Indium-doped zinc oxide nanorods were electrochemically deposited at low temperature on ITO substrates. The synthesized ZnO-arrayed layers were investigated by using X-ray diffraction, scanning electron microscopy, UV–vis transmittance, electrochemical impedance spectroscopy, and photocurrent spectroscopy. X-ray diffraction analysis demonstrates that the electrodeposited films are crystalline and present the hexagonal Würtzite ZnO phase with preferential (002) orientation. The ZnO films obtained forms aligned hexagonal nanorods, and depending on the increasing In concentration, the surface morphologies of the films are changed. The ln-doped ZnO nanorods (NRs) are well-aligned with the c-axis being perpendicular to the substrates when the ln concentration was between 0 and 2 at.%. of In, the grown films with In contents up to 4 at.%, changes in the optical band gap from 3.31 to 3.39 eV, and the blue shift in the band gap energy was attributed to the Burstein–Moss effect. The effect of In concentration on the photocurrent generated by films shows that the obtained thin films can be used as a photovoltaic material. Changes in the photocurrent response and the electronic disorder were also discussed in the light of In doping. It was found that the carrier density of IZO thin films varied between 1.06?×?1018 and 1.88?×?1018 cm?3 when the In concentration was between 0 and 4 at.%.
Pure and Ag-doped zinc oxide sol–gel thin films were prepared by spin-coating process. Pure and Ag–ZnO films, containing 2–8% Ag, were annealed at 500?°C for 2?h. All thin films were prepared and characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), atomic force microscopy (AFM), and UV–visible spectroscopy. X-ray diffraction studies show the polycrystalline nature with hexagonal wurtzite structure of ZnO and Ag:ZnO thin films. The crystallite size of the prepared samples reduced with increasing Ag doping concentrations. AFM and SEM results indicated that the average crystallite size decreased as Ag doping concentration increased. The transmittance spectra were then recorded at wavelengths ranging from 300 to 1000?nm. The films produced yielded high transmission at visible regions. The optical band gap energy of spin-coated films also decreased as Ag doping concentration increased. In particular, their optical band gap energies were 3.75, 3.55, 3.4, 3.3, and 3.23?eV at 0%, 2%, 4%, 6%, and 8%, respectively. Antibacterial activity of pure and Ag-doped zinc oxide against Escherichia coli and Staphylococcus aureus was evaluated by international recognized test (JIS Z 2801). The results showed that pure and Ag-doped ZnO thin film has an antibacterial inhibition zone against E. coli and S. aureus. Gram-positive bacteria seemed to be more resistant to pure and Ag-doped ZnO thin film than gram-negative bacteria. The test shows incrementally increasing in antibacterial activity of the thin films when dopant ratio increased under UV light.
In this paper, a facile immobilization of copper hexacyanoferrate nanoparticles (CuHCFNP) on a paraffin wax-impregnated graphite electrode (PIGE) was carried out using the room-temperature ionic liquid (RTIL) 1-ethyl-3-methylimidazolium tetrafluoroborate (EMIMBF4) as an ionic binder. The characteristics of the CuHCFNP/EMIMBF4 gel-modified electrode were investigated by cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS) techniques, and the modified electrode morphology was also characterized using field emission scanning electron microscopy (FESEM). The electrocatalytic behavior of butylated hydroxyl anisole (BHA) at the modified electrode has been investigated in 0.1 M KNO3 in static and dynamic conditions. Under the optimum conditions, the oxidation peak current was proportional to the BHA concentration in the range from 1.5 to 1000 μM with a detection limit of 0.5 μM (S/N = 3). The proposed method was applied to determine BHA content in real samples with satisfactory results.
