Black Phosphorus Quantum Dots

As a unique two‐dimensional nanomaterial, layered black phosphorus (BP) nanosheets have shown promising applications in electronics. Although mechanical exfoliation was successfully used to prepare BP nanosheets, it is still a challenge to produce novel BP nanostructures in high yield. A facile top‐down approach for preparation of black phosphorus quantum dots (BPQDs) in solution is presented. The obtained BPQDs have a lateral size of 4.9±1.6 nm and thickness of 1.9±0.9 nm (ca. 4±2 layers). As a proof‐of‐concept application, by using BPQDs mixed with polyvinylpyrrolidone as the active layer, a flexible memory device was successfully fabricated that exhibits a nonvolatile rewritable memory effect with a high ON/OFF current ratio and good stability.     

Black Phosphorus Quantum Dots

As a unique two‐dimensional nanomaterial, layered black phosphorus (BP) nanosheets have shown promising applications in electronics. Although mechanical exfoliation was successfully used to prepare BP nanosheets, it is still a challenge to produce novel BP nanostructures in high yield. A facile top‐down approach for preparation of black phosphorus quantum dots (BPQDs) in solution is presented. The obtained BPQDs have a lateral size of 4.9±1.6 nm and thickness of 1.9±0.9 nm (ca. 4±2 layers). As a proof‐of‐concept application, by using BPQDs mixed with polyvinylpyrrolidone as the active layer, a flexible memory device was successfully fabricated that exhibits a nonvolatile rewritable memory effect with a high ON/OFF current ratio and good stability.     

高质量CdSe量子点的水相制备与表征

以巯基丁二酸为稳定剂, 亚硒酸钠为硒源, 制备了高质量水溶性CdSe量子点. 研究了反应时间、 镉与硒的摩尔比及镉与巯基丁二酸的摩尔比等实验条件对CdSe量子点光谱性能的影响. 分别用紫外-可见光谱、 荧光光谱、 X射线粉末衍射和透射电子显微镜等对量子点进行表征. 结果表明, 采用这种方法制得的CdSe量子点为立方晶型, 量子点的荧光发射峰在518～562 nm范围内连续可调, 并且发射峰的半峰宽始终保持在35 nm左右, 荧光量子产率可达21%.     

Ultrafast Preparation of Black Phosphorus Quantum Dots for Efficient Humidity Sensing

Black phosphorus quantum dots (BPQDs) have been prepared by a high turbulent shear rate generated from a household kitchen blender. A layer‐by‐layer disintegration mechanism of bulk BP crystals is suggested. As‐synthesized BPQDs have shown excellent humidity sensing and photothermal converting properties. Importantly, this work not only explores potential applications for the BPQDs but also provides a successful paradigm for preparing the QDs of other layered materials.     

一锅合成绿色到近红外发射的CdTe量子点

以3-巯基丙酸(MPA)为稳定剂,采用水相合成法制备了从绿色到近红外发射的CdTe量子点。系统研究了反应液pH值、镉和碲的物质的量之比及镉和3-巯基丙酸的物质的量之比等实验条件对CdTe量子点体系的发射波长和荧光量子产率的影响。在pH值为10.5,且nCd2+∶nTe2-∶nMPA=1∶0.05∶1.1的条件下,回流0.5 h,CdTe量子点体系在569 nm波长处的荧光量子产率达到30.8%;在7 h的回流时间内,制备的量子点的波长覆盖范围为525～730 nm。分别用X射线粉末衍射、透射电镜和红外光谱对CdTe量子点的晶体结构、形貌及表面基团进行表征。     

Strongly green-photoluminescent graphene quantum dots for bioimaging applications

Strongly fluorescent graphene quantum dots (GQDs) have been prepared by one-step solvothermal method with PL quantum yield as high as 11.4%. The GQDs have high stability and can be dissolved in most polar solvents. Because of fine biocompatibility and low toxicity, GQDs are demonstrated to be excellent bioimaging agents.     

Exciton states of quantum confined ZnO nanorods

Photoluminescence (PL) of zinc oxide (ZnO) nanorods with an average thickness of 5 nm and a length of 30 nm is blue-shifted compared to the bulk due to quantum confinement effects. The exciton states remain relatively stable at a high carrier density due to a smaller exciton size and an enhanced exciton binding energy in the quantum confined nanorods, whereas the electron-hole plasma states are formed in the bulk at the similar carrier density. A linear dependence of the PL intensity on the excitation intensity also corroborates the assumption that the stable exciton states are responsible for the undisturbed emission at a high carrier density.     

