Fluorescent carbon nanoparticles (CNPs) with diameters of about 3 nm which can emit blue-green light were synthesized through the hydrothermal carbonization of ethylenediaminetetraacetic acid disodium salt (EDTA$2Na). Then, the CNPs were functionalized with spiropyrans to obtain the spiropyranfunctionalized CNPs. The emission of the spiropyran-functionalized CNPs centered at 510 nm could be switched off, while being turned on at 650 nm via energy transfer after UV light irradiation. The process could be reversed by using visible light irradiation. The optical switching of the fluorescence was repeated 10 times without apparent "fatigue", showing excellent photoreversibility and high stability.Spiropyran-functionalized CNPs may find potential applications in biological imaging and labeling, reversible data storage/erasing, as well as individual light-dependent nanoscale devices.
In this paper, a label-free multiplex plasmonic sensor has been developed to selectively determine different metal ions including Fe(3+), Hg(2+), Cu(2+), and Ag(+) ions based on a single type of gold nanorod (GNR). Under proper conditions, these metal ions can react with GNRs, resulting in changes of nanostructure and composition. The determination of Fe(3+), Hg(2+), Cu(2+), and Ag(+) ions is therefore readily implemented due to changes of longitudinal plasmon wavelength (LPW) of nanorods. Moreover, the GNR-based assay can not only determine all four kinds of metal ions successively but also can detect which of any one or several kinds of metal ions. This assay is sensitive to detect Fe(3+), Hg(2+), Cu(2+), and Ag(+) as low as 10(-6), 10(-8), 10(-10), and 10(-8) M, respectively. Importantly, the special nanostructure and composition of the nanorods are induced by these metal ions, which allow this sensor to maintain high selectivity to determine these metal ions. This nanosensor abrogates the need for complicated chemosensors or sophisticated equipment, providing a simple and highly selective detection platform.
Electrochemical
cycling induces transition-metal (TM) ion migration
and oxygen vacancy formation in layered transition-metal oxides, thus
causing performance decay. Here, a combination of ab initio calculations and atomic level imaging is used to explore the TM
migration mechanisms in LiNi1/3Mn1/3Co1/3O2 (NMC333). For the bulk model, TM/Li exchange is an
favorable energy pathway for TM migration. For the surface region
with the presence of oxygen vacancies, TM condensation via substitution
of Li vacancies (TMsub) deciphers the frequently observed
TM segregation phenomena in the surface region. Ni migrates much more
easily in both the bulk and surface regions, highlighting the critical
role of Ni in stabilizing layered cathodes. Moreover, once TM ions
migrate to the Li layer, it is easier for TM ions to diffuse and form
a TM-enriched surface layer. The present study provides vital insights
into the potential paths to tailor layered cathodes with a high structural
stability and superior performance.
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