Surface Of TiO2 Thin Films Research Articles

Measurement and Analysis of Surface Temperature Gradients on Magnetron Sputtered Thin Film Growth Studied Using NiCr/NiSi Thin Film Thermocouples.

In the general analysis of thin-film growth processes, it is often assumed that the temperature of the film growth surface is the same as the temperature of the film growth substrate. However, a temperature gradient exists between the film growth surface and film growth substrate. Using the growth surface of TiO2 thin films as an example, the temperature gradient of the film growth surface is tested and analyzed. A NiCr/NiSi thin-film thermocouple is fabricated using the direct-current pulse magnetron sputtering method. A three-layer NiCr/NiSi thin-film thermocouple temperature measurement system is established to measure the temperature gradient of the film growth surface. The growth surface temperature and substrate temperature of the TiO2 thin films are measured. For a sputtering power density of 0.83W cm- 2, the temperature difference between the first and second layers is 104.79°C, while the temperature difference between the second and third layers is 39.92°C. A standard K-type thermocouple is used to measure the substrate temperature, which is recorded to be 132.05°C, consistent with common measurements of substrate temperature. The heat conduction on the film growth surface in the vacuum chamber is examined and a model for the temperature measurement device during film growth is constructed.

Phase Quantification of Heterogeneous Surfaces Using DFT-Simulated Valence Band Photoemission Spectra.

Quantifying the crystallographic phases present at a surface is an important challenge in fields such as functional materials and surface science. X-ray photoelectron spectroscopy (XPS) is routinely employed in surface characterization to identify and quantify chemical species through core line analysis. Valence band (VB) spectra contain characteristic but complex features that provide information on the electronic density of states (DoS) and thus can be understood theoretically using density functional theory (DFT). Here, we present a method of fitting experimental photoemission spectra with DFT models for quantitative analysis of heterogeneous systems, specifically mapping the anatase to rutile ratio across the surface of mixed-phase TiO2 thin films. The results were correlated with mapped photocatalytic activity measured using a resazurin-based smart ink. This method allows large-scale functional and surface composition mapping in heterogeneous systems and demonstrates the unique insights gained from DFT-simulated spectra on the electronic structure origins of complex VB spectral features.

Effect of the Nanorough Surface of TiO2 Thin Films on the Compatibility with Endothelial Cells.

The cytocompatibility of titanium oxides (TiO2) and oxynitrides (N-TiO2, TiOxNy) thin films depends heavily on the surface topography. Considering that the initial relief of the substrate and the coating are summed up in the final topography of the surface, it can be expected that the same sputtering modes result in different surface topography if the substrate differs. Here, we investigated the problem by examining 16 groups of samples differing in surface topography; 8 of them were hand-abraded and 8 were machine-polished. Magnetron sputtering was performed in a reaction gas medium with various N2:O2 ratios and bias voltages. Abraded and polished uncoated samples served as controls. The surfaces were studied using atomic force microscopy (AFM). The cytocompatibility of coatings was evaluated in terms of cytotoxicity, adhesion, viability, and NO production. It has been shown that the cytocompatibility of thin films largely depends on the surface nanostructure. Both excessively low and excessively high density of peaks, high and low kurtosis of height distribution (Sku), and low rates of mean summit curvature (Ssc) have a negative effect. Optimal cytocompatibility was demonstrated by abraded surface with a TiOxNy thin film sputtered at N2:O2 = 1:1 and Ub = 0 V. The nanopeaks of this surface had a maximum height, a density of about 0.5 per 1 µm2, Sku from 4 to 5, and an Ssc greater than 0.6. We believe that the excessive sharpness of surface nanostructures formed during magnetron sputtering of TiO2 and N-TiO2 films, especially at a high density of these structures, prevents both adhesion of endothelial cells, and their further proliferation and functioning. This effect is apparently due to damage to the cell membrane. At low height, kurtosis, and peak density, the main factor affecting the cell/surface interface is inefficient cell adhesion.

Optically rough TiO2 thin film surface study by laser speckle photography

In this work, TiO2 thin film is exposed to the red laser and the scattered light progresses the self-interference granular appearance of images called speckle patterns. The statistical database of the scattered fingerprints of the object is computed. The speckle images are captured by a Charge Coupled Device(CCD) and are then explored by digital speckle processing to acquire the surface roughness. This technique is appropriate to determine the average optical roughness(Ra) of the specimen and the sub-micron range of Root Mean Square(RMS) values of the sample agreed well by way of the stylus conventional profilometer method.

