[Show abstract][Hide abstract] ABSTRACT: A new relaxor-based ferroelectric ternary system Pb(Lu1/2Nb1/2)O3–Pb(Mg1/3Nb2/3)O3–PbTiO3 (PLN–PMN–PT), with a combination of a high-Curie temperature system Pb(Lu1/2Nb1/2)O3–PbTiO3 (PLN–PT) and a high piezoelectricity system Pb(Mg1/3Nb2/3)O3–PbTiO3 (PMN–PT), was investigated in this paper. Single crystal PLN–PMN–PT with dimensions of Φ20×45 mm3 was grown successfully by the modified Bridgman technique for the first time. The studies of structure and composition of the as-grown crystal showed structural consistency but compositional deviation along the growth direction. The 〈0 0 1〉-oriented wafers of the PLN–PMN–PT single crystal showed excellent electrical properties at room temperature: ε33~4500, tanδ~0.5%, d33~2300 pC/N. The crystal was found to exhibit high Curie temperature (TC~176°C), rhombohedral–tetragonal phase transition temperature (TRT~108 °C) and coercive field (EC~8.1 kV/cm), superior to those of PMN–0.3PT single crystal. Studies of temperature dependence ferroelectric properties showed that high values of k33 and d33 could be maintained up to the TRT. These results showed that PLN–PMN–PT piezoelectric single crystal has a higher Curie temperature and coercive field with excellent electrical properties, making the crystal a promising candidate for high-power transducer applications in a broad temperature range.
[Show abstract][Hide abstract] ABSTRACT: We report that the cathodic preconcentration of electron-insulating As(0) on Au and Pt electrodes can be enhanced by chemical reduction of As(III) and As(V) by electrogenerated H2, as studied by cyclic voltammetry. This finding is used for sensitive anodic stripping voltammetry (ASV) analysis of As(III) and/or As(V) at the Au electrode. About three As(0) monolayers were cathodically preconcentrated on the Pt electrode at -0.3 V (vs. SCE) in 0.5 M aqueous H2SO4, as a result of both the chemical reduction of the solution-state As(III) near the electrode surface by the electrogenerated H2 and the direct electroreduction of As(III) on the highly catalytic surface Pt sites. Only one As(0) monolayer was electrodeposited at -0.2 V (vs. SCE) on the Au electrode in 0.5 M aqueous H2SO4, but about two As(0) monolayers were deposited on the Au electrode at a more negative potential at which the mild evolution of H2 occurred. The electrogenerated H2 could also chemically reduce As(V), though the direct electroreduction of As(V) was sluggish on the Au electrode. Linear sweep ASV (LSASV) oxidation of the preconcentrated As(0) to As(III) and then to As(V) at a fast scan rate gave two sharper and higher anodic peaks on the Au electrode than on the Pt electrode. Based on these observations, sensitive dual-signal LSASV analysis of As(III) and/or As(V) was achieved on the Au electrode, with limits of detection of 1.0 nM for As(III) and 5.4 nM for As(V) under optimized experimental conditions. Our method was successfully applied for analysis of As(III) and/or As(V) in real water samples. The insights into cathodic As(0) deposition provided here may help the better understanding of electrochemical deposition of many other electron-insulating thin films, especially those obeying the electrode material-dependent inner-sphere mechanism, for electrochemical and surface-coating applications.
