Ternary TiO2 Research Articles

Decoration of Carbon Dots on Oxygen-Vacancy-Enriched S-Scheme TiO2 Quantum Dots/TiO2 Oxygen Vacancies Photocatalysts: Impressive Quantum-Dot-Sized Photocatalysts for Remediation of Antibiotics, Bacteria, and Dyes.

Today, cleaning the environment using photocatalytic technology is one of the main research activities. In this study, carbon dots (C-dots) were anchored on oxygen-vacancy-enriched TiO2 quantum dots (QDs)/TiO2 oxygen vacancies (OVs) using a facile procedure. The resultant ternary TiO2 QDs/TiO2 OVs/C-dots photocatalysts with a quantum dot size of almost 4.55 nm were used for detoxification of aqueous solutions containing four antibiotics and three organic dyes as well as inactivation of two pathogenic bacteria, including Escherichia coli and Staphylococcus aureus, upon visible light. The degradation constant of tetracycline over the optimized TiO2 QDs/TiO2 OVs/C-dots nanocomposite reached 714 × 10-4 min-1, which was 17.3, 12.1, and 2.92 times higher than TiO2 QDs, TiO2 OVs, and TQDs/TOVs (1:1) materials, respectively. Effective separation of electron-hole pairs between TiO2 QDs and TiO2 OVs counterparts through decorated C-dots by an established S-scheme system was the main reason for boosted photocatalytic activity. With regard to the facile growth of wheat and lentil seeds in the treated solutions, it is hoped that the TiO2 QDs/TiO2 OVs/C-dots nanocomposite with significant stability could be used to clean up wastewaters.

Incorporation of Cu5FeS4 QDs with Abundant Oxygen Vacancy TiO2 QDs/TiO2 OVs: Double S-Scheme Photocatalysts for Effectual N2 Conversion to NH3 under Simulated Solar Light.

Photocatalytic N2 conversion to NH3 is a green, sustainable pathway with renewable energy sources and carbon neutrality. In this research, ternary TiO2 QDs/TiO2 OVs/Cu5FeS4 nanocomposites were prepared by an easy and affordable procedure and utilized to produce clean ammonia energy without a sacrificial agent. The amount of produced green ammonia by the optimum nanocomposite achieved was 17,274 μmol L-1 g-1, which was approximately 20.9, 6.48, 4.45, 2.26, and 1.45 times higher than those of commercial TiO2, TiO2 QDs, TiO2 OVs, Cu5FeS4, and TiO2 QDs/TiO2 OVs photocatalysts, respectively. Lattice compatibility through the developed homojunction within TiO2 QDs/TiO2 OVs and the integration of Cu5FeS4 nanoparticles led to the establishment of a double S-scheme homo/heterojunction system, which improved the photocatalytic activity by maintaining electrons and holes with high oxidation and reduction power and greatly reduced the recombination of charges, which led to the acceleration of charge transfer and migration. Besides, the promoted surface area compared to the pure components, introducing oxygen vacancies, and reducing the particle size boosted the photocatalytic N2 conversion to NH3. The results of this research are a basis for the rational design of homojunction/heterojunction visible-light-responsive systems for photocatalytic nitrogen fixation reactions.

Facile synthesis of reduced graphene oxide and graphitic carbon nitride modified titanium dioxide nanospheres for photoanode of dye-sensitized solar cell

Titanium dioxide/reduced graphene oxide nanocomposites (TiO2/rGO NCs) have been broadly utilized as photoanode materials for dye-sensitized solar cell (DSSC). Nevertheless, photoelectric conversion efficiency (PCE) of DSSC is diminished due to recombination of charges takes place between photoanode and electrolyte interface. Herein, we have prepared a triplet structure nanocomposite composed of TiO2 nanospheres, rGO and graphitic carbon nitride (TiO2 NS/rGO/g-C3N4 NC) for photoanode of DSSC. The ternary TiO2 NS/rGO/g-C3N4 NC photoanode has enhanced dye absorption considerably and as a consequence, improved light harvesting efficiency. Besides, the introduction of rGO and g-C3N4 on the TiO2 NS has effectually speeded up the transport of electrons and minimized the recombination of photogenerated charges. Consequently, the DSSC integrated with ternary TiO2 NS/rGO/g-C3N4 NC photoanode has exhibited ∼41 % increment in the PCE of 5.77 % when compared to PCE of the pristine TiO2 NS photoanode (4.10 %). This finding has proposed a simplistic approach to advance photovoltaic performance of the DSSC.