第二近红外窗口荧光Ag2Te量子点的合成

以巯基辛烷为表面配体, 通过调控Ag前体和Te前体的比例, 制备了第二近红外窗口荧光Ag₂Te量子点. 采用透射电子显微镜(TEM)、 X射线衍射光谱(XRD)、 X射线光电子能谱(XPS)、 紫外-可见-近红外吸收光谱和荧光光谱等对产物进行了表征. 结果表明, 制得了粒径均一、 分散性好的油溶性Ag₂Te量子点, 其最大荧光发射波长位于1320 nm, 荧光量子产率高达4.2%.     

Tuning Optical Properties of Si Quantum Dots by π‐Conjugated Capping Molecules

The absorption and photoluminescence (PL) properties of silicon quantum dots (QDs) are greatly influenced by their size and surface chemistry. Herein, we examined the optical properties of three Si QDs with increasing σ–π conjugation length: octyl‐, (trimethylsilyl)vinyl‐, and 2‐phenylvinyl‐capped Si QDs. The PL photon energy obtained from as‐prepared samples decreased by 0.1–0.3 eV, while the PL excitation (PLE) extended from 360 nm (octyl‐capped Si QDs) to 400 nm (2‐phenylvinyl‐capped Si QDs). A vibrational PL feature was observed in all samples with an energy separation of about 0.192±0.013 eV, which was explained based on electron–phonon coupling. After soft oxidization through drying, all samples showed blue PL with maxima at approximately 410 nm. A similar high‐energy peak was observed with the bare Si QD sample. The changes in the optical properties of Si QDs were mainly explained by the formation of additional states arising from the strong σ–π conjugation and QD oxidation.     

CdS量子点的制备及细胞膜初步荧光标记

以巯基乙酸为稳定剂,通过控制反应温度、反应时间及pH值,在水相中合成了稳定的受激发出紫光、蓝光、绿光、黄光和红光的CdS量子点;通过紫外可见吸收光谱、荧光光谱和X射线衍射谱(XRD)对产物的光学性能和晶体结构进行了表征,结果表明所合成的CdS量子点分散性较好,量子产率为8%,为立方晶型,粒径约1 nm;利用荧光倒置显微镜观察了量子点在洋葱内表皮细胞膜上聚集及受激发射荧光行为,实现细胞膜初步标记.     

Ca2+ Induced Crosslinking of AIE‐Active Polyarylene Ether Nitrile into Fluorescent Polymeric Nanoparticles for Cellular Bioimaging

Biocompatible fluorescent polymeric nanoparticles (FPNs) are promising luminescent probes in cellular bioimaging, while the fabrication of high‐quantum‐yield FPN using nonconjugated heterochain polymers derived from step‐growth polymerization is still in its infancy. Herein, the nonconjugated polyarylene ether nitrile (PEN) is endowed with aggregation‐induced emission (AIE) feature by incorporation of an AIEgen named of 1,2‐di(4‐hydroxyphenyl)‐1,2‐diphenylethene into macromolecular backbone. Furthermore, the AIE‐active PEN is crosslinked into water soluble fluorescent nanospheres showing good biocompatibility and strong emission ≈480 nm with a quantum yield of 21% in the presence of Ca²⁺, which allows the successful bioimaging of cancer cells. Due to the facile fabrication of FPNs and their effective bioimaging performance, the current work will open the way for the biomedical applications of various high performance polyarylene ethers.     

芴与噻吩发光共聚物的合成及其电致发光性能

采用Suzuki偶合方法合成出了一系列新型的 9,9 二辛基芴 (DOF)和噻吩 (Th)的共聚物 .其中 ,DOF与Th的投料比 (摩尔比 )分别为 95∶5 (PTF5 )、90∶1 0 (PTF1 0 )、85∶1 5 (PTF1 5 )、70∶3 0 (PTF3 0 )、5 0∶5 0 (PTF5 0 ) .所有的聚合物均可溶于常用的有机溶剂 ,如THF,CHCl3等 ,其分子量在 60 0 0～ 5 3 0 0 0之间 .当在聚芴主链中引入噻吩后 ,其发光波长发生了红移 ,最大发光波长由PTF5时的 490nm红移到PTF5 0时的 5 41nm .随着聚芴主链中噻吩含量的增加 ,最大电致发光和光致发光效率都逐渐降低 由这些聚合物所制得的器件 ,最大电致发光效率为PTF5和PTF1 0的 0 45 %.由此表明 ,在聚芴主链中引入少量的低带隙单体噻吩可以调节聚芴的发光颜色及发光效率     

Effect of CdS Interlayer on Properties of CdTe Based Quantum Dots

Highly luminescent thioglycolic acid-capped CdTe-based core/shell quantum dots (QDs) were synthesized through encapsulating CdTe QDs in various inorganic shells including CdS, ZnS and CdZnS. CdTe/CdS core/shell QDs exhibited a significant redshift of emission peaks (a maximum emission peak of 652 nm for the core/shell QDs and 575 nm for CdTe cores) with increasing shell thickness. In contrast, the redshift of photoluminescence (PL) peak wavelength of CdTe/ZnS QDs was less than 15 nm. The PL peak wavelengths of the core/shell QDs depended strongly on core size and shell thickness. The PL quantum yields (QYs) of the CdTe/CdS core/shell QDs are up to 67 % while that of CdTe/ZnS core/shell QDs is 45 %. A composite CdZnS shell made CdTe cores a high PL QY up to 51 % and broadly adjusted PL spectra (a maximum PL peak wavelength of 664 nm). The epitaxial growth of the shell was confirmed by X-ray powder diffraction analysis and luminescence decay experiments. Because of high PL QYs, tunable PL spectra, and low toxicity from a ZnS surface layer, CdTe/CdZnS core/shell QDs will be great potential for bioapplications.     

