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Han-Youl Ryu
GaN-based blue laser diodes (LDs) may exhibit anomalous temperature characteristics such as a very high characteristic temperature (T 0) or even negative T 0. In this work, temperature-dependent characteristics of GaN-based blue LDs with InGaN double quantum well (QW) structures were investigated using numerical simulations. The temperature-dependent threshold current is found to become increasingly anomalous as the thickness or doping concentration of the barrier layer between QWs increases. For a properly chosen barrier thickness and doping concentration, very high T 0 of >10,000 K can be obtained...
December 2017: Nanoscale Research Letters
Ghader Hosseinzadeh, Ali Maghari, Seyed Morteza Famil Farniya, Amir Homayoun Keihan, Ali A Moosavi-Movahedi
Interaction of quantum dots (QDs) and proteins strongly influenced by the surface characteristics of the QDs at the protein-QD interface. For a precise control of these surface-related interactions, it is necessary to improve our understanding in this field. In this regard, in the present work, the interaction between the insulin and differently functionalized ZnS quantum dots (QDs) were studied. The ZnS QDs were functionalized with various functional groups of hydroxyl (OH), carboxyl (COOH), amine (NH2), and amino acid (COOH and NH2)...
August 1, 2017: Materials Science & Engineering. C, Materials for Biological Applications
Junjian Li, Gancheng Zuo, Xiaoliang Qi, Wei Wei, Xiaohao Pan, Ting Su, Jianfa Zhang, Wei Dong
We report that nitrogen doped carbon dots (N-CDs) represent a viable fluorescent probe for the determination of Ag(+). The N-CDs can be fairly easily prepared by a hydrothermal treatment method using Salecan and dicyandiamide as the precursors, display excitation/emission maxima of 350/438nm. The N-CDs have an average diameter of about 3.8nm. The N-CDs exhibited blue fluorescence (quantum yield of 13.2%) and could response to Ag(+) selectively and sensitively. Other ions nearly had no interference. The probe has excellent selectivity, high sensitivity, and a linear response range that extends from 0 to 40μM...
August 1, 2017: Materials Science & Engineering. C, Materials for Biological Applications
Xu Zhang, Yamin Wang, Yanbao Zhao, Lei Sun
In this work, pH-sensitive "dual-switch" porous silica (pSiO2) nanoparticles (NPs) were constructed for drug delivery. Poly(acrylic acid) (PAA) was grafting onto the internal and external surfaces of amino groups functionalized porous silica (pSiO2-NH2) NPs by the amidation between the amino groups and the carboxyl groups of PAA for pH triggered drug release. The resultant pSiO2/PAA NPs have an average diameter of 50-60nm and high specific surface area (914m(2)·g(-1)). To improve the loading capacity, ZnO quantum dots (QDs) were used to block the partial pores of pSiO2/PAA and the loading capacity reached to 28% for methotrexate (MTX) model drug...
August 1, 2017: Materials Science & Engineering. C, Materials for Biological Applications
Don Betowski
The purpose of this research was to develop a predictive model for the phototoxicity potential of carbon nanomaterials (fullerenols and single-walled carbon nanotubes). This model is based on the quantum mechanical (ab initio) calculations on these carbon-based materials and comparison of the triplet excited states of these materials to published work relating phototoxicity of polynuclear aromatic hydrocarbons (PAH) to their predictive triplet excited state energy. A successful outcome will add another tool to the arsenal of predictive methods for the U...
March 31, 2017: Journal of Molecular Graphics & Modelling
Han-Don Um, Deokjae Choi, Ahreum Choi, Ji Hoon Seo, Kwanyong Seo
We demonstrate here an embedded metal electrode for highly efficient organic-inorganic hybrid nanowire solar cells. The electrode proposed here is an effective alternative to the conventional bus and finger electrode which leads to a localized short circuit at a direct Si/metal contact and has a poor collection efficiency due to a nonoptimized electrode design. In our design, an Ag/SiO2 electrode is embedded into a Si substrate while being positioned between Si nanowire (SiNW) arrays underneath poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS), facilitating suppressed recombination at the Si/Ag interface and notable improvements in the fabrication reproducibility...
May 22, 2017: ACS Nano
Xiao-Gen Xiong, Takeshi Yanai
The Projector Augmented Wave (PAW) method developed by Blochl is well recognized as an efficient, accurate pseudopotential approach in solid-state density functional theory (DFT) calculations with plane-wave basis. Here we present an approach to incorporate the PAW method into the Gauss-type function (GTF) based DFT implementation, which is widely used for molecular quantum chemistry calculations. The nodal and high-exponent GTF components of valence molecular orbitals (MOs) are removed or pseudized by the ultrasoft PAW treatment, while there is elaborate transparency to construct accurate and well-controlled pseudopotential from all-electron atomic description and to reconstruct all-electron form of valence MOs from the pseudo MOs...
