The Ion Sensitive Field Effect Transistor (ISFET) operation based onpolycrystalline silicon thin film transistors is reported. These devices can be fabricated oninexpensive disposable substrates such as glass or plastics and are, therefore, promisingcandidates for low cost single-use intelligent multisensors. In this work we have developedan extended gate structure with PE-CVD Si₃N₄ deposited on top of a conductor, which alsoprovides the electrical connection to the remote TFT gate. Nearly ideal pH sensitivity(54 mV/pH) and stable operation have been achieved. Temperature effects have also beencharacterized. A penicillin sensor has been fabricated by functionalizing the sensing areawith penicillinase. The shift increases almost linearly upon the increase of penicillinconcentration until saturation is reached for ~ 7 mM. Poly-Si TFT structures with a goldsensing area have been also successfully applied to field-effect detection of DNA. Full article

This work presents a sensitive method for the determination of trace antimonybased on the antimony-pyrogallol red (PGR) adsorption at a carbon paste electrode (CPE).The optimal conditions were to use an electrode containing 25% paraffin oil and 75%high purity graphite powder as working electrode, a 0.10 mol/L HCl solution containing3.0×10-5 mol/L PGR as accumulation medium and a 0.20 mol/L HCl solution aselectrolyte with an accumulation time of 150 s and a reduction time of 60 s at -0.50 Vfollowed with a sweep from -0.50 V to 0.20 V. The mechanism of the electrode reactionwas discussed. Interferences of other metal ions were studied as well. The detection limitwas 1×10^-9 mol/L. The linear range was from 2.0×10^-9 mol/L to 5.0×10^-7 mol/L.Application of the proposed method to the determination of antimony in water andhuman hair samples gave good results. Full article

A simple and promising H₂O₂ biosensor has been developed by successfulentrapment of horseradish peroxidase (HRP) in a gelatine matrix which was cross-linkedwith formaldehyde. The large microscopic surface area and porous morphology of thegelatine matrix lead to high enzyme loading and the enzyme entrapped in this matrix canretain its bioactivity. This biosensor exhibited a fast amperometric response to hydrogenperoxide (H₂O₂). The linear range for H₂O₂ determination was from 2.5×10^-5 to2.5×10^-3 M, with a detection limit of 2.0×10^-6 M based on S / N = 3. This biosensorpossessed very good reproducibility. Full article

An amperometric biosensor for hydrogen peroxide (H₂O₂) was developed viaan easy and effective enzyme immobilization method with the “sandwich” configuration:ferrocene-chitosan: HRP: chitosan-glyoxal using a glassy carbon electrode as the basicelectrode. In order to prevent the loss of immobilized HRP under optimized conditions,the biosensor surface was cross-linked with glyoxal. Ferrocene was selected andimmobilized on the glassy carbon electrode surface as a mediator. The fabricationprocedure was systematically optimized to improve the biosensor performance. Thebiosensor had a fast response of less than 10 s to H₂O₂, with a linear range of 3.5×10^-5 to1.1×10^-3 M, and a detection limit of 8.0×10^-6 M based on S/N = 3. Full article

A new kind of bio-nanocomposite photoelectrode was fabricated through directimmobilization of the bacterial photosynthetic reaction center (RC) proteins on ananocrystalline TiO₂ matrix prepared by anodic electrodeposition. The near-infrared (NIR)-visible absorption and fluorescence emission spectra displayed that structure and activity ofthe RC remained unaltered on the nano-TiO₂ film surface. High efficient light-harvesting ofthe NIR light energy by RC contributed to the distinct enhancement of the photoelectricconversion on such nanoporous matrix, which would provide a new strategy to developversatile biomimic energy convertors or photoelectric sensors. Full article

A novel technique was developed, that was high throughput simultaneousscreening of multiple resistance protein expression based on a protein array system. Themethod combined the advantage of the specificity of enzyme-linked immunosorbentassays with the sensitivity and high throughput of microspot. In this system, the multipleresistance protein arrays were created by spotting the captured antibodies onto the glassslide. The arrays were then incubated with cell samples of leukemia patients. The boundproteins were recognized by biotin-conjugated antibodies and detected by CCD.Experiments demonstrated that three multiple resistance proteins, including Pgp, MRPand BCRP which are members of the ATP-binding-cassette (ABC) superfamily ofmembrane transporters could be simultaneously detected using this new approach.Research work shows the result is coincident with flow cytometry (FCM) (P>0.01). Itprovided a methodology to develop many high-density protein array systems to detect avariety of proteins. The protein arrays will provide a powerful tool to identify theleukemia cell protein expression and rapidly validate their MDR determination. Full article

