An overview of commonly used semiconductor nanoparticles in photocatalysis

The depletion of non-renewable resources and rise in global warming has caused great concern to humankind. With a view to use renewable source of energy and to eliminate hazardous chemical compounds from air, soil, and water, photocatalysis utilizing solar energy is becoming a rapidly expanding technology. Semiconductor nanoparticles have the ability to undergo photoinduced electron transfer to an adsorbed particle governed by the band energy positions of the semiconductor and the redox potential of the adsorbate. A brief overview of metal oxides and sulphides that can act as sensitizers for light-induced redox processes due to their electronic structure is presented here.     

Preconcentration method on modified silica fiber for chromium speciation

A new method involving pre-concentration on modified silica fiber is described for the speciation of chromium(III) [Cr(III)] and chromium(VI) [Cr(VI)] in aqueous media. This method is based on the different chelating behavior of Cr(III) and Cr(VI) with morpholine-4-carbodithioate (MDTC). Both complexes are extracted on silica fiber modified by sol-gel technology by using 3-aminopropyltriethoxysilane (APS) as a precursor. All extracted samples are directly injected into an high-performance liquid chromatography injector for the simultaneous determination of Cr(III) and Cr(VI). Cr(VI) forms two different complexes, and Cr(III) forms a single complex with MDTC. Therefore, the concentration of Cr(VI) is determined directly from the peak area obtained at 5.4 min; whereas, the assay of Cr(III) is based on subtracting the peak area of Cr(VI) from the total peak area obtained at 4.3 min. Under the optimized conditions, the limits of detection for Cr(III) and Cr(VI) are found to be 0.7 ng/mL and 0.2 ng/mL, respectively.     

One-pot synthesis of trichloromethyl carbinols from primary alcohols

Versatile trichloromethyl carbinols can be prepared in one pot from primary alcohols by treatment with Dess-Martin periodinane (DMP) in CHCl(3) followed by introduction of commercially available 1,5,7-triazabicyclo[4.4.0]dec-5-ene (TBD). A modification of the method was used to convert chiral primary alcohol (R)-(-)-2,2-dimethyl-1,3-dioxolane-4-methanol to the corresponding trichloromethyl carbinol with complete stereochemical fidelity, despite the reactant proceeding through a base-sensitive aldehyde intermediate.     

An analytic algorithm for time fractional nonlinear reaction–diffusion equation based on a new iterative method

A new analytic algorithm for highly nonlinear time fractional reaction–diffusion equations is proposed in this paper. The proposed method is an amalgamation of variational iteration method (VIM), Adomian decomposition method (ADM) and further refined by introducing a new correction functional. This new correction functional is obtained from the standard correction functional of VIM by introducing an auxiliary parameter γ and an auxiliary function H(x) in it. Further, a sequence G_n(x, t), with suitably chosen support, is also introduced in the new correction functional. The algorithm is easy to implement and only four to six iterations are sufficient for fairly accurate solutions. The algorithm is tested on Fitzhugh – Nagumo and generalized Fisher equations with nonlinearity ranging from 2 to 5.     

Extensional rheology of a shear-thickening cornstarch and water suspension

A filament-stretching rheometer is used to measure the extensional viscosity of a shear-thickening suspension of cornstarch in water. The experiments are performed at a concentration of 55 wt.%. The shear rheology of these suspensions demonstrates a strong shear-thickening behavior. The extensional rheology of the suspensions demonstrates a Newtonian response at low extension rates. At moderate strain rates, the fluid strain hardens. The speed of the strain hardening and the extensional viscosity achieved increase quickly with increasing extension rate. Above a critical extension rate, the extensional viscosity goes through a maximum and the fluid filaments fail through a brittle fracture at a constant tensile stress. The glassy response of the suspension is likely the result of jamming of particles or clusters of particles at these high extension rates. This same mechanism is responsible for the shear thickening of these suspensions. In capillary breakup extensional rheometry, measurement of these suspensions demonstrates a divergence in the extensional viscosity as the fluid stops draining after a modest strain is accumulated.     

