Ag TiO2 Research Articles

Possibilities of single particle—ICP-MS for determining/characterizing titanium dioxide and silver nanoparticles in human urine

ObjectiveThe current use of nanoparticles in personal care and cosmetics, food safety, agriculture, medicine and pharmacy has led to a growing concern on the toxicity of these emerging materials to humans and also to the environment. Nanoparticles assessment (determination and size distribution) is a challenge mainly due to limitations of the current analytical instrumentation, but also because nanoparticles in foodstuff and environmental samples are usually found at low concentrations. The scenario is even more critical when dealing with clinical samples, mainly when trying to assess nanoparticles at basal levels in complex samples such as blood and urine. The aim of this paper is to find data regarding the presence of nanoparticles at basal levels in urine human samples. MethodsThe use of single particle – inductively couple plasma – mass spectrometry (sp-ICP-MS) has been explored to determine and characterize silver and titanium dioxide nanoparticles in human urine. Urine samples were directly diluted (1:5 to 1:10) with 1%(v/v) glycerol before sp-ICP-MS measurements, and efforts were made for validating the over-all procedure. ResultsThe limit of detection and quantification for Ag NPs were 5.72 × 103 and 1.91 × 104 Ag NPs mL−1, respectively; whereas, values for TiO2 NP concentrations were 4.31 × 103 and 1.44 × 104 TiO2 NPs mL−1. The limit of detection in size after applying several methods (3σ/5σ criteria) was found to be within the 8–9 nm for Ag NPs, and from 15 to 18 nm for TiO2 NPs. Within-batch precision for Ag NP concentration was 15% (11% for mean size of nanoparticle distributions). Repeatability for TiO2 NPs was 25% (TiO2 NP concentration) and 9% (TiO2 NP mean size). Good analytical recovery rates were found for spiked experiments with Ag NP standards of 40 and 60 nm (values within the 104–106% range), and also for TiO2 NPs of 50 and 100 nm (96–98%). Finally, basal levels of Ag NPs and TiO2 NPs, as well as total Ag and Ti concentrations, in human urine were assessed. Low Ag and Ag NP concentrations were found. Ag NPs exhibited mean sizes of approximately 16–17 nm. Total Ti levels, however, were higher than total Ag concentration, and TiO2 NP concentrations within the 1.56 × 104–2.80 × 104 NPs mL−1 range were measured (TiO2 NP mean sizes were from 76 to 98 nm).

Mechanical and wear behaviour of nanostructure TiO2–Ag coating on cobalt chromium alloys by air plasma spray and high velocity oxy-fuel

Cobalt chromium alloys constitutes the base of one important group of biometallic with excellent mechanical properties. However, due to its non-bioactive and non-antimicrobial surface, cobalt chromium alloys are vulnerable to wear corrosive attack and bacterial infection. Hence, coating cobalt chromium alloys surface with superior biomaterials is the best proven techniques. In this work, nanostructure silver adopted titanium dioxide coating was deposited on cobalt chromium alloys using air plasma spray (APS) and high velocity oxy-fuel (HVOF) techniques. Nanostructure TiO2–Ag coating demonstrated superior hardness, wear resistance and lower coefficient of friction when compared to bare CoCr alloys. Reduced plastic deformation detected by microstructural analysis indicate that the interference of nano-structure coating in metallic matrix help lower the wear rate of the sample. Meanwhile, low porosity of the coating produced by HVOF technique shown a better wear resistance result than APS technique.

One-pot Synthesis of Ag–TiO2–Sepiolite Nanocomposites with Excellent Antibacterial Activity

A novel Ag–TiO2-sepiolite antibacterial nanocomposite was prepared by a one-pot solvothermal method in acetic acid–water solution. The ternary nanostructures consist of Ag-decorated TiO2 nanoparticles (NPs) supported with sepiolite nanofibers. Sepiolite served as a template for reducing the agglomeration of TiO2 NPs and improving the interface reactions between the nanocomposite and bacteria cells. Ag NPs were introduced to enhance the absorption of visible light, and suppress the recombination of electron–hole pair. The synergistic effects of TiO2, Ag NPs and sepiolite nanofibers led to the superior antibacterial activity of the Ag–TiO2-sepiolite nanocomposite against Gram-negative Escherichia coli and Gram-positive Staphylococcus aureus.

