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Quantum dot

Jiri Kudr, Lukas Richtera, Kledi Xhaxhiu, David Hynek, Zbynek Heger, Ondrej Zitka, Vojtech Adam
Here, we aimed our attention at the synthesis of carbon dots (C-dots) with the ability to interact with DNA to suggest an approach for the detection of DNA damage. Primarily, C-dots modified with amine moieties were synthesized using the one-step microwave pyrolysis of citric acid in the presence of diethylenetriamine. The C-dots showed strong photoluminescence with a quantum yield of 4%. In addition, the C-dots (2.8±0.8nm) possessed a good colloidal stability and exhibited a positive surface charge (ζ=36mV) at a neutral pH...
February 9, 2017: Biosensors & Bioelectronics
Dong Li, Hu Xu, Dan Li, Yuhong Wang
Since controlling hydrogen ion concentration (i.e. pH) is fairly important in various fields, developing a facile pH detection method is highly desired. Owing to the superior optical properties, semiconductor quantum dots (QDs) have been developed as a promising alternative for organic fluorophores in fluorescence analysis. In this study, a hydrophilic p-aminothiophenol (pATP) capped CdSe/ZnS QDs (denoted as pATP-QDs) as a selective "turn-on" fluorescence probe for pH in aqueous media is reported. The pATP-QDs probe easily obtained via ligand exchange are characterized by various analytic techniques including ultraviolet-visible, fourier transform infrared, fluorescence, time-resolved fluorescence spectroscopies, and transmission electron microscope etc...
May 1, 2017: Talanta
Ojodomo J Achadu, Tebello Nyokong
The fabrication of maleimide-derivatized graphene quantum dots (M-GQDs) and zinc phthalocyanine (2) as novel sensor probes for the selective detection of biothiols (cysteine, homocysteine or glutathione) through the rapid and specific Michael addition reaction between biothiols and the maleimide-derivatized probes is presented in this study. GQDs directly functionalized with maleimide units (M-GQDs) were synthesized and deployed for biothiols recognition following the principle of Michael addition. M-GQDs probe was found to be highly sensitive and selective towards biothiols detection in the nanomolar range in aqueous solution and at physiological pH (7...
May 1, 2017: Talanta
Jiahong Pan, Zengyao Zheng, Jianying Yang, Yaoyu Wu, Fushen Lu, Yaowen Chen, Wenhua Gao
A novel fluorescence sensor based on controlling the surface passivation degree of carbon quantum dots (CQDs) was developed for glutathione (GSH) detection. First, we found that the fluorescence intensity of the CQDs which was obtained by directly pyrolyzing citric acid would increased largely after the surface passivation treatment by 1-ethyl-3-(3-dimethylaminopropyl)-carbodiimide (EDC). In the light of this phenomenon, we designed a simple, rapid and selective fluorescence sensor based on the surface passivated CQDs...
May 1, 2017: Talanta
T Konishi, E Clarke, C W Burrows, J J Bomphrey, R Murray, G R Bell
The lateral ordering of arrays of self-assembled InAs-GaAs quantum dots (QDs) has been quantified as a function of growth rate, using the Hopkins-Skellam index (HSI). Coherent QD arrays have a spatial distribution which is neither random nor ordered, but intermediate. The lateral ordering improves as the growth rate is increased and can be explained by more spatially regular nucleation as the QD density increases. By contrast, large and irregular 3D islands are distributed randomly on the surface. This is consistent with a random selection of the mature QDs relaxing by dislocation nucleation at a later stage in the growth, independently of each QD's surroundings...
February 13, 2017: Scientific Reports
Gu Zhang, E Novais, Harold U Baranger
We show that placing a quantum system in contact with an environment can enhance non-Fermi-liquid correlations, rather than destroy quantum effects, as is typical. The system consists of two quantum dots in series with two leads; the highly resistive leads couple charge flow through the dots to the electromagnetic environment, the source of quantum noise. While the charge transport inhibits a quantum phase transition, the quantum noise reduces charge transport and restores the transition. We find a non-Fermi-liquid intermediate fixed point for all strengths of the noise...
February 3, 2017: Physical Review Letters
Hyo-Jun Kim, Min-Ho Shin, Joo-Suc Kim, Se-Eun Kim, Young-Joo Kim
An optically efficient structure was proposed and fabricated to realize high brightness organic light emitting diode (OLED) displays based on a white OLED prepared with the air-gapped bridges on the quantum dot (QD) patterns. Compared with a conventional white OLED display, in our experiments, the optical intensity of the proposed OLED display shows the enhancement of 58.2% in the red color and 16.8% in the green color after applying the air-gapped bridge structure on QD patterns of 20 wt% concentration. This enhancement comes from the two facts that the QD patterns downconvert unnecessary blue or blue/green light to the required green or red light and the air-gapped bridges increase the color conversion efficiency of QDs by optical recycling using total internal reflection (TIR) at the interface...
