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Quantum dot

Enaam Jamal Al Dine, Sophie Marchal, Raphaël Schneider, Batoul Hamie, Jaafar Ghanbaja, Thibault Roques-Carmes, Tayssir Hamieh, Joumana Toufaily, Eric Gaffet, Halima Alem
Biocompatible thermo-responsive copolymers based on 2-(2-methoxyethoxy) ethyl methacrylate (MEO2MA) and oligo (ethylene glycol) methacrylate (OEGMA) were grown from the surface of ZnO Quantum Dots (QDs) by Surface Initiated Atom Transfer Radical Polymerization with Activators Regenerated by electron Transfer (SI-ARGET ATRP) in order to design smart and fluorescent core/shell nanosystems to be used towards cancer cells. Tunable lower critical solution temperature (LCST) values were obtained and studied in water and in culture medium...
June 15, 2018: Bioconjugate Chemistry
Xing Wang, Meizhen Gao
Porous Co3O4/SnO2 quantum dot (QD) heterojunctions with a strong synergistic effect are successfully synthesized in this paper. Owing to the strong synergistic effect between Co3O4 and SnO2QDs, Co3O4/SnO2QD heterostructures possess more Co2+ ions for a faster Co2+/Co0 redox reaction in the process of sensing of reducing gases and electrochemical reactions, and more oxygen vacancies for more active sites and reduced charge transfer resistance on the surface. These advantages are demonstrated to significantly enhance the gas sensitivity to xylene and greatly improve the catalysis for the oxygen evolution reaction (OER)...
June 15, 2018: Nanoscale
P Bardella, L Drzewietzki, M Krakowski, I Krestnikov, S Breuer
In this Letter, the pulse generation and pulse train stability of a tapered two-section InAs/InGaAs quantum dot laser emitting at 1250 nm are numerically predicted and experimentally verified. Simulations based on a multi-section delayed differential equation model are used to properly design a laser source able to generate stable mode-locked pulses at a 15 GHz repetition rate with picosecond width and output power larger than 1 W, and to identify the device stability regions depending on the bias conditions...
June 15, 2018: Optics Letters
Yaohong Zhang, Guohua Wu, Chao Ding, Feng Liu, Yingfang Yao, Yong Zhou, Congping Wu, Naoki Nakazawa, Qingxun Huang, Taro Toyoda, Ruixiang Wang, Shuzi Hayase, Zhigang Zou, Qing Shen
Lead selenide (PbSe) colloidal quantum dots (CQDs) are considered to be a strong candidate for high-efficiency colloidal quantum dot solar cells (CQDSCs) due to its efficient multiple exciton generation. However, currently, even the best PbSe CQDSCs can only display open-circuit voltage (Voc) about 0.530 V. Here, we introduce a solution-phase ligand exchange method to prepare PbI2-capped PbSe (PbSe-PbI2) CQD inks, and for the first time, the absorber layer of PbSe CQDSCs was deposited in one step by using this PbSe-PbI2 CQD inks...
June 15, 2018: Journal of Physical Chemistry Letters
Yishen Tian, Chen Xin, Shuang Liu, Ying Liu, Shufeng Liu
Herein, a general protein conversion and analysis strategy was well developed for homogenous, label-free, and sensitive protein detection, which was on the basis of the affinity binding-induced Hg2+ releasing for protein conversion, and the succeeding Hg2+ doping-induced ZnSe quantum dot (QD) photoluminescence for signal readout. Two DNA motifs were designed, and each of which was conjugated with a protein-specific recognition ligand. The mercury ions were initially introduced into one DNA motif by T-Hg2+-T interaction...
June 15, 2018: ACS Sensors
Chunlei Xia, Songyuan Tao, Shoujun Zhu, Yubin Song, Tanglue Feng, Qingsen Zeng, Junjun Liu, Bai Yang
Hydrothermal/solvothermal treatment have been widely used to prepare carbonized polymer dots (CPDs) by the condensation and carbonization of small molecules and/or polymers. However, the basic scientific issues of nucleation and growth process, morphology and size control, yield increase, and PL mechanism have not been well-investigated. In this work, enlightened by the principle of soap-free emulsion polymerization, CPDs with ultrahigh yield rate (ca. 85%) were obtained by hydrothermal addition polymerization and carbonization (HAPC) of monomer...
June 15, 2018: Chemistry: a European Journal
Meijiao Zhang, Shizhu Zang, Guangbo Ge, Lingling Jin, Yi Xin, Huizhen Li, Pingkun Liu, Xudong Hou, Dacheng Hao, Lu Chen, Qi Zhou, Jie Hou
CD22 is an important drug target for the treatment of autoimmune diseases and B cell-derived malignancies. In this study, N-acetylneuraminic acid functionalized quantum dots nanoconjugate was synthesized and used for targeting and fluorescence imaging of CD22 on living cells. The nanoprobe was prepared by conjugating N-acetylneuraminic acid (NANA) on the carboxyl groups modified CdSe/ZnS quantum dots (COOH-QDs) via NHS/EDC mediated esterification. The NANA-QDs nanoprobe showed excellent size distribution, very low cytotoxicity and super fluorescent properties for biological imaging applications...
