Single-Step Synthesis of Silver-Doped Titanium Dioxide: Influence of Silver on Structural, Textural, and Photocatalytic Properties

Evaluation of antifungal activity of visible light-activated doped TiO2 nanoparticles

Titanium dioxide (TiO2) is a well-known material for its biomedical applications, among which its implementation as a photosensitizer in photodynamic therapy has attracted considerable interest due to its photocatalytic properties, biocompatibility, high chemical stability, and low toxicity. However, the photoactivation of TiO2 requires ultraviolet light, which may lead to cell mutation and consequently cancer. To address these challenges, recent research has focused on the incorporation of metal dopants into the TiO2 lattice to shift the band gap to lower energies by introducing allowed energy states within the band gap, thus ensuring the harnessing of visible light. This study presents the synthesis, characterization, and application of TiO2 nanoparticles (NPs) in their undoped, doped, and co-doped forms for antimicrobial photodynamic therapy (APDT) against Candida albicans. Blue light with a wavelength of 450 nm was used, with doses ranging from 20 to 60 J/cm2 and an NP concentration of 500 µg/ml. It was observed that doping TiO2 with Cu, Fe, Ag ions, and co-doping Cu:Fe into the TiO2 nanostructure enhanced the visible light photoactivity of TiO2 NPs. Experimental studies were done to investigate the effects of different ions doped into the TiO2 crystal lattice on their structural, optical, morphological, and chemical composition for APDT applications. In particular, Ag-doped TiO2 emerged as the best candidate, achieving 90-100% eradication of C. albicans.

Green synthesis of aminated hyaluronic acid-based silver nanoparticles on modified titanium dioxide surface: Influence of size and chemical composition on their biological properties

This is the first report on an efficient, "environmentally friendly" chemical reduction method for the synthesis of aminated hyaluronic acid-based silver nanoparticles on the modified surface of titanium dioxide nanoparticles aimed for biological applications. Silver nanoparticles exhibit well-known physical-chemical and optical properties appropriate for different biological applications. Modifying the nanoparticles leads to a change in their expected bioactivity. This represents an important topic for the current research. We have developed a novel aminated hyaluronic acid (HA-EDA)-based protocol to obtain silver nanoparticles, in which HA-EDA was used for the first time as a reducing and stabilizing agent. The effect of the size of silver nanoparticles on the titanium dioxide surface and the chemical composition of the obtained materials were investigated by TEM, XRD, XPS, ATR-FTIR, Raman spectroscopy, NMR and H2-TPR analyses. The antioxidant, in vitro biocompatibility, and antimicrobial activity of the fabricated composites have been evaluated. The results prove that the prepared materials exhibit antimicrobial, antioxidant, and anti-inflammatory activity, thus providing protection against infection and supporting tissue regeneration, these two key effects being of paramount importance for promoting wound healing.

Light-Driven Nitrogen Fixation to Ammonia over Aqueous-Dispersed Mo-Doped TiO2 Colloidal Nanocrystals

Photocatalytic nitrogen fixation to ammonia and nitrates holds great promise as a sustainable route powered by solar energy and fed with renewable energy resources (N2 and H2O). This technology is currently under deep investigation to overcome the limited efficiency of the process. The rational design of efficient and robust photocatalysts is crucial to boost the photocatalytic performance. Widely used bulk materials generally suffer from charge recombination due to poor interfacial charge transfer and difficult surface diffusion. To overcome this limitation, this work explores the use of aqueous-dispersed colloidal semiconductor nanocrystals (NCs) with precise morphological control, better carrier mobility, and stronger redox ability. Here, the TiO2 framework has been modified via aliovalent molybdenum doping, and resulting Mo-TiO2 NCs have been functionalized with charged terminating hydroxyl groups (OH-) for the simultaneous production of ammonia, nitrites, and nitrates via photocatalytic nitrogen reduction in water, which has not been previously found in the literature. Our results demonstrate the positive effect of Mo-doping and nanostructuration on the overall N2 fixation performance. Ammonia production rates are found to be dependent on the Mo-doping loading. 5Mo-TiO2 delivers the highest NH4+ yield rate (ca. 105.3 μmol g-1 L-1 h-1) with an outstanding 90% selectivity, which is almost four times higher than that obtained over bare TiO2. The wide range of advance characterization techniques used in this work reveals that Mo-doping enhances charge-transfer processes and carriers lifetime as a consequence of the creation of new intra band gap states in Mo-doped TiO2 NCs.

