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Quantum dots

Wojciech Rudno-Rudziński, Marcin Syperek, Janusz Andrzejewski, Ernest Rogowicz, Gadi Eisenstein, Sven Bauer, Vitalii I Sichkovskyi, Johann P Reithmaier, Grzegorz Sęk
We investigate a hybrid system containing an In0.53 Ga0.47 As quantum well (QW), separated by a thin 2 nm In0.53 Ga0.23 Al0.24 As barrier from 1.55 µm emitting InAs quantum dots (QDs), grown by molecular beam epitaxy on an InP substrate. Photoreflectance and photoluminescence (PL) spectroscopies are used to identify optical transitions in the system, with support of 8-band kp modelling. The main part of the work constitute the measurements and analysis of thermal quenching of PL for a set of samples with different QW widths (3-6 nm)...
August 17, 2018: Scientific Reports
Jean de Dieu Habimana, Jian Ji, Fuwei Pi, Eric Karangwa, Jiadi Sun, Wei Guo, Fangchao Cui, Jingdong Shao, Claudine Ntakirutimana, Xiulan Sun
Herein, a novel class-specific artificial receptor-based on molecularly imprinted polymer (MIP)-coated quantum dots (QDs@MIP) was synthesized, characterized, and used for the detection and quantification of the bacterial quorum signaling molecules N-acyl-homoserine lactones (AHLs), a class of autoinducers from Gram-negative bacteria. The QDs@MIP was prepared by surface imprinting technique under controlled conditions using CdSe/ZnS QDs as the signal transducing material. The synthesis of the QDs@MIP was characterized by transmission electron microscopy, scanning electron microscopy, Fourier transform infrared spectroscopy, X-ray diffraction analysis, and fluorescence spectroscopy...
November 15, 2018: Analytica Chimica Acta
Chee Fai Fong, Yasutomo Ota, Satoshi Iwamoto, Yasuhiko Arakawa
Light with nonzero orbital angular momentum (OAM) or twisted light is promising for quantum communication applications such as OAM-entangled photonic qubits. Methods and devices for the conversion of the photonic OAM to photonic spin angular momentum (SAM), as well as for the photonic SAM to electronic SAM transformation are known but the direct conversion between the photonic OAM and electronic SAM is not available within a single device. Here, we propose a scheme which converts photonic OAM to electronic SAM and vice versa within a single nanophotonic device...
August 6, 2018: Optics Express
Feng Gao, Chuan-Lu Yang, Mei-Shan Wang, Xiao-Guang Ma, Wen-Wang Liu
The feasibility of the hybrid nanocomposites of the graphene quantum dot (GQD) and the phenoxazine-based dyes as the efficient sensitizer of the dye-sensitized solar cell (DSSC) is investigated. Based on the first principles density functional theory (DFT), the geometrical structures of the separate GQDs, the phenoxazine-based dyes, and their hybridized nanocomposites are fully optimized. The energy stabilities of the obtained structures are confirmed by harmonic frequency analysis. The optical absorptions of the optimized structures are calculated with the time-dependent DFT (TDDFT)...
August 6, 2018: Spectrochimica Acta. Part A, Molecular and Biomolecular Spectroscopy
Wenqin Shi, Vincent Callewaert, Bernardo Barbiellini, Rolando Saniz, Maik Butterling, Werner Egger, Marcel Dickmann, Christoph Hugenschmidt, Behtash Shakeri, Robert W Meulenberg, Ekkes Brück, Bart Partoens, Arun Bansil, Stephan W H Eijt
Previous studies have shown that positron-annihilation spectroscopy is a highly sensitive probe of the electronic structure and surface composition of ligand-capped semiconductor quantum dots (QDs) embedded in thin films. The nature of the associated positron state, however, whether the positron is confined inside the QDs or localized at their surfaces, has so far remained unresolved. Our positron-annihilation lifetime spectroscopy studies of CdSe QDs reveal the presence of a strong lifetime component in the narrow range of 358-371 ps, indicating abundant trapping and annihilation of positrons at the surfaces of the QDs...
August 3, 2018: Physical Review Letters
Wei Li, Frank Jäckel
Semiconducting quantum dots (QDs) have been considered as promising building blocks of solar energy harvesting systems because of size-dependent electronic structures, e.g. QD-metal heterostructures for solar-driven H2 production. In order to design improved systems, it is crucial to understand size-dependent QD-metal interfacial electron transfer dynamics, picosecond processes in particular. Here, we report that the transfer rates of photogenerated electrons in Pt-decorated CdS QDs can be varied over more than two orders of magnitude by controlling the QD size...