August 1, 2018: Journal of Biomedical Nanotechnology
Bo Wang, Congyang Zhang, Shouqiang Huang, Zhichun Li, Long Kong, Ling Jin, Junhui Wang, Kaifeng Wu, Liang Li
Lead halide perovskite nanocrystals (NCs) as promising optoelectronic materials are intensively researched. However, the instability is one of the biggest challenges needed to overcome before fulfill their practical applications. To improve their stability, we present a postsynthetic controlled phase transformation of CsPbBr3 toward CsPbBr3/Rb4PbBr6 core/shell structure triggered by rubidium oleate treatment. The resulted core/shell NCs show exceptional photostability both in solution and on-chip. The solution of CsPbBr3/Rb4PbBr6 NCs can remain over 90% of the initial emission photoluminescence quantum yields (PLQY) after 42 h of intense light-emitting diodes illumination (450 nm, 175 mW/cm2), which is even better than the conventional CdSe/CdS quantum dots whose emission drop to 50% after 18 h under the same condition...
June 15, 2018: ACS Applied Materials & Interfaces
Kyuyoung Heo, Caroline Miesch, Jun-Hee Na, Todd Emrick, Ryan C Hayward
Nanoparticles may act as compatibilizing agents for blending of immiscible polymers, leading to changes in blend morphology through a variety of mechanisms including interfacial adsorption, aggregation, and nucleation of polymer crystals. Herein, we report an approach to define highly structured donor/acceptor networks based on poly(3-hexylthiophene) (P3HT) and CdSe quantum dots (QDs) by demixing from an insulating polystyrene (PS) matrix. The incorporation of QDs led to laterally phase-separated co-continuous structures with sub-micrometer dimensions, and promoted crystallization of P3HT, yielding highly interconnected P3HT/QD hybrid nanowires embedded in the polymer matrix...
June 14, 2018: Soft Matter
Ying Zhang, Chen Yang, Dongliang Yang, Zhouwei Shao, Yanling Hu, Jia Chen, Lihui Yuwen, Lixin Weng, Zhimin Luo, Lianhui Wang
The production of reactive oxygen species (ROS) from graphene oxide quantum dots (GOQDs) and chemically reduced GOQDs (rGOQDs) was studied. This shows that GOQDs and rGOQDs produce ROS including singlet oxygen (1O2), hydrogen peroxide (H2O2) and superoxide anion (O2˙-). Interestingly, the rGOQDs exhibit a higher yield of ROS under white light in comparison with GOQDs, indicating the enhanced photodynamic effect through chemical reduction of GOQDs. Studies on the relation between their structures and the yield of ROS demonstrate that the reduction of GOQDs with hydrazine hydrate decreases the band gap and valence band of GOQDs and results in more electron-hole pairs, which leads to an improvement in the yield of ROS from rGOQDs...
June 14, 2018: Physical Chemistry Chemical Physics: PCCP
Gianluca Grimaldi, Ryan W Crisp, Stephanie Ten Brinck, Felipe Zapata, Michiko van Ouwendorp, Nicolas Renaud, Nicholas Kirkwood, Wiel H Evers, Sachin Kinge, Ivan Infante, Laurens D A Siebbeles, Arjan J Houtepen
Thermalization losses limit the photon-to-power conversion of solar cells at the high-energy side of the solar spectrum, as electrons quickly lose their energy relaxing to the band edge. Hot-electron transfer could reduce these losses. Here, we demonstrate fast and efficient hot-electron transfer between lead selenide and cadmium selenide quantum dots assembled in a quantum-dot heterojunction solid. In this system, the energy structure of the absorber material and of the electron extracting material can be easily tuned via a variation of quantum-dot size, allowing us to tailor the energetics of the transfer process for device applications...
June 13, 2018: Nature Communications
Gopal Krishna Dixit, Madhav Ranganathan
The role of elastic anisotropy on quantum dot formation and evolution on a 
 pre-patterned substrate is evaluated within the framework of a continuum model. 
 We first extend the formulation for surface evolution to take elastic anisotropy 
 into account. Using a small slope approximation, we derive the evolution 
 equation and show how it can be numerically implemented up to linear and second 
 order for stripe and egg-carton patterned substrates using an accurate and 
 efficient procedure...
June 13, 2018: Nanotechnology
Elżbieta Trynkiewicz, Benedykt R Jany, Arkadiusz Janas, Franciszek Krok
Ion-beam sputtering of two-component substrates constitutes an alternative route for the nanofabrication of 3D (three-dimensional) structures, such as quantum dots or nanowires with unique properties like a high degree of local ordering. To allow for feasibility in precision manufacturing, control and optimization it is necessary to completely understand all the phenomena behind the evolution of nanostructures. The formation and development during the ion irradiation of similar features has been extensively studied for almost a half of century, but only over the last few years have new results appeared, ones stimulating real progress within this field...
