Synthesis, characterization and electrochromic properties of copolymer of 3-{[4-(thien-3-yl-methoxy)phenoxy]methyl}thiophene with thiophene

(3-{[4-(Thien-3-yl-methoxy)phenoxy]methyl}thiophene) (TMPMT) was synthesized via the reaction of 3-bromomethylthiophene with hydroquinone and characterized by nuclear magnetic resonance (NMR) and Fourier transform infrared spectroscopy (FTIR). Electrochemical copolymerization of TMPMT with thiophene in acetonitrile/boron trifluoride diethyl etherate (AN/BFEE) solvent mixture was achieved using tetrabutylammonium tetrafluoroborate (TBAFB) as the supporting electrolyte. Resulting copolymer was characterized via cyclic voltammetry (CV), Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), four probe technique conductivity measurement and UV-Vis spectroscopy. Spectroelectrochemical analysis of the copolymer [P(TTMT-co-Th)] revealed that π-π^∗ electronic transition occurs at 427 nm with a band gap value of 2.20 eV. Copolymer gives brown color at the fully reduced state whereas; at fully oxidized state the film has a gray-blue color. Kinetic studies were carried out at the maximum contrast wavelength upon measuring the percent transmittance, T% (7.6%) and switching time (2.0 s) to examine the switching ability of the copolymer. Dual type electrochromic device (ECD) of P(TMPMT-co-Th) and poly(3,4-ethylenedioxythiophene) (PEDOT) was constructed. Spectroelectrochemistry, switching ability, open circuit memory and stability of the device were examined by UV-Vis spectroscopy and cyclic voltammetry. The device switches between brown and blue at switching voltages of 0.0 V and 2.8 V with a short switching time of 1.4 s.     

Synthesis and characterization of poly(3-thiophene acetic acid)/Fe3O4 nanocomposite

Poly(3-thiophene acetic acid)/Fe₃O₄ nanocomposite is synthesized by the precipitation of Fe₃O₄ in the presence of poly(3-thiophene acetic acid) (P3TAA). Structural, surface, morphological, thermal properties and conductivity characterization/evaluation of the nanocomposite were performed by XRD, FT-IR, TEM, TGA, and conductivity measurements, respectively. The capping of P3TAA around Fe₃O₄ nanoparticles was confirmed by FT-IR spectroscopy, the interaction being via bridging oxygens of the carboxylate and the nanoparticle surface through bidentate binding. The crystallite and particle size were obtained as 9 ± 2 nm and 11 ± 1 nm from XRD line profile fitting and TEM image analysis, respectively, which reveal nearly single crystalline nature of Fe₃O₄ nanoparticles. Magnetization measurements reveal that P3TAA coated magnetite particles do not saturate at higher fields. There is no coercivity and remanence revealing superparamagnetic character. Magnetic particle size calculated from the theoretical fitting as 9.1 nm which coincides the values determined from TEM micrographs and XRD line profile fitting. The comparison to the TEM particle size reveals slightly modified magnetically dead nanoparticle surface.     

Comparative study of photoelectric properties of a copolymer and the corresponding homopolymers based on poly(3-alkylthiophene)s

