Keywords : titanium dioxide

Investigation of Doped Titanium Dioxide in Anatase Phase. Study ab initio using Density Functional Theory

Paulo José Pereira de Oliveira; Fabielle Castelan Marques; Arlan da Silva Gonçalves; Greice Kelly dos Santos Brito; Enzo Victorio Andrade; Marcos Pedro Dalmaso Pinto

Advanced Materials Letters, 2020, Volume 11, Issue 1, Pages 1-5
DOI: 10.5185/amlett.2020.011459

Global warming has generated great concern worldwide. One way to control this problem is to use clean renewable energy new sources. Among the energy sources, we can mention hydrogen gas, produced by water photocatalysis by mean of a semiconductor material. In this work, we report a study about band gap and absorption spectra by mean of the density functional theory of the anatase allotropic form of titanium dioxide doped with Ruthenium. The results indicated systematic decrease of the band gap and increase of the absorbance at the visible region with the increase of the amount of dopant.

Modification of mesoporous titanium dioxide with cobalt oxide electrocatalyst for enhanced oxygen evolution reaction

Mabrook S. Amer; Mohamed A. Ghanem; Prabhakarn Arunachalam; Abdullah M. Al-Mayouf; Talal A. Aljohani

Advanced Materials Letters, 2019, Volume 10, Issue 2, Pages 136-144
DOI: 10.5185/amlett.2019.2139

Water electrolysis is an attractive approach for hydrogen production process and has enormous potential for sustainable clean energy development. This work demonstrates a controllable and reliable method for in-situ decorating of mesoporous titanium dioxide (m-TiO2) support with low loading (0.1- 2.1 wt. %) of cobalt oxide for an efficient electrocatalytic oxygen evolution (OE) in alkaline solution. The ordered (m-TiO2) support modified with cobalt oxide and having uniform mesopores (3-5 nm pore diameter) and a crystalline framework is successfully prepared via soft-template strategy using Pluronic ® F127 triblock copolymer as a mesopores template. Compared to the pure TiO2 mesoporous, the entire Co oxide doped (Co(x)/m-TiO2) catalysts exhibit greatly enhanced OE activity in spite of the low loading of Co oxide electrocatalyst. The Co(2.1)/m-TiO2 catalyst with 2.1 wt. % of Co oxide was the OER most active robust electrocatalyst with a mass activity of 31.5 mA cm 2 mg −1 , the specific activity of 12.6 mA cm −2 at h = 350 mV and 200 mV decrease in overpotential (h) compared to bare m-TiO2. The enhanced OE activity of (Co(x)/m-TiO2) catalysts was attributed to the existence of a uniform distribution of Co oxide electrocatalyst supported on a highly porous structure of the TiO2 substrate.

Benefits and risks of nanozerovalent iron, titanium dioxide nanoparticles and carbon nanotubes for water treatment technologies

David G. Rickerby

Advanced Materials Letters, 2017, Volume 8, Issue 12, Pages 1132-1144
DOI: 10.5185/amlett.2017.1524

An overview is presented of potential improvements in performance that can be achieved by using three different types of nanomaterials in water treatment applications: (i) zerovalent iron for reducing concentrations of chlorinated hydrocarbons and heavy metals in groundwater; (ii) titanium dioxide for photocatalytic drinking water purification, enabling reduced consumption of chemicals for disinfection; (iii) carbon nanotube membrane filters that transport water molecules at elevated  fluxes, while rejecting other molecules and ions. The distinctive characteristics of the nanomaterials, such as high specific surface area, enhanced reactivity and adsorption capacity, have already led to significant increases in efficiency. Future developments are expected based on surface modification of zerovalent iron to improve its reactivity and transport characteristics, advanced chemical synthesis methods to increase the area of photoreactive facets and doping to inhibit electron-hole recombination or to allow visible light photocatalysis in titanium dioxide, and functionalization of carbon nanotubes to increase ion rejection rates. Implementation of these innovative methods for removal of contaminants from water will be contingent on reduction of the present high cost of the nanomaterials and assessment of the possible risks associated with their, as yet only partly understood, toxic and ecotoxic properties. 

