Electrochemiluminescence and chemiluminescence of a carboxylic acid derivative of ruthenium(II) tris-(2,2′-bipyridine) chelate synthesized for labeling purposes

Synthesis, purification and characterization of [4-ethoxycarbonyl-4′-carboxy-2,2′-bipyridine]bis(2,2′-bipyridine) ruthenium(II) hexafluorophosphate is described. This complex is shown to be electrochemiluminescent in aqueous solution during cathodic pulse polarization of thin insulating film-coated electrodes. Electrochemiluminescence (ECL) lifetime of the complex was observed to be ca. 40 μs at oxide-coated n-silicon electrodes; thus time-resolved detection is also possible. The ECL emission maximum of this carboxylate derivative is somewhat red-shifted when compared with an unmodified Ru(bpy)₃²⁺. Because the present complex can be easily covalently coupled with antibodies and oligonucleotides it is usable as an electrochemiluminescent label in various bioaffinity assays. The present chelates also produce strong chemiluminescence during dissolution of metallic magnesium in aqueous solution.     

Formation of low-temperature cirrus from H2SO4/H2O aerosol droplets

We present experimental results obtained with a differential scanning calorimeter (DSC) that indicate the small ice particles in low-temperature cirrus clouds are not completely solid but rather coated with an unfrozen H2SO4/H2O overlayer. Our results provide a new look on the formation, development, and microphysical properties of low-temperature cirrus clouds.     

Mass and thermal accommodation during gas-liquid condensation of water

In this Letter we report, for the first time, direct and simultaneous determinations of mass and thermal accommodation coefficients for water vapor condensation in air, based on the observation of droplet growth kinetics in an expansion cloud chamber. Our experiments exclude values below 0.85 for the thermal and below 0.4 for the mass accommodation coefficients at temperatures ranging from 250 to 290 K. Both coefficients are likely to be 1 for all studied conditions. Previously available experimental data on the mass accommodation coefficient for water span about 3 orders of magnitude. Our results provide new and firm insight to cloud microphysics and consequently to the global radiative balance.     

Current status of modern analytical luminescence methods

Modern analytical luminescence methods and their recent applications are reviewed with emphasis on the most sensitive methods that can be expected to be useful in future microanalytical systems such as μ-TAS, lab-on-chip, point-of-care (POC) and high throughput screening (HTS) applications. Photoluminescence (PL) is presently the most important group of analytical techniques utilising luminescence. Because of the rapidly increasing popularity of electrochemiluminescence (ECL) and its applications, we have given particular attention to ECL mechanisms and techniques. Due to the present and future importance of capillary electrophoresis (CE) as a separation method, the CE detection methods based on luminescence are also considered in a relatively detailed way. For those researchers, designing novel experiments and assays, experimental set-ups, and apparatus we include web links to the manufacturers of some fairly rare reagents, as well as modern instrument components.     

Cathodic europium(III) electroluminescence at an oxide-coated aluminum electrode

Electroluminescence is produced at an oxide-coated aluminum electrode during cathodic polarization of the electrode in an acetate solution containing nitrate and traces of europium(III). The europium(III) ion in the ⁵D₀ state is the emitter. Linear log-log calibration plots are obtained for the range 1 × 10^?8?1 × 10^?5 M europium(III). A mechanism for the cathodic luminescence is proposed.     

Preparation of β-caryophyllene oxidation products and their determination in ambient aerosol samples

Oxidation of β-caryophyllene with ozone followed by reduction was carried out in dichloromethane. Reaction led to the formation of β-caryophyllene aldehyde (11%, purity 90.8%) and β-nocaryophyllone aldehyde (79%, purity 99%). Compounds were purified and separated by liquid–liquid extraction and flash chromatography. Identifications were achieved by electron-impact and electrospray ionization mass spectrometry, and precise structures were confirmed by one and two-dimensional nuclear magnetic resonance spectroscopy. The prepared compounds were used in the analysis of ambient aerosol samples collected during spring 2003 at Hyytiälä, Finland. β-Nocaryophyllone aldehyde was positively identified and quantified in ambient aerosol samples for the first time. The amount of quantified β-nocaryophyllone aldehyde of aerosol origin was 17.4?±?1.0 ng m^?3 of sampled air. Comparison with previous findings led to the conclusion that oxidation products of β-caryophyllene participate in biogenic aerosol formation over boreal forest during late spring.     

