Verma et al. Nanoscale Res Lett 2011, 6:16 http://www.nanoscalereslett.com/content/6/1/16 N A N O E X P R E S S Open Access Biofabrication of Anisotropic Gold Nanotriangles Using Extract of Endophytic Aspergillus clavatus as a Dual Functional Reductant and Stabilizer Vijay C Verma1*, Santosh K Singh1, Ravindra Solanki2, Satya Prakash3 Abstract Biosynthesis of metal and semiconductor nanoparticles using microorganisms has emerged as a more eco-friendly, simpler and reproducible alternative to the chemical synthesis, allowing the generation of rare forms such as nanotriangles and prisms. Here, we report the endophytic fungus Aspergillus clavatus, isolated from surface sterilized stem tissues of Azadirachta indica A. Juss., when incubated with an aqueous solution of chloroaurate ions produces a diverse mixture of intracellular gold nanoparticles (AuNPs), especially nanotriangles (GNT) in the size range from 20 to 35 nm. These structures (GNT) are of special interest since they possess distinct plasmonic features in the visible and IR regions, which equipped them with unique physical and optical properties exploitable in vital applications such as optics, electronics, catalysis and biomedicine. The reaction process was simple and convenient to handle and was monitored using ultraviolet–visible spectroscopy (UV–vis). The morphology and crystalline nature of the GNTs were determined from transmission electron microscopy (TEM), atomic force spectroscopy (AFM) and X-ray diffraction (XRD) spectroscopy. This proposed mechanistic principal might serve as a set of design rule for the synthesis of anisotropic nanostructures with desired architecture and can be amenable for the large scale commercial production and technical applications. Introduction At present, there is a greater need to develop safe, reliable, clean and eco-friendly methods for the prepara- tion of nanoparticles and other high structured nanoma- terials. With the rapid development of new chemical/ physical methods, concern for environmental contami- nations is regularly heightened as the chemical proce- dures involved in the synthesis of nanomaterials generates a large amount of hazardous by-products. Thus, there is an urgent need for ‘green chemistry’ that includes clean, nontoxic and environment-friendly methods of nanoparticle synthesis with precise control over the shape and size. In the recent years, ‘green synthesis’ of the nanoparticles has paid much more attention in the rapidly growing area of nanoscience and nanotechnology [1-5]. Utilization of cheap nontoxic che- micals, eco-friendly solvents and renewable materials are some of the pivotal issues that merit important concern * Correspondence: chandravcv@gmail.com 1Centre of Experimental Medicine and Surgery, Institute of Medical Sciences, Banaras Hindu University, Varanasi 221005, India. Full list of author information is available at the end of the article in a green synthesis strategy for nanomaterials. In this context, biological synthesis of nanoparticles as an emerging highlight of the intersection of nanotechnology and biotechnology has received increasing attention to come up the need of environmentally benign technolo- gies in nanomaterial synthesis, not only because it reduce the use and generation of hazardous substances to human health and environment but also in providing the facile and convenient entry to produce multiple inorganic nanoparticles [6]. Thus, synthesis of nanoma- terials using microorganisms is compatible with the green chemistry principles, resulted in a surge of interest in scientists towards biological systems for inspiration [7-9]. Many microbes are known to produce highly structured metallic nanoparticles with very similar prop- erties to that of chemically synthesized materials, while having precise control over size, shape and monodisper- sity. The magnetosome or the magnetotactic bacteria synthesize the magnetic nanoparticles in nature since long back, which is a very good biosystem to learn the basic principles of biofabrication [10]. Many prokaryotes like Pseudomonas stutzeri [11] and Schizosacchromyces © 2010 Verma et al. This is an Open Access article distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/2.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.