Aluminum-doped ZnO thin films with pebble-like structures have been successfully deposited on glass substrates by successive ionic layer adsorption reaction method. The effect of percentage composition of the aluminum dopant on the flower-like clusters of the ZnO nanostructures on the structure, morphology, and optical properties was investigated. The ZnO thin films which were crystallized in hexagonal wurtzite structures with crystallite sizes of 44, 51, 56, and 43 nm for the intrinsic and 1, 3, and 5% Al-doped ZnO thin films, respectively. Preferred orientation of crystallites is in all cases in [001] direction perpendicular to the sample surface The Raman spectroscopy revealed decrease in the intensity of the ZnO characteristic peak due to the substitution of the Zn2+ atoms by the Al3+ and attributed to potential fluctuations of the alloy disorder. The introduction of the Al3+ dopant significantly increased the optical band gap.
The present trend to increase the energy density of electrochemical supercapacitor is to hybrid the electrochemical double layer capacitance electrode materials of carbon with loading or encapsulation of transition metal oxide or conductive polymeric pseudocapacitor materials as the binary or ternary hybrid electrochemical active materials. In this work, we selected polyaniline salt-sulfonated carbon hybrid (PANI-SA?CSA) as a cheaper electrode material for supercapacitor electrode. Sulfonated carbon (CSA) was prepared from hydrothermal carbonization of furaldehyde and p-toluenesulfonic acid. Polyaniline-sulfate salt containing sulfonated carbon was prepared by chemical oxidative polymerization of aniline using ammonium persulfate in presence of sulfuric acid and sulfonated carbon via aqueous, emulsion and interfacial polymerization pathways. Formation of hybrid material was confirmed from scanning electron microscopy. Among the hybrid prepared with three different polymerization pathways, hybrid prepared by aqueous polymerization pathway showed better electrochemical performance. The specific capacitance of the hybrid prepared via aqueous polymerization was 600 F g?1, which is higher than that of the pristine PANI-SA (350 F g?1) and CSA (30 F g?1). Hybrid material was subjected for 8000 charge-discharge cycles and at 8000 cycles; it showed 88% retention of its original specific capacitance value of 485 F g?1 with coulombic efficiency (97–100%). These results showed that CSA micro spheres prevent the degradation of PANI-SA chains during charge/discharge cycles. Specific capacitance, cycle life, low solution resistance, low charge transfer resistance and high phase angle value of PANI-SA?CSA supercapacitor cell indicates a higher performance supercapacitor system.
Graphical abstract Synthesis of hybrid of sulfonated carbon with polyaniline sulfate salt and its supercapacitor performance Ravi Bolagam, Palaniappan Srinivasan,* Rajender Boddula
In this study, sodium salts of saturated linear carboxylic acids with the general formula CH3(CH2)n?2COONa (n = 14, 18)—labeled NaC14 and NaC18—were used to inhibit the corrosion of metallic lead via the development of protective coatings for lead heritage objects. The salts were dissolved in water/ethanol 1:1 (V/V) mixture at 50 °C to increase their solubility, and the coatings were formed by immersing lead samples in the resulted solutions for 24 h. The coatings were characterized by scanning electron microscopy, Fourier transform infrared spectroscopy, X-ray diffraction, and X-ray photoelectron spectroscopy. A hydrophobic layer of lead carboxylates appeared to form on the metal surface, and its corrosion inhibition properties were examined by linear sweep voltammetry and electrochemical impedance spectroscopy in a corrosive solution simulating the environment of museums with uncontrolled conditions. The lead carboxylates formed a protective barrier that inhibited further lead corrosion.
A gold bare template modified with self-assembled layers (SAMs) composed of gold nanoparticles and organic S-containing compound: cysteamine and dihydrolipoic acid were prepared. The electrode with SAMs endowed with gold nanoparticles gave a high catalytic effect for dopamine electrooxidation alone and in the presence of biogenic interfering compounds: ascorbic acid and uric acid in solution at pH 7. For this novel sensor, a linear relationship between the current response of dopamine at the potential of peak maximum (jp) and the concentration of this compound in solution (cDA) was found over the range 0.1 μM to 0.85 mM with the detection limit of 0.023 μM.
