共查询到20条相似文献,搜索用时 15 毫秒
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Jonathan Britton Edith Antunes Tebello Nyokong 《Inorganic chemistry communications》2009,12(9):828-831
CdTe Qds capped with mercapto propionic acid (MPA) were covalently linked to zinc tetraamino phthalocyanine (ZnTAPc) using N-ethyl-N(3-dimethylaminopropyl) carbodiimide (EDC) and N-hydroxy succinimide (NHS) as the coupling agents. The results presented give evidence in favour of the formation of an amide bond between ZnTAPc and CdTe QDs. Both the linked ZnTAPc–QD complexes and a mixture of QDs and ZnTAPc (i.e. without chemical linking) showed Förster resonance energy transfer (FRET). ZnTAPc quenched the QDs emission, giving quenching constants in the order of 103 M−1. 相似文献
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《Ceramics International》2021,47(20):28642-28649
Ti3C2Tx MXene has attracted remarkable attention due to its promising applications in energy storage and sensors. However, traditional MXene preparation methods used HF as etchant, which was highly toxic and harmful to human and environment. Moreover, the aqueous etchants will also result in the combination of OH, O and F groups on the surfaces, making it difficult to control the varieties and contents of the surface terminations. In this paper, a green and mild electrochemical exfoliation method was proposed to synthesize Ti3C2Fx and synchronously control its fluorination degree on the surface. A non-aqueous ionic liquid, [BMIM][PF6]-based solution was used as electrolyte. The as-prepared Ti3C2Fx was fluorinated with the CF and TiF3 groups, which were electrochemically active and contributed to the excellent cycling stability of the MXene anode-based Li-ion batteries. These findings provided a facile strategy to prepare MXene materials and dope MXene with tailored property for MXene-based energy devices applications. 相似文献
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In this study, phosphate glasses embedded with Fe2O3 quantum dots were prepared via a conventional melt quenching technology with further heat treatment. The effect of Fe2O3 content on the structural, optical and magneto-optical properties was investigated. The results showed that the addition of Fe2O3 had no obvious influence on the structure units that built up the host glass and the amorphous nature of glass. In the glass matrix, the existence of Fe2O3 quantum dots was confirmed by high resolution transmission electron microscope. Meanwhile, optical study clearly demonstrated a red shift in optical cut-off wavelength resulted from the size quantization effect. The highest Verdet constant (22.33°/T-cm) was measured for the glass containing 1 mol% Fe2O3, which was ~ 7 times higher than that of the glass matrix. As the increment of Fe2O3 contents, a phase evolution of Fe2O3 quantum dots from amorphous phase to γ-Fe2O3 phase was recorded due to the Ostwald Ripening effect. Interestingly, a concentration quenching phenomenon in Verdet constant was observed along with the phase evolution of Fe2O3 quantum dots. When the content of Fe2O3 is up to 2 mol%, the glass exhibited paramagnetism with the Verdet constant of ? 2.833°/T-cm. This finding can provide a new idea for the development of quantum dot embedded magneto-optical glass. 相似文献
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《Ceramics International》2022,48(17):25111-25119
Electromagnetic wave (EMW) absorbing materials have been widely applied in the fields of military and engineering areas. It is of great significance to develop high-performance EMW absorbing materials. This work assembled the sandwich-like Ti3C2Tx based nanocomposites by the microwave-assisted annealing of CoFe-MOF@Ti3C2Tx (CFMF@Ti3C2Tx) precursors at different temperatures. Results show that, as the heat treatment temperature is 450 °C, the sandwich-like Ti3C2Tx@CoFe@TiO2 nanocomposites present better EMW absorption properties. The minimum reflection loss (RL) value was ?62.9 dB at 17.95 GHz with a thin thickness of 1.2 mm. Moreover, the effective absorption bandwidth (EAB) value was 5.02 GHz (12.74–17.76 GHz) with a thickness of 1.4 mm. The application of microwave-assisted annealing contributed to the formation of CoFe nanoparticles and TiO2 nanoparticles because of the ultra-fast heating rate. The introduction of the nanoparticles enhanced the multiple polarization, optimized the impedance matching and introduced magnetic loss, leading to the improvement of EMW absorption. When the annealing temperature further increased to 550 °C, the EMW absorbing performance was weakened, which was mainly correlated with the decrement of the interface area due to the increase of the TiO2 nanoparticle size and CoFe nanoparticle size. Thus, the loss effect of the multiple interface polarization weakens in the EMW absorption. In addition, the high permittivity of Ti3C2Tx disappears, which deteriorated the impedance matching and attenuation ability of EMW. Ultimately, sandwich-like Ti3C2Tx@CoFe@TiO2 nanocomposite with satisfactory EMW absorbing properties is established, promising for various EMW absorbing applications. 相似文献