Synthesis of Ag–TiO2 hybrid nanoparticles with enhanced photocatalytic activity by a facile wet chemical method

Combining TiO2 nanostructures with noble metal nanoparticles has emerged as a recent trend to engineer efficient photocatalysts. In this work, Ag–TiO2 hybrid nanoparticles were synthesized by CTAB-assisted wet chemical synthesis of TiO2 combined with citrate reduction of Ag+ ions. Transmission electron microscopy studies revealed attachment of Ag nanoparticles on to TiO2 nanoparticles, while UV–Vis absorption spectroscopy indicated improvement in absorbance of TiO2 nanoparticles upon Ag nanoparticles loading. The photocatalytic degradation capability of Ag–TiO2 hybrid nanoparticles was investigated through decomposition of methylene blue (MB) dye under solar light illumination. Ag–TiO2 hybrid nanoparticles showed enhanced photocatalytic efficiency of 89.2% under sun light irradiation for 60 min, which was almost 1.7 times higher than that of TiO2 nanoparticles. Our PL results indicated suppressed charge recombination in TiO2 nanoparticles upon attachment of Ag nanoparticles. Reduced charge recombination and improved sun light utilization capacity of Ag–TiO2 nanohybrids resulted in their enhanced photocatalytic activity. The synthesized Ag–TiO2 hybrid nanoparticles are promising for applications in environmental remediation.

Novel Z-Scheme Ag/TiO2/AgMIL-101(Cr) as an efficient photocatalyst for nitrogen production from nitrate

Z-Scheme Ag/TiO2/AgMIL-101(Cr) was prepared by co-doping Ag and TiO2 with AgMIL-101(Cr) via solvothermal synthesis combined with sol-gel method. Ag and anatase TiO2 nanoparticles were well dispersed on the surface of AgMIL-101(Cr) with octahedral structure. 5 wt% Ag and 50% TiO2 co-doping on the AgMIL-101(Cr) (Ag5T50Ag5M) exhibited large specific surface area (346.5 m2·g−1) and narrow band gap 2.16 eV. Only 10 min of UV light irradiation resulted in the conversion of nitrate and nitrogen selectivity up to 100% over Ag5T50Ag5M. After 5 cycles of nitrate removal, the conversion of nitrate remained 90% indicating that catalyst had stable reusability. Moreover, instead of formic acid, ofloxacin (OFX) was used as a hole scavenger to evaluate the ability of Ag5T50Ag5M for the nitrate reduction. The result showed that the concentration of OFX was important factor to affect the conversion of nitrate. Based on the above discussion about the characterization and photocatalytic nitrate reduction, combined with the photoluminescence and electrochemical measurement results, the enhanced conversion of nitrate and nitrogen selectivity was reasonably explained. Finally, the route of electron transfer during the three constituents constructed Z-Scheme system and the mechanism of nitrate reduction to nitrogen was presumed.

Rational design of a polypyrrole-based competent bifunctional magnetic nanocatalyst.

The combination of conducting polymers with semiconductors for the fabrication of organic/inorganic hybrid nanocatalysts is one of the most promising research areas for many applications. In this work, the synthesized nanocomposite combines several advantages such as the photoresponse shift from the UV region toward visible light by narrowing the band gap of the semiconductor, magnetic separation ability and dual applications including the catalytic reduction of p-nitrophenol (PNP) and the photocatalytic degradation of methylene blue (MB) dye. In addition to the core magnetite nanoparticles (NPs), the synthesized nanocomposite contains polypyrrole (PPY) and TiO2 shells that are decorated with silver metal NPs to prevent electron–hole recombination and to enhance the catalytic performance. Indeed, the catalytic PNP reduction experiments reveal that the synthesized nanocomposite exhibits significantly high catalytic activity with a rate constant of 0.1169 min−1. Moreover, the photocatalytic experiments show that the synthesized nanophotocatalyst has a boosting effect toward MB dye degradation under normal daytime visible light irradiation with a rate constant of 6.38 × 10−2 min−1. The synergetic effect between silver NPs, PPY and TiO2 is thought to play a fundamental role in enhancing the photocatalytic activity.