Electrodeposition is a common technique for coating metallic or semiconducting substrates. The growth of the layers occurs through faradaic processes in which charges are transferred across the substrate-electrolyte interface. Since more than one reaction can occur simultaneously, it is important to study the faradaic efficiency (ε) associated to the growth of the desired layers and relate it to other parameters in order to optimize the process. In this work, an indirect method to determine the faradaic efficiency of electrodeposits with porosity (p) is proposed. The method was satisfactorily applied to porous β-Ni(OH)2 films obtained by light-assisted anodic electrodeposition. These films were grown using different electrolyte concentrations (C) and temperatures (T). In this case, a direct dependence of p and ε with C and T was found.
LiMn2O4 is one of the most promising cathode materials due to its high abundance and low cost. However, the practical application of LiMn2O4 is greatly limited owing to its low volumetric energy density. Therefore, increasing its energy density is an urgent problem to be resolved. Herein, using the simple and mass production preferred solid-state reaction, surficial Nb-doped LiMn2O4 composed of the truncated octahedral or spherical-like primary particles are successfully synthesized. Auger electron spectroscopy (AES) and X-ray diffraction (XRD) characterizations confirm that most of Nb5+ enrich in the surficial layer of the particles to form a LiMn2-xNbxO4 phase. This kind of doping can increase the specific discharge capacity of LiMn2O4 materials. Contrast with the pristine LiMn2O4, the discharge capacity of LiMn1.99Nb0.01O4-based 18650R-type battery increases from 1497 to 1705 mAh with the volumetric energy density increasing by ~?13.9%, benefiting from the joint increments of the specific discharge capacity from 119.5 to 123.7 mAh g?1 and the compacted density from 2.81 to 3.10 g cm?3. Furthermore, the capacity retention after 500 cycles at 1 C (1500 mA) is also improved by 17.1%.
An electrochemical chiral sensor was designed based on graphene (GR) as a catalyst for signal enhancement. Hydrocortisone has been immobilized as a chiral selector on GR to discriminate electrochemical signals of mandelic acid (MA) enantiomers. A two-step electrodeposition strategy was used to fabricate hydrocortisone-loaded overoxidized polypyrrole film (HC-OPPy) on graphene-modified glassy carbon electrode, which was successfully utilized as a working electrode for direct monitoring of MA enantiomers based on an inhibitory sensing mechanism. The stepwise modification of the surface was confirmed by cyclic voltammetry, impedance spectroscopy, and scanning electron microscopy. Because of the different interactions of enantiomers with the chiral electroactive platform, voltammetric signals with different intensities were observed for S-MA and R-MA at 1.36 and 1.40 V (vs. Ag/AgCl), respectively. The introduced design for the chiral sensor, with exploiting the chemometrics tools such as partial least squares, principle component regression, and genetic algorithm, was able to discriminate highly overlapping signals of MA enantiomers in their mixtures. The hydrocortisone-based sensor showed a linear response towards MA enantiomers within a concentration range of 1.0–25 mM with a detection limit of 0.25 mM (S/N = 3). The sensor not only extends the enantioselective sensing of MA enantiomers but also stimulates new opportunities for investigating stereo-selective behavior of hydrocortisone. The recognition mechanism was also investigated using docking analysis and DFT calculations.
The effect of dip time variations on electrochemical performance of polypyrrole (PPy)-copper hydroxide hybrid thin-film electrodes was studied well in depth. Synthesis was carried out using a successive ionic layer adsorption and reaction (SILAR) method via an aqueous route, using 0.1 M pyrrole, 0.1 M Cu(NO3)2, and H2O2. The electrochemical analysis was made by using cyclic voltammetry (CV), galvanostatic charge-discharge (GCD) analysis, and electrochemical impedance spectroscopy (EIS). Scanning electron microscopy (SEM) image of optimized electrode shows nanolamellae-like structures. The characteristic peak observed in Fourier transform infrared (FTIR) analysis at 1558 cm?1 validates the existence of PPy in hybrid electrode material, while the peaks observed at 21.5° and 44.5° in X-ray diffraction (XRD) patterns are evidence for triclinic Cu(OH)2. The observed maximum values of specific capacitance (SC), specific power (SP), specific energy (SE), and coulombic efficiency (η) of the optimized electrode are 56.05 F/g, 10.48 Wh/kg, 11.11 kW/kg, and 46.47%, respectively. For originality and value, the SILAR synthesis of PPy-Cu(OH)2 hybrid thin-film electrodes was carried out for the very first time. Synthesized electrodes showed improved surface structures and electrochemical stability than the pristine PPy electrodes which are necessary for the supercapacitive applications.