Removal of ceftriaxone sodium antibiotic from pharmaceutical wastewater using an activated carbon based TiO2 composite: Adsorption and photocatalytic degradation evaluation

The water pollution becomes a serious concern for the sustainability of ecosystems due to the existence of pharmaceutical products (ceftriaxone (CEF) antibiotic). Even in low concentration of CEF has lethal effects on ecosystem and human health. To remove CEF, TiO₂ is considered as an effective and efficient nanoparticles, however its performance is reduced due to wider energy gap and rapid recombination of charge carriers. In this study, activated carbon based TiO₂ (ACT-X) heterogeneous nanocomposites were synthesized to improve the intrinsic properties of TiO₂ and their adsorption-photocatalytic performance for the removal of CEF. The characterization results revealed that ACT-X composites have slower recombination of charge carriers, lower energy band gap (3.05 eV), and better light absorption under visible region of light. From ACT-X composites, the ACT-4 photocatalyst has achieved highest photocatalytic degradation (99.6%) and COD removal up (99.2%). The results of radical scavengers showed that photocatalytic degradation of CEF is mainly occurred due to superoxide and hydroxyl radicals. Meanwhile, the reusability of ACT-4 up to five cycles shows more than 80% photocatalytic degradation, which make the process more economical. The highest experimental adsorption capacity is achieved up to 844.8 mg g^-1 using ACT-4. The favorable and multilayer heterogeneous adsorption is carried out according to the well-fitted data with pseudo-second-order and Freundlich models, respectively. These results indicate that the carbon-based TiO₂ composites can be used as a green, stable, efficient, effective, reusable, renewable, and sustainable photocatalyst to eliminate the pharmaceutical pollutants (antibiotics) via adsorption and photocatalytic degradation processes.

Efficient nitrate reduction in water using an integrated photocatalyst adsorbent based on chitosan-titanium dioxide nanocomposite

Globally, there exists a huge concern on the increased discharge of nitrates to the natural water resources out of various anthropogenic activities as it causes serious environmental pollution and associated harmful effects. In the present work, sol-gel-derived functional nanocomposites based on silver (Ag) and nitrogen (N)-doped titanium dioxide (TiO2)-coated chitosan nanocomposites were successfully synthesized in the form of beads, and their application for the reduction of nitrates in water was studied. The synthesized nanocomposite beads were characterized for their structural, textural, and morphological features using X-ray diffraction analysis, Fourier transform infrared spectroscopy, UV-visible spectroscopy, BET surface area analysis, Scanning electron microscopy, Transmission electron microscopy, and X-ray photoelectron spectroscopy. A uniform coating of doped titania species on the chitosan porous structure was achieved through electrostatic interaction. Adsorption/photocatalytic reduction of nitrates was further carried out using functional nanocomposite beads by monitoring the nitrate concentration of the model contaminated water, in an adsorption study under dark condition and photocatalytic study under UV/sunlight for a definite time period. Drying conditions of the nanocomposite beads were found to have a significant effect on the adsorption cum photocatalytic efficiencies of the nanocomposite. The freeze-dried chitosan-titania nanocomposite beads containing 0.5 mol% Ag exhibited an adsorption efficiency of ~ 43.5% (under dark for 30 min) and photocatalytic reduction capability of ~ 95% (under sunlight for 2 h), whereas the oven dried beads of the same composition exhibits adsorption and photocatalytic efficiencies of 40% (under dark for 30 min) and 70% (under UV light for 2 h) respectively, towards the reduction of nitrate ions in an aqueous solution. Continuous flow adsorption cum photocatalytic study using the oven-dried nanocomposite beads was also carried out with the help of an experimental setup fabricated in-house and under varying experimental conditions such as flow rate, bed height, and concentration of feed solution. Nitrate reduction efficiency of 87.6% and an adsorption capacity of 7.9 mg g-1 were obtained for the nanocomposite beads in the continuous flow adsorption cum photocatalysis experiment for up to 8 h when using an inlet concentration of 100 ppm, bed height 12 cm, and flow rate 5.0 mL min-1. A representative fixed-bed column adsorption experiment performed with oven dried nanocomposite beads in a real groundwater sample collected from the Palakkad District of Kerala shows promising results for nitrate reduction (85.9% efficiency) along with a significant removal rate for the other anions as well. Thus, the adsorption cum photocatalytic nitrate reduction efficiency of the functional nanocomposite material makes them suitable for the reduction of nitrates from water/wastewater through an integrated nanocomposite approach.

