The effect of carbon nanotubes in enhancing the thermal transport properties of PCM during solidification

This study is aimed to prepare a novel class of nanofluid phase change material (NFPCM) by dispersing a small amount of multi-walled carbon nanotubes (MWCNT) in liquid paraffin, to enhance the heat transfer properties and examine the characteristics of the NFPCM during the solidification process. The stable NFPCMs are prepared by dispersing the MWCNT in liquid paraffin at 30°C with volume fractions of 0.15, 0.3, 0.45 and 0.6% without any dispersing agents. The rheology measurement illustrates the Newtonian fluid behavior in the shear stress range of 1–10?Pa. The differential scanning calorimetric results showed that there is no observable variation in the freezing/melting temperature of the NFPCM, and only a small observable change in the latent heat values. The thermal conductivity of various NFPCM is measured. The enhancement in thermal conductivity increases with the increased volume fraction of the MWCNT, and shows a weak dependence on the temperature. Further, for the NFPCM with a volume fraction of 0.6%, there is an appreciable increase in heat transfer with a reduction in the solidification time of 33.64%. The enhancement in the heat transfer performance would alleviate the major problems that have been encountered in the conventional phase change materials since several years.     

Mechanical characterization of HIV‐1 with a solid‐state nanopore sensor

Enveloped viruses fuse with cells to transfer their genetic materials and infect the host cell. Fusion requires deformation of both viral and cellular membranes. Since the rigidity of viral membrane is a key factor in their infectivity, studying the rigidity of viral particles is of great significance in understating viral infection. In this paper, a nanopore is used as a single molecule sensor to characterize the deformation of pseudo‐type human immunodeficiency virus type 1 at sub‐micron scale. Non‐infective immature viruses were found to be more rigid than infective mature viruses. In addition, the effects of cholesterol and membrane proteins on the mechanical properties of mature viruses were investigated by chemically modifying the membranes. Furthermore, the deformability of single virus particles was analyzed through a recapturing technique, where the same virus was analyzed twice. The findings demonstrate the ability of nanopore resistive pulse sensing to characterize the deformation of a single virus as opposed to average ensemble measurements.     

Sb–C Bond Cleavage Reaction on a Triruthenium Cluster and the Formation of a Bridging Phenylacyl Unit

Syntheses and single crystal X-ray structures of an open triruthenium acyl carbonyl cluster [(C₆H₅)₂SbRu₃(COC₆H₅)(CO)₁₀] (1) and a simple triruthenium Ru₃(CO)₉[(C₆H₅)₂PCH₂P(C₆H₅)₂]Sb(C₆H₅)₃ (2) are reported. Formation of compound (1) at room temperature from [Ru₃(CO)₁₂] and [Sb(C₆H₅)₃] is unique, a similar reaction with Ru₃(CO)₁₀[(C₆H₅)₂PCH₂P(C₆H₅)₂] under identical conditions results in compound (2), with Sb(C₆H₅)₃ occupying an equatorial site. IR, ¹H, ¹³C NMR spectra of the compounds are reported. The X-ray crystal structure of (1) consist of 2 crystallography distinct molecules and shows Ru–Sb distances in the range: 2.6361(6)–2.6273(7) Å and Ru–Ru distances in the range: 2.8236(7)–2.9855(7) Å. Ru–O distances in the bridging carbonyl are: 2.137(4), 2.158(4) Å. The Sb–Ru–Ru angles in the two molecules of the asymmetric unit are in the range of 73.78(2)–77.52° indicating the puckered nature. Compound (2) has bond parameters comparable to those of Ru₃(CO)₁₀[(C₆H₅)₂PCH₂P(C₆H₅)₂]. The present study shows for the first time that the cleaving of Sb–C bond at room temperature is possible under non-ionic conditions, though there have been many instances of P–C and As–C bond cleavages reported previously.     

FTIR, FT-Raman spectra and ab initio DFT vibrational analysis of 2-bromo-4-methyl-phenylamine

The FTIR and FT-Raman spectra of 2-bromo-4-methyl-phenylamine (BMP) have been recorded. From the standard geometrical parameters the geometry of BMP was optimized at ab initio and DFT levels of theory with complete relaxation in the potential energy surface using 6-311+g(d,p) and 6-311+g(2df,2p) basis sets. Several thermodynamic parameters were also calculated for the minimum energy conformer at ab initio and DFT level of theories. The harmonic vibrational frequencies were calculated and the scaled values have been compared with experimental FTIR and FT-Raman spectra. Majority of the computed wavenumbers were found to be in good agreement with the experimental observations. The experimental spectra also coincide satisfactorily with those of theoretically constructed bar type spectrograms.     