A New Study on the Effect of Pure Anatase TiO2 Film Thickness on Gentian Violet Photodegradation Under Sunlight: Considering the Effect of Hole Scavengers

In this paper, pure anatase TiO2 thin films were grown on glass substrates by using sol-gel dip-coating method. To study the physical, chemical and optical properties of the deposits, TiO2 thin films were synthesized with thickness (241.5, 258.19, 230.33 and 302.35 nm). XRD patterns show that TiO2 films were grown with unique anatase phase (101). The photocatalytic test shows that film (~ 302 nm) gives high photodegradation of gentian violet (GV) under sunlight irradiation due to the low number of defect sites. The increase in film thickness and the decrease of surface roughness and crystal size decrease the number of defect sites in the material which lead to low recombination rate of charge carriers. The use of Ag+ as hole scavenger increases the photocatalytic activity 4.75 times within the first hour. The photocatalysis process showed that Ag+ can be reduced on the surface of photoactivated TiO2 thin films to obtain sun-photodeposited/dip-coated AgO/TiO2 (p-n) heterojunction. HIGHLIGHTS Pure anatase TiO2 thin films were successfullysynthesized via sol-gel dip-coating method High thickness (302 nm) of TiO2 thin film exhibits high photocatalytic activity for photodegradation of GV under sunlight irradiation The presence of Ag+ in wastewater shows high photocatalytic activity of TiO2 films with 4.75 times within the first hour The possibility of sun-photodeposited/dip-coated of (p-n) AgO/TiO2 heterojunction is discussed GRAPHICAL ABSTRACT

Experimental analysis of folic acid adsorption on TiO2 thin-films

TiO 2 thin-films functionalized with specific biomolecules have been used in the fabrication of highly sensitive and selective electrochemical biosensors focused on detecting a variety of diseases. Among the biosensors of scientific and technological interest are those obtained from the functionalization of nanomaterials with folic acid to recognize folate receptors; their importance lies in the fact that these receptors are overexpressed in most abnormal cells, and their identification can allow the detection of tumor cells and the photothermal treatment of cancer. This work presents a methodology for fabricating TiO2 thin-films and functionalizing them with folic acid. X-ray photoelectron spectroscopy, atomic force microscopy, Raman spectroscopy, and contact angle measurements were used to examine the adsorption of folic acid on TiO2 thin-film surfaces grown by pulsed laser deposition. XPS and Raman analysis indicated that the interaction of folic acid with the TiO2 surface occurred either through the pteridine ring or through the carboxylic groups of the glutamic acid portion.

INTERACTION OF TIO2 NANOPARTICLES AND PROTEINS OF AN IMMUNE COMPLEX IN PHOTOLUMINESCENCE BASED BIOSENSOR

Interaction between nanostructured semiconductor thin layers and immune complex based proteins is a fundamental issue of the formation of nanobiointerface in the various biosensors, in particular, optical biosensors. In this work, the main aspects of the interaction between photoluminescent TiO2 nanoparticles and Bovine leucosis virus (BLV) protein gp51, used as a model protein, during the formation of photoluminescence based immunosensor have been discussed. The antigens of gp51 were immobilized on the surface of a nanostructured TiO2 thin film formed on the glass substrates. As a result, an increase of the photoluminescence (PL) signal intensity and PL peak shift from 517 nm to 499 nm were observed. An incubation of TiO2/gp51 structure in a solution containing anti-gp51 antibodies resulted in the backward PL peak shift from 499 nm to 516 nm and decrease of the PL intensity. The main reason of the changes in the PL spectra (i.e. PL maxima shifts and PL intensity variations) as a result of BLV protein gp51 adsorption on the surface TiO2 thin film is an electrostatic interaction between negatively charged surface of TiO2 and positively charged atoms and groups provided by the adsorbed gp51 protein due to the presence of partial uncompensated charges within the proteins.

