共查询到20条相似文献,搜索用时 31 毫秒
1.
Sylwia Nowakowska Aneliia Wäckerlin Ignacio Piquero‐Zulaica Jan Nowakowski Shigeki Kawai Christian Wäckerlin Manfred Matena Thomas Nijs Shadi Fatayer Olha Popova Aisha Ahsan S. Fatemeh Mousavi Toni Ivas Ernst Meyer Meike Stöhr J. Enrique Ortega Jonas Björk Lutz H. Gade Jorge Lobo‐Checa Thomas A. Jung 《Small (Weinheim an der Bergstrasse, Germany)》2016,12(28):3757-3763
2.
Mona Rafipoor Rieke Koll Jan‐Philip Merkl Lisa Sarah Fruhner Horst Weller Holger Lange 《Small (Weinheim an der Bergstrasse, Germany)》2019,15(5)
Core/shell quantum dots/quantum rods are nanocrystals with typical application scenarios as ensembles. Resonance energy transfer is a possible process between adjacent nanocrystals. Highly excited nanocrystals can also relax energy by multiexciton recombination, competing against the energy transfer. The two processes have different dependencies and can be convolved, resulting in collective properties different from the superposition of the individual nanocrystals. A platform to study the interplay of energy transfer and multiexciton recombination is presented. CdSe/CdS quantum dot/quantum rods encapsulated in amphiphilic micelles with an interparticle distance control by spacer ligands are used for time‐resolved photoluminescence and transient absorption experiments. At exciton populations around one, the ensemble starts to be in a state where energy transfer can trigger multiexciton Auger recombination, altering the collective dynamics. 相似文献
3.
Ultrasensitive Surface‐Enhanced Raman Spectroscopy Detection Based on Amorphous Molybdenum Oxide Quantum Dots
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Surface‐enhanced Raman spectroscopy (SERS) based on plasmonic semiconductive material has been proved to be an efficient tool to detect trace of substances, while the relatively weak plasmon resonance compared with noble metal materials restricts its practical application. Herein, for the first time a facile method to fabricate amorphous HxMoO3 quantum dots with tunable plasmon resonance is developed by a controlled oxidization route. The as‐prepared amorphous HxMoO3 quantum dots show tunable plasmon resonance in the region of visible and near‐infrared light. Moreover, the tunability induced by SC CO2 is analyzed by a molecule kinetic theory combined with a molecular thermodynamic model. More importantly, the ultrahigh enhancement factor of amorphous HxMoO3 quantum dots detecting on methyl blue can be up to 9.5 × 105 with expending the limit of detection to 10?9 m . Such a remarkable porperty can also be found in this HxMoO3‐based sensor with Rh6G and RhB as probe molecules, suggesting that the amorphous HxMoO3 quantum dot is an efficient candidate for SERS on molecule detection in high precision. 相似文献
4.
目的 研究木包装箱在全生命周期过程中对环境的影响,对比钢边箱和传统木箱对环境的影响.方法 通过全生命周期分析软件eBalance分析2款木包装箱从产品生产、物流运输到使用后的废物管理整个生命周期的物耗、能耗及向环境中的排放,对其数据清单进行分类、特征化和归一化计算,得到木包装箱3个流程的主要环境影响类型和对应指标值.结果 传统木箱在产品生产、物流运输和废物管理流程的LCIA加权综合指标分别为6.87514×10?9,1.93549×10?12,5.20×10?13,其中胶合板生产在产品生产过程中的占比为99.86%,胶合板处理在废物管理过程中的占比为99.82%;钢边箱在产品生产、物流运输和废物管理流程的LCIA加权综合指标分别为6.53463×10?9,3.57256×10?13,2.96531×10?13,其中胶合板生产在产品生产过程中的占比为97.43%,胶合板处理在废物管理过程中的占比为99.38%;钢边箱对环境影响的总量比传统木箱小约5%.结论 木包装箱全生命周期的环境影响主要体现在胶合板的生产和废物管理过程中,木包装箱在设计、生产加工、运输、废弃物处理等方面都有较大的改进余地,钢边箱比传统木箱更具有环境友好性,对木包装箱绿色化的生产设计具有参考意义. 相似文献
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Recommendations for accurate heat capacity measurements using a Quantum Design physical property measurement system 总被引:1,自引:0,他引:1
Catherine A. Kennedy 《低温学》2007,47(2):107-112
A commercial instrument for determination of heat capacities of solids from ca. 400 K to 0.4 K, the physical property measurement system from Quantum Design, has been used to determine the heat capacities of a standard samples (sapphire [single crystal] and copper). We extend previous tests of the PPMS in three important ways: to temperatures as low as 0.4 K; to samples with poor thermal conductivity; to compare uncertainty with accuracy. We find that the accuracy of heat capacity determinations can be within 1% for 5 K < T < 300 K and 5% for 0.7 K < T < 5 K. Careful attention should be paid to the relative uncertainty for each data point, as determined from multiple measurements. While we have found that it is possible in some circumstances to obtain excellent results by measurement of samples that contribute more than ca. 1/3 to the total heat capacity, there is no “ideal” sample mass and sample geometry also is an important consideration. In fact, our studies of pressed pellets of zirconium tungstate, a poor thermal conductor, show that several samples of different masses should be determined for the highest degree of certainty. 相似文献
6.
