Green synthesis of metal nanoparticles using plants

Nanomaterials (NMs) have gained prominence in technological advancements due to their tunable physical, chemical and biological properties with enhanced performance over their bulk counterparts. NMs are categorized depending on their size, composition, shape, and origin. The ability to predict the unique properties of NMs increases the value of each classification. Due to increased growth of production of NMs and their industrial applications, issues relating to toxicity are inevitable. The aim of this review is to compare synthetic (engineered) and naturally occurring nanoparticles (NPs) and nanostructured materials (NSMs) to identify their nanoscale properties and to define the specific knowledge gaps related to the risk assessment of NPs and NSMs in the environment. The review presents an overview of the history and classifications of NMs and gives an overview of the various sources of NPs and NSMs, from natural to synthetic, and their toxic effects towards mammalian cells and tissue. Additionally, the types of toxic reactions associated with NPs and NSMs and the regulations implemented by different countries to reduce the associated risks are also discussed.

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Review on nanoparticles and nanostructured materials: history, sources, toxicity and regulations.

Silver nanoparticles are nanoparticles of silver which are in the range of 1 and 100 nm in size. Silver nanoparticles have unique properties which help in molecular diagnostics, in therapies, as well as in devices that are used in several medical procedures. The major methods used for silver nanoparticle synthesis are the physical and chemical methods. The problem with the chemical and physical methods is that the synthesis is expensive and can also have toxic substances absorbed onto them. To overcome this, the biological method provides a feasible alternative. The major biological systems involved in this are bacteria, fungi, and plant extracts. The major applications of silver nanoparticles in the medical field include diagnostic applications and therapeutic applications. In most of the therapeutic applications, it is the antimicrobial property that is being majorly explored, though the anti-inflammatory property has its fair share of applications. Though silver nanoparticles are rampantly used in many medical procedures and devices as well as in various biological fields, they have their drawbacks due to nanotoxicity. This review provides a comprehensive view on the mechanism of action, production, applications in the medical field, and the health and environmental concerns that are allegedly caused due to these nanoparticles. The focus is on effective and efficient synthesis of silver nanoparticles while exploring their various prospective applications besides trying to understand the current scenario in the debates on the toxicity concerns these nanoparticles pose.

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Silver nanoparticles: mechanism of antimicrobial action, synthesis, medical applications, and toxicity effects

Synthesis of metallic nanoparticles using plant extracts.

Biological synthesis of metal nanoparticles by microbes.

Plant system: nature's nanofactory.

Synthesis of TiO2 nanoparticles using microorganisms.

Complex impedance analysis of polycrystalline Pb2Bi3LaTi5O18, prepared by a high-temperature solid-state reaction technique has been carried out. XRD analysis indicated the formation of a single-phase orthorhombic structure. Impedance plots were used as a tool to analyse the behaviour of the sample as a function of frequency and temperature. The bulk resistance has been observed to decrease with rise in temperature showing a typical negative temperature coefficient of resistance (NTCR) type behaviour like that of semiconductors. The ac impedance studies revealed the presence of grain boundary effect at 450°C and showed polydispersive non Debye-type dielectric relaxation. The frequency dependent ac conductivity at different temperatures indicated that the conduction process is thermally activated process. The activation energy for bulk (0.67 eV) and grain boundary (0.73 eV) was estimated from the temperature variation of respective conductivities.

Complex impedance studies on tungsten-bronze electroceramic: Pb2Bi3LaTi5O18

Impedance spectroscopy of (Na0.5Bi0.5)(Zr0.25Ti0.75)O3 lead-free ceramic

A green, low-cost, and reproducible Cycas leaf–negotiated synthesis of silver nanoparticles is reported. X-ray and transmission electron microscopy (TEM) analyses are performed to ascertain the formation of Ag nanoparticles. Nanoparticles almost spherical in shape having the size of 2–6 nm are found. Rietveld analysis to the X-ray data indicated that Ag nanoparticles have fcc unit cell structure. Ultraviolet (UV)-visible study revealed the surface plasmon resonance at 449 nm. An effort has been made to understand the possible involved mechanism for the biosynthesis of Ag nanoparticles. Present procedure offers the benefit of eco-friendliness and amenability for large-scale production through scaling up.

https://www.tandfonline.com/doi/pdf/10.1080/19430871003684572

Kamal Prasad

Papers

Plant system: nature's nanofactory.

Synthesis of TiO2 nanoparticles using microorganisms.

Complex impedance studies on tungsten-bronze electroceramic: Pb2Bi3LaTi5O18

Impedance spectroscopy of (Na0.5Bi0.5)(Zr0.25Ti0.75)O3 lead-free ceramic

Green Synthesis of Silver Nanoparticles UsingCycasLeaf