壳聚糖共价键合化学修饰电极测定亚硝酸根

用共价键合法把壳聚糖修饰在玻碳电极表面,研究了NO-2在修饰电极上的阳极溶出伏安特性.实验结果表明:修饰电极在0.1 mol/L NaNO3(pH 2.60)底液中对NO-2有良好的吸附性和选择性,其峰电流与NO-2的浓度在1.5×10-6～1.0×10-3 mol/L范围内呈较好的线性关系;检测限可达2.0×10-7 mol/L.将壳聚糖修饰电极应用于雨水、湖水中NO-2的测定,结果满意.     

pH敏感性叶酸修饰羧甲基壳聚糖纳米粒子作为紫杉醇载体的研究

将活化的叶酸分子连接到O-羧甲基壳聚糖(O-CMCS)上.以CaCl2为交联剂,通过离子交联法制备叶酸修饰的O-CMCS纳米粒子(FCC NPs),并开展了从FCC NPs作为抗癌药物紫杉醇(PTX)载体的研究.结果表明:FCC NPs呈球形,粒子大小约190 nm,对PTX的载药量和包封率均受PTX加入量的影响.该纳米粒子对药物的释放具有较好的pH敏感性,能够增强PTX在癌细胞处的富集.同时,该纳米粒子无细胞毒性,纳米粒子表面由于叶酸的存在使其具有较好的细胞靶向性,且载药纳米粒子对癌细胞生长具有良好的抑制作用.     

pH荧光纳米传感器的研制及表征

利用溶胶-凝胶技术制得了单分散性很好的二氧化硅纳米微球,通过共价偶联方式引入对pH变化敏感的荧光素异硫氰酸酯（FITC）,这种FITC功能化二氧化硅纳米微球（FITC功能化硅微球）可作为pH荧光纳米传感器。当pH值从4.0变至7.5时,荧光强度增大约30倍。该传感器灵敏度高,响应速度快,容易制备,光稳定性好,可望用于单细胞的pH分析。     

聚苯胺修饰碳纤维针型复合微pH传感器

由电聚合法用聚苯胺修饰碳纤维电极作为ＰＨ敏感电极。把Ｋ３Ｆｅ（ＣＮ）６／Ｋ４Ｆｅ（ＣＮ）６体系填入医用注射针头内成为参比电极。把经聚苯胺修饰的碳纤维电极安置入该针型参比电极内构成复合针型微ｐＨ传感器。在ＰＨ ２～１２范围内，该传感器呈现超Ｎｅｒｎｓｔ响应，斜率为－７８ ｍＶ／ｐＨ；响应时间<１ｍｉｎ。该传感器成功地应用于在体ｐＨ测定以及水果内微区ｐＨ测定。     

壳聚糖溶液pH对载细胞海藻酸钠-壳聚糖微胶囊性能的影响

以激光共聚焦扫描显微镜为研究手段, 原位直观地考察了在不同pH条件下聚电解质膜的络合程度和蛋白扩散情况. 通过分析pH值对微胶囊膜性能的影响规律, 并结合不同种类细胞对环境pH的敏感特性, 确定了制备细胞培养用海藻酸钠-壳聚糖微胶囊的最佳pH值. 结果表明, 当壳聚糖溶液的pH值由3.50增加到6.50, 微胶囊膜的络合深度呈现高-低-高的趋势, 而微胶囊膜的膨胀性能呈现低-高-低的趋势, 模型蛋白通过微囊膜的扩散呈现低-高-低的趋势, 拐点均出现在pH=4.00和5.50处. 结合动物细胞及微生物细胞对环境pH耐受能力的考察, 确定制备微囊化动物细胞时, 微胶囊成膜反应溶液的最佳pH值为5.50; 制备微囊化大肠杆菌时, 反应溶液的最佳pH值为5.00; 制备微囊化酵母菌时, 反应溶液的最佳pH值为4.50.     

