Twv

That facilitate self-assembly mediated by metal ion coordination, and one of the most common is the terpyridyl moiety. Thus, two porphyrins bearing a single terpyridyl group can be dimerized by addition of a wide variety of metals 175-178 . In a similar approach, coordinating metalloporphyrins around a central chemical entity that bears more than one ligand capable of coordinating in the axial position can make discrete open multimers of porphyrins. If the central mul-titopic ligand is...

Size Determination of Nanocrystallites by Low Wavenumber Raman Spectroscopy

Because of the strong size dependence of the optoelectronic properties of nanocrystalline samples, the determination of the crystallite sizes is a crucial point in the characterization of nanocrystallites. Besides methods like high resolution transmission electron microscopy and X-ray diffractometry, low-wavenumber Raman spectroscopy was established as a fast method to determine the average dot size. The modes in the low-wavenumber range of quantum dot samples can be attributed to the torsional...

Hartree Fock Approximation Of Coulomb Interaction Between 3d Confined Electrons

Schematic representation of a 2D parabolic potential (left) with cylindrical symmetry in the xy-plane showing equally spaced energy levels and the square potential (right) with the first two quantized levels in the z-direction such that E1z E0z hw. Reprinted with permission from 112 , J.-P. Leburton and S. Nagaraja, Optical Spectroscopy of Low Dimensional Semiconductor, NATO ASI Ser. E, Vol. 344, p. 235. 1997, Kluwer Academic. which given the two-body interaction (20) can only be...

Quantum Yield

Photodegradation of pollutants is a direct way to examine the performance of semiconductor nanoparticles for photo-catalysis. Quantum yield (quantum efficiency) is a criterion for measuring the efficiency of a photocatalytic reaction. It is defined as the number of consumed or destroyed molecules per absorbed photon 150 . In the case of multiple reactants, quantum yield is sometimes based on the consumption of a particular reactant. Nevertheless, precise determination of actual absorbed photons...

Processing Of Infrared Photodetectors

An infrared FPA device consists of two parts. The first one is the sensor array which is used to convert the infrared radiation into the electrically readable signal. In a QWIP, this signal is the photocurrent. The second part of the QWIP is the electrical circuit array, also called the readout circuit (ROC), which is used to transfer the electrically readable signals generated in very pixels of the array in a series manner. Such a signal transferring mode is very convenient for further data...

Introduction

One of the most important physical parameters to describe the quality of a piece of semiconductor material is the electron scattering length le. Also referred to as the mean-free path, it stands for the average distance between the randomly distributed scatterers in the material, such as lattice defects, impurities, and phonons. The electron mean-free path is typically a few nanometers (1 nm 10-9 m) in silicon and about 100-200 nm in high-quality compound semiconductors such as GaAs. The...

Technology For Qwip Material

The quantum well is the core for the infrared detector operation. Conventional infrared detector materials of HgCdTe and InSb utilize inter-band transitions for photon excitation, whereas the QWIP utilizes the inter-subband optical transitions. In HgCdTe and InSb, the optimized material size is of micrometer order determined by the diffusion length of photoexcited carriers and surface-state induced energy band bending. The subband alignment in the QWIP is directly determined by the quantum well...

Bze

STM image of a periodic array of Fe islands nucleated on the dislocation network of a Cu bilayer on Pt(111) at 250 K. Reprinted with permission from 46 , H. Brune et al., Nature, 394, 451 (1998). 1998, Macmillan Magazines Ltd. the Cu film. This strain relief mechanism gives rise to a characteristic pattern of orthogonal stripes at the film surface. Mass selected Ag7 clusters have been deposited at two different impact energies (20 and 95 eV) on a similar dislocation network formed by...

Nomenclature and Chemical Structures of Vesicle Forming Glycerophospholipids

Although the basic principles of vesicle formation are for all types of vesicle-forming amphiphiles in the end the same independently of whether they are charged, neutral, or polymeric the descriptions in Sections 2 and 3 focus on just one particular group of phospholipids, the so-called phosphatidylcholines (PCs). POPC (see Fig. 1) is a particular PC, namely more precisely, (also called Since the nomenclature of glycerophos-pholipids (such as POPC) is often not so well known to those not...

Summary

After nearly 40 years of intense research, synthetic supramolecular chemistry has developed a wide variety of tools, methods, and strategies to form a staggering number of self-assembled and self-organized nanoscaled entities with diverse functions. Because porphyrins are rigid molecules, they have predictable shapes and orientations therefore, these molecules are very often used as techtons. Porphyrins can act as monotopic caps, as linear linkers, as 90 turns, as bifurcating T-shaped...

Control of Highly Ordered States

Some organogelators form highly ordered structures like those in aqueous bilayer membranes. Therefore, it is a convenient method to arrange the functional groups in the molecular assemblies. The arrangement and control of functional groups will certainly be an invaluable technique in many application fields such as sensors, molecular devices, and nano fabrication. Lipophilic peptide-derived organogelators such as G-10 and G-11 show specific chirality, which is detectable by CD spectroscopic...

