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Quantum dot

Pan Deng, Li-Qiang Lu, Wei-Cheng Cao, Xi-Ke Tian
The phosphorescent l-cysteine modified manganese-doped zinc sulfide quantum dots (l-cys-MnZnS QDs) was developed for a highly sensitive detection of permanganate anions (MnO4(-)). l-cys-MnZnS QDs, which were easily synthesized in aqueous media using safe and low-cost materials, can emit intense phosphorescence even though the solution was not deoxygenated. However, the phosphorescence of l-cys-Mn-ZnS QDs was strongly quenched by MnO4(-) ascribed to the oxidation of l-cys and the increase of surface defects on l-cys-MnZnS QDs...
October 19, 2016: Spectrochimica Acta. Part A, Molecular and Biomolecular Spectroscopy
Damián Rodríguez Sartori, Cristian R Lillo, Juan J Romero, María Laura Dell Arciprete, Alejandro Miñán, Mónica Fernández Lorenzo de Mele, Mónica C Gonzalez
Grafting of polyethylene glycol (PEG) to ultrasmall photoluminescent silicon dots (SiDs) is expected to improve and expand the applications of these particles to aqueous environments and biological systems. Herein we report a novel one-pot synthesis of robust, highly water compatible PEG-coated SiDs (denoted as PEG-SiDs) of (3.3 ± 0.5) nm size. The nanoparticles' synthesis is based on the liquid phase oxidation of magnesium silicide using PEG as reaction media and leading to high PEG density grafting. PEG-SiDs enhanced photophysical, photosensitising, and solution properties in aqueous environments are described and compared to those of 2 nm size PEG-coated SiDs with low PEG density grafting (denoted as PEG-NHSiDs) obtained from a multistep synthesis strategy...
October 24, 2016: Nanotechnology
Lina G AbdulHalim, Zahra Hooshmand, Manas R Parida, Shawkat M Aly, Duy Le, Xin Zhang, Talat S Rahman, Matthew Pelton, Yaroslav Losovyj, Peter A Dowben, Osman M Bakr, Omar F Mohammed, Khabiboulakh Katsiev
Noble metal nanoclusters (NCs) play a pivotal role in bridging the gap between molecules and quantum dots. Fundamental understanding of the evolution of the structural, optical, and electronic properties of these materials in various environments is of paramount importance for many applications. Using state-of-the-art spectroscopy, we provide the first decisive experimental evidence that the structural, electronic, and optical properties of Ag44(MNBA)30 NCs can now be tailored by controlling the chemical environment...
October 24, 2016: Inorganic Chemistry
Ying Zhao, Xiangxing Xu, Xiaozeng You
Organic-inorganic perovskite materials, typically methylammonium lead trihalide (MAPbX3: MA = methylammonium; X = Br, I), are recently attract enormous attention for their distinguished photo-electronic properties. The control of morphology, composition and dispersability of MAPbX3 perovskite nanocrystals is crucial for the property tailoring and still a major challenge. Here we report the synthesis of colloidal MAPbBrxI3-x(0 ≤ x ≤ 3) nanocrystals at room temperature by using alkyl carboxylate as capping ligands...
October 24, 2016: Scientific Reports
Eunkeu Oh, Alan L Huston, Andrew Shabaev, Alexander Efros, Marc Currie, Kimihiro Susumu, Konrad Bussmann, Ramasis Goswami, Fredrik K Fatemi, Igor L Medintz
Luminescent gold nanocrystals (AuNCs) are a recently-developed material with potential optic, electronic and biological applications. They also demonstrate energy transfer (ET) acceptor/sensitization properties which have been ascribed to Förster resonance energy transfer (FRET) and, to a lesser extent, nanosurface energy transfer (NSET). Here, we investigate AuNC acceptor interactions with three structurally/functionally-distinct donor classes including organic dyes, metal chelates and semiconductor quantum dots (QDs)...
October 24, 2016: Scientific Reports
Ting Liu, Jiang Xue Dong, Shi Gang Liu, Na Li, Shu Min Lin, Yu Zhu Fan, Jing Lie Lei, Hong Qun Luo, Nian Bing Li
A stable silver nanoparticles/carbon quantum dots (Ag/CQDs) composite was prepared by using CQDs as reducing and stabilizing agent. The CQDs synthesized with polyethyleneimine (PEI) showed an extraordinary reducibility. When Hg(2+) was presented in the Ag/CQDs composite solution, a color change from yellow to colorless was observed, accompanied by a shift of surface plasmon resonance (SPR) band and decrease in absorbance of the Ag/CQDs composite. On the basis of the further studies on TEM, XPS and XRD analysis, the possible mechanism is attributed to the formation of a silver-mercury amalgam...