Supercritical carbon dioxide-assisted TiO2/g-C3N4 heterostructures tuning for efficient interfacial charge transfer and formaldehyde photo-degradation

Long exposure to formaldehyde has been a concern for causing respiratory problems and TiO2/g-C3N4 composite is a potential choice to address this issue. This study developed a supercritical carbon dioxide (ScCO2)-assisted method to fabricate TiO2/g-C3N4 composites with two distinct heterostructures. The g-C3N4 nanosheet/TiO2 nanoparticle (denoted as type 1 heterostructure) heterojunction could accelerate electron migration because of its large interfacial surface contact. The ternary TiO2{101}/g-C3N4/TiO2{001} heterojunction (denoted as type 2 heterostructure) was synthesized for the first time, further promoting the separation of photogenerated electron/hole pairs under full-spectrum irradiation because it provided an additional migration channel for photocarriers. By loading different amounts of TiO2, the heterostructures were modulated, thereby influencing the photoactivity of the composites. The TiO2/g-C3N4 composite with 58% TiO2 loading possessed the best photocatalytic performance, achieving the highest rate constant for formaldehyde degradation, approximately 7 times higher than pure bulk g-C3N4 under either visible or full-spectrum light. Under full-spectrum irradiation, the maximum decomposition rate approached nearly 100% within 90 min. The tuned heterostructures facilitated the generation of O2·− and·OH, which were dominant active oxygen radicals responsible for formaldehyde removal under light irradiation. Thus, this study developed a green route to synthesize composites with tunable heterojunctions and enhanced photocatalytic activity that can be used for indoor air pollutant degradation.

The construction of TiO2 NTs/Ag3PO4–AgBr by SILAR deposition as promising photocatalysts for hydrogen production and pollutant treatment

The construction of ternary TiO2 NTs/Ag3PO4–AgBr photocatalysts was carried out by the SILAR deposition of Ag3PO4 and AgBr on TiO2 nanotube arrays (TiO2 NTs) for enhancing the photocatalytic application in H2 evolution and dyeing wastewater remediation. The adjustment of Ag3PO4/AgBr deposition cycles was used to optimize the optical absorption and photocatalytic property. The TiO2 NTs/Ag3PO4–AgBr (5) prepared with 5 cycle deposition of Ag3PO4 and AgBr exhibited the optimal photoelectric activity and photocatalytic performances. The photocatalytic rate constants for the degradation of MO, RhB and MB dyes achieved 1.35 × 10−2, 3.30 × 10−2 and 4.47 × 10−2 min−1, respectively, and the visible light-driven photocatalytic H2 evolution rate achieves 46.87 μmol cm−2 h−1. •O2− radicals exhibited the key influence on the organic dye degradation, and the as-prepared photocatalysts showed exceedingly high photocatalytic activity and stability. Furthermore, the photocatalytic mechanism was proposed based on the ESR result.

Multifunctional TiO2 Nanotube-Matrix Composites with Enhanced Photocatalysis and Lithium-Ion Storage Performances.