Noble metal-doped TiO2 thin films in the efficient removal of Mordant Orange-1: insights of degradation process

Nanocomposite Ag⁰(NPs)/TiO₂ is synthesised in a facile template method enabling nanoparticles of reduced Ag evenly distributed within the titania network. The morphological studies of nanocomposites were extensively performed employing SEM/EDX (scanning electron microscopy/energy dispersive X-ray), TEM (transmission electron microscopy) and AFM (atomic force microscopy). Moreover, the bandgap energies of materials were obtained using the diffuse reflectance spectrometer (DRS). The newer insights in the photocatalytic elimination of Mordant Orange-1 (MO1) was obtained using the nanocomposite thin film for various parametric studies utilising the UV-A and LED illuminations. The kinetics of degradation of MO1 was performed, and the rate constant was favoured at lower concentrations of MO1. Moreover, the elimination efficiency of MO1 was favoured with a decrease in solution pH. The NPOC results inferred that a fairly good extent of MO1 was mineralised using a thin-film catalyst for both the UV-A and LED illuminations. The minimal effect of several co-ions demonstrated the applicability of thin films in the elimination of MO1, and the stability of the thin film has shown the potential applicability of thin-film catalysts. Further, the mechanism of photocatalytic degradation was demonstrated with the radical scavenger studies and ascertained the reaction pathways.

Study on Photocatalytic Performance of Ag/TiO2 Modified Cement Mortar

In this paper, Ag-TiO₂ photocatalysts with different Ag contents (1 mol%–5 mol%) were prepared and applied to cement mortar. The photocatalytic performance of Ag-TiO₂ and photocatalytic cement mortar under UV light and simulated solar light was evaluated. The results showed that Ag loading on the surface of TiO₂ could reduce its band gap width and increase its absorbance in the visible region, and 2% Ag-TiO₂ had the highest photocatalytic activity under UV light, the degradation rate of methyl orange (MO) was 95.5% at 30 min, and the first-order reaction constant k was 0.0980 min⁻¹, which was 61.7% higher than that of TiO₂, and 5% Ag-TiO₂ had the highest photocatalytic activity under solar light, the degradation rate of methylene blue (MB) was 69.8% at 40 min, and the first-order reaction constant k was 0.0294 min⁻¹, which was 90.9% higher than that of TiO₂. The photocatalytic mortar prepared by the spraying method has high photocatalytic performance, The MO degradation rate of sample S2 under UV light was 87.5% after 120 min, MB degradation rate of sample S5 under solar light was 75.4% after 120 min. The photocatalytic reaction conforms to the zero-order reaction kinetics, which was 1.5 times–3.3 times higher than that of the mixed samples and has no effect on the mechanical properties of mortar.

Rhodamine B Photodegradation in Aqueous Solutions Containing Nitrogen Doped TiO2 and Carbon Nanotubes Composites

In this work, new results concerning the potential of mixtures based on nitrogen doped titanium dioxide (TiO₂:N) and carbon nanotubes (CNTs) as possible catalyst candidates for the rhodamine B (RhB) UV photodegradation are reported. The RhB photodegradation was evaluated by UV-VIS absorption spectroscopy using samples of TiO₂:N and CNTs of the type of single-walled carbon nanotubes (SWNTs), double-wall carbon nanotubes (DWNTs), multi-wall carbon nanotubes (MWNTs), and single-walled carbon nanotubes functionalized with carboxyl groups (SWNT-COOH) having various concentrations of CNTs. The best photocatalytic performance was obtained for sample containing TiO₂:N and 2.5 wt.% SWNTs-COOH, when approx. 85% of dye removal was achieved after 300 min. of UV irradiation. The reaction kinetics of RhB aqueous solutions containing TiO₂:N/CNT mixtures followed a complex first-order kinetic model. The TiO₂:N/CNTs catalyst induced higher photodegradation efficiency of RhB than TiO₂:N due to the presence of CNTs, which act as adsorbent and dispersing agent and capture the photogenerated electrons of TiO₂:N hindering the electron-hole recombination.

Phytosynthesis of Titanium Dioxide Nanoparticles Using King of Bitter Andrographis paniculata and Its Embryonic Toxicology Evaluation and Biomedical Potential

Phytosynthesis particles are the efficient activity of biomedical and environmental. In this present study, the green synthesis of titanium dioxide (TiO₂) nanoparticles using the king of bitter herbal plant Andrographis paniculata was synthesized and characterized using XRD, SEM, HRTEM, AFM, and antimicrobial, antioxidant, and antidiabetic activities. The size of the particles HRTEM shows 50 nm, and SEM shows the spherical shape, which reveals the synthesis of TiO₂ nanoparticles. XRD spectrum shows crystallinity of nanoparticles, and an average size is calculated about 22.97 nm. The phytosynthesis TiO₂ shows the antioxidant and antidiabetic activities. Similarly, toxicity studies have demonstrated the hatching and viability LD 50 value of TiO₂ 250 μg/L. The current study's findings suggested that phytosynthesis TiO₂ using extract of Andrographis paniculata exposure to potential hazard factors to biomedical and environmental uses.