May 22, 2017: Journal of Chemical Theory and Computation
Koki Ando, Mitsutaka Yamaguchi, Seiichi Yamamoto, Toshiyuki Toshito, Naoki Kawachi
Imaging of secondary electron bremsstrahlung x-ray emitted during proton irradiation is a possible method for measurement of the proton beam distribution in phantom. However, it is not clear that the method is used for range estimation of protons. For this purpose, we developed a low-energy x-ray camera and conducted imaging of the bremsstrahlung x-ray produced during irradiation of proton beams. We used a 20 mm  ×  20 mm  ×  1 mm finely grooved GAGG scintillator that was optically coupled to a one-inch square high quantum efficiency (HQE)-type position-sensitive photomultiplier tube to form an imaging detector...
May 22, 2017: Physics in Medicine and Biology
Zhiyang Qi, Yusheng Zhai, Long Wen, Qilong Wang, Qin Chen, Sami Iqbal, Guangdian Chen, Ji Xu, Yan Tu
Heterojunction between metal and silicon (Si) is an attractive route to extend the response of Si-based photodiodes into the near-infrared (NIR) region, so-called Schottky barrier diodes. Photons absorbed into a metallic nanostructure excite the surface plasmon resonances (SPRs), which can be damped non-radiatively through the creation of hot electrons. Unfortunately, quantum efficiency of hot electron detectors remains low due to low optical absorption and poor electron injection efficiency. In this study, we propose an efficient and low-cost plasmonic hot electron NIR photodetector based on Au nanoparticle (Au NP)-decorated Si pyramid Schottky junction...
May 22, 2017: Nanotechnology
David Mark Wilkins, David E Manolopoulos, Silvio Pipolo, Damien Laage, James T Hynes
We combine classical and ring polymer molecular dynamics simulations with the molecular jump model to provide a molecular description of the nuclear quantum effects (NQEs) on water reorientation and hydrogen-bond dynamics in liquid H2O and D2O. We show that while the net NQEs is negligible in D2O, it leads to a ∼13% acceleration in H2O dynamics compared to a classical description. Large angular jumps exchanging hydrogen-bond partners are the dominant reorientation pathway (just as in a classical description); the faster reorientation dynamics arise from the increased jump rate constant...
May 22, 2017: Journal of Physical Chemistry Letters
Kevin Whitham, Tobias Hanrath
The formation of epitaxially connected quantum dot solids involves a complex interplay of interfacial assembly, surface chemistry, and irreversible directed attachment. We describe the basic mechanism in context of a coherent phase transition with distinct nucleation and propagation steps. The proposed mechanism explains how defects in the pre-assembled structure influence nucleation and how basic geometric relationships govern the transformation from hexagonal assemblies of isolated dots to interconnected solids with square symmetry...
May 22, 2017: Journal of Physical Chemistry Letters
Jiaqi Guo, Dongfei Liu, Ilari Filpponen, Leena-Sisko Johansson, Jani-Markus Malho, Sakeena Quraishi, Falk Liebner, Hélder A Santos, Orlando J Rojas
We present an approach to construct biocompatible and photoluminescent hybrid materials comprised of carbon quantum dots (CQD) and TEMPO-oxidized cellulose nanocrystals (TO-CNC). First, the amino-functionalized carbon quantum dots (NH2-CQD) were synthesized using a simple microwave method and the TO-CNCs were prepared by hydrochloric acid (HCl) hydrolysis followed by TEMPO-mediated oxidation. The conjugation of NH2-CQD and TO-CNC was conducted via carbodiimide-assisted coupling chemistry. The synthesized TO-CNC@CQD hybrid nanomaterials were characterized using X-ray photoelectron spectroscopy, cryo-transmittance electron microscopy, confocal microscopy and fluorescence spectroscopy...
May 22, 2017: Biomacromolecules
Wenhui Liu, Qi Wang, Yan Zheng, Shubin Wang, Yan Yan, Yanzhao Yang
In this study, a method of one-step separation and recycling of high purity Pd(ii) and Pt(iv) using an ionic liquid, 1-butyl-3-benzimidazolium bromate ([HBBIm]Br), was investigated. The effects of [HBBIm]Br concentration, initial metal concentration, and loading capacity of [HBBIm]Br were examined in detail. It was observed that [HBBIm]Br was a very effective extractant for selectively extracting Pd(ii) and precipitating Pt(iv). Through selectively extracting Pd(ii) and precipitating Pt(iv), each metal with high purity was separately obtained from mixed Pd(ii) and Pt(iv) multi-metal solution...
