Conducting Glass Electrode Research Articles

(Invited) Stabilization and Activation of Cuprous Oxide Photocathodes for Effective Reduction of Carbon Dioxide

Among representative examples of semiconducting materials for the selective reduction of carbon dioxide to desired small organic molecules (fuels, utility chemicals), there are transition metal oxides (p-type semiconductors), in particular Cu-based oxides, such as Cu2O, CuFeO2, CuBi2O4, CuNb2O6, CuO and Cu2O) that are capable of generating electrons with use of solar visible light. Selectivity of the catalytic systems largely depends on the activing adsorptive (CO2) phenomena and the affinity of catalytic centers to the adsorbed carbon monoxide intermediates leading to their protonation or hydrogenation. Here application of aqueous or water-containing electrolytes is generally preferred. Furthermore, a compromise must be reached between the activity of a catalyst toward hydrogen evolution (water splitting), its ability to promote reductive adsorption of CO2 and to generate moderate coverages of H atoms capable of stabilizing subsequent reduced intermediates.Our interest concentrates on copper(I) oxides but their practical use requires means of stabilization without poisoning or deactivation. To improve stability against photocorrosion, to assure the sufficient electron-hole pair separation, as well as to increase population of electrons in the conduction band, mixed oxide systems combining the p-type semiconductor (e.g. Cu2O) with n-type semiconductors such as TiO2, SrTiO3 or KTaO3 have been proposed. To meet requirements for practical Cu2O-based photocathodes, not only the ability to absorb efficiently visible light and to assure fast interfacial electron transfers but also the stability issues need to be addressed.Contrary to the poor performance of the pristine (bare) copper(I) oxide photocathode, the visible-light-illuminated photoelectrochemical reduction of carbon dioxide has been successfully performed using the p-type Cu2O-semiconductor (deposited onto the transparent fluorine-doped conducting glass electrode) over-coated with the ultra-thin films of various polymer (poly(4-vinyl pyridine, oligoaniline) or polynuclear type materials (titanium, zirconium and tungsten oxides).. In this respect, ultra-thin films of functionalized carbon nanostructures, supramolecular complexes (with nitrogen containing ligands and certain transition metal sites) or robust bacterial biofilms could also be advantageous. For example, A biofilm formed by a strain of Yersinia enterocolitica (Y. enterocolitica) is characterized by high physicochemical stability over a wide pH range (4-10) and temperatures (0-40°C).Also oligoaniline or tungsten oxide over-layers could be fabricated on copper(I) oxide surfaces. Under such conditions, the copper(I) oxide photoelectrode does not change the oxidation state during photoelectrochemical diagnostic experiments. Thus certain robust (not necessarily thin) over-layers could exhibit the effect of stabilization of Cu2O against photocorrosion. Among important issues is the ability of CO2 to undergo adsorption (and activation toward reduction to CO) at both bare and modified surfaces of Cu2O. The proposed bi-layered photocathode has been demonstrated to produce such simple organic fuels as alcohols. Introduction of co-catalytic centers, e.g. palladium in a form of supramolecular complexes could also be advantageous.

Polyvinylidene Fluoride (PVDF) Crystallization Kinetics in an Electric Field

To study the effect of applied electric field on polymer crystallization, the crystallization of polyvinylidene fluoride (PVDF) was observed under modified polarized optical microscopy. The PVDF melts were crystallized based on programmed temperature, changes between two transparent conductive glass electrodes, on which a DC electric field was applied. The observations revealed that without the electric field, crystallizations below 160 °C resulted in only α-form crystals, while, at elevated temperatures, the formation of γ-form crystals also occurred. By applying the electric field at 1.7 kV/cm, γ-form crystals started emerging at the slightly lower temperature of 158 °C. Further examinations showed that both crystals, α-form and γ-form, grew at a greater rate with increasing field strength. A careful calculation of the Avrami parameters supported the data that the electric field enhanced the crystallization kinetics. Careful calculation based on the Laurientz–Hoffmann approach revealed that applying the electric field decreased the required energy for PVDF crystallization. The folding surface free energy of the PVDF crystallization, 1.76 × 10−2 Jm−2, was reduced to 1.57 × 10−2 Jm−2 and 1.43 × 10−2 Jm−2 after applying electric fields of 0.8 and 1.7 kVcm−1, respectively. We suggest that the electric field promoted the polymer chain alignment during the crystallization; as a result, it accelerated the polymer crystallization and lowered the energy requirement for crystallization.