Recent progress on Ag/TiO2 photocatalysts: photocatalytic and bactericidal behaviors

For many decades, titanium dioxide (TiO₂) semiconductor has been extensively applied in several environmental applications due to its higher photocatalytic performances toward different organic pollutants, pharmaceutical compounds, and bacteria. However, its shortfall response to visible light, and the expeditious recombination rate of the photogenerated electron-hole pairs, hampers its utilization. Doping TiO₂ semiconductor with silver nanoparticles is a sound strategy to (1) extend its photocatalytic activity to visible light, (2) prevent the electron/holes pairs recombination due to the formation of the Schottky barrier at the interfaces with TiO₂ that act as an electron-trapping center, and (3) enhance its bactericide performances. This review focuses on the recent progress on silver-doped titanium dioxide (Ag/TiO₂)-based photocatalysts. It addresses a wide range of Ag/TiO₂ synthesis techniques, their physicochemical properties and discusses thoroughly the important role of silver (Ag) nanoparticles in enhancing the removal capacity and antibacterial performances of the Ag/TiO₂ photocatalysts.

Photocatalytic Conversion of Organic Pollutants in Air: Quantum Yields Using a Silver/Nitrogen/TiO2 Mesoporous Semiconductor under Visible Light

This research studies the photocatalytic conversion of methanol (25–90 µmol/L range) as a volatile organic compound (VOC) surrogate into CO2, using a N/Ag/TiO2 photocatalyst under visible light irradiation in a Photo-CREC Air unit. The N/Ag/TiO2 mesh supported photocatalyst is prepared via the solvothermal method. While the bare-TiO2 is inactive under visible light, the N/Ag/TiO2 2 wt.% loaded stainless-steel woven mesh displays 35% quantum yields, with 80% absorbed photons and 60% methanol conversion in a 110 min irradiation period. Results obtained are assigned to silver surface plasmon resonance, silver and nitrogen species synergistic impacts on band gap, and their influence on particle agglomerate size and semiconductor acidity. The determined quantum yields under visible light in a Photo-CREC Air unit, are the highest reported in the technical literature, that these authors are aware of, with this opening unique opportunity for the use of visible light for the purification of air from VOC contaminants.

Fabrication of highly and poorly oxidized silver oxide/silver/tin(IV) oxide nanocomposites and their comparative anti-pathogenic properties towards hazardous food pathogens

Herein, we report the fabrication of highly oxidized silver oxide/silver/tin(IV) oxide (HOSBTO or Ag³⁺-enriched AgO/Ag/SnO₂) nanocomposite under a robust oxidative environment created with the use of concentrated nitric acid. Tin(IV) hydroxide nanofluid is added to the reaction mixture as a stabilizer for the Ag³⁺-enriched silver oxide in the nanocomposite. The formation of Ag nanoparticles in this nanocomposite originates from the decomposition of silver oxides during calcination at 600 °C. For comparison, poorly oxidized silver oxide/silver/tin(IV) oxide (POSBTO with formula AgO/Ag/SnO₂) nanocomposite has also been prepared by following the same synthetic procedures, except for the use of concentrated nitric acid. Finally, we studied in detail the anti-pathogenic capabilities of both nanocomposites against four hazardous pathogens, including pathogenic fish bacterium (Stenotrophomonas maltophilia stain EP10), oomycete (Phytophthora cactorum strain P-25), and two different strains of pathogenic strawberry fungus, BRSP08 and BRSP09 (Collectotrichum siamense). The bioassays reveal that the as-prepared HOSBTO and POSBTO nanocomposites exhibit significant inhibitory activities against the tested pathogenic bacterium, oomycete, and fungus in a dose-dependent manner. However, the degree of dose-dependent effectiveness of the two nanocomposites against each pathogen largely varies.

Photodeposition of Silver on Zinc/Calcium Ferrite Nanoparticles: A Contribution to Efficient Effluent Remediation and Catalyst Reutilization

The efficient photodegradation of textile dyes is still a challenge, especially considering resistant azo dyes. In this work, zinc/calcium mixed ferrite nanoparticles prepared by the sol–gel method were coupled with silver by a photodeposition method to enhance the photocatalytic potency. The obtained zinc/calcium ferrites are mainly cubic-shaped nanoparticles sized 15 ± 2 nm determined from TEM and XRD and an optical bandgap of 1.6 eV. Magnetic measurements indicate a superparamagnetic behavior with saturation magnetizations of 44.22 emu/g and 27.97 emu/g, respectively, for Zn/Ca ferrite and Zn/Ca ferrite with photodeposited silver. The zinc/calcium ferrite nanoparticles with photodeposited silver showed efficient photodegradation of the textile azo dyes C.I. Reactive Blue 250 and C.I. Reactive Yellow 145. Subsequent cycles of the use of the photocatalyst indicate the possibility of magnetic recovery and reutilization without a significant loss of efficiency.