颜色可调的高荧光CdTe量子点的水相合成

以亚碲酸钠为碲源,硼氢化钠为还原剂,一步合成了巯基丁二酸(MSA)稳定的CdTe量子点.研究了反应液pH值、镉与碲的摩尔比及镉与巯基丁二酸的摩尔比等实验条件对CdTe量子点体系荧光量子产率的影响,并用荧光光谱、X射线粉末衍射及透射电子显微镜等对其进行了表征.结果表明,CdTe量子点具有闪锌矿结构,形貌呈球状;在pH=1...     

红色荧光碳量子点用于肿瘤微酸环境诊断

Cancer remains a major global cause of morbidity and mortality. Diagnosis at an early stage can significantly improve the survival of cancer patients. Cancers of different origins often have vastly different genotypes and phenotypes. Therefore, it is challenging to establish a universal strategy for cancer detection. Universal cancer detection can be potentially achieved by using pH-responsive probes. An acidic microenvironment is mainly caused by lactic acid accumulation in rapidly growing tumor cells. Based on the difference in pH between tumor and normal tissues, fluorescent materials that respond to a pH of around 6.8 are ideal for tumor detection. Carbon quantum dots (CQDs) have attracted much attention in bioimaging owing to their outstanding characteristics such as stable photoluminescence, low cytotoxicity, excellent biocompatibility, and resistance to photobleaching. In this study, red fluorescent CQDs (R-CQDs) were synthesized by the solvothermal treatment of 4-(dimethylamino) phenol in the presence of potassium periodate. The UV-Vis spectrum of the R-CQDs showed a characteristic absorption peak at 545 nm. The photoluminescence spectrum revealed an emission peak at 640 nm. The brightness of this photoluminescence peak was quantified to be 12.8% in terms of the absolute quantum yield (QY). Transmission electron microscopy (TEM) images showed that the R-CQDs have uniform sizes with an average diameter of 4 nm and a lattice spacing of 0.21 nm. Fourier transform infrared (FT-IR) spectroscopy and X-ray photoelectron spectroscopy (XPS) confirmed that the R-CQDs have a large number of carboxyl groups. The Raman spectrum of the R-CQDs showed the characteristic D band at 1340 cm^-1 and G band at 1585 cm^-1. The X-ray powder diffraction (XRD) pattern showed a broad (002) peak centered at around 23°. The R-CQDs were responsive to highly acidic or alkaline conditions. The incorporation of a block copolymer (MeO-PEG-PDPA), prepared by atom transfer radical polymerization (ATRP), on the R-CQDs produced pH-responsive fluorescent CQDs (pRF-R-CQDs). Photoluminescence (PL) spectra showed that the pRF-R-CQDs were responsive at pH 6.8. At pH > 6.8, the fluorescence of the pRF-R-CQDs would be quenched because of deprotonation of the amine groups. In contrast, protonation of the amine groups would lead to a dramatic increase in fluorescence emission. TEM images showed that the pRF-R-CQDs self-assemble and disassemble at pH 6.8 because of their pH-responsive properties. Compared with most existing fluorescent materials, the pRF-R-CQDs can effectively resist photobleaching and autofluorescence. Moreover, these pRF-R-CQDs have minimal toxicity and can distinguish tumors from normal tissues. Therefore, pRF-R-CQDs have great potential for use as a universal material in tumor microenvironment diagnosis.     

Chlorine Modulation Fluorescent Performance of Seaweed-Derived Graphene Quantum Dots for Long-Wavelength Excitation Cell-Imaging Application

Biological imaging is an essential means of disease diagnosis. However, semiconductor quantum dots that are used in bioimaging applications comprise toxic metal elements that are nonbiodegradable, causing serious environmental problems. Herein, we developed a novel ecofriendly solvothermal method that uses ethanol as a solvent and doping with chlorine atoms to prepare highly fluorescent graphene quantum dots (GQDs) from seaweed. The GQDs doped with chlorine atoms exhibit high-intensity white fluorescence. Thus, their preliminary application in bioimaging has been confirmed. In addition, clear cell imaging could be performed at an excitation wavelength of 633 nm.     