One-step preparation of SnO2-AuNPs as nanocomposites on photoelectrodes to enhance photoelectrochemical detection of nitrite and superoxide

The integration of plasmonic metal nanoparticles and semiconductors improves the photoelectric conversion efficiency. We describe here a simple method for preparing photoelectrodes modified with nanocomposites of tin oxide (SnO2) and gold nanoparticles (AuNPs). This preparation process is more convenient, economical, and efficient than the previous methods. The nanocomposite of SnO2-AuNPs on indium tin oxide (ITO) conductive glass electrodes enhanced photoelectric conversion and increased conductivity. The electrodes prepared with SnO2-AuNPs nanocomposites were used as photoanodes in photoelectrochemical methods for the determination of nitrite (NO2−) and superoxide radical (O2−). The detection of superoxide radicals was achieved by stoichiometric conversion of superoxide radicals to nitrite, which overcomes a common problem of chemical instability of superoxide radicals. The photoelectrochemical method for the determination of NO2− had a detection limit of 0.1 nmol/L and a linear dynamic range from 10−9 to 10−5 mol/L. The method was successfully used to assess the photochemical generation of O2− by irradiating a photosensitizer, rose bengal (RB). The photoelectrochemical responses increased with the concentration of the photosensitizer and the time of photo irradiation (532 nm) as expected.

Preparation of ZnO compact layer using vacuum ultraviolet for dye-sensitized solar cells

Vacuum ultraviolet (VUV) light with a wavelength of 172 nm has the capacity to convert the oxygen contained metal organic precursor into metal oxide. Here, zinc acetate precursor thin film is directly converted into ZnO thin film by the irradiation of 172 nm VUV light rather than the high temperature sintering. The converting processes were demonstrated by the measurements of FTIR, XRD, SEM and XPS. And then the effect of irradiating time on the morphology, thickness and transparence of the prepared ZnO thin films was discussed. The ZnO thin film was further used as the compact layer in the photoelectrode of dye-sensitized solar cell (DSSC) to suppress the recombination processes of photogenerated electrons on the conducting glass electrode. For the different irradiation times, the photoelectric conversion efficiency of DSSC based on the compact layer prepared by the irradiation for 30 min is the highest reaching 10.27%, which is also higher than that of DSSCs without the compact layer and even with the compact layer prepared by the high temperature sintering. The uniform, dense, pinhole-free and amorphous ZnO thin film on the conducting glass substrate can be successfully prepared using the VUV irradiation technology for the compact layer of DSSCs.

Investigating the variation in the optical properties of TiO2 thin-film utilized in bifacial solar cells using machine learning algorithm

Among various solar cell architectures, dye-sensitized solar cells (DSSCs) and perovskite solar cells have demonstrated the capability of being bifacial as both can be fabricated on conducting glass electrodes. In both cells, TiO2 plays a key role in the optoelectronic properties of the cell. Various studies have reported a range of recipes and deposition techniques for TiO2 thin films. Such variety introduces some uncertainties into the optical properties of the prepared films as well as in the process repeatability. Here, we utilized machine learning methods to correlate the film porosity to the film refractive index, making it capable of studying the impact of varying the fabrication and deposition techniques. Image postprocessing for scanning electron microscope measurements was utilized to estimate the film porosity, and the refractive index was calculated from the T–λ spectra. Four sets of samples with complete bifacial DSSCs were fabricated and characterized. They recorded a maximum current of 23.42 mA. They were fabricated using carboxymethyl cellulose-based suspension and deposited via the spin-coating sol-gel method. The fabricated cells showed an overall conversion efficiency of 7.9% under optical injection of the AM1.5G spectrum from the front side and LED indoor lighting from the counter electrode.