Deposition of charged particles under an electrical field which is expressed as the electrophoretic deposition (EPD) is a fast and simple method of nanoparticle coating. In this research, a comprehensive study was performed to improve the TiO2 film properties by application of modulated electrical fields with different amplitudes, waveforms, and frequencies. The suspension parameters (solvent composition, electrical conductivity, and additive concentration) were also optimized. Final photo-electrodes were characterized with scanning electron microscopy (SEM), atomic force microscopy (AFM), physicochemical, polarization, and photo-electrochemical studies. Based on the results, less particle consumption with better substrate coverage was obtained by applying modulated electrical fields. In the I-V test, the photo-electrodes constructed by applying AC signals with the square waveform at 100 Hz and sinusoidal waveform at 1 kHz showed photo-current density enhancement of about 21 and 18 times (in 1 V vs. Ag/AgCl), respectively, and about 40 % less deposited particle mass in comparison to the photo-electrode prepared in conventional DC electrical field. AC electrical fields could also be used with suspensions containing water as the green solvent. All observations in the EPD processing were successfully interpreted with an electrochemical circuit model that was developed based on the electrochemical impedance spectroscopy (EIS) results and analysis of deposition current.
We report herein one of our recent studies on nanostructured ZnO electrodes for application in dye-sensitized solar cells, focusing on achieving a higher open-circuit voltage (VOC). ZnO films were obtained through solution-processed routes including pyrolytic conversion of layered hydroxide zinc acetate (LHZA) films deposited on a fluorine-doped tin oxide-coated conducting glass substrate by a chemical bath deposition method. The morphology of the initial LHZA and the converted ZnO films was tuned from a thick (approximately 12 μm) flower bed-/lawn-like bilayer structure to a thin (1.2 μm) lawn-like quasi-monolayer structure by decreasing the Zn source concentration in the chemical bath. VOC was found to be enhanced with this morphological change from 0.692 (the bilayer structure) to 0.735 V (the quasi-monolayer structure). Fine tuning of the quasi-monolayer structure by introducing the grain growth effect led to VOC of the cell as high as 0.807 V, although a short-circuit photocurrent density (JSC) remained low. Further attempts were then made to increase JSC while maintaining the high VOC. When the thickness of the lawn-like monolayer film was increased up to approximately 5 μm, the resultant cell showed VOC?=?0.750 V, JSC?=?6.20 mA cm?2 and a conversion efficiency (η) of 2.83%. The film with a modified flower bed-/lawn-like bilayer structure approximately 11 μm in thickness finally yielded VOC?=?0.741 V, JSC?=?13.6 mA cm?2, and η?=?5.44%. 相似文献
MoS2 thin films with marigold flower-like nanostructures were grown on conductive fluorine-doped tin oxide (FTO) substrates through a one-step hydrothermal synthesis for their application as counter electrodes (CEs) in dye-sensitized solar cells (DSSCs). Different MoS2 thin film samples (A–D) were grown on FTO slides using different concentrations of precursors (sodium molybdate and thioacetamide), while keeping the Mo/S molar ratio constant (1:4.6), in all samples. The effect of varying precursor concentrations (3.2–12.6 mM on MoS2 basis) on the structure of the nanostructured thin films and their performance as DSSC-CEs was investigated. Scanning electron microscopy revealed a material with an infolded petal-like morphology. With increasing precursor concentration, the petal-like structures tended to form bunched nanostructures (100–300 nm) resembling marigold flowers. X-ray diffraction analysis, X-ray photoelectron, and Raman spectroscopy studies showed that the thin films were composed of hexagonal MoS2 with good crystallinity. Hall effect measurements revealed MoS2 to be a p-type semiconductor with a carrier mobility of 219.80 cm2 V?1 s?1 at room temperature. The electrochemical properties of the thin films were examined using cyclic voltammetry and electrochemical impedance spectroscopy. The marigold flower-like MoS2 thin films showed excellent electrocatalytic activity towards the I¯/I3¯ reaction and low charge transfer resistance (Rct) values of 14.77 Ω cm?1, which was close to that of Pt electrode (12.30 Ω cm?1). The maximum power conversion efficiency obtained with MoS2 CE-based DSSCs was 6.32%, which was comparable to a Pt CE-based DSSC (6.38%) under one sun illumination. Similarly, the maximum incident photon-to-charge carrier efficiency exhibited by MoS2 CE-based DSSCs was 65.84%, which was also comparable to a Pt CE-based DSSC (68.38%). The study demonstrated that the marigold flower-like nanostructured MoS2 films are a promising alternative to the conventional Pt-based CEs in DSSCs.
