共查询到20条相似文献,搜索用时 15 毫秒
1.
Chuanxi Wang Yu Wang Lin Xu Dan Zhang Mingxia Liu Xiangwei Li Hongchen Sun Quan Lin Bai Yang 《Small (Weinheim an der Bergstrasse, Germany)》2012,8(20):3137-3142
Low toxicity and fluorescent nanomaterials have many advantages in biological imaging. Herein, a novel and facile aqueous‐phase approach to prepare biocompatible and fluorescent Ag2S nanoclusters (NCs) is designed and investigated. The resultant Ag2S NCs show tunable luminescence from the visible red (624 nm) to the near infrared (NIR; 724 nm) corresponding to the increasing size of the NCs. The key for preparing tunable fluorescent Ag2S NCs is the proper choice of capping reagent, glutathione (GSH), and the novel sulfur‐hydrazine hydrate complex as the S2? source. As a naturally occurring and readily available tripeptide, GSH functions as an important scaffold to prevent NCs from growing large nanoparticles. Additionally, GSH is a small biomolecule with several functional groups, including carboxyl and amino groups, which suggests the resultant Ag2S NCs are well‐dispersed in aqueous solution. These advantages make the as‐prepared Ag2S NCs potentially applicable to biological labeling as well. For example, the resultant Ag2S NCs are used as a probe for MC3T3‐EI cellular imaging. 相似文献
2.
Dongdong Wang Zhen Guo Jiajia Zhou Jian Chen Gaozheng Zhao Ruhui Chen Mengni He Zhenbang Liu Haibao Wang Qianwang Chen 《Small (Weinheim an der Bergstrasse, Germany)》2015,11(44):5956-5967
The versatile Mn3[Co(CN)6]2@SiO2@Ag core–shell NCs are prepared by a simple coprecipitation method. Ag nanoparticles with an average diameter of 12 nm deposited on the surface of Mn3[Co(CN)6]2@SiO2 through S–Ag bonding are fabricated in ethanol solution by reducing silver nitrate (AgNO3) with NaBH4. The NCs possess T1–T2 dual‐modal magnetic resonance imaging ability. The inner Prussian blue analogs (PBAs) Mn3[Co(CN)6]2 exhibit bright two‐photon fluorescence (TPF) imaging when excited at 730 nm. Moreover, the TPF imaging intensity displays 1.85‐fold enhancement after loading of Ag nanoparticles. Besides, the sample also has multicolor fluorescence imaging ability under 403, 488, and 543 nm single photon excitation. The as‐synthesized Mn3[Co(CN)6]2@SiO2@Ag NCs show a DOX loading capacity of 600 mg g−1 and exhibit an excellent ability of near‐infrared (NIR)‐responsive drug release and photothermal therapy (PTT) which is induced from the relative high absorbance in NIR region. The combined chemotherapy and PTT against cancer cells in vitro test shows high therapeutic efficiency. The multimodal treatment and imaging could lead to this material a potential multifunctional system for biomedical diagnosis and therapy. 相似文献
3.
Zhaohui Shen Suling Zhao Dandan Song Zheng Xu Bo Qiao Pengjie Song Qiongyu Bai Jingyue Cao Gaoqian Zhang Wageh Swelm 《Small (Weinheim an der Bergstrasse, Germany)》2020,16(26)
Lead halide perovskites and their applications in the optoelectronic field have garnered intensive interest over the years. Inorganic perovskites (IHP), though a novel class of material, are considered as one of the most promising optoelectronic materials. These materials are widely used in detectors, solar cells, and other devices, owing to their excellent charge‐transport properties, high defect tolerance, composition‐ and size‐dependent luminescence, narrow emission, and high photoluminescence quantum yield. In recent years, numerous encouraging achievements have been realized, especially in the research of CsPbX3 (X = Cl, Br, I) nanocrystals (NCs) and surface engineering. Therefore, it is necessary to summarize the principles and effects of these surface engineering optimization methods. It is also important to scientifically guide the applications and promote the development of perovskites more efficiently. Herein, the principles of surface ligands are reviewed, and various surface treatment methods used in CsPbX3 NCs as well as quantum‐dot light‐emitting diodes are presented. Finally, a brief outlook on CsPbX3 NC surface engineering is offered, illustrating the present challenges and the direction in which future investigations are intended to obtain high‐quality CsPbX3 NCs that can be utilized in more applications. 相似文献
4.
