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Nitrogen-doped graphene (NDG)/titanium dioxide (TiO2) nanoparticles were coated on indium-tin oxide (ITO) glass substrates to fabricate NDG-TiO2 nanocomposite electrodes. 3-methylthiophene (3MT) was electrochemically deposited on the NDG-TiO2 films to form poly(3-methylthiophene) (P3MT/NDG/TiO2) composite electrochromic electrodes. The introduction of NDG and TiO2 mesoporous films significantly increased the initial maximum optical contrast (ΔT%) to 70% as compared 41% of pure ITO electrodes, whereas the P3MT/NDG/TiO2 composite electrodes enhanced the adhesion of P3MT polymers to the NDG/TiO2/ITO substrate, thereby increasing the long-term stability of the corresponding electrochromic devices. Experimental results reveal that P3MT/NDG/TiO2 composite electrodes retained up to 90% of ΔT%, relative to 70% remaining ΔT% of pure ITO electrodes. This illustrates the enhanced long-term stability achieved through the introduction of a NDG-TiO2 nanocomposite films in electrochromic devices. These devices demonstrated excellent response time characteristics and ΔT% value of 6 s and ca. of 70%, respectively. This work has shown that conductive polymer/NDG/TiO2 composite electrodes are well suited to electrochromic devices for the promotion of performance and stability.

This study presents a two-stage hydrothermal process to synthesize anatase TiO 2 nanoparticles. The first stage formed sodium titanate (Na 2 Ti 9 O 19 ). Octahedral TiO 6 in Na 2 Ti 9 O 19 shares crystal edges similar to those of octahedral TiO 6 in anatase TiO 2 . This study used Na 2 Ti 9 O 19 as an intermediary to generate pure anatase TiO 2 . The second stage involves disintegrating the structure of the Na 2 Ti 9 O 19 crystals through an ion exchange of Na + in Na 2 Ti 9 O 19 with H + in HNO 3 , resulting in the formation of pure anatase TiO 2 nanoparticles (7 to 10 nm). The static (acid addition) and space repulsion (binder addition) methods (surface area with BET = 81.594 m 2 g −1 ) were used to hinder the coalescence of TiO 2 nanoparticles. The proposed approach produces well-dispersed nanoparticles compared to the method using only static repulsion (surface area with BET = 68.071 m 2 g −1 ). These two TiO 2 materials were used to prepare photoelectrodes with a film thickness of approximately 6 μm in dye-sensitized solar cells (DSSCs), which achieved device efficiencies of 6.23% and 4.66%, respectively.

A systematic analysis for mixed dyes of D131, D149, and N3 ternary components on performance of dye-sensitized solar cells (DSSCs) has been performed. Using an experimental design of mixture, empirical models are fitted and plotted as contour diagrams, which facilitate revealing the synergistic/antagonistic effects between these mixed dyes. Dye co-sensitization effects in DSSCs are proved by the photo-physic properties, efficiency of the DSSC devices, and kinetic parameters of photo-electron transfer. The performance of DSSCs is significantly affected by the composition of dyes. The optimal efficiency (ca. 9.5%) of these mixed-dye DSSCs exists at the composition of 1/2 D149–1/2 N3. This composition appears to help conveying the charge transfer from the excited dye molecules to the conduction band of TiO 2 , leading to a higher efficiency of the assembled devices. Supplementary study of the electrochemical impedance are in support of enhancing charge transfer of TiO 2 (e − ) with the co-sensitized dyes.

This study investigates the electrocatalytic activities of carbon nanotubes (CNTs) in temperature-responsive poly(N-isopropylacrylamide) (PNIPAAm) composites with a low critical solution temperature of about 32 °C. The composite cast on a glassy carbon electrode (GCE) as working electrode was investigated by cyclic voltammetry (CV) using potassium ferricyanide as a probe. The factors examined included the temperature (25 and 37 °C, denoted as 25f and 37f) at which GCE was modified, content of CNT in the composite, acid treatment of CNT, and working temperature (25 and 37 °C, denoted as 25aq and 37aq) of GCE. The CV data revealed that a higher content of CNT and COOH-functionalized CNT (fCNT) in the composite exhibited a higher electrocatalytic activity. The electrocatalytic activity of the modified GCE was also found to be significantly temperature dependent. The fCNT/PNIPAAm composite with the 25f–37aq temperature combination exhibited strong electrocatalytic activity and highly selective detection ability for the three analytes (dopamine, uric acid, and ascorbic acid). In contrast, the same composite with the other three combinations (25f–25aq, 37f–25aq, and 37f–37aq) and the CNT/PNIPAAm composite with all four combinations exhibited insignificant electrocatalytic activity and no selective detection ability.

