Chemical Degradation of Methylene Blue Dye Using TiO2/Au Nanoparticles

Regenerated and reformed gold and titanium dioxide quantum dots from waste for sustainable and efficient environmental monitoring

Driven by the urgent need for sustainable materials in advanced technologies, this study investigates the potential of regenerated and reformed waste materials containing Au and TiO2 quantum dots (R-Au-TiO2 QDs), derived from industrial waste, as a viable alternative to commercial TiO2 (C-TiO2) for photocatalytic applications. The R-Au-TiO2 QDs demonstrate a high purity of 99.8 wt% and a particle size of less than 10 nm. The presence of Au (0.24 wt%) further enhances the photocatalytic performance of R-Au-TiO2 QDs through localized surface plasmon resonance (LSPR), leading to superior degradation rates of methylene blue (MB) when deposited on flexible aluminum foil substrates under UV and solar light. R-Au-TiO2 QDs achieve a degradation rate of 82.5% with a rate constant of 0.029 min-1 under UV light, representing a 28% increase in degradation rate and a 70% increase in the rate constant compared to 64.5% and 0.017 min-1, respectively, for C-TiO2. Under the solar simulator, R-Au-TiO2 QDs also outperform C-TiO2, achieving a degradation rate of 68%, further highlighting their effectiveness. These results are attributed to smaller particle size, higher surface area, enhanced light absorption and improved charge separation in the R-Au-TiO2 hybrid material. This study demonstrates that R-Au-TiO2 QDs not only match, but often surpass, the performance of commercial TiO2, offering a cost-effective and environmentally friendly solution for UV sensing, environmental monitoring, and water purification systems. These findings advocate for the strategic utilization of waste resources containing valuable elements to regenerate high-performance materials, thereby contributing to the development of a circular and sustainable economy.

Photocatalytic effect of gold-zinc oxide composite nanostructures for the selective and controlled killing of antibiotic-resistant bacteria and the removal of resistant bacterial biofilms from the body

Infections involving antibiotic-resistant bacteria have become a major problem. Pathogenic bacteria use mechanisms such as drug target bypass, target modification, and biofilm formation to evade treatment. To respond to these problems, antibacterial research using metal and metal oxide nanoparticles is currently active. Nanoparticles treat bacterial infections through reactive oxygen species generation or antibacterial ion release. However, their application has faced problems related to human compatibility, as they react non-specifically, targeting both mammalian and bacterial cells. In addition, ZnO nanoparticles show low antibacterial activity against Gram-negative bacteria. Thus, the demand for antibacterial substances with enhanced specificity and improved efficacy is increasing. We bound gold to the surface of ZnO nanoparticles, enabling photocatalytic and photothermal actions through visible light irradiation. To improve bacterial specificity, Concanavalin A (Con A), a lectin that can specifically target bacterial membrane lipopolysaccharides, was conjugated with the nanoparticles. We showed that Con A-conjugated Au/ZnO nanoparticles (Au/ZnO-Con A) exhibit photocatalytic and photothermal effects under white light, enhancing their antibacterial ability, and through enhanced specificity, increased antibacterial and anti-biofilm abilities were confirmed. The developed particles showed the potential to alleviate antibiotic resistance in a bacterial skin infection model, presenting a new platform for treating bacterial infections.

Structural and Spectroscopic Characterization of TiO2 Nanocrystalline Materials Synthesized by Different Methods

Nanocrystalline materials based on titanium dioxide possess unique properties, including photocatalytic and antibacterial activities. Despite many approaches have already been utilized to fabricate and characterize pure and doped TiO2, a systematic description of its nanostructured samples depending on the synthesis method has not been presented yet. In this study, we shed new light on the process-structure relationships of nanocrystalline TiO2-based powders fabricated by extraction-pyrolytic, hydrothermal, and sol-gel techniques. The comprehensive analysis of the fabricated nanocrystalline TiO2-based powders with different anatase/rutile phase content is performed by scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDX), Raman spectroscopy, and X-ray photoelectron spectroscopy (XPS). The hydrothermal and sol-gel methods are also used to grow TiO2 particles doped with Cu and Er-Yb. The correlation between synthesis parameters (pyrolysis and annealing temperature) and properties of the produced materials is studied. Particular attention is paid to Raman spectroscopy and the detailed comparison of our obtained data with existing experimental and theoretical studies.

Controlling nanoparticle placement in Au/TiO2 inverse opal photocatalysts

Gold nanoparticle-loaded titania (Au/TiO2) inverse opals are highly ordered three-dimensional photonic structures with enhanced photocatalytic properties. However, fine control over the placement of the Au nanoparticles in the inverse opal structures remains challenging with traditional preparative methods. Here, we present a multi-component co-assembly strategy to prepare high-quality Au/TiO2 inverse opal films in which Au nanoparticles are either located on, or inside the TiO2 matrix, as verified using electron tomography. We report that Au nanoparticles embedded in the TiO2 support exhibit enhanced thermal and mechanical stability compared to non-embedded nanoparticles that are more prone to both leaching and sintering.

