Amine‐Responsive Adaptable Nanospaces: Fluorescent Porous Coordination Polymer for Molecular Recognition

Flexible and dynamic porous coordination polymers (PCPs) with well‐defined nanospaces composed of chromophoric organic linkers provide a scaffold for encapsulation of versatile guest molecules through noncovalent interactions. PCPs thus provide a potential platform for molecular recognition. Herein, we report a flexible 3D supramolecular framework {[Zn(ndc)(o‐phen)]?DMF}_n (o‐phen=1,10‐phenanthroline, ndc=2,6‐napthalenedicarboxylate) with confined nanospaces that can accommodate different electron‐donating aromatic amine guests with selective turn‐on emission signaling. This system serves as a molecular recognition platform through an emission‐readout process. Such unprecedented tunable emission with different amines is attributed to its emissive charge‐transfer (CT) complexation with o‐phen linkers. In certain cases this CT emission is further amplified by energy transfer from the chromophoric linker unit ndc, as evidenced by single‐crystal X‐ray structural characterization.     

Positronium annihilation in liquids in the framework of non-local interaction

In the bubble model of ortho positronium (o-Ps) annihilation in liquid the origin of the trapping of o-Ps is the electron-exchange repulsive interaction between the electron of o-Ps and the electron of the medium. The corresponding effective interaction is non-local in nature. However, in the prevalent bubble model, this effective interaction is usually treated as local (model) potential (sharp or smooth). In the present study, we have taken an approach to consider this trapping interaction as non-local in nature, which is included through a model separable non-local function to tackle the problem in analytically solvable manner. The analytical calculations show that this non-local interaction effectively acts as a gauge potential in the energy of the Ps atom in parameter (bubble radius) space. The computed bubble variables obtained using experimental Ps annihilation data are shown. A comparison between the present data with the calculated results using prevalent bubble model has been presented. Discussions have been made on the input parameter dependencies of the computed data.     

Complete Convergence of Martingale Arrays

We study complete convergence of martingale arrays under rather weak conditions. Our results considerably strengthen many of the results available in the literature. As a tool, we establish a martingale analogue of an inequality of Hoffman-Jørgensen which was earlier known only for independent random variables.     

A quasi random search technique for functional fitting of detector responses

The problem of nonlinear optimization is encountered while fitting the observed response of certain radiation detectors. In this paper the development of an optimizing technique based on quasi random search is described. The performance of this technique is compared with other existing methods of gradient search and linear Taylor differential correction technique in the case of fitting the photopeak responses of Nal(Tl) detectors. Our results are favourable especially when the observed data are associated with poor statistics.     

Use of threshold activation technique in estimating energy distributions of accelerator produced neutrons

A study of effective implementation of threshold activation technique for neutron spectral analysis in the environment of an alpha-cyclotron target is presented. The activation data are analysed using LOUHI-82 code. Optimal choices of the regularization parameters of the code are studied and discussed. Energy distribution of neutrons emitted from thick targets of Be, C and Ta irradiated by 40–45 MeV alphas is discussed.     

Electronic absorption spectra of 1,2,3-trimethyl benzene

The electronic absorption spectra of 1,2,3-trimethyl benzene in the vapour and solid phases and in an isobutyl alcohol rigid glass at 90°K are described in this paper. Some characteristic features of the vibrational structure of the spectra are discussed.     

Intensification of the reaction between Udaipur rock phosphate and sulphuric acid by means of ultrasound

The solid-liquid reaction between Udaipur rock phosphate and different concentrations of sulphuric acid is found to be greatly enhanced when the reaction is carried out in the presence of high intensity ultrasound (800 kHz and 80 W cm^?2). Even coarser rock particles up to 50 mesh (BSS) can be effectively decomposed in the presence of ultrasound to such an extent that is suitable for utilization in a commercial phosphatic fertilizer plant, which is not otherwise possible. The ultrasound helps the diffusion of reactants on to the solid rock particles and also inhibits the coating of calcium sulphate, formed during the reaction, on the unreacted solid rock particles. The decomposition curve of Udaipur rock phosphate at 80°C with different concentrations of sulphuric acid contains two maxima and two minima which are controlled by the concentration of H₃O⁺, HSO₄^? and SO₄^2? ions in the medium as the reaction proceeds. It is found that the presence of ultrasound reduces the difference between these maxima and minima and the decomposition is increased in all cases.     

Influence of high intensity ultrasound on wet process phosphoric acid

High intensity ultrasound (800 kHz and 80 Wcm^-2) is passed through phosphoric acid of different origins and concentrations. Its influence on fluorine content, viscosity, density, colour and tendency to form sludge on ageing is observed. The quantity of fluorine in all samples of acid goes on decreasing with the time of exposure to ultrasound. Due to removal of fluorine by the ultrasound, the tendency of the acids to form sludge also decreases. The evolution of fluorine from the wet process phosphoric acid may be due to the decomposition of H₂SiF₆ present in the acid to HF and SiF₄ by the enormous amount of energy released due to cavitation. The exposed acid thus becomes purer, and can be concentrated and transported easily without sludge formation.     

Fabrication of a metal nanoparticles and polymer nanofibers composite material by an in situ chemical synthetic route

This work demonstrated a facile route for the synthesis of poly(3,5-dimethyl aniline) nanofibers by polymerization of 3,5-dimethyl aniline using Pd-acetate as the oxidant. The reduction of Pd ion is accompanied by oxidative polymerization of 3,5-dimethyl aniline, leading to a metal-polymer composite material. Palladium nanoparticles (approximately 2 nm) are uniformly distributed throughout the polymer that makes the composite material a unique morphology. The resultant composite material was characterized by means of different techniques. IR and Raman spectra provide the information on the chemical structure of the polymer. TEM images show the morphology of the polymer and size of the metal particles.