February 17, 2017: Scientific Reports
J Du, M Zhang, Z Guo, J Chen, X Zhu, G Hu, P Peng, Z Zheng, H Zhang
We fabricate ultrasmall phosphorene quantum dots (PQDs) with an average size of 2.6 ± 0.9 nm using a liquid exfoliation method involving ultrasound probe sonication followed by bath sonication. By coupling the as-prepared PQDs with microfiber evanescent light field, the PQD-based saturable absorber (SA) device exhibits ultrafast nonlinear saturable absorption property, with an optical modulation depth of 8.1% at the telecommunication band. With the integration of the all-fiber PQD-based SA, a continuous-wave passively mode-locked erbium-doped (Er-doped) laser cavity delivers stable, self-starting pulses with a pulse duration of 0...
February 17, 2017: Scientific Reports
Youling He, Jiangling He, Haoran Zhang, Yingliang Liu, Bingfu Lei
Owning to the hydrogen-band interactions, blue-light-emitting luminescent carbon dots (CDs) synthesized by one-pot hydrothermal treatment were successfully assembled into Eu(3+) doped mesoporous aluminas (MAs). Interesting, dual-emissive CDs/MAs co-doped materials with higher quantum yield (QY), long-term stability, mesoporous structure, high thermal stability, and large surface areas were obtained. Furthermore, the obtained CDs/MAs co-doped materials possessed tunable color, and excellent temperature sensitivity due to the existing of energy transfer between CDs and Eu(3+) ion...
February 9, 2017: Journal of Colloid and Interface Science
Chien Y Lin, Jung Y Huang, Leu-Wei Lo
Cell-penetrating peptides (CPPs) can translocate across cell membranes, and thus have great potential for the cellular delivery of macromolecular cargoes. However, the mechanism of this cellular uptake process is not yet fully understood. In this study, a time-lapse single-particle light-sheet microscopy technique was implemented to obtain a parallel visualization of the translocating process of individual human immunodeficiency virus 1 (HIV-1) transactivator of transcription (Tat) peptide conjugated quantum dots (TatP-QDs) in complex cellular terrains...
February 10, 2017: Sensors
Jun-Rong He, Lin Yi, Hua-Mei Li
The self-similar propagation of asymptotic optical beams in semiconductor waveguides doped with quantum dots is reported. The possibility of controlling the shape of output asymptotic optical beams is demonstrated. The analytical results are confirmed by numerical simulations. We give a possible experimental protocol to generate the obtained asymptotic parabolic beams in realistic waveguides. As a generalization to the present work, the self-similar propagation of asymptotic optical beams is proposed in a power-law nonlinear medium...
January 2017: Physical Review. E
Zhen Wu, Jiao Hu, Tao Zeng, Zhi-Ling Zhang, Jianjun Chen, Gary Wong, Xiangguo Qiu, Wenjun Liu, George F Gao, Yuhai Bi, Dai-Wen Pang
The 2014-16 Ebola virus (EBOV) outbreak in West Africa has attracted widespread concern. Rapid and sensitive detection methods are urgently needed for diagnosis and treatment of the disease. Here, we propose a novel method for EBOV detection based on efficient amplification of electroluminescent nanospheres (ENs) coupled with immunomagnetic separation. Uniform ENs are made by embedding abundant amounts of CdSe/ZnS quantum dots (QDs) into copolymer nanospheres through simple ultrasound. Compared to QDs, ENs can enhance electroluminescence (ECL) signals by approximately 85-fold, achieving a signal-to-background ratio high enough for EBOV detection...
February 7, 2017: Analytical Chemistry
Song Wang, Yajun Zhang, Guangsheng Pang, Yingwei Zhang, Shaojun Guo
The design of graphene quantum dots (GQDs)-aptamer bioconjugates as the new sensing platform is very important for developing high-sensitivity fluorescent biosensors; however, achieving new bioconjugates is still a great challenge. Herein, we report the development of a new high-sensitivity fluorescent aptasensor for the detection of ochratoxin A (OTA) based on tuning aggregation/disaggregation behavior of GQDs by structure-switching aptamers. The fluorescence sensing process for OTA detection involved two key steps: (1) cDNA-aptamer (cDNA, complementary to part of the OTA aptamer) hybridization induced the aggregation of GQD (fluorescence quenching) after cDNA was added into the GQDs-aptamer bioconjugate solution, and (2) the target of OTA triggered disaggregation of GQD aggregates (fluorescence recovery)...
