414 research outputs found
Synthesis of Colloidal Metal Chalcogenide Nanocrystals
A method of synthesizing colloidal nanocrystals is disclosed using metal oxides or metal salts as a precursor. The metal oxides or metal salts are combined with a ligand and then heated in combination with a coordinating solvent. Upon heating, the metal oxides or salts are converted to stable soluble metal complexes. The metal complexes are formed by cationic species combining with the ligands and/or with the coordinating solvent. Finally, an elemental chalcogenic precursor, for example, Se, Te, or S, is introduced into the soluble metal complex to complete the formation of the nanocrystals at a controllable rate. High-quality CdSe, CdTe, and CdS nanocrystals are produced when CdO is used as the cadmium precursor. With the present method, the size, size distribution, and shape (dots or rods) of the resulting nanocrystals can be controlled during growth. For example, the resulting nanocrystals are nearly monodisperse without any size separation. Further, the method represents a major step towards a green chemistry approach for synthesizing high-quality semiconductor nanocrystals
Trajectory-Aware Body Interaction Transformer for Multi-Person Pose Forecasting
Multi-person pose forecasting remains a challenging problem, especially in
modeling fine-grained human body interaction in complex crowd scenarios.
Existing methods typically represent the whole pose sequence as a temporal
series, yet overlook interactive influences among people based on skeletal body
parts. In this paper, we propose a novel Trajectory-Aware Body Interaction
Transformer (TBIFormer) for multi-person pose forecasting via effectively
modeling body part interactions. Specifically, we construct a Temporal Body
Partition Module that transforms all the pose sequences into a Multi-Person
Body-Part sequence to retain spatial and temporal information based on body
semantics. Then, we devise a Social Body Interaction Self-Attention (SBI-MSA)
module, utilizing the transformed sequence to learn body part dynamics for
inter- and intra-individual interactions. Furthermore, different from prior
Euclidean distance-based spatial encodings, we present a novel and efficient
Trajectory-Aware Relative Position Encoding for SBI-MSA to offer discriminative
spatial information and additional interactive clues. On both short- and
long-term horizons, we empirically evaluate our framework on CMU-Mocap,
MuPoTS-3D as well as synthesized datasets (6 ~ 10 persons), and demonstrate
that our method greatly outperforms the state-of-the-art methods. Code will be
made publicly available upon acceptance.Comment: Accepted by CVPR2023, 8 pages, 6 figures. arXiv admin note: text
overlap with arXiv:2208.0922
Deciphering Charging Status, Absolute Quantum Efficiency, and Absorption Cross Section of MultiCarrier States in Single Colloidal Quantum Dot
Upon photo- or electrical-excitation, colloidal quantum dots (QDs) are often
found in multi-carrier states due to multi-photon absorption and photo-charging
of the QDs. While many of these multi-carrier states are observed in single-dot
spectroscopy, their properties are not well studied due to random
charging/discharging, emission intensity intermittency, and uncontrolled
surface defects of single QD. Here we report in-situ deciphering the charging
status, and precisely assessing the absorption cross section, and determining
the absolute emission quantum yield of mono-exciton and biexciton states for
neutral, positively-charged, and negatively-charged single core/shell CdSe/CdS
QD. We uncover very different photon statistics of the three charge states in
single QD and unambiguously identify their charge sign together with the
information of their photoluminescence decay dynamics. We then show their
distinct photoluminescence saturation behaviors and evaluated the absolute
values of absorption cross sections and quantum efficiencies of monoexcitons
and biexcitons. We demonstrate that addition of an extra hole or electron in a
QD changes not only its emission properties but also varies its absorption
cross section
Synthesis of colloidal metal chalcogenide nanocrystals
A method of synthesizing colloidal nanocrystals is disclosed using metal oxides or metal salts as a precursor. The metal oxides or metal salts are combined with a ligand and then heated in combination with a coordinating solvent. Upon heating, the metal oxides or salts are converted to stable soluble metal complexes. The metal complexes are formed by cationic species combining with the ligands and/or with the coordinating solvent. Finally, an elemental chalcogenic precursor, for example, Se, Te, or S, is introduced into the soluble metal complex to complete the formation of the nanocrystals at a controllable rate. High-quality CdSe, CdTe, and CdS nanocrystals are produced when CdO is used as the cadmium precursor. With the present method, the size, size distribution, and shape (dots or rods) of the resulting nanocrystals can be controlled during growth. For example, the resulting nanocrystals are nearly monodisperse without any size separation. Further, the method represents a major step towards a green chemistry approach for synthesizing high-quality semiconductor nanocrystals
Colloidal metal chalcogenide nanocrystals
A method of synthesizing colloidal nanocrystals is disclosed using metal oxides or metal salts as a precursor. The metal oxides or metal salts are combined with a ligand and then heated in combination with a coordinating solvent. Upon heating, the metal oxides or salts are converted to stable soluble metal complexes. The metal complexes are formed by cationic species combining with the ligands and/or with the coordinating solvent. Finally, an elemental chalcogenic precursor, for example, Se, Te, or S, is introduced into the soluble metal complex to complete the formation of the nanocrystals at a controllable rate. High-quality CdSe, CdTe, and CdS nanocrystals are produced when CdO is used as the cadmium precursor. With the present method, the size, size distribution, and shape (dots or rods) of the resulting nanocrystals can be controlled during growth. For example, the resulting nanocrystals are nearly monodisperse without any size separation. This method represents a major step towards a green chemistry approach for synthesizing high-quality semiconductor nanocrystals
Metal doped semiconductor nanocrystals and methods of making the same
Provide doped semiconductor nanocrystals and methods of making the same
Synthesis of stable colloidal nanocrystals using organic dendrons
A method for stabilizing colloidal suspensions of nanocrystals or nanoparticles in a solvent or solid matrix is provided by coating the nanocrystals with bulky organic molecules, specifically dendrons, is described. By coating nanocrystals with a dense organic dendron coat and further cross-linking the dendron ligands, oxidation of the nanocrystals and dissociation of the ligands are avoided. This invention allows nanocrystals to undergo rigorous purification and processing. It may regularly be applied to a variety of nanocrystals
- …