Design of Metal@Titanium Oxide Nano-heterodimers by Laser-Driven Photodeposition: Growth Mechanism and Modeling

In order to circumvent the usual nucleation of randomly distributed tiny metallic dots photodeposited on TiO₂ nanoparticles (NPs) induced by conventional UV lamps, we propose to synthesize well-controlled nanoheterodimers (NHDs) using lasers focused inside microfluidic reactors to strongly photoactivate redox reactions of active ions flowing along with nanoparticles in water solution. Since the flux of photons issued from a focused laser may be orders of magnitude higher than that reachable with classical lamps, the production of electron-hole pairs is tremendously increased, ensuring a large availability of carriers for the deposition and favoring the growth of a single metallic dot as compared to secondary nucleation events. We show that the growth of single silver or gold nanodots can be controlled by varying the beam intensity, the concentration of the metallic salt, and the flow velocity inside the microreactor. The confrontation to a build-in model of the metallic nanodot light-induced growth onto the surface of TiO₂ NPs shows the emergence of a predictable "master behavior" on which individual growths obtained from various tested conditions do collapse. We also characterized the associated quantum yield. Eventually, we successfully confronted our model to growth data from the literature in the case of silver on TiO₂ and gold on II-VI semiconducting NPs triggered by UV lamps. It shows that for the photosynthesis of NHDs the efficiency of the electron-hole pair production rate matters much more than the number of pairs produced and that the use of laser light can provide a photodeposition-based synthesis at the nanoscale.

Preparation and photocatalytic performance of silver-modified and nitrogen-doped TiO2 nanomaterials with oxygen vacancies

A modified hydrothermal method for the synthesis of TiO₂ material to achieve a more efficient visible light response.

Microfiltration Membranes Modified with Composition of Titanium Oxide and Silver Oxide by Magnetron Sputtering

In this work, the authors present the possibility of modification of polymer membranes by TiO₂ + AgO coating created by the magnetron sputtering method. The two-component TiO₂ + AgO coating can improve and shape new functional properties such as bactericidal and photocatalytic properties. The influence of magnetron power changes on the structure of the membrane was investigated as well. The structure and elemental composition of TiO₂ + AgO coatings were analyzed using SEM and EDS technique. All deposited coatings caused a total inhibition of the growth of two investigated colonies of Escherichia coli and Bacillus subtilis on the surface. The photocatalytic properties for membranes covered with oxide coatings were tested under UV irradiation and visible light. The filtration result show that polymer membranes covered with two-component TiO₂ + AgO coatings have a permeate flux similar to the non-coated membranes.

Photoelectrochemical enzymatic sensor for glucose based on Au@C/TiO2 nanorod arrays

In this work, a photoelectrochemical (PEC) glucose biosensor was synthesized on the basis of a type of Au@C/TiO₂ composite by using an unsophisticated secondary hydrothermal strategy. The compounded Au@C/TiO₂ material was characterized by XRD, SEM, TEM, UV-vis, and XPS to identify the composition and the purity of the phase. Glucose oxidase (GODx) was immobilized on the Au@C/TiO₂. The PEC biosensor presented satisfactory stability and outstanding reproducibility. The range and the sensitivity of the linear measurement were 0.1–1.6 mM and 29.76 μA mM⁻¹ cm⁻², respectively, and the detection limit was low (0.049 mM). The GODx/Au@C/TiO₂/FTO biosensor presented excellent efficiency in detecting glucose, suggesting the great potential application of this synthesized material in PEC biosensors.

In this work, a photoelectrochemical (PEC) glucose biosensor was synthesized on the basis of a type of Au@C/TiO₂ composite by using an unsophisticated secondary hydrothermal strategy.