February 7, 2017: Analytical Chemistry
Bin Yang, Beibei Chen, Man He, Bin Hu
We report a sensitive, selective, simple, and reliable magnetic immunoassay protocol for detection and imaging of HepG2 cells. After being captured by Cs-doped multicore magnetic nanoparticles (MMNPs), HepG2 cells were labeled by CdSe/ZnS quantum dots (QDs), which could be visualized by fluorescence imaging using the photoluminescence property of QDs, and subsequently, they can be counted by inductively coupled plasma mass spectrometry (ICP-MS) with Cd/Cs as elemental tag. Because of the superior photoluminescence properties and the large quantities of detectable Cd atoms contained in the QDs core, QDs play a dual function role in this assay, making the method easier and more comprehensive than other similar approaches...
February 7, 2017: Analytical Chemistry
Jacob Katriel, H E Montgomery
Hund's rules apply to pairs of atomic states which, in the limit of weak interelectronic repulsion, belong to a common configuration. We examine the asymptotic behavior of the energy difference between states belonging to such pairs (ΔE) as a function of the nuclear charge (Z) at both Z→∞ (ignoring relativistic effects) and at Z→Zc, where Zc is the critical charge below which the outermost electron is not bound. We find that the ratio ΔEZ(2) is non-monotonic, having a maximum at some intermediate value of Z...
February 14, 2017: Journal of Chemical Physics
Si Zhu, Bei Shi, Yating Wan, Evelyn L Hu, Kei May Lau
InAs/InAlGaAs quantum dot active layers within microcavity resonators offer the potential of ultra-low-threshold lasing in the 1.55 μm telecom window. Here, we demonstrate the first quantum dot microdisk laser with single-mode emission around 1.55 μm under continuous-wave optical pumping up to 170 K. The extracted threshold is as low as 32 μW at 77 K. This result lays the foundation of an alternative to quantum-well microlasers for low-threshold and highly compact monolithically integratable light emitting sources in fiber communication...
February 15, 2017: Optics Letters
Weiqiang Xie, Thilo Stöferle, Gabriele Rainò, Tangi Aubert, Suzanne Bisschop, Yunpeng Zhu, Rainer F Mahrt, Pieter Geiregat, Edouard Brainis, Zeger Hens, Dries Van Thourhout
Hybrid silicon nitride (SiN)-quantum-dot (QD) microlasers coupled to a passive SiN output waveguide with a 7 µm diameter and a record-low threshold density of 27 µJ cm(-2) are demonstrated. A new design and processing scheme offers long-term stability and facilitates in-depth QD material and device characterization, thereby opening new paths for optical communication, sensing, and on-chip cavity quantum optics based on colloidal QDs.
February 15, 2017: Advanced Materials
Abdolraouf Samadi-Maybodi, Ali Tilehkan, Mohammad-Rasool Sadeghi-Maleki
A simple, sensitive and selective chemiluminescence method is proposed for the determination of Acetylcysteine and Diclofenac in pharmaceutical samples. The method is based on the measuring light intensity of NaHCO3-H2O2 @ CdS chemiluminescence system in the absence and presence of Acetylcysteine and Diclofenac. It was found that the intensity of chemiluminescence is increased by addition of acetylcysteine while the light intensity is decreased with increasing diclofenac concentration. The CdS quantum dots nanoparticles were characterized by X-ray diffraction (XRD), Scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR), UV-Vis spectrophotometry and Fluorescence spectroscopy...
February 14, 2017: Journal of Fluorescence
Zijie Xu, Teng Li, Fayin Zhang, Xiaodan Hong, Shuyao Xie, Meidan Ye, Wenxi Guo, Xiangyang Liu
The rapid development of modern electronics has given rise to a higher demand for flexible and wearable energy sources. Flexible transparent conducting electrodes (TCEs) are one of the essential components of flexible/wearable thin-film solar cells (SCs). In this regard, we present highly transparent and conducting CuS-nanosheet (NS) networks with an optimized sheet resistance (Rs) as low as 50 Ω sq(-1) at 85% transmittance as a counter electrode (CE) for flexible quantum-dot solar cells (QDSCs). The CuS NS network electrode exhibits remarkable mechanical flexibility under bending tests compared to traditional ITO/plastic substrates and sputtered CuS films...
February 15, 2017: Nanoscale
Gil Aizik, Nir Waiskopf, Majd Agbaria, Yael Levi-Kalisman, Uri Banin, Gershon Golomb
Quantum Dots (QDs), semiconductor nanocrystals, are fluorescent nanoparticles of growing interest as an imaging tool of a diseased tissue. However, a major concern is their biocompatibility, cytotoxicity and fluorescence instability in biological milieu, impeding their use in biomedical applications, in general, and for inflammation imaging, in particular. In addition, for an efficient fluorescent signal at the desired tissue, and avoiding systemic biodistribution and possible toxicity, targeting is desired...
February 14, 2017: ACS Nano
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