As a multifunctional material, TiO2 shows excellent performance in catalytic degradation and lithium-ion storage. However, high electron-hole pair recombination, poor conductivity, and low theoretical capacity severely limit the practical application of TiO2. Herein, TiO2 nanotube (TiO2 NT) with a novel double-layer honeycomb structure were prepared by two-step electrochemical anodization. Honeycombed TiO2 NT arrays possess clean top surfaces and a long-range ordering, which greatly facilitates the preparation of high-performance binary and ternary materials. A binary TiO2 nanotube@Au nanoparticle (TiO2 NT@Au NP) composite accompanied by appropriately concentrated and uniformly distributed gold particles was prepared in this work. Interestingly, the TiO2 nanotube@Au nanoparticle (TiO2 NT@Au NP) composites not only showed the excellent catalytic degradation effect of methylene blue, but also demonstrated large lithium-ion storage capacity (310.6 μAh cm-2, 1.6 times of pristine TiO2 NT). Based on the realization of the controllable fabrication of binary TiO2 nanotube@MoS2 nanosheet (TiO2 NT@MoS2 NS) composite, ternary TiO2 nanotube@MoS2 nanosheet@Au nanoparticle (TiO2 NT@MoS2 NS@Au NP) composite with abundant defects and highly ordered structure was also innovatively designed and fabricated. As expected, the TiO2 NT@MoS2 NS@Au NP anode exhibits extremely high initial discharge specific capacity (487.4 μAh cm-2, 2.6 times of pristine TiO2 NT) and excellent capacity retention (81.0%).

Relaxation processes in TiO2–V2O5–P2O5 glass-ceramics

Bulk samples of the ternary TiO2–V2O5–P2O5 system have been synthesized by the melt-quenching technique. X-ray diffraction and scanning electron microscopy with energy-dispersive spectroscopy were applied for structure and composition identification, whereby the presence of NASICON and Rutile type structures were identified. Dielectric properties were measured using impedance spectroscopy, at frequencies from 10 mHz to 1 MHz, and temperatures between 40 °C and 190 °C.Different relaxation models were applied to fit the experimental data. The electrical conductivity and activation energy of the glass matrix and crystalline particles were calculated and correlated to the structure of the material. The impedance spectra were analyzed with the complex dielectric modulus and the Distribution Function of Relaxation Times method to corroborate and complement the results of equivalent circuit models. The grain conductivity was shown to reach 10-1 S/m at 190 °C for the NASICON sample.

Simultaneous Adsorption and Photocatalysis Processes Based on Ternary TiO2–CuxS–Fly Ash Hetero-Structures

Ternary composites of TiO2–CuxS–fly ash were used in simultaneous adsorption and photocatalysis processes for the removal of organic (dye) pollutants. Composites of semiconductor (TiO2, CuxS) nanomaterials hosted within matrices of fly ash, such as film heterostructures, are promising materials for advanced wastewater treatment. The combination of adsorption and photocatalysis processes was investigated in the removal of methylene blue (MB), considered as a standard in photocatalysis. Ternary film heterostructures obtained by doctor blade technique allows overcoming the separation step of particles from treated wastewater. The comparison between the adsorption and photodegradation tests performed with TiO2–CuxS–fly ash showed that in dark conditions, the MB removal was 75% after 360 min, while in the presence of UV radiation, almost total dismissal of MB was achieved in the same treatment period. The degradation rate of MB, when H2O2 is used as an electron acceptor, could reach 90% in adsorption and 99% in simultaneous adsorption/photocatalysis processes. The adsorption isotherm was found to follow the Langmuir and Freundlich models.

In situ fabrication of ternary TiO2 doped grafted chitosan/hydroxyapatite nanocomposite with improved catalytic performance for the removal of organic dyes: Experimental and systemic studies

A hetero-structured photocatalysts with enhanced mineralization capacity has been obtained significant consideration due to their improved performance in environmental purification process. Wrapping of TiO2 and hydroxyapatite with suitable biopolymer will improve the specific surface area, porosity, stability and provides enhanced degradation efficiency. Herein, TiO2 reinforced hydroxyapatite (TiO2@CS-Hpt) nanocomposite matrix was synthesized proficiently by co-precipitation technique. Here, chitosan acted as a spine in the fabrication and afforded the surface for a composite generation. Photocatalysis was the method used universally for elimination of inorganic and organic impurities from water. Herein, an integrated flexible TiO2 imprinted chitosan/hydroxyapatite (TiO2@CS-Hpt) composite was fabricated and utilized for treating water contaminated with of Methylene Blue (MB) and Rhodamine B (RhB) dyes, via photo-degradation method. The prepared TiO2@CS-Hpt was characterized extensively using FTIR, XRD, SEM-EDX, TEM, PL and UV/Vis-DRS techniques. X-ray photoelectron spectroscopy served to confirm that the dyes underwent photo-reduction. The DRS results implies the reduction in band gap to of TiO2@CS-Hpt 2.01 eV as against 3.23 eV of TiO2. The results specified that the maximum degradation were 98.6 % and 96.7 % for MB and RhB respectively, in the experiment with the initial dye concentration 50 mg L−1, 0.1 g L−1 of photocatalyst, TiO2@CS-Hpt, pH 7 and under 120 min of light exposure. The photocatalyst reusability has been retained up to seven cycles and the practical applicability for the treatment of water/wastewater was ensured by field trial.

