Fluorescent dyes in solid matrices have many potential applications provided that their high optical efficiencies are achieved. We present here gold nanoparticles formed and incorporated together with fluorescent dye Rhodamine B into a film of polyvinyl alcohol (PVA). The increase of fluorescence of the dye results from its interaction with surface plasmons. The electric charge on the gold nanoparticles and the distance between them and the dye molecules has a significant effect on the fluorescence intensity. Fluorescence enhancement of 74% was achieved for the negatively charged particles. Dynamic measurements reveal decrease of fluorescent lifetimes of the dye in presence of gold nanoparticles. Our findings enable utilization of films with enhanced fluorescence in optical materials such as luminescence solar concentrators, solid state tunable laser and active waveguides.
Author(s): Liraz Larush [sup.1], Shlomo Magdassi [sup.] [sup.2] KEYWORDS : fluorescence; imaging; indocyanine green; nanoparticles; NIR In the last few decades, much attention has been focused on the potential use [...]Aims: Indocyanine green (ICG) is a US FDA-approved near-infrared fluorescent, water-soluble dye used for diagnostics in vitro and in vivo. The aim of this study was to develop insoluble nanoparticles based on a cationic polymer, ICG and a targeting molecule. The particles are intended for oral administration in the colon, having fluorescence in near-infrared, thus enabling remote detection. Materials methods: An aqueous dispersion of particles formed from Eudragit-RS by simple precipitation method possessing a mean size of approximately 100 nm and zeta potential of +16 mV was produced. Results: These particles are capable of binding both ICG and fluorescein isothiocyanate-IgG via noncovalent interactions. These composite particles retain the emission characteristics of the fluorescent precursors and also exhibit potential specific recognition ability. The particles were stable in intestinal fluid and are composed only of materials that are FDA approved. Conclusion: The nanoparticles may be suitable for in vivo imaging and therapy by oral delivery systems.
Silicon nanocrystals stabilized by an ionic liquid, dimethylimidazolium iodide, were synthesized by chemical reduction of SiBr.sub.4 with metallic Na in an organic solvent, diglyme. The nanoparticles were crystalline with a diamond cubic lattice and average size of 3.5 nm. Solid state 13.sup.C- and 29.sup.Si-NMR CP MAS spectra indicate the formation of imidazolium carbene, which ligates the Si atoms at the surface of the nanoparticles. The synthesized Si nanoparticles exhibit photoluminescence with an emission maximum in the red spectral range when excited at 320 nm. The origin of this luminescence is suggested to be mainly related to quantum confinement.
Reverse micelles system is suggested as a direct tool to study the influence of membrane matrix composition on the activity and structure of membrane-associated enzymes with the use of acid phosphatase (AP) as an example. In reverse micelles the functioning of the monomeric and dimeric forms of AP could be separately observed by variation of the size of the micelles. We found that including the lipids into the micellar system can dramatically affect the enzyme functioning even at low lipid content (2% w/w), and this effect depends on the lipid nature. Structural studies using CD spectroscopy and DLS methods have shown that the influence of lipid composition on the enzyme properties might be caused by the interaction of lipids with the enzyme as well as by the influence of lipids on structure and properties of the micellar matrix.
A new liposome-based near-infrared probe that combines both imaging and targeting abilities was developed for application in medical imaging. The near-infrared fluorescent molecule indocyanine green (ICG), and the cetuximab monoclonal antibody for epidermal growth factor receptor (EGFR) were attached to liposomes by passive adsorption. It was found that ICG molecules adsorbed to the liposomes are more fluorescent than free ICG and have a larger quantum yield. Cetuximab-adsorbed fluorescent liposomes preserved EGFR recognition, as is evident from internalization and selective binding to A431 colon carcinoma cells overexpressing EGFR. The binding of cetuximab-targeted fluorescent liposomes to A431 compared with IEC-6 cells (normal enterocytes expressing physiological EGFR levels) was greater by a factor of 3.5, ensuring imaging abilities with available fluorescent equipment. Due to relatively high quantum yield and specific tumor cell-recognizing ability, this technology deserves further in vivo evaluation for imaging and diagnostic purposes.From the Clinical Editor A new liposome-based near-infrared probe combining both imaging and targeting abilities is reported. Due to relatively high quantum yield and EGFR-expressing tumor cell specificity, this technology deserves further in vivo evaluation for imaging and diagnostic purposes.
At present there is no metallic ink that enables formation of conductive patterns at room temperature by a single printing step. Printing conductive features by metallic nanoparticle-based inks must be followed by sintering while heating to elevated temperatures, thus preventing their utilization on most plastic substrates used in plastic electronics. In this report we present a new silver nanoparticle-based conductive ink, having a built-in sintering mechanism, which is triggered during drying of the printed pattern. The nanoparticles that are stabilized by a polymer undergo self-sintering spontaneously, due to the presence of a destabilizing agent, which comes into action only during drying of the printed pattern. The destabilizing-agent, which contains Cl- ions, causes detachment of the anchoring groups' of the stabilizer from the nanoparticles surface and thus enables their coalescence and sintering. It was found that the new metallic ink leads to very high conductivities, by a single printing step: up to 41% of the conductivity of bulk silver was achieved, the highest reported conductivity of a printed pattern that is obtained from nanoparticles at room temperature.
