Preparation of a Novel COOH Ion Implantation Sensor and Its Application

A novel ion implantation sensor (DNA/COOH/ITO) based on DNA immobilization in COOH/ITO probe was manufactured for the first time. The surface morphologies of the electrodes were characterized by X‐ray photoelectron spectroscopy (XPS), field‐emission‐scanning electron microscopy (FSEM) and electrochemical methods. In a 0.5 mol/L PBS solution, a sensitive oxidation peak of DNA on the COOH/ITO electrode was obtained by voltammetry. The electrochemical behavior of DNA was studied. And the oxidative peak potential of DNA was +0.400 V (vs. Ag/AgCl). Its peak current was proportional to the concentration of DNA over the range of 1.0×10^?8?1.0×10^?6 mol/L with a detection limit of 5.0×10^?9 mol/L (about 0.5 ng/mL). This sensor was applied to the direct detection of DNA samples.     

Electrochemical Synthesis of Chitosan‐co‐polyaniline/WO3⋅nH2O Composite Electrode for Amperometric Detection of NO2 Gas

An electrode of hydrated tungsten oxide (WO₃?nH₂O) embedded chitosan‐co‐polyaniline (CHIT‐co‐PANI) composite was electrochemically prepared on an indium tin oxide (ITO) coated glass surface using mineral acid as a supporting electrolyte. The resulting CHIT‐co‐PANI/WO₃?nH₂O/ITO electrode was characterized using ultraviolet‐visible spectroscopy (UV‐vis), Fourier transform infrared spectroscopy (FTIR), cyclic voltammetry (CV), and scanning electron microscopy (SEM). The composite electrode exhibited a three‐dimensional nanofibrous structure with the diameter of the nanofibers ranging from 20 to 100 nm. The CHIT‐co‐PANI/WO₃?nH₂O/ITO electrode allowed for the low potential detection of NO₂ gas in acidic medium. The NO₂ gas sensing characteristics were studied by measuring change in the current with respect to concentration and time. Using the CHIT‐co‐PANI/WO₃?nH₂O/ITO electrode, NO₂ gas was detected electrochemically without interference at pH 2.0 and 0.25 V vs. Ag/AgCl. The current of the electrochemical cell with the CHIT‐co‐PANI/WO₃?nH₂O/ITO electrode decreased linearly with an increase in NO₂ gas concentration in a range from 100 to 500 ppb with a response time of eight seconds.     

Synthesis of Carbon Nanofibers for Mediatorless Sensitive Detection of NADH

Highly sensitive amperometric detection of dihydronicotinamide adenine dinucleotide (NADH) by using novel synthesized carbon nanofibers (CNFs) without addition of any mediator has been proposed. The CNFs were prepared by combination of electrospinning technique with thermal treatment method and were applied without any oxidation pretreatment to construct the electrochemical sensor. In amperometric detection of NADH, a linear range up to 11.45 μM with a low detection limit of 20 nM was obtained with the CNF‐modified carbon paste electrode (CNF‐CPE). Good selectivity was exhibited for the simultaneous detection of NADH and its common interferent of ascorbic acid (AA) by differential pulse voltammogram. The attractive electrochemical performance and the versatile preparation process of the CNF‐CPE made it a promising candidate for designing effective NADH sensor.     

Glassy Carbon Electrodes Modified with Multiwall Carbon Nanotubes Dispersed in Polylysine

We report the analytical performance of glassy carbon electrodes (GCE) modified with a dispersion of multiwall carbon nanotubes (MWCNT) in polylysine (Plys) (GCE/MWCNT‐Plys). The resulting electrodes show an excellent electrocatalytic activity towards different bioanalytes like ascorbic acid, uric acid and hydrogen peroxide, with important decrease in their oxidation overvoltages. The dispersion of 1.0 mg/mL MWCNT in 1.0 mg/mL polylysine is highly stable, since after 2 weeks the sensitivity for hydrogen peroxide at GCE modified with this dispersion remained in a 90% of the original value. The MWCNT‐Plys layer immobilized on glassy carbon electrodes has been also used as a platform to build supramolecular architectures by self‐assembling of polyelectrolytes based on the polycationic nature of the polylysine used to disperse the nanotubes. The self‐assembling of glucose oxidase has allowed us to obtain a supramolecular multistructure for glucose biosensing. The influence of glucose oxidase concentration and adsorption time as well as the effect of using polylysine or MWCNT‐Plys as polycationic layers for further adsorption of GOx is also evaluated.     

Highly enantioselective fluorescent recognition of amino acid derivatives by unsymmetrical salan sensors

Novel unsymmetrical salan fluorescent sensors 2a and 2b have been designed and synthesized. The chiral recognition of N-Boc-protected amino acids by 2a and 2b has been investigated. Sensor 2a possesses higher sensitivity and enantioselectivity than sensor 2b does. Job analysis and nonlinear regression results show that 2a can form a 1:1 stoichiometric complex with a N-Boc-protected amino acid. The obtained response selectivities and the association constants indicate that 2a is a highly enantioselective and sensitive fluorescent sensor toward N-Boc-protected amino acids.     

