Transistors

Field effect transistors (FETs) play a significant role in modern electronics as they are inherent parts of various devices, for example, computer chips. It is crucial to develop novel device geometries to optimize gate electrostatics needed for efficient ON-OFF switching for highly scaled molecular transistors with short channels 1 . Composite materials based on the coupling of conducting organic polymers (COPs) and carbon nanotubes (CNTs) offer an attractive route to introduce electronic...

Silica Based Porous Materials

A wide variety of different porous materials are known. Following the classification by IUPAC, they can be grouped by the size of their pores microporous solids with pore diameters up to 2 nm with zeolites and metal-organic frameworks (so-called MOF structures) as the most prominent representatives, mesoporous solids with pore sizes between 2 and 50 nm, e.g. aerogels, pillared clays, or M41S phases, and macroporous solids with pore sizes larger than 50 nm, such as foams or glasses. In addition,...

Bridged Polysilsesquioxanes

Bridged polysilsesquioxanes are a rather new family of hybrid inorganic-organic materials that are prepared via sol-gel processing of monomers that contain a bridging organic group and two or more trialkoxysilyl groups 53, 117, 118 . The use of these bridged presursors, such as X3Si-R'-SiX3 (R' is an organic spacer, X Cl, Br, OR) allows the formation of homogeneous molecular hybrid inorganic-organic materials, which have a high degree of local organization. The organic spacer can be varied in...

Conclusion and Prospects

Hybrid nanocomposite materials based on conducting organic polymers have become an important part for the development of energy-related applications. Especially in the area of energy storage and conversion devices, conducting organic polymers, in synergy with a wide range of inorganic materials, have established a new path for the generation of new materials with improved and novel properties. In this chapter, we have focused our discussion on the progress that hybrid nanocomposite materials...

Optical Biosensors

During the last three decades we have witnessed remarkable research and development activity aimed at the realization of optical sensors for the measurement of chemical and biological quantities. The first optical chemical sensors were based on the measurement of changes in the absorption spectrum and were developed for the measurement of CO. and O2 concentrations 6 . Since then, a large variety of optical methods have been used in chemical sensors and biosensors including ellip-sometry,...

Bilayers with TiO2

8.3.1.1 TiO2 Poly(p-Phenylene Vinylene) Savenije et al. have used the flash-photolysis TRMC to monitor charge separation between a smooth film of anatase TiO2 (ca 80 nm) and spin coated layers of MEH-PPV (20-140 nm thick) on nanosecond flash-photolysis in the polymer absorption band at 544 nm 129 . The quantum efficiency of electron injection into the TiO2 per incident photon is ca 6 for thicknesses in the range of 30-50 nm of the polymer layer. The charge separation persisted well into the...

Bulk vs Fine Particles

The initial interest to work with fine particles and thin films of magnetic materials was kindled reading well-known texts 1, 2 . In contrast to macroscopic bulk features, fine particles of magnetic materials in pure form have shown some interesting features leading to fascinating technical applications. The spectrum of applications is tremendous which at one end we have high-efficiency motor, fridge magnet, and storage media devices and high frequency applications at the other. For such...

Characteristics and Applications of Hybrimers

Based on the above synthesis schemes, numerous hybrimers have been developed in recent years. This development yields many interesting new materials, with improved mechanical properties tunable between those of glasses and those of polymers, with improved optical properties (efficiency, stability, new functions, etc) and with improved catalytic or membrane based properties 60-62, 105-109, 119, 123, 124 . Due to the nano-scale structure and processing, the hybrimers are transparent amorphous...

Hybrids Incorporating Optically Active Centres 12321 Organic Dyes

Sol-gel derived dyes containing transparent matrices are an alternative to traditional liquid phase dye lasers since these gels are prepared under mild temperature conditions and they can be easily enriched with laser dyes without damaging them. Moreover, as the solubility of most dyes is limited in pure silica matrices, intensive efforts have been made in the last decade to synthesize dyes containing organic-inorganic hybrids 65, 66, 111-114 . Figure 12.19 depicts a few representative...