As semiconducting materials in organic light-emitting devices (OLEDs), a novel, highly soluble poly[(3-octylthiophene)-co-(3-(2-ethyl-1-hexylthiophene))] (P3OTIOT) and the corresponding homopolymers (poly(3-octylthiophene) (P3OT) and poly(3-isooctylthiophene) (P3IOT)) were prepared by an FeCl₃-oxidative approach to compare their photoelectric properties. Characterization of the polymers included FT-IR, ¹H NMR, gel permeation chromatography (GPC), thermo-gravimetric analysis (TGA), UV-vis spectroscopy, photoluminescence (PL) and electroluminescence (EL). P3OTIOT and P3OT depicted excellent solubility in common organic solvents. TGA studies showed that all of the materials exhibited very good thermal stabilities, losing 5% of their weight on heating to 300 °C. The optical property investigations showed that the band-gap energy of P3OTIOT was similar to that of P3OT (2.43 eV) at 2.45 eV and 6% lower than that of P3IOT (2.6 eV) in CHCl₃ solution. In PL spectra, the emission maxima of P3OTIOT and P3IOT were 50 nm and 130 nm blue-shifted with respect to that of P3OT, respectively. However, the PL intensity of P3OTIOT was seven times higher than that of P3OT. Single layer polymer light-emitting devices (PLEDs) with the ITO/polymer/Ag configurations were fabricated by the spin-coating method with P3OT, P3IOT and P3OTIOT as the EL materials, which exhibited red (650 nm), orange-red (610 nm) and yellow-green (525 nm) EL, respectively. The external EL quantum efficiencies (QE) of P3IOT and P3OTIOT devices are 6.4 × 10⁻³% and 5.1 × 10⁻³% which are about five and four times higher than that of the P3OT device (1.2 × 10⁻³%), respectively. The turn-on voltage of the P3OTIOT device (5 V) is between that of the P3OT (4.5 V) and P3IOT (6 V) devices. These results indicated that the P3OTIOT combined the photoelectric properties of P3OT and P3IOT with excellent solubility, processability, low band-gap energy, high QE and low turn-on voltage in the PLEDs, and they might be excellent polymeric materials for applications in organic light-emitting diodes, light-emitting electrochemical cells and polymer solar cells.     

Synthesis and electropolymerization of 5,12-dihydrothieno[3′,4′:2,3][1,4]dioxocino[6,7-b]quinoxaline and its electrochromic properties

Synthesis of a new thiophene-based monomer; 5,12-dihydrothieno[3′,4′:2,3][1,4]dioxocino[6,7-b]quinoxaline (DDQ), was realized. The chemical structure of the monomer was characterized by ¹H NMR, FTIR and mass spectroscopy techniques. Electrochemical polymerization of DDQ and characterization of the resulting polymer [P(DDQ)] was performed. Moreover, the spectroelectrochemical and electrochromic properties of the polymer film were investigated. P(DDQ) has a low oxidation potential (0.9 V) and low band gap (1.73 eV) compared to polythiophene. In addition, dual-type polymer electrochromic device (ECD) based on P(DDQ) with poly(3,4-ethylenedioxythiophene) (PEDOT) was constructed. Spectroelectrochemistry, electrochromic switching, stability and open-circuit stability of the device were studied. It was observed that polymer have good switching time, reasonable contrast and optical memory.     

Electroactive aromatic polyamides and polyimides with adamantylphenoxy-substituted triphenylamine units

A new triphenylamine-containing aromatic diamine monomer, 4-[4-(1-adamantyl)phenoxy]-4′,4″-diaminotriphenylamine, was synthesized from cesium fluoride-mediated N,N-diarylation of 4-(1-adamantyl)-4′-aminodiphenyl ether with 4-fluoronitrobenzene and subsequent reduction of the resultant dinitro compound. Novel electroactive aromatic polyamides and polyimides with adamantylphenoxy-substituted triphenylamine moieties were prepared from the newly synthesized diamine monomer with aromatic dicarboxylic acids and tetracarboxylic dianhydrides, respectively. All the resulting polymers were amorphous and most of them were readily soluble in polar solvents such as N-methyl-2-pyrrolidone (NMP) and N,N-dimethylacetamide (DMAc) and could be solution-cast into transparent and strong films with good mechanical properties. These polymers exhibited glass-transition temperatures between 254 and 310 °C, and they were fairly stable up to a temperature above 450 °C for the polyamides and above 500 °C for the polyimides. These polymers exhibited strong UV-vis absorption maxima at 293-346 nm in solution, and the photoluminescence spectra of polyamides showed maximum bands around 408-452 nm in the blue region. Cyclic voltammograms of the polyamide and polyimide films on an indium-tin oxide (ITO)-coated glass substrate exhibited one pair of reversible redox couples at half-wave oxidation potentials (E_1/2) around 0.83-0.86 V and 1.12-1.13 V, respectively, versus Ag/AgCl in an acetonitrile solution. All the polymer films revealed good electrochemical and electrochromic stability by repeatedly switching electrode voltages between 0.0 V and 1.1-1.4 V, with coloration change from the pale yellowish neutral state to the green or blue oxidized state.     

