Fluorescence Enhancement of Carbendazim Fungicide in Cucurbit[6]uril

The potential increase in fluorescence of a benzimidazole-type fungicide (carbendazim) due to complexation with cucurbit[6]uril is reported. The fluorescence of the probe carbendazim in aqueous Na₂SO₄ solution (pH=7.61) at room temperature is found to increase by a maximum factor of ∼10.0 and blue-shifted up to ∼11±1 nm with the increase in cucurbit[6]uril concentration up to ∼5 mM. This fluorescence enhancement is the result of formation of a 1:1 guest-host inclusion complex, in which the guest carbendazim is incorporated inside the hydrophobic cavity of the host curbit[6]uril through the amido-ester part. Such mode of inclusion is supported by NMR spectral measurements, in which upon encapsulation, the resonance of the methyl-protons of the amido-ester moiety is shifted significantly to upfield in the ¹H NMR spectrum. Also, to assess the formation of inclusion complex, solid samples prepared by co-evaporation have been studied, using differential scanning calorimetry (DSC). Measurement of the enhancement as a function of cucurbit[6]uril concentrations yielded a value of the equilibrium constant (K _a ) of 271±10 M⁻¹ at 25°C. From the temperature dependence of the equilibrium constants, ΔH and ΔS values have been negative in sign, indicating the dipole-dipole interactions and the steric factors associated with the formation of this inclusion complex. It might be proposed that the spectral changes due to the inclusion of carbendazim are the result of decrease in the polarity of the surrounded media rather than the loss of carbendazim rotational mobility.     

Fluorescence Spectroscopic Studies on Plasma-Chemically Modified Polymer Surfaces with Fluorophore-Labeled Functionalities

Molecular engineering of polymer surfaces that includes the attachment of functional molecules to existing or previously generated reactive chemical groups like e.g., − OH, − NH₂, or − CHO requires simple strategies and tools for the controlled generation of surface functionalities and their derivatization as well as for their identification and eventually quantification. Here, we systematically investigate the plasma-chemical surface modification of polypropylene films in combination with dansyl labeling chemistry and conventional, yet costly, XPS and highly sensitive fluorescence spectroscopy for the detection of surface groups. Based on these results, the potential of and requirements on the fluorometric characterization and quantification of surfaces functionalities are discussed.     

光谱法研究葫芦[6]脲与土霉素的分子识别作用

采用荧光光谱和紫外光谱研究葫芦[6]脲(CB[6])与土霉素(OTC)的分子识别作用。实验结果表明,随着主体分子的加入,OTC荧光强度和紫外吸收强度均增强,说明主客体之间发生了相互作用;进一步通过荧光光谱、紫外光谱和直线拟合法(Benesi-Hildebrand)确定了CB[6]与OTC形成1∶1型的包结物;在酸性环境下CB[6]与OTC能形成1∶1型的稳定的包结物,在碱性环境下不能形成稳定的包结物;同时计算了主客体在298,308和328 K下包结的平衡常数K_s和CB[6]与OTC的分子识别过程的熵变、焓变和吉布斯自由能变。不同温度下的吉布斯自由能变ΔG均小于0,而熵变和焓变为正值,其包结过程是疏水作用力驱动且自发的吸热的过程。     

光谱法研究八元瓜环与硫堇及多菌灵的主客体相互作用

利用紫外-可见吸收光谱法及荧光光谱法研究了八元瓜环与三环碱性染料硫堇及常用杀菌剂多菌灵的超分子相互作用,探讨了主客体相互作用的机制及光谱变化,并对其分析检测性能进行了研究。结果表明： 在0.01 mol·L-1的盐酸溶液中,八元瓜环与硫堇形成了摩尔比为1∶2主客体复合物,且八元瓜环能使硫堇的荧光发生猝灭;在八元瓜环/硫堇体系中加入多菌灵后,多菌灵能使体系的荧光增强,从而形成了荧光的“开-关”效应,其原因可能是由于八元瓜环与硫堇及多菌灵形成了主客体配合物而引起的。此外,测试了超分子体系的线性范围及检出限,并对酸度、共存物质对体系的影响进行了测试。结果表明多菌灵的浓度在0～3.5 μmol·L-1范围内与体系荧光强度呈线性关系,线性方程为I_f=0.45c+32.24,相关系数为0.999,检出限为9.39×10-8 mol·L-1。选择了常见离子及结构类似的苯并咪唑类杀菌剂对体系进行干扰测定,结果表明在一定浓度时,常见离子及结构类似的苯并咪唑类杀菌剂对多菌灵的检测不造成干扰。该结果为超分子配合物在农药残留检测方面的应用提供理论依据。     

