Deposition Of Titanium Dioxide Nanoparticles Research Articles

Deposition of titanium dioxide nanoparticles onto engineered rough surfaces with controlled heights and properties

Understanding the influence of surface roughness on the deposition of nanoparticles is important to a variety of environmental and industrial processes. In this work, slanted columnar thin films (SCTFs) were engineered to serve as an analogue for rough surfaces with controlled height and surface properties. The deposition of titanium dioxide nanoparticles (TiO2NPs) onto alumina- or silica-coated SCTFs (Al2O3-Si-SCTF, SiO2-Si-SCTF) with varying heights (50 nm, 100 nm, and 200 nm) was measured using a combined quartz crystal microbalance with dissipation monitoring (QCM-D) and generalized ellipsometry (GE) technique. No TiO2NP deposition was observed on flat, silica-coated QCM-D sensors or rough, 100 nm thick SiO2-Si-SCTF. TiO2NP deposition onto Al2O3-Si-SCTFs in ultra-pure water was significantly higher than on the flat alumina-coated QCM-D sensor, and deposition increased as the roughness height increased. The nanoparticle attachment was sensitive to the local flow field and the interaction energy between nanoparticles and the QCM-D sensor. At a higher ionic strength condition (100 mM NaCl), TiO2NP aggregates with varying sizes formed a rigid layer on top of SCTFs. For the first time, deposition of nanoparticles was measured as a function of roughness height, and the impact of roughness on the properties of the attached nanoparticle layers was revealed. This finding indicates that key parameters describing surface roughness should be explicitly included into models to accurately predict the transport of nanoparticles in the subsurface.

Combined quartz crystal microbalance with dissipation (QCM-D) and generalized ellipsometry (GE) to characterize the deposition of titanium dioxide nanoparticles on model rough surfaces

Measuring the interactions between engineered nanoparticles and natural substrates (e.g. soils and sediments) has been very challenging due to highly heterogeneous and rough natural surfaces. In this study, three-dimensional nanostructured slanted columnar thin films (SCTFs), with well-defined roughness height and spacing, have been used to mimic surface roughness. Interactions between titanium dioxide nanoparticles (TiO2NP), the most extensively manufactured engineered nanomaterials, and SCTF coated surfaces were measured using a quartz crystal microbalance with dissipation monitoring (QCM-D). In parallel, in-situ generalized ellipsometry (GE) was coupled with QCM-D to simultaneously measure the amount of TiO2NP deposited on the surface of SCTF. While GE is insensitive to effects of mechanical water entrapment variations in roughness spaces, we found that the viscoelastic model, a typical QCM-D model analysis approach, overestimates the mass of deposited TiO2NP. This overestimation arises from overlaid frequency changes caused by particle deposition as well as additional water entrapment and partial water displacement upon nanoparticle adsorption. Here, we demonstrate a new approach to model QCM-D data, accounting for both viscoelastic effects and the effects of roughness-retained water. Finally, the porosity of attached TiO2NP layer was determined by coupling the areal mass density determined by QCM-D and independent GE measurements.

Effect of different-sized colloids on the transport and deposition of titanium dioxide nanoparticles in quartz sand

Colloids (non-biological and biological) with different sizes are ubiquitous in natural environment. The investigations regarding the influence of different-sized colloids on the transport and deposition behaviors of engineered-nanoparticles in porous media yet are still largely lacking. This study investigated the effects of different-sized non-biological and biological colloids on the transport of titanium dioxide nanoparticles (nTiO2) in quartz sand under both electrostatically favorable and unfavorable conditions. Fluorescent carboxylate-modified polystyrene latex microspheres (CML) with sizes of 0.2–2 μm were utilized as model non-biological colloids, while Gram-negative Escherichia coli (∼1 μm) and Gram-positive Bacillus subtilis (∼2 μm) were employed as model biological colloids. Under the examined solution conditions, both breakthrough curves and retained profiles of nTiO2 with different-sized CML particles/bacteria were similar as those without colloids under favorable conditions, indicating that the copresence of model colloids in suspensions had negligible effects on the transport and deposition of nTiO2 under favorable conditions. In contrast, higher breakthrough curves and lower retained profiles of nTiO2 with CML particles/bacteria relative to those without copresent colloids were observed under unfavorable conditions. Clearly, the copresence of model colloids increased the transport and decreased the deposition of nTiO2 in quartz sand under unfavorable conditions (solution conditions examined in present study). Both competition of deposition sites on quartz sand surfaces and the enhanced stability/dispersion of nTiO2 induced by copresent colloids were found to be responsible for the increased nTiO2 transport with colloids under unfavorable conditions. Moreover, the smallest colloids had the highest coverage on sand surface and most significant dispersion effect on nTiO2, resulting in the greatest nTiO2 transport.