Self-doped conducting polyaniline-modified indium tin oxide (ITO) electrodes were prepared by cyclic voltammetry on ITO substrates in aniline (AN) and o-aminobenzene sulfonic acid (OSA) mixed monomer solutions with AN/OSA mole ratios of 25/75, 50/50, and 75/25, followed by investigations on electrocatalytic activities of the copolymers to redox reactions of Fe(CN)63−/4− as a probe in aqueous solutions of different pH using cyclic voltammetry. For a given pH, the P(25AN-co-75OSA)-modified ITO electrode demonstrated the highest current density, followed by the P(50AN-co-50OSA)- and by the P(75AN-co-25OSA)-modified ITO electrodes. It can be concluded that a higher content of OSA (sulfonate) in the copolymer exhibited a higher extent of self-doping in the copolymer, leading to a higher electrocatalytic activity to redox reactions of the probe. The electrocatalytic activities of the copolymers decreased with increasing pH. The P(25AN-co-75OSA)-modified ITO electrode was electroactive for sensing the redox reactions of the probe in aqueous solutions of up to pH 7, the P(50AN-co-50OSA)-modified ITO electrode was electroactive for up to only pH 5, but the P(75AN-co-25OSA)-modified ITO electrode was not electroactive in aqueous solution of pH even as low as 2.

Organic dyes are synthesized containing bridging ethylenedioxythiophenes (EDOT) between the electron donors and electron acceptors (2-cyanoacetic acid) on carbazole–triphenylamines. These compounds are then characterized by photophysical, electrochemical, and theoretical computational methods. Nanocrystalline TiO 2 -based dye-sensitized solar cells (DSSCs) are fabricated using these dye molecules as light-harvesting sensitizers. The overall efficiency of the sensitized cells is high (5.20%) compared to the efficiency of a cis-di(thiocyanato)-bis(2,2′-bipyridyl)-4,4′-dicarboxylate ruthenium (II) (N3 dye)-sensitized device (7.57%) fabricated and measured under the same conditions. The dye (ETPA3) containing one carbazole, two EDOT bridges, and two 2-cyanoacetic acid groups appears to assist in the charge transfer from the excited dye molecules to the conduction band of TiO 2 , leading to the higher efficiency of the devices using assembled with this dye. A supplementary study of the electrochemical impedance supports the enhancement of the charge transfer of TiO 2 (e − ) with the ETPA3 dye. A computational examination of the ETPA3 compound also indicates higher charge transfer efficiency in the electronically excited state.

A biosensor electrode possessing highly sensitive and selective determination of dopamine (DA) is fabricated. This electrode, a silver (Ag) thin film on indium-tin-oxide glass, is treated with a silver sulfide (Ag2S) film using electrochemical deposition. Active Ag ion is easier to form on Ag2S than on pristine Ag, which prefers to attract ascorbic acid (AA). The Ag2S layer reduces the oxidation potential of AA due to the electrostatic interaction, which results in well-separation of mixed oxidation responses to both of DA and AA. Besides, the Ag2S-modified electrode exhibits dramatic electrocatalytic effect on the oxidation of DA in the presence of AA. In 0.1 M phosphate buffer solution at pH ∼ 7.0, the differential pulse voltammetric peak intensity linearly correlates with DA concentration in two regions, viz. 1.0–10, and 10–100 μM, with correlation coefficient of 0.998 and 0.995, respectively. The lowest concentration limit of 1.0 μM DA can be detected. The interference of AA effectively diminishes in the mixed solution. These features make the Ag2S significant for selective and sensitive measurement of DA in the presence of excess AA.

The electrodeposition of platinum microparticles into a 2,5-diaminobenzenesulfonic acid-modified polyaniline (SPANI) film on IrO 2 electrodes and its electrosorption for methanol and sorbitol, respectively, are described. Electrodeposited platinum microparticles under constant potential are dispersed in a three-dimensional array in porous SPANI films as evidenced by Auger electron spectroscopy (AES). Characterization of the Pt/SPANI/IrO 2 electrodes by SEM shows that the deposition procedure yields spherical catalyst particles. X-ray photoelectron spectroscopy (XPS) results show that there is not significant variability in the binding energy of carbon and nitrogen, respectively, on SPANI chains for different Pt loadings. For catalyst loading of ca. 7 mg cm −2 deposited at −200 mV, the electrosorption coverages of sorbitol are always greater than that of methanol about 15%. In comparison to sorbitol, the readsorption of methanol on Pt catalyst site occurs significantly during electrosorption.