BiOBr and BiOCl decorated on TiO2 QDs: Impressively increased photocatalytic performance for the degradation of pollutants under visible light

BiOBr and BiOCl were decorated on TiO2 QDs through n-p-p heterojunctions by a simple strategy and they were applied for degradation of three organic dyes upon visible illumination. The obtained photocatalysts were analyzed via XRD, FESEM, EDX, UV–vis DRS, PL, BET, TEM, HRTEM, FT-IR, EIS, XPS, and transient photocurrent measurements. The TiO2 QDs/BiOBr/BiOCl nanocomposite with 20% wt. of BiOBr and 30% wt. of BiOCl displayed superior photoability in the degradation of methylene blue, rhodamine B, and fuchsine, which was almost 34.5, 176, and 78.7-times larger than TiO2 and 27.8, 13.5, and 51.5-folds greater than TiO2 QDs, respectively. The results show that the construction of intimate n-p-p heterojunctions between BiOBr, TiO2 QDs, and BiOCl counterparts leads to enhanced visible-light harvesting and improved charge separation, resulted efficiently increased photocatalytic activity. The trapping results proved that h+, •O2−, and OH• species have considerable effects on the degradation reaction. We think that the improved efficiency of the ternary TiO2 QDS/BiOBr/BiOCl photocatalyst is a splendid alternative for the removal of toxic contaminants from wastewater.

Phase formation, stability and heat capacity of ternary TiO2–CeO2–ZrO2 solid solutions

Tetragonal zirconia based solid solutions are important materials for thermal barrier coatings (TBCs). The introduction of the third component to binary zirconia systems is regarded as a promising way to design novel high performance TBCs. The work reports the investigation of solid solution formation in ternary TiO2–CeO2–ZrO2 system in the range 600–1100 °C obtained by using co-precipitation from mixed aqueous solution and freeze-drying. Phase evolution and stability of solid solutions were investigated using DSC, qualitative and quantitative XRD analysis with Rietveld refinement technique. The factors affecting the kinetics of phase formation i.e. powders dispersity, agglomerate strength, crystallite size, Ce3+/Ce4+ ratio were studied using PSD, XRD and ESCA techniques. The heat capacity dependence on temperature was measured experimentally for the first time for 5TiO2–9CeO2–86ZrO2 composition via calorimetry technique using DSC. The obtained data significantly contributes to the schematic phase diagram suggested in the literature and allows to choose the optimal synthesis and processing conditions of ternary system compositions for their use for novel TBCs fabrication.

Highly efficient, visible active TiO2/CdS/ZnS photocatalyst, study of activity in an ultra low energy consumption LED based photo reactor

Nano Titania is the promising material for the photocatalytic process used in the minimization of the organic pollutant. However, there is need to enhance its absorption and surface properties to design a material having high efficacy. In this study, we report the synthesis of binary and ternary TiO2 nano-composites using the CdS and ZnS nanoparticles by adopting the low temperature two-step hydrothermal approach. The synthesized materials were characterized by using XRD, UV-DRS, FESEM, HRTEM, XPS and BET surface area analyzer. The photocatalytic activity was evaluated by taking the Rhodamine B (RhB) as model pollutant by employing an ultra low LED photo reactor. It was found that, the ternary TiO2/CdS/ZnS composite containing 10% ZnS and 20% CdS in wt. ratio showed the best activity towards the removal of RhB. The enhanced activity was due to improvement in the absorbance in the visible region and formation of heterojunction, which enhanced the lifetime of photoinduced charged species by the reduction in charge recombination. Reactive species, prominently responsible for degradation was identified by the scavenger action. The degradation pathway by which the RhB degraded is also discussed and found that degradation pathway altered with pH of solution.

