Cannabidiol-Mediated Green Synthesis, Characterization, and Cytotoxicity of Metal Nanoparticles in Human Keratinocyte Cells.

This study investigated a unique one-pot microwave-assisted green synthesis method of gold (Au) and silver (Ag) nanoparticles (NPs) using cannabidiol (CBD) as a capping and reducing agent. Furthermore, Au and Ag NPs were also chemically synthesized using poly(vinyl pyrrolidone), which functioned as reference materials when comparing the size, shape, and cytotoxicity of NPs. Synthesis parameters such as reaction time, temperature, and precursor molar ratio were optimized to control the size and shape of the biosynthesized NPs. Various characterization techniques such as transmission electron microscopy, ultraviolet-visible spectroscopy, Fourier transform infrared spectroscopy, and X-ray diffraction were used to confirm the formation and properties of Au and Ag NPs. Both biosynthesized metal NPs were spherical and monodispersed, with average particle sizes of 8.4 nm (Au-CBD) and 4.8 nm (Ag-CBD). This study also explored the potential cytotoxicity of CBD-capped NPs in human keratinocyte cells, which was observed to be of minimal concern. The novel synthesis approach presented in this study is free from harsh chemical reagents; therefore, these NPs can be used in a wide array of applications, including the pharmaceutical and biomedical fields.

Oxidative Coupling of 1-Naphthols over Noble and Base Metal Catalysts.

Bismuth-promoted platinum catalysts were tested for the oxidative coupling of 2- and 4-substituted 1-naphthols at different temperatures and ambient pressure. The principal final products are the 3,3'-substituted 1,1'-binaphthalenylidene-4,4'-diones and the 4,4'-substituted 2,2'-binaphthalenylidene-1,1'-diones, respectively. Hydrogen peroxide was used as the oxidant. Only naphthols with electron-donating substituents reacted. The corresponding binaphthalenyl diols can be considered as reaction intermediates. Yields of up to 99 % were obtained from 2-methyl-1-naphthol as the starting material within 20 minutes. Probably for steric reasons, the diol is the final product obtained from 2-ethyl-1-naphthol. For 4-methoxy-1-naphthol the outcome is determined by the reaction temperature. At 25 °C the expected 1,1'-dione is the major product, whereas at 60 °C 1'-hydroxy-4'-methoxy-2,2'-binaphthalenyl-1,4-dione is formed; the loss of one methoxy unit and the preservation of the hydroxy group can be explained by the competitive cleavage of one of the two OMe bonds at higher temperature. Unpromoted platinum and a range of other metallic catalysts, including gold and Raney nickel, were also found to be active. The products obtained are brightly colored solids that could be used as dyes. The method described is truly catalytic and environmentally benign. The potential of the technique justifies further research to expand on the applicability of this novel method.

Influence of citric acid on SnO2 nanoparticles synthesized by wet chemical processes.

Tin oxide (SnO2) nanoparticles with size range of 19 to 100 nm were successfully synthesized using wet chemical process (i.e., chemical precipitation and sol-gel processes). The samples were analysed by X-Ray diffraction, Scanning electron microscopy, Energy dispersive X-ray spectroscopy, Raman and FTIR spectroscopy, BET surface area and Thermogravimetric analyses. The results showed that variation of citric acid concentration directly influences the particle size and the BET specific surface area. The XRD analysis revealed that nanoparticles were phase pure and that all materials exhibited a tetragonal rutile structure of SnO2. Characterisation of the materials was carried out using techniques such as scanning electron microscopy, X-ray diffraction, Fourier Transform Infrared spectroscopy, Thermogravimetric and BET analyses.

CoS-carbon nanotube heterostructure: one-step synthesis and optical properties.

This article reports on the synthesis, characterization, and optical properties of a cobalt sulphide (CoS) quantum dot (QD)-decorated multi-walled carbon nanotube (MWCNT) heterostructure. A novel one-pot chemical-solution route has been used for the in situ synthesis of a CoS-decorated MWCNT heterostructure without disturbing the inherent structure of the MWCNTs. The synthesized heterostructure has been extensively characterized by scanning electron microscopy, scanning transmission electron microscopy, energy dispersive X-ray spectroscopy, X-ray photoelectron spectroscopy, X-ray diffraction, and Fourier transform infrared spectrometry. The UV-absorption and fluorescence spectral properties of pristine MWCNTs are significantly improved after heterostructure formation with CoS-QDs.

A comparison of purification procedures for multi-walled carbon nanotubes produced by chemical vapour deposition.

