Facile and versatile ligand analysis method of colloidal quantum dot

Colloidal quantum-dots (QDs) are highly attractive materials for various optoelectronic applications owing to their easy maneuverability, high functionality, wide applicability, and low cost of mass-production. QDs usually consist of two components: the inorganic nano-crystalline particle and organic ligands that passivate the surface of the inorganic particle. The organic component is also critical for tuning electronic properties of QDs as well as solubilizing QDs in various solvents. However, despite extensive effort to understand the chemistry of ligands, it has been challenging to develop an efficient and reliable method for identifying and quantifying ligands on the QD surface. Herein, we developed a novel method of analyzing ligands in a mild yet accurate fashion. We found that oxidizing agents, as a heterogeneous catalyst in a different phase from QDs, can efficiently disrupt the interaction between the inorganic particle and organic ligands, and the subsequent simple phase fractionation step can isolate the ligand-containing phase from the oxidizer-containing phase and the insoluble precipitates. Our novel analysis procedure ensures to minimize the exposure of ligand molecules to oxidizing agents as well as to prepare homogeneous samples that can be readily analyzed by diverse analytical techniques, such as nuclear magnetic resonance spectroscopy and gas-chromatography mass-spectrometry. © 2021, The Author(s).1

Highly Luminescent and Photostable Quantum Dot–Silica Monolith and Its Application to Light-Emitting Diodes

A highly luminescent and photostable quantum dot–silica monolith (QD–SM) substance was prepared by preliminary surface exchange of the QDs and base-catalyzed sol–gel condensation of silica. The SM was heavily doped with 6-mercaptohexanol exchanged QDs up to 12 vol % (26 wt %) without particle aggregation. Propylamine catalyst was important in maintaining the original luminescence of the QDs in the SM during sol–gel condensation. The silica layer was a good barrier against oxygen and moisture, so that the QD–SM maintained its initial luminescence after high-power UV radiation (∼1 W) for 200 h and through the 150 °C LED encapsulant curing process. Green and red light-emitting QD–SMs were applied as color-converting layers on blue LEDs, and the external quantum efficiency reached up to 89% for the green QD–SM and 63% for the red one. A white LED made with a mixture of green and red QDs in the SM, in which the color coordinate was adjusted at (0.23, 0.21) in CIE1931 color space for a backlight application, showed an efficacy of 47 lm/W, the highest value yet reported

Self-Assembled Coatings for Controlling Biomolecular Adsorption on Surfaces

We have investigated a series of molecular and polymeric approaches for generating adherent thin films that impart anti-fouling characteristics to oxide surfaces. These films incorporate oligo- or poly(ethylene glycol) moieties that are expressed in high density in the near-surface region. In our molecular approach, oligo(ethylene glycol)-terminated n-alkyl-trichlorosilanes, RO(CH₂CH₂O)₃(CH₂)₁₁SiCl₃, have been designed so to spontaneously adsorb onto oxide surfaces and produce densely packed films. Another strategy uses a surface initiated polymerization to generate reactive anchored polymer chains that are then chemically modified to incorporate oligo(ethylene glycol) units. Lastly, a comb copolymer comprising a poly(acrylic acid) backbone and different grafting ratios of a linear poly(ethylene oxide-r-propylene oxide) chain has been prepared that adsorbs onto surfaces and forms a poly(ethylene glycol)-exposing film in single step. These surface coatings provide varying levels of protein and cellular resistance that can be related to molecular-scale elements of their surface structure.Singapore-MIT Alliance (SMA

Highly polarized light emission by isotropic quantum dots integrated with magnetically aligned segmented nanowires

In this work, we demonstrate a proof-of-concept system for generating highly polarized light from colloidal quantum dots (QDs) coupled with magnetically aligned segmented Au/Ni/Au nanowires (NWs). Optical characterizations reveal that the optimized QD-NW coupled structures emit highly polarized light with an s-to p-polarization (s/p) contrast as high as 15:1 corresponding to a degree of polarization of 0.88. These experimental results are supported by the finite-difference time-domain simulations, which demonstrate the interplay between the inter-NW distance and the degree of polarization.Published versio

Determination of the Energy Band Gap Depending on the Oxidized Structures of Quantum Dots

Theoretical and experimental studies on the changes of the optical properties of CdSe/CdS/ZnS (core/double-shell) quantum dots (QDs) during the oxidation process were first performed. An effective medium approach using the modified Khon–Sham equation presents a new method to predict the effects of the oxidation and to determine the oxidized ratio of nanoscale materials by a quantitative comparison with the experimental photoluminescence (PL) changes. As the oxidation progressed from the CdSe/CdS/ZnS nanocrystal surface, the PL peak shifted to longer wavelength and the quantum efficiency (QE) continuously decreased. It was also found that such changes were accelerated when the thickness of the outermost ZnS shell became thinner than a monolayer. The radial wave functions showed that the electron carriers rapidly extended into the shell region while the hole carriers spread very little into the core region. This indicates that the electrons are the key carriers to induce the changes in the energy band gap and the QE

Transcriptomic characteristics according to tumor size and SUVmax in papillary thyroid cancer patients.

