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Quantum dot

Hanbing Rao, Yao Gao, Hongwei Ge, Zhaoyi Zhang, Xin Liu, Yan Yang, Yaqin Liu, Wei Liu, Ping Zou, Yanying Wang, Xianxiang Wang, Hua He, Xianying Zeng
This work established a fluorescence approach for detecting ascorbic acid (AA) based on Cu-ZnCdS quantum dots (Cu-ZnCdS QDs) and α-MnO2 nanorods. Cu-ZnCdS QDs and α-MnO2 nanorods were characterized by high-resolution transmission electron microscopy (HRTEM), fluorescence spectroscopy, inductively coupled plasma optical emission spectroscopy (ICP-OES) and X-ray diffraction (XRD). In the presence of α-MnO2 nanorods, the fluorescence of Cu-ZnCdS QDs was greatly quenched through the inner filter effect (IFE)...
June 23, 2017: Analytical and Bioanalytical Chemistry
Hao Xu, Hjalmar Brismar, Ying Fu
We carefully characterized the fluorescence blinking of single colloidal CdSe-CdS/ZnS core-multishell quantum dots (QDs) with different surface modifications, including octadecylamine (ODA) coated QDs dispersed in chloroform, aqueous 3-mercaptopropionic acids (3MPA) coated QDs in HEPES solution treated by Ca(2+) ions and ethylene glycol tetraacetic acid (EGTA, Ca(2+) chelator), and aqueous 3MPA-QDs treated by glycerol. It was found that the on- and off-state probability density distributions displayed different rules...
June 16, 2017: Journal of Colloid and Interface Science
Antoine Reigue, Jake Iles-Smith, Fabian Lux, Léonard Monniello, Mathieu Bernard, Florent Margaillan, Aristide Lemaitre, Anthony Martinez, Dara P S McCutcheon, Jesper Mørk, Richard Hostein, Valia Voliotis
We investigate the temperature dependence of photon coherence properties through two-photon interference (TPI) measurements from a single quantum dot (QD) under resonant excitation. We show that the loss of indistinguishability is related only to the electron-phonon coupling and is not affected by spectral diffusion. Through these measurements and a complementary microscopic theory, we identify two independent separate decoherence processes, both of which are associated with phonons. Below 10 K, we find that the relaxation of the vibrational lattice is the dominant contribution to the loss of TPI visibility...
June 9, 2017: Physical Review Letters
Samir Bounouar, Max Strauß, Alexander Carmele, Peter Schnauber, Alexander Thoma, Manuel Gschrey, Jan-Hindrik Schulze, André Strittmatter, Sven Rodt, Andreas Knorr, Stephan Reitzenstein
The two-photon dressing of a "three-level ladder" system, here the ground state, the exciton, and the biexciton of a semiconductor quantum dot, leads to new eigenstates and allows one to manipulate the time ordering of the paired photons without unitary postprocessing. We show that, after spectral postselection of the single dressed states, the time ordering of the cascaded photons can be removed or conserved. Our joint experimental and theoretical study demonstrates the high potential of a "ladder" system to be a versatile source of orthogonally polarized, bunched or antibunched pairs of photons...
June 9, 2017: Physical Review Letters
Long Wu, Fan Ding, Wenmin Yin, Jing Ma, Biru Wang, Axiu Nie, Heyou Han
Aflatoxin B1 (AFB1), one of the most toxic chemical carcinogens, has been widely studied. It remains challenging to develop simple, accurate and sensitive analytical methods for the detection of AFB1 in food matrices. In this work, based on dual-signaling strategy, a ratiometric aptasensor was designed and verified for the accurate and sensitive detection of AFB1. The electrochemical method was first used as a model to verify the specific interaction between AFB1 and the aptamer, in which ferrocene (Fc) and methylene blue (MB) anchored DNA sequences were acted as dual signals...
June 23, 2017: Analytical Chemistry
Mark Friesen, Joydip Ghosh, M A Eriksson, S N Coppersmith
Quantum computing promises significant speed-up for certain types of computational problems. However, robust implementations of semiconducting qubits must overcome the effects of charge noise that currently limit coherence during gate operations. Here we describe a scheme for protecting solid-state qubits from uniform electric field fluctuations by generalizing the concept of a decoherence-free subspace for spins, and we propose a specific physical implementation: a quadrupole charge qubit formed in a triple quantum dot...
June 23, 2017: Nature Communications
Mariana P Cabrera, Paulo E Cabral Filho, Camila M C M Silva, Rita M Oliveira, Carlos F G C Geraldes, M Margarida C A Castro, Benilde F O Costa, Marta S C Henriques, José A Paixão, Luiz B Carvalho, Beate S Santos, Fernando Hallwass, Adriana Fontes, Giovannia A L Pereira
This work reports on highly fluorescent and superparamagnetic bimodal nanoparticles (BNPs) obtained by a simple and efficient method as probes for fluorescence analysis and/or contrast agents for MRI. These promising BNPs with small dimensions (ca. 17 nm) consist of superparamagnetic iron oxide nanoparticles (SPIONs) covalently bound with CdTe quantum dots (ca. 3 nm). The chemical structure of the magnetic part of BNPs is predominantly magnetite, with minor goethite and maghemite contributions, as shown by Mössbauer spectroscopy, which is compatible with the x-ray diffraction data...
