جستجوی مقالات مرتبط با کلیدواژه « tio2 nanoparticles » در نشریات گروه « پزشکی »

In the present study, natural and synthetic adsorbents were used to remove nickel ions through the adsorption process. First, TiO2 nanoparticles (NPs) were prepared through the sol-gel method. The synthesized samples were then characterized using X-ray diffraction spectroscopy (XRD), Fourier transform-infrared (FTIR) spectroscopy, scanning electron microscopy (SEM), transmission electron microscopy (TEM), and N2 adsorption/desorption isotherms (BET). The influences of different operational parameters including adsorbate content, pH, adsorbent concentration, contact time, ionic strength, and stirring speed were also explored. According to the results, the pseudo-second-order kinetic model showed the best performance in evaluating the experimental data when using both adsorbents. The adsorption of nickel cations by the thin film membrane on the surface of TiO2 NPs is a rate-determining step of the removal reaction. The removal rate constants of nickel ions from aqueous solutions by TiO2 NPs and pomegranate peel were evaluated to be 0.013 and 0.018 g mg-1 min-1, respectively. The thermodynamic parameters such as Gibbs free energy, enthalpy, and entropy were also determined. Nickel removal processes in all cases were endothermic and spontaneous. The removal mechanism also followed physical adsorption. Equilibrium data were fitted with Langmuir, Freundlich, Temkin, and Dubinin–Radushkevich models. The results showed that the adsorption of Ni2+ on TiO2 NPs and pomegranate peel followed Freundlich and Temkin isothermal models, respectively. Based on the calculated removal percentage, TiO2 is a better adsorbent for removing Ni2+ from the aqueous medium as compared to pomegranate peel.

Objective This study aimed to investigate and compare the properties of titanium dioxide (TiO2) and TiO2/Chitosan (TiO2/CS) NPs and their effect on wound healing and bone defect repair. TiO2 NPs synthesized and modified using of CS. Methods to evaluate the modification surface changes of NPs FTIR analyses were used. The size of NPs was evaluated by PCS and TEM. MTT assay was performed to compare the effects of various concentrations of NPs in cell culture. Here, the examination group was divided into two groups: the burn model treatment group and the bone defect treatment model. Histomorphologic observations were performed to evaluate and compare the results. Results The TEM image showed a spherical shape and smooth surface with a particle size on a nanometric scale. The particle size of TiO2 NPs modified with CS depicted in TEM images is in agreement with the results obtained by PCS results. Furthermore, the images show that the particles exhibit a spherical shape, and a matrix without aggregation. Cytotoxicity assay on mesenchymal stem cells (MSCs) approved nontoxic effects of TiO2/CS with dose of 1 and 5 µg/ml. The data also demonstrated that coating the TiO2 NPs with CS at higher concentrations significantly increases their biocompatibility. Histological investigations revealed that skin and bone regeneration in the experimental classes by TiO2/CS was remarkably enhanced than other groups. The process of synthesis of NPs has effective influences on their bioactivity and cytotoxicity. Conclusion Covering TiO2 NPs with chitosan is highly suggested for tissue regeneration and engineering applications.

Chemical agents, in combination with mechanical methods, play an important role in reducing microbial plaque on denture surfaces. However, these methods might change the mechanical behavior of acrylic resins, including microhardness and surface roughness. This in vitro study investigated the effect of two disinfectants, i.e., water and sodium hypochlorite, on the microhardness of conventional heat-cured and TiO2 nanoparticle-reinforced acrylic resins.

Sixty acrylic resin specimens were divided into two groups, and the samples in each group were randomly assigned to three subgroups (n=10). Heat-cured specimens and 1 wt% TiO2 acrylic resin were prepared and immersed in three solutions: water, a solution prepared with NatureDent pills, and 1% sodium hypochlorite for 30, 60, and 90 days. Microhardness tests were performed on each sample at each immersion stage. The data were analyzed using descriptive statistical methods, three-way and one-way ANOVA, repeated-measures t test, and Tukey HSD tests using SPSS 17. P values<0.05 were considered significant.

All three independent parameters, including resin, solution, and time, significantly affected microhardness (P<0.05). The microhardness of both specimen types, i.e., conventional heat-cured and TiO2 nanoparticle-reinforced acrylic resins, immersed for 30, 60, and 90 days, was the highest and lowest in water and hypochlorite solutions, respectively. Regarding 90 days, the microhardness values of conventional heat-cured and TiO2 nanoparticle-reinforced acrylic resins were 17.050±0.094 and 19.953±0.053 in water, 15.675±0.069 and 18.965±0.037 in hypochlorite, and 16.713±0.122 and 19.39±20.113 in NatureDent solutions, respectively.

Disinfecting two types of acrylic resin specimens decreased their microhardness as a function of immersion time for up to 90 days in the three solutions. However, the magnitude of hardness lost was less for TiO2 nanoparticles-reinforced acrylic resin.