Xixiang Zhu Hengxing Xu Yongtao Liu Jia Zhang Miaosheng Wang Ilia N. Ivanov Olga S. Ovchinnikova Bin Hu 《Advanced materials (Deerfield Beach, Fla.)》2019,31(49)
A new approach to generate a two‐photon up‐conversion photoluminescence (PL) by directly exciting the gap states with continuous‐wave (CW) infrared photoexcitation in solution‐processing quasi‐2D perovskite films [(PEA)2(MA)4Pb5Br16 with n = 5] is reported. Specifically, a visible PL peaked at 520 nm is observed with the quadratic power dependence by exciting the gap states with CW 980 nm laser excitation, indicating a two‐photon up‐conversion PL occurring in quasi‐2D perovskite films. Decreasing the gap states by reducing the n value leads to a dramatic decrease in the two‐photon up‐conversion PL signal. This confirms that the gap states are indeed responsible for generating the two‐photon up‐conversion PL in quasi‐2D perovskites. Furthermore, mechanical scratching indicates that the different‐n‐value nanoplates are essentially uniformly formed in the quasi‐2D perovskite films toward generating multi‐photon up‐conversion light emission. More importantly, the two‐photon up‐conversion PL is found to be sensitive to an external magnetic field, indicating that the gap states are essentially formed as spatially extended states ready for multi‐photon excitation. Polarization‐dependent up‐conversion PL studies reveal that the gap states experience the orbit–orbit interaction through Coulomb polarization to form spatially extended states toward developing multi‐photon up‐conversion light emission in quasi‐2D perovskites. 相似文献
5.
Lei Jiang Haizhen Ding Mingsheng Xu Xiaolong Hu Shengli Li Mingzhu Zhang Qiong Zhang Qiyang Wang Siyu Lu Yupeng Tian Hong Bi 《Small (Weinheim an der Bergstrasse, Germany)》2020,16(19)
Carbon dots (CDs), with excellent optical property and cytocompatibility, are an ideal class of nanomaterials applied in the field of biomedicine. However, the weak response of CDs in the near‐infrared (NIR) region impedes their practical applications. Here, UV–vis–NIR full‐range responsive fluorine and nitrogen doped CDs (N‐CDs‐F) are designed and synthesized that own a favorable donor‐π‐acceptor (D‐π‐A) configuration and exhibit excellent two‐photon (λex = 1060 nm), three‐photon (λex = 1600 nm), and four‐photon (λex = 2000 nm) excitation upconversion fluorescence. D‐π‐A‐conjugated CDs prepared by solvothermal synthesis under the assistance of ammonia fluoride are reported and are endowed with larger multiphoton absorption (MPA) cross sections (3PA: 9.55 × 10?80 cm6 s2 photon?2, 4PA: 6.32 × 10?80 cm8 s3 photon?3) than conventional organic compounds. Furthermore, the N‐CDs‐F show bright deep‐red to NIR fluorescence both in vitro and in vivo, and can even stain the nucleoli of tumor cells. A plausible mechanism is proposed on the basis of the strong inter‐dot and intra‐dot hydrogen bonds through N? H···F that can facilitate the expanding of conjugated sp2 domains, and thus not only result in lower highest occupied molecular orbital‐lowest unoccupied molecular orbital energy level but also larger MPA cross sections than those of undoped CDs. 相似文献
6.