全固态复合碳纤维氧化钨pH传感器的研制及应用

采用电化学修饰法制备了一种可直接测定固体、半固体及糊状物表面和内部pH值的传感器,并对该传感器的制备工艺、性能、测试条件和干扰物的影响进行了讨论.结果表明:该传感器内阻低,响应时间快(小于25 s),测量范围广(pH 2 ～12),准确度高,重复性好,响应斜率为60.01 mV/pH.该传感器除了能用于传统领域外,还可用于临床检测、食品加工、生物化工等领域.     

基于碳纳米管修饰电极/鸟嘌呤电化学体系的固体电位型pH传感器

根据鸟嘌呤在短单壁碳纳米管修饰玻碳电极(S-SWCNT/GCE)上发生的电催化氧化特性,及其氧化电位对支持电解质溶液的pH值具有灵敏的响应,制备了以鸟嘌呤为指示剂的固体电位型pH传感器。在优化各种影响因素后,其电位在pH2.0~12.0范围内具有线性响应,回归方程为Epa(V)=-0.0497pH 0.8931。该传感器制备简单,使用方便,响应时间<20 s。在pH响应范围内待测液中离子强度对测定没有影响。酸碱滴定终点具有明显的突跃。对Na 、K 和Ca2 的选择性系数小。已成功地应用于实际样品的测定。     

利用pH传感器研究中和反应过程中pH的突变

利用pH传感器的实时检测功能,并借助数据采集器和计算机直接生成数据曲线,便可以便捷、直观地反映中和反应过程中pH的变化,帮助学生认识“突变”的存在,加深理解酸碱中和滴定方法的原理。pH变化曲线可用来研究弱酸、弱碱、多元弱酸盐等参与的反应,还可对其进行数学建模以及进行相关讨论。     

pH响应壳聚糖衍生物的合成与自组装

以甲烷磺酸为反应溶剂,将己酰氯接枝到壳聚糖(CS)侧基上,得到可溶于常见有机溶剂的己酰化壳聚糖(HC);亲水性聚乙二醇单甲醚(mPEG)通过活泼酯法接枝到HC上,最终获得两亲性壳聚糖衍生物PEG-g-HC。用红外光谱(FT-IR)、核磁共振(1H-NMR)与紫外-可见光谱(UV-Vis)表征产物结构,用动态光散射、透射电镜与荧光光谱等方法研究了PEG-g-HC的自组装行为。结果表明:通过改变己酰氯与CS的投料比可调节HC的取代度;随着HC中己酰基取代度增大,HC在水介质中溶解的临界pH随之降低;PEG-g-HC可自组装为球形胶束,通过改变HC中己酰基的取代度可调控其pH响应行为。     

A pH optical and fluorescent sensor based on rhodamine modified on activated cellulose paper

A rhodamine‐based colorimetric and fluorescent pH chemosensor ( RhA ) was designed and synthesized via a coupling reaction between rhodamine ethylenediamine and succinic anhydride. RhA showed excellent pH response in aqueous solutions. In addition, common cations (Na⁺, K⁺, Ag⁺, Mg²⁺, Ca²⁺, Pb²⁺, Co²⁺, Ni²⁺, Cu²⁺, Zn²⁺, Cd²⁺, Hg²⁺, Al³⁺, Cr³⁺, Fe³⁺, Au³⁺, Pt²⁺, and Ru²⁺) did not interfere with the pH response. As it has the potential to be used as a portable pH sensor, RhA was immobilized on activated cellulose paper using N,N'‐dicyclohexylcarbodiimide (DCC) and N,N'‐dimethylpyridin‐4‐amine (DMAP) as the coupling reagent to obtain a composite pH sensor ( CP‐RhA ). CP‐RhA was characterized by ATR‐FTIR, UV–vis, and fluorescence spectroscopy, and by scanning electron microscopy (SEM). CP‐RhA showed a rapid response in the pH range 1–8 through color and fluorescence changes. DFT calculations showed a blue‐shifted spectrum in the protonated form compared to the neutral form. Moreover, the pH sensor paper could be reused by dipping in NaOH. Thus, our work demonstrates the potential of the rhodamine dye composite for visualizing pH changes in real systems.     