June 13, 2018: Journal of Physics. Condensed Matter: An Institute of Physics Journal
Antonio Martinez, John R Barker, Riccardo Di Prieto
A methodology describing Coulomb blockade in the Non-equilibrium Green Function formalism is presented. We carried out ballistic and dissipative simulations through a 1D quantum dot using an Einstein phonon model. Inelastic phonons with different energies have been considered. The methodology incorporates the short-range Coulomb interaction between two electrons through the use of a two-particle Green's function. Unlike previous work, the quantum dot has spatial resolution i.e. it is not just parameterized by the energy level and coupling constants of the dot...
June 13, 2018: Journal of Physics. Condensed Matter: An Institute of Physics Journal
Liang Guo, Jiechao Ge, Pengfei Wang
Conjugated polymer dots (Pdots, also named polymer nanoparticles, PNPs), which consist of π-conjugated organic polymers, are novel organic nanomaterials with size in the range of 1-100 nm. Compared with traditional organic small molecules, semiconductor quantum dots, and inorganic nanomaterials, the Pdots exhibit significant potential applications in biological imaging, sensing and detection, drug delivery, and theranostics, due to their advantages of special optical properties, diverse structure, easy surface modification, and good biocompatibility...
June 13, 2018: Photochemistry and Photobiology
Shujie Wang, Xiaoyu Dou, Ling Chen, Yan Fang, Aqiang Wang, Huaibin Shen, Zuliang Du
Extracting light from quantum dot light emitting diodes (QLEDs) by applying optical-functional nanostructures inside and outside the devices is essential for their commercial application in illumination and displays. In this paper, we demonstrate the highly effective extraction of waveguided light from the active region of QLEDs by embedding internal grating patterns fabricated using a nanoimprint lithography technique. The grating couples out waveguide mode power into the substrate without changing the device's electrical properties, resulting in an increase in both the external quantum efficiency and luminous efficiency for a green QLED from 11...
June 13, 2018: Nanoscale
Feng Ding, Yibei Zhan, Xiaoju Lu, Yao Sun
In recent years, owing to unsatisfactory clinical imaging clarity and depths in the living body for early diagnosis and prognosis, novel imaging modalities with high bioimaging performance have been actively explored. The remarkable headway made in the second near-infrared region (NIR-II, 1000-1700 nm) has promoted the development of biomedical imaging significantly. NIR-II fluorescence imaging possesses a number of merits which prevail over the traditional and NIR-I (400-900 nm) imaging modalities in fundamental research, such as reduced photon scattering, as well as auto-fluorescence and improved penetration depth...
May 21, 2018: Chemical Science
Zhezhe Wang, Xinxin Xing, Yue Yang, Rongjun Zhao, Tong Zou, Zidong Wang, Yude Wang
Highly luminescent CdS quantum dots capped with thioglycolic acid (TGA@CdS QDs) were synthesized from cadmium chloride and thiourea as cadmium and sulfur sources via simple hydrothermal method. The room temperature photoluminescence (RTPL) properties of TGA@CdS QDs were investigated. The results indicate that the polarity of the solvent and the surface trap state resulted in the broadness Stokes shift between the maximum absorption wavelength and the emission wavelength of TGA@CdS QDs. The Co2+ sensing properties of fluorescence determination were investigated using TGA@CdS QDs...
June 12, 2018: Scientific Reports
Yi Luo, Ming Li, Lang Sun, Yongjie Xu, Ming Li, Guanghui Hu, Tao Tang, Jianfeng Wen, Xinyu Li, Jiye Zhang, Liang Wang
Sulfur-doped graphene quantum dots (S-GQDs) were synthesized by two facile hydrothermal technologies. The photoluminescence (PL) properties of the GQDs and S-GQDs samples were mainly investigated. Through regulating the content of S powders in S-GQDs synthesizing process, the optimal S-GQDs have a high S/C atomic ratio of 19.53%. The S doping introduce more functional groups on the C sp2 skeleton of S-3 sample and result in the appearance of the strong absorption band in the UV region. In comparison with other reported S-GQDs, the S-GQDs exhibit overwhelming high fluorescence quantum yield (57%) and excitation-independent emission, resulting from the outcome of the doped sulfur atoms...
June 7, 2018: Journal of Colloid and Interface Science
Xiu-Li Liang, Ning Bao, Xiliang Luo, Shou-Nian Ding
In this work, quaternary CdZnTeS quantum dots (QDs) with a particularly strong electrochemiluminescence (ECL) were synthesized as ECL signal labels. The strong ECL signals can be obtained at both cathode and anode with the ECL efficiencies of 19.78% and 1.62%, respectively. The sandwich-structured ECL immunosensors for the detection of alpha-fetoprotein (AFP) and cancer antigen 125 (CA125) were accomplished with direct ECL image analysis. Under optimal conditions, the QDs-based ECL image immunoanalysis possessed good linearity from 0...
June 5, 2018: Biosensors & Bioelectronics
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