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Transparent glass of xEu2O3-(100-x)TeO2 binary system is obtained by using the melt-quenching method and especially studied for x = 5 in xEu2O3-(100-x)TeO2 composition. Optical properties such as transmission, excitation, and emission spectra of Eu2O3-TeO2 glass-ceramics are studied and carefully compared for the samples heated at different temperatures. The one step heat-treatment affects the crystallinities as well as phase formation and yields cubic [Eu2Te6O15], orthorhombic [TeO2], and tetragonal [TeO2] phases depending on the heat treating temperature. Glass-ceramics of Eu3+-doped tetragonal [TeO2] shows stronger emission intensity at wavelength of 613 nm with an excitation wavelength of 394 nm compared with that from cubic [Eu2Te6O15] or Eu3+-doped orthorhombic [TeO2]. Enhancement of emission intensity in Eu3+-doped tetragonal [TeO2] is related to the local environment of Eu3+ ions substituted in tetragonal TeO2 lattice.

A new disposable amperometric biosensor for sarcosine (Sar, a biomarker for prostate cancer) was designed based on screen-printed carbon electrodes, Prussian blue, polymer dispersed reduced graphene oxide (P-rGO) nanosheets, and sarcosine oxidase (SOx). Poly(sodium 4-styrenesulfonate-r-LAHEMA) denoted as PSSL was newly synthesized as dispersant for rGO. The P-rGO was utilized for SOx immobilization, the sulfonate and disulfide functionalities in PSSL enable physical adsorption of SOx and its bioactivity and stability properties were improved. The biosensor was optimized by various enzyme concentration, applied potential, and operating pH. Under the optimized conditions, the biosensor exhibited maximum current responses within 5 s at an applied potential of −0.1 V vs. integrated Ag/AgCl reference electrode. The biosensor had a dynamic linear range of 10–400 μM, with a sensitivity of 9.04 μA mM−1 cm−2 and a low detection limit of 0.66 μM (S/N = 3). Additionally, the biosensor possesses strong anti-interference capability, high reproducibility, and storage stability over 3 weeks. Furthermore, its clinical applicability was tested in urine samples from both prostate cancer patients and healthy control, and the analytical recoveries were satisfactory. Therefore, this biosensor has significant potential in the rapid and non-invasive point-of-care testing for prostate cancer diagnosis.

A long-life electrochemical sensor for the continuous analysis of heavy metal ions (Zn(II), Cd(II), Pb(II), Cu(II), and Hg(II)) was developed using the graphene oxide (GO) anchored-functionalized polyterthiophene (poly[3′-(2-aminopyrimidyl)-2,2′:5′,2′′-terthiophene], polyPATT) composite. The PATT monomer was synthesized and polymerized with GO to form the composite using a potential cycling method, followed by Nafion coating. The modified sensor surface was characterized employing electrochemical and surface analysis methods. Experimental variables affecting the analytical performance were optimized. Interference effects of other metal ions having similar redox potentials were also investigated. The performance of chronocoulometry (CC) without predeposition was compared with the results of square wave anodic stripping voltammetry (SWASV) with predeposition. The dynamic range of CC for the target ions were between 1 ppb and 10 ppm, respectively with the detection limits between 0.05 (±0.05) and 0.20 (±0.15) ppb for the CC method without predeposition, and between 0.08 (±0.05) and 0.30 (±0.12) ppb for the SWASV with 300 sec of deposition time (n=3). The reliability of the method was evaluated by continuously analysing environmental water samples using a single sensor probe in a flow system for 93 days.

In this study, GO-Cu2O composite films were grown on fluorine-doped tin-oxide (FTO) substrates with various amounts of GO by using an electrochemical deposition. We investigated the effects of the GO content on the morphological, structural, optical, and photoelectrochemical (PEC) properties of the GO-Cu2O composite film and on its XPS spectrum. The highest XRD (111) peak intensity was obtained for the 10-wt% sample, which had an optical energy band gap of 2.15 eV. However, the highest photocurrent density was -4.74 mA/cm2 for the 1-wt% sample, which had an optical energy band gap of 1.94 eV. The photocurrent density for the 1-wt% sample was approximately 1.75 times greater than that for the 0-wt% sample. From the XPS measurements, we observed that the oxygen concentration for the sample with 1-wt% GO was higher than it was for the 0-wt% GO, which may have improved the photocurrent density of the sample with 1-wt% GO.

In this work, graphene oxide–cuprous oxide (GO–Cu 2 O) composite films were grown on fluorine-doped tin oxide substrates by electrochemical deposition. We investigated the effects of the annealing temperature on the morphological, structural, optical and photoelectrochemical (PEC) properties of GO–Cu 2 O composite films. As a result, our work shows that while GO–Cu 2 O composite films exhibit the highest XRD (111) peak intensity at 300 °C sample, the highest photocurrent density value obtained was −4.75 mA/cm 2 at 200 °C sample (using 0.17 V versus a reversible hydrogen electrode (RHE)). In addition, a reduction reaction at 300 °C sample was observed using XPS analysis from the shift in the O1s peak in addition to a weaker O1s peak intensity.