The Journal of Physical Chemistry C 05/2015; 119(21):150512180440005. DOI:10.1021/acs.jpcc.5b01435 · 4.77 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Electrochemical/chemical oxidative synthesis and biosensing/biofuel cell applications of poly(L-DOPA) (PD) are studied versus polydopamine (PDA) as a recent hotspot biomaterial. The enzyme electrode developed by coelectrodeposition of PD and glucose oxidase (GOx), uricase or tyrosinase shows biosensing performance superior to the corresponding PDA-based enzyme electrode. The chemical oxidative polymerization of L-DOPA (PDC) by NaAuCl4 in GOx-containing neutral aqueous solution is used to immobilize GOx and gold nanoparticles (AuNPs). The thus-prepared chitosan (CS)/GOx-PDC-AuNPs/Auplate/Au electrode working in the first-generation biosensing mode responds linearly to glucose concentration with a sensitivity of 152 μA mM-1 cm-2, which is larger than those of the CS/GOx-PDAC-AuNPs/Auplate/Au electrode, the CS/GOx-poly(3-anilineboronic acid) (PABA)-AuNPs/Auplate/Au electrode and most reported GOx-based enzyme electrodes. This PDC-based enzyme electrode also works well in the second-generation biosensing mode and as an excellent bioanode in biofuel cell construction, probably because PD as an amino acid polymer has the higher biocompatibility and the more favorable affinity to the enzyme than PDA. The PD material of great convenience in synthesis, outstanding biocompatibility for preparing high-performance bionanocomposites, and strong capability of multifunctional coatings on many surfaces may find wide applications in diversified fields including biotechnology and surface-coating.
[Show abstract][Hide abstract] ABSTRACT: An electrochemical sandwich immunoassay method that can be sensitive to a few protein molecules (human immunoglobulin G or human prostate-specific antigen) is reported, based on HAuCl4-NH2OH redox reaction to enlarge the size of second antibody labeled gold nanoparticles and in situ microliter-droplet anodic stripping voltammetry analysis with enhanced cathodic preconcentration of gold.
Chemical Communications 04/2015; 51(40). DOI:10.1039/c5cc01439e · 6.83 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: In situ observations of the phase symmetry and domain evolution of (K0.25Na0.75)NbO3 single crystals under bipolar electric fields have been performed for both pseudocubic (110) and (001) orientations using polarized light microscopy and X-ray diffraction. The macroscopic symmetry was identified to be a monoclinic C type phase with the spontaneous polarization direction close to <054>. The electric field-driven domain morphology and evolution model were also presented. It was found that, under an antiparallel electric field, the approximately 180° domain switching process in a pseudocubic (101) sample consists of three steps: two ~60° domain switching and a ~90° domain switching, and the ~90° domain switching process in the pseudocubic (001) sample is composed of two ~60° switching steps.
[Show abstract][Hide abstract] ABSTRACT: Bismuth layer-structured ferroelectric ceramics of Na0.5Bi4.5−x
Ti4O15 (NBT-x, 0.0 ⩽ x ⩽ 0.4) were synthesized by a traditional solid-state reaction. The effect of (Nd,Ce) substitution for A-site on the microstructure and electrical properties of Na0.5Bi4.5Ti4O15 (NBT)-based piezoelectric ceramics was investigated. X-ray diffraction (XRD) analysis revealed that the (Nd,Ce)-modified NBT ceramics have a pure four-layer Aurivillius type structure. The piezoelectric properties of NBT ceramics were significantly improved by the modification of neodymium and cerium. The Curie temperature T
C gradually decreased from 638 °C to 618 °C with increasing the (Nd,Ce) modification. The piezoelectric constant d
33, mechanical quality factor Q
m, dielectric loss tanδ and Curie temperature T
C of the Na0.5Bi4.3(Nd0.5Ce0.5)0.2Ti4O15 ceramic were found to be 28 pC/N, 3239, 0.0032 and 630 °C, respectively. Thermal annealing studies indicated that the (Nd,Ce)-modified NBT ceramics possess stable piezoelectric properties, demonstrating that the Na0.5Bi4.3(Nd0.5Ce0.5)0.2Ti4O15 ceramic is a promising candidate for high temperature applications.
