Colloidal quantum dots can control the bandgap by controlling the particle size, and are capable of solution processing, which is cost competitive, and has a narrow half width of the emission wavelength.Using these characteristics, it is possible to utilize various kinds of LED, solar cell, and bio imaging.Among them, indium phosphide (InP) quantum dots have a bandgap capable of emitting light in the near-infrared region from the visible light region, and are less toxic to humans and the environment than cadmium-based quantum dots, and are attracting attention as next generation light emitting materials.However, the limited choice and high cost of P precursors have a negative impact on their practical applicability. In this work, I report the large-scale synthesis of highly luminescent InP@ZnS QDs from an elemental P precursor (P4), which was simply synthesized via the sublimation of red P powder. The size of the InP QDs was controlled by varying the reaction parameters such as the reaction time and temperature, and the type of In precursors. This way, the photoluminescence properties of the synthesized InP@ZnS QDs could be easily tuned across the entire visible range, while their quantum yield could be increased up to 60% via the optimization of reaction conditions. Furthermore, possible reaction pathways for the formation of InP QDs using the P4 precursor have been investigated with nuclear magnetic resonance spectroscopy and it was demonstrated that the direct reaction of P4 precursor with In precursor produces InP structures without the formation of intermediate species. The large-scale production of InP@ZnS QDs was demonstrated by yielding more than 6 g of QDs per onebatch reaction.In the case of InP using different precursor P except the Tris(Trimethylsilyl) phosphine ((TMS)3P) there has been a problem that the size distribution is poor. Two kinds of P precursors with different reactivities were used to separate the nucleation and growth processes and to induce growth along the Lamer mechanism to produce uniform particles. For this, (TMS)3P and DEAP were used as fast reacting P precursors, and P4 was used as a slow reacting P precursor. Through this, the possibility of uniform particle formation was observed. I strongly believe that the newly developed approach bears the potential to be widely used for manufacturing inexpensive high-quality QD emitters. Blank page Contents

Output power of thermoelectric generators depends on device engineering minimizing heat loss as well as inherent material properties. However, the device engineering has been largely neglected due to the limited flat or angular shape of devices. Considering that the surface of most heat sources where these planar devices are attached is curved, a considerable amount of heat loss is inevitable. To address this issue, here, we present the shape-engineerable thermoelectric painting, geometrically compatible to surfaces of any shape. We prepared Bi2Te3-based inorganic paints using the molecular Sb2Te3 chalcogenidometalate as a sintering aid for thermoelectric particles, with ZT values of 0.67 for n-type and 1.21 for p-type painted materials that compete the bulk values. Devices directly brush-painted onto curved surfaces produced the high output power of 4.0 mW cm−2. This approach paves the way to designing materials and devices that can be easily transferred to other applications.

The discovery of SnSe single crystals with record high thermoelectric efficiency along the b-axis has led to the search for ways to synthesize polycrystalline SnSe with similar efficiencies. However, due to weak texturing and difficulties in doping, such high thermoelectric efficiencies have not been realized in polycrystals or thin films. Here, we show that highly textured and hole doped SnSe thin films with thermoelectric power factors at the single crystal level can be prepared by solution process. Purification step in the synthetic process produced a SnSe-based chalcogenidometallate precursor, which decomposes to form the SnSe2 phase. We show that the strong textures of the thin films in the b–c plane originate from the transition of two dimensional SnSe2 to SnSe. This composition change-driven transition offers wide control over composition and doping of the thin films. Our optimum SnSe thin films exhibit a thermoelectric power factor of 4.27 μW cm−1 K−2.

We report a strategy toward the synthesis of colloidal nanocrystals capped with inorganic molybdenum and tungsten sulfide ligands. MoS4(2-) and WS4(2-) thiometalates were utilized to replace organic ligands capping a wide range of nanocrystals such as metals, semiconductors, and well-conserved primary properties of nanocrystals in polar media. Especially, MoS4(2-)- and WS4(2-)-capped CdSe nanocryatals showed the dramatic enhancement of photoluminescence properties by the photo-oxidation treatment, which originated from the preferential formation of MoSxOy layers on the CdSe surface. The highest quantum yield reached up to 51%. Furthermore, we studied the charge-transport properties of MoS4(2-)-capped PbS nanocryatals by the fabrication of a field-effect transistor and photodetectors. Finally, MoS4(2-)- and WS4(2-)-capped nanocrystals were used for the production of two-dimensional MoS2 and WS2 thin layers on nanostructures by heat treatment. Such versatility of these thiometalate ligands offers an additional degree of control over the functionality of nanocrystals for optoelectronic and catalytic applications.

Molybdenum sulfides have attracted widespread attention as promising nonprecious-metal catalysts for the hydrogen evolution reaction (HER). Since the MoS2 edge was proposed as a major active site, molecular and polymeric analogues to the MoS2 edge have been widely explored as the HER catalysts. In particular, amorphous MoS x coordination polymers have been considered as active HER catalysts because they are rich in unsaturated Mo–S coordination, which is the characteristic of the active MoS2 edge. Herein, we report that the simple monomeric thiomolybdate (MoS4 2–) could adopt a polymeric chain structure, which exhibited high HER activity; its turnover frequency surpassed those of dimeric [Mo2S12]2–- and trimeric [Mo3S13]2–-derived MoS x catalysts. This high HER activity of monomeric MoS4 2– is attributed to the polymerization of MoS4 2– anions, generating active molecular analogues that comprise monomeric S2– sites bridging Mo­(V) and Mo­(IV). Density functional theory calculations of possible polymeric chain structures identified the Mo­(IV)­Mo­(V)2(S2 2–)2(S2–)5 unit as the most plausible structure that best matched the experimentally deduced structure. The Gibbs free energy for hydrogen adsorption on the bridging S2– (μ-S2–) site in Mo­(IV)­Mo­(V)2(S2 2–)2(S2–)5 was found to be −0.05 eV, which is close to the thermoneutral state. Combined analyses by resonance Raman spectroscopy and extended X-ray absorption fine structure suggested the role of Mo–oxo (MoO x ) species to generate the active Mo­(V)–(μ-S2–)–Mo­(IV) center for effective hydrogen adsorption.