Ag Nanoparticles Supported on a Resorcinol‐Phenylenediamine‐Based Covalent Organic Framework for Chemical Fixation of CO2

Covalent organic frameworks are a new class of crystalline organic polymers possessing a high surface area and ordered pores. Judicious selection of building blocks leads to strategic heteroatom inclusion into the COF structure. Owing to their high surface area, exceptional stability and molecular tunability, COFs are adopted for various potential applications. The heteroatoms lining in the pores of COF favor synergistic host–guest interaction to enhance a targeted property. In this report, we have synthesized a resorcinol‐phenylenediamine‐based COF which selectively adsorbs CO₂ into its micropores (12 Å). The heat of adsorption value (32 kJ mol^?1) obtained from the virial model at zero‐loading of CO₂ indicates its favorable interaction with the framework. Furthermore, we have anchored small‐sized Ag nanoparticles (≈4–5 nm) on the COF and used the composite for chemical fixation of CO₂ to alkylidene cyclic carbonates by reacting with propargyl alcohols under ambient conditions. Ag@COF catalyzes the reaction selectively with an excellent yield of 90 %. Recyclability of the catalyst has been demonstrated up to five consecutive cycles. The post‐catalysis characterizations reveal the integrity of the catalyst even after five reaction cycles. This study emphasizes the ability of COF for simultaneous adsorption and chemical fixation of CO₂ into corresponding cyclic carbonates.     

Computer-aided design of an eight bit binary counter N-MOS chip for large scale integration (LSI)

An integrated eight bit synchronous binary counter along with input/output circuits: gate protection, two phase clock, pad-out has been designed for MOS LSI. The counter has a master-slave flip-flop and a combinational logic to generate the next state, and outgoing carry outputs from this stage. The combination logic has been implemented using pass transistors and thus acts as a steering type logic. This type of logic is very fast, consumes lesser power and needs significantly less area for its implementation.Latest CAD techniques: interactive Graphics system of Applicon AGS/860 LSI Design Station, MOS circuit simulation program MSINC and Design Rule Check (DRC) program have been used for design and chip layout. The entire chip has been laid out in the area of 3 × 3 mm² including test devices and structures for testability analysis. The design is based on LOCOS N-MOS (E-D) technology and 8 micron design rules. The Electromask pattern generation (PG) tape has been prepared from Applicon for making chrome masks.A set of six masks have been used for the fabrication of device and die encapsulated in dual-in line package and tested for its performance. Counter works up to 5 MHz clock frequency as expected from design calculations. From 25 stage ring oscillator frequency measurement the gate delay comes out to be 6 nS.The counter design could easily be substituted as a sub-system/building block or cell in any MOS LSI system design where it makes a part of it.     

Accuracy of conventional inversion charge modeling in scaled down MOS devices

The density of surface inversion charge in MOS structures is typically calculated using the relation Q = cox(V_G − V_T). In the present article we try to quantitatively assess the goodness of this relation in the case of MOS devices scaled down according to constant field scaling and constant voltage scaling principles by comparing the inversion charge given by this relation to the inversion charge obtained by numerically solving the Poisson equation in one dimension. It turns out that while in the case of constant field scaling the conventional relation for inversion charge becomes progressively erroneous, the same is not true for devices scaled down according to constant voltage scaling.     

Load balancing clustering and routing for IoT-enabled wireless sensor networks

Internet of things (IoT) devices are equipped with a number of interconnected sensor nodes that relies on ubiquitous connectivity between sensor devices to optimize information automation processes. Because of the extensive deployments in adverse areas and unsupervised nature of wireless sensor networks (WSNs), energy efficiency is a significant aim in these networks. Network survival time can be extended by optimizing its energy consumption. It has been a complex struggle for researchers to develop energy-efficient routing protocols in the field of WSNs. Energy consumption, path reliability and Quality of Service (QoS) in WSNs became important factors to be focused on enforcing an efficient routing strategy. A hybrid optimization technique presented in this paper is a combination of fuzzy c-means and Grey Wolf optimization (GWO) techniques for clustering. The proposed scheme was evaluated on different parameters such as total energy consumed, packet delivery ratio, packet drop rate, throughput, delay, remaining energy and total network lifetime. According to the results of the simulation, the proposed scheme improves energy efficiency and throughput by about 30% and packet delivery ratio and latency by about 10%, compared with existing protocols such as Chemical Reaction Approach based Cluster Formation (CHRA), Hybrid Optimal Based Cluster Formation (HOBCF), GWO-based clustering (GWO-C) and Cat Swarm Optimization based Energy-Efficient Reliable sectoring Scheme with prediction algorithms (P_CSO_EERSS). The study concludes that the protocol suitable for creating IoT monitoring system network lifetime is an important criteria.     

UWB Multilayer Patch Antenna with EBG Structure for IEEE-C,X, Ku and K Band Applications

In this article, a dual-layered ultra-wideband hexagonal-shaped patch antenna with an EBG structure is presented for IEEE C, X, Ku and K band applications. Parametric analysis of slots, notches, substrate height, substrate stacking, and EBG structures demonstrates the intermediate and finally optimized results. The proposed antenna (A₉) is considered for desired specifications after a systematic investigation of ten different antennas (A₀–A₉). Experimental ultra-wideband (5.1–19.7 GHz) with an impedance bandwidth (S₁₁?<????10 dB) of 117.7% and 5.7dBi peak gain is observed for the proposed antenna. A constant group delay in the entire frequency range with a maximum group delay of 0.85 ns at resonating peaks is observed.