[Show abstract][Hide abstract] ABSTRACT: Simultaneous electroanalysis of isoniazid and uric acid (UA) was achieved at a poly(sulfosalicylic acid) (PSA) and carboxylated graphene (CG)-modified glassy carbon electrode (GCE). The CG cast-coated on the GCE was cathodically reduced to form electroreduced CG (ERCG), while the PSA was electrochemically synthesized on the ERCG/GCE. Electrochemical quartz crystal microbalance was used to investigate the electrodeposition processes. The surface morphologies and electrochemical properties of the PSA/ERCG/GCE were studied by scanning electron microscopy, cyclic voltammetry (CV) and electrochemical impedance spectroscopy. The electrochemical behaviors of isoniazid and UA at PSA/ERCG/GCE were investigated by CV and differential pulse voltammetry (DPV), giving well defined and well separated oxidation peaks of isoniazid and UA. The PSA/ERCG/GCE exhibited notably enhanced electro-oxidation signals of isoniazid and UA in NH3-NH4Cl buffer solution (pH 9.0), as compared with bare GCE and PSA/GCE. Under optimum conditions, the DPV peak currents at PSA/ERCG/GCE responded linearly to isoniazid concentration from 0.05 to 15 μM and to UA concentration from 0.02 to 15 μM, with limits of detection of 12 nM for both isoniazid and UA, which is an improvement compared to many other reported techniques. The PSA/ERCG/GCE was successfully applied to the simultaneous determination of isoniazid and UA in urine substrate samples.
Sensors and Actuators B Chemical 02/2015; 207. DOI:10.1016/j.snb.2014.10.002 · 4.29 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: A series of (Na0.5Bi0.5)TiO3–PbTiO3 (NBT–PT) single crystals with compositions near the morphotropic phase boundary (MPB) region were grown by the modified Bridgman technique. The dependence of structure on composition was measured, and the MPB region of the NBT–PT system was confirmed. The dielectric properties of the NBT–PT single crystals were investigated, and the phase transition behaviour of the NBT–PT single crystals during heating was examined. With increasing addition of PT, the coercive field of the NBT–PT crystals decreased to levels much lower than that of the pure NBT system; such a change allowed easy poling of the NBT–PT crystals and the resultant piezoelectric properties were significantly enhanced. The electromechanical coupling factor of the crystals showed relatively constant thermal stability at the depolarization temperature (Td). Finally, studies of the domain evolution of NBT–0.09PT showed the disappearance of domains at the Td, which indicates that phase transition at the Td is related to changes in domain structures.
Ceramics International 01/2015; 41(5):6722-6728. DOI:10.1016/j.ceramint.2015.01.115 · 2.09 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: A carboxylated graphene (CG) modified glassy carbon electrode (GCE) was prepared by cast-coating a CG solution on a GCE surface, for quantitative analysis of nicotine based on cyclic voltammetry after potentiostatic enrichment of nicotine at −1.1 V for 240 s in 0.1 M KH2PO4–Na2HPO4 buffer solution (pH 7.0). At this enrichment potential, partially electroreduced CG (ERCG) was obtained, as characterized by Fourier transform infrared spectroscopy, Raman spectroscopy, X-ray photoelectron spectroscopy, scanning electron microscopy and electrochemistry techniques. The oxidation peak current of nicotine at the ERCG/GCE after a semi-derivative treatment responded linearly to nicotine concentration from 2 to 5 μM and from 5 to 60 μM, with a limit of detection of 0.1 μM. The ERCG/GCE gave analytical performance superior to that at a bare GCE, and the semi-derivative treatment notably improved the signal resolution. The ERCG/GCE was used to determine nicotine in real tobacco samples, with recoveries over 95%.
[Show abstract][Hide abstract] ABSTRACT: Ternary ferroelectric single crystal Pb(In1/2Nb1/2)O3-Pb(Mg1/3Nb2/3)O3-PbTiO3 (PIN-PMN-PT) was grown by the modified Bridgman method. The compositional variation of different regions of the crystals was measured, and the segregation regularity of the crystals was proposed. Variations in the dielectric properties and domain structures of the PIN-PMN-PT single crystals were investigated as a function of temperature and composition, and the phase transformation behavior of the crystals was observed. The PIN-PMN-PT crystals showed high Curie temperatures (T C = 160-210 °C), ferroelectric phase transition temperatures (T R-T up to 132 °C) and coercive fields (E C = 6-8 kV/cm) as well as excellent piezoelectric properties (d 33 up to 2,800 pC/N) and electromechanical coefficients (k 33 > 0.90). As the temperature increased, k 33 values remained relatively constant and d 33 increased gradually prior to ferroelectric phase transformation, and these results reflect the wide temperature usage range of PIN-PMN-PT single crystals. The polarization (P r ) and E C of the crystals showed unique trends during the phase transformation process; high P r and E C values can be maintained prior to depolarization, which indicates that the PIN-PMN-PT single crystals are candidate materials for high-power applications. In summary, PIN-PMN-PT single crystals with ultrahigh electric properties, large coercive fields and excellent thermal stability may potentially be applied in harsh environments.
