The Extent of Heavy Metal Pollution by Chemical Partitioning and Risk Assessment Code of Sediments of Sewage-Fed Fishery Ponds at East Kolkata Wetland, a Ramsar Site, India.

Sewage contaminated with toxic metals is being naturally treated in ponds at East Kolkata Wetlands (EKW) for fish cultivation traditionally. From the aquatic phase, these metals get settled on sediment and undergo partitioning. Some fractions are available and may accumulate in the cultivated products. The present study highlights the degree of partition of heavy metals Lead (Pb), Cadmium (Cd) and Chromium (Cr) in these pond sediments. The study reveals that Pb and Cr are significant (39% and 30%, respectively) in Fe-Mn bound fractions. Residual fraction is in the order of Pb > Cr > Cd. The easily available fraction of metals recorded higher in Cd (43.0%) and Cr (42.0%).The risk assessment code (RAC) analysis records that these metals could be considered as potential risk group of metals for higher mobility and availability in these pond ecosystems and is a significant concern for aquaculture products.

Nanojacketing and dejacketing of ds-DNA: a nondestructive characterization of a nanojacketed sample by impedance spectroscopy.

A facile approach of nanojacketing DNA in intact conformation is evolved by the in situ polymerization of o-methoxyaniline (OMA) at 30 °C using HAuCl4 as an oxidant and DNA as a soft template. It concomitantly produces poly(o-methoxyaniline) (POMA) and a Au nanojacket encapsulating the double stranded DNA (ds-DNA). The POMA chains remain adhered to the Au nanojacket, facilitating the dissolution of nanojacketed DNA (DNA-Au-POMA) in organic solvent without affecting its conformation. Digestion of the nanojacketed system with saturated iodine solution dejackets the ds-DNA with retention of its conformation, leaving the POMA nanotube. The nanojacketing and dejacketing phenomena are established by transmission electron microscopy (TEM), UV-vis spectroscopy, and CD spectroscopy, and the nanostructure is further characterized by FTIR, X-ray diffraction (XRD), and X-ray photoelectron spectroscopy (XPS). The impedance study of the DNA-Au-POMA sample suggests the Cole-Cole plots at both the impedance and modulus planes and the values of capacitance and electron-transfer resistance of the material (R(et)) are calculated to be 13.74 pF and 388 kΩ, respectively. The presence of a single Debye peak in both the impedance and modulus vs frequency plots suggests an isotropic nature of the system, and the frequency dependent ac-conductivity suggests the presence of short-range translational and reorientational (localized) hopping of charge carriers at lower and higher frequency region.

Nondestructive characterization of Li+ ion-doped multifunctional poly(vinylidene fluoride)-g-poly(dimethyl amino ethyl methacrylate) by impedance spectroscopy.

Poly(vinylidene fluoride) (PVDF)-graft-poly(dimethyl amino ethyl methacrylate) (PDMAEMA) (PD copolymer) is produced via atom transfer radical polymerization from PVDF solution in N-methyl-2-pyrrolidone. PD copolymer is doped with 1% and 5% (w/w) Li(+) ion to produce PDLi1 and PDLi5 samples, respectively. In PD copolymer, the crystalline structure of PVDF changes from α polymorph to a mixture of α and ß polymorph, and it transforms completely to piezoelectric ß polymorph on doping with 1% (w/w) Li(+) ion. The impedance behavior of PVDF changes on grafting, and that of the PD graft copolymer also changes with increasing Li(+) ion dopant concentration. In the Nyquist plots, PVDF exhibits a straight line character, and a curvature has appeared in the PD graft copolymer; on doping the latter with Li(+) ion (1% w/w), the curvature increases and a semicircle is completed on 5% Li(+) doping. Fitting the data from the Z-view program, the Ohmic resistance of PDLi1 is found to be 78 MΩ having capacitance with constant phase element (CPE) = 1.38 nF while for the PDLi5 sample the resistance decreases to16.1 MΩ with a small increase in CPE to 1.46 nF. The modulus plane plots for PDLi1 and PDLi5 samples also exhibit only one peak supporting the presence of only one equivalent resistance-capacitance circuit with constant phase element in both PDLi1 and PDLi5 samples. Both the impedance and modulus vs frequency plots of PDLi1 and PDLi5 samples exhibit a single Debye peak suggesting isotropic nature of the samples. For PVDF and PDMAEMA, ac-conductivity increases linearly with angular frequency, but in the case of PDLi1 and PDLi5 samples, it remains at first invariant in the frequency range 1-10(2) Hz, and above 10(2) Hz, an increase in conductivity with frequency occurs obeying the double power law. In the temperature variation of conductivity, PVDF exhibits its typical insulating nature, and in the PD graft copolymer, the conductivity decreases with increase of temperature (metallic-like behavior) due to gradual breaking of supramolecular interaction. The temperature variation of ac-conductivity of the Li(+)-doped PD graft copolymer suggests that both the ionic and supramolecular contributions of conductivity operate; the former increases and the latter decreases with rise in temperature showing a maximum. The temperature-dependent FTIR spectra of PDLi1 and PDLi5 samples support the gradual breaking of supramolecular interactions with increase of temperature.

