The micro-photoluminescence (μ-PL) spectra of a single CdTe/CdSe quasi- type II core-shell colloidal quantum dots (CQDs) unambiguously reveal an emission of a biexciton (2X), a triexciton (3X) and a quadraexciton (4X) under continuous-wave excitation. The CQDs were characterized by optical measurements and theoretical consideration of carrier's wavefunctions distribution of a quasi-type II core-shell structure.

Synthesis of Au, Ag monometallic, and Au-Ag bimetallic nanoparticles have been synthesized by successive reduction of metal salts with ascorbic acid on prefabricated seeds in the presence of cetyltrimethylammonium bromide (C16H33)N(CH3)3Br (CTAB), as a cationic surfactant, is presented in this paper. This coverage method for the prefabricated seeds is uniform, although in some cases deviations from a spherical shape are observed with the formation of nanorods or nanoprisms. Results using high-resolution STEM-XEDS elemental mapping suggest that the actual distribution of the two metals within the multilayer spheres may involve partial alloying of the metals.

Pure and Cu-doped quantum dots of ZnSe@ZnS were synthesized in aqueous phase using microwave irradiation at 140 °C. X-ray diffraction analyses suggested the development of a ZnSe-ZnS structure. UV-vis measurements evidenced that the presence of Cu species in quantum dots caused the blue shift of exciton peaks with respect to pure, i.e. non doped ones. Photoluminescence spectra of quantum dots synthesized at Zn/Cu mole ratios of 1/0.001 and 1/0.005 exhibited a very strong emission peak centered on ˜ 515 nm. On the contrary, a weak emission peak was observed at 412 nm in pure ZnSe@ZnS quantum dots. The observed emission at 515 nm was attributed to the internal doping of Cu species, which should have induced d-d transitions in the host lattice. Quenching of the luminescence at 515 nm was observed for nominal Cu concentrations above 0.005 mM.

Solid state sintering of Ag nanoparticles was used to bond Cu wires to Cu foils at temperatures less than 250°C. The Ag nanoparticles are coated with an organic shell to prevent sintering at room temperature. After annealing the nanoparticles at 200°C, the decomposition of the organic shell was confirmed using TGA and Raman spectroscopy. The joint strength was measured by tensile shear tests, which shows that the joint strength increases as the bonding temperature increases. Metallic bond between Ag nanoparticles and Cu was achieved with no contamination. Bonds formed by our method, was confirmed to withstand temperatures higher than the bonding temperatures.

Semiconductors or metal nanoparticles (NPs) using their monolayer bindings with self-assembly chemicals are an attractive topic for device researchers. Electrical performance of such structures can be investigated for a particular application, such as memory device. Currently, Au NPs has been reported to show a substantial potential in the memory applications. In this study, Au NP and gluing layer were fabricated through a new method of monolayer formation of a chemical bonding or gluing. In this study, a new NPs memory system was fabricated by using organic semiconductor, i.e., pentacene as the active layer, evaporated Au as electrode, SiO2 as the gate insulator layer on silicon wafer. In addition, Au NPs coated with binding chemicals were used as charge storage elements on an APTES (3-amino-propyltriethoxysilane) as a gluing layer. In order to investigate chemical binding of Au NP to the gate insulator layer, GPTMS (3-glycidoxy-propyltrimethoxysilane) were coated on the Au NPs. As a result of that, a layer of gold nanoparticles has been incorporated into a metal-pentacene-insulator-semiconductor (MPIS) structure. The MPIS device with the Au NP exhibited a hysteresis in its capacitance versus voltage analysis. Charge storage in the layer of nanoparticles is thought to be responsible for this effect.

