Hybrid Silver Nanowire/Titanium Oxides Nanocomposites as Anode for Dye‐Sensitized Solar Cell Application

In this study, we investigated the effect of adding metallic nanowires in the anode of dye‐sensitized solar cell (DSSC) to improve the photovoltaic efficiency. Photo‐excited electrons can be efficiently transferred to the electrode through the network of the dispersed metallic nanowires added in the anode. We compared the photovoltaic performance with the anodes of standard P‐25, the silver nanowire/P‐25, and the TiO₂ coated silver nanowire/P‐25 DSSC. The DSSC with TiO₂ coated silver nanowires shows significantly improved (about 1.5 and 2.0 times) photovoltaic efficiency and structural durability compared with that of the standard P‐25 and the silver nanowires without coating DSSC. The TiO₂ coated silver nanowire can resist the redox chemical corrosions by iodide ions since they are protected from contact with electrolytes during the photovoltaic reaction by the coated thin TiO₂ layer. The presence of the metal network (silver nanowires) improves the production and transportation of light generated current so as to the photovoltaic efficiency.     

Effects of Core‐modification on Porphyrin Sensitizers to the Efficiencies of Dye‐sensitized Solar Cells

To study dye‐sensitized solar cells (DSSCs) with core‐modified porphyrins as the sensitizing dyes, three porphyrins with an ethynyl benzoic acid as an anchoring group are prepared. The properties of free‐base regular porphyrin (N4), thiaporphyrin (N3S) and oxaporphyrin (N3O) were thoroughly studied by spectroscopic methods, DFT calculations, and photovoltaic measurements. Replacing one of the porphyrinic core nitrogen atoms by oxygen or sulfur considerably changes the absorption spectra. The Soret band of the N3O and N3S observed bathochromic shifts of 3‐9 nm while the Q band reaches 700 nm to the near‐infrared region. The overall conversion efficiencies of the DSSCs based on these porphyrins are in the order N4 (3.66%) ? N3S (0.22%) > N3O (0.01%). The time‐correlated single photon counting observed short fluorescence lifetimes for N3O adsorbed both on TiO₂ and Al₂O₃ which explicates the poor efficiency of DSSC using N3O as the photosensitizer.     

Photoluminescence Properties of Quinidine and Quinidine Sulfate in the Sol‐gel System

The emission spectra of quinidine and quinidine sulfate doped in sol‐gels (tetraethoxysiliane system) have been measured during the sol‐gel transformation. Shifts in the emission spectra from 370 nm to 435 nm were observed in both molecules as the system changed from sol stage to dried glass over a period of two weeks. These shifts are attributed to the conformational changes of the doped molecules. In addition, the process of the signal changes was observed by an emerging new band at ?435 nm with a concomitant decline of the original band at 370 nm during the sol‐gel transformation. These results indicate that the conformational changes induced by the sol‐gel transformation are accomplished in one step instead of several intermediate states.     

Enhanced Efficiency of Dye–sensitized Solar Cells Based on Bulk Synthesized TiO2 Nanorods Annealed at Different Temperatures

In this study, bulk TiO₂ nanorods are synthesized by hydrothermal method in order to be used in the dye‐sensitized solar cells (DSSCs). These nanorods are annealed at different temperatures and deposited electrophoretically. The influence of post heat treatment has been thoroughly investigated on fabricated DSSCs using electrochemical impedance spectroscopy (EIS). The results have revealed that the diameter, size and density of the prepared bulk nanorods are function of annealing temperatures. Optimization of the prepared DSSCs has led to an improved efficiency (ca. 3.82%) under AM 1.5 simulated sunlight.     

Synthesis of Pure Cementitious Phases by Sol‐Gel Process as Precursor

Calcium silicates and aluminates are the main constituents of ordinary Portland cement (OPC) and calcium aluminate cements (CAC) and therefore the pure phases are of great importance for the investigation of interactions between binder and additives or admixtures. Additionally, investigations on clinker phases doped with foreign ions enable the improvement of the performance of cements. For this purpose great amounts of pure phases are needed. These phases are hard to synthesize via a solid state reaction of solid educts. Thus there is a need for a new, more efficient route to synthesize these phases. The sol‐gel process as precursor provides an alternative to the conventional method. In this paper experimental evidence is presented for an improved synthesis of calcium silicates and aluminates via sol‐gel processes, the characterisation of these clinker phases and their hydration behaviour.     