光谱法考察对称四甲基六元瓜环与二氯化-二(2-苯并咪唑)丁烷的分子识别

以对称四甲基六元瓜环为主体,二氯化-二(2,2’-苯并咪唑)丁烷为客体,采用荧光光谱法和紫外吸收光谱法研究了主客体的相互作用。实验结果表明,主体对客体具有较强的包结识别能力,主客体之间可形成1∶1及2∶1的包结配合物,紫外吸收光谱法测得配合物的包结常数为K_(1∶1)=4.79±0.01×104 L·mol-1, K_(2∶1)=8.51±0.01×1010 L2·mol-2; 荧光光谱法测得配合物的包结常数为K_(1∶1)=7.02±0.01×104 L·mol-1, K_(2∶1)=2.88±0.01×1010 L2·mol-2,两种方法结果一致。     

Polymer adsorption on the surface of highly dispersed silica

Attempts at modification of silica surface with a polymer (natural latex) directly in the course of the precipitation process have been made. The effects of temperature, non-ionic surfactants and silane coupling agent in preparation of poly[cis-isoprene]-coated silica on the precipitation of polymer/silica composites initiated by ammonium salts (NH₄Cl, (NH₄)₂SO₄, NH₄HCO₃), have been studied. The influence of the process parameters on the quality of the silicas obtained and the character of the polymer adsorption on the silica surface has been determined along with the effect of the surface impregnation with natural latex on physicochemical parameters of the silicas (bulk density, capacities to absorb water, dibutyl phthalate and paraffin oil) and their surface structure.     

利用发射光谱进行常压介质阻挡放电等离子体诊断及其在材料表面改性上的应用(英文)

使用介质阻挡放电光谱诊断装置,对常压介质阻挡放电在材料改性过程中的等离子体发射光谱进行测量,记录和比较了空气、氦气和氩气常压介质阻挡放电等离子体发射光谱,并运用氩元素谱线的相对强度来诊断电子温度等物理参量,以达到对材料表面改性过程的实时监控。工作的结果对常压介质阻挡放电及其在材料改性上的应用具有重要的意义     

光谱法研究羟基葫芦[6]脲与甲基橙的分子识别作用

采用紫外和荧光光谱法研究羟基葫芦[6]脲(HOCB6)与甲基橙(MO)之间的包结作用,考察了溶液的pH值、常见有机溶剂和表面活性剂等对该包结物的形成及荧光强度的影响。实验结果表明,随着主体分子的加入,MO荧光增强且蓝移,说明客体被纳入主体分子的疏水性穴腔,形成内包结物。主客体分子之间主要通过疏水作用形成1∶1型的HOCB6-MO包结物,其包结常数为1.41×102 L·mol-1。同时采用葫芦[6]脲(CB6)、对-二甲氨甲基杯[8]芳烃和β-环糊精与MO的作用进行比较。研究发现,MO也能与葫芦[6]脲形成1∶1型的内包结物,但包结常数较小(34.65 L·mol-1);与β-环糊精形成1∶2型的内包结物,其包结常数为6.14×106 L2·mol-2;与对-二甲氨甲基杯[8]芳烃形成1∶1型的外包结物,导致荧光强烈猝灭,包结常数为1.35×104 L·mol-1。     