Silica nanoparticles with metallic nanoclusters are of great interest in many applications from bio imaging to optical devices. The nanometric size of metallic particles induces specific absorption properties due to surface plasmon resonance. This absorption mainly depends on the morphology of the nanoparticles. If the encapsulation of metallic nanoparticles into a silica shell is now well developed, there is a great interest on the synthesis of either silica nanoparticles covered by metallic nanoparticles or silica cores with metallic shells. Two main ways are described in the literature to bind metallic nanoparticles onto the silica nanoparticles. The first way consists on the mixing of a metallic colloidal sol with another sol containing silica nanoparticles bringing at their surface the suitable chemical functions, able to properly interact with the metal nanoparticles. The second way consists on the use of a reducing agent to reduce the metallic ions introduced successively into a suspension of silica nanoparticles. Herein is proposed an original third method based on a double surface functionalization of the silica nanoparticles. This method is actually based on an in-situ reduction of metallic ions by two chemical function (amino and thiol) previously grafted onto the surface of the silica nanoparticles. The silica nanoparticles are synthesized by a reverse micro-emulsion sol-gel process. This synthesis gives monodispersed silica nanoparticles of 40 nm diameter. The surface functionalization of the silica nanoparticles is performed by sol-gel reactions within the micro-emulsion, using two silane-coupling agents owning either a thiol function or a diamino function.The functionalized silica shell increases the chemical activity of the surface of the nanoparticles. But the capability of this functionalized surface to reduce metallic ions depends mainly on the chemical function used. Two examples are given in this study: the diamino functions, which reduce the copper ions, and the combination of the diamino and the thiol functions in a silver nitrate solutionwhich induces the growth of small silver nanoparticles (4-5 nm) on the silica nanoparticles’ surface.

A novel synthesis route to organic-capped and colloidal ZnO quantum dots (QDs) has been developed. Specifically, zinc-di-butoxide was hydrolyzed with very dilute water (100˜600 mass ppm) dissolved in hydrophilic benzylamine and polymerized to ZnO by dehydration condensation. After formation of ZnO QDs with 2˜3 nm in diameter, growth of the QDs and exchange the surface capping ligand from hydroxyl groups and/or benzylamine to oleylamine were developed by heating the colloidal solution with oleylamine. The size of the ZnO QDs finally obtained was in the range 3˜5 nm in diameter. The QDs show high dispersibility in various organic solvents. Clear UV emission due to exciton recombination was observed; and its energy was varied according to the quantum size effect from 3.39 to 3.54 eV. By using lithium-free zinc-di-butoxide as a starting material, the defect-related VIS emission was successfully decreased and the UV emission becomes dominant. The influence of water concentration in benzylamine and oleylamine on UV emission intensity was also investigated.

A novel three dimensional (3D) self-assembled hierarchical bismuth oxide was prepared via a sol-gel synthesis with the aid of capping agent of polyethylene glycol-8000 (PEG-8000) at 85 ℃ in 45 min. The morphology evolution was studied versus reaction time and interpreted in terms of growth mechanisms. The as-grown 3D hierarchical flower-like bismuth oxide was crystalline cubic gamma-phase. The morphology and crystal phase of these 3D cubic gamma-phase bismuth oxide flowers were not changed with heating up to 600 ℃. The flower-like morphology was attributed to modification of the growth kinetics by the capping agent from the PEG-OH bond bridging with bismuth ions. Europium doped gadolinium oxide shell were further deposited on the bismuth oxide cores through sol-gel synthesis showing good photoluminescence characteristics at 610 and 622 nm under the excitation at 280 nm.

