Sensitized TiO2 Nanoparticles Research Articles

Ionic liquid based surfactant-free microemulsion as a new protocol for preparation of visible light active poly(methyl methacrylate)/TiO2 nanocomposite

The practical application of sensitized TiO2 nanocomposites is very satisfying due to their high photon utilization in visible light, simple recovery without affecting the photocatalytic performance, high energy efficiency, low potential environmental risk, and low operational costs. The objective of this study is developing the ionic liquid (IL)-based surfactant-free microemulsion, as a soft template, for preparation of a novel type of sensitized poly(methyl methacrylate)/TiO2 nanocomposite (PMMA/TiO2/IL). For this purpose, a series of visible light-responsive PMMA/TiO2/IL transparent nanocomposites were prepared in microemulsion composed of methyl methacrylate monomer, 1-buthyl-3-methylimidazolium tetrafluoroborate ([bmim][BF4]), and 1-buthanol as amphi-solvent. Techniques such as diffuse reflectance spectroscopy (DRS)), attenuated total reflectance-fourier transform infrared (ATR-FTIR) spectroscopy, atomic force microscopy (AFM), field emission scanning electron microscopy (FE-SEM), and energy dispersive X-ray analysis (EDX) were used to characterize prepared nanocomposites. Photocatalytic degradation of methyl orange dye under visible light illumination, as an application in wastewater treatment, with the investigation of the influence of TiO2 content in the nanocomposite, pH, and nanocomposite reusability on photodegradation efficiency was studied and maximum value of 93.9% obtained at optimum conditions. The FESEM analysis indicated that the utilization of a relatively low amount of ionic liquid and also in absence of the surfactant ensures the monodispersity of the visible light sensitized TiO2 nanoparticles in the polymer matrix.

Ionic liquid based surfactant-free microemulsion as a new protocol for preparation of visible light active poly(methyl methacrylate)/TiO2 nanocomposite

The practical application of sensitized TiO2 nanocomposites is very satisfying due to their high photon utilization in visible light, simple recovery without affecting the photocatalytic performance, high energy efficiency, low potential environmental risk, and low operational costs. The objective of this study is developing the ionic liquid (IL)-based surfactant-free microemulsion, as a soft template, for preparation of a novel type of sensitized poly(methyl methacrylate)/TiO2 nanocomposite (PMMA/TiO2/IL). For this purpose, a series of visible light-responsive PMMA/TiO2/IL transparent nanocomposites were prepared in microemulsion composed of methyl methacrylate monomer, 1-buthyl-3-methylimidazolium tetrafluoroborate ([bmim][BF4]), and 1-buthanol as amphi-solvent. Techniques such as diffuse reflectance spectroscopy (DRS)), attenuated total reflectance-fourier transform infrared (ATR-FTIR) spectroscopy, atomic force microscopy (AFM), field emission scanning electron microscopy (FE-SEM), and energy dispersive X-ray analysis (EDX) were used to characterize prepared nanocomposites. Photocatalytic degradation of methyl orange dye under visible light illumination, as an application in wastewater treatment, with the investigation of the influence of TiO2 content in the nanocomposite, pH, and nanocomposite reusability on photodegradation efficiency was studied and maximum value of 93.9% obtained at optimum conditions. The FESEM analysis indicated that the utilization of a relatively low amount of ionic liquid and also in absence of the surfactant ensures the monodispersity of the visible light sensitized TiO2 nanoparticles in the polymer matrix.

Bilayer coatings based on silica materials and iron (III) phthalocyanine – Sensitized TiO2 photocatalyst

This study presents a sol-gel method for preparation of bilayer coatings based on silica materials and iron (III) phthalocyanine - sensitized TiO2 nanoparticles (TiO2–Fe(III)Pc), deposited on glass surfaces. Silica materials were synthetized using organosilane precursors (dimethoxydimethylsilane (DMDMES), octyltriethoxysilane (OTES), and/or hexadecyltrimethoxysilane (HDTMES)), with a two-step acid reaction. The materials properties have been investigated using FT-IR and UV–vis spectroscopy, AFM analysis, and water contact angle. The photo-degradation experiments of thin films were developed using methylene blue as a standard contaminant. FT-IR spectra confirmed the successful grafting of silica materials onto the surface of TiO2–Fe(III)Pc nanoparticles. AFM analysis indicated that the thin films present a different nanostructure depending on the silica matrix and the existence of TiO2–Fe(III)Pc nanoparticles. Contact angle measurements showed that sol-gel coatings exhibit hydrophobic behavior (>99 ± 2°), before and after photo-degradation test. The presence of nanoparticles plays an important role in the development of coatings with photo-catalytic property.

