP) with two different block compositions (asymmetric L1 and symmetric L2) that contain hydroxyl-functionalized ferrocene small molecules (FMs). Because of the selective hydrogen interaction between the hydroxyl groups of FM and pyridine groups in P4VP block, the small FMs can preferentially disperse in the P4VP nanodomain, which can be used as nanostructured charge-trapping nanocomposite electret (L1-FMX and L2-FMX) under solvent-annealing process. The charge-storage functionalities can be easily tailored by morphologies of the hybrid nanocomposite thin film and spatial distribution of the FM molecules in which the relative molecular mass of block copolymers and the FM loading ratio can further control both of them. These block copolymer nanocomposite thin film electrets with charge-controlling guest FM for OFETs memory devices exhibit significant features including the ternary bits storage, high-density trapping sites, charge-carrier trapping of both polarities (ambipolar trapping), and solution processing that can make important progress for future advanced storage and memory technology.

Gravure printed sol–gel derived AlOOH hybrid nanocomposite thin films for printed electronics

We report a sol–gel approach to fabricate aluminum oxyhydroxide (AlOOH)-based inks for the gravure printing of high-dielectric-constant nanocomposite films.

Polypyrrole–NiO hybrid nanocomposite films: highly selective, sensitive, and reproducible NO2 sensors

Polypyrrole–nickel oxide (PPy–NiO) hybrid nanocomposite thin-film sensor was prepared by spin-coating method on glass substrate. The PPy–NiO hybrid nanocomposite thin film sensors were used to study room temperature gas-sensing properties for oxidizing (NO2, Cl2) as well as reducing (NO2, H2S, C2H5OH, NH3, and Cl2) gases. It was revealed that PPy–NiO (50 %) hybrid nanocomposite thin-film sensor could detect NO2 at low concentration (100 ppm) with very high selectivity (47 % compared with Cl2) and high sensitivity (47 %), with better stability (90 %) and reproducibility. The response and recovery times were changed significantly with NO2 concentration.

Polypyrrole-NiO hybrid nanocomposite: Structural, morphological, optical and electrical transport studies

Polypyrrole (PPy)-nickel oxide (NiO) hybrid nanocomposite thin films have been prepared by spin coating method. The PPy–NiO hybrid nanocomposites were characterized for structural, morphological, optical and electrical analysis, and the results were compared with the pure PPy films. The structural and optoelectronic properties of PPy–NiO hybrid nanocomposites are quite different from those of pure PPy and NiO nanoparticles, which were attributed to the strong interaction between the PPy and NiO nanoparticles. The XRD pattern shows that broad peak of PPy becoming weaker on increasing the content of NiO nanoparticles in the PPy–NiO hybrid nanocomposites. Also the diffraction peaks of NiO nanoparticles in PPy–NiO (10–50wt%) nanocomposites were found to shift to lower 2θ values. The morphological studies revealed that the transformation of granular morphology of PPy to the nanospheres and clusters in the PPy–NiO hybrid nanocomposites. FTIR spectra of PPy–NiO hybrid nanocomposites, revealed that the main absorption at 1204cm−1 and 1559cm−1 are affected by the presence of NiO nanoparticle in pure PPy and get shifted to 1216cm−1 and 1570cm−1 respectively indicates, insertion of NiO nanoparticles in the PPy–NiO hybrid nanocomposite. UV–vis absorption spectrum of PPy corresponding to λmax=442nm is blue shifted to λmax=375nm in the PPy–NiO hybrid nanocomposites, reveals strong interaction between PPy and NiO nanoparticles. The room temperature dc electrical conductivity is increased from 8.66×10−9 to 4.08×10−7(Ω/cm)−1 as the content of NiO nanoparticles increased from 10 to 50 inwt% in the PPy–NiO hybrid nanocomposites.

THEORETICAL INVESTIGATION OF INTRABAND, INFRARED ABSORBANCE IN INORGANIC/ORGANIC NANOCOMPOSITE THIN FILMS WITH VARYING COLLOIDAL QUANTUM DOT SURFACE LIGAND MATERIALS

Hybrid nanocomposite thin films, composed of inorganic colloidal quantum dots (CQDs) embedded in a matrix of organic conjugated polymer, have shown promise as a method for room-temperature infrared detection due to the three-dimensional confinement of the CQD and significantly lower dark currents compared to inorganic detectors. However, in order to improve device performance, the excited charges must be efficiently promoted out of the CQD, which is surrounded by an insulating surface ligand. These short, organic molecules, which are required to prevent agglomeration of CQDs in solution, have been shown to inhibit charge transfer into and out of the CQD. In this work, the transfer matrix method is utilized to calculate the quantized energy levels and wavefunctions in the conduction band of the CdSe CQD for a variety of surface ligand materials. These results are used to calculate the absorption coefficient for a size distribution of CQDs and are compared with measured Fourier Transform Infrared absorbance spectra. Finally, the effect of the ligand on the calculated absorption coefficient will be used to optimize the design for an infrared photoconductor.