Thermoinduced and Photoinduced Sustainable Hydrophilic Surface of Sputtered-TiO2 Thin Film

To achieve self-cleaning at a low maintenance cost, we investigated the possibility of obtaining a sustainable hydrophilic surface of TiO2 thin film. As the hydrophilicity of TiO2 films fabricated by FTS has not yet been studied, we deposited TiOx using FTS, and then TiO2 was formed through additional treatment. Hydrophilic surfaces were obtained by thermoinduced and photoinduced methods. UV irradiation led to the conversion of Ti4+ to Ti3+ in the lattice structure and an increase in the number of OH groups on the surface, and annealing induced the formation of Ti3+ defect sites, as well as organic degradation and changes in the crystal structure. Through the annealing process, the water contact angle of as-deposited film was decreased from 78.7° to 35.7°, and crystallinity changed from amorphous to anatase. These changes contributed to the formation of a hydrophilic surface and reduced the water contact angle by up to 10.8°. After the formation of a hydrophilic surface through annealing and UV irradiation, the sample returned to its original state. We confirmed that the water contact angle of the returned sample was decreased through exposure to sunlight; it reduced the water contact angle of the returned sample by 15.2°. Thus, the results revealed that the crystallinity influences the hydrophilicity and its sustainability for TiO2 films under sunlight.

Study on photocatalytic properties of Cu2O/TiO2 heterojunction composite films

Cu2O/TiO2 semiconductor heterostructure photocatalytic composite thin films were prepared by the sol-gel method and magnetron sputtering technology. Uniform and transparent TiO2 thin films were prepared by sol dipping and pulling with butyl titanate as the raw material. P-type Cu2O thin films were reactive sputtered on the surface of TiO2 thin films with metal Cu as target source. The catalysts were characterized by SEM, XRD and UV-Vis. The photocatalytic activity of heterojunction composite films under simulated sunlight was investigated by dye degradation experiments, and its mechanism is discussed. The results show that the heterojunction film formed by the composite of TiO2 and Cu2O has good photocatalytic activity under simulated sunlight. The heterojunction composite expands the light response range and light response intensity of the catalyst and improves the quantum efficiency. It is a kind of photocatalytic composite film that makes full use of solar energy.

Multifractal study of TiO2 thin films deposited by MO-CVD method: The role of precursor amount and substrate temperature

Since TiO2 thin film is an important semiconductor with many applications in various fields, in this work we studied surface morphology of TiO2 thin films deposited by metal-organic chemical vapor deposition method using multifractal technique. In order to do this, AFM images of prepared TiO2 thin films were analyzed by multifractal method and the effects of the precursor amount and substrate temperature on multifractality of The TiO2 thin films surface were investigated. Multifractal nature of surface of TiO2 thin films deposited with different amounts of precursor at two different positions of substrate with different temperatures was detected using multifractal analysis of the AFM images. The multifractal spectrum f(α) obtained from AFM images indicated that the Δf and width of spectrum are functions dependent on precursor amount and substrate temperature. The obtained data showed that local fluctuation and hight distribution increase with increasing in temperature of substrate for high amount of precursor. Also, it was observed that the substrate temperature has no effect on width of multifractal spectrum at low amount of precursor. Our results clearly showed that morphological complexity of the TiO2 surface and the effect of the precursor amount and temperature of substrate are satisfactorily described by perform multifractal analysis on AFM images. These results can be used in the design and manufacture of interface layer for application in laptops, planer device, transparent electrode, solar cell, sensors and optical devices.

Surface and photocatalytic properties of TiO2 thin films prepared by non-aqueous surfactant assisted sol-gel method

Titanium dioxide (TiO2) thin films are prepared on glass substrates using sol-gel spin coating method. Titanium tetraisopropoxide (TTIP) precursor is used to prepare TiO2 sol-gels using Ethanol solvent. Acetyl acetone (AcAc) and Acetic acid (AA) are used as modifiers and Cetyltrimethylammonium Bromide (CTAB) surfactant as pore-forming agent. A clear transparent TiO2 sol-gel is obtained without precipitation only when both AA and AcAc are present in the TiO2 sol. A worm-like structure is observed in the film at 0.1 M TTIP and changed to the flake-like structure in the film at 0.4 M TTIP. The TiO2 thin films are non-porous and porous when CTAB is below and above the concentration of 0.8 g per 0.01 mol TTIP. The critical micelle concentrationis found to exist between 0.6 to 0.8 g CTAB per 0.01 mol TTIP. Grazing Incidence X-ray diffraction and Raman analysis confirm the presence of anatase phase in the 3 and 4 times coated TiO2 thin films. The field emission scanning electron microscopy analysis shows that a highly homogeneous and uniform thin film is obtained with TiO2 sol-gel composition of 0.2 M TTIP, 0.1 M AcAc, 0.09 M AA and 1 g of CTAB per 0.01 mol TTIP. The photocatalytic activity of the TiO2 films is determined by investigating the photodegradation of methylene blue (MB) in aqueous solution. The TiO2 thin film with 110.7 nm and 145.3 nm thickness showed 42.6 % and 58.4 % degradation of MB, respectively, at 60 min of photocatalytic reaction under UV light irradiation.

