Self-assembled one-pot synthesis of red luminescent CdS:Mn/Mn(OH)2 nanoparticles

We report a novel method of growing red luminescent (635 nm) Mn-doped CdS (CdS:Mn) nanoparticles capped by an inorganic shell of Mn(OH)₂. CdSO₄, Na₂S₂O₃ and Mn(NO₃)₂ were used as the precursors, and thioglycerol (C₃H₈O₂S) was employed as the capping agent and also the catalyst of the reaction. Using these materials resulted in very slow rate of the reaction and particles growth. The self-assembled one-pot process was performed at pH of 8 and Mn:Cd ratio of 10, and took about 10 days for completion. CdS:Mn nanoparticles are slowly formed in the first day of the process; however, the luminescence is weak. After 7 days, the solution turns white turbid through the formation of additional particles, which precipitate on the walls on the next day. At this stage, a relatively strong red luminescence at 635 nm appears from transparent solution of the CdS:Mn nanoparticles. The white deposit on the walls turns to dark-brown color and luminescence increases on the 9th day. Finally, the CdS:Mn nanoparticles agglomerate and precipitate out of the solution on 10th day. X-ray diffraction and optical spectroscopy showed crystalline phase CdS nanoparticles with an average size of 3.6 nm. We explain the luminescence enhancement based on the formation of a Mn(OH)₂ shell on the surface of the CdS:Mn nanoparticles during the precipitation stage. This can passivate the S dangling bonds located on the particles surface. As the surface Cd sites are previously capped with thioglycerol molecules, a complete surface passivation is achieved and results in emergence of high-intensity luminescence.     

One-pot synthesis of 3,4-dihydropyrimidin-2(1H)-ones,thiones and 2-selenoxo DHPMs using 1-butyl-3-methylimidazolium hydrogen sulfate as non-halogenated ionic liquid

Abstract

1-Butyl-3-methylimidazolium hydrogen sulfate ([BMIM][HSO₄]) as a non-halogenated ionic liquid (IL) was used for the synthesis of 3,4-dihydropyrimidin-2(1H)-ones and thiones or 2-selenoxo DHPMs in a Biginelli type multi-component reaction. By using this ionic liquid, the reaction time was significantly reduced and the products were obtained in good to high yields. Also, in this method, the synthesis of novel 2-selenoxo DHPMs is introduced in the presence of this ionic liquid and their structures were determined by ¹H and ¹³C NMR, FT-IR, and Elemental analysis.     

A new approach to extraction and preconcentration of Ce(III) from aqueous solutions using magnetic reduced graphene oxide decorated with thioglycolic-acid-capped CdTe QDs

In the present study, a nanocomposite consisting of magnetic reduced graphene oxide decorated with thioglycolic-acid-capped CdTe quantum dots (TGA/CdTe QDs/Fe₃O₄/rGO) was synthesised using simple ‘hydrothermal method’ and applied as a nanosorbent for extraction and preconcentration of cerium (Ce)(III) from aqueous solutions prior to inductively coupled plasma-optical emission spectroscopy detection. Under the optimised extraction conditions, the calibration graph for Ce(III) was linear in a concentration range of 0.1–511.0 μg L^?1 with a correlation coefficient of 0.9986. A detection limit of 0.1 μg L^?1 Ce(III) with an enrichment factor of 125 was obtained. Precisions, expressed as relative standard deviation for single-sorbent repeatability and sorbent-to-sorbent reproducibility, were 3.6% and 9.1% (n = 5), respectively. Finally, spiked sea, mineral and tap waters were analysed to evaluate the performance of the proposed method. The high recoveries indicated that the suggested protocol was acceptable for determination of Ce(III) ions in the water samples. The use of QDs and study of their ability for preconcentration of metal ions is an important achievement towards designing novel adsorbents with high efficiency.     

A new phosphorothioic triamide structure: P(S)[NHCH2C6H5]3

The structure of N,N′,N′′‐tribenzylphosphorothioic triamide, C₂₁H₂₄N₃PS, (I), and analysis of the bond‐angle sums at the N atoms for this compound, and for 74 structures with a P(S)[N]₃ skeleton and the N atom in a three‐coordinate geometry found in the Cambridge Structural Database [CSD; Groom & Allen (2014). Angew. Chem. Int. Ed. 53 , 662–671], are reported. For (I), the bond‐angle sum at one of the N atoms [359 (1)°] shows a nearly planar configuration, while the other two show a nonplanar geometry with bond‐angle sums of 342 (1) and 347 (1)°. The location of the atoms attached to the nonplanar N atoms suggests an anti orientation of the corresponding lone electron pairs (LEPs) on these N atoms with respect to the P=S group. For 74 structures with a P(S)[N]₃ skeleton and with the N atom in a three‐coordinate geometry, the bond‐angle sums at the N atoms were found to be in the range 293–360°. Among 307 such three‐coordinate N atoms, 39% (120 N atoms) have bond‐angle sums in the range 359–360°, in accordance with sp² hybridization, and 45% (138 N atoms) have bond‐angle sums in the range 352–359°, with hybridization close to sp². For the orientation of the LEP with respect to the P=S group, the anti orientation was found to be a general rule for N atoms, with the corresponding bond‐angle sums deviating by more than 8° from the planar value of 360°. In the title structure, the S atom takes part in intermolecular (N—H...)(N—H...)S hydrogen bonds, connecting the molecules into extended chains parallel to the b axis. The co‐operation of one N atom in an N—H...S hydrogen bond as an H‐atom donor, and in an N—H...N hydrogen bond as an acceptor, is a novel feature of the crystal structure.     