Vijay Kumar Sharma Sayim Gokyar Yusuf Kelestemur Talha Erdem Emre Unal Hilmi Volkan Demir 《Small (Weinheim an der Bergstrasse, Germany)》2014,10(23):4961-4966
In this work, dual‐modal (fluorescence and magnetic resonance) imaging capabilities of water‐soluble, low‐toxicity, monodisperse Mn‐doped ZnSe nanocrystals (NCs) with a size (6.5 nm) below the optimum kidney cutoff limit (10 nm) are reported. Synthesizing Mn‐doped ZnSe NCs with varying Mn2+ concentrations, a systematic investigation of the optical properties of these NCs by using photoluminescence (PL) and time resolved fluorescence are demonstrated. The elemental properties of these NCs using X‐ray photoelectron spectroscopy and inductive coupled plasma‐mass spectroscopy confirming Mn2+ doping is confined to the core of these NCs are also presented. It is observed that with increasing Mn2+ concentration the PL intensity first increases, reaching a maximum at Mn2+ concentration of 3.2 at% (achieving a PL quantum yield (QY) of 37%), after which it starts to decrease. Here, this high‐efficiency sample is demonstrated for applications in dual‐modal imaging. These NCs are further made water‐soluble by ligand exchange using 3‐mercaptopropionic acid, preserving their PL QY as high as 18%. At the same time, these NCs exhibit high relaxivity (≈2.95 mM?1 s?1) to obtain MR contrast at 25 °C, 3 T. Therefore, the Mn2+ doping in these water‐soluble Cd‐free NCs are sufficient to produce contrast for both fluorescence and magnetic resonance imaging techniques. 相似文献
7.
Self‐Assembled Au/CdSe Nanocrystal Clusters for Plasmon‐Mediated Photocatalytic Hydrogen Evolution
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Run Shi Yinhu Cao Yanjun Bao Yufei Zhao Geoffrey I. N. Waterhouse Zheyu Fang Li‐Zhu Wu Chen‐Ho Tung Yadong Yin Tierui Zhang 《Advanced materials (Deerfield Beach, Fla.)》2017,29(27)
Plasmon‐mediated photocatalytic systems generally suffer from poor efficiency due to weak absorption overlap and thus limited energy transfer between the plasmonic metal and the semiconductor. Herein, a near‐ideal plasmon‐mediated photocatalyst system is developed. Au/CdSe nanocrystal clusters (NCs) are successfully fabricated through a facile emulsion‐based self‐assembly approach, containing Au nanoparticles (NPs) of size 2.8, 4.6, 7.2, or 9.0 nm and CdSe quantum dots (QDs) of size ≈3.3 nm. Under visible‐light irradiation, the Au/CdSe NCs with 7.2 nm Au NPs afford very stable operation and a remarkable H2‐evolution rate of (10× higher than bare CdSe NCs). Plasmon resonance energy transfer from the Au NPs to the CdSe QDs, which enhances charge‐carrier generation in the semiconductor and suppresses bulk recombination, is responsible for the outstanding photocatalytic performance. The approach used here to fabricate the Au/CdSe NCs is suitable for the construction of other plasmon‐mediated photocatalysts. 相似文献
8.
Cobalt Phosphide Double‐Shelled Nanocages: Broadband Light‐Harvesting Nanostructures for Efficient Photothermal Therapy and Self‐Powered Photoelectrochemical Biosensing
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Jingqi Tian Houjuan Zhu Jie Chen Xinting Zheng Hongwei Duan Kanyi Pu Peng Chen 《Small (Weinheim an der Bergstrasse, Germany)》2017,13(22)
Ultra‐broadband light‐absorbing materials are highly desired for effective solar‐energy harvesting. Herein, novel cobalt phosphide double‐shelled nanocages (CoP‐NCs) are synthesized. Uniquely, these CoP‐NCs are able to nonselectively absorb light spanning the full solar spectrum, benefiting from its electronic properties and hollow nanostructure. They promise a wide range of applications involving solar energy utilization. As proof‐of‐concept demonstrations, CoP‐NCs are employed here as effective photothermal agents to ablate cancer cells by utilizing their ability of near‐infrared heat conversion, and as photoactive material for self‐powered photoelectrochemical sensing by taking advantage of their ability of photon‐to‐electricity conversion. 相似文献
9.
10.
