Photosensitive self-assembled membrane of cysteine against copper corrosion

Complex self-assembled membrane (SAM) was prepared by modifying the adsorption of cysteine with fluorescent reagent sodium 1-naphthylamine diacetate (NADA) on copper surface. The SAM has a fluorescence emission at 430 nm. Its protective effects against copper corrosion were investigated by potentiodynamic polarization curves and electrochemical impedance spectroscopy (EIS) in 0.5 M NaCl solution. It suppresses cathodic current densities and shifts the corrosion potential toward more positive values. The variation of the fluorescence intensity is correlated to that of the impedance resistance. The fluorescence detection provides a potential monitoring method for the protection of the SAM on copper surface.     

Two-dimensional multiwavelength fluorescence spectra of dipicolinic acid and calcium dipicolinate

Dipicolinic acid (DPA) and the Ca2+ complex of DPA (CaDPA) are major chemical components of bacterial spores. With fluorescence being considered for the detection and identification of spores, it is important to understand the optical properties of the major components of the spores. We report in some detail on the room-temperature fluorescence excitation and emission spectra of DPA and its calcium ion complex and provide a comparison of the excitation-emission spectrum in a dry, wet paste and aqueous form. DPA solutions have weak, if any, fluorescence, with increased fluorescence when the DPA is dry. After exposure to a broad source UV light of the DPA, wet or dry, we observe a large increase in fluorescence with a maximum intensity emission peak at around 440 nm for excitation light with a wavelength of around 360 nm. There is a slight blueshift in the absorption spectra of UV-exposed DPA from the unexposed DPA solution. CaDPA in solution shows a slight fluorescence with increased fluorescence in the dry form, and a substantial increase of fluorescence was observed after UV exposure with an emission peak of around 410 nm for excitation around 305 nm. The detailed excitation-emission spectra are necessary for better interpretation of the fluorescence spectra of bacterial spores where DPA is a major chemical component.     

煅烧工艺对氧化锌铝(AZO)粉体光学性能的影响

采用聚丙烯酰胺凝胶法制备高浓度Al掺杂ZnO(AZO)前驱体(x(Al)=5.5mol%、6.5mol%), 研究煅烧工艺对AZO粉体光学性能的影响. 结果表明: 随着煅烧温度升高, Al在ZnO中的固溶度降低。当煅烧温度为750℃时, 生成ZnAl₂O₄相。提高煅烧温度, 粉体的紫外吸收峰从366 nm红移至373 nm; 延长煅烧时间, 紫外吸收峰发生蓝移, 吸收强度明显增大。室温下AZO粉体光致发光(PL)光谱主要由354 nm的紫外发射峰、406 nm的近边紫外发射峰和430 nm的蓝光发射峰组成。     

Scintillation and dosimeter properties of <Superscript>6</Superscript>LiF/CaF<Subscript>2</Subscript>:Eu eutectic composites

We investigated scintillation and dosimeter properties of ⁶LiF/CaF₂ eutectic composites doped with different concentrations of Eu (0.005, 0.02, 0.1, 0.3, and 1.0). In the photoluminescence (PL) and scintillation spectra, an emission peak at 430 nm due to the 5d–4f transitions of Eu²⁺ was observed. The intensity of PL and scintillation for ⁶LiF/CaF₂:0.005%Eu was the highest among the samples tested. In thermally stimulated luminescence (TSL), several glow peaks of ⁶LiF/CaF₂:0.005%Eu were observed after X-ray irradiation of 1000 mGy. The TSL response exhibited a linear response against X-ray dose over a dose range of 1–10,000 mGy. In optically stimulated luminescence (OSL), an emission peak was observed at 430 nm during a stimulation by 630 nm light after X-ray irradiation of 1000 mGy. The OSL intensity was the highest for ⁶LiF/CaF₂:0.005%Eu among all the samples investigated.     

