Colloidal stabilization of CeO2 nanomaterials with polyacrylic acid, polyvinyl alcohol or natural organic matter

Engineered nanomaterials (ENM) such as nano-sized cerium dioxide (CeO₂) are increasingly applied. Meanwhile, concerns on their environmental fate are rising. Understanding the fate of ENM within and between environmental compartments such as surface water and groundwater is crucial for the protection of drinking water resources. Therefore, the colloidal stability of CeO₂ ENM (2 mg L^-1) was assessed with various surface coatings featuring different physico-chemical properties such as weakly anionic polyvinyl alcohol (PVA), strongly anionic polyacrylic acid (PAA) or complex natural organic matter (NOM) at various water compositions in batch experiments (pH 2-12, ionic strength 0-5 mM KCl or CaCl₂). While uncoated CeO₂ ENM aggregate in the range of pH 4-8 in 1 mM KCl solution, the results show that PAA, PVA and NOM surface coatings stabilize CeO₂-ENM at neutral and alkaline pH in 1 mM KCl solution. Stabilization by PAA and NOM is associated with strongly negative zeta potentials below -20 mV, suggesting electrostatic repulsion as stabilization mechanism. No aggregation was detected up to 5 mM KCl for PAA- and NOM-coated CeO₂ ENM. In contrast, CaCl₂ induced aggregation at >2.2 mM CaCl₂ for PAA and NOM-coated CeO₂ ENM respectively. PVA-coated ENM showed zeta potentials of -15 mV to -5 mV in the presence of 0-5 mM ionic strength, suggesting steric effects as stabilization mechanism. The hydrodynamic diameter of PVA-coated ENM was larger compared to PAA and NOM at low ionic strength, but the size did not increase with ionic strength of the suspensions. The effect of ionic strength and counter ion valency (pH 7) on the colloidal stability of ENM depends on the prevailing stabilization mechanism of the organic coating. NOM can be similarly effective in colloidal stabilization of CeO₂-ENM as PAA. Our results suggest natural Ca-rich waters will lead to ENM agglomeration even of coated CeO₂-ENM.

Carbon Nanomaterials for Targeted Cancer Therapy Drugs: A Critical Review

Cancer represents one of the main causes of human death in developed countries. Most current therapies, unfortunately, carry a number of side effects, such as toxicity and damage to healthy cells, as well as the risk of resistance and recurrence. Therefore, cancer research is trying to develop therapeutic procedures with minimal negative consequences. The use of nanomaterial-based systems appears to be one of them. In recent years, great progress has been made in the field using nanomaterials with high potential in biomedical applications. Carbon nanomaterials, thanks to their unique physicochemical properties, are gaining more and more popularity in cancer therapy. They are valued especially for their ability to deliver drugs or small therapeutic molecules to these cells. Through surface functionalization, they can specifically target tumor tissues, increasing the therapeutic potential and significantly reducing the adverse effects of therapy. Their potential future use could, therefore, be as vehicles for drug delivery. This review presents the latest findings of research studies using carbon nanomaterials in the treatment of various types of cancer. To carry out this study, different databases such as Web of Science, PubMed, MEDLINE and Google Scholar were employed. The findings of research studies chosen from more than 2000 viewed scientific publications from the last 15 years were compared.

One-dimensional fossil-like γ-Fe2O3@carbon nanostructure: preparation, structural characterization and application as adsorbent for fast and selective recovery of gold ions from aqueous solution

One-dimensional (1D) magnetic nanostructures with high thermal stability have important industrial applications, but their fabrication remains a big challenge. Herein we demonstrate a scalable approach for the preparation of stable 1D γ-Fe2O3@carbon, which is also applicable for other metal oxide-core and carbon-shell nanostructures, such as 1D TiO2@carbon. One-dimensional ferric oxyhydroxide (α-FeO(OH)) was initially prepared by a hydrothermal method, followed by carbon coating through hydrothermal treatment of the resulting metal oxide in glucose solution. After calcination in N2 gas at 500 °C and subsequent exposure to air, the initial carbon-coated 1D α-Fe2O3 was converted to 1D γ-Fe2O3@carbon, which was very stable without any observed changes even after 1.5 years of storage under ambient conditions. The materials were then used as adsorbents and found to be highly selective towards Au (III) adsorption, of which the maximum adsorption capacity is about 600 mg Au/g sorbent (1132 mg Au/g carbon). The spent sorbent containing Au after adsorption can be readily collected by applying a magnetic field due to the presence of the magnetic core, and the adsorbed Au particles are subsequently recovered after the combustion and dissolution of the sorbent. This work demonstrates not only a facile approach to the fabrication of robust 1D magnetic materials with a stable carbon shell, but also a possible cyanide-free process for the fast and selective recovery of gold from electronic waste and industrial water.