A comparison of three different purification procedures for multi-walled carbon nanotubes (MWCNTs) produced by chemical vapour deposition (CVD) has been presented. The methods involved gas-phase oxidation by calcination, liquid-phase oxidation by H2O2, hydrothermal treatment and acid refluxing in HCl. Sample purity was documented with the Raman spectroscopy, Transmission electron microscopy (TEM), Scanning electron microscopy (SEM) and thermo gravimetric analysis (TGA). The Raman spectroscopy, SEM and TEM results showed that the liquid phase oxidation-acid refluxing route successfully eliminated most of the impurities without damaging the nanotube structure. TGA analysis showed in increase in density of MWCNTs with better oxidation resistance after purification and the metal content was reduced from 23.8 wt% to 5.4 wt%.

The effect of calcination on multi-walled carbon nanotubes produced by dc-arc discharge.

Multi-walled carbon nanotubes were synthesized by dc-arc discharge in helium atmosphere and the effect of calcination at different temperatures ranging from 300-600 degrees C was studied in detail. The degree of degradation to the structural integrity of the multi-walled carbon nanotubes during the thermal process was studied by Raman spectroscopy, Scanning electron microscopy and High resolution transmission electron microscopy. The thermal behaviour of the as prepared and calcined samples was investigated by thermogravimetric analysis. Calcination in air at 400 degrees C for 2 hours was found to be an efficient and simple method to eliminate carbonaceous impurities from the nanotube bundles with minimal damage to the tube walls and length. The impurities were oxidized at a faster rate when compared to the nanotubes and gave good yield of about 50%. The nanotubes were observed to be damaged at temperature higher than 450 degrees C. The results show that this method is less destructive when compared liquid phase oxidation with 5 M HNO3.

Purification of multi-walled carbon nanotubes.

The discovery of carbon nanotubes (CNTs) has stimulated intensive research to characterize their structure and to determine their physical properties, both by direct measurement and through predictive methods. Many of the fundamental and remarkable properties of CNTs are now well-known, and their exploitation in a wide range of applications forms a large part of research currently in progress. However, the absence of a reliable, large-volume production capacity, simple and efficient purification methods, the high cost of carbon nanotubes and the fact that there is little selectivity in controlling the properties of the product are factors that have principally inhibited the commercialization of CNT technologies. Ever since CNTs were detected, considerable efforts have been directed at their synthesis, characterization and functionalization. Nevertheless, the CNT sample obtained by different techniques has the disadvantage of containing non-CNT impurities, such as graphitic particles, fullerenes, residual catalyst particles and amorphous carbon, which degrade the intrinsic properties of these materials. If the carbon nanotube is ever to accomplish its promise as an industrial material, large and high-quality aliquots, will be required. A number of purification methods involving elimination processes, such as physical separation, gas-phase and liquid-phase oxidation, in combination with chemical treatments, have been developed for nanotube materials. Though the quantitative determination of purity remains controversial, reported yields are best regarded with an appropriate level of scepticism on the method of assay. This review highlights the past and recent developments in the purification of multi-walled carbon nanotubes.

Purification of laser synthesized SWCNTs by different methods: a comparative study.

A comparison of different purification procedures for single walled carbon nanotubes (SWCNTs) synthesized by laser-vapourization has been presented. The methods involved gas-phase oxidation by calcination, liquid-phase oxidation by H2O2, hydrothermal treatment and acid refluxing in HCI. Sample purity is documented with Raman spectroscopy, Transmission electron microscopy, Scanning electron microscopy and thermogravimetric analysis. Multi-spot analyses were done to check the homogeneity of the purified samples. Different purification processes produced SWCNT material with purity in the range of 48-78%. Raman and TEM results suggested that prolonged calcination results in selective etching of larger diameter nanotubes. SEM and TGA analyses showed increase in density of SWCNTs with better oxidation resistance after purification.

Purification of single-walled carbon nanotubes.

The discovery of carbon nanotubes (CNTs) created much excitement and stimulated extensive research into the properties of nanometer-scale cylindrical networks. From then on, various methods for the synthesis and characterization of aligned CNTs-both single-walled (SWCNTs) and multi-walled (MWCNTs) by different methods have been hotly pursued. Unfortunately, most methods currently in use produce raw multi component solid products, only a small fraction of which contains carbon nanotubes. The balance of the material is composed of residual catalyst particles (some of which are encased in concentric graphitic shells), fullerenes, other graphitic materials and amorphous carbon. These impurities cause a serious impediment for their detailed characterization and applications. If the carbon nanotube is ever to fulfill its promise as an engineering material, large, high quality aliquots will be required. A number of purification methods involving elimination processes such as physical separation, gas phase and liquid phase oxidation in combination with chemical treatments have been developed for nanotube materials. Though the quantitative determination of purity remains controversial, reported yields are best regarded with an appropriate level of skepticism on the method of assay. In this article, a review is given on the past and recent advances in purification of SWCNTs.