In this research, an azobenzenecarboxylic acid was used as a sufficient co-adsorbent in combination with N719 dye. As it is found from the results, an optimized concentration of the co-absorbent leads to the highest efficiency. The dye-sensitized solar cells (DSSCs) parameters such as short-circuit current (Jsc), open-circuit voltage (Voc) and conversion efficiency (η) were obtained -14.87 mA/cm 2 , 0.765 V and 5.20% respectively. Based on the results, the N719/Azobenzenecarboxylic-based system shows a significant increase in Voc and Jsc, resulting in an ∼21% improvement in the efficiency. A higher conversion efficiency for the co-adsorbent-based systems was assigned to their enhanced η, which is attributed to reduced dye aggregation, higher electron injection and increased Voc. This corresponded to the improved electron density in the TiO 2 conduction band of the photoanode and reduced charge recombination revealed through electrochemical impedance spectroscopy measurements. Also, evidence was provided for a long charge life time and a high resistance of charge recombination for the co-absorbed solar cells.

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Summary In this research, to optimize the surface of the photoanode, two different types of surface coatings were used and their effects on the photovoltaic parameters were investigated. Also, to compare the two different electrolytic systems based on liquid and gel‐state electrolyte, the novel magnetic core‐shell nanocellulose/titanium chloride (Fe3O4@)NCs/TiCl) nanocomposite was introduced into a polymeric system as a nanofiller to decrease the crystallinity of the polymer and enhance the diffusion of triiodide ions in quasisolid‐state dye‐sensitized solar cells (QS‐DSSCs). For this purpose, Fe3O4@)NCs/TiCl was synthesized by coprecipitation of Fe3+ and Fe2+ ions in the presence of nanocellulose and then used as magnetic support for bonding TiCl4 to prepare QS‐DSSCs. Containing a 10.0 wt% magnetic nanocomposite, it displayed a higher apparent diffusion coefficient (Dapp) for I3− ions (4.10 × 10−6 cm2/s) than the gel polymeric electrolyte (GPE) did (1.35 × 10−6 cm2/s). GPEs were characterized using various techniques including current density‐voltage curves, AC impedance measurements, and linear sweep voltammetry (LSV). The photovoltaic values for the short‐circuit current density (Jsc), open‐circuit voltage (VOC), and fill factor (FF) and the energy conversion efficiency (η) of the novel Fe3O4@NCs/TiCl nanocomposite–based QS‐DSSCs were 14.90 mA cm−2, 0.757 V, 64%, and 7.22%, respectively.

A modified carbon paste electrode with 2,2 0 -(1,3-propanediylbisnitriloethylidine)bis-hydroquinone (PBNBH) and TiO 2 nanoparticles has been fabricated and used to study the catalytic oxidation of dopamine (DA), uric acid (UA) and tryptophan (Trp). The overpotential of DA reduced about 0.36 V. Based on its strong catalytic function toward the oxidation of DA, UA and Trp, the modified electrode resolved the overlapping voltammetric response of DA, UA and Trp into three well-defined voltammetric peaks with square wave voltammetry (SWV), which can be used for the simultaneous determination of these species in a mixture. The catalytic peak currents obtained from SWV were linearly dependent on the DA concentration in the range 2.0-10.0 mM and 10.0-1000.0 mM with correlation coefficients of 0.9993 and 0.9998, respectively. The detection limit (2s) for DA was 0.47 mM. The modified electrode showed good sensitivity and selectivity and has been applied to the determination of DA, UA and Trp simultaneously in real samples with satisfactory results.

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