A novel BSA immobilizing manner on modified titanium surface ameliorates osteoblast performance

Surface modification of medical and dental devices, to improve their biocorrosion resistance and biocompatibility, can be achieved with the multidisciplinary field of biomaterials. Nanostructured titanium dioxide (TiO2) has been employed as surface modifier of titanium-based biomaterials because it can prevent the failure of the devices due to wear mechanisms. Moreover, this oxide surface is mostly terminated by hydroxyl groups (-OH) that can be directly functionalized with biomolecules to improve the biocompatibility of these devices. We explored the influence of 3-aminopropyltrimethoxysilane (APTMS) molecules as spacers in bovine serum albumin (BSA) protein immobilization on the physically hydroxylated surfaces of rutile phase TiO2 films grown by reactive Radio Frequency (RF) magnetron sputtering. X-ray Photoelectron Spectroscopy (XPS) was used to examine the adsorption of BSA and APTMS on the hydroxylated surface of TiO2 thin films. For biological tests, BSA was directly immobilized on the film surface and on the APTMS monolayer. Biological analysis found better osteoblast performance considering gene markers related to cell adhesion after interacting directly with the surface modified by the immobilization of BSA, especially on the surface where this protein was immobilized by APTMS. Additionally, we addressed the relevance of this biointerfaces on extracellular matrix remodeling by zymography analysis. Altogether, our data provides new insights about the cellular and molecular mechanisms covering the improved osteoblastic response of the proposed surface modification.

Surface and electronic properties of rutile TiO2 thin films coated with PbO2

Binary films of semiconductors have lots of potential applications in material science. Initially, these films were based on In2O3 but, because of its high coast, alternative materials to replace it have been intensely sought after. In this sense, TiO2 and PbO2 are both n-type degenerated semiconductors, which can be good alternatives due to its easy preparation and low cost. Its unique characteristics justify investigating the properties of films composed of both materials. Structural and electronic surface properties of thin films with crystallographic planes (0 0 1), (0 1 0), (1 0 1), and (1 1 0) of TiO2 coated with PbO2 (TiO2/PbO2), both in rutile form, have been investigated in this study. Pure TiO2 and PbO2 bulk and TiO2 thin films have also been studied for comparison purposes. Periodic quantum mechanics DFT calculations have been performed using B3LYP hybrid density functional and taking into account long-range interactions. In both bulks, the energy near the top of the valence band comes mainly from the O 2p orbitals. In the PbO2 the states in the lower energy region of the conducting band are basically composed of Pb 6s and 6p orbitals, while in TiO2 those states come mainly from the Ti 3d orbitals. The relative stability of the TiO2 thin films (surfaces) follows the sequence (1 1 0) > (0 1 0) > (1 0 1) > (0 0 1), but changes substantially in the TiO2/PbO2 binary thin films increasing as (0 1 0) > (1 0 1) > (0 0 1) > (1 1 0). Band gap energies of the four studied pure TiO2 thin films are practically the same as the bulk. However, there is a remarkable decrease in the band gap energies of binary films compared to pure TiO2 films. The decrease in the bottom of the conduction band is due to the contribution of Pb 6s and 6p orbitals at energies below the bottom of the conduction band of the pure TiO2 films.