Effects of Ag0-modification and Fe3+-doping on the structural, optical and photocatalytic properties of TiO2.

Pure TiO2, Ag0-modified TiO2, Fe3+-doped TiO2, and Ag0-modified/Fe3+-doped TiO2 photocatalysts were synthesized via sol–gel technology. The crystal structure, element composition and surface morphology of the obtained photocatalysts were characterized via XRD, XPS, SEM and TEM, respectively. The results indicate that Ag–TiO2 samples show higher photocatalytic activity than pure TiO2. Unexpectedly, the photocatalytic activities of Fe–TiO2 and 1% Ag/1% Fe–TiO2 are lower than pure TiO2. To analyze the main factors affecting photocatalytic performance, the samples were further investigated by PL, DRS and BET. The results prove that the additions of Ag and Fe are advantageous for inhibiting the recombination of photoinduced pairs and improving the utilization of light. Fe–TiO2 and 1% Ag/1% Fe–TiO2 exhibit smaller specific surface areas than pure TiO2, which is the primary reason for their reduced photocatalytic performances.

A ternary Ag–TiO2/reduced graphene oxide nanocomposite as the anode material for lithium ion batteries

A Ag–TiO2/rGO nanocomposite exhibits enhanced electrochemical performance with good stability, as the intra-/inter-grain connectivity is increased between nanosized Ag and TiO2 particles on the reduced graphene oxide surface.

Local temperature control of hybrid plasmonic nano-antennas

Local enhanced heat generation in plasmonic nano-antennas caused by the finite conductivity of metals can cause local super-heating areas, a disadvantage to the normal work of nano-antennas. In this work, an approach to simultaneously enabling near-field intensity enhancement at the operating wavelength in the visible and local operating temperature control of hybrid plasmonic antennas is studied. Results show that the operating temperature for the pure Au or Ag nanoparticles (NP) is very high at a low intensity of incident light in vacuum, owing to a negligible thermal radiation dissipation in the infrared region. Thus, different dielectric spheres (i.e., Al2O3, SiO2, and TiO2) were introduced to enhance the thermal radiation dissipation of the hybrid plasmonic antennas. The hybrid antennas obtained greater absorption ability and near-field enhancement compared to pure plasmonic NPs. Additionally, the hybrid antennas showed great thermal emittance capability compared to pure plasmonic NPs. The Ag–TiO2 hybrid antenna obtained the lowest temperature increase among the three hybrid systems while maintaining the highest near-field enhancement. The sharp absorption peaks or near-field enhancement spectra of the Ag–TiO2 hybrid antennas can be attributed to the excitation of the whispering gallery mode coupled with the surface plasmon mode, resulting in an enhanced absorption or near-field enhancement. The absorption cross section, the near-field intensity enhancement, and the thermal emittance of the Ag–TiO2 hybrid antennas increase with the size of the TiO2 sphere. A saturation value exists for the TiO2 sphere size to reduce the temperature increase at a specific intensity of incident light. In addition, air convection with the consideration of size effect also can further reduce the operating temperature of the hybrid antenna.

Highly efficient plasmonic dye-sensitized solar cells with silver nanowires and TiO2 nanofibres incorporated multi-layered photoanode