Tuning of type-I and type-II mechanisms for visible light degradation in tris(styryl)benzene-sensitized TiO2 nanoparticles

The visible light activation of TiO2 have been carried out by sensitization method using robust and metal-free tris(styryl)benzene (TSB) compounds as efficient sensitizers, which can be easily prepared. TSB compounds decorated with three carboxylic acid (3COOH) or aldehyde (3CHO) groups have been tightly incorporated to the surface of TiO2 nanoparticles through different chemical linkage. The synthesized materials have been deeply characterized by different spectroscopic and analytical techniques to investigate the effect of TSB sensitizers in the photocatalytic properties of TiO2. Comparative and exhaustive optical studies have been performed in solution between TSB compunds and sensitized TiO2 nanoparticles, computational studies have been also carried to shed light on the sensitization process. The results reveal different mechanisms of sensitization (Type I and Type II) between the 3CHO and 3COOH compounds and TiO2 nanoparticles. Thus, the influence of electronic injection mechanism (direct or indirect) has been studied and mechanisms have been proposed for photodegradation of dye pollutants under UV and visible irradiation. TiO2 nanoparticles sensitized with 3COOH (TiO2–3COOH) exhibited the best visible photocatalytic activity with a removal efficiency around 98% for methylene blue in 30 min and methyl orange after 60 min.

Sensitization of TiO2 nanoparticles with natural dyes extracts for photocatalytic activity under visible light

Titanium dioxide (TiO2) is the most used semiconductor for heterogeneous photocatalysis. However, TiO2 is activated only by ultraviolet radiation (wavelength less than 390 nm) and only 5% of the sunlight spectrum corresponds to the UV radiation, therefore restricting the efficiency of titania catalysts. Aiming to obtain more efficient photocatalytic TiO2 nanoparticles under visible light, the goal of this study is the sensitization of this semiconductor with natural dye extracts, consequently enabling the absorption of energy in the visible light spectrum. Four natural dyes were used, blackberry and hibiscus (anthocyanins group) and urucum and curcuma (carotenoids group), which were extracted by the solid-liquid extraction method. The Evonik P25 titanium dioxide was used and the sensitization of the nanoparticles was by the liquid route. Samples were characterized by UV–visible spectrophotometry, differential thermal analysis and thermal gravimetric analysis (DTA/TGA), Fourier-transform infrared spectroscopy (FTIR) and pH control. A solution of curcuma was used to determine the photocatalytic activity of the sensitized TiO2 NPs under visible light. As a result, TiO2 without sensitization degraded only 11% of the dye solution, whereas the sensitized catalysts degraded on a range of 51–73%, showing that sensitized TiO2 nanoparticles have a significant increase in the degradability of organic compounds under visible light. The sensitization of TiO2 nanoparticles with natural dye extract has a great potential to increase the photocatalytic efficiency in the visible spectrum, especially in environments without ultraviolet radiation.