Titanium dioxide (TiO2) and silver/titanium dioxide (Ag/TiO2) thin films with self-cleaning properties

Ana Flávia R. Silva; Nelcy D. S. Mohallem; Marcelo M. Viana

Advanced Materials Letters, 2017, Volume 8, Issue 4, Pages 444-448
DOI: 10.5185/amlett.2017.7093

In this work, TiO2 and Ag/TiO2 thin films were synthesized on glass by combination of sol-gel method and dip-coating deposition technique. Thermal treatment in temperatures ranging from 100 °C to 500 °C was used to evaluate changes in structure, morphology and texture of these materials. Adherent and microcrack-free films were obtained. The structural and morphological evolution with temperature was studied by X-ray diffraction (XRD) and high resolution transmission electron microscopy (HRTEM). Average particle size and roughness were determined by atomic force microscopy (AFM). The films were tested for wettability by measuring the contact angle between a drop of distilled water and the material surface. Results of hydrophobic/hydrophilic tests using UV-C irradiation showed that the films change their hydrophobic character to hydrophilic reaching even the superhydrophilic character which indicates their potential application as self-cleaning coatings. 

Impedimetric And Voltammetry Sensing Of Xanthine Using Nanocomposites

Jagriti Narang; Nitesh Malhotra; Chaitali Singhal; C. S. Pundir

Advanced Materials Letters, 2016, Volume 7, Issue 7, Pages 555-560
DOI: 10.5185/amlett.2016.6163

An electrochemical biosensor based on xanthine oxidase (XOx), titanium dioxide nanoparticles and carboxylated multi-walled carbon nanotubes (TiO2/c-MWCNT) nano-composites for sensitive detection of xanthine has been developed. TiO2/MWCNT nano-composites were used as the sensing platform in order to immobilize XOx and magnify the sensor response. FTO electrode was employed to amplify electrochemical signal in the buffer solution. Detailed morphological, electrochemical, structural and optical characterization of XOx/TiO2-NPs/c-MWCNT/FTO electrode was done using XRD, DLS, SEM, EIS, CV and shows quick response time (within 30s), linearity as 0.5- 500 µM, lower detection value of 0.05 micromolar with signal: noise ratio of 3, excellent reproducibility, high selectivity and shelf life of about 8 weeks under refrigerated conditions. The developed biosensor was further used to determine the xanthine levels in the labeo fish samples obtained from market. The accuracy of the developed biosensor was cross-checked by the customary enzymic colorimetric method (99% correlation). Thus, the existing research confirms the development of a highly sensitive, stable and a reliable bio-sensing method to detect the freshness of fish samples.

Using Titanium Dioxide/carbon Nanotubes To Remove Humic Acids In Water

Y. P. Tsai; J. C. Yang; P. C. Chuang; C. C. Chou; J. W. Lin

Advanced Materials Letters, 2016, Volume 7, Issue 2, Pages 95-97
DOI: 10.5185/amlett.2016.6100

This study used multi-walled carbon nanotubes (MWCNTs), TiO2 and their mixture (TiO2/CNT) to remove humic acids (HA) in water. The thermodynamic parameters with respect to the adsorption of MWCNTs, including free energy of adsorption (ΔG 0 ), enthalpy (ΔH 0 ), and entropy (ΔS 0 ) changes, are further calculated in the study. The ΔH 0 data showed the adsorption of HA onto MWCNTs is an endothermic physisorption. The ΔG 0 data indicates the adsorption of HA onto MWCNTs was spontaneous and thermodynamically favorable. Photocatalytic experiments showed 60 mgl -1 of HAs were completely degraded and mineralized as CO2 after 5 h UV irradiation by 0.8 gl -1 of TiO2, indicating the efficiency of TiO2 for the removal of HA is better than CNTs. The experiments of TiO2/CNT indicated the photocatalytic efficiency of TiO2 in the presence of CNTs was not improved, even worse than TiO2 alone. However, the photocatalytic efficiency of TiO2/CNT mixture became better than TiO2 alone due to the supply of oxygen by aeration, ascribing to the reason that the provided oxygen might be adsorbed on the surface of CNTs and accept e- as well as form •O2 - , which also leads to the formation of •OH - in the system. 