Development of pH sensor based on aromatic polyurethane matrix

The synthesized aromatic polyurethane (APU)-based all-solid-state (ASS) pH sensor was developed with the same APU-based reference site in an ASS multi sensing electrode. The best analytical performance (the linear range of pH 3.0–11.5, slopes of 57 mV pH⁻¹) was obtained with the membrane composition of 33:66:1 (wt.%) of APU/plasticizer (NPOE)/ionophore (N,N-dioctadecylmethylamine) with the addition of lipophilic additive (KTpClPB, 5 mol.%). This ASSE exhibits more advantages of increasing stability, reducing membrane resistance and reducing anion interference.     

Determination of carbaryl pesticide using amperometric acetylcholinesterase sensor formed by electrochemically deposited chitosan

A sensitive, fast and cheap sensor for quantitative determination of carbaryl pesticide using amperometric acetylcholinesterase (AChE) sensor based on electrochemically deposited chitosan was reported. From a mildly acidic chitosan solution, a chitosan film is electrochemically deposited on Au electrode surface via a negative voltage bias, leading to a stable AChE sensor. The characteristics of the deposited layer were observed to be dependent upon the deposition time, pH, and the chitosan concentration. Fourier-transform infrared spectra proved that the immobilized enzyme could preserve their native structure due to the excellent biocompatibility and non-toxicity of chitosan. Under the optimal experimental conditions, the carbaryl inhibition on AChE-CHIT/Au was proportional to its concentration in two ranges, from 0.005 to 0.1 μg/ml and 0.5 to 5 μg/ml, with the correlation coefficients of 0.9966 and 0.9982, respectively. The detection limit was 0.003 μg/ml taken as the concentration equivalent to a 10% decrease in signal. The determination of carbaryl in garlic samples obtained from export of farm base showed acceptable accuracy. The developed sensor exhibited good fabrication reproducibility and acceptable stability, which provided a new promising tool for pesticide analysis.     

Use of a poly(4,4′-diaminobiphenyl) chemically modified electrode as a pH sensor

A chemically modified electrode (CME) for use as a potentiometric pH sensor was constructed by electropolymerizing a poly(4,4′-diaminobiphenyl) coating on a platinum electrode. The resulting CME gave a linear response to pH in the range 1–12 with a slope of ?56 mV pH^?1. The CME functioned well in titration experiments and in pH measurements. No significant interference of a coexisting redox couple with the pH measurements was observed. The mechanism of the pH response of the CME is considered.     

CCD camera full range pH sensor array

Changes in colors of an array of optical sensors that responds in full pH range were recorded using a CCD camera. The data of the camera were transferred to the computer through a capture card. Simple software was written to read the specific color of each sensor. In order to associate sensor array responses with pH values, a number of different mathematics and chemometrics methods were investigated and compared. The results show that the use of “Microsoft Excel's Solver” provides results which are in very good agreement with those obtained with chemometric methods such as artificial neural network (ANN) and partial least square (PLS) methods.     

Bifunctional sensor of nitric oxide and oxygen based on hematite nanotubes embedded in chitosan matrix

A novel hybrid bifunctional sensing platform for simultaneous determination of NO and O₂ has been developed, whereby hematite nanotubes are immobilized into the chitosan matrix onto a gold electrode (labeled as HeNTs-Chi/Au). The HeNTs distributed in porous-structured chitosan matrix not only offer abundant active sites for bifunctional sensing of NO and O₂, but also facilitate oxidation of NO and reduction of O₂ dramatically. Straight calibration curves are achieved in analyte concentration ranges of 5.0 × 10⁻⁸ to 1.25 × 10⁻⁶ mol L⁻¹ for NO and 2.5 × 10⁻⁷ to 6.0 × 10⁻⁶ mol L⁻¹ for O₂. Also, the detection limits are low of 8.0 × 10⁻⁹ mol L⁻¹ for NO and 5.0 × 10⁻⁸ mol L⁻¹ for O₂. Such an efficient bifunctional sensor for NO and O₂ offers great potential in quantitation of NO levels in biological and medical systems, since NO level is highly regulated by various reactive oxygen species.     