Bioactive compounds like curcumin can be incorporated into food packaging formulation either to enhance physico-mechanical properties or to improve the biological activity of the packaging systems. Furthermore, it enables the packaging to monitor the changes in food quality. In the present study, the effect of curcumin concentration (0.2, 0.4 and 0.6%) on physico-mechanical and biological activity of soluble soy bean polysaccharide (SSPS)/TiO2 nanoparticles nanocomposites were investigated. Additionally, the release behavior of this bioactive compound from the developed film was tested. Finally, the color changing of SSPS/TiO2 nanoparticles/curcumin nanocomposites in contact with different mediums were examined. When the curcumin concentration increased up to a certain point (0.4 %), the physical and mechanical properties of the film improved, but beyond this point, an opposite effect was observed. SSPS/TiO2 nanocomposite showed strong antibacterial activity against both gram positive and negative bacteria. Small amount of curcumin released in ethanol as a food simulant. The films incorporated by curcumin can be used as promising packaging systems for non-destructively detecting quality and freshness of foods.

In this work, an efficient photocatalyst based on β-cyclodextrin-glycine-modified TiO2 nanoparticles (TiO2-Gly-βCD NPs) was successfully synthesized. The photocatalytic activity of the prepared TiO2-Gly-βCD was tested on the degradation of methylene blue (MB) and methyl orange (MO) dyes. The enhanced surface properties of TiO2-Gly-βCD photocatalyst generated excellent photocatalytic performance for the photocatalytic degradation of dyes in aqueous solution. These were strongly attributed to the presence of the functional hydroxyl groups and the inner cores of the hydrophobic cavity in β-CD to form inclusion complexes with organic molecules. As compared to the pure TiO2 and TiO2 modified by Gly, the dye degradation rate under UV irradiation was considerably enhanced by TiO2/Gly/βCD as a photocatalyst. In addition, the sonocatalytic degradation of dyes was investigated, and it was found that the ultrasonic waves slightly enhanced the degradation time of dyes. The results indicated that the first-order kinetic model well describes the degradation of MB and MO dyes by TiO2-Gly-βCD. Furthermore, the chemical oxygen demand (COD) values were determined for real industrial wastewater and treated wastewater.

Photocatalytic process is used as a suitable method for o-chlorophenol removal. In this study, the efficiency of a mixture of modified fly ash and TiO2 nanoparticles in photocatalytic removal of o-chlorophenol was evaluated.
After acid washing of fly ash, the absorbent was oxidized with potassium permanganate. Then, the substrate mixture of modified fly ash and TiO2 nanoparticles was used for photocatalytic decomposition of o-chlorophenol.
The percentage of carbon increased from 77.94% to 86.52% after acid washing of fly ash and absorption efficiency increased from 58.8% up to 83.3%. During the oxidation of acid washed fly ash, absorption efficiency reached to 93.27%. Photocatalytic removal efficiency of o-chlorophenol by mixture of modified fly ash and TiO2 increased to 98.9%. Photocatalytic removal efficiency of o-chlorophenol by TiO2/UV and without use of fly ash was 78.7%.
Industrial application of this method recommended because of the simple modification, high efficiency removal and prevention of environment pollution.

This study describes the adsorption and photocatalytic removal of  methylene blue (MB) from aqueous solution by surface-modified TiO2 nanoparticles under ultraviolet irradiation in a batch system. The 5-sulfosalicylic acid grafted TiO2 (5-SA-TiO2) as a photocatalyst was characterized by means of XRD, FTIR and SEM  techniques. The surface of TiO2 nanoparticles was modified by 5-sulfosalicylic acid (5-SA) to increase performance by altering surface properties. Notably, in contrast with the adsorption process, the remarkable removal enhancement of  MB dye was observed by photocatalytic degradation process from aqueous solution. The adsorption and photocatalytic degradation kinetics of MB using 5-SA-TiO2 nanoparticles have also been investigated. The results show that the photocatalytic degradation was good fit with the  pseudo-first-order kinetic model (R2 > 0.99). The adsorption isotherm of  MB onto modified TiO2 nanoparticles fitted into the Temkin equation. In addition, thermodynamic studies indicate the spontaneous behavior of adsorption and photocatalytic degradation processes.

Heavy metals such as cadmium and lead are the most important toxins spreading through various ways like water, soil, and air in nature and easily enter human food chain. It is essential to determine the cumulative and harmful effects of these metals in nutrients, especially in cow milk because it is a unique source of food for all ages and it contains both essential and nonessential trace elements.
A total of 100 milk samples were directly collected from healthy cows in Zabol located on east of Iran. The samples were tested to determine lead and cadmium residues. The rates of the heavy metals were determined using a Rayleigh atomic absorption spectrum equipped with hollow cathode lamps (HCL) at 283.3 nm for lead (Pb) and at 228.8 nm for cadmium (Cd). By using the photo-catalytic titanium dioxide nanoparticles, these toxic metals were removed.
The mean ± SD of the concentration of lead and cadmium in raw milk were 9.175± 2.5 and 4.557 ± 1.081 ppb, respectively. Also, the P-values of Kalmogorov– Smiranov test for lead and cadmium were respectively 0.057 ppb (P>0.05) and 0.435 ppb (P>0.05). TiO2 nanoparticles were used to eliminate and remove lead and cadmium in milk samples. The results showed that there was a significant difference between lead and cadmium contents before and after adding TiO2 nanoparticles (P According to results of this study, there was a very low amount of toxic metals. So, it seems that it is not necessary to use TiO2 in milk samples but these days it used frequently as an additive to some samples like milk to remove these pollutants.

