Selective detection of ZnO nanoparticles in aqueous suspension by capillary electrophoresis analysis using dithiothreitol and L-cysteine adsorbates

Adsorption of l-Cysteine and Cysteamine on Zinc Oxide Nanoparticles

The reaction of l-cysteine and cysteamine hydrochloride with zinc oxide nanoparticles (ZnO NPs), by stirring excess reactant with the NPs in ethanol, has been studied by thermal gravimetric analysis (TGA), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD), and Raman spectroscopy. l-Cysteine adsorption occurs via the thiol functional group, and there is no evidence for bonding via the carboxylic acid or amine functionalities. However, Raman spectroscopy and XPS reveal some protonated thiol, suggesting unbound l-cysteine is also present, as confirmed by XRD that shows the presence of l-cysteine crystallites. In the case of cysteamine/ZnO, TGA indicates that a large fraction of the sample is organic, and Raman spectroscopy reveals a dramatic shift in the C-S stretch from 796 cm-1 for unreacted cysteamine to 837 cm-1 for the reacted cysteamine. It is postulated that the acidic and chelating nature of the reaction causes dissolution of some Zn2+ ions that form a Zn(II) coordination complex with cysteamine. These studies have implications for biomolecular applications in which ZnO nanoparticles are used for biosensors, bioimaging, and drug delivery.

Colorimetric determination of biothiols with AuNPs@MoS2 NSs as a peroxidase mimetic enzyme

The synthesis of AuNPs@MoS2 NSs was achieved and the sensing of biothiols was carried out using AuNPs@MoS2 NSs as enzyme mimics.

Contributions of Capillary Electrophoresis in Analytical Nanometrology: A Critical View

An overview on the increasing role of capillary electrophoresis in characterization and direct analysis of nanomaterials is herein presented. The niche of electrophoretic approaches in nanometrology is so relevant that nonmetallic, metal, metal oxide nanoparticles, and quantum dots have been analyzed to be targeted via capillary electrophoresis with conventional detection systems or coupling arrangements aimed at increasing selectivity and sensitivity toward either pristine or conjugated nanoparticles. Moreover, parameters altering intrinsic properties of nanoparticles may be optimized to gather the desired results and identify nanomaterials according to their size, shape, or associations with binding agents. The usefulness and quickness of capillary electrophoresis for quantifying or screening ultrasmall-sized particles enables this technique to set an example for analysis of standards or previously synthesized nanostructures in research or routine laboratories. Abundant evidence of the suitability of electrophoretic approaches for characterization and direct determination of nanomaterials in actual samples has been provided in this review, together with a discussion about hyphenation with state-of-the art detectors and comparison between capillary electrophoresis with other separation approaches. This permits scientific community to be optimistic in the short term.

A new nanometrological strategy for titanium dioxide nanoparticles screening and confirmation in personal care products by CE-spICP-MS

A new nanometrological approach was developed for screening of titania nanoparticles by capillary electrophoresis after adsorption of a target analyte namely l-cysteine onto the nanoparticles in a sodium phosphate buffer, followed by titanium elemental analysis by means of inductively-coupled plasma-mass spectrometry and size distribution measurements by single-particle mode. This analytical strategy involved a first screening of nanotitania in actual samples by electrophoresis, sensitivity being enhanced by cysteine which acts as a nanoparticles stabiliser. Detection and quantitation limits were 0.31 ng μL^-1 and 1.03 ng μL^-1 respectively for anatase nanoparticles in capillary electrophoresis, and a high amount of titanium was found in the samples subject to study (lip balm and two types of toothpaste) by total elemental analysis. Besides, the potential of single-particle modality for inductively-coupled plasma-mass spectrometry was exploited for a verification of particle size distribution, then confirming the presence of titanium dioxide nanoparticles as an ingredient in the composition of the real samples and validating the overall strategy herein presented.