New hole-transport polyurethanes applied to polymer light-emitting diodes

Polymeric light-emitting diodes (PLEDs) using high-performance hole-transport polyurethanes (PUs) have been fabricated. The PUs were prepared from the condensation polymerization of (E, E)-1,4-bis(2-hydroxystyryl)benzene, an oligo para-phenylene-(E)-vinylene (OPV) unit, with toluene diisocyanate (TDI), isophorone diisocyanate (IPDI) or dicyclohexylmethane 4,4′-diisocyanate (H₁₂MDI), respectively. The condensation polymerization was end-capped with 4-tert-butylphenol as the terminal group. The PLED having the PU layer inserted between PEDOT:PSS (HIL) and MEH-PPV (EML) demonstrated superior current efficiency and low turn-on voltage when comparing to the reference devices of ITO/MEH-PPV(50 nm)/Ca(10 nm)/Ag(100 nm) as well as ITO/PEDOT:PSS(30 nm)/MEH-PPV(50 nm)/Ca(10 nm)/Ag(100 nm). In particularly, the best device performance was realized with the PU of OPV-IPDI as the hole-transport layer, resulting 53 times and 2.72 times of current efficiency enhancement as well as 1.5 V and 1 V voltage reduction of the turn-on voltage, respectively, when compared against the reference devices. Besides, our experiments also showed that the PU polymer could also be applied for flexible PLED with similar performance enhancement. Based on the promising results, we concluded that OPV-IPDI was a good hole-transport material for light-emitting diode application.     

A soluble and multichromic conducting polythiophene derivative

A new soluble polythiophene derivative was synthesized by both chemical and electrochemical oxidative polymerization of 1-4-nitrophenyl-2,5-di(2-thienyl)-1H-pyrrole (SNSNO₂). Chemical method produces a polymer which is completely soluble in organic solvents. The structures of both the monomer and the soluble polymer were elucidated by ¹H and ¹³C-NMR and FTIR. The average molecular weight has been determined by GPC to be Mn = 6.3 × 10³ for the chemically synthesized polymer. P(SNSNO₂) was also synthesized via potentiostatic electrochemical polymerization. Characterizations of the resulting polymer were performed by cyclic voltammetry CV, FTIR and UV-Vis spectroscopy. Four-probe technique was used to measure the conductivities of the samples. Moreover, the spectroelectrochemical and electrochromic properties of the polymer film were investigated. In addition, dual type polymer electrochromic devices ECDs based on P(SNSNO₂) with poly3,4-ethylenedioxythiophene (PEDOT) were constructed. Spectroelectrochemistry, electrochromic switching and open circuit stability of the devices were studied. They were found to have good switching times, reasonable contrasts and optical memories.     

Synthesis and characterization of alternative donor-acceptor arranged poly(arylene ethynylene)s derived from 1,4-diketo-3,6-diphenylpyrrolo[3,4-c]pyrrole (DPP)

