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abstract: Abstract H2 is an important energy carrier for replacing fossil fuel in the future due to its high energy density and environmental friendliness. As a sustainable H2 generation method, photocatalytic H2 production by water splitting has attracted much interest. Here, oil soluble ZnxCd1 xS quantum dot (ZCS QD) with a uniform particle size distribution were prepared by a hot injection method. However, no photocatalytic H2 production activity was observed for the oil soluble ZCS QD due to its hydrophobicity. Thus, the oil soluble ZCS QD was converted into a water soluble ZCS QD by a ligand exchange method. The water soluble ZCS QD exhibited excellent photocatalytic H2 production performance in the presence of glycerin and Ni2+ with an apparent quantum efficiency of 15.9% under irradiation of 420 nm light. Further, the photocatalytic H2 generation activity of the ZCS QD was ~10.7 times higher than that of the ZnxCd1 xS relative samples prepared by the conventional co precipitation method. This work will inspire the design and fabrication of other semiconductor QD photocatalysts because QD exhibits excellent separation efficiency for photogenerated electron hole pairs due to its small crystallite size.
author_names: Rongrong Gao

Bei Cheng

Jiajie Fan

Jiaguo Yu

Wingkei Ho
title: Zn Cd1 S quantum dot with enhanced photocatalytic H2 production performance
year: 2021

abstract: Quantum gates between spin qubits can be implemented leveraging the natural Heisenberg exchange interaction between two electrons in contact with each other. This interaction is controllable by electrically tailoring the overlap between electronic wave functions in quantum dot systems, as long as they occupy neighboring dots. An alternative route is the exploration of superexchange the coupling between remote spins mediated by a third idle electron that bridges the distance between quantum dots. We experimentally demonstrate direct exchange coupling and provide evidence for second neighbor mediated superexchange in a linear array of three single electron spin qubits in silicon, inferred from the electron spin resonance frequency spectra. We confirm theoretically, through atomistic modeling, that the device geometry only allows for sizable direct exchange coupling for neighboring dots, while next nearest neighbor coupling cannot stem from the vanishingly small tail of the electronic wave function of the remote dots, and is only possible if mediated.
author_names: Kok Wai Chan

Harshad Sahasrabudhe

Wister Huang

Henry Yang

Menno Veldhorst

Jason C C Hwang

Fahd A Mohiyaddin

Fay E Hudson

Kohei M Itoh

Andre Saraiva

Andrea Morello

Arne Laucht

Rajib Rahman

Andrew S Dzurak
title: Exchange Coupling in a Linear Chain of Three Quantum Dot Spin Qubits in Silicon.
venue: Nano letters
year: 2021

abstract: Interleukin 6 (IL 6) acts as both a proinflammatory and anti inflammatory cytokine and is generally utilized as an important diagnostic biomarker for sepsis. In addition, the high levels of IL 6 measured in plasma have been associated with pathological inflammation. A novel quartz crystal microbalance (QCM) immunoassay method was presented for high sensitivity and selectivity detection of interleukin 6 (IL 6) based on gold nanoparticles functionalized sulfur doped graphene quantum dot (AuNPs/S GQD) and hollow ZnS CdS nanocage (h ZnS CdS NC) Firstly, AuNPs/S GQD nanocomposite was synthesized in the presence of tetrachloroauric acid and then conjugated onto anti IL 6 antibodies by amino gold affinity. The sandwich type QCM immunoassay probe was prepared by immune reaction between AuNPs/S GQD/QCM immobilized with anti IL 6 capture antibodies and h ZnS CdS NC including detection anti IL 6 antibodies in the presence of target IL 6. The prepared QCM immunoassay probe was characterized by transmission electron microscopy (TEM) scanning electron microscope (SEM) x ray diffraction (XRD) method, x ray photoelectron spectroscopy (XPS) Raman spectroscopy, UV vis spectroscopy, Fourier transform infrared spectroscopy (FTIR) cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS) The QCM immunosensor showed a linearity range (0.01 2.0 pg mL 1) and a low detection limit (3.33 fg mL 1) Lastly, high stable and selective QCM immunosensor was applied to prepared plasma samples with good recovery.
author_names: Necip Atar