Since the study of Al³⁺ ion on the enzyme activity by using of electrochemical techniques was rarely found in available literatures, the differential-pulse polarography (DPP) technique was applied to study the effects of Al³⁺ ion on the glutamate dehydrogenase (GDH) activity in the catalytical reaction of α-KG +NADH+NH⁴⁺ ⇔ L-Glu+NAD⁺+H₂O by monitoring the DPP reduction current of NAD⁺. At the plant and animal physiologically relevant pH values (pH=6.5 and 7.5), the GDH enzyme activities were strongly depended on the concentrations of the metal ion in the assay mixture solutions. In the lower Al (III) concentration solutions (<30 μM), the inhibitory effects were shown, which are in accordance with the recently biological findings. With the increase of Al (III) concentrations (30~80 μM), the enzyme GDH activities were activated. However, once the concentration of Al (III) arrived to near 0.1 mM level (>80μM), the inhibition effects of Al (III) were shown again. The cyclic voltammetry of NAD⁺ and NAD⁺-GDH in the presence of Al (III) can help to explain some biological phenomena. According to the differential-pulse polarography and cyclic voltammetry experiments, the present research confirmed that the electrochemical technique is a convenient and reliable sensor for accurate determination of enzyme activity in biological and environmental samples. Full article

The redox protein and enzyme, such as hemoglobin (Hb), horseradish peroxidase(HRP) and glucose oxidase (GOx), was immobilized on the surface of the carbon nanotubemodified glassy carbon (CNT/GC) electrode, respectively. The cyclic voltammetric resultsindicated that the redox protein and enzyme underwent effective and stable direct electrontransfer reaction with a pair of nearly symmetrical redox peaks. The formal redox potential,E^0’, was almost independent on the scan rates, the average value of E^0’ for Hb, HRP andGOx was –0.343 ± 0.001, –0.319 ± 0.002 and –0.456 ± 0.0008 V (vs. SCE，pH 6.9),respectively. The dependence of E^0’ on the pH solution indicated that the direct electrontransfer of Hb and HRP was a one-electron-transfer reaction process coupled with oneproton-transfer, while the GOx was a two-electron-transfer coupled with two-protontransfer.The apparent heterogeneous electron transfer rate constant (k_s) was 1.25 ± 0.25,2.07 ± 0.69 and 1.74 ± 0.42 s^-1 for Hb, HRP and GOx, respectively. The method presentedhere can be easily extended to immobilize other redox enzymes or proteins and obtain theirdirect electrochemistry. Full article

The calibration of pH meters including the pH glass electrode, ISE electrodes,buffers, and the general background for calibration are reviewed. Understanding of basicconcepts of pH, pOH, and electrode mechanism is emphasized. New concepts of pH, pOH,as well as critical examination of activity, and activity coefficients are given. Theemergence of new solid state pH electrodes and replacement of the salt bridge with aconducting wire have opened up a new horizon for pH measurements. A pH buffer solutionwith a conducting wire may be used as a stable reference electrode. The misleadingunlimited linear Nernstian slope should be discarded. Calibration curves with 3 nonlinearportions for the entire 0—14 pH range due to the isoelectric point change effect areexplained. The potential measurement with stirring or unstirring and effects by double layer(DL) and triple layer (TL) will be discussed. Full article

Tannic acid-doped polypyrrole (PPY/TA) films have been grown on goldelectrodes for selective electrochemical detection of dopamine (DA). Electrochemicalquartz crystal microbalance (EQCM) studies revealed that, in vivid contrast toperchlorate-doped polypyrrole films (PPY/ClO4-), the redox switching of PPY/TA filmsin aqueous solutions involved only cation transport if the solution pH was greater than3~4. The PPY/TA Au electrodes also exhibited attractive permselectivity forelectroactive cations, namely, effectively blocking the electrochemical reactions ofanionic ferricyanide and ascorbic acid (AA) while well retaining the electrochemicalactivities of hexaammineruthenium (III) and dopamine as cationic species. A 500 HzPPY/TA film could effectively block the redox current of up to 5.0 mM AA. Thecoexistence of ascorbic acid in the measurement solution notably enhanced the currentsignal for dopamine oxidation, due probably to the chemical regeneration of dopaminethrough an ascorbic acid-catalyzed reduction of the electro-oxidation product ofdopamine (EC’ mechanism), and the greatest amplification was found at an ascorbic acidconcentration of 1.0 mM. The differential pulse voltammetry peak current for DAoxidation was linear with DA concentration in the range of 0 to 10 μM, with sensitivityof 0.125 and 0.268 μA/μM, as well as lower detection limit of 2.0 and 0.3 μM in a PBSsolution without AA and with 1.0 mM coexisting AA, respectively. Full article

