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Quantum dot

Oscar A Douglas-Gallardo, Cristián Gabriel Sánchez, Esteban Vöhringer-Martinez
Nowadays, the search for efficient methods able to reduce the high atmospheric carbon dioxide concentration has turned into a very dynamic research area. Several environmental problems have been closely associated with the high atmospheric level of this greenhouse gas. Here, a novel system based on the use of surface-functionalized silicon quantum dots (sf-SiQDs) is theoretically proposed as a versatile device to bind carbon dioxide. Within this approach, carbon dioxide trapping is modulated by a photoinduced charge redistribution between the capping molecule and the silicon quantum dots (SiQDs)...
April 14, 2018: Journal of Chemical Physics
Isadora Martini Garcia, Vicente Castelo Branco Leitune, Fernanda Visioli, Susana Maria Werner Samuel, Fabrício Mezzomo Collares
OBJECTIVE: To evaluate the influence of zinc oxide quantum dots (ZnOQDs ) into an experimental adhesive resin regarding the antibacterial activity against Streptococcus mutans and the cytotoxicity against pulp fibroblasts. MATERIALS AND METHODS: ZnOQDs were synthesized by sol-gel process and were incorporated into 2-hydroxyethyl methacrylate (HEMA). An experimental adhesive resin was formulated by mixing 66.6 wt.% bisphenol A glycol dimethacrylate (BisGMA) and 33...
April 10, 2018: Journal of Dentistry
Zunxian Yang, Yuxiang Zhang, Jiahui Liu, Jingwei Ai, Shouqiang Lai, Zhiwei Zhao, Bingqing Ye, Yushuai Ruan, Tailiang Guo, Xuebin Yu, Gengxu Chen, Yuanyuan Lin, Sheng Xu
Semiconductor quantum dots (QDs) have attracted extensive attention due to their remarkable optical and electrical characteristics. While the practical application of quantum dots and further the quantum dot composite films have greatly been hindered mainly owing to their essential drawbacks of extreme unstability under the oxygen and water environments. Herein, one simple method has been employed to enhance enormously the stability of CdxZn1-xSeyS1-y quantum dot composite film by a combination of CdxZn1-xSeyS1-y quantum dots and particular polyvinylidene Fluoride (PVDF), which is characteristic of closely arranged molecular chains and strong hydrogen bonds...
April 13, 2018: ACS Applied Materials & Interfaces
Gauri M Nabar, Jessica O Winter, Barbara E Wyslouzil
The interfacial instability method has emerged as a viable approach for encapsulating high concentrations of nanoparticles (NPs) within morphologically diverse micelles. In this method, transient interfacial instabilities at the surface of an emulsion droplet guide self-assembly of block co-polymers and NP encapsulants. Although used by many groups, there are no systematic investigations exploring the relationship between NP properties and micelle morphology. Here, the effect of quantum dot (QD) and superparamagnetic iron oxide NP (SPION) concentration on the shape, size, and surface deformation of initially spherical poly(styrene-b-ethylene oxide) (PS-b-PEO) micelles was examined...
April 13, 2018: Soft Matter
A-Young Lee, Hyun-Soo Ra, Dohyun Kwak, Jeong Min-Hye, Jeong-Hyun Park, Yeon-Su Kang, Weon-Sik Chae, Jong-Soo Lee
Recently, black phosphorus (BP) with direct band gap exhibited excellent potential for optoelectronic applications due to its high charge carrier mobility and low dark current as well as the variable band gap of 0.3 eV to 1.5 eV depending on the number of layers. However, few-layer BP-based phototransistors (photo-FETs) have been limited in sensitivity and wavelength selectivity. To overcome the drawback of these photo-FETs, we studied hybrid photo-FETs combined with the novel properties of the two materials between the channel and sensitizer layers...
April 13, 2018: ACS Applied Materials & Interfaces
Nassim Ben Brahim, Mélanie Poggi, Jean-Christophe Lambry, Naim Bel Haj Mohamed, Rafik Ben Chaâbane, Michel Negrerie
We aimed to quantify the interaction of water-soluble-functionalized CdS quantum dots (QDs) with metal cations from their composition and physical properties. From the diameter of thioglycerol-capped nanoparticles (TG-CdS QDs) measured by electronic microscopy ( D = 12.3 ± 0.3 nm), we calculated the molecular mass of the individual particle MAQD = (3 ± 0.5) × 106 g·mol-1 and its molar absorption coefficient ε450 = 21 × 106 M-1 ·cm-1 . We built a three-dimensional model of the TG-CdS QDs in agreement with the structural data, which allowed us to quantify the number of thioglycerol grafted chains to ∼2000 per QD...