Strategies for Tuning Optoelectronic Properties of TiO2 Nanomaterials for Solar Photovoltaic Studies

Third generation solar cells are mainly focusing on the use of nanomaterials as host components for solar-to-electrical conversions. Among the various nanomaterials, TiO2 is one of the most promising candidates used in solar devices due to their remarkable structural and opto-electrical properties. However, bare TiO2 nanomaterials have the various constraints in efficient solar energy conversions. In the present research endeavors, TiO2 nanomaterials have been modified with the different strategies such as dyad anchoring, dye-quantum dot sensitization, composites of carbon nanostructures with sensitizers, metal ion doping with sensitizers so as to tune its optoelectronic properties for efficient solar energy harvesting. In addition, the interconnectivity between the various components and their optoelectronic properties of modified TiO2 for solar energy conversions have been studied in detail. In the dyad system, a supramolecular ruthenium(II)phthalocyanine··peryleneimide (RuPc···PI) has been anchored on the surfaces of TiO2 and thereafter these TiO2-dyad sensitized solar cells have assembled in a bottom-up fashion. Upon photo-irradiation at air-mass (AM) 1.5, the dyad-based solar devices convert solar light to electricity of 2.1%; which is higher than that of individual dyes. In next strategies, the synthesized CdS quantum dots (QDs) have connected electrostatically to the surfaces of TiO2 nanoparticles (NPs) and thereafter, this binary hybrid heterojunction is further self-assembled physically with N719 dye to form ternary TiO2 NPs-CdS QDs-N719 photoelectrodes. These co-sensitization devices reported the solar energy conversion efficiency (η) up to 2.35 %. In addition, anatase TiO2 NPs is anchored on the surface of functionalized carbon nanostructures (MWCNTs or RGO); which is further sensitized with Ru(II) dyes for solar devices having efficiency reached to 6.21%. In another modification, Cr(III) as well as Mo(VI) ions are inserted into TiO2 host lattice and then their composites with CNs are further sensitized for boosting the solar energy conversions and reached up to 7.69 % of efficiency. Figure 1

Preparation of novel ternary TiO2 QDs/CDs/AgI nanocomposites with superior visible-light induced photocatalytic activity

In this research, visible-light-induced TiO2 QDs/CDs/AgI photocatalysts were synthesized by simple refluxing strategy. Various instruments such as TEM, HRTEM, FESEM, EDX, XRD, XPS, PL, EIS, photocurrent, FT-IR, BET, UV–vis DRS, and Mott–Sckottky were exploited to investigate their characteristics. Photocatalytic abilities of the as-obtained samples were assessed by decomposition of MB, fuchsine, RhB, and phenol upon visible light. The optimum TiO2 QDs/CDs/AgI (30%) nanocomposite completely degraded RhB after 30 min. This enhancement is about 77, 6, and 2.7 times as premiere as those of the bare TiO2, TiO2 QDs, and TiO2 QDs/CDs (0.25 mL) samples, respectively. These increments of photocatalytic ability is credited to the more generation and transfer of e–/h+ pairs among TiO2 QDs, CDs, and AgI counterparts and improved textural features. The higher photocatalytic activity and long-term stability results proved that the TiO2 QDs/CDs/AgI (30%) nanocomposite could be an auspicious candidate for the elimination of different organic contaminants in the ecosystem. Moreover, a reasonable mechanism for the photodegradation of pollutants was also proposed.