For potential ultrafast optical sensor application, both VO₂ thin films andnanocomposite crystal-Si enriched SiO₂ thin films grown on fused quartz substrates weresuccessfully prepared using pulsed laser deposition (PLD) and RF co-sputteringtechniques. In photoluminescence (PL) measurement c-Si/SiO₂ film containsnanoparticles of crystal Si exhibits strong red emission with the band maximum rangingfrom 580 to 750 nm. With ultrashort pulsed laser excitation all films show extremelyintense and ultrafast nonlinear optical (NLO) response. The recorded holography fromall these thin films in a degenerate-four-wave-mixing configuration shows extremelylarge third-order response. For VO₂ thin films, an optically induced semiconductor-tometalphase transition (PT) immediately occurred upon laser excitation. it accompanied.It turns out that the fast excited state dynamics was responsible to the induced PT. For c-Si/SiO₂ film, its NLO response comes from the contribution of charge carriers created bylaser excitation in conduction band of the c-Si nanoparticles. It was verified byintroducing Eu³⁺ which is often used as a probe sensing the environment variations. Itturns out that the entire excited state dynamical process associated with the creation,movement and trapping of the charge carriers has a characteristic 500 ps duration. Full article

A stable Fe(4-TMPyP)-DNA-PADDA (FePyDP) film was characterized onpyrolytic graphite electrode (PGE) or an indium-tin oxide (ITO) electrode through thesupramolecular interaction between water-soluble iron porphyrin (Fe(4-TMPyP)) and DNAtemplate, where PADDA (poly(acrylamide-co-diallyldimethylammonium chloride) isemployed as a co-immobilizing polymer. Cyclic voltammetry of FePyDP film showed a pairof reversible Fe^III/Fe^II redox peaks and an irreversible Fe^IV/Fe^III peak at –0.13 V and 0.89vs. Ag|AgCl in pH 7.4 PBS, respectively. An excellent catalytic reduction of NO wasdisplayed at –0.61 V vs. Ag|AgCl at a FePyDP film modified electrode.Chronoamperometric experiments demonstrated a rapid response to the reduction of NOwith a linear range from 0.1 to 90 μM and a detection limit of 30 nM at a signal-to-noiseratio of 3. On the other hand, it is the first time to apply high-valent iron porphyrin ascatalyst at modified electrode for NO catalytic oxidation at 0.89 vs. Ag|AgCl. The sensorshows a high selectivity of some endogenous electroactive substances in biological systems.The mechanism of response of the sensors to NO is preliminary studied. Full article

Trace amounts of nitric oxide (NO) have been determined in aqueous phosphate buffersolutions (pH=7.4) by using a glassy carbon electrode coated with three charge-different polymerfilms. The glassy carbon electrode was coated first with negatively charged Nafion film containingtetrakis(pentafluorophenylporphyrin) iron(III) chloride (Fe(III)TPFPP) as the NO oxidation catalyst,and then with positively charged poly(acrylamide-co-diallyldimethylammonium chloride) (PADDA)and with neutral poly(dimethylsiloxane) (silicone) at the outermost layer. This polymer-coatedelectrode showed an excellent selectivity towards NO against possible concomitants in blood such asnitrite, ascorbic acid, uric acid, and dopamine. All current ratios between each concomitant and NOat the cyclic voltammogram was in 10^-3 ~ 10^-4. This type of electrode showed a detection limit of80 nM for NO. It was speculated from the electrochemical study in methanol that high-valent oxoiron(IV) of Fe(TPFPP) participated in the catalytic oxidation of NO. Full article

Large area highly uniform and ordered polypyrrole nanowire and nanotubearrays were fabricated by chemical oxidation polymerization with the help of a porousanodic aluminium oxide (AAO) template. Under 0.2 moL/L pyrrole (H₂O) and 0.2 moL/LFeCl₃ (H₂O) pattern, polypyrrole nanowire arrays were obtained after 2.0 hourspolymerization reaction in a two-compartment reaction cell. When the reaction wasstopped after 15 minutes, polypyrrole nanotube arrays have been formed. The diameter,length and density of compositive nanowires and nanotubes could be controlled byparameters of AAO template. Full article