Toward a modeling study of thermal conductivity of nanofluids using LSSVM strategy

Journal of Thermal Analysis and Calorimetry - In the present study, a comprehensive model based on least square support vector machine algorithm (LSSVM) was developed to estimate thermal...     

Design theory and some forbidden configurations

In this paper we relate $t$‐designs to a forbidden configuration problem in extremal set theory. Let ${\mathbf{1}}_t{\mathbf{0}}_{?}$ denote a column of $t$ 1's on top of $?$ 0's. Let $q?{\mathbf{1}}_t{\mathbf{0}}_{?}$ denote the $\left(t+?\right)\times q$ matrix consisting of $t$ rows of $q$ 1's and $?$ rows of $q$ 0's. We consider extremal problems for matrices avoiding certain submatrices. Let $A$ be a (0, 1)‐matrix forbidding any $\left(t+?\right)\times \left(\lambda +2\right)$ submatrix $\left(\lambda +2\right)?{\mathbf{1}}_t{\mathbf{0}}_{?}$. Assume $A$ is $m$‐rowed and only columns of sum $t+1,t+2,\text{…},m??$ are allowed to be repeated. Assume that $A$ has the maximum number of columns subject to the given restrictions. Assume $m$ is sufficiently large. Then $A$ has each column of sum $0,1,\text{…},t$ and $m??+1,m??+2,\text{…},m$ exactly once and, given the appropriate divisibility condition, the columns of sum $t+1$ correspond to a $t$‐design with block size $t+1$ and parameter $\lambda$. The proof derives a basic upper bound on the number of columns of $A$ by a pigeonhole argument and then a careful argument, for large m, reduces the bound by a substantial amount down to the value given by design‐based constructions. We extend in a few directions.     

A fuzzy programming approach for dynamic virtual hub location problem

Hub location problem has been used in transportation network to exploit economies of scale. For example, a controversial issue in the planning of air transportation networks is inclement weather or emergency conditions. In this situation, hub facilities would not be able to provide a good service to their spoke nodes temporarily. Thus, some other kinds of predetermined underutilized facilities in the network are used as virtual hubs to host some or all connections of original hubs to recover the incurred incapacitation and increase network flexibility and demand flow. In such an unexpected situation, it is not unreasonable to expect that some information be imprecise or vague. To deal with this issue, fuzzy concept is used to pose a more realistic problem. Here, we present a fuzzy integer liner programming approach to propose a dynamic virtual hub location problem with the aim of minimizing transportation cost in the network. We examine the effectiveness of our model using the well-known CAB data set.     

Gain enhancement in two-stream free electron laser with a planar wiggler and an axial guide magnetic field

The theory for a two-stream free electron laser (FEL) consisting of a relativistic electron beam transported along the axis of a planar wiggler in the presence of an axial guiding magnetic field is proposed and investigated. The electron trajectories and the small signal gain are derived. The characteristic of the linear gain and the normalized maximum gain are studied numerically. The result shows that the normalized maximum gain is considerably enhanced in comparison with that of the single stream. The effect of the difference between the energies of the two beams in this configuration of FEL is also considered, and we find that the gain is affected by the energy differences between groups 1 and 2.     

Near-white emitting QD-LED based on hydrophilic CdS nanocrystals

In this work we report fabrication of a nanocrystal (NC)-based hybrid organic–inorganic LED with structure of ITO/PEDOT:PSS/PVK/CdS-NCs/(Al or Mg:Ag). The hydrophilic CdS NCs were synthesized using a novel aqueous thermochemical method at 80 °C and sizes (around 2 nm) were controlled by thioglycolic acid (TGA) as the capping agent. The favorite feature of these NCs is their relatively high emission intensity and broad, near-white emission. The hydrophilic CdS NCs were successfully spin coated using Triton X-100 as the wetting agent. The fabricated LEDs demonstrated a turn on voltage about 7 V for Al metallic contact. The electroluminescence was a broad spectrum at 540 and 170 nm width, which was about 50 nm red shifted compared to photoluminescence spectra. The CIE color coordinates of the LED at (0.33, 0.43) demonstrated a near white light LED with an emission on green–yellow boundary of white. Annealing of the device up to 190 °C had a positive effect on the performance, possibly due to better contacts between layers. Replacing Al contacts with Mg:Ag reduced the turn-on voltage to 6 V and changed CIE color coordinate to (0.32, 0.41). The EL peak was also shifted to 525 nm, with a brightness of 15 Cd/m² at working voltage of 15 V. The current efficiency and external quantum efficiency of device were 0.08 Cd/A and 0.03% at current densities higher than 10 mA/cm².