Si衬底用化学方法清洗后,表面大约残余1.0 nm厚SiO2薄膜.利用原子力显微镜(AFM)和反射高能电子衍射(RHEED)来研究温度和Ge蒸发厚度对在SiO2薄膜表面生长的Ge量子点的影响.实验结果表明,当衬底温度超过500 ℃时,SiO2开始与Ge原子发生化学反应,并形成与Si(111)表面直接外延的Ge量子点.在650 ℃时,只有Ge的厚度达到0.5nm时,Ge量子点才开始形成. 相似文献
7.
Maisara Othman Richard Ritikos Noor Hamizah Khanis Nur Maisarah Abdul RashidSiti Meriam Ab. Gani Saadah Abdul Rahman 《Materials Chemistry and Physics》2014
Carbon nitride (CNx) thin films were deposited using radio frequency plasma enhanced chemical vapor deposition (rf PECVD) from a mixture of ethane (C2H6), nitrogen (N2) and hydrogen (H2) gases. The C2H6 and N2 flow rates were kept constant, while the H2 flow rate was varied. The effects of hydrogen dilution on the growth rate and structural properties of the films were studied. It was found that a significant increase in the films growth rate was observed with the introduction of H2 at as low as 25 standard cubic centimeters per minute (sccm). A set of CNx films deposited from C2H6:N2 mixture without any inclusions of H2 were also presented in this work as a reference to compare the differences between those two sets and to understand the roles of H2 to the films properties. At highest H2 flow rate, the structure of the films changed from polymeric to graphitic and the quenching of PL was observed. Furthermore, higher N incorporation with lower Eg was obtained for these films compared to those of C2H6:N2 films. The change in the structure of the films corresponds to changes in their chemical bonding. As N incorporation increased, the porosity of the films increases and thus affects the disorder in the film structures. 相似文献
8.
Quantum beat spectroscopy on excitons in GaN 总被引:1,自引:0,他引:1
R. Zimmermann M. R. Hofmann A. Euteneuer J. M bius D. Weber W. W. Rü hle E. O. G bel B. K. Meyer H. Amano I. Akasaki 《Materials Science and Engineering: B》1997,50(1-3):205-207
We present four wave mixing experiments on excitons in GaN. The four wave mixing transients exhibit strong modulations yielding a splitting of the A- and the B-exciton of 7.98 meV. In addition, we obtain a biexciton binding energy for A-excitons of 5.7 meV. 相似文献
9.
Single Nucleobase Identification Using Biophysical Signatures from Nanoelectronic Quantum Tunneling
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Lee E. Korshoj Sepideh Afsari Sajida Khan Anushree Chatterjee Prashant Nagpal 《Small (Weinheim an der Bergstrasse, Germany)》2017,13(11)
Nanoelectronic DNA sequencing can provide an important alternative to sequencing‐by‐synthesis by reducing sample preparation time, cost, and complexity as a high‐throughput next‐generation technique with accurate single‐molecule identification. However, sample noise and signature overlap continue to prevent high‐resolution and accurate sequencing results. Probing the molecular orbitals of chemically distinct DNA nucleobases offers a path for facile sequence identification, but molecular entropy (from nucleotide conformations) makes such identification difficult when relying only on the energies of lowest‐unoccupied and highest‐occupied molecular orbitals (LUMO and HOMO). Here, nine biophysical parameters are developed to better characterize molecular orbitals of individual nucleobases, intended for single‐molecule DNA sequencing using quantum tunneling of charges. For this analysis, theoretical models for quantum tunneling are combined with transition voltage spectroscopy to obtain measurable parameters unique to the molecule within an electronic junction. Scanning tunneling spectroscopy is then used to measure these nine biophysical parameters for DNA nucleotides, and a modified machine learning algorithm identified nucleobases. The new parameters significantly improve base calling over merely using LUMO and HOMO frontier orbital energies. Furthermore, high accuracies for identifying DNA nucleobases were observed at different pH conditions. These results have significant implications for developing a robust and accurate high‐throughput nanoelectronic DNA sequencing technique. 相似文献
10.