Silole‐Based Red Fluorescent Organic Dots for Bright Two‐Photon Fluorescence In vitro Cell and In vivo Blood Vessel Imaging
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Bin Chen Guangxue Feng Bairong He Chiching Goh Shidang Xu Gabriel Ramos‐Ortiz Laura Aparicio‐Ixta Jian Zhou Laiguan Ng Zujin Zhao Bin Liu Ben Zhong Tang 《Small (Weinheim an der Bergstrasse, Germany)》2016,12(6):782-792
Robust luminescent dyes with efficient two‐photon fluorescence are highly desirable for biological imaging applications, but those suitable for organic dots fabrication are still rare because of aggregation‐caused quenching. In this work, a red fluorescent silole, 2,5‐bis[5‐(dimesitylboranyl)thiophen‐2‐yl]‐1‐methyl‐1,3,4‐triphenylsilole ((MesB)2DTTPS), is synthesized and characterized. (MesB)2DTTPS exhibits enhanced fluorescence efficiency in nanoaggregates, indicative of aggregation‐enhanced emission (AEE). The organic dots fabricated by encapsulating (MesB)2DTTPS within lipid‐PEG show red fluorescence peaking at 598 nm and a high fluorescence quantum yield of 32%. Upon excitation at 820 nm, the dots show a large two‐photon absorption cross section of 3.43 × 105 GM, which yields a two‐photon action cross section of 1.09 × 105 GM. These (MesB)2DTTPS dots show good biocompatibility and are successfully applied to one‐photon and two‐photon fluorescence imaging of MCF‐7 cells and two‐photon in vivo visualization of the blood vascular of mouse muscle in a high‐contrast and noninvasive manner. Moreover, the 3D blood vasculature located at the mouse ear skin with a depth of over 100 μm can also be visualized clearly, providing the spatiotemporal information about the whole blood vascular network. 相似文献
11.
Yibin Deng Li Huang Hong Yang Hengte Ke Hui He Zhengqing Guo Tao Yang Aijun Zhu Hong Wu Huabing Chen 《Small (Weinheim an der Bergstrasse, Germany)》2017,13(6)
Smart nanoparticles are increasingly important in a variety of applications such as cancer therapy. However, it is still a major challenge to develop light‐responsive nanoparticles that can maximize the potency of synergistic thermo‐chemotherapy under light irradiation. Here, spatially confined cyanine‐anchored silica nanochannels loaded with chemotherapeutic doxorubicin (CS‐DOX‐NCs) for light‐driven synergistic cancer therapy are introduced. CS‐DOX‐NCs possess a J‐type aggregation conformation of cyanine dye within the nanochannels and encapsulate doxorubicin through the π–π interaction with cyanine dye. Under near‐infrared light irradiation, CS‐DOX‐NCs produce the enhanced photothermal conversion efficiency through the maximized nonradiative transition of J‐type Cypate aggregates, trigger the light‐driven drug release through the destabilization of temperature‐sensitive π–π interaction, and generate the effective intracellular translocation of doxorubicin from the lysosomes to cytoplasma through reactive oxygen species‐mediated lysosomal disruption, thereby causing the potent in vivo hyperthermia and intracellular trafficking of drug into cytoplasma at tumors. Moreover, CS‐DOX‐NCs possess good resistance to photobleaching and preferable tumor accumulation, facilitating severe photoinduced cell damage, and subsequent synergy between photothermal and chemotherapeutic therapy with tumor ablation. These findings provide new insights of light‐driven nanoparticles for synergistic cancer therapy. 相似文献
12.
Xiaodong Zhang Fu‐Gen Wu Peidang Liu Ning Gu Zhan Chen 《Small (Weinheim an der Bergstrasse, Germany)》2014,10(24):5170-5177
Glutathione (GSH) can significantly and selectively enhance the fluorescence intensity of Au nanoclusters (NCs) prepared by blending HAuCl4 and histidine in solution. The quantum yield of the Au NCs after adding GSH can reach above 10%. Besides, GSH capping shifts the excitation peak of Au NCs from ultraviolet (386 nm) to visible light (414 nm) and improves the stability of the Au NCs. The cytotoxicities of the Au NCs with and without GSH for normal lung cells (ATII) and cancerous lung cells (A549) are evaluated. The GSH‐capped Au NCs have much less cytotoxicity to both normal and cancer cells, as compared to those without GSH. For Au NCs without GSH, less cytotoxicity is observed in cancer cells than in normal cells. In addtion, the Au NCs can selectively detect GSH over cysteine and homocysteine, the two biothiols which commonly exist in cells that can seriously affect GSH detection. Most importantly, Au NCs without GSH can selectively image the cancer cells, especially for the liver cancer cells whose GSH content is much higher than other cell types. This property makes the Au NCs a powerful probe to distinguish cancer cells from normal cells. 相似文献
13.
