Study Of Novel Functional Sensing Materials-Based Electrochemical And Optical Sensors

Carrier-based chemical sensors are widely used in many fields with well-established theory. However, some drawbacks of electrodes, such as components leakage, inadequate selectivity, potential instability, short lifetime, and so on, limit their applications. Meanwhile, microsensors represents a new promising field of research and applications in clinical monitoring and environmental analysis due to their compact size, low cost, and high sensitivity in small sample volume. Thus, the miniaturization of sensors is essential for life science. Moreover, for optical sensors, developing fluorescent probe-based optodes that can be directly employed in biological fluids is important. In order to exploit these chemical sensors with more ideally properties, my works have been completed as following:(1) Designed and synthesized clickable type of K+-selective ionophore and Ca2+-selective ionophore. These ionophores could be easily immobilized in azide-modified poly (vinyl chloride) (N3PVC) matrix by azide-alkyne Huisgen cycloaddition ("click chemistry") to fabricate potentiometric and optical sensors. Formation of the triazole linkers in the polymer matrix decreased the solubility of functionalized PVC significantly. Azidation of PVC for 12 h that was followed by Cu(I) catalyzed cycloaddition produced the ionophore-grafted PVC with good solubility and film forming property. The solid-contact electrode prepared with plasticized functional polymer exhibited Nernstian response to K+ from 10-6 to 10- M, good selectivity and improved lifetime. Such K+-selective ionophore grafted polymer had also been used to prepare optical sensors with ETH 5294 as chromoionophore. The measuring range and selectivity of the optodes were comparable to the ones of ion-selective electrodes. For Ca2+-selective functional polymer, it was found that the flexibility of immobilized ionophore was critical. This phenomenon could be ascribed to the stoichiometry of the ionophore and Ca2+(3:1). Increasing the space between the triazole and modified ionophore was beneficial to the electrode perforrmance.(2) Fabricated highly sensitive and selective sulfate-selective sensors based on a class of squaramide-based tripodal molecules. Compared with the reported tripodal ionophore with urea, squaramide groups as superior hydrogen bonding donor were introduced into the tripodal structure to obtain new ionophores with better performance. Three derivatives with unsubstituted (I), p-carbon trifluoride (II), and p-nitro (III) phenyl groups were attached to squaramide groups, respectively. Electron withdrawing p-nitrophenyl groups gave higher enhancement in the hydrogen bond donor ability of squaramide so that Ionophore III was chosen as the best candidate for sulfate ion recognition. Such membrane exhibited Nernstian slope of-30.2 mV-decade-1 to sulfate ions with a linear range from 1 μM to 100 mM in potentiometric measurement. The selectivity coefficients of the proposed sensor over H2PO4-, Cl-, Br-, NO3-, SCN-, I=- and ClO4- were -4.3,-3.4,-2.5,-0.6,+3.1,+3.4 and +5.9, respectively, which was much higher than the existing sulfate-selective sensors. The new sensors with high selectivity were successfully applied for the quantification of sulfate in cell lysates and drinking water with good recoveries.(3) Fabricated durable all solid-contact H2PO4--selective electrodes using a facile one-step drop casting method. The ion-sensing components uranyl salophene and multiwall carbon nanotubes (MWCNTs) composites were doped directly on a solid substrate. The optimized hybrid film-based solid-state electrodes demonstrated improved selectivity and lower detection limit for H2PO4- than the reported Ionophore I-based CHEMFETs. Due to the hydrophobicity of MWCNTs incorporated membrane, our polymer-MWCNTs composite membrane presented remarkable long-term potential stability in comparison with traditional ion-sensing membrane without MWCNTs. The sensitivity of polymer-MWCNTs membranes for H2PO4 was near to Nernstian response after the conditioning in flowing cell for 115 hours, which exhibited extended lifetime. The application of the new sensor was verified in imitated eutrophicated water samples, and the result was comparable to the value using classic spectrometry. This robust, reusable and maintenance-free ion sensor will be suitable for on-line continuous H2PO4- determination in environmental and clinical application.(4) Fabricated screen-printed Au electrode, solid-contact microelectrodes and liquid membrane microelectrodes based on ion-selective sensing membranes. Their response characteristics, such as response time and linear range, were evaluated. For MWCNTs-based screen-printed electrodes showed a Nernstian slope of -60.0 mV-decade-1 to phosphate in a linear range from 10 μM to 10 mM. The response characteristics of Ca2+-selective and H+-selective solid-contact microelectrodes were also evaluated. And the pH of single cell was monitored by H+-selective microelectrodes successfully. Besides, for further size minizaturation, micro-and nano-liquid membrane electrodes were studied. (5) Designed and synthesized a near infrared fluorescent dye (aza-bodipy) functionalized with boronic acid groups for the preparation of optodes to measure glucose in whole blood. Boronic acid groups as electron deficient group on aza-bodipy was reacted with hydrogen peroxide into electron rich phenolic group leading to the red-shift of emission wavelength from 682 to 724 nm. The emission in near infrared region offered low-level background interference from whole blood. Therefore, the dual-wavelength emission guaranteed our probe to measure glucose in whole blood accurately after the conversion of glucose into hydrogen peroxide using glucose oxidase. To facilitate the blood test, the probe was immobilized into thin hydrophobic polymer films to prepare disposal glucose optode, which could detect glucose in the solution from 60 μM to 100 mM. The concentration of glucose in 40-fold diluted whole blood was determined using our optode and the reference method, respectively. The consistence in the concentrations obtained from these two assays revealed the success of our azaBDPBA based optodes for the clinic assay of glucose in whole blood.