共查询到20条相似文献,搜索用时 15 毫秒
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Xin Tong Xiang‐Tian Kong Yufeng Zhou Fabiola Navarro‐Pardo Gurpreet Singh Selopal Shuhui Sun Alexander O. Govorov Haiguang Zhao Zhiming M. Wang Federico Rosei 《Liver Transplantation》2018,8(2)
“Giant” core/shell quantum dots (g‐QDs) are a promising class of materials for future optoelectronic technologies due to their superior chemical‐ and photostability compared to bare QDs and core/thin shell QDs. However, inadequate light absorption in the visible and near‐infrared (NIR) region and frequent use of toxic heavy metals (e.g., Cd and Pb) are still major challenges for most g‐QDs (e.g., CdSe/CdS) synthesized to date. The synthesis of NIR, heavy metal‐free, Zn‐treated spherical CuInSe2/CuInS2 g‐QDs is reported using the sequential cation exchange method. These g‐QDs exhibit tunable NIR optical absorption and photoluminescence (PL) properties. Transient fluorescence spectroscopy shows prolonged lifetime with increasing shell thickness, indicating the formation of quasi type‐II band alignment, which is further confirmed by simulations. As a proof‐of‐concept, as‐synthesized g‐QDs are used to sensitize TiO2 as a photoanode in a photoelectrochemical (PEC) cell, demonstrating an efficient and stable PEC system. These results pave the way toward synthesizing NIR heavy metal‐free g‐QDs, which are very promising components of future optoelectronic technologies. 相似文献
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Mohamad I. Nugraha Hyunho Kim Bin Sun Md Azimul Haque Francisco Pelayo Garcia de Arquer Diego Rosas Villalva Abdulrahman El‐Labban Edward H. Sargent Husam N. Alshareef Derya Baran 《Liver Transplantation》2019,9(13)
Colloidal quantum dots (CQDs) are demonstrated to be promising materials to realize high‐performance thermoelectrics owing to their low thermal conductivity. The most studied CQD films, however, are using long ligands that require high processing and operation temperature (>400 °C) to achieve optimum thermoelectric performance. Here the thermoelectric properties of CQD films cross‐linked using short ligands that allow strong inter‐QD coupling are reported. Using the ligands, p‐type thermoelectric solids are demonstrated with a high Seebeck coefficient and power factor of 400 μV K?1 and 30 µW m?1 K?2, respectively, leading to maximum ZT of 0.02 at a lower measurement temperature (<400 K) and lower processing temperature (<300 °C). These ligands further reduce the annealing temperature to 175 °C, significantly increasing the Seebeck coefficient of the CQD films to 580 μV K?1. This high Seebeck coefficient with a superior ZT near room temperature compared to previously reported high temperature‐annealed CQD films is ascribed to the smaller grain size, which enables the retainment of quantum confinement and significantly increases the hole effective mass in the films. This study provides a pathway to approach quantum confinement for achieving a high Seebeck coefficient yet strong inter‐QD coupling, which offers a step toward low‐temperature‐processed high‐performance thermoelectric generators. 相似文献
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Thomas P. Brennan Pendar Ardalan Han‐Bo‐Ram Lee Jonathan R. Bakke I‐Kang Ding Michael D. McGehee Stacey F. Bent 《Liver Transplantation》2011,1(6):1169-1175
Functioning quantum dot (QD) sensitized solar cells have been fabricated using the vacuum deposition technique atomic layer deposition (ALD). Utilizing the incubation period of CdS growth by ALD on TiO2, we are able to grow QDs of adjustable size which act as sensitizers for solid‐state QD‐sensitized solar cells (ssQDSSC). The size of QDs, studied with transmission electron microscopy (TEM), varied with the number of ALD cycles from 1‐10 nm. Photovoltaic devices with the QDs were fabricated and characterized using a ssQDSSC device architecture with 2,2',7,7'‐tetrakis‐(N,N‐di‐p methoxyphenylamine) 9,9'‐spirobifluorene (spiro‐OMeTAD) as the solid‐state hole conductor. The ALD approach described here can be applied to fabrication of quantum‐confined structures for a variety of applications, including solar electricity and solar fuels. Because ALD provides the ability to deposit many materials in very high aspect ratio substrates, this work introduces a strategy by which material and optical properties of QD sensitizers may be adjusted not only by the size of the particles but also in the future by the composition. 相似文献
