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Quantum dots

Wenxiao Gai, Die Ling Zhao, Tai-Shung Chung
We have incorporated Na+ -functionalized carbon quantum dots (Na-CQDs) into the polyamide layer via interfacial polymerization reaction and developed novel thin film nanocomposite (TFN) hollow fiber membranes for brackish water desalination. Comparing with the conventional thin film composite (TFC) membranes, the TFN membranes comprising Na-CQDs have a larger effective surface area, thinner polyamide layer and more hydrophilic oxygen-containing groups in the polyamide layer. Besides, the interstitial space among the polyamide chains becomes larger due to the presence of Na-CQDs...
February 4, 2019: Water Research
Qiao Liu, Chao Liu, Guang Zhu, Haifeng Xu, Xiao Jie Zhang, Chongju Hu, Yong Xie, Keying Zhang, Hongyan Wang
An electrochemiluminescence (ECL) based method is described for the determination of the activity of the enzyme uracil-DNA glycosylase (UDG). It is based on the use of nicking enzyme-assisted signal amplification and catalytic hairpin assembly. UDG can recognize and hydrolyze the uracil bases from the stem of hairpin DNA1 (HP1). This causes the opening of HP1 to form a straight strand DNA. The straight HP1 can hybridize with hairpin DNA2 (HP2) to form a DNA duplex. In the presence of nicking enzyme, it can recognize and cut the specific sequences in the HP2 of the DNA duplex, and a subsequent release of HP1...
February 15, 2019: Mikrochimica Acta
Song Chen, Weiran Cao, Taili Liu, Sai-Wing Tsang, Yixing Yang, Xiaolin Yan, Lei Qian
The operating lifetime of blue quantum-dot light-emitting diodes (QLED) is currently a short slab for this emerging display technology. To pinpoint the origin of device degradation, here we apply multiple techniques to monitor the electric-field distribution and space-charge accumulation across the multilayered structure before and after lifetime tests. Evident by charge-modulated electro-absorption and capacitance-voltage characteristics, the excited electrons in blue quantum dots (QD) are prone to cross the type II junction between the QD emission layer and the electron-transporting layer (ETL) due to the offset of conduction band minimum, leading to space-charge accumulation and operating-voltage rise in the ETL...
February 15, 2019: Nature Communications
Mahsa Haddad Irani-Nezhad, Javad Hassanzadeh, Alireza Khataee, Yasin Orooji
Currently, researchers are looking for nanomaterials with peroxidase-like activity to replace natural peroxidase enzymes. For this purpose, WS₂ quantum dots (WS₂ QDs) were synthesized via a solvothermal method, which improved the mimetic behavior. The resulting WS₂ QDs with a size of 1⁻1.5 nm had a high fluorescence emission, dependent on the excitation wavelength. WS₂ QDs with uniform morphology showed a high catalytic effect in destroying H₂O₂. The peroxidase-like activity of synthesized nanostructures was studied in H₂O₂ chemical and electrochemical reduction systems...
February 14, 2019: Molecules: a Journal of Synthetic Chemistry and Natural Product Chemistry
Wuding Hong, Huijuan Kuang, Xingping He, Lin Yang, Pengfei Yang, Bolu Chen, Zoraida P Aguilar, Hengyi Xu
The toxicity, especially the transgenerational toxicity of quantum dots (QDs) in vivo, is still scarcely understood in spite of great promising applications of QDs in biomedicine. In this study, the maternal status, pregnancy outcome, and fetus development of parental generation (P0) to offspring in three generations (F3) were investigated after Kunming mice perinatal (GD 13-PND 5) exposure to Cd containing QDs (CdSe/ZnS QDs) and CdCl₂. The results show CdSe/ZnS QDs induced placenta injuries in P0 and diminished placenta diameters in F1 and F2...
February 14, 2019: Nanomaterials
Fuheng You, Mingyue Zhu, Lijun Ding, Yuhuan Xu, Kun Wang
Rational design and fabrication of Z-scheme visible-light-driven photoactive materials have drawn much attention owing to their great potential in handling environment and energy crisis. In this work, Z-scheme Bi2 S3 /nitrogen-doped graphene quantum dots (NGQDs) with superior photoelectric conversion efficiency were designed and fabricated, which demonstrated enhanced photoactivity compared with Bi2 S3 owing to the improved separation efficiency of photogenerated electron and hole pairs. The emphasis was put on designing Z-scheme Bi2 S3 /NGQDs, and then the mechanism of Z-scheme charge transfer mode was verified by the electron spin resonance (ESR) technique...
February 5, 2019: Biosensors & Bioelectronics
Man Qu, Yuexiu Qiu, Rongrong Lv, Ying Yue, Ran Liu, Fei Yang, Dayong Wang, Yunhui Li
Quantum dots (QDs), considered as a type of excellent semiconductor nanomaterial, are widely employed and have a number of important applications. However, QDs have the potential to produce adverse effects and toxicity with the underlying molecular mechanisms not well understood. Herein, Caenorhabditis elegans was used for in vivo toxicity assessment to detect the reproductive toxicity of CdTe QDs. We found that exposure to CdTe QDs particles (≥ 50 mg/L) resulted in a defect in reproductive capacity, dysfunctional proliferation and differentiation, as well as an imbalance in oogenesis by reducing the number of cells in pachytene and diakinesis...