Fluorescence sensing of zinc(II) using ordered mesoporous silica material (MCM-41) functionalized with N-(quinolin-8-yl)-2-[3-(triethoxysilyl)propylamino]acetamide

A novel fluorescent zinc sensor was designed and synthesized on ordered mesoporous silica material, MCM-41, with N-(quinolin-8-yl)-2-[3-(triethoxysilyl)propylamino]acetamide (QTEPA; 3) using a simple one-step molecular self-assembly of the silane. The solution and solid samples were characterized using solid-state nuclear magnetic resonance, transmission electron microscopy, diffuse-reflectance infrared Fourier transform, and thermogravimetric analysis techniques. The QTEPA-modified MCM-41 (4) shows 3-fold fluorescence emission enhancement and about a 55 nm red shift upon addition of 1 μM Zn(II) ions in a Tris-HCl (pH 7.22) aqueous buffer solution. The UV-vis absorption maximum is at 330 ± 5 nm, and the fluorescence emission maximum wavelength is at 468 nm, with an increase in quantum yield from 0.032 to 0.106 under the same conditions. The presence of other metal ions has no observable effect on the sensitivity and selectivity of 4. This system selectively detects Zn(II) ions with submicromolar detection to a limit of 0.1 μM. The MCM-41-based systems have the advantage that they can be employed in aqueous solutions without any aggregation.     

离子液体辅助微波法水相合成Cu-In-Zn-S/ZnS量子点及其在白光LED中的应用

Cu-In-Zn-S(CIZS)量子点具有毒性低、发射谱覆盖范围广、Stokes位移大等特点, 在照明领域具有广阔的应用前景。通过离子液体辅助微波法水相合成CIZS量子点, 系统研究了反应时间、配体添加量和前驱体溶液pH对样品的物相组成、显微形貌以及荧光性能的影响。结果表明, 与未添加离子液体制备的样品相比, 离子液体的引入提高了反应速率, 可有效地将反应时间由180 min缩短至30 min; 随着反应时间的延长, 量子点的粒径增大, 其发射峰位由609.2 nm红移至634.6 nm。随着n_{GSH(谷胱甘肽)}/n_(CuInZn)的增大, 量子点的粒径逐渐增大, 导致其发射峰位由622.6 nm红移至631.6 nm, 同时量子点的发光强度逐渐增强; 当该比值为15时, 量子点的荧光强度最高。此外, 随着pH的增大, 去质子化的-SH和-NH₂与量子点的作用逐渐增强, 有效地钝化了量子点的表面态, 使其荧光强度逐渐上升, 当pH为8.5时, 样品的荧光性能最佳, 同时量子点的平均水合粒径由99 nm增大至241 nm; 量子点溶液的Zeta电位为-27.7~-41.1 mV, 说明量子点溶液具有优异的稳定性。通过ZnS表面修饰可有效提高量子点的荧光强度。将CIZS/ZnS量子点与蓝光芯片结合, 获得了显色指数为85.6、发光效率为34.8 lm/W的白光LED器件, 为水相制备的多元量子点在白光LED中的应用提供了参考。     

A study of ZnGa2O4 phosphor prepared by the solid method

In this study, the mixtures of ZnO and Ga2O3 powder with addition of LiCl flux were fired, the raw material mixing ratio, doping with Mn2+ and firing atmosphere effects on phosphor characteristics were investigated. When fired at 1200 °C, its phosphor powder emits a broad-band spectrum range between 375 nm to 700 nm, with a peak at 470 nm. The optimal composition of phosphors is about ZnO/Ga2O5=47/53. Manganese-doped ZnGa2O4, fired in air, exhibits two new emission bands with peaks at 506 nm (Mn2+ emission centre) and 666 nm (Mn4+ emission centre). However, if fired under vacuum, the emission spectrum presents only the 506 nm peak with increased intensity. The 666 nm emission peak derived from a little Mn2 oxidized to Mn4+ which substituted Ga3+ to occupy the B sites of the spinel structure. The emission intensity of the 506 nm peak of Zn1-xMnxGa2O4 is strongest when [Mn2+] x=0.006 and decreases markedly as the concentration of Mn2+ exceeds x=0.01. Most of the substitutional Mn2+ doping species in spinel ZnGa2O4 occupy the zinc sites. The luminescent band was associated to the spin-forbidden transition, 4T1(4G)6A1 (6S). © 1998 Kluwer Academic Publishers     