Enhancing Quantum Dots for Bioimaging using Advanced Surface Chemistry and Advanced Optical Microscopy: Application to Silicon Quantum Dots (SiQDs)
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Xiaoyu Cheng Elizabeth Hinde Stuart B. Lowe Peter J. Reece Katharina Gaus J. Justin Gooding 《Advanced materials (Deerfield Beach, Fla.)》2015,27(40):6144-6150
11.
In contrast to non-doped diamond-like-carbon (DLC) coatings, reliable chemical evidence of the reactions between metal-doped DLC coatings and oil additives under tribological conditions using state-of-the-art surface-sensitive chemical analyses is still scarce. In this study we have investigated the reactivity of metal-doped (Ti, WC) DLC coatings with the extreme-pressure (EP) dialkyl dithiophosphate additive — without the presence of a steel counter body in the contact that befogs the actual coating reactions. Static “reactivity” experiments without any tribological or mechanical effects were also performed to provide a further insight into the lubrication mechanisms. The results confirmed the chemical reactions between the EP additive and all the DLC coatings, as well as their oxidation during the tribological contacts. We measured an about 10-times higher chemical activity (a 25-fold P/S ratio increase) for the Ti-doped DLC compared to the WC-doped or non-doped DLC, which also agrees with it having the lowest amount of wear in this study. We suggest that the Ti-DLC boundary lubrication is achieved via binding sites at the O vacancies present in the Ti-doped DLC coating. The data also clearly show, in contrast to most of literature reports, that even though small, some direct chemical activity between the W-DLC and the dialkyl dithiophosphate EP additive is also possible without any iron catalytic effect. However, the chemical changes were significantly smaller, also allowing coating graphitization, which might be one of the reasons for the 50% higher wear of the WC-doped compared to the Ti-doped DLC. 相似文献
12.
利用离面双弯曲过滤阴极其空电弧沉积系统,在Ф200mm单晶硅片上制备四面体非晶碳薄膜。利用Dectek3型表面轮廓仪检验膜厚均匀性(小于5%),并利用扫描电子显微镜(SEM)、原子力显微镜(AFM)、激光拉曼光谱(Raman)、X射线光电子谱(XPS)以及纳米压痕(Nano—Indenter)仪器测试薄膜的性能和结构。结果表明:试验制备的薄膜是四面体非晶碳薄膜,其中sp^3键含量高达80%以上,薄膜表面纯净,几乎没有大颗粒的污染,表面粗糙度(Rq)小于0.3nm(取样面积1μm^2),薄膜硬度可达50GPa,杨氏弹性模量高于550GPa。 相似文献
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Core level and valence band investigation of WO3 thin films with synchrotron radiation 总被引:1,自引:0,他引:1
L. Ottaviano F. BussolottiL. Lozzi M. PassacantandoS. La Rosa S. Santucci 《Thin solid films》2003,436(1):9-16
In this work, the electronic properties of the surface of WO3 films with thickness of 150 nm, thermally evaporated in high vacuum onto Si(100) substrates and pre-treated in air by a 24-h-long annealing at 300 °C and 500 °C (obtaining polycrystalline monoclinic samples) have been studied by surface and bulk sensitive core level (W 4f) and angle integrated valence band photoemission using synchrotron radiation (ELETTRA Synchrotron). The photon energy ranged from 50 eV to 200 eV. The line shape analysis of W 4f core level spectra has shown that the surface presents a sub-stoichiometric WO3 component assigned to oxygen vacancies ultimately responsible for the gas sensitivity of this material. Correspondingly, valence band spectra show well-defined metallic states W 5d in the gap and near the Fermi level. The variations of surface chemical composition caused by Ultra High Vacuum annealing, and prolonged exposure to UV beam has been monitored by changes in spectral line shape. A general consequence of annealing in vacuum is the segregation of oxygen from the bulk toward the surface as confirmed by independent scanning tunnelling spectroscopy measurements. 相似文献
15.
Abdelilah Majjane Abdelkrim Chahine Mohamed Et-tabirou Bousselham Echchahed Trong-On Do Peter Mc Breen 《Materials Chemistry and Physics》2014
Barium vanadophosphate glasses, having composition 50BaO–xV2O5–(50 − x)P2O5, (x = 0–50 mol%), were prepared by conventional melt quench method. Density, molar volume and glass transition temperature (Tg) were measured as a function of V2O5 content. Structural investigation was done using XPS and FTIR spectroscopy. First, substitution of the P2O5 by the V2O5 in the metaphosphate 50BaO–50P2O5 glass increases the density and Tg and decreases the molar volume. When the amount of V2O5 increases, all these properties show a reverse trend. XPS measurement found in the O1s, P2p, and V2p core level spectra indicate the presence of primarily P–O–P, P–O–V and V–O–V structural bonds, the asymmetry in the P 2p spectra indeed arises from the spin-orbit splitting of P 2p core level, and more than one valence state of V ions being present. IR spectroscopy reveals the depolymerization of the phosphate glass network by systematic conversion of metaphosphate chains into pyrophosphate groups and then orthophosphate groups. Even though metaphosphate to pyrophosphate conversion is taking place due to breaking of P–O–P linkages, formation of P–O–V and P–O–Ba linkages provide cross linking between short P-structural units, which make the glass network more rigid. Above 10–20 mol% V2O5 content, network is highly depolymerized due to the formation of orthophosphate units and V–O–V bridge bonds, resulting in poor cross-linking, making the glass network less rigid. 相似文献
16.
