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41.
以(NH4)6Mo7O24·4H2O和Bi(NO3)3·5H2O为原料,采用普通水热法制备Bi2Mo O6光催化剂,研究p H值对制备该光催化剂的影响。对所制备的系列样品,采用X-射线衍射仪(XRD)、扫描电子显微镜(SEM)、比表面积分析仪、X射线光电子能谱仪(XPS)和紫外-可见漫反射(UV-Vis DRS)进行表征。结果表明:p H值对Bi2Mo O6晶体的物相组成、形貌和光催化性能均有显著影响。p H值为1~7时,所制备的样品为纯相Bi2Mo O6,p H值为9或11时,出现第二相Bi3.64Mo0.36O6.55;随着p H值的升高,形貌依次为纳米棒、纳米片和无规则纳米颗粒。在可见光(λ≥420 nm)照射下,通过光催化降解罗丹明B(Rhodamine B,Rh B),探讨了制备Bi2Mo O6的p H值对其可见光催化活性的影响。当p H=7时,制备的样品光催化效果最好,光照50 min后对初始浓度为5 mg·L-1的罗丹明B溶液的降解率为85%。 相似文献
42.
采用聚乙二醇单甲醚(mPEG)为亲水段,聚赖氨酸(PzLL)为疏水段,通过二硫键和碳氮双键串联桥连合成了两嵌段共聚物(mPEG-CN-SS-PzLL),其中的二硫键具有还原敏感性,碳氮双键具有pH酸敏感性。通过红外光谱和核磁共振谱等手段测试分析了产物的化学结构。将聚合物通过透析法自组装制备得到双刺激响应型纳米载药粒子。结果表明:该纳米载药粒子的药物包封率较高,达到52%。该载药系统在还原环境或酸性环境下具有良好的体外释药性能。 相似文献
43.
Microwire Chronoamperometric Determination of Concentration,Diffusivity, and Salinity for Simultaneous Oxygen and Proton Reduction 下载免费PDF全文
A microwire chronoamperometric method is reported employing a 25 µm diameter platinum microwire for multi‐parameter electroanalysis with digital simulation‐based evaluation (employing DigiElch 4.F). Concentration and diffusion coefficient data are obtained for the reduction of oxygen and for the reduction of protons individually and simultaneously in saline (0.1 M to 4.0 M NaCl) electrolyte media. The diffusion coefficient and concentration data for oxygen allows salinity levels to be estimated. The microwire chronoamperometry method offers versatility and precision due to (i) a slow approach to steady state (when compared to microdisc methods) and (ii) insignificant viscosity effects (when compared to hydrodynamic methods). 相似文献
44.
Acid‐Labile Thermoresponsive Copolymers That Combine Fast pH‐Triggered Hydrolysis and High Stability under Neutral Conditions 下载免费PDF全文
Dr. Qilu Zhang Zhanyao Hou Benoit Louage Dr. Dingying Zhou Nane Vanparijs Prof. Dr. Bruno G. De Geest Prof. Dr. Richard Hoogenboom 《Angewandte Chemie (International ed. in English)》2015,54(37):10879-10883
Biodegradable polymeric materials are intensively used in biomedical applications. Of particular interest for drug‐delivery applications are polymers that are stable at pH 7.4, that is, in the blood stream, but rapidly hydrolyze under acidic conditions, such as those encountered in the endo/lysosome or the tumor microenvironment. However, an increase in the acidic‐degradation rate of acid‐labile groups goes hand in hand with higher instability of the polymer at pH 7.4 or during storage, thus posing an intrinsic limitation on fast degradation under acidic conditions. Herein, we report that a combination of acid‐labile dimethyldioxolane side chains and hydroxyethyl side chains leads to acid‐degradable thermoresponsive polymers that are quickly hydrolyzed under slightly acidic conditions but stable at pH 7.4 or during storage. We ascribe these properties to high hydration of the hydroxy‐containing collapsed polymer globules in conjunction with autocatalytic acceleration of the hydrolysis reactions by the hydroxy groups. 相似文献
45.