Enhanced photocatalytic degradation of hazardous industrial pollutants with inorganic–organic TiO2–SnO2–GO hybrid nanocomposites

This study reports the photocatalytic degradation of hazardous dyes, methylene blue and reactive orange 4 (RO4) using various compositions of binary TiO2–SnO2 and ternary TiO2–SnO2–GO hybrid nanocomposites under UV-light irradiation. The ternary inorganic–organic hybrid nanocomposites degrade these dyes more efficiently as compared to binary nanocomposites. Novel addition of graphene oxide (GO) to binary composites leads to enhanced degradation ability of the resulting ternary nanocomposite, owing to increase in oxidative potential and surface to volume ratio. The structural, morphological and optical properties of the composites and their constituents have been investigated by X-ray diffraction, high-resolution transmission electron microscopy (HR-TEM), Fourier-transform infrared spectroscopy, Raman spectroscopy and UV–Vis spectroscopy. The HR-TEM images confirm the formation of inorganic–organic hybrid nanocomposites, with ternary nanocomposites having smaller particle size. Raman spectra confirm the proper mixing of various constituents of the composites. The ternary nanocomposites show ultrahigh degradation efficiency as compared to binary nanocomposites. Specifically, ternary nanocomposite with 0.10 mg GO, degraded 99.2% RO4 in just 15 min as compared to binary nanocomposite which degraded 98% RO4 in 50 min. The present study provides a new insight in the field of hybrid nanocomposite photocatalysis for degradation of hazardous dyes in wastewater.

MOF-derived hollow TiO2@C/FeTiO3 nanoparticles as photoanodes with enhanced full spectrum light PEC activities

In the current work, the ternary TiO2@C/FeTiO3 (TCF) hollow nanotubes are synthesized using MOF-Fe nanorods as a sacrificial template and precursor via the thermal carbonization under N2 atmospheres. Due to such delicate structure features that consist of hollow needle-like framework, middle conductive-layer carbon and monodisperse FeTiO3 nanoparticles embedded on carbon layer, the hollow TCF composites can effectively harvest full spectrum light energy, enhance the interfacial charge separation and suppressed the recombination of photogenerated electron-hole pairs, resulting in enhanced photoelectrocatalytic (PEC) activity. Among as-synthesized samples, TCF-20% photoanode exhibits the best performance towards the degradation of phenol under full spectrum light irradiation with an anodic bias of 1.5 V vs. SCE and the degradation rate constant is 0.586 h−1, which is 2.75 times larger than that of the corresponding sum of both EC and PC process. In addition, triple synergistic effects of the possible mechanism with the enhancement of PEC activity was proposed on the basis of PEC degradation results. This work also opens a new insight for synthesis of photocatalysts based on novel MOFs.

Preparation and enhanced visible-light photoelectrocatalytic activity of ternary TiO2[sbnd]ZnO/RGO nanocomposites

TiO2ZnO/RGO nanocomposite was successfully synthesized via a hydrothermal method. The morphology, structure and photocatalytic performance were characterized by XRD, TEM, XPS, FT-IR, UV–vis DRS, CV and EIS. The photocatalytic performance of ZnO, TiO2, TiO2ZnO and TiO2ZnO/RGO for degradation of methyl orange (MO) were explored under visible-light irradiation. Results showed that the TiO2ZnO/RGO nanocomposite exhibited the best photocatalytic activity due to the improved light utilization and charge transfer property, which is consistent with the EIS results of the charge-transfer resistance of TiO2 > TiO2ZnO > TiO2ZnO/RGO > ZnO. Meanwhile, for TiO2ZnO/RGO nanocomposite in the decomposition of methyl orange (MO) under visible-light irradiation, the degradation kinetics was faster than the other samples, which could be completed within 100 min. The results suggested that TiO2ZnO/RGO nanocomposite has a promising in practice for applications in water and wastewater treatment.