Mehmet Lutfi Yola
title: A novel QCM immunosensor development based on gold nanoparticles functionalized sulfur doped graphene quantum dot and h ZnS CdS NC for Interleukin 6 detection.
venue: Analytica chimica acta
year: 2021

abstract: Abstract Exploring electrocatalysts with optimal electronic structure and understanding the relationship between electronic structure and activity are highly required for designing advanced OER catalysts. Recently, introducing nanocarbon materials into LDHs has been demonstrated as an effective way to improve the OER activity; however, deeply understanding the regulating effect of nanocarbon on the electronic structure of LDHs is still a critical challenge. Herein, it is reported that the regulating of the surface electronic structure of nickel based layered double hydroxides (NiM LDHs (M Fe, Co, Mn) by adsorbing graphene quantum dot (GQDs) The Ni based LDHs/GQDs delivers enhanced OER activity, and particularly NiFe LDH/GQDs achieves an ultralow overpotential of 189 mV (10 mA cm 2) and superior performance in rechargeable Zn air battery tests. Combining with theoretical calculations and X ray photoelectron spectroscopy, we ascribe the excellent OER activity of Ni based LDHs/GQDs to the strong interaction between NiFe LDH and GQDs, which changes the charge distribution around metal ions and triggers the charge accumulation of the active Ni species. The above results demonstrate the significance of controlling the surface electronic structure for designing advanced 3d metal electrocatalysts.
author_names: Xingqun Zheng

Xiaoling Hu

Qiannan Zhao

Peng Yu

Chuan Jing

Yuxin Zhang

Guangsheng Huang

Bin Jiang

Chaohe Xu

Fu-sheng Pan
title: Electrostatic adsorbing graphene quantum dot into nickel based layered double hydroxides: Electron absorption/donor effects enhanced oxygen electrocatalytic activity
year: 2021

abstract: Graphical abstract This perspective describes the advances and challenges of emerging perovskite quantum dot solar cells. The strategies on ligand capping, defect passivation, and composition engineering together with future prospects are discussed. Download Download high res image (197KB) Download Download full size image
author_names: Aili Wang

Zhiwen Jin

Ming Cheng

Feng Hao

Liming Ding
title: Advances in perovskite quantum dot solar cells
year: 2021

abstract: All inorganic CsPbI 3 perovskite quantum dots have received substantial research interest for photovoltaic applications because of higher efficiency compared to solar cells using other quantum dots materials and the various exciting properties that perovskites have to offer. These quantum dot devices also exhibit good mechanical stability amongst various thin film photovoltaic technologies. We demonstrate higher mechanical endurance of quantum dot films compared to bulk thin film and highlight the importance of further research on high performance and flexible optoelectronic devices using nanoscale grains as an advantage. Specifically, we develop a hybrid interfacial architecture consisting of CsPbI 3 quantum dot/PCBM heterojunction, enabling an energy cascade for efficient charge transfer and mechanical adhesion. The champion CsPbI 3 quantum dot solar cell has an efficiency of 15.1% (stabilized power output of 14.61% which is among the highest report to date. Building on this strategy, we further demonstrate a highest efficiency of 12.3% in flexible quantum dot photovoltaics. Perovskite quantum dots film has better mechanical stability and structural integrity compared to bulk thin film. Here, the authors demonstrate higher endurance of quantum dot films and develop hybrid CsPbI3 QD/PCBM device with PCE of 15.1% and 12.3% on rigid and flexible substrates, respectively.
author_names: Long Hu

Qian Zhao

Shujuan Huang

Jianghui Zheng

Xinwei Guan

Robert J Patterson

Jiyun Kim

Lei Shi

Chun-Ho Lin

Qi Lei

Dewei Chu

Wan Tao

Soshan Cheong

Richard D Tilley

Anita W Y Ho-baillie

Joseph M Luther

Jianyu Yuan

Tom Wu
title: Flexible and efficient perovskite quantum dot solar cells via hybrid interfacial architecture
venue: Nature communications
year: 2021

abstract: Quantum key distribution is demonstrated over an urban open air link using entangled light from a semiconductor nanostructure. Quantum key distribution exchanging a random secret key relying on a quantum mechanical resource is the core feature of secure quantum networks. Entanglement based protocols offer additional layers of security and scale favorably with quantum repeaters, but the stringent requirements set on the photon source have made their use situational so far. Semiconductor based quantum emitters are a promising solution in this scenario, ensuring on demand generation of near unity fidelity entangled photons with record low multiphoton emission, the latter feature countering some of the best eavesdropping attacks. Here, we use a coherently driven quantum dot to experimentally demonstrate a modified Ekert quantum key distribution protocol with two quantum channel approaches: both a 250 m long single mode fiber and in free space, connecting two buildings within the campus of Sapienza University in Rome. Our field study highlights that quantum dot entangled photon sources are ready to go beyond laboratory experiments, thus opening the way to real life quantum communication.
author_names: Francesco Basso Basset