Luminescent nanoparticles such as quantum dots (QDs) are beginning to appear in SSL devices and other commercial products. The allure of QDs in SSL these applications is the potential to provide enhanced device performance (e.g., improved energy efficiency, better color rendering properties, etc.) than is possible with conventional technologies. When used in SSL and other applications, QDs are typically incorporated into or coated onto a solid organic or inorganic matrix and then are excited using external stimuli (e.g., blue light with a maximum wavelength of 450 nm). This structure is vastly different from the colloidal environment in which QDs are typically synthesized and characterized. Bridging the gap between the measurements typically acquired by QD providers and those needed by potential end-users is currently difficult due to the absence of agreed upon standard test methods. Measurements taken in colloidal QD suspensions often do not translate to solid-phase material characterizations due to a variety of factors including sample preparation methods (e.g., temperature, solvents, etc), QD concentrations, and effects arising from the presence of the solid matrix. Additionally, solid samples are more likely to exhibit diffuse reflectance and/or diffuse transmittance necessitating the use of an integrating sphere and a computer-controlled spectrometer to acquire accurate readings. This paper discusses the development of a standard test method to measure the quantum efficiency of QDs contained in solid organic and inorganic matrices. This standard is being developed under the auspices of the International Electrotechnical Commission, Technical Committee 113 on Nano-electrotechnologies.

Colloidal Europium-doped In2O3 nanocrystals were successfully prepared in a noncoordinating solvent using indium (III) and europium (III) acetates as precursors. The concentration of doped europium was varied up to 2.88 at%. Linear electrogyration induced by coherent circularly-polarized light was observed from samples in which europium-doped In2O3 nanocrystals were embedded in photopolymer oligoethracryalte matrices. The result on ˜2.5 at% europium-doped sample shows that the maximal linear electrogyration could reach to ˜12 deg./mm at an electric field of 120V/cm for He-Ne laser.

We characterized the optical nonlinearities of CdSe nanocrystals surrounded by rod-like CdS shells with ultrafast measurements of time-resolved photoluminescence. We measured the exciton-exciton interaction to be, depending on structure details, attractive or repulsive, by as much as 29 meV, due to the unique band alignment in the CdSe/CdS. This feature makes CdSe/CdS dot/rods promising gain media for solution-processable lasers, as it appears combined with 80% photoluminescence quantum yield, narrow size and shape distributions and the antenna effect of the CdS rod shell enhancing optical absorption by more than a factor 50 with respect to bare dots.

Copper nanoparticle was prepared by liquid phase reduction technique. Cu2+ was reduced to copper particle by adopting different types of reductants. Ascorbic acid (C6H8O6), phosphinic acid (H3PO2), titanium sulfate (Ti2(SO4)3) and sodium borohydride (NaBH4) were chosen as reductant, respectively. The effect of reaction driving force upon the average size of copper particle was investigated in the paper. It can be concluded that there is a firm relationship between the reaction driving force and the average size of copper particle. The average size of copper particle decreases with the increasing of reaction driving force.

The transport of electric charge is an important phenomenon in the systems like interacting quantum dots and molecules, and in polymers, including DNA molecules. We expect that in these nanostructure systems the key role is played by the interaction of the charge carriers with the optical phonons. We show the role of the multiple scattering of the charge carriers on the optical phonons in the inter-molecular transfer. The charge carrier transport based on this mechanism will be discussed theoretically and compared with the earlier experimental results on the charge transport in molecular Donor-Acceptor charge transfer crystals and also in other systems. In order to treat theoretically the electron transfer between two zero-dimensional nanostructures, we will use the model of two interacting quantum dots coupled by the electron inter-dot tunneling mechanism. A connection with the popular Marcus semiclassical charge transfer theory between molecules is also shown. We will use the nonequilibrium quantum electronic transport theory based on the nonequilibrium Green's functions.

In this paper, we report that the experimental procedures for the preparation of conductive color powders that were aggregated from color pigment and conductive materials. We first modified the pigment and make the particles surface to have charges (ex: positive) and modified another conductive materials like ITO、Au、Ag particles or conductive polymer to be opposite charges (ex: negative). Then these two kinds of charge particles will aggregate in appropriate processing by static electricity and form a powder. After annealing treatment, the conductive color powder with ITO particles reveals good thermal stability and lower surface resistivity.