Study of the open and closed loop characteristics of a tractor and a single axle towed implement system

Accurate automatic guidance of towed implements is important for performing agricultural field operations and for gaining the ultimate benefit from such systems. The study of open and closed loop system responses of a vehicle-implement system can be helpful in the design of practical guidance controllers. Open loop analysis of the kinematic and dynamic models revealed that the higher order dynamics captured by the tractor and implement dynamic model had an impact on simulated responses at higher operating velocities and on higher input frequencies. In addition, a dynamic model with tire relaxation length dynamics was also studied. The various model responses were compared with the experimental responses. Closed loop system characteristics were studied by using a linear quadratic regulator (LQR) controller. The tractor position and heading and implement heading states along with respective rate states were fed back to close the loop. Steering dynamics were also added to the dynamic model closed loop analysis, which helped to achieve a realistic closed loop steering angle history. The closed loop system dynamics became faster as the forward velocity was increased. The open and closed loop response analysis performed in this work provided an understanding about the system at various forward velocities, which will help to design and develop efficient and robust tractor and towed implement guidance controller.     

Tertiary phosphine-appended transition metal ferrocenyl dithiocarbamates: Syntheses,Hirshfeld surface,and electrochemical analyses

Five new heteroleptic complexes of Cu(I), Ag(I), and Ni(II) having formulae [Cu₃(dtc)₂(dppf)₂]PF₆ ( Cu-I ), [Cu₃(dtc)₂(dppe)₂]PF₆ ( Cu-II ), [Cu(PPh₃)₂(dtc)] ( Cu-III ), [Ag₃(dtc)₂(PPh₃)₂]NO₃ ( Ag-I ), and [Ni(dtc)(dppf)]PF₆ ( Ni-I ) (dtc = N-ethanol-N-methylferrocenyl-dithiocarbamate; dppf = 1,1′-bis(diphenylphosphino)ferrocene; dppe = 1,1′-bis(diphenylphosphino)ethane; PPh₃ = tripheylphosphine) have been synthesized and characterized using elemental analysis, Fourier-transform infrared, multinuclear nuclear magnetic resonance, UV–Vis spectroscopy, and single-crystal X-ray diffraction. The single-crystal X-ray diffraction studies indicate that Ag-I forms a rare trinuclear cluster in which the geometry around the two silver centers Ag1 and Ag3 is distorted tetrahedral, whereas the third silver center Ag2 shows a distorted trigonal planar geometry. The Ni-I complex has a distorted square-planar geometry around the Ni center. In addition, a side product [Ag₂{S₂(dppf)₂}] ( Ag-II ) was obtained during an attempt to synthesize [Ag(dppf)(dtc)], where the two Ag centers are bridged by two sulfido centers and coordinated with two phosphorus centers of the dppf ligand to give rise to a distorted tetrahedral geometry. The solid-state structures of Ag-I , Ni-I , and Ag-II are stabilized by a variety of weak interactions. The nature of these interactions has been addressed with the help of Hirshfeld surface analyses. In addition, the weak argentophilic interaction in Ag-I and Ag-II have been studied using quantum theory of atoms in molecules and natural bond orbital calculations. The electrochemical properties of the complexes have been investigated using cyclic voltammetry, where Cu-I and Cu-II exhibited two quasi-reversible waves, whereas Cu-III , Ag-I , Ag-II , and Ni-I exhibited only one quasi-reversible peak.     

Thermo-hydraulic and entropy generation analysis of recharging microchannel using water-based graphene–silver hybrid nanofluid

Journal of Thermal Analysis and Calorimetry - This work numerically investigates thermo-hydraulic and entropy generation characteristics of water-based graphene–silver (Gr–Ag) hybrid...     

Pyrazine Based Type-I Sensitizing Assemblies for Photoreduction of Cu(II) in ‘One-Pot Three-Component’ CuAAC Reaction Under Aerial Conditions

Photosensitizing assemblies of pyrazine derivative PDA have been developed which exhibit a high photostability, ‘lighted’ excited state, balanced redox potential, high transportation potential and activate oxygen via type-I pathway only. These PDA assemblies in combination with Cu(II) ions catalyze the CuAAC reaction via in situ reduction of Cu(II) ions without any reducing or stabilizing agent. The present protocol has wide substrate scope with recyclability of the catalytic system up to six catalytic cycles and is applicable to gram-scale synthesis.     

Synthesis and Biological Evaluation of Novel 1,2,3-Triazole Based Pyrido[4,3-d]pyrimidines as Potent Anticancer and EGFR Inhibitors

Russian Journal of General Chemistry - This study is devoted to the efficient and practical synthesis of a novel series of pyrido[4,3-d]pyrimidine derivatives attached to 1,2,3-triazole ring and...