August 17, 2018: Nanoscale
Jiajun Song, Peng Lin, Yi-Fan Ruan, Wei-Wei Zhao, Weiwei Wei, Jin Hu, Shanming Ke, Xierong Zeng, Jing-Juan Xu, Hong-Yuan Chen, Wei Ren, Feng Yan
Organic bioelectronics have shown promising applications for various sensing purposes due to their significant advantages in term of high flexibility, portability, easy fabrication, and biocompatibility. Here, a new type of organic device, organic photo-electrochemical transistor (OPECT), is reported, which is the combination of an organic electrochemical transistor and a photo-electrochemical gate electrode modified with CdS quantum dots (QDs). Thanks to the inherent amplification function of the transistor, the OPECT-based biosensor exhibits much higher sensitivity than that of a traditional biosensor...
August 16, 2018: Advanced Healthcare Materials
Qianchun Zhang, Siqi Xie, Yanqun Yang, Yun Wu, Xingyi Wang, Jincheng Wu, Li Zhang, Junyu Chen, Yuan Wang
A facile, green, and high-output hydrothermal synthesis was proposed for the fabrication of highly fluorescent nitrogen-doped carbon quantum dots (N-doped CDs). The nitrogen content in N-doped CDs reached 19.2% and demonstrated strong blue fluorescence emission was obtained with fluorescence quantum yield (QY) of up to 32.9%, which exhibit high fluorescence quantum yield, high photostability, and excellent biocompatibility. The N-doped CDs possess high photostability, low toxicity, and excellent biocompatibility, based on which the N-doped CDs were successfully applied as a fluorescence probe for cell imaging...
2018: Journal of Analytical Methods in Chemistry
Zheng Zhang, Yun Lei, Liyang Zhao, Zicong Jiang, Zhong Ouyang
Graphene quantum dots (GQDs) decorated Al-doped ZnS composites were prepared using the solvothermal process, and the hydrothermal method was used to prepare GQDs. Various spectroscopic techniques were used to characterize the products, and the results show that Al-ZnS attached GQD composites present lattice fringes that can be assigned to ZnS and GQDs, respectively. The absorption peaks of Al-ZnS/GQDs are red-shifted because of the doping of aluminum and the incorporation of GQDs. The luminescence intensity of Al-ZnS/GQDs shows a downward trend with the addition of GQDs...
August 16, 2018: Materials
Rubab Amin, Jacob B Khurgin, Volker J Sorger
Electro-optic modulators perform a key function for data processing and communication. Rapid growth in data volume and increasing bits per second rates demand increased transmitter and thus modulator performance. Recent years have seen the introduction of new materials and modulator designs to include polaritonic optical modes aimed at achieving advanced performance in terms of speed, energy efficiency, and footprint. Such ad hoc modulator designs, however, leave a universal design for these novel material classes of devices missing...
June 11, 2018: Optics Express
Lorenzo Luigi Columbo, Paolo Bardella, Mariangela Gioannini
We studied theoretically coherent phenomena in the multimode dynamics of single section semiconductor ring lasers with quantum dots (QDs) active region. In the unidirectional ring configuration our simulations show the occurrence of self-mode-locking in the system leading to ultra-short pulses (sub-picoseconds) with a terahertz repetition rate. As confirmed by the linear stability analysis (LSA) of the traveling wave (TW) solutions this phenomenon is triggered by an analogous of the Risken-Nummedal-Graham-Haken (RNGH) instability affecting the multimode dynamics of two-level lasers...
July 23, 2018: Optics Express
Lingling Ran, Haiyang Li, Wenzhi Wu, Yachen Gao, Zhijun Chai, Jin Xiao, Qinghua Li, Degui Kong
In this study, the ultrafast optical properties of type-II CdZnS/ZnSe core-shell quantum dots were investigated using the Z-scan and transient absorption technique with femtosecond pulses. With 800-nm wavelength excitation, the CdZnS/ZnSe quantum dots exhibited two-photon absorption, and the two-photon absorption cross section was obtained as about 3.37 × 106 GM. In addition, the transfer time of electrons and the recombination lifetime of a single exciton were obtained. For the photoluminescence of the CdZnS/ZnSe quantum dots at temperatures from 80 to 280 K, the peak position redshifted by 60 meV, width broadened by 3 meV, and intensity decreased by a factor of four...
July 9, 2018: Optics Express
Pengcheng Lin, Qi Yan, Zhan Wei, Ying Chen, Fang Chen, Zhuoran Huang, Xiaoxin Li, Huiyuan Wang, Xuezhen Wang, Zhengdong Cheng
All-inorganic perovskite quantum dots (PQDs) have been effectively incorporated in the three-dimensional ordered structure of blue phase liquid crystals (BPLCs) to stabilize the BPLCs. Uniform dispersion, reduced phase transition temperature, widened BP temperature range, dynamic and fast electro-optical response and static optical display of selective reflection mode and photoluminescence mode have been confirmed with a given concentration of PQDs. Such a novel strategy of assembling all-inorganic PQDs in BPLCs shows favorable prospects for wide-range and near room temperature BPLCs, responsive BPLCs, multifunctional display materials and tunable bandgap lasers...
