Highly emitting perovskite quantum dots are finally available in water
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Correspondence
Highly emitting perovskite quantum dots are finally available in water Guocan Jiang and Nikolai Gaponik, Physical Chemistry, TU Dresden, 01062 Dresden, Germany Address all correspondence to Nikolai Gaponik at [email protected] (Received 29 July 2018; accepted 5 September 2018)
Abstract The interest on strongly emitting colloidal perovskite nanoparticles has been arisen explosively since several years. The versatility of the synthesis and the resulting scale-up, as well as high performance in terms of photoluminescence quantum yields and narrow spectra make these nanocrystals extremely attractive in optoelectronics. However, commonly known instability of these nanoparticles in aqueous environment is an important issue limiting their applications. This letter highlights a recent report by Geng et al. presenting direct aqueous synthesis of strongly emitting perovskite nanocrystals. One can foresee extrapolation of these results toward other perovskites including those based on Pb-free materials.
Since the seminal publications of Zhang et al.[1] and Protesescu et al.,[2,3] the interest on strongly emitting colloidal perovskite nanoparticles has explosively increased. Indeed, the versatility of the synthesis and the resulting potential scale-up, as well as high performance in terms of photoluminescence quantum yields and narrow spectral widths make these nanocrystals extremely attractive in optoelectronics, e.g. in light-emitting diodes (LEDs), display technologies, and lasing. Apart from those potential applications, strongly emitting materials with narrow emission and broad absorption bands are always demanded for bio-labelling and bio-imaging provided they possess reasonable stability in aqueous environment and in common biological buffers. Taking into account reported inherent instability of the lead–halide perovskites toward water, the research on making these nanocrystals water compatible was mainly focused on better ways of encapsulation. The shells based on polymers and oxides were suggested to increase the nanocrystal stability toward ambient conditions considering as a rule the exposure of the optoelectronic devices to humidity and atmospheric oxygen.[4,5] The resulting materials were typically reported as suspensions or dispersions of partly aggregated powders. If one, however, considers the applications in bio-environment, the size of an individual nanoparticles does matter a lot, and should be maintained as small as possible.[6] The about 30 years’ experience of scientists dealing with colloidal quantum dots shows that the proper phase transfer to aqueous environment is a very challenging task demanding material-depending multistep procedures of designing and constructing a series of inorganic and organic stabilizing shells.[7] The alternative solution can be a direct synthesis in water environment. Although, the possible choice of nanoparticles, which can be synthesized in water delivering stable strongly emitting
colloids is typically limited to the families of II–VI, I
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