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Wenwen Liu Maiwen Zhang Matthew Li Brenda Li Wenyao Zhang Gaoran Li Meiling Xiao Jianbing Zhu Aiping Yu Zhongwei Chen 《Liver Transplantation》2020,10(8)
Micro‐supercapacitors (MSCs) as a new class of energy storage devices have attracted great attention due to their unique merits. However, the narrow operating voltage, slow frequency response, and relatively low energy density of MSCs are still insufficient. Therefore, an effective strategy to improve their electrochemical performance by innovating upon the design from various aspects remains a huge challenge. Here, surface and structural engineering by downsizing to quantum dot scale, doping heteroatoms, creating more structural defects, and introducing rich functional groups to two dimensional (2D) materials is employed to tailor their physicochemical properties. The resulting nitrogen‐doped graphene quantum dots (N‐GQDs) and molybdenum disulfide quantum dots (MoS2‐QDs) show outstanding electrochemical performance as negative and positive electrode materials, respectively. Importantly, the obtained N‐GQDs//MoS2‐QDs asymmetric MSCs device exhibits a large operating voltage up to 1.5 V (far exceeding that of most reported MSCs), an ultrafast frequency response (with a short time constant of 0.087 ms), a high energy density of 0.55 mWh cm?3, and long‐term cycling stability. This work not only provides a novel concept for the design of MSCs with enhanced performance but also may have broad application in other energy storage and conversion devices based on QDs materials. 相似文献
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Chloé Bureau-Oxton Julien Camirand Lemyre Michel Pioro-Ladrière 《Journal of visualized experiments : JoVE》2013,(81)
A quantum computer is a computer composed of quantum bits (qubits) that takes advantage of quantum effects, such as superposition of states and entanglement, to solve certain problems exponentially faster than with the best known algorithms on a classical computer. Gate-defined lateral quantum dots on GaAs/AlGaAs are one of many avenues explored for the implementation of a qubit. When properly fabricated, such a device is able to trap a small number of electrons in a certain region of space. The spin states of these electrons can then be used to implement the logical 0 and 1 of the quantum bit. Given the nanometer scale of these quantum dots, cleanroom facilities offering specialized equipment- such as scanning electron microscopes and e-beam evaporators- are required for their fabrication. Great care must be taken throughout the fabrication process to maintain cleanliness of the sample surface and to avoid damaging the fragile gates of the structure. This paper presents the detailed fabrication protocol of gate-defined lateral quantum dots from the wafer to a working device. Characterization methods and representative results are also briefly discussed. Although this paper concentrates on double quantum dots, the fabrication process remains the same for single or triple dots or even arrays of quantum dots. Moreover, the protocol can be adapted to fabricate lateral quantum dots on other substrates, such as Si/SiGe. 相似文献
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Grigorios Itskos Paris Papagiorgis Demetra Tsokkou Andreas Othonos Felix Hermerschmidt Solon P. Economopoulos Maksym Yarema Wolfgang Heiss Stelios Choulis 《Liver Transplantation》2013,3(11):1490-1499
The photophysics of bulk heterojunctions of a high‐performance, low‐gap silicon‐bridged dithiophene polymer with oleic acid capped PbS quantum dots (QDs) are studied to assess the material potential for light harvesting in the visible‐ and IR‐light ranges. By employing a wide range of nanocrystal sizes, systematic dependences of electron and hole transfer on quantum‐dot size are established for the first time on a low‐gap polymer–dot system. The studied system exhibits type II band offsets for dot sizes up to ca. 4 nm, whch allow fast hole transfer from the quantum dots to the polymer that competes favorably with the intrinsic QD recombination. Electron transfer from the polymer is also observed although it is less competitive with the fast polymer exciton recombination for most QD sizes studied. The incorporation of a fullerene derivative provides efficient electron‐quenching sites that improve interfacial polymer‐exciton dissociation in ternary polymer–fullerene–QD blends. The study indicates that programmable band offsets that allow both electron and hole extraction can be produced for efficient light harvesting based on this low‐gap polymer‐PbS QD composite. 相似文献