July 9, 2018: Optics Express
Sarah Uvin, Sulakshna Kumari, Andreas De Groote, Steven Verstuyft, Guy Lepage, Peter Verheyen, Joris Van Campenhout, Geert Morthier, Dries Van Thourhout, Gunther Roelkens
In this paper we report a single mode InAs/GaAs quantum dot distributed feedback laser at 1.3 μm wavelength heterogeneously integrated on a Si photonics waveguide circuit. Single mode lasing around 1300 nm with a side-mode suppression ratio higher than 40 dB is demonstrated. High temperature operation with continuous wave lasing up to 100°C is obtained. Threshold current densities as low as 205 A/cm2 were measured. These devices are attractive candidates to use in uncooled silicon photonic transceivers in data centers...
July 9, 2018: Optics Express
Jiaying Wang, Stefan Wagner, Wenjun Chen, Yuesong Shi, Abdoulaye Ndao, Leon Li, Boubacar Kante, Donald J Sirbuly, Max C Lemme, Oscar Vazquez Mena
A novel layer-by-layer 3D architecture allowing to expand device fabrication in the vertical direction and integrating functional nanomaterials is presented by emulating civil engineering. The architecture uses SU-8 pillars as structural columns which supports multiple horizontal suspended thin films. The films then serves as platforms for the integration of nanomaterials and nano devices. Multiple graphene layers suspended across SU-8 pillars with precise control on their vertical spacing are demonstrated...
August 16, 2018: ACS Applied Materials & Interfaces
Tingting Cui, Zhijie Zhu, Rui Cheng, Yu-Long Tong, Gang Peng, Cai-Feng Wang, Su Chen
Microfluidic spinning technology (MST) has drawn much attention owing to its ideal platform towards ordered fluorescent fibers, along with their largely-scale manipulation, high efficiency, flexibility, and environmental-friendly. Here, we employed the MST to fabricate a series of uniform fluorescent microfibers. By adjusting the microfluidic spinning parameters, the as-prepared microfibers with various diameters are successfully obtained. For more practice, these regular arranged fibers could be formed to versatile fluorescent codes by use of various microfluidic chips...
August 16, 2018: ACS Applied Materials & Interfaces
Ye Wang, Philip D Howes, Eunjung Kim, Christopher D Spicer, Michael R Thomas, Yiyang Lin, Spencer W Crowder, Isaac J Pence, Molly M Stevens
Advances in nanotechnology have provided new opportunities for the design of next-generation nucleic acid biosensors and diagnostics. Indeed, combining advances in functional nanoparticles, DNA nanotechnology, and nuclease-enzyme-based amplification can give rise to new assays with advantageous properties. In this work, we developed a microRNA (miRNA) assay using bright fluorescent quantum dots (QDs), simple DNA probes, and the enzyme duplex-specific nuclease. We employed an isothermal target-recycling mechanism, where a single miRNA target triggers the cleavage of many DNA signal probes...
August 16, 2018: ACS Applied Materials & Interfaces
Huan Zhang, Hui He, Xuemei Jiang, Zhining Xia, Weili Wei
Two dimensional (2D) transition metal dichalcogenides (TMDs) had attracted enormous interests owing to their extraordinary optical, physical and chemical properties. Herein, we prepared for the first time a series of chiral TMD QDs from MoS2 and WS2 bulk crystals by covalent modification with chiral ligands cysteine and penicillamine. The chiral TMD QDs were carefully investigated by spectroscopic and microscopic techniques. Their chiral optical activity was confirmed by distinct circular dichroism signals different to those of the chiral ligands...
August 16, 2018: ACS Applied Materials & Interfaces
Hongguang Li, Shengju Zhou, Linwen Zhang, Mengjun Chen, Wei Pan, Jingcheng Hao, Yongqiang Feng
Fullerenols have been known for decades. However, their photoluminescent (PL) properties and applications in supramolecular chemistry have not been well addressed. In this paper, we developed a strategy to purify the as-prepared fullerenols and systematically studied their photoluminescence and capabilities to form supramolecular self-assemblies. It was found that fullerenols show wavelength-dependent emission with an absolute fluorescent quantum yield of ∼3.5%. The PL characteristics are reminiscent of carbon dots, especially those obtained from top-down method...
August 16, 2018: Chemistry: a European Journal
Songmao Chen, Caiman Yan, Yong Tang, Jiasheng Li, Xinrui Ding, Longshi Rao, Zongtao Li
White light-emitting diodes (WLEDs) based on quantum dots (QDs) are gaining increasing attention due to their excellent color quality. QDs films with planar structure are universally applied in WLEDs for color conversion, while they still face great challenges in high light extraction and thermal stability. In this study, a QDs film with a spherical shell structure was proposed to improve the optical and thermal performance for WLEDs. Compared with the conventional planar structure, the luminous efficacy of the QDs spherical shell structure is improved by 12...
August 15, 2018: Nanomaterials
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