超分子荧光探针用于环境水样中百草枯的测定

基于七元瓜环可使中性红的荧光增强从而设计荧光探针,当在荧光探针中加入百草枯后荧光强度又逐渐降低,利用此种超分子配合物的荧光“开-关”效应,从而建立了一种新颖的检测百草枯的荧光方法。当百草枯浓度在(1~8)×10-6 mol·L-1范围内,百草枯浓度与探针的荧光强度具有良好的线性关系,且检出限为1.4×10-8 mol·L-1,加标回收率为104%~108%,可在河水样品中检测百草枯的含量。     

Effect of surface modification on dielectric and magnetic properties of metal powder/polymer nanocomposites

Metal nanopowder (Co and Fe)/polymer composites, both with and without surface modification by behenic acid, were fabricated and their dielectric and magnetic properties were measured at 1 GHz to study the effect of surface modification on the electromagnetic properties. The relative permittivity and the real part of the permeability of the composites with surface modified powders were higher than those with unmodified powders. Related dielectric losses remained at almost the same level, but magnetic losses were somewhat increased. The increase of relative permittivity could result from the increased volume fraction of interphase with a slightly higher relative permittivity at the particle/polymer interface than that of the bulk polymer. The increase in the real part of the permeability may be caused by suppression of the induced demagnetizing field due to suppression of eddy currents by a better particle distribution and a decrease in effective agglomerate size because of the surface modification.     

Theoretical study on complexation of the perchlorate,permanganate, pertechnate and perrhenate anions with dodecabenzylbambus[6]uril

By using quantum chemical calculations, the most probable structures of the anionic complex species dodecabenzylbambus[6]uril–ClO₄^?, dodecabenzylbambus[6]uril–MnO₄^?, dodecabenzylbambus[6]uril–TcO₄^? and dodecabenzylbambus[6]uril–ReO₄^? were derived. In these four complexes, each of the considered anions, included in the macrocyclic cavity, is bound by 12 weak hydrogen bonds between methine hydrogen atoms on the convex face of glycoluril units and the respective anion. Further, the corresponding interaction energies of the investigated four anionic complexes were calculated; the absolute values of these calculated energies increase in the series of ReO₄^? < TcO₄^? < MnO₄^? < ClO₄^?.     

Effect of the surface-modifying macromolecules on the duration of the surface functionalization

Functionalization of polystyrene films by the preferential surface enrichment of surface-modifying macromolecules (SMM) to achieve a hydrophilic surface with long effective duration is described. The comb-like amphiphilic copolymers (PKG-g-PS) based on styrene-maleic anhydride copolynier (SMA) backbone was synthesized by esterification of SMA with poly(ethylene glycol) (PEG). When PEG-g-PS was melt blended with polystyrene, the preferential surface enrichment of PEG-g-PS was much evident resulting in the large increase of the surface polarity. The effective duration of the surface functionalizatoin was also hugely extended as SMMs were added into the blends. Furthermore, more polyether chain segments on PEG-g-PS could selectively migrate to the surface by the inducement of polar solvent. Compared with the PEG-g-PS/PS and PEG/PEG-g-PS/PS blends, the surface polarity and the effective duration of surface modification both increased greatly when PEG-g-PS was used as the compatibilizer of PEG/PS blends. It was an effective solution to balance the conflict between the duration and efficiency of the surface-modifying additives.     

A versatile method for the preparation of end-functional polymers onto SiO2 nanoparticles by a combination of surface-initiated ATRP and Huisgen [3 + 2] cycloaddition

A versatile method was developed for the chain-end functionalization of the grafted polymer chains for surface modification of nanoparticles with functionalized groups through a combination of surface-initiated atom-transfer radical polymerization (ATRP) and Huisgen [3 + 2] cycloaddition. First, the surface of SiO₂ nanoparticles was modified with poly(methyl methacrylate) (PMMA) brushes via the “grafting from” approach. The terminal bromides of PMMA-grafted SiO₂ nanoparticles were then transformed into an azide function by nucleophilic substitution. These azido-terminated PMMA brushes on the nanoparticle surface were reacted with alkyne-terminated functional end group via Huisgen [3 + 2] cycloaddition. FTIR and ¹H NMR spectra indicated quantitative transformation of the chain ends of PMMA brushes onto SiO₂ nanoparticles into the desired functional group. And, the dispersibility of the end-functional polymer-grafted SiO₂ nanoparticles was investigated with a transmission electron microscope (TEM).     