Characterisation and deployment of an immobilised pH sensor spot towards surface ocean pH measurements

The oceans are a major sink for anthropogenic atmospheric carbon dioxide, and the uptake causes changes to the marine carbonate system and has wide ranging effects on flora and fauna. It is crucial to develop analytical systems that allow us to follow the increase in oceanic pCO₂ and corresponding reduction in pH. Miniaturised sensor systems using immobilised fluorescence indicator spots are attractive for this purpose because of their simple design and low power requirements. The technology is increasingly used for oceanic dissolved oxygen measurements.     

pH and ionic sensitive chitosan/carboxymethyl chitosan IPN complex films for the controlled release of coenzyme A

pH and ionic sensitive interpenetrating polymer network (IPN) complex films based on chitosan (CS) and carboxymethyl chitosan (CM-CS) were prepared by using glutaraldehyde as crosslinking agent. Its structure was characterized by FT-IR, which indicated that the IPN was formed. The films were studied by swelling, weight loss with time, and release of coenzyme A (CoA). It was found that the IPN films were sensitive to pH and ionic strength of the medium. The cumulative release rate of CoA decreased with CoA loading content, ionic strength or crosslinking agent increasing. The composition of the IPN films and pH of release medium also had significant effect on the release of CoA. The differences in the rates and amounts of released CoA may be attributed to the swelling behavior, the degradation of films, and interaction between drug molecule and polymer matrix. These results suggested CS/CM-CS IPN films could be used as drug delivery carrier.     

Phenolphthalein immobilized membrane for an optical pH sensor

A phenolphthalein immobilized cellulose membrane for an optical pH sensor was described. The phenolphthalein was first reacted with the formaldehyde to produce a series of prepolymers with many hydroxymethyl groups. In this paper, the prepolymers was abbreviated to phenolphthalein-formaldehyde (PPF). Then the PPF was covalently immobilized to the diacetylcellulose membrane via hydroxymethyl groups. Finally the membrane was hydrolyzed in the 0.1 M NaOH solution for 24 h to reduce the response time. Advantageous features of the pH-sensitive membrane include (a) a large dynamic range from pH 8.0 to 12.50, or even broader, (b) rapid response time (2–30 s), (c) easy of fabrication, and (d) a promising material for determination of high pH values. The immobilized PPF has a broader dynamic range from 8.0 to 12.50 than the free phenolphthalein from pH 8.0 to 11.0, and this was due to the newly produced methylenes in our investigation.     

A hetero-core structured fiber optic pH sensor

Novel spectroscopic sensor based on a hetero-core structured fiber optic is described in this paper. The hetero-core structured fiber optic consists of multi mode fibers and a short piece of single mode fiber which was inserted in the multi mode fibers. Phenol red and/or cresol red as pH sensitive dyes were immobilized on the surface of the hetero-core portion by using sol-gel method, and the pH change detection was performed by immersing the hetero-core portion into the solution. In the case that the cresol-red immobilized fiber was immersed in the alkaline and/or acidic solution, the peak wavelength of the propagating loss spectra were about 575 and 545 nm, respectively. These propagating loss spectra were similar to that of the absorbance spectra of the dye solution. In the propagating loss spectra of phenol-red immobilized fiber, these spectra were similar to that of the dye solution. The colorimetric change of the dye in the support matrix was reversible, and the response time of the sensor was within 30 s.