Hybrid organic and inorganic solar cell based on a cyanine dye and quantum dots

The combination of organic dyes with quantum dots (QDs) in solar cells can lead to more improvement in photovoltaic performance for such types of solar cells. Due to the quantum confinement, the photoluminescence (PL) of QDs can be tuned to match the absorption spectra of applied organic dyes. Herein, we introduce a new hybrid solar cell based on monomethine cyanine dye co-sensitized by CdS and CdTe/CdS core shell. The cyanine dye tends to aggregate on the surface of colloidal QDs due to electrostatic attraction followed by energy and electron transfer from QDs to cyanine dye. Electrophoretic deposition method was carried out to assist the cyanine dye loading on the surface of TiO2 thin film and the highest power conversion efficiency was 0.89% in case of cyanine dye co-sensitized by CdTe/CdS with open circuit voltage of 0.78 V and a photocurrent of 1.80 mA/ cm2.

3-Mercaptopropionic acid functionalization of titanium dioxide thin films

Abstract Nanostructured titanium dioxide (TiO2) films are commonly employed as surface modifiers on medical and dental metallic implants, presenting promising results related to interactions with living tissues, promoting improvements in the in vivo biocorrosion resistance and increased bioactivity when compared to non-coated metallic materials. In addition to these properties, titanium dioxide is also well recognized for its biocompatibility. However, considering the necessary integration with surrounding tissues when this oxide is applied as implant coatings, there are many aspects of the adhesion mechanisms located at the interface between the biological environment and the oxide surface that still need to be addressed. Specifically regarding the surface chemistry, these oxides are mainly terminated by hydroxyl groups (-OH) that are readily functionalized by different molecules, such as the 3-mercaptopropionic acid (MPA). In this contribution, X-ray photoelectron spectroscopy (XPS) and atomic force microscopy (AFM) were used to examine the adsorption of MPA on anatase- and rutile-phase forms of TiO2 thin film surfaces grown by RF magnetron sputtering. According to the obtained results, both anatase and rutile TiO2 films present similarities in roughness and thickness. However, different responses to interaction with the MPA molecules were observed, wherein the functionalization was seen to occur only for the rutile phase.

Inertial impaction and surface diffusion-assisted rapid dye molecule adsorption on TiO2 thin films for highly efficient dye-sensitized solar cells

An effective and versatile single-stage aerosol impactor was specially designed to rapidly coat the surface of TiO2 thin films with a controlled amount of dye molecules via inertial impaction and surface diffusion to speed-up the manufacturing process and enhance the photovoltaic performance of dye-sensitized solar cells (DSSCs). By theoretically determining the specific dimensions of the aerosol accelerating nozzle and experimentally controlling the mixing ratio between the sheath gas and dye aerosol flow rates in the single-stage aerosol impactor, the speed and quality of dye adsorption on the TiO2 thin films of the photoelectrodes could be systematically assessed in terms of the photovoltaic performance of the DSSCs, including open-circuit voltage, short-circuit current, fill factor, and power conversion efficiency (PCE). It was found that the aerosol impactor-assisted dye coating method developed in this study significantly reduced the duration of dye adsorption (aerosol coating duration = 20–60 min) and increased the PCE of the DSSCs to 7.28%. Using this methodology, dye-coating was ∼20 times faster and the fabricated device has 23% higher PCE compared to the DSSC fabricated by the conventional dip coating method (dip-coating duration = 1200 min, PCE = 5.92%). These results proved that the single-stage aerosol impactor designed in this study is a very effective and versatile device for rapidly coating the surface of TiO2 thin films with dye molecules using sufficient inertial impaction, which enables the introduced dye molecules to infiltrate and quickly adsorb on the surface of TiO2 nanoparticles accumulated in the DSSC photoelectrodes.

Effect of Configuration on the Photocatalytic Activity of AgNPs-TiO2 System

This paper studies the effect of the configuration of silver nanoparticles (AgNPs)-TiO2 on the visible-light-driven photocatalytic activity (PA). Three configurations were fabricated by vacuum thermal deposition: configuration I, AgNPs deposited on the surface of TiO2 thin films; configuration II, AgNPs deposited on a glass and covered by TiO2 thin films; and configuration III, AgNPs deposited on the surface of TiO2 thin films and covered by TiO2. The PAs of the three configurations were studied and compared. Our study indicates that configuration II is the most cost-efficient one, while configuration III could obtain the highest visible light-induced PA. The maximum of PA could be achieved when the top layer of TiO2 is less than 2 nm. The mechanisms were discussed from three aspects, the influence of TiO2 thickness on the localized surface plasma resonance (LSPR) of AgNPs, the separation, and the transportation of hot carriers. By this study, the most effective way to make use of the PA of TiO2-AgNPs was scientifically searched out.