The deposition of titanium dioxide nanoparticles by means of a hollow cathode plasma jet in dc regime

TiO nanoparticles are being investigated in this work. Nanoparticles were obtained in Ar plasma on monocrystaline Si(111) substrate by means of a gas-phase deposition using a low pressure hollow cathode plasma jet. The material of the cathode is pure titanium. Oxygen was introduced separately from argon through an inlet in the chamber. The nanoparticle growth mechanism is qualitatively discussed. The morphology of the surfaces of thin films was investigated by an atomic force microscope. The chemical composition of the thin films was investigated by means of an energy-dispersive x-ray analysis and x-ray photoelectron spectroscopy. A cylindrical Langmuir probe and a fiber optic thermometer was used for measurements of plasma parameters and neutral gas temperature respectively. The relationship between plasma parameters and the films’ morphology is particularly explained.

Solid-phase microextraction of phthalate esters from aqueous media by electrophoretically deposited TiO2 nanoparticles on a stainless steel fiber

A novel SPME fiber was prepared by electrophoretic deposition of titanium dioxide nanoparticles (nano-TiO2) on a stainless steel wire. It was used in the direct immersion solid-phase microextraction (DI-SPME) of four phthalate esters from aqueous samples prior to gas chromatographic (GC) analysis. The effects of various parameters on the efficiency of the SPME process such as the mode of extraction, extraction temperature, film thickness of the SPME fiber, salt content, extraction time and stirring rate were investigated. The comparison of the fiber with another homemade poly(3,4-ethylenedioxythiophene)-TiO2 (PEDOT-TiO2) nanocomposite fiber and a commercial polydimethylsiloxane (PDMS) fiber showed the better extraction efficiency of the nano-TiO2 fiber for phthalate esters. Under optimized conditions, the limit of detection (LOD) for the phthalate esters varied between 0.05 and 0.12μgL−1. The inter-day and intra-day relative standard deviations for various phthalate esters at 10μgL−1 concentration level (n=6) using a single fiber were 6.6–7.5% and 8.3–11.1%, respectively. The fiber to fiber repeatabilities (n=4), expressed as relative standard deviation (RSD%), were between 8.9% and 10.2% at 10μgL−1 concentration level. The linear ranges varied between 0.5 and 1000μgL−1. The method was successfully applied to the analysis of the bottled mineral water sample with recoveries from 86 to 107%.

Laser deposition of TiO2 nanoparticles on glass fabric

In this research work light laser irradiation was used for deposition of titanium dioxide nanoparticles on the surface of glass mat. For this purpose TiO2 nanoparticles were evenly applied on the surface of a glass fiber mat. The glass fiber mat containing the metals was then irradiated with the laser light beam (100μs). The morphology of the fabrics was observed using a Scanning Electron Microscope. An X-ray fluorescence spectrum and energy dispersive X-ray were used for elemental analysis. Also mechanical properties and air permeability of the irradiated samples were analyzed and the results show that both tenacity and elongation of laser irradiated sample are reduced but the air permeability is improved after laser irradiation. The photocatalytic activities of TiO2 deposited glass fabrics were assessed by analyzing the decrease in concentration of the Orange II as a colorant after exposure to UV irradiation. The results clarify that the Orange II concentration decreases continuously, concomitant with the UV irradiation time up to 270min.

Influence of natural organic matter on the aggregation and deposition of titanium dioxide nanoparticles

The aggregation kinetics of TiO 2 nanoparticles was studied in the absence and presence of Suwanee River humic acid (SRHA) in either NaCl or CaCl 2 electrolytes. The CCC[Ca 2+]/CCC[Na +] ratios were found to yield a proportionality fraction of z −7.2 (in the absence of SRHA) and z −5.6 (in the presence of SRHA), near the theoretical prediction of z −6, where z is the cation's valence. SRHA drastically increased the stability of TiO 2 nanoparticles under most conditions, due to the combined effect of increased electrostatic and steric repulsions. Deposition rates of TiO 2 nanoparticles onto a silica surface were quantitatively measured using a quartz crystal microbalance with dissipation (QCM-D) over a broad range of solution (pH and ionic strength, IS) conditions, and the effects of the SRHA on particle deposition behavior were evaluated. In general, zeta potential can be used to predict the interaction energies between particles or particles and surfaces, and from there an inference can be made as to the potential for aggregation and deposition. The presence of SRHA significantly hinders TiO 2 deposition onto silica surfaces via steric repulsion in addition to repulsive electrostatics even under high ionic strength, which has important implications for the mobility of these nanoparticles.