Silver nanoparticles: Synthesis, investigation techniques, and properties

The unique silver properties, especially in the form of nanoparticles (NPs), allow to utilize them in numerous applications. For instance, Ag NPs can be utilized for the production of electronic and solar energy harvesting devices, in advanced analytical techniques (NALDI, SERS), catalysis and photocatalysis. Moreover, the Ag NPs can be useful in medicine for bioimaging, biosensing as well as in antibacterial and anticancer therapies. The Ag NPs utilization requires comprehensive knowledge about their features regarding the synthesis approaches as well as exploitation conditions. Unfortunately, a large number of scientific articles provide only restricted information according to the objects under investigation. Additionally, the results could be affected by artifacts introduced with exploited equipment, the utilized technique or sample preparation stages. However, it is rather difficult to get information about problems, which may occur during the studies. Thus, the review provides information about novel trends in the Ag NPs synthesis, among which the physical, chemical, and biological approaches can be found. Basic information about approaches for the control of critical parameters of NPs, i.e. size and shape, was also revealed. It was shown, that the reducing agent, stabilizer, the synthesis environment, including trace ions, have a direct impact on the Ag NPs properties. Further, the capabilities of modern analytical techniques for Ag NPs and nanocomposites investigations were shown, among other microscopic (optical, TEM, SEM, STEM, AFM), spectroscopic (UV-Vis, IR, Raman, NMR, electron spectroscopy, XRD), spectrometric (MALDI-TOF MS, SIMS, ICP-MS), and separation (CE, FFF, gel electrophoresis) techniques were described. The limitations and possible artifacts of the techniques were mentioned. A large number of presented techniques is a distinguishing feature, which makes the review different from others. Finally, the physicochemical and biological properties of Ag NPs were demonstrated. It was shown, that Ag NPs features are dependent on their basic parameters, such as size, shape, chemical composition, etc. At the end of the review, the modern theories of the Ag NPs toxic mechanism were shown in a way that has never been presented before. The review should be helpful for scientists in their own studies, as it can help to prepare experiments more carefully.

Effect of the preparation method and metal content on the synthesis of metal modified titanium oxide used for the removal of salicylic acid under UV light

Titanium dioxide modified with Ag and Fe was synthesized using two preparation methods, characterized and applied to the photocatalytic degradation of salicylic acid in aqueous solution. The modified TiO₂ samples were prepared by the sol-gel and wet impregnation methods starting from titanium(IV) isopropoxide and using AgNO₃ and Fe(NO₃)₃·9H₂O as precursors of the modifiers, with their content varying between 0 and 5 wt.%. Catalysts characterization was based on powder X-ray diffraction (PXRD), nitrogen physisorption at 77 K, temperature programmed reduction (H₂-TPR), chemisorption of NH₃ at 343 K and X-ray photoelectron spectroscopy (XPS). The photocatalytic degradation of salicylic acid by modified TiO₂ was investigated under ultraviolet irradiation at 298 K considering various concentrations of the catalyst, between 100 and 1000 mg_catalyst/dm³, and of the organic molecule, between 0 and 15 mg/dm³. The catalysts most active in the degradation of salicylic acid were those having the highest Fe content.

Photocatalytic oxidation of nitric oxide over AgNPs/TiO2-loaded carbon fiber cloths

Series of AgNPs/TiO₂-loaded carbon fiber cloth (CFC) composites were prepared by incorporation of pristine TiO₂ and three AgNPs-modified TiO₂ additives onto the surface of four commercial CFCs. AgNPs/TiO₂ photocatalysts were synthesized by the wet impregnation method, including NaBH₄ reduction of silver ions. The silver content in the modified photocatalyst was assessed by inductively coupled plasma optical emission spectrometry (ICP-OES) as well as XRD analysis. It can be indicated that silver was successfully reduced to Ag nanoparticles what was confirmed by UV-Vis/DRS as well as XRD methods. The photocatalytic activity of the AgNPs/TiO₂-loaded CFCs was evaluated during the photocatalytic oxidation (PCO) tests of nitric oxide (NO) acting as a model air contaminant under UV light. It was found that the highest NO removal rate was observed for the AgNPs/TiO₂-loaded CFC material containing 3.70 wt% of AgNPs. Modification of TiO₂ with AgNPs stabilized the photocatalytic efficiency of the composites during 5 as well as 24 consecutive NO photooxidation cycles. It was also concluded that the presence of AgNPs was a key factor responsible for hindering NO₂ formation.

Ag- or Cu-modified geopolymer filters for water treatment manufactured by 3D printing, direct foaming, or granulation

In this work, we compared the main characteristics of highly porous geopolymer components for water treatment applications manufactured by 3D printing, direct foaming, or granulation. Furthermore, different approaches to impregnate the materials with Ag or Cu were evaluated to obtain filters with disinfecting or catalytic properties. The results revealed that all of the investigated manufacturing methods enabled the fabrication of components that possessed mesoporosity, suitable mechanical strength, and water permeability, even though their morphologies were completely different. Total porosity and compressive strength values were 28 vol% and 16 MPa for 3D-printed, 70–79 vol% and 1 MPa for direct-foamed, and 27 vol% and 10 MPa for granule samples. Both the filter preparation and the metal impregnation method affected the amount, oxidation state, and stability of Ag and Cu in the filters. However, it was possible to prepare filters with low metal leaching between a pH of 3–7, so that the released Ag and Cu concentrations were within drinking water standards.