Cationic IrIII Emitters with Near-Infrared Emission Beyond 800 nm and Their Use in Light-Emitting Electrochemical Cells

Solid-state near-infrared (NIR) light-emitting devices have recently received considerable attention as NIR light sources that can penetrate deep into human tissue and are suitable for bioimaging and labeling. In addition, solid-state NIR light-emitting electrochemical cells (LECs) have shown several promising advantages over NIR organic light-emitting devices (OLEDs). However, among the reported NIR LECs based on ionic transition-metal complexes (iTMCs), there is currently no iridium-based LEC that displays NIR electroluminescence (EL) peaks near to or above 800 nm. In this report we demonstrate a simple method for adjusting the energy gap between the highest-occupied molecular orbital (HOMO) and the lowest-unoccupied molecular orbital (LUMO) of iridium-based iTMCs to generate NIR emission. We describe a series of novel ionic iridium complexes with very small energy gaps, namely NIR1 – NIR6 , in which 2,3-diphenylbenzo[g]quinoxaline moieties mainly take charge of the HOMO energy levels and 2,2′-biquinoline, 2-(quinolin-2-yl)quinazoline, and 2,2′-bibenzo[d]thiazole moieties mainly control the LUMO energy levels. All the complexes exhibited NIR phosphorescence, with emission maxima up to 850 nm, and have been applied as components in LECs, showing a maximum external quantum efficiency (EQE) of 0.05 % in the EL devices. By using a host–guest emissive system, with the iridium complex RED as the host and the complex NIR3 or NIR6 as guest, the highest EQE of the LECs can be further enhanced to above 0.1 %.     

2D Monoelemental Germanene Quantum Dots: Synthesis as Robust Photothermal Agents for Photonic Cancer Nanomedicine

As a new family member of the emerging two‐dimensional (2D) monoelemental materials (Xenes), germanene has shown promising advantages over the prototypical 2D Xenes, such as black phosphorus (BP) and graphene. However, efficient manufacture of novel germanene nanostructures is still a challenge. Herein, a simple top‐down approach for the liquid‐exfoliation of ultra‐small germanene quantum dots (GeQDs) is presented. The prepared GeQDs possess an average lateral size of about 4.5 nm and thickness of about 2.2 nm. The functionalized GeQDs were demonstrated to be robust photothermal agents (PTAs) with outstanding photothermal conversion efficacy (higher than those of graphene and BPQDs), superior stability, and excellent biocompatibility. As a proof‐of‐principle, 2D GeQDs‐based PTAs were used in fluorescence/photoacoustic/photothermal‐imaging‐guided hyperpyrexia ablation of tumors. This work could expand the application of 2D germanene to the field of photonic cancer nanomedicine.     

Photoluminescence from CdS Quantum Dots in Silica Gel

CdS semiconductor nanocrystals were grown as quantum dots (QDs) inside a silica matrix obtained by the sol-gelmethod and assisted in the mother liquid by high powerultrasounds. Small-angle neutron scattering (SANS) accountsfor a 3.6 nm crystal size homogeneously distributed. Optical excitation from the third harmonic of a Nd:YAG ns laser wasfocused on the sample to study the photoluminescence (PL) atroom temperature. The PL spectrum shows radiative processfrom intrinsic transitions and a broad band corresponding tothe traps. Variable stripe length (VSL) method was used to measure the optical gain spectra by the growth of theamplified luminescence. A broad optical gain spectrumproduced by the biexciton-exciton transitions revealing thestimulated emission from the CdS QDs. It is also observed ared-shift of the PL emission crystal size-dependent.     

Synthesis of Aqueous CdTe Nanocrystals with High Efficient Blue‐Green Emission of Exciton

As one of the most popular nanocrystals (NCs), aqueous CdTe NCs have very weak green emission under conventional synthesis conditions. In this work, we report the first example of blue‐emitting CdTe NCs directly synthesized in aqueous solution by slowing down the growth rate after nucleation. The key for the synthesis is the optimization of NC growth conditions, namely pH range of 7.5 to 8.5, TGA/Cd ratio of 3.6, Cd/Te ratio of 10, and Te concentration of 2×10^?5 mol/L, to get a slow growth rate after nucleation. The as‐prepared blue‐emitting CdTe NCs have small size (as small as 1.9 nm) and bright emission [with 4% photoluminescence quantum yield (PL QY) at 486 nm and 17% PLQY at 500 nm]. Transmission electron microscopy (TEM) images of the as‐prepared CdTe show monodispersed NCs which exhibit cubic zinc blend structure. Moreover, time‐resolved PL decay and X‐ray photoelectron spectroscopy (XPS) results show the as‐prepared NCs have better surface modification by ligand, which makes these luminescent small CdTe NCs have higher photoluminescence quantum yield, compared with NCs synthesized under conventional conditions.