Synthesis of blue fluorescence CdS quantum dots stabilized by L-cysteine in aqueous phase

In this paper we report a novel synthesis method of blue fluorescence CdS quantum dots stabilized by L-cysteine in aqueous phase. When pH value of the core/shell CdTe/CdS colloid solution changed from 11.6 to 1.5, blue fluorescence CdS QDs was obtained. The fluorescence emission wavelength yielded a hypsochromic shift from 540 nm to 438 nm corresponding to the absorption peak position gave a hypsochromic shift from 518 nm to 352 nm. The CdS QDs were characterized by XPS and TEM. And the photostability of CdS QDs solution irradiated with UV lamp under open air condition at room temperature was very stable.     

CdTe量子点的微波合成及其在双光子显微成像中的应用

采用微波辐射加热的方法,以亚碲酸钠(Na2TeO3)作碲源,以谷胱甘肽(GSH)作稳定剂,在水相中合成出高质量的CdTe量子点。所合成量子点的发射波长从515～630nm可调,荧光量子产率(PLQYs)最高达95%。利用X射线粉末衍射(XRD)、高分辨透射电镜(HRTEM)、紫外-可见吸收光谱(UV-Vis)和荧光发射光谱(PL)等技术表征产物的物相结构和光学性质。用双光子激发荧光法研究CdTe量子点的双光子吸收性质。用双光子激发荧光成像技术,以发红光的CdTe量子点作为双光子荧光探针成功标记了人肺腺癌细胞(A549)。     

Confocal fluorescence polarization microscopy in turbid media: effects of scattering-induced depolarization

We present an experimental and theoretical study of confocal fluorescence polarization microscopy in turbid media. We have performed an experimental study using a fluorophore-embedded polymer rod immersed in aqueous suspensions of 0.1 and 0.5 microm diameter polystyrene microspheres. A Monte Carlo approach to simulate confocal fluorescence polarization imaging in scattering media is also presented. It incorporates a detailed model of polarized fluorescence generation that includes sampling of elliptical polarization, excited-state molecular rotational Brownian motion, and dipole fluorescence emission. Using both approaches, we determine the effects of the number of scattering events, target depth, photon scattering statistics, objective numerical aperture, and pinhole size on confocal anisotropy imaging. From this detailed analysis and comparison of experiment with simulation, we determine that fluorescence polarization is maintained to depths at which meaningful intensity images can be acquired.     

Non-linear optical properties of zinc oxide nanowires

High quality zinc oxide (ZnO) nanowires were grown on n-type Si (100) using vapor-liquid-solid process. We obtained the photoluminescence spectra of ZnO nanowires based on nonlinear optical process using an ultrashort wavelength femtosecond laser as a pumping source. The spectra shows the second harmonic generation phenomenon, as well as the exciton-exciton collision peak at 388 nm and the green emission peak at 515 nm caused by oxygen vacancy. A laser emission peak near 392 nm was observed when pump intensity surpassed 52 mJ/cm2 and a sharp peak about 0.5 nm wide emerged when the energy intensity reached 700 mJ/cm2. We attribute this excitation process to a two-photon absorption process enhanced by Rabi oscillation.     

NIR‐II‐Excited Intravital Two‐Photon Microscopy Distinguishes Deep Cerebral and Tumor Vasculatures with an Ultrabright NIR‐I AIE Luminogen

Intravital fluorescence imaging of vasculature morphology and dynamics in the brain and in tumors with large penetration depth and high signal‐to‐background ratio (SBR) is highly desirable for the study and theranostics of vascular‐related diseases and cancers. Herein, a highly bright fluorophore (BTPETQ) with long‐wavelength absorption and aggregation‐induced near‐infrared (NIR) emission (maximum at ≈700 nm) is designed for intravital two‐photon fluorescence (2PF) imaging of a mouse brain and tumor vasculatures under NIR‐II light (1200 nm) excitation. BTPETQ dots fabricated via nanoprecipitation show uniform size of around 42 nm and a high quantum yield of 19 ± 1% in aqueous media. The 2PF imaging of the mouse brain vasculatures labeled by BTPETQ dots reveals a 3D blood vessel network with an ultradeep depth of 924 µm. In addition, BTPETQ dots show enhanced 2PF in tumor vasculatures due to their unique leaky structures, which facilitates the differentiation of normal blood vessels from tumor vessels with high SBR in deep tumor tissues. Moreover, the extravasation and accumulation of BTPETQ dots in deep tumor (more than 900 µm) is visualized under NIR‐II excitation. This study highlights the importance of developing NIR‐II light excitable efficient NIR fluorophores for in vivo deep tissue and high contrast tumor imaging.     