References

Chapin DM, Fuller CS, Pearson GL (1954) A new silicon p-n junction photocell for converting solar radiation into electrical power. J Appl Phys 25 676. 2. Shockley W, Queisser HJ (1961) Detailed balance limit of efficiency of p-n junction solar cells. JApplPhys 32 510. 3. Zhao J, Wang A, Green MA, Ferrazza F (1998) 19.8 efficient honeycomb textured multi-crystalline and 24.4 monocrystalline silicon solar cells. App Phys Lett 73 1991. 4. Shultz O, Glunz SW, Goldschmidt JC, Lautenschlager H,...

Photoinduced Migration of Monomers or Oligomers

Volume deformation in the photosensitive materials can be either positive or negative, and depends on the material, system and composition. In the case of azo-polymers, liquid crystals and sol-gel materials, a negative volume change, compaction or shrinking in the exposed regions has been observed. The opposite deformation i.e. volume expansion has been found in some azo-polymers, fluoro-zirconate or chalcogenide glasses, and many photopolymers. Understanding of the mechanisms of deformation...

Spherical Microcavities as Photonic Atoms

Extending the ideas of the linear combination of atomic orbitals method to the classical wave case, it was recently suggested that Mie resonances (WGM) of a single spherical microcavity play the same role as the atomic orbitals in the electronic case and the spatial distributions of WGM can be described by analogy with the orbitals in a hydrogen atom 54 . In the absence of gain, the WGM resonances can be characterized by a mode number n (angular quantum number), a mode order f (radial quantum...

Synthesis of Hybrimers

Siloxane-based hybrid materials hybrimers prepared by sol-gel process present many advantages for the design of materials 60-62, 66, 67, 71 . Firstly, many precursors are commercially available or can be modified or synthesized secondly, the control of precursor reactivity can be achieved by controlling the catalysts thirdly, transparent films or monoliths having good robustness can be easily processed and finally, the resulting materials are not toxic. Figure 13.1 shows a schematic diagram of...

Applications of Magnetic Nanocomposites

Application of nanostructure materials is vast and fascinating. The range of application includes cosmetic and sun block, nanofilters, coatings for cutting tools, tennis balls, materials for vehicles, catalysis, sensors, vitamins and additives in food and drug delivery etc. All such applications are for the benefit of mankind. The basic iron oxide and its alloys were the initial soft ferrites which were applied to high frequency applications - heavy duty and light duty multipliers used in cores...

Embedded Magnetic Nanoparticles 11521 Ion Exchange Resin

The polymer matrix may either be commercial based or in-lab synthesized ion-exchange resin. Ziolo et al. 36 selected a commercial ion-exchange resin, which was composed of sulphonated polysterene cross linked with divinyl benzene to form a three-dimensional, porous polymer network. The dry resin exhibited the property of cation exchange . The cross linked resin was in the form of spherical beads of diameter 30-150 mm. The resin was exchanged with Fe II or Fe III from an aqueous solution of the...

Metal Oxide Polymer Magnetic Nanocomposites

Metal salts MX when dissolved in an aqueous medium dissociate into ions in the solution. The negative charge of anions Xz- balances the positive charge of the atom Mz 7 . When a polymer structure provider polyvinyl alcohol - PVA, polyvinyl acetate, polyethylene glycol, etc. is added to the metal compound, particularly nitrates, following the solution evaporation process, two phenomena are known to occur. Firstly, during addition of optimum amount of the polymer material to the mixed metal...

Magnetobiosensors

In recent years, there has been an increasing interest to use magnetic nanocomposites in biomedical applications. Magnetic nanoparticles are suitable for use in biosensor applications since their magnetic properties allow relatively easy and remote detection. Their large surface-to-volume ratio and mobility speed up the chemical reactions, e.g. in micro cavities where the mixing is otherwise slow. New methods have been presented in order to quantify the amount of biomolecules in a liquid using...