TiO2-embedded mesoporous silica with lower porosity is beneficial to adsorb the pollutants and retard UV filter absorption: A possible application for outdoor skin protection

The purpose of the current investigation was to develop multifunctional TiO₂-embedded mesoporous silica incorporating avobenzone to protect against environmental stress through pollutant adsorption and UVA protection. We sought to explore the effect of the mesoporous porosity on the capability of contaminant capture and the suppression of avobenzone skin penetration. The porosity of the mesoporous silica was tuned by adjusting the ratio of template triblock copolymers (Pluronic P123 and F68). The Pluronic P123:F68 ratios of 3:1, 2:2, and 1:3 produced mesoporous silica with pore volumes of 0.66 (TiO₂/SBA-L), 0.47 (TiO₂/SBA-M), and 0.25 (TiO₂/SBA-S) cm³/g, respectively. X-ray scattering and electron microscopy confirmed the SBA-15 structure of the as-prepared material had a size of 3-5 μm. The maximum adsorbability of fluoranthene and methylene blue was found to be 43% and 53% for the TiO₂/SBA-S under UVA light, respectively. The avobenzone loaded into the mesoporous silica demonstrated the synergistic effect of in vitro UVA protection, reaching an UVA/UVB absorbance ratio of near 1.5 (Boots star rating = 5). The encapsulation of avobenzone into the TiO₂/SBA-S lessened cutaneous avobenzone absorption from 0.76 to 0.50 nmol/mg, whereas no reduction was detected for the TiO₂/SBA-L. The avobenzone-loaded TiO₂/SBA-S hydrogel exhibited a greater improvement in skin barrier recovery and proinflammatory mediator mitigation compared to the SBA-S hydrogel (without TiO₂). The cytokines/chemokines in the photoaged skin were reduced by two- to three-fold after TiO₂/SBA-S treatment compared to the non-treatment control. Our data suggested that the mesoporous formulation with low porosity and a specific surface area showed effective adsorbability and UVA protection, with reduced UVA filter absorption. The versatility of the developed mesoporous system indicated a promising potential for outdoor skin protection.

Gold nanoparticles loaded on TiO2 nanoparticles doped with N2 as an efficient electrocatalyst for glucose oxidation: preparation, characterization, and electrocatalytic properties

A powder of titanium oxide nanoparticles (TiO2 NPs) was synthesized in this study by anodizing in 0.7 M HClO4 and then annealing in N2 at 450 °C for 3 h to produce TiO2 NPs-N2 powder as a catalyst. These TiO2 NPs-N2 nanoparticles were then encrusted with Au nanoparticles utilizing the photodeposition procedure with tetrachloroauric acid (HAuCl4) and isopropanol as sacrificial donors. With a surface area of 121 m2g−1, the Au NPs/TiO2 NPs-N2 powder catalyst has a high surface area, according to the Barrett–Joyner–Halenda technique. According to X-ray diffraction (XRD) analysis, TiO2 NPs-N2 contained uniformly integrated Au nanoparticles with an average crystallite size of about 26.8 nm. The XRD patterns showed that the prepared Au NPs/TiO2 NPs-N2 were crystallites and nano-sized. The transmission electron microscopy image revealed the spherical shape of the nanoparticles and their tendency for agglomeration. Utilizing the cyclic voltammetry, the electrochemical properties of the catalyst TiO2 NPs powders in a basic glucose solution were investigated. The electrocatalytic activity and stability of the loaded Au NPs/TiO2 NPs-N2 powder on the working electrode for the electrocatalytic oxidation of glucose were astonishingly high. The Au NPs/TiO2 NPs-N2 catalyst demonstrated electrocatalytic characteristics that were superior to a commercially available polycrystalline gold electrode in the application involving glucose alkaline fuel cells.

Visible Light-Induced Photocatalyst with Au/TiO2 Nanocomposites Fabricated through Pulsed Laser-Induced Photolysis

Gold–titanium oxide nanocomposites (Au–TiO2 NCPs) were fabricated through pulsed laser-induced photolysis (PIPS) and verified to be usable for the visible light catalytic degradation of methylene blue (MB). The PIPS method can produce a sufficient amount of NCPs quickly and has potential to be commercialized. In contrast to other studies, we clarified the optical spectrum of the light sources, including peak power, bandwidth, and total intensity used for photodegradation reactions and discovered that the photodegradation efficiency of the produced Au–TiO2 NCPs in the wavelength range of 405 nm could reach 37% in 30 min due to the charge transfer between Au and TiO2. The control experiment shows that the addition of individual Au and TiO2 nanoparticles (NPs) to an MB solution has no enhancement of degradation ability under visible light illumination. The photodegradation of Au–TiO2 NCPs can be further improved by increasing the concentrations of auric acid and TiO2 NPs in a precursor under PIPS fabrication.

NanoUPLC-QTOF-MS/MS Determination of Major Rosuvastatin Degradation Products Generated by Gamma Radiation in Aqueous Solution

Rosuvastatin, a member of the statin family of drugs, is used to regulate high cholesterol levels in the human body. Moreover, rosuvastatin and other statins demonstrate a protective role against free radical-induced oxidative stress. Our research aimed to investigate the end-products of free radical-induced degradation of rosuvastatin. To induce the radical degradation, an aqueous solution of rosuvastatin was irradiated using different doses of gamma radiation (50-1000 Gy) under oxidative conditions. Rosuvastatin and related degradation products were separated on nanoC18 column under gradient elution, and identification was carried out on hyphenated nanoUPLC and nanoESI-QTOF mass spectrometer system. Elemental composition analysis using highly accurate mass measurements together with isotope fitting algorithm identified nine major degradation products. This is the first study of gamma radiation-induced degradation of rosuvastatin, where chemical structures, MS/MS fragmentation pathways and formation mechanisms of the resulting degradation products are detailly described. The presented results contribute to the understanding of the degradation pathway of rosuvastatin and possibly other statins under gamma radiation conditions.