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Quantum dots (QDs)/elastomer (VM) composite nanofibers have been fabricated via electrospinning method with the assistance of small amount (1 wt%) of ionic liquid. Without ionic liquid, polymer solution underwent an electrospraying process within the electric field and only individual droplets rather than continuous fibers were observed. Both fixed electrode and rotating disk electrode were used to collect the products. The latter one turned out to be much more advanced in collecting separated, aligned and narrow-size distributed composite nanofibers. With fixed electrode, even though nanofibers were obtained initially, the as-spun fibers were easily to merge together due to the flexible non-crystalline nature of the VM chains and finally formed a condensed thin film. Strong fluorescent emission was observed in the composite nanofibers with a QD loading of 3 and 5 wt%, respectively. The optical property of QDs was not degraded after dispersing in the polymer solution as evidenced by the UV-Vis absorption at 562 nm and 592 nm, and strong photoluminescent emission at 612 nm. In addition, differential scanning calorimetry (DSC) analysis revealed a strong interaction between ionic liquid and the polymer chains, which well explains the function of the ionic liquid on producing fiber structure of VM. An enhanced thermal stability of the elastomer in the composite nanofibers is observed as compared to that of the pure elastomer fibers. 相似文献
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Yunfeng Shi Lin Liu Huan Pang Hongli Zhou Guanqing Zhang Yangyan Ou Xiaoyin Zhang Jimin Du Wangchuan Xiao 《Nanoscale research letters》2014,9(1):115
A new strategy for facile preparation of highly luminescent CdTe quantum dots (QDs) within amine-terminated hyperbranched poly(amidoamine)s (HPAMAM) was proposed in this paper. CdTe precursors were first prepared by adding NaHTe to aqueous Cd2+ chelated by 3-mercaptopropionic sodium (MPA-Na), and then HPAMAM was introduced to stabilize the CdTe precursors. After microwave irradiation, highly fluorescent and stable CdTe QDs stabilized by MPA-Na and HPAMAM were obtained. The CdTe QDs showed a high quantum yield (QY) up to 58%. By preparing CdTe QDs within HPAMAM, the biocompatibility properties of HPAMAM and the optical, electrical properties of CdTe QDs can be combined, endowing the CdTe QDs with biocompatibility. The resulting CdTe QDs can be directly used in biomedical fields, and their potential application in bio-imaging was investigated. 相似文献
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ABSTRACT: Noble-metal nanostructure allows us to tune optical and electrical properties, which has high utility for real-world application. We studied surface plasmon induced emission of semiconductor quantum dots (QDs) on engineered metallic nanostructures. Highly passive organic ZnS capped CdSe QDs were spin coated on poly-(methyl methacrylate) (PMMA) covered Ag films which brought QDs near to metallic surface. We obtained the enhanced electromagnetic field and reduced fluorescence lifetimes from CdSe/ZnS quantum dots (QDs) due to the strong coupling of emitters wave function with the Ag plasmon resonance. Observed changes include a six-fold increase in the fluorescence intensity and striking reduction in fluorescence lifetimes of CdSe/ZnS QDs on rough Ag nanoneedle compared to the case of smooth surfaces. The advantages of using those nanocomposites are expected for high efficiency light-emitting diodes, platform fabrication of biological and environmental monitoring, and high contrast imaging. 相似文献
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硫量子点具有发光强度高、毒性低和光化学性能稳定等优势,广泛应用于细胞成像、光电转换和化学催化等领域。鉴于此,本文系统综述了硫量子点的合成方法,光学性能和应用背景。硫量子点的合成方法可分为“自下而上法”和“自上而下法”,对比发现“自上而下法”合成的硫量子点具有更高的荧光量子产率。分析了硫量子点的光学性质,表明其具有紫外吸收特性、荧光特性、光致发光、电化学发光以及光学稳定性。最后,系统介绍了硫量子点在荧光探针、生物成像以及发光器件等领域的重要应用。基于以上分析,深刻剖析了当下硫量子点在前沿应用中亟待解决的问题,展望了未来硫量子点在生物医学、光电催化等新行业、新领域的发展方向。 相似文献