Info

200 400 600 800 1000 Time delay ps Fig. 8.9 a PIA spectrum of a nc-ZnO MDMO-PPV blend on quartz solid line and of MDMO-PPV on TiO2 dashed line . b Time-resolved pump-probe spectroscopy, monitoring the intensity of the radical cation band at 0.56 eV, after excitation at 2.43 eV 510 nm . The inset shows the transient absorption at short time delays. Reprinted with permission from Adv. Mater. 2004, 16, 1009 112 . Copyright 2004 Wiley-VCH 200 400 600 800 1000 Time delay ps Fig. 8.9 a PIA spectrum...

Filling Nanoporous Semiconductors with Conjugated Polymers

Porous TiO2 electrodes like those used in the DSSCs have a high surface area. When used in a bulk heterojunction of a conjugated polymer and a nanoporous semiconductor, this high surface area is advantageous for charge generation. Consequently, the idea of replacing the dye and liquid electrolyte by a semiconducting polymer that takes care of light absorption, electron injection, and hole transport has been explored in recent years. While this principle is very attractive and would also lead to...

Introduction to Solar Cells

Edmond Becquerel discovered the photovoltaic effect in 1838, when he observed a small voltage and current when two silver halide coated platinum plates immersed in an acidic solution were exposed to light. Only far into the next century a major improvement was achieved over 50 years ago, the first silicon solar cell was developed by Chapin, Fuller, and Pearson of Bell Telephone Laboratories 1 . Molecular Materials and Nanosystems, Eindhoven University of Technology, PO Box 513, 5600 MB...

Superparamagnetic Contrast Agents

First introduced as contrast agents in the mid-1980s 132-134 hybrid superparamag-netic nanocomposites have been used in MRI for localization and diagnosis of brain and cardiac infarcts, liver lesions or tumors, where the nanoparticles tend to accumulate at higher levels due to the difference in tissue composition and or endocytotic uptake processes 135 and references therein . Especially promising results have been obtained in the improvement of sensitivity of detection and delineation of...

Other Light Absorbing Nanoparticles

While the majority of hybrid nanoparticle-polymer solar cells involving quantum dots that absorb light outside the UV region relate to cadmium and lead salts as described in the previous paragraphs, other particles also have received some attention. In each case the rationale behind this approach is to utilize the extended wavelength absorption of the inorganic quantum dot into the near infrared to enhance the spectral coverage and harvest more photons from the sunlight. 8.2.3.1 CuInS2 and...

Mechanical Properties

Mainly, morphology determines the mechanical properties of the epoxy-silica SSQO nanocomposites. The hybrids with the bicontinuous morphology of the epoxy and silica phases display a dramatic increase in modulus. The rubbery modulus of the epoxy-silica network DGEBA-D2000-TEOS, sequential polymerization is enhanced by two orders of magnitude at a low silica content, 7 vol , with respect to the reference epoxide network. The mechanical behavior and moduli, moreover, depend on the volume fraction...

Optical Waveguides

Optical waveguides are micro-optical devices transmitting light by confining it within the high refractive index core surrounded by low refractive index cladding, through the phenomenon of total internal reflection 6 , Optical waveguides in optically transparent dielectric materials such as silica and polymers have long been of interest for integrated optical circuit devices. Silica optical waveguides have the advantages of robustness, excellent optical characteristics, and compatibility with...

Microlens Arrays

Microlens arrays MLA in which the microlenses are arranged in 1D or 2D pattern in a plate are important micro-optical components for beam dispersion expansion and conversion collimation 2 . MLAs have been extensively used in many optical applications such as scanning system, large area display, beam homogenizer, optical coupling, and optical interconnection. Many researchers have been exploring various techniques to fabricate MLAs including the photoresist thermal reflow method, 8, 193 the...

