Interactions of sub-five-nanometer diameter colloidal palladium nanoparticles in solution investigated via liquid cell transmission electron microscopy

Strategy for optimizing experimental settings for studying low atomic number colloidal assemblies using liquid phase scanning transmission electron microscopy

Observing processes of nanoscale materials of low atomic number is possible using liquid phase electron microscopy (LP-EM). However, the achievable spatial resolution (d) is limited by radiation damage. Here, we examine a strategy for optimizing LP-EM experiments based on an analytical model and experimental measurements, and develop a method for quantifying image quality at ultra low electron dose D_e using scanning transmission electron microscopy (STEM). As experimental test case we study the formation of a colloidal binary system containing 30 nm diameter SiO₂ nanoparticles (SiONPs), and 100 nm diameter polystyrene microspheres (PMs). We show that annular dark field (DF) STEM is preferred over bright field (BF) STEM for practical reasons. Precise knowledge of the material's density is crucial for the calculations in order to match experimental data. To calculate the detectability of nano-objects in an image, the Rose criterion for single pixels is expanded to a model of the signal to noise ratio obtained for multiple pixels spanning the image of an object. Using optimized settings, it is possible to visualize the radiation-sensitive, hierarchical low-Z binary structures, and identify both components.

Synchronous removal of emulsions and organic dye over palladium nanoparticles anchored cellulose-based membrane

Membrane is a considerable precursor for emulsions separation and organic dyes degradation used in water purification and oil reclamation. However, the tedious preparation method, the surface smears easily, and low degradation efficiency, these characteristics usually significantly hinder its applicability toward wastewater governance. Herein, a green, facile, and efficient fabrication strategy to prepare a bi-functional palladium nanoparticles (PdNPs)-loaded bacterial cellulose membrane (BCMPd) is proposed. A tri-functional bacterial cellulose membrane (BCM) was obtained by percolating bacterial cellulose (BC) on a basal membrane, and BCM served as a support, reducing agent, and stabilizer in the subsequent reduction of PdNPs. Bi-functional BCMPd was successfully obtained and used for continuously removing emulsions and reducing methylene blue (MB) from simulated wastewater via the integration of physical sieving and chemical reaction. Meanwhile, the enhancement factors for the water transfer ability and demulsification capacity correlated directly with the wettability and surface structure of BCMPd. Furthermore, the dosage of BC was adjusted to reveal the mechanism for the enhanced water transferability and demulsification capacity. Notably, PdNPs of BCMPd decreased Fermi potential difference between BH_4- and MB, accelerating the electron transfer of the reduction reaction and thus exhibiting a remarkable MB degradation efficiency. Together, the information obtained in this work can be useful for comprehensively addressing the bottleneck of forming a cost-effective, eco-friendly, and bi-functional membrane reactor, providing an alternative approach for better treatment of complex wastewater.