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A facile approach to introduce carboxyl groups onto the surface of CdSe quantum dots (QD) was achieved via oleic acid ligands self-assembly, and then CdSe quantum dots/epoxy fluorescence nanocomposites were successfully fabricated. The surface constitution of QD, the better dispersibility of QD in epoxy matrix, and the reactivity with epoxy of carboxyl groups functionalized QD were characterized by Fourier transform infrared (FT-IR), transmission electron microscopy (TEM), and differential scanning calorimetry (DSC), respectively. As the result of surface modification, the carboxyl groups functionalized QD could be stably and homogenously dispersed in chloroform and acid anhydride cured epoxy matrix. The fresh fluorescence as well as the toughening behavior of the QD/epoxy nanocomposites was presented. 相似文献
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《Ceramics International》2019,45(16):19902-19909
Two-dimensional (2D) MXenes have attracted much attention due to their unique structural characteristics and novel performance in a variety of functions. The fabrication of 2D Ti3C2 MXene by acid etching usually requires a long period of over 10 h. In this work, we report on the rapid preparation, thermal stability and electromagnetic interference (EMI) shielding effectiveness of 2D Ti3C2 MXene. With the processing conditions optimized by adjusting the etching time and temperature, Ti3C2 MXene with a scattered accordion-like structure has been successfully achieved by etching Ti3AlC2 powders with 40% HF at 50 °C for only 0.5 h. The as-synthesized Ti3C2 was stable at temperatures up to 300 °C in air, but stable in vacuum at temperatures up to 800 °C. The as-synthesized Ti3C2 MXene has good EMI shielding performance. The total shielding effectiveness of Ti3C2 in a WAX matrix exceeded 20 dB in the whole frequency ranging from 2 to 18 GHz. The maximum shielding effectiveness value achieved to 34 dB at 18 GHz as the Ti3C2 content was up to 70 wt%. This work provides an approach for the large scale preparation of the Ti3C2 MXene. 相似文献
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Xizhen Zhang Lizhu Guo Yuhang Zhang Chuanhui Cheng Yi Cheng Xiangping Li Jinsu Zhang Sai Xu Yongze Cao Jiashi Sun Lihong Cheng Baojiu Chen 《Journal of the American Ceramic Society》2020,103(9):5028-5035
We have fabricated CsPbBr3 perovskite quantum dots (QDs) in a multi-component borate glass by melt-quenching technique. Transmission electron microscopy (TEM) reveals a cubic phase CsPbBr3 crystal for QDs. As the treatment temperature or the treatment time duration increases, the photoluminescence (PL) peak shifts to long wavelength in the range of 510 to 525 nm, and the full width at half-maximum varies in the range of 24 to 18 nm. The absorption edge shifts to low energy side in the range of 2.54 to 2.41 eV. The different photoluminescence excitation spectra (PLE) reflect the change of microstructure for different samples. The PL peak wavelength and line-shape are independent of excitation wavelength. These results of spectra show typical exciton emission characteristics. As treatment conditions strengthens, photoluminescence quantum yield (PLQY) first increases and then decreases, having the best PLQY 86.9%. Bi-exponential fitting curves show that short lifetime τ1 continuously decreases. Long lifetime τ2, weight for long lifetime component, and average lifetime τavg first increase and then decrease. The PLQY values are affected by both τ1 and τ2, which are relative to the crystal quality in the interior and the surface of QDs, respectively. The high PLQY value corresponds to medium treatment condition, which is attributed to a balanced effect of crystal quality in interior and the surface of QDs. 相似文献
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《Ceramics International》2017,43(11):8372-8377
Real-time monitoring of trace NO2 emission has been an emerging challenge in environment and health sectors lately. Aiming to overcome this challenge, NO2 gas sensors based on cuprous oxide quantum dots (Cu2O QDs) anchored onto reduced graphene oxide (RGO) nanosheets serving as a sensitive layer were prepared in this report. Apart from a series of purposive measurements, various characterization techniques such as XRD, Raman, XPS and TEM were employed as well to assist the exploration of sensors performance to NO2 gas. The experimental results revealed a 580% response enhancement for prepared RGO/Cu2O sensors compared with pure RGO counterparts, as well as an excellent selectivity. In a specific experiment, the sensing response attained 4.8% and 29.3% toward 20 ppb and 100 ppb NO2 respectively at 60 °C, which was larger than most Cu2O based resistive gas sensors. Moreover, further subtle modulation of this RGO/Cu2O nanocomposites led to a preferable room-temperature response of 37.8% toward 100 ppb NO2, which also offered a favorable stability of 98.1% response retention after four exposures within ten days. The obtained results imply that the prepared RGO/Cu2O QDs sensors possess a competitive capability of trace NO2 detection. 相似文献