This paper reports the voltammetric determination of 17β-estradiol in urine and buttermilk samples using a simple detector based on a carbon paste electrode (CPE) modified with copper(II) oxide (CuO). The CuO was obtained by the Pechini method and characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), and energy-dispersive (EDS), Fourier transform infrared (FTIR), and Raman spectroscopies. Cyclic voltammetry (CV) and square-wave voltammetry (SWV) demonstrated that the CuO-modified carbon paste electrode (CuO/CPE detector) displayed much higher electrocatalytic activity in the 17β-estradiol oxidation reaction than the CPE without modification, exhibiting a low detection limit of 21.0 nmol L?1 with a wide linear range from 60.0 to 800.0 nmol L?1 (R = 0.998). Satisfactory results were obtained for the determination of 17β-estradiol in human urine and buttermilk samples. The proposed electrochemical detector offers high repeatability, stability, fast response, low cost, and potential for practical application in the quantification of this hormone.
As a promising Li-ion battery cathode active material, lithium-rich manganese-based layer-structured oxides suffer from inferior cycle performance and poor rate capability. Herein, Nb-doped Li1.2Mn0.54Ni0.13Co0.13O2 is prepared by a sol-gel method, and the effects of Nb doping on its electrochemical performance are investigated. It is concluded that the Nb-doped Li1.2Mn0.54Ni0.13Co0.13O2, has a good layered structure along c-axis independent on the amount of Nb dopant and little cationic mixing. Nb doping for Li1.2Mn0.54Ni0.13Co0.13O2 has no obvious influence on its morphology. It is found that Nb doping can enhance the electrochemical activity of Li1.2Mn0.54Ni0.13Co0.13O2, such as improved rate performance and cycle performance under high rate conditions. Li1.2Mn0.54Ni0.13Co0.13O2 doped with 0.015 Nb shows the best cycle performance under the high rate with the capacity maintenance of 95.4% after 100 cycles under 5 C rate, which is higher than that of the undoped one by 10.5%.
We obtained Tannin-4-azobenzoic acid (azo dye) by the conventional method of diazotization and coupling of aromatic amines. The properties of the azo dye were characterized via ultraviolet-visible (UV–vis), infrared (IR), and nuclear magnetic resonance (NMR) spectroscopy. Nanocrystalline titanium dioxide (TiO2) thin films were deposited by hydrothermal method onto fluorine-doped tin (IV) oxide (FTO)-coated glass substrate at 353 K for 4 h. The as-deposited and annealed films were characterized for structural, morphological, optical, thickness, and wettability properties. The synthesized metal free azo dye was used to sensitize the prepared TiO2 thin film with thickness of 26 μm. The photoelectrochemical (PEC) performance of TiO2 sensitized with the azo dye was evaluated in polyiodide (0.1 M KI + 0.01 M I2 + 0.1 M KCl) electrolyte at 40 mW cm?2 illumination intensity. The cell yielded a short circuit current of 2.82 mA, open circuit voltage of 314.3 mV, a fill factor of 0.30, and a photovoltaic conversion efficiency value of 0.64%.