Cyclic voltammetric and characterization studies on first row transition metal complexes of a new high molecular weight dithiocarbamate ligand padtc

Transition Metal Chemistry -     

An unusual stereochemical outcome of radical cyclization: synthesis of (+)-biotin

An enantioselective synthesis of (+)-biotin 1 starting from naturally available cysteine is described. The key steps are the unusual stereochemical outcome of radical cyclization of compound 10 to prepare 5,5-fused system 11, and the introduction of C4-sidechain at C₆ in 13 via a Grignard reaction.     

A convenient synthesis of s-(5′-deoxy-5′-adenosyl)- (±) -2-methylhomocysteine

The synthesis of $\text{S}$-(5′-deoxy-5′-adenosyl)-+-2-methylhomocysteine in two steps from ^+--2-methylmethionine is described.     

M(S)2(I)2 (M=Zn,Cd) and Hg(S)3I Coordination Environment of Transition Metal Complexes – Synthesis,Spectral, and Single Crystal X‐ray Structural Investigations

Three new transition metal complexes [Zn(bipyrtds)I₂]( 1 ), [Cd(bipyrtds)I₂] ( 2 ) and [Hg(pipdtc)I]( 3 ) (where bipyrtds = bipyrrolidine thiuamdisulfide and pipdtc = piperidinecarbodithioate) were prepared by the reaction of the corresponding biscarbodithioates with iodine and were characterized by elemental analysis, IR and NMR spectra. The structures of all the three complexes were determined by single crystal X‐ray crystallography. Compounds 1 and 2 contain four coordinated metal atoms and both Zn^II and Cd^II complexes are isostrucutral. Interestingly, complex 3 was found to contain effectively four coordinated mercury atom as a dimer with a relatively long Hg‐S (3.084Å) bond. The IR studies are in keeping with the observed thioureide distances. ¹H NMR spectra of 1 and 2 show clear differences in environments of α‐ and β‐CH₂ protons. However, in 1 a broad signal was observed at 4.02 ppm for α‐protons and a multiplet at 2.10 for β‐protons. For 2 , two triplets appeared at 4.26 and 4.03 ppm for α‐protons and two quintets appeared in the range of 2.18 and 2.28 ppm for β‐protons. Complex 3 gave three sets of signals. Variation of stereochemical environment with respect to α and β protons of the rings is very clearly observed in the NMR spectra.     

Synthesis,Spectral, Cyclic Voltammetric Studies,and Single Crystal X‐Ray Structure Determination of the Planar NiS2P2, NiS2PN,and NiS2PC Chromophores

Synthesis, spectral and cyclic voltammetric characterization of [Ni(dedtc)(4‐MP)₂](ClO₄) ( 1 ), [Ni(dedtc)(4‐MP)(NCS)]( 2 ), [Ni(dedtc)(PPh₃)(NCS)] ( 3 ) and [Ni(dedtc)(PPh₃)(CN)] ( 4 ) (dedtc = diethyldithiocarbamate, 4‐MP = tri(4‐methylphenyl)phosphine, PPh₃ = triphenylphophine) are reported. IR spectra of complexes 1‐4 show the characteristic thioureide (C‐N) bands at higher wave numbers compared to that of the parent dithiocarbamate complex [Ni(dedtc)₂]. The d‐d transitions are observed in the region 452—482 nm. The CV studies clearly show the presence of reduced electron density on the nickel ions in mixed ligand complexes 1‐4 compared to the parent dithiocarbamate. Single crystal X‐ray structure studies show all the complexes to containplanar NiS₂P₂, NiS₂PN, and NiS₂PC chromophores in keeping with the observed diamagnetism. In all the complexes the Ni‐S distances are asymmetric. The thioureide C‐N distance of the complexes 1‐4 are less thanthe C‐N distance observed in the parent [Ni(dedtc)₂].     

Experimental (FTIR and FT-Raman) and ab initio and DFT study of vibrational frequencies of 5-amino-2-nitrobenzoic acid

The FTIR and FT-Raman spectra of 5-amino-2-nitrobenzoic acid (ANB) have been recorded in the region 400-4000cm(-1). The observed frequencies were assigned to different modes of vibrations on the basis of fundamental, combination and overtones. The geometry has been optimized with complete relaxation on the potential energy surface at HF, MP2 and B3LYP level of theories using 6-311++G(d,p) basis set and compared with the crystal data. The possible hydrogen bond interaction has been estimated taking a model compound. Further harmonic vibrational frequency calculations have been carried out at HF and B3LYP levels and the scaled values were in good agreement with majority of the experimental observations. The theoretically constructed spectra coincide satisfactorily with those of experimental spectra.