Ultrafine Cu2ZnSnS4 quantum dots functionalized TiO2 nanotube arrays for potential optoelectronic applications

Tremendous progress has been made in power conversion efficiency (PCE) of thin-film photovoltaics over the past few years, yet most current high-efficient photoactive layer usually contains rare or toxic elements accompanied by expensive and complicated vacuum processes, which increases the cost and limits the scope of the applications in the long run. Here we present a synergistic effect of quantum effect of an earth-abundant and low toxic ultrafine Cu2ZnSnS4 (CZTS) quantum dots (QDs) and low charge recombination in one dimensional TiO2 nanotube arrays for optoelectronic devices. By ligands exchange, the as-obtained ultrafine CZTS QDs have been robustly anchored to a highly ordered TiO2 nanotube arrays (TNAs) to be served as a function layer in a simple QDs sensitized solar cells. Such ultrafine CZTS QDs based solar cells exhibit significant enhancement up to 457% in PCE compared to that of CZTS QDs with larger size. The CZTS QDs functionalized TNAs has also shown excellent charge transport capability with lower recombination rate than QDs sensitized TiO2 nanoparticles and it is expected to be used as a low-cost environment-friendly function layer for various potential optoelectronic applications.

Environmentally-friendly halloysite nanotubes@chitosan/polyvinyl alcohol/non-woven fabric hybrid membranes with a uniform hierarchical porous structure for air filtration

An environmentally-friendly halloysite nanotubes@chitosan/polyvinyl alcohol/non-woven fabric (HNTs@CS/PVA/NWF) hybrid membrane with a uniform hierarchical porous structure for air filtration was prepared using a developed dip coating method combined with nonsolvent induced phase separation (NIPS) and the surface deposition of HNTs. Additionally, a TiO2/H2O2 photocatalysis approach was developed to improve the hydrophilicity of the polyester NWF. It was found that the porous CS/PVA blend was embedded into the NWF to frame a reinforced composite membrane with an intact polymer membrane. The results showed that the structure and properties of the resultant membranes were closely related to the thickness of the casting solution and the presence of HNTs. The filtration efficiency (FE) and pressure drop (PD) of the resultant membranes under a face velocity of 5.3 cm s−1 were 96.8% and 143.9 Pa, respectively. The filtration performance was mainly attributed to the direct interception on the membrane surface as well as the strong interactions and diffusion adsorption caused by the CS/PVA matrix and HNTs, respectively. Furthermore, the antibacterial rate of the resultant membranes reached to 99.6% for E. coli and 99.1% for S. aureus due to the synergistic effects of the CS component and the sensitized TiO2 nanoparticles.

Self‐powered Photoelectrochemical Sensor for Gallic Acid Exploiting a CdSe/ZnS Core‐shell Quantum Dot Sensitized TiO2 as Photoanode

AbstractHerein is described the development of a self‐powered sensor for gallic acid (GA) determination exploiting CdSe/ZnS quantum dot sensitized TiO2 nanoparticles (CdSe/ZnS/TiO2/FTO) as photoanode and an all copper oxide photocathode (CuO/Cu2O/FTO) to reduce water. A two‐chamber self‐powered photoelectrochemical cell was employed in order to maintain separated the photoelectrodes. The self‐powered photoelectrochemical cell is based on water reduction in the cathodic chamber while gallic acid acts as a hole scavenger in the anodic chamber to generate the necessary cell output to drive GA oxidation in the anodic compartment. Electrochemical impedance measurements were performed to evaluate the electronic characteristics of CdSe/ZnS/TiO2/FTO photoanode and CuO/Cu2O/FTO photocathode in terms of flat band potential, carrier density, and nature of semiconductor. Under optimized conditions, the self‐powered photoelectrochemical cell presented a wide linear response range for GA from 1 μmol L−1 up to 200 μmol L−1.

Kinetics of in situ desorption of dye molecules on sensitized TiO2 nanoparticles in a high concentration solution: ion parasitic adsorption process and mass reference.

The reverse process of dye molecule adsorption on the surface of nanoparticles, that is, the desorption process, has long been neglected in the field of dye-sensitized solar cells (DSCs). It is crucial to develop an in situ technology that controls the rate of dye desorption. Meanwhile, controlling the coverage of dye-sensitized films is still a major challenge. The work presented in this paper applies a simple and effective method to study the in situ mass change responses on dye-sensitized TiO2 films over different potential ranges. The result shows that dye molecule desorption is accompanied by the adsorption of ions in solution. Due to this parasitic adsorption process, the frequency responses in the electrochemical quartz crystal microbalance (EQCM) test cannot be completely attributable to dye molecule desorption. We established a new model to eliminate the impact of this parasitic adsorption process. The kinetics of in situ desorption of dye molecules on sensitized TiO2 nanoparticles in a high-concentration solution was studied. We found that the in situ desorption of dye could be described by pseudo-first-order kinetics. The results suggest that the dye in situ desorption rate is dependent on the bias voltage, and the coverage of dye on the surface of TiO2 films can be further controlled. In-depth research of the dye desorption process is theoretically significant to study DSC stability, new dye synthesis and complex interface structures.