Concomitant synthesis of polyaniline and highly branched gold nanoparticles in the presence of DNA.

The reduction of chloroauric acid using aniline adsorbed on DNA produces highly branched dendritic gold nanoparticles with concomitant formation of polyaniline (PANI) in contrast to the formation of spherical Au nanoparticles in the absence of DNA. The conformation of DNA remains intact in the process as evident from circular dichroism (CD) spectra. The UV-Vis spectrum exhibits a broad absorption peak at 520-900 nm, for a combined effect of the gold surface plasmon and π band to localized polaron band transition of DNA-doped PANI. Both the dendritic Au-PANI-DNA and the spherical Au-PANI systems emit two peaks for excitation with radiation of 300 nm and the intensity ratio of the emission and FRET peak is higher in the dendritic Au-PANI than that in the spherical Au-PANI system. The dc-conductivity values of spherical Au-PANI and dendritic Au-PANI-DNA systems are 1.2×10(-10) and 1.7×10(-8) S/cm at 30°C, respectively.

Biomolecular hybrid of poly(3-thiophene acetic acid) and double stranded DNA: optical and conductivity properties.

A new biomolecular hybrid of poly(3-thiophene acetic acid) (PTAA) and double stranded deoxyribonucleic acid (ds-DNA) is prepared. The transmission electron microscopy (TEM) images exhibit fibrillar network morphology making a nanostructured self-assembly of PTAA-DNA hybrid. The confocal fluorescence image of PTAA shows green fluorescence exhibiting agglomeration in the pure state but the spreading of green fluorescence over the network superstructure in the hybrids indicating the immobilization of PTAA on DNA surfaces. Fourier transform infrared (FTIR) spectra indicate hydrogen bonding between -COOH groups of PTAA and P=O groups of Na-DNA. Circular dichroism (CD) spectra denote that DNA conformation remains unaltered during hybrid preparation. A blue shift of the pi-pi* absorption peak of PTAA in the hybrid solutions occurs with aging time. The photoluminescence intensity in the hybrid solution increases with a concomitant blue shift of the emission peak with aging time, and it is faster with increased DNA concentration. Possible reasons of different optical behavior are discussed in the light of duplex and triplex hybrid formation. Dynamic light scattering study indicates an increased particle size of PTAA with addition of DNA favoring the hybrid particles to remain in solution. The dc-conductivity of the hybrids decreases from that of PTAA with an increase of Na-DNA concentration, and the current (I)-voltage (V) curves indicate a semiconducting nature of the hybrids.

Bimetallic Au(core)-Ag(shell) nanoparticles from interfacial redox process using poly(o-methoxyaniline).

Stable Au(core)-Ag(shell) bimetallic nanoparticles are produced in organic medium through an interfacial redox method using the redox property of an organically soluble conducting polymer poly(o-methoxyaniline) (POMA). The transition of the emeraldine base (EB) form of POMA to its pernigraniline base (PB) form occurs during nanoparticle formation and also the nitrogen atoms of POMA (PB) stabilize the nanoparticles via coordination. TEM images indicate that the interfacial redox replacement reaction between Au (III) in aqueous medium and Ag (0) in organic medium produces bimetallic nanoparticles with Au(core)-Ag(shell) morphology. The formation of such type of core-shell morphology is due to the different standard reduction potentials of the metal ions. The core-shell thickness of the bimetallic nanoparticle can be regulated by changing the POMA (EB) concentration in the organic layer.

Growth of different shape Au nanoparticles through an interfacial redox process using a conducting polymer.

An interesting interfacial redox method is developed for the preparation of Au nanoparticles of various shapes in organic medium using Au seeds in aqueous medium without using phase-transfer reagent. The conversion, stabilization, and the transfer of gold nanoparticles to the organic phase is accomplished using the reducing and solubility properties of poly(o-methoxy aniline) in chloroform. The preparatory method is simple, and the Au nanoparticles are free from excess oxidant and external stabilizer. The characterizations of the metal nanoparticles are made using transmission electron microscopy, UV-vis spectra, electron diffraction and energy-dispersive X-ray techniques. Au nanoparticles of various shapes, for example, hexagonal, pentagonal, triangular, rod-shaped, etc. are produced together. A mechanism of the formation of differently shaped nanoparticles is proposed from catalytic reduction of Au(3+) ion by POMA on the Au seed surface followed by the growth of nanoparticles from the exposed Miller planes of seed surfaces.

RNA-poly(o-methoxyaniline) hybrid templated growth of silver nanoparticles and nanojacketing: physical and electronic properties.