Influence of Semiconductor Nanocrystal Concentration on Polymer Hole Transport in Hybrid Nanocomposites

This article investigates hole transport in poly[2-methoxy-5-(2'-ethyl-hexyloxy)-1,4-phenylene vinylene] (MEH-PPV)/CdSe colloidal quantum dot (CQD) nanocomposites using a modified time-of-flight photoconductivity technique. The measured hole drift mobilities are analyzed in the context of Bässler’s Gaussian disorder model and the correlated disorder model in order to determine the polymer internal morphology of hybrid nanocomposite thin films. This work shows that increasing the CdSe CQD concentration decreases the polymer hole mobility from ~5.9 × 10−6 cm2/Vs in an MEH-PPV film to ~8.1 × 10−8 cm2/Vs in a 20:80 (wt%) MEH-PPV:CdSe CQD nanocomposite film (measured at 25 °C and ~2 × 105 V/cm). The corresponding disorder parameters indicate increasing disruption of interchain interaction with increasing CQD concentration. This work quantifies polymer chain morphology in hybrid nanocomposite thin films and provides useful information regarding the optimal use of semiconductor nanocrystals in conjugated polymer-based optoelectronics.

Calculation of Intraband Absorption Coefficients in Organic/Inorganic Nanocomposites: Effects of Colloidal Quantum Dot Surface Ligand and Dot Size

Hybrid nanocomposite thin films composed of inorganic colloidal quantum dots (CQDs) embedded in an organic conjugated polymer have shown promise as a method for room-temperature infrared detection due to the 3-D confinement of the CQD. The CQDs are coated with a surface ligand material which is comprised of short, organic molecules that prevent the CQDs from aggregating when placed in solution. These surface ligand materials behave as a thin, insulating layer that has been shown to prevent efficient transfer of excited carriers into and out of the CQD. Therefore, it is important to understand the effect that the surface ligand material has on the optical properties of the nanocomposite materials in order to design more efficient hybrid nanocomposite optoelectronic devices. In this paper, we calculate the infrared, intraband absorption coefficient for CQDs in a nanocomposite thin film. The model is verified by comparing the calculated absorption coefficient spectrum to a measured FTIR absorbance spectrum for a specific hybrid nanocomposite material system. Importantly, the CQD surface ligand is included in the model explicitly, which enables the selection of the surface ligand material to be considered as a design parameter for infrared, intraband absorption in hybrid nanocomposites. In addition, the CQD average size is also treated as design parameter in order to tune the infrared, intraband absorption coefficient in hybrid nanocomposites.

Tetrapropylammonium-manganese oxide/polypyrrole hybrid nanocomposite thin films as novel electrode materials for supercapacitors

Tetrapropylammonium-manganese oxide/polypyrrole (TPA-MO/Ppy) hybrid nanocomposite with molar ratios of TPA-MO/Ppy 4:1, 2:1 and 1:1 were successfully prepared by a combination of in situ polymerization and the sol–gel process. The microstructure of hybrid nanocomposite thin film samples was observed to be significantly affected by synthesis parameters, most notably the molar ratio of reactants and post-synthesis calcination temperature. Samples with higher pyrrole contents appeared to possess higher specific surface areas, which ranged from 132 to 281 m 2 g −1. SEM micrographs indicated that all nanocomposite thin films were highly fibrous and porous in nature. Optimum doping of manganese oxide with conducting polypyrrole had led to the formation of novel nanocomposite with nanofibrillar structures which consisted of interconnected manganese oxide and polypyrrole nanoclusters. Optimized nanocomposite films showed higher charge capacities which could be attributed to enhanced material utilization as a result of optimized microstuctural parameters in particular, specific surface areas.

Room-temperature, mid-infrared photodetection in colloidal quantum dot/conjugated polymer hybrid nanocomposites: a new approach to quantum dot infrared photodetectors

A unique and distinct approach to unipolar, intraband transitions appropriate for room-temperature, mid- and long-wave-infrared (IR) photodetection is to use active regions comprising colloidal quantum dots (CQDs) synthesized by inorganic chemistry embedded in conjugated polymers. The polymer not only enhances quantum confinement of and electron localization in CQDs, but it also assists in the conduction of electrons photogenerated by the absorption of IR light. Preliminary demonstrations of intraband, mid-wave IR absorption and Fourier transform IR (FTIR) spectral response at room temperature in CdSe/MEH-CN-PPV hybrid nanocomposite thin films are promising, yet the inherent lack of control over hybrid nanocomposite morphology due to solution-based deposition is an inherent challenge. Matrix-assisted pulsed laser evaporation is a vacuum-based deposition technique that could address this challenge by providing more homogeneous distributions of CQDs in hybrid nanocomposite thin films.