Two approaches for elaborating sensitized TiO2 nanoparticles of potential effect in photodynamic therapy

Two approaches for elaborating sensitized TiO2 nanoparticles of potential effect in photodynamic therapy

A facile solvothermal approach of novel Bi2S3/TiO2/RGO composites with excellent visible light degradation activity for methylene blue

In this paper, novel photocatalyst Bi2S3/TiO2/RGO composites were successfully fabricated by a facile solvothermal method. During this process, TiO2 was coupled with Bi2S3 to generate Bi2S3 sensitized TiO2 nanoparticles, and graphene oxide (GO) was reduced to reduced graphene oxide (RGO), which was uniformly covered with plenty of Bi2S3 and TiO2. The as-prepared samples were characterized by scanning electron microscope (SEM), transmission electron microscopy (TEM), specific surface areas (BET), X-ray diffraction (XRD), Fourier transform infrared (FTIR), Raman, X-ray photoelectron spectroscopy (XPS), UV–vis diffuse reflectance spectroscopy (UV–vis DRS) and photoluminescence (PL) spectroscopy. The results confirmed that Bi2S3 could act as an optical filter, which could be activated under visible light. And the introduction of Bi2S3 could improve the response of TiO2 nanoparticles for visible light. In addition, the Bi2S3/TiO2 in Bi2S3/TiO2/RGO composites had more uniform dispersion on the surface of graphene with less agglomeration in comparison with the Bi2S3/TiO2. Graphene can provide conductive electron channels for separation of the electrons and inhibit the recombination of electrons and holes. Furthermore, the photocatalytic activity of Bi2S3/TiO2/RGO composites was evaluated through the degradation of methylene blue (MB) under visible light irradiation. The Bi2S3/TiO2/RGO composites showed the highest photocatalytic activity among the referred photocatalysts, with about 3-fold increase in photocatalytic efficiency over TiO2 nanoparticles. The mechanism of high photocatalytic activity was also discussed.

Visible light-induced degradation of phenolic compounds by Sudan black dye sensitized TiO2 nanoparticles as an advanced photocatalytic material

Using a simple impregnation process, the present study has introduced a novel route for the photosensitization of TiO2 nanoparticles using Sudan black B dye as a sensitizer. DRS, XRD, FE-SEM, BET, UV–Vis, FT-IR and TGA–DSC analyses were considered for characterization of the synthesized purple powder as a visible light photocatalyst for removal of the phenolic pollutant. The band gap of the dye-sensitized TiO2 and corresponding BET surface area were 2.9 eV and 50.0 m2 g−1, respectively. Based on the results, Sudan Black sensitized TiO2 photocatalyst outperforms the pure commercial TiO2 (Degussa P25) in terms of phenol degradation under visible light. Under a 100-min photo-catalytic experiment, dye-sensitized TiO2 removed 96 % of the phenol content. The Sudan black B dye-sensitized TiO2 is expected to show further interesting physical characteristics related to potential uses.

Transient Interactions of Agglomerates of Sensitized TiO2 Nanoparticles in Colloidal Suspensions

We present the study of dye-sensitized nanoparticles and their agglomerates with stochastic electrochemistry. We use a fluorine doped tin oxide (FTO) ultramicroelectrode (UME) with diameter in the range of 40 to 80 micrometers. To prepare the UME a sheet of perfluoroalkoxy alkane (PFA) is perforated to produce a recessed micro disk of the transparent conductive oxide. We demonstrate that the detection of the colloidal nanoparticles (NPs) sensitized with N719 is achieved via the interactions between agglomerates of the NPs that collide with the FTO. The NPs photooxidize MeOH and we detect the charge transfer from the NPs to the FTO ultramicroelectrode. The interactions between the dye sensitized NPs and the FTO yields oscillations that increase with exposure time. This increment in oscillation amplitude is assigned to changes in the aggregation of the NPs during the illumination even in the presence of 0.1 M supporting electrolyte. The formation of agglomerates is verified by dynamic light scattering and indicates that the agglomerates are able to separate photo-generated electrons and inject the carriers to the UME.

