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Formation of Crystalline Metal Nanoparticles by Marine Isolates and Their Microbial Consortium
Yn, Lee Shi,Lee, Yang Soo,Sathishkumar, Muthuswamy,Krishnamurthy, Sneha,Yun, Yeoung-Sang American Society of Civil Engineers 2016 Journal of environmental engineering Vol.142 No.9
<P>The present study reports that microbes from marine sediments can reduce noble metal ions (Au, Ag, and Pt) to their nanoparticles (NPs). The microbes were initially screened for the synthesis of gold (Au) NPs through bioreduction. The cell-free extracts (CFE) of the most promising strain, Photobacterium sp. (MB 8), was further subjected to the synthesis of Ag, Au, and Pt NPs. The resulting metal NPs were characterized by UV-Vis spectrophotometry and transmission electron microscopy (TEM). The TEM results revealed the presence of well-dispersed NPs in the presence of CFE. The residual concentration of metal ions was measured by inductively coupled plasma mass spectrometry (ICP-MS). X-ray diffraction (XRD) analysis of the NPs confirmed the presence of crystalline Au and AgCl NPs. However, no peaks for the presence of crystalline Pt were observed. X-ray photon spectrometry (XPS) analysis of NPs obtained from synthetic wastewater confirmed the formation of nano-sized zero-valent Au and Ag. The consortium of microbes was found to be more efficient in bioreduction of ionic metals to zero-valent form than an individual strain.</P>
Sneha, Krishnamurthy,Yn, Lee Shi,Yeoung-Sang, Yun American Scientific Publishers 2015 Journal of Nanoscience and Nanotechnology Vol.15 No.1
<P>We demonstrate the effects extract amount, pH and temperature on the formation of gold nanoparticles (AuNP) using Ocimum santum plant extract. The average AuNP size, shape, and particle number can be controlled by simply varying the pH, temperature and amount of plant extract in the reaction medium. Acidic pH was found to be ideal for the formation of AuNPs. UV-visible spectra for the reaction of the plant extract with 1 mM HAuCl4 solution showed that the highest intensity of surface plasmon resonance (SPR) occurred at pH 3. Transmission electron microscopy (TEM) showed that temperature can be used to control the aspect ratio and the relative amount of gold nanoplatelets (triangular and hexagonal). Increasing the temperature decreased the population of gold nanoplatelets and increased the number of spherical NPs, and nanoplatelet population was found to be highest at 20 degrees C and 30 degrees C.</P>
Biosynthesis of Au Nanoparticles Using Cumin Seed Powder Extract
Sneha, Krishnamurthy,Sathishkumar, Muthuswamy,Lee, Shi Yn,Bae, Min A.,Yun, Yeoung-Sang American Scientific Publishers 2011 Journal of Nanoscience and Nanotechnology Vol.11 No.2
<P>Cumin seed was investigated for synthesis of gold nanoparticles. Polydispersed particles were obtained at pH 3 and 30 degrees C, and the effect of temperature and pH on synthesis of gold nanoparticles was analyzed. TEM images showed that amount of platelets formed were predominant at lower temperature where as more number of monodispersed spherical particle of size 1-10 nm were perceived at high temperatures. The gold nanoparticles particles formed at higher pH were stable, uniform and spherical in shape. XPS analysis showed the presence of pure gold nanoparticles.</P>