Studies of Luminescence Performance on Carbazole Donor and Quinoline Acceptor Based Conjugated Polymer

We report on the synthesis of conjugated polymer (CV-QP) containing carbazole (donor) and quinoline (acceptor) using Wittig methodology. The structural, optical and thermal properties of the polymer were investigated by FT-IR, NMR, GPC, UV, PL, cyclic voltammetry, atomic force microscopy (AFM) and thermogravimetric analysis (TGA). The polymer exhibits thermal stability upto 200 °C and shows good solubility in common organic solvents. The polymer has optical absorption band in a thin film at 360 nm and emission band formed at 473 nm. The optical energy band gap was found to be 2.69 eV as calculated from the onset absorption edge. Fluorescence quenching of the polymer CV-QP was found by using DMA (electron donor) and DMTP (electron acceptor). AFM image indicated that triangular shaped particles were observed and the particle size was found as 1.1 μm. The electrochemical studies of CV-QP reveal that, the highest occupied molecular orbital (HOMO) and lowest unoccupied molecular orbital (LUMO) energy levels of the CV-QP are 6.35 and 3.70 eV, which indicated that the polymers are expected to provide charge transporting properties for the development of polymer light-emitting diodes (PLEDs).     

Synthesis of Polylactide under Inert Atmosphere and Vacuum

The ring-opening polymerization (ROP) of L- lactide was carried out in bulk using various initiators along with triphenylphosphine (PPh₃) as co-initiator. Equimolar addition of triphenylphosphine increased the molecular masses of polylactide (PLA). The polymerization was carried out at 403.15 K up to 155 hr. Different experiments were carried out over a wide range of monomer to initiator (M_o/I_o) ratios. It was found that maximum molecular weight of polylactide was observed when M_o/I_o ratio was 2500–2700. Polymerization reactions were carried out under two different environments in the reaction vessel, an inert cover and a partial vacuum. The average molecular weight of polylactide was determined by using size exclusion chromatography. The increase of polymerization time increased the weight average molecular weight but after prolonged reaction time, the molecular weight decreased gradually.     

Potentiometric Study of Coated Graphite Electrode and Polymeric Membrane Electrode for the Determination of Sm3+ Ion

Preliminary studies on the two Schiff bases N2‐((3H‐indol‐3‐yl)methylene)‐6‐phenyl‐1,3,5‐triazine‐2,4‐diamine (L₁) and N2,N4‐bis((3H‐indol‐3‐yl)methylene)‐6‐phenyl‐1,3,5‐triazine‐2,4‐diamine (L₂) have shown that they can act as Sm³⁺ selective electrodes. The performances of a polymeric membrane electrode and a coated graphite electrode based on L₂ were compared and the CGE proved to be better, as it shows a low detection limit of 1.8×10^?8 mol L^?1, a Nernstian slope of 19.6±0.4 mV decade^?1 of activity with a response time of 11 s in the pH range of 3.0–9.0. The CGE was used to determine Sm³⁺ in medicinal plants and soil samples. It was also used to determine fluoride ions in mouthwash samples and in toothpaste.     

Uncovering the true mechanism of optical detection of HSO(4)(-) in water by Schiff-base receptors - hydrolysis vs. hydrogen bonding

The mechanism of optical detection of HSO(4)(-) in aqueous medium by Schiff-base receptors has previously been proposed to depend on selective hydrogen-bond interactions. Here, we clearly demonstrate for the first time that the acidic nature of this anion gives rise to hydrolysis of the Schiff base, which leads to the optical changes observed in this family of receptors.     

Comparison of microwave-assisted and conventional preparations of cyclic imides

Microwave-assisted preparation of several cyclic imides was performed with four different cyclic anhydrides. All the reactions are significantly faster and the isolated yields are significantly higher compared to conventionally heated reactions. Furthermore, many of these reactions can be performed with a minimal amount of solvent, thereby enabling the synthetic chemist to obtain high quantities of pure cyclic imides in a matter of hours.     

On the complexity of the herding attack and some related attacks on hash functions

In this article, we analyze the complexity of the construction of the 2 ^k -diamond structure proposed by Kelsey and Kohno (LNCS, Vol 4004, pp 183–200, 2006). We point out a flaw in their analysis and show that their construction may not produce the desired diamond structure. We then give a more rigorous and detailed complexity analysis of the construction of a diamond structure. For this, we appeal to random graph theory (in particular, to the theory of random intersection graphs), which allows us to determine sharp necessary and sufficient conditions for the message complexity (i.e., the number of hash computations required to build the required structure). We also analyze the computational complexity for constructing a diamond structure, which has not been previously studied in the literature. Finally, we study the impact of our analysis on herding and other attacks that use the diamond structure as a subroutine. Precisely, our results shows the following:

1. The message complexity for the construction of a diamond structure is ${\sqrt{k}}$ times more than the amount previously stated in literature.

1. The time complexity is n times the message complexity, where n is the size of hash value.

Due to the above two results, the herding attack (Kelsey and Kohno, LNCS, Vol 4004, pp 183–200, 2006) and the second preimage attack (Andreeva et?al., LNCS, Vol 4965, pp 270–288, 2008) on iterated hash functions have increased complexity. We also show that the message complexity of herding and second preimage attacks on “hash twice” is n times the complexity claimed by Andreeva et?al. (LNCS, Vol 5867, pp 393–414, 2009), by giving a more detailed analysis of the attack.     

Field dependent nilpotent symmetry for gauge theories

We present predictions for the inclusive production of D mesons at the CERN LHC in the general-mass variable-flavor-number scheme at next-to-leading order. Detailed numerical results are compared to data where available, or presented in a way to ease future comparisons with experimental results. We also point out that measurements at large rapidity have the potential to pin down models of intrinsic charm.     

Synthesis of 1D β-MnO2 for high-performance supercapacitor application

Journal of Solid State Electrochemistry - Electrochemical supercapacitors (ESs) still need to overcome development obstacles in order to realize their full potential while being acknowledged as a...     

Holy Water: Photo-Brightening in Quasi-2D Perovskite Films under Ambient Enables Highly Performing Light-Emitting Diodes

Quasi-2D perovskites provide new opportunities for lighting and display applications due to their high radiative recombination and excellent stability. However, seldom attention has been placed on their self-stability/working operation under ambient storage. Herein, quasi-2D perovskites/Polyethylene oxide (PEO) films are studied, showing an unforeseen photo-brightening effect under ambient storage (i.e., an increase of the photoluminescence quantum yield from 55% to 74% after 100 days). In stark contrast, those stored under a dark/inert atmosphere show a significant decrease down to 38%. This counterintuitive phenomenon responds to the increasing radiative recombination rate caused by the passivation of the surface Br vacancies in the presence of physically adsorbed water molecules, as corroborated by in situ/ex situ X-ray photoelectron spectroscopy and density functional theory calculations. Capitalizing on this surprising effect, stable light-emitting diodes (LEDs) using quasi-2D perovskites/PEO color filters are fabricated, realizing high stabilities of ≈400 h@10 mA under operating ambient conditions, representing a 20-fold enhancement compared to LEDs with 3D counter partners. Hence, this study reveals a unique insight into the impact of water passivation on the optical/structural properties of quasi-2D perovskite films, broadening their applications under operating ambient conditions.