     

A simple iridium catalyst with a single resolved stereocenter for enantioselective allylic amination. Catalyst selection from mechanistic analysis

A study of the relationship between the stereochemical elements of a phosphoramidite ligand and the stereoselectivity of iridium-catalyzed amination of allylic carbonates is reported. During catalyst activation, a complex of a phosphoramidite ligand possessing one axial chiral binaphtholate group and two resolved phenethyl substituents converts to a more reactive cyclometalated complex containing one distal chiral substituent at nitrogen, one substituent that becomes part of the metalacycle, and one unperturbed binaphtholate group. Systematic changes were made to the different stereochemical elements. Replacement of the distal chiral phenethyl substituent with a large achiral cycloalkyl group led to a catalyst that reacts with rates and enantioselectivities that are similar to those of the original catalyst with the phenethyl group. Studies of the reactions of diastereomeric ligands containing (R) or (S) binaphtholate groups on phosphorus, along with one (R)-phenethyl and one achiral cyclododecyl group on nitrogen, show that the complexes of the two diastereomeric ligands undergo cyclometalation at much different rates. To access both diastereomeric catalysts and to determine if the reaction can occur selectively with an even simpler ligand containing a phenethyl substituent at nitrogen as the only resolved stereochemical element, the catalyst derived from a phosphoramidite containing a biphenolate group was studied. Catalysts generated from this ligand were shown to react in all cases examined with nearly the same rates, regioselectivities, and enantioselectivities as catalysts derived from the original more elaborate ligand. The absolute stereochemistry of the product implies that the major enantiomer is formed from the (R(a),R(c))-atropisomer of the catalyst containing the biphenolate group.     

Synthesis and Spectroscopic [Electronic,IR, NMR (1H, 13C, 89Y)] Characterization of Hexaisopropoxoniobates and ‐Tantalates of Yttrium(III) and Lanthanides(III)

Hexaisopropoxoniobates/tantalates of lathanides of the type [Ln{(μ‐OPrⁱ)₂M(OPrⁱ)₄}₃] (M = Nb, Ln = Y( 1 ), La( 2 ), Nd( 3 ), Er( 4 ), Lu( 5 ); M = Ta, Ln = Y( 6 ), Gd( 7 )) have been prepared by the reactions of LnCl₃.3PrⁱOH with three equivalents of KM(OPrⁱ)₆ in benzene. Reactions in 1:2 molar ratio of LnCl₃.3PrⁱOH with KTa(OPrⁱ)₆ yielded derivatives of the type [{(PrⁱO)₃Ta(μ‐OPrⁱ)₃}Ln{(μ‐OPrⁱ)₂Ta(OPrⁱ)₄}(Cl)] (Ln = Y( 8 ), Gd( 9 )), which on interactions with one equivalent of KOPrⁱ afforded [{(PrⁱO)₃Ta(μ‐OPrⁱ)₃}Ln {(μ‐OPrⁱ)₂Ta(OPrⁱ)₄}(OPrⁱ)] (Ln = Y( 10 ), Gd( 11 )). All these derivatives have been characterized by elemental analyses and molecular weight measurements as well as by their spectroscopic [IR, ¹H and ¹³C NMR (Y, La, Lu), electronic (Nd, Er)] studies. ⁸⁹Y NMR studies have also been carried out on derivatives ( 6 ), ( 8 ), and ( 10 ).     

Reactions of metal iodides as a simple route to heterometallics: synthesis, structural transformations, thermal and luminescent properties of novel hybrid iodoargentate derivatives templated by [YL8]3+ or [YL7]3+ cations (L = DMF or DMSO)

A 1 : 3 molar reaction of YI3 and AgI in dimethylformamide (DMF) in the presence of NH4I afforded [Y(DMF)8][Ag3(mu3-I)(mu-I)3I2] (1) with good yield, whereas the similar reaction in dimethylsulfoxide (DMSO) gave complexes [Y(DMSO)8][Ag2(mu-I)3I2] (2) and/or [Y(DMSO)8]2[Ag4(mu3-I)2(mu-I)4I2][I]2 (3), depending on the reaction and crystallization conditions. These discrete heterometallic hybrid compounds 1-3 undergo solid- and solution-state transformations via condensation of iodoargentate anions. So in the confined and solvent-free environment of paratone, crystals of 1 transformed into a 1D zig-zag structure [Y(DMF)8]3+[Ag6(mu4-I)2(mu3-I)2(mu-I)5]1infinity(3-) (4), whereas those of 2 were first converted into 3 and finally into [Y(DMSO)7]4[Ag4(mu3-I)4I4]3 (5). In solution phase, re-crystalization of 1 or 2 from DMSO-toluene gave 3 as an exclusive species, whereas reaction of 1 with 3 equiv of AgI in DMF afforded 4 with good yield. Alternatively, 4 could also be synthesized with excellent yield from a 1 : 6 molar reaction of YI3 and AgI. The above transformations suggest that, for a given metal-organic cation, an iodometallate cluster with higher nuclearity is thermodynamically more stable. Single crystal X-ray structures are reported for all the compounds and a mechanism for the structural transformation of 2 to 3 is proposed. In addition, spectroscopic, thermo-gravimetric and luminescent properties of the complexes 1, 3 and 4, which were obtained exclusively and in pure form, are also described.