Doh Chang Lee

ADVERTISEMENT RETURN TO ISSUEPREVCommunicationNEXTHighly Stable Cesium Lead Halide Perovskite Nanocrystals through in Situ Lead Halide Inorganic PassivationJu Young Woo†‡, Youngsik Kim‡§, Jungmin Bae#, Tae Gun Kim∥#, Jeong Won Kim∥#, Doh C. Lee*†, and Sohee Jeong*‡§View Author Information† Department of Chemical and Biomolecular Engineering (BK21+ Program), KAIST Institute for the NanoCentury, Korea Advanced Institute of Science and Technology (KAIST), Daejeon 305-701, Korea‡ Nano-Convergence Re

CdSe/Zn1-X CdX S core/shell heterostructured quantum dots (QDs) with varying shell thicknesses are studied as the active material in a series of electroluminescent devices. "Giant" CdSe/Zn1-X CdX S QDs (e.g., CdSe core radius of 2 nm and Zn1-X CdX S shell thickness of 6.3 nm) demonstrate a high device efficiency (peak EQE = 7.4%) and a record-high brightness (>100 000 cd m(-2) ) of deep-red emission, along with improved device stability.

Colloidal FePt nanocrystals, 6 nm in diameter, were synthesized and then coated with silica (SiO2) shells. The silica shell thickness could be varied from 10 to 25 nm. As-made FePt@SiO2 nanocrystals have low magnetocrystalline anisotropy due to a compositionally disordered FePt core. When films of FePt@SiO2 particles are annealed under hydrogen at 650 degrees C or above, the FePt core transforms to the compositionally ordered L1(0) phase, and superparamagnetic blocking temperatures exceeding roo

The fast degradation of lead selenide (PbSe) nanocrystal quantum dots (NQDs) in ambient conditions impedes widespread deployment of the highly excitonic, thus versatile, colloidal NQDs. Here we report a simple in situ post-synthetic halide salt treatment that results in size-independent air stability of PbSe NQDs without significantly altering their optoelectronic characteristics. From TEM, NMR, and XPS results and DFT calculations, we propose that the unprecedented size-independent air stabilit

Thick inorganic shells endow colloidal nanocrystals (NCs) with enhanced photochemical stability and suppression of photoluminescence intermittency (also known as blinking). However, the progress of using thick-shell heterostructure NCs in applications has been limited due to the low photoluminescence quantum yield (PL QY ≤ 60%) at room temperature. Here, we demonstrate thick-shell NCs with CdS/CdSe/CdS seed/spherical quantum well/shell (SQW) geometry that exhibit near-unity PL QY at room tempera

In this study, we synthesized Ge nanocrystals and studied the effects of variables such as solvents, reducing agents, reaction temperature, and capping ligands. The resulting nanocrystals showed infrared photoluminescence with quantum yields as high as approximately 8% and enhanced resistance to oxidation. Size analysis of the samples by transmission electron microscopy revealed that the size dependence of the emission is consistent with the effects of quantum confinement.

Multiwall carbon nanotubes (MWNTs) were synthesized in supercritical toluene at 600 degrees C and approximately 12.4 MPa using ferrocene, Fe, or FePt nanocrystals as growth catalysts. Toluene serves as both the carbon source for nanotube formation and the solvent. In contrast to vapor-phase synthetic routes, the supercritical solvent provides high precursor concentration and a homogeneous reaction environment with dispersed growth catalyst particles. Both carbon filaments and MWNTs are produced

We report the photocatalytic conversion of CO2 to CH4 using CuPt alloy nanoclusters anchored on TiO2. As the size of CuPt alloy nanoclusters decreases, the photocatalytic activity improves significantly. Small CuPt nanoclusters strongly bind CO2 intermediates and have a stronger interaction with the TiO2 support, which also contributes to an increased CH4 generation rate. The alloying and size effects prove to be the key to efficient CO2 reduction, highlighting a strategic platform for the desig

We examine the effects of chlorine-passivation of Cd surface atoms on photocatalytic H 2 O reduction by CdSe NCs. Transient absorption spectroscopy reveals that Cl passivation removes electron trap states in CdSe NCs, which is also reflected in an increase of photoluminescence quantum yield, e.g., from 9 to 22% after the Cl treatment. Size-tunable energy states in CdSe NCs enable the systematic investigation of surface defects and their effect on the photocatalytic hydrogen generation rate. It t

We report on the fabrication of a siloxane-encapsulated quantum dot (QD) film (QD-silox film), which exhibits stable emission intensity for over 1 month even at elevated temperature and humidity. QD-silox films are solidified via free radical addition reaction between oligosiloxane resin and ligand molecules on QDs. We prepare the QD-oligosiloxane resin by sol-gel condensation reaction of silane precursors with QDs blended in the precursor solution, forgoing ligand-exchange of QDs. The resulting

Under pressure! The synthesis of crystalline silicon nanowires can be carried out in organic solvents at reaction temperatures of up to 450–500°C under high-pressure conditions. Gold particles are used as seeds, and organosilanes are employed as the silicon source. The decomposition chemistry of the organosilanes determines the quality of the nanowires formed (see picture of an Si nanowire with an Si/Au tip).

Advances in nanotechnology have enabled precise design of catalytic sites for CO₂ photoreduction, pushing product selectivity to near unity. However, activity of most nanostructured photocatalysts remains underwhelming due to fast recombination of photogenerated electron-hole pairs and sluggish hole transfer. To address these issues, we construct colloidal CdS nanosheets (NSs) with the large basal planes terminated by S^2- atomic layers as intrinsic photocatalysts (CdS-S<sup

We present the synthesis of composite PbSe/CdSe/CdS nanocrystals with two distinct geometries: core/shell/shell structures and tetrapods. These novel nanostructures exhibit extremely long carrier decay times up to 20 micros that are combined with high emission efficiencies in the infrared. The increase in carrier lifetimes is attributed to the reduction of the electron-hole overlap as a result of delocalization of the electron wave function into the outer CdS shell or arms. The ultralong carrier