Large-scale two dimensional ordering of silica nanospheres on GaN substrates was fabricated using spin-coating and observed using Matlab-based Nomarski image processing, which was developed to calculate the surface coverage of 2D and 3D ordering of silica nanospheres on GaN substrates. Optimal spin coating condition and SDS concentration were investigated with Nomarski image processing and an SEM. The details on spin coating process parameters or SDS concentration vs. surface coverage of silica nanospheres on GaN substrate are discussed, along with a theoretical exploration of the effects of nanosphere patterning on photonic crystals fabricated using this method.

Sufficiently dense films of cerium oxide nanocrystals modified with decanoic acid, with sizes of ˜9 nm, were fabricated on the surface by modifying a silicon substrate with 3,4-dihydroxyhydrocinnamic acid, where catechol group lied at the top. By doing this, no further pretreatment for the modified cerium oxide nanocrystals is required to fix them chemically on the substrate. Selective adhesion between nanocyrstals and the substrate for the two-dimensional assembly can be attributed to the chemical bonding formed by on-site ligand exchange between carboxyl and catechol groups.

Monodisperse ZnO quantum dots (QDs) with a particle size of about 5 nm have been synthesized. Isopropanol together with hexane were utilized to precipitate ZnO nanoparticles to form condensed phases, ranging from white flocculation, to gel-like fluid, and to transparent solid. The morphology and structure in the transparent ZnO solid was characterized by UV-vis, X-ray diffraction, small-angle X-ray scattering, transmission electron microscopy, and scanning electron microscopy. The mechanisms for the formation of transparent ZnO QDs close-packed structure were monitored via UV-vis spectra, and found likely to be a colloidal crystal. The colloidal crystal is transparent and absorbs UV light efficiently. Possible conditions for the formation of the ZnO QDs colloidal crystal are discussed.

The crystallinity of colloidal CdTe nanoparticles has been enhanced post synthesis. This control over the nanoparticles’ properties has been achieved using non-adiabatic thermal processing. The technique preserves the polymer capping and hence introduces no adverse effects on the nanoparticles’ optical properties. The crystallinity is probed primarily through Raman spectroscopy in a hollow core photonic crystal fiber and x-ray diffraction powder studies.

Nanofluids are engineered colloidal suspensions of nanometer-sized particles in a carrier fluid and are receiving significant attention because of their potential applications in heat transfer area. Theoretical investigations have shown that the enhanced thermal conductivity observed in nanofluids is due to nanoparticle clustering and networking. This provides a low resistance path to the heat flowing through the fluid. However, the surface coating of the nanoparticles, which is often used to provide stable dispersion over the long term, may act as a thermal barrier, reducing the effective thermal conductivity of the nanofluid. Moreover, nanofluids with the same type of nanoparticles may exhibit different effective thermal conductivities, depending upon the thermal properties and thickness of the coating. In this context, thermal conductivity characterization of well dispersed iron oxide nanoparticles with two different surface coatings was carried out employing the transient hot wire technique. The diameter of the iron oxide core was 35 nm and the coatings used were aminosilane and carboxymethyl-dextran (CMX) of 7nm in thickness. Preliminary results suggest that effective thermal conductivity of CMX coated nanoparticle suspensions is slightly higher than that of aminosilane coated nanoparticles. In both cases, the effective thermal conductivity is higher than that predicted by the Maxwell model for composite media.

The surface of freshly etched silicon nanoparticles (Si-NPs) was covalently bonded with alkyl groups and esters via thermally induced hydrosilylation. The surface chemistry of functionalized Si-NPs was analyzed at different air exposure time by means of Fourier transform infrared spectroscopy (FTIR). We observed that the stability of functionalized Si-NPs significantly depends on the type of organic ligands attached to their surface. Ester-terminated Si-NPs exhibit higher stability compared to that are bonded with alkyl groups. We show that the use of esters with large spatial configuration causes a lower surface coverage of Si-NPs but at the same time offers better protection against surface oxidation.