February 12, 2019: Ecotoxicology and Environmental Safety
Kristian E Dalle, Julien Warnan, Jane J Leung, Bertrand Reuillard, Isabell S Karmel, Erwin Reisner
The synthesis of renewable fuels from abundant water or the greenhouse gas CO2 is a major step toward creating sustainable and scalable energy storage technologies. In the last few decades, much attention has focused on the development of nonprecious metal-based catalysts and, in more recent years, their integration in solid-state support materials and devices that operate in water. This review surveys the literature on 3d metal-based molecular catalysts and focuses on their immobilization on heterogeneous solid-state supports for electro-, photo-, and photoelectrocatalytic synthesis of fuels in aqueous media...
February 15, 2019: Chemical Reviews
Xin Tang, Matthew M Ackerman, Guohua Shen, Philippe Guyot-Sionnest
Electronic eye cameras are receiving increasing interest due to their unique advantages such as wide field of view, low aberrations, and simple imaging optics compared to conventional planar focal plane arrays. However, the spectral sensing ranges of most electronic eyes are confined to the visible, which is limited by the energy gaps of the sensing materials and by fabrication obstacles. Here, a potential route leading to infrared electronic eyes is demonstrated by exploring flexible colloidal quantum dot (CQD) photovoltaic detectors...
February 15, 2019: Small
Yue Zhao, Zhixiang Jiang, Tao Wang, Tong Song, Juping Li, Ping Yang
The stability of quantum dots (QDs) in phosphate buffered saline (PBS) solutions plays an important role in the bio-applications. Red-emitting CdTe QDs with high PL efficiency were prepared using thiogliycolic acid as a capping agent. The assembly of the QDs in various buffer components was investigated. Using buffer components such as NaCl, KCl, and phosphate salts as scaffolds, the assembly of CdTe QDs occurred on a slide glass in the re-crystalline process of buffer components. The QDs were homogeneously assembled into the composites with leaf or flake shapes...
July 1, 2019: Journal of Nanoscience and Nanotechnology
Fei Fang, Feifei Chen, Yayu Huang, Zhenhao Zhao, Bocheng Lv, Jialin Sun, Feng Lin, Youwei Yao, Qi Zhang, Hong Lin, Xian Cui, Jinquan Wei
Ultrafine droplets play important roles in many fields. Here, we prepare ultrafine droplets with volumes in femtoliter scale by applying an electrostatic field between a needle and substrate. The diameter of liquid is reduced significantly to about 1/50 that of the needle tip. By using some solvents consisting of small molecules, ultrafine droplets eject from the needle tip. The volume of the ultrafine droplets depend on the strength of the electrostatic field and properties of the liquid. Ultrafine droplets containing perovskite quantum dots are also ejected on the substrate by using this jetting method...
July 1, 2019: Journal of Nanoscience and Nanotechnology
Yu-Juan Chen, Zhao-En Liu, Qian Yang, Chun-Feng Wang, Ke-Lei Zhuo
A facile one-pot hydrothermal method for fabricating nitrogen-doped carbon dots (N-CDs) was developed by using citric acid as a carbon source and guanidine carbonate as a nitrogen and carbon source. X-ray diffraction, X-ray photoelectron spectroscopy, and Fourier transform infrared spectra indicated that the N-CDs were rich in elemental nitrogen. They had excellent stability in the presence of various salt concentrations and under UV irradiation. The N-CDs exhibited high quantum yields (52%), as well as down-conversion and up-conversion photoluminescence...
July 1, 2019: Journal of Nanoscience and Nanotechnology
G Ramalingam, C Ragupathi, K Kaviyarasu, D Letsholathebe, S B Mohamed, C Maria Magdalane, G T Mola, Abdulgalim B Isaev, M Maaza
Research on CdSe/ZnS core-shell quantum dots (QDs) was synthesized by a chemical route using bio-conjugated organic amino acid (L-Cysteine). The structural, morphological, and optical properties of the nanocrystal powder samples were analyzed using various characterization techniques. The diameter of the resulting QDs was about 3 nm with uniform size distribution. The optical properties QDs exhibited an absorption and emission peak at 515 and 525 nm respectively, at room temperature. The QDs through emission in the spectral range at 516-535 nm is special for their application in green LEDs and white-light generation...