A series of donor-acceptor type poly(arylene ethynylene)s (PAEs) have been synthesized through Sonogashira polycondensation. The polymers consist of an electron donating 9,9-bis(2-ethylhexyl)-9H-fluorene, triphenylamine, 1,4-dialkoxybenzene or 9-(2-ethylhexyl)-9H-carbazole unit and an electron accepting 2,5-bis(2-ethylhexyl)-3,6-diphenylpyrrolo[3,4-c]pyrrole-1,4(2H,5H)-dione (EH-DPP) unit, alternately connected through ethynyl bridge. The polymers exhibit weight-average molecular weights (M_w) up to 68, 500 and are soluble in chlorobenzene, dichlorobenzene, THF, chloroform and toluene. A brilliant red solution with absorption maxima between 491 and 500 nm was observed for all the polymers. An intense red fluorescent with photoemission maxima between 551 and 571 nm was observed from polymer solutions. The polymers showed good thermal stability with decomposition temperature more than 260 °C at 5% weight loss. Onset oxidation potentials of the polymers were observed between 1.30 and 1.58 V with HOMO energy levels in the range of −6.10 to −6.38 eV. The OLED devices were fabricated with configuration of ITO/PEDOT:PSS/polymer/LiF/Al for all the polymers and EL maxima between 666 and 684 nm were observed.     

An enhanced biosensor for glutamate based on self-assembled carbon nanotubes and dendrimer-encapsulated platinum nanobiocomposites-doped polypyrrole film

An enhanced amperometric biosensor based on incorporating one kind of unique nanobiocomposite as dopant within an electropolymerized polypyrrole film has been investigated. The nanobiocomposite was synthesized by self-assembling glutamate dehydrogenase (GLDH) and poly(amidoamine) dendrimer-encapsulated platinum nanoparticles (Pt-DENs) onto multiwall carbon nanotubes (CNTs). ζ-Potentials and high-resolution transmission electron microscopy (HRTEM) confirmed the uniform growth of the layer-by-layer nanostructures onto the carboxyl-functionalized CNTs. The size of Pt nanoparticles is approximately 3 nm. The (GLDH/Pt-DENs)_n/CNTs/Ppy hybrid film was obtained by electropolymerization of pyrrole onto glassy carbon electrodes and characterized with scanning electron microscopy (SEM), cyclic voltammetry (CV) and other electrochemical measurements. All methods indicated that the (GLDH/Pt-DENs)_n/CNTs nanobiocomposites were entrapped within the porous polypyrrole film and resulted in a hybrid film that showed a high electrocatalytic ability toward the oxidation of glutamate at a potential 0.2 V versus Ag/AgCl. The biosensor shows performance characteristics with high sensitivity (51.48 μA mM⁻¹), rapid response (within 3 s), low detection limit (about 10 nM), low level of interference and excellent reproducibility and stability.     

Fluorine cleavage of the light blue heteroleptic triplet emitter FIrpic

The lifetime stability of devices containing FIrpic as emitter has been a major concern for organic blue light emitting devices (OLEDs). To gain a deeper knowledge about the purity of FIrpic (bis[2-(4,6-difluorophenyl)pyridyl-N,C2′]iridium (III)) emitters and how the purity is influenced by sublimation steps, non-sublimated and sublimated FIrpic material was analyzed via liquid chromatography coupled with electron spray ionization mass spectrometry (LC/ESI/MS). Cleavage of an electron-withdrawing group from one of the ligands of the heteroleptic phosphorescent emitter could be identified in sublimated FIrpic material via LC/ESI/MS. A detailed chemical analysis using LC/ESI/MS was carried out for complete blue emitting devices of the following structure: indium-tin-oxide (ITO)/50 nm (α-4,4′-bis[(1-naphthyl)phenylamino]-1,1′-biphenyl) (α-NPD)/10 nm 4,4′,4″-tris(carbazol-9-yl)triphenylamine (TCTA)/100 nm TCTA:8% FIrpic/50 nm 1,1′-biphenyl-4′-oxy)-bis(8-hydroxy-2-methylquinolinato)-aluminum (BAlq)/1 nm LiF/100 nm Al. Two isomers of (FIrpic-1F) could be detected in an aged OLED. Changes in the ligand systems of FIrpic, especially the loss of fluorine during the deposition process can alter the emissive properties of the blue phosphorescent emitter. Beside isomer formation and chemical degradation of FIrpic, substantial degradation was observed for the hole transport material α-NPD in driven OLEDs.     