H MAS and H[Na] double resonance NMR studies on the modification of surface hydroxyl groups of γ-alumina by sodium

The modification of surface hydroxyl groups with sodium in a series of Na₂CO₃-γ-Al₂O₃ catalysts was investigated as a function of both the Na₂CO₃ loading and the calcination temperature by means of ¹H magic angle spinning (MAS) and ¹H[²³Na] spin-echo double resonance NMR techniques. The ¹H NMR experiments revealed that sodium ions are homogeneously distributed over the alumina surface and closely coordinated with the surface hydroxyl groups. In the catalysts calcined at 250 °C, the acidic hydroxyl groups (with a chemical shift of 2.0 ppm) are preferentially associated with sodium ions at low Na₂CO₃ coverages (5 and 10%), while both the acidic and the basic (0 ppm) hydroxyl groups are accessible for sodium ions at high coverages (15 and 20%). The coordination causes a low-field shift of about 2 ppm in the ¹H MAS spectra, and a broad signal at 4.5 ppm appears. It is interesting that the 4.5 ppm signal is completely suppressed in the ¹H[²³Na] MAS experiments, providing direct evidence that a strong interaction exists between adsorbed sodium ions and the surface hydroxyl groups. Increasing the calcination temperature to 450 °C results in preferential removal of the acidic hydroxyl groups, and only the most basic hydroxyl groups remain when the calcination temperature is raised to 600 °C. This is attributed to the formation of the coordinated species which enhances the acidity of the surface hydroxyl groups and prompts their dehydroxylation, especially at high calcination temperature. Correlation of the ¹H MAS NMR results and catalytic activity measurements indicates that the basic hydroxyl groups are essential for the carbonyl sulfide hydrolysis reaction.     

离子液体[bmim][PF6]对氧杂蒽酮光解行为的影响

选择氧杂蒽酮(XAN)为探针分子,利用纳秒级瞬态光解技术研究在1-丁基-3-甲基咪唑六氟磷酸盐离子液体([bmim][PF6])以及离子液体与常规溶剂中的光化学行为,探索不同溶剂对氧杂蒽酮激发三线态态(3 XAN*)的最大吸收峰的影响:3 XAN*在纯乙腈(MeCN)中的吸收峰在630nm,而在[bmim][PF6]作溶剂的体系中激发态的吸收峰发生蓝移,而且纯离子液体体系中3 XAN*的产额显著增加。进一步探索离子液体对光诱导3 XAN*与萘(NAP)之间的能量转移及与N,N-二甲基苯胺(DMA)之间的电子转移的影响,结果表明:[bmim][PF6]/MeCN的二元体系中随着[bmim][PF6]浓度的增大,氧杂蒽酮与萘之间的能量转移速率减小,测得在乙腈和纯离子液体中3 XAN*与NAP之间能量转移速率常数分别为1.2×1010 mol·L-1·s-1和1.1×108 mol·L-1·s-1。     

Effect of pH values on surface modification and solubility of phosphate bioglass-ceramics in the CaO–P2O5–Na2O–SrO–ZnO system

The bioactive glass-ceramics in the CaO–P₂O₅–Na₂O–SrO–ZnO system were synthesized by the sol–gel technique, and then chemically treated at different pH values to study the solubility and surface modification. Samples sintered at 650 °C for 4 h consisted of the crystalline phase β-Ca₂P₂O₇ and the glass matrix. After soaking in the solution at pH 1.0, the residual glass matrix on the surface appeared entirely dissolved and no new phase could be detected. Whereas at pH 3.0, web-like layer exhibiting peaks corresponding to CaP₂O₆ was formed and covered the entire surface of the sample. When conducted at pH 10.0, only part of the glass matrix was dissolved and a new phase Ca₄P₆O₁₉ was precipitated, forming the petaline layer. The chemical treatment can easily change the surface morphologies and phase composition of this bioactive glass-ceramics. The higher level of surface roughness resulting from the new-formed layer would improve the interface bonding and benefit for cell adhesion.     

