Colloidal clusters of icosahedrons and face-centred cubes

Bi-magnetic Mn3O4@Ni core-shell binary superparticles: Self-assembly preparation and magnetic behaviors

Binary superparticles formed by self-assembling two different types of nanoparticles may utilize the synergistic interactions and create advanced multifunctional materials. Bi-magnetic superparticles with a core-shell structure have unique properties due to their specific spatial configurations. Herein, we built Mn3O4@Ni core-shell binary superparticles via an emulsion self-assembly technique. The superparticles are generated with a spherical morphology, and have a typical average size of about 240 nm. By altering the ratio of the two magnetic nanoparticles, the thickness of Ni shells can be adjusted. Oleic acid ligands are crucial for the formation of core-shell structure. Magnetic analysis suggests that core-shell superparticles display dual-phase magnetic interactions, contrasting with the single-phase magnetic behaviors of commonly core-shell magnetic nanoparticles. The calculation on the effective magnetic anisotropy constants indicates that the presence of Ni shell layers reduces the dipole interactions among the Mn3O4 core particles. Due to the presence of Ni nanoparticle shells, the blocking temperature of Mn3O4 is reduced, while the Curie temperature of Mn3O4 is independent on Ni content. Tunable magnetic properties can be achieved by modulating the Ni nanoparticle shell thickness. This study offers insights for the development of core-shell superparticles with varied magnetic characteristics.

Photovoltaic Energy Conversion and Storage of Micro-Supercapacitors Based on Emulsion Self-Assembly of Upconverting Nanoparticles

With the rapid need for new kinds of portable and wearable electronics, we must look to develop flexible, small-volume, and high-performance supercapacitors that can be easily produced and stored in a sustainable way. An integrated system simultaneously converting recyclable energy to electricity and storing energy is sought after. Here we report photovoltaic energy conversion and storage integrated micro-supercapacitors (MSCs) with asymmetric, flexible, and all-solid-state performances constructed from thousands of close-packed upconverting nanoparticles (UCNPs) via an emulsion-based self-assembly process using oleic acid (OA)-capped upconverting nanoparticles. The carbonated-UCNPs supraparticles (CSPs) are further coated with polypyrrole (PPy) to improve their electrochemical performance. Such a design can develop CSPs@PPy as electrode materials with high gravimetric capacitance, 308.6 F g^-1 at 0.6 A g^-1. The fabricated MSCs exhibit excellent areal capacitance, C _s = 21.8 mF cm^-2 at 0.36 A cm^-2 and E = 0.00684 mWh cm^-2, and have superior flexibility and cycling ability. The MSC devices have a sensitive near-infrared ray (NIR) photoelectrical response capability, which can capture the NIR of sunlight to convert it into electrical energy and store the electric energy due to an excellent capacitive performance. We propose a method for multifunctional integration of energy conversion and storage, and provide future research directions and potential applications of self-powered flexible wearable photonic electronics.