Shixun Wang Xinyu Shen Yu Zhang Xingwei Zhuang Dingke Xue Xiangtong Zhang Jinlei Wu Jinyang Zhu Zhifeng Shi Stephen V. Kershaw William W. Yu Andrey L. Rogach 《Small (Weinheim an der Bergstrasse, Germany)》2019,15(34)
All‐inorganic cesium lead halide perovskite nanocrystals (NCs) have demonstrated excellent optical properties and an encouraging potential for optoelectronic applications; however, mixed‐halide perovskites, especially CsPb(Cl/Br)3 NCs, still show lower photoluminescence quantum yields (PL QY) than the corresponding single‐halide materials. Herein, anhydrous oxalic acid is used to post‐treat CsPb(Cl/Br)3 NCs in order to initially remove surface defects and halide vacancies, and thus, to improve their PL QY from 11% to 89% for the emission of 451 nm. Furthermore, due to the continuous chelating reaction with the oxalate ion, chloride anions from the mixed‐halide CsPb(Cl/Br)3 perovskite NCs could be extracted, and green emitting CsPbBr3 NCs with PL QY of 85% at 511 nm emission are obtained. Besides being useful to improve the emission of CsPb(Cl/Br)3 NCs, the oxalic acid treatment strategy introduced here provides a further tool to adjust the distribution of halide anions in mixed‐halide perovskites without using any halide additives. 相似文献
14.
Shin‐Yi Tang Henry Medina Yu‐Ting Yen Chia‐Wei Chen Tzu‐Yi Yang Kung‐Hwa Wei Yu‐Lun Chueh 《Small (Weinheim an der Bergstrasse, Germany)》2019,15(8)
A facile approach for the synthesis of Au‐ and Pt‐decorated CuInS2 nanocrystals (CIS NCs) as sensitizer materials on the top of MoS2 bilayers is demonstrated. A single surfactant (oleylamine) is used to prepare such heterostructured noble metal decorated CIS NCs from the pristine CIS. Such a feasible way to synthesize heterostructured noble metal decorated CIS NCs from the single surfactant can stimulate the development of the functionalized heterostructured NCs in large scale for practical applications such as solar cells and photodetectors. Photodetectors based on MoS2 bilayers with the synthesized nanocrystals display enhanced photocurrent, almost 20–40 times higher responsivity and the On/Off ratio is enlarged one order of magnitude compared with the pristine MoS2 bilayers‐based photodetectors. Remarkably, by using Pt‐ or Au‐decorated CIS NCs, the photocurrent enhancement of MoS2 photodetectors can be tuned between blue (405 nm) to green (532 nm). The strategy described here acts as a perspective to significantly improve the performance of MoS2‐based photodetectors with the controllable absorption wavelengths in the visible light range, showing the feasibility of the possible color detection. 相似文献
15.
Byung Joon Moon Sang Jin Kim Seungmin Lee Aram Lee Hyunjung Lee Dong Su Lee Tae‐Wook Kim Seoung‐Ki Lee Sukang Bae Sang Hyun Lee 《Advanced materials (Deerfield Beach, Fla.)》2019,31(33)
Lead‐(Pb‐) halide perovskite nanocrystals (NCs) are interesting nanomaterials due to their excellent optical properties, such as narrow‐band emission, high photoluminescence (PL) efficiency, and wide color gamut. However, these NCs have several critical problems, such as the high toxicity of Pb, its tendency to accumulate in the human body, and phase instability. Although Pb‐free metal (Bi, Sn, etc.) halide perovskite NCs have recently been reported as possible alternatives, they exhibit poor optical and electrical properties as well as abundant intrinsic defect sites. For the first time, the synthesis and optical characterization of cesium ytterbium triiodide (CsYbI3) cubic perovskite NCs with highly uniform size distribution and high crystallinity using a simple hot‐injection method are reported. Strong excitation‐independent emission and high quantum yields for the prepared NCs are verified using photoluminescence measurements. Furthermore, these CsYbI3 NCs exhibit potential for use in organic–inorganic hybrid photodetectors as a photoactive layer. The as‐prepared samples exhibit clear on–off switching behavior as well as high photoresponsivity (2.4 × 103 A W?1) and external quantum efficiency (EQE, 5.8 × 105%) due to effective exciton dissociation and charge transport. These results suggest that CsYbI3 NCs offer tremendous opportunities in electronic and optoelectronic applications, such as chemical sensors, light emitting diodes (LEDs), and energy conversion and storage devices. 相似文献
16.