Significance of ammonia in growth of atmospheric nanoclusters

We apply accurate quantum chemistry methods to study the thermochemistry of molecular clusters containing ammonia, water, and sulfuric acid and investigate initial reaction steps in atmospheric nucleation by calculating free energies for the related reactions. The results indicate that ammonia is a key reactant enhancing the growth of small water-sulfuric acid clusters in atmospheric conditions. The role of ammonia becomes significant when the nanoclusters contain more than one or two sulfuric acid molecules. This implies a lower limit of 1:3 for the NH3/H2SO4 mole ratio of atmospheric sulfuric acid-water-ammonia clusters.     

Electrochemical Generation of Hot Electrons in Fully Aqueous Solutions at Tetrahedral Amorphous Carbon Thin Film Electrodes and Electrochemiluminescence Immunoassay of Serum Amyloid A

Electrochemistry of hot electrons in fully aqueous solutions at tetrahedral amorphous carbon thin film electrodes is discussed. The generation of these highly reducing chemical species was confirmed by normal pulse voltammetry and several electrochemiluminescent systems. Electron transfer into pre-existing solvent cavities was observed at approximately −2.65 V vs. Ag/AgCl (sat.). Electrogenerated hot electrons were utilized as chemiluminescent mediators in heterogeneous sandwich immunoassay of Serum Amyloid A. The calibration curve was linear over four orders of magnitude and the detection limit was 85 ng L⁻¹ that demonstrates the efficiency of hot electron generation at this electrode material.     

Binary homogeneous nucleation in water-succinic acid and water-glutaric acid systems

Binary homogeneous nucleation of water-succinic acid and water-glutaric acid systems have been investigated. The numerical approach was based on the classical nucleation theory. Usually, nucleation is discussed in terms of kinetics, but the thermodynamics involved is undoubtedly equally important. In this paper we studied the above mentioned binary systems giving a quantitative insight into the nucleation process and a detailed consideration of the thermodynamics involved. Both diacids in study are in solid state at room temperature. They behave in environment according to their liquid state properties because of the absence of crystalline lattice energies, and therefore their subcooled liquid state thermodynamics have to be considered. The lack of consistent thermodynamic data for pure organic components and their aqueous solutions represent a high source of uncertainty. However, the present simulations indicate that in atmospheric conditions these binary systems will not form new particles.     

The carrier gas pressure effect in a laminar flow diffusion chamber, homogeneous nucleation of n-butanol in helium

Homogeneous nucleation rate isotherms of n-butanol+helium were measured in a laminar flow diffusion chamber at total pressures ranging from 50 to 210 kPa to investigate the effect of carrier gas pressure on nucleation. Nucleation temperatures ranged from 265 to 280 K and the measured nucleation rates were between 10(2) and 10(6) cm(-3) s(-1). The measured nucleation rates decreased as a function of increasing pressure. The pressure effect was strongest at pressures below 100 kPa. This negative carrier gas effect was also temperature dependent. At nucleation temperature of 280 K and at the same saturation ratio, the maximum deviation between nucleation rates measured at 50 and 210 kPa was about three orders of magnitude. At nucleation temperature of 265 K, the effect was negligible. Qualitatively the results resemble those measured in a thermal diffusion cloud chamber. Also the slopes of the isothermal nucleation rates as a function of saturation ratio were different as a function of total pressure, 50 kPa isotherms yielded the steepest slopes, and 210 kPa isotherms the shallowest slopes. Several sources of inaccuracies were considered in the interpretation of the results: uncertainties in the transport properties, nonideal behavior of the vapor-carrier gas mixture, and shortcomings of the used mathematical model. Operation characteristics of the laminar flow diffusion chamber at both under-and over-pressure were determined to verify a correct and stable operation of the device. We conclude that a negative carrier gas pressure effect is seen in the laminar flow diffusion chamber and it cannot be totally explained with the aforementioned reasons.