April 12, 2018: Inorganic Chemistry
Christopher Melnychuk, Philippe Guyot-Sionnest
The biexciton lifetimes in HgTe colloidal quantum dots are measured as a function of particle size. Samples produced by two synthetic methods, leading to partially aggregated or well-dispersed particles, exhibit markedly different dynamics. The relaxation characteristics of partially aggregated HgTe inhibit reliable determinations of the Auger lifetime. In well-dispersed HgTe quantum dots, the biexciton lifetime increases approximately linearly with particle volume, confirming trends observed in other systems...
April 12, 2018: Journal of Physical Chemistry Letters
Ruptanu Banerjee, Amit Jaiswal
Lateral flow immunoassay (LFIA) technology is a paper-based, point-of-care strip biosensor designed to detect a specific analyte in a given sample. This type of assay is now of great interest to researchers for its cost-effectiveness, simplicity, portability and rapidness of detection of analytes, including but not limited to areas such as agriculture, food, biomedicine and pathogen detection. Various nanoparticles (such as metal nanoparticles, carbon-based nanoparticles, quantum dots, lanthanides and up-converting phosphor) functionalized by an antibody to detect an analyte protein or molecular marker present in the surface of an infectious pathogen are used for in LFIAs...
April 12, 2018: Analyst
Minoru Fujii, Hiroshi Sugimoto, Shinya Kano
Heavily boron and phosphorus codoped silicon quantum dots (QDs) are dispersible in water without organic ligands and exhibit near infrared luminescence. We summarize the fundamental properties and demonstrate the formation of a variety of nanocomposites.
April 12, 2018: Chemical Communications: Chem Comm
Yue Hu, Zhao Yi Miao, Xiaojing Zhang, Xiaotong Yang, Yingying Tang, Sheng Yu, ChenXiao Shan, Hongmei Wen, Dong Zhu
The currently utilized ligand fishing for bioactive molecular screening from complex matrixes cannot perform imaging screening. Here, we developed a new solid-phase ligand fishing coupled with in situ imaging protocol for the specific enrichment and identification of heat shock protein 90 (Hsp 90) inhibitors from Tripterygium wilfordii, utilizing a multiple-layer and microkernel-based mesoporous nanostructure composed of a protective silica coating CdTe quantum dots (QDs) core and a mesoporous silica shell, i...
April 12, 2018: Analytical Chemistry
Andreas Wolk, Marta Rosenthal, Stephan Neuhaus, Klaus Huber, Katharina Brassat, Jörg K N Lindner, Richard Grothe, Guido Grundmeier, Wolfgang Bremser, René Wilhelm
Dodecyl amine edge functionalized few-layer graphene oxide quantum dots were synthesized in good yields. The covalent functionalization was demonstrated with NMR and AFM-IR. The resulting structure and particle size was measured with AFM and HRTEM. The thermal stability of the compound was investigated and showed a stability of up to 220 °C. The modified graphene oxide quantum dots showed excellent solubility in various organic solvents, including ethers, methanol, toluene, n-hexane, heptane, xylene, dichloromethane and toluene...
April 11, 2018: Scientific Reports
Wen-Jin Zhang, Chun-Yang Pan, Fan Cao, Haoran Wang, Xuyong Yang
Herein, we report a new series of ultra-stable Cd-free Ag:Zn-Ga-S/ZnS quantum dots (QDs) with an overall short emission wavelength tunable from 370 to 540 nm via a facile one-pot non-injection method. The highest PL quantum yield of the resultant core/shell QDs could be up to 85%, and the exceptional luminescence could be maintained not only at 300 °C but also after phase transfer.
April 9, 2018: Chemical Communications: Chem Comm
Sungyeap Hong, Cheolho Lee
Enzyme-linked immunosorbent assay (ELISA) and polymerase chain reaction (PCR), widely used for the detection of plant viruses, are not easily performed, resulting in a demand for an innovative and more efficient diagnostic method. This paper summarizes the characteristics and research trends of biosensors focusing on the physicochemical properties of both interface elements and bioconjugates. In particular, the topological and photophysical properties of quantum dots (QDs) are discussed, along with QD-based biosensors and their practical applications...
April 2018: Plant Pathology Journal
Perla Pérez-Treviño, Héctor Hernández-De la Cerda, Jorge Pérez-Treviño, Oscar Raúl Fajardo-Ramírez, Noemí García, Julio Altamirano
Patients with breast cancer (BC) overexpressing HER2 (HER2+) are selected for Trastuzumab treatment, which blocks HER2 and improves cancer prognosis. However, HER2+ diagnosis, by the gold standard, immunohistochemistry, could lead to errors, associated to: a) variability in sample manipulation (thin 2D sections), b) use of subjective algorithms, and c) heterogeneity of HER2 expression within the tissue. Therefore, we explored HER2 3D detection by multiplexed imaging of Affibody-Quantum Dots conjugates (Aff-QD), ratiometric analysis (RMAFI ) and thresholding, using BC multicellular tumor spheroids (BC-MTS) (~120 μm of diameter) as 3D model of BC...