Copper oxide nanoleaves covered with loose nickel oxide nanoparticles for sensitive and selective non-enzymatic nitrite sensors

In this work, we developed a new method for preparing copper oxide (CuO) nanostructures, designed and prepared a CuONiO modified fluorine-doped SnO2 transparent conductive glass (FTO) electrode for electrochemical sensor to effectively detect the nitrite. The leaf-shaped CuO nanostructures grow uniformly on the FTO electrode, resulting in the increased contact area and reduced transfer resistance. The NiO nanoparticles effectively dispersed in the gaps between the leaves can further improve the electron transfer and reduce the diffusion resistance. The electrochemical results demonstrated that the prepared electrode exhibited high sensitivity (7.2 mA mM−1 cm−2), broad linear range (0.001–1.8 mM) and low detection limit (0.013 μM). Moreover, the prepared sensor also reflected good reproducibility, stability and anti-interference in the detection of actual samples, which provides a good application prospect for metal oxides used in water quality and environmental monitoring.

Simply amplificated signal in electrochemiluminescence sensor using nano-gold film as a bridge

Normally, analytical applications of metal oxide semiconductors (MOS) in electrochemiluminescence (ECL) sensors need to be coupled with electrochemical catalysts, some special coreactants or resonance energy transfer method, since MOS exhibited relatively low ECL intensity. In this research, we developed a simple ECL intensity enhancement method for MOS by covering a nanogold-film (NAuF) on the surface of fluorine-doped tin oxide-coated (FTO) conductive glass electrode. Aminated MnO2 nanoparticles (NH-MnO2) was chosen as exemplary MOS emitter to discuss the role of NAuF in ECL system. The results indicated that the NAuF bridged ECL sensor using NH-MnO2 as emitter (NH-MnO2-NAuF/FTO) exhibited a stronger ECL intensity and extremely better stability. In furazolidone (FZD) determination test, the quenched ECL intensity showed a good linear relationship to FZD concentrations in the range 1.0 × 10−8 M ∼ 1.0 × 10−5 M, with a detection limit of 6.6 × 10−9 M, in optimized conditions. Given these attributes, we developed a novel platform for ECL system that could simply enhance the intensity and stability. This work also efficiently offered insights into application potential of ECL analysis.

(Invited) Photoelectrochemical Reduction of CO2 at Poly(4-vinylpyridine)-Stabilized Copper(I) Oxide Semiconductor Decorated with Palladium Cocatalyst

Poly(4-vinylpyridine)-modified copper(I) oxide photocathodes, bare or decorated with palladium nanoparticles, can be used for the visible-light-driven selective reduction of CO2, mostly to carbon monoxide (in the absence of Pd co-catalyst) and methanol (in the presence of Pd co-catalyst). The photocathode materials, which are composed of hierarchically deposited (onto transparent fluorine-doped conducting glass electrode) Cu2O (inner layer) and poly(4-vinylpyridine), P4VP, polyelectrolyte film (outer-layer), with or without dispersed Pd-nanoparticles, have been fabricated and, subsequently, examined using electrochemical methodology, atomic force microscopy and various spectroscopic techniques, including Raman approach. While the physicochemical characteristics of Cu2O, including the oxide identity and its semiconducting properties, are not largely affected by the interfacial modification with P4VP, the photostability of the hybrid photocathode is significantly improved. The P4VP-modified Cu2O photocathodes exhibit reasonable durability during photoelectrochemical reduction of CO2 upon illumination with sunlight in semi-neutral medium (Na2SO4). On the whole, the photoelectrochemical reduction of CO2 proceeds at potentials starting from ca 0.55 V (vs RHE), which are substantially (almost 800 mV) more positive, in comparison to those characteristic of the conventional electrochemical reduction in the dark. Introduction of palladium co-catalyst seems to improve distribution (collection and transport) of photoelectrons at the photoelectrochemical interface and affects the CO2-electroreduction mechanism.

Photoelectrochemical Reduction of CO2 at Poly(4‐Vinylpyridine)‐Stabilized Copper(I) Oxide Semiconductor: Feasibility of Interfacial Decoration with Palladium Cocatalyst