Thin-film oxygen sensors using a luminescent polynuclear gold(I) complex

Robust thin-film oxygen sensors were fabricated by encapsulating a lipophilic, polynuclear gold(I) complex, bis{m-(bis(diphenylphosphino)octadecylamine-P,P′)}dichlorodigold(I), in oxygen permeable polystyrene and ormosil matrices. Strong phosphorescence, which was quenched by gaseous and dissolved oxygen, was observed from both matrices. The polystyrene encapsulated dye exhibited downward-turning Stern–Volmer plots which were well fitted by a two-site model. The ormosil trapped complex showed linear Stern–Volmer plots for dissolved oxygen quenching but was downward turning for gaseous oxygen. No leaching was observed when the ormosil based sensors were immersed in flowing water over an 8 h period. Both films exhibited fully reversible response and recovery to changing oxygen concentration with rapid response times.     

Highly selective fluorescent recognition of Zn2+ based on naphthalene macrocyclic derivative

A new macrocyclic chemosensor containing two naphthalene fluorophores has been synthesized. The fluorescent properties of this receptor has been studied in the presence of various metal ions such as Na⁺, Ag⁺, Cr³⁺, Mn²⁺, Fe³⁺, Co²⁺, Ni²⁺, Cu²⁺, Zn²⁺, Cd²⁺ and Pb²⁺. When increasing concentrations of Zn²⁺ ions were introduced, the emission of L was drastically increased (EFE = 4.34). This special change was not observed when other metal ions were used; such highly selective fluorescent response indicates that this receptor can easily discriminate Zn²⁺ ions from other similar species. Model calculations at DFT level further suggest the possible interaction mode, and relatively steric position between the host and guest also influence the optical response.     

可视化阵列传感器技术鉴别不同香型白酒

决定白酒香型的物质种类繁多,成分复杂.采用可视化阵列传感器技术对中国白酒五大香型的代表酒样进行检测,在可视化区分的基础上采用分层聚类分析、主成分分析等统计分析方法,对检测结果进行分析.不同香型的白酒在聚类分析中可以正确归类,利用主成分分析得到的前3个主成分所代表的白酒75.8%的信息量就可以将不同香型白酒完全区分开,表...     

Effects of anionic surfactant SDS on the photophysical properties of two fluorescent molecular sensors

Two fluorescent molecular sensors CS1 and CS2 were designed and synthesized to probe the aggregate behavior of anionic surfactant SDS. CS1 was based on the photo-induced electron transfer (PET) mechanism, while CS2 was founded on the intramolecular charge transfer (ICT) mechanism. The photophysical properties of CS1–2 in anionic surfactant sodium dodecyl sulfate (SDS) solution were studied by fluorescence and UV–vis methods. The experimental results show that significant absorption and emission spectral responses of CS1 were observed with the addition of SDS: the absorbance and fluorescence intensity decreased first and then increased. The plot of fluorescence intensity of CS1 versus SDS concentration showed two break points, which might be ascribed to the critical micellar concentration (cmc) and the formation of premicelle (cac) aggregate, respectively. But the solution’s color of CS2 changed from yellow to red with increasing SDS concentrations. The large red-shift in both absorption (50 nm) and emission (55 nm) spectra of CS2 was resulted from the protonation of the electron accepting moiety (NC nitrogen), which enhanced the “push–pull” interaction of the ICT fluorophore. This was facilitated by the increase of local H⁺ concentration around SDS premicelle and micelle. As a consequence, pK_a values of CS1 and CS2 were elevated in SDS micelle.     

非标记夹心式电化学可卡因适体传感器的研究

设计一种基于双链核酸适体的非标记夹心式电化学适体传感器, 建立简单、高灵敏度的可卡因分析方法. 首先将末端巯基修饰的捕获适体探针组装在金电极表面, 构建可卡因适体传感器. 该传感器与目标分子可卡因和部分互补的检测适体探针作用后, 在电极表面形成适体/可卡因/适体复合物. 以六氨合钌为信号分子, 基于单链适体和适体/可卡因/适体复合物对六氨合钌吸附量的不同, 通过计时电量法检测电极表面吸附六氨合钌的还原电量, 进行可卡因的分析检测. 在优化的条件下, 还原电量与可卡因浓度在1～50 mmol/L范围内呈良好的线性关系, 检出限为0.1 mmol/L. 用于血清中可卡因的检测, 回收率为96.4%～104%. 该方法简单, 灵敏度高, 可作为一种通用型的适体传感器模型.