Journal of Materials Science Materials in Electronics 01/2015; DOI:10.1007/s10854-015-3023-2 · 1.97 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Single crystals of x at.% Fe+0.95(Na1/2Bi1/2)TiO3-0.05BaTiO3 (x%-Fe:NBBT5, x=0.1, 0.2 and 0.5) with ultrahigh ferroelectric response were developed by introducing defect associations. The giant field-induced bipolar and unipolar strains, i.e. Smax~1.1%, εmax/Emax ~1300 pm/V, d33~600 pC/N and permittivity tunability ~120% demonstrate that they are promising candidates as lead-free ferroelectrics. The presence of ferromagnetic properties further provides new application potential as multiferroic materials. The defect chemistry and domain structure were studied systematically. The effects of microscopic defect functional centers on macroscopic properties were discussed in detail.
[Show abstract][Hide abstract] ABSTRACT: Polarized Raman spectroscopy has been performed to investigate the effects of the electric field on 0.68PbMg(1/3)Nb(2/3)O(3)-0.32PbTiO(3) (PMN-32PT) relaxor single crystal. Based on the group theory analysis, the Raman modes of PMN-32PT single crystal at zero-field are assigned to the monoclinic structure. The electric-field-evolution of Raman spectra reveal that a structural transition to tetragonal phase is initiated at a threshold electric field E-1 and completed at higher field E-2. In the intermediate field range from E-1 to E-2, the structure of the crystal is determined to be a coexistence of monoclinic and tetragonal phases. These results of the Raman spectra allow us to better understand the field-induced ultrahigh macroscopic strain in the relaxor ferroelectrics. (C) 2014 AIP Publishing LLC.
[Show abstract][Hide abstract] ABSTRACT: Dielectric, ferroelectric and piezoelectric properties of lead-free Na1/2Bi1/2TiO3–xK1/2Bi1/2TiO3 (NBT–xKBT) ferroelectric single crystals were characterized systematically. With increasing KBT concentration, the remanent polarization and coercive electric field decrease, while the piezoelectric constant and the electromechanical coupling coefficient increase. The evolution of average and local structures as a function of temperature and composition was investigated using in-situ X-ray diffraction and Raman spectroscopy. The structure/property relationship of NBT–xKBT single crystals was discussed in detail.
Solid State Communications 08/2014; 201. DOI:10.1016/j.ssc.2014.08.007 · 1.70 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Lead‐free single crystal (Na1/2Bi1/2)TiO3–1.5 at.%Bi(Zn1/2Ti1/2)O3 (NBT–1.5BZT) with dimension of Φ35 mm × 12 mm was successfully grown by a top‐seeded solution growth technique. The average and local structure were studied by a combination of X‐ray diffraction and Raman spectroscopy. The electric and optical properties of ‐oriented single crystals were investigated systematically. Compared with pure NBT, the piezoelectric constant and transmission coefficient were both enhanced, that is, from 62 pC/N and ~60% to 121 pC/N and ~70%, respectively. Furthermore, domain structure observation suggested that the ‐oriented tetragonal ferroelastic domains in NBT were suppressed at room temperature with addition of BZT, which was responsible for the improved piezoelectric and optical properties of NBT–1.5BZT single crystal.