Plasmon‐Enhanced Photoelectrical Hydrogen Evolution on Monolayer MoS2 Decorated Cu1.75S‐Au Nanocrystals
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Jiabin Cui Rui Jiang Wenli Lu Suying Xu Leyu Wang 《Small (Weinheim an der Bergstrasse, Germany)》2017,13(8)
Hydrogen production from water splitting through an efficient photoelectrochemical route requires photoinduced electron transfer from light harvesters to efficient electrocatalysts. Here, the plasmon‐enhanced photoelectrical nanocatalysts (NCs) have been successfully developed by coating a monolayer MoS2 on the Cu1.75S‐Au hetero‐nanoparticle for hydrogen evolution reaction (HER). The plasmonic NCs dramatically improve the HER, leading to 29.5‐fold increase of current under 650 nm excitation (1.0 W cm?2). These NCs generate an exceptionally high current density of 200 mA cm?2 at overpotential of 182.8 mV with a Tafel slope of 39 mV per decade and excellent stability, which is better than or comparable to the Pt‐free catalysts with carbon rod as counter electrode. The enhanced HER performance can be attributed to the significantly improved broad light absorption (400–3000 nm), more efficient charge separation and abundant active edge sites of monolayer MoS2. The studies may provide a facile strategy for the fabrication of efficient plasmon‐enhanced photoelectrical NCs for HER. 相似文献
17.
Shape‐Controlled Synthesis of High‐Quality Cu7S4 Nanocrystals for Efficient Light‐Induced Water Evaporation
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Changbo Zhang Cong Yan Zhenjie Xue Wei Yu Yinde Xie Tie Wang 《Small (Weinheim an der Bergstrasse, Germany)》2016,12(38):5320-5328
Copper sulfides (Cu2–xS), are a novel kind of photothermal material exhibiting significant photothermal conversion efficiency, making them very attractive in various energy conversion related devices. Preparing high quality uniform Cu2‐xS nanocrystals (NCs) is a top priority for further energy‐and sustainability relevant nanodevices. Here, a shape‐controlled high quality Cu7S4 NCs synthesis strategy is reported using sulfur in 1‐octadecene as precursor by varying the heating temperature, as well as its forming mechanism. The performance of the Cu7S4 NCs is further explored for light‐driven water evaporation without the need of heating the bulk liquid to the boiling point, and the results suggest that as‐synthesized highly monodisperse NCs perform higher evaporation rate than polydisperse NCs under the identical morphology. Furthermore, disk‐like NCs exhibit higher water evaporation rate than spherical NCs. The water evaporation rate can be further enhanced by assembling the organic phase Cu7S4 NCs into a dense film on the aqueous solution surface. The maximum photothermal conversion efficiency is as high as 77.1%. 相似文献
18.