Sol Gel Hybrids for Electronic Applications Hermetic Coatings for Microelectronics and Energy Storage

Abstract Hermetic seals are an essential part of microelectronics, namely, micro-electromechanical systems MEMS displays using organic-light emitting diodes OLEDs and electrochemical devices, such as microbatteries. Hermetic seals have to prevent humidity and other gases from reaching devices and degrading their performance. Typically, the barriers are applied once the devices have been assembled, and, consequently, the sealing material has to be hermetic at low processing temperatures. Hybrid...

Highly Photosensitive Sol Gel Hybrid Nano Materials for Direct Photo Fabrication of Micro Optical Elements

Abstract In this review chapter, the photosensitivity mechanisms in the sol-gel hybrid nanomaterials are covered with the aim of showing how large photoin-duced changes in the refractive index and or volume can be obtained. Applying the photo-fabrication technique to these highly photosensitive sol-gel hybrid nanomaterials, a series of micro-optical elements such as diffractive gratings, optical waveguides, and microlenses are described. The emphasis is laid on the advantages brought by such...

ZnO Nanoparticles

Beek et al. chose to use ZnO instead of TiO2 or CdSe 112 . ZnO is a non-toxic, crystalline material and at room temperature the stable phase is a wurtzite type crystal. In contrast to TiO2 , crystalline ZnO is already formed at temperatures as low as 4 C 113 . ZnO has a direct band gap at 3.2 eV, a conduction band level of - 4.4 V vs. vacuum 114 , and an electron mobility exceeding 100 cm2 Vs 115, 116 , Crystalline ZnO nanoparticles nc-ZnO , soluble in organic solvents, have been mixed with...

CdSe and CdTe Nanoparticles

So far, the best photovoltaic response for hybrid devices has been realized using cadmium selenide CdSe nanoparticles mixed with conjugated polymers as explored by Alivisatos and Greenham. CdSe nanoparticles also harvest solar light and the size of the nanoparticles can be tuned for optimal light absorption. First examples on CdSe nanoparticles nc-CdSe in poly vinylene MEH-PPV showed external monochromatic quantum efficiencies up to 12 40, 41 . In these devices, the nc-CdSe MEH-PPV blend was...

PbS PbSe and PbTe Nanoparticles

Lead sulfide PbS and lead selenide PbSe colloids absorb light in the near- to mid-infrared region and can be beneficial to increase the overlap of the absorption spectrum of the photoactive layer with the emission of the sun. The optical properties of colloidal semiconductor nanocrystals strongly depend on the size of the particle. Fig. 8.6 Scanning electron micrographs of an original template of tetrapod array on ITO a and several composites produced by subsequent deposition of P3HT. P3HT was...

TiO2 Nanoparticles

Transparent semiconducting metal oxides like TiO2 and ZnO are promising materials to be used as the electron accepting material in combination with p-type conjugated polymers. These metal oxides are not considered to be toxic and are available in abundance. First examples of blends from TiO2 nanoparticles and PPV have shown only moderate external quantum efficiencies of a few percent and short circuit currents of tens of microamperes. In one example, PPV was obtained by thermal conversion of a...

Teos

Hydrolysis Si OEt 4 n H2O Si OEt 4-n OH n n EtOH 13 condensation I I II 1.4 Si-OH RO-Si----Si-O-Si- H2O The sol-gel reactions make possible a relatively easy incorporation of a pure inorganic phase into an organic matrix. A low-temperature procedure, high purity of reactants, and the possibility of mixing of precursors of organic and inorganic phases at the molecular level are the main advantages of this technique. Alcohols ethanol, isopropanol or THF are usually used as solvents for the...

Interpenetrating Epoxy Silica Networks

Teos Amine

Various kinds of hybrid epoxy-silica networks with in situ formed silica have been synthesized and investigated 19, 24, 25, 28, 45, 141 . Usually, the silicaphase was produced within the network matrix by the hydrolytic polycondensation of TEOS. However, the nonaqueous synthesis of nanosilica in an epoxy matrix has also been reported 46 . We will describe the formation, structure, and properties of the epoxy-silica interpenetrating network IPN DGEBA-D2OOO-TEOS, consisting of the epoxide-amine...