Preparation of GOD/Sol‐Gel Silica Film on Prussian Blue Modified Electrode for Glucose Biosensor Application

A novel amperometric glucose biosensor was fabricated by in situ incorporating glucose oxidase (GOD) within the sol‐gel silica film on a Prussian blue (PB) modified electrode. The method is simple and controllable, which combined the merits of in situ immobilizing biomolecules in sol‐gel silica film by electrochemical method and the synergic catalysis effects of PB and GOD molecules. Scanning electron microscopy (SEM) showed that the GOD/sol‐gel silica film was homogeneous with a large number of three‐dimensional nanopores, which not only enhanced mass transport, but also maintained the active configuration of the enzyme molecule and prevented the leakage of enzyme, therefore improved the stability and sensitivity of the biosensor. The fabricated biosensor showed fast response time (10 s), high sensitivity (26.6 mA cm^?2 M^?1), long‐term stability, good suppression of interference, and linear range of 0.01 mM–5.8 mM with a low detection limit of 0.94 μM for the detection of glucose. In addition, the biosensor was successfully applied to determine glucose in human serum samples.     

Renewable Surface Sol‐gel Derived Carbon Ceramic Electrode Modified with Copper Complex and Its Application as an Amperometric Sensor for Bromate Detection

A sol‐gel technique was used for the preparation of a three dimensional carbon composite electrode modified with [Cu(bpy)₂]Br₂ complex. A reversible redox couple of Cu(II)/Cu(I) is observed at the electrode surface. The electrochemical behavior and stability of the modified electrode was characterized by cyclic voltammetry. The charge transfer coefficient (α) and charge transfer rate constant (K_s) for the modified electrode were determined by cyclic voltammetry, which were found to be 0.46 and 14.2 s^?1, respectively. The modified electrode showed excellent catalytic activity toward bromate reduction at significantly reduced overpotentials and can be used successfully for amperometric detection of bromate. Under the optimized conditions, the calibration plots are linear in the concentration range 0.5 μM ?200μM. Detection limit (signal to noise is 3) and sensitivity were found to be 0.1 μM and 20 nA / μM, respectively. These analytical parameters compare favorably with those obtained with modern analytical techniques. The modified carbon ceramic electrode doped with Cu‐Complex shows a good reproducibility, a short response time (t<2 s), remarkable long term stability (>4 months) and especially good surface renewability by simple mechanical polishing (RSD for 6 successive polishing is 1.5%).     

Sol‐Gel Preparation and Characterization of Codoped Yttrium Aluminium Garnet Powders

A sol‐gel method has been developed to prepare lanthanide‐codoped yttrium aluminium garnet (Y₃Al₅O₁₂, YAG) ceramic samples. The XRD patterns of the polycrystalline Y₃Al₅O₁₂:Nd,Ho and Y₃Al₅O₁₂:Nd,Er powders sintered at 1000 °C showed the formation of monophasic garnet materials. A homogeneous distribution of rare‐earth dopants in the YAG lattice was achieved in both cases. The morphological characterization of lanthanide‐codoped YAG by scanning electron microscopy (SEM) showed the formation of highly agglomerated nanocrystalline samples. The luminescence properties of sol‐gel derived doubly activated yttrium aluminium garnet samples were also investigated in the present study.     

Development of Voltammetric Sensor for Determination of Tryptophan Using MWCNTs‐modified Sol‐gel Electrode

In the present work, an electrochemical sensor was developed for simple and sensitive determination of tryptophan (Trp) using multi‐walled carbon nanotubes modified sol‐gel electrode (MWCNTs/SGE). The electrocatalytic oxidation of tryptophan was investigated by cyclic voltammetry (CV) and differential pulse voltammetry (DPV). It was found that the oxidation peak current of Trp at the MWCNTs/SGE was greatly improved compared with that of the bare SGE. Furthermore, at the MWCNTs/SGE, the anodic peak potential of Trp is shifted about 220 mV to more negative value indicated that modified electrode has better electrocatalytic activity for electro‐oxidation of Trp. The anodic peak currents increased linearly with the concentration of tryptophan in the range of 0.2 × 10^?6 to 15 × 10^?6 M with a detection limit of 0.139 × 10^?6 M (at an S/N = 3).     