Electrosyntheses of high quality poly(5-methylindole) films in mixed electrolytes of boron trifluoride diethyl etherate and diethyl ether

High quality poly(5-methylindole) (P5MeI) films, especially with good fluorescence properties, were synthesized electrochemically by direct anodic oxidation of 5-methylindole in boron trifluoride diethyl etherate (BFEE) containing additional 50% diethyl ether (EE) (by volume). The oxidation potential onset of 5-methylindole in this medium was measured to be only 0.84 V vs. SCE, which was much lower than that determined in acetonitrile + 0.1 mol L⁻¹ TBATFB (1.08 V vs. SCE). P5MeI films obtained from this medium showed good electrochemical behavior and good thermal stability with conductivity of 10⁻² S cm⁻¹, indicating that BFEE was a better medium than acetonitrile for the electrosyntheses of P5MeI films. Dedoped P5MeI films were thoroughly soluble in strong polar solvent such as dimethyl sulfoxide (DMSO). ¹H NMR spectroscopy and FT infrared spectrum of dedoped P5MeI films strongly suggested that the monomers were linked via the positions 2 and 3. Fluorescent spectral studies indicated that P5MeI was a good violet-blue light emitter with the excitation and emission wavelength of 310 nm and 418 nm, respectively. To the best of our knowledge, this is the first case that 5-methyl group substituted polyindole films with good fluorescence properties can be electrodeposited.     

Electrochemical and electrochromic properties of novel aromatic poly(amine-amide)s derived from N,N′-bis(4-carboxyphenyl)-N,N′-diphenyl-1,4-phenylenediamine

A series of novel triphenylamine-containing aromatic poly(amine-amide)s were prepared from the dicarboxylic acid, N,N′-bis(4-carboxyphenyl)-N,N′-diphenyl-1,4-phenylenediamine, and various diamines by direct phosphorylation polycondensation. All the poly(amine-amide)s were amorphous, soluble in a variety of organic solvents, and could be solution cast into transparent, tough, and flexible films with good mechanical properties. They had useful levels of thermal stability associated with relatively high glass-transition temperatures (195-280 °C). These polymers exhibited strong UV-Vis absorption bands at 330-346 nm and their photoluminescence showed maximum bands around 516-535 nm in NMP solution. The hole-transporting and electrochromic properties are examined by electrochemical and spectroelectrochemical methods. Cyclic voltammograms of the poly(amine-amide)s prepared by casting polymer solution onto an indium-tin oxide (ITO)-coated glass substrate exhibited two reversible oxidative redox couples at potential 0.73-0.78 V and 1.12-1.18 V, respectively vs Ag/AgCl in acetonitrile solution. All the poly(amine-amide)s exhibited excellent reversibility of electrochromic characteristics by continuous ten cyclic scans between 0.0 and 1.40 V, with a color change from original pale yellowish neutral form to the green and then to blue oxidized forms.     

Synthesis and electropolymerization of 1,2-bis(thiophen-3-ylmethoxy)benzene and its electrochromic properties and electrochromic device application

A new thiophene-based monomer; 1,2-bis(thiophen-3-ylmethoxy)benzene (BTMB) has been synthesized and chemical structure of the monomer was characterized. Polymerization of BTMB and characterization of the resulting polymer P(BTMB) were performed. Spectroelectrochemical analysis of the P(BTMB) reflected electronic transitions at 400 nm, 520 nm and ～720 nm, corresponding to π–π* transition, polaron and bipolaron band formation respectively. Switching ability was evaluated by a kinetic study via measuring the transmittance (%T) at the maximum contrast. Dual type all polymer electrochromic device (ECD) based on P(BTMB) and poly(ethylene dioxythiophene) (PEDOT) was constructed. Spectroelectrochemistry and switching ability of the devices were investigated by UV–vis spectroscopy.     

