Size-controlled, hollow and hierarchically porous Co2Ni2 alloy nanocubes for efficient oxygen reduction in microbial fuel cells

Uniform, hollow-structure and hierarchically porous materials often produce surprisingly outstanding electrocatalytic performance. Besides, fabrication of highly active and stable non-noble metal-based alloys remains a huge challenge. Herein, a facile synthetic...

Effects of Co-Solvent Nature and Acid Concentration in the Size and Morphology of Wrinkled Mesoporous Silica Nanoparticles for Drug Delivery Applications

Hierarchically porous materials, such as wrinkled mesoporous silica (WMS), have gained interest in the last couple of decades, because of their wide range of applications in fields such as nanomedicine, energy, and catalysis. The mechanism of formation of these nanostructures is not fully understood, despite various groups reporting very comprehensive studies. Furthermore, achieving particle diameters of 100 nm or less has proven difficult. In this study, the effects on particle size, pore size, and particle morphology of several co-solvents were evaluated. Additionally, varying concentrations of acid during synthesis affected the particle sizes, yielding particles smaller than 100 nm. The morphology and physical properties of the nanoparticles were characterized by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), and dynamic light scattering (DLS). Homogeneous and spherical WMS, with the desired radial wrinkle morphology and particle sizes smaller than 100 nm, were obtained. The effect of the nature of the co-solvents and the concentration of acid are explained within the frame of previously reported mechanisms of formation, to further elucidate this intricate process.

Diffusion and reaction in pore hierarchies by the two-region model

The two-region (“Kärger”) model of diffusion in complex pore spaces is exploited for quantitating mass transfer in hierarchically organized nanoporous materials, consisting of a continuous microporous bulk phase permeated by a network of transport pores. With the implications that the diffusivity in the transport pores significantly exceeds the diffusivity in the micropores and that the relative population of the transport pores is far below that of the micropores, overall transport depends on only three independent parameters. Depending on their interrelation, enhancement of the overall mass transfer is found to be ensured by two fundamentally different mechanisms. They are referred to as the limiting cases of fast and slow exchange, with the respective time constants of molecular uptake being controlled by different parameters. Complemented with reaction terms, the two-region model may equally successfully be applied to the quantitation of the combined effect of diffusion and reaction in terms of the effectiveness factor. Generalization of the classical Thiele concept is shown to provide an excellent estimate of the effectiveness factor of a chemical reaction in hierarchically porous materials, solely based on the intrinsic reaction rate and the time constant of molecular uptake relevant to the given conditions.

Hierarchically porous materials and green chemistry—an interview with Ming-Yuan He

Many examples of hierarchies are present in nature, such as water transport in leaf vein systems, the respiratory system, the blood circulatory system, etc. Hierarchically structuring a material over different length scales by mimicking natural systems can provide an opportunity to render the material suitable for a variety of functions. Tremendous research over the past decade has focused on the synthesis and applications of hierarchically structured porous materials. This rapidly evolving field has attracted great interest from both academia and industry. China is at the forefront of this field, and a scientific leader of this research is Professor Ming-Yuan He of East China Normal University. Professor He was elected to the Chinese Academy of Sciences in 1995, and he received the Prize for Scientific and Technological Progress from the Ho Leung Ho Li Foundation in 2001. He also won the National Catalysis Achievement Award of China in 2012 and the National Zeolite Lifetime Achievement Award of China in 2019. Professor He's research interests focus on new catalytic materials and oil-refining catalysts and processes. He is a pioneer in the area of green chemistry in China and actively promotes the development of green chemistry and chemical engineering. NSR recently interviewed Professor He about the current achievements and future prospects of hierarchically structured porous materials. This interview is dedicated to Professor He on the occasion of his 80th birthday, in recognition of his distinguished contributions to many aspects in the field of catalytic science and technology.