A Fast Response Strontium Ion‐Selective Electrode Prepared by Sol‐Gel Membrane Technique

A sol‐gel electrode, based on 6‐(4‐nitrophenyl)‐2‐phenyl‐4,4‐dipropyl‐3,5‐diaza‐bicyclo [3,1,0] hex‐2‐ene (NPDBH) as a neutral ionophore, was successfully developed for the detection of Sr²⁺ in aqueous solutions. Theoretical calculations confirmed NPDBH selectivity toward strontium in comparison with some other metal ions. The electrode responds to Sr²⁺ ion with a sensitivity of 29.1±0.4 mV/decade over the range 8.0×10^?7–1.0×10^?1 M. Selectivity coefficients determined by matched potential method (MPM) indicate high selectivity for strontium ions. The electrode has a fast response time of 11 s and a working pH range of 3.0–10.0. The sol‐gel electrode shows detection limit of 7.5×10^?8 M.     

Adsorption of 4‐tert‐Butylpyridine on TiO2 Surface in Dye‐Sensitized Solar Cells

4‐tert‐Butylpyridine (4‐TBP) has been widely used as additive in dye‐sensitized solar cells (DSC), owing to its improvement of the fill factor and the open circuit voltage of DSC. In this paper, the adsorption of 4‐TBP on the rutile TiO₂(110) surface in DSC was studied by using the density functional theory at DFT/B3LYP level. By comparing the results with those attained from experiments, it was concluded that the 4‐TBP could chemiadsorb on the incompletely covered surface Ti atoms in the electrode. The probable mechanism of compressed recombination by coordinated 4‐TBP in DSC was proposed.     

The Effect of Ionic Liquid Covalent Bonding to Sol‐Gel Processed Film on Ion Accumulation and Transfer

Accumulation of electroactive anions into a silicate film with covalently bonded room temperature ionic liquid film deposited on an indium tin oxide electrode was studied and compared with an electrode modified with an unconfined room temperature ionic liquid. A thin film containing imidazolium cationic groups was obtained by sol‐gel processing of the ionic liquid precursor 1‐methyl‐3‐(3‐trimethoxysilylpropyl)imidazolium bis(trifluoromethylsulfonyl)imide together with tetramethylorthosilicate on the electrode surface. Profilometry shows that the obtained film is not smooth and its approximate thickness is above 1 μm. It is to some extent permeable for a neutral redox probe – 1,1′‐ferrocene dimethanol. However, it acts as a sponge for electroactive ions like Fe(CN)₆^3?, Fe(CN)₆^4? and IrCl₆^3?. This effect can be traced by cyclic voltammetry down to a concentration equal to 10^?7 mol dm^?3. Some accumulation of the redox active ions also occurs at the electrode modified with the ionic liquid precursor, but the voltammetric signal is significantly smaller compare with the bare electrode. The electrochemical oxidation of the redox liquid t‐butyloferrocene deposited on silicate confined ionic liquid film is followed by the expulsion of the electrogenerated cation into an aqueous solution. On the other hand, the voltammetry obtained with the electrode modified with t‐butyloferrocene solution in the ionic liquid precursor exhibits anion sensitive voltammetry. This is explained by anion insertion into the unconfined ionic liquid deposit following t‐butylferricinium cation formation.     