小球藻内叶绿素a荧光特征的研究

由于叶绿素a外环境极性的不同,其荧光行为有很大的改变。通过小球藻体内叶绿素荧光光谱特性的研究,发现其体内叶绿素的激发波长有在丙酮溶剂中的相同,均为430 nm,但发射波长为680 nm,红移了13 nm。利用小球藻的叶绿素荧光强度进行水体中叶绿素a的定量检测,在浓度为1~100μg/L的浓度范围内,相对荧光强度与叶绿素浓度有很好的相关性,线性方程为y=0.5338x+1.8515,线性相关系数R2为0.9974。     

罗丹明B的荧光猝灭法测定钢铁中微量钨

本文研究了在酸介质中,NaCl存在的条件下,罗丹明B与钨酸根WO_4~_(2-)络合生成三元络合物使罗丹明B试剂荧光猝灭。以365 nm为最大激发波长,测定594 nm最大发射荧光强度。用钠型Dowex50W—X4离子交换树脂胶柱交换分离溶液中共存的磷酸根、重铬酸根、Cr~(3+)、Fe~(3+)等干扰离子,利用罗丹明B荧光强度减弱的程度和钨含量呈线性关系,测定钢样中微量钨。     

Strategy of fabricating enriched gold nanoparticles based on electrochemical methods

In this work, we report a new and clean electrochemical pathway to prepare enriched gold nanoparticles in aqueous solutions via the aid of chitosan without addition of any other stabilizer and reductant. First, an Au substrate was cycled in a deoxygenated aqueous solution containing 0.1 N NaCl and 1 g/L chitosan from − 0.28 to + 1.22 V vs Ag/AgCl at 500 mV/s with 500 scans. Then the Au working electrode was immediately replaced by a Pt electrode, and a cathodic overpotential of 0.6 V from the open circuit potential (OCP) of ca. 0.84 V vs Ag/AgCl was applied under sonification to synthesize Au nanoparticles. Experimental results indicate the concentration and the particle sizes of prepared Au nanoparticles are ca. 50 ppm and 10 nm in diameter, respectively. No aggregation of Au nanoparticles is observed in an ambient atmosphere for at least 3 months.     

Aggregation‐Induced Nonlinear Optical Effects of AIEgen Nanocrystals for Ultradeep In Vivo Bioimaging

Nonlinear optical microscopy has become a powerful tool in bioimaging research due to its unique capabilities of deep optical sectioning, high‐spatial‐resolution imaging, and 3D reconstruction of biological specimens. Developing organic fluorescent probes with strong nonlinear optical effects, in particular third‐harmonic generation (THG), is promising for exploiting nonlinear microscopic imaging for biomedical applications. Herein, a simple method for preparing organic nanocrystals based on an aggregation‐induced emission (AIE) luminogen (DCCN) with bright near‐infrared emission is successfully demonstrated. Aggregation‐induced nonlinear optical effects, including two‐photon fluorescence (2PF), three‐photon fluorescence (3PF), and THG, of DCCN are observed in nanoparticles, especially for crystalline nanoparticles. The nanocrystals of DCCN are successfully applied for 2PF microscopy at 1040 nm NIR‐II excitation and THG microscopy at 1560 nm NIR‐II excitation, respectively, to reconstruct the 3D vasculature of the mouse cerebral vasculature. Impressively, the THG microscopy provides much higher spatial resolution and brightness than the 2PF microscopy and can visualize small vessels with diameters of ≈2.7 µm at the deepest depth of 800 µm in a mouse brain. Thus, this is expected to inspire new insights into the development of advanced AIE materials with multiple nonlinearity, in particular THG, for multimodal nonlinear optical microscopy.     