Transparent conductive coatings are essential for fabrication of a variety of printed electronic devices such as flexible displays and solar cells. We report on a simple method to obtain such coatings by using aqueous dispersions of silver nanoparticles in an evaporative lithography process which is performed directly onto plastic substrates. In essence, a droplet containing silver nanoparticles is placed on top of a metallic mesh, instantaneously spreading over the mesh and the plastic substrate, and after the flow of the dispersion towards the wires of the mesh and drying, a transparent grid composed of the nanoparticles is formed. The silver nanoparticles are tailored to self-sinter upon short exposure to HCl vapors, due to the presence of polyacrylic acid salt on the surface of the particles. Therefore, immediate sintering of the silver nanoparticles in the thin lines of the grid occurs even at room temperature, enabling formation of transparent, flexible conductive grid on heat-sensitive substrates. The process yielded a conductive array having a very low sheet resistance, 9 ± 0.8 Ω/□, and a transparency above 75%. The application of the flexible conductive grid, which can replace conventional and expensive ITO, is demonstrated in an electroluminescent (EL) device.
A novel volatile microemulsion formed by the catanionic surfactant hexadecyltrimethylammonium octylsulfonate (TA(16)So(8)), heptane and water has been explored as a template for producing nanoparticles of hydrophobic organic materials. Butylated hydroxytoluene (BHT) was employed as the model hydrophobic substance. First, the oil-in-water microemulsion was formed, containing TA16So8 as the single emulsifier and BHT dispersed in the volatile microphase. Microstructure characterization by self-diffusion NMR revealed that BHT was indeed incorporated into the oil droplets and that the mean diameter of the main droplet population was 30 nm, larger than in the BHT-free microemulsion. Next, a rapid solvent and water removal by freeze drying allowed converting the microemulsion droplets into nanoparticles in the form of a dry, fine powder. This powder was freely dispersible in water to yield a stable suspension of amorphous BHT particles with a mean size of 19 nm and zeta-potential of +37 mV. The solid nanoparticles in the aqueous dispersion were thus smaller than the initial microemulsion droplets. For comparison, a conventional o/w microemulsion composed of CTAB and sec-butanol was also tested as a template for BHT particle formation by the same process, and it was found that it yielded crystalline particles of micrometre size. On the basis of our results, we anticipate the catanionic microemulsion method to be an efficient one for producing size-controlled, water-dispersible nanoparticles of other hydrophobic organic materials.
The inhibitory effect of ammonium glycyrrhizinate (AG) on crystallization of celecoxib (CXB) nanoparticles in aqueous medium was studied. CXB nanoparticles in powder form were prepared by rapid evaporation of all solvents from a volatile oil-in-water microemulsion. A powder containing 13 wt % CXB was obtained by immediate conversion of microemulsion droplets into nanoparticles by spray drying. CXB was amorphous in this powder, which could be easily dispersed 1 wt % in water as nanoparticles. However, these particles crystallized rapidly upon dispersion, and a significant particle growth was observed. The natural surfactant, AG, which is US Food and Drug Administration approved for oral administration, inhibited crystallization of CXB, enabling a stable dispersion of nanoparticles with average size of 14 nm. Molecular dynamics simulations revealed rapid attachment of glycyrrhizinate to the growing CXB crystal and suggested that crystallization inhibition is due to interactions between the hydrophobic part of glycyrrhizinate and the phenyl moieties of CXB. (C) 2011 Wiley-Liss, Inc. and the American Pharmacists Association J Pharm Sci 100:4390-4400, 2011
We describe here a new and simple method for preparation of polyurea nanocapsules from nanodroplets that were obtained by the phase inversion temperature (PIT) method. In the first stage, a nano-emulsion was prepared, by a heating-cooling cycle, in which the oil phase contained an oil soluble monomer (toluene 2,4-diisocyanate (TDI)). In the second stage, a water-soluble monomer and crosslinker (diethylenetriamine (DETA)) was added, leading to formation of a polymeric shell by an interfacial polycondensation reaction. The new method was demonstrated for obtaining nanocapsules of about 100 nm, in which hexadecane, dodecane, or decane were the core materials, without using any special equipment. The morphology and structure of the nanocapsules were evaluated by attenuated total reflection Fourier transform infrared (ATR-FTIR) measurements and electron microscopy. The thermal behavior of the nanocapsules containing hexadecane was studied by Differential Scanning Calorimetry (DSC) measurements, indicating that such nanocapsules can be utilized in thermal energy storage. Copyright (C) 2010 John Wiley & Sons, Ltd.