Solid state electrochromic device applications of N-(2-(thiophen-3-yl)methylcarbonyloxyethyl) maleimide

Homopolymer and copolymer of N-(2-(thiophen-3-yl)methylcarbonyloxyethyl) maleimide (NMThi) with thiophene [P(NMThi-co-Th)] were synthesized electrochemically in acetonitrile/borontrifluoride ethylether solvent mixture (1:1, v/v). Spectroelectrochemical analysis of the resulting copolymer reflected electronic transitions at 488 and 718 nm revealing π to π¹ transition and polaron formation, respectively. Switching ability was evaluated by a kinetic study via measuring the transmittance (%T) at the maximum contrast. Dual-type polymer electrochromic devices (ECDs) based on homopolymer (P(NMThi) and copolymer P(NMThi-co-Th) were constructed with poly(3,4-ethylenedioxythiophene) (PEDOT). Spectroelectrochemistry and switching ability of the devices were investigated by UV–vis spectroscopy and cyclic voltammetry.     

Synthesis, photophysics and electroluminescence of new vinylene-copolymers with 2,4,6-triphenylpyridine kinked segments along the main chain

Two new vinylene alternating copolymers F and C that contained 2,4,6-triphenylpyridine as a common moiety and fluorene or carbazole, respectively, as an alternating moiety were prepared by Heck coupling. They showed an outstanding thermal stability being stable up to approximately 350 °C and had relatively high glass transition temperatures (140 and 111 °C). The existence of the 2,4,6-triphenylpyridine kinked units along the polymer backbone caused a partial interruption of the π-conjugation. The copolymers emitted blue-green light with emission maximum at 446-464 nm and quantum yields of 0.52 and 0.28 in THF solution. The electrochemical properties of copolymers F and C, including HOMO and LUMO levels, were estimated from their cyclic voltammograms. Their electroluminescence (EL) emission maxima (greater than 500 nm) showed significant red-shifts relative to the PL maxima, which has been explained by the direct cross recombination transition between electrons and holes trapped on carbazole or triphenylpyridine subunits. Moreover, the emission colors transform gradually with increasing bias and approach to white color at about 30 ∼ 35 V. The maximal luminance (maximal luminance efficiency) of the EL devices (ITO/PEDOT:PSS/F or C/Ca/Al) were 647 cd/m² (0.13 cd/A) or 615 cd/m² (0.10 cd/A), respectively.     

Two novel triphenylamine-substituted poly(p-phenylenevinylene) derivatives: synthesis, photo- and electroluminescent properties

Two novel triphenylamine-substituted poly(p-phenylenevinylene) derivatives, P1 and P2, have been successfully synthesized through the Witting-Horner reaction. The structures and properties of the monomers and the resulting polymers were characterized by using ¹H NMR, FT-IR, GPC, TGA, UV-vis absorption spectroscopy, cyclic voltammetry (CV) and electroluminescence (EL) spectroscopy. The obtained polymers exhibited good thermal stability and high photoluminescence quantum yield (0.42-0.90). The polymer light-emitting diodes (PLEDs) with the configuration of ITO/PEDOT/polymers/Ca/Al were fabricated. The single-layer device based on P1 and P2 emitted stable blue and yellow light with the turn-on voltage of 4 and 6 V, respectively. The maximum luminance of 3003 cd/m² at 10 V was obtained for device P2.     

Novel cyclopenta[def]phenanthrene based blue emitting oligomers for OLEDs

Novel blue emitters, oligo-MCPPs (tri-MCPP, tetra-MCPP, and penta-MCPP), have been synthesized and characterized. The introduction of cyclopenta[def]phenanthrene (CPP) units into the structure of oligo-MCPPs gave LEDs with high efficiency and pure blue emission. UV-visible absorption spectra of the thin films of these compounds appear at 333-354 nm, and their maximum PL emission at 416-447 nm. Multilayer organic EL devices with oligo-MCPPs as an emitting layer showed the turn-on voltage of about 4.8 V, the maximum brightness of 1076 cd/m² (at 8.2 V), the maximum luminescence efficiency of 0.81 cd/A, and the CIE coordinates of (0.17, 0.14) with blue color.     