Ag2CO3 sensitized TiO2 nanoparticles prepared in ionic liquid medium: A new Ag2CO3/TiO2/RTIL heterostructure with highly efficient photocatalytic activity

A visible light active Ag2CO3/TiO2/2-hydroxylethylammonium formate (RTIL) nanocomposite has been synthesized via loading Ag2CO3 flower-like particles on TiO2/RTIL by a simple precipitation method. TiO2 nanoparticles were prepared by the modified sol–gel method using 2-hydroxylethylammonium formate (RTIL) as an ionic liquid. The prepared photocatalysts were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), Fourier transform-infra red spectroscopy (FTIR) and Diffuse reflectance UV–vis spectroscopy (DRS) techniques. The photocatalytic performance of the synthesized photocatalysts was investigated by the photodegradation of acid blue 92 (AB92) dye under both visible and UV light irradiations. It was divulged that the Ag2CO3/TiO2/RTIL heterostructure noticeably exhibited an improvement in both efficiency and rate of AB92 photodegradation in comparison with both TiO2 samples. The enhanced photocatalytic activity of Ag2CO3/TiO2/RTIL nanocomposite is mainly attributed to the promoted absorption of light and more efficient suppression of charge carrier recombination. The possible mechanism for the improved photocatalytic properties of the Ag2CO3/TiO2/RTIL nanocomposite was also discussed.

Sensitization of Tio2 Nanoparticles With Cobalt Phthalocyanine: An Active Photocatalyst for Degradation of 4-Chlorophenol under Visible Light

In this work, preparation and visible light induced photocatalytic activity of sulphonated cobalt phthalocyanine complex sensitized TiO2 nanoparticles (CoPcS-TNP) as photocatalyst for photocatalytic degradation of 4-chlorophenol (4-CP) has been reported. The study carried out using XRD, DRS, FT-IR, nitrogen physisorption and TEM techniques. Results revealed that TiO2 nanoparticles possessed only the anatase phase with crystal sizes of about 7-10nm. The doping amount of CoPcS remarkably affected the activity of TiO2 nanoparticles as photocatalyst. Oxalic acid, pyruvic acid and malonic acid were the major intermediate species at the final stage of the degradation process as identified by gas chromatography-mass spectrometery.

Performance of Caesalpinia sappan heartwood extract as photo sensitizer for dye sensitized solar cells

A natural dye extracted from Caesalpinia sappan heartwood was used as photo sensitizer for the first time to fabricate titanium dioxide (TiO2) nanoparticles based dye sensitized solar cells. Brazilin and brazilein are the major pigments present in the natural dye and their optimized molecular structure were calculated using Density functional theory (DFT) at 6-31G (d) level. The HOMO–LUMO were performed to reveal the energy gap using optimized structure. Pure TiO2 nanoparticles in anatase phase were synthesized by sol–gel technique. The pure and natural dye sensitized TiO2 nanoparticles were subjected to structural, optical, spectral and morphological studies. Low cost and environment friendly dye sensitized solar cells were fabricated using natural dye sensitized TiO2 based photo anode. The solar light to electron conversion efficiency of Caesalpinia sappan heartwood extract sensitized dye sensitized solar cell is 1.1%.