Journal of the American Ceramic Society 06/2014; 97(6). DOI:10.1111/jace.12847 · 2.61 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: We report a new and efficient protocol for rapid electrodeposition of a gold-Prussian blue ((Au-PB)REd) nanocomposite with ultrahigh electroactivity on an Au electrode by cyclic voltammetry in 0.1 M aqueous K2SO4 containing 1 mM K3Fe(CN)6, 1 mM HAuCl4, and 0.1 mM Fe2(SO4)3, and an electrochemical quartz crystal microbalance and scanning electron microscopy were utilized to investigate the electrodeposition. The (Au-PB)REd/Au electrode was then cast-coated with a urate oxidase (UOx)-poly(anilineboronic acid) (PABA)-Pt nanoparticle (PtNP) bionanocomposite and chitosan (CS) for high-performance amperometric biosensing of uric acid (UA) in the dual-potential mode. The UOx-PABA-PtNP bionanocomposite was prepared through chemical oxidation of anilineboronic acid (ABA) by sodium chloroplatinate in the presence of UOx. The thus-fabricated CS/UOx-PABA-PtNP/(Au-PB)REd/Au enzyme electrode worked well under optimized conditions through both oxidation and reduction determination of enzyme-generated H2O2, which responded linearly to UA concentrations from 0.3 μM to 0.65 mM with a sensitivity of 223 μA mM(-1) cm(-2) and a limit of detection (LOD) of 0.2 μM (0.7 V vs. SCE), and from 0.2 μM to 0.25 mM with a sensitivity of 247 μA mM(-1) cm(-2) and a LOD of 0.1 μM (-0.05 V vs. SCE), being superior to most analogues hitherto reported for biosensing of UA.
The Analyst 04/2014; 139(11). DOI:10.1039/c3an02390g · 4.11 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: A micro-Raman scattering technique was used to investigate the electric-field and temperature dependent phase stability of Mn-doped Na1/2Bi1/2TiO3-5.0at. %BaTiO3 single crystal. The Ti–O mode was found to exhibit a slight shift at a low electric field (E = 10 kV/cm) and splitting at higher electric field (E ≥ 30 kV/cm), ascribed to field-induced local distortion and phase transition, respectively. The temperature-dependent Raman scattering was also measured over a wide range of 150–800 K to study the phase stability of poled samples. A new Raman mode at about 200 cm−1 and an anomaly in intensity of the Ti-O modes were detected at 390 K, indicating a ferroelectric to antiferroelectric phase transition. The frequency shift of TiO6 octahedral modes implied a transition to a paraelectric state at 550 K. Furthermore, the Ti-O and TiO6 octahedral modes were found to be sustained in the high-temperature paraelectric state.
[Show abstract][Hide abstract] ABSTRACT: Giant bipolar and unipolar strains i.e. Smax > 0.5%, εmax/Emax > 1000 pm V–1 have been observed in Mn-doped Na0.5Bi0.5TiO3–6BaTiO3 single crystals after being annealed. Temperature-dependent impedance spectra were studied and activation energies of oxygen vacancies were calculated accordingly. The two different binding energies present in X-ray photoelectron spectra for Na and Bi were assigned to different coordinate environments. However, titanium exhibits only one oxidation state (e.g. Ti4+). The site occupation and valence fluctuation of Mn were characterized by electric paramagnetic resonance spectra.
Scripta Materialia 03/2014; 75:50–53. DOI:10.1016/j.scriptamat.2013.11.017 · 2.97 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Eu3+-doped Na0.5Bi0.5TiO3 (Eu:NBT) single crystals were grown by a top-seeded solution growth method. Photoluminescence emission and excitation spectra of Eu:NBT were investigated. The two transitions in 7F0 → 5D0 excitation spectra reveal that Eu3+ ions were incorporated into two adjacent crystallographic sites in NBT, i.e., Bi3+ and Na+ sites. The former has a symmetrical surrounding, while the later has a disordered environment, which was confirmed by decay curve measurements. The dielectric dispersion behavior was depressed and the piezoelectric and ferroelectric properties were improved after Eu doping.
Applied Physics A 01/2014; 114(2). DOI:10.1007/s00339-013-8176-3 · 1.69 Impact Factor