Investigation of palladium catalysts in mesoporous silica support for CO oxidation and CO2 adsorption

The oxidation of Carbon monoxide (CO) to Carbon dioxide (CO2) is one of the most extensively investigated reactions in the field of heterogeneous catalysis, and it occurs via molecular rearrangements induced by catalytic metal atoms with oxygen intermediates. CO oxidation and CO2 capture are instrumental processes in the reduction of green-house gas emissions, both of which are used in low-temperature CO oxidation in the catalytic converters of vehicles. CO oxidation and CO2 adsorption at different temperatures are evaluated for palladium-supported silica aerogel (Pd/SiO2). The synthesized catalyst was active and stable for low-temperature CO oxidation. The catalytic activity was enhanced after the first cycle due to the reconditioning of the catalyst's pores. It was found that the presence of oxide forms of palladium in the SiO2 microstructure, influences the performance of the catalysts due to oxygen vacancies that increases the frequency of active sites. CO2 gas adsorption onto Pd/SiO2 was investigated at a wide-ranging temperature from 16 to 120 °C and pressures ∼1 MPa as determined from the isotherms that were evaluated, where CO2 showed the highest equilibrium adsorption capacity at 16 °C. The Langmuir model was employed to study the equilibrium adsorption behavior. Finally, the effect of moisture on CO oxidation and CO2 adsorption was considered to account for usage in real-world applications. Overall, mesoporous Pd/SiO2 aerogel shows potential as a material capable of removing CO from the environment and capturing CO2 at low temperatures.

Silica and carbon decorated silica nanosheet impact on primary human immune cells

Silica nanosheets (SiO₂ NS) are considered to be a promising material in clinical practice for diagnosis and therapy applications. However, an appropriate surface functionalization is essential to guarantee high biocompatibility and molecule loading ability. Although SiO₂ NS are chemically stable, its effects on immune systems are still being explored. In this work, we successfully synthesized a novel 2D multilayer SiO₂ NS and SiO₂ NS coated with carbon (C/SiO₂ NS), and evaluated their impact on human Peripheral Blood Mononuclear Cells (PBMCs) and some immune cell subpopulations. We demonstrated that the immune response is strongly dependent on the surface functionalities of the SiO₂ NS. Ex vivo experiments showed an increase in biocompatibility of C/SiO₂ NS compared to SiO₂ NS, resulting in a lowering of hemoglobin release together with a reduction in cellular toxicity and cellular activation. However, none of them are directly involved in the activation of the acute inflammation process with a consequent release of pro-inflammatory cytokines. The obtained results provide an important direction towards the biomedical applications of silica nanosheets, rendering them an attractive material for the development of future immunological therapies.

An investigation of physico-chemical properties of a new polyimide–silica composites

In the present study, a novel diamine 1,4-bis[4-(hydrazonomethyl)phenoxy]butane (4-BHPB) has been successfully synthesized by a facile method.

STM studies of 1-D noble metal growth on silicon

Our scanning tunneling microscopy (STM) studies show that noble metals (Ag, Au) form a wide variety of 1-D structures on the high-index Si(5 5 12) surface. At coverages below 0.25 monolayer (ML), both metals grow as overlayer rows with an inter-row spacing of approximately 5 nm. At higher coverages and annealing temperatures, the underlying Si reconstruction is removed, but periodic row structures persist. Au can also induce faceting to nearby planes, e.g. (7 7 15) and (2 2 5), at temperatures above 500 degrees C. For all coverages and annealing temperatures studied here (0.02-1 ML, 450-800 degrees C), the Si(5 5 12) template initiates 1-D growth of the deposited noble metals.