夫勒烯二氮杂桥衍生物对吡啶荧光猝灭机制以及它的电化学的研究

用荧光光谱研究了富勒烯二氮杂桥衍生物(eddy2)对吡啶荧光的猝灭机制,发现吡啶在426.27 nm处有荧光发射峰,当向吡啶中分别加入C₆₀和eddy2时,原有的发射峰强度明显减弱,且向短波长稍有移位,C₆₀和eddy2对吡啶荧光有猝灭作用。吡啶-C60和吡啶-eddy2体系的猝灭过程是分子之间结合形成了复合物引起的静态猝灭。eddy2对吡啶的离解常数为K_D＝2.28×10-6 (mol·L-1),结合常数K_S＝4.39×10-5 (L·mol-1)。同时研究了eddy2的电化学行为,发现eddy2的前3个还原峰电位比母体C₆₀的峰电位正移,表明eddy2的电化学还原比C₆₀的电化学还原容易,更容易接收电子。     

Effect of current density on the microstructure and corrosion behaviour of plasma electrolytic oxidation treated AM50 magnesium alloy

Plasma electrolytic oxidation (PEO) of an AM50 magnesium alloy was accomplished in a silicate-based electrolyte using a DC power source. Coatings were produced at three current densities, i.e. 15 mA cm⁻², 75 mA cm⁻², and 150 mA cm⁻² and were characterised for thickness, roughness, microstructural morphology, phase composition, and corrosion resistance. Even though the 15 min treated coatings produced at higher current density levels were thicker, they showed poor corrosion resistance when compared to that of the coatings obtained at 15 mA cm⁻². Short-term treatments (2 min and 5 min) at 150 mA cm⁻² yielded coatings of thickness and corrosion resistance comparable to that of the low current density coatings. The superior corrosion resistance of the low thickness coatings is attributed to the better pore morphology and compactness of the layer.     

Effect of dielectric coating on the electron work function and the surface stress of a metal

The electron work function, contact potential difference, and surface stress of the elastically deformed faces of the metal covered by a dielectric are calculated by using the Kohn–Sham method and stabilized jellium model. Our calculations demonstrate the opposite deformation dependencies of the work function and contact potential difference. Dielectric coating leads to a negative change in the work function and a positive change in the contact potential difference. It is shown that the measurements of the contact potential difference of a deformed face by the Kelvin method give only the change in the value of the one-electron effective potential in the plane of a virtual image behind the surface, rather than the value of the electron work function. The obtained values of the electron work function and surface stress for Al, Au, Cu, and Zn are in agreement with the results of experiments for polycrystals.     

Surface Modification of Para-Aramid Fiber by Direct Fluorination and its Effect on the Interface of Aramid/Epoxy Composites

Surface modification of a para-aramid fiber (DAFIII) was performed by direct fluorination. The properties of treated and untreated fibers were characterized and compared in detail by mechanical testing, Fourier transform infrared (FTIR) spectroscopy characterization, X-ray photoelectron spectroscopy (XPS) analysis and static contact angle measurements. The results showed that little damage of the fiber occurred after direct fluorine treatment, and the content of polar groups on the fibers surfaces were increased significantly, which resulted in a lower value of contact angle. The interlaminar shear strength (ILSS) of DAFIII fiber/epoxy composites and the tensile strength of NOL-ring specimens increased by 33% and 12%, increasing to 56.2 MPa and 2340 MPa, respectively, which indicated that the interfacial adhesion between the matrix and the aramid fiber was improved significantly by the fluorination treatment. Further tests showed that the durability of the direct fluorination treatment on the aramid fiber was also satisfactory.