TiO2 nanoparticles (NPs) might be considered as the most important photosensitizer due to high photocatalytic and sonocatalytic efficiency, low toxicity, excellent biocompatibility, low cost and high chemical stability. TiO2-NPs normally tend to aggregate in physiological medium and which results to decreased cell viability and inducing expression of stress-related genes. Thus dispersion and stability of TiO2 NPs should be considered in biological application. This paper deals on various dispersing methods such as ultrasonication, electrostatic, steric electrosteric stabilization that suppress agglomeration and stabilizes the dispersed NPs in aqueous medium.Sonication breaks up agglomerated NPs in a solvent. The results showed that probe sonication performs better than bath sonication in dispersing TiO2 agglomerates, but sonication couldn’t prevent long term aggregation of nanoparticles and in order to form stable dispersions, it is not enough to break nanoparticles apart. Agglomerated NPs can be separated by overcoming the weaker attractive forces by electrostatic, steric or electrosteric interactions. Electrostatic stabilization takes place when charges accumulate at the surface of particles. At values of potential more than 30 mV or less than -30 mV no agglomeration occurs. Ionic strength and pH influence on electrostatic stabilization; when pH is far from the isoelectric point, agglomeration is suppressed. In a sterically stabilized dispersion large molecules such as polymers, surfactants and biomolecules, adsorbed on to the surface of particles suppress re-agglomeration. PEG is a hydrophilic polymer, non-toxic and non-immunogenic, and has favorable pharmacokinetics and tissue distribution. PEGylation of NPs not only prevents agglomeration, but also enhances their biocompatibility and increases the in vivo circulation time.

 This study was aimed to determine the TiO 2 /zeolite photocatalytic activity for removing red Safranin dye form aqueous phase. 

 In this study, TiO 2 nanoparticles were produced using sol-gel method and 2.5 ml sol-gel was coated on 1.2222 g of zeolite. X-ray diffraction (XRD) and scanning electron microscopy (SEM) were applied to specify the structure and morphology of TiO 2 nanoparticles. The effect of TiO 2 coating on zeolite, ultraviolet (UV) radiation intensity, initial concentration of dye and the type of photocatalyst substrate (fixed and moving) on photocatalytic process was investigated. 

 According to XRD results, the TiO 2 nanoparticles had two phases including anatase (80.5%) and rutile (19.5%). The uniformity of nanoparticles was obvious in the SEM images. The removal efficiency of TiO 2 coated on zeolite was higher than TiO 2 photocatalysis with increasing UV radiation intensity from 2.4 w/m 2 to 3.9 w/m 2 , the photocatalytic efficiency was also enhanced. The removal efficiency decreased from 91.61% to 77.91% by increasing the red Safranin dye concentration from 10 mg/L to 50 mg/L. The moving bed of TiO 2 /zeolite photocatalyst had a higher efficiency than the fixed bed. 

 In over all, the TiO 2 /zeolite photocatalyst was much more effective than TiO 2 photocatalyst for Safranin dye removal from the aqueous phase. With increasing UV radiation intensity and decreasing dye concentration photocatalytic efficiency, was improved. TiO 2 /zeolite photocatalyst with fixed bed is recommended to be used in water treatment. The most important problem of using moving-bed TiO 2 /zeolite photocatalyst in the water treatment is opacity.

Volatile organic compounds are considered as a group of major environmental pollutants and toluene is recognized as one of the representatives. In this research, the photocatalytic activity for toluene removal was studied over TiO2 nanoparticles embeded on activated carbon. Laboratory-scale experiments were conducted in a fixed-bed reactor equipped with 4 w and 8 w UV lamps (peak wavelength at 365 nm) to determine the oxidation rates of toluene. The photocatalyst was extensively characterized by means of X- ray diffraction and scan electronmicroscopy. Experiments were conducted under general laboratory temperature (25ºC±2) while the irradiation was provided by the UV lamps. The dependence of the reaction rate on light intensity as well as the deactivation of the catalyst were determined. The results indicated that the rate of the photocatalytic process increased with increasing the intensity of UV irradiation. Using the UV-A lamps, the decomposition rate of toluene was 98%. The stabilized photocatalyst presented remarkable stability (no deactivation and excellent repeatability). The catalyst could be regenerated by UV irradiation in the absence of gas phase. The control experiments confirmed that the photocatalytic effects of toluene onto the TiO2/activated carbon catalysts in the dark conditions were negligible. Reproducibility tests proved that the photocatalytic activity of the photocatalyst remains intact even after several experiments of new added toluene quantities. The study demonstrated that the TiO2/activated carbon catalyst may be a practical and promising way to degrade the toluene under ultraviolet irradiation.