Green chemistry approaches for the synthesis of metallic nanoparticles have become a new and promising field of research in recent years. Synthesis of metal nanoparticles [like gold (Au), silver (Ag), lead (Pb), platinum (Pt), copper (Cu), iron (Fe), cadmium (Cd), and other metal oxides such as titanium oxide (TiO), zinc oxide (ZnO), etc.] by various chemical and physical approaches as well as the biological approaches mediated by number of microorganisms have been actively found. Plant-mediated synthesis approaches are found to be more reliable and economic route to synthesize these metal nanoparticles. Owing to the biodiversity of plant biomasses, the actual mechanism by which the plant constituents have contributed to the synthetic process is yet to be fully known. Although the feasibility of controlling, the size and shape of nanoparticles by variation in reaction conditions have been demonstrated in many studies. Conventionally, nanoparticles are synthesized by chemicals and physicochemical methods using several chemicals which later on become accountable for various risk due to their general toxicity, so that solving the objective biological approaches is coming up to fill these gaps. The plant-mediated synthesis process undergoes highly controlled approaches for making them suitable for metal nanoparticle synthesis. In addition, biological synthesis of metallic nanoparticles is inexpensive, one-step, and eco-friendly method. In addition, the plant-mediated nanoparticles are used as potential pharmaceutical agents for various diseases such as malaria, HIV, cancer, hepatitis, and other diseases. Including this some other relevant information regarding nanopharmaceutical products, companies that are involve in the manufacturing and commercialization process and their clinical trial status are also discussed. This review article gives an overview of the plant-mediated synthesis of metal nanoparticles, possible compounds, and mechanisms that might be responsible for the reduction process as well as the potential pharmacological applications, currently available nanopharmaceutical products and their marketing status.

Green synthesis of c-Gd 2 S 3 nanoparticles was carried out using low-temperature hydrothermal route in autoclave. A 1:1 mixture of ionic liquid 1-ethyl-3-methylimidazolium ethyl sulfate, ([EMIM][EtSO4]), and water was used as a solvent. Synthesized nanoparticles were characterized by x-ray powder diffraction (XRPD), scanning electron microscopy (SEM), UV-visible spectroscopy (UV-vis), particle size by dynamic light scattering (DLS) technique, and photoluminescence (PL) studies. XRPD suggests cubic Th 3 P 4 -type structure for obtained Gd 2 S 3 nanoparticles. The size of synthesized nanoparticles is about 86 nm. Optical band gap for these nanoparticles estimated from electronic spectrum is 2.95 eV which shows blue shift from values reported for bulk Gd 2 S 3 due to pronounced quantum mechanical effect. These nanoparticles show sharp emission peak at 385 nm and a broad shoulder at 475 nm when excited at 260 nm.

Cadmium sulphide (CdS) nanoparticles doped with Co 2? and co-doped with Co 2? and rare earth metallic ions have been prepared by co-precipitation method. The synthesized nanoparticles have been characterized by X-ray powder diffraction studies, energy dispersive X-ray analysis, scanning electron microscopy (SEM), transmission electron microscopy (TEM), UV-visible spectroscopy, particle size by dynamic light scattering and photoluminescence studies. The X-ray diffraction results indicate that CdS nanoparticles can be co-doped with cobalt and rare earth metallic ions without altering XRD pattern. The particle size calculated from XRD results is in range of 40-50 nm. SEM results show that the synthesized particles are spherical in shape and TEM results reveal that synthesized particles have a very small size nearing to Bohr radius for bulk CdS. Absorption spectra of all the samples show strong blue shift from bulk CdS. Interesting luminescence characteristics have been observed for co-doped CdS nanoparticles at room temperature. The relative fluorescence intensity of co-doped samples is significantly higher than that of undoped and Co 2? doped CdS nanoparticles.

Cadmium sulphide (CdS) nanoparticles doped with Cu 2+ and co-doped with rare earth metallic ions (Ln 3+ ) have been synthesized by co-precipitation method. The synthesized nanoparticles were characterized by powder X-ray diffraction studies (PXRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), particle size by dynamic light scattering (DLS), UV-visible spectroscopy (UV), and photoluminescence (PL) studies. It is observed that CdS nanoparticles can be co-doped with copper and rare earth metallic ions without altering XRD pattern as indicated by X-ray diffraction results. SEM and TEM results show that synthesized particles have spherical aggregation. Absorption spectra of all the samples show strong blue shift from bulk CdS. Interesting luminescence pattern with enhanced intensity has been observed for co-doped CdS nanoparticles at room temperature.

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