Angular-Dependent Metal-Enhanced Fluorescence from Silver Island Films

In this letter we report the observation of angular-dependent Metal Enhanced Fluorescence (MEF) from fluorophores deposited onto silver island films (SiFs). When illuminated with laser light (473 nm) at angles of 45 and 90 degrees from the surface, SiFs scattered light at wide observation angles biased by the direction of the incident light. We observed angular-dependent MEF (10-fold) from FITC-HSA immobilized onto the SiFs, again slightly biased with respect to the direction of the incident light. We also measured the photostability of FITC from the back of the glass substrate at angles of 225 and 340 degrees.     

Interfacial and micellar properties of anionic azo dye-surfactant binary systems

The association of an anionic dye C.I. Reactive Orange 16 (RO16) and different types of surfactants, i.e., anionic surfactant sodium dodecylsulfate, nonionic surfactants poly(oxyethylene) ethers (C _m POE₁₀, m = 12, 16, and 18; C₁₂POE _n , n = 4, 10, and 23), was investigated using tensiometry in a certain micellar concentration range. RO16 was shown to aggregate in water when its concentration is above the threshold value. The surface tension lowering and critical micellar concentration (CMC) values were interpreted on the same grounds as those for surfactants mixtures. The tensiometric measurements of dye-surfactant systems are carried out as a function of the molar concentration of solution at 25°C. Using Rubingh’s regular solution theory, the values of interaction parameters were found to be negative for all studied binary mixtures. These negative values indicate that there is an attractive interaction of the surfactants in mixed micelles and reflect synergistic behavior of a mixture. In all studied systems, deviations from ideal behavior were observed depending on the type of surfactant. Interaction parameters calculated using regular solution theory are changed from −2.62 to −12.43. The smallest deviation from ideal behavior is obtained for the RO16-C₁₂POE₄ mixed system; i.e., in the case when nonionic surfactant has the shortest alkyl chain and the smallest number of ethylene oxide units. The text was submitted by the authors in English.     

Metal-Enhanced Fluorescence Solution-Based Sensing Platform

In recent years our laboratories have reported the favorable effects for fluorophores placed in close proximity to surface immobilized silver nanostructures. These include; greater quantum yields, reduced lifetimes (increased photostability) and directional emission. However, while these findings are likely to find multifarious applications for surface assays based on enhanced fluorescence detection, a solution based enhanced sensing platform has yet to be realized. In this short, note, we show how SiO2-coated silver colloids, indeed provide for a solution based enhanced fluorescence sensing platform with a 3-5 fold enhancement typically observed.     

Variations in raindrop size distributions measured at Rome

Summary The knowledge of raindrop size distributions is of great interest to cloud physicists, radar meteorologists and communication engineers. Beginning from the Winter 1986–87, the Precipitation Group of the Atmospheric Physics Institute installed on the roof of the Institute building in Roma-Eur a disdrometer RD-69. The sensor is an electromechanical device with surface of 50 cm² able to measure the raindrop diameter with a precision of 5% and a resolution (delay between two drops hitting the sensor) of one millisecond. After the calibration, significant precipitations were recorded continuously, with a sample period of 1 minute, during the whole life of the storms. It can be expected that a knowledge of the drop size distributions, and in particular of the differences between distrubitions, can be used to infer details of the storm and the environment. In this work the first results of the analyses are presented. Particular attention was conferred to the variation characteristics of the precipitation type (thunderstorm and widespread) as well as to the variations of the distributions in short time intervals, that may be caused by different effects, for example the growth and decay of a precipitation cell or the movement of a cell combined with the different fall velocities of small and large drops. Paper presented at the IV Congresso del Gruppo Nazionale per la Fisica dell'Atmosfera e dell'Oceano, June 22–24, 1987, Rome.     

Synthesis,characterization, and fluorescence phenomena of 1‐naphthoxy and 1‐naphthylamino substituted cyclotriphosphazenes

The reactions of hexachlorocyclotriphosphazene N₃P₃Cl₆ ( 1 ) with 1‐naphthol and 1‐naphthylamine have been examined. The reaction of 1 with sodium 1‐naphthoxy gave the hexakis(1‐naphthoxy)cyclotriphosphazene ( 2 ) in high yield. Geminal 2,2‐di(1‐naphthylamino)‐4,4,6,6‐tetrachlorocyclotriphosphazene ( 3 ) was obtained from the reaction of 1 with 1‐naphthylamine. The structures of phosphazene derivatives were defined by elemental analysis, FTIR, UV‐‐visible, and ¹H, ¹³C, ³¹P NMR spectroscopy. The fluorescence intensity of the compounds was measured in THF and CH₂Cl₂. © 2008 Wiley Periodicals, Inc. Heteroatom Chem 19:158–162, 2008; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/hc.20400     

Anionic cobalt-platinum-ethynyl (CoPt–C<Subscript>2</Subscript>H) metal-organic subnanoparticles: a DFT modeling study

Anionic CoPt-ethynyl metal-organic clusters have been investigated comprehensively. The lowest energetic of anionic Co _n Pt _m (ethynyl) clusters have been generally found as 3D structure but with low symmetrical point groups. Our results indicate that the most preferred dissociation channel of the studied clusters is Co atom ejection and the favorable dissociation channel is independent of cluster size. The anionic Pt₅C₂H cluster shows the highest chemical stability according to the HOMO-LUMO Gap analysis. The C₂H generally prefers to bind on a bridge site with a few exceptions. The Co_4?5 nanoparticles have a lengthening effect on the C≡C bond of the ethynyl molecule, which may be valuable for C≡C bond activation. In addition, the lowest and the highest vibrational frequencies are reported to guide further experimental studies.     

Investigations on the Q and CT Bands of Cytochrome c Submonolayer Adsorbed on an Alumina Surface Using Broadband Spectroscopy with Single-Mode Integrated Optical Waveguides

In this work, we report experimental results on the molar absorptivity of cytochrome c adsorbed at different submonolayer levels onto an aluminum oxide waveguide surface; our data show a clear dependence of the protein optical properties on its surface density. The measurements were performed using the broadband, single-mode, integrated optical waveguide spectroscopic technique, which is an extremely sensitive tool able to reach submonolayer levels of detection required for this type of studies. This investigation focuses on the molar absorptivity at the Q-band (centered at 525 nm) and, for the first time to our knowledge, the weak charge transfer (CT) band (centered at 695 nm) of surface-adsorbed cyt c. Polarized light in the spectral region from 450 to 775 nm was all-coupled into an alumina thin film, which functioned as a single-mode planar optical waveguide. The alumina thin-film waveguide used for this work had a thickness of 180 nm and was deposited on a glass substrate by the atomic layer deposition process. The protein submonolayer was formed on the alumina waveguide surface through electrostatic adsorption from an aqueous buffer solution at neutral pH. The optical properties of the surface-adsorbed cyt c were investigated for bulk protein concentrations ranging from 5 nM to 8200 nM in the aqueous buffer solution. For a protein surface density of 2.3 pmol/cm(2), the molar absorptivity measured at the charge transfer band was 335 M(-1) cm(-1), and for a surface density of 15 pmol/cm(2) was 720 M(-1) cm(-1), which is much closer to the value of cyt c dissolved in an aqueous neutral buffer (830 M(-1) cm(-1)). The modification of the protein molar absorptivity and its dependence on the surface density can most likely be attributed to conformational changes of the surface-adsorbed species.