Poly(4‐vinylpyridine)‐modified copper(I) oxide photocathodes, bare or decorated with palladium nanoparticles, can be used for the visible‐light‐driven selective reduction of CO2, mostly to methanol and carbon monoxide (in the absence of Pd cocatalyst) or formic acid and carbon monoxide (in the presence of Pd cocatalyst). The photocathode materials, which are composed of hierarchically deposited (onto transparent fluorine‐doped conducting glass electrode) Cu2O (inner layer) and poly(4‐vinylpyridine) (P4VP) polyelectrolyte film (outer‐layer), with or without dispersed Pd nanoparticles, have been fabricated and examined using electrochemical methodology, atomic force microscopy, and various spectroscopic techniques, including the Raman approach. While the physicochemical characteristics of Cu2O, including the oxide identity and its semiconducting properties, are not largely affected by the interfacial modification with P4VP, the photostability of the hybrid photocathode is significantly improved. The P4VP‐modified Cu2O exhibits reasonable durability during photoelectrochemical reduction of CO2 upon illumination with sunlight in semi‐neutral medium (Na2SO4). While Cu2O can be identified using Raman spectroscopy as the sole bulk component of the semiconducting film, the XPS data imply that the Cu2O surface is likely to be partially reduced during prolonged operation. Introduction of palladium cocatalyst seems to improve distribution (collection and transport) of photoelectrons at the photoelectrochemical interface and affects the CO2‐electroreduction mechanism.

Electrocatalytic Properties of a Novel β-PbO2/Halloysite Nanotube Composite Electrode

To improve the efficiency of electrochemical degradation of wastewater, lead dioxide was synthesized by a hydrothermal method with low cost, simple operation, and high conversion rate. β-PbO2/HNT composites were prepared by a hydrothermal method with Halloysite nanotubes (HNTs) and β-PbO2. The PbO2/HNT/ITO electrode was prepared by modifying the β-PbO2/HNT composite on an indium tin oxide (ITO) conductive glass electrode. The morphology of the material was characterized by scanning electron microscopy and transmission electron microscopy. The electrochemical performance of the electrode was measured by cyclic voltammetry, the galvanostatic charge–discharge method, and the AC impedance method. Electrolysis of typical dye wastewater by electrochemical oxidation was carried out. The effect of electrochemical degradation of wastewater with new electrodes was investigated and the degree of electrodes falling off was compared. The solubility of electrodes was investigated by inductively coupled plasma mass spectrometry lead element analysis of wastewater. The results showed that the β-PbO2/HNT electrodes were prepared successfully and had good charge–discharge performance and lifetime. The removal rate of electrolytic dye wastewater was 85.86%, and the degradation effect was better than that of pure PbO2 electrodes. In this work, a new type of β-PbO2/HNT/ITO electrode has been prepared, which improved the degradation efficiency of wastewater and opened up the prospect of HNT application.

Photoelectrochemical reduction of CO2: Stabilization and enhancement of activity of copper(I) oxide semiconductor by over-coating with tungsten carbide and carbide-derived carbons

Hybrid photocathode materials, which are composed of hierarchically deposited (onto the transparent fluorine-doped conducting glass electrode) copper(I) oxide (inner layer) and robust carbon structures, such as carbide derived carbons (CDC) or mixture of CDC with 70% (weight) tungsten carbide (WC-CDC), have been fabricated and examined using electrochemical methods, X-ray diffraction and various spectroscopic approaches including Raman technique. The resulting systems have been characterized by good stability and have exhibited high photoelectrochemical activity toward reduction of CO2 upon illumination with sunlight in the Na2SO4 neutral medium. While the semiconducting properties of Cu2O are not largely affected by the interfacial modification with CDC and WC-CDC, the photostability of the hybrid photocathode is significantly improved. The stabilization effect should reflect the capacitive properties of CDC and WC-CDC. The capability of CDC and WC-CDC over-layers to undergo efficient double-layer-type charging/discharging should facilitate collection and transport of photoelectrons and inhibit recombination of photogenerated electron-hole pairs. The relatively higher photoelectrochemical activity of the Cu2O system over-coated with WC-CDC, relative to the one containing CDC only, seems to reflect specific interactions between CO2 and WC-CDC thus inducing reduction of CO2 adsorbates.

