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The remarkable size-dependent attributes of nano-sized materials have influenced all dimensions of human existence rendering nanotechnology a fascinating field of research in biomedicine. Much like metal nanoparticles amounting to their exceptional optical, electrical and antimicrobial properties, silver has attracted much interest over the decades. Owing to their reconfigurable physicochemical properties and a huge array of biomedical applications, silver nanoparticles have fascinated the thought of researchers in the recent past. Although numerous physical, chemical and photochemical procedures are routinely used to prepare silver nanoparticles, yet the usage of harmful reagents for reduction and stabilization processes confines their widespread acceptability. In such a pursuit, green synthesis approach stands out an optimal method of preparation of silver nanoparticles in terms of involvement of lesser cost and environment-friendly, non-toxic reducing and stabilizing agents. This chapter presents the different methods of preparation of silver nanoparticles in detail along with the in vitro characterization methods used to characterize the formulated nanoparticles.

Nanotechnology and nanomaterials, with their unique properties, are expanding the use of up-to-date technology in a variety of sectors, including health care, agriculture, pharmaceuticals, and robotics, among others. Various nanotools are used to explore targeted delivery of drugs with minimum adverse effects and maximum utility. The metal nanoparticles possess superior properties for which they are widely applicable in nanotechnology whereas these properties are negligible in bulk materials like silver, gold, and other metals and cannot find any application owing to their inherent physicochemical, optical, electrical, and magnetic properties. In general, the transition and noble metals used in the synthesis of metal nanoparticles are cost-effective, and the steps involved in the synthesis of metallic nanoparticles are not complex. Silver nanoparticles (AgNPs) possess high surface plasmon resonance, have high thermal stability, and exhibit good electrical conductivity. Also, AgNPs possess intrinsic antimicrobial properties that are used extensively to inhibit the growth or completely kill specific disease-causing microbes. In this chapter, we review the mechanism of action and application of AgNPs as antifungal agents against fungal infections in plants and humans.

Nanoscience opens the window for a sea of applications due to the significant properties of nanostructures (NSs) such as optical, electrical, mechanical, magnetic, catalytic, etc. The properties leading to specific applications are due to the constitution of the NSs and preferentially the morphology of the NSs. Among the varieties of NSs, metal nanoparticles (NPs) are more used in applications. NPs can be categorized as monometallic NPs (MNPs) or bimetallic NPs (BNPs) according to the number of metal ions involved in the NP constitution. In this context, details about the structure, methods of synthesis, and applications in various fields are discussed. The applicability of BNPs is more compared to MNPs due to the enhancement of properties due to the small size effect, quantum size effect, surface effect, and the quantum tunneling effect. Nowadays, green synthesis is in discussion for NP synthesis due to its safety, simplicity, and nonrequirement of costly solvents, chemicals, toxicity reduction, and stabilizing agents. NP synthesis by the extracts of different plant parts, whole plants, or secondary metabolites of plants is the principle of green synthesis. Sometimes microbial flora are also used for green synthesis, but the limitations of microorganism selection, growth, and scalability limit their application. BNPs synthesized by green synthesis have wide applications in the field of biomedicine, environment, agriculture, imaging, catalysis, and biosensing.

A facile synthetic route and growth mechanism of heterobimetallic cubical nanoparticles Au@AgCl and Ag@AgCl@Au have been developed using Muntingia calabura flower extract. The formation of nanoparticles has been confirmed through UV-Vis, powder X-ray diffraction and electron microscopy. The elemental composition of the nanoparticles has been evidenced by EDS analysis. Combing the UV-Vis spectral analysis and powder X-ray diffraction studies, the composition of bimetallic nanoparticles are assigned as Au@AgClNP and Ag@AgCl@AuNP. The prepared nanoparticles display good antibacterial activity which is comparable to standard kanamycin and ampicillin.

Herein, a facile scale up and shape variable synthesis of gold nanoparticle (AuNP) and reaction mechanism by natural xanthone derivative (mangiferin) has been reported. Mangiferin (C19H18O11; 1,3,6,7-tetrahydroxyxanthone-C2-β- d -glucoside), a xanthone derivative is isolated from Mangifera indica L. leaves which efficiently reduces Au3+ ions to Au0 and stabilizes the formed AuNP. The structural, optical and plasmonic properties of synthesized AuNP have been investigated through different instrumental techniques like UV–Vis and FTIR spectroscopy, powder XRD, FESEM and TEM analysis. It is observed that variation of the concentration of Au3+ ions and mangiferin has a great effect on controlling size and shape of nanoparticles. The role of reaction temperature is also notable. An interesting observation is that with same concentration ratio of HAuCl4/mangiferin (0.025 mM/0.002%) at the room temperature kidney shaped AuNP is produced, whereas it is spherical at boiling temperature. Moreover, mangiferin allows high scale synthesis of AuNPs (0.025 mM to 10 mM) without changing the particles size and shape. The mechanistic investigation through UV–Vis, FTIR and GCMS analyses reveal the cleavage of glucose unit and oxidation of phenolic OH groups during AuNP formation. Non-toxicity of mangiferin conjugated AuNP on normal human breast cell line (MCF-10A) suggesting its future application as a drug delivery system and other related medicinal purposes.

In situ Al-4.5Cu-5TiB2 composite has been processed through stir casting method, in which, the TiB2 particles have been precipitated in situ by mixed salt route involving reactions between K2TiF6 and KBF4.The as-cast specimens containing 20 volume percent liquid content have been subjected to three mushy state roll passes, each leading to 5 percent reduction in thickness. The grain structure has been found to be globular in the mushy state rolled composites. Measurements along the cross-section have shown decrease in average grain size and increase in hardness, as one proceeds along the direction of rolling. On the other hand, grain size and hardness have been found to be more or less similar, when compared for sections perpendicular to the rolling direction.