A one pot synthesis protocol is presented for the realization of organic/inorganic hybrid nanostructures comprised of polyaniline and vanadium oxide. The polyaniline/vanadium oxide hybrid morphology is tailored by controlling the relative concentration of reactants which resulted in diverse morphologies ranging from nanorods, combined nano/microrods to porous nano/microspheres. Temporal evolution of morphology is investigated to elucidate the formation mechanism in detail. The prepared composites exhibit enhanced thermal stability in comparison to pure polyaniline which may be attributed to the strong chemical combination of vanadium oxide and polyaniline within the composites as prevailed by FTIR and TGA analysis of the products. This simple and controllable approach for synthesizing the organic/inorganic hybrid material should have future applications in energy storage devices, sensors and many more. 相似文献
17.
Hamed Dehghanpour Baruj Iklim Bozkaya Betul Canimkurbey Ahmet Tarik Isik Farzan Shabani Savas Delikanli Sushant Shendre Onur Erdem Furkan Isik Hilmi Volkan Demir 《Small (Weinheim an der Bergstrasse, Germany)》2023,19(29):2206582
Semiconductor colloidal quantum wells (CQWs) provide anisotropic emission behavior originating from their anisotropic optical transition dipole moments (TDMs). Here, solution-processed colloidal quantum well light-emitting diodes (CQW-LEDs) of a single all-face-down oriented self-assembled monolayer (SAM) film of CQWs that collectively enable a supreme level of IP TDMs at 92% in the ensemble emission are shown. This significantly enhances the outcoupling efficiency from 22% (of standard randomly-oriented emitters) to 34% (of face-down oriented emitters) in the LED. As a result, the external quantum efficiency reaches a record high level of 18.1% for the solution-processed type of CQW-LEDs, putting their efficiency performance on par with the hybrid organic-inorganic evaporation-based CQW-LEDs and all other best solution-processed LEDs. This SAM-CQW-LED architecture allows for a high maximum brightness of 19,800 cd m−2 with a long operational lifetime of 247 h at 100 cd m−2 as well as a stable saturated deep-red emission (651 nm) with a low turn-on voltage of 1.7 eV at a current density of 1 mA cm−2 and a high J90 of 99.58 mA cm−2. These findings indicate the effectiveness of oriented self-assembly of CQWs as an electrically-driven emissive layer in improving outcoupling and external quantum efficiencies in the CQW-LEDs. 相似文献
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本文报道了一类组成为50SiO2-10Al2O3-20ZnF2-20SrF2-3YbF3-0.05ErF3(mol%)的氟氧化物玻璃陶瓷的制备及其量子剪裁发光行为。XRD和TEM分析结果显示,玻璃陶瓷中均匀分布有尺度10~40nm的SrF2析晶相。光谱研究表明,玻璃陶瓷在Er3+激发峰波长377nm激发下存在Er3+向Yb3+的有效能量传递,可实现包括量子剪裁效应在内的波长变换功能。随着热处理温度的升高,玻璃陶瓷的近红外977nm发光逐渐增强,荧光寿命显著增长。 相似文献
20.
C.H. Huang N.F. Wang Y.Z. Tsai C.C. Liu C.I. Hung M.P. Houng 《Materials Chemistry and Physics》2008,110(2-3):299-302
The characterizations of SiOCH films using oxygen plasma treatment depends linearly on the O2/CO flow rate ratio. According to the results of Fourier transform infrared spectroscopy (FTIR) and X-ray photoelectron spectroscopy (XPS) analyses, it was found that the carbon composition decreases with increasing O2/CO flow rate ratio, because more carbon in the Si–O–C and Si–CH3 bonds on the film surface would be converted by oxygen radicals. It was believed that the oxygen plasma could oxidize the SiOCH films and form a SiOx interfacial capping layer without much porosity. Moreover, the result of FTIR analysis revealed that there was no water absorbed on the film. A SiO2-like capping layer formed at the SiOCH film by the O2/CO flow rate ratio of 0.75 had nearly the same dielectric properties from the result of capacitance–voltage (C–V) measurement in our research. 相似文献