July 1, 2019: Journal of Nanoscience and Nanotechnology
Weicong Kuang, Qing Zhong, Xiaoli Ye, Yayuan Yan, Yunhua Yang, Jingxian Zhang, Langhuan Huang, Shaozao Tan, Qingshan Shi
Due to secondary pollution from bactericidal substances, the importance of eliminating microbial contamination has become a controversial topic. Three antibacterial nanorod materials of carbon quantum dots-zinc oxide (1/3CQDs-ZnO, CQDs-ZnO, and 2CQDs-ZnO), in which ZnO nanorods are surrounded by carbon quantum dots (CQDs), were successful prepared via in-situ sol-gel chemistry. Antibacterial nanorods of CQDs-ZnO had strong antibacterial activity under visible light irradiation, and a concentration of 0.1 mg/L was able to kill more than 96% of bacteria...
July 1, 2019: Journal of Nanoscience and Nanotechnology
Harleen Kaur
The fluorescence labeling of aptamers is a useful technology for aptamer tracking and imaging on the cells. The aptamer SL₂-B, against the heparin binding domain (HBD) of VEGF165 protein, was linked to QDs, producing the QD-SL₂-B aptamer conjugate. The QDs and the QD-aptamer conjugate were characterized and photobleaching effect was studied prior to the cellular incubation. Fluorescence imaging showed that the QD-SL₂-B aptamer conjugate could specifically recognize Hep G2 liver cancer cells and is taken up by the cells without addition of any external transfecting or cell permeabilizing agent...
July 1, 2019: Journal of Nanoscience and Nanotechnology
Zhiqiang Ji, Enkeleda Dervishi, Stephen K Doorn, Milan Sykora
Electronic structure of a series of bottom-up synthesized GQDs smaller than 2 nm was investigated by ensemble level spectro-electrochemistry, yielding insights not available previously from ensemble studies. The results show that for the strongly confined GQDs the dependence of the band gap on the GQD size deviates from the prediction of the standard Dirac fermion model, but agrees well with the models explicitly accounting for the electron-electron interactions. The HOMO/LUMO energy levels are found to be distributed nearly symmetrically around the 0V value vs...
February 14, 2019: Journal of Physical Chemistry Letters
D Bharathi, R Hari Krishna, B Siddlingeshwar, Darshan Devang Divakar, Abdulaziz Abdullah Alkheraif
In spite copper oxide being one of the essential micronutrient, copper oxide in its nano size is found to be toxic in nature; this instigates for the detection of copper oxides in trace levels. In the present study, we demonstrate simple cost effective detection method for CuO/Cu2 O using carbon quantum dots (CQD) by fluorescence quenching technique. CuO/Cu2 O nanoparticles are synthesised by mere variation of fuel ratio by solution combustion technique. The resulting oxides are characterized by various analytical and spectroscopic techniques...
February 4, 2019: Journal of Hazardous Materials
Chenghao Bi, Shixun Wang, Qiang Li, Stephen V Kershaw, Jianjun Tian, Andrey L Rogach
All-inorganic perovskite quantum dots (QDs) have emerged as potentially promising materials for lighting and displays, but their poor thermal stability restricts their practical application. In addition, optical characteristics of the blue-emitting CsPbX3 QDs lag behind their red and green emitting counterparts. Herein, we addressed these two issues by doping divalent Cu2+ ions into the perovskite lattice to form CsPb1-xCuxX3 QDs. Extended X-ray absorption fine structure (EXAFS) measurements reveal that doping smaller Cu2+ guest ions induces a lattice contraction and eliminates halide vacancies, which leads to an increased lattice formation energy and improved short-range order of the doped perovskite QDs...
February 14, 2019: Journal of Physical Chemistry Letters
Yueli Liu, Haoran Wang, Keqiang Chen, Tingqiang Yang, Shuang Yang, Wen Chen
Novel CuSbS2 quantum dots (QDs)/reduced graphene oxide (rGO) composites are self-assembled via a hot injection method, and CuSbS2 QDs exhibit a nearly mono-dispersion on rGO surface. The gas sensors based on CuSbS2 QDs/rGO composites show the relatively good gas responses towards NH3 with an outstanding detection limit of 500 ppb and average response time of 50 seconds at room temperature, and the visible light illumination is proven to further promote the sensing performance of the composites. The study of sensing mechanism reveals that the acidic sites on the surface play an extremely important role in NH3 adsorption of the composites, and the reaction between NH3 molecules and the pre-adsorbed oxygen ions finally leads to the generation of NO molecules...
February 14, 2019: ACS Applied Materials & Interfaces
Pedro H de Oliveira Neto, João P C C Rodrigues, Leonardo E de Sousa, Ricardo Gargano, Wiliam F da Cunha
In this work, we investigate the adsorption process of CO2 in graphene quantum dots from the electronic structure and spectroscopic properties point of view. We discuss how a specific doping scheme could be employed to further enhance the adsorbing properties of the quantum dots. This is evaluated by considering the depth of the potential well, the spectroscopic constants, and the lifetime of the compound. Electronic structure calculations are carried out in the scope of the density functional theory (DFT), whereas discrete variable representation (DVR) and Dunham methodologies are employed to obtain spectroscopic constants and hence the lifetimes of the systems...
February 14, 2019: Journal of Molecular Modeling
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