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Hui Wang Keyu Xie You You Qian Hou Kun Zhang Nan Li Wei Yu Kian Ping Loh Chao Shen Bingqing Wei 《Liver Transplantation》2019,9(34)
With high theoretical energy density, rechargeable metal–gas batteries (e.g., Li–CO2 battery) are considered as one of the most promising energy storage devices. However, their practical applications are hindered by the sluggish reaction kinetics and discharge product accumulation during battery cycling. Currently, the solutions focus on exploration of new catalysts while the thorough understanding of their underlying mechanisms is often ignored. Herein, the interfacial electronic interaction within rationally designed catalysts, ZnS quantum dots/nitrogen‐doped reduced graphene oxide (ZnS QDs/N‐rGO) heterostructures, and their effects on transformation and deposition of discharge products in the Li–CO2 battery are revealed. In this work, the interfacial interaction can both enhance the catalytic activities of ZnS QDs/N‐rGO heterostructures and induce the nucleation of discharge products to form a homogeneous Li2CO3/C film with excellent electronic transmission and high electrochemical activities. When the batteries cycle within a cutoff specific capacity of 1000 mAh g?1 at a current density of 400 mA g?1, the cycling performance of the Li–CO2 battery using a ZnS QDs/N‐rGO cathode is over 3 and 9 times than those coupled with a ZnS nanosheets (NST)/N‐rGO cathode and a N‐rGO cathode, respectively. This work provides comprehensive understandings on designing catalysts for Li–CO2 batteries as well as other rechargeable metal–gas batteries. 相似文献
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Mohamad I. Nugraha Hyunho Kim Bin Sun Saheena Desai F. Pelayo Garcia de Arquer Edward H. Sargent Husam N. Alshareef Derya Baran 《Liver Transplantation》2019,9(28)
Colloidal quantum dots (CQDs) are attractive materials for thermoelectric applications due to their simple and low‐cost processing; advantageously, they also offer low thermal conductivity and high Seebeck coefficient. To date, the majority of CQD thermoelectric films reported upon have been p‐type, while only a few reports are available on n‐type films. High‐performing n‐ and p‐type films are essential for thermoelectric generators (TEGs) with large output voltage and power. Here, high‐thermoelectric‐performance n‐type CQD films are reported and showcased in high‐performance all‐CQD TEGs. By engineering the electronic coupling in the films, a thorough removal of insulating ligands is achieved and this is combined with excellent surface trap passivation. This enables a high thermoelectric power factor of 24 µW m?1 K?2, superior to previously reported n‐type lead chalcogenide CQD films operating near room temperature (<1 µW m?1 K?2). As a result, an all‐CQD film TEG with a large output voltage of 0.25 V and a power density of 0.63 W m?2 at ?T = 50 K is demonstrated, which represents an over fourfold enhancement to previously reported p‐type only CQD TEGs. 相似文献
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Margarida M. Barroso 《The journal of histochemistry and cytochemistry》2011,59(3):237-251
Quantum dots are semiconductor nanocrystals that have broad excitation spectra, narrow emission spectra, tunable emission peaks, long fluorescence lifetimes, negligible photobleaching, and ability to be conjugated to proteins, making them excellent probes for bioimaging applications. Here the author reviews the advantages and disadvantages of using quantum dots in bioimaging applications, such as single-particle tracking and fluorescence resonance energy transfer, to study receptor-mediated transport. 相似文献
