01762nas a2200205 4500008004100000022001400041245007300055210006900128260011000197300001400307490000700321520099400328100001801322700001901340700002501359700001901384700001901403700003001422856010401452 2007 eng d a0959-942800aEffect of halogen addition to monolayer protected gold nanoparticles0 aEffect of halogen addition to monolayer protected gold nanoparti aTHOMAS GRAHAM HOUSE, SCIENCE PARK, MILTON RD, CAMBRIDGE CB4 0WF, CAMBS, ENGLANDbROYAL SOC CHEMISTRYcFEB a1614-16190 v173 a

The effects of N-halosuccinimide and halogen addition to monolayer protected gold nanoparticles (Au NPs) dispersed in organic media are described. Contrary to the expectation that nanoparticles dispersed in organic media are stable against aggregation, N-iodosuccinimide addition induced aggregation of octadecylamine capped gold nanoparticles in chloroform or toluene. It was observed that even KI and CuI addition could bring about the aggregation though they are very sparingly soluble in organic solvents. It was also found that even molecular iodine could bring about the above mentioned aggregation. Interestingly, when CuI is used the aggregated structures readily convert to very thin flat nanostructures upon exposure to an electron beam or UV irradiation. In fact when the aggregation is induced by the addition of KI or N-iodosuccinamide we do not see the flattening of the aggregated structures exemplifying the important role of Cu ions in making these flat structures.

1 aSingh, Sanjay1 aPasricha, Renu1 aBhatta, Umananda, M.1 aSatyam, P., V.1 aSastry, Murali1 aPrasad, Bhagavatula L. V. uhttps://library.ncl.res.in/content/effect-halogen-addition-monolayer-protected-gold-nanoparticles-002718nas a2200265 4500008004100000022001400041245018300055210006900238260007700307300001400384490000600398520169400404653001702098653001902115653001802134653002402152653001102176100002302187700001802210700003002228700002302258700001902281700002402300856012802324 2008 eng d a1439-422700aExtracellular synthesis of crystalline silver nanoparticles and molecular evidence of silver resistance from morganella sp.: towards understanding biochemical synthesis mechanism0 aExtracellular synthesis of crystalline silver nanoparticles and  aPO BOX 10 11 61, D-69451 WEINHEIM, GERMANYbWILEY-V C H VERLAG GMBHcJUN a1415-14220 v93 a

There has been significant progress in the biological synthesis of nanomaterials. However, the molecular mechanism of synthesis of such bio-nanomaterials remains largely unknown. Here, we report the extracellular synthesis of crystalline silver nanoparticles (AgNPs) by using Morganella sp., and show molecular evidence I of silver resistance by elucidating the synthesis mechanism. The AgNPs were 20 +/- 5 nm in diameter and were highly stable at 1 room temperature. The kinetics of AgNPs formation was investigated. Detectable particles were formed after on hour of reaction, and their production remained exponential up to 18 h, and saturated at 24 h. Morganella sp. was found to be highly resistant to silver cations and was able to grow in the presence of more than 0.5 mm AgNO3. Three gene homologues viz. silE, silP and silS were identified in silver-resistant Morganella sp. The homologue of silE from Morganella sp. showed 99% nucleotide sequence similarity with the previously reported gene, silE, which encodes a periplasmic silver-binding protein. The homologues of silP and silS were also highly similar to previously reported sequences. Similar activity was totally absent in closely related Escherichia coli; this suggests that a unique mechanism of extracellular AgNPs synthesis is associated with silver-resistant Morganella sp. The molecular mechanism of silver resistance and its gene products might have a key role to play in the overall synthesis process of AgNPs by Morganella sp. An understanding of such biochemical mechanisms at the molecular level might help in developing an ecologically friendly and cost-effective protocol for microbial AgNPs synthesis.