Electrochemical sensing of mercury ions in electrolyte solutions by nitrogen-doped graphene quantum dot electrodes at ultralow concentrations

Electrochemical detection of mercury ions in aqueous solution was investigated at indium tin oxide (ITO) conducting glass electrode modified by nitrogen-doped graphene quantum dots (N-doped GQDs). The N-doped GQDs with an average particle size of 4.5 nm were synthesized through an infrared-assisted pyrolysis of citric acid and urea at 250 °C. The GQD sample contains high oxidation and amidation level, i.e., O/C and N/C atomic ratios: 37.6% and 30.7%, respectively. The electrochemical sensing toward Hg2+ ions was characterized by cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS). Based on the CV and EIS analyses, both the reductive and oxidative peak currents as well as the equivalent series resistance demonstrate a decreasing trend with increased Hg2+ concentration. The detection limit of N-doped GQD/ITO electrodes toward Hg2+ ions reached 10 ppb with the accumulation time of 32 s. The GQD/ITO electrodes also exhibit superior selectivity toward the target contaminant (i.e. Hg2+ ion). Accordingly, the functionalized GQDs pave the way for engineering the electrochemical sensors capable of detecting toxic Hg2+ ions with superb sensitivity and selectivity.

(Invited) Modification, Activation and Stabilization of Copper(I) Oxide Photocathodes: Competition between Catalytic and Inhibiting Effects during Light-Induced Electoreduction of CO2

Among representative examples of semiconducting materials for the selective reduction of carbon dioxide to desired small organic molecules (fuels, utility chemicals), there are transition metal oxides (p-type semiconductors), in particular Cu-based oxides, such as Cu2O, CuFeO2, CuBi2O4, CuNb2O6, CuO and Cu2O) that are capable of generating electrons with use of solar visible light. Selectivity of the catalytic systems largely depends on the activing adsorptive (CO2) phenomena and the affinity of catalytic centers to the adsorbed carbon monoxide intermediates leading to their protonation or hydrogenation. Here application of aqueous or water-containing electrolytes is generally preferred. Furthermore, a compromise must be reached between the activity of a catalyst toward hydrogen evolution (water reduction) and its ability to promote reductive adsorption of CO2 and to generate moderate coverages of H atoms capable of stabilizing subsequent reduced intermediates. Our interest concentrates on copper(I) oxides but their practical use requires means of stabilization without poisoning or deactivation. To improve stability against photocorrosion, to assure the sufficient electron-hole pair separation, as well as to increase population of electrons in the conduction band, mixed oxide systems combining the p-type semiconductor (e.g. Cu2O) with n-type semiconductors such as TiO2, SrTiO3 or KTaO3 have been proposed. To meet requirements for practical Cu2O-based photocathodes, not only the ability to absorb efficiently visible light and to assure fast interfacial electron transfers but also the stability issue needs to be addressed. Contrary to the poor performance of the pristine (bare) copper(I) oxide photocathode, the visible-light-illuminated photoelectrochemical reduction of carbon dioxide has been successfully performed using the p-type Cu2O-semiconductor (deposited onto the transparent fluorine-doped conducting glass electrode) over-coated with the ultra-thin films of various polymer (poly(4-vinyl pyridine, oligoaniline) or polynuclear type materials (titanium, zirconium and tungsten oxides).. In this respect, ultra-thin films of functionalized carbon nanostructures, supramolecular complexes (with nitrogen containing ligands and certain transition metal sites) or robust bacterial biofilms could also be advantageous. For example, the oligoaniline or tungsten oxide over-layers [1,2] have been generated on copper(I) oxide surfaces. Under such conditions, the copper(I) oxide photoelectrode does not change the oxidation state during photoelectrochemical diagnostic experiments. Thus certain robust (not necessarily thin) could exhibit the effect of stabilization of Cu2O against photocorrosion. Among important issues is the ability of CO2 to undergo adsorption (and activation toward reduction to CO) at both bare and modified surfaces of Cu2O. The proposed bi-layered photocathode has been demonstrated to produce such simple organic fuels as alcohols (mainly methanol and some ethanol). [1] Szaniawska E., Rutkowska I.A., Frik M., Wadas A., Seta E., Krogul-Sobczak A., Rajeshwar K., Kulesza P.J., Electrochim. Acta, 265, 400 (2018). [2] Rutkowska I.A., Szaniawska E., Taniewicz J., Wadas A., Seta E., Kowalski D., Kulesza P.J., J. Electrochem. Soc., 166, H3271 (2019).