Evaluation of Meldola Blue‐Carbon Nanotube‐Sol‐Gel Composite for Electrochemical NADH Sensors and Their Application for Lactate Dehydrogenase‐Based Biosensors

A novel MB‐SWNT‐sol‐gel nanocomposite material was prepared by the sol‐gel process incorporating a redox mediator and carbon nanotubes. The electrocatalytic properties of the nanomaterial based sensor toward NADH oxidation were studied by electrochemical measurements. Significant enhancement of oxidation current is obtained at electrodes modified by MB‐SWNT‐sol‐gel in comparison with the analogous carbon black and/or graphite composite modified electrode. The usefulness of the nanocomposite material as a matrix for immobilizing enzymes is also demonstrated. Analytical parameters of D ‐lactate biosensors with and without SWNT in the hybrid film were compared demonstrating that performance of the biosensor was significantly improved when introducing SWNT.     

A novel strategy to increase performance of solid‐phase microextraction fibers: Electrodeposition of sol‐gel films on highly porous substrate

In the present work, the effect of substrate porosity for preparation of solid‐phase microextraction (SPME) fibers was investigated. The fibers were prepared by electrodeposition of sol‐gel coatings using negative potentials on porous Cu wire and compared with previous reported technique for preparation of SPME fibers using positive potentials on smooth gold wire. Porous substrate was prepared by electrodeposition of a thin layer of Cu on a Cu wire. The extraction capability of prepared fibers was evaluated through extraction of some aromatic hydrocarbons from the headspace of aqueous samples. The effect of substrate porosity and some operating parameters on extraction efficiency was optimized. The results showed that extraction efficiency of SPME fibers highly depends on porosity of the substrate. The LOD ranged from 0.005 to 0.010 ng/mL and repeatability at the 1 ng/mL was below 12%. Electrodeposited films were characterized for their surface morphology and thermal stability using SEM and thermogravimetric analysis, respectively. SEM analysis revealed formation of porous substrate and subsequently porous coating on the wire surface and thermogravimetric analysis showed high thermal stability of the prepared fiber.     

The Preparation of Dye Sensitized Solar Cell (DSSC) from TiO2 and Tamarillo Extract

Energy crisis is what being faced by every country today. Many efforts have been devoted to overcome the problems. One of several offered solutions is to develop solar cells (SCs) since solar energy is abundant and free to use. Especially in a tropical country like Indonesia, solar energy is available a whole year with quite high power 450 mWcm^-2. Several types of SCs, especially silicon-based, have been mass-produced and applied in our daily life. Silicon-based SC has high efficiency yet has high price. Dye Sensitized Solar Cell is an inexpensive type of SC. The natural ingredients could be utilized as dyes for DSSC. In this research, tamarillo extract was employed as the dye for TiO₂-based DSSC. TiO₂ powder was spin-coated on top of Fluorine- Doped Tin Oxide (FTO) conductive glass and calcined at 550 ̊C, 650 ̊C and 750 ̊C each for 60 and 120 min. Scanning ElectronMicroscope (SEM) and X-Ray Diffractometer (XRD) were used to characterize the morphology and structure of the material. Brunauer-Emmet-Teller (BET) analysis was utilized to measure the material active surface area. As the result, the sample calcined at 650 ̊C for 60 minutes showed the highest electrical performance of 542.5 mV and 0.356 mAcm^-2 which corresponded to an SC efficiency of 0.043%. This result was supported by the BET analysis showing the sample calcined at 650 ̊C for 60 min had the largest active surface area of 9.3 m²g^-1. A large active surface area enabled more dye and electrolyte to be stored inside the material so that photon adsorptions from solar energy became more effective and resulting in higher efficiency. Despite of the small efficiency, this work demonstrated the opportunities of tamarillo and TiO₂ to be applied as a DSSC.     

溶胶凝胶法制备CNT／ZnO纳米复合材料及其光催化性研究

Chemistry and Chemical Engineer School, Henan Institute of Science and Technology, Xinxiang, Henan 453003, China     

Copper Oxide Nanoparticle Modified Sol–Gel‐Derived Carbon Ceramic by Microwave Irradiation,and Its Application for Determination of Adenine at Very Low Potential

In this work the copper oxide nanoparticles simultaneous with sol–gel‐derived carbon ceramic production were synthesized and doped in ceramic by microwave irradiation in a few minutes without using any catalyst and organic solvent. The ceramic composition was characterized by X‐ray diffraction (XRD), X‐ray photoelectron spectroscopy (XPS) and Fourier transforms infrared (FT‐IR), and its surface morphology was investigated by scanning electron microscopy (SEM). The proposed ceramic with detection limit of 0.1 µM, was used for electrocatalytic determination of adenine at potential about 700 mV lower than its usual oxidation potential.     