May 22, 2017: Dalton Transactions: An International Journal of Inorganic Chemistry
Lixin Zang, Huimin Zhao, Xueyu Ji, Wenwu Cao, Zhiguo Zhang, Peisong Meng
Conventional photodynamic therapy (PDT) uses red light for deeper penetration. A natural compound, aloe emodin (AE) with anticancer and photosensitising capabilities, excited by blue light, is proposed to treat superficial diseases. The photophysical properties and singlet oxygen quantum yield (ΦΔ) of AE, as well as the cytotoxic effects of AE on human cells, were investigated. The absorption and emission spectra of AE were analyzed. The ΦΔ of AE was measured by a relative method. In order to study the relationship between ΦΔ and the oxygen concentration, the dependence of ΦΔ on the oxygen concentration was investigated...
May 22, 2017: Photochemical & Photobiological Sciences
Keisuke Kawashima, Hiroshi Ishikita
Using the cyanobacterial and plant photosystem I (PSI) crystal structures and by considering the protonation states of all titratable residues, redox potentials (Em) of the two phylloquinones--A1A and A1B--were calculated. The calculated Em values were Em(A1A) = -773 mV and Em(A1B) = -818 mV for the plant PSI structure and Em(A1A) = -612 mV and Em(A1B) = -719 mV for the cyanobacterial PSI structure. Our analysis of the PSI crystal structures suggested that the side-chain orientations of Lys-B542 and Gln-B678 in the cyanobacterial crystal structure differ from these side-chain orientations in the plant crystal structure...
May 22, 2017: Biochemistry
Chengzhi Luo, Junji Jia, Youning Gong, Zhongchi Wang, Qiang Fu, Chunxu Pan
Sensitivity, durability, and multifunction are the essential requirements for a high- performance wearable sensor. Here, we report a novel multifunctional sensor with high sensitivity and durability by using a buckled spider silk-like single-walled carbon nanotubes (SSL-SWNTs) film as the conducting network and a crack-shaped Au film as the sensitive transducer. Its high sensitivity is inspired by the crack-shaped structure of the spider's slit organs, while the high durability is inspired by the mechanical robustness of the spider silk...
May 22, 2017: ACS Applied Materials & Interfaces
Chun Du, Jun Wang, Xiao Liu, Jie Yang, Kun Cao, Yanwei Wen, Rong Chen, Bin Shan
Photoelectrochemical water splitting holds great potential for solar energy conversion and storage with zero greenhouse gas emission. Integration of a suitable co-catalyst with an absorber material enables the realization of highly efficient photocleavage of water. Herein, nanostructured hematite film was coated with an ultrathin and conformal CoOx overlayer through atomic layer deposition (ALD). The best performing hybrid hematite with a 2-3 nm ALD CoOx overlayer yielded a remarkable turn on potential of 0...
May 22, 2017: Physical Chemistry Chemical Physics: PCCP
H Khani, M Esmaeilzadeh, F Kanjouri
Generation of large currents, versatile functionality, and simple structures are of fundamental importance in the development of adiabatic quantum pump devices with nanoscale dimensions. In the present study, we propose an adiabatic quantum pump with a simple structure based on molybdenum disulfide, MoS2, to generate large spin and valley resolved currents. We show that pure and fully polarized spin and valley currents can be easily generated by employing two potential gates and using an exchange magnetic field...
May 22, 2017: Physical Chemistry Chemical Physics: PCCP
Dong-Qiang He, Hai-Yan Lu, Meng Li, Chuan-Feng Chen
A new class of chiral organic molecules was synthesized with CPL properties based on helical aromatic esters. The molecules not only show blue fluorescence with high quantum yields in solution and films, but also exhibit intense CPL with large glum.
May 22, 2017: Chemical Communications: Chem Comm
Carmen Palacios-Berraquero, Dhiren M Kara, Alejandro R-P Montblanch, Matteo Barbone, Pawel Latawiec, Duhee Yoon, Anna K Ott, Marko Loncar, Andrea C Ferrari, Mete Atatüre
Quantum light emitters have been observed in atomically thin layers of transition metal dichalcogenides. However, they are found at random locations within the host material and usually in low densities, hindering experiments aiming to investigate this new class of emitters. Here, we create deterministic arrays of hundreds of quantum emitters in tungsten diselenide and tungsten disulphide monolayers, emitting across a range of wavelengths in the visible spectrum (610-680 nm and 740-820 nm), with a greater spectral stability than their randomly occurring counterparts...
May 22, 2017: Nature Communications
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