An Electrochemical Sensor for the Detection of Cu2+ Based on Gold Nanoflowers‐modifed Electrode and DNAzyme Functionalized Au@MIL‐101 (Fe)

AbstractIn this study, we developed an electrochemical sensor for sensitive detection of Cu2+ based on gold nanoflowers (AuNFs)‐modified electrode and DNAzyme functionalized Au@MIL‐101(Fe) (MIL: Materials of Institute Lavoisier). The AuNFs‐modified indium tin oxide modified conductive glass electrode(AuNFs/ITO) prepared via electrodeposition showed improved electronic transport properties and provided more active sites to adsorb large amounts of oligonucleotide substrate (DNA1) via thiol‐gold bonds. The stable Au@MIL‐101(Fe) could guarantee the sensitivity because of its intrinsic peroxidase mimic property, while the Cu2+‐dependent DNA‐cleaving DNAzyme linked to Au@MIL‐101(Fe) achieved the selectivity toward Cu2+. After the DNAzyme substrate strand (DNA2) was cleaved into two parts due to the presence of Cu2+, the oligonucleotide fragment linked to MIL‐101(Fe) was able to hybridize with DNA1 adsorbed onto the surface of AuNFs/ITO. Due to the peroxidase‐like catalytic activity of MIL‐101(Fe) and the affinity recognition property of DNAzyme toward Cu2+, the electrochemical biosensor showed a sensitive detection range from 0.001 to 100 μM, a detection limit of 0.457 nM and a high selectivity, demonstrating its potential for Cu2+ detection in real environmental samples.

Sandwiched Growth of Micron-thick MAPbI3 Crystals for Waterproof Perovskite Solar Cells

Perovskite solar cells usually adopt the normal or inverted structure, where the active layer is barely isolated from metal contacts and the atmosphere. By coating two conductive glass electrodes w...

Voltage and frequency dependence of negative capacitance behavior in a Graphene-TiO2 nanocomposite photoanode based on quantum dot sensitized solar cells

In this letter, we investigated negative capacitance (NC) effect in nanocomposite based quantum dot sensitized solar cells. TiO2 and graphene-TiO2 nanocomposite photoanode based on quantum dot sensitized solar cells (QDSSCs) were fabricated and the capacitance-voltage (C–V), capacitance-frequency (C-f) and conductance-voltage (G/ω-V) characteristics were studied by attention the series resistance (Rs) effect. Admittance spectroscopy of QDSSCs were measured in a variable voltage and frequency ranges of (−2 V) - (+2 V) and 10 kHz-10 MHz, respectively. Capacitance values are exhibited a behavior transition from the positive to negative value after 50 kHz. As the capacitance values decreases, conductance increases in the NC region. Negative capacitance effect of meaning that QDSSC indicates an inductive behavior. Inductive behavior, which means that electrons injects from fluorine-doped tin oxide (FTO) conductive glass electrode to photoanode (graphene-TiO2). Also, NC phenomenon has not form significant effect on Rs.

Preparation of a ZIF-67 Derived Thin Film Electrode via Electrophoretic Deposition for Efficient Electrocatalytic Oxidation of Vanillin.

The electrophoretic deposition method is employed to deposit uniform metal organic framework thin films. ZIF-67 particles dispersed in isopropanol move to a cathode as an electric field is applied on two conducting glass electrodes, the uniform ZIF-67 thin film can be formed on the conducting glass substrate. As the deposition time is fixed at 1 min, the prepared film thickness can be adjusted from 1.0 to 7.0 μm by applying different electric fields from 20 to 60 V·cm-1. The deposited ZIF-67 thin film is further converted into porous Co9S8 thin films by the vulcanization with S powder. The porous thin films vulcanized at different temperatures are characterized by the measurements of scanning electron microscope, X-ray photoelectron spectroscopy, X-ray powder diffraction, high resolution transmission electron microscopy, and Fourier transform infrared spectra. The prepared porous Co9S8 thin films are used as the thin film electrode to catalyze the degradation of vanillin. The Co9S8 thin film vulcanized at 500 °C shows better catalytic performance than the bare glassy carbon electrode and the electrodes vulcanized at other temperatures. The electrocatalytic degradation enhancement mechanism is analyzed by the measurements of Tafel curves and electrochemical impedance spectroscopies. It can be developed as a feasible method for the electrocatalytic detection of vanillin.