Low-cost synthesis of titanium dioxide anatase nanoclusters as advanced materials for hydrogen photoproduction

Sub-nm titanium dioxide (TiO2) clusters are synthesized via the hydrolysis of TiCl4 in order to produce clean and surfactant-free oxide surfaces. By controlling the synthesis, stable TiO2 nanoclusters with well-defined size distributions are obtained. The prepared clusters are characterized using transmission electron microscopy (TEM), scanning electron microscopy (SEM) and Raman spectroscopy in order to gain information about the size and morphology of the material. Photoresponsive methylene blue dye monitoring and hydrogen production under UV irradiation are described in detail and performed. The rate order of photodegradation and hydrogen photoproduction under UV light irradiation of the samples is increased by decreasing the size of TiO2 nanoparticles from 47 nm to 3 nm. The hydrogen evolution rate of TiO2 nanoclusters with size lower than 5 nm is about 3.03 times and 1.96 times faster than that of 47 nm of TiO2 and 12 nm of TiO2, respectively. The enhanced photocatalytic performance suggests that the ternary TiO2 nanoclusters can serve as a highly efficient catalyst for photodegradation of organic pollutants in aquatic environments and hydrogen production from water splitting.

Hydrothermal synthesis of 3D urchin-like Ag/TiO2/reduced graphene oxide composites and its enhanced photocatalytic performance

Innovative 3D urchin-like ternary TiO2 composites, which combine Ag nanoparticles with graphene, have been successfully synthesized through a simple hydrothermal method. This process employed nontoxic and mild dihydrate sodium citrate as a reducing agent. During the hydrothermal process, graphene oxide and AgNO3 were reduced to reduced graphene oxide (RGO) and Ag, respectively. Subsequently, they were grown on the surface of rutile TiO2 with a 3D urchin-like microsphere (1.5 μm). The as-prepared 3D urchin-like composites were characterized by X-ray diffraction, SEM and TEM. These techniques were also employed to ensure the morphology of urchin-like and rutile phase of TiO2. FT-IR, Raman spectroscopy and XPS characterization demonstrated the successful reduction in AgNO3 and graphite oxide to metallic Ag and RGO. The UV–visible spectrum of the ternary composite displayed strong absorption in the visible light region, which was attributed to the efficient electron transport of well-dispersed Ag nanoparticles (20–40 nm) and the formation of Ti–O–C bond between graphene and titania. The synthesized urchin-like ternary composite exhibited enhanced photocatalytic activity (98.7 %) for Rhodamine B degradation. This work provides a very convenient chemical route to the scalable production of Ag/TiO2/RGO ternary composite photocatalyst for potential applications in solving the environmental problems and energy issues. Also, the proposed mechanism underlying the photocatalytic degradation of Rhodamine B dyes was discussed. Fourier transform infrared (FTIR) spectra of pure UT, UTG and Ag–UTG composite. The scheme of proposed mechanism for the photocatalytic degradation of RhB on Ag–UTG.

Electrochemical immunosensor constructed using TiO2 nanotubes as immobilization scaffold and tracing tag

A ternary TiO2 nanotube (TNT) composite and a signal antibody and horseradish peroxidase (HRP) functionalized TNT were designed as an electrode scaffold for immobilization of high quantity of capture antibody and a tracing tag for immunosensing, respectively. The polyaniline (PANI) was coated on TNTs by chemical oxidative polymerization, and gold nanoparticles were deposited on TNT-PANI with a routine chemical reduction. Various techniques including scanning electron microscopy, energy dispersive X-ray, transmission electron microscope, X-ray diffraction, Fourier transform infrared spectra, X-ray photoelectron spectra, impedance and electrochemical techniques were used to characterize the nano-materials. Using bis(sulfosuccinimidyl) suberate as amino cross-linker, the TNT composite could be further functionalized with protein G′ for oriented immobilization of capture antibody on electrode surface. Upon sandwich-type immunoreaction, the signal antibody on the tracing tag was quantitatively captured on the surface to generate sensitive electrochemical response with a H2O2 mediated HRP catalytic reaction. With α-fetoprotein as an analyte model, the immunosensor showed a linear range of 0.01–350ngmL−1 with a detection limit of 1.5pgmL−1. The accelerated electron transfer by the ternary composite, oriented immobilization of capture antibody and high loading of HRP on the TNT tracing tag greatly amplified the electrochemical signal, and led to the superior performance of the immunoassay.