Three nanobiocomposites (PRAg31, PRAg11, and PRAg13; the numbers indicate the weight ratios of poly(o-methoxyaniline) (POMA) and ribonucleic acid (RNA), respectively), produced from the same amount of POMA (P) and silver nitrate (AgNO(3)) with differing proportions of RNA (R) are prepared by aging the aqueous solutions of the mixture for 3 weeks at 30 degrees C. The scanning and transmission electron microscopy (SEM and TEM) indicate Ag nanoparticle formation on the hybrid fiber surface and in the PRAg31 system the hybrid fibrils become coated with metallic Ag, the phenomenon being termed as "nanojacketting". The circular dichroism (CD) spectra indicate a small distortion of RNA conformation from A helix toward B helix. FTIR and UV-vis spectra suggest that POMA (emeraldine base, EB) being doped by Ag(+) become oxidized to its pernigraniline base (PB) form and reduce Ag(+) to metallic Ag. The Ag nanoparticles thus produced become stabilized on the fibril surface by co-ordination through nitrogen atoms of POMA (PB) chains. The much slower red shift of pi band to polaron band transition peak in PRAg31 than that of the other two nanobiocomposites is indicative of difficulty in conformational transitions of POMA chain in the "nanojacketted" hybrid fibrils. The dc-conductivity values of the nanobiocomposites are two orders higher than that of the pure POMA-RNA hybrids. The PRAg31 system exhibits rectification property in the I-V characteristic curves and a probable explanation based on the feasibility of p-n junction formation arising from the transfer of lone pair of electrons of nitrogen of POMA (p-type) to the Ag nanoparticles (n-type) has been offered.

Self assembly of poly(o-methoxy aniline) with RNA and RNA/DNA hybrids: physical properties and conformational change of poly(o-methoxy aniline).

Biomolecular hybrids of a conducting polymer [poly(o-methoxy aniline) (POMA)] and RNA are prepared at the three different compositions by mixing aqueous solutions of diethyl, 2-hydroxy ethyl, ammonium salt of RNA (type IX from Torula Yeast) and POMA (ES, emeraldine salt; doping level [Cl]/[N]=0.52). A slow increase of pH up to 30 h of aging occurs in the mixture till it levels up. The TEM micrographs indicate a fibrillar network structure in all the hybrid compositions (POMA: RNA=1:3, 1:1, 3:1, by weight). In the complexes three types of supramolecular interactions, viz. (i) electrostatic, (ii) H-bonding and (iii) pi-pi interactions, are evident from the FTIR spectroscopy. The CD spectra indicate a small distortion of A-RNA conformation towards its B form during the hybrid formation. Time and temperature dependent UV-vis spectral studies indicate a slow red shift of the pi-band to polaron band transition peak (lambda(max)) for the uncoiling of the POMA (P) chain on the RNA (R) surface. The repulsive interaction between the radical cations of POMA (ES) absorbed on the RNA surface is attributed to the conformational change causing the uncoiling of POMA chain. UV-vis spectral study indicates that the uncoiling and attachment of POMA on RNA surface is much faster than that on DNA (D). In POMA-RNA-DNA (PRD) hybrid solutions slower red shift of lambda(max) indicates more disordered array of the phosphate groups than that in PR and PD systems. The conductivity values of the PR hybrids (10(-)(6) S/cm(-1)) are three orders higher than that of RNA, rendering the PR hybrids to be useful for fabricating good biosensors. In the PRD hybrids conductivity decreases by two orders than those of PR and PD hybrids suggesting a disorder arrangement of POMA chains in the PRD hybrids. The I-V characteristic curves of the PR and PRD hybrids indicate a semiconducting nature of the hybrids.

Preparation of size-controlled, highly populated, stable, and nearly monodispersed Ag nanoparticles in an organic medium from a simple interfacial redox process using a conducting polymer.

The reducing property of an organically soluble conducting polymer (poly(o-methoxyaniline), POMA) is used to prepare monodisperse, size-controlled, highly populated, and highly stable silver nanoparticles in an organic medium through an interfacial redox process with an aqueous AgNO3 solution. The transition of emeraldine base (EB) to the pernigraniline base (PB) form of POMA occurs during nanoparticle formation, and the nitrogen atoms of POMA(PB) stabilize Ag nanoparticles by coordination to the adsorbed Ag(+) on the nanoparticle surface. The conductivity of the nanocomposite is on the order of 10(-11) S/cm, indicating that no doping of POMA occurs under the preparation conditions. The nanoparticles are free of excess oxidant and external stabilizer particles. The POMA (EB) concentration tailors the size of nanoparticles, and at its higher concentration (0.01% POMA with 0.01 N AgNO3), very dense Ag nanoparticles (6 x 10(15) particles/m(2)) of almost uniform size and shape are produced. The rate constant and Avrami exponent values of the nanoparticle formation are measured from the time-dependent UV-vis spectra using the Avrami equation. The Avrami exponent (n) values are close to 1, indicating 2D athermal nucleation with the circular shape of the nuclei having diffusion-controlled growth. The rate constant values are almost independent of AgNO3 concentration but are strongly dependent on POMA concentration. The higher rate constant with increasing POMA(EB) concentration has been attributed for the lowering of nanoparticle size due to increased nucleation density.