The electrical stability and reliability of molybdenum disulfide (MoS2) thin film transistors (TFTs) were investigated by associating thickness-dependent structural defects with degradation mechanism. Patterned MoS2 films with different thicknesses were fabricated for use as transistor channels via the modified multi-step chemical vapor deposition method. X-ray photoelectron spectroscopic (XPS) analyses revealed that highly layered and stoichiometric MoS2 films of up to ∼3 nm thickness were formed around the surface, whereas Mo metal bonds were dominant around the bottom of the films (9 nm). Variations in transistor properties of the thus prepared MoS2 films were examined by applying positive and negative bias stress (PBS and NBS, respectively). The experimental data indicated that MoS2 TFTs with 3-nm-thick films exhibited stable behavior under both PBS and NBS conditions, whereas those with 9-nm-thick films exhibited clear shifts in electrical performance ( △ V t h △ μ s a t s ). These results, together with XPS analyses, revealed that the instability of the MoS2 TFTs under PBS is dominated by sulfur interstitials, whereas their instability under NBS is caused by oxygen vacancies and metallic Mo defects. Additional details about the correlation between the atomic structural defects, which are generated due to insufficient sulfurization of thick films, and the electrical instability of the MoS2 TFTs were discussed.

A Cu(II)-Poly(terthiophene carboxylic acid) (pTTC)/Nafion modified glassy carbon electrode has been used for the chiral recognition and discrimination of d- and l-prolines by the catalytic oxygen reduction pro- cess and the shape of crystals formed on the electrode surface. The cyclic voltammetry with the modified elec- trode in the presence of oxygen recognized d- and l-form of prolines by exhibiting a difference in the peak poten- tial and the peak current of the oxygen reduction. The effect of pH and proline concentration on the peak cur- rent and the peak potential of oxygen have been studied. The SEM studies on the nature of crystals formed on a proline-Cu(II)pTTC complex. The oxidation state of the copper species present at the electrode surface was characterized by ESCA.

A non-enzymatic potentiometric glucose sensor for the determination of glucose in the micomolar level in saliva was developed based on a molecularly imprinted polymer (MIP) binding on a conducting polymer layer. A MIP containing acrylamide, and aminophenyl boronic acid, as a host molecule to glucose, was immobilized on benzoic acid-functionalized poly(terthiophene) (pTBA) by the amide bond formation onto a gold nanoparticles deposited-screen printed carbon electrode (pTBA/AuNPs/SPCE). Aromatic boronic acid was incorporated into the MIP layer to stably capture glucose and create a potentiometric signal through the changed pKa value of polymer film by the formation of boronate anion-glucose complex with generation of H+ ions by the cis-diol reaction. Reversible binding and extraction of glucose on the sensor surface was observed using a quartz crystal microbalance. Each layer of the sensor probe was characterized by cyclic voltammetry, electrochemical impedance spectroscopy, X-ray photoelectron spectroscopy, and atomic force microscopy. The potentiometric response at the optimized conditions exhibited a wide linear dynamic range of 3.2×10-7 to 1.0×10-3M, with a detection limit of 1.9 (±0.15)×10-7M. The sensor probe revealed an excellent selectivity and sensitivity for glucose compared to other saccharides. In addition, the reliability of the proposed glucose sensor was evaluated in physiological fluid samples of saliva and finger prick blood.

The effect substitution of Ti4+ at the Fe4+ site in a CaFe2O4-MgFe2O4 bulk hetero-junction (BH) lattice photocatalyst was explored and the Ti ion concentration was optimized to fabricate an efficient photocatalyst. A BH consisting of an optimum dopant concentration (Ti+4) level of x = 0.03 exhibited an increased band gap and generated a 1.5 times higher photocurrent. The newly fabricated Ti ion doped photocatalyst showed an enhanced quantum yield (upto ∼13.3%) for photodecomposition of a H2O-CH3OH mixture, as compared to its undoped BH counterpart under visible light (λ ≥ 420 nm). In contrast, the material doped with a very high Ti-dopant concentration displayed deteriorated photochemical properties. An efficient charge-separation induced by Ti-ion doping seems to be responsible for the higher photocatalytic activity in a doped bulk BH.

