@article { ISI:000205747600006, title = {Extra-/intracellular biosynthesis of gold nanoparticles by an alkalotolerant fungus, trichothecium sp.}, journal = {Journal of Biomedical Nanotechnology}, volume = {1}, number = {1}, year = {2005}, month = {MAR}, pages = {47-53}, publisher = {AMER SCIENTIFIC PUBLISHERS}, type = {Article}, address = {25650 NORTH LEWIS WAY, STEVENSON RANCH, CA 91381-1439 USA}, abstract = {

The development of reliable, eco-friendly processes for the synthesis of nanoscale materials is an important aspect of nanotechnology. As part of our ongoing investigation into the use of fungi for nanoparticle synthesis, we report herein that depending on the reaction conditions of the fungus Trichothecium sp. with aqueous gold ions, gold nanoparticle synthesis can be controlled to occur either within the biomass or extracellularly. Moreover, we have found that reaction of gold ions with the Trichothecium sp. fungal biomass under stationary conditions results in the rapid extracellular formation of gold nanoparticles of spherical, rod-like and triangular morphology whereas reaction of the biomass under shaking conditions resulted in intracellular growth of the nanoparticles. It is believed that on changing the reaction conditions of the fungus with gold ions, the enzymes and proteins which are being released into the medium under stationary conditions do not get released under shaking conditions resulting in the formation of extracellular or intracellular gold nanoparticles respectively. The gold nanoparticles are not toxic to the cells and the cells continued to grow after the biosynthesis of the gold nanoparticles in both the cases.

}, keywords = {Biosynthesis, enzymes, Fungus, Gold, Morphology Control, Nanoparticles}, issn = {1550-7033}, doi = {10.1166/jbn.2005.012}, author = {Ahmad, Absar and Senapati, Satyajyoti and Khan, Mohammad Islam and Kumar, Rajiv and Sastry, Murali} } @article { ISI:000232129900020, title = {Synthesis of gold nanospheres and nanotriangles by the Turkevich approach}, journal = {Journal of Nanoscience and Nanotechnology}, volume = {5}, number = {10}, year = {2005}, month = {OCT}, pages = {1721-1727}, publisher = {AMER SCIENTIFIC PUBLISHERS}, type = {Article}, address = {25650 NORTH LEWIS WAY, STEVENSON RANCH, CA 91381-1439 USA}, abstract = {

Gold nanoparticles of triangular morphology possess interesting optical properties with potential application in medicine and infrared absorbing coatings, however, little is known about conditions that favor their growth. In this paper, we have reinvestigated a time-tested recipe for the formation of gold nanospheres by citrate reduction of aqueous gold ions under boiling conditions (Turkevich recipe). Our principle findings are that gold nanotriangle formation is kinetically controlled and is highly favored at low temperatures. Furthermore, the presence of chloride ions from the precursor chloroaurate ions plays a major role in promoting the growth of [111] oriented triangular/truncated triangular particles. The presence of bromide and iodide ions that possess the ability to replace surface-bound chloride ions inhibits triangle formation to varying degrees.

}, keywords = {Crystal growth, Gold, halides, nanospheres, nanotriangles, Temperature effect}, issn = {1533-4880}, doi = {10.1166/jnn.2005.192}, author = {Shankar, S. S. and Bhargava, S. and Sastry, Murali} } @article { ISI:000244909500021, title = {Spider silk as an active scaffold in the assembly of gold nanoparticles and application of the gold-silk bioconjugate in vapor sensing}, journal = {Small}, volume = {3}, number = {3}, year = {2007}, month = {MAR}, pages = {466-473}, publisher = {WILEY-V C H VERLAG GMBH}, type = {Article}, address = {PO BOX 10 11 61, D-69451 WEINHEIM, GERMANY}, abstract = {

Spider silk is being viewed with interest by materials scientists due to its excellent resilience and mechanical properties. In this paper we show that spider silk is an excellent scaffold for the one-step synthesis and assembly of gold nanoparticles. Formation of a gold nanoparticle-spider-silk bioconjugate material is accomplished by simple reaction of the fibers with aqueous chloroauric acid. The gold nanoparticles thus formed are strongly bound to the spider-silk fiber surface enabling study of the electrical properties of the nano bioconjugate. Using the well-known contraction/expansion behavior of the fibers in solvents of varying polarity, we show that exposure of the gold nanoparticle-spider silk bioconjugate to vapors of methanol and chloroform leads to changes in electrical transport through the nanoparticles and thus, the possibility of developing a vapor sensor. The bioconjugate shows excellent response time and cycling efficiency to methanol vapors. The activation energy of electron transport from one gold nanoparticle to another in the nanobiocojugate was determined from temperature-dependent electron-transport measurements to be approximately 1.7 eV.

}, keywords = {bioconjugates, Gold, Nanoparticles, sensors, spider silk}, issn = {1613-6810}, doi = {10.1002/smll.200600413}, author = {Singh, Amit and Hede, Shantesh and Sastry, Murali} }