Info

Experimental room temperature Raman spectra for purified single wall carbon nanotubes excited at five different laser excitation wavelengths. The laser wavelength and power density for each spectrum are indicated, as are the vibrational frequencies (in cm-1) 5 . The equivalent incident photon energies for the laser excitation are 1320 nm 0.94 eV 1064 nm 1.17 eV 780 nm 1.58 eV 647.1 nm 1.92 eV 514.5 nm 2.41 eV. Reprinted with permission from 5 , A. M. Rao et al., Science 275, 187...

PolyDLlactidecoglycolide Nanoparticles

The most widely used emulsion solvent evaporation method for preparation of nanoparticles using PLGA requires surfactants to stabilize the dispersed particle 62 . This method often has a problem in that the surfactant remains at the surface of the particles and hence is difficult to remove especially where PVA is used as surfactant. Other surfactants such as span series or tween series, PEO, etc. are also used to stabilize with some disadvantages like removal of solvents, toxicity, low particle...

References

Pockels, Nature 43, 437 (1891). 2. A. Pockels, Nature 46, 418 (1892). 3. A. Pockels, Nature 48, 152 (1893). 4. A. Pockels, Nature 50, 223 (1894). 5. L. Rayleigh, Philos. Mag. 48, 321 (1899). 6. W. B. Hardy, Proc. R. Soc. London A 86, 610 (1912). 7. H. Devaux, Smithsonian Inst. Ann. Rep. 261 (1913). 8. I. Langmuir, J. Am. Chem. Soc. 39, 1848 (1917). 9. I. Langmuir, Trans. Faraday Soc. 15, 62 (1920). 10. K. Blodgett, J. Am. Chem. Soc. 57, 1007 (1935). 11. K. Blodgett, Phys. Rev. 51, 964...

By Dehydration and Rehydration

The dehydration of a vesicle suspension followed by a controlled rehydration at a temperature above Tm leads to the fusion of small vesicles present in the suspension, resulting finally in the formation mainly of MLVs 147-149 . This procedure is based on the instability of dried SUVs and a lipid lamellae formation (SUV fusion) during the water removal. The resulting vesicle suspensions are referred to as dehydration-rehydration vesicles or dried-reconstituted vesicles (DRVs) 31 . DRVs are often...

By the Detergent Depletion Method

If a bilayer-forming lipid is mixed in an aqueous solution with a micelle-forming surfactant (often called detergent, from the Latin word detergere, meaning to wipe off or to clean) under such conditions that the detergent molecules dominate, mixed detergent lipid micelles are formed 240-243 . These aggregates are composed of bilayer-forming amphiphiles as well as micelle-forming amphiphiles and are disc-like, sheet-like, or cylindrical structures. In the detergent-depletion method (also called...

What Are Vesicles Liposomes 11 Introduction

Vesicles more precisely normal vesicles are a particular type of polymolecular aggregate polymolecular assembly of certain amphipathic molecules, formed in aqueous solution. A vesicle is composed of one or more closed shells which are usually 4-5 nm thick that entrap a small volume of the aqueous solution in which the vesicle is formed. Vesicles are often spherical under osmotically balanced conditions and can have diameters between about 20 nm and more than 0.1 mm. If an analogous type of...

Lamellar Phase and Gel Phase

A liquid crystalline state also called the mesophase of a substance is a state between a pure crystal characterized by a high order of rigid molecules and a pure liquid characterized by rapid molecular motions of disordered molecules 32 . There are dozens of different liquid crystalline states, all characterized by a different degree of molecular mobility and order. Liquid crystals can be produced either by heating a particular crystalline solid called a thermotropic liquid crystal or by...

Layerby Layer Deposited Films

Only a few examples of films containing porphyrins made by the layer-by-layer technique are cited, because to date the degree of organization after the first layer is somewhat limited. Briefly, the process involves dipping a charged substrate into a solution containing an organic molecule or polymer of the opposite charge. After annealing and rinsing, it is dipped into a second solution that has molecules or polymers with the opposite charge as the first. This can be repeated, but the...

Technologies for Production of DNA Nanoparticles

Two major technological approaches to the production of DNA nanocarriers can be distinguished conventional nanoparticle preparation as described in Section 3 and the Figure 12. Structure of type 2 adenovirus according to Stewart and Burnett 189 . Adenoviruses consist of a core containing linear double stranded DNA of 40 kilo base pairs which is surrounded by a complex capsid. They do not possess a lipid envelope. The average size of adenovirus particles ranges between 70 and 110 nm. The genomic...

Influence Of A Perpendicular Electric Field Upon A Quantum Well

Upon the application of an electric field perpendicular to a quantum well, the quantum well becomes tilted Fig. 1 changing the density of state the group velocity and the wavefunction of the electron. The effects of an applied electric field on the energy dependence of the density of states and the wavefunction for a symmetric quantum wells are investigated within this section. The redistribution of the density of states is calculated by using the method of the logarithmic derivative of the...

