The comparison of manganese spectral lines for self-absorption reduction in LIBS using laser-induced fluorescence

The detection of manganese(Mn)in steel by laser-induced breakdown spectroscopy(LIBS)provides essential information for steelmaking.However,self-absorption greatly disrupts the LIBS spectral lines of Mn with high content.In this study,to minimize self-absorption for Mn spectral lines in LIBS,laser-induced fluorescence(LIF)was applied.Compared with conventional LIBS,the self-absorption factors(α)of Mn I 403.08,403.31,and 403.45 nm lines were reduced by 90%,88%,and 88%,respectively;the root mean square errors of crossvalidation were decreased by 88%,85%,and 87%,respectively;the average relative errors were reduced by 93%,90%,and 91%,respectively;and average relative standard deviations were decreased by 29%,32%,and 33%,respectively.The LIBS-LIF was shown to successfully minimize the self-absorption effect and spectral intensity fluctuation and improve detection accuracy.

Unveiling size-fluorescence correlation of organic nanoparticles and its use in nanoparticle size determination

Quantitatively establishing the correlation between nanoparticle size and fluorescence is essential for understanding the behavior and functionality of fluorescent nanoparticles(FNPs).However,such exploration focusing on organic FNPs has not been achieved to date.Herein,we employ the use of supramolecular polymeric FNPs prepared from tetraphenylethylene-based bis-ureidopyrimidinone monomers(bis-UPys)to relate the size to the fluorescence of organic nanoparticles.At an equal concentration of bis-UPys,a logarithmic relationship between them is built with a correlation coefficient higher than 0.96.Theoretical calculations indicate that variations in fluorescence intensity among FNPs of different sizes are attributed to the distinct molecular packing environments at the surface and within the interior of the nanoparticles.This leads to different nonradiative decay rates of the embedded and exposed bis-UPys and thereby changes the overall fluorescence quantum yield of nanoparticles due to their different specific surface areas.The established fluorescence intensity-size correlation possesses fine universality and reliability,and it is successfully utilized to estimate the sizes of other nanoparticles,including those in highly diluted dispersions of FNPs.This work paves a new way for the simple and real-time determination of nanoparticle sizes and offers an attractive paradigm to optimize nanoparticle functionalities by the size effect.

Visualization of supramolecular assembly by aggregation-induced emission

Supramolecular architectures are constructed by the self-assembly of small building blocks via the use of metal-ligand coordination,π–πstacking interactions,hydrogen bonding,host-guest interactions,and other noncovalent driving forces,which confer unique dynamic reversibility and stimulus responsiveness to the supramolecular materials and also lead to the demand of expensive and complex equipment for the characterization of supramolecular assembly processes.Fortunately,the self-assembly processes bring the monomeric chromophores together,offering possibilities to establish ties between the supramolecular assembly and aggregation-induced emission(AIE)techniques.Compared to conventional luminescent molecules,AIE luminogens(AIEgens)exhibit significant fluorescence enhancement upon the restriction of molecular motions,thus displaying the advantages of signal amplification and low background noises.Given the above,the real-time,sensitive,and in situ visualization of the formation of self-assemblies and their stimuli responsiveness based on AIE becomes accessible.Here,we review recent works that encompass the visualization of supramolecular assembly-related behaviors by means of AIE characteristics of chromophores.The organization of this review will be by different types of supramolecular architectures,including metallacycles/cages,micelles/vesicles,supramolecular polymers,and supramolecular gels.An overview of future opportunities and challenges for the real-time monitoring of supramolecular assembly by AIE is also provided.