Conductive polymer precursors, including carboxylic acid, cyano groups, amino groups, 5,2′:5′,2″-terthiophene–3′-carboxylic acid (TTCA), 3′-cyano-5,2′:5′,2″-terthiophene (CTT), and 3′,4′-diamino-2,2′:5′,2″-terthiophene (DATT) are synthesized. Electrochemically polymerized films of the precursors on a nanocrystalline TiO 2 layer are examined as photo sensitizers, and the cell performance is compared. The photovoltaic cells are assembled with a polymer-coated TiO 2 layer treated with TiCl 4 as an anode and a Pt layer as a cathode in a propionitrile solution containing an iodide ion-based redox electrolyte. The charge-transfer processes of polymer-dyed cells are studied using impedance spectroscopy. The polymer dyes on the TiO 2 surfaces are characterized by scanning electron microscope (SEM), atomic force microscope (AFM), transmission electron microscope (TEM), and X-ray photoelectron spectroscopy (XPS). XPS results show that the conducting polymer dye, bearing a carboxylic acid group, is more strongly bound to the TiO 2 layer in comparison with other groups. Various experimental parameters affecting the cell efficiency are optimized, including the scan rate, number of potential cycles, and terthiophene monomer concentration. Of these polymers, the best cell efficiency is attained for poly-TTCA containing a carboxylic acid group. The optimized cell with the poly-TTCA dye shows a short-circuit current of 6.78 mA cm −2 , an open-circuit voltage of 0.54 V, and a fill factor of 63.6. An energy conversion efficiency of 2.32% is obtained with a cell area of 0.24 cm 2 under an air mass 1.5 solar simulated light irradiation of 100 mW cm −2 .

Radiofrequency glow discharge optical emission spectrometry(RF-GD-OES) was used to quantitatively analyze the depth of nanometric Cr/Ni multilayers on a silicon substrate. The technique permitted the rapid and accurate depth profiling of multilayers, down to the nanometer range. The analytical parameters were optimized for the RF-GD-OES depth quantitative analysis of Cr/Ni multilayers on a Si substrate. To validate the RF-GD-OES results, a TEM image was obtained in addition to performing the AES and SIMS depth profiling. confirm the validity of the GD-OES data, TEM imagewas obtained and both AES depth profiling, and SIMS depth profiling were preformed. The findings indicate that RF-GD-OES is a promising analytical tool for the accurate and rapid depth profiling of nanometric metal multilayers on semiconducting substrates.

ZnO thin films, codoped with Al and Ga, were prepared on fused quartz (FQ) and cyclo-olefin polymer (COP) substrates using a radial frequency magnetron sputtering technique at room temperature, without the introducing of oxygen. The elemental distributions of Al, Ga, Zn and O throughout the films were found and no compositional variation in working pressure was observed. A resistivity of 0.03–4.07 Ω cm in AGZ/FQ films ( Fig. 2 b and 0.04–5.73 Ω cm in AGZ/COP films as well as a transmittance of above 85% were obtained by appropriate control of the working pressure. Compared with the band gap energy of single crystal ZnO, the band gap energy of the AGZ/FQ thin film was somewhat higher. The band gap energy of the AGZ/FQ films showed a tendency to increase with the working pressure employed.

Electrochemistry of cytochrome c (cyt c) at biomimetic phospholipid layers was studied in a phosphate buffer solution, which were formed with dilauroyl phosphatidic acid (DLPA, C12:0), dipalmitoyl phosphatidic acid (DPPA, C16:0), distearoyl phosphatidic acid (DSPA, C18:0), and palmitoyl–oleoyl phosphatidic acid (POPA, C16:0–18:1). The lipid-layers formed firstly at the air/water interface were immediately transferred onto the electrode surface using the Langmuir–Blodgett (LB) technique. The electrochemical properties of cyt c at the lipid covered electrodes depended on the orientation, number of layers of phospholipids, tail (or head) group down, and vice versa. Atomic force microscopy (AFM) images of cyt c adsorbed on the POPA monolayer (showing the head group diameter of POPA to be ca. 0.7 nm) formed on highly oriented pyrolytic graphite (HOPG) displayed uniform surface morphology of lipid layer and clumps of aggregated cyt c molecules with a minimum size corresponding to four cyt c molecules. The heterogeneous electron transfer rate constants, k0 values, of cyt c were determined to be 1.02 × 10−3, 0.98 × 10−3, and 0.67 × 10−3 cm/s for the lipid monolayer in the tail down orientation (X-type) of POPA, DLPA, and DPPA, and 0.67 × 10−3 and 0.50 × 10−3 cm/s for the head down orientation (Z-type) of POPA and DLPA monolayers, respectively.

