Water soluble nanoparticles (NPs) with a high emission property were synthesized via hydrothermal routes. In this report, we chose thiol ligand N-acetyl-L-cysteine as the ideal stabilizer and have successfully employed it to synthesize readily size-controllable CdTe NPs in a reaction of only one step. Hydrothermal synthesis of CdTe NPs has been carried out in neutral or basic conditions so far. We found out that the pH value of precursor solutions plays an important role in the uniformity of the particle size. Actually, high quality CdTe NPs were synthesized under mild acidic conditions of pH 5. The resultant NPs indicated good visible light-emitting properties and stability. Further, the experimental results showed that the reaction temperature influenced significantly the growth rate and the maximum size of the NPs. The CdTe NPs with a high photoluminescence quantum yield (the highest value: 57%) and narrower half width at half maximum (the narrowest value: 33 nm) were attained in very short time, within 40 minutes, reaching diameters of 2.3 to 4.3 nm. The PL intensity was increased with an increase in the reaction time, reflecting the suppression of nonradiative recombination processes. Furthermore, the formation of CdTe/CdS core-shell structures was discussed from the viewpoint of PL dynamics and X-ray diffraction studies.
One of the most interesting processes in energy-related catalysis is steam-assisted catalytic cracking. Herein, ZSM-12 (MTW) zeolite was modified by impregnation to improve the selectivity to olefins in the presence of steam. ZSM-12 zeolite was synthesized hydrothermally and modified by incorporating ZSM-12 zeolite with lanthanum (La), cerium (Ce), and boron (B). Two different ammonium solutions were used in the ion-exchange of the synthesized ZSM-12 zeolite, namely, ammonium nitrate and ammonium fluoride. Each group was impregnated with 2 wt % of lanthanum, cerium, or boron. Catalytic performance was evaluated using steam catalytic cracking of n-hexane. H-ZSM-12 zeolite exchanged with ammonium nitrate and impregnated with lanthanum and cerium has conversion above 50 C-mol %. However, impregnation with boron reduced the active sites, and the conversion was 20 C-mol %. On the other hand, exchanging the samples with ammonium fluoride led to the loss of the active sites and the conversion was around 20 C-mol % in the presence of lanthanum, cerium, and boron.
Abstract CuInS2 (CIS) nanoparticles (NPs) were hydrothermally prepared by the reaction of Cu2+, In2+, and Na2S in the presence of N-acetyl-l-cysteine as a stabilizer. The X-ray diffraction pattern of the resultant CIS NPs indicated that the chalcopyrite NPs could be obtained. The X-ray photoelectron spectroscopy data suggested that Cu2+ is reduced to Cu+ during the reaction process. The absorption and photoluminescence peaks of the NPs were clearly red-shifted with increasing size of the particles. Our method will aid in the synthesis of other I–III–VI ternary compounds.
Abstract We have investigated the optical properties of ZnSe quantum dots (QDs) prepared by a hydrothermal method. The photoluminescence (PL)-decay profiles become slower with an increase in temperature up to 160 K, contrary to an ordinary behaviour due to thermal quenching. The temperature dependence of the PL-decay profile is explained by a three-state model consisting of a ground state and two excited states of the lower-lying bound-exciton and higher-lying dark-exciton states. The analysis of the temperature dependence of the decay time indicates that the dark-exciton state contributes to the PL-decay process in the ZnSe QDs.
Abstract The title nanoparticles are hydrothermally prepared from aqueous mixtures of N‐acetyl‐L‐cysteine, CuCl 2 , InCl 3 , and Na 2 S (autoclave, 180 °C, 5—20 min).
This study aims to report the hydrothermal synthesis of water-soluble Mn-doped ZnSe-ZnS alloy quantum dots (QDs), wherein manganese (Mn2+) serves as an emission center. The alloy composition was co...
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