The effect of incorporating silver nanowires (Ag NWs) and TiO2 nanofibers (NFs) into a tri-layer photoanode of dye sensitized solar cells (DSSCs) have been investigated. Ag NWs with diameter 60–90 nm and length of 1–2 μm were synthesized via polyol reduction method. TiO2 nanofibers (NFs) with diameter 80–120 nm were prepared by electrospinning. The DSSC with tri-layer photoanode made with a composite of TiO2 P25, Ag NWs and TiO2 NFs sandwiched between two TiO2 P25 layers exhibited power conversion efficiency of 9.74% and open circuit voltage (Voc), short circuit current density (Jsc) and fill factor (FF) of 727.4 mV, 19.8 mA cm−2 and 67.6% respectively under the irradiance of 100 mW cm−2. The efficiency of the reference DSSC with TiO2 P25/P25/P25 tri-layer photoanode of the same thickness was found to be 6.69%. The efficiency enhancement of the DSSC with Ag NWs and TiO2 NF incorporated composite, tri-layer photoanode compared to the reference DSSC is 45.6%. This is evidently due to the enhancement in short-circuit photocurrent density (Jsc) by (a) localized surface plasmon resonance effect by Ag NWs and (b) increased light harvesting by multiple scattering events by the presence of TiO2 NFs.

Functionalization of titania nanotubes with electrophoretically deposited silver and calcium phosphate nanoparticles: Structure, composition and antibacterial assay

Herein TiO2 nanotubes (NTs) were fabricated via electrochemical anodization and coated with silver and calcium phosphate (CaP) nanoparticles (NPs) by electrophoretic deposition. Scanning electron microscopy (SEM) and energy-dispersive X-ray spectroscopy (EDX) revealed that Ag and CaP NPs were successfully deposited onto the TiO2 NTs. Using X-ray diffraction, only anatase and Ti were observed after deposition of Ag and CaP NPs. However, X-ray photoelectron spectroscopy (XPS) analysis revealed that the binding energy (BE) of the Ag and CaP NP core levels corresponded to metallic Ag, hydroxyapatite and amorphous calcium phosphate, based on the knowledge that CaP NPs synthesized by precipitation have the nanocrystalline structure of hydroxyapatite. The application of Ag NPs allows for decreasing the water contact angle and thus increasing the surface free energy. It was concluded that the CaP NP surfaces are superhydrophilic. A significant antimicrobial effect was observed on the TiO2 NT surface after the application of Ag NPs and/or CaP NPs compared with that of the pure TiO2 NTs. Thus, fabrication of TiO2 NTs, Ag NPs and CaP NPs with PEI is promising for diverse biomedical applications, such as in constructing a biocompatible coating on the surface of Ti that includes an antimicrobial effect.

Development of antimicrobial leather modified with Ag–TiO2 nanoparticles for footwear industry

The proposed work aims to functionalize leathers for footwear industry with antimicrobial properties based on Ag–TiO2 nanoparticles. The synthesis of nanoparticles was carried out by the hydrothermal method with significant advantages in terms of time, energy savings and low cost. Anatase TiO2 nanoparticles with dimensions below 10nm were obtained as observed by X-ray diffraction and transmission electron microscopy. Fourier transform infrared spectroscopy showed that the based structure of leather was not modified by the addition of the nanoparticles. The antimicrobial activity was evaluated and it was observed that Ag containing leathers gained antimicrobial activity. In addition, the nanoparticles were found to be non-cytotoxic. This achievement, by itself, should be quite appealing to the footwear industry as it could consist in a solid value-preposition given the commonness of fungal infections promoted by humidity, poor breathability and temperature that promote the expansion of the microflora of the skin.

Antibacterial and photocatalytic activity of anatase phase Ag‐doped TiO 2 nanoparticles

A simple and new solid-state molten-salt method to synthesise silver (Ag)-doped titanium dioxide (TiO2) nanoparticles for solar light-induced photocatalytic applications is examined. Ag-doped TiO2 nanoparticles with varied Ag content ranging from 3 to 10% were synthesised by a single-step molten-salt synthesis method. The effect of Ag content on the antibacterial and photocatalytic activity of nanoparticles was tested. The prepared nanoparticles were studied by scanning electron microscopy (SEM), energy-dispersive X-ray (EDX) spectrometry, ultraviolet–visible (UV–vis) diffusive reflectance spectrometer (UV–vis DRS) and powder X-ray diffraction. The SEM image of nanoparticles clearly showed the presence of agglomerated spherical particles. The EDX analysis of the particles confirmed successful doping of particles in the presence of the Ag in the particles. The doping of Ag in TiO2 produced TiO2 pure anatase phase. According to UV–vis DRS results, increasing Ag-doped content in the Ag-doped TiO2 resulted in a higher visible absorption capability of the materials. Ag doping also improved the antibacterial and photocatalytic activity of TiO2 nanoparticles. The maximum photocatalytic activity under light irradiation was observed for 5% Ag-doped TiO2.

