**Abstract**

Materials with structural elements, clusters and crystallites or molecules with size dimension in the range 1–100 nm and/or 4–20 Å have found potential and real applications as antimicrobial agents, catalysts, nano-filters in waste water treatments and scale forming ions removal etc. These nano/micro-structured materials possess large surface area which is one of the most important properties needed in different fields of applications. In this short review, the different protocols available for the synthesis ranging from green chemistry to chemical reduction methods, structural characterization, morphology and applications of nanostructured materials such as layered double hydroxides, silver and molybdenum oxides have been discussed.

**Keywords:** nanomaterials, chemical reduction, green chemistry, layered double hydroxides, antimicrobial agents

## **1. Introduction**

The synthesis of inorganic nanostructured materials, their stabilization, morphology and properties are the main issues of interest in different research groups. The interest is not only for their applications in chemical technology, catalysis, magnetic data storage and sensing [1], but also for their antimicrobial activities and waste-water treatment. More often than not, marine sediments and water environments are contaminated by urban runoffs, industrial and domestic effluents and oil spills [2]. The presence of such contaminants as polycyclic aromatic hydrocarbons (PAHs), poly chlorinated biphenyls (PCBs), dichlorodiphenyltrichloroethane (DDT) and heavy metals like mercury, lead and manganese poses risk to both human health and the aquatic biota [3]. Functionalized magnetic metal oxide nanoparticles [4, 5], silver nanoparticles as well as nanostructured layered double hydroxides have proven useful in the remediation of toxic waste in the water environment, inhibition of bacterial and fungi activities [6] and removal of scale forming ions from oil wells [7].

Different protocols have been employed in the synthesis of nanostructured materials by different research groups. These synthetic protocols are generally grouped into two categories: "top-down" and "bottom-up" approach. In the topdown approach (milling or attrition), bulk solid is broken into smaller and smaller portions, until nanometer size is reached. The bottom-up method of nanoparticle synthesis involves nucleation of atoms followed by their growth in a self-assembly fashion to form the nanomaterial. Here we will look at the different nanostructured materials prepared by bottom-up methods such as hydrothermal, [8, 9] combustion synthesis [10], gas-phase methods [11, 12], microwave synthesis and sol-gel processing [13].