Aqueous Phase Photodegradation Of Rhodamine B And P-nitrophenol Desctruction Using Titania Based Nanocomposites

Suranjan Sikdar; Sayantan Pathak; Tanmay K Ghorai

Advanced Materials Letters, 2015, Volume 6, Issue 10, Pages 867-873
DOI: 10.5185/amlett.2015.5858

Heterogeneous photocatalysts offer great potential for converting photon energy into chemical energy for decomposition and destruction of organic contaminants from organic molecules i.e. Rhodamine B (RhB) and p-nitophenol (p-NP) under UV light. The titania based novel MxNbxTi1-2xO2-x/2 (M = Cr, Fe; x = 0.01-0.2) was prepared by tetra and tri-podal amine type binder with iron or chromium support using sol–gel method followed by calcination at 150 o C in an auto generated pressure. The photodegradation performance of the optimized catalyst was compared with synthesized nano-compositions, P-25 titania with RhB and p-NP. The particle sizes, surface area, mesopore sizes of CrxNbxTi1-2xO2-x/2 (x = 0.01) (CNT1) and FexNbxTi1-2xO2-x/2 (x = 0.01) (FNT1) are 12±1 and 10±2 nm, SBET=162 and 145 m 2 g −1 , 4.9 and 4-5 nm, respectively. The energy band gap of CNT1, FNT1 and NT was found to be 1.85, 2.06 and 2.1 eV, respectively. The importance of CNT1 powders is that it shows good photocatalytic activity for the degradation of Rhodamine B (RhB) within only 180 min and the importance of FNT1 powders is that it reduces the p-NP to p-aminophenol using a little bit of NaBH4 (0.054 g) within 10 min as compared to pure anatase TiO2 and other compositions of MxNbxTi1-2xO2-x/2 (M = Cr, Fe).

X-ray Photoelectron Spectroscopy Study Of Adsorption Of (3-mercaptopropyl)trimethoxysilane And N-propyltriethoxysilane On A Rutile TiO2(110) Surface

Shilpi Chaudhary; Ashley R. Head; Joachim Schnadt

Advanced Materials Letters, 2015, Volume 6, Issue 4, Pages 279-283
DOI: 10.5185/amlett.2015.SMS1

We have studied the adsorption of two silane compounds, (3-mercaptopropyl) trimethoxysilane (MPTMS) and n-propyltriethoxysilane (PTES), on a rutile TiO2(110) surface using angle dependent X-ray photoelectron spectroscopy. The observation of the S 2p line, in the case of MPTMS, and the C 1s line for both MPTMS and PTES confirms the adsorption of the molecules. For a dose of 122 Langmuirs of MPTMS we find room temperature coverage of 0.55 monolayers, while for a 60 Langmuir dose of PTES the coverage is found to be 0.89 monolayers. Thus, MPTMS has a considerably lower sticking coefficient on the rutile TiO2(110) surface than PTES. Both PTES and MPTES are found to bind dissociatively to the surface. An analysis of angle dependent data further suggests that for MPTMS the thiol group and thus alkyl chain points away from the surface, while for a 0.5 monolayer coverage of PTES the alkyl chain is oriented towards the surface. A higher coverage, ~1 monolayer, the behavior seems to be reversed for at least a fraction of all molecules. Temperature programmed XPS measurements suggest that the oxy groups of both molecules desorb from the surface at 550 K, which is in accordance with literature. The present study thus provides information on how these silane coupling agents bind to titanium oxide and what their molecular orientation is on the surface.

Formation Of TiO2 Thin Films By A Modified Sol-gel Route And Characterization Of Structural, Optical And Electrochromic Properties

Fatma Pinar Gokdemir; vecihe Ece Yuzbasioglu; Bahadir Keskin; Orhan Ozdemir; Kubilay Kutlu

Advanced Materials Letters, 2014, Volume 5, Issue 7, Pages 367-371
DOI: 10.5185/amlett.2014.amwc.1007

Through a modified sol gel route with titanium isopropoxide (TIP) and acetic acid, titanium dioxide (TiO2) thin films were deposited by dip coating. Employing acetic acid as modifier and without inclusion of water in hydrolysis leaded to control the degree of condensation-oligorimerization of the precursor and formation of anatase phase only upon annealing. Direct allowed energy band gap 3.87 eV verified the anatase phase of the film. Impact of temperature on structural properties was deduced by FTIR and UV-Visible spectroscopies. Due to the reduction in band gap with increase in annealing temperature, injected Li + charge amount dropped in anatase compared to the amorphous (unannealed) films.