April 4, 2018: Translational Oncology
Yang Zhao, Lu Tan, Xiaoshan Gao, Guifen Jie, Tingyu Huang
Herein, we successfully devised a novel photoelectrochemical (PEC) platform for ultrasensitive detection of adenosine by target-triggering cascade multiple cycle amplification based on the silver nanoparticles-assisted ion-exchange reaction with CdTe quantum dots (QDs). In the presence of target adenosine, DNA s1 is released from the aptamer and then hybridizes with hairpin DNA (HP1), which could initiate the cycling cleavage process under the reaction of nicking endonuclease. Then the product (DNA b) of cycle I could act as the "DNA trigger" of cycle II to further generate a large number of DNA s1, which again go back to cycle I, thus a cascade multiple DNA cycle amplification was carried out to produce abundant DNA c...
March 30, 2018: Biosensors & Bioelectronics
Jezid Miranda, Cristina Paules, Soumyalekshmi Nair, Andrew Lai, Carlos Palma, Katherin Scholz-Romero, Gregory E Rice, Eduard Gratacos, Fatima Crispi, Carlos Salomon
INTRODUCTION: Placenta-derived exosomes may represent an additional pathway by which the placenta communicates with the maternal system to induce maternal vascular adaptations to pregnancy and it may be affected during Fetal growth restriction (FGR). The objective of this study was to quantify the concentration of total and placenta-derived exosomes in maternal and fetal circulation in small fetuses classified as FGR or small for gestational age (SGA). METHODS: Prospective cohort study in singleton term gestations including 10 normally grown fetuses and 20 small fetuses, sub-classified into SGA and FGR accordingly to birth weight (BW) percentile and fetoplacental Doppler...
April 2018: Placenta
YongXi Cheng, ZhenHua Li, JianHua Wei, YiHang Nie, YiJing Yan
Based on the hierarchical equations of motion approach, we study the time-dependent transport properties of a strongly correlated quantum dot system in the Kondo regime (KR), mixed valence regime (MVR), and empty orbital regime (EOR). We find that the transient current in KR shows the strongest nonlinear response and the most distinct oscillation behaviors. Both behaviors become weaker in MVR and diminish in EOR. To understand the physical insight, we examine also the corresponding dot occupancies and the spectral functions, with their dependence on the Coulomb interaction, temperature, and applied step bias voltage...
April 7, 2018: Journal of Chemical Physics
Abhilash Patra, Subrata Jana, Prasanjit Samal
The construction of meta generalized gradient approximations based on the density matrix expansion (DME) is considered as one of the most accurate techniques to design semilocal exchange energy functionals in two-dimensional density functional formalism. The exchange holes modeled using DME possess unique features that make it a superior entity. Parameterized semilocal exchange energy functionals based on the DME are proposed. The use of different forms of the momentum and flexible parameters is to subsume the non-uniform effects of the density in the newly constructed semilocal functionals...
April 7, 2018: Journal of Chemical Physics
Yingqi Cui, Xianhui Cui, Li Zhang, Yujuan Xie, Mingli Yang
Ligand passivation is often used to suppress the surface trap states of semiconductor quantum dots (QDs) for their continuous photoluminescence output. The suppression process is related to the electrophilic/nucleophilic activity of surface atoms that varies with the structure and size of QD and the electron donating/accepting nature of ligand. Based on first-principles-based descriptors and cluster models, the electrophilic/nucleophilic activities of bare and chloride-coated CdSe clusters were studied to reveal the suppression mechanism of Cl-passivated QDs and compared to experimental observations...
April 7, 2018: Journal of Chemical Physics
Effat Alemzadeh, Ali Dehshahri, Keramatolah Izadpanah, Fatemeh Ahmadi
Nanoparticles have been gained much attention for biomedical applications. A promising type of nanocarriers is viral nanoparticles (VNPs) which are natural bio-nanomaterials derived from different type of viruses. Amongst VNPs, plant VNPs present several pros over general nanoparticles such as liposomes, dendrimers or quantum dots. Some of these advantages include: degradability, safety for human, known structures to atomic level, possibility of attaching ligand with vigorous control on structure, availability for genetic and chemical manipulations and very flexible methods to prepare them...
March 26, 2018: Colloids and Surfaces. B, Biointerfaces
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