The SUVmax is a measure of FDG uptake and is related with tumor aggressiveness in thyroid cancer, however, its association with molecular pathways is unclear. Here, we investigated the relationship between SUVmax and gene expression profiles in 80 papillary thyroid cancer (PTC) patients. We conducted an analysis of DEGs and enriched pathways in relation to SUVmax and tumor size. SUVmax showed a positive correlation with tumor size and correlated with glucose metabolic process. The genes that indicate thyroid differentiation, such as SLC5A5 and TPO, were negatively correlated with SUVmax. Unsupervised analysis revealed that SUVmax positively correlated with DNA replication(r = 0.29, p = 0.009), pyrimidine metabolism(r = 0.50, p < 0.0001) and purine metabolism (r = 0.42, p = 0.0001). Based on subgroups analysis, we identified that PSG5, TFF3, SOX2, SL5A5, SLC5A7, HOXD10, FER1L6, and IFNA1 genes were found to be significantly associated with tumor aggressiveness. Both high SUVmax PTMC and macro-PTC are enriched in pathways of DNA replication and cell cycle, however, gene sets for purine metabolic pathways are enriched only in high SUVmax macro-PTC but not in high SUVmax PTMC. Our findings demonstrate the molecular characteristics of high SUVmax tumor and metabolism involved in tumor growth in differentiated thyroid cancer

Bone marrow–derived circulating progenitor cells fail to transdifferentiate into adipocytes in adult adipose tissues in mice

Little is known about whether bone marrow–derived circulating progenitor cells (BMDCPCs) can transdifferentiate into adipocytes in adipose tissues or play a role in expanding adipocyte number during adipose tissue growth. Using a mouse bone marrow transplantation model, we addressed whether BMDCPCs can transdifferentiate into adipocytes under standard conditions as well as in the settings of diet-induced obesity, rosiglitazone treatment, and exposure to G-CSF. We also addressed the possibility of transdifferentiation to adipocytes in a murine parabiosis model. In each of these settings, our findings indicated that BMDCPCs did not transdifferentiate into either unilocular or multilocular adipocytes in adipose tissues. Most BMDCPCs became resident and phagocytic macrophages in adipose tissues — which resembled transdifferentiated multilocular adipocytes by appearance, but displayed cell surface markers characteristic for macrophages — in the absence of adipocyte marker expression. When exposed to adipogenic medium in vitro, bone marrow cells differentiated into multilocular, but not unilocular, adipocytes, but transdifferentiation was not observed in vivo, even in the contexts of adipose tissue regrowth or dermal wound healing. Our results suggest that BMDCPCs do not transdifferentiate into adipocytes in vivo and play little, if any, role in expanding the number of adipocytes during the growth of adipose tissues

Chitooligosaccharide Induces Mitochondrial Biogenesis and Increases Exercise Endurance through the Activation of Sirt1 and AMPK in Rats

<div><p>By catabolizing glucose and lipids, mitochondria produce ATPs to meet energy demands. When the number and activity of mitochondria are not sufficient, the human body becomes easily fatigued due to the lack of ATP, thus the control of the quantity and function of mitochondria is important to optimize energy balance. By increasing mitochondrial capacity? it may be possible to enhance energy metabolism and improve exercise endurance. Here, through the screening of various functional food ingredients, we found that chitooligosaccharide (COS) is an effective inducer of mitochondrial biogenesis. In rodents, COS increased the mitochondrial content in skeletal muscle and enhanced exercise endurance. In cultured myocytes, the expression of major regulators of mitochondrial biogenesis and key components of mitochondrial electron transfer chain was increased upon COS treatment. COS-mediated induction of mitochondrial biogenesis was achieved in part by the activation of silent information regulator two ortholog 1 (Sirt1) and AMP-activated protein kinase (AMPK). Taken together, our data suggest that COS could act as an exercise mimetic by inducing mitochondrial biogenesis and enhancing exercise endurance through the activation of Sirt1 and AMPK.</p> </div