Pt-nanoparticles were synthesized and introduced into a carbon paste electrode (CPE), and the resulting modified electrode was applied to the anodic stripping voltammetry of copper(II) ions. The synthesized Pt-nanoparticles were characterized by cyclic voltammetry, scanning electron microscopy and X-ray photoelectron spectroscopy techniques to confirm the purity and the size of the prepared Pt-nanoparticles (ca. 20 nm). This incorporated material seems to act as catalysts with preconcentration sites for copper(II) species that enhances the sensitivity of Cu(II) ions to Cu(I) species at a deposition potential of −0.6 V in an aqueous solution. The experimental conditions, such as, the electrode composition, pH of the solution, pre-concentration time, were optimized for the determination of Cu(II) ion using as-prepared electrode. The sensitivity changes on the different binder materials and the presence of surfactants in the test solution. The interference effect of the coexisted metals were also investigated. In the presence of surfactants, especially TritonX-100, the Cu(II) detection limit was lowered to 3.9×10−9 M. However, the Pt-nanoparticle modified CPE begins to degrade when the period of deposition exceeds to 10 min. Linear response for copper(II) was found in the concentration range between 3.9×10−8 M and 1.6×10−6 M, with an estimated detection limit of 1.6×10−8 M (1.0 ppb) and relative standard deviation was 4.2% (n=5).

The performance of a poly(1,8-diaminonaphthalene)-modified electrode for the determination of the Se(IV) ion in an aqueous medium was investigated with anodic stripping voltammetry without the pretreating of the sample. The experimental parameters for the analysis of Se(IV) were optimized and the characteristics of this polymer-modified electrode were investigated by using cyclic voltammetry. The Se(IV) ions were chemically deposited onto the surface of the pDAN-Au electrode in an acidic medium. The detection limit employing the anodic stripping differential pulse voltammetry was 9.0×10−9 M for Se(IV) with 4.4 % of RSD. Satisfactory result for the determination of Se(IV) was acquired employing a certified standard urine reference material, SRM's 2670 (trace element in urine) with 4.1 ppb of SD.

New approach for the determination of Ag(I) ion was performed by using a carbon paste electrode (CPE) containing N,N'-Diphenyl oxamide (DPO) with anodic stripping voltammetry. The CMEs have been prepared by making carbon paste mixtures containing an appropriate amount of DPO salt coated onto graphite particles to analyze trace metal ions via complexation followed by stripping voltammetry. Various experimental parameters affecting the response, such as pH, deposition time, temperature, and electrode composition, were carefully optimized. Using differential pulse anodic stripping voltammetry, the logarithmic linear response range for the Ag(I) ion was 1.0 x 10 - 7 - 5.0 x 10 - 9 M at the deposition time of 10 ruin, with the detection limit was 7.0 × 10 - 1 0 M. The detection limit adopted from anodic stripping differential pulse voltammetry was 7.0 x 10 - 1 0 M for silver and the relative standard deviation was ′ 3.2% at a 5.0 x 10 - 8 M of Ag(I) ion (n = 7). The proposed electrode shows a very good selectivity for Ag(I) in a standard solution containing several metals at optimized conditions.

Hydrogen ion selective membranes formulated with 3140 RTV silicone rubber (SR) in PVC were studied to extend the life time of solid state ion sensors through improved membrane adhesion. All solid state hydrogen ion selective electrodes were prepared by incorporation of tridodecyl amine (TDDA) as an ionophore, potassium tetrakis[3,5-bis(p-chlorophenyl)borate (KTpClPB) as a lipophilic additive, bis(2-ethylhexyl)adipate (DOA) as a plasticizer. Their linear dynamic range was pH 2.0-11.0 and showed the near Nernstian slope of 55.1±0.2 mV/pH (r=0.999). The influences from alkali and alkaline earth metal ions were studied for the response of the final ISE membrane composition. Impedance spectroscopic data showed that the resistance was increased by increasing SR content in PVC. Brewster Angle Microscopy (BAM) image showed clear differences according to the SR compositions in PVC. Life time of the all solid state membrane electrode was extended to about 2 months by preparing the membrane with PVC and SR. The standard reference material from NIST (2181 HEPES Free acid and 2182 NaHEPESate) was tested for the ISE and it gave a good result.

A water sensor for a nonaqueous solvent was fabricated using poly(1,5-diaminonapthalene (DAN) nanofibers, which were prepared through a catalytic chemical polymerization of the DAN monomer using Fe(III) salt as the catalyst. Poly(1,5-DAN) nanofibers were characterized by atomic force microscope (AFM), transmission electron microscope (TEM), scanning electron microscope (SEM), and UV-vis spectroscopy. The electrochemical properties of poly(1,5-DAN) nanofibers were investigated using cyclic voltammetry (CV). The electrochemical activity of poly(1,5-DAN) nanofibers was utilized for water sensing. The fabrication of water sensor was followed by placing one drop (about 2 microL) of 0.01% poly(1,5-DAN) nanofibers solution in the gap between two split gold electrodes (PBSA) and completely dried. The response of the water sensor in an acetonitrile solution was evaluated under optimized conditions. The linear dynamic range was from 0.05 to 20%, and the detection limit was determined to be 0.01%. The response of this sensor was shown to be comparable to that obtained with the Karl Fischer titration method.