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In attempts to obtain high-capacity Prussian blue nanomaterials, current efforts are predominantly focused on the particle-ensemble-level understanding of their structure–activity relationships. Complementarily, it would be insightful to screen out extraordinary individuals from the nanoparticle population. Using a simple and efficient technique of bright-field microscopy, this work enables, for the first time, quantitative characterization of the overall two-redox-center electrochemistry of single Prussian blue nanoparticles many at a time. Quantitative optical voltammograms with little interference from solvent breakdown and non-Faradaic electrode charging/discharging are extracted for each single nanoparticle, revealing clear heterogeneity among them. On this basis, the microscopic method allows a detailed comparative analysis between the two redox-active sites. It is found that while the synthesized nanoparticles show a similar specific capacity of the high-spin (HS-Fe) sites with STD/mean = 30%, most individual nanoparticles exhibit monodispersedly small capacities of the low-spin iron (LS-Fe) sites, only about 17±1of the HS-Fe capacity. Most importantly, it is discovered that there is always a small fraction (∼8%) of the single nanoparticles showing an impressively tripled LS-Fe capacity. Facilitated by optical imaging, the discovery of this easily overlooked extraordinary subpopulation confers alternative opportunities for targeted efforts for material chemists to improve synthesis and material design based on these unusual individuals, which in turn implies the general significance of nanoparticle screening.

Single-nanoparticle studies often need one or a series of nanoparticle populations that are designed with differences in a nominally particular structural parameter to clarify the structure–activity relationship (SAR). However, the heterogeneity of various properties within any population would make it rather difficult to approach an ideal one-parameter control. In situ modification ensures the same nanoparticle to be investigated and also avoids complicating effects from the otherwise often needed ex situ operations. Herein, we apply electrochemical cycling to single platinum nanoparticles and optically examine their SAR. An electrocatalytic fluorescent microscopic method is established to evaluate the apparent catalytic activity of a number of single nanoparticles toward the oxygen reduction reaction. Meanwhile, dark-field microscopy with the substrate electrode under a cyclic potential control is found to be able to assess the electrochemically active surface area (ECSA) of single nanoparticles via induced chloride redox electrochemistry. Consequently, nanoparticles with drastically increased catalytic activity are discovered to have larger ECSAs upon potential regulation, and interestingly, there are also a few particles with decreased activity, as opposed to the overall trend, that all develop a smaller ECSA in the process. The deactivated nanoparticles against the overall enhancement effects of potential cycling are revealed for the first time. As such, the SAR of single nanoparticles when subjected to an in situ structural control is optically demonstrated.

In order to better study the characteristics of energy internet of pelagic island, this paper summarizes the latest research progress of energy internet, divides the research of energy internet into mainland energy internet and island energy internet, and consider that island energy internet should include two core networks of electric energy and thermal energy. Based on the study of the structure and control strategy of core hardware equipment including energy router, energy switch and energy interface, a three-section structure of island energy internet based on these three core hardware devices is proposed to optimize the current research structure of energy internet. With the geographical location, the optimization on generation of wind power, solar power and other renewable energy on resource island is applied with multiple objective particle swarm optimization (MOPSO). The capacity on various sources including battery and fresh water of energy exchange vessel optimized. Finally, the case study about pelagic islands indicated the feasibility of pelagic island energy internet. Finally, the structure of an island energy internet is built.