October 17, 2016: Journal of Hazardous Materials
Tao Le, Yong Xie, Liqian Zhu, Lei Zhang
To monitor the levels of furazolidone in edible animal tissues, a fluorescent sensor was developed for the determination of 3-amino-2-oxazolidinone (AOZ), the metabolite of furazolidone, featuring an immunochromatographic test strip assay (ITSA) integrated with a quantum dot (QD) label. The optimal QD-based ITSA sensor exhibits good dynamic linear detection for AOZ over the range of 0.1 to 100 μg/L, with a 50% inhibitory concentration (IC50) of 1.06 μg/L. The decision limit and the detection capability were 0...
October 22, 2016: Journal of Agricultural and Food Chemistry
Mona M A Abdel-Mottaleb, Alf Lamprecht
Recently, a selective preferential accumulation of polymeric nanoparticles (in the size range around 100nm) has been observed in the follicular system of dermatitis skin. The present investigation aimed at clearly investigating the effect of irritant contact dermatitis on the barrier permeability for colloidal systems below this size range, namely quantum dots and hydrophilic macromolecules. Irritant dermatitis was induced in mice and the penetrability of quantum dots (5nm) and hydrophilic dextran molecules has been tracked in both healthy and inflamed skin using confocal laser scanning microscopy...
October 19, 2016: International Journal of Pharmaceutics
Shuyun Zhu, Lei He, Fang Zhang, Mengyuan Li, Shulin Jiao, Yan Li, Mengyuan Chen, Xian-En Zhao, Hua Wang
A highly sensitive fluorimetric assay has been developed for the evaluation of glutathione reductase (GR) activity and the screening of its inhibitors by using carbon quantum dots (CQDs) as the signal reporter. The detection mechanism is based on the following facts: (1) the fluorescence of CQDs can be quenched by Hg(II) through the strong CQDs-Hg(II) coordination; (2) GR can catalyze the reduction of oxidized glutathione (GSSG) into reduced glutathione (GSH), so that the fluorescence recovery of CQDs would take place resulting from the strong GSH-Hg(II) interaction; (3) GR can lose its catalytic reduction of GSSG in the presence of its inhibitors, which will inhibit the recovery of the quenched fluorescence of CQDs...
December 1, 2016: Talanta
Yanhong Ma, Ziang Zhang, Yueling Xu, Ming Ma, Bo Chen, Lin Wei, Lehui Xiao
In this work, we demonstrated a convenient and green strategy for the synthesis of bright and water-soluble carbon dots (CDs) by carbonizing sodium citrate and glutathione together in a hydrothermal method for the first time. Without post surface modification, the as-synthesized CDs display fluorescence quantum yield (QY) as high as 21.03% and show superior stability not only in concentrated salt solutions but also in neutral and alkaline media. The probe exhibits selective and sensitive recognition capability towards mercury ion (Hg(2+)) in aqueous solution...
December 1, 2016: Talanta
Weidan Na, Qing Liu, Bowen Sui, Tianyu Hu, Xingguang Su
A novel and effective fluorescence strategy was developed for sensitive and selective detection of acid phosphatase (ACP). A förster resonance energy transfer (FRET) biosensor was established by attaching nile red (NR) to graphene quantum dots (GQDs) via lecithin/β-Cyclodextrin (lecithin/β-CD) complex as the linker. The introduction of lecithin/β-CD would brought GQDs-NR pair close enough through both electrostatic interaction and hydrophobic interaction, thereby making the FRET occur and thus resulting in the fluorescence quenching of GQDs (donor) and meanwhile the fluorescence enhancement of NR (acceptor)...
December 1, 2016: Talanta
Yaqi Li, Li Sun, Qian Liu, En Han, Nan Hao, Liuping Zhang, Shanshan Wang, Jianrong Cai, Kun Wang
A methodology for detection of the Cauliflower Mosaic Virus 35S(CaMV35S) promoter was developed to distinguish transgenic from non-transgenic soybean samples by using photoelectrochemical (PEC) biosensor. In this PEC biosensing system, the as-prepared gold nanoparticles-reduced graphene oxide acted as a nanocarrier to immobilize the thiol-functional probe (probe1), and the SiO2@CdTe quantum dots (QDs) core-shell nanoparticles tagged with the amino-functional probe (probe2) acted as signal indicators, respectively...
December 1, 2016: Talanta
Yanying Wang, Xiangyang Yu, Xiaoxue Ye, Kangbing Wu, Tsunghsueh Wu, Chunya Li
Gold nanorods (AuNRs) integrated with ZnCdHgSe near-infrared quantum dots (AuNRs-ZnCdHgSe QDs) were successfully synthesized and characterized by transmission electron microscope, X-ray photoelectron spectroscopy, and X-ray diffraction. A glassy carbon electrode was decorated with the aforementioned AuNRs-ZnCdHgSe QDs nanocomposite, which provides a biocompatible interface for the subsequent immobilization of prostate specific antibody (anti-PSA). After being successively treated with glutaraldehyde vapor and bovine serum albumin solution, a photoelectrochemical immunosensing platform based on anti-PSA/AuNRs-ZnCdHgSe QDs/GCE was established...