Marta Espina Palanco Klaus Bo Mogensen Katrin Kneipp 《Journal of Raman spectroscopy : JRS》2016,47(2):156-161
We report surface‐enhanced Raman studies on intact plant material using onion layers as a biological target, and silver nanoaggregates and silver island films as enhancing plasmonic structures. Surface‐enhanced Raman scattering (SERS) enhancement allows the detection of strong Raman signatures of chemical constituents of the surface of the onion layer such as cellulose, proteins, and flavonols. Because of long‐time incubation, SERS sensors can access the extracellular space in the inner of the layer. The location of silver nanoparticles inside the onion layer has been monitored by the SERS images collected from chemicals present in the onion and/or reporter molecules attached to the nanoparticles. Our studies show a competitive adsorption of intrinsic bio molecules of the onion layer and reporter molecules. Different spectra from different places of the layer indicate the complex heterogeneous chemical structure of the plant material. The pH‐sensitive reporter molecule para mercapto benzoic acid attached to the nanoparticles allows us to infer pH values inside the extracellular matrix of the onion layer. Copyright © 2015 John Wiley & Sons, Ltd. 相似文献
46.
Responsive mechanism of 2-(2'-hydroxyphenyl)benzoxazole-based two-photon fluorescent probes for zinc and hydroxide ions 下载免费PDF全文
Response theory is used to investigate one- and two-photon absorption(TPA) as well as the emission properties of a series of potential zinc ion and pH sensitive materials containing 2-(2’-hydroxyphenyl)benzoxazole(HPBO) end groups.Special emphasis is placed on the evolution of their optical properties upon combining with zinc ions or deprotonation.Our calculated results indicate that upon combining with zinc ions or deprotonation,these HPBO derivatives show drastic changes in their one-photon absorption(OPA),emission,and TPA properties.Moreover,the mechanisms of the probes are analyzed and found to be an intramolecular charge transfer.These compounds are thus proved to be excellent candidates for two-photon fluorescent zinc and pH probes. 相似文献
47.
Facile synthesis of thermosensitive functional polyaspartamide derivatives by click chemistry 下载免费PDF全文
Guangyan Zhang Yunti Zhang Yanfeng Chu Yingying Ma Renxi Zhuo Xulin Jiang 《Journal of polymer science. Part A, Polymer chemistry》2015,53(10):1296-1303
Biodegradable and thermosensitive polyaspartamide derivatives containing pendant azide groups P(Asp‐Az)X‐HPAs were synthesized from poly(l ‐succinimide) via the ring‐opening reaction with 2‐azidoethylamine (Az) and 5‐hydroxypentylamine (HPA). Then hydrophobic phenethyl (PEA) and imidazole (IMZ) moieties were introduced successfully with very high reaction efficiency above 90% to the side chains of P(Asp‐Az)X‐HPA by click reaction to obtain thermoresponsive polyaspartamide derivatives containing pendant aromatic rings P(Asp‐Az)X‐HPA‐PEAs and the thermo/pH‐responsive polyaspartamide derivatives containing pendant imidazole rings P(Asp‐Az)X‐HPA‐IMZs, respectively. The thermoresponsive behaviors of P(Asp‐Az)X‐HPA‐PEAs and P(Asp‐Az)X‐HPA‐IMZs were confirmed by dynamic light scattering (DLS) and transmittance measurements, and the cloud point can be tuned by designed amounts of azide groups and can be further adjusted by the grafting molar percentage of hydrophobic phenethyl or imidazole moieties to the side chains of P(Asp‐Az)X‐HPA via click chemistry. The pH‐responsive behavior of P(Asp‐Az)X‐HPA‐IMZs can also be tuned. These results indicate that the obtained polyaspartamide‐based functional polymers can be further functionalized with hydrophilic long PEG chain and/or targeted moieties via click chemistry for drug delivery. © 2015 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2015 , 53, 1296–1303 相似文献
48.