Surface Modification of TiO2Nanoparticles with Phenyltrimethoxysilane in Dye-sensitized Solar Cells

Phenyltrimethoxysilane (PTMS) was anchored onto the sensitized TiO2 nanoparticles. This insulating molecular layer effectively inhibited the charge recombination at the interface of TiO2/electrolyte in the dye–sensitized solar cells (DSCs) without sacrificing the dye-loading capacity of the nanocrystalline TiO2. DSCs using PTMSmodified TiO2 exhibited a short-circuit current (JSC) of 15.9 mA/cm 2 , an open-circuit voltage (VOC) of 789 mV, and a fill factor (FF) of 68.2%, yielding an overall conversion efficiency () of 8.55% under 100 mW/cm 2 illumination. The resulting cell efficiency was improved by ~10% as compared with the reference cell.

Voltage and Frequency Dependent Impedances of Dye-sensitized Solar Cell

This paper describes a derivation of the dynamic impedance of a dye-sensitized solar cell (DSSC) and its characterization using a frequency response analyzer (FRA). The dynamic impedance equation as a function of voltage and frequency is presented. Testing is done on a DSSC, fabricated from a fluorine-doped SnO2 (FTO) conducting glass, ruthenium (II) dye (N719) sensitized TiO2 nanoparticles, an iodide-triiodide electrolyte, and a Pt counter electrode. At each bias voltage, impedance locus is plotted in a complex plane. Intercepts of each semicircular impedance loci yield series, dynamic, and shunt resistance of the cell. Experimental results could be used to analyze characteristics of AC equivalent circuit components.

Facile preparation of squarylium dye sensitized TiO2 nanoparticles and their enhanced visible-light photocatalytic activity

A squarylium dye, 1,3-bis[(3,3-dimethylindolin-2-ylidene)methyl]squaraine (ISQ) sensitized TiO2 nanoparticles photocatalysts with different mass ratio of ISQ to TiO2 were facilely prepared by blending ISQ and TiO2 in ethanol solution. The resulting composite photocatalysts were characterized by the X-ray diffraction (XRD), scanning electron microscopy (SEM), Fourier transform infrared spectra (FT-IR) and UV–vis diffuse reflectance spectroscope (DRS). The visible light photocatalytic activities of ISQ sensitized TiO2 nanoparticles were evaluated using the degradation of methylene blue (MB) as a photodegradation target. The results showed that photo-response of the ISQ sensitized TiO2 nanoparticles were remarkably extended to visible-light region, and the ISQ dye sensitized TiO2 exhibited significantly enhanced photocatalytic activity under visible light irradiation. The maximum photocatalytic activity of the ISQ sensitized TiO2 was found at a composite photocatalyst (mass ratio of ISQ to TiO2 was 1:3), and its degradation efficiency of MB reached approximately 98% in 2h under visible light irradiation. Furthermore, a possible mechanism for the photocatalytic oxidative degradation was also proposed.

Visible Light Photocatalytic Activity of Porphyrin Tin(IV) Sensitized TiO2 Nanoparticles for the Degradation of 4-Nitrophenol and Methyl Orange

A stable metalloporphyrin sensitized TiO2 (Degussa P25) photocatalyst was prepared by using trans-dihydroxo[5,10,15,20-tetraphenylporphyrin]tin(IV) (SnP) as a sensitizer in a simple impregnation process. The solid diffuse reflectance ultraviolet-visible (UV-vis) spectrum of the SnP sensitized TiO2 photocatalyst (SnP-TiO2) indicated that there existed interaction between SnP and TiO2. It was found that SnP-TiO2 exhibited an enhanced visible light photocatalytic activity as compared with that over P25 for the degradation of 4-nitrophenol (4-NP) and methyl orange (MO) in aqueous solutions. The mechanism exploration showed that the degradation of MO and 4-NP experienced two different ways, that is, MO was photodegraded by reactive oxygen species and 4-NP was directly photodegraded by the excited state of SnP. Furthermore, it was found that the loading content of SnP had an important influence on the photocatalytic activity of TiO2. The maximum photocatalytic efficiency was achieved when the contents of SnP were 25 mg and 30 mg per gram TiO2 for MO and 4-NP, respectively. Importantly, SnP-TiO2 was particularly stable and the photocatalytic activity was hardly decreased after being recycled seven times in the presence of oxygen, which could be attributed to the easy reductive regeneration of SnP.