• Bulletin of the Korean Chemical Society
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• v.32 no.10
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• pp.3738-3742
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• 2011

Bismuth tribromide ($BiBr_3$) catalyzed Mannich-type reactions of N-acyliminium ions which generated in situ from N-benzyloxycarbonylamino p-tolylsulfones have been developed. In the presence of catalytic amount of $BiBr_3$, N-benzyloxycarbonylamino p-tolylsulfones prepared from aromatic and aliphatic aldehydes reacted with silyl enol ether and silyl enol ester under mild reaction conditions to afford N-Cbz-protected ${\beta}$-amino ketones and N-Cbz-protected ${\beta}$-amino esters in moderate to good yield, respectively.

• Journal of the Korean institute of surface engineering
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• v.51 no.1
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• pp.79-85
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• 2018

We systematically investigated the optical properties of sub-micron sized methylammonium lead tribromide ($CH_3NH_3PbBr_3$) cubes in the range of 100 to 700 nm, which were prepared by a surfactant-free precipitation method. We found that despite the strong absorbance, their photoluminescence quantum yield (PLQY) is very low as 0.009~0.011 % for whole range of sizes. Surfactant-free synthesis approach results in nanocubes that has no surface passivating reagents (e.g. surfactants) on their surface. As-prepared particles contain a large number of surface defects that may cause the low PLQY. The role of the surface defects were investigated in their photoluminescence decay process, which can be correlated with the particle size. Larger particles are characterized by a slower decay rate compared to smaller particles due to a large number of surface defects in the smaller particles that trap more excitons in the fluorescence decay process. These experimental results provide new insights into the fundamental relationship between surface state and optical properties.

• Journal of the Korean Chemical Society
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• v.21 no.4
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• pp.227-234
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• 1977

The reaction of phenylhydrazine with bromine in sulfuric acid solution has been studied kinetically. The pseudo-second-order rate constant is approximately inversely proportional to hydrogen-ion concentration when the concentration of sulfuric acid is lower than 1M. arom the study of the effect of potassium bromide concentration on the rate constant, it is concluded that both neutral bromine and tribromide ion participate in the reaction, the rate constants in 0.01M $H_2SO_4$ being $5{\times}10^5M^{-1},sec^{-1}\;and\;0. 7{\times}10^5M^{-1},sec^{-1}$, respectively at $20^{\circ}C$. The pseudo-second-order rate constant of 2.4-dinitrophenylhydrazine-bromine reaction is independent of hydrogen ion concentration. From the KBr addition experiment, the rate constants for $Br_2\;and\;Br_3^-$ were obtained as $1.2{\times}10^5M^{-1},sec^{-1}\;and\;2.0{\times}10^4M^{-1},sec^{-1}$, respectively.

• Journal of the Korean institute of surface engineering
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• v.52 no.2
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• pp.90-95
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• 2019

Methylammonium lead bromide ($MAPbBr_3$) has attracted a lot of attention due to their excellent optoelectronic properties such as the compositional flexibility relevant to photoluminescence (PL) and UV-Vis absorbance spectrum, high diffusion length, and photoluminescence quantum yield (PLQY). Despite such advantages of organic-inorganic perovskite materials, more systematic study on manipulation of their optoelectronic properties in homo- or heterovalent metal ions doped halide perovskite nanocrystals is lacking. In this study, we systematically investigated the optical properties of colloidal $CH_3NH_3Pb_{1-x}Sn_xCl_{2x}Br_{3-2x}$ particles by addition of $SnCl_2$ into the typical methylammonium lead tribromide ($CH_3NH_3PbBr_3$) precursor solution. We found that only 1% addition of $SnCl_2$ shows a significant blue-shift from 540 nm to 420 nm in UV-Vis absorbance spectrum due to the strong quantum confinement effect. Furthermore, continuous blue-shift in photoluminescence spectra was observed as the amount of Cl increases. These experimental results provide new insights into the replacement of Pb within $MAPbBr_3$, required for the broadening of their application.