Polyindole (PIn) nanowires were formed on a lambda-DNA template by chemical oxidation of indole using aqueous FeCl3. The resulting nanowires are smooth, regular, conductive and had diameters in the range of 5-30 nm. These features allow them to be aligned by molecular combing and studied by scanned conductance microscopy, conductive AFM, and two-terminal I-V measurements. Using this combination of measurements, we find that the conductivity of PIn/DNA nanowires is between 2.5 and 40 S cm(-1) at room temperature, which is substantially greater than that in previous reports on the bulk polyindole conductivity (typically 10(-2)-10(-1) S cm(-1)). The conductance at zero bias shows an Arrhenius-type of dependence on temperature over the range of 233 to 373 K, and the values observed upon heating and cooling are repeatable within 5%; this behavior is consistent with a hopping mechanism of conductivity.

Electroless templating on DNA is established as a means to prepare high aspect ratio nanowires via aqueous reactions at room temperature. In this report we show how Pd nanowires with extremely small grain sizes (< 2 nm) can be prepared by reduction of PdCl4(2-) in the presence of lambda-DNA. In AFM images the wires are smooth and uniform in appearance, but the grain size estimated by the Scherrer treatment of line broadening in X-ray diffraction is less than the diameter of the wires from AFM (of order 10 nm). Electrical characterisation of single nanowires by conductive AFM shows ohmic behaviour, but with high contact resistances and a resistivity (-10(-2) omega cm) much higher than the bulk value for Pd metal (-10(-5) cm @ 20 degrees C). These observations can be accounted for by a model of the nanowire growth mechanism which naturally leads to the formation of a granular metal. Using a simple combing technique with control of the surface hydrophilicity, DNA-templated Pd nanowires have also been prepared as networks on an Si/SiO2 substrate. These networks are highly convenient for the preparation of two-terminal electronic sensors for the detection of hydrogen gas. The response of these hydrogen sensors is presented and a model of the sensor response in terms of the diffusion of hydrogen into the nanowires is described. The granular structure of the nanowires makes them relatively poor conductors, but they retain a useful sensitivity to hydrogen gas.

DNA strands have been used as templates for the self-assembly of smooth and conductive cuprous oxide (Cu₂O) nanowires of diameter 12-23 nm and whose length is determined by the template (16 μm for λ-DNA). A combination of spectroscopic, diffraction and probe microscopy techniques showed that these nanowires comprise single crystallites of Cu₂O bound to the DNA molecules which fused together over time in a process analogous to Ostwald ripening, but driven by the free energy of interaction with the template as well as the surface tension. Electrical characterization of the nanowires by a non-contact method, scanned conductance microscopy and by contact mode conductive AFM showed the wires are electrically conductive. The conductivity estimated from the AFM cross section and the zero-bias conductance in conductive AFM experiments was 2.2-3.3 S cm⁻¹. These Cu₂O nanowires are amongst the thinnest reported and show evidence of strong quantum confinement in electronic spectra.

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A cost-effective method for the biosynthesis of copper nanoparticles (Cu-NPLs) using Tilia extract under optimum conditions has been presented. The use of Tilia extracts for the synthesis of Cu-NPLs has been investigated for the first time. The Cu-NPLs are stable due to in situ bio-capping by the Tilia extract residues. Formation of metallic Cu was revealed by UV-vis and XRD analyses. UV-vis of Cu-NPLs showed an SPR characteristic peak at 563 nm (energy bandgap = 2.1 eV). Morphology and size of the as-prepared Cu-NPLs were determined using SEM and TEM studies. TEM observations show that the produced Cu-NPLs are hemispherical in shape with different diameters in the range 4.7–17.4 nm. The electrical conductivity of the Cu-NPLs was determined as 1.04 × 10−6 S cm-1 (at T = 120 K). The antimicrobial studies exhibited relatively high activity against pathogenic bacteria like Gram-positive & Gram-negative bacteria. Anticancer studies demonstrated the in vitro cytotoxicity value of Cu-NPLs against tested human colon cancer Caco-2 cells, human hepatic cancer HepG2 cells and human breast cancer Mcf-7 cells. To conclude, Cu-NPLs are promising in electronic devices and they possess a potential anticancer application for some human cancer therapy as well.

This report has two principal goals. First, to synthesis Se nanoparticles (Se-NPLs) via a green approach. Secondly, to explore the photocatalytic activity of Se-NPLs towards the decolorization of sunset yellow (SSY) azo-dye and to test its activity against some types of human cancers. Green synthesis of Se-NPLs from the leaf extracts of Drumstick was developed. Bio-synthesized Se-NPLs were characterized using FTIR, UV-vis, photoluminescence (PL), X-ray powder diffraction (XRD), scanning electron microscopy (SEM), energy dispersive analysis Xray (EDAX) and transmission electron microscopy (TEM) analyses. The UV-vis absorption maximum between 200 and 400 nm was due to the formation of SPR of Se-NPLs. FTIR revealed the Se-NPLs were synthesized, capped and stabilized with biomolecules present in the plant extracts. Se-NPLs exhibited an excitation peak at 399 nm and produced an emission peak at 599 nm. EDAX profile provided a signal of atomic Se (1.45 Kev).XRD confirmed the crystalline nature of Se-NPLs. SEM and TEM observations show that spherical Se particles appeared with diameters ranging from 23 to 35 nm. A possible mechanism of the reduction of (SeO 3 2 À ) to (Se 0 ) was discussed. The electrical conductivity was measured with temperature and the activation energy was calculated. The photocatalytic study conducted that Se-NPLs have the efficiency to degrade sunset yellow dye and the mechanism of degradation has been proposed. Se-NPLs have been shown to be effective against three types of human cancers (Caco-2 cells, HepG2 cells, and Mcf-7 cells). Se-NPLs are potent anticancer and inhibit the growth of the three cancer cells as indicated by the IC 50 values. To conclude, the green-synthesized Se-NPLs may be a candidate for further evaluation as a chemotherapeutic agent for some human cancer treatment.

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