Nanoparticle Production of Zingiber officinale Roscoe Rhizome Extracts by ESS (expansion of supercritical solution)

Aims: To propose a modified RESS method of herbal pharmaceutical extracts nanoparticle production. Background: A vast number of methods have been applied to water-insoluble pharmaceuticals to improve their solubility. Nanoparticle production of pharmaceuticals is considered as one of the high-speed ways to improve solubility. Objective: Supercritical CO2 was applied to extract Zingiber officinale Roscoe rhizome pharmaceutical. Then a modified RESS (rapid expansion of supercritical solution) method, called ESS (expansion of supercritical solution), was exerted to obtain NPs (nanoparticles) of the extracted pharmaceuticals. Methods: Initially, applying high pressure in supercritical CO2 contributed to the extract dissolution such that supercritical CO2 was saturated with the sample. Then by decreasing the pressure, an expansion occurred in the saturated medium. This expansion reduced the power of supercritical CO2 solvent and induced the sample nanoparticle nucleation in the needle valve. Conclusion: Unlike rapid expansion of supercritical solution methodology, in this technique, the initial and secondary pressures were permanently above the critical pressure to provide a gentle expansion, which contributes to the production of uniform and small particles. The obtained uniform NPs had a narrow size distribution. Consequently, ESS technique can be considered as an efficient technique for improving the solubility of hydrophobic pharmaceuticals such as [6]-gingerol.

Synthesis of silver nanoparticles on a solid surface using a classical photographic method

A classical photographic method, the Becquerel method, produces a positive image comprised of silver nanoparticles on a silver surface. The particles are grown by exposing an iodised silver plate to light in the blue or ultraviolet, which initiates the formation of particles, followed by development (growth) with light in the red portion of the spectrum. Because the Becquerel method is essentially a means of producing a surface of patterned nanoparticles, it also has potential technological applications. This thesis is a systematic investigation of the Becquerel method. . It was determined that the initiation of nanoparticles is effective for wavelengths in the range 447 to 254 nm. The sudden rise in nanoparticle production around 447 nm implicates direct excitation of the AgI layer in the initiation step; however, the behaviour of the action spectrum at shorter wavelengths implies an electron-mediated mechanism. It is possible that both direct excitation and electron-mediated processes occur in the ultraviolet. Scanning electron micrographs indicate that nanoparticle morphology may be dependent on the initiation wavelength, with longer wavelengths producing a variety of shapes, while shorter wavelengths produce primarily dots. Nanoparticle growth (development) was achieved with all wavelengths studied; however, shorter wavelengths photons were more effective than longer wavelengths. The results from a study of the aging of the AgI film suggested that there is period of one or two days during which the film ‘matures,’ becoming more effective for nanoparticle production.

Synthesis of silver nanoparticles on a solid surface using a classical photographic method

A classical photographic method, the Becquerel method, produces a positive image comprised of silver nanoparticles on a silver surface. The particles are grown by exposing an iodised silver plate to light in the blue or ultraviolet, which initiates the formation of particles, followed by development (growth) with light in the red portion of the spectrum. Because the Becquerel method is essentially a means of producing a surface of patterned nanoparticles, it also has potential technological applications. This thesis is a systematic investigation of the Becquerel method. . It was determined that the initiation of nanoparticles is effective for wavelengths in the range 447 to 254 nm. The sudden rise in nanoparticle production around 447 nm implicates direct excitation of the AgI layer in the initiation step; however, the behaviour of the action spectrum at shorter wavelengths implies an electron-mediated mechanism. It is possible that both direct excitation and electron-mediated processes occur in the ultraviolet. Scanning electron micrographs indicate that nanoparticle morphology may be dependent on the initiation wavelength, with longer wavelengths producing a variety of shapes, while shorter wavelengths produce primarily dots. Nanoparticle growth (development) was achieved with all wavelengths studied; however, shorter wavelengths photons were more effective than longer wavelengths. The results from a study of the aging of the AgI film suggested that there is period of one or two days during which the film ‘matures,’ becoming more effective for nanoparticle production.