Nanotechnology is the creation, manipulation and use of materials at the nanometre size scale (1 to 100 nm). At this size scale there are significant differences in many material properties that are normally not seen in the same materials at larger scales. Although nanoscale materials can be produced using a variety of traditional physical and chemical processes, it is now possible to biologically synthesize materials via environment-friendly green chemistry based techniques. In recent years, the convergence between nanotechnology and biology has created the new field of nanobiotechnology that incorporates the use of biological entities such as actinomycetes algae, bacteria, fungi, viruses, yeasts, and plants in a number of biochemical and biophysical processes. The biological synthesis via nanobiotechnology processes have a significant potential to boost nanoparticles production without the use of harsh, toxic, and expensive chemicals commonly used in conventional physical and chemical processes. The aim of this review is to provide an overview of recent trends in synthesizing nanoparticles via biological entities and their potential applications.

Today there is a growing need to develop reliable, sustainable, and ecofriendly protocols for manufacturing a wide range of metal and metal oxide nanoparticles. The biogenic synthesis of nanoparticles via nanobiotechnology based techniques has the potential to deliver clean manufacturing technologies. These new clean technologies can significantly reduce environmental contamination and decease the hazards to human health resulting from the use of toxic chemicals and solvents currently used in conventional industrial fabrication processes. The largely unexplored marine environment that covers approximately 70% of the earth's surface is home to many naturally occurring and renewable marine plants. The present review summarizes current research into the biogenic synthesis of metal and metal oxide nanoparticles via marine algae (commonly known as seaweeds) and seagrasses. Both groups of marine plants contain a wide variety of biologically active compounds and secondary metabolites that enables these plants to act as biological factories for the manufacture of metal and metal oxide nanoparticles.

Direct-absorption solar collectors have the potential to offer an unlimited source of renewable energy with minimal environmental impact. Unfortunately, their performance is limited by the absorption efficiency of the working fluid. Nanoparticles of functionalized carbon nanospheres (CNS) have the potential to improve the photothermal properties of the working fluid. CNS are produced by the pyrolysis of acetylene gas in a tube-based electric furnace/chemical vapor deposition apparatus. The reaction takes place at 1000°C in the presence of nitrogen gas without the use of a catalyst. The synthesized CNS were examined and characterized using field-emission scanning electron microscopy, transmission electron microscopy, X-ray diffraction spectroscopy, Raman spectroscopy, thermal gravimetric analysis, and ultraviolet-visible analysis. The CNS powders with a mean particle size of 210 nm were then functionalized using tetraethylammonium hydroxide ([C2H5]4 N[OH]) and used to produce a series of aqueous nanofluids with varying mass content. The photothermal response of both the nanofluids and films composed of CNS were investigated under 1000 W/m(2) solar irradiation.