The present paper is focused toward the preparation of the flexible and free-standing blend solid polymer electrolyte films based on PEO-PVP complexed with NaPF6 by the solution cast technique. The structural/morphological features of the synthesized polymer nanocomposite films have been investigated in detail using X-ray diffraction, Fourier transform infra-red spectroscopy, Field emission scanning electron microscope, and Atomic force microscopy techniques. The film PEO-PVP?+?NaPF6 (\( \ddot{\mathrm{O}}/{\mathrm{Na}}^{+}= \)8) exhibits highest ionic conductivity ~?5.92?×?10?6 S cm?1 at 40 °C and ~?2.46?×?10?4 S cm?1 at 100 °C. The temperature-dependent conductivity shows an Arrhenius type behavior and activation energy decreases with the addition of salt. The high temperature (100 °C) conductivity monitoring is done for the optimized PEO-PVP?+?NaPF6 (\( \ddot{\mathrm{O}}/{\mathrm{Na}}^{+}= \)8) highly conductive system and the conductivity is still maintained stable up to 160 h (approx. 7 days). The thermal transitions parameters were measured by the differential scanning calorimetry (DSC) measurements. The prepared polymer electrolyte film displays the smoother surface on addition of salt and a thermal stability up to 300 °C. The ion transference number (tion) for the highest conducting sample is found to be 0.997 and evidence that the present system is ion dominating with negligible electron contribution. Both linear sweep voltammetry and cyclic voltammetry supports the use of prepared polymer electrolyte with long-term cycle stability and thermal stability for the solid-state sodium ion batteries. Finally, a two peak percolation mechanism has been proposed on the basis of experimental findings.
A new zinc-layered hydroxide-L-phenylalanate (ZLH-LP)-modified multiwalled carbon nanotube (MWCNT) was prepared as a new material of paste electrode for the detection of paracetamol (PCM) in 1.0?×?10?1 M phosphate buffer solution and at pH 7.5. The electrochemical characterization of the MWCNTs/ZLH-LP paste electrode was characterized by square wave voltammetry, electrochemical impedance spectroscopy, and cyclic voltammetry while the morphology properties of the MWCNTs, ZLH-LP, and MWCNTs/ZLH-LP were investigated using transmission electron microscopy and scanning electron microscopy. Under optimized conditions, the MWCNTs/ZLH-LP paste electrode demonstrated an excellent electrocatalytic activity towards oxidation of PCM in the linear responses’ ranges from 7.0?×?10?7 M to 1.0?×?10?4 M (correlation coefficient, 0.996) with the limit of detection obtained at 8.3?×?10?8 M. As a conclusion, the MWCNTs/ZLH-LP paste electrode revealed good repeatability, reproducibility, and stability, and was found to be applicable for use in pharmaceutical tablet samples.
Li[Ni1/3Co1/3Mn1/3]O2 (NCM 111) is a promising alternative to LiCoO2, as it is less expensive, more structurally stable, and has better safety characteristics. However, its capacity of 155 mAh g?1 is quite low, and cycling at potentials above 4.5 V leads to rapid capacity deterioration. Here, we report a successful synthesis of lithium-rich layered oxides (LLOs) with a core of LiMO2 (R-3m, M?=?Ni, Co) and a shell of Li2MnO3 (C2/m) (the molar ratio of Ni, Co to Mn is the same as that in NCM 111). The core–shell structure of these LLOs was confirmed by XRD, TEM, and XPS. The Rietveld refinement data showed that these LLOs possess less Li+/Ni2+ cation disorder and stronger M*–O (M*?=?Mn, Co, Ni) bonds than NCM 111. The core–shell material Li1.15Na0.5(Ni1/3Co1/3)core(Mn1/3)shellO2 can be cycled to a high upper cutoff potential of 4.7 V, delivers a high discharge capacity of 218 mAh g?1 at 20 mA g?1, and retains 90 % of its discharge capacity at 100 mA g?1 after 90 cycles; thus, the use of this material in lithium ion batteries could substantially increase their energy density.
Graphical Abstract Average voltage vs. number of cycles for the core–shell and pristine materials at 20 mA g?1 for 10 cycles followed by 90 cycles at 100 mA g?1