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Guangchao Li Zhoulan Yin Huajun Guo Zhixing Wang Guochun Yan Zhewei Yang Yong Liu Xiaobo Ji Jiexi Wang 《Liver Transplantation》2019,9(2)
Lithium‐ion hybrid supercapacitors (LICs) are considered as a promising candidate in energy storage systems. Taking the factor of sluggish kinetics behavior, battery‐type anode plays a significant role in improving the performance of LICs. Here, onion‐shaped graphene‐like derivatives are synthesized via carbonization of metalorganic quantum dots (MQDs) accompanied with in situ catalytic graphitization by reduced metal. Notably MQDs, exhibiting water‐soluble character and ultrafine particles (2.5–5.5 nm) morphology, are prepared by the amidation reaction. The carbonized sample exhibits highly graphitic tendency with graphitization degree up to 95.6%, and shows graphene‐like porous structure, appropriate amorphous carbon decoration characteristic, as well as N‐doping and defective nature. When employed as anode material in LICs, it shows high energy density of 83.7 Wh kg–1 and high power density of 6527 W kg–1 when the mass ratio of cathode to anode is 1:1 and the operating voltage ranges from 2.0 to 4.0 V. It also possesses the long cyclic stability with the energy density retention maintains at 97.3% after 10 000 cycles at 5.0 A g–1. In addition, the energy density is further increased by altering cathode/anode mass ratio and extending working voltage. This work provides a novel strategy to develop unique carbon materials for energy storage. 相似文献
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Quantum Dots: Enhanced Photovoltaic Performance of Inverted Polymer Solar Cells Utilizing Multifunctional Quantum‐Dot Monolayers (Adv. Energy Mater. 2/2015)
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Byung Joon Moon Sungjae Cho Kyu Seung Lee Sukang Bae Sanghyun Lee Jun Yeon Hwang Basavaraj Angadi Yeonjin Yi Min Park Dong Ick Son 《Liver Transplantation》2015,5(2)
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目的:探讨链亲和素修饰的CdSe/ZnS核壳结构量子点(CdSe/ZnS-SA)对稳定转染pcDNA3.1/APP595/596质粒的人胚肾(HEK293)细胞的短期毒性作用.方法:将CdSe/ZnS-SA量子点与稳定转染pcD-NA3.1/APP595/596质粒的HEK293细胞共培育,在倒置荧光显微镜下观察细胞形态学变化;MTT法测定细胞活性;流式细胞术检测细胞凋亡率.结果:终浓度为2.5 nmol/L-20 nmol/L的CdSe/ZnS-SA量子点与HEK293细胞分别共育8h、16h、24 h后,细胞的形态无明显改变;终浓度为2.5 nmol/L-25 nmol/L的CdSe/ZnS-SA量子点与HEK293细胞分别共育8h、16 h、24 h,各处理组与对照组间,各处理组间的吸光度值、细胞凋亡率差异均无统计学意义(P>0.05).结论:一定浓度范围的CdSe/ZnS-SA量子点在短期内对稳定转染pcDNA3.1/APP595/596质粒的HEK293细胞无明显的毒性作用,具有较好的生物相容性. 相似文献
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Single-molecule imaging is an important tool for understanding the mechanisms of biomolecular function and for visualizing the spatial and temporal heterogeneity of molecular behaviors that underlie cellular biology 1-4. To image an individual molecule of interest, it is typically conjugated to a fluorescent tag (dye, protein, bead, or quantum dot) and observed with epifluorescence or total internal reflection fluorescence (TIRF) microscopy. While dyes and fluorescent proteins have been the mainstay of fluorescence imaging for decades, their fluorescence is unstable under high photon fluxes necessary to observe individual molecules, yielding only a few seconds of observation before complete loss of signal. Latex beads and dye-labeled beads provide improved signal stability but at the expense of drastically larger hydrodynamic size, which can deleteriously alter the diffusion and behavior of the molecule under study.Quantum dots (QDs) offer a balance between these two problematic regimes. These nanoparticles are composed of semiconductor materials and can be engineered with a hydrodynamically compact size with exceptional resistance to photodegradation 5. Thus in recent years QDs have been instrumental in enabling long-term observation of complex macromolecular behavior on the single molecule level. However these particles have still been found to exhibit impaired diffusion in crowded molecular environments such as the cellular cytoplasm and the neuronal synaptic cleft, where their sizes are still too large 4,6,7.Recently we have engineered the cores and surface coatings of QDs for minimized hydrodynamic size, while balancing offsets to colloidal stability, photostability, brightness, and