Synthesis Of Porous Titania And Its Application To Dye-sensitized Solar Cells

Ammar Elsanousi; Kamal Khalifa Taha; Nazar Elamin

Advanced Materials Letters, 2013, Volume 4, Issue 12, Pages 905-909
DOI: 10.5185/amlett.2013.5472

Nanocrystalline porous titania with rutile and anatase bi-phase structure has been fabricated by the sol-gel method without the introduction of any surfactant, using tetrabutile titanate as precursor. The porous material was integrated as an electrode in a dye-sensitized solar cell as an electrode and its photoelectrical parameters were measured. Experimental measurements showed that the cell exhibits higher values of short-circuit current density and overall conversion efficiency compared to P25 (typical commercial titania powder) cells. The overall conversion efficiency of both samples was calculated to be 2.81 and 1.57 for the prepared and commercial (P-25) sample respectively. This drastic increase in the conversion efficiency of the prepared sample was attributed to its high surface area and porous structure, allowing more sensitizer dye to be chemically anchored in the electrode and, as a consequence, improved the light harvesting drastically. These results indicate that it is possible to achieve commendable conversion efficiencies using porous bi-phase titania.

Effect Of Morphology On Thermal Stability Of Core-shell Polyaniline/TiO2 Nanocomposites

Ameena Parveen; Aashis S. Roy

Advanced Materials Letters, 2013, Volume 4, Issue 9, Pages 696-701
DOI: 10.5185/amlett.2012.12481

Polyaniline/TiO2 nanocomposites have been prepared by sol-gel technique using citric acid and saturated solution of α-dextrose as a surfactant in presence of hydroxyl group at an anomeric position in sugar chain. The FTIR spectrum indicates the benzenoid, quinoid and MO peaks confirm the formation of PANI/TiO2 nanocomposites. The XRD studies show the monoclinic structure and the TEM study of nano TiO2 reveals that the average particles size is 9 ±2 nm whereas the composite size is 13 ± 2 nm and further it is observed that the TiO2 nanoparticles are intercalated to form a core shell of PANI. The formation of core shell is significant up to 30wt% observed from the SEM. The TGA-DSC curves show the thermal stability of polyaniline and its nanocomposites at 660 °C of temperature.

New Synthetic Approach, Mesoporous properties And Photocatalytic Activity Of Titania adapted Chromium-niobate Nanocatalysts

Tanmay K. Ghorai; Prasanta Dhak

Advanced Materials Letters, 2013, Volume 4, Issue 2, Pages 121-130
DOI: 10.5185/amlett.2012.7382

Mesoporous titania adapted chromium-niobate nanocatalysts CrxNbxTi1-2xO2-x/2 (x = 0.01-0.2) were synthesized by a new synthetic approach, using N,N,N',N'-tetrakis(2-hydroxyethyl)ethylenediamine (edteH4) precursors and their photocatalytic activities were investigated. TiO2 nanomaterials have continued to be highly active in photocatalytic applications because these are useful to break down the organic molecules in water for endorsing the diffusion of reactants and products. CrxNbxTi1-2xO2-x/2 (x = 0.01)(CNT1) nanoparticles with the smaller particle sizes 12±1 nm and have mesoporous characteristics (SBET = 162 m 2 g −1 ). The energy band gap of CNT1 was found 1.85 eV obtained from optical emission spectrum. The XRD peaks revealed a mixture of anatase and rutile phases in the synthesized powders. EPR spectroscopy showed the characteristic features of Nb 5+ ions, whose existence was confirmed by XPS. The CNT1 powders display good (2.5 times greater) photocatalytic activity for degradation of Rhodamine B (RhB) as opposed to pure anatase TiO2 and other compositions of CrxNbxTi1-2xO2-x/2.