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利用太阳能光催化技术生产清洁燃料、降解污染物及转化高附加值产品,是解决当前能源短缺和环境污染问题的有效途径。随着对金属卤化物钙钛矿的深入研究,成功开发出一系列能够制备出成分和形貌控制精确、产物均匀性好、结晶度高的钙钛矿量子点的合成方法,使钙钛矿量子点应用到光催化领域中。综述了热注入法、配体辅助再沉淀法、溶剂热法、微波辅助法等金属卤化物钙钛矿量子点的合成方法及金属卤化物钙钛矿量子点在光催化析氢、光催化还原二氧化碳、光催化合成有机物以及光催化降解有机物等方面的研究进展,最后对金属卤化物钙钛矿光催化剂的发展前景进行了展望。 相似文献
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Baotong Hu Yiwang Bao Xiaojia Su Detian Wan Qingguo Feng Salvatore Grasso Chunfeng Hu 《International Journal of Applied Ceramic Technology》2021,18(5):1863-1871
In this work, ultrafast thermal shock of Ti3AlC2 ceramic was evaluated in water and air by utilizing the induction heating method. First, the annealed samples were heated to the set temperature in tens of seconds and dropped into the cooling water within 0.1 s which is rather short not to degrade the sample temperature. Compared to the traditional thermal shock method when quenching in water, the abnormal thermal shock phenomenon did not occur, which is owing to that no dense oxide layers were formed on the samples’ surface to act as the thermal barrier. The continuous decrease in residual flexural strength when quenched in water is associated with water infiltration, chemical reaction, and large surface tensile stress. The residual strength has 27.25 MPa upon 1250°C. Second, at the same testing temperature, the residual flexural strength when quenched in air maintains a high value of 388 MPa up to 1400°C. Dense oxide scales existed on the quenched surface of Ti3AlC2 samples. The results exhibit that Ti3AlC2 ceramic possesses excellent thermal shock resistance in water and air, suitable to be applied in extreme environments. 相似文献
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Xiuying Ni Jun Zhao Feng Gong Gang Li 《International Journal of Applied Ceramic Technology》2021,18(3):972-980
Al2O3/(W, Ti)C/TiN/Mo/Ni multidimensional graded ceramics and homogeneous reference ceramic were prepared by two step hot press sintering. The thermal shock and thermal fatigue resistance of the multidimensional graded ceramics were tested using the water quenching method. Scanning electron microscopy (SEM) and optical microscope were used to investigate microscopic failure mechanism of ceramics. The results showed that the retained flexural strength of two-dimensional and one-dimensional graded ceramics was almost same, but higher than that of the homogeneous ceramic. The crack growth (∆c) of homogeneous ceramic increased rapidly, while that of two-dimensional graded ceramics is the lowest. Hence, thermal fatigue resistance of the two-dimensional graded ceramics was highest. The residual compressive stress in the first layer induced by the optimal graded structure played an important role. In addition, the increasing toughness on the crack propagation path by adding different amounts of metals was also a contributing factor. 相似文献
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Yingying Chen Deli Ma Qinggang Li Jun Ji Zhenyu Zhang Yuhang Du Sique Chen Hailing Yang Yulin Wei Guopu Shi Baocai Pan Junyan Wu Zhi Wang 《International Journal of Applied Ceramic Technology》2023,20(2):1248-1259
Ti3SiC2/Al2O3 multilayered composites were prepared by the combination of tape casting and hot pressing sintering. The slurry was produced by adjusting the amounts of each organic material, including triethyl phosphate (TEP) as a dispersion, polyvinyl butyrate (PVB) as a binder, dioctyl phthalate (DOP) as a plasticizer, and anhydrous ethanol as an organic solvent. When TEP content was 3 wt.%, PVB content was 4.5 wt.%, R-value (DOP/PVB) was 1.4, and solid content was 38 wt.%; the cast film with a smooth surface, good flexibility, and uniform thickness was obtained after defoaming, tape casting, and drying. Three samples were prepared, namely, S1–S3. The S1 was monolithic Ti3SiC2/Al2O3 (mass ratio is 1:1) composites. S2 and S3 were Ti3SiC2/Al2O3 multilayered composites, which matrix layers were Ti3SiC2/Al2O3 composites (mass ratio is 1:1) and Al2O3, respectively, and their interface layer was Ti3SiC2. S1–S3 were also sintered at 1550°C. The bending strength of multilayered materials were lower than that of monolithic material, but the fracture toughness of multilayered materials significantly increased. Due to the introduction of Ti3SiC2 interface layer, the friction coefficient and wear rate of Ti3SiC2/Al2O3 multilayered composites were reduced by 30.7% and 33.8%, respectively, compared with monolithic material. 相似文献