Wenjuan Guo Tieshi Wang Xinde Tang Qun Zhang Faqi Yu Meishan Pei 《Journal of polymer science. Part A, Polymer chemistry》2014,52(15):2131-2138
Triple stimuli (temperature/pH/photo)‐responsive amphiphilic glycopolymer, poly(2‐(dimethylamino)ethyl methacrylate‐co‐6‐O‐methacryloyl‐1,2,3,4‐di‐O‐isopropylidene‐D‐galactopyranose)‐b‐poly(4‐(4‐methoxyphenylazo)phenoxy methacrylate) [P(DMAEMA‐co‐MAIpGP)‐b‐PMAZO] was synthesized by atom transfer radical polymerization, followed by the hydrolysis of MAIpGP groups, resulting in the target product poly(2‐(dimethylamino)ethyl methacrylate‐co‐6‐O‐methacryloyl‐D‐galactopyranose)‐b‐poly(4‐(4‐methoxyphenylazo)phenoxy methacrylate) [P(DMAEMA‐co‐MAGP)‐b‐PMAZO]. The composition, moleculer weight, and moleculer weight distribution of the resultant polymers were characterized by 1H NMR and gel permeation chromatography. The micelles formed in aqueous solutions were simulated by various chemical and physical stimuli and characterized by dynamic light scattering, transmission electron microscopy, and UV‐vis spectroscopy. It was found that the glycopolymer is responsive to three different types of stimulus (light, temperature, and pH). The poly(2‐(dimethylamino) ethyl methacrylate) segments give thermo‐ and pH‐responsiveness. The presence of the azobenzene moiety endows the block copolymer to exhibit light‐responsiveness due to its reversible trans‐cis isomerization conversion. The triple stimuli‐responsive glycopolymer micelles can simulate biomacromolecues in vivo/in vitro environment and can be expected to open up new applications in various fields. © 2014 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2014 , 52, 2131–2138 相似文献
49.
《Journal of Polymer Science.Polymer Physics》2018,56(12):914-923
N,N‐dialkylaminoethyl methacrylate (DAEA) monomers are extensively used to prepare multi‐responsive polymers. However, these monomers face high risk of hydrolysis in their ester groups when being polymerized in water‐containing medias. Here, NMR spectroscopy was employed to continuously track the hydrolysis and solubility of four widely used DAEA monomers [CH2CH2R1COO(CH2)2N(R2)2; R1 = H or CH3; R2 = CH3, CH2CH3 or CH(CH3)2] under typical polymerization conditions. With this technique, the hydrolysis reactivity and absolute hydrolysis amount of these monomers are separately examined, and then their kinetic correlations with solubility, molecular structure, pH, and temperature are established, so that the hydrolysis of DAEA monomers and even other esters with similar cyclic structure can be predicted. The present efforts are expected to provide a general understanding for the hydrolysis of all the DAEA monomers, benefitting to the optimization of polymerization toward well‐defined DAEA copolymers, as well as the design of smart soft matter for specific applications. © 2018 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2018 , 56, 914–923 相似文献
50.
Monika Cichocka 《光谱学快报》2018,51(2):118-121
The intracellular brain pH in phosphorus magnetic resonance spectroscopy is calculated using the chemical shift between the inorganic phosphate and phosphocreatine with the Henderson–Hasselbalch equations. Researchers use various mathematical formulas that have different parameters and get various results for the same input data as a consequence. Thus, the aim of this article was to determine the mathematical formulas that allow the conversion of the pH values obtained by the most popular analysis methods to each other. To determine the relationships between pH results and the applied mathematical formula, the pH values were calculated using two algorithms for the theoretical chemical shift values. The pH results were compared with each other using the appropriate t-tests. Mathematical formulas were designed to simplify the conversion of pH values obtained by two data analysis methods to each other. The pH values with were obtained this way did not differ significantly from the pH values calculated directly from the given formula. The computed mathematical formulas will make it possible to simplify pH conversions without knowing the chemical shift between inorganic phosphate and phosphocreatine but only basing on the final pH values obtained by one of the formulas. 相似文献