Simultaneous determination of cefotaxime and desacetylcefotaxime in real urine sample using voltammetric and high-performance liquid chromatographic methods

Two rapid, accurate and sensitive methods are developed and validated for the quantitative simultaneous determination of cefotaxime (CFX) and its active metabolite desacetylcefotaxime (DCFX) in urine.Based on the previous results which showed the four electron reduction of CFX at ≈ −0.5 V, and the new findings that DCFX reduction occurred at more positive potential (−0.23 V), the new adsorptive stripping differential pulse voltammetric (AdSDPV) method was developed for determination of CFX in the presence of DCFX. Linear responses were observed over a wide concentration range (0.07-0.52 μg/ml for CFX and 0.22-1.3 μg/ml for DCFX) in urine.The second assay involves subsequent separation on a reversed-phase HPLC column, with ultraviolet detection at 262 nm. Retention times were 4.057 and 1.960 min for CFX and DCFX, respectively. Linear responses were observed over a wide range, 0.55-6.60 μg/ml for CFX and 1.10-11.00 μg/ml for DCFX, in urine.The statistical evaluation for both methods was examined by means of within-day repeatability (n = 5) and day-to-day precision (n = 3) and was found to be satisfactory with high accuracy and precision.     

Preparation of cobalt-tetraphenylporphyrin/reduced graphene oxide nanocomposite and its application on hydrogen peroxide biosensor

A novel cobalt-tetraphenylporphyrin/reduced graphene oxide (CoTPP/RGO) nanocomposite was prepared by a π–π stacking interaction and characterized by ultraviolet–visible absorption spectroscopy (UV–vis), Fourier transform infrared spectroscopy (FTIR) and electrochemical impedance spectroscopy (EIS). The CoTPP/RGO nanocomposite exhibited high electrocatalytic activity both for oxidation and reduction of H₂O₂. The current response was linear to H₂O₂ concentration with the concentration range from 1.0 × 10⁻⁷ to 2.4 × 10⁻³ mol L⁻¹ (R = 0.998) at the reductive potential of −0.20 V and from 1.0 × 10⁻⁷ to 4.6 × 10⁻⁴ mol L⁻¹ (R = 0.996) at the oxidative potential of +0.50 V. The H₂O₂ biosensor showed good anti-interfering ability towards oxidative interferences at the oxidative potential of +0.50 V and good anti-interfering ability towards reductive interferences at the reductive potential of −0.20 V.     

Bias-current modulation technique of a radio-frequency glow discharge plasma for atomic emission analysis associated with a fast Fourier transform analyzer

A measuring method using a fast Fourier transform (FFT) analyzer is suggested to estimate the emission intensity from a radio-frequency (RF)-powered glow discharge plasma for atomic emission analysis. The FFT analyzer has an ability to disperse the components by frequency from an overall signal, and thus works as a selective detector in modulation spectroscopy. In the RF glow discharge plasma, a dc bias current can be introduced by connecting an external electric circuit with the discharge lamp, which predominantly enhances the emission intensities. Further, the bias current can be pulsated with a switching device to modulate the emission intensities, and then the modulated component was selectively detected with the FFT analyzer. This method greatly improved the data precision. The emission intensity of the Cu I 324.75-nm line in an Fe-based alloy sample containing 0.043 mass% Cu could be estimated with a relative standard deviation of 0.20%. The 3σ detection limits of Cu in Fe-based alloys could be obtained to be 2.3 × 10^− 6 mass% Cu for Cu I 324.75 nm and 6.8 × 10^− 6 mass% Cu for Cu I 327.40 nm.