Mauro Valeri

Emanuele Roccia

Valerio Muredda

Davide Poderini

Julia Neuwirth

Nicolo Spagnolo

Michele B Rota

Gonzalo Carvacho

Fabio Sciarrino

Rinaldo Trotta
title: Quantum key distribution with entangled photons generated on demand by a quantum dot
venue: Science Advances
year: 2021

abstract: Abstract Quantum dot light emitting diodes (QLEDs) are unarguably the most successful member of rapidly developing family of devices based on quantum dots (type II VI group compounds) Herein, the electroluminescence properties and fabrication/characterization technologies of QLEDs are reviewed. Particular emphasis is devoted to the dynamic processes of charge carriers and the related characterization technology because QLEDs are electro optic conversion devices whose performance is to a great extent determined by the carrier transport/distribution and exciton formation. The utility of spectroscopic technologies, including steady/transient electroluminescence and photoluminescence, electro absorption spectrum, and differential absorption spectrum are explained. Additionally, displacement current measurement technology is also discussed due to its potential to characterize the trapped charges within the devices. The strategies to improve the device performance by interface modification and QD design are summarized and the corresponding physics and chemistry mechanisms are discussed. Finally, a summary and outlook are shown about the challenge faced by QLED, as well as possible pathway to enhancing the device performance.
title: A review on the electroluminescence properties of quantum dot light emitting diodes
year: 2021

abstract: Abstract Transition metal oxides are one of the promising materials for energy storage because they have rich redox reactions with good stability. In this study, CuMnO2 nanocrystals and CuMnO2/graphene quantum dot (GQD) composite were synthesized by hydrothermal method and used in constructing a new supercapacitor. GQD has been applied to increase specific capacity and improve efficiency of the supercapacitor. Various methods were used to identify the synthesized nanocomposite and to study its morphology, structure and surface area. Cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS) were used to record and track the electrochemical behavior of the synthesized nanocomposite used as an electrode material. The study of changes in the capacity of CuMnO2/GQD and CuMnO2 electrodes during 5000 consecutive charge/discharge cycles showed that the stability of the electrode made of nanocomposite is higher and its capacity after this number of cycles reached 83.3% while the capacity of the electrode made with CuMnO2 nanoparticles has reached 65.4% The specific capacity of CuMnO2/GQD nanocomposite and CuMnO2 nanoparticles at a current density of 1 A g 1 was calculated to be 520.2 and 381.5 C g 1, respectively. The maximum specific energy of CuMnO2/GQD//AC asymmetric supercapacitor was obtained at a specific power of 1108.1 W kg 1 equal to 47.9 Wh Kg 1. Asymmetric supercapacitor capacitance decreased by only less than 13.3% after 5000 charge and discharge cycles, which is a very good cycle life compared to similar materials. All these results indicate that the CuMnO2/GQD nanocomposite can be deliberated as a possible option for fast and stable supercapacitor.
author_names: Mohammad Ashourdan

Abolfazl Semnani

Foroozan Hasanpour

Seyyed Ebrahim Moosavifard
title: Synthesis of CuMnO2/graphene quantum dot nanocomposites as novel electrode materials for high performance supercapacitors
year: 2021

abstract: We investigate room temperature lasing of terahertz quantum cascade lasers using quantum dot chains as active material suitable for wireless communication and imaging technologies. To make band structure calculations for such extended systems of coupled quantum dots possible, we developed a `linear combination of quantum dot orbitals' method, based on single quantum dot wave functions. Our results demonstrate strong vertical emission of coupled quantum dots, reduced phonon coupling, and in plane scattering, enabling room temperature lasing with significantly reduced threshold current densities.
author_names: Alexander Mittelstadt

Ludwig A Th Greif

Stefan Thomas Jagsch

Andrei Schliwa
title: Terahertz lasing at room temperature: A numerical study of a vertical emitting quantum cascade laser based on a quantum dot superlattice
year: 2021