Experimental investigation for stability and surface properties of TiO2 and Al2O3 water-based nanofluids

Journal of Thermal Analysis and Calorimetry - Nanofluids have gained recent attention because of their potential applications in diverse engineering fields like enhancing thermal transport,...     

Kinetics of proton transfer in a green fluorescent protein: A laser-induced pH jump study

The sub-millisecond protonation dynamics of the chromophore in S65T mutant form of the green fluorescent protein (GFP) was tracked after a rapid pH jump following laser-induced proton release from the caged photolabile compoundo-nitrobenzaldehyde. Following a jump in pH from 8 to 5 (which is achieved within 2 μs), the fluorescence of S65T GFP decreased as a single exponential with a time constant of ∼90 μs. This decay is interpreted as the conversion of the deprotonated fluorescent GFP chromophore to a protonated non-fluorescent species. The protonation kinetics showed dependence on the bulk viscosity of the solvent, and therefore implicates bulk solvent-controlled protein dynamics in the protonation process. The protonation is proposed to be a sequential process involving two steps: (a) proton transfer from solvent to the chromophore, and (b) internal structural rearrangements to stabilize a protonated chromophore. The possible implications of these observations to protein dynamics in general is discussed     

Bounds on the inverses of nonnegative triangular matrices with monotonicity properties

Some bounds on the entries and on the norm of the inverse of triangular matrices with nonnegative and monotone entries are found. All the results are obtained by exploiting the properties of the fundamental matrix of the recurrence relation which generates the sequence of the entries of the inverse matrix. One of the results generalizes a theorem contained in a recent article of one of the authors about Toeplitz matrices.     

A Two‐Dimensional Coordination Compound as a Zinc Ion Selective Luminescent Probe for Biological Applications

A 2D coordination compound {[Cu₂(HL)(N₃)]?ClO₄}_∞ ( 1 ; H₃L=2,6‐bis(hydroxyethyliminoethyl)‐4‐methyl phenol) was synthesized and characterized by single‐crystal X‐ray diffraction to be a polymer in the crystalline state. Each [Cu₂(HL)(N₃)]⁺ species is connected to its adjacent unit by a bridging alkoxide oxygen atom of the ligand to form a helical propagation along the crystallographic a axis. The adjacent helical frameworks are connected by a ligand alcoholic oxygen atom along the crystallographic b axis to produce pleated 2D sheets. In solution, 1 dissociates into [Cu₂(HL)₂(H₃L)]?2H₂O ( 2 ); the monomer displays high selectivity for Zn²⁺ and can be used in HEPES buffer (pH 7.4) as a zinc ion selective luminescent probe for biological application. The system shows a nearly 19‐fold Zn²⁺‐selective chelation‐enhanced fluorescence response in the working buffer. Application of 2 to cultured living cells (B16F10 mouse melanoma and A375 human melanoma) and rat hippocampal slices was also studied by fluorescence microscopy.     

Intra-annular cyclophane diamines as proton sponges: a computational study

Gas-phase proton affinities of cyclophanes containing intra-annular amino groups were calculated using density functional theory (DFT) at the B3LYP/6-31+G^∗∗//B3LYP/6-31G^∗ level. They are higher in magnitude as those for proton sponges such as 1,8-bisaminonaphthalene, however, they are slightly weaker bases than 1,8-bis(dimethylamino)naphthalene. The high basicity of the cyclophane diamines is attributed mainly to their structural flexibility, which allows them to maximize the hydrogen bond strength in the cations by achieving N-H?N linearity, while strain relief upon protonation is less important. Another contributing factor is the stabilizing interaction of the added proton with adjacent phenyl π systems of the cyclophanes. Barriers for proton transfer between the nitrogen atoms of the diamine cations are also reported.     

Chemistry of azoimidazoles. Synthesis,spectral characterization and redox studies of N(1)-benzyl-2-(arylazo)imidazolepalladium(II)chloride

Arylazoimidazoles (2) are N,N-chelating ligands. The polymerization trend of the azolate system is restricted via N(1)-benzylation. The parent molecules (2), N(1)-benzylated products (3) and palladium complexes (4) were made by standard methods. The ligands (3) and complexes (4) are new. They have been characterized by elemental analysis, i.r., u.v.-vis. and high resolution 1H-n.m.r. spectral data. Redox studies were carried out by cyclic voltammetry. On complexation, azo reduction is shifted anodically.     

Synthesis of conjugated diacetylene, metal-chelating monomers for polymerizable monolayer assemblies

[see structure]. Self-assembled monolayers (SAMs) of thiols on gold have been used for numerous applications. For protein targeting applications, one successful strategy is to use a metal-chelating SAM. It has also been demonstrated that polymerized SAMs are much more stable than non-polymerized counterparts. We report herein, the synthesis of several polymerizable, metal-chelating thiols capable of complexing luminescent lanthanide ions.     

Effect of heat treatment on the physico-chemical properties and catalytic activity of manganese nodules leached residue towards decomposition of hydrogen peroxide

The effect of calcination temperature on the physico-chemical characterization of manganese nodule leached residue (MNLR) and water-washed manganese nodule leached residue (WMNLR) has been investigated on the basis of chemical analysis, XRD, TG-DTA, FTIR, surface hydroxyl groups, surface oxygen, reducing and oxidizing sites, surface area. XRD and IR confirm the presence of amorphous iron oxyhydroxides, delta-MnO2, which are converted to alpha-Fe2O3 and gamma-Mn2O3 phases above 400 degrees C of calcination, respectively. A solid solution of Fe2O3 and Mn2O3 is formed above 700 degrees C. The surface area, surface hydroxyl group, surface oxygen, reducing and oxidizing sites increase with the increase in calcination temperature up to 400 degrees C and then decrease with further rise in calcination temperature up to 700 degrees C. The catalytic activity of the sample towards H2O2 decomposition shows the similar trend as surface properties. A suitable Mn(3+)Mn4+ couple favours H2O2 decomposition reaction. The activity has been correlated with various physico-chemical properties.