Manufacturing of Volumetric Glass–Based Composites with Single‐ and Double‐QD Doping

Quantum dot (QD)‐based light‐emitting materials are gaining increased attention because of their easily tunable optical properties desired for various applications in biology, optoelectronics, and photonics. However, few methods can be used to manufacture volumetric materials doped with more than one type of QD other than QD‐polymer hybrids, and they often require complicated preparation processes and are prone to luminescence quenching by QD aggregation and separation from the matrix. Here, simultaneous doping of a volumetric glass‐based nanocomposite with two types of QDs is demonstrated for the first time in a single‐step process using the nanoparticle direct doping method. Glass rods doped with CdTe, CdSe/ZnS, or co‐doped with both QDs, are obtained. Photoluminescence and lifetime experiments confirm temperature‐dependent double emission with maxima at 596 and 720 nm with mean lifetimes up to 16 ns, as well as radiative energy transfer from the short wavelength–emitting QDs to the long wavelength–emitting QDs. This approach may enable the simple and cost‐efficient manufacturing of bulk materials that produce multicolor luminescence with cascade excitation pumping. Applications that could benefit from this include broadband optical fiber amplifiers, backlight systems in LCD screens, high‐power LEDs, or down‐converting solar concentrators used to increase the efficiency of solar panels.     

Direct observation of aziridinium ions in a 2-(N,N-dibenzylamino)- to 1-(N,N-dibenzylamino)phosphonate rearrangement

Aziridinium mesylates stable in the reaction medium for several hours to over a week were observed in a rearrangement of dimethyl (1R,2S)-2-(N,N-dibenzylamino)-1-mesyloxyethylphosphonates substituted at C2 with Bn, i-Pr and t-Bu to the respective 1-(N,N-dibenzylamino)-2-mesyloxyethylphosphonates. Rates of formation of these aziridinium mesylates and rates of their reactions with poorly nucleophilic mesylate anion were governed by steric and electronic factors. The conformation of (2S,3S)-1,1-dibenzyl-2-(tert-butyl)-3-(dimethoxyphosphoryl)aziridinium mesylate in solution was established based on ¹H and ¹³C NMR spectroscopic studies including a NOESY experiment.     

Modelling spur chemistry for alkaline and acidic water at high temperatures

The effect of pH and associated ionic strength on the primary yields in the radiolysis of pressurised water has been assessed by diffusion-kinetic calculations for temperatures in the range 100–300°C. Account has been taken for ionic strength I up to 0.1 mol kg⁻¹, assuming that the counter ions of H⁺ in acid solutions and of OH⁻ in base solutions have unit charge. In acid solutions, the H⁺ ions react with e⁻ _aq. The decrease in G(e⁻ _aq) and the increase in G(H) with decreasing pH becomes substantial for [H⁺] ≥ 1 × 10⁻⁴ m, but the primary yields of oxidising species are almost constant. In alkaline solutions, the OH⁻ anions affect the spur chemistry of radiation-generated protons and hydroxyl radicals for [OH⁻] ≥ 1 × 10⁻⁴ m. The scavenging of H atoms and hydrogen peroxide becomes significant for [OH⁻] ≥ 1 × 10⁻² m. The total yields G(OH) + G(O⁻) and G(H₂O₂) + G(HO₂ ⁻) are independent of base concentration below 0.01 m. In more alkaline solutions, G(OH) + G(O⁻) increases, whereas G(H₂O₂) + G(HO₂ ⁻) decreases with increasing [OH⁻]. Calculations showed the substantial yield of the reaction O⁻ + e⁻ _aq in 0.1 m base solution. Spur chemistry in alkaline hydrogenated water is not affected by the presence of H₂ if less than 0.001 m of hydrogen is added.     

TLC in a Search for Structural Limitations of Spontaneous Oscillatory In-Vitro Chiral Conversion. α-Hydroxybutyric and Mandelic Acids

JPC – Journal of Planar Chromatography – Modern TLC - As a result of our earlier studies, we were the first research group to report the spontaneous oscillatory in-vitro chiral...     