Antifouling and anti-algal effects of chitosan nanocomposite (TiO2/Ag) and pristine (TiO2 and Ag) films on marine microalgae Dunaliella salina

Biofouling is the main problem for marine water systems such as the immersed leisure vessels, oceanographic sensors, heat exchangers, and ship hulls. The obstacle of biofouling created by barnacles, mussels, bacteria, and micro and/or macro algal species. To overcome this problem, some metal nanoparticles incorporated films and membranes were employed to control the biofouling. In this study, metal nanoparticles (Ag NPs and TiO2) of different concentrations (0.25, 0.5, 0.75 wt %) were incorporated with chitosan polymer to fabricate nanocomposite and pristine films. The biofouling inhibition was examined using the marine microalgal species Dunaliella salina. The higher performance in algal viability (45.42 ± 0.36%) was observed by TiO2 and concentration maintained Ag NPs incorporated chitosan nanocomposite (0.5 wt% Ag/ 0.75 wt% TiO2) films under UV-C condition, in comparison with other nanocomposite and pristine concentrations. The same concentration showed higher activity in the slime formation (Glycocalyx test), mass assessment, exo-polymeric substances (EPS), and membrane damages (LPO) under UV-C condition. The release of silver ions (Ag+) and uptake of Ag showed good performance of Ag NPs incorporated nanocomposite film at higher concentration (0.5 wt% TiO2/ 0.75 wt% Ag). The surface morphology of nanocomposite were characterized using SEM, and AFM, and the surface modifications of chitosan nanocomposites were examined by XRD, and FTIR. TiO2 and Ag NPs being photoactive induce more ROS that damage the cell membrane leading to algal cell death and control of biofouling formation.

Enhanced Photocatalytic Efficiency of a Least Active Ag-TiO2 by Amine Adsorption.

An Ag–TiO2 photocatalyst with 3.5 atom % silver content, synthesized by a single step sol–gel method, possessed silver nanoparticles (AgNPs; 1–5 nm) on the TiO2 surface, but owing to the nonplasmonic nature of AgNPs and the wide band gap of TiO2, this material exhibited poor activity in a photocatalytic degradation reaction. However, this least active Ag–TiO2 catalyst showed a sudden increase in activity during a photocatalytic amine self-coupling reaction showing the highest activity, which was interpreted as amine (reactant) adsorption-driven activity enhancement. We found that amine adsorption occurred over AgNPs converting into plasmonic AgNPs as well as on the TiO2 surface reducing the band gap and therefore facilitated the visible light excitation and the electron-transfer process efficiently, resulting into overall enhancement in the photocatalytic activity. Thus, a very efficient, stable, and visible light active photocatalyst (amine-adsorbed Ag–TiO2) was developed by simply adsorbing an amine in the least active Ag–TiO2 photocatalyst.

Bio-synthesis of finely distributed Ag nanoparticle-decorated TiO2 nanorods for sunlight-induced photoelectrochemical water splitting

Ag nanoparticles (NPs) grafted on TiO2 nanorods (NRs) using electroactive biofilms (EABs) were assessed as photoanodes for water splitting under solar light irradiance. EABs-assisted bio-reduction leads to the uniform decoration of spherical Ag NPs (10–40nm) and stronger attachment to the Ag–TiO2 interface due to the prior adsorption of Ag+ ions. Plasmonic interaction of Ag NPs with TiO2 NRs showed stronger adsorption in visible range due to surface plasmon resonance. Compared to TiO2 NRs, Ag–TiO2 NRs/FTO exhibited 8 times higher current density under solar light irradiation due to enhanced visible light absorption, SPR effect, and efficient electron-hole separation.