Chien‐Liang Liu Yung‐Kang Peng Shang‐Wei Chou Wei‐Hsuan Tseng Yu‐Jui Tseng Hsieh‐Chih Chen Jong‐Kai Hsiao Pi‐Tai Chou 《Small (Weinheim an der Bergstrasse, Germany)》2014,10(19):3962-3969
The room‐temperature, aqueous‐phase synthesis of iron‐oxide nanoparticles (IO NPs) with glutathione (GSH) is reported. The simple, one‐step reduction involves GSH as a capping agent and tetrakis(hydroxymethyl)phosphonium chloride (THPC) as the reducing agent; GSH is an anti‐oxidant that is abundant in the human body while THPC is commonly used in the synthesis of noble‐metal clusters. Due to their low magnetization and good water‐dispersibility, the resulting GSH‐IO NPs, which are 3.72 ± 0.12 nm in diameter, exhibit a low r2 relaxivity (8.28 mm ?1s?1) and r2/r1 ratio (2.28)—both of which are critical for T1 contrast agents. This, together with the excellent biocompatibility, makes these NPs an ideal candidate to be a T1 contrast agent. Its capability in cellular imaging is illustrated by the high signal intensity in the T1‐weighted magnetic resonance imaging (MRI) of treated HeLa cells. Surprisingly, the GSH‐IO NPs escape ingestion by the hepatic reticuloendothelial system, enabling strong vascular enhancement at the internal carotid artery and superior sagittal sinus, where detection of the thrombus is critical for diagnosing a stroke. Moreover, serial T1‐ and T2‐weighted time‐dependent MR images are resolved for a rat's kidneys, unveiling detailed cortical‐medullary anatomy and renal physiological functions. The newly developed GSH‐IO NPs thus open a new dimension in efforts towards high‐performance, long‐circulating MRI contrast agents that have biotargeting potential. 相似文献
19.
Haoran Wang Yongjiang Dou Piaoyang Shen Lingmei Kong Hao Yuan Yun Luo Xiaoyu Zhang Xuyong Yang 《Small (Weinheim an der Bergstrasse, Germany)》2020,16(20)
Color‐saturated red light‐emitting diodes (LEDs) with emission wavelengths at around 620–640 nm are an essential part of high‐definition displays. Metal halide perovskites with very narrow emission linewidth are promising emitters, and rapid progress has been made in perovskite‐based LEDs (PeLEDs); however, the efficiency of the current color—pure red PeLEDs—still far lags behind those of other‐colored ones. Here, a simple but efficient strategy is reported to gradually down‐shift the Fermi level of perovskite nanocrystals (NCs) by controlling the interaction between NCs and their surface molecular electron acceptor—benzyl iodide with aromatic rings—and realize p‐doping in the color‐saturated 625 nm emitting NCs, which significantly reduces the hole injection barrier in devices. Besides, both the luminescence efficiency and electric conductivity of perovskite NCs are enhanced as additional advantages as the result of surface defects passivation. As a result, the external quantum efficiency for the resulting LED is increased from 4.5% to 12.9% after benzyl iodide treatment, making this device the best‐performing color‐saturated red PeLED so far. It is further found that the hole injection plays a more critical role than the photoluminescence efficiency of perovskite emitter in determining the LED performance, which implies design principles for efficient thin‐film planar LEDs. 相似文献
20.
Magneto‐Photoluminescence Based on Two‐Photon Excitation in Lanthanide‐Doped Up‐Conversion Crystal Particles
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Hengxing Xu Wei Qin Mingxing Li Ting Wu Bin Hu 《Small (Weinheim an der Bergstrasse, Germany)》2017,13(16)
Experimental studies on magneto‐photoluminescence based on two‐photon excitation in up‐conversion Y2O2S:Er, Yb crystal particles are reported. It is found that the up‐conversion photoluminescence generated by two‐photon excitation exhibits magnetic field effects at room temperature, leading to a two‐photon excitation‐induced magneto‐photoluminescence, when the two‐photon excitation exceeds the critical intensity. By considering the spin selection rule in electronic transitions, it is proposed that spin‐antiparallel and spin‐parallel transition dipoles with spin mixing are accountable for the observed magneto‐photoluminescence. Specifically, the two‐photon excitation generates spin‐antiparallel electric dipoles between 4S3/2–4I15/2 in Er3+ ions. The antiparallel spins are conserved by exchange interaction within dipoles. When the photoexcitation exceeds the critical intensity, the Coulomb screening can decrease the exchange interaction. Consequently, the spin–orbital coupling can partially convert the antiparallel dipoles into parallel dipoles, generating a spin mixing. Eventually, the populations between antiparallel and parallel dipoles reach an equilibrium established by the competition between exchange interaction and spin–orbital coupling. Applying a magnetic field can break the equilibrium by disturbing spin mixing through introducing spin precessions, changing the spin populations on antiparallel and parallel dipoles and leading to the magneto‐photoluminescence. Therefore, spin‐dependent transition dipoles present a convenient mechanism to realize magneto‐photoluminescence in multiphoton up‐conversion crystal particles. 相似文献