Enhanced Solar Light Photocatalytic Activity of Ag Doped TiO2-Ag3PO4 Composites

Composites comprised of Ag₃PO₄ and bare TiO₂ (TiO₂@Ag₃PO₄) or silver doped TiO₂ (Ag@TiO₂–Ag₃PO₄) have been synthesized by coupling sol–gel and precipitation methods. For the sake of comparison, also the bare components have been similarly prepared. All the samples have been characterized by X-ray diffraction (XRD), UV-vis diffuse reflectance spectroscopy (DRS), scanning electron microscopy (SEM), Fourier transformed infrared spectroscopy (FTIR), photoelectrochemical measurements, and specific surface area (SSA) analysis. The optoelectronic and structural features of the samples have been related to their photocatalytic activity for the degradation of 4–nitrophenol under solar and UV light irradiation. Coupling Ag₃PO₄ with silver doped TiO₂ mitigates photocorrosion of the Ag₃PO₄ counterpart, and remarkably improves the photocatalytic activity under solar light irradiation with respect to the components, to the TiO₂–Ag₃PO₄ sample, and to the benchmark TiO₂ Evonik P25. These features open the route to future applications of this material in the field of environmental remediation.

Enhanced Visible Light Photocatalytic Activity of N and Ag Doped and Co-Doped TiO2 Synthesized by Using an In-Situ Solvothermal Method for Gas Phase Ammonia Removal

Single doping and co-doping of N and Ag on TiO2 were successfully prepared by using an in-situ solvothermal method and their structural properties and chemical compositions were characterized. The results indicated that all photocatalysts displayed in TiO2 anatase crystal phase, and a small mesoporous structure was observed in the doped materials. The main roles of N and Ag on the property and photocatalytic activity of TiO2 were different. The N doping has significantly enhanced homogenous surface morphology and specific surface area of the photocatalyst. While Ag doping was narrowing the band gap energy, extending light absorption toward a visible region by surface plasmon resonance as well as delaying the recombination rate of electron and hole of TiO2. The existence of N in TiO2 lattice was observed in two structural linkages such as substitutional nitrogen (Ti-O-N) and interstitial nitrogen (O-Ti-N). Silver species could be in the form of Ag0 and Ag2O. The photocatalytic performance of the photocatalysts coated on stainless steel mesh was investigated by the degradation of aqueous MB and gas phase NH3 under visible LED light illumination for three recycling runs. The highest photocatalytic activity and recyclability were reached in 5% N/Ag-TiO2 showing the efficiency of 98.82% for methylene blue (MB) dye degradation and 37.5% for NH3 removal in 6 h, which was 2.7 and 4.3 times, respectively. This is greater than that of pure TiO2. This was due to the synergistic effect of N and Ag doping.

Visible-Light Active Titanium Dioxide Nanomaterials with Bactericidal Properties

This article provides an overview of current research into the development, synthesis, photocatalytic bacterial activity, biocompatibility and cytotoxic properties of various visible-light active titanium dioxide (TiO2) nanoparticles (NPs) and their nanocomposites. To achieve antibacterial inactivation under visible light, TiO2 NPs are doped with metal and non-metal elements, modified with carbonaceous nanomaterials, and coupled with other metal oxide semiconductors. Transition metals introduce a localized d-electron state just below the conduction band of TiO2 NPs, thereby narrowing the bandgap and causing a red shift of the optical absorption edge into the visible region. Silver nanoparticles of doped TiO2 NPs experience surface plasmon resonance under visible light excitation, leading to the injection of hot electrons into the conduction band of TiO2 NPs to generate reactive oxygen species (ROS) for bacterial killing. The modification of TiO2 NPs with carbon nanotubes and graphene sheets also achieve the efficient creation of ROS under visible light irradiation. Furthermore, titanium-based alloy implants in orthopedics with enhanced antibacterial activity and biocompatibility can be achieved by forming a surface layer of Ag-doped titania nanotubes. By incorporating TiO2 NPs and Cu-doped TiO2 NPs into chitosan or the textile matrix, the resulting polymer nanocomposites exhibit excellent antimicrobial properties that can have applications as fruit/food wrapping films, self-cleaning fabrics, medical scaffolds and wound dressings. Considering the possible use of visible-light active TiO2 nanomaterials for various applications, their toxicity impact on the environment and public health is also addressed.

Green synthesis of Ag/TiO2 Nanocomposite Assisted by Gambier Leaf (Uncaria gambir Roxb) Extract

Studies of green synthesis of nanoparticles mediated by plants extract is extensively explored and studied in recent time due to eco-friendliness, cost-effectiveness, and use a minimum amount of toxic chemicals in the process of inorganic material synthesis. In this study, the immobilization of silver nanoparticles on the surface of titanium dioxide (TiO2) was carried out using Uncaria gambier Roxb. leaf extract as a silver ion (Ag+) reducing agent. The synthesized Ag/TiO2 nanocomposite was characterized by UV-Vis spectroscopy, X-ray diffraction (XRD), and Diffuse Reflectance Spectroscopy (DRS). The formation of silver nanoparticles was confirmed through UV-Vis spectroscopic analysis, which showed a silver surface plasmon resonance (SPR) band at 426 nm. The X-ray diffraction pattern shows that Ag can inhibit the transition of the anatase into rutile phase. The presence of Ag particles in TiO2 can increase the absorption ability from an initial wavelength of 407 nm to 438 nm. Based on the results of Rhodamin B degradation, it can be seen that Ag/TiO2 has a higher photocatalytic activity than bare TiO2 with 99% percent degradation at 120 minutes of irradiation time.