July 14, 2017: Nanotechnology
Shuhua Li, Shixin Zhou, Yunchao Li, Xiaohong Li, Jia Zhu, Louzhen Fan, Shihe Yang
IR780 iodide (IR780) is recognized as an effective theranostic agent for simultaneous near-infrared (NIR) fluorescence imaging and photothermal therapy (PTT). However, the rigid chloro-cyclohexenyl ring makes IR780 insoluble in almost all pharmaceutically acceptable solvents, which inevitably limits its clinical application. We report folic acid (FA)-functionalized graphene quantum dots (GQDs-FA) containing a large and intact sp2-domain with carboxyl groups around the edge. Such GQDs-FA possess exceptionally high loading capacity for IR780 via strong π-π stacking interactions, and the water solubility of IR780 is improved by over 2400-fold after loading onto GQDs-FA (IR780/GQDs-FA)...
June 23, 2017: ACS Applied Materials & Interfaces
Feng Li, Tianyu Li, Chenxing Sun, Jiahao Xia, Yang Jiao, Huaping Xu
Heteroatom doping is an effective way to adjust the fluorescent properties of carbon quantum dots. However, selenium-doped carbon dots have rarely been reported even though selenium has unique chemical properties like redox-responsive properties owing to its special electronegativity. Herein, a facile and high-output strategy to fabricate selenium-doped carbon quantum dots (Se-CQDs) with green fluorescence (quantum yield 7.6 %) is developed through the hydrothermal treatment of selenocystine under mild conditions...
June 23, 2017: Angewandte Chemie
M Calic, C Jarlov, P Gallo, B Dwir, A Rudra, E Kapon
A system of two site-controlled semiconductor quantum dots (QDs) is deterministically integrated with a photonic crystal membrane nano-cavity. The two QDs are identified via their reproducible emission spectral features, and their coupling to the fundamental cavity mode is established by emission co-polarization and cavity feeding features. A theoretical model accounting for phonon interaction and pure dephasing reproduces the observed results and permits extraction of the light-matter coupling constant for this system...
June 22, 2017: Scientific Reports
Diego Mendez-Gonzalez, Enrique Lopez-Cabarcos, Jorge Rubio-Retama, Marco Laurenti
In recent years, considerable efforts have been done to better understand the peculiar emission properties of upconverting materials due to their widespread applications in different and important technological fields such as upconversion-based photoactivated cancer therapies, photoactivated drug-delivery, magnetic resonance imaging contrast agents, bioimaging. However, one of the most promising applications of upconverting materials concerns the field of sensing, due to their unique emission properties. In fact, the minimal autofluorescence, blinking, photo-bleaching, and high photostability makes them an excellent alternative to organic dyes or quantum dots...
June 10, 2017: Advances in Colloid and Interface Science
Wei Tao, Xiaoyuan Ji, Xiaoding Xu, Mohammad Ariful Islam, Zhongjun Li, Si Chen, Phei Er Saw, Han Zhang, Zameer Bharwani, Zilei Guo, Jinjun Shi, Omid Farokhzad
Photothermal therapy (PTT) has shown significant potential for cancer therapy. However, developing nanomaterials (NMs)-based photothermal agents (PTAs) with satisfactory photothermal conversion efficacy (PTCE) and biocompatibility remains a key challenge. Herein, a new generation of PTAs based on two-dimensional (2D) antimonene quantum dots (AMQDs) was developed by a novel liquid exfoliation method. Surface modification of AMQDs with polyethylene glycol (PEG) significantly enhanced both biocompatibility and stability in physiological medium...
June 22, 2017: Angewandte Chemie
Zhenwei Ren, Jiankun Sun, Hui Li, Peng Mao, Yuanzhi Wei, Xinhua Zhong, Jinsong Hu, Shiyong Yang, Jizheng Wang
Due to their wide tunable bandgaps, high absorption coefficients, easy solution processabilities, and high stabilities in air, lead sulfide (PbS) quantum dots (QDs) are increasingly regarded as promising material candidates for next-generation light, low-cost, and flexible photodetectors. Current single-layer PbS-QD photodetectors suffer from shortcomings of large dark currents, low on-off ratios, and slow light responses. Integration with metal nanoparticles, organics, and high-conducting graphene/nanotube to form hybrid PbS-QD devices are proved capable of enhancing photoresponsivity; but these approaches always bring in other problems that can severely hamper the improvement of the overall device performance...