Voltammetric study of gold-supported lipid membranes in the presence of perfluorooctanesulphonic acid

The effect of perfluorooctanesulphonic acid (PFOS) on lipid membranes was studied using supported 1,2-dimyristoyl-sn-glycero-3-phosphocholine (DMPC) bilayer as the model membrane. Phospholipid bilayer was deposited on gold electrode using a combination of the Langmuir–Blodgett and Langmuir–Schaefer (LB/LS) techniques. Electrodes were modified with two different types of membranes: DMPC bilayers initially containing PFOS and pure DMPC bilayers later exposed to the PFOS solutions. Such approach allowed studying both the changes in membrane characteristic imposed by the perfluorinated compound present in the model membrane and the process of its incorporation into the membrane. Studies with anticancer drug doxorubicin revealed that PFOS inhibits drug transport through the phospholipid bilayer and its effect can be compared to that of cholesterol. Moreover, the different trends observed in the changes in electron transfer rate constant (k_s) calculated for ferricyanides and in peak current of hexaamineruthenium chloride showed that electrostatic interactions between electroactive probes and PFOS molecules incorporating into phospholipid bilayers play an important role and should be taken into account while explaining the interactions of perfluorooctanesulphonic acid with model biological membranes.     

Deformation of gradient shape as a result of preferential adsorption of solvents in mixed mobile phases

Gradient elution has been studied in typical normal and reversed-phase systems. Deformations of gradient profiles have been evidenced as a result of preferential adsorption of modifiers of the mobile phase. This phenomenon was pronounced in the normal-phase system, for which gradient profiles deviated significantly from those programmed. This influenced the retention and shapes of band profiles of the eluting solute. Hence, in order to predict gradient propagation correctly the adsorption equilibrium of modifiers has been quantified. Moreover, at low modifier content, deformations of band profiles of the solute has been registered as a result of the competitive adsorption in the system solute-modifier. This effect has been predicted by a competitive adsorption model. For the reversed-phase systems the influence of the modifier adsorption on gradient propagation was insignificant for typical mobile phases investigated. Therefore, the work has been focused on gradient predictions in the normal-phase system.     

Synthesis and physicochemical properties of new fluorescent derivatives of cytosine

Sixteen new fluorescent N⁴‐(E)‐stilbenyloxyalkylcarbonyl‐cytosines 9–16 and N⁴‐(E)‐stilbenyloxyalkylcarbonyl‐1‐methylcytosines 17–24 have been synthesized. The differences in ¹H and ¹³C NMR spectra in two solvents (DMSO and TFA) have been pointed out and discussed. Assignment of the signals in the spectra of the compounds 9–24 in NMR in DMSO‐d₆ solutions has been made the basis of the homonuclear (COSY) and heteronuclear (HETCOR) spectra. The effect of the substituent (Cl, Br, NO₂) on the stilbene moiety on the fluorescence spectrum of each compound has been discussed.     

Determination of Poly (Diallyldimethylammonium Chloride ) via Spectrophotometric Titration with Coomassie Brilliant Blue G Dye

Poly(diallyldimethylammonium chloride) (PDDA) is used as organic coagulant in water purification and auxiliary agent in paper production. Determination of PDDA in aqueous solutions is carried out usually by means of polyelectrolyte titration using streaming current detector or o-Toluidine Blue dye for endpoint recognition. The proposed method of PDDA assay takes advantage of Coomassie Brilliant Blue G dye having strong affinity to cationic macromolecules. Titration of PDDA solution with the dye is carried out measuring absorbance at 585 nm. Inflection points of the obtained zigzag photometric curves have good repeatability provided that titration rate is low enough to attain endpoint for 1 hour or more. The method assures rectilinear calibration (R2=0.999 5) in the broad range of PDDA concentrations from 0.3 to 9.6 mg·dm-3.     

Evolution of the truncated Mellin moments of the parton distributions in QCD analysis

We review evolution equations for the truncated Mellin moments of the parton distributions and some their applications in QCD analysis. The main finding of the presented approach is that the nth truncated moment of the parton distribution obeys also the DGLAP equation but with a rescaled splitting function P′(z) = z ⁿ P(z). This allows one to avoid the problem of dealing with the experimentally unexplored Bjorken-x region. The evolution equations for truncated moments are universal—they are valid in each order of perturbation expansion and can be useful additional tool in analysis of unpolarized as well as polarized nucleon structure functions.