10aBiosynthesis10aMorganella sp.10aNanoparticles10asil gene homologues10aSilver1 aParikh, Rasesh, Y.1 aSingh, Sanjay1 aPrasad, Bhagavatula L. V.1 aPatole, Milind, S.1 aSastry, Murali1 aShouche, Yogesh, S. uhttps://library.ncl.res.in/content/extracellular-synthesis-crystalline-silver-nanoparticles-and-molecular-evidence-silver-001609nas a2200193 4500008004100000022001400041245011900055210006900174260012500243300001100368490000700379520078800386100001601174700002001190700002101210700002301231700003001254856013101284 2010 eng d a0003-695100aEnhancement of anisotropic conductivity, elastic, and dielectric constants in a liquid crystal-gold nanorod system0 aEnhancement of anisotropic conductivity elastic and dielectric c aCIRCULATION & FULFILLMENT DIV, 2 HUNTINGTON QUADRANGLE, STE 1 N O 1, MELVILLE, NY 11747-4501 USAbAMER INST PHYSICScOCT a1519130 v973 a

We report electrical conductivity (sigma), dielectric constant (epsilon) and the elastic constant measurements in a nematic liquid crystal (LC) doped with small concentrations of gold nanorods. This LC-nanoparticle complex, shows not only orders of magnitude higher sigma, but also stabilizes its anisotropy. The epsilon data suggests an increased ordering in the nematic phase, and an improved antiparallel correlation of the molecules in the isotropic phase. Surprisingly, an anisotropic enhancement of the Frank elasticity is also seen. We suggest a possible electro/magnetomechanical conductivity switch and also provide explanations based on the aspect ratio of the nanoparticles vis-a-vis the LC molecules. (c) 2010 American Institute of Physics. [doi:10.1063/1.3499744]

1 aSridevi, S.1 aPrasad, Krishna1 aNair, Geetha, G.1 aD'Britto, Virginia1 aPrasad, Bhagavatula L. V. uhttps://library.ncl.res.in/content/enhancement-anisotropic-conductivity-elastic-and-dielectric-constants-liquid-crystal-gold-001313nas a2200157 4500008004100000022001400041245009400055210006900149260007300218300001200291490001100303520067200314100002100986700003001007856011801037 2012 eng d a0009-261400aEffect of digestive ripening agent on nanoparticle size in the digestive ripening process0 aEffect of digestive ripening agent on nanoparticle size in the d aPO BOX 211, 1000 AE AMSTERDAM, NETHERLANDSbELSEVIER SCIENCE BVcFEB a101-1040 v525-263 a

Digestive ripening is an efficient method that leads to monodispersed nanoparticles from polydispersed ones. A systematic investigation of digestive ripening with different agents viz. dodecanethiol and dodecylamine on different metallic systems is presented. It is shown that both the metallic system involved and the digestive ripening agent have influences on the final size distribution. Further, it is demonstrated that the interaction strength between the different metals and the digestive ripening agents based on Hard Soft Acid Base principles could be invoked to explain the variation in nanoparticle size. (C) 2012 Elsevier B.V. All rights reserved.

1 aSahu, Puspanjali1 aPrasad, Bhagavatula L. V. uhttps://library.ncl.res.in/content/effect-digestive-ripening-agent-nanoparticle-size-digestive-ripening-process-001822nas a2200193 4500008004100000022001400041245011000055210006900165260007100234300001600305490000800321520104600329100002501375700002301400700001701423700003001440700002701470856013101497 2013 eng d a1520-610600aExclusion from hexagonal mesophase surfactant domains drives end-to-end enchainment of rod-like particles0 aExclusion from hexagonal mesophase surfactant domains drives end a1155 16TH ST, NW, WASHINGTON, DC 20036 USAbAMER CHEMICAL SOCcOCT a12661-126680 v1173 a

Anisotropic rod-like particles assemble end-to-end when the surfactant/water matrix in which they are dispersed is cooled from the isotropic to the lyotropic hexagonal phase. We demonstrate the formation of such end-to-end assemblies for gold nanorods, which are tens of nanometers in size, as well as for micrometer-sized ellipsoidal polystyrene particles. In both cases, the particles are well-dispersed in the low-viscosity surfactant/water phase above the isotropic-H-1 transition temperature. On cooling into the H-1 phase, mesophase domains form and the particles are expelled to the isotropic phase. As the H-1 domains grow and finally impinge, the particles are localized at the domain boundaries where they reorient and assemble end-to-end. Remarkably, we observe the formation of end-to-end assemblies of gold nanorods even for volume fractions as low as 2 x 10(-6) in the initially dispersed state. The extent of particle ``enchainment'' increases with the particle concentration and with the aspect ratio of the particles.

1 aSharma, Kamendra, P.1 aGanai, Anal, Kumar1 aSen, Debasis1 aPrasad, Bhagavatula L. V.1 aKumaraswamy, Guruswamy uhttps://library.ncl.res.in/content/exclusion-hexagonal-mesophase-surfactant-domains-drives-end-end-enchainment-rod-particles-0