Green Synthesis of Ag–TiO2 Supported on Porous Glass with Enhanced Photocatalytic Performance for Oxidative Desulfurization and Removal of Dyes under Visible Light

As the energy shortage and environmental problem become the worldwide concern, the green synthesis of catalysts and their green applications have long been pursued. Here we proposed a facile catalyst synthesis approach in which Ag–TiO2 composites were prepared through an in situ reduction at room temperature without severe conditions or hydrogen atmosphere. Porous glass (PG) was chosen as the support, and the as-prepared Ag–TiO2/PG was equipped with the remarkable merits of intense visible light absorbance, effective separation of electron–hole pairs, high surface areas for adsorption, and abundant reactive sites for the photocatalytic oxidation. Conversions of 95.2% and 92.1% for dibenzothiophene (DBT) and benzothiophene (BT), respectively, were realized under irradiation of energy-saving visible light emitting diodes (LEDs), complying with the principles of “green chemistry”. Moreover, none of the external oxidants, such as H2O2 or O2, was introduced, greatly increasing the viability of industrial appli...

Concurrent photocatalytic degradation of organic contaminants and photocathodic protection of steel Ag–TiO2 composites

In this study, coupled titanium dioxide-silver composite and steel electrode pairs were investigated for their use in cathodic protection under illuminated and dark conditions to prevent corrosion and enhance contaminant degradation under photocatalysis. A series of photoelectrochemical tests were used to determine the properties of the photoanode and identify the cathodic protection behaviour in the presence and absence of organic/inorganic contaminants. Additionally, corrosion-prone steel was used to test the principle of photocathodic protection in reducing oxide formation and mass loss under base metal and welded materials.

Fabrication of efficient dye-sensitized solar cells with photoanode containing TiO2–Au and TiO2–Ag plasmonic nanocomposites

Herein, we report the effect of incorporation of two types of plasmonic nanocomposites, TiO2–Au and TiO2–Ag in different ratios, in the TiO2 photoanode of dye-sensitized solar cells (DSSCs). Electrophoretic deposition technique (EPD) has been utilized for the deposition of these nanocomposite photoanodes. The high-resolution transmission electron microscopy reveals that the nanocomposites, TiO2–Au and TiO2–Ag, have a wide size distribution of Au (5–60 nm) and Ag (20–130 nm) nanoparticles embedded in the TiO2 matrix. The UV–Visible absorption spectra of these nanocomposite films reveal the enhancement in the optical density due to the plasmonic effect. The DSSC based on photoanode consists of plasmonic nanocomposite TiO2–Au:TiO2–Ag (3:1 ratio) showed power conversion efficiency (PCE) of 10.9% which is 187% higher than that pristine TiO2 counterpart. The enhancement in the PCE has been confirmed by the photoluminescence and electro-impedance spectroscopy indicating that both Au and Ag play an important role in enhancing the PCE of DSSCs due to the plasmonic effect.

Synthesis of silver and sulphur codoped TiO2 nanoparticles for photocatalytic degradation of methylene blue

In the present work, silver and sulphur codoped TiO2 (Ag–S/TiO2) photocatalysts were effectively prepared by sol–gel technique. The prepared samples were characterized using X-ray diffraction (XRD), scanning electron microscopy (SEM), high-resolution transmission electron microscopy (HRTEM), energy dispersive x-ray analysis (EDX), Fourier transform infrared (FTIR) spectroscopy, diffuse reflectance UV–Vis spectroscopy (UV-DRS) and photoluminescence (PL). The XRD patterns consisted of anatase crystalline phases and the particle size and shape of the prepared samples were observed by SEM and HR-TEM. The presence of doping ions was confirmed by EDX analysis, the decreased band-gap energy of Ag–S codoped TiO2 nanoparticles was investigated by UV-DRS. The decreased in the intensity of Ag–S codoped TiO2 was absorbed due to the lower separation of electron–hole pairs were confirmed by PL spectrum. The Ag–S codoped TiO2 showed higher photocatalytic activity than pure and single-doped TiO2 in the photodegradation of methylene blue (MB) aqueous solution under visible light irradiation. The given work was a good model to associate the considering of the synergistic effect of metal and non-metal codoped TiO2 in the photocatalysis and photo electrochemistry.