nonspecific binding that have hindered the utility of compact QDs in the past 8,9. The goal of this article is to demonstrate the synthesis, modification, and characterization of these optimized nanocrystals, composed of an alloyed HgxCd1-xSe core coated with an insulating CdyZn1-yS shell, further coated with a multidentate polymer ligand modified with short polyethylene glycol (PEG) chains (Figure 1). Compared with conventional CdSe nanocrystals, HgxCd1-xSe alloys offer greater quantum yields of fluorescence, fluorescence at red and near-infrared wavelengths for enhanced signal-to-noise in cells, and excitation at non-cytotoxic visible wavelengths. Multidentate polymer coatings bind to the nanocrystal surface in a closed and flat conformation to minimize hydrodynamic size, and PEG neutralizes the surface charge to minimize nonspecific binding to cells and biomolecules. The end result is a brightly fluorescent nanocrystal with emission between 550-800 nm and a total hydrodynamic size near 12 nm. This is in the same size range as many soluble globular proteins in cells, and substantially smaller than conventional PEGylated QDs (25-35 nm). 相似文献
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Decai Gong Bin Wang Jingyi Zhu Ramakrishna Podila Apparao M. Rao Xinzhi Yu Zhi Xu Bingan Lu 《Liver Transplantation》2017,7(3)
Rechargeable sodium–iodine batteries represent a promising scalable electrochemical energy storage alternative as sodium and iodine are both low cost and widely abundant elements. Here, the authors demonstrate a rechargeable sodium–iodine battery that employs free‐standing iodine quantum dots (IQDs) decorated reduced graphene oxide (IQDs@RGO) as the cathode. Consistent with the density functional theory the authors find the Na+ ions to intercalate into the I unit cell forming stable NaI, and the battery exhibits high capacity, outstanding cycle stability (with a reversible specific capacity of 141 mA h g?1 after 500 cycles at current density of 100 mA g?1), and high rate performance (170, 146, 127, 112, and 95 mA h g?1 at current densities of 100, 200, 400, 600, and 1000 mA g?1, respectively). The reversible reactions, I2/I3 ? and I3 ?/I? redox couples on insertion of Na+ ions, are confirmed via in situ Raman spectroscopy. Notably, even after 500 cycles the morphology and structure of the IQDs exhibit no noticeable change implying their use as a stable cathode material for sodium–iodine batteries. Moreover, the IQDs based flexible full‐cells also exhibit high capacity and long cycle life (the capacity with 123 mA h g?1 at current density of 100 mA g?1 after 100 cycles). 相似文献
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Tran Van Tam Sung Gu Kang Mun Ho Kim Seung Geol Lee Seung Hyun Hur Jin Suk Chung Won Mook Choi 《Liver Transplantation》2019,9(26)
Herein, a facile, one‐step hydrothermal route to synthesize novel all‐carbon‐based composites composed of B‐doped graphene quantum dots anchored on a graphene hydrogel (GH‐BGQD) is demonstrated. The obtained GH‐BGQD material has a unique 3D architecture with high porosity and large specific surface area, exhibiting abundant catalytic active sites of B‐GQDs as well as enhanced electrolyte mass transport and ion diffusion. Therefore, the prepared GH‐BGQD composites exhibit a superior trifunctional electrocatalytic activity toward the oxygen reduction reaction, oxygen evolution reaction, and hydrogen evolution reaction with excellent long‐term stability and durability comparable to those of commercial Pt/C and Ir/C catalysts. A flexible solid‐state Zn–air battery using a GH‐BGQD air electrode achieves an open‐circuit voltage of 1.40 V, a stable discharge voltage of 1.23 V for 100 h, a specific capacity of 687 mAh g?1, and a peak power density of 112 mW cm?2. Also, a water electrolysis cell using GH‐BGQD electrodes delivers a current density of 10 mA cm?2 at cell voltage of 1.61 V, with remarkable stability during 70 h of operation. Finally, the trifunctional GH‐BGQD catalyst is employed for water electrolysis cell powered by the prepared Zn–air batteries, providing a new strategy for the carbon‐based multifunctional electrocatalysts for electrochemical energy devices. 相似文献
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