Photoluminescence and structural properties of the nitrogen doped TiO2 and the influence of SiO2 and Ag nanoparticles

Mixtures of nitrogen-doped titanium dioxide (TiO₂:N) with different concentrations of Ag and/or SiO₂ particles (0.5, 1 and 2 wt.%) were prepared in solid state by mechanico-chemical interactions. Using UV-VIS spectroscopy, Raman scattering, photoluminescence (PL) and photoluminescence excitation (PLE), the influence of the particles on the host material is evaluated. UV-VIS spectroscopy studies indicate a TiO₂:N band gap shift to the UV range with increasing concentrations of SiO₂ and Ag particles. PL intensities decrease with increasing concentrations of Ag and/or SiO₂ particles in the TiO₂:N host matrix, which in turn could effectively restrict the electron and hole recombination. To explain these processes, the different de-excitation ways will be advanced, taking into account the energy levels diagram of TiO₂:N/Ag, TiO₂:N/SiO₂ and TiO₂:N/Ag/SiO₂ systems. PLE spectra show a gradual decrease in their relative intensities after 165 min of continuous irradiation due to photosensitivity of TiO₂:N. The plasmonic effect of Ag particles in the TiO₂:N/Ag system is highlighted for the first time by PLE studies.

Enhanced visible light photocatalytic activity of N, F-codoped TiO2 powders with high thermal stability

Doping non-metals onto TiO₂ has been regarded as a promising way to gain a more effective photocatalyst. In this paper, N, F-codoped TiO₂ was synthesized by the sol-gel method, demonstrating both high adsorption capacity and high photocatalytic activity under visible light irradiation. Samples were characterized by X-ray diffraction, scanning electron microscopy (SEM), X-ray photoelectron spectroscopy and UV-visible diffuse reflectance spectra (UV-vis DRS). The results show that N, F-codoping can reduce the impact of calcination temperature on the structure and morphology of the sample, resulting in the sample exhibiting good thermal stability, even when the calcination temperature changes in a large range, instead of rutile, the anatase around 20 nm is the only phase in N, F-codoped samples. It can be clearly observed from the SEM images that N, F-codoped samples calcined at different temperatures are in the state of scattered particles with small size and good dispersed property. And it is vivid that the absorption intensity of N, F-codoped TiO₂ samples in the visible light range increases substantially in DRS. According to the result of photocatalytic activity experiment, N, F-codoped TiO₂ samples calcined at 973 K exhibited the highest degradation rate for Methylene Blue.

Enhanced Photocatalytic Reduction of Cr(VI) by Combined Magnetic TiO2-Based NFs and Ammonium Oxalate Hole Scavengers

Heavy metal pollution of wastewater with coexisting organic contaminants has become a serious threat to human survival and development. In particular, hexavalent chromium, which is released into industrial wastewater, is both toxic and carcinogenic. TiO2 photocatalysts have attracted much attention due to their potential photodegradation and photoreduction abilities. Though TiO2 demonstrates high photocatalytic performance, it is a difficult material to recycle after the photocatalytic reaction. Considering the secondary pollution caused by the photocatalysts, in this study we prepared Ag/Fe3O4/TiO2 nanofibers (NFs) that could be magnetically separated using hydrothermal synthesis, which was considered a benign and effective resolution. For the photocatalytic test, the removal of Cr(VI) was carried out by Ag/Fe3O4/TiO2 nanofibers combined with ammonium oxalate (AO). AO acted as a hole scavenger to enhance the electron-hole separation ability, thereby dramatically enhancing the photoreduction efficiency of Cr(VI). The reaction rate constant for Ag/Fe3O4/TiO2 NFs in the binary system reached 0.260 min−1, 6.95 times of that of Ag/Fe3O4/TiO2 NFs in a single system (0.038 min−1). The optimized Ag/Fe3O4/TiO2 NFs exhibited high efficiency and maintained their photoreduction efficiency at 90% with a recyclability of 87% after five cycles. Hence, taking into account the high magnetic separation behavior, Ag/Fe3O4/TiO2 NFs with a high recycling capability are a potential photocatalyst for wastewater treatment.