Multiphoton optical image guided spectroscopy method for characterization of collagen-based materials modified by glycation

The cross-linking with reducing sugars, known as glycation, is used to increase stiffness and strength of tissues and artificial collagen-based scaffolds. Nondestructive characterization methods that report on the structures within these materials could clarify the effects of glycation. For doing this nondestructive evaluation, we employed an in situ one-photon fluorescence as well as multiphoton microscopy method that combined two-photon fluorescence and second harmonic generation signals. We incubated collagen hydrogels with glyceraldehyde, ribose, and glucose and observed an increase in the in situ fluorescence and structural alterations within the materials during the course of glycation. The two-photon fluorescence emission maximum was observed at about 460 nm. The fluorescence emission in the one-photon excitation experiment (λ(ex) = 360 nm) was broad with peaks centered at 445 and 460 nm. The 460 nm emission component subsequently became dominant during the course of glycation with glyceraldehyde. For the ribose, in addition to the 460 nm peak, the 445 nm component persisted. The glucose glycated hydrogels exhibited broad fluorescence that did not increase significantly even after 6 weeks. As determined from measuring the fluorescence intensity at the 460 nm maximum, glycation with glyceraldehyde was faster compared to ribose and generated stronger fluorescence signals. Upon excitation of glycated samples with 330 nm light, different emission peaks were observed.     

Poly(ethylene glycol) Vesicles: Self-Assembled Site for Luminescence Generation

Fluorescence in poly(ethylene glycol) (PEGs 400-12000) solutions is reported here for the first time. PEG solutions form a vesicular organization with the hydrophilic groups attached at both ends which arrange themselves beyond a particular concentration and offer electron-dense regions at the center of the vesicle. These vesicles provide an inherent site for fluorescence generation in PEG solutions. Fluorescence emission was observed at ～380 nm with an excitation wavelength of 300 nm. PEG of molecular weight 6000 was found to show maximum emission intensity at a particular concentration. The formation of PEG vesicles (～1 nm size) was confirmed by dynamic light scattering (DLS) and confocal laser microscopy. On addition of metal ions the polymeric vesicle breaks up to monomeric PEG, and hence, the fluorescence intensity decreases with a red shift. Fluorescence lifetime measurements indicate the nature of complexation of the metals with PEG. Since PEGs are used as one of the phases in aqueous biphasic systems (ABS) of liquid-liquid extractions, the nature of the fluorescence emission spectrum of the PEG phase after extraction was studied. Metal extraction in the PEG-rich phase of an ABS leads to quenching of fluorescence in PEG.     

Glow curves and the emission of flux-grown BaFCl:Na crystals

The thermoluminescence glow curves and the emission spectra of flux-grown BaFCl:Na crystals were recorded. An additional TL peak at 320 K, an optical absorption band at 570 nm and an emission peak at 490 nm have been seen in X/-irradiated crystals. Bleaching, room-temperature annealing and high-temperature emission results led us to conclude that the sodium impurity is responsible for the additional glow peak, optical absorption band and emission peak.     

Photoluminescence of Ga<Subscript>2</Subscript>S<Subscript>3</Subscript>:Eu nanocrystals

The photoluminescence (PL) of Ga₂S₃-5 mol % Eu₂O₃ nanocrystals prepared by mechanical comminution of the initial compound has been studied in the temperature range from 77 to 300 K. It is established that the PL spectrum of nanocrystals, in comparison to that of a massive sample, extends over a broader wavelength interval (430–620 nm) and has two maxima (at 507 and 556 nm) instead of one. The intensity of emission from nanocrystals is significantly higher than that from the massive crystal. The halfwidth in both cases varies with the temperature in proportion to T ^1/2. The intensity of emission at 556 nm for nanocrystals depends on the temperature as lgI ～ 1/T, this dependence having three linear portions corresponding to an activation energy of 0.04, 0.16, and 0.43 eV. The PL bands with maxima at 507 and 556 nm are assigned to the intracenter 4f ⁶5d4f ⁷ transitions in Eu²⁺ ions.