Interaction mechanism between TiO2 nanostructures and bovine leukemia virus proteins in photoluminescence-based immunosensors.

In this research a mechanism of interaction between a semiconducting TiO2 layer and bovine leukemia virus protein gp51, applied in the design of photoluminescence-based immunosensors, is proposed and discussed. Protein gp51 was adsorbed on the surface of a nanostructured TiO2 thin film, formed on glass substrates (TiO2/glass). A photoluminescence (PL) peak shift from 517 nm to 499 nm was observed after modification of the TiO2/glass by adsorbed gp51 (gp51/TiO2/glass). After incubation of the gp51/TiO2/glass in a solution containing anti-gp51, a new structure (anti-gp51/gp51/TiO2/glass) was formed and the PL peak shifted backwards from 499 nm to 516 nm. The above-mentioned PL shifts are attributed to the variations in the self-trapped exciton energy level, which were induced by the changes of electrostatic interaction between the adsorbed gp51 and the negatively charged TiO2 surface. The strength of the electric field affecting the photoluminescence centers, was determined from variations between the PL-spectra of TiO2/glass, gp51/TiO2/glass and anti-gp51/gp51/TiO2/glass. The principle of how these electric field variations are induced has been predicted. The highlighted origin of the changes in the photoluminescence spectra of TiO2 after its protein modification reveals an understanding of the interaction mechanism between TiO2 and proteins that is the key issue responsible for biosensor performance.

SINTESIS LAPISAN TIPIS TiO2 BERPORI YANG DIMODIFIKASI OLEH NITROGEN DENGAN METODE PEROKSO SOL-GEL, KARAKTERISASI DAN APLIKASINYA SEBAGAI MATERIAL PEMBERSIH DIRI (SELF CLEANING MATERIAL)

The photocatalytic properties of TiO2 compound in anatase phase can be activated under visible light by nitrogen modification and its ability can be increased by generated porous structure using polietilen glikol (PEG) on TiO2 thin film surface. The porous N/TiO2 thin films were prepared by heating aqueous peroxotitanate thin films by addition of polietilen glikol (PEG) deposited uniformly on superhydrophilic uncoated glass at 500 oC for 1 h. The result of X-ray diffraction (XRD) confirmed the resence of only anatase phase for all samples. The UV-Vis spectroscopy showed the synthesized porous N/TiO2 thin films exhibit the absorption in the visible range (400-500 nm). Photocatalytic activity of porous N/ TiO2 thin films were evaluated by using fourier transform-infrared spectroscopy (FTIR) to determine the ability of this photocatalyst for stearic acid degradation under visible light irradiation. The result showed that N/TiO2/PEG-2.1 thin film degraded the stearic acid was about 87,86%, which was 1,12 times higher than that of N-doped TiO2 and 9,9 times higher than that of undoped TiO2 thin film.

Patterning of wettability using the photocatalytic decomposition of hydrophobic self-assembled monolayer on the TiO2 pattern

We report a patterning process for an octadecylphosphonic acid self-assembled monolayer (ODP-SAM) using TiO2 patterns fabricated by a combined use of reactive sputtering and CF4 plasma etching. The ODP-SAM with the remaining outer region of TiO2 patterns can be used as a constant hydrophobic region. The photocatalytic decomposition of the ODP-SAM on TiO2 thin films can be applied to the formation of hydrophobic/hydrophilic wettability patterns. The photoresponsive wettability of TiO2 thin films with different surface morphologies was examined on films deposited under different sputtering conditions. The contact angle on the ODP-SAM/TiO2 surface was successfully changed from 134.8 to 0° by exposing the raw TiO2 surface after the photodecomposition of the ODP-SAM, whereas the contact angle on the ODP-SAM in the outer region of TiO2 patterns remained constant at 112.1°. The width of the wettability switching range of the raw surface of sputter-deposited TiO2 thin films can be controlled by changing the deposition conditions of the TiO2 thin films. Droplet generation solely through the bottom surface with wettability patterns defined by a combined use of an ODP-SAM and TiO2 patterns in a microchannel was also demonstrated.