An improved strategy for transferring and adhering thin nanoporous alumina membranes onto conducting transparent electrodes for template assisted electrodeposition of high aspect ratio semiconductor nanowires with increased optical absorption

This article presents a new method for transferring and enhancing the adhesion of thin nanoporous alumina (NPA) membranes onto non-atomically flat substrates like fluorine-doped tin oxide (FTO) coated glass. The study reports use of glycerol as an additive to reduce the brittleness of the polystyrene filler that was used to fill the pores of the NPA membrane. Additionally, a new reflux-based method is reported here for the complete removal of the polystryrene filler from the porous channels of alumina. The adhesion between an NPA membrane and an underlying electrode was enhanced by electrodepositing a thin (∼40 nm) intermediate layer of the conducting polymer polyaniline (PANI). The PANI layer acts as an efficient electrostatic adhesive between the NPA and the conducting glass electrode and ensures ultra-strong adhesion of the NPA membrane, which can survive the harsh conditions of CdTe nanowire electrodeposition (60 °C temperature and an acidic electrolyte) without delamination for 30 min. The resulting nanowires clearly templated the structure of NPA and displayed free-standing nanowires over a large area with a diameter of around 60 nm, a length of approximately 2.8 μm (aspect ratio ∼47) and an areal density of 5.9 × 1012 nanowires cm−2. Total optical absorption measurement on the free-standing CdTe nanowires exhibited a 45% enhancement over a wavelength range of 350–1400 nm as compared to a CdTe planar thin film of same thickness.

Electrocatalytic and Photoelectrochemical Reduction of Carbon Dioxide at Hierarchical Hybrid Films of Copper(I) Oxide Decorated with Tungsten(VI) Oxide Nanowires

Unique hybrid systems for electroreduction of CO2 under both conventional and visible-light-induced conditions are proposed and designed here by over-coating copper(I) oxide with tungsten(VI) oxide nanowires. When Cu2O and WO3 nanostructures are sequentially deposited on glassy carbon substrate, the resulting system has exhibited high electrocatalytic activity toward reduction of CO2 in phosphate buffer of pH = 6.1. By introducing WO3, the Cu-based system becomes more selective against the competitive hydrogen evolution and exhibits higher CO2-reduction currents relative to the performance of single components. During electroreduction, highly catalytic Cu sites are generated or intercalated within WO3 nanowires partially reduced to mixed-valence hydrogen-absorbing tungsten(VI,V) oxide bronzes, HxWO3, co-existing with sub-stoichiometric tungsten(VI,IV) oxides, WO3-y. Strong adsorption and activation of CO2 molecule has been demonstrated at the WO3-decorated Cu2O interface. Under photoelectrochemical conditions involving illumination with sun-light, the proposed hierarchical system of Cu2O semiconductor deposited onto the transparent fluorine-doped conducting glass electrode and decorated with WO3 nanowires is well-behaved and active toward CO2-reduction in the Na2SO4 neutral medium. In addition to the Cu2O stabilization effect, the heterojunction formed by p-type Cu2O and n-type WO3 semiconductors seems to facilitate charge distribution and separation at the photoelectrochemical interface.

Nanostructured titania based electrochemical impedimetric biosensor for non-invasive cancer detection

In the present work, the utilisation of bio-functionalised TiO2 nanoparticles has been reported for biosensing application especially in oral cancer detection. The bio-sensing electrode was fabricated on indium tin oxide coated conducting glass electrode using electrophoretic deposition technique. The proposed technique holds tremendous potential to make the approach effectively simple, label-free and most importantly a non-invasive technique. The prepared nanoparticles were characterised using x-ray diffractometer; Fourier transforms infrared spectroscopy, and x-ray photoelectron spectroscopy. In conjunction with this, the morphological studies of immunoelectrode (bovine serum albumin/anti-CYFRA-21-1/(3-aminopropyl)triethoxysilane/TiO2/indium tin oxide) were conducted by field emission scanning electron microscopy. The average roughness of various electrodes were investigated through atomic force microscopy. The biosensing properties of fabricated immunoelectrode were investigated using differential pulse voltammetry and cyclic voltammetry. However, the electrochemical response studies were carried out by using electrochemical impedance spectroscopy technique to measure the concentration of oral cancer biomarker (CYFRA 21-1). Additionally, we have also calculated the sensitivity and stability of fabricated immunoelectrode. It has been observed that the fabricated immunoelectrode shows a high sensitivity of 0.573 Ω mL ng−1, linear detection range of 0–12 ng mL−1, lower detection limit of 0.24 ng mL−1 and having a stability of 5 weeks.