Application of Poly(3‐hexylthiophene) Functionalized with an Anchoring Group in Dye‐sensitized Solar Cells

A series of three poly(3‐hexylthiophene) functionalized either with a cyanoacetic acid (CA) or a rhodanine‐3‐acetic acid anchoring groups were synthesized and characterized. The TiO₂ based dye‐sensitized solar cells have been fabricated and performances were tested. We show that shorter chain length (15 thiophene units) linked to CA binding group gives good performances as J_sc, V_oc, FF and η(%) were 6.93(mA · cm⁻²), 0.65(V), 0.67 and 3.02%, respectively. A maximum IPCE of ≈50% at 500 nm was recorded with a liquid electrolyte, under AM 1.5 simulated solar irradiance.

     

UV‐Irradiation Cured Organic‐inorganic Hybrid Nanocomposite Initiated by Ethoxysilane‐modified Multifunctional Polymeric Photoinitiator through Sol‐gel Process

The UV‐cured organic‐inorganic hybrid nanocomposite (nano‐Si‐m‐PI) was prepared through the photopolymerization of acrylic resin initiated by ethoxysilane‐modified multifunctional oligomeric photoinitiator (Si‐m‐PI). The esterification reaction of 2‐hydroxy‐4′‐(2‐hydroxyethoxy)‐2‐methylpropiophenone (Irgacure 2959) with thioglycolic acid, and the following addition reactions with dipentaerythritol hexaacrylate and then 3‐aminopropyltriethoxysilane were carried out for preparing the Si‐m‐PI. The Si‐m‐PI exhibits the similar UV absorption and molar extinction coefficient with Irgacure 2959. The photoinitiating activity study by photo‐DSC analysis showed that the Si‐m‐PI possesses high photopolymerization rate at the peak maximum (R_p^max) and final unsaturation conversion (P^f) in the cured hybrid films. From the scanning electron microscope (SEM) observation, the SiO₂ nanoparticles dispersed uniformly in the formed nano‐Si‐m‐PI, whereas the aggregation of nanoparticals occurred in nano‐Irg, which was prepared through the photopolymerization of acrylic resin initiated by Irgacure 2959. Moreover, compared with the UV‐cured pure polymer and nano‐Irg, the nano‐Si‐m‐PI showed remarkably enhanced thermal stability and mechanical properties.     

On‐Line Monolithic Enzyme Reactor Fabricated by Sol‐Gel Process for Elimination of Ascorbic Acid While Monitoring Dopamine

Catecholamine, a well‐known neurotransmitter, is released to restore heart function after the occurrence of cardiac ischemia. Endogenous ascorbic acid interferes considerably with the monitoring of neurotransmitters such as catecholamine and glutamate. In this work we have successfully developed a nanoliter volume monolithic enzyme reactor and integrated it with a carbon film electrode for monitoring dopamine in order to scavenge such electroactive interferents as ascorbic acid. A monolithic silica support prepared by the sol‐gel process has a large through‐pore structure and a nanoporous surface. The low back pressure resulting from the large though‐pore structure makes it possible to immobilize the enzyme and introduce fluid into the flow monitoring system by using a microsyringe pump. Ascorbate oxidase (AOx) was immobilized on the nanoporous surface of a monolithic matrix by physical adsorption and used for converting the ascorbic acid into its electrochemically inert form, dehydroascorbic acid, while monitoring dopamine. We showed that more than 99.8% of 100 μM of ascorbic acid could be converted to its oxidized form in the monolithic enzyme reactor. We succeeded in monitoring dopamine at a concentration of less than 100 nM in the presence of 50 μM of ascorbic acid. Therefore, this work demonstrated that a monolithic silica support offers excellent potential in regards to realizing a highly selective enzymatic reactor for biosensors.