Fabrication and Characterization of Polyaniline–ZnO Hybrid Nanocomposite Thin Films

Polyaniline (PANI)-ZnO nanocomposite thin film has been successfully fabricated on glass substrates by using vacuum deposition technique. The as-grown PANI-ZnO nanocomposite thin films have been characterized using X-ray diffraction, Scanning Electron Microscopy, Atomic Force Microscopy, UV-visible spectrophotometer and Fourier Transform Infrared (FTIR) spectroscopy, respectively. X-ray diffraction of as-grown film shows the reflection of ZnO nanoparticles along with a broad peak of PANI. The surface morphology of nanocomposite films has been investigated using scanning electron microscopy and atomic force microscopy. The hypsochromic shift of the UV absorption band corresponding to pi-pi* transition in polymeric chain of PANI and a band at 504 cm(-1) due to ZnO nanoparticles has been observed in the FTIR spectra. The hydrogen bonding between the imine group of PANI and ZnO nanoparticle has been confirmed from the presence of the absorbance band at 1151 cm(-1) in the FTIR spectra of the nanocomposite thin films.

Hybrid Sol–gel thin films for magneto-optical applications: Chemical, optical and tribological study

Sol–gel processes are promising strategies to prepare materials with synergetic or complementary behaviour between a polymer and an inorganic matrix interacting at the molecular scale. The conditions of soft chemistry allow the integration of photocurable organic compounds into an inorganic network, opening the way to the creation of new nanocomposite materials deposited on wide surfaces. The objective of the present study is to develop a process in order to prepare doped thin solid film for magneto-optical applications. The main steps of the process are the deposition (by hydrolysis condensation) and characterization of an organically modified silicon alkoxide containing zirconium alkoxide to modulate the refractive index of the film. After deposition, UV irradiation allows to develop an organic structure entangled in the inorganic network. For various applications, tribological studies on these new materials cannot be bypassed since these future components may be submitted to various mechanical solicitations. The resulting thin films, exhibiting a high transparency with a modulable refractive index, have a great potential to be used for components in integrated optical devices. The friction and wear behavior of the films has been investigated depending on the deposition conditions, mainly the organic conversion ratio ranging between 6 and 98%. The organic conversion ratio corresponds to the range of organic network within the film. For the lowest organic conversion ratios, the films do not withstand the friction tests and exhibit poor wear resistance. For conversion ratios above 60%, friction coefficients in the 0.1 range have been recorded, with a significant wear resistance. The tribological behaviors of such inorganic-organic hybrid nanocomposite thin films tested in standard conditions are discussed in agreement with their structure and composition. The potentiality to reach both wear resistance and outstanding optical properties will be evaluated.

Transparent high refractive index nanocomposite thin films

This work reports the preparation of acetic acid-modified TiO 2 nanoparticles by sol–gel synthesis method. The nanoparticles can be incorporated directly into the polymer matrix to form transparent high refractive index nanocomposite thin films. The result shows that increasing the titania content in the hybrid nanocomposite thin films can significantly increase the refractive index. Hybrid nanocomposite thin film with refractive index value of 2.38 had been prepared. All prepared films also exhibit excellent optical transparency in the visible region.

Linear electro-optical behavior of hybrid nanocomposites based on silicon carbide nanocrystals and polymer matrices

An electro-optical activity has been recently reported for hybrid nanocomposite thin films where inorganic silicon carbide nanocrystals $(\mathrm{ncSiC})$ are incorporated into polymer matrices. The role of the interface $\mathrm{SiC}$ polymer is suggested as the origin of the observed second order nonlinear optical susceptibility in the hybrid materials based on poly-(methylmethacrylate) (PMMA) or poly-($N$-vinylcarbazole) matrices. In this work, we report an analysis of the electro-optical response of this hybrid system as a function of the $\mathrm{ncSiC}$ content and surface state in order to precise the interface effect in the observed phenomenon. Two specific $\mathrm{ncSiC}$ samples with similar morphology and different surface states are incorporated in the PMMA matrix. The effective Pockels parameters of the corresponding hybrid nanocomposites have been estimated up to $7.59\ifmmode\pm\else\textpm\fi{}0.74\phantom{\rule{0.3em}{0ex}}\mathrm{pm}∕\mathrm{V}$ ($1\phantom{\rule{0.3em}{0ex}}\mathrm{wt}.\phantom{\rule{0.2em}{0ex}}%$ of $\mathrm{ncSiC}$ in the matrix). The interfacial region $\mathrm{ncSiC}$ polymer is found to play the main role in the observed effect. Particularly, the electronic defects on the $\mathrm{ncSiC}$ nanocrystal surface modify the interfacial electrical interactions between the two components. The results are interpreted and discussed on the basis of the strong influence of these active centers in the interfacial region at the nanoscale, which are found to monitor the local hyperpolarizabilities and the macroscopic nonlinear optical susceptibilities. This approach allows us to complete the description and understanding of the electro-optical response in the hybrid $\mathrm{SiC}$/polymer systems.