Modern printing is based on digitizing information and then representing it on a substrate, such as paper, pixel by pixel. One of the most common methods of digital printing is through inkjet printers. The process of inkjet printing is very complicated, and the ink used must meet certain chemical and physicochemical requirements including those related to storage stability; jetting performance; color management; wetting; and adhesion on substrates. Obviously, these requirements — which represent different scientific disciplines such as colloid chemistry, chemical engineering, and physics — indicate the need for an interdisciplinary book that will cover all aspects of making and utilizing inkjet inks.
This book provides basic and essential information on the important parameters which determine ink performance. It covers not only the conventional use of inkjet technology on graphic applications, but also the extension of this method to print various functional materials, such as the use of conductive inks to print light-emitting diodes (LEDs) and three-dimensional structures. Thus, the book will serve a large community: industrial chemists who deal with ink formulations and synthesis of chemicals for inks; chemical engineers and physicists who deal with the rheological and flow properties of inks; and researchers in academic institutes who seek to develop novel applications based on inkjet printing of new materials.
An electrodeposition process is provided for depositing a film of org. nanoparticles from liq. dispersion on conductive surfaces. A special feature of the nanoparticles is their ability to aggregate as a response to pH change. The diffusing phase was formed by polylactic acid (43.9 mg) dissoln. in acetone (7.5 mL) and this phase was added dropwise to the dispersing phase of water (TDW, 20 mL) contg. Na oleate (22.2 mg) and NaOH (0.3 mg) while applying continuous moderate stirring to give a dispersion of polylactic acid nanoparticles (av. diam. 153 nm). [on SciFinder(R)]
A process is disclosed for low temp. sintering of a pattern on a substrate. The substrate is precoated with a film of said nanoparticles and subsequently treated with said at least one sintering agent. The nanoparticles and at least one sintering agent are pre-formulated in an aq. dispersion, said dispersion being applied onto the substrate and allowed to dry at 5-150°. Nanoparticles comprising at least one metal silver, copper, gold, indium, tin, iron, cobalt, platinum, titanium, titanium oxide, silicon, silicon oxide or any oxide or alloy thereof. Said sintering agent contains chloride, e.g., poly(diallyldimethylammonium chloride) (PDAC). Said polymer is selected amongst polyimides and polypyrroles. A dispersant is selected from polycarboxylic acid esters, unsatd. polyamides, polycarboxylic acids, alkylamine salts of polycarboxylic acids, polyacrylate dispersants, polyethyleneimine dispersants and polyurethane dispersants. Said substrate is selected from glass, polymeric films, plain paper, porous paper, nonporous paper, coated paper, flexible paper, copier paper, photo paper, glossy photopaper, semi-glossy photopaper, heavy wt. matte paper, billboard paper, vinyl paper, high gloss polymeric films, transparent conductive materials, and plastics: polyethylene terephthalate PET, polyacrylates (PA), polyethylene naphthalate (PEN), polyethersulfone (PES), polyethylene (PE), polyimide (PI), polypropylene (PP) and polycarbonate (PC). [on SciFinder(R)]
A process for prodn. of silica nanocapsules comprises (a) obtaining a nanoemulsion of an aq. phase and an oil phase and at least one surfactant, the nanoemulsion being formed by the process comprising (i) forming an oil-in-water (O/W) emulsion of an aq. phase and an oil phase comprising at least one hydrophobic material and at least one silica precursor in the presence of at least one surfactant, (ii) heating the O/W emulsion above its phase inversion temp. (PIT) to obtain a water-in-oil (W/O) emulsion, and (iii) cooling the W/O emulsion below the PIT temp., thereby forming a nanoemulsion of oil droplets in water, and (b) inducing interfacial polymn. of the silica precursor around the oil droplets in the nanoemulsions thereby obtaining the silica nanocapsules. The hydrophobic material is selected from a wide range of oils and waxes, and the process may be used to encapsulate drugs, bioactive compds., cosmetic materials, flavoring agents, colorants, and antioxidants. [on SciFinder(R)]
Dispersion of carbon nanotubes (CNTs) in a liquid medium requires separation of the bundles, a process which is usually achieved by sonication for prolonged time, and is suitable for low sample volumes. A rapid and simple process for producing dispersions of multi-wall carbon nanotubes (MWCNTs) was developed, by using a high pressure homogenization process (HPH). Dispersions of MWCNTs were prepared in aqueous solutions containing ethoxylated octyl phenol, and were compared to dispersions prepared by the conventional sonication method. They were evaluated by rapid measurement of sedimentation rate during centrifugation, and results compared to other evaluation methods. It was found that samples processed by HPH for a short time yielded similar dispersions to those obtained by sonication for prolonged time, and that the first pass through the homogenizer, which takes less than a minute, is the most significant in breaking up the bundle. The process can be used in a continuous mode for large volumes, and is very suitable for large-scale industrial production. Evaluation of the CNT dispersions by centrifugal sedimentation analysis correlates well with other time-consuming methods.