3139wileyonlinelibrary.com discriminable emission peaks as the monitored signals, and to suppress absolute and relative detecting errors, high absolute and relative temperature sensitivities are required.In this aspect, conventional investigations focus on the thermally coupled level pairs (TCL) of rare earth ions (for example, 2 H 11/2 and 4 S 3/2 level for Er 3+). [7][8][9][10][11][12][13][14][15] Typically, with variation of temperature, population in the upper and lower levels of TCL would change oppositely, inducing variation in FIR of these two levels. For this type of temperature sensing materials, a narrow energy gap between TCL would favor the absolute temperature sensitivity ( S a ), but be harmful to the relative temperature sensitivity ( S r ). In addition, the narrow energy gap would induce overlap of the two monitored emission peaks, resulting in an inferior signal discriminability. [ 9,12 ] In contract, a wide energy gap between TCL would benefi t S r and the signal discriminability, but weaken the thermal coupling of TCL, leading to a low S a . [ 13,15 ] Generally speaking, in the TCL-based optical thermometry, simultaneously promoting S a , S r and signal discriminability is almost impossible.Other kinds of thermometry strategy have also been introduced into the optical thermometric technique. For example, the phonon assisted energy transfer between Eu 3+ and Tb 3+ ions has been utilized in optical thermometry. [16][17][18][19] However, this kind of thermometry is usually applicable only at temperature below 320 K. Nanocomposites containing quantum dots and rare earth ions have also been applied as thermometric materials relying on the different thermal quenching behaviors of quantum dots and rare earth ions. [ 20,21 ] However, FIR of these materials is easily infl uenced by other environment parameters (such as pH value), which would introduce error in temperature detection. Apparently, searching for new thermometry strategy to develop high-performance luminescent temperature sensing materials is highly desired.In previous studies, the metal-to-metal intervalence charge transfer (IVCT) processes between lanthanide (Pr 3+ or Tb 3+ ) and d 0 electron confi gured transition metal ions (Ti 4+ , V 5+ , Nb 5+ , Mo 6+ , or W 6+ ) in oxide crystals have been demonstrated to be an effective pathway to excite the corresponding lanthanide ions. [22][23][24][25][26] Moreover, IVCT can provide an effi cient quenching A Novel Optical Thermometry Strategy Based on Diverse Thermal Response from Two Intervalence Charge Transfer StatesYan Gao , Feng Huang , * Hang Lin , Jiangcong Zhou , Ju Xu , and Yuansheng Wang * In this work, a novel thermometry strategy based on the diversity in thermal quenching behavior of two intervalence charge transfer (IVCT) states in oxide crystals is proposed, which provides a promising route to design selfreferencing optical temperature sensing material with superior temperature sensitivity and signal discriminability.
Colloidal lead halide perovskite quantum dots, due to their optical versatility and facile solution processability, have been recently recognized as components of various optoelectronic devices. Detailed understanding of their exciton recombination dynamics at the single-particle level is necessary for utilizing their full potential. We conducted spectroscopic studies of the excitons and biexciton dynamics in single CsPbBr 3 perovskite quantum dots. It was found that while the rates of radiative recombination remain essentially constant, the overall relaxation process is dominated by nonradiative recombination of single excitons and biexcitons. The radiative lifetime scaling is determined to be ∼1.0 for single exciton and ∼4.4 for biexcitons. A linear dependence of fluorescence lifetime vs intensity distribution agrees well with the prediction of the model of multiple recombination centers. The blinking mechanism of CsPbBr 3 quantum dots is addressed by considering the trion states under higher excitation powers.
The emergence and spread of mobilized colistin resistance (mcr) genes have triggered extensive concerns worldwide. Here, we characterized the global distribution of mcr-9, a newly-identified variant of mcr, by assembling the data set of mcr-9-positive isolates from GenBank database and the literature available. Genetic features of all the mcr-9-harboring plasmids were determined by bioinformatic analysis. We showed that mcr-9 is globally distributed in 21 countries across six continents, with a wide dissemination among various species of Enterobacteriaceae strains from human, animal, food and environment. IncHI2-ST1 plasmids were found to be the predominant replicon type carrying mcr-9. Comparative genomics highlighted that IncHI2-type plasmids may also serve as a critical reservoir of mcr-9, from which different types of circulating plasmids acquired the mcr-9. Results revealed that the rcnR-rcnA-pcoE-pcoS-IS903-mcr-9-wbuC structure was consistent in most mcr-9 cassettes, suggesting a relatively unitary model involved in the mobilization of mcr-9. It is most likely that the spread of mcr-9 was mainly attributed to the conjugation and recombination events of mcr-9-carrying plasmids. In summary, our results provide a comprehensive picture of the distribution and genetic environment of mcr-9, and demonstrate the central roles played by IncHI2 plasmids in the worldwide dissemination of mcr-9. Antibiotic resistance poses a great threat to global public health and carbapenem-resistant Enterobacteriaceae is triggering a health crisis worldwide 1,2. Colistin, a cationic cyclic-peptide, is one of the last-resort antibiotics to defend against severe infections caused by carbapenem-resistant Enterobacteriaceae 3. However, since the initial discovery of a plasmid-mediated mobilized colistin resistance gene (mcr-1) in China in late 2015 4 , a number of diversified bacterial strains carrying mcr-1 have been detected across over 50 countries covering six continents 5. The prevalent plasmid-borne MCR enzyme can catalyze chemical addition of phosphoethanolamine to lipid A moiety of bacterial lipopolysaccharides, the target of colistin, which consequently promotes colistin resistance 6. In recent years, a growing number of mcr-like genes (namely, from mcr-2 to mcr-10) have been identified 7-14. These ongoing discoveries indicate a rapid evolution of MCR family under selective pressures, which raise global health concerns. mcr-9 is a newly emerging variant of the mobilized colistin resistance determinants, which was first identified in a clinical Salmonella enterica isolate in the USA in May, 2019 13. Since its initial identification, mcr-9 has been reported in several other countries, such as China 15 , Sweden 16 , and France 17. Not only that, in silico analysis using the GenBank database indicated that mcr-9 had already been presented in a number of Enterobacteriaceae isolates recovered worldwide 13,17. The high prevalence of mcr-9 suggests one more threat to public health. However, little information is available about the glo...
State-of-the-art progress in strategy design based on the Ln3+ luminescence involving dual emission construction for ratiometric luminescence thermometry is reviewed.
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