In nanoparticle biosynthesis, identification and/or characterization of extract and its biochemicals, playing a key role to control the morphology of nanoparticle, are important to minimize the synthesis steps, and thus to reduce environmental risks and cost. Ocimum sanctum plant leaves were subject to sequential solvent fractionation with different polarity (hexane, chloroform, n-butanol and water). In the steps, the four dried fractions were extracted and used for biogenic synthesis of gold nanoparticles. Gold nanoparticles of varying shape and size were synthesized according to the extraction solvents, i.e., chloroform fraction (circular discs with rough edges), hexane fraction (spherical nanoparticles smaller than 100 nm), aqueous fraction (large, anisotropic platelets with defined edges) and n-butanol fraction (Au aggregates). In second step, we identified the biochemicals in the extracts using gas chromatography−mass spectrometry (GC−MS). Methyl eugenol and β-caryophyllene were observed in the hexane fraction and eight known compounds, i.e., glycerol, phosphoric acid, succinic acid, tartaric acid, D-gluconic acid, and myo-inositol, 2-methoxy-4-vinylphenol and ferulic acid were identified in the aqueous fraction. Further, we checked that some identified biochemicals, i.e., ferulic acid, caryophyllene and 2 methoxy-4-vinylphenol synthesized microscale sheets, spherical particles and a branched nanostructure, respectively.

Cumin seed was investigated for synthesis of gold nanoparticles. Polydispersed particles were obtained at pH 3 and 30 degrees C, and the effect of temperature and pH on synthesis of gold nanoparticles was analyzed. TEM images showed that amount of platelets formed were predominant at lower temperature where as more number of monodispersed spherical particle of size 1-10 nm were perceived at high temperatures. The gold nanoparticles particles formed at higher pH were stable, uniform and spherical in shape. XPS analysis showed the presence of pure gold nanoparticles.

This article presents a comprehensive review of the laser-based guided ultrasonic waves propagation imaging (G-UPI) system and respective signal/data processing methods related to the nondestructive testing and evaluation of thin-walled structures. The primary goal of this study is to review and recognize various processing methods, explain the working principles of the most influential methods, and highlight outstanding capabilities. In addition, the suitability of the methods for multiple types of damage and defect in various materials and structures are presented. At the same time, success stories of difficult-to-inspect cases are highlighted. Its secondary goal is to compare and discuss the merits and demerits of the laser-scanning part of the system for ultrasound generation and acquisition to provide a guideline for scanning scheme or hardware selection. Finally, the potential challenges and prospects of the G-UPI are discussed. It is expected that this review would serve as an entrance key for newcomers and a reference point for researchers to explore the opportunities for further improvement in the laser ultrasound-based evaluation of critical engineering structures.

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