November 2, 2016: Analytica Chimica Acta
J S Rojas-Arias, B A Rodríguez, H Vinck-Posada
Dipolaritons are quasiparticles that arise in coupled quantum wells embedded in a microcavity, they are a superposition of a photon, a direct exciton and an indirect exciton. We propose the existence of dipolaritons in a system of two coupled quantum dots inside a microcavity in direct analogy with the quantum well case and find that, despite some similarities, dipolaritons in quantum dots have different properties and can lead to true dark polariton states. We use a finite system theory to study the effects of the magnetic field on the system, including the emission, and find that it can be used as a control parameter of the properties of excitons and dipolaritons, and the overall magnetic behaviour of the structure...
October 21, 2016: Journal of Physics. Condensed Matter: An Institute of Physics Journal
Piotr Stefański
We consider a model of a Josephson junction mediated by a quantum dot. An additional normal electrode coupled to the dot allows its density of states to be probed. The junction is made out of two topological superconducting wires with Majorana end states. The two of them, on each side and in the proximity of the junction, convert into a Dirac fermion inside the dot. It is shown that both the density of states of the dot and the phase-biased current through the junction can exhibit [Formula: see text] periodicity in the superconducting phase difference, when the particle-hole symmetry of the junction is broken...
October 21, 2016: Journal of Physics. Condensed Matter: An Institute of Physics Journal
Takeshi Suzuki, Rohan Singh, Manfred Bayer, Arne Ludwig, Andreas D Wieck, Steven T Cundiff
Coherent control of a strongly inhomogeneously broadened system, namely, InAs self-assembled quantum dots, is demonstrated. To circumvent the deleterious effects of the inhomogeneous broadening, which usually masks the results of coherent manipulation, we use prepulse two-dimensional coherent spectroscopy to provide a size-selective readout of the ground, exciton, and biexciton states. The dependence on the timing of the prepulse is due to the dynamics of the coherently generated populations. To further validate the results, we performed prepulse polarization dependent measurements and confirmed the behavior expected from selection rules...
October 7, 2016: Physical Review Letters
Hamid Reza Samadikhah, Maryam Nikkhah, Saman Hosseinkhani
Two quantum dots (QDs), a green emitter, CdSe and a red emitter, CdSe with ZnS shell are encapsulated into novel liposomes in two different formulations including cationic liposomes. Quantum dots have proven themselves as powerful inorganic fluorescent probes, especially for long-term, multiplexed imaging and detection. Upon delivery into a cell, in endocytic vesicles such as endosomes, their fluorescence is quenched. We have investigated the potential toxic effects, photophysical properties and cell internalization of QDs in new formulation of liposomes as an in vitro vesicle model...
October 21, 2016: Luminescence: the Journal of Biological and Chemical Luminescence
Karen Peynshaert, Stefaan J Soenen, Bella B Manshian, Shareen H Doak, Kevin Braeckmans, Stefaan C De Smedt, Katrien Remaut
: In the last decade the interest in autophagy got an incredible boost and the phenomenon quickly turned into an extensive research field. Interestingly, dysfunction of this cytoplasmic clearance system has been proposed to lie at the root of multiple diseases including cancer. We therefore consider it crucial from a toxicological point of view to investigate if nanomaterials that are developed for biomedical applications interfere with this cellular process. Here, we study the highly promising 'gradient alloyed' quantum dots (QDs) that differ from conventional ones by their gradient core composition which allows for better fluorescent properties...
October 17, 2016: Acta Biomaterialia
Zhong-Xia Wang, Fen-Ying Kong, Wei Wang
Graphene quantum dots-like structures of highly enriched nitrogen-based dual-color single-functional polymer carbon nanosheets (GLNPCNs) with an average diameter as large as 170 nm (~5 layers) are prepared by a facile hydrothermal method. Intermolecular C5H5N5···C5H5N5 or/and C2H5OH chemical polymerization interactions in the liquid state of the peripheral crown ether-like "hole" decorated compound GLNPCNs lead to a fascinating 2D supramolecular polymer architecture, which exhibits near-ultraviolet (NUV) fluorescence, narrow full width at half maximum, and excellent practical application capability...
October 20, 2016: Chemistry: a European Journal
Houcem Maaoui, Florina Teodoresu, Qian Wang, Guo-Hui Pan, Ahmed Addad, Radhouane Chtourou, Sabine Szunerits, Rabah Boukherroub
Perturbations in glucose homeostasis is critical for human health, as hyperglycemia (defining diabetes) leads to premature death caused by macrovascular and microvascular complications. However, the simple and accurate detection of glucose in the blood at low cost remains a challenging task, although it is of great importance for the diagnosis and therapy of diabetic patients. In this work, carbon quantum dots decorated with copper oxide nanostructures (CQDs/Cu₂O) are prepared by a simple hydrothermal approach, and their potential for electrochemical non-enzymatic glucose sensing is evaluated...
October 18, 2016: Sensors
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