Hydroxyapatite interactions with copper complexes

Hybrid Hydroxyapatite-Metal Complex Materials Derived from Amino Acids and Nucleobases

Calcium phosphates (CaPs) and their substituted derivatives encompass a large number of compounds with a vast presence in nature that have aroused a great interest for decades. In particular, hydroxyapatite (HAp, Ca10(OH)2(PO4)6) is the most abundant CaP mineral and is significant in the biological world, at least in part due to being a major compound in bones and teeth. HAp exhibits excellent properties, such as safety, stability, hardness, biocompatibility, and osteoconductivity, among others. Even some of its drawbacks, such as its fragility, can be redirected thanks to another essential feature: its great versatility. This is based on the compound's tendency to undergo substitutions of its constituent ions and to incorporate or anchor new molecules on its surface and pores. Thus, its affinity for biomolecules makes it an optimal compound for multiple applications, mainly, but not only, in biological and biomedical fields. The present review provides a chemical and structural context to explain the affinity of HAp for biomolecules such as proteins and nucleic acids to generate hybrid materials. A size-dependent criterium of increasing complexity is applied, ranging from amino acids/nucleobases to the corresponding macromolecules. The incorporation of metal ions or metal complexes into these functionalized compounds is also discussed.

Insights on forming N,O-coordinated Cu single-atom catalysts for electrochemical reduction CO2 to methane

Single-atom catalysts (SACs) are promising candidates to catalyze electrochemical CO₂ reduction (ECR) due to maximized atomic utilization. However, products are usually limited to CO instead of hydrocarbons or oxygenates due to unfavorable high energy barrier for further electron transfer on synthesized single atom catalytic sites. Here we report a novel partial-carbonization strategy to modify the electronic structures of center atoms on SACs for lowering the overall endothermic energy of key intermediates. A carbon-dots-based SAC margined with unique CuN₂O₂ sites was synthesized for the first time. The introduction of oxygen ligands brings remarkably high Faradaic efficiency (78%) and selectivity (99% of ECR products) for electrochemical converting CO₂ to CH₄ with current density of 40 mA·cm^-2 in aqueous electrolytes, surpassing most reported SACs which stop at two-electron reduction. Theoretical calculations further revealed that the high selectivity and activity on CuN₂O₂ active sites are due to the proper elevated CH₄ and H₂ energy barrier and fine-tuned electronic structure of Cu active sites.

Single-atom catalysts (SACs) are promising candidates to catalyze CO₂ reduction for the formation of high value hydrocarbons but most of the reactions yield CO. Here, the authors show a low-temperature calcining process to fabricate a carbon-dots-based SAC to efficiently convert CO₂ to methane.

Selective adsorption of lead, copper and antimony in runoff water from a small arms shooting range with a combination of charcoal and iron hydroxide

Metals and metalloids from ammunition residues at small arms shooting ranges leach into the soil and surrounding watercourses and may pose a threat to exposed wildlife and humans. To reduce the potential impact of heavy metal on the environment a field study was performed with different sorbents in order to reduce the metal concentration in polluted water from a shooting range. Two sorbents were tested in situ for their ability to reduce the concentration of Cu, Sb and Pb: Brimac(®) charcoal and Kemira(®) iron hydroxide. The mean sorption of Cu, Sb and Pb was 85%, 65%, and 88% respectively when using the charcoal and 60%, 85% and 92% respectively with the iron hydroxide. Even better sorption of the elements was achieved when the two sorbents were combined in order to increase their selectivity. The best results were achieved in the filter in which the water percolated the charcoal first and the iron hydroxide last, with a mean sorption of Cu, Sb and Pb of 89%, 90% and 93% respectively. This preparation gave a significant better sorption of Cu compared to the filter in which the water percolated the iron hydroxide first and the charcoal last. The different effect between the two filters may be due to pH, since charcoal has alkaline properties and iron hydroxide has acidic properties. For large scale experiments or in filter devices we therefore recommend use of a combination of different reactive sorbents.

Use of sorbents for purification of lead, copper and antimony in runoff water from small arms shooting ranges

Different sorbents were tested in situ for their ability to reduce the concentration of Cu, Sb and Pb in drainage water from a shooting range. The sorbents tested were: Brimac(®) charcoal, olivine mixed with elemental iron powder, magnetite and Kemira(®) iron hydroxide. The mean sorption of Cu, Sb and Pb was 84%, 66%, 85% with Brimac(®) charcoal and 58%, 78% and 69% with Kemira(®) iron hydroxide. Good sorption of Cu and Pb was achieved using olivine with 5% elemental Fe powder, which resulted in a sorption of 81% and 87%, respectively. The Fe-olivine filters were less efficient in reducing the concentration of Sb, but increasing the Fe content improved Sb sorption. In periods with high concentrations of Pb, Cu and Sb in the creek, such as during precipitation, the sorbent efficacy improved. This might be due to changes in the physico-chemical form of the metals, or to a higher fraction of elements being physically retained in the form of particles or colloids.