June 22, 2017: Advanced Materials
Dandan Chen, Qiong Li, Zihui Meng, Lei Guo, Ying Tang, Zhihe Liu, Shengyan Yin, Weiping Qin, Zhen Yuan, Xuanjun Zhang, Changfeng Wu
Stem cell therapy holds promise for treatment of intractable diseases and injured organs. For clinical translation, it is pivotal to understand the homing, engraftment, and differentiation processes of stem cells in a living body. Here we report near-infrared (NIR) fluorescent semiconductor polymer dots (Pdots) for bright labeling and tracking of human mesenchymal stem cells (MSCs). The Pdots exhibit narrow-band emission at 775 nm with a quantum yield of 22%, among the highest value for various NIR probes. The Pdots together with a cell penetrating peptide are able to track stem cells over two weeks without disturbing their multipotent properties, as confirmed by the analyses on cell proliferation, differentiation, stem-cell markers, and immunophenotyping...
2017: Theranostics
Chenghui Xia, Johannes D Meeldijk, Hans C Gerritsen, Celso de Mello Donega
Copper indium sulfide (CIS) quantum dots (QDs) are attractive as labels for biomedical imaging, since they have large absorption coefficients across a broad spectral range, size- and composition-tunable photoluminescence from the visible to the near-infrared, and low toxicity. However, the application of NIR-emitting CIS QDs is still hindered by large size and shape dispersions and low photoluminescence quantum yields (PLQYs). In this work, we develop an efficient pathway to synthesize highly luminescent NIR-emitting wurtzite CIS/ZnS QDs, starting from template Cu2-x S nanocrystals (NCs), which are converted by topotactic partial Cu(+) for In(3+) exchange into CIS NCs...
June 13, 2017: Chemistry of Materials: a Publication of the American Chemical Society
Ivan Shtepliuk, Nuala M Caffrey, Tihomir Iakimov, Volodymyr Khranovskyy, Igor A Abrikosov, Rositsa Yakimova
The promise of graphene and its derivatives as next generation sensors for real-time detection of toxic heavy metals (HM) requires a clear understanding of behavior of these metals on the graphene surface and response of the graphene to adsorption events. Our calculations herein were focused on the investigation of the interaction between three HMs, namely Cd, Hg and Pb, with graphene quantum dots (GQDs). We determine binding energies and heights of both neutral and charged HM ions on these GQDs. The results show that the adsorption energy of donor-like physisorbed neutral Pb atoms is larger than that of either Cd or Hg...
June 21, 2017: Scientific Reports
Chengfei Zhao, Kangying Wang, Qihong Cai, Haijian Tu, Linghong Pan, Liumin Yu
Nitrogen-doped carbon quantum dots (N-CQDs) with citric acid and ethylenediamine as raw materials were synthesized by an efficient one-step strategy. The N-CQDs showed a special property that the fluorescence was quenched by Fe(3+). The quenched fluorescence of N-CQDs could be recovered by glutathione (GSH). Therefore, a "signal-on" fluorescent sensor was developed to detect GSH. The fluorescent sensor could favorably avoid the interference of ascorbic acid, dopamine, glucose, oxidized glutathione and other amino acids in the detecting process of GSH...
June 21, 2017: Preparative Biochemistry & Biotechnology
Ankit Jain, Oleksandr Voznyy, Marek Korkusinski, Pawel Hawrylak, Edward H Sargent
It has previously been found that Auger processes can lead to femtosec- ond carrier trapping in quantum dots, limiting their performance in opto- electronic applications that rely on radiative recombination. Here, using atomistic simulations, we investigate whether a shell can protect carriers from Auger-assisted trapping. For these studies we investigate CdSe/CdS core-shell quantum dots having total diameters reaching up to 10 nm. We find trapping lifetimes as fast as 1 ps for 2 nm shells, and we report that shells as thick as 6 nm are required to suppress trapping fully...
June 21, 2017: Journal of Physical Chemistry Letters
Hongmei Yang, Yan Zhang, Li Li, Lina Zhang, Feifei Lan, Jinghua Yu
This paper describes the design and construction of sudoku-like lab-on-paper platform, in which dual enhancement of reaction intermediates strategy was incorporated for multiplexed competitive electrochemiluminescence (ECL) cyto-assay. Benefit from the sudoku-like structure, integrated multifunction were obtained on such elaborately devised platform, including specific reagents storage, multiple samples immobilization, residual automatic washing, and signal collection. By utilizing semicarbazide (SE) and silver nanoparticles (AgNPs) as dual enhancers, more ECL intermediates could be obtained in the graphene quantum dots (GQDs) and peroxydisulfate system, resulting in the production of more excited state GQDs to emit light...
June 21, 2017: Analytical Chemistry
Jin Zhang, Junkai Ma, Fangdan Shi, Demei Tian, Haibing Li
How to convert the weak chiral-interaction into the macroscopic properties of materials remains a huge challenge. Here, this study develops highly fluorescent, selectively chiral-responsive liquid quantum dots (liquid QDs) based on the hydrophobic interaction between the chiral chains and the oleic acid-stabilized QDs, which have been designated as (S)-1810-QDs. The fluorescence spectrum and liquidity of thermal control demonstrate the fluorescence properties and the fluidic behavior of (S)-1810-QDs in the solvent-free state...
June 21, 2017: Advanced Materials
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