Beam Resists

Electron beam lithography is the technology providing the highest resolution structures and, thus, it is the predominant tool used in nanolithography. On the other hand often electron beam lithography could also serve as a benchmark to evaluate the ultimate resolution capabilities of the different resist systems. The best known high resolution e-beam resist is poly methyl methacrylate PMMA , which actually is one of the simpler resist systems, since it is a one component resist. Although this...

R

Typical reactions encountered in chemically amplified resists. introduced for 248 nm resists but are currently used also in numerous systems designed for 193 and 157 nm lithography. Acid catalyzed main chain cleavage represents another interesting case 73 . On the other hand one of the first systems proposed for 248 nm lithography was a negative resist based on acid catalyzed cross-linking of phenolic polymer by melamine through trans-etherification reactions 74 . Similar formulations...

Subsidiary Equations

We first consider the set of equations in relation to MESFET modeling, in which there are no quantum wells formed at the layer interfaces. In this case there is no need to solve the Schr dinger equation explicitly. For the nondegenerate approximation, which is valid when the pure semiconductor is not too highly doped with impurities, the electron density is given by the simple exponential form Here, kB 1.38 x 10-23 JK-1 is the Boltzmann constant, and Nc 2 2wm kBTeh-2 15 where m is the effective...

Cross Linking of Amphiphilic Macromolecules

Nanoparticles have been prepared from polysaccharides, proteins, and amphiphilic macromolecules by inducing their aggregation followed by stabilization by either heat denat-uration or chemical cross-linking. It can be done by a water-in-oil emulsion system or in aqueous environment. The cross-linking technique was first used by Kramer et al. in 1974 16 . In this technique, an aqueous solution of protein was emulsified in oil using a high-speed homog-enizer sonicator and the water-in-oil...

ULVs and OLVs Prepared by the Proliposome Method

This method is related to the ethanol injection method described in Section 3.18 in the sense that ethanol is also used as a cosolvent. An initial mixture called proliposome mixture 224 containing vesicle-forming amphiphiles egg PCs 225 , soybean PCs, or hydrogenated soybean PCs 224 , ethanol or glycerol or propyleneglycol , and water is converted into vesicles by a dilution step 224-226 . It is a method that seems to be particularly applicable to the bulk production of lipid vesicles. The...

Porphyrin Polymers and Aggregates

What distinguishes the simple open multimers from the polymers discussed in this section is largely the fact that two or more of the components of the self-assembling system are at least ditopic. Though they have a long, rich history, coordination polymers are of renewed interest in nanoscaled materials see, e.g., 194 . The simplest cases, Fig. 7A, B, C are merely polymeric forms of the dimers discussed earlier, but more complex polymers can be formed such as in Fig. 7D and E . Again, since the...

Ssi Msi Lsi Vlsi Ulsi Glsi 1960 1965 1970 1975 1980 1985 1990 1995 2000

Energy band structures of an -MOS structure under the gate bias of a VG 0, b VG Vth. Figure 3. Growth in the number of components per IC. Reprinted with permission from 4 , H. Veendrick, Deep-submircon CMOS IC, p. vii. Kluwer Academic, Dordrecht, 2000. 2000, Kluwer Academic Publishers. A similar conclusion was derived by Lee and Park from their research activities in the field 52 . Moreover, we have room-temperature single-electron storage effects that support the pursuit of...

By the Electroformation Method

If the swelling of PCs or other phospholipids in water or in an aqueous solution with low ionic strength is carried out in a controlled way by applying an alternating electric field, instead of myelin figures, GUVs form, with diameters typically between 5 and 200 m, depending on the chemical structure of the lipids used, on the lipid composition, on the swelling medium, and on the external electric field parameters 102-104 . The vesicles are often formed under a light microscope in a specially...

C2h5o C2h5o

Micelles with acetal groups on their surface freeze dried micelles dissolved in H2O and acidified with HCl polypropylene PPO -PEO block copolymer or with tetra-functional PEO-PPO 2-N-CH2-CH2-N- PPO-PEO 2 72 . Such coats are bound to the core of the nanosphere by the hydrophobic interactions of the PPO chains, while PEO chains protrude into the surrounding medium and form a steric barrier, which hinders the adsorption of certain plasma proteins onto the surface of such particles. On the other...

Solvent Displacement or Nanoprecipitation

In this method, the organic solvent selected is completely dissolved in the external aqueous phase thus there is no need for evaporation or extraction for polymer precipitation. Polymer and drug are dissolved in acetone, ethanol, or methanol and incorporated under magnetic stirring into an aqueous solution of surfactant. The organic solvent diffuses instantaneously to the external aqueous phase followed by precipitation of the polymer and drug. After the formation of nanoparticles, solvent is...

Polyethylene glycol Coated Nanospheres

Nanospheres of PLA, PLG, or poly e-caprolactone coated with PEG may be used for intravenous drug delivery. PEG and PEO denote essentially identical polymers. The only difference between the respective notations is that methoxy groups in PEO may replace the terminal hydrox-yls of PEG. PEG coating of nanospheres provides protection against interaction with the blood components, which induce removal of the foreign particles from the blood. PEG b Figure 5. a Poly ethylene oxide...